2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
23 * Pedro Roque : Fast Retransmit/Recovery.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
56 * J Hadi Salim: ECN support
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
64 #define pr_fmt(fmt) "TCP: " fmt
67 #include <linux/slab.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <linux/kernel.h>
71 #include <linux/prefetch.h>
74 #include <net/inet_common.h>
75 #include <linux/ipsec.h>
76 #include <asm/unaligned.h>
77 #include <linux/errqueue.h>
79 int sysctl_tcp_timestamps __read_mostly
= 1;
80 int sysctl_tcp_window_scaling __read_mostly
= 1;
81 int sysctl_tcp_sack __read_mostly
= 1;
82 int sysctl_tcp_fack __read_mostly
= 1;
83 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
84 int sysctl_tcp_max_reordering __read_mostly
= 300;
85 EXPORT_SYMBOL(sysctl_tcp_reordering
);
86 int sysctl_tcp_dsack __read_mostly
= 1;
87 int sysctl_tcp_app_win __read_mostly
= 31;
88 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
89 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
91 /* rfc5961 challenge ack rate limiting */
92 int sysctl_tcp_challenge_ack_limit
= 100;
94 int sysctl_tcp_stdurg __read_mostly
;
95 int sysctl_tcp_rfc1337 __read_mostly
;
96 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
97 int sysctl_tcp_frto __read_mostly
= 2;
99 int sysctl_tcp_thin_dupack __read_mostly
;
101 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
102 int sysctl_tcp_early_retrans __read_mostly
= 3;
103 int sysctl_tcp_invalid_ratelimit __read_mostly
= HZ
/2;
105 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
106 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
107 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
108 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
109 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
110 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
111 #define FLAG_ECE 0x40 /* ECE in this ACK */
112 #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
113 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
114 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
115 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
116 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
117 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
118 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
120 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
121 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
122 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
123 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
125 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
126 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
128 /* Adapt the MSS value used to make delayed ack decision to the
131 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
133 struct inet_connection_sock
*icsk
= inet_csk(sk
);
134 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
137 icsk
->icsk_ack
.last_seg_size
= 0;
139 /* skb->len may jitter because of SACKs, even if peer
140 * sends good full-sized frames.
142 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
143 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
144 icsk
->icsk_ack
.rcv_mss
= len
;
146 /* Otherwise, we make more careful check taking into account,
147 * that SACKs block is variable.
149 * "len" is invariant segment length, including TCP header.
151 len
+= skb
->data
- skb_transport_header(skb
);
152 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
153 /* If PSH is not set, packet should be
154 * full sized, provided peer TCP is not badly broken.
155 * This observation (if it is correct 8)) allows
156 * to handle super-low mtu links fairly.
158 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
159 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
160 /* Subtract also invariant (if peer is RFC compliant),
161 * tcp header plus fixed timestamp option length.
162 * Resulting "len" is MSS free of SACK jitter.
164 len
-= tcp_sk(sk
)->tcp_header_len
;
165 icsk
->icsk_ack
.last_seg_size
= len
;
167 icsk
->icsk_ack
.rcv_mss
= len
;
171 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
172 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
173 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
177 static void tcp_incr_quickack(struct sock
*sk
)
179 struct inet_connection_sock
*icsk
= inet_csk(sk
);
180 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
184 if (quickacks
> icsk
->icsk_ack
.quick
)
185 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
188 static void tcp_enter_quickack_mode(struct sock
*sk
)
190 struct inet_connection_sock
*icsk
= inet_csk(sk
);
191 tcp_incr_quickack(sk
);
192 icsk
->icsk_ack
.pingpong
= 0;
193 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
196 /* Send ACKs quickly, if "quick" count is not exhausted
197 * and the session is not interactive.
200 static bool tcp_in_quickack_mode(struct sock
*sk
)
202 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
203 const struct dst_entry
*dst
= __sk_dst_get(sk
);
205 return (dst
&& dst_metric(dst
, RTAX_QUICKACK
)) ||
206 (icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
);
209 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
211 if (tp
->ecn_flags
& TCP_ECN_OK
)
212 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
215 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
217 if (tcp_hdr(skb
)->cwr
)
218 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
221 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
223 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
226 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
228 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
229 case INET_ECN_NOT_ECT
:
230 /* Funny extension: if ECT is not set on a segment,
231 * and we already seen ECT on a previous segment,
232 * it is probably a retransmit.
234 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
235 tcp_enter_quickack_mode((struct sock
*)tp
);
238 if (tcp_ca_needs_ecn((struct sock
*)tp
))
239 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
241 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
242 /* Better not delay acks, sender can have a very low cwnd */
243 tcp_enter_quickack_mode((struct sock
*)tp
);
244 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
246 tp
->ecn_flags
|= TCP_ECN_SEEN
;
249 if (tcp_ca_needs_ecn((struct sock
*)tp
))
250 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
251 tp
->ecn_flags
|= TCP_ECN_SEEN
;
256 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
258 if (tp
->ecn_flags
& TCP_ECN_OK
)
259 __tcp_ecn_check_ce(tp
, skb
);
262 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
264 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
265 tp
->ecn_flags
&= ~TCP_ECN_OK
;
268 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
270 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
271 tp
->ecn_flags
&= ~TCP_ECN_OK
;
274 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
276 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
281 /* Buffer size and advertised window tuning.
283 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
286 static void tcp_sndbuf_expand(struct sock
*sk
)
288 const struct tcp_sock
*tp
= tcp_sk(sk
);
292 /* Worst case is non GSO/TSO : each frame consumes one skb
293 * and skb->head is kmalloced using power of two area of memory
295 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
297 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
299 per_mss
= roundup_pow_of_two(per_mss
) +
300 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
302 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
303 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
305 /* Fast Recovery (RFC 5681 3.2) :
306 * Cubic needs 1.7 factor, rounded to 2 to include
307 * extra cushion (application might react slowly to POLLOUT)
309 sndmem
= 2 * nr_segs
* per_mss
;
311 if (sk
->sk_sndbuf
< sndmem
)
312 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
315 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
317 * All tcp_full_space() is split to two parts: "network" buffer, allocated
318 * forward and advertised in receiver window (tp->rcv_wnd) and
319 * "application buffer", required to isolate scheduling/application
320 * latencies from network.
321 * window_clamp is maximal advertised window. It can be less than
322 * tcp_full_space(), in this case tcp_full_space() - window_clamp
323 * is reserved for "application" buffer. The less window_clamp is
324 * the smoother our behaviour from viewpoint of network, but the lower
325 * throughput and the higher sensitivity of the connection to losses. 8)
327 * rcv_ssthresh is more strict window_clamp used at "slow start"
328 * phase to predict further behaviour of this connection.
329 * It is used for two goals:
330 * - to enforce header prediction at sender, even when application
331 * requires some significant "application buffer". It is check #1.
332 * - to prevent pruning of receive queue because of misprediction
333 * of receiver window. Check #2.
335 * The scheme does not work when sender sends good segments opening
336 * window and then starts to feed us spaghetti. But it should work
337 * in common situations. Otherwise, we have to rely on queue collapsing.
340 /* Slow part of check#2. */
341 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
343 struct tcp_sock
*tp
= tcp_sk(sk
);
345 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
346 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
348 while (tp
->rcv_ssthresh
<= window
) {
349 if (truesize
<= skb
->len
)
350 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
358 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
360 struct tcp_sock
*tp
= tcp_sk(sk
);
363 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
364 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
365 !tcp_under_memory_pressure(sk
)) {
368 /* Check #2. Increase window, if skb with such overhead
369 * will fit to rcvbuf in future.
371 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
372 incr
= 2 * tp
->advmss
;
374 incr
= __tcp_grow_window(sk
, skb
);
377 incr
= max_t(int, incr
, 2 * skb
->len
);
378 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
380 inet_csk(sk
)->icsk_ack
.quick
|= 1;
385 /* 3. Tuning rcvbuf, when connection enters established state. */
386 static void tcp_fixup_rcvbuf(struct sock
*sk
)
388 u32 mss
= tcp_sk(sk
)->advmss
;
391 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
392 tcp_default_init_rwnd(mss
);
394 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
395 * Allow enough cushion so that sender is not limited by our window
397 if (sysctl_tcp_moderate_rcvbuf
)
400 if (sk
->sk_rcvbuf
< rcvmem
)
401 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
404 /* 4. Try to fixup all. It is made immediately after connection enters
407 void tcp_init_buffer_space(struct sock
*sk
)
409 struct tcp_sock
*tp
= tcp_sk(sk
);
412 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
413 tcp_fixup_rcvbuf(sk
);
414 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
415 tcp_sndbuf_expand(sk
);
417 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
418 tp
->rcvq_space
.time
= tcp_time_stamp
;
419 tp
->rcvq_space
.seq
= tp
->copied_seq
;
421 maxwin
= tcp_full_space(sk
);
423 if (tp
->window_clamp
>= maxwin
) {
424 tp
->window_clamp
= maxwin
;
426 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
427 tp
->window_clamp
= max(maxwin
-
428 (maxwin
>> sysctl_tcp_app_win
),
432 /* Force reservation of one segment. */
433 if (sysctl_tcp_app_win
&&
434 tp
->window_clamp
> 2 * tp
->advmss
&&
435 tp
->window_clamp
+ tp
->advmss
> maxwin
)
436 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
438 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
439 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
442 /* 5. Recalculate window clamp after socket hit its memory bounds. */
443 static void tcp_clamp_window(struct sock
*sk
)
445 struct tcp_sock
*tp
= tcp_sk(sk
);
446 struct inet_connection_sock
*icsk
= inet_csk(sk
);
448 icsk
->icsk_ack
.quick
= 0;
450 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
451 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
452 !tcp_under_memory_pressure(sk
) &&
453 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
454 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
457 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
458 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
461 /* Initialize RCV_MSS value.
462 * RCV_MSS is an our guess about MSS used by the peer.
463 * We haven't any direct information about the MSS.
464 * It's better to underestimate the RCV_MSS rather than overestimate.
465 * Overestimations make us ACKing less frequently than needed.
466 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
468 void tcp_initialize_rcv_mss(struct sock
*sk
)
470 const struct tcp_sock
*tp
= tcp_sk(sk
);
471 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
473 hint
= min(hint
, tp
->rcv_wnd
/ 2);
474 hint
= min(hint
, TCP_MSS_DEFAULT
);
475 hint
= max(hint
, TCP_MIN_MSS
);
477 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
479 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
481 /* Receiver "autotuning" code.
483 * The algorithm for RTT estimation w/o timestamps is based on
484 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
485 * <http://public.lanl.gov/radiant/pubs.html#DRS>
487 * More detail on this code can be found at
488 * <http://staff.psc.edu/jheffner/>,
489 * though this reference is out of date. A new paper
492 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
494 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
500 if (new_sample
!= 0) {
501 /* If we sample in larger samples in the non-timestamp
502 * case, we could grossly overestimate the RTT especially
503 * with chatty applications or bulk transfer apps which
504 * are stalled on filesystem I/O.
506 * Also, since we are only going for a minimum in the
507 * non-timestamp case, we do not smooth things out
508 * else with timestamps disabled convergence takes too
512 m
-= (new_sample
>> 3);
520 /* No previous measure. */
524 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
525 tp
->rcv_rtt_est
.rtt
= new_sample
;
528 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
530 if (tp
->rcv_rtt_est
.time
== 0)
532 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
534 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
537 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
538 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
541 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
542 const struct sk_buff
*skb
)
544 struct tcp_sock
*tp
= tcp_sk(sk
);
545 if (tp
->rx_opt
.rcv_tsecr
&&
546 (TCP_SKB_CB(skb
)->end_seq
-
547 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
548 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
552 * This function should be called every time data is copied to user space.
553 * It calculates the appropriate TCP receive buffer space.
555 void tcp_rcv_space_adjust(struct sock
*sk
)
557 struct tcp_sock
*tp
= tcp_sk(sk
);
561 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
562 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
565 /* Number of bytes copied to user in last RTT */
566 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
567 if (copied
<= tp
->rcvq_space
.space
)
571 * copied = bytes received in previous RTT, our base window
572 * To cope with packet losses, we need a 2x factor
573 * To cope with slow start, and sender growing its cwin by 100 %
574 * every RTT, we need a 4x factor, because the ACK we are sending
575 * now is for the next RTT, not the current one :
576 * <prev RTT . ><current RTT .. ><next RTT .... >
579 if (sysctl_tcp_moderate_rcvbuf
&&
580 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
581 int rcvwin
, rcvmem
, rcvbuf
;
583 /* minimal window to cope with packet losses, assuming
584 * steady state. Add some cushion because of small variations.
586 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
588 /* If rate increased by 25%,
589 * assume slow start, rcvwin = 3 * copied
590 * If rate increased by 50%,
591 * assume sender can use 2x growth, rcvwin = 4 * copied
594 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
596 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
599 rcvwin
+= (rcvwin
>> 1);
602 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
603 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
606 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
607 if (rcvbuf
> sk
->sk_rcvbuf
) {
608 sk
->sk_rcvbuf
= rcvbuf
;
610 /* Make the window clamp follow along. */
611 tp
->window_clamp
= rcvwin
;
614 tp
->rcvq_space
.space
= copied
;
617 tp
->rcvq_space
.seq
= tp
->copied_seq
;
618 tp
->rcvq_space
.time
= tcp_time_stamp
;
621 /* There is something which you must keep in mind when you analyze the
622 * behavior of the tp->ato delayed ack timeout interval. When a
623 * connection starts up, we want to ack as quickly as possible. The
624 * problem is that "good" TCP's do slow start at the beginning of data
625 * transmission. The means that until we send the first few ACK's the
626 * sender will sit on his end and only queue most of his data, because
627 * he can only send snd_cwnd unacked packets at any given time. For
628 * each ACK we send, he increments snd_cwnd and transmits more of his
631 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
633 struct tcp_sock
*tp
= tcp_sk(sk
);
634 struct inet_connection_sock
*icsk
= inet_csk(sk
);
637 inet_csk_schedule_ack(sk
);
639 tcp_measure_rcv_mss(sk
, skb
);
641 tcp_rcv_rtt_measure(tp
);
643 now
= tcp_time_stamp
;
645 if (!icsk
->icsk_ack
.ato
) {
646 /* The _first_ data packet received, initialize
647 * delayed ACK engine.
649 tcp_incr_quickack(sk
);
650 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
652 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
654 if (m
<= TCP_ATO_MIN
/ 2) {
655 /* The fastest case is the first. */
656 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
657 } else if (m
< icsk
->icsk_ack
.ato
) {
658 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
659 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
660 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
661 } else if (m
> icsk
->icsk_rto
) {
662 /* Too long gap. Apparently sender failed to
663 * restart window, so that we send ACKs quickly.
665 tcp_incr_quickack(sk
);
669 icsk
->icsk_ack
.lrcvtime
= now
;
671 tcp_ecn_check_ce(tp
, skb
);
674 tcp_grow_window(sk
, skb
);
677 /* Called to compute a smoothed rtt estimate. The data fed to this
678 * routine either comes from timestamps, or from segments that were
679 * known _not_ to have been retransmitted [see Karn/Partridge
680 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
681 * piece by Van Jacobson.
682 * NOTE: the next three routines used to be one big routine.
683 * To save cycles in the RFC 1323 implementation it was better to break
684 * it up into three procedures. -- erics
686 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
688 struct tcp_sock
*tp
= tcp_sk(sk
);
689 long m
= mrtt_us
; /* RTT */
690 u32 srtt
= tp
->srtt_us
;
692 /* The following amusing code comes from Jacobson's
693 * article in SIGCOMM '88. Note that rtt and mdev
694 * are scaled versions of rtt and mean deviation.
695 * This is designed to be as fast as possible
696 * m stands for "measurement".
698 * On a 1990 paper the rto value is changed to:
699 * RTO = rtt + 4 * mdev
701 * Funny. This algorithm seems to be very broken.
702 * These formulae increase RTO, when it should be decreased, increase
703 * too slowly, when it should be increased quickly, decrease too quickly
704 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
705 * does not matter how to _calculate_ it. Seems, it was trap
706 * that VJ failed to avoid. 8)
709 m
-= (srtt
>> 3); /* m is now error in rtt est */
710 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
712 m
= -m
; /* m is now abs(error) */
713 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
714 /* This is similar to one of Eifel findings.
715 * Eifel blocks mdev updates when rtt decreases.
716 * This solution is a bit different: we use finer gain
717 * for mdev in this case (alpha*beta).
718 * Like Eifel it also prevents growth of rto,
719 * but also it limits too fast rto decreases,
720 * happening in pure Eifel.
725 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
727 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
728 if (tp
->mdev_us
> tp
->mdev_max_us
) {
729 tp
->mdev_max_us
= tp
->mdev_us
;
730 if (tp
->mdev_max_us
> tp
->rttvar_us
)
731 tp
->rttvar_us
= tp
->mdev_max_us
;
733 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
734 if (tp
->mdev_max_us
< tp
->rttvar_us
)
735 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
736 tp
->rtt_seq
= tp
->snd_nxt
;
737 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
740 /* no previous measure. */
741 srtt
= m
<< 3; /* take the measured time to be rtt */
742 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
743 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
744 tp
->mdev_max_us
= tp
->rttvar_us
;
745 tp
->rtt_seq
= tp
->snd_nxt
;
747 tp
->srtt_us
= max(1U, srtt
);
750 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
751 * Note: TCP stack does not yet implement pacing.
752 * FQ packet scheduler can be used to implement cheap but effective
753 * TCP pacing, to smooth the burst on large writes when packets
754 * in flight is significantly lower than cwnd (or rwin)
756 static void tcp_update_pacing_rate(struct sock
*sk
)
758 const struct tcp_sock
*tp
= tcp_sk(sk
);
761 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
762 rate
= (u64
)tp
->mss_cache
* 2 * (USEC_PER_SEC
<< 3);
764 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
766 if (likely(tp
->srtt_us
))
767 do_div(rate
, tp
->srtt_us
);
769 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
770 * without any lock. We want to make sure compiler wont store
771 * intermediate values in this location.
773 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
774 sk
->sk_max_pacing_rate
);
777 /* Calculate rto without backoff. This is the second half of Van Jacobson's
778 * routine referred to above.
