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>
71 #include <linux/prefetch.h>
74 #include <net/inet_common.h>
75 #include <linux/ipsec.h>
76 #include <asm/unaligned.h>
77 #include <linux/errqueue.h>
79 int sysctl_tcp_timestamps __read_mostly
= 1;
80 int sysctl_tcp_window_scaling __read_mostly
= 1;
81 int sysctl_tcp_sack __read_mostly
= 1;
82 int sysctl_tcp_fack __read_mostly
= 1;
83 int sysctl_tcp_max_reordering __read_mostly
= 300;
84 int sysctl_tcp_dsack __read_mostly
= 1;
85 int sysctl_tcp_app_win __read_mostly
= 31;
86 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
87 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
88 EXPORT_SYMBOL(sysctl_tcp_timestamps
);
90 /* rfc5961 challenge ack rate limiting */
91 int sysctl_tcp_challenge_ack_limit
= 1000;
93 int sysctl_tcp_stdurg __read_mostly
;
94 int sysctl_tcp_rfc1337 __read_mostly
;
95 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
96 int sysctl_tcp_frto __read_mostly
= 2;
97 int sysctl_tcp_min_rtt_wlen __read_mostly
= 300;
99 int sysctl_tcp_thin_dupack __read_mostly
;
101 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
102 int sysctl_tcp_early_retrans __read_mostly
= 3;
103 int sysctl_tcp_invalid_ratelimit __read_mostly
= HZ
/2;
105 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
106 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
107 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
108 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
109 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
110 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
111 #define FLAG_ECE 0x40 /* ECE in this ACK */
112 #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
113 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
114 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
115 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
116 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
117 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
118 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
120 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
121 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
122 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
123 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
125 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
126 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
128 #define REXMIT_NONE 0 /* no loss recovery to do */
129 #define REXMIT_LOST 1 /* retransmit packets marked lost */
130 #define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
132 /* Adapt the MSS value used to make delayed ack decision to the
135 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
137 struct inet_connection_sock
*icsk
= inet_csk(sk
);
138 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
141 icsk
->icsk_ack
.last_seg_size
= 0;
143 /* skb->len may jitter because of SACKs, even if peer
144 * sends good full-sized frames.
146 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
147 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
148 icsk
->icsk_ack
.rcv_mss
= len
;
150 /* Otherwise, we make more careful check taking into account,
151 * that SACKs block is variable.
153 * "len" is invariant segment length, including TCP header.
155 len
+= skb
->data
- skb_transport_header(skb
);
156 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
157 /* If PSH is not set, packet should be
158 * full sized, provided peer TCP is not badly broken.
159 * This observation (if it is correct 8)) allows
160 * to handle super-low mtu links fairly.
162 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
163 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
164 /* Subtract also invariant (if peer is RFC compliant),
165 * tcp header plus fixed timestamp option length.
166 * Resulting "len" is MSS free of SACK jitter.
168 len
-= tcp_sk(sk
)->tcp_header_len
;
169 icsk
->icsk_ack
.last_seg_size
= len
;
171 icsk
->icsk_ack
.rcv_mss
= len
;
175 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
176 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
177 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
181 static void tcp_incr_quickack(struct sock
*sk
)
183 struct inet_connection_sock
*icsk
= inet_csk(sk
);
184 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
188 if (quickacks
> icsk
->icsk_ack
.quick
)
189 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
192 static void tcp_enter_quickack_mode(struct sock
*sk
)
194 struct inet_connection_sock
*icsk
= inet_csk(sk
);
195 tcp_incr_quickack(sk
);
196 icsk
->icsk_ack
.pingpong
= 0;
197 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
200 /* Send ACKs quickly, if "quick" count is not exhausted
201 * and the session is not interactive.
204 static bool tcp_in_quickack_mode(struct sock
*sk
)
206 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
207 const struct dst_entry
*dst
= __sk_dst_get(sk
);
209 return (dst
&& dst_metric(dst
, RTAX_QUICKACK
)) ||
210 (icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
);
213 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
215 if (tp
->ecn_flags
& TCP_ECN_OK
)
216 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
219 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
221 if (tcp_hdr(skb
)->cwr
)
222 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
225 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
227 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
230 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
232 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
233 case INET_ECN_NOT_ECT
:
234 /* Funny extension: if ECT is not set on a segment,
235 * and we already seen ECT on a previous segment,
236 * it is probably a retransmit.
238 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
239 tcp_enter_quickack_mode((struct sock
*)tp
);
242 if (tcp_ca_needs_ecn((struct sock
*)tp
))
243 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
245 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
246 /* Better not delay acks, sender can have a very low cwnd */
247 tcp_enter_quickack_mode((struct sock
*)tp
);
248 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
250 tp
->ecn_flags
|= TCP_ECN_SEEN
;
253 if (tcp_ca_needs_ecn((struct sock
*)tp
))
254 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
255 tp
->ecn_flags
|= TCP_ECN_SEEN
;
260 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
262 if (tp
->ecn_flags
& TCP_ECN_OK
)
263 __tcp_ecn_check_ce(tp
, skb
);
266 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
268 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
269 tp
->ecn_flags
&= ~TCP_ECN_OK
;
272 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
274 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
275 tp
->ecn_flags
&= ~TCP_ECN_OK
;
278 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
280 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
285 /* Buffer size and advertised window tuning.
287 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
290 static void tcp_sndbuf_expand(struct sock
*sk
)
292 const struct tcp_sock
*tp
= tcp_sk(sk
);
293 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
297 /* Worst case is non GSO/TSO : each frame consumes one skb
298 * and skb->head is kmalloced using power of two area of memory
300 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
302 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
304 per_mss
= roundup_pow_of_two(per_mss
) +
305 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
307 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
308 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
310 /* Fast Recovery (RFC 5681 3.2) :
311 * Cubic needs 1.7 factor, rounded to 2 to include
312 * extra cushion (application might react slowly to POLLOUT)
314 sndmem
= ca_ops
->sndbuf_expand
? ca_ops
->sndbuf_expand(sk
) : 2;
315 sndmem
*= nr_segs
* per_mss
;
317 if (sk
->sk_sndbuf
< sndmem
)
318 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
321 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
323 * All tcp_full_space() is split to two parts: "network" buffer, allocated
324 * forward and advertised in receiver window (tp->rcv_wnd) and
325 * "application buffer", required to isolate scheduling/application
326 * latencies from network.
327 * window_clamp is maximal advertised window. It can be less than
328 * tcp_full_space(), in this case tcp_full_space() - window_clamp
329 * is reserved for "application" buffer. The less window_clamp is
330 * the smoother our behaviour from viewpoint of network, but the lower
331 * throughput and the higher sensitivity of the connection to losses. 8)
333 * rcv_ssthresh is more strict window_clamp used at "slow start"
334 * phase to predict further behaviour of this connection.
335 * It is used for two goals:
336 * - to enforce header prediction at sender, even when application
337 * requires some significant "application buffer". It is check #1.
338 * - to prevent pruning of receive queue because of misprediction
339 * of receiver window. Check #2.
341 * The scheme does not work when sender sends good segments opening
342 * window and then starts to feed us spaghetti. But it should work
343 * in common situations. Otherwise, we have to rely on queue collapsing.
346 /* Slow part of check#2. */
347 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
349 struct tcp_sock
*tp
= tcp_sk(sk
);
351 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
352 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
354 while (tp
->rcv_ssthresh
<= window
) {
355 if (truesize
<= skb
->len
)
356 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
364 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
366 struct tcp_sock
*tp
= tcp_sk(sk
);
369 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
370 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
371 !tcp_under_memory_pressure(sk
)) {
374 /* Check #2. Increase window, if skb with such overhead
375 * will fit to rcvbuf in future.
377 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
378 incr
= 2 * tp
->advmss
;
380 incr
= __tcp_grow_window(sk
, skb
);
383 incr
= max_t(int, incr
, 2 * skb
->len
);
384 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
386 inet_csk(sk
)->icsk_ack
.quick
|= 1;
391 /* 3. Tuning rcvbuf, when connection enters established state. */
392 static void tcp_fixup_rcvbuf(struct sock
*sk
)
394 u32 mss
= tcp_sk(sk
)->advmss
;
397 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
398 tcp_default_init_rwnd(mss
);
400 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
401 * Allow enough cushion so that sender is not limited by our window
403 if (sysctl_tcp_moderate_rcvbuf
)
406 if (sk
->sk_rcvbuf
< rcvmem
)
407 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
410 /* 4. Try to fixup all. It is made immediately after connection enters
413 void tcp_init_buffer_space(struct sock
*sk
)
415 struct tcp_sock
*tp
= tcp_sk(sk
);
418 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
419 tcp_fixup_rcvbuf(sk
);
420 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
421 tcp_sndbuf_expand(sk
);
423 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
424 tp
->rcvq_space
.time
= tcp_time_stamp
;
425 tp
->rcvq_space
.seq
= tp
->copied_seq
;
427 maxwin
= tcp_full_space(sk
);
429 if (tp
->window_clamp
>= maxwin
) {
430 tp
->window_clamp
= maxwin
;
432 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
433 tp
->window_clamp
= max(maxwin
-
434 (maxwin
>> sysctl_tcp_app_win
),
438 /* Force reservation of one segment. */
439 if (sysctl_tcp_app_win
&&
440 tp
->window_clamp
> 2 * tp
->advmss
&&
441 tp
->window_clamp
+ tp
->advmss
> maxwin
)
442 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
444 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
445 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
448 /* 5. Recalculate window clamp after socket hit its memory bounds. */
449 static void tcp_clamp_window(struct sock
*sk
)
451 struct tcp_sock
*tp
= tcp_sk(sk
);
452 struct inet_connection_sock
*icsk
= inet_csk(sk
);
454 icsk
->icsk_ack
.quick
= 0;
456 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
457 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
458 !tcp_under_memory_pressure(sk
) &&
459 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
460 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
463 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
464 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
467 /* Initialize RCV_MSS value.
468 * RCV_MSS is an our guess about MSS used by the peer.
469 * We haven't any direct information about the MSS.
470 * It's better to underestimate the RCV_MSS rather than overestimate.
471 * Overestimations make us ACKing less frequently than needed.
472 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
474 void tcp_initialize_rcv_mss(struct sock
*sk
)
476 const struct tcp_sock
*tp
= tcp_sk(sk
);
477 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
479 hint
= min(hint
, tp
->rcv_wnd
/ 2);
480 hint
= min(hint
, TCP_MSS_DEFAULT
);
481 hint
= max(hint
, TCP_MIN_MSS
);
483 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
485 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
487 /* Receiver "autotuning" code.
489 * The algorithm for RTT estimation w/o timestamps is based on
490 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
491 * <http://public.lanl.gov/radiant/pubs.html#DRS>
493 * More detail on this code can be found at
494 * <http://staff.psc.edu/jheffner/>,
495 * though this reference is out of date. A new paper
498 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
500 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
506 if (new_sample
!= 0) {
507 /* If we sample in larger samples in the non-timestamp
508 * case, we could grossly overestimate the RTT especially
509 * with chatty applications or bulk transfer apps which
510 * are stalled on filesystem I/O.
512 * Also, since we are only going for a minimum in the
513 * non-timestamp case, we do not smooth things out
514 * else with timestamps disabled convergence takes too
518 m
-= (new_sample
>> 3);
526 /* No previous measure. */
530 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
531 tp
->rcv_rtt_est
.rtt
= new_sample
;
534 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
536 if (tp
->rcv_rtt_est
.time
== 0)
538 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
540 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
543 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
544 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
547 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
548 const struct sk_buff
*skb
)
550 struct tcp_sock
*tp
= tcp_sk(sk
);
551 if (tp
->rx_opt
.rcv_tsecr
&&
552 (TCP_SKB_CB(skb
)->end_seq
-
553 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
554 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
558 * This function should be called every time data is copied to user space.
559 * It calculates the appropriate TCP receive buffer space.
561 void tcp_rcv_space_adjust(struct sock
*sk
)
563 struct tcp_sock
*tp
= tcp_sk(sk
);
567 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
568 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
571 /* Number of bytes copied to user in last RTT */
572 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
573 if (copied
<= tp
->rcvq_space
.space
)
577 * copied = bytes received in previous RTT, our base window
578 * To cope with packet losses, we need a 2x factor
579 * To cope with slow start, and sender growing its cwin by 100 %
580 * every RTT, we need a 4x factor, because the ACK we are sending
581 * now is for the next RTT, not the current one :
582 * <prev RTT . ><current RTT .. ><next RTT .... >
585 if (sysctl_tcp_moderate_rcvbuf
&&
586 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
587 int rcvwin
, rcvmem
, rcvbuf
;
589 /* minimal window to cope with packet losses, assuming
590 * steady state. Add some cushion because of small variations.
592 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
594 /* If rate increased by 25%,
595 * assume slow start, rcvwin = 3 * copied
596 * If rate increased by 50%,
597 * assume sender can use 2x growth, rcvwin = 4 * copied
600 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
602 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
605 rcvwin
+= (rcvwin
>> 1);
608 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
609 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
612 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
613 if (rcvbuf
> sk
->sk_rcvbuf
) {
614 sk
->sk_rcvbuf
= rcvbuf
;
616 /* Make the window clamp follow along. */
617 tp
->window_clamp
= rcvwin
;
620 tp
->rcvq_space
.space
= copied
;
623 tp
->rcvq_space
.seq
= tp
->copied_seq
;
624 tp
->rcvq_space
.time
= tcp_time_stamp
;
627 /* There is something which you must keep in mind when you analyze the
628 * behavior of the tp->ato delayed ack timeout interval. When a
629 * connection starts up, we want to ack as quickly as possible. The
630 * problem is that "good" TCP's do slow start at the beginning of data
631 * transmission. The means that until we send the first few ACK's the
632 * sender will sit on his end and only queue most of his data, because
633 * he can only send snd_cwnd unacked packets at any given time. For
634 * each ACK we send, he increments snd_cwnd and transmits more of his
637 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
639 struct tcp_sock
*tp
= tcp_sk(sk
);
640 struct inet_connection_sock
*icsk
= inet_csk(sk
);
643 inet_csk_schedule_ack(sk
);
645 tcp_measure_rcv_mss(sk
, skb
);
647 tcp_rcv_rtt_measure(tp
);
649 now
= tcp_time_stamp
;
651 if (!icsk
->icsk_ack
.ato
) {
652 /* The _first_ data packet received, initialize
653 * delayed ACK engine.
655 tcp_incr_quickack(sk
);
656 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
658 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
660 if (m
<= TCP_ATO_MIN
/ 2) {
661 /* The fastest case is the first. */
662 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
663 } else if (m
< icsk
->icsk_ack
.ato
) {
664 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
665 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
666 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
667 } else if (m
> icsk
->icsk_rto
) {
668 /* Too long gap. Apparently sender failed to
669 * restart window, so that we send ACKs quickly.
671 tcp_incr_quickack(sk
);
675 icsk
->icsk_ack
.lrcvtime
= now
;
677 tcp_ecn_check_ce(tp
, skb
);
680 tcp_grow_window(sk
, skb
);
683 /* Called to compute a smoothed rtt estimate. The data fed to this
684 * routine either comes from timestamps, or from segments that were
685 * known _not_ to have been retransmitted [see Karn/Partridge
686 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
687 * piece by Van Jacobson.
688 * NOTE: the next three routines used to be one big routine.
689 * To save cycles in the RFC 1323 implementation it was better to break
690 * it up into three procedures. -- erics
692 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
694 struct tcp_sock
*tp
= tcp_sk(sk
);
695 long m
= mrtt_us
; /* RTT */
696 u32 srtt
= tp
->srtt_us
;
698 /* The following amusing code comes from Jacobson's
699 * article in SIGCOMM '88. Note that rtt and mdev
700 * are scaled versions of rtt and mean deviation.
701 * This is designed to be as fast as possible
702 * m stands for "measurement".
704 * On a 1990 paper the rto value is changed to:
705 * RTO = rtt + 4 * mdev
707 * Funny. This algorithm seems to be very broken.
708 * These formulae increase RTO, when it should be decreased, increase
709 * too slowly, when it should be increased quickly, decrease too quickly
710 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
711 * does not matter how to _calculate_ it. Seems, it was trap
712 * that VJ failed to avoid. 8)
715 m
-= (srtt
>> 3); /* m is now error in rtt est */
716 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
718 m
= -m
; /* m is now abs(error) */
719 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
720 /* This is similar to one of Eifel findings.
721 * Eifel blocks mdev updates when rtt decreases.
722 * This solution is a bit different: we use finer gain
723 * for mdev in this case (alpha*beta).
724 * Like Eifel it also prevents growth of rto,
725 * but also it limits too fast rto decreases,
726 * happening in pure Eifel.
731 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
733 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
734 if (tp
->mdev_us
> tp
->mdev_max_us
) {
735 tp
->mdev_max_us
= tp
->mdev_us
;
736 if (tp
->mdev_max_us
> tp
->rttvar_us
)
737 tp
->rttvar_us
= tp
->mdev_max_us
;
739 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
740 if (tp
->mdev_max_us
< tp
->rttvar_us
)
741 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
742 tp
->rtt_seq
= tp
->snd_nxt
;
743 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
746 /* no previous measure. */
747 srtt
= m
<< 3; /* take the measured time to be rtt */
748 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
749 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
750 tp
->mdev_max_us
= tp
->rttvar_us
;
751 tp
->rtt_seq
= tp
->snd_nxt
;
753 tp
->srtt_us
= max(1U, srtt
);
756 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
757 * Note: TCP stack does not yet implement pacing.
758 * FQ packet scheduler can be used to implement cheap but effective
759 * TCP pacing, to smooth the burst on large writes when packets
760 * in flight is significantly lower than cwnd (or rwin)
762 int sysctl_tcp_pacing_ss_ratio __read_mostly
= 200;
763 int sysctl_tcp_pacing_ca_ratio __read_mostly
= 120;
765 static void tcp_update_pacing_rate(struct sock
*sk
)
767 const struct tcp_sock
*tp
= tcp_sk(sk
);
770 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
771 rate
= (u64
)tp
->mss_cache
* ((USEC_PER_SEC
/ 100) << 3);
773 /* current rate is (cwnd * mss) / srtt
774 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
775 * In Congestion Avoidance phase, set it to 120 % the current rate.
777 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
778 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
779 * end of slow start and should slow down.
781 if (tp
->snd_cwnd
< tp
->snd_ssthresh
/ 2)
782 rate
*= sysctl_tcp_pacing_ss_ratio
;
784 rate
*= sysctl_tcp_pacing_ca_ratio
;
786 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
788 if (likely(tp
->srtt_us
))
789 do_div(rate
, tp
->srtt_us
);
791 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
792 * without any lock. We want to make sure compiler wont store
793 * intermediate values in this location.
795 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
796 sk
->sk_max_pacing_rate
);
799 /* Calculate rto without backoff. This is the second half of Van Jacobson's
800 * routine referred to above.
802 static void tcp_set_rto(struct sock
*sk
)
804 const struct tcp_sock
*tp
= tcp_sk(sk
);
805 /* Old crap is replaced with new one. 8)
808 * 1. If rtt variance happened to be less 50msec, it is hallucination.
809 * It cannot be less due to utterly erratic ACK generation made
810 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
811 * to do with delayed acks, because at cwnd>2 true delack timeout
812 * is invisible. Actually, Linux-2.4 also generates erratic
813 * ACKs in some circumstances.
815 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
817 /* 2. Fixups made earlier cannot be right.
818 * If we do not estimate RTO correctly without them,
819 * all the algo is pure shit and should be replaced
820 * with correct one. It is exactly, which we pretend to do.
823 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
824 * guarantees that rto is higher.
