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.
6 * Implementation of the Transmission Control Protocol(TCP).
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>
23 * Pedro Roque : Fast Retransmit/Recovery.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
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
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
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
56 * J Hadi Salim: ECN support
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
64 #define pr_fmt(fmt) "TCP: " fmt
67 #include <linux/slab.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <linux/kernel.h>
71 #include <linux/prefetch.h>
74 #include <net/inet_common.h>
75 #include <linux/ipsec.h>
76 #include <asm/unaligned.h>
77 #include <linux/errqueue.h>
79 int sysctl_tcp_fack __read_mostly
;
80 int sysctl_tcp_max_reordering __read_mostly
= 300;
81 int sysctl_tcp_dsack __read_mostly
= 1;
82 int sysctl_tcp_app_win __read_mostly
= 31;
83 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
84 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
86 /* rfc5961 challenge ack rate limiting */
87 int sysctl_tcp_challenge_ack_limit
= 1000;
89 int sysctl_tcp_stdurg __read_mostly
;
90 int sysctl_tcp_rfc1337 __read_mostly
;
91 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
92 int sysctl_tcp_frto __read_mostly
= 2;
93 int sysctl_tcp_min_rtt_wlen __read_mostly
= 300;
94 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
95 int sysctl_tcp_early_retrans __read_mostly
= 3;
96 int sysctl_tcp_invalid_ratelimit __read_mostly
= HZ
/2;
98 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
99 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
100 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
101 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
102 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
103 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
104 #define FLAG_ECE 0x40 /* ECE in this ACK */
105 #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
106 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
107 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
108 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
109 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
110 #define FLAG_SET_XMIT_TIMER 0x1000 /* Set TLP or RTO timer */
111 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
112 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
113 #define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */
115 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
116 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
117 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
118 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
120 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
121 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
123 #define REXMIT_NONE 0 /* no loss recovery to do */
124 #define REXMIT_LOST 1 /* retransmit packets marked lost */
125 #define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
127 static void tcp_gro_dev_warn(struct sock
*sk
, const struct sk_buff
*skb
,
130 static bool __once __read_mostly
;
133 struct net_device
*dev
;
138 dev
= dev_get_by_index_rcu(sock_net(sk
), skb
->skb_iif
);
139 if (!dev
|| len
>= dev
->mtu
)
140 pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
141 dev
? dev
->name
: "Unknown driver");
146 /* Adapt the MSS value used to make delayed ack decision to the
149 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
151 struct inet_connection_sock
*icsk
= inet_csk(sk
);
152 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
155 icsk
->icsk_ack
.last_seg_size
= 0;
157 /* skb->len may jitter because of SACKs, even if peer
158 * sends good full-sized frames.
160 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
161 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
162 icsk
->icsk_ack
.rcv_mss
= min_t(unsigned int, len
,
164 /* Account for possibly-removed options */
165 if (unlikely(len
> icsk
->icsk_ack
.rcv_mss
+
166 MAX_TCP_OPTION_SPACE
))
167 tcp_gro_dev_warn(sk
, skb
, len
);
169 /* Otherwise, we make more careful check taking into account,
170 * that SACKs block is variable.
172 * "len" is invariant segment length, including TCP header.
174 len
+= skb
->data
- skb_transport_header(skb
);
175 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
176 /* If PSH is not set, packet should be
177 * full sized, provided peer TCP is not badly broken.
178 * This observation (if it is correct 8)) allows
179 * to handle super-low mtu links fairly.
181 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
182 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
183 /* Subtract also invariant (if peer is RFC compliant),
184 * tcp header plus fixed timestamp option length.
185 * Resulting "len" is MSS free of SACK jitter.
187 len
-= tcp_sk(sk
)->tcp_header_len
;
188 icsk
->icsk_ack
.last_seg_size
= len
;
190 icsk
->icsk_ack
.rcv_mss
= len
;
194 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
195 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
196 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
200 static void tcp_incr_quickack(struct sock
*sk
)
202 struct inet_connection_sock
*icsk
= inet_csk(sk
);
203 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
207 if (quickacks
> icsk
->icsk_ack
.quick
)
208 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
211 static void tcp_enter_quickack_mode(struct sock
*sk
)
213 struct inet_connection_sock
*icsk
= inet_csk(sk
);
214 tcp_incr_quickack(sk
);
215 icsk
->icsk_ack
.pingpong
= 0;
216 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
219 /* Send ACKs quickly, if "quick" count is not exhausted
220 * and the session is not interactive.
223 static bool tcp_in_quickack_mode(struct sock
*sk
)
225 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
226 const struct dst_entry
*dst
= __sk_dst_get(sk
);
228 return (dst
&& dst_metric(dst
, RTAX_QUICKACK
)) ||
229 (icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
);
232 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
234 if (tp
->ecn_flags
& TCP_ECN_OK
)
235 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
238 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
240 if (tcp_hdr(skb
)->cwr
)
241 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
244 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
246 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
249 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
251 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
252 case INET_ECN_NOT_ECT
:
253 /* Funny extension: if ECT is not set on a segment,
254 * and we already seen ECT on a previous segment,
255 * it is probably a retransmit.
257 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
258 tcp_enter_quickack_mode((struct sock
*)tp
);
261 if (tcp_ca_needs_ecn((struct sock
*)tp
))
262 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
264 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
265 /* Better not delay acks, sender can have a very low cwnd */
266 tcp_enter_quickack_mode((struct sock
*)tp
);
267 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
269 tp
->ecn_flags
|= TCP_ECN_SEEN
;
272 if (tcp_ca_needs_ecn((struct sock
*)tp
))
273 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
274 tp
->ecn_flags
|= TCP_ECN_SEEN
;
279 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
281 if (tp
->ecn_flags
& TCP_ECN_OK
)
282 __tcp_ecn_check_ce(tp
, skb
);
285 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
287 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
288 tp
->ecn_flags
&= ~TCP_ECN_OK
;
291 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
293 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
294 tp
->ecn_flags
&= ~TCP_ECN_OK
;
297 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
299 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
304 /* Buffer size and advertised window tuning.
306 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
309 static void tcp_sndbuf_expand(struct sock
*sk
)
311 const struct tcp_sock
*tp
= tcp_sk(sk
);
312 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
316 /* Worst case is non GSO/TSO : each frame consumes one skb
317 * and skb->head is kmalloced using power of two area of memory
319 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
321 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
323 per_mss
= roundup_pow_of_two(per_mss
) +
324 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
326 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
327 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
329 /* Fast Recovery (RFC 5681 3.2) :
330 * Cubic needs 1.7 factor, rounded to 2 to include
331 * extra cushion (application might react slowly to POLLOUT)
333 sndmem
= ca_ops
->sndbuf_expand
? ca_ops
->sndbuf_expand(sk
) : 2;
334 sndmem
*= nr_segs
* per_mss
;
336 if (sk
->sk_sndbuf
< sndmem
)
337 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
340 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
342 * All tcp_full_space() is split to two parts: "network" buffer, allocated
343 * forward and advertised in receiver window (tp->rcv_wnd) and
344 * "application buffer", required to isolate scheduling/application
345 * latencies from network.
346 * window_clamp is maximal advertised window. It can be less than
347 * tcp_full_space(), in this case tcp_full_space() - window_clamp
348 * is reserved for "application" buffer. The less window_clamp is
349 * the smoother our behaviour from viewpoint of network, but the lower
350 * throughput and the higher sensitivity of the connection to losses. 8)
352 * rcv_ssthresh is more strict window_clamp used at "slow start"
353 * phase to predict further behaviour of this connection.
354 * It is used for two goals:
355 * - to enforce header prediction at sender, even when application
356 * requires some significant "application buffer". It is check #1.
357 * - to prevent pruning of receive queue because of misprediction
358 * of receiver window. Check #2.
360 * The scheme does not work when sender sends good segments opening
361 * window and then starts to feed us spaghetti. But it should work
362 * in common situations. Otherwise, we have to rely on queue collapsing.
365 /* Slow part of check#2. */
366 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
368 struct tcp_sock
*tp
= tcp_sk(sk
);
370 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
371 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
373 while (tp
->rcv_ssthresh
<= window
) {
374 if (truesize
<= skb
->len
)
375 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
383 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
385 struct tcp_sock
*tp
= tcp_sk(sk
);
388 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
389 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
390 !tcp_under_memory_pressure(sk
)) {
393 /* Check #2. Increase window, if skb with such overhead
394 * will fit to rcvbuf in future.
396 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
397 incr
= 2 * tp
->advmss
;
399 incr
= __tcp_grow_window(sk
, skb
);
402 incr
= max_t(int, incr
, 2 * skb
->len
);
403 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
405 inet_csk(sk
)->icsk_ack
.quick
|= 1;
410 /* 3. Tuning rcvbuf, when connection enters established state. */
411 static void tcp_fixup_rcvbuf(struct sock
*sk
)
413 u32 mss
= tcp_sk(sk
)->advmss
;
416 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
417 tcp_default_init_rwnd(mss
);
419 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
420 * Allow enough cushion so that sender is not limited by our window
422 if (sysctl_tcp_moderate_rcvbuf
)
425 if (sk
->sk_rcvbuf
< rcvmem
)
426 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
429 /* 4. Try to fixup all. It is made immediately after connection enters
432 void tcp_init_buffer_space(struct sock
*sk
)
434 struct tcp_sock
*tp
= tcp_sk(sk
);
437 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
438 tcp_fixup_rcvbuf(sk
);
439 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
440 tcp_sndbuf_expand(sk
);
442 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
443 tcp_mstamp_refresh(tp
);
444 tp
->rcvq_space
.time
= tp
->tcp_mstamp
;
445 tp
->rcvq_space
.seq
= tp
->copied_seq
;
447 maxwin
= tcp_full_space(sk
);
449 if (tp
->window_clamp
>= maxwin
) {
450 tp
->window_clamp
= maxwin
;
452 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
453 tp
->window_clamp
= max(maxwin
-
454 (maxwin
>> sysctl_tcp_app_win
),
458 /* Force reservation of one segment. */
459 if (sysctl_tcp_app_win
&&
460 tp
->window_clamp
> 2 * tp
->advmss
&&
461 tp
->window_clamp
+ tp
->advmss
> maxwin
)
462 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
464 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
465 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
468 /* 5. Recalculate window clamp after socket hit its memory bounds. */
469 static void tcp_clamp_window(struct sock
*sk
)
471 struct tcp_sock
*tp
= tcp_sk(sk
);
472 struct inet_connection_sock
*icsk
= inet_csk(sk
);
474 icsk
->icsk_ack
.quick
= 0;
476 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
477 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
478 !tcp_under_memory_pressure(sk
) &&
479 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
480 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
483 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
484 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
487 /* Initialize RCV_MSS value.
488 * RCV_MSS is an our guess about MSS used by the peer.
489 * We haven't any direct information about the MSS.
490 * It's better to underestimate the RCV_MSS rather than overestimate.
491 * Overestimations make us ACKing less frequently than needed.
492 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
494 void tcp_initialize_rcv_mss(struct sock
*sk
)
496 const struct tcp_sock
*tp
= tcp_sk(sk
);
497 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
499 hint
= min(hint
, tp
->rcv_wnd
/ 2);
500 hint
= min(hint
, TCP_MSS_DEFAULT
);
501 hint
= max(hint
, TCP_MIN_MSS
);
503 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
505 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
507 /* Receiver "autotuning" code.
509 * The algorithm for RTT estimation w/o timestamps is based on
510 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
511 * <http://public.lanl.gov/radiant/pubs.html#DRS>
513 * More detail on this code can be found at
514 * <http://staff.psc.edu/jheffner/>,
515 * though this reference is out of date. A new paper
518 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
520 u32 new_sample
= tp
->rcv_rtt_est
.rtt_us
;
526 if (new_sample
!= 0) {
527 /* If we sample in larger samples in the non-timestamp
528 * case, we could grossly overestimate the RTT especially
529 * with chatty applications or bulk transfer apps which
530 * are stalled on filesystem I/O.
532 * Also, since we are only going for a minimum in the
533 * non-timestamp case, we do not smooth things out
534 * else with timestamps disabled convergence takes too
538 m
-= (new_sample
>> 3);
546 /* No previous measure. */
550 tp
->rcv_rtt_est
.rtt_us
= new_sample
;
553 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
557 if (tp
->rcv_rtt_est
.time
== 0)
559 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
561 delta_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, tp
->rcv_rtt_est
.time
);
562 tcp_rcv_rtt_update(tp
, delta_us
, 1);
565 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
566 tp
->rcv_rtt_est
.time
= tp
->tcp_mstamp
;
569 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
570 const struct sk_buff
*skb
)
572 struct tcp_sock
*tp
= tcp_sk(sk
);
574 if (tp
->rx_opt
.rcv_tsecr
&&
575 (TCP_SKB_CB(skb
)->end_seq
-
576 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
)) {
577 u32 delta
= tcp_time_stamp(tp
) - tp
->rx_opt
.rcv_tsecr
;
578 u32 delta_us
= delta
* (USEC_PER_SEC
/ TCP_TS_HZ
);
580 tcp_rcv_rtt_update(tp
, delta_us
, 0);
585 * This function should be called every time data is copied to user space.
586 * It calculates the appropriate TCP receive buffer space.
588 void tcp_rcv_space_adjust(struct sock
*sk
)
590 struct tcp_sock
*tp
= tcp_sk(sk
);
594 time
= tcp_stamp_us_delta(tp
->tcp_mstamp
, tp
->rcvq_space
.time
);
595 if (time
< (tp
->rcv_rtt_est
.rtt_us
>> 3) || tp
->rcv_rtt_est
.rtt_us
== 0)
598 /* Number of bytes copied to user in last RTT */
599 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
600 if (copied
<= tp
->rcvq_space
.space
)
604 * copied = bytes received in previous RTT, our base window
605 * To cope with packet losses, we need a 2x factor
606 * To cope with slow start, and sender growing its cwin by 100 %
607 * every RTT, we need a 4x factor, because the ACK we are sending
608 * now is for the next RTT, not the current one :
609 * <prev RTT . ><current RTT .. ><next RTT .... >
612 if (sysctl_tcp_moderate_rcvbuf
&&
613 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
614 int rcvwin
, rcvmem
, rcvbuf
;
616 /* minimal window to cope with packet losses, assuming
617 * steady state. Add some cushion because of small variations.
619 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
621 /* If rate increased by 25%,
622 * assume slow start, rcvwin = 3 * copied
623 * If rate increased by 50%,
624 * assume sender can use 2x growth, rcvwin = 4 * copied
627 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
629 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
632 rcvwin
+= (rcvwin
>> 1);
635 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
636 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
639 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
640 if (rcvbuf
> sk
->sk_rcvbuf
) {
641 sk
->sk_rcvbuf
= rcvbuf
;
643 /* Make the window clamp follow along. */
644 tp
->window_clamp
= rcvwin
;
647 tp
->rcvq_space
.space
= copied
;
650 tp
->rcvq_space
.seq
= tp
->copied_seq
;
651 tp
->rcvq_space
.time
= tp
->tcp_mstamp
;
654 /* There is something which you must keep in mind when you analyze the
655 * behavior of the tp->ato delayed ack timeout interval. When a
656 * connection starts up, we want to ack as quickly as possible. The
657 * problem is that "good" TCP's do slow start at the beginning of data
658 * transmission. The means that until we send the first few ACK's the
659 * sender will sit on his end and only queue most of his data, because
660 * he can only send snd_cwnd unacked packets at any given time. For
661 * each ACK we send, he increments snd_cwnd and transmits more of his
664 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
666 struct tcp_sock
*tp
= tcp_sk(sk
);
667 struct inet_connection_sock
*icsk
= inet_csk(sk
);
670 inet_csk_schedule_ack(sk
);
672 tcp_measure_rcv_mss(sk
, skb
);
674 tcp_rcv_rtt_measure(tp
);
678 if (!icsk
->icsk_ack
.ato
) {
679 /* The _first_ data packet received, initialize
680 * delayed ACK engine.
682 tcp_incr_quickack(sk
);
683 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
685 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
687 if (m
<= TCP_ATO_MIN
/ 2) {
688 /* The fastest case is the first. */
689 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
690 } else if (m
< icsk
->icsk_ack
.ato
) {
691 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
692 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
693 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
694 } else if (m
> icsk
->icsk_rto
) {
695 /* Too long gap. Apparently sender failed to
696 * restart window, so that we send ACKs quickly.
698 tcp_incr_quickack(sk
);
702 icsk
->icsk_ack
.lrcvtime
= now
;
704 tcp_ecn_check_ce(tp
, skb
);
707 tcp_grow_window(sk
, skb
);
710 /* Called to compute a smoothed rtt estimate. The data fed to this
711 * routine either comes from timestamps, or from segments that were
712 * known _not_ to have been retransmitted [see Karn/Partridge
713 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
714 * piece by Van Jacobson.
715 * NOTE: the next three routines used to be one big routine.
716 * To save cycles in the RFC 1323 implementation it was better to break
717 * it up into three procedures. -- erics
719 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
721 struct tcp_sock
*tp
= tcp_sk(sk
);
722 long m
= mrtt_us
; /* RTT */
723 u32 srtt
= tp
->srtt_us
;
725 /* The following amusing code comes from Jacobson's
726 * article in SIGCOMM '88. Note that rtt and mdev
727 * are scaled versions of rtt and mean deviation.
728 * This is designed to be as fast as possible
729 * m stands for "measurement".
731 * On a 1990 paper the rto value is changed to:
732 * RTO = rtt + 4 * mdev
734 * Funny. This algorithm seems to be very broken.
735 * These formulae increase RTO, when it should be decreased, increase
736 * too slowly, when it should be increased quickly, decrease too quickly
737 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
738 * does not matter how to _calculate_ it. Seems, it was trap
739 * that VJ failed to avoid. 8)
742 m
-= (srtt
>> 3); /* m is now error in rtt est */
743 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
745 m
= -m
; /* m is now abs(error) */
746 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
747 /* This is similar to one of Eifel findings.
748 * Eifel blocks mdev updates when rtt decreases.
749 * This solution is a bit different: we use finer gain
750 * for mdev in this case (alpha*beta).
751 * Like Eifel it also prevents growth of rto,
752 * but also it limits too fast rto decreases,
753 * happening in pure Eifel.
758 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
760 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
761 if (tp
->mdev_us
> tp
->mdev_max_us
) {
762 tp
->mdev_max_us
= tp
->mdev_us
;
763 if (tp
->mdev_max_us
> tp
->rttvar_us
)
764 tp
->rttvar_us
= tp
->mdev_max_us
;
766 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
767 if (tp
->mdev_max_us
< tp
->rttvar_us
)
768 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
769 tp
->rtt_seq
= tp
->snd_nxt
;
770 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
773 /* no previous measure. */
774 srtt
= m
<< 3; /* take the measured time to be rtt */
775 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
776 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
777 tp
->mdev_max_us
= tp
->rttvar_us
;
778 tp
->rtt_seq
= tp
->snd_nxt
;
780 tp
->srtt_us
= max(1U, srtt
);
783 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
784 * Note: TCP stack does not yet implement pacing.
785 * FQ packet scheduler can be used to implement cheap but effective
786 * TCP pacing, to smooth the burst on large writes when packets
787 * in flight is significantly lower than cwnd (or rwin)
789 int sysctl_tcp_pacing_ss_ratio __read_mostly
= 200;
790 int sysctl_tcp_pacing_ca_ratio __read_mostly
= 120;
792 static void tcp_update_pacing_rate(struct sock
*sk
)
794 const struct tcp_sock
*tp
= tcp_sk(sk
);
797 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
798 rate
= (u64
)tp
->mss_cache
* ((USEC_PER_SEC
/ 100) << 3);
800 /* current rate is (cwnd * mss) / srtt
801 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
802 * In Congestion Avoidance phase, set it to 120 % the current rate.
804 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
805 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
806 * end of slow start and should slow down.
808 if (tp
->snd_cwnd
< tp
->snd_ssthresh
/ 2)
809 rate
*= sysctl_tcp_pacing_ss_ratio
;
811 rate
*= sysctl_tcp_pacing_ca_ratio
;
813 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
815 if (likely(tp
->srtt_us
))
816 do_div(rate
, tp
->srtt_us
);
818 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
819 * without any lock. We want to make sure compiler wont store
820 * intermediate values in this location.
822 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
823 sk
->sk_max_pacing_rate
);
826 /* Calculate rto without backoff. This is the second half of Van Jacobson's
827 * routine referred to above.
