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).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
23 * Pedro Roque : Fast Retransmit/Recovery.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
56 * J Hadi Salim: ECN support
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
65 #include <linux/slab.h>
66 #include <linux/module.h>
67 #include <linux/sysctl.h>
68 #include <linux/kernel.h>
71 #include <net/inet_common.h>
72 #include <linux/ipsec.h>
73 #include <asm/unaligned.h>
74 #include <net/netdma.h>
76 int sysctl_tcp_timestamps __read_mostly
= 1;
77 int sysctl_tcp_window_scaling __read_mostly
= 1;
78 int sysctl_tcp_sack __read_mostly
= 1;
79 int sysctl_tcp_fack __read_mostly
= 1;
80 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
81 EXPORT_SYMBOL(sysctl_tcp_reordering
);
82 int sysctl_tcp_ecn __read_mostly
= 2;
83 EXPORT_SYMBOL(sysctl_tcp_ecn
);
84 int sysctl_tcp_dsack __read_mostly
= 1;
85 int sysctl_tcp_app_win __read_mostly
= 31;
86 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
87 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
89 int sysctl_tcp_stdurg __read_mostly
;
90 int sysctl_tcp_rfc1337 __read_mostly
;
91 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
92 int sysctl_tcp_frto __read_mostly
= 2;
93 int sysctl_tcp_frto_response __read_mostly
;
94 int sysctl_tcp_nometrics_save __read_mostly
;
96 int sysctl_tcp_thin_dupack __read_mostly
;
98 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
99 int sysctl_tcp_abc __read_mostly
;
101 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
102 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
103 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
104 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
105 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
106 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
107 #define FLAG_ECE 0x40 /* ECE in this ACK */
108 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
109 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
110 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
111 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
112 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
113 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
114 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
116 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
117 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
118 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
119 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
120 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
122 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
123 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
125 /* Adapt the MSS value used to make delayed ack decision to the
128 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
130 struct inet_connection_sock
*icsk
= inet_csk(sk
);
131 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
134 icsk
->icsk_ack
.last_seg_size
= 0;
136 /* skb->len may jitter because of SACKs, even if peer
137 * sends good full-sized frames.
139 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
140 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
141 icsk
->icsk_ack
.rcv_mss
= len
;
143 /* Otherwise, we make more careful check taking into account,
144 * that SACKs block is variable.
146 * "len" is invariant segment length, including TCP header.
148 len
+= skb
->data
- skb_transport_header(skb
);
149 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
150 /* If PSH is not set, packet should be
151 * full sized, provided peer TCP is not badly broken.
152 * This observation (if it is correct 8)) allows
153 * to handle super-low mtu links fairly.
155 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
156 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
157 /* Subtract also invariant (if peer is RFC compliant),
158 * tcp header plus fixed timestamp option length.
159 * Resulting "len" is MSS free of SACK jitter.
161 len
-= tcp_sk(sk
)->tcp_header_len
;
162 icsk
->icsk_ack
.last_seg_size
= len
;
164 icsk
->icsk_ack
.rcv_mss
= len
;
168 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
169 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
170 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
174 static void tcp_incr_quickack(struct sock
*sk
)
176 struct inet_connection_sock
*icsk
= inet_csk(sk
);
177 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
181 if (quickacks
> icsk
->icsk_ack
.quick
)
182 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
185 static void tcp_enter_quickack_mode(struct sock
*sk
)
187 struct inet_connection_sock
*icsk
= inet_csk(sk
);
188 tcp_incr_quickack(sk
);
189 icsk
->icsk_ack
.pingpong
= 0;
190 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
193 /* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
197 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
199 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
200 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
203 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
205 if (tp
->ecn_flags
& TCP_ECN_OK
)
206 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
209 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
211 if (tcp_hdr(skb
)->cwr
)
212 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
215 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
217 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
220 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
222 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
225 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
226 case INET_ECN_NOT_ECT
:
227 /* Funny extension: if ECT is not set on a segment,
228 * and we already seen ECT on a previous segment,
229 * it is probably a retransmit.
231 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
232 tcp_enter_quickack_mode((struct sock
*)tp
);
235 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
238 tp
->ecn_flags
|= TCP_ECN_SEEN
;
242 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, struct tcphdr
*th
)
244 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
245 tp
->ecn_flags
&= ~TCP_ECN_OK
;
248 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
250 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
251 tp
->ecn_flags
&= ~TCP_ECN_OK
;
254 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
256 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
261 /* Buffer size and advertised window tuning.
263 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
266 static void tcp_fixup_sndbuf(struct sock
*sk
)
268 int sndmem
= SKB_TRUESIZE(tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
);
270 if (sk
->sk_sndbuf
< 3 * sndmem
) {
271 sk
->sk_sndbuf
= 3 * sndmem
;
272 if (sk
->sk_sndbuf
> sysctl_tcp_wmem
[2])
273 sk
->sk_sndbuf
= sysctl_tcp_wmem
[2];
277 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
279 * All tcp_full_space() is split to two parts: "network" buffer, allocated
280 * forward and advertised in receiver window (tp->rcv_wnd) and
281 * "application buffer", required to isolate scheduling/application
282 * latencies from network.
283 * window_clamp is maximal advertised window. It can be less than
284 * tcp_full_space(), in this case tcp_full_space() - window_clamp
285 * is reserved for "application" buffer. The less window_clamp is
286 * the smoother our behaviour from viewpoint of network, but the lower
287 * throughput and the higher sensitivity of the connection to losses. 8)
289 * rcv_ssthresh is more strict window_clamp used at "slow start"
290 * phase to predict further behaviour of this connection.
291 * It is used for two goals:
292 * - to enforce header prediction at sender, even when application
293 * requires some significant "application buffer". It is check #1.
294 * - to prevent pruning of receive queue because of misprediction
295 * of receiver window. Check #2.
297 * The scheme does not work when sender sends good segments opening
298 * window and then starts to feed us spaghetti. But it should work
299 * in common situations. Otherwise, we have to rely on queue collapsing.
302 /* Slow part of check#2. */
303 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
305 struct tcp_sock
*tp
= tcp_sk(sk
);
307 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
308 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
310 while (tp
->rcv_ssthresh
<= window
) {
311 if (truesize
<= skb
->len
)
312 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
320 static void tcp_grow_window(struct sock
*sk
, struct sk_buff
*skb
)
322 struct tcp_sock
*tp
= tcp_sk(sk
);
325 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
326 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
327 !tcp_memory_pressure
) {
330 /* Check #2. Increase window, if skb with such overhead
331 * will fit to rcvbuf in future.
333 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
334 incr
= 2 * tp
->advmss
;
336 incr
= __tcp_grow_window(sk
, skb
);
339 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
341 inet_csk(sk
)->icsk_ack
.quick
|= 1;
346 /* 3. Tuning rcvbuf, when connection enters established state. */
348 static void tcp_fixup_rcvbuf(struct sock
*sk
)
350 struct tcp_sock
*tp
= tcp_sk(sk
);
351 int rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
353 /* Try to select rcvbuf so that 4 mss-sized segments
354 * will fit to window and corresponding skbs will fit to our rcvbuf.
355 * (was 3; 4 is minimum to allow fast retransmit to work.)
357 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
359 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
360 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
363 /* 4. Try to fixup all. It is made immediately after connection enters
366 static void tcp_init_buffer_space(struct sock
*sk
)
368 struct tcp_sock
*tp
= tcp_sk(sk
);
371 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
372 tcp_fixup_rcvbuf(sk
);
373 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
374 tcp_fixup_sndbuf(sk
);
376 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
378 maxwin
= tcp_full_space(sk
);
380 if (tp
->window_clamp
>= maxwin
) {
381 tp
->window_clamp
= maxwin
;
383 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
384 tp
->window_clamp
= max(maxwin
-
385 (maxwin
>> sysctl_tcp_app_win
),
389 /* Force reservation of one segment. */
390 if (sysctl_tcp_app_win
&&
391 tp
->window_clamp
> 2 * tp
->advmss
&&
392 tp
->window_clamp
+ tp
->advmss
> maxwin
)
393 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
395 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
396 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
399 /* 5. Recalculate window clamp after socket hit its memory bounds. */
400 static void tcp_clamp_window(struct sock
*sk
)
402 struct tcp_sock
*tp
= tcp_sk(sk
);
403 struct inet_connection_sock
*icsk
= inet_csk(sk
);
405 icsk
->icsk_ack
.quick
= 0;
407 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
408 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
409 !tcp_memory_pressure
&&
410 atomic_long_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
411 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
414 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
415 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
418 /* Initialize RCV_MSS value.
419 * RCV_MSS is an our guess about MSS used by the peer.
420 * We haven't any direct information about the MSS.
421 * It's better to underestimate the RCV_MSS rather than overestimate.
422 * Overestimations make us ACKing less frequently than needed.
423 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
425 void tcp_initialize_rcv_mss(struct sock
*sk
)
427 struct tcp_sock
*tp
= tcp_sk(sk
);
428 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
430 hint
= min(hint
, tp
->rcv_wnd
/ 2);
431 hint
= min(hint
, TCP_MSS_DEFAULT
);
432 hint
= max(hint
, TCP_MIN_MSS
);
434 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
436 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
438 /* Receiver "autotuning" code.
440 * The algorithm for RTT estimation w/o timestamps is based on
441 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
442 * <http://public.lanl.gov/radiant/pubs.html#DRS>
444 * More detail on this code can be found at
445 * <http://staff.psc.edu/jheffner/>,
446 * though this reference is out of date. A new paper
449 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
451 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
457 if (new_sample
!= 0) {
458 /* If we sample in larger samples in the non-timestamp
459 * case, we could grossly overestimate the RTT especially
460 * with chatty applications or bulk transfer apps which
461 * are stalled on filesystem I/O.
463 * Also, since we are only going for a minimum in the
464 * non-timestamp case, we do not smooth things out
465 * else with timestamps disabled convergence takes too
469 m
-= (new_sample
>> 3);
471 } else if (m
< new_sample
)
474 /* No previous measure. */
478 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
479 tp
->rcv_rtt_est
.rtt
= new_sample
;
482 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
484 if (tp
->rcv_rtt_est
.time
== 0)
486 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
488 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
491 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
492 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
495 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
496 const struct sk_buff
*skb
)
498 struct tcp_sock
*tp
= tcp_sk(sk
);
499 if (tp
->rx_opt
.rcv_tsecr
&&
500 (TCP_SKB_CB(skb
)->end_seq
-
501 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
502 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
506 * This function should be called every time data is copied to user space.
507 * It calculates the appropriate TCP receive buffer space.
509 void tcp_rcv_space_adjust(struct sock
*sk
)
511 struct tcp_sock
*tp
= tcp_sk(sk
);
515 if (tp
->rcvq_space
.time
== 0)
518 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
519 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
522 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
524 space
= max(tp
->rcvq_space
.space
, space
);
526 if (tp
->rcvq_space
.space
!= space
) {
529 tp
->rcvq_space
.space
= space
;
531 if (sysctl_tcp_moderate_rcvbuf
&&
532 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
533 int new_clamp
= space
;
535 /* Receive space grows, normalize in order to
536 * take into account packet headers and sk_buff
537 * structure overhead.
542 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
543 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
546 space
= min(space
, sysctl_tcp_rmem
[2]);
547 if (space
> sk
->sk_rcvbuf
) {
548 sk
->sk_rcvbuf
= space
;
550 /* Make the window clamp follow along. */
551 tp
->window_clamp
= new_clamp
;
557 tp
->rcvq_space
.seq
= tp
->copied_seq
;
558 tp
->rcvq_space
.time
= tcp_time_stamp
;
561 /* There is something which you must keep in mind when you analyze the
562 * behavior of the tp->ato delayed ack timeout interval. When a
563 * connection starts up, we want to ack as quickly as possible. The
564 * problem is that "good" TCP's do slow start at the beginning of data
565 * transmission. The means that until we send the first few ACK's the
566 * sender will sit on his end and only queue most of his data, because
567 * he can only send snd_cwnd unacked packets at any given time. For
568 * each ACK we send, he increments snd_cwnd and transmits more of his
571 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
573 struct tcp_sock
*tp
= tcp_sk(sk
);
574 struct inet_connection_sock
*icsk
= inet_csk(sk
);
577 inet_csk_schedule_ack(sk
);
579 tcp_measure_rcv_mss(sk
, skb
);
581 tcp_rcv_rtt_measure(tp
);
583 now
= tcp_time_stamp
;
585 if (!icsk
->icsk_ack
.ato
) {
586 /* The _first_ data packet received, initialize
587 * delayed ACK engine.
589 tcp_incr_quickack(sk
);
590 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
592 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
594 if (m
<= TCP_ATO_MIN
/ 2) {
595 /* The fastest case is the first. */
596 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
597 } else if (m
< icsk
->icsk_ack
.ato
) {
598 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
599 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
600 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
601 } else if (m
> icsk
->icsk_rto
) {
602 /* Too long gap. Apparently sender failed to
603 * restart window, so that we send ACKs quickly.
605 tcp_incr_quickack(sk
);
609 icsk
->icsk_ack
.lrcvtime
= now
;
611 TCP_ECN_check_ce(tp
, skb
);
614 tcp_grow_window(sk
, skb
);
617 /* Called to compute a smoothed rtt estimate. The data fed to this
618 * routine either comes from timestamps, or from segments that were
619 * known _not_ to have been retransmitted [see Karn/Partridge
620 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
621 * piece by Van Jacobson.
622 * NOTE: the next three routines used to be one big routine.
623 * To save cycles in the RFC 1323 implementation it was better to break
624 * it up into three procedures. -- erics
626 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
628 struct tcp_sock
*tp
= tcp_sk(sk
);
629 long m
= mrtt
; /* RTT */
631 /* The following amusing code comes from Jacobson's
632 * article in SIGCOMM '88. Note that rtt and mdev
633 * are scaled versions of rtt and mean deviation.
634 * This is designed to be as fast as possible
635 * m stands for "measurement".
637 * On a 1990 paper the rto value is changed to:
638 * RTO = rtt + 4 * mdev
640 * Funny. This algorithm seems to be very broken.
641 * These formulae increase RTO, when it should be decreased, increase
642 * too slowly, when it should be increased quickly, decrease too quickly
643 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
644 * does not matter how to _calculate_ it. Seems, it was trap
645 * that VJ failed to avoid. 8)
650 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
651 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
653 m
= -m
; /* m is now abs(error) */
654 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
655 /* This is similar to one of Eifel findings.
656 * Eifel blocks mdev updates when rtt decreases.
657 * This solution is a bit different: we use finer gain
658 * for mdev in this case (alpha*beta).
659 * Like Eifel it also prevents growth of rto,
660 * but also it limits too fast rto decreases,
661 * happening in pure Eifel.
666 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
668 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
669 if (tp
->mdev
> tp
->mdev_max
) {
670 tp
->mdev_max
= tp
->mdev
;
671 if (tp
->mdev_max
> tp
->rttvar
)
672 tp
->rttvar
= tp
->mdev_max
;
674 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
675 if (tp
->mdev_max
< tp
->rttvar
)
676 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
677 tp
->rtt_seq
= tp
->snd_nxt
;
678 tp
->mdev_max
= tcp_rto_min(sk
);
681 /* no previous measure. */
682 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
683 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
684 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
685 tp
->rtt_seq
= tp
->snd_nxt
;
689 /* Calculate rto without backoff. This is the second half of Van Jacobson's
690 * routine referred to above.
692 static inline void tcp_set_rto(struct sock
*sk
)
694 const struct tcp_sock
*tp
= tcp_sk(sk
);
695 /* Old crap is replaced with new one. 8)
698 * 1. If rtt variance happened to be less 50msec, it is hallucination.
699 * It cannot be less due to utterly erratic ACK generation made
700 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
701 * to do with delayed acks, because at cwnd>2 true delack timeout
702 * is invisible. Actually, Linux-2.4 also generates erratic
703 * ACKs in some circumstances.
705 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
707 /* 2. Fixups made earlier cannot be right.
708 * If we do not estimate RTO correctly without them,
709 * all the algo is pure shit and should be replaced
710 * with correct one. It is exactly, which we pretend to do.
713 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
714 * guarantees that rto is higher.
719 /* Save metrics learned by this TCP session.
720 This function is called only, when TCP finishes successfully
721 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
723 void tcp_update_metrics(struct sock
*sk
)
725 struct tcp_sock
*tp
= tcp_sk(sk
);
726 struct dst_entry
*dst
= __sk_dst_get(sk
);
728 if (sysctl_tcp_nometrics_save
)
733 if (dst
&& (dst
->flags
& DST_HOST
)) {
734 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_metric_set(dst
, RTAX_RTT
, 0);
748 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
751 /* If newly calculated rtt larger than stored one,
752 * store new one. Otherwise, use EWMA. Remember,
753 * rtt overestimation is always better than underestimation.
755 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
757 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
759 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
762 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
767 /* Scale deviation to rttvar fixed point */
772 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
776 var
-= (var
- m
) >> 2;
778 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
781 if (tcp_in_initial_slowstart(tp
)) {
782 /* Slow start still did not finish. */
783 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
784 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
785 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
786 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_cwnd
>> 1);
787 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
788 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
789 dst_metric_set(dst
, RTAX_CWND
, tp
->snd_cwnd
);
790 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
791 icsk
->icsk_ca_state
== TCP_CA_Open
) {
792 /* Cong. avoidance phase, cwnd is reliable. */
793 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
794 dst_metric_set(dst
, RTAX_SSTHRESH
,
795 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
));
796 if (!dst_metric_locked(dst
, RTAX_CWND
))
797 dst_metric_set(dst
, RTAX_CWND
,
798 (dst_metric(dst
, RTAX_CWND
) +
801 /* Else slow start did not finish, cwnd is non-sense,
802 ssthresh may be also invalid.
