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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#include <linux/mm.h>
65#include <linux/slab.h>
66#include <linux/module.h>
67#include <linux/sysctl.h>
68#include <linux/kernel.h>
69#include <net/dst.h>
70#include <net/tcp.h>
71#include <net/inet_common.h>
72#include <linux/ipsec.h>
73#include <asm/unaligned.h>
74#include <net/netdma.h>
75
76int sysctl_tcp_timestamps __read_mostly = 1;
77int sysctl_tcp_window_scaling __read_mostly = 1;
78int sysctl_tcp_sack __read_mostly = 1;
79int sysctl_tcp_fack __read_mostly = 1;
80int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
81EXPORT_SYMBOL(sysctl_tcp_reordering);
82int sysctl_tcp_ecn __read_mostly = 2;
83EXPORT_SYMBOL(sysctl_tcp_ecn);
84int sysctl_tcp_dsack __read_mostly = 1;
85int sysctl_tcp_app_win __read_mostly = 31;
86int sysctl_tcp_adv_win_scale __read_mostly = 2;
87EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
88
89int sysctl_tcp_stdurg __read_mostly;
90int sysctl_tcp_rfc1337 __read_mostly;
91int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
92int sysctl_tcp_frto __read_mostly = 2;
93int sysctl_tcp_frto_response __read_mostly;
94int sysctl_tcp_nometrics_save __read_mostly;
95
96int sysctl_tcp_thin_dupack __read_mostly;
97
98int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
99int sysctl_tcp_abc __read_mostly;
100
101#define FLAG_DATA 0x01 /* Incoming frame contained data. */
102#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
103#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
104#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
105#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
106#define FLAG_DATA_SACKED 0x20 /* New SACK. */
107#define FLAG_ECE 0x40 /* ECE in this ACK */
108#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
109#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
110#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
111#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
112#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
113#define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
114#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
115
116#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
117#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
118#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
119#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
120#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
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/* Adapt the MSS value used to make delayed ack decision to the
126 * real world.
127 */
128static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
129{
130 struct inet_connection_sock *icsk = inet_csk(sk);
131 const unsigned int lss = icsk->icsk_ack.last_seg_size;
132 unsigned int len;
133
134 icsk->icsk_ack.last_seg_size = 0;
135
136 /* skb->len may jitter because of SACKs, even if peer
137 * sends good full-sized frames.
138 */
139 len = skb_shinfo(skb)->gso_size ? : skb->len;
140 if (len >= icsk->icsk_ack.rcv_mss) {
141 icsk->icsk_ack.rcv_mss = len;
142 } else {
143 /* Otherwise, we make more careful check taking into account,
144 * that SACKs block is variable.
145 *
146 * "len" is invariant segment length, including TCP header.
147 */
148 len += skb->data - skb_transport_header(skb);
149 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
150 /* If PSH is not set, packet should be
151 * full sized, provided peer TCP is not badly broken.
152 * This observation (if it is correct 8)) allows
153 * to handle super-low mtu links fairly.
154 */
155 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
156 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
157 /* Subtract also invariant (if peer is RFC compliant),
158 * tcp header plus fixed timestamp option length.
159 * Resulting "len" is MSS free of SACK jitter.
160 */
161 len -= tcp_sk(sk)->tcp_header_len;
162 icsk->icsk_ack.last_seg_size = len;
163 if (len == lss) {
164 icsk->icsk_ack.rcv_mss = len;
165 return;
166 }
167 }
168 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
169 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
170 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
171 }
172}
173
174static void tcp_incr_quickack(struct sock *sk)
175{
176 struct inet_connection_sock *icsk = inet_csk(sk);
177 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
178
179 if (quickacks == 0)
180 quickacks = 2;
181 if (quickacks > icsk->icsk_ack.quick)
182 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
183}
184
185static void tcp_enter_quickack_mode(struct sock *sk)
186{
187 struct inet_connection_sock *icsk = inet_csk(sk);
188 tcp_incr_quickack(sk);
189 icsk->icsk_ack.pingpong = 0;
190 icsk->icsk_ack.ato = TCP_ATO_MIN;
191}
192
193/* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
195 */
196
197static inline int tcp_in_quickack_mode(const struct sock *sk)
198{
199 const struct inet_connection_sock *icsk = inet_csk(sk);
200 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
201}
202
203static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp)
204{
205 if (tp->ecn_flags & TCP_ECN_OK)
206 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
207}
208
209static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb)
210{
211 if (tcp_hdr(skb)->cwr)
212 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
213}
214
215static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp)
216{
217 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
218}
219
220static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb)
221{
222 if (tp->ecn_flags & TCP_ECN_OK) {
223 if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags))
224 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
225 /* Funny extension: if ECT is not set on a segment,
226 * it is surely retransmit. It is not in ECN RFC,
227 * but Linux follows this rule. */
228 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags)))
229 tcp_enter_quickack_mode((struct sock *)tp);
230 }
231}
232
233static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th)
234{
235 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
236 tp->ecn_flags &= ~TCP_ECN_OK;
237}
238
239static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th)
240{
241 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
242 tp->ecn_flags &= ~TCP_ECN_OK;
243}
244
245static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th)
246{
247 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
248 return 1;
249 return 0;
250}
251
252/* Buffer size and advertised window tuning.
253 *
254 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
255 */
256
257static void tcp_fixup_sndbuf(struct sock *sk)
258{
259 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
260 sizeof(struct sk_buff);
261
262 if (sk->sk_sndbuf < 3 * sndmem) {
263 sk->sk_sndbuf = 3 * sndmem;
264 if (sk->sk_sndbuf > sysctl_tcp_wmem[2])
265 sk->sk_sndbuf = sysctl_tcp_wmem[2];
266 }
267}
268
269/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
270 *
271 * All tcp_full_space() is split to two parts: "network" buffer, allocated
272 * forward and advertised in receiver window (tp->rcv_wnd) and
273 * "application buffer", required to isolate scheduling/application
274 * latencies from network.
275 * window_clamp is maximal advertised window. It can be less than
276 * tcp_full_space(), in this case tcp_full_space() - window_clamp
277 * is reserved for "application" buffer. The less window_clamp is
278 * the smoother our behaviour from viewpoint of network, but the lower
279 * throughput and the higher sensitivity of the connection to losses. 8)
280 *
281 * rcv_ssthresh is more strict window_clamp used at "slow start"
282 * phase to predict further behaviour of this connection.
283 * It is used for two goals:
284 * - to enforce header prediction at sender, even when application
285 * requires some significant "application buffer". It is check #1.
286 * - to prevent pruning of receive queue because of misprediction
287 * of receiver window. Check #2.
288 *
289 * The scheme does not work when sender sends good segments opening
290 * window and then starts to feed us spaghetti. But it should work
291 * in common situations. Otherwise, we have to rely on queue collapsing.
292 */
293
294/* Slow part of check#2. */
295static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
296{
297 struct tcp_sock *tp = tcp_sk(sk);
298 /* Optimize this! */
299 int truesize = tcp_win_from_space(skb->truesize) >> 1;
300 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
301
302 while (tp->rcv_ssthresh <= window) {
303 if (truesize <= skb->len)
304 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
305
306 truesize >>= 1;
307 window >>= 1;
308 }
309 return 0;
310}
311
312static void tcp_grow_window(struct sock *sk, struct sk_buff *skb)
313{
314 struct tcp_sock *tp = tcp_sk(sk);
315
316 /* Check #1 */
317 if (tp->rcv_ssthresh < tp->window_clamp &&
318 (int)tp->rcv_ssthresh < tcp_space(sk) &&
319 !tcp_memory_pressure) {
320 int incr;
321
322 /* Check #2. Increase window, if skb with such overhead
323 * will fit to rcvbuf in future.
324 */
325 if (tcp_win_from_space(skb->truesize) <= skb->len)
326 incr = 2 * tp->advmss;
327 else
328 incr = __tcp_grow_window(sk, skb);
329
330 if (incr) {
331 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
332 tp->window_clamp);
333 inet_csk(sk)->icsk_ack.quick |= 1;
334 }
335 }
336}
337
338/* 3. Tuning rcvbuf, when connection enters established state. */
339
340static void tcp_fixup_rcvbuf(struct sock *sk)
341{
342 struct tcp_sock *tp = tcp_sk(sk);
343 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
344
345 /* Try to select rcvbuf so that 4 mss-sized segments
346 * will fit to window and corresponding skbs will fit to our rcvbuf.
347 * (was 3; 4 is minimum to allow fast retransmit to work.)
348 */
349 while (tcp_win_from_space(rcvmem) < tp->advmss)
350 rcvmem += 128;
351 if (sk->sk_rcvbuf < 4 * rcvmem)
352 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
353}
354
355/* 4. Try to fixup all. It is made immediately after connection enters
356 * established state.
357 */
358static void tcp_init_buffer_space(struct sock *sk)
359{
360 struct tcp_sock *tp = tcp_sk(sk);
361 int maxwin;
362
363 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
364 tcp_fixup_rcvbuf(sk);
365 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
366 tcp_fixup_sndbuf(sk);
367
368 tp->rcvq_space.space = tp->rcv_wnd;
369
370 maxwin = tcp_full_space(sk);
371
372 if (tp->window_clamp >= maxwin) {
373 tp->window_clamp = maxwin;
374
375 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
376 tp->window_clamp = max(maxwin -
377 (maxwin >> sysctl_tcp_app_win),
378 4 * tp->advmss);
379 }
380
381 /* Force reservation of one segment. */
382 if (sysctl_tcp_app_win &&
383 tp->window_clamp > 2 * tp->advmss &&
384 tp->window_clamp + tp->advmss > maxwin)
385 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
386
387 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
388 tp->snd_cwnd_stamp = tcp_time_stamp;
389}
390
391/* 5. Recalculate window clamp after socket hit its memory bounds. */
392static void tcp_clamp_window(struct sock *sk)
393{
394 struct tcp_sock *tp = tcp_sk(sk);
395 struct inet_connection_sock *icsk = inet_csk(sk);
396
397 icsk->icsk_ack.quick = 0;
398
399 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
400 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
401 !tcp_memory_pressure &&
402 atomic_long_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
403 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
404 sysctl_tcp_rmem[2]);
405 }
406 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
407 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
408}
409
410/* Initialize RCV_MSS value.
411 * RCV_MSS is an our guess about MSS used by the peer.
412 * We haven't any direct information about the MSS.
413 * It's better to underestimate the RCV_MSS rather than overestimate.
414 * Overestimations make us ACKing less frequently than needed.
415 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
416 */
417void tcp_initialize_rcv_mss(struct sock *sk)
418{
419 struct tcp_sock *tp = tcp_sk(sk);
420 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
421
422 hint = min(hint, tp->rcv_wnd / 2);
423 hint = min(hint, TCP_MSS_DEFAULT);
424 hint = max(hint, TCP_MIN_MSS);
425
426 inet_csk(sk)->icsk_ack.rcv_mss = hint;
427}
428EXPORT_SYMBOL(tcp_initialize_rcv_mss);
429
430/* Receiver "autotuning" code.
431 *
432 * The algorithm for RTT estimation w/o timestamps is based on
433 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
434 * <http://public.lanl.gov/radiant/pubs.html#DRS>
435 *
436 * More detail on this code can be found at
437 * <http://staff.psc.edu/jheffner/>,
438 * though this reference is out of date. A new paper
439 * is pending.
440 */
441static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
442{
443 u32 new_sample = tp->rcv_rtt_est.rtt;
444 long m = sample;
445
446 if (m == 0)
447 m = 1;
448
449 if (new_sample != 0) {
450 /* If we sample in larger samples in the non-timestamp
451 * case, we could grossly overestimate the RTT especially
452 * with chatty applications or bulk transfer apps which
453 * are stalled on filesystem I/O.
454 *
455 * Also, since we are only going for a minimum in the
456 * non-timestamp case, we do not smooth things out
457 * else with timestamps disabled convergence takes too
458 * long.
459 */
460 if (!win_dep) {
461 m -= (new_sample >> 3);
462 new_sample += m;
463 } else if (m < new_sample)
464 new_sample = m << 3;
465 } else {
466 /* No previous measure. */
467 new_sample = m << 3;
468 }
469
470 if (tp->rcv_rtt_est.rtt != new_sample)
471 tp->rcv_rtt_est.rtt = new_sample;
472}
473
474static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
475{
476 if (tp->rcv_rtt_est.time == 0)
477 goto new_measure;
478 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
479 return;
480 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1);
481
482new_measure:
483 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
484 tp->rcv_rtt_est.time = tcp_time_stamp;
485}
486
487static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
488 const struct sk_buff *skb)
489{
490 struct tcp_sock *tp = tcp_sk(sk);
491 if (tp->rx_opt.rcv_tsecr &&
492 (TCP_SKB_CB(skb)->end_seq -
493 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
494 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
495}
496
497/*
498 * This function should be called every time data is copied to user space.
499 * It calculates the appropriate TCP receive buffer space.
500 */
501void tcp_rcv_space_adjust(struct sock *sk)
502{
503 struct tcp_sock *tp = tcp_sk(sk);
504 int time;
505 int space;
506
507 if (tp->rcvq_space.time == 0)
508 goto new_measure;
509
510 time = tcp_time_stamp - tp->rcvq_space.time;
511 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
512 return;
513
514 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
515
516 space = max(tp->rcvq_space.space, space);
517
518 if (tp->rcvq_space.space != space) {
519 int rcvmem;
520
521 tp->rcvq_space.space = space;
522
523 if (sysctl_tcp_moderate_rcvbuf &&
524 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
525 int new_clamp = space;
526
527 /* Receive space grows, normalize in order to
528 * take into account packet headers and sk_buff
529 * structure overhead.
530 */
531 space /= tp->advmss;
532 if (!space)
533 space = 1;
534 rcvmem = (tp->advmss + MAX_TCP_HEADER +
535 16 + sizeof(struct sk_buff));
536 while (tcp_win_from_space(rcvmem) < tp->advmss)
537 rcvmem += 128;
538 space *= rcvmem;
539 space = min(space, sysctl_tcp_rmem[2]);
540 if (space > sk->sk_rcvbuf) {
541 sk->sk_rcvbuf = space;
542
543 /* Make the window clamp follow along. */
544 tp->window_clamp = new_clamp;
545 }
546 }
547 }
548
549new_measure:
550 tp->rcvq_space.seq = tp->copied_seq;
551 tp->rcvq_space.time = tcp_time_stamp;
552}
553
554/* There is something which you must keep in mind when you analyze the
555 * behavior of the tp->ato delayed ack timeout interval. When a
556 * connection starts up, we want to ack as quickly as possible. The
557 * problem is that "good" TCP's do slow start at the beginning of data
558 * transmission. The means that until we send the first few ACK's the
559 * sender will sit on his end and only queue most of his data, because
560 * he can only send snd_cwnd unacked packets at any given time. For
561 * each ACK we send, he increments snd_cwnd and transmits more of his
562 * queue. -DaveM
563 */
564static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
565{
566 struct tcp_sock *tp = tcp_sk(sk);
567 struct inet_connection_sock *icsk = inet_csk(sk);
568 u32 now;
569
570 inet_csk_schedule_ack(sk);
571
572 tcp_measure_rcv_mss(sk, skb);
573
574 tcp_rcv_rtt_measure(tp);
575
576 now = tcp_time_stamp;
577
578 if (!icsk->icsk_ack.ato) {
579 /* The _first_ data packet received, initialize
580 * delayed ACK engine.
581 */
582 tcp_incr_quickack(sk);
583 icsk->icsk_ack.ato = TCP_ATO_MIN;
584 } else {
585 int m = now - icsk->icsk_ack.lrcvtime;
586
587 if (m <= TCP_ATO_MIN / 2) {
588 /* The fastest case is the first. */
589 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
590 } else if (m < icsk->icsk_ack.ato) {
591 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
592 if (icsk->icsk_ack.ato > icsk->icsk_rto)
593 icsk->icsk_ack.ato = icsk->icsk_rto;
594 } else if (m > icsk->icsk_rto) {
595 /* Too long gap. Apparently sender failed to
596 * restart window, so that we send ACKs quickly.
597 */
598 tcp_incr_quickack(sk);
599 sk_mem_reclaim(sk);
600 }
601 }
602 icsk->icsk_ack.lrcvtime = now;
603
604 TCP_ECN_check_ce(tp, skb);
605
606 if (skb->len >= 128)
607 tcp_grow_window(sk, skb);
608}
609
610/* Called to compute a smoothed rtt estimate. The data fed to this
611 * routine either comes from timestamps, or from segments that were
612 * known _not_ to have been retransmitted [see Karn/Partridge
613 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
614 * piece by Van Jacobson.
615 * NOTE: the next three routines used to be one big routine.
616 * To save cycles in the RFC 1323 implementation it was better to break
617 * it up into three procedures. -- erics
618 */
619static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
620{
621 struct tcp_sock *tp = tcp_sk(sk);
622 long m = mrtt; /* RTT */
623
624 /* The following amusing code comes from Jacobson's
625 * article in SIGCOMM '88. Note that rtt and mdev
626 * are scaled versions of rtt and mean deviation.
627 * This is designed to be as fast as possible
628 * m stands for "measurement".
629 *
630 * On a 1990 paper the rto value is changed to:
631 * RTO = rtt + 4 * mdev
632 *
633 * Funny. This algorithm seems to be very broken.
634 * These formulae increase RTO, when it should be decreased, increase
635 * too slowly, when it should be increased quickly, decrease too quickly
636 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
637 * does not matter how to _calculate_ it. Seems, it was trap
638 * that VJ failed to avoid. 8)
639 */
640 if (m == 0)
641 m = 1;
642 if (tp->srtt != 0) {
643 m -= (tp->srtt >> 3); /* m is now error in rtt est */
644 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
645 if (m < 0) {
646 m = -m; /* m is now abs(error) */
647 m -= (tp->mdev >> 2); /* similar update on mdev */
648 /* This is similar to one of Eifel findings.
649 * Eifel blocks mdev updates when rtt decreases.
650 * This solution is a bit different: we use finer gain
651 * for mdev in this case (alpha*beta).
652 * Like Eifel it also prevents growth of rto,
653 * but also it limits too fast rto decreases,
654 * happening in pure Eifel.
655 */
656 if (m > 0)
657 m >>= 3;
658 } else {
659 m -= (tp->mdev >> 2); /* similar update on mdev */
660 }
661 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
662 if (tp->mdev > tp->mdev_max) {
663 tp->mdev_max = tp->mdev;
664 if (tp->mdev_max > tp->rttvar)
665 tp->rttvar = tp->mdev_max;
666 }
667 if (after(tp->snd_una, tp->rtt_seq)) {
668 if (tp->mdev_max < tp->rttvar)
669 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2;
670 tp->rtt_seq = tp->snd_nxt;
671 tp->mdev_max = tcp_rto_min(sk);
672 }
673 } else {
674 /* no previous measure. */
675 tp->srtt = m << 3; /* take the measured time to be rtt */
676 tp->mdev = m << 1; /* make sure rto = 3*rtt */
677 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
678 tp->rtt_seq = tp->snd_nxt;
679 }
680}
681
682/* Calculate rto without backoff. This is the second half of Van Jacobson's
683 * routine referred to above.
684 */
685static inline void tcp_set_rto(struct sock *sk)
686{
687 const struct tcp_sock *tp = tcp_sk(sk);
688 /* Old crap is replaced with new one. 8)
689 *
690 * More seriously:
691 * 1. If rtt variance happened to be less 50msec, it is hallucination.
692 * It cannot be less due to utterly erratic ACK generation made
693 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
694 * to do with delayed acks, because at cwnd>2 true delack timeout
695 * is invisible. Actually, Linux-2.4 also generates erratic
696 * ACKs in some circumstances.
697 */
698 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
699
700 /* 2. Fixups made earlier cannot be right.
701 * If we do not estimate RTO correctly without them,
702 * all the algo is pure shit and should be replaced
703 * with correct one. It is exactly, which we pretend to do.
704 */
705
706 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
707 * guarantees that rto is higher.
708 */
709 tcp_bound_rto(sk);
710}
711
712/* Save metrics learned by this TCP session.
713 This function is called only, when TCP finishes successfully
714 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
715 */
716void tcp_update_metrics(struct sock *sk)
717{
718 struct tcp_sock *tp = tcp_sk(sk);
719 struct dst_entry *dst = __sk_dst_get(sk);
720
721 if (sysctl_tcp_nometrics_save)
722 return;
723
724 dst_confirm(dst);
725
726 if (dst && (dst->flags & DST_HOST)) {
727 const struct inet_connection_sock *icsk = inet_csk(sk);
728 int m;
729 unsigned long rtt;
730
731 if (icsk->icsk_backoff || !tp->srtt) {
732 /* This session failed to estimate rtt. Why?
733 * Probably, no packets returned in time.
734 * Reset our results.
735 */
736 if (!(dst_metric_locked(dst, RTAX_RTT)))
737 dst->metrics[RTAX_RTT - 1] = 0;
738 return;
739 }
740
741 rtt = dst_metric_rtt(dst, RTAX_RTT);
742 m = rtt - tp->srtt;
743
744 /* If newly calculated rtt larger than stored one,
745 * store new one. Otherwise, use EWMA. Remember,
746 * rtt overestimation is always better than underestimation.
747 */
748 if (!(dst_metric_locked(dst, RTAX_RTT))) {
749 if (m <= 0)
750 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt);
751 else
752 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3));
753 }
754
755 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
756 unsigned long var;
757 if (m < 0)
758 m = -m;
759
760 /* Scale deviation to rttvar fixed point */
761 m >>= 1;
762 if (m < tp->mdev)
763 m = tp->mdev;
764
765 var = dst_metric_rtt(dst, RTAX_RTTVAR);
766 if (m >= var)
767 var = m;
768 else
769 var -= (var - m) >> 2;
770
771 set_dst_metric_rtt(dst, RTAX_RTTVAR, var);
772 }
773
774 if (tcp_in_initial_slowstart(tp)) {
775 /* Slow start still did not finish. */
776 if (dst_metric(dst, RTAX_SSTHRESH) &&
777 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
778 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
779 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
780 if (!dst_metric_locked(dst, RTAX_CWND) &&
781 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
782 dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd;
783 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
784 icsk->icsk_ca_state == TCP_CA_Open) {
785 /* Cong. avoidance phase, cwnd is reliable. */
786 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
787 dst->metrics[RTAX_SSTHRESH-1] =
788 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
789 if (!dst_metric_locked(dst, RTAX_CWND))
790 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1;
791 } else {
792 /* Else slow start did not finish, cwnd is non-sense,
793 ssthresh may be also invalid.
