2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
25 * Pedro Roque : Fast Retransmit/Recovery.
27 * Retransmit queue handled by TCP.
28 * Better retransmit timer handling.
29 * New congestion avoidance.
33 * Eric : Fast Retransmit.
34 * Randy Scott : MSS option defines.
35 * Eric Schenk : Fixes to slow start algorithm.
36 * Eric Schenk : Yet another double ACK bug.
37 * Eric Schenk : Delayed ACK bug fixes.
38 * Eric Schenk : Floyd style fast retrans war avoidance.
39 * David S. Miller : Don't allow zero congestion window.
40 * Eric Schenk : Fix retransmitter so that it sends
41 * next packet on ack of previous packet.
42 * Andi Kleen : Moved open_request checking here
43 * and process RSTs for open_requests.
44 * Andi Kleen : Better prune_queue, and other fixes.
45 * Andrey Savochkin: Fix RTT measurements in the presence of
47 * Andrey Savochkin: Check sequence numbers correctly when
48 * removing SACKs due to in sequence incoming
50 * Andi Kleen: Make sure we never ack data there is not
51 * enough room for. Also make this condition
52 * a fatal error if it might still happen.
53 * Andi Kleen: Add tcp_measure_rcv_mss to make
54 * connections with MSS<min(MTU,ann. MSS)
55 * work without delayed acks.
56 * Andi Kleen: Process packets with PSH set in the
58 * J Hadi Salim: ECN support
61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
62 * engine. Lots of bugs are found.
63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
75 int sysctl_tcp_timestamps __read_mostly
= 1;
76 int sysctl_tcp_window_scaling __read_mostly
= 1;
77 int sysctl_tcp_sack __read_mostly
= 1;
78 int sysctl_tcp_fack __read_mostly
= 1;
79 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
80 int sysctl_tcp_ecn __read_mostly
;
81 int sysctl_tcp_dsack __read_mostly
= 1;
82 int sysctl_tcp_app_win __read_mostly
= 31;
83 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
85 int sysctl_tcp_stdurg __read_mostly
;
86 int sysctl_tcp_rfc1337 __read_mostly
;
87 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
88 int sysctl_tcp_frto __read_mostly
;
89 int sysctl_tcp_frto_response __read_mostly
;
90 int sysctl_tcp_nometrics_save __read_mostly
;
92 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
93 int sysctl_tcp_abc __read_mostly
;
95 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
96 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
97 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
98 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
99 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
100 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
101 #define FLAG_ECE 0x40 /* ECE in this ACK */
102 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
103 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
105 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
106 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained DSACK info */
108 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
109 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
110 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
111 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
112 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
114 #define IsSackFrto() (sysctl_tcp_frto == 0x2)
116 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
117 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|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_transport_header(skb
);
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(tcp_hdr(skb
)) & 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 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
200 if (tp
->ecn_flags
&TCP_ECN_OK
)
201 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
204 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
206 if (tcp_hdr(skb
)->cwr
)
207 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
210 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
212 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
215 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, struct sk_buff
*skb
)
217 if (tp
->ecn_flags
&TCP_ECN_OK
) {
218 if (INET_ECN_is_ce(TCP_SKB_CB(skb
)->flags
))
219 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
220 /* Funny extension: if ECT is not set on a segment,
221 * it is surely retransmit. It is not in ECN RFC,
222 * but Linux follows this rule. */
223 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb
)->flags
)))
224 tcp_enter_quickack_mode((struct sock
*)tp
);
228 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, struct tcphdr
*th
)
230 if ((tp
->ecn_flags
&TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
231 tp
->ecn_flags
&= ~TCP_ECN_OK
;
234 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
236 if ((tp
->ecn_flags
&TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
237 tp
->ecn_flags
&= ~TCP_ECN_OK
;
240 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
242 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
&TCP_ECN_OK
))
247 /* Buffer size and advertised window tuning.
249 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
252 static void tcp_fixup_sndbuf(struct sock
*sk
)
254 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
255 sizeof(struct sk_buff
);
257 if (sk
->sk_sndbuf
< 3 * sndmem
)
258 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
261 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
263 * All tcp_full_space() is split to two parts: "network" buffer, allocated
264 * forward and advertised in receiver window (tp->rcv_wnd) and
265 * "application buffer", required to isolate scheduling/application
266 * latencies from network.
267 * window_clamp is maximal advertised window. It can be less than
268 * tcp_full_space(), in this case tcp_full_space() - window_clamp
269 * is reserved for "application" buffer. The less window_clamp is
270 * the smoother our behaviour from viewpoint of network, but the lower
271 * throughput and the higher sensitivity of the connection to losses. 8)
273 * rcv_ssthresh is more strict window_clamp used at "slow start"
274 * phase to predict further behaviour of this connection.
275 * It is used for two goals:
276 * - to enforce header prediction at sender, even when application
277 * requires some significant "application buffer". It is check #1.
278 * - to prevent pruning of receive queue because of misprediction
279 * of receiver window. Check #2.
281 * The scheme does not work when sender sends good segments opening
282 * window and then starts to feed us spaghetti. But it should work
283 * in common situations. Otherwise, we have to rely on queue collapsing.
286 /* Slow part of check#2. */
287 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
289 struct tcp_sock
*tp
= tcp_sk(sk
);
291 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
292 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
294 while (tp
->rcv_ssthresh
<= window
) {
295 if (truesize
<= skb
->len
)
296 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
304 static void tcp_grow_window(struct sock
*sk
,
307 struct tcp_sock
*tp
= tcp_sk(sk
);
310 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
311 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
312 !tcp_memory_pressure
) {
315 /* Check #2. Increase window, if skb with such overhead
316 * will fit to rcvbuf in future.
318 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
321 incr
= __tcp_grow_window(sk
, skb
);
324 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
325 inet_csk(sk
)->icsk_ack
.quick
|= 1;
330 /* 3. Tuning rcvbuf, when connection enters established state. */
332 static void tcp_fixup_rcvbuf(struct sock
*sk
)
334 struct tcp_sock
*tp
= tcp_sk(sk
);
335 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
337 /* Try to select rcvbuf so that 4 mss-sized segments
338 * will fit to window and corresponding skbs will fit to our rcvbuf.
339 * (was 3; 4 is minimum to allow fast retransmit to work.)
341 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
343 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
344 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
347 /* 4. Try to fixup all. It is made immediately after connection enters
350 static void tcp_init_buffer_space(struct sock
*sk
)
352 struct tcp_sock
*tp
= tcp_sk(sk
);
355 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
356 tcp_fixup_rcvbuf(sk
);
357 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
358 tcp_fixup_sndbuf(sk
);
360 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
362 maxwin
= tcp_full_space(sk
);
364 if (tp
->window_clamp
>= maxwin
) {
365 tp
->window_clamp
= maxwin
;
367 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
368 tp
->window_clamp
= max(maxwin
-
369 (maxwin
>> sysctl_tcp_app_win
),
373 /* Force reservation of one segment. */
374 if (sysctl_tcp_app_win
&&
375 tp
->window_clamp
> 2 * tp
->advmss
&&
376 tp
->window_clamp
+ tp
->advmss
> maxwin
)
377 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
379 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
380 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
383 /* 5. Recalculate window clamp after socket hit its memory bounds. */
384 static void tcp_clamp_window(struct sock
*sk
)
386 struct tcp_sock
*tp
= tcp_sk(sk
);
387 struct inet_connection_sock
*icsk
= inet_csk(sk
);
389 icsk
->icsk_ack
.quick
= 0;
391 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
392 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
393 !tcp_memory_pressure
&&
394 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
395 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
398 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
399 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
403 /* Initialize RCV_MSS value.
404 * RCV_MSS is an our guess about MSS used by the peer.
405 * We haven't any direct information about the MSS.
406 * It's better to underestimate the RCV_MSS rather than overestimate.
407 * Overestimations make us ACKing less frequently than needed.
408 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
410 void tcp_initialize_rcv_mss(struct sock
*sk
)
412 struct tcp_sock
*tp
= tcp_sk(sk
);
413 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
415 hint
= min(hint
, tp
->rcv_wnd
/2);
416 hint
= min(hint
, TCP_MIN_RCVMSS
);
417 hint
= max(hint
, TCP_MIN_MSS
);
419 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
422 /* Receiver "autotuning" code.
424 * The algorithm for RTT estimation w/o timestamps is based on
425 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
426 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
428 * More detail on this code can be found at
429 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
430 * though this reference is out of date. A new paper
433 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
435 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
441 if (new_sample
!= 0) {
442 /* If we sample in larger samples in the non-timestamp
443 * case, we could grossly overestimate the RTT especially
444 * with chatty applications or bulk transfer apps which
445 * are stalled on filesystem I/O.
447 * Also, since we are only going for a minimum in the
448 * non-timestamp case, we do not smooth things out
449 * else with timestamps disabled convergence takes too
453 m
-= (new_sample
>> 3);
455 } else if (m
< new_sample
)
458 /* No previous measure. */
462 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
463 tp
->rcv_rtt_est
.rtt
= new_sample
;
466 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
468 if (tp
->rcv_rtt_est
.time
== 0)
470 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
472 tcp_rcv_rtt_update(tp
,
473 jiffies
- tp
->rcv_rtt_est
.time
,
477 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
478 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
481 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
483 struct tcp_sock
*tp
= tcp_sk(sk
);
484 if (tp
->rx_opt
.rcv_tsecr
&&
485 (TCP_SKB_CB(skb
)->end_seq
-
486 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
487 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
491 * This function should be called every time data is copied to user space.
492 * It calculates the appropriate TCP receive buffer space.
494 void tcp_rcv_space_adjust(struct sock
*sk
)
496 struct tcp_sock
*tp
= tcp_sk(sk
);
500 if (tp
->rcvq_space
.time
== 0)
503 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
504 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
505 tp
->rcv_rtt_est
.rtt
== 0)
508 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
510 space
= max(tp
->rcvq_space
.space
, space
);
512 if (tp
->rcvq_space
.space
!= space
) {
515 tp
->rcvq_space
.space
= space
;
517 if (sysctl_tcp_moderate_rcvbuf
&&
518 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
519 int new_clamp
= space
;
521 /* Receive space grows, normalize in order to
522 * take into account packet headers and sk_buff
523 * structure overhead.
528 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
529 16 + sizeof(struct sk_buff
));
530 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
533 space
= min(space
, sysctl_tcp_rmem
[2]);
534 if (space
> sk
->sk_rcvbuf
) {
535 sk
->sk_rcvbuf
= space
;
537 /* Make the window clamp follow along. */
538 tp
->window_clamp
= new_clamp
;
544 tp
->rcvq_space
.seq
= tp
->copied_seq
;
545 tp
->rcvq_space
.time
= tcp_time_stamp
;
548 /* There is something which you must keep in mind when you analyze the
549 * behavior of the tp->ato delayed ack timeout interval. When a
550 * connection starts up, we want to ack as quickly as possible. The
551 * problem is that "good" TCP's do slow start at the beginning of data
552 * transmission. The means that until we send the first few ACK's the
553 * sender will sit on his end and only queue most of his data, because
554 * he can only send snd_cwnd unacked packets at any given time. For
555 * each ACK we send, he increments snd_cwnd and transmits more of his
558 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
560 struct tcp_sock
*tp
= tcp_sk(sk
);
561 struct inet_connection_sock
*icsk
= inet_csk(sk
);
564 inet_csk_schedule_ack(sk
);
566 tcp_measure_rcv_mss(sk
, skb
);
568 tcp_rcv_rtt_measure(tp
);
570 now
= tcp_time_stamp
;
572 if (!icsk
->icsk_ack
.ato
) {
573 /* The _first_ data packet received, initialize
574 * delayed ACK engine.
576 tcp_incr_quickack(sk
);
577 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
579 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
581 if (m
<= TCP_ATO_MIN
/2) {
582 /* The fastest case is the first. */
583 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
584 } else if (m
< icsk
->icsk_ack
.ato
) {
585 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
586 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
587 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
588 } else if (m
> icsk
->icsk_rto
) {
589 /* Too long gap. Apparently sender failed to
590 * restart window, so that we send ACKs quickly.
592 tcp_incr_quickack(sk
);
593 sk_stream_mem_reclaim(sk
);
596 icsk
->icsk_ack
.lrcvtime
= now
;
598 TCP_ECN_check_ce(tp
, skb
);
601 tcp_grow_window(sk
, skb
);
604 static u32
tcp_rto_min(struct sock
*sk
)
606 struct dst_entry
*dst
= __sk_dst_get(sk
);
607 u32 rto_min
= TCP_RTO_MIN
;
609 if (dst
&& dst_metric_locked(dst
, RTAX_RTO_MIN
))
610 rto_min
= dst
->metrics
[RTAX_RTO_MIN
-1];
614 /* Called to compute a smoothed rtt estimate. The data fed to this
615 * routine either comes from timestamps, or from segments that were
616 * known _not_ to have been retransmitted [see Karn/Partridge
617 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
618 * piece by Van Jacobson.
619 * NOTE: the next three routines used to be one big routine.
620 * To save cycles in the RFC 1323 implementation it was better to break
621 * it up into three procedures. -- erics
623 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
625 struct tcp_sock
*tp
= tcp_sk(sk
);
626 long m
= mrtt
; /* RTT */
628 /* The following amusing code comes from Jacobson's
629 * article in SIGCOMM '88. Note that rtt and mdev
630 * are scaled versions of rtt and mean deviation.
631 * This is designed to be as fast as possible
632 * m stands for "measurement".
634 * On a 1990 paper the rto value is changed to:
635 * RTO = rtt + 4 * mdev
637 * Funny. This algorithm seems to be very broken.
638 * These formulae increase RTO, when it should be decreased, increase
639 * too slowly, when it should be increased quickly, decrease too quickly
640 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
641 * does not matter how to _calculate_ it. Seems, it was trap
642 * that VJ failed to avoid. 8)
647 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
648 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
650 m
= -m
; /* m is now abs(error) */
651 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
652 /* This is similar to one of Eifel findings.
653 * Eifel blocks mdev updates when rtt decreases.
654 * This solution is a bit different: we use finer gain
655 * for mdev in this case (alpha*beta).
656 * Like Eifel it also prevents growth of rto,
657 * but also it limits too fast rto decreases,
658 * happening in pure Eifel.
663 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
665 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
666 if (tp
->mdev
> tp
->mdev_max
) {
667 tp
->mdev_max
= tp
->mdev
;
668 if (tp
->mdev_max
> tp
->rttvar
)
669 tp
->rttvar
= tp
->mdev_max
;
671 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
672 if (tp
->mdev_max
< tp
->rttvar
)
673 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
674 tp
->rtt_seq
= tp
->snd_nxt
;
675 tp
->mdev_max
= tcp_rto_min(sk
);
678 /* no previous measure. */
679 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
680 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
681 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
682 tp
->rtt_seq
= tp
->snd_nxt
;
686 /* Calculate rto without backoff. This is the second half of Van Jacobson's
687 * routine referred to above.
689 static inline void tcp_set_rto(struct sock
*sk
)
691 const struct tcp_sock
*tp
= tcp_sk(sk
);
692 /* Old crap is replaced with new one. 8)
695 * 1. If rtt variance happened to be less 50msec, it is hallucination.
696 * It cannot be less due to utterly erratic ACK generation made
697 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
698 * to do with delayed acks, because at cwnd>2 true delack timeout
699 * is invisible. Actually, Linux-2.4 also generates erratic
700 * ACKs in some circumstances.
