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
64 #define pr_fmt(fmt) "TCP: " fmt
67 #include <linux/slab.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <linux/kernel.h>
73 #include <net/inet_common.h>
74 #include <linux/ipsec.h>
75 #include <asm/unaligned.h>
76 #include <net/netdma.h>
78 int sysctl_tcp_timestamps __read_mostly
= 1;
79 int sysctl_tcp_window_scaling __read_mostly
= 1;
80 int sysctl_tcp_sack __read_mostly
= 1;
81 int sysctl_tcp_fack __read_mostly
= 1;
82 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
83 EXPORT_SYMBOL(sysctl_tcp_reordering
);
84 int sysctl_tcp_ecn __read_mostly
= 2;
85 EXPORT_SYMBOL(sysctl_tcp_ecn
);
86 int sysctl_tcp_dsack __read_mostly
= 1;
87 int sysctl_tcp_app_win __read_mostly
= 31;
88 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
89 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
91 int sysctl_tcp_stdurg __read_mostly
;
92 int sysctl_tcp_rfc1337 __read_mostly
;
93 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
94 int sysctl_tcp_frto __read_mostly
= 2;
95 int sysctl_tcp_frto_response __read_mostly
;
96 int sysctl_tcp_nometrics_save __read_mostly
;
98 int sysctl_tcp_thin_dupack __read_mostly
;
100 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
101 int sysctl_tcp_abc __read_mostly
;
102 int sysctl_tcp_early_retrans __read_mostly
= 2;
104 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
105 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
106 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
107 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
108 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
109 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
110 #define FLAG_ECE 0x40 /* ECE in this ACK */
111 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
112 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
113 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
114 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
115 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
116 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
118 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
119 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
120 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
121 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
122 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
124 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
125 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
127 /* Adapt the MSS value used to make delayed ack decision to the
130 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
132 struct inet_connection_sock
*icsk
= inet_csk(sk
);
133 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
136 icsk
->icsk_ack
.last_seg_size
= 0;
138 /* skb->len may jitter because of SACKs, even if peer
139 * sends good full-sized frames.
141 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
142 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
143 icsk
->icsk_ack
.rcv_mss
= len
;
145 /* Otherwise, we make more careful check taking into account,
146 * that SACKs block is variable.
148 * "len" is invariant segment length, including TCP header.
150 len
+= skb
->data
- skb_transport_header(skb
);
151 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
152 /* If PSH is not set, packet should be
153 * full sized, provided peer TCP is not badly broken.
154 * This observation (if it is correct 8)) allows
155 * to handle super-low mtu links fairly.
157 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
158 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
159 /* Subtract also invariant (if peer is RFC compliant),
160 * tcp header plus fixed timestamp option length.
161 * Resulting "len" is MSS free of SACK jitter.
163 len
-= tcp_sk(sk
)->tcp_header_len
;
164 icsk
->icsk_ack
.last_seg_size
= len
;
166 icsk
->icsk_ack
.rcv_mss
= len
;
170 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
171 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
172 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
176 static void tcp_incr_quickack(struct sock
*sk
)
178 struct inet_connection_sock
*icsk
= inet_csk(sk
);
179 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
183 if (quickacks
> icsk
->icsk_ack
.quick
)
184 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
187 static void tcp_enter_quickack_mode(struct sock
*sk
)
189 struct inet_connection_sock
*icsk
= inet_csk(sk
);
190 tcp_incr_quickack(sk
);
191 icsk
->icsk_ack
.pingpong
= 0;
192 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
195 /* Send ACKs quickly, if "quick" count is not exhausted
196 * and the session is not interactive.
199 static inline bool tcp_in_quickack_mode(const struct sock
*sk
)
201 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
203 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
206 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
208 if (tp
->ecn_flags
& TCP_ECN_OK
)
209 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
212 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
214 if (tcp_hdr(skb
)->cwr
)
215 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
218 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
220 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
223 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
225 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
228 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
229 case INET_ECN_NOT_ECT
:
230 /* Funny extension: if ECT is not set on a segment,
231 * and we already seen ECT on a previous segment,
232 * it is probably a retransmit.
234 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
235 tcp_enter_quickack_mode((struct sock
*)tp
);
238 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
241 tp
->ecn_flags
|= TCP_ECN_SEEN
;
245 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
247 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
248 tp
->ecn_flags
&= ~TCP_ECN_OK
;
251 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
253 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
254 tp
->ecn_flags
&= ~TCP_ECN_OK
;
257 static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
259 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
264 /* Buffer size and advertised window tuning.
266 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
269 static void tcp_fixup_sndbuf(struct sock
*sk
)
271 int sndmem
= SKB_TRUESIZE(tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
);
273 sndmem
*= TCP_INIT_CWND
;
274 if (sk
->sk_sndbuf
< sndmem
)
275 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
278 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
280 * All tcp_full_space() is split to two parts: "network" buffer, allocated
281 * forward and advertised in receiver window (tp->rcv_wnd) and
282 * "application buffer", required to isolate scheduling/application
283 * latencies from network.
284 * window_clamp is maximal advertised window. It can be less than
285 * tcp_full_space(), in this case tcp_full_space() - window_clamp
286 * is reserved for "application" buffer. The less window_clamp is
287 * the smoother our behaviour from viewpoint of network, but the lower
288 * throughput and the higher sensitivity of the connection to losses. 8)
290 * rcv_ssthresh is more strict window_clamp used at "slow start"
291 * phase to predict further behaviour of this connection.
292 * It is used for two goals:
293 * - to enforce header prediction at sender, even when application
294 * requires some significant "application buffer". It is check #1.
295 * - to prevent pruning of receive queue because of misprediction
296 * of receiver window. Check #2.
298 * The scheme does not work when sender sends good segments opening
299 * window and then starts to feed us spaghetti. But it should work
300 * in common situations. Otherwise, we have to rely on queue collapsing.
303 /* Slow part of check#2. */
304 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
306 struct tcp_sock
*tp
= tcp_sk(sk
);
308 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
309 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
311 while (tp
->rcv_ssthresh
<= window
) {
312 if (truesize
<= skb
->len
)
313 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
321 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
323 struct tcp_sock
*tp
= tcp_sk(sk
);
326 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
327 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
328 !sk_under_memory_pressure(sk
)) {
331 /* Check #2. Increase window, if skb with such overhead
332 * will fit to rcvbuf in future.
334 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
335 incr
= 2 * tp
->advmss
;
337 incr
= __tcp_grow_window(sk
, skb
);
340 incr
= max_t(int, incr
, 2 * skb
->len
);
341 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
343 inet_csk(sk
)->icsk_ack
.quick
|= 1;
348 /* 3. Tuning rcvbuf, when connection enters established state. */
350 static void tcp_fixup_rcvbuf(struct sock
*sk
)
352 u32 mss
= tcp_sk(sk
)->advmss
;
353 u32 icwnd
= TCP_DEFAULT_INIT_RCVWND
;
356 /* Limit to 10 segments if mss <= 1460,
357 * or 14600/mss segments, with a minimum of two segments.
360 icwnd
= max_t(u32
, (1460 * TCP_DEFAULT_INIT_RCVWND
) / mss
, 2);
362 rcvmem
= SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
);
363 while (tcp_win_from_space(rcvmem
) < mss
)
368 if (sk
->sk_rcvbuf
< rcvmem
)
369 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
372 /* 4. Try to fixup all. It is made immediately after connection enters
375 static void tcp_init_buffer_space(struct sock
*sk
)
377 struct tcp_sock
*tp
= tcp_sk(sk
);
380 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
381 tcp_fixup_rcvbuf(sk
);
382 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
383 tcp_fixup_sndbuf(sk
);
385 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
387 maxwin
= tcp_full_space(sk
);
389 if (tp
->window_clamp
>= maxwin
) {
390 tp
->window_clamp
= maxwin
;
392 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
393 tp
->window_clamp
= max(maxwin
-
394 (maxwin
>> sysctl_tcp_app_win
),
398 /* Force reservation of one segment. */
399 if (sysctl_tcp_app_win
&&
400 tp
->window_clamp
> 2 * tp
->advmss
&&
401 tp
->window_clamp
+ tp
->advmss
> maxwin
)
402 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
404 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
405 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
408 /* 5. Recalculate window clamp after socket hit its memory bounds. */
409 static void tcp_clamp_window(struct sock
*sk
)
411 struct tcp_sock
*tp
= tcp_sk(sk
);
412 struct inet_connection_sock
*icsk
= inet_csk(sk
);
414 icsk
->icsk_ack
.quick
= 0;
416 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
417 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
418 !sk_under_memory_pressure(sk
) &&
419 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
420 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
423 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
424 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
427 /* Initialize RCV_MSS value.
428 * RCV_MSS is an our guess about MSS used by the peer.
429 * We haven't any direct information about the MSS.
430 * It's better to underestimate the RCV_MSS rather than overestimate.
431 * Overestimations make us ACKing less frequently than needed.
432 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
434 void tcp_initialize_rcv_mss(struct sock
*sk
)
436 const struct tcp_sock
*tp
= tcp_sk(sk
);
437 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
439 hint
= min(hint
, tp
->rcv_wnd
/ 2);
440 hint
= min(hint
, TCP_MSS_DEFAULT
);
441 hint
= max(hint
, TCP_MIN_MSS
);
443 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
445 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
447 /* Receiver "autotuning" code.
449 * The algorithm for RTT estimation w/o timestamps is based on
450 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
451 * <http://public.lanl.gov/radiant/pubs.html#DRS>
453 * More detail on this code can be found at
454 * <http://staff.psc.edu/jheffner/>,
455 * though this reference is out of date. A new paper
458 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
460 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
466 if (new_sample
!= 0) {
467 /* If we sample in larger samples in the non-timestamp
468 * case, we could grossly overestimate the RTT especially
469 * with chatty applications or bulk transfer apps which
470 * are stalled on filesystem I/O.
472 * Also, since we are only going for a minimum in the
473 * non-timestamp case, we do not smooth things out
474 * else with timestamps disabled convergence takes too
478 m
-= (new_sample
>> 3);
486 /* No previous measure. */
490 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
491 tp
->rcv_rtt_est
.rtt
= new_sample
;
494 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
496 if (tp
->rcv_rtt_est
.time
== 0)
498 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
500 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
503 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
504 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
507 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
508 const struct sk_buff
*skb
)
510 struct tcp_sock
*tp
= tcp_sk(sk
);
511 if (tp
->rx_opt
.rcv_tsecr
&&
512 (TCP_SKB_CB(skb
)->end_seq
-
513 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
514 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
518 * This function should be called every time data is copied to user space.
519 * It calculates the appropriate TCP receive buffer space.
521 void tcp_rcv_space_adjust(struct sock
*sk
)
523 struct tcp_sock
*tp
= tcp_sk(sk
);
527 if (tp
->rcvq_space
.time
== 0)
530 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
531 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
534 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
536 space
= max(tp
->rcvq_space
.space
, space
);
538 if (tp
->rcvq_space
.space
!= space
) {
541 tp
->rcvq_space
.space
= space
;
543 if (sysctl_tcp_moderate_rcvbuf
&&
544 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
545 int new_clamp
= space
;
547 /* Receive space grows, normalize in order to
548 * take into account packet headers and sk_buff
549 * structure overhead.
554 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
555 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
558 space
= min(space
, sysctl_tcp_rmem
[2]);
559 if (space
> sk
->sk_rcvbuf
) {
560 sk
->sk_rcvbuf
= space
;
562 /* Make the window clamp follow along. */
563 tp
->window_clamp
= new_clamp
;
569 tp
->rcvq_space
.seq
= tp
->copied_seq
;
570 tp
->rcvq_space
.time
= tcp_time_stamp
;
573 /* There is something which you must keep in mind when you analyze the
574 * behavior of the tp->ato delayed ack timeout interval. When a
575 * connection starts up, we want to ack as quickly as possible. The
576 * problem is that "good" TCP's do slow start at the beginning of data
577 * transmission. The means that until we send the first few ACK's the
578 * sender will sit on his end and only queue most of his data, because
579 * he can only send snd_cwnd unacked packets at any given time. For
580 * each ACK we send, he increments snd_cwnd and transmits more of his
583 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
585 struct tcp_sock
*tp
= tcp_sk(sk
);
586 struct inet_connection_sock
*icsk
= inet_csk(sk
);
589 inet_csk_schedule_ack(sk
);
591 tcp_measure_rcv_mss(sk
, skb
);
593 tcp_rcv_rtt_measure(tp
);
595 now
= tcp_time_stamp
;
597 if (!icsk
->icsk_ack
.ato
) {
598 /* The _first_ data packet received, initialize
599 * delayed ACK engine.
601 tcp_incr_quickack(sk
);
602 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
604 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
606 if (m
<= TCP_ATO_MIN
/ 2) {
607 /* The fastest case is the first. */
608 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
609 } else if (m
< icsk
->icsk_ack
.ato
) {
610 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
611 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
612 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
613 } else if (m
> icsk
->icsk_rto
) {
614 /* Too long gap. Apparently sender failed to
615 * restart window, so that we send ACKs quickly.
617 tcp_incr_quickack(sk
);
621 icsk
->icsk_ack
.lrcvtime
= now
;
623 TCP_ECN_check_ce(tp
, skb
);
626 tcp_grow_window(sk
, skb
);
629 /* Called to compute a smoothed rtt estimate. The data fed to this
630 * routine either comes from timestamps, or from segments that were
631 * known _not_ to have been retransmitted [see Karn/Partridge
632 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
633 * piece by Van Jacobson.
634 * NOTE: the next three routines used to be one big routine.
635 * To save cycles in the RFC 1323 implementation it was better to break
636 * it up into three procedures. -- erics
638 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
640 struct tcp_sock
*tp
= tcp_sk(sk
);
641 long m
= mrtt
; /* RTT */
643 /* The following amusing code comes from Jacobson's
644 * article in SIGCOMM '88. Note that rtt and mdev
645 * are scaled versions of rtt and mean deviation.
646 * This is designed to be as fast as possible
647 * m stands for "measurement".
649 * On a 1990 paper the rto value is changed to:
650 * RTO = rtt + 4 * mdev
652 * Funny. This algorithm seems to be very broken.
653 * These formulae increase RTO, when it should be decreased, increase
654 * too slowly, when it should be increased quickly, decrease too quickly
655 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
656 * does not matter how to _calculate_ it. Seems, it was trap
657 * that VJ failed to avoid. 8)
662 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
663 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
665 m
= -m
; /* m is now abs(error) */
666 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
667 /* This is similar to one of Eifel findings.
668 * Eifel blocks mdev updates when rtt decreases.
669 * This solution is a bit different: we use finer gain
670 * for mdev in this case (alpha*beta).
671 * Like Eifel it also prevents growth of rto,
672 * but also it limits too fast rto decreases,
673 * happening in pure Eifel.
678 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
680 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
681 if (tp
->mdev
> tp
->mdev_max
) {
682 tp
->mdev_max
= tp
->mdev
;
683 if (tp
->mdev_max
> tp
->rttvar
)
684 tp
->rttvar
= tp
->mdev_max
;
686 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
687 if (tp
->mdev_max
< tp
->rttvar
)
688 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
689 tp
->rtt_seq
= tp
->snd_nxt
;
690 tp
->mdev_max
= tcp_rto_min(sk
);
693 /* no previous measure. */
694 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
695 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
696 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
697 tp
->rtt_seq
= tp
->snd_nxt
;
701 /* Calculate rto without backoff. This is the second half of Van Jacobson's
702 * routine referred to above.
704 static inline void tcp_set_rto(struct sock
*sk
)
706 const struct tcp_sock
*tp
= tcp_sk(sk
);
707 /* Old crap is replaced with new one. 8)
710 * 1. If rtt variance happened to be less 50msec, it is hallucination.
711 * It cannot be less due to utterly erratic ACK generation made
712 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
713 * to do with delayed acks, because at cwnd>2 true delack timeout
714 * is invisible. Actually, Linux-2.4 also generates erratic
715 * ACKs in some circumstances.
717 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
719 /* 2. Fixups made earlier cannot be right.
720 * If we do not estimate RTO correctly without them,
721 * all the algo is pure shit and should be replaced
722 * with correct one. It is exactly, which we pretend to do.
725 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
726 * guarantees that rto is higher.
731 /* Save metrics learned by this TCP session.
732 This function is called only, when TCP finishes successfully
733 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
735 void tcp_update_metrics(struct sock
*sk
)
737 struct tcp_sock
*tp
= tcp_sk(sk
);
738 struct dst_entry
*dst
= __sk_dst_get(sk
);
740 if (sysctl_tcp_nometrics_save
)
745 if (dst
&& (dst
->flags
& DST_HOST
)) {
746 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
750 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
751 /* This session failed to estimate rtt. Why?
752 * Probably, no packets returned in time.
755 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
756 dst_metric_set(dst
, RTAX_RTT
, 0);
760 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
763 /* If newly calculated rtt larger than stored one,
764 * store new one. Otherwise, use EWMA. Remember,
765 * rtt overestimation is always better than underestimation.
767 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
769 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
771 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
774 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
779 /* Scale deviation to rttvar fixed point */
784 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
788 var
-= (var
- m
) >> 2;
790 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
793 if (tcp_in_initial_slowstart(tp
)) {
794 /* Slow start still did not finish. */
795 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
796 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
797 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
798 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_cwnd
>> 1);
799 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
800 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
801 dst_metric_set(dst
, RTAX_CWND
, tp
->snd_cwnd
);
802 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
803 icsk
->icsk_ca_state
== TCP_CA_Open
) {
804 /* Cong. avoidance phase, cwnd is reliable. */
805 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
806 dst_metric_set(dst
, RTAX_SSTHRESH
,
807 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
));
808 if (!dst_metric_locked(dst
, RTAX_CWND
))
809 dst_metric_set(dst
, RTAX_CWND
,
810 (dst_metric(dst
, RTAX_CWND
) +
813 /* Else slow start did not finish, cwnd is non-sense,
814 ssthresh may be also invalid.