829 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
831 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
834 cwnd
= TCP_INIT_CWND
;
835 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
839 * Packet counting of FACK is based on in-order assumptions, therefore TCP
840 * disables it when reordering is detected
842 void tcp_disable_fack(struct tcp_sock
*tp
)
844 /* RFC3517 uses different metric in lost marker => reset on change */
846 tp
->lost_skb_hint
= NULL
;
847 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
850 /* Take a notice that peer is sending D-SACKs */
851 static void tcp_dsack_seen(struct tcp_sock
*tp
)
853 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
856 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
859 struct tcp_sock
*tp
= tcp_sk(sk
);
860 if (metric
> tp
->reordering
) {
863 tp
->reordering
= min(sysctl_tcp_max_reordering
, metric
);
865 /* This exciting event is worth to be remembered. 8) */
867 mib_idx
= LINUX_MIB_TCPTSREORDER
;
868 else if (tcp_is_reno(tp
))
869 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
870 else if (tcp_is_fack(tp
))
871 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
873 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
875 NET_INC_STATS(sock_net(sk
), mib_idx
);
876 #if FASTRETRANS_DEBUG > 1
877 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
878 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
882 tp
->undo_marker
? tp
->undo_retrans
: 0);
884 tcp_disable_fack(tp
);
888 tcp_disable_early_retrans(tp
);
892 /* This must be called before lost_out is incremented */
893 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
895 if (!tp
->retransmit_skb_hint
||
896 before(TCP_SKB_CB(skb
)->seq
,
897 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
898 tp
->retransmit_skb_hint
= skb
;
901 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
902 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
905 /* Sum the number of packets on the wire we have marked as lost.
906 * There are two cases we care about here:
907 * a) Packet hasn't been marked lost (nor retransmitted),
908 * and this is the first loss.
909 * b) Packet has been marked both lost and retransmitted,
910 * and this means we think it was lost again.
912 static void tcp_sum_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
914 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
916 if (!(sacked
& TCPCB_LOST
) ||
917 ((sacked
& TCPCB_LOST
) && (sacked
& TCPCB_SACKED_RETRANS
)))
918 tp
->lost
+= tcp_skb_pcount(skb
);
921 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
923 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
924 tcp_verify_retransmit_hint(tp
, skb
);
926 tp
->lost_out
+= tcp_skb_pcount(skb
);
927 tcp_sum_lost(tp
, skb
);
928 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
932 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
, struct sk_buff
*skb
)
934 tcp_verify_retransmit_hint(tp
, skb
);
936 tcp_sum_lost(tp
, skb
);
937 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
938 tp
->lost_out
+= tcp_skb_pcount(skb
);
939 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
943 /* This procedure tags the retransmission queue when SACKs arrive.
945 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
946 * Packets in queue with these bits set are counted in variables
947 * sacked_out, retrans_out and lost_out, correspondingly.
949 * Valid combinations are:
950 * Tag InFlight Description
951 * 0 1 - orig segment is in flight.
952 * S 0 - nothing flies, orig reached receiver.
953 * L 0 - nothing flies, orig lost by net.
954 * R 2 - both orig and retransmit are in flight.
955 * L|R 1 - orig is lost, retransmit is in flight.
956 * S|R 1 - orig reached receiver, retrans is still in flight.
957 * (L|S|R is logically valid, it could occur when L|R is sacked,
958 * but it is equivalent to plain S and code short-curcuits it to S.
959 * L|S is logically invalid, it would mean -1 packet in flight 8))
961 * These 6 states form finite state machine, controlled by the following events:
962 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
963 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
964 * 3. Loss detection event of two flavors:
965 * A. Scoreboard estimator decided the packet is lost.
966 * A'. Reno "three dupacks" marks head of queue lost.
967 * A''. Its FACK modification, head until snd.fack is lost.
968 * B. SACK arrives sacking SND.NXT at the moment, when the
969 * segment was retransmitted.
970 * 4. D-SACK added new rule: D-SACK changes any tag to S.
972 * It is pleasant to note, that state diagram turns out to be commutative,
973 * so that we are allowed not to be bothered by order of our actions,
974 * when multiple events arrive simultaneously. (see the function below).
976 * Reordering detection.
977 * --------------------
978 * Reordering metric is maximal distance, which a packet can be displaced
979 * in packet stream. With SACKs we can estimate it:
981 * 1. SACK fills old hole and the corresponding segment was not
982 * ever retransmitted -> reordering. Alas, we cannot use it
983 * when segment was retransmitted.
984 * 2. The last flaw is solved with D-SACK. D-SACK arrives
985 * for retransmitted and already SACKed segment -> reordering..
986 * Both of these heuristics are not used in Loss state, when we cannot
987 * account for retransmits accurately.
989 * SACK block validation.
990 * ----------------------
992 * SACK block range validation checks that the received SACK block fits to
993 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
994 * Note that SND.UNA is not included to the range though being valid because
995 * it means that the receiver is rather inconsistent with itself reporting
996 * SACK reneging when it should advance SND.UNA. Such SACK block this is
997 * perfectly valid, however, in light of RFC2018 which explicitly states
998 * that "SACK block MUST reflect the newest segment. Even if the newest
999 * segment is going to be discarded ...", not that it looks very clever
1000 * in case of head skb. Due to potentional receiver driven attacks, we
1001 * choose to avoid immediate execution of a walk in write queue due to
1002 * reneging and defer head skb's loss recovery to standard loss recovery
1003 * procedure that will eventually trigger (nothing forbids us doing this).
1005 * Implements also blockage to start_seq wrap-around. Problem lies in the
1006 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1007 * there's no guarantee that it will be before snd_nxt (n). The problem
1008 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1011 * <- outs wnd -> <- wrapzone ->
1012 * u e n u_w e_w s n_w
1014 * |<------------+------+----- TCP seqno space --------------+---------->|
1015 * ...-- <2^31 ->| |<--------...
1016 * ...---- >2^31 ------>| |<--------...
1018 * Current code wouldn't be vulnerable but it's better still to discard such
1019 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1020 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1021 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1022 * equal to the ideal case (infinite seqno space without wrap caused issues).
1024 * With D-SACK the lower bound is extended to cover sequence space below
1025 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1026 * again, D-SACK block must not to go across snd_una (for the same reason as
1027 * for the normal SACK blocks, explained above). But there all simplicity
1028 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1029 * fully below undo_marker they do not affect behavior in anyway and can
1030 * therefore be safely ignored. In rare cases (which are more or less
1031 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1032 * fragmentation and packet reordering past skb's retransmission. To consider
1033 * them correctly, the acceptable range must be extended even more though
1034 * the exact amount is rather hard to quantify. However, tp->max_window can
1035 * be used as an exaggerated estimate.
1037 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
1038 u32 start_seq
, u32 end_seq
)
1040 /* Too far in future, or reversed (interpretation is ambiguous) */
1041 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1044 /* Nasty start_seq wrap-around check (see comments above) */
1045 if (!before(start_seq
, tp
->snd_nxt
))
1048 /* In outstanding window? ...This is valid exit for D-SACKs too.
1049 * start_seq == snd_una is non-sensical (see comments above)
1051 if (after(start_seq
, tp
->snd_una
))
1054 if (!is_dsack
|| !tp
->undo_marker
)
1057 /* ...Then it's D-SACK, and must reside below snd_una completely */
1058 if (after(end_seq
, tp
->snd_una
))
1061 if (!before(start_seq
, tp
->undo_marker
))
1065 if (!after(end_seq
, tp
->undo_marker
))
1068 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1069 * start_seq < undo_marker and end_seq >= undo_marker.
1071 return !before(start_seq
, end_seq
- tp
->max_window
);
1074 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1075 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1078 struct tcp_sock
*tp
= tcp_sk(sk
);
1079 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1080 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1081 bool dup_sack
= false;
1083 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1086 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1087 } else if (num_sacks
> 1) {
1088 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1089 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1091 if (!after(end_seq_0
, end_seq_1
) &&
1092 !before(start_seq_0
, start_seq_1
)) {
1095 NET_INC_STATS(sock_net(sk
),
1096 LINUX_MIB_TCPDSACKOFORECV
);
1100 /* D-SACK for already forgotten data... Do dumb counting. */
1101 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1102 !after(end_seq_0
, prior_snd_una
) &&
1103 after(end_seq_0
, tp
->undo_marker
))
1109 struct tcp_sacktag_state
{
1112 /* Timestamps for earliest and latest never-retransmitted segment
1113 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1114 * but congestion control should still get an accurate delay signal.
1116 struct skb_mstamp first_sackt
;
1117 struct skb_mstamp last_sackt
;
1118 struct rate_sample
*rate
;
1122 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1123 * the incoming SACK may not exactly match but we can find smaller MSS
1124 * aligned portion of it that matches. Therefore we might need to fragment
1125 * which may fail and creates some hassle (caller must handle error case
1128 * FIXME: this could be merged to shift decision code
1130 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1131 u32 start_seq
, u32 end_seq
)
1135 unsigned int pkt_len
;
1138 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1139 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1141 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1142 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1143 mss
= tcp_skb_mss(skb
);
1144 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1147 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1151 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1156 /* Round if necessary so that SACKs cover only full MSSes
1157 * and/or the remaining small portion (if present)
1159 if (pkt_len
> mss
) {
1160 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1161 if (!in_sack
&& new_len
< pkt_len
) {
1163 if (new_len
>= skb
->len
)
1168 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1176 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1177 static u8
tcp_sacktag_one(struct sock
*sk
,
1178 struct tcp_sacktag_state
*state
, u8 sacked
,
1179 u32 start_seq
, u32 end_seq
,
1180 int dup_sack
, int pcount
,
1181 const struct skb_mstamp
*xmit_time
)
1183 struct tcp_sock
*tp
= tcp_sk(sk
);
1184 int fack_count
= state
->fack_count
;
1186 /* Account D-SACK for retransmitted packet. */
1187 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1188 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1189 after(end_seq
, tp
->undo_marker
))
1191 if (sacked
& TCPCB_SACKED_ACKED
)
1192 state
->reord
= min(fack_count
, state
->reord
);
1195 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1196 if (!after(end_seq
, tp
->snd_una
))
1199 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1200 tcp_rack_advance(tp
, xmit_time
, sacked
);
1202 if (sacked
& TCPCB_SACKED_RETRANS
) {
1203 /* If the segment is not tagged as lost,
1204 * we do not clear RETRANS, believing
1205 * that retransmission is still in flight.
1207 if (sacked
& TCPCB_LOST
) {
1208 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1209 tp
->lost_out
-= pcount
;
1210 tp
->retrans_out
-= pcount
;
1213 if (!(sacked
& TCPCB_RETRANS
)) {
1214 /* New sack for not retransmitted frame,
1215 * which was in hole. It is reordering.
1217 if (before(start_seq
,
1218 tcp_highest_sack_seq(tp
)))
1219 state
->reord
= min(fack_count
,
1221 if (!after(end_seq
, tp
->high_seq
))
1222 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1223 if (state
->first_sackt
.v64
== 0)
1224 state
->first_sackt
= *xmit_time
;
1225 state
->last_sackt
= *xmit_time
;
1228 if (sacked
& TCPCB_LOST
) {
1229 sacked
&= ~TCPCB_LOST
;
1230 tp
->lost_out
-= pcount
;
1234 sacked
|= TCPCB_SACKED_ACKED
;
1235 state
->flag
|= FLAG_DATA_SACKED
;
1236 tp
->sacked_out
+= pcount
;
1237 tp
->delivered
+= pcount
; /* Out-of-order packets delivered */
1239 fack_count
+= pcount
;
1241 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1242 if (!tcp_is_fack(tp
) && tp
->lost_skb_hint
&&
1243 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1244 tp
->lost_cnt_hint
+= pcount
;
1246 if (fack_count
> tp
->fackets_out
)
1247 tp
->fackets_out
= fack_count
;
1250 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1251 * frames and clear it. undo_retrans is decreased above, L|R frames
1252 * are accounted above as well.
1254 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1255 sacked
&= ~TCPCB_SACKED_RETRANS
;
1256 tp
->retrans_out
-= pcount
;
1262 /* Shift newly-SACKed bytes from this skb to the immediately previous
1263 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1265 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1266 struct tcp_sacktag_state
*state
,
1267 unsigned int pcount
, int shifted
, int mss
,
1270 struct tcp_sock
*tp
= tcp_sk(sk
);
1271 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1272 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1273 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1277 /* Adjust counters and hints for the newly sacked sequence
1278 * range but discard the return value since prev is already
1279 * marked. We must tag the range first because the seq
1280 * advancement below implicitly advances
1281 * tcp_highest_sack_seq() when skb is highest_sack.
1283 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1284 start_seq
, end_seq
, dup_sack
, pcount
,
1286 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1288 if (skb
== tp
->lost_skb_hint
)
1289 tp
->lost_cnt_hint
+= pcount
;
1291 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1292 TCP_SKB_CB(skb
)->seq
+= shifted
;
1294 tcp_skb_pcount_add(prev
, pcount
);
1295 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1296 tcp_skb_pcount_add(skb
, -pcount
);
1298 /* When we're adding to gso_segs == 1, gso_size will be zero,
1299 * in theory this shouldn't be necessary but as long as DSACK
1300 * code can come after this skb later on it's better to keep
1301 * setting gso_size to something.
1303 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1304 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1306 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1307 if (tcp_skb_pcount(skb
) <= 1)
1308 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1310 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1311 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1314 BUG_ON(!tcp_skb_pcount(skb
));
1315 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1319 /* Whole SKB was eaten :-) */
1321 if (skb
== tp
->retransmit_skb_hint
)
1322 tp
->retransmit_skb_hint
= prev
;
1323 if (skb
== tp
->lost_skb_hint
) {
1324 tp
->lost_skb_hint
= prev
;
1325 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1328 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1329 TCP_SKB_CB(prev
)->eor
= TCP_SKB_CB(skb
)->eor
;
1330 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1331 TCP_SKB_CB(prev
)->end_seq
++;
1333 if (skb
== tcp_highest_sack(sk
))
1334 tcp_advance_highest_sack(sk
, skb
);
1336 tcp_skb_collapse_tstamp(prev
, skb
);
1337 if (unlikely(TCP_SKB_CB(prev
)->tx
.delivered_mstamp
.v64
))
1338 TCP_SKB_CB(prev
)->tx
.delivered_mstamp
.v64
= 0;
1340 tcp_unlink_write_queue(skb
, sk
);
1341 sk_wmem_free_skb(sk
, skb
);
1343 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1348 /* I wish gso_size would have a bit more sane initialization than
1349 * something-or-zero which complicates things
1351 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1353 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1356 /* Shifting pages past head area doesn't work */
1357 static int skb_can_shift(const struct sk_buff
*skb
)
1359 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1362 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1365 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1366 struct tcp_sacktag_state
*state
,
1367 u32 start_seq
, u32 end_seq
,
1370 struct tcp_sock
*tp
= tcp_sk(sk
);
1371 struct sk_buff
*prev
;
1377 if (!sk_can_gso(sk
))
1380 /* Normally R but no L won't result in plain S */
1382 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1384 if (!skb_can_shift(skb
))
1386 /* This frame is about to be dropped (was ACKed). */
1387 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1390 /* Can only happen with delayed DSACK + discard craziness */
1391 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1393 prev
= tcp_write_queue_prev(sk
, skb
);
1395 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1398 if (!tcp_skb_can_collapse_to(prev
))
1401 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1402 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1406 pcount
= tcp_skb_pcount(skb
);
1407 mss
= tcp_skb_seglen(skb
);
1409 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1410 * drop this restriction as unnecessary
1412 if (mss
!= tcp_skb_seglen(prev
))
1415 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1417 /* CHECKME: This is non-MSS split case only?, this will
1418 * cause skipped skbs due to advancing loop btw, original
1419 * has that feature too
1421 if (tcp_skb_pcount(skb
) <= 1)
1424 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1426 /* TODO: head merge to next could be attempted here
1427 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1428 * though it might not be worth of the additional hassle
1430 * ...we can probably just fallback to what was done
1431 * previously. We could try merging non-SACKed ones
1432 * as well but it probably isn't going to buy off
1433 * because later SACKs might again split them, and
1434 * it would make skb timestamp tracking considerably
1440 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1442 BUG_ON(len
> skb
->len
);
1444 /* MSS boundaries should be honoured or else pcount will
1445 * severely break even though it makes things bit trickier.
1446 * Optimize common case to avoid most of the divides
1448 mss
= tcp_skb_mss(skb
);
1450 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1451 * drop this restriction as unnecessary
1453 if (mss
!= tcp_skb_seglen(prev
))
1458 } else if (len
< mss
) {
1466 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1467 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1470 if (!skb_shift(prev
, skb
, len
))
1472 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1475 /* Hole filled allows collapsing with the next as well, this is very
1476 * useful when hole on every nth skb pattern happens
1478 if (prev
== tcp_write_queue_tail(sk
))
1480 skb
= tcp_write_queue_next(sk
, prev
);
1482 if (!skb_can_shift(skb
) ||
1483 (skb
== tcp_send_head(sk
)) ||
1484 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1485 (mss
!= tcp_skb_seglen(skb
)))
1489 if (skb_shift(prev
, skb
, len
)) {
1490 pcount
+= tcp_skb_pcount(skb
);
1491 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1495 state
->fack_count
+= pcount
;
1502 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1506 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1507 struct tcp_sack_block
*next_dup
,
1508 struct tcp_sacktag_state
*state
,
1509 u32 start_seq
, u32 end_seq
,
1512 struct tcp_sock
*tp
= tcp_sk(sk
);
1513 struct sk_buff
*tmp
;
1515 tcp_for_write_queue_from(skb
, sk
) {
1517 bool dup_sack
= dup_sack_in
;
1519 if (skb
== tcp_send_head(sk
))
1522 /* queue is in-order => we can short-circuit the walk early */
1523 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1527 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1528 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1529 next_dup
->start_seq
,
1535 /* skb reference here is a bit tricky to get right, since
1536 * shifting can eat and free both this skb and the next,
1537 * so not even _safe variant of the loop is enough.
1540 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1541 start_seq
, end_seq
, dup_sack
);
1550 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1556 if (unlikely(in_sack
< 0))
1560 TCP_SKB_CB(skb
)->sacked
=
1563 TCP_SKB_CB(skb
)->sacked
,
1564 TCP_SKB_CB(skb
)->seq
,
1565 TCP_SKB_CB(skb
)->end_seq
,
1567 tcp_skb_pcount(skb
),
1569 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1571 if (!before(TCP_SKB_CB(skb
)->seq
,
1572 tcp_highest_sack_seq(tp
)))
1573 tcp_advance_highest_sack(sk
, skb
);
1576 state
->fack_count
+= tcp_skb_pcount(skb
);
1581 /* Avoid all extra work that is being done by sacktag while walking in
1584 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1585 struct tcp_sacktag_state
*state
,
1588 tcp_for_write_queue_from(skb
, sk
) {
1589 if (skb
== tcp_send_head(sk
))
1592 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1595 state
->fack_count
+= tcp_skb_pcount(skb
);
1600 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1602 struct tcp_sack_block
*next_dup
,
1603 struct tcp_sacktag_state
*state
,
1609 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1610 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1611 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1612 next_dup
->start_seq
, next_dup
->end_seq
,
1619 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1621 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1625 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1626 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1628 struct tcp_sock
*tp
= tcp_sk(sk
);
1629 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1630 TCP_SKB_CB(ack_skb
)->sacked
);
1631 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1632 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1633 struct tcp_sack_block
*cache
;
1634 struct sk_buff
*skb
;
1635 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1637 bool found_dup_sack
= false;
1639 int first_sack_index
;
1642 state
->reord
= tp
->packets_out
;
1644 if (!tp
->sacked_out
) {
1645 if (WARN_ON(tp
->fackets_out
))
1646 tp
->fackets_out
= 0;
1647 tcp_highest_sack_reset(sk
);
1650 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1651 num_sacks
, prior_snd_una
);
1652 if (found_dup_sack
) {
1653 state
->flag
|= FLAG_DSACKING_ACK
;
1654 tp
->delivered
++; /* A spurious retransmission is delivered */
1657 /* Eliminate too old ACKs, but take into
1658 * account more or less fresh ones, they can
1659 * contain valid SACK info.