702 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
704 /* 2. Fixups made earlier cannot be right.
705 * If we do not estimate RTO correctly without them,
706 * all the algo is pure shit and should be replaced
707 * with correct one. It is exactly, which we pretend to do.
711 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
712 * guarantees that rto is higher.
714 static inline void tcp_bound_rto(struct sock
*sk
)
716 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
717 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
720 /* Save metrics learned by this TCP session.
721 This function is called only, when TCP finishes successfully
722 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
724 void tcp_update_metrics(struct sock
*sk
)
726 struct tcp_sock
*tp
= tcp_sk(sk
);
727 struct dst_entry
*dst
= __sk_dst_get(sk
);
729 if (sysctl_tcp_nometrics_save
)
734 if (dst
&& (dst
->flags
&DST_HOST
)) {
735 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
738 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
739 /* This session failed to estimate rtt. Why?
740 * Probably, no packets returned in time.
743 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
744 dst
->metrics
[RTAX_RTT
-1] = 0;
748 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
750 /* If newly calculated rtt larger than stored one,
751 * store new one. Otherwise, use EWMA. Remember,
752 * rtt overestimation is always better than underestimation.
754 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
756 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
758 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
761 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
765 /* Scale deviation to rttvar fixed point */
770 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
771 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
773 dst
->metrics
[RTAX_RTTVAR
-1] -=
774 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
777 if (tp
->snd_ssthresh
>= 0xFFFF) {
778 /* Slow start still did not finish. */
779 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
780 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
781 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
782 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
783 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
784 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
785 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
786 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
787 icsk
->icsk_ca_state
== TCP_CA_Open
) {
788 /* Cong. avoidance phase, cwnd is reliable. */
789 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
790 dst
->metrics
[RTAX_SSTHRESH
-1] =
791 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
792 if (!dst_metric_locked(dst
, RTAX_CWND
))
793 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
795 /* Else slow start did not finish, cwnd is non-sense,
796 ssthresh may be also invalid.
798 if (!dst_metric_locked(dst
, RTAX_CWND
))
799 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
800 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
801 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
802 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
803 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
806 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
807 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
808 tp
->reordering
!= sysctl_tcp_reordering
)
809 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
814 /* Numbers are taken from RFC3390.
816 * John Heffner states:
818 * The RFC specifies a window of no more than 4380 bytes
819 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
820 * is a bit misleading because they use a clamp at 4380 bytes
821 * rather than use a multiplier in the relevant range.
823 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
825 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
828 if (tp
->mss_cache
> 1460)
831 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
833 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
836 /* Set slow start threshold and cwnd not falling to slow start */
837 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
839 struct tcp_sock
*tp
= tcp_sk(sk
);
840 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
842 tp
->prior_ssthresh
= 0;
844 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
847 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
848 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
849 tcp_packets_in_flight(tp
) + 1U);
850 tp
->snd_cwnd_cnt
= 0;
851 tp
->high_seq
= tp
->snd_nxt
;
852 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
853 TCP_ECN_queue_cwr(tp
);
855 tcp_set_ca_state(sk
, TCP_CA_CWR
);
860 * Packet counting of FACK is based on in-order assumptions, therefore TCP
861 * disables it when reordering is detected
863 static void tcp_disable_fack(struct tcp_sock
*tp
)
865 tp
->rx_opt
.sack_ok
&= ~2;
868 /* Take a notice that peer is sending DSACKs */
869 static void tcp_dsack_seen(struct tcp_sock
*tp
)
871 tp
->rx_opt
.sack_ok
|= 4;
874 /* Initialize metrics on socket. */
876 static void tcp_init_metrics(struct sock
*sk
)
878 struct tcp_sock
*tp
= tcp_sk(sk
);
879 struct dst_entry
*dst
= __sk_dst_get(sk
);
886 if (dst_metric_locked(dst
, RTAX_CWND
))
887 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
888 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
889 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
890 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
891 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
893 if (dst_metric(dst
, RTAX_REORDERING
) &&
894 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
895 tcp_disable_fack(tp
);
896 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
899 if (dst_metric(dst
, RTAX_RTT
) == 0)
902 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
905 /* Initial rtt is determined from SYN,SYN-ACK.
906 * The segment is small and rtt may appear much
907 * less than real one. Use per-dst memory
908 * to make it more realistic.
910 * A bit of theory. RTT is time passed after "normal" sized packet
911 * is sent until it is ACKed. In normal circumstances sending small
912 * packets force peer to delay ACKs and calculation is correct too.
913 * The algorithm is adaptive and, provided we follow specs, it
914 * NEVER underestimate RTT. BUT! If peer tries to make some clever
915 * tricks sort of "quick acks" for time long enough to decrease RTT
916 * to low value, and then abruptly stops to do it and starts to delay
917 * ACKs, wait for troubles.
919 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
920 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
921 tp
->rtt_seq
= tp
->snd_nxt
;
923 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
924 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
925 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
929 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
931 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
932 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
936 /* Play conservative. If timestamps are not
937 * supported, TCP will fail to recalculate correct
938 * rtt, if initial rto is too small. FORGET ALL AND RESET!
940 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
942 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
943 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
947 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
950 struct tcp_sock
*tp
= tcp_sk(sk
);
951 if (metric
> tp
->reordering
) {
952 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
954 /* This exciting event is worth to be remembered. 8) */
956 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
957 else if (tcp_is_reno(tp
))
958 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
959 else if (tcp_is_fack(tp
))
960 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
962 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
963 #if FASTRETRANS_DEBUG > 1
964 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
965 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
969 tp
->undo_marker
? tp
->undo_retrans
: 0);
971 tcp_disable_fack(tp
);
975 /* This procedure tags the retransmission queue when SACKs arrive.
977 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
978 * Packets in queue with these bits set are counted in variables
979 * sacked_out, retrans_out and lost_out, correspondingly.
981 * Valid combinations are:
982 * Tag InFlight Description
983 * 0 1 - orig segment is in flight.
984 * S 0 - nothing flies, orig reached receiver.
985 * L 0 - nothing flies, orig lost by net.
986 * R 2 - both orig and retransmit are in flight.
987 * L|R 1 - orig is lost, retransmit is in flight.
988 * S|R 1 - orig reached receiver, retrans is still in flight.
989 * (L|S|R is logically valid, it could occur when L|R is sacked,
990 * but it is equivalent to plain S and code short-curcuits it to S.
991 * L|S is logically invalid, it would mean -1 packet in flight 8))
993 * These 6 states form finite state machine, controlled by the following events:
994 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
995 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
996 * 3. Loss detection event of one of three flavors:
997 * A. Scoreboard estimator decided the packet is lost.
998 * A'. Reno "three dupacks" marks head of queue lost.
999 * A''. Its FACK modfication, head until snd.fack is lost.
1000 * B. SACK arrives sacking data transmitted after never retransmitted
1001 * hole was sent out.
1002 * C. SACK arrives sacking SND.NXT at the moment, when the
1003 * segment was retransmitted.
1004 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1006 * It is pleasant to note, that state diagram turns out to be commutative,
1007 * so that we are allowed not to be bothered by order of our actions,
1008 * when multiple events arrive simultaneously. (see the function below).
1010 * Reordering detection.
1011 * --------------------
1012 * Reordering metric is maximal distance, which a packet can be displaced
1013 * in packet stream. With SACKs we can estimate it:
1015 * 1. SACK fills old hole and the corresponding segment was not
1016 * ever retransmitted -> reordering. Alas, we cannot use it
1017 * when segment was retransmitted.
1018 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1019 * for retransmitted and already SACKed segment -> reordering..
1020 * Both of these heuristics are not used in Loss state, when we cannot
1021 * account for retransmits accurately.
1023 * SACK block validation.
1024 * ----------------------
1026 * SACK block range validation checks that the received SACK block fits to
1027 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1028 * Note that SND.UNA is not included to the range though being valid because
1029 * it means that the receiver is rather inconsistent with itself (reports
1030 * SACK reneging when it should advance SND.UNA).
1032 * Implements also blockage to start_seq wrap-around. Problem lies in the
1033 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1034 * there's no guarantee that it will be before snd_nxt (n). The problem
1035 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1038 * <- outs wnd -> <- wrapzone ->
1039 * u e n u_w e_w s n_w
1041 * |<------------+------+----- TCP seqno space --------------+---------->|
1042 * ...-- <2^31 ->| |<--------...
1043 * ...---- >2^31 ------>| |<--------...
1045 * Current code wouldn't be vulnerable but it's better still to discard such
1046 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1047 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1048 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1049 * equal to the ideal case (infinite seqno space without wrap caused issues).
1051 * With D-SACK the lower bound is extended to cover sequence space below
1052 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1053 * again, DSACK block must not to go across snd_una (for the same reason as
1054 * for the normal SACK blocks, explained above). But there all simplicity
1055 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1056 * fully below undo_marker they do not affect behavior in anyway and can
1057 * therefore be safely ignored. In rare cases (which are more or less
1058 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1059 * fragmentation and packet reordering past skb's retransmission. To consider
1060 * them correctly, the acceptable range must be extended even more though
1061 * the exact amount is rather hard to quantify. However, tp->max_window can
1062 * be used as an exaggerated estimate.
1064 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1065 u32 start_seq
, u32 end_seq
)
1067 /* Too far in future, or reversed (interpretation is ambiguous) */
1068 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1071 /* Nasty start_seq wrap-around check (see comments above) */
1072 if (!before(start_seq
, tp
->snd_nxt
))
1075 /* In outstanding window? ...This is valid exit for DSACKs too.
1076 * start_seq == snd_una is non-sensical (see comments above)
1078 if (after(start_seq
, tp
->snd_una
))
1081 if (!is_dsack
|| !tp
->undo_marker
)
1084 /* ...Then it's D-SACK, and must reside below snd_una completely */
1085 if (!after(end_seq
, tp
->snd_una
))
1088 if (!before(start_seq
, tp
->undo_marker
))
1092 if (!after(end_seq
, tp
->undo_marker
))
1095 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1096 * start_seq < undo_marker and end_seq >= undo_marker.
1098 return !before(start_seq
, end_seq
- tp
->max_window
);
1102 static int tcp_check_dsack(struct tcp_sock
*tp
, struct sk_buff
*ack_skb
,
1103 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1106 u32 start_seq_0
= ntohl(get_unaligned(&sp
[0].start_seq
));
1107 u32 end_seq_0
= ntohl(get_unaligned(&sp
[0].end_seq
));
1110 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1113 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
1114 } else if (num_sacks
> 1) {
1115 u32 end_seq_1
= ntohl(get_unaligned(&sp
[1].end_seq
));
1116 u32 start_seq_1
= ntohl(get_unaligned(&sp
[1].start_seq
));
1118 if (!after(end_seq_0
, end_seq_1
) &&
1119 !before(start_seq_0
, start_seq_1
)) {
1122 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
1126 /* D-SACK for already forgotten data... Do dumb counting. */
1128 !after(end_seq_0
, prior_snd_una
) &&
1129 after(end_seq_0
, tp
->undo_marker
))
1136 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
1138 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1139 struct tcp_sock
*tp
= tcp_sk(sk
);
1140 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1141 TCP_SKB_CB(ack_skb
)->sacked
);
1142 struct tcp_sack_block_wire
*sp
= (struct tcp_sack_block_wire
*)(ptr
+2);
1143 struct sk_buff
*cached_skb
;
1144 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
1145 int reord
= tp
->packets_out
;
1147 u32 lost_retrans
= 0;
1149 int found_dup_sack
= 0;
1150 int cached_fack_count
;
1152 int first_sack_index
;
1154 if (!tp
->sacked_out
) {
1155 tp
->fackets_out
= 0;
1156 tp
->highest_sack
= tp
->snd_una
;
1158 prior_fackets
= tp
->fackets_out
;
1160 found_dup_sack
= tcp_check_dsack(tp
, ack_skb
, sp
,
1161 num_sacks
, prior_snd_una
);
1163 flag
|= FLAG_DSACKING_ACK
;
1165 /* Eliminate too old ACKs, but take into
1166 * account more or less fresh ones, they can
1167 * contain valid SACK info.
1169 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1173 * if the only SACK change is the increase of the end_seq of
1174 * the first block then only apply that SACK block
1175 * and use retrans queue hinting otherwise slowpath */
1177 for (i
= 0; i
< num_sacks
; i
++) {
1178 __be32 start_seq
= sp
[i
].start_seq
;
1179 __be32 end_seq
= sp
[i
].end_seq
;
1182 if (tp
->recv_sack_cache
[i
].start_seq
!= start_seq
)
1185 if ((tp
->recv_sack_cache
[i
].start_seq
!= start_seq
) ||
1186 (tp
->recv_sack_cache
[i
].end_seq
!= end_seq
))
1189 tp
->recv_sack_cache
[i
].start_seq
= start_seq
;
1190 tp
->recv_sack_cache
[i
].end_seq
= end_seq
;
1192 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1193 for (; i
< ARRAY_SIZE(tp
->recv_sack_cache
); i
++) {
1194 tp
->recv_sack_cache
[i
].start_seq
= 0;
1195 tp
->recv_sack_cache
[i
].end_seq
= 0;
1198 first_sack_index
= 0;
1203 tp
->fastpath_skb_hint
= NULL
;
1205 /* order SACK blocks to allow in order walk of the retrans queue */
1206 for (i
= num_sacks
-1; i
> 0; i
--) {
1207 for (j
= 0; j
< i
; j
++){
1208 if (after(ntohl(sp
[j
].start_seq
),
1209 ntohl(sp
[j
+1].start_seq
))){
1210 struct tcp_sack_block_wire tmp
;
1216 /* Track where the first SACK block goes to */
1217 if (j
== first_sack_index
)
1218 first_sack_index
= j
+1;
1225 /* clear flag as used for different purpose in following code */
1228 /* Use SACK fastpath hint if valid */
1229 cached_skb
= tp
->fastpath_skb_hint
;
1230 cached_fack_count
= tp
->fastpath_cnt_hint
;
1232 cached_skb
= tcp_write_queue_head(sk
);
1233 cached_fack_count
= 0;
1236 for (i
=0; i
<num_sacks
; i
++, sp
++) {
1237 struct sk_buff
*skb
;
1238 __u32 start_seq
= ntohl(sp
->start_seq
);
1239 __u32 end_seq
= ntohl(sp
->end_seq
);
1241 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1243 if (!tcp_is_sackblock_valid(tp
, dup_sack
, start_seq
, end_seq
)) {
1245 if (!tp
->undo_marker
)
1246 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO
);
1248 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD
);
1250 NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD
);
1255 fack_count
= cached_fack_count
;
1257 /* Event "B" in the comment above. */
1258 if (after(end_seq
, tp
->high_seq
))
1259 flag
|= FLAG_DATA_LOST
;
1261 tcp_for_write_queue_from(skb
, sk
) {
1262 int in_sack
, pcount
;
1265 if (skb
== tcp_send_head(sk
))
1269 cached_fack_count
= fack_count
;
1270 if (i
== first_sack_index
) {
1271 tp
->fastpath_skb_hint
= skb
;
1272 tp
->fastpath_cnt_hint
= fack_count
;
1275 /* The retransmission queue is always in order, so
1276 * we can short-circuit the walk early.