794 */
795 if (!dst_metric_locked(dst, RTAX_CWND))
796 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1;
797 if (dst_metric(dst, RTAX_SSTHRESH) &&
798 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
799 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH))
800 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
801 }
802
803 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
804 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering &&
805 tp->reordering != sysctl_tcp_reordering)
806 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
807 }
808 }
809}
810
811__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
812{
813 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
814
815 if (!cwnd)
816 cwnd = rfc3390_bytes_to_packets(tp->mss_cache);
817 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
818}
819
820/* Set slow start threshold and cwnd not falling to slow start */
821void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
822{
823 struct tcp_sock *tp = tcp_sk(sk);
824 const struct inet_connection_sock *icsk = inet_csk(sk);
825
826 tp->prior_ssthresh = 0;
827 tp->bytes_acked = 0;
828 if (icsk->icsk_ca_state < TCP_CA_CWR) {
829 tp->undo_marker = 0;
830 if (set_ssthresh)
831 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
832 tp->snd_cwnd = min(tp->snd_cwnd,
833 tcp_packets_in_flight(tp) + 1U);
834 tp->snd_cwnd_cnt = 0;
835 tp->high_seq = tp->snd_nxt;
836 tp->snd_cwnd_stamp = tcp_time_stamp;
837 TCP_ECN_queue_cwr(tp);
838
839 tcp_set_ca_state(sk, TCP_CA_CWR);
840 }
841}
842
843/*
844 * Packet counting of FACK is based on in-order assumptions, therefore TCP
845 * disables it when reordering is detected
846 */
847static void tcp_disable_fack(struct tcp_sock *tp)
848{
849 /* RFC3517 uses different metric in lost marker => reset on change */
850 if (tcp_is_fack(tp))
851 tp->lost_skb_hint = NULL;
852 tp->rx_opt.sack_ok &= ~2;
853}
854
855/* Take a notice that peer is sending D-SACKs */
856static void tcp_dsack_seen(struct tcp_sock *tp)
857{
858 tp->rx_opt.sack_ok |= 4;
859}
860
861/* Initialize metrics on socket. */
862
863static void tcp_init_metrics(struct sock *sk)
864{
865 struct tcp_sock *tp = tcp_sk(sk);
866 struct dst_entry *dst = __sk_dst_get(sk);
867
868 if (dst == NULL)
869 goto reset;
870
871 dst_confirm(dst);
872
873 if (dst_metric_locked(dst, RTAX_CWND))
874 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
875 if (dst_metric(dst, RTAX_SSTHRESH)) {
876 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
877 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
878 tp->snd_ssthresh = tp->snd_cwnd_clamp;
879 }
880 if (dst_metric(dst, RTAX_REORDERING) &&
881 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
882 tcp_disable_fack(tp);
883 tp->reordering = dst_metric(dst, RTAX_REORDERING);
884 }
885
886 if (dst_metric(dst, RTAX_RTT) == 0)
887 goto reset;
888
889 if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
890 goto reset;
891
892 /* Initial rtt is determined from SYN,SYN-ACK.
893 * The segment is small and rtt may appear much
894 * less than real one. Use per-dst memory
895 * to make it more realistic.
896 *
897 * A bit of theory. RTT is time passed after "normal" sized packet
898 * is sent until it is ACKed. In normal circumstances sending small
899 * packets force peer to delay ACKs and calculation is correct too.
900 * The algorithm is adaptive and, provided we follow specs, it
901 * NEVER underestimate RTT. BUT! If peer tries to make some clever
902 * tricks sort of "quick acks" for time long enough to decrease RTT
903 * to low value, and then abruptly stops to do it and starts to delay
904 * ACKs, wait for troubles.
905 */
906 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) {
907 tp->srtt = dst_metric_rtt(dst, RTAX_RTT);
908 tp->rtt_seq = tp->snd_nxt;
909 }
910 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) {
911 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR);
912 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
913 }
914 tcp_set_rto(sk);
915 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
916 goto reset;
917
918cwnd:
919 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
920 tp->snd_cwnd_stamp = tcp_time_stamp;
921 return;
922
923reset:
924 /* Play conservative. If timestamps are not
925 * supported, TCP will fail to recalculate correct
926 * rtt, if initial rto is too small. FORGET ALL AND RESET!
927 */
928 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
929 tp->srtt = 0;
930 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
931 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
932 }
933 goto cwnd;
934}
935
936static void tcp_update_reordering(struct sock *sk, const int metric,
937 const int ts)
938{
939 struct tcp_sock *tp = tcp_sk(sk);
940 if (metric > tp->reordering) {
941 int mib_idx;
942
943 tp->reordering = min(TCP_MAX_REORDERING, metric);
944
945 /* This exciting event is worth to be remembered. 8) */
946 if (ts)
947 mib_idx = LINUX_MIB_TCPTSREORDER;
948 else if (tcp_is_reno(tp))
949 mib_idx = LINUX_MIB_TCPRENOREORDER;
950 else if (tcp_is_fack(tp))
951 mib_idx = LINUX_MIB_TCPFACKREORDER;
952 else
953 mib_idx = LINUX_MIB_TCPSACKREORDER;
954
955 NET_INC_STATS_BH(sock_net(sk), mib_idx);
956#if FASTRETRANS_DEBUG > 1
957 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
958 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
959 tp->reordering,
960 tp->fackets_out,
961 tp->sacked_out,
962 tp->undo_marker ? tp->undo_retrans : 0);
963#endif
964 tcp_disable_fack(tp);
965 }
966}
967
968/* This must be called before lost_out is incremented */
969static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
970{
971 if ((tp->retransmit_skb_hint == NULL) ||
972 before(TCP_SKB_CB(skb)->seq,
973 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
974 tp->retransmit_skb_hint = skb;
975
976 if (!tp->lost_out ||
977 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
978 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
979}
980
981static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
982{
983 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
984 tcp_verify_retransmit_hint(tp, skb);
985
986 tp->lost_out += tcp_skb_pcount(skb);
987 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
988 }
989}
990
991static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
992 struct sk_buff *skb)
993{
994 tcp_verify_retransmit_hint(tp, skb);
995
996 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
997 tp->lost_out += tcp_skb_pcount(skb);
998 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
999 }
1000}
1001
1002/* This procedure tags the retransmission queue when SACKs arrive.
1003 *
1004 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1005 * Packets in queue with these bits set are counted in variables
1006 * sacked_out, retrans_out and lost_out, correspondingly.
1007 *
1008 * Valid combinations are:
1009 * Tag InFlight Description
1010 * 0 1 - orig segment is in flight.
1011 * S 0 - nothing flies, orig reached receiver.
1012 * L 0 - nothing flies, orig lost by net.
1013 * R 2 - both orig and retransmit are in flight.
1014 * L|R 1 - orig is lost, retransmit is in flight.
1015 * S|R 1 - orig reached receiver, retrans is still in flight.
1016 * (L|S|R is logically valid, it could occur when L|R is sacked,
1017 * but it is equivalent to plain S and code short-curcuits it to S.
1018 * L|S is logically invalid, it would mean -1 packet in flight 8))
1019 *
1020 * These 6 states form finite state machine, controlled by the following events:
1021 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1022 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1023 * 3. Loss detection event of one of three flavors:
1024 * A. Scoreboard estimator decided the packet is lost.
1025 * A'. Reno "three dupacks" marks head of queue lost.
1026 * A''. Its FACK modfication, head until snd.fack is lost.
1027 * B. SACK arrives sacking data transmitted after never retransmitted
1028 * hole was sent out.
1029 * C. SACK arrives sacking SND.NXT at the moment, when the
1030 * segment was retransmitted.
1031 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1032 *
1033 * It is pleasant to note, that state diagram turns out to be commutative,
1034 * so that we are allowed not to be bothered by order of our actions,
1035 * when multiple events arrive simultaneously. (see the function below).
1036 *
1037 * Reordering detection.
1038 * --------------------
1039 * Reordering metric is maximal distance, which a packet can be displaced
1040 * in packet stream. With SACKs we can estimate it:
1041 *
1042 * 1. SACK fills old hole and the corresponding segment was not
1043 * ever retransmitted -> reordering. Alas, we cannot use it
1044 * when segment was retransmitted.
1045 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1046 * for retransmitted and already SACKed segment -> reordering..
1047 * Both of these heuristics are not used in Loss state, when we cannot
1048 * account for retransmits accurately.
1049 *
1050 * SACK block validation.
1051 * ----------------------
1052 *
1053 * SACK block range validation checks that the received SACK block fits to
1054 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1055 * Note that SND.UNA is not included to the range though being valid because
1056 * it means that the receiver is rather inconsistent with itself reporting
1057 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1058 * perfectly valid, however, in light of RFC2018 which explicitly states
1059 * that "SACK block MUST reflect the newest segment. Even if the newest
1060 * segment is going to be discarded ...", not that it looks very clever
1061 * in case of head skb. Due to potentional receiver driven attacks, we
1062 * choose to avoid immediate execution of a walk in write queue due to
1063 * reneging and defer head skb's loss recovery to standard loss recovery
1064 * procedure that will eventually trigger (nothing forbids us doing this).
1065 *
1066 * Implements also blockage to start_seq wrap-around. Problem lies in the
1067 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1068 * there's no guarantee that it will be before snd_nxt (n). The problem
1069 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1070 * wrap (s_w):
1071 *
1072 * <- outs wnd -> <- wrapzone ->
1073 * u e n u_w e_w s n_w
1074 * | | | | | | |
1075 * |<------------+------+----- TCP seqno space --------------+---------->|
1076 * ...-- <2^31 ->| |<--------...
1077 * ...---- >2^31 ------>| |<--------...
1078 *
1079 * Current code wouldn't be vulnerable but it's better still to discard such
1080 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1081 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1082 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1083 * equal to the ideal case (infinite seqno space without wrap caused issues).
1084 *
1085 * With D-SACK the lower bound is extended to cover sequence space below
1086 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1087 * again, D-SACK block must not to go across snd_una (for the same reason as
1088 * for the normal SACK blocks, explained above). But there all simplicity
1089 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1090 * fully below undo_marker they do not affect behavior in anyway and can
1091 * therefore be safely ignored. In rare cases (which are more or less
1092 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1093 * fragmentation and packet reordering past skb's retransmission. To consider
1094 * them correctly, the acceptable range must be extended even more though
1095 * the exact amount is rather hard to quantify. However, tp->max_window can
1096 * be used as an exaggerated estimate.
1097 */
1098static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
1099 u32 start_seq, u32 end_seq)
1100{
1101 /* Too far in future, or reversed (interpretation is ambiguous) */
1102 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1103 return 0;
1104
1105 /* Nasty start_seq wrap-around check (see comments above) */
1106 if (!before(start_seq, tp->snd_nxt))
1107 return 0;
1108
1109 /* In outstanding window? ...This is valid exit for D-SACKs too.
1110 * start_seq == snd_una is non-sensical (see comments above)
1111 */
1112 if (after(start_seq, tp->snd_una))
1113 return 1;
1114
1115 if (!is_dsack || !tp->undo_marker)
1116 return 0;
1117
1118 /* ...Then it's D-SACK, and must reside below snd_una completely */
1119 if (!after(end_seq, tp->snd_una))
1120 return 0;
1121
1122 if (!before(start_seq, tp->undo_marker))
1123 return 1;
1124
1125 /* Too old */
1126 if (!after(end_seq, tp->undo_marker))
1127 return 0;
1128
1129 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1130 * start_seq < undo_marker and end_seq >= undo_marker.
1131 */
1132 return !before(start_seq, end_seq - tp->max_window);
1133}
1134
1135/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1136 * Event "C". Later note: FACK people cheated me again 8), we have to account
1137 * for reordering! Ugly, but should help.
1138 *
1139 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1140 * less than what is now known to be received by the other end (derived from
1141 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1142 * retransmitted skbs to avoid some costly processing per ACKs.
1143 */
1144static void tcp_mark_lost_retrans(struct sock *sk)
1145{
1146 const struct inet_connection_sock *icsk = inet_csk(sk);
1147 struct tcp_sock *tp = tcp_sk(sk);
1148 struct sk_buff *skb;
1149 int cnt = 0;
1150 u32 new_low_seq = tp->snd_nxt;
1151 u32 received_upto = tcp_highest_sack_seq(tp);
1152
1153 if (!tcp_is_fack(tp) || !tp->retrans_out ||
1154 !after(received_upto, tp->lost_retrans_low) ||
1155 icsk->icsk_ca_state != TCP_CA_Recovery)
1156 return;
1157
1158 tcp_for_write_queue(skb, sk) {
1159 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
1160
1161 if (skb == tcp_send_head(sk))
1162 break;
1163 if (cnt == tp->retrans_out)
1164 break;
1165 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1166 continue;
1167
1168 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
1169 continue;
1170
1171 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1172 * constraint here (see above) but figuring out that at
1173 * least tp->reordering SACK blocks reside between ack_seq
1174 * and received_upto is not easy task to do cheaply with
1175 * the available datastructures.
1176 *
1177 * Whether FACK should check here for tp->reordering segs
1178 * in-between one could argue for either way (it would be
1179 * rather simple to implement as we could count fack_count
1180 * during the walk and do tp->fackets_out - fack_count).
1181 */
1182 if (after(received_upto, ack_seq)) {
1183 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1184 tp->retrans_out -= tcp_skb_pcount(skb);
1185
1186 tcp_skb_mark_lost_uncond_verify(tp, skb);
1187 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
1188 } else {
1189 if (before(ack_seq, new_low_seq))
1190 new_low_seq = ack_seq;
1191 cnt += tcp_skb_pcount(skb);
1192 }
1193 }
1194
1195 if (tp->retrans_out)
1196 tp->lost_retrans_low = new_low_seq;
1197}
1198
1199static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb,
1200 struct tcp_sack_block_wire *sp, int num_sacks,
1201 u32 prior_snd_una)
1202{
1203 struct tcp_sock *tp = tcp_sk(sk);
1204 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1205 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
1206 int dup_sack = 0;
1207
1208 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1209 dup_sack = 1;
1210 tcp_dsack_seen(tp);
1211 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
1212 } else if (num_sacks > 1) {
1213 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1214 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
1215
1216 if (!after(end_seq_0, end_seq_1) &&
1217 !before(start_seq_0, start_seq_1)) {
1218 dup_sack = 1;
1219 tcp_dsack_seen(tp);
1220 NET_INC_STATS_BH(sock_net(sk),
1221 LINUX_MIB_TCPDSACKOFORECV);
1222 }
1223 }
1224
1225 /* D-SACK for already forgotten data... Do dumb counting. */
1226 if (dup_sack &&
1227 !after(end_seq_0, prior_snd_una) &&
1228 after(end_seq_0, tp->undo_marker))
1229 tp->undo_retrans--;
1230
1231 return dup_sack;
1232}
1233
1234struct tcp_sacktag_state {
1235 int reord;
1236 int fack_count;
1237 int flag;
1238};
1239
1240/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1241 * the incoming SACK may not exactly match but we can find smaller MSS
1242 * aligned portion of it that matches. Therefore we might need to fragment
1243 * which may fail and creates some hassle (caller must handle error case
1244 * returns).
1245 *
1246 * FIXME: this could be merged to shift decision code
1247 */
1248static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1249 u32 start_seq, u32 end_seq)
1250{
1251 int in_sack, err;
1252 unsigned int pkt_len;
1253 unsigned int mss;
1254
1255 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1256 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1257
1258 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1259 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1260 mss = tcp_skb_mss(skb);
1261 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1262
1263 if (!in_sack) {
1264 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1265 if (pkt_len < mss)
1266 pkt_len = mss;
1267 } else {
1268 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1269 if (pkt_len < mss)
1270 return -EINVAL;
1271 }
1272
1273 /* Round if necessary so that SACKs cover only full MSSes
1274 * and/or the remaining small portion (if present)
1275 */
1276 if (pkt_len > mss) {
1277 unsigned int new_len = (pkt_len / mss) * mss;
1278 if (!in_sack && new_len < pkt_len) {
1279 new_len += mss;
1280 if (new_len > skb->len)
1281 return 0;
1282 }
1283 pkt_len = new_len;
1284 }
1285 err = tcp_fragment(sk, skb, pkt_len, mss);
1286 if (err < 0)
1287 return err;
1288 }
1289
1290 return in_sack;
1291}
1292
1293static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
1294 struct tcp_sacktag_state *state,
1295 int dup_sack, int pcount)
1296{
1297 struct tcp_sock *tp = tcp_sk(sk);
1298 u8 sacked = TCP_SKB_CB(skb)->sacked;
1299 int fack_count = state->fack_count;
1300
1301 /* Account D-SACK for retransmitted packet. */
1302 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1303 if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1304 tp->undo_retrans--;
1305 if (sacked & TCPCB_SACKED_ACKED)
1306 state->reord = min(fack_count, state->reord);
1307 }
1308
1309 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1310 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1311 return sacked;
1312
1313 if (!(sacked & TCPCB_SACKED_ACKED)) {
1314 if (sacked & TCPCB_SACKED_RETRANS) {
1315 /* If the segment is not tagged as lost,
1316 * we do not clear RETRANS, believing
1317 * that retransmission is still in flight.
1318 */
1319 if (sacked & TCPCB_LOST) {
1320 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1321 tp->lost_out -= pcount;
1322 tp->retrans_out -= pcount;
1323 }
1324 } else {
1325 if (!(sacked & TCPCB_RETRANS)) {
1326 /* New sack for not retransmitted frame,
1327 * which was in hole. It is reordering.
1328 */
1329 if (before(TCP_SKB_CB(skb)->seq,
1330 tcp_highest_sack_seq(tp)))
1331 state->reord = min(fack_count,
1332 state->reord);
1333
1334 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1335 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
1336 state->flag |= FLAG_ONLY_ORIG_SACKED;
1337 }
1338
1339 if (sacked & TCPCB_LOST) {
1340 sacked &= ~TCPCB_LOST;
1341 tp->lost_out -= pcount;
1342 }
1343 }
1344
1345 sacked |= TCPCB_SACKED_ACKED;
1346 state->flag |= FLAG_DATA_SACKED;
1347 tp->sacked_out += pcount;
1348
1349 fack_count += pcount;
1350
1351 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1352 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
1353 before(TCP_SKB_CB(skb)->seq,
1354 TCP_SKB_CB(tp->lost_skb_hint)->seq))
1355 tp->lost_cnt_hint += pcount;
1356
1357 if (fack_count > tp->fackets_out)
1358 tp->fackets_out = fack_count;
1359 }
1360
1361 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1362 * frames and clear it. undo_retrans is decreased above, L|R frames
1363 * are accounted above as well.
1364 */
1365 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1366 sacked &= ~TCPCB_SACKED_RETRANS;
1367 tp->retrans_out -= pcount;
1368 }
1369
1370 return sacked;
1371}
1372
1373static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
1374 struct tcp_sacktag_state *state,
1375 unsigned int pcount, int shifted, int mss,
1376 int dup_sack)
1377{
1378 struct tcp_sock *tp = tcp_sk(sk);
1379 struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
1380
1381 BUG_ON(!pcount);
1382
1383 /* Tweak before seqno plays */
1384 if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint &&
1385 !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq))
1386 tp->lost_cnt_hint += pcount;
1387
1388 TCP_SKB_CB(prev)->end_seq += shifted;
1389 TCP_SKB_CB(skb)->seq += shifted;
1390
1391 skb_shinfo(prev)->gso_segs += pcount;
1392 BUG_ON(skb_shinfo(skb)->gso_segs < pcount);
1393 skb_shinfo(skb)->gso_segs -= pcount;
1394
1395 /* When we're adding to gso_segs == 1, gso_size will be zero,
1396 * in theory this shouldn't be necessary but as long as DSACK
1397 * code can come after this skb later on it's better to keep
1398 * setting gso_size to something.
1399 */
1400 if (!skb_shinfo(prev)->gso_size) {
1401 skb_shinfo(prev)->gso_size = mss;
1402 skb_shinfo(prev)->gso_type = sk->sk_gso_type;
1403 }
1404
1405 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1406 if (skb_shinfo(skb)->gso_segs <= 1) {
1407 skb_shinfo(skb)->gso_size = 0;
1408 skb_shinfo(skb)->gso_type = 0;
1409 }
1410
1411 /* We discard results */
1412 tcp_sacktag_one(skb, sk, state, dup_sack, pcount);
1413
1414 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1415 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1416
1417 if (skb->len > 0) {
1418 BUG_ON(!tcp_skb_pcount(skb));
1419 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
1420 return 0;
1421 }
1422
1423 /* Whole SKB was eaten :-) */
1424
1425 if (skb == tp->retransmit_skb_hint)
1426 tp->retransmit_skb_hint = prev;
1427 if (skb == tp->scoreboard_skb_hint)
1428 tp->scoreboard_skb_hint = prev;
1429 if (skb == tp->lost_skb_hint) {
1430 tp->lost_skb_hint = prev;
1431 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1432 }
1433
1434 TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags;
1435 if (skb == tcp_highest_sack(sk))
1436 tcp_advance_highest_sack(sk, skb);
1437
1438 tcp_unlink_write_queue(skb, sk);
1439 sk_wmem_free_skb(sk, skb);
1440
1441 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
1442
1443 return 1;
1444}
1445
1446/* I wish gso_size would have a bit more sane initialization than
1447 * something-or-zero which complicates things
1448 */
1449static int tcp_skb_seglen(struct sk_buff *skb)
1450{
1451 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
1452}
1453
1454/* Shifting pages past head area doesn't work */
1455static int skb_can_shift(struct sk_buff *skb)
1456{
1457 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1458}
1459
1460/* Try collapsing SACK blocks spanning across multiple skbs to a single
1461 * skb.
1462 */
1463static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
1464 struct tcp_sacktag_state *state,
1465 u32 start_seq, u32 end_seq,
1466 int dup_sack)
1467{
1468 struct tcp_sock *tp = tcp_sk(sk);
1469 struct sk_buff *prev;
1470 int mss;
1471 int pcount = 0;
1472 int len;
1473 int in_sack;
1474
1475 if (!sk_can_gso(sk))
1476 goto fallback;
1477
1478 /* Normally R but no L won't result in plain S */
1479 if (!dup_sack &&
1480 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
1481 goto fallback;
1482 if (!skb_can_shift(skb))
1483 goto fallback;
1484 /* This frame is about to be dropped (was ACKed). */
1485 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1486 goto fallback;
1487
1488 /* Can only happen with delayed DSACK + discard craziness */
1489 if (unlikely(skb == tcp_write_queue_head(sk)))
1490 goto fallback;
1491 prev = tcp_write_queue_prev(sk, skb);
1492
1493 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1494 goto fallback;
1495
1496 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1497 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1498
1499 if (in_sack) {
1500 len = skb->len;
1501 pcount = tcp_skb_pcount(skb);
1502 mss = tcp_skb_seglen(skb);
1503
1504 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1505 * drop this restriction as unnecessary
1506 */
1507 if (mss != tcp_skb_seglen(prev))
1508 goto fallback;
1509 } else {
1510 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1511 goto noop;
1512 /* CHECKME: This is non-MSS split case only?, this will
1513 * cause skipped skbs due to advancing loop btw, original
1514 * has that feature too
1515 */
1516 if (tcp_skb_pcount(skb) <= 1)
1517 goto noop;
1518
1519 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1520 if (!in_sack) {
1521 /* TODO: head merge to next could be attempted here
1522 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1523 * though it might not be worth of the additional hassle
1524 *
1525 * ...we can probably just fallback to what was done
1526 * previously. We could try merging non-SACKed ones
1527 * as well but it probably isn't going to buy off
1528 * because later SACKs might again split them, and
1529 * it would make skb timestamp tracking considerably
1530 * harder problem.
1531 */
1532 goto fallback;
1533 }
1534
1535 len = end_seq - TCP_SKB_CB(skb)->seq;
1536 BUG_ON(len < 0);
1537 BUG_ON(len > skb->len);
1538
1539 /* MSS boundaries should be honoured or else pcount will
1540 * severely break even though it makes things bit trickier.
