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).
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
25 * Pedro Roque : Fast Retransmit/Recovery.
27 * Retransmit queue handled by TCP.
28 * Better retransmit timer handling.
29 * New congestion avoidance.
33 * Eric : Fast Retransmit.
34 * Randy Scott : MSS option defines.
35 * Eric Schenk : Fixes to slow start algorithm.
36 * Eric Schenk : Yet another double ACK bug.
37 * Eric Schenk : Delayed ACK bug fixes.
38 * Eric Schenk : Floyd style fast retrans war avoidance.
39 * David S. Miller : Don't allow zero congestion window.
40 * Eric Schenk : Fix retransmitter so that it sends
41 * next packet on ack of previous packet.
42 * Andi Kleen : Moved open_request checking here
43 * and process RSTs for open_requests.
44 * Andi Kleen : Better prune_queue, and other fixes.
45 * Andrey Savochkin: Fix RTT measurements in the presence of
47 * Andrey Savochkin: Check sequence numbers correctly when
48 * removing SACKs due to in sequence incoming
50 * Andi Kleen: Make sure we never ack data there is not
51 * enough room for. Also make this condition
52 * a fatal error if it might still happen.
53 * Andi Kleen: Add tcp_measure_rcv_mss to make
54 * connections with MSS<min(MTU,ann. MSS)
55 * work without delayed acks.
56 * Andi Kleen: Process packets with PSH set in the
58 * J Hadi Salim: ECN support
61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
62 * engine. Lots of bugs are found.
63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
75 int sysctl_tcp_timestamps __read_mostly
= 1;
76 int sysctl_tcp_window_scaling __read_mostly
= 1;
77 int sysctl_tcp_sack __read_mostly
= 1;
78 int sysctl_tcp_fack __read_mostly
= 1;
79 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
80 int sysctl_tcp_ecn __read_mostly
;
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
= 2;
85 int sysctl_tcp_stdurg __read_mostly
;
86 int sysctl_tcp_rfc1337 __read_mostly
;
87 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
88 int sysctl_tcp_frto __read_mostly
;
89 int sysctl_tcp_frto_response __read_mostly
;
90 int sysctl_tcp_nometrics_save __read_mostly
;
92 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
93 int sysctl_tcp_abc __read_mostly
;
95 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
96 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
97 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
98 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
99 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
100 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
101 #define FLAG_ECE 0x40 /* ECE in this ACK */
102 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
103 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
105 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
107 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
108 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
109 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
110 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
111 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
113 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
114 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
115 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
117 #define IsSackFrto() (sysctl_tcp_frto == 0x2)
119 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
121 /* Adapt the MSS value used to make delayed ack decision to the
124 static void tcp_measure_rcv_mss(struct sock
*sk
,
125 const struct sk_buff
*skb
)
127 struct inet_connection_sock
*icsk
= inet_csk(sk
);
128 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
131 icsk
->icsk_ack
.last_seg_size
= 0;
133 /* skb->len may jitter because of SACKs, even if peer
134 * sends good full-sized frames.
136 len
= skb_shinfo(skb
)->gso_size
?: skb
->len
;
137 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
138 icsk
->icsk_ack
.rcv_mss
= len
;
140 /* Otherwise, we make more careful check taking into account,
141 * that SACKs block is variable.
143 * "len" is invariant segment length, including TCP header.
145 len
+= skb
->data
- skb_transport_header(skb
);
146 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
147 /* If PSH is not set, packet should be
148 * full sized, provided peer TCP is not badly broken.
149 * This observation (if it is correct 8)) allows
150 * to handle super-low mtu links fairly.
152 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
153 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
154 /* Subtract also invariant (if peer is RFC compliant),
155 * tcp header plus fixed timestamp option length.
156 * Resulting "len" is MSS free of SACK jitter.
158 len
-= tcp_sk(sk
)->tcp_header_len
;
159 icsk
->icsk_ack
.last_seg_size
= len
;
161 icsk
->icsk_ack
.rcv_mss
= len
;
165 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
166 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
167 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
171 static void tcp_incr_quickack(struct sock
*sk
)
173 struct inet_connection_sock
*icsk
= inet_csk(sk
);
174 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
178 if (quickacks
> icsk
->icsk_ack
.quick
)
179 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
182 void tcp_enter_quickack_mode(struct sock
*sk
)
184 struct inet_connection_sock
*icsk
= inet_csk(sk
);
185 tcp_incr_quickack(sk
);
186 icsk
->icsk_ack
.pingpong
= 0;
187 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
190 /* Send ACKs quickly, if "quick" count is not exhausted
191 * and the session is not interactive.
194 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
196 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
197 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
200 /* Buffer size and advertised window tuning.
202 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
205 static void tcp_fixup_sndbuf(struct sock
*sk
)
207 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
208 sizeof(struct sk_buff
);
210 if (sk
->sk_sndbuf
< 3 * sndmem
)
211 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
214 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
216 * All tcp_full_space() is split to two parts: "network" buffer, allocated
217 * forward and advertised in receiver window (tp->rcv_wnd) and
218 * "application buffer", required to isolate scheduling/application
219 * latencies from network.
220 * window_clamp is maximal advertised window. It can be less than
221 * tcp_full_space(), in this case tcp_full_space() - window_clamp
222 * is reserved for "application" buffer. The less window_clamp is
223 * the smoother our behaviour from viewpoint of network, but the lower
224 * throughput and the higher sensitivity of the connection to losses. 8)
226 * rcv_ssthresh is more strict window_clamp used at "slow start"
227 * phase to predict further behaviour of this connection.
228 * It is used for two goals:
229 * - to enforce header prediction at sender, even when application
230 * requires some significant "application buffer". It is check #1.
231 * - to prevent pruning of receive queue because of misprediction
232 * of receiver window. Check #2.
234 * The scheme does not work when sender sends good segments opening
235 * window and then starts to feed us spaghetti. But it should work
236 * in common situations. Otherwise, we have to rely on queue collapsing.
239 /* Slow part of check#2. */
240 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
242 struct tcp_sock
*tp
= tcp_sk(sk
);
244 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
245 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
247 while (tp
->rcv_ssthresh
<= window
) {
248 if (truesize
<= skb
->len
)
249 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
257 static void tcp_grow_window(struct sock
*sk
,
260 struct tcp_sock
*tp
= tcp_sk(sk
);
263 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
264 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
265 !tcp_memory_pressure
) {
268 /* Check #2. Increase window, if skb with such overhead
269 * will fit to rcvbuf in future.
271 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
274 incr
= __tcp_grow_window(sk
, skb
);
277 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
278 inet_csk(sk
)->icsk_ack
.quick
|= 1;
283 /* 3. Tuning rcvbuf, when connection enters established state. */
285 static void tcp_fixup_rcvbuf(struct sock
*sk
)
287 struct tcp_sock
*tp
= tcp_sk(sk
);
288 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
290 /* Try to select rcvbuf so that 4 mss-sized segments
291 * will fit to window and corresponding skbs will fit to our rcvbuf.
292 * (was 3; 4 is minimum to allow fast retransmit to work.)
294 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
296 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
297 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
300 /* 4. Try to fixup all. It is made immediately after connection enters
303 static void tcp_init_buffer_space(struct sock
*sk
)
305 struct tcp_sock
*tp
= tcp_sk(sk
);
308 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
309 tcp_fixup_rcvbuf(sk
);
310 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
311 tcp_fixup_sndbuf(sk
);
313 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
315 maxwin
= tcp_full_space(sk
);
317 if (tp
->window_clamp
>= maxwin
) {
318 tp
->window_clamp
= maxwin
;
320 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
321 tp
->window_clamp
= max(maxwin
-
322 (maxwin
>> sysctl_tcp_app_win
),
326 /* Force reservation of one segment. */
327 if (sysctl_tcp_app_win
&&
328 tp
->window_clamp
> 2 * tp
->advmss
&&
329 tp
->window_clamp
+ tp
->advmss
> maxwin
)
330 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
332 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
333 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
336 /* 5. Recalculate window clamp after socket hit its memory bounds. */
337 static void tcp_clamp_window(struct sock
*sk
)
339 struct tcp_sock
*tp
= tcp_sk(sk
);
340 struct inet_connection_sock
*icsk
= inet_csk(sk
);
342 icsk
->icsk_ack
.quick
= 0;
344 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
345 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
346 !tcp_memory_pressure
&&
347 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
348 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
351 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
352 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
356 /* Initialize RCV_MSS value.
357 * RCV_MSS is an our guess about MSS used by the peer.
358 * We haven't any direct information about the MSS.
359 * It's better to underestimate the RCV_MSS rather than overestimate.
360 * Overestimations make us ACKing less frequently than needed.
361 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
363 void tcp_initialize_rcv_mss(struct sock
*sk
)
365 struct tcp_sock
*tp
= tcp_sk(sk
);
366 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
368 hint
= min(hint
, tp
->rcv_wnd
/2);
369 hint
= min(hint
, TCP_MIN_RCVMSS
);
370 hint
= max(hint
, TCP_MIN_MSS
);
372 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
375 /* Receiver "autotuning" code.
377 * The algorithm for RTT estimation w/o timestamps is based on
378 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
379 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
381 * More detail on this code can be found at
382 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
383 * though this reference is out of date. A new paper
386 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
388 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
394 if (new_sample
!= 0) {
395 /* If we sample in larger samples in the non-timestamp
396 * case, we could grossly overestimate the RTT especially
397 * with chatty applications or bulk transfer apps which
398 * are stalled on filesystem I/O.
400 * Also, since we are only going for a minimum in the
401 * non-timestamp case, we do not smooth things out
402 * else with timestamps disabled convergence takes too
406 m
-= (new_sample
>> 3);
408 } else if (m
< new_sample
)
411 /* No previous measure. */
415 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
416 tp
->rcv_rtt_est
.rtt
= new_sample
;
419 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
421 if (tp
->rcv_rtt_est
.time
== 0)
423 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
425 tcp_rcv_rtt_update(tp
,
426 jiffies
- tp
->rcv_rtt_est
.time
,
430 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
431 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
434 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
436 struct tcp_sock
*tp
= tcp_sk(sk
);
437 if (tp
->rx_opt
.rcv_tsecr
&&
438 (TCP_SKB_CB(skb
)->end_seq
-
439 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
440 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
444 * This function should be called every time data is copied to user space.
445 * It calculates the appropriate TCP receive buffer space.
447 void tcp_rcv_space_adjust(struct sock
*sk
)
449 struct tcp_sock
*tp
= tcp_sk(sk
);
453 if (tp
->rcvq_space
.time
== 0)
456 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
457 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
458 tp
->rcv_rtt_est
.rtt
== 0)
461 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
463 space
= max(tp
->rcvq_space
.space
, space
);
465 if (tp
->rcvq_space
.space
!= space
) {
468 tp
->rcvq_space
.space
= space
;
470 if (sysctl_tcp_moderate_rcvbuf
&&
471 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
472 int new_clamp
= space
;
474 /* Receive space grows, normalize in order to
475 * take into account packet headers and sk_buff
476 * structure overhead.
481 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
482 16 + sizeof(struct sk_buff
));
483 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
486 space
= min(space
, sysctl_tcp_rmem
[2]);
487 if (space
> sk
->sk_rcvbuf
) {
488 sk
->sk_rcvbuf
= space
;
490 /* Make the window clamp follow along. */
491 tp
->window_clamp
= new_clamp
;
497 tp
->rcvq_space
.seq
= tp
->copied_seq
;
498 tp
->rcvq_space
.time
= tcp_time_stamp
;
501 /* There is something which you must keep in mind when you analyze the
502 * behavior of the tp->ato delayed ack timeout interval. When a
503 * connection starts up, we want to ack as quickly as possible. The
504 * problem is that "good" TCP's do slow start at the beginning of data
505 * transmission. The means that until we send the first few ACK's the
506 * sender will sit on his end and only queue most of his data, because
507 * he can only send snd_cwnd unacked packets at any given time. For
508 * each ACK we send, he increments snd_cwnd and transmits more of his
511 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
513 struct tcp_sock
*tp
= tcp_sk(sk
);
514 struct inet_connection_sock
*icsk
= inet_csk(sk
);
517 inet_csk_schedule_ack(sk
);
519 tcp_measure_rcv_mss(sk
, skb
);
521 tcp_rcv_rtt_measure(tp
);
523 now
= tcp_time_stamp
;
525 if (!icsk
->icsk_ack
.ato
) {
526 /* The _first_ data packet received, initialize
527 * delayed ACK engine.
529 tcp_incr_quickack(sk
);
530 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
532 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
534 if (m
<= TCP_ATO_MIN
/2) {
535 /* The fastest case is the first. */
536 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
537 } else if (m
< icsk
->icsk_ack
.ato
) {
538 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
539 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
540 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
541 } else if (m
> icsk
->icsk_rto
) {
542 /* Too long gap. Apparently sender failed to
543 * restart window, so that we send ACKs quickly.
545 tcp_incr_quickack(sk
);
546 sk_stream_mem_reclaim(sk
);
549 icsk
->icsk_ack
.lrcvtime
= now
;
551 TCP_ECN_check_ce(tp
, skb
);
554 tcp_grow_window(sk
, skb
);
557 /* Called to compute a smoothed rtt estimate. The data fed to this
558 * routine either comes from timestamps, or from segments that were
559 * known _not_ to have been retransmitted [see Karn/Partridge
560 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
561 * piece by Van Jacobson.
562 * NOTE: the next three routines used to be one big routine.
563 * To save cycles in the RFC 1323 implementation it was better to break
564 * it up into three procedures. -- erics
566 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
568 struct tcp_sock
*tp
= tcp_sk(sk
);
569 long m
= mrtt
; /* RTT */
571 /* The following amusing code comes from Jacobson's
572 * article in SIGCOMM '88. Note that rtt and mdev
573 * are scaled versions of rtt and mean deviation.
574 * This is designed to be as fast as possible
575 * m stands for "measurement".
577 * On a 1990 paper the rto value is changed to:
578 * RTO = rtt + 4 * mdev
580 * Funny. This algorithm seems to be very broken.
581 * These formulae increase RTO, when it should be decreased, increase
582 * too slowly, when it should be increased quickly, decrease too quickly
583 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
584 * does not matter how to _calculate_ it. Seems, it was trap
585 * that VJ failed to avoid. 8)
590 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
591 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
593 m
= -m
; /* m is now abs(error) */
594 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
595 /* This is similar to one of Eifel findings.
596 * Eifel blocks mdev updates when rtt decreases.
597 * This solution is a bit different: we use finer gain
598 * for mdev in this case (alpha*beta).
599 * Like Eifel it also prevents growth of rto,
600 * but also it limits too fast rto decreases,
601 * happening in pure Eifel.
606 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
608 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
609 if (tp
->mdev
> tp
->mdev_max
) {
610 tp
->mdev_max
= tp
->mdev
;
611 if (tp
->mdev_max
> tp
->rttvar
)
612 tp
->rttvar
= tp
->mdev_max
;
614 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
615 if (tp
->mdev_max
< tp
->rttvar
)
616 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
617 tp
->rtt_seq
= tp
->snd_nxt
;
618 tp
->mdev_max
= TCP_RTO_MIN
;
621 /* no previous measure. */
622 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
623 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
624 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
625 tp
->rtt_seq
= tp
->snd_nxt
;
629 /* Calculate rto without backoff. This is the second half of Van Jacobson's
630 * routine referred to above.
