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
66 #include <linux/config.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
71 #include <net/inet_common.h>
72 #include <linux/ipsec.h>
73 #include <asm/unaligned.h>
75 int sysctl_tcp_timestamps
= 1;
76 int sysctl_tcp_window_scaling
= 1;
77 int sysctl_tcp_sack
= 1;
78 int sysctl_tcp_fack
= 1;
79 int sysctl_tcp_reordering
= TCP_FASTRETRANS_THRESH
;
81 int sysctl_tcp_dsack
= 1;
82 int sysctl_tcp_app_win
= 31;
83 int sysctl_tcp_adv_win_scale
= 2;
85 int sysctl_tcp_stdurg
;
86 int sysctl_tcp_rfc1337
;
87 int sysctl_tcp_max_orphans
= NR_FILE
;
89 int sysctl_tcp_nometrics_save
;
91 int sysctl_tcp_moderate_rcvbuf
= 1;
92 int sysctl_tcp_abc
= 1;
94 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
95 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
96 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
98 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
99 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
100 #define FLAG_ECE 0x40 /* ECE in this ACK */
101 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
102 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
105 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
106 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
107 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
109 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
110 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
111 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
113 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
115 /* Adapt the MSS value used to make delayed ack decision to the
118 static inline void tcp_measure_rcv_mss(struct sock
*sk
,
119 const struct sk_buff
*skb
)
121 struct inet_connection_sock
*icsk
= inet_csk(sk
);
122 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
125 icsk
->icsk_ack
.last_seg_size
= 0;
127 /* skb->len may jitter because of SACKs, even if peer
128 * sends good full-sized frames.
131 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
132 icsk
->icsk_ack
.rcv_mss
= len
;
134 /* Otherwise, we make more careful check taking into account,
135 * that SACKs block is variable.
137 * "len" is invariant segment length, including TCP header.
139 len
+= skb
->data
- skb
->h
.raw
;
140 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
141 /* If PSH is not set, packet should be
142 * full sized, provided peer TCP is not badly broken.
143 * This observation (if it is correct 8)) allows
144 * to handle super-low mtu links fairly.
146 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
147 !(tcp_flag_word(skb
->h
.th
)&TCP_REMNANT
))) {
148 /* Subtract also invariant (if peer is RFC compliant),
149 * tcp header plus fixed timestamp option length.
150 * Resulting "len" is MSS free of SACK jitter.
152 len
-= tcp_sk(sk
)->tcp_header_len
;
153 icsk
->icsk_ack
.last_seg_size
= len
;
155 icsk
->icsk_ack
.rcv_mss
= len
;
159 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
163 static void tcp_incr_quickack(struct sock
*sk
)
165 struct inet_connection_sock
*icsk
= inet_csk(sk
);
166 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
170 if (quickacks
> icsk
->icsk_ack
.quick
)
171 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
174 void tcp_enter_quickack_mode(struct sock
*sk
)
176 struct inet_connection_sock
*icsk
= inet_csk(sk
);
177 tcp_incr_quickack(sk
);
178 icsk
->icsk_ack
.pingpong
= 0;
179 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
182 /* Send ACKs quickly, if "quick" count is not exhausted
183 * and the session is not interactive.
186 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
188 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
189 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
192 /* Buffer size and advertised window tuning.
194 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
197 static void tcp_fixup_sndbuf(struct sock
*sk
)
199 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
200 sizeof(struct sk_buff
);
202 if (sk
->sk_sndbuf
< 3 * sndmem
)
203 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
206 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
208 * All tcp_full_space() is split to two parts: "network" buffer, allocated
209 * forward and advertised in receiver window (tp->rcv_wnd) and
210 * "application buffer", required to isolate scheduling/application
211 * latencies from network.
212 * window_clamp is maximal advertised window. It can be less than
213 * tcp_full_space(), in this case tcp_full_space() - window_clamp
214 * is reserved for "application" buffer. The less window_clamp is
215 * the smoother our behaviour from viewpoint of network, but the lower
216 * throughput and the higher sensitivity of the connection to losses. 8)
218 * rcv_ssthresh is more strict window_clamp used at "slow start"
219 * phase to predict further behaviour of this connection.
220 * It is used for two goals:
221 * - to enforce header prediction at sender, even when application
222 * requires some significant "application buffer". It is check #1.
223 * - to prevent pruning of receive queue because of misprediction
224 * of receiver window. Check #2.
226 * The scheme does not work when sender sends good segments opening
227 * window and then starts to feed us spaghetti. But it should work
228 * in common situations. Otherwise, we have to rely on queue collapsing.
231 /* Slow part of check#2. */
232 static int __tcp_grow_window(const struct sock
*sk
, struct tcp_sock
*tp
,
233 const struct sk_buff
*skb
)
236 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
237 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
239 while (tp
->rcv_ssthresh
<= window
) {
240 if (truesize
<= skb
->len
)
241 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
249 static inline void tcp_grow_window(struct sock
*sk
, struct tcp_sock
*tp
,
253 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
254 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
255 !tcp_memory_pressure
) {
258 /* Check #2. Increase window, if skb with such overhead
259 * will fit to rcvbuf in future.
261 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
264 incr
= __tcp_grow_window(sk
, tp
, skb
);
267 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
268 inet_csk(sk
)->icsk_ack
.quick
|= 1;
273 /* 3. Tuning rcvbuf, when connection enters established state. */
275 static void tcp_fixup_rcvbuf(struct sock
*sk
)
277 struct tcp_sock
*tp
= tcp_sk(sk
);
278 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
280 /* Try to select rcvbuf so that 4 mss-sized segments
281 * will fit to window and corresponding skbs will fit to our rcvbuf.
282 * (was 3; 4 is minimum to allow fast retransmit to work.)
284 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
286 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
287 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
290 /* 4. Try to fixup all. It is made immediately after connection enters
293 static void tcp_init_buffer_space(struct sock
*sk
)
295 struct tcp_sock
*tp
= tcp_sk(sk
);
298 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
299 tcp_fixup_rcvbuf(sk
);
300 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
301 tcp_fixup_sndbuf(sk
);
303 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
305 maxwin
= tcp_full_space(sk
);
307 if (tp
->window_clamp
>= maxwin
) {
308 tp
->window_clamp
= maxwin
;
310 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
311 tp
->window_clamp
= max(maxwin
-
312 (maxwin
>> sysctl_tcp_app_win
),
316 /* Force reservation of one segment. */
317 if (sysctl_tcp_app_win
&&
318 tp
->window_clamp
> 2 * tp
->advmss
&&
319 tp
->window_clamp
+ tp
->advmss
> maxwin
)
320 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
322 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
323 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
326 /* 5. Recalculate window clamp after socket hit its memory bounds. */
327 static void tcp_clamp_window(struct sock
*sk
, struct tcp_sock
*tp
)
329 struct inet_connection_sock
*icsk
= inet_csk(sk
);
331 icsk
->icsk_ack
.quick
= 0;
333 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
334 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
335 !tcp_memory_pressure
&&
336 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
337 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
340 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
341 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
344 /* Receiver "autotuning" code.
346 * The algorithm for RTT estimation w/o timestamps is based on
347 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
348 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
350 * More detail on this code can be found at
351 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
352 * though this reference is out of date. A new paper
355 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
357 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
363 if (new_sample
!= 0) {
364 /* If we sample in larger samples in the non-timestamp
365 * case, we could grossly overestimate the RTT especially
366 * with chatty applications or bulk transfer apps which
367 * are stalled on filesystem I/O.
369 * Also, since we are only going for a minimum in the
370 * non-timestamp case, we do not smoother things out
371 * else with timestamps disabled convergence takes too
375 m
-= (new_sample
>> 3);
377 } else if (m
< new_sample
)
380 /* No previous measure. */
384 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
385 tp
->rcv_rtt_est
.rtt
= new_sample
;
388 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
390 if (tp
->rcv_rtt_est
.time
== 0)
392 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
394 tcp_rcv_rtt_update(tp
,
395 jiffies
- tp
->rcv_rtt_est
.time
,
399 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
400 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
403 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
405 struct tcp_sock
*tp
= tcp_sk(sk
);
406 if (tp
->rx_opt
.rcv_tsecr
&&
407 (TCP_SKB_CB(skb
)->end_seq
-
408 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
409 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
413 * This function should be called every time data is copied to user space.
414 * It calculates the appropriate TCP receive buffer space.
416 void tcp_rcv_space_adjust(struct sock
*sk
)
418 struct tcp_sock
*tp
= tcp_sk(sk
);
422 if (tp
->rcvq_space
.time
== 0)
425 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
426 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
427 tp
->rcv_rtt_est
.rtt
== 0)
430 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
432 space
= max(tp
->rcvq_space
.space
, space
);
434 if (tp
->rcvq_space
.space
!= space
) {
437 tp
->rcvq_space
.space
= space
;
439 if (sysctl_tcp_moderate_rcvbuf
) {
440 int new_clamp
= space
;
442 /* Receive space grows, normalize in order to
443 * take into account packet headers and sk_buff
444 * structure overhead.
449 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
450 16 + sizeof(struct sk_buff
));
451 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
454 space
= min(space
, sysctl_tcp_rmem
[2]);
455 if (space
> sk
->sk_rcvbuf
) {
456 sk
->sk_rcvbuf
= space
;
458 /* Make the window clamp follow along. */
459 tp
->window_clamp
= new_clamp
;
465 tp
->rcvq_space
.seq
= tp
->copied_seq
;
466 tp
->rcvq_space
.time
= tcp_time_stamp
;
469 /* There is something which you must keep in mind when you analyze the
470 * behavior of the tp->ato delayed ack timeout interval. When a
471 * connection starts up, we want to ack as quickly as possible. The
472 * problem is that "good" TCP's do slow start at the beginning of data
473 * transmission. The means that until we send the first few ACK's the
474 * sender will sit on his end and only queue most of his data, because
475 * he can only send snd_cwnd unacked packets at any given time. For
476 * each ACK we send, he increments snd_cwnd and transmits more of his
479 static void tcp_event_data_recv(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
481 struct inet_connection_sock
*icsk
= inet_csk(sk
);
484 inet_csk_schedule_ack(sk
);
486 tcp_measure_rcv_mss(sk
, skb
);
488 tcp_rcv_rtt_measure(tp
);
490 now
= tcp_time_stamp
;
492 if (!icsk
->icsk_ack
.ato
) {
493 /* The _first_ data packet received, initialize
494 * delayed ACK engine.
496 tcp_incr_quickack(sk
);
497 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
499 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
501 if (m
<= TCP_ATO_MIN
/2) {
502 /* The fastest case is the first. */
503 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
504 } else if (m
< icsk
->icsk_ack
.ato
) {
505 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
506 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
507 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
508 } else if (m
> icsk
->icsk_rto
) {
509 /* Too long gap. Apparently sender failed to
510 * restart window, so that we send ACKs quickly.
512 tcp_incr_quickack(sk
);
513 sk_stream_mem_reclaim(sk
);
516 icsk
->icsk_ack
.lrcvtime
= now
;
518 TCP_ECN_check_ce(tp
, skb
);
521 tcp_grow_window(sk
, tp
, skb
);
524 /* Called to compute a smoothed rtt estimate. The data fed to this
525 * routine either comes from timestamps, or from segments that were
526 * known _not_ to have been retransmitted [see Karn/Partridge
527 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
528 * piece by Van Jacobson.
529 * NOTE: the next three routines used to be one big routine.
530 * To save cycles in the RFC 1323 implementation it was better to break
531 * it up into three procedures. -- erics
533 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
535 struct tcp_sock
*tp
= tcp_sk(sk
);
536 long m
= mrtt
; /* RTT */
538 /* The following amusing code comes from Jacobson's
539 * article in SIGCOMM '88. Note that rtt and mdev
540 * are scaled versions of rtt and mean deviation.
541 * This is designed to be as fast as possible
542 * m stands for "measurement".
544 * On a 1990 paper the rto value is changed to:
545 * RTO = rtt + 4 * mdev
547 * Funny. This algorithm seems to be very broken.
548 * These formulae increase RTO, when it should be decreased, increase
549 * too slowly, when it should be increased fastly, decrease too fastly
550 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
551 * does not matter how to _calculate_ it. Seems, it was trap
552 * that VJ failed to avoid. 8)
557 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
558 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
560 m
= -m
; /* m is now abs(error) */
561 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
562 /* This is similar to one of Eifel findings.
563 * Eifel blocks mdev updates when rtt decreases.
564 * This solution is a bit different: we use finer gain
565 * for mdev in this case (alpha*beta).
566 * Like Eifel it also prevents growth of rto,
567 * but also it limits too fast rto decreases,
568 * happening in pure Eifel.
573 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
575 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
576 if (tp
->mdev
> tp
->mdev_max
) {
577 tp
->mdev_max
= tp
->mdev
;
578 if (tp
->mdev_max
> tp
->rttvar
)
579 tp
->rttvar
= tp
->mdev_max
;
581 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
582 if (tp
->mdev_max
< tp
->rttvar
)
583 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
584 tp
->rtt_seq
= tp
->snd_nxt
;
585 tp
->mdev_max
= TCP_RTO_MIN
;
588 /* no previous measure. */
589 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
590 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
591 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
592 tp
->rtt_seq
= tp
->snd_nxt
;
596 /* Calculate rto without backoff. This is the second half of Van Jacobson's
597 * routine referred to above.
599 static inline void tcp_set_rto(struct sock
*sk
)
601 const struct tcp_sock
*tp
= tcp_sk(sk
);
602 /* Old crap is replaced with new one. 8)
605 * 1. If rtt variance happened to be less 50msec, it is hallucination.