1278 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1281 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1282 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1284 pcount
= tcp_skb_pcount(skb
);
1286 if (pcount
> 1 && !in_sack
&&
1287 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1288 unsigned int pkt_len
;
1290 in_sack
= !after(start_seq
,
1291 TCP_SKB_CB(skb
)->seq
);
1294 pkt_len
= (start_seq
-
1295 TCP_SKB_CB(skb
)->seq
);
1297 pkt_len
= (end_seq
-
1298 TCP_SKB_CB(skb
)->seq
);
1299 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
))
1301 pcount
= tcp_skb_pcount(skb
);
1304 fack_count
+= pcount
;
1306 sacked
= TCP_SKB_CB(skb
)->sacked
;
1308 /* Account D-SACK for retransmitted packet. */
1309 if ((dup_sack
&& in_sack
) &&
1310 (sacked
& TCPCB_RETRANS
) &&
1311 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1314 /* The frame is ACKed. */
1315 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1316 if (sacked
&TCPCB_RETRANS
) {
1317 if ((dup_sack
&& in_sack
) &&
1318 (sacked
&TCPCB_SACKED_ACKED
))
1319 reord
= min(fack_count
, reord
);
1321 /* If it was in a hole, we detected reordering. */
1322 if (fack_count
< prior_fackets
&&
1323 !(sacked
&TCPCB_SACKED_ACKED
))
1324 reord
= min(fack_count
, reord
);
1327 /* Nothing to do; acked frame is about to be dropped. */
1331 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1332 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1333 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1334 lost_retrans
= end_seq
;
1339 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1340 if (sacked
& TCPCB_SACKED_RETRANS
) {
1341 /* If the segment is not tagged as lost,
1342 * we do not clear RETRANS, believing
1343 * that retransmission is still in flight.
1345 if (sacked
& TCPCB_LOST
) {
1346 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1347 tp
->lost_out
-= tcp_skb_pcount(skb
);
1348 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1350 /* clear lost hint */
1351 tp
->retransmit_skb_hint
= NULL
;
1354 /* New sack for not retransmitted frame,
1355 * which was in hole. It is reordering.
1357 if (!(sacked
& TCPCB_RETRANS
) &&
1358 fack_count
< prior_fackets
)
1359 reord
= min(fack_count
, reord
);
1361 if (sacked
& TCPCB_LOST
) {
1362 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1363 tp
->lost_out
-= tcp_skb_pcount(skb
);
1365 /* clear lost hint */
1366 tp
->retransmit_skb_hint
= NULL
;
1368 /* SACK enhanced F-RTO detection.
1369 * Set flag if and only if non-rexmitted
1370 * segments below frto_highmark are
1371 * SACKed (RFC4138; Appendix B).
1372 * Clearing correct due to in-order walk
1374 if (after(end_seq
, tp
->frto_highmark
)) {
1375 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1377 if (!(sacked
& TCPCB_RETRANS
))
1378 flag
|= FLAG_ONLY_ORIG_SACKED
;
1382 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1383 flag
|= FLAG_DATA_SACKED
;
1384 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1386 if (fack_count
> tp
->fackets_out
)
1387 tp
->fackets_out
= fack_count
;
1389 if (after(TCP_SKB_CB(skb
)->seq
,
1391 tp
->highest_sack
= TCP_SKB_CB(skb
)->seq
;
1393 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1394 reord
= min(fack_count
, reord
);
1397 /* D-SACK. We can detect redundant retransmission
1398 * in S|R and plain R frames and clear it.
1399 * undo_retrans is decreased above, L|R frames
1400 * are accounted above as well.
1403 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1404 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1405 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1406 tp
->retransmit_skb_hint
= NULL
;
1411 /* Check for lost retransmit. This superb idea is
1412 * borrowed from "ratehalving". Event "C".
1413 * Later note: FACK people cheated me again 8),
1414 * we have to account for reordering! Ugly,
1417 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1418 struct sk_buff
*skb
;
1420 tcp_for_write_queue(skb
, sk
) {
1421 if (skb
== tcp_send_head(sk
))
1423 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1425 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1427 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1428 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1430 !before(lost_retrans
,
1431 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1433 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1434 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1436 /* clear lost hint */
1437 tp
->retransmit_skb_hint
= NULL
;
1439 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1440 tp
->lost_out
+= tcp_skb_pcount(skb
);
1441 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1442 flag
|= FLAG_DATA_SACKED
;
1443 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1449 tcp_verify_left_out(tp
);
1451 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
&&
1452 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1453 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1455 #if FASTRETRANS_DEBUG > 0
1456 BUG_TRAP((int)tp
->sacked_out
>= 0);
1457 BUG_TRAP((int)tp
->lost_out
>= 0);
1458 BUG_TRAP((int)tp
->retrans_out
>= 0);
1459 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1464 /* F-RTO can only be used if TCP has never retransmitted anything other than
1465 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1467 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1469 struct tcp_sock
*tp
= tcp_sk(sk
);
1472 holes
= max(tp
->lost_out
, 1U);
1473 holes
= min(holes
, tp
->packets_out
);
1475 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1476 tp
->sacked_out
= tp
->packets_out
- holes
;
1477 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1481 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1483 static void tcp_add_reno_sack(struct sock
*sk
)
1485 struct tcp_sock
*tp
= tcp_sk(sk
);
1487 tcp_check_reno_reordering(sk
, 0);
1488 tcp_verify_left_out(tp
);
1491 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1493 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1495 struct tcp_sock
*tp
= tcp_sk(sk
);
1498 /* One ACK acked hole. The rest eat duplicate ACKs. */
1499 if (acked
-1 >= tp
->sacked_out
)
1502 tp
->sacked_out
-= acked
-1;
1504 tcp_check_reno_reordering(sk
, acked
);
1505 tcp_verify_left_out(tp
);
1508 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1513 int tcp_use_frto(struct sock
*sk
)
1515 const struct tcp_sock
*tp
= tcp_sk(sk
);
1516 struct sk_buff
*skb
;
1518 if (!sysctl_tcp_frto
)
1524 /* Avoid expensive walking of rexmit queue if possible */
1525 if (tp
->retrans_out
> 1)
1528 skb
= tcp_write_queue_head(sk
);
1529 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
1530 tcp_for_write_queue_from(skb
, sk
) {
1531 if (skb
== tcp_send_head(sk
))
1533 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1535 /* Short-circuit when first non-SACKed skb has been checked */
1536 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
))
1542 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1543 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1544 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1545 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1546 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1547 * bits are handled if the Loss state is really to be entered (in
1548 * tcp_enter_frto_loss).
1550 * Do like tcp_enter_loss() would; when RTO expires the second time it
1552 * "Reduce ssthresh if it has not yet been made inside this window."
1554 void tcp_enter_frto(struct sock
*sk
)
1556 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1557 struct tcp_sock
*tp
= tcp_sk(sk
);
1558 struct sk_buff
*skb
;
1560 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1561 tp
->snd_una
== tp
->high_seq
||
1562 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1563 !icsk
->icsk_retransmits
)) {
1564 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1565 /* Our state is too optimistic in ssthresh() call because cwnd
1566 * is not reduced until tcp_enter_frto_loss() when previous FRTO
1567 * recovery has not yet completed. Pattern would be this: RTO,
1568 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1570 * RFC4138 should be more specific on what to do, even though
1571 * RTO is quite unlikely to occur after the first Cumulative ACK
1572 * due to back-off and complexity of triggering events ...
1574 if (tp
->frto_counter
) {
1576 stored_cwnd
= tp
->snd_cwnd
;
1578 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1579 tp
->snd_cwnd
= stored_cwnd
;
1581 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1583 /* ... in theory, cong.control module could do "any tricks" in
1584 * ssthresh(), which means that ca_state, lost bits and lost_out
1585 * counter would have to be faked before the call occurs. We
1586 * consider that too expensive, unlikely and hacky, so modules
1587 * using these in ssthresh() must deal these incompatibility
1588 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1590 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1593 tp
->undo_marker
= tp
->snd_una
;
1594 tp
->undo_retrans
= 0;
1596 skb
= tcp_write_queue_head(sk
);
1597 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1598 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1599 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1601 tcp_verify_left_out(tp
);
1603 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1604 * The last condition is necessary at least in tp->frto_counter case.
1606 if (IsSackFrto() && (tp
->frto_counter
||
1607 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1608 after(tp
->high_seq
, tp
->snd_una
)) {
1609 tp
->frto_highmark
= tp
->high_seq
;
1611 tp
->frto_highmark
= tp
->snd_nxt
;
1613 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1614 tp
->high_seq
= tp
->snd_nxt
;
1615 tp
->frto_counter
= 1;
1618 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1619 * which indicates that we should follow the traditional RTO recovery,
1620 * i.e. mark everything lost and do go-back-N retransmission.
1622 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1624 struct tcp_sock
*tp
= tcp_sk(sk
);
1625 struct sk_buff
*skb
;
1628 tp
->retrans_out
= 0;
1629 if (tcp_is_reno(tp
))
1630 tcp_reset_reno_sack(tp
);
1632 tcp_for_write_queue(skb
, sk
) {
1633 if (skb
== tcp_send_head(sk
))
1636 * Count the retransmission made on RTO correctly (only when
1637 * waiting for the first ACK and did not get it)...
1639 if ((tp
->frto_counter
== 1) && !(flag
&FLAG_DATA_ACKED
)) {
1640 /* For some reason this R-bit might get cleared? */
1641 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1642 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1643 /* ...enter this if branch just for the first segment */
1644 flag
|= FLAG_DATA_ACKED
;
1646 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1649 /* Don't lost mark skbs that were fwd transmitted after RTO */
1650 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) &&
1651 !after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
)) {
1652 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1653 tp
->lost_out
+= tcp_skb_pcount(skb
);
1656 tcp_verify_left_out(tp
);
1658 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1659 tp
->snd_cwnd_cnt
= 0;
1660 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1661 tp
->undo_marker
= 0;
1662 tp
->frto_counter
= 0;
1664 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1665 sysctl_tcp_reordering
);
1666 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1667 tp
->high_seq
= tp
->frto_highmark
;
1668 TCP_ECN_queue_cwr(tp
);
1670 clear_all_retrans_hints(tp
);
1673 void tcp_clear_retrans(struct tcp_sock
*tp
)
1675 tp
->retrans_out
= 0;
1677 tp
->fackets_out
= 0;
1681 tp
->undo_marker
= 0;
1682 tp
->undo_retrans
= 0;
1685 /* Enter Loss state. If "how" is not zero, forget all SACK information
1686 * and reset tags completely, otherwise preserve SACKs. If receiver
1687 * dropped its ofo queue, we will know this due to reneging detection.
1689 void tcp_enter_loss(struct sock
*sk
, int how
)
1691 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1692 struct tcp_sock
*tp
= tcp_sk(sk
);
1693 struct sk_buff
*skb
;
1696 /* Reduce ssthresh if it has not yet been made inside this window. */
1697 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1698 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1699 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1700 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1701 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1704 tp
->snd_cwnd_cnt
= 0;
1705 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1707 tp
->bytes_acked
= 0;
1708 tcp_clear_retrans(tp
);
1710 /* Push undo marker, if it was plain RTO and nothing
1711 * was retransmitted. */
1713 tp
->undo_marker
= tp
->snd_una
;
1715 tcp_for_write_queue(skb
, sk
) {
1716 if (skb
== tcp_send_head(sk
))
1718 cnt
+= tcp_skb_pcount(skb
);
1719 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1720 tp
->undo_marker
= 0;
1721 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1722 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1723 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1724 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1725 tp
->lost_out
+= tcp_skb_pcount(skb
);
1727 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1728 tp
->fackets_out
= cnt
;
1731 tcp_verify_left_out(tp
);
1733 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1734 sysctl_tcp_reordering
);
1735 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1736 tp
->high_seq
= tp
->snd_nxt
;
1737 TCP_ECN_queue_cwr(tp
);
1738 /* Abort FRTO algorithm if one is in progress */
1739 tp
->frto_counter
= 0;
1741 clear_all_retrans_hints(tp
);
1744 static int tcp_check_sack_reneging(struct sock
*sk
)
1746 struct sk_buff
*skb
;
1748 /* If ACK arrived pointing to a remembered SACK,
1749 * it means that our remembered SACKs do not reflect
1750 * real state of receiver i.e.
1751 * receiver _host_ is heavily congested (or buggy).
1752 * Do processing similar to RTO timeout.
1754 if ((skb
= tcp_write_queue_head(sk
)) != NULL
&&
1755 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1756 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1757 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1759 tcp_enter_loss(sk
, 1);
1760 icsk
->icsk_retransmits
++;
1761 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1762 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1763 icsk
->icsk_rto
, TCP_RTO_MAX
);
1769 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1771 return tcp_is_reno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1774 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1776 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1779 static inline int tcp_head_timedout(struct sock
*sk
)
1781 struct tcp_sock
*tp
= tcp_sk(sk
);
1783 return tp
->packets_out
&&
1784 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
1787 /* Linux NewReno/SACK/FACK/ECN state machine.
1788 * --------------------------------------
1790 * "Open" Normal state, no dubious events, fast path.
1791 * "Disorder" In all the respects it is "Open",
1792 * but requires a bit more attention. It is entered when
1793 * we see some SACKs or dupacks. It is split of "Open"
1794 * mainly to move some processing from fast path to slow one.
1795 * "CWR" CWND was reduced due to some Congestion Notification event.
1796 * It can be ECN, ICMP source quench, local device congestion.
1797 * "Recovery" CWND was reduced, we are fast-retransmitting.
1798 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1800 * tcp_fastretrans_alert() is entered:
1801 * - each incoming ACK, if state is not "Open"
1802 * - when arrived ACK is unusual, namely:
1807 * Counting packets in flight is pretty simple.
1809 * in_flight = packets_out - left_out + retrans_out
1811 * packets_out is SND.NXT-SND.UNA counted in packets.
1813 * retrans_out is number of retransmitted segments.
1815 * left_out is number of segments left network, but not ACKed yet.
1817 * left_out = sacked_out + lost_out
1819 * sacked_out: Packets, which arrived to receiver out of order
1820 * and hence not ACKed. With SACKs this number is simply
1821 * amount of SACKed data. Even without SACKs
1822 * it is easy to give pretty reliable estimate of this number,
1823 * counting duplicate ACKs.
1825 * lost_out: Packets lost by network. TCP has no explicit
1826 * "loss notification" feedback from network (for now).
1827 * It means that this number can be only _guessed_.
1828 * Actually, it is the heuristics to predict lossage that
1829 * distinguishes different algorithms.
1831 * F.e. after RTO, when all the queue is considered as lost,
1832 * lost_out = packets_out and in_flight = retrans_out.
1834 * Essentially, we have now two algorithms counting
1837 * FACK: It is the simplest heuristics. As soon as we decided
1838 * that something is lost, we decide that _all_ not SACKed
1839 * packets until the most forward SACK are lost. I.e.
1840 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1841 * It is absolutely correct estimate, if network does not reorder
1842 * packets. And it loses any connection to reality when reordering
1843 * takes place. We use FACK by default until reordering
1844 * is suspected on the path to this destination.
1846 * NewReno: when Recovery is entered, we assume that one segment
1847 * is lost (classic Reno). While we are in Recovery and
1848 * a partial ACK arrives, we assume that one more packet
1849 * is lost (NewReno). This heuristics are the same in NewReno
1852 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1853 * deflation etc. CWND is real congestion window, never inflated, changes
1854 * only according to classic VJ rules.