632 static inline void tcp_set_rto(struct sock
*sk
)
634 const struct tcp_sock
*tp
= tcp_sk(sk
);
635 /* Old crap is replaced with new one. 8)
638 * 1. If rtt variance happened to be less 50msec, it is hallucination.
639 * It cannot be less due to utterly erratic ACK generation made
640 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
641 * to do with delayed acks, because at cwnd>2 true delack timeout
642 * is invisible. Actually, Linux-2.4 also generates erratic
643 * ACKs in some circumstances.
645 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
647 /* 2. Fixups made earlier cannot be right.
648 * If we do not estimate RTO correctly without them,
649 * all the algo is pure shit and should be replaced
650 * with correct one. It is exactly, which we pretend to do.
654 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
655 * guarantees that rto is higher.
657 static inline void tcp_bound_rto(struct sock
*sk
)
659 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
660 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
663 /* Save metrics learned by this TCP session.
664 This function is called only, when TCP finishes successfully
665 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
667 void tcp_update_metrics(struct sock
*sk
)
669 struct tcp_sock
*tp
= tcp_sk(sk
);
670 struct dst_entry
*dst
= __sk_dst_get(sk
);
672 if (sysctl_tcp_nometrics_save
)
677 if (dst
&& (dst
->flags
&DST_HOST
)) {
678 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
681 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
682 /* This session failed to estimate rtt. Why?
683 * Probably, no packets returned in time.
686 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
687 dst
->metrics
[RTAX_RTT
-1] = 0;
691 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
693 /* If newly calculated rtt larger than stored one,
694 * store new one. Otherwise, use EWMA. Remember,
695 * rtt overestimation is always better than underestimation.
697 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
699 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
701 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
704 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
708 /* Scale deviation to rttvar fixed point */
713 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
714 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
716 dst
->metrics
[RTAX_RTTVAR
-1] -=
717 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
720 if (tp
->snd_ssthresh
>= 0xFFFF) {
721 /* Slow start still did not finish. */
722 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
723 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
724 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
725 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
726 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
727 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
728 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
729 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
730 icsk
->icsk_ca_state
== TCP_CA_Open
) {
731 /* Cong. avoidance phase, cwnd is reliable. */
732 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
733 dst
->metrics
[RTAX_SSTHRESH
-1] =
734 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
735 if (!dst_metric_locked(dst
, RTAX_CWND
))
736 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
738 /* Else slow start did not finish, cwnd is non-sense,
739 ssthresh may be also invalid.
741 if (!dst_metric_locked(dst
, RTAX_CWND
))
742 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
743 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
744 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
745 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
746 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
749 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
750 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
751 tp
->reordering
!= sysctl_tcp_reordering
)
752 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
757 /* Numbers are taken from RFC2414. */
758 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
760 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
763 if (tp
->mss_cache
> 1460)
766 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
768 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
771 /* Set slow start threshold and cwnd not falling to slow start */
772 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
774 struct tcp_sock
*tp
= tcp_sk(sk
);
775 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
777 tp
->prior_ssthresh
= 0;
779 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
782 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
783 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
784 tcp_packets_in_flight(tp
) + 1U);
785 tp
->snd_cwnd_cnt
= 0;
786 tp
->high_seq
= tp
->snd_nxt
;
787 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
788 TCP_ECN_queue_cwr(tp
);
790 tcp_set_ca_state(sk
, TCP_CA_CWR
);
794 /* Initialize metrics on socket. */
796 static void tcp_init_metrics(struct sock
*sk
)
798 struct tcp_sock
*tp
= tcp_sk(sk
);
799 struct dst_entry
*dst
= __sk_dst_get(sk
);
806 if (dst_metric_locked(dst
, RTAX_CWND
))
807 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
808 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
809 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
810 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
811 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
813 if (dst_metric(dst
, RTAX_REORDERING
) &&
814 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
815 tp
->rx_opt
.sack_ok
&= ~2;
816 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
819 if (dst_metric(dst
, RTAX_RTT
) == 0)
822 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
825 /* Initial rtt is determined from SYN,SYN-ACK.
826 * The segment is small and rtt may appear much
827 * less than real one. Use per-dst memory
828 * to make it more realistic.
830 * A bit of theory. RTT is time passed after "normal" sized packet
831 * is sent until it is ACKed. In normal circumstances sending small
832 * packets force peer to delay ACKs and calculation is correct too.
833 * The algorithm is adaptive and, provided we follow specs, it
834 * NEVER underestimate RTT. BUT! If peer tries to make some clever
835 * tricks sort of "quick acks" for time long enough to decrease RTT
836 * to low value, and then abruptly stops to do it and starts to delay
837 * ACKs, wait for troubles.
839 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
840 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
841 tp
->rtt_seq
= tp
->snd_nxt
;
843 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
844 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
845 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
849 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
851 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
852 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
856 /* Play conservative. If timestamps are not
857 * supported, TCP will fail to recalculate correct
858 * rtt, if initial rto is too small. FORGET ALL AND RESET!
860 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
862 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
863 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
867 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
870 struct tcp_sock
*tp
= tcp_sk(sk
);
871 if (metric
> tp
->reordering
) {
872 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
874 /* This exciting event is worth to be remembered. 8) */
876 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
878 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
880 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
882 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
883 #if FASTRETRANS_DEBUG > 1
884 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
885 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
889 tp
->undo_marker
? tp
->undo_retrans
: 0);
891 /* Disable FACK yet. */
892 tp
->rx_opt
.sack_ok
&= ~2;
896 /* This procedure tags the retransmission queue when SACKs arrive.
898 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
899 * Packets in queue with these bits set are counted in variables
900 * sacked_out, retrans_out and lost_out, correspondingly.
902 * Valid combinations are:
903 * Tag InFlight Description
904 * 0 1 - orig segment is in flight.
905 * S 0 - nothing flies, orig reached receiver.
906 * L 0 - nothing flies, orig lost by net.
907 * R 2 - both orig and retransmit are in flight.
908 * L|R 1 - orig is lost, retransmit is in flight.
909 * S|R 1 - orig reached receiver, retrans is still in flight.
910 * (L|S|R is logically valid, it could occur when L|R is sacked,
911 * but it is equivalent to plain S and code short-curcuits it to S.
912 * L|S is logically invalid, it would mean -1 packet in flight 8))
914 * These 6 states form finite state machine, controlled by the following events:
915 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
916 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
917 * 3. Loss detection event of one of three flavors:
918 * A. Scoreboard estimator decided the packet is lost.
919 * A'. Reno "three dupacks" marks head of queue lost.
920 * A''. Its FACK modfication, head until snd.fack is lost.
921 * B. SACK arrives sacking data transmitted after never retransmitted
923 * C. SACK arrives sacking SND.NXT at the moment, when the
924 * segment was retransmitted.
925 * 4. D-SACK added new rule: D-SACK changes any tag to S.
927 * It is pleasant to note, that state diagram turns out to be commutative,
928 * so that we are allowed not to be bothered by order of our actions,
929 * when multiple events arrive simultaneously. (see the function below).
931 * Reordering detection.
932 * --------------------
933 * Reordering metric is maximal distance, which a packet can be displaced
934 * in packet stream. With SACKs we can estimate it:
936 * 1. SACK fills old hole and the corresponding segment was not
937 * ever retransmitted -> reordering. Alas, we cannot use it
938 * when segment was retransmitted.
939 * 2. The last flaw is solved with D-SACK. D-SACK arrives
940 * for retransmitted and already SACKed segment -> reordering..
941 * Both of these heuristics are not used in Loss state, when we cannot
942 * account for retransmits accurately.
945 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
947 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
948 struct tcp_sock
*tp
= tcp_sk(sk
);
949 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
950 TCP_SKB_CB(ack_skb
)->sacked
);
951 struct tcp_sack_block_wire
*sp
= (struct tcp_sack_block_wire
*)(ptr
+2);
952 struct sk_buff
*cached_skb
;
953 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
954 int reord
= tp
->packets_out
;
956 u32 lost_retrans
= 0;
958 int found_dup_sack
= 0;
959 int cached_fack_count
;
961 int first_sack_index
;
965 prior_fackets
= tp
->fackets_out
;
967 /* Check for D-SACK. */
968 if (before(ntohl(sp
[0].start_seq
), TCP_SKB_CB(ack_skb
)->ack_seq
)) {
970 tp
->rx_opt
.sack_ok
|= 4;
971 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
972 } else if (num_sacks
> 1 &&
973 !after(ntohl(sp
[0].end_seq
), ntohl(sp
[1].end_seq
)) &&
974 !before(ntohl(sp
[0].start_seq
), ntohl(sp
[1].start_seq
))) {
976 tp
->rx_opt
.sack_ok
|= 4;
977 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
980 /* D-SACK for already forgotten data...
981 * Do dumb counting. */
982 if (found_dup_sack
&&
983 !after(ntohl(sp
[0].end_seq
), prior_snd_una
) &&
984 after(ntohl(sp
[0].end_seq
), tp
->undo_marker
))
987 /* Eliminate too old ACKs, but take into
988 * account more or less fresh ones, they can
989 * contain valid SACK info.
991 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
995 * if the only SACK change is the increase of the end_seq of
996 * the first block then only apply that SACK block
997 * and use retrans queue hinting otherwise slowpath */
999 for (i
= 0; i
< num_sacks
; i
++) {
1000 __be32 start_seq
= sp
[i
].start_seq
;
1001 __be32 end_seq
= sp
[i
].end_seq
;
1004 if (tp
->recv_sack_cache
[i
].start_seq
!= start_seq
)
1007 if ((tp
->recv_sack_cache
[i
].start_seq
!= start_seq
) ||
1008 (tp
->recv_sack_cache
[i
].end_seq
!= end_seq
))
1011 tp
->recv_sack_cache
[i
].start_seq
= start_seq
;
1012 tp
->recv_sack_cache
[i
].end_seq
= end_seq
;
1014 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1015 for (; i
< ARRAY_SIZE(tp
->recv_sack_cache
); i
++) {
1016 tp
->recv_sack_cache
[i
].start_seq
= 0;
1017 tp
->recv_sack_cache
[i
].end_seq
= 0;
1020 first_sack_index
= 0;
1025 tp
->fastpath_skb_hint
= NULL
;
1027 /* order SACK blocks to allow in order walk of the retrans queue */
1028 for (i
= num_sacks
-1; i
> 0; i
--) {
1029 for (j
= 0; j
< i
; j
++){
1030 if (after(ntohl(sp
[j
].start_seq
),
1031 ntohl(sp
[j
+1].start_seq
))){
1032 struct tcp_sack_block_wire tmp
;
1038 /* Track where the first SACK block goes to */
1039 if (j
== first_sack_index
)
1040 first_sack_index
= j
+1;
1047 /* clear flag as used for different purpose in following code */
1050 /* Use SACK fastpath hint if valid */
1051 cached_skb
= tp
->fastpath_skb_hint
;
1052 cached_fack_count
= tp
->fastpath_cnt_hint
;
1054 cached_skb
= tcp_write_queue_head(sk
);
1055 cached_fack_count
= 0;
1058 for (i
=0; i
<num_sacks
; i
++, sp
++) {
1059 struct sk_buff
*skb
;
1060 __u32 start_seq
= ntohl(sp
->start_seq
);
1061 __u32 end_seq
= ntohl(sp
->end_seq
);
1063 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1066 fack_count
= cached_fack_count
;
1068 /* Event "B" in the comment above. */
1069 if (after(end_seq
, tp
->high_seq
))
1070 flag
|= FLAG_DATA_LOST
;
1072 tcp_for_write_queue_from(skb
, sk
) {
1073 int in_sack
, pcount
;
1076 if (skb
== tcp_send_head(sk
))
1080 cached_fack_count
= fack_count
;
1081 if (i
== first_sack_index
) {
1082 tp
->fastpath_skb_hint
= skb
;
1083 tp
->fastpath_cnt_hint
= fack_count
;
1086 /* The retransmission queue is always in order, so
1087 * we can short-circuit the walk early.
1089 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1092 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1093 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1095 pcount
= tcp_skb_pcount(skb
);
1097 if (pcount
> 1 && !in_sack
&&
1098 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1099 unsigned int pkt_len
;
1101 in_sack
= !after(start_seq
,
1102 TCP_SKB_CB(skb
)->seq
);
1105 pkt_len
= (start_seq
-
1106 TCP_SKB_CB(skb
)->seq
);
1108 pkt_len
= (end_seq
-
1109 TCP_SKB_CB(skb
)->seq
);
1110 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
))
1112 pcount
= tcp_skb_pcount(skb
);
1115 fack_count
+= pcount
;
1117 sacked
= TCP_SKB_CB(skb
)->sacked
;
1119 /* Account D-SACK for retransmitted packet. */
1120 if ((dup_sack
&& in_sack
) &&
1121 (sacked
& TCPCB_RETRANS
) &&
1122 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1125 /* The frame is ACKed. */
1126 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1127 if (sacked
&TCPCB_RETRANS
) {
1128 if ((dup_sack
&& in_sack
) &&
1129 (sacked
&TCPCB_SACKED_ACKED
))
1130 reord
= min(fack_count
, reord
);
1132 /* If it was in a hole, we detected reordering. */
1133 if (fack_count
< prior_fackets
&&
1134 !(sacked
&TCPCB_SACKED_ACKED
))
1135 reord
= min(fack_count
, reord
);
1138 /* Nothing to do; acked frame is about to be dropped. */
1142 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1143 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1144 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1145 lost_retrans
= end_seq
;
1150 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1151 if (sacked
& TCPCB_SACKED_RETRANS
) {
1152 /* If the segment is not tagged as lost,
1153 * we do not clear RETRANS, believing
1154 * that retransmission is still in flight.
1156 if (sacked
& TCPCB_LOST
) {
1157 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1158 tp
->lost_out
-= tcp_skb_pcount(skb
);
1159 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1161 /* clear lost hint */
1162 tp
->retransmit_skb_hint
= NULL
;
1165 /* New sack for not retransmitted frame,
1166 * which was in hole. It is reordering.
1168 if (!(sacked
& TCPCB_RETRANS
) &&
1169 fack_count
< prior_fackets
)
1170 reord
= min(fack_count
, reord
);
1172 if (sacked
& TCPCB_LOST
) {
1173 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1174 tp
->lost_out
-= tcp_skb_pcount(skb
);
1176 /* clear lost hint */
1177 tp
->retransmit_skb_hint
= NULL
;
1179 /* SACK enhanced F-RTO detection.
1180 * Set flag if and only if non-rexmitted
1181 * segments below frto_highmark are
1182 * SACKed (RFC4138; Appendix B).
