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 presnce 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 spagetti. 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_full_space(sk
)/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 correspoding 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 iimediately 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 unsigned int app_win
= tp
->rcv_nxt
- tp
->copied_seq
;
334 icsk
->icsk_ack
.quick
= 0;
336 skb_queue_walk(&tp
->out_of_order_queue
, skb
) {
340 /* If overcommit is due to out of order segments,
341 * do not clamp window. Try to expand rcvbuf instead.
344 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
345 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
346 !tcp_memory_pressure
&&
347 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0])
348 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
351 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
) {
353 if (atomic_read(&sk
->sk_rmem_alloc
) >= 2 * sk
->sk_rcvbuf
)
355 if (app_win
> icsk
->icsk_ack
.rcv_mss
)
356 app_win
-= icsk
->icsk_ack
.rcv_mss
;
357 app_win
= max(app_win
, 2U*tp
->advmss
);
359 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
363 /* Receiver "autotuning" code.
365 * The algorithm for RTT estimation w/o timestamps is based on
366 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
367 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
369 * More detail on this code can be found at
370 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
371 * though this reference is out of date. A new paper
374 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
376 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
382 if (new_sample
!= 0) {
383 /* If we sample in larger samples in the non-timestamp
384 * case, we could grossly overestimate the RTT especially
385 * with chatty applications or bulk transfer apps which
386 * are stalled on filesystem I/O.
388 * Also, since we are only going for a minimum in the
389 * non-timestamp case, we do not smoothe things out
390 * else with timestamps disabled convergance takes too
394 m
-= (new_sample
>> 3);
396 } else if (m
< new_sample
)
399 /* No previous mesaure. */
403 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
404 tp
->rcv_rtt_est
.rtt
= new_sample
;
407 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
409 if (tp
->rcv_rtt_est
.time
== 0)
411 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
413 tcp_rcv_rtt_update(tp
,
414 jiffies
- tp
->rcv_rtt_est
.time
,
418 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
419 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
422 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
424 struct tcp_sock
*tp
= tcp_sk(sk
);
425 if (tp
->rx_opt
.rcv_tsecr
&&
426 (TCP_SKB_CB(skb
)->end_seq
-
427 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
428 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
432 * This function should be called every time data is copied to user space.
433 * It calculates the appropriate TCP receive buffer space.
435 void tcp_rcv_space_adjust(struct sock
*sk
)
437 struct tcp_sock
*tp
= tcp_sk(sk
);
441 if (tp
->rcvq_space
.time
== 0)
444 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
445 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
446 tp
->rcv_rtt_est
.rtt
== 0)
449 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
451 space
= max(tp
->rcvq_space
.space
, space
);
453 if (tp
->rcvq_space
.space
!= space
) {
456 tp
->rcvq_space
.space
= space
;
458 if (sysctl_tcp_moderate_rcvbuf
) {
459 int new_clamp
= space
;
461 /* Receive space grows, normalize in order to
462 * take into account packet headers and sk_buff
463 * structure overhead.
468 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
469 16 + sizeof(struct sk_buff
));
470 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
473 space
= min(space
, sysctl_tcp_rmem
[2]);
474 if (space
> sk
->sk_rcvbuf
) {
475 sk
->sk_rcvbuf
= space
;
477 /* Make the window clamp follow along. */
478 tp
->window_clamp
= new_clamp
;
484 tp
->rcvq_space
.seq
= tp
->copied_seq
;
485 tp
->rcvq_space
.time
= tcp_time_stamp
;
488 /* There is something which you must keep in mind when you analyze the
489 * behavior of the tp->ato delayed ack timeout interval. When a
490 * connection starts up, we want to ack as quickly as possible. The
491 * problem is that "good" TCP's do slow start at the beginning of data
492 * transmission. The means that until we send the first few ACK's the
493 * sender will sit on his end and only queue most of his data, because
494 * he can only send snd_cwnd unacked packets at any given time. For
495 * each ACK we send, he increments snd_cwnd and transmits more of his
498 static void tcp_event_data_recv(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
500 struct inet_connection_sock
*icsk
= inet_csk(sk
);
503 inet_csk_schedule_ack(sk
);
505 tcp_measure_rcv_mss(sk
, skb
);
507 tcp_rcv_rtt_measure(tp
);
509 now
= tcp_time_stamp
;
511 if (!icsk
->icsk_ack
.ato
) {
512 /* The _first_ data packet received, initialize
513 * delayed ACK engine.
515 tcp_incr_quickack(sk
);
516 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
518 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
520 if (m
<= TCP_ATO_MIN
/2) {
521 /* The fastest case is the first. */
522 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
523 } else if (m
< icsk
->icsk_ack
.ato
) {
524 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
525 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
526 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
527 } else if (m
> icsk
->icsk_rto
) {
528 /* Too long gap. Apparently sender falled to
529 * restart window, so that we send ACKs quickly.
531 tcp_incr_quickack(sk
);
532 sk_stream_mem_reclaim(sk
);
535 icsk
->icsk_ack
.lrcvtime
= now
;
537 TCP_ECN_check_ce(tp
, skb
);
540 tcp_grow_window(sk
, tp
, skb
);
543 /* Called to compute a smoothed rtt estimate. The data fed to this
544 * routine either comes from timestamps, or from segments that were
545 * known _not_ to have been retransmitted [see Karn/Partridge
546 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
547 * piece by Van Jacobson.
548 * NOTE: the next three routines used to be one big routine.
549 * To save cycles in the RFC 1323 implementation it was better to break
550 * it up into three procedures. -- erics
552 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
554 struct tcp_sock
*tp
= tcp_sk(sk
);
555 long m
= mrtt
; /* RTT */
557 /* The following amusing code comes from Jacobson's
558 * article in SIGCOMM '88. Note that rtt and mdev
559 * are scaled versions of rtt and mean deviation.
560 * This is designed to be as fast as possible
561 * m stands for "measurement".
563 * On a 1990 paper the rto value is changed to:
564 * RTO = rtt + 4 * mdev
566 * Funny. This algorithm seems to be very broken.
567 * These formulae increase RTO, when it should be decreased, increase
568 * too slowly, when it should be incresed fastly, decrease too fastly
569 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
570 * does not matter how to _calculate_ it. Seems, it was trap
571 * that VJ failed to avoid. 8)
576 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
577 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
579 m
= -m
; /* m is now abs(error) */
580 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
581 /* This is similar to one of Eifel findings.
582 * Eifel blocks mdev updates when rtt decreases.
583 * This solution is a bit different: we use finer gain
584 * for mdev in this case (alpha*beta).
585 * Like Eifel it also prevents growth of rto,
586 * but also it limits too fast rto decreases,
587 * happening in pure Eifel.
592 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
594 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
595 if (tp
->mdev
> tp
->mdev_max
) {
596 tp
->mdev_max
= tp
->mdev
;
597 if (tp
->mdev_max
> tp
->rttvar
)
598 tp
->rttvar
= tp
->mdev_max
;
600 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
601 if (tp
->mdev_max
< tp
->rttvar
)
602 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
603 tp
->rtt_seq
= tp
->snd_nxt
;
604 tp
->mdev_max
= TCP_RTO_MIN
;
607 /* no previous measure. */
608 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
609 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
610 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
611 tp
->rtt_seq
= tp
->snd_nxt
;
615 /* Calculate rto without backoff. This is the second half of Van Jacobson's
616 * routine referred to above.
618 static inline void tcp_set_rto(struct sock
*sk
)
620 const struct tcp_sock
*tp
= tcp_sk(sk
);
621 /* Old crap is replaced with new one. 8)
624 * 1. If rtt variance happened to be less 50msec, it is hallucination.
625 * It cannot be less due to utterly erratic ACK generation made
626 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
627 * to do with delayed acks, because at cwnd>2 true delack timeout
628 * is invisible. Actually, Linux-2.4 also generates erratic
629 * ACKs in some curcumstances.
631 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
633 /* 2. Fixups made earlier cannot be right.
634 * If we do not estimate RTO correctly without them,
635 * all the algo is pure shit and should be replaced
636 * with correct one. It is exaclty, which we pretend to do.
640 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
641 * guarantees that rto is higher.
643 static inline void tcp_bound_rto(struct sock
*sk
)
645 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
646 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
649 /* Save metrics learned by this TCP session.
650 This function is called only, when TCP finishes successfully
651 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
653 void tcp_update_metrics(struct sock
*sk
)
655 struct tcp_sock
*tp
= tcp_sk(sk
);
656 struct dst_entry
*dst
= __sk_dst_get(sk
);
658 if (sysctl_tcp_nometrics_save
)
663 if (dst
&& (dst
->flags
&DST_HOST
)) {
664 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
667 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
668 /* This session failed to estimate rtt. Why?
669 * Probably, no packets returned in time.
672 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
673 dst
->metrics
[RTAX_RTT
-1] = 0;
677 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
679 /* If newly calculated rtt larger than stored one,
680 * store new one. Otherwise, use EWMA. Remember,
681 * rtt overestimation is always better than underestimation.
683 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
685 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
687 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
690 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
694 /* Scale deviation to rttvar fixed point */
699 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
700 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
702 dst
->metrics
[RTAX_RTTVAR
-1] -=
703 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
706 if (tp
->snd_ssthresh
>= 0xFFFF) {
707 /* Slow start still did not finish. */
708 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
709 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
710 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
711 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
712 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
713 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
714 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
715 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
716 icsk
->icsk_ca_state
== TCP_CA_Open
) {
717 /* Cong. avoidance phase, cwnd is reliable. */
718 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
719 dst
->metrics
[RTAX_SSTHRESH
-1] =
720 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
721 if (!dst_metric_locked(dst
, RTAX_CWND
))
722 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
724 /* Else slow start did not finish, cwnd is non-sense,
725 ssthresh may be also invalid.
727 if (!dst_metric_locked(dst
, RTAX_CWND
))
728 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
729 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
730 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
731 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
732 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
735 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
736 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
737 tp
->reordering
!= sysctl_tcp_reordering
)
738 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
743 /* Numbers are taken from RFC2414. */
744 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
746 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
749 if (tp
->mss_cache
> 1460)
752 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
754 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
757 /* Initialize metrics on socket. */
759 static void tcp_init_metrics(struct sock
*sk
)
761 struct tcp_sock
*tp
= tcp_sk(sk
);
762 struct dst_entry
*dst
= __sk_dst_get(sk
);
769 if (dst_metric_locked(dst
, RTAX_CWND
))
770 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
771 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
772 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
773 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
774 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
776 if (dst_metric(dst
, RTAX_REORDERING
) &&
777 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
778 tp
->rx_opt
.sack_ok
&= ~2;
779 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
782 if (dst_metric(dst
, RTAX_RTT
) == 0)
785 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
788 /* Initial rtt is determined from SYN,SYN-ACK.
789 * The segment is small and rtt may appear much
790 * less than real one. Use per-dst memory
791 * to make it more realistic.
793 * A bit of theory. RTT is time passed after "normal" sized packet
794 * is sent until it is ACKed. In normal curcumstances sending small
795 * packets force peer to delay ACKs and calculation is correct too.
796 * The algorithm is adaptive and, provided we follow specs, it
797 * NEVER underestimate RTT. BUT! If peer tries to make some clever
798 * tricks sort of "quick acks" for time long enough to decrease RTT
799 * to low value, and then abruptly stops to do it and starts to delay
800 * ACKs, wait for troubles.
802 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
803 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
804 tp
->rtt_seq
= tp
->snd_nxt
;
806 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
807 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
808 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
812 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
814 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
815 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
819 /* Play conservative. If timestamps are not
820 * supported, TCP will fail to recalculate correct
821 * rtt, if initial rto is too small. FORGET ALL AND RESET!
823 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
825 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
826 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
830 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
833 struct tcp_sock
*tp
= tcp_sk(sk
);
834 if (metric
> tp
->reordering
) {
835 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
837 /* This exciting event is worth to be remembered. 8) */
839 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
841 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
843 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
845 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
846 #if FASTRETRANS_DEBUG > 1
847 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
848 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
852 tp
->undo_marker
? tp
->undo_retrans
: 0);
854 /* Disable FACK yet. */
855 tp
->rx_opt
.sack_ok
&= ~2;
859 /* This procedure tags the retransmission queue when SACKs arrive.
861 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
862 * Packets in queue with these bits set are counted in variables
863 * sacked_out, retrans_out and lost_out, correspondingly.
865 * Valid combinations are:
866 * Tag InFlight Description
867 * 0 1 - orig segment is in flight.
868 * S 0 - nothing flies, orig reached receiver.
869 * L 0 - nothing flies, orig lost by net.
870 * R 2 - both orig and retransmit are in flight.
871 * L|R 1 - orig is lost, retransmit is in flight.
872 * S|R 1 - orig reached receiver, retrans is still in flight.