816 if (!dst_metric_locked(dst
, RTAX_CWND
))
817 dst_metric_set(dst
, RTAX_CWND
,
818 (dst_metric(dst
, RTAX_CWND
) +
819 tp
->snd_ssthresh
) >> 1);
820 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
821 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
822 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
823 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_ssthresh
);
826 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
827 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
828 tp
->reordering
!= sysctl_tcp_reordering
)
829 dst_metric_set(dst
, RTAX_REORDERING
, tp
->reordering
);
834 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
836 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
839 cwnd
= TCP_INIT_CWND
;
840 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
843 /* Set slow start threshold and cwnd not falling to slow start */
844 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
846 struct tcp_sock
*tp
= tcp_sk(sk
);
847 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
849 tp
->prior_ssthresh
= 0;
851 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
854 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
855 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
856 tcp_packets_in_flight(tp
) + 1U);
857 tp
->snd_cwnd_cnt
= 0;
858 tp
->high_seq
= tp
->snd_nxt
;
859 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
860 TCP_ECN_queue_cwr(tp
);
862 tcp_set_ca_state(sk
, TCP_CA_CWR
);
867 * Packet counting of FACK is based on in-order assumptions, therefore TCP
868 * disables it when reordering is detected
870 static void tcp_disable_fack(struct tcp_sock
*tp
)
872 /* RFC3517 uses different metric in lost marker => reset on change */
874 tp
->lost_skb_hint
= NULL
;
875 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
878 /* Take a notice that peer is sending D-SACKs */
879 static void tcp_dsack_seen(struct tcp_sock
*tp
)
881 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
884 /* Initialize metrics on socket. */
886 static void tcp_init_metrics(struct sock
*sk
)
888 struct tcp_sock
*tp
= tcp_sk(sk
);
889 struct dst_entry
*dst
= __sk_dst_get(sk
);
896 if (dst_metric_locked(dst
, RTAX_CWND
))
897 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
898 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
899 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
900 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
901 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
903 /* ssthresh may have been reduced unnecessarily during.
904 * 3WHS. Restore it back to its initial default.
906 tp
->snd_ssthresh
= TCP_INFINITE_SSTHRESH
;
908 if (dst_metric(dst
, RTAX_REORDERING
) &&
909 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
910 tcp_disable_fack(tp
);
911 tcp_disable_early_retrans(tp
);
912 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
915 if (dst_metric(dst
, RTAX_RTT
) == 0 || tp
->srtt
== 0)
918 /* Initial rtt is determined from SYN,SYN-ACK.
919 * The segment is small and rtt may appear much
920 * less than real one. Use per-dst memory
921 * to make it more realistic.
923 * A bit of theory. RTT is time passed after "normal" sized packet
924 * is sent until it is ACKed. In normal circumstances sending small
925 * packets force peer to delay ACKs and calculation is correct too.
926 * The algorithm is adaptive and, provided we follow specs, it
927 * NEVER underestimate RTT. BUT! If peer tries to make some clever
928 * tricks sort of "quick acks" for time long enough to decrease RTT
929 * to low value, and then abruptly stops to do it and starts to delay
930 * ACKs, wait for troubles.
932 if (dst_metric_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
933 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
934 tp
->rtt_seq
= tp
->snd_nxt
;
936 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
937 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
938 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
943 /* RFC6298: 5.7 We've failed to get a valid RTT sample from
944 * 3WHS. This is most likely due to retransmission,
945 * including spurious one. Reset the RTO back to 3secs
946 * from the more aggressive 1sec to avoid more spurious
949 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_FALLBACK
;
950 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_FALLBACK
;
952 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
953 * retransmitted. In light of RFC6298 more aggressive 1sec
954 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
955 * retransmission has occurred.
957 if (tp
->total_retrans
> 1)
960 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
961 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
964 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
967 struct tcp_sock
*tp
= tcp_sk(sk
);
968 if (metric
> tp
->reordering
) {
971 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
973 /* This exciting event is worth to be remembered. 8) */
975 mib_idx
= LINUX_MIB_TCPTSREORDER
;
976 else if (tcp_is_reno(tp
))
977 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
978 else if (tcp_is_fack(tp
))
979 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
981 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
983 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
984 #if FASTRETRANS_DEBUG > 1
985 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
986 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
990 tp
->undo_marker
? tp
->undo_retrans
: 0);
992 tcp_disable_fack(tp
);
996 tcp_disable_early_retrans(tp
);
999 /* This must be called before lost_out is incremented */
1000 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1002 if ((tp
->retransmit_skb_hint
== NULL
) ||
1003 before(TCP_SKB_CB(skb
)->seq
,
1004 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1005 tp
->retransmit_skb_hint
= skb
;
1007 if (!tp
->lost_out
||
1008 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
1009 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1012 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1014 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1015 tcp_verify_retransmit_hint(tp
, skb
);
1017 tp
->lost_out
+= tcp_skb_pcount(skb
);
1018 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1022 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
1023 struct sk_buff
*skb
)
1025 tcp_verify_retransmit_hint(tp
, skb
);
1027 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1028 tp
->lost_out
+= tcp_skb_pcount(skb
);
1029 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1033 /* This procedure tags the retransmission queue when SACKs arrive.
1035 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1036 * Packets in queue with these bits set are counted in variables
1037 * sacked_out, retrans_out and lost_out, correspondingly.
1039 * Valid combinations are:
1040 * Tag InFlight Description
1041 * 0 1 - orig segment is in flight.
1042 * S 0 - nothing flies, orig reached receiver.
1043 * L 0 - nothing flies, orig lost by net.
1044 * R 2 - both orig and retransmit are in flight.
1045 * L|R 1 - orig is lost, retransmit is in flight.
1046 * S|R 1 - orig reached receiver, retrans is still in flight.
1047 * (L|S|R is logically valid, it could occur when L|R is sacked,
1048 * but it is equivalent to plain S and code short-curcuits it to S.
1049 * L|S is logically invalid, it would mean -1 packet in flight 8))
1051 * These 6 states form finite state machine, controlled by the following events:
1052 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1053 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1054 * 3. Loss detection event of two flavors:
1055 * A. Scoreboard estimator decided the packet is lost.
1056 * A'. Reno "three dupacks" marks head of queue lost.
1057 * A''. Its FACK modification, head until snd.fack is lost.
1058 * B. SACK arrives sacking SND.NXT at the moment, when the
1059 * segment was retransmitted.
1060 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1062 * It is pleasant to note, that state diagram turns out to be commutative,
1063 * so that we are allowed not to be bothered by order of our actions,
1064 * when multiple events arrive simultaneously. (see the function below).
1066 * Reordering detection.
1067 * --------------------
1068 * Reordering metric is maximal distance, which a packet can be displaced
1069 * in packet stream. With SACKs we can estimate it:
1071 * 1. SACK fills old hole and the corresponding segment was not
1072 * ever retransmitted -> reordering. Alas, we cannot use it
1073 * when segment was retransmitted.
1074 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1075 * for retransmitted and already SACKed segment -> reordering..
1076 * Both of these heuristics are not used in Loss state, when we cannot
1077 * account for retransmits accurately.
1079 * SACK block validation.
1080 * ----------------------
1082 * SACK block range validation checks that the received SACK block fits to
1083 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1084 * Note that SND.UNA is not included to the range though being valid because
1085 * it means that the receiver is rather inconsistent with itself reporting
1086 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1087 * perfectly valid, however, in light of RFC2018 which explicitly states
1088 * that "SACK block MUST reflect the newest segment. Even if the newest
1089 * segment is going to be discarded ...", not that it looks very clever
1090 * in case of head skb. Due to potentional receiver driven attacks, we
1091 * choose to avoid immediate execution of a walk in write queue due to
1092 * reneging and defer head skb's loss recovery to standard loss recovery
1093 * procedure that will eventually trigger (nothing forbids us doing this).
1095 * Implements also blockage to start_seq wrap-around. Problem lies in the
1096 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1097 * there's no guarantee that it will be before snd_nxt (n). The problem
1098 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1101 * <- outs wnd -> <- wrapzone ->
1102 * u e n u_w e_w s n_w
1104 * |<------------+------+----- TCP seqno space --------------+---------->|
1105 * ...-- <2^31 ->| |<--------...
1106 * ...---- >2^31 ------>| |<--------...
1108 * Current code wouldn't be vulnerable but it's better still to discard such
1109 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1110 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1111 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1112 * equal to the ideal case (infinite seqno space without wrap caused issues).
1114 * With D-SACK the lower bound is extended to cover sequence space below
1115 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1116 * again, D-SACK block must not to go across snd_una (for the same reason as
1117 * for the normal SACK blocks, explained above). But there all simplicity
1118 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1119 * fully below undo_marker they do not affect behavior in anyway and can
1120 * therefore be safely ignored. In rare cases (which are more or less
1121 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1122 * fragmentation and packet reordering past skb's retransmission. To consider
1123 * them correctly, the acceptable range must be extended even more though
1124 * the exact amount is rather hard to quantify. However, tp->max_window can
1125 * be used as an exaggerated estimate.
1127 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
1128 u32 start_seq
, u32 end_seq
)
1130 /* Too far in future, or reversed (interpretation is ambiguous) */
1131 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1134 /* Nasty start_seq wrap-around check (see comments above) */
1135 if (!before(start_seq
, tp
->snd_nxt
))
1138 /* In outstanding window? ...This is valid exit for D-SACKs too.
1139 * start_seq == snd_una is non-sensical (see comments above)
1141 if (after(start_seq
, tp
->snd_una
))
1144 if (!is_dsack
|| !tp
->undo_marker
)
1147 /* ...Then it's D-SACK, and must reside below snd_una completely */
1148 if (after(end_seq
, tp
->snd_una
))
1151 if (!before(start_seq
, tp
->undo_marker
))
1155 if (!after(end_seq
, tp
->undo_marker
))
1158 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1159 * start_seq < undo_marker and end_seq >= undo_marker.
1161 return !before(start_seq
, end_seq
- tp
->max_window
);
1164 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1165 * Event "B". Later note: FACK people cheated me again 8), we have to account
1166 * for reordering! Ugly, but should help.
1168 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1169 * less than what is now known to be received by the other end (derived from
1170 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1171 * retransmitted skbs to avoid some costly processing per ACKs.
1173 static void tcp_mark_lost_retrans(struct sock
*sk
)
1175 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1176 struct tcp_sock
*tp
= tcp_sk(sk
);
1177 struct sk_buff
*skb
;
1179 u32 new_low_seq
= tp
->snd_nxt
;
1180 u32 received_upto
= tcp_highest_sack_seq(tp
);
1182 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1183 !after(received_upto
, tp
->lost_retrans_low
) ||
1184 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1187 tcp_for_write_queue(skb
, sk
) {
1188 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1190 if (skb
== tcp_send_head(sk
))
1192 if (cnt
== tp
->retrans_out
)
1194 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1197 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1200 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1201 * constraint here (see above) but figuring out that at
1202 * least tp->reordering SACK blocks reside between ack_seq
1203 * and received_upto is not easy task to do cheaply with
1204 * the available datastructures.
1206 * Whether FACK should check here for tp->reordering segs
1207 * in-between one could argue for either way (it would be
1208 * rather simple to implement as we could count fack_count
1209 * during the walk and do tp->fackets_out - fack_count).
1211 if (after(received_upto
, ack_seq
)) {
1212 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1213 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1215 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1216 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1218 if (before(ack_seq
, new_low_seq
))
1219 new_low_seq
= ack_seq
;
1220 cnt
+= tcp_skb_pcount(skb
);
1224 if (tp
->retrans_out
)
1225 tp
->lost_retrans_low
= new_low_seq
;
1228 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1229 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1232 struct tcp_sock
*tp
= tcp_sk(sk
);
1233 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1234 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1235 bool dup_sack
= false;
1237 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1240 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1241 } else if (num_sacks
> 1) {
1242 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1243 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1245 if (!after(end_seq_0
, end_seq_1
) &&
1246 !before(start_seq_0
, start_seq_1
)) {
1249 NET_INC_STATS_BH(sock_net(sk
),
1250 LINUX_MIB_TCPDSACKOFORECV
);
1254 /* D-SACK for already forgotten data... Do dumb counting. */
1255 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
&&
1256 !after(end_seq_0
, prior_snd_una
) &&
1257 after(end_seq_0
, tp
->undo_marker
))
1263 struct tcp_sacktag_state
{
1269 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1270 * the incoming SACK may not exactly match but we can find smaller MSS
1271 * aligned portion of it that matches. Therefore we might need to fragment
1272 * which may fail and creates some hassle (caller must handle error case
1275 * FIXME: this could be merged to shift decision code
1277 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1278 u32 start_seq
, u32 end_seq
)
1282 unsigned int pkt_len
;
1285 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1286 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1288 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1289 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1290 mss
= tcp_skb_mss(skb
);
1291 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1294 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1298 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1303 /* Round if necessary so that SACKs cover only full MSSes
1304 * and/or the remaining small portion (if present)
1306 if (pkt_len
> mss
) {
1307 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1308 if (!in_sack
&& new_len
< pkt_len
) {
1310 if (new_len
> skb
->len
)
1315 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1323 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1324 static u8
tcp_sacktag_one(struct sock
*sk
,
1325 struct tcp_sacktag_state
*state
, u8 sacked
,
1326 u32 start_seq
, u32 end_seq
,
1327 bool dup_sack
, int pcount
)
1329 struct tcp_sock
*tp
= tcp_sk(sk
);
1330 int fack_count
= state
->fack_count
;
1332 /* Account D-SACK for retransmitted packet. */
1333 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1334 if (tp
->undo_marker
&& tp
->undo_retrans
&&
1335 after(end_seq
, tp
->undo_marker
))
1337 if (sacked
& TCPCB_SACKED_ACKED
)
1338 state
->reord
= min(fack_count
, state
->reord
);
1341 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1342 if (!after(end_seq
, tp
->snd_una
))
1345 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1346 if (sacked
& TCPCB_SACKED_RETRANS
) {
1347 /* If the segment is not tagged as lost,
1348 * we do not clear RETRANS, believing
1349 * that retransmission is still in flight.
1351 if (sacked
& TCPCB_LOST
) {
1352 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1353 tp
->lost_out
-= pcount
;
1354 tp
->retrans_out
-= pcount
;
1357 if (!(sacked
& TCPCB_RETRANS
)) {
1358 /* New sack for not retransmitted frame,
1359 * which was in hole. It is reordering.
1361 if (before(start_seq
,
1362 tcp_highest_sack_seq(tp
)))
1363 state
->reord
= min(fack_count
,
1366 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1367 if (!after(end_seq
, tp
->frto_highmark
))
1368 state
->flag
|= FLAG_ONLY_ORIG_SACKED
;
1371 if (sacked
& TCPCB_LOST
) {
1372 sacked
&= ~TCPCB_LOST
;
1373 tp
->lost_out
-= pcount
;
1377 sacked
|= TCPCB_SACKED_ACKED
;
1378 state
->flag
|= FLAG_DATA_SACKED
;
1379 tp
->sacked_out
+= pcount
;
1381 fack_count
+= pcount
;
1383 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1384 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1385 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1386 tp
->lost_cnt_hint
+= pcount
;
1388 if (fack_count
> tp
->fackets_out
)
1389 tp
->fackets_out
= fack_count
;
1392 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1393 * frames and clear it. undo_retrans is decreased above, L|R frames
1394 * are accounted above as well.
1396 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1397 sacked
&= ~TCPCB_SACKED_RETRANS
;
1398 tp
->retrans_out
-= pcount
;
1404 /* Shift newly-SACKed bytes from this skb to the immediately previous
1405 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1407 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1408 struct tcp_sacktag_state
*state
,
1409 unsigned int pcount
, int shifted
, int mss
,
1412 struct tcp_sock
*tp
= tcp_sk(sk
);
1413 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1414 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1415 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1419 /* Adjust counters and hints for the newly sacked sequence
1420 * range but discard the return value since prev is already
1421 * marked. We must tag the range first because the seq
1422 * advancement below implicitly advances
1423 * tcp_highest_sack_seq() when skb is highest_sack.
1425 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1426 start_seq
, end_seq
, dup_sack
, pcount
);
1428 if (skb
== tp
->lost_skb_hint
)
1429 tp
->lost_cnt_hint
+= pcount
;
1431 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1432 TCP_SKB_CB(skb
)->seq
+= shifted
;
1434 skb_shinfo(prev
)->gso_segs
+= pcount
;
1435 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1436 skb_shinfo(skb
)->gso_segs
-= pcount
;
1438 /* When we're adding to gso_segs == 1, gso_size will be zero,
1439 * in theory this shouldn't be necessary but as long as DSACK
1440 * code can come after this skb later on it's better to keep
1441 * setting gso_size to something.
1443 if (!skb_shinfo(prev
)->gso_size
) {
1444 skb_shinfo(prev
)->gso_size
= mss
;
1445 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1448 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1449 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1450 skb_shinfo(skb
)->gso_size
= 0;
1451 skb_shinfo(skb
)->gso_type
= 0;
1454 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1455 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1458 BUG_ON(!tcp_skb_pcount(skb
));
1459 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1463 /* Whole SKB was eaten :-) */
1465 if (skb
== tp
->retransmit_skb_hint
)
1466 tp
->retransmit_skb_hint
= prev
;
1467 if (skb
== tp
->scoreboard_skb_hint
)
1468 tp
->scoreboard_skb_hint
= prev
;
1469 if (skb
== tp
->lost_skb_hint
) {
1470 tp
->lost_skb_hint
= prev
;
1471 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1474 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(prev
)->tcp_flags
;
1475 if (skb
== tcp_highest_sack(sk
))
1476 tcp_advance_highest_sack(sk
, skb
);
1478 tcp_unlink_write_queue(skb
, sk
);
1479 sk_wmem_free_skb(sk
, skb
);
1481 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1486 /* I wish gso_size would have a bit more sane initialization than
1487 * something-or-zero which complicates things
1489 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1491 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1494 /* Shifting pages past head area doesn't work */
1495 static int skb_can_shift(const struct sk_buff
*skb
)
1497 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1500 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1503 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1504 struct tcp_sacktag_state
*state
,
1505 u32 start_seq
, u32 end_seq
,
1508 struct tcp_sock
*tp
= tcp_sk(sk
);
1509 struct sk_buff
*prev
;
1515 if (!sk_can_gso(sk
))
1518 /* Normally R but no L won't result in plain S */
1520 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1522 if (!skb_can_shift(skb
))
1524 /* This frame is about to be dropped (was ACKed). */
1525 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1528 /* Can only happen with delayed DSACK + discard craziness */
1529 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1531 prev
= tcp_write_queue_prev(sk
, skb
);
1533 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1536 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1537 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1541 pcount
= tcp_skb_pcount(skb
);
1542 mss
= tcp_skb_seglen(skb
);
1544 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1545 * drop this restriction as unnecessary
1547 if (mss
!= tcp_skb_seglen(prev
))
1550 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1552 /* CHECKME: This is non-MSS split case only?, this will
1553 * cause skipped skbs due to advancing loop btw, original
1554 * has that feature too
1556 if (tcp_skb_pcount(skb
) <= 1)
1559 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1561 /* TODO: head merge to next could be attempted here
1562 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1563 * though it might not be worth of the additional hassle
1565 * ...we can probably just fallback to what was done
1566 * previously. We could try merging non-SACKed ones
1567 * as well but it probably isn't going to buy off
1568 * because later SACKs might again split them, and
1569 * it would make skb timestamp tracking considerably
1575 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1577 BUG_ON(len
> skb
->len
);
1579 /* MSS boundaries should be honoured or else pcount will
1580 * severely break even though it makes things bit trickier.
