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tcp: minimize false-positives on TCP/GRO check
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1 /*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21 /*
22 * Changes:
23 * Pedro Roque : Fast Retransmit/Recovery.
24 * Two receive queues.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
28 * Header prediction.
29 * Variable renaming.
30 *
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
44 * timestamps.
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
47 * data segments.
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
55 * fast path.
56 * J Hadi Salim: ECN support
57 * Andrei Gurtov,
58 * Pasi Sarolahti,
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
62 */
63
64 #define pr_fmt(fmt) "TCP: " fmt
65
66 #include <linux/mm.h>
67 #include <linux/slab.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <linux/kernel.h>
71 #include <linux/prefetch.h>
72 #include <net/dst.h>
73 #include <net/tcp.h>
74 #include <net/inet_common.h>
75 #include <linux/ipsec.h>
76 #include <asm/unaligned.h>
77 #include <linux/errqueue.h>
78
79 int sysctl_tcp_timestamps __read_mostly = 1;
80 int sysctl_tcp_window_scaling __read_mostly = 1;
81 int sysctl_tcp_sack __read_mostly = 1;
82 int sysctl_tcp_fack __read_mostly;
83 int sysctl_tcp_max_reordering __read_mostly = 300;
84 int sysctl_tcp_dsack __read_mostly = 1;
85 int sysctl_tcp_app_win __read_mostly = 31;
86 int sysctl_tcp_adv_win_scale __read_mostly = 1;
87 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
88 EXPORT_SYMBOL(sysctl_tcp_timestamps);
89
90 /* rfc5961 challenge ack rate limiting */
91 int sysctl_tcp_challenge_ack_limit = 1000;
92
93 int sysctl_tcp_stdurg __read_mostly;
94 int sysctl_tcp_rfc1337 __read_mostly;
95 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
96 int sysctl_tcp_frto __read_mostly = 2;
97 int sysctl_tcp_min_rtt_wlen __read_mostly = 300;
98 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
99 int sysctl_tcp_early_retrans __read_mostly = 3;
100 int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
101
102 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
103 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
104 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
105 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
106 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
107 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
108 #define FLAG_ECE 0x40 /* ECE in this ACK */
109 #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
110 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
111 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
112 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
113 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
114 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
115 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
116
117 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
118 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
119 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
120 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
121
122 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
123 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
124
125 #define REXMIT_NONE 0 /* no loss recovery to do */
126 #define REXMIT_LOST 1 /* retransmit packets marked lost */
127 #define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
128
129 static void tcp_gro_dev_warn(struct sock *sk, const struct sk_buff *skb,
130 unsigned int len)
131 {
132 static bool __once __read_mostly;
133
134 if (!__once) {
135 struct net_device *dev;
136
137 __once = true;
138
139 rcu_read_lock();
140 dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif);
141 if (!dev || len >= dev->mtu)
142 pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
143 dev ? dev->name : "Unknown driver");
144 rcu_read_unlock();
145 }
146 }
147
148 /* Adapt the MSS value used to make delayed ack decision to the
149 * real world.
150 */
151 static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
152 {
153 struct inet_connection_sock *icsk = inet_csk(sk);
154 const unsigned int lss = icsk->icsk_ack.last_seg_size;
155 unsigned int len;
156
157 icsk->icsk_ack.last_seg_size = 0;
158
159 /* skb->len may jitter because of SACKs, even if peer
160 * sends good full-sized frames.
161 */
162 len = skb_shinfo(skb)->gso_size ? : skb->len;
163 if (len >= icsk->icsk_ack.rcv_mss) {
164 icsk->icsk_ack.rcv_mss = min_t(unsigned int, len,
165 tcp_sk(sk)->advmss);
166 /* Account for possibly-removed options */
167 if (unlikely(len > icsk->icsk_ack.rcv_mss +
168 MAX_TCP_OPTION_SPACE))
169 tcp_gro_dev_warn(sk, skb, len);
170 } else {
171 /* Otherwise, we make more careful check taking into account,
172 * that SACKs block is variable.
173 *
174 * "len" is invariant segment length, including TCP header.
175 */
176 len += skb->data - skb_transport_header(skb);
177 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
178 /* If PSH is not set, packet should be
179 * full sized, provided peer TCP is not badly broken.
180 * This observation (if it is correct 8)) allows
181 * to handle super-low mtu links fairly.
182 */
183 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
184 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
185 /* Subtract also invariant (if peer is RFC compliant),
186 * tcp header plus fixed timestamp option length.
187 * Resulting "len" is MSS free of SACK jitter.
188 */
189 len -= tcp_sk(sk)->tcp_header_len;
190 icsk->icsk_ack.last_seg_size = len;
191 if (len == lss) {
192 icsk->icsk_ack.rcv_mss = len;
193 return;
194 }
195 }
196 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
197 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
198 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
199 }
200 }
201
202 static void tcp_incr_quickack(struct sock *sk)
203 {
204 struct inet_connection_sock *icsk = inet_csk(sk);
205 unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
206
207 if (quickacks == 0)
208 quickacks = 2;
209 if (quickacks > icsk->icsk_ack.quick)
210 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
211 }
212
213 static void tcp_enter_quickack_mode(struct sock *sk)
214 {
215 struct inet_connection_sock *icsk = inet_csk(sk);
216 tcp_incr_quickack(sk);
217 icsk->icsk_ack.pingpong = 0;
218 icsk->icsk_ack.ato = TCP_ATO_MIN;
219 }
220
221 /* Send ACKs quickly, if "quick" count is not exhausted
222 * and the session is not interactive.
223 */
224
225 static bool tcp_in_quickack_mode(struct sock *sk)
226 {
227 const struct inet_connection_sock *icsk = inet_csk(sk);
228 const struct dst_entry *dst = __sk_dst_get(sk);
229
230 return (dst && dst_metric(dst, RTAX_QUICKACK)) ||
231 (icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong);
232 }
233
234 static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
235 {
236 if (tp->ecn_flags & TCP_ECN_OK)
237 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
238 }
239
240 static void tcp_ecn_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb)
241 {
242 if (tcp_hdr(skb)->cwr)
243 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
244 }
245
246 static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp)
247 {
248 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
249 }
250
251 static void __tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
252 {
253 switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
254 case INET_ECN_NOT_ECT:
255 /* Funny extension: if ECT is not set on a segment,
256 * and we already seen ECT on a previous segment,
257 * it is probably a retransmit.
258 */
259 if (tp->ecn_flags & TCP_ECN_SEEN)
260 tcp_enter_quickack_mode((struct sock *)tp);
261 break;
262 case INET_ECN_CE:
263 if (tcp_ca_needs_ecn((struct sock *)tp))
264 tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_IS_CE);
265
266 if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
267 /* Better not delay acks, sender can have a very low cwnd */
268 tcp_enter_quickack_mode((struct sock *)tp);
269 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
270 }
271 tp->ecn_flags |= TCP_ECN_SEEN;
272 break;
273 default:
274 if (tcp_ca_needs_ecn((struct sock *)tp))
275 tcp_ca_event((struct sock *)tp, CA_EVENT_ECN_NO_CE);
276 tp->ecn_flags |= TCP_ECN_SEEN;
277 break;
278 }
279 }
280
281 static void tcp_ecn_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
282 {
283 if (tp->ecn_flags & TCP_ECN_OK)
284 __tcp_ecn_check_ce(tp, skb);
285 }
286
287 static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th)
288 {
289 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
290 tp->ecn_flags &= ~TCP_ECN_OK;
291 }
292
293 static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th)
294 {
295 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
296 tp->ecn_flags &= ~TCP_ECN_OK;
297 }
298
299 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th)
300 {
301 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
302 return true;
303 return false;
304 }
305
306 /* Buffer size and advertised window tuning.
307 *
308 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
309 */
310
311 static void tcp_sndbuf_expand(struct sock *sk)
312 {
313 const struct tcp_sock *tp = tcp_sk(sk);
314 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
315 int sndmem, per_mss;
316 u32 nr_segs;
317
318 /* Worst case is non GSO/TSO : each frame consumes one skb
319 * and skb->head is kmalloced using power of two area of memory
320 */
321 per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
322 MAX_TCP_HEADER +
323 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
324
325 per_mss = roundup_pow_of_two(per_mss) +
326 SKB_DATA_ALIGN(sizeof(struct sk_buff));
327
328 nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd);
329 nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
330
331 /* Fast Recovery (RFC 5681 3.2) :
332 * Cubic needs 1.7 factor, rounded to 2 to include
333 * extra cushion (application might react slowly to POLLOUT)
334 */
335 sndmem = ca_ops->sndbuf_expand ? ca_ops->sndbuf_expand(sk) : 2;
336 sndmem *= nr_segs * per_mss;
337
338 if (sk->sk_sndbuf < sndmem)
339 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
340 }
341
342 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
343 *
344 * All tcp_full_space() is split to two parts: "network" buffer, allocated
345 * forward and advertised in receiver window (tp->rcv_wnd) and
346 * "application buffer", required to isolate scheduling/application
347 * latencies from network.
348 * window_clamp is maximal advertised window. It can be less than
349 * tcp_full_space(), in this case tcp_full_space() - window_clamp
350 * is reserved for "application" buffer. The less window_clamp is
351 * the smoother our behaviour from viewpoint of network, but the lower
352 * throughput and the higher sensitivity of the connection to losses. 8)
353 *
354 * rcv_ssthresh is more strict window_clamp used at "slow start"
355 * phase to predict further behaviour of this connection.
356 * It is used for two goals:
357 * - to enforce header prediction at sender, even when application
358 * requires some significant "application buffer". It is check #1.
359 * - to prevent pruning of receive queue because of misprediction
360 * of receiver window. Check #2.
361 *
362 * The scheme does not work when sender sends good segments opening
363 * window and then starts to feed us spaghetti. But it should work
364 * in common situations. Otherwise, we have to rely on queue collapsing.
365 */
366
367 /* Slow part of check#2. */
368 static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
369 {
370 struct tcp_sock *tp = tcp_sk(sk);
371 /* Optimize this! */
372 int truesize = tcp_win_from_space(skb->truesize) >> 1;
373 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
374
375 while (tp->rcv_ssthresh <= window) {
376 if (truesize <= skb->len)
377 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
378
379 truesize >>= 1;
380 window >>= 1;
381 }
382 return 0;
383 }
384
385 static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
386 {
387 struct tcp_sock *tp = tcp_sk(sk);
388
389 /* Check #1 */
390 if (tp->rcv_ssthresh < tp->window_clamp &&
391 (int)tp->rcv_ssthresh < tcp_space(sk) &&
392 !tcp_under_memory_pressure(sk)) {
393 int incr;
394
395 /* Check #2. Increase window, if skb with such overhead
396 * will fit to rcvbuf in future.
397 */
398 if (tcp_win_from_space(skb->truesize) <= skb->len)
399 incr = 2 * tp->advmss;
400 else
401 incr = __tcp_grow_window(sk, skb);
402
403 if (incr) {
404 incr = max_t(int, incr, 2 * skb->len);
405 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
406 tp->window_clamp);
407 inet_csk(sk)->icsk_ack.quick |= 1;
408 }
409 }
410 }
411
412 /* 3. Tuning rcvbuf, when connection enters established state. */
413 static void tcp_fixup_rcvbuf(struct sock *sk)
414 {
415 u32 mss = tcp_sk(sk)->advmss;
416 int rcvmem;
417
418 rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
419 tcp_default_init_rwnd(mss);
420
421 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
422 * Allow enough cushion so that sender is not limited by our window
423 */
424 if (sysctl_tcp_moderate_rcvbuf)
425 rcvmem <<= 2;
426
427 if (sk->sk_rcvbuf < rcvmem)
428 sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]);
429 }
430
431 /* 4. Try to fixup all. It is made immediately after connection enters
432 * established state.
433 */
434 void tcp_init_buffer_space(struct sock *sk)
435 {
436 struct tcp_sock *tp = tcp_sk(sk);
437 int maxwin;
438
439 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
440 tcp_fixup_rcvbuf(sk);
441 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
442 tcp_sndbuf_expand(sk);
443
444 tp->rcvq_space.space = tp->rcv_wnd;
445 tp->rcvq_space.time = tcp_time_stamp;
446 tp->rcvq_space.seq = tp->copied_seq;
447
448 maxwin = tcp_full_space(sk);
449
450 if (tp->window_clamp >= maxwin) {
451 tp->window_clamp = maxwin;
452
453 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
454 tp->window_clamp = max(maxwin -
455 (maxwin >> sysctl_tcp_app_win),
456 4 * tp->advmss);
457 }
458
459 /* Force reservation of one segment. */
460 if (sysctl_tcp_app_win &&
461 tp->window_clamp > 2 * tp->advmss &&
462 tp->window_clamp + tp->advmss > maxwin)
463 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
464
465 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
466 tp->snd_cwnd_stamp = tcp_time_stamp;
467 }
468
469 /* 5. Recalculate window clamp after socket hit its memory bounds. */
470 static void tcp_clamp_window(struct sock *sk)
471 {
472 struct tcp_sock *tp = tcp_sk(sk);
473 struct inet_connection_sock *icsk = inet_csk(sk);
474
475 icsk->icsk_ack.quick = 0;
476
477 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
478 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
479 !tcp_under_memory_pressure(sk) &&
480 sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) {
481 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
482 sysctl_tcp_rmem[2]);
483 }
484 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
485 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
486 }
487
488 /* Initialize RCV_MSS value.
489 * RCV_MSS is an our guess about MSS used by the peer.
490 * We haven't any direct information about the MSS.
491 * It's better to underestimate the RCV_MSS rather than overestimate.
492 * Overestimations make us ACKing less frequently than needed.
493 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
494 */
495 void tcp_initialize_rcv_mss(struct sock *sk)
496 {
497 const struct tcp_sock *tp = tcp_sk(sk);
498 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
499
500 hint = min(hint, tp->rcv_wnd / 2);
501 hint = min(hint, TCP_MSS_DEFAULT);
502 hint = max(hint, TCP_MIN_MSS);
503
504 inet_csk(sk)->icsk_ack.rcv_mss = hint;
505 }
506 EXPORT_SYMBOL(tcp_initialize_rcv_mss);
507
508 /* Receiver "autotuning" code.
509 *
510 * The algorithm for RTT estimation w/o timestamps is based on
511 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
512 * <http://public.lanl.gov/radiant/pubs.html#DRS>
513 *
514 * More detail on this code can be found at
515 * <http://staff.psc.edu/jheffner/>,
516 * though this reference is out of date. A new paper
517 * is pending.
518 */
519 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
520 {
521 u32 new_sample = tp->rcv_rtt_est.rtt;
522 long m = sample;
523
524 if (m == 0)
525 m = 1;
526
527 if (new_sample != 0) {
528 /* If we sample in larger samples in the non-timestamp
529 * case, we could grossly overestimate the RTT especially
530 * with chatty applications or bulk transfer apps which
531 * are stalled on filesystem I/O.
532 *
533 * Also, since we are only going for a minimum in the
534 * non-timestamp case, we do not smooth things out
535 * else with timestamps disabled convergence takes too
536 * long.
537 */
538 if (!win_dep) {
539 m -= (new_sample >> 3);
540 new_sample += m;
541 } else {
542 m <<= 3;
543 if (m < new_sample)
544 new_sample = m;
545 }
546 } else {
547 /* No previous measure. */
548 new_sample = m << 3;
549 }
550
551 if (tp->rcv_rtt_est.rtt != new_sample)
552 tp->rcv_rtt_est.rtt = new_sample;
553 }
554
555 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
556 {
557 if (tp->rcv_rtt_est.time == 0)
558 goto new_measure;
559 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
560 return;
561 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1);
562
563 new_measure:
564 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
565 tp->rcv_rtt_est.time = tcp_time_stamp;
566 }
567
568 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
569 const struct sk_buff *skb)
570 {
571 struct tcp_sock *tp = tcp_sk(sk);
572 if (tp->rx_opt.rcv_tsecr &&
573 (TCP_SKB_CB(skb)->end_seq -
574 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
575 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
576 }
577
578 /*
579 * This function should be called every time data is copied to user space.
580 * It calculates the appropriate TCP receive buffer space.
581 */
582 void tcp_rcv_space_adjust(struct sock *sk)
583 {
584 struct tcp_sock *tp = tcp_sk(sk);
585 int time;
586 int copied;
587
588 time = tcp_time_stamp - tp->rcvq_space.time;
589 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
590 return;
591
592 /* Number of bytes copied to user in last RTT */
593 copied = tp->copied_seq - tp->rcvq_space.seq;
594 if (copied <= tp->rcvq_space.space)
595 goto new_measure;
596
597 /* A bit of theory :
598 * copied = bytes received in previous RTT, our base window
599 * To cope with packet losses, we need a 2x factor
600 * To cope with slow start, and sender growing its cwin by 100 %
601 * every RTT, we need a 4x factor, because the ACK we are sending
602 * now is for the next RTT, not the current one :
603 * <prev RTT . ><current RTT .. ><next RTT .... >
604 */
605
606 if (sysctl_tcp_moderate_rcvbuf &&
607 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
608 int rcvwin, rcvmem, rcvbuf;
609
610 /* minimal window to cope with packet losses, assuming
611 * steady state. Add some cushion because of small variations.
612 */
613 rcvwin = (copied << 1) + 16 * tp->advmss;
614
615 /* If rate increased by 25%,
616 * assume slow start, rcvwin = 3 * copied
617 * If rate increased by 50%,
618 * assume sender can use 2x growth, rcvwin = 4 * copied
619 */
620 if (copied >=
621 tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) {
622 if (copied >=
623 tp->rcvq_space.space + (tp->rcvq_space.space >> 1))
624 rcvwin <<= 1;
625 else
626 rcvwin += (rcvwin >> 1);
627 }
628
629 rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
630 while (tcp_win_from_space(rcvmem) < tp->advmss)
631 rcvmem += 128;
632
633 rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]);
634 if (rcvbuf > sk->sk_rcvbuf) {
635 sk->sk_rcvbuf = rcvbuf;
636
637 /* Make the window clamp follow along. */
638 tp->window_clamp = rcvwin;
639 }
640 }
641 tp->rcvq_space.space = copied;
642
643 new_measure:
644 tp->rcvq_space.seq = tp->copied_seq;
645 tp->rcvq_space.time = tcp_time_stamp;
646 }
647
648 /* There is something which you must keep in mind when you analyze the
649 * behavior of the tp->ato delayed ack timeout interval. When a
650 * connection starts up, we want to ack as quickly as possible. The
651 * problem is that "good" TCP's do slow start at the beginning of data
652 * transmission. The means that until we send the first few ACK's the
653 * sender will sit on his end and only queue most of his data, because
654 * he can only send snd_cwnd unacked packets at any given time. For
655 * each ACK we send, he increments snd_cwnd and transmits more of his
656 * queue. -DaveM
657 */
658 static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
659 {
660 struct tcp_sock *tp = tcp_sk(sk);
661 struct inet_connection_sock *icsk = inet_csk(sk);
662 u32 now;
663
664 inet_csk_schedule_ack(sk);
665
666 tcp_measure_rcv_mss(sk, skb);
667
668 tcp_rcv_rtt_measure(tp);
669
670 now = tcp_time_stamp;
671
672 if (!icsk->icsk_ack.ato) {
673 /* The _first_ data packet received, initialize
674 * delayed ACK engine.
675 */
676 tcp_incr_quickack(sk);
677 icsk->icsk_ack.ato = TCP_ATO_MIN;
678 } else {
679 int m = now - icsk->icsk_ack.lrcvtime;
680
681 if (m <= TCP_ATO_MIN / 2) {
682 /* The fastest case is the first. */
683 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
684 } else if (m < icsk->icsk_ack.ato) {
685 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
686 if (icsk->icsk_ack.ato > icsk->icsk_rto)
687 icsk->icsk_ack.ato = icsk->icsk_rto;
688 } else if (m > icsk->icsk_rto) {
689 /* Too long gap. Apparently sender failed to
690 * restart window, so that we send ACKs quickly.
691 */
692 tcp_incr_quickack(sk);
693 sk_mem_reclaim(sk);
694 }
695 }
696 icsk->icsk_ack.lrcvtime = now;
697
698 tcp_ecn_check_ce(tp, skb);
699
700 if (skb->len >= 128)
701 tcp_grow_window(sk, skb);
702 }
703
704 /* Called to compute a smoothed rtt estimate. The data fed to this
705 * routine either comes from timestamps, or from segments that were
706 * known _not_ to have been retransmitted [see Karn/Partridge
707 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
708 * piece by Van Jacobson.
709 * NOTE: the next three routines used to be one big routine.
710 * To save cycles in the RFC 1323 implementation it was better to break
711 * it up into three procedures. -- erics
712 */
713 static void tcp_rtt_estimator(struct sock *sk, long mrtt_us)
714 {
715 struct tcp_sock *tp = tcp_sk(sk);
716 long m = mrtt_us; /* RTT */
717 u32 srtt = tp->srtt_us;
718
719 /* The following amusing code comes from Jacobson's
720 * article in SIGCOMM '88. Note that rtt and mdev
721 * are scaled versions of rtt and mean deviation.
722 * This is designed to be as fast as possible
723 * m stands for "measurement".
724 *
725 * On a 1990 paper the rto value is changed to:
726 * RTO = rtt + 4 * mdev
727 *
728 * Funny. This algorithm seems to be very broken.
729 * These formulae increase RTO, when it should be decreased, increase
730 * too slowly, when it should be increased quickly, decrease too quickly
731 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
732 * does not matter how to _calculate_ it. Seems, it was trap
733 * that VJ failed to avoid. 8)
734 */
735 if (srtt != 0) {
736 m -= (srtt >> 3); /* m is now error in rtt est */
737 srtt += m; /* rtt = 7/8 rtt + 1/8 new */
738 if (m < 0) {
739 m = -m; /* m is now abs(error) */
740 m -= (tp->mdev_us >> 2); /* similar update on mdev */
741 /* This is similar to one of Eifel findings.
742 * Eifel blocks mdev updates when rtt decreases.
743 * This solution is a bit different: we use finer gain
744 * for mdev in this case (alpha*beta).
745 * Like Eifel it also prevents growth of rto,
746 * but also it limits too fast rto decreases,
747 * happening in pure Eifel.
748 */
749 if (m > 0)
750 m >>= 3;
751 } else {
752 m -= (tp->mdev_us >> 2); /* similar update on mdev */
753 }
754 tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */
755 if (tp->mdev_us > tp->mdev_max_us) {
756 tp->mdev_max_us = tp->mdev_us;
757 if (tp->mdev_max_us > tp->rttvar_us)
758 tp->rttvar_us = tp->mdev_max_us;
759 }
760 if (after(tp->snd_una, tp->rtt_seq)) {
761 if (tp->mdev_max_us < tp->rttvar_us)
762 tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2;
763 tp->rtt_seq = tp->snd_nxt;
764 tp->mdev_max_us = tcp_rto_min_us(sk);
765 }
766 } else {
767 /* no previous measure. */
768 srtt = m << 3; /* take the measured time to be rtt */
769 tp->mdev_us = m << 1; /* make sure rto = 3*rtt */
770 tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk));
771 tp->mdev_max_us = tp->rttvar_us;
772 tp->rtt_seq = tp->snd_nxt;
773 }
774 tp->srtt_us = max(1U, srtt);
775 }
776
777 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
778 * Note: TCP stack does not yet implement pacing.
779 * FQ packet scheduler can be used to implement cheap but effective
780 * TCP pacing, to smooth the burst on large writes when packets
781 * in flight is significantly lower than cwnd (or rwin)
782 */
783 int sysctl_tcp_pacing_ss_ratio __read_mostly = 200;
784 int sysctl_tcp_pacing_ca_ratio __read_mostly = 120;
785
786 static void tcp_update_pacing_rate(struct sock *sk)
787 {
788 const struct tcp_sock *tp = tcp_sk(sk);
789 u64 rate;
790
791 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
792 rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
793
794 /* current rate is (cwnd * mss) / srtt
795 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
796 * In Congestion Avoidance phase, set it to 120 % the current rate.
797 *
798 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
799 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
800 * end of slow start and should slow down.
801 */
802 if (tp->snd_cwnd < tp->snd_ssthresh / 2)
803 rate *= sysctl_tcp_pacing_ss_ratio;
804 else
805 rate *= sysctl_tcp_pacing_ca_ratio;
806
807 rate *= max(tp->snd_cwnd, tp->packets_out);
808
809 if (likely(tp->srtt_us))
810 do_div(rate, tp->srtt_us);
811
812 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
813 * without any lock. We want to make sure compiler wont store
814 * intermediate values in this location.
815 */
816 ACCESS_ONCE(sk->sk_pacing_rate) = min_t(u64, rate,
817 sk->sk_max_pacing_rate);
818 }
819
820 /* Calculate rto without backoff. This is the second half of Van Jacobson's
821 * routine referred to above.
822 */
823 static void tcp_set_rto(struct sock *sk)
824 {
825 const struct tcp_sock *tp = tcp_sk(sk);
826 /* Old crap is replaced with new one. 8)
827 *
828 * More seriously:
829 * 1. If rtt variance happened to be less 50msec, it is hallucination.
830 * It cannot be less due to utterly erratic ACK generation made
831 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
832 * to do with delayed acks, because at cwnd>2 true delack timeout
833 * is invisible. Actually, Linux-2.4 also generates erratic
834 * ACKs in some circumstances.
835 */
836 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
837
838 /* 2. Fixups made earlier cannot be right.
839 * If we do not estimate RTO correctly without them,
840 * all the algo is pure shit and should be replaced
841 * with correct one. It is exactly, which we pretend to do.
842 */
843
844 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
845 * guarantees that rto is higher.