804 if (!dst_metric_locked(dst
, RTAX_CWND
))
805 dst_metric_set(dst
, RTAX_CWND
,
806 (dst_metric(dst
, RTAX_CWND
) +
807 tp
->snd_ssthresh
) >> 1);
808 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
809 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
810 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
811 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_ssthresh
);
814 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
815 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
816 tp
->reordering
!= sysctl_tcp_reordering
)
817 dst_metric_set(dst
, RTAX_REORDERING
, tp
->reordering
);
822 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
824 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
827 cwnd
= TCP_INIT_CWND
;
828 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
831 /* Set slow start threshold and cwnd not falling to slow start */
832 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
834 struct tcp_sock
*tp
= tcp_sk(sk
);
835 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
837 tp
->prior_ssthresh
= 0;
839 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
842 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
843 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
844 tcp_packets_in_flight(tp
) + 1U);
845 tp
->snd_cwnd_cnt
= 0;
846 tp
->high_seq
= tp
->snd_nxt
;
847 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
848 TCP_ECN_queue_cwr(tp
);
850 tcp_set_ca_state(sk
, TCP_CA_CWR
);
855 * Packet counting of FACK is based on in-order assumptions, therefore TCP
856 * disables it when reordering is detected
858 static void tcp_disable_fack(struct tcp_sock
*tp
)
860 /* RFC3517 uses different metric in lost marker => reset on change */
862 tp
->lost_skb_hint
= NULL
;
863 tp
->rx_opt
.sack_ok
&= ~2;
866 /* Take a notice that peer is sending D-SACKs */
867 static void tcp_dsack_seen(struct tcp_sock
*tp
)
869 tp
->rx_opt
.sack_ok
|= 4;
872 /* Initialize metrics on socket. */
874 static void tcp_init_metrics(struct sock
*sk
)
876 struct tcp_sock
*tp
= tcp_sk(sk
);
877 struct dst_entry
*dst
= __sk_dst_get(sk
);
884 if (dst_metric_locked(dst
, RTAX_CWND
))
885 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
886 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
887 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
888 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
889 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
891 /* ssthresh may have been reduced unnecessarily during.
892 * 3WHS. Restore it back to its initial default.
894 tp
->snd_ssthresh
= TCP_INFINITE_SSTHRESH
;
896 if (dst_metric(dst
, RTAX_REORDERING
) &&
897 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
898 tcp_disable_fack(tp
);
899 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
902 if (dst_metric(dst
, RTAX_RTT
) == 0 || tp
->srtt
== 0)
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_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
920 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
921 tp
->rtt_seq
= tp
->snd_nxt
;
923 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
924 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
925 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
930 /* RFC2988bis: We've failed to get a valid RTT sample from
931 * 3WHS. This is most likely due to retransmission,
932 * including spurious one. Reset the RTO back to 3secs
933 * from the more aggressive 1sec to avoid more spurious
936 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_FALLBACK
;
937 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_FALLBACK
;
939 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
940 * retransmitted. In light of RFC2988bis' more aggressive 1sec
941 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
942 * retransmission has occurred.
944 if (tp
->total_retrans
> 1)
947 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
948 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
951 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
954 struct tcp_sock
*tp
= tcp_sk(sk
);
955 if (metric
> tp
->reordering
) {
958 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
960 /* This exciting event is worth to be remembered. 8) */
962 mib_idx
= LINUX_MIB_TCPTSREORDER
;
963 else if (tcp_is_reno(tp
))
964 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
965 else if (tcp_is_fack(tp
))
966 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
968 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
970 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
971 #if FASTRETRANS_DEBUG > 1
972 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
973 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
977 tp
->undo_marker
? tp
->undo_retrans
: 0);
979 tcp_disable_fack(tp
);
983 /* This must be called before lost_out is incremented */
984 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
986 if ((tp
->retransmit_skb_hint
== NULL
) ||
987 before(TCP_SKB_CB(skb
)->seq
,
988 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
989 tp
->retransmit_skb_hint
= skb
;
992 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
993 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
996 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
998 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
999 tcp_verify_retransmit_hint(tp
, skb
);
1001 tp
->lost_out
+= tcp_skb_pcount(skb
);
1002 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1006 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
1007 struct sk_buff
*skb
)
1009 tcp_verify_retransmit_hint(tp
, skb
);
1011 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1012 tp
->lost_out
+= tcp_skb_pcount(skb
);
1013 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1017 /* This procedure tags the retransmission queue when SACKs arrive.
1019 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1020 * Packets in queue with these bits set are counted in variables
1021 * sacked_out, retrans_out and lost_out, correspondingly.
1023 * Valid combinations are:
1024 * Tag InFlight Description
1025 * 0 1 - orig segment is in flight.
1026 * S 0 - nothing flies, orig reached receiver.
1027 * L 0 - nothing flies, orig lost by net.
1028 * R 2 - both orig and retransmit are in flight.
1029 * L|R 1 - orig is lost, retransmit is in flight.
1030 * S|R 1 - orig reached receiver, retrans is still in flight.
1031 * (L|S|R is logically valid, it could occur when L|R is sacked,
1032 * but it is equivalent to plain S and code short-curcuits it to S.
1033 * L|S is logically invalid, it would mean -1 packet in flight 8))
1035 * These 6 states form finite state machine, controlled by the following events:
1036 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1037 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1038 * 3. Loss detection event of one of three flavors:
1039 * A. Scoreboard estimator decided the packet is lost.
1040 * A'. Reno "three dupacks" marks head of queue lost.
1041 * A''. Its FACK modfication, head until snd.fack is lost.
1042 * B. SACK arrives sacking data transmitted after never retransmitted
1043 * hole was sent out.
1044 * C. SACK arrives sacking SND.NXT at the moment, when the
1045 * segment was retransmitted.
1046 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1048 * It is pleasant to note, that state diagram turns out to be commutative,
1049 * so that we are allowed not to be bothered by order of our actions,
1050 * when multiple events arrive simultaneously. (see the function below).
1052 * Reordering detection.
1053 * --------------------
1054 * Reordering metric is maximal distance, which a packet can be displaced
1055 * in packet stream. With SACKs we can estimate it:
1057 * 1. SACK fills old hole and the corresponding segment was not
1058 * ever retransmitted -> reordering. Alas, we cannot use it
1059 * when segment was retransmitted.
1060 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1061 * for retransmitted and already SACKed segment -> reordering..
1062 * Both of these heuristics are not used in Loss state, when we cannot
1063 * account for retransmits accurately.
1065 * SACK block validation.
1066 * ----------------------
1068 * SACK block range validation checks that the received SACK block fits to
1069 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1070 * Note that SND.UNA is not included to the range though being valid because
1071 * it means that the receiver is rather inconsistent with itself reporting
1072 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1073 * perfectly valid, however, in light of RFC2018 which explicitly states
1074 * that "SACK block MUST reflect the newest segment. Even if the newest
1075 * segment is going to be discarded ...", not that it looks very clever
1076 * in case of head skb. Due to potentional receiver driven attacks, we
1077 * choose to avoid immediate execution of a walk in write queue due to
1078 * reneging and defer head skb's loss recovery to standard loss recovery
1079 * procedure that will eventually trigger (nothing forbids us doing this).
1081 * Implements also blockage to start_seq wrap-around. Problem lies in the
1082 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1083 * there's no guarantee that it will be before snd_nxt (n). The problem
1084 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1087 * <- outs wnd -> <- wrapzone ->
1088 * u e n u_w e_w s n_w
1090 * |<------------+------+----- TCP seqno space --------------+---------->|
1091 * ...-- <2^31 ->| |<--------...
1092 * ...---- >2^31 ------>| |<--------...
1094 * Current code wouldn't be vulnerable but it's better still to discard such
1095 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1096 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1097 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1098 * equal to the ideal case (infinite seqno space without wrap caused issues).
1100 * With D-SACK the lower bound is extended to cover sequence space below
1101 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1102 * again, D-SACK block must not to go across snd_una (for the same reason as
1103 * for the normal SACK blocks, explained above). But there all simplicity
1104 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1105 * fully below undo_marker they do not affect behavior in anyway and can
1106 * therefore be safely ignored. In rare cases (which are more or less
1107 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1108 * fragmentation and packet reordering past skb's retransmission. To consider
1109 * them correctly, the acceptable range must be extended even more though
1110 * the exact amount is rather hard to quantify. However, tp->max_window can
1111 * be used as an exaggerated estimate.
1113 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1114 u32 start_seq
, u32 end_seq
)
1116 /* Too far in future, or reversed (interpretation is ambiguous) */
1117 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1120 /* Nasty start_seq wrap-around check (see comments above) */
1121 if (!before(start_seq
, tp
->snd_nxt
))
1124 /* In outstanding window? ...This is valid exit for D-SACKs too.
1125 * start_seq == snd_una is non-sensical (see comments above)
1127 if (after(start_seq
, tp
->snd_una
))
1130 if (!is_dsack
|| !tp
->undo_marker
)
1133 /* ...Then it's D-SACK, and must reside below snd_una completely */
1134 if (after(end_seq
, tp
->snd_una
))
1137 if (!before(start_seq
, tp
->undo_marker
))
1141 if (!after(end_seq
, tp
->undo_marker
))
1144 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1145 * start_seq < undo_marker and end_seq >= undo_marker.
1147 return !before(start_seq
, end_seq
- tp
->max_window
);
1150 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1151 * Event "C". Later note: FACK people cheated me again 8), we have to account
1152 * for reordering! Ugly, but should help.
1154 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1155 * less than what is now known to be received by the other end (derived from
1156 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1157 * retransmitted skbs to avoid some costly processing per ACKs.
1159 static void tcp_mark_lost_retrans(struct sock
*sk
)
1161 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1162 struct tcp_sock
*tp
= tcp_sk(sk
);
1163 struct sk_buff
*skb
;
1165 u32 new_low_seq
= tp
->snd_nxt
;
1166 u32 received_upto
= tcp_highest_sack_seq(tp
);
1168 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1169 !after(received_upto
, tp
->lost_retrans_low
) ||
1170 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1173 tcp_for_write_queue(skb
, sk
) {
1174 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1176 if (skb
== tcp_send_head(sk
))
1178 if (cnt
== tp
->retrans_out
)
1180 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1183 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1186 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1187 * constraint here (see above) but figuring out that at
1188 * least tp->reordering SACK blocks reside between ack_seq
1189 * and received_upto is not easy task to do cheaply with
1190 * the available datastructures.
1192 * Whether FACK should check here for tp->reordering segs
1193 * in-between one could argue for either way (it would be
1194 * rather simple to implement as we could count fack_count
1195 * during the walk and do tp->fackets_out - fack_count).
1197 if (after(received_upto
, ack_seq
)) {
1198 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1199 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1201 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1202 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1204 if (before(ack_seq
, new_low_seq
))
1205 new_low_seq
= ack_seq
;
1206 cnt
+= tcp_skb_pcount(skb
);
1210 if (tp
->retrans_out
)
1211 tp
->lost_retrans_low
= new_low_seq
;
1214 static int tcp_check_dsack(struct sock
*sk
, struct sk_buff
*ack_skb
,
1215 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1218 struct tcp_sock
*tp
= tcp_sk(sk
);
1219 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1220 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1223 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1226 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1227 } else if (num_sacks
> 1) {
1228 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1229 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1231 if (!after(end_seq_0
, end_seq_1
) &&
1232 !before(start_seq_0
, start_seq_1
)) {
1235 NET_INC_STATS_BH(sock_net(sk
),
1236 LINUX_MIB_TCPDSACKOFORECV
);
1240 /* D-SACK for already forgotten data... Do dumb counting. */
1241 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
&&
1242 !after(end_seq_0
, prior_snd_una
) &&
1243 after(end_seq_0
, tp
->undo_marker
))
1249 struct tcp_sacktag_state
{
1255 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1256 * the incoming SACK may not exactly match but we can find smaller MSS
1257 * aligned portion of it that matches. Therefore we might need to fragment
1258 * which may fail and creates some hassle (caller must handle error case
1261 * FIXME: this could be merged to shift decision code
1263 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1264 u32 start_seq
, u32 end_seq
)
1267 unsigned int pkt_len
;
1270 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1271 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1273 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1274 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1275 mss
= tcp_skb_mss(skb
);
1276 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1279 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1283 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1288 /* Round if necessary so that SACKs cover only full MSSes
1289 * and/or the remaining small portion (if present)
1291 if (pkt_len
> mss
) {
1292 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1293 if (!in_sack
&& new_len
< pkt_len
) {
1295 if (new_len
> skb
->len
)
1300 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1308 static u8
tcp_sacktag_one(struct sk_buff
*skb
, struct sock
*sk
,
1309 struct tcp_sacktag_state
*state
,
1310 int dup_sack
, int pcount
)
1312 struct tcp_sock
*tp
= tcp_sk(sk
);
1313 u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1314 int fack_count
= state
->fack_count
;
1316 /* Account D-SACK for retransmitted packet. */
1317 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1318 if (tp
->undo_marker
&& tp
->undo_retrans
&&
1319 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1321 if (sacked
& TCPCB_SACKED_ACKED
)
1322 state
->reord
= min(fack_count
, state
->reord
);
1325 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1326 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1329 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1330 if (sacked
& TCPCB_SACKED_RETRANS
) {
1331 /* If the segment is not tagged as lost,
1332 * we do not clear RETRANS, believing
1333 * that retransmission is still in flight.
1335 if (sacked
& TCPCB_LOST
) {
1336 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1337 tp
->lost_out
-= pcount
;
1338 tp
->retrans_out
-= pcount
;
1341 if (!(sacked
& TCPCB_RETRANS
)) {
1342 /* New sack for not retransmitted frame,
1343 * which was in hole. It is reordering.
1345 if (before(TCP_SKB_CB(skb
)->seq
,
1346 tcp_highest_sack_seq(tp
)))
1347 state
->reord
= min(fack_count
,
1350 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1351 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
))
1352 state
->flag
|= FLAG_ONLY_ORIG_SACKED
;
1355 if (sacked
& TCPCB_LOST
) {
1356 sacked
&= ~TCPCB_LOST
;
1357 tp
->lost_out
-= pcount
;
1361 sacked
|= TCPCB_SACKED_ACKED
;
1362 state
->flag
|= FLAG_DATA_SACKED
;
1363 tp
->sacked_out
+= pcount
;
1365 fack_count
+= pcount
;
1367 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1368 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1369 before(TCP_SKB_CB(skb
)->seq
,
1370 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1371 tp
->lost_cnt_hint
+= pcount
;
1373 if (fack_count
> tp
->fackets_out
)
1374 tp
->fackets_out
= fack_count
;
1377 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1378 * frames and clear it. undo_retrans is decreased above, L|R frames
1379 * are accounted above as well.
1381 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1382 sacked
&= ~TCPCB_SACKED_RETRANS
;
1383 tp
->retrans_out
-= pcount
;
1389 static int tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1390 struct tcp_sacktag_state
*state
,
1391 unsigned int pcount
, int shifted
, int mss
,
1394 struct tcp_sock
*tp
= tcp_sk(sk
);
1395 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1399 if (skb
== tp
->lost_skb_hint
)
1400 tp
->lost_cnt_hint
+= pcount
;
1402 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1403 TCP_SKB_CB(skb
)->seq
+= shifted
;
1405 skb_shinfo(prev
)->gso_segs
+= pcount
;
1406 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1407 skb_shinfo(skb
)->gso_segs
-= pcount
;
1409 /* When we're adding to gso_segs == 1, gso_size will be zero,
1410 * in theory this shouldn't be necessary but as long as DSACK
1411 * code can come after this skb later on it's better to keep
1412 * setting gso_size to something.
