1 // SPDX-License-Identifier: GPL-2.0
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
7 * Implementation of the Transmission Control Protocol(TCP).
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 * Florian La Roche, <flla@stud.uni-sb.de>
14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 * Matthew Dillon, <dillon@apollo.west.oic.com>
18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 * Jorge Cwik, <jorge@laser.satlink.net>
24 * Pedro Roque : Fast Retransmit/Recovery.
26 * Retransmit queue handled by TCP.
27 * Better retransmit timer handling.
28 * New congestion avoidance.
32 * Eric : Fast Retransmit.
33 * Randy Scott : MSS option defines.
34 * Eric Schenk : Fixes to slow start algorithm.
35 * Eric Schenk : Yet another double ACK bug.
36 * Eric Schenk : Delayed ACK bug fixes.
37 * Eric Schenk : Floyd style fast retrans war avoidance.
38 * David S. Miller : Don't allow zero congestion window.
39 * Eric Schenk : Fix retransmitter so that it sends
40 * next packet on ack of previous packet.
41 * Andi Kleen : Moved open_request checking here
42 * and process RSTs for open_requests.
43 * Andi Kleen : Better prune_queue, and other fixes.
44 * Andrey Savochkin: Fix RTT measurements in the presence of
46 * Andrey Savochkin: Check sequence numbers correctly when
47 * removing SACKs due to in sequence incoming
49 * Andi Kleen: Make sure we never ack data there is not
50 * enough room for. Also make this condition
51 * a fatal error if it might still happen.
52 * Andi Kleen: Add tcp_measure_rcv_mss to make
53 * connections with MSS<min(MTU,ann. MSS)
54 * work without delayed acks.
55 * Andi Kleen: Process packets with PSH set in the
57 * J Hadi Salim: ECN support
60 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
61 * engine. Lots of bugs are found.
62 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
65 #define pr_fmt(fmt) "TCP: " fmt
68 #include <linux/slab.h>
69 #include <linux/module.h>
70 #include <linux/sysctl.h>
71 #include <linux/kernel.h>
72 #include <linux/prefetch.h>
75 #include <net/inet_common.h>
76 #include <linux/ipsec.h>
77 #include <asm/unaligned.h>
78 #include <linux/errqueue.h>
79 #include <trace/events/tcp.h>
80 #include <linux/static_key.h>
82 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
84 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
85 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
86 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
87 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
88 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
89 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
90 #define FLAG_ECE 0x40 /* ECE in this ACK */
91 #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
92 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
93 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
94 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
95 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
96 #define FLAG_SET_XMIT_TIMER 0x1000 /* Set TLP or RTO timer */
97 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
98 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
99 #define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */
101 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
102 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
103 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE|FLAG_DSACKING_ACK)
104 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
106 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
107 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
109 #define REXMIT_NONE 0 /* no loss recovery to do */
110 #define REXMIT_LOST 1 /* retransmit packets marked lost */
111 #define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
113 static void tcp_gro_dev_warn(struct sock
*sk
, const struct sk_buff
*skb
,
116 static bool __once __read_mostly
;
119 struct net_device
*dev
;
124 dev
= dev_get_by_index_rcu(sock_net(sk
), skb
->skb_iif
);
125 if (!dev
|| len
>= dev
->mtu
)
126 pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
127 dev
? dev
->name
: "Unknown driver");
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
= min_t(unsigned int, len
,
150 /* Account for possibly-removed options */
151 if (unlikely(len
> icsk
->icsk_ack
.rcv_mss
+
152 MAX_TCP_OPTION_SPACE
))
153 tcp_gro_dev_warn(sk
, skb
, len
);
155 /* Otherwise, we make more careful check taking into account,
156 * that SACKs block is variable.
158 * "len" is invariant segment length, including TCP header.
160 len
+= skb
->data
- skb_transport_header(skb
);
161 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
162 /* If PSH is not set, packet should be
163 * full sized, provided peer TCP is not badly broken.
164 * This observation (if it is correct 8)) allows
165 * to handle super-low mtu links fairly.
167 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
168 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
169 /* Subtract also invariant (if peer is RFC compliant),
170 * tcp header plus fixed timestamp option length.
171 * Resulting "len" is MSS free of SACK jitter.
173 len
-= tcp_sk(sk
)->tcp_header_len
;
174 icsk
->icsk_ack
.last_seg_size
= len
;
176 icsk
->icsk_ack
.rcv_mss
= len
;
180 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
181 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
182 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
186 static void tcp_incr_quickack(struct sock
*sk
)
188 struct inet_connection_sock
*icsk
= inet_csk(sk
);
189 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
193 if (quickacks
> icsk
->icsk_ack
.quick
)
194 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
197 static void tcp_enter_quickack_mode(struct sock
*sk
)
199 struct inet_connection_sock
*icsk
= inet_csk(sk
);
200 tcp_incr_quickack(sk
);
201 icsk
->icsk_ack
.pingpong
= 0;
202 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
205 /* Send ACKs quickly, if "quick" count is not exhausted
206 * and the session is not interactive.
209 static bool tcp_in_quickack_mode(struct sock
*sk
)
211 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
212 const struct dst_entry
*dst
= __sk_dst_get(sk
);
214 return (dst
&& dst_metric(dst
, RTAX_QUICKACK
)) ||
215 (icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
);
218 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
220 if (tp
->ecn_flags
& TCP_ECN_OK
)
221 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
224 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
226 if (tcp_hdr(skb
)->cwr
)
227 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
230 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
232 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
235 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
237 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
238 case INET_ECN_NOT_ECT
:
239 /* Funny extension: if ECT is not set on a segment,
240 * and we already seen ECT on a previous segment,
241 * it is probably a retransmit.
243 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
244 tcp_enter_quickack_mode((struct sock
*)tp
);
247 if (tcp_ca_needs_ecn((struct sock
*)tp
))
248 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
250 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
251 /* Better not delay acks, sender can have a very low cwnd */
252 tcp_enter_quickack_mode((struct sock
*)tp
);
253 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
255 tp
->ecn_flags
|= TCP_ECN_SEEN
;
258 if (tcp_ca_needs_ecn((struct sock
*)tp
))
259 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
260 tp
->ecn_flags
|= TCP_ECN_SEEN
;
265 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
267 if (tp
->ecn_flags
& TCP_ECN_OK
)
268 __tcp_ecn_check_ce(tp
, skb
);
271 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
273 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
274 tp
->ecn_flags
&= ~TCP_ECN_OK
;
277 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
279 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
280 tp
->ecn_flags
&= ~TCP_ECN_OK
;
283 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
285 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
290 /* Buffer size and advertised window tuning.
292 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
295 static void tcp_sndbuf_expand(struct sock
*sk
)
297 const struct tcp_sock
*tp
= tcp_sk(sk
);
298 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
302 /* Worst case is non GSO/TSO : each frame consumes one skb
303 * and skb->head is kmalloced using power of two area of memory
305 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
307 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
309 per_mss
= roundup_pow_of_two(per_mss
) +
310 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
312 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
313 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
315 /* Fast Recovery (RFC 5681 3.2) :
316 * Cubic needs 1.7 factor, rounded to 2 to include
317 * extra cushion (application might react slowly to POLLOUT)
319 sndmem
= ca_ops
->sndbuf_expand
? ca_ops
->sndbuf_expand(sk
) : 2;
320 sndmem
*= nr_segs
* per_mss
;
322 if (sk
->sk_sndbuf
< sndmem
)
323 sk
->sk_sndbuf
= min(sndmem
, sock_net(sk
)->ipv4
.sysctl_tcp_wmem
[2]);
326 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
328 * All tcp_full_space() is split to two parts: "network" buffer, allocated
329 * forward and advertised in receiver window (tp->rcv_wnd) and
330 * "application buffer", required to isolate scheduling/application
331 * latencies from network.
332 * window_clamp is maximal advertised window. It can be less than
333 * tcp_full_space(), in this case tcp_full_space() - window_clamp
334 * is reserved for "application" buffer. The less window_clamp is
335 * the smoother our behaviour from viewpoint of network, but the lower
336 * throughput and the higher sensitivity of the connection to losses. 8)
338 * rcv_ssthresh is more strict window_clamp used at "slow start"
339 * phase to predict further behaviour of this connection.
340 * It is used for two goals:
341 * - to enforce header prediction at sender, even when application
342 * requires some significant "application buffer". It is check #1.
343 * - to prevent pruning of receive queue because of misprediction
344 * of receiver window. Check #2.
346 * The scheme does not work when sender sends good segments opening
347 * window and then starts to feed us spaghetti. But it should work
348 * in common situations. Otherwise, we have to rely on queue collapsing.
351 /* Slow part of check#2. */
352 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
354 struct tcp_sock
*tp
= tcp_sk(sk
);
356 int truesize
= tcp_win_from_space(sk
, skb
->truesize
) >> 1;
357 int window
= tcp_win_from_space(sk
, sock_net(sk
)->ipv4
.sysctl_tcp_rmem
[2]) >> 1;
359 while (tp
->rcv_ssthresh
<= window
) {
360 if (truesize
<= skb
->len
)
361 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
369 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
371 struct tcp_sock
*tp
= tcp_sk(sk
);
374 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
375 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
376 !tcp_under_memory_pressure(sk
)) {
379 /* Check #2. Increase window, if skb with such overhead
380 * will fit to rcvbuf in future.
382 if (tcp_win_from_space(sk
, skb
->truesize
) <= skb
->len
)
383 incr
= 2 * tp
->advmss
;
385 incr
= __tcp_grow_window(sk
, skb
);
388 incr
= max_t(int, incr
, 2 * skb
->len
);
389 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
391 inet_csk(sk
)->icsk_ack
.quick
|= 1;
396 /* 3. Tuning rcvbuf, when connection enters established state. */
397 static void tcp_fixup_rcvbuf(struct sock
*sk
)
399 u32 mss
= tcp_sk(sk
)->advmss
;
402 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
403 tcp_default_init_rwnd(mss
);
405 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
406 * Allow enough cushion so that sender is not limited by our window
408 if (sock_net(sk
)->ipv4
.sysctl_tcp_moderate_rcvbuf
)
411 if (sk
->sk_rcvbuf
< rcvmem
)
412 sk
->sk_rcvbuf
= min(rcvmem
, sock_net(sk
)->ipv4
.sysctl_tcp_rmem
[2]);
415 /* 4. Try to fixup all. It is made immediately after connection enters
418 void tcp_init_buffer_space(struct sock
*sk
)
420 int tcp_app_win
= sock_net(sk
)->ipv4
.sysctl_tcp_app_win
;
421 struct tcp_sock
*tp
= tcp_sk(sk
);
424 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
425 tcp_fixup_rcvbuf(sk
);
426 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
427 tcp_sndbuf_expand(sk
);
429 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
430 tcp_mstamp_refresh(tp
);
431 tp
->rcvq_space
.time
= tp
->tcp_mstamp
;
432 tp
->rcvq_space
.seq
= tp
->copied_seq
;
434 maxwin
= tcp_full_space(sk
);
436 if (tp
->window_clamp
>= maxwin
) {
437 tp
->window_clamp
= maxwin
;
439 if (tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
440 tp
->window_clamp
= max(maxwin
-
441 (maxwin
>> tcp_app_win
),
445 /* Force reservation of one segment. */
447 tp
->window_clamp
> 2 * tp
->advmss
&&
448 tp
->window_clamp
+ tp
->advmss
> maxwin
)
449 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
451 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
452 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
455 /* 5. Recalculate window clamp after socket hit its memory bounds. */
456 static void tcp_clamp_window(struct sock
*sk
)
458 struct tcp_sock
*tp
= tcp_sk(sk
);
459 struct inet_connection_sock
*icsk
= inet_csk(sk
);
460 struct net
*net
= sock_net(sk
);
462 icsk
->icsk_ack
.quick
= 0;
464 if (sk
->sk_rcvbuf
< net
->ipv4
.sysctl_tcp_rmem
[2] &&
465 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
466 !tcp_under_memory_pressure(sk
) &&
467 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
468 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
469 net
->ipv4
.sysctl_tcp_rmem
[2]);
471 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
472 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
475 /* Initialize RCV_MSS value.
476 * RCV_MSS is an our guess about MSS used by the peer.
477 * We haven't any direct information about the MSS.
478 * It's better to underestimate the RCV_MSS rather than overestimate.
479 * Overestimations make us ACKing less frequently than needed.
480 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
482 void tcp_initialize_rcv_mss(struct sock
*sk
)
484 const struct tcp_sock
*tp
= tcp_sk(sk
);
485 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
487 hint
= min(hint
, tp
->rcv_wnd
/ 2);
488 hint
= min(hint
, TCP_MSS_DEFAULT
);
489 hint
= max(hint
, TCP_MIN_MSS
);
491 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
493 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
495 /* Receiver "autotuning" code.
497 * The algorithm for RTT estimation w/o timestamps is based on
498 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
499 * <http://public.lanl.gov/radiant/pubs.html#DRS>
501 * More detail on this code can be found at
502 * <http://staff.psc.edu/jheffner/>,
503 * though this reference is out of date. A new paper
506 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
508 u32 new_sample
= tp
->rcv_rtt_est
.rtt_us
;
511 if (new_sample
!= 0) {
512 /* If we sample in larger samples in the non-timestamp
513 * case, we could grossly overestimate the RTT especially
514 * with chatty applications or bulk transfer apps which
515 * are stalled on filesystem I/O.
517 * Also, since we are only going for a minimum in the
518 * non-timestamp case, we do not smooth things out
519 * else with timestamps disabled convergence takes too
523 m
-= (new_sample
>> 3);
531 /* No previous measure. */
535 tp
->rcv_rtt_est
.rtt_us
= new_sample
;
538 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
542 if (tp
->rcv_rtt_est
.time
== 0)
544 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
546 delta_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, tp
->rcv_rtt_est
.time
);
549 tcp_rcv_rtt_update(tp
, delta_us
, 1);
552 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
553 tp
->rcv_rtt_est
.time
= tp
->tcp_mstamp
;
556 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
557 const struct sk_buff
*skb
)
559 struct tcp_sock
*tp
= tcp_sk(sk
);
561 if (tp
->rx_opt
.rcv_tsecr
&&
562 (TCP_SKB_CB(skb
)->end_seq
-
563 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
)) {
564 u32 delta
= tcp_time_stamp(tp
) - tp
->rx_opt
.rcv_tsecr
;
569 delta_us
= delta
* (USEC_PER_SEC
/ TCP_TS_HZ
);
570 tcp_rcv_rtt_update(tp
, delta_us
, 0);
575 * This function should be called every time data is copied to user space.
576 * It calculates the appropriate TCP receive buffer space.
578 void tcp_rcv_space_adjust(struct sock
*sk
)
580 struct tcp_sock
*tp
= tcp_sk(sk
);
584 tcp_mstamp_refresh(tp
);
585 time
= tcp_stamp_us_delta(tp
->tcp_mstamp
, tp
->rcvq_space
.time
);
586 if (time
< (tp
->rcv_rtt_est
.rtt_us
>> 3) || tp
->rcv_rtt_est
.rtt_us
== 0)
589 /* Number of bytes copied to user in last RTT */
590 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
591 if (copied
<= tp
->rcvq_space
.space
)
595 * copied = bytes received in previous RTT, our base window
596 * To cope with packet losses, we need a 2x factor
597 * To cope with slow start, and sender growing its cwin by 100 %
598 * every RTT, we need a 4x factor, because the ACK we are sending
599 * now is for the next RTT, not the current one :
600 * <prev RTT . ><current RTT .. ><next RTT .... >
603 if (sock_net(sk
)->ipv4
.sysctl_tcp_moderate_rcvbuf
&&
604 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
605 int rcvwin
, rcvmem
, rcvbuf
;
607 /* minimal window to cope with packet losses, assuming
608 * steady state. Add some cushion because of small variations.
610 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
612 /* If rate increased by 25%,
613 * assume slow start, rcvwin = 3 * copied
614 * If rate increased by 50%,
615 * assume sender can use 2x growth, rcvwin = 4 * copied
618 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
620 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
623 rcvwin
+= (rcvwin
>> 1);
626 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
627 while (tcp_win_from_space(sk
, rcvmem
) < tp
->advmss
)
630 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
,
631 sock_net(sk
)->ipv4
.sysctl_tcp_rmem
[2]);
632 if (rcvbuf
> sk
->sk_rcvbuf
) {
633 sk
->sk_rcvbuf
= rcvbuf
;
635 /* Make the window clamp follow along. */
636 tp
->window_clamp
= rcvwin
;
639 tp
->rcvq_space
.space
= copied
;
642 tp
->rcvq_space
.seq
= tp
->copied_seq
;
643 tp
->rcvq_space
.time
= tp
->tcp_mstamp
;
646 /* There is something which you must keep in mind when you analyze the
647 * behavior of the tp->ato delayed ack timeout interval. When a
648 * connection starts up, we want to ack as quickly as possible. The
649 * problem is that "good" TCP's do slow start at the beginning of data
650 * transmission. The means that until we send the first few ACK's the
651 * sender will sit on his end and only queue most of his data, because
652 * he can only send snd_cwnd unacked packets at any given time. For
653 * each ACK we send, he increments snd_cwnd and transmits more of his
656 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
658 struct tcp_sock
*tp
= tcp_sk(sk
);
659 struct inet_connection_sock
*icsk
= inet_csk(sk
);
662 inet_csk_schedule_ack(sk
);
664 tcp_measure_rcv_mss(sk
, skb
);
666 tcp_rcv_rtt_measure(tp
);
670 if (!icsk
->icsk_ack
.ato
) {
671 /* The _first_ data packet received, initialize
672 * delayed ACK engine.
674 tcp_incr_quickack(sk
);
675 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
677 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
679 if (m
<= TCP_ATO_MIN
/ 2) {
680 /* The fastest case is the first. */
681 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
682 } else if (m
< icsk
->icsk_ack
.ato
) {
683 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
684 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
685 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
686 } else if (m
> icsk
->icsk_rto
) {
687 /* Too long gap. Apparently sender failed to
688 * restart window, so that we send ACKs quickly.
690 tcp_incr_quickack(sk
);
694 icsk
->icsk_ack
.lrcvtime
= now
;
696 tcp_ecn_check_ce(tp
, skb
);
699 tcp_grow_window(sk
, skb
);
702 /* Called to compute a smoothed rtt estimate. The data fed to this
703 * routine either comes from timestamps, or from segments that were
704 * known _not_ to have been retransmitted [see Karn/Partridge
705 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
706 * piece by Van Jacobson.
707 * NOTE: the next three routines used to be one big routine.
708 * To save cycles in the RFC 1323 implementation it was better to break
709 * it up into three procedures. -- erics
711 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
713 struct tcp_sock
*tp
= tcp_sk(sk
);
714 long m
= mrtt_us
; /* RTT */
715 u32 srtt
= tp
->srtt_us
;
717 /* The following amusing code comes from Jacobson's
718 * article in SIGCOMM '88. Note that rtt and mdev
719 * are scaled versions of rtt and mean deviation.
720 * This is designed to be as fast as possible
721 * m stands for "measurement".
723 * On a 1990 paper the rto value is changed to:
724 * RTO = rtt + 4 * mdev
726 * Funny. This algorithm seems to be very broken.
727 * These formulae increase RTO, when it should be decreased, increase
728 * too slowly, when it should be increased quickly, decrease too quickly
729 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
730 * does not matter how to _calculate_ it. Seems, it was trap
731 * that VJ failed to avoid. 8)
734 m
-= (srtt
>> 3); /* m is now error in rtt est */
735 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
737 m
= -m
; /* m is now abs(error) */
738 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
739 /* This is similar to one of Eifel findings.
740 * Eifel blocks mdev updates when rtt decreases.
741 * This solution is a bit different: we use finer gain
742 * for mdev in this case (alpha*beta).
743 * Like Eifel it also prevents growth of rto,
744 * but also it limits too fast rto decreases,
745 * happening in pure Eifel.
750 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
752 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
753 if (tp
->mdev_us
> tp
->mdev_max_us
) {
754 tp
->mdev_max_us
= tp
->mdev_us
;
755 if (tp
->mdev_max_us
> tp
->rttvar_us
)
756 tp
->rttvar_us
= tp
->mdev_max_us
;
758 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
759 if (tp
->mdev_max_us
< tp
->rttvar_us
)
760 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
761 tp
->rtt_seq
= tp
->snd_nxt
;
762 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
765 /* no previous measure. */
766 srtt
= m
<< 3; /* take the measured time to be rtt */
767 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
768 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
769 tp
->mdev_max_us
= tp
->rttvar_us
;
770 tp
->rtt_seq
= tp
->snd_nxt
;
772 tp
->srtt_us
= max(1U, srtt
);
775 static void tcp_update_pacing_rate(struct sock
*sk
)
777 const struct tcp_sock
*tp
= tcp_sk(sk
);
780 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
781 rate
= (u64
)tp
->mss_cache
* ((USEC_PER_SEC
/ 100) << 3);
783 /* current rate is (cwnd * mss) / srtt
784 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
785 * In Congestion Avoidance phase, set it to 120 % the current rate.