1541 * Optimize common case to avoid most of the divides
1542 */
1543 mss = tcp_skb_mss(skb);
1544
1545 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1546 * drop this restriction as unnecessary
1547 */
1548 if (mss != tcp_skb_seglen(prev))
1549 goto fallback;
1550
1551 if (len == mss) {
1552 pcount = 1;
1553 } else if (len < mss) {
1554 goto noop;
1555 } else {
1556 pcount = len / mss;
1557 len = pcount * mss;
1558 }
1559 }
1560
1561 if (!skb_shift(prev, skb, len))
1562 goto fallback;
1563 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
1564 goto out;
1565
1566 /* Hole filled allows collapsing with the next as well, this is very
1567 * useful when hole on every nth skb pattern happens
1568 */
1569 if (prev == tcp_write_queue_tail(sk))
1570 goto out;
1571 skb = tcp_write_queue_next(sk, prev);
1572
1573 if (!skb_can_shift(skb) ||
1574 (skb == tcp_send_head(sk)) ||
1575 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
1576 (mss != tcp_skb_seglen(skb)))
1577 goto out;
1578
1579 len = skb->len;
1580 if (skb_shift(prev, skb, len)) {
1581 pcount += tcp_skb_pcount(skb);
1582 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
1583 }
1584
1585out:
1586 state->fack_count += pcount;
1587 return prev;
1588
1589noop:
1590 return skb;
1591
1592fallback:
1593 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
1594 return NULL;
1595}
1596
1597static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1598 struct tcp_sack_block *next_dup,
1599 struct tcp_sacktag_state *state,
1600 u32 start_seq, u32 end_seq,
1601 int dup_sack_in)
1602{
1603 struct tcp_sock *tp = tcp_sk(sk);
1604 struct sk_buff *tmp;
1605
1606 tcp_for_write_queue_from(skb, sk) {
1607 int in_sack = 0;
1608 int dup_sack = dup_sack_in;
1609
1610 if (skb == tcp_send_head(sk))
1611 break;
1612
1613 /* queue is in-order => we can short-circuit the walk early */
1614 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1615 break;
1616
1617 if ((next_dup != NULL) &&
1618 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1619 in_sack = tcp_match_skb_to_sack(sk, skb,
1620 next_dup->start_seq,
1621 next_dup->end_seq);
1622 if (in_sack > 0)
1623 dup_sack = 1;
1624 }
1625
1626 /* skb reference here is a bit tricky to get right, since
1627 * shifting can eat and free both this skb and the next,
1628 * so not even _safe variant of the loop is enough.
1629 */
1630 if (in_sack <= 0) {
1631 tmp = tcp_shift_skb_data(sk, skb, state,
1632 start_seq, end_seq, dup_sack);
1633 if (tmp != NULL) {
1634 if (tmp != skb) {
1635 skb = tmp;
1636 continue;
1637 }
1638
1639 in_sack = 0;
1640 } else {
1641 in_sack = tcp_match_skb_to_sack(sk, skb,
1642 start_seq,
1643 end_seq);
1644 }
1645 }
1646
1647 if (unlikely(in_sack < 0))
1648 break;
1649
1650 if (in_sack) {
1651 TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk,
1652 state,
1653 dup_sack,
1654 tcp_skb_pcount(skb));
1655
1656 if (!before(TCP_SKB_CB(skb)->seq,
1657 tcp_highest_sack_seq(tp)))
1658 tcp_advance_highest_sack(sk, skb);
1659 }
1660
1661 state->fack_count += tcp_skb_pcount(skb);
1662 }
1663 return skb;
1664}
1665
1666/* Avoid all extra work that is being done by sacktag while walking in
1667 * a normal way
1668 */
1669static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
1670 struct tcp_sacktag_state *state,
1671 u32 skip_to_seq)
1672{
1673 tcp_for_write_queue_from(skb, sk) {
1674 if (skb == tcp_send_head(sk))
1675 break;
1676
1677 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
1678 break;
1679
1680 state->fack_count += tcp_skb_pcount(skb);
1681 }
1682 return skb;
1683}
1684
1685static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1686 struct sock *sk,
1687 struct tcp_sack_block *next_dup,
1688 struct tcp_sacktag_state *state,
1689 u32 skip_to_seq)
1690{
1691 if (next_dup == NULL)
1692 return skb;
1693
1694 if (before(next_dup->start_seq, skip_to_seq)) {
1695 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
1696 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1697 next_dup->start_seq, next_dup->end_seq,
1698 1);
1699 }
1700
1701 return skb;
1702}
1703
1704static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache)
1705{
1706 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1707}
1708
1709static int
1710tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
1711 u32 prior_snd_una)
1712{
1713 const struct inet_connection_sock *icsk = inet_csk(sk);
1714 struct tcp_sock *tp = tcp_sk(sk);
1715 unsigned char *ptr = (skb_transport_header(ack_skb) +
1716 TCP_SKB_CB(ack_skb)->sacked);
1717 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
1718 struct tcp_sack_block sp[TCP_NUM_SACKS];
1719 struct tcp_sack_block *cache;
1720 struct tcp_sacktag_state state;
1721 struct sk_buff *skb;
1722 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
1723 int used_sacks;
1724 int found_dup_sack = 0;
1725 int i, j;
1726 int first_sack_index;
1727
1728 state.flag = 0;
1729 state.reord = tp->packets_out;
1730
1731 if (!tp->sacked_out) {
1732 if (WARN_ON(tp->fackets_out))
1733 tp->fackets_out = 0;
1734 tcp_highest_sack_reset(sk);
1735 }
1736
1737 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
1738 num_sacks, prior_snd_una);
1739 if (found_dup_sack)
1740 state.flag |= FLAG_DSACKING_ACK;
1741
1742 /* Eliminate too old ACKs, but take into
1743 * account more or less fresh ones, they can
1744 * contain valid SACK info.
1745 */
1746 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1747 return 0;
1748
1749 if (!tp->packets_out)
1750 goto out;
1751
1752 used_sacks = 0;
1753 first_sack_index = 0;
1754 for (i = 0; i < num_sacks; i++) {
1755 int dup_sack = !i && found_dup_sack;
1756
1757 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1758 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
1759
1760 if (!tcp_is_sackblock_valid(tp, dup_sack,
1761 sp[used_sacks].start_seq,
1762 sp[used_sacks].end_seq)) {
1763 int mib_idx;
1764
1765 if (dup_sack) {
1766 if (!tp->undo_marker)
1767 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
1768 else
1769 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
1770 } else {
1771 /* Don't count olds caused by ACK reordering */
1772 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1773 !after(sp[used_sacks].end_seq, tp->snd_una))
1774 continue;
1775 mib_idx = LINUX_MIB_TCPSACKDISCARD;
1776 }
1777
1778 NET_INC_STATS_BH(sock_net(sk), mib_idx);
1779 if (i == 0)
1780 first_sack_index = -1;
1781 continue;
1782 }
1783
1784 /* Ignore very old stuff early */
1785 if (!after(sp[used_sacks].end_seq, prior_snd_una))
1786 continue;
1787
1788 used_sacks++;
1789 }
1790
1791 /* order SACK blocks to allow in order walk of the retrans queue */
1792 for (i = used_sacks - 1; i > 0; i--) {
1793 for (j = 0; j < i; j++) {
1794 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
1795 swap(sp[j], sp[j + 1]);
1796
1797 /* Track where the first SACK block goes to */
1798 if (j == first_sack_index)
1799 first_sack_index = j + 1;
1800 }
1801 }
1802 }
1803
1804 skb = tcp_write_queue_head(sk);
1805 state.fack_count = 0;
1806 i = 0;
1807
1808 if (!tp->sacked_out) {
1809 /* It's already past, so skip checking against it */
1810 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1811 } else {
1812 cache = tp->recv_sack_cache;
1813 /* Skip empty blocks in at head of the cache */
1814 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1815 !cache->end_seq)
1816 cache++;
1817 }
1818
1819 while (i < used_sacks) {
1820 u32 start_seq = sp[i].start_seq;
1821 u32 end_seq = sp[i].end_seq;
1822 int dup_sack = (found_dup_sack && (i == first_sack_index));
1823 struct tcp_sack_block *next_dup = NULL;
1824
1825 if (found_dup_sack && ((i + 1) == first_sack_index))
1826 next_dup = &sp[i + 1];
1827
1828 /* Event "B" in the comment above. */
1829 if (after(end_seq, tp->high_seq))
1830 state.flag |= FLAG_DATA_LOST;
1831
1832 /* Skip too early cached blocks */
1833 while (tcp_sack_cache_ok(tp, cache) &&
1834 !before(start_seq, cache->end_seq))
1835 cache++;
1836
1837 /* Can skip some work by looking recv_sack_cache? */
1838 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1839 after(end_seq, cache->start_seq)) {
1840
1841 /* Head todo? */
1842 if (before(start_seq, cache->start_seq)) {
1843 skb = tcp_sacktag_skip(skb, sk, &state,
1844 start_seq);
1845 skb = tcp_sacktag_walk(skb, sk, next_dup,
1846 &state,
1847 start_seq,
1848 cache->start_seq,
1849 dup_sack);
1850 }
1851
1852 /* Rest of the block already fully processed? */
1853 if (!after(end_seq, cache->end_seq))
1854 goto advance_sp;
1855
1856 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
1857 &state,
1858 cache->end_seq);
1859
1860 /* ...tail remains todo... */
1861 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
1862 /* ...but better entrypoint exists! */
1863 skb = tcp_highest_sack(sk);
1864 if (skb == NULL)
1865 break;
1866 state.fack_count = tp->fackets_out;
1867 cache++;
1868 goto walk;
1869 }
1870
1871 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq);
1872 /* Check overlap against next cached too (past this one already) */
1873 cache++;
1874 continue;
1875 }
1876
1877 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
1878 skb = tcp_highest_sack(sk);
1879 if (skb == NULL)
1880 break;
1881 state.fack_count = tp->fackets_out;
1882 }
1883 skb = tcp_sacktag_skip(skb, sk, &state, start_seq);
1884
1885walk:
1886 skb = tcp_sacktag_walk(skb, sk, next_dup, &state,
1887 start_seq, end_seq, dup_sack);
1888
1889advance_sp:
1890 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1891 * due to in-order walk
1892 */
1893 if (after(end_seq, tp->frto_highmark))
1894 state.flag &= ~FLAG_ONLY_ORIG_SACKED;
1895
1896 i++;
1897 }
1898
1899 /* Clear the head of the cache sack blocks so we can skip it next time */
1900 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
1901 tp->recv_sack_cache[i].start_seq = 0;
1902 tp->recv_sack_cache[i].end_seq = 0;
1903 }
1904 for (j = 0; j < used_sacks; j++)
1905 tp->recv_sack_cache[i++] = sp[j];
1906
1907 tcp_mark_lost_retrans(sk);
1908
1909 tcp_verify_left_out(tp);
1910
1911 if ((state.reord < tp->fackets_out) &&
1912 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
1913 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
1914 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0);
1915
1916out:
1917
1918#if FASTRETRANS_DEBUG > 0
1919 WARN_ON((int)tp->sacked_out < 0);
1920 WARN_ON((int)tp->lost_out < 0);
1921 WARN_ON((int)tp->retrans_out < 0);
1922 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
1923#endif
1924 return state.flag;
1925}
1926
1927/* Limits sacked_out so that sum with lost_out isn't ever larger than
1928 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1929 */
1930static int tcp_limit_reno_sacked(struct tcp_sock *tp)
1931{
1932 u32 holes;
1933
1934 holes = max(tp->lost_out, 1U);
1935 holes = min(holes, tp->packets_out);
1936
1937 if ((tp->sacked_out + holes) > tp->packets_out) {
1938 tp->sacked_out = tp->packets_out - holes;
1939 return 1;
1940 }
1941 return 0;
1942}
1943
1944/* If we receive more dupacks than we expected counting segments
1945 * in assumption of absent reordering, interpret this as reordering.
1946 * The only another reason could be bug in receiver TCP.
1947 */
1948static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1949{
1950 struct tcp_sock *tp = tcp_sk(sk);
1951 if (tcp_limit_reno_sacked(tp))
1952 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1953}
1954
1955/* Emulate SACKs for SACKless connection: account for a new dupack. */
1956
1957static void tcp_add_reno_sack(struct sock *sk)
1958{
1959 struct tcp_sock *tp = tcp_sk(sk);
1960 tp->sacked_out++;
1961 tcp_check_reno_reordering(sk, 0);
1962 tcp_verify_left_out(tp);
1963}
1964
1965/* Account for ACK, ACKing some data in Reno Recovery phase. */
1966
1967static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1968{
1969 struct tcp_sock *tp = tcp_sk(sk);
1970
1971 if (acked > 0) {
1972 /* One ACK acked hole. The rest eat duplicate ACKs. */
1973 if (acked - 1 >= tp->sacked_out)
1974 tp->sacked_out = 0;
1975 else
1976 tp->sacked_out -= acked - 1;
1977 }
1978 tcp_check_reno_reordering(sk, acked);
1979 tcp_verify_left_out(tp);
1980}
1981
1982static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1983{
1984 tp->sacked_out = 0;
1985}
1986
1987static int tcp_is_sackfrto(const struct tcp_sock *tp)
1988{
1989 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp);
1990}
1991
1992/* F-RTO can only be used if TCP has never retransmitted anything other than
1993 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1994 */
1995int tcp_use_frto(struct sock *sk)
1996{
1997 const struct tcp_sock *tp = tcp_sk(sk);
1998 const struct inet_connection_sock *icsk = inet_csk(sk);
1999 struct sk_buff *skb;
2000
2001 if (!sysctl_tcp_frto)
2002 return 0;
2003
2004 /* MTU probe and F-RTO won't really play nicely along currently */
2005 if (icsk->icsk_mtup.probe_size)
2006 return 0;
2007
2008 if (tcp_is_sackfrto(tp))
2009 return 1;
2010
2011 /* Avoid expensive walking of rexmit queue if possible */
2012 if (tp->retrans_out > 1)
2013 return 0;
2014
2015 skb = tcp_write_queue_head(sk);
2016 if (tcp_skb_is_last(sk, skb))
2017 return 1;
2018 skb = tcp_write_queue_next(sk, skb); /* Skips head */
2019 tcp_for_write_queue_from(skb, sk) {
2020 if (skb == tcp_send_head(sk))
2021 break;
2022 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2023 return 0;
2024 /* Short-circuit when first non-SACKed skb has been checked */
2025 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2026 break;
2027 }
2028 return 1;
2029}
2030
2031/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2032 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2033 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2034 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2035 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2036 * bits are handled if the Loss state is really to be entered (in
2037 * tcp_enter_frto_loss).
2038 *
2039 * Do like tcp_enter_loss() would; when RTO expires the second time it
2040 * does:
2041 * "Reduce ssthresh if it has not yet been made inside this window."
2042 */
2043void tcp_enter_frto(struct sock *sk)
2044{
2045 const struct inet_connection_sock *icsk = inet_csk(sk);
2046 struct tcp_sock *tp = tcp_sk(sk);
2047 struct sk_buff *skb;
2048
2049 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) ||
2050 tp->snd_una == tp->high_seq ||
2051 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) &&
2052 !icsk->icsk_retransmits)) {
2053 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2054 /* Our state is too optimistic in ssthresh() call because cwnd
2055 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2056 * recovery has not yet completed. Pattern would be this: RTO,
2057 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2058 * up here twice).
2059 * RFC4138 should be more specific on what to do, even though
2060 * RTO is quite unlikely to occur after the first Cumulative ACK
2061 * due to back-off and complexity of triggering events ...
2062 */
2063 if (tp->frto_counter) {
2064 u32 stored_cwnd;
2065 stored_cwnd = tp->snd_cwnd;
2066 tp->snd_cwnd = 2;
2067 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2068 tp->snd_cwnd = stored_cwnd;
2069 } else {
2070 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2071 }
2072 /* ... in theory, cong.control module could do "any tricks" in
2073 * ssthresh(), which means that ca_state, lost bits and lost_out
2074 * counter would have to be faked before the call occurs. We
2075 * consider that too expensive, unlikely and hacky, so modules
2076 * using these in ssthresh() must deal these incompatibility
2077 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2078 */
2079 tcp_ca_event(sk, CA_EVENT_FRTO);
2080 }
2081
2082 tp->undo_marker = tp->snd_una;
2083 tp->undo_retrans = 0;
2084
2085 skb = tcp_write_queue_head(sk);
2086 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2087 tp->undo_marker = 0;
2088 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2089 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2090 tp->retrans_out -= tcp_skb_pcount(skb);
2091 }
2092 tcp_verify_left_out(tp);
2093
2094 /* Too bad if TCP was application limited */
2095 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
2096
2097 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2098 * The last condition is necessary at least in tp->frto_counter case.
2099 */
2100 if (tcp_is_sackfrto(tp) && (tp->frto_counter ||
2101 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) &&
2102 after(tp->high_seq, tp->snd_una)) {
2103 tp->frto_highmark = tp->high_seq;
2104 } else {
2105 tp->frto_highmark = tp->snd_nxt;
2106 }
2107 tcp_set_ca_state(sk, TCP_CA_Disorder);
2108 tp->high_seq = tp->snd_nxt;
2109 tp->frto_counter = 1;
2110}
2111
2112/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2113 * which indicates that we should follow the traditional RTO recovery,
2114 * i.e. mark everything lost and do go-back-N retransmission.
2115 */
2116static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
2117{
2118 struct tcp_sock *tp = tcp_sk(sk);
2119 struct sk_buff *skb;
2120
2121 tp->lost_out = 0;
2122 tp->retrans_out = 0;
2123 if (tcp_is_reno(tp))
2124 tcp_reset_reno_sack(tp);
2125
2126 tcp_for_write_queue(skb, sk) {
2127 if (skb == tcp_send_head(sk))
2128 break;
2129
2130 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2131 /*
2132 * Count the retransmission made on RTO correctly (only when
2133 * waiting for the first ACK and did not get it)...
2134 */
2135 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) {
2136 /* For some reason this R-bit might get cleared? */
2137 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
2138 tp->retrans_out += tcp_skb_pcount(skb);
2139 /* ...enter this if branch just for the first segment */
2140 flag |= FLAG_DATA_ACKED;
2141 } else {
2142 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2143 tp->undo_marker = 0;
2144 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2145 }
2146
2147 /* Marking forward transmissions that were made after RTO lost
2148 * can cause unnecessary retransmissions in some scenarios,
2149 * SACK blocks will mitigate that in some but not in all cases.
2150 * We used to not mark them but it was causing break-ups with
2151 * receivers that do only in-order receival.
2152 *
2153 * TODO: we could detect presence of such receiver and select
2154 * different behavior per flow.
2155 */
2156 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2157 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2158 tp->lost_out += tcp_skb_pcount(skb);
2159 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
2160 }
2161 }
2162 tcp_verify_left_out(tp);
2163
2164 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments;
2165 tp->snd_cwnd_cnt = 0;
2166 tp->snd_cwnd_stamp = tcp_time_stamp;
2167 tp->frto_counter = 0;
2168 tp->bytes_acked = 0;
2169
2170 tp->reordering = min_t(unsigned int, tp->reordering,
2171 sysctl_tcp_reordering);
2172 tcp_set_ca_state(sk, TCP_CA_Loss);
2173 tp->high_seq = tp->snd_nxt;
2174 TCP_ECN_queue_cwr(tp);
2175
2176 tcp_clear_all_retrans_hints(tp);
2177}
2178
2179static void tcp_clear_retrans_partial(struct tcp_sock *tp)
2180{
2181 tp->retrans_out = 0;
2182 tp->lost_out = 0;
2183
2184 tp->undo_marker = 0;
2185 tp->undo_retrans = 0;
2186}
2187
2188void tcp_clear_retrans(struct tcp_sock *tp)
2189{
2190 tcp_clear_retrans_partial(tp);
2191
2192 tp->fackets_out = 0;
2193 tp->sacked_out = 0;
2194}
2195
2196/* Enter Loss state. If "how" is not zero, forget all SACK information
2197 * and reset tags completely, otherwise preserve SACKs. If receiver
2198 * dropped its ofo queue, we will know this due to reneging detection.
2199 */
2200void tcp_enter_loss(struct sock *sk, int how)
2201{
2202 const struct inet_connection_sock *icsk = inet_csk(sk);
2203 struct tcp_sock *tp = tcp_sk(sk);
2204 struct sk_buff *skb;
2205
2206 /* Reduce ssthresh if it has not yet been made inside this window. */
2207 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
2208 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
2209 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2210 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2211 tcp_ca_event(sk, CA_EVENT_LOSS);
2212 }
2213 tp->snd_cwnd = 1;
2214 tp->snd_cwnd_cnt = 0;
2215 tp->snd_cwnd_stamp = tcp_time_stamp;
2216
2217 tp->bytes_acked = 0;
2218 tcp_clear_retrans_partial(tp);
2219
2220 if (tcp_is_reno(tp))
2221 tcp_reset_reno_sack(tp);
2222
2223 if (!how) {
2224 /* Push undo marker, if it was plain RTO and nothing
2225 * was retransmitted. */
2226 tp->undo_marker = tp->snd_una;
2227 } else {
2228 tp->sacked_out = 0;
2229 tp->fackets_out = 0;
2230 }
2231 tcp_clear_all_retrans_hints(tp);
2232
2233 tcp_for_write_queue(skb, sk) {
2234 if (skb == tcp_send_head(sk))
2235 break;
2236
2237 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2238 tp->undo_marker = 0;
2239 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
2240 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
2241 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
2242 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2243 tp->lost_out += tcp_skb_pcount(skb);
2244 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
2245 }
2246 }
2247 tcp_verify_left_out(tp);
2248
2249 tp->reordering = min_t(unsigned int, tp->reordering,
2250 sysctl_tcp_reordering);
2251 tcp_set_ca_state(sk, TCP_CA_Loss);
2252 tp->high_seq = tp->snd_nxt;
2253 TCP_ECN_queue_cwr(tp);
2254 /* Abort F-RTO algorithm if one is in progress */
2255 tp->frto_counter = 0;
2256}
2257
2258/* If ACK arrived pointing to a remembered SACK, it means that our
2259 * remembered SACKs do not reflect real state of receiver i.e.
2260 * receiver _host_ is heavily congested (or buggy).
2261 *
2262 * Do processing similar to RTO timeout.
2263 */
2264static int tcp_check_sack_reneging(struct sock *sk, int flag)
2265{
2266 if (flag & FLAG_SACK_RENEGING) {
2267 struct inet_connection_sock *icsk = inet_csk(sk);
2268 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
2269
2270 tcp_enter_loss(sk, 1);
2271 icsk->icsk_retransmits++;
2272 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
2273 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2274 icsk->icsk_rto, TCP_RTO_MAX);
2275 return 1;
2276 }
2277 return 0;
2278}
2279
2280static inline int tcp_fackets_out(struct tcp_sock *tp)
2281{
2282 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
2283}
2284
2285/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2286 * counter when SACK is enabled (without SACK, sacked_out is used for
2287 * that purpose).
2288 *
2289 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2290 * segments up to the highest received SACK block so far and holes in
2291 * between them.