873 * (L|S|R is logically valid, it could occur when L|R is sacked,
874 * but it is equivalent to plain S and code short-curcuits it to S.
875 * L|S is logically invalid, it would mean -1 packet in flight 8))
877 * These 6 states form finite state machine, controlled by the following events:
878 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
879 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
880 * 3. Loss detection event of one of three flavors:
881 * A. Scoreboard estimator decided the packet is lost.
882 * A'. Reno "three dupacks" marks head of queue lost.
883 * A''. Its FACK modfication, head until snd.fack is lost.
884 * B. SACK arrives sacking data transmitted after never retransmitted
886 * C. SACK arrives sacking SND.NXT at the moment, when the
887 * segment was retransmitted.
888 * 4. D-SACK added new rule: D-SACK changes any tag to S.
890 * It is pleasant to note, that state diagram turns out to be commutative,
891 * so that we are allowed not to be bothered by order of our actions,
892 * when multiple events arrive simultaneously. (see the function below).
894 * Reordering detection.
895 * --------------------
896 * Reordering metric is maximal distance, which a packet can be displaced
897 * in packet stream. With SACKs we can estimate it:
899 * 1. SACK fills old hole and the corresponding segment was not
900 * ever retransmitted -> reordering. Alas, we cannot use it
901 * when segment was retransmitted.
902 * 2. The last flaw is solved with D-SACK. D-SACK arrives
903 * for retransmitted and already SACKed segment -> reordering..
904 * Both of these heuristics are not used in Loss state, when we cannot
905 * account for retransmits accurately.
908 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
910 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
911 struct tcp_sock
*tp
= tcp_sk(sk
);
912 unsigned char *ptr
= ack_skb
->h
.raw
+ TCP_SKB_CB(ack_skb
)->sacked
;
913 struct tcp_sack_block
*sp
= (struct tcp_sack_block
*)(ptr
+2);
914 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
915 int reord
= tp
->packets_out
;
917 u32 lost_retrans
= 0;
923 prior_fackets
= tp
->fackets_out
;
925 for (i
=0; i
<num_sacks
; i
++, sp
++) {
927 __u32 start_seq
= ntohl(sp
->start_seq
);
928 __u32 end_seq
= ntohl(sp
->end_seq
);
932 /* Check for D-SACK. */
934 u32 ack
= TCP_SKB_CB(ack_skb
)->ack_seq
;
936 if (before(start_seq
, ack
)) {
938 tp
->rx_opt
.sack_ok
|= 4;
939 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
940 } else if (num_sacks
> 1 &&
941 !after(end_seq
, ntohl(sp
[1].end_seq
)) &&
942 !before(start_seq
, ntohl(sp
[1].start_seq
))) {
944 tp
->rx_opt
.sack_ok
|= 4;
945 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
948 /* D-SACK for already forgotten data...
949 * Do dumb counting. */
951 !after(end_seq
, prior_snd_una
) &&
952 after(end_seq
, tp
->undo_marker
))
955 /* Eliminate too old ACKs, but take into
956 * account more or less fresh ones, they can
957 * contain valid SACK info.
959 if (before(ack
, prior_snd_una
- tp
->max_window
))
963 /* Event "B" in the comment above. */
964 if (after(end_seq
, tp
->high_seq
))
965 flag
|= FLAG_DATA_LOST
;
967 sk_stream_for_retrans_queue(skb
, sk
) {
971 /* The retransmission queue is always in order, so
972 * we can short-circuit the walk early.
974 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
977 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
978 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
980 pcount
= tcp_skb_pcount(skb
);
982 if (pcount
> 1 && !in_sack
&&
983 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
984 unsigned int pkt_len
;
986 in_sack
= !after(start_seq
,
987 TCP_SKB_CB(skb
)->seq
);
990 pkt_len
= (start_seq
-
991 TCP_SKB_CB(skb
)->seq
);
994 TCP_SKB_CB(skb
)->seq
);
995 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->tso_size
))
997 pcount
= tcp_skb_pcount(skb
);
1000 fack_count
+= pcount
;
1002 sacked
= TCP_SKB_CB(skb
)->sacked
;
1004 /* Account D-SACK for retransmitted packet. */
1005 if ((dup_sack
&& in_sack
) &&
1006 (sacked
& TCPCB_RETRANS
) &&
1007 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1010 /* The frame is ACKed. */
1011 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1012 if (sacked
&TCPCB_RETRANS
) {
1013 if ((dup_sack
&& in_sack
) &&
1014 (sacked
&TCPCB_SACKED_ACKED
))
1015 reord
= min(fack_count
, reord
);
1017 /* If it was in a hole, we detected reordering. */
1018 if (fack_count
< prior_fackets
&&
1019 !(sacked
&TCPCB_SACKED_ACKED
))
1020 reord
= min(fack_count
, reord
);
1023 /* Nothing to do; acked frame is about to be dropped. */
1027 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1028 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1029 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1030 lost_retrans
= end_seq
;
1035 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1036 if (sacked
& TCPCB_SACKED_RETRANS
) {
1037 /* If the segment is not tagged as lost,
1038 * we do not clear RETRANS, believing
1039 * that retransmission is still in flight.
1041 if (sacked
& TCPCB_LOST
) {
1042 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1043 tp
->lost_out
-= tcp_skb_pcount(skb
);
1044 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1047 /* New sack for not retransmitted frame,
1048 * which was in hole. It is reordering.
1050 if (!(sacked
& TCPCB_RETRANS
) &&
1051 fack_count
< prior_fackets
)
1052 reord
= min(fack_count
, reord
);
1054 if (sacked
& TCPCB_LOST
) {
1055 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1056 tp
->lost_out
-= tcp_skb_pcount(skb
);
1060 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1061 flag
|= FLAG_DATA_SACKED
;
1062 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1064 if (fack_count
> tp
->fackets_out
)
1065 tp
->fackets_out
= fack_count
;
1067 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1068 reord
= min(fack_count
, reord
);
1071 /* D-SACK. We can detect redundant retransmission
1072 * in S|R and plain R frames and clear it.
1073 * undo_retrans is decreased above, L|R frames
1074 * are accounted above as well.
1077 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1078 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1079 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1084 /* Check for lost retransmit. This superb idea is
1085 * borrowed from "ratehalving". Event "C".
1086 * Later note: FACK people cheated me again 8),
1087 * we have to account for reordering! Ugly,
1090 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1091 struct sk_buff
*skb
;
1093 sk_stream_for_retrans_queue(skb
, sk
) {
1094 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1096 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1098 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1099 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1101 !before(lost_retrans
,
1102 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1104 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1105 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1107 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1108 tp
->lost_out
+= tcp_skb_pcount(skb
);
1109 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1110 flag
|= FLAG_DATA_SACKED
;
1111 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1117 tp
->left_out
= tp
->sacked_out
+ tp
->lost_out
;
1119 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
)
1120 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1122 #if FASTRETRANS_DEBUG > 0
1123 BUG_TRAP((int)tp
->sacked_out
>= 0);
1124 BUG_TRAP((int)tp
->lost_out
>= 0);
1125 BUG_TRAP((int)tp
->retrans_out
>= 0);
1126 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1131 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1132 * segments to see from the next ACKs whether any data was really missing.
1133 * If the RTO was spurious, new ACKs should arrive.
1135 void tcp_enter_frto(struct sock
*sk
)
1137 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1138 struct tcp_sock
*tp
= tcp_sk(sk
);
1139 struct sk_buff
*skb
;
1141 tp
->frto_counter
= 1;
1143 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1144 tp
->snd_una
== tp
->high_seq
||
1145 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1146 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1147 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1148 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1151 /* Have to clear retransmission markers here to keep the bookkeeping
1152 * in shape, even though we are not yet in Loss state.
1153 * If something was really lost, it is eventually caught up
1154 * in tcp_enter_frto_loss.
1156 tp
->retrans_out
= 0;
1157 tp
->undo_marker
= tp
->snd_una
;
1158 tp
->undo_retrans
= 0;
1160 sk_stream_for_retrans_queue(skb
, sk
) {
1161 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_RETRANS
;
1163 tcp_sync_left_out(tp
);
1165 tcp_set_ca_state(sk
, TCP_CA_Open
);
1166 tp
->frto_highmark
= tp
->snd_nxt
;
1169 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1170 * which indicates that we should follow the traditional RTO recovery,
1171 * i.e. mark everything lost and do go-back-N retransmission.
1173 static void tcp_enter_frto_loss(struct sock
*sk
)
1175 struct tcp_sock
*tp
= tcp_sk(sk
);
1176 struct sk_buff
*skb
;
1181 tp
->fackets_out
= 0;
1183 sk_stream_for_retrans_queue(skb
, sk
) {
1184 cnt
+= tcp_skb_pcount(skb
);
1185 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1186 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1188 /* Do not mark those segments lost that were
1189 * forward transmitted after RTO
1191 if (!after(TCP_SKB_CB(skb
)->end_seq
,
1192 tp
->frto_highmark
)) {
1193 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1194 tp
->lost_out
+= tcp_skb_pcount(skb
);
1197 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1198 tp
->fackets_out
= cnt
;
1201 tcp_sync_left_out(tp
);
1203 tp
->snd_cwnd
= tp
->frto_counter
+ tcp_packets_in_flight(tp
)+1;
1204 tp
->snd_cwnd_cnt
= 0;
1205 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1206 tp
->undo_marker
= 0;
1207 tp
->frto_counter
= 0;
1209 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1210 sysctl_tcp_reordering
);
1211 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1212 tp
->high_seq
= tp
->frto_highmark
;
1213 TCP_ECN_queue_cwr(tp
);
1216 void tcp_clear_retrans(struct tcp_sock
*tp
)
1219 tp
->retrans_out
= 0;
1221 tp
->fackets_out
= 0;
1225 tp
->undo_marker
= 0;
1226 tp
->undo_retrans
= 0;
1229 /* Enter Loss state. If "how" is not zero, forget all SACK information
1230 * and reset tags completely, otherwise preserve SACKs. If receiver
1231 * dropped its ofo queue, we will know this due to reneging detection.
1233 void tcp_enter_loss(struct sock
*sk
, int how
)
1235 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1236 struct tcp_sock
*tp
= tcp_sk(sk
);
1237 struct sk_buff
*skb
;
1240 /* Reduce ssthresh if it has not yet been made inside this window. */
1241 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1242 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1243 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1244 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1245 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1248 tp
->snd_cwnd_cnt
= 0;
1249 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1251 tp
->bytes_acked
= 0;
1252 tcp_clear_retrans(tp
);
1254 /* Push undo marker, if it was plain RTO and nothing
1255 * was retransmitted. */
1257 tp
->undo_marker
= tp
->snd_una
;
1259 sk_stream_for_retrans_queue(skb
, sk
) {
1260 cnt
+= tcp_skb_pcount(skb
);
1261 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1262 tp
->undo_marker
= 0;
1263 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1264 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1265 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1266 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1267 tp
->lost_out
+= tcp_skb_pcount(skb
);
1269 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1270 tp
->fackets_out
= cnt
;
1273 tcp_sync_left_out(tp
);
1275 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1276 sysctl_tcp_reordering
);
1277 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1278 tp
->high_seq
= tp
->snd_nxt
;
1279 TCP_ECN_queue_cwr(tp
);
1282 static int tcp_check_sack_reneging(struct sock
*sk
)
1284 struct sk_buff
*skb
;
1286 /* If ACK arrived pointing to a remembered SACK,
1287 * it means that our remembered SACKs do not reflect
1288 * real state of receiver i.e.
1289 * receiver _host_ is heavily congested (or buggy).
1290 * Do processing similar to RTO timeout.
1292 if ((skb
= skb_peek(&sk
->sk_write_queue
)) != NULL
&&
1293 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1294 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1295 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1297 tcp_enter_loss(sk
, 1);
1298 icsk
->icsk_retransmits
++;
1299 tcp_retransmit_skb(sk
, skb_peek(&sk
->sk_write_queue
));
1300 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1301 icsk
->icsk_rto
, TCP_RTO_MAX
);
1307 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1309 return IsReno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1312 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1314 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1317 static inline int tcp_head_timedout(struct sock
*sk
, struct tcp_sock
*tp
)
1319 return tp
->packets_out
&&
1320 tcp_skb_timedout(sk
, skb_peek(&sk
->sk_write_queue
));
1323 /* Linux NewReno/SACK/FACK/ECN state machine.
1324 * --------------------------------------
1326 * "Open" Normal state, no dubious events, fast path.
1327 * "Disorder" In all the respects it is "Open",
1328 * but requires a bit more attention. It is entered when
1329 * we see some SACKs or dupacks. It is split of "Open"
1330 * mainly to move some processing from fast path to slow one.
1331 * "CWR" CWND was reduced due to some Congestion Notification event.
1332 * It can be ECN, ICMP source quench, local device congestion.
1333 * "Recovery" CWND was reduced, we are fast-retransmitting.