787 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
788 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
789 * end of slow start and should slow down.
791 if (tp
->snd_cwnd
< tp
->snd_ssthresh
/ 2)
792 rate
*= sock_net(sk
)->ipv4
.sysctl_tcp_pacing_ss_ratio
;
794 rate
*= sock_net(sk
)->ipv4
.sysctl_tcp_pacing_ca_ratio
;
796 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
798 if (likely(tp
->srtt_us
))
799 do_div(rate
, tp
->srtt_us
);
801 /* WRITE_ONCE() is needed because sch_fq fetches sk_pacing_rate
802 * without any lock. We want to make sure compiler wont store
803 * intermediate values in this location.
805 WRITE_ONCE(sk
->sk_pacing_rate
, min_t(u64
, rate
,
806 sk
->sk_max_pacing_rate
));
809 /* Calculate rto without backoff. This is the second half of Van Jacobson's
810 * routine referred to above.
812 static void tcp_set_rto(struct sock
*sk
)
814 const struct tcp_sock
*tp
= tcp_sk(sk
);
815 /* Old crap is replaced with new one. 8)
818 * 1. If rtt variance happened to be less 50msec, it is hallucination.
819 * It cannot be less due to utterly erratic ACK generation made
820 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
821 * to do with delayed acks, because at cwnd>2 true delack timeout
822 * is invisible. Actually, Linux-2.4 also generates erratic
823 * ACKs in some circumstances.
825 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
827 /* 2. Fixups made earlier cannot be right.
828 * If we do not estimate RTO correctly without them,
829 * all the algo is pure shit and should be replaced
830 * with correct one. It is exactly, which we pretend to do.
833 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
834 * guarantees that rto is higher.
839 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
841 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
844 cwnd
= TCP_INIT_CWND
;
845 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
848 /* Take a notice that peer is sending D-SACKs */
849 static void tcp_dsack_seen(struct tcp_sock
*tp
)
851 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
852 tp
->rack
.dsack_seen
= 1;
855 /* It's reordering when higher sequence was delivered (i.e. sacked) before
856 * some lower never-retransmitted sequence ("low_seq"). The maximum reordering
857 * distance is approximated in full-mss packet distance ("reordering").
859 static void tcp_check_sack_reordering(struct sock
*sk
, const u32 low_seq
,
862 struct tcp_sock
*tp
= tcp_sk(sk
);
863 const u32 mss
= tp
->mss_cache
;
866 fack
= tcp_highest_sack_seq(tp
);
867 if (!before(low_seq
, fack
))
870 metric
= fack
- low_seq
;
871 if ((metric
> tp
->reordering
* mss
) && mss
) {
872 #if FASTRETRANS_DEBUG > 1
873 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
874 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
878 tp
->undo_marker
? tp
->undo_retrans
: 0);
880 tp
->reordering
= min_t(u32
, (metric
+ mss
- 1) / mss
,
881 sock_net(sk
)->ipv4
.sysctl_tcp_max_reordering
);
885 /* This exciting event is worth to be remembered. 8) */
886 NET_INC_STATS(sock_net(sk
),
887 ts
? LINUX_MIB_TCPTSREORDER
: LINUX_MIB_TCPSACKREORDER
);
890 /* This must be called before lost_out is incremented */
891 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
893 if (!tp
->retransmit_skb_hint
||
894 before(TCP_SKB_CB(skb
)->seq
,
895 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
896 tp
->retransmit_skb_hint
= skb
;
899 /* Sum the number of packets on the wire we have marked as lost.
900 * There are two cases we care about here:
901 * a) Packet hasn't been marked lost (nor retransmitted),
902 * and this is the first loss.
903 * b) Packet has been marked both lost and retransmitted,
904 * and this means we think it was lost again.
906 static void tcp_sum_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
908 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
910 if (!(sacked
& TCPCB_LOST
) ||
911 ((sacked
& TCPCB_LOST
) && (sacked
& TCPCB_SACKED_RETRANS
)))
912 tp
->lost
+= tcp_skb_pcount(skb
);
915 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
917 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
918 tcp_verify_retransmit_hint(tp
, skb
);
920 tp
->lost_out
+= tcp_skb_pcount(skb
);
921 tcp_sum_lost(tp
, skb
);
922 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
926 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
, struct sk_buff
*skb
)
928 tcp_verify_retransmit_hint(tp
, skb
);
930 tcp_sum_lost(tp
, skb
);
931 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
932 tp
->lost_out
+= tcp_skb_pcount(skb
);
933 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
937 /* This procedure tags the retransmission queue when SACKs arrive.
939 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
940 * Packets in queue with these bits set are counted in variables
941 * sacked_out, retrans_out and lost_out, correspondingly.
943 * Valid combinations are:
944 * Tag InFlight Description
945 * 0 1 - orig segment is in flight.
946 * S 0 - nothing flies, orig reached receiver.
947 * L 0 - nothing flies, orig lost by net.
948 * R 2 - both orig and retransmit are in flight.
949 * L|R 1 - orig is lost, retransmit is in flight.
950 * S|R 1 - orig reached receiver, retrans is still in flight.
951 * (L|S|R is logically valid, it could occur when L|R is sacked,
952 * but it is equivalent to plain S and code short-curcuits it to S.
953 * L|S is logically invalid, it would mean -1 packet in flight 8))
955 * These 6 states form finite state machine, controlled by the following events:
956 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
957 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
958 * 3. Loss detection event of two flavors:
959 * A. Scoreboard estimator decided the packet is lost.
960 * A'. Reno "three dupacks" marks head of queue lost.
961 * B. SACK arrives sacking SND.NXT at the moment, when the
962 * segment was retransmitted.
963 * 4. D-SACK added new rule: D-SACK changes any tag to S.
965 * It is pleasant to note, that state diagram turns out to be commutative,
966 * so that we are allowed not to be bothered by order of our actions,
967 * when multiple events arrive simultaneously. (see the function below).
969 * Reordering detection.
970 * --------------------
971 * Reordering metric is maximal distance, which a packet can be displaced
972 * in packet stream. With SACKs we can estimate it:
974 * 1. SACK fills old hole and the corresponding segment was not
975 * ever retransmitted -> reordering. Alas, we cannot use it
976 * when segment was retransmitted.
977 * 2. The last flaw is solved with D-SACK. D-SACK arrives
978 * for retransmitted and already SACKed segment -> reordering..
979 * Both of these heuristics are not used in Loss state, when we cannot
980 * account for retransmits accurately.
982 * SACK block validation.
983 * ----------------------
985 * SACK block range validation checks that the received SACK block fits to
986 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
987 * Note that SND.UNA is not included to the range though being valid because
988 * it means that the receiver is rather inconsistent with itself reporting
989 * SACK reneging when it should advance SND.UNA. Such SACK block this is
990 * perfectly valid, however, in light of RFC2018 which explicitly states
991 * that "SACK block MUST reflect the newest segment. Even if the newest
992 * segment is going to be discarded ...", not that it looks very clever
993 * in case of head skb. Due to potentional receiver driven attacks, we
994 * choose to avoid immediate execution of a walk in write queue due to
995 * reneging and defer head skb's loss recovery to standard loss recovery
996 * procedure that will eventually trigger (nothing forbids us doing this).
998 * Implements also blockage to start_seq wrap-around. Problem lies in the
999 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1000 * there's no guarantee that it will be before snd_nxt (n). The problem
1001 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1004 * <- outs wnd -> <- wrapzone ->
1005 * u e n u_w e_w s n_w
1007 * |<------------+------+----- TCP seqno space --------------+---------->|
1008 * ...-- <2^31 ->| |<--------...
1009 * ...---- >2^31 ------>| |<--------...
1011 * Current code wouldn't be vulnerable but it's better still to discard such
1012 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1013 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1014 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1015 * equal to the ideal case (infinite seqno space without wrap caused issues).
1017 * With D-SACK the lower bound is extended to cover sequence space below
1018 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1019 * again, D-SACK block must not to go across snd_una (for the same reason as
1020 * for the normal SACK blocks, explained above). But there all simplicity
1021 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1022 * fully below undo_marker they do not affect behavior in anyway and can
1023 * therefore be safely ignored. In rare cases (which are more or less
1024 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1025 * fragmentation and packet reordering past skb's retransmission. To consider
1026 * them correctly, the acceptable range must be extended even more though
1027 * the exact amount is rather hard to quantify. However, tp->max_window can
1028 * be used as an exaggerated estimate.
1030 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
1031 u32 start_seq
, u32 end_seq
)
1033 /* Too far in future, or reversed (interpretation is ambiguous) */
1034 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1037 /* Nasty start_seq wrap-around check (see comments above) */
1038 if (!before(start_seq
, tp
->snd_nxt
))
1041 /* In outstanding window? ...This is valid exit for D-SACKs too.
1042 * start_seq == snd_una is non-sensical (see comments above)
1044 if (after(start_seq
, tp
->snd_una
))
1047 if (!is_dsack
|| !tp
->undo_marker
)
1050 /* ...Then it's D-SACK, and must reside below snd_una completely */
1051 if (after(end_seq
, tp
->snd_una
))
1054 if (!before(start_seq
, tp
->undo_marker
))
1058 if (!after(end_seq
, tp
->undo_marker
))
1061 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1062 * start_seq < undo_marker and end_seq >= undo_marker.
1064 return !before(start_seq
, end_seq
- tp
->max_window
);
1067 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1068 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1071 struct tcp_sock
*tp
= tcp_sk(sk
);
1072 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1073 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1074 bool dup_sack
= false;
1076 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1079 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1080 } else if (num_sacks
> 1) {
1081 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1082 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1084 if (!after(end_seq_0
, end_seq_1
) &&
1085 !before(start_seq_0
, start_seq_1
)) {
1088 NET_INC_STATS(sock_net(sk
),
1089 LINUX_MIB_TCPDSACKOFORECV
);
1093 /* D-SACK for already forgotten data... Do dumb counting. */
1094 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1095 !after(end_seq_0
, prior_snd_una
) &&
1096 after(end_seq_0
, tp
->undo_marker
))
1102 struct tcp_sacktag_state
{
1104 /* Timestamps for earliest and latest never-retransmitted segment
1105 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1106 * but congestion control should still get an accurate delay signal.
1110 struct rate_sample
*rate
;
1112 unsigned int mss_now
;
1115 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1116 * the incoming SACK may not exactly match but we can find smaller MSS
1117 * aligned portion of it that matches. Therefore we might need to fragment
1118 * which may fail and creates some hassle (caller must handle error case
1121 * FIXME: this could be merged to shift decision code
1123 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1124 u32 start_seq
, u32 end_seq
)
1128 unsigned int pkt_len
;
1131 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1132 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1134 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1135 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1136 mss
= tcp_skb_mss(skb
);
1137 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1140 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1144 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1149 /* Round if necessary so that SACKs cover only full MSSes
1150 * and/or the remaining small portion (if present)
1152 if (pkt_len
> mss
) {
1153 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1154 if (!in_sack
&& new_len
< pkt_len
)
1159 if (pkt_len
>= skb
->len
&& !in_sack
)
1162 err
= tcp_fragment(sk
, TCP_FRAG_IN_RTX_QUEUE
, skb
,
1163 pkt_len
, mss
, GFP_ATOMIC
);
1171 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1172 static u8
tcp_sacktag_one(struct sock
*sk
,
1173 struct tcp_sacktag_state
*state
, u8 sacked
,
1174 u32 start_seq
, u32 end_seq
,
1175 int dup_sack
, int pcount
,
1178 struct tcp_sock
*tp
= tcp_sk(sk
);
1180 /* Account D-SACK for retransmitted packet. */
1181 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1182 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1183 after(end_seq
, tp
->undo_marker
))
1185 if ((sacked
& TCPCB_SACKED_ACKED
) &&
1186 before(start_seq
, state
->reord
))
1187 state
->reord
= start_seq
;
1190 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1191 if (!after(end_seq
, tp
->snd_una
))
1194 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1195 tcp_rack_advance(tp
, sacked
, end_seq
, xmit_time
);
1197 if (sacked
& TCPCB_SACKED_RETRANS
) {
1198 /* If the segment is not tagged as lost,
1199 * we do not clear RETRANS, believing
1200 * that retransmission is still in flight.
1202 if (sacked
& TCPCB_LOST
) {
1203 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1204 tp
->lost_out
-= pcount
;
1205 tp
->retrans_out
-= pcount
;
1208 if (!(sacked
& TCPCB_RETRANS
)) {
1209 /* New sack for not retransmitted frame,
1210 * which was in hole. It is reordering.
1212 if (before(start_seq
,
1213 tcp_highest_sack_seq(tp
)) &&
1214 before(start_seq
, state
->reord
))
1215 state
->reord
= start_seq
;
1217 if (!after(end_seq
, tp
->high_seq
))
1218 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1219 if (state
->first_sackt
== 0)
1220 state
->first_sackt
= xmit_time
;
1221 state
->last_sackt
= xmit_time
;
1224 if (sacked
& TCPCB_LOST
) {
1225 sacked
&= ~TCPCB_LOST
;
1226 tp
->lost_out
-= pcount
;
1230 sacked
|= TCPCB_SACKED_ACKED
;
1231 state
->flag
|= FLAG_DATA_SACKED
;
1232 tp
->sacked_out
+= pcount
;
1233 tp
->delivered
+= pcount
; /* Out-of-order packets delivered */
1235 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1236 if (tp
->lost_skb_hint
&&
1237 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1238 tp
->lost_cnt_hint
+= pcount
;
1241 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1242 * frames and clear it. undo_retrans is decreased above, L|R frames
1243 * are accounted above as well.
1245 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1246 sacked
&= ~TCPCB_SACKED_RETRANS
;
1247 tp
->retrans_out
-= pcount
;
1253 /* Shift newly-SACKed bytes from this skb to the immediately previous
1254 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1256 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*prev
,
1257 struct sk_buff
*skb
,
1258 struct tcp_sacktag_state
*state
,
1259 unsigned int pcount
, int shifted
, int mss
,
1262 struct tcp_sock
*tp
= tcp_sk(sk
);
1263 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1264 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1268 /* Adjust counters and hints for the newly sacked sequence
1269 * range but discard the return value since prev is already
1270 * marked. We must tag the range first because the seq
1271 * advancement below implicitly advances
1272 * tcp_highest_sack_seq() when skb is highest_sack.
1274 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1275 start_seq
, end_seq
, dup_sack
, pcount
,
1277 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1279 if (skb
== tp
->lost_skb_hint
)
1280 tp
->lost_cnt_hint
+= pcount
;
1282 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1283 TCP_SKB_CB(skb
)->seq
+= shifted
;
1285 tcp_skb_pcount_add(prev
, pcount
);
1286 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1287 tcp_skb_pcount_add(skb
, -pcount
);
1289 /* When we're adding to gso_segs == 1, gso_size will be zero,
1290 * in theory this shouldn't be necessary but as long as DSACK
1291 * code can come after this skb later on it's better to keep
1292 * setting gso_size to something.
1294 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1295 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1297 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1298 if (tcp_skb_pcount(skb
) <= 1)
1299 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1301 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1302 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1305 BUG_ON(!tcp_skb_pcount(skb
));
1306 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1310 /* Whole SKB was eaten :-) */
1312 if (skb
== tp
->retransmit_skb_hint
)
1313 tp
->retransmit_skb_hint
= prev
;
1314 if (skb
== tp
->lost_skb_hint
) {
1315 tp
->lost_skb_hint
= prev
;
1316 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1319 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1320 TCP_SKB_CB(prev
)->eor
= TCP_SKB_CB(skb
)->eor
;
1321 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1322 TCP_SKB_CB(prev
)->end_seq
++;
1324 if (skb
== tcp_highest_sack(sk
))
1325 tcp_advance_highest_sack(sk
, skb
);
1327 tcp_skb_collapse_tstamp(prev
, skb
);
1328 if (unlikely(TCP_SKB_CB(prev
)->tx
.delivered_mstamp
))
1329 TCP_SKB_CB(prev
)->tx
.delivered_mstamp
= 0;
1331 tcp_rtx_queue_unlink_and_free(skb
, sk
);
1333 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1338 /* I wish gso_size would have a bit more sane initialization than
1339 * something-or-zero which complicates things
1341 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1343 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1346 /* Shifting pages past head area doesn't work */
1347 static int skb_can_shift(const struct sk_buff
*skb
)
1349 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1352 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1355 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1356 struct tcp_sacktag_state
*state
,
1357 u32 start_seq
, u32 end_seq
,
1360 struct tcp_sock
*tp
= tcp_sk(sk
);
1361 struct sk_buff
*prev
;
1367 if (!sk_can_gso(sk
))
1370 /* Normally R but no L won't result in plain S */
1372 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1374 if (!skb_can_shift(skb
))
1376 /* This frame is about to be dropped (was ACKed). */
1377 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1380 /* Can only happen with delayed DSACK + discard craziness */
1381 prev
= skb_rb_prev(skb
);
1385 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1388 if (!tcp_skb_can_collapse_to(prev
))
1391 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1392 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1396 pcount
= tcp_skb_pcount(skb
);
1397 mss
= tcp_skb_seglen(skb
);
1399 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1400 * drop this restriction as unnecessary
1402 if (mss
!= tcp_skb_seglen(prev
))
1405 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1407 /* CHECKME: This is non-MSS split case only?, this will
1408 * cause skipped skbs due to advancing loop btw, original
1409 * has that feature too
1411 if (tcp_skb_pcount(skb
) <= 1)
1414 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1416 /* TODO: head merge to next could be attempted here
1417 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1418 * though it might not be worth of the additional hassle
1420 * ...we can probably just fallback to what was done
1421 * previously. We could try merging non-SACKed ones
1422 * as well but it probably isn't going to buy off
1423 * because later SACKs might again split them, and
1424 * it would make skb timestamp tracking considerably
1430 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1432 BUG_ON(len
> skb
->len
);
1434 /* MSS boundaries should be honoured or else pcount will
1435 * severely break even though it makes things bit trickier.
1436 * Optimize common case to avoid most of the divides
1438 mss
= tcp_skb_mss(skb
);
1440 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1441 * drop this restriction as unnecessary
1443 if (mss
!= tcp_skb_seglen(prev
))
1448 } else if (len
< mss
) {
1456 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1457 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1460 if (!skb_shift(prev
, skb
, len
))
1462 if (!tcp_shifted_skb(sk
, prev
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1465 /* Hole filled allows collapsing with the next as well, this is very
1466 * useful when hole on every nth skb pattern happens
1468 skb
= skb_rb_next(prev
);
1472 if (!skb_can_shift(skb
) ||
1473 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1474 (mss
!= tcp_skb_seglen(skb
)))
1478 if (skb_shift(prev
, skb
, len
)) {
1479 pcount
+= tcp_skb_pcount(skb
);
1480 tcp_shifted_skb(sk
, prev
, skb
, state
, tcp_skb_pcount(skb
),
1491 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1495 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1496 struct tcp_sack_block
*next_dup
,
1497 struct tcp_sacktag_state
*state
,
1498 u32 start_seq
, u32 end_seq
,
1501 struct tcp_sock
*tp
= tcp_sk(sk
);
1502 struct sk_buff
*tmp
;
1504 skb_rbtree_walk_from(skb
) {
1506 bool dup_sack
= dup_sack_in
;
1508 /* queue is in-order => we can short-circuit the walk early */
1509 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1513 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1514 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1515 next_dup
->start_seq
,
1521 /* skb reference here is a bit tricky to get right, since
1522 * shifting can eat and free both this skb and the next,
1523 * so not even _safe variant of the loop is enough.