2292 *
2293 * With reordering, holes may still be in flight, so RFC3517 recovery
2294 * uses pure sacked_out (total number of SACKed segments) even though
2295 * it violates the RFC that uses duplicate ACKs, often these are equal
2296 * but when e.g. out-of-window ACKs or packet duplication occurs,
2297 * they differ. Since neither occurs due to loss, TCP should really
2298 * ignore them.
2299 */
2300static inline int tcp_dupack_heuristics(struct tcp_sock *tp)
2301{
2302 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
2303}
2304
2305static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
2306{
2307 return tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto;
2308}
2309
2310static inline int tcp_head_timedout(struct sock *sk)
2311{
2312 struct tcp_sock *tp = tcp_sk(sk);
2313
2314 return tp->packets_out &&
2315 tcp_skb_timedout(sk, tcp_write_queue_head(sk));
2316}
2317
2318/* Linux NewReno/SACK/FACK/ECN state machine.
2319 * --------------------------------------
2320 *
2321 * "Open" Normal state, no dubious events, fast path.
2322 * "Disorder" In all the respects it is "Open",
2323 * but requires a bit more attention. It is entered when
2324 * we see some SACKs or dupacks. It is split of "Open"
2325 * mainly to move some processing from fast path to slow one.
2326 * "CWR" CWND was reduced due to some Congestion Notification event.
2327 * It can be ECN, ICMP source quench, local device congestion.
2328 * "Recovery" CWND was reduced, we are fast-retransmitting.
2329 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2330 *
2331 * tcp_fastretrans_alert() is entered:
2332 * - each incoming ACK, if state is not "Open"
2333 * - when arrived ACK is unusual, namely:
2334 * * SACK
2335 * * Duplicate ACK.
2336 * * ECN ECE.
2337 *
2338 * Counting packets in flight is pretty simple.
2339 *
2340 * in_flight = packets_out - left_out + retrans_out
2341 *
2342 * packets_out is SND.NXT-SND.UNA counted in packets.
2343 *
2344 * retrans_out is number of retransmitted segments.
2345 *
2346 * left_out is number of segments left network, but not ACKed yet.
2347 *
2348 * left_out = sacked_out + lost_out
2349 *
2350 * sacked_out: Packets, which arrived to receiver out of order
2351 * and hence not ACKed. With SACKs this number is simply
2352 * amount of SACKed data. Even without SACKs
2353 * it is easy to give pretty reliable estimate of this number,
2354 * counting duplicate ACKs.
2355 *
2356 * lost_out: Packets lost by network. TCP has no explicit
2357 * "loss notification" feedback from network (for now).
2358 * It means that this number can be only _guessed_.
2359 * Actually, it is the heuristics to predict lossage that
2360 * distinguishes different algorithms.
2361 *
2362 * F.e. after RTO, when all the queue is considered as lost,
2363 * lost_out = packets_out and in_flight = retrans_out.
2364 *
2365 * Essentially, we have now two algorithms counting
2366 * lost packets.
2367 *
2368 * FACK: It is the simplest heuristics. As soon as we decided
2369 * that something is lost, we decide that _all_ not SACKed
2370 * packets until the most forward SACK are lost. I.e.
2371 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2372 * It is absolutely correct estimate, if network does not reorder
2373 * packets. And it loses any connection to reality when reordering
2374 * takes place. We use FACK by default until reordering
2375 * is suspected on the path to this destination.
2376 *
2377 * NewReno: when Recovery is entered, we assume that one segment
2378 * is lost (classic Reno). While we are in Recovery and
2379 * a partial ACK arrives, we assume that one more packet
2380 * is lost (NewReno). This heuristics are the same in NewReno
2381 * and SACK.
2382 *
2383 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2384 * deflation etc. CWND is real congestion window, never inflated, changes
2385 * only according to classic VJ rules.
2386 *
2387 * Really tricky (and requiring careful tuning) part of algorithm
2388 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2389 * The first determines the moment _when_ we should reduce CWND and,
2390 * hence, slow down forward transmission. In fact, it determines the moment
2391 * when we decide that hole is caused by loss, rather than by a reorder.
2392 *
2393 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2394 * holes, caused by lost packets.
2395 *
2396 * And the most logically complicated part of algorithm is undo
2397 * heuristics. We detect false retransmits due to both too early
2398 * fast retransmit (reordering) and underestimated RTO, analyzing
2399 * timestamps and D-SACKs. When we detect that some segments were
2400 * retransmitted by mistake and CWND reduction was wrong, we undo
2401 * window reduction and abort recovery phase. This logic is hidden
2402 * inside several functions named tcp_try_undo_<something>.
2403 */
2404
2405/* This function decides, when we should leave Disordered state
2406 * and enter Recovery phase, reducing congestion window.
2407 *
2408 * Main question: may we further continue forward transmission
2409 * with the same cwnd?
2410 */
2411static int tcp_time_to_recover(struct sock *sk)
2412{
2413 struct tcp_sock *tp = tcp_sk(sk);
2414 __u32 packets_out;
2415
2416 /* Do not perform any recovery during F-RTO algorithm */
2417 if (tp->frto_counter)
2418 return 0;
2419
2420 /* Trick#1: The loss is proven. */
2421 if (tp->lost_out)
2422 return 1;
2423
2424 /* Not-A-Trick#2 : Classic rule... */
2425 if (tcp_dupack_heuristics(tp) > tp->reordering)
2426 return 1;
2427
2428 /* Trick#3 : when we use RFC2988 timer restart, fast
2429 * retransmit can be triggered by timeout of queue head.
2430 */
2431 if (tcp_is_fack(tp) && tcp_head_timedout(sk))
2432 return 1;
2433
2434 /* Trick#4: It is still not OK... But will it be useful to delay
2435 * recovery more?
2436 */
2437 packets_out = tp->packets_out;
2438 if (packets_out <= tp->reordering &&
2439 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
2440 !tcp_may_send_now(sk)) {
2441 /* We have nothing to send. This connection is limited
2442 * either by receiver window or by application.
2443 */
2444 return 1;
2445 }
2446
2447 /* If a thin stream is detected, retransmit after first
2448 * received dupack. Employ only if SACK is supported in order
2449 * to avoid possible corner-case series of spurious retransmissions
2450 * Use only if there are no unsent data.
2451 */
2452 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) &&
2453 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 &&
2454 tcp_is_sack(tp) && !tcp_send_head(sk))
2455 return 1;
2456
2457 return 0;
2458}
2459
2460/* New heuristics: it is possible only after we switched to restart timer
2461 * each time when something is ACKed. Hence, we can detect timed out packets
2462 * during fast retransmit without falling to slow start.
2463 *
2464 * Usefulness of this as is very questionable, since we should know which of
2465 * the segments is the next to timeout which is relatively expensive to find
2466 * in general case unless we add some data structure just for that. The
2467 * current approach certainly won't find the right one too often and when it
2468 * finally does find _something_ it usually marks large part of the window
2469 * right away (because a retransmission with a larger timestamp blocks the
2470 * loop from advancing). -ij
2471 */
2472static void tcp_timeout_skbs(struct sock *sk)
2473{
2474 struct tcp_sock *tp = tcp_sk(sk);
2475 struct sk_buff *skb;
2476
2477 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk))
2478 return;
2479
2480 skb = tp->scoreboard_skb_hint;
2481 if (tp->scoreboard_skb_hint == NULL)
2482 skb = tcp_write_queue_head(sk);
2483
2484 tcp_for_write_queue_from(skb, sk) {
2485 if (skb == tcp_send_head(sk))
2486 break;
2487 if (!tcp_skb_timedout(sk, skb))
2488 break;
2489
2490 tcp_skb_mark_lost(tp, skb);
2491 }
2492
2493 tp->scoreboard_skb_hint = skb;
2494
2495 tcp_verify_left_out(tp);
2496}
2497
2498/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2499 * is against sacked "cnt", otherwise it's against facked "cnt"
2500 */
2501static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
2502{
2503 struct tcp_sock *tp = tcp_sk(sk);
2504 struct sk_buff *skb;
2505 int cnt, oldcnt;
2506 int err;
2507 unsigned int mss;
2508
2509 WARN_ON(packets > tp->packets_out);
2510 if (tp->lost_skb_hint) {
2511 skb = tp->lost_skb_hint;
2512 cnt = tp->lost_cnt_hint;
2513 /* Head already handled? */
2514 if (mark_head && skb != tcp_write_queue_head(sk))
2515 return;
2516 } else {
2517 skb = tcp_write_queue_head(sk);
2518 cnt = 0;
2519 }
2520
2521 tcp_for_write_queue_from(skb, sk) {
2522 if (skb == tcp_send_head(sk))
2523 break;
2524 /* TODO: do this better */
2525 /* this is not the most efficient way to do this... */
2526 tp->lost_skb_hint = skb;
2527 tp->lost_cnt_hint = cnt;
2528
2529 if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
2530 break;
2531
2532 oldcnt = cnt;
2533 if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
2534 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2535 cnt += tcp_skb_pcount(skb);
2536
2537 if (cnt > packets) {
2538 if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) ||
2539 (oldcnt >= packets))
2540 break;
2541
2542 mss = skb_shinfo(skb)->gso_size;
2543 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss);
2544 if (err < 0)
2545 break;
2546 cnt = packets;
2547 }
2548
2549 tcp_skb_mark_lost(tp, skb);
2550
2551 if (mark_head)
2552 break;
2553 }
2554 tcp_verify_left_out(tp);
2555}
2556
2557/* Account newly detected lost packet(s) */
2558
2559static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
2560{
2561 struct tcp_sock *tp = tcp_sk(sk);
2562
2563 if (tcp_is_reno(tp)) {
2564 tcp_mark_head_lost(sk, 1, 1);
2565 } else if (tcp_is_fack(tp)) {
2566 int lost = tp->fackets_out - tp->reordering;
2567 if (lost <= 0)
2568 lost = 1;
2569 tcp_mark_head_lost(sk, lost, 0);
2570 } else {
2571 int sacked_upto = tp->sacked_out - tp->reordering;
2572 if (sacked_upto >= 0)
2573 tcp_mark_head_lost(sk, sacked_upto, 0);
2574 else if (fast_rexmit)
2575 tcp_mark_head_lost(sk, 1, 1);
2576 }
2577
2578 tcp_timeout_skbs(sk);
2579}
2580
2581/* CWND moderation, preventing bursts due to too big ACKs
2582 * in dubious situations.
2583 */
2584static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
2585{
2586 tp->snd_cwnd = min(tp->snd_cwnd,
2587 tcp_packets_in_flight(tp) + tcp_max_burst(tp));
2588 tp->snd_cwnd_stamp = tcp_time_stamp;
2589}
2590
2591/* Lower bound on congestion window is slow start threshold
2592 * unless congestion avoidance choice decides to overide it.
2593 */
2594static inline u32 tcp_cwnd_min(const struct sock *sk)
2595{
2596 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2597
2598 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
2599}
2600
2601/* Decrease cwnd each second ack. */
2602static void tcp_cwnd_down(struct sock *sk, int flag)
2603{
2604 struct tcp_sock *tp = tcp_sk(sk);
2605 int decr = tp->snd_cwnd_cnt + 1;
2606
2607 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) ||
2608 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) {
2609 tp->snd_cwnd_cnt = decr & 1;
2610 decr >>= 1;
2611
2612 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
2613 tp->snd_cwnd -= decr;
2614
2615 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
2616 tp->snd_cwnd_stamp = tcp_time_stamp;
2617 }
2618}
2619
2620/* Nothing was retransmitted or returned timestamp is less
2621 * than timestamp of the first retransmission.
2622 */
2623static inline int tcp_packet_delayed(struct tcp_sock *tp)
2624{
2625 return !tp->retrans_stamp ||
2626 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2627 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp));
2628}
2629
2630/* Undo procedures. */
2631
2632#if FASTRETRANS_DEBUG > 1
2633static void DBGUNDO(struct sock *sk, const char *msg)
2634{
2635 struct tcp_sock *tp = tcp_sk(sk);
2636 struct inet_sock *inet = inet_sk(sk);
2637
2638 if (sk->sk_family == AF_INET) {
2639 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2640 msg,
2641 &inet->inet_daddr, ntohs(inet->inet_dport),
2642 tp->snd_cwnd, tcp_left_out(tp),
2643 tp->snd_ssthresh, tp->prior_ssthresh,
2644 tp->packets_out);
2645 }
2646#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2647 else if (sk->sk_family == AF_INET6) {
2648 struct ipv6_pinfo *np = inet6_sk(sk);
2649 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2650 msg,
2651 &np->daddr, ntohs(inet->inet_dport),
2652 tp->snd_cwnd, tcp_left_out(tp),
2653 tp->snd_ssthresh, tp->prior_ssthresh,
2654 tp->packets_out);
2655 }
2656#endif
2657}
2658#else
2659#define DBGUNDO(x...) do { } while (0)
2660#endif
2661
2662static void tcp_undo_cwr(struct sock *sk, const int undo)
2663{
2664 struct tcp_sock *tp = tcp_sk(sk);
2665
2666 if (tp->prior_ssthresh) {
2667 const struct inet_connection_sock *icsk = inet_csk(sk);
2668
2669 if (icsk->icsk_ca_ops->undo_cwnd)
2670 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
2671 else
2672 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
2673
2674 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
2675 tp->snd_ssthresh = tp->prior_ssthresh;
2676 TCP_ECN_withdraw_cwr(tp);
2677 }
2678 } else {
2679 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
2680 }
2681 tcp_moderate_cwnd(tp);
2682 tp->snd_cwnd_stamp = tcp_time_stamp;
2683}
2684
2685static inline int tcp_may_undo(struct tcp_sock *tp)
2686{
2687 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
2688}
2689
2690/* People celebrate: "We love our President!" */
2691static int tcp_try_undo_recovery(struct sock *sk)
2692{
2693 struct tcp_sock *tp = tcp_sk(sk);
2694
2695 if (tcp_may_undo(tp)) {
2696 int mib_idx;
2697
2698 /* Happy end! We did not retransmit anything
2699 * or our original transmission succeeded.
2700 */
2701 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
2702 tcp_undo_cwr(sk, 1);
2703 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
2704 mib_idx = LINUX_MIB_TCPLOSSUNDO;
2705 else
2706 mib_idx = LINUX_MIB_TCPFULLUNDO;
2707
2708 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2709 tp->undo_marker = 0;
2710 }
2711 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
2712 /* Hold old state until something *above* high_seq
2713 * is ACKed. For Reno it is MUST to prevent false
2714 * fast retransmits (RFC2582). SACK TCP is safe. */
2715 tcp_moderate_cwnd(tp);
2716 return 1;
2717 }
2718 tcp_set_ca_state(sk, TCP_CA_Open);
2719 return 0;
2720}
2721
2722/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2723static void tcp_try_undo_dsack(struct sock *sk)
2724{
2725 struct tcp_sock *tp = tcp_sk(sk);
2726
2727 if (tp->undo_marker && !tp->undo_retrans) {
2728 DBGUNDO(sk, "D-SACK");
2729 tcp_undo_cwr(sk, 1);
2730 tp->undo_marker = 0;
2731 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
2732 }
2733}
2734
2735/* We can clear retrans_stamp when there are no retransmissions in the
2736 * window. It would seem that it is trivially available for us in
2737 * tp->retrans_out, however, that kind of assumptions doesn't consider
2738 * what will happen if errors occur when sending retransmission for the
2739 * second time. ...It could the that such segment has only
2740 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2741 * the head skb is enough except for some reneging corner cases that
2742 * are not worth the effort.
2743 *
2744 * Main reason for all this complexity is the fact that connection dying
2745 * time now depends on the validity of the retrans_stamp, in particular,
2746 * that successive retransmissions of a segment must not advance
2747 * retrans_stamp under any conditions.
2748 */
2749static int tcp_any_retrans_done(struct sock *sk)
2750{
2751 struct tcp_sock *tp = tcp_sk(sk);
2752 struct sk_buff *skb;
2753
2754 if (tp->retrans_out)
2755 return 1;
2756
2757 skb = tcp_write_queue_head(sk);
2758 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
2759 return 1;
2760
2761 return 0;
2762}
2763
2764/* Undo during fast recovery after partial ACK. */
2765
2766static int tcp_try_undo_partial(struct sock *sk, int acked)
2767{
2768 struct tcp_sock *tp = tcp_sk(sk);
2769 /* Partial ACK arrived. Force Hoe's retransmit. */
2770 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);
2771
2772 if (tcp_may_undo(tp)) {
2773 /* Plain luck! Hole if filled with delayed
2774 * packet, rather than with a retransmit.
2775 */
2776 if (!tcp_any_retrans_done(sk))
2777 tp->retrans_stamp = 0;
2778
2779 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
2780
2781 DBGUNDO(sk, "Hoe");
2782 tcp_undo_cwr(sk, 0);
2783 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
2784
2785 /* So... Do not make Hoe's retransmit yet.
2786 * If the first packet was delayed, the rest
2787 * ones are most probably delayed as well.
2788 */
2789 failed = 0;
2790 }
2791 return failed;
2792}
2793
2794/* Undo during loss recovery after partial ACK. */
2795static int tcp_try_undo_loss(struct sock *sk)
2796{
2797 struct tcp_sock *tp = tcp_sk(sk);
2798
2799 if (tcp_may_undo(tp)) {
2800 struct sk_buff *skb;
2801 tcp_for_write_queue(skb, sk) {
2802 if (skb == tcp_send_head(sk))
2803 break;
2804 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2805 }
2806
2807 tcp_clear_all_retrans_hints(tp);
2808
2809 DBGUNDO(sk, "partial loss");
2810 tp->lost_out = 0;
2811 tcp_undo_cwr(sk, 1);
2812 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
2813 inet_csk(sk)->icsk_retransmits = 0;
2814 tp->undo_marker = 0;
2815 if (tcp_is_sack(tp))
2816 tcp_set_ca_state(sk, TCP_CA_Open);
2817 return 1;
2818 }
2819 return 0;
2820}
2821
2822static inline void tcp_complete_cwr(struct sock *sk)
2823{
2824 struct tcp_sock *tp = tcp_sk(sk);
2825 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2826 tp->snd_cwnd_stamp = tcp_time_stamp;
2827 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
2828}
2829
2830static void tcp_try_keep_open(struct sock *sk)
2831{
2832 struct tcp_sock *tp = tcp_sk(sk);
2833 int state = TCP_CA_Open;
2834
2835 if (tcp_left_out(tp) || tcp_any_retrans_done(sk) || tp->undo_marker)
2836 state = TCP_CA_Disorder;
2837
2838 if (inet_csk(sk)->icsk_ca_state != state) {
2839 tcp_set_ca_state(sk, state);
2840 tp->high_seq = tp->snd_nxt;
2841 }
2842}
2843
2844static void tcp_try_to_open(struct sock *sk, int flag)
2845{
2846 struct tcp_sock *tp = tcp_sk(sk);
2847
2848 tcp_verify_left_out(tp);
2849
2850 if (!tp->frto_counter && !tcp_any_retrans_done(sk))
2851 tp->retrans_stamp = 0;
2852
2853 if (flag & FLAG_ECE)
2854 tcp_enter_cwr(sk, 1);
2855
2856 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
2857 tcp_try_keep_open(sk);
2858 tcp_moderate_cwnd(tp);
2859 } else {
2860 tcp_cwnd_down(sk, flag);
2861 }
2862}
2863
2864static void tcp_mtup_probe_failed(struct sock *sk)
2865{
2866 struct inet_connection_sock *icsk = inet_csk(sk);
2867
2868 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2869 icsk->icsk_mtup.probe_size = 0;
2870}
2871
2872static void tcp_mtup_probe_success(struct sock *sk)
2873{
2874 struct tcp_sock *tp = tcp_sk(sk);
2875 struct inet_connection_sock *icsk = inet_csk(sk);
2876
2877 /* FIXME: breaks with very large cwnd */
2878 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2879 tp->snd_cwnd = tp->snd_cwnd *
2880 tcp_mss_to_mtu(sk, tp->mss_cache) /
2881 icsk->icsk_mtup.probe_size;
2882 tp->snd_cwnd_cnt = 0;
2883 tp->snd_cwnd_stamp = tcp_time_stamp;
2884 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2885
2886 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2887 icsk->icsk_mtup.probe_size = 0;
2888 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2889}
2890
2891/* Do a simple retransmit without using the backoff mechanisms in
2892 * tcp_timer. This is used for path mtu discovery.
2893 * The socket is already locked here.
2894 */
2895void tcp_simple_retransmit(struct sock *sk)
2896{
2897 const struct inet_connection_sock *icsk = inet_csk(sk);
2898 struct tcp_sock *tp = tcp_sk(sk);
2899 struct sk_buff *skb;
2900 unsigned int mss = tcp_current_mss(sk);
2901 u32 prior_lost = tp->lost_out;
2902
2903 tcp_for_write_queue(skb, sk) {
2904 if (skb == tcp_send_head(sk))
2905 break;
2906 if (tcp_skb_seglen(skb) > mss &&
2907 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2908 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2909 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2910 tp->retrans_out -= tcp_skb_pcount(skb);
2911 }
2912 tcp_skb_mark_lost_uncond_verify(tp, skb);
2913 }
2914 }
2915
2916 tcp_clear_retrans_hints_partial(tp);
2917
2918 if (prior_lost == tp->lost_out)
2919 return;
2920
2921 if (tcp_is_reno(tp))
2922 tcp_limit_reno_sacked(tp);
2923
2924 tcp_verify_left_out(tp);
2925
2926 /* Don't muck with the congestion window here.
2927 * Reason is that we do not increase amount of _data_
2928 * in network, but units changed and effective
2929 * cwnd/ssthresh really reduced now.
2930 */
2931 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2932 tp->high_seq = tp->snd_nxt;
2933 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2934 tp->prior_ssthresh = 0;
2935 tp->undo_marker = 0;
2936 tcp_set_ca_state(sk, TCP_CA_Loss);
2937 }
2938 tcp_xmit_retransmit_queue(sk);
2939}
2940EXPORT_SYMBOL(tcp_simple_retransmit);
2941
2942/* Process an event, which can update packets-in-flight not trivially.
2943 * Main goal of this function is to calculate new estimate for left_out,
2944 * taking into account both packets sitting in receiver's buffer and
2945 * packets lost by network.
2946 *
2947 * Besides that it does CWND reduction, when packet loss is detected
2948 * and changes state of machine.
2949 *
2950 * It does _not_ decide what to send, it is made in function
2951 * tcp_xmit_retransmit_queue().
2952 */
2953static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
2954{
2955 struct inet_connection_sock *icsk = inet_csk(sk);
2956 struct tcp_sock *tp = tcp_sk(sk);
2957 int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
2958 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
2959 (tcp_fackets_out(tp) > tp->reordering));
2960 int fast_rexmit = 0, mib_idx;
2961
2962 if (WARN_ON(!tp->packets_out && tp->sacked_out))
2963 tp->sacked_out = 0;
2964 if (WARN_ON(!tp->sacked_out && tp->fackets_out))
2965 tp->fackets_out = 0;
2966
2967 /* Now state machine starts.