846 */
847 tcp_bound_rto(sk);
848 }
849
850 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
851 {
852 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
853
854 if (!cwnd)
855 cwnd = TCP_INIT_CWND;
856 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
857 }
858
859 /*
860 * Packet counting of FACK is based on in-order assumptions, therefore TCP
861 * disables it when reordering is detected
862 */
863 void tcp_disable_fack(struct tcp_sock *tp)
864 {
865 /* RFC3517 uses different metric in lost marker => reset on change */
866 if (tcp_is_fack(tp))
867 tp->lost_skb_hint = NULL;
868 tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED;
869 }
870
871 /* Take a notice that peer is sending D-SACKs */
872 static void tcp_dsack_seen(struct tcp_sock *tp)
873 {
874 tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
875 }
876
877 static void tcp_update_reordering(struct sock *sk, const int metric,
878 const int ts)
879 {
880 struct tcp_sock *tp = tcp_sk(sk);
881 if (metric > tp->reordering) {
882 int mib_idx;
883
884 tp->reordering = min(sysctl_tcp_max_reordering, metric);
885
886 /* This exciting event is worth to be remembered. 8) */
887 if (ts)
888 mib_idx = LINUX_MIB_TCPTSREORDER;
889 else if (tcp_is_reno(tp))
890 mib_idx = LINUX_MIB_TCPRENOREORDER;
891 else if (tcp_is_fack(tp))
892 mib_idx = LINUX_MIB_TCPFACKREORDER;
893 else
894 mib_idx = LINUX_MIB_TCPSACKREORDER;
895
896 NET_INC_STATS(sock_net(sk), mib_idx);
897 #if FASTRETRANS_DEBUG > 1
898 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
899 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
900 tp->reordering,
901 tp->fackets_out,
902 tp->sacked_out,
903 tp->undo_marker ? tp->undo_retrans : 0);
904 #endif
905 tcp_disable_fack(tp);
906 }
907
908 tp->rack.reord = 1;
909 }
910
911 /* This must be called before lost_out is incremented */
912 static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
913 {
914 if (!tp->retransmit_skb_hint ||
915 before(TCP_SKB_CB(skb)->seq,
916 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
917 tp->retransmit_skb_hint = skb;
918 }
919
920 /* Sum the number of packets on the wire we have marked as lost.
921 * There are two cases we care about here:
922 * a) Packet hasn't been marked lost (nor retransmitted),
923 * and this is the first loss.
924 * b) Packet has been marked both lost and retransmitted,
925 * and this means we think it was lost again.
926 */
927 static void tcp_sum_lost(struct tcp_sock *tp, struct sk_buff *skb)
928 {
929 __u8 sacked = TCP_SKB_CB(skb)->sacked;
930
931 if (!(sacked & TCPCB_LOST) ||
932 ((sacked & TCPCB_LOST) && (sacked & TCPCB_SACKED_RETRANS)))
933 tp->lost += tcp_skb_pcount(skb);
934 }
935
936 static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
937 {
938 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
939 tcp_verify_retransmit_hint(tp, skb);
940
941 tp->lost_out += tcp_skb_pcount(skb);
942 tcp_sum_lost(tp, skb);
943 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
944 }
945 }
946
947 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)
948 {
949 tcp_verify_retransmit_hint(tp, skb);
950
951 tcp_sum_lost(tp, skb);
952 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
953 tp->lost_out += tcp_skb_pcount(skb);
954 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
955 }
956 }
957
958 /* This procedure tags the retransmission queue when SACKs arrive.
959 *
960 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
961 * Packets in queue with these bits set are counted in variables
962 * sacked_out, retrans_out and lost_out, correspondingly.
963 *
964 * Valid combinations are:
965 * Tag InFlight Description
966 * 0 1 - orig segment is in flight.
967 * S 0 - nothing flies, orig reached receiver.
968 * L 0 - nothing flies, orig lost by net.
969 * R 2 - both orig and retransmit are in flight.
970 * L|R 1 - orig is lost, retransmit is in flight.
971 * S|R 1 - orig reached receiver, retrans is still in flight.
972 * (L|S|R is logically valid, it could occur when L|R is sacked,
973 * but it is equivalent to plain S and code short-curcuits it to S.
974 * L|S is logically invalid, it would mean -1 packet in flight 8))
975 *
976 * These 6 states form finite state machine, controlled by the following events:
977 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
978 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
979 * 3. Loss detection event of two flavors:
980 * A. Scoreboard estimator decided the packet is lost.
981 * A'. Reno "three dupacks" marks head of queue lost.
982 * A''. Its FACK modification, head until snd.fack is lost.
983 * B. SACK arrives sacking SND.NXT at the moment, when the
984 * segment was retransmitted.
985 * 4. D-SACK added new rule: D-SACK changes any tag to S.
986 *
987 * It is pleasant to note, that state diagram turns out to be commutative,
988 * so that we are allowed not to be bothered by order of our actions,
989 * when multiple events arrive simultaneously. (see the function below).
990 *
991 * Reordering detection.
992 * --------------------
993 * Reordering metric is maximal distance, which a packet can be displaced
994 * in packet stream. With SACKs we can estimate it:
995 *
996 * 1. SACK fills old hole and the corresponding segment was not
997 * ever retransmitted -> reordering. Alas, we cannot use it
998 * when segment was retransmitted.
999 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1000 * for retransmitted and already SACKed segment -> reordering..
1001 * Both of these heuristics are not used in Loss state, when we cannot
1002 * account for retransmits accurately.
1003 *
1004 * SACK block validation.
1005 * ----------------------
1006 *
1007 * SACK block range validation checks that the received SACK block fits to
1008 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1009 * Note that SND.UNA is not included to the range though being valid because
1010 * it means that the receiver is rather inconsistent with itself reporting
1011 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1012 * perfectly valid, however, in light of RFC2018 which explicitly states
1013 * that "SACK block MUST reflect the newest segment. Even if the newest
1014 * segment is going to be discarded ...", not that it looks very clever
1015 * in case of head skb. Due to potentional receiver driven attacks, we
1016 * choose to avoid immediate execution of a walk in write queue due to
1017 * reneging and defer head skb's loss recovery to standard loss recovery
1018 * procedure that will eventually trigger (nothing forbids us doing this).
1019 *
1020 * Implements also blockage to start_seq wrap-around. Problem lies in the
1021 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1022 * there's no guarantee that it will be before snd_nxt (n). The problem
1023 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1024 * wrap (s_w):
1025 *
1026 * <- outs wnd -> <- wrapzone ->
1027 * u e n u_w e_w s n_w
1028 * | | | | | | |
1029 * |<------------+------+----- TCP seqno space --------------+---------->|
1030 * ...-- <2^31 ->| |<--------...
1031 * ...---- >2^31 ------>| |<--------...
1032 *
1033 * Current code wouldn't be vulnerable but it's better still to discard such
1034 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1035 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1036 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1037 * equal to the ideal case (infinite seqno space without wrap caused issues).
1038 *
1039 * With D-SACK the lower bound is extended to cover sequence space below
1040 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1041 * again, D-SACK block must not to go across snd_una (for the same reason as
1042 * for the normal SACK blocks, explained above). But there all simplicity
1043 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1044 * fully below undo_marker they do not affect behavior in anyway and can
1045 * therefore be safely ignored. In rare cases (which are more or less
1046 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1047 * fragmentation and packet reordering past skb's retransmission. To consider
1048 * them correctly, the acceptable range must be extended even more though
1049 * the exact amount is rather hard to quantify. However, tp->max_window can
1050 * be used as an exaggerated estimate.
1051 */
1052 static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack,
1053 u32 start_seq, u32 end_seq)
1054 {
1055 /* Too far in future, or reversed (interpretation is ambiguous) */
1056 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1057 return false;
1058
1059 /* Nasty start_seq wrap-around check (see comments above) */
1060 if (!before(start_seq, tp->snd_nxt))
1061 return false;
1062
1063 /* In outstanding window? ...This is valid exit for D-SACKs too.
1064 * start_seq == snd_una is non-sensical (see comments above)
1065 */
1066 if (after(start_seq, tp->snd_una))
1067 return true;
1068
1069 if (!is_dsack || !tp->undo_marker)
1070 return false;
1071
1072 /* ...Then it's D-SACK, and must reside below snd_una completely */
1073 if (after(end_seq, tp->snd_una))
1074 return false;
1075
1076 if (!before(start_seq, tp->undo_marker))
1077 return true;
1078
1079 /* Too old */
1080 if (!after(end_seq, tp->undo_marker))
1081 return false;
1082
1083 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1084 * start_seq < undo_marker and end_seq >= undo_marker.
1085 */
1086 return !before(start_seq, end_seq - tp->max_window);
1087 }
1088
1089 static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
1090 struct tcp_sack_block_wire *sp, int num_sacks,
1091 u32 prior_snd_una)
1092 {
1093 struct tcp_sock *tp = tcp_sk(sk);
1094 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1095 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
1096 bool dup_sack = false;
1097
1098 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1099 dup_sack = true;
1100 tcp_dsack_seen(tp);
1101 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
1102 } else if (num_sacks > 1) {
1103 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1104 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
1105
1106 if (!after(end_seq_0, end_seq_1) &&
1107 !before(start_seq_0, start_seq_1)) {
1108 dup_sack = true;
1109 tcp_dsack_seen(tp);
1110 NET_INC_STATS(sock_net(sk),
1111 LINUX_MIB_TCPDSACKOFORECV);
1112 }
1113 }
1114
1115 /* D-SACK for already forgotten data... Do dumb counting. */
1116 if (dup_sack && tp->undo_marker && tp->undo_retrans > 0 &&
1117 !after(end_seq_0, prior_snd_una) &&
1118 after(end_seq_0, tp->undo_marker))
1119 tp->undo_retrans--;
1120
1121 return dup_sack;
1122 }
1123
1124 struct tcp_sacktag_state {
1125 int reord;
1126 int fack_count;
1127 /* Timestamps for earliest and latest never-retransmitted segment
1128 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1129 * but congestion control should still get an accurate delay signal.
1130 */
1131 struct skb_mstamp first_sackt;
1132 struct skb_mstamp last_sackt;
1133 struct skb_mstamp ack_time; /* Timestamp when the S/ACK was received */
1134 struct rate_sample *rate;
1135 int flag;
1136 };
1137
1138 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1139 * the incoming SACK may not exactly match but we can find smaller MSS
1140 * aligned portion of it that matches. Therefore we might need to fragment
1141 * which may fail and creates some hassle (caller must handle error case
1142 * returns).
1143 *
1144 * FIXME: this could be merged to shift decision code
1145 */
1146 static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1147 u32 start_seq, u32 end_seq)
1148 {
1149 int err;
1150 bool in_sack;
1151 unsigned int pkt_len;
1152 unsigned int mss;
1153
1154 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1155 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1156
1157 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1158 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1159 mss = tcp_skb_mss(skb);
1160 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1161
1162 if (!in_sack) {
1163 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1164 if (pkt_len < mss)
1165 pkt_len = mss;
1166 } else {
1167 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1168 if (pkt_len < mss)
1169 return -EINVAL;
1170 }
1171
1172 /* Round if necessary so that SACKs cover only full MSSes
1173 * and/or the remaining small portion (if present)
1174 */
1175 if (pkt_len > mss) {
1176 unsigned int new_len = (pkt_len / mss) * mss;
1177 if (!in_sack && new_len < pkt_len) {
1178 new_len += mss;
1179 if (new_len >= skb->len)
1180 return 0;
1181 }
1182 pkt_len = new_len;
1183 }
1184 err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC);
1185 if (err < 0)
1186 return err;
1187 }
1188
1189 return in_sack;
1190 }
1191
1192 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1193 static u8 tcp_sacktag_one(struct sock *sk,
1194 struct tcp_sacktag_state *state, u8 sacked,
1195 u32 start_seq, u32 end_seq,
1196 int dup_sack, int pcount,
1197 const struct skb_mstamp *xmit_time)
1198 {
1199 struct tcp_sock *tp = tcp_sk(sk);
1200 int fack_count = state->fack_count;
1201
1202 /* Account D-SACK for retransmitted packet. */
1203 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1204 if (tp->undo_marker && tp->undo_retrans > 0 &&
1205 after(end_seq, tp->undo_marker))
1206 tp->undo_retrans--;
1207 if (sacked & TCPCB_SACKED_ACKED)
1208 state->reord = min(fack_count, state->reord);
1209 }
1210
1211 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1212 if (!after(end_seq, tp->snd_una))
1213 return sacked;
1214
1215 if (!(sacked & TCPCB_SACKED_ACKED)) {
1216 tcp_rack_advance(tp, sacked, end_seq,
1217 xmit_time, &state->ack_time);
1218
1219 if (sacked & TCPCB_SACKED_RETRANS) {
1220 /* If the segment is not tagged as lost,
1221 * we do not clear RETRANS, believing
1222 * that retransmission is still in flight.
1223 */
1224 if (sacked & TCPCB_LOST) {
1225 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1226 tp->lost_out -= pcount;
1227 tp->retrans_out -= pcount;
1228 }
1229 } else {
1230 if (!(sacked & TCPCB_RETRANS)) {
1231 /* New sack for not retransmitted frame,
1232 * which was in hole. It is reordering.
1233 */
1234 if (before(start_seq,
1235 tcp_highest_sack_seq(tp)))
1236 state->reord = min(fack_count,
1237 state->reord);
1238 if (!after(end_seq, tp->high_seq))
1239 state->flag |= FLAG_ORIG_SACK_ACKED;
1240 if (state->first_sackt.v64 == 0)
1241 state->first_sackt = *xmit_time;
1242 state->last_sackt = *xmit_time;
1243 }
1244
1245 if (sacked & TCPCB_LOST) {
1246 sacked &= ~TCPCB_LOST;
1247 tp->lost_out -= pcount;
1248 }
1249 }
1250
1251 sacked |= TCPCB_SACKED_ACKED;
1252 state->flag |= FLAG_DATA_SACKED;
1253 tp->sacked_out += pcount;
1254 tp->delivered += pcount; /* Out-of-order packets delivered */
1255
1256 fack_count += pcount;
1257
1258 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1259 if (!tcp_is_fack(tp) && tp->lost_skb_hint &&
1260 before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
1261 tp->lost_cnt_hint += pcount;
1262
1263 if (fack_count > tp->fackets_out)
1264 tp->fackets_out = fack_count;
1265 }
1266
1267 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1268 * frames and clear it. undo_retrans is decreased above, L|R frames
1269 * are accounted above as well.
1270 */
1271 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1272 sacked &= ~TCPCB_SACKED_RETRANS;
1273 tp->retrans_out -= pcount;
1274 }
1275
1276 return sacked;
1277 }
1278
1279 /* Shift newly-SACKed bytes from this skb to the immediately previous
1280 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1281 */
1282 static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
1283 struct tcp_sacktag_state *state,
1284 unsigned int pcount, int shifted, int mss,
1285 bool dup_sack)
1286 {
1287 struct tcp_sock *tp = tcp_sk(sk);
1288 struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
1289 u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */
1290 u32 end_seq = start_seq + shifted; /* end of newly-SACKed */
1291
1292 BUG_ON(!pcount);
1293
1294 /* Adjust counters and hints for the newly sacked sequence
1295 * range but discard the return value since prev is already
1296 * marked. We must tag the range first because the seq
1297 * advancement below implicitly advances
1298 * tcp_highest_sack_seq() when skb is highest_sack.
1299 */
1300 tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
1301 start_seq, end_seq, dup_sack, pcount,
1302 &skb->skb_mstamp);
1303 tcp_rate_skb_delivered(sk, skb, state->rate);
1304
1305 if (skb == tp->lost_skb_hint)
1306 tp->lost_cnt_hint += pcount;
1307
1308 TCP_SKB_CB(prev)->end_seq += shifted;
1309 TCP_SKB_CB(skb)->seq += shifted;
1310
1311 tcp_skb_pcount_add(prev, pcount);
1312 BUG_ON(tcp_skb_pcount(skb) < pcount);
1313 tcp_skb_pcount_add(skb, -pcount);
1314
1315 /* When we're adding to gso_segs == 1, gso_size will be zero,
1316 * in theory this shouldn't be necessary but as long as DSACK
1317 * code can come after this skb later on it's better to keep
1318 * setting gso_size to something.
1319 */
1320 if (!TCP_SKB_CB(prev)->tcp_gso_size)
1321 TCP_SKB_CB(prev)->tcp_gso_size = mss;
1322
1323 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1324 if (tcp_skb_pcount(skb) <= 1)
1325 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1326
1327 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1328 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1329
1330 if (skb->len > 0) {
1331 BUG_ON(!tcp_skb_pcount(skb));
1332 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTED);
1333 return false;
1334 }
1335
1336 /* Whole SKB was eaten :-) */
1337
1338 if (skb == tp->retransmit_skb_hint)
1339 tp->retransmit_skb_hint = prev;
1340 if (skb == tp->lost_skb_hint) {
1341 tp->lost_skb_hint = prev;
1342 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1343 }
1344
1345 TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1346 TCP_SKB_CB(prev)->eor = TCP_SKB_CB(skb)->eor;
1347 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1348 TCP_SKB_CB(prev)->end_seq++;
1349
1350 if (skb == tcp_highest_sack(sk))
1351 tcp_advance_highest_sack(sk, skb);
1352
1353 tcp_skb_collapse_tstamp(prev, skb);
1354 if (unlikely(TCP_SKB_CB(prev)->tx.delivered_mstamp.v64))
1355 TCP_SKB_CB(prev)->tx.delivered_mstamp.v64 = 0;
1356
1357 tcp_unlink_write_queue(skb, sk);
1358 sk_wmem_free_skb(sk, skb);
1359
1360 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKMERGED);
1361
1362 return true;
1363 }
1364
1365 /* I wish gso_size would have a bit more sane initialization than
1366 * something-or-zero which complicates things
1367 */
1368 static int tcp_skb_seglen(const struct sk_buff *skb)
1369 {
1370 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
1371 }
1372
1373 /* Shifting pages past head area doesn't work */
1374 static int skb_can_shift(const struct sk_buff *skb)
1375 {
1376 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1377 }
1378
1379 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1380 * skb.
1381 */
1382 static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
1383 struct tcp_sacktag_state *state,
1384 u32 start_seq, u32 end_seq,
1385 bool dup_sack)
1386 {
1387 struct tcp_sock *tp = tcp_sk(sk);
1388 struct sk_buff *prev;
1389 int mss;
1390 int pcount = 0;
1391 int len;
1392 int in_sack;
1393
1394 if (!sk_can_gso(sk))
1395 goto fallback;
1396
1397 /* Normally R but no L won't result in plain S */
1398 if (!dup_sack &&
1399 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
1400 goto fallback;
1401 if (!skb_can_shift(skb))
1402 goto fallback;
1403 /* This frame is about to be dropped (was ACKed). */
1404 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1405 goto fallback;
1406
1407 /* Can only happen with delayed DSACK + discard craziness */
1408 if (unlikely(skb == tcp_write_queue_head(sk)))
1409 goto fallback;
1410 prev = tcp_write_queue_prev(sk, skb);
1411
1412 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1413 goto fallback;
1414
1415 if (!tcp_skb_can_collapse_to(prev))
1416 goto fallback;
1417
1418 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1419 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1420
1421 if (in_sack) {
1422 len = skb->len;
1423 pcount = tcp_skb_pcount(skb);
1424 mss = tcp_skb_seglen(skb);
1425
1426 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1427 * drop this restriction as unnecessary
1428 */
1429 if (mss != tcp_skb_seglen(prev))
1430 goto fallback;
1431 } else {
1432 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1433 goto noop;
1434 /* CHECKME: This is non-MSS split case only?, this will
1435 * cause skipped skbs due to advancing loop btw, original
1436 * has that feature too
1437 */
1438 if (tcp_skb_pcount(skb) <= 1)
1439 goto noop;
1440
1441 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1442 if (!in_sack) {
1443 /* TODO: head merge to next could be attempted here
1444 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1445 * though it might not be worth of the additional hassle
1446 *
1447 * ...we can probably just fallback to what was done
1448 * previously. We could try merging non-SACKed ones
1449 * as well but it probably isn't going to buy off
1450 * because later SACKs might again split them, and
1451 * it would make skb timestamp tracking considerably
1452 * harder problem.
1453 */
1454 goto fallback;
1455 }
1456
1457 len = end_seq - TCP_SKB_CB(skb)->seq;
1458 BUG_ON(len < 0);
1459 BUG_ON(len > skb->len);
1460
1461 /* MSS boundaries should be honoured or else pcount will
1462 * severely break even though it makes things bit trickier.
1463 * Optimize common case to avoid most of the divides
1464 */
1465 mss = tcp_skb_mss(skb);
1466
1467 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1468 * drop this restriction as unnecessary
1469 */
1470 if (mss != tcp_skb_seglen(prev))
1471 goto fallback;
1472
1473 if (len == mss) {
1474 pcount = 1;
1475 } else if (len < mss) {
1476 goto noop;
1477 } else {
1478 pcount = len / mss;
1479 len = pcount * mss;
1480 }
1481 }
1482
1483 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1484 if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
1485 goto fallback;
1486
1487 if (!skb_shift(prev, skb, len))
1488 goto fallback;
1489 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
1490 goto out;
1491
1492 /* Hole filled allows collapsing with the next as well, this is very
1493 * useful when hole on every nth skb pattern happens
1494 */
1495 if (prev == tcp_write_queue_tail(sk))
1496 goto out;
1497 skb = tcp_write_queue_next(sk, prev);
1498
1499 if (!skb_can_shift(skb) ||
1500 (skb == tcp_send_head(sk)) ||
1501 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
1502 (mss != tcp_skb_seglen(skb)))
1503 goto out;
1504
1505 len = skb->len;
1506 if (skb_shift(prev, skb, len)) {
1507 pcount += tcp_skb_pcount(skb);
1508 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
1509 }
1510
1511 out:
1512 state->fack_count += pcount;
1513 return prev;
1514
1515 noop:
1516 return skb;
1517
1518 fallback:
1519 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
1520 return NULL;
1521 }
1522
1523 static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1524 struct tcp_sack_block *next_dup,
1525 struct tcp_sacktag_state *state,
1526 u32 start_seq, u32 end_seq,
1527 bool dup_sack_in)
1528 {
1529 struct tcp_sock *tp = tcp_sk(sk);
1530 struct sk_buff *tmp;
1531
1532 tcp_for_write_queue_from(skb, sk) {
1533 int in_sack = 0;
1534 bool dup_sack = dup_sack_in;
1535
1536 if (skb == tcp_send_head(sk))
1537 break;
1538
1539 /* queue is in-order => we can short-circuit the walk early */
1540 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1541 break;
1542
1543 if (next_dup &&
1544 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1545 in_sack = tcp_match_skb_to_sack(sk, skb,
1546 next_dup->start_seq,
1547 next_dup->end_seq);
1548 if (in_sack > 0)
1549 dup_sack = true;
1550 }
1551
1552 /* skb reference here is a bit tricky to get right, since
1553 * shifting can eat and free both this skb and the next,
1554 * so not even _safe variant of the loop is enough.
1555 */
1556 if (in_sack <= 0) {
1557 tmp = tcp_shift_skb_data(sk, skb, state,
1558 start_seq, end_seq, dup_sack);
1559 if (tmp) {
1560 if (tmp != skb) {
1561 skb = tmp;
1562 continue;
1563 }
1564
1565 in_sack = 0;
1566 } else {
1567 in_sack = tcp_match_skb_to_sack(sk, skb,
1568 start_seq,
1569 end_seq);
1570 }
1571 }
1572
1573 if (unlikely(in_sack < 0))
1574 break;
1575
1576 if (in_sack) {
1577 TCP_SKB_CB(skb)->sacked =
1578 tcp_sacktag_one(sk,
1579 state,
1580 TCP_SKB_CB(skb)->sacked,
1581 TCP_SKB_CB(skb)->seq,
1582 TCP_SKB_CB(skb)->end_seq,
1583 dup_sack,
1584 tcp_skb_pcount(skb),
1585 &skb->skb_mstamp);
1586 tcp_rate_skb_delivered(sk, skb, state->rate);
1587
1588 if (!before(TCP_SKB_CB(skb)->seq,
1589 tcp_highest_sack_seq(tp)))
1590 tcp_advance_highest_sack(sk, skb);
1591 }
1592
1593 state->fack_count += tcp_skb_pcount(skb);
1594 }
1595 return skb;
1596 }
1597
1598 /* Avoid all extra work that is being done by sacktag while walking in
1599 * a normal way
1600 */
1601 static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
1602 struct tcp_sacktag_state *state,
1603 u32 skip_to_seq)
1604 {
1605 tcp_for_write_queue_from(skb, sk) {
1606 if (skb == tcp_send_head(sk))
1607 break;
1608
1609 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
1610 break;
1611
1612 state->fack_count += tcp_skb_pcount(skb);
1613 }
1614 return skb;
1615 }
1616
1617 static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1618 struct sock *sk,
1619 struct tcp_sack_block *next_dup,
1620 struct tcp_sacktag_state *state,
1621 u32 skip_to_seq)
1622 {
1623 if (!next_dup)
1624 return skb;
1625
1626 if (before(next_dup->start_seq, skip_to_seq)) {
1627 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
1628 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1629 next_dup->start_seq, next_dup->end_seq,
1630 1);
1631 }
1632
1633 return skb;
1634 }
1635
1636 static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache)
1637 {
1638 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1639 }
1640
1641 static int
1642 tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
1643 u32 prior_snd_una, struct tcp_sacktag_state *state)
1644 {
1645 struct tcp_sock *tp = tcp_sk(sk);
1646 const unsigned char *ptr = (skb_transport_header(ack_skb) +
1647 TCP_SKB_CB(ack_skb)->sacked);
1648 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
1649 struct tcp_sack_block sp[TCP_NUM_SACKS];
1650 struct tcp_sack_block *cache;
1651 struct sk_buff *skb;
1652 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
1653 int used_sacks;
1654 bool found_dup_sack = false;
1655 int i, j;
1656 int first_sack_index;
1657
1658 state->flag = 0;
1659 state->reord = tp->packets_out;
1660
1661 if (!tp->sacked_out) {
1662 if (WARN_ON(tp->fackets_out))
1663 tp->fackets_out = 0;
1664 tcp_highest_sack_reset(sk);
1665 }
1666
1667 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
1668 num_sacks, prior_snd_una);
1669 if (found_dup_sack) {
1670 state->flag |= FLAG_DSACKING_ACK;
1671 tp->delivered++; /* A spurious retransmission is delivered */
1672 }
1673
1674 /* Eliminate too old ACKs, but take into
1675 * account more or less fresh ones, they can
1676 * contain valid SACK info.
