2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
25 * Pedro Roque : Fast Retransmit/Recovery.
27 * Retransmit queue handled by TCP.
28 * Better retransmit timer handling.
29 * New congestion avoidance.
33 * Eric : Fast Retransmit.
34 * Randy Scott : MSS option defines.
35 * Eric Schenk : Fixes to slow start algorithm.
36 * Eric Schenk : Yet another double ACK bug.
37 * Eric Schenk : Delayed ACK bug fixes.
38 * Eric Schenk : Floyd style fast retrans war avoidance.
39 * David S. Miller : Don't allow zero congestion window.
40 * Eric Schenk : Fix retransmitter so that it sends
41 * next packet on ack of previous packet.
42 * Andi Kleen : Moved open_request checking here
43 * and process RSTs for open_requests.
44 * Andi Kleen : Better prune_queue, and other fixes.
45 * Andrey Savochkin: Fix RTT measurements in the presence of
47 * Andrey Savochkin: Check sequence numbers correctly when
48 * removing SACKs due to in sequence incoming
50 * Andi Kleen: Make sure we never ack data there is not
51 * enough room for. Also make this condition
52 * a fatal error if it might still happen.
53 * Andi Kleen: Add tcp_measure_rcv_mss to make
54 * connections with MSS<min(MTU,ann. MSS)
55 * work without delayed acks.
56 * Andi Kleen: Process packets with PSH set in the
58 * J Hadi Salim: ECN support
61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
62 * engine. Lots of bugs are found.
63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
75 int sysctl_tcp_timestamps __read_mostly
= 1;
76 int sysctl_tcp_window_scaling __read_mostly
= 1;
77 int sysctl_tcp_sack __read_mostly
= 1;
78 int sysctl_tcp_fack __read_mostly
= 1;
79 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
80 int sysctl_tcp_ecn __read_mostly
;
81 int sysctl_tcp_dsack __read_mostly
= 1;
82 int sysctl_tcp_app_win __read_mostly
= 31;
83 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
85 int sysctl_tcp_stdurg __read_mostly
;
86 int sysctl_tcp_rfc1337 __read_mostly
;
87 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
88 int sysctl_tcp_frto __read_mostly
;
89 int sysctl_tcp_frto_response __read_mostly
;
90 int sysctl_tcp_nometrics_save __read_mostly
;
92 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
93 int sysctl_tcp_abc __read_mostly
;
95 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
96 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
97 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
98 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
99 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
100 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
101 #define FLAG_ECE 0x40 /* ECE in this ACK */
102 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
103 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
106 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
107 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
108 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
109 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
111 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
112 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
113 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
115 #define IsSackFrto() (sysctl_tcp_frto == 0x2)
117 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
119 /* Adapt the MSS value used to make delayed ack decision to the
122 static void tcp_measure_rcv_mss(struct sock
*sk
,
123 const struct sk_buff
*skb
)
125 struct inet_connection_sock
*icsk
= inet_csk(sk
);
126 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
129 icsk
->icsk_ack
.last_seg_size
= 0;
131 /* skb->len may jitter because of SACKs, even if peer
132 * sends good full-sized frames.
134 len
= skb_shinfo(skb
)->gso_size
?: skb
->len
;
135 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
136 icsk
->icsk_ack
.rcv_mss
= len
;
138 /* Otherwise, we make more careful check taking into account,
139 * that SACKs block is variable.
141 * "len" is invariant segment length, including TCP header.
143 len
+= skb
->data
- skb
->h
.raw
;
144 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
145 /* If PSH is not set, packet should be
146 * full sized, provided peer TCP is not badly broken.
147 * This observation (if it is correct 8)) allows
148 * to handle super-low mtu links fairly.
150 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
151 !(tcp_flag_word(skb
->h
.th
)&TCP_REMNANT
))) {
152 /* Subtract also invariant (if peer is RFC compliant),
153 * tcp header plus fixed timestamp option length.
154 * Resulting "len" is MSS free of SACK jitter.
156 len
-= tcp_sk(sk
)->tcp_header_len
;
157 icsk
->icsk_ack
.last_seg_size
= len
;
159 icsk
->icsk_ack
.rcv_mss
= len
;
163 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
164 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
165 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
169 static void tcp_incr_quickack(struct sock
*sk
)
171 struct inet_connection_sock
*icsk
= inet_csk(sk
);
172 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
176 if (quickacks
> icsk
->icsk_ack
.quick
)
177 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
180 void tcp_enter_quickack_mode(struct sock
*sk
)
182 struct inet_connection_sock
*icsk
= inet_csk(sk
);
183 tcp_incr_quickack(sk
);
184 icsk
->icsk_ack
.pingpong
= 0;
185 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
188 /* Send ACKs quickly, if "quick" count is not exhausted
189 * and the session is not interactive.
192 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
194 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
195 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
198 /* Buffer size and advertised window tuning.
200 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
203 static void tcp_fixup_sndbuf(struct sock
*sk
)
205 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
206 sizeof(struct sk_buff
);
208 if (sk
->sk_sndbuf
< 3 * sndmem
)
209 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
212 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
214 * All tcp_full_space() is split to two parts: "network" buffer, allocated
215 * forward and advertised in receiver window (tp->rcv_wnd) and
216 * "application buffer", required to isolate scheduling/application
217 * latencies from network.
218 * window_clamp is maximal advertised window. It can be less than
219 * tcp_full_space(), in this case tcp_full_space() - window_clamp
220 * is reserved for "application" buffer. The less window_clamp is
221 * the smoother our behaviour from viewpoint of network, but the lower
222 * throughput and the higher sensitivity of the connection to losses. 8)
224 * rcv_ssthresh is more strict window_clamp used at "slow start"
225 * phase to predict further behaviour of this connection.
226 * It is used for two goals:
227 * - to enforce header prediction at sender, even when application
228 * requires some significant "application buffer". It is check #1.
229 * - to prevent pruning of receive queue because of misprediction
230 * of receiver window. Check #2.
232 * The scheme does not work when sender sends good segments opening
233 * window and then starts to feed us spaghetti. But it should work
234 * in common situations. Otherwise, we have to rely on queue collapsing.
237 /* Slow part of check#2. */
238 static int __tcp_grow_window(const struct sock
*sk
, struct tcp_sock
*tp
,
239 const struct sk_buff
*skb
)
242 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
243 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
245 while (tp
->rcv_ssthresh
<= window
) {
246 if (truesize
<= skb
->len
)
247 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
255 static void tcp_grow_window(struct sock
*sk
, struct tcp_sock
*tp
,
259 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
260 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
261 !tcp_memory_pressure
) {
264 /* Check #2. Increase window, if skb with such overhead
265 * will fit to rcvbuf in future.
267 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
270 incr
= __tcp_grow_window(sk
, tp
, skb
);
273 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
274 inet_csk(sk
)->icsk_ack
.quick
|= 1;
279 /* 3. Tuning rcvbuf, when connection enters established state. */
281 static void tcp_fixup_rcvbuf(struct sock
*sk
)
283 struct tcp_sock
*tp
= tcp_sk(sk
);
284 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
286 /* Try to select rcvbuf so that 4 mss-sized segments
287 * will fit to window and corresponding skbs will fit to our rcvbuf.
288 * (was 3; 4 is minimum to allow fast retransmit to work.)
290 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
292 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
293 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
296 /* 4. Try to fixup all. It is made immediately after connection enters
299 static void tcp_init_buffer_space(struct sock
*sk
)
301 struct tcp_sock
*tp
= tcp_sk(sk
);
304 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
305 tcp_fixup_rcvbuf(sk
);
306 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
307 tcp_fixup_sndbuf(sk
);
309 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
311 maxwin
= tcp_full_space(sk
);
313 if (tp
->window_clamp
>= maxwin
) {
314 tp
->window_clamp
= maxwin
;
316 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
317 tp
->window_clamp
= max(maxwin
-
318 (maxwin
>> sysctl_tcp_app_win
),
322 /* Force reservation of one segment. */
323 if (sysctl_tcp_app_win
&&
324 tp
->window_clamp
> 2 * tp
->advmss
&&
325 tp
->window_clamp
+ tp
->advmss
> maxwin
)
326 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
328 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
329 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
332 /* 5. Recalculate window clamp after socket hit its memory bounds. */
333 static void tcp_clamp_window(struct sock
*sk
, struct tcp_sock
*tp
)
335 struct inet_connection_sock
*icsk
= inet_csk(sk
);
337 icsk
->icsk_ack
.quick
= 0;
339 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
340 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
341 !tcp_memory_pressure
&&
342 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
343 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
346 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
347 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
351 /* Initialize RCV_MSS value.
352 * RCV_MSS is an our guess about MSS used by the peer.
353 * We haven't any direct information about the MSS.
354 * It's better to underestimate the RCV_MSS rather than overestimate.
355 * Overestimations make us ACKing less frequently than needed.
356 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
358 void tcp_initialize_rcv_mss(struct sock
*sk
)
360 struct tcp_sock
*tp
= tcp_sk(sk
);
361 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
363 hint
= min(hint
, tp
->rcv_wnd
/2);
364 hint
= min(hint
, TCP_MIN_RCVMSS
);
365 hint
= max(hint
, TCP_MIN_MSS
);
367 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
370 /* Receiver "autotuning" code.
372 * The algorithm for RTT estimation w/o timestamps is based on
373 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
374 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
376 * More detail on this code can be found at
377 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
378 * though this reference is out of date. A new paper
381 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
383 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
389 if (new_sample
!= 0) {
390 /* If we sample in larger samples in the non-timestamp
391 * case, we could grossly overestimate the RTT especially
392 * with chatty applications or bulk transfer apps which
393 * are stalled on filesystem I/O.
395 * Also, since we are only going for a minimum in the
396 * non-timestamp case, we do not smooth things out
397 * else with timestamps disabled convergence takes too
401 m
-= (new_sample
>> 3);
403 } else if (m
< new_sample
)
406 /* No previous measure. */
410 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
411 tp
->rcv_rtt_est
.rtt
= new_sample
;
414 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
416 if (tp
->rcv_rtt_est
.time
== 0)
418 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
420 tcp_rcv_rtt_update(tp
,
421 jiffies
- tp
->rcv_rtt_est
.time
,
425 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
426 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
429 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
431 struct tcp_sock
*tp
= tcp_sk(sk
);
432 if (tp
->rx_opt
.rcv_tsecr
&&
433 (TCP_SKB_CB(skb
)->end_seq
-
434 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
435 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
439 * This function should be called every time data is copied to user space.
440 * It calculates the appropriate TCP receive buffer space.
442 void tcp_rcv_space_adjust(struct sock
*sk
)
444 struct tcp_sock
*tp
= tcp_sk(sk
);
448 if (tp
->rcvq_space
.time
== 0)
451 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
452 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
453 tp
->rcv_rtt_est
.rtt
== 0)
456 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
458 space
= max(tp
->rcvq_space
.space
, space
);
460 if (tp
->rcvq_space
.space
!= space
) {
463 tp
->rcvq_space
.space
= space
;
465 if (sysctl_tcp_moderate_rcvbuf
&&
466 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
467 int new_clamp
= space
;
469 /* Receive space grows, normalize in order to
470 * take into account packet headers and sk_buff
471 * structure overhead.
476 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
477 16 + sizeof(struct sk_buff
));
478 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
481 space
= min(space
, sysctl_tcp_rmem
[2]);
482 if (space
> sk
->sk_rcvbuf
) {
483 sk
->sk_rcvbuf
= space
;
485 /* Make the window clamp follow along. */
486 tp
->window_clamp
= new_clamp
;
492 tp
->rcvq_space
.seq
= tp
->copied_seq
;
493 tp
->rcvq_space
.time
= tcp_time_stamp
;
496 /* There is something which you must keep in mind when you analyze the
497 * behavior of the tp->ato delayed ack timeout interval. When a
498 * connection starts up, we want to ack as quickly as possible. The
499 * problem is that "good" TCP's do slow start at the beginning of data
500 * transmission. The means that until we send the first few ACK's the
501 * sender will sit on his end and only queue most of his data, because
502 * he can only send snd_cwnd unacked packets at any given time. For
503 * each ACK we send, he increments snd_cwnd and transmits more of his
506 static void tcp_event_data_recv(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
508 struct inet_connection_sock
*icsk
= inet_csk(sk
);
511 inet_csk_schedule_ack(sk
);
513 tcp_measure_rcv_mss(sk
, skb
);
515 tcp_rcv_rtt_measure(tp
);
517 now
= tcp_time_stamp
;
519 if (!icsk
->icsk_ack
.ato
) {
520 /* The _first_ data packet received, initialize
521 * delayed ACK engine.
523 tcp_incr_quickack(sk
);
524 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
526 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
528 if (m
<= TCP_ATO_MIN
/2) {
529 /* The fastest case is the first. */
530 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
531 } else if (m
< icsk
->icsk_ack
.ato
) {
532 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
533 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
534 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
535 } else if (m
> icsk
->icsk_rto
) {
536 /* Too long gap. Apparently sender failed to
537 * restart window, so that we send ACKs quickly.
539 tcp_incr_quickack(sk
);
540 sk_stream_mem_reclaim(sk
);
543 icsk
->icsk_ack
.lrcvtime
= now
;
545 TCP_ECN_check_ce(tp
, skb
);
548 tcp_grow_window(sk
, tp
, skb
);
551 /* Called to compute a smoothed rtt estimate. The data fed to this
552 * routine either comes from timestamps, or from segments that were
553 * known _not_ to have been retransmitted [see Karn/Partridge
554 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
555 * piece by Van Jacobson.
556 * NOTE: the next three routines used to be one big routine.
557 * To save cycles in the RFC 1323 implementation it was better to break
558 * it up into three procedures. -- erics
560 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
562 struct tcp_sock
*tp
= tcp_sk(sk
);
563 long m
= mrtt
; /* RTT */
565 /* The following amusing code comes from Jacobson's
566 * article in SIGCOMM '88. Note that rtt and mdev
567 * are scaled versions of rtt and mean deviation.
568 * This is designed to be as fast as possible
569 * m stands for "measurement".
571 * On a 1990 paper the rto value is changed to:
572 * RTO = rtt + 4 * mdev
574 * Funny. This algorithm seems to be very broken.
575 * These formulae increase RTO, when it should be decreased, increase
576 * too slowly, when it should be increased quickly, decrease too quickly
577 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
578 * does not matter how to _calculate_ it. Seems, it was trap
579 * that VJ failed to avoid. 8)
584 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
585 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
587 m
= -m
; /* m is now abs(error) */
588 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
589 /* This is similar to one of Eifel findings.
590 * Eifel blocks mdev updates when rtt decreases.
591 * This solution is a bit different: we use finer gain
592 * for mdev in this case (alpha*beta).
593 * Like Eifel it also prevents growth of rto,
594 * but also it limits too fast rto decreases,
595 * happening in pure Eifel.
600 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
602 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
603 if (tp
->mdev
> tp
->mdev_max
) {
604 tp
->mdev_max
= tp
->mdev
;
605 if (tp
->mdev_max
> tp
->rttvar
)
606 tp
->rttvar
= tp
->mdev_max
;
608 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
609 if (tp
->mdev_max
< tp
->rttvar
)
610 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
611 tp
->rtt_seq
= tp
->snd_nxt
;
612 tp
->mdev_max
= TCP_RTO_MIN
;
615 /* no previous measure. */
616 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
617 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
618 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
619 tp
->rtt_seq
= tp
->snd_nxt
;
623 /* Calculate rto without backoff. This is the second half of Van Jacobson's
624 * routine referred to above.