1526 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1527 start_seq
, end_seq
, dup_sack
);
1536 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1542 if (unlikely(in_sack
< 0))
1546 TCP_SKB_CB(skb
)->sacked
=
1549 TCP_SKB_CB(skb
)->sacked
,
1550 TCP_SKB_CB(skb
)->seq
,
1551 TCP_SKB_CB(skb
)->end_seq
,
1553 tcp_skb_pcount(skb
),
1555 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1556 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1557 list_del_init(&skb
->tcp_tsorted_anchor
);
1559 if (!before(TCP_SKB_CB(skb
)->seq
,
1560 tcp_highest_sack_seq(tp
)))
1561 tcp_advance_highest_sack(sk
, skb
);
1567 static struct sk_buff
*tcp_sacktag_bsearch(struct sock
*sk
,
1568 struct tcp_sacktag_state
*state
,
1571 struct rb_node
*parent
, **p
= &sk
->tcp_rtx_queue
.rb_node
;
1572 struct sk_buff
*skb
;
1576 skb
= rb_to_skb(parent
);
1577 if (before(seq
, TCP_SKB_CB(skb
)->seq
)) {
1578 p
= &parent
->rb_left
;
1581 if (!before(seq
, TCP_SKB_CB(skb
)->end_seq
)) {
1582 p
= &parent
->rb_right
;
1590 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1591 struct tcp_sacktag_state
*state
,
1594 if (skb
&& after(TCP_SKB_CB(skb
)->seq
, skip_to_seq
))
1597 return tcp_sacktag_bsearch(sk
, state
, skip_to_seq
);
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
->snd_nxt
;
1644 if (!tp
->sacked_out
)
1645 tcp_highest_sack_reset(sk
);
1647 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1648 num_sacks
, prior_snd_una
);
1649 if (found_dup_sack
) {
1650 state
->flag
|= FLAG_DSACKING_ACK
;
1651 tp
->delivered
++; /* A spurious retransmission is delivered */
1654 /* Eliminate too old ACKs, but take into
1655 * account more or less fresh ones, they can
1656 * contain valid SACK info.
1658 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1661 if (!tp
->packets_out
)
1665 first_sack_index
= 0;
1666 for (i
= 0; i
< num_sacks
; i
++) {
1667 bool dup_sack
= !i
&& found_dup_sack
;
1669 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1670 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1672 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1673 sp
[used_sacks
].start_seq
,
1674 sp
[used_sacks
].end_seq
)) {
1678 if (!tp
->undo_marker
)
1679 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1681 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1683 /* Don't count olds caused by ACK reordering */
1684 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1685 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1687 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1690 NET_INC_STATS(sock_net(sk
), mib_idx
);
1692 first_sack_index
= -1;
1696 /* Ignore very old stuff early */
1697 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1703 /* order SACK blocks to allow in order walk of the retrans queue */
1704 for (i
= used_sacks
- 1; i
> 0; i
--) {
1705 for (j
= 0; j
< i
; j
++) {
1706 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1707 swap(sp
[j
], sp
[j
+ 1]);
1709 /* Track where the first SACK block goes to */
1710 if (j
== first_sack_index
)
1711 first_sack_index
= j
+ 1;
1716 state
->mss_now
= tcp_current_mss(sk
);
1720 if (!tp
->sacked_out
) {
1721 /* It's already past, so skip checking against it */
1722 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1724 cache
= tp
->recv_sack_cache
;
1725 /* Skip empty blocks in at head of the cache */
1726 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1731 while (i
< used_sacks
) {
1732 u32 start_seq
= sp
[i
].start_seq
;
1733 u32 end_seq
= sp
[i
].end_seq
;
1734 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1735 struct tcp_sack_block
*next_dup
= NULL
;
1737 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1738 next_dup
= &sp
[i
+ 1];
1740 /* Skip too early cached blocks */
1741 while (tcp_sack_cache_ok(tp
, cache
) &&
1742 !before(start_seq
, cache
->end_seq
))
1745 /* Can skip some work by looking recv_sack_cache? */
1746 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1747 after(end_seq
, cache
->start_seq
)) {
1750 if (before(start_seq
, cache
->start_seq
)) {
1751 skb
= tcp_sacktag_skip(skb
, sk
, state
,
1753 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1760 /* Rest of the block already fully processed? */
1761 if (!after(end_seq
, cache
->end_seq
))
1764 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1768 /* ...tail remains todo... */
1769 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1770 /* ...but better entrypoint exists! */
1771 skb
= tcp_highest_sack(sk
);
1778 skb
= tcp_sacktag_skip(skb
, sk
, state
, cache
->end_seq
);
1779 /* Check overlap against next cached too (past this one already) */
1784 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1785 skb
= tcp_highest_sack(sk
);
1789 skb
= tcp_sacktag_skip(skb
, sk
, state
, start_seq
);
1792 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
1793 start_seq
, end_seq
, dup_sack
);
1799 /* Clear the head of the cache sack blocks so we can skip it next time */
1800 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1801 tp
->recv_sack_cache
[i
].start_seq
= 0;
1802 tp
->recv_sack_cache
[i
].end_seq
= 0;
1804 for (j
= 0; j
< used_sacks
; j
++)
1805 tp
->recv_sack_cache
[i
++] = sp
[j
];
1807 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
|| tp
->undo_marker
)
1808 tcp_check_sack_reordering(sk
, state
->reord
, 0);
1810 tcp_verify_left_out(tp
);
1813 #if FASTRETRANS_DEBUG > 0
1814 WARN_ON((int)tp
->sacked_out
< 0);
1815 WARN_ON((int)tp
->lost_out
< 0);
1816 WARN_ON((int)tp
->retrans_out
< 0);
1817 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1822 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1823 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1825 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1829 holes
= max(tp
->lost_out
, 1U);
1830 holes
= min(holes
, tp
->packets_out
);
1832 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1833 tp
->sacked_out
= tp
->packets_out
- holes
;
1839 /* If we receive more dupacks than we expected counting segments
1840 * in assumption of absent reordering, interpret this as reordering.
1841 * The only another reason could be bug in receiver TCP.
1843 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1845 struct tcp_sock
*tp
= tcp_sk(sk
);
1847 if (!tcp_limit_reno_sacked(tp
))
1850 tp
->reordering
= min_t(u32
, tp
->packets_out
+ addend
,
1851 sock_net(sk
)->ipv4
.sysctl_tcp_max_reordering
);
1852 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRENOREORDER
);
1855 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1857 static void tcp_add_reno_sack(struct sock
*sk
)
1859 struct tcp_sock
*tp
= tcp_sk(sk
);
1860 u32 prior_sacked
= tp
->sacked_out
;
1863 tcp_check_reno_reordering(sk
, 0);
1864 if (tp
->sacked_out
> prior_sacked
)
1865 tp
->delivered
++; /* Some out-of-order packet is delivered */
1866 tcp_verify_left_out(tp
);
1869 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1871 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1873 struct tcp_sock
*tp
= tcp_sk(sk
);
1876 /* One ACK acked hole. The rest eat duplicate ACKs. */
1877 tp
->delivered
+= max_t(int, acked
- tp
->sacked_out
, 1);
1878 if (acked
- 1 >= tp
->sacked_out
)
1881 tp
->sacked_out
-= acked
- 1;
1883 tcp_check_reno_reordering(sk
, acked
);
1884 tcp_verify_left_out(tp
);
1887 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1892 void tcp_clear_retrans(struct tcp_sock
*tp
)
1894 tp
->retrans_out
= 0;
1896 tp
->undo_marker
= 0;
1897 tp
->undo_retrans
= -1;
1901 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1903 tp
->undo_marker
= tp
->snd_una
;
1904 /* Retransmission still in flight may cause DSACKs later. */
1905 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1908 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1909 * and reset tags completely, otherwise preserve SACKs. If receiver
1910 * dropped its ofo queue, we will know this due to reneging detection.
1912 void tcp_enter_loss(struct sock
*sk
)
1914 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1915 struct tcp_sock
*tp
= tcp_sk(sk
);
1916 struct net
*net
= sock_net(sk
);
1917 struct sk_buff
*skb
;
1918 bool new_recovery
= icsk
->icsk_ca_state
< TCP_CA_Recovery
;
1919 bool is_reneg
; /* is receiver reneging on SACKs? */
1922 /* Reduce ssthresh if it has not yet been made inside this window. */
1923 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1924 !after(tp
->high_seq
, tp
->snd_una
) ||
1925 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1926 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1927 tp
->prior_cwnd
= tp
->snd_cwnd
;
1928 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1929 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1933 tp
->snd_cwnd_cnt
= 0;
1934 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
1936 tp
->retrans_out
= 0;
1939 if (tcp_is_reno(tp
))
1940 tcp_reset_reno_sack(tp
);
1942 skb
= tcp_rtx_queue_head(sk
);
1943 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1945 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1947 /* Mark SACK reneging until we recover from this loss event. */
1948 tp
->is_sack_reneg
= 1;
1950 tcp_clear_all_retrans_hints(tp
);
1952 skb_rbtree_walk_from(skb
) {
1953 mark_lost
= (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
1956 tcp_sum_lost(tp
, skb
);
1957 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1959 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1960 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1961 tp
->lost_out
+= tcp_skb_pcount(skb
);
1964 tcp_verify_left_out(tp
);
1966 /* Timeout in disordered state after receiving substantial DUPACKs
1967 * suggests that the degree of reordering is over-estimated.
1969 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1970 tp
->sacked_out
>= net
->ipv4
.sysctl_tcp_reordering
)
1971 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1972 net
->ipv4
.sysctl_tcp_reordering
);
1973 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1974 tp
->high_seq
= tp
->snd_nxt
;
1975 tcp_ecn_queue_cwr(tp
);
1977 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1978 * loss recovery is underway except recurring timeout(s) on
1979 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1981 * In theory F-RTO can be used repeatedly during loss recovery.
1982 * In practice this interacts badly with broken middle-boxes that
1983 * falsely raise the receive window, which results in repeated
1984 * timeouts and stop-and-go behavior.
1986 tp
->frto
= net
->ipv4
.sysctl_tcp_frto
&&
1987 (new_recovery
|| icsk
->icsk_retransmits
) &&
1988 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1991 /* If ACK arrived pointing to a remembered SACK, it means that our
1992 * remembered SACKs do not reflect real state of receiver i.e.
1993 * receiver _host_ is heavily congested (or buggy).
1995 * To avoid big spurious retransmission bursts due to transient SACK
1996 * scoreboard oddities that look like reneging, we give the receiver a
1997 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
1998 * restore sanity to the SACK scoreboard. If the apparent reneging
1999 * persists until this RTO then we'll clear the SACK scoreboard.
2001 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2003 if (flag
& FLAG_SACK_RENEGING
) {
2004 struct tcp_sock
*tp
= tcp_sk(sk
);
2005 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2006 msecs_to_jiffies(10));
2008 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2009 delay
, TCP_RTO_MAX
);
2015 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2016 * counter when SACK is enabled (without SACK, sacked_out is used for
2019 * With reordering, holes may still be in flight, so RFC3517 recovery
2020 * uses pure sacked_out (total number of SACKed segments) even though
2021 * it violates the RFC that uses duplicate ACKs, often these are equal
2022 * but when e.g. out-of-window ACKs or packet duplication occurs,
2023 * they differ. Since neither occurs due to loss, TCP should really
2026 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2028 return tp
->sacked_out
+ 1;
2031 /* Linux NewReno/SACK/ECN state machine.
2032 * --------------------------------------
2034 * "Open" Normal state, no dubious events, fast path.
2035 * "Disorder" In all the respects it is "Open",
2036 * but requires a bit more attention. It is entered when
2037 * we see some SACKs or dupacks. It is split of "Open"
2038 * mainly to move some processing from fast path to slow one.
2039 * "CWR" CWND was reduced due to some Congestion Notification event.
2040 * It can be ECN, ICMP source quench, local device congestion.
2041 * "Recovery" CWND was reduced, we are fast-retransmitting.
2042 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2044 * tcp_fastretrans_alert() is entered:
2045 * - each incoming ACK, if state is not "Open"
2046 * - when arrived ACK is unusual, namely:
2051 * Counting packets in flight is pretty simple.
2053 * in_flight = packets_out - left_out + retrans_out
2055 * packets_out is SND.NXT-SND.UNA counted in packets.
2057 * retrans_out is number of retransmitted segments.
2059 * left_out is number of segments left network, but not ACKed yet.
2061 * left_out = sacked_out + lost_out
2063 * sacked_out: Packets, which arrived to receiver out of order
2064 * and hence not ACKed. With SACKs this number is simply
2065 * amount of SACKed data. Even without SACKs
2066 * it is easy to give pretty reliable estimate of this number,
2067 * counting duplicate ACKs.
2069 * lost_out: Packets lost by network. TCP has no explicit
2070 * "loss notification" feedback from network (for now).
2071 * It means that this number can be only _guessed_.
2072 * Actually, it is the heuristics to predict lossage that
2073 * distinguishes different algorithms.
2075 * F.e. after RTO, when all the queue is considered as lost,
2076 * lost_out = packets_out and in_flight = retrans_out.
2078 * Essentially, we have now a few algorithms detecting
2081 * If the receiver supports SACK:
2083 * RFC6675/3517: It is the conventional algorithm. A packet is
2084 * considered lost if the number of higher sequence packets
2085 * SACKed is greater than or equal the DUPACK thoreshold
2086 * (reordering). This is implemented in tcp_mark_head_lost and
2087 * tcp_update_scoreboard.
2089 * RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
2090 * (2017-) that checks timing instead of counting DUPACKs.
2091 * Essentially a packet is considered lost if it's not S/ACKed
2092 * after RTT + reordering_window, where both metrics are
2093 * dynamically measured and adjusted. This is implemented in
2094 * tcp_rack_mark_lost.
2096 * If the receiver does not support SACK:
2098 * NewReno (RFC6582): in Recovery we assume that one segment
2099 * is lost (classic Reno). While we are in Recovery and
2100 * a partial ACK arrives, we assume that one more packet
2101 * is lost (NewReno). This heuristics are the same in NewReno
2104 * Really tricky (and requiring careful tuning) part of algorithm
2105 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2106 * The first determines the moment _when_ we should reduce CWND and,
2107 * hence, slow down forward transmission. In fact, it determines the moment
2108 * when we decide that hole is caused by loss, rather than by a reorder.
2110 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2111 * holes, caused by lost packets.
2113 * And the most logically complicated part of algorithm is undo
2114 * heuristics. We detect false retransmits due to both too early
2115 * fast retransmit (reordering) and underestimated RTO, analyzing
2116 * timestamps and D-SACKs. When we detect that some segments were
2117 * retransmitted by mistake and CWND reduction was wrong, we undo
2118 * window reduction and abort recovery phase. This logic is hidden
2119 * inside several functions named tcp_try_undo_<something>.
2122 /* This function decides, when we should leave Disordered state
2123 * and enter Recovery phase, reducing congestion window.
2125 * Main question: may we further continue forward transmission
2126 * with the same cwnd?
2128 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2130 struct tcp_sock
*tp
= tcp_sk(sk
);
2132 /* Trick#1: The loss is proven. */
2136 /* Not-A-Trick#2 : Classic rule... */
2137 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2143 /* Detect loss in event "A" above by marking head of queue up as lost.
2144 * For non-SACK(Reno) senders, the first "packets" number of segments
2145 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2146 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2147 * the maximum SACKed segments to pass before reaching this limit.
2149 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2151 struct tcp_sock
*tp
= tcp_sk(sk
);
2152 struct sk_buff
*skb
;
2153 int cnt
, oldcnt
, lost
;
2155 /* Use SACK to deduce losses of new sequences sent during recovery */
2156 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2158 WARN_ON(packets
> tp
->packets_out
);
2159 skb
= tp
->lost_skb_hint
;
2161 /* Head already handled? */
2162 if (mark_head
&& after(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
))
2164 cnt
= tp
->lost_cnt_hint
;
2166 skb
= tcp_rtx_queue_head(sk
);
2170 skb_rbtree_walk_from(skb
) {
2171 /* TODO: do this better */
2172 /* this is not the most efficient way to do this... */
2173 tp
->lost_skb_hint
= skb
;
2174 tp
->lost_cnt_hint
= cnt
;
2176 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2180 if (tcp_is_reno(tp
) ||
2181 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2182 cnt
+= tcp_skb_pcount(skb
);
2184 if (cnt
> packets
) {
2185 if (tcp_is_sack(tp
) ||
2186 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2187 (oldcnt
>= packets
))
2190 mss
= tcp_skb_mss(skb
);
2191 /* If needed, chop off the prefix to mark as lost. */
2192 lost
= (packets
- oldcnt
) * mss
;
2193 if (lost
< skb
->len
&&
2194 tcp_fragment(sk
, TCP_FRAG_IN_RTX_QUEUE
, skb
,
2195 lost
, mss
, GFP_ATOMIC
) < 0)
2200 tcp_skb_mark_lost(tp
, skb
);
2205 tcp_verify_left_out(tp
);
2208 /* Account newly detected lost packet(s) */
2210 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2212 struct tcp_sock
*tp
= tcp_sk(sk
);
2214 if (tcp_is_reno(tp
)) {
2215 tcp_mark_head_lost(sk
, 1, 1);
2217 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2218 if (sacked_upto
>= 0)
2219 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2220 else if (fast_rexmit
)
2221 tcp_mark_head_lost(sk
, 1, 1);
2225 static bool tcp_tsopt_ecr_before(const struct tcp_sock
*tp
, u32 when
)
2227 return tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2228 before(tp
->rx_opt
.rcv_tsecr
, when
);
2231 /* skb is spurious retransmitted if the returned timestamp echo
2232 * reply is prior to the skb transmission time
2234 static bool tcp_skb_spurious_retrans(const struct tcp_sock
*tp
,
2235 const struct sk_buff
*skb
)
2237 return (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
) &&
2238 tcp_tsopt_ecr_before(tp
, tcp_skb_timestamp(skb
));
2241 /* Nothing was retransmitted or returned timestamp is less
2242 * than timestamp of the first retransmission.
2244 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2246 return !tp
->retrans_stamp
||
2247 tcp_tsopt_ecr_before(tp
, tp
->retrans_stamp
);
2250 /* Undo procedures. */
2252 /* We can clear retrans_stamp when there are no retransmissions in the
2253 * window. It would seem that it is trivially available for us in
2254 * tp->retrans_out, however, that kind of assumptions doesn't consider
2255 * what will happen if errors occur when sending retransmission for the
2256 * second time. ...It could the that such segment has only
2257 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2258 * the head skb is enough except for some reneging corner cases that
2259 * are not worth the effort.
2261 * Main reason for all this complexity is the fact that connection dying
2262 * time now depends on the validity of the retrans_stamp, in particular,
2263 * that successive retransmissions of a segment must not advance
2264 * retrans_stamp under any conditions.
2266 static bool tcp_any_retrans_done(const struct sock
*sk
)
2268 const struct tcp_sock
*tp
= tcp_sk(sk
);
2269 struct sk_buff
*skb
;
2271 if (tp
->retrans_out
)
2274 skb
= tcp_rtx_queue_head(sk
);
2275 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2281 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2283 #if FASTRETRANS_DEBUG > 1
2284 struct tcp_sock
*tp
= tcp_sk(sk
);
2285 struct inet_sock
*inet
= inet_sk(sk
);
2287 if (sk
->sk_family
== AF_INET
) {
2288 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2290 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2291 tp
->snd_cwnd
, tcp_left_out(tp
),
2292 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2295 #if IS_ENABLED(CONFIG_IPV6)
2296 else if (sk
->sk_family
== AF_INET6
) {
2297 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2299 &sk
->sk_v6_daddr
, ntohs(inet
->inet_dport
),
2300 tp
->snd_cwnd
, tcp_left_out(tp
),
2301 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2308 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2310 struct tcp_sock
*tp
= tcp_sk(sk
);
2313 struct sk_buff
*skb
;
2315 skb_rbtree_walk(skb
, &sk
->tcp_rtx_queue
) {
2316 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2319 tcp_clear_all_retrans_hints(tp
);
2322 if (tp
->prior_ssthresh
) {
2323 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2325 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2327 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2328 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2329 tcp_ecn_withdraw_cwr(tp
);
2332 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2333 tp
->undo_marker
= 0;
2334 tp
->rack
.advanced
= 1; /* Force RACK to re-exam losses */
2337 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2339 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2342 /* People celebrate: "We love our President!" */
2343 static bool tcp_try_undo_recovery(struct sock
*sk
)
2345 struct tcp_sock
*tp
= tcp_sk(sk
);
2347 if (tcp_may_undo(tp
)) {
2350 /* Happy end! We did not retransmit anything
2351 * or our original transmission succeeded.