1414 if (!skb_shinfo(prev
)->gso_size
) {
1415 skb_shinfo(prev
)->gso_size
= mss
;
1416 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1419 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1420 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1421 skb_shinfo(skb
)->gso_size
= 0;
1422 skb_shinfo(skb
)->gso_type
= 0;
1425 /* We discard results */
1426 tcp_sacktag_one(skb
, sk
, state
, dup_sack
, pcount
);
1428 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1429 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1432 BUG_ON(!tcp_skb_pcount(skb
));
1433 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1437 /* Whole SKB was eaten :-) */
1439 if (skb
== tp
->retransmit_skb_hint
)
1440 tp
->retransmit_skb_hint
= prev
;
1441 if (skb
== tp
->scoreboard_skb_hint
)
1442 tp
->scoreboard_skb_hint
= prev
;
1443 if (skb
== tp
->lost_skb_hint
) {
1444 tp
->lost_skb_hint
= prev
;
1445 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1448 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(prev
)->tcp_flags
;
1449 if (skb
== tcp_highest_sack(sk
))
1450 tcp_advance_highest_sack(sk
, skb
);
1452 tcp_unlink_write_queue(skb
, sk
);
1453 sk_wmem_free_skb(sk
, skb
);
1455 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1460 /* I wish gso_size would have a bit more sane initialization than
1461 * something-or-zero which complicates things
1463 static int tcp_skb_seglen(struct sk_buff
*skb
)
1465 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1468 /* Shifting pages past head area doesn't work */
1469 static int skb_can_shift(struct sk_buff
*skb
)
1471 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1474 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1477 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1478 struct tcp_sacktag_state
*state
,
1479 u32 start_seq
, u32 end_seq
,
1482 struct tcp_sock
*tp
= tcp_sk(sk
);
1483 struct sk_buff
*prev
;
1489 if (!sk_can_gso(sk
))
1492 /* Normally R but no L won't result in plain S */
1494 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1496 if (!skb_can_shift(skb
))
1498 /* This frame is about to be dropped (was ACKed). */
1499 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1502 /* Can only happen with delayed DSACK + discard craziness */
1503 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1505 prev
= tcp_write_queue_prev(sk
, skb
);
1507 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1510 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1511 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1515 pcount
= tcp_skb_pcount(skb
);
1516 mss
= tcp_skb_seglen(skb
);
1518 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1519 * drop this restriction as unnecessary
1521 if (mss
!= tcp_skb_seglen(prev
))
1524 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1526 /* CHECKME: This is non-MSS split case only?, this will
1527 * cause skipped skbs due to advancing loop btw, original
1528 * has that feature too
1530 if (tcp_skb_pcount(skb
) <= 1)
1533 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1535 /* TODO: head merge to next could be attempted here
1536 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1537 * though it might not be worth of the additional hassle
1539 * ...we can probably just fallback to what was done
1540 * previously. We could try merging non-SACKed ones
1541 * as well but it probably isn't going to buy off
1542 * because later SACKs might again split them, and
1543 * it would make skb timestamp tracking considerably
1549 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1551 BUG_ON(len
> skb
->len
);
1553 /* MSS boundaries should be honoured or else pcount will
1554 * severely break even though it makes things bit trickier.
1555 * Optimize common case to avoid most of the divides
1557 mss
= tcp_skb_mss(skb
);
1559 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1560 * drop this restriction as unnecessary
1562 if (mss
!= tcp_skb_seglen(prev
))
1567 } else if (len
< mss
) {
1575 if (!skb_shift(prev
, skb
, len
))
1577 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1580 /* Hole filled allows collapsing with the next as well, this is very
1581 * useful when hole on every nth skb pattern happens
1583 if (prev
== tcp_write_queue_tail(sk
))
1585 skb
= tcp_write_queue_next(sk
, prev
);
1587 if (!skb_can_shift(skb
) ||
1588 (skb
== tcp_send_head(sk
)) ||
1589 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1590 (mss
!= tcp_skb_seglen(skb
)))
1594 if (skb_shift(prev
, skb
, len
)) {
1595 pcount
+= tcp_skb_pcount(skb
);
1596 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1600 state
->fack_count
+= pcount
;
1607 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1611 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1612 struct tcp_sack_block
*next_dup
,
1613 struct tcp_sacktag_state
*state
,
1614 u32 start_seq
, u32 end_seq
,
1617 struct tcp_sock
*tp
= tcp_sk(sk
);
1618 struct sk_buff
*tmp
;
1620 tcp_for_write_queue_from(skb
, sk
) {
1622 int dup_sack
= dup_sack_in
;
1624 if (skb
== tcp_send_head(sk
))
1627 /* queue is in-order => we can short-circuit the walk early */
1628 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1631 if ((next_dup
!= NULL
) &&
1632 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1633 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1634 next_dup
->start_seq
,
1640 /* skb reference here is a bit tricky to get right, since
1641 * shifting can eat and free both this skb and the next,
1642 * so not even _safe variant of the loop is enough.
1645 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1646 start_seq
, end_seq
, dup_sack
);
1655 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1661 if (unlikely(in_sack
< 0))
1665 TCP_SKB_CB(skb
)->sacked
= tcp_sacktag_one(skb
, sk
,
1668 tcp_skb_pcount(skb
));
1670 if (!before(TCP_SKB_CB(skb
)->seq
,
1671 tcp_highest_sack_seq(tp
)))
1672 tcp_advance_highest_sack(sk
, skb
);
1675 state
->fack_count
+= tcp_skb_pcount(skb
);
1680 /* Avoid all extra work that is being done by sacktag while walking in
1683 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1684 struct tcp_sacktag_state
*state
,
1687 tcp_for_write_queue_from(skb
, sk
) {
1688 if (skb
== tcp_send_head(sk
))
1691 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1694 state
->fack_count
+= tcp_skb_pcount(skb
);
1699 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1701 struct tcp_sack_block
*next_dup
,
1702 struct tcp_sacktag_state
*state
,
1705 if (next_dup
== NULL
)
1708 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1709 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1710 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1711 next_dup
->start_seq
, next_dup
->end_seq
,
1718 static int tcp_sack_cache_ok(struct tcp_sock
*tp
, struct tcp_sack_block
*cache
)
1720 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1724 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
,
1727 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1728 struct tcp_sock
*tp
= tcp_sk(sk
);
1729 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1730 TCP_SKB_CB(ack_skb
)->sacked
);
1731 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1732 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1733 struct tcp_sack_block
*cache
;
1734 struct tcp_sacktag_state state
;
1735 struct sk_buff
*skb
;
1736 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1738 int found_dup_sack
= 0;
1740 int first_sack_index
;
1743 state
.reord
= tp
->packets_out
;
1745 if (!tp
->sacked_out
) {
1746 if (WARN_ON(tp
->fackets_out
))
1747 tp
->fackets_out
= 0;
1748 tcp_highest_sack_reset(sk
);
1751 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1752 num_sacks
, prior_snd_una
);
1754 state
.flag
|= FLAG_DSACKING_ACK
;
1756 /* Eliminate too old ACKs, but take into
1757 * account more or less fresh ones, they can
1758 * contain valid SACK info.
1760 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1763 if (!tp
->packets_out
)
1767 first_sack_index
= 0;
1768 for (i
= 0; i
< num_sacks
; i
++) {
1769 int dup_sack
= !i
&& found_dup_sack
;
1771 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1772 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1774 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1775 sp
[used_sacks
].start_seq
,
1776 sp
[used_sacks
].end_seq
)) {
1780 if (!tp
->undo_marker
)
1781 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1783 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1785 /* Don't count olds caused by ACK reordering */
1786 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1787 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1789 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1792 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1794 first_sack_index
= -1;
1798 /* Ignore very old stuff early */
1799 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1805 /* order SACK blocks to allow in order walk of the retrans queue */
1806 for (i
= used_sacks
- 1; i
> 0; i
--) {
1807 for (j
= 0; j
< i
; j
++) {
1808 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1809 swap(sp
[j
], sp
[j
+ 1]);
1811 /* Track where the first SACK block goes to */
1812 if (j
== first_sack_index
)
1813 first_sack_index
= j
+ 1;
1818 skb
= tcp_write_queue_head(sk
);
1819 state
.fack_count
= 0;
1822 if (!tp
->sacked_out
) {
1823 /* It's already past, so skip checking against it */
1824 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1826 cache
= tp
->recv_sack_cache
;
1827 /* Skip empty blocks in at head of the cache */
1828 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1833 while (i
< used_sacks
) {
1834 u32 start_seq
= sp
[i
].start_seq
;
1835 u32 end_seq
= sp
[i
].end_seq
;
1836 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1837 struct tcp_sack_block
*next_dup
= NULL
;
1839 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1840 next_dup
= &sp
[i
+ 1];
1842 /* Event "B" in the comment above. */
1843 if (after(end_seq
, tp
->high_seq
))
1844 state
.flag
|= FLAG_DATA_LOST
;
1846 /* Skip too early cached blocks */
1847 while (tcp_sack_cache_ok(tp
, cache
) &&
1848 !before(start_seq
, cache
->end_seq
))
1851 /* Can skip some work by looking recv_sack_cache? */
1852 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1853 after(end_seq
, cache
->start_seq
)) {
1856 if (before(start_seq
, cache
->start_seq
)) {
1857 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1859 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1866 /* Rest of the block already fully processed? */
1867 if (!after(end_seq
, cache
->end_seq
))
1870 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1874 /* ...tail remains todo... */
1875 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1876 /* ...but better entrypoint exists! */
1877 skb
= tcp_highest_sack(sk
);
1880 state
.fack_count
= tp
->fackets_out
;
1885 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1886 /* Check overlap against next cached too (past this one already) */
1891 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1892 skb
= tcp_highest_sack(sk
);
1895 state
.fack_count
= tp
->fackets_out
;
1897 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1900 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1901 start_seq
, end_seq
, dup_sack
);
1904 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1905 * due to in-order walk
1907 if (after(end_seq
, tp
->frto_highmark
))
1908 state
.flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1913 /* Clear the head of the cache sack blocks so we can skip it next time */
1914 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1915 tp
->recv_sack_cache
[i
].start_seq
= 0;
1916 tp
->recv_sack_cache
[i
].end_seq
= 0;
1918 for (j
= 0; j
< used_sacks
; j
++)
1919 tp
->recv_sack_cache
[i
++] = sp
[j
];
1921 tcp_mark_lost_retrans(sk
);
1923 tcp_verify_left_out(tp
);
1925 if ((state
.reord
< tp
->fackets_out
) &&
1926 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1927 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1928 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1932 #if FASTRETRANS_DEBUG > 0
1933 WARN_ON((int)tp
->sacked_out
< 0);
1934 WARN_ON((int)tp
->lost_out
< 0);
1935 WARN_ON((int)tp
->retrans_out
< 0);
1936 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1941 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1942 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1944 static int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1948 holes
= max(tp
->lost_out
, 1U);
1949 holes
= min(holes
, tp
->packets_out
);
1951 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1952 tp
->sacked_out
= tp
->packets_out
- holes
;
1958 /* If we receive more dupacks than we expected counting segments
1959 * in assumption of absent reordering, interpret this as reordering.
1960 * The only another reason could be bug in receiver TCP.
1962 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1964 struct tcp_sock
*tp
= tcp_sk(sk
);
1965 if (tcp_limit_reno_sacked(tp
))
1966 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1969 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1971 static void tcp_add_reno_sack(struct sock
*sk
)
1973 struct tcp_sock
*tp
= tcp_sk(sk
);
1975 tcp_check_reno_reordering(sk
, 0);
1976 tcp_verify_left_out(tp
);
1979 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1981 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1983 struct tcp_sock
*tp
= tcp_sk(sk
);
1986 /* One ACK acked hole. The rest eat duplicate ACKs. */
1987 if (acked
- 1 >= tp
->sacked_out
)
1990 tp
->sacked_out
-= acked
- 1;
1992 tcp_check_reno_reordering(sk
, acked
);
1993 tcp_verify_left_out(tp
);
1996 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
2001 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
2003 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
2006 /* F-RTO can only be used if TCP has never retransmitted anything other than
2007 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
2009 int tcp_use_frto(struct sock
*sk
)
2011 const struct tcp_sock
*tp
= tcp_sk(sk
);
2012 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2013 struct sk_buff
*skb
;
2015 if (!sysctl_tcp_frto
)
2018 /* MTU probe and F-RTO won't really play nicely along currently */
2019 if (icsk
->icsk_mtup
.probe_size
)
2022 if (tcp_is_sackfrto(tp
))
2025 /* Avoid expensive walking of rexmit queue if possible */
2026 if (tp
->retrans_out
> 1)
2029 skb
= tcp_write_queue_head(sk
);
2030 if (tcp_skb_is_last(sk
, skb
))
2032 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
2033 tcp_for_write_queue_from(skb
, sk
) {
2034 if (skb
== tcp_send_head(sk
))
2036 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2038 /* Short-circuit when first non-SACKed skb has been checked */
2039 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2045 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2046 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2047 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2048 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2049 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2050 * bits are handled if the Loss state is really to be entered (in
2051 * tcp_enter_frto_loss).
2053 * Do like tcp_enter_loss() would; when RTO expires the second time it
2055 * "Reduce ssthresh if it has not yet been made inside this window."
2057 void tcp_enter_frto(struct sock
*sk
)
2059 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2060 struct tcp_sock
*tp
= tcp_sk(sk
);
2061 struct sk_buff
*skb
;
2063 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
2064 tp
->snd_una
== tp
->high_seq
||
2065 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
2066 !icsk
->icsk_retransmits
)) {
2067 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2068 /* Our state is too optimistic in ssthresh() call because cwnd
2069 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2070 * recovery has not yet completed. Pattern would be this: RTO,
2071 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2073 * RFC4138 should be more specific on what to do, even though
2074 * RTO is quite unlikely to occur after the first Cumulative ACK
2075 * due to back-off and complexity of triggering events ...
2077 if (tp
->frto_counter
) {
2079 stored_cwnd
= tp
->snd_cwnd
;
2081 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2082 tp
->snd_cwnd
= stored_cwnd
;
2084 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2086 /* ... in theory, cong.control module could do "any tricks" in
2087 * ssthresh(), which means that ca_state, lost bits and lost_out
2088 * counter would have to be faked before the call occurs. We
2089 * consider that too expensive, unlikely and hacky, so modules
2090 * using these in ssthresh() must deal these incompatibility
2091 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2093 tcp_ca_event(sk
, CA_EVENT_FRTO
);
2096 tp
->undo_marker
= tp
->snd_una
;
2097 tp
->undo_retrans
= 0;
2099 skb
= tcp_write_queue_head(sk
);
2100 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2101 tp
->undo_marker
= 0;
2102 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2103 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2104 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2106 tcp_verify_left_out(tp
);
2108 /* Too bad if TCP was application limited */
2109 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2111 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2112 * The last condition is necessary at least in tp->frto_counter case.
2114 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
2115 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
2116 after(tp
->high_seq
, tp
->snd_una
)) {
2117 tp
->frto_highmark
= tp
->high_seq
;
2119 tp
->frto_highmark
= tp
->snd_nxt
;
2121 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
2122 tp
->high_seq
= tp
->snd_nxt
;
2123 tp
->frto_counter
= 1;
2126 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2127 * which indicates that we should follow the traditional RTO recovery,
2128 * i.e. mark everything lost and do go-back-N retransmission.
2130 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
2132 struct tcp_sock
*tp
= tcp_sk(sk
);
2133 struct sk_buff
*skb
;
2136 tp
->retrans_out
= 0;
2137 if (tcp_is_reno(tp
))
2138 tcp_reset_reno_sack(tp
);
2140 tcp_for_write_queue(skb
, sk
) {
2141 if (skb
== tcp_send_head(sk
))
2144 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2146 * Count the retransmission made on RTO correctly (only when
2147 * waiting for the first ACK and did not get it)...
2149 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
2150 /* For some reason this R-bit might get cleared? */
2151 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
2152 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2153 /* ...enter this if branch just for the first segment */
2154 flag
|= FLAG_DATA_ACKED
;
2156 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2157 tp
->undo_marker
= 0;
2158 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2161 /* Marking forward transmissions that were made after RTO lost
2162 * can cause unnecessary retransmissions in some scenarios,
2163 * SACK blocks will mitigate that in some but not in all cases.
2164 * We used to not mark them but it was causing break-ups with
2165 * receivers that do only in-order receival.
2167 * TODO: we could detect presence of such receiver and select
2168 * different behavior per flow.
2170 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2171 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2172 tp
->lost_out
+= tcp_skb_pcount(skb
);
2173 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2176 tcp_verify_left_out(tp
);
2178 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
2179 tp
->snd_cwnd_cnt
= 0;
2180 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2181 tp
->frto_counter
= 0;
2182 tp
->bytes_acked
= 0;
2184 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2185 sysctl_tcp_reordering
);
2186 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2187 tp
->high_seq
= tp
->snd_nxt
;
2188 TCP_ECN_queue_cwr(tp
);
2190 tcp_clear_all_retrans_hints(tp
);
2193 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
2195 tp
->retrans_out
= 0;
2198 tp
->undo_marker
= 0;
2199 tp
->undo_retrans
= 0;
2202 void tcp_clear_retrans(struct tcp_sock
*tp
)
2204 tcp_clear_retrans_partial(tp
);
2206 tp
->fackets_out
= 0;
2210 /* Enter Loss state. If "how" is not zero, forget all SACK information
2211 * and reset tags completely, otherwise preserve SACKs. If receiver
2212 * dropped its ofo queue, we will know this due to reneging detection.
2214 void tcp_enter_loss(struct sock
*sk
, int how
)
2216 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2217 struct tcp_sock
*tp
= tcp_sk(sk
);
2218 struct sk_buff
*skb
;
2220 /* Reduce ssthresh if it has not yet been made inside this window. */
2221 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
2222 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2223 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2224 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2225 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2228 tp
->snd_cwnd_cnt
= 0;
2229 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2231 tp
->bytes_acked
= 0;
2232 tcp_clear_retrans_partial(tp
);
2234 if (tcp_is_reno(tp
))
2235 tcp_reset_reno_sack(tp
);
2238 /* Push undo marker, if it was plain RTO and nothing
2239 * was retransmitted. */
2240 tp
->undo_marker
= tp
->snd_una
;
2243 tp
->fackets_out
= 0;
2245 tcp_clear_all_retrans_hints(tp
);
2247 tcp_for_write_queue(skb
, sk
) {
2248 if (skb
== tcp_send_head(sk
))
2251 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2252 tp
->undo_marker
= 0;
2253 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
2254 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
2255 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2256 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2257 tp
->lost_out
+= tcp_skb_pcount(skb
);
2258 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2261 tcp_verify_left_out(tp
);
2263 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2264 sysctl_tcp_reordering
);
2265 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2266 tp
->high_seq
= tp
->snd_nxt
;
2267 TCP_ECN_queue_cwr(tp
);
2268 /* Abort F-RTO algorithm if one is in progress */
2269 tp
->frto_counter
= 0;
2272 /* If ACK arrived pointing to a remembered SACK, it means that our
2273 * remembered SACKs do not reflect real state of receiver i.e.