606 * It cannot be less due to utterly erratic ACK generation made
607 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
608 * to do with delayed acks, because at cwnd>2 true delack timeout
609 * is invisible. Actually, Linux-2.4 also generates erratic
610 * ACKs in some circumstances.
612 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
614 /* 2. Fixups made earlier cannot be right.
615 * If we do not estimate RTO correctly without them,
616 * all the algo is pure shit and should be replaced
617 * with correct one. It is exactly, which we pretend to do.
621 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
622 * guarantees that rto is higher.
624 static inline void tcp_bound_rto(struct sock
*sk
)
626 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
627 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
630 /* Save metrics learned by this TCP session.
631 This function is called only, when TCP finishes successfully
632 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
634 void tcp_update_metrics(struct sock
*sk
)
636 struct tcp_sock
*tp
= tcp_sk(sk
);
637 struct dst_entry
*dst
= __sk_dst_get(sk
);
639 if (sysctl_tcp_nometrics_save
)
644 if (dst
&& (dst
->flags
&DST_HOST
)) {
645 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
648 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
649 /* This session failed to estimate rtt. Why?
650 * Probably, no packets returned in time.
653 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
654 dst
->metrics
[RTAX_RTT
-1] = 0;
658 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
660 /* If newly calculated rtt larger than stored one,
661 * store new one. Otherwise, use EWMA. Remember,
662 * rtt overestimation is always better than underestimation.
664 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
666 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
668 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
671 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
675 /* Scale deviation to rttvar fixed point */
680 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
681 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
683 dst
->metrics
[RTAX_RTTVAR
-1] -=
684 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
687 if (tp
->snd_ssthresh
>= 0xFFFF) {
688 /* Slow start still did not finish. */
689 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
690 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
691 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
692 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
693 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
694 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
695 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
696 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
697 icsk
->icsk_ca_state
== TCP_CA_Open
) {
698 /* Cong. avoidance phase, cwnd is reliable. */
699 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
700 dst
->metrics
[RTAX_SSTHRESH
-1] =
701 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
702 if (!dst_metric_locked(dst
, RTAX_CWND
))
703 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
705 /* Else slow start did not finish, cwnd is non-sense,
706 ssthresh may be also invalid.
708 if (!dst_metric_locked(dst
, RTAX_CWND
))
709 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
710 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
711 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
712 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
713 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
716 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
717 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
718 tp
->reordering
!= sysctl_tcp_reordering
)
719 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
724 /* Numbers are taken from RFC2414. */
725 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
727 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
730 if (tp
->mss_cache
> 1460)
733 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
735 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
738 /* Initialize metrics on socket. */
740 static void tcp_init_metrics(struct sock
*sk
)
742 struct tcp_sock
*tp
= tcp_sk(sk
);
743 struct dst_entry
*dst
= __sk_dst_get(sk
);
750 if (dst_metric_locked(dst
, RTAX_CWND
))
751 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
752 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
753 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
754 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
755 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
757 if (dst_metric(dst
, RTAX_REORDERING
) &&
758 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
759 tp
->rx_opt
.sack_ok
&= ~2;
760 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
763 if (dst_metric(dst
, RTAX_RTT
) == 0)
766 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
769 /* Initial rtt is determined from SYN,SYN-ACK.
770 * The segment is small and rtt may appear much
771 * less than real one. Use per-dst memory
772 * to make it more realistic.
774 * A bit of theory. RTT is time passed after "normal" sized packet
775 * is sent until it is ACKed. In normal circumstances sending small
776 * packets force peer to delay ACKs and calculation is correct too.
777 * The algorithm is adaptive and, provided we follow specs, it
778 * NEVER underestimate RTT. BUT! If peer tries to make some clever
779 * tricks sort of "quick acks" for time long enough to decrease RTT
780 * to low value, and then abruptly stops to do it and starts to delay
781 * ACKs, wait for troubles.
783 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
784 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
785 tp
->rtt_seq
= tp
->snd_nxt
;
787 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
788 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
789 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
793 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
795 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
796 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
800 /* Play conservative. If timestamps are not
801 * supported, TCP will fail to recalculate correct
802 * rtt, if initial rto is too small. FORGET ALL AND RESET!
804 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
806 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
807 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
811 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
814 struct tcp_sock
*tp
= tcp_sk(sk
);
815 if (metric
> tp
->reordering
) {
816 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
818 /* This exciting event is worth to be remembered. 8) */
820 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
822 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
824 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
826 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
827 #if FASTRETRANS_DEBUG > 1
828 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
829 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
833 tp
->undo_marker
? tp
->undo_retrans
: 0);
835 /* Disable FACK yet. */
836 tp
->rx_opt
.sack_ok
&= ~2;
840 /* This procedure tags the retransmission queue when SACKs arrive.
842 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
843 * Packets in queue with these bits set are counted in variables
844 * sacked_out, retrans_out and lost_out, correspondingly.
846 * Valid combinations are:
847 * Tag InFlight Description
848 * 0 1 - orig segment is in flight.
849 * S 0 - nothing flies, orig reached receiver.
850 * L 0 - nothing flies, orig lost by net.
851 * R 2 - both orig and retransmit are in flight.
852 * L|R 1 - orig is lost, retransmit is in flight.
853 * S|R 1 - orig reached receiver, retrans is still in flight.
854 * (L|S|R is logically valid, it could occur when L|R is sacked,
855 * but it is equivalent to plain S and code short-curcuits it to S.
856 * L|S is logically invalid, it would mean -1 packet in flight 8))
858 * These 6 states form finite state machine, controlled by the following events:
859 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
860 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
861 * 3. Loss detection event of one of three flavors:
862 * A. Scoreboard estimator decided the packet is lost.
863 * A'. Reno "three dupacks" marks head of queue lost.
864 * A''. Its FACK modfication, head until snd.fack is lost.
865 * B. SACK arrives sacking data transmitted after never retransmitted
867 * C. SACK arrives sacking SND.NXT at the moment, when the
868 * segment was retransmitted.
869 * 4. D-SACK added new rule: D-SACK changes any tag to S.
871 * It is pleasant to note, that state diagram turns out to be commutative,
872 * so that we are allowed not to be bothered by order of our actions,
873 * when multiple events arrive simultaneously. (see the function below).
875 * Reordering detection.
876 * --------------------
877 * Reordering metric is maximal distance, which a packet can be displaced
878 * in packet stream. With SACKs we can estimate it:
880 * 1. SACK fills old hole and the corresponding segment was not
881 * ever retransmitted -> reordering. Alas, we cannot use it
882 * when segment was retransmitted.
883 * 2. The last flaw is solved with D-SACK. D-SACK arrives
884 * for retransmitted and already SACKed segment -> reordering..
885 * Both of these heuristics are not used in Loss state, when we cannot
886 * account for retransmits accurately.
889 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
891 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
892 struct tcp_sock
*tp
= tcp_sk(sk
);
893 unsigned char *ptr
= ack_skb
->h
.raw
+ TCP_SKB_CB(ack_skb
)->sacked
;
894 struct tcp_sack_block
*sp
= (struct tcp_sack_block
*)(ptr
+2);
895 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
896 int reord
= tp
->packets_out
;
898 u32 lost_retrans
= 0;
904 prior_fackets
= tp
->fackets_out
;
906 for (i
=0; i
<num_sacks
; i
++, sp
++) {
908 __u32 start_seq
= ntohl(sp
->start_seq
);
909 __u32 end_seq
= ntohl(sp
->end_seq
);
913 /* Check for D-SACK. */
915 u32 ack
= TCP_SKB_CB(ack_skb
)->ack_seq
;
917 if (before(start_seq
, ack
)) {
919 tp
->rx_opt
.sack_ok
|= 4;
920 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
921 } else if (num_sacks
> 1 &&
922 !after(end_seq
, ntohl(sp
[1].end_seq
)) &&
923 !before(start_seq
, ntohl(sp
[1].start_seq
))) {
925 tp
->rx_opt
.sack_ok
|= 4;
926 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
929 /* D-SACK for already forgotten data...
930 * Do dumb counting. */
932 !after(end_seq
, prior_snd_una
) &&
933 after(end_seq
, tp
->undo_marker
))
936 /* Eliminate too old ACKs, but take into
937 * account more or less fresh ones, they can
938 * contain valid SACK info.
940 if (before(ack
, prior_snd_una
- tp
->max_window
))
944 /* Event "B" in the comment above. */
945 if (after(end_seq
, tp
->high_seq
))
946 flag
|= FLAG_DATA_LOST
;
948 sk_stream_for_retrans_queue(skb
, sk
) {
952 /* The retransmission queue is always in order, so
953 * we can short-circuit the walk early.
955 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
958 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
959 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
961 pcount
= tcp_skb_pcount(skb
);
963 if (pcount
> 1 && !in_sack
&&
964 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
965 unsigned int pkt_len
;
967 in_sack
= !after(start_seq
,
968 TCP_SKB_CB(skb
)->seq
);
971 pkt_len
= (start_seq
-
972 TCP_SKB_CB(skb
)->seq
);
975 TCP_SKB_CB(skb
)->seq
);
976 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->tso_size
))
978 pcount
= tcp_skb_pcount(skb
);
981 fack_count
+= pcount
;
983 sacked
= TCP_SKB_CB(skb
)->sacked
;
985 /* Account D-SACK for retransmitted packet. */
986 if ((dup_sack
&& in_sack
) &&
987 (sacked
& TCPCB_RETRANS
) &&
988 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
991 /* The frame is ACKed. */
992 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
993 if (sacked
&TCPCB_RETRANS
) {
994 if ((dup_sack
&& in_sack
) &&
995 (sacked
&TCPCB_SACKED_ACKED
))
996 reord
= min(fack_count
, reord
);
998 /* If it was in a hole, we detected reordering. */
999 if (fack_count
< prior_fackets
&&
1000 !(sacked
&TCPCB_SACKED_ACKED
))
1001 reord
= min(fack_count
, reord
);
1004 /* Nothing to do; acked frame is about to be dropped. */
1008 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1009 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1010 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1011 lost_retrans
= end_seq
;
1016 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1017 if (sacked
& TCPCB_SACKED_RETRANS
) {
1018 /* If the segment is not tagged as lost,
1019 * we do not clear RETRANS, believing
1020 * that retransmission is still in flight.
1022 if (sacked
& TCPCB_LOST
) {
1023 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1024 tp
->lost_out
-= tcp_skb_pcount(skb
);
1025 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1028 /* New sack for not retransmitted frame,
1029 * which was in hole. It is reordering.
1031 if (!(sacked
& TCPCB_RETRANS
) &&
1032 fack_count
< prior_fackets
)
1033 reord
= min(fack_count
, reord
);
1035 if (sacked
& TCPCB_LOST
) {
1036 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1037 tp
->lost_out
-= tcp_skb_pcount(skb
);
1041 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1042 flag
|= FLAG_DATA_SACKED
;
1043 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1045 if (fack_count
> tp
->fackets_out
)
1046 tp
->fackets_out
= fack_count
;
1048 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1049 reord
= min(fack_count
, reord
);
1052 /* D-SACK. We can detect redundant retransmission
1053 * in S|R and plain R frames and clear it.
1054 * undo_retrans is decreased above, L|R frames
1055 * are accounted above as well.
1058 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1059 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1060 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1065 /* Check for lost retransmit. This superb idea is
1066 * borrowed from "ratehalving". Event "C".
1067 * Later note: FACK people cheated me again 8),
1068 * we have to account for reordering! Ugly,
1071 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1072 struct sk_buff
*skb
;
1074 sk_stream_for_retrans_queue(skb
, sk
) {
1075 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1077 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1079 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1080 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1082 !before(lost_retrans
,
1083 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1085 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1086 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1088 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1089 tp
->lost_out
+= tcp_skb_pcount(skb
);
1090 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1091 flag
|= FLAG_DATA_SACKED
;
1092 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1098 tp
->left_out
= tp
->sacked_out
+ tp
->lost_out
;
1100 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
)
1101 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1103 #if FASTRETRANS_DEBUG > 0
1104 BUG_TRAP((int)tp
->sacked_out
>= 0);
1105 BUG_TRAP((int)tp
->lost_out
>= 0);
1106 BUG_TRAP((int)tp
->retrans_out
>= 0);
1107 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1112 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1113 * segments to see from the next ACKs whether any data was really missing.
1114 * If the RTO was spurious, new ACKs should arrive.
1116 void tcp_enter_frto(struct sock
*sk
)
1118 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1119 struct tcp_sock
*tp
= tcp_sk(sk
);
1120 struct sk_buff
*skb
;
1122 tp
->frto_counter
= 1;
1124 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1125 tp
->snd_una
== tp
->high_seq
||
1126 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1127 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1128 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1129 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1132 /* Have to clear retransmission markers here to keep the bookkeeping
1133 * in shape, even though we are not yet in Loss state.
1134 * If something was really lost, it is eventually caught up
1135 * in tcp_enter_frto_loss.
1137 tp
->retrans_out
= 0;
1138 tp
->undo_marker
= tp
->snd_una
;
1139 tp
->undo_retrans
= 0;
1141 sk_stream_for_retrans_queue(skb
, sk
) {
1142 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_RETRANS
;
1144 tcp_sync_left_out(tp
);
1146 tcp_set_ca_state(sk
, TCP_CA_Open
);
1147 tp
->frto_highmark
= tp
->snd_nxt
;
1150 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1151 * which indicates that we should follow the traditional RTO recovery,
1152 * i.e. mark everything lost and do go-back-N retransmission.