2353 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2354 tcp_undo_cwnd_reduction(sk
, false);
2355 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2356 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2358 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2360 NET_INC_STATS(sock_net(sk
), mib_idx
);
2361 } else if (tp
->rack
.reo_wnd_persist
) {
2362 tp
->rack
.reo_wnd_persist
--;
2364 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2365 /* Hold old state until something *above* high_seq
2366 * is ACKed. For Reno it is MUST to prevent false
2367 * fast retransmits (RFC2582). SACK TCP is safe. */
2368 if (!tcp_any_retrans_done(sk
))
2369 tp
->retrans_stamp
= 0;
2372 tcp_set_ca_state(sk
, TCP_CA_Open
);
2373 tp
->is_sack_reneg
= 0;
2377 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2378 static bool tcp_try_undo_dsack(struct sock
*sk
)
2380 struct tcp_sock
*tp
= tcp_sk(sk
);
2382 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2383 tp
->rack
.reo_wnd_persist
= min(TCP_RACK_RECOVERY_THRESH
,
2384 tp
->rack
.reo_wnd_persist
+ 1);
2385 DBGUNDO(sk
, "D-SACK");
2386 tcp_undo_cwnd_reduction(sk
, false);
2387 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2393 /* Undo during loss recovery after partial ACK or using F-RTO. */
2394 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2396 struct tcp_sock
*tp
= tcp_sk(sk
);
2398 if (frto_undo
|| tcp_may_undo(tp
)) {
2399 tcp_undo_cwnd_reduction(sk
, true);
2401 DBGUNDO(sk
, "partial loss");
2402 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2404 NET_INC_STATS(sock_net(sk
),
2405 LINUX_MIB_TCPSPURIOUSRTOS
);
2406 inet_csk(sk
)->icsk_retransmits
= 0;
2407 if (frto_undo
|| tcp_is_sack(tp
)) {
2408 tcp_set_ca_state(sk
, TCP_CA_Open
);
2409 tp
->is_sack_reneg
= 0;
2416 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2417 * It computes the number of packets to send (sndcnt) based on packets newly
2419 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2420 * cwnd reductions across a full RTT.
2421 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2422 * But when the retransmits are acked without further losses, PRR
2423 * slow starts cwnd up to ssthresh to speed up the recovery.
2425 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2427 struct tcp_sock
*tp
= tcp_sk(sk
);
2429 tp
->high_seq
= tp
->snd_nxt
;
2430 tp
->tlp_high_seq
= 0;
2431 tp
->snd_cwnd_cnt
= 0;
2432 tp
->prior_cwnd
= tp
->snd_cwnd
;
2433 tp
->prr_delivered
= 0;
2435 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2436 tcp_ecn_queue_cwr(tp
);
2439 void tcp_cwnd_reduction(struct sock
*sk
, int newly_acked_sacked
, int flag
)
2441 struct tcp_sock
*tp
= tcp_sk(sk
);
2443 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2445 if (newly_acked_sacked
<= 0 || WARN_ON_ONCE(!tp
->prior_cwnd
))
2448 tp
->prr_delivered
+= newly_acked_sacked
;
2450 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2452 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2453 } else if ((flag
& FLAG_RETRANS_DATA_ACKED
) &&
2454 !(flag
& FLAG_LOST_RETRANS
)) {
2455 sndcnt
= min_t(int, delta
,
2456 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2457 newly_acked_sacked
) + 1);
2459 sndcnt
= min(delta
, newly_acked_sacked
);
2461 /* Force a fast retransmit upon entering fast recovery */
2462 sndcnt
= max(sndcnt
, (tp
->prr_out
? 0 : 1));
2463 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2466 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2468 struct tcp_sock
*tp
= tcp_sk(sk
);
2470 if (inet_csk(sk
)->icsk_ca_ops
->cong_control
)
2473 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2474 if (tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
&&
2475 (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
|| tp
->undo_marker
)) {
2476 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2477 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2479 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2482 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2483 void tcp_enter_cwr(struct sock
*sk
)
2485 struct tcp_sock
*tp
= tcp_sk(sk
);
2487 tp
->prior_ssthresh
= 0;
2488 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2489 tp
->undo_marker
= 0;
2490 tcp_init_cwnd_reduction(sk
);
2491 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2494 EXPORT_SYMBOL(tcp_enter_cwr
);
2496 static void tcp_try_keep_open(struct sock
*sk
)
2498 struct tcp_sock
*tp
= tcp_sk(sk
);
2499 int state
= TCP_CA_Open
;
2501 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2502 state
= TCP_CA_Disorder
;
2504 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2505 tcp_set_ca_state(sk
, state
);
2506 tp
->high_seq
= tp
->snd_nxt
;
2510 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2512 struct tcp_sock
*tp
= tcp_sk(sk
);
2514 tcp_verify_left_out(tp
);
2516 if (!tcp_any_retrans_done(sk
))
2517 tp
->retrans_stamp
= 0;
2519 if (flag
& FLAG_ECE
)
2522 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2523 tcp_try_keep_open(sk
);
2527 static void tcp_mtup_probe_failed(struct sock
*sk
)
2529 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2531 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2532 icsk
->icsk_mtup
.probe_size
= 0;
2533 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPFAIL
);
2536 static void tcp_mtup_probe_success(struct sock
*sk
)
2538 struct tcp_sock
*tp
= tcp_sk(sk
);
2539 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2541 /* FIXME: breaks with very large cwnd */
2542 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2543 tp
->snd_cwnd
= tp
->snd_cwnd
*
2544 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2545 icsk
->icsk_mtup
.probe_size
;
2546 tp
->snd_cwnd_cnt
= 0;
2547 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2548 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2550 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2551 icsk
->icsk_mtup
.probe_size
= 0;
2552 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2553 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPSUCCESS
);
2556 /* Do a simple retransmit without using the backoff mechanisms in
2557 * tcp_timer. This is used for path mtu discovery.
2558 * The socket is already locked here.
2560 void tcp_simple_retransmit(struct sock
*sk
)
2562 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2563 struct tcp_sock
*tp
= tcp_sk(sk
);
2564 struct sk_buff
*skb
;
2565 unsigned int mss
= tcp_current_mss(sk
);
2567 skb_rbtree_walk(skb
, &sk
->tcp_rtx_queue
) {
2568 if (tcp_skb_seglen(skb
) > mss
&&
2569 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2570 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2571 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2572 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2574 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2578 tcp_clear_retrans_hints_partial(tp
);
2583 if (tcp_is_reno(tp
))
2584 tcp_limit_reno_sacked(tp
);
2586 tcp_verify_left_out(tp
);
2588 /* Don't muck with the congestion window here.
2589 * Reason is that we do not increase amount of _data_
2590 * in network, but units changed and effective
2591 * cwnd/ssthresh really reduced now.
2593 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2594 tp
->high_seq
= tp
->snd_nxt
;
2595 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2596 tp
->prior_ssthresh
= 0;
2597 tp
->undo_marker
= 0;
2598 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2600 tcp_xmit_retransmit_queue(sk
);
2602 EXPORT_SYMBOL(tcp_simple_retransmit
);
2604 void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2606 struct tcp_sock
*tp
= tcp_sk(sk
);
2609 if (tcp_is_reno(tp
))
2610 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2612 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2614 NET_INC_STATS(sock_net(sk
), mib_idx
);
2616 tp
->prior_ssthresh
= 0;
2619 if (!tcp_in_cwnd_reduction(sk
)) {
2621 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2622 tcp_init_cwnd_reduction(sk
);
2624 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2627 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2628 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2630 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
,
2633 struct tcp_sock
*tp
= tcp_sk(sk
);
2634 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2636 if ((flag
& FLAG_SND_UNA_ADVANCED
) &&
2637 tcp_try_undo_loss(sk
, false))
2640 /* The ACK (s)acks some never-retransmitted data meaning not all
2641 * the data packets before the timeout were lost. Therefore we
2642 * undo the congestion window and state. This is essentially
2643 * the operation in F-RTO (RFC5682 section 3.1 step 3.b). Since
2644 * a retransmitted skb is permantly marked, we can apply such an
2645 * operation even if F-RTO was not used.
2647 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2648 tcp_try_undo_loss(sk
, tp
->undo_marker
))
2651 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2652 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2653 if (flag
& FLAG_DATA_SACKED
|| is_dupack
)
2654 tp
->frto
= 0; /* Step 3.a. loss was real */
2655 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2656 tp
->high_seq
= tp
->snd_nxt
;
2657 /* Step 2.b. Try send new data (but deferred until cwnd
2658 * is updated in tcp_ack()). Otherwise fall back to
2659 * the conventional recovery.
2661 if (!tcp_write_queue_empty(sk
) &&
2662 after(tcp_wnd_end(tp
), tp
->snd_nxt
)) {
2663 *rexmit
= REXMIT_NEW
;
2671 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2672 tcp_try_undo_recovery(sk
);
2675 if (tcp_is_reno(tp
)) {
2676 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2677 * delivered. Lower inflight to clock out (re)tranmissions.
2679 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2680 tcp_add_reno_sack(sk
);
2681 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2682 tcp_reset_reno_sack(tp
);
2684 *rexmit
= REXMIT_LOST
;
2687 /* Undo during fast recovery after partial ACK. */
2688 static bool tcp_try_undo_partial(struct sock
*sk
, u32 prior_snd_una
)
2690 struct tcp_sock
*tp
= tcp_sk(sk
);
2692 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2693 /* Plain luck! Hole if filled with delayed
2694 * packet, rather than with a retransmit. Check reordering.
2696 tcp_check_sack_reordering(sk
, prior_snd_una
, 1);
2698 /* We are getting evidence that the reordering degree is higher
2699 * than we realized. If there are no retransmits out then we
2700 * can undo. Otherwise we clock out new packets but do not
2701 * mark more packets lost or retransmit more.
2703 if (tp
->retrans_out
)
2706 if (!tcp_any_retrans_done(sk
))
2707 tp
->retrans_stamp
= 0;
2709 DBGUNDO(sk
, "partial recovery");
2710 tcp_undo_cwnd_reduction(sk
, true);
2711 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2712 tcp_try_keep_open(sk
);
2718 static void tcp_rack_identify_loss(struct sock
*sk
, int *ack_flag
)
2720 struct tcp_sock
*tp
= tcp_sk(sk
);
2722 /* Use RACK to detect loss */
2723 if (sock_net(sk
)->ipv4
.sysctl_tcp_recovery
& TCP_RACK_LOSS_DETECTION
) {
2724 u32 prior_retrans
= tp
->retrans_out
;
2726 tcp_rack_mark_lost(sk
);
2727 if (prior_retrans
> tp
->retrans_out
)
2728 *ack_flag
|= FLAG_LOST_RETRANS
;
2732 static bool tcp_force_fast_retransmit(struct sock
*sk
)
2734 struct tcp_sock
*tp
= tcp_sk(sk
);
2736 return after(tcp_highest_sack_seq(tp
),
2737 tp
->snd_una
+ tp
->reordering
* tp
->mss_cache
);
2740 /* Process an event, which can update packets-in-flight not trivially.
2741 * Main goal of this function is to calculate new estimate for left_out,
2742 * taking into account both packets sitting in receiver's buffer and
2743 * packets lost by network.
2745 * Besides that it updates the congestion state when packet loss or ECN
2746 * is detected. But it does not reduce the cwnd, it is done by the
2747 * congestion control later.
2749 * It does _not_ decide what to send, it is made in function
2750 * tcp_xmit_retransmit_queue().
2752 static void tcp_fastretrans_alert(struct sock
*sk
, const u32 prior_snd_una
,
2753 bool is_dupack
, int *ack_flag
, int *rexmit
)
2755 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2756 struct tcp_sock
*tp
= tcp_sk(sk
);
2757 int fast_rexmit
= 0, flag
= *ack_flag
;
2758 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2759 tcp_force_fast_retransmit(sk
));
2761 if (!tp
->packets_out
&& tp
->sacked_out
)
2764 /* Now state machine starts.
2765 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2766 if (flag
& FLAG_ECE
)
2767 tp
->prior_ssthresh
= 0;
2769 /* B. In all the states check for reneging SACKs. */
2770 if (tcp_check_sack_reneging(sk
, flag
))
2773 /* C. Check consistency of the current state. */
2774 tcp_verify_left_out(tp
);
2776 /* D. Check state exit conditions. State can be terminated
2777 * when high_seq is ACKed. */
2778 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2779 WARN_ON(tp
->retrans_out
!= 0);
2780 tp
->retrans_stamp
= 0;
2781 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2782 switch (icsk
->icsk_ca_state
) {
2784 /* CWR is to be held something *above* high_seq
2785 * is ACKed for CWR bit to reach receiver. */
2786 if (tp
->snd_una
!= tp
->high_seq
) {
2787 tcp_end_cwnd_reduction(sk
);
2788 tcp_set_ca_state(sk
, TCP_CA_Open
);
2792 case TCP_CA_Recovery
:
2793 if (tcp_is_reno(tp
))
2794 tcp_reset_reno_sack(tp
);
2795 if (tcp_try_undo_recovery(sk
))
2797 tcp_end_cwnd_reduction(sk
);
2802 /* E. Process state. */
2803 switch (icsk
->icsk_ca_state
) {
2804 case TCP_CA_Recovery
:
2805 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2806 if (tcp_is_reno(tp
) && is_dupack
)
2807 tcp_add_reno_sack(sk
);
2809 if (tcp_try_undo_partial(sk
, prior_snd_una
))
2811 /* Partial ACK arrived. Force fast retransmit. */
2812 do_lost
= tcp_is_reno(tp
) ||
2813 tcp_force_fast_retransmit(sk
);
2815 if (tcp_try_undo_dsack(sk
)) {
2816 tcp_try_keep_open(sk
);
2819 tcp_rack_identify_loss(sk
, ack_flag
);
2822 tcp_process_loss(sk
, flag
, is_dupack
, rexmit
);
2823 tcp_rack_identify_loss(sk
, ack_flag
);
2824 if (!(icsk
->icsk_ca_state
== TCP_CA_Open
||
2825 (*ack_flag
& FLAG_LOST_RETRANS
)))
2827 /* Change state if cwnd is undone or retransmits are lost */
2830 if (tcp_is_reno(tp
)) {
2831 if (flag
& FLAG_SND_UNA_ADVANCED
)
2832 tcp_reset_reno_sack(tp
);
2834 tcp_add_reno_sack(sk
);
2837 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2838 tcp_try_undo_dsack(sk
);
2840 tcp_rack_identify_loss(sk
, ack_flag
);
2841 if (!tcp_time_to_recover(sk
, flag
)) {
2842 tcp_try_to_open(sk
, flag
);
2846 /* MTU probe failure: don't reduce cwnd */
2847 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2848 icsk
->icsk_mtup
.probe_size
&&
2849 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2850 tcp_mtup_probe_failed(sk
);
2851 /* Restores the reduction we did in tcp_mtup_probe() */
2853 tcp_simple_retransmit(sk
);
2857 /* Otherwise enter Recovery state */
2858 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2863 tcp_update_scoreboard(sk
, fast_rexmit
);
2864 *rexmit
= REXMIT_LOST
;
2867 static void tcp_update_rtt_min(struct sock
*sk
, u32 rtt_us
)
2869 u32 wlen
= sock_net(sk
)->ipv4
.sysctl_tcp_min_rtt_wlen
* HZ
;
2870 struct tcp_sock
*tp
= tcp_sk(sk
);
2872 minmax_running_min(&tp
->rtt_min
, wlen
, tcp_jiffies32
,
2873 rtt_us
? : jiffies_to_usecs(1));
2876 static bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2877 long seq_rtt_us
, long sack_rtt_us
,
2878 long ca_rtt_us
, struct rate_sample
*rs
)
2880 const struct tcp_sock
*tp
= tcp_sk(sk
);
2882 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2883 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2884 * Karn's algorithm forbids taking RTT if some retransmitted data
2885 * is acked (RFC6298).
2888 seq_rtt_us
= sack_rtt_us
;
2890 /* RTTM Rule: A TSecr value received in a segment is used to
2891 * update the averaged RTT measurement only if the segment
2892 * acknowledges some new data, i.e., only if it advances the
2893 * left edge of the send window.
2894 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2896 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2897 flag
& FLAG_ACKED
) {
2898 u32 delta
= tcp_time_stamp(tp
) - tp
->rx_opt
.rcv_tsecr
;
2899 u32 delta_us
= delta
* (USEC_PER_SEC
/ TCP_TS_HZ
);
2901 seq_rtt_us
= ca_rtt_us
= delta_us
;
2903 rs
->rtt_us
= ca_rtt_us
; /* RTT of last (S)ACKed packet (or -1) */
2907 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
2908 * always taken together with ACK, SACK, or TS-opts. Any negative
2909 * values will be skipped with the seq_rtt_us < 0 check above.
2911 tcp_update_rtt_min(sk
, ca_rtt_us
);
2912 tcp_rtt_estimator(sk
, seq_rtt_us
);
2915 /* RFC6298: only reset backoff on valid RTT measurement. */
2916 inet_csk(sk
)->icsk_backoff
= 0;
2920 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2921 void tcp_synack_rtt_meas(struct sock
*sk
, struct request_sock
*req
)
2923 struct rate_sample rs
;
2926 if (req
&& !req
->num_retrans
&& tcp_rsk(req
)->snt_synack
)
2927 rtt_us
= tcp_stamp_us_delta(tcp_clock_us(), tcp_rsk(req
)->snt_synack
);
2929 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, rtt_us
, -1L, rtt_us
, &rs
);
2933 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2935 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2937 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2938 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_jiffies32
;
2941 /* Restart timer after forward progress on connection.
2942 * RFC2988 recommends to restart timer to now+rto.
2944 void tcp_rearm_rto(struct sock
*sk
)
2946 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2947 struct tcp_sock
*tp
= tcp_sk(sk
);
2949 /* If the retrans timer is currently being used by Fast Open
2950 * for SYN-ACK retrans purpose, stay put.
2952 if (tp
->fastopen_rsk
)
2955 if (!tp
->packets_out
) {
2956 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2958 u32 rto
= inet_csk(sk
)->icsk_rto
;
2959 /* Offset the time elapsed after installing regular RTO */
2960 if (icsk
->icsk_pending
== ICSK_TIME_REO_TIMEOUT
||
2961 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
2962 s64 delta_us
= tcp_rto_delta_us(sk
);
2963 /* delta_us may not be positive if the socket is locked
2964 * when the retrans timer fires and is rescheduled.
2966 rto
= usecs_to_jiffies(max_t(int, delta_us
, 1));
2968 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
2973 /* Try to schedule a loss probe; if that doesn't work, then schedule an RTO. */
2974 static void tcp_set_xmit_timer(struct sock
*sk
)
2976 if (!tcp_schedule_loss_probe(sk
, true))
2980 /* If we get here, the whole TSO packet has not been acked. */
2981 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
2983 struct tcp_sock
*tp
= tcp_sk(sk
);
2986 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
2988 packets_acked
= tcp_skb_pcount(skb
);
2989 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2991 packets_acked
-= tcp_skb_pcount(skb
);
2993 if (packets_acked
) {
2994 BUG_ON(tcp_skb_pcount(skb
) == 0);
2995 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
2998 return packets_acked
;
3001 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3004 const struct skb_shared_info
*shinfo
;
3006 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3007 if (likely(!TCP_SKB_CB(skb
)->txstamp_ack
))
3010 shinfo
= skb_shinfo(skb
);
3011 if (!before(shinfo
->tskey
, prior_snd_una
) &&
3012 before(shinfo
->tskey
, tcp_sk(sk
)->snd_una
)) {
3013 tcp_skb_tsorted_save(skb
) {
3014 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3015 } tcp_skb_tsorted_restore(skb
);
3019 /* Remove acknowledged frames from the retransmission queue. If our packet
3020 * is before the ack sequence we can discard it as it's confirmed to have
3021 * arrived at the other end.