1661 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1664 if (!tp
->packets_out
)
1668 first_sack_index
= 0;
1669 for (i
= 0; i
< num_sacks
; i
++) {
1670 bool dup_sack
= !i
&& found_dup_sack
;
1672 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1673 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1675 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1676 sp
[used_sacks
].start_seq
,
1677 sp
[used_sacks
].end_seq
)) {
1681 if (!tp
->undo_marker
)
1682 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1684 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1686 /* Don't count olds caused by ACK reordering */
1687 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1688 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1690 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1693 NET_INC_STATS(sock_net(sk
), mib_idx
);
1695 first_sack_index
= -1;
1699 /* Ignore very old stuff early */
1700 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1706 /* order SACK blocks to allow in order walk of the retrans queue */
1707 for (i
= used_sacks
- 1; i
> 0; i
--) {
1708 for (j
= 0; j
< i
; j
++) {
1709 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1710 swap(sp
[j
], sp
[j
+ 1]);
1712 /* Track where the first SACK block goes to */
1713 if (j
== first_sack_index
)
1714 first_sack_index
= j
+ 1;
1719 skb
= tcp_write_queue_head(sk
);
1720 state
->fack_count
= 0;
1723 if (!tp
->sacked_out
) {
1724 /* It's already past, so skip checking against it */
1725 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1727 cache
= tp
->recv_sack_cache
;
1728 /* Skip empty blocks in at head of the cache */
1729 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1734 while (i
< used_sacks
) {
1735 u32 start_seq
= sp
[i
].start_seq
;
1736 u32 end_seq
= sp
[i
].end_seq
;
1737 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1738 struct tcp_sack_block
*next_dup
= NULL
;
1740 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1741 next_dup
= &sp
[i
+ 1];
1743 /* Skip too early cached blocks */
1744 while (tcp_sack_cache_ok(tp
, cache
) &&
1745 !before(start_seq
, cache
->end_seq
))
1748 /* Can skip some work by looking recv_sack_cache? */
1749 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1750 after(end_seq
, cache
->start_seq
)) {
1753 if (before(start_seq
, cache
->start_seq
)) {
1754 skb
= tcp_sacktag_skip(skb
, sk
, state
,
1756 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1763 /* Rest of the block already fully processed? */
1764 if (!after(end_seq
, cache
->end_seq
))
1767 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1771 /* ...tail remains todo... */
1772 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1773 /* ...but better entrypoint exists! */
1774 skb
= tcp_highest_sack(sk
);
1777 state
->fack_count
= tp
->fackets_out
;
1782 skb
= tcp_sacktag_skip(skb
, sk
, state
, cache
->end_seq
);
1783 /* Check overlap against next cached too (past this one already) */
1788 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1789 skb
= tcp_highest_sack(sk
);
1792 state
->fack_count
= tp
->fackets_out
;
1794 skb
= tcp_sacktag_skip(skb
, sk
, state
, start_seq
);
1797 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
1798 start_seq
, end_seq
, dup_sack
);
1804 /* Clear the head of the cache sack blocks so we can skip it next time */
1805 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1806 tp
->recv_sack_cache
[i
].start_seq
= 0;
1807 tp
->recv_sack_cache
[i
].end_seq
= 0;
1809 for (j
= 0; j
< used_sacks
; j
++)
1810 tp
->recv_sack_cache
[i
++] = sp
[j
];
1812 if ((state
->reord
< tp
->fackets_out
) &&
1813 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1814 tcp_update_reordering(sk
, tp
->fackets_out
- state
->reord
, 0);
1816 tcp_verify_left_out(tp
);
1819 #if FASTRETRANS_DEBUG > 0
1820 WARN_ON((int)tp
->sacked_out
< 0);
1821 WARN_ON((int)tp
->lost_out
< 0);
1822 WARN_ON((int)tp
->retrans_out
< 0);
1823 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1828 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1829 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1831 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1835 holes
= max(tp
->lost_out
, 1U);
1836 holes
= min(holes
, tp
->packets_out
);
1838 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1839 tp
->sacked_out
= tp
->packets_out
- holes
;
1845 /* If we receive more dupacks than we expected counting segments
1846 * in assumption of absent reordering, interpret this as reordering.
1847 * The only another reason could be bug in receiver TCP.
1849 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1851 struct tcp_sock
*tp
= tcp_sk(sk
);
1852 if (tcp_limit_reno_sacked(tp
))
1853 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1856 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1858 static void tcp_add_reno_sack(struct sock
*sk
)
1860 struct tcp_sock
*tp
= tcp_sk(sk
);
1861 u32 prior_sacked
= tp
->sacked_out
;
1864 tcp_check_reno_reordering(sk
, 0);
1865 if (tp
->sacked_out
> prior_sacked
)
1866 tp
->delivered
++; /* Some out-of-order packet is delivered */
1867 tcp_verify_left_out(tp
);
1870 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1872 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1874 struct tcp_sock
*tp
= tcp_sk(sk
);
1877 /* One ACK acked hole. The rest eat duplicate ACKs. */
1878 tp
->delivered
+= max_t(int, acked
- tp
->sacked_out
, 1);
1879 if (acked
- 1 >= tp
->sacked_out
)
1882 tp
->sacked_out
-= acked
- 1;
1884 tcp_check_reno_reordering(sk
, acked
);
1885 tcp_verify_left_out(tp
);
1888 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1893 void tcp_clear_retrans(struct tcp_sock
*tp
)
1895 tp
->retrans_out
= 0;
1897 tp
->undo_marker
= 0;
1898 tp
->undo_retrans
= -1;
1899 tp
->fackets_out
= 0;
1903 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1905 tp
->undo_marker
= tp
->snd_una
;
1906 /* Retransmission still in flight may cause DSACKs later. */
1907 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1910 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1911 * and reset tags completely, otherwise preserve SACKs. If receiver
1912 * dropped its ofo queue, we will know this due to reneging detection.
1914 void tcp_enter_loss(struct sock
*sk
)
1916 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1917 struct tcp_sock
*tp
= tcp_sk(sk
);
1918 struct net
*net
= sock_net(sk
);
1919 struct sk_buff
*skb
;
1920 bool new_recovery
= icsk
->icsk_ca_state
< TCP_CA_Recovery
;
1921 bool is_reneg
; /* is receiver reneging on SACKs? */
1924 /* Reduce ssthresh if it has not yet been made inside this window. */
1925 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1926 !after(tp
->high_seq
, tp
->snd_una
) ||
1927 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1928 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1929 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1930 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1934 tp
->snd_cwnd_cnt
= 0;
1935 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1937 tp
->retrans_out
= 0;
1940 if (tcp_is_reno(tp
))
1941 tcp_reset_reno_sack(tp
);
1943 skb
= tcp_write_queue_head(sk
);
1944 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1946 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1948 tp
->fackets_out
= 0;
1950 tcp_clear_all_retrans_hints(tp
);
1952 tcp_for_write_queue(skb
, sk
) {
1953 if (skb
== tcp_send_head(sk
))
1956 mark_lost
= (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
1959 tcp_sum_lost(tp
, skb
);
1960 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1962 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1963 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1964 tp
->lost_out
+= tcp_skb_pcount(skb
);
1965 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1968 tcp_verify_left_out(tp
);
1970 /* Timeout in disordered state after receiving substantial DUPACKs
1971 * suggests that the degree of reordering is over-estimated.
1973 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1974 tp
->sacked_out
>= net
->ipv4
.sysctl_tcp_reordering
)
1975 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1976 net
->ipv4
.sysctl_tcp_reordering
);
1977 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1978 tp
->high_seq
= tp
->snd_nxt
;
1979 tcp_ecn_queue_cwr(tp
);
1981 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1982 * loss recovery is underway except recurring timeout(s) on
1983 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1985 tp
->frto
= sysctl_tcp_frto
&&
1986 (new_recovery
|| icsk
->icsk_retransmits
) &&
1987 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1990 /* If ACK arrived pointing to a remembered SACK, it means that our
1991 * remembered SACKs do not reflect real state of receiver i.e.
1992 * receiver _host_ is heavily congested (or buggy).
1994 * To avoid big spurious retransmission bursts due to transient SACK
1995 * scoreboard oddities that look like reneging, we give the receiver a
1996 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
1997 * restore sanity to the SACK scoreboard. If the apparent reneging
1998 * persists until this RTO then we'll clear the SACK scoreboard.
2000 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2002 if (flag
& FLAG_SACK_RENEGING
) {
2003 struct tcp_sock
*tp
= tcp_sk(sk
);
2004 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2005 msecs_to_jiffies(10));
2007 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2008 delay
, TCP_RTO_MAX
);
2014 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2016 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2019 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2020 * counter when SACK is enabled (without SACK, sacked_out is used for
2023 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2024 * segments up to the highest received SACK block so far and holes in
2027 * With reordering, holes may still be in flight, so RFC3517 recovery
2028 * uses pure sacked_out (total number of SACKed segments) even though
2029 * it violates the RFC that uses duplicate ACKs, often these are equal
2030 * but when e.g. out-of-window ACKs or packet duplication occurs,
2031 * they differ. Since neither occurs due to loss, TCP should really
2034 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2036 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2039 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2041 struct tcp_sock
*tp
= tcp_sk(sk
);
2042 unsigned long delay
;
2044 /* Delay early retransmit and entering fast recovery for
2045 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2046 * available, or RTO is scheduled to fire first.
2048 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
2049 (flag
& FLAG_ECE
) || !tp
->srtt_us
)
2052 delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 5),
2053 msecs_to_jiffies(2));
2055 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2058 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2063 /* Linux NewReno/SACK/FACK/ECN state machine.
2064 * --------------------------------------
2066 * "Open" Normal state, no dubious events, fast path.
2067 * "Disorder" In all the respects it is "Open",
2068 * but requires a bit more attention. It is entered when
2069 * we see some SACKs or dupacks. It is split of "Open"
2070 * mainly to move some processing from fast path to slow one.
2071 * "CWR" CWND was reduced due to some Congestion Notification event.
2072 * It can be ECN, ICMP source quench, local device congestion.
2073 * "Recovery" CWND was reduced, we are fast-retransmitting.
2074 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2076 * tcp_fastretrans_alert() is entered:
2077 * - each incoming ACK, if state is not "Open"
2078 * - when arrived ACK is unusual, namely:
2083 * Counting packets in flight is pretty simple.
2085 * in_flight = packets_out - left_out + retrans_out
2087 * packets_out is SND.NXT-SND.UNA counted in packets.
2089 * retrans_out is number of retransmitted segments.
2091 * left_out is number of segments left network, but not ACKed yet.
2093 * left_out = sacked_out + lost_out
2095 * sacked_out: Packets, which arrived to receiver out of order
2096 * and hence not ACKed. With SACKs this number is simply
2097 * amount of SACKed data. Even without SACKs
2098 * it is easy to give pretty reliable estimate of this number,
2099 * counting duplicate ACKs.
2101 * lost_out: Packets lost by network. TCP has no explicit
2102 * "loss notification" feedback from network (for now).
2103 * It means that this number can be only _guessed_.
2104 * Actually, it is the heuristics to predict lossage that
2105 * distinguishes different algorithms.
2107 * F.e. after RTO, when all the queue is considered as lost,
2108 * lost_out = packets_out and in_flight = retrans_out.
2110 * Essentially, we have now two algorithms counting
2113 * FACK: It is the simplest heuristics. As soon as we decided
2114 * that something is lost, we decide that _all_ not SACKed
2115 * packets until the most forward SACK are lost. I.e.
2116 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2117 * It is absolutely correct estimate, if network does not reorder
2118 * packets. And it loses any connection to reality when reordering
2119 * takes place. We use FACK by default until reordering
2120 * is suspected on the path to this destination.
2122 * NewReno: when Recovery is entered, we assume that one segment
2123 * is lost (classic Reno). While we are in Recovery and
2124 * a partial ACK arrives, we assume that one more packet
2125 * is lost (NewReno). This heuristics are the same in NewReno
2128 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2129 * deflation etc. CWND is real congestion window, never inflated, changes
2130 * only according to classic VJ rules.
2132 * Really tricky (and requiring careful tuning) part of algorithm
2133 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2134 * The first determines the moment _when_ we should reduce CWND and,
2135 * hence, slow down forward transmission. In fact, it determines the moment
2136 * when we decide that hole is caused by loss, rather than by a reorder.
2138 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2139 * holes, caused by lost packets.
2141 * And the most logically complicated part of algorithm is undo
2142 * heuristics. We detect false retransmits due to both too early
2143 * fast retransmit (reordering) and underestimated RTO, analyzing
2144 * timestamps and D-SACKs. When we detect that some segments were
2145 * retransmitted by mistake and CWND reduction was wrong, we undo
2146 * window reduction and abort recovery phase. This logic is hidden
2147 * inside several functions named tcp_try_undo_<something>.
2150 /* This function decides, when we should leave Disordered state
2151 * and enter Recovery phase, reducing congestion window.
2153 * Main question: may we further continue forward transmission
2154 * with the same cwnd?
2156 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2158 struct tcp_sock
*tp
= tcp_sk(sk
);
2160 int tcp_reordering
= sock_net(sk
)->ipv4
.sysctl_tcp_reordering
;
2162 /* Trick#1: The loss is proven. */
2166 /* Not-A-Trick#2 : Classic rule... */
2167 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2170 /* Trick#4: It is still not OK... But will it be useful to delay
2173 packets_out
= tp
->packets_out
;
2174 if (packets_out
<= tp
->reordering
&&
2175 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, tcp_reordering
) &&
2176 !tcp_may_send_now(sk
)) {
2177 /* We have nothing to send. This connection is limited
2178 * either by receiver window or by application.
2183 /* If a thin stream is detected, retransmit after first
2184 * received dupack. Employ only if SACK is supported in order
2185 * to avoid possible corner-case series of spurious retransmissions
2186 * Use only if there are no unsent data.
2188 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2189 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2190 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2193 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2194 * retransmissions due to small network reorderings, we implement
2195 * Mitigation A.3 in the RFC and delay the retransmission for a short
2196 * interval if appropriate.
2198 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2199 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2200 !tcp_may_send_now(sk
))
2201 return !tcp_pause_early_retransmit(sk
, flag
);
2206 /* Detect loss in event "A" above by marking head of queue up as lost.
2207 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2208 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2209 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2210 * the maximum SACKed segments to pass before reaching this limit.
2212 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2214 struct tcp_sock
*tp
= tcp_sk(sk
);
2215 struct sk_buff
*skb
;
2216 int cnt
, oldcnt
, lost
;
2218 /* Use SACK to deduce losses of new sequences sent during recovery */
2219 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2221 WARN_ON(packets
> tp
->packets_out
);
2222 if (tp
->lost_skb_hint
) {
2223 skb
= tp
->lost_skb_hint
;
2224 cnt
= tp
->lost_cnt_hint
;
2225 /* Head already handled? */
2226 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2229 skb
= tcp_write_queue_head(sk
);
2233 tcp_for_write_queue_from(skb
, sk
) {
2234 if (skb
== tcp_send_head(sk
))
2236 /* TODO: do this better */
2237 /* this is not the most efficient way to do this... */
2238 tp
->lost_skb_hint
= skb
;
2239 tp
->lost_cnt_hint
= cnt
;
2241 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2245 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2246 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2247 cnt
+= tcp_skb_pcount(skb
);
2249 if (cnt
> packets
) {
2250 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2251 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2252 (oldcnt
>= packets
))
2255 mss
= tcp_skb_mss(skb
);
2256 /* If needed, chop off the prefix to mark as lost. */
2257 lost
= (packets
- oldcnt
) * mss
;
2258 if (lost
< skb
->len
&&
2259 tcp_fragment(sk
, skb
, lost
, mss
, GFP_ATOMIC
) < 0)
2264 tcp_skb_mark_lost(tp
, skb
);
2269 tcp_verify_left_out(tp
);
2272 /* Account newly detected lost packet(s) */
2274 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2276 struct tcp_sock
*tp
= tcp_sk(sk
);
2278 if (tcp_is_reno(tp
)) {
2279 tcp_mark_head_lost(sk
, 1, 1);
2280 } else if (tcp_is_fack(tp
)) {
2281 int lost
= tp
->fackets_out
- tp
->reordering
;
2284 tcp_mark_head_lost(sk
, lost
, 0);
2286 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2287 if (sacked_upto
>= 0)
2288 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2289 else if (fast_rexmit
)
2290 tcp_mark_head_lost(sk
, 1, 1);
2294 static bool tcp_tsopt_ecr_before(const struct tcp_sock
*tp
, u32 when
)
2296 return tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2297 before(tp
->rx_opt
.rcv_tsecr
, when
);
2300 /* skb is spurious retransmitted if the returned timestamp echo
2301 * reply is prior to the skb transmission time
2303 static bool tcp_skb_spurious_retrans(const struct tcp_sock
*tp
,
2304 const struct sk_buff
*skb
)
2306 return (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
) &&
2307 tcp_tsopt_ecr_before(tp
, tcp_skb_timestamp(skb
));
2310 /* Nothing was retransmitted or returned timestamp is less
2311 * than timestamp of the first retransmission.
2313 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2315 return !tp
->retrans_stamp
||
2316 tcp_tsopt_ecr_before(tp
, tp
->retrans_stamp
);
2319 /* Undo procedures. */
2321 /* We can clear retrans_stamp when there are no retransmissions in the
2322 * window. It would seem that it is trivially available for us in
2323 * tp->retrans_out, however, that kind of assumptions doesn't consider
2324 * what will happen if errors occur when sending retransmission for the
2325 * second time. ...It could the that such segment has only
2326 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2327 * the head skb is enough except for some reneging corner cases that
2328 * are not worth the effort.
2330 * Main reason for all this complexity is the fact that connection dying
2331 * time now depends on the validity of the retrans_stamp, in particular,
2332 * that successive retransmissions of a segment must not advance
2333 * retrans_stamp under any conditions.
2335 static bool tcp_any_retrans_done(const struct sock
*sk
)
2337 const struct tcp_sock
*tp
= tcp_sk(sk
);
2338 struct sk_buff
*skb
;
2340 if (tp
->retrans_out
)
2343 skb
= tcp_write_queue_head(sk
);
2344 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2350 #if FASTRETRANS_DEBUG > 1
2351 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2353 struct tcp_sock
*tp
= tcp_sk(sk
);
2354 struct inet_sock
*inet
= inet_sk(sk
);
2356 if (sk
->sk_family
== AF_INET
) {
2357 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2359 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2360 tp
->snd_cwnd
, tcp_left_out(tp
),
2361 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2364 #if IS_ENABLED(CONFIG_IPV6)
2365 else if (sk
->sk_family
== AF_INET6
) {
2366 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2368 &sk
->sk_v6_daddr
, ntohs(inet
->inet_dport
),
2369 tp
->snd_cwnd
, tcp_left_out(tp
),
2370 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2376 #define DBGUNDO(x...) do { } while (0)
2379 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2381 struct tcp_sock
*tp
= tcp_sk(sk
);
2384 struct sk_buff
*skb
;
2386 tcp_for_write_queue(skb
, sk
) {
2387 if (skb
== tcp_send_head(sk
))
2389 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2392 tcp_clear_all_retrans_hints(tp
);
2395 if (tp
->prior_ssthresh
) {
2396 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2398 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2400 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2401 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2402 tcp_ecn_withdraw_cwr(tp
);
2405 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2406 tp
->undo_marker
= 0;
2409 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2411 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2414 /* People celebrate: "We love our President!" */
2415 static bool tcp_try_undo_recovery(struct sock
*sk
)
2417 struct tcp_sock
*tp
= tcp_sk(sk
);
2419 if (tcp_may_undo(tp
)) {
2422 /* Happy end! We did not retransmit anything
2423 * or our original transmission succeeded.