780 static void tcp_set_rto(struct sock
*sk
)
782 const struct tcp_sock
*tp
= tcp_sk(sk
);
783 /* Old crap is replaced with new one. 8)
786 * 1. If rtt variance happened to be less 50msec, it is hallucination.
787 * It cannot be less due to utterly erratic ACK generation made
788 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
789 * to do with delayed acks, because at cwnd>2 true delack timeout
790 * is invisible. Actually, Linux-2.4 also generates erratic
791 * ACKs in some circumstances.
793 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
795 /* 2. Fixups made earlier cannot be right.
796 * If we do not estimate RTO correctly without them,
797 * all the algo is pure shit and should be replaced
798 * with correct one. It is exactly, which we pretend to do.
801 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
802 * guarantees that rto is higher.
807 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
809 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
812 cwnd
= TCP_INIT_CWND
;
813 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
817 * Packet counting of FACK is based on in-order assumptions, therefore TCP
818 * disables it when reordering is detected
820 void tcp_disable_fack(struct tcp_sock
*tp
)
822 /* RFC3517 uses different metric in lost marker => reset on change */
824 tp
->lost_skb_hint
= NULL
;
825 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
828 /* Take a notice that peer is sending D-SACKs */
829 static void tcp_dsack_seen(struct tcp_sock
*tp
)
831 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
834 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
837 struct tcp_sock
*tp
= tcp_sk(sk
);
838 if (metric
> tp
->reordering
) {
841 tp
->reordering
= min(sysctl_tcp_max_reordering
, metric
);
843 /* This exciting event is worth to be remembered. 8) */
845 mib_idx
= LINUX_MIB_TCPTSREORDER
;
846 else if (tcp_is_reno(tp
))
847 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
848 else if (tcp_is_fack(tp
))
849 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
851 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
853 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
854 #if FASTRETRANS_DEBUG > 1
855 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
856 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
860 tp
->undo_marker
? tp
->undo_retrans
: 0);
862 tcp_disable_fack(tp
);
866 tcp_disable_early_retrans(tp
);
869 /* This must be called before lost_out is incremented */
870 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
872 if (!tp
->retransmit_skb_hint
||
873 before(TCP_SKB_CB(skb
)->seq
,
874 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
875 tp
->retransmit_skb_hint
= skb
;
878 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
879 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
882 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
884 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
885 tcp_verify_retransmit_hint(tp
, skb
);
887 tp
->lost_out
+= tcp_skb_pcount(skb
);
888 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
892 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
895 tcp_verify_retransmit_hint(tp
, skb
);
897 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
898 tp
->lost_out
+= tcp_skb_pcount(skb
);
899 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
903 /* This procedure tags the retransmission queue when SACKs arrive.
905 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
906 * Packets in queue with these bits set are counted in variables
907 * sacked_out, retrans_out and lost_out, correspondingly.
909 * Valid combinations are:
910 * Tag InFlight Description
911 * 0 1 - orig segment is in flight.
912 * S 0 - nothing flies, orig reached receiver.
913 * L 0 - nothing flies, orig lost by net.
914 * R 2 - both orig and retransmit are in flight.
915 * L|R 1 - orig is lost, retransmit is in flight.
916 * S|R 1 - orig reached receiver, retrans is still in flight.
917 * (L|S|R is logically valid, it could occur when L|R is sacked,
918 * but it is equivalent to plain S and code short-curcuits it to S.
919 * L|S is logically invalid, it would mean -1 packet in flight 8))
921 * These 6 states form finite state machine, controlled by the following events:
922 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
923 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
924 * 3. Loss detection event of two flavors:
925 * A. Scoreboard estimator decided the packet is lost.
926 * A'. Reno "three dupacks" marks head of queue lost.
927 * A''. Its FACK modification, head until snd.fack is lost.
928 * B. SACK arrives sacking SND.NXT at the moment, when the
929 * segment was retransmitted.
930 * 4. D-SACK added new rule: D-SACK changes any tag to S.
932 * It is pleasant to note, that state diagram turns out to be commutative,
933 * so that we are allowed not to be bothered by order of our actions,
934 * when multiple events arrive simultaneously. (see the function below).
936 * Reordering detection.
937 * --------------------
938 * Reordering metric is maximal distance, which a packet can be displaced
939 * in packet stream. With SACKs we can estimate it:
941 * 1. SACK fills old hole and the corresponding segment was not
942 * ever retransmitted -> reordering. Alas, we cannot use it
943 * when segment was retransmitted.
944 * 2. The last flaw is solved with D-SACK. D-SACK arrives
945 * for retransmitted and already SACKed segment -> reordering..
946 * Both of these heuristics are not used in Loss state, when we cannot
947 * account for retransmits accurately.
949 * SACK block validation.
950 * ----------------------
952 * SACK block range validation checks that the received SACK block fits to
953 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
954 * Note that SND.UNA is not included to the range though being valid because
955 * it means that the receiver is rather inconsistent with itself reporting
956 * SACK reneging when it should advance SND.UNA. Such SACK block this is
957 * perfectly valid, however, in light of RFC2018 which explicitly states
958 * that "SACK block MUST reflect the newest segment. Even if the newest
959 * segment is going to be discarded ...", not that it looks very clever
960 * in case of head skb. Due to potentional receiver driven attacks, we
961 * choose to avoid immediate execution of a walk in write queue due to
962 * reneging and defer head skb's loss recovery to standard loss recovery
963 * procedure that will eventually trigger (nothing forbids us doing this).
965 * Implements also blockage to start_seq wrap-around. Problem lies in the
966 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
967 * there's no guarantee that it will be before snd_nxt (n). The problem
968 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
971 * <- outs wnd -> <- wrapzone ->
972 * u e n u_w e_w s n_w
974 * |<------------+------+----- TCP seqno space --------------+---------->|
975 * ...-- <2^31 ->| |<--------...
976 * ...---- >2^31 ------>| |<--------...
978 * Current code wouldn't be vulnerable but it's better still to discard such
979 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
980 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
981 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
982 * equal to the ideal case (infinite seqno space without wrap caused issues).
984 * With D-SACK the lower bound is extended to cover sequence space below
985 * SND.UNA down to undo_marker, which is the last point of interest. Yet
986 * again, D-SACK block must not to go across snd_una (for the same reason as
987 * for the normal SACK blocks, explained above). But there all simplicity
988 * ends, TCP might receive valid D-SACKs below that. As long as they reside
989 * fully below undo_marker they do not affect behavior in anyway and can
990 * therefore be safely ignored. In rare cases (which are more or less
991 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
992 * fragmentation and packet reordering past skb's retransmission. To consider
993 * them correctly, the acceptable range must be extended even more though
994 * the exact amount is rather hard to quantify. However, tp->max_window can
995 * be used as an exaggerated estimate.
997 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
998 u32 start_seq
, u32 end_seq
)
1000 /* Too far in future, or reversed (interpretation is ambiguous) */
1001 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1004 /* Nasty start_seq wrap-around check (see comments above) */
1005 if (!before(start_seq
, tp
->snd_nxt
))
1008 /* In outstanding window? ...This is valid exit for D-SACKs too.
1009 * start_seq == snd_una is non-sensical (see comments above)
1011 if (after(start_seq
, tp
->snd_una
))
1014 if (!is_dsack
|| !tp
->undo_marker
)
1017 /* ...Then it's D-SACK, and must reside below snd_una completely */
1018 if (after(end_seq
, tp
->snd_una
))
1021 if (!before(start_seq
, tp
->undo_marker
))
1025 if (!after(end_seq
, tp
->undo_marker
))
1028 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1029 * start_seq < undo_marker and end_seq >= undo_marker.
1031 return !before(start_seq
, end_seq
- tp
->max_window
);
1034 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1035 * Event "B". Later note: FACK people cheated me again 8), we have to account
1036 * for reordering! Ugly, but should help.
1038 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1039 * less than what is now known to be received by the other end (derived from
1040 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1041 * retransmitted skbs to avoid some costly processing per ACKs.
1043 static void tcp_mark_lost_retrans(struct sock
*sk
, int *flag
)
1045 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1046 struct tcp_sock
*tp
= tcp_sk(sk
);
1047 struct sk_buff
*skb
;
1049 u32 new_low_seq
= tp
->snd_nxt
;
1050 u32 received_upto
= tcp_highest_sack_seq(tp
);
1052 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1053 !after(received_upto
, tp
->lost_retrans_low
) ||
1054 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1057 tcp_for_write_queue(skb
, sk
) {
1058 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1060 if (skb
== tcp_send_head(sk
))
1062 if (cnt
== tp
->retrans_out
)
1064 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1067 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1070 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1071 * constraint here (see above) but figuring out that at
1072 * least tp->reordering SACK blocks reside between ack_seq
1073 * and received_upto is not easy task to do cheaply with
1074 * the available datastructures.
1076 * Whether FACK should check here for tp->reordering segs
1077 * in-between one could argue for either way (it would be
1078 * rather simple to implement as we could count fack_count
1079 * during the walk and do tp->fackets_out - fack_count).
1081 if (after(received_upto
, ack_seq
)) {
1082 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1083 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1084 *flag
|= FLAG_LOST_RETRANS
;
1085 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1086 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1088 if (before(ack_seq
, new_low_seq
))
1089 new_low_seq
= ack_seq
;
1090 cnt
+= tcp_skb_pcount(skb
);
1094 if (tp
->retrans_out
)
1095 tp
->lost_retrans_low
= new_low_seq
;
1098 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1099 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1102 struct tcp_sock
*tp
= tcp_sk(sk
);
1103 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1104 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1105 bool dup_sack
= false;
1107 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1110 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1111 } else if (num_sacks
> 1) {
1112 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1113 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1115 if (!after(end_seq_0
, end_seq_1
) &&
1116 !before(start_seq_0
, start_seq_1
)) {
1119 NET_INC_STATS_BH(sock_net(sk
),
1120 LINUX_MIB_TCPDSACKOFORECV
);
1124 /* D-SACK for already forgotten data... Do dumb counting. */
1125 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1126 !after(end_seq_0
, prior_snd_una
) &&
1127 after(end_seq_0
, tp
->undo_marker
))
1133 struct tcp_sacktag_state
{
1136 /* Timestamps for earliest and latest never-retransmitted segment
1137 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1138 * but congestion control should still get an accurate delay signal.
1140 struct skb_mstamp first_sackt
;
1141 struct skb_mstamp last_sackt
;
1145 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1146 * the incoming SACK may not exactly match but we can find smaller MSS
1147 * aligned portion of it that matches. Therefore we might need to fragment
1148 * which may fail and creates some hassle (caller must handle error case
1151 * FIXME: this could be merged to shift decision code
1153 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1154 u32 start_seq
, u32 end_seq
)
1158 unsigned int pkt_len
;
1161 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1162 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1164 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1165 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1166 mss
= tcp_skb_mss(skb
);
1167 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1170 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1174 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1179 /* Round if necessary so that SACKs cover only full MSSes
1180 * and/or the remaining small portion (if present)
1182 if (pkt_len
> mss
) {
1183 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1184 if (!in_sack
&& new_len
< pkt_len
) {
1186 if (new_len
>= skb
->len
)
1191 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1199 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1200 static u8
tcp_sacktag_one(struct sock
*sk
,
1201 struct tcp_sacktag_state
*state
, u8 sacked
,
1202 u32 start_seq
, u32 end_seq
,
1203 int dup_sack
, int pcount
,
1204 const struct skb_mstamp
*xmit_time
)
1206 struct tcp_sock
*tp
= tcp_sk(sk
);
1207 int fack_count
= state
->fack_count
;
1209 /* Account D-SACK for retransmitted packet. */
1210 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1211 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1212 after(end_seq
, tp
->undo_marker
))
1214 if (sacked
& TCPCB_SACKED_ACKED
)
1215 state
->reord
= min(fack_count
, state
->reord
);
1218 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1219 if (!after(end_seq
, tp
->snd_una
))
1222 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1223 if (sacked
& TCPCB_SACKED_RETRANS
) {
1224 /* If the segment is not tagged as lost,
1225 * we do not clear RETRANS, believing
1226 * that retransmission is still in flight.
1228 if (sacked
& TCPCB_LOST
) {
1229 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1230 tp
->lost_out
-= pcount
;
1231 tp
->retrans_out
-= pcount
;
1234 if (!(sacked
& TCPCB_RETRANS
)) {
1235 /* New sack for not retransmitted frame,
1236 * which was in hole. It is reordering.
1238 if (before(start_seq
,
1239 tcp_highest_sack_seq(tp
)))
1240 state
->reord
= min(fack_count
,
1242 if (!after(end_seq
, tp
->high_seq
))
1243 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1244 if (state
->first_sackt
.v64
== 0)
1245 state
->first_sackt
= *xmit_time
;
1246 state
->last_sackt
= *xmit_time
;
1249 if (sacked
& TCPCB_LOST
) {
1250 sacked
&= ~TCPCB_LOST
;
1251 tp
->lost_out
-= pcount
;
1255 sacked
|= TCPCB_SACKED_ACKED
;
1256 state
->flag
|= FLAG_DATA_SACKED
;
1257 tp
->sacked_out
+= pcount
;
1259 fack_count
+= pcount
;
1261 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1262 if (!tcp_is_fack(tp
) && tp
->lost_skb_hint
&&
1263 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1264 tp
->lost_cnt_hint
+= pcount
;
1266 if (fack_count
> tp
->fackets_out
)
1267 tp
->fackets_out
= fack_count
;
1270 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1271 * frames and clear it. undo_retrans is decreased above, L|R frames
1272 * are accounted above as well.
1274 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1275 sacked
&= ~TCPCB_SACKED_RETRANS
;
1276 tp
->retrans_out
-= pcount
;
1282 /* Shift newly-SACKed bytes from this skb to the immediately previous
1283 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1285 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1286 struct tcp_sacktag_state
*state
,
1287 unsigned int pcount
, int shifted
, int mss
,
1290 struct tcp_sock
*tp
= tcp_sk(sk
);
1291 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1292 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1293 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1297 /* Adjust counters and hints for the newly sacked sequence
1298 * range but discard the return value since prev is already
1299 * marked. We must tag the range first because the seq
1300 * advancement below implicitly advances
1301 * tcp_highest_sack_seq() when skb is highest_sack.
1303 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1304 start_seq
, end_seq
, dup_sack
, pcount
,
1307 if (skb
== tp
->lost_skb_hint
)
1308 tp
->lost_cnt_hint
+= pcount
;
1310 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1311 TCP_SKB_CB(skb
)->seq
+= shifted
;
1313 tcp_skb_pcount_add(prev
, pcount
);
1314 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1315 tcp_skb_pcount_add(skb
, -pcount
);
1317 /* When we're adding to gso_segs == 1, gso_size will be zero,
1318 * in theory this shouldn't be necessary but as long as DSACK
1319 * code can come after this skb later on it's better to keep
1320 * setting gso_size to something.
1322 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1323 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1325 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1326 if (tcp_skb_pcount(skb
) <= 1)
1327 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1329 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1330 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1333 BUG_ON(!tcp_skb_pcount(skb
));
1334 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1338 /* Whole SKB was eaten :-) */
1340 if (skb
== tp
->retransmit_skb_hint
)
1341 tp
->retransmit_skb_hint
= prev
;
1342 if (skb
== tp
->lost_skb_hint
) {
1343 tp
->lost_skb_hint
= prev
;
1344 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1347 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1348 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1349 TCP_SKB_CB(prev
)->end_seq
++;
1351 if (skb
== tcp_highest_sack(sk
))
1352 tcp_advance_highest_sack(sk
, skb
);
1354 tcp_unlink_write_queue(skb
, sk
);
1355 sk_wmem_free_skb(sk
, skb
);
1357 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1362 /* I wish gso_size would have a bit more sane initialization than
1363 * something-or-zero which complicates things
1365 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1367 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1370 /* Shifting pages past head area doesn't work */
1371 static int skb_can_shift(const struct sk_buff
*skb
)
1373 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1376 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1379 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1380 struct tcp_sacktag_state
*state
,
1381 u32 start_seq
, u32 end_seq
,
1384 struct tcp_sock
*tp
= tcp_sk(sk
);
1385 struct sk_buff
*prev
;
1391 if (!sk_can_gso(sk
))
1394 /* Normally R but no L won't result in plain S */
1396 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1398 if (!skb_can_shift(skb
))
1400 /* This frame is about to be dropped (was ACKed). */
1401 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1404 /* Can only happen with delayed DSACK + discard craziness */
1405 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1407 prev
= tcp_write_queue_prev(sk
, skb
);
1409 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1412 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1413 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1417 pcount
= tcp_skb_pcount(skb
);
1418 mss
= tcp_skb_seglen(skb
);
1420 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1421 * drop this restriction as unnecessary
1423 if (mss
!= tcp_skb_seglen(prev
))
1426 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1428 /* CHECKME: This is non-MSS split case only?, this will
1429 * cause skipped skbs due to advancing loop btw, original
1430 * has that feature too
1432 if (tcp_skb_pcount(skb
) <= 1)
1435 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1437 /* TODO: head merge to next could be attempted here
1438 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1439 * though it might not be worth of the additional hassle
1441 * ...we can probably just fallback to what was done
1442 * previously. We could try merging non-SACKed ones
1443 * as well but it probably isn't going to buy off
1444 * because later SACKs might again split them, and
1445 * it would make skb timestamp tracking considerably
1451 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1453 BUG_ON(len
> skb
->len
);
1455 /* MSS boundaries should be honoured or else pcount will
1456 * severely break even though it makes things bit trickier.