1581 * Optimize common case to avoid most of the divides
1583 mss
= tcp_skb_mss(skb
);
1585 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1586 * drop this restriction as unnecessary
1588 if (mss
!= tcp_skb_seglen(prev
))
1593 } else if (len
< mss
) {
1601 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1602 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1605 if (!skb_shift(prev
, skb
, len
))
1607 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1610 /* Hole filled allows collapsing with the next as well, this is very
1611 * useful when hole on every nth skb pattern happens
1613 if (prev
== tcp_write_queue_tail(sk
))
1615 skb
= tcp_write_queue_next(sk
, prev
);
1617 if (!skb_can_shift(skb
) ||
1618 (skb
== tcp_send_head(sk
)) ||
1619 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1620 (mss
!= tcp_skb_seglen(skb
)))
1624 if (skb_shift(prev
, skb
, len
)) {
1625 pcount
+= tcp_skb_pcount(skb
);
1626 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1630 state
->fack_count
+= pcount
;
1637 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1641 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1642 struct tcp_sack_block
*next_dup
,
1643 struct tcp_sacktag_state
*state
,
1644 u32 start_seq
, u32 end_seq
,
1647 struct tcp_sock
*tp
= tcp_sk(sk
);
1648 struct sk_buff
*tmp
;
1650 tcp_for_write_queue_from(skb
, sk
) {
1652 bool dup_sack
= dup_sack_in
;
1654 if (skb
== tcp_send_head(sk
))
1657 /* queue is in-order => we can short-circuit the walk early */
1658 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1661 if ((next_dup
!= NULL
) &&
1662 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1663 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1664 next_dup
->start_seq
,
1670 /* skb reference here is a bit tricky to get right, since
1671 * shifting can eat and free both this skb and the next,
1672 * so not even _safe variant of the loop is enough.
1675 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1676 start_seq
, end_seq
, dup_sack
);
1685 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1691 if (unlikely(in_sack
< 0))
1695 TCP_SKB_CB(skb
)->sacked
=
1698 TCP_SKB_CB(skb
)->sacked
,
1699 TCP_SKB_CB(skb
)->seq
,
1700 TCP_SKB_CB(skb
)->end_seq
,
1702 tcp_skb_pcount(skb
));
1704 if (!before(TCP_SKB_CB(skb
)->seq
,
1705 tcp_highest_sack_seq(tp
)))
1706 tcp_advance_highest_sack(sk
, skb
);
1709 state
->fack_count
+= tcp_skb_pcount(skb
);
1714 /* Avoid all extra work that is being done by sacktag while walking in
1717 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1718 struct tcp_sacktag_state
*state
,
1721 tcp_for_write_queue_from(skb
, sk
) {
1722 if (skb
== tcp_send_head(sk
))
1725 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1728 state
->fack_count
+= tcp_skb_pcount(skb
);
1733 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1735 struct tcp_sack_block
*next_dup
,
1736 struct tcp_sacktag_state
*state
,
1739 if (next_dup
== NULL
)
1742 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1743 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1744 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1745 next_dup
->start_seq
, next_dup
->end_seq
,
1752 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1754 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1758 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1761 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1762 struct tcp_sock
*tp
= tcp_sk(sk
);
1763 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1764 TCP_SKB_CB(ack_skb
)->sacked
);
1765 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1766 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1767 struct tcp_sack_block
*cache
;
1768 struct tcp_sacktag_state state
;
1769 struct sk_buff
*skb
;
1770 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1772 bool found_dup_sack
= false;
1774 int first_sack_index
;
1777 state
.reord
= tp
->packets_out
;
1779 if (!tp
->sacked_out
) {
1780 if (WARN_ON(tp
->fackets_out
))
1781 tp
->fackets_out
= 0;
1782 tcp_highest_sack_reset(sk
);
1785 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1786 num_sacks
, prior_snd_una
);
1788 state
.flag
|= FLAG_DSACKING_ACK
;
1790 /* Eliminate too old ACKs, but take into
1791 * account more or less fresh ones, they can
1792 * contain valid SACK info.
1794 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1797 if (!tp
->packets_out
)
1801 first_sack_index
= 0;
1802 for (i
= 0; i
< num_sacks
; i
++) {
1803 bool dup_sack
= !i
&& found_dup_sack
;
1805 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1806 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1808 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1809 sp
[used_sacks
].start_seq
,
1810 sp
[used_sacks
].end_seq
)) {
1814 if (!tp
->undo_marker
)
1815 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1817 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1819 /* Don't count olds caused by ACK reordering */
1820 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1821 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1823 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1826 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1828 first_sack_index
= -1;
1832 /* Ignore very old stuff early */
1833 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1839 /* order SACK blocks to allow in order walk of the retrans queue */
1840 for (i
= used_sacks
- 1; i
> 0; i
--) {
1841 for (j
= 0; j
< i
; j
++) {
1842 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1843 swap(sp
[j
], sp
[j
+ 1]);
1845 /* Track where the first SACK block goes to */
1846 if (j
== first_sack_index
)
1847 first_sack_index
= j
+ 1;
1852 skb
= tcp_write_queue_head(sk
);
1853 state
.fack_count
= 0;
1856 if (!tp
->sacked_out
) {
1857 /* It's already past, so skip checking against it */
1858 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1860 cache
= tp
->recv_sack_cache
;
1861 /* Skip empty blocks in at head of the cache */
1862 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1867 while (i
< used_sacks
) {
1868 u32 start_seq
= sp
[i
].start_seq
;
1869 u32 end_seq
= sp
[i
].end_seq
;
1870 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1871 struct tcp_sack_block
*next_dup
= NULL
;
1873 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1874 next_dup
= &sp
[i
+ 1];
1876 /* Skip too early cached blocks */
1877 while (tcp_sack_cache_ok(tp
, cache
) &&
1878 !before(start_seq
, cache
->end_seq
))
1881 /* Can skip some work by looking recv_sack_cache? */
1882 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1883 after(end_seq
, cache
->start_seq
)) {
1886 if (before(start_seq
, cache
->start_seq
)) {
1887 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1889 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1896 /* Rest of the block already fully processed? */
1897 if (!after(end_seq
, cache
->end_seq
))
1900 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1904 /* ...tail remains todo... */
1905 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1906 /* ...but better entrypoint exists! */
1907 skb
= tcp_highest_sack(sk
);
1910 state
.fack_count
= tp
->fackets_out
;
1915 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1916 /* Check overlap against next cached too (past this one already) */
1921 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1922 skb
= tcp_highest_sack(sk
);
1925 state
.fack_count
= tp
->fackets_out
;
1927 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1930 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1931 start_seq
, end_seq
, dup_sack
);
1934 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1935 * due to in-order walk
1937 if (after(end_seq
, tp
->frto_highmark
))
1938 state
.flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1943 /* Clear the head of the cache sack blocks so we can skip it next time */
1944 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1945 tp
->recv_sack_cache
[i
].start_seq
= 0;
1946 tp
->recv_sack_cache
[i
].end_seq
= 0;
1948 for (j
= 0; j
< used_sacks
; j
++)
1949 tp
->recv_sack_cache
[i
++] = sp
[j
];
1951 tcp_mark_lost_retrans(sk
);
1953 tcp_verify_left_out(tp
);
1955 if ((state
.reord
< tp
->fackets_out
) &&
1956 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1957 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1958 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1962 #if FASTRETRANS_DEBUG > 0
1963 WARN_ON((int)tp
->sacked_out
< 0);
1964 WARN_ON((int)tp
->lost_out
< 0);
1965 WARN_ON((int)tp
->retrans_out
< 0);
1966 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1971 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1972 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1974 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1978 holes
= max(tp
->lost_out
, 1U);
1979 holes
= min(holes
, tp
->packets_out
);
1981 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1982 tp
->sacked_out
= tp
->packets_out
- holes
;
1988 /* If we receive more dupacks than we expected counting segments
1989 * in assumption of absent reordering, interpret this as reordering.
1990 * The only another reason could be bug in receiver TCP.
1992 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1994 struct tcp_sock
*tp
= tcp_sk(sk
);
1995 if (tcp_limit_reno_sacked(tp
))
1996 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1999 /* Emulate SACKs for SACKless connection: account for a new dupack. */
2001 static void tcp_add_reno_sack(struct sock
*sk
)
2003 struct tcp_sock
*tp
= tcp_sk(sk
);
2005 tcp_check_reno_reordering(sk
, 0);
2006 tcp_verify_left_out(tp
);
2009 /* Account for ACK, ACKing some data in Reno Recovery phase. */
2011 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
2013 struct tcp_sock
*tp
= tcp_sk(sk
);
2016 /* One ACK acked hole. The rest eat duplicate ACKs. */
2017 if (acked
- 1 >= tp
->sacked_out
)
2020 tp
->sacked_out
-= acked
- 1;
2022 tcp_check_reno_reordering(sk
, acked
);
2023 tcp_verify_left_out(tp
);
2026 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
2031 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
2033 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
2036 /* F-RTO can only be used if TCP has never retransmitted anything other than
2037 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
2039 bool tcp_use_frto(struct sock
*sk
)
2041 const struct tcp_sock
*tp
= tcp_sk(sk
);
2042 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2043 struct sk_buff
*skb
;
2045 if (!sysctl_tcp_frto
)
2048 /* MTU probe and F-RTO won't really play nicely along currently */
2049 if (icsk
->icsk_mtup
.probe_size
)
2052 if (tcp_is_sackfrto(tp
))
2055 /* Avoid expensive walking of rexmit queue if possible */
2056 if (tp
->retrans_out
> 1)
2059 skb
= tcp_write_queue_head(sk
);
2060 if (tcp_skb_is_last(sk
, skb
))
2062 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
2063 tcp_for_write_queue_from(skb
, sk
) {
2064 if (skb
== tcp_send_head(sk
))
2066 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2068 /* Short-circuit when first non-SACKed skb has been checked */
2069 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2075 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2076 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2077 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2078 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2079 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2080 * bits are handled if the Loss state is really to be entered (in
2081 * tcp_enter_frto_loss).
2083 * Do like tcp_enter_loss() would; when RTO expires the second time it
2085 * "Reduce ssthresh if it has not yet been made inside this window."
2087 void tcp_enter_frto(struct sock
*sk
)
2089 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2090 struct tcp_sock
*tp
= tcp_sk(sk
);
2091 struct sk_buff
*skb
;
2093 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
2094 tp
->snd_una
== tp
->high_seq
||
2095 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
2096 !icsk
->icsk_retransmits
)) {
2097 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2098 /* Our state is too optimistic in ssthresh() call because cwnd
2099 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2100 * recovery has not yet completed. Pattern would be this: RTO,
2101 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2103 * RFC4138 should be more specific on what to do, even though
2104 * RTO is quite unlikely to occur after the first Cumulative ACK
2105 * due to back-off and complexity of triggering events ...
2107 if (tp
->frto_counter
) {
2109 stored_cwnd
= tp
->snd_cwnd
;
2111 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2112 tp
->snd_cwnd
= stored_cwnd
;
2114 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2116 /* ... in theory, cong.control module could do "any tricks" in
2117 * ssthresh(), which means that ca_state, lost bits and lost_out
2118 * counter would have to be faked before the call occurs. We
2119 * consider that too expensive, unlikely and hacky, so modules
2120 * using these in ssthresh() must deal these incompatibility
2121 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2123 tcp_ca_event(sk
, CA_EVENT_FRTO
);
2126 tp
->undo_marker
= tp
->snd_una
;
2127 tp
->undo_retrans
= 0;
2129 skb
= tcp_write_queue_head(sk
);
2130 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2131 tp
->undo_marker
= 0;
2132 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2133 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2134 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2136 tcp_verify_left_out(tp
);
2138 /* Too bad if TCP was application limited */
2139 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2141 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2142 * The last condition is necessary at least in tp->frto_counter case.
2144 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
2145 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
2146 after(tp
->high_seq
, tp
->snd_una
)) {
2147 tp
->frto_highmark
= tp
->high_seq
;
2149 tp
->frto_highmark
= tp
->snd_nxt
;
2151 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
2152 tp
->high_seq
= tp
->snd_nxt
;
2153 tp
->frto_counter
= 1;
2156 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2157 * which indicates that we should follow the traditional RTO recovery,
2158 * i.e. mark everything lost and do go-back-N retransmission.
2160 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
2162 struct tcp_sock
*tp
= tcp_sk(sk
);
2163 struct sk_buff
*skb
;
2166 tp
->retrans_out
= 0;
2167 if (tcp_is_reno(tp
))
2168 tcp_reset_reno_sack(tp
);
2170 tcp_for_write_queue(skb
, sk
) {
2171 if (skb
== tcp_send_head(sk
))
2174 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2176 * Count the retransmission made on RTO correctly (only when
2177 * waiting for the first ACK and did not get it)...
2179 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
2180 /* For some reason this R-bit might get cleared? */
2181 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
2182 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2183 /* ...enter this if branch just for the first segment */
2184 flag
|= FLAG_DATA_ACKED
;
2186 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2187 tp
->undo_marker
= 0;
2188 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2191 /* Marking forward transmissions that were made after RTO lost
2192 * can cause unnecessary retransmissions in some scenarios,
2193 * SACK blocks will mitigate that in some but not in all cases.
2194 * We used to not mark them but it was causing break-ups with
2195 * receivers that do only in-order receival.
2197 * TODO: we could detect presence of such receiver and select
2198 * different behavior per flow.
2200 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2201 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2202 tp
->lost_out
+= tcp_skb_pcount(skb
);
2203 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2206 tcp_verify_left_out(tp
);
2208 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
2209 tp
->snd_cwnd_cnt
= 0;
2210 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2211 tp
->frto_counter
= 0;
2212 tp
->bytes_acked
= 0;
2214 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2215 sysctl_tcp_reordering
);
2216 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2217 tp
->high_seq
= tp
->snd_nxt
;
2218 TCP_ECN_queue_cwr(tp
);
2220 tcp_clear_all_retrans_hints(tp
);
2223 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
2225 tp
->retrans_out
= 0;
2228 tp
->undo_marker
= 0;
2229 tp
->undo_retrans
= 0;
2232 void tcp_clear_retrans(struct tcp_sock
*tp
)
2234 tcp_clear_retrans_partial(tp
);
2236 tp
->fackets_out
= 0;
2240 /* Enter Loss state. If "how" is not zero, forget all SACK information
2241 * and reset tags completely, otherwise preserve SACKs. If receiver
2242 * dropped its ofo queue, we will know this due to reneging detection.
2244 void tcp_enter_loss(struct sock
*sk
, int how
)
2246 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2247 struct tcp_sock
*tp
= tcp_sk(sk
);
2248 struct sk_buff
*skb
;
2250 /* Reduce ssthresh if it has not yet been made inside this window. */
2251 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
2252 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2253 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2254 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2255 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2258 tp
->snd_cwnd_cnt
= 0;
2259 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2261 tp
->bytes_acked
= 0;
2262 tcp_clear_retrans_partial(tp
);
2264 if (tcp_is_reno(tp
))
2265 tcp_reset_reno_sack(tp
);
2268 /* Push undo marker, if it was plain RTO and nothing
2269 * was retransmitted. */
2270 tp
->undo_marker
= tp
->snd_una
;
2273 tp
->fackets_out
= 0;
2275 tcp_clear_all_retrans_hints(tp
);
2277 tcp_for_write_queue(skb
, sk
) {
2278 if (skb
== tcp_send_head(sk
))
2281 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2282 tp
->undo_marker
= 0;
2283 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
2284 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
2285 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2286 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2287 tp
->lost_out
+= tcp_skb_pcount(skb
);
2288 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2291 tcp_verify_left_out(tp
);
2293 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2294 sysctl_tcp_reordering
);
2295 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2296 tp
->high_seq
= tp
->snd_nxt
;
2297 TCP_ECN_queue_cwr(tp
);
2298 /* Abort F-RTO algorithm if one is in progress */
2299 tp
->frto_counter
= 0;
2302 /* If ACK arrived pointing to a remembered SACK, it means that our
2303 * remembered SACKs do not reflect real state of receiver i.e.
2304 * receiver _host_ is heavily congested (or buggy).
2306 * Do processing similar to RTO timeout.
2308 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2310 if (flag
& FLAG_SACK_RENEGING
) {
2311 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2312 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2314 tcp_enter_loss(sk
, 1);
2315 icsk
->icsk_retransmits
++;
2316 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
2317 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2318 icsk
->icsk_rto
, TCP_RTO_MAX
);
2324 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2326 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2329 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2330 * counter when SACK is enabled (without SACK, sacked_out is used for
2333 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2334 * segments up to the highest received SACK block so far and holes in
2337 * With reordering, holes may still be in flight, so RFC3517 recovery
2338 * uses pure sacked_out (total number of SACKed segments) even though
2339 * it violates the RFC that uses duplicate ACKs, often these are equal
2340 * but when e.g. out-of-window ACKs or packet duplication occurs,
2341 * they differ. Since neither occurs due to loss, TCP should really
2344 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2346 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2349 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2351 struct tcp_sock
*tp
= tcp_sk(sk
);
2352 unsigned long delay
;
2354 /* Delay early retransmit and entering fast recovery for
2355 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2356 * available, or RTO is scheduled to fire first.