829 static void tcp_set_rto(struct sock
*sk
)
831 const struct tcp_sock
*tp
= tcp_sk(sk
);
832 /* Old crap is replaced with new one. 8)
835 * 1. If rtt variance happened to be less 50msec, it is hallucination.
836 * It cannot be less due to utterly erratic ACK generation made
837 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
838 * to do with delayed acks, because at cwnd>2 true delack timeout
839 * is invisible. Actually, Linux-2.4 also generates erratic
840 * ACKs in some circumstances.
842 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
844 /* 2. Fixups made earlier cannot be right.
845 * If we do not estimate RTO correctly without them,
846 * all the algo is pure shit and should be replaced
847 * with correct one. It is exactly, which we pretend to do.
850 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
851 * guarantees that rto is higher.
856 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
858 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
861 cwnd
= TCP_INIT_CWND
;
862 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
866 * Packet counting of FACK is based on in-order assumptions, therefore TCP
867 * disables it when reordering is detected
869 void tcp_disable_fack(struct tcp_sock
*tp
)
871 /* RFC3517 uses different metric in lost marker => reset on change */
873 tp
->lost_skb_hint
= NULL
;
874 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
877 /* Take a notice that peer is sending D-SACKs */
878 static void tcp_dsack_seen(struct tcp_sock
*tp
)
880 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
883 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
886 struct tcp_sock
*tp
= tcp_sk(sk
);
889 if (WARN_ON_ONCE(metric
< 0))
892 if (metric
> tp
->reordering
) {
893 tp
->reordering
= min(sysctl_tcp_max_reordering
, metric
);
895 #if FASTRETRANS_DEBUG > 1
896 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
897 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
901 tp
->undo_marker
? tp
->undo_retrans
: 0);
903 tcp_disable_fack(tp
);
908 /* This exciting event is worth to be remembered. 8) */
910 mib_idx
= LINUX_MIB_TCPTSREORDER
;
911 else if (tcp_is_reno(tp
))
912 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
913 else if (tcp_is_fack(tp
))
914 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
916 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
918 NET_INC_STATS(sock_net(sk
), mib_idx
);
921 /* This must be called before lost_out is incremented */
922 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
924 if (!tp
->retransmit_skb_hint
||
925 before(TCP_SKB_CB(skb
)->seq
,
926 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
927 tp
->retransmit_skb_hint
= skb
;
930 /* Sum the number of packets on the wire we have marked as lost.
931 * There are two cases we care about here:
932 * a) Packet hasn't been marked lost (nor retransmitted),
933 * and this is the first loss.
934 * b) Packet has been marked both lost and retransmitted,
935 * and this means we think it was lost again.
937 static void tcp_sum_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
939 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
941 if (!(sacked
& TCPCB_LOST
) ||
942 ((sacked
& TCPCB_LOST
) && (sacked
& TCPCB_SACKED_RETRANS
)))
943 tp
->lost
+= tcp_skb_pcount(skb
);
946 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
948 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
949 tcp_verify_retransmit_hint(tp
, skb
);
951 tp
->lost_out
+= tcp_skb_pcount(skb
);
952 tcp_sum_lost(tp
, skb
);
953 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
957 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
, struct sk_buff
*skb
)
959 tcp_verify_retransmit_hint(tp
, skb
);
961 tcp_sum_lost(tp
, skb
);
962 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
963 tp
->lost_out
+= tcp_skb_pcount(skb
);
964 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
968 /* This procedure tags the retransmission queue when SACKs arrive.
970 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
971 * Packets in queue with these bits set are counted in variables
972 * sacked_out, retrans_out and lost_out, correspondingly.
974 * Valid combinations are:
975 * Tag InFlight Description
976 * 0 1 - orig segment is in flight.
977 * S 0 - nothing flies, orig reached receiver.
978 * L 0 - nothing flies, orig lost by net.
979 * R 2 - both orig and retransmit are in flight.
980 * L|R 1 - orig is lost, retransmit is in flight.
981 * S|R 1 - orig reached receiver, retrans is still in flight.
982 * (L|S|R is logically valid, it could occur when L|R is sacked,
983 * but it is equivalent to plain S and code short-curcuits it to S.
984 * L|S is logically invalid, it would mean -1 packet in flight 8))
986 * These 6 states form finite state machine, controlled by the following events:
987 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
988 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
989 * 3. Loss detection event of two flavors:
990 * A. Scoreboard estimator decided the packet is lost.
991 * A'. Reno "three dupacks" marks head of queue lost.
992 * A''. Its FACK modification, head until snd.fack is lost.
993 * B. SACK arrives sacking SND.NXT at the moment, when the
994 * segment was retransmitted.
995 * 4. D-SACK added new rule: D-SACK changes any tag to S.
997 * It is pleasant to note, that state diagram turns out to be commutative,
998 * so that we are allowed not to be bothered by order of our actions,
999 * when multiple events arrive simultaneously. (see the function below).
1001 * Reordering detection.
1002 * --------------------
1003 * Reordering metric is maximal distance, which a packet can be displaced
1004 * in packet stream. With SACKs we can estimate it:
1006 * 1. SACK fills old hole and the corresponding segment was not
1007 * ever retransmitted -> reordering. Alas, we cannot use it
1008 * when segment was retransmitted.
1009 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1010 * for retransmitted and already SACKed segment -> reordering..
1011 * Both of these heuristics are not used in Loss state, when we cannot
1012 * account for retransmits accurately.
1014 * SACK block validation.
1015 * ----------------------
1017 * SACK block range validation checks that the received SACK block fits to
1018 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1019 * Note that SND.UNA is not included to the range though being valid because
1020 * it means that the receiver is rather inconsistent with itself reporting
1021 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1022 * perfectly valid, however, in light of RFC2018 which explicitly states
1023 * that "SACK block MUST reflect the newest segment. Even if the newest
1024 * segment is going to be discarded ...", not that it looks very clever
1025 * in case of head skb. Due to potentional receiver driven attacks, we
1026 * choose to avoid immediate execution of a walk in write queue due to
1027 * reneging and defer head skb's loss recovery to standard loss recovery
1028 * procedure that will eventually trigger (nothing forbids us doing this).
1030 * Implements also blockage to start_seq wrap-around. Problem lies in the
1031 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1032 * there's no guarantee that it will be before snd_nxt (n). The problem
1033 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1036 * <- outs wnd -> <- wrapzone ->
1037 * u e n u_w e_w s n_w
1039 * |<------------+------+----- TCP seqno space --------------+---------->|
1040 * ...-- <2^31 ->| |<--------...
1041 * ...---- >2^31 ------>| |<--------...
1043 * Current code wouldn't be vulnerable but it's better still to discard such
1044 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1045 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1046 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1047 * equal to the ideal case (infinite seqno space without wrap caused issues).
1049 * With D-SACK the lower bound is extended to cover sequence space below
1050 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1051 * again, D-SACK block must not to go across snd_una (for the same reason as
1052 * for the normal SACK blocks, explained above). But there all simplicity
1053 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1054 * fully below undo_marker they do not affect behavior in anyway and can
1055 * therefore be safely ignored. In rare cases (which are more or less
1056 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1057 * fragmentation and packet reordering past skb's retransmission. To consider
1058 * them correctly, the acceptable range must be extended even more though
1059 * the exact amount is rather hard to quantify. However, tp->max_window can
1060 * be used as an exaggerated estimate.
1062 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
1063 u32 start_seq
, u32 end_seq
)
1065 /* Too far in future, or reversed (interpretation is ambiguous) */
1066 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1069 /* Nasty start_seq wrap-around check (see comments above) */
1070 if (!before(start_seq
, tp
->snd_nxt
))
1073 /* In outstanding window? ...This is valid exit for D-SACKs too.
1074 * start_seq == snd_una is non-sensical (see comments above)
1076 if (after(start_seq
, tp
->snd_una
))
1079 if (!is_dsack
|| !tp
->undo_marker
)
1082 /* ...Then it's D-SACK, and must reside below snd_una completely */
1083 if (after(end_seq
, tp
->snd_una
))
1086 if (!before(start_seq
, tp
->undo_marker
))
1090 if (!after(end_seq
, tp
->undo_marker
))
1093 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1094 * start_seq < undo_marker and end_seq >= undo_marker.
1096 return !before(start_seq
, end_seq
- tp
->max_window
);
1099 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1100 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1103 struct tcp_sock
*tp
= tcp_sk(sk
);
1104 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1105 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1106 bool dup_sack
= false;
1108 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1111 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1112 } else if (num_sacks
> 1) {
1113 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1114 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1116 if (!after(end_seq_0
, end_seq_1
) &&
1117 !before(start_seq_0
, start_seq_1
)) {
1120 NET_INC_STATS(sock_net(sk
),
1121 LINUX_MIB_TCPDSACKOFORECV
);
1125 /* D-SACK for already forgotten data... Do dumb counting. */
1126 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1127 !after(end_seq_0
, prior_snd_una
) &&
1128 after(end_seq_0
, tp
->undo_marker
))
1134 struct tcp_sacktag_state
{
1137 /* Timestamps for earliest and latest never-retransmitted segment
1138 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1139 * but congestion control should still get an accurate delay signal.
1143 struct rate_sample
*rate
;
1147 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1148 * the incoming SACK may not exactly match but we can find smaller MSS
1149 * aligned portion of it that matches. Therefore we might need to fragment
1150 * which may fail and creates some hassle (caller must handle error case
1153 * FIXME: this could be merged to shift decision code
1155 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1156 u32 start_seq
, u32 end_seq
)
1160 unsigned int pkt_len
;
1163 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1164 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1166 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1167 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1168 mss
= tcp_skb_mss(skb
);
1169 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1172 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1176 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1181 /* Round if necessary so that SACKs cover only full MSSes
1182 * and/or the remaining small portion (if present)
1184 if (pkt_len
> mss
) {
1185 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1186 if (!in_sack
&& new_len
< pkt_len
)
1191 if (pkt_len
>= skb
->len
&& !in_sack
)
1194 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1202 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1203 static u8
tcp_sacktag_one(struct sock
*sk
,
1204 struct tcp_sacktag_state
*state
, u8 sacked
,
1205 u32 start_seq
, u32 end_seq
,
1206 int dup_sack
, int pcount
,
1209 struct tcp_sock
*tp
= tcp_sk(sk
);
1210 int fack_count
= state
->fack_count
;
1212 /* Account D-SACK for retransmitted packet. */
1213 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1214 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1215 after(end_seq
, tp
->undo_marker
))
1217 if (sacked
& TCPCB_SACKED_ACKED
)
1218 state
->reord
= min(fack_count
, state
->reord
);
1221 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1222 if (!after(end_seq
, tp
->snd_una
))
1225 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1226 tcp_rack_advance(tp
, sacked
, end_seq
, xmit_time
);
1228 if (sacked
& TCPCB_SACKED_RETRANS
) {
1229 /* If the segment is not tagged as lost,
1230 * we do not clear RETRANS, believing
1231 * that retransmission is still in flight.
1233 if (sacked
& TCPCB_LOST
) {
1234 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1235 tp
->lost_out
-= pcount
;
1236 tp
->retrans_out
-= pcount
;
1239 if (!(sacked
& TCPCB_RETRANS
)) {
1240 /* New sack for not retransmitted frame,
1241 * which was in hole. It is reordering.
1243 if (before(start_seq
,
1244 tcp_highest_sack_seq(tp
)))
1245 state
->reord
= min(fack_count
,
1247 if (!after(end_seq
, tp
->high_seq
))
1248 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1249 if (state
->first_sackt
== 0)
1250 state
->first_sackt
= xmit_time
;
1251 state
->last_sackt
= xmit_time
;
1254 if (sacked
& TCPCB_LOST
) {
1255 sacked
&= ~TCPCB_LOST
;
1256 tp
->lost_out
-= pcount
;
1260 sacked
|= TCPCB_SACKED_ACKED
;
1261 state
->flag
|= FLAG_DATA_SACKED
;
1262 tp
->sacked_out
+= pcount
;
1263 tp
->delivered
+= pcount
; /* Out-of-order packets delivered */
1265 fack_count
+= pcount
;
1267 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1268 if (!tcp_is_fack(tp
) && tp
->lost_skb_hint
&&
1269 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1270 tp
->lost_cnt_hint
+= pcount
;
1272 if (fack_count
> tp
->fackets_out
)
1273 tp
->fackets_out
= fack_count
;
1276 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1277 * frames and clear it. undo_retrans is decreased above, L|R frames
1278 * are accounted above as well.
1280 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1281 sacked
&= ~TCPCB_SACKED_RETRANS
;
1282 tp
->retrans_out
-= pcount
;
1288 /* Shift newly-SACKed bytes from this skb to the immediately previous
1289 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1291 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1292 struct tcp_sacktag_state
*state
,
1293 unsigned int pcount
, int shifted
, int mss
,
1296 struct tcp_sock
*tp
= tcp_sk(sk
);
1297 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1298 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1299 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1303 /* Adjust counters and hints for the newly sacked sequence
1304 * range but discard the return value since prev is already
1305 * marked. We must tag the range first because the seq
1306 * advancement below implicitly advances
1307 * tcp_highest_sack_seq() when skb is highest_sack.
1309 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1310 start_seq
, end_seq
, dup_sack
, pcount
,
1312 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1314 if (skb
== tp
->lost_skb_hint
)
1315 tp
->lost_cnt_hint
+= pcount
;
1317 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1318 TCP_SKB_CB(skb
)->seq
+= shifted
;
1320 tcp_skb_pcount_add(prev
, pcount
);
1321 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1322 tcp_skb_pcount_add(skb
, -pcount
);
1324 /* When we're adding to gso_segs == 1, gso_size will be zero,
1325 * in theory this shouldn't be necessary but as long as DSACK
1326 * code can come after this skb later on it's better to keep
1327 * setting gso_size to something.
1329 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1330 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1332 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1333 if (tcp_skb_pcount(skb
) <= 1)
1334 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1336 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1337 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1340 BUG_ON(!tcp_skb_pcount(skb
));
1341 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1345 /* Whole SKB was eaten :-) */
1347 if (skb
== tp
->retransmit_skb_hint
)
1348 tp
->retransmit_skb_hint
= prev
;
1349 if (skb
== tp
->lost_skb_hint
) {
1350 tp
->lost_skb_hint
= prev
;
1351 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1354 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1355 TCP_SKB_CB(prev
)->eor
= TCP_SKB_CB(skb
)->eor
;
1356 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1357 TCP_SKB_CB(prev
)->end_seq
++;
1359 if (skb
== tcp_highest_sack(sk
))
1360 tcp_advance_highest_sack(sk
, skb
);
1362 tcp_skb_collapse_tstamp(prev
, skb
);
1363 if (unlikely(TCP_SKB_CB(prev
)->tx
.delivered_mstamp
))
1364 TCP_SKB_CB(prev
)->tx
.delivered_mstamp
= 0;
1366 tcp_unlink_write_queue(skb
, sk
);
1367 sk_wmem_free_skb(sk
, skb
);
1369 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1374 /* I wish gso_size would have a bit more sane initialization than
1375 * something-or-zero which complicates things
1377 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1379 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1382 /* Shifting pages past head area doesn't work */
1383 static int skb_can_shift(const struct sk_buff
*skb
)
1385 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1388 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1391 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1392 struct tcp_sacktag_state
*state
,
1393 u32 start_seq
, u32 end_seq
,
1396 struct tcp_sock
*tp
= tcp_sk(sk
);
1397 struct sk_buff
*prev
;
1403 if (!sk_can_gso(sk
))
1406 /* Normally R but no L won't result in plain S */
1408 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1410 if (!skb_can_shift(skb
))
1412 /* This frame is about to be dropped (was ACKed). */
1413 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1416 /* Can only happen with delayed DSACK + discard craziness */
1417 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1419 prev
= tcp_write_queue_prev(sk
, skb
);
1421 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1424 if (!tcp_skb_can_collapse_to(prev
))
1427 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1428 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1432 pcount
= tcp_skb_pcount(skb
);
1433 mss
= tcp_skb_seglen(skb
);
1435 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1436 * drop this restriction as unnecessary
1438 if (mss
!= tcp_skb_seglen(prev
))
1441 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1443 /* CHECKME: This is non-MSS split case only?, this will
1444 * cause skipped skbs due to advancing loop btw, original
1445 * has that feature too
1447 if (tcp_skb_pcount(skb
) <= 1)
1450 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1452 /* TODO: head merge to next could be attempted here
1453 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1454 * though it might not be worth of the additional hassle
1456 * ...we can probably just fallback to what was done
1457 * previously. We could try merging non-SACKed ones
1458 * as well but it probably isn't going to buy off
1459 * because later SACKs might again split them, and
1460 * it would make skb timestamp tracking considerably
1466 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1468 BUG_ON(len
> skb
->len
);
1470 /* MSS boundaries should be honoured or else pcount will
1471 * severely break even though it makes things bit trickier.
1472 * Optimize common case to avoid most of the divides
1474 mss
= tcp_skb_mss(skb
);
1476 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1477 * drop this restriction as unnecessary
1479 if (mss
!= tcp_skb_seglen(prev
))
1484 } else if (len
< mss
) {
1492 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1493 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1496 if (!skb_shift(prev
, skb
, len
))
1498 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1501 /* Hole filled allows collapsing with the next as well, this is very
1502 * useful when hole on every nth skb pattern happens
1504 if (prev
== tcp_write_queue_tail(sk
))
1506 skb
= tcp_write_queue_next(sk
, prev
);
1508 if (!skb_can_shift(skb
) ||
1509 (skb
== tcp_send_head(sk
)) ||
1510 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1511 (mss
!= tcp_skb_seglen(skb
)))
1515 if (skb_shift(prev
, skb
, len
)) {
1516 pcount
+= tcp_skb_pcount(skb
);
1517 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1521 state
->fack_count
+= pcount
;
1528 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1532 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1533 struct tcp_sack_block
*next_dup
,
1534 struct tcp_sacktag_state
*state
,
1535 u32 start_seq
, u32 end_seq
,
1538 struct tcp_sock
*tp
= tcp_sk(sk
);
1539 struct sk_buff
*tmp
;
1541 tcp_for_write_queue_from(skb
, sk
) {
1543 bool dup_sack
= dup_sack_in
;
1545 if (skb
== tcp_send_head(sk
))
1548 /* queue is in-order => we can short-circuit the walk early */
1549 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1553 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1554 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1555 next_dup
->start_seq
,
1561 /* skb reference here is a bit tricky to get right, since
1562 * shifting can eat and free both this skb and the next,
1563 * so not even _safe variant of the loop is enough.
1566 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1567 start_seq
, end_seq
, dup_sack
);
1576 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1582 if (unlikely(in_sack
< 0))
1586 TCP_SKB_CB(skb
)->sacked
=
1589 TCP_SKB_CB(skb
)->sacked
,
1590 TCP_SKB_CB(skb
)->seq
,
1591 TCP_SKB_CB(skb
)->end_seq
,
1593 tcp_skb_pcount(skb
),
1595 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1597 if (!before(TCP_SKB_CB(skb
)->seq
,
1598 tcp_highest_sack_seq(tp
)))
1599 tcp_advance_highest_sack(sk
, skb
);
1602 state
->fack_count
+= tcp_skb_pcount(skb
);
1607 /* Avoid all extra work that is being done by sacktag while walking in
1610 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1611 struct tcp_sacktag_state
*state
,
1614 tcp_for_write_queue_from(skb
, sk
) {
1615 if (skb
== tcp_send_head(sk
))
1618 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1621 state
->fack_count
+= tcp_skb_pcount(skb
);
1626 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1628 struct tcp_sack_block
*next_dup
,
1629 struct tcp_sacktag_state
*state
,
1635 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1636 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1637 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1638 next_dup
->start_seq
, next_dup
->end_seq
,
1645 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1647 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1651 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1652 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1654 struct tcp_sock
*tp
= tcp_sk(sk
);
1655 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1656 TCP_SKB_CB(ack_skb
)->sacked
);
1657 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1658 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1659 struct tcp_sack_block
*cache
;
1660 struct sk_buff
*skb
;
1661 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1663 bool found_dup_sack
= false;
1665 int first_sack_index
;
1668 state
->reord
= tp
->packets_out
;
1670 if (!tp
->sacked_out
) {
1671 if (WARN_ON(tp
->fackets_out
))
1672 tp
->fackets_out
= 0;
1673 tcp_highest_sack_reset(sk
);
1676 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1677 num_sacks
, prior_snd_una
);
1678 if (found_dup_sack
) {
1679 state
->flag
|= FLAG_DSACKING_ACK
;
1680 tp
->delivered
++; /* A spurious retransmission is delivered */
1683 /* Eliminate too old ACKs, but take into
1684 * account more or less fresh ones, they can
1685 * contain valid SACK info.
