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 EXPORT_SYMBOL(sysctl_tcp_reordering
);
85 int sysctl_tcp_dsack __read_mostly
= 1;
86 int sysctl_tcp_app_win __read_mostly
= 31;
87 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
88 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
90 /* rfc5961 challenge ack rate limiting */
91 int sysctl_tcp_challenge_ack_limit
= 100;
93 int sysctl_tcp_stdurg __read_mostly
;
94 int sysctl_tcp_rfc1337 __read_mostly
;
95 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
96 int sysctl_tcp_frto __read_mostly
= 2;
98 int sysctl_tcp_thin_dupack __read_mostly
;
100 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
101 int sysctl_tcp_early_retrans __read_mostly
= 3;
103 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
104 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
105 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
106 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
107 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
108 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
109 #define FLAG_ECE 0x40 /* ECE in this ACK */
110 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
111 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
112 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
113 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
114 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
115 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
117 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
118 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
119 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
120 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
122 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
123 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
125 /* Adapt the MSS value used to make delayed ack decision to the
128 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
130 struct inet_connection_sock
*icsk
= inet_csk(sk
);
131 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
134 icsk
->icsk_ack
.last_seg_size
= 0;
136 /* skb->len may jitter because of SACKs, even if peer
137 * sends good full-sized frames.
139 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
140 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
141 icsk
->icsk_ack
.rcv_mss
= len
;
143 /* Otherwise, we make more careful check taking into account,
144 * that SACKs block is variable.
146 * "len" is invariant segment length, including TCP header.
148 len
+= skb
->data
- skb_transport_header(skb
);
149 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
150 /* If PSH is not set, packet should be
151 * full sized, provided peer TCP is not badly broken.
152 * This observation (if it is correct 8)) allows
153 * to handle super-low mtu links fairly.
155 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
156 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
157 /* Subtract also invariant (if peer is RFC compliant),
158 * tcp header plus fixed timestamp option length.
159 * Resulting "len" is MSS free of SACK jitter.
161 len
-= tcp_sk(sk
)->tcp_header_len
;
162 icsk
->icsk_ack
.last_seg_size
= len
;
164 icsk
->icsk_ack
.rcv_mss
= len
;
168 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
169 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
170 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
174 static void tcp_incr_quickack(struct sock
*sk
)
176 struct inet_connection_sock
*icsk
= inet_csk(sk
);
177 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
181 if (quickacks
> icsk
->icsk_ack
.quick
)
182 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
185 static void tcp_enter_quickack_mode(struct sock
*sk
)
187 struct inet_connection_sock
*icsk
= inet_csk(sk
);
188 tcp_incr_quickack(sk
);
189 icsk
->icsk_ack
.pingpong
= 0;
190 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
193 /* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
197 static inline bool tcp_in_quickack_mode(const struct sock
*sk
)
199 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
201 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
204 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
206 if (tp
->ecn_flags
& TCP_ECN_OK
)
207 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
210 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
212 if (tcp_hdr(skb
)->cwr
)
213 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
216 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
218 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
221 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
223 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
224 case INET_ECN_NOT_ECT
:
225 /* Funny extension: if ECT is not set on a segment,
226 * and we already seen ECT on a previous segment,
227 * it is probably a retransmit.
229 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
230 tcp_enter_quickack_mode((struct sock
*)tp
);
233 if (tcp_ca_needs_ecn((struct sock
*)tp
))
234 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
236 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
237 /* Better not delay acks, sender can have a very low cwnd */
238 tcp_enter_quickack_mode((struct sock
*)tp
);
239 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
241 tp
->ecn_flags
|= TCP_ECN_SEEN
;
244 if (tcp_ca_needs_ecn((struct sock
*)tp
))
245 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
246 tp
->ecn_flags
|= TCP_ECN_SEEN
;
251 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
253 if (tp
->ecn_flags
& TCP_ECN_OK
)
254 __tcp_ecn_check_ce(tp
, skb
);
257 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
259 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
260 tp
->ecn_flags
&= ~TCP_ECN_OK
;
263 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
265 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
266 tp
->ecn_flags
&= ~TCP_ECN_OK
;
269 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
271 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
276 /* Buffer size and advertised window tuning.
278 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
281 static void tcp_sndbuf_expand(struct sock
*sk
)
283 const struct tcp_sock
*tp
= tcp_sk(sk
);
287 /* Worst case is non GSO/TSO : each frame consumes one skb
288 * and skb->head is kmalloced using power of two area of memory
290 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
292 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
294 per_mss
= roundup_pow_of_two(per_mss
) +
295 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
297 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
298 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
300 /* Fast Recovery (RFC 5681 3.2) :
301 * Cubic needs 1.7 factor, rounded to 2 to include
302 * extra cushion (application might react slowly to POLLOUT)
304 sndmem
= 2 * nr_segs
* per_mss
;
306 if (sk
->sk_sndbuf
< sndmem
)
307 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
310 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
312 * All tcp_full_space() is split to two parts: "network" buffer, allocated
313 * forward and advertised in receiver window (tp->rcv_wnd) and
314 * "application buffer", required to isolate scheduling/application
315 * latencies from network.
316 * window_clamp is maximal advertised window. It can be less than
317 * tcp_full_space(), in this case tcp_full_space() - window_clamp
318 * is reserved for "application" buffer. The less window_clamp is
319 * the smoother our behaviour from viewpoint of network, but the lower
320 * throughput and the higher sensitivity of the connection to losses. 8)
322 * rcv_ssthresh is more strict window_clamp used at "slow start"
323 * phase to predict further behaviour of this connection.