1334 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1336 * tcp_fastretrans_alert() is entered:
1337 * - each incoming ACK, if state is not "Open"
1338 * - when arrived ACK is unusual, namely:
1343 * Counting packets in flight is pretty simple.
1345 * in_flight = packets_out - left_out + retrans_out
1347 * packets_out is SND.NXT-SND.UNA counted in packets.
1349 * retrans_out is number of retransmitted segments.
1351 * left_out is number of segments left network, but not ACKed yet.
1353 * left_out = sacked_out + lost_out
1355 * sacked_out: Packets, which arrived to receiver out of order
1356 * and hence not ACKed. With SACKs this number is simply
1357 * amount of SACKed data. Even without SACKs
1358 * it is easy to give pretty reliable estimate of this number,
1359 * counting duplicate ACKs.
1361 * lost_out: Packets lost by network. TCP has no explicit
1362 * "loss notification" feedback from network (for now).
1363 * It means that this number can be only _guessed_.
1364 * Actually, it is the heuristics to predict lossage that
1365 * distinguishes different algorithms.
1367 * F.e. after RTO, when all the queue is considered as lost,
1368 * lost_out = packets_out and in_flight = retrans_out.
1370 * Essentially, we have now two algorithms counting
1373 * FACK: It is the simplest heuristics. As soon as we decided
1374 * that something is lost, we decide that _all_ not SACKed
1375 * packets until the most forward SACK are lost. I.e.
1376 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1377 * It is absolutely correct estimate, if network does not reorder
1378 * packets. And it loses any connection to reality when reordering
1379 * takes place. We use FACK by default until reordering
1380 * is suspected on the path to this destination.
1382 * NewReno: when Recovery is entered, we assume that one segment
1383 * is lost (classic Reno). While we are in Recovery and
1384 * a partial ACK arrives, we assume that one more packet
1385 * is lost (NewReno). This heuristics are the same in NewReno
1388 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1389 * deflation etc. CWND is real congestion window, never inflated, changes
1390 * only according to classic VJ rules.
1392 * Really tricky (and requiring careful tuning) part of algorithm
1393 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1394 * The first determines the moment _when_ we should reduce CWND and,
1395 * hence, slow down forward transmission. In fact, it determines the moment
1396 * when we decide that hole is caused by loss, rather than by a reorder.
1398 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1399 * holes, caused by lost packets.
1401 * And the most logically complicated part of algorithm is undo
1402 * heuristics. We detect false retransmits due to both too early
1403 * fast retransmit (reordering) and underestimated RTO, analyzing
1404 * timestamps and D-SACKs. When we detect that some segments were
1405 * retransmitted by mistake and CWND reduction was wrong, we undo
1406 * window reduction and abort recovery phase. This logic is hidden
1407 * inside several functions named tcp_try_undo_<something>.
1410 /* This function decides, when we should leave Disordered state
1411 * and enter Recovery phase, reducing congestion window.
1413 * Main question: may we further continue forward transmission
1414 * with the same cwnd?
1416 static int tcp_time_to_recover(struct sock
*sk
, struct tcp_sock
*tp
)
1420 /* Trick#1: The loss is proven. */
1424 /* Not-A-Trick#2 : Classic rule... */
1425 if (tcp_fackets_out(tp
) > tp
->reordering
)
1428 /* Trick#3 : when we use RFC2988 timer restart, fast
1429 * retransmit can be triggered by timeout of queue head.
1431 if (tcp_head_timedout(sk
, tp
))
1434 /* Trick#4: It is still not OK... But will it be useful to delay
1437 packets_out
= tp
->packets_out
;
1438 if (packets_out
<= tp
->reordering
&&
1439 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1440 !tcp_may_send_now(sk
, tp
)) {
1441 /* We have nothing to send. This connection is limited
1442 * either by receiver window or by application.
1450 /* If we receive more dupacks than we expected counting segments
1451 * in assumption of absent reordering, interpret this as reordering.
1452 * The only another reason could be bug in receiver TCP.
1454 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1456 struct tcp_sock
*tp
= tcp_sk(sk
);
1459 holes
= max(tp
->lost_out
, 1U);
1460 holes
= min(holes
, tp
->packets_out
);
1462 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1463 tp
->sacked_out
= tp
->packets_out
- holes
;
1464 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1468 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1470 static void tcp_add_reno_sack(struct sock
*sk
)
1472 struct tcp_sock
*tp
= tcp_sk(sk
);
1474 tcp_check_reno_reordering(sk
, 0);
1475 tcp_sync_left_out(tp
);
1478 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1480 static void tcp_remove_reno_sacks(struct sock
*sk
, struct tcp_sock
*tp
, int acked
)
1483 /* One ACK acked hole. The rest eat duplicate ACKs. */
1484 if (acked
-1 >= tp
->sacked_out
)
1487 tp
->sacked_out
-= acked
-1;
1489 tcp_check_reno_reordering(sk
, acked
);
1490 tcp_sync_left_out(tp
);
1493 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1496 tp
->left_out
= tp
->lost_out
;
1499 /* Mark head of queue up as lost. */
1500 static void tcp_mark_head_lost(struct sock
*sk
, struct tcp_sock
*tp
,
1501 int packets
, u32 high_seq
)
1503 struct sk_buff
*skb
;
1506 BUG_TRAP(cnt
<= tp
->packets_out
);
1508 sk_stream_for_retrans_queue(skb
, sk
) {
1509 cnt
-= tcp_skb_pcount(skb
);
1510 if (cnt
< 0 || after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1512 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1513 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1514 tp
->lost_out
+= tcp_skb_pcount(skb
);
1517 tcp_sync_left_out(tp
);
1520 /* Account newly detected lost packet(s) */
1522 static void tcp_update_scoreboard(struct sock
*sk
, struct tcp_sock
*tp
)
1525 int lost
= tp
->fackets_out
- tp
->reordering
;
1528 tcp_mark_head_lost(sk
, tp
, lost
, tp
->high_seq
);
1530 tcp_mark_head_lost(sk
, tp
, 1, tp
->high_seq
);
1533 /* New heuristics: it is possible only after we switched
1534 * to restart timer each time when something is ACKed.
1535 * Hence, we can detect timed out packets during fast
1536 * retransmit without falling to slow start.
1538 if (tcp_head_timedout(sk
, tp
)) {
1539 struct sk_buff
*skb
;
1541 sk_stream_for_retrans_queue(skb
, sk
) {
1542 if (tcp_skb_timedout(sk
, skb
) &&
1543 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1544 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1545 tp
->lost_out
+= tcp_skb_pcount(skb
);
1548 tcp_sync_left_out(tp
);
1552 /* CWND moderation, preventing bursts due to too big ACKs
1553 * in dubious situations.
1555 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
1557 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
1558 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
1559 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1562 /* Decrease cwnd each second ack. */
1563 static void tcp_cwnd_down(struct sock
*sk
)
1565 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1566 struct tcp_sock
*tp
= tcp_sk(sk
);
1567 int decr
= tp
->snd_cwnd_cnt
+ 1;
1569 tp
->snd_cwnd_cnt
= decr
&1;
1572 if (decr
&& tp
->snd_cwnd
> icsk
->icsk_ca_ops
->min_cwnd(sk
))
1573 tp
->snd_cwnd
-= decr
;
1575 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
1576 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1579 /* Nothing was retransmitted or returned timestamp is less
1580 * than timestamp of the first retransmission.
1582 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
1584 return !tp
->retrans_stamp
||
1585 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
1586 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
1589 /* Undo procedures. */
1591 #if FASTRETRANS_DEBUG > 1
1592 static void DBGUNDO(struct sock
*sk
, struct tcp_sock
*tp
, const char *msg
)
1594 struct inet_sock
*inet
= inet_sk(sk
);
1595 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1597 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
1598 tp
->snd_cwnd
, tp
->left_out
,
1599 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
1603 #define DBGUNDO(x...) do { } while (0)
1606 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
1608 struct tcp_sock
*tp
= tcp_sk(sk
);
1610 if (tp
->prior_ssthresh
) {
1611 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1613 if (icsk
->icsk_ca_ops
->undo_cwnd
)
1614 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
1616 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
1618 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
1619 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
1620 TCP_ECN_withdraw_cwr(tp
);
1623 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1625 tcp_moderate_cwnd(tp
);
1626 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1629 static inline int tcp_may_undo(struct tcp_sock
*tp
)
1631 return tp
->undo_marker
&&
1632 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
1635 /* People celebrate: "We love our President!" */
1636 static int tcp_try_undo_recovery(struct sock
*sk
, struct tcp_sock
*tp
)
1638 if (tcp_may_undo(tp
)) {
1639 /* Happy end! We did not retransmit anything
1640 * or our original transmission succeeded.
1642 DBGUNDO(sk
, tp
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
1643 tcp_undo_cwr(sk
, 1);
1644 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
1645 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1647 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
1648 tp
->undo_marker
= 0;
1650 if (tp
->snd_una
== tp
->high_seq
&& IsReno(tp
)) {
1651 /* Hold old state until something *above* high_seq
1652 * is ACKed. For Reno it is MUST to prevent false
1653 * fast retransmits (RFC2582). SACK TCP is safe. */
1654 tcp_moderate_cwnd(tp
);
1657 tcp_set_ca_state(sk
, TCP_CA_Open
);
1661 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1662 static void tcp_try_undo_dsack(struct sock
*sk
, struct tcp_sock
*tp
)
1664 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
1665 DBGUNDO(sk
, tp
, "D-SACK");
1666 tcp_undo_cwr(sk
, 1);
1667 tp
->undo_marker
= 0;
1668 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
1672 /* Undo during fast recovery after partial ACK. */
1674 static int tcp_try_undo_partial(struct sock
*sk
, struct tcp_sock
*tp
,
1677 /* Partial ACK arrived. Force Hoe's retransmit. */
1678 int failed
= IsReno(tp
) || tp
->fackets_out
>tp
->reordering
;
1680 if (tcp_may_undo(tp
)) {
1681 /* Plain luck! Hole if filled with delayed
1682 * packet, rather than with a retransmit.
1684 if (tp
->retrans_out
== 0)
1685 tp
->retrans_stamp
= 0;
1687 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
1689 DBGUNDO(sk
, tp
, "Hoe");
1690 tcp_undo_cwr(sk
, 0);
1691 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
1693 /* So... Do not make Hoe's retransmit yet.
1694 * If the first packet was delayed, the rest
1695 * ones are most probably delayed as well.
1702 /* Undo during loss recovery after partial ACK. */
1703 static int tcp_try_undo_loss(struct sock
*sk
, struct tcp_sock
*tp
)
1705 if (tcp_may_undo(tp
)) {
1706 struct sk_buff
*skb
;
1707 sk_stream_for_retrans_queue(skb
, sk
) {
1708 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1710 DBGUNDO(sk
, tp
, "partial loss");
1712 tp
->left_out
= tp
->sacked_out
;
1713 tcp_undo_cwr(sk
, 1);
1714 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1715 inet_csk(sk
)->icsk_retransmits
= 0;
1716 tp
->undo_marker
= 0;
1718 tcp_set_ca_state(sk
, TCP_CA_Open
);
1724 static inline void tcp_complete_cwr(struct sock
*sk
)
1726 struct tcp_sock
*tp
= tcp_sk(sk
);
1727 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1728 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1729 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
1732 static void tcp_try_to_open(struct sock
*sk
, struct tcp_sock
*tp
, int flag
)
1734 tp
->left_out
= tp
->sacked_out
;
1736 if (tp
->retrans_out
== 0)
1737 tp
->retrans_stamp
= 0;
1742 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
1743 int state
= TCP_CA_Open
;
1745 if (tp
->left_out
|| tp
->retrans_out
|| tp
->undo_marker
)
1746 state
= TCP_CA_Disorder
;
1748 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
1749 tcp_set_ca_state(sk
, state
);
1750 tp
->high_seq
= tp
->snd_nxt
;
1752 tcp_moderate_cwnd(tp
);
1758 /* Process an event, which can update packets-in-flight not trivially.
1759 * Main goal of this function is to calculate new estimate for left_out,
1760 * taking into account both packets sitting in receiver's buffer and
1761 * packets lost by network.
1763 * Besides that it does CWND reduction, when packet loss is detected
1764 * and changes state of machine.
1766 * It does _not_ decide what to send, it is made in function
1767 * tcp_xmit_retransmit_queue().
1770 tcp_fastretrans_alert(struct sock
*sk
, u32 prior_snd_una
,
1771 int prior_packets
, int flag
)
1773 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1774 struct tcp_sock
*tp
= tcp_sk(sk
);
1775 int is_dupack
= (tp
->snd_una
== prior_snd_una
&& !(flag
&FLAG_NOT_DUP
));
1777 /* Some technical things:
1778 * 1. Reno does not count dupacks (sacked_out) automatically. */
1779 if (!tp
->packets_out
)
1781 /* 2. SACK counts snd_fack in packets inaccurately. */
1782 if (tp
->sacked_out
== 0)
1783 tp
->fackets_out
= 0;
1785 /* Now state machine starts.