1457 * Optimize common case to avoid most of the divides
1459 mss
= tcp_skb_mss(skb
);
1461 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1462 * drop this restriction as unnecessary
1464 if (mss
!= tcp_skb_seglen(prev
))
1469 } else if (len
< mss
) {
1477 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1478 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1481 if (!skb_shift(prev
, skb
, len
))
1483 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1486 /* Hole filled allows collapsing with the next as well, this is very
1487 * useful when hole on every nth skb pattern happens
1489 if (prev
== tcp_write_queue_tail(sk
))
1491 skb
= tcp_write_queue_next(sk
, prev
);
1493 if (!skb_can_shift(skb
) ||
1494 (skb
== tcp_send_head(sk
)) ||
1495 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1496 (mss
!= tcp_skb_seglen(skb
)))
1500 if (skb_shift(prev
, skb
, len
)) {
1501 pcount
+= tcp_skb_pcount(skb
);
1502 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1506 state
->fack_count
+= pcount
;
1513 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1517 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1518 struct tcp_sack_block
*next_dup
,
1519 struct tcp_sacktag_state
*state
,
1520 u32 start_seq
, u32 end_seq
,
1523 struct tcp_sock
*tp
= tcp_sk(sk
);
1524 struct sk_buff
*tmp
;
1526 tcp_for_write_queue_from(skb
, sk
) {
1528 bool dup_sack
= dup_sack_in
;
1530 if (skb
== tcp_send_head(sk
))
1533 /* queue is in-order => we can short-circuit the walk early */
1534 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1538 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1539 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1540 next_dup
->start_seq
,
1546 /* skb reference here is a bit tricky to get right, since
1547 * shifting can eat and free both this skb and the next,
1548 * so not even _safe variant of the loop is enough.
1551 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1552 start_seq
, end_seq
, dup_sack
);
1561 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1567 if (unlikely(in_sack
< 0))
1571 TCP_SKB_CB(skb
)->sacked
=
1574 TCP_SKB_CB(skb
)->sacked
,
1575 TCP_SKB_CB(skb
)->seq
,
1576 TCP_SKB_CB(skb
)->end_seq
,
1578 tcp_skb_pcount(skb
),
1581 if (!before(TCP_SKB_CB(skb
)->seq
,
1582 tcp_highest_sack_seq(tp
)))
1583 tcp_advance_highest_sack(sk
, skb
);
1586 state
->fack_count
+= tcp_skb_pcount(skb
);
1591 /* Avoid all extra work that is being done by sacktag while walking in
1594 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1595 struct tcp_sacktag_state
*state
,
1598 tcp_for_write_queue_from(skb
, sk
) {
1599 if (skb
== tcp_send_head(sk
))
1602 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1605 state
->fack_count
+= tcp_skb_pcount(skb
);
1610 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1612 struct tcp_sack_block
*next_dup
,
1613 struct tcp_sacktag_state
*state
,
1619 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1620 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1621 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1622 next_dup
->start_seq
, next_dup
->end_seq
,
1629 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1631 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1635 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1636 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1638 struct tcp_sock
*tp
= tcp_sk(sk
);
1639 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1640 TCP_SKB_CB(ack_skb
)->sacked
);
1641 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1642 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1643 struct tcp_sack_block
*cache
;
1644 struct sk_buff
*skb
;
1645 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1647 bool found_dup_sack
= false;
1649 int first_sack_index
;
1652 state
->reord
= tp
->packets_out
;
1654 if (!tp
->sacked_out
) {
1655 if (WARN_ON(tp
->fackets_out
))
1656 tp
->fackets_out
= 0;
1657 tcp_highest_sack_reset(sk
);
1660 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1661 num_sacks
, prior_snd_una
);
1663 state
->flag
|= FLAG_DSACKING_ACK
;
1665 /* Eliminate too old ACKs, but take into
1666 * account more or less fresh ones, they can
1667 * contain valid SACK info.
1669 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1672 if (!tp
->packets_out
)
1676 first_sack_index
= 0;
1677 for (i
= 0; i
< num_sacks
; i
++) {
1678 bool dup_sack
= !i
&& found_dup_sack
;
1680 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1681 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1683 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1684 sp
[used_sacks
].start_seq
,
1685 sp
[used_sacks
].end_seq
)) {
1689 if (!tp
->undo_marker
)
1690 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1692 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1694 /* Don't count olds caused by ACK reordering */
1695 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1696 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1698 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1701 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1703 first_sack_index
= -1;
1707 /* Ignore very old stuff early */
1708 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1714 /* order SACK blocks to allow in order walk of the retrans queue */
1715 for (i
= used_sacks
- 1; i
> 0; i
--) {
1716 for (j
= 0; j
< i
; j
++) {
1717 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1718 swap(sp
[j
], sp
[j
+ 1]);
1720 /* Track where the first SACK block goes to */
1721 if (j
== first_sack_index
)
1722 first_sack_index
= j
+ 1;
1727 skb
= tcp_write_queue_head(sk
);
1728 state
->fack_count
= 0;
1731 if (!tp
->sacked_out
) {
1732 /* It's already past, so skip checking against it */
1733 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1735 cache
= tp
->recv_sack_cache
;
1736 /* Skip empty blocks in at head of the cache */
1737 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1742 while (i
< used_sacks
) {
1743 u32 start_seq
= sp
[i
].start_seq
;
1744 u32 end_seq
= sp
[i
].end_seq
;
1745 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1746 struct tcp_sack_block
*next_dup
= NULL
;
1748 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1749 next_dup
= &sp
[i
+ 1];
1751 /* Skip too early cached blocks */
1752 while (tcp_sack_cache_ok(tp
, cache
) &&
1753 !before(start_seq
, cache
->end_seq
))
1756 /* Can skip some work by looking recv_sack_cache? */
1757 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1758 after(end_seq
, cache
->start_seq
)) {
1761 if (before(start_seq
, cache
->start_seq
)) {
1762 skb
= tcp_sacktag_skip(skb
, sk
, state
,
1764 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1771 /* Rest of the block already fully processed? */
1772 if (!after(end_seq
, cache
->end_seq
))
1775 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1779 /* ...tail remains todo... */
1780 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1781 /* ...but better entrypoint exists! */
1782 skb
= tcp_highest_sack(sk
);
1785 state
->fack_count
= tp
->fackets_out
;
1790 skb
= tcp_sacktag_skip(skb
, sk
, state
, cache
->end_seq
);
1791 /* Check overlap against next cached too (past this one already) */
1796 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1797 skb
= tcp_highest_sack(sk
);
1800 state
->fack_count
= tp
->fackets_out
;
1802 skb
= tcp_sacktag_skip(skb
, sk
, state
, start_seq
);
1805 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
1806 start_seq
, end_seq
, dup_sack
);
1812 /* Clear the head of the cache sack blocks so we can skip it next time */
1813 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1814 tp
->recv_sack_cache
[i
].start_seq
= 0;
1815 tp
->recv_sack_cache
[i
].end_seq
= 0;
1817 for (j
= 0; j
< used_sacks
; j
++)
1818 tp
->recv_sack_cache
[i
++] = sp
[j
];
1820 if ((state
->reord
< tp
->fackets_out
) &&
1821 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1822 tcp_update_reordering(sk
, tp
->fackets_out
- state
->reord
, 0);
1824 tcp_mark_lost_retrans(sk
, &state
->flag
);
1825 tcp_verify_left_out(tp
);
1828 #if FASTRETRANS_DEBUG > 0
1829 WARN_ON((int)tp
->sacked_out
< 0);
1830 WARN_ON((int)tp
->lost_out
< 0);
1831 WARN_ON((int)tp
->retrans_out
< 0);
1832 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1837 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1838 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1840 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1844 holes
= max(tp
->lost_out
, 1U);
1845 holes
= min(holes
, tp
->packets_out
);
1847 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1848 tp
->sacked_out
= tp
->packets_out
- holes
;
1854 /* If we receive more dupacks than we expected counting segments
1855 * in assumption of absent reordering, interpret this as reordering.
1856 * The only another reason could be bug in receiver TCP.
1858 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1860 struct tcp_sock
*tp
= tcp_sk(sk
);
1861 if (tcp_limit_reno_sacked(tp
))
1862 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1865 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1867 static void tcp_add_reno_sack(struct sock
*sk
)
1869 struct tcp_sock
*tp
= tcp_sk(sk
);
1871 tcp_check_reno_reordering(sk
, 0);
1872 tcp_verify_left_out(tp
);
1875 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1877 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1879 struct tcp_sock
*tp
= tcp_sk(sk
);
1882 /* One ACK acked hole. The rest eat duplicate ACKs. */
1883 if (acked
- 1 >= tp
->sacked_out
)
1886 tp
->sacked_out
-= acked
- 1;
1888 tcp_check_reno_reordering(sk
, acked
);
1889 tcp_verify_left_out(tp
);
1892 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1897 void tcp_clear_retrans(struct tcp_sock
*tp
)
1899 tp
->retrans_out
= 0;
1901 tp
->undo_marker
= 0;
1902 tp
->undo_retrans
= -1;
1903 tp
->fackets_out
= 0;
1907 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1909 tp
->undo_marker
= tp
->snd_una
;
1910 /* Retransmission still in flight may cause DSACKs later. */
1911 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1914 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1915 * and reset tags completely, otherwise preserve SACKs. If receiver
1916 * dropped its ofo queue, we will know this due to reneging detection.
1918 void tcp_enter_loss(struct sock
*sk
)
1920 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1921 struct tcp_sock
*tp
= tcp_sk(sk
);
1922 struct sk_buff
*skb
;
1923 bool new_recovery
= false;
1924 bool is_reneg
; /* is receiver reneging on SACKs? */
1926 /* Reduce ssthresh if it has not yet been made inside this window. */
1927 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1928 !after(tp
->high_seq
, tp
->snd_una
) ||
1929 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1930 new_recovery
= true;
1931 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1932 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1933 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1937 tp
->snd_cwnd_cnt
= 0;
1938 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1940 tp
->retrans_out
= 0;
1943 if (tcp_is_reno(tp
))
1944 tcp_reset_reno_sack(tp
);
1946 skb
= tcp_write_queue_head(sk
);
1947 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1949 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1951 tp
->fackets_out
= 0;
1953 tcp_clear_all_retrans_hints(tp
);
1955 tcp_for_write_queue(skb
, sk
) {
1956 if (skb
== tcp_send_head(sk
))
1959 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1960 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || is_reneg
) {
1961 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1962 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1963 tp
->lost_out
+= tcp_skb_pcount(skb
);
1964 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1967 tcp_verify_left_out(tp
);
1969 /* Timeout in disordered state after receiving substantial DUPACKs
1970 * suggests that the degree of reordering is over-estimated.
1972 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1973 tp
->sacked_out
>= sysctl_tcp_reordering
)
1974 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1975 sysctl_tcp_reordering
);
1976 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1977 tp
->high_seq
= tp
->snd_nxt
;
1978 tcp_ecn_queue_cwr(tp
);
1980 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1981 * loss recovery is underway except recurring timeout(s) on
1982 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1984 tp
->frto
= sysctl_tcp_frto
&&
1985 (new_recovery
|| icsk
->icsk_retransmits
) &&
1986 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1989 /* If ACK arrived pointing to a remembered SACK, it means that our
1990 * remembered SACKs do not reflect real state of receiver i.e.
1991 * receiver _host_ is heavily congested (or buggy).
1993 * To avoid big spurious retransmission bursts due to transient SACK
1994 * scoreboard oddities that look like reneging, we give the receiver a
1995 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
1996 * restore sanity to the SACK scoreboard. If the apparent reneging
1997 * persists until this RTO then we'll clear the SACK scoreboard.
1999 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2001 if (flag
& FLAG_SACK_RENEGING
) {
2002 struct tcp_sock
*tp
= tcp_sk(sk
);
2003 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2004 msecs_to_jiffies(10));
2006 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2007 delay
, TCP_RTO_MAX
);
2013 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2015 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2018 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2019 * counter when SACK is enabled (without SACK, sacked_out is used for
2022 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2023 * segments up to the highest received SACK block so far and holes in
2026 * With reordering, holes may still be in flight, so RFC3517 recovery
2027 * uses pure sacked_out (total number of SACKed segments) even though
2028 * it violates the RFC that uses duplicate ACKs, often these are equal
2029 * but when e.g. out-of-window ACKs or packet duplication occurs,
2030 * they differ. Since neither occurs due to loss, TCP should really
2033 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2035 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2038 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2040 struct tcp_sock
*tp
= tcp_sk(sk
);
2041 unsigned long delay
;
2043 /* Delay early retransmit and entering fast recovery for
2044 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2045 * available, or RTO is scheduled to fire first.
2047 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
2048 (flag
& FLAG_ECE
) || !tp
->srtt_us
)
2051 delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 5),
2052 msecs_to_jiffies(2));
2054 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2057 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2062 /* Linux NewReno/SACK/FACK/ECN state machine.
2063 * --------------------------------------
2065 * "Open" Normal state, no dubious events, fast path.
2066 * "Disorder" In all the respects it is "Open",
2067 * but requires a bit more attention. It is entered when
2068 * we see some SACKs or dupacks. It is split of "Open"
2069 * mainly to move some processing from fast path to slow one.
2070 * "CWR" CWND was reduced due to some Congestion Notification event.
2071 * It can be ECN, ICMP source quench, local device congestion.
2072 * "Recovery" CWND was reduced, we are fast-retransmitting.
2073 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2075 * tcp_fastretrans_alert() is entered:
2076 * - each incoming ACK, if state is not "Open"
2077 * - when arrived ACK is unusual, namely:
2082 * Counting packets in flight is pretty simple.
2084 * in_flight = packets_out - left_out + retrans_out
2086 * packets_out is SND.NXT-SND.UNA counted in packets.
2088 * retrans_out is number of retransmitted segments.
2090 * left_out is number of segments left network, but not ACKed yet.
2092 * left_out = sacked_out + lost_out
2094 * sacked_out: Packets, which arrived to receiver out of order
2095 * and hence not ACKed. With SACKs this number is simply
2096 * amount of SACKed data. Even without SACKs
2097 * it is easy to give pretty reliable estimate of this number,
2098 * counting duplicate ACKs.
2100 * lost_out: Packets lost by network. TCP has no explicit
2101 * "loss notification" feedback from network (for now).
2102 * It means that this number can be only _guessed_.
2103 * Actually, it is the heuristics to predict lossage that
2104 * distinguishes different algorithms.
2106 * F.e. after RTO, when all the queue is considered as lost,
2107 * lost_out = packets_out and in_flight = retrans_out.
2109 * Essentially, we have now two algorithms counting
2112 * FACK: It is the simplest heuristics. As soon as we decided
2113 * that something is lost, we decide that _all_ not SACKed
2114 * packets until the most forward SACK are lost. I.e.
2115 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2116 * It is absolutely correct estimate, if network does not reorder
2117 * packets. And it loses any connection to reality when reordering
2118 * takes place. We use FACK by default until reordering
2119 * is suspected on the path to this destination.
2121 * NewReno: when Recovery is entered, we assume that one segment
2122 * is lost (classic Reno). While we are in Recovery and
2123 * a partial ACK arrives, we assume that one more packet
2124 * is lost (NewReno). This heuristics are the same in NewReno
2127 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2128 * deflation etc. CWND is real congestion window, never inflated, changes
2129 * only according to classic VJ rules.
2131 * Really tricky (and requiring careful tuning) part of algorithm
2132 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2133 * The first determines the moment _when_ we should reduce CWND and,
2134 * hence, slow down forward transmission. In fact, it determines the moment
2135 * when we decide that hole is caused by loss, rather than by a reorder.
2137 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2138 * holes, caused by lost packets.
2140 * And the most logically complicated part of algorithm is undo
2141 * heuristics. We detect false retransmits due to both too early
2142 * fast retransmit (reordering) and underestimated RTO, analyzing
2143 * timestamps and D-SACKs. When we detect that some segments were
2144 * retransmitted by mistake and CWND reduction was wrong, we undo
2145 * window reduction and abort recovery phase. This logic is hidden
2146 * inside several functions named tcp_try_undo_<something>.
2149 /* This function decides, when we should leave Disordered state
2150 * and enter Recovery phase, reducing congestion window.
2152 * Main question: may we further continue forward transmission
2153 * with the same cwnd?
2155 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2157 struct tcp_sock
*tp
= tcp_sk(sk
);
2160 /* Trick#1: The loss is proven. */
2164 /* Not-A-Trick#2 : Classic rule... */
2165 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2168 /* Trick#4: It is still not OK... But will it be useful to delay
2171 packets_out
= tp
->packets_out
;
2172 if (packets_out
<= tp
->reordering
&&
2173 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2174 !tcp_may_send_now(sk
)) {
2175 /* We have nothing to send. This connection is limited
2176 * either by receiver window or by application.
2181 /* If a thin stream is detected, retransmit after first
2182 * received dupack. Employ only if SACK is supported in order
2183 * to avoid possible corner-case series of spurious retransmissions
2184 * Use only if there are no unsent data.
2186 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2187 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2188 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2191 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2192 * retransmissions due to small network reorderings, we implement
2193 * Mitigation A.3 in the RFC and delay the retransmission for a short
2194 * interval if appropriate.
2196 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2197 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2198 !tcp_may_send_now(sk
))
2199 return !tcp_pause_early_retransmit(sk
, flag
);
2204 /* Detect loss in event "A" above by marking head of queue up as lost.
2205 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2206 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2207 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2208 * the maximum SACKed segments to pass before reaching this limit.
2210 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2212 struct tcp_sock
*tp
= tcp_sk(sk
);
2213 struct sk_buff
*skb
;
2217 /* Use SACK to deduce losses of new sequences sent during recovery */
2218 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2220 WARN_ON(packets
> tp
->packets_out
);
2221 if (tp
->lost_skb_hint
) {
2222 skb
= tp
->lost_skb_hint
;
2223 cnt
= tp
->lost_cnt_hint
;
2224 /* Head already handled? */
2225 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2228 skb
= tcp_write_queue_head(sk
);
2232 tcp_for_write_queue_from(skb
, sk
) {
2233 if (skb
== tcp_send_head(sk
))
2235 /* TODO: do this better */
2236 /* this is not the most efficient way to do this... */
2237 tp
->lost_skb_hint
= skb
;
2238 tp
->lost_cnt_hint
= cnt
;
2240 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2244 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2245 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2246 cnt
+= tcp_skb_pcount(skb
);
2248 if (cnt
> packets
) {
2249 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2250 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2251 (oldcnt
>= packets
))
2254 mss
= tcp_skb_mss(skb
);
2255 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
,
2262 tcp_skb_mark_lost(tp
, skb
);
2267 tcp_verify_left_out(tp
);
2270 /* Account newly detected lost packet(s) */
2272 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2274 struct tcp_sock
*tp
= tcp_sk(sk
);
2276 if (tcp_is_reno(tp
)) {
2277 tcp_mark_head_lost(sk
, 1, 1);
2278 } else if (tcp_is_fack(tp
)) {
2279 int lost
= tp
->fackets_out
- tp
->reordering
;
2282 tcp_mark_head_lost(sk
, lost
, 0);
2284 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2285 if (sacked_upto
>= 0)
2286 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2287 else if (fast_rexmit
)
2288 tcp_mark_head_lost(sk
, 1, 1);
2292 /* CWND moderation, preventing bursts due to too big ACKs
2293 * in dubious situations.