2968 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2969 if (flag & FLAG_ECE)
2970 tp->prior_ssthresh = 0;
2971
2972 /* B. In all the states check for reneging SACKs. */
2973 if (tcp_check_sack_reneging(sk, flag))
2974 return;
2975
2976 /* C. Process data loss notification, provided it is valid. */
2977 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
2978 before(tp->snd_una, tp->high_seq) &&
2979 icsk->icsk_ca_state != TCP_CA_Open &&
2980 tp->fackets_out > tp->reordering) {
2981 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering, 0);
2982 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS);
2983 }
2984
2985 /* D. Check consistency of the current state. */
2986 tcp_verify_left_out(tp);
2987
2988 /* E. Check state exit conditions. State can be terminated
2989 * when high_seq is ACKed. */
2990 if (icsk->icsk_ca_state == TCP_CA_Open) {
2991 WARN_ON(tp->retrans_out != 0);
2992 tp->retrans_stamp = 0;
2993 } else if (!before(tp->snd_una, tp->high_seq)) {
2994 switch (icsk->icsk_ca_state) {
2995 case TCP_CA_Loss:
2996 icsk->icsk_retransmits = 0;
2997 if (tcp_try_undo_recovery(sk))
2998 return;
2999 break;
3000
3001 case TCP_CA_CWR:
3002 /* CWR is to be held something *above* high_seq
3003 * is ACKed for CWR bit to reach receiver. */
3004 if (tp->snd_una != tp->high_seq) {
3005 tcp_complete_cwr(sk);
3006 tcp_set_ca_state(sk, TCP_CA_Open);
3007 }
3008 break;
3009
3010 case TCP_CA_Disorder:
3011 tcp_try_undo_dsack(sk);
3012 if (!tp->undo_marker ||
3013 /* For SACK case do not Open to allow to undo
3014 * catching for all duplicate ACKs. */
3015 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) {
3016 tp->undo_marker = 0;
3017 tcp_set_ca_state(sk, TCP_CA_Open);
3018 }
3019 break;
3020
3021 case TCP_CA_Recovery:
3022 if (tcp_is_reno(tp))
3023 tcp_reset_reno_sack(tp);
3024 if (tcp_try_undo_recovery(sk))
3025 return;
3026 tcp_complete_cwr(sk);
3027 break;
3028 }
3029 }
3030
3031 /* F. Process state. */
3032 switch (icsk->icsk_ca_state) {
3033 case TCP_CA_Recovery:
3034 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
3035 if (tcp_is_reno(tp) && is_dupack)
3036 tcp_add_reno_sack(sk);
3037 } else
3038 do_lost = tcp_try_undo_partial(sk, pkts_acked);
3039 break;
3040 case TCP_CA_Loss:
3041 if (flag & FLAG_DATA_ACKED)
3042 icsk->icsk_retransmits = 0;
3043 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED)
3044 tcp_reset_reno_sack(tp);
3045 if (!tcp_try_undo_loss(sk)) {
3046 tcp_moderate_cwnd(tp);
3047 tcp_xmit_retransmit_queue(sk);
3048 return;
3049 }
3050 if (icsk->icsk_ca_state != TCP_CA_Open)
3051 return;
3052 /* Loss is undone; fall through to processing in Open state. */
3053 default:
3054 if (tcp_is_reno(tp)) {
3055 if (flag & FLAG_SND_UNA_ADVANCED)
3056 tcp_reset_reno_sack(tp);
3057 if (is_dupack)
3058 tcp_add_reno_sack(sk);
3059 }
3060
3061 if (icsk->icsk_ca_state == TCP_CA_Disorder)
3062 tcp_try_undo_dsack(sk);
3063
3064 if (!tcp_time_to_recover(sk)) {
3065 tcp_try_to_open(sk, flag);
3066 return;
3067 }
3068
3069 /* MTU probe failure: don't reduce cwnd */
3070 if (icsk->icsk_ca_state < TCP_CA_CWR &&
3071 icsk->icsk_mtup.probe_size &&
3072 tp->snd_una == tp->mtu_probe.probe_seq_start) {
3073 tcp_mtup_probe_failed(sk);
3074 /* Restores the reduction we did in tcp_mtup_probe() */
3075 tp->snd_cwnd++;
3076 tcp_simple_retransmit(sk);
3077 return;
3078 }
3079
3080 /* Otherwise enter Recovery state */
3081
3082 if (tcp_is_reno(tp))
3083 mib_idx = LINUX_MIB_TCPRENORECOVERY;
3084 else
3085 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
3086
3087 NET_INC_STATS_BH(sock_net(sk), mib_idx);
3088
3089 tp->high_seq = tp->snd_nxt;
3090 tp->prior_ssthresh = 0;
3091 tp->undo_marker = tp->snd_una;
3092 tp->undo_retrans = tp->retrans_out;
3093
3094 if (icsk->icsk_ca_state < TCP_CA_CWR) {
3095 if (!(flag & FLAG_ECE))
3096 tp->prior_ssthresh = tcp_current_ssthresh(sk);
3097 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
3098 TCP_ECN_queue_cwr(tp);
3099 }
3100
3101 tp->bytes_acked = 0;
3102 tp->snd_cwnd_cnt = 0;
3103 tcp_set_ca_state(sk, TCP_CA_Recovery);
3104 fast_rexmit = 1;
3105 }
3106
3107 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
3108 tcp_update_scoreboard(sk, fast_rexmit);
3109 tcp_cwnd_down(sk, flag);
3110 tcp_xmit_retransmit_queue(sk);
3111}
3112
3113static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt)
3114{
3115 tcp_rtt_estimator(sk, seq_rtt);
3116 tcp_set_rto(sk);
3117 inet_csk(sk)->icsk_backoff = 0;
3118}
3119
3120/* Read draft-ietf-tcplw-high-performance before mucking
3121 * with this code. (Supersedes RFC1323)
3122 */
3123static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
3124{
3125 /* RTTM Rule: A TSecr value received in a segment is used to
3126 * update the averaged RTT measurement only if the segment
3127 * acknowledges some new data, i.e., only if it advances the
3128 * left edge of the send window.
3129 *
3130 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3131 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3132 *
3133 * Changed: reset backoff as soon as we see the first valid sample.
3134 * If we do not, we get strongly overestimated rto. With timestamps
3135 * samples are accepted even from very old segments: f.e., when rtt=1
3136 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3137 * answer arrives rto becomes 120 seconds! If at least one of segments
3138 * in window is lost... Voila. --ANK (010210)
3139 */
3140 struct tcp_sock *tp = tcp_sk(sk);
3141
3142 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr);
3143}
3144
3145static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
3146{
3147 /* We don't have a timestamp. Can only use
3148 * packets that are not retransmitted to determine
3149 * rtt estimates. Also, we must not reset the
3150 * backoff for rto until we get a non-retransmitted
3151 * packet. This allows us to deal with a situation
3152 * where the network delay has increased suddenly.
3153 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3154 */
3155
3156 if (flag & FLAG_RETRANS_DATA_ACKED)
3157 return;
3158
3159 tcp_valid_rtt_meas(sk, seq_rtt);
3160}
3161
3162static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
3163 const s32 seq_rtt)
3164{
3165 const struct tcp_sock *tp = tcp_sk(sk);
3166 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3167 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
3168 tcp_ack_saw_tstamp(sk, flag);
3169 else if (seq_rtt >= 0)
3170 tcp_ack_no_tstamp(sk, seq_rtt, flag);
3171}
3172
3173static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
3174{
3175 const struct inet_connection_sock *icsk = inet_csk(sk);
3176 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight);
3177 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
3178}
3179
3180/* Restart timer after forward progress on connection.
3181 * RFC2988 recommends to restart timer to now+rto.
3182 */
3183static void tcp_rearm_rto(struct sock *sk)
3184{
3185 struct tcp_sock *tp = tcp_sk(sk);
3186
3187 if (!tp->packets_out) {
3188 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
3189 } else {
3190 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3191 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3192 }
3193}
3194
3195/* If we get here, the whole TSO packet has not been acked. */
3196static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
3197{
3198 struct tcp_sock *tp = tcp_sk(sk);
3199 u32 packets_acked;
3200
3201 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
3202
3203 packets_acked = tcp_skb_pcount(skb);
3204 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3205 return 0;
3206 packets_acked -= tcp_skb_pcount(skb);
3207
3208 if (packets_acked) {
3209 BUG_ON(tcp_skb_pcount(skb) == 0);
3210 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
3211 }
3212
3213 return packets_acked;
3214}
3215
3216/* Remove acknowledged frames from the retransmission queue. If our packet
3217 * is before the ack sequence we can discard it as it's confirmed to have
3218 * arrived at the other end.
3219 */
3220static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
3221 u32 prior_snd_una)
3222{
3223 struct tcp_sock *tp = tcp_sk(sk);
3224 const struct inet_connection_sock *icsk = inet_csk(sk);
3225 struct sk_buff *skb;
3226 u32 now = tcp_time_stamp;
3227 int fully_acked = 1;
3228 int flag = 0;
3229 u32 pkts_acked = 0;
3230 u32 reord = tp->packets_out;
3231 u32 prior_sacked = tp->sacked_out;
3232 s32 seq_rtt = -1;
3233 s32 ca_seq_rtt = -1;
3234 ktime_t last_ackt = net_invalid_timestamp();
3235
3236 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
3237 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
3238 u32 acked_pcount;
3239 u8 sacked = scb->sacked;
3240
3241 /* Determine how many packets and what bytes were acked, tso and else */
3242 if (after(scb->end_seq, tp->snd_una)) {
3243 if (tcp_skb_pcount(skb) == 1 ||
3244 !after(tp->snd_una, scb->seq))
3245 break;
3246
3247 acked_pcount = tcp_tso_acked(sk, skb);
3248 if (!acked_pcount)
3249 break;
3250
3251 fully_acked = 0;
3252 } else {
3253 acked_pcount = tcp_skb_pcount(skb);
3254 }
3255
3256 if (sacked & TCPCB_RETRANS) {
3257 if (sacked & TCPCB_SACKED_RETRANS)
3258 tp->retrans_out -= acked_pcount;
3259 flag |= FLAG_RETRANS_DATA_ACKED;
3260 ca_seq_rtt = -1;
3261 seq_rtt = -1;
3262 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1))
3263 flag |= FLAG_NONHEAD_RETRANS_ACKED;
3264 } else {
3265 ca_seq_rtt = now - scb->when;
3266 last_ackt = skb->tstamp;
3267 if (seq_rtt < 0) {
3268 seq_rtt = ca_seq_rtt;
3269 }
3270 if (!(sacked & TCPCB_SACKED_ACKED))
3271 reord = min(pkts_acked, reord);
3272 }
3273
3274 if (sacked & TCPCB_SACKED_ACKED)
3275 tp->sacked_out -= acked_pcount;
3276 if (sacked & TCPCB_LOST)
3277 tp->lost_out -= acked_pcount;
3278
3279 tp->packets_out -= acked_pcount;
3280 pkts_acked += acked_pcount;
3281
3282 /* Initial outgoing SYN's get put onto the write_queue
3283 * just like anything else we transmit. It is not
3284 * true data, and if we misinform our callers that
3285 * this ACK acks real data, we will erroneously exit
3286 * connection startup slow start one packet too
3287 * quickly. This is severely frowned upon behavior.
3288 */
3289 if (!(scb->flags & TCPHDR_SYN)) {
3290 flag |= FLAG_DATA_ACKED;
3291 } else {
3292 flag |= FLAG_SYN_ACKED;
3293 tp->retrans_stamp = 0;
3294 }
3295
3296 if (!fully_acked)
3297 break;
3298
3299 tcp_unlink_write_queue(skb, sk);
3300 sk_wmem_free_skb(sk, skb);
3301 tp->scoreboard_skb_hint = NULL;
3302 if (skb == tp->retransmit_skb_hint)
3303 tp->retransmit_skb_hint = NULL;
3304 if (skb == tp->lost_skb_hint)
3305 tp->lost_skb_hint = NULL;
3306 }
3307
3308 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3309 tp->snd_up = tp->snd_una;
3310
3311 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
3312 flag |= FLAG_SACK_RENEGING;
3313
3314 if (flag & FLAG_ACKED) {
3315 const struct tcp_congestion_ops *ca_ops
3316 = inet_csk(sk)->icsk_ca_ops;
3317
3318 if (unlikely(icsk->icsk_mtup.probe_size &&
3319 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3320 tcp_mtup_probe_success(sk);
3321 }
3322
3323 tcp_ack_update_rtt(sk, flag, seq_rtt);
3324 tcp_rearm_rto(sk);
3325
3326 if (tcp_is_reno(tp)) {
3327 tcp_remove_reno_sacks(sk, pkts_acked);
3328 } else {
3329 int delta;
3330
3331 /* Non-retransmitted hole got filled? That's reordering */
3332 if (reord < prior_fackets)
3333 tcp_update_reordering(sk, tp->fackets_out - reord, 0);
3334
3335 delta = tcp_is_fack(tp) ? pkts_acked :
3336 prior_sacked - tp->sacked_out;
3337 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
3338 }
3339
3340 tp->fackets_out -= min(pkts_acked, tp->fackets_out);
3341
3342 if (ca_ops->pkts_acked) {
3343 s32 rtt_us = -1;
3344
3345 /* Is the ACK triggering packet unambiguous? */
3346 if (!(flag & FLAG_RETRANS_DATA_ACKED)) {
3347 /* High resolution needed and available? */
3348 if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
3349 !ktime_equal(last_ackt,
3350 net_invalid_timestamp()))
3351 rtt_us = ktime_us_delta(ktime_get_real(),
3352 last_ackt);
3353 else if (ca_seq_rtt > 0)
3354 rtt_us = jiffies_to_usecs(ca_seq_rtt);
3355 }
3356
3357 ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
3358 }
3359 }
3360
3361#if FASTRETRANS_DEBUG > 0
3362 WARN_ON((int)tp->sacked_out < 0);
3363 WARN_ON((int)tp->lost_out < 0);
3364 WARN_ON((int)tp->retrans_out < 0);
3365 if (!tp->packets_out && tcp_is_sack(tp)) {
3366 icsk = inet_csk(sk);
3367 if (tp->lost_out) {
3368 printk(KERN_DEBUG "Leak l=%u %d\n",
3369 tp->lost_out, icsk->icsk_ca_state);
3370 tp->lost_out = 0;
3371 }
3372 if (tp->sacked_out) {
3373 printk(KERN_DEBUG "Leak s=%u %d\n",
3374 tp->sacked_out, icsk->icsk_ca_state);
3375 tp->sacked_out = 0;
3376 }
3377 if (tp->retrans_out) {
3378 printk(KERN_DEBUG "Leak r=%u %d\n",
3379 tp->retrans_out, icsk->icsk_ca_state);
3380 tp->retrans_out = 0;
3381 }
3382 }
3383#endif
3384 return flag;
3385}
3386
3387static void tcp_ack_probe(struct sock *sk)
3388{
3389 const struct tcp_sock *tp = tcp_sk(sk);
3390 struct inet_connection_sock *icsk = inet_csk(sk);
3391
3392 /* Was it a usable window open? */
3393
3394 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
3395 icsk->icsk_backoff = 0;
3396 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
3397 /* Socket must be waked up by subsequent tcp_data_snd_check().
3398 * This function is not for random using!
3399 */
3400 } else {
3401 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3402 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3403 TCP_RTO_MAX);
3404 }
3405}
3406
3407static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
3408{
3409 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
3410 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
3411}
3412
3413static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
3414{
3415 const struct tcp_sock *tp = tcp_sk(sk);
3416 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
3417 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
3418}
3419
3420/* Check that window update is acceptable.
3421 * The function assumes that snd_una<=ack<=snd_next.
3422 */
3423static inline int tcp_may_update_window(const struct tcp_sock *tp,
3424 const u32 ack, const u32 ack_seq,
3425 const u32 nwin)
3426{
3427 return after(ack, tp->snd_una) ||
3428 after(ack_seq, tp->snd_wl1) ||
3429 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
3430}
3431
3432/* Update our send window.
3433 *
3434 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3435 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3436 */
3437static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack,
3438 u32 ack_seq)
3439{
3440 struct tcp_sock *tp = tcp_sk(sk);
3441 int flag = 0;
3442 u32 nwin = ntohs(tcp_hdr(skb)->window);
3443
3444 if (likely(!tcp_hdr(skb)->syn))
3445 nwin <<= tp->rx_opt.snd_wscale;
3446
3447 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3448 flag |= FLAG_WIN_UPDATE;
3449 tcp_update_wl(tp, ack_seq);
3450
3451 if (tp->snd_wnd != nwin) {
3452 tp->snd_wnd = nwin;
3453
3454 /* Note, it is the only place, where
3455 * fast path is recovered for sending TCP.
3456 */
3457 tp->pred_flags = 0;
3458 tcp_fast_path_check(sk);
3459
3460 if (nwin > tp->max_window) {
3461 tp->max_window = nwin;
3462 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
3463 }
3464 }
3465 }
3466
3467 tp->snd_una = ack;
3468
3469 return flag;
3470}
3471
3472/* A very conservative spurious RTO response algorithm: reduce cwnd and
3473 * continue in congestion avoidance.
3474 */
3475static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
3476{
3477 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
3478 tp->snd_cwnd_cnt = 0;
3479 tp->bytes_acked = 0;
3480 TCP_ECN_queue_cwr(tp);
3481 tcp_moderate_cwnd(tp);
3482}
3483
3484/* A conservative spurious RTO response algorithm: reduce cwnd using
3485 * rate halving and continue in congestion avoidance.
3486 */
3487static void tcp_ratehalving_spur_to_response(struct sock *sk)
3488{
3489 tcp_enter_cwr(sk, 0);
3490}
3491
3492static void tcp_undo_spur_to_response(struct sock *sk, int flag)
3493{
3494 if (flag & FLAG_ECE)
3495 tcp_ratehalving_spur_to_response(sk);
3496 else
3497 tcp_undo_cwr(sk, 1);
3498}
3499
3500/* F-RTO spurious RTO detection algorithm (RFC4138)
3501 *
3502 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3503 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3504 * window (but not to or beyond highest sequence sent before RTO):
3505 * On First ACK, send two new segments out.
3506 * On Second ACK, RTO was likely spurious. Do spurious response (response
3507 * algorithm is not part of the F-RTO detection algorithm
3508 * given in RFC4138 but can be selected separately).
3509 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3510 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3511 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3512 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3513 *
3514 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3515 * original window even after we transmit two new data segments.
3516 *
3517 * SACK version:
3518 * on first step, wait until first cumulative ACK arrives, then move to
3519 * the second step. In second step, the next ACK decides.
3520 *
3521 * F-RTO is implemented (mainly) in four functions:
3522 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3523 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3524 * called when tcp_use_frto() showed green light
3525 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3526 * - tcp_enter_frto_loss() is called if there is not enough evidence
3527 * to prove that the RTO is indeed spurious. It transfers the control
3528 * from F-RTO to the conventional RTO recovery
3529 */
3530static int tcp_process_frto(struct sock *sk, int flag)
3531{
3532 struct tcp_sock *tp = tcp_sk(sk);
3533
3534 tcp_verify_left_out(tp);
3535
3536 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3537 if (flag & FLAG_DATA_ACKED)
3538 inet_csk(sk)->icsk_retransmits = 0;
3539
3540 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) ||
3541 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
3542 tp->undo_marker = 0;
3543
3544 if (!before(tp->snd_una, tp->frto_highmark)) {
3545 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
3546 return 1;
3547 }
3548
3549 if (!tcp_is_sackfrto(tp)) {
3550 /* RFC4138 shortcoming in step 2; should also have case c):
3551 * ACK isn't duplicate nor advances window, e.g., opposite dir
3552 * data, winupdate
3553 */
3554 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP))
3555 return 1;
3556
3557 if (!(flag & FLAG_DATA_ACKED)) {
3558 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3),
3559 flag);
3560 return 1;
3561 }
3562 } else {
3563 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
3564 /* Prevent sending of new data. */
3565 tp->snd_cwnd = min(tp->snd_cwnd,
3566 tcp_packets_in_flight(tp));
3567 return 1;
3568 }
3569
3570 if ((tp->frto_counter >= 2) &&
3571 (!(flag & FLAG_FORWARD_PROGRESS) ||
3572 ((flag & FLAG_DATA_SACKED) &&
3573 !(flag & FLAG_ONLY_ORIG_SACKED)))) {
3574 /* RFC4138 shortcoming (see comment above) */
3575 if (!(flag & FLAG_FORWARD_PROGRESS) &&
3576 (flag & FLAG_NOT_DUP))
3577 return 1;
3578
3579 tcp_enter_frto_loss(sk, 3, flag);
3580 return 1;
3581 }
3582 }
3583
3584 if (tp->frto_counter == 1) {
3585 /* tcp_may_send_now needs to see updated state */
3586 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
3587 tp->frto_counter = 2;
3588
3589 if (!tcp_may_send_now(sk))
3590 tcp_enter_frto_loss(sk, 2, flag);
3591
3592 return 1;
3593 } else {
3594 switch (sysctl_tcp_frto_response) {
3595 case 2:
3596 tcp_undo_spur_to_response(sk, flag);
3597 break;
3598 case 1:
3599 tcp_conservative_spur_to_response(tp);
3600 break;
3601 default:
3602 tcp_ratehalving_spur_to_response(sk);
3603 break;
3604 }
3605 tp->frto_counter = 0;
3606 tp->undo_marker = 0;
3607 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS);
3608 }
3609 return 0;
3610}
3611
3612/* This routine deals with incoming acks, but not outgoing ones. */
3613static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
3614{
3615 struct inet_connection_sock *icsk = inet_csk(sk);
3616 struct tcp_sock *tp = tcp_sk(sk);
3617 u32 prior_snd_una = tp->snd_una;
3618 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3619 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3620 u32 prior_in_flight;
3621 u32 prior_fackets;
3622 int prior_packets;
3623 int frto_cwnd = 0;
3624
3625 /* If the ack is older than previous acks
3626 * then we can probably ignore it.
3627 */
3628 if (before(ack, prior_snd_una))
3629 goto old_ack;
3630
3631 /* If the ack includes data we haven't sent yet, discard
3632 * this segment (RFC793 Section 3.9).
3633 */
3634 if (after(ack, tp->snd_nxt))
3635 goto invalid_ack;
3636
3637 if (after(ack, prior_snd_una))
3638 flag |= FLAG_SND_UNA_ADVANCED;
3639
3640 if (sysctl_tcp_abc) {
3641 if (icsk->icsk_ca_state < TCP_CA_CWR)
3642 tp->bytes_acked += ack - prior_snd_una;
3643 else if (icsk->icsk_ca_state == TCP_CA_Loss)
3644 /* we assume just one segment left network */
3645 tp->bytes_acked += min(ack - prior_snd_una,
3646 tp->mss_cache);
3647 }
3648
3649 prior_fackets = tp->fackets_out;
3650 prior_in_flight = tcp_packets_in_flight(tp);
3651
3652 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
3653 /* Window is constant, pure forward advance.
3654 * No more checks are required.
3655 * Note, we use the fact that SND.UNA>=SND.WL2.
3656 */
3657 tcp_update_wl(tp, ack_seq);
3658 tp->snd_una = ack;
3659 flag |= FLAG_WIN_UPDATE;
3660
3661 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
3662
3663 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS);
3664 } else {
3665 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3666 flag |= FLAG_DATA;
3667 else
3668 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS);
3669
3670 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
3671
3672 if (TCP_SKB_CB(skb)->sacked)
3673 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3674
3675 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
3676 flag |= FLAG_ECE;
3677
3678 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
3679 }
3680
3681 /* We passed data and got it acked, remove any soft error
3682 * log. Something worked...