324 * It is used for two goals:
325 * - to enforce header prediction at sender, even when application
326 * requires some significant "application buffer". It is check #1.
327 * - to prevent pruning of receive queue because of misprediction
328 * of receiver window. Check #2.
330 * The scheme does not work when sender sends good segments opening
331 * window and then starts to feed us spaghetti. But it should work
332 * in common situations. Otherwise, we have to rely on queue collapsing.
335 /* Slow part of check#2. */
336 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
338 struct tcp_sock
*tp
= tcp_sk(sk
);
340 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
341 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
343 while (tp
->rcv_ssthresh
<= window
) {
344 if (truesize
<= skb
->len
)
345 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
353 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
355 struct tcp_sock
*tp
= tcp_sk(sk
);
358 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
359 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
360 !sk_under_memory_pressure(sk
)) {
363 /* Check #2. Increase window, if skb with such overhead
364 * will fit to rcvbuf in future.
366 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
367 incr
= 2 * tp
->advmss
;
369 incr
= __tcp_grow_window(sk
, skb
);
372 incr
= max_t(int, incr
, 2 * skb
->len
);
373 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
375 inet_csk(sk
)->icsk_ack
.quick
|= 1;
380 /* 3. Tuning rcvbuf, when connection enters established state. */
381 static void tcp_fixup_rcvbuf(struct sock
*sk
)
383 u32 mss
= tcp_sk(sk
)->advmss
;
386 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
387 tcp_default_init_rwnd(mss
);
389 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
390 * Allow enough cushion so that sender is not limited by our window
392 if (sysctl_tcp_moderate_rcvbuf
)
395 if (sk
->sk_rcvbuf
< rcvmem
)
396 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
399 /* 4. Try to fixup all. It is made immediately after connection enters
402 void tcp_init_buffer_space(struct sock
*sk
)
404 struct tcp_sock
*tp
= tcp_sk(sk
);
407 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
408 tcp_fixup_rcvbuf(sk
);
409 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
410 tcp_sndbuf_expand(sk
);
412 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
413 tp
->rcvq_space
.time
= tcp_time_stamp
;
414 tp
->rcvq_space
.seq
= tp
->copied_seq
;
416 maxwin
= tcp_full_space(sk
);
418 if (tp
->window_clamp
>= maxwin
) {
419 tp
->window_clamp
= maxwin
;
421 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
422 tp
->window_clamp
= max(maxwin
-
423 (maxwin
>> sysctl_tcp_app_win
),
427 /* Force reservation of one segment. */
428 if (sysctl_tcp_app_win
&&
429 tp
->window_clamp
> 2 * tp
->advmss
&&
430 tp
->window_clamp
+ tp
->advmss
> maxwin
)
431 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
433 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
434 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
437 /* 5. Recalculate window clamp after socket hit its memory bounds. */
438 static void tcp_clamp_window(struct sock
*sk
)
440 struct tcp_sock
*tp
= tcp_sk(sk
);
441 struct inet_connection_sock
*icsk
= inet_csk(sk
);
443 icsk
->icsk_ack
.quick
= 0;
445 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
446 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
447 !sk_under_memory_pressure(sk
) &&
448 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
449 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
452 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
453 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
456 /* Initialize RCV_MSS value.
457 * RCV_MSS is an our guess about MSS used by the peer.
458 * We haven't any direct information about the MSS.
459 * It's better to underestimate the RCV_MSS rather than overestimate.
460 * Overestimations make us ACKing less frequently than needed.
461 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
463 void tcp_initialize_rcv_mss(struct sock
*sk
)
465 const struct tcp_sock
*tp
= tcp_sk(sk
);
466 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
468 hint
= min(hint
, tp
->rcv_wnd
/ 2);
469 hint
= min(hint
, TCP_MSS_DEFAULT
);
470 hint
= max(hint
, TCP_MIN_MSS
);
472 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
474 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
476 /* Receiver "autotuning" code.
478 * The algorithm for RTT estimation w/o timestamps is based on
479 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
480 * <http://public.lanl.gov/radiant/pubs.html#DRS>
482 * More detail on this code can be found at
483 * <http://staff.psc.edu/jheffner/>,
484 * though this reference is out of date. A new paper
487 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
489 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
495 if (new_sample
!= 0) {
496 /* If we sample in larger samples in the non-timestamp
497 * case, we could grossly overestimate the RTT especially
498 * with chatty applications or bulk transfer apps which
499 * are stalled on filesystem I/O.
501 * Also, since we are only going for a minimum in the
502 * non-timestamp case, we do not smooth things out
503 * else with timestamps disabled convergence takes too
507 m
-= (new_sample
>> 3);
515 /* No previous measure. */
519 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
520 tp
->rcv_rtt_est
.rtt
= new_sample
;
523 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
525 if (tp
->rcv_rtt_est
.time
== 0)
527 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
529 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
532 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
533 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
536 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
537 const struct sk_buff
*skb
)
539 struct tcp_sock
*tp
= tcp_sk(sk
);
540 if (tp
->rx_opt
.rcv_tsecr
&&
541 (TCP_SKB_CB(skb
)->end_seq
-
542 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
543 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
547 * This function should be called every time data is copied to user space.
548 * It calculates the appropriate TCP receive buffer space.