2295 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2297 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2298 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2299 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2302 /* Nothing was retransmitted or returned timestamp is less
2303 * than timestamp of the first retransmission.
2305 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2307 return !tp
->retrans_stamp
||
2308 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2309 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2312 /* Undo procedures. */
2314 /* We can clear retrans_stamp when there are no retransmissions in the
2315 * window. It would seem that it is trivially available for us in
2316 * tp->retrans_out, however, that kind of assumptions doesn't consider
2317 * what will happen if errors occur when sending retransmission for the
2318 * second time. ...It could the that such segment has only
2319 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2320 * the head skb is enough except for some reneging corner cases that
2321 * are not worth the effort.
2323 * Main reason for all this complexity is the fact that connection dying
2324 * time now depends on the validity of the retrans_stamp, in particular,
2325 * that successive retransmissions of a segment must not advance
2326 * retrans_stamp under any conditions.
2328 static bool tcp_any_retrans_done(const struct sock
*sk
)
2330 const struct tcp_sock
*tp
= tcp_sk(sk
);
2331 struct sk_buff
*skb
;
2333 if (tp
->retrans_out
)
2336 skb
= tcp_write_queue_head(sk
);
2337 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2343 #if FASTRETRANS_DEBUG > 1
2344 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2346 struct tcp_sock
*tp
= tcp_sk(sk
);
2347 struct inet_sock
*inet
= inet_sk(sk
);
2349 if (sk
->sk_family
== AF_INET
) {
2350 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2352 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2353 tp
->snd_cwnd
, tcp_left_out(tp
),
2354 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2357 #if IS_ENABLED(CONFIG_IPV6)
2358 else if (sk
->sk_family
== AF_INET6
) {
2359 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2360 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2362 &np
->daddr
, ntohs(inet
->inet_dport
),
2363 tp
->snd_cwnd
, tcp_left_out(tp
),
2364 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2370 #define DBGUNDO(x...) do { } while (0)
2373 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2375 struct tcp_sock
*tp
= tcp_sk(sk
);
2378 struct sk_buff
*skb
;
2380 tcp_for_write_queue(skb
, sk
) {
2381 if (skb
== tcp_send_head(sk
))
2383 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2386 tcp_clear_all_retrans_hints(tp
);
2389 if (tp
->prior_ssthresh
) {
2390 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2392 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2393 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2395 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2397 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2398 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2399 tcp_ecn_withdraw_cwr(tp
);
2402 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2404 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2405 tp
->undo_marker
= 0;
2408 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2410 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2413 /* People celebrate: "We love our President!" */
2414 static bool tcp_try_undo_recovery(struct sock
*sk
)
2416 struct tcp_sock
*tp
= tcp_sk(sk
);
2418 if (tcp_may_undo(tp
)) {
2421 /* Happy end! We did not retransmit anything
2422 * or our original transmission succeeded.
2424 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2425 tcp_undo_cwnd_reduction(sk
, false);
2426 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2427 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2429 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2431 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2433 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2434 /* Hold old state until something *above* high_seq
2435 * is ACKed. For Reno it is MUST to prevent false
2436 * fast retransmits (RFC2582). SACK TCP is safe. */
2437 tcp_moderate_cwnd(tp
);
2438 if (!tcp_any_retrans_done(sk
))
2439 tp
->retrans_stamp
= 0;
2442 tcp_set_ca_state(sk
, TCP_CA_Open
);
2446 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2447 static bool tcp_try_undo_dsack(struct sock
*sk
)
2449 struct tcp_sock
*tp
= tcp_sk(sk
);
2451 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2452 DBGUNDO(sk
, "D-SACK");
2453 tcp_undo_cwnd_reduction(sk
, false);
2454 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2460 /* Undo during loss recovery after partial ACK or using F-RTO. */
2461 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2463 struct tcp_sock
*tp
= tcp_sk(sk
);
2465 if (frto_undo
|| tcp_may_undo(tp
)) {
2466 tcp_undo_cwnd_reduction(sk
, true);
2468 DBGUNDO(sk
, "partial loss");
2469 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2471 NET_INC_STATS_BH(sock_net(sk
),
2472 LINUX_MIB_TCPSPURIOUSRTOS
);
2473 inet_csk(sk
)->icsk_retransmits
= 0;
2474 if (frto_undo
|| tcp_is_sack(tp
))
2475 tcp_set_ca_state(sk
, TCP_CA_Open
);
2481 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2482 * It computes the number of packets to send (sndcnt) based on packets newly
2484 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2485 * cwnd reductions across a full RTT.
2486 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2487 * But when the retransmits are acked without further losses, PRR
2488 * slow starts cwnd up to ssthresh to speed up the recovery.
2490 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2492 struct tcp_sock
*tp
= tcp_sk(sk
);
2494 tp
->high_seq
= tp
->snd_nxt
;
2495 tp
->tlp_high_seq
= 0;
2496 tp
->snd_cwnd_cnt
= 0;
2497 tp
->prior_cwnd
= tp
->snd_cwnd
;
2498 tp
->prr_delivered
= 0;
2500 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2501 tcp_ecn_queue_cwr(tp
);
2504 static void tcp_cwnd_reduction(struct sock
*sk
, const int prior_unsacked
,
2505 int fast_rexmit
, int flag
)
2507 struct tcp_sock
*tp
= tcp_sk(sk
);
2509 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2510 int newly_acked_sacked
= prior_unsacked
-
2511 (tp
->packets_out
- tp
->sacked_out
);
2513 tp
->prr_delivered
+= newly_acked_sacked
;
2515 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2517 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2518 } else if ((flag
& FLAG_RETRANS_DATA_ACKED
) &&
2519 !(flag
& FLAG_LOST_RETRANS
)) {
2520 sndcnt
= min_t(int, delta
,
2521 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2522 newly_acked_sacked
) + 1);
2524 sndcnt
= min(delta
, newly_acked_sacked
);
2526 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2527 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2530 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2532 struct tcp_sock
*tp
= tcp_sk(sk
);
2534 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2535 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2536 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2537 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2538 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2540 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2543 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2544 void tcp_enter_cwr(struct sock
*sk
)
2546 struct tcp_sock
*tp
= tcp_sk(sk
);
2548 tp
->prior_ssthresh
= 0;
2549 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2550 tp
->undo_marker
= 0;
2551 tcp_init_cwnd_reduction(sk
);
2552 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2555 EXPORT_SYMBOL(tcp_enter_cwr
);
2557 static void tcp_try_keep_open(struct sock
*sk
)
2559 struct tcp_sock
*tp
= tcp_sk(sk
);
2560 int state
= TCP_CA_Open
;
2562 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2563 state
= TCP_CA_Disorder
;
2565 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2566 tcp_set_ca_state(sk
, state
);
2567 tp
->high_seq
= tp
->snd_nxt
;
2571 static void tcp_try_to_open(struct sock
*sk
, int flag
, const int prior_unsacked
)
2573 struct tcp_sock
*tp
= tcp_sk(sk
);
2575 tcp_verify_left_out(tp
);
2577 if (!tcp_any_retrans_done(sk
))
2578 tp
->retrans_stamp
= 0;
2580 if (flag
& FLAG_ECE
)
2583 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2584 tcp_try_keep_open(sk
);
2586 tcp_cwnd_reduction(sk
, prior_unsacked
, 0, flag
);
2590 static void tcp_mtup_probe_failed(struct sock
*sk
)
2592 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2594 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2595 icsk
->icsk_mtup
.probe_size
= 0;
2598 static void tcp_mtup_probe_success(struct sock
*sk
)
2600 struct tcp_sock
*tp
= tcp_sk(sk
);
2601 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2603 /* FIXME: breaks with very large cwnd */
2604 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2605 tp
->snd_cwnd
= tp
->snd_cwnd
*
2606 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2607 icsk
->icsk_mtup
.probe_size
;
2608 tp
->snd_cwnd_cnt
= 0;
2609 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2610 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2612 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2613 icsk
->icsk_mtup
.probe_size
= 0;
2614 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2617 /* Do a simple retransmit without using the backoff mechanisms in
2618 * tcp_timer. This is used for path mtu discovery.
2619 * The socket is already locked here.
2621 void tcp_simple_retransmit(struct sock
*sk
)
2623 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2624 struct tcp_sock
*tp
= tcp_sk(sk
);
2625 struct sk_buff
*skb
;
2626 unsigned int mss
= tcp_current_mss(sk
);
2627 u32 prior_lost
= tp
->lost_out
;
2629 tcp_for_write_queue(skb
, sk
) {
2630 if (skb
== tcp_send_head(sk
))
2632 if (tcp_skb_seglen(skb
) > mss
&&
2633 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2634 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2635 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2636 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2638 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2642 tcp_clear_retrans_hints_partial(tp
);
2644 if (prior_lost
== tp
->lost_out
)
2647 if (tcp_is_reno(tp
))
2648 tcp_limit_reno_sacked(tp
);
2650 tcp_verify_left_out(tp
);
2652 /* Don't muck with the congestion window here.
2653 * Reason is that we do not increase amount of _data_
2654 * in network, but units changed and effective
2655 * cwnd/ssthresh really reduced now.
2657 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2658 tp
->high_seq
= tp
->snd_nxt
;
2659 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2660 tp
->prior_ssthresh
= 0;
2661 tp
->undo_marker
= 0;
2662 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2664 tcp_xmit_retransmit_queue(sk
);
2666 EXPORT_SYMBOL(tcp_simple_retransmit
);
2668 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2670 struct tcp_sock
*tp
= tcp_sk(sk
);
2673 if (tcp_is_reno(tp
))
2674 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2676 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2678 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2680 tp
->prior_ssthresh
= 0;
2683 if (!tcp_in_cwnd_reduction(sk
)) {
2685 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2686 tcp_init_cwnd_reduction(sk
);
2688 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2691 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2692 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2694 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
)
2696 struct tcp_sock
*tp
= tcp_sk(sk
);
2697 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2699 if ((flag
& FLAG_SND_UNA_ADVANCED
) &&
2700 tcp_try_undo_loss(sk
, false))
2703 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2704 /* Step 3.b. A timeout is spurious if not all data are
2705 * lost, i.e., never-retransmitted data are (s)acked.
2707 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2708 tcp_try_undo_loss(sk
, true))
2711 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2712 if (flag
& FLAG_DATA_SACKED
|| is_dupack
)
2713 tp
->frto
= 0; /* Step 3.a. loss was real */
2714 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2715 tp
->high_seq
= tp
->snd_nxt
;
2716 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
2718 if (after(tp
->snd_nxt
, tp
->high_seq
))
2719 return; /* Step 2.b */
2725 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2726 tcp_try_undo_recovery(sk
);
2729 if (tcp_is_reno(tp
)) {
2730 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2731 * delivered. Lower inflight to clock out (re)tranmissions.
2733 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2734 tcp_add_reno_sack(sk
);
2735 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2736 tcp_reset_reno_sack(tp
);
2738 tcp_xmit_retransmit_queue(sk
);
2741 /* Undo during fast recovery after partial ACK. */
2742 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
,
2743 const int prior_unsacked
, int flag
)
2745 struct tcp_sock
*tp
= tcp_sk(sk
);
2747 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2748 /* Plain luck! Hole if filled with delayed
2749 * packet, rather than with a retransmit.
2751 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2753 /* We are getting evidence that the reordering degree is higher
2754 * than we realized. If there are no retransmits out then we
2755 * can undo. Otherwise we clock out new packets but do not
2756 * mark more packets lost or retransmit more.
2758 if (tp
->retrans_out
) {
2759 tcp_cwnd_reduction(sk
, prior_unsacked
, 0, flag
);
2763 if (!tcp_any_retrans_done(sk
))
2764 tp
->retrans_stamp
= 0;
2766 DBGUNDO(sk
, "partial recovery");
2767 tcp_undo_cwnd_reduction(sk
, true);
2768 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2769 tcp_try_keep_open(sk
);
2775 /* Process an event, which can update packets-in-flight not trivially.
2776 * Main goal of this function is to calculate new estimate for left_out,
2777 * taking into account both packets sitting in receiver's buffer and
2778 * packets lost by network.
2780 * Besides that it does CWND reduction, when packet loss is detected
2781 * and changes state of machine.
2783 * It does _not_ decide what to send, it is made in function
2784 * tcp_xmit_retransmit_queue().
2786 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2787 const int prior_unsacked
,
2788 bool is_dupack
, int flag
)
2790 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2791 struct tcp_sock
*tp
= tcp_sk(sk
);
2792 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2793 (tcp_fackets_out(tp
) > tp
->reordering
));
2794 int fast_rexmit
= 0;
2796 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2798 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2799 tp
->fackets_out
= 0;
2801 /* Now state machine starts.
2802 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2803 if (flag
& FLAG_ECE
)
2804 tp
->prior_ssthresh
= 0;
2806 /* B. In all the states check for reneging SACKs. */
2807 if (tcp_check_sack_reneging(sk
, flag
))
2810 /* C. Check consistency of the current state. */
2811 tcp_verify_left_out(tp
);
2813 /* D. Check state exit conditions. State can be terminated
2814 * when high_seq is ACKed. */
2815 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2816 WARN_ON(tp
->retrans_out
!= 0);
2817 tp
->retrans_stamp
= 0;
2818 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2819 switch (icsk
->icsk_ca_state
) {
2821 /* CWR is to be held something *above* high_seq
2822 * is ACKed for CWR bit to reach receiver. */
2823 if (tp
->snd_una
!= tp
->high_seq
) {
2824 tcp_end_cwnd_reduction(sk
);
2825 tcp_set_ca_state(sk
, TCP_CA_Open
);
2829 case TCP_CA_Recovery
:
2830 if (tcp_is_reno(tp
))
2831 tcp_reset_reno_sack(tp
);
2832 if (tcp_try_undo_recovery(sk
))
2834 tcp_end_cwnd_reduction(sk
);
2839 /* E. Process state. */
2840 switch (icsk
->icsk_ca_state
) {
2841 case TCP_CA_Recovery
:
2842 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2843 if (tcp_is_reno(tp
) && is_dupack
)
2844 tcp_add_reno_sack(sk
);
2846 if (tcp_try_undo_partial(sk
, acked
, prior_unsacked
, flag
))
2848 /* Partial ACK arrived. Force fast retransmit. */
2849 do_lost
= tcp_is_reno(tp
) ||
2850 tcp_fackets_out(tp
) > tp
->reordering
;
2852 if (tcp_try_undo_dsack(sk
)) {
2853 tcp_try_keep_open(sk
);
2858 tcp_process_loss(sk
, flag
, is_dupack
);
2859 if (icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2860 !(flag
& FLAG_LOST_RETRANS
))
2862 /* Change state if cwnd is undone or retransmits are lost */
2864 if (tcp_is_reno(tp
)) {
2865 if (flag
& FLAG_SND_UNA_ADVANCED
)
2866 tcp_reset_reno_sack(tp
);
2868 tcp_add_reno_sack(sk
);
2871 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2872 tcp_try_undo_dsack(sk
);
2874 if (!tcp_time_to_recover(sk
, flag
)) {
2875 tcp_try_to_open(sk
, flag
, prior_unsacked
);
2879 /* MTU probe failure: don't reduce cwnd */
2880 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2881 icsk
->icsk_mtup
.probe_size
&&
2882 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2883 tcp_mtup_probe_failed(sk
);
2884 /* Restores the reduction we did in tcp_mtup_probe() */
2886 tcp_simple_retransmit(sk
);
2890 /* Otherwise enter Recovery state */
2891 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2896 tcp_update_scoreboard(sk
, fast_rexmit
);
2897 tcp_cwnd_reduction(sk
, prior_unsacked
, fast_rexmit
, flag
);
2898 tcp_xmit_retransmit_queue(sk
);
2901 static inline bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2902 long seq_rtt_us
, long sack_rtt_us
)
2904 const struct tcp_sock
*tp
= tcp_sk(sk
);
2906 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2907 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2908 * Karn's algorithm forbids taking RTT if some retransmitted data
2909 * is acked (RFC6298).
2911 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2915 seq_rtt_us
= sack_rtt_us
;
2917 /* RTTM Rule: A TSecr value received in a segment is used to
2918 * update the averaged RTT measurement only if the segment
2919 * acknowledges some new data, i.e., only if it advances the
2920 * left edge of the send window.
2921 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2923 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2925 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
2930 tcp_rtt_estimator(sk
, seq_rtt_us
);
2933 /* RFC6298: only reset backoff on valid RTT measurement. */
2934 inet_csk(sk
)->icsk_backoff
= 0;
2938 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2939 static void tcp_synack_rtt_meas(struct sock
*sk
, const u32 synack_stamp
)
2941 struct tcp_sock
*tp
= tcp_sk(sk
);
2942 long seq_rtt_us
= -1L;
2944 if (synack_stamp
&& !tp
->total_retrans
)
2945 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- synack_stamp
);
2947 /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
2948 * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
2951 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, seq_rtt_us
, -1L);
2954 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2956 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2958 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2959 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2962 /* Restart timer after forward progress on connection.
2963 * RFC2988 recommends to restart timer to now+rto.
2965 void tcp_rearm_rto(struct sock
*sk
)
2967 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2968 struct tcp_sock
*tp
= tcp_sk(sk
);
2970 /* If the retrans timer is currently being used by Fast Open
2971 * for SYN-ACK retrans purpose, stay put.
2973 if (tp
->fastopen_rsk
)
2976 if (!tp
->packets_out
) {
2977 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2979 u32 rto
= inet_csk(sk
)->icsk_rto
;
2980 /* Offset the time elapsed after installing regular RTO */
2981 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
2982 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
2983 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
2984 const u32 rto_time_stamp
=
2985 tcp_skb_timestamp(skb
) + rto
;
2986 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
2987 /* delta may not be positive if the socket is locked
2988 * when the retrans timer fires and is rescheduled.