3683 */
3684 sk->sk_err_soft = 0;
3685 icsk->icsk_probes_out = 0;
3686 tp->rcv_tstamp = tcp_time_stamp;
3687 prior_packets = tp->packets_out;
3688 if (!prior_packets)
3689 goto no_queue;
3690
3691 /* See if we can take anything off of the retransmit queue. */
3692 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
3693
3694 if (tp->frto_counter)
3695 frto_cwnd = tcp_process_frto(sk, flag);
3696 /* Guarantee sacktag reordering detection against wrap-arounds */
3697 if (before(tp->frto_highmark, tp->snd_una))
3698 tp->frto_highmark = 0;
3699
3700 if (tcp_ack_is_dubious(sk, flag)) {
3701 /* Advance CWND, if state allows this. */
3702 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
3703 tcp_may_raise_cwnd(sk, flag))
3704 tcp_cong_avoid(sk, ack, prior_in_flight);
3705 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out,
3706 flag);
3707 } else {
3708 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
3709 tcp_cong_avoid(sk, ack, prior_in_flight);
3710 }
3711
3712 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
3713 dst_confirm(__sk_dst_get(sk));
3714
3715 return 1;
3716
3717no_queue:
3718 /* If this ack opens up a zero window, clear backoff. It was
3719 * being used to time the probes, and is probably far higher than
3720 * it needs to be for normal retransmission.
3721 */
3722 if (tcp_send_head(sk))
3723 tcp_ack_probe(sk);
3724 return 1;
3725
3726invalid_ack:
3727 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3728 return -1;
3729
3730old_ack:
3731 if (TCP_SKB_CB(skb)->sacked) {
3732 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3733 if (icsk->icsk_ca_state == TCP_CA_Open)
3734 tcp_try_keep_open(sk);
3735 }
3736
3737 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3738 return 0;
3739}
3740
3741/* Look for tcp options. Normally only called on SYN and SYNACK packets.
3742 * But, this can also be called on packets in the established flow when
3743 * the fast version below fails.
3744 */
3745void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
3746 u8 **hvpp, int estab)
3747{
3748 unsigned char *ptr;
3749 struct tcphdr *th = tcp_hdr(skb);
3750 int length = (th->doff * 4) - sizeof(struct tcphdr);
3751
3752 ptr = (unsigned char *)(th + 1);
3753 opt_rx->saw_tstamp = 0;
3754
3755 while (length > 0) {
3756 int opcode = *ptr++;
3757 int opsize;
3758
3759 switch (opcode) {
3760 case TCPOPT_EOL:
3761 return;
3762 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3763 length--;
3764 continue;
3765 default:
3766 opsize = *ptr++;
3767 if (opsize < 2) /* "silly options" */
3768 return;
3769 if (opsize > length)
3770 return; /* don't parse partial options */
3771 switch (opcode) {
3772 case TCPOPT_MSS:
3773 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
3774 u16 in_mss = get_unaligned_be16(ptr);
3775 if (in_mss) {
3776 if (opt_rx->user_mss &&
3777 opt_rx->user_mss < in_mss)
3778 in_mss = opt_rx->user_mss;
3779 opt_rx->mss_clamp = in_mss;
3780 }
3781 }
3782 break;
3783 case TCPOPT_WINDOW:
3784 if (opsize == TCPOLEN_WINDOW && th->syn &&
3785 !estab && sysctl_tcp_window_scaling) {
3786 __u8 snd_wscale = *(__u8 *)ptr;
3787 opt_rx->wscale_ok = 1;
3788 if (snd_wscale > 14) {
3789 if (net_ratelimit())
3790 printk(KERN_INFO "tcp_parse_options: Illegal window "
3791 "scaling value %d >14 received.\n",
3792 snd_wscale);
3793 snd_wscale = 14;
3794 }
3795 opt_rx->snd_wscale = snd_wscale;
3796 }
3797 break;
3798 case TCPOPT_TIMESTAMP:
3799 if ((opsize == TCPOLEN_TIMESTAMP) &&
3800 ((estab && opt_rx->tstamp_ok) ||
3801 (!estab && sysctl_tcp_timestamps))) {
3802 opt_rx->saw_tstamp = 1;
3803 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
3804 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
3805 }
3806 break;
3807 case TCPOPT_SACK_PERM:
3808 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
3809 !estab && sysctl_tcp_sack) {
3810 opt_rx->sack_ok = 1;
3811 tcp_sack_reset(opt_rx);
3812 }
3813 break;
3814
3815 case TCPOPT_SACK:
3816 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3817 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3818 opt_rx->sack_ok) {
3819 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3820 }
3821 break;
3822#ifdef CONFIG_TCP_MD5SIG
3823 case TCPOPT_MD5SIG:
3824 /*
3825 * The MD5 Hash has already been
3826 * checked (see tcp_v{4,6}_do_rcv()).
3827 */
3828 break;
3829#endif
3830 case TCPOPT_COOKIE:
3831 /* This option is variable length.
3832 */
3833 switch (opsize) {
3834 case TCPOLEN_COOKIE_BASE:
3835 /* not yet implemented */
3836 break;
3837 case TCPOLEN_COOKIE_PAIR:
3838 /* not yet implemented */
3839 break;
3840 case TCPOLEN_COOKIE_MIN+0:
3841 case TCPOLEN_COOKIE_MIN+2:
3842 case TCPOLEN_COOKIE_MIN+4:
3843 case TCPOLEN_COOKIE_MIN+6:
3844 case TCPOLEN_COOKIE_MAX:
3845 /* 16-bit multiple */
3846 opt_rx->cookie_plus = opsize;
3847 *hvpp = ptr;
3848 break;
3849 default:
3850 /* ignore option */
3851 break;
3852 }
3853 break;
3854 }
3855
3856 ptr += opsize-2;
3857 length -= opsize;
3858 }
3859 }
3860}
3861EXPORT_SYMBOL(tcp_parse_options);
3862
3863static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)
3864{
3865 __be32 *ptr = (__be32 *)(th + 1);
3866
3867 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3868 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3869 tp->rx_opt.saw_tstamp = 1;
3870 ++ptr;
3871 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3872 ++ptr;
3873 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3874 return 1;
3875 }
3876 return 0;
3877}
3878
3879/* Fast parse options. This hopes to only see timestamps.
3880 * If it is wrong it falls back on tcp_parse_options().
3881 */
3882static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
3883 struct tcp_sock *tp, u8 **hvpp)
3884{
3885 /* In the spirit of fast parsing, compare doff directly to constant
3886 * values. Because equality is used, short doff can be ignored here.
3887 */
3888 if (th->doff == (sizeof(*th) / 4)) {
3889 tp->rx_opt.saw_tstamp = 0;
3890 return 0;
3891 } else if (tp->rx_opt.tstamp_ok &&
3892 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
3893 if (tcp_parse_aligned_timestamp(tp, th))
3894 return 1;
3895 }
3896 tcp_parse_options(skb, &tp->rx_opt, hvpp, 1);
3897 return 1;
3898}
3899
3900#ifdef CONFIG_TCP_MD5SIG
3901/*
3902 * Parse MD5 Signature option
3903 */
3904u8 *tcp_parse_md5sig_option(struct tcphdr *th)
3905{
3906 int length = (th->doff << 2) - sizeof (*th);
3907 u8 *ptr = (u8*)(th + 1);
3908
3909 /* If the TCP option is too short, we can short cut */
3910 if (length < TCPOLEN_MD5SIG)
3911 return NULL;
3912
3913 while (length > 0) {
3914 int opcode = *ptr++;
3915 int opsize;
3916
3917 switch(opcode) {
3918 case TCPOPT_EOL:
3919 return NULL;
3920 case TCPOPT_NOP:
3921 length--;
3922 continue;
3923 default:
3924 opsize = *ptr++;
3925 if (opsize < 2 || opsize > length)
3926 return NULL;
3927 if (opcode == TCPOPT_MD5SIG)
3928 return opsize == TCPOLEN_MD5SIG ? ptr : NULL;
3929 }
3930 ptr += opsize - 2;
3931 length -= opsize;
3932 }
3933 return NULL;
3934}
3935EXPORT_SYMBOL(tcp_parse_md5sig_option);
3936#endif
3937
3938static inline void tcp_store_ts_recent(struct tcp_sock *tp)
3939{
3940 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3941 tp->rx_opt.ts_recent_stamp = get_seconds();
3942}
3943
3944static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3945{
3946 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3947 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3948 * extra check below makes sure this can only happen
3949 * for pure ACK frames. -DaveM
3950 *
3951 * Not only, also it occurs for expired timestamps.
3952 */
3953
3954 if (tcp_paws_check(&tp->rx_opt, 0))
3955 tcp_store_ts_recent(tp);
3956 }
3957}
3958
3959/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3960 *
3961 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3962 * it can pass through stack. So, the following predicate verifies that
3963 * this segment is not used for anything but congestion avoidance or
3964 * fast retransmit. Moreover, we even are able to eliminate most of such
3965 * second order effects, if we apply some small "replay" window (~RTO)
3966 * to timestamp space.
3967 *
3968 * All these measures still do not guarantee that we reject wrapped ACKs
3969 * on networks with high bandwidth, when sequence space is recycled fastly,
3970 * but it guarantees that such events will be very rare and do not affect
3971 * connection seriously. This doesn't look nice, but alas, PAWS is really
3972 * buggy extension.
3973 *
3974 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3975 * states that events when retransmit arrives after original data are rare.
3976 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3977 * the biggest problem on large power networks even with minor reordering.
3978 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3979 * up to bandwidth of 18Gigabit/sec. 8) ]
3980 */
3981
3982static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
3983{
3984 struct tcp_sock *tp = tcp_sk(sk);
3985 struct tcphdr *th = tcp_hdr(skb);
3986 u32 seq = TCP_SKB_CB(skb)->seq;
3987 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3988
3989 return (/* 1. Pure ACK with correct sequence number. */
3990 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3991
3992 /* 2. ... and duplicate ACK. */
3993 ack == tp->snd_una &&
3994
3995 /* 3. ... and does not update window. */
3996 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3997
3998 /* 4. ... and sits in replay window. */
3999 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
4000}
4001
4002static inline int tcp_paws_discard(const struct sock *sk,
4003 const struct sk_buff *skb)
4004{
4005 const struct tcp_sock *tp = tcp_sk(sk);
4006
4007 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
4008 !tcp_disordered_ack(sk, skb);
4009}
4010
4011/* Check segment sequence number for validity.
4012 *
4013 * Segment controls are considered valid, if the segment
4014 * fits to the window after truncation to the window. Acceptability
4015 * of data (and SYN, FIN, of course) is checked separately.
4016 * See tcp_data_queue(), for example.
4017 *
4018 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4019 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4020 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4021 * (borrowed from freebsd)
4022 */
4023
4024static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
4025{
4026 return !before(end_seq, tp->rcv_wup) &&
4027 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
4028}
4029
4030/* When we get a reset we do this. */
4031static void tcp_reset(struct sock *sk)
4032{
4033 /* We want the right error as BSD sees it (and indeed as we do). */
4034 switch (sk->sk_state) {
4035 case TCP_SYN_SENT:
4036 sk->sk_err = ECONNREFUSED;
4037 break;
4038 case TCP_CLOSE_WAIT:
4039 sk->sk_err = EPIPE;
4040 break;
4041 case TCP_CLOSE:
4042 return;
4043 default:
4044 sk->sk_err = ECONNRESET;
4045 }
4046 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4047 smp_wmb();
4048
4049 if (!sock_flag(sk, SOCK_DEAD))
4050 sk->sk_error_report(sk);
4051
4052 tcp_done(sk);
4053}
4054
4055/*
4056 * Process the FIN bit. This now behaves as it is supposed to work
4057 * and the FIN takes effect when it is validly part of sequence
4058 * space. Not before when we get holes.
4059 *
4060 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4061 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4062 * TIME-WAIT)
4063 *
4064 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4065 * close and we go into CLOSING (and later onto TIME-WAIT)
4066 *
4067 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4068 */
4069static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
4070{
4071 struct tcp_sock *tp = tcp_sk(sk);
4072
4073 inet_csk_schedule_ack(sk);
4074
4075 sk->sk_shutdown |= RCV_SHUTDOWN;
4076 sock_set_flag(sk, SOCK_DONE);
4077
4078 switch (sk->sk_state) {
4079 case TCP_SYN_RECV:
4080 case TCP_ESTABLISHED:
4081 /* Move to CLOSE_WAIT */
4082 tcp_set_state(sk, TCP_CLOSE_WAIT);
4083 inet_csk(sk)->icsk_ack.pingpong = 1;
4084 break;
4085
4086 case TCP_CLOSE_WAIT:
4087 case TCP_CLOSING:
4088 /* Received a retransmission of the FIN, do
4089 * nothing.
4090 */
4091 break;
4092 case TCP_LAST_ACK:
4093 /* RFC793: Remain in the LAST-ACK state. */
4094 break;
4095
4096 case TCP_FIN_WAIT1:
4097 /* This case occurs when a simultaneous close
4098 * happens, we must ack the received FIN and
4099 * enter the CLOSING state.
4100 */
4101 tcp_send_ack(sk);
4102 tcp_set_state(sk, TCP_CLOSING);
4103 break;
4104 case TCP_FIN_WAIT2:
4105 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4106 tcp_send_ack(sk);
4107 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4108 break;
4109 default:
4110 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4111 * cases we should never reach this piece of code.
4112 */
4113 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
4114 __func__, sk->sk_state);
4115 break;
4116 }
4117
4118 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4119 * Probably, we should reset in this case. For now drop them.
4120 */
4121 __skb_queue_purge(&tp->out_of_order_queue);
4122 if (tcp_is_sack(tp))
4123 tcp_sack_reset(&tp->rx_opt);
4124 sk_mem_reclaim(sk);
4125
4126 if (!sock_flag(sk, SOCK_DEAD)) {
4127 sk->sk_state_change(sk);
4128
4129 /* Do not send POLL_HUP for half duplex close. */
4130 if (sk->sk_shutdown == SHUTDOWN_MASK ||
4131 sk->sk_state == TCP_CLOSE)
4132 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
4133 else
4134 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
4135 }
4136}
4137
4138static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
4139 u32 end_seq)
4140{
4141 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
4142 if (before(seq, sp->start_seq))
4143 sp->start_seq = seq;
4144 if (after(end_seq, sp->end_seq))
4145 sp->end_seq = end_seq;
4146 return 1;
4147 }
4148 return 0;
4149}
4150
4151static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
4152{
4153 struct tcp_sock *tp = tcp_sk(sk);
4154
4155 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
4156 int mib_idx;
4157
4158 if (before(seq, tp->rcv_nxt))
4159 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
4160 else
4161 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
4162
4163 NET_INC_STATS_BH(sock_net(sk), mib_idx);
4164
4165 tp->rx_opt.dsack = 1;
4166 tp->duplicate_sack[0].start_seq = seq;
4167 tp->duplicate_sack[0].end_seq = end_seq;
4168 }
4169}
4170
4171static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
4172{
4173 struct tcp_sock *tp = tcp_sk(sk);
4174
4175 if (!tp->rx_opt.dsack)
4176 tcp_dsack_set(sk, seq, end_seq);
4177 else
4178 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
4179}
4180
4181static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
4182{
4183 struct tcp_sock *tp = tcp_sk(sk);
4184
4185 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4186 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4187 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4188 tcp_enter_quickack_mode(sk);
4189
4190 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
4191 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4192
4193 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
4194 end_seq = tp->rcv_nxt;
4195 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
4196 }
4197 }
4198
4199 tcp_send_ack(sk);
4200}
4201
4202/* These routines update the SACK block as out-of-order packets arrive or
4203 * in-order packets close up the sequence space.
4204 */
4205static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
4206{
4207 int this_sack;
4208 struct tcp_sack_block *sp = &tp->selective_acks[0];
4209 struct tcp_sack_block *swalk = sp + 1;
4210
4211 /* See if the recent change to the first SACK eats into
4212 * or hits the sequence space of other SACK blocks, if so coalesce.
4213 */
4214 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
4215 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
4216 int i;
4217
4218 /* Zap SWALK, by moving every further SACK up by one slot.
4219 * Decrease num_sacks.
4220 */
4221 tp->rx_opt.num_sacks--;
4222 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
4223 sp[i] = sp[i + 1];
4224 continue;
4225 }
4226 this_sack++, swalk++;
4227 }
4228}
4229
4230static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
4231{
4232 struct tcp_sock *tp = tcp_sk(sk);
4233 struct tcp_sack_block *sp = &tp->selective_acks[0];
4234 int cur_sacks = tp->rx_opt.num_sacks;
4235 int this_sack;
4236
4237 if (!cur_sacks)
4238 goto new_sack;
4239
4240 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
4241 if (tcp_sack_extend(sp, seq, end_seq)) {
4242 /* Rotate this_sack to the first one. */
4243 for (; this_sack > 0; this_sack--, sp--)
4244 swap(*sp, *(sp - 1));
4245 if (cur_sacks > 1)
4246 tcp_sack_maybe_coalesce(tp);
4247 return;
4248 }
4249 }
4250
4251 /* Could not find an adjacent existing SACK, build a new one,
4252 * put it at the front, and shift everyone else down. We
4253 * always know there is at least one SACK present already here.
4254 *
4255 * If the sack array is full, forget about the last one.
4256 */
4257 if (this_sack >= TCP_NUM_SACKS) {
4258 this_sack--;
4259 tp->rx_opt.num_sacks--;
4260 sp--;
4261 }
4262 for (; this_sack > 0; this_sack--, sp--)
4263 *sp = *(sp - 1);
4264
4265new_sack:
4266 /* Build the new head SACK, and we're done. */
4267 sp->start_seq = seq;
4268 sp->end_seq = end_seq;
4269 tp->rx_opt.num_sacks++;
4270}
4271
4272/* RCV.NXT advances, some SACKs should be eaten. */
4273
4274static void tcp_sack_remove(struct tcp_sock *tp)
4275{
4276 struct tcp_sack_block *sp = &tp->selective_acks[0];
4277 int num_sacks = tp->rx_opt.num_sacks;
4278 int this_sack;
4279
4280 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4281 if (skb_queue_empty(&tp->out_of_order_queue)) {
4282 tp->rx_opt.num_sacks = 0;
4283 return;
4284 }
4285
4286 for (this_sack = 0; this_sack < num_sacks;) {
4287 /* Check if the start of the sack is covered by RCV.NXT. */
4288 if (!before(tp->rcv_nxt, sp->start_seq)) {
4289 int i;
4290
4291 /* RCV.NXT must cover all the block! */
4292 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
4293
4294 /* Zap this SACK, by moving forward any other SACKS. */
4295 for (i=this_sack+1; i < num_sacks; i++)
4296 tp->selective_acks[i-1] = tp->selective_acks[i];
4297 num_sacks--;
4298 continue;
4299 }
4300 this_sack++;
4301 sp++;
4302 }
4303 tp->rx_opt.num_sacks = num_sacks;
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 */
4309static void tcp_ofo_queue(struct sock *sk)
4310{
4311 struct tcp_sock *tp = tcp_sk(sk);
4312 __u32 dsack_high = tp->rcv_nxt;
4313 struct sk_buff *skb;
4314
4315 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
4316 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4317 break;
4318
4319 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4320 __u32 dsack = dsack_high;
4321 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4322 dsack_high = TCP_SKB_CB(skb)->end_seq;
4323 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
4324 }
4325
4326 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4327 SOCK_DEBUG(sk, "ofo packet was already received\n");
4328 __skb_unlink(skb, &tp->out_of_order_queue);
4329 __kfree_skb(skb);
4330 continue;
4331 }
4332 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
4333 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4334 TCP_SKB_CB(skb)->end_seq);
4335
4336 __skb_unlink(skb, &tp->out_of_order_queue);
4337 __skb_queue_tail(&sk->sk_receive_queue, skb);
4338 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4339 if (tcp_hdr(skb)->fin)
4340 tcp_fin(skb, sk, tcp_hdr(skb));
4341 }
4342}
4343
4344static int tcp_prune_ofo_queue(struct sock *sk);
4345static int tcp_prune_queue(struct sock *sk);
4346
4347static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size)
4348{
4349 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4350 !sk_rmem_schedule(sk, size)) {
4351
4352 if (tcp_prune_queue(sk) < 0)
4353 return -1;
4354
4355 if (!sk_rmem_schedule(sk, size)) {
4356 if (!tcp_prune_ofo_queue(sk))
4357 return -1;
4358
4359 if (!sk_rmem_schedule(sk, size))
4360 return -1;
4361 }
4362 }
4363 return 0;
4364}
4365
4366static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
4367{
4368 struct tcphdr *th = tcp_hdr(skb);
4369 struct tcp_sock *tp = tcp_sk(sk);
4370 int eaten = -1;
4371
4372 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
4373 goto drop;
4374
4375 skb_dst_drop(skb);
4376 __skb_pull(skb, th->doff * 4);
4377
4378 TCP_ECN_accept_cwr(tp, skb);
4379
4380 tp->rx_opt.dsack = 0;
4381
4382 /* Queue data for delivery to the user.
4383 * Packets in sequence go to the receive queue.
4384 * Out of sequence packets to the out_of_order_queue.
4385 */
4386 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4387 if (tcp_receive_window(tp) == 0)
4388 goto out_of_window;
4389
4390 /* Ok. In sequence. In window. */
4391 if (tp->ucopy.task == current &&
4392 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
4393 sock_owned_by_user(sk) && !tp->urg_data) {
4394 int chunk = min_t(unsigned int, skb->len,
4395 tp->ucopy.len);
4396
4397 __set_current_state(TASK_RUNNING);
4398
4399 local_bh_enable();
4400 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
4401 tp->ucopy.len -= chunk;
4402 tp->copied_seq += chunk;
4403 eaten = (chunk == skb->len && !th->fin);
4404 tcp_rcv_space_adjust(sk);
4405 }
4406 local_bh_disable();
4407 }
4408
4409 if (eaten <= 0) {
4410queue_and_out:
4411 if (eaten < 0 &&
4412 tcp_try_rmem_schedule(sk, skb->truesize))
4413 goto drop;
4414
4415 skb_set_owner_r(skb, sk);
4416 __skb_queue_tail(&sk->sk_receive_queue, skb);
4417 }
4418 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4419 if (skb->len)
4420 tcp_event_data_recv(sk, skb);
4421 if (th->fin)
4422 tcp_fin(skb, sk, th);
4423
4424 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4425 tcp_ofo_queue(sk);
4426
4427 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4428 * gap in queue is filled.