550 void tcp_rcv_space_adjust(struct sock
*sk
)
552 struct tcp_sock
*tp
= tcp_sk(sk
);
556 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
557 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
560 /* Number of bytes copied to user in last RTT */
561 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
562 if (copied
<= tp
->rcvq_space
.space
)
566 * copied = bytes received in previous RTT, our base window
567 * To cope with packet losses, we need a 2x factor
568 * To cope with slow start, and sender growing its cwin by 100 %
569 * every RTT, we need a 4x factor, because the ACK we are sending
570 * now is for the next RTT, not the current one :
571 * <prev RTT . ><current RTT .. ><next RTT .... >
574 if (sysctl_tcp_moderate_rcvbuf
&&
575 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
576 int rcvwin
, rcvmem
, rcvbuf
;
578 /* minimal window to cope with packet losses, assuming
579 * steady state. Add some cushion because of small variations.
581 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
583 /* If rate increased by 25%,
584 * assume slow start, rcvwin = 3 * copied
585 * If rate increased by 50%,
586 * assume sender can use 2x growth, rcvwin = 4 * copied
589 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
591 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
594 rcvwin
+= (rcvwin
>> 1);
597 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
598 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
601 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
602 if (rcvbuf
> sk
->sk_rcvbuf
) {
603 sk
->sk_rcvbuf
= rcvbuf
;
605 /* Make the window clamp follow along. */
606 tp
->window_clamp
= rcvwin
;
609 tp
->rcvq_space
.space
= copied
;
612 tp
->rcvq_space
.seq
= tp
->copied_seq
;
613 tp
->rcvq_space
.time
= tcp_time_stamp
;
616 /* There is something which you must keep in mind when you analyze the
617 * behavior of the tp->ato delayed ack timeout interval. When a
618 * connection starts up, we want to ack as quickly as possible. The
619 * problem is that "good" TCP's do slow start at the beginning of data
620 * transmission. The means that until we send the first few ACK's the
621 * sender will sit on his end and only queue most of his data, because
622 * he can only send snd_cwnd unacked packets at any given time. For
623 * each ACK we send, he increments snd_cwnd and transmits more of his
626 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
628 struct tcp_sock
*tp
= tcp_sk(sk
);
629 struct inet_connection_sock
*icsk
= inet_csk(sk
);
632 inet_csk_schedule_ack(sk
);
634 tcp_measure_rcv_mss(sk
, skb
);
636 tcp_rcv_rtt_measure(tp
);
638 now
= tcp_time_stamp
;
640 if (!icsk
->icsk_ack
.ato
) {
641 /* The _first_ data packet received, initialize
642 * delayed ACK engine.
644 tcp_incr_quickack(sk
);
645 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
647 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
649 if (m
<= TCP_ATO_MIN
/ 2) {
650 /* The fastest case is the first. */
651 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
652 } else if (m
< icsk
->icsk_ack
.ato
) {
653 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
654 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
655 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
656 } else if (m
> icsk
->icsk_rto
) {
657 /* Too long gap. Apparently sender failed to
658 * restart window, so that we send ACKs quickly.
660 tcp_incr_quickack(sk
);
664 icsk
->icsk_ack
.lrcvtime
= now
;
666 tcp_ecn_check_ce(tp
, skb
);
669 tcp_grow_window(sk
, skb
);
672 /* Called to compute a smoothed rtt estimate. The data fed to this
673 * routine either comes from timestamps, or from segments that were
674 * known _not_ to have been retransmitted [see Karn/Partridge
675 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
676 * piece by Van Jacobson.
677 * NOTE: the next three routines used to be one big routine.
678 * To save cycles in the RFC 1323 implementation it was better to break
679 * it up into three procedures. -- erics
681 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
683 struct tcp_sock
*tp
= tcp_sk(sk
);
684 long m
= mrtt_us
; /* RTT */
685 u32 srtt
= tp
->srtt_us
;
687 /* The following amusing code comes from Jacobson's
688 * article in SIGCOMM '88. Note that rtt and mdev
689 * are scaled versions of rtt and mean deviation.
690 * This is designed to be as fast as possible
691 * m stands for "measurement".
693 * On a 1990 paper the rto value is changed to:
694 * RTO = rtt + 4 * mdev
696 * Funny. This algorithm seems to be very broken.
697 * These formulae increase RTO, when it should be decreased, increase
698 * too slowly, when it should be increased quickly, decrease too quickly
699 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
700 * does not matter how to _calculate_ it. Seems, it was trap
701 * that VJ failed to avoid. 8)
704 m
-= (srtt
>> 3); /* m is now error in rtt est */
705 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
707 m
= -m
; /* m is now abs(error) */
708 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
709 /* This is similar to one of Eifel findings.
710 * Eifel blocks mdev updates when rtt decreases.
711 * This solution is a bit different: we use finer gain
712 * for mdev in this case (alpha*beta).
713 * Like Eifel it also prevents growth of rto,
714 * but also it limits too fast rto decreases,
715 * happening in pure Eifel.
720 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
722 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
723 if (tp
->mdev_us
> tp
->mdev_max_us
) {
724 tp
->mdev_max_us
= tp
->mdev_us
;
725 if (tp
->mdev_max_us
> tp
->rttvar_us
)
726 tp
->rttvar_us
= tp
->mdev_max_us
;
728 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
729 if (tp
->mdev_max_us
< tp
->rttvar_us
)
730 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
731 tp
->rtt_seq
= tp
->snd_nxt
;
732 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
735 /* no previous measure. */
736 srtt
= m
<< 3; /* take the measured time to be rtt */
737 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
738 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
739 tp
->mdev_max_us
= tp
->rttvar_us
;
740 tp
->rtt_seq
= tp
->snd_nxt
;
742 tp
->srtt_us
= max(1U, srtt
);
745 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
746 * Note: TCP stack does not yet implement pacing.