1677 */
1678 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1679 return 0;
1680
1681 if (!tp->packets_out)
1682 goto out;
1683
1684 used_sacks = 0;
1685 first_sack_index = 0;
1686 for (i = 0; i < num_sacks; i++) {
1687 bool dup_sack = !i && found_dup_sack;
1688
1689 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1690 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
1691
1692 if (!tcp_is_sackblock_valid(tp, dup_sack,
1693 sp[used_sacks].start_seq,
1694 sp[used_sacks].end_seq)) {
1695 int mib_idx;
1696
1697 if (dup_sack) {
1698 if (!tp->undo_marker)
1699 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
1700 else
1701 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
1702 } else {
1703 /* Don't count olds caused by ACK reordering */
1704 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1705 !after(sp[used_sacks].end_seq, tp->snd_una))
1706 continue;
1707 mib_idx = LINUX_MIB_TCPSACKDISCARD;
1708 }
1709
1710 NET_INC_STATS(sock_net(sk), mib_idx);
1711 if (i == 0)
1712 first_sack_index = -1;
1713 continue;
1714 }
1715
1716 /* Ignore very old stuff early */
1717 if (!after(sp[used_sacks].end_seq, prior_snd_una))
1718 continue;
1719
1720 used_sacks++;
1721 }
1722
1723 /* order SACK blocks to allow in order walk of the retrans queue */
1724 for (i = used_sacks - 1; i > 0; i--) {
1725 for (j = 0; j < i; j++) {
1726 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
1727 swap(sp[j], sp[j + 1]);
1728
1729 /* Track where the first SACK block goes to */
1730 if (j == first_sack_index)
1731 first_sack_index = j + 1;
1732 }
1733 }
1734 }
1735
1736 skb = tcp_write_queue_head(sk);
1737 state->fack_count = 0;
1738 i = 0;
1739
1740 if (!tp->sacked_out) {
1741 /* It's already past, so skip checking against it */
1742 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1743 } else {
1744 cache = tp->recv_sack_cache;
1745 /* Skip empty blocks in at head of the cache */
1746 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1747 !cache->end_seq)
1748 cache++;
1749 }
1750
1751 while (i < used_sacks) {
1752 u32 start_seq = sp[i].start_seq;
1753 u32 end_seq = sp[i].end_seq;
1754 bool dup_sack = (found_dup_sack && (i == first_sack_index));
1755 struct tcp_sack_block *next_dup = NULL;
1756
1757 if (found_dup_sack && ((i + 1) == first_sack_index))
1758 next_dup = &sp[i + 1];
1759
1760 /* Skip too early cached blocks */
1761 while (tcp_sack_cache_ok(tp, cache) &&
1762 !before(start_seq, cache->end_seq))
1763 cache++;
1764
1765 /* Can skip some work by looking recv_sack_cache? */
1766 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1767 after(end_seq, cache->start_seq)) {
1768
1769 /* Head todo? */
1770 if (before(start_seq, cache->start_seq)) {
1771 skb = tcp_sacktag_skip(skb, sk, state,
1772 start_seq);
1773 skb = tcp_sacktag_walk(skb, sk, next_dup,
1774 state,
1775 start_seq,
1776 cache->start_seq,
1777 dup_sack);
1778 }
1779
1780 /* Rest of the block already fully processed? */
1781 if (!after(end_seq, cache->end_seq))
1782 goto advance_sp;
1783
1784 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
1785 state,
1786 cache->end_seq);
1787
1788 /* ...tail remains todo... */
1789 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
1790 /* ...but better entrypoint exists! */
1791 skb = tcp_highest_sack(sk);
1792 if (!skb)
1793 break;
1794 state->fack_count = tp->fackets_out;
1795 cache++;
1796 goto walk;
1797 }
1798
1799 skb = tcp_sacktag_skip(skb, sk, state, cache->end_seq);
1800 /* Check overlap against next cached too (past this one already) */
1801 cache++;
1802 continue;
1803 }
1804
1805 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
1806 skb = tcp_highest_sack(sk);
1807 if (!skb)
1808 break;
1809 state->fack_count = tp->fackets_out;
1810 }
1811 skb = tcp_sacktag_skip(skb, sk, state, start_seq);
1812
1813 walk:
1814 skb = tcp_sacktag_walk(skb, sk, next_dup, state,
1815 start_seq, end_seq, dup_sack);
1816
1817 advance_sp:
1818 i++;
1819 }
1820
1821 /* Clear the head of the cache sack blocks so we can skip it next time */
1822 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
1823 tp->recv_sack_cache[i].start_seq = 0;
1824 tp->recv_sack_cache[i].end_seq = 0;
1825 }
1826 for (j = 0; j < used_sacks; j++)
1827 tp->recv_sack_cache[i++] = sp[j];
1828
1829 if ((state->reord < tp->fackets_out) &&
1830 ((inet_csk(sk)->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker))
1831 tcp_update_reordering(sk, tp->fackets_out - state->reord, 0);
1832
1833 tcp_verify_left_out(tp);
1834 out:
1835
1836 #if FASTRETRANS_DEBUG > 0
1837 WARN_ON((int)tp->sacked_out < 0);
1838 WARN_ON((int)tp->lost_out < 0);
1839 WARN_ON((int)tp->retrans_out < 0);
1840 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
1841 #endif
1842 return state->flag;
1843 }
1844
1845 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1846 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1847 */
1848 static bool tcp_limit_reno_sacked(struct tcp_sock *tp)
1849 {
1850 u32 holes;
1851
1852 holes = max(tp->lost_out, 1U);
1853 holes = min(holes, tp->packets_out);
1854
1855 if ((tp->sacked_out + holes) > tp->packets_out) {
1856 tp->sacked_out = tp->packets_out - holes;
1857 return true;
1858 }
1859 return false;
1860 }
1861
1862 /* If we receive more dupacks than we expected counting segments
1863 * in assumption of absent reordering, interpret this as reordering.
1864 * The only another reason could be bug in receiver TCP.
1865 */
1866 static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1867 {
1868 struct tcp_sock *tp = tcp_sk(sk);
1869 if (tcp_limit_reno_sacked(tp))
1870 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1871 }
1872
1873 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1874
1875 static void tcp_add_reno_sack(struct sock *sk)
1876 {
1877 struct tcp_sock *tp = tcp_sk(sk);
1878 u32 prior_sacked = tp->sacked_out;
1879
1880 tp->sacked_out++;
1881 tcp_check_reno_reordering(sk, 0);
1882 if (tp->sacked_out > prior_sacked)
1883 tp->delivered++; /* Some out-of-order packet is delivered */
1884 tcp_verify_left_out(tp);
1885 }
1886
1887 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1888
1889 static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1890 {
1891 struct tcp_sock *tp = tcp_sk(sk);
1892
1893 if (acked > 0) {
1894 /* One ACK acked hole. The rest eat duplicate ACKs. */
1895 tp->delivered += max_t(int, acked - tp->sacked_out, 1);
1896 if (acked - 1 >= tp->sacked_out)
1897 tp->sacked_out = 0;
1898 else
1899 tp->sacked_out -= acked - 1;
1900 }
1901 tcp_check_reno_reordering(sk, acked);
1902 tcp_verify_left_out(tp);
1903 }
1904
1905 static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1906 {
1907 tp->sacked_out = 0;
1908 }
1909
1910 void tcp_clear_retrans(struct tcp_sock *tp)
1911 {
1912 tp->retrans_out = 0;
1913 tp->lost_out = 0;
1914 tp->undo_marker = 0;
1915 tp->undo_retrans = -1;
1916 tp->fackets_out = 0;
1917 tp->sacked_out = 0;
1918 }
1919
1920 static inline void tcp_init_undo(struct tcp_sock *tp)
1921 {
1922 tp->undo_marker = tp->snd_una;
1923 /* Retransmission still in flight may cause DSACKs later. */
1924 tp->undo_retrans = tp->retrans_out ? : -1;
1925 }
1926
1927 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1928 * and reset tags completely, otherwise preserve SACKs. If receiver
1929 * dropped its ofo queue, we will know this due to reneging detection.
1930 */
1931 void tcp_enter_loss(struct sock *sk)
1932 {
1933 const struct inet_connection_sock *icsk = inet_csk(sk);
1934 struct tcp_sock *tp = tcp_sk(sk);
1935 struct net *net = sock_net(sk);
1936 struct sk_buff *skb;
1937 bool is_reneg; /* is receiver reneging on SACKs? */
1938 bool mark_lost;
1939
1940 /* Reduce ssthresh if it has not yet been made inside this window. */
1941 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1942 !after(tp->high_seq, tp->snd_una) ||
1943 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1944 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1945 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1946 tcp_ca_event(sk, CA_EVENT_LOSS);
1947 tcp_init_undo(tp);
1948 }
1949 tp->snd_cwnd = 1;
1950 tp->snd_cwnd_cnt = 0;
1951 tp->snd_cwnd_stamp = tcp_time_stamp;
1952
1953 tp->retrans_out = 0;
1954 tp->lost_out = 0;
1955
1956 if (tcp_is_reno(tp))
1957 tcp_reset_reno_sack(tp);
1958
1959 skb = tcp_write_queue_head(sk);
1960 is_reneg = skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED);
1961 if (is_reneg) {
1962 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
1963 tp->sacked_out = 0;
1964 tp->fackets_out = 0;
1965 }
1966 tcp_clear_all_retrans_hints(tp);
1967
1968 tcp_for_write_queue(skb, sk) {
1969 if (skb == tcp_send_head(sk))
1970 break;
1971
1972 mark_lost = (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) ||
1973 is_reneg);
1974 if (mark_lost)
1975 tcp_sum_lost(tp, skb);
1976 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1977 if (mark_lost) {
1978 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1979 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1980 tp->lost_out += tcp_skb_pcount(skb);
1981 }
1982 }
1983 tcp_verify_left_out(tp);
1984
1985 /* Timeout in disordered state after receiving substantial DUPACKs
1986 * suggests that the degree of reordering is over-estimated.
1987 */
1988 if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
1989 tp->sacked_out >= net->ipv4.sysctl_tcp_reordering)
1990 tp->reordering = min_t(unsigned int, tp->reordering,
1991 net->ipv4.sysctl_tcp_reordering);
1992 tcp_set_ca_state(sk, TCP_CA_Loss);
1993 tp->high_seq = tp->snd_nxt;
1994 tcp_ecn_queue_cwr(tp);
1995
1996 /* F-RTO RFC5682 sec 3.1 step 1 mandates to disable F-RTO
1997 * if a previous recovery is underway, otherwise it may incorrectly
1998 * call a timeout spurious if some previously retransmitted packets
1999 * are s/acked (sec 3.2). We do not apply that retriction since
2000 * retransmitted skbs are permanently tagged with TCPCB_EVER_RETRANS
2001 * so FLAG_ORIG_SACK_ACKED is always correct. But we do disable F-RTO
2002 * on PTMU discovery to avoid sending new data.
2003 */
2004 tp->frto = sysctl_tcp_frto && !inet_csk(sk)->icsk_mtup.probe_size;
2005 }
2006
2007 /* If ACK arrived pointing to a remembered SACK, it means that our
2008 * remembered SACKs do not reflect real state of receiver i.e.
2009 * receiver _host_ is heavily congested (or buggy).
2010 *
2011 * To avoid big spurious retransmission bursts due to transient SACK
2012 * scoreboard oddities that look like reneging, we give the receiver a
2013 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2014 * restore sanity to the SACK scoreboard. If the apparent reneging
2015 * persists until this RTO then we'll clear the SACK scoreboard.
2016 */
2017 static bool tcp_check_sack_reneging(struct sock *sk, int flag)
2018 {
2019 if (flag & FLAG_SACK_RENEGING) {
2020 struct tcp_sock *tp = tcp_sk(sk);
2021 unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4),
2022 msecs_to_jiffies(10));
2023
2024 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2025 delay, TCP_RTO_MAX);
2026 return true;
2027 }
2028 return false;
2029 }
2030
2031 static inline int tcp_fackets_out(const struct tcp_sock *tp)
2032 {
2033 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
2034 }
2035
2036 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2037 * counter when SACK is enabled (without SACK, sacked_out is used for
2038 * that purpose).
2039 *
2040 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2041 * segments up to the highest received SACK block so far and holes in
2042 * between them.
2043 *
2044 * With reordering, holes may still be in flight, so RFC3517 recovery
2045 * uses pure sacked_out (total number of SACKed segments) even though
2046 * it violates the RFC that uses duplicate ACKs, often these are equal
2047 * but when e.g. out-of-window ACKs or packet duplication occurs,
2048 * they differ. Since neither occurs due to loss, TCP should really
2049 * ignore them.
2050 */
2051 static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
2052 {
2053 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
2054 }
2055
2056 /* Linux NewReno/SACK/FACK/ECN state machine.
2057 * --------------------------------------
2058 *
2059 * "Open" Normal state, no dubious events, fast path.
2060 * "Disorder" In all the respects it is "Open",
2061 * but requires a bit more attention. It is entered when
2062 * we see some SACKs or dupacks. It is split of "Open"
2063 * mainly to move some processing from fast path to slow one.
2064 * "CWR" CWND was reduced due to some Congestion Notification event.
2065 * It can be ECN, ICMP source quench, local device congestion.
2066 * "Recovery" CWND was reduced, we are fast-retransmitting.
2067 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2068 *
2069 * tcp_fastretrans_alert() is entered:
2070 * - each incoming ACK, if state is not "Open"
2071 * - when arrived ACK is unusual, namely:
2072 * * SACK
2073 * * Duplicate ACK.
2074 * * ECN ECE.
2075 *
2076 * Counting packets in flight is pretty simple.
2077 *
2078 * in_flight = packets_out - left_out + retrans_out
2079 *
2080 * packets_out is SND.NXT-SND.UNA counted in packets.
2081 *
2082 * retrans_out is number of retransmitted segments.
2083 *
2084 * left_out is number of segments left network, but not ACKed yet.
2085 *
2086 * left_out = sacked_out + lost_out
2087 *
2088 * sacked_out: Packets, which arrived to receiver out of order
2089 * and hence not ACKed. With SACKs this number is simply
2090 * amount of SACKed data. Even without SACKs
2091 * it is easy to give pretty reliable estimate of this number,
2092 * counting duplicate ACKs.
2093 *
2094 * lost_out: Packets lost by network. TCP has no explicit
2095 * "loss notification" feedback from network (for now).
2096 * It means that this number can be only _guessed_.
2097 * Actually, it is the heuristics to predict lossage that
2098 * distinguishes different algorithms.
2099 *
2100 * F.e. after RTO, when all the queue is considered as lost,
2101 * lost_out = packets_out and in_flight = retrans_out.
2102 *
2103 * Essentially, we have now a few algorithms detecting
2104 * lost packets.
2105 *
2106 * If the receiver supports SACK:
2107 *
2108 * RFC6675/3517: It is the conventional algorithm. A packet is
2109 * considered lost if the number of higher sequence packets
2110 * SACKed is greater than or equal the DUPACK thoreshold
2111 * (reordering). This is implemented in tcp_mark_head_lost and
2112 * tcp_update_scoreboard.
2113 *
2114 * RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
2115 * (2017-) that checks timing instead of counting DUPACKs.
2116 * Essentially a packet is considered lost if it's not S/ACKed
2117 * after RTT + reordering_window, where both metrics are
2118 * dynamically measured and adjusted. This is implemented in
2119 * tcp_rack_mark_lost.
2120 *
2121 * FACK (Disabled by default. Subsumbed by RACK):
2122 * It is the simplest heuristics. As soon as we decided
2123 * that something is lost, we decide that _all_ not SACKed
2124 * packets until the most forward SACK are lost. I.e.
2125 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2126 * It is absolutely correct estimate, if network does not reorder
2127 * packets. And it loses any connection to reality when reordering
2128 * takes place. We use FACK by default until reordering
2129 * is suspected on the path to this destination.
2130 *
2131 * If the receiver does not support SACK:
2132 *
2133 * NewReno (RFC6582): in Recovery we assume that one segment
2134 * is lost (classic Reno). While we are in Recovery and
2135 * a partial ACK arrives, we assume that one more packet
2136 * is lost (NewReno). This heuristics are the same in NewReno
2137 * and SACK.
2138 *
2139 * Really tricky (and requiring careful tuning) part of algorithm
2140 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2141 * The first determines the moment _when_ we should reduce CWND and,
2142 * hence, slow down forward transmission. In fact, it determines the moment
2143 * when we decide that hole is caused by loss, rather than by a reorder.
2144 *
2145 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2146 * holes, caused by lost packets.
2147 *
2148 * And the most logically complicated part of algorithm is undo
2149 * heuristics. We detect false retransmits due to both too early
2150 * fast retransmit (reordering) and underestimated RTO, analyzing
2151 * timestamps and D-SACKs. When we detect that some segments were
2152 * retransmitted by mistake and CWND reduction was wrong, we undo
2153 * window reduction and abort recovery phase. This logic is hidden
2154 * inside several functions named tcp_try_undo_<something>.
2155 */
2156
2157 /* This function decides, when we should leave Disordered state
2158 * and enter Recovery phase, reducing congestion window.
2159 *
2160 * Main question: may we further continue forward transmission
2161 * with the same cwnd?
2162 */
2163 static bool tcp_time_to_recover(struct sock *sk, int flag)
2164 {
2165 struct tcp_sock *tp = tcp_sk(sk);
2166
2167 /* Trick#1: The loss is proven. */
2168 if (tp->lost_out)
2169 return true;
2170
2171 /* Not-A-Trick#2 : Classic rule... */
2172 if (tcp_dupack_heuristics(tp) > tp->reordering)
2173 return true;
2174
2175 return false;
2176 }
2177
2178 /* Detect loss in event "A" above by marking head of queue up as lost.
2179 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2180 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2181 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2182 * the maximum SACKed segments to pass before reaching this limit.
2183 */
2184 static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
2185 {
2186 struct tcp_sock *tp = tcp_sk(sk);
2187 struct sk_buff *skb;
2188 int cnt, oldcnt, lost;
2189 unsigned int mss;
2190 /* Use SACK to deduce losses of new sequences sent during recovery */
2191 const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq;
2192
2193 WARN_ON(packets > tp->packets_out);
2194 if (tp->lost_skb_hint) {
2195 skb = tp->lost_skb_hint;
2196 cnt = tp->lost_cnt_hint;
2197 /* Head already handled? */
2198 if (mark_head && skb != tcp_write_queue_head(sk))
2199 return;
2200 } else {
2201 skb = tcp_write_queue_head(sk);
2202 cnt = 0;
2203 }
2204
2205 tcp_for_write_queue_from(skb, sk) {
2206 if (skb == tcp_send_head(sk))
2207 break;
2208 /* TODO: do this better */
2209 /* this is not the most efficient way to do this... */
2210 tp->lost_skb_hint = skb;
2211 tp->lost_cnt_hint = cnt;
2212
2213 if (after(TCP_SKB_CB(skb)->end_seq, loss_high))
2214 break;
2215
2216 oldcnt = cnt;
2217 if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
2218 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2219 cnt += tcp_skb_pcount(skb);
2220
2221 if (cnt > packets) {
2222 if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) ||
2223 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) ||
2224 (oldcnt >= packets))
2225 break;
2226
2227 mss = tcp_skb_mss(skb);
2228 /* If needed, chop off the prefix to mark as lost. */
2229 lost = (packets - oldcnt) * mss;
2230 if (lost < skb->len &&
2231 tcp_fragment(sk, skb, lost, mss, GFP_ATOMIC) < 0)
2232 break;
2233 cnt = packets;
2234 }
2235
2236 tcp_skb_mark_lost(tp, skb);
2237
2238 if (mark_head)
2239 break;
2240 }
2241 tcp_verify_left_out(tp);
2242 }
2243
2244 /* Account newly detected lost packet(s) */
2245
2246 static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
2247 {
2248 struct tcp_sock *tp = tcp_sk(sk);
2249
2250 if (tcp_is_reno(tp)) {
2251 tcp_mark_head_lost(sk, 1, 1);
2252 } else if (tcp_is_fack(tp)) {
2253 int lost = tp->fackets_out - tp->reordering;
2254 if (lost <= 0)
2255 lost = 1;
2256 tcp_mark_head_lost(sk, lost, 0);
2257 } else {
2258 int sacked_upto = tp->sacked_out - tp->reordering;
2259 if (sacked_upto >= 0)
2260 tcp_mark_head_lost(sk, sacked_upto, 0);
2261 else if (fast_rexmit)
2262 tcp_mark_head_lost(sk, 1, 1);
2263 }
2264 }
2265
2266 static bool tcp_tsopt_ecr_before(const struct tcp_sock *tp, u32 when)
2267 {
2268 return tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2269 before(tp->rx_opt.rcv_tsecr, when);
2270 }
2271
2272 /* skb is spurious retransmitted if the returned timestamp echo
2273 * reply is prior to the skb transmission time
2274 */
2275 static bool tcp_skb_spurious_retrans(const struct tcp_sock *tp,
2276 const struct sk_buff *skb)
2277 {
2278 return (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) &&
2279 tcp_tsopt_ecr_before(tp, tcp_skb_timestamp(skb));
2280 }
2281
2282 /* Nothing was retransmitted or returned timestamp is less
2283 * than timestamp of the first retransmission.
2284 */
2285 static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
2286 {
2287 return !tp->retrans_stamp ||
2288 tcp_tsopt_ecr_before(tp, tp->retrans_stamp);
2289 }
2290
2291 /* Undo procedures. */
2292
2293 /* We can clear retrans_stamp when there are no retransmissions in the
2294 * window. It would seem that it is trivially available for us in
2295 * tp->retrans_out, however, that kind of assumptions doesn't consider
2296 * what will happen if errors occur when sending retransmission for the
2297 * second time. ...It could the that such segment has only
2298 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2299 * the head skb is enough except for some reneging corner cases that
2300 * are not worth the effort.
2301 *
2302 * Main reason for all this complexity is the fact that connection dying
2303 * time now depends on the validity of the retrans_stamp, in particular,
2304 * that successive retransmissions of a segment must not advance
2305 * retrans_stamp under any conditions.
2306 */
2307 static bool tcp_any_retrans_done(const struct sock *sk)
2308 {
2309 const struct tcp_sock *tp = tcp_sk(sk);
2310 struct sk_buff *skb;
2311
2312 if (tp->retrans_out)
2313 return true;
2314
2315 skb = tcp_write_queue_head(sk);
2316 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
2317 return true;
2318
2319 return false;
2320 }
2321
2322 #if FASTRETRANS_DEBUG > 1
2323 static void DBGUNDO(struct sock *sk, const char *msg)
2324 {
2325 struct tcp_sock *tp = tcp_sk(sk);
2326 struct inet_sock *inet = inet_sk(sk);
2327
2328 if (sk->sk_family == AF_INET) {
2329 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2330 msg,
2331 &inet->inet_daddr, ntohs(inet->inet_dport),
2332 tp->snd_cwnd, tcp_left_out(tp),
2333 tp->snd_ssthresh, tp->prior_ssthresh,
2334 tp->packets_out);
2335 }
2336 #if IS_ENABLED(CONFIG_IPV6)
2337 else if (sk->sk_family == AF_INET6) {
2338 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2339 msg,
2340 &sk->sk_v6_daddr, ntohs(inet->inet_dport),
2341 tp->snd_cwnd, tcp_left_out(tp),
2342 tp->snd_ssthresh, tp->prior_ssthresh,
2343 tp->packets_out);
2344 }
2345 #endif
2346 }
2347 #else
2348 #define DBGUNDO(x...) do { } while (0)
2349 #endif
2350
2351 static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
2352 {
2353 struct tcp_sock *tp = tcp_sk(sk);
2354
2355 if (unmark_loss) {
2356 struct sk_buff *skb;
2357
2358 tcp_for_write_queue(skb, sk) {
2359 if (skb == tcp_send_head(sk))
2360 break;
2361 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2362 }
2363 tp->lost_out = 0;
2364 tcp_clear_all_retrans_hints(tp);
2365 }
2366
2367 if (tp->prior_ssthresh) {
2368 const struct inet_connection_sock *icsk = inet_csk(sk);
2369
2370 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
2371
2372 if (tp->prior_ssthresh > tp->snd_ssthresh) {
2373 tp->snd_ssthresh = tp->prior_ssthresh;
2374 tcp_ecn_withdraw_cwr(tp);
2375 }
2376 }
2377 tp->snd_cwnd_stamp = tcp_time_stamp;
2378 tp->undo_marker = 0;
2379 }
2380
2381 static inline bool tcp_may_undo(const struct tcp_sock *tp)
2382 {
2383 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
2384 }
2385
2386 /* People celebrate: "We love our President!" */
2387 static bool tcp_try_undo_recovery(struct sock *sk)
2388 {
2389 struct tcp_sock *tp = tcp_sk(sk);
2390
2391 if (tcp_may_undo(tp)) {
2392 int mib_idx;
2393
2394 /* Happy end! We did not retransmit anything
2395 * or our original transmission succeeded.
2396 */
2397 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
2398 tcp_undo_cwnd_reduction(sk, false);
2399 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
2400 mib_idx = LINUX_MIB_TCPLOSSUNDO;
2401 else
2402 mib_idx = LINUX_MIB_TCPFULLUNDO;
2403
2404 NET_INC_STATS(sock_net(sk), mib_idx);
2405 }
2406 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
2407 /* Hold old state until something *above* high_seq
2408 * is ACKed. For Reno it is MUST to prevent false
2409 * fast retransmits (RFC2582). SACK TCP is safe. */
2410 if (!tcp_any_retrans_done(sk))
2411 tp->retrans_stamp = 0;
2412 return true;
2413 }
2414 tcp_set_ca_state(sk, TCP_CA_Open);
2415 return false;
2416 }
2417
2418 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2419 static bool tcp_try_undo_dsack(struct sock *sk)
2420 {
2421 struct tcp_sock *tp = tcp_sk(sk);
2422
2423 if (tp->undo_marker && !tp->undo_retrans) {
2424 DBGUNDO(sk, "D-SACK");
2425 tcp_undo_cwnd_reduction(sk, false);
2426 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
2427 return true;
2428 }
2429 return false;
2430 }
2431
2432 /* Undo during loss recovery after partial ACK or using F-RTO. */
2433 static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
2434 {
2435 struct tcp_sock *tp = tcp_sk(sk);
2436
2437 if (frto_undo || tcp_may_undo(tp)) {
2438 tcp_undo_cwnd_reduction(sk, true);
2439
2440 DBGUNDO(sk, "partial loss");
2441 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
2442 if (frto_undo)
2443 NET_INC_STATS(sock_net(sk),
2444 LINUX_MIB_TCPSPURIOUSRTOS);
2445 inet_csk(sk)->icsk_retransmits = 0;
2446 if (frto_undo || tcp_is_sack(tp))
2447 tcp_set_ca_state(sk, TCP_CA_Open);
2448 return true;
2449 }
2450 return false;
2451 }
2452
2453 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2454 * It computes the number of packets to send (sndcnt) based on packets newly
2455 * delivered:
2456 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2457 * cwnd reductions across a full RTT.
2458 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2459 * But when the retransmits are acked without further losses, PRR
2460 * slow starts cwnd up to ssthresh to speed up the recovery.