3023 static int tcp_clean_rtx_queue(struct sock
*sk
, u32 prior_fack
,
3025 struct tcp_sacktag_state
*sack
)
3027 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3028 u64 first_ackt
, last_ackt
;
3029 struct tcp_sock
*tp
= tcp_sk(sk
);
3030 u32 prior_sacked
= tp
->sacked_out
;
3031 u32 reord
= tp
->snd_nxt
; /* lowest acked un-retx un-sacked seq */
3032 struct sk_buff
*skb
, *next
;
3033 bool fully_acked
= true;
3034 long sack_rtt_us
= -1L;
3035 long seq_rtt_us
= -1L;
3036 long ca_rtt_us
= -1L;
3038 u32 last_in_flight
= 0;
3044 for (skb
= skb_rb_first(&sk
->tcp_rtx_queue
); skb
; skb
= next
) {
3045 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3046 const u32 start_seq
= scb
->seq
;
3047 u8 sacked
= scb
->sacked
;
3050 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3052 /* Determine how many packets and what bytes were acked, tso and else */
3053 if (after(scb
->end_seq
, tp
->snd_una
)) {
3054 if (tcp_skb_pcount(skb
) == 1 ||
3055 !after(tp
->snd_una
, scb
->seq
))
3058 acked_pcount
= tcp_tso_acked(sk
, skb
);
3061 fully_acked
= false;
3063 acked_pcount
= tcp_skb_pcount(skb
);
3066 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3067 if (sacked
& TCPCB_SACKED_RETRANS
)
3068 tp
->retrans_out
-= acked_pcount
;
3069 flag
|= FLAG_RETRANS_DATA_ACKED
;
3070 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3071 last_ackt
= skb
->skb_mstamp
;
3072 WARN_ON_ONCE(last_ackt
== 0);
3074 first_ackt
= last_ackt
;
3076 last_in_flight
= TCP_SKB_CB(skb
)->tx
.in_flight
;
3077 if (before(start_seq
, reord
))
3079 if (!after(scb
->end_seq
, tp
->high_seq
))
3080 flag
|= FLAG_ORIG_SACK_ACKED
;
3083 if (sacked
& TCPCB_SACKED_ACKED
) {
3084 tp
->sacked_out
-= acked_pcount
;
3085 } else if (tcp_is_sack(tp
)) {
3086 tp
->delivered
+= acked_pcount
;
3087 if (!tcp_skb_spurious_retrans(tp
, skb
))
3088 tcp_rack_advance(tp
, sacked
, scb
->end_seq
,
3091 if (sacked
& TCPCB_LOST
)
3092 tp
->lost_out
-= acked_pcount
;
3094 tp
->packets_out
-= acked_pcount
;
3095 pkts_acked
+= acked_pcount
;
3096 tcp_rate_skb_delivered(sk
, skb
, sack
->rate
);
3098 /* Initial outgoing SYN's get put onto the write_queue
3099 * just like anything else we transmit. It is not
3100 * true data, and if we misinform our callers that
3101 * this ACK acks real data, we will erroneously exit
3102 * connection startup slow start one packet too
3103 * quickly. This is severely frowned upon behavior.
3105 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3106 flag
|= FLAG_DATA_ACKED
;
3108 flag
|= FLAG_SYN_ACKED
;
3109 tp
->retrans_stamp
= 0;
3115 next
= skb_rb_next(skb
);
3116 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3117 tp
->retransmit_skb_hint
= NULL
;
3118 if (unlikely(skb
== tp
->lost_skb_hint
))
3119 tp
->lost_skb_hint
= NULL
;
3120 tcp_rtx_queue_unlink_and_free(skb
, sk
);
3124 tcp_chrono_stop(sk
, TCP_CHRONO_BUSY
);
3126 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3127 tp
->snd_up
= tp
->snd_una
;
3129 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3130 flag
|= FLAG_SACK_RENEGING
;
3132 if (likely(first_ackt
) && !(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3133 seq_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, first_ackt
);
3134 ca_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, last_ackt
);
3136 if (sack
->first_sackt
) {
3137 sack_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, sack
->first_sackt
);
3138 ca_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, sack
->last_sackt
);
3140 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
,
3141 ca_rtt_us
, sack
->rate
);
3143 if (flag
& FLAG_ACKED
) {
3144 flag
|= FLAG_SET_XMIT_TIMER
; /* set TLP or RTO timer */
3145 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3146 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3147 tcp_mtup_probe_success(sk
);
3150 if (tcp_is_reno(tp
)) {
3151 tcp_remove_reno_sacks(sk
, pkts_acked
);
3155 /* Non-retransmitted hole got filled? That's reordering */
3156 if (before(reord
, prior_fack
))
3157 tcp_check_sack_reordering(sk
, reord
, 0);
3159 delta
= prior_sacked
- tp
->sacked_out
;
3160 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3162 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3163 sack_rtt_us
> tcp_stamp_us_delta(tp
->tcp_mstamp
, skb
->skb_mstamp
)) {
3164 /* Do not re-arm RTO if the sack RTT is measured from data sent
3165 * after when the head was last (re)transmitted. Otherwise the
3166 * timeout may continue to extend in loss recovery.
3168 flag
|= FLAG_SET_XMIT_TIMER
; /* set TLP or RTO timer */
3171 if (icsk
->icsk_ca_ops
->pkts_acked
) {
3172 struct ack_sample sample
= { .pkts_acked
= pkts_acked
,
3173 .rtt_us
= sack
->rate
->rtt_us
,
3174 .in_flight
= last_in_flight
};
3176 icsk
->icsk_ca_ops
->pkts_acked(sk
, &sample
);
3179 #if FASTRETRANS_DEBUG > 0
3180 WARN_ON((int)tp
->sacked_out
< 0);
3181 WARN_ON((int)tp
->lost_out
< 0);
3182 WARN_ON((int)tp
->retrans_out
< 0);
3183 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3184 icsk
= inet_csk(sk
);
3186 pr_debug("Leak l=%u %d\n",
3187 tp
->lost_out
, icsk
->icsk_ca_state
);
3190 if (tp
->sacked_out
) {
3191 pr_debug("Leak s=%u %d\n",
3192 tp
->sacked_out
, icsk
->icsk_ca_state
);
3195 if (tp
->retrans_out
) {
3196 pr_debug("Leak r=%u %d\n",
3197 tp
->retrans_out
, icsk
->icsk_ca_state
);
3198 tp
->retrans_out
= 0;
3205 static void tcp_ack_probe(struct sock
*sk
)
3207 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3208 struct sk_buff
*head
= tcp_send_head(sk
);
3209 const struct tcp_sock
*tp
= tcp_sk(sk
);
3211 /* Was it a usable window open? */
3214 if (!after(TCP_SKB_CB(head
)->end_seq
, tcp_wnd_end(tp
))) {
3215 icsk
->icsk_backoff
= 0;
3216 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3217 /* Socket must be waked up by subsequent tcp_data_snd_check().
3218 * This function is not for random using!
3221 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3223 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3228 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3230 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3231 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3234 /* Decide wheather to run the increase function of congestion control. */
3235 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3237 /* If reordering is high then always grow cwnd whenever data is
3238 * delivered regardless of its ordering. Otherwise stay conservative
3239 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3240 * new SACK or ECE mark may first advance cwnd here and later reduce
3241 * cwnd in tcp_fastretrans_alert() based on more states.
3243 if (tcp_sk(sk
)->reordering
> sock_net(sk
)->ipv4
.sysctl_tcp_reordering
)
3244 return flag
& FLAG_FORWARD_PROGRESS
;
3246 return flag
& FLAG_DATA_ACKED
;
3249 /* The "ultimate" congestion control function that aims to replace the rigid
3250 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3251 * It's called toward the end of processing an ACK with precise rate
3252 * information. All transmission or retransmission are delayed afterwards.
3254 static void tcp_cong_control(struct sock
*sk
, u32 ack
, u32 acked_sacked
,
3255 int flag
, const struct rate_sample
*rs
)
3257 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3259 if (icsk
->icsk_ca_ops
->cong_control
) {
3260 icsk
->icsk_ca_ops
->cong_control(sk
, rs
);
3264 if (tcp_in_cwnd_reduction(sk
)) {
3265 /* Reduce cwnd if state mandates */
3266 tcp_cwnd_reduction(sk
, acked_sacked
, flag
);
3267 } else if (tcp_may_raise_cwnd(sk
, flag
)) {
3268 /* Advance cwnd if state allows */
3269 tcp_cong_avoid(sk
, ack
, acked_sacked
);
3271 tcp_update_pacing_rate(sk
);
3274 /* Check that window update is acceptable.
3275 * The function assumes that snd_una<=ack<=snd_next.
3277 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3278 const u32 ack
, const u32 ack_seq
,
3281 return after(ack
, tp
->snd_una
) ||
3282 after(ack_seq
, tp
->snd_wl1
) ||
3283 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3286 /* If we update tp->snd_una, also update tp->bytes_acked */
3287 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3289 u32 delta
= ack
- tp
->snd_una
;
3291 sock_owned_by_me((struct sock
*)tp
);
3292 tp
->bytes_acked
+= delta
;
3296 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3297 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3299 u32 delta
= seq
- tp
->rcv_nxt
;
3301 sock_owned_by_me((struct sock
*)tp
);
3302 tp
->bytes_received
+= delta
;
3306 /* Update our send window.
3308 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3309 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3311 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3314 struct tcp_sock
*tp
= tcp_sk(sk
);
3316 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3318 if (likely(!tcp_hdr(skb
)->syn
))
3319 nwin
<<= tp
->rx_opt
.snd_wscale
;
3321 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3322 flag
|= FLAG_WIN_UPDATE
;
3323 tcp_update_wl(tp
, ack_seq
);
3325 if (tp
->snd_wnd
!= nwin
) {
3328 /* Note, it is the only place, where
3329 * fast path is recovered for sending TCP.
3332 tcp_fast_path_check(sk
);
3334 if (!tcp_write_queue_empty(sk
))
3335 tcp_slow_start_after_idle_check(sk
);
3337 if (nwin
> tp
->max_window
) {
3338 tp
->max_window
= nwin
;
3339 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3344 tcp_snd_una_update(tp
, ack
);
3349 static bool __tcp_oow_rate_limited(struct net
*net
, int mib_idx
,
3350 u32
*last_oow_ack_time
)
3352 if (*last_oow_ack_time
) {
3353 s32 elapsed
= (s32
)(tcp_jiffies32
- *last_oow_ack_time
);
3355 if (0 <= elapsed
&& elapsed
< net
->ipv4
.sysctl_tcp_invalid_ratelimit
) {
3356 NET_INC_STATS(net
, mib_idx
);
3357 return true; /* rate-limited: don't send yet! */
3361 *last_oow_ack_time
= tcp_jiffies32
;
3363 return false; /* not rate-limited: go ahead, send dupack now! */
3366 /* Return true if we're currently rate-limiting out-of-window ACKs and
3367 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3368 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3369 * attacks that send repeated SYNs or ACKs for the same connection. To
3370 * do this, we do not send a duplicate SYNACK or ACK if the remote
3371 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3373 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3374 int mib_idx
, u32
*last_oow_ack_time
)
3376 /* Data packets without SYNs are not likely part of an ACK loop. */
3377 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3381 return __tcp_oow_rate_limited(net
, mib_idx
, last_oow_ack_time
);
3384 /* RFC 5961 7 [ACK Throttling] */
3385 static void tcp_send_challenge_ack(struct sock
*sk
, const struct sk_buff
*skb
)
3387 /* unprotected vars, we dont care of overwrites */
3388 static u32 challenge_timestamp
;
3389 static unsigned int challenge_count
;
3390 struct tcp_sock
*tp
= tcp_sk(sk
);
3391 struct net
*net
= sock_net(sk
);
3394 /* First check our per-socket dupack rate limit. */
3395 if (__tcp_oow_rate_limited(net
,
3396 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3397 &tp
->last_oow_ack_time
))
3400 /* Then check host-wide RFC 5961 rate limit. */
3402 if (now
!= challenge_timestamp
) {
3403 u32 ack_limit
= net
->ipv4
.sysctl_tcp_challenge_ack_limit
;
3404 u32 half
= (ack_limit
+ 1) >> 1;
3406 challenge_timestamp
= now
;
3407 WRITE_ONCE(challenge_count
, half
+ prandom_u32_max(ack_limit
));
3409 count
= READ_ONCE(challenge_count
);
3411 WRITE_ONCE(challenge_count
, count
- 1);
3412 NET_INC_STATS(net
, LINUX_MIB_TCPCHALLENGEACK
);
3417 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3419 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3420 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3423 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3425 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3426 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3427 * extra check below makes sure this can only happen
3428 * for pure ACK frames. -DaveM
3430 * Not only, also it occurs for expired timestamps.
3433 if (tcp_paws_check(&tp
->rx_opt
, 0))
3434 tcp_store_ts_recent(tp
);
3438 /* This routine deals with acks during a TLP episode.
3439 * We mark the end of a TLP episode on receiving TLP dupack or when
3440 * ack is after tlp_high_seq.
3441 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3443 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3445 struct tcp_sock
*tp
= tcp_sk(sk
);
3447 if (before(ack
, tp
->tlp_high_seq
))
3450 if (flag
& FLAG_DSACKING_ACK
) {
3451 /* This DSACK means original and TLP probe arrived; no loss */
3452 tp
->tlp_high_seq
= 0;
3453 } else if (after(ack
, tp
->tlp_high_seq
)) {
3454 /* ACK advances: there was a loss, so reduce cwnd. Reset
3455 * tlp_high_seq in tcp_init_cwnd_reduction()
3457 tcp_init_cwnd_reduction(sk
);
3458 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3459 tcp_end_cwnd_reduction(sk
);
3460 tcp_try_keep_open(sk
);
3461 NET_INC_STATS(sock_net(sk
),
3462 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3463 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3464 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3465 /* Pure dupack: original and TLP probe arrived; no loss */
3466 tp
->tlp_high_seq
= 0;
3470 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3472 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3474 if (icsk
->icsk_ca_ops
->in_ack_event
)
3475 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3478 /* Congestion control has updated the cwnd already. So if we're in
3479 * loss recovery then now we do any new sends (for FRTO) or
3480 * retransmits (for CA_Loss or CA_recovery) that make sense.
3482 static void tcp_xmit_recovery(struct sock
*sk
, int rexmit
)
3484 struct tcp_sock
*tp
= tcp_sk(sk
);
3486 if (rexmit
== REXMIT_NONE
)
3489 if (unlikely(rexmit
== 2)) {
3490 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
3492 if (after(tp
->snd_nxt
, tp
->high_seq
))
3496 tcp_xmit_retransmit_queue(sk
);
3499 /* This routine deals with incoming acks, but not outgoing ones. */
3500 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3502 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3503 struct tcp_sock
*tp
= tcp_sk(sk
);
3504 struct tcp_sacktag_state sack_state
;
3505 struct rate_sample rs
= { .prior_delivered
= 0 };
3506 u32 prior_snd_una
= tp
->snd_una
;
3507 bool is_sack_reneg
= tp
->is_sack_reneg
;
3508 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3509 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3510 bool is_dupack
= false;
3511 int prior_packets
= tp
->packets_out
;
3512 u32 delivered
= tp
->delivered
;
3513 u32 lost
= tp
->lost
;
3514 int rexmit
= REXMIT_NONE
; /* Flag to (re)transmit to recover losses */
3517 sack_state
.first_sackt
= 0;
3518 sack_state
.rate
= &rs
;
3520 /* We very likely will need to access rtx queue. */
3521 prefetch(sk
->tcp_rtx_queue
.rb_node
);
3523 /* If the ack is older than previous acks
3524 * then we can probably ignore it.
3526 if (before(ack
, prior_snd_una
)) {
3527 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3528 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3529 if (!(flag
& FLAG_NO_CHALLENGE_ACK
))
3530 tcp_send_challenge_ack(sk
, skb
);
3536 /* If the ack includes data we haven't sent yet, discard
3537 * this segment (RFC793 Section 3.9).
3539 if (after(ack
, tp
->snd_nxt
))
3542 if (after(ack
, prior_snd_una
)) {
3543 flag
|= FLAG_SND_UNA_ADVANCED
;
3544 icsk
->icsk_retransmits
= 0;
3547 prior_fack
= tcp_is_sack(tp
) ? tcp_highest_sack_seq(tp
) : tp
->snd_una
;
3548 rs
.prior_in_flight
= tcp_packets_in_flight(tp
);
3550 /* ts_recent update must be made after we are sure that the packet
3553 if (flag
& FLAG_UPDATE_TS_RECENT
)
3554 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3556 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3557 /* Window is constant, pure forward advance.
3558 * No more checks are required.
3559 * Note, we use the fact that SND.UNA>=SND.WL2.
3561 tcp_update_wl(tp
, ack_seq
);
3562 tcp_snd_una_update(tp
, ack
);
3563 flag
|= FLAG_WIN_UPDATE
;
3565 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3567 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3569 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3571 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3574 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3576 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3578 if (TCP_SKB_CB(skb
)->sacked
)
3579 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3582 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3584 ack_ev_flags
|= CA_ACK_ECE
;
3587 if (flag
& FLAG_WIN_UPDATE
)
3588 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3590 tcp_in_ack_event(sk
, ack_ev_flags
);
3593 /* We passed data and got it acked, remove any soft error
3594 * log. Something worked...
3596 sk
->sk_err_soft
= 0;
3597 icsk
->icsk_probes_out
= 0;
3598 tp
->rcv_tstamp
= tcp_jiffies32
;
3602 /* See if we can take anything off of the retransmit queue. */
3603 flag
|= tcp_clean_rtx_queue(sk
, prior_fack
, prior_snd_una
, &sack_state
);
3605 tcp_rack_update_reo_wnd(sk
, &rs
);
3607 if (tp
->tlp_high_seq
)
3608 tcp_process_tlp_ack(sk
, ack
, flag
);
3609 /* If needed, reset TLP/RTO timer; RACK may later override this. */
3610 if (flag
& FLAG_SET_XMIT_TIMER
)
3611 tcp_set_xmit_timer(sk
);
3613 if (tcp_ack_is_dubious(sk
, flag
)) {
3614 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3615 tcp_fastretrans_alert(sk
, prior_snd_una
, is_dupack
, &flag
,
3619 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3622 delivered
= tp
->delivered
- delivered
; /* freshly ACKed or SACKed */
3623 lost
= tp
->lost
- lost
; /* freshly marked lost */
3624 tcp_rate_gen(sk
, delivered
, lost
, is_sack_reneg
, sack_state
.rate
);
3625 tcp_cong_control(sk
, ack
, delivered
, flag
, sack_state
.rate
);
3626 tcp_xmit_recovery(sk
, rexmit
);
3630 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3631 if (flag
& FLAG_DSACKING_ACK
)
3632 tcp_fastretrans_alert(sk
, prior_snd_una
, is_dupack
, &flag
,
3634 /* If this ack opens up a zero window, clear backoff. It was
3635 * being used to time the probes, and is probably far higher than
3636 * it needs to be for normal retransmission.
3640 if (tp
->tlp_high_seq
)
3641 tcp_process_tlp_ack(sk
, ack
, flag
);
3645 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3649 /* If data was SACKed, tag it and see if we should send more data.
3650 * If data was DSACKed, see if we can undo a cwnd reduction.
3652 if (TCP_SKB_CB(skb
)->sacked
) {
3653 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3655 tcp_fastretrans_alert(sk
, prior_snd_una
, is_dupack
, &flag
,
3657 tcp_xmit_recovery(sk
, rexmit
);
3660 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3664 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
3665 bool syn
, struct tcp_fastopen_cookie
*foc
,
3668 /* Valid only in SYN or SYN-ACK with an even length. */
3669 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
3672 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3673 len
<= TCP_FASTOPEN_COOKIE_MAX
)
3674 memcpy(foc
->val
, cookie
, len
);
3681 static void smc_parse_options(const struct tcphdr
*th
,
3682 struct tcp_options_received
*opt_rx
,
3683 const unsigned char *ptr
,
3686 #if IS_ENABLED(CONFIG_SMC)
3687 if (static_branch_unlikely(&tcp_have_smc
)) {
3688 if (th
->syn
&& !(opsize
& 1) &&
3689 opsize
>= TCPOLEN_EXP_SMC_BASE
&&
3690 get_unaligned_be32(ptr
) == TCPOPT_SMC_MAGIC
)
3696 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3697 * But, this can also be called on packets in the established flow when
3698 * the fast version below fails.