1786 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1788 tp
->prior_ssthresh
= 0;
1790 /* B. In all the states check for reneging SACKs. */
1791 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
1794 /* C. Process data loss notification, provided it is valid. */
1795 if ((flag
&FLAG_DATA_LOST
) &&
1796 before(tp
->snd_una
, tp
->high_seq
) &&
1797 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
1798 tp
->fackets_out
> tp
->reordering
) {
1799 tcp_mark_head_lost(sk
, tp
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
1800 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
1803 /* D. Synchronize left_out to current state. */
1804 tcp_sync_left_out(tp
);
1806 /* E. Check state exit conditions. State can be terminated
1807 * when high_seq is ACKed. */
1808 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
1809 if (!sysctl_tcp_frto
)
1810 BUG_TRAP(tp
->retrans_out
== 0);
1811 tp
->retrans_stamp
= 0;
1812 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
1813 switch (icsk
->icsk_ca_state
) {
1815 icsk
->icsk_retransmits
= 0;
1816 if (tcp_try_undo_recovery(sk
, tp
))
1821 /* CWR is to be held something *above* high_seq
1822 * is ACKed for CWR bit to reach receiver. */
1823 if (tp
->snd_una
!= tp
->high_seq
) {
1824 tcp_complete_cwr(sk
);
1825 tcp_set_ca_state(sk
, TCP_CA_Open
);
1829 case TCP_CA_Disorder
:
1830 tcp_try_undo_dsack(sk
, tp
);
1831 if (!tp
->undo_marker
||
1832 /* For SACK case do not Open to allow to undo
1833 * catching for all duplicate ACKs. */
1834 IsReno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
1835 tp
->undo_marker
= 0;
1836 tcp_set_ca_state(sk
, TCP_CA_Open
);
1840 case TCP_CA_Recovery
:
1842 tcp_reset_reno_sack(tp
);
1843 if (tcp_try_undo_recovery(sk
, tp
))
1845 tcp_complete_cwr(sk
);
1850 /* F. Process state. */
1851 switch (icsk
->icsk_ca_state
) {
1852 case TCP_CA_Recovery
:
1853 if (prior_snd_una
== tp
->snd_una
) {
1854 if (IsReno(tp
) && is_dupack
)
1855 tcp_add_reno_sack(sk
);
1857 int acked
= prior_packets
- tp
->packets_out
;
1859 tcp_remove_reno_sacks(sk
, tp
, acked
);
1860 is_dupack
= tcp_try_undo_partial(sk
, tp
, acked
);
1864 if (flag
&FLAG_DATA_ACKED
)
1865 icsk
->icsk_retransmits
= 0;
1866 if (!tcp_try_undo_loss(sk
, tp
)) {
1867 tcp_moderate_cwnd(tp
);
1868 tcp_xmit_retransmit_queue(sk
);
1871 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1873 /* Loss is undone; fall through to processing in Open state. */
1876 if (tp
->snd_una
!= prior_snd_una
)
1877 tcp_reset_reno_sack(tp
);
1879 tcp_add_reno_sack(sk
);
1882 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
1883 tcp_try_undo_dsack(sk
, tp
);
1885 if (!tcp_time_to_recover(sk
, tp
)) {
1886 tcp_try_to_open(sk
, tp
, flag
);
1890 /* Otherwise enter Recovery state */
1893 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
1895 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
1897 tp
->high_seq
= tp
->snd_nxt
;
1898 tp
->prior_ssthresh
= 0;
1899 tp
->undo_marker
= tp
->snd_una
;
1900 tp
->undo_retrans
= tp
->retrans_out
;
1902 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
1903 if (!(flag
&FLAG_ECE
))
1904 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1905 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1906 TCP_ECN_queue_cwr(tp
);
1909 tp
->bytes_acked
= 0;
1910 tp
->snd_cwnd_cnt
= 0;
1911 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
1914 if (is_dupack
|| tcp_head_timedout(sk
, tp
))
1915 tcp_update_scoreboard(sk
, tp
);
1917 tcp_xmit_retransmit_queue(sk
);
1920 /* Read draft-ietf-tcplw-high-performance before mucking
1921 * with this code. (Superceeds RFC1323)
1923 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
1925 /* RTTM Rule: A TSecr value received in a segment is used to
1926 * update the averaged RTT measurement only if the segment
1927 * acknowledges some new data, i.e., only if it advances the
1928 * left edge of the send window.
1930 * See draft-ietf-tcplw-high-performance-00, section 3.3.
1931 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
1933 * Changed: reset backoff as soon as we see the first valid sample.
1934 * If we do not, we get strongly overstimated rto. With timestamps
1935 * samples are accepted even from very old segments: f.e., when rtt=1
1936 * increases to 8, we retransmit 5 times and after 8 seconds delayed
1937 * answer arrives rto becomes 120 seconds! If at least one of segments
1938 * in window is lost... Voila. --ANK (010210)
1940 struct tcp_sock
*tp
= tcp_sk(sk
);
1941 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
1942 tcp_rtt_estimator(sk
, seq_rtt
);
1944 inet_csk(sk
)->icsk_backoff
= 0;
1948 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
1950 /* We don't have a timestamp. Can only use
1951 * packets that are not retransmitted to determine
1952 * rtt estimates. Also, we must not reset the
1953 * backoff for rto until we get a non-retransmitted
1954 * packet. This allows us to deal with a situation
1955 * where the network delay has increased suddenly.
1956 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
1959 if (flag
& FLAG_RETRANS_DATA_ACKED
)
1962 tcp_rtt_estimator(sk
, seq_rtt
);
1964 inet_csk(sk
)->icsk_backoff
= 0;
1968 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
1971 const struct tcp_sock
*tp
= tcp_sk(sk
);
1972 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
1973 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
1974 tcp_ack_saw_tstamp(sk
, flag
);
1975 else if (seq_rtt
>= 0)
1976 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
1979 static inline void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 rtt
,
1980 u32 in_flight
, int good
)
1982 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1983 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, rtt
, in_flight
, good
);
1984 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
1987 /* Restart timer after forward progress on connection.
1988 * RFC2988 recommends to restart timer to now+rto.
1991 static inline void tcp_ack_packets_out(struct sock
*sk
, struct tcp_sock
*tp
)
1993 if (!tp
->packets_out
) {
1994 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
1996 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2000 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
2001 __u32 now
, __s32
*seq_rtt
)
2003 struct tcp_sock
*tp
= tcp_sk(sk
);
2004 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2005 __u32 seq
= tp
->snd_una
;
2006 __u32 packets_acked
;
2009 /* If we get here, the whole TSO packet has not been
2012 BUG_ON(!after(scb
->end_seq
, seq
));
2014 packets_acked
= tcp_skb_pcount(skb
);
2015 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
2017 packets_acked
-= tcp_skb_pcount(skb
);
2019 if (packets_acked
) {
2020 __u8 sacked
= scb
->sacked
;
2022 acked
|= FLAG_DATA_ACKED
;
2024 if (sacked
& TCPCB_RETRANS
) {
2025 if (sacked
& TCPCB_SACKED_RETRANS
)
2026 tp
->retrans_out
-= packets_acked
;
2027 acked
|= FLAG_RETRANS_DATA_ACKED
;
2029 } else if (*seq_rtt
< 0)
2030 *seq_rtt
= now
- scb
->when
;
2031 if (sacked
& TCPCB_SACKED_ACKED
)
2032 tp
->sacked_out
-= packets_acked
;
2033 if (sacked
& TCPCB_LOST
)
2034 tp
->lost_out
-= packets_acked
;
2035 if (sacked
& TCPCB_URG
) {
2037 !before(seq
, tp
->snd_up
))
2040 } else if (*seq_rtt
< 0)
2041 *seq_rtt
= now
- scb
->when
;
2043 if (tp
->fackets_out
) {
2044 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2045 tp
->fackets_out
-= dval
;
2047 tp
->packets_out
-= packets_acked
;
2049 BUG_ON(tcp_skb_pcount(skb
) == 0);
2050 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2056 static inline u32
tcp_usrtt(const struct sk_buff
*skb
)
2058 struct timeval tv
, now
;
2060 do_gettimeofday(&now
);
2061 skb_get_timestamp(skb
, &tv
);
2062 return (now
.tv_sec
- tv
.tv_sec
) * 1000000 + (now
.tv_usec
- tv
.tv_usec
);
2065 /* Remove acknowledged frames from the retransmission queue. */
2066 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2068 struct tcp_sock
*tp
= tcp_sk(sk
);
2069 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2070 struct sk_buff
*skb
;
2071 __u32 now
= tcp_time_stamp
;
2075 void (*rtt_sample
)(struct sock
*sk
, u32 usrtt
)
2076 = icsk
->icsk_ca_ops
->rtt_sample
;
2078 while ((skb
= skb_peek(&sk
->sk_write_queue
)) &&
2079 skb
!= sk
->sk_send_head
) {
2080 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2081 __u8 sacked
= scb
->sacked
;
2083 /* If our packet is before the ack sequence we can
2084 * discard it as it's confirmed to have arrived at
2087 if (after(scb
->end_seq
, tp
->snd_una
)) {
2088 if (tcp_skb_pcount(skb
) > 1 &&
2089 after(tp
->snd_una
, scb
->seq
))
2090 acked
|= tcp_tso_acked(sk
, skb
,
2095 /* Initial outgoing SYN's get put onto the write_queue
2096 * just like anything else we transmit. It is not
2097 * true data, and if we misinform our callers that
2098 * this ACK acks real data, we will erroneously exit
2099 * connection startup slow start one packet too
2100 * quickly. This is severely frowned upon behavior.
2102 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2103 acked
|= FLAG_DATA_ACKED
;
2106 acked
|= FLAG_SYN_ACKED
;
2107 tp
->retrans_stamp
= 0;
2111 if (sacked
& TCPCB_RETRANS
) {
2112 if(sacked
& TCPCB_SACKED_RETRANS
)
2113 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2114 acked
|= FLAG_RETRANS_DATA_ACKED
;
2116 } else if (seq_rtt
< 0) {
2117 seq_rtt
= now
- scb
->when
;
2119 (*rtt_sample
)(sk
, tcp_usrtt(skb
));
2121 if (sacked
& TCPCB_SACKED_ACKED
)
2122 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2123 if (sacked
& TCPCB_LOST
)
2124 tp
->lost_out
-= tcp_skb_pcount(skb
);
2125 if (sacked
& TCPCB_URG
) {
2127 !before(scb
->end_seq
, tp
->snd_up
))
2130 } else if (seq_rtt
< 0) {
2131 seq_rtt
= now
- scb
->when
;
2133 (*rtt_sample
)(sk
, tcp_usrtt(skb
));
2135 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2136 tcp_packets_out_dec(tp
, skb
);
2137 __skb_unlink(skb
, &sk
->sk_write_queue
);
2138 sk_stream_free_skb(sk
, skb
);
2141 if (acked
&FLAG_ACKED
) {
2142 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2143 tcp_ack_packets_out(sk
, tp
);
2145 if (icsk
->icsk_ca_ops
->pkts_acked
)
2146 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
);
2149 #if FASTRETRANS_DEBUG > 0
2150 BUG_TRAP((int)tp
->sacked_out
>= 0);
2151 BUG_TRAP((int)tp
->lost_out
>= 0);
2152 BUG_TRAP((int)tp
->retrans_out
>= 0);
2153 if (!tp
->packets_out
&& tp
->rx_opt
.sack_ok
) {
2154 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2156 printk(KERN_DEBUG
"Leak l=%u %d\n",
2157 tp
->lost_out
, icsk
->icsk_ca_state
);
2160 if (tp
->sacked_out
) {
2161 printk(KERN_DEBUG
"Leak s=%u %d\n",
2162 tp
->sacked_out
, icsk
->icsk_ca_state
);
2165 if (tp
->retrans_out
) {
2166 printk(KERN_DEBUG
"Leak r=%u %d\n",
2167 tp
->retrans_out
, icsk
->icsk_ca_state
);
2168 tp
->retrans_out
= 0;
2172 *seq_rtt_p
= seq_rtt
;
2176 static void tcp_ack_probe(struct sock
*sk
)
2178 const struct tcp_sock
*tp
= tcp_sk(sk
);
2179 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2181 /* Was it a usable window open? */
2183 if (!after(TCP_SKB_CB(sk
->sk_send_head
)->end_seq
,
2184 tp
->snd_una
+ tp
->snd_wnd
)) {
2185 icsk
->icsk_backoff
= 0;
2186 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2187 /* Socket must be waked up by subsequent tcp_data_snd_check().
2188 * This function is not for random using!