2274 * receiver _host_ is heavily congested (or buggy).
2276 * Do processing similar to RTO timeout.
2278 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2280 if (flag
& FLAG_SACK_RENEGING
) {
2281 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2282 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2284 tcp_enter_loss(sk
, 1);
2285 icsk
->icsk_retransmits
++;
2286 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
2287 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2288 icsk
->icsk_rto
, TCP_RTO_MAX
);
2294 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
2296 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2299 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2300 * counter when SACK is enabled (without SACK, sacked_out is used for
2303 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2304 * segments up to the highest received SACK block so far and holes in
2307 * With reordering, holes may still be in flight, so RFC3517 recovery
2308 * uses pure sacked_out (total number of SACKed segments) even though
2309 * it violates the RFC that uses duplicate ACKs, often these are equal
2310 * but when e.g. out-of-window ACKs or packet duplication occurs,
2311 * they differ. Since neither occurs due to loss, TCP should really
2314 static inline int tcp_dupack_heuristics(struct tcp_sock
*tp
)
2316 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2319 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
2321 return tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
;
2324 static inline int tcp_head_timedout(struct sock
*sk
)
2326 struct tcp_sock
*tp
= tcp_sk(sk
);
2328 return tp
->packets_out
&&
2329 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2332 /* Linux NewReno/SACK/FACK/ECN state machine.
2333 * --------------------------------------
2335 * "Open" Normal state, no dubious events, fast path.
2336 * "Disorder" In all the respects it is "Open",
2337 * but requires a bit more attention. It is entered when
2338 * we see some SACKs or dupacks. It is split of "Open"
2339 * mainly to move some processing from fast path to slow one.
2340 * "CWR" CWND was reduced due to some Congestion Notification event.
2341 * It can be ECN, ICMP source quench, local device congestion.
2342 * "Recovery" CWND was reduced, we are fast-retransmitting.
2343 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2345 * tcp_fastretrans_alert() is entered:
2346 * - each incoming ACK, if state is not "Open"
2347 * - when arrived ACK is unusual, namely:
2352 * Counting packets in flight is pretty simple.
2354 * in_flight = packets_out - left_out + retrans_out
2356 * packets_out is SND.NXT-SND.UNA counted in packets.
2358 * retrans_out is number of retransmitted segments.
2360 * left_out is number of segments left network, but not ACKed yet.
2362 * left_out = sacked_out + lost_out
2364 * sacked_out: Packets, which arrived to receiver out of order
2365 * and hence not ACKed. With SACKs this number is simply
2366 * amount of SACKed data. Even without SACKs
2367 * it is easy to give pretty reliable estimate of this number,
2368 * counting duplicate ACKs.
2370 * lost_out: Packets lost by network. TCP has no explicit
2371 * "loss notification" feedback from network (for now).
2372 * It means that this number can be only _guessed_.
2373 * Actually, it is the heuristics to predict lossage that
2374 * distinguishes different algorithms.
2376 * F.e. after RTO, when all the queue is considered as lost,
2377 * lost_out = packets_out and in_flight = retrans_out.
2379 * Essentially, we have now two algorithms counting
2382 * FACK: It is the simplest heuristics. As soon as we decided
2383 * that something is lost, we decide that _all_ not SACKed
2384 * packets until the most forward SACK are lost. I.e.
2385 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2386 * It is absolutely correct estimate, if network does not reorder
2387 * packets. And it loses any connection to reality when reordering
2388 * takes place. We use FACK by default until reordering
2389 * is suspected on the path to this destination.
2391 * NewReno: when Recovery is entered, we assume that one segment
2392 * is lost (classic Reno). While we are in Recovery and
2393 * a partial ACK arrives, we assume that one more packet
2394 * is lost (NewReno). This heuristics are the same in NewReno
2397 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2398 * deflation etc. CWND is real congestion window, never inflated, changes
2399 * only according to classic VJ rules.
2401 * Really tricky (and requiring careful tuning) part of algorithm
2402 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2403 * The first determines the moment _when_ we should reduce CWND and,
2404 * hence, slow down forward transmission. In fact, it determines the moment
2405 * when we decide that hole is caused by loss, rather than by a reorder.
2407 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2408 * holes, caused by lost packets.
2410 * And the most logically complicated part of algorithm is undo
2411 * heuristics. We detect false retransmits due to both too early
2412 * fast retransmit (reordering) and underestimated RTO, analyzing
2413 * timestamps and D-SACKs. When we detect that some segments were
2414 * retransmitted by mistake and CWND reduction was wrong, we undo
2415 * window reduction and abort recovery phase. This logic is hidden
2416 * inside several functions named tcp_try_undo_<something>.
2419 /* This function decides, when we should leave Disordered state
2420 * and enter Recovery phase, reducing congestion window.
2422 * Main question: may we further continue forward transmission
2423 * with the same cwnd?
2425 static int tcp_time_to_recover(struct sock
*sk
)
2427 struct tcp_sock
*tp
= tcp_sk(sk
);
2430 /* Do not perform any recovery during F-RTO algorithm */
2431 if (tp
->frto_counter
)
2434 /* Trick#1: The loss is proven. */
2438 /* Not-A-Trick#2 : Classic rule... */
2439 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2442 /* Trick#3 : when we use RFC2988 timer restart, fast
2443 * retransmit can be triggered by timeout of queue head.
2445 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2448 /* Trick#4: It is still not OK... But will it be useful to delay
2451 packets_out
= tp
->packets_out
;
2452 if (packets_out
<= tp
->reordering
&&
2453 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2454 !tcp_may_send_now(sk
)) {
2455 /* We have nothing to send. This connection is limited
2456 * either by receiver window or by application.
2461 /* If a thin stream is detected, retransmit after first
2462 * received dupack. Employ only if SACK is supported in order
2463 * to avoid possible corner-case series of spurious retransmissions
2464 * Use only if there are no unsent data.
2466 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2467 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2468 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2474 /* New heuristics: it is possible only after we switched to restart timer
2475 * each time when something is ACKed. Hence, we can detect timed out packets
2476 * during fast retransmit without falling to slow start.
2478 * Usefulness of this as is very questionable, since we should know which of
2479 * the segments is the next to timeout which is relatively expensive to find
2480 * in general case unless we add some data structure just for that. The
2481 * current approach certainly won't find the right one too often and when it
2482 * finally does find _something_ it usually marks large part of the window
2483 * right away (because a retransmission with a larger timestamp blocks the
2484 * loop from advancing). -ij
2486 static void tcp_timeout_skbs(struct sock
*sk
)
2488 struct tcp_sock
*tp
= tcp_sk(sk
);
2489 struct sk_buff
*skb
;
2491 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2494 skb
= tp
->scoreboard_skb_hint
;
2495 if (tp
->scoreboard_skb_hint
== NULL
)
2496 skb
= tcp_write_queue_head(sk
);
2498 tcp_for_write_queue_from(skb
, sk
) {
2499 if (skb
== tcp_send_head(sk
))
2501 if (!tcp_skb_timedout(sk
, skb
))
2504 tcp_skb_mark_lost(tp
, skb
);
2507 tp
->scoreboard_skb_hint
= skb
;
2509 tcp_verify_left_out(tp
);
2512 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2513 * is against sacked "cnt", otherwise it's against facked "cnt"
2515 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2517 struct tcp_sock
*tp
= tcp_sk(sk
);
2518 struct sk_buff
*skb
;
2523 WARN_ON(packets
> tp
->packets_out
);
2524 if (tp
->lost_skb_hint
) {
2525 skb
= tp
->lost_skb_hint
;
2526 cnt
= tp
->lost_cnt_hint
;
2527 /* Head already handled? */
2528 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2531 skb
= tcp_write_queue_head(sk
);
2535 tcp_for_write_queue_from(skb
, sk
) {
2536 if (skb
== tcp_send_head(sk
))
2538 /* TODO: do this better */
2539 /* this is not the most efficient way to do this... */
2540 tp
->lost_skb_hint
= skb
;
2541 tp
->lost_cnt_hint
= cnt
;
2543 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->high_seq
))
2547 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2548 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2549 cnt
+= tcp_skb_pcount(skb
);
2551 if (cnt
> packets
) {
2552 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2553 (oldcnt
>= packets
))
2556 mss
= skb_shinfo(skb
)->gso_size
;
2557 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2563 tcp_skb_mark_lost(tp
, skb
);
2568 tcp_verify_left_out(tp
);
2571 /* Account newly detected lost packet(s) */
2573 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2575 struct tcp_sock
*tp
= tcp_sk(sk
);
2577 if (tcp_is_reno(tp
)) {
2578 tcp_mark_head_lost(sk
, 1, 1);
2579 } else if (tcp_is_fack(tp
)) {
2580 int lost
= tp
->fackets_out
- tp
->reordering
;
2583 tcp_mark_head_lost(sk
, lost
, 0);
2585 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2586 if (sacked_upto
>= 0)
2587 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2588 else if (fast_rexmit
)
2589 tcp_mark_head_lost(sk
, 1, 1);
2592 tcp_timeout_skbs(sk
);
2595 /* CWND moderation, preventing bursts due to too big ACKs
2596 * in dubious situations.
2598 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2600 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2601 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2602 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2605 /* Lower bound on congestion window is slow start threshold
2606 * unless congestion avoidance choice decides to overide it.
2608 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2610 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2612 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2615 /* Decrease cwnd each second ack. */
2616 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2618 struct tcp_sock
*tp
= tcp_sk(sk
);
2619 int decr
= tp
->snd_cwnd_cnt
+ 1;
2621 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2622 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2623 tp
->snd_cwnd_cnt
= decr
& 1;
2626 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2627 tp
->snd_cwnd
-= decr
;
2629 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2630 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2634 /* Nothing was retransmitted or returned timestamp is less
2635 * than timestamp of the first retransmission.
2637 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2639 return !tp
->retrans_stamp
||
2640 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2641 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2644 /* Undo procedures. */
2646 #if FASTRETRANS_DEBUG > 1
2647 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2649 struct tcp_sock
*tp
= tcp_sk(sk
);
2650 struct inet_sock
*inet
= inet_sk(sk
);
2652 if (sk
->sk_family
== AF_INET
) {
2653 printk(KERN_DEBUG
"Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2655 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2656 tp
->snd_cwnd
, tcp_left_out(tp
),
2657 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2660 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2661 else if (sk
->sk_family
== AF_INET6
) {
2662 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2663 printk(KERN_DEBUG
"Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2665 &np
->daddr
, ntohs(inet
->inet_dport
),
2666 tp
->snd_cwnd
, tcp_left_out(tp
),
2667 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2673 #define DBGUNDO(x...) do { } while (0)
2676 static void tcp_undo_cwr(struct sock
*sk
, const bool undo_ssthresh
)
2678 struct tcp_sock
*tp
= tcp_sk(sk
);
2680 if (tp
->prior_ssthresh
) {
2681 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2683 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2684 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2686 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2688 if (undo_ssthresh
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2689 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2690 TCP_ECN_withdraw_cwr(tp
);
2693 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2695 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2698 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2700 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2703 /* People celebrate: "We love our President!" */
2704 static int tcp_try_undo_recovery(struct sock
*sk
)
2706 struct tcp_sock
*tp
= tcp_sk(sk
);
2708 if (tcp_may_undo(tp
)) {
2711 /* Happy end! We did not retransmit anything
2712 * or our original transmission succeeded.
2714 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2715 tcp_undo_cwr(sk
, true);
2716 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2717 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2719 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2721 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2722 tp
->undo_marker
= 0;
2724 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2725 /* Hold old state until something *above* high_seq
2726 * is ACKed. For Reno it is MUST to prevent false
2727 * fast retransmits (RFC2582). SACK TCP is safe. */
2728 tcp_moderate_cwnd(tp
);
2731 tcp_set_ca_state(sk
, TCP_CA_Open
);
2735 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2736 static void tcp_try_undo_dsack(struct sock
*sk
)
2738 struct tcp_sock
*tp
= tcp_sk(sk
);
2740 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2741 DBGUNDO(sk
, "D-SACK");
2742 tcp_undo_cwr(sk
, true);
2743 tp
->undo_marker
= 0;
2744 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2748 /* We can clear retrans_stamp when there are no retransmissions in the
2749 * window. It would seem that it is trivially available for us in
2750 * tp->retrans_out, however, that kind of assumptions doesn't consider
2751 * what will happen if errors occur when sending retransmission for the
2752 * second time. ...It could the that such segment has only
2753 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2754 * the head skb is enough except for some reneging corner cases that
2755 * are not worth the effort.
2757 * Main reason for all this complexity is the fact that connection dying
2758 * time now depends on the validity of the retrans_stamp, in particular,
2759 * that successive retransmissions of a segment must not advance
2760 * retrans_stamp under any conditions.
2762 static int tcp_any_retrans_done(struct sock
*sk
)
2764 struct tcp_sock
*tp
= tcp_sk(sk
);
2765 struct sk_buff
*skb
;
2767 if (tp
->retrans_out
)
2770 skb
= tcp_write_queue_head(sk
);
2771 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2777 /* Undo during fast recovery after partial ACK. */
2779 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2781 struct tcp_sock
*tp
= tcp_sk(sk
);
2782 /* Partial ACK arrived. Force Hoe's retransmit. */
2783 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2785 if (tcp_may_undo(tp
)) {
2786 /* Plain luck! Hole if filled with delayed
2787 * packet, rather than with a retransmit.
2789 if (!tcp_any_retrans_done(sk
))
2790 tp
->retrans_stamp
= 0;
2792 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2795 tcp_undo_cwr(sk
, false);
2796 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2798 /* So... Do not make Hoe's retransmit yet.
2799 * If the first packet was delayed, the rest
2800 * ones are most probably delayed as well.
2807 /* Undo during loss recovery after partial ACK. */
2808 static int tcp_try_undo_loss(struct sock
*sk
)
2810 struct tcp_sock
*tp
= tcp_sk(sk
);
2812 if (tcp_may_undo(tp
)) {
2813 struct sk_buff
*skb
;
2814 tcp_for_write_queue(skb
, sk
) {
2815 if (skb
== tcp_send_head(sk
))
2817 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2820 tcp_clear_all_retrans_hints(tp
);
2822 DBGUNDO(sk
, "partial loss");
2824 tcp_undo_cwr(sk
, true);
2825 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2826 inet_csk(sk
)->icsk_retransmits
= 0;
2827 tp
->undo_marker
= 0;
2828 if (tcp_is_sack(tp
))
2829 tcp_set_ca_state(sk
, TCP_CA_Open
);
2835 static inline void tcp_complete_cwr(struct sock
*sk
)
2837 struct tcp_sock
*tp
= tcp_sk(sk
);
2839 /* Do not moderate cwnd if it's already undone in cwr or recovery. */
2840 if (tp
->undo_marker
) {
2841 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
)
2842 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2844 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2845 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2847 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2850 static void tcp_try_keep_open(struct sock
*sk
)
2852 struct tcp_sock
*tp
= tcp_sk(sk
);
2853 int state
= TCP_CA_Open
;
2855 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
) || tp
->undo_marker
)
2856 state
= TCP_CA_Disorder
;
2858 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2859 tcp_set_ca_state(sk
, state
);
2860 tp
->high_seq
= tp
->snd_nxt
;
2864 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2866 struct tcp_sock
*tp
= tcp_sk(sk
);
2868 tcp_verify_left_out(tp
);
2870 if (!tp
->frto_counter
&& !tcp_any_retrans_done(sk
))
2871 tp
->retrans_stamp
= 0;
2873 if (flag
& FLAG_ECE
)
2874 tcp_enter_cwr(sk
, 1);
2876 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2877 tcp_try_keep_open(sk
);
2878 tcp_moderate_cwnd(tp
);
2880 tcp_cwnd_down(sk
, flag
);
2884 static void tcp_mtup_probe_failed(struct sock
*sk
)
2886 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2888 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2889 icsk
->icsk_mtup
.probe_size
= 0;
2892 static void tcp_mtup_probe_success(struct sock
*sk
)
2894 struct tcp_sock
*tp
= tcp_sk(sk
);
2895 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2897 /* FIXME: breaks with very large cwnd */
2898 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2899 tp
->snd_cwnd
= tp
->snd_cwnd
*
2900 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2901 icsk
->icsk_mtup
.probe_size
;
2902 tp
->snd_cwnd_cnt
= 0;
2903 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2904 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2906 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2907 icsk
->icsk_mtup
.probe_size
= 0;
2908 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2911 /* Do a simple retransmit without using the backoff mechanisms in
2912 * tcp_timer. This is used for path mtu discovery.
2913 * The socket is already locked here.
2915 void tcp_simple_retransmit(struct sock
*sk
)
2917 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2918 struct tcp_sock
*tp
= tcp_sk(sk
);
2919 struct sk_buff
*skb
;
2920 unsigned int mss
= tcp_current_mss(sk
);
2921 u32 prior_lost
= tp
->lost_out
;
2923 tcp_for_write_queue(skb
, sk
) {
2924 if (skb
== tcp_send_head(sk
))
2926 if (tcp_skb_seglen(skb
) > mss
&&
2927 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2928 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2929 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2930 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2932 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2936 tcp_clear_retrans_hints_partial(tp
);
2938 if (prior_lost
== tp
->lost_out
)
2941 if (tcp_is_reno(tp
))
2942 tcp_limit_reno_sacked(tp
);
2944 tcp_verify_left_out(tp
);
2946 /* Don't muck with the congestion window here.