2425 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2426 tcp_undo_cwnd_reduction(sk
, false);
2427 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2428 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2430 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2432 NET_INC_STATS(sock_net(sk
), mib_idx
);
2434 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2435 /* Hold old state until something *above* high_seq
2436 * is ACKed. For Reno it is MUST to prevent false
2437 * fast retransmits (RFC2582). SACK TCP is safe. */
2438 if (!tcp_any_retrans_done(sk
))
2439 tp
->retrans_stamp
= 0;
2442 tcp_set_ca_state(sk
, TCP_CA_Open
);
2446 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2447 static bool tcp_try_undo_dsack(struct sock
*sk
)
2449 struct tcp_sock
*tp
= tcp_sk(sk
);
2451 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2452 DBGUNDO(sk
, "D-SACK");
2453 tcp_undo_cwnd_reduction(sk
, false);
2454 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2460 /* Undo during loss recovery after partial ACK or using F-RTO. */
2461 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2463 struct tcp_sock
*tp
= tcp_sk(sk
);
2465 if (frto_undo
|| tcp_may_undo(tp
)) {
2466 tcp_undo_cwnd_reduction(sk
, true);
2468 DBGUNDO(sk
, "partial loss");
2469 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2471 NET_INC_STATS(sock_net(sk
),
2472 LINUX_MIB_TCPSPURIOUSRTOS
);
2473 inet_csk(sk
)->icsk_retransmits
= 0;
2474 if (frto_undo
|| tcp_is_sack(tp
))
2475 tcp_set_ca_state(sk
, TCP_CA_Open
);
2481 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2482 * It computes the number of packets to send (sndcnt) based on packets newly
2484 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2485 * cwnd reductions across a full RTT.
2486 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2487 * But when the retransmits are acked without further losses, PRR
2488 * slow starts cwnd up to ssthresh to speed up the recovery.
2490 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2492 struct tcp_sock
*tp
= tcp_sk(sk
);
2494 tp
->high_seq
= tp
->snd_nxt
;
2495 tp
->tlp_high_seq
= 0;
2496 tp
->snd_cwnd_cnt
= 0;
2497 tp
->prior_cwnd
= tp
->snd_cwnd
;
2498 tp
->prr_delivered
= 0;
2500 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2501 tcp_ecn_queue_cwr(tp
);
2504 static void tcp_cwnd_reduction(struct sock
*sk
, int newly_acked_sacked
,
2507 struct tcp_sock
*tp
= tcp_sk(sk
);
2509 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2511 if (newly_acked_sacked
<= 0 || WARN_ON_ONCE(!tp
->prior_cwnd
))
2514 tp
->prr_delivered
+= newly_acked_sacked
;
2516 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2518 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2519 } else if ((flag
& FLAG_RETRANS_DATA_ACKED
) &&
2520 !(flag
& FLAG_LOST_RETRANS
)) {
2521 sndcnt
= min_t(int, delta
,
2522 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2523 newly_acked_sacked
) + 1);
2525 sndcnt
= min(delta
, newly_acked_sacked
);
2527 /* Force a fast retransmit upon entering fast recovery */
2528 sndcnt
= max(sndcnt
, (tp
->prr_out
? 0 : 1));
2529 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2532 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2534 struct tcp_sock
*tp
= tcp_sk(sk
);
2536 if (inet_csk(sk
)->icsk_ca_ops
->cong_control
)
2539 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2540 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2541 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2542 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2543 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2545 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2548 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2549 void tcp_enter_cwr(struct sock
*sk
)
2551 struct tcp_sock
*tp
= tcp_sk(sk
);
2553 tp
->prior_ssthresh
= 0;
2554 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2555 tp
->undo_marker
= 0;
2556 tcp_init_cwnd_reduction(sk
);
2557 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2560 EXPORT_SYMBOL(tcp_enter_cwr
);
2562 static void tcp_try_keep_open(struct sock
*sk
)
2564 struct tcp_sock
*tp
= tcp_sk(sk
);
2565 int state
= TCP_CA_Open
;
2567 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2568 state
= TCP_CA_Disorder
;
2570 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2571 tcp_set_ca_state(sk
, state
);
2572 tp
->high_seq
= tp
->snd_nxt
;
2576 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2578 struct tcp_sock
*tp
= tcp_sk(sk
);
2580 tcp_verify_left_out(tp
);
2582 if (!tcp_any_retrans_done(sk
))
2583 tp
->retrans_stamp
= 0;
2585 if (flag
& FLAG_ECE
)
2588 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2589 tcp_try_keep_open(sk
);
2593 static void tcp_mtup_probe_failed(struct sock
*sk
)
2595 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2597 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2598 icsk
->icsk_mtup
.probe_size
= 0;
2599 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPFAIL
);
2602 static void tcp_mtup_probe_success(struct sock
*sk
)
2604 struct tcp_sock
*tp
= tcp_sk(sk
);
2605 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2607 /* FIXME: breaks with very large cwnd */
2608 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2609 tp
->snd_cwnd
= tp
->snd_cwnd
*
2610 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2611 icsk
->icsk_mtup
.probe_size
;
2612 tp
->snd_cwnd_cnt
= 0;
2613 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2614 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2616 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2617 icsk
->icsk_mtup
.probe_size
= 0;
2618 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2619 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPSUCCESS
);
2622 /* Do a simple retransmit without using the backoff mechanisms in
2623 * tcp_timer. This is used for path mtu discovery.
2624 * The socket is already locked here.
2626 void tcp_simple_retransmit(struct sock
*sk
)
2628 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2629 struct tcp_sock
*tp
= tcp_sk(sk
);
2630 struct sk_buff
*skb
;
2631 unsigned int mss
= tcp_current_mss(sk
);
2632 u32 prior_lost
= tp
->lost_out
;
2634 tcp_for_write_queue(skb
, sk
) {
2635 if (skb
== tcp_send_head(sk
))
2637 if (tcp_skb_seglen(skb
) > mss
&&
2638 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2639 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2640 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2641 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2643 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2647 tcp_clear_retrans_hints_partial(tp
);
2649 if (prior_lost
== tp
->lost_out
)
2652 if (tcp_is_reno(tp
))
2653 tcp_limit_reno_sacked(tp
);
2655 tcp_verify_left_out(tp
);
2657 /* Don't muck with the congestion window here.
2658 * Reason is that we do not increase amount of _data_
2659 * in network, but units changed and effective
2660 * cwnd/ssthresh really reduced now.
2662 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2663 tp
->high_seq
= tp
->snd_nxt
;
2664 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2665 tp
->prior_ssthresh
= 0;
2666 tp
->undo_marker
= 0;
2667 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2669 tcp_xmit_retransmit_queue(sk
);
2671 EXPORT_SYMBOL(tcp_simple_retransmit
);
2673 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2675 struct tcp_sock
*tp
= tcp_sk(sk
);
2678 if (tcp_is_reno(tp
))
2679 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2681 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2683 NET_INC_STATS(sock_net(sk
), mib_idx
);
2685 tp
->prior_ssthresh
= 0;
2688 if (!tcp_in_cwnd_reduction(sk
)) {
2690 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2691 tcp_init_cwnd_reduction(sk
);
2693 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2696 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2697 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2699 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
,
2702 struct tcp_sock
*tp
= tcp_sk(sk
);
2703 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2705 if ((flag
& FLAG_SND_UNA_ADVANCED
) &&
2706 tcp_try_undo_loss(sk
, false))
2709 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2710 /* Step 3.b. A timeout is spurious if not all data are
2711 * lost, i.e., never-retransmitted data are (s)acked.
2713 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2714 tcp_try_undo_loss(sk
, true))
2717 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2718 if (flag
& FLAG_DATA_SACKED
|| is_dupack
)
2719 tp
->frto
= 0; /* Step 3.a. loss was real */
2720 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2721 tp
->high_seq
= tp
->snd_nxt
;
2722 /* Step 2.b. Try send new data (but deferred until cwnd
2723 * is updated in tcp_ack()). Otherwise fall back to
2724 * the conventional recovery.
2726 if (tcp_send_head(sk
) &&
2727 after(tcp_wnd_end(tp
), tp
->snd_nxt
)) {
2728 *rexmit
= REXMIT_NEW
;
2736 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2737 tcp_try_undo_recovery(sk
);
2740 if (tcp_is_reno(tp
)) {
2741 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2742 * delivered. Lower inflight to clock out (re)tranmissions.
2744 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2745 tcp_add_reno_sack(sk
);
2746 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2747 tcp_reset_reno_sack(tp
);
2749 *rexmit
= REXMIT_LOST
;
2752 /* Undo during fast recovery after partial ACK. */
2753 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
)
2755 struct tcp_sock
*tp
= tcp_sk(sk
);
2757 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2758 /* Plain luck! Hole if filled with delayed
2759 * packet, rather than with a retransmit.
2761 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2763 /* We are getting evidence that the reordering degree is higher
2764 * than we realized. If there are no retransmits out then we
2765 * can undo. Otherwise we clock out new packets but do not
2766 * mark more packets lost or retransmit more.
2768 if (tp
->retrans_out
)
2771 if (!tcp_any_retrans_done(sk
))
2772 tp
->retrans_stamp
= 0;
2774 DBGUNDO(sk
, "partial recovery");
2775 tcp_undo_cwnd_reduction(sk
, true);
2776 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2777 tcp_try_keep_open(sk
);
2783 /* Process an event, which can update packets-in-flight not trivially.
2784 * Main goal of this function is to calculate new estimate for left_out,
2785 * taking into account both packets sitting in receiver's buffer and
2786 * packets lost by network.
2788 * Besides that it updates the congestion state when packet loss or ECN
2789 * is detected. But it does not reduce the cwnd, it is done by the
2790 * congestion control later.
2792 * It does _not_ decide what to send, it is made in function
2793 * tcp_xmit_retransmit_queue().
2795 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2796 bool is_dupack
, int *ack_flag
, int *rexmit
)
2798 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2799 struct tcp_sock
*tp
= tcp_sk(sk
);
2800 int fast_rexmit
= 0, flag
= *ack_flag
;
2801 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2802 (tcp_fackets_out(tp
) > tp
->reordering
));
2804 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2806 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2807 tp
->fackets_out
= 0;
2809 /* Now state machine starts.
2810 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2811 if (flag
& FLAG_ECE
)
2812 tp
->prior_ssthresh
= 0;
2814 /* B. In all the states check for reneging SACKs. */
2815 if (tcp_check_sack_reneging(sk
, flag
))
2818 /* C. Check consistency of the current state. */
2819 tcp_verify_left_out(tp
);
2821 /* D. Check state exit conditions. State can be terminated
2822 * when high_seq is ACKed. */
2823 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2824 WARN_ON(tp
->retrans_out
!= 0);
2825 tp
->retrans_stamp
= 0;
2826 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2827 switch (icsk
->icsk_ca_state
) {
2829 /* CWR is to be held something *above* high_seq
2830 * is ACKed for CWR bit to reach receiver. */
2831 if (tp
->snd_una
!= tp
->high_seq
) {
2832 tcp_end_cwnd_reduction(sk
);
2833 tcp_set_ca_state(sk
, TCP_CA_Open
);
2837 case TCP_CA_Recovery
:
2838 if (tcp_is_reno(tp
))
2839 tcp_reset_reno_sack(tp
);
2840 if (tcp_try_undo_recovery(sk
))
2842 tcp_end_cwnd_reduction(sk
);
2847 /* Use RACK to detect loss */
2848 if (sysctl_tcp_recovery
& TCP_RACK_LOST_RETRANS
&&
2849 tcp_rack_mark_lost(sk
)) {
2850 flag
|= FLAG_LOST_RETRANS
;
2851 *ack_flag
|= FLAG_LOST_RETRANS
;
2854 /* E. Process state. */
2855 switch (icsk
->icsk_ca_state
) {
2856 case TCP_CA_Recovery
:
2857 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2858 if (tcp_is_reno(tp
) && is_dupack
)
2859 tcp_add_reno_sack(sk
);
2861 if (tcp_try_undo_partial(sk
, acked
))
2863 /* Partial ACK arrived. Force fast retransmit. */
2864 do_lost
= tcp_is_reno(tp
) ||
2865 tcp_fackets_out(tp
) > tp
->reordering
;
2867 if (tcp_try_undo_dsack(sk
)) {
2868 tcp_try_keep_open(sk
);
2873 tcp_process_loss(sk
, flag
, is_dupack
, rexmit
);
2874 if (icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2875 !(flag
& FLAG_LOST_RETRANS
))
2877 /* Change state if cwnd is undone or retransmits are lost */
2879 if (tcp_is_reno(tp
)) {
2880 if (flag
& FLAG_SND_UNA_ADVANCED
)
2881 tcp_reset_reno_sack(tp
);
2883 tcp_add_reno_sack(sk
);
2886 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2887 tcp_try_undo_dsack(sk
);
2889 if (!tcp_time_to_recover(sk
, flag
)) {
2890 tcp_try_to_open(sk
, flag
);
2894 /* MTU probe failure: don't reduce cwnd */
2895 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2896 icsk
->icsk_mtup
.probe_size
&&
2897 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2898 tcp_mtup_probe_failed(sk
);
2899 /* Restores the reduction we did in tcp_mtup_probe() */
2901 tcp_simple_retransmit(sk
);
2905 /* Otherwise enter Recovery state */
2906 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2911 tcp_update_scoreboard(sk
, fast_rexmit
);
2912 *rexmit
= REXMIT_LOST
;
2915 static void tcp_update_rtt_min(struct sock
*sk
, u32 rtt_us
)
2917 struct tcp_sock
*tp
= tcp_sk(sk
);
2918 u32 wlen
= sysctl_tcp_min_rtt_wlen
* HZ
;
2920 minmax_running_min(&tp
->rtt_min
, wlen
, tcp_time_stamp
,
2921 rtt_us
? : jiffies_to_usecs(1));
2924 static inline bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2925 long seq_rtt_us
, long sack_rtt_us
,
2928 const struct tcp_sock
*tp
= tcp_sk(sk
);
2930 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2931 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2932 * Karn's algorithm forbids taking RTT if some retransmitted data
2933 * is acked (RFC6298).
2936 seq_rtt_us
= sack_rtt_us
;
2938 /* RTTM Rule: A TSecr value received in a segment is used to
2939 * update the averaged RTT measurement only if the segment
2940 * acknowledges some new data, i.e., only if it advances the
2941 * left edge of the send window.
2942 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2944 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2946 seq_rtt_us
= ca_rtt_us
= jiffies_to_usecs(tcp_time_stamp
-
2947 tp
->rx_opt
.rcv_tsecr
);
2951 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
2952 * always taken together with ACK, SACK, or TS-opts. Any negative
2953 * values will be skipped with the seq_rtt_us < 0 check above.
2955 tcp_update_rtt_min(sk
, ca_rtt_us
);
2956 tcp_rtt_estimator(sk
, seq_rtt_us
);
2959 /* RFC6298: only reset backoff on valid RTT measurement. */
2960 inet_csk(sk
)->icsk_backoff
= 0;
2964 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2965 void tcp_synack_rtt_meas(struct sock
*sk
, struct request_sock
*req
)
2969 if (req
&& !req
->num_retrans
&& tcp_rsk(req
)->snt_synack
.v64
) {
2970 struct skb_mstamp now
;
2972 skb_mstamp_get(&now
);
2973 rtt_us
= skb_mstamp_us_delta(&now
, &tcp_rsk(req
)->snt_synack
);
2976 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, rtt_us
, -1L, rtt_us
);
2980 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2982 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2984 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2985 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2988 /* Restart timer after forward progress on connection.
2989 * RFC2988 recommends to restart timer to now+rto.
2991 void tcp_rearm_rto(struct sock
*sk
)
2993 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2994 struct tcp_sock
*tp
= tcp_sk(sk
);
2996 /* If the retrans timer is currently being used by Fast Open
2997 * for SYN-ACK retrans purpose, stay put.
2999 if (tp
->fastopen_rsk
)
3002 if (!tp
->packets_out
) {
3003 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3005 u32 rto
= inet_csk(sk
)->icsk_rto
;
3006 /* Offset the time elapsed after installing regular RTO */
3007 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3008 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
3009 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
3010 const u32 rto_time_stamp
=
3011 tcp_skb_timestamp(skb
) + rto
;
3012 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
3013 /* delta may not be positive if the socket is locked
3014 * when the retrans timer fires and is rescheduled.
3019 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
3024 /* This function is called when the delayed ER timer fires. TCP enters
3025 * fast recovery and performs fast-retransmit.
3027 void tcp_resume_early_retransmit(struct sock
*sk
)
3029 struct tcp_sock
*tp
= tcp_sk(sk
);
3033 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3034 if (!tp
->do_early_retrans
)
3037 tcp_enter_recovery(sk
, false);
3038 tcp_update_scoreboard(sk
, 1);
3039 tcp_xmit_retransmit_queue(sk
);
3042 /* If we get here, the whole TSO packet has not been acked. */
3043 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3045 struct tcp_sock
*tp
= tcp_sk(sk
);
3048 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3050 packets_acked
= tcp_skb_pcount(skb
);
3051 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3053 packets_acked
-= tcp_skb_pcount(skb
);
3055 if (packets_acked
) {
3056 BUG_ON(tcp_skb_pcount(skb
) == 0);
3057 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3060 return packets_acked
;
3063 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3066 const struct skb_shared_info
*shinfo
;
3068 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3069 if (likely(!TCP_SKB_CB(skb
)->txstamp_ack
))
3072 shinfo
= skb_shinfo(skb
);
3073 if (!before(shinfo
->tskey
, prior_snd_una
) &&
3074 before(shinfo
->tskey
, tcp_sk(sk
)->snd_una
))
3075 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3078 /* Remove acknowledged frames from the retransmission queue. If our packet
3079 * is before the ack sequence we can discard it as it's confirmed to have
3080 * arrived at the other end.
3082 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3083 u32 prior_snd_una
, int *acked
,
3084 struct tcp_sacktag_state
*sack
,
3085 struct skb_mstamp
*now
)
3087 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3088 struct skb_mstamp first_ackt
, last_ackt
;
3089 struct tcp_sock
*tp
= tcp_sk(sk
);
3090 u32 prior_sacked
= tp
->sacked_out
;
3091 u32 reord
= tp
->packets_out
;
3092 bool fully_acked
= true;
3093 long sack_rtt_us
= -1L;
3094 long seq_rtt_us
= -1L;
3095 long ca_rtt_us
= -1L;
3096 struct sk_buff
*skb
;
3098 u32 last_in_flight
= 0;
3104 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3105 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3106 u8 sacked
= scb
->sacked
;
3109 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3111 /* Determine how many packets and what bytes were acked, tso and else */
3112 if (after(scb
->end_seq
, tp
->snd_una
)) {
3113 if (tcp_skb_pcount(skb
) == 1 ||
3114 !after(tp
->snd_una
, scb
->seq
))
3117 acked_pcount
= tcp_tso_acked(sk
, skb
);
3120 fully_acked
= false;
3122 /* Speedup tcp_unlink_write_queue() and next loop */
3123 prefetchw(skb
->next
);
3124 acked_pcount
= tcp_skb_pcount(skb
);
3127 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3128 if (sacked
& TCPCB_SACKED_RETRANS
)
3129 tp
->retrans_out
-= acked_pcount
;
3130 flag
|= FLAG_RETRANS_DATA_ACKED
;
3131 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3132 last_ackt
= skb
->skb_mstamp
;
3133 WARN_ON_ONCE(last_ackt
.v64
== 0);
3134 if (!first_ackt
.v64
)
3135 first_ackt
= last_ackt
;
3137 last_in_flight
= TCP_SKB_CB(skb
)->tx
.in_flight
;
3138 reord
= min(pkts_acked
, reord
);
3139 if (!after(scb
->end_seq
, tp
->high_seq
))
3140 flag
|= FLAG_ORIG_SACK_ACKED
;
3143 if (sacked
& TCPCB_SACKED_ACKED
) {
3144 tp
->sacked_out
-= acked_pcount
;
3145 } else if (tcp_is_sack(tp
)) {
3146 tp
->delivered
+= acked_pcount
;
3147 if (!tcp_skb_spurious_retrans(tp
, skb
))
3148 tcp_rack_advance(tp
, &skb
->skb_mstamp
, sacked
);
3150 if (sacked
& TCPCB_LOST
)
3151 tp
->lost_out
-= acked_pcount
;
3153 tp
->packets_out
-= acked_pcount
;
3154 pkts_acked
+= acked_pcount
;
3155 tcp_rate_skb_delivered(sk
, skb
, sack
->rate
);
3157 /* Initial outgoing SYN's get put onto the write_queue
3158 * just like anything else we transmit. It is not
3159 * true data, and if we misinform our callers that
3160 * this ACK acks real data, we will erroneously exit
3161 * connection startup slow start one packet too
3162 * quickly. This is severely frowned upon behavior.