1154 static void tcp_enter_frto_loss(struct sock
*sk
)
1156 struct tcp_sock
*tp
= tcp_sk(sk
);
1157 struct sk_buff
*skb
;
1162 tp
->fackets_out
= 0;
1164 sk_stream_for_retrans_queue(skb
, sk
) {
1165 cnt
+= tcp_skb_pcount(skb
);
1166 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1167 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1169 /* Do not mark those segments lost that were
1170 * forward transmitted after RTO
1172 if (!after(TCP_SKB_CB(skb
)->end_seq
,
1173 tp
->frto_highmark
)) {
1174 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1175 tp
->lost_out
+= tcp_skb_pcount(skb
);
1178 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1179 tp
->fackets_out
= cnt
;
1182 tcp_sync_left_out(tp
);
1184 tp
->snd_cwnd
= tp
->frto_counter
+ tcp_packets_in_flight(tp
)+1;
1185 tp
->snd_cwnd_cnt
= 0;
1186 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1187 tp
->undo_marker
= 0;
1188 tp
->frto_counter
= 0;
1190 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1191 sysctl_tcp_reordering
);
1192 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1193 tp
->high_seq
= tp
->frto_highmark
;
1194 TCP_ECN_queue_cwr(tp
);
1197 void tcp_clear_retrans(struct tcp_sock
*tp
)
1200 tp
->retrans_out
= 0;
1202 tp
->fackets_out
= 0;
1206 tp
->undo_marker
= 0;
1207 tp
->undo_retrans
= 0;
1210 /* Enter Loss state. If "how" is not zero, forget all SACK information
1211 * and reset tags completely, otherwise preserve SACKs. If receiver
1212 * dropped its ofo queue, we will know this due to reneging detection.
1214 void tcp_enter_loss(struct sock
*sk
, int how
)
1216 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1217 struct tcp_sock
*tp
= tcp_sk(sk
);
1218 struct sk_buff
*skb
;
1221 /* Reduce ssthresh if it has not yet been made inside this window. */
1222 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1223 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1224 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1225 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1226 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1229 tp
->snd_cwnd_cnt
= 0;
1230 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1232 tp
->bytes_acked
= 0;
1233 tcp_clear_retrans(tp
);
1235 /* Push undo marker, if it was plain RTO and nothing
1236 * was retransmitted. */
1238 tp
->undo_marker
= tp
->snd_una
;
1240 sk_stream_for_retrans_queue(skb
, sk
) {
1241 cnt
+= tcp_skb_pcount(skb
);
1242 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1243 tp
->undo_marker
= 0;
1244 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1245 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1246 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1247 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1248 tp
->lost_out
+= tcp_skb_pcount(skb
);
1250 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1251 tp
->fackets_out
= cnt
;
1254 tcp_sync_left_out(tp
);
1256 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1257 sysctl_tcp_reordering
);
1258 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1259 tp
->high_seq
= tp
->snd_nxt
;
1260 TCP_ECN_queue_cwr(tp
);
1263 static int tcp_check_sack_reneging(struct sock
*sk
)
1265 struct sk_buff
*skb
;
1267 /* If ACK arrived pointing to a remembered SACK,
1268 * it means that our remembered SACKs do not reflect
1269 * real state of receiver i.e.
1270 * receiver _host_ is heavily congested (or buggy).
1271 * Do processing similar to RTO timeout.
1273 if ((skb
= skb_peek(&sk
->sk_write_queue
)) != NULL
&&
1274 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1275 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1276 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1278 tcp_enter_loss(sk
, 1);
1279 icsk
->icsk_retransmits
++;
1280 tcp_retransmit_skb(sk
, skb_peek(&sk
->sk_write_queue
));
1281 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1282 icsk
->icsk_rto
, TCP_RTO_MAX
);
1288 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1290 return IsReno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1293 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1295 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1298 static inline int tcp_head_timedout(struct sock
*sk
, struct tcp_sock
*tp
)
1300 return tp
->packets_out
&&
1301 tcp_skb_timedout(sk
, skb_peek(&sk
->sk_write_queue
));
1304 /* Linux NewReno/SACK/FACK/ECN state machine.
1305 * --------------------------------------
1307 * "Open" Normal state, no dubious events, fast path.
1308 * "Disorder" In all the respects it is "Open",
1309 * but requires a bit more attention. It is entered when
1310 * we see some SACKs or dupacks. It is split of "Open"
1311 * mainly to move some processing from fast path to slow one.
1312 * "CWR" CWND was reduced due to some Congestion Notification event.
1313 * It can be ECN, ICMP source quench, local device congestion.
1314 * "Recovery" CWND was reduced, we are fast-retransmitting.
1315 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1317 * tcp_fastretrans_alert() is entered:
1318 * - each incoming ACK, if state is not "Open"
1319 * - when arrived ACK is unusual, namely:
1324 * Counting packets in flight is pretty simple.
1326 * in_flight = packets_out - left_out + retrans_out
1328 * packets_out is SND.NXT-SND.UNA counted in packets.
1330 * retrans_out is number of retransmitted segments.
1332 * left_out is number of segments left network, but not ACKed yet.
1334 * left_out = sacked_out + lost_out
1336 * sacked_out: Packets, which arrived to receiver out of order
1337 * and hence not ACKed. With SACKs this number is simply
1338 * amount of SACKed data. Even without SACKs
1339 * it is easy to give pretty reliable estimate of this number,
1340 * counting duplicate ACKs.
1342 * lost_out: Packets lost by network. TCP has no explicit
1343 * "loss notification" feedback from network (for now).
1344 * It means that this number can be only _guessed_.
1345 * Actually, it is the heuristics to predict lossage that
1346 * distinguishes different algorithms.
1348 * F.e. after RTO, when all the queue is considered as lost,
1349 * lost_out = packets_out and in_flight = retrans_out.
1351 * Essentially, we have now two algorithms counting
1354 * FACK: It is the simplest heuristics. As soon as we decided
1355 * that something is lost, we decide that _all_ not SACKed
1356 * packets until the most forward SACK are lost. I.e.
1357 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1358 * It is absolutely correct estimate, if network does not reorder
1359 * packets. And it loses any connection to reality when reordering
1360 * takes place. We use FACK by default until reordering
1361 * is suspected on the path to this destination.
1363 * NewReno: when Recovery is entered, we assume that one segment
1364 * is lost (classic Reno). While we are in Recovery and
1365 * a partial ACK arrives, we assume that one more packet
1366 * is lost (NewReno). This heuristics are the same in NewReno
1369 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1370 * deflation etc. CWND is real congestion window, never inflated, changes
1371 * only according to classic VJ rules.
1373 * Really tricky (and requiring careful tuning) part of algorithm
1374 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1375 * The first determines the moment _when_ we should reduce CWND and,
1376 * hence, slow down forward transmission. In fact, it determines the moment
1377 * when we decide that hole is caused by loss, rather than by a reorder.
1379 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1380 * holes, caused by lost packets.
1382 * And the most logically complicated part of algorithm is undo
1383 * heuristics. We detect false retransmits due to both too early
1384 * fast retransmit (reordering) and underestimated RTO, analyzing
1385 * timestamps and D-SACKs. When we detect that some segments were
1386 * retransmitted by mistake and CWND reduction was wrong, we undo
1387 * window reduction and abort recovery phase. This logic is hidden
1388 * inside several functions named tcp_try_undo_<something>.
1391 /* This function decides, when we should leave Disordered state
1392 * and enter Recovery phase, reducing congestion window.
1394 * Main question: may we further continue forward transmission
1395 * with the same cwnd?
1397 static int tcp_time_to_recover(struct sock
*sk
, struct tcp_sock
*tp
)
1401 /* Trick#1: The loss is proven. */
1405 /* Not-A-Trick#2 : Classic rule... */
1406 if (tcp_fackets_out(tp
) > tp
->reordering
)
1409 /* Trick#3 : when we use RFC2988 timer restart, fast
1410 * retransmit can be triggered by timeout of queue head.
1412 if (tcp_head_timedout(sk
, tp
))
1415 /* Trick#4: It is still not OK... But will it be useful to delay
1418 packets_out
= tp
->packets_out
;
1419 if (packets_out
<= tp
->reordering
&&
1420 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1421 !tcp_may_send_now(sk
, tp
)) {
1422 /* We have nothing to send. This connection is limited
1423 * either by receiver window or by application.
1431 /* If we receive more dupacks than we expected counting segments
1432 * in assumption of absent reordering, interpret this as reordering.
1433 * The only another reason could be bug in receiver TCP.
1435 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1437 struct tcp_sock
*tp
= tcp_sk(sk
);
1440 holes
= max(tp
->lost_out
, 1U);
1441 holes
= min(holes
, tp
->packets_out
);
1443 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1444 tp
->sacked_out
= tp
->packets_out
- holes
;
1445 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1449 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1451 static void tcp_add_reno_sack(struct sock
*sk
)
1453 struct tcp_sock
*tp
= tcp_sk(sk
);
1455 tcp_check_reno_reordering(sk
, 0);
1456 tcp_sync_left_out(tp
);
1459 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1461 static void tcp_remove_reno_sacks(struct sock
*sk
, struct tcp_sock
*tp
, int acked
)
1464 /* One ACK acked hole. The rest eat duplicate ACKs. */
1465 if (acked
-1 >= tp
->sacked_out
)
1468 tp
->sacked_out
-= acked
-1;
1470 tcp_check_reno_reordering(sk
, acked
);
1471 tcp_sync_left_out(tp
);
1474 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1477 tp
->left_out
= tp
->lost_out
;
1480 /* Mark head of queue up as lost. */
1481 static void tcp_mark_head_lost(struct sock
*sk
, struct tcp_sock
*tp
,
1482 int packets
, u32 high_seq
)
1484 struct sk_buff
*skb
;
1487 BUG_TRAP(cnt
<= tp
->packets_out
);
1489 sk_stream_for_retrans_queue(skb
, sk
) {
1490 cnt
-= tcp_skb_pcount(skb
);
1491 if (cnt
< 0 || after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1493 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1494 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1495 tp
->lost_out
+= tcp_skb_pcount(skb
);
1498 tcp_sync_left_out(tp
);
1501 /* Account newly detected lost packet(s) */
1503 static void tcp_update_scoreboard(struct sock
*sk
, struct tcp_sock
*tp
)
1506 int lost
= tp
->fackets_out
- tp
->reordering
;
1509 tcp_mark_head_lost(sk
, tp
, lost
, tp
->high_seq
);
1511 tcp_mark_head_lost(sk
, tp
, 1, tp
->high_seq
);
1514 /* New heuristics: it is possible only after we switched
1515 * to restart timer each time when something is ACKed.
1516 * Hence, we can detect timed out packets during fast
1517 * retransmit without falling to slow start.
1519 if (tcp_head_timedout(sk
, tp
)) {
1520 struct sk_buff
*skb
;
1522 sk_stream_for_retrans_queue(skb
, sk
) {
1523 if (tcp_skb_timedout(sk
, skb
) &&
1524 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1525 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1526 tp
->lost_out
+= tcp_skb_pcount(skb
);
1529 tcp_sync_left_out(tp
);
1533 /* CWND moderation, preventing bursts due to too big ACKs
1534 * in dubious situations.
1536 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
1538 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
1539 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
1540 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1543 /* Decrease cwnd each second ack. */
1544 static void tcp_cwnd_down(struct sock
*sk
)
1546 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1547 struct tcp_sock
*tp
= tcp_sk(sk
);
1548 int decr
= tp
->snd_cwnd_cnt
+ 1;
1550 tp
->snd_cwnd_cnt
= decr
&1;
1553 if (decr
&& tp
->snd_cwnd
> icsk
->icsk_ca_ops
->min_cwnd(sk
))
1554 tp
->snd_cwnd
-= decr
;
1556 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
1557 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1560 /* Nothing was retransmitted or returned timestamp is less
1561 * than timestamp of the first retransmission.
1563 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
1565 return !tp
->retrans_stamp
||
1566 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
1567 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
1570 /* Undo procedures. */
1572 #if FASTRETRANS_DEBUG > 1
1573 static void DBGUNDO(struct sock
*sk
, struct tcp_sock
*tp
, const char *msg
)
1575 struct inet_sock
*inet
= inet_sk(sk
);
1576 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1578 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
1579 tp
->snd_cwnd
, tp
->left_out
,
1580 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
1584 #define DBGUNDO(x...) do { } while (0)
1587 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
1589 struct tcp_sock
*tp
= tcp_sk(sk
);
1591 if (tp
->prior_ssthresh
) {
1592 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1594 if (icsk
->icsk_ca_ops
->undo_cwnd
)
1595 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
1597 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
1599 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
1600 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
1601 TCP_ECN_withdraw_cwr(tp
);
1604 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1606 tcp_moderate_cwnd(tp
);
1607 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1610 static inline int tcp_may_undo(struct tcp_sock
*tp
)
1612 return tp
->undo_marker
&&
1613 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
1616 /* People celebrate: "We love our President!" */
1617 static int tcp_try_undo_recovery(struct sock
*sk
, struct tcp_sock
*tp
)
1619 if (tcp_may_undo(tp
)) {
1620 /* Happy end! We did not retransmit anything
1621 * or our original transmission succeeded.