626 static inline void tcp_set_rto(struct sock
*sk
)
628 const struct tcp_sock
*tp
= tcp_sk(sk
);
629 /* Old crap is replaced with new one. 8)
632 * 1. If rtt variance happened to be less 50msec, it is hallucination.
633 * It cannot be less due to utterly erratic ACK generation made
634 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
635 * to do with delayed acks, because at cwnd>2 true delack timeout
636 * is invisible. Actually, Linux-2.4 also generates erratic
637 * ACKs in some circumstances.
639 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
641 /* 2. Fixups made earlier cannot be right.
642 * If we do not estimate RTO correctly without them,
643 * all the algo is pure shit and should be replaced
644 * with correct one. It is exactly, which we pretend to do.
648 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
649 * guarantees that rto is higher.
651 static inline void tcp_bound_rto(struct sock
*sk
)
653 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
654 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
657 /* Save metrics learned by this TCP session.
658 This function is called only, when TCP finishes successfully
659 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
661 void tcp_update_metrics(struct sock
*sk
)
663 struct tcp_sock
*tp
= tcp_sk(sk
);
664 struct dst_entry
*dst
= __sk_dst_get(sk
);
666 if (sysctl_tcp_nometrics_save
)
671 if (dst
&& (dst
->flags
&DST_HOST
)) {
672 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
675 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
676 /* This session failed to estimate rtt. Why?
677 * Probably, no packets returned in time.
680 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
681 dst
->metrics
[RTAX_RTT
-1] = 0;
685 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
687 /* If newly calculated rtt larger than stored one,
688 * store new one. Otherwise, use EWMA. Remember,
689 * rtt overestimation is always better than underestimation.
691 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
693 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
695 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
698 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
702 /* Scale deviation to rttvar fixed point */
707 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
708 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
710 dst
->metrics
[RTAX_RTTVAR
-1] -=
711 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
714 if (tp
->snd_ssthresh
>= 0xFFFF) {
715 /* Slow start still did not finish. */
716 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
717 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
718 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
719 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
720 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
721 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
722 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
723 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
724 icsk
->icsk_ca_state
== TCP_CA_Open
) {
725 /* Cong. avoidance phase, cwnd is reliable. */
726 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
727 dst
->metrics
[RTAX_SSTHRESH
-1] =
728 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
729 if (!dst_metric_locked(dst
, RTAX_CWND
))
730 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
732 /* Else slow start did not finish, cwnd is non-sense,
733 ssthresh may be also invalid.
735 if (!dst_metric_locked(dst
, RTAX_CWND
))
736 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
737 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
738 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
739 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
740 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
743 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
744 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
745 tp
->reordering
!= sysctl_tcp_reordering
)
746 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
751 /* Numbers are taken from RFC2414. */
752 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
754 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
757 if (tp
->mss_cache
> 1460)
760 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
762 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
765 /* Set slow start threshold and cwnd not falling to slow start */
766 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
768 struct tcp_sock
*tp
= tcp_sk(sk
);
769 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
771 tp
->prior_ssthresh
= 0;
773 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
776 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
777 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
778 tcp_packets_in_flight(tp
) + 1U);
779 tp
->snd_cwnd_cnt
= 0;
780 tp
->high_seq
= tp
->snd_nxt
;
781 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
782 TCP_ECN_queue_cwr(tp
);
784 tcp_set_ca_state(sk
, TCP_CA_CWR
);
788 /* Initialize metrics on socket. */
790 static void tcp_init_metrics(struct sock
*sk
)
792 struct tcp_sock
*tp
= tcp_sk(sk
);
793 struct dst_entry
*dst
= __sk_dst_get(sk
);
800 if (dst_metric_locked(dst
, RTAX_CWND
))
801 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
802 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
803 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
804 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
805 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
807 if (dst_metric(dst
, RTAX_REORDERING
) &&
808 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
809 tp
->rx_opt
.sack_ok
&= ~2;
810 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
813 if (dst_metric(dst
, RTAX_RTT
) == 0)
816 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
819 /* Initial rtt is determined from SYN,SYN-ACK.
820 * The segment is small and rtt may appear much
821 * less than real one. Use per-dst memory
822 * to make it more realistic.
824 * A bit of theory. RTT is time passed after "normal" sized packet
825 * is sent until it is ACKed. In normal circumstances sending small
826 * packets force peer to delay ACKs and calculation is correct too.
827 * The algorithm is adaptive and, provided we follow specs, it
828 * NEVER underestimate RTT. BUT! If peer tries to make some clever
829 * tricks sort of "quick acks" for time long enough to decrease RTT
830 * to low value, and then abruptly stops to do it and starts to delay
831 * ACKs, wait for troubles.
833 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
834 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
835 tp
->rtt_seq
= tp
->snd_nxt
;
837 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
838 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
839 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
843 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
845 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
846 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
850 /* Play conservative. If timestamps are not
851 * supported, TCP will fail to recalculate correct
852 * rtt, if initial rto is too small. FORGET ALL AND RESET!
854 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
856 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
857 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
861 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
864 struct tcp_sock
*tp
= tcp_sk(sk
);
865 if (metric
> tp
->reordering
) {
866 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
868 /* This exciting event is worth to be remembered. 8) */
870 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
872 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
874 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
876 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
877 #if FASTRETRANS_DEBUG > 1
878 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
879 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
883 tp
->undo_marker
? tp
->undo_retrans
: 0);
885 /* Disable FACK yet. */
886 tp
->rx_opt
.sack_ok
&= ~2;
890 /* This procedure tags the retransmission queue when SACKs arrive.
892 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
893 * Packets in queue with these bits set are counted in variables
894 * sacked_out, retrans_out and lost_out, correspondingly.
896 * Valid combinations are:
897 * Tag InFlight Description
898 * 0 1 - orig segment is in flight.
899 * S 0 - nothing flies, orig reached receiver.
900 * L 0 - nothing flies, orig lost by net.
901 * R 2 - both orig and retransmit are in flight.
902 * L|R 1 - orig is lost, retransmit is in flight.
903 * S|R 1 - orig reached receiver, retrans is still in flight.
904 * (L|S|R is logically valid, it could occur when L|R is sacked,
905 * but it is equivalent to plain S and code short-curcuits it to S.
906 * L|S is logically invalid, it would mean -1 packet in flight 8))
908 * These 6 states form finite state machine, controlled by the following events:
909 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
910 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
911 * 3. Loss detection event of one of three flavors:
912 * A. Scoreboard estimator decided the packet is lost.
913 * A'. Reno "three dupacks" marks head of queue lost.
914 * A''. Its FACK modfication, head until snd.fack is lost.
915 * B. SACK arrives sacking data transmitted after never retransmitted
917 * C. SACK arrives sacking SND.NXT at the moment, when the
918 * segment was retransmitted.
919 * 4. D-SACK added new rule: D-SACK changes any tag to S.
921 * It is pleasant to note, that state diagram turns out to be commutative,
922 * so that we are allowed not to be bothered by order of our actions,
923 * when multiple events arrive simultaneously. (see the function below).
925 * Reordering detection.
926 * --------------------
927 * Reordering metric is maximal distance, which a packet can be displaced
928 * in packet stream. With SACKs we can estimate it:
930 * 1. SACK fills old hole and the corresponding segment was not
931 * ever retransmitted -> reordering. Alas, we cannot use it
932 * when segment was retransmitted.
933 * 2. The last flaw is solved with D-SACK. D-SACK arrives
934 * for retransmitted and already SACKed segment -> reordering..
935 * Both of these heuristics are not used in Loss state, when we cannot
936 * account for retransmits accurately.
939 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
941 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
942 struct tcp_sock
*tp
= tcp_sk(sk
);
943 unsigned char *ptr
= ack_skb
->h
.raw
+ TCP_SKB_CB(ack_skb
)->sacked
;
944 struct tcp_sack_block_wire
*sp
= (struct tcp_sack_block_wire
*)(ptr
+2);
945 struct sk_buff
*cached_skb
;
946 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
947 int reord
= tp
->packets_out
;
949 u32 lost_retrans
= 0;
952 int cached_fack_count
;
954 int first_sack_index
;
958 prior_fackets
= tp
->fackets_out
;
960 /* Check for D-SACK. */
961 if (before(ntohl(sp
[0].start_seq
), TCP_SKB_CB(ack_skb
)->ack_seq
)) {
963 tp
->rx_opt
.sack_ok
|= 4;
964 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
965 } else if (num_sacks
> 1 &&
966 !after(ntohl(sp
[0].end_seq
), ntohl(sp
[1].end_seq
)) &&
967 !before(ntohl(sp
[0].start_seq
), ntohl(sp
[1].start_seq
))) {
969 tp
->rx_opt
.sack_ok
|= 4;
970 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
973 /* D-SACK for already forgotten data...
974 * Do dumb counting. */
976 !after(ntohl(sp
[0].end_seq
), prior_snd_una
) &&
977 after(ntohl(sp
[0].end_seq
), tp
->undo_marker
))
980 /* Eliminate too old ACKs, but take into
981 * account more or less fresh ones, they can
982 * contain valid SACK info.
984 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
988 * if the only SACK change is the increase of the end_seq of
989 * the first block then only apply that SACK block
990 * and use retrans queue hinting otherwise slowpath */
992 for (i
= 0; i
< num_sacks
; i
++) {
993 __be32 start_seq
= sp
[i
].start_seq
;
994 __be32 end_seq
= sp
[i
].end_seq
;
997 if (tp
->recv_sack_cache
[i
].start_seq
!= start_seq
)
1000 if ((tp
->recv_sack_cache
[i
].start_seq
!= start_seq
) ||
1001 (tp
->recv_sack_cache
[i
].end_seq
!= end_seq
))
1004 tp
->recv_sack_cache
[i
].start_seq
= start_seq
;
1005 tp
->recv_sack_cache
[i
].end_seq
= end_seq
;
1007 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1008 for (; i
< ARRAY_SIZE(tp
->recv_sack_cache
); i
++) {
1009 tp
->recv_sack_cache
[i
].start_seq
= 0;
1010 tp
->recv_sack_cache
[i
].end_seq
= 0;
1013 first_sack_index
= 0;
1018 tp
->fastpath_skb_hint
= NULL
;
1020 /* order SACK blocks to allow in order walk of the retrans queue */
1021 for (i
= num_sacks
-1; i
> 0; i
--) {
1022 for (j
= 0; j
< i
; j
++){
1023 if (after(ntohl(sp
[j
].start_seq
),
1024 ntohl(sp
[j
+1].start_seq
))){
1025 struct tcp_sack_block_wire tmp
;
1031 /* Track where the first SACK block goes to */
1032 if (j
== first_sack_index
)
1033 first_sack_index
= j
+1;
1040 /* clear flag as used for different purpose in following code */
1043 /* Use SACK fastpath hint if valid */
1044 cached_skb
= tp
->fastpath_skb_hint
;
1045 cached_fack_count
= tp
->fastpath_cnt_hint
;
1047 cached_skb
= sk
->sk_write_queue
.next
;
1048 cached_fack_count
= 0;
1051 for (i
=0; i
<num_sacks
; i
++, sp
++) {
1052 struct sk_buff
*skb
;
1053 __u32 start_seq
= ntohl(sp
->start_seq
);
1054 __u32 end_seq
= ntohl(sp
->end_seq
);
1058 fack_count
= cached_fack_count
;
1060 /* Event "B" in the comment above. */
1061 if (after(end_seq
, tp
->high_seq
))
1062 flag
|= FLAG_DATA_LOST
;
1064 sk_stream_for_retrans_queue_from(skb
, sk
) {
1065 int in_sack
, pcount
;
1069 cached_fack_count
= fack_count
;
1070 if (i
== first_sack_index
) {
1071 tp
->fastpath_skb_hint
= skb
;
1072 tp
->fastpath_cnt_hint
= fack_count
;
1075 /* The retransmission queue is always in order, so
1076 * we can short-circuit the walk early.
1078 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1081 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1082 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1084 pcount
= tcp_skb_pcount(skb
);
1086 if (pcount
> 1 && !in_sack
&&
1087 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1088 unsigned int pkt_len
;
1090 in_sack
= !after(start_seq
,
1091 TCP_SKB_CB(skb
)->seq
);
1094 pkt_len
= (start_seq
-
1095 TCP_SKB_CB(skb
)->seq
);
1097 pkt_len
= (end_seq
-
1098 TCP_SKB_CB(skb
)->seq
);
1099 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
))
1101 pcount
= tcp_skb_pcount(skb
);
1104 fack_count
+= pcount
;
1106 sacked
= TCP_SKB_CB(skb
)->sacked
;
1108 /* Account D-SACK for retransmitted packet. */
1109 if ((dup_sack
&& in_sack
) &&
1110 (sacked
& TCPCB_RETRANS
) &&
1111 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1114 /* The frame is ACKed. */
1115 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1116 if (sacked
&TCPCB_RETRANS
) {
1117 if ((dup_sack
&& in_sack
) &&
1118 (sacked
&TCPCB_SACKED_ACKED
))
1119 reord
= min(fack_count
, reord
);
1121 /* If it was in a hole, we detected reordering. */
1122 if (fack_count
< prior_fackets
&&
1123 !(sacked
&TCPCB_SACKED_ACKED
))
1124 reord
= min(fack_count
, reord
);
1127 /* Nothing to do; acked frame is about to be dropped. */
1131 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1132 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1133 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1134 lost_retrans
= end_seq
;
1139 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1140 if (sacked
& TCPCB_SACKED_RETRANS
) {
1141 /* If the segment is not tagged as lost,
1142 * we do not clear RETRANS, believing
1143 * that retransmission is still in flight.
1145 if (sacked
& TCPCB_LOST
) {
1146 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1147 tp
->lost_out
-= tcp_skb_pcount(skb
);
1148 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1150 /* clear lost hint */
1151 tp
->retransmit_skb_hint
= NULL
;
1154 /* New sack for not retransmitted frame,
1155 * which was in hole. It is reordering.
1157 if (!(sacked
& TCPCB_RETRANS
) &&
1158 fack_count
< prior_fackets
)
1159 reord
= min(fack_count
, reord
);
1161 if (sacked
& TCPCB_LOST
) {
1162 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1163 tp
->lost_out
-= tcp_skb_pcount(skb
);
1165 /* clear lost hint */
1166 tp
->retransmit_skb_hint
= NULL
;
1168 /* SACK enhanced F-RTO detection.
1169 * Set flag if and only if non-rexmitted
1170 * segments below frto_highmark are
1171 * SACKed (RFC4138; Appendix B).
1172 * Clearing correct due to in-order walk
1174 if (after(end_seq
, tp
->frto_highmark
)) {
1175 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1177 if (!(sacked
& TCPCB_RETRANS
))
1178 flag
|= FLAG_ONLY_ORIG_SACKED
;
1182 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1183 flag
|= FLAG_DATA_SACKED
;
1184 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1186 if (fack_count
> tp
->fackets_out
)
1187 tp
->fackets_out
= fack_count
;
1189 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1190 reord
= min(fack_count
, reord
);
1193 /* D-SACK. We can detect redundant retransmission
1194 * in S|R and plain R frames and clear it.