1687 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1690 if (!tp
->packets_out
)
1694 first_sack_index
= 0;
1695 for (i
= 0; i
< num_sacks
; i
++) {
1696 bool dup_sack
= !i
&& found_dup_sack
;
1698 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1699 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1701 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1702 sp
[used_sacks
].start_seq
,
1703 sp
[used_sacks
].end_seq
)) {
1707 if (!tp
->undo_marker
)
1708 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1710 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1712 /* Don't count olds caused by ACK reordering */
1713 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1714 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1716 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1719 NET_INC_STATS(sock_net(sk
), mib_idx
);
1721 first_sack_index
= -1;
1725 /* Ignore very old stuff early */
1726 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1732 /* order SACK blocks to allow in order walk of the retrans queue */
1733 for (i
= used_sacks
- 1; i
> 0; i
--) {
1734 for (j
= 0; j
< i
; j
++) {
1735 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1736 swap(sp
[j
], sp
[j
+ 1]);
1738 /* Track where the first SACK block goes to */
1739 if (j
== first_sack_index
)
1740 first_sack_index
= j
+ 1;
1745 skb
= tcp_write_queue_head(sk
);
1746 state
->fack_count
= 0;
1749 if (!tp
->sacked_out
) {
1750 /* It's already past, so skip checking against it */
1751 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1753 cache
= tp
->recv_sack_cache
;
1754 /* Skip empty blocks in at head of the cache */
1755 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1760 while (i
< used_sacks
) {
1761 u32 start_seq
= sp
[i
].start_seq
;
1762 u32 end_seq
= sp
[i
].end_seq
;
1763 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1764 struct tcp_sack_block
*next_dup
= NULL
;
1766 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1767 next_dup
= &sp
[i
+ 1];
1769 /* Skip too early cached blocks */
1770 while (tcp_sack_cache_ok(tp
, cache
) &&
1771 !before(start_seq
, cache
->end_seq
))
1774 /* Can skip some work by looking recv_sack_cache? */
1775 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1776 after(end_seq
, cache
->start_seq
)) {
1779 if (before(start_seq
, cache
->start_seq
)) {
1780 skb
= tcp_sacktag_skip(skb
, sk
, state
,
1782 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1789 /* Rest of the block already fully processed? */
1790 if (!after(end_seq
, cache
->end_seq
))
1793 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1797 /* ...tail remains todo... */
1798 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1799 /* ...but better entrypoint exists! */
1800 skb
= tcp_highest_sack(sk
);
1803 state
->fack_count
= tp
->fackets_out
;
1808 skb
= tcp_sacktag_skip(skb
, sk
, state
, cache
->end_seq
);
1809 /* Check overlap against next cached too (past this one already) */
1814 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1815 skb
= tcp_highest_sack(sk
);
1818 state
->fack_count
= tp
->fackets_out
;
1820 skb
= tcp_sacktag_skip(skb
, sk
, state
, start_seq
);
1823 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
1824 start_seq
, end_seq
, dup_sack
);
1830 /* Clear the head of the cache sack blocks so we can skip it next time */
1831 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1832 tp
->recv_sack_cache
[i
].start_seq
= 0;
1833 tp
->recv_sack_cache
[i
].end_seq
= 0;
1835 for (j
= 0; j
< used_sacks
; j
++)
1836 tp
->recv_sack_cache
[i
++] = sp
[j
];
1838 if ((state
->reord
< tp
->fackets_out
) &&
1839 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1840 tcp_update_reordering(sk
, tp
->fackets_out
- state
->reord
, 0);
1842 tcp_verify_left_out(tp
);
1845 #if FASTRETRANS_DEBUG > 0
1846 WARN_ON((int)tp
->sacked_out
< 0);
1847 WARN_ON((int)tp
->lost_out
< 0);
1848 WARN_ON((int)tp
->retrans_out
< 0);
1849 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1854 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1855 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1857 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1861 holes
= max(tp
->lost_out
, 1U);
1862 holes
= min(holes
, tp
->packets_out
);
1864 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1865 tp
->sacked_out
= tp
->packets_out
- holes
;
1871 /* If we receive more dupacks than we expected counting segments
1872 * in assumption of absent reordering, interpret this as reordering.
1873 * The only another reason could be bug in receiver TCP.
1875 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1877 struct tcp_sock
*tp
= tcp_sk(sk
);
1878 if (tcp_limit_reno_sacked(tp
))
1879 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1882 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1884 static void tcp_add_reno_sack(struct sock
*sk
)
1886 struct tcp_sock
*tp
= tcp_sk(sk
);
1887 u32 prior_sacked
= tp
->sacked_out
;
1890 tcp_check_reno_reordering(sk
, 0);
1891 if (tp
->sacked_out
> prior_sacked
)
1892 tp
->delivered
++; /* Some out-of-order packet is delivered */
1893 tcp_verify_left_out(tp
);
1896 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1898 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1900 struct tcp_sock
*tp
= tcp_sk(sk
);
1903 /* One ACK acked hole. The rest eat duplicate ACKs. */
1904 tp
->delivered
+= max_t(int, acked
- tp
->sacked_out
, 1);
1905 if (acked
- 1 >= tp
->sacked_out
)
1908 tp
->sacked_out
-= acked
- 1;
1910 tcp_check_reno_reordering(sk
, acked
);
1911 tcp_verify_left_out(tp
);
1914 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1919 void tcp_clear_retrans(struct tcp_sock
*tp
)
1921 tp
->retrans_out
= 0;
1923 tp
->undo_marker
= 0;
1924 tp
->undo_retrans
= -1;
1925 tp
->fackets_out
= 0;
1929 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1931 tp
->undo_marker
= tp
->snd_una
;
1932 /* Retransmission still in flight may cause DSACKs later. */
1933 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1936 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1937 * and reset tags completely, otherwise preserve SACKs. If receiver
1938 * dropped its ofo queue, we will know this due to reneging detection.
1940 void tcp_enter_loss(struct sock
*sk
)
1942 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1943 struct tcp_sock
*tp
= tcp_sk(sk
);
1944 struct net
*net
= sock_net(sk
);
1945 struct sk_buff
*skb
;
1946 bool new_recovery
= icsk
->icsk_ca_state
< TCP_CA_Recovery
;
1947 bool is_reneg
; /* is receiver reneging on SACKs? */
1950 /* Reduce ssthresh if it has not yet been made inside this window. */
1951 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1952 !after(tp
->high_seq
, tp
->snd_una
) ||
1953 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1954 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1955 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1956 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1960 tp
->snd_cwnd_cnt
= 0;
1961 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
1963 tp
->retrans_out
= 0;
1966 if (tcp_is_reno(tp
))
1967 tcp_reset_reno_sack(tp
);
1969 skb
= tcp_write_queue_head(sk
);
1970 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1972 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1974 tp
->fackets_out
= 0;
1976 tcp_clear_all_retrans_hints(tp
);
1978 tcp_for_write_queue(skb
, sk
) {
1979 if (skb
== tcp_send_head(sk
))
1982 mark_lost
= (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
1985 tcp_sum_lost(tp
, skb
);
1986 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1988 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1989 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1990 tp
->lost_out
+= tcp_skb_pcount(skb
);
1993 tcp_verify_left_out(tp
);
1995 /* Timeout in disordered state after receiving substantial DUPACKs
1996 * suggests that the degree of reordering is over-estimated.
1998 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1999 tp
->sacked_out
>= net
->ipv4
.sysctl_tcp_reordering
)
2000 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2001 net
->ipv4
.sysctl_tcp_reordering
);
2002 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2003 tp
->high_seq
= tp
->snd_nxt
;
2004 tcp_ecn_queue_cwr(tp
);
2006 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
2007 * loss recovery is underway except recurring timeout(s) on
2008 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
2010 * In theory F-RTO can be used repeatedly during loss recovery.
2011 * In practice this interacts badly with broken middle-boxes that
2012 * falsely raise the receive window, which results in repeated
2013 * timeouts and stop-and-go behavior.
2015 tp
->frto
= sysctl_tcp_frto
&&
2016 (new_recovery
|| icsk
->icsk_retransmits
) &&
2017 !inet_csk(sk
)->icsk_mtup
.probe_size
;
2020 /* If ACK arrived pointing to a remembered SACK, it means that our
2021 * remembered SACKs do not reflect real state of receiver i.e.
2022 * receiver _host_ is heavily congested (or buggy).
2024 * To avoid big spurious retransmission bursts due to transient SACK
2025 * scoreboard oddities that look like reneging, we give the receiver a
2026 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2027 * restore sanity to the SACK scoreboard. If the apparent reneging
2028 * persists until this RTO then we'll clear the SACK scoreboard.
2030 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2032 if (flag
& FLAG_SACK_RENEGING
) {
2033 struct tcp_sock
*tp
= tcp_sk(sk
);
2034 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2035 msecs_to_jiffies(10));
2037 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2038 delay
, TCP_RTO_MAX
);
2044 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2046 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2049 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2050 * counter when SACK is enabled (without SACK, sacked_out is used for
2053 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2054 * segments up to the highest received SACK block so far and holes in
2057 * With reordering, holes may still be in flight, so RFC3517 recovery
2058 * uses pure sacked_out (total number of SACKed segments) even though
2059 * it violates the RFC that uses duplicate ACKs, often these are equal
2060 * but when e.g. out-of-window ACKs or packet duplication occurs,
2061 * they differ. Since neither occurs due to loss, TCP should really
2064 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2066 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2069 /* Linux NewReno/SACK/FACK/ECN state machine.
2070 * --------------------------------------
2072 * "Open" Normal state, no dubious events, fast path.
2073 * "Disorder" In all the respects it is "Open",
2074 * but requires a bit more attention. It is entered when
2075 * we see some SACKs or dupacks. It is split of "Open"
2076 * mainly to move some processing from fast path to slow one.
2077 * "CWR" CWND was reduced due to some Congestion Notification event.
2078 * It can be ECN, ICMP source quench, local device congestion.
2079 * "Recovery" CWND was reduced, we are fast-retransmitting.
2080 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2082 * tcp_fastretrans_alert() is entered:
2083 * - each incoming ACK, if state is not "Open"
2084 * - when arrived ACK is unusual, namely:
2089 * Counting packets in flight is pretty simple.
2091 * in_flight = packets_out - left_out + retrans_out
2093 * packets_out is SND.NXT-SND.UNA counted in packets.
2095 * retrans_out is number of retransmitted segments.
2097 * left_out is number of segments left network, but not ACKed yet.
2099 * left_out = sacked_out + lost_out
2101 * sacked_out: Packets, which arrived to receiver out of order
2102 * and hence not ACKed. With SACKs this number is simply
2103 * amount of SACKed data. Even without SACKs
2104 * it is easy to give pretty reliable estimate of this number,
2105 * counting duplicate ACKs.
2107 * lost_out: Packets lost by network. TCP has no explicit
2108 * "loss notification" feedback from network (for now).
2109 * It means that this number can be only _guessed_.
2110 * Actually, it is the heuristics to predict lossage that
2111 * distinguishes different algorithms.
2113 * F.e. after RTO, when all the queue is considered as lost,
2114 * lost_out = packets_out and in_flight = retrans_out.
2116 * Essentially, we have now a few algorithms detecting
2119 * If the receiver supports SACK:
2121 * RFC6675/3517: It is the conventional algorithm. A packet is
2122 * considered lost if the number of higher sequence packets
2123 * SACKed is greater than or equal the DUPACK thoreshold
2124 * (reordering). This is implemented in tcp_mark_head_lost and
2125 * tcp_update_scoreboard.
2127 * RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
2128 * (2017-) that checks timing instead of counting DUPACKs.
2129 * Essentially a packet is considered lost if it's not S/ACKed
2130 * after RTT + reordering_window, where both metrics are
2131 * dynamically measured and adjusted. This is implemented in
2132 * tcp_rack_mark_lost.
2134 * FACK (Disabled by default. Subsumbed by RACK):
2135 * It is the simplest heuristics. As soon as we decided
2136 * that something is lost, we decide that _all_ not SACKed
2137 * packets until the most forward SACK are lost. I.e.
2138 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2139 * It is absolutely correct estimate, if network does not reorder
2140 * packets. And it loses any connection to reality when reordering
2141 * takes place. We use FACK by default until reordering
2142 * is suspected on the path to this destination.
2144 * If the receiver does not support SACK:
2146 * NewReno (RFC6582): in Recovery we assume that one segment
2147 * is lost (classic Reno). While we are in Recovery and
2148 * a partial ACK arrives, we assume that one more packet
2149 * is lost (NewReno). This heuristics are the same in NewReno
2152 * Really tricky (and requiring careful tuning) part of algorithm
2153 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2154 * The first determines the moment _when_ we should reduce CWND and,
2155 * hence, slow down forward transmission. In fact, it determines the moment
2156 * when we decide that hole is caused by loss, rather than by a reorder.
2158 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2159 * holes, caused by lost packets.
2161 * And the most logically complicated part of algorithm is undo
2162 * heuristics. We detect false retransmits due to both too early
2163 * fast retransmit (reordering) and underestimated RTO, analyzing
2164 * timestamps and D-SACKs. When we detect that some segments were
2165 * retransmitted by mistake and CWND reduction was wrong, we undo
2166 * window reduction and abort recovery phase. This logic is hidden
2167 * inside several functions named tcp_try_undo_<something>.
2170 /* This function decides, when we should leave Disordered state
2171 * and enter Recovery phase, reducing congestion window.
2173 * Main question: may we further continue forward transmission
2174 * with the same cwnd?
2176 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2178 struct tcp_sock
*tp
= tcp_sk(sk
);
2180 /* Trick#1: The loss is proven. */
2184 /* Not-A-Trick#2 : Classic rule... */
2185 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2191 /* Detect loss in event "A" above by marking head of queue up as lost.
2192 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2193 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2194 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2195 * the maximum SACKed segments to pass before reaching this limit.
2197 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2199 struct tcp_sock
*tp
= tcp_sk(sk
);
2200 struct sk_buff
*skb
;
2201 int cnt
, oldcnt
, lost
;
2203 /* Use SACK to deduce losses of new sequences sent during recovery */
2204 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2206 WARN_ON(packets
> tp
->packets_out
);
2207 if (tp
->lost_skb_hint
) {
2208 skb
= tp
->lost_skb_hint
;
2209 cnt
= tp
->lost_cnt_hint
;
2210 /* Head already handled? */
2211 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2214 skb
= tcp_write_queue_head(sk
);
2218 tcp_for_write_queue_from(skb
, sk
) {
2219 if (skb
== tcp_send_head(sk
))
2221 /* TODO: do this better */
2222 /* this is not the most efficient way to do this... */
2223 tp
->lost_skb_hint
= skb
;
2224 tp
->lost_cnt_hint
= cnt
;
2226 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2230 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2231 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2232 cnt
+= tcp_skb_pcount(skb
);
2234 if (cnt
> packets
) {
2235 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2236 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2237 (oldcnt
>= packets
))
2240 mss
= tcp_skb_mss(skb
);
2241 /* If needed, chop off the prefix to mark as lost. */
2242 lost
= (packets
- oldcnt
) * mss
;
2243 if (lost
< skb
->len
&&
2244 tcp_fragment(sk
, skb
, lost
, mss
, GFP_ATOMIC
) < 0)
2249 tcp_skb_mark_lost(tp
, skb
);
2254 tcp_verify_left_out(tp
);
2257 /* Account newly detected lost packet(s) */
2259 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2261 struct tcp_sock
*tp
= tcp_sk(sk
);
2263 if (tcp_is_reno(tp
)) {
2264 tcp_mark_head_lost(sk
, 1, 1);
2265 } else if (tcp_is_fack(tp
)) {
2266 int lost
= tp
->fackets_out
- tp
->reordering
;
2269 tcp_mark_head_lost(sk
, lost
, 0);
2271 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2272 if (sacked_upto
>= 0)
2273 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2274 else if (fast_rexmit
)
2275 tcp_mark_head_lost(sk
, 1, 1);
2279 static bool tcp_tsopt_ecr_before(const struct tcp_sock
*tp
, u32 when
)
2281 return tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2282 before(tp
->rx_opt
.rcv_tsecr
, when
);
2285 /* skb is spurious retransmitted if the returned timestamp echo
2286 * reply is prior to the skb transmission time
2288 static bool tcp_skb_spurious_retrans(const struct tcp_sock
*tp
,
2289 const struct sk_buff
*skb
)
2291 return (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
) &&
2292 tcp_tsopt_ecr_before(tp
, tcp_skb_timestamp(skb
));
2295 /* Nothing was retransmitted or returned timestamp is less
2296 * than timestamp of the first retransmission.
2298 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2300 return !tp
->retrans_stamp
||
2301 tcp_tsopt_ecr_before(tp
, tp
->retrans_stamp
);
2304 /* Undo procedures. */
2306 /* We can clear retrans_stamp when there are no retransmissions in the
2307 * window. It would seem that it is trivially available for us in
2308 * tp->retrans_out, however, that kind of assumptions doesn't consider
2309 * what will happen if errors occur when sending retransmission for the
2310 * second time. ...It could the that such segment has only
2311 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2312 * the head skb is enough except for some reneging corner cases that
2313 * are not worth the effort.
2315 * Main reason for all this complexity is the fact that connection dying
2316 * time now depends on the validity of the retrans_stamp, in particular,
2317 * that successive retransmissions of a segment must not advance
2318 * retrans_stamp under any conditions.
2320 static bool tcp_any_retrans_done(const struct sock
*sk
)
2322 const struct tcp_sock
*tp
= tcp_sk(sk
);
2323 struct sk_buff
*skb
;
2325 if (tp
->retrans_out
)
2328 skb
= tcp_write_queue_head(sk
);
2329 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2335 #if FASTRETRANS_DEBUG > 1
2336 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2338 struct tcp_sock
*tp
= tcp_sk(sk
);
2339 struct inet_sock
*inet
= inet_sk(sk
);
2341 if (sk
->sk_family
== AF_INET
) {
2342 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2344 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2345 tp
->snd_cwnd
, tcp_left_out(tp
),
2346 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2349 #if IS_ENABLED(CONFIG_IPV6)
2350 else if (sk
->sk_family
== AF_INET6
) {
2351 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2353 &sk
->sk_v6_daddr
, ntohs(inet
->inet_dport
),
2354 tp
->snd_cwnd
, tcp_left_out(tp
),
2355 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2361 #define DBGUNDO(x...) do { } while (0)
2364 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2366 struct tcp_sock
*tp
= tcp_sk(sk
);
2369 struct sk_buff
*skb
;
2371 tcp_for_write_queue(skb
, sk
) {
2372 if (skb
== tcp_send_head(sk
))
2374 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2377 tcp_clear_all_retrans_hints(tp
);
2380 if (tp
->prior_ssthresh
) {
2381 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2383 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2385 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2386 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2387 tcp_ecn_withdraw_cwr(tp
);
2390 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2391 tp
->undo_marker
= 0;
2394 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2396 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2399 /* People celebrate: "We love our President!" */
2400 static bool tcp_try_undo_recovery(struct sock
*sk
)
2402 struct tcp_sock
*tp
= tcp_sk(sk
);
2404 if (tcp_may_undo(tp
)) {
2407 /* Happy end! We did not retransmit anything
2408 * or our original transmission succeeded.