1183 * Clearing correct due to in-order walk
1185 if (after(end_seq
, tp
->frto_highmark
)) {
1186 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1188 if (!(sacked
& TCPCB_RETRANS
))
1189 flag
|= FLAG_ONLY_ORIG_SACKED
;
1193 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1194 flag
|= FLAG_DATA_SACKED
;
1195 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1197 if (fack_count
> tp
->fackets_out
)
1198 tp
->fackets_out
= fack_count
;
1200 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1201 reord
= min(fack_count
, reord
);
1204 /* D-SACK. We can detect redundant retransmission
1205 * in S|R and plain R frames and clear it.
1206 * undo_retrans is decreased above, L|R frames
1207 * are accounted above as well.
1210 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1211 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1212 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1213 tp
->retransmit_skb_hint
= NULL
;
1218 /* Check for lost retransmit. This superb idea is
1219 * borrowed from "ratehalving". Event "C".
1220 * Later note: FACK people cheated me again 8),
1221 * we have to account for reordering! Ugly,
1224 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1225 struct sk_buff
*skb
;
1227 tcp_for_write_queue(skb
, sk
) {
1228 if (skb
== tcp_send_head(sk
))
1230 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1232 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1234 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1235 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1237 !before(lost_retrans
,
1238 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1240 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1241 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1243 /* clear lost hint */
1244 tp
->retransmit_skb_hint
= NULL
;
1246 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1247 tp
->lost_out
+= tcp_skb_pcount(skb
);
1248 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1249 flag
|= FLAG_DATA_SACKED
;
1250 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1256 tp
->left_out
= tp
->sacked_out
+ tp
->lost_out
;
1258 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
&&
1259 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1260 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1262 #if FASTRETRANS_DEBUG > 0
1263 BUG_TRAP((int)tp
->sacked_out
>= 0);
1264 BUG_TRAP((int)tp
->lost_out
>= 0);
1265 BUG_TRAP((int)tp
->retrans_out
>= 0);
1266 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1271 /* F-RTO can only be used if TCP has never retransmitted anything other than
1272 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1274 int tcp_use_frto(struct sock
*sk
)
1276 const struct tcp_sock
*tp
= tcp_sk(sk
);
1277 struct sk_buff
*skb
;
1279 if (!sysctl_tcp_frto
)
1285 /* Avoid expensive walking of rexmit queue if possible */
1286 if (tp
->retrans_out
> 1)
1289 skb
= tcp_write_queue_head(sk
);
1290 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
1291 tcp_for_write_queue_from(skb
, sk
) {
1292 if (skb
== tcp_send_head(sk
))
1294 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1296 /* Short-circuit when first non-SACKed skb has been checked */
1297 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
))
1303 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1304 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1305 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1306 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1307 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1308 * bits are handled if the Loss state is really to be entered (in
1309 * tcp_enter_frto_loss).
1311 * Do like tcp_enter_loss() would; when RTO expires the second time it
1313 * "Reduce ssthresh if it has not yet been made inside this window."
1315 void tcp_enter_frto(struct sock
*sk
)
1317 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1318 struct tcp_sock
*tp
= tcp_sk(sk
);
1319 struct sk_buff
*skb
;
1321 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1322 tp
->snd_una
== tp
->high_seq
||
1323 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1324 !icsk
->icsk_retransmits
)) {
1325 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1326 /* Our state is too optimistic in ssthresh() call because cwnd
1327 * is not reduced until tcp_enter_frto_loss() when previous FRTO
1328 * recovery has not yet completed. Pattern would be this: RTO,
1329 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1331 * RFC4138 should be more specific on what to do, even though
1332 * RTO is quite unlikely to occur after the first Cumulative ACK
1333 * due to back-off and complexity of triggering events ...
1335 if (tp
->frto_counter
) {
1337 stored_cwnd
= tp
->snd_cwnd
;
1339 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1340 tp
->snd_cwnd
= stored_cwnd
;
1342 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1344 /* ... in theory, cong.control module could do "any tricks" in
1345 * ssthresh(), which means that ca_state, lost bits and lost_out
1346 * counter would have to be faked before the call occurs. We
1347 * consider that too expensive, unlikely and hacky, so modules
1348 * using these in ssthresh() must deal these incompatibility
1349 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1351 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1354 tp
->undo_marker
= tp
->snd_una
;
1355 tp
->undo_retrans
= 0;
1357 skb
= tcp_write_queue_head(sk
);
1358 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1359 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1360 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1362 tcp_sync_left_out(tp
);
1364 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1365 * The last condition is necessary at least in tp->frto_counter case.
1367 if (IsSackFrto() && (tp
->frto_counter
||
1368 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1369 after(tp
->high_seq
, tp
->snd_una
)) {
1370 tp
->frto_highmark
= tp
->high_seq
;
1372 tp
->frto_highmark
= tp
->snd_nxt
;
1374 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1375 tp
->high_seq
= tp
->snd_nxt
;
1376 tp
->frto_counter
= 1;
1379 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1380 * which indicates that we should follow the traditional RTO recovery,
1381 * i.e. mark everything lost and do go-back-N retransmission.
1383 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1385 struct tcp_sock
*tp
= tcp_sk(sk
);
1386 struct sk_buff
*skb
;
1391 tp
->fackets_out
= 0;
1392 tp
->retrans_out
= 0;
1394 tcp_for_write_queue(skb
, sk
) {
1395 if (skb
== tcp_send_head(sk
))
1397 cnt
+= tcp_skb_pcount(skb
);
1399 * Count the retransmission made on RTO correctly (only when
1400 * waiting for the first ACK and did not get it)...
1402 if ((tp
->frto_counter
== 1) && !(flag
&FLAG_DATA_ACKED
)) {
1403 /* For some reason this R-bit might get cleared? */
1404 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1405 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1406 /* ...enter this if branch just for the first segment */
1407 flag
|= FLAG_DATA_ACKED
;
1409 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1411 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1413 /* Do not mark those segments lost that were
1414 * forward transmitted after RTO
1416 if (!after(TCP_SKB_CB(skb
)->end_seq
,
1417 tp
->frto_highmark
)) {
1418 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1419 tp
->lost_out
+= tcp_skb_pcount(skb
);
1422 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1423 tp
->fackets_out
= cnt
;
1426 tcp_sync_left_out(tp
);
1428 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1429 tp
->snd_cwnd_cnt
= 0;
1430 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1431 tp
->undo_marker
= 0;
1432 tp
->frto_counter
= 0;
1434 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1435 sysctl_tcp_reordering
);
1436 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1437 tp
->high_seq
= tp
->frto_highmark
;
1438 TCP_ECN_queue_cwr(tp
);
1440 clear_all_retrans_hints(tp
);
1443 void tcp_clear_retrans(struct tcp_sock
*tp
)
1446 tp
->retrans_out
= 0;
1448 tp
->fackets_out
= 0;
1452 tp
->undo_marker
= 0;
1453 tp
->undo_retrans
= 0;
1456 /* Enter Loss state. If "how" is not zero, forget all SACK information
1457 * and reset tags completely, otherwise preserve SACKs. If receiver
1458 * dropped its ofo queue, we will know this due to reneging detection.
1460 void tcp_enter_loss(struct sock
*sk
, int how
)
1462 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1463 struct tcp_sock
*tp
= tcp_sk(sk
);
1464 struct sk_buff
*skb
;
1467 /* Reduce ssthresh if it has not yet been made inside this window. */
1468 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1469 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1470 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1471 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1472 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1475 tp
->snd_cwnd_cnt
= 0;
1476 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1478 tp
->bytes_acked
= 0;
1479 tcp_clear_retrans(tp
);
1481 /* Push undo marker, if it was plain RTO and nothing
1482 * was retransmitted. */
1484 tp
->undo_marker
= tp
->snd_una
;
1486 tcp_for_write_queue(skb
, sk
) {
1487 if (skb
== tcp_send_head(sk
))
1489 cnt
+= tcp_skb_pcount(skb
);
1490 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1491 tp
->undo_marker
= 0;
1492 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1493 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1494 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1495 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1496 tp
->lost_out
+= tcp_skb_pcount(skb
);
1498 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1499 tp
->fackets_out
= cnt
;
1502 tcp_sync_left_out(tp
);
1504 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1505 sysctl_tcp_reordering
);
1506 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1507 tp
->high_seq
= tp
->snd_nxt
;
1508 TCP_ECN_queue_cwr(tp
);
1509 /* Abort FRTO algorithm if one is in progress */
1510 tp
->frto_counter
= 0;
1512 clear_all_retrans_hints(tp
);
1515 static int tcp_check_sack_reneging(struct sock
*sk
)
1517 struct sk_buff
*skb
;
1519 /* If ACK arrived pointing to a remembered SACK,
1520 * it means that our remembered SACKs do not reflect
1521 * real state of receiver i.e.
1522 * receiver _host_ is heavily congested (or buggy).
1523 * Do processing similar to RTO timeout.
1525 if ((skb
= tcp_write_queue_head(sk
)) != NULL
&&
1526 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1527 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1528 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1530 tcp_enter_loss(sk
, 1);
1531 icsk
->icsk_retransmits
++;
1532 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1533 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1534 icsk
->icsk_rto
, TCP_RTO_MAX
);
1540 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1542 return IsReno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1545 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1547 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1550 static inline int tcp_head_timedout(struct sock
*sk
)
1552 struct tcp_sock
*tp
= tcp_sk(sk
);
1554 return tp
->packets_out
&&
1555 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
1558 /* Linux NewReno/SACK/FACK/ECN state machine.
1559 * --------------------------------------
1561 * "Open" Normal state, no dubious events, fast path.
1562 * "Disorder" In all the respects it is "Open",
1563 * but requires a bit more attention. It is entered when
1564 * we see some SACKs or dupacks. It is split of "Open"
1565 * mainly to move some processing from fast path to slow one.
1566 * "CWR" CWND was reduced due to some Congestion Notification event.
1567 * It can be ECN, ICMP source quench, local device congestion.
1568 * "Recovery" CWND was reduced, we are fast-retransmitting.
1569 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1571 * tcp_fastretrans_alert() is entered:
1572 * - each incoming ACK, if state is not "Open"
1573 * - when arrived ACK is unusual, namely:
1578 * Counting packets in flight is pretty simple.
1580 * in_flight = packets_out - left_out + retrans_out
1582 * packets_out is SND.NXT-SND.UNA counted in packets.
1584 * retrans_out is number of retransmitted segments.
1586 * left_out is number of segments left network, but not ACKed yet.
1588 * left_out = sacked_out + lost_out
1590 * sacked_out: Packets, which arrived to receiver out of order
1591 * and hence not ACKed. With SACKs this number is simply
1592 * amount of SACKed data. Even without SACKs
1593 * it is easy to give pretty reliable estimate of this number,
1594 * counting duplicate ACKs.
1596 * lost_out: Packets lost by network. TCP has no explicit
1597 * "loss notification" feedback from network (for now).
1598 * It means that this number can be only _guessed_.
1599 * Actually, it is the heuristics to predict lossage that
1600 * distinguishes different algorithms.
1602 * F.e. after RTO, when all the queue is considered as lost,
1603 * lost_out = packets_out and in_flight = retrans_out.
1605 * Essentially, we have now two algorithms counting
1608 * FACK: It is the simplest heuristics. As soon as we decided
1609 * that something is lost, we decide that _all_ not SACKed
1610 * packets until the most forward SACK are lost. I.e.
1611 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1612 * It is absolutely correct estimate, if network does not reorder
1613 * packets. And it loses any connection to reality when reordering
1614 * takes place. We use FACK by default until reordering
1615 * is suspected on the path to this destination.
1617 * NewReno: when Recovery is entered, we assume that one segment
1618 * is lost (classic Reno). While we are in Recovery and
1619 * a partial ACK arrives, we assume that one more packet
1620 * is lost (NewReno). This heuristics are the same in NewReno
1623 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1624 * deflation etc. CWND is real congestion window, never inflated, changes
1625 * only according to classic VJ rules.
1627 * Really tricky (and requiring careful tuning) part of algorithm
1628 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1629 * The first determines the moment _when_ we should reduce CWND and,
1630 * hence, slow down forward transmission. In fact, it determines the moment
1631 * when we decide that hole is caused by loss, rather than by a reorder.
1633 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1634 * holes, caused by lost packets.
1636 * And the most logically complicated part of algorithm is undo
1637 * heuristics. We detect false retransmits due to both too early
1638 * fast retransmit (reordering) and underestimated RTO, analyzing
1639 * timestamps and D-SACKs. When we detect that some segments were
1640 * retransmitted by mistake and CWND reduction was wrong, we undo
1641 * window reduction and abort recovery phase. This logic is hidden
1642 * inside several functions named tcp_try_undo_<something>.
1645 /* This function decides, when we should leave Disordered state
1646 * and enter Recovery phase, reducing congestion window.
1648 * Main question: may we further continue forward transmission
1649 * with the same cwnd?
1651 static int tcp_time_to_recover(struct sock
*sk
)
1653 struct tcp_sock
*tp
= tcp_sk(sk
);
1656 /* Do not perform any recovery during FRTO algorithm */
1657 if (tp
->frto_counter
)
1660 /* Trick#1: The loss is proven. */
1664 /* Not-A-Trick#2 : Classic rule... */
1665 if (tcp_fackets_out(tp
) > tp
->reordering
)
1668 /* Trick#3 : when we use RFC2988 timer restart, fast
1669 * retransmit can be triggered by timeout of queue head.
1671 if (tcp_head_timedout(sk
))
1674 /* Trick#4: It is still not OK... But will it be useful to delay
1677 packets_out
= tp
->packets_out
;
1678 if (packets_out
<= tp
->reordering
&&
1679 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1680 !tcp_may_send_now(sk
)) {
1681 /* We have nothing to send. This connection is limited
1682 * either by receiver window or by application.
1690 /* If we receive more dupacks than we expected counting segments
1691 * in assumption of absent reordering, interpret this as reordering.
1692 * The only another reason could be bug in receiver TCP.