1195 * undo_retrans is decreased above, L|R frames
1196 * are accounted above as well.
1199 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1200 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1201 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1202 tp
->retransmit_skb_hint
= NULL
;
1207 /* Check for lost retransmit. This superb idea is
1208 * borrowed from "ratehalving". Event "C".
1209 * Later note: FACK people cheated me again 8),
1210 * we have to account for reordering! Ugly,
1213 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1214 struct sk_buff
*skb
;
1216 sk_stream_for_retrans_queue(skb
, sk
) {
1217 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1219 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1221 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1222 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1224 !before(lost_retrans
,
1225 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1227 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1228 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1230 /* clear lost hint */
1231 tp
->retransmit_skb_hint
= NULL
;
1233 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1234 tp
->lost_out
+= tcp_skb_pcount(skb
);
1235 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1236 flag
|= FLAG_DATA_SACKED
;
1237 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1243 tp
->left_out
= tp
->sacked_out
+ tp
->lost_out
;
1245 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
&&
1246 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1247 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1249 #if FASTRETRANS_DEBUG > 0
1250 BUG_TRAP((int)tp
->sacked_out
>= 0);
1251 BUG_TRAP((int)tp
->lost_out
>= 0);
1252 BUG_TRAP((int)tp
->retrans_out
>= 0);
1253 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1258 /* F-RTO can only be used if these conditions are satisfied:
1259 * - there must be some unsent new data
1260 * - the advertised window should allow sending it
1261 * - TCP has never retransmitted anything other than head (SACK enhanced
1262 * variant from Appendix B of RFC4138 is more robust here)
1264 int tcp_use_frto(struct sock
*sk
)
1266 const struct tcp_sock
*tp
= tcp_sk(sk
);
1267 struct sk_buff
*skb
;
1269 if (!sysctl_tcp_frto
|| !sk
->sk_send_head
||
1270 after(TCP_SKB_CB(sk
->sk_send_head
)->end_seq
,
1271 tp
->snd_una
+ tp
->snd_wnd
))
1277 /* Avoid expensive walking of rexmit queue if possible */
1278 if (tp
->retrans_out
> 1)
1281 skb
= skb_peek(&sk
->sk_write_queue
)->next
; /* Skips head */
1282 sk_stream_for_retrans_queue_from(skb
, sk
) {
1283 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1285 /* Short-circuit when first non-SACKed skb has been checked */
1286 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
))
1292 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1293 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1294 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1295 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1296 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1297 * bits are handled if the Loss state is really to be entered (in
1298 * tcp_enter_frto_loss).
1300 * Do like tcp_enter_loss() would; when RTO expires the second time it
1302 * "Reduce ssthresh if it has not yet been made inside this window."
1304 void tcp_enter_frto(struct sock
*sk
)
1306 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1307 struct tcp_sock
*tp
= tcp_sk(sk
);
1308 struct sk_buff
*skb
;
1310 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1311 tp
->snd_una
== tp
->high_seq
||
1312 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1313 !icsk
->icsk_retransmits
)) {
1314 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1315 /* Our state is too optimistic in ssthresh() call because cwnd
1316 * is not reduced until tcp_enter_frto_loss() when previous FRTO
1317 * recovery has not yet completed. Pattern would be this: RTO,
1318 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1320 * RFC4138 should be more specific on what to do, even though
1321 * RTO is quite unlikely to occur after the first Cumulative ACK
1322 * due to back-off and complexity of triggering events ...
1324 if (tp
->frto_counter
) {
1326 stored_cwnd
= tp
->snd_cwnd
;
1328 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1329 tp
->snd_cwnd
= stored_cwnd
;
1331 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1333 /* ... in theory, cong.control module could do "any tricks" in
1334 * ssthresh(), which means that ca_state, lost bits and lost_out
1335 * counter would have to be faked before the call occurs. We
1336 * consider that too expensive, unlikely and hacky, so modules
1337 * using these in ssthresh() must deal these incompatibility
1338 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1340 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1343 tp
->undo_marker
= tp
->snd_una
;
1344 tp
->undo_retrans
= 0;
1346 skb
= skb_peek(&sk
->sk_write_queue
);
1347 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1348 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1349 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1351 tcp_sync_left_out(tp
);
1353 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1354 * The last condition is necessary at least in tp->frto_counter case.
1356 if (IsSackFrto() && (tp
->frto_counter
||
1357 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1358 after(tp
->high_seq
, tp
->snd_una
)) {
1359 tp
->frto_highmark
= tp
->high_seq
;
1361 tp
->frto_highmark
= tp
->snd_nxt
;
1363 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1364 tp
->high_seq
= tp
->snd_nxt
;
1365 tp
->frto_counter
= 1;
1368 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1369 * which indicates that we should follow the traditional RTO recovery,
1370 * i.e. mark everything lost and do go-back-N retransmission.
1372 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1374 struct tcp_sock
*tp
= tcp_sk(sk
);
1375 struct sk_buff
*skb
;
1380 tp
->fackets_out
= 0;
1381 tp
->retrans_out
= 0;
1383 sk_stream_for_retrans_queue(skb
, sk
) {
1384 cnt
+= tcp_skb_pcount(skb
);
1386 * Count the retransmission made on RTO correctly (only when
1387 * waiting for the first ACK and did not get it)...
1389 if ((tp
->frto_counter
== 1) && !(flag
&FLAG_DATA_ACKED
)) {
1390 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1391 /* ...enter this if branch just for the first segment */
1392 flag
|= FLAG_DATA_ACKED
;
1394 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1396 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1398 /* Do not mark those segments lost that were
1399 * forward transmitted after RTO
1401 if (!after(TCP_SKB_CB(skb
)->end_seq
,
1402 tp
->frto_highmark
)) {
1403 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1404 tp
->lost_out
+= tcp_skb_pcount(skb
);
1407 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1408 tp
->fackets_out
= cnt
;
1411 tcp_sync_left_out(tp
);
1413 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1414 tp
->snd_cwnd_cnt
= 0;
1415 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1416 tp
->undo_marker
= 0;
1417 tp
->frto_counter
= 0;
1419 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1420 sysctl_tcp_reordering
);
1421 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1422 tp
->high_seq
= tp
->frto_highmark
;
1423 TCP_ECN_queue_cwr(tp
);
1425 clear_all_retrans_hints(tp
);
1428 void tcp_clear_retrans(struct tcp_sock
*tp
)
1431 tp
->retrans_out
= 0;
1433 tp
->fackets_out
= 0;
1437 tp
->undo_marker
= 0;
1438 tp
->undo_retrans
= 0;
1441 /* Enter Loss state. If "how" is not zero, forget all SACK information
1442 * and reset tags completely, otherwise preserve SACKs. If receiver
1443 * dropped its ofo queue, we will know this due to reneging detection.
1445 void tcp_enter_loss(struct sock
*sk
, int how
)
1447 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1448 struct tcp_sock
*tp
= tcp_sk(sk
);
1449 struct sk_buff
*skb
;
1452 /* Reduce ssthresh if it has not yet been made inside this window. */
1453 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1454 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1455 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1456 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1457 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1460 tp
->snd_cwnd_cnt
= 0;
1461 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1463 tp
->bytes_acked
= 0;
1464 tcp_clear_retrans(tp
);
1466 /* Push undo marker, if it was plain RTO and nothing
1467 * was retransmitted. */
1469 tp
->undo_marker
= tp
->snd_una
;
1471 sk_stream_for_retrans_queue(skb
, sk
) {
1472 cnt
+= tcp_skb_pcount(skb
);
1473 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1474 tp
->undo_marker
= 0;
1475 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1476 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1477 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1478 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1479 tp
->lost_out
+= tcp_skb_pcount(skb
);
1481 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1482 tp
->fackets_out
= cnt
;
1485 tcp_sync_left_out(tp
);
1487 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1488 sysctl_tcp_reordering
);
1489 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1490 tp
->high_seq
= tp
->snd_nxt
;
1491 TCP_ECN_queue_cwr(tp
);
1493 clear_all_retrans_hints(tp
);
1496 static int tcp_check_sack_reneging(struct sock
*sk
)
1498 struct sk_buff
*skb
;
1500 /* If ACK arrived pointing to a remembered SACK,
1501 * it means that our remembered SACKs do not reflect
1502 * real state of receiver i.e.
1503 * receiver _host_ is heavily congested (or buggy).
1504 * Do processing similar to RTO timeout.
1506 if ((skb
= skb_peek(&sk
->sk_write_queue
)) != NULL
&&
1507 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1508 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1509 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1511 tcp_enter_loss(sk
, 1);
1512 icsk
->icsk_retransmits
++;
1513 tcp_retransmit_skb(sk
, skb_peek(&sk
->sk_write_queue
));
1514 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1515 icsk
->icsk_rto
, TCP_RTO_MAX
);
1521 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1523 return IsReno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1526 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1528 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1531 static inline int tcp_head_timedout(struct sock
*sk
, struct tcp_sock
*tp
)
1533 return tp
->packets_out
&&
1534 tcp_skb_timedout(sk
, skb_peek(&sk
->sk_write_queue
));
1537 /* Linux NewReno/SACK/FACK/ECN state machine.
1538 * --------------------------------------
1540 * "Open" Normal state, no dubious events, fast path.
1541 * "Disorder" In all the respects it is "Open",
1542 * but requires a bit more attention. It is entered when
1543 * we see some SACKs or dupacks. It is split of "Open"
1544 * mainly to move some processing from fast path to slow one.
1545 * "CWR" CWND was reduced due to some Congestion Notification event.
1546 * It can be ECN, ICMP source quench, local device congestion.
1547 * "Recovery" CWND was reduced, we are fast-retransmitting.
1548 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1550 * tcp_fastretrans_alert() is entered:
1551 * - each incoming ACK, if state is not "Open"
1552 * - when arrived ACK is unusual, namely:
1557 * Counting packets in flight is pretty simple.
1559 * in_flight = packets_out - left_out + retrans_out
1561 * packets_out is SND.NXT-SND.UNA counted in packets.
1563 * retrans_out is number of retransmitted segments.
1565 * left_out is number of segments left network, but not ACKed yet.
1567 * left_out = sacked_out + lost_out
1569 * sacked_out: Packets, which arrived to receiver out of order
1570 * and hence not ACKed. With SACKs this number is simply
1571 * amount of SACKed data. Even without SACKs
1572 * it is easy to give pretty reliable estimate of this number,
1573 * counting duplicate ACKs.
1575 * lost_out: Packets lost by network. TCP has no explicit
1576 * "loss notification" feedback from network (for now).
1577 * It means that this number can be only _guessed_.
1578 * Actually, it is the heuristics to predict lossage that
1579 * distinguishes different algorithms.
1581 * F.e. after RTO, when all the queue is considered as lost,
1582 * lost_out = packets_out and in_flight = retrans_out.
1584 * Essentially, we have now two algorithms counting
1587 * FACK: It is the simplest heuristics. As soon as we decided
1588 * that something is lost, we decide that _all_ not SACKed
1589 * packets until the most forward SACK are lost. I.e.
1590 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1591 * It is absolutely correct estimate, if network does not reorder
1592 * packets. And it loses any connection to reality when reordering
1593 * takes place. We use FACK by default until reordering
1594 * is suspected on the path to this destination.
1596 * NewReno: when Recovery is entered, we assume that one segment
1597 * is lost (classic Reno). While we are in Recovery and
1598 * a partial ACK arrives, we assume that one more packet
1599 * is lost (NewReno). This heuristics are the same in NewReno
1602 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1603 * deflation etc. CWND is real congestion window, never inflated, changes
1604 * only according to classic VJ rules.
1606 * Really tricky (and requiring careful tuning) part of algorithm
1607 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1608 * The first determines the moment _when_ we should reduce CWND and,
1609 * hence, slow down forward transmission. In fact, it determines the moment
1610 * when we decide that hole is caused by loss, rather than by a reorder.
1612 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1613 * holes, caused by lost packets.
1615 * And the most logically complicated part of algorithm is undo
1616 * heuristics. We detect false retransmits due to both too early
1617 * fast retransmit (reordering) and underestimated RTO, analyzing
1618 * timestamps and D-SACKs. When we detect that some segments were
1619 * retransmitted by mistake and CWND reduction was wrong, we undo
1620 * window reduction and abort recovery phase. This logic is hidden
1621 * inside several functions named tcp_try_undo_<something>.
1624 /* This function decides, when we should leave Disordered state
1625 * and enter Recovery phase, reducing congestion window.
1627 * Main question: may we further continue forward transmission
1628 * with the same cwnd?
1630 static int tcp_time_to_recover(struct sock
*sk
, struct tcp_sock
*tp
)
1634 /* Do not perform any recovery during FRTO algorithm */
1635 if (tp
->frto_counter
)
1638 /* Trick#1: The loss is proven. */
1642 /* Not-A-Trick#2 : Classic rule... */
1643 if (tcp_fackets_out(tp
) > tp
->reordering
)
1646 /* Trick#3 : when we use RFC2988 timer restart, fast
1647 * retransmit can be triggered by timeout of queue head.
1649 if (tcp_head_timedout(sk
, tp
))
1652 /* Trick#4: It is still not OK... But will it be useful to delay
1655 packets_out
= tp
->packets_out
;
1656 if (packets_out
<= tp
->reordering
&&
1657 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1658 !tcp_may_send_now(sk
, tp
)) {
1659 /* We have nothing to send. This connection is limited
1660 * either by receiver window or by application.
1668 /* If we receive more dupacks than we expected counting segments
1669 * in assumption of absent reordering, interpret this as reordering.
1670 * The only another reason could be bug in receiver TCP.