4429 */
4430 if (skb_queue_empty(&tp->out_of_order_queue))
4431 inet_csk(sk)->icsk_ack.pingpong = 0;
4432 }
4433
4434 if (tp->rx_opt.num_sacks)
4435 tcp_sack_remove(tp);
4436
4437 tcp_fast_path_check(sk);
4438
4439 if (eaten > 0)
4440 __kfree_skb(skb);
4441 else if (!sock_flag(sk, SOCK_DEAD))
4442 sk->sk_data_ready(sk, 0);
4443 return;
4444 }
4445
4446 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4447 /* A retransmit, 2nd most common case. Force an immediate ack. */
4448 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4449 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4450
4451out_of_window:
4452 tcp_enter_quickack_mode(sk);
4453 inet_csk_schedule_ack(sk);
4454drop:
4455 __kfree_skb(skb);
4456 return;
4457 }
4458
4459 /* Out of window. F.e. zero window probe. */
4460 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
4461 goto out_of_window;
4462
4463 tcp_enter_quickack_mode(sk);
4464
4465 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4466 /* Partial packet, seq < rcv_next < end_seq */
4467 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
4468 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4469 TCP_SKB_CB(skb)->end_seq);
4470
4471 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
4472
4473 /* If window is closed, drop tail of packet. But after
4474 * remembering D-SACK for its head made in previous line.
4475 */
4476 if (!tcp_receive_window(tp))
4477 goto out_of_window;
4478 goto queue_and_out;
4479 }
4480
4481 TCP_ECN_check_ce(tp, skb);
4482
4483 if (tcp_try_rmem_schedule(sk, skb->truesize))
4484 goto drop;
4485
4486 /* Disable header prediction. */
4487 tp->pred_flags = 0;
4488 inet_csk_schedule_ack(sk);
4489
4490 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
4491 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4492
4493 skb_set_owner_r(skb, sk);
4494
4495 if (!skb_peek(&tp->out_of_order_queue)) {
4496 /* Initial out of order segment, build 1 SACK. */
4497 if (tcp_is_sack(tp)) {
4498 tp->rx_opt.num_sacks = 1;
4499 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
4500 tp->selective_acks[0].end_seq =
4501 TCP_SKB_CB(skb)->end_seq;
4502 }
4503 __skb_queue_head(&tp->out_of_order_queue, skb);
4504 } else {
4505 struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue);
4506 u32 seq = TCP_SKB_CB(skb)->seq;
4507 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4508
4509 if (seq == TCP_SKB_CB(skb1)->end_seq) {
4510 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
4511
4512 if (!tp->rx_opt.num_sacks ||
4513 tp->selective_acks[0].end_seq != seq)
4514 goto add_sack;
4515
4516 /* Common case: data arrive in order after hole. */
4517 tp->selective_acks[0].end_seq = end_seq;
4518 return;
4519 }
4520
4521 /* Find place to insert this segment. */
4522 while (1) {
4523 if (!after(TCP_SKB_CB(skb1)->seq, seq))
4524 break;
4525 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) {
4526 skb1 = NULL;
4527 break;
4528 }
4529 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1);
4530 }
4531
4532 /* Do skb overlap to previous one? */
4533 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4534 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4535 /* All the bits are present. Drop. */
4536 __kfree_skb(skb);
4537 tcp_dsack_set(sk, seq, end_seq);
4538 goto add_sack;
4539 }
4540 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
4541 /* Partial overlap. */
4542 tcp_dsack_set(sk, seq,
4543 TCP_SKB_CB(skb1)->end_seq);
4544 } else {
4545 if (skb_queue_is_first(&tp->out_of_order_queue,
4546 skb1))
4547 skb1 = NULL;
4548 else
4549 skb1 = skb_queue_prev(
4550 &tp->out_of_order_queue,
4551 skb1);
4552 }
4553 }
4554 if (!skb1)
4555 __skb_queue_head(&tp->out_of_order_queue, skb);
4556 else
4557 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
4558
4559 /* And clean segments covered by new one as whole. */
4560 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) {
4561 skb1 = skb_queue_next(&tp->out_of_order_queue, skb);
4562
4563 if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
4564 break;
4565 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4566 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4567 end_seq);
4568 break;
4569 }
4570 __skb_unlink(skb1, &tp->out_of_order_queue);
4571 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4572 TCP_SKB_CB(skb1)->end_seq);
4573 __kfree_skb(skb1);
4574 }
4575
4576add_sack:
4577 if (tcp_is_sack(tp))
4578 tcp_sack_new_ofo_skb(sk, seq, end_seq);
4579 }
4580}
4581
4582static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
4583 struct sk_buff_head *list)
4584{
4585 struct sk_buff *next = NULL;
4586
4587 if (!skb_queue_is_last(list, skb))
4588 next = skb_queue_next(list, skb);
4589
4590 __skb_unlink(skb, list);
4591 __kfree_skb(skb);
4592 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
4593
4594 return next;
4595}
4596
4597/* Collapse contiguous sequence of skbs head..tail with
4598 * sequence numbers start..end.
4599 *
4600 * If tail is NULL, this means until the end of the list.
4601 *
4602 * Segments with FIN/SYN are not collapsed (only because this
4603 * simplifies code)
4604 */
4605static void
4606tcp_collapse(struct sock *sk, struct sk_buff_head *list,
4607 struct sk_buff *head, struct sk_buff *tail,
4608 u32 start, u32 end)
4609{
4610 struct sk_buff *skb, *n;
4611 bool end_of_skbs;
4612
4613 /* First, check that queue is collapsible and find
4614 * the point where collapsing can be useful. */
4615 skb = head;
4616restart:
4617 end_of_skbs = true;
4618 skb_queue_walk_from_safe(list, skb, n) {
4619 if (skb == tail)
4620 break;
4621 /* No new bits? It is possible on ofo queue. */
4622 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4623 skb = tcp_collapse_one(sk, skb, list);
4624 if (!skb)
4625 break;
4626 goto restart;
4627 }
4628
4629 /* The first skb to collapse is:
4630 * - not SYN/FIN and
4631 * - bloated or contains data before "start" or
4632 * overlaps to the next one.
4633 */
4634 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin &&
4635 (tcp_win_from_space(skb->truesize) > skb->len ||
4636 before(TCP_SKB_CB(skb)->seq, start))) {
4637 end_of_skbs = false;
4638 break;
4639 }
4640
4641 if (!skb_queue_is_last(list, skb)) {
4642 struct sk_buff *next = skb_queue_next(list, skb);
4643 if (next != tail &&
4644 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) {
4645 end_of_skbs = false;
4646 break;
4647 }
4648 }
4649
4650 /* Decided to skip this, advance start seq. */
4651 start = TCP_SKB_CB(skb)->end_seq;
4652 }
4653 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin)
4654 return;
4655
4656 while (before(start, end)) {
4657 struct sk_buff *nskb;
4658 unsigned int header = skb_headroom(skb);
4659 int copy = SKB_MAX_ORDER(header, 0);
4660
4661 /* Too big header? This can happen with IPv6. */
4662 if (copy < 0)
4663 return;
4664 if (end - start < copy)
4665 copy = end - start;
4666 nskb = alloc_skb(copy + header, GFP_ATOMIC);
4667 if (!nskb)
4668 return;
4669
4670 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head);
4671 skb_set_network_header(nskb, (skb_network_header(skb) -
4672 skb->head));
4673 skb_set_transport_header(nskb, (skb_transport_header(skb) -
4674 skb->head));
4675 skb_reserve(nskb, header);
4676 memcpy(nskb->head, skb->head, header);
4677 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
4678 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
4679 __skb_queue_before(list, skb, nskb);
4680 skb_set_owner_r(nskb, sk);
4681
4682 /* Copy data, releasing collapsed skbs. */
4683 while (copy > 0) {
4684 int offset = start - TCP_SKB_CB(skb)->seq;
4685 int size = TCP_SKB_CB(skb)->end_seq - start;
4686
4687 BUG_ON(offset < 0);
4688 if (size > 0) {
4689 size = min(copy, size);
4690 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
4691 BUG();
4692 TCP_SKB_CB(nskb)->end_seq += size;
4693 copy -= size;
4694 start += size;
4695 }
4696 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4697 skb = tcp_collapse_one(sk, skb, list);
4698 if (!skb ||
4699 skb == tail ||
4700 tcp_hdr(skb)->syn ||
4701 tcp_hdr(skb)->fin)
4702 return;
4703 }
4704 }
4705 }
4706}
4707
4708/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4709 * and tcp_collapse() them until all the queue is collapsed.
4710 */
4711static void tcp_collapse_ofo_queue(struct sock *sk)
4712{
4713 struct tcp_sock *tp = tcp_sk(sk);
4714 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
4715 struct sk_buff *head;
4716 u32 start, end;
4717
4718 if (skb == NULL)
4719 return;
4720
4721 start = TCP_SKB_CB(skb)->seq;
4722 end = TCP_SKB_CB(skb)->end_seq;
4723 head = skb;
4724
4725 for (;;) {
4726 struct sk_buff *next = NULL;
4727
4728 if (!skb_queue_is_last(&tp->out_of_order_queue, skb))
4729 next = skb_queue_next(&tp->out_of_order_queue, skb);
4730 skb = next;
4731
4732 /* Segment is terminated when we see gap or when
4733 * we are at the end of all the queue. */
4734 if (!skb ||
4735 after(TCP_SKB_CB(skb)->seq, end) ||
4736 before(TCP_SKB_CB(skb)->end_seq, start)) {
4737 tcp_collapse(sk, &tp->out_of_order_queue,
4738 head, skb, start, end);
4739 head = skb;
4740 if (!skb)
4741 break;
4742 /* Start new segment */
4743 start = TCP_SKB_CB(skb)->seq;
4744 end = TCP_SKB_CB(skb)->end_seq;
4745 } else {
4746 if (before(TCP_SKB_CB(skb)->seq, start))
4747 start = TCP_SKB_CB(skb)->seq;
4748 if (after(TCP_SKB_CB(skb)->end_seq, end))
4749 end = TCP_SKB_CB(skb)->end_seq;
4750 }
4751 }
4752}
4753
4754/*
4755 * Purge the out-of-order queue.
4756 * Return true if queue was pruned.
4757 */
4758static int tcp_prune_ofo_queue(struct sock *sk)
4759{
4760 struct tcp_sock *tp = tcp_sk(sk);
4761 int res = 0;
4762
4763 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4764 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED);
4765 __skb_queue_purge(&tp->out_of_order_queue);
4766
4767 /* Reset SACK state. A conforming SACK implementation will
4768 * do the same at a timeout based retransmit. When a connection
4769 * is in a sad state like this, we care only about integrity
4770 * of the connection not performance.
4771 */
4772 if (tp->rx_opt.sack_ok)
4773 tcp_sack_reset(&tp->rx_opt);
4774 sk_mem_reclaim(sk);
4775 res = 1;
4776 }
4777 return res;
4778}
4779
4780/* Reduce allocated memory if we can, trying to get
4781 * the socket within its memory limits again.
4782 *
4783 * Return less than zero if we should start dropping frames
4784 * until the socket owning process reads some of the data
4785 * to stabilize the situation.
4786 */
4787static int tcp_prune_queue(struct sock *sk)
4788{
4789 struct tcp_sock *tp = tcp_sk(sk);
4790
4791 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
4792
4793 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED);
4794
4795 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
4796 tcp_clamp_window(sk);
4797 else if (tcp_memory_pressure)
4798 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
4799
4800 tcp_collapse_ofo_queue(sk);
4801 if (!skb_queue_empty(&sk->sk_receive_queue))
4802 tcp_collapse(sk, &sk->sk_receive_queue,
4803 skb_peek(&sk->sk_receive_queue),
4804 NULL,
4805 tp->copied_seq, tp->rcv_nxt);
4806 sk_mem_reclaim(sk);
4807
4808 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4809 return 0;
4810
4811 /* Collapsing did not help, destructive actions follow.
4812 * This must not ever occur. */
4813
4814 tcp_prune_ofo_queue(sk);
4815
4816 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4817 return 0;
4818
4819 /* If we are really being abused, tell the caller to silently
4820 * drop receive data on the floor. It will get retransmitted
4821 * and hopefully then we'll have sufficient space.
4822 */
4823 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED);
4824
4825 /* Massive buffer overcommit. */
4826 tp->pred_flags = 0;
4827 return -1;
4828}
4829
4830/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4831 * As additional protections, we do not touch cwnd in retransmission phases,
4832 * and if application hit its sndbuf limit recently.
4833 */
4834void tcp_cwnd_application_limited(struct sock *sk)
4835{
4836 struct tcp_sock *tp = tcp_sk(sk);
4837
4838 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
4839 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
4840 /* Limited by application or receiver window. */
4841 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
4842 u32 win_used = max(tp->snd_cwnd_used, init_win);
4843 if (win_used < tp->snd_cwnd) {
4844 tp->snd_ssthresh = tcp_current_ssthresh(sk);
4845 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
4846 }
4847 tp->snd_cwnd_used = 0;
4848 }
4849 tp->snd_cwnd_stamp = tcp_time_stamp;
4850}
4851
4852static int tcp_should_expand_sndbuf(struct sock *sk)
4853{
4854 struct tcp_sock *tp = tcp_sk(sk);
4855
4856 /* If the user specified a specific send buffer setting, do
4857 * not modify it.
4858 */
4859 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
4860 return 0;
4861
4862 /* If we are under global TCP memory pressure, do not expand. */
4863 if (tcp_memory_pressure)
4864 return 0;
4865
4866 /* If we are under soft global TCP memory pressure, do not expand. */
4867 if (atomic_long_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
4868 return 0;
4869
4870 /* If we filled the congestion window, do not expand. */
4871 if (tp->packets_out >= tp->snd_cwnd)
4872 return 0;
4873
4874 return 1;
4875}
4876
4877/* When incoming ACK allowed to free some skb from write_queue,
4878 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4879 * on the exit from tcp input handler.
4880 *
4881 * PROBLEM: sndbuf expansion does not work well with largesend.
4882 */
4883static void tcp_new_space(struct sock *sk)
4884{
4885 struct tcp_sock *tp = tcp_sk(sk);
4886
4887 if (tcp_should_expand_sndbuf(sk)) {
4888 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
4889 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
4890 int demanded = max_t(unsigned int, tp->snd_cwnd,
4891 tp->reordering + 1);
4892 sndmem *= 2 * demanded;
4893 if (sndmem > sk->sk_sndbuf)
4894 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
4895 tp->snd_cwnd_stamp = tcp_time_stamp;
4896 }
4897
4898 sk->sk_write_space(sk);
4899}
4900
4901static void tcp_check_space(struct sock *sk)
4902{
4903 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
4904 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
4905 if (sk->sk_socket &&
4906 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
4907 tcp_new_space(sk);
4908 }
4909}
4910
4911static inline void tcp_data_snd_check(struct sock *sk)
4912{
4913 tcp_push_pending_frames(sk);
4914 tcp_check_space(sk);
4915}
4916
4917/*
4918 * Check if sending an ack is needed.
4919 */
4920static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4921{
4922 struct tcp_sock *tp = tcp_sk(sk);
4923
4924 /* More than one full frame received... */
4925 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
4926 /* ... and right edge of window advances far enough.
4927 * (tcp_recvmsg() will send ACK otherwise). Or...
4928 */
4929 __tcp_select_window(sk) >= tp->rcv_wnd) ||
4930 /* We ACK each frame or... */
4931 tcp_in_quickack_mode(sk) ||
4932 /* We have out of order data. */
4933 (ofo_possible && skb_peek(&tp->out_of_order_queue))) {
4934 /* Then ack it now */
4935 tcp_send_ack(sk);
4936 } else {
4937 /* Else, send delayed ack. */
4938 tcp_send_delayed_ack(sk);
4939 }
4940}
4941
4942static inline void tcp_ack_snd_check(struct sock *sk)
4943{
4944 if (!inet_csk_ack_scheduled(sk)) {
4945 /* We sent a data segment already. */
4946 return;
4947 }
4948 __tcp_ack_snd_check(sk, 1);
4949}
4950
4951/*
4952 * This routine is only called when we have urgent data
4953 * signaled. Its the 'slow' part of tcp_urg. It could be
4954 * moved inline now as tcp_urg is only called from one
4955 * place. We handle URGent data wrong. We have to - as
4956 * BSD still doesn't use the correction from RFC961.
4957 * For 1003.1g we should support a new option TCP_STDURG to permit
4958 * either form (or just set the sysctl tcp_stdurg).
4959 */
4960
4961static void tcp_check_urg(struct sock *sk, struct tcphdr *th)
4962{
4963 struct tcp_sock *tp = tcp_sk(sk);
4964 u32 ptr = ntohs(th->urg_ptr);
4965
4966 if (ptr && !sysctl_tcp_stdurg)
4967 ptr--;
4968 ptr += ntohl(th->seq);
4969
4970 /* Ignore urgent data that we've already seen and read. */
4971 if (after(tp->copied_seq, ptr))
4972 return;
4973
4974 /* Do not replay urg ptr.
4975 *
4976 * NOTE: interesting situation not covered by specs.
4977 * Misbehaving sender may send urg ptr, pointing to segment,
4978 * which we already have in ofo queue. We are not able to fetch
4979 * such data and will stay in TCP_URG_NOTYET until will be eaten
4980 * by recvmsg(). Seems, we are not obliged to handle such wicked
4981 * situations. But it is worth to think about possibility of some
4982 * DoSes using some hypothetical application level deadlock.
4983 */
4984 if (before(ptr, tp->rcv_nxt))
4985 return;
4986
4987 /* Do we already have a newer (or duplicate) urgent pointer? */
4988 if (tp->urg_data && !after(ptr, tp->urg_seq))
4989 return;
4990
4991 /* Tell the world about our new urgent pointer. */
4992 sk_send_sigurg(sk);
4993
4994 /* We may be adding urgent data when the last byte read was
4995 * urgent. To do this requires some care. We cannot just ignore
4996 * tp->copied_seq since we would read the last urgent byte again
4997 * as data, nor can we alter copied_seq until this data arrives
4998 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4999 *
5000 * NOTE. Double Dutch. Rendering to plain English: author of comment
5001 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5002 * and expect that both A and B disappear from stream. This is _wrong_.
5003 * Though this happens in BSD with high probability, this is occasional.
5004 * Any application relying on this is buggy. Note also, that fix "works"
5005 * only in this artificial test. Insert some normal data between A and B and we will
5006 * decline of BSD again. Verdict: it is better to remove to trap
5007 * buggy users.
5008 */
5009 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
5010 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
5011 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
5012 tp->copied_seq++;
5013 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
5014 __skb_unlink(skb, &sk->sk_receive_queue);
5015 __kfree_skb(skb);
5016 }
5017 }
5018
5019 tp->urg_data = TCP_URG_NOTYET;
5020 tp->urg_seq = ptr;
5021
5022 /* Disable header prediction. */
5023 tp->pred_flags = 0;
5024}
5025
5026/* This is the 'fast' part of urgent handling. */
5027static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
5028{
5029 struct tcp_sock *tp = tcp_sk(sk);
5030
5031 /* Check if we get a new urgent pointer - normally not. */
5032 if (th->urg)
5033 tcp_check_urg(sk, th);
5034
5035 /* Do we wait for any urgent data? - normally not... */
5036 if (tp->urg_data == TCP_URG_NOTYET) {
5037 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
5038 th->syn;
5039
5040 /* Is the urgent pointer pointing into this packet? */
5041 if (ptr < skb->len) {
5042 u8 tmp;
5043 if (skb_copy_bits(skb, ptr, &tmp, 1))
5044 BUG();
5045 tp->urg_data = TCP_URG_VALID | tmp;
5046 if (!sock_flag(sk, SOCK_DEAD))
5047 sk->sk_data_ready(sk, 0);
5048 }
5049 }
5050}
5051
5052static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
5053{
5054 struct tcp_sock *tp = tcp_sk(sk);
5055 int chunk = skb->len - hlen;
5056 int err;
5057
5058 local_bh_enable();
5059 if (skb_csum_unnecessary(skb))
5060 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
5061 else
5062 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
5063 tp->ucopy.iov);
5064
5065 if (!err) {
5066 tp->ucopy.len -= chunk;
5067 tp->copied_seq += chunk;
5068 tcp_rcv_space_adjust(sk);
5069 }
5070
5071 local_bh_disable();
5072 return err;
5073}
5074
5075static __sum16 __tcp_checksum_complete_user(struct sock *sk,
5076 struct sk_buff *skb)
5077{
5078 __sum16 result;
5079
5080 if (sock_owned_by_user(sk)) {
5081 local_bh_enable();
5082 result = __tcp_checksum_complete(skb);
5083 local_bh_disable();
5084 } else {
5085 result = __tcp_checksum_complete(skb);
5086 }
5087 return result;
5088}
5089
5090static inline int tcp_checksum_complete_user(struct sock *sk,
5091 struct sk_buff *skb)
5092{
5093 return !skb_csum_unnecessary(skb) &&
5094 __tcp_checksum_complete_user(sk, skb);
5095}
5096
5097#ifdef CONFIG_NET_DMA
5098static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
5099 int hlen)
5100{
5101 struct tcp_sock *tp = tcp_sk(sk);
5102 int chunk = skb->len - hlen;
5103 int dma_cookie;
5104 int copied_early = 0;
5105
5106 if (tp->ucopy.wakeup)
5107 return 0;
5108
5109 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
5110 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY);
5111
5112 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
5113
5114 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
5115 skb, hlen,
5116 tp->ucopy.iov, chunk,
5117 tp->ucopy.pinned_list);
5118
5119 if (dma_cookie < 0)
5120 goto out;
5121
5122 tp->ucopy.dma_cookie = dma_cookie;
5123 copied_early = 1;
5124
5125 tp->ucopy.len -= chunk;
5126 tp->copied_seq += chunk;
5127 tcp_rcv_space_adjust(sk);
5128
5129 if ((tp->ucopy.len == 0) ||
5130 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||
5131 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
5132 tp->ucopy.wakeup = 1;
5133 sk->sk_data_ready(sk, 0);
5134 }
5135 } else if (chunk > 0) {
5136 tp->ucopy.wakeup = 1;
5137 sk->sk_data_ready(sk, 0);
5138 }
5139out:
5140 return copied_early;
5141}
5142#endif /* CONFIG_NET_DMA */
5143
5144/* Does PAWS and seqno based validation of an incoming segment, flags will
5145 * play significant role here.
5146 */
5147static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5148 struct tcphdr *th, int syn_inerr)
5149{
5150 u8 *hash_location;
5151 struct tcp_sock *tp = tcp_sk(sk);
5152
5153 /* RFC1323: H1. Apply PAWS check first. */
5154 if (tcp_fast_parse_options(skb, th, tp, &hash_location) &&
5155 tp->rx_opt.saw_tstamp &&
5156 tcp_paws_discard(sk, skb)) {
5157 if (!th->rst) {
5158 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5159 tcp_send_dupack(sk, skb);
5160 goto discard;
5161 }
5162 /* Reset is accepted even if it did not pass PAWS. */
5163 }
5164
5165 /* Step 1: check sequence number */
5166 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
5167 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5168 * (RST) segments are validated by checking their SEQ-fields."
5169 * And page 69: "If an incoming segment is not acceptable,
5170 * an acknowledgment should be sent in reply (unless the RST
5171 * bit is set, if so drop the segment and return)".
5172 */
5173 if (!th->rst)
5174 tcp_send_dupack(sk, skb);
5175 goto discard;
5176 }
5177
5178 /* Step 2: check RST bit */
5179 if (th->rst) {
5180 tcp_reset(sk);
5181 goto discard;
5182 }
5183
5184 /* ts_recent update must be made after we are sure that the packet
5185 * is in window.