1856 * Really tricky (and requiring careful tuning) part of algorithm
1857 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1858 * The first determines the moment _when_ we should reduce CWND and,
1859 * hence, slow down forward transmission. In fact, it determines the moment
1860 * when we decide that hole is caused by loss, rather than by a reorder.
1862 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1863 * holes, caused by lost packets.
1865 * And the most logically complicated part of algorithm is undo
1866 * heuristics. We detect false retransmits due to both too early
1867 * fast retransmit (reordering) and underestimated RTO, analyzing
1868 * timestamps and D-SACKs. When we detect that some segments were
1869 * retransmitted by mistake and CWND reduction was wrong, we undo
1870 * window reduction and abort recovery phase. This logic is hidden
1871 * inside several functions named tcp_try_undo_<something>.
1874 /* This function decides, when we should leave Disordered state
1875 * and enter Recovery phase, reducing congestion window.
1877 * Main question: may we further continue forward transmission
1878 * with the same cwnd?
1880 static int tcp_time_to_recover(struct sock
*sk
)
1882 struct tcp_sock
*tp
= tcp_sk(sk
);
1885 /* Do not perform any recovery during FRTO algorithm */
1886 if (tp
->frto_counter
)
1889 /* Trick#1: The loss is proven. */
1893 /* Not-A-Trick#2 : Classic rule... */
1894 if (tcp_fackets_out(tp
) > tp
->reordering
)
1897 /* Trick#3 : when we use RFC2988 timer restart, fast
1898 * retransmit can be triggered by timeout of queue head.
1900 if (tcp_head_timedout(sk
))
1903 /* Trick#4: It is still not OK... But will it be useful to delay
1906 packets_out
= tp
->packets_out
;
1907 if (packets_out
<= tp
->reordering
&&
1908 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1909 !tcp_may_send_now(sk
)) {
1910 /* We have nothing to send. This connection is limited
1911 * either by receiver window or by application.
1919 /* RFC: This is from the original, I doubt that this is necessary at all:
1920 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
1921 * retransmitted past LOST markings in the first place? I'm not fully sure
1922 * about undo and end of connection cases, which can cause R without L?
1924 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
,
1925 struct sk_buff
*skb
)
1927 if ((tp
->retransmit_skb_hint
!= NULL
) &&
1928 before(TCP_SKB_CB(skb
)->seq
,
1929 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1930 tp
->retransmit_skb_hint
= NULL
;
1933 /* Mark head of queue up as lost. */
1934 static void tcp_mark_head_lost(struct sock
*sk
,
1935 int packets
, u32 high_seq
)
1937 struct tcp_sock
*tp
= tcp_sk(sk
);
1938 struct sk_buff
*skb
;
1941 BUG_TRAP(packets
<= tp
->packets_out
);
1942 if (tp
->lost_skb_hint
) {
1943 skb
= tp
->lost_skb_hint
;
1944 cnt
= tp
->lost_cnt_hint
;
1946 skb
= tcp_write_queue_head(sk
);
1950 tcp_for_write_queue_from(skb
, sk
) {
1951 if (skb
== tcp_send_head(sk
))
1953 /* TODO: do this better */
1954 /* this is not the most efficient way to do this... */
1955 tp
->lost_skb_hint
= skb
;
1956 tp
->lost_cnt_hint
= cnt
;
1957 cnt
+= tcp_skb_pcount(skb
);
1958 if (cnt
> packets
|| after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1960 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1961 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1962 tp
->lost_out
+= tcp_skb_pcount(skb
);
1963 tcp_verify_retransmit_hint(tp
, skb
);
1966 tcp_verify_left_out(tp
);
1969 /* Account newly detected lost packet(s) */
1971 static void tcp_update_scoreboard(struct sock
*sk
)
1973 struct tcp_sock
*tp
= tcp_sk(sk
);
1975 if (tcp_is_fack(tp
)) {
1976 int lost
= tp
->fackets_out
- tp
->reordering
;
1979 tcp_mark_head_lost(sk
, lost
, tp
->high_seq
);
1981 tcp_mark_head_lost(sk
, 1, tp
->high_seq
);
1984 /* New heuristics: it is possible only after we switched
1985 * to restart timer each time when something is ACKed.
1986 * Hence, we can detect timed out packets during fast
1987 * retransmit without falling to slow start.
1989 if (!tcp_is_reno(tp
) && tcp_head_timedout(sk
)) {
1990 struct sk_buff
*skb
;
1992 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
1993 : tcp_write_queue_head(sk
);
1995 tcp_for_write_queue_from(skb
, sk
) {
1996 if (skb
== tcp_send_head(sk
))
1998 if (!tcp_skb_timedout(sk
, skb
))
2001 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
2002 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2003 tp
->lost_out
+= tcp_skb_pcount(skb
);
2004 tcp_verify_retransmit_hint(tp
, skb
);
2008 tp
->scoreboard_skb_hint
= skb
;
2010 tcp_verify_left_out(tp
);
2014 /* CWND moderation, preventing bursts due to too big ACKs
2015 * in dubious situations.
2017 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2019 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2020 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
2021 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2024 /* Lower bound on congestion window is slow start threshold
2025 * unless congestion avoidance choice decides to overide it.
2027 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2029 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2031 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2034 /* Decrease cwnd each second ack. */
2035 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2037 struct tcp_sock
*tp
= tcp_sk(sk
);
2038 int decr
= tp
->snd_cwnd_cnt
+ 1;
2040 if ((flag
&(FLAG_ANY_PROGRESS
|FLAG_DSACKING_ACK
)) ||
2041 (tcp_is_reno(tp
) && !(flag
&FLAG_NOT_DUP
))) {
2042 tp
->snd_cwnd_cnt
= decr
&1;
2045 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2046 tp
->snd_cwnd
-= decr
;
2048 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
2049 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2053 /* Nothing was retransmitted or returned timestamp is less
2054 * than timestamp of the first retransmission.
2056 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2058 return !tp
->retrans_stamp
||
2059 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2060 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
2063 /* Undo procedures. */
2065 #if FASTRETRANS_DEBUG > 1
2066 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2068 struct tcp_sock
*tp
= tcp_sk(sk
);
2069 struct inet_sock
*inet
= inet_sk(sk
);
2071 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
2073 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
2074 tp
->snd_cwnd
, tcp_left_out(tp
),
2075 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2079 #define DBGUNDO(x...) do { } while (0)
2082 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
2084 struct tcp_sock
*tp
= tcp_sk(sk
);
2086 if (tp
->prior_ssthresh
) {
2087 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2089 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2090 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2092 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
2094 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2095 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2096 TCP_ECN_withdraw_cwr(tp
);
2099 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2101 tcp_moderate_cwnd(tp
);
2102 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2104 /* There is something screwy going on with the retrans hints after
2106 clear_all_retrans_hints(tp
);
2109 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2111 return tp
->undo_marker
&&
2112 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2115 /* People celebrate: "We love our President!" */
2116 static int tcp_try_undo_recovery(struct sock
*sk
)
2118 struct tcp_sock
*tp
= tcp_sk(sk
);
2120 if (tcp_may_undo(tp
)) {
2121 /* Happy end! We did not retransmit anything
2122 * or our original transmission succeeded.
2124 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2125 tcp_undo_cwr(sk
, 1);
2126 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2127 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2129 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
2130 tp
->undo_marker
= 0;
2132 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2133 /* Hold old state until something *above* high_seq
2134 * is ACKed. For Reno it is MUST to prevent false
2135 * fast retransmits (RFC2582). SACK TCP is safe. */
2136 tcp_moderate_cwnd(tp
);
2139 tcp_set_ca_state(sk
, TCP_CA_Open
);
2143 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2144 static void tcp_try_undo_dsack(struct sock
*sk
)
2146 struct tcp_sock
*tp
= tcp_sk(sk
);
2148 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2149 DBGUNDO(sk
, "D-SACK");
2150 tcp_undo_cwr(sk
, 1);
2151 tp
->undo_marker
= 0;
2152 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
2156 /* Undo during fast recovery after partial ACK. */
2158 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2160 struct tcp_sock
*tp
= tcp_sk(sk
);
2161 /* Partial ACK arrived. Force Hoe's retransmit. */
2162 int failed
= tcp_is_reno(tp
) || tp
->fackets_out
>tp
->reordering
;
2164 if (tcp_may_undo(tp
)) {
2165 /* Plain luck! Hole if filled with delayed
2166 * packet, rather than with a retransmit.
2168 if (tp
->retrans_out
== 0)
2169 tp
->retrans_stamp
= 0;
2171 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2174 tcp_undo_cwr(sk
, 0);
2175 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
2177 /* So... Do not make Hoe's retransmit yet.
2178 * If the first packet was delayed, the rest
2179 * ones are most probably delayed as well.
2186 /* Undo during loss recovery after partial ACK. */
2187 static int tcp_try_undo_loss(struct sock
*sk
)
2189 struct tcp_sock
*tp
= tcp_sk(sk
);
2191 if (tcp_may_undo(tp
)) {
2192 struct sk_buff
*skb
;
2193 tcp_for_write_queue(skb
, sk
) {
2194 if (skb
== tcp_send_head(sk
))
2196 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2199 clear_all_retrans_hints(tp
);
2201 DBGUNDO(sk
, "partial loss");
2203 tcp_undo_cwr(sk
, 1);
2204 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2205 inet_csk(sk
)->icsk_retransmits
= 0;
2206 tp
->undo_marker
= 0;
2207 if (tcp_is_sack(tp
))
2208 tcp_set_ca_state(sk
, TCP_CA_Open
);
2214 static inline void tcp_complete_cwr(struct sock
*sk
)
2216 struct tcp_sock
*tp
= tcp_sk(sk
);
2217 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2218 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2219 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2222 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2224 struct tcp_sock
*tp
= tcp_sk(sk
);
2226 tcp_verify_left_out(tp
);
2228 if (tp
->retrans_out
== 0)
2229 tp
->retrans_stamp
= 0;
2232 tcp_enter_cwr(sk
, 1);
2234 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2235 int state
= TCP_CA_Open
;
2237 if (tcp_left_out(tp
) || tp
->retrans_out
|| tp
->undo_marker
)
2238 state
= TCP_CA_Disorder
;
2240 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2241 tcp_set_ca_state(sk
, state
);
2242 tp
->high_seq
= tp
->snd_nxt
;
2244 tcp_moderate_cwnd(tp
);
2246 tcp_cwnd_down(sk
, flag
);
2250 static void tcp_mtup_probe_failed(struct sock
*sk
)
2252 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2254 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2255 icsk
->icsk_mtup
.probe_size
= 0;
2258 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2260 struct tcp_sock
*tp
= tcp_sk(sk
);
2261 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2263 /* FIXME: breaks with very large cwnd */
2264 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2265 tp
->snd_cwnd
= tp
->snd_cwnd
*
2266 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2267 icsk
->icsk_mtup
.probe_size
;
2268 tp
->snd_cwnd_cnt
= 0;
2269 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2270 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2272 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2273 icsk
->icsk_mtup
.probe_size
= 0;
2274 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2278 /* Process an event, which can update packets-in-flight not trivially.
2279 * Main goal of this function is to calculate new estimate for left_out,
2280 * taking into account both packets sitting in receiver's buffer and
2281 * packets lost by network.
2283 * Besides that it does CWND reduction, when packet loss is detected
2284 * and changes state of machine.
2286 * It does _not_ decide what to send, it is made in function
2287 * tcp_xmit_retransmit_queue().
2290 tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
, int flag
)
2292 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2293 struct tcp_sock
*tp
= tcp_sk(sk
);
2294 int is_dupack
= !(flag
&(FLAG_SND_UNA_ADVANCED
|FLAG_NOT_DUP
));
2295 int do_lost
= is_dupack
|| ((flag
&FLAG_DATA_SACKED
) &&
2296 (tp
->fackets_out
> tp
->reordering
));
2298 /* Some technical things:
2299 * 1. Reno does not count dupacks (sacked_out) automatically. */
2300 if (!tp
->packets_out
)
2302 /* 2. SACK counts snd_fack in packets inaccurately. */
2303 if (tp
->sacked_out
== 0)
2304 tp
->fackets_out
= 0;
2306 /* Now state machine starts.
2307 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2309 tp
->prior_ssthresh
= 0;
2311 /* B. In all the states check for reneging SACKs. */
2312 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
2315 /* C. Process data loss notification, provided it is valid. */
2316 if ((flag
&FLAG_DATA_LOST
) &&
2317 before(tp
->snd_una
, tp
->high_seq
) &&
2318 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2319 tp
->fackets_out
> tp
->reordering
) {
2320 tcp_mark_head_lost(sk
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
2321 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2324 /* D. Check consistency of the current state. */
2325 tcp_verify_left_out(tp
);
2327 /* E. Check state exit conditions. State can be terminated
2328 * when high_seq is ACKed. */
2329 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2330 BUG_TRAP(tp
->retrans_out
== 0);
2331 tp
->retrans_stamp
= 0;
2332 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2333 switch (icsk
->icsk_ca_state
) {
2335 icsk
->icsk_retransmits
= 0;
2336 if (tcp_try_undo_recovery(sk
))
2341 /* CWR is to be held something *above* high_seq
2342 * is ACKed for CWR bit to reach receiver. */
2343 if (tp
->snd_una
!= tp
->high_seq
) {
2344 tcp_complete_cwr(sk
);
2345 tcp_set_ca_state(sk
, TCP_CA_Open
);
2349 case TCP_CA_Disorder
:
2350 tcp_try_undo_dsack(sk
);
2351 if (!tp
->undo_marker
||
2352 /* For SACK case do not Open to allow to undo
2353 * catching for all duplicate ACKs. */
2354 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2355 tp
->undo_marker
= 0;
2356 tcp_set_ca_state(sk
, TCP_CA_Open
);
2360 case TCP_CA_Recovery
:
2361 if (tcp_is_reno(tp
))
2362 tcp_reset_reno_sack(tp
);
2363 if (tcp_try_undo_recovery(sk
))
2365 tcp_complete_cwr(sk
);
2370 /* F. Process state. */
2371 switch (icsk
->icsk_ca_state
) {
2372 case TCP_CA_Recovery
:
2373 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2374 if (tcp_is_reno(tp
) && is_dupack
)
2375 tcp_add_reno_sack(sk
);
2377 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
2380 if (flag
&FLAG_DATA_ACKED
)
2381 icsk
->icsk_retransmits
= 0;
2382 if (!tcp_try_undo_loss(sk
)) {
2383 tcp_moderate_cwnd(tp
);
2384 tcp_xmit_retransmit_queue(sk
);
2387 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2389 /* Loss is undone; fall through to processing in Open state. */
2391 if (tcp_is_reno(tp
)) {
2392 if (flag
& FLAG_SND_UNA_ADVANCED
)
2393 tcp_reset_reno_sack(tp
);
2395 tcp_add_reno_sack(sk
);
2398 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2399 tcp_try_undo_dsack(sk
);
2401 if (!tcp_time_to_recover(sk
)) {
2402 tcp_try_to_open(sk
, flag
);
2406 /* MTU probe failure: don't reduce cwnd */
2407 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2408 icsk
->icsk_mtup
.probe_size
&&
2409 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2410 tcp_mtup_probe_failed(sk
);
2411 /* Restores the reduction we did in tcp_mtup_probe() */
2413 tcp_simple_retransmit(sk
);
2417 /* Otherwise enter Recovery state */
2419 if (tcp_is_reno(tp
))
2420 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2422 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2424 tp
->high_seq
= tp
->snd_nxt
;
2425 tp
->prior_ssthresh
= 0;
2426 tp
->undo_marker
= tp
->snd_una
;
2427 tp
->undo_retrans
= tp
->retrans_out
;
2429 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2430 if (!(flag
&FLAG_ECE
))
2431 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2432 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2433 TCP_ECN_queue_cwr(tp
);
2436 tp
->bytes_acked
= 0;
2437 tp
->snd_cwnd_cnt
= 0;
2438 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2441 if (do_lost
|| tcp_head_timedout(sk
))
2442 tcp_update_scoreboard(sk
);
2443 tcp_cwnd_down(sk
, flag
);
2444 tcp_xmit_retransmit_queue(sk
);
2447 /* Read draft-ietf-tcplw-high-performance before mucking
2448 * with this code. (Supersedes RFC1323)
2450 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2452 /* RTTM Rule: A TSecr value received in a segment is used to
2453 * update the averaged RTT measurement only if the segment
2454 * acknowledges some new data, i.e., only if it advances the
2455 * left edge of the send window.