2191 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2192 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2197 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2199 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2200 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2203 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2205 const struct tcp_sock
*tp
= tcp_sk(sk
);
2206 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2207 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2210 /* Check that window update is acceptable.
2211 * The function assumes that snd_una<=ack<=snd_next.
2213 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2214 const u32 ack_seq
, const u32 nwin
)
2216 return (after(ack
, tp
->snd_una
) ||
2217 after(ack_seq
, tp
->snd_wl1
) ||
2218 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2221 /* Update our send window.
2223 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2224 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2226 static int tcp_ack_update_window(struct sock
*sk
, struct tcp_sock
*tp
,
2227 struct sk_buff
*skb
, u32 ack
, u32 ack_seq
)
2230 u32 nwin
= ntohs(skb
->h
.th
->window
);
2232 if (likely(!skb
->h
.th
->syn
))
2233 nwin
<<= tp
->rx_opt
.snd_wscale
;
2235 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2236 flag
|= FLAG_WIN_UPDATE
;
2237 tcp_update_wl(tp
, ack
, ack_seq
);
2239 if (tp
->snd_wnd
!= nwin
) {
2242 /* Note, it is the only place, where
2243 * fast path is recovered for sending TCP.
2246 tcp_fast_path_check(sk
, tp
);
2248 if (nwin
> tp
->max_window
) {
2249 tp
->max_window
= nwin
;
2250 tcp_sync_mss(sk
, tp
->pmtu_cookie
);
2260 static void tcp_process_frto(struct sock
*sk
, u32 prior_snd_una
)
2262 struct tcp_sock
*tp
= tcp_sk(sk
);
2264 tcp_sync_left_out(tp
);
2266 if (tp
->snd_una
== prior_snd_una
||
2267 !before(tp
->snd_una
, tp
->frto_highmark
)) {
2268 /* RTO was caused by loss, start retransmitting in
2269 * go-back-N slow start
2271 tcp_enter_frto_loss(sk
);
2275 if (tp
->frto_counter
== 1) {
2276 /* First ACK after RTO advances the window: allow two new
2279 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2281 /* Also the second ACK after RTO advances the window.
2282 * The RTO was likely spurious. Reduce cwnd and continue
2283 * in congestion avoidance
2285 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2286 tcp_moderate_cwnd(tp
);
2289 /* F-RTO affects on two new ACKs following RTO.
2290 * At latest on third ACK the TCP behavor is back to normal.
2292 tp
->frto_counter
= (tp
->frto_counter
+ 1) % 3;
2295 /* This routine deals with incoming acks, but not outgoing ones. */
2296 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2298 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2299 struct tcp_sock
*tp
= tcp_sk(sk
);
2300 u32 prior_snd_una
= tp
->snd_una
;
2301 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2302 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2303 u32 prior_in_flight
;
2307 /* If the ack is newer than sent or older than previous acks
2308 * then we can probably ignore it.
2310 if (after(ack
, tp
->snd_nxt
))
2311 goto uninteresting_ack
;
2313 if (before(ack
, prior_snd_una
))
2316 if (sysctl_tcp_abc
&& icsk
->icsk_ca_state
< TCP_CA_CWR
)
2317 tp
->bytes_acked
+= ack
- prior_snd_una
;
2319 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2320 /* Window is constant, pure forward advance.
2321 * No more checks are required.
2322 * Note, we use the fact that SND.UNA>=SND.WL2.
2324 tcp_update_wl(tp
, ack
, ack_seq
);
2326 flag
|= FLAG_WIN_UPDATE
;
2328 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2330 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2332 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2335 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2337 flag
|= tcp_ack_update_window(sk
, tp
, skb
, ack
, ack_seq
);
2339 if (TCP_SKB_CB(skb
)->sacked
)
2340 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2342 if (TCP_ECN_rcv_ecn_echo(tp
, skb
->h
.th
))
2345 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
2348 /* We passed data and got it acked, remove any soft error
2349 * log. Something worked...
2351 sk
->sk_err_soft
= 0;
2352 tp
->rcv_tstamp
= tcp_time_stamp
;
2353 prior_packets
= tp
->packets_out
;
2357 prior_in_flight
= tcp_packets_in_flight(tp
);
2359 /* See if we can take anything off of the retransmit queue. */
2360 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
2362 if (tp
->frto_counter
)
2363 tcp_process_frto(sk
, prior_snd_una
);
2365 if (tcp_ack_is_dubious(sk
, flag
)) {
2366 /* Advanve CWND, if state allows this. */
2367 if ((flag
& FLAG_DATA_ACKED
) && tcp_may_raise_cwnd(sk
, flag
))
2368 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 0);
2369 tcp_fastretrans_alert(sk
, prior_snd_una
, prior_packets
, flag
);
2371 if ((flag
& FLAG_DATA_ACKED
))
2372 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 1);
2375 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
2376 dst_confirm(sk
->sk_dst_cache
);
2381 icsk
->icsk_probes_out
= 0;
2383 /* If this ack opens up a zero window, clear backoff. It was
2384 * being used to time the probes, and is probably far higher than
2385 * it needs to be for normal retransmission.
2387 if (sk
->sk_send_head
)
2392 if (TCP_SKB_CB(skb
)->sacked
)
2393 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2396 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
2401 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2402 * But, this can also be called on packets in the established flow when
2403 * the fast version below fails.
2405 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
2408 struct tcphdr
*th
= skb
->h
.th
;
2409 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
2411 ptr
= (unsigned char *)(th
+ 1);
2412 opt_rx
->saw_tstamp
= 0;
2421 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
2426 if (opsize
< 2) /* "silly options" */
2428 if (opsize
> length
)
2429 return; /* don't parse partial options */
2432 if(opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
2433 u16 in_mss
= ntohs(get_unaligned((__u16
*)ptr
));
2435 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
2436 in_mss
= opt_rx
->user_mss
;
2437 opt_rx
->mss_clamp
= in_mss
;
2442 if(opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
2443 if (sysctl_tcp_window_scaling
) {
2444 __u8 snd_wscale
= *(__u8
*) ptr
;
2445 opt_rx
->wscale_ok
= 1;
2446 if (snd_wscale
> 14) {
2448 printk(KERN_INFO
"tcp_parse_options: Illegal window "
2449 "scaling value %d >14 received.\n",
2453 opt_rx
->snd_wscale
= snd_wscale
;
2456 case TCPOPT_TIMESTAMP
:
2457 if(opsize
==TCPOLEN_TIMESTAMP
) {
2458 if ((estab
&& opt_rx
->tstamp_ok
) ||
2459 (!estab
&& sysctl_tcp_timestamps
)) {
2460 opt_rx
->saw_tstamp
= 1;
2461 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__u32
*)ptr
));
2462 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__u32
*)(ptr
+4)));
2466 case TCPOPT_SACK_PERM
:
2467 if(opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
2468 if (sysctl_tcp_sack
) {
2469 opt_rx
->sack_ok
= 1;
2470 tcp_sack_reset(opt_rx
);
2476 if((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
2477 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
2479 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
2488 /* Fast parse options. This hopes to only see timestamps.
2489 * If it is wrong it falls back on tcp_parse_options().
2491 static inline int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
2492 struct tcp_sock
*tp
)
2494 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
2495 tp
->rx_opt
.saw_tstamp
= 0;
2497 } else if (tp
->rx_opt
.tstamp_ok
&&
2498 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
2499 __u32
*ptr
= (__u32
*)(th
+ 1);
2500 if (*ptr
== ntohl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
2501 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
2502 tp
->rx_opt
.saw_tstamp
= 1;
2504 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
2506 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
2510 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
2514 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
2516 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
2517 tp
->rx_opt
.ts_recent_stamp
= xtime
.tv_sec
;
2520 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
2522 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
2523 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2524 * extra check below makes sure this can only happen
2525 * for pure ACK frames. -DaveM
2527 * Not only, also it occurs for expired timestamps.
2530 if((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
2531 xtime
.tv_sec
>= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
2532 tcp_store_ts_recent(tp
);
2536 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2538 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2539 * it can pass through stack. So, the following predicate verifies that
2540 * this segment is not used for anything but congestion avoidance or
2541 * fast retransmit. Moreover, we even are able to eliminate most of such
2542 * second order effects, if we apply some small "replay" window (~RTO)
2543 * to timestamp space.
2545 * All these measures still do not guarantee that we reject wrapped ACKs
2546 * on networks with high bandwidth, when sequence space is recycled fastly,
2547 * but it guarantees that such events will be very rare and do not affect
2548 * connection seriously. This doesn't look nice, but alas, PAWS is really
2551 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2552 * states that events when retransmit arrives after original data are rare.
2553 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2554 * the biggest problem on large power networks even with minor reordering.
2555 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2556 * up to bandwidth of 18Gigabit/sec. 8) ]
2559 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
2561 struct tcp_sock
*tp
= tcp_sk(sk
);
2562 struct tcphdr
*th
= skb
->h
.th
;
2563 u32 seq
= TCP_SKB_CB(skb
)->seq
;
2564 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2566 return (/* 1. Pure ACK with correct sequence number. */
2567 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
2569 /* 2. ... and duplicate ACK. */
2570 ack
== tp
->snd_una
&&
2572 /* 3. ... and does not update window. */
2573 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
2575 /* 4. ... and sits in replay window. */
2576 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
2579 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
2581 const struct tcp_sock
*tp
= tcp_sk(sk
);
2582 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
2583 xtime
.tv_sec
< tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
2584 !tcp_disordered_ack(sk
, skb
));
2587 /* Check segment sequence number for validity.
2589 * Segment controls are considered valid, if the segment
2590 * fits to the window after truncation to the window. Acceptability
2591 * of data (and SYN, FIN, of course) is checked separately.
2592 * See tcp_data_queue(), for example.
2594 * Also, controls (RST is main one) are accepted using RCV.WUP instead
2595 * of RCV.NXT. Peer still did not advance his SND.UNA when we
2596 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2597 * (borrowed from freebsd)
2600 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2602 return !before(end_seq
, tp
->rcv_wup
) &&
2603 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
2606 /* When we get a reset we do this. */
2607 static void tcp_reset(struct sock
*sk
)
2609 /* We want the right error as BSD sees it (and indeed as we do). */
2610 switch (sk
->sk_state
) {
2612 sk
->sk_err
= ECONNREFUSED
;
2614 case TCP_CLOSE_WAIT
:
2620 sk
->sk_err
= ECONNRESET
;
2623 if (!sock_flag(sk
, SOCK_DEAD
))
2624 sk
->sk_error_report(sk
);
2630 * Process the FIN bit. This now behaves as it is supposed to work
2631 * and the FIN takes effect when it is validly part of sequence
2632 * space. Not before when we get holes.
2634 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2635 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
2638 * If we are in FINWAIT-1, a received FIN indicates simultaneous
2639 * close and we go into CLOSING (and later onto TIME-WAIT)
2641 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2643 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
2645 struct tcp_sock
*tp
= tcp_sk(sk
);
2647 inet_csk_schedule_ack(sk
);
2649 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
2650 sock_set_flag(sk
, SOCK_DONE
);
2652 switch (sk
->sk_state
) {
2654 case TCP_ESTABLISHED
:
2655 /* Move to CLOSE_WAIT */
2656 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
2657 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
2660 case TCP_CLOSE_WAIT
:
2662 /* Received a retransmission of the FIN, do
2667 /* RFC793: Remain in the LAST-ACK state. */
2671 /* This case occurs when a simultaneous close
2672 * happens, we must ack the received FIN and
2673 * enter the CLOSING state.
2676 tcp_set_state(sk
, TCP_CLOSING
);
2679 /* Received a FIN -- send ACK and enter TIME_WAIT. */
2681 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
2684 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2685 * cases we should never reach this piece of code.
2687 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
2688 __FUNCTION__
, sk
->sk_state
);
2692 /* It _is_ possible, that we have something out-of-order _after_ FIN.
2693 * Probably, we should reset in this case. For now drop them.
2695 __skb_queue_purge(&tp
->out_of_order_queue
);
2696 if (tp
->rx_opt
.sack_ok
)
2697 tcp_sack_reset(&tp
->rx_opt
);
2698 sk_stream_mem_reclaim(sk
);
2700 if (!sock_flag(sk
, SOCK_DEAD
)) {
2701 sk
->sk_state_change(sk
);
2703 /* Do not send POLL_HUP for half duplex close. */
2704 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
2705 sk
->sk_state
== TCP_CLOSE
)
2706 sk_wake_async(sk
, 1, POLL_HUP
);
2708 sk_wake_async(sk
, 1, POLL_IN
);
2712 static __inline__
int
2713 tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
2715 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
2716 if (before(seq
, sp
->start_seq
))
2717 sp
->start_seq
= seq
;
2718 if (after(end_seq
, sp
->end_seq
))
2719 sp
->end_seq
= end_seq
;
2725 static inline void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2727 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
2728 if (before(seq
, tp
->rcv_nxt
))
2729 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
2731 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
2733 tp
->rx_opt
.dsack
= 1;
2734 tp
->duplicate_sack
[0].start_seq
= seq
;
2735 tp
->duplicate_sack
[0].end_seq
= end_seq
;
2736 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
2740 static inline void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2742 if (!tp
->rx_opt
.dsack
)
2743 tcp_dsack_set(tp
, seq
, end_seq
);
2745 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
2748 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
2750 struct tcp_sock
*tp
= tcp_sk(sk
);
2752 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
2753 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
2754 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
2755 tcp_enter_quickack_mode(sk
);
2757 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
2758 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
2760 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
2761 end_seq
= tp
->rcv_nxt
;
2762 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
2769 /* These routines update the SACK block as out-of-order packets arrive or
2770 * in-order packets close up the sequence space.