5186 */
5187 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
5188
5189 /* step 3: check security and precedence [ignored] */
5190
5191 /* step 4: Check for a SYN in window. */
5192 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
5193 if (syn_inerr)
5194 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5195 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
5196 tcp_reset(sk);
5197 return -1;
5198 }
5199
5200 return 1;
5201
5202discard:
5203 __kfree_skb(skb);
5204 return 0;
5205}
5206
5207/*
5208 * TCP receive function for the ESTABLISHED state.
5209 *
5210 * It is split into a fast path and a slow path. The fast path is
5211 * disabled when:
5212 * - A zero window was announced from us - zero window probing
5213 * is only handled properly in the slow path.
5214 * - Out of order segments arrived.
5215 * - Urgent data is expected.
5216 * - There is no buffer space left
5217 * - Unexpected TCP flags/window values/header lengths are received
5218 * (detected by checking the TCP header against pred_flags)
5219 * - Data is sent in both directions. Fast path only supports pure senders
5220 * or pure receivers (this means either the sequence number or the ack
5221 * value must stay constant)
5222 * - Unexpected TCP option.
5223 *
5224 * When these conditions are not satisfied it drops into a standard
5225 * receive procedure patterned after RFC793 to handle all cases.
5226 * The first three cases are guaranteed by proper pred_flags setting,
5227 * the rest is checked inline. Fast processing is turned on in
5228 * tcp_data_queue when everything is OK.
5229 */
5230int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
5231 struct tcphdr *th, unsigned len)
5232{
5233 struct tcp_sock *tp = tcp_sk(sk);
5234 int res;
5235
5236 /*
5237 * Header prediction.
5238 * The code loosely follows the one in the famous
5239 * "30 instruction TCP receive" Van Jacobson mail.
5240 *
5241 * Van's trick is to deposit buffers into socket queue
5242 * on a device interrupt, to call tcp_recv function
5243 * on the receive process context and checksum and copy
5244 * the buffer to user space. smart...
5245 *
5246 * Our current scheme is not silly either but we take the
5247 * extra cost of the net_bh soft interrupt processing...
5248 * We do checksum and copy also but from device to kernel.
5249 */
5250
5251 tp->rx_opt.saw_tstamp = 0;
5252
5253 /* pred_flags is 0xS?10 << 16 + snd_wnd
5254 * if header_prediction is to be made
5255 * 'S' will always be tp->tcp_header_len >> 2
5256 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5257 * turn it off (when there are holes in the receive
5258 * space for instance)
5259 * PSH flag is ignored.
5260 */
5261
5262 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
5263 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
5264 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
5265 int tcp_header_len = tp->tcp_header_len;
5266
5267 /* Timestamp header prediction: tcp_header_len
5268 * is automatically equal to th->doff*4 due to pred_flags
5269 * match.
5270 */
5271
5272 /* Check timestamp */
5273 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
5274 /* No? Slow path! */
5275 if (!tcp_parse_aligned_timestamp(tp, th))
5276 goto slow_path;
5277
5278 /* If PAWS failed, check it more carefully in slow path */
5279 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
5280 goto slow_path;
5281
5282 /* DO NOT update ts_recent here, if checksum fails
5283 * and timestamp was corrupted part, it will result
5284 * in a hung connection since we will drop all
5285 * future packets due to the PAWS test.
5286 */
5287 }
5288
5289 if (len <= tcp_header_len) {
5290 /* Bulk data transfer: sender */
5291 if (len == tcp_header_len) {
5292 /* Predicted packet is in window by definition.
5293 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5294 * Hence, check seq<=rcv_wup reduces to:
5295 */
5296 if (tcp_header_len ==
5297 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5298 tp->rcv_nxt == tp->rcv_wup)
5299 tcp_store_ts_recent(tp);
5300
5301 /* We know that such packets are checksummed
5302 * on entry.
5303 */
5304 tcp_ack(sk, skb, 0);
5305 __kfree_skb(skb);
5306 tcp_data_snd_check(sk);
5307 return 0;
5308 } else { /* Header too small */
5309 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5310 goto discard;
5311 }
5312 } else {
5313 int eaten = 0;
5314 int copied_early = 0;
5315
5316 if (tp->copied_seq == tp->rcv_nxt &&
5317 len - tcp_header_len <= tp->ucopy.len) {
5318#ifdef CONFIG_NET_DMA
5319 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
5320 copied_early = 1;
5321 eaten = 1;
5322 }
5323#endif
5324 if (tp->ucopy.task == current &&
5325 sock_owned_by_user(sk) && !copied_early) {
5326 __set_current_state(TASK_RUNNING);
5327
5328 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
5329 eaten = 1;
5330 }
5331 if (eaten) {
5332 /* Predicted packet is in window by definition.
5333 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5334 * Hence, check seq<=rcv_wup reduces to:
5335 */
5336 if (tcp_header_len ==
5337 (sizeof(struct tcphdr) +
5338 TCPOLEN_TSTAMP_ALIGNED) &&
5339 tp->rcv_nxt == tp->rcv_wup)
5340 tcp_store_ts_recent(tp);
5341
5342 tcp_rcv_rtt_measure_ts(sk, skb);
5343
5344 __skb_pull(skb, tcp_header_len);
5345 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
5346 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER);
5347 }
5348 if (copied_early)
5349 tcp_cleanup_rbuf(sk, skb->len);
5350 }
5351 if (!eaten) {
5352 if (tcp_checksum_complete_user(sk, skb))
5353 goto csum_error;
5354
5355 /* Predicted packet is in window by definition.
5356 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5357 * Hence, check seq<=rcv_wup reduces to:
5358 */
5359 if (tcp_header_len ==
5360 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5361 tp->rcv_nxt == tp->rcv_wup)
5362 tcp_store_ts_recent(tp);
5363
5364 tcp_rcv_rtt_measure_ts(sk, skb);
5365
5366 if ((int)skb->truesize > sk->sk_forward_alloc)
5367 goto step5;
5368
5369 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS);
5370
5371 /* Bulk data transfer: receiver */
5372 __skb_pull(skb, tcp_header_len);
5373 __skb_queue_tail(&sk->sk_receive_queue, skb);
5374 skb_set_owner_r(skb, sk);
5375 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
5376 }
5377
5378 tcp_event_data_recv(sk, skb);
5379
5380 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
5381 /* Well, only one small jumplet in fast path... */
5382 tcp_ack(sk, skb, FLAG_DATA);
5383 tcp_data_snd_check(sk);
5384 if (!inet_csk_ack_scheduled(sk))
5385 goto no_ack;
5386 }
5387
5388 if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
5389 __tcp_ack_snd_check(sk, 0);
5390no_ack:
5391#ifdef CONFIG_NET_DMA
5392 if (copied_early)
5393 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
5394 else
5395#endif
5396 if (eaten)
5397 __kfree_skb(skb);
5398 else
5399 sk->sk_data_ready(sk, 0);
5400 return 0;
5401 }
5402 }
5403
5404slow_path:
5405 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
5406 goto csum_error;
5407
5408 /*
5409 * Standard slow path.
5410 */
5411
5412 res = tcp_validate_incoming(sk, skb, th, 1);
5413 if (res <= 0)
5414 return -res;
5415
5416step5:
5417 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
5418 goto discard;
5419
5420 tcp_rcv_rtt_measure_ts(sk, skb);
5421
5422 /* Process urgent data. */
5423 tcp_urg(sk, skb, th);
5424
5425 /* step 7: process the segment text */
5426 tcp_data_queue(sk, skb);
5427
5428 tcp_data_snd_check(sk);
5429 tcp_ack_snd_check(sk);
5430 return 0;
5431
5432csum_error:
5433 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5434
5435discard:
5436 __kfree_skb(skb);
5437 return 0;
5438}
5439EXPORT_SYMBOL(tcp_rcv_established);
5440
5441static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
5442 struct tcphdr *th, unsigned len)
5443{
5444 u8 *hash_location;
5445 struct inet_connection_sock *icsk = inet_csk(sk);
5446 struct tcp_sock *tp = tcp_sk(sk);
5447 struct tcp_cookie_values *cvp = tp->cookie_values;
5448 int saved_clamp = tp->rx_opt.mss_clamp;
5449
5450 tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0);
5451
5452 if (th->ack) {
5453 /* rfc793:
5454 * "If the state is SYN-SENT then
5455 * first check the ACK bit
5456 * If the ACK bit is set
5457 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5458 * a reset (unless the RST bit is set, if so drop
5459 * the segment and return)"
5460 *
5461 * We do not send data with SYN, so that RFC-correct
5462 * test reduces to:
5463 */
5464 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
5465 goto reset_and_undo;
5466
5467 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5468 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
5469 tcp_time_stamp)) {
5470 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED);
5471 goto reset_and_undo;
5472 }
5473
5474 /* Now ACK is acceptable.
5475 *
5476 * "If the RST bit is set
5477 * If the ACK was acceptable then signal the user "error:
5478 * connection reset", drop the segment, enter CLOSED state,
5479 * delete TCB, and return."
5480 */
5481
5482 if (th->rst) {
5483 tcp_reset(sk);
5484 goto discard;
5485 }
5486
5487 /* rfc793:
5488 * "fifth, if neither of the SYN or RST bits is set then
5489 * drop the segment and return."
5490 *
5491 * See note below!
5492 * --ANK(990513)
5493 */
5494 if (!th->syn)
5495 goto discard_and_undo;
5496
5497 /* rfc793:
5498 * "If the SYN bit is on ...
5499 * are acceptable then ...
5500 * (our SYN has been ACKed), change the connection
5501 * state to ESTABLISHED..."
5502 */
5503
5504 TCP_ECN_rcv_synack(tp, th);
5505
5506 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5507 tcp_ack(sk, skb, FLAG_SLOWPATH);
5508
5509 /* Ok.. it's good. Set up sequence numbers and
5510 * move to established.
5511 */
5512 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5513 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5514
5515 /* RFC1323: The window in SYN & SYN/ACK segments is
5516 * never scaled.
5517 */
5518 tp->snd_wnd = ntohs(th->window);
5519 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5520
5521 if (!tp->rx_opt.wscale_ok) {
5522 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
5523 tp->window_clamp = min(tp->window_clamp, 65535U);
5524 }
5525
5526 if (tp->rx_opt.saw_tstamp) {
5527 tp->rx_opt.tstamp_ok = 1;
5528 tp->tcp_header_len =
5529 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5530 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5531 tcp_store_ts_recent(tp);
5532 } else {
5533 tp->tcp_header_len = sizeof(struct tcphdr);
5534 }
5535
5536 if (tcp_is_sack(tp) && sysctl_tcp_fack)
5537 tcp_enable_fack(tp);
5538
5539 tcp_mtup_init(sk);
5540 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5541 tcp_initialize_rcv_mss(sk);
5542
5543 /* Remember, tcp_poll() does not lock socket!
5544 * Change state from SYN-SENT only after copied_seq
5545 * is initialized. */
5546 tp->copied_seq = tp->rcv_nxt;
5547
5548 if (cvp != NULL &&
5549 cvp->cookie_pair_size > 0 &&
5550 tp->rx_opt.cookie_plus > 0) {
5551 int cookie_size = tp->rx_opt.cookie_plus
5552 - TCPOLEN_COOKIE_BASE;
5553 int cookie_pair_size = cookie_size
5554 + cvp->cookie_desired;
5555
5556 /* A cookie extension option was sent and returned.
5557 * Note that each incoming SYNACK replaces the
5558 * Responder cookie. The initial exchange is most
5559 * fragile, as protection against spoofing relies
5560 * entirely upon the sequence and timestamp (above).
5561 * This replacement strategy allows the correct pair to
5562 * pass through, while any others will be filtered via
5563 * Responder verification later.
5564 */
5565 if (sizeof(cvp->cookie_pair) >= cookie_pair_size) {
5566 memcpy(&cvp->cookie_pair[cvp->cookie_desired],
5567 hash_location, cookie_size);
5568 cvp->cookie_pair_size = cookie_pair_size;
5569 }
5570 }
5571
5572 smp_mb();
5573 tcp_set_state(sk, TCP_ESTABLISHED);
5574
5575 security_inet_conn_established(sk, skb);
5576
5577 /* Make sure socket is routed, for correct metrics. */
5578 icsk->icsk_af_ops->rebuild_header(sk);
5579
5580 tcp_init_metrics(sk);
5581
5582 tcp_init_congestion_control(sk);
5583
5584 /* Prevent spurious tcp_cwnd_restart() on first data
5585 * packet.
5586 */
5587 tp->lsndtime = tcp_time_stamp;
5588
5589 tcp_init_buffer_space(sk);
5590
5591 if (sock_flag(sk, SOCK_KEEPOPEN))
5592 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
5593
5594 if (!tp->rx_opt.snd_wscale)
5595 __tcp_fast_path_on(tp, tp->snd_wnd);
5596 else
5597 tp->pred_flags = 0;
5598
5599 if (!sock_flag(sk, SOCK_DEAD)) {
5600 sk->sk_state_change(sk);
5601 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5602 }
5603
5604 if (sk->sk_write_pending ||
5605 icsk->icsk_accept_queue.rskq_defer_accept ||
5606 icsk->icsk_ack.pingpong) {
5607 /* Save one ACK. Data will be ready after
5608 * several ticks, if write_pending is set.
5609 *
5610 * It may be deleted, but with this feature tcpdumps
5611 * look so _wonderfully_ clever, that I was not able
5612 * to stand against the temptation 8) --ANK
5613 */
5614 inet_csk_schedule_ack(sk);
5615 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
5616 icsk->icsk_ack.ato = TCP_ATO_MIN;
5617 tcp_incr_quickack(sk);
5618 tcp_enter_quickack_mode(sk);
5619 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
5620 TCP_DELACK_MAX, TCP_RTO_MAX);
5621
5622discard:
5623 __kfree_skb(skb);
5624 return 0;
5625 } else {
5626 tcp_send_ack(sk);
5627 }
5628 return -1;
5629 }
5630
5631 /* No ACK in the segment */
5632
5633 if (th->rst) {
5634 /* rfc793:
5635 * "If the RST bit is set
5636 *
5637 * Otherwise (no ACK) drop the segment and return."
5638 */
5639
5640 goto discard_and_undo;
5641 }
5642
5643 /* PAWS check. */
5644 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
5645 tcp_paws_reject(&tp->rx_opt, 0))
5646 goto discard_and_undo;
5647
5648 if (th->syn) {
5649 /* We see SYN without ACK. It is attempt of
5650 * simultaneous connect with crossed SYNs.
5651 * Particularly, it can be connect to self.
5652 */
5653 tcp_set_state(sk, TCP_SYN_RECV);
5654
5655 if (tp->rx_opt.saw_tstamp) {
5656 tp->rx_opt.tstamp_ok = 1;
5657 tcp_store_ts_recent(tp);
5658 tp->tcp_header_len =
5659 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5660 } else {
5661 tp->tcp_header_len = sizeof(struct tcphdr);
5662 }
5663
5664 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5665 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5666
5667 /* RFC1323: The window in SYN & SYN/ACK segments is
5668 * never scaled.
5669 */
5670 tp->snd_wnd = ntohs(th->window);
5671 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5672 tp->max_window = tp->snd_wnd;
5673
5674 TCP_ECN_rcv_syn(tp, th);
5675
5676 tcp_mtup_init(sk);
5677 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5678 tcp_initialize_rcv_mss(sk);
5679
5680 tcp_send_synack(sk);
5681#if 0
5682 /* Note, we could accept data and URG from this segment.
5683 * There are no obstacles to make this.
5684 *
5685 * However, if we ignore data in ACKless segments sometimes,
5686 * we have no reasons to accept it sometimes.
5687 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5688 * is not flawless. So, discard packet for sanity.
5689 * Uncomment this return to process the data.
5690 */
5691 return -1;
5692#else
5693 goto discard;
5694#endif
5695 }
5696 /* "fifth, if neither of the SYN or RST bits is set then
5697 * drop the segment and return."
5698 */
5699
5700discard_and_undo:
5701 tcp_clear_options(&tp->rx_opt);
5702 tp->rx_opt.mss_clamp = saved_clamp;
5703 goto discard;
5704
5705reset_and_undo:
5706 tcp_clear_options(&tp->rx_opt);
5707 tp->rx_opt.mss_clamp = saved_clamp;
5708 return 1;
5709}
5710
5711/*
5712 * This function implements the receiving procedure of RFC 793 for
5713 * all states except ESTABLISHED and TIME_WAIT.
5714 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5715 * address independent.
5716 */
5717
5718int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
5719 struct tcphdr *th, unsigned len)
5720{
5721 struct tcp_sock *tp = tcp_sk(sk);
5722 struct inet_connection_sock *icsk = inet_csk(sk);
5723 int queued = 0;
5724 int res;
5725
5726 tp->rx_opt.saw_tstamp = 0;
5727
5728 switch (sk->sk_state) {
5729 case TCP_CLOSE:
5730 goto discard;
5731
5732 case TCP_LISTEN:
5733 if (th->ack)
5734 return 1;
5735
5736 if (th->rst)
5737 goto discard;
5738
5739 if (th->syn) {
5740 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
5741 return 1;
5742
5743 /* Now we have several options: In theory there is
5744 * nothing else in the frame. KA9Q has an option to
5745 * send data with the syn, BSD accepts data with the
5746 * syn up to the [to be] advertised window and
5747 * Solaris 2.1 gives you a protocol error. For now
5748 * we just ignore it, that fits the spec precisely
5749 * and avoids incompatibilities. It would be nice in
5750 * future to drop through and process the data.
5751 *
5752 * Now that TTCP is starting to be used we ought to
5753 * queue this data.
5754 * But, this leaves one open to an easy denial of
5755 * service attack, and SYN cookies can't defend
5756 * against this problem. So, we drop the data
5757 * in the interest of security over speed unless
5758 * it's still in use.
5759 */
5760 kfree_skb(skb);
5761 return 0;
5762 }
5763 goto discard;
5764
5765 case TCP_SYN_SENT:
5766 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
5767 if (queued >= 0)
5768 return queued;
5769
5770 /* Do step6 onward by hand. */
5771 tcp_urg(sk, skb, th);
5772 __kfree_skb(skb);
5773 tcp_data_snd_check(sk);
5774 return 0;
5775 }
5776
5777 res = tcp_validate_incoming(sk, skb, th, 0);
5778 if (res <= 0)
5779 return -res;
5780
5781 /* step 5: check the ACK field */
5782 if (th->ack) {
5783 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0;
5784
5785 switch (sk->sk_state) {
5786 case TCP_SYN_RECV:
5787 if (acceptable) {
5788 tp->copied_seq = tp->rcv_nxt;
5789 smp_mb();
5790 tcp_set_state(sk, TCP_ESTABLISHED);
5791 sk->sk_state_change(sk);
5792
5793 /* Note, that this wakeup is only for marginal
5794 * crossed SYN case. Passively open sockets
5795 * are not waked up, because sk->sk_sleep ==
5796 * NULL and sk->sk_socket == NULL.
5797 */
5798 if (sk->sk_socket)
5799 sk_wake_async(sk,
5800 SOCK_WAKE_IO, POLL_OUT);
5801
5802 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
5803 tp->snd_wnd = ntohs(th->window) <<
5804 tp->rx_opt.snd_wscale;
5805 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5806
5807 /* tcp_ack considers this ACK as duplicate
5808 * and does not calculate rtt.
5809 * Force it here.
5810 */
5811 tcp_ack_update_rtt(sk, 0, 0);
5812
5813 if (tp->rx_opt.tstamp_ok)
5814 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5815
5816 /* Make sure socket is routed, for
5817 * correct metrics.
5818 */
5819 icsk->icsk_af_ops->rebuild_header(sk);
5820
5821 tcp_init_metrics(sk);
5822
5823 tcp_init_congestion_control(sk);
5824
5825 /* Prevent spurious tcp_cwnd_restart() on
5826 * first data packet.
5827 */
5828 tp->lsndtime = tcp_time_stamp;
5829
5830 tcp_mtup_init(sk);
5831 tcp_initialize_rcv_mss(sk);
5832 tcp_init_buffer_space(sk);
5833 tcp_fast_path_on(tp);
5834 } else {
5835 return 1;
5836 }
5837 break;
5838
5839 case TCP_FIN_WAIT1:
5840 if (tp->snd_una == tp->write_seq) {
5841 tcp_set_state(sk, TCP_FIN_WAIT2);
5842 sk->sk_shutdown |= SEND_SHUTDOWN;
5843 dst_confirm(__sk_dst_get(sk));
5844
5845 if (!sock_flag(sk, SOCK_DEAD))
5846 /* Wake up lingering close() */
5847 sk->sk_state_change(sk);
5848 else {
5849 int tmo;
5850
5851 if (tp->linger2 < 0 ||
5852 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5853 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
5854 tcp_done(sk);
5855 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
5856 return 1;
5857 }
5858
5859 tmo = tcp_fin_time(sk);
5860 if (tmo > TCP_TIMEWAIT_LEN) {
5861 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
5862 } else if (th->fin || sock_owned_by_user(sk)) {
5863 /* Bad case. We could lose such FIN otherwise.
5864 * It is not a big problem, but it looks confusing
5865 * and not so rare event. We still can lose it now,
5866 * if it spins in bh_lock_sock(), but it is really
5867 * marginal case.
5868 */
5869 inet_csk_reset_keepalive_timer(sk, tmo);
5870 } else {
5871 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
5872 goto discard;
5873 }
5874 }
5875 }
5876 break;
5877
5878 case TCP_CLOSING:
5879 if (tp->snd_una == tp->write_seq) {
5880 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
5881 goto discard;
5882 }
5883 break;
5884
5885 case TCP_LAST_ACK:
5886 if (tp->snd_una == tp->write_seq) {
5887 tcp_update_metrics(sk);
5888 tcp_done(sk);
5889 goto discard;
5890 }
5891 break;
5892 }
5893 } else
5894 goto discard;
5895
5896 /* step 6: check the URG bit */
5897 tcp_urg(sk, skb, th);
5898
5899 /* step 7: process the segment text */
5900 switch (sk->sk_state) {
5901 case TCP_CLOSE_WAIT:
5902 case TCP_CLOSING:
5903 case TCP_LAST_ACK:
5904 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
5905 break;
5906 case TCP_FIN_WAIT1:
5907 case TCP_FIN_WAIT2:
5908 /* RFC 793 says to queue data in these states,
5909 * RFC 1122 says we MUST send a reset.
5910 * BSD 4.4 also does reset.
5911 */
5912 if (sk->sk_shutdown & RCV_SHUTDOWN) {
5913 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5914 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
5915 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
5916 tcp_reset(sk);
5917 return 1;
5918 }
5919 }
5920 /* Fall through */
5921 case TCP_ESTABLISHED:
5922 tcp_data_queue(sk, skb);
5923 queued = 1;
5924 break;
5925 }
5926
5927 /* tcp_data could move socket to TIME-WAIT */
5928 if (sk->sk_state != TCP_CLOSE) {
5929 tcp_data_snd_check(sk);
5930 tcp_ack_snd_check(sk);
5931 }
5932
5933 if (!queued) {
5934discard:
5935 __kfree_skb(skb);
5936 }
5937 return 0;
5938}
5939EXPORT_SYMBOL(tcp_rcv_state_process);