2993 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
2998 /* This function is called when the delayed ER timer fires. TCP enters
2999 * fast recovery and performs fast-retransmit.
3001 void tcp_resume_early_retransmit(struct sock
*sk
)
3003 struct tcp_sock
*tp
= tcp_sk(sk
);
3007 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3008 if (!tp
->do_early_retrans
)
3011 tcp_enter_recovery(sk
, false);
3012 tcp_update_scoreboard(sk
, 1);
3013 tcp_xmit_retransmit_queue(sk
);
3016 /* If we get here, the whole TSO packet has not been acked. */
3017 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3019 struct tcp_sock
*tp
= tcp_sk(sk
);
3022 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3024 packets_acked
= tcp_skb_pcount(skb
);
3025 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3027 packets_acked
-= tcp_skb_pcount(skb
);
3029 if (packets_acked
) {
3030 BUG_ON(tcp_skb_pcount(skb
) == 0);
3031 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3034 return packets_acked
;
3037 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3040 const struct skb_shared_info
*shinfo
;
3042 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3043 if (likely(!(sk
->sk_tsflags
& SOF_TIMESTAMPING_TX_ACK
)))
3046 shinfo
= skb_shinfo(skb
);
3047 if ((shinfo
->tx_flags
& SKBTX_ACK_TSTAMP
) &&
3048 between(shinfo
->tskey
, prior_snd_una
, tcp_sk(sk
)->snd_una
- 1))
3049 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3052 /* Remove acknowledged frames from the retransmission queue. If our packet
3053 * is before the ack sequence we can discard it as it's confirmed to have
3054 * arrived at the other end.
3056 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3058 struct tcp_sacktag_state
*sack
)
3060 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3061 struct skb_mstamp first_ackt
, last_ackt
, now
;
3062 struct tcp_sock
*tp
= tcp_sk(sk
);
3063 u32 prior_sacked
= tp
->sacked_out
;
3064 u32 reord
= tp
->packets_out
;
3065 bool fully_acked
= true;
3066 long sack_rtt_us
= -1L;
3067 long seq_rtt_us
= -1L;
3068 long ca_rtt_us
= -1L;
3069 struct sk_buff
*skb
;
3076 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3077 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3078 u8 sacked
= scb
->sacked
;
3081 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3083 /* Determine how many packets and what bytes were acked, tso and else */
3084 if (after(scb
->end_seq
, tp
->snd_una
)) {
3085 if (tcp_skb_pcount(skb
) == 1 ||
3086 !after(tp
->snd_una
, scb
->seq
))
3089 acked_pcount
= tcp_tso_acked(sk
, skb
);
3093 fully_acked
= false;
3095 /* Speedup tcp_unlink_write_queue() and next loop */
3096 prefetchw(skb
->next
);
3097 acked_pcount
= tcp_skb_pcount(skb
);
3100 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3101 if (sacked
& TCPCB_SACKED_RETRANS
)
3102 tp
->retrans_out
-= acked_pcount
;
3103 flag
|= FLAG_RETRANS_DATA_ACKED
;
3104 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3105 last_ackt
= skb
->skb_mstamp
;
3106 WARN_ON_ONCE(last_ackt
.v64
== 0);
3107 if (!first_ackt
.v64
)
3108 first_ackt
= last_ackt
;
3110 reord
= min(pkts_acked
, reord
);
3111 if (!after(scb
->end_seq
, tp
->high_seq
))
3112 flag
|= FLAG_ORIG_SACK_ACKED
;
3115 if (sacked
& TCPCB_SACKED_ACKED
)
3116 tp
->sacked_out
-= acked_pcount
;
3117 if (sacked
& TCPCB_LOST
)
3118 tp
->lost_out
-= acked_pcount
;
3120 tp
->packets_out
-= acked_pcount
;
3121 pkts_acked
+= acked_pcount
;
3123 /* Initial outgoing SYN's get put onto the write_queue
3124 * just like anything else we transmit. It is not
3125 * true data, and if we misinform our callers that
3126 * this ACK acks real data, we will erroneously exit
3127 * connection startup slow start one packet too
3128 * quickly. This is severely frowned upon behavior.
3130 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3131 flag
|= FLAG_DATA_ACKED
;
3133 flag
|= FLAG_SYN_ACKED
;
3134 tp
->retrans_stamp
= 0;
3140 tcp_unlink_write_queue(skb
, sk
);
3141 sk_wmem_free_skb(sk
, skb
);
3142 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3143 tp
->retransmit_skb_hint
= NULL
;
3144 if (unlikely(skb
== tp
->lost_skb_hint
))
3145 tp
->lost_skb_hint
= NULL
;
3148 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3149 tp
->snd_up
= tp
->snd_una
;
3151 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3152 flag
|= FLAG_SACK_RENEGING
;
3154 skb_mstamp_get(&now
);
3155 if (likely(first_ackt
.v64
)) {
3156 seq_rtt_us
= skb_mstamp_us_delta(&now
, &first_ackt
);
3157 ca_rtt_us
= skb_mstamp_us_delta(&now
, &last_ackt
);
3159 if (sack
->first_sackt
.v64
) {
3160 sack_rtt_us
= skb_mstamp_us_delta(&now
, &sack
->first_sackt
);
3161 ca_rtt_us
= skb_mstamp_us_delta(&now
, &sack
->last_sackt
);
3164 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
);
3166 if (flag
& FLAG_ACKED
) {
3168 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3169 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3170 tcp_mtup_probe_success(sk
);
3173 if (tcp_is_reno(tp
)) {
3174 tcp_remove_reno_sacks(sk
, pkts_acked
);
3178 /* Non-retransmitted hole got filled? That's reordering */
3179 if (reord
< prior_fackets
)
3180 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3182 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3183 prior_sacked
- tp
->sacked_out
;
3184 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3187 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3189 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3190 sack_rtt_us
> skb_mstamp_us_delta(&now
, &skb
->skb_mstamp
)) {
3191 /* Do not re-arm RTO if the sack RTT is measured from data sent
3192 * after when the head was last (re)transmitted. Otherwise the
3193 * timeout may continue to extend in loss recovery.
3198 if (icsk
->icsk_ca_ops
->pkts_acked
)
3199 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
, ca_rtt_us
);
3201 #if FASTRETRANS_DEBUG > 0
3202 WARN_ON((int)tp
->sacked_out
< 0);
3203 WARN_ON((int)tp
->lost_out
< 0);
3204 WARN_ON((int)tp
->retrans_out
< 0);
3205 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3206 icsk
= inet_csk(sk
);
3208 pr_debug("Leak l=%u %d\n",
3209 tp
->lost_out
, icsk
->icsk_ca_state
);
3212 if (tp
->sacked_out
) {
3213 pr_debug("Leak s=%u %d\n",
3214 tp
->sacked_out
, icsk
->icsk_ca_state
);
3217 if (tp
->retrans_out
) {
3218 pr_debug("Leak r=%u %d\n",
3219 tp
->retrans_out
, icsk
->icsk_ca_state
);
3220 tp
->retrans_out
= 0;
3227 static void tcp_ack_probe(struct sock
*sk
)
3229 const struct tcp_sock
*tp
= tcp_sk(sk
);
3230 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3232 /* Was it a usable window open? */
3234 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3235 icsk
->icsk_backoff
= 0;
3236 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3237 /* Socket must be waked up by subsequent tcp_data_snd_check().
3238 * This function is not for random using!
3241 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3243 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3248 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3250 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3251 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3254 /* Decide wheather to run the increase function of congestion control. */
3255 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3257 if (tcp_in_cwnd_reduction(sk
))
3260 /* If reordering is high then always grow cwnd whenever data is
3261 * delivered regardless of its ordering. Otherwise stay conservative
3262 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3263 * new SACK or ECE mark may first advance cwnd here and later reduce
3264 * cwnd in tcp_fastretrans_alert() based on more states.
3266 if (tcp_sk(sk
)->reordering
> sysctl_tcp_reordering
)
3267 return flag
& FLAG_FORWARD_PROGRESS
;
3269 return flag
& FLAG_DATA_ACKED
;
3272 /* Check that window update is acceptable.
3273 * The function assumes that snd_una<=ack<=snd_next.
3275 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3276 const u32 ack
, const u32 ack_seq
,
3279 return after(ack
, tp
->snd_una
) ||
3280 after(ack_seq
, tp
->snd_wl1
) ||
3281 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3284 /* If we update tp->snd_una, also update tp->bytes_acked */
3285 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3287 u32 delta
= ack
- tp
->snd_una
;
3289 u64_stats_update_begin(&tp
->syncp
);
3290 tp
->bytes_acked
+= delta
;
3291 u64_stats_update_end(&tp
->syncp
);
3295 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3296 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3298 u32 delta
= seq
- tp
->rcv_nxt
;
3300 u64_stats_update_begin(&tp
->syncp
);
3301 tp
->bytes_received
+= delta
;
3302 u64_stats_update_end(&tp
->syncp
);
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 (nwin
> tp
->max_window
) {
3335 tp
->max_window
= nwin
;
3336 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3341 tcp_snd_una_update(tp
, ack
);
3346 /* Return true if we're currently rate-limiting out-of-window ACKs and
3347 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3348 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3349 * attacks that send repeated SYNs or ACKs for the same connection. To
3350 * do this, we do not send a duplicate SYNACK or ACK if the remote
3351 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3353 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3354 int mib_idx
, u32
*last_oow_ack_time
)
3356 /* Data packets without SYNs are not likely part of an ACK loop. */
3357 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3359 goto not_rate_limited
;
3361 if (*last_oow_ack_time
) {
3362 s32 elapsed
= (s32
)(tcp_time_stamp
- *last_oow_ack_time
);
3364 if (0 <= elapsed
&& elapsed
< sysctl_tcp_invalid_ratelimit
) {
3365 NET_INC_STATS_BH(net
, mib_idx
);
3366 return true; /* rate-limited: don't send yet! */
3370 *last_oow_ack_time
= tcp_time_stamp
;
3373 return false; /* not rate-limited: go ahead, send dupack now! */
3376 /* RFC 5961 7 [ACK Throttling] */
3377 static void tcp_send_challenge_ack(struct sock
*sk
, const struct sk_buff
*skb
)
3379 /* unprotected vars, we dont care of overwrites */
3380 static u32 challenge_timestamp
;
3381 static unsigned int challenge_count
;
3382 struct tcp_sock
*tp
= tcp_sk(sk
);
3385 /* First check our per-socket dupack rate limit. */
3386 if (tcp_oow_rate_limited(sock_net(sk
), skb
,
3387 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3388 &tp
->last_oow_ack_time
))
3391 /* Then check the check host-wide RFC 5961 rate limit. */
3393 if (now
!= challenge_timestamp
) {
3394 challenge_timestamp
= now
;
3395 challenge_count
= 0;
3397 if (++challenge_count
<= sysctl_tcp_challenge_ack_limit
) {
3398 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3403 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3405 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3406 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3409 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3411 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3412 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3413 * extra check below makes sure this can only happen
3414 * for pure ACK frames. -DaveM
3416 * Not only, also it occurs for expired timestamps.
3419 if (tcp_paws_check(&tp
->rx_opt
, 0))
3420 tcp_store_ts_recent(tp
);
3424 /* This routine deals with acks during a TLP episode.
3425 * We mark the end of a TLP episode on receiving TLP dupack or when
3426 * ack is after tlp_high_seq.
3427 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3429 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3431 struct tcp_sock
*tp
= tcp_sk(sk
);
3433 if (before(ack
, tp
->tlp_high_seq
))
3436 if (flag
& FLAG_DSACKING_ACK
) {
3437 /* This DSACK means original and TLP probe arrived; no loss */
3438 tp
->tlp_high_seq
= 0;
3439 } else if (after(ack
, tp
->tlp_high_seq
)) {
3440 /* ACK advances: there was a loss, so reduce cwnd. Reset
3441 * tlp_high_seq in tcp_init_cwnd_reduction()
3443 tcp_init_cwnd_reduction(sk
);
3444 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3445 tcp_end_cwnd_reduction(sk
);
3446 tcp_try_keep_open(sk
);
3447 NET_INC_STATS_BH(sock_net(sk
),
3448 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3449 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3450 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3451 /* Pure dupack: original and TLP probe arrived; no loss */
3452 tp
->tlp_high_seq
= 0;
3456 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3458 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3460 if (icsk
->icsk_ca_ops
->in_ack_event
)
3461 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3464 /* This routine deals with incoming acks, but not outgoing ones. */
3465 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3467 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3468 struct tcp_sock
*tp
= tcp_sk(sk
);
3469 struct tcp_sacktag_state sack_state
;
3470 u32 prior_snd_una
= tp
->snd_una
;
3471 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3472 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3473 bool is_dupack
= false;
3475 int prior_packets
= tp
->packets_out
;
3476 const int prior_unsacked
= tp
->packets_out
- tp
->sacked_out
;
3477 int acked
= 0; /* Number of packets newly acked */
3479 sack_state
.first_sackt
.v64
= 0;
3481 /* We very likely will need to access write queue head. */
3482 prefetchw(sk
->sk_write_queue
.next
);
3484 /* If the ack is older than previous acks
3485 * then we can probably ignore it.
3487 if (before(ack
, prior_snd_una
)) {
3488 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3489 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3490 tcp_send_challenge_ack(sk
, skb
);
3496 /* If the ack includes data we haven't sent yet, discard
3497 * this segment (RFC793 Section 3.9).
3499 if (after(ack
, tp
->snd_nxt
))
3502 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3503 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3506 if (after(ack
, prior_snd_una
)) {
3507 flag
|= FLAG_SND_UNA_ADVANCED
;
3508 icsk
->icsk_retransmits
= 0;
3511 prior_fackets
= tp
->fackets_out
;
3513 /* ts_recent update must be made after we are sure that the packet
3516 if (flag
& FLAG_UPDATE_TS_RECENT
)
3517 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3519 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3520 /* Window is constant, pure forward advance.
3521 * No more checks are required.
3522 * Note, we use the fact that SND.UNA>=SND.WL2.
3524 tcp_update_wl(tp
, ack_seq
);
3525 tcp_snd_una_update(tp
, ack
);
3526 flag
|= FLAG_WIN_UPDATE
;
3528 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3530 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3532 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3534 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3537 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3539 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3541 if (TCP_SKB_CB(skb
)->sacked
)
3542 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3545 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3547 ack_ev_flags
|= CA_ACK_ECE
;
3550 if (flag
& FLAG_WIN_UPDATE
)
3551 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3553 tcp_in_ack_event(sk
, ack_ev_flags
);
3556 /* We passed data and got it acked, remove any soft error
3557 * log. Something worked...
3559 sk
->sk_err_soft
= 0;
3560 icsk
->icsk_probes_out
= 0;
3561 tp
->rcv_tstamp
= tcp_time_stamp
;
3565 /* See if we can take anything off of the retransmit queue. */
3566 acked
= tp
->packets_out
;
3567 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
,
3569 acked
-= tp
->packets_out
;
3571 if (tcp_ack_is_dubious(sk
, flag
)) {
3572 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3573 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3576 if (tp
->tlp_high_seq
)
3577 tcp_process_tlp_ack(sk
, ack
, flag
);
3579 /* Advance cwnd if state allows */
3580 if (tcp_may_raise_cwnd(sk
, flag
))
3581 tcp_cong_avoid(sk
, ack
, acked
);
3583 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3584 struct dst_entry
*dst
= __sk_dst_get(sk
);
3589 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3590 tcp_schedule_loss_probe(sk
);
3591 tcp_update_pacing_rate(sk
);
3595 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3596 if (flag
& FLAG_DSACKING_ACK
)
3597 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3599 /* If this ack opens up a zero window, clear backoff. It was
3600 * being used to time the probes, and is probably far higher than
3601 * it needs to be for normal retransmission.
3603 if (tcp_send_head(sk
))
3606 if (tp
->tlp_high_seq
)
3607 tcp_process_tlp_ack(sk
, ack
, flag
);
3611 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3615 /* If data was SACKed, tag it and see if we should send more data.
3616 * If data was DSACKed, see if we can undo a cwnd reduction.
3618 if (TCP_SKB_CB(skb
)->sacked
) {
3619 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3621 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3625 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3629 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
3630 bool syn
, struct tcp_fastopen_cookie
*foc
,
3633 /* Valid only in SYN or SYN-ACK with an even length. */
3634 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
3637 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3638 len
<= TCP_FASTOPEN_COOKIE_MAX
)
3639 memcpy(foc
->val
, cookie
, len
);
3646 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3647 * But, this can also be called on packets in the established flow when
3648 * the fast version below fails.
3650 void tcp_parse_options(const struct sk_buff
*skb
,
3651 struct tcp_options_received
*opt_rx
, int estab
,
3652 struct tcp_fastopen_cookie
*foc
)
3654 const unsigned char *ptr
;
3655 const struct tcphdr
*th
= tcp_hdr(skb
);
3656 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3658 ptr
= (const unsigned char *)(th
+ 1);
3659 opt_rx
->saw_tstamp
= 0;
3661 while (length
> 0) {
3662 int opcode
= *ptr
++;
3668 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3673 if (opsize
< 2) /* "silly options" */
3675 if (opsize
> length
)
3676 return; /* don't parse partial options */
3679 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3680 u16 in_mss
= get_unaligned_be16(ptr
);
3682 if (opt_rx
->user_mss
&&
3683 opt_rx
->user_mss
< in_mss
)
3684 in_mss
= opt_rx
->user_mss
;
3685 opt_rx
->mss_clamp
= in_mss
;
3690 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3691 !estab
&& sysctl_tcp_window_scaling
) {
3692 __u8 snd_wscale
= *(__u8
*)ptr
;
3693 opt_rx
->wscale_ok
= 1;
3694 if (snd_wscale
> 14) {
3695 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3700 opt_rx
->snd_wscale
= snd_wscale
;
3703 case TCPOPT_TIMESTAMP
:
3704 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3705 ((estab
&& opt_rx
->tstamp_ok
) ||
3706 (!estab
&& sysctl_tcp_timestamps
))) {
3707 opt_rx
->saw_tstamp
= 1;
3708 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3709 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3712 case TCPOPT_SACK_PERM
:
3713 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3714 !estab
&& sysctl_tcp_sack
) {
3715 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3716 tcp_sack_reset(opt_rx
);
3721 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3722 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3724 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3727 #ifdef CONFIG_TCP_MD5SIG
3730 * The MD5 Hash has already been
3731 * checked (see tcp_v{4,6}_do_rcv()).