2461 */
2462 static void tcp_init_cwnd_reduction(struct sock *sk)
2463 {
2464 struct tcp_sock *tp = tcp_sk(sk);
2465
2466 tp->high_seq = tp->snd_nxt;
2467 tp->tlp_high_seq = 0;
2468 tp->snd_cwnd_cnt = 0;
2469 tp->prior_cwnd = tp->snd_cwnd;
2470 tp->prr_delivered = 0;
2471 tp->prr_out = 0;
2472 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
2473 tcp_ecn_queue_cwr(tp);
2474 }
2475
2476 void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag)
2477 {
2478 struct tcp_sock *tp = tcp_sk(sk);
2479 int sndcnt = 0;
2480 int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
2481
2482 if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd))
2483 return;
2484
2485 tp->prr_delivered += newly_acked_sacked;
2486 if (delta < 0) {
2487 u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
2488 tp->prior_cwnd - 1;
2489 sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;
2490 } else if ((flag & FLAG_RETRANS_DATA_ACKED) &&
2491 !(flag & FLAG_LOST_RETRANS)) {
2492 sndcnt = min_t(int, delta,
2493 max_t(int, tp->prr_delivered - tp->prr_out,
2494 newly_acked_sacked) + 1);
2495 } else {
2496 sndcnt = min(delta, newly_acked_sacked);
2497 }
2498 /* Force a fast retransmit upon entering fast recovery */
2499 sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
2500 tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
2501 }
2502
2503 static inline void tcp_end_cwnd_reduction(struct sock *sk)
2504 {
2505 struct tcp_sock *tp = tcp_sk(sk);
2506
2507 if (inet_csk(sk)->icsk_ca_ops->cong_control)
2508 return;
2509
2510 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2511 if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR ||
2512 (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
2513 tp->snd_cwnd = tp->snd_ssthresh;
2514 tp->snd_cwnd_stamp = tcp_time_stamp;
2515 }
2516 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
2517 }
2518
2519 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2520 void tcp_enter_cwr(struct sock *sk)
2521 {
2522 struct tcp_sock *tp = tcp_sk(sk);
2523
2524 tp->prior_ssthresh = 0;
2525 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
2526 tp->undo_marker = 0;
2527 tcp_init_cwnd_reduction(sk);
2528 tcp_set_ca_state(sk, TCP_CA_CWR);
2529 }
2530 }
2531 EXPORT_SYMBOL(tcp_enter_cwr);
2532
2533 static void tcp_try_keep_open(struct sock *sk)
2534 {
2535 struct tcp_sock *tp = tcp_sk(sk);
2536 int state = TCP_CA_Open;
2537
2538 if (tcp_left_out(tp) || tcp_any_retrans_done(sk))
2539 state = TCP_CA_Disorder;
2540
2541 if (inet_csk(sk)->icsk_ca_state != state) {
2542 tcp_set_ca_state(sk, state);
2543 tp->high_seq = tp->snd_nxt;
2544 }
2545 }
2546
2547 static void tcp_try_to_open(struct sock *sk, int flag)
2548 {
2549 struct tcp_sock *tp = tcp_sk(sk);
2550
2551 tcp_verify_left_out(tp);
2552
2553 if (!tcp_any_retrans_done(sk))
2554 tp->retrans_stamp = 0;
2555
2556 if (flag & FLAG_ECE)
2557 tcp_enter_cwr(sk);
2558
2559 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
2560 tcp_try_keep_open(sk);
2561 }
2562 }
2563
2564 static void tcp_mtup_probe_failed(struct sock *sk)
2565 {
2566 struct inet_connection_sock *icsk = inet_csk(sk);
2567
2568 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2569 icsk->icsk_mtup.probe_size = 0;
2570 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPFAIL);
2571 }
2572
2573 static void tcp_mtup_probe_success(struct sock *sk)
2574 {
2575 struct tcp_sock *tp = tcp_sk(sk);
2576 struct inet_connection_sock *icsk = inet_csk(sk);
2577
2578 /* FIXME: breaks with very large cwnd */
2579 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2580 tp->snd_cwnd = tp->snd_cwnd *
2581 tcp_mss_to_mtu(sk, tp->mss_cache) /
2582 icsk->icsk_mtup.probe_size;
2583 tp->snd_cwnd_cnt = 0;
2584 tp->snd_cwnd_stamp = tcp_time_stamp;
2585 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2586
2587 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2588 icsk->icsk_mtup.probe_size = 0;
2589 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2590 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPSUCCESS);
2591 }
2592
2593 /* Do a simple retransmit without using the backoff mechanisms in
2594 * tcp_timer. This is used for path mtu discovery.
2595 * The socket is already locked here.
2596 */
2597 void tcp_simple_retransmit(struct sock *sk)
2598 {
2599 const struct inet_connection_sock *icsk = inet_csk(sk);
2600 struct tcp_sock *tp = tcp_sk(sk);
2601 struct sk_buff *skb;
2602 unsigned int mss = tcp_current_mss(sk);
2603 u32 prior_lost = tp->lost_out;
2604
2605 tcp_for_write_queue(skb, sk) {
2606 if (skb == tcp_send_head(sk))
2607 break;
2608 if (tcp_skb_seglen(skb) > mss &&
2609 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2610 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2611 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2612 tp->retrans_out -= tcp_skb_pcount(skb);
2613 }
2614 tcp_skb_mark_lost_uncond_verify(tp, skb);
2615 }
2616 }
2617
2618 tcp_clear_retrans_hints_partial(tp);
2619
2620 if (prior_lost == tp->lost_out)
2621 return;
2622
2623 if (tcp_is_reno(tp))
2624 tcp_limit_reno_sacked(tp);
2625
2626 tcp_verify_left_out(tp);
2627
2628 /* Don't muck with the congestion window here.
2629 * Reason is that we do not increase amount of _data_
2630 * in network, but units changed and effective
2631 * cwnd/ssthresh really reduced now.
2632 */
2633 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2634 tp->high_seq = tp->snd_nxt;
2635 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2636 tp->prior_ssthresh = 0;
2637 tp->undo_marker = 0;
2638 tcp_set_ca_state(sk, TCP_CA_Loss);
2639 }
2640 tcp_xmit_retransmit_queue(sk);
2641 }
2642 EXPORT_SYMBOL(tcp_simple_retransmit);
2643
2644 void tcp_enter_recovery(struct sock *sk, bool ece_ack)
2645 {
2646 struct tcp_sock *tp = tcp_sk(sk);
2647 int mib_idx;
2648
2649 if (tcp_is_reno(tp))
2650 mib_idx = LINUX_MIB_TCPRENORECOVERY;
2651 else
2652 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
2653
2654 NET_INC_STATS(sock_net(sk), mib_idx);
2655
2656 tp->prior_ssthresh = 0;
2657 tcp_init_undo(tp);
2658
2659 if (!tcp_in_cwnd_reduction(sk)) {
2660 if (!ece_ack)
2661 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2662 tcp_init_cwnd_reduction(sk);
2663 }
2664 tcp_set_ca_state(sk, TCP_CA_Recovery);
2665 }
2666
2667 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2668 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2669 */
2670 static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
2671 int *rexmit)
2672 {
2673 struct tcp_sock *tp = tcp_sk(sk);
2674 bool recovered = !before(tp->snd_una, tp->high_seq);
2675
2676 if ((flag & FLAG_SND_UNA_ADVANCED) &&
2677 tcp_try_undo_loss(sk, false))
2678 return;
2679
2680 /* The ACK (s)acks some never-retransmitted data meaning not all
2681 * the data packets before the timeout were lost. Therefore we
2682 * undo the congestion window and state. This is essentially
2683 * the operation in F-RTO (RFC5682 section 3.1 step 3.b). Since
2684 * a retransmitted skb is permantly marked, we can apply such an
2685 * operation even if F-RTO was not used.
2686 */
2687 if ((flag & FLAG_ORIG_SACK_ACKED) &&
2688 tcp_try_undo_loss(sk, tp->undo_marker))
2689 return;
2690
2691 if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2692 if (after(tp->snd_nxt, tp->high_seq)) {
2693 if (flag & FLAG_DATA_SACKED || is_dupack)
2694 tp->frto = 0; /* Step 3.a. loss was real */
2695 } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
2696 tp->high_seq = tp->snd_nxt;
2697 /* Step 2.b. Try send new data (but deferred until cwnd
2698 * is updated in tcp_ack()). Otherwise fall back to
2699 * the conventional recovery.
2700 */
2701 if (tcp_send_head(sk) &&
2702 after(tcp_wnd_end(tp), tp->snd_nxt)) {
2703 *rexmit = REXMIT_NEW;
2704 return;
2705 }
2706 tp->frto = 0;
2707 }
2708 }
2709
2710 if (recovered) {
2711 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2712 tcp_try_undo_recovery(sk);
2713 return;
2714 }
2715 if (tcp_is_reno(tp)) {
2716 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2717 * delivered. Lower inflight to clock out (re)tranmissions.
2718 */
2719 if (after(tp->snd_nxt, tp->high_seq) && is_dupack)
2720 tcp_add_reno_sack(sk);
2721 else if (flag & FLAG_SND_UNA_ADVANCED)
2722 tcp_reset_reno_sack(tp);
2723 }
2724 *rexmit = REXMIT_LOST;
2725 }
2726
2727 /* Undo during fast recovery after partial ACK. */
2728 static bool tcp_try_undo_partial(struct sock *sk, const int acked)
2729 {
2730 struct tcp_sock *tp = tcp_sk(sk);
2731
2732 if (tp->undo_marker && tcp_packet_delayed(tp)) {
2733 /* Plain luck! Hole if filled with delayed
2734 * packet, rather than with a retransmit.
2735 */
2736 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
2737
2738 /* We are getting evidence that the reordering degree is higher
2739 * than we realized. If there are no retransmits out then we
2740 * can undo. Otherwise we clock out new packets but do not
2741 * mark more packets lost or retransmit more.
2742 */
2743 if (tp->retrans_out)
2744 return true;
2745
2746 if (!tcp_any_retrans_done(sk))
2747 tp->retrans_stamp = 0;
2748
2749 DBGUNDO(sk, "partial recovery");
2750 tcp_undo_cwnd_reduction(sk, true);
2751 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
2752 tcp_try_keep_open(sk);
2753 return true;
2754 }
2755 return false;
2756 }
2757
2758 static void tcp_rack_identify_loss(struct sock *sk, int *ack_flag,
2759 const struct skb_mstamp *ack_time)
2760 {
2761 struct tcp_sock *tp = tcp_sk(sk);
2762
2763 /* Use RACK to detect loss */
2764 if (sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION) {
2765 u32 prior_retrans = tp->retrans_out;
2766
2767 tcp_rack_mark_lost(sk, ack_time);
2768 if (prior_retrans > tp->retrans_out)
2769 *ack_flag |= FLAG_LOST_RETRANS;
2770 }
2771 }
2772
2773 /* Process an event, which can update packets-in-flight not trivially.
2774 * Main goal of this function is to calculate new estimate for left_out,
2775 * taking into account both packets sitting in receiver's buffer and
2776 * packets lost by network.
2777 *
2778 * Besides that it updates the congestion state when packet loss or ECN
2779 * is detected. But it does not reduce the cwnd, it is done by the
2780 * congestion control later.
2781 *
2782 * It does _not_ decide what to send, it is made in function
2783 * tcp_xmit_retransmit_queue().
2784 */
2785 static void tcp_fastretrans_alert(struct sock *sk, const int acked,
2786 bool is_dupack, int *ack_flag, int *rexmit,
2787 const struct skb_mstamp *ack_time)
2788 {
2789 struct inet_connection_sock *icsk = inet_csk(sk);
2790 struct tcp_sock *tp = tcp_sk(sk);
2791 int fast_rexmit = 0, flag = *ack_flag;
2792 bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
2793 (tcp_fackets_out(tp) > tp->reordering));
2794
2795 if (WARN_ON(!tp->packets_out && tp->sacked_out))
2796 tp->sacked_out = 0;
2797 if (WARN_ON(!tp->sacked_out && tp->fackets_out))
2798 tp->fackets_out = 0;
2799
2800 /* Now state machine starts.
2801 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2802 if (flag & FLAG_ECE)
2803 tp->prior_ssthresh = 0;
2804
2805 /* B. In all the states check for reneging SACKs. */
2806 if (tcp_check_sack_reneging(sk, flag))
2807 return;
2808
2809 /* C. Check consistency of the current state. */
2810 tcp_verify_left_out(tp);
2811
2812 /* D. Check state exit conditions. State can be terminated
2813 * when high_seq is ACKed. */
2814 if (icsk->icsk_ca_state == TCP_CA_Open) {
2815 WARN_ON(tp->retrans_out != 0);
2816 tp->retrans_stamp = 0;
2817 } else if (!before(tp->snd_una, tp->high_seq)) {
2818 switch (icsk->icsk_ca_state) {
2819 case TCP_CA_CWR:
2820 /* CWR is to be held something *above* high_seq
2821 * is ACKed for CWR bit to reach receiver. */
2822 if (tp->snd_una != tp->high_seq) {
2823 tcp_end_cwnd_reduction(sk);
2824 tcp_set_ca_state(sk, TCP_CA_Open);
2825 }
2826 break;
2827
2828 case TCP_CA_Recovery:
2829 if (tcp_is_reno(tp))
2830 tcp_reset_reno_sack(tp);
2831 if (tcp_try_undo_recovery(sk))
2832 return;
2833 tcp_end_cwnd_reduction(sk);
2834 break;
2835 }
2836 }
2837
2838 /* E. Process state. */
2839 switch (icsk->icsk_ca_state) {
2840 case TCP_CA_Recovery:
2841 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
2842 if (tcp_is_reno(tp) && is_dupack)
2843 tcp_add_reno_sack(sk);
2844 } else {
2845 if (tcp_try_undo_partial(sk, acked))
2846 return;
2847 /* Partial ACK arrived. Force fast retransmit. */
2848 do_lost = tcp_is_reno(tp) ||
2849 tcp_fackets_out(tp) > tp->reordering;
2850 }
2851 if (tcp_try_undo_dsack(sk)) {
2852 tcp_try_keep_open(sk);
2853 return;
2854 }
2855 tcp_rack_identify_loss(sk, ack_flag, ack_time);
2856 break;
2857 case TCP_CA_Loss:
2858 tcp_process_loss(sk, flag, is_dupack, rexmit);
2859 tcp_rack_identify_loss(sk, ack_flag, ack_time);
2860 if (!(icsk->icsk_ca_state == TCP_CA_Open ||
2861 (*ack_flag & FLAG_LOST_RETRANS)))
2862 return;
2863 /* Change state if cwnd is undone or retransmits are lost */
2864 default:
2865 if (tcp_is_reno(tp)) {
2866 if (flag & FLAG_SND_UNA_ADVANCED)
2867 tcp_reset_reno_sack(tp);
2868 if (is_dupack)
2869 tcp_add_reno_sack(sk);
2870 }
2871
2872 if (icsk->icsk_ca_state <= TCP_CA_Disorder)
2873 tcp_try_undo_dsack(sk);
2874
2875 tcp_rack_identify_loss(sk, ack_flag, ack_time);
2876 if (!tcp_time_to_recover(sk, flag)) {
2877 tcp_try_to_open(sk, flag);
2878 return;
2879 }
2880
2881 /* MTU probe failure: don't reduce cwnd */
2882 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2883 icsk->icsk_mtup.probe_size &&
2884 tp->snd_una == tp->mtu_probe.probe_seq_start) {
2885 tcp_mtup_probe_failed(sk);
2886 /* Restores the reduction we did in tcp_mtup_probe() */
2887 tp->snd_cwnd++;
2888 tcp_simple_retransmit(sk);
2889 return;
2890 }
2891
2892 /* Otherwise enter Recovery state */
2893 tcp_enter_recovery(sk, (flag & FLAG_ECE));
2894 fast_rexmit = 1;
2895 }
2896
2897 if (do_lost)
2898 tcp_update_scoreboard(sk, fast_rexmit);
2899 *rexmit = REXMIT_LOST;
2900 }
2901
2902 static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us)
2903 {
2904 struct tcp_sock *tp = tcp_sk(sk);
2905 u32 wlen = sysctl_tcp_min_rtt_wlen * HZ;
2906
2907 minmax_running_min(&tp->rtt_min, wlen, tcp_time_stamp,
2908 rtt_us ? : jiffies_to_usecs(1));
2909 }
2910
2911 static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,
2912 long seq_rtt_us, long sack_rtt_us,
2913 long ca_rtt_us)
2914 {
2915 const struct tcp_sock *tp = tcp_sk(sk);
2916
2917 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2918 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2919 * Karn's algorithm forbids taking RTT if some retransmitted data
2920 * is acked (RFC6298).
2921 */
2922 if (seq_rtt_us < 0)
2923 seq_rtt_us = sack_rtt_us;
2924
2925 /* RTTM Rule: A TSecr value received in a segment is used to
2926 * update the averaged RTT measurement only if the segment
2927 * acknowledges some new data, i.e., only if it advances the
2928 * left edge of the send window.
2929 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2930 */
2931 if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2932 flag & FLAG_ACKED)
2933 seq_rtt_us = ca_rtt_us = jiffies_to_usecs(tcp_time_stamp -
2934 tp->rx_opt.rcv_tsecr);
2935 if (seq_rtt_us < 0)
2936 return false;
2937
2938 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
2939 * always taken together with ACK, SACK, or TS-opts. Any negative
2940 * values will be skipped with the seq_rtt_us < 0 check above.
2941 */
2942 tcp_update_rtt_min(sk, ca_rtt_us);
2943 tcp_rtt_estimator(sk, seq_rtt_us);
2944 tcp_set_rto(sk);
2945
2946 /* RFC6298: only reset backoff on valid RTT measurement. */
2947 inet_csk(sk)->icsk_backoff = 0;
2948 return true;
2949 }
2950
2951 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2952 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
2953 {
2954 long rtt_us = -1L;
2955
2956 if (req && !req->num_retrans && tcp_rsk(req)->snt_synack.v64) {
2957 struct skb_mstamp now;
2958
2959 skb_mstamp_get(&now);
2960 rtt_us = skb_mstamp_us_delta(&now, &tcp_rsk(req)->snt_synack);
2961 }
2962
2963 tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, rtt_us, -1L, rtt_us);
2964 }
2965
2966
2967 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
2968 {
2969 const struct inet_connection_sock *icsk = inet_csk(sk);
2970
2971 icsk->icsk_ca_ops->cong_avoid(sk, ack, acked);
2972 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
2973 }
2974
2975 /* Restart timer after forward progress on connection.
2976 * RFC2988 recommends to restart timer to now+rto.
2977 */
2978 void tcp_rearm_rto(struct sock *sk)
2979 {
2980 const struct inet_connection_sock *icsk = inet_csk(sk);
2981 struct tcp_sock *tp = tcp_sk(sk);
2982
2983 /* If the retrans timer is currently being used by Fast Open
2984 * for SYN-ACK retrans purpose, stay put.
2985 */
2986 if (tp->fastopen_rsk)
2987 return;
2988
2989 if (!tp->packets_out) {
2990 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
2991 } else {
2992 u32 rto = inet_csk(sk)->icsk_rto;
2993 /* Offset the time elapsed after installing regular RTO */
2994 if (icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
2995 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
2996 struct sk_buff *skb = tcp_write_queue_head(sk);
2997 const u32 rto_time_stamp =
2998 tcp_skb_timestamp(skb) + rto;
2999 s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
3000 /* delta may not be positive if the socket is locked
3001 * when the retrans timer fires and is rescheduled.
3002 */
3003 if (delta > 0)
3004 rto = delta;
3005 }
3006 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
3007 TCP_RTO_MAX);
3008 }
3009 }
3010
3011 /* If we get here, the whole TSO packet has not been acked. */
3012 static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
3013 {
3014 struct tcp_sock *tp = tcp_sk(sk);
3015 u32 packets_acked;
3016
3017 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
3018
3019 packets_acked = tcp_skb_pcount(skb);
3020 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3021 return 0;
3022 packets_acked -= tcp_skb_pcount(skb);
3023
3024 if (packets_acked) {
3025 BUG_ON(tcp_skb_pcount(skb) == 0);
3026 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
3027 }
3028
3029 return packets_acked;
3030 }
3031
3032 static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
3033 u32 prior_snd_una)
3034 {
3035 const struct skb_shared_info *shinfo;
3036
3037 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3038 if (likely(!TCP_SKB_CB(skb)->txstamp_ack))
3039 return;
3040
3041 shinfo = skb_shinfo(skb);
3042 if (!before(shinfo->tskey, prior_snd_una) &&
3043 before(shinfo->tskey, tcp_sk(sk)->snd_una))
3044 __skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK);
3045 }
3046
3047 /* Remove acknowledged frames from the retransmission queue. If our packet
3048 * is before the ack sequence we can discard it as it's confirmed to have
3049 * arrived at the other end.
3050 */
3051 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
3052 u32 prior_snd_una, int *acked,
3053 struct tcp_sacktag_state *sack)
3054 {
3055 const struct inet_connection_sock *icsk = inet_csk(sk);
3056 struct skb_mstamp first_ackt, last_ackt;
3057 struct skb_mstamp *now = &sack->ack_time;
3058 struct tcp_sock *tp = tcp_sk(sk);
3059 u32 prior_sacked = tp->sacked_out;
3060 u32 reord = tp->packets_out;
3061 bool fully_acked = true;
3062 long sack_rtt_us = -1L;
3063 long seq_rtt_us = -1L;
3064 long ca_rtt_us = -1L;
3065 struct sk_buff *skb;
3066 u32 pkts_acked = 0;
3067 u32 last_in_flight = 0;
3068 bool rtt_update;
3069 int flag = 0;
3070
3071 first_ackt.v64 = 0;
3072
3073 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
3074 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
3075 u8 sacked = scb->sacked;
3076 u32 acked_pcount;
3077
3078 tcp_ack_tstamp(sk, skb, prior_snd_una);
3079
3080 /* Determine how many packets and what bytes were acked, tso and else */
3081 if (after(scb->end_seq, tp->snd_una)) {
3082 if (tcp_skb_pcount(skb) == 1 ||
3083 !after(tp->snd_una, scb->seq))
3084 break;
3085
3086 acked_pcount = tcp_tso_acked(sk, skb);
3087 if (!acked_pcount)
3088 break;
3089 fully_acked = false;
3090 } else {
3091 /* Speedup tcp_unlink_write_queue() and next loop */
3092 prefetchw(skb->next);
3093 acked_pcount = tcp_skb_pcount(skb);
3094 }
3095
3096 if (unlikely(sacked & TCPCB_RETRANS)) {
3097 if (sacked & TCPCB_SACKED_RETRANS)
3098 tp->retrans_out -= acked_pcount;
3099 flag |= FLAG_RETRANS_DATA_ACKED;
3100 } else if (!(sacked & TCPCB_SACKED_ACKED)) {
3101 last_ackt = skb->skb_mstamp;
3102 WARN_ON_ONCE(last_ackt.v64 == 0);
3103 if (!first_ackt.v64)
3104 first_ackt = last_ackt;
3105
3106 last_in_flight = TCP_SKB_CB(skb)->tx.in_flight;
3107 reord = min(pkts_acked, reord);
3108 if (!after(scb->end_seq, tp->high_seq))
3109 flag |= FLAG_ORIG_SACK_ACKED;
3110 }
3111
3112 if (sacked & TCPCB_SACKED_ACKED) {
3113 tp->sacked_out -= acked_pcount;
3114 } else if (tcp_is_sack(tp)) {
3115 tp->delivered += acked_pcount;
3116 if (!tcp_skb_spurious_retrans(tp, skb))
3117 tcp_rack_advance(tp, sacked, scb->end_seq,
3118 &skb->skb_mstamp,
3119 &sack->ack_time);
3120 }
3121 if (sacked & TCPCB_LOST)
3122 tp->lost_out -= acked_pcount;
3123
3124 tp->packets_out -= acked_pcount;
3125 pkts_acked += acked_pcount;
3126 tcp_rate_skb_delivered(sk, skb, sack->rate);
3127
3128 /* Initial outgoing SYN's get put onto the write_queue
3129 * just like anything else we transmit. It is not
3130 * true data, and if we misinform our callers that
3131 * this ACK acks real data, we will erroneously exit
3132 * connection startup slow start one packet too
3133 * quickly. This is severely frowned upon behavior.
3134 */
3135 if (likely(!(scb->tcp_flags & TCPHDR_SYN))) {
3136 flag |= FLAG_DATA_ACKED;
3137 } else {
3138 flag |= FLAG_SYN_ACKED;
3139 tp->retrans_stamp = 0;
3140 }
3141
3142 if (!fully_acked)
3143 break;
3144
3145 tcp_unlink_write_queue(skb, sk);
3146 sk_wmem_free_skb(sk, skb);
3147 if (unlikely(skb == tp->retransmit_skb_hint))
3148 tp->retransmit_skb_hint = NULL;
3149 if (unlikely(skb == tp->lost_skb_hint))
3150 tp->lost_skb_hint = NULL;
3151 }
3152
3153 if (!skb)
3154 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
3155
3156 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3157 tp->snd_up = tp->snd_una;
3158
3159 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
3160 flag |= FLAG_SACK_RENEGING;
3161
3162 if (likely(first_ackt.v64) && !(flag & FLAG_RETRANS_DATA_ACKED)) {
3163 seq_rtt_us = skb_mstamp_us_delta(now, &first_ackt);
3164 ca_rtt_us = skb_mstamp_us_delta(now, &last_ackt);
3165 }
3166 if (sack->first_sackt.v64) {
3167 sack_rtt_us = skb_mstamp_us_delta(now, &sack->first_sackt);
3168 ca_rtt_us = skb_mstamp_us_delta(now, &sack->last_sackt);
3169 }
3170 sack->rate->rtt_us = ca_rtt_us; /* RTT of last (S)ACKed packet, or -1 */
3171 rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us,
3172 ca_rtt_us);
3173
3174 if (flag & FLAG_ACKED) {
3175 tcp_rearm_rto(sk);
3176 if (unlikely(icsk->icsk_mtup.probe_size &&
3177 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3178 tcp_mtup_probe_success(sk);
3179 }
3180
3181 if (tcp_is_reno(tp)) {
3182 tcp_remove_reno_sacks(sk, pkts_acked);
3183 } else {
3184 int delta;
3185
3186 /* Non-retransmitted hole got filled? That's reordering */
3187 if (reord < prior_fackets)
3188 tcp_update_reordering(sk, tp->fackets_out - reord, 0);
3189
3190 delta = tcp_is_fack(tp) ? pkts_acked :
3191 prior_sacked - tp->sacked_out;
3192 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
3193 }
3194
3195 tp->fackets_out -= min(pkts_acked, tp->fackets_out);
3196
3197 } else if (skb && rtt_update && sack_rtt_us >= 0 &&
3198 sack_rtt_us > skb_mstamp_us_delta(now, &skb->skb_mstamp)) {
3199 /* Do not re-arm RTO if the sack RTT is measured from data sent
3200 * after when the head was last (re)transmitted. Otherwise the
3201 * timeout may continue to extend in loss recovery.