3700 void tcp_parse_options(const struct net
*net
,
3701 const struct sk_buff
*skb
,
3702 struct tcp_options_received
*opt_rx
, int estab
,
3703 struct tcp_fastopen_cookie
*foc
)
3705 const unsigned char *ptr
;
3706 const struct tcphdr
*th
= tcp_hdr(skb
);
3707 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3709 ptr
= (const unsigned char *)(th
+ 1);
3710 opt_rx
->saw_tstamp
= 0;
3712 while (length
> 0) {
3713 int opcode
= *ptr
++;
3719 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3724 if (opsize
< 2) /* "silly options" */
3726 if (opsize
> length
)
3727 return; /* don't parse partial options */
3730 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3731 u16 in_mss
= get_unaligned_be16(ptr
);
3733 if (opt_rx
->user_mss
&&
3734 opt_rx
->user_mss
< in_mss
)
3735 in_mss
= opt_rx
->user_mss
;
3736 opt_rx
->mss_clamp
= in_mss
;
3741 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3742 !estab
&& net
->ipv4
.sysctl_tcp_window_scaling
) {
3743 __u8 snd_wscale
= *(__u8
*)ptr
;
3744 opt_rx
->wscale_ok
= 1;
3745 if (snd_wscale
> TCP_MAX_WSCALE
) {
3746 net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n",
3750 snd_wscale
= TCP_MAX_WSCALE
;
3752 opt_rx
->snd_wscale
= snd_wscale
;
3755 case TCPOPT_TIMESTAMP
:
3756 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3757 ((estab
&& opt_rx
->tstamp_ok
) ||
3758 (!estab
&& net
->ipv4
.sysctl_tcp_timestamps
))) {
3759 opt_rx
->saw_tstamp
= 1;
3760 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3761 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3764 case TCPOPT_SACK_PERM
:
3765 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3766 !estab
&& net
->ipv4
.sysctl_tcp_sack
) {
3767 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3768 tcp_sack_reset(opt_rx
);
3773 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3774 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3776 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3779 #ifdef CONFIG_TCP_MD5SIG
3782 * The MD5 Hash has already been
3783 * checked (see tcp_v{4,6}_do_rcv()).
3787 case TCPOPT_FASTOPEN
:
3788 tcp_parse_fastopen_option(
3789 opsize
- TCPOLEN_FASTOPEN_BASE
,
3790 ptr
, th
->syn
, foc
, false);
3794 /* Fast Open option shares code 254 using a
3795 * 16 bits magic number.
3797 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
3798 get_unaligned_be16(ptr
) ==
3799 TCPOPT_FASTOPEN_MAGIC
)
3800 tcp_parse_fastopen_option(opsize
-
3801 TCPOLEN_EXP_FASTOPEN_BASE
,
3802 ptr
+ 2, th
->syn
, foc
, true);
3804 smc_parse_options(th
, opt_rx
, ptr
,
3814 EXPORT_SYMBOL(tcp_parse_options
);
3816 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3818 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3820 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3821 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3822 tp
->rx_opt
.saw_tstamp
= 1;
3824 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3827 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3829 tp
->rx_opt
.rcv_tsecr
= 0;
3835 /* Fast parse options. This hopes to only see timestamps.
3836 * If it is wrong it falls back on tcp_parse_options().
3838 static bool tcp_fast_parse_options(const struct net
*net
,
3839 const struct sk_buff
*skb
,
3840 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3842 /* In the spirit of fast parsing, compare doff directly to constant
3843 * values. Because equality is used, short doff can be ignored here.
3845 if (th
->doff
== (sizeof(*th
) / 4)) {
3846 tp
->rx_opt
.saw_tstamp
= 0;
3848 } else if (tp
->rx_opt
.tstamp_ok
&&
3849 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3850 if (tcp_parse_aligned_timestamp(tp
, th
))
3854 tcp_parse_options(net
, skb
, &tp
->rx_opt
, 1, NULL
);
3855 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3856 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3861 #ifdef CONFIG_TCP_MD5SIG
3863 * Parse MD5 Signature option
3865 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3867 int length
= (th
->doff
<< 2) - sizeof(*th
);
3868 const u8
*ptr
= (const u8
*)(th
+ 1);
3870 /* If the TCP option is too short, we can short cut */
3871 if (length
< TCPOLEN_MD5SIG
)
3874 while (length
> 0) {
3875 int opcode
= *ptr
++;
3886 if (opsize
< 2 || opsize
> length
)
3888 if (opcode
== TCPOPT_MD5SIG
)
3889 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3896 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3899 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3901 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3902 * it can pass through stack. So, the following predicate verifies that
3903 * this segment is not used for anything but congestion avoidance or
3904 * fast retransmit. Moreover, we even are able to eliminate most of such
3905 * second order effects, if we apply some small "replay" window (~RTO)
3906 * to timestamp space.
3908 * All these measures still do not guarantee that we reject wrapped ACKs
3909 * on networks with high bandwidth, when sequence space is recycled fastly,
3910 * but it guarantees that such events will be very rare and do not affect
3911 * connection seriously. This doesn't look nice, but alas, PAWS is really
3914 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3915 * states that events when retransmit arrives after original data are rare.
3916 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3917 * the biggest problem on large power networks even with minor reordering.
3918 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3919 * up to bandwidth of 18Gigabit/sec. 8) ]
3922 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3924 const struct tcp_sock
*tp
= tcp_sk(sk
);
3925 const struct tcphdr
*th
= tcp_hdr(skb
);
3926 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3927 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3929 return (/* 1. Pure ACK with correct sequence number. */
3930 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3932 /* 2. ... and duplicate ACK. */
3933 ack
== tp
->snd_una
&&
3935 /* 3. ... and does not update window. */
3936 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3938 /* 4. ... and sits in replay window. */
3939 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3942 static inline bool tcp_paws_discard(const struct sock
*sk
,
3943 const struct sk_buff
*skb
)
3945 const struct tcp_sock
*tp
= tcp_sk(sk
);
3947 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3948 !tcp_disordered_ack(sk
, skb
);
3951 /* Check segment sequence number for validity.
3953 * Segment controls are considered valid, if the segment
3954 * fits to the window after truncation to the window. Acceptability
3955 * of data (and SYN, FIN, of course) is checked separately.
3956 * See tcp_data_queue(), for example.
3958 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3959 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3960 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3961 * (borrowed from freebsd)
3964 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3966 return !before(end_seq
, tp
->rcv_wup
) &&
3967 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3970 /* When we get a reset we do this. */
3971 void tcp_reset(struct sock
*sk
)
3973 trace_tcp_receive_reset(sk
);
3975 /* We want the right error as BSD sees it (and indeed as we do). */
3976 switch (sk
->sk_state
) {
3978 sk
->sk_err
= ECONNREFUSED
;
3980 case TCP_CLOSE_WAIT
:
3986 sk
->sk_err
= ECONNRESET
;
3988 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3993 if (!sock_flag(sk
, SOCK_DEAD
))
3994 sk
->sk_error_report(sk
);
3998 * Process the FIN bit. This now behaves as it is supposed to work
3999 * and the FIN takes effect when it is validly part of sequence
4000 * space. Not before when we get holes.
4002 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4003 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4006 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4007 * close and we go into CLOSING (and later onto TIME-WAIT)
4009 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4011 void tcp_fin(struct sock
*sk
)
4013 struct tcp_sock
*tp
= tcp_sk(sk
);
4015 inet_csk_schedule_ack(sk
);
4017 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4018 sock_set_flag(sk
, SOCK_DONE
);
4020 switch (sk
->sk_state
) {
4022 case TCP_ESTABLISHED
:
4023 /* Move to CLOSE_WAIT */
4024 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4025 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4028 case TCP_CLOSE_WAIT
:
4030 /* Received a retransmission of the FIN, do
4035 /* RFC793: Remain in the LAST-ACK state. */
4039 /* This case occurs when a simultaneous close
4040 * happens, we must ack the received FIN and
4041 * enter the CLOSING state.
4044 tcp_set_state(sk
, TCP_CLOSING
);
4047 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4049 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4052 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4053 * cases we should never reach this piece of code.
4055 pr_err("%s: Impossible, sk->sk_state=%d\n",
4056 __func__
, sk
->sk_state
);
4060 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4061 * Probably, we should reset in this case. For now drop them.
4063 skb_rbtree_purge(&tp
->out_of_order_queue
);
4064 if (tcp_is_sack(tp
))
4065 tcp_sack_reset(&tp
->rx_opt
);
4068 if (!sock_flag(sk
, SOCK_DEAD
)) {
4069 sk
->sk_state_change(sk
);
4071 /* Do not send POLL_HUP for half duplex close. */
4072 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4073 sk
->sk_state
== TCP_CLOSE
)
4074 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4076 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4080 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4083 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4084 if (before(seq
, sp
->start_seq
))
4085 sp
->start_seq
= seq
;
4086 if (after(end_seq
, sp
->end_seq
))
4087 sp
->end_seq
= end_seq
;
4093 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4095 struct tcp_sock
*tp
= tcp_sk(sk
);
4097 if (tcp_is_sack(tp
) && sock_net(sk
)->ipv4
.sysctl_tcp_dsack
) {
4100 if (before(seq
, tp
->rcv_nxt
))
4101 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4103 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4105 NET_INC_STATS(sock_net(sk
), mib_idx
);
4107 tp
->rx_opt
.dsack
= 1;
4108 tp
->duplicate_sack
[0].start_seq
= seq
;
4109 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4113 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4115 struct tcp_sock
*tp
= tcp_sk(sk
);
4117 if (!tp
->rx_opt
.dsack
)
4118 tcp_dsack_set(sk
, seq
, end_seq
);
4120 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4123 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4125 struct tcp_sock
*tp
= tcp_sk(sk
);
4127 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4128 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4129 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4130 tcp_enter_quickack_mode(sk
);
4132 if (tcp_is_sack(tp
) && sock_net(sk
)->ipv4
.sysctl_tcp_dsack
) {
4133 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4135 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4136 end_seq
= tp
->rcv_nxt
;
4137 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4144 /* These routines update the SACK block as out-of-order packets arrive or
4145 * in-order packets close up the sequence space.
4147 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4150 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4151 struct tcp_sack_block
*swalk
= sp
+ 1;
4153 /* See if the recent change to the first SACK eats into
4154 * or hits the sequence space of other SACK blocks, if so coalesce.
4156 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4157 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4160 /* Zap SWALK, by moving every further SACK up by one slot.
4161 * Decrease num_sacks.
4163 tp
->rx_opt
.num_sacks
--;
4164 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4168 this_sack
++, swalk
++;
4172 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4174 struct tcp_sock
*tp
= tcp_sk(sk
);
4175 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4176 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4182 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4183 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4184 /* Rotate this_sack to the first one. */
4185 for (; this_sack
> 0; this_sack
--, sp
--)
4186 swap(*sp
, *(sp
- 1));
4188 tcp_sack_maybe_coalesce(tp
);
4193 /* Could not find an adjacent existing SACK, build a new one,
4194 * put it at the front, and shift everyone else down. We
4195 * always know there is at least one SACK present already here.
4197 * If the sack array is full, forget about the last one.
4199 if (this_sack
>= TCP_NUM_SACKS
) {
4201 tp
->rx_opt
.num_sacks
--;
4204 for (; this_sack
> 0; this_sack
--, sp
--)
4208 /* Build the new head SACK, and we're done. */
4209 sp
->start_seq
= seq
;
4210 sp
->end_seq
= end_seq
;
4211 tp
->rx_opt
.num_sacks
++;
4214 /* RCV.NXT advances, some SACKs should be eaten. */
4216 static void tcp_sack_remove(struct tcp_sock
*tp
)
4218 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4219 int num_sacks
= tp
->rx_opt
.num_sacks
;
4222 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4223 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4224 tp
->rx_opt
.num_sacks
= 0;
4228 for (this_sack
= 0; this_sack
< num_sacks
;) {
4229 /* Check if the start of the sack is covered by RCV.NXT. */
4230 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4233 /* RCV.NXT must cover all the block! */
4234 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4236 /* Zap this SACK, by moving forward any other SACKS. */
4237 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4238 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4245 tp
->rx_opt
.num_sacks
= num_sacks
;
4249 * tcp_try_coalesce - try to merge skb to prior one
4251 * @dest: destination queue
4253 * @from: buffer to add in queue
4254 * @fragstolen: pointer to boolean
4256 * Before queueing skb @from after @to, try to merge them
4257 * to reduce overall memory use and queue lengths, if cost is small.
4258 * Packets in ofo or receive queues can stay a long time.
4259 * Better try to coalesce them right now to avoid future collapses.
4260 * Returns true if caller should free @from instead of queueing it
4262 static bool tcp_try_coalesce(struct sock
*sk
,
4264 struct sk_buff
*from
,
4269 *fragstolen
= false;
4271 /* Its possible this segment overlaps with prior segment in queue */
4272 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4275 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4278 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4279 sk_mem_charge(sk
, delta
);
4280 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4281 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4282 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4283 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4285 if (TCP_SKB_CB(from
)->has_rxtstamp
) {
4286 TCP_SKB_CB(to
)->has_rxtstamp
= true;
4287 to
->tstamp
= from
->tstamp
;
4293 static void tcp_drop(struct sock
*sk
, struct sk_buff
*skb
)
4295 sk_drops_add(sk
, skb
);
4299 /* This one checks to see if we can put data from the
4300 * out_of_order queue into the receive_queue.
4302 static void tcp_ofo_queue(struct sock
*sk
)
4304 struct tcp_sock
*tp
= tcp_sk(sk
);
4305 __u32 dsack_high
= tp
->rcv_nxt
;
4306 bool fin
, fragstolen
, eaten
;
4307 struct sk_buff
*skb
, *tail
;
4310 p
= rb_first(&tp
->out_of_order_queue
);
4313 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4316 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4317 __u32 dsack
= dsack_high
;
4318 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4319 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4320 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4323 rb_erase(&skb
->rbnode
, &tp
->out_of_order_queue
);
4325 if (unlikely(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))) {
4326 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4330 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4331 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4332 TCP_SKB_CB(skb
)->end_seq
);
4334 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4335 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4336 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4337 fin
= TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
;
4339 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4341 kfree_skb_partial(skb
, fragstolen
);
4343 if (unlikely(fin
)) {
4345 /* tcp_fin() purges tp->out_of_order_queue,
4346 * so we must end this loop right now.
4353 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4354 static int tcp_prune_queue(struct sock
*sk
);
4356 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4359 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4360 !sk_rmem_schedule(sk
, skb
, size
)) {
4362 if (tcp_prune_queue(sk
) < 0)
4365 while (!sk_rmem_schedule(sk
, skb
, size
)) {
4366 if (!tcp_prune_ofo_queue(sk
))
4373 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4375 struct tcp_sock
*tp
= tcp_sk(sk
);
4376 struct rb_node
**p
, *parent
;
4377 struct sk_buff
*skb1
;
4381 tcp_ecn_check_ce(tp
, skb
);
4383 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4384 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4389 /* Disable header prediction. */
4391 inet_csk_schedule_ack(sk
);
4393 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4394 seq
= TCP_SKB_CB(skb
)->seq
;
4395 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4396 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4397 tp
->rcv_nxt
, seq
, end_seq
);
4399 p
= &tp
->out_of_order_queue
.rb_node
;
4400 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4401 /* Initial out of order segment, build 1 SACK. */
4402 if (tcp_is_sack(tp
)) {
4403 tp
->rx_opt
.num_sacks
= 1;
4404 tp
->selective_acks
[0].start_seq
= seq
;
4405 tp
->selective_acks
[0].end_seq
= end_seq
;
4407 rb_link_node(&skb
->rbnode
, NULL
, p
);
4408 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4409 tp
->ooo_last_skb
= skb
;
4413 /* In the typical case, we are adding an skb to the end of the list.
4414 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4416 if (tcp_try_coalesce(sk
, tp
->ooo_last_skb
,
4417 skb
, &fragstolen
)) {
4419 tcp_grow_window(sk
, skb
);
4420 kfree_skb_partial(skb
, fragstolen
);
4424 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4425 if (!before(seq
, TCP_SKB_CB(tp
->ooo_last_skb
)->end_seq
)) {
4426 parent
= &tp
->ooo_last_skb
->rbnode
;
4427 p
= &parent
->rb_right
;
4431 /* Find place to insert this segment. Handle overlaps on the way. */
4435 skb1
= rb_to_skb(parent
);
4436 if (before(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4437 p
= &parent
->rb_left
;
4440 if (before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4441 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4442 /* All the bits are present. Drop. */
4443 NET_INC_STATS(sock_net(sk
),
4444 LINUX_MIB_TCPOFOMERGE
);
4447 tcp_dsack_set(sk
, seq
, end_seq
);
4450 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4451 /* Partial overlap. */
4452 tcp_dsack_set(sk
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
4454 /* skb's seq == skb1's seq and skb covers skb1.
4455 * Replace skb1 with skb.
4457 rb_replace_node(&skb1
->rbnode
, &skb
->rbnode
,
4458 &tp
->out_of_order_queue
);
4459 tcp_dsack_extend(sk
,
4460 TCP_SKB_CB(skb1
)->seq
,
4461 TCP_SKB_CB(skb1
)->end_seq
);
4462 NET_INC_STATS(sock_net(sk
),
4463 LINUX_MIB_TCPOFOMERGE
);
4467 } else if (tcp_try_coalesce(sk
, skb1
,
4468 skb
, &fragstolen
)) {
4471 p
= &parent
->rb_right
;
4474 /* Insert segment into RB tree. */
4475 rb_link_node(&skb
->rbnode
, parent
, p
);
4476 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4479 /* Remove other segments covered by skb. */
4480 while ((skb1
= skb_rb_next(skb
)) != NULL
) {
4481 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4483 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4484 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4488 rb_erase(&skb1
->rbnode
, &tp
->out_of_order_queue
);
4489 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4490 TCP_SKB_CB(skb1
)->end_seq
);
4491 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4494 /* If there is no skb after us, we are the last_skb ! */
4496 tp
->ooo_last_skb
= skb
;
4499 if (tcp_is_sack(tp
))
4500 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4503 tcp_grow_window(sk
, skb
);
4505 skb_set_owner_r(skb
, sk
);
4509 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4513 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4515 __skb_pull(skb
, hdrlen
);
4517 tcp_try_coalesce(sk
, tail
,
4518 skb
, fragstolen
)) ? 1 : 0;
4519 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
4521 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4522 skb_set_owner_r(skb
, sk
);
4527 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4529 struct sk_buff
*skb
;
4537 if (size
> PAGE_SIZE
) {
4538 int npages
= min_t(size_t, size
>> PAGE_SHIFT
, MAX_SKB_FRAGS
);
4540 data_len
= npages
<< PAGE_SHIFT
;
4541 size
= data_len
+ (size
& ~PAGE_MASK
);
4543 skb
= alloc_skb_with_frags(size
- data_len
, data_len
,
4544 PAGE_ALLOC_COSTLY_ORDER
,
4545 &err
, sk
->sk_allocation
);
4549 skb_put(skb
, size
- data_len
);
4550 skb
->data_len
= data_len
;
4553 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4556 err
= skb_copy_datagram_from_iter(skb
, 0, &msg
->msg_iter
, size
);
4560 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4561 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4562 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4564 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4565 WARN_ON_ONCE(fragstolen
); /* should not happen */
4577 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4579 struct tcp_sock
*tp
= tcp_sk(sk
);
4583 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
) {
4588 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4590 tcp_ecn_accept_cwr(tp
, skb
);
4592 tp
->rx_opt
.dsack
= 0;
4594 /* Queue data for delivery to the user.
4595 * Packets in sequence go to the receive queue.
4596 * Out of sequence packets to the out_of_order_queue.
4598 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4599 if (tcp_receive_window(tp
) == 0)
4602 /* Ok. In sequence. In window. */
4604 if (skb_queue_len(&sk
->sk_receive_queue
) == 0)
4605 sk_forced_mem_schedule(sk
, skb
->truesize
);
4606 else if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4609 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4610 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4612 tcp_event_data_recv(sk
, skb
);
4613 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4616 if (!RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4619 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4620 * gap in queue is filled.
4622 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
4623 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4626 if (tp
->rx_opt
.num_sacks
)
4627 tcp_sack_remove(tp
);
4629 tcp_fast_path_check(sk
);
4632 kfree_skb_partial(skb
, fragstolen
);
4633 if (!sock_flag(sk
, SOCK_DEAD
))
4634 sk
->sk_data_ready(sk
);
4638 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4639 /* A retransmit, 2nd most common case. Force an immediate ack. */
4640 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4641 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4644 tcp_enter_quickack_mode(sk
);
4645 inet_csk_schedule_ack(sk
);
4651 /* Out of window. F.e. zero window probe. */
4652 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4655 tcp_enter_quickack_mode(sk
);
4657 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4658 /* Partial packet, seq < rcv_next < end_seq */
4659 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4660 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4661 TCP_SKB_CB(skb
)->end_seq
);
4663 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4665 /* If window is closed, drop tail of packet. But after
4666 * remembering D-SACK for its head made in previous line.