1623 DBGUNDO(sk
, tp
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
1624 tcp_undo_cwr(sk
, 1);
1625 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
1626 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1628 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
1629 tp
->undo_marker
= 0;
1631 if (tp
->snd_una
== tp
->high_seq
&& IsReno(tp
)) {
1632 /* Hold old state until something *above* high_seq
1633 * is ACKed. For Reno it is MUST to prevent false
1634 * fast retransmits (RFC2582). SACK TCP is safe. */
1635 tcp_moderate_cwnd(tp
);
1638 tcp_set_ca_state(sk
, TCP_CA_Open
);
1642 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1643 static void tcp_try_undo_dsack(struct sock
*sk
, struct tcp_sock
*tp
)
1645 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
1646 DBGUNDO(sk
, tp
, "D-SACK");
1647 tcp_undo_cwr(sk
, 1);
1648 tp
->undo_marker
= 0;
1649 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
1653 /* Undo during fast recovery after partial ACK. */
1655 static int tcp_try_undo_partial(struct sock
*sk
, struct tcp_sock
*tp
,
1658 /* Partial ACK arrived. Force Hoe's retransmit. */
1659 int failed
= IsReno(tp
) || tp
->fackets_out
>tp
->reordering
;
1661 if (tcp_may_undo(tp
)) {
1662 /* Plain luck! Hole if filled with delayed
1663 * packet, rather than with a retransmit.
1665 if (tp
->retrans_out
== 0)
1666 tp
->retrans_stamp
= 0;
1668 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
1670 DBGUNDO(sk
, tp
, "Hoe");
1671 tcp_undo_cwr(sk
, 0);
1672 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
1674 /* So... Do not make Hoe's retransmit yet.
1675 * If the first packet was delayed, the rest
1676 * ones are most probably delayed as well.
1683 /* Undo during loss recovery after partial ACK. */
1684 static int tcp_try_undo_loss(struct sock
*sk
, struct tcp_sock
*tp
)
1686 if (tcp_may_undo(tp
)) {
1687 struct sk_buff
*skb
;
1688 sk_stream_for_retrans_queue(skb
, sk
) {
1689 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1691 DBGUNDO(sk
, tp
, "partial loss");
1693 tp
->left_out
= tp
->sacked_out
;
1694 tcp_undo_cwr(sk
, 1);
1695 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1696 inet_csk(sk
)->icsk_retransmits
= 0;
1697 tp
->undo_marker
= 0;
1699 tcp_set_ca_state(sk
, TCP_CA_Open
);
1705 static inline void tcp_complete_cwr(struct sock
*sk
)
1707 struct tcp_sock
*tp
= tcp_sk(sk
);
1708 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1709 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1710 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
1713 static void tcp_try_to_open(struct sock
*sk
, struct tcp_sock
*tp
, int flag
)
1715 tp
->left_out
= tp
->sacked_out
;
1717 if (tp
->retrans_out
== 0)
1718 tp
->retrans_stamp
= 0;
1723 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
1724 int state
= TCP_CA_Open
;
1726 if (tp
->left_out
|| tp
->retrans_out
|| tp
->undo_marker
)
1727 state
= TCP_CA_Disorder
;
1729 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
1730 tcp_set_ca_state(sk
, state
);
1731 tp
->high_seq
= tp
->snd_nxt
;
1733 tcp_moderate_cwnd(tp
);
1739 /* Process an event, which can update packets-in-flight not trivially.
1740 * Main goal of this function is to calculate new estimate for left_out,
1741 * taking into account both packets sitting in receiver's buffer and
1742 * packets lost by network.
1744 * Besides that it does CWND reduction, when packet loss is detected
1745 * and changes state of machine.
1747 * It does _not_ decide what to send, it is made in function
1748 * tcp_xmit_retransmit_queue().
1751 tcp_fastretrans_alert(struct sock
*sk
, u32 prior_snd_una
,
1752 int prior_packets
, int flag
)
1754 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1755 struct tcp_sock
*tp
= tcp_sk(sk
);
1756 int is_dupack
= (tp
->snd_una
== prior_snd_una
&& !(flag
&FLAG_NOT_DUP
));
1758 /* Some technical things:
1759 * 1. Reno does not count dupacks (sacked_out) automatically. */
1760 if (!tp
->packets_out
)
1762 /* 2. SACK counts snd_fack in packets inaccurately. */
1763 if (tp
->sacked_out
== 0)
1764 tp
->fackets_out
= 0;
1766 /* Now state machine starts.
1767 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1769 tp
->prior_ssthresh
= 0;
1771 /* B. In all the states check for reneging SACKs. */
1772 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
1775 /* C. Process data loss notification, provided it is valid. */
1776 if ((flag
&FLAG_DATA_LOST
) &&
1777 before(tp
->snd_una
, tp
->high_seq
) &&
1778 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
1779 tp
->fackets_out
> tp
->reordering
) {
1780 tcp_mark_head_lost(sk
, tp
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
1781 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
1784 /* D. Synchronize left_out to current state. */
1785 tcp_sync_left_out(tp
);
1787 /* E. Check state exit conditions. State can be terminated
1788 * when high_seq is ACKed. */
1789 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
1790 if (!sysctl_tcp_frto
)
1791 BUG_TRAP(tp
->retrans_out
== 0);
1792 tp
->retrans_stamp
= 0;
1793 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
1794 switch (icsk
->icsk_ca_state
) {
1796 icsk
->icsk_retransmits
= 0;
1797 if (tcp_try_undo_recovery(sk
, tp
))
1802 /* CWR is to be held something *above* high_seq
1803 * is ACKed for CWR bit to reach receiver. */
1804 if (tp
->snd_una
!= tp
->high_seq
) {
1805 tcp_complete_cwr(sk
);
1806 tcp_set_ca_state(sk
, TCP_CA_Open
);
1810 case TCP_CA_Disorder
:
1811 tcp_try_undo_dsack(sk
, tp
);
1812 if (!tp
->undo_marker
||
1813 /* For SACK case do not Open to allow to undo
1814 * catching for all duplicate ACKs. */
1815 IsReno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
1816 tp
->undo_marker
= 0;
1817 tcp_set_ca_state(sk
, TCP_CA_Open
);
1821 case TCP_CA_Recovery
:
1823 tcp_reset_reno_sack(tp
);
1824 if (tcp_try_undo_recovery(sk
, tp
))
1826 tcp_complete_cwr(sk
);
1831 /* F. Process state. */
1832 switch (icsk
->icsk_ca_state
) {
1833 case TCP_CA_Recovery
:
1834 if (prior_snd_una
== tp
->snd_una
) {
1835 if (IsReno(tp
) && is_dupack
)
1836 tcp_add_reno_sack(sk
);
1838 int acked
= prior_packets
- tp
->packets_out
;
1840 tcp_remove_reno_sacks(sk
, tp
, acked
);
1841 is_dupack
= tcp_try_undo_partial(sk
, tp
, acked
);
1845 if (flag
&FLAG_DATA_ACKED
)
1846 icsk
->icsk_retransmits
= 0;
1847 if (!tcp_try_undo_loss(sk
, tp
)) {
1848 tcp_moderate_cwnd(tp
);
1849 tcp_xmit_retransmit_queue(sk
);
1852 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1854 /* Loss is undone; fall through to processing in Open state. */
1857 if (tp
->snd_una
!= prior_snd_una
)
1858 tcp_reset_reno_sack(tp
);
1860 tcp_add_reno_sack(sk
);
1863 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
1864 tcp_try_undo_dsack(sk
, tp
);
1866 if (!tcp_time_to_recover(sk
, tp
)) {
1867 tcp_try_to_open(sk
, tp
, flag
);
1871 /* Otherwise enter Recovery state */
1874 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
1876 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
1878 tp
->high_seq
= tp
->snd_nxt
;
1879 tp
->prior_ssthresh
= 0;
1880 tp
->undo_marker
= tp
->snd_una
;
1881 tp
->undo_retrans
= tp
->retrans_out
;
1883 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
1884 if (!(flag
&FLAG_ECE
))
1885 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1886 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1887 TCP_ECN_queue_cwr(tp
);
1890 tp
->bytes_acked
= 0;
1891 tp
->snd_cwnd_cnt
= 0;
1892 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
1895 if (is_dupack
|| tcp_head_timedout(sk
, tp
))
1896 tcp_update_scoreboard(sk
, tp
);
1898 tcp_xmit_retransmit_queue(sk
);
1901 /* Read draft-ietf-tcplw-high-performance before mucking
1902 * with this code. (Supersedes RFC1323)
1904 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
1906 /* RTTM Rule: A TSecr value received in a segment is used to
1907 * update the averaged RTT measurement only if the segment
1908 * acknowledges some new data, i.e., only if it advances the
1909 * left edge of the send window.
1911 * See draft-ietf-tcplw-high-performance-00, section 3.3.
1912 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
1914 * Changed: reset backoff as soon as we see the first valid sample.
1915 * If we do not, we get strongly overestimated rto. With timestamps
1916 * samples are accepted even from very old segments: f.e., when rtt=1
1917 * increases to 8, we retransmit 5 times and after 8 seconds delayed
1918 * answer arrives rto becomes 120 seconds! If at least one of segments
1919 * in window is lost... Voila. --ANK (010210)
1921 struct tcp_sock
*tp
= tcp_sk(sk
);
1922 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
1923 tcp_rtt_estimator(sk
, seq_rtt
);
1925 inet_csk(sk
)->icsk_backoff
= 0;
1929 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
1931 /* We don't have a timestamp. Can only use
1932 * packets that are not retransmitted to determine
1933 * rtt estimates. Also, we must not reset the
1934 * backoff for rto until we get a non-retransmitted
1935 * packet. This allows us to deal with a situation
1936 * where the network delay has increased suddenly.
1937 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
1940 if (flag
& FLAG_RETRANS_DATA_ACKED
)
1943 tcp_rtt_estimator(sk
, seq_rtt
);
1945 inet_csk(sk
)->icsk_backoff
= 0;
1949 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
1952 const struct tcp_sock
*tp
= tcp_sk(sk
);
1953 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
1954 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
1955 tcp_ack_saw_tstamp(sk
, flag
);
1956 else if (seq_rtt
>= 0)
1957 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
1960 static inline void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 rtt
,
1961 u32 in_flight
, int good
)
1963 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1964 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, rtt
, in_flight
, good
);
1965 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
1968 /* Restart timer after forward progress on connection.
1969 * RFC2988 recommends to restart timer to now+rto.
1972 static inline void tcp_ack_packets_out(struct sock
*sk
, struct tcp_sock
*tp
)
1974 if (!tp
->packets_out
) {
1975 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
1977 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
1981 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
1982 __u32 now
, __s32
*seq_rtt
)
1984 struct tcp_sock
*tp
= tcp_sk(sk
);
1985 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
1986 __u32 seq
= tp
->snd_una
;
1987 __u32 packets_acked
;
1990 /* If we get here, the whole TSO packet has not been
1993 BUG_ON(!after(scb
->end_seq
, seq
));
1995 packets_acked
= tcp_skb_pcount(skb
);
1996 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
1998 packets_acked
-= tcp_skb_pcount(skb
);
2000 if (packets_acked
) {
2001 __u8 sacked
= scb
->sacked
;
2003 acked
|= FLAG_DATA_ACKED
;
2005 if (sacked
& TCPCB_RETRANS
) {
2006 if (sacked
& TCPCB_SACKED_RETRANS
)
2007 tp
->retrans_out
-= packets_acked
;
2008 acked
|= FLAG_RETRANS_DATA_ACKED
;
2010 } else if (*seq_rtt
< 0)
2011 *seq_rtt
= now
- scb
->when
;
2012 if (sacked
& TCPCB_SACKED_ACKED
)
2013 tp
->sacked_out
-= packets_acked
;
2014 if (sacked
& TCPCB_LOST
)
2015 tp
->lost_out
-= packets_acked
;
2016 if (sacked
& TCPCB_URG
) {
2018 !before(seq
, tp
->snd_up
))
2021 } else if (*seq_rtt
< 0)
2022 *seq_rtt
= now
- scb
->when
;
2024 if (tp
->fackets_out
) {
2025 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2026 tp
->fackets_out
-= dval
;
2028 tp
->packets_out
-= packets_acked
;
2030 BUG_ON(tcp_skb_pcount(skb
) == 0);
2031 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2037 static inline u32
tcp_usrtt(const struct sk_buff
*skb
)
2039 struct timeval tv
, now
;
2041 do_gettimeofday(&now
);
2042 skb_get_timestamp(skb
, &tv
);
2043 return (now
.tv_sec
- tv
.tv_sec
) * 1000000 + (now
.tv_usec
- tv
.tv_usec
);
2046 /* Remove acknowledged frames from the retransmission queue. */
2047 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2049 struct tcp_sock
*tp
= tcp_sk(sk
);
2050 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2051 struct sk_buff
*skb
;
2052 __u32 now
= tcp_time_stamp
;
2056 void (*rtt_sample
)(struct sock
*sk
, u32 usrtt
)
2057 = icsk
->icsk_ca_ops
->rtt_sample
;
2059 while ((skb
= skb_peek(&sk
->sk_write_queue
)) &&
2060 skb
!= sk
->sk_send_head
) {
2061 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2062 __u8 sacked
= scb
->sacked
;
2064 /* If our packet is before the ack sequence we can
2065 * discard it as it's confirmed to have arrived at
2068 if (after(scb
->end_seq
, tp
->snd_una
)) {
2069 if (tcp_skb_pcount(skb
) > 1 &&
2070 after(tp
->snd_una
, scb
->seq
))
2071 acked
|= tcp_tso_acked(sk
, skb
,
2076 /* Initial outgoing SYN's get put onto the write_queue
2077 * just like anything else we transmit. It is not
2078 * true data, and if we misinform our callers that
2079 * this ACK acks real data, we will erroneously exit
2080 * connection startup slow start one packet too
2081 * quickly. This is severely frowned upon behavior.