3202 */
3203 tcp_rearm_rto(sk);
3204 }
3205
3206 if (icsk->icsk_ca_ops->pkts_acked) {
3207 struct ack_sample sample = { .pkts_acked = pkts_acked,
3208 .rtt_us = ca_rtt_us,
3209 .in_flight = last_in_flight };
3210
3211 icsk->icsk_ca_ops->pkts_acked(sk, &sample);
3212 }
3213
3214 #if FASTRETRANS_DEBUG > 0
3215 WARN_ON((int)tp->sacked_out < 0);
3216 WARN_ON((int)tp->lost_out < 0);
3217 WARN_ON((int)tp->retrans_out < 0);
3218 if (!tp->packets_out && tcp_is_sack(tp)) {
3219 icsk = inet_csk(sk);
3220 if (tp->lost_out) {
3221 pr_debug("Leak l=%u %d\n",
3222 tp->lost_out, icsk->icsk_ca_state);
3223 tp->lost_out = 0;
3224 }
3225 if (tp->sacked_out) {
3226 pr_debug("Leak s=%u %d\n",
3227 tp->sacked_out, icsk->icsk_ca_state);
3228 tp->sacked_out = 0;
3229 }
3230 if (tp->retrans_out) {
3231 pr_debug("Leak r=%u %d\n",
3232 tp->retrans_out, icsk->icsk_ca_state);
3233 tp->retrans_out = 0;
3234 }
3235 }
3236 #endif
3237 *acked = pkts_acked;
3238 return flag;
3239 }
3240
3241 static void tcp_ack_probe(struct sock *sk)
3242 {
3243 const struct tcp_sock *tp = tcp_sk(sk);
3244 struct inet_connection_sock *icsk = inet_csk(sk);
3245
3246 /* Was it a usable window open? */
3247
3248 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
3249 icsk->icsk_backoff = 0;
3250 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
3251 /* Socket must be waked up by subsequent tcp_data_snd_check().
3252 * This function is not for random using!
3253 */
3254 } else {
3255 unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
3256
3257 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3258 when, TCP_RTO_MAX);
3259 }
3260 }
3261
3262 static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
3263 {
3264 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
3265 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
3266 }
3267
3268 /* Decide wheather to run the increase function of congestion control. */
3269 static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
3270 {
3271 /* If reordering is high then always grow cwnd whenever data is
3272 * delivered regardless of its ordering. Otherwise stay conservative
3273 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3274 * new SACK or ECE mark may first advance cwnd here and later reduce
3275 * cwnd in tcp_fastretrans_alert() based on more states.
3276 */
3277 if (tcp_sk(sk)->reordering > sock_net(sk)->ipv4.sysctl_tcp_reordering)
3278 return flag & FLAG_FORWARD_PROGRESS;
3279
3280 return flag & FLAG_DATA_ACKED;
3281 }
3282
3283 /* The "ultimate" congestion control function that aims to replace the rigid
3284 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3285 * It's called toward the end of processing an ACK with precise rate
3286 * information. All transmission or retransmission are delayed afterwards.
3287 */
3288 static void tcp_cong_control(struct sock *sk, u32 ack, u32 acked_sacked,
3289 int flag, const struct rate_sample *rs)
3290 {
3291 const struct inet_connection_sock *icsk = inet_csk(sk);
3292
3293 if (icsk->icsk_ca_ops->cong_control) {
3294 icsk->icsk_ca_ops->cong_control(sk, rs);
3295 return;
3296 }
3297
3298 if (tcp_in_cwnd_reduction(sk)) {
3299 /* Reduce cwnd if state mandates */
3300 tcp_cwnd_reduction(sk, acked_sacked, flag);
3301 } else if (tcp_may_raise_cwnd(sk, flag)) {
3302 /* Advance cwnd if state allows */
3303 tcp_cong_avoid(sk, ack, acked_sacked);
3304 }
3305 tcp_update_pacing_rate(sk);
3306 }
3307
3308 /* Check that window update is acceptable.
3309 * The function assumes that snd_una<=ack<=snd_next.
3310 */
3311 static inline bool tcp_may_update_window(const struct tcp_sock *tp,
3312 const u32 ack, const u32 ack_seq,
3313 const u32 nwin)
3314 {
3315 return after(ack, tp->snd_una) ||
3316 after(ack_seq, tp->snd_wl1) ||
3317 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
3318 }
3319
3320 /* If we update tp->snd_una, also update tp->bytes_acked */
3321 static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
3322 {
3323 u32 delta = ack - tp->snd_una;
3324
3325 sock_owned_by_me((struct sock *)tp);
3326 tp->bytes_acked += delta;
3327 tp->snd_una = ack;
3328 }
3329
3330 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3331 static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
3332 {
3333 u32 delta = seq - tp->rcv_nxt;
3334
3335 sock_owned_by_me((struct sock *)tp);
3336 tp->bytes_received += delta;
3337 tp->rcv_nxt = seq;
3338 }
3339
3340 /* Update our send window.
3341 *
3342 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3343 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3344 */
3345 static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack,
3346 u32 ack_seq)
3347 {
3348 struct tcp_sock *tp = tcp_sk(sk);
3349 int flag = 0;
3350 u32 nwin = ntohs(tcp_hdr(skb)->window);
3351
3352 if (likely(!tcp_hdr(skb)->syn))
3353 nwin <<= tp->rx_opt.snd_wscale;
3354
3355 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3356 flag |= FLAG_WIN_UPDATE;
3357 tcp_update_wl(tp, ack_seq);
3358
3359 if (tp->snd_wnd != nwin) {
3360 tp->snd_wnd = nwin;
3361
3362 /* Note, it is the only place, where
3363 * fast path is recovered for sending TCP.
3364 */
3365 tp->pred_flags = 0;
3366 tcp_fast_path_check(sk);
3367
3368 if (tcp_send_head(sk))
3369 tcp_slow_start_after_idle_check(sk);
3370
3371 if (nwin > tp->max_window) {
3372 tp->max_window = nwin;
3373 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
3374 }
3375 }
3376 }
3377
3378 tcp_snd_una_update(tp, ack);
3379
3380 return flag;
3381 }
3382
3383 static bool __tcp_oow_rate_limited(struct net *net, int mib_idx,
3384 u32 *last_oow_ack_time)
3385 {
3386 if (*last_oow_ack_time) {
3387 s32 elapsed = (s32)(tcp_time_stamp - *last_oow_ack_time);
3388
3389 if (0 <= elapsed && elapsed < sysctl_tcp_invalid_ratelimit) {
3390 NET_INC_STATS(net, mib_idx);
3391 return true; /* rate-limited: don't send yet! */
3392 }
3393 }
3394
3395 *last_oow_ack_time = tcp_time_stamp;
3396
3397 return false; /* not rate-limited: go ahead, send dupack now! */
3398 }
3399
3400 /* Return true if we're currently rate-limiting out-of-window ACKs and
3401 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3402 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3403 * attacks that send repeated SYNs or ACKs for the same connection. To
3404 * do this, we do not send a duplicate SYNACK or ACK if the remote
3405 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3406 */
3407 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
3408 int mib_idx, u32 *last_oow_ack_time)
3409 {
3410 /* Data packets without SYNs are not likely part of an ACK loop. */
3411 if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) &&
3412 !tcp_hdr(skb)->syn)
3413 return false;
3414
3415 return __tcp_oow_rate_limited(net, mib_idx, last_oow_ack_time);
3416 }
3417
3418 /* RFC 5961 7 [ACK Throttling] */
3419 static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
3420 {
3421 /* unprotected vars, we dont care of overwrites */
3422 static u32 challenge_timestamp;
3423 static unsigned int challenge_count;
3424 struct tcp_sock *tp = tcp_sk(sk);
3425 u32 count, now;
3426
3427 /* First check our per-socket dupack rate limit. */
3428 if (__tcp_oow_rate_limited(sock_net(sk),
3429 LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
3430 &tp->last_oow_ack_time))
3431 return;
3432
3433 /* Then check host-wide RFC 5961 rate limit. */
3434 now = jiffies / HZ;
3435 if (now != challenge_timestamp) {
3436 u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1;
3437
3438 challenge_timestamp = now;
3439 WRITE_ONCE(challenge_count, half +
3440 prandom_u32_max(sysctl_tcp_challenge_ack_limit));
3441 }
3442 count = READ_ONCE(challenge_count);
3443 if (count > 0) {
3444 WRITE_ONCE(challenge_count, count - 1);
3445 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK);
3446 tcp_send_ack(sk);
3447 }
3448 }
3449
3450 static void tcp_store_ts_recent(struct tcp_sock *tp)
3451 {
3452 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3453 tp->rx_opt.ts_recent_stamp = get_seconds();
3454 }
3455
3456 static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3457 {
3458 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3459 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3460 * extra check below makes sure this can only happen
3461 * for pure ACK frames. -DaveM
3462 *
3463 * Not only, also it occurs for expired timestamps.
3464 */
3465
3466 if (tcp_paws_check(&tp->rx_opt, 0))
3467 tcp_store_ts_recent(tp);
3468 }
3469 }
3470
3471 /* This routine deals with acks during a TLP episode.
3472 * We mark the end of a TLP episode on receiving TLP dupack or when
3473 * ack is after tlp_high_seq.
3474 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3475 */
3476 static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
3477 {
3478 struct tcp_sock *tp = tcp_sk(sk);
3479
3480 if (before(ack, tp->tlp_high_seq))
3481 return;
3482
3483 if (flag & FLAG_DSACKING_ACK) {
3484 /* This DSACK means original and TLP probe arrived; no loss */
3485 tp->tlp_high_seq = 0;
3486 } else if (after(ack, tp->tlp_high_seq)) {
3487 /* ACK advances: there was a loss, so reduce cwnd. Reset
3488 * tlp_high_seq in tcp_init_cwnd_reduction()
3489 */
3490 tcp_init_cwnd_reduction(sk);
3491 tcp_set_ca_state(sk, TCP_CA_CWR);
3492 tcp_end_cwnd_reduction(sk);
3493 tcp_try_keep_open(sk);
3494 NET_INC_STATS(sock_net(sk),
3495 LINUX_MIB_TCPLOSSPROBERECOVERY);
3496 } else if (!(flag & (FLAG_SND_UNA_ADVANCED |
3497 FLAG_NOT_DUP | FLAG_DATA_SACKED))) {
3498 /* Pure dupack: original and TLP probe arrived; no loss */
3499 tp->tlp_high_seq = 0;
3500 }
3501 }
3502
3503 static inline void tcp_in_ack_event(struct sock *sk, u32 flags)
3504 {
3505 const struct inet_connection_sock *icsk = inet_csk(sk);
3506
3507 if (icsk->icsk_ca_ops->in_ack_event)
3508 icsk->icsk_ca_ops->in_ack_event(sk, flags);
3509 }
3510
3511 /* Congestion control has updated the cwnd already. So if we're in
3512 * loss recovery then now we do any new sends (for FRTO) or
3513 * retransmits (for CA_Loss or CA_recovery) that make sense.
3514 */
3515 static void tcp_xmit_recovery(struct sock *sk, int rexmit)
3516 {
3517 struct tcp_sock *tp = tcp_sk(sk);
3518
3519 if (rexmit == REXMIT_NONE)
3520 return;
3521
3522 if (unlikely(rexmit == 2)) {
3523 __tcp_push_pending_frames(sk, tcp_current_mss(sk),
3524 TCP_NAGLE_OFF);
3525 if (after(tp->snd_nxt, tp->high_seq))
3526 return;
3527 tp->frto = 0;
3528 }
3529 tcp_xmit_retransmit_queue(sk);
3530 }
3531
3532 /* This routine deals with incoming acks, but not outgoing ones. */
3533 static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
3534 {
3535 struct inet_connection_sock *icsk = inet_csk(sk);
3536 struct tcp_sock *tp = tcp_sk(sk);
3537 struct tcp_sacktag_state sack_state;
3538 struct rate_sample rs = { .prior_delivered = 0 };
3539 u32 prior_snd_una = tp->snd_una;
3540 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3541 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3542 bool is_dupack = false;
3543 u32 prior_fackets;
3544 int prior_packets = tp->packets_out;
3545 u32 delivered = tp->delivered;
3546 u32 lost = tp->lost;
3547 int acked = 0; /* Number of packets newly acked */
3548 int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */
3549
3550 sack_state.first_sackt.v64 = 0;
3551 sack_state.rate = &rs;
3552
3553 /* We very likely will need to access write queue head. */
3554 prefetchw(sk->sk_write_queue.next);
3555
3556 /* If the ack is older than previous acks
3557 * then we can probably ignore it.
3558 */
3559 if (before(ack, prior_snd_una)) {
3560 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3561 if (before(ack, prior_snd_una - tp->max_window)) {
3562 tcp_send_challenge_ack(sk, skb);
3563 return -1;
3564 }
3565 goto old_ack;
3566 }
3567
3568 /* If the ack includes data we haven't sent yet, discard
3569 * this segment (RFC793 Section 3.9).
3570 */
3571 if (after(ack, tp->snd_nxt))
3572 goto invalid_ack;
3573
3574 skb_mstamp_get(&sack_state.ack_time);
3575
3576 if (icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
3577 tcp_rearm_rto(sk);
3578
3579 if (after(ack, prior_snd_una)) {
3580 flag |= FLAG_SND_UNA_ADVANCED;
3581 icsk->icsk_retransmits = 0;
3582 }
3583
3584 prior_fackets = tp->fackets_out;
3585 rs.prior_in_flight = tcp_packets_in_flight(tp);
3586
3587 /* ts_recent update must be made after we are sure that the packet
3588 * is in window.
3589 */
3590 if (flag & FLAG_UPDATE_TS_RECENT)
3591 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3592
3593 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
3594 /* Window is constant, pure forward advance.
3595 * No more checks are required.
3596 * Note, we use the fact that SND.UNA>=SND.WL2.
3597 */
3598 tcp_update_wl(tp, ack_seq);
3599 tcp_snd_una_update(tp, ack);
3600 flag |= FLAG_WIN_UPDATE;
3601
3602 tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
3603
3604 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS);
3605 } else {
3606 u32 ack_ev_flags = CA_ACK_SLOWPATH;
3607
3608 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3609 flag |= FLAG_DATA;
3610 else
3611 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPUREACKS);
3612
3613 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
3614
3615 if (TCP_SKB_CB(skb)->sacked)
3616 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3617 &sack_state);
3618
3619 if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
3620 flag |= FLAG_ECE;
3621 ack_ev_flags |= CA_ACK_ECE;
3622 }
3623
3624 if (flag & FLAG_WIN_UPDATE)
3625 ack_ev_flags |= CA_ACK_WIN_UPDATE;
3626
3627 tcp_in_ack_event(sk, ack_ev_flags);
3628 }
3629
3630 /* We passed data and got it acked, remove any soft error
3631 * log. Something worked...
3632 */
3633 sk->sk_err_soft = 0;
3634 icsk->icsk_probes_out = 0;
3635 tp->rcv_tstamp = tcp_time_stamp;
3636 if (!prior_packets)
3637 goto no_queue;
3638
3639 /* See if we can take anything off of the retransmit queue. */
3640 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una, &acked,
3641 &sack_state);
3642
3643 if (tcp_ack_is_dubious(sk, flag)) {
3644 is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
3645 tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit,
3646 &sack_state.ack_time);
3647 }
3648 if (tp->tlp_high_seq)
3649 tcp_process_tlp_ack(sk, ack, flag);
3650
3651 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
3652 sk_dst_confirm(sk);
3653
3654 if (icsk->icsk_pending == ICSK_TIME_RETRANS)
3655 tcp_schedule_loss_probe(sk);
3656 delivered = tp->delivered - delivered; /* freshly ACKed or SACKed */
3657 lost = tp->lost - lost; /* freshly marked lost */
3658 tcp_rate_gen(sk, delivered, lost, &sack_state.ack_time,
3659 sack_state.rate);
3660 tcp_cong_control(sk, ack, delivered, flag, sack_state.rate);
3661 tcp_xmit_recovery(sk, rexmit);
3662 return 1;
3663
3664 no_queue:
3665 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3666 if (flag & FLAG_DSACKING_ACK)
3667 tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit,
3668 &sack_state.ack_time);
3669 /* If this ack opens up a zero window, clear backoff. It was
3670 * being used to time the probes, and is probably far higher than
3671 * it needs to be for normal retransmission.
3672 */
3673 if (tcp_send_head(sk))
3674 tcp_ack_probe(sk);
3675
3676 if (tp->tlp_high_seq)
3677 tcp_process_tlp_ack(sk, ack, flag);
3678 return 1;
3679
3680 invalid_ack:
3681 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3682 return -1;
3683
3684 old_ack:
3685 /* If data was SACKed, tag it and see if we should send more data.
3686 * If data was DSACKed, see if we can undo a cwnd reduction.
3687 */
3688 if (TCP_SKB_CB(skb)->sacked) {
3689 skb_mstamp_get(&sack_state.ack_time);
3690 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3691 &sack_state);
3692 tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit,
3693 &sack_state.ack_time);
3694 tcp_xmit_recovery(sk, rexmit);
3695 }
3696
3697 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3698 return 0;
3699 }
3700
3701 static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
3702 bool syn, struct tcp_fastopen_cookie *foc,
3703 bool exp_opt)
3704 {
3705 /* Valid only in SYN or SYN-ACK with an even length. */
3706 if (!foc || !syn || len < 0 || (len & 1))
3707 return;
3708
3709 if (len >= TCP_FASTOPEN_COOKIE_MIN &&
3710 len <= TCP_FASTOPEN_COOKIE_MAX)
3711 memcpy(foc->val, cookie, len);
3712 else if (len != 0)
3713 len = -1;
3714 foc->len = len;
3715 foc->exp = exp_opt;
3716 }
3717
3718 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3719 * But, this can also be called on packets in the established flow when
3720 * the fast version below fails.
3721 */
3722 void tcp_parse_options(const struct sk_buff *skb,
3723 struct tcp_options_received *opt_rx, int estab,
3724 struct tcp_fastopen_cookie *foc)
3725 {
3726 const unsigned char *ptr;
3727 const struct tcphdr *th = tcp_hdr(skb);
3728 int length = (th->doff * 4) - sizeof(struct tcphdr);
3729
3730 ptr = (const unsigned char *)(th + 1);
3731 opt_rx->saw_tstamp = 0;
3732
3733 while (length > 0) {
3734 int opcode = *ptr++;
3735 int opsize;
3736
3737 switch (opcode) {
3738 case TCPOPT_EOL:
3739 return;
3740 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3741 length--;
3742 continue;
3743 default:
3744 opsize = *ptr++;
3745 if (opsize < 2) /* "silly options" */
3746 return;
3747 if (opsize > length)
3748 return; /* don't parse partial options */
3749 switch (opcode) {
3750 case TCPOPT_MSS:
3751 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
3752 u16 in_mss = get_unaligned_be16(ptr);
3753 if (in_mss) {
3754 if (opt_rx->user_mss &&
3755 opt_rx->user_mss < in_mss)
3756 in_mss = opt_rx->user_mss;
3757 opt_rx->mss_clamp = in_mss;
3758 }
3759 }
3760 break;
3761 case TCPOPT_WINDOW:
3762 if (opsize == TCPOLEN_WINDOW && th->syn &&
3763 !estab && sysctl_tcp_window_scaling) {
3764 __u8 snd_wscale = *(__u8 *)ptr;
3765 opt_rx->wscale_ok = 1;
3766 if (snd_wscale > 14) {
3767 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3768 __func__,
3769 snd_wscale);
3770 snd_wscale = 14;
3771 }
3772 opt_rx->snd_wscale = snd_wscale;
3773 }
3774 break;
3775 case TCPOPT_TIMESTAMP:
3776 if ((opsize == TCPOLEN_TIMESTAMP) &&
3777 ((estab && opt_rx->tstamp_ok) ||
3778 (!estab && sysctl_tcp_timestamps))) {
3779 opt_rx->saw_tstamp = 1;
3780 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
3781 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
3782 }
3783 break;
3784 case TCPOPT_SACK_PERM:
3785 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
3786 !estab && sysctl_tcp_sack) {
3787 opt_rx->sack_ok = TCP_SACK_SEEN;
3788 tcp_sack_reset(opt_rx);
3789 }
3790 break;
3791
3792 case TCPOPT_SACK:
3793 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3794 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3795 opt_rx->sack_ok) {
3796 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3797 }
3798 break;
3799 #ifdef CONFIG_TCP_MD5SIG
3800 case TCPOPT_MD5SIG:
3801 /*
3802 * The MD5 Hash has already been
3803 * checked (see tcp_v{4,6}_do_rcv()).
3804 */
3805 break;
3806 #endif
3807 case TCPOPT_FASTOPEN:
3808 tcp_parse_fastopen_option(
3809 opsize - TCPOLEN_FASTOPEN_BASE,
3810 ptr, th->syn, foc, false);
3811 break;
3812
3813 case TCPOPT_EXP:
3814 /* Fast Open option shares code 254 using a
3815 * 16 bits magic number.
3816 */
3817 if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&
3818 get_unaligned_be16(ptr) ==
3819 TCPOPT_FASTOPEN_MAGIC)
3820 tcp_parse_fastopen_option(opsize -
3821 TCPOLEN_EXP_FASTOPEN_BASE,
3822 ptr + 2, th->syn, foc, true);
3823 break;
3824
3825 }
3826 ptr += opsize-2;
3827 length -= opsize;
3828 }
3829 }
3830 }
3831 EXPORT_SYMBOL(tcp_parse_options);
3832
3833 static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th)
3834 {
3835 const __be32 *ptr = (const __be32 *)(th + 1);
3836
3837 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3838 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3839 tp->rx_opt.saw_tstamp = 1;
3840 ++ptr;
3841 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3842 ++ptr;
3843 if (*ptr)
3844 tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
3845 else
3846 tp->rx_opt.rcv_tsecr = 0;
3847 return true;
3848 }
3849 return false;
3850 }
3851
3852 /* Fast parse options. This hopes to only see timestamps.
3853 * If it is wrong it falls back on tcp_parse_options().
3854 */
3855 static bool tcp_fast_parse_options(const struct sk_buff *skb,
3856 const struct tcphdr *th, struct tcp_sock *tp)
3857 {
3858 /* In the spirit of fast parsing, compare doff directly to constant
3859 * values. Because equality is used, short doff can be ignored here.
3860 */
3861 if (th->doff == (sizeof(*th) / 4)) {
3862 tp->rx_opt.saw_tstamp = 0;
3863 return false;
3864 } else if (tp->rx_opt.tstamp_ok &&
3865 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
3866 if (tcp_parse_aligned_timestamp(tp, th))
3867 return true;
3868 }
3869
3870 tcp_parse_options(skb, &tp->rx_opt, 1, NULL);
3871 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
3872 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
3873
3874 return true;
3875 }
3876
3877 #ifdef CONFIG_TCP_MD5SIG
3878 /*
3879 * Parse MD5 Signature option
3880 */
3881 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th)
3882 {
3883 int length = (th->doff << 2) - sizeof(*th);
3884 const u8 *ptr = (const u8 *)(th + 1);
3885
3886 /* If the TCP option is too short, we can short cut */
3887 if (length < TCPOLEN_MD5SIG)
3888 return NULL;
3889
3890 while (length > 0) {
3891 int opcode = *ptr++;
3892 int opsize;
3893
3894 switch (opcode) {
3895 case TCPOPT_EOL:
3896 return NULL;
3897 case TCPOPT_NOP:
3898 length--;
3899 continue;
3900 default:
3901 opsize = *ptr++;
3902 if (opsize < 2 || opsize > length)
3903 return NULL;
3904 if (opcode == TCPOPT_MD5SIG)
3905 return opsize == TCPOLEN_MD5SIG ? ptr : NULL;
3906 }
3907 ptr += opsize - 2;
3908 length -= opsize;
3909 }
3910 return NULL;
3911 }
3912 EXPORT_SYMBOL(tcp_parse_md5sig_option);
3913 #endif
3914
3915 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3916 *
3917 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3918 * it can pass through stack. So, the following predicate verifies that
3919 * this segment is not used for anything but congestion avoidance or
3920 * fast retransmit. Moreover, we even are able to eliminate most of such
3921 * second order effects, if we apply some small "replay" window (~RTO)
3922 * to timestamp space.
3923 *
3924 * All these measures still do not guarantee that we reject wrapped ACKs
3925 * on networks with high bandwidth, when sequence space is recycled fastly,
3926 * but it guarantees that such events will be very rare and do not affect
3927 * connection seriously. This doesn't look nice, but alas, PAWS is really
3928 * buggy extension.
3929 *
3930 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3931 * states that events when retransmit arrives after original data are rare.
3932 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3933 * the biggest problem on large power networks even with minor reordering.
3934 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3935 * up to bandwidth of 18Gigabit/sec. 8) ]
3936 */
3937
3938 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
3939 {
3940 const struct tcp_sock *tp = tcp_sk(sk);
3941 const struct tcphdr *th = tcp_hdr(skb);
3942 u32 seq = TCP_SKB_CB(skb)->seq;
3943 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3944
3945 return (/* 1. Pure ACK with correct sequence number. */
3946 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3947
3948 /* 2. ... and duplicate ACK. */
3949 ack == tp->snd_una &&
3950
3951 /* 3. ... and does not update window. */
3952 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3953
3954 /* 4. ... and sits in replay window. */
3955 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
3956 }
3957
3958 static inline bool tcp_paws_discard(const struct sock *sk,
3959 const struct sk_buff *skb)
3960 {
3961 const struct tcp_sock *tp = tcp_sk(sk);
3962
3963 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
3964 !tcp_disordered_ack(sk, skb);
3965 }
3966
3967 /* Check segment sequence number for validity.
3968 *
3969 * Segment controls are considered valid, if the segment
3970 * fits to the window after truncation to the window. Acceptability
3971 * of data (and SYN, FIN, of course) is checked separately.
3972 * See tcp_data_queue(), for example.