3164 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3165 flag
|= FLAG_DATA_ACKED
;
3167 flag
|= FLAG_SYN_ACKED
;
3168 tp
->retrans_stamp
= 0;
3174 tcp_unlink_write_queue(skb
, sk
);
3175 sk_wmem_free_skb(sk
, skb
);
3176 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3177 tp
->retransmit_skb_hint
= NULL
;
3178 if (unlikely(skb
== tp
->lost_skb_hint
))
3179 tp
->lost_skb_hint
= NULL
;
3183 tcp_chrono_stop(sk
, TCP_CHRONO_BUSY
);
3185 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3186 tp
->snd_up
= tp
->snd_una
;
3188 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3189 flag
|= FLAG_SACK_RENEGING
;
3191 if (likely(first_ackt
.v64
) && !(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3192 seq_rtt_us
= skb_mstamp_us_delta(now
, &first_ackt
);
3193 ca_rtt_us
= skb_mstamp_us_delta(now
, &last_ackt
);
3195 if (sack
->first_sackt
.v64
) {
3196 sack_rtt_us
= skb_mstamp_us_delta(now
, &sack
->first_sackt
);
3197 ca_rtt_us
= skb_mstamp_us_delta(now
, &sack
->last_sackt
);
3199 sack
->rate
->rtt_us
= ca_rtt_us
; /* RTT of last (S)ACKed packet, or -1 */
3200 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
,
3203 if (flag
& FLAG_ACKED
) {
3205 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3206 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3207 tcp_mtup_probe_success(sk
);
3210 if (tcp_is_reno(tp
)) {
3211 tcp_remove_reno_sacks(sk
, pkts_acked
);
3215 /* Non-retransmitted hole got filled? That's reordering */
3216 if (reord
< prior_fackets
)
3217 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3219 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3220 prior_sacked
- tp
->sacked_out
;
3221 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3224 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3226 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3227 sack_rtt_us
> skb_mstamp_us_delta(now
, &skb
->skb_mstamp
)) {
3228 /* Do not re-arm RTO if the sack RTT is measured from data sent
3229 * after when the head was last (re)transmitted. Otherwise the
3230 * timeout may continue to extend in loss recovery.
3235 if (icsk
->icsk_ca_ops
->pkts_acked
) {
3236 struct ack_sample sample
= { .pkts_acked
= pkts_acked
,
3237 .rtt_us
= ca_rtt_us
,
3238 .in_flight
= last_in_flight
};
3240 icsk
->icsk_ca_ops
->pkts_acked(sk
, &sample
);
3243 #if FASTRETRANS_DEBUG > 0
3244 WARN_ON((int)tp
->sacked_out
< 0);
3245 WARN_ON((int)tp
->lost_out
< 0);
3246 WARN_ON((int)tp
->retrans_out
< 0);
3247 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3248 icsk
= inet_csk(sk
);
3250 pr_debug("Leak l=%u %d\n",
3251 tp
->lost_out
, icsk
->icsk_ca_state
);
3254 if (tp
->sacked_out
) {
3255 pr_debug("Leak s=%u %d\n",
3256 tp
->sacked_out
, icsk
->icsk_ca_state
);
3259 if (tp
->retrans_out
) {
3260 pr_debug("Leak r=%u %d\n",
3261 tp
->retrans_out
, icsk
->icsk_ca_state
);
3262 tp
->retrans_out
= 0;
3266 *acked
= pkts_acked
;
3270 static void tcp_ack_probe(struct sock
*sk
)
3272 const struct tcp_sock
*tp
= tcp_sk(sk
);
3273 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3275 /* Was it a usable window open? */
3277 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3278 icsk
->icsk_backoff
= 0;
3279 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3280 /* Socket must be waked up by subsequent tcp_data_snd_check().
3281 * This function is not for random using!
3284 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3286 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3291 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3293 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3294 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3297 /* Decide wheather to run the increase function of congestion control. */
3298 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3300 /* If reordering is high then always grow cwnd whenever data is
3301 * delivered regardless of its ordering. Otherwise stay conservative
3302 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3303 * new SACK or ECE mark may first advance cwnd here and later reduce
3304 * cwnd in tcp_fastretrans_alert() based on more states.
3306 if (tcp_sk(sk
)->reordering
> sock_net(sk
)->ipv4
.sysctl_tcp_reordering
)
3307 return flag
& FLAG_FORWARD_PROGRESS
;
3309 return flag
& FLAG_DATA_ACKED
;
3312 /* The "ultimate" congestion control function that aims to replace the rigid
3313 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3314 * It's called toward the end of processing an ACK with precise rate
3315 * information. All transmission or retransmission are delayed afterwards.
3317 static void tcp_cong_control(struct sock
*sk
, u32 ack
, u32 acked_sacked
,
3318 int flag
, const struct rate_sample
*rs
)
3320 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3322 if (icsk
->icsk_ca_ops
->cong_control
) {
3323 icsk
->icsk_ca_ops
->cong_control(sk
, rs
);
3327 if (tcp_in_cwnd_reduction(sk
)) {
3328 /* Reduce cwnd if state mandates */
3329 tcp_cwnd_reduction(sk
, acked_sacked
, flag
);
3330 } else if (tcp_may_raise_cwnd(sk
, flag
)) {
3331 /* Advance cwnd if state allows */
3332 tcp_cong_avoid(sk
, ack
, acked_sacked
);
3334 tcp_update_pacing_rate(sk
);
3337 /* Check that window update is acceptable.
3338 * The function assumes that snd_una<=ack<=snd_next.
3340 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3341 const u32 ack
, const u32 ack_seq
,
3344 return after(ack
, tp
->snd_una
) ||
3345 after(ack_seq
, tp
->snd_wl1
) ||
3346 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3349 /* If we update tp->snd_una, also update tp->bytes_acked */
3350 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3352 u32 delta
= ack
- tp
->snd_una
;
3354 sock_owned_by_me((struct sock
*)tp
);
3355 tp
->bytes_acked
+= delta
;
3359 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3360 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3362 u32 delta
= seq
- tp
->rcv_nxt
;
3364 sock_owned_by_me((struct sock
*)tp
);
3365 tp
->bytes_received
+= delta
;
3369 /* Update our send window.
3371 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3372 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3374 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3377 struct tcp_sock
*tp
= tcp_sk(sk
);
3379 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3381 if (likely(!tcp_hdr(skb
)->syn
))
3382 nwin
<<= tp
->rx_opt
.snd_wscale
;
3384 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3385 flag
|= FLAG_WIN_UPDATE
;
3386 tcp_update_wl(tp
, ack_seq
);
3388 if (tp
->snd_wnd
!= nwin
) {
3391 /* Note, it is the only place, where
3392 * fast path is recovered for sending TCP.
3395 tcp_fast_path_check(sk
);
3397 if (tcp_send_head(sk
))
3398 tcp_slow_start_after_idle_check(sk
);
3400 if (nwin
> tp
->max_window
) {
3401 tp
->max_window
= nwin
;
3402 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3407 tcp_snd_una_update(tp
, ack
);
3412 static bool __tcp_oow_rate_limited(struct net
*net
, int mib_idx
,
3413 u32
*last_oow_ack_time
)
3415 if (*last_oow_ack_time
) {
3416 s32 elapsed
= (s32
)(tcp_time_stamp
- *last_oow_ack_time
);
3418 if (0 <= elapsed
&& elapsed
< sysctl_tcp_invalid_ratelimit
) {
3419 NET_INC_STATS(net
, mib_idx
);
3420 return true; /* rate-limited: don't send yet! */
3424 *last_oow_ack_time
= tcp_time_stamp
;
3426 return false; /* not rate-limited: go ahead, send dupack now! */
3429 /* Return true if we're currently rate-limiting out-of-window ACKs and
3430 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3431 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3432 * attacks that send repeated SYNs or ACKs for the same connection. To
3433 * do this, we do not send a duplicate SYNACK or ACK if the remote
3434 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3436 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3437 int mib_idx
, u32
*last_oow_ack_time
)
3439 /* Data packets without SYNs are not likely part of an ACK loop. */
3440 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3444 return __tcp_oow_rate_limited(net
, mib_idx
, last_oow_ack_time
);
3447 /* RFC 5961 7 [ACK Throttling] */
3448 static void tcp_send_challenge_ack(struct sock
*sk
, const struct sk_buff
*skb
)
3450 /* unprotected vars, we dont care of overwrites */
3451 static u32 challenge_timestamp
;
3452 static unsigned int challenge_count
;
3453 struct tcp_sock
*tp
= tcp_sk(sk
);
3456 /* First check our per-socket dupack rate limit. */
3457 if (__tcp_oow_rate_limited(sock_net(sk
),
3458 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3459 &tp
->last_oow_ack_time
))
3462 /* Then check host-wide RFC 5961 rate limit. */
3464 if (now
!= challenge_timestamp
) {
3465 u32 half
= (sysctl_tcp_challenge_ack_limit
+ 1) >> 1;
3467 challenge_timestamp
= now
;
3468 WRITE_ONCE(challenge_count
, half
+
3469 prandom_u32_max(sysctl_tcp_challenge_ack_limit
));
3471 count
= READ_ONCE(challenge_count
);
3473 WRITE_ONCE(challenge_count
, count
- 1);
3474 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3479 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3481 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3482 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3485 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3487 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3488 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3489 * extra check below makes sure this can only happen
3490 * for pure ACK frames. -DaveM
3492 * Not only, also it occurs for expired timestamps.
3495 if (tcp_paws_check(&tp
->rx_opt
, 0))
3496 tcp_store_ts_recent(tp
);
3500 /* This routine deals with acks during a TLP episode.
3501 * We mark the end of a TLP episode on receiving TLP dupack or when
3502 * ack is after tlp_high_seq.
3503 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3505 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3507 struct tcp_sock
*tp
= tcp_sk(sk
);
3509 if (before(ack
, tp
->tlp_high_seq
))
3512 if (flag
& FLAG_DSACKING_ACK
) {
3513 /* This DSACK means original and TLP probe arrived; no loss */
3514 tp
->tlp_high_seq
= 0;
3515 } else if (after(ack
, tp
->tlp_high_seq
)) {
3516 /* ACK advances: there was a loss, so reduce cwnd. Reset
3517 * tlp_high_seq in tcp_init_cwnd_reduction()
3519 tcp_init_cwnd_reduction(sk
);
3520 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3521 tcp_end_cwnd_reduction(sk
);
3522 tcp_try_keep_open(sk
);
3523 NET_INC_STATS(sock_net(sk
),
3524 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3525 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3526 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3527 /* Pure dupack: original and TLP probe arrived; no loss */
3528 tp
->tlp_high_seq
= 0;
3532 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3534 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3536 if (icsk
->icsk_ca_ops
->in_ack_event
)
3537 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3540 /* Congestion control has updated the cwnd already. So if we're in
3541 * loss recovery then now we do any new sends (for FRTO) or
3542 * retransmits (for CA_Loss or CA_recovery) that make sense.
3544 static void tcp_xmit_recovery(struct sock
*sk
, int rexmit
)
3546 struct tcp_sock
*tp
= tcp_sk(sk
);
3548 if (rexmit
== REXMIT_NONE
)
3551 if (unlikely(rexmit
== 2)) {
3552 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
3554 if (after(tp
->snd_nxt
, tp
->high_seq
))
3558 tcp_xmit_retransmit_queue(sk
);
3561 /* This routine deals with incoming acks, but not outgoing ones. */
3562 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3564 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3565 struct tcp_sock
*tp
= tcp_sk(sk
);
3566 struct tcp_sacktag_state sack_state
;
3567 struct rate_sample rs
= { .prior_delivered
= 0 };
3568 u32 prior_snd_una
= tp
->snd_una
;
3569 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3570 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3571 bool is_dupack
= false;
3573 int prior_packets
= tp
->packets_out
;
3574 u32 delivered
= tp
->delivered
;
3575 u32 lost
= tp
->lost
;
3576 int acked
= 0; /* Number of packets newly acked */
3577 int rexmit
= REXMIT_NONE
; /* Flag to (re)transmit to recover losses */
3578 struct skb_mstamp now
;
3580 sack_state
.first_sackt
.v64
= 0;
3581 sack_state
.rate
= &rs
;
3583 /* We very likely will need to access write queue head. */
3584 prefetchw(sk
->sk_write_queue
.next
);
3586 /* If the ack is older than previous acks
3587 * then we can probably ignore it.
3589 if (before(ack
, prior_snd_una
)) {
3590 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3591 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3592 tcp_send_challenge_ack(sk
, skb
);
3598 /* If the ack includes data we haven't sent yet, discard
3599 * this segment (RFC793 Section 3.9).
3601 if (after(ack
, tp
->snd_nxt
))
3604 skb_mstamp_get(&now
);
3606 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3607 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3610 if (after(ack
, prior_snd_una
)) {
3611 flag
|= FLAG_SND_UNA_ADVANCED
;
3612 icsk
->icsk_retransmits
= 0;
3615 prior_fackets
= tp
->fackets_out
;
3616 rs
.prior_in_flight
= tcp_packets_in_flight(tp
);
3618 /* ts_recent update must be made after we are sure that the packet
3621 if (flag
& FLAG_UPDATE_TS_RECENT
)
3622 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3624 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3625 /* Window is constant, pure forward advance.
3626 * No more checks are required.
3627 * Note, we use the fact that SND.UNA>=SND.WL2.
3629 tcp_update_wl(tp
, ack_seq
);
3630 tcp_snd_una_update(tp
, ack
);
3631 flag
|= FLAG_WIN_UPDATE
;
3633 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3635 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3637 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3639 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3642 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3644 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3646 if (TCP_SKB_CB(skb
)->sacked
)
3647 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3650 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3652 ack_ev_flags
|= CA_ACK_ECE
;
3655 if (flag
& FLAG_WIN_UPDATE
)
3656 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3658 tcp_in_ack_event(sk
, ack_ev_flags
);
3661 /* We passed data and got it acked, remove any soft error
3662 * log. Something worked...
3664 sk
->sk_err_soft
= 0;
3665 icsk
->icsk_probes_out
= 0;
3666 tp
->rcv_tstamp
= tcp_time_stamp
;
3670 /* See if we can take anything off of the retransmit queue. */
3671 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
, &acked
,
3674 if (tcp_ack_is_dubious(sk
, flag
)) {
3675 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3676 tcp_fastretrans_alert(sk
, acked
, is_dupack
, &flag
, &rexmit
);
3678 if (tp
->tlp_high_seq
)
3679 tcp_process_tlp_ack(sk
, ack
, flag
);
3681 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3682 struct dst_entry
*dst
= __sk_dst_get(sk
);
3687 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3688 tcp_schedule_loss_probe(sk
);
3689 delivered
= tp
->delivered
- delivered
; /* freshly ACKed or SACKed */
3690 lost
= tp
->lost
- lost
; /* freshly marked lost */
3691 tcp_rate_gen(sk
, delivered
, lost
, &now
, &rs
);
3692 tcp_cong_control(sk
, ack
, delivered
, flag
, &rs
);
3693 tcp_xmit_recovery(sk
, rexmit
);
3697 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3698 if (flag
& FLAG_DSACKING_ACK
)
3699 tcp_fastretrans_alert(sk
, acked
, is_dupack
, &flag
, &rexmit
);
3700 /* If this ack opens up a zero window, clear backoff. It was
3701 * being used to time the probes, and is probably far higher than
3702 * it needs to be for normal retransmission.
3704 if (tcp_send_head(sk
))
3707 if (tp
->tlp_high_seq
)
3708 tcp_process_tlp_ack(sk
, ack
, flag
);
3712 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3716 /* If data was SACKed, tag it and see if we should send more data.
3717 * If data was DSACKed, see if we can undo a cwnd reduction.
3719 if (TCP_SKB_CB(skb
)->sacked
) {
3720 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3722 tcp_fastretrans_alert(sk
, acked
, is_dupack
, &flag
, &rexmit
);
3723 tcp_xmit_recovery(sk
, rexmit
);
3726 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3730 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
3731 bool syn
, struct tcp_fastopen_cookie
*foc
,
3734 /* Valid only in SYN or SYN-ACK with an even length. */
3735 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
3738 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3739 len
<= TCP_FASTOPEN_COOKIE_MAX
)
3740 memcpy(foc
->val
, cookie
, len
);
3747 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3748 * But, this can also be called on packets in the established flow when
3749 * the fast version below fails.
3751 void tcp_parse_options(const struct sk_buff
*skb
,
3752 struct tcp_options_received
*opt_rx
, int estab
,
3753 struct tcp_fastopen_cookie
*foc
)
3755 const unsigned char *ptr
;
3756 const struct tcphdr
*th
= tcp_hdr(skb
);
3757 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3759 ptr
= (const unsigned char *)(th
+ 1);
3760 opt_rx
->saw_tstamp
= 0;
3762 while (length
> 0) {
3763 int opcode
= *ptr
++;
3769 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3774 if (opsize
< 2) /* "silly options" */
3776 if (opsize
> length
)
3777 return; /* don't parse partial options */
3780 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3781 u16 in_mss
= get_unaligned_be16(ptr
);
3783 if (opt_rx
->user_mss
&&
3784 opt_rx
->user_mss
< in_mss
)
3785 in_mss
= opt_rx
->user_mss
;
3786 opt_rx
->mss_clamp
= in_mss
;
3791 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3792 !estab
&& sysctl_tcp_window_scaling
) {
3793 __u8 snd_wscale
= *(__u8
*)ptr
;
3794 opt_rx
->wscale_ok
= 1;
3795 if (snd_wscale
> 14) {
3796 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3801 opt_rx
->snd_wscale
= snd_wscale
;
3804 case TCPOPT_TIMESTAMP
:
3805 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3806 ((estab
&& opt_rx
->tstamp_ok
) ||
3807 (!estab
&& sysctl_tcp_timestamps
))) {
3808 opt_rx
->saw_tstamp
= 1;
3809 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3810 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3813 case TCPOPT_SACK_PERM
:
3814 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3815 !estab
&& sysctl_tcp_sack
) {
3816 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3817 tcp_sack_reset(opt_rx
);
3822 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3823 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3825 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3828 #ifdef CONFIG_TCP_MD5SIG
3831 * The MD5 Hash has already been
3832 * checked (see tcp_v{4,6}_do_rcv()).
3836 case TCPOPT_FASTOPEN
:
3837 tcp_parse_fastopen_option(
3838 opsize
- TCPOLEN_FASTOPEN_BASE
,
3839 ptr
, th
->syn
, foc
, false);
3843 /* Fast Open option shares code 254 using a
3844 * 16 bits magic number.
3846 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
3847 get_unaligned_be16(ptr
) ==
3848 TCPOPT_FASTOPEN_MAGIC
)
3849 tcp_parse_fastopen_option(opsize
-
3850 TCPOLEN_EXP_FASTOPEN_BASE
,
3851 ptr
+ 2, th
->syn
, foc
, true);
3860 EXPORT_SYMBOL(tcp_parse_options
);
3862 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3864 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3866 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3867 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3868 tp
->rx_opt
.saw_tstamp
= 1;
3870 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3873 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3875 tp
->rx_opt
.rcv_tsecr
= 0;
3881 /* Fast parse options. This hopes to only see timestamps.