2083 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2084 acked
|= FLAG_DATA_ACKED
;
2087 acked
|= FLAG_SYN_ACKED
;
2088 tp
->retrans_stamp
= 0;
2092 if (sacked
& TCPCB_RETRANS
) {
2093 if(sacked
& TCPCB_SACKED_RETRANS
)
2094 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2095 acked
|= FLAG_RETRANS_DATA_ACKED
;
2097 } else if (seq_rtt
< 0) {
2098 seq_rtt
= now
- scb
->when
;
2100 (*rtt_sample
)(sk
, tcp_usrtt(skb
));
2102 if (sacked
& TCPCB_SACKED_ACKED
)
2103 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2104 if (sacked
& TCPCB_LOST
)
2105 tp
->lost_out
-= tcp_skb_pcount(skb
);
2106 if (sacked
& TCPCB_URG
) {
2108 !before(scb
->end_seq
, tp
->snd_up
))
2111 } else if (seq_rtt
< 0) {
2112 seq_rtt
= now
- scb
->when
;
2114 (*rtt_sample
)(sk
, tcp_usrtt(skb
));
2116 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2117 tcp_packets_out_dec(tp
, skb
);
2118 __skb_unlink(skb
, &sk
->sk_write_queue
);
2119 sk_stream_free_skb(sk
, skb
);
2122 if (acked
&FLAG_ACKED
) {
2123 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2124 tcp_ack_packets_out(sk
, tp
);
2126 if (icsk
->icsk_ca_ops
->pkts_acked
)
2127 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
);
2130 #if FASTRETRANS_DEBUG > 0
2131 BUG_TRAP((int)tp
->sacked_out
>= 0);
2132 BUG_TRAP((int)tp
->lost_out
>= 0);
2133 BUG_TRAP((int)tp
->retrans_out
>= 0);
2134 if (!tp
->packets_out
&& tp
->rx_opt
.sack_ok
) {
2135 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2137 printk(KERN_DEBUG
"Leak l=%u %d\n",
2138 tp
->lost_out
, icsk
->icsk_ca_state
);
2141 if (tp
->sacked_out
) {
2142 printk(KERN_DEBUG
"Leak s=%u %d\n",
2143 tp
->sacked_out
, icsk
->icsk_ca_state
);
2146 if (tp
->retrans_out
) {
2147 printk(KERN_DEBUG
"Leak r=%u %d\n",
2148 tp
->retrans_out
, icsk
->icsk_ca_state
);
2149 tp
->retrans_out
= 0;
2153 *seq_rtt_p
= seq_rtt
;
2157 static void tcp_ack_probe(struct sock
*sk
)
2159 const struct tcp_sock
*tp
= tcp_sk(sk
);
2160 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2162 /* Was it a usable window open? */
2164 if (!after(TCP_SKB_CB(sk
->sk_send_head
)->end_seq
,
2165 tp
->snd_una
+ tp
->snd_wnd
)) {
2166 icsk
->icsk_backoff
= 0;
2167 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2168 /* Socket must be waked up by subsequent tcp_data_snd_check().
2169 * This function is not for random using!
2172 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2173 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2178 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2180 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2181 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2184 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2186 const struct tcp_sock
*tp
= tcp_sk(sk
);
2187 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2188 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2191 /* Check that window update is acceptable.
2192 * The function assumes that snd_una<=ack<=snd_next.
2194 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2195 const u32 ack_seq
, const u32 nwin
)
2197 return (after(ack
, tp
->snd_una
) ||
2198 after(ack_seq
, tp
->snd_wl1
) ||
2199 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2202 /* Update our send window.
2204 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2205 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2207 static int tcp_ack_update_window(struct sock
*sk
, struct tcp_sock
*tp
,
2208 struct sk_buff
*skb
, u32 ack
, u32 ack_seq
)
2211 u32 nwin
= ntohs(skb
->h
.th
->window
);
2213 if (likely(!skb
->h
.th
->syn
))
2214 nwin
<<= tp
->rx_opt
.snd_wscale
;
2216 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2217 flag
|= FLAG_WIN_UPDATE
;
2218 tcp_update_wl(tp
, ack
, ack_seq
);
2220 if (tp
->snd_wnd
!= nwin
) {
2223 /* Note, it is the only place, where
2224 * fast path is recovered for sending TCP.
2227 tcp_fast_path_check(sk
, tp
);
2229 if (nwin
> tp
->max_window
) {
2230 tp
->max_window
= nwin
;
2231 tcp_sync_mss(sk
, tp
->pmtu_cookie
);
2241 static void tcp_process_frto(struct sock
*sk
, u32 prior_snd_una
)
2243 struct tcp_sock
*tp
= tcp_sk(sk
);
2245 tcp_sync_left_out(tp
);
2247 if (tp
->snd_una
== prior_snd_una
||
2248 !before(tp
->snd_una
, tp
->frto_highmark
)) {
2249 /* RTO was caused by loss, start retransmitting in
2250 * go-back-N slow start
2252 tcp_enter_frto_loss(sk
);
2256 if (tp
->frto_counter
== 1) {
2257 /* First ACK after RTO advances the window: allow two new
2260 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2262 /* Also the second ACK after RTO advances the window.
2263 * The RTO was likely spurious. Reduce cwnd and continue
2264 * in congestion avoidance
2266 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2267 tcp_moderate_cwnd(tp
);
2270 /* F-RTO affects on two new ACKs following RTO.
2271 * At latest on third ACK the TCP behavior is back to normal.
2273 tp
->frto_counter
= (tp
->frto_counter
+ 1) % 3;
2276 /* This routine deals with incoming acks, but not outgoing ones. */
2277 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2279 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2280 struct tcp_sock
*tp
= tcp_sk(sk
);
2281 u32 prior_snd_una
= tp
->snd_una
;
2282 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2283 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2284 u32 prior_in_flight
;
2288 /* If the ack is newer than sent or older than previous acks
2289 * then we can probably ignore it.
2291 if (after(ack
, tp
->snd_nxt
))
2292 goto uninteresting_ack
;
2294 if (before(ack
, prior_snd_una
))
2297 if (sysctl_tcp_abc
&& icsk
->icsk_ca_state
< TCP_CA_CWR
)
2298 tp
->bytes_acked
+= ack
- prior_snd_una
;
2300 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2301 /* Window is constant, pure forward advance.
2302 * No more checks are required.
2303 * Note, we use the fact that SND.UNA>=SND.WL2.
2305 tcp_update_wl(tp
, ack
, ack_seq
);
2307 flag
|= FLAG_WIN_UPDATE
;
2309 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2311 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2313 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2316 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2318 flag
|= tcp_ack_update_window(sk
, tp
, skb
, ack
, ack_seq
);
2320 if (TCP_SKB_CB(skb
)->sacked
)
2321 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2323 if (TCP_ECN_rcv_ecn_echo(tp
, skb
->h
.th
))
2326 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
2329 /* We passed data and got it acked, remove any soft error
2330 * log. Something worked...
2332 sk
->sk_err_soft
= 0;
2333 tp
->rcv_tstamp
= tcp_time_stamp
;
2334 prior_packets
= tp
->packets_out
;
2338 prior_in_flight
= tcp_packets_in_flight(tp
);
2340 /* See if we can take anything off of the retransmit queue. */
2341 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
2343 if (tp
->frto_counter
)
2344 tcp_process_frto(sk
, prior_snd_una
);
2346 if (tcp_ack_is_dubious(sk
, flag
)) {
2347 /* Advance CWND, if state allows this. */
2348 if ((flag
& FLAG_DATA_ACKED
) && tcp_may_raise_cwnd(sk
, flag
))
2349 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 0);
2350 tcp_fastretrans_alert(sk
, prior_snd_una
, prior_packets
, flag
);
2352 if ((flag
& FLAG_DATA_ACKED
))
2353 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 1);
2356 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
2357 dst_confirm(sk
->sk_dst_cache
);
2362 icsk
->icsk_probes_out
= 0;
2364 /* If this ack opens up a zero window, clear backoff. It was
2365 * being used to time the probes, and is probably far higher than
2366 * it needs to be for normal retransmission.
2368 if (sk
->sk_send_head
)
2373 if (TCP_SKB_CB(skb
)->sacked
)
2374 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2377 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
2382 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2383 * But, this can also be called on packets in the established flow when
2384 * the fast version below fails.
2386 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
2389 struct tcphdr
*th
= skb
->h
.th
;
2390 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
2392 ptr
= (unsigned char *)(th
+ 1);
2393 opt_rx
->saw_tstamp
= 0;
2402 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
2407 if (opsize
< 2) /* "silly options" */
2409 if (opsize
> length
)
2410 return; /* don't parse partial options */
2413 if(opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
2414 u16 in_mss
= ntohs(get_unaligned((__u16
*)ptr
));
2416 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
2417 in_mss
= opt_rx
->user_mss
;
2418 opt_rx
->mss_clamp
= in_mss
;
2423 if(opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
2424 if (sysctl_tcp_window_scaling
) {
2425 __u8 snd_wscale
= *(__u8
*) ptr
;
2426 opt_rx
->wscale_ok
= 1;
2427 if (snd_wscale
> 14) {
2429 printk(KERN_INFO
"tcp_parse_options: Illegal window "
2430 "scaling value %d >14 received.\n",
2434 opt_rx
->snd_wscale
= snd_wscale
;
2437 case TCPOPT_TIMESTAMP
:
2438 if(opsize
==TCPOLEN_TIMESTAMP
) {
2439 if ((estab
&& opt_rx
->tstamp_ok
) ||
2440 (!estab
&& sysctl_tcp_timestamps
)) {
2441 opt_rx
->saw_tstamp
= 1;
2442 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__u32
*)ptr
));
2443 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__u32
*)(ptr
+4)));
2447 case TCPOPT_SACK_PERM
:
2448 if(opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
2449 if (sysctl_tcp_sack
) {
2450 opt_rx
->sack_ok
= 1;
2451 tcp_sack_reset(opt_rx
);
2457 if((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
2458 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
2460 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
2469 /* Fast parse options. This hopes to only see timestamps.
2470 * If it is wrong it falls back on tcp_parse_options().
2472 static inline int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
2473 struct tcp_sock
*tp
)
2475 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
2476 tp
->rx_opt
.saw_tstamp
= 0;
2478 } else if (tp
->rx_opt
.tstamp_ok
&&
2479 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
2480 __u32
*ptr
= (__u32
*)(th
+ 1);
2481 if (*ptr
== ntohl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
2482 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
2483 tp
->rx_opt
.saw_tstamp
= 1;
2485 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
2487 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
2491 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
2495 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
2497 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
2498 tp
->rx_opt
.ts_recent_stamp
= xtime
.tv_sec
;
2501 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
2503 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
2504 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2505 * extra check below makes sure this can only happen
2506 * for pure ACK frames. -DaveM
2508 * Not only, also it occurs for expired timestamps.
2511 if((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
2512 xtime
.tv_sec
>= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
2513 tcp_store_ts_recent(tp
);
2517 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2519 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2520 * it can pass through stack. So, the following predicate verifies that
2521 * this segment is not used for anything but congestion avoidance or
2522 * fast retransmit. Moreover, we even are able to eliminate most of such
2523 * second order effects, if we apply some small "replay" window (~RTO)
2524 * to timestamp space.
2526 * All these measures still do not guarantee that we reject wrapped ACKs
2527 * on networks with high bandwidth, when sequence space is recycled fastly,
2528 * but it guarantees that such events will be very rare and do not affect
2529 * connection seriously. This doesn't look nice, but alas, PAWS is really
2532 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2533 * states that events when retransmit arrives after original data are rare.
2534 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2535 * the biggest problem on large power networks even with minor reordering.
2536 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2537 * up to bandwidth of 18Gigabit/sec. 8) ]
2540 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
2542 struct tcp_sock
*tp
= tcp_sk(sk
);
2543 struct tcphdr
*th
= skb
->h
.th
;
2544 u32 seq
= TCP_SKB_CB(skb
)->seq
;
2545 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2547 return (/* 1. Pure ACK with correct sequence number. */
2548 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
2550 /* 2. ... and duplicate ACK. */
2551 ack
== tp
->snd_una
&&
2553 /* 3. ... and does not update window. */
2554 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
2556 /* 4. ... and sits in replay window. */
2557 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
2560 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
2562 const struct tcp_sock
*tp
= tcp_sk(sk
);
2563 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
2564 xtime
.tv_sec
< tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
2565 !tcp_disordered_ack(sk
, skb
));
2568 /* Check segment sequence number for validity.
2570 * Segment controls are considered valid, if the segment
2571 * fits to the window after truncation to the window. Acceptability
2572 * of data (and SYN, FIN, of course) is checked separately.
2573 * See tcp_data_queue(), for example.
2575 * Also, controls (RST is main one) are accepted using RCV.WUP instead
2576 * of RCV.NXT. Peer still did not advance his SND.UNA when we
2577 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2578 * (borrowed from freebsd)
2581 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2583 return !before(end_seq
, tp
->rcv_wup
) &&
2584 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
2587 /* When we get a reset we do this. */
2588 static void tcp_reset(struct sock
*sk
)
2590 /* We want the right error as BSD sees it (and indeed as we do). */
2591 switch (sk
->sk_state
) {
2593 sk
->sk_err
= ECONNREFUSED
;
2595 case TCP_CLOSE_WAIT
:
2601 sk
->sk_err
= ECONNRESET
;
2604 if (!sock_flag(sk
, SOCK_DEAD
))
2605 sk
->sk_error_report(sk
);
2611 * Process the FIN bit. This now behaves as it is supposed to work
2612 * and the FIN takes effect when it is validly part of sequence
2613 * space. Not before when we get holes.