2410 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2411 tcp_undo_cwnd_reduction(sk
, false);
2412 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2413 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2415 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2417 NET_INC_STATS(sock_net(sk
), mib_idx
);
2419 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2420 /* Hold old state until something *above* high_seq
2421 * is ACKed. For Reno it is MUST to prevent false
2422 * fast retransmits (RFC2582). SACK TCP is safe. */
2423 if (!tcp_any_retrans_done(sk
))
2424 tp
->retrans_stamp
= 0;
2427 tcp_set_ca_state(sk
, TCP_CA_Open
);
2431 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2432 static bool tcp_try_undo_dsack(struct sock
*sk
)
2434 struct tcp_sock
*tp
= tcp_sk(sk
);
2436 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2437 DBGUNDO(sk
, "D-SACK");
2438 tcp_undo_cwnd_reduction(sk
, false);
2439 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2445 /* Undo during loss recovery after partial ACK or using F-RTO. */
2446 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2448 struct tcp_sock
*tp
= tcp_sk(sk
);
2450 if (frto_undo
|| tcp_may_undo(tp
)) {
2451 tcp_undo_cwnd_reduction(sk
, true);
2453 DBGUNDO(sk
, "partial loss");
2454 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2456 NET_INC_STATS(sock_net(sk
),
2457 LINUX_MIB_TCPSPURIOUSRTOS
);
2458 inet_csk(sk
)->icsk_retransmits
= 0;
2459 if (frto_undo
|| tcp_is_sack(tp
))
2460 tcp_set_ca_state(sk
, TCP_CA_Open
);
2466 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2467 * It computes the number of packets to send (sndcnt) based on packets newly
2469 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2470 * cwnd reductions across a full RTT.
2471 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2472 * But when the retransmits are acked without further losses, PRR
2473 * slow starts cwnd up to ssthresh to speed up the recovery.
2475 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2477 struct tcp_sock
*tp
= tcp_sk(sk
);
2479 tp
->high_seq
= tp
->snd_nxt
;
2480 tp
->tlp_high_seq
= 0;
2481 tp
->snd_cwnd_cnt
= 0;
2482 tp
->prior_cwnd
= tp
->snd_cwnd
;
2483 tp
->prr_delivered
= 0;
2485 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2486 tcp_ecn_queue_cwr(tp
);
2489 void tcp_cwnd_reduction(struct sock
*sk
, int newly_acked_sacked
, int flag
)
2491 struct tcp_sock
*tp
= tcp_sk(sk
);
2493 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2495 if (newly_acked_sacked
<= 0 || WARN_ON_ONCE(!tp
->prior_cwnd
))
2498 tp
->prr_delivered
+= newly_acked_sacked
;
2500 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2502 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2503 } else if ((flag
& FLAG_RETRANS_DATA_ACKED
) &&
2504 !(flag
& FLAG_LOST_RETRANS
)) {
2505 sndcnt
= min_t(int, delta
,
2506 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2507 newly_acked_sacked
) + 1);
2509 sndcnt
= min(delta
, newly_acked_sacked
);
2511 /* Force a fast retransmit upon entering fast recovery */
2512 sndcnt
= max(sndcnt
, (tp
->prr_out
? 0 : 1));
2513 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2516 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2518 struct tcp_sock
*tp
= tcp_sk(sk
);
2520 if (inet_csk(sk
)->icsk_ca_ops
->cong_control
)
2523 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2524 if (tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
&&
2525 (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
|| tp
->undo_marker
)) {
2526 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2527 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2529 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2532 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2533 void tcp_enter_cwr(struct sock
*sk
)
2535 struct tcp_sock
*tp
= tcp_sk(sk
);
2537 tp
->prior_ssthresh
= 0;
2538 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2539 tp
->undo_marker
= 0;
2540 tcp_init_cwnd_reduction(sk
);
2541 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2544 EXPORT_SYMBOL(tcp_enter_cwr
);
2546 static void tcp_try_keep_open(struct sock
*sk
)
2548 struct tcp_sock
*tp
= tcp_sk(sk
);
2549 int state
= TCP_CA_Open
;
2551 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2552 state
= TCP_CA_Disorder
;
2554 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2555 tcp_set_ca_state(sk
, state
);
2556 tp
->high_seq
= tp
->snd_nxt
;
2560 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2562 struct tcp_sock
*tp
= tcp_sk(sk
);
2564 tcp_verify_left_out(tp
);
2566 if (!tcp_any_retrans_done(sk
))
2567 tp
->retrans_stamp
= 0;
2569 if (flag
& FLAG_ECE
)
2572 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2573 tcp_try_keep_open(sk
);
2577 static void tcp_mtup_probe_failed(struct sock
*sk
)
2579 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2581 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2582 icsk
->icsk_mtup
.probe_size
= 0;
2583 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPFAIL
);
2586 static void tcp_mtup_probe_success(struct sock
*sk
)
2588 struct tcp_sock
*tp
= tcp_sk(sk
);
2589 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2591 /* FIXME: breaks with very large cwnd */
2592 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2593 tp
->snd_cwnd
= tp
->snd_cwnd
*
2594 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2595 icsk
->icsk_mtup
.probe_size
;
2596 tp
->snd_cwnd_cnt
= 0;
2597 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2598 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2600 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2601 icsk
->icsk_mtup
.probe_size
= 0;
2602 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2603 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPSUCCESS
);
2606 /* Do a simple retransmit without using the backoff mechanisms in
2607 * tcp_timer. This is used for path mtu discovery.
2608 * The socket is already locked here.
2610 void tcp_simple_retransmit(struct sock
*sk
)
2612 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2613 struct tcp_sock
*tp
= tcp_sk(sk
);
2614 struct sk_buff
*skb
;
2615 unsigned int mss
= tcp_current_mss(sk
);
2616 u32 prior_lost
= tp
->lost_out
;
2618 tcp_for_write_queue(skb
, sk
) {
2619 if (skb
== tcp_send_head(sk
))
2621 if (tcp_skb_seglen(skb
) > mss
&&
2622 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2623 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2624 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2625 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2627 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2631 tcp_clear_retrans_hints_partial(tp
);
2633 if (prior_lost
== tp
->lost_out
)
2636 if (tcp_is_reno(tp
))
2637 tcp_limit_reno_sacked(tp
);
2639 tcp_verify_left_out(tp
);
2641 /* Don't muck with the congestion window here.
2642 * Reason is that we do not increase amount of _data_
2643 * in network, but units changed and effective
2644 * cwnd/ssthresh really reduced now.
2646 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2647 tp
->high_seq
= tp
->snd_nxt
;
2648 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2649 tp
->prior_ssthresh
= 0;
2650 tp
->undo_marker
= 0;
2651 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2653 tcp_xmit_retransmit_queue(sk
);
2655 EXPORT_SYMBOL(tcp_simple_retransmit
);
2657 void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2659 struct tcp_sock
*tp
= tcp_sk(sk
);
2662 if (tcp_is_reno(tp
))
2663 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2665 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2667 NET_INC_STATS(sock_net(sk
), mib_idx
);
2669 tp
->prior_ssthresh
= 0;
2672 if (!tcp_in_cwnd_reduction(sk
)) {
2674 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2675 tcp_init_cwnd_reduction(sk
);
2677 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2680 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2681 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2683 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
,
2686 struct tcp_sock
*tp
= tcp_sk(sk
);
2687 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2689 if ((flag
& FLAG_SND_UNA_ADVANCED
) &&
2690 tcp_try_undo_loss(sk
, false))
2693 /* The ACK (s)acks some never-retransmitted data meaning not all
2694 * the data packets before the timeout were lost. Therefore we
2695 * undo the congestion window and state. This is essentially
2696 * the operation in F-RTO (RFC5682 section 3.1 step 3.b). Since
2697 * a retransmitted skb is permantly marked, we can apply such an
2698 * operation even if F-RTO was not used.
2700 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2701 tcp_try_undo_loss(sk
, tp
->undo_marker
))
2704 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2705 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2706 if (flag
& FLAG_DATA_SACKED
|| is_dupack
)
2707 tp
->frto
= 0; /* Step 3.a. loss was real */
2708 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2709 tp
->high_seq
= tp
->snd_nxt
;
2710 /* Step 2.b. Try send new data (but deferred until cwnd
2711 * is updated in tcp_ack()). Otherwise fall back to
2712 * the conventional recovery.
2714 if (tcp_send_head(sk
) &&
2715 after(tcp_wnd_end(tp
), tp
->snd_nxt
)) {
2716 *rexmit
= REXMIT_NEW
;
2724 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2725 tcp_try_undo_recovery(sk
);
2728 if (tcp_is_reno(tp
)) {
2729 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2730 * delivered. Lower inflight to clock out (re)tranmissions.
2732 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2733 tcp_add_reno_sack(sk
);
2734 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2735 tcp_reset_reno_sack(tp
);
2737 *rexmit
= REXMIT_LOST
;
2740 /* Undo during fast recovery after partial ACK. */
2741 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
)
2743 struct tcp_sock
*tp
= tcp_sk(sk
);
2745 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2746 /* Plain luck! Hole if filled with delayed
2747 * packet, rather than with a retransmit.
2749 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2751 /* We are getting evidence that the reordering degree is higher
2752 * than we realized. If there are no retransmits out then we
2753 * can undo. Otherwise we clock out new packets but do not
2754 * mark more packets lost or retransmit more.
2756 if (tp
->retrans_out
)
2759 if (!tcp_any_retrans_done(sk
))
2760 tp
->retrans_stamp
= 0;
2762 DBGUNDO(sk
, "partial recovery");
2763 tcp_undo_cwnd_reduction(sk
, true);
2764 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2765 tcp_try_keep_open(sk
);
2771 static void tcp_rack_identify_loss(struct sock
*sk
, int *ack_flag
)
2773 struct tcp_sock
*tp
= tcp_sk(sk
);
2775 /* Use RACK to detect loss */
2776 if (sysctl_tcp_recovery
& TCP_RACK_LOSS_DETECTION
) {
2777 u32 prior_retrans
= tp
->retrans_out
;
2779 tcp_rack_mark_lost(sk
);
2780 if (prior_retrans
> tp
->retrans_out
)
2781 *ack_flag
|= FLAG_LOST_RETRANS
;
2785 /* Process an event, which can update packets-in-flight not trivially.
2786 * Main goal of this function is to calculate new estimate for left_out,
2787 * taking into account both packets sitting in receiver's buffer and
2788 * packets lost by network.
2790 * Besides that it updates the congestion state when packet loss or ECN
2791 * is detected. But it does not reduce the cwnd, it is done by the
2792 * congestion control later.
2794 * It does _not_ decide what to send, it is made in function
2795 * tcp_xmit_retransmit_queue().
2797 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2798 bool is_dupack
, int *ack_flag
, int *rexmit
)
2800 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2801 struct tcp_sock
*tp
= tcp_sk(sk
);
2802 int fast_rexmit
= 0, flag
= *ack_flag
;
2803 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2804 (tcp_fackets_out(tp
) > tp
->reordering
));
2806 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2808 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2809 tp
->fackets_out
= 0;
2811 /* Now state machine starts.
2812 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2813 if (flag
& FLAG_ECE
)
2814 tp
->prior_ssthresh
= 0;
2816 /* B. In all the states check for reneging SACKs. */
2817 if (tcp_check_sack_reneging(sk
, flag
))
2820 /* C. Check consistency of the current state. */
2821 tcp_verify_left_out(tp
);
2823 /* D. Check state exit conditions. State can be terminated
2824 * when high_seq is ACKed. */
2825 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2826 WARN_ON(tp
->retrans_out
!= 0);
2827 tp
->retrans_stamp
= 0;
2828 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2829 switch (icsk
->icsk_ca_state
) {
2831 /* CWR is to be held something *above* high_seq
2832 * is ACKed for CWR bit to reach receiver. */
2833 if (tp
->snd_una
!= tp
->high_seq
) {
2834 tcp_end_cwnd_reduction(sk
);
2835 tcp_set_ca_state(sk
, TCP_CA_Open
);
2839 case TCP_CA_Recovery
:
2840 if (tcp_is_reno(tp
))
2841 tcp_reset_reno_sack(tp
);
2842 if (tcp_try_undo_recovery(sk
))
2844 tcp_end_cwnd_reduction(sk
);
2849 /* E. Process state. */
2850 switch (icsk
->icsk_ca_state
) {
2851 case TCP_CA_Recovery
:
2852 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2853 if (tcp_is_reno(tp
) && is_dupack
)
2854 tcp_add_reno_sack(sk
);
2856 if (tcp_try_undo_partial(sk
, acked
))
2858 /* Partial ACK arrived. Force fast retransmit. */
2859 do_lost
= tcp_is_reno(tp
) ||
2860 tcp_fackets_out(tp
) > tp
->reordering
;
2862 if (tcp_try_undo_dsack(sk
)) {
2863 tcp_try_keep_open(sk
);
2866 tcp_rack_identify_loss(sk
, ack_flag
);
2869 tcp_process_loss(sk
, flag
, is_dupack
, rexmit
);
2870 tcp_rack_identify_loss(sk
, ack_flag
);
2871 if (!(icsk
->icsk_ca_state
== TCP_CA_Open
||
2872 (*ack_flag
& FLAG_LOST_RETRANS
)))
2874 /* Change state if cwnd is undone or retransmits are lost */
2876 if (tcp_is_reno(tp
)) {
2877 if (flag
& FLAG_SND_UNA_ADVANCED
)
2878 tcp_reset_reno_sack(tp
);
2880 tcp_add_reno_sack(sk
);
2883 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2884 tcp_try_undo_dsack(sk
);
2886 tcp_rack_identify_loss(sk
, ack_flag
);
2887 if (!tcp_time_to_recover(sk
, flag
)) {
2888 tcp_try_to_open(sk
, flag
);
2892 /* MTU probe failure: don't reduce cwnd */
2893 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2894 icsk
->icsk_mtup
.probe_size
&&
2895 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2896 tcp_mtup_probe_failed(sk
);
2897 /* Restores the reduction we did in tcp_mtup_probe() */
2899 tcp_simple_retransmit(sk
);
2903 /* Otherwise enter Recovery state */
2904 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2909 tcp_update_scoreboard(sk
, fast_rexmit
);
2910 *rexmit
= REXMIT_LOST
;
2913 static void tcp_update_rtt_min(struct sock
*sk
, u32 rtt_us
)
2915 struct tcp_sock
*tp
= tcp_sk(sk
);
2916 u32 wlen
= sysctl_tcp_min_rtt_wlen
* HZ
;
2918 minmax_running_min(&tp
->rtt_min
, wlen
, tcp_jiffies32
,
2919 rtt_us
? : jiffies_to_usecs(1));
2922 static bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2923 long seq_rtt_us
, long sack_rtt_us
,
2924 long ca_rtt_us
, struct rate_sample
*rs
)
2926 const struct tcp_sock
*tp
= tcp_sk(sk
);
2928 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2929 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2930 * Karn's algorithm forbids taking RTT if some retransmitted data
2931 * is acked (RFC6298).
2934 seq_rtt_us
= sack_rtt_us
;
2936 /* RTTM Rule: A TSecr value received in a segment is used to
2937 * update the averaged RTT measurement only if the segment
2938 * acknowledges some new data, i.e., only if it advances the
2939 * left edge of the send window.
2940 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2942 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2943 flag
& FLAG_ACKED
) {
2944 u32 delta
= tcp_time_stamp(tp
) - tp
->rx_opt
.rcv_tsecr
;
2945 u32 delta_us
= delta
* (USEC_PER_SEC
/ TCP_TS_HZ
);
2947 seq_rtt_us
= ca_rtt_us
= delta_us
;
2949 rs
->rtt_us
= ca_rtt_us
; /* RTT of last (S)ACKed packet (or -1) */
2953 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
2954 * always taken together with ACK, SACK, or TS-opts. Any negative
2955 * values will be skipped with the seq_rtt_us < 0 check above.
2957 tcp_update_rtt_min(sk
, ca_rtt_us
);
2958 tcp_rtt_estimator(sk
, seq_rtt_us
);
2961 /* RFC6298: only reset backoff on valid RTT measurement. */
2962 inet_csk(sk
)->icsk_backoff
= 0;
2966 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2967 void tcp_synack_rtt_meas(struct sock
*sk
, struct request_sock
*req
)
2969 struct rate_sample rs
;
2972 if (req
&& !req
->num_retrans
&& tcp_rsk(req
)->snt_synack
)
2973 rtt_us
= tcp_stamp_us_delta(tcp_clock_us(), tcp_rsk(req
)->snt_synack
);
2975 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, rtt_us
, -1L, rtt_us
, &rs
);
2979 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2981 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2983 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2984 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_jiffies32
;
2987 /* Restart timer after forward progress on connection.
2988 * RFC2988 recommends to restart timer to now+rto.
2990 void tcp_rearm_rto(struct sock
*sk
)
2992 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2993 struct tcp_sock
*tp
= tcp_sk(sk
);
2995 /* If the retrans timer is currently being used by Fast Open
2996 * for SYN-ACK retrans purpose, stay put.
2998 if (tp
->fastopen_rsk
)
3001 if (!tp
->packets_out
) {
3002 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3004 u32 rto
= inet_csk(sk
)->icsk_rto
;
3005 /* Offset the time elapsed after installing regular RTO */
3006 if (icsk
->icsk_pending
== ICSK_TIME_REO_TIMEOUT
||
3007 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
3008 s64 delta_us
= tcp_rto_delta_us(sk
);
3009 /* delta_us may not be positive if the socket is locked
3010 * when the retrans timer fires and is rescheduled.
3013 rto
= usecs_to_jiffies(delta_us
);
3015 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
3020 /* Try to schedule a loss probe; if that doesn't work, then schedule an RTO. */
3021 static void tcp_set_xmit_timer(struct sock
*sk
)
3023 if (!tcp_schedule_loss_probe(sk
))
3027 /* If we get here, the whole TSO packet has not been acked. */
3028 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3030 struct tcp_sock
*tp
= tcp_sk(sk
);
3033 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3035 packets_acked
= tcp_skb_pcount(skb
);
3036 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3038 packets_acked
-= tcp_skb_pcount(skb
);
3040 if (packets_acked
) {
3041 BUG_ON(tcp_skb_pcount(skb
) == 0);
3042 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3045 return packets_acked
;
3048 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3051 const struct skb_shared_info
*shinfo
;
3053 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3054 if (likely(!TCP_SKB_CB(skb
)->txstamp_ack
))
3057 shinfo
= skb_shinfo(skb
);
3058 if (!before(shinfo
->tskey
, prior_snd_una
) &&
3059 before(shinfo
->tskey
, tcp_sk(sk
)->snd_una
))
3060 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3063 /* Remove acknowledged frames from the retransmission queue. If our packet
3064 * is before the ack sequence we can discard it as it's confirmed to have
3065 * arrived at the other end.
3067 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3068 u32 prior_snd_una
, int *acked
,
3069 struct tcp_sacktag_state
*sack
)
3071 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3072 u64 first_ackt
, last_ackt
;
3073 struct tcp_sock
*tp
= tcp_sk(sk
);
3074 u32 prior_sacked
= tp
->sacked_out
;
3075 u32 reord
= tp
->packets_out
;
3076 bool fully_acked
= true;
3077 long sack_rtt_us
= -1L;
3078 long seq_rtt_us
= -1L;
3079 long ca_rtt_us
= -1L;
3080 struct sk_buff
*skb
;
3082 u32 last_in_flight
= 0;
3088 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3089 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3090 u8 sacked
= scb
->sacked
;
3093 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3095 /* Determine how many packets and what bytes were acked, tso and else */
3096 if (after(scb
->end_seq
, tp
->snd_una
)) {
3097 if (tcp_skb_pcount(skb
) == 1 ||
3098 !after(tp
->snd_una
, scb
->seq
))
3101 acked_pcount
= tcp_tso_acked(sk
, skb
);
3104 fully_acked
= false;
3106 /* Speedup tcp_unlink_write_queue() and next loop */
3107 prefetchw(skb
->next
);
3108 acked_pcount
= tcp_skb_pcount(skb
);
3111 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3112 if (sacked
& TCPCB_SACKED_RETRANS
)
3113 tp
->retrans_out
-= acked_pcount
;
3114 flag
|= FLAG_RETRANS_DATA_ACKED
;
3115 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3116 last_ackt
= skb
->skb_mstamp
;
3117 WARN_ON_ONCE(last_ackt
== 0);
3119 first_ackt
= last_ackt
;
3121 last_in_flight
= TCP_SKB_CB(skb
)->tx
.in_flight
;
3122 reord
= min(pkts_acked
, reord
);
3123 if (!after(scb
->end_seq
, tp
->high_seq
))
3124 flag
|= FLAG_ORIG_SACK_ACKED
;
3127 if (sacked
& TCPCB_SACKED_ACKED
) {
3128 tp
->sacked_out
-= acked_pcount
;
3129 } else if (tcp_is_sack(tp
)) {
3130 tp
->delivered
+= acked_pcount
;
3131 if (!tcp_skb_spurious_retrans(tp
, skb
))
3132 tcp_rack_advance(tp
, sacked
, scb
->end_seq
,
3135 if (sacked
& TCPCB_LOST
)
3136 tp
->lost_out
-= acked_pcount
;
3138 tp
->packets_out
-= acked_pcount
;
3139 pkts_acked
+= acked_pcount
;
3140 tcp_rate_skb_delivered(sk
, skb
, sack
->rate
);
3142 /* Initial outgoing SYN's get put onto the write_queue
3143 * just like anything else we transmit. It is not
3144 * true data, and if we misinform our callers that
3145 * this ACK acks real data, we will erroneously exit
3146 * connection startup slow start one packet too
3147 * quickly. This is severely frowned upon behavior.