2947 * Reason is that we do not increase amount of _data_
2948 * in network, but units changed and effective
2949 * cwnd/ssthresh really reduced now.
2951 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2952 tp
->high_seq
= tp
->snd_nxt
;
2953 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2954 tp
->prior_ssthresh
= 0;
2955 tp
->undo_marker
= 0;
2956 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2958 tcp_xmit_retransmit_queue(sk
);
2960 EXPORT_SYMBOL(tcp_simple_retransmit
);
2962 /* This function implements the PRR algorithm, specifcally the PRR-SSRB
2963 * (proportional rate reduction with slow start reduction bound) as described in
2964 * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt.
2965 * It computes the number of packets to send (sndcnt) based on packets newly
2967 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2968 * cwnd reductions across a full RTT.
2969 * 2) If packets in flight is lower than ssthresh (such as due to excess
2970 * losses and/or application stalls), do not perform any further cwnd
2971 * reductions, but instead slow start up to ssthresh.
2973 static void tcp_update_cwnd_in_recovery(struct sock
*sk
, int newly_acked_sacked
,
2974 int fast_rexmit
, int flag
)
2976 struct tcp_sock
*tp
= tcp_sk(sk
);
2978 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2980 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
2981 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2983 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2985 sndcnt
= min_t(int, delta
,
2986 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2987 newly_acked_sacked
) + 1);
2990 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2991 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2994 /* Process an event, which can update packets-in-flight not trivially.
2995 * Main goal of this function is to calculate new estimate for left_out,
2996 * taking into account both packets sitting in receiver's buffer and
2997 * packets lost by network.
2999 * Besides that it does CWND reduction, when packet loss is detected
3000 * and changes state of machine.
3002 * It does _not_ decide what to send, it is made in function
3003 * tcp_xmit_retransmit_queue().
3005 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
,
3006 int newly_acked_sacked
, int flag
)
3008 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3009 struct tcp_sock
*tp
= tcp_sk(sk
);
3010 int is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3011 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
3012 (tcp_fackets_out(tp
) > tp
->reordering
));
3013 int fast_rexmit
= 0, mib_idx
;
3015 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
3017 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
3018 tp
->fackets_out
= 0;
3020 /* Now state machine starts.
3021 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
3022 if (flag
& FLAG_ECE
)
3023 tp
->prior_ssthresh
= 0;
3025 /* B. In all the states check for reneging SACKs. */
3026 if (tcp_check_sack_reneging(sk
, flag
))
3029 /* C. Process data loss notification, provided it is valid. */
3030 if (tcp_is_fack(tp
) && (flag
& FLAG_DATA_LOST
) &&
3031 before(tp
->snd_una
, tp
->high_seq
) &&
3032 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
3033 tp
->fackets_out
> tp
->reordering
) {
3034 tcp_mark_head_lost(sk
, tp
->fackets_out
- tp
->reordering
, 0);
3035 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSS
);
3038 /* D. Check consistency of the current state. */
3039 tcp_verify_left_out(tp
);
3041 /* E. Check state exit conditions. State can be terminated
3042 * when high_seq is ACKed. */
3043 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
3044 WARN_ON(tp
->retrans_out
!= 0);
3045 tp
->retrans_stamp
= 0;
3046 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
3047 switch (icsk
->icsk_ca_state
) {
3049 icsk
->icsk_retransmits
= 0;
3050 if (tcp_try_undo_recovery(sk
))
3055 /* CWR is to be held something *above* high_seq
3056 * is ACKed for CWR bit to reach receiver. */
3057 if (tp
->snd_una
!= tp
->high_seq
) {
3058 tcp_complete_cwr(sk
);
3059 tcp_set_ca_state(sk
, TCP_CA_Open
);
3063 case TCP_CA_Disorder
:
3064 tcp_try_undo_dsack(sk
);
3065 if (!tp
->undo_marker
||
3066 /* For SACK case do not Open to allow to undo
3067 * catching for all duplicate ACKs. */
3068 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
3069 tp
->undo_marker
= 0;
3070 tcp_set_ca_state(sk
, TCP_CA_Open
);
3074 case TCP_CA_Recovery
:
3075 if (tcp_is_reno(tp
))
3076 tcp_reset_reno_sack(tp
);
3077 if (tcp_try_undo_recovery(sk
))
3079 tcp_complete_cwr(sk
);
3084 /* F. Process state. */
3085 switch (icsk
->icsk_ca_state
) {
3086 case TCP_CA_Recovery
:
3087 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3088 if (tcp_is_reno(tp
) && is_dupack
)
3089 tcp_add_reno_sack(sk
);
3091 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
3094 if (flag
& FLAG_DATA_ACKED
)
3095 icsk
->icsk_retransmits
= 0;
3096 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
3097 tcp_reset_reno_sack(tp
);
3098 if (!tcp_try_undo_loss(sk
)) {
3099 tcp_moderate_cwnd(tp
);
3100 tcp_xmit_retransmit_queue(sk
);
3103 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
3105 /* Loss is undone; fall through to processing in Open state. */
3107 if (tcp_is_reno(tp
)) {
3108 if (flag
& FLAG_SND_UNA_ADVANCED
)
3109 tcp_reset_reno_sack(tp
);
3111 tcp_add_reno_sack(sk
);
3114 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
3115 tcp_try_undo_dsack(sk
);
3117 if (!tcp_time_to_recover(sk
)) {
3118 tcp_try_to_open(sk
, flag
);
3122 /* MTU probe failure: don't reduce cwnd */
3123 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3124 icsk
->icsk_mtup
.probe_size
&&
3125 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3126 tcp_mtup_probe_failed(sk
);
3127 /* Restores the reduction we did in tcp_mtup_probe() */
3129 tcp_simple_retransmit(sk
);
3133 /* Otherwise enter Recovery state */
3135 if (tcp_is_reno(tp
))
3136 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
3138 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
3140 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3142 tp
->high_seq
= tp
->snd_nxt
;
3143 tp
->prior_ssthresh
= 0;
3144 tp
->undo_marker
= tp
->snd_una
;
3145 tp
->undo_retrans
= tp
->retrans_out
;
3147 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
3148 if (!(flag
& FLAG_ECE
))
3149 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
3150 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
3151 TCP_ECN_queue_cwr(tp
);
3154 tp
->bytes_acked
= 0;
3155 tp
->snd_cwnd_cnt
= 0;
3156 tp
->prior_cwnd
= tp
->snd_cwnd
;
3157 tp
->prr_delivered
= 0;
3159 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
3163 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
3164 tcp_update_scoreboard(sk
, fast_rexmit
);
3165 tp
->prr_delivered
+= newly_acked_sacked
;
3166 tcp_update_cwnd_in_recovery(sk
, newly_acked_sacked
, fast_rexmit
, flag
);
3167 tcp_xmit_retransmit_queue(sk
);
3170 void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
3172 tcp_rtt_estimator(sk
, seq_rtt
);
3174 inet_csk(sk
)->icsk_backoff
= 0;
3176 EXPORT_SYMBOL(tcp_valid_rtt_meas
);
3178 /* Read draft-ietf-tcplw-high-performance before mucking
3179 * with this code. (Supersedes RFC1323)
3181 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
3183 /* RTTM Rule: A TSecr value received in a segment is used to
3184 * update the averaged RTT measurement only if the segment
3185 * acknowledges some new data, i.e., only if it advances the
3186 * left edge of the send window.
3188 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3189 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3191 * Changed: reset backoff as soon as we see the first valid sample.
3192 * If we do not, we get strongly overestimated rto. With timestamps
3193 * samples are accepted even from very old segments: f.e., when rtt=1
3194 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3195 * answer arrives rto becomes 120 seconds! If at least one of segments
3196 * in window is lost... Voila. --ANK (010210)
3198 struct tcp_sock
*tp
= tcp_sk(sk
);
3200 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
3203 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
3205 /* We don't have a timestamp. Can only use
3206 * packets that are not retransmitted to determine
3207 * rtt estimates. Also, we must not reset the
3208 * backoff for rto until we get a non-retransmitted
3209 * packet. This allows us to deal with a situation
3210 * where the network delay has increased suddenly.
3211 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3214 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3217 tcp_valid_rtt_meas(sk
, seq_rtt
);
3220 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3223 const struct tcp_sock
*tp
= tcp_sk(sk
);
3224 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3225 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3226 tcp_ack_saw_tstamp(sk
, flag
);
3227 else if (seq_rtt
>= 0)
3228 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
3231 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
3233 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3234 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
3235 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
3238 /* Restart timer after forward progress on connection.
3239 * RFC2988 recommends to restart timer to now+rto.
3241 static void tcp_rearm_rto(struct sock
*sk
)
3243 struct tcp_sock
*tp
= tcp_sk(sk
);
3245 if (!tp
->packets_out
) {
3246 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3248 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3249 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3253 /* If we get here, the whole TSO packet has not been acked. */
3254 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3256 struct tcp_sock
*tp
= tcp_sk(sk
);
3259 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3261 packets_acked
= tcp_skb_pcount(skb
);
3262 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3264 packets_acked
-= tcp_skb_pcount(skb
);
3266 if (packets_acked
) {
3267 BUG_ON(tcp_skb_pcount(skb
) == 0);
3268 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3271 return packets_acked
;
3274 /* Remove acknowledged frames from the retransmission queue. If our packet
3275 * is before the ack sequence we can discard it as it's confirmed to have
3276 * arrived at the other end.
3278 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3281 struct tcp_sock
*tp
= tcp_sk(sk
);
3282 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3283 struct sk_buff
*skb
;
3284 u32 now
= tcp_time_stamp
;
3285 int fully_acked
= 1;
3288 u32 reord
= tp
->packets_out
;
3289 u32 prior_sacked
= tp
->sacked_out
;
3291 s32 ca_seq_rtt
= -1;
3292 ktime_t last_ackt
= net_invalid_timestamp();
3294 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3295 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3297 u8 sacked
= scb
->sacked
;
3299 /* Determine how many packets and what bytes were acked, tso and else */
3300 if (after(scb
->end_seq
, tp
->snd_una
)) {
3301 if (tcp_skb_pcount(skb
) == 1 ||
3302 !after(tp
->snd_una
, scb
->seq
))
3305 acked_pcount
= tcp_tso_acked(sk
, skb
);
3311 acked_pcount
= tcp_skb_pcount(skb
);
3314 if (sacked
& TCPCB_RETRANS
) {
3315 if (sacked
& TCPCB_SACKED_RETRANS
)
3316 tp
->retrans_out
-= acked_pcount
;
3317 flag
|= FLAG_RETRANS_DATA_ACKED
;
3320 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
3321 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
3323 ca_seq_rtt
= now
- scb
->when
;
3324 last_ackt
= skb
->tstamp
;
3326 seq_rtt
= ca_seq_rtt
;
3328 if (!(sacked
& TCPCB_SACKED_ACKED
))
3329 reord
= min(pkts_acked
, reord
);
3332 if (sacked
& TCPCB_SACKED_ACKED
)
3333 tp
->sacked_out
-= acked_pcount
;
3334 if (sacked
& TCPCB_LOST
)
3335 tp
->lost_out
-= acked_pcount
;
3337 tp
->packets_out
-= acked_pcount
;
3338 pkts_acked
+= acked_pcount
;
3340 /* Initial outgoing SYN's get put onto the write_queue
3341 * just like anything else we transmit. It is not
3342 * true data, and if we misinform our callers that
3343 * this ACK acks real data, we will erroneously exit
3344 * connection startup slow start one packet too
3345 * quickly. This is severely frowned upon behavior.
3347 if (!(scb
->tcp_flags
& TCPHDR_SYN
)) {
3348 flag
|= FLAG_DATA_ACKED
;
3350 flag
|= FLAG_SYN_ACKED
;
3351 tp
->retrans_stamp
= 0;
3357 tcp_unlink_write_queue(skb
, sk
);
3358 sk_wmem_free_skb(sk
, skb
);
3359 tp
->scoreboard_skb_hint
= NULL
;
3360 if (skb
== tp
->retransmit_skb_hint
)
3361 tp
->retransmit_skb_hint
= NULL
;
3362 if (skb
== tp
->lost_skb_hint
)
3363 tp
->lost_skb_hint
= NULL
;
3366 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3367 tp
->snd_up
= tp
->snd_una
;
3369 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3370 flag
|= FLAG_SACK_RENEGING
;
3372 if (flag
& FLAG_ACKED
) {
3373 const struct tcp_congestion_ops
*ca_ops
3374 = inet_csk(sk
)->icsk_ca_ops
;
3376 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3377 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3378 tcp_mtup_probe_success(sk
);
3381 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3384 if (tcp_is_reno(tp
)) {
3385 tcp_remove_reno_sacks(sk
, pkts_acked
);
3389 /* Non-retransmitted hole got filled? That's reordering */
3390 if (reord
< prior_fackets
)
3391 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3393 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3394 prior_sacked
- tp
->sacked_out
;
3395 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3398 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3400 if (ca_ops
->pkts_acked
) {
3403 /* Is the ACK triggering packet unambiguous? */
3404 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3405 /* High resolution needed and available? */
3406 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3407 !ktime_equal(last_ackt
,
3408 net_invalid_timestamp()))
3409 rtt_us
= ktime_us_delta(ktime_get_real(),
3411 else if (ca_seq_rtt
>= 0)
3412 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3415 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3419 #if FASTRETRANS_DEBUG > 0
3420 WARN_ON((int)tp
->sacked_out
< 0);
3421 WARN_ON((int)tp
->lost_out
< 0);
3422 WARN_ON((int)tp
->retrans_out
< 0);
3423 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3424 icsk
= inet_csk(sk
);
3426 printk(KERN_DEBUG
"Leak l=%u %d\n",
3427 tp
->lost_out
, icsk
->icsk_ca_state
);
3430 if (tp
->sacked_out
) {
3431 printk(KERN_DEBUG
"Leak s=%u %d\n",
3432 tp
->sacked_out
, icsk
->icsk_ca_state
);
3435 if (tp
->retrans_out
) {
3436 printk(KERN_DEBUG
"Leak r=%u %d\n",
3437 tp
->retrans_out
, icsk
->icsk_ca_state
);
3438 tp
->retrans_out
= 0;
3445 static void tcp_ack_probe(struct sock
*sk
)
3447 const struct tcp_sock
*tp
= tcp_sk(sk
);
3448 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3450 /* Was it a usable window open? */
3452 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3453 icsk
->icsk_backoff
= 0;
3454 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3455 /* Socket must be waked up by subsequent tcp_data_snd_check().
3456 * This function is not for random using!
3459 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3460 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3465 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3467 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3468 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3471 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3473 const struct tcp_sock
*tp
= tcp_sk(sk
);
3474 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3475 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3478 /* Check that window update is acceptable.
3479 * The function assumes that snd_una<=ack<=snd_next.
3481 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3482 const u32 ack
, const u32 ack_seq
,
3485 return after(ack
, tp
->snd_una
) ||
3486 after(ack_seq
, tp
->snd_wl1
) ||
3487 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3490 /* Update our send window.
3492 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3493 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3495 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
3498 struct tcp_sock
*tp
= tcp_sk(sk
);
3500 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3502 if (likely(!tcp_hdr(skb
)->syn
))
3503 nwin
<<= tp
->rx_opt
.snd_wscale
;
3505 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3506 flag
|= FLAG_WIN_UPDATE
;
3507 tcp_update_wl(tp
, ack_seq
);
3509 if (tp
->snd_wnd
!= nwin
) {
3512 /* Note, it is the only place, where
3513 * fast path is recovered for sending TCP.
3516 tcp_fast_path_check(sk
);
3518 if (nwin
> tp
->max_window
) {
3519 tp
->max_window
= nwin
;
3520 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3530 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3531 * continue in congestion avoidance.
3533 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3535 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3536 tp
->snd_cwnd_cnt
= 0;
3537 tp
->bytes_acked
= 0;
3538 TCP_ECN_queue_cwr(tp
);
3539 tcp_moderate_cwnd(tp
);
3542 /* A conservative spurious RTO response algorithm: reduce cwnd using
3543 * rate halving and continue in congestion avoidance.
3545 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3547 tcp_enter_cwr(sk
, 0);
3550 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3552 if (flag
& FLAG_ECE
)
3553 tcp_ratehalving_spur_to_response(sk
);
3555 tcp_undo_cwr(sk
, true);
3558 /* F-RTO spurious RTO detection algorithm (RFC4138)
3560 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3561 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3562 * window (but not to or beyond highest sequence sent before RTO):
3563 * On First ACK, send two new segments out.
3564 * On Second ACK, RTO was likely spurious. Do spurious response (response
3565 * algorithm is not part of the F-RTO detection algorithm
3566 * given in RFC4138 but can be selected separately).
3567 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3568 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3569 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3570 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3572 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3573 * original window even after we transmit two new data segments.
3576 * on first step, wait until first cumulative ACK arrives, then move to
3577 * the second step. In second step, the next ACK decides.