2457 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2458 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2460 * Changed: reset backoff as soon as we see the first valid sample.
2461 * If we do not, we get strongly overestimated rto. With timestamps
2462 * samples are accepted even from very old segments: f.e., when rtt=1
2463 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2464 * answer arrives rto becomes 120 seconds! If at least one of segments
2465 * in window is lost... Voila. --ANK (010210)
2467 struct tcp_sock
*tp
= tcp_sk(sk
);
2468 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2469 tcp_rtt_estimator(sk
, seq_rtt
);
2471 inet_csk(sk
)->icsk_backoff
= 0;
2475 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2477 /* We don't have a timestamp. Can only use
2478 * packets that are not retransmitted to determine
2479 * rtt estimates. Also, we must not reset the
2480 * backoff for rto until we get a non-retransmitted
2481 * packet. This allows us to deal with a situation
2482 * where the network delay has increased suddenly.
2483 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2486 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2489 tcp_rtt_estimator(sk
, seq_rtt
);
2491 inet_csk(sk
)->icsk_backoff
= 0;
2495 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2498 const struct tcp_sock
*tp
= tcp_sk(sk
);
2499 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2500 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2501 tcp_ack_saw_tstamp(sk
, flag
);
2502 else if (seq_rtt
>= 0)
2503 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2506 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
,
2507 u32 in_flight
, int good
)
2509 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2510 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
, good
);
2511 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2514 /* Restart timer after forward progress on connection.
2515 * RFC2988 recommends to restart timer to now+rto.
2517 static void tcp_rearm_rto(struct sock
*sk
)
2519 struct tcp_sock
*tp
= tcp_sk(sk
);
2521 if (!tp
->packets_out
) {
2522 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2524 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2528 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
2529 __u32 now
, __s32
*seq_rtt
)
2531 struct tcp_sock
*tp
= tcp_sk(sk
);
2532 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2533 __u32 seq
= tp
->snd_una
;
2534 __u32 packets_acked
;
2537 /* If we get here, the whole TSO packet has not been
2540 BUG_ON(!after(scb
->end_seq
, seq
));
2542 packets_acked
= tcp_skb_pcount(skb
);
2543 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
2545 packets_acked
-= tcp_skb_pcount(skb
);
2547 if (packets_acked
) {
2548 __u8 sacked
= scb
->sacked
;
2550 acked
|= FLAG_DATA_ACKED
;
2552 if (sacked
& TCPCB_RETRANS
) {
2553 if (sacked
& TCPCB_SACKED_RETRANS
)
2554 tp
->retrans_out
-= packets_acked
;
2555 acked
|= FLAG_RETRANS_DATA_ACKED
;
2557 } else if (*seq_rtt
< 0)
2558 *seq_rtt
= now
- scb
->when
;
2559 if (sacked
& TCPCB_SACKED_ACKED
)
2560 tp
->sacked_out
-= packets_acked
;
2561 if (sacked
& TCPCB_LOST
)
2562 tp
->lost_out
-= packets_acked
;
2563 if (sacked
& TCPCB_URG
) {
2565 !before(seq
, tp
->snd_up
))
2568 } else if (*seq_rtt
< 0)
2569 *seq_rtt
= now
- scb
->when
;
2571 if (tp
->fackets_out
) {
2572 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2573 tp
->fackets_out
-= dval
;
2575 /* hint's skb might be NULL but we don't need to care */
2576 tp
->fastpath_cnt_hint
-= min_t(u32
, packets_acked
,
2577 tp
->fastpath_cnt_hint
);
2578 tp
->packets_out
-= packets_acked
;
2580 BUG_ON(tcp_skb_pcount(skb
) == 0);
2581 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2587 /* Remove acknowledged frames from the retransmission queue. */
2588 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2590 struct tcp_sock
*tp
= tcp_sk(sk
);
2591 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2592 struct sk_buff
*skb
;
2593 __u32 now
= tcp_time_stamp
;
2595 int prior_packets
= tp
->packets_out
;
2597 ktime_t last_ackt
= net_invalid_timestamp();
2599 while ((skb
= tcp_write_queue_head(sk
)) &&
2600 skb
!= tcp_send_head(sk
)) {
2601 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2602 __u8 sacked
= scb
->sacked
;
2604 /* If our packet is before the ack sequence we can
2605 * discard it as it's confirmed to have arrived at
2608 if (after(scb
->end_seq
, tp
->snd_una
)) {
2609 if (tcp_skb_pcount(skb
) > 1 &&
2610 after(tp
->snd_una
, scb
->seq
))
2611 acked
|= tcp_tso_acked(sk
, skb
,
2616 /* Initial outgoing SYN's get put onto the write_queue
2617 * just like anything else we transmit. It is not
2618 * true data, and if we misinform our callers that
2619 * this ACK acks real data, we will erroneously exit
2620 * connection startup slow start one packet too
2621 * quickly. This is severely frowned upon behavior.
2623 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2624 acked
|= FLAG_DATA_ACKED
;
2626 acked
|= FLAG_SYN_ACKED
;
2627 tp
->retrans_stamp
= 0;
2630 /* MTU probing checks */
2631 if (icsk
->icsk_mtup
.probe_size
) {
2632 if (!after(tp
->mtu_probe
.probe_seq_end
, TCP_SKB_CB(skb
)->end_seq
)) {
2633 tcp_mtup_probe_success(sk
, skb
);
2638 if (sacked
& TCPCB_RETRANS
) {
2639 if (sacked
& TCPCB_SACKED_RETRANS
)
2640 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2641 acked
|= FLAG_RETRANS_DATA_ACKED
;
2643 } else if (seq_rtt
< 0) {
2644 seq_rtt
= now
- scb
->when
;
2645 last_ackt
= skb
->tstamp
;
2647 if (sacked
& TCPCB_SACKED_ACKED
)
2648 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2649 if (sacked
& TCPCB_LOST
)
2650 tp
->lost_out
-= tcp_skb_pcount(skb
);
2651 if (sacked
& TCPCB_URG
) {
2653 !before(scb
->end_seq
, tp
->snd_up
))
2656 } else if (seq_rtt
< 0) {
2657 seq_rtt
= now
- scb
->when
;
2658 last_ackt
= skb
->tstamp
;
2660 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2661 tp
->packets_out
-= tcp_skb_pcount(skb
);
2662 tcp_unlink_write_queue(skb
, sk
);
2663 sk_stream_free_skb(sk
, skb
);
2664 clear_all_retrans_hints(tp
);
2667 if (acked
&FLAG_ACKED
) {
2668 u32 pkts_acked
= prior_packets
- tp
->packets_out
;
2669 const struct tcp_congestion_ops
*ca_ops
2670 = inet_csk(sk
)->icsk_ca_ops
;
2672 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2675 if (tcp_is_reno(tp
))
2676 tcp_remove_reno_sacks(sk
, pkts_acked
);
2678 if (ca_ops
->pkts_acked
) {
2681 /* Is the ACK triggering packet unambiguous? */
2682 if (!(acked
& FLAG_RETRANS_DATA_ACKED
)) {
2683 /* High resolution needed and available? */
2684 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
2685 !ktime_equal(last_ackt
,
2686 net_invalid_timestamp()))
2687 rtt_us
= ktime_us_delta(ktime_get_real(),
2689 else if (seq_rtt
> 0)
2690 rtt_us
= jiffies_to_usecs(seq_rtt
);
2693 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
2697 #if FASTRETRANS_DEBUG > 0
2698 BUG_TRAP((int)tp
->sacked_out
>= 0);
2699 BUG_TRAP((int)tp
->lost_out
>= 0);
2700 BUG_TRAP((int)tp
->retrans_out
>= 0);
2701 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
2702 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2704 printk(KERN_DEBUG
"Leak l=%u %d\n",
2705 tp
->lost_out
, icsk
->icsk_ca_state
);
2708 if (tp
->sacked_out
) {
2709 printk(KERN_DEBUG
"Leak s=%u %d\n",
2710 tp
->sacked_out
, icsk
->icsk_ca_state
);
2713 if (tp
->retrans_out
) {
2714 printk(KERN_DEBUG
"Leak r=%u %d\n",
2715 tp
->retrans_out
, icsk
->icsk_ca_state
);
2716 tp
->retrans_out
= 0;
2720 *seq_rtt_p
= seq_rtt
;
2724 static void tcp_ack_probe(struct sock
*sk
)
2726 const struct tcp_sock
*tp
= tcp_sk(sk
);
2727 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2729 /* Was it a usable window open? */
2731 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2732 tp
->snd_una
+ tp
->snd_wnd
)) {
2733 icsk
->icsk_backoff
= 0;
2734 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2735 /* Socket must be waked up by subsequent tcp_data_snd_check().
2736 * This function is not for random using!
2739 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2740 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2745 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2747 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2748 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2751 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2753 const struct tcp_sock
*tp
= tcp_sk(sk
);
2754 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2755 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2758 /* Check that window update is acceptable.
2759 * The function assumes that snd_una<=ack<=snd_next.
2761 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2762 const u32 ack_seq
, const u32 nwin
)
2764 return (after(ack
, tp
->snd_una
) ||
2765 after(ack_seq
, tp
->snd_wl1
) ||
2766 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2769 /* Update our send window.
2771 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2772 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2774 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
2777 struct tcp_sock
*tp
= tcp_sk(sk
);
2779 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
2781 if (likely(!tcp_hdr(skb
)->syn
))
2782 nwin
<<= tp
->rx_opt
.snd_wscale
;
2784 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2785 flag
|= FLAG_WIN_UPDATE
;
2786 tcp_update_wl(tp
, ack
, ack_seq
);
2788 if (tp
->snd_wnd
!= nwin
) {
2791 /* Note, it is the only place, where
2792 * fast path is recovered for sending TCP.
2795 tcp_fast_path_check(sk
);
2797 if (nwin
> tp
->max_window
) {
2798 tp
->max_window
= nwin
;
2799 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
2809 /* A very conservative spurious RTO response algorithm: reduce cwnd and
2810 * continue in congestion avoidance.
2812 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
2814 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2815 tp
->snd_cwnd_cnt
= 0;
2816 TCP_ECN_queue_cwr(tp
);
2817 tcp_moderate_cwnd(tp
);
2820 /* A conservative spurious RTO response algorithm: reduce cwnd using
2821 * rate halving and continue in congestion avoidance.
2823 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
2825 tcp_enter_cwr(sk
, 0);
2828 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
2831 tcp_ratehalving_spur_to_response(sk
);
2833 tcp_undo_cwr(sk
, 1);
2836 /* F-RTO spurious RTO detection algorithm (RFC4138)
2838 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
2839 * comments). State (ACK number) is kept in frto_counter. When ACK advances
2840 * window (but not to or beyond highest sequence sent before RTO):
2841 * On First ACK, send two new segments out.
2842 * On Second ACK, RTO was likely spurious. Do spurious response (response
2843 * algorithm is not part of the F-RTO detection algorithm
2844 * given in RFC4138 but can be selected separately).
2845 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
2846 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
2847 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
2848 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
2850 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2851 * original window even after we transmit two new data segments.
2854 * on first step, wait until first cumulative ACK arrives, then move to
2855 * the second step. In second step, the next ACK decides.
2857 * F-RTO is implemented (mainly) in four functions:
2858 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2859 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2860 * called when tcp_use_frto() showed green light
2861 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2862 * - tcp_enter_frto_loss() is called if there is not enough evidence
2863 * to prove that the RTO is indeed spurious. It transfers the control
2864 * from F-RTO to the conventional RTO recovery
2866 static int tcp_process_frto(struct sock
*sk
, int flag
)
2868 struct tcp_sock
*tp
= tcp_sk(sk
);
2870 tcp_verify_left_out(tp
);
2872 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2873 if (flag
&FLAG_DATA_ACKED
)
2874 inet_csk(sk
)->icsk_retransmits
= 0;
2876 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
2877 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
2881 if (!IsSackFrto() || tcp_is_reno(tp
)) {
2882 /* RFC4138 shortcoming in step 2; should also have case c):
2883 * ACK isn't duplicate nor advances window, e.g., opposite dir
2886 if (!(flag
&FLAG_ANY_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2889 if (!(flag
&FLAG_DATA_ACKED
)) {
2890 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
2895 if (!(flag
&FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
2896 /* Prevent sending of new data. */
2897 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2898 tcp_packets_in_flight(tp
));
2902 if ((tp
->frto_counter
>= 2) &&
2903 (!(flag
&FLAG_FORWARD_PROGRESS
) ||
2904 ((flag
&FLAG_DATA_SACKED
) && !(flag
&FLAG_ONLY_ORIG_SACKED
)))) {
2905 /* RFC4138 shortcoming (see comment above) */
2906 if (!(flag
&FLAG_FORWARD_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2909 tcp_enter_frto_loss(sk
, 3, flag
);
2914 if (tp
->frto_counter
== 1) {
2915 /* Sending of the next skb must be allowed or no FRTO */
2916 if (!tcp_send_head(sk
) ||
2917 after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2918 tp
->snd_una
+ tp
->snd_wnd
)) {
2919 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3),
2924 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2925 tp
->frto_counter
= 2;
2928 switch (sysctl_tcp_frto_response
) {
2930 tcp_undo_spur_to_response(sk
, flag
);
2933 tcp_conservative_spur_to_response(tp
);
2936 tcp_ratehalving_spur_to_response(sk
);
2939 tp
->frto_counter
= 0;
2944 /* This routine deals with incoming acks, but not outgoing ones. */
2945 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2947 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2948 struct tcp_sock
*tp
= tcp_sk(sk
);
2949 u32 prior_snd_una
= tp
->snd_una
;
2950 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2951 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2952 u32 prior_in_flight
;
2957 /* If the ack is newer than sent or older than previous acks
2958 * then we can probably ignore it.
2960 if (after(ack
, tp
->snd_nxt
))
2961 goto uninteresting_ack
;
2963 if (before(ack
, prior_snd_una
))
2966 if (after(ack
, prior_snd_una
))
2967 flag
|= FLAG_SND_UNA_ADVANCED
;
2969 if (sysctl_tcp_abc
) {
2970 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
2971 tp
->bytes_acked
+= ack
- prior_snd_una
;
2972 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
2973 /* we assume just one segment left network */
2974 tp
->bytes_acked
+= min(ack
- prior_snd_una
, tp
->mss_cache
);
2977 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2978 /* Window is constant, pure forward advance.