3973 *
3974 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3975 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3976 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3977 * (borrowed from freebsd)
3978 */
3979
3980 static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
3981 {
3982 return !before(end_seq, tp->rcv_wup) &&
3983 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
3984 }
3985
3986 /* When we get a reset we do this. */
3987 void tcp_reset(struct sock *sk)
3988 {
3989 /* We want the right error as BSD sees it (and indeed as we do). */
3990 switch (sk->sk_state) {
3991 case TCP_SYN_SENT:
3992 sk->sk_err = ECONNREFUSED;
3993 break;
3994 case TCP_CLOSE_WAIT:
3995 sk->sk_err = EPIPE;
3996 break;
3997 case TCP_CLOSE:
3998 return;
3999 default:
4000 sk->sk_err = ECONNRESET;
4001 }
4002 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4003 smp_wmb();
4004
4005 if (!sock_flag(sk, SOCK_DEAD))
4006 sk->sk_error_report(sk);
4007
4008 tcp_done(sk);
4009 }
4010
4011 /*
4012 * Process the FIN bit. This now behaves as it is supposed to work
4013 * and the FIN takes effect when it is validly part of sequence
4014 * space. Not before when we get holes.
4015 *
4016 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4017 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4018 * TIME-WAIT)
4019 *
4020 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4021 * close and we go into CLOSING (and later onto TIME-WAIT)
4022 *
4023 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4024 */
4025 void tcp_fin(struct sock *sk)
4026 {
4027 struct tcp_sock *tp = tcp_sk(sk);
4028
4029 inet_csk_schedule_ack(sk);
4030
4031 sk->sk_shutdown |= RCV_SHUTDOWN;
4032 sock_set_flag(sk, SOCK_DONE);
4033
4034 switch (sk->sk_state) {
4035 case TCP_SYN_RECV:
4036 case TCP_ESTABLISHED:
4037 /* Move to CLOSE_WAIT */
4038 tcp_set_state(sk, TCP_CLOSE_WAIT);
4039 inet_csk(sk)->icsk_ack.pingpong = 1;
4040 break;
4041
4042 case TCP_CLOSE_WAIT:
4043 case TCP_CLOSING:
4044 /* Received a retransmission of the FIN, do
4045 * nothing.
4046 */
4047 break;
4048 case TCP_LAST_ACK:
4049 /* RFC793: Remain in the LAST-ACK state. */
4050 break;
4051
4052 case TCP_FIN_WAIT1:
4053 /* This case occurs when a simultaneous close
4054 * happens, we must ack the received FIN and
4055 * enter the CLOSING state.
4056 */
4057 tcp_send_ack(sk);
4058 tcp_set_state(sk, TCP_CLOSING);
4059 break;
4060 case TCP_FIN_WAIT2:
4061 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4062 tcp_send_ack(sk);
4063 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4064 break;
4065 default:
4066 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4067 * cases we should never reach this piece of code.
4068 */
4069 pr_err("%s: Impossible, sk->sk_state=%d\n",
4070 __func__, sk->sk_state);
4071 break;
4072 }
4073
4074 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4075 * Probably, we should reset in this case. For now drop them.
4076 */
4077 skb_rbtree_purge(&tp->out_of_order_queue);
4078 if (tcp_is_sack(tp))
4079 tcp_sack_reset(&tp->rx_opt);
4080 sk_mem_reclaim(sk);
4081
4082 if (!sock_flag(sk, SOCK_DEAD)) {
4083 sk->sk_state_change(sk);
4084
4085 /* Do not send POLL_HUP for half duplex close. */
4086 if (sk->sk_shutdown == SHUTDOWN_MASK ||
4087 sk->sk_state == TCP_CLOSE)
4088 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
4089 else
4090 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
4091 }
4092 }
4093
4094 static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
4095 u32 end_seq)
4096 {
4097 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
4098 if (before(seq, sp->start_seq))
4099 sp->start_seq = seq;
4100 if (after(end_seq, sp->end_seq))
4101 sp->end_seq = end_seq;
4102 return true;
4103 }
4104 return false;
4105 }
4106
4107 static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
4108 {
4109 struct tcp_sock *tp = tcp_sk(sk);
4110
4111 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
4112 int mib_idx;
4113
4114 if (before(seq, tp->rcv_nxt))
4115 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
4116 else
4117 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
4118
4119 NET_INC_STATS(sock_net(sk), mib_idx);
4120
4121 tp->rx_opt.dsack = 1;
4122 tp->duplicate_sack[0].start_seq = seq;
4123 tp->duplicate_sack[0].end_seq = end_seq;
4124 }
4125 }
4126
4127 static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
4128 {
4129 struct tcp_sock *tp = tcp_sk(sk);
4130
4131 if (!tp->rx_opt.dsack)
4132 tcp_dsack_set(sk, seq, end_seq);
4133 else
4134 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
4135 }
4136
4137 static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
4138 {
4139 struct tcp_sock *tp = tcp_sk(sk);
4140
4141 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4142 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4143 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4144 tcp_enter_quickack_mode(sk);
4145
4146 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
4147 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4148
4149 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
4150 end_seq = tp->rcv_nxt;
4151 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
4152 }
4153 }
4154
4155 tcp_send_ack(sk);
4156 }
4157
4158 /* These routines update the SACK block as out-of-order packets arrive or
4159 * in-order packets close up the sequence space.
4160 */
4161 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
4162 {
4163 int this_sack;
4164 struct tcp_sack_block *sp = &tp->selective_acks[0];
4165 struct tcp_sack_block *swalk = sp + 1;
4166
4167 /* See if the recent change to the first SACK eats into
4168 * or hits the sequence space of other SACK blocks, if so coalesce.
4169 */
4170 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
4171 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
4172 int i;
4173
4174 /* Zap SWALK, by moving every further SACK up by one slot.
4175 * Decrease num_sacks.
4176 */
4177 tp->rx_opt.num_sacks--;
4178 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
4179 sp[i] = sp[i + 1];
4180 continue;
4181 }
4182 this_sack++, swalk++;
4183 }
4184 }
4185
4186 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
4187 {
4188 struct tcp_sock *tp = tcp_sk(sk);
4189 struct tcp_sack_block *sp = &tp->selective_acks[0];
4190 int cur_sacks = tp->rx_opt.num_sacks;
4191 int this_sack;
4192
4193 if (!cur_sacks)
4194 goto new_sack;
4195
4196 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
4197 if (tcp_sack_extend(sp, seq, end_seq)) {
4198 /* Rotate this_sack to the first one. */
4199 for (; this_sack > 0; this_sack--, sp--)
4200 swap(*sp, *(sp - 1));
4201 if (cur_sacks > 1)
4202 tcp_sack_maybe_coalesce(tp);
4203 return;
4204 }
4205 }
4206
4207 /* Could not find an adjacent existing SACK, build a new one,
4208 * put it at the front, and shift everyone else down. We
4209 * always know there is at least one SACK present already here.
4210 *
4211 * If the sack array is full, forget about the last one.
4212 */
4213 if (this_sack >= TCP_NUM_SACKS) {
4214 this_sack--;
4215 tp->rx_opt.num_sacks--;
4216 sp--;
4217 }
4218 for (; this_sack > 0; this_sack--, sp--)
4219 *sp = *(sp - 1);
4220
4221 new_sack:
4222 /* Build the new head SACK, and we're done. */
4223 sp->start_seq = seq;
4224 sp->end_seq = end_seq;
4225 tp->rx_opt.num_sacks++;
4226 }
4227
4228 /* RCV.NXT advances, some SACKs should be eaten. */
4229
4230 static void tcp_sack_remove(struct tcp_sock *tp)
4231 {
4232 struct tcp_sack_block *sp = &tp->selective_acks[0];
4233 int num_sacks = tp->rx_opt.num_sacks;
4234 int this_sack;
4235
4236 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4237 if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4238 tp->rx_opt.num_sacks = 0;
4239 return;
4240 }
4241
4242 for (this_sack = 0; this_sack < num_sacks;) {
4243 /* Check if the start of the sack is covered by RCV.NXT. */
4244 if (!before(tp->rcv_nxt, sp->start_seq)) {
4245 int i;
4246
4247 /* RCV.NXT must cover all the block! */
4248 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
4249
4250 /* Zap this SACK, by moving forward any other SACKS. */
4251 for (i = this_sack+1; i < num_sacks; i++)
4252 tp->selective_acks[i-1] = tp->selective_acks[i];
4253 num_sacks--;
4254 continue;
4255 }
4256 this_sack++;
4257 sp++;
4258 }
4259 tp->rx_opt.num_sacks = num_sacks;
4260 }
4261
4262 /**
4263 * tcp_try_coalesce - try to merge skb to prior one
4264 * @sk: socket
4265 * @to: prior buffer
4266 * @from: buffer to add in queue
4267 * @fragstolen: pointer to boolean
4268 *
4269 * Before queueing skb @from after @to, try to merge them
4270 * to reduce overall memory use and queue lengths, if cost is small.
4271 * Packets in ofo or receive queues can stay a long time.
4272 * Better try to coalesce them right now to avoid future collapses.
4273 * Returns true if caller should free @from instead of queueing it
4274 */
4275 static bool tcp_try_coalesce(struct sock *sk,
4276 struct sk_buff *to,
4277 struct sk_buff *from,
4278 bool *fragstolen)
4279 {
4280 int delta;
4281
4282 *fragstolen = false;
4283
4284 /* Its possible this segment overlaps with prior segment in queue */
4285 if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
4286 return false;
4287
4288 if (!skb_try_coalesce(to, from, fragstolen, &delta))
4289 return false;
4290
4291 atomic_add(delta, &sk->sk_rmem_alloc);
4292 sk_mem_charge(sk, delta);
4293 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
4294 TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
4295 TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
4296 TCP_SKB_CB(to)->tcp_flags |= TCP_SKB_CB(from)->tcp_flags;
4297 return true;
4298 }
4299
4300 static void tcp_drop(struct sock *sk, struct sk_buff *skb)
4301 {
4302 sk_drops_add(sk, skb);
4303 __kfree_skb(skb);
4304 }
4305
4306 /* This one checks to see if we can put data from the
4307 * out_of_order queue into the receive_queue.
4308 */
4309 static void tcp_ofo_queue(struct sock *sk)
4310 {
4311 struct tcp_sock *tp = tcp_sk(sk);
4312 __u32 dsack_high = tp->rcv_nxt;
4313 bool fin, fragstolen, eaten;
4314 struct sk_buff *skb, *tail;
4315 struct rb_node *p;
4316
4317 p = rb_first(&tp->out_of_order_queue);
4318 while (p) {
4319 skb = rb_entry(p, struct sk_buff, rbnode);
4320 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4321 break;
4322
4323 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4324 __u32 dsack = dsack_high;
4325 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4326 dsack_high = TCP_SKB_CB(skb)->end_seq;
4327 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
4328 }
4329 p = rb_next(p);
4330 rb_erase(&skb->rbnode, &tp->out_of_order_queue);
4331
4332 if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) {
4333 SOCK_DEBUG(sk, "ofo packet was already received\n");
4334 tcp_drop(sk, skb);
4335 continue;
4336 }
4337 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
4338 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4339 TCP_SKB_CB(skb)->end_seq);
4340
4341 tail = skb_peek_tail(&sk->sk_receive_queue);
4342 eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
4343 tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
4344 fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
4345 if (!eaten)
4346 __skb_queue_tail(&sk->sk_receive_queue, skb);
4347 else
4348 kfree_skb_partial(skb, fragstolen);
4349
4350 if (unlikely(fin)) {
4351 tcp_fin(sk);
4352 /* tcp_fin() purges tp->out_of_order_queue,
4353 * so we must end this loop right now.
4354 */
4355 break;
4356 }
4357 }
4358 }
4359
4360 static bool tcp_prune_ofo_queue(struct sock *sk);
4361 static int tcp_prune_queue(struct sock *sk);
4362
4363 static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb,
4364 unsigned int size)
4365 {
4366 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4367 !sk_rmem_schedule(sk, skb, size)) {
4368
4369 if (tcp_prune_queue(sk) < 0)
4370 return -1;
4371
4372 while (!sk_rmem_schedule(sk, skb, size)) {
4373 if (!tcp_prune_ofo_queue(sk))
4374 return -1;
4375 }
4376 }
4377 return 0;
4378 }
4379
4380 static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
4381 {
4382 struct tcp_sock *tp = tcp_sk(sk);
4383 struct rb_node **p, *q, *parent;
4384 struct sk_buff *skb1;
4385 u32 seq, end_seq;
4386 bool fragstolen;
4387
4388 tcp_ecn_check_ce(tp, skb);
4389
4390 if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
4391 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP);
4392 tcp_drop(sk, skb);
4393 return;
4394 }
4395
4396 /* Disable header prediction. */
4397 tp->pred_flags = 0;
4398 inet_csk_schedule_ack(sk);
4399
4400 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
4401 seq = TCP_SKB_CB(skb)->seq;
4402 end_seq = TCP_SKB_CB(skb)->end_seq;
4403 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
4404 tp->rcv_nxt, seq, end_seq);
4405
4406 p = &tp->out_of_order_queue.rb_node;
4407 if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4408 /* Initial out of order segment, build 1 SACK. */
4409 if (tcp_is_sack(tp)) {
4410 tp->rx_opt.num_sacks = 1;
4411 tp->selective_acks[0].start_seq = seq;
4412 tp->selective_acks[0].end_seq = end_seq;
4413 }
4414 rb_link_node(&skb->rbnode, NULL, p);
4415 rb_insert_color(&skb->rbnode, &tp->out_of_order_queue);
4416 tp->ooo_last_skb = skb;
4417 goto end;
4418 }
4419
4420 /* In the typical case, we are adding an skb to the end of the list.
4421 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4422 */
4423 if (tcp_try_coalesce(sk, tp->ooo_last_skb, skb, &fragstolen)) {
4424 coalesce_done:
4425 tcp_grow_window(sk, skb);
4426 kfree_skb_partial(skb, fragstolen);
4427 skb = NULL;
4428 goto add_sack;
4429 }
4430 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4431 if (!before(seq, TCP_SKB_CB(tp->ooo_last_skb)->end_seq)) {
4432 parent = &tp->ooo_last_skb->rbnode;
4433 p = &parent->rb_right;
4434 goto insert;
4435 }
4436
4437 /* Find place to insert this segment. Handle overlaps on the way. */
4438 parent = NULL;
4439 while (*p) {
4440 parent = *p;
4441 skb1 = rb_entry(parent, struct sk_buff, rbnode);
4442 if (before(seq, TCP_SKB_CB(skb1)->seq)) {
4443 p = &parent->rb_left;
4444 continue;
4445 }
4446 if (before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4447 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4448 /* All the bits are present. Drop. */
4449 NET_INC_STATS(sock_net(sk),
4450 LINUX_MIB_TCPOFOMERGE);
4451 __kfree_skb(skb);
4452 skb = NULL;
4453 tcp_dsack_set(sk, seq, end_seq);
4454 goto add_sack;
4455 }
4456 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
4457 /* Partial overlap. */
4458 tcp_dsack_set(sk, seq, TCP_SKB_CB(skb1)->end_seq);
4459 } else {
4460 /* skb's seq == skb1's seq and skb covers skb1.
4461 * Replace skb1 with skb.
4462 */
4463 rb_replace_node(&skb1->rbnode, &skb->rbnode,
4464 &tp->out_of_order_queue);
4465 tcp_dsack_extend(sk,
4466 TCP_SKB_CB(skb1)->seq,
4467 TCP_SKB_CB(skb1)->end_seq);
4468 NET_INC_STATS(sock_net(sk),
4469 LINUX_MIB_TCPOFOMERGE);
4470 __kfree_skb(skb1);
4471 goto merge_right;
4472 }
4473 } else if (tcp_try_coalesce(sk, skb1, skb, &fragstolen)) {
4474 goto coalesce_done;
4475 }
4476 p = &parent->rb_right;
4477 }
4478 insert:
4479 /* Insert segment into RB tree. */
4480 rb_link_node(&skb->rbnode, parent, p);
4481 rb_insert_color(&skb->rbnode, &tp->out_of_order_queue);
4482
4483 merge_right:
4484 /* Remove other segments covered by skb. */
4485 while ((q = rb_next(&skb->rbnode)) != NULL) {
4486 skb1 = rb_entry(q, struct sk_buff, rbnode);
4487
4488 if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
4489 break;
4490 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4491 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4492 end_seq);
4493 break;
4494 }
4495 rb_erase(&skb1->rbnode, &tp->out_of_order_queue);
4496 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4497 TCP_SKB_CB(skb1)->end_seq);
4498 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
4499 tcp_drop(sk, skb1);
4500 }
4501 /* If there is no skb after us, we are the last_skb ! */
4502 if (!q)
4503 tp->ooo_last_skb = skb;
4504
4505 add_sack:
4506 if (tcp_is_sack(tp))
4507 tcp_sack_new_ofo_skb(sk, seq, end_seq);
4508 end:
4509 if (skb) {
4510 tcp_grow_window(sk, skb);
4511 skb_condense(skb);
4512 skb_set_owner_r(skb, sk);
4513 }
4514 }
4515
4516 static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
4517 bool *fragstolen)
4518 {
4519 int eaten;
4520 struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
4521
4522 __skb_pull(skb, hdrlen);
4523 eaten = (tail &&
4524 tcp_try_coalesce(sk, tail, skb, fragstolen)) ? 1 : 0;
4525 tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
4526 if (!eaten) {
4527 __skb_queue_tail(&sk->sk_receive_queue, skb);
4528 skb_set_owner_r(skb, sk);
4529 }
4530 return eaten;
4531 }
4532
4533 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
4534 {
4535 struct sk_buff *skb;
4536 int err = -ENOMEM;
4537 int data_len = 0;
4538 bool fragstolen;
4539
4540 if (size == 0)
4541 return 0;
4542
4543 if (size > PAGE_SIZE) {
4544 int npages = min_t(size_t, size >> PAGE_SHIFT, MAX_SKB_FRAGS);
4545
4546 data_len = npages << PAGE_SHIFT;
4547 size = data_len + (size & ~PAGE_MASK);
4548 }
4549 skb = alloc_skb_with_frags(size - data_len, data_len,
4550 PAGE_ALLOC_COSTLY_ORDER,
4551 &err, sk->sk_allocation);
4552 if (!skb)
4553 goto err;
4554
4555 skb_put(skb, size - data_len);
4556 skb->data_len = data_len;
4557 skb->len = size;
4558
4559 if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
4560 goto err_free;
4561
4562 err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
4563 if (err)
4564 goto err_free;
4565
4566 TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
4567 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
4568 TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
4569
4570 if (tcp_queue_rcv(sk, skb, 0, &fragstolen)) {
4571 WARN_ON_ONCE(fragstolen); /* should not happen */
4572 __kfree_skb(skb);
4573 }
4574 return size;
4575
4576 err_free:
4577 kfree_skb(skb);
4578 err:
4579 return err;
4580
4581 }
4582
4583 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
4584 {
4585 struct tcp_sock *tp = tcp_sk(sk);
4586 bool fragstolen = false;
4587 int eaten = -1;
4588
4589 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
4590 __kfree_skb(skb);
4591 return;
4592 }
4593 skb_dst_drop(skb);
4594 __skb_pull(skb, tcp_hdr(skb)->doff * 4);
4595
4596 tcp_ecn_accept_cwr(tp, skb);
4597
4598 tp->rx_opt.dsack = 0;
4599
4600 /* Queue data for delivery to the user.
4601 * Packets in sequence go to the receive queue.
4602 * Out of sequence packets to the out_of_order_queue.
4603 */
4604 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4605 if (tcp_receive_window(tp) == 0)
4606 goto out_of_window;
4607
4608 /* Ok. In sequence. In window. */
4609 if (tp->ucopy.task == current &&
4610 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
4611 sock_owned_by_user(sk) && !tp->urg_data) {
4612 int chunk = min_t(unsigned int, skb->len,
4613 tp->ucopy.len);
4614
4615 __set_current_state(TASK_RUNNING);
4616
4617 if (!skb_copy_datagram_msg(skb, 0, tp->ucopy.msg, chunk)) {
4618 tp->ucopy.len -= chunk;
4619 tp->copied_seq += chunk;
4620 eaten = (chunk == skb->len);
4621 tcp_rcv_space_adjust(sk);
4622 }
4623 }
4624
4625 if (eaten <= 0) {
4626 queue_and_out:
4627 if (eaten < 0) {
4628 if (skb_queue_len(&sk->sk_receive_queue) == 0)
4629 sk_forced_mem_schedule(sk, skb->truesize);
4630 else if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
4631 goto drop;
4632 }
4633 eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
4634 }
4635 tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
4636 if (skb->len)
4637 tcp_event_data_recv(sk, skb);
4638 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
4639 tcp_fin(sk);
4640
4641 if (!RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4642 tcp_ofo_queue(sk);
4643
4644 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4645 * gap in queue is filled.
4646 */
4647 if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
4648 inet_csk(sk)->icsk_ack.pingpong = 0;
4649 }
4650
4651 if (tp->rx_opt.num_sacks)
4652 tcp_sack_remove(tp);
4653
4654 tcp_fast_path_check(sk);
4655
4656 if (eaten > 0)
4657 kfree_skb_partial(skb, fragstolen);
4658 if (!sock_flag(sk, SOCK_DEAD))
4659 sk->sk_data_ready(sk);
4660 return;
4661 }
4662
4663 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4664 /* A retransmit, 2nd most common case. Force an immediate ack. */
4665 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4666 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4667
4668 out_of_window:
4669 tcp_enter_quickack_mode(sk);
4670 inet_csk_schedule_ack(sk);
4671 drop:
4672 tcp_drop(sk, skb);
4673 return;
4674 }
4675
4676 /* Out of window. F.e. zero window probe. */
4677 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
4678 goto out_of_window;
4679
4680 tcp_enter_quickack_mode(sk);
4681
4682 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4683 /* Partial packet, seq < rcv_next < end_seq */
4684 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
4685 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4686 TCP_SKB_CB(skb)->end_seq);
4687
4688 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
4689
4690 /* If window is closed, drop tail of packet. But after
4691 * remembering D-SACK for its head made in previous line.
4692 */
4693 if (!tcp_receive_window(tp))
4694 goto out_of_window;
4695 goto queue_and_out;
4696 }
4697
4698 tcp_data_queue_ofo(sk, skb);
4699 }
4700
4701 static struct sk_buff *tcp_skb_next(struct sk_buff *skb, struct sk_buff_head *list)
4702 {
4703 if (list)
4704 return !skb_queue_is_last(list, skb) ? skb->next : NULL;
4705
4706 return rb_entry_safe(rb_next(&skb->rbnode), struct sk_buff, rbnode);
4707 }
4708
4709 static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
4710 struct sk_buff_head *list,
4711 struct rb_root *root)
4712 {
4713 struct sk_buff *next = tcp_skb_next(skb, list);
4714
4715 if (list)
4716 __skb_unlink(skb, list);
4717 else
4718 rb_erase(&skb->rbnode, root);
4719
4720 __kfree_skb(skb);
4721 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
4722
4723 return next;
4724 }
4725
4726 /* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
4727 static void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
4728 {
4729 struct rb_node **p = &root->rb_node;
4730 struct rb_node *parent = NULL;
4731 struct sk_buff *skb1;
4732
4733 while (*p) {
4734 parent = *p;
4735 skb1 = rb_entry(parent, struct sk_buff, rbnode);
4736 if (before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb1)->seq))
4737 p = &parent->rb_left;
4738 else
4739 p = &parent->rb_right;
4740 }
4741 rb_link_node(&skb->rbnode, parent, p);
4742 rb_insert_color(&skb->rbnode, root);
4743 }
4744
4745 /* Collapse contiguous sequence of skbs head..tail with
4746 * sequence numbers start..end.
4747 *
4748 * If tail is NULL, this means until the end of the queue.
4749 *
4750 * Segments with FIN/SYN are not collapsed (only because this
4751 * simplifies code)
4752 */
4753 static void
4754 tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root,
4755 struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end)
4756 {
4757 struct sk_buff *skb = head, *n;
4758 struct sk_buff_head tmp;
4759 bool end_of_skbs;
4760
4761 /* First, check that queue is collapsible and find
4762 * the point where collapsing can be useful.
4763 */
4764 restart:
4765 for (end_of_skbs = true; skb != NULL && skb != tail; skb = n) {
4766 n = tcp_skb_next(skb, list);
4767
4768 /* No new bits? It is possible on ofo queue. */
4769 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4770 skb = tcp_collapse_one(sk, skb, list, root);
4771 if (!skb)
4772 break;
4773 goto restart;
4774 }
4775
4776 /* The first skb to collapse is:
4777 * - not SYN/FIN and
4778 * - bloated or contains data before "start" or
4779 * overlaps to the next one.
4780 */
4781 if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) &&
4782 (tcp_win_from_space(skb->truesize) > skb->len ||
4783 before(TCP_SKB_CB(skb)->seq, start))) {
4784 end_of_skbs = false;
4785 break;
4786 }
4787
4788 if (n && n != tail &&
4789 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(n)->seq) {
4790 end_of_skbs = false;
4791 break;
4792 }
4793
4794 /* Decided to skip this, advance start seq. */
4795 start = TCP_SKB_CB(skb)->end_seq;
4796 }
4797 if (end_of_skbs ||
4798 (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
4799 return;
4800
4801 __skb_queue_head_init(&tmp);
4802
4803 while (before(start, end)) {
4804 int copy = min_t(int, SKB_MAX_ORDER(0, 0), end - start);
4805 struct sk_buff *nskb;
4806
4807 nskb = alloc_skb(copy, GFP_ATOMIC);
4808 if (!nskb)
4809 break;
4810
4811 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
4812 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
4813 if (list)
4814 __skb_queue_before(list, skb, nskb);
4815 else
4816 __skb_queue_tail(&tmp, nskb); /* defer rbtree insertion */
4817 skb_set_owner_r(nskb, sk);
4818
4819 /* Copy data, releasing collapsed skbs. */
4820 while (copy > 0) {
4821 int offset = start - TCP_SKB_CB(skb)->seq;
4822 int size = TCP_SKB_CB(skb)->end_seq - start;
4823
4824 BUG_ON(offset < 0);
4825 if (size > 0) {
4826 size = min(copy, size);
4827 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
4828 BUG();
4829 TCP_SKB_CB(nskb)->end_seq += size;
4830 copy -= size;
4831 start += size;
4832 }
4833 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4834 skb = tcp_collapse_one(sk, skb, list, root);
4835 if (!skb ||
4836 skb == tail ||
4837 (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
4838 goto end;
4839 }
4840 }
4841 }
4842 end:
4843 skb_queue_walk_safe(&tmp, skb, n)
4844 tcp_rbtree_insert(root, skb);
4845 }
4846
4847 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4848 * and tcp_collapse() them until all the queue is collapsed.