3579 * F-RTO is implemented (mainly) in four functions:
3580 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3581 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3582 * called when tcp_use_frto() showed green light
3583 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3584 * - tcp_enter_frto_loss() is called if there is not enough evidence
3585 * to prove that the RTO is indeed spurious. It transfers the control
3586 * from F-RTO to the conventional RTO recovery
3588 static int tcp_process_frto(struct sock
*sk
, int flag
)
3590 struct tcp_sock
*tp
= tcp_sk(sk
);
3592 tcp_verify_left_out(tp
);
3594 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3595 if (flag
& FLAG_DATA_ACKED
)
3596 inet_csk(sk
)->icsk_retransmits
= 0;
3598 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3599 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3600 tp
->undo_marker
= 0;
3602 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3603 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3607 if (!tcp_is_sackfrto(tp
)) {
3608 /* RFC4138 shortcoming in step 2; should also have case c):
3609 * ACK isn't duplicate nor advances window, e.g., opposite dir
3612 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3615 if (!(flag
& FLAG_DATA_ACKED
)) {
3616 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3621 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3622 /* Prevent sending of new data. */
3623 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3624 tcp_packets_in_flight(tp
));
3628 if ((tp
->frto_counter
>= 2) &&
3629 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3630 ((flag
& FLAG_DATA_SACKED
) &&
3631 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3632 /* RFC4138 shortcoming (see comment above) */
3633 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3634 (flag
& FLAG_NOT_DUP
))
3637 tcp_enter_frto_loss(sk
, 3, flag
);
3642 if (tp
->frto_counter
== 1) {
3643 /* tcp_may_send_now needs to see updated state */
3644 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3645 tp
->frto_counter
= 2;
3647 if (!tcp_may_send_now(sk
))
3648 tcp_enter_frto_loss(sk
, 2, flag
);
3652 switch (sysctl_tcp_frto_response
) {
3654 tcp_undo_spur_to_response(sk
, flag
);
3657 tcp_conservative_spur_to_response(tp
);
3660 tcp_ratehalving_spur_to_response(sk
);
3663 tp
->frto_counter
= 0;
3664 tp
->undo_marker
= 0;
3665 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3670 /* This routine deals with incoming acks, but not outgoing ones. */
3671 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
3673 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3674 struct tcp_sock
*tp
= tcp_sk(sk
);
3675 u32 prior_snd_una
= tp
->snd_una
;
3676 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3677 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3678 u32 prior_in_flight
;
3681 int prior_sacked
= tp
->sacked_out
;
3682 int newly_acked_sacked
= 0;
3685 /* If the ack is older than previous acks
3686 * then we can probably ignore it.
3688 if (before(ack
, prior_snd_una
))
3691 /* If the ack includes data we haven't sent yet, discard
3692 * this segment (RFC793 Section 3.9).
3694 if (after(ack
, tp
->snd_nxt
))
3697 if (after(ack
, prior_snd_una
))
3698 flag
|= FLAG_SND_UNA_ADVANCED
;
3700 if (sysctl_tcp_abc
) {
3701 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3702 tp
->bytes_acked
+= ack
- prior_snd_una
;
3703 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3704 /* we assume just one segment left network */
3705 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3709 prior_fackets
= tp
->fackets_out
;
3710 prior_in_flight
= tcp_packets_in_flight(tp
);
3712 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3713 /* Window is constant, pure forward advance.
3714 * No more checks are required.
3715 * Note, we use the fact that SND.UNA>=SND.WL2.
3717 tcp_update_wl(tp
, ack_seq
);
3719 flag
|= FLAG_WIN_UPDATE
;
3721 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3723 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3725 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3728 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3730 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3732 if (TCP_SKB_CB(skb
)->sacked
)
3733 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3735 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3738 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3741 /* We passed data and got it acked, remove any soft error
3742 * log. Something worked...
3744 sk
->sk_err_soft
= 0;
3745 icsk
->icsk_probes_out
= 0;
3746 tp
->rcv_tstamp
= tcp_time_stamp
;
3747 prior_packets
= tp
->packets_out
;
3751 /* See if we can take anything off of the retransmit queue. */
3752 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3754 newly_acked_sacked
= (prior_packets
- prior_sacked
) -
3755 (tp
->packets_out
- tp
->sacked_out
);
3757 if (tp
->frto_counter
)
3758 frto_cwnd
= tcp_process_frto(sk
, flag
);
3759 /* Guarantee sacktag reordering detection against wrap-arounds */
3760 if (before(tp
->frto_highmark
, tp
->snd_una
))
3761 tp
->frto_highmark
= 0;
3763 if (tcp_ack_is_dubious(sk
, flag
)) {
3764 /* Advance CWND, if state allows this. */
3765 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3766 tcp_may_raise_cwnd(sk
, flag
))
3767 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3768 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
,
3769 newly_acked_sacked
, flag
);
3771 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3772 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3775 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3776 dst_confirm(__sk_dst_get(sk
));
3781 /* If this ack opens up a zero window, clear backoff. It was
3782 * being used to time the probes, and is probably far higher than
3783 * it needs to be for normal retransmission.
3785 if (tcp_send_head(sk
))
3790 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3794 if (TCP_SKB_CB(skb
)->sacked
) {
3795 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3796 if (icsk
->icsk_ca_state
== TCP_CA_Open
)
3797 tcp_try_keep_open(sk
);
3800 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3804 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3805 * But, this can also be called on packets in the established flow when
3806 * the fast version below fails.
3808 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3809 u8
**hvpp
, int estab
)
3812 struct tcphdr
*th
= tcp_hdr(skb
);
3813 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3815 ptr
= (unsigned char *)(th
+ 1);
3816 opt_rx
->saw_tstamp
= 0;
3818 while (length
> 0) {
3819 int opcode
= *ptr
++;
3825 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3830 if (opsize
< 2) /* "silly options" */
3832 if (opsize
> length
)
3833 return; /* don't parse partial options */
3836 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3837 u16 in_mss
= get_unaligned_be16(ptr
);
3839 if (opt_rx
->user_mss
&&
3840 opt_rx
->user_mss
< in_mss
)
3841 in_mss
= opt_rx
->user_mss
;
3842 opt_rx
->mss_clamp
= in_mss
;
3847 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3848 !estab
&& sysctl_tcp_window_scaling
) {
3849 __u8 snd_wscale
= *(__u8
*)ptr
;
3850 opt_rx
->wscale_ok
= 1;
3851 if (snd_wscale
> 14) {
3852 if (net_ratelimit())
3853 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3854 "scaling value %d >14 received.\n",
3858 opt_rx
->snd_wscale
= snd_wscale
;
3861 case TCPOPT_TIMESTAMP
:
3862 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3863 ((estab
&& opt_rx
->tstamp_ok
) ||
3864 (!estab
&& sysctl_tcp_timestamps
))) {
3865 opt_rx
->saw_tstamp
= 1;
3866 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3867 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3870 case TCPOPT_SACK_PERM
:
3871 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3872 !estab
&& sysctl_tcp_sack
) {
3873 opt_rx
->sack_ok
= 1;
3874 tcp_sack_reset(opt_rx
);
3879 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3880 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3882 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3885 #ifdef CONFIG_TCP_MD5SIG
3888 * The MD5 Hash has already been
3889 * checked (see tcp_v{4,6}_do_rcv()).
3894 /* This option is variable length.
3897 case TCPOLEN_COOKIE_BASE
:
3898 /* not yet implemented */
3900 case TCPOLEN_COOKIE_PAIR
:
3901 /* not yet implemented */
3903 case TCPOLEN_COOKIE_MIN
+0:
3904 case TCPOLEN_COOKIE_MIN
+2:
3905 case TCPOLEN_COOKIE_MIN
+4:
3906 case TCPOLEN_COOKIE_MIN
+6:
3907 case TCPOLEN_COOKIE_MAX
:
3908 /* 16-bit multiple */
3909 opt_rx
->cookie_plus
= opsize
;
3924 EXPORT_SYMBOL(tcp_parse_options
);
3926 static int tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, struct tcphdr
*th
)
3928 __be32
*ptr
= (__be32
*)(th
+ 1);
3930 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3931 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3932 tp
->rx_opt
.saw_tstamp
= 1;
3934 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3936 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3942 /* Fast parse options. This hopes to only see timestamps.
3943 * If it is wrong it falls back on tcp_parse_options().
3945 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3946 struct tcp_sock
*tp
, u8
**hvpp
)
3948 /* In the spirit of fast parsing, compare doff directly to constant
3949 * values. Because equality is used, short doff can be ignored here.
3951 if (th
->doff
== (sizeof(*th
) / 4)) {
3952 tp
->rx_opt
.saw_tstamp
= 0;
3954 } else if (tp
->rx_opt
.tstamp_ok
&&
3955 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3956 if (tcp_parse_aligned_timestamp(tp
, th
))
3959 tcp_parse_options(skb
, &tp
->rx_opt
, hvpp
, 1);
3963 #ifdef CONFIG_TCP_MD5SIG
3965 * Parse MD5 Signature option
3967 u8
*tcp_parse_md5sig_option(struct tcphdr
*th
)
3969 int length
= (th
->doff
<< 2) - sizeof (*th
);
3970 u8
*ptr
= (u8
*)(th
+ 1);
3972 /* If the TCP option is too short, we can short cut */
3973 if (length
< TCPOLEN_MD5SIG
)
3976 while (length
> 0) {
3977 int opcode
= *ptr
++;
3988 if (opsize
< 2 || opsize
> length
)
3990 if (opcode
== TCPOPT_MD5SIG
)
3991 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3998 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
4001 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
4003 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
4004 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
4007 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
4009 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
4010 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
4011 * extra check below makes sure this can only happen
4012 * for pure ACK frames. -DaveM
4014 * Not only, also it occurs for expired timestamps.
4017 if (tcp_paws_check(&tp
->rx_opt
, 0))
4018 tcp_store_ts_recent(tp
);
4022 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4024 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4025 * it can pass through stack. So, the following predicate verifies that
4026 * this segment is not used for anything but congestion avoidance or
4027 * fast retransmit. Moreover, we even are able to eliminate most of such
4028 * second order effects, if we apply some small "replay" window (~RTO)
4029 * to timestamp space.
4031 * All these measures still do not guarantee that we reject wrapped ACKs
4032 * on networks with high bandwidth, when sequence space is recycled fastly,
4033 * but it guarantees that such events will be very rare and do not affect
4034 * connection seriously. This doesn't look nice, but alas, PAWS is really
4037 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4038 * states that events when retransmit arrives after original data are rare.
4039 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4040 * the biggest problem on large power networks even with minor reordering.
4041 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4042 * up to bandwidth of 18Gigabit/sec. 8) ]
4045 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
4047 struct tcp_sock
*tp
= tcp_sk(sk
);
4048 struct tcphdr
*th
= tcp_hdr(skb
);
4049 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4050 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
4052 return (/* 1. Pure ACK with correct sequence number. */
4053 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
4055 /* 2. ... and duplicate ACK. */
4056 ack
== tp
->snd_una
&&
4058 /* 3. ... and does not update window. */
4059 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
4061 /* 4. ... and sits in replay window. */
4062 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
4065 static inline int tcp_paws_discard(const struct sock
*sk
,
4066 const struct sk_buff
*skb
)
4068 const struct tcp_sock
*tp
= tcp_sk(sk
);
4070 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
4071 !tcp_disordered_ack(sk
, skb
);
4074 /* Check segment sequence number for validity.
4076 * Segment controls are considered valid, if the segment
4077 * fits to the window after truncation to the window. Acceptability
4078 * of data (and SYN, FIN, of course) is checked separately.
4079 * See tcp_data_queue(), for example.
4081 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4082 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4083 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4084 * (borrowed from freebsd)
4087 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4089 return !before(end_seq
, tp
->rcv_wup
) &&
4090 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4093 /* When we get a reset we do this. */
4094 static void tcp_reset(struct sock
*sk
)
4096 /* We want the right error as BSD sees it (and indeed as we do). */
4097 switch (sk
->sk_state
) {
4099 sk
->sk_err
= ECONNREFUSED
;
4101 case TCP_CLOSE_WAIT
:
4107 sk
->sk_err
= ECONNRESET
;
4109 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4112 if (!sock_flag(sk
, SOCK_DEAD
))
4113 sk
->sk_error_report(sk
);
4119 * Process the FIN bit. This now behaves as it is supposed to work
4120 * and the FIN takes effect when it is validly part of sequence
4121 * space. Not before when we get holes.
4123 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4124 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4127 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4128 * close and we go into CLOSING (and later onto TIME-WAIT)
4130 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4132 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
4134 struct tcp_sock
*tp
= tcp_sk(sk
);
4136 inet_csk_schedule_ack(sk
);
4138 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4139 sock_set_flag(sk
, SOCK_DONE
);
4141 switch (sk
->sk_state
) {
4143 case TCP_ESTABLISHED
:
4144 /* Move to CLOSE_WAIT */
4145 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4146 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4149 case TCP_CLOSE_WAIT
:
4151 /* Received a retransmission of the FIN, do
4156 /* RFC793: Remain in the LAST-ACK state. */
4160 /* This case occurs when a simultaneous close
4161 * happens, we must ack the received FIN and
4162 * enter the CLOSING state.
4165 tcp_set_state(sk
, TCP_CLOSING
);
4168 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4170 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4173 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4174 * cases we should never reach this piece of code.
4176 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
4177 __func__
, sk
->sk_state
);
4181 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4182 * Probably, we should reset in this case. For now drop them.
4184 __skb_queue_purge(&tp
->out_of_order_queue
);
4185 if (tcp_is_sack(tp
))
4186 tcp_sack_reset(&tp
->rx_opt
);
4189 if (!sock_flag(sk
, SOCK_DEAD
)) {
4190 sk
->sk_state_change(sk
);
4192 /* Do not send POLL_HUP for half duplex close. */
4193 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4194 sk
->sk_state
== TCP_CLOSE
)
4195 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4197 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4201 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4204 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4205 if (before(seq
, sp
->start_seq
))
4206 sp
->start_seq
= seq
;
4207 if (after(end_seq
, sp
->end_seq
))
4208 sp
->end_seq
= end_seq
;
4214 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4216 struct tcp_sock
*tp
= tcp_sk(sk
);
4218 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4221 if (before(seq
, tp
->rcv_nxt
))
4222 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4224 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4226 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4228 tp
->rx_opt
.dsack
= 1;
4229 tp
->duplicate_sack
[0].start_seq
= seq
;
4230 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4234 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4236 struct tcp_sock
*tp
= tcp_sk(sk
);
4238 if (!tp
->rx_opt
.dsack
)
4239 tcp_dsack_set(sk
, seq
, end_seq
);
4241 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4244 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
4246 struct tcp_sock
*tp
= tcp_sk(sk
);
4248 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4249 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4250 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4251 tcp_enter_quickack_mode(sk
);
4253 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4254 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4256 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4257 end_seq
= tp
->rcv_nxt
;
4258 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4265 /* These routines update the SACK block as out-of-order packets arrive or
4266 * in-order packets close up the sequence space.
4268 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4271 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4272 struct tcp_sack_block
*swalk
= sp
+ 1;
4274 /* See if the recent change to the first SACK eats into
4275 * or hits the sequence space of other SACK blocks, if so coalesce.
4277 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4278 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4281 /* Zap SWALK, by moving every further SACK up by one slot.
4282 * Decrease num_sacks.
4284 tp
->rx_opt
.num_sacks
--;
4285 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4289 this_sack
++, swalk
++;
4293 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4295 struct tcp_sock
*tp
= tcp_sk(sk
);
4296 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4297 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4303 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4304 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4305 /* Rotate this_sack to the first one. */
4306 for (; this_sack
> 0; this_sack
--, sp
--)
4307 swap(*sp
, *(sp
- 1));
4309 tcp_sack_maybe_coalesce(tp
);
4314 /* Could not find an adjacent existing SACK, build a new one,
4315 * put it at the front, and shift everyone else down. We
4316 * always know there is at least one SACK present already here.
4318 * If the sack array is full, forget about the last one.
4320 if (this_sack
>= TCP_NUM_SACKS
) {
4322 tp
->rx_opt
.num_sacks
--;
4325 for (; this_sack
> 0; this_sack
--, sp
--)
4329 /* Build the new head SACK, and we're done. */
4330 sp
->start_seq
= seq
;
4331 sp
->end_seq
= end_seq
;
4332 tp
->rx_opt
.num_sacks
++;
4335 /* RCV.NXT advances, some SACKs should be eaten. */
4337 static void tcp_sack_remove(struct tcp_sock
*tp
)
4339 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4340 int num_sacks
= tp
->rx_opt
.num_sacks
;
4343 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4344 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4345 tp
->rx_opt
.num_sacks
= 0;
4349 for (this_sack
= 0; this_sack
< num_sacks
;) {
4350 /* Check if the start of the sack is covered by RCV.NXT. */
4351 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4354 /* RCV.NXT must cover all the block! */
4355 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4357 /* Zap this SACK, by moving forward any other SACKS. */
4358 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4359 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4366 tp
->rx_opt
.num_sacks
= num_sacks
;
4369 /* This one checks to see if we can put data from the
4370 * out_of_order queue into the receive_queue.