2615 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2616 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
2619 * If we are in FINWAIT-1, a received FIN indicates simultaneous
2620 * close and we go into CLOSING (and later onto TIME-WAIT)
2622 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2624 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
2626 struct tcp_sock
*tp
= tcp_sk(sk
);
2628 inet_csk_schedule_ack(sk
);
2630 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
2631 sock_set_flag(sk
, SOCK_DONE
);
2633 switch (sk
->sk_state
) {
2635 case TCP_ESTABLISHED
:
2636 /* Move to CLOSE_WAIT */
2637 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
2638 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
2641 case TCP_CLOSE_WAIT
:
2643 /* Received a retransmission of the FIN, do
2648 /* RFC793: Remain in the LAST-ACK state. */
2652 /* This case occurs when a simultaneous close
2653 * happens, we must ack the received FIN and
2654 * enter the CLOSING state.
2657 tcp_set_state(sk
, TCP_CLOSING
);
2660 /* Received a FIN -- send ACK and enter TIME_WAIT. */
2662 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
2665 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2666 * cases we should never reach this piece of code.
2668 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
2669 __FUNCTION__
, sk
->sk_state
);
2673 /* It _is_ possible, that we have something out-of-order _after_ FIN.
2674 * Probably, we should reset in this case. For now drop them.
2676 __skb_queue_purge(&tp
->out_of_order_queue
);
2677 if (tp
->rx_opt
.sack_ok
)
2678 tcp_sack_reset(&tp
->rx_opt
);
2679 sk_stream_mem_reclaim(sk
);
2681 if (!sock_flag(sk
, SOCK_DEAD
)) {
2682 sk
->sk_state_change(sk
);
2684 /* Do not send POLL_HUP for half duplex close. */
2685 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
2686 sk
->sk_state
== TCP_CLOSE
)
2687 sk_wake_async(sk
, 1, POLL_HUP
);
2689 sk_wake_async(sk
, 1, POLL_IN
);
2693 static __inline__
int
2694 tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
2696 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
2697 if (before(seq
, sp
->start_seq
))
2698 sp
->start_seq
= seq
;
2699 if (after(end_seq
, sp
->end_seq
))
2700 sp
->end_seq
= end_seq
;
2706 static inline void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2708 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
2709 if (before(seq
, tp
->rcv_nxt
))
2710 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
2712 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
2714 tp
->rx_opt
.dsack
= 1;
2715 tp
->duplicate_sack
[0].start_seq
= seq
;
2716 tp
->duplicate_sack
[0].end_seq
= end_seq
;
2717 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
2721 static inline void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2723 if (!tp
->rx_opt
.dsack
)
2724 tcp_dsack_set(tp
, seq
, end_seq
);
2726 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
2729 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
2731 struct tcp_sock
*tp
= tcp_sk(sk
);
2733 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
2734 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
2735 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
2736 tcp_enter_quickack_mode(sk
);
2738 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
2739 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
2741 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
2742 end_seq
= tp
->rcv_nxt
;
2743 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
2750 /* These routines update the SACK block as out-of-order packets arrive or
2751 * in-order packets close up the sequence space.
2753 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
2756 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
2757 struct tcp_sack_block
*swalk
= sp
+1;
2759 /* See if the recent change to the first SACK eats into
2760 * or hits the sequence space of other SACK blocks, if so coalesce.
2762 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
2763 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
2766 /* Zap SWALK, by moving every further SACK up by one slot.
2767 * Decrease num_sacks.
2769 tp
->rx_opt
.num_sacks
--;
2770 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
2771 for(i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
2775 this_sack
++, swalk
++;
2779 static __inline__
void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
2783 tmp
= sack1
->start_seq
;
2784 sack1
->start_seq
= sack2
->start_seq
;
2785 sack2
->start_seq
= tmp
;
2787 tmp
= sack1
->end_seq
;
2788 sack1
->end_seq
= sack2
->end_seq
;
2789 sack2
->end_seq
= tmp
;
2792 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
2794 struct tcp_sock
*tp
= tcp_sk(sk
);
2795 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
2796 int cur_sacks
= tp
->rx_opt
.num_sacks
;
2802 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
2803 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
2804 /* Rotate this_sack to the first one. */
2805 for (; this_sack
>0; this_sack
--, sp
--)
2806 tcp_sack_swap(sp
, sp
-1);
2808 tcp_sack_maybe_coalesce(tp
);
2813 /* Could not find an adjacent existing SACK, build a new one,
2814 * put it at the front, and shift everyone else down. We
2815 * always know there is at least one SACK present already here.
2817 * If the sack array is full, forget about the last one.
2819 if (this_sack
>= 4) {
2821 tp
->rx_opt
.num_sacks
--;
2824 for(; this_sack
> 0; this_sack
--, sp
--)
2828 /* Build the new head SACK, and we're done. */
2829 sp
->start_seq
= seq
;
2830 sp
->end_seq
= end_seq
;
2831 tp
->rx_opt
.num_sacks
++;
2832 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
2835 /* RCV.NXT advances, some SACKs should be eaten. */
2837 static void tcp_sack_remove(struct tcp_sock
*tp
)
2839 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
2840 int num_sacks
= tp
->rx_opt
.num_sacks
;
2843 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
2844 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
2845 tp
->rx_opt
.num_sacks
= 0;
2846 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
2850 for(this_sack
= 0; this_sack
< num_sacks
; ) {
2851 /* Check if the start of the sack is covered by RCV.NXT. */
2852 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
2855 /* RCV.NXT must cover all the block! */
2856 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
2858 /* Zap this SACK, by moving forward any other SACKS. */
2859 for (i
=this_sack
+1; i
< num_sacks
; i
++)
2860 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
2867 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
2868 tp
->rx_opt
.num_sacks
= num_sacks
;
2869 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
2873 /* This one checks to see if we can put data from the
2874 * out_of_order queue into the receive_queue.
2876 static void tcp_ofo_queue(struct sock
*sk
)
2878 struct tcp_sock
*tp
= tcp_sk(sk
);
2879 __u32 dsack_high
= tp
->rcv_nxt
;
2880 struct sk_buff
*skb
;
2882 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
2883 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
2886 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
2887 __u32 dsack
= dsack_high
;
2888 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
2889 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
2890 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
2893 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
2894 SOCK_DEBUG(sk
, "ofo packet was already received \n");
2895 __skb_unlink(skb
, &tp
->out_of_order_queue
);
2899 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
2900 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
2901 TCP_SKB_CB(skb
)->end_seq
);
2903 __skb_unlink(skb
, &tp
->out_of_order_queue
);
2904 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
2905 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
2907 tcp_fin(skb
, sk
, skb
->h
.th
);
2911 static int tcp_prune_queue(struct sock
*sk
);
2913 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
2915 struct tcphdr
*th
= skb
->h
.th
;
2916 struct tcp_sock
*tp
= tcp_sk(sk
);
2919 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
2922 __skb_pull(skb
, th
->doff
*4);
2924 TCP_ECN_accept_cwr(tp
, skb
);
2926 if (tp
->rx_opt
.dsack
) {
2927 tp
->rx_opt
.dsack
= 0;
2928 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
2929 4 - tp
->rx_opt
.tstamp_ok
);
2932 /* Queue data for delivery to the user.
2933 * Packets in sequence go to the receive queue.
2934 * Out of sequence packets to the out_of_order_queue.
2936 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
2937 if (tcp_receive_window(tp
) == 0)
2940 /* Ok. In sequence. In window. */
2941 if (tp
->ucopy
.task
== current
&&
2942 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
2943 sock_owned_by_user(sk
) && !tp
->urg_data
) {
2944 int chunk
= min_t(unsigned int, skb
->len
,
2947 __set_current_state(TASK_RUNNING
);
2950 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
2951 tp
->ucopy
.len
-= chunk
;
2952 tp
->copied_seq
+= chunk
;
2953 eaten
= (chunk
== skb
->len
&& !th
->fin
);
2954 tcp_rcv_space_adjust(sk
);
2962 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
2963 !sk_stream_rmem_schedule(sk
, skb
))) {
2964 if (tcp_prune_queue(sk
) < 0 ||
2965 !sk_stream_rmem_schedule(sk
, skb
))
2968 sk_stream_set_owner_r(skb
, sk
);
2969 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
2971 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
2973 tcp_event_data_recv(sk
, tp
, skb
);
2975 tcp_fin(skb
, sk
, th
);
2977 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
2980 /* RFC2581. 4.2. SHOULD send immediate ACK, when
2981 * gap in queue is filled.
2983 if (skb_queue_empty(&tp
->out_of_order_queue
))
2984 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
2987 if (tp
->rx_opt
.num_sacks
)
2988 tcp_sack_remove(tp
);
2990 tcp_fast_path_check(sk
, tp
);
2994 else if (!sock_flag(sk
, SOCK_DEAD
))
2995 sk
->sk_data_ready(sk
, 0);
2999 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3000 /* A retransmit, 2nd most common case. Force an immediate ack. */
3001 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3002 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3005 tcp_enter_quickack_mode(sk
);
3006 inet_csk_schedule_ack(sk
);
3012 /* Out of window. F.e. zero window probe. */
3013 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3016 tcp_enter_quickack_mode(sk
);
3018 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3019 /* Partial packet, seq < rcv_next < end_seq */
3020 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3021 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3022 TCP_SKB_CB(skb
)->end_seq
);
3024 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3026 /* If window is closed, drop tail of packet. But after
3027 * remembering D-SACK for its head made in previous line.
3029 if (!tcp_receive_window(tp
))
3034 TCP_ECN_check_ce(tp
, skb
);
3036 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3037 !sk_stream_rmem_schedule(sk
, skb
)) {
3038 if (tcp_prune_queue(sk
) < 0 ||
3039 !sk_stream_rmem_schedule(sk
, skb
))
3043 /* Disable header prediction. */
3045 inet_csk_schedule_ack(sk
);
3047 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3048 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3050 sk_stream_set_owner_r(skb
, sk
);
3052 if (!skb_peek(&tp
->out_of_order_queue
)) {
3053 /* Initial out of order segment, build 1 SACK. */
3054 if (tp
->rx_opt
.sack_ok
) {
3055 tp
->rx_opt
.num_sacks
= 1;
3056 tp
->rx_opt
.dsack
= 0;
3057 tp
->rx_opt
.eff_sacks
= 1;
3058 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3059 tp
->selective_acks
[0].end_seq
=
3060 TCP_SKB_CB(skb
)->end_seq
;
3062 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3064 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3065 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3066 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3068 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3069 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3071 if (!tp
->rx_opt
.num_sacks
||
3072 tp
->selective_acks
[0].end_seq
!= seq
)
3075 /* Common case: data arrive in order after hole. */
3076 tp
->selective_acks
[0].end_seq
= end_seq
;
3080 /* Find place to insert this segment. */
3082 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3084 } while ((skb1
= skb1
->prev
) !=
3085 (struct sk_buff
*)&tp
->out_of_order_queue
);
3087 /* Do skb overlap to previous one? */
3088 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3089 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3090 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3091 /* All the bits are present. Drop. */
3093 tcp_dsack_set(tp
, seq
, end_seq
);
3096 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3097 /* Partial overlap. */
3098 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3103 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3105 /* And clean segments covered by new one as whole. */
3106 while ((skb1
= skb
->next
) !=
3107 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3108 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3109 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3110 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3113 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3114 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3119 if (tp
->rx_opt
.sack_ok
)
3120 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3124 /* Collapse contiguous sequence of skbs head..tail with
3125 * sequence numbers start..end.
3126 * Segments with FIN/SYN are not collapsed (only because this
3130 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3131 struct sk_buff
*head
, struct sk_buff
*tail
,
3134 struct sk_buff
*skb
;
3136 /* First, check that queue is collapsible and find
3137 * the point where collapsing can be useful. */
3138 for (skb
= head
; skb
!= tail
; ) {
3139 /* No new bits? It is possible on ofo queue. */
3140 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3141 struct sk_buff
*next
= skb
->next
;
3142 __skb_unlink(skb
, list
);
3144 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3149 /* The first skb to collapse is:
3151 * - bloated or contains data before "start" or
3152 * overlaps to the next one.
3154 if (!skb
->h
.th
->syn
&& !skb
->h
.th
->fin
&&
3155 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3156 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3157 (skb
->next
!= tail
&&
3158 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3161 /* Decided to skip this, advance start seq. */
3162 start
= TCP_SKB_CB(skb
)->end_seq
;
3165 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3168 while (before(start
, end
)) {
3169 struct sk_buff
*nskb
;
3170 int header
= skb_headroom(skb
);
3171 int copy
= SKB_MAX_ORDER(header
, 0);
3173 /* Too big header? This can happen with IPv6. */
3176 if (end
-start
< copy
)
3178 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3181 skb_reserve(nskb
, header
);
3182 memcpy(nskb
->head
, skb
->head
, header
);
3183 nskb
->nh
.raw
= nskb
->head
+ (skb
->nh
.raw
-skb
->head
);
3184 nskb
->h
.raw
= nskb
->head
+ (skb
->h
.raw
-skb
->head
);
3185 nskb
->mac
.raw
= nskb
->head
+ (skb
->mac
.raw
-skb
->head
);
3186 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3187 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3188 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3189 sk_stream_set_owner_r(nskb
, sk
);
3191 /* Copy data, releasing collapsed skbs. */
3193 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3194 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3196 if (offset
< 0) BUG();
3198 size
= min(copy
, size
);
3199 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3201 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3205 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3206 struct sk_buff
*next
= skb
->next
;
3207 __skb_unlink(skb
, list
);
3209 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3211 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3218 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3219 * and tcp_collapse() them until all the queue is collapsed.