3735 case TCPOPT_FASTOPEN
:
3736 tcp_parse_fastopen_option(
3737 opsize
- TCPOLEN_FASTOPEN_BASE
,
3738 ptr
, th
->syn
, foc
, false);
3742 /* Fast Open option shares code 254 using a
3743 * 16 bits magic number.
3745 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
3746 get_unaligned_be16(ptr
) ==
3747 TCPOPT_FASTOPEN_MAGIC
)
3748 tcp_parse_fastopen_option(opsize
-
3749 TCPOLEN_EXP_FASTOPEN_BASE
,
3750 ptr
+ 2, th
->syn
, foc
, true);
3759 EXPORT_SYMBOL(tcp_parse_options
);
3761 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3763 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3765 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3766 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3767 tp
->rx_opt
.saw_tstamp
= 1;
3769 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3772 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3774 tp
->rx_opt
.rcv_tsecr
= 0;
3780 /* Fast parse options. This hopes to only see timestamps.
3781 * If it is wrong it falls back on tcp_parse_options().
3783 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3784 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3786 /* In the spirit of fast parsing, compare doff directly to constant
3787 * values. Because equality is used, short doff can be ignored here.
3789 if (th
->doff
== (sizeof(*th
) / 4)) {
3790 tp
->rx_opt
.saw_tstamp
= 0;
3792 } else if (tp
->rx_opt
.tstamp_ok
&&
3793 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3794 if (tcp_parse_aligned_timestamp(tp
, th
))
3798 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3799 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3800 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3805 #ifdef CONFIG_TCP_MD5SIG
3807 * Parse MD5 Signature option
3809 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3811 int length
= (th
->doff
<< 2) - sizeof(*th
);
3812 const u8
*ptr
= (const u8
*)(th
+ 1);
3814 /* If the TCP option is too short, we can short cut */
3815 if (length
< TCPOLEN_MD5SIG
)
3818 while (length
> 0) {
3819 int opcode
= *ptr
++;
3830 if (opsize
< 2 || opsize
> length
)
3832 if (opcode
== TCPOPT_MD5SIG
)
3833 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3840 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3843 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3845 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3846 * it can pass through stack. So, the following predicate verifies that
3847 * this segment is not used for anything but congestion avoidance or
3848 * fast retransmit. Moreover, we even are able to eliminate most of such
3849 * second order effects, if we apply some small "replay" window (~RTO)
3850 * to timestamp space.
3852 * All these measures still do not guarantee that we reject wrapped ACKs
3853 * on networks with high bandwidth, when sequence space is recycled fastly,
3854 * but it guarantees that such events will be very rare and do not affect
3855 * connection seriously. This doesn't look nice, but alas, PAWS is really
3858 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3859 * states that events when retransmit arrives after original data are rare.
3860 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3861 * the biggest problem on large power networks even with minor reordering.
3862 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3863 * up to bandwidth of 18Gigabit/sec. 8) ]
3866 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3868 const struct tcp_sock
*tp
= tcp_sk(sk
);
3869 const struct tcphdr
*th
= tcp_hdr(skb
);
3870 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3871 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3873 return (/* 1. Pure ACK with correct sequence number. */
3874 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3876 /* 2. ... and duplicate ACK. */
3877 ack
== tp
->snd_una
&&
3879 /* 3. ... and does not update window. */
3880 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3882 /* 4. ... and sits in replay window. */
3883 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3886 static inline bool tcp_paws_discard(const struct sock
*sk
,
3887 const struct sk_buff
*skb
)
3889 const struct tcp_sock
*tp
= tcp_sk(sk
);
3891 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3892 !tcp_disordered_ack(sk
, skb
);
3895 /* Check segment sequence number for validity.
3897 * Segment controls are considered valid, if the segment
3898 * fits to the window after truncation to the window. Acceptability
3899 * of data (and SYN, FIN, of course) is checked separately.
3900 * See tcp_data_queue(), for example.
3902 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3903 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3904 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3905 * (borrowed from freebsd)
3908 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3910 return !before(end_seq
, tp
->rcv_wup
) &&
3911 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3914 /* When we get a reset we do this. */
3915 void tcp_reset(struct sock
*sk
)
3917 /* We want the right error as BSD sees it (and indeed as we do). */
3918 switch (sk
->sk_state
) {
3920 sk
->sk_err
= ECONNREFUSED
;
3922 case TCP_CLOSE_WAIT
:
3928 sk
->sk_err
= ECONNRESET
;
3930 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3933 if (!sock_flag(sk
, SOCK_DEAD
))
3934 sk
->sk_error_report(sk
);
3940 * Process the FIN bit. This now behaves as it is supposed to work
3941 * and the FIN takes effect when it is validly part of sequence
3942 * space. Not before when we get holes.
3944 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3945 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3948 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3949 * close and we go into CLOSING (and later onto TIME-WAIT)
3951 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3953 static void tcp_fin(struct sock
*sk
)
3955 struct tcp_sock
*tp
= tcp_sk(sk
);
3957 inet_csk_schedule_ack(sk
);
3959 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3960 sock_set_flag(sk
, SOCK_DONE
);
3962 switch (sk
->sk_state
) {
3964 case TCP_ESTABLISHED
:
3965 /* Move to CLOSE_WAIT */
3966 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3967 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3970 case TCP_CLOSE_WAIT
:
3972 /* Received a retransmission of the FIN, do
3977 /* RFC793: Remain in the LAST-ACK state. */
3981 /* This case occurs when a simultaneous close
3982 * happens, we must ack the received FIN and
3983 * enter the CLOSING state.
3986 tcp_set_state(sk
, TCP_CLOSING
);
3989 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3991 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3994 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3995 * cases we should never reach this piece of code.
3997 pr_err("%s: Impossible, sk->sk_state=%d\n",
3998 __func__
, sk
->sk_state
);
4002 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4003 * Probably, we should reset in this case. For now drop them.
4005 __skb_queue_purge(&tp
->out_of_order_queue
);
4006 if (tcp_is_sack(tp
))
4007 tcp_sack_reset(&tp
->rx_opt
);
4010 if (!sock_flag(sk
, SOCK_DEAD
)) {
4011 sk
->sk_state_change(sk
);
4013 /* Do not send POLL_HUP for half duplex close. */
4014 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4015 sk
->sk_state
== TCP_CLOSE
)
4016 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4018 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4022 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4025 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4026 if (before(seq
, sp
->start_seq
))
4027 sp
->start_seq
= seq
;
4028 if (after(end_seq
, sp
->end_seq
))
4029 sp
->end_seq
= end_seq
;
4035 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4037 struct tcp_sock
*tp
= tcp_sk(sk
);
4039 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4042 if (before(seq
, tp
->rcv_nxt
))
4043 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4045 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4047 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4049 tp
->rx_opt
.dsack
= 1;
4050 tp
->duplicate_sack
[0].start_seq
= seq
;
4051 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4055 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4057 struct tcp_sock
*tp
= tcp_sk(sk
);
4059 if (!tp
->rx_opt
.dsack
)
4060 tcp_dsack_set(sk
, seq
, end_seq
);
4062 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4065 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4067 struct tcp_sock
*tp
= tcp_sk(sk
);
4069 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4070 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4071 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4072 tcp_enter_quickack_mode(sk
);
4074 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4075 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4077 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4078 end_seq
= tp
->rcv_nxt
;
4079 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4086 /* These routines update the SACK block as out-of-order packets arrive or
4087 * in-order packets close up the sequence space.
4089 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4092 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4093 struct tcp_sack_block
*swalk
= sp
+ 1;
4095 /* See if the recent change to the first SACK eats into
4096 * or hits the sequence space of other SACK blocks, if so coalesce.
4098 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4099 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4102 /* Zap SWALK, by moving every further SACK up by one slot.
4103 * Decrease num_sacks.
4105 tp
->rx_opt
.num_sacks
--;
4106 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4110 this_sack
++, swalk
++;
4114 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4116 struct tcp_sock
*tp
= tcp_sk(sk
);
4117 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4118 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4124 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4125 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4126 /* Rotate this_sack to the first one. */
4127 for (; this_sack
> 0; this_sack
--, sp
--)
4128 swap(*sp
, *(sp
- 1));
4130 tcp_sack_maybe_coalesce(tp
);
4135 /* Could not find an adjacent existing SACK, build a new one,
4136 * put it at the front, and shift everyone else down. We
4137 * always know there is at least one SACK present already here.
4139 * If the sack array is full, forget about the last one.
4141 if (this_sack
>= TCP_NUM_SACKS
) {
4143 tp
->rx_opt
.num_sacks
--;
4146 for (; this_sack
> 0; this_sack
--, sp
--)
4150 /* Build the new head SACK, and we're done. */
4151 sp
->start_seq
= seq
;
4152 sp
->end_seq
= end_seq
;
4153 tp
->rx_opt
.num_sacks
++;
4156 /* RCV.NXT advances, some SACKs should be eaten. */
4158 static void tcp_sack_remove(struct tcp_sock
*tp
)
4160 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4161 int num_sacks
= tp
->rx_opt
.num_sacks
;
4164 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4165 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4166 tp
->rx_opt
.num_sacks
= 0;
4170 for (this_sack
= 0; this_sack
< num_sacks
;) {
4171 /* Check if the start of the sack is covered by RCV.NXT. */
4172 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4175 /* RCV.NXT must cover all the block! */
4176 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4178 /* Zap this SACK, by moving forward any other SACKS. */
4179 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4180 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4187 tp
->rx_opt
.num_sacks
= num_sacks
;
4191 * tcp_try_coalesce - try to merge skb to prior one
4194 * @from: buffer to add in queue
4195 * @fragstolen: pointer to boolean
4197 * Before queueing skb @from after @to, try to merge them
4198 * to reduce overall memory use and queue lengths, if cost is small.
4199 * Packets in ofo or receive queues can stay a long time.
4200 * Better try to coalesce them right now to avoid future collapses.
4201 * Returns true if caller should free @from instead of queueing it
4203 static bool tcp_try_coalesce(struct sock
*sk
,
4205 struct sk_buff
*from
,
4210 *fragstolen
= false;
4212 /* Its possible this segment overlaps with prior segment in queue */
4213 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4216 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4219 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4220 sk_mem_charge(sk
, delta
);
4221 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4222 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4223 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4224 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4228 /* This one checks to see if we can put data from the
4229 * out_of_order queue into the receive_queue.
4231 static void tcp_ofo_queue(struct sock
*sk
)
4233 struct tcp_sock
*tp
= tcp_sk(sk
);
4234 __u32 dsack_high
= tp
->rcv_nxt
;
4235 struct sk_buff
*skb
, *tail
;
4236 bool fragstolen
, eaten
;
4238 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4239 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4242 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4243 __u32 dsack
= dsack_high
;
4244 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4245 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4246 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4249 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4250 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4251 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4255 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4256 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4257 TCP_SKB_CB(skb
)->end_seq
);
4259 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4260 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4261 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4263 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4264 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4267 kfree_skb_partial(skb
, fragstolen
);
4271 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4272 static int tcp_prune_queue(struct sock
*sk
);
4274 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4277 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4278 !sk_rmem_schedule(sk
, skb
, size
)) {
4280 if (tcp_prune_queue(sk
) < 0)
4283 if (!sk_rmem_schedule(sk
, skb
, size
)) {
4284 if (!tcp_prune_ofo_queue(sk
))
4287 if (!sk_rmem_schedule(sk
, skb
, size
))
4294 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4296 struct tcp_sock
*tp
= tcp_sk(sk
);
4297 struct sk_buff
*skb1
;
4300 tcp_ecn_check_ce(tp
, skb
);
4302 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4303 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4308 /* Disable header prediction. */
4310 inet_csk_schedule_ack(sk
);
4312 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4313 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4314 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4316 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4318 /* Initial out of order segment, build 1 SACK. */
4319 if (tcp_is_sack(tp
)) {
4320 tp
->rx_opt
.num_sacks
= 1;
4321 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4322 tp
->selective_acks
[0].end_seq
=
4323 TCP_SKB_CB(skb
)->end_seq
;
4325 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4329 seq
= TCP_SKB_CB(skb
)->seq
;
4330 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4332 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4335 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4336 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4338 tcp_grow_window(sk
, skb
);
4339 kfree_skb_partial(skb
, fragstolen
);
4343 if (!tp
->rx_opt
.num_sacks
||
4344 tp
->selective_acks
[0].end_seq
!= seq
)
4347 /* Common case: data arrive in order after hole. */
4348 tp
->selective_acks
[0].end_seq
= end_seq
;
4352 /* Find place to insert this segment. */
4354 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4356 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4360 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4363 /* Do skb overlap to previous one? */
4364 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4365 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4366 /* All the bits are present. Drop. */
4367 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4370 tcp_dsack_set(sk
, seq
, end_seq
);
4373 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4374 /* Partial overlap. */
4375 tcp_dsack_set(sk
, seq
,
4376 TCP_SKB_CB(skb1
)->end_seq
);
4378 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4382 skb1
= skb_queue_prev(
4383 &tp
->out_of_order_queue
,
4388 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4390 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4392 /* And clean segments covered by new one as whole. */
4393 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4394 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4396 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4398 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4399 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4403 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4404 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4405 TCP_SKB_CB(skb1
)->end_seq
);
4406 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4411 if (tcp_is_sack(tp
))
4412 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4415 tcp_grow_window(sk
, skb
);
4416 skb_set_owner_r(skb
, sk
);
4420 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4424 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4426 __skb_pull(skb
, hdrlen
);
4428 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4429 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
4431 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4432 skb_set_owner_r(skb
, sk
);
4437 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4439 struct sk_buff
*skb
;
4445 skb
= alloc_skb(size
, sk
->sk_allocation
);
4449 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4452 if (memcpy_from_msg(skb_put(skb
, size
), msg
, size
))
4455 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4456 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4457 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4459 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4460 WARN_ON_ONCE(fragstolen
); /* should not happen */
4471 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4473 struct tcp_sock
*tp
= tcp_sk(sk
);
4475 bool fragstolen
= false;
4477 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4481 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4483 tcp_ecn_accept_cwr(tp
, skb
);
4485 tp
->rx_opt
.dsack
= 0;
4487 /* Queue data for delivery to the user.
4488 * Packets in sequence go to the receive queue.
4489 * Out of sequence packets to the out_of_order_queue.
4491 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4492 if (tcp_receive_window(tp
) == 0)
4495 /* Ok. In sequence. In window. */
4496 if (tp
->ucopy
.task
== current
&&
4497 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4498 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4499 int chunk
= min_t(unsigned int, skb
->len
,
4502 __set_current_state(TASK_RUNNING
);
4505 if (!skb_copy_datagram_msg(skb
, 0, tp
->ucopy
.msg
, chunk
)) {
4506 tp
->ucopy
.len
-= chunk
;
4507 tp
->copied_seq
+= chunk
;
4508 eaten
= (chunk
== skb
->len
);
4509 tcp_rcv_space_adjust(sk
);
4517 if (skb_queue_len(&sk
->sk_receive_queue
) == 0)
4518 sk_forced_mem_schedule(sk
, skb
->truesize
);
4519 else if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4522 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4524 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4526 tcp_event_data_recv(sk
, skb
);
4527 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4530 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4533 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4534 * gap in queue is filled.
4536 if (skb_queue_empty(&tp
->out_of_order_queue
))
4537 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4540 if (tp
->rx_opt
.num_sacks
)
4541 tcp_sack_remove(tp
);
4543 tcp_fast_path_check(sk
);
4546 kfree_skb_partial(skb
, fragstolen
);
4547 if (!sock_flag(sk
, SOCK_DEAD
))
4548 sk
->sk_data_ready(sk
);
4552 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4553 /* A retransmit, 2nd most common case. Force an immediate ack. */
4554 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4555 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4558 tcp_enter_quickack_mode(sk
);
4559 inet_csk_schedule_ack(sk
);
4565 /* Out of window. F.e. zero window probe. */
4566 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4569 tcp_enter_quickack_mode(sk
);
4571 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4572 /* Partial packet, seq < rcv_next < end_seq */
4573 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4574 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4575 TCP_SKB_CB(skb
)->end_seq
);
4577 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4579 /* If window is closed, drop tail of packet. But after
4580 * remembering D-SACK for its head made in previous line.
4582 if (!tcp_receive_window(tp
))
4587 tcp_data_queue_ofo(sk
, skb
);
4590 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4591 struct sk_buff_head
*list
)
4593 struct sk_buff
*next
= NULL
;
4595 if (!skb_queue_is_last(list
, skb
))
4596 next
= skb_queue_next(list
, skb
);
4598 __skb_unlink(skb
, list
);
4600 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4605 /* Collapse contiguous sequence of skbs head..tail with
4606 * sequence numbers start..end.
4608 * If tail is NULL, this means until the end of the list.
4610 * Segments with FIN/SYN are not collapsed (only because this
4614 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4615 struct sk_buff
*head
, struct sk_buff
*tail
,
4618 struct sk_buff
*skb
, *n
;
4621 /* First, check that queue is collapsible and find
4622 * the point where collapsing can be useful. */
4626 skb_queue_walk_from_safe(list
, skb
, n
) {
4629 /* No new bits? It is possible on ofo queue. */
4630 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4631 skb
= tcp_collapse_one(sk
, skb
, list
);
4637 /* The first skb to collapse is:
4639 * - bloated or contains data before "start" or
4640 * overlaps to the next one.