4668 if (!tcp_receive_window(tp
))
4673 tcp_data_queue_ofo(sk
, skb
);
4676 static struct sk_buff
*tcp_skb_next(struct sk_buff
*skb
, struct sk_buff_head
*list
)
4679 return !skb_queue_is_last(list
, skb
) ? skb
->next
: NULL
;
4681 return skb_rb_next(skb
);
4684 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4685 struct sk_buff_head
*list
,
4686 struct rb_root
*root
)
4688 struct sk_buff
*next
= tcp_skb_next(skb
, list
);
4691 __skb_unlink(skb
, list
);
4693 rb_erase(&skb
->rbnode
, root
);
4696 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4701 /* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
4702 void tcp_rbtree_insert(struct rb_root
*root
, struct sk_buff
*skb
)
4704 struct rb_node
**p
= &root
->rb_node
;
4705 struct rb_node
*parent
= NULL
;
4706 struct sk_buff
*skb1
;
4710 skb1
= rb_to_skb(parent
);
4711 if (before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb1
)->seq
))
4712 p
= &parent
->rb_left
;
4714 p
= &parent
->rb_right
;
4716 rb_link_node(&skb
->rbnode
, parent
, p
);
4717 rb_insert_color(&skb
->rbnode
, root
);
4720 /* Collapse contiguous sequence of skbs head..tail with
4721 * sequence numbers start..end.
4723 * If tail is NULL, this means until the end of the queue.
4725 * Segments with FIN/SYN are not collapsed (only because this
4729 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
, struct rb_root
*root
,
4730 struct sk_buff
*head
, struct sk_buff
*tail
, u32 start
, u32 end
)
4732 struct sk_buff
*skb
= head
, *n
;
4733 struct sk_buff_head tmp
;
4736 /* First, check that queue is collapsible and find
4737 * the point where collapsing can be useful.
4740 for (end_of_skbs
= true; skb
!= NULL
&& skb
!= tail
; skb
= n
) {
4741 n
= tcp_skb_next(skb
, list
);
4743 /* No new bits? It is possible on ofo queue. */
4744 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4745 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
4751 /* The first skb to collapse is:
4753 * - bloated or contains data before "start" or
4754 * overlaps to the next one.
4756 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4757 (tcp_win_from_space(sk
, skb
->truesize
) > skb
->len
||
4758 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4759 end_of_skbs
= false;
4763 if (n
&& n
!= tail
&&
4764 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(n
)->seq
) {
4765 end_of_skbs
= false;
4769 /* Decided to skip this, advance start seq. */
4770 start
= TCP_SKB_CB(skb
)->end_seq
;
4773 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4776 __skb_queue_head_init(&tmp
);
4778 while (before(start
, end
)) {
4779 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4780 struct sk_buff
*nskb
;
4782 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4786 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4787 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4789 __skb_queue_before(list
, skb
, nskb
);
4791 __skb_queue_tail(&tmp
, nskb
); /* defer rbtree insertion */
4792 skb_set_owner_r(nskb
, sk
);
4794 /* Copy data, releasing collapsed skbs. */
4796 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4797 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4801 size
= min(copy
, size
);
4802 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4804 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4808 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4809 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
4812 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4818 skb_queue_walk_safe(&tmp
, skb
, n
)
4819 tcp_rbtree_insert(root
, skb
);
4822 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4823 * and tcp_collapse() them until all the queue is collapsed.
4825 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4827 struct tcp_sock
*tp
= tcp_sk(sk
);
4828 struct sk_buff
*skb
, *head
;
4831 skb
= skb_rb_first(&tp
->out_of_order_queue
);
4834 tp
->ooo_last_skb
= skb_rb_last(&tp
->out_of_order_queue
);
4837 start
= TCP_SKB_CB(skb
)->seq
;
4838 end
= TCP_SKB_CB(skb
)->end_seq
;
4840 for (head
= skb
;;) {
4841 skb
= skb_rb_next(skb
);
4843 /* Range is terminated when we see a gap or when
4844 * we are at the queue end.
4847 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4848 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4849 tcp_collapse(sk
, NULL
, &tp
->out_of_order_queue
,
4850 head
, skb
, start
, end
);
4854 if (unlikely(before(TCP_SKB_CB(skb
)->seq
, start
)))
4855 start
= TCP_SKB_CB(skb
)->seq
;
4856 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4857 end
= TCP_SKB_CB(skb
)->end_seq
;
4862 * Clean the out-of-order queue to make room.
4863 * We drop high sequences packets to :
4864 * 1) Let a chance for holes to be filled.
4865 * 2) not add too big latencies if thousands of packets sit there.
4866 * (But if application shrinks SO_RCVBUF, we could still end up
4867 * freeing whole queue here)
4869 * Return true if queue has shrunk.
4871 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4873 struct tcp_sock
*tp
= tcp_sk(sk
);
4874 struct rb_node
*node
, *prev
;
4876 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
4879 NET_INC_STATS(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4880 node
= &tp
->ooo_last_skb
->rbnode
;
4882 prev
= rb_prev(node
);
4883 rb_erase(node
, &tp
->out_of_order_queue
);
4884 tcp_drop(sk
, rb_to_skb(node
));
4886 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
&&
4887 !tcp_under_memory_pressure(sk
))
4891 tp
->ooo_last_skb
= rb_to_skb(prev
);
4893 /* Reset SACK state. A conforming SACK implementation will
4894 * do the same at a timeout based retransmit. When a connection
4895 * is in a sad state like this, we care only about integrity
4896 * of the connection not performance.
4898 if (tp
->rx_opt
.sack_ok
)
4899 tcp_sack_reset(&tp
->rx_opt
);
4903 /* Reduce allocated memory if we can, trying to get
4904 * the socket within its memory limits again.
4906 * Return less than zero if we should start dropping frames
4907 * until the socket owning process reads some of the data
4908 * to stabilize the situation.
4910 static int tcp_prune_queue(struct sock
*sk
)
4912 struct tcp_sock
*tp
= tcp_sk(sk
);
4914 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4916 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4918 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4919 tcp_clamp_window(sk
);
4920 else if (tcp_under_memory_pressure(sk
))
4921 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4923 tcp_collapse_ofo_queue(sk
);
4924 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4925 tcp_collapse(sk
, &sk
->sk_receive_queue
, NULL
,
4926 skb_peek(&sk
->sk_receive_queue
),
4928 tp
->copied_seq
, tp
->rcv_nxt
);
4931 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4934 /* Collapsing did not help, destructive actions follow.
4935 * This must not ever occur. */
4937 tcp_prune_ofo_queue(sk
);
4939 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4942 /* If we are really being abused, tell the caller to silently
4943 * drop receive data on the floor. It will get retransmitted
4944 * and hopefully then we'll have sufficient space.
4946 NET_INC_STATS(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4948 /* Massive buffer overcommit. */
4953 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4955 const struct tcp_sock
*tp
= tcp_sk(sk
);
4957 /* If the user specified a specific send buffer setting, do
4960 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4963 /* If we are under global TCP memory pressure, do not expand. */
4964 if (tcp_under_memory_pressure(sk
))
4967 /* If we are under soft global TCP memory pressure, do not expand. */
4968 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4971 /* If we filled the congestion window, do not expand. */
4972 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
4978 /* When incoming ACK allowed to free some skb from write_queue,
4979 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4980 * on the exit from tcp input handler.
4982 * PROBLEM: sndbuf expansion does not work well with largesend.
4984 static void tcp_new_space(struct sock
*sk
)
4986 struct tcp_sock
*tp
= tcp_sk(sk
);
4988 if (tcp_should_expand_sndbuf(sk
)) {
4989 tcp_sndbuf_expand(sk
);
4990 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
4993 sk
->sk_write_space(sk
);
4996 static void tcp_check_space(struct sock
*sk
)
4998 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4999 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
5000 /* pairs with tcp_poll() */
5002 if (sk
->sk_socket
&&
5003 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
5005 if (!test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
5006 tcp_chrono_stop(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
5011 static inline void tcp_data_snd_check(struct sock
*sk
)
5013 tcp_push_pending_frames(sk
);
5014 tcp_check_space(sk
);
5018 * Check if sending an ack is needed.
5020 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5022 struct tcp_sock
*tp
= tcp_sk(sk
);
5024 /* More than one full frame received... */
5025 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5026 /* ... and right edge of window advances far enough.
5027 * (tcp_recvmsg() will send ACK otherwise). Or...
5029 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
5030 /* We ACK each frame or... */
5031 tcp_in_quickack_mode(sk
) ||
5032 /* We have out of order data. */
5033 (ofo_possible
&& !RB_EMPTY_ROOT(&tp
->out_of_order_queue
))) {
5034 /* Then ack it now */
5037 /* Else, send delayed ack. */
5038 tcp_send_delayed_ack(sk
);
5042 static inline void tcp_ack_snd_check(struct sock
*sk
)
5044 if (!inet_csk_ack_scheduled(sk
)) {
5045 /* We sent a data segment already. */
5048 __tcp_ack_snd_check(sk
, 1);
5052 * This routine is only called when we have urgent data
5053 * signaled. Its the 'slow' part of tcp_urg. It could be
5054 * moved inline now as tcp_urg is only called from one
5055 * place. We handle URGent data wrong. We have to - as
5056 * BSD still doesn't use the correction from RFC961.
5057 * For 1003.1g we should support a new option TCP_STDURG to permit
5058 * either form (or just set the sysctl tcp_stdurg).
5061 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5063 struct tcp_sock
*tp
= tcp_sk(sk
);
5064 u32 ptr
= ntohs(th
->urg_ptr
);
5066 if (ptr
&& !sock_net(sk
)->ipv4
.sysctl_tcp_stdurg
)
5068 ptr
+= ntohl(th
->seq
);
5070 /* Ignore urgent data that we've already seen and read. */
5071 if (after(tp
->copied_seq
, ptr
))
5074 /* Do not replay urg ptr.
5076 * NOTE: interesting situation not covered by specs.
5077 * Misbehaving sender may send urg ptr, pointing to segment,
5078 * which we already have in ofo queue. We are not able to fetch
5079 * such data and will stay in TCP_URG_NOTYET until will be eaten
5080 * by recvmsg(). Seems, we are not obliged to handle such wicked
5081 * situations. But it is worth to think about possibility of some
5082 * DoSes using some hypothetical application level deadlock.
5084 if (before(ptr
, tp
->rcv_nxt
))
5087 /* Do we already have a newer (or duplicate) urgent pointer? */
5088 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5091 /* Tell the world about our new urgent pointer. */
5094 /* We may be adding urgent data when the last byte read was
5095 * urgent. To do this requires some care. We cannot just ignore
5096 * tp->copied_seq since we would read the last urgent byte again
5097 * as data, nor can we alter copied_seq until this data arrives
5098 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5100 * NOTE. Double Dutch. Rendering to plain English: author of comment
5101 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5102 * and expect that both A and B disappear from stream. This is _wrong_.
5103 * Though this happens in BSD with high probability, this is occasional.
5104 * Any application relying on this is buggy. Note also, that fix "works"
5105 * only in this artificial test. Insert some normal data between A and B and we will
5106 * decline of BSD again. Verdict: it is better to remove to trap
5109 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5110 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5111 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5113 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5114 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5119 tp
->urg_data
= TCP_URG_NOTYET
;
5122 /* Disable header prediction. */
5126 /* This is the 'fast' part of urgent handling. */
5127 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5129 struct tcp_sock
*tp
= tcp_sk(sk
);
5131 /* Check if we get a new urgent pointer - normally not. */
5133 tcp_check_urg(sk
, th
);
5135 /* Do we wait for any urgent data? - normally not... */
5136 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5137 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5140 /* Is the urgent pointer pointing into this packet? */
5141 if (ptr
< skb
->len
) {
5143 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5145 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5146 if (!sock_flag(sk
, SOCK_DEAD
))
5147 sk
->sk_data_ready(sk
);
5152 /* Accept RST for rcv_nxt - 1 after a FIN.
5153 * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
5154 * FIN is sent followed by a RST packet. The RST is sent with the same
5155 * sequence number as the FIN, and thus according to RFC 5961 a challenge
5156 * ACK should be sent. However, Mac OSX rate limits replies to challenge
5157 * ACKs on the closed socket. In addition middleboxes can drop either the
5158 * challenge ACK or a subsequent RST.
5160 static bool tcp_reset_check(const struct sock
*sk
, const struct sk_buff
*skb
)
5162 struct tcp_sock
*tp
= tcp_sk(sk
);
5164 return unlikely(TCP_SKB_CB(skb
)->seq
== (tp
->rcv_nxt
- 1) &&
5165 (1 << sk
->sk_state
) & (TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
|
5169 /* Does PAWS and seqno based validation of an incoming segment, flags will
5170 * play significant role here.
5172 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5173 const struct tcphdr
*th
, int syn_inerr
)
5175 struct tcp_sock
*tp
= tcp_sk(sk
);
5176 bool rst_seq_match
= false;
5178 /* RFC1323: H1. Apply PAWS check first. */
5179 if (tcp_fast_parse_options(sock_net(sk
), skb
, th
, tp
) &&
5180 tp
->rx_opt
.saw_tstamp
&&
5181 tcp_paws_discard(sk
, skb
)) {
5183 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5184 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5185 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5186 &tp
->last_oow_ack_time
))
5187 tcp_send_dupack(sk
, skb
);
5190 /* Reset is accepted even if it did not pass PAWS. */
5193 /* Step 1: check sequence number */
5194 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5195 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5196 * (RST) segments are validated by checking their SEQ-fields."
5197 * And page 69: "If an incoming segment is not acceptable,
5198 * an acknowledgment should be sent in reply (unless the RST
5199 * bit is set, if so drop the segment and return)".
5204 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5205 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5206 &tp
->last_oow_ack_time
))
5207 tcp_send_dupack(sk
, skb
);
5208 } else if (tcp_reset_check(sk
, skb
)) {
5214 /* Step 2: check RST bit */
5216 /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
5217 * FIN and SACK too if available):
5218 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
5219 * the right-most SACK block,
5221 * RESET the connection
5223 * Send a challenge ACK
5225 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
||
5226 tcp_reset_check(sk
, skb
)) {
5227 rst_seq_match
= true;
5228 } else if (tcp_is_sack(tp
) && tp
->rx_opt
.num_sacks
> 0) {
5229 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
5230 int max_sack
= sp
[0].end_seq
;
5233 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;
5235 max_sack
= after(sp
[this_sack
].end_seq
,
5237 sp
[this_sack
].end_seq
: max_sack
;
5240 if (TCP_SKB_CB(skb
)->seq
== max_sack
)
5241 rst_seq_match
= true;
5247 /* Disable TFO if RST is out-of-order
5248 * and no data has been received
5249 * for current active TFO socket
5251 if (tp
->syn_fastopen
&& !tp
->data_segs_in
&&
5252 sk
->sk_state
== TCP_ESTABLISHED
)
5253 tcp_fastopen_active_disable(sk
);
5254 tcp_send_challenge_ack(sk
, skb
);
5259 /* step 3: check security and precedence [ignored] */
5261 /* step 4: Check for a SYN
5262 * RFC 5961 4.2 : Send a challenge ack
5267 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5268 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5269 tcp_send_challenge_ack(sk
, skb
);
5281 * TCP receive function for the ESTABLISHED state.
5283 * It is split into a fast path and a slow path. The fast path is
5285 * - A zero window was announced from us - zero window probing
5286 * is only handled properly in the slow path.
5287 * - Out of order segments arrived.
5288 * - Urgent data is expected.
5289 * - There is no buffer space left
5290 * - Unexpected TCP flags/window values/header lengths are received
5291 * (detected by checking the TCP header against pred_flags)
5292 * - Data is sent in both directions. Fast path only supports pure senders
5293 * or pure receivers (this means either the sequence number or the ack
5294 * value must stay constant)
5295 * - Unexpected TCP option.
5297 * When these conditions are not satisfied it drops into a standard
5298 * receive procedure patterned after RFC793 to handle all cases.
5299 * The first three cases are guaranteed by proper pred_flags setting,
5300 * the rest is checked inline. Fast processing is turned on in
5301 * tcp_data_queue when everything is OK.
5303 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5304 const struct tcphdr
*th
)
5306 unsigned int len
= skb
->len
;
5307 struct tcp_sock
*tp
= tcp_sk(sk
);
5309 tcp_mstamp_refresh(tp
);
5310 if (unlikely(!sk
->sk_rx_dst
))
5311 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5313 * Header prediction.
5314 * The code loosely follows the one in the famous
5315 * "30 instruction TCP receive" Van Jacobson mail.
5317 * Van's trick is to deposit buffers into socket queue
5318 * on a device interrupt, to call tcp_recv function
5319 * on the receive process context and checksum and copy
5320 * the buffer to user space. smart...
5322 * Our current scheme is not silly either but we take the
5323 * extra cost of the net_bh soft interrupt processing...
5324 * We do checksum and copy also but from device to kernel.
5327 tp
->rx_opt
.saw_tstamp
= 0;
5329 /* pred_flags is 0xS?10 << 16 + snd_wnd
5330 * if header_prediction is to be made
5331 * 'S' will always be tp->tcp_header_len >> 2
5332 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5333 * turn it off (when there are holes in the receive
5334 * space for instance)
5335 * PSH flag is ignored.
5338 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5339 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5340 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5341 int tcp_header_len
= tp
->tcp_header_len
;
5343 /* Timestamp header prediction: tcp_header_len
5344 * is automatically equal to th->doff*4 due to pred_flags
5348 /* Check timestamp */
5349 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5350 /* No? Slow path! */
5351 if (!tcp_parse_aligned_timestamp(tp
, th
))
5354 /* If PAWS failed, check it more carefully in slow path */
5355 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5358 /* DO NOT update ts_recent here, if checksum fails
5359 * and timestamp was corrupted part, it will result
5360 * in a hung connection since we will drop all
5361 * future packets due to the PAWS test.
5365 if (len
<= tcp_header_len
) {
5366 /* Bulk data transfer: sender */
5367 if (len
== tcp_header_len
) {
5368 /* Predicted packet is in window by definition.
5369 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5370 * Hence, check seq<=rcv_wup reduces to:
5372 if (tcp_header_len
==
5373 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5374 tp
->rcv_nxt
== tp
->rcv_wup
)
5375 tcp_store_ts_recent(tp
);
5377 /* We know that such packets are checksummed
5380 tcp_ack(sk
, skb
, 0);
5382 tcp_data_snd_check(sk
);
5384 } else { /* Header too small */
5385 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5390 bool fragstolen
= false;
5392 if (tcp_checksum_complete(skb
))
5395 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5398 /* Predicted packet is in window by definition.
5399 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5400 * Hence, check seq<=rcv_wup reduces to:
5402 if (tcp_header_len
==
5403 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5404 tp
->rcv_nxt
== tp
->rcv_wup
)
5405 tcp_store_ts_recent(tp
);
5407 tcp_rcv_rtt_measure_ts(sk
, skb
);
5409 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5411 /* Bulk data transfer: receiver */
5412 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5415 tcp_event_data_recv(sk
, skb
);
5417 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5418 /* Well, only one small jumplet in fast path... */
5419 tcp_ack(sk
, skb
, FLAG_DATA
);
5420 tcp_data_snd_check(sk
);
5421 if (!inet_csk_ack_scheduled(sk
))
5425 __tcp_ack_snd_check(sk
, 0);
5428 kfree_skb_partial(skb
, fragstolen
);
5429 sk
->sk_data_ready(sk
);
5435 if (len
< (th
->doff
<< 2) || tcp_checksum_complete(skb
))
5438 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5442 * Standard slow path.
5445 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5449 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5452 tcp_rcv_rtt_measure_ts(sk
, skb
);
5454 /* Process urgent data. */
5455 tcp_urg(sk
, skb
, th
);
5457 /* step 7: process the segment text */
5458 tcp_data_queue(sk
, skb
);
5460 tcp_data_snd_check(sk
);
5461 tcp_ack_snd_check(sk
);
5465 TCP_INC_STATS(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5466 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5471 EXPORT_SYMBOL(tcp_rcv_established
);
5473 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5475 struct tcp_sock
*tp
= tcp_sk(sk
);
5476 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5478 tcp_set_state(sk
, TCP_ESTABLISHED
);
5479 icsk
->icsk_ack
.lrcvtime
= tcp_jiffies32
;
5482 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5483 security_inet_conn_established(sk
, skb
);
5486 tcp_init_transfer(sk
, BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB
);
5488 /* Prevent spurious tcp_cwnd_restart() on first data
5491 tp
->lsndtime
= tcp_jiffies32
;
5493 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5494 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5496 if (!tp
->rx_opt
.snd_wscale
)
5497 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5502 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5503 struct tcp_fastopen_cookie
*cookie
)
5505 struct tcp_sock
*tp
= tcp_sk(sk
);
5506 struct sk_buff
*data
= tp
->syn_data
? tcp_rtx_queue_head(sk
) : NULL
;
5507 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
5508 bool syn_drop
= false;
5510 if (mss
== tp
->rx_opt
.user_mss
) {
5511 struct tcp_options_received opt
;
5513 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5514 tcp_clear_options(&opt
);
5515 opt
.user_mss
= opt
.mss_clamp
= 0;
5516 tcp_parse_options(sock_net(sk
), synack
, &opt
, 0, NULL
);
5517 mss
= opt
.mss_clamp
;
5520 if (!tp
->syn_fastopen
) {
5521 /* Ignore an unsolicited cookie */
5523 } else if (tp
->total_retrans
) {
5524 /* SYN timed out and the SYN-ACK neither has a cookie nor
5525 * acknowledges data. Presumably the remote received only
5526 * the retransmitted (regular) SYNs: either the original
5527 * SYN-data or the corresponding SYN-ACK was dropped.