1672 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1674 struct tcp_sock
*tp
= tcp_sk(sk
);
1677 holes
= max(tp
->lost_out
, 1U);
1678 holes
= min(holes
, tp
->packets_out
);
1680 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1681 tp
->sacked_out
= tp
->packets_out
- holes
;
1682 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1686 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1688 static void tcp_add_reno_sack(struct sock
*sk
)
1690 struct tcp_sock
*tp
= tcp_sk(sk
);
1692 tcp_check_reno_reordering(sk
, 0);
1693 tcp_sync_left_out(tp
);
1696 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1698 static void tcp_remove_reno_sacks(struct sock
*sk
, struct tcp_sock
*tp
, int acked
)
1701 /* One ACK acked hole. The rest eat duplicate ACKs. */
1702 if (acked
-1 >= tp
->sacked_out
)
1705 tp
->sacked_out
-= acked
-1;
1707 tcp_check_reno_reordering(sk
, acked
);
1708 tcp_sync_left_out(tp
);
1711 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1714 tp
->left_out
= tp
->lost_out
;
1717 /* Mark head of queue up as lost. */
1718 static void tcp_mark_head_lost(struct sock
*sk
, struct tcp_sock
*tp
,
1719 int packets
, u32 high_seq
)
1721 struct sk_buff
*skb
;
1724 BUG_TRAP(packets
<= tp
->packets_out
);
1725 if (tp
->lost_skb_hint
) {
1726 skb
= tp
->lost_skb_hint
;
1727 cnt
= tp
->lost_cnt_hint
;
1729 skb
= sk
->sk_write_queue
.next
;
1733 sk_stream_for_retrans_queue_from(skb
, sk
) {
1734 /* TODO: do this better */
1735 /* this is not the most efficient way to do this... */
1736 tp
->lost_skb_hint
= skb
;
1737 tp
->lost_cnt_hint
= cnt
;
1738 cnt
+= tcp_skb_pcount(skb
);
1739 if (cnt
> packets
|| after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1741 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1742 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1743 tp
->lost_out
+= tcp_skb_pcount(skb
);
1745 /* clear xmit_retransmit_queue hints
1746 * if this is beyond hint */
1747 if(tp
->retransmit_skb_hint
!= NULL
&&
1748 before(TCP_SKB_CB(skb
)->seq
,
1749 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
)) {
1751 tp
->retransmit_skb_hint
= NULL
;
1755 tcp_sync_left_out(tp
);
1758 /* Account newly detected lost packet(s) */
1760 static void tcp_update_scoreboard(struct sock
*sk
, struct tcp_sock
*tp
)
1763 int lost
= tp
->fackets_out
- tp
->reordering
;
1766 tcp_mark_head_lost(sk
, tp
, lost
, tp
->high_seq
);
1768 tcp_mark_head_lost(sk
, tp
, 1, tp
->high_seq
);
1771 /* New heuristics: it is possible only after we switched
1772 * to restart timer each time when something is ACKed.
1773 * Hence, we can detect timed out packets during fast
1774 * retransmit without falling to slow start.
1776 if (!IsReno(tp
) && tcp_head_timedout(sk
, tp
)) {
1777 struct sk_buff
*skb
;
1779 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
1780 : sk
->sk_write_queue
.next
;
1782 sk_stream_for_retrans_queue_from(skb
, sk
) {
1783 if (!tcp_skb_timedout(sk
, skb
))
1786 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1787 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1788 tp
->lost_out
+= tcp_skb_pcount(skb
);
1790 /* clear xmit_retrans hint */
1791 if (tp
->retransmit_skb_hint
&&
1792 before(TCP_SKB_CB(skb
)->seq
,
1793 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1795 tp
->retransmit_skb_hint
= NULL
;
1799 tp
->scoreboard_skb_hint
= skb
;
1801 tcp_sync_left_out(tp
);
1805 /* CWND moderation, preventing bursts due to too big ACKs
1806 * in dubious situations.
1808 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
1810 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
1811 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
1812 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1815 /* Lower bound on congestion window is slow start threshold
1816 * unless congestion avoidance choice decides to overide it.
1818 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
1820 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1822 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
1825 /* Decrease cwnd each second ack. */
1826 static void tcp_cwnd_down(struct sock
*sk
)
1828 struct tcp_sock
*tp
= tcp_sk(sk
);
1829 int decr
= tp
->snd_cwnd_cnt
+ 1;
1831 tp
->snd_cwnd_cnt
= decr
&1;
1834 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
1835 tp
->snd_cwnd
-= decr
;
1837 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
1838 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1841 /* Nothing was retransmitted or returned timestamp is less
1842 * than timestamp of the first retransmission.
1844 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
1846 return !tp
->retrans_stamp
||
1847 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
1848 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
1851 /* Undo procedures. */
1853 #if FASTRETRANS_DEBUG > 1
1854 static void DBGUNDO(struct sock
*sk
, struct tcp_sock
*tp
, const char *msg
)
1856 struct inet_sock
*inet
= inet_sk(sk
);
1857 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1859 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
1860 tp
->snd_cwnd
, tp
->left_out
,
1861 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
1865 #define DBGUNDO(x...) do { } while (0)
1868 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
1870 struct tcp_sock
*tp
= tcp_sk(sk
);
1872 if (tp
->prior_ssthresh
) {
1873 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1875 if (icsk
->icsk_ca_ops
->undo_cwnd
)
1876 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
1878 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
1880 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
1881 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
1882 TCP_ECN_withdraw_cwr(tp
);
1885 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1887 tcp_moderate_cwnd(tp
);
1888 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1890 /* There is something screwy going on with the retrans hints after
1892 clear_all_retrans_hints(tp
);
1895 static inline int tcp_may_undo(struct tcp_sock
*tp
)
1897 return tp
->undo_marker
&&
1898 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
1901 /* People celebrate: "We love our President!" */
1902 static int tcp_try_undo_recovery(struct sock
*sk
, struct tcp_sock
*tp
)
1904 if (tcp_may_undo(tp
)) {
1905 /* Happy end! We did not retransmit anything
1906 * or our original transmission succeeded.
1908 DBGUNDO(sk
, tp
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
1909 tcp_undo_cwr(sk
, 1);
1910 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
1911 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1913 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
1914 tp
->undo_marker
= 0;
1916 if (tp
->snd_una
== tp
->high_seq
&& IsReno(tp
)) {
1917 /* Hold old state until something *above* high_seq
1918 * is ACKed. For Reno it is MUST to prevent false
1919 * fast retransmits (RFC2582). SACK TCP is safe. */
1920 tcp_moderate_cwnd(tp
);
1923 tcp_set_ca_state(sk
, TCP_CA_Open
);
1927 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1928 static void tcp_try_undo_dsack(struct sock
*sk
, struct tcp_sock
*tp
)
1930 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
1931 DBGUNDO(sk
, tp
, "D-SACK");
1932 tcp_undo_cwr(sk
, 1);
1933 tp
->undo_marker
= 0;
1934 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
1938 /* Undo during fast recovery after partial ACK. */
1940 static int tcp_try_undo_partial(struct sock
*sk
, struct tcp_sock
*tp
,
1943 /* Partial ACK arrived. Force Hoe's retransmit. */
1944 int failed
= IsReno(tp
) || tp
->fackets_out
>tp
->reordering
;
1946 if (tcp_may_undo(tp
)) {
1947 /* Plain luck! Hole if filled with delayed
1948 * packet, rather than with a retransmit.
1950 if (tp
->retrans_out
== 0)
1951 tp
->retrans_stamp
= 0;
1953 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
1955 DBGUNDO(sk
, tp
, "Hoe");
1956 tcp_undo_cwr(sk
, 0);
1957 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
1959 /* So... Do not make Hoe's retransmit yet.
1960 * If the first packet was delayed, the rest
1961 * ones are most probably delayed as well.
1968 /* Undo during loss recovery after partial ACK. */
1969 static int tcp_try_undo_loss(struct sock
*sk
, struct tcp_sock
*tp
)
1971 if (tcp_may_undo(tp
)) {
1972 struct sk_buff
*skb
;
1973 sk_stream_for_retrans_queue(skb
, sk
) {
1974 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1977 clear_all_retrans_hints(tp
);
1979 DBGUNDO(sk
, tp
, "partial loss");
1981 tp
->left_out
= tp
->sacked_out
;
1982 tcp_undo_cwr(sk
, 1);
1983 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1984 inet_csk(sk
)->icsk_retransmits
= 0;
1985 tp
->undo_marker
= 0;
1987 tcp_set_ca_state(sk
, TCP_CA_Open
);
1993 static inline void tcp_complete_cwr(struct sock
*sk
)
1995 struct tcp_sock
*tp
= tcp_sk(sk
);
1996 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1997 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1998 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2001 static void tcp_try_to_open(struct sock
*sk
, struct tcp_sock
*tp
, int flag
)
2003 tp
->left_out
= tp
->sacked_out
;
2005 if (tp
->retrans_out
== 0)
2006 tp
->retrans_stamp
= 0;
2009 tcp_enter_cwr(sk
, 1);
2011 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2012 int state
= TCP_CA_Open
;
2014 if (tp
->left_out
|| tp
->retrans_out
|| tp
->undo_marker
)
2015 state
= TCP_CA_Disorder
;
2017 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2018 tcp_set_ca_state(sk
, state
);
2019 tp
->high_seq
= tp
->snd_nxt
;
2021 tcp_moderate_cwnd(tp
);
2027 static void tcp_mtup_probe_failed(struct sock
*sk
)
2029 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2031 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2032 icsk
->icsk_mtup
.probe_size
= 0;
2035 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2037 struct tcp_sock
*tp
= tcp_sk(sk
);
2038 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2040 /* FIXME: breaks with very large cwnd */
2041 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2042 tp
->snd_cwnd
= tp
->snd_cwnd
*
2043 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2044 icsk
->icsk_mtup
.probe_size
;
2045 tp
->snd_cwnd_cnt
= 0;
2046 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2047 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2049 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2050 icsk
->icsk_mtup
.probe_size
= 0;
2051 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2055 /* Process an event, which can update packets-in-flight not trivially.
2056 * Main goal of this function is to calculate new estimate for left_out,
2057 * taking into account both packets sitting in receiver's buffer and
2058 * packets lost by network.
2060 * Besides that it does CWND reduction, when packet loss is detected
2061 * and changes state of machine.
2063 * It does _not_ decide what to send, it is made in function
2064 * tcp_xmit_retransmit_queue().
2067 tcp_fastretrans_alert(struct sock
*sk
, u32 prior_snd_una
,
2068 int prior_packets
, int flag
)
2070 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2071 struct tcp_sock
*tp
= tcp_sk(sk
);
2072 int is_dupack
= (tp
->snd_una
== prior_snd_una
&& !(flag
&FLAG_NOT_DUP
));
2074 /* Some technical things:
2075 * 1. Reno does not count dupacks (sacked_out) automatically. */
2076 if (!tp
->packets_out
)
2078 /* 2. SACK counts snd_fack in packets inaccurately. */
2079 if (tp
->sacked_out
== 0)
2080 tp
->fackets_out
= 0;
2082 /* Now state machine starts.
2083 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2085 tp
->prior_ssthresh
= 0;
2087 /* B. In all the states check for reneging SACKs. */
2088 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
2091 /* C. Process data loss notification, provided it is valid. */
2092 if ((flag
&FLAG_DATA_LOST
) &&
2093 before(tp
->snd_una
, tp
->high_seq
) &&
2094 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2095 tp
->fackets_out
> tp
->reordering
) {
2096 tcp_mark_head_lost(sk
, tp
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
2097 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2100 /* D. Synchronize left_out to current state. */
2101 tcp_sync_left_out(tp
);
2103 /* E. Check state exit conditions. State can be terminated
2104 * when high_seq is ACKed. */
2105 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2106 BUG_TRAP(tp
->retrans_out
== 0);
2107 tp
->retrans_stamp
= 0;
2108 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2109 switch (icsk
->icsk_ca_state
) {
2111 icsk
->icsk_retransmits
= 0;
2112 if (tcp_try_undo_recovery(sk
, tp
))
2117 /* CWR is to be held something *above* high_seq
2118 * is ACKed for CWR bit to reach receiver. */
2119 if (tp
->snd_una
!= tp
->high_seq
) {
2120 tcp_complete_cwr(sk
);
2121 tcp_set_ca_state(sk
, TCP_CA_Open
);
2125 case TCP_CA_Disorder
:
2126 tcp_try_undo_dsack(sk
, tp
);
2127 if (!tp
->undo_marker
||
2128 /* For SACK case do not Open to allow to undo
2129 * catching for all duplicate ACKs. */
2130 IsReno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2131 tp
->undo_marker
= 0;
2132 tcp_set_ca_state(sk
, TCP_CA_Open
);
2136 case TCP_CA_Recovery
:
2138 tcp_reset_reno_sack(tp
);
2139 if (tcp_try_undo_recovery(sk
, tp
))
2141 tcp_complete_cwr(sk
);
2146 /* F. Process state. */
2147 switch (icsk
->icsk_ca_state
) {
2148 case TCP_CA_Recovery
:
2149 if (prior_snd_una
== tp
->snd_una
) {
2150 if (IsReno(tp
) && is_dupack
)
2151 tcp_add_reno_sack(sk
);
2153 int acked
= prior_packets
- tp
->packets_out
;
2155 tcp_remove_reno_sacks(sk
, tp
, acked
);
2156 is_dupack
= tcp_try_undo_partial(sk
, tp
, acked
);
2160 if (flag
&FLAG_DATA_ACKED
)
2161 icsk
->icsk_retransmits
= 0;
2162 if (!tcp_try_undo_loss(sk
, tp
)) {
2163 tcp_moderate_cwnd(tp
);
2164 tcp_xmit_retransmit_queue(sk
);
2167 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2169 /* Loss is undone; fall through to processing in Open state. */
2172 if (tp
->snd_una
!= prior_snd_una
)
2173 tcp_reset_reno_sack(tp
);
2175 tcp_add_reno_sack(sk
);
2178 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2179 tcp_try_undo_dsack(sk
, tp
);
2181 if (!tcp_time_to_recover(sk
, tp
)) {
2182 tcp_try_to_open(sk
, tp
, flag
);
2186 /* MTU probe failure: don't reduce cwnd */
2187 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2188 icsk
->icsk_mtup
.probe_size
&&
2189 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2190 tcp_mtup_probe_failed(sk
);
2191 /* Restores the reduction we did in tcp_mtup_probe() */
2193 tcp_simple_retransmit(sk
);
2197 /* Otherwise enter Recovery state */
2200 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2202 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2204 tp
->high_seq
= tp
->snd_nxt
;
2205 tp
->prior_ssthresh
= 0;
2206 tp
->undo_marker
= tp
->snd_una
;
2207 tp
->undo_retrans
= tp
->retrans_out
;
2209 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2210 if (!(flag
&FLAG_ECE
))
2211 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2212 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2213 TCP_ECN_queue_cwr(tp
);
2216 tp
->bytes_acked
= 0;
2217 tp
->snd_cwnd_cnt
= 0;
2218 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2221 if (is_dupack
|| tcp_head_timedout(sk
, tp
))
2222 tcp_update_scoreboard(sk
, tp
);
2224 tcp_xmit_retransmit_queue(sk
);
2227 /* Read draft-ietf-tcplw-high-performance before mucking
2228 * with this code. (Supersedes RFC1323)
2230 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2232 /* RTTM Rule: A TSecr value received in a segment is used to
2233 * update the averaged RTT measurement only if the segment
2234 * acknowledges some new data, i.e., only if it advances the
2235 * left edge of the send window.
2237 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2238 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2240 * Changed: reset backoff as soon as we see the first valid sample.
2241 * If we do not, we get strongly overestimated rto. With timestamps
2242 * samples are accepted even from very old segments: f.e., when rtt=1
2243 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2244 * answer arrives rto becomes 120 seconds! If at least one of segments
2245 * in window is lost... Voila. --ANK (010210)
2247 struct tcp_sock
*tp
= tcp_sk(sk
);
2248 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2249 tcp_rtt_estimator(sk
, seq_rtt
);
2251 inet_csk(sk
)->icsk_backoff
= 0;
2255 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2257 /* We don't have a timestamp. Can only use
2258 * packets that are not retransmitted to determine
2259 * rtt estimates. Also, we must not reset the
2260 * backoff for rto until we get a non-retransmitted
2261 * packet. This allows us to deal with a situation
2262 * where the network delay has increased suddenly.