1694 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1696 struct tcp_sock
*tp
= tcp_sk(sk
);
1699 holes
= max(tp
->lost_out
, 1U);
1700 holes
= min(holes
, tp
->packets_out
);
1702 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1703 tp
->sacked_out
= tp
->packets_out
- holes
;
1704 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1708 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1710 static void tcp_add_reno_sack(struct sock
*sk
)
1712 struct tcp_sock
*tp
= tcp_sk(sk
);
1714 tcp_check_reno_reordering(sk
, 0);
1715 tcp_sync_left_out(tp
);
1718 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1720 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1722 struct tcp_sock
*tp
= tcp_sk(sk
);
1725 /* One ACK acked hole. The rest eat duplicate ACKs. */
1726 if (acked
-1 >= tp
->sacked_out
)
1729 tp
->sacked_out
-= acked
-1;
1731 tcp_check_reno_reordering(sk
, acked
);
1732 tcp_sync_left_out(tp
);
1735 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1738 tp
->left_out
= tp
->lost_out
;
1741 /* Mark head of queue up as lost. */
1742 static void tcp_mark_head_lost(struct sock
*sk
,
1743 int packets
, u32 high_seq
)
1745 struct tcp_sock
*tp
= tcp_sk(sk
);
1746 struct sk_buff
*skb
;
1749 BUG_TRAP(packets
<= tp
->packets_out
);
1750 if (tp
->lost_skb_hint
) {
1751 skb
= tp
->lost_skb_hint
;
1752 cnt
= tp
->lost_cnt_hint
;
1754 skb
= tcp_write_queue_head(sk
);
1758 tcp_for_write_queue_from(skb
, sk
) {
1759 if (skb
== tcp_send_head(sk
))
1761 /* TODO: do this better */
1762 /* this is not the most efficient way to do this... */
1763 tp
->lost_skb_hint
= skb
;
1764 tp
->lost_cnt_hint
= cnt
;
1765 cnt
+= tcp_skb_pcount(skb
);
1766 if (cnt
> packets
|| after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1768 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1769 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1770 tp
->lost_out
+= tcp_skb_pcount(skb
);
1772 /* clear xmit_retransmit_queue hints
1773 * if this is beyond hint */
1774 if (tp
->retransmit_skb_hint
!= NULL
&&
1775 before(TCP_SKB_CB(skb
)->seq
,
1776 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1777 tp
->retransmit_skb_hint
= NULL
;
1781 tcp_sync_left_out(tp
);
1784 /* Account newly detected lost packet(s) */
1786 static void tcp_update_scoreboard(struct sock
*sk
)
1788 struct tcp_sock
*tp
= tcp_sk(sk
);
1791 int lost
= tp
->fackets_out
- tp
->reordering
;
1794 tcp_mark_head_lost(sk
, lost
, tp
->high_seq
);
1796 tcp_mark_head_lost(sk
, 1, tp
->high_seq
);
1799 /* New heuristics: it is possible only after we switched
1800 * to restart timer each time when something is ACKed.
1801 * Hence, we can detect timed out packets during fast
1802 * retransmit without falling to slow start.
1804 if (!IsReno(tp
) && tcp_head_timedout(sk
)) {
1805 struct sk_buff
*skb
;
1807 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
1808 : tcp_write_queue_head(sk
);
1810 tcp_for_write_queue_from(skb
, sk
) {
1811 if (skb
== tcp_send_head(sk
))
1813 if (!tcp_skb_timedout(sk
, skb
))
1816 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1817 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1818 tp
->lost_out
+= tcp_skb_pcount(skb
);
1820 /* clear xmit_retrans hint */
1821 if (tp
->retransmit_skb_hint
&&
1822 before(TCP_SKB_CB(skb
)->seq
,
1823 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1825 tp
->retransmit_skb_hint
= NULL
;
1829 tp
->scoreboard_skb_hint
= skb
;
1831 tcp_sync_left_out(tp
);
1835 /* CWND moderation, preventing bursts due to too big ACKs
1836 * in dubious situations.
1838 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
1840 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
1841 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
1842 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1845 /* Lower bound on congestion window is slow start threshold
1846 * unless congestion avoidance choice decides to overide it.
1848 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
1850 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1852 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
1855 /* Decrease cwnd each second ack. */
1856 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
1858 struct tcp_sock
*tp
= tcp_sk(sk
);
1859 int decr
= tp
->snd_cwnd_cnt
+ 1;
1861 if ((flag
&FLAG_ANY_PROGRESS
) ||
1862 (IsReno(tp
) && !(flag
&FLAG_NOT_DUP
))) {
1863 tp
->snd_cwnd_cnt
= decr
&1;
1866 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
1867 tp
->snd_cwnd
-= decr
;
1869 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
1870 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1874 /* Nothing was retransmitted or returned timestamp is less
1875 * than timestamp of the first retransmission.
1877 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
1879 return !tp
->retrans_stamp
||
1880 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
1881 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
1884 /* Undo procedures. */
1886 #if FASTRETRANS_DEBUG > 1
1887 static void DBGUNDO(struct sock
*sk
, const char *msg
)
1889 struct tcp_sock
*tp
= tcp_sk(sk
);
1890 struct inet_sock
*inet
= inet_sk(sk
);
1892 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1894 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
1895 tp
->snd_cwnd
, tp
->left_out
,
1896 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
1900 #define DBGUNDO(x...) do { } while (0)
1903 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
1905 struct tcp_sock
*tp
= tcp_sk(sk
);
1907 if (tp
->prior_ssthresh
) {
1908 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1910 if (icsk
->icsk_ca_ops
->undo_cwnd
)
1911 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
1913 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
1915 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
1916 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
1917 TCP_ECN_withdraw_cwr(tp
);
1920 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1922 tcp_moderate_cwnd(tp
);
1923 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1925 /* There is something screwy going on with the retrans hints after
1927 clear_all_retrans_hints(tp
);
1930 static inline int tcp_may_undo(struct tcp_sock
*tp
)
1932 return tp
->undo_marker
&&
1933 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
1936 /* People celebrate: "We love our President!" */
1937 static int tcp_try_undo_recovery(struct sock
*sk
)
1939 struct tcp_sock
*tp
= tcp_sk(sk
);
1941 if (tcp_may_undo(tp
)) {
1942 /* Happy end! We did not retransmit anything
1943 * or our original transmission succeeded.
1945 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
1946 tcp_undo_cwr(sk
, 1);
1947 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
1948 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1950 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
1951 tp
->undo_marker
= 0;
1953 if (tp
->snd_una
== tp
->high_seq
&& IsReno(tp
)) {
1954 /* Hold old state until something *above* high_seq
1955 * is ACKed. For Reno it is MUST to prevent false
1956 * fast retransmits (RFC2582). SACK TCP is safe. */
1957 tcp_moderate_cwnd(tp
);
1960 tcp_set_ca_state(sk
, TCP_CA_Open
);
1964 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1965 static void tcp_try_undo_dsack(struct sock
*sk
)
1967 struct tcp_sock
*tp
= tcp_sk(sk
);
1969 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
1970 DBGUNDO(sk
, "D-SACK");
1971 tcp_undo_cwr(sk
, 1);
1972 tp
->undo_marker
= 0;
1973 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
1977 /* Undo during fast recovery after partial ACK. */
1979 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
1981 struct tcp_sock
*tp
= tcp_sk(sk
);
1982 /* Partial ACK arrived. Force Hoe's retransmit. */
1983 int failed
= IsReno(tp
) || tp
->fackets_out
>tp
->reordering
;
1985 if (tcp_may_undo(tp
)) {
1986 /* Plain luck! Hole if filled with delayed
1987 * packet, rather than with a retransmit.
1989 if (tp
->retrans_out
== 0)
1990 tp
->retrans_stamp
= 0;
1992 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
1995 tcp_undo_cwr(sk
, 0);
1996 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
1998 /* So... Do not make Hoe's retransmit yet.
1999 * If the first packet was delayed, the rest
2000 * ones are most probably delayed as well.
2007 /* Undo during loss recovery after partial ACK. */
2008 static int tcp_try_undo_loss(struct sock
*sk
)
2010 struct tcp_sock
*tp
= tcp_sk(sk
);
2012 if (tcp_may_undo(tp
)) {
2013 struct sk_buff
*skb
;
2014 tcp_for_write_queue(skb
, sk
) {
2015 if (skb
== tcp_send_head(sk
))
2017 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2020 clear_all_retrans_hints(tp
);
2022 DBGUNDO(sk
, "partial loss");
2024 tp
->left_out
= tp
->sacked_out
;
2025 tcp_undo_cwr(sk
, 1);
2026 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2027 inet_csk(sk
)->icsk_retransmits
= 0;
2028 tp
->undo_marker
= 0;
2030 tcp_set_ca_state(sk
, TCP_CA_Open
);
2036 static inline void tcp_complete_cwr(struct sock
*sk
)
2038 struct tcp_sock
*tp
= tcp_sk(sk
);
2039 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2040 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2041 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2044 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2046 struct tcp_sock
*tp
= tcp_sk(sk
);
2048 tcp_sync_left_out(tp
);
2050 if (tp
->retrans_out
== 0)
2051 tp
->retrans_stamp
= 0;
2054 tcp_enter_cwr(sk
, 1);
2056 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2057 int state
= TCP_CA_Open
;
2059 if (tp
->left_out
|| tp
->retrans_out
|| tp
->undo_marker
)
2060 state
= TCP_CA_Disorder
;
2062 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2063 tcp_set_ca_state(sk
, state
);
2064 tp
->high_seq
= tp
->snd_nxt
;
2066 tcp_moderate_cwnd(tp
);
2068 tcp_cwnd_down(sk
, flag
);
2072 static void tcp_mtup_probe_failed(struct sock
*sk
)
2074 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2076 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2077 icsk
->icsk_mtup
.probe_size
= 0;
2080 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2082 struct tcp_sock
*tp
= tcp_sk(sk
);
2083 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2085 /* FIXME: breaks with very large cwnd */
2086 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2087 tp
->snd_cwnd
= tp
->snd_cwnd
*
2088 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2089 icsk
->icsk_mtup
.probe_size
;
2090 tp
->snd_cwnd_cnt
= 0;
2091 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2092 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2094 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2095 icsk
->icsk_mtup
.probe_size
= 0;
2096 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2100 /* Process an event, which can update packets-in-flight not trivially.
2101 * Main goal of this function is to calculate new estimate for left_out,
2102 * taking into account both packets sitting in receiver's buffer and
2103 * packets lost by network.
2105 * Besides that it does CWND reduction, when packet loss is detected
2106 * and changes state of machine.
2108 * It does _not_ decide what to send, it is made in function
2109 * tcp_xmit_retransmit_queue().
2112 tcp_fastretrans_alert(struct sock
*sk
, u32 prior_snd_una
,
2113 int prior_packets
, int flag
)
2115 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2116 struct tcp_sock
*tp
= tcp_sk(sk
);
2117 int is_dupack
= !(flag
&(FLAG_SND_UNA_ADVANCED
|FLAG_NOT_DUP
));
2118 int do_lost
= is_dupack
|| ((flag
&FLAG_DATA_SACKED
) &&
2119 (tp
->fackets_out
> tp
->reordering
));
2121 /* Some technical things:
2122 * 1. Reno does not count dupacks (sacked_out) automatically. */
2123 if (!tp
->packets_out
)
2125 /* 2. SACK counts snd_fack in packets inaccurately. */
2126 if (tp
->sacked_out
== 0)
2127 tp
->fackets_out
= 0;
2129 /* Now state machine starts.
2130 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2132 tp
->prior_ssthresh
= 0;
2134 /* B. In all the states check for reneging SACKs. */
2135 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
2138 /* C. Process data loss notification, provided it is valid. */
2139 if ((flag
&FLAG_DATA_LOST
) &&
2140 before(tp
->snd_una
, tp
->high_seq
) &&
2141 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2142 tp
->fackets_out
> tp
->reordering
) {
2143 tcp_mark_head_lost(sk
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
2144 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2147 /* D. Synchronize left_out to current state. */
2148 tcp_sync_left_out(tp
);
2150 /* E. Check state exit conditions. State can be terminated
2151 * when high_seq is ACKed. */
2152 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2153 BUG_TRAP(tp
->retrans_out
== 0);
2154 tp
->retrans_stamp
= 0;
2155 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2156 switch (icsk
->icsk_ca_state
) {
2158 icsk
->icsk_retransmits
= 0;
2159 if (tcp_try_undo_recovery(sk
))
2164 /* CWR is to be held something *above* high_seq
2165 * is ACKed for CWR bit to reach receiver. */
2166 if (tp
->snd_una
!= tp
->high_seq
) {
2167 tcp_complete_cwr(sk
);
2168 tcp_set_ca_state(sk
, TCP_CA_Open
);
2172 case TCP_CA_Disorder
:
2173 tcp_try_undo_dsack(sk
);
2174 if (!tp
->undo_marker
||
2175 /* For SACK case do not Open to allow to undo
2176 * catching for all duplicate ACKs. */
2177 IsReno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2178 tp
->undo_marker
= 0;
2179 tcp_set_ca_state(sk
, TCP_CA_Open
);
2183 case TCP_CA_Recovery
:
2185 tcp_reset_reno_sack(tp
);
2186 if (tcp_try_undo_recovery(sk
))
2188 tcp_complete_cwr(sk
);
2193 /* F. Process state. */
2194 switch (icsk
->icsk_ca_state
) {
2195 case TCP_CA_Recovery
:
2196 if (prior_snd_una
== tp
->snd_una
) {
2197 if (IsReno(tp
) && is_dupack
)
2198 tcp_add_reno_sack(sk
);
2200 int acked
= prior_packets
- tp
->packets_out
;
2202 tcp_remove_reno_sacks(sk
, acked
);
2203 do_lost
= tcp_try_undo_partial(sk
, acked
);
2207 if (flag
&FLAG_DATA_ACKED
)
2208 icsk
->icsk_retransmits
= 0;
2209 if (!tcp_try_undo_loss(sk
)) {
2210 tcp_moderate_cwnd(tp
);
2211 tcp_xmit_retransmit_queue(sk
);
2214 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2216 /* Loss is undone; fall through to processing in Open state. */
2219 if (tp
->snd_una
!= prior_snd_una
)
2220 tcp_reset_reno_sack(tp
);
2222 tcp_add_reno_sack(sk
);
2225 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2226 tcp_try_undo_dsack(sk
);
2228 if (!tcp_time_to_recover(sk
)) {
2229 tcp_try_to_open(sk
, flag
);
2233 /* MTU probe failure: don't reduce cwnd */
2234 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2235 icsk
->icsk_mtup
.probe_size
&&
2236 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2237 tcp_mtup_probe_failed(sk
);
2238 /* Restores the reduction we did in tcp_mtup_probe() */
2240 tcp_simple_retransmit(sk
);
2244 /* Otherwise enter Recovery state */
2247 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2249 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2251 tp
->high_seq
= tp
->snd_nxt
;
2252 tp
->prior_ssthresh
= 0;
2253 tp
->undo_marker
= tp
->snd_una
;
2254 tp
->undo_retrans
= tp
->retrans_out
;
2256 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2257 if (!(flag
&FLAG_ECE
))
2258 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2259 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2260 TCP_ECN_queue_cwr(tp
);
2263 tp
->bytes_acked
= 0;
2264 tp
->snd_cwnd_cnt
= 0;
2265 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2268 if (do_lost
|| tcp_head_timedout(sk
))
2269 tcp_update_scoreboard(sk
);
2270 tcp_cwnd_down(sk
, flag
);
2271 tcp_xmit_retransmit_queue(sk
);
2274 /* Read draft-ietf-tcplw-high-performance before mucking
2275 * with this code. (Supersedes RFC1323)
2277 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2279 /* RTTM Rule: A TSecr value received in a segment is used to
2280 * update the averaged RTT measurement only if the segment
2281 * acknowledges some new data, i.e., only if it advances the
2282 * left edge of the send window.
2284 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2285 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2287 * Changed: reset backoff as soon as we see the first valid sample.