2358 if (sysctl_tcp_early_retrans
< 2 || (flag
& FLAG_ECE
) || !tp
->srtt
)
2361 delay
= max_t(unsigned long, (tp
->srtt
>> 5), msecs_to_jiffies(2));
2362 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2365 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, delay
, TCP_RTO_MAX
);
2366 tp
->early_retrans_delayed
= 1;
2370 static inline int tcp_skb_timedout(const struct sock
*sk
,
2371 const struct sk_buff
*skb
)
2373 return tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
;
2376 static inline int tcp_head_timedout(const struct sock
*sk
)
2378 const struct tcp_sock
*tp
= tcp_sk(sk
);
2380 return tp
->packets_out
&&
2381 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2384 /* Linux NewReno/SACK/FACK/ECN state machine.
2385 * --------------------------------------
2387 * "Open" Normal state, no dubious events, fast path.
2388 * "Disorder" In all the respects it is "Open",
2389 * but requires a bit more attention. It is entered when
2390 * we see some SACKs or dupacks. It is split of "Open"
2391 * mainly to move some processing from fast path to slow one.
2392 * "CWR" CWND was reduced due to some Congestion Notification event.
2393 * It can be ECN, ICMP source quench, local device congestion.
2394 * "Recovery" CWND was reduced, we are fast-retransmitting.
2395 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2397 * tcp_fastretrans_alert() is entered:
2398 * - each incoming ACK, if state is not "Open"
2399 * - when arrived ACK is unusual, namely:
2404 * Counting packets in flight is pretty simple.
2406 * in_flight = packets_out - left_out + retrans_out
2408 * packets_out is SND.NXT-SND.UNA counted in packets.
2410 * retrans_out is number of retransmitted segments.
2412 * left_out is number of segments left network, but not ACKed yet.
2414 * left_out = sacked_out + lost_out
2416 * sacked_out: Packets, which arrived to receiver out of order
2417 * and hence not ACKed. With SACKs this number is simply
2418 * amount of SACKed data. Even without SACKs
2419 * it is easy to give pretty reliable estimate of this number,
2420 * counting duplicate ACKs.
2422 * lost_out: Packets lost by network. TCP has no explicit
2423 * "loss notification" feedback from network (for now).
2424 * It means that this number can be only _guessed_.
2425 * Actually, it is the heuristics to predict lossage that
2426 * distinguishes different algorithms.
2428 * F.e. after RTO, when all the queue is considered as lost,
2429 * lost_out = packets_out and in_flight = retrans_out.
2431 * Essentially, we have now two algorithms counting
2434 * FACK: It is the simplest heuristics. As soon as we decided
2435 * that something is lost, we decide that _all_ not SACKed
2436 * packets until the most forward SACK are lost. I.e.
2437 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2438 * It is absolutely correct estimate, if network does not reorder
2439 * packets. And it loses any connection to reality when reordering
2440 * takes place. We use FACK by default until reordering
2441 * is suspected on the path to this destination.
2443 * NewReno: when Recovery is entered, we assume that one segment
2444 * is lost (classic Reno). While we are in Recovery and
2445 * a partial ACK arrives, we assume that one more packet
2446 * is lost (NewReno). This heuristics are the same in NewReno
2449 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2450 * deflation etc. CWND is real congestion window, never inflated, changes
2451 * only according to classic VJ rules.
2453 * Really tricky (and requiring careful tuning) part of algorithm
2454 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2455 * The first determines the moment _when_ we should reduce CWND and,
2456 * hence, slow down forward transmission. In fact, it determines the moment
2457 * when we decide that hole is caused by loss, rather than by a reorder.
2459 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2460 * holes, caused by lost packets.
2462 * And the most logically complicated part of algorithm is undo
2463 * heuristics. We detect false retransmits due to both too early
2464 * fast retransmit (reordering) and underestimated RTO, analyzing
2465 * timestamps and D-SACKs. When we detect that some segments were
2466 * retransmitted by mistake and CWND reduction was wrong, we undo
2467 * window reduction and abort recovery phase. This logic is hidden
2468 * inside several functions named tcp_try_undo_<something>.
2471 /* This function decides, when we should leave Disordered state
2472 * and enter Recovery phase, reducing congestion window.
2474 * Main question: may we further continue forward transmission
2475 * with the same cwnd?
2477 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2479 struct tcp_sock
*tp
= tcp_sk(sk
);
2482 /* Do not perform any recovery during F-RTO algorithm */
2483 if (tp
->frto_counter
)
2486 /* Trick#1: The loss is proven. */
2490 /* Not-A-Trick#2 : Classic rule... */
2491 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2494 /* Trick#3 : when we use RFC2988 timer restart, fast
2495 * retransmit can be triggered by timeout of queue head.
2497 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2500 /* Trick#4: It is still not OK... But will it be useful to delay
2503 packets_out
= tp
->packets_out
;
2504 if (packets_out
<= tp
->reordering
&&
2505 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2506 !tcp_may_send_now(sk
)) {
2507 /* We have nothing to send. This connection is limited
2508 * either by receiver window or by application.
2513 /* If a thin stream is detected, retransmit after first
2514 * received dupack. Employ only if SACK is supported in order
2515 * to avoid possible corner-case series of spurious retransmissions
2516 * Use only if there are no unsent data.
2518 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2519 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2520 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2523 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2524 * retransmissions due to small network reorderings, we implement
2525 * Mitigation A.3 in the RFC and delay the retransmission for a short
2526 * interval if appropriate.
2528 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2529 (tp
->packets_out
== (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2530 !tcp_may_send_now(sk
))
2531 return !tcp_pause_early_retransmit(sk
, flag
);
2536 /* New heuristics: it is possible only after we switched to restart timer
2537 * each time when something is ACKed. Hence, we can detect timed out packets
2538 * during fast retransmit without falling to slow start.
2540 * Usefulness of this as is very questionable, since we should know which of
2541 * the segments is the next to timeout which is relatively expensive to find
2542 * in general case unless we add some data structure just for that. The
2543 * current approach certainly won't find the right one too often and when it
2544 * finally does find _something_ it usually marks large part of the window
2545 * right away (because a retransmission with a larger timestamp blocks the
2546 * loop from advancing). -ij
2548 static void tcp_timeout_skbs(struct sock
*sk
)
2550 struct tcp_sock
*tp
= tcp_sk(sk
);
2551 struct sk_buff
*skb
;
2553 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2556 skb
= tp
->scoreboard_skb_hint
;
2557 if (tp
->scoreboard_skb_hint
== NULL
)
2558 skb
= tcp_write_queue_head(sk
);
2560 tcp_for_write_queue_from(skb
, sk
) {
2561 if (skb
== tcp_send_head(sk
))
2563 if (!tcp_skb_timedout(sk
, skb
))
2566 tcp_skb_mark_lost(tp
, skb
);
2569 tp
->scoreboard_skb_hint
= skb
;
2571 tcp_verify_left_out(tp
);
2574 /* Detect loss in event "A" above by marking head of queue up as lost.
2575 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2576 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2577 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2578 * the maximum SACKed segments to pass before reaching this limit.
2580 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2582 struct tcp_sock
*tp
= tcp_sk(sk
);
2583 struct sk_buff
*skb
;
2587 /* Use SACK to deduce losses of new sequences sent during recovery */
2588 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2590 WARN_ON(packets
> tp
->packets_out
);
2591 if (tp
->lost_skb_hint
) {
2592 skb
= tp
->lost_skb_hint
;
2593 cnt
= tp
->lost_cnt_hint
;
2594 /* Head already handled? */
2595 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2598 skb
= tcp_write_queue_head(sk
);
2602 tcp_for_write_queue_from(skb
, sk
) {
2603 if (skb
== tcp_send_head(sk
))
2605 /* TODO: do this better */
2606 /* this is not the most efficient way to do this... */
2607 tp
->lost_skb_hint
= skb
;
2608 tp
->lost_cnt_hint
= cnt
;
2610 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2614 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2615 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2616 cnt
+= tcp_skb_pcount(skb
);
2618 if (cnt
> packets
) {
2619 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2620 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2621 (oldcnt
>= packets
))
2624 mss
= skb_shinfo(skb
)->gso_size
;
2625 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2631 tcp_skb_mark_lost(tp
, skb
);
2636 tcp_verify_left_out(tp
);
2639 /* Account newly detected lost packet(s) */
2641 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2643 struct tcp_sock
*tp
= tcp_sk(sk
);
2645 if (tcp_is_reno(tp
)) {
2646 tcp_mark_head_lost(sk
, 1, 1);
2647 } else if (tcp_is_fack(tp
)) {
2648 int lost
= tp
->fackets_out
- tp
->reordering
;
2651 tcp_mark_head_lost(sk
, lost
, 0);
2653 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2654 if (sacked_upto
>= 0)
2655 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2656 else if (fast_rexmit
)
2657 tcp_mark_head_lost(sk
, 1, 1);
2660 tcp_timeout_skbs(sk
);
2663 /* CWND moderation, preventing bursts due to too big ACKs
2664 * in dubious situations.
2666 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2668 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2669 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2670 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2673 /* Lower bound on congestion window is slow start threshold
2674 * unless congestion avoidance choice decides to overide it.
2676 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2678 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2680 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2683 /* Decrease cwnd each second ack. */
2684 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2686 struct tcp_sock
*tp
= tcp_sk(sk
);
2687 int decr
= tp
->snd_cwnd_cnt
+ 1;
2689 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2690 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2691 tp
->snd_cwnd_cnt
= decr
& 1;
2694 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2695 tp
->snd_cwnd
-= decr
;
2697 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2698 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2702 /* Nothing was retransmitted or returned timestamp is less
2703 * than timestamp of the first retransmission.
2705 static inline int tcp_packet_delayed(const struct tcp_sock
*tp
)
2707 return !tp
->retrans_stamp
||
2708 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2709 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2712 /* Undo procedures. */
2714 #if FASTRETRANS_DEBUG > 1
2715 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2717 struct tcp_sock
*tp
= tcp_sk(sk
);
2718 struct inet_sock
*inet
= inet_sk(sk
);
2720 if (sk
->sk_family
== AF_INET
) {
2721 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2723 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2724 tp
->snd_cwnd
, tcp_left_out(tp
),
2725 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2728 #if IS_ENABLED(CONFIG_IPV6)
2729 else if (sk
->sk_family
== AF_INET6
) {
2730 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2731 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2733 &np
->daddr
, ntohs(inet
->inet_dport
),
2734 tp
->snd_cwnd
, tcp_left_out(tp
),
2735 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2741 #define DBGUNDO(x...) do { } while (0)
2744 static void tcp_undo_cwr(struct sock
*sk
, const bool undo_ssthresh
)
2746 struct tcp_sock
*tp
= tcp_sk(sk
);
2748 if (tp
->prior_ssthresh
) {
2749 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2751 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2752 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2754 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2756 if (undo_ssthresh
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2757 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2758 TCP_ECN_withdraw_cwr(tp
);
2761 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2763 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2766 static inline int tcp_may_undo(const struct tcp_sock
*tp
)
2768 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2771 /* People celebrate: "We love our President!" */
2772 static bool tcp_try_undo_recovery(struct sock
*sk
)
2774 struct tcp_sock
*tp
= tcp_sk(sk
);
2776 if (tcp_may_undo(tp
)) {
2779 /* Happy end! We did not retransmit anything
2780 * or our original transmission succeeded.
2782 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2783 tcp_undo_cwr(sk
, true);
2784 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2785 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2787 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2789 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2790 tp
->undo_marker
= 0;
2792 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2793 /* Hold old state until something *above* high_seq
2794 * is ACKed. For Reno it is MUST to prevent false
2795 * fast retransmits (RFC2582). SACK TCP is safe. */
2796 tcp_moderate_cwnd(tp
);
2799 tcp_set_ca_state(sk
, TCP_CA_Open
);
2803 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2804 static void tcp_try_undo_dsack(struct sock
*sk
)
2806 struct tcp_sock
*tp
= tcp_sk(sk
);
2808 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2809 DBGUNDO(sk
, "D-SACK");
2810 tcp_undo_cwr(sk
, true);
2811 tp
->undo_marker
= 0;
2812 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2816 /* We can clear retrans_stamp when there are no retransmissions in the
2817 * window. It would seem that it is trivially available for us in
2818 * tp->retrans_out, however, that kind of assumptions doesn't consider
2819 * what will happen if errors occur when sending retransmission for the
2820 * second time. ...It could the that such segment has only
2821 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2822 * the head skb is enough except for some reneging corner cases that
2823 * are not worth the effort.
2825 * Main reason for all this complexity is the fact that connection dying
2826 * time now depends on the validity of the retrans_stamp, in particular,
2827 * that successive retransmissions of a segment must not advance
2828 * retrans_stamp under any conditions.
2830 static bool tcp_any_retrans_done(const struct sock
*sk
)
2832 const struct tcp_sock
*tp
= tcp_sk(sk
);
2833 struct sk_buff
*skb
;
2835 if (tp
->retrans_out
)
2838 skb
= tcp_write_queue_head(sk
);
2839 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2845 /* Undo during fast recovery after partial ACK. */
2847 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2849 struct tcp_sock
*tp
= tcp_sk(sk
);
2850 /* Partial ACK arrived. Force Hoe's retransmit. */
2851 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2853 if (tcp_may_undo(tp
)) {
2854 /* Plain luck! Hole if filled with delayed
2855 * packet, rather than with a retransmit.
2857 if (!tcp_any_retrans_done(sk
))
2858 tp
->retrans_stamp
= 0;
2860 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2863 tcp_undo_cwr(sk
, false);
2864 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2866 /* So... Do not make Hoe's retransmit yet.
2867 * If the first packet was delayed, the rest
2868 * ones are most probably delayed as well.
2875 /* Undo during loss recovery after partial ACK. */
2876 static bool tcp_try_undo_loss(struct sock
*sk
)
2878 struct tcp_sock
*tp
= tcp_sk(sk
);
2880 if (tcp_may_undo(tp
)) {
2881 struct sk_buff
*skb
;
2882 tcp_for_write_queue(skb
, sk
) {
2883 if (skb
== tcp_send_head(sk
))
2885 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2888 tcp_clear_all_retrans_hints(tp
);
2890 DBGUNDO(sk
, "partial loss");
2892 tcp_undo_cwr(sk
, true);
2893 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2894 inet_csk(sk
)->icsk_retransmits
= 0;
2895 tp
->undo_marker
= 0;
2896 if (tcp_is_sack(tp
))
2897 tcp_set_ca_state(sk
, TCP_CA_Open
);
2903 static inline void tcp_complete_cwr(struct sock
*sk
)
2905 struct tcp_sock
*tp
= tcp_sk(sk
);
2907 /* Do not moderate cwnd if it's already undone in cwr or recovery. */
2908 if (tp
->undo_marker
) {
2909 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
) {
2910 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2911 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2912 } else if (tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
) {
2913 /* PRR algorithm. */
2914 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2915 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2918 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2921 static void tcp_try_keep_open(struct sock
*sk
)
2923 struct tcp_sock
*tp
= tcp_sk(sk
);
2924 int state
= TCP_CA_Open
;
2926 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2927 state
= TCP_CA_Disorder
;
2929 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2930 tcp_set_ca_state(sk
, state
);
2931 tp
->high_seq
= tp
->snd_nxt
;
2935 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2937 struct tcp_sock
*tp
= tcp_sk(sk
);
2939 tcp_verify_left_out(tp
);
2941 if (!tp
->frto_counter
&& !tcp_any_retrans_done(sk
))
2942 tp
->retrans_stamp
= 0;
2944 if (flag
& FLAG_ECE
)
2945 tcp_enter_cwr(sk
, 1);
2947 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2948 tcp_try_keep_open(sk
);
2949 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2950 tcp_moderate_cwnd(tp
);
2952 tcp_cwnd_down(sk
, flag
);
2956 static void tcp_mtup_probe_failed(struct sock
*sk
)
2958 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2960 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2961 icsk
->icsk_mtup
.probe_size
= 0;
2964 static void tcp_mtup_probe_success(struct sock
*sk
)
2966 struct tcp_sock
*tp
= tcp_sk(sk
);
2967 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2969 /* FIXME: breaks with very large cwnd */
2970 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2971 tp
->snd_cwnd
= tp
->snd_cwnd
*
2972 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2973 icsk
->icsk_mtup
.probe_size
;
2974 tp
->snd_cwnd_cnt
= 0;
2975 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2976 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2978 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2979 icsk
->icsk_mtup
.probe_size
= 0;
2980 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2983 /* Do a simple retransmit without using the backoff mechanisms in
2984 * tcp_timer. This is used for path mtu discovery.
2985 * The socket is already locked here.
2987 void tcp_simple_retransmit(struct sock
*sk
)
2989 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2990 struct tcp_sock
*tp
= tcp_sk(sk
);
2991 struct sk_buff
*skb
;
2992 unsigned int mss
= tcp_current_mss(sk
);
2993 u32 prior_lost
= tp
->lost_out
;
2995 tcp_for_write_queue(skb
, sk
) {
2996 if (skb
== tcp_send_head(sk
))
2998 if (tcp_skb_seglen(skb
) > mss
&&
2999 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
3000 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
3001 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
3002 tp
->retrans_out
-= tcp_skb_pcount(skb
);
3004 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
3008 tcp_clear_retrans_hints_partial(tp
);
3010 if (prior_lost
== tp
->lost_out
)
3013 if (tcp_is_reno(tp
))
3014 tcp_limit_reno_sacked(tp
);
3016 tcp_verify_left_out(tp
);
3018 /* Don't muck with the congestion window here.
3019 * Reason is that we do not increase amount of _data_
3020 * in network, but units changed and effective
3021 * cwnd/ssthresh really reduced now.