2263 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2266 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2269 tcp_rtt_estimator(sk
, seq_rtt
);
2271 inet_csk(sk
)->icsk_backoff
= 0;
2275 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2278 const struct tcp_sock
*tp
= tcp_sk(sk
);
2279 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2280 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2281 tcp_ack_saw_tstamp(sk
, flag
);
2282 else if (seq_rtt
>= 0)
2283 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2286 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 rtt
,
2287 u32 in_flight
, int good
)
2289 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2290 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, rtt
, in_flight
, good
);
2291 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2294 /* Restart timer after forward progress on connection.
2295 * RFC2988 recommends to restart timer to now+rto.
2298 static void tcp_ack_packets_out(struct sock
*sk
, struct tcp_sock
*tp
)
2300 if (!tp
->packets_out
) {
2301 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2303 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2307 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
2308 __u32 now
, __s32
*seq_rtt
)
2310 struct tcp_sock
*tp
= tcp_sk(sk
);
2311 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2312 __u32 seq
= tp
->snd_una
;
2313 __u32 packets_acked
;
2316 /* If we get here, the whole TSO packet has not been
2319 BUG_ON(!after(scb
->end_seq
, seq
));
2321 packets_acked
= tcp_skb_pcount(skb
);
2322 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
2324 packets_acked
-= tcp_skb_pcount(skb
);
2326 if (packets_acked
) {
2327 __u8 sacked
= scb
->sacked
;
2329 acked
|= FLAG_DATA_ACKED
;
2331 if (sacked
& TCPCB_RETRANS
) {
2332 if (sacked
& TCPCB_SACKED_RETRANS
)
2333 tp
->retrans_out
-= packets_acked
;
2334 acked
|= FLAG_RETRANS_DATA_ACKED
;
2336 } else if (*seq_rtt
< 0)
2337 *seq_rtt
= now
- scb
->when
;
2338 if (sacked
& TCPCB_SACKED_ACKED
)
2339 tp
->sacked_out
-= packets_acked
;
2340 if (sacked
& TCPCB_LOST
)
2341 tp
->lost_out
-= packets_acked
;
2342 if (sacked
& TCPCB_URG
) {
2344 !before(seq
, tp
->snd_up
))
2347 } else if (*seq_rtt
< 0)
2348 *seq_rtt
= now
- scb
->when
;
2350 if (tp
->fackets_out
) {
2351 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2352 tp
->fackets_out
-= dval
;
2354 tp
->packets_out
-= packets_acked
;
2356 BUG_ON(tcp_skb_pcount(skb
) == 0);
2357 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2363 static u32
tcp_usrtt(struct timeval
*tv
)
2367 do_gettimeofday(&now
);
2368 return (now
.tv_sec
- tv
->tv_sec
) * 1000000 + (now
.tv_usec
- tv
->tv_usec
);
2371 /* Remove acknowledged frames from the retransmission queue. */
2372 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2374 struct tcp_sock
*tp
= tcp_sk(sk
);
2375 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2376 struct sk_buff
*skb
;
2377 __u32 now
= tcp_time_stamp
;
2381 void (*rtt_sample
)(struct sock
*sk
, u32 usrtt
)
2382 = icsk
->icsk_ca_ops
->rtt_sample
;
2383 struct timeval tv
= { .tv_sec
= 0, .tv_usec
= 0 };
2385 while ((skb
= skb_peek(&sk
->sk_write_queue
)) &&
2386 skb
!= sk
->sk_send_head
) {
2387 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2388 __u8 sacked
= scb
->sacked
;
2390 /* If our packet is before the ack sequence we can
2391 * discard it as it's confirmed to have arrived at
2394 if (after(scb
->end_seq
, tp
->snd_una
)) {
2395 if (tcp_skb_pcount(skb
) > 1 &&
2396 after(tp
->snd_una
, scb
->seq
))
2397 acked
|= tcp_tso_acked(sk
, skb
,
2402 /* Initial outgoing SYN's get put onto the write_queue
2403 * just like anything else we transmit. It is not
2404 * true data, and if we misinform our callers that
2405 * this ACK acks real data, we will erroneously exit
2406 * connection startup slow start one packet too
2407 * quickly. This is severely frowned upon behavior.
2409 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2410 acked
|= FLAG_DATA_ACKED
;
2413 acked
|= FLAG_SYN_ACKED
;
2414 tp
->retrans_stamp
= 0;
2417 /* MTU probing checks */
2418 if (icsk
->icsk_mtup
.probe_size
) {
2419 if (!after(tp
->mtu_probe
.probe_seq_end
, TCP_SKB_CB(skb
)->end_seq
)) {
2420 tcp_mtup_probe_success(sk
, skb
);
2425 if (sacked
& TCPCB_RETRANS
) {
2426 if(sacked
& TCPCB_SACKED_RETRANS
)
2427 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2428 acked
|= FLAG_RETRANS_DATA_ACKED
;
2430 } else if (seq_rtt
< 0) {
2431 seq_rtt
= now
- scb
->when
;
2432 skb_get_timestamp(skb
, &tv
);
2434 if (sacked
& TCPCB_SACKED_ACKED
)
2435 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2436 if (sacked
& TCPCB_LOST
)
2437 tp
->lost_out
-= tcp_skb_pcount(skb
);
2438 if (sacked
& TCPCB_URG
) {
2440 !before(scb
->end_seq
, tp
->snd_up
))
2443 } else if (seq_rtt
< 0) {
2444 seq_rtt
= now
- scb
->when
;
2445 skb_get_timestamp(skb
, &tv
);
2447 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2448 tcp_packets_out_dec(tp
, skb
);
2449 __skb_unlink(skb
, &sk
->sk_write_queue
);
2450 sk_stream_free_skb(sk
, skb
);
2451 clear_all_retrans_hints(tp
);
2454 if (acked
&FLAG_ACKED
) {
2455 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2456 tcp_ack_packets_out(sk
, tp
);
2457 if (rtt_sample
&& !(acked
& FLAG_RETRANS_DATA_ACKED
))
2458 (*rtt_sample
)(sk
, tcp_usrtt(&tv
));
2460 if (icsk
->icsk_ca_ops
->pkts_acked
)
2461 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
);
2464 #if FASTRETRANS_DEBUG > 0
2465 BUG_TRAP((int)tp
->sacked_out
>= 0);
2466 BUG_TRAP((int)tp
->lost_out
>= 0);
2467 BUG_TRAP((int)tp
->retrans_out
>= 0);
2468 if (!tp
->packets_out
&& tp
->rx_opt
.sack_ok
) {
2469 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2471 printk(KERN_DEBUG
"Leak l=%u %d\n",
2472 tp
->lost_out
, icsk
->icsk_ca_state
);
2475 if (tp
->sacked_out
) {
2476 printk(KERN_DEBUG
"Leak s=%u %d\n",
2477 tp
->sacked_out
, icsk
->icsk_ca_state
);
2480 if (tp
->retrans_out
) {
2481 printk(KERN_DEBUG
"Leak r=%u %d\n",
2482 tp
->retrans_out
, icsk
->icsk_ca_state
);
2483 tp
->retrans_out
= 0;
2487 *seq_rtt_p
= seq_rtt
;
2491 static void tcp_ack_probe(struct sock
*sk
)
2493 const struct tcp_sock
*tp
= tcp_sk(sk
);
2494 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2496 /* Was it a usable window open? */
2498 if (!after(TCP_SKB_CB(sk
->sk_send_head
)->end_seq
,
2499 tp
->snd_una
+ tp
->snd_wnd
)) {
2500 icsk
->icsk_backoff
= 0;
2501 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2502 /* Socket must be waked up by subsequent tcp_data_snd_check().
2503 * This function is not for random using!
2506 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2507 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2512 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2514 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2515 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2518 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2520 const struct tcp_sock
*tp
= tcp_sk(sk
);
2521 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2522 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2525 /* Check that window update is acceptable.
2526 * The function assumes that snd_una<=ack<=snd_next.
2528 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2529 const u32 ack_seq
, const u32 nwin
)
2531 return (after(ack
, tp
->snd_una
) ||
2532 after(ack_seq
, tp
->snd_wl1
) ||
2533 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2536 /* Update our send window.
2538 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2539 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2541 static int tcp_ack_update_window(struct sock
*sk
, struct tcp_sock
*tp
,
2542 struct sk_buff
*skb
, u32 ack
, u32 ack_seq
)
2545 u32 nwin
= ntohs(skb
->h
.th
->window
);
2547 if (likely(!skb
->h
.th
->syn
))
2548 nwin
<<= tp
->rx_opt
.snd_wscale
;
2550 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2551 flag
|= FLAG_WIN_UPDATE
;
2552 tcp_update_wl(tp
, ack
, ack_seq
);
2554 if (tp
->snd_wnd
!= nwin
) {
2557 /* Note, it is the only place, where
2558 * fast path is recovered for sending TCP.
2561 tcp_fast_path_check(sk
, tp
);
2563 if (nwin
> tp
->max_window
) {
2564 tp
->max_window
= nwin
;
2565 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
2575 /* A very conservative spurious RTO response algorithm: reduce cwnd and
2576 * continue in congestion avoidance.
2578 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
2580 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2581 tp
->snd_cwnd_cnt
= 0;
2582 tcp_moderate_cwnd(tp
);
2585 /* A conservative spurious RTO response algorithm: reduce cwnd using
2586 * rate halving and continue in congestion avoidance.
2588 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
2590 struct tcp_sock
*tp
= tcp_sk(sk
);
2591 tcp_enter_cwr(sk
, 0);
2592 tp
->high_seq
= tp
->frto_highmark
; /* Smoother w/o this? - ij */
2595 static void tcp_undo_spur_to_response(struct sock
*sk
)
2597 tcp_undo_cwr(sk
, 1);
2600 /* F-RTO spurious RTO detection algorithm (RFC4138)
2602 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
2603 * comments). State (ACK number) is kept in frto_counter. When ACK advances
2604 * window (but not to or beyond highest sequence sent before RTO):
2605 * On First ACK, send two new segments out.
2606 * On Second ACK, RTO was likely spurious. Do spurious response (response
2607 * algorithm is not part of the F-RTO detection algorithm
2608 * given in RFC4138 but can be selected separately).
2609 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
2610 * and TCP falls back to conventional RTO recovery.
2612 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2613 * original window even after we transmit two new data segments.
2616 * on first step, wait until first cumulative ACK arrives, then move to
2617 * the second step. In second step, the next ACK decides.
2619 * F-RTO is implemented (mainly) in four functions:
2620 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2621 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2622 * called when tcp_use_frto() showed green light
2623 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2624 * - tcp_enter_frto_loss() is called if there is not enough evidence
2625 * to prove that the RTO is indeed spurious. It transfers the control
2626 * from F-RTO to the conventional RTO recovery
2628 static int tcp_process_frto(struct sock
*sk
, u32 prior_snd_una
, int flag
)
2630 struct tcp_sock
*tp
= tcp_sk(sk
);
2632 tcp_sync_left_out(tp
);
2634 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2635 if (flag
&FLAG_DATA_ACKED
)
2636 inet_csk(sk
)->icsk_retransmits
= 0;
2638 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
2639 tcp_enter_frto_loss(sk
, tp
->frto_counter
+ 1, flag
);
2643 if (!IsSackFrto() || IsReno(tp
)) {
2644 /* RFC4138 shortcoming in step 2; should also have case c):
2645 * ACK isn't duplicate nor advances window, e.g., opposite dir
2648 if ((tp
->snd_una
== prior_snd_una
) && (flag
&FLAG_NOT_DUP
) &&
2649 !(flag
&FLAG_FORWARD_PROGRESS
))
2652 if (!(flag
&FLAG_DATA_ACKED
)) {
2653 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
2658 if (!(flag
&FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
2659 /* Prevent sending of new data. */
2660 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2661 tcp_packets_in_flight(tp
));
2665 if ((tp
->frto_counter
== 2) &&
2666 (!(flag
&FLAG_FORWARD_PROGRESS
) ||
2667 ((flag
&FLAG_DATA_SACKED
) && !(flag
&FLAG_ONLY_ORIG_SACKED
)))) {
2668 /* RFC4138 shortcoming (see comment above) */
2669 if (!(flag
&FLAG_FORWARD_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2672 tcp_enter_frto_loss(sk
, 3, flag
);
2677 if (tp
->frto_counter
== 1) {
2678 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2679 tp
->frto_counter
= 2;
2681 } else /* frto_counter == 2 */ {
2682 switch (sysctl_tcp_frto_response
) {
2684 tcp_undo_spur_to_response(sk
);
2687 tcp_conservative_spur_to_response(tp
);
2690 tcp_ratehalving_spur_to_response(sk
);
2693 tp
->frto_counter
= 0;
2698 /* This routine deals with incoming acks, but not outgoing ones. */
2699 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2701 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2702 struct tcp_sock
*tp
= tcp_sk(sk
);
2703 u32 prior_snd_una
= tp
->snd_una
;
2704 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2705 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2706 u32 prior_in_flight
;
2711 /* If the ack is newer than sent or older than previous acks
2712 * then we can probably ignore it.
2714 if (after(ack
, tp
->snd_nxt
))
2715 goto uninteresting_ack
;
2717 if (before(ack
, prior_snd_una
))
2720 if (sysctl_tcp_abc
) {
2721 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
2722 tp
->bytes_acked
+= ack
- prior_snd_una
;
2723 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
2724 /* we assume just one segment left network */
2725 tp
->bytes_acked
+= min(ack
- prior_snd_una
, tp
->mss_cache
);
2728 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2729 /* Window is constant, pure forward advance.
2730 * No more checks are required.
2731 * Note, we use the fact that SND.UNA>=SND.WL2.
2733 tcp_update_wl(tp
, ack
, ack_seq
);
2735 flag
|= FLAG_WIN_UPDATE
;
2737 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2739 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2741 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2744 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2746 flag
|= tcp_ack_update_window(sk
, tp
, skb
, ack
, ack_seq
);
2748 if (TCP_SKB_CB(skb
)->sacked
)
2749 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2751 if (TCP_ECN_rcv_ecn_echo(tp
, skb
->h
.th
))
2754 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
2757 /* We passed data and got it acked, remove any soft error
2758 * log. Something worked...
2760 sk
->sk_err_soft
= 0;
2761 tp
->rcv_tstamp
= tcp_time_stamp
;
2762 prior_packets
= tp
->packets_out
;
2766 prior_in_flight
= tcp_packets_in_flight(tp
);
2768 /* See if we can take anything off of the retransmit queue. */
2769 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
2771 if (tp
->frto_counter
)
2772 frto_cwnd
= tcp_process_frto(sk
, prior_snd_una
, flag
);
2774 if (tcp_ack_is_dubious(sk
, flag
)) {
2775 /* Advance CWND, if state allows this. */
2776 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
2777 tcp_may_raise_cwnd(sk
, flag
))
2778 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 0);
2779 tcp_fastretrans_alert(sk
, prior_snd_una
, prior_packets
, flag
);
2781 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
2782 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 1);
2785 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
2786 dst_confirm(sk
->sk_dst_cache
);
2791 icsk
->icsk_probes_out
= 0;
2793 /* If this ack opens up a zero window, clear backoff. It was
2794 * being used to time the probes, and is probably far higher than
2795 * it needs to be for normal retransmission.