2979 * No more checks are required.
2980 * Note, we use the fact that SND.UNA>=SND.WL2.
2982 tcp_update_wl(tp
, ack
, ack_seq
);
2984 flag
|= FLAG_WIN_UPDATE
;
2986 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2988 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2990 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2993 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2995 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
2997 if (TCP_SKB_CB(skb
)->sacked
)
2998 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3000 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3003 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3006 /* We passed data and got it acked, remove any soft error
3007 * log. Something worked...
3009 sk
->sk_err_soft
= 0;
3010 tp
->rcv_tstamp
= tcp_time_stamp
;
3011 prior_packets
= tp
->packets_out
;
3015 prior_in_flight
= tcp_packets_in_flight(tp
);
3017 /* See if we can take anything off of the retransmit queue. */
3018 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
3020 if (tp
->frto_counter
)
3021 frto_cwnd
= tcp_process_frto(sk
, flag
);
3023 if (tcp_ack_is_dubious(sk
, flag
)) {
3024 /* Advance CWND, if state allows this. */
3025 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3026 tcp_may_raise_cwnd(sk
, flag
))
3027 tcp_cong_avoid(sk
, ack
, prior_in_flight
, 0);
3028 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
, flag
);
3030 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3031 tcp_cong_avoid(sk
, ack
, prior_in_flight
, 1);
3034 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
3035 dst_confirm(sk
->sk_dst_cache
);
3040 icsk
->icsk_probes_out
= 0;
3042 /* If this ack opens up a zero window, clear backoff. It was
3043 * being used to time the probes, and is probably far higher than
3044 * it needs to be for normal retransmission.
3046 if (tcp_send_head(sk
))
3051 if (TCP_SKB_CB(skb
)->sacked
)
3052 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3055 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3060 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3061 * But, this can also be called on packets in the established flow when
3062 * the fast version below fails.
3064 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
3067 struct tcphdr
*th
= tcp_hdr(skb
);
3068 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
3070 ptr
= (unsigned char *)(th
+ 1);
3071 opt_rx
->saw_tstamp
= 0;
3073 while (length
> 0) {
3080 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3085 if (opsize
< 2) /* "silly options" */
3087 if (opsize
> length
)
3088 return; /* don't parse partial options */
3091 if (opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3092 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
3094 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
3095 in_mss
= opt_rx
->user_mss
;
3096 opt_rx
->mss_clamp
= in_mss
;
3101 if (opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
3102 if (sysctl_tcp_window_scaling
) {
3103 __u8 snd_wscale
= *(__u8
*) ptr
;
3104 opt_rx
->wscale_ok
= 1;
3105 if (snd_wscale
> 14) {
3106 if (net_ratelimit())
3107 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3108 "scaling value %d >14 received.\n",
3112 opt_rx
->snd_wscale
= snd_wscale
;
3115 case TCPOPT_TIMESTAMP
:
3116 if (opsize
==TCPOLEN_TIMESTAMP
) {
3117 if ((estab
&& opt_rx
->tstamp_ok
) ||
3118 (!estab
&& sysctl_tcp_timestamps
)) {
3119 opt_rx
->saw_tstamp
= 1;
3120 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
3121 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
3125 case TCPOPT_SACK_PERM
:
3126 if (opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
3127 if (sysctl_tcp_sack
) {
3128 opt_rx
->sack_ok
= 1;
3129 tcp_sack_reset(opt_rx
);
3135 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3136 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3138 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3141 #ifdef CONFIG_TCP_MD5SIG
3144 * The MD5 Hash has already been
3145 * checked (see tcp_v{4,6}_do_rcv()).
3157 /* Fast parse options. This hopes to only see timestamps.
3158 * If it is wrong it falls back on tcp_parse_options().
3160 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3161 struct tcp_sock
*tp
)
3163 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
3164 tp
->rx_opt
.saw_tstamp
= 0;
3166 } else if (tp
->rx_opt
.tstamp_ok
&&
3167 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
3168 __be32
*ptr
= (__be32
*)(th
+ 1);
3169 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3170 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3171 tp
->rx_opt
.saw_tstamp
= 1;
3173 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3175 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3179 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
3183 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3185 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3186 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3189 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3191 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3192 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3193 * extra check below makes sure this can only happen
3194 * for pure ACK frames. -DaveM
3196 * Not only, also it occurs for expired timestamps.
3199 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
3200 get_seconds() >= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
3201 tcp_store_ts_recent(tp
);
3205 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3207 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3208 * it can pass through stack. So, the following predicate verifies that
3209 * this segment is not used for anything but congestion avoidance or
3210 * fast retransmit. Moreover, we even are able to eliminate most of such
3211 * second order effects, if we apply some small "replay" window (~RTO)
3212 * to timestamp space.
3214 * All these measures still do not guarantee that we reject wrapped ACKs
3215 * on networks with high bandwidth, when sequence space is recycled fastly,
3216 * but it guarantees that such events will be very rare and do not affect
3217 * connection seriously. This doesn't look nice, but alas, PAWS is really
3220 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3221 * states that events when retransmit arrives after original data are rare.
3222 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3223 * the biggest problem on large power networks even with minor reordering.
3224 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3225 * up to bandwidth of 18Gigabit/sec. 8) ]
3228 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3230 struct tcp_sock
*tp
= tcp_sk(sk
);
3231 struct tcphdr
*th
= tcp_hdr(skb
);
3232 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3233 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3235 return (/* 1. Pure ACK with correct sequence number. */
3236 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3238 /* 2. ... and duplicate ACK. */
3239 ack
== tp
->snd_una
&&
3241 /* 3. ... and does not update window. */
3242 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3244 /* 4. ... and sits in replay window. */
3245 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3248 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
3250 const struct tcp_sock
*tp
= tcp_sk(sk
);
3251 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3252 get_seconds() < tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3253 !tcp_disordered_ack(sk
, skb
));
3256 /* Check segment sequence number for validity.
3258 * Segment controls are considered valid, if the segment
3259 * fits to the window after truncation to the window. Acceptability
3260 * of data (and SYN, FIN, of course) is checked separately.
3261 * See tcp_data_queue(), for example.
3263 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3264 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3265 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3266 * (borrowed from freebsd)
3269 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3271 return !before(end_seq
, tp
->rcv_wup
) &&
3272 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3275 /* When we get a reset we do this. */
3276 static void tcp_reset(struct sock
*sk
)
3278 /* We want the right error as BSD sees it (and indeed as we do). */
3279 switch (sk
->sk_state
) {
3281 sk
->sk_err
= ECONNREFUSED
;
3283 case TCP_CLOSE_WAIT
:
3289 sk
->sk_err
= ECONNRESET
;
3292 if (!sock_flag(sk
, SOCK_DEAD
))
3293 sk
->sk_error_report(sk
);
3299 * Process the FIN bit. This now behaves as it is supposed to work
3300 * and the FIN takes effect when it is validly part of sequence
3301 * space. Not before when we get holes.
3303 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3304 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3307 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3308 * close and we go into CLOSING (and later onto TIME-WAIT)
3310 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3312 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3314 struct tcp_sock
*tp
= tcp_sk(sk
);
3316 inet_csk_schedule_ack(sk
);
3318 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3319 sock_set_flag(sk
, SOCK_DONE
);
3321 switch (sk
->sk_state
) {
3323 case TCP_ESTABLISHED
:
3324 /* Move to CLOSE_WAIT */
3325 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3326 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3329 case TCP_CLOSE_WAIT
:
3331 /* Received a retransmission of the FIN, do
3336 /* RFC793: Remain in the LAST-ACK state. */
3340 /* This case occurs when a simultaneous close
3341 * happens, we must ack the received FIN and
3342 * enter the CLOSING state.
3345 tcp_set_state(sk
, TCP_CLOSING
);
3348 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3350 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3353 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3354 * cases we should never reach this piece of code.
3356 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3357 __FUNCTION__
, sk
->sk_state
);
3361 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3362 * Probably, we should reset in this case. For now drop them.
3364 __skb_queue_purge(&tp
->out_of_order_queue
);
3365 if (tcp_is_sack(tp
))
3366 tcp_sack_reset(&tp
->rx_opt
);
3367 sk_stream_mem_reclaim(sk
);
3369 if (!sock_flag(sk
, SOCK_DEAD
)) {
3370 sk
->sk_state_change(sk
);
3372 /* Do not send POLL_HUP for half duplex close. */
3373 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3374 sk
->sk_state
== TCP_CLOSE
)
3375 sk_wake_async(sk
, 1, POLL_HUP
);
3377 sk_wake_async(sk
, 1, POLL_IN
);
3381 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
3383 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3384 if (before(seq
, sp
->start_seq
))
3385 sp
->start_seq
= seq
;
3386 if (after(end_seq
, sp
->end_seq
))
3387 sp
->end_seq
= end_seq
;
3393 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3395 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3396 if (before(seq
, tp
->rcv_nxt
))
3397 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
3399 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
3401 tp
->rx_opt
.dsack
= 1;
3402 tp
->duplicate_sack
[0].start_seq
= seq
;
3403 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3404 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
3408 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3410 if (!tp
->rx_opt
.dsack
)
3411 tcp_dsack_set(tp
, seq
, end_seq
);
3413 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3416 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3418 struct tcp_sock
*tp
= tcp_sk(sk
);
3420 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3421 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3422 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3423 tcp_enter_quickack_mode(sk
);
3425 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3426 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3428 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3429 end_seq
= tp
->rcv_nxt
;
3430 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3437 /* These routines update the SACK block as out-of-order packets arrive or
3438 * in-order packets close up the sequence space.
3440 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3443 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3444 struct tcp_sack_block
*swalk
= sp
+1;
3446 /* See if the recent change to the first SACK eats into
3447 * or hits the sequence space of other SACK blocks, if so coalesce.
3449 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
3450 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3453 /* Zap SWALK, by moving every further SACK up by one slot.
3454 * Decrease num_sacks.
3456 tp
->rx_opt
.num_sacks
--;
3457 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3458 for (i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3462 this_sack
++, swalk
++;
3466 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
3470 tmp
= sack1
->start_seq
;
3471 sack1
->start_seq
= sack2
->start_seq
;
3472 sack2
->start_seq
= tmp
;
3474 tmp
= sack1
->end_seq
;
3475 sack1
->end_seq
= sack2
->end_seq
;
3476 sack2
->end_seq
= tmp
;
3479 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3481 struct tcp_sock
*tp
= tcp_sk(sk
);
3482 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3483 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3489 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
3490 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3491 /* Rotate this_sack to the first one. */
3492 for (; this_sack
>0; this_sack
--, sp
--)
3493 tcp_sack_swap(sp
, sp
-1);
3495 tcp_sack_maybe_coalesce(tp
);
3500 /* Could not find an adjacent existing SACK, build a new one,
3501 * put it at the front, and shift everyone else down. We
3502 * always know there is at least one SACK present already here.
3504 * If the sack array is full, forget about the last one.
3506 if (this_sack
>= 4) {
3508 tp
->rx_opt
.num_sacks
--;
3511 for (; this_sack
> 0; this_sack
--, sp
--)
3515 /* Build the new head SACK, and we're done. */
3516 sp
->start_seq
= seq
;
3517 sp
->end_seq
= end_seq
;
3518 tp
->rx_opt
.num_sacks
++;
3519 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3522 /* RCV.NXT advances, some SACKs should be eaten. */
3524 static void tcp_sack_remove(struct tcp_sock
*tp
)
3526 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3527 int num_sacks
= tp
->rx_opt
.num_sacks
;
3530 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3531 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3532 tp
->rx_opt
.num_sacks
= 0;
3533 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3537 for (this_sack
= 0; this_sack
< num_sacks
; ) {
3538 /* Check if the start of the sack is covered by RCV.NXT. */
3539 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3542 /* RCV.NXT must cover all the block! */
3543 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3545 /* Zap this SACK, by moving forward any other SACKS. */
3546 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3547 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3554 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3555 tp
->rx_opt
.num_sacks
= num_sacks
;
3556 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3560 /* This one checks to see if we can put data from the
3561 * out_of_order queue into the receive_queue.
3563 static void tcp_ofo_queue(struct sock
*sk
)
3565 struct tcp_sock
*tp
= tcp_sk(sk
);
3566 __u32 dsack_high
= tp
->rcv_nxt
;
3567 struct sk_buff
*skb
;
3569 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3570 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3573 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3574 __u32 dsack
= dsack_high
;
3575 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3576 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3577 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3580 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3581 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3582 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3586 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3587 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3588 TCP_SKB_CB(skb
)->end_seq
);
3590 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3591 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3592 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3593 if (tcp_hdr(skb
)->fin
)
3594 tcp_fin(skb
, sk
, tcp_hdr(skb
));
3598 static int tcp_prune_queue(struct sock
*sk
);
3600 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3602 struct tcphdr
*th
= tcp_hdr(skb
);
3603 struct tcp_sock
*tp
= tcp_sk(sk
);
3606 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3609 __skb_pull(skb
, th
->doff
*4);
3611 TCP_ECN_accept_cwr(tp
, skb
);
3613 if (tp
->rx_opt
.dsack
) {
3614 tp
->rx_opt
.dsack
= 0;
3615 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3616 4 - tp
->rx_opt
.tstamp_ok
);
3619 /* Queue data for delivery to the user.
3620 * Packets in sequence go to the receive queue.
3621 * Out of sequence packets to the out_of_order_queue.
3623 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3624 if (tcp_receive_window(tp
) == 0)
3627 /* Ok. In sequence. In window. */
3628 if (tp
->ucopy
.task
== current
&&
3629 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3630 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3631 int chunk
= min_t(unsigned int, skb
->len
,
3634 __set_current_state(TASK_RUNNING
);
3637 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3638 tp
->ucopy
.len
-= chunk
;
3639 tp
->copied_seq
+= chunk
;
3640 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3641 tcp_rcv_space_adjust(sk
);
3649 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3650 !sk_stream_rmem_schedule(sk
, skb
))) {
3651 if (tcp_prune_queue(sk
) < 0 ||
3652 !sk_stream_rmem_schedule(sk
, skb
))
3655 sk_stream_set_owner_r(skb
, sk
);
3656 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3658 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3660 tcp_event_data_recv(sk
, skb
);
3662 tcp_fin(skb
, sk
, th
);
3664 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3667 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3668 * gap in queue is filled.
3670 if (skb_queue_empty(&tp
->out_of_order_queue
))
3671 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3674 if (tp
->rx_opt
.num_sacks
)
3675 tcp_sack_remove(tp
);
3677 tcp_fast_path_check(sk
);
3681 else if (!sock_flag(sk
, SOCK_DEAD
))
3682 sk
->sk_data_ready(sk
, 0);
3686 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3687 /* A retransmit, 2nd most common case. Force an immediate ack. */
3688 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3689 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3692 tcp_enter_quickack_mode(sk
);
3693 inet_csk_schedule_ack(sk
);
3699 /* Out of window. F.e. zero window probe. */
3700 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3703 tcp_enter_quickack_mode(sk
);
3705 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3706 /* Partial packet, seq < rcv_next < end_seq */
3707 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3708 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3709 TCP_SKB_CB(skb
)->end_seq
);
3711 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3713 /* If window is closed, drop tail of packet. But after
3714 * remembering D-SACK for its head made in previous line.