3023 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
3024 tp
->high_seq
= tp
->snd_nxt
;
3025 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3026 tp
->prior_ssthresh
= 0;
3027 tp
->undo_marker
= 0;
3028 tcp_set_ca_state(sk
, TCP_CA_Loss
);
3030 tcp_xmit_retransmit_queue(sk
);
3032 EXPORT_SYMBOL(tcp_simple_retransmit
);
3034 /* This function implements the PRR algorithm, specifcally the PRR-SSRB
3035 * (proportional rate reduction with slow start reduction bound) as described in
3036 * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt.
3037 * It computes the number of packets to send (sndcnt) based on packets newly
3039 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
3040 * cwnd reductions across a full RTT.
3041 * 2) If packets in flight is lower than ssthresh (such as due to excess
3042 * losses and/or application stalls), do not perform any further cwnd
3043 * reductions, but instead slow start up to ssthresh.
3045 static void tcp_update_cwnd_in_recovery(struct sock
*sk
, int newly_acked_sacked
,
3046 int fast_rexmit
, int flag
)
3048 struct tcp_sock
*tp
= tcp_sk(sk
);
3050 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
3052 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
3053 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
3055 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
3057 sndcnt
= min_t(int, delta
,
3058 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
3059 newly_acked_sacked
) + 1);
3062 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
3063 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
3066 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
3068 struct tcp_sock
*tp
= tcp_sk(sk
);
3071 if (tcp_is_reno(tp
))
3072 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
3074 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
3076 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3078 tp
->high_seq
= tp
->snd_nxt
;
3079 tp
->prior_ssthresh
= 0;
3080 tp
->undo_marker
= tp
->snd_una
;
3081 tp
->undo_retrans
= tp
->retrans_out
;
3083 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
3085 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
3086 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
3087 TCP_ECN_queue_cwr(tp
);
3090 tp
->bytes_acked
= 0;
3091 tp
->snd_cwnd_cnt
= 0;
3092 tp
->prior_cwnd
= tp
->snd_cwnd
;
3093 tp
->prr_delivered
= 0;
3095 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
3098 /* Process an event, which can update packets-in-flight not trivially.
3099 * Main goal of this function is to calculate new estimate for left_out,
3100 * taking into account both packets sitting in receiver's buffer and
3101 * packets lost by network.
3103 * Besides that it does CWND reduction, when packet loss is detected
3104 * and changes state of machine.
3106 * It does _not_ decide what to send, it is made in function
3107 * tcp_xmit_retransmit_queue().
3109 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
,
3110 int newly_acked_sacked
, bool is_dupack
,
3113 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3114 struct tcp_sock
*tp
= tcp_sk(sk
);
3115 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
3116 (tcp_fackets_out(tp
) > tp
->reordering
));
3117 int fast_rexmit
= 0;
3119 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
3121 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
3122 tp
->fackets_out
= 0;
3124 /* Now state machine starts.
3125 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
3126 if (flag
& FLAG_ECE
)
3127 tp
->prior_ssthresh
= 0;
3129 /* B. In all the states check for reneging SACKs. */
3130 if (tcp_check_sack_reneging(sk
, flag
))
3133 /* C. Check consistency of the current state. */
3134 tcp_verify_left_out(tp
);
3136 /* D. Check state exit conditions. State can be terminated
3137 * when high_seq is ACKed. */
3138 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
3139 WARN_ON(tp
->retrans_out
!= 0);
3140 tp
->retrans_stamp
= 0;
3141 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
3142 switch (icsk
->icsk_ca_state
) {
3144 icsk
->icsk_retransmits
= 0;
3145 if (tcp_try_undo_recovery(sk
))
3150 /* CWR is to be held something *above* high_seq
3151 * is ACKed for CWR bit to reach receiver. */
3152 if (tp
->snd_una
!= tp
->high_seq
) {
3153 tcp_complete_cwr(sk
);
3154 tcp_set_ca_state(sk
, TCP_CA_Open
);
3158 case TCP_CA_Recovery
:
3159 if (tcp_is_reno(tp
))
3160 tcp_reset_reno_sack(tp
);
3161 if (tcp_try_undo_recovery(sk
))
3163 tcp_complete_cwr(sk
);
3168 /* E. Process state. */
3169 switch (icsk
->icsk_ca_state
) {
3170 case TCP_CA_Recovery
:
3171 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3172 if (tcp_is_reno(tp
) && is_dupack
)
3173 tcp_add_reno_sack(sk
);
3175 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
3178 if (flag
& FLAG_DATA_ACKED
)
3179 icsk
->icsk_retransmits
= 0;
3180 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
3181 tcp_reset_reno_sack(tp
);
3182 if (!tcp_try_undo_loss(sk
)) {
3183 tcp_moderate_cwnd(tp
);
3184 tcp_xmit_retransmit_queue(sk
);
3187 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
3189 /* Loss is undone; fall through to processing in Open state. */
3191 if (tcp_is_reno(tp
)) {
3192 if (flag
& FLAG_SND_UNA_ADVANCED
)
3193 tcp_reset_reno_sack(tp
);
3195 tcp_add_reno_sack(sk
);
3198 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
3199 tcp_try_undo_dsack(sk
);
3201 if (!tcp_time_to_recover(sk
, flag
)) {
3202 tcp_try_to_open(sk
, flag
);
3206 /* MTU probe failure: don't reduce cwnd */
3207 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3208 icsk
->icsk_mtup
.probe_size
&&
3209 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3210 tcp_mtup_probe_failed(sk
);
3211 /* Restores the reduction we did in tcp_mtup_probe() */
3213 tcp_simple_retransmit(sk
);
3217 /* Otherwise enter Recovery state */
3218 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
3222 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
3223 tcp_update_scoreboard(sk
, fast_rexmit
);
3224 tp
->prr_delivered
+= newly_acked_sacked
;
3225 tcp_update_cwnd_in_recovery(sk
, newly_acked_sacked
, fast_rexmit
, flag
);
3226 tcp_xmit_retransmit_queue(sk
);
3229 void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
3231 tcp_rtt_estimator(sk
, seq_rtt
);
3233 inet_csk(sk
)->icsk_backoff
= 0;
3235 EXPORT_SYMBOL(tcp_valid_rtt_meas
);
3237 /* Read draft-ietf-tcplw-high-performance before mucking
3238 * with this code. (Supersedes RFC1323)
3240 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
3242 /* RTTM Rule: A TSecr value received in a segment is used to
3243 * update the averaged RTT measurement only if the segment
3244 * acknowledges some new data, i.e., only if it advances the
3245 * left edge of the send window.
3247 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3248 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3250 * Changed: reset backoff as soon as we see the first valid sample.
3251 * If we do not, we get strongly overestimated rto. With timestamps
3252 * samples are accepted even from very old segments: f.e., when rtt=1
3253 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3254 * answer arrives rto becomes 120 seconds! If at least one of segments
3255 * in window is lost... Voila. --ANK (010210)
3257 struct tcp_sock
*tp
= tcp_sk(sk
);
3259 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
3262 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
3264 /* We don't have a timestamp. Can only use
3265 * packets that are not retransmitted to determine
3266 * rtt estimates. Also, we must not reset the
3267 * backoff for rto until we get a non-retransmitted
3268 * packet. This allows us to deal with a situation
3269 * where the network delay has increased suddenly.
3270 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3273 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3276 tcp_valid_rtt_meas(sk
, seq_rtt
);
3279 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3282 const struct tcp_sock
*tp
= tcp_sk(sk
);
3283 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3284 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3285 tcp_ack_saw_tstamp(sk
, flag
);
3286 else if (seq_rtt
>= 0)
3287 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
3290 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
3292 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3293 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
3294 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
3297 /* Restart timer after forward progress on connection.
3298 * RFC2988 recommends to restart timer to now+rto.
3300 void tcp_rearm_rto(struct sock
*sk
)
3302 struct tcp_sock
*tp
= tcp_sk(sk
);
3304 if (!tp
->packets_out
) {
3305 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3307 u32 rto
= inet_csk(sk
)->icsk_rto
;
3308 /* Offset the time elapsed after installing regular RTO */
3309 if (tp
->early_retrans_delayed
) {
3310 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
3311 const u32 rto_time_stamp
= TCP_SKB_CB(skb
)->when
+ rto
;
3312 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
3313 /* delta may not be positive if the socket is locked
3314 * when the delayed ER timer fires and is rescheduled.
3319 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
3322 tp
->early_retrans_delayed
= 0;
3325 /* This function is called when the delayed ER timer fires. TCP enters
3326 * fast recovery and performs fast-retransmit.
3328 void tcp_resume_early_retransmit(struct sock
*sk
)
3330 struct tcp_sock
*tp
= tcp_sk(sk
);
3334 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3335 if (!tp
->do_early_retrans
)
3338 tcp_enter_recovery(sk
, false);
3339 tcp_update_scoreboard(sk
, 1);
3340 tcp_xmit_retransmit_queue(sk
);
3343 /* If we get here, the whole TSO packet has not been acked. */
3344 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3346 struct tcp_sock
*tp
= tcp_sk(sk
);
3349 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3351 packets_acked
= tcp_skb_pcount(skb
);
3352 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3354 packets_acked
-= tcp_skb_pcount(skb
);
3356 if (packets_acked
) {
3357 BUG_ON(tcp_skb_pcount(skb
) == 0);
3358 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3361 return packets_acked
;
3364 /* Remove acknowledged frames from the retransmission queue. If our packet
3365 * is before the ack sequence we can discard it as it's confirmed to have
3366 * arrived at the other end.
3368 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3371 struct tcp_sock
*tp
= tcp_sk(sk
);
3372 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3373 struct sk_buff
*skb
;
3374 u32 now
= tcp_time_stamp
;
3375 int fully_acked
= true;
3378 u32 reord
= tp
->packets_out
;
3379 u32 prior_sacked
= tp
->sacked_out
;
3381 s32 ca_seq_rtt
= -1;
3382 ktime_t last_ackt
= net_invalid_timestamp();
3384 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3385 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3387 u8 sacked
= scb
->sacked
;
3389 /* Determine how many packets and what bytes were acked, tso and else */
3390 if (after(scb
->end_seq
, tp
->snd_una
)) {
3391 if (tcp_skb_pcount(skb
) == 1 ||
3392 !after(tp
->snd_una
, scb
->seq
))
3395 acked_pcount
= tcp_tso_acked(sk
, skb
);
3399 fully_acked
= false;
3401 acked_pcount
= tcp_skb_pcount(skb
);
3404 if (sacked
& TCPCB_RETRANS
) {
3405 if (sacked
& TCPCB_SACKED_RETRANS
)
3406 tp
->retrans_out
-= acked_pcount
;
3407 flag
|= FLAG_RETRANS_DATA_ACKED
;
3410 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
3411 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
3413 ca_seq_rtt
= now
- scb
->when
;
3414 last_ackt
= skb
->tstamp
;
3416 seq_rtt
= ca_seq_rtt
;
3418 if (!(sacked
& TCPCB_SACKED_ACKED
))
3419 reord
= min(pkts_acked
, reord
);
3422 if (sacked
& TCPCB_SACKED_ACKED
)
3423 tp
->sacked_out
-= acked_pcount
;
3424 if (sacked
& TCPCB_LOST
)
3425 tp
->lost_out
-= acked_pcount
;
3427 tp
->packets_out
-= acked_pcount
;
3428 pkts_acked
+= acked_pcount
;
3430 /* Initial outgoing SYN's get put onto the write_queue
3431 * just like anything else we transmit. It is not
3432 * true data, and if we misinform our callers that
3433 * this ACK acks real data, we will erroneously exit
3434 * connection startup slow start one packet too
3435 * quickly. This is severely frowned upon behavior.
3437 if (!(scb
->tcp_flags
& TCPHDR_SYN
)) {
3438 flag
|= FLAG_DATA_ACKED
;
3440 flag
|= FLAG_SYN_ACKED
;
3441 tp
->retrans_stamp
= 0;
3447 tcp_unlink_write_queue(skb
, sk
);
3448 sk_wmem_free_skb(sk
, skb
);
3449 tp
->scoreboard_skb_hint
= NULL
;
3450 if (skb
== tp
->retransmit_skb_hint
)
3451 tp
->retransmit_skb_hint
= NULL
;
3452 if (skb
== tp
->lost_skb_hint
)
3453 tp
->lost_skb_hint
= NULL
;
3456 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3457 tp
->snd_up
= tp
->snd_una
;
3459 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3460 flag
|= FLAG_SACK_RENEGING
;
3462 if (flag
& FLAG_ACKED
) {
3463 const struct tcp_congestion_ops
*ca_ops
3464 = inet_csk(sk
)->icsk_ca_ops
;
3466 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3467 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3468 tcp_mtup_probe_success(sk
);
3471 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3474 if (tcp_is_reno(tp
)) {
3475 tcp_remove_reno_sacks(sk
, pkts_acked
);
3479 /* Non-retransmitted hole got filled? That's reordering */
3480 if (reord
< prior_fackets
)
3481 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3483 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3484 prior_sacked
- tp
->sacked_out
;
3485 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3488 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3490 if (ca_ops
->pkts_acked
) {
3493 /* Is the ACK triggering packet unambiguous? */
3494 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3495 /* High resolution needed and available? */
3496 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3497 !ktime_equal(last_ackt
,
3498 net_invalid_timestamp()))
3499 rtt_us
= ktime_us_delta(ktime_get_real(),
3501 else if (ca_seq_rtt
>= 0)
3502 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3505 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3509 #if FASTRETRANS_DEBUG > 0
3510 WARN_ON((int)tp
->sacked_out
< 0);
3511 WARN_ON((int)tp
->lost_out
< 0);
3512 WARN_ON((int)tp
->retrans_out
< 0);
3513 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3514 icsk
= inet_csk(sk
);
3516 pr_debug("Leak l=%u %d\n",
3517 tp
->lost_out
, icsk
->icsk_ca_state
);
3520 if (tp
->sacked_out
) {
3521 pr_debug("Leak s=%u %d\n",
3522 tp
->sacked_out
, icsk
->icsk_ca_state
);
3525 if (tp
->retrans_out
) {
3526 pr_debug("Leak r=%u %d\n",
3527 tp
->retrans_out
, icsk
->icsk_ca_state
);
3528 tp
->retrans_out
= 0;
3535 static void tcp_ack_probe(struct sock
*sk
)
3537 const struct tcp_sock
*tp
= tcp_sk(sk
);
3538 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3540 /* Was it a usable window open? */
3542 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3543 icsk
->icsk_backoff
= 0;
3544 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3545 /* Socket must be waked up by subsequent tcp_data_snd_check().
3546 * This function is not for random using!
3549 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3550 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3555 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3557 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3558 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3561 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3563 const struct tcp_sock
*tp
= tcp_sk(sk
);
3564 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3565 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3568 /* Check that window update is acceptable.
3569 * The function assumes that snd_una<=ack<=snd_next.
3571 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3572 const u32 ack
, const u32 ack_seq
,
3575 return after(ack
, tp
->snd_una
) ||
3576 after(ack_seq
, tp
->snd_wl1
) ||
3577 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3580 /* Update our send window.
3582 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3583 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3585 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3588 struct tcp_sock
*tp
= tcp_sk(sk
);
3590 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3592 if (likely(!tcp_hdr(skb
)->syn
))
3593 nwin
<<= tp
->rx_opt
.snd_wscale
;
3595 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3596 flag
|= FLAG_WIN_UPDATE
;
3597 tcp_update_wl(tp
, ack_seq
);
3599 if (tp
->snd_wnd
!= nwin
) {
3602 /* Note, it is the only place, where
3603 * fast path is recovered for sending TCP.
3606 tcp_fast_path_check(sk
);
3608 if (nwin
> tp
->max_window
) {
3609 tp
->max_window
= nwin
;
3610 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3620 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3621 * continue in congestion avoidance.
3623 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3625 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3626 tp
->snd_cwnd_cnt
= 0;
3627 tp
->bytes_acked
= 0;
3628 TCP_ECN_queue_cwr(tp
);
3629 tcp_moderate_cwnd(tp
);
3632 /* A conservative spurious RTO response algorithm: reduce cwnd using
3633 * rate halving and continue in congestion avoidance.
3635 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3637 tcp_enter_cwr(sk
, 0);
3640 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3642 if (flag
& FLAG_ECE
)
3643 tcp_ratehalving_spur_to_response(sk
);
3645 tcp_undo_cwr(sk
, true);
3648 /* F-RTO spurious RTO detection algorithm (RFC4138)
3650 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3651 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3652 * window (but not to or beyond highest sequence sent before RTO):
3653 * On First ACK, send two new segments out.
3654 * On Second ACK, RTO was likely spurious. Do spurious response (response
3655 * algorithm is not part of the F-RTO detection algorithm
3656 * given in RFC4138 but can be selected separately).
3657 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3658 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3659 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3660 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3662 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3663 * original window even after we transmit two new data segments.
3666 * on first step, wait until first cumulative ACK arrives, then move to
3667 * the second step. In second step, the next ACK decides.