2288 * If we do not, we get strongly overestimated rto. With timestamps
2289 * samples are accepted even from very old segments: f.e., when rtt=1
2290 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2291 * answer arrives rto becomes 120 seconds! If at least one of segments
2292 * in window is lost... Voila. --ANK (010210)
2294 struct tcp_sock
*tp
= tcp_sk(sk
);
2295 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2296 tcp_rtt_estimator(sk
, seq_rtt
);
2298 inet_csk(sk
)->icsk_backoff
= 0;
2302 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2304 /* We don't have a timestamp. Can only use
2305 * packets that are not retransmitted to determine
2306 * rtt estimates. Also, we must not reset the
2307 * backoff for rto until we get a non-retransmitted
2308 * packet. This allows us to deal with a situation
2309 * where the network delay has increased suddenly.
2310 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2313 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2316 tcp_rtt_estimator(sk
, seq_rtt
);
2318 inet_csk(sk
)->icsk_backoff
= 0;
2322 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2325 const struct tcp_sock
*tp
= tcp_sk(sk
);
2326 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2327 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2328 tcp_ack_saw_tstamp(sk
, flag
);
2329 else if (seq_rtt
>= 0)
2330 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2333 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 rtt
,
2334 u32 in_flight
, int good
)
2336 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2337 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, rtt
, in_flight
, good
);
2338 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2341 /* Restart timer after forward progress on connection.
2342 * RFC2988 recommends to restart timer to now+rto.
2345 static void tcp_ack_packets_out(struct sock
*sk
)
2347 struct tcp_sock
*tp
= tcp_sk(sk
);
2349 if (!tp
->packets_out
) {
2350 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2352 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2356 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
2357 __u32 now
, __s32
*seq_rtt
)
2359 struct tcp_sock
*tp
= tcp_sk(sk
);
2360 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2361 __u32 seq
= tp
->snd_una
;
2362 __u32 packets_acked
;
2365 /* If we get here, the whole TSO packet has not been
2368 BUG_ON(!after(scb
->end_seq
, seq
));
2370 packets_acked
= tcp_skb_pcount(skb
);
2371 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
2373 packets_acked
-= tcp_skb_pcount(skb
);
2375 if (packets_acked
) {
2376 __u8 sacked
= scb
->sacked
;
2378 acked
|= FLAG_DATA_ACKED
;
2380 if (sacked
& TCPCB_RETRANS
) {
2381 if (sacked
& TCPCB_SACKED_RETRANS
)
2382 tp
->retrans_out
-= packets_acked
;
2383 acked
|= FLAG_RETRANS_DATA_ACKED
;
2385 } else if (*seq_rtt
< 0)
2386 *seq_rtt
= now
- scb
->when
;
2387 if (sacked
& TCPCB_SACKED_ACKED
)
2388 tp
->sacked_out
-= packets_acked
;
2389 if (sacked
& TCPCB_LOST
)
2390 tp
->lost_out
-= packets_acked
;
2391 if (sacked
& TCPCB_URG
) {
2393 !before(seq
, tp
->snd_up
))
2396 } else if (*seq_rtt
< 0)
2397 *seq_rtt
= now
- scb
->when
;
2399 if (tp
->fackets_out
) {
2400 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2401 tp
->fackets_out
-= dval
;
2403 tp
->packets_out
-= packets_acked
;
2405 BUG_ON(tcp_skb_pcount(skb
) == 0);
2406 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2412 /* Remove acknowledged frames from the retransmission queue. */
2413 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2415 struct tcp_sock
*tp
= tcp_sk(sk
);
2416 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2417 struct sk_buff
*skb
;
2418 __u32 now
= tcp_time_stamp
;
2420 int prior_packets
= tp
->packets_out
;
2422 ktime_t last_ackt
= net_invalid_timestamp();
2424 while ((skb
= tcp_write_queue_head(sk
)) &&
2425 skb
!= tcp_send_head(sk
)) {
2426 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2427 __u8 sacked
= scb
->sacked
;
2429 /* If our packet is before the ack sequence we can
2430 * discard it as it's confirmed to have arrived at
2433 if (after(scb
->end_seq
, tp
->snd_una
)) {
2434 if (tcp_skb_pcount(skb
) > 1 &&
2435 after(tp
->snd_una
, scb
->seq
))
2436 acked
|= tcp_tso_acked(sk
, skb
,
2441 /* Initial outgoing SYN's get put onto the write_queue
2442 * just like anything else we transmit. It is not
2443 * true data, and if we misinform our callers that
2444 * this ACK acks real data, we will erroneously exit
2445 * connection startup slow start one packet too
2446 * quickly. This is severely frowned upon behavior.
2448 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2449 acked
|= FLAG_DATA_ACKED
;
2451 acked
|= FLAG_SYN_ACKED
;
2452 tp
->retrans_stamp
= 0;
2455 /* MTU probing checks */
2456 if (icsk
->icsk_mtup
.probe_size
) {
2457 if (!after(tp
->mtu_probe
.probe_seq_end
, TCP_SKB_CB(skb
)->end_seq
)) {
2458 tcp_mtup_probe_success(sk
, skb
);
2463 if (sacked
& TCPCB_RETRANS
) {
2464 if (sacked
& TCPCB_SACKED_RETRANS
)
2465 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2466 acked
|= FLAG_RETRANS_DATA_ACKED
;
2468 } else if (seq_rtt
< 0) {
2469 seq_rtt
= now
- scb
->when
;
2470 last_ackt
= skb
->tstamp
;
2472 if (sacked
& TCPCB_SACKED_ACKED
)
2473 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2474 if (sacked
& TCPCB_LOST
)
2475 tp
->lost_out
-= tcp_skb_pcount(skb
);
2476 if (sacked
& TCPCB_URG
) {
2478 !before(scb
->end_seq
, tp
->snd_up
))
2481 } else if (seq_rtt
< 0) {
2482 seq_rtt
= now
- scb
->when
;
2483 last_ackt
= skb
->tstamp
;
2485 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2486 tcp_packets_out_dec(tp
, skb
);
2487 tcp_unlink_write_queue(skb
, sk
);
2488 sk_stream_free_skb(sk
, skb
);
2489 clear_all_retrans_hints(tp
);
2492 if (acked
&FLAG_ACKED
) {
2493 u32 pkts_acked
= prior_packets
- tp
->packets_out
;
2494 const struct tcp_congestion_ops
*ca_ops
2495 = inet_csk(sk
)->icsk_ca_ops
;
2497 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2498 tcp_ack_packets_out(sk
);
2500 /* Is the ACK triggering packet unambiguous? */
2501 if (acked
& FLAG_RETRANS_DATA_ACKED
)
2502 last_ackt
= net_invalid_timestamp();
2504 if (ca_ops
->pkts_acked
)
2505 ca_ops
->pkts_acked(sk
, pkts_acked
, last_ackt
);
2508 #if FASTRETRANS_DEBUG > 0
2509 BUG_TRAP((int)tp
->sacked_out
>= 0);
2510 BUG_TRAP((int)tp
->lost_out
>= 0);
2511 BUG_TRAP((int)tp
->retrans_out
>= 0);
2512 if (!tp
->packets_out
&& tp
->rx_opt
.sack_ok
) {
2513 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2515 printk(KERN_DEBUG
"Leak l=%u %d\n",
2516 tp
->lost_out
, icsk
->icsk_ca_state
);
2519 if (tp
->sacked_out
) {
2520 printk(KERN_DEBUG
"Leak s=%u %d\n",
2521 tp
->sacked_out
, icsk
->icsk_ca_state
);
2524 if (tp
->retrans_out
) {
2525 printk(KERN_DEBUG
"Leak r=%u %d\n",
2526 tp
->retrans_out
, icsk
->icsk_ca_state
);
2527 tp
->retrans_out
= 0;
2531 *seq_rtt_p
= seq_rtt
;
2535 static void tcp_ack_probe(struct sock
*sk
)
2537 const struct tcp_sock
*tp
= tcp_sk(sk
);
2538 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2540 /* Was it a usable window open? */
2542 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2543 tp
->snd_una
+ tp
->snd_wnd
)) {
2544 icsk
->icsk_backoff
= 0;
2545 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2546 /* Socket must be waked up by subsequent tcp_data_snd_check().
2547 * This function is not for random using!
2550 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2551 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2556 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2558 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2559 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2562 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2564 const struct tcp_sock
*tp
= tcp_sk(sk
);
2565 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2566 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2569 /* Check that window update is acceptable.
2570 * The function assumes that snd_una<=ack<=snd_next.
2572 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2573 const u32 ack_seq
, const u32 nwin
)
2575 return (after(ack
, tp
->snd_una
) ||
2576 after(ack_seq
, tp
->snd_wl1
) ||
2577 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2580 /* Update our send window.
2582 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2583 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2585 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
2588 struct tcp_sock
*tp
= tcp_sk(sk
);
2590 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
2592 if (likely(!tcp_hdr(skb
)->syn
))
2593 nwin
<<= tp
->rx_opt
.snd_wscale
;
2595 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2596 flag
|= FLAG_WIN_UPDATE
;
2597 tcp_update_wl(tp
, ack
, ack_seq
);
2599 if (tp
->snd_wnd
!= nwin
) {
2602 /* Note, it is the only place, where
2603 * fast path is recovered for sending TCP.
2606 tcp_fast_path_check(sk
);
2608 if (nwin
> tp
->max_window
) {
2609 tp
->max_window
= nwin
;
2610 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
2620 /* A very conservative spurious RTO response algorithm: reduce cwnd and
2621 * continue in congestion avoidance.
2623 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
2625 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2626 tp
->snd_cwnd_cnt
= 0;
2627 TCP_ECN_queue_cwr(tp
);
2628 tcp_moderate_cwnd(tp
);
2631 /* A conservative spurious RTO response algorithm: reduce cwnd using
2632 * rate halving and continue in congestion avoidance.
2634 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
2636 tcp_enter_cwr(sk
, 0);
2639 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
2642 tcp_ratehalving_spur_to_response(sk
);
2644 tcp_undo_cwr(sk
, 1);
2647 /* F-RTO spurious RTO detection algorithm (RFC4138)
2649 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
2650 * comments). State (ACK number) is kept in frto_counter. When ACK advances
2651 * window (but not to or beyond highest sequence sent before RTO):
2652 * On First ACK, send two new segments out.
2653 * On Second ACK, RTO was likely spurious. Do spurious response (response
2654 * algorithm is not part of the F-RTO detection algorithm
2655 * given in RFC4138 but can be selected separately).
2656 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
2657 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
2658 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
2659 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
2661 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2662 * original window even after we transmit two new data segments.
2665 * on first step, wait until first cumulative ACK arrives, then move to
2666 * the second step. In second step, the next ACK decides.
2668 * F-RTO is implemented (mainly) in four functions:
2669 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2670 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2671 * called when tcp_use_frto() showed green light
2672 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2673 * - tcp_enter_frto_loss() is called if there is not enough evidence
2674 * to prove that the RTO is indeed spurious. It transfers the control
2675 * from F-RTO to the conventional RTO recovery
2677 static int tcp_process_frto(struct sock
*sk
, u32 prior_snd_una
, int flag
)
2679 struct tcp_sock
*tp
= tcp_sk(sk
);
2681 tcp_sync_left_out(tp
);
2683 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2684 if (flag
&FLAG_DATA_ACKED
)
2685 inet_csk(sk
)->icsk_retransmits
= 0;
2687 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
2688 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
2692 if (!IsSackFrto() || IsReno(tp
)) {
2693 /* RFC4138 shortcoming in step 2; should also have case c):
2694 * ACK isn't duplicate nor advances window, e.g., opposite dir
2697 if ((tp
->snd_una
== prior_snd_una
) && (flag
&FLAG_NOT_DUP
) &&
2698 !(flag
&FLAG_FORWARD_PROGRESS
))
2701 if (!(flag
&FLAG_DATA_ACKED
)) {
2702 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
2707 if (!(flag
&FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
2708 /* Prevent sending of new data. */
2709 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2710 tcp_packets_in_flight(tp
));
2714 if ((tp
->frto_counter
>= 2) &&
2715 (!(flag
&FLAG_FORWARD_PROGRESS
) ||
2716 ((flag
&FLAG_DATA_SACKED
) && !(flag
&FLAG_ONLY_ORIG_SACKED
)))) {
2717 /* RFC4138 shortcoming (see comment above) */
2718 if (!(flag
&FLAG_FORWARD_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2721 tcp_enter_frto_loss(sk
, 3, flag
);
2726 if (tp
->frto_counter
== 1) {
2727 /* Sending of the next skb must be allowed or no FRTO */
2728 if (!tcp_send_head(sk
) ||
2729 after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2730 tp
->snd_una
+ tp
->snd_wnd
)) {
2731 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3),
2736 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2737 tp
->frto_counter
= 2;
2740 switch (sysctl_tcp_frto_response
) {
2742 tcp_undo_spur_to_response(sk
, flag
);
2745 tcp_conservative_spur_to_response(tp
);
2748 tcp_ratehalving_spur_to_response(sk
);
2751 tp
->frto_counter
= 0;
2756 /* This routine deals with incoming acks, but not outgoing ones. */
2757 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2759 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2760 struct tcp_sock
*tp
= tcp_sk(sk
);
2761 u32 prior_snd_una
= tp
->snd_una
;
2762 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2763 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2764 u32 prior_in_flight
;
2769 /* If the ack is newer than sent or older than previous acks
2770 * then we can probably ignore it.
2772 if (after(ack
, tp
->snd_nxt
))
2773 goto uninteresting_ack
;
2775 if (before(ack
, prior_snd_una
))
2778 if (after(ack
, prior_snd_una
))
2779 flag
|= FLAG_SND_UNA_ADVANCED
;
2781 if (sysctl_tcp_abc
) {
2782 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
2783 tp
->bytes_acked
+= ack
- prior_snd_una
;
2784 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
2785 /* we assume just one segment left network */
2786 tp
->bytes_acked
+= min(ack
- prior_snd_una
, tp
->mss_cache
);
2789 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2790 /* Window is constant, pure forward advance.
2791 * No more checks are required.
2792 * Note, we use the fact that SND.UNA>=SND.WL2.
2794 tcp_update_wl(tp
, ack
, ack_seq
);
2796 flag
|= FLAG_WIN_UPDATE
;
2798 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2800 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2802 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2805 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2807 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
2809 if (TCP_SKB_CB(skb
)->sacked
)
2810 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2812 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
2815 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
2818 /* We passed data and got it acked, remove any soft error
2819 * log. Something worked...
2821 sk
->sk_err_soft
= 0;
2822 tp
->rcv_tstamp
= tcp_time_stamp
;
2823 prior_packets
= tp
->packets_out
;
2827 prior_in_flight
= tcp_packets_in_flight(tp
);
2829 /* See if we can take anything off of the retransmit queue. */
2830 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
2832 if (tp
->frto_counter
)
2833 frto_cwnd
= tcp_process_frto(sk
, prior_snd_una
, flag
);
2835 if (tcp_ack_is_dubious(sk
, flag
)) {
2836 /* Advance CWND, if state allows this. */
2837 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
2838 tcp_may_raise_cwnd(sk
, flag
))
2839 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 0);
2840 tcp_fastretrans_alert(sk
, prior_snd_una
, prior_packets
, flag
);
2842 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
2843 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 1);
2846 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
2847 dst_confirm(sk
->sk_dst_cache
);
2852 icsk
->icsk_probes_out
= 0;
2854 /* If this ack opens up a zero window, clear backoff. It was
2855 * being used to time the probes, and is probably far higher than
2856 * it needs to be for normal retransmission.