4642 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4643 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4644 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4645 end_of_skbs
= false;
4649 if (!skb_queue_is_last(list
, skb
)) {
4650 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4652 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4653 end_of_skbs
= false;
4658 /* Decided to skip this, advance start seq. */
4659 start
= TCP_SKB_CB(skb
)->end_seq
;
4662 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4665 while (before(start
, end
)) {
4666 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4667 struct sk_buff
*nskb
;
4669 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4673 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4674 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4675 __skb_queue_before(list
, skb
, nskb
);
4676 skb_set_owner_r(nskb
, sk
);
4678 /* Copy data, releasing collapsed skbs. */
4680 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4681 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4685 size
= min(copy
, size
);
4686 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4688 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4692 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4693 skb
= tcp_collapse_one(sk
, skb
, list
);
4696 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4703 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4704 * and tcp_collapse() them until all the queue is collapsed.
4706 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4708 struct tcp_sock
*tp
= tcp_sk(sk
);
4709 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4710 struct sk_buff
*head
;
4716 start
= TCP_SKB_CB(skb
)->seq
;
4717 end
= TCP_SKB_CB(skb
)->end_seq
;
4721 struct sk_buff
*next
= NULL
;
4723 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4724 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4727 /* Segment is terminated when we see gap or when
4728 * we are at the end of all the queue. */
4730 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4731 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4732 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4733 head
, skb
, start
, end
);
4737 /* Start new segment */
4738 start
= TCP_SKB_CB(skb
)->seq
;
4739 end
= TCP_SKB_CB(skb
)->end_seq
;
4741 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4742 start
= TCP_SKB_CB(skb
)->seq
;
4743 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4744 end
= TCP_SKB_CB(skb
)->end_seq
;
4750 * Purge the out-of-order queue.
4751 * Return true if queue was pruned.
4753 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4755 struct tcp_sock
*tp
= tcp_sk(sk
);
4758 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4759 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4760 __skb_queue_purge(&tp
->out_of_order_queue
);
4762 /* Reset SACK state. A conforming SACK implementation will
4763 * do the same at a timeout based retransmit. When a connection
4764 * is in a sad state like this, we care only about integrity
4765 * of the connection not performance.
4767 if (tp
->rx_opt
.sack_ok
)
4768 tcp_sack_reset(&tp
->rx_opt
);
4775 /* Reduce allocated memory if we can, trying to get
4776 * the socket within its memory limits again.
4778 * Return less than zero if we should start dropping frames
4779 * until the socket owning process reads some of the data
4780 * to stabilize the situation.
4782 static int tcp_prune_queue(struct sock
*sk
)
4784 struct tcp_sock
*tp
= tcp_sk(sk
);
4786 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4788 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4790 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4791 tcp_clamp_window(sk
);
4792 else if (tcp_under_memory_pressure(sk
))
4793 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4795 tcp_collapse_ofo_queue(sk
);
4796 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4797 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4798 skb_peek(&sk
->sk_receive_queue
),
4800 tp
->copied_seq
, tp
->rcv_nxt
);
4803 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4806 /* Collapsing did not help, destructive actions follow.
4807 * This must not ever occur. */
4809 tcp_prune_ofo_queue(sk
);
4811 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4814 /* If we are really being abused, tell the caller to silently
4815 * drop receive data on the floor. It will get retransmitted
4816 * and hopefully then we'll have sufficient space.
4818 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4820 /* Massive buffer overcommit. */
4825 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4827 const struct tcp_sock
*tp
= tcp_sk(sk
);
4829 /* If the user specified a specific send buffer setting, do
4832 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4835 /* If we are under global TCP memory pressure, do not expand. */
4836 if (tcp_under_memory_pressure(sk
))
4839 /* If we are under soft global TCP memory pressure, do not expand. */
4840 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4843 /* If we filled the congestion window, do not expand. */
4844 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
4850 /* When incoming ACK allowed to free some skb from write_queue,
4851 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4852 * on the exit from tcp input handler.
4854 * PROBLEM: sndbuf expansion does not work well with largesend.
4856 static void tcp_new_space(struct sock
*sk
)
4858 struct tcp_sock
*tp
= tcp_sk(sk
);
4860 if (tcp_should_expand_sndbuf(sk
)) {
4861 tcp_sndbuf_expand(sk
);
4862 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4865 sk
->sk_write_space(sk
);
4868 static void tcp_check_space(struct sock
*sk
)
4870 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4871 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4872 /* pairs with tcp_poll() */
4873 smp_mb__after_atomic();
4874 if (sk
->sk_socket
&&
4875 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4880 static inline void tcp_data_snd_check(struct sock
*sk
)
4882 tcp_push_pending_frames(sk
);
4883 tcp_check_space(sk
);
4887 * Check if sending an ack is needed.
4889 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4891 struct tcp_sock
*tp
= tcp_sk(sk
);
4893 /* More than one full frame received... */
4894 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4895 /* ... and right edge of window advances far enough.
4896 * (tcp_recvmsg() will send ACK otherwise). Or...
4898 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4899 /* We ACK each frame or... */
4900 tcp_in_quickack_mode(sk
) ||
4901 /* We have out of order data. */
4902 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4903 /* Then ack it now */
4906 /* Else, send delayed ack. */
4907 tcp_send_delayed_ack(sk
);
4911 static inline void tcp_ack_snd_check(struct sock
*sk
)
4913 if (!inet_csk_ack_scheduled(sk
)) {
4914 /* We sent a data segment already. */
4917 __tcp_ack_snd_check(sk
, 1);
4921 * This routine is only called when we have urgent data
4922 * signaled. Its the 'slow' part of tcp_urg. It could be
4923 * moved inline now as tcp_urg is only called from one
4924 * place. We handle URGent data wrong. We have to - as
4925 * BSD still doesn't use the correction from RFC961.
4926 * For 1003.1g we should support a new option TCP_STDURG to permit
4927 * either form (or just set the sysctl tcp_stdurg).
4930 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
4932 struct tcp_sock
*tp
= tcp_sk(sk
);
4933 u32 ptr
= ntohs(th
->urg_ptr
);
4935 if (ptr
&& !sysctl_tcp_stdurg
)
4937 ptr
+= ntohl(th
->seq
);
4939 /* Ignore urgent data that we've already seen and read. */
4940 if (after(tp
->copied_seq
, ptr
))
4943 /* Do not replay urg ptr.
4945 * NOTE: interesting situation not covered by specs.
4946 * Misbehaving sender may send urg ptr, pointing to segment,
4947 * which we already have in ofo queue. We are not able to fetch
4948 * such data and will stay in TCP_URG_NOTYET until will be eaten
4949 * by recvmsg(). Seems, we are not obliged to handle such wicked
4950 * situations. But it is worth to think about possibility of some
4951 * DoSes using some hypothetical application level deadlock.
4953 if (before(ptr
, tp
->rcv_nxt
))
4956 /* Do we already have a newer (or duplicate) urgent pointer? */
4957 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4960 /* Tell the world about our new urgent pointer. */
4963 /* We may be adding urgent data when the last byte read was
4964 * urgent. To do this requires some care. We cannot just ignore
4965 * tp->copied_seq since we would read the last urgent byte again
4966 * as data, nor can we alter copied_seq until this data arrives
4967 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4969 * NOTE. Double Dutch. Rendering to plain English: author of comment
4970 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4971 * and expect that both A and B disappear from stream. This is _wrong_.
4972 * Though this happens in BSD with high probability, this is occasional.
4973 * Any application relying on this is buggy. Note also, that fix "works"
4974 * only in this artificial test. Insert some normal data between A and B and we will
4975 * decline of BSD again. Verdict: it is better to remove to trap
4978 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4979 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4980 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4982 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4983 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4988 tp
->urg_data
= TCP_URG_NOTYET
;
4991 /* Disable header prediction. */
4995 /* This is the 'fast' part of urgent handling. */
4996 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
4998 struct tcp_sock
*tp
= tcp_sk(sk
);
5000 /* Check if we get a new urgent pointer - normally not. */
5002 tcp_check_urg(sk
, th
);
5004 /* Do we wait for any urgent data? - normally not... */
5005 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5006 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5009 /* Is the urgent pointer pointing into this packet? */
5010 if (ptr
< skb
->len
) {
5012 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5014 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5015 if (!sock_flag(sk
, SOCK_DEAD
))
5016 sk
->sk_data_ready(sk
);
5021 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5023 struct tcp_sock
*tp
= tcp_sk(sk
);
5024 int chunk
= skb
->len
- hlen
;
5028 if (skb_csum_unnecessary(skb
))
5029 err
= skb_copy_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
, chunk
);
5031 err
= skb_copy_and_csum_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
);
5034 tp
->ucopy
.len
-= chunk
;
5035 tp
->copied_seq
+= chunk
;
5036 tcp_rcv_space_adjust(sk
);
5043 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5044 struct sk_buff
*skb
)
5048 if (sock_owned_by_user(sk
)) {
5050 result
= __tcp_checksum_complete(skb
);
5053 result
= __tcp_checksum_complete(skb
);
5058 static inline bool tcp_checksum_complete_user(struct sock
*sk
,
5059 struct sk_buff
*skb
)
5061 return !skb_csum_unnecessary(skb
) &&
5062 __tcp_checksum_complete_user(sk
, skb
);
5065 /* Does PAWS and seqno based validation of an incoming segment, flags will
5066 * play significant role here.
5068 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5069 const struct tcphdr
*th
, int syn_inerr
)
5071 struct tcp_sock
*tp
= tcp_sk(sk
);
5073 /* RFC1323: H1. Apply PAWS check first. */
5074 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5075 tcp_paws_discard(sk
, skb
)) {
5077 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5078 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5079 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5080 &tp
->last_oow_ack_time
))
5081 tcp_send_dupack(sk
, skb
);
5084 /* Reset is accepted even if it did not pass PAWS. */
5087 /* Step 1: check sequence number */
5088 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5089 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5090 * (RST) segments are validated by checking their SEQ-fields."
5091 * And page 69: "If an incoming segment is not acceptable,
5092 * an acknowledgment should be sent in reply (unless the RST
5093 * bit is set, if so drop the segment and return)".
5098 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5099 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5100 &tp
->last_oow_ack_time
))
5101 tcp_send_dupack(sk
, skb
);
5106 /* Step 2: check RST bit */
5109 * If sequence number exactly matches RCV.NXT, then
5110 * RESET the connection
5112 * Send a challenge ACK
5114 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
)
5117 tcp_send_challenge_ack(sk
, skb
);
5121 /* step 3: check security and precedence [ignored] */
5123 /* step 4: Check for a SYN
5124 * RFC 5961 4.2 : Send a challenge ack
5129 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5130 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5131 tcp_send_challenge_ack(sk
, skb
);
5143 * TCP receive function for the ESTABLISHED state.
5145 * It is split into a fast path and a slow path. The fast path is
5147 * - A zero window was announced from us - zero window probing
5148 * is only handled properly in the slow path.
5149 * - Out of order segments arrived.
5150 * - Urgent data is expected.
5151 * - There is no buffer space left
5152 * - Unexpected TCP flags/window values/header lengths are received
5153 * (detected by checking the TCP header against pred_flags)
5154 * - Data is sent in both directions. Fast path only supports pure senders
5155 * or pure receivers (this means either the sequence number or the ack
5156 * value must stay constant)
5157 * - Unexpected TCP option.
5159 * When these conditions are not satisfied it drops into a standard
5160 * receive procedure patterned after RFC793 to handle all cases.
5161 * The first three cases are guaranteed by proper pred_flags setting,
5162 * the rest is checked inline. Fast processing is turned on in
5163 * tcp_data_queue when everything is OK.
5165 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5166 const struct tcphdr
*th
, unsigned int len
)
5168 struct tcp_sock
*tp
= tcp_sk(sk
);
5170 if (unlikely(!sk
->sk_rx_dst
))
5171 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5173 * Header prediction.
5174 * The code loosely follows the one in the famous
5175 * "30 instruction TCP receive" Van Jacobson mail.
5177 * Van's trick is to deposit buffers into socket queue
5178 * on a device interrupt, to call tcp_recv function
5179 * on the receive process context and checksum and copy
5180 * the buffer to user space. smart...
5182 * Our current scheme is not silly either but we take the
5183 * extra cost of the net_bh soft interrupt processing...
5184 * We do checksum and copy also but from device to kernel.
5187 tp
->rx_opt
.saw_tstamp
= 0;
5189 /* pred_flags is 0xS?10 << 16 + snd_wnd
5190 * if header_prediction is to be made
5191 * 'S' will always be tp->tcp_header_len >> 2
5192 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5193 * turn it off (when there are holes in the receive
5194 * space for instance)
5195 * PSH flag is ignored.
5198 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5199 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5200 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5201 int tcp_header_len
= tp
->tcp_header_len
;
5203 /* Timestamp header prediction: tcp_header_len
5204 * is automatically equal to th->doff*4 due to pred_flags
5208 /* Check timestamp */
5209 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5210 /* No? Slow path! */
5211 if (!tcp_parse_aligned_timestamp(tp
, th
))
5214 /* If PAWS failed, check it more carefully in slow path */
5215 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5218 /* DO NOT update ts_recent here, if checksum fails
5219 * and timestamp was corrupted part, it will result
5220 * in a hung connection since we will drop all
5221 * future packets due to the PAWS test.
5225 if (len
<= tcp_header_len
) {
5226 /* Bulk data transfer: sender */
5227 if (len
== tcp_header_len
) {
5228 /* Predicted packet is in window by definition.
5229 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5230 * Hence, check seq<=rcv_wup reduces to:
5232 if (tcp_header_len
==
5233 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5234 tp
->rcv_nxt
== tp
->rcv_wup
)
5235 tcp_store_ts_recent(tp
);
5237 /* We know that such packets are checksummed
5240 tcp_ack(sk
, skb
, 0);
5242 tcp_data_snd_check(sk
);
5244 } else { /* Header too small */
5245 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5250 bool fragstolen
= false;
5252 if (tp
->ucopy
.task
== current
&&
5253 tp
->copied_seq
== tp
->rcv_nxt
&&
5254 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5255 sock_owned_by_user(sk
)) {
5256 __set_current_state(TASK_RUNNING
);
5258 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5259 /* Predicted packet is in window by definition.
5260 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5261 * Hence, check seq<=rcv_wup reduces to:
5263 if (tcp_header_len
==
5264 (sizeof(struct tcphdr
) +
5265 TCPOLEN_TSTAMP_ALIGNED
) &&
5266 tp
->rcv_nxt
== tp
->rcv_wup
)
5267 tcp_store_ts_recent(tp
);
5269 tcp_rcv_rtt_measure_ts(sk
, skb
);
5271 __skb_pull(skb
, tcp_header_len
);
5272 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
5273 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5278 if (tcp_checksum_complete_user(sk
, skb
))
5281 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5284 /* Predicted packet is in window by definition.
5285 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5286 * Hence, check seq<=rcv_wup reduces to:
5288 if (tcp_header_len
==
5289 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5290 tp
->rcv_nxt
== tp
->rcv_wup
)
5291 tcp_store_ts_recent(tp
);
5293 tcp_rcv_rtt_measure_ts(sk
, skb
);
5295 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5297 /* Bulk data transfer: receiver */
5298 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5302 tcp_event_data_recv(sk
, skb
);
5304 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5305 /* Well, only one small jumplet in fast path... */
5306 tcp_ack(sk
, skb
, FLAG_DATA
);
5307 tcp_data_snd_check(sk
);
5308 if (!inet_csk_ack_scheduled(sk
))
5312 __tcp_ack_snd_check(sk
, 0);
5315 kfree_skb_partial(skb
, fragstolen
);
5316 sk
->sk_data_ready(sk
);
5322 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5325 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5329 * Standard slow path.
5332 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5336 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5339 tcp_rcv_rtt_measure_ts(sk
, skb
);
5341 /* Process urgent data. */
5342 tcp_urg(sk
, skb
, th
);
5344 /* step 7: process the segment text */
5345 tcp_data_queue(sk
, skb
);
5347 tcp_data_snd_check(sk
);
5348 tcp_ack_snd_check(sk
);
5352 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5353 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5358 EXPORT_SYMBOL(tcp_rcv_established
);
5360 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5362 struct tcp_sock
*tp
= tcp_sk(sk
);
5363 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5365 tcp_set_state(sk
, TCP_ESTABLISHED
);
5368 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5369 security_inet_conn_established(sk
, skb
);
5372 /* Make sure socket is routed, for correct metrics. */
5373 icsk
->icsk_af_ops
->rebuild_header(sk
);
5375 tcp_init_metrics(sk
);
5377 tcp_init_congestion_control(sk
);
5379 /* Prevent spurious tcp_cwnd_restart() on first data
5382 tp
->lsndtime
= tcp_time_stamp
;
5384 tcp_init_buffer_space(sk
);
5386 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5387 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5389 if (!tp
->rx_opt
.snd_wscale
)
5390 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5394 if (!sock_flag(sk
, SOCK_DEAD
)) {
5395 sk
->sk_state_change(sk
);
5396 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5400 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5401 struct tcp_fastopen_cookie
*cookie
)
5403 struct tcp_sock
*tp
= tcp_sk(sk
);
5404 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5405 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
5406 bool syn_drop
= false;
5408 if (mss
== tp
->rx_opt
.user_mss
) {
5409 struct tcp_options_received opt
;
5411 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5412 tcp_clear_options(&opt
);
5413 opt
.user_mss
= opt
.mss_clamp
= 0;
5414 tcp_parse_options(synack
, &opt
, 0, NULL
);
5415 mss
= opt
.mss_clamp
;
5418 if (!tp
->syn_fastopen
) {
5419 /* Ignore an unsolicited cookie */
5421 } else if (tp
->total_retrans
) {
5422 /* SYN timed out and the SYN-ACK neither has a cookie nor
5423 * acknowledges data. Presumably the remote received only
5424 * the retransmitted (regular) SYNs: either the original
5425 * SYN-data or the corresponding SYN-ACK was dropped.
5427 syn_drop
= (cookie
->len
< 0 && data
);
5428 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
5429 /* We requested a cookie but didn't get it. If we did not use
5430 * the (old) exp opt format then try so next time (try_exp=1).