3149 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3150 flag
|= FLAG_DATA_ACKED
;
3152 flag
|= FLAG_SYN_ACKED
;
3153 tp
->retrans_stamp
= 0;
3159 tcp_unlink_write_queue(skb
, sk
);
3160 sk_wmem_free_skb(sk
, skb
);
3161 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3162 tp
->retransmit_skb_hint
= NULL
;
3163 if (unlikely(skb
== tp
->lost_skb_hint
))
3164 tp
->lost_skb_hint
= NULL
;
3168 tcp_chrono_stop(sk
, TCP_CHRONO_BUSY
);
3170 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3171 tp
->snd_up
= tp
->snd_una
;
3173 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3174 flag
|= FLAG_SACK_RENEGING
;
3176 if (likely(first_ackt
) && !(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3177 seq_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, first_ackt
);
3178 ca_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, last_ackt
);
3180 if (sack
->first_sackt
) {
3181 sack_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, sack
->first_sackt
);
3182 ca_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, sack
->last_sackt
);
3184 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
,
3185 ca_rtt_us
, sack
->rate
);
3187 if (flag
& FLAG_ACKED
) {
3188 flag
|= FLAG_SET_XMIT_TIMER
; /* set TLP or RTO timer */
3189 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3190 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3191 tcp_mtup_probe_success(sk
);
3194 if (tcp_is_reno(tp
)) {
3195 tcp_remove_reno_sacks(sk
, pkts_acked
);
3199 /* Non-retransmitted hole got filled? That's reordering */
3200 if (reord
< prior_fackets
&& reord
<= tp
->fackets_out
)
3201 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3203 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3204 prior_sacked
- tp
->sacked_out
;
3205 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3208 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3210 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3211 sack_rtt_us
> tcp_stamp_us_delta(tp
->tcp_mstamp
, skb
->skb_mstamp
)) {
3212 /* Do not re-arm RTO if the sack RTT is measured from data sent
3213 * after when the head was last (re)transmitted. Otherwise the
3214 * timeout may continue to extend in loss recovery.
3216 flag
|= FLAG_SET_XMIT_TIMER
; /* set TLP or RTO timer */
3219 if (icsk
->icsk_ca_ops
->pkts_acked
) {
3220 struct ack_sample sample
= { .pkts_acked
= pkts_acked
,
3221 .rtt_us
= sack
->rate
->rtt_us
,
3222 .in_flight
= last_in_flight
};
3224 icsk
->icsk_ca_ops
->pkts_acked(sk
, &sample
);
3227 #if FASTRETRANS_DEBUG > 0
3228 WARN_ON((int)tp
->sacked_out
< 0);
3229 WARN_ON((int)tp
->lost_out
< 0);
3230 WARN_ON((int)tp
->retrans_out
< 0);
3231 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3232 icsk
= inet_csk(sk
);
3234 pr_debug("Leak l=%u %d\n",
3235 tp
->lost_out
, icsk
->icsk_ca_state
);
3238 if (tp
->sacked_out
) {
3239 pr_debug("Leak s=%u %d\n",
3240 tp
->sacked_out
, icsk
->icsk_ca_state
);
3243 if (tp
->retrans_out
) {
3244 pr_debug("Leak r=%u %d\n",
3245 tp
->retrans_out
, icsk
->icsk_ca_state
);
3246 tp
->retrans_out
= 0;
3250 *acked
= pkts_acked
;
3254 static void tcp_ack_probe(struct sock
*sk
)
3256 const struct tcp_sock
*tp
= tcp_sk(sk
);
3257 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3259 /* Was it a usable window open? */
3261 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3262 icsk
->icsk_backoff
= 0;
3263 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3264 /* Socket must be waked up by subsequent tcp_data_snd_check().
3265 * This function is not for random using!
3268 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3270 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3275 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3277 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3278 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3281 /* Decide wheather to run the increase function of congestion control. */
3282 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3284 /* If reordering is high then always grow cwnd whenever data is
3285 * delivered regardless of its ordering. Otherwise stay conservative
3286 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3287 * new SACK or ECE mark may first advance cwnd here and later reduce
3288 * cwnd in tcp_fastretrans_alert() based on more states.
3290 if (tcp_sk(sk
)->reordering
> sock_net(sk
)->ipv4
.sysctl_tcp_reordering
)
3291 return flag
& FLAG_FORWARD_PROGRESS
;
3293 return flag
& FLAG_DATA_ACKED
;
3296 /* The "ultimate" congestion control function that aims to replace the rigid
3297 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3298 * It's called toward the end of processing an ACK with precise rate
3299 * information. All transmission or retransmission are delayed afterwards.
3301 static void tcp_cong_control(struct sock
*sk
, u32 ack
, u32 acked_sacked
,
3302 int flag
, const struct rate_sample
*rs
)
3304 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3306 if (icsk
->icsk_ca_ops
->cong_control
) {
3307 icsk
->icsk_ca_ops
->cong_control(sk
, rs
);
3311 if (tcp_in_cwnd_reduction(sk
)) {
3312 /* Reduce cwnd if state mandates */
3313 tcp_cwnd_reduction(sk
, acked_sacked
, flag
);
3314 } else if (tcp_may_raise_cwnd(sk
, flag
)) {
3315 /* Advance cwnd if state allows */
3316 tcp_cong_avoid(sk
, ack
, acked_sacked
);
3318 tcp_update_pacing_rate(sk
);
3321 /* Check that window update is acceptable.
3322 * The function assumes that snd_una<=ack<=snd_next.
3324 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3325 const u32 ack
, const u32 ack_seq
,
3328 return after(ack
, tp
->snd_una
) ||
3329 after(ack_seq
, tp
->snd_wl1
) ||
3330 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3333 /* If we update tp->snd_una, also update tp->bytes_acked */
3334 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3336 u32 delta
= ack
- tp
->snd_una
;
3338 sock_owned_by_me((struct sock
*)tp
);
3339 tp
->bytes_acked
+= delta
;
3343 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3344 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3346 u32 delta
= seq
- tp
->rcv_nxt
;
3348 sock_owned_by_me((struct sock
*)tp
);
3349 tp
->bytes_received
+= delta
;
3353 /* Update our send window.
3355 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3356 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3358 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3361 struct tcp_sock
*tp
= tcp_sk(sk
);
3363 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3365 if (likely(!tcp_hdr(skb
)->syn
))
3366 nwin
<<= tp
->rx_opt
.snd_wscale
;
3368 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3369 flag
|= FLAG_WIN_UPDATE
;
3370 tcp_update_wl(tp
, ack_seq
);
3372 if (tp
->snd_wnd
!= nwin
) {
3375 /* Note, it is the only place, where
3376 * fast path is recovered for sending TCP.
3379 tcp_fast_path_check(sk
);
3381 if (tcp_send_head(sk
))
3382 tcp_slow_start_after_idle_check(sk
);
3384 if (nwin
> tp
->max_window
) {
3385 tp
->max_window
= nwin
;
3386 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3391 tcp_snd_una_update(tp
, ack
);
3396 static bool __tcp_oow_rate_limited(struct net
*net
, int mib_idx
,
3397 u32
*last_oow_ack_time
)
3399 if (*last_oow_ack_time
) {
3400 s32 elapsed
= (s32
)(tcp_jiffies32
- *last_oow_ack_time
);
3402 if (0 <= elapsed
&& elapsed
< sysctl_tcp_invalid_ratelimit
) {
3403 NET_INC_STATS(net
, mib_idx
);
3404 return true; /* rate-limited: don't send yet! */
3408 *last_oow_ack_time
= tcp_jiffies32
;
3410 return false; /* not rate-limited: go ahead, send dupack now! */
3413 /* Return true if we're currently rate-limiting out-of-window ACKs and
3414 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3415 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3416 * attacks that send repeated SYNs or ACKs for the same connection. To
3417 * do this, we do not send a duplicate SYNACK or ACK if the remote
3418 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3420 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3421 int mib_idx
, u32
*last_oow_ack_time
)
3423 /* Data packets without SYNs are not likely part of an ACK loop. */
3424 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3428 return __tcp_oow_rate_limited(net
, mib_idx
, last_oow_ack_time
);
3431 /* RFC 5961 7 [ACK Throttling] */
3432 static void tcp_send_challenge_ack(struct sock
*sk
, const struct sk_buff
*skb
)
3434 /* unprotected vars, we dont care of overwrites */
3435 static u32 challenge_timestamp
;
3436 static unsigned int challenge_count
;
3437 struct tcp_sock
*tp
= tcp_sk(sk
);
3440 /* First check our per-socket dupack rate limit. */
3441 if (__tcp_oow_rate_limited(sock_net(sk
),
3442 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3443 &tp
->last_oow_ack_time
))
3446 /* Then check host-wide RFC 5961 rate limit. */
3448 if (now
!= challenge_timestamp
) {
3449 u32 half
= (sysctl_tcp_challenge_ack_limit
+ 1) >> 1;
3451 challenge_timestamp
= now
;
3452 WRITE_ONCE(challenge_count
, half
+
3453 prandom_u32_max(sysctl_tcp_challenge_ack_limit
));
3455 count
= READ_ONCE(challenge_count
);
3457 WRITE_ONCE(challenge_count
, count
- 1);
3458 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3463 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3465 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3466 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3469 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3471 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3472 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3473 * extra check below makes sure this can only happen
3474 * for pure ACK frames. -DaveM
3476 * Not only, also it occurs for expired timestamps.
3479 if (tcp_paws_check(&tp
->rx_opt
, 0))
3480 tcp_store_ts_recent(tp
);
3484 /* This routine deals with acks during a TLP episode.
3485 * We mark the end of a TLP episode on receiving TLP dupack or when
3486 * ack is after tlp_high_seq.
3487 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3489 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3491 struct tcp_sock
*tp
= tcp_sk(sk
);
3493 if (before(ack
, tp
->tlp_high_seq
))
3496 if (flag
& FLAG_DSACKING_ACK
) {
3497 /* This DSACK means original and TLP probe arrived; no loss */
3498 tp
->tlp_high_seq
= 0;
3499 } else if (after(ack
, tp
->tlp_high_seq
)) {
3500 /* ACK advances: there was a loss, so reduce cwnd. Reset
3501 * tlp_high_seq in tcp_init_cwnd_reduction()
3503 tcp_init_cwnd_reduction(sk
);
3504 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3505 tcp_end_cwnd_reduction(sk
);
3506 tcp_try_keep_open(sk
);
3507 NET_INC_STATS(sock_net(sk
),
3508 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3509 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3510 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3511 /* Pure dupack: original and TLP probe arrived; no loss */
3512 tp
->tlp_high_seq
= 0;
3516 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3518 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3520 if (icsk
->icsk_ca_ops
->in_ack_event
)
3521 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3524 /* Congestion control has updated the cwnd already. So if we're in
3525 * loss recovery then now we do any new sends (for FRTO) or
3526 * retransmits (for CA_Loss or CA_recovery) that make sense.
3528 static void tcp_xmit_recovery(struct sock
*sk
, int rexmit
)
3530 struct tcp_sock
*tp
= tcp_sk(sk
);
3532 if (rexmit
== REXMIT_NONE
)
3535 if (unlikely(rexmit
== 2)) {
3536 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
3538 if (after(tp
->snd_nxt
, tp
->high_seq
))
3542 tcp_xmit_retransmit_queue(sk
);
3545 /* This routine deals with incoming acks, but not outgoing ones. */
3546 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3548 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3549 struct tcp_sock
*tp
= tcp_sk(sk
);
3550 struct tcp_sacktag_state sack_state
;
3551 struct rate_sample rs
= { .prior_delivered
= 0 };
3552 u32 prior_snd_una
= tp
->snd_una
;
3553 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3554 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3555 bool is_dupack
= false;
3557 int prior_packets
= tp
->packets_out
;
3558 u32 delivered
= tp
->delivered
;
3559 u32 lost
= tp
->lost
;
3560 int acked
= 0; /* Number of packets newly acked */
3561 int rexmit
= REXMIT_NONE
; /* Flag to (re)transmit to recover losses */
3563 sack_state
.first_sackt
= 0;
3564 sack_state
.rate
= &rs
;
3566 /* We very likely will need to access write queue head. */
3567 prefetchw(sk
->sk_write_queue
.next
);
3569 /* If the ack is older than previous acks
3570 * then we can probably ignore it.
3572 if (before(ack
, prior_snd_una
)) {
3573 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3574 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3575 if (!(flag
& FLAG_NO_CHALLENGE_ACK
))
3576 tcp_send_challenge_ack(sk
, skb
);
3582 /* If the ack includes data we haven't sent yet, discard
3583 * this segment (RFC793 Section 3.9).
3585 if (after(ack
, tp
->snd_nxt
))
3588 if (after(ack
, prior_snd_una
)) {
3589 flag
|= FLAG_SND_UNA_ADVANCED
;
3590 icsk
->icsk_retransmits
= 0;
3593 prior_fackets
= tp
->fackets_out
;
3594 rs
.prior_in_flight
= tcp_packets_in_flight(tp
);
3596 /* ts_recent update must be made after we are sure that the packet
3599 if (flag
& FLAG_UPDATE_TS_RECENT
)
3600 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3602 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3603 /* Window is constant, pure forward advance.
3604 * No more checks are required.
3605 * Note, we use the fact that SND.UNA>=SND.WL2.
3607 tcp_update_wl(tp
, ack_seq
);
3608 tcp_snd_una_update(tp
, ack
);
3609 flag
|= FLAG_WIN_UPDATE
;
3611 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3613 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3615 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3617 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3620 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3622 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3624 if (TCP_SKB_CB(skb
)->sacked
)
3625 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3628 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3630 ack_ev_flags
|= CA_ACK_ECE
;
3633 if (flag
& FLAG_WIN_UPDATE
)
3634 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3636 tcp_in_ack_event(sk
, ack_ev_flags
);
3639 /* We passed data and got it acked, remove any soft error
3640 * log. Something worked...
3642 sk
->sk_err_soft
= 0;
3643 icsk
->icsk_probes_out
= 0;
3644 tp
->rcv_tstamp
= tcp_jiffies32
;
3648 /* See if we can take anything off of the retransmit queue. */
3649 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
, &acked
,
3652 if (tp
->tlp_high_seq
)
3653 tcp_process_tlp_ack(sk
, ack
, flag
);
3654 /* If needed, reset TLP/RTO timer; RACK may later override this. */
3655 if (flag
& FLAG_SET_XMIT_TIMER
)
3656 tcp_set_xmit_timer(sk
);
3658 if (tcp_ack_is_dubious(sk
, flag
)) {
3659 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3660 tcp_fastretrans_alert(sk
, acked
, is_dupack
, &flag
, &rexmit
);
3663 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3666 delivered
= tp
->delivered
- delivered
; /* freshly ACKed or SACKed */
3667 lost
= tp
->lost
- lost
; /* freshly marked lost */
3668 tcp_rate_gen(sk
, delivered
, lost
, sack_state
.rate
);
3669 tcp_cong_control(sk
, ack
, delivered
, flag
, sack_state
.rate
);
3670 tcp_xmit_recovery(sk
, rexmit
);
3674 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3675 if (flag
& FLAG_DSACKING_ACK
)
3676 tcp_fastretrans_alert(sk
, acked
, is_dupack
, &flag
, &rexmit
);
3677 /* If this ack opens up a zero window, clear backoff. It was
3678 * being used to time the probes, and is probably far higher than
3679 * it needs to be for normal retransmission.
3681 if (tcp_send_head(sk
))
3684 if (tp
->tlp_high_seq
)
3685 tcp_process_tlp_ack(sk
, ack
, flag
);
3689 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3693 /* If data was SACKed, tag it and see if we should send more data.
3694 * If data was DSACKed, see if we can undo a cwnd reduction.
3696 if (TCP_SKB_CB(skb
)->sacked
) {
3697 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3699 tcp_fastretrans_alert(sk
, acked
, is_dupack
, &flag
, &rexmit
);
3700 tcp_xmit_recovery(sk
, rexmit
);
3703 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3707 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
3708 bool syn
, struct tcp_fastopen_cookie
*foc
,
3711 /* Valid only in SYN or SYN-ACK with an even length. */
3712 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
3715 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3716 len
<= TCP_FASTOPEN_COOKIE_MAX
)
3717 memcpy(foc
->val
, cookie
, len
);
3724 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3725 * But, this can also be called on packets in the established flow when
3726 * the fast version below fails.
3728 void tcp_parse_options(const struct net
*net
,
3729 const struct sk_buff
*skb
,
3730 struct tcp_options_received
*opt_rx
, int estab
,
3731 struct tcp_fastopen_cookie
*foc
)
3733 const unsigned char *ptr
;
3734 const struct tcphdr
*th
= tcp_hdr(skb
);
3735 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3737 ptr
= (const unsigned char *)(th
+ 1);
3738 opt_rx
->saw_tstamp
= 0;
3740 while (length
> 0) {
3741 int opcode
= *ptr
++;
3747 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3752 if (opsize
< 2) /* "silly options" */
3754 if (opsize
> length
)
3755 return; /* don't parse partial options */
3758 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3759 u16 in_mss
= get_unaligned_be16(ptr
);
3761 if (opt_rx
->user_mss
&&
3762 opt_rx
->user_mss
< in_mss
)
3763 in_mss
= opt_rx
->user_mss
;
3764 opt_rx
->mss_clamp
= in_mss
;
3769 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3770 !estab
&& net
->ipv4
.sysctl_tcp_window_scaling
) {
3771 __u8 snd_wscale
= *(__u8
*)ptr
;
3772 opt_rx
->wscale_ok
= 1;
3773 if (snd_wscale
> TCP_MAX_WSCALE
) {
3774 net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n",
3778 snd_wscale
= TCP_MAX_WSCALE
;
3780 opt_rx
->snd_wscale
= snd_wscale
;
3783 case TCPOPT_TIMESTAMP
:
3784 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3785 ((estab
&& opt_rx
->tstamp_ok
) ||
3786 (!estab
&& net
->ipv4
.sysctl_tcp_timestamps
))) {
3787 opt_rx
->saw_tstamp
= 1;
3788 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3789 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3792 case TCPOPT_SACK_PERM
:
3793 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3794 !estab
&& net
->ipv4
.sysctl_tcp_sack
) {
3795 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3796 tcp_sack_reset(opt_rx
);
3801 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3802 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3804 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3807 #ifdef CONFIG_TCP_MD5SIG
3810 * The MD5 Hash has already been
3811 * checked (see tcp_v{4,6}_do_rcv()).
3815 case TCPOPT_FASTOPEN
:
3816 tcp_parse_fastopen_option(
3817 opsize
- TCPOLEN_FASTOPEN_BASE
,
3818 ptr
, th
->syn
, foc
, false);
3822 /* Fast Open option shares code 254 using a
3823 * 16 bits magic number.
3825 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
3826 get_unaligned_be16(ptr
) ==
3827 TCPOPT_FASTOPEN_MAGIC
)
3828 tcp_parse_fastopen_option(opsize
-
3829 TCPOLEN_EXP_FASTOPEN_BASE
,
3830 ptr
+ 2, th
->syn
, foc
, true);
3839 EXPORT_SYMBOL(tcp_parse_options
);
3841 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3843 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3845 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3846 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3847 tp
->rx_opt
.saw_tstamp
= 1;
3849 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3852 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3854 tp
->rx_opt
.rcv_tsecr
= 0;
3860 /* Fast parse options. This hopes to only see timestamps.
3861 * If it is wrong it falls back on tcp_parse_options().
3863 static bool tcp_fast_parse_options(const struct net
*net
,
3864 const struct sk_buff
*skb
,
3865 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3867 /* In the spirit of fast parsing, compare doff directly to constant
3868 * values. Because equality is used, short doff can be ignored here.