2858 if (tcp_send_head(sk
))
2863 if (TCP_SKB_CB(skb
)->sacked
)
2864 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2867 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
2872 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2873 * But, this can also be called on packets in the established flow when
2874 * the fast version below fails.
2876 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
2879 struct tcphdr
*th
= tcp_hdr(skb
);
2880 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
2882 ptr
= (unsigned char *)(th
+ 1);
2883 opt_rx
->saw_tstamp
= 0;
2885 while (length
> 0) {
2892 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
2897 if (opsize
< 2) /* "silly options" */
2899 if (opsize
> length
)
2900 return; /* don't parse partial options */
2903 if (opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
2904 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
2906 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
2907 in_mss
= opt_rx
->user_mss
;
2908 opt_rx
->mss_clamp
= in_mss
;
2913 if (opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
2914 if (sysctl_tcp_window_scaling
) {
2915 __u8 snd_wscale
= *(__u8
*) ptr
;
2916 opt_rx
->wscale_ok
= 1;
2917 if (snd_wscale
> 14) {
2918 if (net_ratelimit())
2919 printk(KERN_INFO
"tcp_parse_options: Illegal window "
2920 "scaling value %d >14 received.\n",
2924 opt_rx
->snd_wscale
= snd_wscale
;
2927 case TCPOPT_TIMESTAMP
:
2928 if (opsize
==TCPOLEN_TIMESTAMP
) {
2929 if ((estab
&& opt_rx
->tstamp_ok
) ||
2930 (!estab
&& sysctl_tcp_timestamps
)) {
2931 opt_rx
->saw_tstamp
= 1;
2932 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
2933 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
2937 case TCPOPT_SACK_PERM
:
2938 if (opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
2939 if (sysctl_tcp_sack
) {
2940 opt_rx
->sack_ok
= 1;
2941 tcp_sack_reset(opt_rx
);
2947 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
2948 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
2950 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
2953 #ifdef CONFIG_TCP_MD5SIG
2956 * The MD5 Hash has already been
2957 * checked (see tcp_v{4,6}_do_rcv()).
2969 /* Fast parse options. This hopes to only see timestamps.
2970 * If it is wrong it falls back on tcp_parse_options().
2972 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
2973 struct tcp_sock
*tp
)
2975 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
2976 tp
->rx_opt
.saw_tstamp
= 0;
2978 } else if (tp
->rx_opt
.tstamp_ok
&&
2979 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
2980 __be32
*ptr
= (__be32
*)(th
+ 1);
2981 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
2982 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
2983 tp
->rx_opt
.saw_tstamp
= 1;
2985 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
2987 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
2991 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
2995 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
2997 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
2998 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3001 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3003 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3004 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3005 * extra check below makes sure this can only happen
3006 * for pure ACK frames. -DaveM
3008 * Not only, also it occurs for expired timestamps.
3011 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
3012 get_seconds() >= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
3013 tcp_store_ts_recent(tp
);
3017 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3019 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3020 * it can pass through stack. So, the following predicate verifies that
3021 * this segment is not used for anything but congestion avoidance or
3022 * fast retransmit. Moreover, we even are able to eliminate most of such
3023 * second order effects, if we apply some small "replay" window (~RTO)
3024 * to timestamp space.
3026 * All these measures still do not guarantee that we reject wrapped ACKs
3027 * on networks with high bandwidth, when sequence space is recycled fastly,
3028 * but it guarantees that such events will be very rare and do not affect
3029 * connection seriously. This doesn't look nice, but alas, PAWS is really
3032 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3033 * states that events when retransmit arrives after original data are rare.
3034 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3035 * the biggest problem on large power networks even with minor reordering.
3036 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3037 * up to bandwidth of 18Gigabit/sec. 8) ]
3040 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3042 struct tcp_sock
*tp
= tcp_sk(sk
);
3043 struct tcphdr
*th
= tcp_hdr(skb
);
3044 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3045 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3047 return (/* 1. Pure ACK with correct sequence number. */
3048 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3050 /* 2. ... and duplicate ACK. */
3051 ack
== tp
->snd_una
&&
3053 /* 3. ... and does not update window. */
3054 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3056 /* 4. ... and sits in replay window. */
3057 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3060 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
3062 const struct tcp_sock
*tp
= tcp_sk(sk
);
3063 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3064 get_seconds() < tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3065 !tcp_disordered_ack(sk
, skb
));
3068 /* Check segment sequence number for validity.
3070 * Segment controls are considered valid, if the segment
3071 * fits to the window after truncation to the window. Acceptability
3072 * of data (and SYN, FIN, of course) is checked separately.
3073 * See tcp_data_queue(), for example.
3075 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3076 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3077 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3078 * (borrowed from freebsd)
3081 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3083 return !before(end_seq
, tp
->rcv_wup
) &&
3084 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3087 /* When we get a reset we do this. */
3088 static void tcp_reset(struct sock
*sk
)
3090 /* We want the right error as BSD sees it (and indeed as we do). */
3091 switch (sk
->sk_state
) {
3093 sk
->sk_err
= ECONNREFUSED
;
3095 case TCP_CLOSE_WAIT
:
3101 sk
->sk_err
= ECONNRESET
;
3104 if (!sock_flag(sk
, SOCK_DEAD
))
3105 sk
->sk_error_report(sk
);
3111 * Process the FIN bit. This now behaves as it is supposed to work
3112 * and the FIN takes effect when it is validly part of sequence
3113 * space. Not before when we get holes.
3115 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3116 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3119 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3120 * close and we go into CLOSING (and later onto TIME-WAIT)
3122 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3124 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3126 struct tcp_sock
*tp
= tcp_sk(sk
);
3128 inet_csk_schedule_ack(sk
);
3130 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3131 sock_set_flag(sk
, SOCK_DONE
);
3133 switch (sk
->sk_state
) {
3135 case TCP_ESTABLISHED
:
3136 /* Move to CLOSE_WAIT */
3137 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3138 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3141 case TCP_CLOSE_WAIT
:
3143 /* Received a retransmission of the FIN, do
3148 /* RFC793: Remain in the LAST-ACK state. */
3152 /* This case occurs when a simultaneous close
3153 * happens, we must ack the received FIN and
3154 * enter the CLOSING state.
3157 tcp_set_state(sk
, TCP_CLOSING
);
3160 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3162 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3165 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3166 * cases we should never reach this piece of code.
3168 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3169 __FUNCTION__
, sk
->sk_state
);
3173 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3174 * Probably, we should reset in this case. For now drop them.
3176 __skb_queue_purge(&tp
->out_of_order_queue
);
3177 if (tp
->rx_opt
.sack_ok
)
3178 tcp_sack_reset(&tp
->rx_opt
);
3179 sk_stream_mem_reclaim(sk
);
3181 if (!sock_flag(sk
, SOCK_DEAD
)) {
3182 sk
->sk_state_change(sk
);
3184 /* Do not send POLL_HUP for half duplex close. */
3185 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3186 sk
->sk_state
== TCP_CLOSE
)
3187 sk_wake_async(sk
, 1, POLL_HUP
);
3189 sk_wake_async(sk
, 1, POLL_IN
);
3193 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
3195 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3196 if (before(seq
, sp
->start_seq
))
3197 sp
->start_seq
= seq
;
3198 if (after(end_seq
, sp
->end_seq
))
3199 sp
->end_seq
= end_seq
;
3205 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3207 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3208 if (before(seq
, tp
->rcv_nxt
))
3209 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
3211 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
3213 tp
->rx_opt
.dsack
= 1;
3214 tp
->duplicate_sack
[0].start_seq
= seq
;
3215 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3216 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
3220 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3222 if (!tp
->rx_opt
.dsack
)
3223 tcp_dsack_set(tp
, seq
, end_seq
);
3225 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3228 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3230 struct tcp_sock
*tp
= tcp_sk(sk
);
3232 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3233 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3234 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3235 tcp_enter_quickack_mode(sk
);
3237 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3238 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3240 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3241 end_seq
= tp
->rcv_nxt
;
3242 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3249 /* These routines update the SACK block as out-of-order packets arrive or
3250 * in-order packets close up the sequence space.
3252 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3255 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3256 struct tcp_sack_block
*swalk
= sp
+1;
3258 /* See if the recent change to the first SACK eats into
3259 * or hits the sequence space of other SACK blocks, if so coalesce.
3261 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
3262 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3265 /* Zap SWALK, by moving every further SACK up by one slot.
3266 * Decrease num_sacks.
3268 tp
->rx_opt
.num_sacks
--;
3269 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3270 for (i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3274 this_sack
++, swalk
++;
3278 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
3282 tmp
= sack1
->start_seq
;
3283 sack1
->start_seq
= sack2
->start_seq
;
3284 sack2
->start_seq
= tmp
;
3286 tmp
= sack1
->end_seq
;
3287 sack1
->end_seq
= sack2
->end_seq
;
3288 sack2
->end_seq
= tmp
;
3291 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3293 struct tcp_sock
*tp
= tcp_sk(sk
);
3294 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3295 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3301 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
3302 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3303 /* Rotate this_sack to the first one. */
3304 for (; this_sack
>0; this_sack
--, sp
--)
3305 tcp_sack_swap(sp
, sp
-1);
3307 tcp_sack_maybe_coalesce(tp
);
3312 /* Could not find an adjacent existing SACK, build a new one,
3313 * put it at the front, and shift everyone else down. We
3314 * always know there is at least one SACK present already here.
3316 * If the sack array is full, forget about the last one.
3318 if (this_sack
>= 4) {
3320 tp
->rx_opt
.num_sacks
--;
3323 for (; this_sack
> 0; this_sack
--, sp
--)
3327 /* Build the new head SACK, and we're done. */
3328 sp
->start_seq
= seq
;
3329 sp
->end_seq
= end_seq
;
3330 tp
->rx_opt
.num_sacks
++;
3331 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3334 /* RCV.NXT advances, some SACKs should be eaten. */
3336 static void tcp_sack_remove(struct tcp_sock
*tp
)
3338 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3339 int num_sacks
= tp
->rx_opt
.num_sacks
;
3342 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3343 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3344 tp
->rx_opt
.num_sacks
= 0;
3345 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3349 for (this_sack
= 0; this_sack
< num_sacks
; ) {
3350 /* Check if the start of the sack is covered by RCV.NXT. */
3351 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3354 /* RCV.NXT must cover all the block! */
3355 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3357 /* Zap this SACK, by moving forward any other SACKS. */
3358 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3359 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3366 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3367 tp
->rx_opt
.num_sacks
= num_sacks
;
3368 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3372 /* This one checks to see if we can put data from the
3373 * out_of_order queue into the receive_queue.
3375 static void tcp_ofo_queue(struct sock
*sk
)
3377 struct tcp_sock
*tp
= tcp_sk(sk
);
3378 __u32 dsack_high
= tp
->rcv_nxt
;
3379 struct sk_buff
*skb
;
3381 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3382 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3385 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3386 __u32 dsack
= dsack_high
;
3387 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3388 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3389 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3392 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3393 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3394 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3398 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3399 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3400 TCP_SKB_CB(skb
)->end_seq
);
3402 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3403 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3404 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3405 if (tcp_hdr(skb
)->fin
)
3406 tcp_fin(skb
, sk
, tcp_hdr(skb
));
3410 static int tcp_prune_queue(struct sock
*sk
);
3412 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3414 struct tcphdr
*th
= tcp_hdr(skb
);
3415 struct tcp_sock
*tp
= tcp_sk(sk
);
3418 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3421 __skb_pull(skb
, th
->doff
*4);
3423 TCP_ECN_accept_cwr(tp
, skb
);
3425 if (tp
->rx_opt
.dsack
) {
3426 tp
->rx_opt
.dsack
= 0;
3427 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3428 4 - tp
->rx_opt
.tstamp_ok
);
3431 /* Queue data for delivery to the user.
3432 * Packets in sequence go to the receive queue.
3433 * Out of sequence packets to the out_of_order_queue.
3435 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3436 if (tcp_receive_window(tp
) == 0)
3439 /* Ok. In sequence. In window. */
3440 if (tp
->ucopy
.task
== current
&&
3441 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3442 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3443 int chunk
= min_t(unsigned int, skb
->len
,
3446 __set_current_state(TASK_RUNNING
);
3449 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3450 tp
->ucopy
.len
-= chunk
;
3451 tp
->copied_seq
+= chunk
;
3452 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3453 tcp_rcv_space_adjust(sk
);
3461 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3462 !sk_stream_rmem_schedule(sk
, skb
))) {
3463 if (tcp_prune_queue(sk
) < 0 ||
3464 !sk_stream_rmem_schedule(sk
, skb
))
3467 sk_stream_set_owner_r(skb
, sk
);
3468 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3470 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3472 tcp_event_data_recv(sk
, skb
);
3474 tcp_fin(skb
, sk
, th
);
3476 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3479 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3480 * gap in queue is filled.
3482 if (skb_queue_empty(&tp
->out_of_order_queue
))
3483 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3486 if (tp
->rx_opt
.num_sacks
)
3487 tcp_sack_remove(tp
);
3489 tcp_fast_path_check(sk
);
3493 else if (!sock_flag(sk
, SOCK_DEAD
))
3494 sk
->sk_data_ready(sk
, 0);
3498 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3499 /* A retransmit, 2nd most common case. Force an immediate ack. */
3500 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3501 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3504 tcp_enter_quickack_mode(sk
);
3505 inet_csk_schedule_ack(sk
);
3511 /* Out of window. F.e. zero window probe. */
3512 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3515 tcp_enter_quickack_mode(sk
);
3517 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3518 /* Partial packet, seq < rcv_next < end_seq */
3519 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3520 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3521 TCP_SKB_CB(skb
)->end_seq
);
3523 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3525 /* If window is closed, drop tail of packet. But after
3526 * remembering D-SACK for its head made in previous line.