3882 * If it is wrong it falls back on tcp_parse_options().
3884 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3885 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3887 /* In the spirit of fast parsing, compare doff directly to constant
3888 * values. Because equality is used, short doff can be ignored here.
3890 if (th
->doff
== (sizeof(*th
) / 4)) {
3891 tp
->rx_opt
.saw_tstamp
= 0;
3893 } else if (tp
->rx_opt
.tstamp_ok
&&
3894 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3895 if (tcp_parse_aligned_timestamp(tp
, th
))
3899 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3900 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3901 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3906 #ifdef CONFIG_TCP_MD5SIG
3908 * Parse MD5 Signature option
3910 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3912 int length
= (th
->doff
<< 2) - sizeof(*th
);
3913 const u8
*ptr
= (const u8
*)(th
+ 1);
3915 /* If the TCP option is too short, we can short cut */
3916 if (length
< TCPOLEN_MD5SIG
)
3919 while (length
> 0) {
3920 int opcode
= *ptr
++;
3931 if (opsize
< 2 || opsize
> length
)
3933 if (opcode
== TCPOPT_MD5SIG
)
3934 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3941 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3944 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3946 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3947 * it can pass through stack. So, the following predicate verifies that
3948 * this segment is not used for anything but congestion avoidance or
3949 * fast retransmit. Moreover, we even are able to eliminate most of such
3950 * second order effects, if we apply some small "replay" window (~RTO)
3951 * to timestamp space.
3953 * All these measures still do not guarantee that we reject wrapped ACKs
3954 * on networks with high bandwidth, when sequence space is recycled fastly,
3955 * but it guarantees that such events will be very rare and do not affect
3956 * connection seriously. This doesn't look nice, but alas, PAWS is really
3959 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3960 * states that events when retransmit arrives after original data are rare.
3961 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3962 * the biggest problem on large power networks even with minor reordering.
3963 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3964 * up to bandwidth of 18Gigabit/sec. 8) ]
3967 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3969 const struct tcp_sock
*tp
= tcp_sk(sk
);
3970 const struct tcphdr
*th
= tcp_hdr(skb
);
3971 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3972 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3974 return (/* 1. Pure ACK with correct sequence number. */
3975 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3977 /* 2. ... and duplicate ACK. */
3978 ack
== tp
->snd_una
&&
3980 /* 3. ... and does not update window. */
3981 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3983 /* 4. ... and sits in replay window. */
3984 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3987 static inline bool tcp_paws_discard(const struct sock
*sk
,
3988 const struct sk_buff
*skb
)
3990 const struct tcp_sock
*tp
= tcp_sk(sk
);
3992 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3993 !tcp_disordered_ack(sk
, skb
);
3996 /* Check segment sequence number for validity.
3998 * Segment controls are considered valid, if the segment
3999 * fits to the window after truncation to the window. Acceptability
4000 * of data (and SYN, FIN, of course) is checked separately.
4001 * See tcp_data_queue(), for example.
4003 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4004 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4005 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4006 * (borrowed from freebsd)
4009 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4011 return !before(end_seq
, tp
->rcv_wup
) &&
4012 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4015 /* When we get a reset we do this. */
4016 void tcp_reset(struct sock
*sk
)
4018 /* We want the right error as BSD sees it (and indeed as we do). */
4019 switch (sk
->sk_state
) {
4021 sk
->sk_err
= ECONNREFUSED
;
4023 case TCP_CLOSE_WAIT
:
4029 sk
->sk_err
= ECONNRESET
;
4031 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4034 if (!sock_flag(sk
, SOCK_DEAD
))
4035 sk
->sk_error_report(sk
);
4041 * Process the FIN bit. This now behaves as it is supposed to work
4042 * and the FIN takes effect when it is validly part of sequence
4043 * space. Not before when we get holes.
4045 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4046 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4049 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4050 * close and we go into CLOSING (and later onto TIME-WAIT)
4052 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4054 void tcp_fin(struct sock
*sk
)
4056 struct tcp_sock
*tp
= tcp_sk(sk
);
4058 inet_csk_schedule_ack(sk
);
4060 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4061 sock_set_flag(sk
, SOCK_DONE
);
4063 switch (sk
->sk_state
) {
4065 case TCP_ESTABLISHED
:
4066 /* Move to CLOSE_WAIT */
4067 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4068 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4071 case TCP_CLOSE_WAIT
:
4073 /* Received a retransmission of the FIN, do
4078 /* RFC793: Remain in the LAST-ACK state. */
4082 /* This case occurs when a simultaneous close
4083 * happens, we must ack the received FIN and
4084 * enter the CLOSING state.
4087 tcp_set_state(sk
, TCP_CLOSING
);
4090 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4092 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4095 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4096 * cases we should never reach this piece of code.
4098 pr_err("%s: Impossible, sk->sk_state=%d\n",
4099 __func__
, sk
->sk_state
);
4103 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4104 * Probably, we should reset in this case. For now drop them.
4106 skb_rbtree_purge(&tp
->out_of_order_queue
);
4107 if (tcp_is_sack(tp
))
4108 tcp_sack_reset(&tp
->rx_opt
);
4111 if (!sock_flag(sk
, SOCK_DEAD
)) {
4112 sk
->sk_state_change(sk
);
4114 /* Do not send POLL_HUP for half duplex close. */
4115 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4116 sk
->sk_state
== TCP_CLOSE
)
4117 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4119 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4123 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4126 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4127 if (before(seq
, sp
->start_seq
))
4128 sp
->start_seq
= seq
;
4129 if (after(end_seq
, sp
->end_seq
))
4130 sp
->end_seq
= end_seq
;
4136 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4138 struct tcp_sock
*tp
= tcp_sk(sk
);
4140 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4143 if (before(seq
, tp
->rcv_nxt
))
4144 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4146 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4148 NET_INC_STATS(sock_net(sk
), mib_idx
);
4150 tp
->rx_opt
.dsack
= 1;
4151 tp
->duplicate_sack
[0].start_seq
= seq
;
4152 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4156 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4158 struct tcp_sock
*tp
= tcp_sk(sk
);
4160 if (!tp
->rx_opt
.dsack
)
4161 tcp_dsack_set(sk
, seq
, end_seq
);
4163 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4166 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4168 struct tcp_sock
*tp
= tcp_sk(sk
);
4170 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4171 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4172 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4173 tcp_enter_quickack_mode(sk
);
4175 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4176 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4178 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4179 end_seq
= tp
->rcv_nxt
;
4180 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4187 /* These routines update the SACK block as out-of-order packets arrive or
4188 * in-order packets close up the sequence space.
4190 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4193 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4194 struct tcp_sack_block
*swalk
= sp
+ 1;
4196 /* See if the recent change to the first SACK eats into
4197 * or hits the sequence space of other SACK blocks, if so coalesce.
4199 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4200 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4203 /* Zap SWALK, by moving every further SACK up by one slot.
4204 * Decrease num_sacks.
4206 tp
->rx_opt
.num_sacks
--;
4207 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4211 this_sack
++, swalk
++;
4215 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4217 struct tcp_sock
*tp
= tcp_sk(sk
);
4218 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4219 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4225 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4226 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4227 /* Rotate this_sack to the first one. */
4228 for (; this_sack
> 0; this_sack
--, sp
--)
4229 swap(*sp
, *(sp
- 1));
4231 tcp_sack_maybe_coalesce(tp
);
4236 /* Could not find an adjacent existing SACK, build a new one,
4237 * put it at the front, and shift everyone else down. We
4238 * always know there is at least one SACK present already here.
4240 * If the sack array is full, forget about the last one.
4242 if (this_sack
>= TCP_NUM_SACKS
) {
4244 tp
->rx_opt
.num_sacks
--;
4247 for (; this_sack
> 0; this_sack
--, sp
--)
4251 /* Build the new head SACK, and we're done. */
4252 sp
->start_seq
= seq
;
4253 sp
->end_seq
= end_seq
;
4254 tp
->rx_opt
.num_sacks
++;
4257 /* RCV.NXT advances, some SACKs should be eaten. */
4259 static void tcp_sack_remove(struct tcp_sock
*tp
)
4261 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4262 int num_sacks
= tp
->rx_opt
.num_sacks
;
4265 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4266 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4267 tp
->rx_opt
.num_sacks
= 0;
4271 for (this_sack
= 0; this_sack
< num_sacks
;) {
4272 /* Check if the start of the sack is covered by RCV.NXT. */
4273 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4276 /* RCV.NXT must cover all the block! */
4277 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4279 /* Zap this SACK, by moving forward any other SACKS. */
4280 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4281 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4288 tp
->rx_opt
.num_sacks
= num_sacks
;
4292 * tcp_try_coalesce - try to merge skb to prior one
4295 * @from: buffer to add in queue
4296 * @fragstolen: pointer to boolean
4298 * Before queueing skb @from after @to, try to merge them
4299 * to reduce overall memory use and queue lengths, if cost is small.
4300 * Packets in ofo or receive queues can stay a long time.
4301 * Better try to coalesce them right now to avoid future collapses.
4302 * Returns true if caller should free @from instead of queueing it
4304 static bool tcp_try_coalesce(struct sock
*sk
,
4306 struct sk_buff
*from
,
4311 *fragstolen
= false;
4313 /* Its possible this segment overlaps with prior segment in queue */
4314 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4317 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4320 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4321 sk_mem_charge(sk
, delta
);
4322 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4323 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4324 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4325 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4329 static void tcp_drop(struct sock
*sk
, struct sk_buff
*skb
)
4331 sk_drops_add(sk
, skb
);
4335 /* This one checks to see if we can put data from the
4336 * out_of_order queue into the receive_queue.
4338 static void tcp_ofo_queue(struct sock
*sk
)
4340 struct tcp_sock
*tp
= tcp_sk(sk
);
4341 __u32 dsack_high
= tp
->rcv_nxt
;
4342 bool fin
, fragstolen
, eaten
;
4343 struct sk_buff
*skb
, *tail
;
4346 p
= rb_first(&tp
->out_of_order_queue
);
4348 skb
= rb_entry(p
, struct sk_buff
, rbnode
);
4349 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4352 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4353 __u32 dsack
= dsack_high
;
4354 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4355 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4356 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4359 rb_erase(&skb
->rbnode
, &tp
->out_of_order_queue
);
4361 if (unlikely(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))) {
4362 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4366 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4367 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4368 TCP_SKB_CB(skb
)->end_seq
);
4370 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4371 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4372 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4373 fin
= TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
;
4375 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4377 kfree_skb_partial(skb
, fragstolen
);
4379 if (unlikely(fin
)) {
4381 /* tcp_fin() purges tp->out_of_order_queue,
4382 * so we must end this loop right now.
4389 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4390 static int tcp_prune_queue(struct sock
*sk
);
4392 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4395 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4396 !sk_rmem_schedule(sk
, skb
, size
)) {
4398 if (tcp_prune_queue(sk
) < 0)
4401 while (!sk_rmem_schedule(sk
, skb
, size
)) {
4402 if (!tcp_prune_ofo_queue(sk
))
4409 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4411 struct tcp_sock
*tp
= tcp_sk(sk
);
4412 struct rb_node
**p
, *q
, *parent
;
4413 struct sk_buff
*skb1
;
4417 tcp_ecn_check_ce(tp
, skb
);
4419 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4420 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4425 /* Disable header prediction. */
4427 inet_csk_schedule_ack(sk
);
4429 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4430 seq
= TCP_SKB_CB(skb
)->seq
;
4431 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4432 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4433 tp
->rcv_nxt
, seq
, end_seq
);
4435 p
= &tp
->out_of_order_queue
.rb_node
;
4436 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4437 /* Initial out of order segment, build 1 SACK. */
4438 if (tcp_is_sack(tp
)) {
4439 tp
->rx_opt
.num_sacks
= 1;
4440 tp
->selective_acks
[0].start_seq
= seq
;
4441 tp
->selective_acks
[0].end_seq
= end_seq
;
4443 rb_link_node(&skb
->rbnode
, NULL
, p
);
4444 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4445 tp
->ooo_last_skb
= skb
;
4449 /* In the typical case, we are adding an skb to the end of the list.
4450 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4452 if (tcp_try_coalesce(sk
, tp
->ooo_last_skb
, skb
, &fragstolen
)) {
4454 tcp_grow_window(sk
, skb
);
4455 kfree_skb_partial(skb
, fragstolen
);
4459 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4460 if (!before(seq
, TCP_SKB_CB(tp
->ooo_last_skb
)->end_seq
)) {
4461 parent
= &tp
->ooo_last_skb
->rbnode
;
4462 p
= &parent
->rb_right
;
4466 /* Find place to insert this segment. Handle overlaps on the way. */
4470 skb1
= rb_entry(parent
, struct sk_buff
, rbnode
);
4471 if (before(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4472 p
= &parent
->rb_left
;
4475 if (before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4476 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4477 /* All the bits are present. Drop. */
4478 NET_INC_STATS(sock_net(sk
),
4479 LINUX_MIB_TCPOFOMERGE
);
4482 tcp_dsack_set(sk
, seq
, end_seq
);
4485 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4486 /* Partial overlap. */
4487 tcp_dsack_set(sk
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
4489 /* skb's seq == skb1's seq and skb covers skb1.
4490 * Replace skb1 with skb.
4492 rb_replace_node(&skb1
->rbnode
, &skb
->rbnode
,
4493 &tp
->out_of_order_queue
);
4494 tcp_dsack_extend(sk
,
4495 TCP_SKB_CB(skb1
)->seq
,
4496 TCP_SKB_CB(skb1
)->end_seq
);
4497 NET_INC_STATS(sock_net(sk
),
4498 LINUX_MIB_TCPOFOMERGE
);
4502 } else if (tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4505 p
= &parent
->rb_right
;
4508 /* Insert segment into RB tree. */
4509 rb_link_node(&skb
->rbnode
, parent
, p
);
4510 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4513 /* Remove other segments covered by skb. */
4514 while ((q
= rb_next(&skb
->rbnode
)) != NULL
) {
4515 skb1
= rb_entry(q
, struct sk_buff
, rbnode
);
4517 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4519 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4520 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4524 rb_erase(&skb1
->rbnode
, &tp
->out_of_order_queue
);
4525 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4526 TCP_SKB_CB(skb1
)->end_seq
);
4527 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4530 /* If there is no skb after us, we are the last_skb ! */
4532 tp
->ooo_last_skb
= skb
;
4535 if (tcp_is_sack(tp
))
4536 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4539 tcp_grow_window(sk
, skb
);
4540 skb_set_owner_r(skb
, sk
);
4544 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4548 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4550 __skb_pull(skb
, hdrlen
);
4552 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4553 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
4555 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4556 skb_set_owner_r(skb
, sk
);
4561 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4563 struct sk_buff
*skb
;
4571 if (size
> PAGE_SIZE
) {
4572 int npages
= min_t(size_t, size
>> PAGE_SHIFT
, MAX_SKB_FRAGS
);
4574 data_len
= npages
<< PAGE_SHIFT
;
4575 size
= data_len
+ (size
& ~PAGE_MASK
);
4577 skb
= alloc_skb_with_frags(size
- data_len
, data_len
,
4578 PAGE_ALLOC_COSTLY_ORDER
,
4579 &err
, sk
->sk_allocation
);
4583 skb_put(skb
, size
- data_len
);
4584 skb
->data_len
= data_len
;
4587 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4590 err
= skb_copy_datagram_from_iter(skb
, 0, &msg
->msg_iter
, size
);
4594 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4595 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4596 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4598 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4599 WARN_ON_ONCE(fragstolen
); /* should not happen */
4611 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4613 struct tcp_sock
*tp
= tcp_sk(sk
);
4614 bool fragstolen
= false;
4617 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
) {
4622 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4624 tcp_ecn_accept_cwr(tp
, skb
);
4626 tp
->rx_opt
.dsack
= 0;
4628 /* Queue data for delivery to the user.
4629 * Packets in sequence go to the receive queue.
4630 * Out of sequence packets to the out_of_order_queue.
4632 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4633 if (tcp_receive_window(tp
) == 0)
4636 /* Ok. In sequence. In window. */
4637 if (tp
->ucopy
.task
== current
&&
4638 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4639 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4640 int chunk
= min_t(unsigned int, skb
->len
,
4643 __set_current_state(TASK_RUNNING
);
4645 if (!skb_copy_datagram_msg(skb
, 0, tp
->ucopy
.msg
, chunk
)) {
4646 tp
->ucopy
.len
-= chunk
;
4647 tp
->copied_seq
+= chunk
;
4648 eaten
= (chunk
== skb
->len
);
4649 tcp_rcv_space_adjust(sk
);
4656 if (skb_queue_len(&sk
->sk_receive_queue
) == 0)
4657 sk_forced_mem_schedule(sk
, skb
->truesize
);
4658 else if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4661 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4663 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4665 tcp_event_data_recv(sk
, skb
);
4666 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4669 if (!RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4672 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4673 * gap in queue is filled.
4675 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
4676 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4679 if (tp
->rx_opt
.num_sacks
)
4680 tcp_sack_remove(tp
);
4682 tcp_fast_path_check(sk
);
4685 kfree_skb_partial(skb
, fragstolen
);
4686 if (!sock_flag(sk
, SOCK_DEAD
))
4687 sk
->sk_data_ready(sk
);
4691 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4692 /* A retransmit, 2nd most common case. Force an immediate ack. */
4693 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4694 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4697 tcp_enter_quickack_mode(sk
);
4698 inet_csk_schedule_ack(sk
);
4704 /* Out of window. F.e. zero window probe. */
4705 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4708 tcp_enter_quickack_mode(sk
);
4710 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4711 /* Partial packet, seq < rcv_next < end_seq */
4712 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4713 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4714 TCP_SKB_CB(skb
)->end_seq
);
4716 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4718 /* If window is closed, drop tail of packet. But after
4719 * remembering D-SACK for its head made in previous line.
4721 if (!tcp_receive_window(tp
))
4726 tcp_data_queue_ofo(sk
, skb
);
4729 static struct sk_buff
*tcp_skb_next(struct sk_buff
*skb
, struct sk_buff_head
*list
)
4732 return !skb_queue_is_last(list
, skb
) ? skb
->next
: NULL
;
4734 return rb_entry_safe(rb_next(&skb
->rbnode
), struct sk_buff
, rbnode
);
4737 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4738 struct sk_buff_head
*list
,
4739 struct rb_root
*root
)
4741 struct sk_buff
*next
= tcp_skb_next(skb
, list
);
4744 __skb_unlink(skb
, list
);
4746 rb_erase(&skb
->rbnode
, root
);
4749 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4754 /* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
4755 static void tcp_rbtree_insert(struct rb_root
*root
, struct sk_buff
*skb
)
4757 struct rb_node
**p
= &root
->rb_node
;
4758 struct rb_node
*parent
= NULL
;
4759 struct sk_buff
*skb1
;
4763 skb1
= rb_entry(parent
, struct sk_buff
, rbnode
);
4764 if (before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb1
)->seq
))
4765 p
= &parent
->rb_left
;
4767 p
= &parent
->rb_right
;
4769 rb_link_node(&skb
->rbnode
, parent
, p
);
4770 rb_insert_color(&skb
->rbnode
, root
);
4773 /* Collapse contiguous sequence of skbs head..tail with
4774 * sequence numbers start..end.
4776 * If tail is NULL, this means until the end of the queue.
4778 * Segments with FIN/SYN are not collapsed (only because this
4782 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
, struct rb_root
*root
,
4783 struct sk_buff
*head
, struct sk_buff
*tail
, u32 start
, u32 end
)
4785 struct sk_buff
*skb
= head
, *n
;
4786 struct sk_buff_head tmp
;
4789 /* First, check that queue is collapsible and find
4790 * the point where collapsing can be useful.
4793 for (end_of_skbs
= true; skb
!= NULL
&& skb
!= tail
; skb
= n
) {
4794 n
= tcp_skb_next(skb
, list
);
4796 /* No new bits? It is possible on ofo queue. */
4797 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4798 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
4804 /* The first skb to collapse is:
4806 * - bloated or contains data before "start" or
4807 * overlaps to the next one.