747 * FQ packet scheduler can be used to implement cheap but effective
748 * TCP pacing, to smooth the burst on large writes when packets
749 * in flight is significantly lower than cwnd (or rwin)
751 static void tcp_update_pacing_rate(struct sock
*sk
)
753 const struct tcp_sock
*tp
= tcp_sk(sk
);
756 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
757 rate
= (u64
)tp
->mss_cache
* 2 * (USEC_PER_SEC
<< 3);
759 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
761 if (likely(tp
->srtt_us
))
762 do_div(rate
, tp
->srtt_us
);
764 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
765 * without any lock. We want to make sure compiler wont store
766 * intermediate values in this location.
768 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
769 sk
->sk_max_pacing_rate
);
772 /* Calculate rto without backoff. This is the second half of Van Jacobson's
773 * routine referred to above.
775 static void tcp_set_rto(struct sock
*sk
)
777 const struct tcp_sock
*tp
= tcp_sk(sk
);
778 /* Old crap is replaced with new one. 8)
781 * 1. If rtt variance happened to be less 50msec, it is hallucination.
782 * It cannot be less due to utterly erratic ACK generation made
783 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
784 * to do with delayed acks, because at cwnd>2 true delack timeout
785 * is invisible. Actually, Linux-2.4 also generates erratic
786 * ACKs in some circumstances.
788 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
790 /* 2. Fixups made earlier cannot be right.
791 * If we do not estimate RTO correctly without them,
792 * all the algo is pure shit and should be replaced
793 * with correct one. It is exactly, which we pretend to do.
796 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
797 * guarantees that rto is higher.
802 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
804 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
807 cwnd
= TCP_INIT_CWND
;
808 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
812 * Packet counting of FACK is based on in-order assumptions, therefore TCP
813 * disables it when reordering is detected
815 void tcp_disable_fack(struct tcp_sock
*tp
)
817 /* RFC3517 uses different metric in lost marker => reset on change */
819 tp
->lost_skb_hint
= NULL
;
820 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
823 /* Take a notice that peer is sending D-SACKs */
824 static void tcp_dsack_seen(struct tcp_sock
*tp
)
826 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
829 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
832 struct tcp_sock
*tp
= tcp_sk(sk
);
833 if (metric
> tp
->reordering
) {
836 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
838 /* This exciting event is worth to be remembered. 8) */
840 mib_idx
= LINUX_MIB_TCPTSREORDER
;
841 else if (tcp_is_reno(tp
))
842 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
843 else if (tcp_is_fack(tp
))
844 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
846 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
848 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
849 #if FASTRETRANS_DEBUG > 1
850 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
851 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
855 tp
->undo_marker
? tp
->undo_retrans
: 0);
857 tcp_disable_fack(tp
);
861 tcp_disable_early_retrans(tp
);
864 /* This must be called before lost_out is incremented */
865 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
867 if ((tp
->retransmit_skb_hint
== NULL
) ||
868 before(TCP_SKB_CB(skb
)->seq
,
869 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
870 tp
->retransmit_skb_hint
= skb
;
873 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
874 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
877 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
879 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
880 tcp_verify_retransmit_hint(tp
, skb
);
882 tp
->lost_out
+= tcp_skb_pcount(skb
);
883 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
887 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
890 tcp_verify_retransmit_hint(tp
, skb
);
892 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
893 tp
->lost_out
+= tcp_skb_pcount(skb
);
894 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
898 /* This procedure tags the retransmission queue when SACKs arrive.
900 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
901 * Packets in queue with these bits set are counted in variables
902 * sacked_out, retrans_out and lost_out, correspondingly.
904 * Valid combinations are:
905 * Tag InFlight Description
906 * 0 1 - orig segment is in flight.
907 * S 0 - nothing flies, orig reached receiver.
908 * L 0 - nothing flies, orig lost by net.
909 * R 2 - both orig and retransmit are in flight.
910 * L|R 1 - orig is lost, retransmit is in flight.
911 * S|R 1 - orig reached receiver, retrans is still in flight.
912 * (L|S|R is logically valid, it could occur when L|R is sacked,
913 * but it is equivalent to plain S and code short-curcuits it to S.
914 * L|S is logically invalid, it would mean -1 packet in flight 8))
916 * These 6 states form finite state machine, controlled by the following events:
917 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
918 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
919 * 3. Loss detection event of two flavors:
920 * A. Scoreboard estimator decided the packet is lost.
921 * A'. Reno "three dupacks" marks head of queue lost.
922 * A''. Its FACK modification, head until snd.fack is lost.
923 * B. SACK arrives sacking SND.NXT at the moment, when the
924 * segment was retransmitted.
925 * 4. D-SACK added new rule: D-SACK changes any tag to S.
927 * It is pleasant to note, that state diagram turns out to be commutative,
928 * so that we are allowed not to be bothered by order of our actions,
929 * when multiple events arrive simultaneously. (see the function below).
931 * Reordering detection.
932 * --------------------
933 * Reordering metric is maximal distance, which a packet can be displaced
934 * in packet stream. With SACKs we can estimate it:
936 * 1. SACK fills old hole and the corresponding segment was not
937 * ever retransmitted -> reordering. Alas, we cannot use it
938 * when segment was retransmitted.
939 * 2. The last flaw is solved with D-SACK. D-SACK arrives
940 * for retransmitted and already SACKed segment -> reordering..
941 * Both of these heuristics are not used in Loss state, when we cannot
942 * account for retransmits accurately.