4372 static void tcp_ofo_queue(struct sock
*sk
)
4374 struct tcp_sock
*tp
= tcp_sk(sk
);
4375 __u32 dsack_high
= tp
->rcv_nxt
;
4376 struct sk_buff
*skb
;
4378 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4379 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4382 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4383 __u32 dsack
= dsack_high
;
4384 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4385 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4386 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4389 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4390 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4391 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4395 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4396 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4397 TCP_SKB_CB(skb
)->end_seq
);
4399 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4400 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4401 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4402 if (tcp_hdr(skb
)->fin
)
4403 tcp_fin(skb
, sk
, tcp_hdr(skb
));
4407 static int tcp_prune_ofo_queue(struct sock
*sk
);
4408 static int tcp_prune_queue(struct sock
*sk
);
4410 static inline int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
4412 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4413 !sk_rmem_schedule(sk
, size
)) {
4415 if (tcp_prune_queue(sk
) < 0)
4418 if (!sk_rmem_schedule(sk
, size
)) {
4419 if (!tcp_prune_ofo_queue(sk
))
4422 if (!sk_rmem_schedule(sk
, size
))
4429 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4431 struct tcphdr
*th
= tcp_hdr(skb
);
4432 struct tcp_sock
*tp
= tcp_sk(sk
);
4435 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4439 __skb_pull(skb
, th
->doff
* 4);
4441 TCP_ECN_accept_cwr(tp
, skb
);
4443 tp
->rx_opt
.dsack
= 0;
4445 /* Queue data for delivery to the user.
4446 * Packets in sequence go to the receive queue.
4447 * Out of sequence packets to the out_of_order_queue.
4449 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4450 if (tcp_receive_window(tp
) == 0)
4453 /* Ok. In sequence. In window. */
4454 if (tp
->ucopy
.task
== current
&&
4455 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4456 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4457 int chunk
= min_t(unsigned int, skb
->len
,
4460 __set_current_state(TASK_RUNNING
);
4463 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4464 tp
->ucopy
.len
-= chunk
;
4465 tp
->copied_seq
+= chunk
;
4466 eaten
= (chunk
== skb
->len
);
4467 tcp_rcv_space_adjust(sk
);
4475 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4478 skb_set_owner_r(skb
, sk
);
4479 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4481 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4483 tcp_event_data_recv(sk
, skb
);
4485 tcp_fin(skb
, sk
, th
);
4487 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4490 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4491 * gap in queue is filled.
4493 if (skb_queue_empty(&tp
->out_of_order_queue
))
4494 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4497 if (tp
->rx_opt
.num_sacks
)
4498 tcp_sack_remove(tp
);
4500 tcp_fast_path_check(sk
);
4504 else if (!sock_flag(sk
, SOCK_DEAD
))
4505 sk
->sk_data_ready(sk
, 0);
4509 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4510 /* A retransmit, 2nd most common case. Force an immediate ack. */
4511 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4512 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4515 tcp_enter_quickack_mode(sk
);
4516 inet_csk_schedule_ack(sk
);
4522 /* Out of window. F.e. zero window probe. */
4523 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4526 tcp_enter_quickack_mode(sk
);
4528 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4529 /* Partial packet, seq < rcv_next < end_seq */
4530 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4531 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4532 TCP_SKB_CB(skb
)->end_seq
);
4534 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4536 /* If window is closed, drop tail of packet. But after
4537 * remembering D-SACK for its head made in previous line.
4539 if (!tcp_receive_window(tp
))
4544 TCP_ECN_check_ce(tp
, skb
);
4546 if (tcp_try_rmem_schedule(sk
, skb
->truesize
))
4549 /* Disable header prediction. */
4551 inet_csk_schedule_ack(sk
);
4553 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4554 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4556 skb_set_owner_r(skb
, sk
);
4558 if (!skb_peek(&tp
->out_of_order_queue
)) {
4559 /* Initial out of order segment, build 1 SACK. */
4560 if (tcp_is_sack(tp
)) {
4561 tp
->rx_opt
.num_sacks
= 1;
4562 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4563 tp
->selective_acks
[0].end_seq
=
4564 TCP_SKB_CB(skb
)->end_seq
;
4566 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4568 struct sk_buff
*skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4569 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4570 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4572 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4573 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4575 if (!tp
->rx_opt
.num_sacks
||
4576 tp
->selective_acks
[0].end_seq
!= seq
)
4579 /* Common case: data arrive in order after hole. */
4580 tp
->selective_acks
[0].end_seq
= end_seq
;
4584 /* Find place to insert this segment. */
4586 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4588 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4592 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4595 /* Do skb overlap to previous one? */
4596 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4597 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4598 /* All the bits are present. Drop. */
4600 tcp_dsack_set(sk
, seq
, end_seq
);
4603 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4604 /* Partial overlap. */
4605 tcp_dsack_set(sk
, seq
,
4606 TCP_SKB_CB(skb1
)->end_seq
);
4608 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4612 skb1
= skb_queue_prev(
4613 &tp
->out_of_order_queue
,
4618 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4620 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4622 /* And clean segments covered by new one as whole. */
4623 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4624 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4626 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4628 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4629 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4633 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4634 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4635 TCP_SKB_CB(skb1
)->end_seq
);
4640 if (tcp_is_sack(tp
))
4641 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4645 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4646 struct sk_buff_head
*list
)
4648 struct sk_buff
*next
= NULL
;
4650 if (!skb_queue_is_last(list
, skb
))
4651 next
= skb_queue_next(list
, skb
);
4653 __skb_unlink(skb
, list
);
4655 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4660 /* Collapse contiguous sequence of skbs head..tail with
4661 * sequence numbers start..end.
4663 * If tail is NULL, this means until the end of the list.
4665 * Segments with FIN/SYN are not collapsed (only because this
4669 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4670 struct sk_buff
*head
, struct sk_buff
*tail
,
4673 struct sk_buff
*skb
, *n
;
4676 /* First, check that queue is collapsible and find
4677 * the point where collapsing can be useful. */
4681 skb_queue_walk_from_safe(list
, skb
, n
) {
4684 /* No new bits? It is possible on ofo queue. */
4685 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4686 skb
= tcp_collapse_one(sk
, skb
, list
);
4692 /* The first skb to collapse is:
4694 * - bloated or contains data before "start" or
4695 * overlaps to the next one.
4697 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4698 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4699 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4700 end_of_skbs
= false;
4704 if (!skb_queue_is_last(list
, skb
)) {
4705 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4707 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4708 end_of_skbs
= false;
4713 /* Decided to skip this, advance start seq. */
4714 start
= TCP_SKB_CB(skb
)->end_seq
;
4716 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4719 while (before(start
, end
)) {
4720 struct sk_buff
*nskb
;
4721 unsigned int header
= skb_headroom(skb
);
4722 int copy
= SKB_MAX_ORDER(header
, 0);
4724 /* Too big header? This can happen with IPv6. */
4727 if (end
- start
< copy
)
4729 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4733 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4734 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4736 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4738 skb_reserve(nskb
, header
);
4739 memcpy(nskb
->head
, skb
->head
, header
);
4740 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4741 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4742 __skb_queue_before(list
, skb
, nskb
);
4743 skb_set_owner_r(nskb
, sk
);
4745 /* Copy data, releasing collapsed skbs. */
4747 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4748 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4752 size
= min(copy
, size
);
4753 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4755 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4759 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4760 skb
= tcp_collapse_one(sk
, skb
, list
);
4763 tcp_hdr(skb
)->syn
||
4771 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4772 * and tcp_collapse() them until all the queue is collapsed.
4774 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4776 struct tcp_sock
*tp
= tcp_sk(sk
);
4777 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4778 struct sk_buff
*head
;
4784 start
= TCP_SKB_CB(skb
)->seq
;
4785 end
= TCP_SKB_CB(skb
)->end_seq
;
4789 struct sk_buff
*next
= NULL
;
4791 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4792 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4795 /* Segment is terminated when we see gap or when
4796 * we are at the end of all the queue. */
4798 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4799 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4800 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4801 head
, skb
, start
, end
);
4805 /* Start new segment */
4806 start
= TCP_SKB_CB(skb
)->seq
;
4807 end
= TCP_SKB_CB(skb
)->end_seq
;
4809 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4810 start
= TCP_SKB_CB(skb
)->seq
;
4811 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4812 end
= TCP_SKB_CB(skb
)->end_seq
;
4818 * Purge the out-of-order queue.
4819 * Return true if queue was pruned.
4821 static int tcp_prune_ofo_queue(struct sock
*sk
)
4823 struct tcp_sock
*tp
= tcp_sk(sk
);
4826 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4827 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4828 __skb_queue_purge(&tp
->out_of_order_queue
);
4830 /* Reset SACK state. A conforming SACK implementation will
4831 * do the same at a timeout based retransmit. When a connection
4832 * is in a sad state like this, we care only about integrity
4833 * of the connection not performance.
4835 if (tp
->rx_opt
.sack_ok
)
4836 tcp_sack_reset(&tp
->rx_opt
);
4843 /* Reduce allocated memory if we can, trying to get
4844 * the socket within its memory limits again.
4846 * Return less than zero if we should start dropping frames
4847 * until the socket owning process reads some of the data
4848 * to stabilize the situation.
4850 static int tcp_prune_queue(struct sock
*sk
)
4852 struct tcp_sock
*tp
= tcp_sk(sk
);
4854 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4856 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4858 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4859 tcp_clamp_window(sk
);
4860 else if (tcp_memory_pressure
)
4861 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4863 tcp_collapse_ofo_queue(sk
);
4864 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4865 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4866 skb_peek(&sk
->sk_receive_queue
),
4868 tp
->copied_seq
, tp
->rcv_nxt
);
4871 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4874 /* Collapsing did not help, destructive actions follow.
4875 * This must not ever occur. */
4877 tcp_prune_ofo_queue(sk
);
4879 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4882 /* If we are really being abused, tell the caller to silently
4883 * drop receive data on the floor. It will get retransmitted
4884 * and hopefully then we'll have sufficient space.
4886 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4888 /* Massive buffer overcommit. */
4893 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4894 * As additional protections, we do not touch cwnd in retransmission phases,
4895 * and if application hit its sndbuf limit recently.
4897 void tcp_cwnd_application_limited(struct sock
*sk
)
4899 struct tcp_sock
*tp
= tcp_sk(sk
);
4901 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4902 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4903 /* Limited by application or receiver window. */
4904 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4905 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4906 if (win_used
< tp
->snd_cwnd
) {
4907 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4908 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4910 tp
->snd_cwnd_used
= 0;
4912 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4915 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4917 struct tcp_sock
*tp
= tcp_sk(sk
);
4919 /* If the user specified a specific send buffer setting, do
4922 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4925 /* If we are under global TCP memory pressure, do not expand. */
4926 if (tcp_memory_pressure
)
4929 /* If we are under soft global TCP memory pressure, do not expand. */
4930 if (atomic_long_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4933 /* If we filled the congestion window, do not expand. */
4934 if (tp
->packets_out
>= tp
->snd_cwnd
)
4940 /* When incoming ACK allowed to free some skb from write_queue,
4941 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4942 * on the exit from tcp input handler.
4944 * PROBLEM: sndbuf expansion does not work well with largesend.
4946 static void tcp_new_space(struct sock
*sk
)
4948 struct tcp_sock
*tp
= tcp_sk(sk
);
4950 if (tcp_should_expand_sndbuf(sk
)) {
4951 int sndmem
= SKB_TRUESIZE(max_t(u32
,
4952 tp
->rx_opt
.mss_clamp
,
4955 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4956 tp
->reordering
+ 1);
4957 sndmem
*= 2 * demanded
;
4958 if (sndmem
> sk
->sk_sndbuf
)
4959 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4960 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4963 sk
->sk_write_space(sk
);
4966 static void tcp_check_space(struct sock
*sk
)
4968 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4969 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4970 if (sk
->sk_socket
&&
4971 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4976 static inline void tcp_data_snd_check(struct sock
*sk
)
4978 tcp_push_pending_frames(sk
);
4979 tcp_check_space(sk
);
4983 * Check if sending an ack is needed.
4985 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4987 struct tcp_sock
*tp
= tcp_sk(sk
);
4989 /* More than one full frame received... */
4990 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4991 /* ... and right edge of window advances far enough.
4992 * (tcp_recvmsg() will send ACK otherwise). Or...
4994 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4995 /* We ACK each frame or... */
4996 tcp_in_quickack_mode(sk
) ||
4997 /* We have out of order data. */
4998 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4999 /* Then ack it now */
5002 /* Else, send delayed ack. */
5003 tcp_send_delayed_ack(sk
);
5007 static inline void tcp_ack_snd_check(struct sock
*sk
)
5009 if (!inet_csk_ack_scheduled(sk
)) {
5010 /* We sent a data segment already. */
5013 __tcp_ack_snd_check(sk
, 1);
5017 * This routine is only called when we have urgent data
5018 * signaled. Its the 'slow' part of tcp_urg. It could be
5019 * moved inline now as tcp_urg is only called from one
5020 * place. We handle URGent data wrong. We have to - as
5021 * BSD still doesn't use the correction from RFC961.
5022 * For 1003.1g we should support a new option TCP_STDURG to permit
5023 * either form (or just set the sysctl tcp_stdurg).
5026 static void tcp_check_urg(struct sock
*sk
, struct tcphdr
*th
)
5028 struct tcp_sock
*tp
= tcp_sk(sk
);
5029 u32 ptr
= ntohs(th
->urg_ptr
);
5031 if (ptr
&& !sysctl_tcp_stdurg
)
5033 ptr
+= ntohl(th
->seq
);
5035 /* Ignore urgent data that we've already seen and read. */
5036 if (after(tp
->copied_seq
, ptr
))
5039 /* Do not replay urg ptr.
5041 * NOTE: interesting situation not covered by specs.
5042 * Misbehaving sender may send urg ptr, pointing to segment,
5043 * which we already have in ofo queue. We are not able to fetch
5044 * such data and will stay in TCP_URG_NOTYET until will be eaten
5045 * by recvmsg(). Seems, we are not obliged to handle such wicked
5046 * situations. But it is worth to think about possibility of some
5047 * DoSes using some hypothetical application level deadlock.
5049 if (before(ptr
, tp
->rcv_nxt
))
5052 /* Do we already have a newer (or duplicate) urgent pointer? */
5053 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5056 /* Tell the world about our new urgent pointer. */
5059 /* We may be adding urgent data when the last byte read was
5060 * urgent. To do this requires some care. We cannot just ignore
5061 * tp->copied_seq since we would read the last urgent byte again
5062 * as data, nor can we alter copied_seq until this data arrives
5063 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5065 * NOTE. Double Dutch. Rendering to plain English: author of comment
5066 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5067 * and expect that both A and B disappear from stream. This is _wrong_.
5068 * Though this happens in BSD with high probability, this is occasional.
5069 * Any application relying on this is buggy. Note also, that fix "works"
5070 * only in this artificial test. Insert some normal data between A and B and we will
5071 * decline of BSD again. Verdict: it is better to remove to trap
5074 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5075 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5076 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5078 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5079 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5084 tp
->urg_data
= TCP_URG_NOTYET
;
5087 /* Disable header prediction. */
5091 /* This is the 'fast' part of urgent handling. */
5092 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
5094 struct tcp_sock
*tp
= tcp_sk(sk
);
5096 /* Check if we get a new urgent pointer - normally not. */
5098 tcp_check_urg(sk
, th
);
5100 /* Do we wait for any urgent data? - normally not... */
5101 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5102 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5105 /* Is the urgent pointer pointing into this packet? */
5106 if (ptr
< skb
->len
) {
5108 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5110 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5111 if (!sock_flag(sk
, SOCK_DEAD
))
5112 sk
->sk_data_ready(sk
, 0);
5117 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5119 struct tcp_sock
*tp
= tcp_sk(sk
);
5120 int chunk
= skb
->len
- hlen
;
5124 if (skb_csum_unnecessary(skb
))
5125 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
5127 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
5131 tp
->ucopy
.len
-= chunk
;
5132 tp
->copied_seq
+= chunk
;
5133 tcp_rcv_space_adjust(sk
);
5140 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5141 struct sk_buff
*skb
)
5145 if (sock_owned_by_user(sk
)) {
5147 result
= __tcp_checksum_complete(skb
);
5150 result
= __tcp_checksum_complete(skb
);
5155 static inline int tcp_checksum_complete_user(struct sock
*sk
,
5156 struct sk_buff
*skb
)
5158 return !skb_csum_unnecessary(skb
) &&
5159 __tcp_checksum_complete_user(sk
, skb
);
5162 #ifdef CONFIG_NET_DMA
5163 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
5166 struct tcp_sock
*tp
= tcp_sk(sk
);
5167 int chunk
= skb
->len
- hlen
;
5169 int copied_early
= 0;
5171 if (tp
->ucopy
.wakeup
)
5174 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
5175 tp
->ucopy
.dma_chan
= dma_find_channel(DMA_MEMCPY
);
5177 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
5179 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
5181 tp
->ucopy
.iov
, chunk
,
5182 tp
->ucopy
.pinned_list
);
5187 tp
->ucopy
.dma_cookie
= dma_cookie
;
5190 tp
->ucopy
.len
-= chunk
;
5191 tp
->copied_seq
+= chunk
;
5192 tcp_rcv_space_adjust(sk
);
5194 if ((tp
->ucopy
.len
== 0) ||
5195 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5196 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5197 tp
->ucopy
.wakeup
= 1;
5198 sk
->sk_data_ready(sk
, 0);
5200 } else if (chunk
> 0) {
5201 tp
->ucopy
.wakeup
= 1;
5202 sk
->sk_data_ready(sk
, 0);
5205 return copied_early
;
5207 #endif /* CONFIG_NET_DMA */
5209 /* Does PAWS and seqno based validation of an incoming segment, flags will
5210 * play significant role here.