4849 */
4850 static void tcp_collapse_ofo_queue(struct sock *sk)
4851 {
4852 struct tcp_sock *tp = tcp_sk(sk);
4853 struct sk_buff *skb, *head;
4854 struct rb_node *p;
4855 u32 start, end;
4856
4857 p = rb_first(&tp->out_of_order_queue);
4858 skb = rb_entry_safe(p, struct sk_buff, rbnode);
4859 new_range:
4860 if (!skb) {
4861 p = rb_last(&tp->out_of_order_queue);
4862 /* Note: This is possible p is NULL here. We do not
4863 * use rb_entry_safe(), as ooo_last_skb is valid only
4864 * if rbtree is not empty.
4865 */
4866 tp->ooo_last_skb = rb_entry(p, struct sk_buff, rbnode);
4867 return;
4868 }
4869 start = TCP_SKB_CB(skb)->seq;
4870 end = TCP_SKB_CB(skb)->end_seq;
4871
4872 for (head = skb;;) {
4873 skb = tcp_skb_next(skb, NULL);
4874
4875 /* Range is terminated when we see a gap or when
4876 * we are at the queue end.
4877 */
4878 if (!skb ||
4879 after(TCP_SKB_CB(skb)->seq, end) ||
4880 before(TCP_SKB_CB(skb)->end_seq, start)) {
4881 tcp_collapse(sk, NULL, &tp->out_of_order_queue,
4882 head, skb, start, end);
4883 goto new_range;
4884 }
4885
4886 if (unlikely(before(TCP_SKB_CB(skb)->seq, start)))
4887 start = TCP_SKB_CB(skb)->seq;
4888 if (after(TCP_SKB_CB(skb)->end_seq, end))
4889 end = TCP_SKB_CB(skb)->end_seq;
4890 }
4891 }
4892
4893 /*
4894 * Clean the out-of-order queue to make room.
4895 * We drop high sequences packets to :
4896 * 1) Let a chance for holes to be filled.
4897 * 2) not add too big latencies if thousands of packets sit there.
4898 * (But if application shrinks SO_RCVBUF, we could still end up
4899 * freeing whole queue here)
4900 *
4901 * Return true if queue has shrunk.
4902 */
4903 static bool tcp_prune_ofo_queue(struct sock *sk)
4904 {
4905 struct tcp_sock *tp = tcp_sk(sk);
4906 struct rb_node *node, *prev;
4907
4908 if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
4909 return false;
4910
4911 NET_INC_STATS(sock_net(sk), LINUX_MIB_OFOPRUNED);
4912 node = &tp->ooo_last_skb->rbnode;
4913 do {
4914 prev = rb_prev(node);
4915 rb_erase(node, &tp->out_of_order_queue);
4916 tcp_drop(sk, rb_entry(node, struct sk_buff, rbnode));
4917 sk_mem_reclaim(sk);
4918 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
4919 !tcp_under_memory_pressure(sk))
4920 break;
4921 node = prev;
4922 } while (node);
4923 tp->ooo_last_skb = rb_entry(prev, struct sk_buff, rbnode);
4924
4925 /* Reset SACK state. A conforming SACK implementation will
4926 * do the same at a timeout based retransmit. When a connection
4927 * is in a sad state like this, we care only about integrity
4928 * of the connection not performance.
4929 */
4930 if (tp->rx_opt.sack_ok)
4931 tcp_sack_reset(&tp->rx_opt);
4932 return true;
4933 }
4934
4935 /* Reduce allocated memory if we can, trying to get
4936 * the socket within its memory limits again.
4937 *
4938 * Return less than zero if we should start dropping frames
4939 * until the socket owning process reads some of the data
4940 * to stabilize the situation.
4941 */
4942 static int tcp_prune_queue(struct sock *sk)
4943 {
4944 struct tcp_sock *tp = tcp_sk(sk);
4945
4946 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
4947
4948 NET_INC_STATS(sock_net(sk), LINUX_MIB_PRUNECALLED);
4949
4950 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
4951 tcp_clamp_window(sk);
4952 else if (tcp_under_memory_pressure(sk))
4953 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
4954
4955 tcp_collapse_ofo_queue(sk);
4956 if (!skb_queue_empty(&sk->sk_receive_queue))
4957 tcp_collapse(sk, &sk->sk_receive_queue, NULL,
4958 skb_peek(&sk->sk_receive_queue),
4959 NULL,
4960 tp->copied_seq, tp->rcv_nxt);
4961 sk_mem_reclaim(sk);
4962
4963 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4964 return 0;
4965
4966 /* Collapsing did not help, destructive actions follow.
4967 * This must not ever occur. */
4968
4969 tcp_prune_ofo_queue(sk);
4970
4971 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4972 return 0;
4973
4974 /* If we are really being abused, tell the caller to silently
4975 * drop receive data on the floor. It will get retransmitted
4976 * and hopefully then we'll have sufficient space.
4977 */
4978 NET_INC_STATS(sock_net(sk), LINUX_MIB_RCVPRUNED);
4979
4980 /* Massive buffer overcommit. */
4981 tp->pred_flags = 0;
4982 return -1;
4983 }
4984
4985 static bool tcp_should_expand_sndbuf(const struct sock *sk)
4986 {
4987 const struct tcp_sock *tp = tcp_sk(sk);
4988
4989 /* If the user specified a specific send buffer setting, do
4990 * not modify it.
4991 */
4992 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
4993 return false;
4994
4995 /* If we are under global TCP memory pressure, do not expand. */
4996 if (tcp_under_memory_pressure(sk))
4997 return false;
4998
4999 /* If we are under soft global TCP memory pressure, do not expand. */
5000 if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0))
5001 return false;
5002
5003 /* If we filled the congestion window, do not expand. */
5004 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
5005 return false;
5006
5007 return true;
5008 }
5009
5010 /* When incoming ACK allowed to free some skb from write_queue,
5011 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
5012 * on the exit from tcp input handler.
5013 *
5014 * PROBLEM: sndbuf expansion does not work well with largesend.
5015 */
5016 static void tcp_new_space(struct sock *sk)
5017 {
5018 struct tcp_sock *tp = tcp_sk(sk);
5019
5020 if (tcp_should_expand_sndbuf(sk)) {
5021 tcp_sndbuf_expand(sk);
5022 tp->snd_cwnd_stamp = tcp_time_stamp;
5023 }
5024
5025 sk->sk_write_space(sk);
5026 }
5027
5028 static void tcp_check_space(struct sock *sk)
5029 {
5030 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
5031 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
5032 /* pairs with tcp_poll() */
5033 smp_mb();
5034 if (sk->sk_socket &&
5035 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
5036 tcp_new_space(sk);
5037 if (!test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
5038 tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
5039 }
5040 }
5041 }
5042
5043 static inline void tcp_data_snd_check(struct sock *sk)
5044 {
5045 tcp_push_pending_frames(sk);
5046 tcp_check_space(sk);
5047 }
5048
5049 /*
5050 * Check if sending an ack is needed.
5051 */
5052 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
5053 {
5054 struct tcp_sock *tp = tcp_sk(sk);
5055
5056 /* More than one full frame received... */
5057 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
5058 /* ... and right edge of window advances far enough.
5059 * (tcp_recvmsg() will send ACK otherwise). Or...
5060 */
5061 __tcp_select_window(sk) >= tp->rcv_wnd) ||
5062 /* We ACK each frame or... */
5063 tcp_in_quickack_mode(sk) ||
5064 /* We have out of order data. */
5065 (ofo_possible && !RB_EMPTY_ROOT(&tp->out_of_order_queue))) {
5066 /* Then ack it now */
5067 tcp_send_ack(sk);
5068 } else {
5069 /* Else, send delayed ack. */
5070 tcp_send_delayed_ack(sk);
5071 }
5072 }
5073
5074 static inline void tcp_ack_snd_check(struct sock *sk)
5075 {
5076 if (!inet_csk_ack_scheduled(sk)) {
5077 /* We sent a data segment already. */
5078 return;
5079 }
5080 __tcp_ack_snd_check(sk, 1);
5081 }
5082
5083 /*
5084 * This routine is only called when we have urgent data
5085 * signaled. Its the 'slow' part of tcp_urg. It could be
5086 * moved inline now as tcp_urg is only called from one
5087 * place. We handle URGent data wrong. We have to - as
5088 * BSD still doesn't use the correction from RFC961.
5089 * For 1003.1g we should support a new option TCP_STDURG to permit
5090 * either form (or just set the sysctl tcp_stdurg).
5091 */
5092
5093 static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
5094 {
5095 struct tcp_sock *tp = tcp_sk(sk);
5096 u32 ptr = ntohs(th->urg_ptr);
5097
5098 if (ptr && !sysctl_tcp_stdurg)
5099 ptr--;
5100 ptr += ntohl(th->seq);
5101
5102 /* Ignore urgent data that we've already seen and read. */
5103 if (after(tp->copied_seq, ptr))
5104 return;
5105
5106 /* Do not replay urg ptr.
5107 *
5108 * NOTE: interesting situation not covered by specs.
5109 * Misbehaving sender may send urg ptr, pointing to segment,
5110 * which we already have in ofo queue. We are not able to fetch
5111 * such data and will stay in TCP_URG_NOTYET until will be eaten
5112 * by recvmsg(). Seems, we are not obliged to handle such wicked
5113 * situations. But it is worth to think about possibility of some
5114 * DoSes using some hypothetical application level deadlock.
5115 */
5116 if (before(ptr, tp->rcv_nxt))
5117 return;
5118
5119 /* Do we already have a newer (or duplicate) urgent pointer? */
5120 if (tp->urg_data && !after(ptr, tp->urg_seq))
5121 return;
5122
5123 /* Tell the world about our new urgent pointer. */
5124 sk_send_sigurg(sk);
5125
5126 /* We may be adding urgent data when the last byte read was
5127 * urgent. To do this requires some care. We cannot just ignore
5128 * tp->copied_seq since we would read the last urgent byte again
5129 * as data, nor can we alter copied_seq until this data arrives
5130 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5131 *
5132 * NOTE. Double Dutch. Rendering to plain English: author of comment
5133 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5134 * and expect that both A and B disappear from stream. This is _wrong_.
5135 * Though this happens in BSD with high probability, this is occasional.
5136 * Any application relying on this is buggy. Note also, that fix "works"
5137 * only in this artificial test. Insert some normal data between A and B and we will
5138 * decline of BSD again. Verdict: it is better to remove to trap
5139 * buggy users.
5140 */
5141 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
5142 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
5143 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
5144 tp->copied_seq++;
5145 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
5146 __skb_unlink(skb, &sk->sk_receive_queue);
5147 __kfree_skb(skb);
5148 }
5149 }
5150
5151 tp->urg_data = TCP_URG_NOTYET;
5152 tp->urg_seq = ptr;
5153
5154 /* Disable header prediction. */
5155 tp->pred_flags = 0;
5156 }
5157
5158 /* This is the 'fast' part of urgent handling. */
5159 static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th)
5160 {
5161 struct tcp_sock *tp = tcp_sk(sk);
5162
5163 /* Check if we get a new urgent pointer - normally not. */
5164 if (th->urg)
5165 tcp_check_urg(sk, th);
5166
5167 /* Do we wait for any urgent data? - normally not... */
5168 if (tp->urg_data == TCP_URG_NOTYET) {
5169 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
5170 th->syn;
5171
5172 /* Is the urgent pointer pointing into this packet? */
5173 if (ptr < skb->len) {
5174 u8 tmp;
5175 if (skb_copy_bits(skb, ptr, &tmp, 1))
5176 BUG();
5177 tp->urg_data = TCP_URG_VALID | tmp;
5178 if (!sock_flag(sk, SOCK_DEAD))
5179 sk->sk_data_ready(sk);
5180 }
5181 }
5182 }
5183
5184 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
5185 {
5186 struct tcp_sock *tp = tcp_sk(sk);
5187 int chunk = skb->len - hlen;
5188 int err;
5189
5190 if (skb_csum_unnecessary(skb))
5191 err = skb_copy_datagram_msg(skb, hlen, tp->ucopy.msg, chunk);
5192 else
5193 err = skb_copy_and_csum_datagram_msg(skb, hlen, tp->ucopy.msg);
5194
5195 if (!err) {
5196 tp->ucopy.len -= chunk;
5197 tp->copied_seq += chunk;
5198 tcp_rcv_space_adjust(sk);
5199 }
5200
5201 return err;
5202 }
5203
5204 /* Accept RST for rcv_nxt - 1 after a FIN.
5205 * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
5206 * FIN is sent followed by a RST packet. The RST is sent with the same
5207 * sequence number as the FIN, and thus according to RFC 5961 a challenge
5208 * ACK should be sent. However, Mac OSX rate limits replies to challenge
5209 * ACKs on the closed socket. In addition middleboxes can drop either the
5210 * challenge ACK or a subsequent RST.
5211 */
5212 static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb)
5213 {
5214 struct tcp_sock *tp = tcp_sk(sk);
5215
5216 return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) &&
5217 (1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK |
5218 TCPF_CLOSING));
5219 }
5220
5221 /* Does PAWS and seqno based validation of an incoming segment, flags will
5222 * play significant role here.
5223 */
5224 static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5225 const struct tcphdr *th, int syn_inerr)
5226 {
5227 struct tcp_sock *tp = tcp_sk(sk);
5228 bool rst_seq_match = false;
5229
5230 /* RFC1323: H1. Apply PAWS check first. */
5231 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
5232 tcp_paws_discard(sk, skb)) {
5233 if (!th->rst) {
5234 NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5235 if (!tcp_oow_rate_limited(sock_net(sk), skb,
5236 LINUX_MIB_TCPACKSKIPPEDPAWS,
5237 &tp->last_oow_ack_time))
5238 tcp_send_dupack(sk, skb);
5239 goto discard;
5240 }
5241 /* Reset is accepted even if it did not pass PAWS. */
5242 }
5243
5244 /* Step 1: check sequence number */
5245 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
5246 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5247 * (RST) segments are validated by checking their SEQ-fields."
5248 * And page 69: "If an incoming segment is not acceptable,
5249 * an acknowledgment should be sent in reply (unless the RST
5250 * bit is set, if so drop the segment and return)".
5251 */
5252 if (!th->rst) {
5253 if (th->syn)
5254 goto syn_challenge;
5255 if (!tcp_oow_rate_limited(sock_net(sk), skb,
5256 LINUX_MIB_TCPACKSKIPPEDSEQ,
5257 &tp->last_oow_ack_time))
5258 tcp_send_dupack(sk, skb);
5259 } else if (tcp_reset_check(sk, skb)) {
5260 tcp_reset(sk);
5261 }
5262 goto discard;
5263 }
5264
5265 /* Step 2: check RST bit */
5266 if (th->rst) {
5267 /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
5268 * FIN and SACK too if available):
5269 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
5270 * the right-most SACK block,
5271 * then
5272 * RESET the connection
5273 * else
5274 * Send a challenge ACK
5275 */
5276 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt ||
5277 tcp_reset_check(sk, skb)) {
5278 rst_seq_match = true;
5279 } else if (tcp_is_sack(tp) && tp->rx_opt.num_sacks > 0) {
5280 struct tcp_sack_block *sp = &tp->selective_acks[0];
5281 int max_sack = sp[0].end_seq;
5282 int this_sack;
5283
5284 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;
5285 ++this_sack) {
5286 max_sack = after(sp[this_sack].end_seq,
5287 max_sack) ?
5288 sp[this_sack].end_seq : max_sack;
5289 }
5290
5291 if (TCP_SKB_CB(skb)->seq == max_sack)
5292 rst_seq_match = true;
5293 }
5294
5295 if (rst_seq_match)
5296 tcp_reset(sk);
5297 else
5298 tcp_send_challenge_ack(sk, skb);
5299 goto discard;
5300 }
5301
5302 /* step 3: check security and precedence [ignored] */
5303
5304 /* step 4: Check for a SYN
5305 * RFC 5961 4.2 : Send a challenge ack
5306 */
5307 if (th->syn) {
5308 syn_challenge:
5309 if (syn_inerr)
5310 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5311 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
5312 tcp_send_challenge_ack(sk, skb);
5313 goto discard;
5314 }
5315
5316 return true;
5317
5318 discard:
5319 tcp_drop(sk, skb);
5320 return false;
5321 }
5322
5323 /*
5324 * TCP receive function for the ESTABLISHED state.
5325 *
5326 * It is split into a fast path and a slow path. The fast path is
5327 * disabled when:
5328 * - A zero window was announced from us - zero window probing
5329 * is only handled properly in the slow path.
5330 * - Out of order segments arrived.
5331 * - Urgent data is expected.
5332 * - There is no buffer space left
5333 * - Unexpected TCP flags/window values/header lengths are received
5334 * (detected by checking the TCP header against pred_flags)
5335 * - Data is sent in both directions. Fast path only supports pure senders
5336 * or pure receivers (this means either the sequence number or the ack
5337 * value must stay constant)
5338 * - Unexpected TCP option.
5339 *
5340 * When these conditions are not satisfied it drops into a standard
5341 * receive procedure patterned after RFC793 to handle all cases.
5342 * The first three cases are guaranteed by proper pred_flags setting,
5343 * the rest is checked inline. Fast processing is turned on in
5344 * tcp_data_queue when everything is OK.
5345 */
5346 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
5347 const struct tcphdr *th, unsigned int len)
5348 {
5349 struct tcp_sock *tp = tcp_sk(sk);
5350
5351 if (unlikely(!sk->sk_rx_dst))
5352 inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
5353 /*
5354 * Header prediction.
5355 * The code loosely follows the one in the famous
5356 * "30 instruction TCP receive" Van Jacobson mail.
5357 *
5358 * Van's trick is to deposit buffers into socket queue
5359 * on a device interrupt, to call tcp_recv function
5360 * on the receive process context and checksum and copy
5361 * the buffer to user space. smart...
5362 *
5363 * Our current scheme is not silly either but we take the
5364 * extra cost of the net_bh soft interrupt processing...
5365 * We do checksum and copy also but from device to kernel.
5366 */
5367
5368 tp->rx_opt.saw_tstamp = 0;
5369
5370 /* pred_flags is 0xS?10 << 16 + snd_wnd
5371 * if header_prediction is to be made
5372 * 'S' will always be tp->tcp_header_len >> 2
5373 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5374 * turn it off (when there are holes in the receive
5375 * space for instance)
5376 * PSH flag is ignored.
5377 */
5378
5379 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
5380 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
5381 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
5382 int tcp_header_len = tp->tcp_header_len;
5383
5384 /* Timestamp header prediction: tcp_header_len
5385 * is automatically equal to th->doff*4 due to pred_flags
5386 * match.
5387 */
5388
5389 /* Check timestamp */
5390 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
5391 /* No? Slow path! */
5392 if (!tcp_parse_aligned_timestamp(tp, th))
5393 goto slow_path;
5394
5395 /* If PAWS failed, check it more carefully in slow path */
5396 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
5397 goto slow_path;
5398
5399 /* DO NOT update ts_recent here, if checksum fails
5400 * and timestamp was corrupted part, it will result
5401 * in a hung connection since we will drop all
5402 * future packets due to the PAWS test.
5403 */
5404 }
5405
5406 if (len <= tcp_header_len) {
5407 /* Bulk data transfer: sender */
5408 if (len == tcp_header_len) {
5409 /* Predicted packet is in window by definition.
5410 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5411 * Hence, check seq<=rcv_wup reduces to:
5412 */
5413 if (tcp_header_len ==
5414 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5415 tp->rcv_nxt == tp->rcv_wup)
5416 tcp_store_ts_recent(tp);
5417
5418 /* We know that such packets are checksummed
5419 * on entry.
5420 */
5421 tcp_ack(sk, skb, 0);
5422 __kfree_skb(skb);
5423 tcp_data_snd_check(sk);
5424 return;
5425 } else { /* Header too small */
5426 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5427 goto discard;
5428 }
5429 } else {
5430 int eaten = 0;
5431 bool fragstolen = false;
5432
5433 if (tp->ucopy.task == current &&
5434 tp->copied_seq == tp->rcv_nxt &&
5435 len - tcp_header_len <= tp->ucopy.len &&
5436 sock_owned_by_user(sk)) {
5437 __set_current_state(TASK_RUNNING);
5438
5439 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
5440 /* Predicted packet is in window by definition.
5441 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5442 * Hence, check seq<=rcv_wup reduces to:
5443 */
5444 if (tcp_header_len ==
5445 (sizeof(struct tcphdr) +
5446 TCPOLEN_TSTAMP_ALIGNED) &&
5447 tp->rcv_nxt == tp->rcv_wup)
5448 tcp_store_ts_recent(tp);
5449
5450 tcp_rcv_rtt_measure_ts(sk, skb);
5451
5452 __skb_pull(skb, tcp_header_len);
5453 tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
5454 NET_INC_STATS(sock_net(sk),
5455 LINUX_MIB_TCPHPHITSTOUSER);
5456 eaten = 1;
5457 }
5458 }
5459 if (!eaten) {
5460 if (tcp_checksum_complete(skb))
5461 goto csum_error;
5462
5463 if ((int)skb->truesize > sk->sk_forward_alloc)
5464 goto step5;
5465
5466 /* Predicted packet is in window by definition.
5467 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5468 * Hence, check seq<=rcv_wup reduces to:
5469 */
5470 if (tcp_header_len ==
5471 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5472 tp->rcv_nxt == tp->rcv_wup)
5473 tcp_store_ts_recent(tp);
5474
5475 tcp_rcv_rtt_measure_ts(sk, skb);
5476
5477 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS);
5478
5479 /* Bulk data transfer: receiver */
5480 eaten = tcp_queue_rcv(sk, skb, tcp_header_len,
5481 &fragstolen);
5482 }
5483
5484 tcp_event_data_recv(sk, skb);
5485
5486 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
5487 /* Well, only one small jumplet in fast path... */
5488 tcp_ack(sk, skb, FLAG_DATA);
5489 tcp_data_snd_check(sk);
5490 if (!inet_csk_ack_scheduled(sk))
5491 goto no_ack;
5492 }
5493
5494 __tcp_ack_snd_check(sk, 0);
5495 no_ack:
5496 if (eaten)
5497 kfree_skb_partial(skb, fragstolen);
5498 sk->sk_data_ready(sk);
5499 return;
5500 }
5501 }
5502
5503 slow_path:
5504 if (len < (th->doff << 2) || tcp_checksum_complete(skb))
5505 goto csum_error;
5506
5507 if (!th->ack && !th->rst && !th->syn)
5508 goto discard;
5509
5510 /*
5511 * Standard slow path.
5512 */
5513
5514 if (!tcp_validate_incoming(sk, skb, th, 1))
5515 return;
5516
5517 step5:
5518 if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0)
5519 goto discard;
5520
5521 tcp_rcv_rtt_measure_ts(sk, skb);
5522
5523 /* Process urgent data. */
5524 tcp_urg(sk, skb, th);
5525
5526 /* step 7: process the segment text */
5527 tcp_data_queue(sk, skb);
5528
5529 tcp_data_snd_check(sk);
5530 tcp_ack_snd_check(sk);
5531 return;
5532
5533 csum_error:
5534 TCP_INC_STATS(sock_net(sk), TCP_MIB_CSUMERRORS);
5535 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5536
5537 discard:
5538 tcp_drop(sk, skb);
5539 }
5540 EXPORT_SYMBOL(tcp_rcv_established);
5541
5542 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
5543 {
5544 struct tcp_sock *tp = tcp_sk(sk);
5545 struct inet_connection_sock *icsk = inet_csk(sk);
5546
5547 tcp_set_state(sk, TCP_ESTABLISHED);
5548 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
5549
5550 if (skb) {
5551 icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
5552 security_inet_conn_established(sk, skb);
5553 }
5554
5555 /* Make sure socket is routed, for correct metrics. */
5556 icsk->icsk_af_ops->rebuild_header(sk);
5557
5558 tcp_init_metrics(sk);
5559
5560 tcp_init_congestion_control(sk);
5561
5562 /* Prevent spurious tcp_cwnd_restart() on first data
5563 * packet.
5564 */
5565 tp->lsndtime = tcp_time_stamp;
5566
5567 tcp_init_buffer_space(sk);
5568
5569 if (sock_flag(sk, SOCK_KEEPOPEN))
5570 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
5571
5572 if (!tp->rx_opt.snd_wscale)
5573 __tcp_fast_path_on(tp, tp->snd_wnd);
5574 else
5575 tp->pred_flags = 0;
5576
5577 if (!sock_flag(sk, SOCK_DEAD)) {
5578 sk->sk_state_change(sk);
5579 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5580 }
5581 }
5582
5583 static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
5584 struct tcp_fastopen_cookie *cookie)
5585 {
5586 struct tcp_sock *tp = tcp_sk(sk);
5587 struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL;
5588 u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
5589 bool syn_drop = false;
5590
5591 if (mss == tp->rx_opt.user_mss) {
5592 struct tcp_options_received opt;
5593
5594 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5595 tcp_clear_options(&opt);
5596 opt.user_mss = opt.mss_clamp = 0;
5597 tcp_parse_options(synack, &opt, 0, NULL);
5598 mss = opt.mss_clamp;
5599 }
5600
5601 if (!tp->syn_fastopen) {
5602 /* Ignore an unsolicited cookie */
5603 cookie->len = -1;
5604 } else if (tp->total_retrans) {
5605 /* SYN timed out and the SYN-ACK neither has a cookie nor
5606 * acknowledges data. Presumably the remote received only
5607 * the retransmitted (regular) SYNs: either the original
5608 * SYN-data or the corresponding SYN-ACK was dropped.
5609 */
5610 syn_drop = (cookie->len < 0 && data);
5611 } else if (cookie->len < 0 && !tp->syn_data) {
5612 /* We requested a cookie but didn't get it. If we did not use
5613 * the (old) exp opt format then try so next time (try_exp=1).