944 * SACK block validation.
945 * ----------------------
947 * SACK block range validation checks that the received SACK block fits to
948 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
949 * Note that SND.UNA is not included to the range though being valid because
950 * it means that the receiver is rather inconsistent with itself reporting
951 * SACK reneging when it should advance SND.UNA. Such SACK block this is
952 * perfectly valid, however, in light of RFC2018 which explicitly states
953 * that "SACK block MUST reflect the newest segment. Even if the newest
954 * segment is going to be discarded ...", not that it looks very clever
955 * in case of head skb. Due to potentional receiver driven attacks, we
956 * choose to avoid immediate execution of a walk in write queue due to
957 * reneging and defer head skb's loss recovery to standard loss recovery
958 * procedure that will eventually trigger (nothing forbids us doing this).
960 * Implements also blockage to start_seq wrap-around. Problem lies in the
961 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
962 * there's no guarantee that it will be before snd_nxt (n). The problem
963 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
966 * <- outs wnd -> <- wrapzone ->
967 * u e n u_w e_w s n_w
969 * |<------------+------+----- TCP seqno space --------------+---------->|
970 * ...-- <2^31 ->| |<--------...
971 * ...---- >2^31 ------>| |<--------...
973 * Current code wouldn't be vulnerable but it's better still to discard such
974 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
975 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
976 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
977 * equal to the ideal case (infinite seqno space without wrap caused issues).
979 * With D-SACK the lower bound is extended to cover sequence space below
980 * SND.UNA down to undo_marker, which is the last point of interest. Yet
981 * again, D-SACK block must not to go across snd_una (for the same reason as
982 * for the normal SACK blocks, explained above). But there all simplicity
983 * ends, TCP might receive valid D-SACKs below that. As long as they reside
984 * fully below undo_marker they do not affect behavior in anyway and can
985 * therefore be safely ignored. In rare cases (which are more or less
986 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
987 * fragmentation and packet reordering past skb's retransmission. To consider
988 * them correctly, the acceptable range must be extended even more though
989 * the exact amount is rather hard to quantify. However, tp->max_window can
990 * be used as an exaggerated estimate.
992 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
993 u32 start_seq
, u32 end_seq
)
995 /* Too far in future, or reversed (interpretation is ambiguous) */
996 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
999 /* Nasty start_seq wrap-around check (see comments above) */
1000 if (!before(start_seq
, tp
->snd_nxt
))
1003 /* In outstanding window? ...This is valid exit for D-SACKs too.
1004 * start_seq == snd_una is non-sensical (see comments above)
1006 if (after(start_seq
, tp
->snd_una
))
1009 if (!is_dsack
|| !tp
->undo_marker
)
1012 /* ...Then it's D-SACK, and must reside below snd_una completely */
1013 if (after(end_seq
, tp
->snd_una
))
1016 if (!before(start_seq
, tp
->undo_marker
))
1020 if (!after(end_seq
, tp
->undo_marker
))
1023 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1024 * start_seq < undo_marker and end_seq >= undo_marker.
1026 return !before(start_seq
, end_seq
- tp
->max_window
);
1029 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1030 * Event "B". Later note: FACK people cheated me again 8), we have to account
1031 * for reordering! Ugly, but should help.
1033 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1034 * less than what is now known to be received by the other end (derived from
1035 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1036 * retransmitted skbs to avoid some costly processing per ACKs.
1038 static void tcp_mark_lost_retrans(struct sock
*sk
)
1040 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1041 struct tcp_sock
*tp
= tcp_sk(sk
);
1042 struct sk_buff
*skb
;
1044 u32 new_low_seq
= tp
->snd_nxt
;
1045 u32 received_upto
= tcp_highest_sack_seq(tp
);
1047 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1048 !after(received_upto
, tp
->lost_retrans_low
) ||
1049 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1052 tcp_for_write_queue(skb
, sk
) {
1053 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1055 if (skb
== tcp_send_head(sk
))
1057 if (cnt
== tp
->retrans_out
)
1059 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1062 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1065 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1066 * constraint here (see above) but figuring out that at
1067 * least tp->reordering SACK blocks reside between ack_seq
1068 * and received_upto is not easy task to do cheaply with
1069 * the available datastructures.
1071 * Whether FACK should check here for tp->reordering segs
1072 * in-between one could argue for either way (it would be
1073 * rather simple to implement as we could count fack_count
1074 * during the walk and do tp->fackets_out - fack_count).