3528 if (!tcp_receive_window(tp
))
3533 TCP_ECN_check_ce(tp
, skb
);
3535 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3536 !sk_stream_rmem_schedule(sk
, skb
)) {
3537 if (tcp_prune_queue(sk
) < 0 ||
3538 !sk_stream_rmem_schedule(sk
, skb
))
3542 /* Disable header prediction. */
3544 inet_csk_schedule_ack(sk
);
3546 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3547 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3549 sk_stream_set_owner_r(skb
, sk
);
3551 if (!skb_peek(&tp
->out_of_order_queue
)) {
3552 /* Initial out of order segment, build 1 SACK. */
3553 if (tp
->rx_opt
.sack_ok
) {
3554 tp
->rx_opt
.num_sacks
= 1;
3555 tp
->rx_opt
.dsack
= 0;
3556 tp
->rx_opt
.eff_sacks
= 1;
3557 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3558 tp
->selective_acks
[0].end_seq
=
3559 TCP_SKB_CB(skb
)->end_seq
;
3561 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3563 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3564 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3565 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3567 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3568 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3570 if (!tp
->rx_opt
.num_sacks
||
3571 tp
->selective_acks
[0].end_seq
!= seq
)
3574 /* Common case: data arrive in order after hole. */
3575 tp
->selective_acks
[0].end_seq
= end_seq
;
3579 /* Find place to insert this segment. */
3581 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3583 } while ((skb1
= skb1
->prev
) !=
3584 (struct sk_buff
*)&tp
->out_of_order_queue
);
3586 /* Do skb overlap to previous one? */
3587 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3588 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3589 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3590 /* All the bits are present. Drop. */
3592 tcp_dsack_set(tp
, seq
, end_seq
);
3595 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3596 /* Partial overlap. */
3597 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3602 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3604 /* And clean segments covered by new one as whole. */
3605 while ((skb1
= skb
->next
) !=
3606 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3607 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3608 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3609 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3612 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3613 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3618 if (tp
->rx_opt
.sack_ok
)
3619 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3623 /* Collapse contiguous sequence of skbs head..tail with
3624 * sequence numbers start..end.
3625 * Segments with FIN/SYN are not collapsed (only because this
3629 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3630 struct sk_buff
*head
, struct sk_buff
*tail
,
3633 struct sk_buff
*skb
;
3635 /* First, check that queue is collapsible and find
3636 * the point where collapsing can be useful. */
3637 for (skb
= head
; skb
!= tail
; ) {
3638 /* No new bits? It is possible on ofo queue. */
3639 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3640 struct sk_buff
*next
= skb
->next
;
3641 __skb_unlink(skb
, list
);
3643 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3648 /* The first skb to collapse is:
3650 * - bloated or contains data before "start" or
3651 * overlaps to the next one.
3653 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
3654 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3655 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3656 (skb
->next
!= tail
&&
3657 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3660 /* Decided to skip this, advance start seq. */
3661 start
= TCP_SKB_CB(skb
)->end_seq
;
3664 if (skb
== tail
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
3667 while (before(start
, end
)) {
3668 struct sk_buff
*nskb
;
3669 int header
= skb_headroom(skb
);
3670 int copy
= SKB_MAX_ORDER(header
, 0);
3672 /* Too big header? This can happen with IPv6. */
3675 if (end
-start
< copy
)
3677 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3681 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
3682 skb_set_network_header(nskb
, (skb_network_header(skb
) -
3684 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
3686 skb_reserve(nskb
, header
);
3687 memcpy(nskb
->head
, skb
->head
, header
);
3688 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3689 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3690 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3691 sk_stream_set_owner_r(nskb
, sk
);
3693 /* Copy data, releasing collapsed skbs. */
3695 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3696 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3700 size
= min(copy
, size
);
3701 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3703 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3707 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3708 struct sk_buff
*next
= skb
->next
;
3709 __skb_unlink(skb
, list
);
3711 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3714 tcp_hdr(skb
)->syn
||
3722 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3723 * and tcp_collapse() them until all the queue is collapsed.
3725 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3727 struct tcp_sock
*tp
= tcp_sk(sk
);
3728 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3729 struct sk_buff
*head
;
3735 start
= TCP_SKB_CB(skb
)->seq
;
3736 end
= TCP_SKB_CB(skb
)->end_seq
;
3742 /* Segment is terminated when we see gap or when
3743 * we are at the end of all the queue. */
3744 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3745 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3746 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3747 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3748 head
, skb
, start
, end
);
3750 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3752 /* Start new segment */
3753 start
= TCP_SKB_CB(skb
)->seq
;
3754 end
= TCP_SKB_CB(skb
)->end_seq
;
3756 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3757 start
= TCP_SKB_CB(skb
)->seq
;
3758 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3759 end
= TCP_SKB_CB(skb
)->end_seq
;
3764 /* Reduce allocated memory if we can, trying to get
3765 * the socket within its memory limits again.
3767 * Return less than zero if we should start dropping frames
3768 * until the socket owning process reads some of the data
3769 * to stabilize the situation.
3771 static int tcp_prune_queue(struct sock
*sk
)
3773 struct tcp_sock
*tp
= tcp_sk(sk
);
3775 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3777 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3779 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3780 tcp_clamp_window(sk
);
3781 else if (tcp_memory_pressure
)
3782 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3784 tcp_collapse_ofo_queue(sk
);
3785 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3786 sk
->sk_receive_queue
.next
,
3787 (struct sk_buff
*)&sk
->sk_receive_queue
,
3788 tp
->copied_seq
, tp
->rcv_nxt
);
3789 sk_stream_mem_reclaim(sk
);
3791 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3794 /* Collapsing did not help, destructive actions follow.
3795 * This must not ever occur. */
3797 /* First, purge the out_of_order queue. */
3798 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3799 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3800 __skb_queue_purge(&tp
->out_of_order_queue
);
3802 /* Reset SACK state. A conforming SACK implementation will
3803 * do the same at a timeout based retransmit. When a connection
3804 * is in a sad state like this, we care only about integrity
3805 * of the connection not performance.
3807 if (tp
->rx_opt
.sack_ok
)
3808 tcp_sack_reset(&tp
->rx_opt
);
3809 sk_stream_mem_reclaim(sk
);
3812 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3815 /* If we are really being abused, tell the caller to silently
3816 * drop receive data on the floor. It will get retransmitted
3817 * and hopefully then we'll have sufficient space.
3819 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
3821 /* Massive buffer overcommit. */
3827 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3828 * As additional protections, we do not touch cwnd in retransmission phases,
3829 * and if application hit its sndbuf limit recently.
3831 void tcp_cwnd_application_limited(struct sock
*sk
)
3833 struct tcp_sock
*tp
= tcp_sk(sk
);
3835 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
3836 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
3837 /* Limited by application or receiver window. */
3838 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
3839 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
3840 if (win_used
< tp
->snd_cwnd
) {
3841 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3842 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
3844 tp
->snd_cwnd_used
= 0;
3846 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3849 static int tcp_should_expand_sndbuf(struct sock
*sk
)
3851 struct tcp_sock
*tp
= tcp_sk(sk
);
3853 /* If the user specified a specific send buffer setting, do
3856 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
3859 /* If we are under global TCP memory pressure, do not expand. */
3860 if (tcp_memory_pressure
)
3863 /* If we are under soft global TCP memory pressure, do not expand. */
3864 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
3867 /* If we filled the congestion window, do not expand. */
3868 if (tp
->packets_out
>= tp
->snd_cwnd
)
3874 /* When incoming ACK allowed to free some skb from write_queue,
3875 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3876 * on the exit from tcp input handler.
3878 * PROBLEM: sndbuf expansion does not work well with largesend.
3880 static void tcp_new_space(struct sock
*sk
)
3882 struct tcp_sock
*tp
= tcp_sk(sk
);
3884 if (tcp_should_expand_sndbuf(sk
)) {
3885 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
3886 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
3887 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
3888 tp
->reordering
+ 1);
3889 sndmem
*= 2*demanded
;
3890 if (sndmem
> sk
->sk_sndbuf
)
3891 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
3892 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3895 sk
->sk_write_space(sk
);
3898 static void tcp_check_space(struct sock
*sk
)
3900 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
3901 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
3902 if (sk
->sk_socket
&&
3903 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
3908 static inline void tcp_data_snd_check(struct sock
*sk
)
3910 tcp_push_pending_frames(sk
);
3911 tcp_check_space(sk
);
3915 * Check if sending an ack is needed.
3917 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
3919 struct tcp_sock
*tp
= tcp_sk(sk
);
3921 /* More than one full frame received... */
3922 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
3923 /* ... and right edge of window advances far enough.
3924 * (tcp_recvmsg() will send ACK otherwise). Or...
3926 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
3927 /* We ACK each frame or... */
3928 tcp_in_quickack_mode(sk
) ||
3929 /* We have out of order data. */
3931 skb_peek(&tp
->out_of_order_queue
))) {
3932 /* Then ack it now */
3935 /* Else, send delayed ack. */
3936 tcp_send_delayed_ack(sk
);
3940 static inline void tcp_ack_snd_check(struct sock
*sk
)
3942 if (!inet_csk_ack_scheduled(sk
)) {
3943 /* We sent a data segment already. */
3946 __tcp_ack_snd_check(sk
, 1);
3950 * This routine is only called when we have urgent data
3951 * signaled. Its the 'slow' part of tcp_urg. It could be
3952 * moved inline now as tcp_urg is only called from one
3953 * place. We handle URGent data wrong. We have to - as
3954 * BSD still doesn't use the correction from RFC961.
3955 * For 1003.1g we should support a new option TCP_STDURG to permit
3956 * either form (or just set the sysctl tcp_stdurg).
3959 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
3961 struct tcp_sock
*tp
= tcp_sk(sk
);
3962 u32 ptr
= ntohs(th
->urg_ptr
);
3964 if (ptr
&& !sysctl_tcp_stdurg
)
3966 ptr
+= ntohl(th
->seq
);
3968 /* Ignore urgent data that we've already seen and read. */
3969 if (after(tp
->copied_seq
, ptr
))
3972 /* Do not replay urg ptr.
3974 * NOTE: interesting situation not covered by specs.
3975 * Misbehaving sender may send urg ptr, pointing to segment,
3976 * which we already have in ofo queue. We are not able to fetch
3977 * such data and will stay in TCP_URG_NOTYET until will be eaten
3978 * by recvmsg(). Seems, we are not obliged to handle such wicked
3979 * situations. But it is worth to think about possibility of some
3980 * DoSes using some hypothetical application level deadlock.
3982 if (before(ptr
, tp
->rcv_nxt
))
3985 /* Do we already have a newer (or duplicate) urgent pointer? */
3986 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
3989 /* Tell the world about our new urgent pointer. */
3992 /* We may be adding urgent data when the last byte read was
3993 * urgent. To do this requires some care. We cannot just ignore
3994 * tp->copied_seq since we would read the last urgent byte again
3995 * as data, nor can we alter copied_seq until this data arrives
3996 * or we break the semantics of SIOCATMARK (and thus sockatmark())
3998 * NOTE. Double Dutch. Rendering to plain English: author of comment
3999 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4000 * and expect that both A and B disappear from stream. This is _wrong_.
4001 * Though this happens in BSD with high probability, this is occasional.
4002 * Any application relying on this is buggy. Note also, that fix "works"
4003 * only in this artificial test. Insert some normal data between A and B and we will
4004 * decline of BSD again. Verdict: it is better to remove to trap
4007 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4008 !sock_flag(sk
, SOCK_URGINLINE
) &&
4009 tp
->copied_seq
!= tp
->rcv_nxt
) {
4010 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4012 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4013 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4018 tp
->urg_data
= TCP_URG_NOTYET
;
4021 /* Disable header prediction. */
4025 /* This is the 'fast' part of urgent handling. */
4026 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
4028 struct tcp_sock
*tp
= tcp_sk(sk
);
4030 /* Check if we get a new urgent pointer - normally not. */
4032 tcp_check_urg(sk
,th
);
4034 /* Do we wait for any urgent data? - normally not... */
4035 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4036 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4039 /* Is the urgent pointer pointing into this packet? */
4040 if (ptr
< skb
->len
) {
4042 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4044 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4045 if (!sock_flag(sk
, SOCK_DEAD
))
4046 sk
->sk_data_ready(sk
, 0);
4051 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4053 struct tcp_sock
*tp
= tcp_sk(sk
);
4054 int chunk
= skb
->len
- hlen
;
4058 if (skb_csum_unnecessary(skb
))
4059 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4061 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4065 tp
->ucopy
.len
-= chunk
;
4066 tp
->copied_seq
+= chunk
;
4067 tcp_rcv_space_adjust(sk
);
4074 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4078 if (sock_owned_by_user(sk
)) {
4080 result
= __tcp_checksum_complete(skb
);
4083 result
= __tcp_checksum_complete(skb
);
4088 static inline int tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4090 return !skb_csum_unnecessary(skb
) &&
4091 __tcp_checksum_complete_user(sk
, skb
);
4094 #ifdef CONFIG_NET_DMA
4095 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4097 struct tcp_sock
*tp
= tcp_sk(sk
);
4098 int chunk
= skb
->len
- hlen
;
4100 int copied_early
= 0;
4102 if (tp
->ucopy
.wakeup
)
4105 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4106 tp
->ucopy
.dma_chan
= get_softnet_dma();
4108 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4110 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4111 skb
, hlen
, tp
->ucopy
.iov
, chunk
, tp
->ucopy
.pinned_list
);
4116 tp
->ucopy
.dma_cookie
= dma_cookie
;
4119 tp
->ucopy
.len
-= chunk
;
4120 tp
->copied_seq
+= chunk
;
4121 tcp_rcv_space_adjust(sk
);
4123 if ((tp
->ucopy
.len
== 0) ||
4124 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
4125 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4126 tp
->ucopy
.wakeup
= 1;
4127 sk
->sk_data_ready(sk
, 0);
4129 } else if (chunk
> 0) {
4130 tp
->ucopy
.wakeup
= 1;
4131 sk
->sk_data_ready(sk
, 0);
4134 return copied_early
;
4136 #endif /* CONFIG_NET_DMA */
4139 * TCP receive function for the ESTABLISHED state.
4141 * It is split into a fast path and a slow path. The fast path is
4143 * - A zero window was announced from us - zero window probing
4144 * is only handled properly in the slow path.
4145 * - Out of order segments arrived.
4146 * - Urgent data is expected.
4147 * - There is no buffer space left
4148 * - Unexpected TCP flags/window values/header lengths are received
4149 * (detected by checking the TCP header against pred_flags)
4150 * - Data is sent in both directions. Fast path only supports pure senders
4151 * or pure receivers (this means either the sequence number or the ack
4152 * value must stay constant)
4153 * - Unexpected TCP option.
4155 * When these conditions are not satisfied it drops into a standard
4156 * receive procedure patterned after RFC793 to handle all cases.
4157 * The first three cases are guaranteed by proper pred_flags setting,
4158 * the rest is checked inline. Fast processing is turned on in
4159 * tcp_data_queue when everything is OK.
4161 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4162 struct tcphdr
*th
, unsigned len
)
4164 struct tcp_sock
*tp
= tcp_sk(sk
);
4167 * Header prediction.
4168 * The code loosely follows the one in the famous
4169 * "30 instruction TCP receive" Van Jacobson mail.
4171 * Van's trick is to deposit buffers into socket queue
4172 * on a device interrupt, to call tcp_recv function
4173 * on the receive process context and checksum and copy
4174 * the buffer to user space. smart...
4176 * Our current scheme is not silly either but we take the
4177 * extra cost of the net_bh soft interrupt processing...
4178 * We do checksum and copy also but from device to kernel.
4181 tp
->rx_opt
.saw_tstamp
= 0;
4183 /* pred_flags is 0xS?10 << 16 + snd_wnd
4184 * if header_prediction is to be made
4185 * 'S' will always be tp->tcp_header_len >> 2
4186 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4187 * turn it off (when there are holes in the receive
4188 * space for instance)
4189 * PSH flag is ignored.