3221 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3223 struct tcp_sock
*tp
= tcp_sk(sk
);
3224 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3225 struct sk_buff
*head
;
3231 start
= TCP_SKB_CB(skb
)->seq
;
3232 end
= TCP_SKB_CB(skb
)->end_seq
;
3238 /* Segment is terminated when we see gap or when
3239 * we are at the end of all the queue. */
3240 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3241 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3242 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3243 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3244 head
, skb
, start
, end
);
3246 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3248 /* Start new segment */
3249 start
= TCP_SKB_CB(skb
)->seq
;
3250 end
= TCP_SKB_CB(skb
)->end_seq
;
3252 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3253 start
= TCP_SKB_CB(skb
)->seq
;
3254 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3255 end
= TCP_SKB_CB(skb
)->end_seq
;
3260 /* Reduce allocated memory if we can, trying to get
3261 * the socket within its memory limits again.
3263 * Return less than zero if we should start dropping frames
3264 * until the socket owning process reads some of the data
3265 * to stabilize the situation.
3267 static int tcp_prune_queue(struct sock
*sk
)
3269 struct tcp_sock
*tp
= tcp_sk(sk
);
3271 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3273 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3275 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3276 tcp_clamp_window(sk
, tp
);
3277 else if (tcp_memory_pressure
)
3278 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3280 tcp_collapse_ofo_queue(sk
);
3281 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3282 sk
->sk_receive_queue
.next
,
3283 (struct sk_buff
*)&sk
->sk_receive_queue
,
3284 tp
->copied_seq
, tp
->rcv_nxt
);
3285 sk_stream_mem_reclaim(sk
);
3287 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3290 /* Collapsing did not help, destructive actions follow.
3291 * This must not ever occur. */
3293 /* First, purge the out_of_order queue. */
3294 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3295 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3296 __skb_queue_purge(&tp
->out_of_order_queue
);
3298 /* Reset SACK state. A conforming SACK implementation will
3299 * do the same at a timeout based retransmit. When a connection
3300 * is in a sad state like this, we care only about integrity
3301 * of the connection not performance.
3303 if (tp
->rx_opt
.sack_ok
)
3304 tcp_sack_reset(&tp
->rx_opt
);
3305 sk_stream_mem_reclaim(sk
);
3308 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3311 /* If we are really being abused, tell the caller to silently
3312 * drop receive data on the floor. It will get retransmitted
3313 * and hopefully then we'll have sufficient space.
3315 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
3317 /* Massive buffer overcommit. */
3323 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3324 * As additional protections, we do not touch cwnd in retransmission phases,
3325 * and if application hit its sndbuf limit recently.
3327 void tcp_cwnd_application_limited(struct sock
*sk
)
3329 struct tcp_sock
*tp
= tcp_sk(sk
);
3331 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
3332 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
3333 /* Limited by application or receiver window. */
3334 u32 win_used
= max(tp
->snd_cwnd_used
, 2U);
3335 if (win_used
< tp
->snd_cwnd
) {
3336 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3337 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
3339 tp
->snd_cwnd_used
= 0;
3341 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3344 static inline int tcp_should_expand_sndbuf(struct sock
*sk
, struct tcp_sock
*tp
)
3346 /* If the user specified a specific send buffer setting, do
3349 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
3352 /* If we are under global TCP memory pressure, do not expand. */
3353 if (tcp_memory_pressure
)
3356 /* If we are under soft global TCP memory pressure, do not expand. */
3357 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
3360 /* If we filled the congestion window, do not expand. */
3361 if (tp
->packets_out
>= tp
->snd_cwnd
)
3367 /* When incoming ACK allowed to free some skb from write_queue,
3368 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3369 * on the exit from tcp input handler.
3371 * PROBLEM: sndbuf expansion does not work well with largesend.
3373 static void tcp_new_space(struct sock
*sk
)
3375 struct tcp_sock
*tp
= tcp_sk(sk
);
3377 if (tcp_should_expand_sndbuf(sk
, tp
)) {
3378 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
3379 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
3380 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
3381 tp
->reordering
+ 1);
3382 sndmem
*= 2*demanded
;
3383 if (sndmem
> sk
->sk_sndbuf
)
3384 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
3385 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3388 sk
->sk_write_space(sk
);
3391 static inline void tcp_check_space(struct sock
*sk
)
3393 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
3394 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
3395 if (sk
->sk_socket
&&
3396 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
3401 static __inline__
void tcp_data_snd_check(struct sock
*sk
, struct tcp_sock
*tp
)
3403 tcp_push_pending_frames(sk
, tp
);
3404 tcp_check_space(sk
);
3408 * Check if sending an ack is needed.
3410 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
3412 struct tcp_sock
*tp
= tcp_sk(sk
);
3414 /* More than one full frame received... */
3415 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
3416 /* ... and right edge of window advances far enough.
3417 * (tcp_recvmsg() will send ACK otherwise). Or...
3419 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
3420 /* We ACK each frame or... */
3421 tcp_in_quickack_mode(sk
) ||
3422 /* We have out of order data. */
3424 skb_peek(&tp
->out_of_order_queue
))) {
3425 /* Then ack it now */
3428 /* Else, send delayed ack. */
3429 tcp_send_delayed_ack(sk
);
3433 static __inline__
void tcp_ack_snd_check(struct sock
*sk
)
3435 if (!inet_csk_ack_scheduled(sk
)) {
3436 /* We sent a data segment already. */
3439 __tcp_ack_snd_check(sk
, 1);
3443 * This routine is only called when we have urgent data
3444 * signaled. Its the 'slow' part of tcp_urg. It could be
3445 * moved inline now as tcp_urg is only called from one
3446 * place. We handle URGent data wrong. We have to - as
3447 * BSD still doesn't use the correction from RFC961.
3448 * For 1003.1g we should support a new option TCP_STDURG to permit
3449 * either form (or just set the sysctl tcp_stdurg).
3452 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
3454 struct tcp_sock
*tp
= tcp_sk(sk
);
3455 u32 ptr
= ntohs(th
->urg_ptr
);
3457 if (ptr
&& !sysctl_tcp_stdurg
)
3459 ptr
+= ntohl(th
->seq
);
3461 /* Ignore urgent data that we've already seen and read. */
3462 if (after(tp
->copied_seq
, ptr
))
3465 /* Do not replay urg ptr.
3467 * NOTE: interesting situation not covered by specs.
3468 * Misbehaving sender may send urg ptr, pointing to segment,
3469 * which we already have in ofo queue. We are not able to fetch
3470 * such data and will stay in TCP_URG_NOTYET until will be eaten
3471 * by recvmsg(). Seems, we are not obliged to handle such wicked
3472 * situations. But it is worth to think about possibility of some
3473 * DoSes using some hypothetical application level deadlock.
3475 if (before(ptr
, tp
->rcv_nxt
))
3478 /* Do we already have a newer (or duplicate) urgent pointer? */
3479 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
3482 /* Tell the world about our new urgent pointer. */
3485 /* We may be adding urgent data when the last byte read was
3486 * urgent. To do this requires some care. We cannot just ignore
3487 * tp->copied_seq since we would read the last urgent byte again
3488 * as data, nor can we alter copied_seq until this data arrives
3489 * or we break the semantics of SIOCATMARK (and thus sockatmark())
3491 * NOTE. Double Dutch. Rendering to plain English: author of comment
3492 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3493 * and expect that both A and B disappear from stream. This is _wrong_.
3494 * Though this happens in BSD with high probability, this is occasional.
3495 * Any application relying on this is buggy. Note also, that fix "works"
3496 * only in this artificial test. Insert some normal data between A and B and we will
3497 * decline of BSD again. Verdict: it is better to remove to trap
3500 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
3501 !sock_flag(sk
, SOCK_URGINLINE
) &&
3502 tp
->copied_seq
!= tp
->rcv_nxt
) {
3503 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
3505 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
3506 __skb_unlink(skb
, &sk
->sk_receive_queue
);
3511 tp
->urg_data
= TCP_URG_NOTYET
;
3514 /* Disable header prediction. */
3518 /* This is the 'fast' part of urgent handling. */
3519 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
3521 struct tcp_sock
*tp
= tcp_sk(sk
);
3523 /* Check if we get a new urgent pointer - normally not. */
3525 tcp_check_urg(sk
,th
);
3527 /* Do we wait for any urgent data? - normally not... */
3528 if (tp
->urg_data
== TCP_URG_NOTYET
) {
3529 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
3532 /* Is the urgent pointer pointing into this packet? */
3533 if (ptr
< skb
->len
) {
3535 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
3537 tp
->urg_data
= TCP_URG_VALID
| tmp
;
3538 if (!sock_flag(sk
, SOCK_DEAD
))
3539 sk
->sk_data_ready(sk
, 0);
3544 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
3546 struct tcp_sock
*tp
= tcp_sk(sk
);
3547 int chunk
= skb
->len
- hlen
;
3551 if (skb
->ip_summed
==CHECKSUM_UNNECESSARY
)
3552 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
3554 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
3558 tp
->ucopy
.len
-= chunk
;
3559 tp
->copied_seq
+= chunk
;
3560 tcp_rcv_space_adjust(sk
);
3567 static int __tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
3571 if (sock_owned_by_user(sk
)) {
3573 result
= __tcp_checksum_complete(skb
);
3576 result
= __tcp_checksum_complete(skb
);
3581 static __inline__
int
3582 tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
3584 return skb
->ip_summed
!= CHECKSUM_UNNECESSARY
&&
3585 __tcp_checksum_complete_user(sk
, skb
);
3589 * TCP receive function for the ESTABLISHED state.
3591 * It is split into a fast path and a slow path. The fast path is
3593 * - A zero window was announced from us - zero window probing
3594 * is only handled properly in the slow path.
3595 * - Out of order segments arrived.
3596 * - Urgent data is expected.
3597 * - There is no buffer space left
3598 * - Unexpected TCP flags/window values/header lengths are received
3599 * (detected by checking the TCP header against pred_flags)
3600 * - Data is sent in both directions. Fast path only supports pure senders
3601 * or pure receivers (this means either the sequence number or the ack
3602 * value must stay constant)
3603 * - Unexpected TCP option.
3605 * When these conditions are not satisfied it drops into a standard
3606 * receive procedure patterned after RFC793 to handle all cases.
3607 * The first three cases are guaranteed by proper pred_flags setting,
3608 * the rest is checked inline. Fast processing is turned on in
3609 * tcp_data_queue when everything is OK.
3611 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
3612 struct tcphdr
*th
, unsigned len
)
3614 struct tcp_sock
*tp
= tcp_sk(sk
);
3617 * Header prediction.
3618 * The code loosely follows the one in the famous
3619 * "30 instruction TCP receive" Van Jacobson mail.
3621 * Van's trick is to deposit buffers into socket queue
3622 * on a device interrupt, to call tcp_recv function
3623 * on the receive process context and checksum and copy
3624 * the buffer to user space. smart...
3626 * Our current scheme is not silly either but we take the
3627 * extra cost of the net_bh soft interrupt processing...
3628 * We do checksum and copy also but from device to kernel.
3631 tp
->rx_opt
.saw_tstamp
= 0;
3633 /* pred_flags is 0xS?10 << 16 + snd_wnd
3634 * if header_prediction is to be made
3635 * 'S' will always be tp->tcp_header_len >> 2
3636 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3637 * turn it off (when there are holes in the receive
3638 * space for instance)
3639 * PSH flag is ignored.
3642 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
3643 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3644 int tcp_header_len
= tp
->tcp_header_len
;
3646 /* Timestamp header prediction: tcp_header_len
3647 * is automatically equal to th->doff*4 due to pred_flags
3651 /* Check timestamp */
3652 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
3653 __u32
*ptr
= (__u32
*)(th
+ 1);
3655 /* No? Slow path! */
3656 if (*ptr
!= ntohl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3657 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
3660 tp
->rx_opt
.saw_tstamp
= 1;
3662 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3664 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3666 /* If PAWS failed, check it more carefully in slow path */
3667 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
3670 /* DO NOT update ts_recent here, if checksum fails
3671 * and timestamp was corrupted part, it will result
3672 * in a hung connection since we will drop all
3673 * future packets due to the PAWS test.
3677 if (len
<= tcp_header_len
) {
3678 /* Bulk data transfer: sender */
3679 if (len
== tcp_header_len
) {
3680 /* Predicted packet is in window by definition.
3681 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3682 * Hence, check seq<=rcv_wup reduces to:
3684 if (tcp_header_len
==
3685 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
3686 tp
->rcv_nxt
== tp
->rcv_wup
)
3687 tcp_store_ts_recent(tp
);
3689 tcp_rcv_rtt_measure_ts(sk
, skb
);
3691 /* We know that such packets are checksummed
3694 tcp_ack(sk
, skb
, 0);
3696 tcp_data_snd_check(sk
, tp
);
3698 } else { /* Header too small */
3699 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
3705 if (tp
->ucopy
.task
== current
&&
3706 tp
->copied_seq
== tp
->rcv_nxt
&&
3707 len
- tcp_header_len
<= tp
->ucopy
.len
&&
3708 sock_owned_by_user(sk
)) {
3709 __set_current_state(TASK_RUNNING
);
3711 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
3712 /* Predicted packet is in window by definition.
3713 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3714 * Hence, check seq<=rcv_wup reduces to:
3716 if (tcp_header_len
==
3717 (sizeof(struct tcphdr
) +
3718 TCPOLEN_TSTAMP_ALIGNED
) &&
3719 tp
->rcv_nxt
== tp
->rcv_wup
)
3720 tcp_store_ts_recent(tp
);
3722 tcp_rcv_rtt_measure_ts(sk
, skb
);
3724 __skb_pull(skb
, tcp_header_len
);
3725 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3726 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
3731 if (tcp_checksum_complete_user(sk
, skb
))
3734 /* Predicted packet is in window by definition.