1076 if (after(received_upto
, ack_seq
)) {
1077 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1078 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1080 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1081 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1083 if (before(ack_seq
, new_low_seq
))
1084 new_low_seq
= ack_seq
;
1085 cnt
+= tcp_skb_pcount(skb
);
1089 if (tp
->retrans_out
)
1090 tp
->lost_retrans_low
= new_low_seq
;
1093 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1094 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1097 struct tcp_sock
*tp
= tcp_sk(sk
);
1098 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1099 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1100 bool dup_sack
= false;
1102 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1105 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1106 } else if (num_sacks
> 1) {
1107 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1108 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1110 if (!after(end_seq_0
, end_seq_1
) &&
1111 !before(start_seq_0
, start_seq_1
)) {
1114 NET_INC_STATS_BH(sock_net(sk
),
1115 LINUX_MIB_TCPDSACKOFORECV
);
1119 /* D-SACK for already forgotten data... Do dumb counting. */
1120 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1121 !after(end_seq_0
, prior_snd_una
) &&
1122 after(end_seq_0
, tp
->undo_marker
))
1128 struct tcp_sacktag_state
{
1131 long rtt_us
; /* RTT measured by SACKing never-retransmitted data */
1135 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1136 * the incoming SACK may not exactly match but we can find smaller MSS
1137 * aligned portion of it that matches. Therefore we might need to fragment
1138 * which may fail and creates some hassle (caller must handle error case
1141 * FIXME: this could be merged to shift decision code
1143 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1144 u32 start_seq
, u32 end_seq
)
1148 unsigned int pkt_len
;
1151 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1152 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1154 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1155 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1156 mss
= tcp_skb_mss(skb
);
1157 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1160 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1164 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1169 /* Round if necessary so that SACKs cover only full MSSes
1170 * and/or the remaining small portion (if present)
1172 if (pkt_len
> mss
) {
1173 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1174 if (!in_sack
&& new_len
< pkt_len
) {
1176 if (new_len
>= skb
->len
)
1181 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1189 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1190 static u8
tcp_sacktag_one(struct sock
*sk
,
1191 struct tcp_sacktag_state
*state
, u8 sacked
,
1192 u32 start_seq
, u32 end_seq
,
1193 int dup_sack
, int pcount
,
1194 const struct skb_mstamp
*xmit_time
)
1196 struct tcp_sock
*tp
= tcp_sk(sk
);
1197 int fack_count
= state
->fack_count
;
1199 /* Account D-SACK for retransmitted packet. */
1200 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1201 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1202 after(end_seq
, tp
->undo_marker
))
1204 if (sacked
& TCPCB_SACKED_ACKED
)
1205 state
->reord
= min(fack_count
, state
->reord
);
1208 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1209 if (!after(end_seq
, tp
->snd_una
))
1212 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1213 if (sacked
& TCPCB_SACKED_RETRANS
) {
1214 /* If the segment is not tagged as lost,
1215 * we do not clear RETRANS, believing
1216 * that retransmission is still in flight.
1218 if (sacked
& TCPCB_LOST
) {
1219 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1220 tp
->lost_out
-= pcount
;
1221 tp
->retrans_out
-= pcount
;
1224 if (!(sacked
& TCPCB_RETRANS
)) {
1225 /* New sack for not retransmitted frame,
1226 * which was in hole. It is reordering.
1228 if (before(start_seq
,
1229 tcp_highest_sack_seq(tp
)))
1230 state
->reord
= min(fack_count
,
1232 if (!after(end_seq
, tp
->high_seq
))
1233 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1234 /* Pick the earliest sequence sacked for RTT */
1235 if (state
->rtt_us
< 0) {
1236 struct skb_mstamp now
;
1238 skb_mstamp_get(&now
);
1239 state
->rtt_us
= skb_mstamp_us_delta(&now
,
1244 if (sacked
& TCPCB_LOST
) {
1245 sacked
&= ~TCPCB_LOST
;
1246 tp
->lost_out
-= pcount
;
1250 sacked
|= TCPCB_SACKED_ACKED
;
1251 state
->flag
|= FLAG_DATA_SACKED
;
1252 tp
->sacked_out
+= pcount
;
1254 fack_count
+= pcount
;
1256 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1257 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1258 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1259 tp
->lost_cnt_hint
+= pcount
;
1261 if (fack_count
> tp
->fackets_out
)
1262 tp
->fackets_out
= fack_count
;
1265 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1266 * frames and clear it. undo_retrans is decreased above, L|R frames
1267 * are accounted above as well.
1269 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1270 sacked
&= ~TCPCB_SACKED_RETRANS
;
1271 tp
->retrans_out
-= pcount
;
1277 /* Shift newly-SACKed bytes from this skb to the immediately previous
1278 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1280 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1281 struct tcp_sacktag_state
*state
,
1282 unsigned int pcount
, int shifted
, int mss
,
1285 struct tcp_sock
*tp
= tcp_sk(sk
);
1286 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1287 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1288 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1292 /* Adjust counters and hints for the newly sacked sequence
1293 * range but discard the return value since prev is already
1294 * marked. We must tag the range first because the seq
1295 * advancement below implicitly advances
1296 * tcp_highest_sack_seq() when skb is highest_sack.
1298 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1299 start_seq
, end_seq
, dup_sack
, pcount
,
1302 if (skb
== tp
->lost_skb_hint
)
1303 tp
->lost_cnt_hint
+= pcount
;
1305 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1306 TCP_SKB_CB(skb
)->seq
+= shifted
;
1308 tcp_skb_pcount_add(prev
, pcount
);
1309 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1310 tcp_skb_pcount_add(skb
, -pcount
);
1312 /* When we're adding to gso_segs == 1, gso_size will be zero,
1313 * in theory this shouldn't be necessary but as long as DSACK
1314 * code can come after this skb later on it's better to keep
1315 * setting gso_size to something.