4192 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4193 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4194 int tcp_header_len
= tp
->tcp_header_len
;
4196 /* Timestamp header prediction: tcp_header_len
4197 * is automatically equal to th->doff*4 due to pred_flags
4201 /* Check timestamp */
4202 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4203 __be32
*ptr
= (__be32
*)(th
+ 1);
4205 /* No? Slow path! */
4206 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4207 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4210 tp
->rx_opt
.saw_tstamp
= 1;
4212 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4214 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4216 /* If PAWS failed, check it more carefully in slow path */
4217 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4220 /* DO NOT update ts_recent here, if checksum fails
4221 * and timestamp was corrupted part, it will result
4222 * in a hung connection since we will drop all
4223 * future packets due to the PAWS test.
4227 if (len
<= tcp_header_len
) {
4228 /* Bulk data transfer: sender */
4229 if (len
== tcp_header_len
) {
4230 /* Predicted packet is in window by definition.
4231 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4232 * Hence, check seq<=rcv_wup reduces to:
4234 if (tcp_header_len
==
4235 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4236 tp
->rcv_nxt
== tp
->rcv_wup
)
4237 tcp_store_ts_recent(tp
);
4239 /* We know that such packets are checksummed
4242 tcp_ack(sk
, skb
, 0);
4244 tcp_data_snd_check(sk
);
4246 } else { /* Header too small */
4247 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4252 int copied_early
= 0;
4254 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4255 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4256 #ifdef CONFIG_NET_DMA
4257 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4262 if (tp
->ucopy
.task
== current
&& sock_owned_by_user(sk
) && !copied_early
) {
4263 __set_current_state(TASK_RUNNING
);
4265 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4269 /* Predicted packet is in window by definition.
4270 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4271 * Hence, check seq<=rcv_wup reduces to:
4273 if (tcp_header_len
==
4274 (sizeof(struct tcphdr
) +
4275 TCPOLEN_TSTAMP_ALIGNED
) &&
4276 tp
->rcv_nxt
== tp
->rcv_wup
)
4277 tcp_store_ts_recent(tp
);
4279 tcp_rcv_rtt_measure_ts(sk
, skb
);
4281 __skb_pull(skb
, tcp_header_len
);
4282 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4283 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4286 tcp_cleanup_rbuf(sk
, skb
->len
);
4289 if (tcp_checksum_complete_user(sk
, skb
))
4292 /* Predicted packet is in window by definition.
4293 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4294 * Hence, check seq<=rcv_wup reduces to:
4296 if (tcp_header_len
==
4297 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4298 tp
->rcv_nxt
== tp
->rcv_wup
)
4299 tcp_store_ts_recent(tp
);
4301 tcp_rcv_rtt_measure_ts(sk
, skb
);
4303 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4306 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4308 /* Bulk data transfer: receiver */
4309 __skb_pull(skb
,tcp_header_len
);
4310 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4311 sk_stream_set_owner_r(skb
, sk
);
4312 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4315 tcp_event_data_recv(sk
, skb
);
4317 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4318 /* Well, only one small jumplet in fast path... */
4319 tcp_ack(sk
, skb
, FLAG_DATA
);
4320 tcp_data_snd_check(sk
);
4321 if (!inet_csk_ack_scheduled(sk
))
4325 __tcp_ack_snd_check(sk
, 0);
4327 #ifdef CONFIG_NET_DMA
4329 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4335 sk
->sk_data_ready(sk
, 0);
4341 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
4345 * RFC1323: H1. Apply PAWS check first.
4347 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4348 tcp_paws_discard(sk
, skb
)) {
4350 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4351 tcp_send_dupack(sk
, skb
);
4354 /* Resets are accepted even if PAWS failed.
4356 ts_recent update must be made after we are sure
4357 that the packet is in window.
4362 * Standard slow path.
4365 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4366 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4367 * (RST) segments are validated by checking their SEQ-fields."
4368 * And page 69: "If an incoming segment is not acceptable,
4369 * an acknowledgment should be sent in reply (unless the RST bit
4370 * is set, if so drop the segment and return)".
4373 tcp_send_dupack(sk
, skb
);
4382 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4384 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4385 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4386 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4393 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4395 tcp_rcv_rtt_measure_ts(sk
, skb
);
4397 /* Process urgent data. */
4398 tcp_urg(sk
, skb
, th
);
4400 /* step 7: process the segment text */
4401 tcp_data_queue(sk
, skb
);
4403 tcp_data_snd_check(sk
);
4404 tcp_ack_snd_check(sk
);
4408 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4415 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4416 struct tcphdr
*th
, unsigned len
)
4418 struct tcp_sock
*tp
= tcp_sk(sk
);
4419 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4420 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4422 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4426 * "If the state is SYN-SENT then
4427 * first check the ACK bit
4428 * If the ACK bit is set
4429 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4430 * a reset (unless the RST bit is set, if so drop
4431 * the segment and return)"
4433 * We do not send data with SYN, so that RFC-correct
4436 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4437 goto reset_and_undo
;
4439 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4440 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4442 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4443 goto reset_and_undo
;
4446 /* Now ACK is acceptable.
4448 * "If the RST bit is set
4449 * If the ACK was acceptable then signal the user "error:
4450 * connection reset", drop the segment, enter CLOSED state,
4451 * delete TCB, and return."
4460 * "fifth, if neither of the SYN or RST bits is set then
4461 * drop the segment and return."
4467 goto discard_and_undo
;
4470 * "If the SYN bit is on ...
4471 * are acceptable then ...
4472 * (our SYN has been ACKed), change the connection
4473 * state to ESTABLISHED..."
4476 TCP_ECN_rcv_synack(tp
, th
);
4478 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4479 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4481 /* Ok.. it's good. Set up sequence numbers and
4482 * move to established.
4484 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4485 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4487 /* RFC1323: The window in SYN & SYN/ACK segments is
4490 tp
->snd_wnd
= ntohs(th
->window
);
4491 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4493 if (!tp
->rx_opt
.wscale_ok
) {
4494 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4495 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4498 if (tp
->rx_opt
.saw_tstamp
) {
4499 tp
->rx_opt
.tstamp_ok
= 1;
4500 tp
->tcp_header_len
=
4501 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4502 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4503 tcp_store_ts_recent(tp
);
4505 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4508 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_fack
)
4509 tp
->rx_opt
.sack_ok
|= 2;
4512 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4513 tcp_initialize_rcv_mss(sk
);
4515 /* Remember, tcp_poll() does not lock socket!
4516 * Change state from SYN-SENT only after copied_seq
4517 * is initialized. */
4518 tp
->copied_seq
= tp
->rcv_nxt
;
4520 tcp_set_state(sk
, TCP_ESTABLISHED
);
4522 security_inet_conn_established(sk
, skb
);
4524 /* Make sure socket is routed, for correct metrics. */
4525 icsk
->icsk_af_ops
->rebuild_header(sk
);
4527 tcp_init_metrics(sk
);
4529 tcp_init_congestion_control(sk
);
4531 /* Prevent spurious tcp_cwnd_restart() on first data
4534 tp
->lsndtime
= tcp_time_stamp
;
4536 tcp_init_buffer_space(sk
);
4538 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4539 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4541 if (!tp
->rx_opt
.snd_wscale
)
4542 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4546 if (!sock_flag(sk
, SOCK_DEAD
)) {
4547 sk
->sk_state_change(sk
);
4548 sk_wake_async(sk
, 0, POLL_OUT
);
4551 if (sk
->sk_write_pending
||
4552 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4553 icsk
->icsk_ack
.pingpong
) {
4554 /* Save one ACK. Data will be ready after
4555 * several ticks, if write_pending is set.
4557 * It may be deleted, but with this feature tcpdumps
4558 * look so _wonderfully_ clever, that I was not able
4559 * to stand against the temptation 8) --ANK
4561 inet_csk_schedule_ack(sk
);
4562 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4563 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4564 tcp_incr_quickack(sk
);
4565 tcp_enter_quickack_mode(sk
);
4566 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4567 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4578 /* No ACK in the segment */
4582 * "If the RST bit is set
4584 * Otherwise (no ACK) drop the segment and return."
4587 goto discard_and_undo
;
4591 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4592 goto discard_and_undo
;
4595 /* We see SYN without ACK. It is attempt of
4596 * simultaneous connect with crossed SYNs.
4597 * Particularly, it can be connect to self.
4599 tcp_set_state(sk
, TCP_SYN_RECV
);
4601 if (tp
->rx_opt
.saw_tstamp
) {
4602 tp
->rx_opt
.tstamp_ok
= 1;
4603 tcp_store_ts_recent(tp
);
4604 tp
->tcp_header_len
=
4605 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4607 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4610 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4611 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4613 /* RFC1323: The window in SYN & SYN/ACK segments is
4616 tp
->snd_wnd
= ntohs(th
->window
);
4617 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4618 tp
->max_window
= tp
->snd_wnd
;
4620 TCP_ECN_rcv_syn(tp
, th
);
4623 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4624 tcp_initialize_rcv_mss(sk
);
4627 tcp_send_synack(sk
);
4629 /* Note, we could accept data and URG from this segment.
4630 * There are no obstacles to make this.
4632 * However, if we ignore data in ACKless segments sometimes,
4633 * we have no reasons to accept it sometimes.
4634 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4635 * is not flawless. So, discard packet for sanity.
4636 * Uncomment this return to process the data.
4643 /* "fifth, if neither of the SYN or RST bits is set then
4644 * drop the segment and return."
4648 tcp_clear_options(&tp
->rx_opt
);
4649 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4653 tcp_clear_options(&tp
->rx_opt
);
4654 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4660 * This function implements the receiving procedure of RFC 793 for
4661 * all states except ESTABLISHED and TIME_WAIT.
4662 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4663 * address independent.
4666 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4667 struct tcphdr
*th
, unsigned len
)
4669 struct tcp_sock
*tp
= tcp_sk(sk
);
4670 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4673 tp
->rx_opt
.saw_tstamp
= 0;
4675 switch (sk
->sk_state
) {
4687 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
4690 /* Now we have several options: In theory there is
4691 * nothing else in the frame. KA9Q has an option to
4692 * send data with the syn, BSD accepts data with the
4693 * syn up to the [to be] advertised window and
4694 * Solaris 2.1 gives you a protocol error. For now
4695 * we just ignore it, that fits the spec precisely
4696 * and avoids incompatibilities. It would be nice in
4697 * future to drop through and process the data.
4699 * Now that TTCP is starting to be used we ought to
4701 * But, this leaves one open to an easy denial of
4702 * service attack, and SYN cookies can't defend
4703 * against this problem. So, we drop the data
4704 * in the interest of security over speed unless
4705 * it's still in use.
4713 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4717 /* Do step6 onward by hand. */
4718 tcp_urg(sk
, skb
, th
);
4720 tcp_data_snd_check(sk
);
4724 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4725 tcp_paws_discard(sk
, skb
)) {
4727 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4728 tcp_send_dupack(sk
, skb
);
4731 /* Reset is accepted even if it did not pass PAWS. */
4734 /* step 1: check sequence number */
4735 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4737 tcp_send_dupack(sk
, skb
);
4741 /* step 2: check RST bit */
4747 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4749 /* step 3: check security and precedence [ignored] */
4753 * Check for a SYN in window.
4755 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4756 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4761 /* step 5: check the ACK field */
4763 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4765 switch (sk
->sk_state
) {
4768 tp
->copied_seq
= tp
->rcv_nxt
;
4770 tcp_set_state(sk
, TCP_ESTABLISHED
);
4771 sk
->sk_state_change(sk
);
4773 /* Note, that this wakeup is only for marginal
4774 * crossed SYN case. Passively open sockets
4775 * are not waked up, because sk->sk_sleep ==
4776 * NULL and sk->sk_socket == NULL.
4778 if (sk
->sk_socket
) {
4779 sk_wake_async(sk
,0,POLL_OUT
);
4782 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4783 tp
->snd_wnd
= ntohs(th
->window
) <<
4784 tp
->rx_opt
.snd_wscale
;
4785 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4786 TCP_SKB_CB(skb
)->seq
);
4788 /* tcp_ack considers this ACK as duplicate
4789 * and does not calculate rtt.
4790 * Fix it at least with timestamps.
4792 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4794 tcp_ack_saw_tstamp(sk
, 0);
4796 if (tp
->rx_opt
.tstamp_ok
)
4797 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4799 /* Make sure socket is routed, for
4802 icsk
->icsk_af_ops
->rebuild_header(sk
);
4804 tcp_init_metrics(sk
);
4806 tcp_init_congestion_control(sk
);
4808 /* Prevent spurious tcp_cwnd_restart() on
4809 * first data packet.
4811 tp
->lsndtime
= tcp_time_stamp
;
4814 tcp_initialize_rcv_mss(sk
);
4815 tcp_init_buffer_space(sk
);
4816 tcp_fast_path_on(tp
);
4823 if (tp
->snd_una
== tp
->write_seq
) {
4824 tcp_set_state(sk
, TCP_FIN_WAIT2
);
4825 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
4826 dst_confirm(sk
->sk_dst_cache
);
4828 if (!sock_flag(sk
, SOCK_DEAD
))
4829 /* Wake up lingering close() */
4830 sk
->sk_state_change(sk
);
4834 if (tp
->linger2
< 0 ||
4835 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4836 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
4838 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4842 tmo
= tcp_fin_time(sk
);
4843 if (tmo
> TCP_TIMEWAIT_LEN
) {
4844 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
4845 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
4846 /* Bad case. We could lose such FIN otherwise.
4847 * It is not a big problem, but it looks confusing
4848 * and not so rare event. We still can lose it now,
4849 * if it spins in bh_lock_sock(), but it is really
4852 inet_csk_reset_keepalive_timer(sk
, tmo
);
4854 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
4862 if (tp
->snd_una
== tp
->write_seq
) {
4863 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4869 if (tp
->snd_una
== tp
->write_seq
) {
4870 tcp_update_metrics(sk
);
4879 /* step 6: check the URG bit */
4880 tcp_urg(sk
, skb
, th
);
4882 /* step 7: process the segment text */
4883 switch (sk
->sk_state
) {
4884 case TCP_CLOSE_WAIT
:
4887 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4891 /* RFC 793 says to queue data in these states,
4892 * RFC 1122 says we MUST send a reset.
4893 * BSD 4.4 also does reset.
4895 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
4896 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4897 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
4898 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4904 case TCP_ESTABLISHED
:
4905 tcp_data_queue(sk
, skb
);
4910 /* tcp_data could move socket to TIME-WAIT */
4911 if (sk
->sk_state
!= TCP_CLOSE
) {
4912 tcp_data_snd_check(sk
);
4913 tcp_ack_snd_check(sk
);
4923 EXPORT_SYMBOL(sysctl_tcp_ecn
);
4924 EXPORT_SYMBOL(sysctl_tcp_reordering
);
4925 EXPORT_SYMBOL(tcp_parse_options
);
4926 EXPORT_SYMBOL(tcp_rcv_established
);
4927 EXPORT_SYMBOL(tcp_rcv_state_process
);
4928 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);