2772 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
2775 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
2776 struct tcp_sack_block
*swalk
= sp
+1;
2778 /* See if the recent change to the first SACK eats into
2779 * or hits the sequence space of other SACK blocks, if so coalesce.
2781 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
2782 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
2785 /* Zap SWALK, by moving every further SACK up by one slot.
2786 * Decrease num_sacks.
2788 tp
->rx_opt
.num_sacks
--;
2789 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
2790 for(i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
2794 this_sack
++, swalk
++;
2798 static __inline__
void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
2802 tmp
= sack1
->start_seq
;
2803 sack1
->start_seq
= sack2
->start_seq
;
2804 sack2
->start_seq
= tmp
;
2806 tmp
= sack1
->end_seq
;
2807 sack1
->end_seq
= sack2
->end_seq
;
2808 sack2
->end_seq
= tmp
;
2811 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
2813 struct tcp_sock
*tp
= tcp_sk(sk
);
2814 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
2815 int cur_sacks
= tp
->rx_opt
.num_sacks
;
2821 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
2822 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
2823 /* Rotate this_sack to the first one. */
2824 for (; this_sack
>0; this_sack
--, sp
--)
2825 tcp_sack_swap(sp
, sp
-1);
2827 tcp_sack_maybe_coalesce(tp
);
2832 /* Could not find an adjacent existing SACK, build a new one,
2833 * put it at the front, and shift everyone else down. We
2834 * always know there is at least one SACK present already here.
2836 * If the sack array is full, forget about the last one.
2838 if (this_sack
>= 4) {
2840 tp
->rx_opt
.num_sacks
--;
2843 for(; this_sack
> 0; this_sack
--, sp
--)
2847 /* Build the new head SACK, and we're done. */
2848 sp
->start_seq
= seq
;
2849 sp
->end_seq
= end_seq
;
2850 tp
->rx_opt
.num_sacks
++;
2851 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
2854 /* RCV.NXT advances, some SACKs should be eaten. */
2856 static void tcp_sack_remove(struct tcp_sock
*tp
)
2858 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
2859 int num_sacks
= tp
->rx_opt
.num_sacks
;
2862 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
2863 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
2864 tp
->rx_opt
.num_sacks
= 0;
2865 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
2869 for(this_sack
= 0; this_sack
< num_sacks
; ) {
2870 /* Check if the start of the sack is covered by RCV.NXT. */
2871 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
2874 /* RCV.NXT must cover all the block! */
2875 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
2877 /* Zap this SACK, by moving forward any other SACKS. */
2878 for (i
=this_sack
+1; i
< num_sacks
; i
++)
2879 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
2886 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
2887 tp
->rx_opt
.num_sacks
= num_sacks
;
2888 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
2892 /* This one checks to see if we can put data from the
2893 * out_of_order queue into the receive_queue.
2895 static void tcp_ofo_queue(struct sock
*sk
)
2897 struct tcp_sock
*tp
= tcp_sk(sk
);
2898 __u32 dsack_high
= tp
->rcv_nxt
;
2899 struct sk_buff
*skb
;
2901 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
2902 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
2905 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
2906 __u32 dsack
= dsack_high
;
2907 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
2908 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
2909 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
2912 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
2913 SOCK_DEBUG(sk
, "ofo packet was already received \n");
2914 __skb_unlink(skb
, &tp
->out_of_order_queue
);
2918 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
2919 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
2920 TCP_SKB_CB(skb
)->end_seq
);
2922 __skb_unlink(skb
, &tp
->out_of_order_queue
);
2923 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
2924 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
2926 tcp_fin(skb
, sk
, skb
->h
.th
);
2930 static int tcp_prune_queue(struct sock
*sk
);
2932 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
2934 struct tcphdr
*th
= skb
->h
.th
;
2935 struct tcp_sock
*tp
= tcp_sk(sk
);
2938 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
2941 __skb_pull(skb
, th
->doff
*4);
2943 TCP_ECN_accept_cwr(tp
, skb
);
2945 if (tp
->rx_opt
.dsack
) {
2946 tp
->rx_opt
.dsack
= 0;
2947 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
2948 4 - tp
->rx_opt
.tstamp_ok
);
2951 /* Queue data for delivery to the user.
2952 * Packets in sequence go to the receive queue.
2953 * Out of sequence packets to the out_of_order_queue.
2955 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
2956 if (tcp_receive_window(tp
) == 0)
2959 /* Ok. In sequence. In window. */
2960 if (tp
->ucopy
.task
== current
&&
2961 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
2962 sock_owned_by_user(sk
) && !tp
->urg_data
) {
2963 int chunk
= min_t(unsigned int, skb
->len
,
2966 __set_current_state(TASK_RUNNING
);
2969 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
2970 tp
->ucopy
.len
-= chunk
;
2971 tp
->copied_seq
+= chunk
;
2972 eaten
= (chunk
== skb
->len
&& !th
->fin
);
2973 tcp_rcv_space_adjust(sk
);
2981 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
2982 !sk_stream_rmem_schedule(sk
, skb
))) {
2983 if (tcp_prune_queue(sk
) < 0 ||
2984 !sk_stream_rmem_schedule(sk
, skb
))
2987 sk_stream_set_owner_r(skb
, sk
);
2988 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
2990 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
2992 tcp_event_data_recv(sk
, tp
, skb
);
2994 tcp_fin(skb
, sk
, th
);
2996 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
2999 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3000 * gap in queue is filled.
3002 if (skb_queue_empty(&tp
->out_of_order_queue
))
3003 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3006 if (tp
->rx_opt
.num_sacks
)
3007 tcp_sack_remove(tp
);
3009 tcp_fast_path_check(sk
, tp
);
3013 else if (!sock_flag(sk
, SOCK_DEAD
))
3014 sk
->sk_data_ready(sk
, 0);
3018 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3019 /* A retransmit, 2nd most common case. Force an immediate ack. */
3020 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3021 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3024 tcp_enter_quickack_mode(sk
);
3025 inet_csk_schedule_ack(sk
);
3031 /* Out of window. F.e. zero window probe. */
3032 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3035 tcp_enter_quickack_mode(sk
);
3037 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3038 /* Partial packet, seq < rcv_next < end_seq */
3039 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3040 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3041 TCP_SKB_CB(skb
)->end_seq
);
3043 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3045 /* If window is closed, drop tail of packet. But after
3046 * remembering D-SACK for its head made in previous line.
3048 if (!tcp_receive_window(tp
))
3053 TCP_ECN_check_ce(tp
, skb
);
3055 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3056 !sk_stream_rmem_schedule(sk
, skb
)) {
3057 if (tcp_prune_queue(sk
) < 0 ||
3058 !sk_stream_rmem_schedule(sk
, skb
))
3062 /* Disable header prediction. */
3064 inet_csk_schedule_ack(sk
);
3066 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3067 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3069 sk_stream_set_owner_r(skb
, sk
);
3071 if (!skb_peek(&tp
->out_of_order_queue
)) {
3072 /* Initial out of order segment, build 1 SACK. */
3073 if (tp
->rx_opt
.sack_ok
) {
3074 tp
->rx_opt
.num_sacks
= 1;
3075 tp
->rx_opt
.dsack
= 0;
3076 tp
->rx_opt
.eff_sacks
= 1;
3077 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3078 tp
->selective_acks
[0].end_seq
=
3079 TCP_SKB_CB(skb
)->end_seq
;
3081 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3083 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3084 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3085 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3087 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3088 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3090 if (!tp
->rx_opt
.num_sacks
||
3091 tp
->selective_acks
[0].end_seq
!= seq
)
3094 /* Common case: data arrive in order after hole. */
3095 tp
->selective_acks
[0].end_seq
= end_seq
;
3099 /* Find place to insert this segment. */
3101 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3103 } while ((skb1
= skb1
->prev
) !=
3104 (struct sk_buff
*)&tp
->out_of_order_queue
);
3106 /* Do skb overlap to previous one? */
3107 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3108 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3109 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3110 /* All the bits are present. Drop. */
3112 tcp_dsack_set(tp
, seq
, end_seq
);
3115 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3116 /* Partial overlap. */
3117 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3122 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3124 /* And clean segments covered by new one as whole. */
3125 while ((skb1
= skb
->next
) !=
3126 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3127 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3128 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3129 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3132 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3133 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3138 if (tp
->rx_opt
.sack_ok
)
3139 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3143 /* Collapse contiguous sequence of skbs head..tail with
3144 * sequence numbers start..end.
3145 * Segments with FIN/SYN are not collapsed (only because this
3149 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3150 struct sk_buff
*head
, struct sk_buff
*tail
,
3153 struct sk_buff
*skb
;
3155 /* First, check that queue is collapsable and find
3156 * the point where collapsing can be useful. */
3157 for (skb
= head
; skb
!= tail
; ) {
3158 /* No new bits? It is possible on ofo queue. */
3159 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3160 struct sk_buff
*next
= skb
->next
;
3161 __skb_unlink(skb
, list
);
3163 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3168 /* The first skb to collapse is:
3170 * - bloated or contains data before "start" or
3171 * overlaps to the next one.
3173 if (!skb
->h
.th
->syn
&& !skb
->h
.th
->fin
&&
3174 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3175 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3176 (skb
->next
!= tail
&&
3177 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3180 /* Decided to skip this, advance start seq. */
3181 start
= TCP_SKB_CB(skb
)->end_seq
;
3184 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3187 while (before(start
, end
)) {
3188 struct sk_buff
*nskb
;
3189 int header
= skb_headroom(skb
);
3190 int copy
= SKB_MAX_ORDER(header
, 0);
3192 /* Too big header? This can happen with IPv6. */
3195 if (end
-start
< copy
)
3197 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3200 skb_reserve(nskb
, header
);
3201 memcpy(nskb
->head
, skb
->head
, header
);
3202 nskb
->nh
.raw
= nskb
->head
+ (skb
->nh
.raw
-skb
->head
);
3203 nskb
->h
.raw
= nskb
->head
+ (skb
->h
.raw
-skb
->head
);
3204 nskb
->mac
.raw
= nskb
->head
+ (skb
->mac
.raw
-skb
->head
);
3205 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3206 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3207 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3208 sk_stream_set_owner_r(nskb
, sk
);
3210 /* Copy data, releasing collapsed skbs. */
3212 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3213 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3215 if (offset
< 0) BUG();
3217 size
= min(copy
, size
);
3218 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3220 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3224 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3225 struct sk_buff
*next
= skb
->next
;
3226 __skb_unlink(skb
, list
);
3228 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3230 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3237 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3238 * and tcp_collapse() them until all the queue is collapsed.
3240 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3242 struct tcp_sock
*tp
= tcp_sk(sk
);
3243 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3244 struct sk_buff
*head
;
3250 start
= TCP_SKB_CB(skb
)->seq
;
3251 end
= TCP_SKB_CB(skb
)->end_seq
;
3257 /* Segment is terminated when we see gap or when
3258 * we are at the end of all the queue. */
3259 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3260 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3261 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3262 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3263 head
, skb
, start
, end
);
3265 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3267 /* Start new segment */
3268 start
= TCP_SKB_CB(skb
)->seq
;
3269 end
= TCP_SKB_CB(skb
)->end_seq
;
3271 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3272 start
= TCP_SKB_CB(skb
)->seq
;
3273 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3274 end
= TCP_SKB_CB(skb
)->end_seq
;
3279 /* Reduce allocated memory if we can, trying to get
3280 * the socket within its memory limits again.
3282 * Return less than zero if we should start dropping frames
3283 * until the socket owning process reads some of the data
3284 * to stabilize the situation.
3286 static int tcp_prune_queue(struct sock
*sk
)
3288 struct tcp_sock
*tp
= tcp_sk(sk
);
3290 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3292 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3294 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3295 tcp_clamp_window(sk
, tp
);
3296 else if (tcp_memory_pressure
)
3297 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3299 tcp_collapse_ofo_queue(sk
);
3300 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3301 sk
->sk_receive_queue
.next
,
3302 (struct sk_buff
*)&sk
->sk_receive_queue
,
3303 tp
->copied_seq
, tp
->rcv_nxt
);
3304 sk_stream_mem_reclaim(sk
);
3306 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3309 /* Collapsing did not help, destructive actions follow.