3870 if (th
->doff
== (sizeof(*th
) / 4)) {
3871 tp
->rx_opt
.saw_tstamp
= 0;
3873 } else if (tp
->rx_opt
.tstamp_ok
&&
3874 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3875 if (tcp_parse_aligned_timestamp(tp
, th
))
3879 tcp_parse_options(net
, skb
, &tp
->rx_opt
, 1, NULL
);
3880 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3881 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3886 #ifdef CONFIG_TCP_MD5SIG
3888 * Parse MD5 Signature option
3890 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3892 int length
= (th
->doff
<< 2) - sizeof(*th
);
3893 const u8
*ptr
= (const u8
*)(th
+ 1);
3895 /* If the TCP option is too short, we can short cut */
3896 if (length
< TCPOLEN_MD5SIG
)
3899 while (length
> 0) {
3900 int opcode
= *ptr
++;
3911 if (opsize
< 2 || opsize
> length
)
3913 if (opcode
== TCPOPT_MD5SIG
)
3914 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3921 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3924 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3926 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3927 * it can pass through stack. So, the following predicate verifies that
3928 * this segment is not used for anything but congestion avoidance or
3929 * fast retransmit. Moreover, we even are able to eliminate most of such
3930 * second order effects, if we apply some small "replay" window (~RTO)
3931 * to timestamp space.
3933 * All these measures still do not guarantee that we reject wrapped ACKs
3934 * on networks with high bandwidth, when sequence space is recycled fastly,
3935 * but it guarantees that such events will be very rare and do not affect
3936 * connection seriously. This doesn't look nice, but alas, PAWS is really
3939 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3940 * states that events when retransmit arrives after original data are rare.
3941 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3942 * the biggest problem on large power networks even with minor reordering.
3943 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3944 * up to bandwidth of 18Gigabit/sec. 8) ]
3947 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3949 const struct tcp_sock
*tp
= tcp_sk(sk
);
3950 const struct tcphdr
*th
= tcp_hdr(skb
);
3951 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3952 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3954 return (/* 1. Pure ACK with correct sequence number. */
3955 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3957 /* 2. ... and duplicate ACK. */
3958 ack
== tp
->snd_una
&&
3960 /* 3. ... and does not update window. */
3961 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3963 /* 4. ... and sits in replay window. */
3964 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3967 static inline bool tcp_paws_discard(const struct sock
*sk
,
3968 const struct sk_buff
*skb
)
3970 const struct tcp_sock
*tp
= tcp_sk(sk
);
3972 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3973 !tcp_disordered_ack(sk
, skb
);
3976 /* Check segment sequence number for validity.
3978 * Segment controls are considered valid, if the segment
3979 * fits to the window after truncation to the window. Acceptability
3980 * of data (and SYN, FIN, of course) is checked separately.
3981 * See tcp_data_queue(), for example.
3983 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3984 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3985 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3986 * (borrowed from freebsd)
3989 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3991 return !before(end_seq
, tp
->rcv_wup
) &&
3992 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3995 /* When we get a reset we do this. */
3996 void tcp_reset(struct sock
*sk
)
3998 /* We want the right error as BSD sees it (and indeed as we do). */
3999 switch (sk
->sk_state
) {
4001 sk
->sk_err
= ECONNREFUSED
;
4003 case TCP_CLOSE_WAIT
:
4009 sk
->sk_err
= ECONNRESET
;
4011 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4016 if (!sock_flag(sk
, SOCK_DEAD
))
4017 sk
->sk_error_report(sk
);
4021 * Process the FIN bit. This now behaves as it is supposed to work
4022 * and the FIN takes effect when it is validly part of sequence
4023 * space. Not before when we get holes.
4025 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4026 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4029 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4030 * close and we go into CLOSING (and later onto TIME-WAIT)
4032 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4034 void tcp_fin(struct sock
*sk
)
4036 struct tcp_sock
*tp
= tcp_sk(sk
);
4038 inet_csk_schedule_ack(sk
);
4040 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4041 sock_set_flag(sk
, SOCK_DONE
);
4043 switch (sk
->sk_state
) {
4045 case TCP_ESTABLISHED
:
4046 /* Move to CLOSE_WAIT */
4047 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4048 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4051 case TCP_CLOSE_WAIT
:
4053 /* Received a retransmission of the FIN, do
4058 /* RFC793: Remain in the LAST-ACK state. */
4062 /* This case occurs when a simultaneous close
4063 * happens, we must ack the received FIN and
4064 * enter the CLOSING state.
4067 tcp_set_state(sk
, TCP_CLOSING
);
4070 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4072 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4075 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4076 * cases we should never reach this piece of code.
4078 pr_err("%s: Impossible, sk->sk_state=%d\n",
4079 __func__
, sk
->sk_state
);
4083 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4084 * Probably, we should reset in this case. For now drop them.
4086 skb_rbtree_purge(&tp
->out_of_order_queue
);
4087 if (tcp_is_sack(tp
))
4088 tcp_sack_reset(&tp
->rx_opt
);
4091 if (!sock_flag(sk
, SOCK_DEAD
)) {
4092 sk
->sk_state_change(sk
);
4094 /* Do not send POLL_HUP for half duplex close. */
4095 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4096 sk
->sk_state
== TCP_CLOSE
)
4097 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4099 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4103 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4106 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4107 if (before(seq
, sp
->start_seq
))
4108 sp
->start_seq
= seq
;
4109 if (after(end_seq
, sp
->end_seq
))
4110 sp
->end_seq
= end_seq
;
4116 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4118 struct tcp_sock
*tp
= tcp_sk(sk
);
4120 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4123 if (before(seq
, tp
->rcv_nxt
))
4124 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4126 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4128 NET_INC_STATS(sock_net(sk
), mib_idx
);
4130 tp
->rx_opt
.dsack
= 1;
4131 tp
->duplicate_sack
[0].start_seq
= seq
;
4132 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4136 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4138 struct tcp_sock
*tp
= tcp_sk(sk
);
4140 if (!tp
->rx_opt
.dsack
)
4141 tcp_dsack_set(sk
, seq
, end_seq
);
4143 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4146 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4148 struct tcp_sock
*tp
= tcp_sk(sk
);
4150 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4151 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4152 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4153 tcp_enter_quickack_mode(sk
);
4155 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4156 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4158 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4159 end_seq
= tp
->rcv_nxt
;
4160 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4167 /* These routines update the SACK block as out-of-order packets arrive or
4168 * in-order packets close up the sequence space.
4170 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4173 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4174 struct tcp_sack_block
*swalk
= sp
+ 1;
4176 /* See if the recent change to the first SACK eats into
4177 * or hits the sequence space of other SACK blocks, if so coalesce.
4179 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4180 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4183 /* Zap SWALK, by moving every further SACK up by one slot.
4184 * Decrease num_sacks.
4186 tp
->rx_opt
.num_sacks
--;
4187 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4191 this_sack
++, swalk
++;
4195 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4197 struct tcp_sock
*tp
= tcp_sk(sk
);
4198 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4199 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4205 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4206 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4207 /* Rotate this_sack to the first one. */
4208 for (; this_sack
> 0; this_sack
--, sp
--)
4209 swap(*sp
, *(sp
- 1));
4211 tcp_sack_maybe_coalesce(tp
);
4216 /* Could not find an adjacent existing SACK, build a new one,
4217 * put it at the front, and shift everyone else down. We
4218 * always know there is at least one SACK present already here.
4220 * If the sack array is full, forget about the last one.
4222 if (this_sack
>= TCP_NUM_SACKS
) {
4224 tp
->rx_opt
.num_sacks
--;
4227 for (; this_sack
> 0; this_sack
--, sp
--)
4231 /* Build the new head SACK, and we're done. */
4232 sp
->start_seq
= seq
;
4233 sp
->end_seq
= end_seq
;
4234 tp
->rx_opt
.num_sacks
++;
4237 /* RCV.NXT advances, some SACKs should be eaten. */
4239 static void tcp_sack_remove(struct tcp_sock
*tp
)
4241 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4242 int num_sacks
= tp
->rx_opt
.num_sacks
;
4245 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4246 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4247 tp
->rx_opt
.num_sacks
= 0;
4251 for (this_sack
= 0; this_sack
< num_sacks
;) {
4252 /* Check if the start of the sack is covered by RCV.NXT. */
4253 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4256 /* RCV.NXT must cover all the block! */
4257 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4259 /* Zap this SACK, by moving forward any other SACKS. */
4260 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4261 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4268 tp
->rx_opt
.num_sacks
= num_sacks
;
4272 * tcp_try_coalesce - try to merge skb to prior one
4275 * @from: buffer to add in queue
4276 * @fragstolen: pointer to boolean
4278 * Before queueing skb @from after @to, try to merge them
4279 * to reduce overall memory use and queue lengths, if cost is small.
4280 * Packets in ofo or receive queues can stay a long time.
4281 * Better try to coalesce them right now to avoid future collapses.
4282 * Returns true if caller should free @from instead of queueing it
4284 static bool tcp_try_coalesce(struct sock
*sk
,
4286 struct sk_buff
*from
,
4291 *fragstolen
= false;
4293 /* Its possible this segment overlaps with prior segment in queue */
4294 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4297 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4300 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4301 sk_mem_charge(sk
, delta
);
4302 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4303 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4304 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4305 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4309 static void tcp_drop(struct sock
*sk
, struct sk_buff
*skb
)
4311 sk_drops_add(sk
, skb
);
4315 /* This one checks to see if we can put data from the
4316 * out_of_order queue into the receive_queue.
4318 static void tcp_ofo_queue(struct sock
*sk
)
4320 struct tcp_sock
*tp
= tcp_sk(sk
);
4321 __u32 dsack_high
= tp
->rcv_nxt
;
4322 bool fin
, fragstolen
, eaten
;
4323 struct sk_buff
*skb
, *tail
;
4326 p
= rb_first(&tp
->out_of_order_queue
);
4328 skb
= rb_entry(p
, struct sk_buff
, rbnode
);
4329 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4332 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4333 __u32 dsack
= dsack_high
;
4334 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4335 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4336 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4339 rb_erase(&skb
->rbnode
, &tp
->out_of_order_queue
);
4341 if (unlikely(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))) {
4342 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4346 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4347 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4348 TCP_SKB_CB(skb
)->end_seq
);
4350 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4351 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4352 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4353 fin
= TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
;
4355 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4357 kfree_skb_partial(skb
, fragstolen
);
4359 if (unlikely(fin
)) {
4361 /* tcp_fin() purges tp->out_of_order_queue,
4362 * so we must end this loop right now.
4369 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4370 static int tcp_prune_queue(struct sock
*sk
);
4372 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4375 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4376 !sk_rmem_schedule(sk
, skb
, size
)) {
4378 if (tcp_prune_queue(sk
) < 0)
4381 while (!sk_rmem_schedule(sk
, skb
, size
)) {
4382 if (!tcp_prune_ofo_queue(sk
))
4389 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4391 struct tcp_sock
*tp
= tcp_sk(sk
);
4392 struct rb_node
**p
, *q
, *parent
;
4393 struct sk_buff
*skb1
;
4397 tcp_ecn_check_ce(tp
, skb
);
4399 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4400 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4405 /* Disable header prediction. */
4407 inet_csk_schedule_ack(sk
);
4409 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4410 seq
= TCP_SKB_CB(skb
)->seq
;
4411 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4412 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4413 tp
->rcv_nxt
, seq
, end_seq
);
4415 p
= &tp
->out_of_order_queue
.rb_node
;
4416 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4417 /* Initial out of order segment, build 1 SACK. */
4418 if (tcp_is_sack(tp
)) {
4419 tp
->rx_opt
.num_sacks
= 1;
4420 tp
->selective_acks
[0].start_seq
= seq
;
4421 tp
->selective_acks
[0].end_seq
= end_seq
;
4423 rb_link_node(&skb
->rbnode
, NULL
, p
);
4424 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4425 tp
->ooo_last_skb
= skb
;
4429 /* In the typical case, we are adding an skb to the end of the list.
4430 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4432 if (tcp_try_coalesce(sk
, tp
->ooo_last_skb
, skb
, &fragstolen
)) {
4434 tcp_grow_window(sk
, skb
);
4435 kfree_skb_partial(skb
, fragstolen
);
4439 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4440 if (!before(seq
, TCP_SKB_CB(tp
->ooo_last_skb
)->end_seq
)) {
4441 parent
= &tp
->ooo_last_skb
->rbnode
;
4442 p
= &parent
->rb_right
;
4446 /* Find place to insert this segment. Handle overlaps on the way. */
4450 skb1
= rb_entry(parent
, struct sk_buff
, rbnode
);
4451 if (before(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4452 p
= &parent
->rb_left
;
4455 if (before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4456 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4457 /* All the bits are present. Drop. */
4458 NET_INC_STATS(sock_net(sk
),
4459 LINUX_MIB_TCPOFOMERGE
);
4462 tcp_dsack_set(sk
, seq
, end_seq
);
4465 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4466 /* Partial overlap. */
4467 tcp_dsack_set(sk
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
4469 /* skb's seq == skb1's seq and skb covers skb1.
4470 * Replace skb1 with skb.
4472 rb_replace_node(&skb1
->rbnode
, &skb
->rbnode
,
4473 &tp
->out_of_order_queue
);
4474 tcp_dsack_extend(sk
,
4475 TCP_SKB_CB(skb1
)->seq
,
4476 TCP_SKB_CB(skb1
)->end_seq
);
4477 NET_INC_STATS(sock_net(sk
),
4478 LINUX_MIB_TCPOFOMERGE
);
4482 } else if (tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4485 p
= &parent
->rb_right
;
4488 /* Insert segment into RB tree. */
4489 rb_link_node(&skb
->rbnode
, parent
, p
);
4490 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4493 /* Remove other segments covered by skb. */
4494 while ((q
= rb_next(&skb
->rbnode
)) != NULL
) {
4495 skb1
= rb_entry(q
, struct sk_buff
, rbnode
);
4497 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4499 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4500 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4504 rb_erase(&skb1
->rbnode
, &tp
->out_of_order_queue
);
4505 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4506 TCP_SKB_CB(skb1
)->end_seq
);
4507 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4510 /* If there is no skb after us, we are the last_skb ! */
4512 tp
->ooo_last_skb
= skb
;
4515 if (tcp_is_sack(tp
))
4516 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4519 tcp_grow_window(sk
, skb
);
4521 skb_set_owner_r(skb
, sk
);
4525 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4529 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4531 __skb_pull(skb
, hdrlen
);
4533 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4534 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
4536 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4537 skb_set_owner_r(skb
, sk
);
4542 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4544 struct sk_buff
*skb
;
4552 if (size
> PAGE_SIZE
) {
4553 int npages
= min_t(size_t, size
>> PAGE_SHIFT
, MAX_SKB_FRAGS
);
4555 data_len
= npages
<< PAGE_SHIFT
;
4556 size
= data_len
+ (size
& ~PAGE_MASK
);
4558 skb
= alloc_skb_with_frags(size
- data_len
, data_len
,
4559 PAGE_ALLOC_COSTLY_ORDER
,
4560 &err
, sk
->sk_allocation
);
4564 skb_put(skb
, size
- data_len
);
4565 skb
->data_len
= data_len
;
4568 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4571 err
= skb_copy_datagram_from_iter(skb
, 0, &msg
->msg_iter
, size
);
4575 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4576 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4577 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4579 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4580 WARN_ON_ONCE(fragstolen
); /* should not happen */
4592 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4594 struct tcp_sock
*tp
= tcp_sk(sk
);
4595 bool fragstolen
= false;
4598 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
) {
4603 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4605 tcp_ecn_accept_cwr(tp
, skb
);
4607 tp
->rx_opt
.dsack
= 0;
4609 /* Queue data for delivery to the user.
4610 * Packets in sequence go to the receive queue.
4611 * Out of sequence packets to the out_of_order_queue.
4613 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4614 if (tcp_receive_window(tp
) == 0)
4617 /* Ok. In sequence. In window. */
4618 if (tp
->ucopy
.task
== current
&&
4619 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4620 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4621 int chunk
= min_t(unsigned int, skb
->len
,
4624 __set_current_state(TASK_RUNNING
);
4626 if (!skb_copy_datagram_msg(skb
, 0, tp
->ucopy
.msg
, chunk
)) {
4627 tp
->ucopy
.len
-= chunk
;
4628 tp
->copied_seq
+= chunk
;
4629 eaten
= (chunk
== skb
->len
);
4630 tcp_rcv_space_adjust(sk
);
4637 if (skb_queue_len(&sk
->sk_receive_queue
) == 0)
4638 sk_forced_mem_schedule(sk
, skb
->truesize
);
4639 else if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4642 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4644 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4646 tcp_event_data_recv(sk
, skb
);
4647 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4650 if (!RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4653 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4654 * gap in queue is filled.
4656 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
4657 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4660 if (tp
->rx_opt
.num_sacks
)
4661 tcp_sack_remove(tp
);
4663 tcp_fast_path_check(sk
);
4666 kfree_skb_partial(skb
, fragstolen
);
4667 if (!sock_flag(sk
, SOCK_DEAD
))
4668 sk
->sk_data_ready(sk
);
4672 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4673 /* A retransmit, 2nd most common case. Force an immediate ack. */
4674 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4675 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4678 tcp_enter_quickack_mode(sk
);
4679 inet_csk_schedule_ack(sk
);
4685 /* Out of window. F.e. zero window probe. */
4686 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4689 tcp_enter_quickack_mode(sk
);
4691 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4692 /* Partial packet, seq < rcv_next < end_seq */
4693 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4694 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4695 TCP_SKB_CB(skb
)->end_seq
);
4697 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4699 /* If window is closed, drop tail of packet. But after
4700 * remembering D-SACK for its head made in previous line.
4702 if (!tcp_receive_window(tp
))
4707 tcp_data_queue_ofo(sk
, skb
);
4710 static struct sk_buff
*tcp_skb_next(struct sk_buff
*skb
, struct sk_buff_head
*list
)
4713 return !skb_queue_is_last(list
, skb
) ? skb
->next
: NULL
;
4715 return rb_entry_safe(rb_next(&skb
->rbnode
), struct sk_buff
, rbnode
);
4718 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4719 struct sk_buff_head
*list
,
4720 struct rb_root
*root
)
4722 struct sk_buff
*next
= tcp_skb_next(skb
, list
);
4725 __skb_unlink(skb
, list
);
4727 rb_erase(&skb
->rbnode
, root
);
4730 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4735 /* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
4736 static void tcp_rbtree_insert(struct rb_root
*root
, struct sk_buff
*skb
)
4738 struct rb_node
**p
= &root
->rb_node
;
4739 struct rb_node
*parent
= NULL
;
4740 struct sk_buff
*skb1
;
4744 skb1
= rb_entry(parent
, struct sk_buff
, rbnode
);
4745 if (before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb1
)->seq
))
4746 p
= &parent
->rb_left
;
4748 p
= &parent
->rb_right
;
4750 rb_link_node(&skb
->rbnode
, parent
, p
);
4751 rb_insert_color(&skb
->rbnode
, root
);
4754 /* Collapse contiguous sequence of skbs head..tail with
4755 * sequence numbers start..end.
4757 * If tail is NULL, this means until the end of the queue.
4759 * Segments with FIN/SYN are not collapsed (only because this
4763 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
, struct rb_root
*root
,
4764 struct sk_buff
*head
, struct sk_buff
*tail
, u32 start
, u32 end
)
4766 struct sk_buff
*skb
= head
, *n
;
4767 struct sk_buff_head tmp
;
4770 /* First, check that queue is collapsible and find
4771 * the point where collapsing can be useful.
4774 for (end_of_skbs
= true; skb
!= NULL
&& skb
!= tail
; skb
= n
) {
4775 n
= tcp_skb_next(skb
, list
);
4777 /* No new bits? It is possible on ofo queue. */
4778 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4779 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
4785 /* The first skb to collapse is:
4787 * - bloated or contains data before "start" or
4788 * overlaps to the next one.