4809 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4810 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4811 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4812 end_of_skbs
= false;
4816 if (n
&& n
!= tail
&&
4817 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(n
)->seq
) {
4818 end_of_skbs
= false;
4822 /* Decided to skip this, advance start seq. */
4823 start
= TCP_SKB_CB(skb
)->end_seq
;
4826 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4829 __skb_queue_head_init(&tmp
);
4831 while (before(start
, end
)) {
4832 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4833 struct sk_buff
*nskb
;
4835 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4839 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4840 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4842 __skb_queue_before(list
, skb
, nskb
);
4844 __skb_queue_tail(&tmp
, nskb
); /* defer rbtree insertion */
4845 skb_set_owner_r(nskb
, sk
);
4847 /* Copy data, releasing collapsed skbs. */
4849 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4850 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4854 size
= min(copy
, size
);
4855 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4857 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4861 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4862 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
4865 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4871 skb_queue_walk_safe(&tmp
, skb
, n
)
4872 tcp_rbtree_insert(root
, skb
);
4875 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4876 * and tcp_collapse() them until all the queue is collapsed.
4878 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4880 struct tcp_sock
*tp
= tcp_sk(sk
);
4881 struct sk_buff
*skb
, *head
;
4885 p
= rb_first(&tp
->out_of_order_queue
);
4886 skb
= rb_entry_safe(p
, struct sk_buff
, rbnode
);
4889 p
= rb_last(&tp
->out_of_order_queue
);
4890 /* Note: This is possible p is NULL here. We do not
4891 * use rb_entry_safe(), as ooo_last_skb is valid only
4892 * if rbtree is not empty.
4894 tp
->ooo_last_skb
= rb_entry(p
, struct sk_buff
, rbnode
);
4897 start
= TCP_SKB_CB(skb
)->seq
;
4898 end
= TCP_SKB_CB(skb
)->end_seq
;
4900 for (head
= skb
;;) {
4901 skb
= tcp_skb_next(skb
, NULL
);
4903 /* Range is terminated when we see a gap or when
4904 * we are at the queue end.
4907 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4908 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4909 tcp_collapse(sk
, NULL
, &tp
->out_of_order_queue
,
4910 head
, skb
, start
, end
);
4914 if (unlikely(before(TCP_SKB_CB(skb
)->seq
, start
)))
4915 start
= TCP_SKB_CB(skb
)->seq
;
4916 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4917 end
= TCP_SKB_CB(skb
)->end_seq
;
4922 * Clean the out-of-order queue to make room.
4923 * We drop high sequences packets to :
4924 * 1) Let a chance for holes to be filled.
4925 * 2) not add too big latencies if thousands of packets sit there.
4926 * (But if application shrinks SO_RCVBUF, we could still end up
4927 * freeing whole queue here)
4929 * Return true if queue has shrunk.
4931 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4933 struct tcp_sock
*tp
= tcp_sk(sk
);
4934 struct rb_node
*node
, *prev
;
4936 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
4939 NET_INC_STATS(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4940 node
= &tp
->ooo_last_skb
->rbnode
;
4942 prev
= rb_prev(node
);
4943 rb_erase(node
, &tp
->out_of_order_queue
);
4944 tcp_drop(sk
, rb_entry(node
, struct sk_buff
, rbnode
));
4946 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
&&
4947 !tcp_under_memory_pressure(sk
))
4951 tp
->ooo_last_skb
= rb_entry(prev
, struct sk_buff
, rbnode
);
4953 /* Reset SACK state. A conforming SACK implementation will
4954 * do the same at a timeout based retransmit. When a connection
4955 * is in a sad state like this, we care only about integrity
4956 * of the connection not performance.
4958 if (tp
->rx_opt
.sack_ok
)
4959 tcp_sack_reset(&tp
->rx_opt
);
4963 /* Reduce allocated memory if we can, trying to get
4964 * the socket within its memory limits again.
4966 * Return less than zero if we should start dropping frames
4967 * until the socket owning process reads some of the data
4968 * to stabilize the situation.
4970 static int tcp_prune_queue(struct sock
*sk
)
4972 struct tcp_sock
*tp
= tcp_sk(sk
);
4974 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4976 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4978 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4979 tcp_clamp_window(sk
);
4980 else if (tcp_under_memory_pressure(sk
))
4981 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4983 tcp_collapse_ofo_queue(sk
);
4984 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4985 tcp_collapse(sk
, &sk
->sk_receive_queue
, NULL
,
4986 skb_peek(&sk
->sk_receive_queue
),
4988 tp
->copied_seq
, tp
->rcv_nxt
);
4991 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4994 /* Collapsing did not help, destructive actions follow.
4995 * This must not ever occur. */
4997 tcp_prune_ofo_queue(sk
);
4999 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5002 /* If we are really being abused, tell the caller to silently
5003 * drop receive data on the floor. It will get retransmitted
5004 * and hopefully then we'll have sufficient space.
5006 NET_INC_STATS(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
5008 /* Massive buffer overcommit. */
5013 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
5015 const struct tcp_sock
*tp
= tcp_sk(sk
);
5017 /* If the user specified a specific send buffer setting, do
5020 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
5023 /* If we are under global TCP memory pressure, do not expand. */
5024 if (tcp_under_memory_pressure(sk
))
5027 /* If we are under soft global TCP memory pressure, do not expand. */
5028 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
5031 /* If we filled the congestion window, do not expand. */
5032 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
5038 /* When incoming ACK allowed to free some skb from write_queue,
5039 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
5040 * on the exit from tcp input handler.
5042 * PROBLEM: sndbuf expansion does not work well with largesend.
5044 static void tcp_new_space(struct sock
*sk
)
5046 struct tcp_sock
*tp
= tcp_sk(sk
);
5048 if (tcp_should_expand_sndbuf(sk
)) {
5049 tcp_sndbuf_expand(sk
);
5050 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
5053 sk
->sk_write_space(sk
);
5056 static void tcp_check_space(struct sock
*sk
)
5058 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
5059 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
5060 /* pairs with tcp_poll() */
5061 smp_mb__after_atomic();
5062 if (sk
->sk_socket
&&
5063 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
5065 if (!test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
5066 tcp_chrono_stop(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
5071 static inline void tcp_data_snd_check(struct sock
*sk
)
5073 tcp_push_pending_frames(sk
);
5074 tcp_check_space(sk
);
5078 * Check if sending an ack is needed.
5080 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5082 struct tcp_sock
*tp
= tcp_sk(sk
);
5084 /* More than one full frame received... */
5085 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5086 /* ... and right edge of window advances far enough.
5087 * (tcp_recvmsg() will send ACK otherwise). Or...
5089 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
5090 /* We ACK each frame or... */
5091 tcp_in_quickack_mode(sk
) ||
5092 /* We have out of order data. */
5093 (ofo_possible
&& !RB_EMPTY_ROOT(&tp
->out_of_order_queue
))) {
5094 /* Then ack it now */
5097 /* Else, send delayed ack. */
5098 tcp_send_delayed_ack(sk
);
5102 static inline void tcp_ack_snd_check(struct sock
*sk
)
5104 if (!inet_csk_ack_scheduled(sk
)) {
5105 /* We sent a data segment already. */
5108 __tcp_ack_snd_check(sk
, 1);
5112 * This routine is only called when we have urgent data
5113 * signaled. Its the 'slow' part of tcp_urg. It could be
5114 * moved inline now as tcp_urg is only called from one
5115 * place. We handle URGent data wrong. We have to - as
5116 * BSD still doesn't use the correction from RFC961.
5117 * For 1003.1g we should support a new option TCP_STDURG to permit
5118 * either form (or just set the sysctl tcp_stdurg).
5121 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5123 struct tcp_sock
*tp
= tcp_sk(sk
);
5124 u32 ptr
= ntohs(th
->urg_ptr
);
5126 if (ptr
&& !sysctl_tcp_stdurg
)
5128 ptr
+= ntohl(th
->seq
);
5130 /* Ignore urgent data that we've already seen and read. */
5131 if (after(tp
->copied_seq
, ptr
))
5134 /* Do not replay urg ptr.
5136 * NOTE: interesting situation not covered by specs.
5137 * Misbehaving sender may send urg ptr, pointing to segment,
5138 * which we already have in ofo queue. We are not able to fetch
5139 * such data and will stay in TCP_URG_NOTYET until will be eaten
5140 * by recvmsg(). Seems, we are not obliged to handle such wicked
5141 * situations. But it is worth to think about possibility of some
5142 * DoSes using some hypothetical application level deadlock.
5144 if (before(ptr
, tp
->rcv_nxt
))
5147 /* Do we already have a newer (or duplicate) urgent pointer? */
5148 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5151 /* Tell the world about our new urgent pointer. */
5154 /* We may be adding urgent data when the last byte read was
5155 * urgent. To do this requires some care. We cannot just ignore
5156 * tp->copied_seq since we would read the last urgent byte again
5157 * as data, nor can we alter copied_seq until this data arrives
5158 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5160 * NOTE. Double Dutch. Rendering to plain English: author of comment
5161 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5162 * and expect that both A and B disappear from stream. This is _wrong_.
5163 * Though this happens in BSD with high probability, this is occasional.
5164 * Any application relying on this is buggy. Note also, that fix "works"
5165 * only in this artificial test. Insert some normal data between A and B and we will
5166 * decline of BSD again. Verdict: it is better to remove to trap
5169 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5170 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5171 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5173 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5174 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5179 tp
->urg_data
= TCP_URG_NOTYET
;
5182 /* Disable header prediction. */
5186 /* This is the 'fast' part of urgent handling. */
5187 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5189 struct tcp_sock
*tp
= tcp_sk(sk
);
5191 /* Check if we get a new urgent pointer - normally not. */
5193 tcp_check_urg(sk
, th
);
5195 /* Do we wait for any urgent data? - normally not... */
5196 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5197 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5200 /* Is the urgent pointer pointing into this packet? */
5201 if (ptr
< skb
->len
) {
5203 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5205 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5206 if (!sock_flag(sk
, SOCK_DEAD
))
5207 sk
->sk_data_ready(sk
);
5212 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5214 struct tcp_sock
*tp
= tcp_sk(sk
);
5215 int chunk
= skb
->len
- hlen
;
5218 if (skb_csum_unnecessary(skb
))
5219 err
= skb_copy_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
, chunk
);
5221 err
= skb_copy_and_csum_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
);
5224 tp
->ucopy
.len
-= chunk
;
5225 tp
->copied_seq
+= chunk
;
5226 tcp_rcv_space_adjust(sk
);
5232 /* Does PAWS and seqno based validation of an incoming segment, flags will
5233 * play significant role here.
5235 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5236 const struct tcphdr
*th
, int syn_inerr
)
5238 struct tcp_sock
*tp
= tcp_sk(sk
);
5239 bool rst_seq_match
= false;
5241 /* RFC1323: H1. Apply PAWS check first. */
5242 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5243 tcp_paws_discard(sk
, skb
)) {
5245 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5246 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5247 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5248 &tp
->last_oow_ack_time
))
5249 tcp_send_dupack(sk
, skb
);
5252 /* Reset is accepted even if it did not pass PAWS. */
5255 /* Step 1: check sequence number */
5256 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5257 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5258 * (RST) segments are validated by checking their SEQ-fields."
5259 * And page 69: "If an incoming segment is not acceptable,
5260 * an acknowledgment should be sent in reply (unless the RST
5261 * bit is set, if so drop the segment and return)".
5266 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5267 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5268 &tp
->last_oow_ack_time
))
5269 tcp_send_dupack(sk
, skb
);
5274 /* Step 2: check RST bit */
5276 /* RFC 5961 3.2 (extend to match against SACK too if available):
5277 * If seq num matches RCV.NXT or the right-most SACK block,
5279 * RESET the connection
5281 * Send a challenge ACK
5283 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
5284 rst_seq_match
= true;
5285 } else if (tcp_is_sack(tp
) && tp
->rx_opt
.num_sacks
> 0) {
5286 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
5287 int max_sack
= sp
[0].end_seq
;
5290 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;
5292 max_sack
= after(sp
[this_sack
].end_seq
,
5294 sp
[this_sack
].end_seq
: max_sack
;
5297 if (TCP_SKB_CB(skb
)->seq
== max_sack
)
5298 rst_seq_match
= true;
5304 tcp_send_challenge_ack(sk
, skb
);
5308 /* step 3: check security and precedence [ignored] */
5310 /* step 4: Check for a SYN
5311 * RFC 5961 4.2 : Send a challenge ack
5316 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5317 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5318 tcp_send_challenge_ack(sk
, skb
);
5330 * TCP receive function for the ESTABLISHED state.
5332 * It is split into a fast path and a slow path. The fast path is
5334 * - A zero window was announced from us - zero window probing
5335 * is only handled properly in the slow path.
5336 * - Out of order segments arrived.
5337 * - Urgent data is expected.
5338 * - There is no buffer space left
5339 * - Unexpected TCP flags/window values/header lengths are received
5340 * (detected by checking the TCP header against pred_flags)
5341 * - Data is sent in both directions. Fast path only supports pure senders
5342 * or pure receivers (this means either the sequence number or the ack
5343 * value must stay constant)
5344 * - Unexpected TCP option.
5346 * When these conditions are not satisfied it drops into a standard
5347 * receive procedure patterned after RFC793 to handle all cases.
5348 * The first three cases are guaranteed by proper pred_flags setting,
5349 * the rest is checked inline. Fast processing is turned on in
5350 * tcp_data_queue when everything is OK.
5352 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5353 const struct tcphdr
*th
, unsigned int len
)
5355 struct tcp_sock
*tp
= tcp_sk(sk
);
5357 if (unlikely(!sk
->sk_rx_dst
))
5358 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5360 * Header prediction.
5361 * The code loosely follows the one in the famous
5362 * "30 instruction TCP receive" Van Jacobson mail.
5364 * Van's trick is to deposit buffers into socket queue
5365 * on a device interrupt, to call tcp_recv function
5366 * on the receive process context and checksum and copy
5367 * the buffer to user space. smart...
5369 * Our current scheme is not silly either but we take the
5370 * extra cost of the net_bh soft interrupt processing...
5371 * We do checksum and copy also but from device to kernel.
5374 tp
->rx_opt
.saw_tstamp
= 0;
5376 /* pred_flags is 0xS?10 << 16 + snd_wnd
5377 * if header_prediction is to be made
5378 * 'S' will always be tp->tcp_header_len >> 2
5379 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5380 * turn it off (when there are holes in the receive
5381 * space for instance)
5382 * PSH flag is ignored.
5385 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5386 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5387 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5388 int tcp_header_len
= tp
->tcp_header_len
;
5390 /* Timestamp header prediction: tcp_header_len
5391 * is automatically equal to th->doff*4 due to pred_flags
5395 /* Check timestamp */
5396 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5397 /* No? Slow path! */
5398 if (!tcp_parse_aligned_timestamp(tp
, th
))
5401 /* If PAWS failed, check it more carefully in slow path */
5402 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5405 /* DO NOT update ts_recent here, if checksum fails
5406 * and timestamp was corrupted part, it will result
5407 * in a hung connection since we will drop all
5408 * future packets due to the PAWS test.
5412 if (len
<= tcp_header_len
) {
5413 /* Bulk data transfer: sender */
5414 if (len
== tcp_header_len
) {
5415 /* Predicted packet is in window by definition.
5416 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5417 * Hence, check seq<=rcv_wup reduces to:
5419 if (tcp_header_len
==
5420 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5421 tp
->rcv_nxt
== tp
->rcv_wup
)
5422 tcp_store_ts_recent(tp
);
5424 /* We know that such packets are checksummed
5427 tcp_ack(sk
, skb
, 0);
5429 tcp_data_snd_check(sk
);
5431 } else { /* Header too small */
5432 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5437 bool fragstolen
= false;
5439 if (tp
->ucopy
.task
== current
&&
5440 tp
->copied_seq
== tp
->rcv_nxt
&&
5441 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5442 sock_owned_by_user(sk
)) {
5443 __set_current_state(TASK_RUNNING
);
5445 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5446 /* Predicted packet is in window by definition.
5447 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5448 * Hence, check seq<=rcv_wup reduces to:
5450 if (tcp_header_len
==
5451 (sizeof(struct tcphdr
) +
5452 TCPOLEN_TSTAMP_ALIGNED
) &&
5453 tp
->rcv_nxt
== tp
->rcv_wup
)
5454 tcp_store_ts_recent(tp
);
5456 tcp_rcv_rtt_measure_ts(sk
, skb
);
5458 __skb_pull(skb
, tcp_header_len
);
5459 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
5460 NET_INC_STATS(sock_net(sk
),
5461 LINUX_MIB_TCPHPHITSTOUSER
);
5466 if (tcp_checksum_complete(skb
))
5469 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5472 /* Predicted packet is in window by definition.
5473 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5474 * Hence, check seq<=rcv_wup reduces to:
5476 if (tcp_header_len
==
5477 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5478 tp
->rcv_nxt
== tp
->rcv_wup
)
5479 tcp_store_ts_recent(tp
);
5481 tcp_rcv_rtt_measure_ts(sk
, skb
);
5483 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5485 /* Bulk data transfer: receiver */
5486 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5490 tcp_event_data_recv(sk
, skb
);
5492 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5493 /* Well, only one small jumplet in fast path... */
5494 tcp_ack(sk
, skb
, FLAG_DATA
);
5495 tcp_data_snd_check(sk
);
5496 if (!inet_csk_ack_scheduled(sk
))
5500 __tcp_ack_snd_check(sk
, 0);
5503 kfree_skb_partial(skb
, fragstolen
);
5504 sk
->sk_data_ready(sk
);
5510 if (len
< (th
->doff
<< 2) || tcp_checksum_complete(skb
))
5513 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5517 * Standard slow path.
5520 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5524 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5527 tcp_rcv_rtt_measure_ts(sk
, skb
);
5529 /* Process urgent data. */
5530 tcp_urg(sk
, skb
, th
);
5532 /* step 7: process the segment text */
5533 tcp_data_queue(sk
, skb
);
5535 tcp_data_snd_check(sk
);
5536 tcp_ack_snd_check(sk
);
5540 TCP_INC_STATS(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5541 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5546 EXPORT_SYMBOL(tcp_rcv_established
);
5548 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5550 struct tcp_sock
*tp
= tcp_sk(sk
);
5551 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5553 tcp_set_state(sk
, TCP_ESTABLISHED
);
5556 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5557 security_inet_conn_established(sk
, skb
);
5560 /* Make sure socket is routed, for correct metrics. */
5561 icsk
->icsk_af_ops
->rebuild_header(sk
);
5563 tcp_init_metrics(sk
);
5565 tcp_init_congestion_control(sk
);
5567 /* Prevent spurious tcp_cwnd_restart() on first data
5570 tp
->lsndtime
= tcp_time_stamp
;
5572 tcp_init_buffer_space(sk
);
5574 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5575 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5577 if (!tp
->rx_opt
.snd_wscale
)
5578 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5582 if (!sock_flag(sk
, SOCK_DEAD
)) {
5583 sk
->sk_state_change(sk
);
5584 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5588 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5589 struct tcp_fastopen_cookie
*cookie
)
5591 struct tcp_sock
*tp
= tcp_sk(sk
);
5592 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5593 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
5594 bool syn_drop
= false;
5596 if (mss
== tp
->rx_opt
.user_mss
) {
5597 struct tcp_options_received opt
;
5599 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5600 tcp_clear_options(&opt
);
5601 opt
.user_mss
= opt
.mss_clamp
= 0;
5602 tcp_parse_options(synack
, &opt
, 0, NULL
);
5603 mss
= opt
.mss_clamp
;
5606 if (!tp
->syn_fastopen
) {
5607 /* Ignore an unsolicited cookie */
5609 } else if (tp
->total_retrans
) {
5610 /* SYN timed out and the SYN-ACK neither has a cookie nor
5611 * acknowledges data. Presumably the remote received only
5612 * the retransmitted (regular) SYNs: either the original
5613 * SYN-data or the corresponding SYN-ACK was dropped.