1317 if (!skb_shinfo(prev
)->gso_size
) {
1318 skb_shinfo(prev
)->gso_size
= mss
;
1319 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1322 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1323 if (tcp_skb_pcount(skb
) <= 1) {
1324 skb_shinfo(skb
)->gso_size
= 0;
1325 skb_shinfo(skb
)->gso_type
= 0;
1328 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1329 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1332 BUG_ON(!tcp_skb_pcount(skb
));
1333 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1337 /* Whole SKB was eaten :-) */
1339 if (skb
== tp
->retransmit_skb_hint
)
1340 tp
->retransmit_skb_hint
= prev
;
1341 if (skb
== tp
->lost_skb_hint
) {
1342 tp
->lost_skb_hint
= prev
;
1343 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1346 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1347 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1348 TCP_SKB_CB(prev
)->end_seq
++;
1350 if (skb
== tcp_highest_sack(sk
))
1351 tcp_advance_highest_sack(sk
, skb
);
1353 tcp_unlink_write_queue(skb
, sk
);
1354 sk_wmem_free_skb(sk
, skb
);
1356 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1361 /* I wish gso_size would have a bit more sane initialization than
1362 * something-or-zero which complicates things
1364 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1366 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1369 /* Shifting pages past head area doesn't work */
1370 static int skb_can_shift(const struct sk_buff
*skb
)
1372 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1375 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1378 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1379 struct tcp_sacktag_state
*state
,
1380 u32 start_seq
, u32 end_seq
,
1383 struct tcp_sock
*tp
= tcp_sk(sk
);
1384 struct sk_buff
*prev
;
1390 if (!sk_can_gso(sk
))
1393 /* Normally R but no L won't result in plain S */
1395 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1397 if (!skb_can_shift(skb
))
1399 /* This frame is about to be dropped (was ACKed). */
1400 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1403 /* Can only happen with delayed DSACK + discard craziness */
1404 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1406 prev
= tcp_write_queue_prev(sk
, skb
);
1408 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1411 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1412 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1416 pcount
= tcp_skb_pcount(skb
);
1417 mss
= tcp_skb_seglen(skb
);
1419 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1420 * drop this restriction as unnecessary
1422 if (mss
!= tcp_skb_seglen(prev
))
1425 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1427 /* CHECKME: This is non-MSS split case only?, this will
1428 * cause skipped skbs due to advancing loop btw, original
1429 * has that feature too
1431 if (tcp_skb_pcount(skb
) <= 1)
1434 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1436 /* TODO: head merge to next could be attempted here
1437 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1438 * though it might not be worth of the additional hassle
1440 * ...we can probably just fallback to what was done
1441 * previously. We could try merging non-SACKed ones
1442 * as well but it probably isn't going to buy off
1443 * because later SACKs might again split them, and
1444 * it would make skb timestamp tracking considerably
1450 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1452 BUG_ON(len
> skb
->len
);
1454 /* MSS boundaries should be honoured or else pcount will
1455 * severely break even though it makes things bit trickier.
1456 * Optimize common case to avoid most of the divides
1458 mss
= tcp_skb_mss(skb
);
1460 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1461 * drop this restriction as unnecessary
1463 if (mss
!= tcp_skb_seglen(prev
))
1468 } else if (len
< mss
) {
1476 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1477 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1480 if (!skb_shift(prev
, skb
, len
))
1482 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1485 /* Hole filled allows collapsing with the next as well, this is very
1486 * useful when hole on every nth skb pattern happens
1488 if (prev
== tcp_write_queue_tail(sk
))
1490 skb
= tcp_write_queue_next(sk
, prev
);
1492 if (!skb_can_shift(skb
) ||
1493 (skb
== tcp_send_head(sk
)) ||
1494 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1495 (mss
!= tcp_skb_seglen(skb
)))
1499 if (skb_shift(prev
, skb
, len
)) {
1500 pcount
+= tcp_skb_pcount(skb
);
1501 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1505 state
->fack_count
+= pcount
;
1512 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1516 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1517 struct tcp_sack_block
*next_dup
,
1518 struct tcp_sacktag_state
*state
,
1519 u32 start_seq
, u32 end_seq
,
1522 struct tcp_sock
*tp
= tcp_sk(sk
);
1523 struct sk_buff
*tmp
;
1525 tcp_for_write_queue_from(skb
, sk
) {
1527 bool dup_sack
= dup_sack_in
;
1529 if (skb
== tcp_send_head(sk
))
1532 /* queue is in-order => we can short-circuit the walk early */
1533 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1536 if ((next_dup
!= NULL
) &&
1537 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1538 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1539 next_dup
->start_seq
,
1545 /* skb reference here is a bit tricky to get right, since
1546 * shifting can eat and free both this skb and the next,
1547 * so not even _safe variant of the loop is enough.
1550 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1551 start_seq
, end_seq
, dup_sack
);
1560 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1566 if (unlikely(in_sack
< 0))
1570 TCP_SKB_CB(skb
)->sacked
=
1573 TCP_SKB_CB(skb
)->sacked
,
1574 TCP_SKB_CB(skb
)->seq
,
1575 TCP_SKB_CB(skb
)->end_seq
,
1577 tcp_skb_pcount(skb
),
1580 if (!before(TCP_SKB_CB(skb
)->seq
,
1581 tcp_highest_sack_seq(tp
)))
1582 tcp_advance_highest_sack(sk
, skb
);
1585 state
->fack_count
+= tcp_skb_pcount(skb
);
1590 /* Avoid all extra work that is being done by sacktag while walking in
1593 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1594 struct tcp_sacktag_state
*state
,
1597 tcp_for_write_queue_from(skb
, sk
) {
1598 if (skb
== tcp_send_head(sk
))
1601 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1604 state
->fack_count
+= tcp_skb_pcount(skb
);
1609 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1611 struct tcp_sack_block
*next_dup
,
1612 struct tcp_sacktag_state
*state
,
1615 if (next_dup
== NULL
)
1618 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1619 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1620 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1621 next_dup
->start_seq
, next_dup
->end_seq
,
1628 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1630 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1634 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1635 u32 prior_snd_una
, long *sack_rtt_us
)
1637 struct tcp_sock
*tp
= tcp_sk(sk
);
1638 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1639 TCP_SKB_CB(ack_skb
)->sacked
);
1640 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1641 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1642 struct tcp_sack_block
*cache
;
1643 struct tcp_sacktag_state state
;
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
;
1655 if (!tp
->sacked_out
) {
1656 if (WARN_ON(tp
->fackets_out
))
1657 tp
->fackets_out
= 0;
1658 tcp_highest_sack_reset(sk
);
1661 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1662 num_sacks
, prior_snd_una
);
1664 state
.flag
|= FLAG_DSACKING_ACK
;
1666 /* Eliminate too old ACKs, but take into
1667 * account more or less fresh ones, they can
1668 * contain valid SACK info.