4790 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4791 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4792 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4793 end_of_skbs
= false;
4797 if (n
&& n
!= tail
&&
4798 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(n
)->seq
) {
4799 end_of_skbs
= false;
4803 /* Decided to skip this, advance start seq. */
4804 start
= TCP_SKB_CB(skb
)->end_seq
;
4807 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4810 __skb_queue_head_init(&tmp
);
4812 while (before(start
, end
)) {
4813 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4814 struct sk_buff
*nskb
;
4816 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4820 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4821 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4823 __skb_queue_before(list
, skb
, nskb
);
4825 __skb_queue_tail(&tmp
, nskb
); /* defer rbtree insertion */
4826 skb_set_owner_r(nskb
, sk
);
4828 /* Copy data, releasing collapsed skbs. */
4830 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4831 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4835 size
= min(copy
, size
);
4836 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4838 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4842 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4843 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
4846 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4852 skb_queue_walk_safe(&tmp
, skb
, n
)
4853 tcp_rbtree_insert(root
, skb
);
4856 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4857 * and tcp_collapse() them until all the queue is collapsed.
4859 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4861 struct tcp_sock
*tp
= tcp_sk(sk
);
4862 struct sk_buff
*skb
, *head
;
4866 p
= rb_first(&tp
->out_of_order_queue
);
4867 skb
= rb_entry_safe(p
, struct sk_buff
, rbnode
);
4870 p
= rb_last(&tp
->out_of_order_queue
);
4871 /* Note: This is possible p is NULL here. We do not
4872 * use rb_entry_safe(), as ooo_last_skb is valid only
4873 * if rbtree is not empty.
4875 tp
->ooo_last_skb
= rb_entry(p
, struct sk_buff
, rbnode
);
4878 start
= TCP_SKB_CB(skb
)->seq
;
4879 end
= TCP_SKB_CB(skb
)->end_seq
;
4881 for (head
= skb
;;) {
4882 skb
= tcp_skb_next(skb
, NULL
);
4884 /* Range is terminated when we see a gap or when
4885 * we are at the queue end.
4888 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4889 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4890 tcp_collapse(sk
, NULL
, &tp
->out_of_order_queue
,
4891 head
, skb
, start
, end
);
4895 if (unlikely(before(TCP_SKB_CB(skb
)->seq
, start
)))
4896 start
= TCP_SKB_CB(skb
)->seq
;
4897 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4898 end
= TCP_SKB_CB(skb
)->end_seq
;
4903 * Clean the out-of-order queue to make room.
4904 * We drop high sequences packets to :
4905 * 1) Let a chance for holes to be filled.
4906 * 2) not add too big latencies if thousands of packets sit there.
4907 * (But if application shrinks SO_RCVBUF, we could still end up
4908 * freeing whole queue here)
4910 * Return true if queue has shrunk.
4912 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4914 struct tcp_sock
*tp
= tcp_sk(sk
);
4915 struct rb_node
*node
, *prev
;
4917 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
4920 NET_INC_STATS(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4921 node
= &tp
->ooo_last_skb
->rbnode
;
4923 prev
= rb_prev(node
);
4924 rb_erase(node
, &tp
->out_of_order_queue
);
4925 tcp_drop(sk
, rb_entry(node
, struct sk_buff
, rbnode
));
4927 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
&&
4928 !tcp_under_memory_pressure(sk
))
4932 tp
->ooo_last_skb
= rb_entry(prev
, struct sk_buff
, rbnode
);
4934 /* Reset SACK state. A conforming SACK implementation will
4935 * do the same at a timeout based retransmit. When a connection
4936 * is in a sad state like this, we care only about integrity
4937 * of the connection not performance.
4939 if (tp
->rx_opt
.sack_ok
)
4940 tcp_sack_reset(&tp
->rx_opt
);
4944 /* Reduce allocated memory if we can, trying to get
4945 * the socket within its memory limits again.
4947 * Return less than zero if we should start dropping frames
4948 * until the socket owning process reads some of the data
4949 * to stabilize the situation.
4951 static int tcp_prune_queue(struct sock
*sk
)
4953 struct tcp_sock
*tp
= tcp_sk(sk
);
4955 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4957 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4959 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4960 tcp_clamp_window(sk
);
4961 else if (tcp_under_memory_pressure(sk
))
4962 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4964 tcp_collapse_ofo_queue(sk
);
4965 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4966 tcp_collapse(sk
, &sk
->sk_receive_queue
, NULL
,
4967 skb_peek(&sk
->sk_receive_queue
),
4969 tp
->copied_seq
, tp
->rcv_nxt
);
4972 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4975 /* Collapsing did not help, destructive actions follow.
4976 * This must not ever occur. */
4978 tcp_prune_ofo_queue(sk
);
4980 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4983 /* If we are really being abused, tell the caller to silently
4984 * drop receive data on the floor. It will get retransmitted
4985 * and hopefully then we'll have sufficient space.
4987 NET_INC_STATS(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4989 /* Massive buffer overcommit. */
4994 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4996 const struct tcp_sock
*tp
= tcp_sk(sk
);
4998 /* If the user specified a specific send buffer setting, do
5001 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
5004 /* If we are under global TCP memory pressure, do not expand. */
5005 if (tcp_under_memory_pressure(sk
))
5008 /* If we are under soft global TCP memory pressure, do not expand. */
5009 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
5012 /* If we filled the congestion window, do not expand. */
5013 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
5019 /* When incoming ACK allowed to free some skb from write_queue,
5020 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
5021 * on the exit from tcp input handler.
5023 * PROBLEM: sndbuf expansion does not work well with largesend.
5025 static void tcp_new_space(struct sock
*sk
)
5027 struct tcp_sock
*tp
= tcp_sk(sk
);
5029 if (tcp_should_expand_sndbuf(sk
)) {
5030 tcp_sndbuf_expand(sk
);
5031 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
5034 sk
->sk_write_space(sk
);
5037 static void tcp_check_space(struct sock
*sk
)
5039 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
5040 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
5041 /* pairs with tcp_poll() */
5043 if (sk
->sk_socket
&&
5044 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
5046 if (!test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
5047 tcp_chrono_stop(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
5052 static inline void tcp_data_snd_check(struct sock
*sk
)
5054 tcp_push_pending_frames(sk
);
5055 tcp_check_space(sk
);
5059 * Check if sending an ack is needed.
5061 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5063 struct tcp_sock
*tp
= tcp_sk(sk
);
5065 /* More than one full frame received... */
5066 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5067 /* ... and right edge of window advances far enough.
5068 * (tcp_recvmsg() will send ACK otherwise). Or...
5070 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
5071 /* We ACK each frame or... */
5072 tcp_in_quickack_mode(sk
) ||
5073 /* We have out of order data. */
5074 (ofo_possible
&& !RB_EMPTY_ROOT(&tp
->out_of_order_queue
))) {
5075 /* Then ack it now */
5078 /* Else, send delayed ack. */
5079 tcp_send_delayed_ack(sk
);
5083 static inline void tcp_ack_snd_check(struct sock
*sk
)
5085 if (!inet_csk_ack_scheduled(sk
)) {
5086 /* We sent a data segment already. */
5089 __tcp_ack_snd_check(sk
, 1);
5093 * This routine is only called when we have urgent data
5094 * signaled. Its the 'slow' part of tcp_urg. It could be
5095 * moved inline now as tcp_urg is only called from one
5096 * place. We handle URGent data wrong. We have to - as
5097 * BSD still doesn't use the correction from RFC961.
5098 * For 1003.1g we should support a new option TCP_STDURG to permit
5099 * either form (or just set the sysctl tcp_stdurg).
5102 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5104 struct tcp_sock
*tp
= tcp_sk(sk
);
5105 u32 ptr
= ntohs(th
->urg_ptr
);
5107 if (ptr
&& !sysctl_tcp_stdurg
)
5109 ptr
+= ntohl(th
->seq
);
5111 /* Ignore urgent data that we've already seen and read. */
5112 if (after(tp
->copied_seq
, ptr
))
5115 /* Do not replay urg ptr.
5117 * NOTE: interesting situation not covered by specs.
5118 * Misbehaving sender may send urg ptr, pointing to segment,
5119 * which we already have in ofo queue. We are not able to fetch
5120 * such data and will stay in TCP_URG_NOTYET until will be eaten
5121 * by recvmsg(). Seems, we are not obliged to handle such wicked
5122 * situations. But it is worth to think about possibility of some
5123 * DoSes using some hypothetical application level deadlock.
5125 if (before(ptr
, tp
->rcv_nxt
))
5128 /* Do we already have a newer (or duplicate) urgent pointer? */
5129 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5132 /* Tell the world about our new urgent pointer. */
5135 /* We may be adding urgent data when the last byte read was
5136 * urgent. To do this requires some care. We cannot just ignore
5137 * tp->copied_seq since we would read the last urgent byte again
5138 * as data, nor can we alter copied_seq until this data arrives
5139 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5141 * NOTE. Double Dutch. Rendering to plain English: author of comment
5142 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5143 * and expect that both A and B disappear from stream. This is _wrong_.
5144 * Though this happens in BSD with high probability, this is occasional.
5145 * Any application relying on this is buggy. Note also, that fix "works"
5146 * only in this artificial test. Insert some normal data between A and B and we will
5147 * decline of BSD again. Verdict: it is better to remove to trap
5150 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5151 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5152 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5154 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5155 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5160 tp
->urg_data
= TCP_URG_NOTYET
;
5163 /* Disable header prediction. */
5167 /* This is the 'fast' part of urgent handling. */
5168 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5170 struct tcp_sock
*tp
= tcp_sk(sk
);
5172 /* Check if we get a new urgent pointer - normally not. */
5174 tcp_check_urg(sk
, th
);
5176 /* Do we wait for any urgent data? - normally not... */
5177 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5178 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5181 /* Is the urgent pointer pointing into this packet? */
5182 if (ptr
< skb
->len
) {
5184 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5186 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5187 if (!sock_flag(sk
, SOCK_DEAD
))
5188 sk
->sk_data_ready(sk
);
5193 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5195 struct tcp_sock
*tp
= tcp_sk(sk
);
5196 int chunk
= skb
->len
- hlen
;
5199 if (skb_csum_unnecessary(skb
))
5200 err
= skb_copy_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
, chunk
);
5202 err
= skb_copy_and_csum_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
);
5205 tp
->ucopy
.len
-= chunk
;
5206 tp
->copied_seq
+= chunk
;
5207 tcp_rcv_space_adjust(sk
);
5213 /* Accept RST for rcv_nxt - 1 after a FIN.
5214 * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
5215 * FIN is sent followed by a RST packet. The RST is sent with the same
5216 * sequence number as the FIN, and thus according to RFC 5961 a challenge
5217 * ACK should be sent. However, Mac OSX rate limits replies to challenge
5218 * ACKs on the closed socket. In addition middleboxes can drop either the
5219 * challenge ACK or a subsequent RST.
5221 static bool tcp_reset_check(const struct sock
*sk
, const struct sk_buff
*skb
)
5223 struct tcp_sock
*tp
= tcp_sk(sk
);
5225 return unlikely(TCP_SKB_CB(skb
)->seq
== (tp
->rcv_nxt
- 1) &&
5226 (1 << sk
->sk_state
) & (TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
|
5230 /* Does PAWS and seqno based validation of an incoming segment, flags will
5231 * play significant role here.
5233 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5234 const struct tcphdr
*th
, int syn_inerr
)
5236 struct tcp_sock
*tp
= tcp_sk(sk
);
5237 bool rst_seq_match
= false;
5239 /* RFC1323: H1. Apply PAWS check first. */
5240 if (tcp_fast_parse_options(sock_net(sk
), skb
, th
, tp
) &&
5241 tp
->rx_opt
.saw_tstamp
&&
5242 tcp_paws_discard(sk
, skb
)) {
5244 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5245 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5246 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5247 &tp
->last_oow_ack_time
))
5248 tcp_send_dupack(sk
, skb
);
5251 /* Reset is accepted even if it did not pass PAWS. */
5254 /* Step 1: check sequence number */
5255 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5256 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5257 * (RST) segments are validated by checking their SEQ-fields."
5258 * And page 69: "If an incoming segment is not acceptable,
5259 * an acknowledgment should be sent in reply (unless the RST
5260 * bit is set, if so drop the segment and return)".
5265 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5266 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5267 &tp
->last_oow_ack_time
))
5268 tcp_send_dupack(sk
, skb
);
5269 } else if (tcp_reset_check(sk
, skb
)) {
5275 /* Step 2: check RST bit */
5277 /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
5278 * FIN and SACK too if available):
5279 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
5280 * the right-most SACK block,
5282 * RESET the connection
5284 * Send a challenge ACK
5286 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
||
5287 tcp_reset_check(sk
, skb
)) {
5288 rst_seq_match
= true;
5289 } else if (tcp_is_sack(tp
) && tp
->rx_opt
.num_sacks
> 0) {
5290 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
5291 int max_sack
= sp
[0].end_seq
;
5294 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;
5296 max_sack
= after(sp
[this_sack
].end_seq
,
5298 sp
[this_sack
].end_seq
: max_sack
;
5301 if (TCP_SKB_CB(skb
)->seq
== max_sack
)
5302 rst_seq_match
= true;
5308 /* Disable TFO if RST is out-of-order
5309 * and no data has been received
5310 * for current active TFO socket
5312 if (tp
->syn_fastopen
&& !tp
->data_segs_in
&&
5313 sk
->sk_state
== TCP_ESTABLISHED
)
5314 tcp_fastopen_active_disable(sk
);
5315 tcp_send_challenge_ack(sk
, skb
);
5320 /* step 3: check security and precedence [ignored] */
5322 /* step 4: Check for a SYN
5323 * RFC 5961 4.2 : Send a challenge ack
5328 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5329 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5330 tcp_send_challenge_ack(sk
, skb
);
5342 * TCP receive function for the ESTABLISHED state.
5344 * It is split into a fast path and a slow path. The fast path is
5346 * - A zero window was announced from us - zero window probing
5347 * is only handled properly in the slow path.
5348 * - Out of order segments arrived.
5349 * - Urgent data is expected.
5350 * - There is no buffer space left
5351 * - Unexpected TCP flags/window values/header lengths are received
5352 * (detected by checking the TCP header against pred_flags)
5353 * - Data is sent in both directions. Fast path only supports pure senders
5354 * or pure receivers (this means either the sequence number or the ack
5355 * value must stay constant)
5356 * - Unexpected TCP option.
5358 * When these conditions are not satisfied it drops into a standard
5359 * receive procedure patterned after RFC793 to handle all cases.
5360 * The first three cases are guaranteed by proper pred_flags setting,
5361 * the rest is checked inline. Fast processing is turned on in
5362 * tcp_data_queue when everything is OK.
5364 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5365 const struct tcphdr
*th
, unsigned int len
)
5367 struct tcp_sock
*tp
= tcp_sk(sk
);
5369 tcp_mstamp_refresh(tp
);
5370 if (unlikely(!sk
->sk_rx_dst
))
5371 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5373 * Header prediction.
5374 * The code loosely follows the one in the famous
5375 * "30 instruction TCP receive" Van Jacobson mail.
5377 * Van's trick is to deposit buffers into socket queue
5378 * on a device interrupt, to call tcp_recv function
5379 * on the receive process context and checksum and copy
5380 * the buffer to user space. smart...
5382 * Our current scheme is not silly either but we take the
5383 * extra cost of the net_bh soft interrupt processing...
5384 * We do checksum and copy also but from device to kernel.
5387 tp
->rx_opt
.saw_tstamp
= 0;
5389 /* pred_flags is 0xS?10 << 16 + snd_wnd
5390 * if header_prediction is to be made
5391 * 'S' will always be tp->tcp_header_len >> 2
5392 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5393 * turn it off (when there are holes in the receive
5394 * space for instance)
5395 * PSH flag is ignored.
5398 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5399 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5400 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5401 int tcp_header_len
= tp
->tcp_header_len
;
5403 /* Timestamp header prediction: tcp_header_len
5404 * is automatically equal to th->doff*4 due to pred_flags
5408 /* Check timestamp */
5409 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5410 /* No? Slow path! */
5411 if (!tcp_parse_aligned_timestamp(tp
, th
))
5414 /* If PAWS failed, check it more carefully in slow path */
5415 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5418 /* DO NOT update ts_recent here, if checksum fails
5419 * and timestamp was corrupted part, it will result
5420 * in a hung connection since we will drop all
5421 * future packets due to the PAWS test.
5425 if (len
<= tcp_header_len
) {
5426 /* Bulk data transfer: sender */
5427 if (len
== tcp_header_len
) {
5428 /* Predicted packet is in window by definition.
5429 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5430 * Hence, check seq<=rcv_wup reduces to:
5432 if (tcp_header_len
==
5433 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5434 tp
->rcv_nxt
== tp
->rcv_wup
)
5435 tcp_store_ts_recent(tp
);
5437 /* We know that such packets are checksummed
5440 tcp_ack(sk
, skb
, 0);
5442 tcp_data_snd_check(sk
);
5444 } else { /* Header too small */
5445 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5450 bool fragstolen
= false;
5452 if (tp
->ucopy
.task
== current
&&
5453 tp
->copied_seq
== tp
->rcv_nxt
&&
5454 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5455 sock_owned_by_user(sk
)) {
5456 __set_current_state(TASK_RUNNING
);
5458 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5459 /* Predicted packet is in window by definition.
5460 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5461 * Hence, check seq<=rcv_wup reduces to:
5463 if (tcp_header_len
==
5464 (sizeof(struct tcphdr
) +
5465 TCPOLEN_TSTAMP_ALIGNED
) &&
5466 tp
->rcv_nxt
== tp
->rcv_wup
)
5467 tcp_store_ts_recent(tp
);
5469 tcp_rcv_rtt_measure_ts(sk
, skb
);
5471 __skb_pull(skb
, tcp_header_len
);
5472 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
5473 NET_INC_STATS(sock_net(sk
),
5474 LINUX_MIB_TCPHPHITSTOUSER
);
5479 if (tcp_checksum_complete(skb
))
5482 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5485 /* Predicted packet is in window by definition.
5486 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5487 * Hence, check seq<=rcv_wup reduces to:
5489 if (tcp_header_len
==
5490 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5491 tp
->rcv_nxt
== tp
->rcv_wup
)
5492 tcp_store_ts_recent(tp
);
5494 tcp_rcv_rtt_measure_ts(sk
, skb
);
5496 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5498 /* Bulk data transfer: receiver */
5499 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5503 tcp_event_data_recv(sk
, skb
);
5505 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5506 /* Well, only one small jumplet in fast path... */
5507 tcp_ack(sk
, skb
, FLAG_DATA
);
5508 tcp_data_snd_check(sk
);
5509 if (!inet_csk_ack_scheduled(sk
))
5513 __tcp_ack_snd_check(sk
, 0);
5516 kfree_skb_partial(skb
, fragstolen
);
5517 sk
->sk_data_ready(sk
);
5523 if (len
< (th
->doff
<< 2) || tcp_checksum_complete(skb
))
5526 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5530 * Standard slow path.
5533 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5537 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5540 tcp_rcv_rtt_measure_ts(sk
, skb
);
5542 /* Process urgent data. */
5543 tcp_urg(sk
, skb
, th
);
5545 /* step 7: process the segment text */
5546 tcp_data_queue(sk
, skb
);
5548 tcp_data_snd_check(sk
);
5549 tcp_ack_snd_check(sk
);
5553 TCP_INC_STATS(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5554 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5559 EXPORT_SYMBOL(tcp_rcv_established
);
5561 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5563 struct tcp_sock
*tp
= tcp_sk(sk
);
5564 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5566 tcp_set_state(sk
, TCP_ESTABLISHED
);
5567 icsk
->icsk_ack
.lrcvtime
= tcp_jiffies32
;
5570 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5571 security_inet_conn_established(sk
, skb
);
5574 /* Make sure socket is routed, for correct metrics. */
5575 icsk
->icsk_af_ops
->rebuild_header(sk
);
5577 tcp_init_metrics(sk
);
5578 tcp_call_bpf(sk
, BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB
);
5579 tcp_init_congestion_control(sk
);
5581 /* Prevent spurious tcp_cwnd_restart() on first data
5584 tp
->lsndtime
= tcp_jiffies32
;
5586 tcp_init_buffer_space(sk
);
5588 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5589 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5591 if (!tp
->rx_opt
.snd_wscale
)
5592 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5598 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5599 struct tcp_fastopen_cookie
*cookie
)
5601 struct tcp_sock
*tp
= tcp_sk(sk
);
5602 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5603 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
5604 bool syn_drop
= false;
5606 if (mss
== tp
->rx_opt
.user_mss
) {
5607 struct tcp_options_received opt
;
5609 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5610 tcp_clear_options(&opt
);
5611 opt
.user_mss
= opt
.mss_clamp
= 0;
5612 tcp_parse_options(sock_net(sk
), synack
, &opt
, 0, NULL
);
5613 mss
= opt
.mss_clamp
;
5616 if (!tp
->syn_fastopen
) {
5617 /* Ignore an unsolicited cookie */
5619 } else if (tp
->total_retrans
) {
5620 /* SYN timed out and the SYN-ACK neither has a cookie nor
5621 * acknowledges data. Presumably the remote received only
5622 * the retransmitted (regular) SYNs: either the original
5623 * SYN-data or the corresponding SYN-ACK was dropped.