2797 if (sk
->sk_send_head
)
2802 if (TCP_SKB_CB(skb
)->sacked
)
2803 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2806 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
2811 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2812 * But, this can also be called on packets in the established flow when
2813 * the fast version below fails.
2815 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
2818 struct tcphdr
*th
= skb
->h
.th
;
2819 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
2821 ptr
= (unsigned char *)(th
+ 1);
2822 opt_rx
->saw_tstamp
= 0;
2831 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
2836 if (opsize
< 2) /* "silly options" */
2838 if (opsize
> length
)
2839 return; /* don't parse partial options */
2842 if(opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
2843 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
2845 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
2846 in_mss
= opt_rx
->user_mss
;
2847 opt_rx
->mss_clamp
= in_mss
;
2852 if(opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
2853 if (sysctl_tcp_window_scaling
) {
2854 __u8 snd_wscale
= *(__u8
*) ptr
;
2855 opt_rx
->wscale_ok
= 1;
2856 if (snd_wscale
> 14) {
2858 printk(KERN_INFO
"tcp_parse_options: Illegal window "
2859 "scaling value %d >14 received.\n",
2863 opt_rx
->snd_wscale
= snd_wscale
;
2866 case TCPOPT_TIMESTAMP
:
2867 if(opsize
==TCPOLEN_TIMESTAMP
) {
2868 if ((estab
&& opt_rx
->tstamp_ok
) ||
2869 (!estab
&& sysctl_tcp_timestamps
)) {
2870 opt_rx
->saw_tstamp
= 1;
2871 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
2872 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
2876 case TCPOPT_SACK_PERM
:
2877 if(opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
2878 if (sysctl_tcp_sack
) {
2879 opt_rx
->sack_ok
= 1;
2880 tcp_sack_reset(opt_rx
);
2886 if((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
2887 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
2889 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
2891 #ifdef CONFIG_TCP_MD5SIG
2894 * The MD5 Hash has already been
2895 * checked (see tcp_v{4,6}_do_rcv()).
2906 /* Fast parse options. This hopes to only see timestamps.
2907 * If it is wrong it falls back on tcp_parse_options().
2909 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
2910 struct tcp_sock
*tp
)
2912 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
2913 tp
->rx_opt
.saw_tstamp
= 0;
2915 } else if (tp
->rx_opt
.tstamp_ok
&&
2916 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
2917 __be32
*ptr
= (__be32
*)(th
+ 1);
2918 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
2919 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
2920 tp
->rx_opt
.saw_tstamp
= 1;
2922 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
2924 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
2928 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
2932 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
2934 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
2935 tp
->rx_opt
.ts_recent_stamp
= xtime
.tv_sec
;
2938 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
2940 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
2941 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2942 * extra check below makes sure this can only happen
2943 * for pure ACK frames. -DaveM
2945 * Not only, also it occurs for expired timestamps.
2948 if((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
2949 xtime
.tv_sec
>= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
2950 tcp_store_ts_recent(tp
);
2954 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2956 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2957 * it can pass through stack. So, the following predicate verifies that
2958 * this segment is not used for anything but congestion avoidance or
2959 * fast retransmit. Moreover, we even are able to eliminate most of such
2960 * second order effects, if we apply some small "replay" window (~RTO)
2961 * to timestamp space.
2963 * All these measures still do not guarantee that we reject wrapped ACKs
2964 * on networks with high bandwidth, when sequence space is recycled fastly,
2965 * but it guarantees that such events will be very rare and do not affect
2966 * connection seriously. This doesn't look nice, but alas, PAWS is really
2969 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2970 * states that events when retransmit arrives after original data are rare.
2971 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2972 * the biggest problem on large power networks even with minor reordering.
2973 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2974 * up to bandwidth of 18Gigabit/sec. 8) ]
2977 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
2979 struct tcp_sock
*tp
= tcp_sk(sk
);
2980 struct tcphdr
*th
= skb
->h
.th
;
2981 u32 seq
= TCP_SKB_CB(skb
)->seq
;
2982 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2984 return (/* 1. Pure ACK with correct sequence number. */
2985 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
2987 /* 2. ... and duplicate ACK. */
2988 ack
== tp
->snd_una
&&
2990 /* 3. ... and does not update window. */
2991 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
2993 /* 4. ... and sits in replay window. */
2994 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
2997 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
2999 const struct tcp_sock
*tp
= tcp_sk(sk
);
3000 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3001 xtime
.tv_sec
< tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3002 !tcp_disordered_ack(sk
, skb
));
3005 /* Check segment sequence number for validity.
3007 * Segment controls are considered valid, if the segment
3008 * fits to the window after truncation to the window. Acceptability
3009 * of data (and SYN, FIN, of course) is checked separately.
3010 * See tcp_data_queue(), for example.
3012 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3013 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3014 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3015 * (borrowed from freebsd)
3018 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3020 return !before(end_seq
, tp
->rcv_wup
) &&
3021 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3024 /* When we get a reset we do this. */
3025 static void tcp_reset(struct sock
*sk
)
3027 /* We want the right error as BSD sees it (and indeed as we do). */
3028 switch (sk
->sk_state
) {
3030 sk
->sk_err
= ECONNREFUSED
;
3032 case TCP_CLOSE_WAIT
:
3038 sk
->sk_err
= ECONNRESET
;
3041 if (!sock_flag(sk
, SOCK_DEAD
))
3042 sk
->sk_error_report(sk
);
3048 * Process the FIN bit. This now behaves as it is supposed to work
3049 * and the FIN takes effect when it is validly part of sequence
3050 * space. Not before when we get holes.
3052 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3053 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3056 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3057 * close and we go into CLOSING (and later onto TIME-WAIT)
3059 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3061 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3063 struct tcp_sock
*tp
= tcp_sk(sk
);
3065 inet_csk_schedule_ack(sk
);
3067 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3068 sock_set_flag(sk
, SOCK_DONE
);
3070 switch (sk
->sk_state
) {
3072 case TCP_ESTABLISHED
:
3073 /* Move to CLOSE_WAIT */
3074 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3075 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3078 case TCP_CLOSE_WAIT
:
3080 /* Received a retransmission of the FIN, do
3085 /* RFC793: Remain in the LAST-ACK state. */
3089 /* This case occurs when a simultaneous close
3090 * happens, we must ack the received FIN and
3091 * enter the CLOSING state.
3094 tcp_set_state(sk
, TCP_CLOSING
);
3097 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3099 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3102 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3103 * cases we should never reach this piece of code.
3105 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3106 __FUNCTION__
, sk
->sk_state
);
3110 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3111 * Probably, we should reset in this case. For now drop them.
3113 __skb_queue_purge(&tp
->out_of_order_queue
);
3114 if (tp
->rx_opt
.sack_ok
)
3115 tcp_sack_reset(&tp
->rx_opt
);
3116 sk_stream_mem_reclaim(sk
);
3118 if (!sock_flag(sk
, SOCK_DEAD
)) {
3119 sk
->sk_state_change(sk
);
3121 /* Do not send POLL_HUP for half duplex close. */
3122 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3123 sk
->sk_state
== TCP_CLOSE
)
3124 sk_wake_async(sk
, 1, POLL_HUP
);
3126 sk_wake_async(sk
, 1, POLL_IN
);
3130 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
3132 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3133 if (before(seq
, sp
->start_seq
))
3134 sp
->start_seq
= seq
;
3135 if (after(end_seq
, sp
->end_seq
))
3136 sp
->end_seq
= end_seq
;
3142 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3144 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3145 if (before(seq
, tp
->rcv_nxt
))
3146 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
3148 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
3150 tp
->rx_opt
.dsack
= 1;
3151 tp
->duplicate_sack
[0].start_seq
= seq
;
3152 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3153 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
3157 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3159 if (!tp
->rx_opt
.dsack
)
3160 tcp_dsack_set(tp
, seq
, end_seq
);
3162 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3165 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3167 struct tcp_sock
*tp
= tcp_sk(sk
);
3169 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3170 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3171 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3172 tcp_enter_quickack_mode(sk
);
3174 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3175 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3177 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3178 end_seq
= tp
->rcv_nxt
;
3179 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3186 /* These routines update the SACK block as out-of-order packets arrive or
3187 * in-order packets close up the sequence space.
3189 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3192 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3193 struct tcp_sack_block
*swalk
= sp
+1;
3195 /* See if the recent change to the first SACK eats into
3196 * or hits the sequence space of other SACK blocks, if so coalesce.
3198 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
3199 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3202 /* Zap SWALK, by moving every further SACK up by one slot.
3203 * Decrease num_sacks.
3205 tp
->rx_opt
.num_sacks
--;
3206 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3207 for(i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3211 this_sack
++, swalk
++;
3215 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
3219 tmp
= sack1
->start_seq
;
3220 sack1
->start_seq
= sack2
->start_seq
;
3221 sack2
->start_seq
= tmp
;
3223 tmp
= sack1
->end_seq
;
3224 sack1
->end_seq
= sack2
->end_seq
;
3225 sack2
->end_seq
= tmp
;
3228 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3230 struct tcp_sock
*tp
= tcp_sk(sk
);
3231 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3232 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3238 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
3239 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3240 /* Rotate this_sack to the first one. */
3241 for (; this_sack
>0; this_sack
--, sp
--)
3242 tcp_sack_swap(sp
, sp
-1);
3244 tcp_sack_maybe_coalesce(tp
);
3249 /* Could not find an adjacent existing SACK, build a new one,
3250 * put it at the front, and shift everyone else down. We
3251 * always know there is at least one SACK present already here.
3253 * If the sack array is full, forget about the last one.
3255 if (this_sack
>= 4) {
3257 tp
->rx_opt
.num_sacks
--;
3260 for(; this_sack
> 0; this_sack
--, sp
--)
3264 /* Build the new head SACK, and we're done. */
3265 sp
->start_seq
= seq
;
3266 sp
->end_seq
= end_seq
;
3267 tp
->rx_opt
.num_sacks
++;
3268 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3271 /* RCV.NXT advances, some SACKs should be eaten. */
3273 static void tcp_sack_remove(struct tcp_sock
*tp
)
3275 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3276 int num_sacks
= tp
->rx_opt
.num_sacks
;
3279 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3280 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3281 tp
->rx_opt
.num_sacks
= 0;
3282 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3286 for(this_sack
= 0; this_sack
< num_sacks
; ) {
3287 /* Check if the start of the sack is covered by RCV.NXT. */
3288 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3291 /* RCV.NXT must cover all the block! */
3292 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3294 /* Zap this SACK, by moving forward any other SACKS. */
3295 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3296 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3303 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3304 tp
->rx_opt
.num_sacks
= num_sacks
;
3305 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3309 /* This one checks to see if we can put data from the
3310 * out_of_order queue into the receive_queue.
3312 static void tcp_ofo_queue(struct sock
*sk
)
3314 struct tcp_sock
*tp
= tcp_sk(sk
);
3315 __u32 dsack_high
= tp
->rcv_nxt
;
3316 struct sk_buff
*skb
;
3318 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3319 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3322 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3323 __u32 dsack
= dsack_high
;
3324 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3325 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3326 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3329 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3330 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3331 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3335 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3336 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3337 TCP_SKB_CB(skb
)->end_seq
);
3339 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3340 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3341 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3343 tcp_fin(skb
, sk
, skb
->h
.th
);
3347 static int tcp_prune_queue(struct sock
*sk
);
3349 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3351 struct tcphdr
*th
= skb
->h
.th
;
3352 struct tcp_sock
*tp
= tcp_sk(sk
);
3355 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3358 __skb_pull(skb
, th
->doff
*4);
3360 TCP_ECN_accept_cwr(tp
, skb
);
3362 if (tp
->rx_opt
.dsack
) {
3363 tp
->rx_opt
.dsack
= 0;
3364 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3365 4 - tp
->rx_opt
.tstamp_ok
);
3368 /* Queue data for delivery to the user.
3369 * Packets in sequence go to the receive queue.
3370 * Out of sequence packets to the out_of_order_queue.
3372 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3373 if (tcp_receive_window(tp
) == 0)
3376 /* Ok. In sequence. In window. */
3377 if (tp
->ucopy
.task
== current
&&
3378 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3379 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3380 int chunk
= min_t(unsigned int, skb
->len
,
3383 __set_current_state(TASK_RUNNING
);
3386 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3387 tp
->ucopy
.len
-= chunk
;
3388 tp
->copied_seq
+= chunk
;
3389 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3390 tcp_rcv_space_adjust(sk
);
3398 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3399 !sk_stream_rmem_schedule(sk
, skb
))) {
3400 if (tcp_prune_queue(sk
) < 0 ||
3401 !sk_stream_rmem_schedule(sk
, skb
))
3404 sk_stream_set_owner_r(skb
, sk
);
3405 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3407 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3409 tcp_event_data_recv(sk
, tp
, skb
);
3411 tcp_fin(skb
, sk
, th
);
3413 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3416 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3417 * gap in queue is filled.
3419 if (skb_queue_empty(&tp
->out_of_order_queue
))
3420 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3423 if (tp
->rx_opt
.num_sacks
)
3424 tcp_sack_remove(tp
);
3426 tcp_fast_path_check(sk
, tp
);
3430 else if (!sock_flag(sk
, SOCK_DEAD
))
3431 sk
->sk_data_ready(sk
, 0);
3435 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3436 /* A retransmit, 2nd most common case. Force an immediate ack. */
3437 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3438 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3441 tcp_enter_quickack_mode(sk
);
3442 inet_csk_schedule_ack(sk
);
3448 /* Out of window. F.e. zero window probe. */
3449 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3452 tcp_enter_quickack_mode(sk
);
3454 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3455 /* Partial packet, seq < rcv_next < end_seq */
3456 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3457 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3458 TCP_SKB_CB(skb
)->end_seq
);
3460 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3462 /* If window is closed, drop tail of packet. But after
3463 * remembering D-SACK for its head made in previous line.
3465 if (!tcp_receive_window(tp
))
3470 TCP_ECN_check_ce(tp
, skb
);
3472 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3473 !sk_stream_rmem_schedule(sk
, skb
)) {
3474 if (tcp_prune_queue(sk
) < 0 ||
3475 !sk_stream_rmem_schedule(sk
, skb
))
3479 /* Disable header prediction. */
3481 inet_csk_schedule_ack(sk
);
3483 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3484 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3486 sk_stream_set_owner_r(skb
, sk
);
3488 if (!skb_peek(&tp
->out_of_order_queue
)) {
3489 /* Initial out of order segment, build 1 SACK. */
3490 if (tp
->rx_opt
.sack_ok
) {
3491 tp
->rx_opt
.num_sacks
= 1;
3492 tp
->rx_opt
.dsack
= 0;
3493 tp
->rx_opt
.eff_sacks
= 1;
3494 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3495 tp
->selective_acks
[0].end_seq
=
3496 TCP_SKB_CB(skb
)->end_seq
;
3498 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3500 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3501 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3502 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3504 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3505 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3507 if (!tp
->rx_opt
.num_sacks
||
3508 tp
->selective_acks
[0].end_seq
!= seq
)
3511 /* Common case: data arrive in order after hole. */
3512 tp
->selective_acks
[0].end_seq
= end_seq
;
3516 /* Find place to insert this segment. */
3518 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3520 } while ((skb1
= skb1
->prev
) !=
3521 (struct sk_buff
*)&tp
->out_of_order_queue
);
3523 /* Do skb overlap to previous one? */
3524 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3525 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3526 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3527 /* All the bits are present. Drop. */
3529 tcp_dsack_set(tp
, seq
, end_seq
);
3532 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3533 /* Partial overlap. */
3534 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3539 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3541 /* And clean segments covered by new one as whole. */
3542 while ((skb1
= skb
->next
) !=
3543 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3544 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3545 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3546 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3549 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3550 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3555 if (tp
->rx_opt
.sack_ok
)
3556 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3560 /* Collapse contiguous sequence of skbs head..tail with
3561 * sequence numbers start..end.