5431 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5433 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
5436 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
5438 if (data
) { /* Retransmit unacked data in SYN */
5439 tcp_for_write_queue_from(data
, sk
) {
5440 if (data
== tcp_send_head(sk
) ||
5441 __tcp_retransmit_skb(sk
, data
))
5445 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5448 tp
->syn_data_acked
= tp
->syn_data
;
5449 if (tp
->syn_data_acked
)
5450 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
5454 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5455 const struct tcphdr
*th
, unsigned int len
)
5457 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5458 struct tcp_sock
*tp
= tcp_sk(sk
);
5459 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5460 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5462 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5463 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5464 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5468 * "If the state is SYN-SENT then
5469 * first check the ACK bit
5470 * If the ACK bit is set
5471 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5472 * a reset (unless the RST bit is set, if so drop
5473 * the segment and return)"
5475 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5476 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5477 goto reset_and_undo
;
5479 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5480 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5482 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5483 goto reset_and_undo
;
5486 /* Now ACK is acceptable.
5488 * "If the RST bit is set
5489 * If the ACK was acceptable then signal the user "error:
5490 * connection reset", drop the segment, enter CLOSED state,
5491 * delete TCB, and return."
5500 * "fifth, if neither of the SYN or RST bits is set then
5501 * drop the segment and return."
5507 goto discard_and_undo
;
5510 * "If the SYN bit is on ...
5511 * are acceptable then ...
5512 * (our SYN has been ACKed), change the connection
5513 * state to ESTABLISHED..."
5516 tcp_ecn_rcv_synack(tp
, th
);
5518 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5519 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5521 /* Ok.. it's good. Set up sequence numbers and
5522 * move to established.
5524 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5525 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5527 /* RFC1323: The window in SYN & SYN/ACK segments is
5530 tp
->snd_wnd
= ntohs(th
->window
);
5532 if (!tp
->rx_opt
.wscale_ok
) {
5533 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5534 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5537 if (tp
->rx_opt
.saw_tstamp
) {
5538 tp
->rx_opt
.tstamp_ok
= 1;
5539 tp
->tcp_header_len
=
5540 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5541 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5542 tcp_store_ts_recent(tp
);
5544 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5547 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5548 tcp_enable_fack(tp
);
5551 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5552 tcp_initialize_rcv_mss(sk
);
5554 /* Remember, tcp_poll() does not lock socket!
5555 * Change state from SYN-SENT only after copied_seq
5556 * is initialized. */
5557 tp
->copied_seq
= tp
->rcv_nxt
;
5561 tcp_finish_connect(sk
, skb
);
5563 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5564 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5567 if (sk
->sk_write_pending
||
5568 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5569 icsk
->icsk_ack
.pingpong
) {
5570 /* Save one ACK. Data will be ready after
5571 * several ticks, if write_pending is set.
5573 * It may be deleted, but with this feature tcpdumps
5574 * look so _wonderfully_ clever, that I was not able
5575 * to stand against the temptation 8) --ANK
5577 inet_csk_schedule_ack(sk
);
5578 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5579 tcp_enter_quickack_mode(sk
);
5580 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5581 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5592 /* No ACK in the segment */
5596 * "If the RST bit is set
5598 * Otherwise (no ACK) drop the segment and return."
5601 goto discard_and_undo
;
5605 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5606 tcp_paws_reject(&tp
->rx_opt
, 0))
5607 goto discard_and_undo
;
5610 /* We see SYN without ACK. It is attempt of
5611 * simultaneous connect with crossed SYNs.
5612 * Particularly, it can be connect to self.
5614 tcp_set_state(sk
, TCP_SYN_RECV
);
5616 if (tp
->rx_opt
.saw_tstamp
) {
5617 tp
->rx_opt
.tstamp_ok
= 1;
5618 tcp_store_ts_recent(tp
);
5619 tp
->tcp_header_len
=
5620 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5622 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5625 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5626 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5628 /* RFC1323: The window in SYN & SYN/ACK segments is
5631 tp
->snd_wnd
= ntohs(th
->window
);
5632 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5633 tp
->max_window
= tp
->snd_wnd
;
5635 tcp_ecn_rcv_syn(tp
, th
);
5638 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5639 tcp_initialize_rcv_mss(sk
);
5641 tcp_send_synack(sk
);
5643 /* Note, we could accept data and URG from this segment.
5644 * There are no obstacles to make this (except that we must
5645 * either change tcp_recvmsg() to prevent it from returning data
5646 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5648 * However, if we ignore data in ACKless segments sometimes,
5649 * we have no reasons to accept it sometimes.
5650 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5651 * is not flawless. So, discard packet for sanity.
5652 * Uncomment this return to process the data.
5659 /* "fifth, if neither of the SYN or RST bits is set then
5660 * drop the segment and return."
5664 tcp_clear_options(&tp
->rx_opt
);
5665 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5669 tcp_clear_options(&tp
->rx_opt
);
5670 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5675 * This function implements the receiving procedure of RFC 793 for
5676 * all states except ESTABLISHED and TIME_WAIT.
5677 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5678 * address independent.
5681 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5682 const struct tcphdr
*th
, unsigned int len
)
5684 struct tcp_sock
*tp
= tcp_sk(sk
);
5685 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5686 struct request_sock
*req
;
5691 tp
->rx_opt
.saw_tstamp
= 0;
5693 switch (sk
->sk_state
) {
5707 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5710 /* Now we have several options: In theory there is
5711 * nothing else in the frame. KA9Q has an option to
5712 * send data with the syn, BSD accepts data with the
5713 * syn up to the [to be] advertised window and
5714 * Solaris 2.1 gives you a protocol error. For now
5715 * we just ignore it, that fits the spec precisely
5716 * and avoids incompatibilities. It would be nice in
5717 * future to drop through and process the data.
5719 * Now that TTCP is starting to be used we ought to
5721 * But, this leaves one open to an easy denial of
5722 * service attack, and SYN cookies can't defend
5723 * against this problem. So, we drop the data
5724 * in the interest of security over speed unless
5725 * it's still in use.
5733 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5737 /* Do step6 onward by hand. */
5738 tcp_urg(sk
, skb
, th
);
5740 tcp_data_snd_check(sk
);
5744 req
= tp
->fastopen_rsk
;
5746 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5747 sk
->sk_state
!= TCP_FIN_WAIT1
);
5749 if (!tcp_check_req(sk
, skb
, req
, true))
5753 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5756 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5759 /* step 5: check the ACK field */
5760 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5761 FLAG_UPDATE_TS_RECENT
) > 0;
5763 switch (sk
->sk_state
) {
5768 /* Once we leave TCP_SYN_RECV, we no longer need req
5772 synack_stamp
= tcp_rsk(req
)->snt_synack
;
5773 tp
->total_retrans
= req
->num_retrans
;
5774 reqsk_fastopen_remove(sk
, req
, false);
5776 synack_stamp
= tp
->lsndtime
;
5777 /* Make sure socket is routed, for correct metrics. */
5778 icsk
->icsk_af_ops
->rebuild_header(sk
);
5779 tcp_init_congestion_control(sk
);
5782 tp
->copied_seq
= tp
->rcv_nxt
;
5783 tcp_init_buffer_space(sk
);
5786 tcp_set_state(sk
, TCP_ESTABLISHED
);
5787 sk
->sk_state_change(sk
);
5789 /* Note, that this wakeup is only for marginal crossed SYN case.
5790 * Passively open sockets are not waked up, because
5791 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5794 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5796 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5797 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5798 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5799 tcp_synack_rtt_meas(sk
, synack_stamp
);
5801 if (tp
->rx_opt
.tstamp_ok
)
5802 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5805 /* Re-arm the timer because data may have been sent out.
5806 * This is similar to the regular data transmission case
5807 * when new data has just been ack'ed.
5809 * (TFO) - we could try to be more aggressive and
5810 * retransmitting any data sooner based on when they
5815 tcp_init_metrics(sk
);
5817 tcp_update_pacing_rate(sk
);
5819 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5820 tp
->lsndtime
= tcp_time_stamp
;
5822 tcp_initialize_rcv_mss(sk
);
5823 tcp_fast_path_on(tp
);
5826 case TCP_FIN_WAIT1
: {
5827 struct dst_entry
*dst
;
5830 /* If we enter the TCP_FIN_WAIT1 state and we are a
5831 * Fast Open socket and this is the first acceptable
5832 * ACK we have received, this would have acknowledged
5833 * our SYNACK so stop the SYNACK timer.
5836 /* Return RST if ack_seq is invalid.
5837 * Note that RFC793 only says to generate a
5838 * DUPACK for it but for TCP Fast Open it seems
5839 * better to treat this case like TCP_SYN_RECV
5844 /* We no longer need the request sock. */
5845 reqsk_fastopen_remove(sk
, req
, false);
5848 if (tp
->snd_una
!= tp
->write_seq
)
5851 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5852 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5854 dst
= __sk_dst_get(sk
);
5858 if (!sock_flag(sk
, SOCK_DEAD
)) {
5859 /* Wake up lingering close() */
5860 sk
->sk_state_change(sk
);
5864 if (tp
->linger2
< 0 ||
5865 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5866 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5868 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5872 tmo
= tcp_fin_time(sk
);
5873 if (tmo
> TCP_TIMEWAIT_LEN
) {
5874 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5875 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5876 /* Bad case. We could lose such FIN otherwise.
5877 * It is not a big problem, but it looks confusing
5878 * and not so rare event. We still can lose it now,
5879 * if it spins in bh_lock_sock(), but it is really
5882 inet_csk_reset_keepalive_timer(sk
, tmo
);
5884 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5891 if (tp
->snd_una
== tp
->write_seq
) {
5892 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5898 if (tp
->snd_una
== tp
->write_seq
) {
5899 tcp_update_metrics(sk
);
5906 /* step 6: check the URG bit */
5907 tcp_urg(sk
, skb
, th
);
5909 /* step 7: process the segment text */
5910 switch (sk
->sk_state
) {
5911 case TCP_CLOSE_WAIT
:
5914 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5918 /* RFC 793 says to queue data in these states,
5919 * RFC 1122 says we MUST send a reset.
5920 * BSD 4.4 also does reset.
5922 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5923 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5924 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5925 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5931 case TCP_ESTABLISHED
:
5932 tcp_data_queue(sk
, skb
);
5937 /* tcp_data could move socket to TIME-WAIT */
5938 if (sk
->sk_state
!= TCP_CLOSE
) {
5939 tcp_data_snd_check(sk
);
5940 tcp_ack_snd_check(sk
);
5949 EXPORT_SYMBOL(tcp_rcv_state_process
);
5951 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
5953 struct inet_request_sock
*ireq
= inet_rsk(req
);
5955 if (family
== AF_INET
)
5956 net_dbg_ratelimited("drop open request from %pI4/%u\n",
5957 &ireq
->ir_rmt_addr
, port
);
5958 #if IS_ENABLED(CONFIG_IPV6)
5959 else if (family
== AF_INET6
)
5960 net_dbg_ratelimited("drop open request from %pI6/%u\n",
5961 &ireq
->ir_v6_rmt_addr
, port
);
5965 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
5967 * If we receive a SYN packet with these bits set, it means a
5968 * network is playing bad games with TOS bits. In order to
5969 * avoid possible false congestion notifications, we disable
5970 * TCP ECN negotiation.
5972 * Exception: tcp_ca wants ECN. This is required for DCTCP
5973 * congestion control: Linux DCTCP asserts ECT on all packets,
5974 * including SYN, which is most optimal solution; however,
5975 * others, such as FreeBSD do not.
5977 static void tcp_ecn_create_request(struct request_sock
*req
,
5978 const struct sk_buff
*skb
,
5979 const struct sock
*listen_sk
,
5980 const struct dst_entry
*dst
)
5982 const struct tcphdr
*th
= tcp_hdr(skb
);
5983 const struct net
*net
= sock_net(listen_sk
);
5984 bool th_ecn
= th
->ece
&& th
->cwr
;
5990 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
5991 ecn_ok
= net
->ipv4
.sysctl_tcp_ecn
|| dst_feature(dst
, RTAX_FEATURE_ECN
);
5993 if ((!ect
&& ecn_ok
) || tcp_ca_needs_ecn(listen_sk
))
5994 inet_rsk(req
)->ecn_ok
= 1;
5997 static void tcp_openreq_init(struct request_sock
*req
,
5998 const struct tcp_options_received
*rx_opt
,
5999 struct sk_buff
*skb
, const struct sock
*sk
)
6001 struct inet_request_sock
*ireq
= inet_rsk(req
);
6003 req
->rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6005 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6006 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6007 tcp_rsk(req
)->snt_synack
= tcp_time_stamp
;
6008 tcp_rsk(req
)->last_oow_ack_time
= 0;
6009 req
->mss
= rx_opt
->mss_clamp
;
6010 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6011 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6012 ireq
->sack_ok
= rx_opt
->sack_ok
;
6013 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6014 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6017 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6018 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6019 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6022 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6023 struct sock
*sk_listener
)
6025 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
);
6028 struct inet_request_sock
*ireq
= inet_rsk(req
);
6030 kmemcheck_annotate_bitfield(ireq
, flags
);
6032 atomic64_set(&ireq
->ir_cookie
, 0);
6033 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6034 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6035 ireq
->ireq_family
= sk_listener
->sk_family
;
6040 EXPORT_SYMBOL(inet_reqsk_alloc
);
6043 * Return true if a syncookie should be sent
6045 static bool tcp_syn_flood_action(struct sock
*sk
,
6046 const struct sk_buff
*skb
,
6049 const char *msg
= "Dropping request";
6050 bool want_cookie
= false;
6051 struct listen_sock
*lopt
;
6053 #ifdef CONFIG_SYN_COOKIES
6054 if (sysctl_tcp_syncookies
) {
6055 msg
= "Sending cookies";
6057 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
6060 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
6062 lopt
= inet_csk(sk
)->icsk_accept_queue
.listen_opt
;
6063 if (!lopt
->synflood_warned
&& sysctl_tcp_syncookies
!= 2) {
6064 lopt
->synflood_warned
= 1;
6065 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6066 proto
, ntohs(tcp_hdr(skb
)->dest
), msg
);
6071 static void tcp_reqsk_record_syn(const struct sock
*sk
,
6072 struct request_sock
*req
,
6073 const struct sk_buff
*skb
)
6075 if (tcp_sk(sk
)->save_syn
) {
6076 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
6079 copy
= kmalloc(len
+ sizeof(u32
), GFP_ATOMIC
);
6082 memcpy(©
[1], skb_network_header(skb
), len
);
6083 req
->saved_syn
= copy
;
6088 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
6089 const struct tcp_request_sock_ops
*af_ops
,
6090 struct sock
*sk
, struct sk_buff
*skb
)
6092 struct tcp_options_received tmp_opt
;
6093 struct request_sock
*req
;
6094 struct tcp_sock
*tp
= tcp_sk(sk
);
6095 struct dst_entry
*dst
= NULL
;
6096 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
6097 bool want_cookie
= false, fastopen
;
6099 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6103 /* TW buckets are converted to open requests without
6104 * limitations, they conserve resources and peer is
6105 * evidently real one.
6107 if ((sysctl_tcp_syncookies
== 2 ||
6108 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
6109 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
6115 /* Accept backlog is full. If we have already queued enough
6116 * of warm entries in syn queue, drop request. It is better than
6117 * clogging syn queue with openreqs with exponentially increasing
6120 if (sk_acceptq_is_full(sk
) && inet_csk_reqsk_queue_young(sk
) > 1) {
6121 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
6125 req
= inet_reqsk_alloc(rsk_ops
, sk
);
6129 tcp_rsk(req
)->af_specific
= af_ops
;
6131 tcp_clear_options(&tmp_opt
);
6132 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
6133 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
6134 tcp_parse_options(skb
, &tmp_opt
, 0, want_cookie
? NULL
: &foc
);
6136 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
6137 tcp_clear_options(&tmp_opt
);
6139 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
6140 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
6142 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6143 inet_rsk(req
)->ir_iif
= sk
->sk_bound_dev_if
;
6145 af_ops
->init_req(req
, sk
, skb
);
6147 if (security_inet_conn_request(sk
, skb
, req
))
6150 if (!want_cookie
&& !isn
) {
6151 /* VJ's idea. We save last timestamp seen
6152 * from the destination in peer table, when entering
6153 * state TIME-WAIT, and check against it before
6154 * accepting new connection request.
6156 * If "isn" is not zero, this request hit alive
6157 * timewait bucket, so that all the necessary checks
6158 * are made in the function processing timewait state.
6160 if (tcp_death_row
.sysctl_tw_recycle
) {
6163 dst
= af_ops
->route_req(sk
, &fl
, req
, &strict
);
6165 if (dst
&& strict
&&
6166 !tcp_peer_is_proven(req
, dst
, true,
6167 tmp_opt
.saw_tstamp
)) {
6168 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSPASSIVEREJECTED
);
6169 goto drop_and_release
;
6172 /* Kill the following clause, if you dislike this way. */
6173 else if (!sysctl_tcp_syncookies
&&
6174 (sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
6175 (sysctl_max_syn_backlog
>> 2)) &&
6176 !tcp_peer_is_proven(req
, dst
, false,
6177 tmp_opt
.saw_tstamp
)) {
6178 /* Without syncookies last quarter of
6179 * backlog is filled with destinations,
6180 * proven to be alive.
6181 * It means that we continue to communicate
6182 * to destinations, already remembered
6183 * to the moment of synflood.
6185 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6187 goto drop_and_release
;
6190 isn
= af_ops
->init_seq(skb
);
6193 dst
= af_ops
->route_req(sk
, &fl
, req
, NULL
);
6198 tcp_ecn_create_request(req
, skb
, sk
, dst
);
6201 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
6202 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
6203 if (!tmp_opt
.tstamp_ok
)
6204 inet_rsk(req
)->ecn_ok
= 0;
6207 tcp_rsk(req
)->snt_isn
= isn
;
6208 tcp_openreq_init_rwin(req
, sk
, dst
);
6209 fastopen
= !want_cookie
&&
6210 tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6211 err
= af_ops
->send_synack(sk
, dst
, &fl
, req
,
6212 skb_get_queue_mapping(skb
), &foc
);
6214 if (err
|| want_cookie
)
6217 tcp_rsk(req
)->tfo_listener
= false;
6218 af_ops
->queue_hash_add(sk
, req
, TCP_TIMEOUT_INIT
);
6220 tcp_reqsk_record_syn(sk
, req
, skb
);
6229 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENDROPS
);
6232 EXPORT_SYMBOL(tcp_conn_request
);