5625 syn_drop
= (cookie
->len
< 0 && data
);
5626 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
5627 /* We requested a cookie but didn't get it. If we did not use
5628 * the (old) exp opt format then try so next time (try_exp=1).
5629 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5631 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
5634 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
5636 if (data
) { /* Retransmit unacked data in SYN */
5637 tcp_for_write_queue_from(data
, sk
) {
5638 if (data
== tcp_send_head(sk
) ||
5639 __tcp_retransmit_skb(sk
, data
, 1))
5643 NET_INC_STATS(sock_net(sk
),
5644 LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5647 tp
->syn_data_acked
= tp
->syn_data
;
5648 if (tp
->syn_data_acked
)
5649 NET_INC_STATS(sock_net(sk
),
5650 LINUX_MIB_TCPFASTOPENACTIVE
);
5652 tcp_fastopen_add_skb(sk
, synack
);
5657 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5658 const struct tcphdr
*th
)
5660 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5661 struct tcp_sock
*tp
= tcp_sk(sk
);
5662 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5663 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5666 tcp_parse_options(sock_net(sk
), skb
, &tp
->rx_opt
, 0, &foc
);
5667 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5668 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5672 * "If the state is SYN-SENT then
5673 * first check the ACK bit
5674 * If the ACK bit is set
5675 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5676 * a reset (unless the RST bit is set, if so drop
5677 * the segment and return)"
5679 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5680 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5681 goto reset_and_undo
;
5683 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5684 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5685 tcp_time_stamp(tp
))) {
5686 NET_INC_STATS(sock_net(sk
),
5687 LINUX_MIB_PAWSACTIVEREJECTED
);
5688 goto reset_and_undo
;
5691 /* Now ACK is acceptable.
5693 * "If the RST bit is set
5694 * If the ACK was acceptable then signal the user "error:
5695 * connection reset", drop the segment, enter CLOSED state,
5696 * delete TCB, and return."
5705 * "fifth, if neither of the SYN or RST bits is set then
5706 * drop the segment and return."
5712 goto discard_and_undo
;
5715 * "If the SYN bit is on ...
5716 * are acceptable then ...
5717 * (our SYN has been ACKed), change the connection
5718 * state to ESTABLISHED..."
5721 tcp_ecn_rcv_synack(tp
, th
);
5723 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5724 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5726 /* Ok.. it's good. Set up sequence numbers and
5727 * move to established.
5729 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5730 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5732 /* RFC1323: The window in SYN & SYN/ACK segments is
5735 tp
->snd_wnd
= ntohs(th
->window
);
5737 if (!tp
->rx_opt
.wscale_ok
) {
5738 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5739 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5742 if (tp
->rx_opt
.saw_tstamp
) {
5743 tp
->rx_opt
.tstamp_ok
= 1;
5744 tp
->tcp_header_len
=
5745 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5746 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5747 tcp_store_ts_recent(tp
);
5749 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5752 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5753 tcp_enable_fack(tp
);
5756 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5757 tcp_initialize_rcv_mss(sk
);
5759 /* Remember, tcp_poll() does not lock socket!
5760 * Change state from SYN-SENT only after copied_seq
5761 * is initialized. */
5762 tp
->copied_seq
= tp
->rcv_nxt
;
5766 tcp_finish_connect(sk
, skb
);
5768 fastopen_fail
= (tp
->syn_fastopen
|| tp
->syn_data
) &&
5769 tcp_rcv_fastopen_synack(sk
, skb
, &foc
);
5771 if (!sock_flag(sk
, SOCK_DEAD
)) {
5772 sk
->sk_state_change(sk
);
5773 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5777 if (sk
->sk_write_pending
||
5778 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5779 icsk
->icsk_ack
.pingpong
) {
5780 /* Save one ACK. Data will be ready after
5781 * several ticks, if write_pending is set.
5783 * It may be deleted, but with this feature tcpdumps
5784 * look so _wonderfully_ clever, that I was not able
5785 * to stand against the temptation 8) --ANK
5787 inet_csk_schedule_ack(sk
);
5788 tcp_enter_quickack_mode(sk
);
5789 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5790 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5801 /* No ACK in the segment */
5805 * "If the RST bit is set
5807 * Otherwise (no ACK) drop the segment and return."
5810 goto discard_and_undo
;
5814 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5815 tcp_paws_reject(&tp
->rx_opt
, 0))
5816 goto discard_and_undo
;
5819 /* We see SYN without ACK. It is attempt of
5820 * simultaneous connect with crossed SYNs.
5821 * Particularly, it can be connect to self.
5823 tcp_set_state(sk
, TCP_SYN_RECV
);
5825 if (tp
->rx_opt
.saw_tstamp
) {
5826 tp
->rx_opt
.tstamp_ok
= 1;
5827 tcp_store_ts_recent(tp
);
5828 tp
->tcp_header_len
=
5829 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5831 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5834 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5835 tp
->copied_seq
= tp
->rcv_nxt
;
5836 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5838 /* RFC1323: The window in SYN & SYN/ACK segments is
5841 tp
->snd_wnd
= ntohs(th
->window
);
5842 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5843 tp
->max_window
= tp
->snd_wnd
;
5845 tcp_ecn_rcv_syn(tp
, th
);
5848 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5849 tcp_initialize_rcv_mss(sk
);
5851 tcp_send_synack(sk
);
5853 /* Note, we could accept data and URG from this segment.
5854 * There are no obstacles to make this (except that we must
5855 * either change tcp_recvmsg() to prevent it from returning data
5856 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5858 * However, if we ignore data in ACKless segments sometimes,
5859 * we have no reasons to accept it sometimes.
5860 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5861 * is not flawless. So, discard packet for sanity.
5862 * Uncomment this return to process the data.
5869 /* "fifth, if neither of the SYN or RST bits is set then
5870 * drop the segment and return."
5874 tcp_clear_options(&tp
->rx_opt
);
5875 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5879 tcp_clear_options(&tp
->rx_opt
);
5880 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5885 * This function implements the receiving procedure of RFC 793 for
5886 * all states except ESTABLISHED and TIME_WAIT.
5887 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5888 * address independent.
5891 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
)
5893 struct tcp_sock
*tp
= tcp_sk(sk
);
5894 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5895 const struct tcphdr
*th
= tcp_hdr(skb
);
5896 struct request_sock
*req
;
5900 switch (sk
->sk_state
) {
5914 /* It is possible that we process SYN packets from backlog,
5915 * so we need to make sure to disable BH right there.
5918 acceptable
= icsk
->icsk_af_ops
->conn_request(sk
, skb
) >= 0;
5929 tp
->rx_opt
.saw_tstamp
= 0;
5930 tcp_mstamp_refresh(tp
);
5931 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
);
5935 /* Do step6 onward by hand. */
5936 tcp_urg(sk
, skb
, th
);
5938 tcp_data_snd_check(sk
);
5942 tcp_mstamp_refresh(tp
);
5943 tp
->rx_opt
.saw_tstamp
= 0;
5944 req
= tp
->fastopen_rsk
;
5946 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5947 sk
->sk_state
!= TCP_FIN_WAIT1
);
5949 if (!tcp_check_req(sk
, skb
, req
, true))
5953 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5956 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5959 /* step 5: check the ACK field */
5960 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5961 FLAG_UPDATE_TS_RECENT
|
5962 FLAG_NO_CHALLENGE_ACK
) > 0;
5965 if (sk
->sk_state
== TCP_SYN_RECV
)
5966 return 1; /* send one RST */
5967 tcp_send_challenge_ack(sk
, skb
);
5970 switch (sk
->sk_state
) {
5973 tcp_synack_rtt_meas(sk
, req
);
5975 /* Once we leave TCP_SYN_RECV, we no longer need req
5979 inet_csk(sk
)->icsk_retransmits
= 0;
5980 reqsk_fastopen_remove(sk
, req
, false);
5982 /* Make sure socket is routed, for correct metrics. */
5983 icsk
->icsk_af_ops
->rebuild_header(sk
);
5984 tcp_call_bpf(sk
, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB
);
5985 tcp_init_congestion_control(sk
);
5988 tp
->copied_seq
= tp
->rcv_nxt
;
5989 tcp_init_buffer_space(sk
);
5992 tcp_set_state(sk
, TCP_ESTABLISHED
);
5993 sk
->sk_state_change(sk
);
5995 /* Note, that this wakeup is only for marginal crossed SYN case.
5996 * Passively open sockets are not waked up, because
5997 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
6000 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
6002 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
6003 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
6004 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
6006 if (tp
->rx_opt
.tstamp_ok
)
6007 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
6010 /* Re-arm the timer because data may have been sent out.
6011 * This is similar to the regular data transmission case
6012 * when new data has just been ack'ed.
6014 * (TFO) - we could try to be more aggressive and
6015 * retransmitting any data sooner based on when they
6020 tcp_init_metrics(sk
);
6022 if (!inet_csk(sk
)->icsk_ca_ops
->cong_control
)
6023 tcp_update_pacing_rate(sk
);
6025 /* Prevent spurious tcp_cwnd_restart() on first data packet */
6026 tp
->lsndtime
= tcp_jiffies32
;
6028 tcp_initialize_rcv_mss(sk
);
6029 tcp_fast_path_on(tp
);
6032 case TCP_FIN_WAIT1
: {
6035 /* If we enter the TCP_FIN_WAIT1 state and we are a
6036 * Fast Open socket and this is the first acceptable
6037 * ACK we have received, this would have acknowledged
6038 * our SYNACK so stop the SYNACK timer.
6041 /* We no longer need the request sock. */
6042 reqsk_fastopen_remove(sk
, req
, false);
6045 if (tp
->snd_una
!= tp
->write_seq
)
6048 tcp_set_state(sk
, TCP_FIN_WAIT2
);
6049 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
6053 if (!sock_flag(sk
, SOCK_DEAD
)) {
6054 /* Wake up lingering close() */
6055 sk
->sk_state_change(sk
);
6059 if (tp
->linger2
< 0) {
6061 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6064 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6065 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6066 /* Receive out of order FIN after close() */
6067 if (tp
->syn_fastopen
&& th
->fin
)
6068 tcp_fastopen_active_disable(sk
);
6070 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6074 tmo
= tcp_fin_time(sk
);
6075 if (tmo
> TCP_TIMEWAIT_LEN
) {
6076 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
6077 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
6078 /* Bad case. We could lose such FIN otherwise.
6079 * It is not a big problem, but it looks confusing
6080 * and not so rare event. We still can lose it now,
6081 * if it spins in bh_lock_sock(), but it is really
6084 inet_csk_reset_keepalive_timer(sk
, tmo
);
6086 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
6093 if (tp
->snd_una
== tp
->write_seq
) {
6094 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
6100 if (tp
->snd_una
== tp
->write_seq
) {
6101 tcp_update_metrics(sk
);
6108 /* step 6: check the URG bit */
6109 tcp_urg(sk
, skb
, th
);
6111 /* step 7: process the segment text */
6112 switch (sk
->sk_state
) {
6113 case TCP_CLOSE_WAIT
:
6116 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
6120 /* RFC 793 says to queue data in these states,
6121 * RFC 1122 says we MUST send a reset.
6122 * BSD 4.4 also does reset.
6124 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
6125 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6126 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6127 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6133 case TCP_ESTABLISHED
:
6134 tcp_data_queue(sk
, skb
);
6139 /* tcp_data could move socket to TIME-WAIT */
6140 if (sk
->sk_state
!= TCP_CLOSE
) {
6141 tcp_data_snd_check(sk
);
6142 tcp_ack_snd_check(sk
);
6151 EXPORT_SYMBOL(tcp_rcv_state_process
);
6153 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
6155 struct inet_request_sock
*ireq
= inet_rsk(req
);
6157 if (family
== AF_INET
)
6158 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6159 &ireq
->ir_rmt_addr
, port
);
6160 #if IS_ENABLED(CONFIG_IPV6)
6161 else if (family
== AF_INET6
)
6162 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6163 &ireq
->ir_v6_rmt_addr
, port
);
6167 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6169 * If we receive a SYN packet with these bits set, it means a
6170 * network is playing bad games with TOS bits. In order to
6171 * avoid possible false congestion notifications, we disable
6172 * TCP ECN negotiation.
6174 * Exception: tcp_ca wants ECN. This is required for DCTCP
6175 * congestion control: Linux DCTCP asserts ECT on all packets,
6176 * including SYN, which is most optimal solution; however,
6177 * others, such as FreeBSD do not.
6179 static void tcp_ecn_create_request(struct request_sock
*req
,
6180 const struct sk_buff
*skb
,
6181 const struct sock
*listen_sk
,
6182 const struct dst_entry
*dst
)
6184 const struct tcphdr
*th
= tcp_hdr(skb
);
6185 const struct net
*net
= sock_net(listen_sk
);
6186 bool th_ecn
= th
->ece
&& th
->cwr
;
6193 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
6194 ecn_ok_dst
= dst_feature(dst
, DST_FEATURE_ECN_MASK
);
6195 ecn_ok
= net
->ipv4
.sysctl_tcp_ecn
|| ecn_ok_dst
;
6197 if ((!ect
&& ecn_ok
) || tcp_ca_needs_ecn(listen_sk
) ||
6198 (ecn_ok_dst
& DST_FEATURE_ECN_CA
) ||
6199 tcp_bpf_ca_needs_ecn((struct sock
*)req
))
6200 inet_rsk(req
)->ecn_ok
= 1;
6203 static void tcp_openreq_init(struct request_sock
*req
,
6204 const struct tcp_options_received
*rx_opt
,
6205 struct sk_buff
*skb
, const struct sock
*sk
)
6207 struct inet_request_sock
*ireq
= inet_rsk(req
);
6209 req
->rsk_rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6211 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6212 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6213 tcp_rsk(req
)->snt_synack
= tcp_clock_us();
6214 tcp_rsk(req
)->last_oow_ack_time
= 0;
6215 req
->mss
= rx_opt
->mss_clamp
;
6216 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6217 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6218 ireq
->sack_ok
= rx_opt
->sack_ok
;
6219 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6220 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6223 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6224 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6225 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6228 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6229 struct sock
*sk_listener
,
6230 bool attach_listener
)
6232 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
,
6236 struct inet_request_sock
*ireq
= inet_rsk(req
);
6238 kmemcheck_annotate_bitfield(ireq
, flags
);
6240 #if IS_ENABLED(CONFIG_IPV6)
6241 ireq
->pktopts
= NULL
;
6243 atomic64_set(&ireq
->ir_cookie
, 0);
6244 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6245 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6246 ireq
->ireq_family
= sk_listener
->sk_family
;
6251 EXPORT_SYMBOL(inet_reqsk_alloc
);
6254 * Return true if a syncookie should be sent
6256 static bool tcp_syn_flood_action(const struct sock
*sk
,
6257 const struct sk_buff
*skb
,
6260 struct request_sock_queue
*queue
= &inet_csk(sk
)->icsk_accept_queue
;
6261 const char *msg
= "Dropping request";
6262 bool want_cookie
= false;
6263 struct net
*net
= sock_net(sk
);
6265 #ifdef CONFIG_SYN_COOKIES
6266 if (net
->ipv4
.sysctl_tcp_syncookies
) {
6267 msg
= "Sending cookies";
6269 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
6272 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
6274 if (!queue
->synflood_warned
&&
6275 net
->ipv4
.sysctl_tcp_syncookies
!= 2 &&
6276 xchg(&queue
->synflood_warned
, 1) == 0)
6277 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6278 proto
, ntohs(tcp_hdr(skb
)->dest
), msg
);
6283 static void tcp_reqsk_record_syn(const struct sock
*sk
,
6284 struct request_sock
*req
,
6285 const struct sk_buff
*skb
)
6287 if (tcp_sk(sk
)->save_syn
) {
6288 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
6291 copy
= kmalloc(len
+ sizeof(u32
), GFP_ATOMIC
);
6294 memcpy(©
[1], skb_network_header(skb
), len
);
6295 req
->saved_syn
= copy
;
6300 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
6301 const struct tcp_request_sock_ops
*af_ops
,
6302 struct sock
*sk
, struct sk_buff
*skb
)
6304 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6305 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
6306 struct tcp_options_received tmp_opt
;
6307 struct tcp_sock
*tp
= tcp_sk(sk
);
6308 struct net
*net
= sock_net(sk
);
6309 struct sock
*fastopen_sk
= NULL
;
6310 struct dst_entry
*dst
= NULL
;
6311 struct request_sock
*req
;
6312 bool want_cookie
= false;
6315 /* TW buckets are converted to open requests without
6316 * limitations, they conserve resources and peer is
6317 * evidently real one.
6319 if ((net
->ipv4
.sysctl_tcp_syncookies
== 2 ||
6320 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
6321 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
6326 if (sk_acceptq_is_full(sk
)) {
6327 NET_INC_STATS(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
6331 req
= inet_reqsk_alloc(rsk_ops
, sk
, !want_cookie
);
6335 tcp_rsk(req
)->af_specific
= af_ops
;
6336 tcp_rsk(req
)->ts_off
= 0;
6338 tcp_clear_options(&tmp_opt
);
6339 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
6340 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
6341 tcp_parse_options(sock_net(sk
), skb
, &tmp_opt
, 0,
6342 want_cookie
? NULL
: &foc
);
6344 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
6345 tcp_clear_options(&tmp_opt
);
6347 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
6348 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
6349 inet_rsk(req
)->no_srccheck
= inet_sk(sk
)->transparent
;
6351 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6352 inet_rsk(req
)->ir_iif
= inet_request_bound_dev_if(sk
, skb
);
6354 af_ops
->init_req(req
, sk
, skb
);
6356 if (security_inet_conn_request(sk
, skb
, req
))
6359 if (tmp_opt
.tstamp_ok
)
6360 tcp_rsk(req
)->ts_off
= af_ops
->init_ts_off(net
, skb
);
6362 if (!want_cookie
&& !isn
) {
6363 /* Kill the following clause, if you dislike this way. */
6364 if (!net
->ipv4
.sysctl_tcp_syncookies
&&
6365 (net
->ipv4
.sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
6366 (net
->ipv4
.sysctl_max_syn_backlog
>> 2)) &&
6367 !tcp_peer_is_proven(req
, dst
)) {
6368 /* Without syncookies last quarter of
6369 * backlog is filled with destinations,
6370 * proven to be alive.
6371 * It means that we continue to communicate
6372 * to destinations, already remembered
6373 * to the moment of synflood.
6375 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6377 goto drop_and_release
;
6380 isn
= af_ops
->init_seq(skb
);
6383 dst
= af_ops
->route_req(sk
, &fl
, req
);
6388 tcp_ecn_create_request(req
, skb
, sk
, dst
);
6391 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
6392 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
6393 if (!tmp_opt
.tstamp_ok
)
6394 inet_rsk(req
)->ecn_ok
= 0;
6397 tcp_rsk(req
)->snt_isn
= isn
;
6398 tcp_rsk(req
)->txhash
= net_tx_rndhash();
6399 tcp_openreq_init_rwin(req
, sk
, dst
);
6401 tcp_reqsk_record_syn(sk
, req
, skb
);
6402 fastopen_sk
= tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6405 af_ops
->send_synack(fastopen_sk
, dst
, &fl
, req
,
6406 &foc
, TCP_SYNACK_FASTOPEN
);
6407 /* Add the child socket directly into the accept queue */
6408 inet_csk_reqsk_queue_add(sk
, req
, fastopen_sk
);
6409 sk
->sk_data_ready(sk
);
6410 bh_unlock_sock(fastopen_sk
);
6411 sock_put(fastopen_sk
);
6413 tcp_rsk(req
)->tfo_listener
= false;
6415 inet_csk_reqsk_queue_hash_add(sk
, req
,
6416 tcp_timeout_init((struct sock
*)req
));
6417 af_ops
->send_synack(sk
, dst
, &fl
, req
, &foc
,
6418 !want_cookie
? TCP_SYNACK_NORMAL
:
6436 EXPORT_SYMBOL(tcp_conn_request
);