3562 * Segments with FIN/SYN are not collapsed (only because this
3566 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3567 struct sk_buff
*head
, struct sk_buff
*tail
,
3570 struct sk_buff
*skb
;
3572 /* First, check that queue is collapsible and find
3573 * the point where collapsing can be useful. */
3574 for (skb
= head
; skb
!= tail
; ) {
3575 /* No new bits? It is possible on ofo queue. */
3576 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3577 struct sk_buff
*next
= skb
->next
;
3578 __skb_unlink(skb
, list
);
3580 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3585 /* The first skb to collapse is:
3587 * - bloated or contains data before "start" or
3588 * overlaps to the next one.
3590 if (!skb
->h
.th
->syn
&& !skb
->h
.th
->fin
&&
3591 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3592 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3593 (skb
->next
!= tail
&&
3594 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3597 /* Decided to skip this, advance start seq. */
3598 start
= TCP_SKB_CB(skb
)->end_seq
;
3601 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3604 while (before(start
, end
)) {
3605 struct sk_buff
*nskb
;
3606 int header
= skb_headroom(skb
);
3607 int copy
= SKB_MAX_ORDER(header
, 0);
3609 /* Too big header? This can happen with IPv6. */
3612 if (end
-start
< copy
)
3614 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3617 skb_reserve(nskb
, header
);
3618 memcpy(nskb
->head
, skb
->head
, header
);
3619 nskb
->nh
.raw
= nskb
->head
+ (skb
->nh
.raw
-skb
->head
);
3620 nskb
->h
.raw
= nskb
->head
+ (skb
->h
.raw
-skb
->head
);
3621 nskb
->mac
.raw
= nskb
->head
+ (skb
->mac
.raw
-skb
->head
);
3622 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3623 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3624 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3625 sk_stream_set_owner_r(nskb
, sk
);
3627 /* Copy data, releasing collapsed skbs. */
3629 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3630 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3634 size
= min(copy
, size
);
3635 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3637 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3641 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3642 struct sk_buff
*next
= skb
->next
;
3643 __skb_unlink(skb
, list
);
3645 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3647 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3654 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3655 * and tcp_collapse() them until all the queue is collapsed.
3657 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3659 struct tcp_sock
*tp
= tcp_sk(sk
);
3660 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3661 struct sk_buff
*head
;
3667 start
= TCP_SKB_CB(skb
)->seq
;
3668 end
= TCP_SKB_CB(skb
)->end_seq
;
3674 /* Segment is terminated when we see gap or when
3675 * we are at the end of all the queue. */
3676 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3677 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3678 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3679 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3680 head
, skb
, start
, end
);
3682 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3684 /* Start new segment */
3685 start
= TCP_SKB_CB(skb
)->seq
;
3686 end
= TCP_SKB_CB(skb
)->end_seq
;
3688 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3689 start
= TCP_SKB_CB(skb
)->seq
;
3690 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3691 end
= TCP_SKB_CB(skb
)->end_seq
;
3696 /* Reduce allocated memory if we can, trying to get
3697 * the socket within its memory limits again.
3699 * Return less than zero if we should start dropping frames
3700 * until the socket owning process reads some of the data
3701 * to stabilize the situation.
3703 static int tcp_prune_queue(struct sock
*sk
)
3705 struct tcp_sock
*tp
= tcp_sk(sk
);
3707 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3709 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3711 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3712 tcp_clamp_window(sk
, tp
);
3713 else if (tcp_memory_pressure
)
3714 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3716 tcp_collapse_ofo_queue(sk
);
3717 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3718 sk
->sk_receive_queue
.next
,
3719 (struct sk_buff
*)&sk
->sk_receive_queue
,
3720 tp
->copied_seq
, tp
->rcv_nxt
);
3721 sk_stream_mem_reclaim(sk
);
3723 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3726 /* Collapsing did not help, destructive actions follow.
3727 * This must not ever occur. */
3729 /* First, purge the out_of_order queue. */
3730 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3731 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3732 __skb_queue_purge(&tp
->out_of_order_queue
);
3734 /* Reset SACK state. A conforming SACK implementation will
3735 * do the same at a timeout based retransmit. When a connection
3736 * is in a sad state like this, we care only about integrity
3737 * of the connection not performance.
3739 if (tp
->rx_opt
.sack_ok
)
3740 tcp_sack_reset(&tp
->rx_opt
);
3741 sk_stream_mem_reclaim(sk
);
3744 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3747 /* If we are really being abused, tell the caller to silently
3748 * drop receive data on the floor. It will get retransmitted
3749 * and hopefully then we'll have sufficient space.
3751 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
3753 /* Massive buffer overcommit. */
3759 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3760 * As additional protections, we do not touch cwnd in retransmission phases,
3761 * and if application hit its sndbuf limit recently.
3763 void tcp_cwnd_application_limited(struct sock
*sk
)
3765 struct tcp_sock
*tp
= tcp_sk(sk
);
3767 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
3768 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
3769 /* Limited by application or receiver window. */
3770 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
3771 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
3772 if (win_used
< tp
->snd_cwnd
) {
3773 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3774 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
3776 tp
->snd_cwnd_used
= 0;
3778 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3781 static int tcp_should_expand_sndbuf(struct sock
*sk
, struct tcp_sock
*tp
)
3783 /* If the user specified a specific send buffer setting, do
3786 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
3789 /* If we are under global TCP memory pressure, do not expand. */
3790 if (tcp_memory_pressure
)
3793 /* If we are under soft global TCP memory pressure, do not expand. */
3794 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
3797 /* If we filled the congestion window, do not expand. */
3798 if (tp
->packets_out
>= tp
->snd_cwnd
)
3804 /* When incoming ACK allowed to free some skb from write_queue,
3805 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3806 * on the exit from tcp input handler.
3808 * PROBLEM: sndbuf expansion does not work well with largesend.
3810 static void tcp_new_space(struct sock
*sk
)
3812 struct tcp_sock
*tp
= tcp_sk(sk
);
3814 if (tcp_should_expand_sndbuf(sk
, tp
)) {
3815 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
3816 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
3817 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
3818 tp
->reordering
+ 1);
3819 sndmem
*= 2*demanded
;
3820 if (sndmem
> sk
->sk_sndbuf
)
3821 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
3822 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3825 sk
->sk_write_space(sk
);
3828 static void tcp_check_space(struct sock
*sk
)
3830 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
3831 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
3832 if (sk
->sk_socket
&&
3833 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
3838 static inline void tcp_data_snd_check(struct sock
*sk
, struct tcp_sock
*tp
)
3840 tcp_push_pending_frames(sk
, tp
);
3841 tcp_check_space(sk
);
3845 * Check if sending an ack is needed.
3847 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
3849 struct tcp_sock
*tp
= tcp_sk(sk
);
3851 /* More than one full frame received... */
3852 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
3853 /* ... and right edge of window advances far enough.
3854 * (tcp_recvmsg() will send ACK otherwise). Or...
3856 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
3857 /* We ACK each frame or... */
3858 tcp_in_quickack_mode(sk
) ||
3859 /* We have out of order data. */
3861 skb_peek(&tp
->out_of_order_queue
))) {
3862 /* Then ack it now */
3865 /* Else, send delayed ack. */
3866 tcp_send_delayed_ack(sk
);
3870 static inline void tcp_ack_snd_check(struct sock
*sk
)
3872 if (!inet_csk_ack_scheduled(sk
)) {
3873 /* We sent a data segment already. */
3876 __tcp_ack_snd_check(sk
, 1);
3880 * This routine is only called when we have urgent data
3881 * signaled. Its the 'slow' part of tcp_urg. It could be
3882 * moved inline now as tcp_urg is only called from one
3883 * place. We handle URGent data wrong. We have to - as
3884 * BSD still doesn't use the correction from RFC961.
3885 * For 1003.1g we should support a new option TCP_STDURG to permit
3886 * either form (or just set the sysctl tcp_stdurg).
3889 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
3891 struct tcp_sock
*tp
= tcp_sk(sk
);
3892 u32 ptr
= ntohs(th
->urg_ptr
);
3894 if (ptr
&& !sysctl_tcp_stdurg
)
3896 ptr
+= ntohl(th
->seq
);
3898 /* Ignore urgent data that we've already seen and read. */
3899 if (after(tp
->copied_seq
, ptr
))
3902 /* Do not replay urg ptr.
3904 * NOTE: interesting situation not covered by specs.
3905 * Misbehaving sender may send urg ptr, pointing to segment,
3906 * which we already have in ofo queue. We are not able to fetch
3907 * such data and will stay in TCP_URG_NOTYET until will be eaten
3908 * by recvmsg(). Seems, we are not obliged to handle such wicked
3909 * situations. But it is worth to think about possibility of some
3910 * DoSes using some hypothetical application level deadlock.
3912 if (before(ptr
, tp
->rcv_nxt
))
3915 /* Do we already have a newer (or duplicate) urgent pointer? */
3916 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
3919 /* Tell the world about our new urgent pointer. */
3922 /* We may be adding urgent data when the last byte read was
3923 * urgent. To do this requires some care. We cannot just ignore
3924 * tp->copied_seq since we would read the last urgent byte again
3925 * as data, nor can we alter copied_seq until this data arrives
3926 * or we break the semantics of SIOCATMARK (and thus sockatmark())
3928 * NOTE. Double Dutch. Rendering to plain English: author of comment
3929 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3930 * and expect that both A and B disappear from stream. This is _wrong_.
3931 * Though this happens in BSD with high probability, this is occasional.
3932 * Any application relying on this is buggy. Note also, that fix "works"
3933 * only in this artificial test. Insert some normal data between A and B and we will
3934 * decline of BSD again. Verdict: it is better to remove to trap
3937 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
3938 !sock_flag(sk
, SOCK_URGINLINE
) &&
3939 tp
->copied_seq
!= tp
->rcv_nxt
) {
3940 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
3942 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
3943 __skb_unlink(skb
, &sk
->sk_receive_queue
);
3948 tp
->urg_data
= TCP_URG_NOTYET
;
3951 /* Disable header prediction. */
3955 /* This is the 'fast' part of urgent handling. */
3956 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
3958 struct tcp_sock
*tp
= tcp_sk(sk
);
3960 /* Check if we get a new urgent pointer - normally not. */
3962 tcp_check_urg(sk
,th
);
3964 /* Do we wait for any urgent data? - normally not... */
3965 if (tp
->urg_data
== TCP_URG_NOTYET
) {
3966 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
3969 /* Is the urgent pointer pointing into this packet? */
3970 if (ptr
< skb
->len
) {
3972 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
3974 tp
->urg_data
= TCP_URG_VALID
| tmp
;
3975 if (!sock_flag(sk
, SOCK_DEAD
))
3976 sk
->sk_data_ready(sk
, 0);
3981 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
3983 struct tcp_sock
*tp
= tcp_sk(sk
);
3984 int chunk
= skb
->len
- hlen
;
3988 if (skb
->ip_summed
==CHECKSUM_UNNECESSARY
)
3989 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
3991 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
3995 tp
->ucopy
.len
-= chunk
;
3996 tp
->copied_seq
+= chunk
;
3997 tcp_rcv_space_adjust(sk
);
4004 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4008 if (sock_owned_by_user(sk
)) {
4010 result
= __tcp_checksum_complete(skb
);
4013 result
= __tcp_checksum_complete(skb
);
4018 static inline int tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4020 return skb
->ip_summed
!= CHECKSUM_UNNECESSARY
&&
4021 __tcp_checksum_complete_user(sk
, skb
);
4024 #ifdef CONFIG_NET_DMA
4025 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4027 struct tcp_sock
*tp
= tcp_sk(sk
);
4028 int chunk
= skb
->len
- hlen
;
4030 int copied_early
= 0;
4032 if (tp
->ucopy
.wakeup
)
4035 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4036 tp
->ucopy
.dma_chan
= get_softnet_dma();
4038 if (tp
->ucopy
.dma_chan
&& skb
->ip_summed
== CHECKSUM_UNNECESSARY
) {
4040 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4041 skb
, hlen
, tp
->ucopy
.iov
, chunk
, tp
->ucopy
.pinned_list
);
4046 tp
->ucopy
.dma_cookie
= dma_cookie
;
4049 tp
->ucopy
.len
-= chunk
;
4050 tp
->copied_seq
+= chunk
;
4051 tcp_rcv_space_adjust(sk
);
4053 if ((tp
->ucopy
.len
== 0) ||
4054 (tcp_flag_word(skb
->h
.th
) & TCP_FLAG_PSH
) ||
4055 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4056 tp
->ucopy
.wakeup
= 1;
4057 sk
->sk_data_ready(sk
, 0);
4059 } else if (chunk
> 0) {
4060 tp
->ucopy
.wakeup
= 1;
4061 sk
->sk_data_ready(sk
, 0);
4064 return copied_early
;
4066 #endif /* CONFIG_NET_DMA */
4069 * TCP receive function for the ESTABLISHED state.
4071 * It is split into a fast path and a slow path. The fast path is
4073 * - A zero window was announced from us - zero window probing
4074 * is only handled properly in the slow path.
4075 * - Out of order segments arrived.
4076 * - Urgent data is expected.
4077 * - There is no buffer space left
4078 * - Unexpected TCP flags/window values/header lengths are received
4079 * (detected by checking the TCP header against pred_flags)
4080 * - Data is sent in both directions. Fast path only supports pure senders
4081 * or pure receivers (this means either the sequence number or the ack
4082 * value must stay constant)
4083 * - Unexpected TCP option.
4085 * When these conditions are not satisfied it drops into a standard
4086 * receive procedure patterned after RFC793 to handle all cases.
4087 * The first three cases are guaranteed by proper pred_flags setting,
4088 * the rest is checked inline. Fast processing is turned on in
4089 * tcp_data_queue when everything is OK.
4091 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4092 struct tcphdr
*th
, unsigned len
)
4094 struct tcp_sock
*tp
= tcp_sk(sk
);
4097 * Header prediction.
4098 * The code loosely follows the one in the famous
4099 * "30 instruction TCP receive" Van Jacobson mail.
4101 * Van's trick is to deposit buffers into socket queue
4102 * on a device interrupt, to call tcp_recv function
4103 * on the receive process context and checksum and copy
4104 * the buffer to user space. smart...
4106 * Our current scheme is not silly either but we take the
4107 * extra cost of the net_bh soft interrupt processing...
4108 * We do checksum and copy also but from device to kernel.
4111 tp
->rx_opt
.saw_tstamp
= 0;
4113 /* pred_flags is 0xS?10 << 16 + snd_wnd
4114 * if header_prediction is to be made
4115 * 'S' will always be tp->tcp_header_len >> 2
4116 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4117 * turn it off (when there are holes in the receive
4118 * space for instance)
4119 * PSH flag is ignored.