5614 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5615 */
5616 try_exp = tp->syn_fastopen_exp ? 2 : 1;
5617 }
5618
5619 tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
5620
5621 if (data) { /* Retransmit unacked data in SYN */
5622 tcp_for_write_queue_from(data, sk) {
5623 if (data == tcp_send_head(sk) ||
5624 __tcp_retransmit_skb(sk, data, 1))
5625 break;
5626 }
5627 tcp_rearm_rto(sk);
5628 NET_INC_STATS(sock_net(sk),
5629 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
5630 return true;
5631 }
5632 tp->syn_data_acked = tp->syn_data;
5633 if (tp->syn_data_acked)
5634 NET_INC_STATS(sock_net(sk),
5635 LINUX_MIB_TCPFASTOPENACTIVE);
5636
5637 tcp_fastopen_add_skb(sk, synack);
5638
5639 return false;
5640 }
5641
5642 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
5643 const struct tcphdr *th)
5644 {
5645 struct inet_connection_sock *icsk = inet_csk(sk);
5646 struct tcp_sock *tp = tcp_sk(sk);
5647 struct tcp_fastopen_cookie foc = { .len = -1 };
5648 int saved_clamp = tp->rx_opt.mss_clamp;
5649
5650 tcp_parse_options(skb, &tp->rx_opt, 0, &foc);
5651 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
5652 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
5653
5654 if (th->ack) {
5655 /* rfc793:
5656 * "If the state is SYN-SENT then
5657 * first check the ACK bit
5658 * If the ACK bit is set
5659 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5660 * a reset (unless the RST bit is set, if so drop
5661 * the segment and return)"
5662 */
5663 if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
5664 after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
5665 goto reset_and_undo;
5666
5667 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5668 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
5669 tcp_time_stamp)) {
5670 NET_INC_STATS(sock_net(sk),
5671 LINUX_MIB_PAWSACTIVEREJECTED);
5672 goto reset_and_undo;
5673 }
5674
5675 /* Now ACK is acceptable.
5676 *
5677 * "If the RST bit is set
5678 * If the ACK was acceptable then signal the user "error:
5679 * connection reset", drop the segment, enter CLOSED state,
5680 * delete TCB, and return."
5681 */
5682
5683 if (th->rst) {
5684 tcp_reset(sk);
5685 goto discard;
5686 }
5687
5688 /* rfc793:
5689 * "fifth, if neither of the SYN or RST bits is set then
5690 * drop the segment and return."
5691 *
5692 * See note below!
5693 * --ANK(990513)
5694 */
5695 if (!th->syn)
5696 goto discard_and_undo;
5697
5698 /* rfc793:
5699 * "If the SYN bit is on ...
5700 * are acceptable then ...
5701 * (our SYN has been ACKed), change the connection
5702 * state to ESTABLISHED..."
5703 */
5704
5705 tcp_ecn_rcv_synack(tp, th);
5706
5707 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5708 tcp_ack(sk, skb, FLAG_SLOWPATH);
5709
5710 /* Ok.. it's good. Set up sequence numbers and
5711 * move to established.
5712 */
5713 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5714 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5715
5716 /* RFC1323: The window in SYN & SYN/ACK segments is
5717 * never scaled.
5718 */
5719 tp->snd_wnd = ntohs(th->window);
5720
5721 if (!tp->rx_opt.wscale_ok) {
5722 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
5723 tp->window_clamp = min(tp->window_clamp, 65535U);
5724 }
5725
5726 if (tp->rx_opt.saw_tstamp) {
5727 tp->rx_opt.tstamp_ok = 1;
5728 tp->tcp_header_len =
5729 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5730 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5731 tcp_store_ts_recent(tp);
5732 } else {
5733 tp->tcp_header_len = sizeof(struct tcphdr);
5734 }
5735
5736 if (tcp_is_sack(tp) && sysctl_tcp_fack)
5737 tcp_enable_fack(tp);
5738
5739 tcp_mtup_init(sk);
5740 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5741 tcp_initialize_rcv_mss(sk);
5742
5743 /* Remember, tcp_poll() does not lock socket!
5744 * Change state from SYN-SENT only after copied_seq
5745 * is initialized. */
5746 tp->copied_seq = tp->rcv_nxt;
5747
5748 smp_mb();
5749
5750 tcp_finish_connect(sk, skb);
5751
5752 if ((tp->syn_fastopen || tp->syn_data) &&
5753 tcp_rcv_fastopen_synack(sk, skb, &foc))
5754 return -1;
5755
5756 if (sk->sk_write_pending ||
5757 icsk->icsk_accept_queue.rskq_defer_accept ||
5758 icsk->icsk_ack.pingpong) {
5759 /* Save one ACK. Data will be ready after
5760 * several ticks, if write_pending is set.
5761 *
5762 * It may be deleted, but with this feature tcpdumps
5763 * look so _wonderfully_ clever, that I was not able
5764 * to stand against the temptation 8) --ANK
5765 */
5766 inet_csk_schedule_ack(sk);
5767 tcp_enter_quickack_mode(sk);
5768 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
5769 TCP_DELACK_MAX, TCP_RTO_MAX);
5770
5771 discard:
5772 tcp_drop(sk, skb);
5773 return 0;
5774 } else {
5775 tcp_send_ack(sk);
5776 }
5777 return -1;
5778 }
5779
5780 /* No ACK in the segment */
5781
5782 if (th->rst) {
5783 /* rfc793:
5784 * "If the RST bit is set
5785 *
5786 * Otherwise (no ACK) drop the segment and return."
5787 */
5788
5789 goto discard_and_undo;
5790 }
5791
5792 /* PAWS check. */
5793 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
5794 tcp_paws_reject(&tp->rx_opt, 0))
5795 goto discard_and_undo;
5796
5797 if (th->syn) {
5798 /* We see SYN without ACK. It is attempt of
5799 * simultaneous connect with crossed SYNs.
5800 * Particularly, it can be connect to self.
5801 */
5802 tcp_set_state(sk, TCP_SYN_RECV);
5803
5804 if (tp->rx_opt.saw_tstamp) {
5805 tp->rx_opt.tstamp_ok = 1;
5806 tcp_store_ts_recent(tp);
5807 tp->tcp_header_len =
5808 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5809 } else {
5810 tp->tcp_header_len = sizeof(struct tcphdr);
5811 }
5812
5813 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5814 tp->copied_seq = tp->rcv_nxt;
5815 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5816
5817 /* RFC1323: The window in SYN & SYN/ACK segments is
5818 * never scaled.
5819 */
5820 tp->snd_wnd = ntohs(th->window);
5821 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5822 tp->max_window = tp->snd_wnd;
5823
5824 tcp_ecn_rcv_syn(tp, th);
5825
5826 tcp_mtup_init(sk);
5827 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5828 tcp_initialize_rcv_mss(sk);
5829
5830 tcp_send_synack(sk);
5831 #if 0
5832 /* Note, we could accept data and URG from this segment.
5833 * There are no obstacles to make this (except that we must
5834 * either change tcp_recvmsg() to prevent it from returning data
5835 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5836 *
5837 * However, if we ignore data in ACKless segments sometimes,
5838 * we have no reasons to accept it sometimes.
5839 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5840 * is not flawless. So, discard packet for sanity.
5841 * Uncomment this return to process the data.
5842 */
5843 return -1;
5844 #else
5845 goto discard;
5846 #endif
5847 }
5848 /* "fifth, if neither of the SYN or RST bits is set then
5849 * drop the segment and return."
5850 */
5851
5852 discard_and_undo:
5853 tcp_clear_options(&tp->rx_opt);
5854 tp->rx_opt.mss_clamp = saved_clamp;
5855 goto discard;
5856
5857 reset_and_undo:
5858 tcp_clear_options(&tp->rx_opt);
5859 tp->rx_opt.mss_clamp = saved_clamp;
5860 return 1;
5861 }
5862
5863 /*
5864 * This function implements the receiving procedure of RFC 793 for
5865 * all states except ESTABLISHED and TIME_WAIT.
5866 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5867 * address independent.
5868 */
5869
5870 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
5871 {
5872 struct tcp_sock *tp = tcp_sk(sk);
5873 struct inet_connection_sock *icsk = inet_csk(sk);
5874 const struct tcphdr *th = tcp_hdr(skb);
5875 struct request_sock *req;
5876 int queued = 0;
5877 bool acceptable;
5878
5879 switch (sk->sk_state) {
5880 case TCP_CLOSE:
5881 goto discard;
5882
5883 case TCP_LISTEN:
5884 if (th->ack)
5885 return 1;
5886
5887 if (th->rst)
5888 goto discard;
5889
5890 if (th->syn) {
5891 if (th->fin)
5892 goto discard;
5893 /* It is possible that we process SYN packets from backlog,
5894 * so we need to make sure to disable BH right there.
5895 */
5896 local_bh_disable();
5897 acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0;
5898 local_bh_enable();
5899
5900 if (!acceptable)
5901 return 1;
5902 consume_skb(skb);
5903 return 0;
5904 }
5905 goto discard;
5906
5907 case TCP_SYN_SENT:
5908 tp->rx_opt.saw_tstamp = 0;
5909 queued = tcp_rcv_synsent_state_process(sk, skb, th);
5910 if (queued >= 0)
5911 return queued;
5912
5913 /* Do step6 onward by hand. */
5914 tcp_urg(sk, skb, th);
5915 __kfree_skb(skb);
5916 tcp_data_snd_check(sk);
5917 return 0;
5918 }
5919
5920 tp->rx_opt.saw_tstamp = 0;
5921 req = tp->fastopen_rsk;
5922 if (req) {
5923 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
5924 sk->sk_state != TCP_FIN_WAIT1);
5925
5926 if (!tcp_check_req(sk, skb, req, true))
5927 goto discard;
5928 }
5929
5930 if (!th->ack && !th->rst && !th->syn)
5931 goto discard;
5932
5933 if (!tcp_validate_incoming(sk, skb, th, 0))
5934 return 0;
5935
5936 /* step 5: check the ACK field */
5937 acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
5938 FLAG_UPDATE_TS_RECENT) > 0;
5939
5940 switch (sk->sk_state) {
5941 case TCP_SYN_RECV:
5942 if (!acceptable)
5943 return 1;
5944
5945 if (!tp->srtt_us)
5946 tcp_synack_rtt_meas(sk, req);
5947
5948 /* Once we leave TCP_SYN_RECV, we no longer need req
5949 * so release it.
5950 */
5951 if (req) {
5952 inet_csk(sk)->icsk_retransmits = 0;
5953 reqsk_fastopen_remove(sk, req, false);
5954 } else {
5955 /* Make sure socket is routed, for correct metrics. */
5956 icsk->icsk_af_ops->rebuild_header(sk);
5957 tcp_init_congestion_control(sk);
5958
5959 tcp_mtup_init(sk);
5960 tp->copied_seq = tp->rcv_nxt;
5961 tcp_init_buffer_space(sk);
5962 }
5963 smp_mb();
5964 tcp_set_state(sk, TCP_ESTABLISHED);
5965 sk->sk_state_change(sk);
5966
5967 /* Note, that this wakeup is only for marginal crossed SYN case.
5968 * Passively open sockets are not waked up, because
5969 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5970 */
5971 if (sk->sk_socket)
5972 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5973
5974 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
5975 tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
5976 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5977
5978 if (tp->rx_opt.tstamp_ok)
5979 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5980
5981 if (req) {
5982 /* Re-arm the timer because data may have been sent out.
5983 * This is similar to the regular data transmission case
5984 * when new data has just been ack'ed.
5985 *
5986 * (TFO) - we could try to be more aggressive and
5987 * retransmitting any data sooner based on when they
5988 * are sent out.
5989 */
5990 tcp_rearm_rto(sk);
5991 } else
5992 tcp_init_metrics(sk);
5993
5994 if (!inet_csk(sk)->icsk_ca_ops->cong_control)
5995 tcp_update_pacing_rate(sk);
5996
5997 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5998 tp->lsndtime = tcp_time_stamp;
5999
6000 tcp_initialize_rcv_mss(sk);
6001 tcp_fast_path_on(tp);
6002 break;
6003
6004 case TCP_FIN_WAIT1: {
6005 int tmo;
6006
6007 /* If we enter the TCP_FIN_WAIT1 state and we are a
6008 * Fast Open socket and this is the first acceptable
6009 * ACK we have received, this would have acknowledged
6010 * our SYNACK so stop the SYNACK timer.
6011 */
6012 if (req) {
6013 /* Return RST if ack_seq is invalid.
6014 * Note that RFC793 only says to generate a
6015 * DUPACK for it but for TCP Fast Open it seems
6016 * better to treat this case like TCP_SYN_RECV
6017 * above.
6018 */
6019 if (!acceptable)
6020 return 1;
6021 /* We no longer need the request sock. */
6022 reqsk_fastopen_remove(sk, req, false);
6023 tcp_rearm_rto(sk);
6024 }
6025 if (tp->snd_una != tp->write_seq)
6026 break;
6027
6028 tcp_set_state(sk, TCP_FIN_WAIT2);
6029 sk->sk_shutdown |= SEND_SHUTDOWN;
6030
6031 sk_dst_confirm(sk);
6032
6033 if (!sock_flag(sk, SOCK_DEAD)) {
6034 /* Wake up lingering close() */
6035 sk->sk_state_change(sk);
6036 break;
6037 }
6038
6039 if (tp->linger2 < 0 ||
6040 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
6041 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
6042 tcp_done(sk);
6043 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6044 return 1;
6045 }
6046
6047 tmo = tcp_fin_time(sk);
6048 if (tmo > TCP_TIMEWAIT_LEN) {
6049 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
6050 } else if (th->fin || sock_owned_by_user(sk)) {
6051 /* Bad case. We could lose such FIN otherwise.
6052 * It is not a big problem, but it looks confusing
6053 * and not so rare event. We still can lose it now,
6054 * if it spins in bh_lock_sock(), but it is really
6055 * marginal case.
6056 */
6057 inet_csk_reset_keepalive_timer(sk, tmo);
6058 } else {
6059 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
6060 goto discard;
6061 }
6062 break;
6063 }
6064
6065 case TCP_CLOSING:
6066 if (tp->snd_una == tp->write_seq) {
6067 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
6068 goto discard;
6069 }
6070 break;
6071
6072 case TCP_LAST_ACK:
6073 if (tp->snd_una == tp->write_seq) {
6074 tcp_update_metrics(sk);
6075 tcp_done(sk);
6076 goto discard;
6077 }
6078 break;
6079 }
6080
6081 /* step 6: check the URG bit */
6082 tcp_urg(sk, skb, th);
6083
6084 /* step 7: process the segment text */
6085 switch (sk->sk_state) {
6086 case TCP_CLOSE_WAIT:
6087 case TCP_CLOSING:
6088 case TCP_LAST_ACK:
6089 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
6090 break;
6091 case TCP_FIN_WAIT1:
6092 case TCP_FIN_WAIT2:
6093 /* RFC 793 says to queue data in these states,
6094 * RFC 1122 says we MUST send a reset.
6095 * BSD 4.4 also does reset.
6096 */
6097 if (sk->sk_shutdown & RCV_SHUTDOWN) {
6098 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
6099 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
6100 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6101 tcp_reset(sk);
6102 return 1;
6103 }
6104 }
6105 /* Fall through */
6106 case TCP_ESTABLISHED:
6107 tcp_data_queue(sk, skb);
6108 queued = 1;
6109 break;
6110 }
6111
6112 /* tcp_data could move socket to TIME-WAIT */
6113 if (sk->sk_state != TCP_CLOSE) {
6114 tcp_data_snd_check(sk);
6115 tcp_ack_snd_check(sk);
6116 }
6117
6118 if (!queued) {
6119 discard:
6120 tcp_drop(sk, skb);
6121 }
6122 return 0;
6123 }
6124 EXPORT_SYMBOL(tcp_rcv_state_process);
6125
6126 static inline void pr_drop_req(struct request_sock *req, __u16 port, int family)
6127 {
6128 struct inet_request_sock *ireq = inet_rsk(req);
6129
6130 if (family == AF_INET)
6131 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6132 &ireq->ir_rmt_addr, port);
6133 #if IS_ENABLED(CONFIG_IPV6)
6134 else if (family == AF_INET6)
6135 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6136 &ireq->ir_v6_rmt_addr, port);
6137 #endif
6138 }
6139
6140 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6141 *
6142 * If we receive a SYN packet with these bits set, it means a
6143 * network is playing bad games with TOS bits. In order to
6144 * avoid possible false congestion notifications, we disable
6145 * TCP ECN negotiation.
6146 *
6147 * Exception: tcp_ca wants ECN. This is required for DCTCP
6148 * congestion control: Linux DCTCP asserts ECT on all packets,
6149 * including SYN, which is most optimal solution; however,
6150 * others, such as FreeBSD do not.
6151 */
6152 static void tcp_ecn_create_request(struct request_sock *req,
6153 const struct sk_buff *skb,
6154 const struct sock *listen_sk,
6155 const struct dst_entry *dst)
6156 {
6157 const struct tcphdr *th = tcp_hdr(skb);
6158 const struct net *net = sock_net(listen_sk);
6159 bool th_ecn = th->ece && th->cwr;
6160 bool ect, ecn_ok;
6161 u32 ecn_ok_dst;
6162
6163 if (!th_ecn)
6164 return;
6165
6166 ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield);
6167 ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK);
6168 ecn_ok = net->ipv4.sysctl_tcp_ecn || ecn_ok_dst;
6169
6170 if ((!ect && ecn_ok) || tcp_ca_needs_ecn(listen_sk) ||
6171 (ecn_ok_dst & DST_FEATURE_ECN_CA))
6172 inet_rsk(req)->ecn_ok = 1;
6173 }
6174
6175 static void tcp_openreq_init(struct request_sock *req,
6176 const struct tcp_options_received *rx_opt,
6177 struct sk_buff *skb, const struct sock *sk)
6178 {
6179 struct inet_request_sock *ireq = inet_rsk(req);
6180
6181 req->rsk_rcv_wnd = 0; /* So that tcp_send_synack() knows! */
6182 req->cookie_ts = 0;
6183 tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
6184 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
6185 skb_mstamp_get(&tcp_rsk(req)->snt_synack);
6186 tcp_rsk(req)->last_oow_ack_time = 0;
6187 req->mss = rx_opt->mss_clamp;
6188 req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
6189 ireq->tstamp_ok = rx_opt->tstamp_ok;
6190 ireq->sack_ok = rx_opt->sack_ok;
6191 ireq->snd_wscale = rx_opt->snd_wscale;
6192 ireq->wscale_ok = rx_opt->wscale_ok;
6193 ireq->acked = 0;
6194 ireq->ecn_ok = 0;
6195 ireq->ir_rmt_port = tcp_hdr(skb)->source;
6196 ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
6197 ireq->ir_mark = inet_request_mark(sk, skb);
6198 }
6199
6200 struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
6201 struct sock *sk_listener,
6202 bool attach_listener)
6203 {
6204 struct request_sock *req = reqsk_alloc(ops, sk_listener,
6205 attach_listener);
6206
6207 if (req) {
6208 struct inet_request_sock *ireq = inet_rsk(req);
6209
6210 kmemcheck_annotate_bitfield(ireq, flags);
6211 ireq->opt = NULL;
6212 #if IS_ENABLED(CONFIG_IPV6)
6213 ireq->pktopts = NULL;
6214 #endif
6215 atomic64_set(&ireq->ir_cookie, 0);
6216 ireq->ireq_state = TCP_NEW_SYN_RECV;
6217 write_pnet(&ireq->ireq_net, sock_net(sk_listener));
6218 ireq->ireq_family = sk_listener->sk_family;
6219 }
6220
6221 return req;
6222 }
6223 EXPORT_SYMBOL(inet_reqsk_alloc);
6224
6225 /*
6226 * Return true if a syncookie should be sent
6227 */
6228 static bool tcp_syn_flood_action(const struct sock *sk,
6229 const struct sk_buff *skb,
6230 const char *proto)
6231 {
6232 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
6233 const char *msg = "Dropping request";
6234 bool want_cookie = false;
6235 struct net *net = sock_net(sk);
6236
6237 #ifdef CONFIG_SYN_COOKIES
6238 if (net->ipv4.sysctl_tcp_syncookies) {
6239 msg = "Sending cookies";
6240 want_cookie = true;
6241 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES);
6242 } else
6243 #endif
6244 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
6245
6246 if (!queue->synflood_warned &&
6247 net->ipv4.sysctl_tcp_syncookies != 2 &&
6248 xchg(&queue->synflood_warned, 1) == 0)
6249 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6250 proto, ntohs(tcp_hdr(skb)->dest), msg);
6251
6252 return want_cookie;
6253 }
6254
6255 static void tcp_reqsk_record_syn(const struct sock *sk,
6256 struct request_sock *req,
6257 const struct sk_buff *skb)
6258 {
6259 if (tcp_sk(sk)->save_syn) {
6260 u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
6261 u32 *copy;
6262
6263 copy = kmalloc(len + sizeof(u32), GFP_ATOMIC);
6264 if (copy) {
6265 copy[0] = len;
6266 memcpy(&copy[1], skb_network_header(skb), len);
6267 req->saved_syn = copy;
6268 }
6269 }
6270 }
6271
6272 int tcp_conn_request(struct request_sock_ops *rsk_ops,
6273 const struct tcp_request_sock_ops *af_ops,
6274 struct sock *sk, struct sk_buff *skb)
6275 {
6276 struct tcp_fastopen_cookie foc = { .len = -1 };
6277 __u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
6278 struct tcp_options_received tmp_opt;
6279 struct tcp_sock *tp = tcp_sk(sk);
6280 struct net *net = sock_net(sk);
6281 struct sock *fastopen_sk = NULL;
6282 struct dst_entry *dst = NULL;
6283 struct request_sock *req;
6284 bool want_cookie = false;
6285 struct flowi fl;
6286
6287 /* TW buckets are converted to open requests without
6288 * limitations, they conserve resources and peer is
6289 * evidently real one.
6290 */
6291 if ((net->ipv4.sysctl_tcp_syncookies == 2 ||
6292 inet_csk_reqsk_queue_is_full(sk)) && !isn) {
6293 want_cookie = tcp_syn_flood_action(sk, skb, rsk_ops->slab_name);
6294 if (!want_cookie)
6295 goto drop;
6296 }
6297
6298 if (sk_acceptq_is_full(sk)) {
6299 NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
6300 goto drop;
6301 }
6302
6303 req = inet_reqsk_alloc(rsk_ops, sk, !want_cookie);
6304 if (!req)
6305 goto drop;
6306
6307 tcp_rsk(req)->af_specific = af_ops;
6308 tcp_rsk(req)->ts_off = 0;
6309
6310 tcp_clear_options(&tmp_opt);
6311 tmp_opt.mss_clamp = af_ops->mss_clamp;
6312 tmp_opt.user_mss = tp->rx_opt.user_mss;
6313 tcp_parse_options(skb, &tmp_opt, 0, want_cookie ? NULL : &foc);
6314
6315 if (want_cookie && !tmp_opt.saw_tstamp)
6316 tcp_clear_options(&tmp_opt);
6317
6318 tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
6319 tcp_openreq_init(req, &tmp_opt, skb, sk);
6320 inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent;
6321
6322 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6323 inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
6324
6325 af_ops->init_req(req, sk, skb);
6326
6327 if (security_inet_conn_request(sk, skb, req))
6328 goto drop_and_free;
6329
6330 if (isn && tmp_opt.tstamp_ok)
6331 af_ops->init_seq(skb, &tcp_rsk(req)->ts_off);
6332
6333 if (!want_cookie && !isn) {
6334 /* VJ's idea. We save last timestamp seen
6335 * from the destination in peer table, when entering
6336 * state TIME-WAIT, and check against it before
6337 * accepting new connection request.
6338 *
6339 * If "isn" is not zero, this request hit alive
6340 * timewait bucket, so that all the necessary checks
6341 * are made in the function processing timewait state.
6342 */
6343 if (net->ipv4.tcp_death_row.sysctl_tw_recycle) {
6344 bool strict;
6345
6346 dst = af_ops->route_req(sk, &fl, req, &strict);
6347
6348 if (dst && strict &&
6349 !tcp_peer_is_proven(req, dst, true,
6350 tmp_opt.saw_tstamp)) {
6351 NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSPASSIVEREJECTED);
6352 goto drop_and_release;
6353 }
6354 }
6355 /* Kill the following clause, if you dislike this way. */
6356 else if (!net->ipv4.sysctl_tcp_syncookies &&
6357 (net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
6358 (net->ipv4.sysctl_max_syn_backlog >> 2)) &&
6359 !tcp_peer_is_proven(req, dst, false,
6360 tmp_opt.saw_tstamp)) {
6361 /* Without syncookies last quarter of
6362 * backlog is filled with destinations,
6363 * proven to be alive.
6364 * It means that we continue to communicate
6365 * to destinations, already remembered
6366 * to the moment of synflood.
6367 */
6368 pr_drop_req(req, ntohs(tcp_hdr(skb)->source),
6369 rsk_ops->family);
6370 goto drop_and_release;
6371 }
6372
6373 isn = af_ops->init_seq(skb, &tcp_rsk(req)->ts_off);
6374 }
6375 if (!dst) {
6376 dst = af_ops->route_req(sk, &fl, req, NULL);
6377 if (!dst)
6378 goto drop_and_free;
6379 }
6380
6381 tcp_ecn_create_request(req, skb, sk, dst);
6382
6383 if (want_cookie) {
6384 isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
6385 tcp_rsk(req)->ts_off = 0;
6386 req->cookie_ts = tmp_opt.tstamp_ok;
6387 if (!tmp_opt.tstamp_ok)
6388 inet_rsk(req)->ecn_ok = 0;
6389 }
6390
6391 tcp_rsk(req)->snt_isn = isn;
6392 tcp_rsk(req)->txhash = net_tx_rndhash();
6393 tcp_openreq_init_rwin(req, sk, dst);
6394 if (!want_cookie) {
6395 tcp_reqsk_record_syn(sk, req, skb);
6396 fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst);
6397 }
6398 if (fastopen_sk) {
6399 af_ops->send_synack(fastopen_sk, dst, &fl, req,
6400 &foc, TCP_SYNACK_FASTOPEN);
6401 /* Add the child socket directly into the accept queue */
6402 inet_csk_reqsk_queue_add(sk, req, fastopen_sk);
6403 sk->sk_data_ready(sk);
6404 bh_unlock_sock(fastopen_sk);
6405 sock_put(fastopen_sk);
6406 } else {
6407 tcp_rsk(req)->tfo_listener = false;
6408 if (!want_cookie)
6409 inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
6410 af_ops->send_synack(sk, dst, &fl, req, &foc,
6411 !want_cookie ? TCP_SYNACK_NORMAL :
6412 TCP_SYNACK_COOKIE);
6413 if (want_cookie) {
6414 reqsk_free(req);
6415 return 0;
6416 }
6417 }
6418 reqsk_put(req);
6419 return 0;
6420
6421 drop_and_release:
6422 dst_release(dst);
6423 drop_and_free:
6424 reqsk_free(req);
6425 drop:
6426 tcp_listendrop(sk);
6427 return 0;
6428 }
6429 EXPORT_SYMBOL(tcp_conn_request);