3310 * This must not ever occur. */
3312 /* First, purge the out_of_order queue. */
3313 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3314 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3315 __skb_queue_purge(&tp
->out_of_order_queue
);
3317 /* Reset SACK state. A conforming SACK implementation will
3318 * do the same at a timeout based retransmit. When a connection
3319 * is in a sad state like this, we care only about integrity
3320 * of the connection not performance.
3322 if (tp
->rx_opt
.sack_ok
)
3323 tcp_sack_reset(&tp
->rx_opt
);
3324 sk_stream_mem_reclaim(sk
);
3327 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3330 /* If we are really being abused, tell the caller to silently
3331 * drop receive data on the floor. It will get retransmitted
3332 * and hopefully then we'll have sufficient space.
3334 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
3336 /* Massive buffer overcommit. */
3342 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3343 * As additional protections, we do not touch cwnd in retransmission phases,
3344 * and if application hit its sndbuf limit recently.
3346 void tcp_cwnd_application_limited(struct sock
*sk
)
3348 struct tcp_sock
*tp
= tcp_sk(sk
);
3350 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
3351 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
3352 /* Limited by application or receiver window. */
3353 u32 win_used
= max(tp
->snd_cwnd_used
, 2U);
3354 if (win_used
< tp
->snd_cwnd
) {
3355 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3356 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
3358 tp
->snd_cwnd_used
= 0;
3360 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3363 static inline int tcp_should_expand_sndbuf(struct sock
*sk
, struct tcp_sock
*tp
)
3365 /* If the user specified a specific send buffer setting, do
3368 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
3371 /* If we are under global TCP memory pressure, do not expand. */
3372 if (tcp_memory_pressure
)
3375 /* If we are under soft global TCP memory pressure, do not expand. */
3376 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
3379 /* If we filled the congestion window, do not expand. */
3380 if (tp
->packets_out
>= tp
->snd_cwnd
)
3386 /* When incoming ACK allowed to free some skb from write_queue,
3387 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3388 * on the exit from tcp input handler.
3390 * PROBLEM: sndbuf expansion does not work well with largesend.
3392 static void tcp_new_space(struct sock
*sk
)
3394 struct tcp_sock
*tp
= tcp_sk(sk
);
3396 if (tcp_should_expand_sndbuf(sk
, tp
)) {
3397 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
3398 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
3399 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
3400 tp
->reordering
+ 1);
3401 sndmem
*= 2*demanded
;
3402 if (sndmem
> sk
->sk_sndbuf
)
3403 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
3404 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3407 sk
->sk_write_space(sk
);
3410 static inline void tcp_check_space(struct sock
*sk
)
3412 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
3413 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
3414 if (sk
->sk_socket
&&
3415 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
3420 static __inline__
void tcp_data_snd_check(struct sock
*sk
, struct tcp_sock
*tp
)
3422 tcp_push_pending_frames(sk
, tp
);
3423 tcp_check_space(sk
);
3427 * Check if sending an ack is needed.
3429 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
3431 struct tcp_sock
*tp
= tcp_sk(sk
);
3433 /* More than one full frame received... */
3434 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
3435 /* ... and right edge of window advances far enough.
3436 * (tcp_recvmsg() will send ACK otherwise). Or...
3438 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
3439 /* We ACK each frame or... */
3440 tcp_in_quickack_mode(sk
) ||
3441 /* We have out of order data. */
3443 skb_peek(&tp
->out_of_order_queue
))) {
3444 /* Then ack it now */
3447 /* Else, send delayed ack. */
3448 tcp_send_delayed_ack(sk
);
3452 static __inline__
void tcp_ack_snd_check(struct sock
*sk
)
3454 if (!inet_csk_ack_scheduled(sk
)) {
3455 /* We sent a data segment already. */
3458 __tcp_ack_snd_check(sk
, 1);
3462 * This routine is only called when we have urgent data
3463 * signalled. Its the 'slow' part of tcp_urg. It could be
3464 * moved inline now as tcp_urg is only called from one
3465 * place. We handle URGent data wrong. We have to - as
3466 * BSD still doesn't use the correction from RFC961.
3467 * For 1003.1g we should support a new option TCP_STDURG to permit
3468 * either form (or just set the sysctl tcp_stdurg).
3471 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
3473 struct tcp_sock
*tp
= tcp_sk(sk
);
3474 u32 ptr
= ntohs(th
->urg_ptr
);
3476 if (ptr
&& !sysctl_tcp_stdurg
)
3478 ptr
+= ntohl(th
->seq
);
3480 /* Ignore urgent data that we've already seen and read. */
3481 if (after(tp
->copied_seq
, ptr
))
3484 /* Do not replay urg ptr.
3486 * NOTE: interesting situation not covered by specs.
3487 * Misbehaving sender may send urg ptr, pointing to segment,
3488 * which we already have in ofo queue. We are not able to fetch
3489 * such data and will stay in TCP_URG_NOTYET until will be eaten
3490 * by recvmsg(). Seems, we are not obliged to handle such wicked
3491 * situations. But it is worth to think about possibility of some
3492 * DoSes using some hypothetical application level deadlock.
3494 if (before(ptr
, tp
->rcv_nxt
))
3497 /* Do we already have a newer (or duplicate) urgent pointer? */
3498 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
3501 /* Tell the world about our new urgent pointer. */
3504 /* We may be adding urgent data when the last byte read was
3505 * urgent. To do this requires some care. We cannot just ignore
3506 * tp->copied_seq since we would read the last urgent byte again
3507 * as data, nor can we alter copied_seq until this data arrives
3508 * or we break the sematics of SIOCATMARK (and thus sockatmark())
3510 * NOTE. Double Dutch. Rendering to plain English: author of comment
3511 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3512 * and expect that both A and B disappear from stream. This is _wrong_.
3513 * Though this happens in BSD with high probability, this is occasional.
3514 * Any application relying on this is buggy. Note also, that fix "works"
3515 * only in this artificial test. Insert some normal data between A and B and we will
3516 * decline of BSD again. Verdict: it is better to remove to trap
3519 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
3520 !sock_flag(sk
, SOCK_URGINLINE
) &&
3521 tp
->copied_seq
!= tp
->rcv_nxt
) {
3522 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
3524 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
3525 __skb_unlink(skb
, &sk
->sk_receive_queue
);
3530 tp
->urg_data
= TCP_URG_NOTYET
;
3533 /* Disable header prediction. */
3537 /* This is the 'fast' part of urgent handling. */
3538 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
3540 struct tcp_sock
*tp
= tcp_sk(sk
);
3542 /* Check if we get a new urgent pointer - normally not. */
3544 tcp_check_urg(sk
,th
);
3546 /* Do we wait for any urgent data? - normally not... */
3547 if (tp
->urg_data
== TCP_URG_NOTYET
) {
3548 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
3551 /* Is the urgent pointer pointing into this packet? */
3552 if (ptr
< skb
->len
) {
3554 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
3556 tp
->urg_data
= TCP_URG_VALID
| tmp
;
3557 if (!sock_flag(sk
, SOCK_DEAD
))
3558 sk
->sk_data_ready(sk
, 0);
3563 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
3565 struct tcp_sock
*tp
= tcp_sk(sk
);
3566 int chunk
= skb
->len
- hlen
;
3570 if (skb
->ip_summed
==CHECKSUM_UNNECESSARY
)
3571 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
3573 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
3577 tp
->ucopy
.len
-= chunk
;
3578 tp
->copied_seq
+= chunk
;
3579 tcp_rcv_space_adjust(sk
);
3586 static int __tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
3590 if (sock_owned_by_user(sk
)) {
3592 result
= __tcp_checksum_complete(skb
);
3595 result
= __tcp_checksum_complete(skb
);
3600 static __inline__
int
3601 tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
3603 return skb
->ip_summed
!= CHECKSUM_UNNECESSARY
&&
3604 __tcp_checksum_complete_user(sk
, skb
);
3608 * TCP receive function for the ESTABLISHED state.
3610 * It is split into a fast path and a slow path. The fast path is
3612 * - A zero window was announced from us - zero window probing
3613 * is only handled properly in the slow path.
3614 * - Out of order segments arrived.
3615 * - Urgent data is expected.
3616 * - There is no buffer space left
3617 * - Unexpected TCP flags/window values/header lengths are received
3618 * (detected by checking the TCP header against pred_flags)
3619 * - Data is sent in both directions. Fast path only supports pure senders
3620 * or pure receivers (this means either the sequence number or the ack
3621 * value must stay constant)
3622 * - Unexpected TCP option.
3624 * When these conditions are not satisfied it drops into a standard
3625 * receive procedure patterned after RFC793 to handle all cases.
3626 * The first three cases are guaranteed by proper pred_flags setting,
3627 * the rest is checked inline. Fast processing is turned on in
3628 * tcp_data_queue when everything is OK.
3630 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
3631 struct tcphdr
*th
, unsigned len
)
3633 struct tcp_sock
*tp
= tcp_sk(sk
);
3636 * Header prediction.
3637 * The code loosely follows the one in the famous
3638 * "30 instruction TCP receive" Van Jacobson mail.
3640 * Van's trick is to deposit buffers into socket queue
3641 * on a device interrupt, to call tcp_recv function
3642 * on the receive process context and checksum and copy
3643 * the buffer to user space. smart...
3645 * Our current scheme is not silly either but we take the
3646 * extra cost of the net_bh soft interrupt processing...
3647 * We do checksum and copy also but from device to kernel.
3650 tp
->rx_opt
.saw_tstamp
= 0;
3652 /* pred_flags is 0xS?10 << 16 + snd_wnd
3653 * if header_predition is to be made
3654 * 'S' will always be tp->tcp_header_len >> 2
3655 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3656 * turn it off (when there are holes in the receive
3657 * space for instance)
3658 * PSH flag is ignored.
3661 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
3662 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3663 int tcp_header_len
= tp
->tcp_header_len
;
3665 /* Timestamp header prediction: tcp_header_len
3666 * is automatically equal to th->doff*4 due to pred_flags
3670 /* Check timestamp */
3671 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
3672 __u32
*ptr
= (__u32
*)(th
+ 1);
3674 /* No? Slow path! */
3675 if (*ptr
!= ntohl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3676 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
3679 tp
->rx_opt
.saw_tstamp
= 1;
3681 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3683 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3685 /* If PAWS failed, check it more carefully in slow path */
3686 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
3689 /* DO NOT update ts_recent here, if checksum fails
3690 * and timestamp was corrupted part, it will result
3691 * in a hung connection since we will drop all
3692 * future packets due to the PAWS test.
3696 if (len
<= tcp_header_len
) {
3697 /* Bulk data transfer: sender */
3698 if (len
== tcp_header_len
) {
3699 /* Predicted packet is in window by definition.
3700 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3701 * Hence, check seq<=rcv_wup reduces to:
3703 if (tcp_header_len
==
3704 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
3705 tp
->rcv_nxt
== tp
->rcv_wup
)
3706 tcp_store_ts_recent(tp
);
3708 tcp_rcv_rtt_measure_ts(sk
, skb
);
3710 /* We know that such packets are checksummed
3713 tcp_ack(sk
, skb
, 0);
3715 tcp_data_snd_check(sk
, tp
);
3717 } else { /* Header too small */
3718 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
3724 if (tp
->ucopy
.task
== current
&&
3725 tp
->copied_seq
== tp
->rcv_nxt
&&
3726 len
- tcp_header_len
<= tp
->ucopy
.len
&&
3727 sock_owned_by_user(sk
)) {
3728 __set_current_state(TASK_RUNNING
);
3730 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
3731 /* Predicted packet is in window by definition.
3732 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3733 * Hence, check seq<=rcv_wup reduces to:
3735 if (tcp_header_len
==
3736 (sizeof(struct tcphdr
) +
3737 TCPOLEN_TSTAMP_ALIGNED
) &&
3738 tp
->rcv_nxt
== tp
->rcv_wup
)
3739 tcp_store_ts_recent(tp
);
3741 tcp_rcv_rtt_measure_ts(sk
, skb
);
3743 __skb_pull(skb
, tcp_header_len
);
3744 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3745 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
3750 if (tcp_checksum_complete_user(sk
, skb
))
3753 /* Predicted packet is in window by definition.
3754 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3755 * Hence, check seq<=rcv_wup reduces to:
3757 if (tcp_header_len
==
3758 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
3759 tp
->rcv_nxt
== tp
->rcv_wup
)
3760 tcp_store_ts_recent(tp
);
3762 tcp_rcv_rtt_measure_ts(sk
, skb
);
3764 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
3767 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
3769 /* Bulk data transfer: receiver */
3770 __skb_pull(skb
,tcp_header_len
);
3771 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3772 sk_stream_set_owner_r(skb
, sk
);
3773 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3776 tcp_event_data_recv(sk
, tp
, skb
);
3778 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
3779 /* Well, only one small jumplet in fast path... */
3780 tcp_ack(sk
, skb
, FLAG_DATA
);
3781 tcp_data_snd_check(sk
, tp
);
3782 if (!inet_csk_ack_scheduled(sk
))
3786 __tcp_ack_snd_check(sk
, 0);
3791 sk
->sk_data_ready(sk
, 0);
3797 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
3801 * RFC1323: H1. Apply PAWS check first.