3716 if (!tcp_receive_window(tp
))
3721 TCP_ECN_check_ce(tp
, skb
);
3723 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3724 !sk_stream_rmem_schedule(sk
, skb
)) {
3725 if (tcp_prune_queue(sk
) < 0 ||
3726 !sk_stream_rmem_schedule(sk
, skb
))
3730 /* Disable header prediction. */
3732 inet_csk_schedule_ack(sk
);
3734 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3735 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3737 sk_stream_set_owner_r(skb
, sk
);
3739 if (!skb_peek(&tp
->out_of_order_queue
)) {
3740 /* Initial out of order segment, build 1 SACK. */
3741 if (tcp_is_sack(tp
)) {
3742 tp
->rx_opt
.num_sacks
= 1;
3743 tp
->rx_opt
.dsack
= 0;
3744 tp
->rx_opt
.eff_sacks
= 1;
3745 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3746 tp
->selective_acks
[0].end_seq
=
3747 TCP_SKB_CB(skb
)->end_seq
;
3749 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3751 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3752 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3753 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3755 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3756 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3758 if (!tp
->rx_opt
.num_sacks
||
3759 tp
->selective_acks
[0].end_seq
!= seq
)
3762 /* Common case: data arrive in order after hole. */
3763 tp
->selective_acks
[0].end_seq
= end_seq
;
3767 /* Find place to insert this segment. */
3769 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3771 } while ((skb1
= skb1
->prev
) !=
3772 (struct sk_buff
*)&tp
->out_of_order_queue
);
3774 /* Do skb overlap to previous one? */
3775 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3776 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3777 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3778 /* All the bits are present. Drop. */
3780 tcp_dsack_set(tp
, seq
, end_seq
);
3783 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3784 /* Partial overlap. */
3785 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3790 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3792 /* And clean segments covered by new one as whole. */
3793 while ((skb1
= skb
->next
) !=
3794 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3795 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3796 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3797 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3800 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3801 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3806 if (tcp_is_sack(tp
))
3807 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3811 /* Collapse contiguous sequence of skbs head..tail with
3812 * sequence numbers start..end.
3813 * Segments with FIN/SYN are not collapsed (only because this
3817 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3818 struct sk_buff
*head
, struct sk_buff
*tail
,
3821 struct sk_buff
*skb
;
3823 /* First, check that queue is collapsible and find
3824 * the point where collapsing can be useful. */
3825 for (skb
= head
; skb
!= tail
; ) {
3826 /* No new bits? It is possible on ofo queue. */
3827 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3828 struct sk_buff
*next
= skb
->next
;
3829 __skb_unlink(skb
, list
);
3831 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3836 /* The first skb to collapse is:
3838 * - bloated or contains data before "start" or
3839 * overlaps to the next one.
3841 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
3842 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3843 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3844 (skb
->next
!= tail
&&
3845 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3848 /* Decided to skip this, advance start seq. */
3849 start
= TCP_SKB_CB(skb
)->end_seq
;
3852 if (skb
== tail
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
3855 while (before(start
, end
)) {
3856 struct sk_buff
*nskb
;
3857 int header
= skb_headroom(skb
);
3858 int copy
= SKB_MAX_ORDER(header
, 0);
3860 /* Too big header? This can happen with IPv6. */
3863 if (end
-start
< copy
)
3865 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3869 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
3870 skb_set_network_header(nskb
, (skb_network_header(skb
) -
3872 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
3874 skb_reserve(nskb
, header
);
3875 memcpy(nskb
->head
, skb
->head
, header
);
3876 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3877 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3878 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3879 sk_stream_set_owner_r(nskb
, sk
);
3881 /* Copy data, releasing collapsed skbs. */
3883 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3884 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3888 size
= min(copy
, size
);
3889 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3891 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3895 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3896 struct sk_buff
*next
= skb
->next
;
3897 __skb_unlink(skb
, list
);
3899 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3902 tcp_hdr(skb
)->syn
||
3910 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3911 * and tcp_collapse() them until all the queue is collapsed.
3913 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3915 struct tcp_sock
*tp
= tcp_sk(sk
);
3916 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3917 struct sk_buff
*head
;
3923 start
= TCP_SKB_CB(skb
)->seq
;
3924 end
= TCP_SKB_CB(skb
)->end_seq
;
3930 /* Segment is terminated when we see gap or when
3931 * we are at the end of all the queue. */
3932 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3933 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3934 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3935 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3936 head
, skb
, start
, end
);
3938 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3940 /* Start new segment */
3941 start
= TCP_SKB_CB(skb
)->seq
;
3942 end
= TCP_SKB_CB(skb
)->end_seq
;
3944 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3945 start
= TCP_SKB_CB(skb
)->seq
;
3946 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3947 end
= TCP_SKB_CB(skb
)->end_seq
;
3952 /* Reduce allocated memory if we can, trying to get
3953 * the socket within its memory limits again.
3955 * Return less than zero if we should start dropping frames
3956 * until the socket owning process reads some of the data
3957 * to stabilize the situation.
3959 static int tcp_prune_queue(struct sock
*sk
)
3961 struct tcp_sock
*tp
= tcp_sk(sk
);
3963 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3965 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3967 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3968 tcp_clamp_window(sk
);
3969 else if (tcp_memory_pressure
)
3970 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3972 tcp_collapse_ofo_queue(sk
);
3973 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3974 sk
->sk_receive_queue
.next
,
3975 (struct sk_buff
*)&sk
->sk_receive_queue
,
3976 tp
->copied_seq
, tp
->rcv_nxt
);
3977 sk_stream_mem_reclaim(sk
);
3979 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3982 /* Collapsing did not help, destructive actions follow.
3983 * This must not ever occur. */
3985 /* First, purge the out_of_order queue. */
3986 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3987 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3988 __skb_queue_purge(&tp
->out_of_order_queue
);
3990 /* Reset SACK state. A conforming SACK implementation will
3991 * do the same at a timeout based retransmit. When a connection
3992 * is in a sad state like this, we care only about integrity
3993 * of the connection not performance.
3995 if (tcp_is_sack(tp
))
3996 tcp_sack_reset(&tp
->rx_opt
);
3997 sk_stream_mem_reclaim(sk
);
4000 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4003 /* If we are really being abused, tell the caller to silently
4004 * drop receive data on the floor. It will get retransmitted
4005 * and hopefully then we'll have sufficient space.
4007 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
4009 /* Massive buffer overcommit. */
4015 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4016 * As additional protections, we do not touch cwnd in retransmission phases,
4017 * and if application hit its sndbuf limit recently.
4019 void tcp_cwnd_application_limited(struct sock
*sk
)
4021 struct tcp_sock
*tp
= tcp_sk(sk
);
4023 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4024 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4025 /* Limited by application or receiver window. */
4026 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4027 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4028 if (win_used
< tp
->snd_cwnd
) {
4029 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4030 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4032 tp
->snd_cwnd_used
= 0;
4034 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4037 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4039 struct tcp_sock
*tp
= tcp_sk(sk
);
4041 /* If the user specified a specific send buffer setting, do
4044 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4047 /* If we are under global TCP memory pressure, do not expand. */
4048 if (tcp_memory_pressure
)
4051 /* If we are under soft global TCP memory pressure, do not expand. */
4052 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4055 /* If we filled the congestion window, do not expand. */
4056 if (tp
->packets_out
>= tp
->snd_cwnd
)
4062 /* When incoming ACK allowed to free some skb from write_queue,
4063 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4064 * on the exit from tcp input handler.
4066 * PROBLEM: sndbuf expansion does not work well with largesend.
4068 static void tcp_new_space(struct sock
*sk
)
4070 struct tcp_sock
*tp
= tcp_sk(sk
);
4072 if (tcp_should_expand_sndbuf(sk
)) {
4073 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
4074 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
4075 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4076 tp
->reordering
+ 1);
4077 sndmem
*= 2*demanded
;
4078 if (sndmem
> sk
->sk_sndbuf
)
4079 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4080 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4083 sk
->sk_write_space(sk
);
4086 static void tcp_check_space(struct sock
*sk
)
4088 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4089 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4090 if (sk
->sk_socket
&&
4091 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4096 static inline void tcp_data_snd_check(struct sock
*sk
)
4098 tcp_push_pending_frames(sk
);
4099 tcp_check_space(sk
);
4103 * Check if sending an ack is needed.
4105 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4107 struct tcp_sock
*tp
= tcp_sk(sk
);
4109 /* More than one full frame received... */
4110 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
4111 /* ... and right edge of window advances far enough.
4112 * (tcp_recvmsg() will send ACK otherwise). Or...
4114 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4115 /* We ACK each frame or... */
4116 tcp_in_quickack_mode(sk
) ||
4117 /* We have out of order data. */
4119 skb_peek(&tp
->out_of_order_queue
))) {
4120 /* Then ack it now */
4123 /* Else, send delayed ack. */
4124 tcp_send_delayed_ack(sk
);
4128 static inline void tcp_ack_snd_check(struct sock
*sk
)
4130 if (!inet_csk_ack_scheduled(sk
)) {
4131 /* We sent a data segment already. */
4134 __tcp_ack_snd_check(sk
, 1);
4138 * This routine is only called when we have urgent data
4139 * signaled. Its the 'slow' part of tcp_urg. It could be
4140 * moved inline now as tcp_urg is only called from one
4141 * place. We handle URGent data wrong. We have to - as
4142 * BSD still doesn't use the correction from RFC961.
4143 * For 1003.1g we should support a new option TCP_STDURG to permit
4144 * either form (or just set the sysctl tcp_stdurg).
4147 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
4149 struct tcp_sock
*tp
= tcp_sk(sk
);
4150 u32 ptr
= ntohs(th
->urg_ptr
);
4152 if (ptr
&& !sysctl_tcp_stdurg
)
4154 ptr
+= ntohl(th
->seq
);
4156 /* Ignore urgent data that we've already seen and read. */
4157 if (after(tp
->copied_seq
, ptr
))
4160 /* Do not replay urg ptr.
4162 * NOTE: interesting situation not covered by specs.
4163 * Misbehaving sender may send urg ptr, pointing to segment,
4164 * which we already have in ofo queue. We are not able to fetch
4165 * such data and will stay in TCP_URG_NOTYET until will be eaten
4166 * by recvmsg(). Seems, we are not obliged to handle such wicked
4167 * situations. But it is worth to think about possibility of some
4168 * DoSes using some hypothetical application level deadlock.
4170 if (before(ptr
, tp
->rcv_nxt
))
4173 /* Do we already have a newer (or duplicate) urgent pointer? */
4174 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4177 /* Tell the world about our new urgent pointer. */
4180 /* We may be adding urgent data when the last byte read was
4181 * urgent. To do this requires some care. We cannot just ignore
4182 * tp->copied_seq since we would read the last urgent byte again
4183 * as data, nor can we alter copied_seq until this data arrives
4184 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4186 * NOTE. Double Dutch. Rendering to plain English: author of comment
4187 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4188 * and expect that both A and B disappear from stream. This is _wrong_.
4189 * Though this happens in BSD with high probability, this is occasional.
4190 * Any application relying on this is buggy. Note also, that fix "works"
4191 * only in this artificial test. Insert some normal data between A and B and we will
4192 * decline of BSD again. Verdict: it is better to remove to trap
4195 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4196 !sock_flag(sk
, SOCK_URGINLINE
) &&
4197 tp
->copied_seq
!= tp
->rcv_nxt
) {
4198 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4200 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4201 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4206 tp
->urg_data
= TCP_URG_NOTYET
;
4209 /* Disable header prediction. */
4213 /* This is the 'fast' part of urgent handling. */
4214 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
4216 struct tcp_sock
*tp
= tcp_sk(sk
);
4218 /* Check if we get a new urgent pointer - normally not. */
4220 tcp_check_urg(sk
,th
);
4222 /* Do we wait for any urgent data? - normally not... */
4223 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4224 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4227 /* Is the urgent pointer pointing into this packet? */
4228 if (ptr
< skb
->len
) {
4230 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4232 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4233 if (!sock_flag(sk
, SOCK_DEAD
))
4234 sk
->sk_data_ready(sk
, 0);
4239 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4241 struct tcp_sock
*tp
= tcp_sk(sk
);
4242 int chunk
= skb
->len
- hlen
;
4246 if (skb_csum_unnecessary(skb
))
4247 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4249 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4253 tp
->ucopy
.len
-= chunk
;
4254 tp
->copied_seq
+= chunk
;
4255 tcp_rcv_space_adjust(sk
);
4262 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4266 if (sock_owned_by_user(sk
)) {
4268 result
= __tcp_checksum_complete(skb
);
4271 result
= __tcp_checksum_complete(skb
);
4276 static inline int tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4278 return !skb_csum_unnecessary(skb
) &&
4279 __tcp_checksum_complete_user(sk
, skb
);
4282 #ifdef CONFIG_NET_DMA
4283 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4285 struct tcp_sock
*tp
= tcp_sk(sk
);
4286 int chunk
= skb
->len
- hlen
;
4288 int copied_early
= 0;
4290 if (tp
->ucopy
.wakeup
)
4293 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4294 tp
->ucopy
.dma_chan
= get_softnet_dma();
4296 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4298 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4299 skb
, hlen
, tp
->ucopy
.iov
, chunk
, tp
->ucopy
.pinned_list
);
4304 tp
->ucopy
.dma_cookie
= dma_cookie
;
4307 tp
->ucopy
.len
-= chunk
;
4308 tp
->copied_seq
+= chunk
;
4309 tcp_rcv_space_adjust(sk
);
4311 if ((tp
->ucopy
.len
== 0) ||
4312 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
4313 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4314 tp
->ucopy
.wakeup
= 1;
4315 sk
->sk_data_ready(sk
, 0);
4317 } else if (chunk
> 0) {
4318 tp
->ucopy
.wakeup
= 1;
4319 sk
->sk_data_ready(sk
, 0);
4322 return copied_early
;
4324 #endif /* CONFIG_NET_DMA */
4327 * TCP receive function for the ESTABLISHED state.
4329 * It is split into a fast path and a slow path. The fast path is
4331 * - A zero window was announced from us - zero window probing
4332 * is only handled properly in the slow path.
4333 * - Out of order segments arrived.
4334 * - Urgent data is expected.
4335 * - There is no buffer space left
4336 * - Unexpected TCP flags/window values/header lengths are received
4337 * (detected by checking the TCP header against pred_flags)
4338 * - Data is sent in both directions. Fast path only supports pure senders
4339 * or pure receivers (this means either the sequence number or the ack
4340 * value must stay constant)
4341 * - Unexpected TCP option.
4343 * When these conditions are not satisfied it drops into a standard
4344 * receive procedure patterned after RFC793 to handle all cases.
4345 * The first three cases are guaranteed by proper pred_flags setting,
4346 * the rest is checked inline. Fast processing is turned on in
4347 * tcp_data_queue when everything is OK.
4349 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4350 struct tcphdr
*th
, unsigned len
)
4352 struct tcp_sock
*tp
= tcp_sk(sk
);
4355 * Header prediction.
4356 * The code loosely follows the one in the famous
4357 * "30 instruction TCP receive" Van Jacobson mail.
4359 * Van's trick is to deposit buffers into socket queue
4360 * on a device interrupt, to call tcp_recv function
4361 * on the receive process context and checksum and copy
4362 * the buffer to user space. smart...
4364 * Our current scheme is not silly either but we take the
4365 * extra cost of the net_bh soft interrupt processing...