3669 * F-RTO is implemented (mainly) in four functions:
3670 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3671 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3672 * called when tcp_use_frto() showed green light
3673 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3674 * - tcp_enter_frto_loss() is called if there is not enough evidence
3675 * to prove that the RTO is indeed spurious. It transfers the control
3676 * from F-RTO to the conventional RTO recovery
3678 static bool tcp_process_frto(struct sock
*sk
, int flag
)
3680 struct tcp_sock
*tp
= tcp_sk(sk
);
3682 tcp_verify_left_out(tp
);
3684 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3685 if (flag
& FLAG_DATA_ACKED
)
3686 inet_csk(sk
)->icsk_retransmits
= 0;
3688 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3689 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3690 tp
->undo_marker
= 0;
3692 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3693 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3697 if (!tcp_is_sackfrto(tp
)) {
3698 /* RFC4138 shortcoming in step 2; should also have case c):
3699 * ACK isn't duplicate nor advances window, e.g., opposite dir
3702 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3705 if (!(flag
& FLAG_DATA_ACKED
)) {
3706 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3711 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3712 /* Prevent sending of new data. */
3713 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3714 tcp_packets_in_flight(tp
));
3718 if ((tp
->frto_counter
>= 2) &&
3719 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3720 ((flag
& FLAG_DATA_SACKED
) &&
3721 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3722 /* RFC4138 shortcoming (see comment above) */
3723 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3724 (flag
& FLAG_NOT_DUP
))
3727 tcp_enter_frto_loss(sk
, 3, flag
);
3732 if (tp
->frto_counter
== 1) {
3733 /* tcp_may_send_now needs to see updated state */
3734 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3735 tp
->frto_counter
= 2;
3737 if (!tcp_may_send_now(sk
))
3738 tcp_enter_frto_loss(sk
, 2, flag
);
3742 switch (sysctl_tcp_frto_response
) {
3744 tcp_undo_spur_to_response(sk
, flag
);
3747 tcp_conservative_spur_to_response(tp
);
3750 tcp_ratehalving_spur_to_response(sk
);
3753 tp
->frto_counter
= 0;
3754 tp
->undo_marker
= 0;
3755 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3760 /* This routine deals with incoming acks, but not outgoing ones. */
3761 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3763 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3764 struct tcp_sock
*tp
= tcp_sk(sk
);
3765 u32 prior_snd_una
= tp
->snd_una
;
3766 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3767 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3768 bool is_dupack
= false;
3769 u32 prior_in_flight
;
3772 int prior_sacked
= tp
->sacked_out
;
3774 int newly_acked_sacked
= 0;
3775 bool frto_cwnd
= false;
3777 /* If the ack is older than previous acks
3778 * then we can probably ignore it.
3780 if (before(ack
, prior_snd_una
))
3783 /* If the ack includes data we haven't sent yet, discard
3784 * this segment (RFC793 Section 3.9).
3786 if (after(ack
, tp
->snd_nxt
))
3789 if (tp
->early_retrans_delayed
)
3792 if (after(ack
, prior_snd_una
))
3793 flag
|= FLAG_SND_UNA_ADVANCED
;
3795 if (sysctl_tcp_abc
) {
3796 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3797 tp
->bytes_acked
+= ack
- prior_snd_una
;
3798 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3799 /* we assume just one segment left network */
3800 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3804 prior_fackets
= tp
->fackets_out
;
3805 prior_in_flight
= tcp_packets_in_flight(tp
);
3807 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3808 /* Window is constant, pure forward advance.
3809 * No more checks are required.
3810 * Note, we use the fact that SND.UNA>=SND.WL2.
3812 tcp_update_wl(tp
, ack_seq
);
3814 flag
|= FLAG_WIN_UPDATE
;
3816 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3818 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3820 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3823 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3825 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3827 if (TCP_SKB_CB(skb
)->sacked
)
3828 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3830 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3833 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3836 /* We passed data and got it acked, remove any soft error
3837 * log. Something worked...
3839 sk
->sk_err_soft
= 0;
3840 icsk
->icsk_probes_out
= 0;
3841 tp
->rcv_tstamp
= tcp_time_stamp
;
3842 prior_packets
= tp
->packets_out
;
3846 /* See if we can take anything off of the retransmit queue. */
3847 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3849 pkts_acked
= prior_packets
- tp
->packets_out
;
3850 newly_acked_sacked
= (prior_packets
- prior_sacked
) -
3851 (tp
->packets_out
- tp
->sacked_out
);
3853 if (tp
->frto_counter
)
3854 frto_cwnd
= tcp_process_frto(sk
, flag
);
3855 /* Guarantee sacktag reordering detection against wrap-arounds */
3856 if (before(tp
->frto_highmark
, tp
->snd_una
))
3857 tp
->frto_highmark
= 0;
3859 if (tcp_ack_is_dubious(sk
, flag
)) {
3860 /* Advance CWND, if state allows this. */
3861 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3862 tcp_may_raise_cwnd(sk
, flag
))
3863 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3864 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3865 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3868 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3869 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3872 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3873 dst_confirm(__sk_dst_get(sk
));
3878 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3879 if (flag
& FLAG_DSACKING_ACK
)
3880 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3882 /* If this ack opens up a zero window, clear backoff. It was
3883 * being used to time the probes, and is probably far higher than
3884 * it needs to be for normal retransmission.
3886 if (tcp_send_head(sk
))
3891 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3895 /* If data was SACKed, tag it and see if we should send more data.
3896 * If data was DSACKed, see if we can undo a cwnd reduction.
3898 if (TCP_SKB_CB(skb
)->sacked
) {
3899 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3900 newly_acked_sacked
= tp
->sacked_out
- prior_sacked
;
3901 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3905 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3909 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3910 * But, this can also be called on packets in the established flow when
3911 * the fast version below fails.
3913 void tcp_parse_options(const struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3914 const u8
**hvpp
, int estab
)
3916 const unsigned char *ptr
;
3917 const struct tcphdr
*th
= tcp_hdr(skb
);
3918 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3920 ptr
= (const unsigned char *)(th
+ 1);
3921 opt_rx
->saw_tstamp
= 0;
3923 while (length
> 0) {
3924 int opcode
= *ptr
++;
3930 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3935 if (opsize
< 2) /* "silly options" */
3937 if (opsize
> length
)
3938 return; /* don't parse partial options */
3941 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3942 u16 in_mss
= get_unaligned_be16(ptr
);
3944 if (opt_rx
->user_mss
&&
3945 opt_rx
->user_mss
< in_mss
)
3946 in_mss
= opt_rx
->user_mss
;
3947 opt_rx
->mss_clamp
= in_mss
;
3952 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3953 !estab
&& sysctl_tcp_window_scaling
) {
3954 __u8 snd_wscale
= *(__u8
*)ptr
;
3955 opt_rx
->wscale_ok
= 1;
3956 if (snd_wscale
> 14) {
3957 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3962 opt_rx
->snd_wscale
= snd_wscale
;
3965 case TCPOPT_TIMESTAMP
:
3966 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3967 ((estab
&& opt_rx
->tstamp_ok
) ||
3968 (!estab
&& sysctl_tcp_timestamps
))) {
3969 opt_rx
->saw_tstamp
= 1;
3970 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3971 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3974 case TCPOPT_SACK_PERM
:
3975 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3976 !estab
&& sysctl_tcp_sack
) {
3977 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3978 tcp_sack_reset(opt_rx
);
3983 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3984 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3986 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3989 #ifdef CONFIG_TCP_MD5SIG
3992 * The MD5 Hash has already been
3993 * checked (see tcp_v{4,6}_do_rcv()).
3998 /* This option is variable length.
4001 case TCPOLEN_COOKIE_BASE
:
4002 /* not yet implemented */
4004 case TCPOLEN_COOKIE_PAIR
:
4005 /* not yet implemented */
4007 case TCPOLEN_COOKIE_MIN
+0:
4008 case TCPOLEN_COOKIE_MIN
+2:
4009 case TCPOLEN_COOKIE_MIN
+4:
4010 case TCPOLEN_COOKIE_MIN
+6:
4011 case TCPOLEN_COOKIE_MAX
:
4012 /* 16-bit multiple */
4013 opt_rx
->cookie_plus
= opsize
;
4028 EXPORT_SYMBOL(tcp_parse_options
);
4030 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
4032 const __be32
*ptr
= (const __be32
*)(th
+ 1);
4034 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4035 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
4036 tp
->rx_opt
.saw_tstamp
= 1;
4038 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4040 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4046 /* Fast parse options. This hopes to only see timestamps.
4047 * If it is wrong it falls back on tcp_parse_options().
4049 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
4050 const struct tcphdr
*th
,
4051 struct tcp_sock
*tp
, const u8
**hvpp
)
4053 /* In the spirit of fast parsing, compare doff directly to constant
4054 * values. Because equality is used, short doff can be ignored here.
4056 if (th
->doff
== (sizeof(*th
) / 4)) {
4057 tp
->rx_opt
.saw_tstamp
= 0;
4059 } else if (tp
->rx_opt
.tstamp_ok
&&
4060 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
4061 if (tcp_parse_aligned_timestamp(tp
, th
))
4064 tcp_parse_options(skb
, &tp
->rx_opt
, hvpp
, 1);
4068 #ifdef CONFIG_TCP_MD5SIG
4070 * Parse MD5 Signature option
4072 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
4074 int length
= (th
->doff
<< 2) - sizeof(*th
);
4075 const u8
*ptr
= (const u8
*)(th
+ 1);
4077 /* If the TCP option is too short, we can short cut */
4078 if (length
< TCPOLEN_MD5SIG
)
4081 while (length
> 0) {
4082 int opcode
= *ptr
++;
4093 if (opsize
< 2 || opsize
> length
)
4095 if (opcode
== TCPOPT_MD5SIG
)
4096 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
4103 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
4106 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
4108 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
4109 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
4112 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
4114 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
4115 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
4116 * extra check below makes sure this can only happen
4117 * for pure ACK frames. -DaveM
4119 * Not only, also it occurs for expired timestamps.
4122 if (tcp_paws_check(&tp
->rx_opt
, 0))
4123 tcp_store_ts_recent(tp
);
4127 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4129 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4130 * it can pass through stack. So, the following predicate verifies that
4131 * this segment is not used for anything but congestion avoidance or
4132 * fast retransmit. Moreover, we even are able to eliminate most of such
4133 * second order effects, if we apply some small "replay" window (~RTO)
4134 * to timestamp space.
4136 * All these measures still do not guarantee that we reject wrapped ACKs
4137 * on networks with high bandwidth, when sequence space is recycled fastly,
4138 * but it guarantees that such events will be very rare and do not affect
4139 * connection seriously. This doesn't look nice, but alas, PAWS is really
4142 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4143 * states that events when retransmit arrives after original data are rare.
4144 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4145 * the biggest problem on large power networks even with minor reordering.
4146 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4147 * up to bandwidth of 18Gigabit/sec. 8) ]
4150 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
4152 const struct tcp_sock
*tp
= tcp_sk(sk
);
4153 const struct tcphdr
*th
= tcp_hdr(skb
);
4154 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4155 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
4157 return (/* 1. Pure ACK with correct sequence number. */
4158 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
4160 /* 2. ... and duplicate ACK. */
4161 ack
== tp
->snd_una
&&
4163 /* 3. ... and does not update window. */
4164 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
4166 /* 4. ... and sits in replay window. */
4167 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
4170 static inline int tcp_paws_discard(const struct sock
*sk
,
4171 const struct sk_buff
*skb
)
4173 const struct tcp_sock
*tp
= tcp_sk(sk
);
4175 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
4176 !tcp_disordered_ack(sk
, skb
);
4179 /* Check segment sequence number for validity.
4181 * Segment controls are considered valid, if the segment
4182 * fits to the window after truncation to the window. Acceptability
4183 * of data (and SYN, FIN, of course) is checked separately.
4184 * See tcp_data_queue(), for example.
4186 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4187 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4188 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4189 * (borrowed from freebsd)
4192 static inline int tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4194 return !before(end_seq
, tp
->rcv_wup
) &&
4195 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4198 /* When we get a reset we do this. */
4199 static void tcp_reset(struct sock
*sk
)
4201 /* We want the right error as BSD sees it (and indeed as we do). */
4202 switch (sk
->sk_state
) {
4204 sk
->sk_err
= ECONNREFUSED
;
4206 case TCP_CLOSE_WAIT
:
4212 sk
->sk_err
= ECONNRESET
;
4214 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4217 if (!sock_flag(sk
, SOCK_DEAD
))
4218 sk
->sk_error_report(sk
);
4224 * Process the FIN bit. This now behaves as it is supposed to work
4225 * and the FIN takes effect when it is validly part of sequence
4226 * space. Not before when we get holes.
4228 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4229 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4232 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4233 * close and we go into CLOSING (and later onto TIME-WAIT)
4235 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4237 static void tcp_fin(struct sock
*sk
)
4239 struct tcp_sock
*tp
= tcp_sk(sk
);
4241 inet_csk_schedule_ack(sk
);
4243 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4244 sock_set_flag(sk
, SOCK_DONE
);
4246 switch (sk
->sk_state
) {
4248 case TCP_ESTABLISHED
:
4249 /* Move to CLOSE_WAIT */
4250 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4251 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4254 case TCP_CLOSE_WAIT
:
4256 /* Received a retransmission of the FIN, do
4261 /* RFC793: Remain in the LAST-ACK state. */
4265 /* This case occurs when a simultaneous close
4266 * happens, we must ack the received FIN and
4267 * enter the CLOSING state.
4270 tcp_set_state(sk
, TCP_CLOSING
);
4273 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4275 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4278 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4279 * cases we should never reach this piece of code.
4281 pr_err("%s: Impossible, sk->sk_state=%d\n",
4282 __func__
, sk
->sk_state
);
4286 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4287 * Probably, we should reset in this case. For now drop them.
4289 __skb_queue_purge(&tp
->out_of_order_queue
);
4290 if (tcp_is_sack(tp
))
4291 tcp_sack_reset(&tp
->rx_opt
);
4294 if (!sock_flag(sk
, SOCK_DEAD
)) {
4295 sk
->sk_state_change(sk
);
4297 /* Do not send POLL_HUP for half duplex close. */
4298 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4299 sk
->sk_state
== TCP_CLOSE
)
4300 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4302 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4306 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4309 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4310 if (before(seq
, sp
->start_seq
))
4311 sp
->start_seq
= seq
;
4312 if (after(end_seq
, sp
->end_seq
))
4313 sp
->end_seq
= end_seq
;
4319 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4321 struct tcp_sock
*tp
= tcp_sk(sk
);
4323 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4326 if (before(seq
, tp
->rcv_nxt
))
4327 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4329 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4331 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4333 tp
->rx_opt
.dsack
= 1;
4334 tp
->duplicate_sack
[0].start_seq
= seq
;
4335 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4339 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4341 struct tcp_sock
*tp
= tcp_sk(sk
);
4343 if (!tp
->rx_opt
.dsack
)
4344 tcp_dsack_set(sk
, seq
, end_seq
);
4346 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4349 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4351 struct tcp_sock
*tp
= tcp_sk(sk
);
4353 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4354 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4355 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4356 tcp_enter_quickack_mode(sk
);
4358 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4359 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4361 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4362 end_seq
= tp
->rcv_nxt
;
4363 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4370 /* These routines update the SACK block as out-of-order packets arrive or
4371 * in-order packets close up the sequence space.
4373 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4376 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4377 struct tcp_sack_block
*swalk
= sp
+ 1;
4379 /* See if the recent change to the first SACK eats into
4380 * or hits the sequence space of other SACK blocks, if so coalesce.
4382 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4383 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4386 /* Zap SWALK, by moving every further SACK up by one slot.
4387 * Decrease num_sacks.
4389 tp
->rx_opt
.num_sacks
--;
4390 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4394 this_sack
++, swalk
++;
4398 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4400 struct tcp_sock
*tp
= tcp_sk(sk
);
4401 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4402 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4408 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4409 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4410 /* Rotate this_sack to the first one. */
4411 for (; this_sack
> 0; this_sack
--, sp
--)
4412 swap(*sp
, *(sp
- 1));
4414 tcp_sack_maybe_coalesce(tp
);
4419 /* Could not find an adjacent existing SACK, build a new one,
4420 * put it at the front, and shift everyone else down. We
4421 * always know there is at least one SACK present already here.
4423 * If the sack array is full, forget about the last one.
4425 if (this_sack
>= TCP_NUM_SACKS
) {
4427 tp
->rx_opt
.num_sacks
--;
4430 for (; this_sack
> 0; this_sack
--, sp
--)
4434 /* Build the new head SACK, and we're done. */
4435 sp
->start_seq
= seq
;
4436 sp
->end_seq
= end_seq
;
4437 tp
->rx_opt
.num_sacks
++;
4440 /* RCV.NXT advances, some SACKs should be eaten. */
4442 static void tcp_sack_remove(struct tcp_sock
*tp
)
4444 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4445 int num_sacks
= tp
->rx_opt
.num_sacks
;
4448 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4449 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4450 tp
->rx_opt
.num_sacks
= 0;
4454 for (this_sack
= 0; this_sack
< num_sacks
;) {
4455 /* Check if the start of the sack is covered by RCV.NXT. */
4456 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4459 /* RCV.NXT must cover all the block! */
4460 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4462 /* Zap this SACK, by moving forward any other SACKS. */
4463 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4464 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4471 tp
->rx_opt
.num_sacks
= num_sacks
;
4474 /* This one checks to see if we can put data from the
4475 * out_of_order queue into the receive_queue.
4477 static void tcp_ofo_queue(struct sock
*sk
)
4479 struct tcp_sock
*tp
= tcp_sk(sk
);
4480 __u32 dsack_high
= tp
->rcv_nxt
;
4481 struct sk_buff
*skb
;
4483 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4484 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4487 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4488 __u32 dsack
= dsack_high
;
4489 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4490 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4491 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4494 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4495 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4496 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4500 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4501 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4502 TCP_SKB_CB(skb
)->end_seq
);
4504 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4505 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4506 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4507 if (tcp_hdr(skb
)->fin
)
4512 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4513 static int tcp_prune_queue(struct sock
*sk
);
4515 static int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
4517 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4518 !sk_rmem_schedule(sk
, size
)) {
4520 if (tcp_prune_queue(sk
) < 0)
4523 if (!sk_rmem_schedule(sk
, size
)) {
4524 if (!tcp_prune_ofo_queue(sk
))
4527 if (!sk_rmem_schedule(sk
, size
))
4535 * tcp_try_coalesce - try to merge skb to prior one
4538 * @from: buffer to add in queue
4539 * @fragstolen: pointer to boolean
4541 * Before queueing skb @from after @to, try to merge them
4542 * to reduce overall memory use and queue lengths, if cost is small.
4543 * Packets in ofo or receive queues can stay a long time.
4544 * Better try to coalesce them right now to avoid future collapses.