3803 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
3804 tcp_paws_discard(sk
, skb
)) {
3806 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
3807 tcp_send_dupack(sk
, skb
);
3810 /* Resets are accepted even if PAWS failed.
3812 ts_recent update must be made after we are sure
3813 that the packet is in window.
3818 * Standard slow path.
3821 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
3822 /* RFC793, page 37: "In all states except SYN-SENT, all reset
3823 * (RST) segments are validated by checking their SEQ-fields."
3824 * And page 69: "If an incoming segment is not acceptable,
3825 * an acknowledgment should be sent in reply (unless the RST bit
3826 * is set, if so drop the segment and return)".
3829 tcp_send_dupack(sk
, skb
);
3838 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3840 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3841 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
3842 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
3849 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
3851 tcp_rcv_rtt_measure_ts(sk
, skb
);
3853 /* Process urgent data. */
3854 tcp_urg(sk
, skb
, th
);
3856 /* step 7: process the segment text */
3857 tcp_data_queue(sk
, skb
);
3859 tcp_data_snd_check(sk
, tp
);
3860 tcp_ack_snd_check(sk
);
3864 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
3871 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
3872 struct tcphdr
*th
, unsigned len
)
3874 struct tcp_sock
*tp
= tcp_sk(sk
);
3875 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
3877 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
3880 struct inet_connection_sock
*icsk
;
3882 * "If the state is SYN-SENT then
3883 * first check the ACK bit
3884 * If the ACK bit is set
3885 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
3886 * a reset (unless the RST bit is set, if so drop
3887 * the segment and return)"
3889 * We do not send data with SYN, so that RFC-correct
3892 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
3893 goto reset_and_undo
;
3895 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
3896 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
3898 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
3899 goto reset_and_undo
;
3902 /* Now ACK is acceptable.
3904 * "If the RST bit is set
3905 * If the ACK was acceptable then signal the user "error:
3906 * connection reset", drop the segment, enter CLOSED state,
3907 * delete TCB, and return."
3916 * "fifth, if neither of the SYN or RST bits is set then
3917 * drop the segment and return."
3923 goto discard_and_undo
;
3926 * "If the SYN bit is on ...
3927 * are acceptable then ...
3928 * (our SYN has been ACKed), change the connection
3929 * state to ESTABLISHED..."
3932 TCP_ECN_rcv_synack(tp
, th
);
3933 if (tp
->ecn_flags
&TCP_ECN_OK
)
3934 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
3936 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
3937 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
3939 /* Ok.. it's good. Set up sequence numbers and
3940 * move to established.
3942 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
3943 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
3945 /* RFC1323: The window in SYN & SYN/ACK segments is
3948 tp
->snd_wnd
= ntohs(th
->window
);
3949 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
3951 if (!tp
->rx_opt
.wscale_ok
) {
3952 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
3953 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
3956 if (tp
->rx_opt
.saw_tstamp
) {
3957 tp
->rx_opt
.tstamp_ok
= 1;
3958 tp
->tcp_header_len
=
3959 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
3960 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
3961 tcp_store_ts_recent(tp
);
3963 tp
->tcp_header_len
= sizeof(struct tcphdr
);
3966 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_fack
)
3967 tp
->rx_opt
.sack_ok
|= 2;
3969 tcp_sync_mss(sk
, tp
->pmtu_cookie
);
3970 tcp_initialize_rcv_mss(sk
);
3972 /* Remember, tcp_poll() does not lock socket!
3973 * Change state from SYN-SENT only after copied_seq
3974 * is initialized. */
3975 tp
->copied_seq
= tp
->rcv_nxt
;
3977 tcp_set_state(sk
, TCP_ESTABLISHED
);
3979 /* Make sure socket is routed, for correct metrics. */
3980 tp
->af_specific
->rebuild_header(sk
);
3982 tcp_init_metrics(sk
);
3984 tcp_init_congestion_control(sk
);
3986 /* Prevent spurious tcp_cwnd_restart() on first data
3989 tp
->lsndtime
= tcp_time_stamp
;
3991 tcp_init_buffer_space(sk
);
3993 if (sock_flag(sk
, SOCK_KEEPOPEN
))
3994 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
3996 if (!tp
->rx_opt
.snd_wscale
)
3997 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4001 if (!sock_flag(sk
, SOCK_DEAD
)) {
4002 sk
->sk_state_change(sk
);
4003 sk_wake_async(sk
, 0, POLL_OUT
);
4006 icsk
= inet_csk(sk
);
4008 if (sk
->sk_write_pending
||
4009 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4010 icsk
->icsk_ack
.pingpong
) {
4011 /* Save one ACK. Data will be ready after
4012 * several ticks, if write_pending is set.
4014 * It may be deleted, but with this feature tcpdumps
4015 * look so _wonderfully_ clever, that I was not able
4016 * to stand against the temptation 8) --ANK
4018 inet_csk_schedule_ack(sk
);
4019 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4020 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4021 tcp_incr_quickack(sk
);
4022 tcp_enter_quickack_mode(sk
);
4023 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4024 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4035 /* No ACK in the segment */
4039 * "If the RST bit is set
4041 * Otherwise (no ACK) drop the segment and return."
4044 goto discard_and_undo
;
4048 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4049 goto discard_and_undo
;
4052 /* We see SYN without ACK. It is attempt of
4053 * simultaneous connect with crossed SYNs.
4054 * Particularly, it can be connect to self.
4056 tcp_set_state(sk
, TCP_SYN_RECV
);
4058 if (tp
->rx_opt
.saw_tstamp
) {
4059 tp
->rx_opt
.tstamp_ok
= 1;
4060 tcp_store_ts_recent(tp
);
4061 tp
->tcp_header_len
=
4062 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4064 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4067 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4068 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4070 /* RFC1323: The window in SYN & SYN/ACK segments is
4073 tp
->snd_wnd
= ntohs(th
->window
);
4074 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4075 tp
->max_window
= tp
->snd_wnd
;
4077 TCP_ECN_rcv_syn(tp
, th
);
4078 if (tp
->ecn_flags
&TCP_ECN_OK
)
4079 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
4081 tcp_sync_mss(sk
, tp
->pmtu_cookie
);
4082 tcp_initialize_rcv_mss(sk
);
4085 tcp_send_synack(sk
);
4087 /* Note, we could accept data and URG from this segment.
4088 * There are no obstacles to make this.
4090 * However, if we ignore data in ACKless segments sometimes,
4091 * we have no reasons to accept it sometimes.
4092 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4093 * is not flawless. So, discard packet for sanity.
4094 * Uncomment this return to process the data.
4101 /* "fifth, if neither of the SYN or RST bits is set then
4102 * drop the segment and return."
4106 tcp_clear_options(&tp
->rx_opt
);
4107 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4111 tcp_clear_options(&tp
->rx_opt
);
4112 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4118 * This function implements the receiving procedure of RFC 793 for
4119 * all states except ESTABLISHED and TIME_WAIT.
4120 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4121 * address independent.
4124 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4125 struct tcphdr
*th
, unsigned len
)
4127 struct tcp_sock
*tp
= tcp_sk(sk
);
4130 tp
->rx_opt
.saw_tstamp
= 0;
4132 switch (sk
->sk_state
) {
4144 if(tp
->af_specific
->conn_request(sk
, skb
) < 0)
4147 /* Now we have several options: In theory there is
4148 * nothing else in the frame. KA9Q has an option to
4149 * send data with the syn, BSD accepts data with the
4150 * syn up to the [to be] advertised window and
4151 * Solaris 2.1 gives you a protocol error. For now
4152 * we just ignore it, that fits the spec precisely
4153 * and avoids incompatibilities. It would be nice in
4154 * future to drop through and process the data.
4156 * Now that TTCP is starting to be used we ought to
4158 * But, this leaves one open to an easy denial of
4159 * service attack, and SYN cookies can't defend
4160 * against this problem. So, we drop the data
4161 * in the interest of security over speed.
4168 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4172 /* Do step6 onward by hand. */
4173 tcp_urg(sk
, skb
, th
);
4175 tcp_data_snd_check(sk
, tp
);
4179 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4180 tcp_paws_discard(sk
, skb
)) {
4182 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4183 tcp_send_dupack(sk
, skb
);
4186 /* Reset is accepted even if it did not pass PAWS. */
4189 /* step 1: check sequence number */
4190 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4192 tcp_send_dupack(sk
, skb
);
4196 /* step 2: check RST bit */
4202 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4204 /* step 3: check security and precedence [ignored] */
4208 * Check for a SYN in window.
4210 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4211 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4216 /* step 5: check the ACK field */
4218 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4220 switch(sk
->sk_state
) {
4223 tp
->copied_seq
= tp
->rcv_nxt
;
4225 tcp_set_state(sk
, TCP_ESTABLISHED
);
4226 sk
->sk_state_change(sk
);
4228 /* Note, that this wakeup is only for marginal
4229 * crossed SYN case. Passively open sockets
4230 * are not waked up, because sk->sk_sleep ==
4231 * NULL and sk->sk_socket == NULL.
4233 if (sk
->sk_socket
) {
4234 sk_wake_async(sk
,0,POLL_OUT
);
4237 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4238 tp
->snd_wnd
= ntohs(th
->window
) <<
4239 tp
->rx_opt
.snd_wscale
;
4240 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4241 TCP_SKB_CB(skb
)->seq
);
4243 /* tcp_ack considers this ACK as duplicate
4244 * and does not calculate rtt.
4245 * Fix it at least with timestamps.
4247 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4249 tcp_ack_saw_tstamp(sk
, 0);
4251 if (tp
->rx_opt
.tstamp_ok
)
4252 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4254 /* Make sure socket is routed, for
4257 tp
->af_specific
->rebuild_header(sk
);
4259 tcp_init_metrics(sk
);
4261 tcp_init_congestion_control(sk
);
4263 /* Prevent spurious tcp_cwnd_restart() on
4264 * first data packet.
4266 tp
->lsndtime
= tcp_time_stamp
;
4268 tcp_initialize_rcv_mss(sk
);
4269 tcp_init_buffer_space(sk
);
4270 tcp_fast_path_on(tp
);
4277 if (tp
->snd_una
== tp
->write_seq
) {
4278 tcp_set_state(sk
, TCP_FIN_WAIT2
);
4279 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
4280 dst_confirm(sk
->sk_dst_cache
);
4282 if (!sock_flag(sk
, SOCK_DEAD
))
4283 /* Wake up lingering close() */
4284 sk
->sk_state_change(sk
);
4288 if (tp
->linger2
< 0 ||
4289 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4290 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
4292 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4296 tmo
= tcp_fin_time(sk
);
4297 if (tmo
> TCP_TIMEWAIT_LEN
) {
4298 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
4299 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
4300 /* Bad case. We could lose such FIN otherwise.
4301 * It is not a big problem, but it looks confusing
4302 * and not so rare event. We still can lose it now,
4303 * if it spins in bh_lock_sock(), but it is really
4306 inet_csk_reset_keepalive_timer(sk
, tmo
);
4308 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
4316 if (tp
->snd_una
== tp
->write_seq
) {
4317 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4323 if (tp
->snd_una
== tp
->write_seq
) {
4324 tcp_update_metrics(sk
);
4333 /* step 6: check the URG bit */
4334 tcp_urg(sk
, skb
, th
);
4336 /* step 7: process the segment text */
4337 switch (sk
->sk_state
) {
4338 case TCP_CLOSE_WAIT
:
4341 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4345 /* RFC 793 says to queue data in these states,
4346 * RFC 1122 says we MUST send a reset.
4347 * BSD 4.4 also does reset.
4349 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
4350 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4351 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
4352 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4358 case TCP_ESTABLISHED
:
4359 tcp_data_queue(sk
, skb
);
4364 /* tcp_data could move socket to TIME-WAIT */
4365 if (sk
->sk_state
!= TCP_CLOSE
) {
4366 tcp_data_snd_check(sk
, tp
);
4367 tcp_ack_snd_check(sk
);
4377 EXPORT_SYMBOL(sysctl_tcp_ecn
);
4378 EXPORT_SYMBOL(sysctl_tcp_reordering
);
4379 EXPORT_SYMBOL(sysctl_tcp_abc
);
4380 EXPORT_SYMBOL(tcp_parse_options
);
4381 EXPORT_SYMBOL(tcp_rcv_established
);
4382 EXPORT_SYMBOL(tcp_rcv_state_process
);