5615 syn_drop
= (cookie
->len
< 0 && data
);
5616 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
5617 /* We requested a cookie but didn't get it. If we did not use
5618 * the (old) exp opt format then try so next time (try_exp=1).
5619 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5621 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
5624 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
5626 if (data
) { /* Retransmit unacked data in SYN */
5627 tcp_for_write_queue_from(data
, sk
) {
5628 if (data
== tcp_send_head(sk
) ||
5629 __tcp_retransmit_skb(sk
, data
, 1))
5633 NET_INC_STATS(sock_net(sk
),
5634 LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5637 tp
->syn_data_acked
= tp
->syn_data
;
5638 if (tp
->syn_data_acked
)
5639 NET_INC_STATS(sock_net(sk
),
5640 LINUX_MIB_TCPFASTOPENACTIVE
);
5642 tcp_fastopen_add_skb(sk
, synack
);
5647 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5648 const struct tcphdr
*th
)
5650 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5651 struct tcp_sock
*tp
= tcp_sk(sk
);
5652 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5653 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5655 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5656 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5657 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5661 * "If the state is SYN-SENT then
5662 * first check the ACK bit
5663 * If the ACK bit is set
5664 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5665 * a reset (unless the RST bit is set, if so drop
5666 * the segment and return)"
5668 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5669 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5670 goto reset_and_undo
;
5672 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5673 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5675 NET_INC_STATS(sock_net(sk
),
5676 LINUX_MIB_PAWSACTIVEREJECTED
);
5677 goto reset_and_undo
;
5680 /* Now ACK is acceptable.
5682 * "If the RST bit is set
5683 * If the ACK was acceptable then signal the user "error:
5684 * connection reset", drop the segment, enter CLOSED state,
5685 * delete TCB, and return."
5694 * "fifth, if neither of the SYN or RST bits is set then
5695 * drop the segment and return."
5701 goto discard_and_undo
;
5704 * "If the SYN bit is on ...
5705 * are acceptable then ...
5706 * (our SYN has been ACKed), change the connection
5707 * state to ESTABLISHED..."
5710 tcp_ecn_rcv_synack(tp
, th
);
5712 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5713 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5715 /* Ok.. it's good. Set up sequence numbers and
5716 * move to established.
5718 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5719 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5721 /* RFC1323: The window in SYN & SYN/ACK segments is
5724 tp
->snd_wnd
= ntohs(th
->window
);
5726 if (!tp
->rx_opt
.wscale_ok
) {
5727 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5728 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5731 if (tp
->rx_opt
.saw_tstamp
) {
5732 tp
->rx_opt
.tstamp_ok
= 1;
5733 tp
->tcp_header_len
=
5734 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5735 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5736 tcp_store_ts_recent(tp
);
5738 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5741 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5742 tcp_enable_fack(tp
);
5745 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5746 tcp_initialize_rcv_mss(sk
);
5748 /* Remember, tcp_poll() does not lock socket!
5749 * Change state from SYN-SENT only after copied_seq
5750 * is initialized. */
5751 tp
->copied_seq
= tp
->rcv_nxt
;
5755 tcp_finish_connect(sk
, skb
);
5757 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5758 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5761 if (sk
->sk_write_pending
||
5762 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5763 icsk
->icsk_ack
.pingpong
) {
5764 /* Save one ACK. Data will be ready after
5765 * several ticks, if write_pending is set.
5767 * It may be deleted, but with this feature tcpdumps
5768 * look so _wonderfully_ clever, that I was not able
5769 * to stand against the temptation 8) --ANK
5771 inet_csk_schedule_ack(sk
);
5772 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5773 tcp_enter_quickack_mode(sk
);
5774 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5775 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5786 /* No ACK in the segment */
5790 * "If the RST bit is set
5792 * Otherwise (no ACK) drop the segment and return."
5795 goto discard_and_undo
;
5799 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5800 tcp_paws_reject(&tp
->rx_opt
, 0))
5801 goto discard_and_undo
;
5804 /* We see SYN without ACK. It is attempt of
5805 * simultaneous connect with crossed SYNs.
5806 * Particularly, it can be connect to self.
5808 tcp_set_state(sk
, TCP_SYN_RECV
);
5810 if (tp
->rx_opt
.saw_tstamp
) {
5811 tp
->rx_opt
.tstamp_ok
= 1;
5812 tcp_store_ts_recent(tp
);
5813 tp
->tcp_header_len
=
5814 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5816 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5819 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5820 tp
->copied_seq
= tp
->rcv_nxt
;
5821 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5823 /* RFC1323: The window in SYN & SYN/ACK segments is
5826 tp
->snd_wnd
= ntohs(th
->window
);
5827 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5828 tp
->max_window
= tp
->snd_wnd
;
5830 tcp_ecn_rcv_syn(tp
, th
);
5833 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5834 tcp_initialize_rcv_mss(sk
);
5836 tcp_send_synack(sk
);
5838 /* Note, we could accept data and URG from this segment.
5839 * There are no obstacles to make this (except that we must
5840 * either change tcp_recvmsg() to prevent it from returning data
5841 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5843 * However, if we ignore data in ACKless segments sometimes,
5844 * we have no reasons to accept it sometimes.
5845 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5846 * is not flawless. So, discard packet for sanity.
5847 * Uncomment this return to process the data.
5854 /* "fifth, if neither of the SYN or RST bits is set then
5855 * drop the segment and return."
5859 tcp_clear_options(&tp
->rx_opt
);
5860 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5864 tcp_clear_options(&tp
->rx_opt
);
5865 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5870 * This function implements the receiving procedure of RFC 793 for
5871 * all states except ESTABLISHED and TIME_WAIT.
5872 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5873 * address independent.
5876 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
)
5878 struct tcp_sock
*tp
= tcp_sk(sk
);
5879 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5880 const struct tcphdr
*th
= tcp_hdr(skb
);
5881 struct request_sock
*req
;
5885 switch (sk
->sk_state
) {
5899 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5908 tp
->rx_opt
.saw_tstamp
= 0;
5909 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
);
5913 /* Do step6 onward by hand. */
5914 tcp_urg(sk
, skb
, th
);
5916 tcp_data_snd_check(sk
);
5920 tp
->rx_opt
.saw_tstamp
= 0;
5921 req
= tp
->fastopen_rsk
;
5923 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5924 sk
->sk_state
!= TCP_FIN_WAIT1
);
5926 if (!tcp_check_req(sk
, skb
, req
, true))
5930 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5933 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5936 /* step 5: check the ACK field */
5937 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5938 FLAG_UPDATE_TS_RECENT
) > 0;
5940 switch (sk
->sk_state
) {
5946 tcp_synack_rtt_meas(sk
, req
);
5948 /* Once we leave TCP_SYN_RECV, we no longer need req
5952 inet_csk(sk
)->icsk_retransmits
= 0;
5953 reqsk_fastopen_remove(sk
, req
, false);
5955 /* Make sure socket is routed, for correct metrics. */
5956 icsk
->icsk_af_ops
->rebuild_header(sk
);
5957 tcp_init_congestion_control(sk
);
5960 tp
->copied_seq
= tp
->rcv_nxt
;
5961 tcp_init_buffer_space(sk
);
5964 tcp_set_state(sk
, TCP_ESTABLISHED
);
5965 sk
->sk_state_change(sk
);
5967 /* Note, that this wakeup is only for marginal crossed SYN case.
5968 * Passively open sockets are not waked up, because
5969 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5972 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5974 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5975 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5976 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5978 if (tp
->rx_opt
.tstamp_ok
)
5979 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5982 /* Re-arm the timer because data may have been sent out.
5983 * This is similar to the regular data transmission case
5984 * when new data has just been ack'ed.
5986 * (TFO) - we could try to be more aggressive and
5987 * retransmitting any data sooner based on when they
5992 tcp_init_metrics(sk
);
5994 if (!inet_csk(sk
)->icsk_ca_ops
->cong_control
)
5995 tcp_update_pacing_rate(sk
);
5997 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5998 tp
->lsndtime
= tcp_time_stamp
;
6000 tcp_initialize_rcv_mss(sk
);
6001 tcp_fast_path_on(tp
);
6004 case TCP_FIN_WAIT1
: {
6005 struct dst_entry
*dst
;
6008 /* If we enter the TCP_FIN_WAIT1 state and we are a
6009 * Fast Open socket and this is the first acceptable
6010 * ACK we have received, this would have acknowledged
6011 * our SYNACK so stop the SYNACK timer.
6014 /* Return RST if ack_seq is invalid.
6015 * Note that RFC793 only says to generate a
6016 * DUPACK for it but for TCP Fast Open it seems
6017 * better to treat this case like TCP_SYN_RECV
6022 /* We no longer need the request sock. */
6023 reqsk_fastopen_remove(sk
, req
, false);
6026 if (tp
->snd_una
!= tp
->write_seq
)
6029 tcp_set_state(sk
, TCP_FIN_WAIT2
);
6030 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
6032 dst
= __sk_dst_get(sk
);
6036 if (!sock_flag(sk
, SOCK_DEAD
)) {
6037 /* Wake up lingering close() */
6038 sk
->sk_state_change(sk
);
6042 if (tp
->linger2
< 0 ||
6043 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6044 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
6046 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6050 tmo
= tcp_fin_time(sk
);
6051 if (tmo
> TCP_TIMEWAIT_LEN
) {
6052 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
6053 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
6054 /* Bad case. We could lose such FIN otherwise.
6055 * It is not a big problem, but it looks confusing
6056 * and not so rare event. We still can lose it now,
6057 * if it spins in bh_lock_sock(), but it is really
6060 inet_csk_reset_keepalive_timer(sk
, tmo
);
6062 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
6069 if (tp
->snd_una
== tp
->write_seq
) {
6070 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
6076 if (tp
->snd_una
== tp
->write_seq
) {
6077 tcp_update_metrics(sk
);
6084 /* step 6: check the URG bit */
6085 tcp_urg(sk
, skb
, th
);
6087 /* step 7: process the segment text */
6088 switch (sk
->sk_state
) {
6089 case TCP_CLOSE_WAIT
:
6092 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
6096 /* RFC 793 says to queue data in these states,
6097 * RFC 1122 says we MUST send a reset.
6098 * BSD 4.4 also does reset.
6100 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
6101 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6102 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6103 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6109 case TCP_ESTABLISHED
:
6110 tcp_data_queue(sk
, skb
);
6115 /* tcp_data could move socket to TIME-WAIT */
6116 if (sk
->sk_state
!= TCP_CLOSE
) {
6117 tcp_data_snd_check(sk
);
6118 tcp_ack_snd_check(sk
);
6127 EXPORT_SYMBOL(tcp_rcv_state_process
);
6129 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
6131 struct inet_request_sock
*ireq
= inet_rsk(req
);
6133 if (family
== AF_INET
)
6134 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6135 &ireq
->ir_rmt_addr
, port
);
6136 #if IS_ENABLED(CONFIG_IPV6)
6137 else if (family
== AF_INET6
)
6138 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6139 &ireq
->ir_v6_rmt_addr
, port
);
6143 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6145 * If we receive a SYN packet with these bits set, it means a
6146 * network is playing bad games with TOS bits. In order to
6147 * avoid possible false congestion notifications, we disable
6148 * TCP ECN negotiation.
6150 * Exception: tcp_ca wants ECN. This is required for DCTCP
6151 * congestion control: Linux DCTCP asserts ECT on all packets,
6152 * including SYN, which is most optimal solution; however,
6153 * others, such as FreeBSD do not.
6155 static void tcp_ecn_create_request(struct request_sock
*req
,
6156 const struct sk_buff
*skb
,
6157 const struct sock
*listen_sk
,
6158 const struct dst_entry
*dst
)
6160 const struct tcphdr
*th
= tcp_hdr(skb
);
6161 const struct net
*net
= sock_net(listen_sk
);
6162 bool th_ecn
= th
->ece
&& th
->cwr
;
6169 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
6170 ecn_ok_dst
= dst_feature(dst
, DST_FEATURE_ECN_MASK
);
6171 ecn_ok
= net
->ipv4
.sysctl_tcp_ecn
|| ecn_ok_dst
;
6173 if ((!ect
&& ecn_ok
) || tcp_ca_needs_ecn(listen_sk
) ||
6174 (ecn_ok_dst
& DST_FEATURE_ECN_CA
))
6175 inet_rsk(req
)->ecn_ok
= 1;
6178 static void tcp_openreq_init(struct request_sock
*req
,
6179 const struct tcp_options_received
*rx_opt
,
6180 struct sk_buff
*skb
, const struct sock
*sk
)
6182 struct inet_request_sock
*ireq
= inet_rsk(req
);
6184 req
->rsk_rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6186 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6187 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6188 skb_mstamp_get(&tcp_rsk(req
)->snt_synack
);
6189 tcp_rsk(req
)->last_oow_ack_time
= 0;
6190 req
->mss
= rx_opt
->mss_clamp
;
6191 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6192 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6193 ireq
->sack_ok
= rx_opt
->sack_ok
;
6194 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6195 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6198 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6199 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6200 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6203 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6204 struct sock
*sk_listener
,
6205 bool attach_listener
)
6207 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
,
6211 struct inet_request_sock
*ireq
= inet_rsk(req
);
6213 kmemcheck_annotate_bitfield(ireq
, flags
);
6215 #if IS_ENABLED(CONFIG_IPV6)
6216 ireq
->pktopts
= NULL
;
6218 atomic64_set(&ireq
->ir_cookie
, 0);
6219 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6220 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6221 ireq
->ireq_family
= sk_listener
->sk_family
;
6226 EXPORT_SYMBOL(inet_reqsk_alloc
);
6229 * Return true if a syncookie should be sent
6231 static bool tcp_syn_flood_action(const struct sock
*sk
,
6232 const struct sk_buff
*skb
,
6235 struct request_sock_queue
*queue
= &inet_csk(sk
)->icsk_accept_queue
;
6236 const char *msg
= "Dropping request";
6237 bool want_cookie
= false;
6238 struct net
*net
= sock_net(sk
);
6240 #ifdef CONFIG_SYN_COOKIES
6241 if (net
->ipv4
.sysctl_tcp_syncookies
) {
6242 msg
= "Sending cookies";
6244 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
6247 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
6249 if (!queue
->synflood_warned
&&
6250 net
->ipv4
.sysctl_tcp_syncookies
!= 2 &&
6251 xchg(&queue
->synflood_warned
, 1) == 0)
6252 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6253 proto
, ntohs(tcp_hdr(skb
)->dest
), msg
);
6258 static void tcp_reqsk_record_syn(const struct sock
*sk
,
6259 struct request_sock
*req
,
6260 const struct sk_buff
*skb
)
6262 if (tcp_sk(sk
)->save_syn
) {
6263 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
6266 copy
= kmalloc(len
+ sizeof(u32
), GFP_ATOMIC
);
6269 memcpy(©
[1], skb_network_header(skb
), len
);
6270 req
->saved_syn
= copy
;
6275 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
6276 const struct tcp_request_sock_ops
*af_ops
,
6277 struct sock
*sk
, struct sk_buff
*skb
)
6279 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6280 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
6281 struct tcp_options_received tmp_opt
;
6282 struct tcp_sock
*tp
= tcp_sk(sk
);
6283 struct net
*net
= sock_net(sk
);
6284 struct sock
*fastopen_sk
= NULL
;
6285 struct dst_entry
*dst
= NULL
;
6286 struct request_sock
*req
;
6287 bool want_cookie
= false;
6290 /* TW buckets are converted to open requests without
6291 * limitations, they conserve resources and peer is
6292 * evidently real one.
6294 if ((net
->ipv4
.sysctl_tcp_syncookies
== 2 ||
6295 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
6296 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
6301 if (sk_acceptq_is_full(sk
)) {
6302 NET_INC_STATS(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
6306 req
= inet_reqsk_alloc(rsk_ops
, sk
, !want_cookie
);
6310 tcp_rsk(req
)->af_specific
= af_ops
;
6311 tcp_rsk(req
)->ts_off
= 0;
6313 tcp_clear_options(&tmp_opt
);
6314 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
6315 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
6316 tcp_parse_options(skb
, &tmp_opt
, 0, want_cookie
? NULL
: &foc
);
6318 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
6319 tcp_clear_options(&tmp_opt
);
6321 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
6322 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
6323 inet_rsk(req
)->no_srccheck
= inet_sk(sk
)->transparent
;
6325 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6326 inet_rsk(req
)->ir_iif
= inet_request_bound_dev_if(sk
, skb
);
6328 af_ops
->init_req(req
, sk
, skb
);
6330 if (security_inet_conn_request(sk
, skb
, req
))
6333 if (isn
&& tmp_opt
.tstamp_ok
)
6334 af_ops
->init_seq(skb
, &tcp_rsk(req
)->ts_off
);
6336 if (!want_cookie
&& !isn
) {
6337 /* VJ's idea. We save last timestamp seen
6338 * from the destination in peer table, when entering
6339 * state TIME-WAIT, and check against it before
6340 * accepting new connection request.
6342 * If "isn" is not zero, this request hit alive
6343 * timewait bucket, so that all the necessary checks
6344 * are made in the function processing timewait state.
6346 if (tcp_death_row
.sysctl_tw_recycle
) {
6349 dst
= af_ops
->route_req(sk
, &fl
, req
, &strict
);
6351 if (dst
&& strict
&&
6352 !tcp_peer_is_proven(req
, dst
, true,
6353 tmp_opt
.saw_tstamp
)) {
6354 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PAWSPASSIVEREJECTED
);
6355 goto drop_and_release
;
6358 /* Kill the following clause, if you dislike this way. */
6359 else if (!net
->ipv4
.sysctl_tcp_syncookies
&&
6360 (sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
6361 (sysctl_max_syn_backlog
>> 2)) &&
6362 !tcp_peer_is_proven(req
, dst
, false,
6363 tmp_opt
.saw_tstamp
)) {
6364 /* Without syncookies last quarter of
6365 * backlog is filled with destinations,
6366 * proven to be alive.
6367 * It means that we continue to communicate
6368 * to destinations, already remembered
6369 * to the moment of synflood.
6371 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6373 goto drop_and_release
;
6376 isn
= af_ops
->init_seq(skb
, &tcp_rsk(req
)->ts_off
);
6379 dst
= af_ops
->route_req(sk
, &fl
, req
, NULL
);
6384 tcp_ecn_create_request(req
, skb
, sk
, dst
);
6387 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
6388 tcp_rsk(req
)->ts_off
= 0;
6389 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
6390 if (!tmp_opt
.tstamp_ok
)
6391 inet_rsk(req
)->ecn_ok
= 0;
6394 tcp_rsk(req
)->snt_isn
= isn
;
6395 tcp_rsk(req
)->txhash
= net_tx_rndhash();
6396 tcp_openreq_init_rwin(req
, sk
, dst
);
6398 tcp_reqsk_record_syn(sk
, req
, skb
);
6399 fastopen_sk
= tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6402 af_ops
->send_synack(fastopen_sk
, dst
, &fl
, req
,
6403 &foc
, TCP_SYNACK_FASTOPEN
);
6404 /* Add the child socket directly into the accept queue */
6405 inet_csk_reqsk_queue_add(sk
, req
, fastopen_sk
);
6406 sk
->sk_data_ready(sk
);
6407 bh_unlock_sock(fastopen_sk
);
6408 sock_put(fastopen_sk
);
6410 tcp_rsk(req
)->tfo_listener
= false;
6412 inet_csk_reqsk_queue_hash_add(sk
, req
, TCP_TIMEOUT_INIT
);
6413 af_ops
->send_synack(sk
, dst
, &fl
, req
, &foc
,
6414 !want_cookie
? TCP_SYNACK_NORMAL
:
6432 EXPORT_SYMBOL(tcp_conn_request
);