4545 * Returns true if caller should free @from instead of queueing it
4547 static bool tcp_try_coalesce(struct sock
*sk
,
4549 struct sk_buff
*from
,
4554 *fragstolen
= false;
4556 if (tcp_hdr(from
)->fin
)
4559 /* Its possible this segment overlaps with prior segment in queue */
4560 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4563 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4566 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4567 sk_mem_charge(sk
, delta
);
4568 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4569 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4570 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4574 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4576 struct tcp_sock
*tp
= tcp_sk(sk
);
4577 struct sk_buff
*skb1
;
4580 TCP_ECN_check_ce(tp
, skb
);
4582 if (tcp_try_rmem_schedule(sk
, skb
->truesize
)) {
4583 /* TODO: should increment a counter */
4588 /* Disable header prediction. */
4590 inet_csk_schedule_ack(sk
);
4592 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4593 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4595 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4597 /* Initial out of order segment, build 1 SACK. */
4598 if (tcp_is_sack(tp
)) {
4599 tp
->rx_opt
.num_sacks
= 1;
4600 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4601 tp
->selective_acks
[0].end_seq
=
4602 TCP_SKB_CB(skb
)->end_seq
;
4604 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4608 seq
= TCP_SKB_CB(skb
)->seq
;
4609 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4611 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4614 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4615 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4617 kfree_skb_partial(skb
, fragstolen
);
4621 if (!tp
->rx_opt
.num_sacks
||
4622 tp
->selective_acks
[0].end_seq
!= seq
)
4625 /* Common case: data arrive in order after hole. */
4626 tp
->selective_acks
[0].end_seq
= end_seq
;
4630 /* Find place to insert this segment. */
4632 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4634 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4638 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4641 /* Do skb overlap to previous one? */
4642 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4643 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4644 /* All the bits are present. Drop. */
4647 tcp_dsack_set(sk
, seq
, end_seq
);
4650 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4651 /* Partial overlap. */
4652 tcp_dsack_set(sk
, seq
,
4653 TCP_SKB_CB(skb1
)->end_seq
);
4655 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4659 skb1
= skb_queue_prev(
4660 &tp
->out_of_order_queue
,
4665 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4667 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4669 /* And clean segments covered by new one as whole. */
4670 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4671 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4673 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4675 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4676 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4680 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4681 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4682 TCP_SKB_CB(skb1
)->end_seq
);
4687 if (tcp_is_sack(tp
))
4688 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4691 skb_set_owner_r(skb
, sk
);
4694 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4698 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4700 __skb_pull(skb
, hdrlen
);
4702 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4703 tcp_sk(sk
)->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4705 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4706 skb_set_owner_r(skb
, sk
);
4711 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4713 struct sk_buff
*skb
;
4717 if (tcp_try_rmem_schedule(sk
, size
+ sizeof(*th
)))
4720 skb
= alloc_skb(size
+ sizeof(*th
), sk
->sk_allocation
);
4724 th
= (struct tcphdr
*)skb_put(skb
, sizeof(*th
));
4725 skb_reset_transport_header(skb
);
4726 memset(th
, 0, sizeof(*th
));
4728 if (memcpy_fromiovec(skb_put(skb
, size
), msg
->msg_iov
, size
))
4731 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4732 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4733 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4735 if (tcp_queue_rcv(sk
, skb
, sizeof(*th
), &fragstolen
)) {
4736 WARN_ON_ONCE(fragstolen
); /* should not happen */
4747 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4749 const struct tcphdr
*th
= tcp_hdr(skb
);
4750 struct tcp_sock
*tp
= tcp_sk(sk
);
4752 bool fragstolen
= false;
4754 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4758 __skb_pull(skb
, th
->doff
* 4);
4760 TCP_ECN_accept_cwr(tp
, skb
);
4762 tp
->rx_opt
.dsack
= 0;
4764 /* Queue data for delivery to the user.
4765 * Packets in sequence go to the receive queue.
4766 * Out of sequence packets to the out_of_order_queue.
4768 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4769 if (tcp_receive_window(tp
) == 0)
4772 /* Ok. In sequence. In window. */
4773 if (tp
->ucopy
.task
== current
&&
4774 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4775 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4776 int chunk
= min_t(unsigned int, skb
->len
,
4779 __set_current_state(TASK_RUNNING
);
4782 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4783 tp
->ucopy
.len
-= chunk
;
4784 tp
->copied_seq
+= chunk
;
4785 eaten
= (chunk
== skb
->len
);
4786 tcp_rcv_space_adjust(sk
);
4794 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4797 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4799 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4801 tcp_event_data_recv(sk
, skb
);
4805 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4808 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4809 * gap in queue is filled.
4811 if (skb_queue_empty(&tp
->out_of_order_queue
))
4812 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4815 if (tp
->rx_opt
.num_sacks
)
4816 tcp_sack_remove(tp
);
4818 tcp_fast_path_check(sk
);
4821 kfree_skb_partial(skb
, fragstolen
);
4822 else if (!sock_flag(sk
, SOCK_DEAD
))
4823 sk
->sk_data_ready(sk
, 0);
4827 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4828 /* A retransmit, 2nd most common case. Force an immediate ack. */
4829 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4830 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4833 tcp_enter_quickack_mode(sk
);
4834 inet_csk_schedule_ack(sk
);
4840 /* Out of window. F.e. zero window probe. */
4841 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4844 tcp_enter_quickack_mode(sk
);
4846 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4847 /* Partial packet, seq < rcv_next < end_seq */
4848 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4849 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4850 TCP_SKB_CB(skb
)->end_seq
);
4852 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4854 /* If window is closed, drop tail of packet. But after
4855 * remembering D-SACK for its head made in previous line.
4857 if (!tcp_receive_window(tp
))
4862 tcp_data_queue_ofo(sk
, skb
);
4865 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4866 struct sk_buff_head
*list
)
4868 struct sk_buff
*next
= NULL
;
4870 if (!skb_queue_is_last(list
, skb
))
4871 next
= skb_queue_next(list
, skb
);
4873 __skb_unlink(skb
, list
);
4875 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4880 /* Collapse contiguous sequence of skbs head..tail with
4881 * sequence numbers start..end.
4883 * If tail is NULL, this means until the end of the list.
4885 * Segments with FIN/SYN are not collapsed (only because this
4889 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4890 struct sk_buff
*head
, struct sk_buff
*tail
,
4893 struct sk_buff
*skb
, *n
;
4896 /* First, check that queue is collapsible and find
4897 * the point where collapsing can be useful. */
4901 skb_queue_walk_from_safe(list
, skb
, n
) {
4904 /* No new bits? It is possible on ofo queue. */
4905 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4906 skb
= tcp_collapse_one(sk
, skb
, list
);
4912 /* The first skb to collapse is:
4914 * - bloated or contains data before "start" or
4915 * overlaps to the next one.
4917 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4918 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4919 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4920 end_of_skbs
= false;
4924 if (!skb_queue_is_last(list
, skb
)) {
4925 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4927 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4928 end_of_skbs
= false;
4933 /* Decided to skip this, advance start seq. */
4934 start
= TCP_SKB_CB(skb
)->end_seq
;
4936 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4939 while (before(start
, end
)) {
4940 struct sk_buff
*nskb
;
4941 unsigned int header
= skb_headroom(skb
);
4942 int copy
= SKB_MAX_ORDER(header
, 0);
4944 /* Too big header? This can happen with IPv6. */
4947 if (end
- start
< copy
)
4949 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4953 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4954 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4956 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4958 skb_reserve(nskb
, header
);
4959 memcpy(nskb
->head
, skb
->head
, header
);
4960 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4961 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4962 __skb_queue_before(list
, skb
, nskb
);
4963 skb_set_owner_r(nskb
, sk
);
4965 /* Copy data, releasing collapsed skbs. */
4967 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4968 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4972 size
= min(copy
, size
);
4973 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4975 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4979 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4980 skb
= tcp_collapse_one(sk
, skb
, list
);
4983 tcp_hdr(skb
)->syn
||
4991 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4992 * and tcp_collapse() them until all the queue is collapsed.
4994 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4996 struct tcp_sock
*tp
= tcp_sk(sk
);
4997 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4998 struct sk_buff
*head
;
5004 start
= TCP_SKB_CB(skb
)->seq
;
5005 end
= TCP_SKB_CB(skb
)->end_seq
;
5009 struct sk_buff
*next
= NULL
;
5011 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
5012 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
5015 /* Segment is terminated when we see gap or when
5016 * we are at the end of all the queue. */
5018 after(TCP_SKB_CB(skb
)->seq
, end
) ||
5019 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
5020 tcp_collapse(sk
, &tp
->out_of_order_queue
,
5021 head
, skb
, start
, end
);
5025 /* Start new segment */
5026 start
= TCP_SKB_CB(skb
)->seq
;
5027 end
= TCP_SKB_CB(skb
)->end_seq
;
5029 if (before(TCP_SKB_CB(skb
)->seq
, start
))
5030 start
= TCP_SKB_CB(skb
)->seq
;
5031 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
5032 end
= TCP_SKB_CB(skb
)->end_seq
;
5038 * Purge the out-of-order queue.
5039 * Return true if queue was pruned.
5041 static bool tcp_prune_ofo_queue(struct sock
*sk
)
5043 struct tcp_sock
*tp
= tcp_sk(sk
);
5046 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
5047 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
5048 __skb_queue_purge(&tp
->out_of_order_queue
);
5050 /* Reset SACK state. A conforming SACK implementation will
5051 * do the same at a timeout based retransmit. When a connection
5052 * is in a sad state like this, we care only about integrity
5053 * of the connection not performance.
5055 if (tp
->rx_opt
.sack_ok
)
5056 tcp_sack_reset(&tp
->rx_opt
);
5063 /* Reduce allocated memory if we can, trying to get
5064 * the socket within its memory limits again.
5066 * Return less than zero if we should start dropping frames
5067 * until the socket owning process reads some of the data
5068 * to stabilize the situation.
5070 static int tcp_prune_queue(struct sock
*sk
)
5072 struct tcp_sock
*tp
= tcp_sk(sk
);
5074 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
5076 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
5078 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
5079 tcp_clamp_window(sk
);
5080 else if (sk_under_memory_pressure(sk
))
5081 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
5083 tcp_collapse_ofo_queue(sk
);
5084 if (!skb_queue_empty(&sk
->sk_receive_queue
))
5085 tcp_collapse(sk
, &sk
->sk_receive_queue
,
5086 skb_peek(&sk
->sk_receive_queue
),
5088 tp
->copied_seq
, tp
->rcv_nxt
);
5091 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5094 /* Collapsing did not help, destructive actions follow.
5095 * This must not ever occur. */
5097 tcp_prune_ofo_queue(sk
);
5099 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5102 /* If we are really being abused, tell the caller to silently
5103 * drop receive data on the floor. It will get retransmitted
5104 * and hopefully then we'll have sufficient space.
5106 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
5108 /* Massive buffer overcommit. */
5113 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
5114 * As additional protections, we do not touch cwnd in retransmission phases,
5115 * and if application hit its sndbuf limit recently.
5117 void tcp_cwnd_application_limited(struct sock
*sk
)
5119 struct tcp_sock
*tp
= tcp_sk(sk
);
5121 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
5122 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
5123 /* Limited by application or receiver window. */
5124 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
5125 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
5126 if (win_used
< tp
->snd_cwnd
) {
5127 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
5128 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
5130 tp
->snd_cwnd_used
= 0;
5132 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
5135 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
5137 const struct tcp_sock
*tp
= tcp_sk(sk
);
5139 /* If the user specified a specific send buffer setting, do
5142 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
5145 /* If we are under global TCP memory pressure, do not expand. */
5146 if (sk_under_memory_pressure(sk
))
5149 /* If we are under soft global TCP memory pressure, do not expand. */
5150 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
5153 /* If we filled the congestion window, do not expand. */
5154 if (tp
->packets_out
>= tp
->snd_cwnd
)
5160 /* When incoming ACK allowed to free some skb from write_queue,
5161 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
5162 * on the exit from tcp input handler.
5164 * PROBLEM: sndbuf expansion does not work well with largesend.
5166 static void tcp_new_space(struct sock
*sk
)
5168 struct tcp_sock
*tp
= tcp_sk(sk
);
5170 if (tcp_should_expand_sndbuf(sk
)) {
5171 int sndmem
= SKB_TRUESIZE(max_t(u32
,
5172 tp
->rx_opt
.mss_clamp
,
5175 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
5176 tp
->reordering
+ 1);
5177 sndmem
*= 2 * demanded
;
5178 if (sndmem
> sk
->sk_sndbuf
)
5179 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
5180 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
5183 sk
->sk_write_space(sk
);
5186 static void tcp_check_space(struct sock
*sk
)
5188 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
5189 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
5190 if (sk
->sk_socket
&&
5191 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
5196 static inline void tcp_data_snd_check(struct sock
*sk
)
5198 tcp_push_pending_frames(sk
);
5199 tcp_check_space(sk
);
5203 * Check if sending an ack is needed.
5205 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5207 struct tcp_sock
*tp
= tcp_sk(sk
);
5209 /* More than one full frame received... */
5210 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5211 /* ... and right edge of window advances far enough.
5212 * (tcp_recvmsg() will send ACK otherwise). Or...
5214 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
5215 /* We ACK each frame or... */
5216 tcp_in_quickack_mode(sk
) ||
5217 /* We have out of order data. */
5218 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
5219 /* Then ack it now */
5222 /* Else, send delayed ack. */
5223 tcp_send_delayed_ack(sk
);
5227 static inline void tcp_ack_snd_check(struct sock
*sk
)
5229 if (!inet_csk_ack_scheduled(sk
)) {
5230 /* We sent a data segment already. */
5233 __tcp_ack_snd_check(sk
, 1);
5237 * This routine is only called when we have urgent data
5238 * signaled. Its the 'slow' part of tcp_urg. It could be
5239 * moved inline now as tcp_urg is only called from one
5240 * place. We handle URGent data wrong. We have to - as
5241 * BSD still doesn't use the correction from RFC961.
5242 * For 1003.1g we should support a new option TCP_STDURG to permit
5243 * either form (or just set the sysctl tcp_stdurg).
5246 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5248 struct tcp_sock
*tp
= tcp_sk(sk
);
5249 u32 ptr
= ntohs(th
->urg_ptr
);
5251 if (ptr
&& !sysctl_tcp_stdurg
)
5253 ptr
+= ntohl(th
->seq
);
5255 /* Ignore urgent data that we've already seen and read. */
5256 if (after(tp
->copied_seq
, ptr
))
5259 /* Do not replay urg ptr.
5261 * NOTE: interesting situation not covered by specs.
5262 * Misbehaving sender may send urg ptr, pointing to segment,
5263 * which we already have in ofo queue. We are not able to fetch
5264 * such data and will stay in TCP_URG_NOTYET until will be eaten
5265 * by recvmsg(). Seems, we are not obliged to handle such wicked
5266 * situations. But it is worth to think about possibility of some
5267 * DoSes using some hypothetical application level deadlock.
5269 if (before(ptr
, tp
->rcv_nxt
))
5272 /* Do we already have a newer (or duplicate) urgent pointer? */
5273 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5276 /* Tell the world about our new urgent pointer. */
5279 /* We may be adding urgent data when the last byte read was
5280 * urgent. To do this requires some care. We cannot just ignore
5281 * tp->copied_seq since we would read the last urgent byte again
5282 * as data, nor can we alter copied_seq until this data arrives
5283 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5285 * NOTE. Double Dutch. Rendering to plain English: author of comment
5286 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5287 * and expect that both A and B disappear from stream. This is _wrong_.
5288 * Though this happens in BSD with high probability, this is occasional.
5289 * Any application relying on this is buggy. Note also, that fix "works"
5290 * only in this artificial test. Insert some normal data between A and B and we will
5291 * decline of BSD again. Verdict: it is better to remove to trap
5294 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5295 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5296 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5298 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5299 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5304 tp
->urg_data
= TCP_URG_NOTYET
;
5307 /* Disable header prediction. */
5311 /* This is the 'fast' part of urgent handling. */
5312 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5314 struct tcp_sock
*tp
= tcp_sk(sk
);
5316 /* Check if we get a new urgent pointer - normally not. */
5318 tcp_check_urg(sk
, th
);
5320 /* Do we wait for any urgent data? - normally not... */
5321 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5322 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5325 /* Is the urgent pointer pointing into this packet? */
5326 if (ptr
< skb
->len
) {
5328 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5330 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5331 if (!sock_flag(sk
, SOCK_DEAD
))
5332 sk
->sk_data_ready(sk
, 0);
5337 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5339 struct tcp_sock
*tp
= tcp_sk(sk
);
5340 int chunk
= skb
->len
- hlen
;
5344 if (skb_csum_unnecessary(skb
))
5345 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
5347 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
5351 tp
->ucopy
.len
-= chunk
;
5352 tp
->copied_seq
+= chunk
;
5353 tcp_rcv_space_adjust(sk
);
5360 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5361 struct sk_buff
*skb
)
5365 if (sock_owned_by_user(sk
)) {
5367 result
= __tcp_checksum_complete(skb
);
5370 result
= __tcp_checksum_complete(skb
);
5375 static inline int tcp_checksum_complete_user(struct sock
*sk
,
5376 struct sk_buff
*skb
)
5378 return !skb_csum_unnecessary(skb
) &&
5379 __tcp_checksum_complete_user(sk
, skb
);
5382 #ifdef CONFIG_NET_DMA
5383 static bool tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
5386 struct tcp_sock
*tp
= tcp_sk(sk
);
5387 int chunk
= skb
->len
- hlen
;
5389 bool copied_early
= false;
5391 if (tp
->ucopy
.wakeup
)
5394 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
5395 tp
->ucopy
.dma_chan
= net_dma_find_channel();
5397 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
5399 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
5401 tp
->ucopy
.iov
, chunk
,
5402 tp
->ucopy
.pinned_list
);
5407 tp
->ucopy
.dma_cookie
= dma_cookie
;
5408 copied_early
= true;
5410 tp
->ucopy
.len
-= chunk
;
5411 tp
->copied_seq
+= chunk
;
5412 tcp_rcv_space_adjust(sk
);
5414 if ((tp
->ucopy
.len
== 0) ||
5415 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5416 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5417 tp
->ucopy
.wakeup
= 1;
5418 sk
->sk_data_ready(sk
, 0);
5420 } else if (chunk
> 0) {
5421 tp
->ucopy
.wakeup
= 1;
5422 sk
->sk_data_ready(sk
, 0);
5425 return copied_early
;
5427 #endif /* CONFIG_NET_DMA */
5429 /* Does PAWS and seqno based validation of an incoming segment, flags will
5430 * play significant role here.