4366 * We do checksum and copy also but from device to kernel.
4369 tp
->rx_opt
.saw_tstamp
= 0;
4371 /* pred_flags is 0xS?10 << 16 + snd_wnd
4372 * if header_prediction is to be made
4373 * 'S' will always be tp->tcp_header_len >> 2
4374 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4375 * turn it off (when there are holes in the receive
4376 * space for instance)
4377 * PSH flag is ignored.
4380 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4381 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4382 int tcp_header_len
= tp
->tcp_header_len
;
4384 /* Timestamp header prediction: tcp_header_len
4385 * is automatically equal to th->doff*4 due to pred_flags
4389 /* Check timestamp */
4390 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4391 __be32
*ptr
= (__be32
*)(th
+ 1);
4393 /* No? Slow path! */
4394 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4395 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4398 tp
->rx_opt
.saw_tstamp
= 1;
4400 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4402 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4404 /* If PAWS failed, check it more carefully in slow path */
4405 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4408 /* DO NOT update ts_recent here, if checksum fails
4409 * and timestamp was corrupted part, it will result
4410 * in a hung connection since we will drop all
4411 * future packets due to the PAWS test.
4415 if (len
<= tcp_header_len
) {
4416 /* Bulk data transfer: sender */
4417 if (len
== tcp_header_len
) {
4418 /* Predicted packet is in window by definition.
4419 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4420 * Hence, check seq<=rcv_wup reduces to:
4422 if (tcp_header_len
==
4423 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4424 tp
->rcv_nxt
== tp
->rcv_wup
)
4425 tcp_store_ts_recent(tp
);
4427 /* We know that such packets are checksummed
4430 tcp_ack(sk
, skb
, 0);
4432 tcp_data_snd_check(sk
);
4434 } else { /* Header too small */
4435 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4440 int copied_early
= 0;
4442 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4443 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4444 #ifdef CONFIG_NET_DMA
4445 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4450 if (tp
->ucopy
.task
== current
&& sock_owned_by_user(sk
) && !copied_early
) {
4451 __set_current_state(TASK_RUNNING
);
4453 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4457 /* Predicted packet is in window by definition.
4458 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4459 * Hence, check seq<=rcv_wup reduces to:
4461 if (tcp_header_len
==
4462 (sizeof(struct tcphdr
) +
4463 TCPOLEN_TSTAMP_ALIGNED
) &&
4464 tp
->rcv_nxt
== tp
->rcv_wup
)
4465 tcp_store_ts_recent(tp
);
4467 tcp_rcv_rtt_measure_ts(sk
, skb
);
4469 __skb_pull(skb
, tcp_header_len
);
4470 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4471 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4474 tcp_cleanup_rbuf(sk
, skb
->len
);
4477 if (tcp_checksum_complete_user(sk
, skb
))
4480 /* Predicted packet is in window by definition.
4481 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4482 * Hence, check seq<=rcv_wup reduces to:
4484 if (tcp_header_len
==
4485 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4486 tp
->rcv_nxt
== tp
->rcv_wup
)
4487 tcp_store_ts_recent(tp
);
4489 tcp_rcv_rtt_measure_ts(sk
, skb
);
4491 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4494 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4496 /* Bulk data transfer: receiver */
4497 __skb_pull(skb
,tcp_header_len
);
4498 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4499 sk_stream_set_owner_r(skb
, sk
);
4500 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4503 tcp_event_data_recv(sk
, skb
);
4505 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4506 /* Well, only one small jumplet in fast path... */
4507 tcp_ack(sk
, skb
, FLAG_DATA
);
4508 tcp_data_snd_check(sk
);
4509 if (!inet_csk_ack_scheduled(sk
))
4513 __tcp_ack_snd_check(sk
, 0);
4515 #ifdef CONFIG_NET_DMA
4517 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4523 sk
->sk_data_ready(sk
, 0);
4529 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
4533 * RFC1323: H1. Apply PAWS check first.
4535 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4536 tcp_paws_discard(sk
, skb
)) {
4538 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4539 tcp_send_dupack(sk
, skb
);
4542 /* Resets are accepted even if PAWS failed.
4544 ts_recent update must be made after we are sure
4545 that the packet is in window.
4550 * Standard slow path.
4553 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4554 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4555 * (RST) segments are validated by checking their SEQ-fields."
4556 * And page 69: "If an incoming segment is not acceptable,
4557 * an acknowledgment should be sent in reply (unless the RST bit
4558 * is set, if so drop the segment and return)".
4561 tcp_send_dupack(sk
, skb
);
4570 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4572 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4573 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4574 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4581 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4583 tcp_rcv_rtt_measure_ts(sk
, skb
);
4585 /* Process urgent data. */
4586 tcp_urg(sk
, skb
, th
);
4588 /* step 7: process the segment text */
4589 tcp_data_queue(sk
, skb
);
4591 tcp_data_snd_check(sk
);
4592 tcp_ack_snd_check(sk
);
4596 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4603 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4604 struct tcphdr
*th
, unsigned len
)
4606 struct tcp_sock
*tp
= tcp_sk(sk
);
4607 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4608 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4610 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4614 * "If the state is SYN-SENT then
4615 * first check the ACK bit
4616 * If the ACK bit is set
4617 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4618 * a reset (unless the RST bit is set, if so drop
4619 * the segment and return)"
4621 * We do not send data with SYN, so that RFC-correct
4624 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4625 goto reset_and_undo
;
4627 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4628 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4630 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4631 goto reset_and_undo
;
4634 /* Now ACK is acceptable.
4636 * "If the RST bit is set
4637 * If the ACK was acceptable then signal the user "error:
4638 * connection reset", drop the segment, enter CLOSED state,
4639 * delete TCB, and return."
4648 * "fifth, if neither of the SYN or RST bits is set then
4649 * drop the segment and return."
4655 goto discard_and_undo
;
4658 * "If the SYN bit is on ...
4659 * are acceptable then ...
4660 * (our SYN has been ACKed), change the connection
4661 * state to ESTABLISHED..."
4664 TCP_ECN_rcv_synack(tp
, th
);
4666 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4667 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4669 /* Ok.. it's good. Set up sequence numbers and
4670 * move to established.
4672 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4673 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4675 /* RFC1323: The window in SYN & SYN/ACK segments is
4678 tp
->snd_wnd
= ntohs(th
->window
);
4679 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4681 if (!tp
->rx_opt
.wscale_ok
) {
4682 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4683 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4686 if (tp
->rx_opt
.saw_tstamp
) {
4687 tp
->rx_opt
.tstamp_ok
= 1;
4688 tp
->tcp_header_len
=
4689 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4690 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4691 tcp_store_ts_recent(tp
);
4693 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4696 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
4697 tcp_enable_fack(tp
);
4700 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4701 tcp_initialize_rcv_mss(sk
);
4703 /* Remember, tcp_poll() does not lock socket!
4704 * Change state from SYN-SENT only after copied_seq
4705 * is initialized. */
4706 tp
->copied_seq
= tp
->rcv_nxt
;
4708 tcp_set_state(sk
, TCP_ESTABLISHED
);
4710 security_inet_conn_established(sk
, skb
);
4712 /* Make sure socket is routed, for correct metrics. */
4713 icsk
->icsk_af_ops
->rebuild_header(sk
);
4715 tcp_init_metrics(sk
);
4717 tcp_init_congestion_control(sk
);
4719 /* Prevent spurious tcp_cwnd_restart() on first data
4722 tp
->lsndtime
= tcp_time_stamp
;
4724 tcp_init_buffer_space(sk
);
4726 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4727 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4729 if (!tp
->rx_opt
.snd_wscale
)
4730 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4734 if (!sock_flag(sk
, SOCK_DEAD
)) {
4735 sk
->sk_state_change(sk
);
4736 sk_wake_async(sk
, 0, POLL_OUT
);
4739 if (sk
->sk_write_pending
||
4740 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4741 icsk
->icsk_ack
.pingpong
) {
4742 /* Save one ACK. Data will be ready after
4743 * several ticks, if write_pending is set.
4745 * It may be deleted, but with this feature tcpdumps
4746 * look so _wonderfully_ clever, that I was not able
4747 * to stand against the temptation 8) --ANK
4749 inet_csk_schedule_ack(sk
);
4750 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4751 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4752 tcp_incr_quickack(sk
);
4753 tcp_enter_quickack_mode(sk
);
4754 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4755 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4766 /* No ACK in the segment */
4770 * "If the RST bit is set
4772 * Otherwise (no ACK) drop the segment and return."
4775 goto discard_and_undo
;
4779 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4780 goto discard_and_undo
;
4783 /* We see SYN without ACK. It is attempt of
4784 * simultaneous connect with crossed SYNs.
4785 * Particularly, it can be connect to self.
4787 tcp_set_state(sk
, TCP_SYN_RECV
);
4789 if (tp
->rx_opt
.saw_tstamp
) {
4790 tp
->rx_opt
.tstamp_ok
= 1;
4791 tcp_store_ts_recent(tp
);
4792 tp
->tcp_header_len
=
4793 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4795 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4798 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4799 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4801 /* RFC1323: The window in SYN & SYN/ACK segments is
4804 tp
->snd_wnd
= ntohs(th
->window
);
4805 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4806 tp
->max_window
= tp
->snd_wnd
;
4808 TCP_ECN_rcv_syn(tp
, th
);
4811 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4812 tcp_initialize_rcv_mss(sk
);
4815 tcp_send_synack(sk
);
4817 /* Note, we could accept data and URG from this segment.
4818 * There are no obstacles to make this.
4820 * However, if we ignore data in ACKless segments sometimes,
4821 * we have no reasons to accept it sometimes.
4822 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4823 * is not flawless. So, discard packet for sanity.
4824 * Uncomment this return to process the data.
4831 /* "fifth, if neither of the SYN or RST bits is set then
4832 * drop the segment and return."
4836 tcp_clear_options(&tp
->rx_opt
);
4837 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4841 tcp_clear_options(&tp
->rx_opt
);
4842 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4848 * This function implements the receiving procedure of RFC 793 for
4849 * all states except ESTABLISHED and TIME_WAIT.
4850 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4851 * address independent.
4854 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4855 struct tcphdr
*th
, unsigned len
)
4857 struct tcp_sock
*tp
= tcp_sk(sk
);
4858 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4861 tp
->rx_opt
.saw_tstamp
= 0;
4863 switch (sk
->sk_state
) {
4875 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
4878 /* Now we have several options: In theory there is
4879 * nothing else in the frame. KA9Q has an option to
4880 * send data with the syn, BSD accepts data with the
4881 * syn up to the [to be] advertised window and
4882 * Solaris 2.1 gives you a protocol error. For now
4883 * we just ignore it, that fits the spec precisely
4884 * and avoids incompatibilities. It would be nice in
4885 * future to drop through and process the data.
4887 * Now that TTCP is starting to be used we ought to
4889 * But, this leaves one open to an easy denial of
4890 * service attack, and SYN cookies can't defend
4891 * against this problem. So, we drop the data
4892 * in the interest of security over speed unless
4893 * it's still in use.
4901 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4905 /* Do step6 onward by hand. */
4906 tcp_urg(sk
, skb
, th
);
4908 tcp_data_snd_check(sk
);
4912 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4913 tcp_paws_discard(sk
, skb
)) {
4915 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4916 tcp_send_dupack(sk
, skb
);
4919 /* Reset is accepted even if it did not pass PAWS. */
4922 /* step 1: check sequence number */
4923 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4925 tcp_send_dupack(sk
, skb
);
4929 /* step 2: check RST bit */
4935 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4937 /* step 3: check security and precedence [ignored] */
4941 * Check for a SYN in window.
4943 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4944 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4949 /* step 5: check the ACK field */
4951 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4953 switch (sk
->sk_state
) {
4956 tp
->copied_seq
= tp
->rcv_nxt
;
4958 tcp_set_state(sk
, TCP_ESTABLISHED
);
4959 sk
->sk_state_change(sk
);
4961 /* Note, that this wakeup is only for marginal
4962 * crossed SYN case. Passively open sockets
4963 * are not waked up, because sk->sk_sleep ==
4964 * NULL and sk->sk_socket == NULL.
4966 if (sk
->sk_socket
) {
4967 sk_wake_async(sk
,0,POLL_OUT
);
4970 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4971 tp
->snd_wnd
= ntohs(th
->window
) <<
4972 tp
->rx_opt
.snd_wscale
;
4973 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4974 TCP_SKB_CB(skb
)->seq
);
4976 /* tcp_ack considers this ACK as duplicate
4977 * and does not calculate rtt.
4978 * Fix it at least with timestamps.
4980 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4982 tcp_ack_saw_tstamp(sk
, 0);
4984 if (tp
->rx_opt
.tstamp_ok
)
4985 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4987 /* Make sure socket is routed, for
4990 icsk
->icsk_af_ops
->rebuild_header(sk
);
4992 tcp_init_metrics(sk
);
4994 tcp_init_congestion_control(sk
);
4996 /* Prevent spurious tcp_cwnd_restart() on
4997 * first data packet.
4999 tp
->lsndtime
= tcp_time_stamp
;
5002 tcp_initialize_rcv_mss(sk
);
5003 tcp_init_buffer_space(sk
);
5004 tcp_fast_path_on(tp
);
5011 if (tp
->snd_una
== tp
->write_seq
) {
5012 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5013 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5014 dst_confirm(sk
->sk_dst_cache
);
5016 if (!sock_flag(sk
, SOCK_DEAD
))
5017 /* Wake up lingering close() */
5018 sk
->sk_state_change(sk
);
5022 if (tp
->linger2
< 0 ||
5023 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5024 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5026 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
5030 tmo
= tcp_fin_time(sk
);
5031 if (tmo
> TCP_TIMEWAIT_LEN
) {
5032 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5033 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5034 /* Bad case. We could lose such FIN otherwise.
5035 * It is not a big problem, but it looks confusing
5036 * and not so rare event. We still can lose it now,
5037 * if it spins in bh_lock_sock(), but it is really
5040 inet_csk_reset_keepalive_timer(sk
, tmo
);
5042 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5050 if (tp
->snd_una
== tp
->write_seq
) {
5051 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5057 if (tp
->snd_una
== tp
->write_seq
) {
5058 tcp_update_metrics(sk
);
5067 /* step 6: check the URG bit */
5068 tcp_urg(sk
, skb
, th
);
5070 /* step 7: process the segment text */
5071 switch (sk
->sk_state
) {
5072 case TCP_CLOSE_WAIT
:
5075 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5079 /* RFC 793 says to queue data in these states,
5080 * RFC 1122 says we MUST send a reset.
5081 * BSD 4.4 also does reset.
5083 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5084 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5085 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5086 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
5092 case TCP_ESTABLISHED
:
5093 tcp_data_queue(sk
, skb
);
5098 /* tcp_data could move socket to TIME-WAIT */
5099 if (sk
->sk_state
!= TCP_CLOSE
) {
5100 tcp_data_snd_check(sk
);
5101 tcp_ack_snd_check(sk
);
5111 EXPORT_SYMBOL(sysctl_tcp_ecn
);
5112 EXPORT_SYMBOL(sysctl_tcp_reordering
);
5113 EXPORT_SYMBOL(tcp_parse_options
);
5114 EXPORT_SYMBOL(tcp_rcv_established
);
5115 EXPORT_SYMBOL(tcp_rcv_state_process
);
5116 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);