5212 static int tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5213 struct tcphdr
*th
, int syn_inerr
)
5216 struct tcp_sock
*tp
= tcp_sk(sk
);
5218 /* RFC1323: H1. Apply PAWS check first. */
5219 if (tcp_fast_parse_options(skb
, th
, tp
, &hash_location
) &&
5220 tp
->rx_opt
.saw_tstamp
&&
5221 tcp_paws_discard(sk
, skb
)) {
5223 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5224 tcp_send_dupack(sk
, skb
);
5227 /* Reset is accepted even if it did not pass PAWS. */
5230 /* Step 1: check sequence number */
5231 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5232 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5233 * (RST) segments are validated by checking their SEQ-fields."
5234 * And page 69: "If an incoming segment is not acceptable,
5235 * an acknowledgment should be sent in reply (unless the RST
5236 * bit is set, if so drop the segment and return)".
5239 tcp_send_dupack(sk
, skb
);
5243 /* Step 2: check RST bit */
5249 /* ts_recent update must be made after we are sure that the packet
5252 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5254 /* step 3: check security and precedence [ignored] */
5256 /* step 4: Check for a SYN in window. */
5257 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5259 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5260 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5273 * TCP receive function for the ESTABLISHED state.
5275 * It is split into a fast path and a slow path. The fast path is
5277 * - A zero window was announced from us - zero window probing
5278 * is only handled properly in the slow path.
5279 * - Out of order segments arrived.
5280 * - Urgent data is expected.
5281 * - There is no buffer space left
5282 * - Unexpected TCP flags/window values/header lengths are received
5283 * (detected by checking the TCP header against pred_flags)
5284 * - Data is sent in both directions. Fast path only supports pure senders
5285 * or pure receivers (this means either the sequence number or the ack
5286 * value must stay constant)
5287 * - Unexpected TCP option.
5289 * When these conditions are not satisfied it drops into a standard
5290 * receive procedure patterned after RFC793 to handle all cases.
5291 * The first three cases are guaranteed by proper pred_flags setting,
5292 * the rest is checked inline. Fast processing is turned on in
5293 * tcp_data_queue when everything is OK.
5295 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5296 struct tcphdr
*th
, unsigned len
)
5298 struct tcp_sock
*tp
= tcp_sk(sk
);
5302 * Header prediction.
5303 * The code loosely follows the one in the famous
5304 * "30 instruction TCP receive" Van Jacobson mail.
5306 * Van's trick is to deposit buffers into socket queue
5307 * on a device interrupt, to call tcp_recv function
5308 * on the receive process context and checksum and copy
5309 * the buffer to user space. smart...
5311 * Our current scheme is not silly either but we take the
5312 * extra cost of the net_bh soft interrupt processing...
5313 * We do checksum and copy also but from device to kernel.
5316 tp
->rx_opt
.saw_tstamp
= 0;
5318 /* pred_flags is 0xS?10 << 16 + snd_wnd
5319 * if header_prediction is to be made
5320 * 'S' will always be tp->tcp_header_len >> 2
5321 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5322 * turn it off (when there are holes in the receive
5323 * space for instance)
5324 * PSH flag is ignored.
5327 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5328 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5329 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5330 int tcp_header_len
= tp
->tcp_header_len
;
5332 /* Timestamp header prediction: tcp_header_len
5333 * is automatically equal to th->doff*4 due to pred_flags
5337 /* Check timestamp */
5338 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5339 /* No? Slow path! */
5340 if (!tcp_parse_aligned_timestamp(tp
, th
))
5343 /* If PAWS failed, check it more carefully in slow path */
5344 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5347 /* DO NOT update ts_recent here, if checksum fails
5348 * and timestamp was corrupted part, it will result
5349 * in a hung connection since we will drop all
5350 * future packets due to the PAWS test.
5354 if (len
<= tcp_header_len
) {
5355 /* Bulk data transfer: sender */
5356 if (len
== tcp_header_len
) {
5357 /* Predicted packet is in window by definition.
5358 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5359 * Hence, check seq<=rcv_wup reduces to:
5361 if (tcp_header_len
==
5362 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5363 tp
->rcv_nxt
== tp
->rcv_wup
)
5364 tcp_store_ts_recent(tp
);
5366 /* We know that such packets are checksummed
5369 tcp_ack(sk
, skb
, 0);
5371 tcp_data_snd_check(sk
);
5373 } else { /* Header too small */
5374 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5379 int copied_early
= 0;
5381 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5382 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5383 #ifdef CONFIG_NET_DMA
5384 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5389 if (tp
->ucopy
.task
== current
&&
5390 sock_owned_by_user(sk
) && !copied_early
) {
5391 __set_current_state(TASK_RUNNING
);
5393 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5397 /* Predicted packet is in window by definition.
5398 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5399 * Hence, check seq<=rcv_wup reduces to:
5401 if (tcp_header_len
==
5402 (sizeof(struct tcphdr
) +
5403 TCPOLEN_TSTAMP_ALIGNED
) &&
5404 tp
->rcv_nxt
== tp
->rcv_wup
)
5405 tcp_store_ts_recent(tp
);
5407 tcp_rcv_rtt_measure_ts(sk
, skb
);
5409 __skb_pull(skb
, tcp_header_len
);
5410 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5411 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5414 tcp_cleanup_rbuf(sk
, skb
->len
);
5417 if (tcp_checksum_complete_user(sk
, skb
))
5420 /* Predicted packet is in window by definition.
5421 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5422 * Hence, check seq<=rcv_wup reduces to:
5424 if (tcp_header_len
==
5425 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5426 tp
->rcv_nxt
== tp
->rcv_wup
)
5427 tcp_store_ts_recent(tp
);
5429 tcp_rcv_rtt_measure_ts(sk
, skb
);
5431 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5434 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5436 /* Bulk data transfer: receiver */
5437 __skb_pull(skb
, tcp_header_len
);
5438 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
5439 skb_set_owner_r(skb
, sk
);
5440 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5443 tcp_event_data_recv(sk
, skb
);
5445 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5446 /* Well, only one small jumplet in fast path... */
5447 tcp_ack(sk
, skb
, FLAG_DATA
);
5448 tcp_data_snd_check(sk
);
5449 if (!inet_csk_ack_scheduled(sk
))
5453 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5454 __tcp_ack_snd_check(sk
, 0);
5456 #ifdef CONFIG_NET_DMA
5458 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5464 sk
->sk_data_ready(sk
, 0);
5470 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5474 * Standard slow path.
5477 res
= tcp_validate_incoming(sk
, skb
, th
, 1);
5482 if (th
->ack
&& tcp_ack(sk
, skb
, FLAG_SLOWPATH
) < 0)
5485 tcp_rcv_rtt_measure_ts(sk
, skb
);
5487 /* Process urgent data. */
5488 tcp_urg(sk
, skb
, th
);
5490 /* step 7: process the segment text */
5491 tcp_data_queue(sk
, skb
);
5493 tcp_data_snd_check(sk
);
5494 tcp_ack_snd_check(sk
);
5498 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5504 EXPORT_SYMBOL(tcp_rcv_established
);
5506 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5507 struct tcphdr
*th
, unsigned len
)
5510 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5511 struct tcp_sock
*tp
= tcp_sk(sk
);
5512 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
5513 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5515 tcp_parse_options(skb
, &tp
->rx_opt
, &hash_location
, 0);
5519 * "If the state is SYN-SENT then
5520 * first check the ACK bit
5521 * If the ACK bit is set
5522 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5523 * a reset (unless the RST bit is set, if so drop
5524 * the segment and return)"
5526 * We do not send data with SYN, so that RFC-correct
5529 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
5530 goto reset_and_undo
;
5532 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5533 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5535 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5536 goto reset_and_undo
;
5539 /* Now ACK is acceptable.
5541 * "If the RST bit is set
5542 * If the ACK was acceptable then signal the user "error:
5543 * connection reset", drop the segment, enter CLOSED state,
5544 * delete TCB, and return."
5553 * "fifth, if neither of the SYN or RST bits is set then
5554 * drop the segment and return."
5560 goto discard_and_undo
;
5563 * "If the SYN bit is on ...
5564 * are acceptable then ...
5565 * (our SYN has been ACKed), change the connection
5566 * state to ESTABLISHED..."
5569 TCP_ECN_rcv_synack(tp
, th
);
5571 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5572 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5574 /* Ok.. it's good. Set up sequence numbers and
5575 * move to established.
5577 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5578 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5580 /* RFC1323: The window in SYN & SYN/ACK segments is
5583 tp
->snd_wnd
= ntohs(th
->window
);
5584 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5586 if (!tp
->rx_opt
.wscale_ok
) {
5587 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5588 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5591 if (tp
->rx_opt
.saw_tstamp
) {
5592 tp
->rx_opt
.tstamp_ok
= 1;
5593 tp
->tcp_header_len
=
5594 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5595 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5596 tcp_store_ts_recent(tp
);
5598 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5601 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5602 tcp_enable_fack(tp
);
5605 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5606 tcp_initialize_rcv_mss(sk
);
5608 /* Remember, tcp_poll() does not lock socket!
5609 * Change state from SYN-SENT only after copied_seq
5610 * is initialized. */
5611 tp
->copied_seq
= tp
->rcv_nxt
;
5614 cvp
->cookie_pair_size
> 0 &&
5615 tp
->rx_opt
.cookie_plus
> 0) {
5616 int cookie_size
= tp
->rx_opt
.cookie_plus
5617 - TCPOLEN_COOKIE_BASE
;
5618 int cookie_pair_size
= cookie_size
5619 + cvp
->cookie_desired
;
5621 /* A cookie extension option was sent and returned.
5622 * Note that each incoming SYNACK replaces the
5623 * Responder cookie. The initial exchange is most
5624 * fragile, as protection against spoofing relies
5625 * entirely upon the sequence and timestamp (above).
5626 * This replacement strategy allows the correct pair to
5627 * pass through, while any others will be filtered via
5628 * Responder verification later.
5630 if (sizeof(cvp
->cookie_pair
) >= cookie_pair_size
) {
5631 memcpy(&cvp
->cookie_pair
[cvp
->cookie_desired
],
5632 hash_location
, cookie_size
);
5633 cvp
->cookie_pair_size
= cookie_pair_size
;
5638 tcp_set_state(sk
, TCP_ESTABLISHED
);
5640 security_inet_conn_established(sk
, skb
);
5642 /* Make sure socket is routed, for correct metrics. */
5643 icsk
->icsk_af_ops
->rebuild_header(sk
);
5645 tcp_init_metrics(sk
);
5647 tcp_init_congestion_control(sk
);
5649 /* Prevent spurious tcp_cwnd_restart() on first data
5652 tp
->lsndtime
= tcp_time_stamp
;
5654 tcp_init_buffer_space(sk
);
5656 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5657 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5659 if (!tp
->rx_opt
.snd_wscale
)
5660 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5664 if (!sock_flag(sk
, SOCK_DEAD
)) {
5665 sk
->sk_state_change(sk
);
5666 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5669 if (sk
->sk_write_pending
||
5670 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5671 icsk
->icsk_ack
.pingpong
) {
5672 /* Save one ACK. Data will be ready after
5673 * several ticks, if write_pending is set.
5675 * It may be deleted, but with this feature tcpdumps
5676 * look so _wonderfully_ clever, that I was not able
5677 * to stand against the temptation 8) --ANK
5679 inet_csk_schedule_ack(sk
);
5680 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5681 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
5682 tcp_incr_quickack(sk
);
5683 tcp_enter_quickack_mode(sk
);
5684 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5685 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5696 /* No ACK in the segment */
5700 * "If the RST bit is set
5702 * Otherwise (no ACK) drop the segment and return."
5705 goto discard_and_undo
;
5709 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5710 tcp_paws_reject(&tp
->rx_opt
, 0))
5711 goto discard_and_undo
;
5714 /* We see SYN without ACK. It is attempt of
5715 * simultaneous connect with crossed SYNs.
5716 * Particularly, it can be connect to self.
5718 tcp_set_state(sk
, TCP_SYN_RECV
);
5720 if (tp
->rx_opt
.saw_tstamp
) {
5721 tp
->rx_opt
.tstamp_ok
= 1;
5722 tcp_store_ts_recent(tp
);
5723 tp
->tcp_header_len
=
5724 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5726 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5729 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5730 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5732 /* RFC1323: The window in SYN & SYN/ACK segments is
5735 tp
->snd_wnd
= ntohs(th
->window
);
5736 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5737 tp
->max_window
= tp
->snd_wnd
;
5739 TCP_ECN_rcv_syn(tp
, th
);
5742 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5743 tcp_initialize_rcv_mss(sk
);
5745 tcp_send_synack(sk
);
5747 /* Note, we could accept data and URG from this segment.
5748 * There are no obstacles to make this.
5750 * However, if we ignore data in ACKless segments sometimes,
5751 * we have no reasons to accept it sometimes.
5752 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5753 * is not flawless. So, discard packet for sanity.
5754 * Uncomment this return to process the data.
5761 /* "fifth, if neither of the SYN or RST bits is set then
5762 * drop the segment and return."
5766 tcp_clear_options(&tp
->rx_opt
);
5767 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5771 tcp_clear_options(&tp
->rx_opt
);
5772 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5777 * This function implements the receiving procedure of RFC 793 for
5778 * all states except ESTABLISHED and TIME_WAIT.
5779 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5780 * address independent.
5783 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5784 struct tcphdr
*th
, unsigned len
)
5786 struct tcp_sock
*tp
= tcp_sk(sk
);
5787 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5791 tp
->rx_opt
.saw_tstamp
= 0;
5793 switch (sk
->sk_state
) {
5805 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5808 /* Now we have several options: In theory there is
5809 * nothing else in the frame. KA9Q has an option to
5810 * send data with the syn, BSD accepts data with the
5811 * syn up to the [to be] advertised window and
5812 * Solaris 2.1 gives you a protocol error. For now
5813 * we just ignore it, that fits the spec precisely
5814 * and avoids incompatibilities. It would be nice in
5815 * future to drop through and process the data.
5817 * Now that TTCP is starting to be used we ought to
5819 * But, this leaves one open to an easy denial of
5820 * service attack, and SYN cookies can't defend
5821 * against this problem. So, we drop the data
5822 * in the interest of security over speed unless
5823 * it's still in use.
5831 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5835 /* Do step6 onward by hand. */
5836 tcp_urg(sk
, skb
, th
);
5838 tcp_data_snd_check(sk
);
5842 res
= tcp_validate_incoming(sk
, skb
, th
, 0);
5846 /* step 5: check the ACK field */
5848 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
) > 0;
5850 switch (sk
->sk_state
) {
5853 tp
->copied_seq
= tp
->rcv_nxt
;
5855 tcp_set_state(sk
, TCP_ESTABLISHED
);
5856 sk
->sk_state_change(sk
);
5858 /* Note, that this wakeup is only for marginal
5859 * crossed SYN case. Passively open sockets
5860 * are not waked up, because sk->sk_sleep ==
5861 * NULL and sk->sk_socket == NULL.
5865 SOCK_WAKE_IO
, POLL_OUT
);
5867 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5868 tp
->snd_wnd
= ntohs(th
->window
) <<
5869 tp
->rx_opt
.snd_wscale
;
5870 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5872 if (tp
->rx_opt
.tstamp_ok
)
5873 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5875 /* Make sure socket is routed, for
5878 icsk
->icsk_af_ops
->rebuild_header(sk
);
5880 tcp_init_metrics(sk
);
5882 tcp_init_congestion_control(sk
);
5884 /* Prevent spurious tcp_cwnd_restart() on
5885 * first data packet.
5887 tp
->lsndtime
= tcp_time_stamp
;
5890 tcp_initialize_rcv_mss(sk
);
5891 tcp_init_buffer_space(sk
);
5892 tcp_fast_path_on(tp
);
5899 if (tp
->snd_una
== tp
->write_seq
) {
5900 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5901 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5902 dst_confirm(__sk_dst_get(sk
));
5904 if (!sock_flag(sk
, SOCK_DEAD
))
5905 /* Wake up lingering close() */
5906 sk
->sk_state_change(sk
);
5910 if (tp
->linger2
< 0 ||
5911 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5912 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5914 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5918 tmo
= tcp_fin_time(sk
);
5919 if (tmo
> TCP_TIMEWAIT_LEN
) {
5920 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5921 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5922 /* Bad case. We could lose such FIN otherwise.
5923 * It is not a big problem, but it looks confusing
5924 * and not so rare event. We still can lose it now,
5925 * if it spins in bh_lock_sock(), but it is really
5928 inet_csk_reset_keepalive_timer(sk
, tmo
);
5930 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5938 if (tp
->snd_una
== tp
->write_seq
) {
5939 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5945 if (tp
->snd_una
== tp
->write_seq
) {
5946 tcp_update_metrics(sk
);
5955 /* step 6: check the URG bit */
5956 tcp_urg(sk
, skb
, th
);
5958 /* step 7: process the segment text */
5959 switch (sk
->sk_state
) {
5960 case TCP_CLOSE_WAIT
:
5963 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5967 /* RFC 793 says to queue data in these states,
5968 * RFC 1122 says we MUST send a reset.
5969 * BSD 4.4 also does reset.
5971 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5972 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5973 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5974 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5980 case TCP_ESTABLISHED
:
5981 tcp_data_queue(sk
, skb
);
5986 /* tcp_data could move socket to TIME-WAIT */
5987 if (sk
->sk_state
!= TCP_CLOSE
) {
5988 tcp_data_snd_check(sk
);
5989 tcp_ack_snd_check(sk
);
5998 EXPORT_SYMBOL(tcp_rcv_state_process
);