5432 static int tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5433 const struct tcphdr
*th
, int syn_inerr
)
5435 const u8
*hash_location
;
5436 struct tcp_sock
*tp
= tcp_sk(sk
);
5438 /* RFC1323: H1. Apply PAWS check first. */
5439 if (tcp_fast_parse_options(skb
, th
, tp
, &hash_location
) &&
5440 tp
->rx_opt
.saw_tstamp
&&
5441 tcp_paws_discard(sk
, skb
)) {
5443 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5444 tcp_send_dupack(sk
, skb
);
5447 /* Reset is accepted even if it did not pass PAWS. */
5450 /* Step 1: check sequence number */
5451 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5452 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5453 * (RST) segments are validated by checking their SEQ-fields."
5454 * And page 69: "If an incoming segment is not acceptable,
5455 * an acknowledgment should be sent in reply (unless the RST
5456 * bit is set, if so drop the segment and return)".
5459 tcp_send_dupack(sk
, skb
);
5463 /* Step 2: check RST bit */
5469 /* ts_recent update must be made after we are sure that the packet
5472 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5474 /* step 3: check security and precedence [ignored] */
5476 /* step 4: Check for a SYN in window. */
5477 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5479 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5480 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5493 * TCP receive function for the ESTABLISHED state.
5495 * It is split into a fast path and a slow path. The fast path is
5497 * - A zero window was announced from us - zero window probing
5498 * is only handled properly in the slow path.
5499 * - Out of order segments arrived.
5500 * - Urgent data is expected.
5501 * - There is no buffer space left
5502 * - Unexpected TCP flags/window values/header lengths are received
5503 * (detected by checking the TCP header against pred_flags)
5504 * - Data is sent in both directions. Fast path only supports pure senders
5505 * or pure receivers (this means either the sequence number or the ack
5506 * value must stay constant)
5507 * - Unexpected TCP option.
5509 * When these conditions are not satisfied it drops into a standard
5510 * receive procedure patterned after RFC793 to handle all cases.
5511 * The first three cases are guaranteed by proper pred_flags setting,
5512 * the rest is checked inline. Fast processing is turned on in
5513 * tcp_data_queue when everything is OK.
5515 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5516 const struct tcphdr
*th
, unsigned int len
)
5518 struct tcp_sock
*tp
= tcp_sk(sk
);
5522 * Header prediction.
5523 * The code loosely follows the one in the famous
5524 * "30 instruction TCP receive" Van Jacobson mail.
5526 * Van's trick is to deposit buffers into socket queue
5527 * on a device interrupt, to call tcp_recv function
5528 * on the receive process context and checksum and copy
5529 * the buffer to user space. smart...
5531 * Our current scheme is not silly either but we take the
5532 * extra cost of the net_bh soft interrupt processing...
5533 * We do checksum and copy also but from device to kernel.
5536 tp
->rx_opt
.saw_tstamp
= 0;
5538 /* pred_flags is 0xS?10 << 16 + snd_wnd
5539 * if header_prediction is to be made
5540 * 'S' will always be tp->tcp_header_len >> 2
5541 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5542 * turn it off (when there are holes in the receive
5543 * space for instance)
5544 * PSH flag is ignored.
5547 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5548 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5549 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5550 int tcp_header_len
= tp
->tcp_header_len
;
5552 /* Timestamp header prediction: tcp_header_len
5553 * is automatically equal to th->doff*4 due to pred_flags
5557 /* Check timestamp */
5558 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5559 /* No? Slow path! */
5560 if (!tcp_parse_aligned_timestamp(tp
, th
))
5563 /* If PAWS failed, check it more carefully in slow path */
5564 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5567 /* DO NOT update ts_recent here, if checksum fails
5568 * and timestamp was corrupted part, it will result
5569 * in a hung connection since we will drop all
5570 * future packets due to the PAWS test.
5574 if (len
<= tcp_header_len
) {
5575 /* Bulk data transfer: sender */
5576 if (len
== tcp_header_len
) {
5577 /* Predicted packet is in window by definition.
5578 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5579 * Hence, check seq<=rcv_wup reduces to:
5581 if (tcp_header_len
==
5582 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5583 tp
->rcv_nxt
== tp
->rcv_wup
)
5584 tcp_store_ts_recent(tp
);
5586 /* We know that such packets are checksummed
5589 tcp_ack(sk
, skb
, 0);
5591 tcp_data_snd_check(sk
);
5593 } else { /* Header too small */
5594 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5599 int copied_early
= 0;
5600 bool fragstolen
= false;
5602 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5603 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5604 #ifdef CONFIG_NET_DMA
5605 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5610 if (tp
->ucopy
.task
== current
&&
5611 sock_owned_by_user(sk
) && !copied_early
) {
5612 __set_current_state(TASK_RUNNING
);
5614 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5618 /* Predicted packet is in window by definition.
5619 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5620 * Hence, check seq<=rcv_wup reduces to:
5622 if (tcp_header_len
==
5623 (sizeof(struct tcphdr
) +
5624 TCPOLEN_TSTAMP_ALIGNED
) &&
5625 tp
->rcv_nxt
== tp
->rcv_wup
)
5626 tcp_store_ts_recent(tp
);
5628 tcp_rcv_rtt_measure_ts(sk
, skb
);
5630 __skb_pull(skb
, tcp_header_len
);
5631 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5632 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5635 tcp_cleanup_rbuf(sk
, skb
->len
);
5638 if (tcp_checksum_complete_user(sk
, skb
))
5641 /* Predicted packet is in window by definition.
5642 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5643 * Hence, check seq<=rcv_wup reduces to:
5645 if (tcp_header_len
==
5646 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5647 tp
->rcv_nxt
== tp
->rcv_wup
)
5648 tcp_store_ts_recent(tp
);
5650 tcp_rcv_rtt_measure_ts(sk
, skb
);
5652 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5655 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5657 /* Bulk data transfer: receiver */
5658 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5662 tcp_event_data_recv(sk
, skb
);
5664 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5665 /* Well, only one small jumplet in fast path... */
5666 tcp_ack(sk
, skb
, FLAG_DATA
);
5667 tcp_data_snd_check(sk
);
5668 if (!inet_csk_ack_scheduled(sk
))
5672 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5673 __tcp_ack_snd_check(sk
, 0);
5675 #ifdef CONFIG_NET_DMA
5677 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5681 kfree_skb_partial(skb
, fragstolen
);
5683 sk
->sk_data_ready(sk
, 0);
5689 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5693 * Standard slow path.
5696 res
= tcp_validate_incoming(sk
, skb
, th
, 1);
5701 if (th
->ack
&& tcp_ack(sk
, skb
, FLAG_SLOWPATH
) < 0)
5704 tcp_rcv_rtt_measure_ts(sk
, skb
);
5706 /* Process urgent data. */
5707 tcp_urg(sk
, skb
, th
);
5709 /* step 7: process the segment text */
5710 tcp_data_queue(sk
, skb
);
5712 tcp_data_snd_check(sk
);
5713 tcp_ack_snd_check(sk
);
5717 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5723 EXPORT_SYMBOL(tcp_rcv_established
);
5725 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5727 struct tcp_sock
*tp
= tcp_sk(sk
);
5728 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5730 tcp_set_state(sk
, TCP_ESTABLISHED
);
5733 security_inet_conn_established(sk
, skb
);
5735 /* Make sure socket is routed, for correct metrics. */
5736 icsk
->icsk_af_ops
->rebuild_header(sk
);
5738 tcp_init_metrics(sk
);
5740 tcp_init_congestion_control(sk
);
5742 /* Prevent spurious tcp_cwnd_restart() on first data
5745 tp
->lsndtime
= tcp_time_stamp
;
5747 tcp_init_buffer_space(sk
);
5749 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5750 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5752 if (!tp
->rx_opt
.snd_wscale
)
5753 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5757 if (!sock_flag(sk
, SOCK_DEAD
)) {
5758 sk
->sk_state_change(sk
);
5759 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5763 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5764 const struct tcphdr
*th
, unsigned int len
)
5766 const u8
*hash_location
;
5767 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5768 struct tcp_sock
*tp
= tcp_sk(sk
);
5769 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
5770 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5772 tcp_parse_options(skb
, &tp
->rx_opt
, &hash_location
, 0);
5776 * "If the state is SYN-SENT then
5777 * first check the ACK bit
5778 * If the ACK bit is set
5779 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5780 * a reset (unless the RST bit is set, if so drop
5781 * the segment and return)"
5783 * We do not send data with SYN, so that RFC-correct
5786 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
5787 goto reset_and_undo
;
5789 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5790 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5792 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5793 goto reset_and_undo
;
5796 /* Now ACK is acceptable.
5798 * "If the RST bit is set
5799 * If the ACK was acceptable then signal the user "error:
5800 * connection reset", drop the segment, enter CLOSED state,
5801 * delete TCB, and return."
5810 * "fifth, if neither of the SYN or RST bits is set then
5811 * drop the segment and return."
5817 goto discard_and_undo
;
5820 * "If the SYN bit is on ...
5821 * are acceptable then ...
5822 * (our SYN has been ACKed), change the connection
5823 * state to ESTABLISHED..."
5826 TCP_ECN_rcv_synack(tp
, th
);
5828 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5829 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5831 /* Ok.. it's good. Set up sequence numbers and
5832 * move to established.
5834 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5835 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5837 /* RFC1323: The window in SYN & SYN/ACK segments is
5840 tp
->snd_wnd
= ntohs(th
->window
);
5841 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5843 if (!tp
->rx_opt
.wscale_ok
) {
5844 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5845 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5848 if (tp
->rx_opt
.saw_tstamp
) {
5849 tp
->rx_opt
.tstamp_ok
= 1;
5850 tp
->tcp_header_len
=
5851 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5852 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5853 tcp_store_ts_recent(tp
);
5855 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5858 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5859 tcp_enable_fack(tp
);
5862 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5863 tcp_initialize_rcv_mss(sk
);
5865 /* Remember, tcp_poll() does not lock socket!
5866 * Change state from SYN-SENT only after copied_seq
5867 * is initialized. */
5868 tp
->copied_seq
= tp
->rcv_nxt
;
5871 cvp
->cookie_pair_size
> 0 &&
5872 tp
->rx_opt
.cookie_plus
> 0) {
5873 int cookie_size
= tp
->rx_opt
.cookie_plus
5874 - TCPOLEN_COOKIE_BASE
;
5875 int cookie_pair_size
= cookie_size
5876 + cvp
->cookie_desired
;
5878 /* A cookie extension option was sent and returned.
5879 * Note that each incoming SYNACK replaces the
5880 * Responder cookie. The initial exchange is most
5881 * fragile, as protection against spoofing relies
5882 * entirely upon the sequence and timestamp (above).
5883 * This replacement strategy allows the correct pair to
5884 * pass through, while any others will be filtered via
5885 * Responder verification later.
5887 if (sizeof(cvp
->cookie_pair
) >= cookie_pair_size
) {
5888 memcpy(&cvp
->cookie_pair
[cvp
->cookie_desired
],
5889 hash_location
, cookie_size
);
5890 cvp
->cookie_pair_size
= cookie_pair_size
;
5896 tcp_finish_connect(sk
, skb
);
5898 if (sk
->sk_write_pending
||
5899 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5900 icsk
->icsk_ack
.pingpong
) {
5901 /* Save one ACK. Data will be ready after
5902 * several ticks, if write_pending is set.
5904 * It may be deleted, but with this feature tcpdumps
5905 * look so _wonderfully_ clever, that I was not able
5906 * to stand against the temptation 8) --ANK
5908 inet_csk_schedule_ack(sk
);
5909 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5910 tcp_enter_quickack_mode(sk
);
5911 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5912 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5923 /* No ACK in the segment */
5927 * "If the RST bit is set
5929 * Otherwise (no ACK) drop the segment and return."
5932 goto discard_and_undo
;
5936 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5937 tcp_paws_reject(&tp
->rx_opt
, 0))
5938 goto discard_and_undo
;
5941 /* We see SYN without ACK. It is attempt of
5942 * simultaneous connect with crossed SYNs.
5943 * Particularly, it can be connect to self.
5945 tcp_set_state(sk
, TCP_SYN_RECV
);
5947 if (tp
->rx_opt
.saw_tstamp
) {
5948 tp
->rx_opt
.tstamp_ok
= 1;
5949 tcp_store_ts_recent(tp
);
5950 tp
->tcp_header_len
=
5951 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5953 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5956 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5957 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5959 /* RFC1323: The window in SYN & SYN/ACK segments is
5962 tp
->snd_wnd
= ntohs(th
->window
);
5963 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5964 tp
->max_window
= tp
->snd_wnd
;
5966 TCP_ECN_rcv_syn(tp
, th
);
5969 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5970 tcp_initialize_rcv_mss(sk
);
5972 tcp_send_synack(sk
);
5974 /* Note, we could accept data and URG from this segment.
5975 * There are no obstacles to make this.
5977 * However, if we ignore data in ACKless segments sometimes,
5978 * we have no reasons to accept it sometimes.
5979 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5980 * is not flawless. So, discard packet for sanity.
5981 * Uncomment this return to process the data.
5988 /* "fifth, if neither of the SYN or RST bits is set then
5989 * drop the segment and return."
5993 tcp_clear_options(&tp
->rx_opt
);
5994 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5998 tcp_clear_options(&tp
->rx_opt
);
5999 tp
->rx_opt
.mss_clamp
= saved_clamp
;
6004 * This function implements the receiving procedure of RFC 793 for
6005 * all states except ESTABLISHED and TIME_WAIT.
6006 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
6007 * address independent.
6010 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
6011 const struct tcphdr
*th
, unsigned int len
)
6013 struct tcp_sock
*tp
= tcp_sk(sk
);
6014 struct inet_connection_sock
*icsk
= inet_csk(sk
);
6018 tp
->rx_opt
.saw_tstamp
= 0;
6020 switch (sk
->sk_state
) {
6034 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
6037 /* Now we have several options: In theory there is
6038 * nothing else in the frame. KA9Q has an option to
6039 * send data with the syn, BSD accepts data with the
6040 * syn up to the [to be] advertised window and
6041 * Solaris 2.1 gives you a protocol error. For now
6042 * we just ignore it, that fits the spec precisely
6043 * and avoids incompatibilities. It would be nice in
6044 * future to drop through and process the data.
6046 * Now that TTCP is starting to be used we ought to
6048 * But, this leaves one open to an easy denial of
6049 * service attack, and SYN cookies can't defend
6050 * against this problem. So, we drop the data
6051 * in the interest of security over speed unless
6052 * it's still in use.
6060 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
6064 /* Do step6 onward by hand. */
6065 tcp_urg(sk
, skb
, th
);
6067 tcp_data_snd_check(sk
);
6071 res
= tcp_validate_incoming(sk
, skb
, th
, 0);
6075 /* step 5: check the ACK field */
6077 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
) > 0;
6079 switch (sk
->sk_state
) {
6082 tp
->copied_seq
= tp
->rcv_nxt
;
6084 tcp_set_state(sk
, TCP_ESTABLISHED
);
6085 sk
->sk_state_change(sk
);
6087 /* Note, that this wakeup is only for marginal
6088 * crossed SYN case. Passively open sockets
6089 * are not waked up, because sk->sk_sleep ==
6090 * NULL and sk->sk_socket == NULL.
6094 SOCK_WAKE_IO
, POLL_OUT
);
6096 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
6097 tp
->snd_wnd
= ntohs(th
->window
) <<
6098 tp
->rx_opt
.snd_wscale
;
6099 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
6101 if (tp
->rx_opt
.tstamp_ok
)
6102 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
6104 /* Make sure socket is routed, for
6107 icsk
->icsk_af_ops
->rebuild_header(sk
);
6109 tcp_init_metrics(sk
);
6111 tcp_init_congestion_control(sk
);
6113 /* Prevent spurious tcp_cwnd_restart() on
6114 * first data packet.
6116 tp
->lsndtime
= tcp_time_stamp
;
6119 tcp_initialize_rcv_mss(sk
);
6120 tcp_init_buffer_space(sk
);
6121 tcp_fast_path_on(tp
);
6128 if (tp
->snd_una
== tp
->write_seq
) {
6129 tcp_set_state(sk
, TCP_FIN_WAIT2
);
6130 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
6131 dst_confirm(__sk_dst_get(sk
));
6133 if (!sock_flag(sk
, SOCK_DEAD
))
6134 /* Wake up lingering close() */
6135 sk
->sk_state_change(sk
);
6139 if (tp
->linger2
< 0 ||
6140 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6141 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
6143 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6147 tmo
= tcp_fin_time(sk
);
6148 if (tmo
> TCP_TIMEWAIT_LEN
) {
6149 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
6150 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
6151 /* Bad case. We could lose such FIN otherwise.
6152 * It is not a big problem, but it looks confusing
6153 * and not so rare event. We still can lose it now,
6154 * if it spins in bh_lock_sock(), but it is really
6157 inet_csk_reset_keepalive_timer(sk
, tmo
);
6159 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
6167 if (tp
->snd_una
== tp
->write_seq
) {
6168 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
6174 if (tp
->snd_una
== tp
->write_seq
) {
6175 tcp_update_metrics(sk
);
6184 /* step 6: check the URG bit */
6185 tcp_urg(sk
, skb
, th
);
6187 /* step 7: process the segment text */
6188 switch (sk
->sk_state
) {
6189 case TCP_CLOSE_WAIT
:
6192 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
6196 /* RFC 793 says to queue data in these states,
6197 * RFC 1122 says we MUST send a reset.
6198 * BSD 4.4 also does reset.
6200 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
6201 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6202 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6203 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6209 case TCP_ESTABLISHED
:
6210 tcp_data_queue(sk
, skb
);
6215 /* tcp_data could move socket to TIME-WAIT */
6216 if (sk
->sk_state
!= TCP_CLOSE
) {
6217 tcp_data_snd_check(sk
);
6218 tcp_ack_snd_check(sk
);
6227 EXPORT_SYMBOL(tcp_rcv_state_process
);