5529 syn_drop
= (cookie
->len
< 0 && data
);
5530 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
5531 /* We requested a cookie but didn't get it. If we did not use
5532 * the (old) exp opt format then try so next time (try_exp=1).
5533 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5535 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
5538 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
5540 if (data
) { /* Retransmit unacked data in SYN */
5541 skb_rbtree_walk_from(data
) {
5542 if (__tcp_retransmit_skb(sk
, data
, 1))
5546 NET_INC_STATS(sock_net(sk
),
5547 LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5550 tp
->syn_data_acked
= tp
->syn_data
;
5551 if (tp
->syn_data_acked
)
5552 NET_INC_STATS(sock_net(sk
),
5553 LINUX_MIB_TCPFASTOPENACTIVE
);
5555 tcp_fastopen_add_skb(sk
, synack
);
5560 static void smc_check_reset_syn(struct tcp_sock
*tp
)
5562 #if IS_ENABLED(CONFIG_SMC)
5563 if (static_branch_unlikely(&tcp_have_smc
)) {
5564 if (tp
->syn_smc
&& !tp
->rx_opt
.smc_ok
)
5570 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5571 const struct tcphdr
*th
)
5573 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5574 struct tcp_sock
*tp
= tcp_sk(sk
);
5575 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5576 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5579 tcp_parse_options(sock_net(sk
), skb
, &tp
->rx_opt
, 0, &foc
);
5580 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5581 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5585 * "If the state is SYN-SENT then
5586 * first check the ACK bit
5587 * If the ACK bit is set
5588 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5589 * a reset (unless the RST bit is set, if so drop
5590 * the segment and return)"
5592 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5593 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5594 goto reset_and_undo
;
5596 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5597 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5598 tcp_time_stamp(tp
))) {
5599 NET_INC_STATS(sock_net(sk
),
5600 LINUX_MIB_PAWSACTIVEREJECTED
);
5601 goto reset_and_undo
;
5604 /* Now ACK is acceptable.
5606 * "If the RST bit is set
5607 * If the ACK was acceptable then signal the user "error:
5608 * connection reset", drop the segment, enter CLOSED state,
5609 * delete TCB, and return."
5618 * "fifth, if neither of the SYN or RST bits is set then
5619 * drop the segment and return."
5625 goto discard_and_undo
;
5628 * "If the SYN bit is on ...
5629 * are acceptable then ...
5630 * (our SYN has been ACKed), change the connection
5631 * state to ESTABLISHED..."
5634 tcp_ecn_rcv_synack(tp
, th
);
5636 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5637 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5639 /* Ok.. it's good. Set up sequence numbers and
5640 * move to established.
5642 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5643 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5645 /* RFC1323: The window in SYN & SYN/ACK segments is
5648 tp
->snd_wnd
= ntohs(th
->window
);
5650 if (!tp
->rx_opt
.wscale_ok
) {
5651 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5652 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5655 if (tp
->rx_opt
.saw_tstamp
) {
5656 tp
->rx_opt
.tstamp_ok
= 1;
5657 tp
->tcp_header_len
=
5658 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5659 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5660 tcp_store_ts_recent(tp
);
5662 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5665 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5666 tcp_initialize_rcv_mss(sk
);
5668 /* Remember, tcp_poll() does not lock socket!
5669 * Change state from SYN-SENT only after copied_seq
5670 * is initialized. */
5671 tp
->copied_seq
= tp
->rcv_nxt
;
5673 smc_check_reset_syn(tp
);
5677 tcp_finish_connect(sk
, skb
);
5679 fastopen_fail
= (tp
->syn_fastopen
|| tp
->syn_data
) &&
5680 tcp_rcv_fastopen_synack(sk
, skb
, &foc
);
5682 if (!sock_flag(sk
, SOCK_DEAD
)) {
5683 sk
->sk_state_change(sk
);
5684 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5688 if (sk
->sk_write_pending
||
5689 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5690 icsk
->icsk_ack
.pingpong
) {
5691 /* Save one ACK. Data will be ready after
5692 * several ticks, if write_pending is set.
5694 * It may be deleted, but with this feature tcpdumps
5695 * look so _wonderfully_ clever, that I was not able
5696 * to stand against the temptation 8) --ANK
5698 inet_csk_schedule_ack(sk
);
5699 tcp_enter_quickack_mode(sk
);
5700 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5701 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5712 /* No ACK in the segment */
5716 * "If the RST bit is set
5718 * Otherwise (no ACK) drop the segment and return."
5721 goto discard_and_undo
;
5725 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5726 tcp_paws_reject(&tp
->rx_opt
, 0))
5727 goto discard_and_undo
;
5730 /* We see SYN without ACK. It is attempt of
5731 * simultaneous connect with crossed SYNs.
5732 * Particularly, it can be connect to self.
5734 tcp_set_state(sk
, TCP_SYN_RECV
);
5736 if (tp
->rx_opt
.saw_tstamp
) {
5737 tp
->rx_opt
.tstamp_ok
= 1;
5738 tcp_store_ts_recent(tp
);
5739 tp
->tcp_header_len
=
5740 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5742 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5745 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5746 tp
->copied_seq
= tp
->rcv_nxt
;
5747 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5749 /* RFC1323: The window in SYN & SYN/ACK segments is
5752 tp
->snd_wnd
= ntohs(th
->window
);
5753 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5754 tp
->max_window
= tp
->snd_wnd
;
5756 tcp_ecn_rcv_syn(tp
, th
);
5759 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5760 tcp_initialize_rcv_mss(sk
);
5762 tcp_send_synack(sk
);
5764 /* Note, we could accept data and URG from this segment.
5765 * There are no obstacles to make this (except that we must
5766 * either change tcp_recvmsg() to prevent it from returning data
5767 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5769 * However, if we ignore data in ACKless segments sometimes,
5770 * we have no reasons to accept it sometimes.
5771 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5772 * is not flawless. So, discard packet for sanity.
5773 * Uncomment this return to process the data.
5780 /* "fifth, if neither of the SYN or RST bits is set then
5781 * drop the segment and return."
5785 tcp_clear_options(&tp
->rx_opt
);
5786 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5790 tcp_clear_options(&tp
->rx_opt
);
5791 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5796 * This function implements the receiving procedure of RFC 793 for
5797 * all states except ESTABLISHED and TIME_WAIT.
5798 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5799 * address independent.
5802 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
)
5804 struct tcp_sock
*tp
= tcp_sk(sk
);
5805 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5806 const struct tcphdr
*th
= tcp_hdr(skb
);
5807 struct request_sock
*req
;
5811 switch (sk
->sk_state
) {
5825 /* It is possible that we process SYN packets from backlog,
5826 * so we need to make sure to disable BH right there.
5829 acceptable
= icsk
->icsk_af_ops
->conn_request(sk
, skb
) >= 0;
5840 tp
->rx_opt
.saw_tstamp
= 0;
5841 tcp_mstamp_refresh(tp
);
5842 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
);
5846 /* Do step6 onward by hand. */
5847 tcp_urg(sk
, skb
, th
);
5849 tcp_data_snd_check(sk
);
5853 tcp_mstamp_refresh(tp
);
5854 tp
->rx_opt
.saw_tstamp
= 0;
5855 req
= tp
->fastopen_rsk
;
5857 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5858 sk
->sk_state
!= TCP_FIN_WAIT1
);
5860 if (!tcp_check_req(sk
, skb
, req
, true))
5864 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5867 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5870 /* step 5: check the ACK field */
5871 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5872 FLAG_UPDATE_TS_RECENT
|
5873 FLAG_NO_CHALLENGE_ACK
) > 0;
5876 if (sk
->sk_state
== TCP_SYN_RECV
)
5877 return 1; /* send one RST */
5878 tcp_send_challenge_ack(sk
, skb
);
5881 switch (sk
->sk_state
) {
5884 tcp_synack_rtt_meas(sk
, req
);
5886 /* Once we leave TCP_SYN_RECV, we no longer need req
5890 inet_csk(sk
)->icsk_retransmits
= 0;
5891 reqsk_fastopen_remove(sk
, req
, false);
5892 /* Re-arm the timer because data may have been sent out.
5893 * This is similar to the regular data transmission case
5894 * when new data has just been ack'ed.
5896 * (TFO) - we could try to be more aggressive and
5897 * retransmitting any data sooner based on when they
5902 tcp_init_transfer(sk
, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB
);
5903 tp
->copied_seq
= tp
->rcv_nxt
;
5906 tcp_set_state(sk
, TCP_ESTABLISHED
);
5907 sk
->sk_state_change(sk
);
5909 /* Note, that this wakeup is only for marginal crossed SYN case.
5910 * Passively open sockets are not waked up, because
5911 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5914 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5916 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5917 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5918 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5920 if (tp
->rx_opt
.tstamp_ok
)
5921 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5923 if (!inet_csk(sk
)->icsk_ca_ops
->cong_control
)
5924 tcp_update_pacing_rate(sk
);
5926 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5927 tp
->lsndtime
= tcp_jiffies32
;
5929 tcp_initialize_rcv_mss(sk
);
5930 tcp_fast_path_on(tp
);
5933 case TCP_FIN_WAIT1
: {
5936 /* If we enter the TCP_FIN_WAIT1 state and we are a
5937 * Fast Open socket and this is the first acceptable
5938 * ACK we have received, this would have acknowledged
5939 * our SYNACK so stop the SYNACK timer.
5942 /* We no longer need the request sock. */
5943 reqsk_fastopen_remove(sk
, req
, false);
5946 if (tp
->snd_una
!= tp
->write_seq
)
5949 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5950 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5954 if (!sock_flag(sk
, SOCK_DEAD
)) {
5955 /* Wake up lingering close() */
5956 sk
->sk_state_change(sk
);
5960 if (tp
->linger2
< 0) {
5962 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5965 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5966 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5967 /* Receive out of order FIN after close() */
5968 if (tp
->syn_fastopen
&& th
->fin
)
5969 tcp_fastopen_active_disable(sk
);
5971 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5975 tmo
= tcp_fin_time(sk
);
5976 if (tmo
> TCP_TIMEWAIT_LEN
) {
5977 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5978 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5979 /* Bad case. We could lose such FIN otherwise.
5980 * It is not a big problem, but it looks confusing
5981 * and not so rare event. We still can lose it now,
5982 * if it spins in bh_lock_sock(), but it is really
5985 inet_csk_reset_keepalive_timer(sk
, tmo
);
5987 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5994 if (tp
->snd_una
== tp
->write_seq
) {
5995 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
6001 if (tp
->snd_una
== tp
->write_seq
) {
6002 tcp_update_metrics(sk
);
6009 /* step 6: check the URG bit */
6010 tcp_urg(sk
, skb
, th
);
6012 /* step 7: process the segment text */
6013 switch (sk
->sk_state
) {
6014 case TCP_CLOSE_WAIT
:
6017 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
6022 /* RFC 793 says to queue data in these states,
6023 * RFC 1122 says we MUST send a reset.
6024 * BSD 4.4 also does reset.
6026 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
6027 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6028 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6029 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6035 case TCP_ESTABLISHED
:
6036 tcp_data_queue(sk
, skb
);
6041 /* tcp_data could move socket to TIME-WAIT */
6042 if (sk
->sk_state
!= TCP_CLOSE
) {
6043 tcp_data_snd_check(sk
);
6044 tcp_ack_snd_check(sk
);
6053 EXPORT_SYMBOL(tcp_rcv_state_process
);
6055 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
6057 struct inet_request_sock
*ireq
= inet_rsk(req
);
6059 if (family
== AF_INET
)
6060 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6061 &ireq
->ir_rmt_addr
, port
);
6062 #if IS_ENABLED(CONFIG_IPV6)
6063 else if (family
== AF_INET6
)
6064 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6065 &ireq
->ir_v6_rmt_addr
, port
);
6069 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6071 * If we receive a SYN packet with these bits set, it means a
6072 * network is playing bad games with TOS bits. In order to
6073 * avoid possible false congestion notifications, we disable
6074 * TCP ECN negotiation.
6076 * Exception: tcp_ca wants ECN. This is required for DCTCP
6077 * congestion control: Linux DCTCP asserts ECT on all packets,
6078 * including SYN, which is most optimal solution; however,
6079 * others, such as FreeBSD do not.
6081 static void tcp_ecn_create_request(struct request_sock
*req
,
6082 const struct sk_buff
*skb
,
6083 const struct sock
*listen_sk
,
6084 const struct dst_entry
*dst
)
6086 const struct tcphdr
*th
= tcp_hdr(skb
);
6087 const struct net
*net
= sock_net(listen_sk
);
6088 bool th_ecn
= th
->ece
&& th
->cwr
;
6095 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
6096 ecn_ok_dst
= dst_feature(dst
, DST_FEATURE_ECN_MASK
);
6097 ecn_ok
= net
->ipv4
.sysctl_tcp_ecn
|| ecn_ok_dst
;
6099 if ((!ect
&& ecn_ok
) || tcp_ca_needs_ecn(listen_sk
) ||
6100 (ecn_ok_dst
& DST_FEATURE_ECN_CA
) ||
6101 tcp_bpf_ca_needs_ecn((struct sock
*)req
))
6102 inet_rsk(req
)->ecn_ok
= 1;
6105 static void tcp_openreq_init(struct request_sock
*req
,
6106 const struct tcp_options_received
*rx_opt
,
6107 struct sk_buff
*skb
, const struct sock
*sk
)
6109 struct inet_request_sock
*ireq
= inet_rsk(req
);
6111 req
->rsk_rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6113 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6114 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6115 tcp_rsk(req
)->snt_synack
= tcp_clock_us();
6116 tcp_rsk(req
)->last_oow_ack_time
= 0;
6117 req
->mss
= rx_opt
->mss_clamp
;
6118 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6119 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6120 ireq
->sack_ok
= rx_opt
->sack_ok
;
6121 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6122 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6125 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6126 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6127 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6128 #if IS_ENABLED(CONFIG_SMC)
6129 ireq
->smc_ok
= rx_opt
->smc_ok
;
6133 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6134 struct sock
*sk_listener
,
6135 bool attach_listener
)
6137 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
,
6141 struct inet_request_sock
*ireq
= inet_rsk(req
);
6143 ireq
->ireq_opt
= NULL
;
6144 #if IS_ENABLED(CONFIG_IPV6)
6145 ireq
->pktopts
= NULL
;
6147 atomic64_set(&ireq
->ir_cookie
, 0);
6148 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6149 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6150 ireq
->ireq_family
= sk_listener
->sk_family
;
6155 EXPORT_SYMBOL(inet_reqsk_alloc
);
6158 * Return true if a syncookie should be sent
6160 static bool tcp_syn_flood_action(const struct sock
*sk
,
6161 const struct sk_buff
*skb
,
6164 struct request_sock_queue
*queue
= &inet_csk(sk
)->icsk_accept_queue
;
6165 const char *msg
= "Dropping request";
6166 bool want_cookie
= false;
6167 struct net
*net
= sock_net(sk
);
6169 #ifdef CONFIG_SYN_COOKIES
6170 if (net
->ipv4
.sysctl_tcp_syncookies
) {
6171 msg
= "Sending cookies";
6173 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
6176 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
6178 if (!queue
->synflood_warned
&&
6179 net
->ipv4
.sysctl_tcp_syncookies
!= 2 &&
6180 xchg(&queue
->synflood_warned
, 1) == 0)
6181 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6182 proto
, ntohs(tcp_hdr(skb
)->dest
), msg
);
6187 static void tcp_reqsk_record_syn(const struct sock
*sk
,
6188 struct request_sock
*req
,
6189 const struct sk_buff
*skb
)
6191 if (tcp_sk(sk
)->save_syn
) {
6192 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
6195 copy
= kmalloc(len
+ sizeof(u32
), GFP_ATOMIC
);
6198 memcpy(©
[1], skb_network_header(skb
), len
);
6199 req
->saved_syn
= copy
;
6204 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
6205 const struct tcp_request_sock_ops
*af_ops
,
6206 struct sock
*sk
, struct sk_buff
*skb
)
6208 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6209 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
6210 struct tcp_options_received tmp_opt
;
6211 struct tcp_sock
*tp
= tcp_sk(sk
);
6212 struct net
*net
= sock_net(sk
);
6213 struct sock
*fastopen_sk
= NULL
;
6214 struct request_sock
*req
;
6215 bool want_cookie
= false;
6216 struct dst_entry
*dst
;
6219 /* TW buckets are converted to open requests without
6220 * limitations, they conserve resources and peer is
6221 * evidently real one.
6223 if ((net
->ipv4
.sysctl_tcp_syncookies
== 2 ||
6224 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
6225 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
6230 if (sk_acceptq_is_full(sk
)) {
6231 NET_INC_STATS(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
6235 req
= inet_reqsk_alloc(rsk_ops
, sk
, !want_cookie
);
6239 tcp_rsk(req
)->af_specific
= af_ops
;
6240 tcp_rsk(req
)->ts_off
= 0;
6242 tcp_clear_options(&tmp_opt
);
6243 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
6244 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
6245 tcp_parse_options(sock_net(sk
), skb
, &tmp_opt
, 0,
6246 want_cookie
? NULL
: &foc
);
6248 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
6249 tcp_clear_options(&tmp_opt
);
6251 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
6252 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
6253 inet_rsk(req
)->no_srccheck
= inet_sk(sk
)->transparent
;
6255 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6256 inet_rsk(req
)->ir_iif
= inet_request_bound_dev_if(sk
, skb
);
6258 af_ops
->init_req(req
, sk
, skb
);
6260 if (security_inet_conn_request(sk
, skb
, req
))
6263 if (tmp_opt
.tstamp_ok
)
6264 tcp_rsk(req
)->ts_off
= af_ops
->init_ts_off(net
, skb
);
6266 dst
= af_ops
->route_req(sk
, &fl
, req
);
6270 if (!want_cookie
&& !isn
) {
6271 /* Kill the following clause, if you dislike this way. */
6272 if (!net
->ipv4
.sysctl_tcp_syncookies
&&
6273 (net
->ipv4
.sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
6274 (net
->ipv4
.sysctl_max_syn_backlog
>> 2)) &&
6275 !tcp_peer_is_proven(req
, dst
)) {
6276 /* Without syncookies last quarter of
6277 * backlog is filled with destinations,
6278 * proven to be alive.
6279 * It means that we continue to communicate
6280 * to destinations, already remembered
6281 * to the moment of synflood.
6283 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6285 goto drop_and_release
;
6288 isn
= af_ops
->init_seq(skb
);
6291 tcp_ecn_create_request(req
, skb
, sk
, dst
);
6294 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
6295 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
6296 if (!tmp_opt
.tstamp_ok
)
6297 inet_rsk(req
)->ecn_ok
= 0;
6300 tcp_rsk(req
)->snt_isn
= isn
;
6301 tcp_rsk(req
)->txhash
= net_tx_rndhash();
6302 tcp_openreq_init_rwin(req
, sk
, dst
);
6304 tcp_reqsk_record_syn(sk
, req
, skb
);
6305 fastopen_sk
= tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6308 af_ops
->send_synack(fastopen_sk
, dst
, &fl
, req
,
6309 &foc
, TCP_SYNACK_FASTOPEN
);
6310 /* Add the child socket directly into the accept queue */
6311 inet_csk_reqsk_queue_add(sk
, req
, fastopen_sk
);
6312 sk
->sk_data_ready(sk
);
6313 bh_unlock_sock(fastopen_sk
);
6314 sock_put(fastopen_sk
);
6316 tcp_rsk(req
)->tfo_listener
= false;
6318 inet_csk_reqsk_queue_hash_add(sk
, req
,
6319 tcp_timeout_init((struct sock
*)req
));
6320 af_ops
->send_synack(sk
, dst
, &fl
, req
, &foc
,
6321 !want_cookie
? TCP_SYNACK_NORMAL
:
6339 EXPORT_SYMBOL(tcp_conn_request
);