3735 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3736 * Hence, check seq<=rcv_wup reduces to:
3738 if (tcp_header_len
==
3739 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
3740 tp
->rcv_nxt
== tp
->rcv_wup
)
3741 tcp_store_ts_recent(tp
);
3743 tcp_rcv_rtt_measure_ts(sk
, skb
);
3745 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
3748 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
3750 /* Bulk data transfer: receiver */
3751 __skb_pull(skb
,tcp_header_len
);
3752 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3753 sk_stream_set_owner_r(skb
, sk
);
3754 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3757 tcp_event_data_recv(sk
, tp
, skb
);
3759 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
3760 /* Well, only one small jumplet in fast path... */
3761 tcp_ack(sk
, skb
, FLAG_DATA
);
3762 tcp_data_snd_check(sk
, tp
);
3763 if (!inet_csk_ack_scheduled(sk
))
3767 __tcp_ack_snd_check(sk
, 0);
3772 sk
->sk_data_ready(sk
, 0);
3778 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
3782 * RFC1323: H1. Apply PAWS check first.
3784 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
3785 tcp_paws_discard(sk
, skb
)) {
3787 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
3788 tcp_send_dupack(sk
, skb
);
3791 /* Resets are accepted even if PAWS failed.
3793 ts_recent update must be made after we are sure
3794 that the packet is in window.
3799 * Standard slow path.
3802 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
3803 /* RFC793, page 37: "In all states except SYN-SENT, all reset
3804 * (RST) segments are validated by checking their SEQ-fields."
3805 * And page 69: "If an incoming segment is not acceptable,
3806 * an acknowledgment should be sent in reply (unless the RST bit
3807 * is set, if so drop the segment and return)".
3810 tcp_send_dupack(sk
, skb
);
3819 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3821 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3822 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
3823 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
3830 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
3832 tcp_rcv_rtt_measure_ts(sk
, skb
);
3834 /* Process urgent data. */
3835 tcp_urg(sk
, skb
, th
);
3837 /* step 7: process the segment text */
3838 tcp_data_queue(sk
, skb
);
3840 tcp_data_snd_check(sk
, tp
);
3841 tcp_ack_snd_check(sk
);
3845 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
3852 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
3853 struct tcphdr
*th
, unsigned len
)
3855 struct tcp_sock
*tp
= tcp_sk(sk
);
3856 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
3858 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
3861 struct inet_connection_sock
*icsk
;
3863 * "If the state is SYN-SENT then
3864 * first check the ACK bit
3865 * If the ACK bit is set
3866 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
3867 * a reset (unless the RST bit is set, if so drop
3868 * the segment and return)"
3870 * We do not send data with SYN, so that RFC-correct
3873 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
3874 goto reset_and_undo
;
3876 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
3877 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
3879 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
3880 goto reset_and_undo
;
3883 /* Now ACK is acceptable.
3885 * "If the RST bit is set
3886 * If the ACK was acceptable then signal the user "error:
3887 * connection reset", drop the segment, enter CLOSED state,
3888 * delete TCB, and return."
3897 * "fifth, if neither of the SYN or RST bits is set then
3898 * drop the segment and return."
3904 goto discard_and_undo
;
3907 * "If the SYN bit is on ...
3908 * are acceptable then ...
3909 * (our SYN has been ACKed), change the connection
3910 * state to ESTABLISHED..."
3913 TCP_ECN_rcv_synack(tp
, th
);
3914 if (tp
->ecn_flags
&TCP_ECN_OK
)
3915 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
3917 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
3918 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
3920 /* Ok.. it's good. Set up sequence numbers and
3921 * move to established.
3923 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
3924 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
3926 /* RFC1323: The window in SYN & SYN/ACK segments is
3929 tp
->snd_wnd
= ntohs(th
->window
);
3930 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
3932 if (!tp
->rx_opt
.wscale_ok
) {
3933 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
3934 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
3937 if (tp
->rx_opt
.saw_tstamp
) {
3938 tp
->rx_opt
.tstamp_ok
= 1;
3939 tp
->tcp_header_len
=
3940 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
3941 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
3942 tcp_store_ts_recent(tp
);
3944 tp
->tcp_header_len
= sizeof(struct tcphdr
);
3947 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_fack
)
3948 tp
->rx_opt
.sack_ok
|= 2;
3950 tcp_sync_mss(sk
, tp
->pmtu_cookie
);
3951 tcp_initialize_rcv_mss(sk
);
3953 /* Remember, tcp_poll() does not lock socket!
3954 * Change state from SYN-SENT only after copied_seq
3955 * is initialized. */
3956 tp
->copied_seq
= tp
->rcv_nxt
;
3958 tcp_set_state(sk
, TCP_ESTABLISHED
);
3960 /* Make sure socket is routed, for correct metrics. */
3961 tp
->af_specific
->rebuild_header(sk
);
3963 tcp_init_metrics(sk
);
3965 tcp_init_congestion_control(sk
);
3967 /* Prevent spurious tcp_cwnd_restart() on first data
3970 tp
->lsndtime
= tcp_time_stamp
;
3972 tcp_init_buffer_space(sk
);
3974 if (sock_flag(sk
, SOCK_KEEPOPEN
))
3975 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
3977 if (!tp
->rx_opt
.snd_wscale
)
3978 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
3982 if (!sock_flag(sk
, SOCK_DEAD
)) {
3983 sk
->sk_state_change(sk
);
3984 sk_wake_async(sk
, 0, POLL_OUT
);
3987 icsk
= inet_csk(sk
);
3989 if (sk
->sk_write_pending
||
3990 icsk
->icsk_accept_queue
.rskq_defer_accept
||
3991 icsk
->icsk_ack
.pingpong
) {
3992 /* Save one ACK. Data will be ready after
3993 * several ticks, if write_pending is set.
3995 * It may be deleted, but with this feature tcpdumps
3996 * look so _wonderfully_ clever, that I was not able
3997 * to stand against the temptation 8) --ANK
3999 inet_csk_schedule_ack(sk
);
4000 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4001 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4002 tcp_incr_quickack(sk
);
4003 tcp_enter_quickack_mode(sk
);
4004 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4005 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4016 /* No ACK in the segment */
4020 * "If the RST bit is set
4022 * Otherwise (no ACK) drop the segment and return."
4025 goto discard_and_undo
;
4029 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4030 goto discard_and_undo
;
4033 /* We see SYN without ACK. It is attempt of
4034 * simultaneous connect with crossed SYNs.
4035 * Particularly, it can be connect to self.
4037 tcp_set_state(sk
, TCP_SYN_RECV
);
4039 if (tp
->rx_opt
.saw_tstamp
) {
4040 tp
->rx_opt
.tstamp_ok
= 1;
4041 tcp_store_ts_recent(tp
);
4042 tp
->tcp_header_len
=
4043 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4045 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4048 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4049 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4051 /* RFC1323: The window in SYN & SYN/ACK segments is
4054 tp
->snd_wnd
= ntohs(th
->window
);
4055 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4056 tp
->max_window
= tp
->snd_wnd
;
4058 TCP_ECN_rcv_syn(tp
, th
);
4059 if (tp
->ecn_flags
&TCP_ECN_OK
)
4060 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
4062 tcp_sync_mss(sk
, tp
->pmtu_cookie
);
4063 tcp_initialize_rcv_mss(sk
);
4066 tcp_send_synack(sk
);
4068 /* Note, we could accept data and URG from this segment.
4069 * There are no obstacles to make this.
4071 * However, if we ignore data in ACKless segments sometimes,
4072 * we have no reasons to accept it sometimes.
4073 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4074 * is not flawless. So, discard packet for sanity.
4075 * Uncomment this return to process the data.
4082 /* "fifth, if neither of the SYN or RST bits is set then
4083 * drop the segment and return."
4087 tcp_clear_options(&tp
->rx_opt
);
4088 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4092 tcp_clear_options(&tp
->rx_opt
);
4093 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4099 * This function implements the receiving procedure of RFC 793 for
4100 * all states except ESTABLISHED and TIME_WAIT.
4101 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4102 * address independent.
4105 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4106 struct tcphdr
*th
, unsigned len
)
4108 struct tcp_sock
*tp
= tcp_sk(sk
);
4111 tp
->rx_opt
.saw_tstamp
= 0;
4113 switch (sk
->sk_state
) {
4125 if(tp
->af_specific
->conn_request(sk
, skb
) < 0)
4128 /* Now we have several options: In theory there is
4129 * nothing else in the frame. KA9Q has an option to
4130 * send data with the syn, BSD accepts data with the
4131 * syn up to the [to be] advertised window and
4132 * Solaris 2.1 gives you a protocol error. For now
4133 * we just ignore it, that fits the spec precisely
4134 * and avoids incompatibilities. It would be nice in
4135 * future to drop through and process the data.
4137 * Now that TTCP is starting to be used we ought to
4139 * But, this leaves one open to an easy denial of
4140 * service attack, and SYN cookies can't defend
4141 * against this problem. So, we drop the data
4142 * in the interest of security over speed.
4149 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4153 /* Do step6 onward by hand. */
4154 tcp_urg(sk
, skb
, th
);
4156 tcp_data_snd_check(sk
, tp
);
4160 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4161 tcp_paws_discard(sk
, skb
)) {
4163 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4164 tcp_send_dupack(sk
, skb
);
4167 /* Reset is accepted even if it did not pass PAWS. */
4170 /* step 1: check sequence number */
4171 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4173 tcp_send_dupack(sk
, skb
);
4177 /* step 2: check RST bit */
4183 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4185 /* step 3: check security and precedence [ignored] */
4189 * Check for a SYN in window.
4191 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4192 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4197 /* step 5: check the ACK field */
4199 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4201 switch(sk
->sk_state
) {
4204 tp
->copied_seq
= tp
->rcv_nxt
;
4206 tcp_set_state(sk
, TCP_ESTABLISHED
);
4207 sk
->sk_state_change(sk
);
4209 /* Note, that this wakeup is only for marginal
4210 * crossed SYN case. Passively open sockets
4211 * are not waked up, because sk->sk_sleep ==
4212 * NULL and sk->sk_socket == NULL.
4214 if (sk
->sk_socket
) {
4215 sk_wake_async(sk
,0,POLL_OUT
);
4218 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4219 tp
->snd_wnd
= ntohs(th
->window
) <<
4220 tp
->rx_opt
.snd_wscale
;
4221 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4222 TCP_SKB_CB(skb
)->seq
);
4224 /* tcp_ack considers this ACK as duplicate
4225 * and does not calculate rtt.
4226 * Fix it at least with timestamps.
4228 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4230 tcp_ack_saw_tstamp(sk
, 0);
4232 if (tp
->rx_opt
.tstamp_ok
)
4233 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4235 /* Make sure socket is routed, for
4238 tp
->af_specific
->rebuild_header(sk
);
4240 tcp_init_metrics(sk
);
4242 tcp_init_congestion_control(sk
);
4244 /* Prevent spurious tcp_cwnd_restart() on
4245 * first data packet.
4247 tp
->lsndtime
= tcp_time_stamp
;
4249 tcp_initialize_rcv_mss(sk
);
4250 tcp_init_buffer_space(sk
);
4251 tcp_fast_path_on(tp
);
4258 if (tp
->snd_una
== tp
->write_seq
) {
4259 tcp_set_state(sk
, TCP_FIN_WAIT2
);
4260 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
4261 dst_confirm(sk
->sk_dst_cache
);
4263 if (!sock_flag(sk
, SOCK_DEAD
))
4264 /* Wake up lingering close() */
4265 sk
->sk_state_change(sk
);
4269 if (tp
->linger2
< 0 ||
4270 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4271 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
4273 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4277 tmo
= tcp_fin_time(sk
);
4278 if (tmo
> TCP_TIMEWAIT_LEN
) {
4279 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
4280 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
4281 /* Bad case. We could lose such FIN otherwise.
4282 * It is not a big problem, but it looks confusing
4283 * and not so rare event. We still can lose it now,
4284 * if it spins in bh_lock_sock(), but it is really
4287 inet_csk_reset_keepalive_timer(sk
, tmo
);
4289 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
4297 if (tp
->snd_una
== tp
->write_seq
) {
4298 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4304 if (tp
->snd_una
== tp
->write_seq
) {
4305 tcp_update_metrics(sk
);
4314 /* step 6: check the URG bit */
4315 tcp_urg(sk
, skb
, th
);
4317 /* step 7: process the segment text */
4318 switch (sk
->sk_state
) {
4319 case TCP_CLOSE_WAIT
:
4322 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4326 /* RFC 793 says to queue data in these states,
4327 * RFC 1122 says we MUST send a reset.
4328 * BSD 4.4 also does reset.
4330 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
4331 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4332 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
4333 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4339 case TCP_ESTABLISHED
:
4340 tcp_data_queue(sk
, skb
);
4345 /* tcp_data could move socket to TIME-WAIT */
4346 if (sk
->sk_state
!= TCP_CLOSE
) {
4347 tcp_data_snd_check(sk
, tp
);
4348 tcp_ack_snd_check(sk
);
4358 EXPORT_SYMBOL(sysctl_tcp_ecn
);
4359 EXPORT_SYMBOL(sysctl_tcp_reordering
);
4360 EXPORT_SYMBOL(sysctl_tcp_abc
);
4361 EXPORT_SYMBOL(tcp_parse_options
);
4362 EXPORT_SYMBOL(tcp_rcv_established
);
4363 EXPORT_SYMBOL(tcp_rcv_state_process
);