4122 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4123 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4124 int tcp_header_len
= tp
->tcp_header_len
;
4126 /* Timestamp header prediction: tcp_header_len
4127 * is automatically equal to th->doff*4 due to pred_flags
4131 /* Check timestamp */
4132 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4133 __be32
*ptr
= (__be32
*)(th
+ 1);
4135 /* No? Slow path! */
4136 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4137 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4140 tp
->rx_opt
.saw_tstamp
= 1;
4142 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4144 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4146 /* If PAWS failed, check it more carefully in slow path */
4147 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4150 /* DO NOT update ts_recent here, if checksum fails
4151 * and timestamp was corrupted part, it will result
4152 * in a hung connection since we will drop all
4153 * future packets due to the PAWS test.
4157 if (len
<= tcp_header_len
) {
4158 /* Bulk data transfer: sender */
4159 if (len
== tcp_header_len
) {
4160 /* Predicted packet is in window by definition.
4161 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4162 * Hence, check seq<=rcv_wup reduces to:
4164 if (tcp_header_len
==
4165 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4166 tp
->rcv_nxt
== tp
->rcv_wup
)
4167 tcp_store_ts_recent(tp
);
4169 /* We know that such packets are checksummed
4172 tcp_ack(sk
, skb
, 0);
4174 tcp_data_snd_check(sk
, tp
);
4176 } else { /* Header too small */
4177 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4182 int copied_early
= 0;
4184 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4185 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4186 #ifdef CONFIG_NET_DMA
4187 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4192 if (tp
->ucopy
.task
== current
&& sock_owned_by_user(sk
) && !copied_early
) {
4193 __set_current_state(TASK_RUNNING
);
4195 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4199 /* Predicted packet is in window by definition.
4200 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4201 * Hence, check seq<=rcv_wup reduces to:
4203 if (tcp_header_len
==
4204 (sizeof(struct tcphdr
) +
4205 TCPOLEN_TSTAMP_ALIGNED
) &&
4206 tp
->rcv_nxt
== tp
->rcv_wup
)
4207 tcp_store_ts_recent(tp
);
4209 tcp_rcv_rtt_measure_ts(sk
, skb
);
4211 __skb_pull(skb
, tcp_header_len
);
4212 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4213 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4216 tcp_cleanup_rbuf(sk
, skb
->len
);
4219 if (tcp_checksum_complete_user(sk
, skb
))
4222 /* Predicted packet is in window by definition.
4223 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4224 * Hence, check seq<=rcv_wup reduces to:
4226 if (tcp_header_len
==
4227 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4228 tp
->rcv_nxt
== tp
->rcv_wup
)
4229 tcp_store_ts_recent(tp
);
4231 tcp_rcv_rtt_measure_ts(sk
, skb
);
4233 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4236 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4238 /* Bulk data transfer: receiver */
4239 __skb_pull(skb
,tcp_header_len
);
4240 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4241 sk_stream_set_owner_r(skb
, sk
);
4242 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4245 tcp_event_data_recv(sk
, tp
, skb
);
4247 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4248 /* Well, only one small jumplet in fast path... */
4249 tcp_ack(sk
, skb
, FLAG_DATA
);
4250 tcp_data_snd_check(sk
, tp
);
4251 if (!inet_csk_ack_scheduled(sk
))
4255 __tcp_ack_snd_check(sk
, 0);
4257 #ifdef CONFIG_NET_DMA
4259 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4265 sk
->sk_data_ready(sk
, 0);
4271 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
4275 * RFC1323: H1. Apply PAWS check first.
4277 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4278 tcp_paws_discard(sk
, skb
)) {
4280 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4281 tcp_send_dupack(sk
, skb
);
4284 /* Resets are accepted even if PAWS failed.
4286 ts_recent update must be made after we are sure
4287 that the packet is in window.
4292 * Standard slow path.
4295 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4296 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4297 * (RST) segments are validated by checking their SEQ-fields."
4298 * And page 69: "If an incoming segment is not acceptable,
4299 * an acknowledgment should be sent in reply (unless the RST bit
4300 * is set, if so drop the segment and return)".
4303 tcp_send_dupack(sk
, skb
);
4312 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4314 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4315 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4316 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4323 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4325 tcp_rcv_rtt_measure_ts(sk
, skb
);
4327 /* Process urgent data. */
4328 tcp_urg(sk
, skb
, th
);
4330 /* step 7: process the segment text */
4331 tcp_data_queue(sk
, skb
);
4333 tcp_data_snd_check(sk
, tp
);
4334 tcp_ack_snd_check(sk
);
4338 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4345 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4346 struct tcphdr
*th
, unsigned len
)
4348 struct tcp_sock
*tp
= tcp_sk(sk
);
4349 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4350 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4352 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4356 * "If the state is SYN-SENT then
4357 * first check the ACK bit
4358 * If the ACK bit is set
4359 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4360 * a reset (unless the RST bit is set, if so drop
4361 * the segment and return)"
4363 * We do not send data with SYN, so that RFC-correct
4366 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4367 goto reset_and_undo
;
4369 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4370 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4372 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4373 goto reset_and_undo
;
4376 /* Now ACK is acceptable.
4378 * "If the RST bit is set
4379 * If the ACK was acceptable then signal the user "error:
4380 * connection reset", drop the segment, enter CLOSED state,
4381 * delete TCB, and return."
4390 * "fifth, if neither of the SYN or RST bits is set then
4391 * drop the segment and return."
4397 goto discard_and_undo
;
4400 * "If the SYN bit is on ...
4401 * are acceptable then ...
4402 * (our SYN has been ACKed), change the connection
4403 * state to ESTABLISHED..."
4406 TCP_ECN_rcv_synack(tp
, th
);
4408 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4409 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4411 /* Ok.. it's good. Set up sequence numbers and
4412 * move to established.
4414 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4415 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4417 /* RFC1323: The window in SYN & SYN/ACK segments is
4420 tp
->snd_wnd
= ntohs(th
->window
);
4421 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4423 if (!tp
->rx_opt
.wscale_ok
) {
4424 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4425 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4428 if (tp
->rx_opt
.saw_tstamp
) {
4429 tp
->rx_opt
.tstamp_ok
= 1;
4430 tp
->tcp_header_len
=
4431 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4432 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4433 tcp_store_ts_recent(tp
);
4435 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4438 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_fack
)
4439 tp
->rx_opt
.sack_ok
|= 2;
4442 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4443 tcp_initialize_rcv_mss(sk
);
4445 /* Remember, tcp_poll() does not lock socket!
4446 * Change state from SYN-SENT only after copied_seq
4447 * is initialized. */
4448 tp
->copied_seq
= tp
->rcv_nxt
;
4450 tcp_set_state(sk
, TCP_ESTABLISHED
);
4452 security_inet_conn_established(sk
, skb
);
4454 /* Make sure socket is routed, for correct metrics. */
4455 icsk
->icsk_af_ops
->rebuild_header(sk
);
4457 tcp_init_metrics(sk
);
4459 tcp_init_congestion_control(sk
);
4461 /* Prevent spurious tcp_cwnd_restart() on first data
4464 tp
->lsndtime
= tcp_time_stamp
;
4466 tcp_init_buffer_space(sk
);
4468 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4469 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4471 if (!tp
->rx_opt
.snd_wscale
)
4472 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4476 if (!sock_flag(sk
, SOCK_DEAD
)) {
4477 sk
->sk_state_change(sk
);
4478 sk_wake_async(sk
, 0, POLL_OUT
);
4481 if (sk
->sk_write_pending
||
4482 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4483 icsk
->icsk_ack
.pingpong
) {
4484 /* Save one ACK. Data will be ready after
4485 * several ticks, if write_pending is set.
4487 * It may be deleted, but with this feature tcpdumps
4488 * look so _wonderfully_ clever, that I was not able
4489 * to stand against the temptation 8) --ANK
4491 inet_csk_schedule_ack(sk
);
4492 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4493 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4494 tcp_incr_quickack(sk
);
4495 tcp_enter_quickack_mode(sk
);
4496 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4497 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4508 /* No ACK in the segment */
4512 * "If the RST bit is set
4514 * Otherwise (no ACK) drop the segment and return."
4517 goto discard_and_undo
;
4521 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4522 goto discard_and_undo
;
4525 /* We see SYN without ACK. It is attempt of
4526 * simultaneous connect with crossed SYNs.
4527 * Particularly, it can be connect to self.
4529 tcp_set_state(sk
, TCP_SYN_RECV
);
4531 if (tp
->rx_opt
.saw_tstamp
) {
4532 tp
->rx_opt
.tstamp_ok
= 1;
4533 tcp_store_ts_recent(tp
);
4534 tp
->tcp_header_len
=
4535 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4537 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4540 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4541 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4543 /* RFC1323: The window in SYN & SYN/ACK segments is
4546 tp
->snd_wnd
= ntohs(th
->window
);
4547 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4548 tp
->max_window
= tp
->snd_wnd
;
4550 TCP_ECN_rcv_syn(tp
, th
);
4553 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4554 tcp_initialize_rcv_mss(sk
);
4557 tcp_send_synack(sk
);
4559 /* Note, we could accept data and URG from this segment.
4560 * There are no obstacles to make this.
4562 * However, if we ignore data in ACKless segments sometimes,
4563 * we have no reasons to accept it sometimes.
4564 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4565 * is not flawless. So, discard packet for sanity.
4566 * Uncomment this return to process the data.
4573 /* "fifth, if neither of the SYN or RST bits is set then
4574 * drop the segment and return."
4578 tcp_clear_options(&tp
->rx_opt
);
4579 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4583 tcp_clear_options(&tp
->rx_opt
);
4584 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4590 * This function implements the receiving procedure of RFC 793 for
4591 * all states except ESTABLISHED and TIME_WAIT.
4592 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4593 * address independent.
4596 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4597 struct tcphdr
*th
, unsigned len
)
4599 struct tcp_sock
*tp
= tcp_sk(sk
);
4600 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4603 tp
->rx_opt
.saw_tstamp
= 0;
4605 switch (sk
->sk_state
) {
4617 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
4620 /* Now we have several options: In theory there is
4621 * nothing else in the frame. KA9Q has an option to
4622 * send data with the syn, BSD accepts data with the
4623 * syn up to the [to be] advertised window and
4624 * Solaris 2.1 gives you a protocol error. For now
4625 * we just ignore it, that fits the spec precisely
4626 * and avoids incompatibilities. It would be nice in
4627 * future to drop through and process the data.
4629 * Now that TTCP is starting to be used we ought to
4631 * But, this leaves one open to an easy denial of
4632 * service attack, and SYN cookies can't defend
4633 * against this problem. So, we drop the data
4634 * in the interest of security over speed unless
4635 * it's still in use.
4643 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4647 /* Do step6 onward by hand. */
4648 tcp_urg(sk
, skb
, th
);
4650 tcp_data_snd_check(sk
, tp
);
4654 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4655 tcp_paws_discard(sk
, skb
)) {
4657 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4658 tcp_send_dupack(sk
, skb
);
4661 /* Reset is accepted even if it did not pass PAWS. */
4664 /* step 1: check sequence number */
4665 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4667 tcp_send_dupack(sk
, skb
);
4671 /* step 2: check RST bit */
4677 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4679 /* step 3: check security and precedence [ignored] */
4683 * Check for a SYN in window.
4685 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4686 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4691 /* step 5: check the ACK field */
4693 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4695 switch(sk
->sk_state
) {
4698 tp
->copied_seq
= tp
->rcv_nxt
;
4700 tcp_set_state(sk
, TCP_ESTABLISHED
);
4701 sk
->sk_state_change(sk
);
4703 /* Note, that this wakeup is only for marginal
4704 * crossed SYN case. Passively open sockets
4705 * are not waked up, because sk->sk_sleep ==
4706 * NULL and sk->sk_socket == NULL.
4708 if (sk
->sk_socket
) {
4709 sk_wake_async(sk
,0,POLL_OUT
);
4712 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4713 tp
->snd_wnd
= ntohs(th
->window
) <<
4714 tp
->rx_opt
.snd_wscale
;
4715 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4716 TCP_SKB_CB(skb
)->seq
);
4718 /* tcp_ack considers this ACK as duplicate
4719 * and does not calculate rtt.
4720 * Fix it at least with timestamps.
4722 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4724 tcp_ack_saw_tstamp(sk
, 0);
4726 if (tp
->rx_opt
.tstamp_ok
)
4727 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4729 /* Make sure socket is routed, for
4732 icsk
->icsk_af_ops
->rebuild_header(sk
);
4734 tcp_init_metrics(sk
);
4736 tcp_init_congestion_control(sk
);
4738 /* Prevent spurious tcp_cwnd_restart() on
4739 * first data packet.
4741 tp
->lsndtime
= tcp_time_stamp
;
4744 tcp_initialize_rcv_mss(sk
);
4745 tcp_init_buffer_space(sk
);
4746 tcp_fast_path_on(tp
);
4753 if (tp
->snd_una
== tp
->write_seq
) {
4754 tcp_set_state(sk
, TCP_FIN_WAIT2
);
4755 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
4756 dst_confirm(sk
->sk_dst_cache
);
4758 if (!sock_flag(sk
, SOCK_DEAD
))
4759 /* Wake up lingering close() */
4760 sk
->sk_state_change(sk
);
4764 if (tp
->linger2
< 0 ||
4765 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4766 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
4768 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4772 tmo
= tcp_fin_time(sk
);
4773 if (tmo
> TCP_TIMEWAIT_LEN
) {
4774 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
4775 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
4776 /* Bad case. We could lose such FIN otherwise.
4777 * It is not a big problem, but it looks confusing
4778 * and not so rare event. We still can lose it now,
4779 * if it spins in bh_lock_sock(), but it is really
4782 inet_csk_reset_keepalive_timer(sk
, tmo
);
4784 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
4792 if (tp
->snd_una
== tp
->write_seq
) {
4793 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4799 if (tp
->snd_una
== tp
->write_seq
) {
4800 tcp_update_metrics(sk
);
4809 /* step 6: check the URG bit */
4810 tcp_urg(sk
, skb
, th
);
4812 /* step 7: process the segment text */
4813 switch (sk
->sk_state
) {
4814 case TCP_CLOSE_WAIT
:
4817 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4821 /* RFC 793 says to queue data in these states,
4822 * RFC 1122 says we MUST send a reset.
4823 * BSD 4.4 also does reset.
4825 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
4826 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4827 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
4828 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4834 case TCP_ESTABLISHED
:
4835 tcp_data_queue(sk
, skb
);
4840 /* tcp_data could move socket to TIME-WAIT */
4841 if (sk
->sk_state
!= TCP_CLOSE
) {
4842 tcp_data_snd_check(sk
, tp
);
4843 tcp_ack_snd_check(sk
);
4853 EXPORT_SYMBOL(sysctl_tcp_ecn
);
4854 EXPORT_SYMBOL(sysctl_tcp_reordering
);
4855 EXPORT_SYMBOL(tcp_parse_options
);
4856 EXPORT_SYMBOL(tcp_rcv_established
);
4857 EXPORT_SYMBOL(tcp_rcv_state_process
);
4858 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);