1670 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1673 if (!tp
->packets_out
)
1677 first_sack_index
= 0;
1678 for (i
= 0; i
< num_sacks
; i
++) {
1679 bool dup_sack
= !i
&& found_dup_sack
;
1681 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1682 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1684 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1685 sp
[used_sacks
].start_seq
,
1686 sp
[used_sacks
].end_seq
)) {
1690 if (!tp
->undo_marker
)
1691 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1693 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1695 /* Don't count olds caused by ACK reordering */
1696 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1697 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1699 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1702 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1704 first_sack_index
= -1;
1708 /* Ignore very old stuff early */
1709 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1715 /* order SACK blocks to allow in order walk of the retrans queue */
1716 for (i
= used_sacks
- 1; i
> 0; i
--) {
1717 for (j
= 0; j
< i
; j
++) {
1718 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1719 swap(sp
[j
], sp
[j
+ 1]);
1721 /* Track where the first SACK block goes to */
1722 if (j
== first_sack_index
)
1723 first_sack_index
= j
+ 1;
1728 skb
= tcp_write_queue_head(sk
);
1729 state
.fack_count
= 0;
1732 if (!tp
->sacked_out
) {
1733 /* It's already past, so skip checking against it */
1734 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1736 cache
= tp
->recv_sack_cache
;
1737 /* Skip empty blocks in at head of the cache */
1738 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1743 while (i
< used_sacks
) {
1744 u32 start_seq
= sp
[i
].start_seq
;
1745 u32 end_seq
= sp
[i
].end_seq
;
1746 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1747 struct tcp_sack_block
*next_dup
= NULL
;
1749 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1750 next_dup
= &sp
[i
+ 1];
1752 /* Skip too early cached blocks */
1753 while (tcp_sack_cache_ok(tp
, cache
) &&
1754 !before(start_seq
, cache
->end_seq
))
1757 /* Can skip some work by looking recv_sack_cache? */
1758 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1759 after(end_seq
, cache
->start_seq
)) {
1762 if (before(start_seq
, cache
->start_seq
)) {
1763 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1765 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1772 /* Rest of the block already fully processed? */
1773 if (!after(end_seq
, cache
->end_seq
))
1776 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1780 /* ...tail remains todo... */
1781 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1782 /* ...but better entrypoint exists! */
1783 skb
= tcp_highest_sack(sk
);
1786 state
.fack_count
= tp
->fackets_out
;
1791 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1792 /* Check overlap against next cached too (past this one already) */
1797 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1798 skb
= tcp_highest_sack(sk
);
1801 state
.fack_count
= tp
->fackets_out
;
1803 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1806 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1807 start_seq
, end_seq
, dup_sack
);
1813 /* Clear the head of the cache sack blocks so we can skip it next time */
1814 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1815 tp
->recv_sack_cache
[i
].start_seq
= 0;
1816 tp
->recv_sack_cache
[i
].end_seq
= 0;
1818 for (j
= 0; j
< used_sacks
; j
++)
1819 tp
->recv_sack_cache
[i
++] = sp
[j
];
1821 tcp_mark_lost_retrans(sk
);
1823 tcp_verify_left_out(tp
);
1825 if ((state
.reord
< tp
->fackets_out
) &&
1826 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1827 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1831 #if FASTRETRANS_DEBUG > 0
1832 WARN_ON((int)tp
->sacked_out
< 0);
1833 WARN_ON((int)tp
->lost_out
< 0);
1834 WARN_ON((int)tp
->retrans_out
< 0);
1835 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1837 *sack_rtt_us
= state
.rtt_us
;
1841 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1842 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1844 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1848 holes
= max(tp
->lost_out
, 1U);
1849 holes
= min(holes
, tp
->packets_out
);
1851 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1852 tp
->sacked_out
= tp
->packets_out
- holes
;
1858 /* If we receive more dupacks than we expected counting segments
1859 * in assumption of absent reordering, interpret this as reordering.
1860 * The only another reason could be bug in receiver TCP.
1862 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1864 struct tcp_sock
*tp
= tcp_sk(sk
);
1865 if (tcp_limit_reno_sacked(tp
))
1866 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1869 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1871 static void tcp_add_reno_sack(struct sock
*sk
)
1873 struct tcp_sock
*tp
= tcp_sk(sk
);
1875 tcp_check_reno_reordering(sk
, 0);
1876 tcp_verify_left_out(tp
);
1879 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1881 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1883 struct tcp_sock
*tp
= tcp_sk(sk
);
1886 /* One ACK acked hole. The rest eat duplicate ACKs. */
1887 if (acked
- 1 >= tp
->sacked_out
)
1890 tp
->sacked_out
-= acked
- 1;
1892 tcp_check_reno_reordering(sk
, acked
);
1893 tcp_verify_left_out(tp
);
1896 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1901 void tcp_clear_retrans(struct tcp_sock
*tp
)
1903 tp
->retrans_out
= 0;
1905 tp
->undo_marker
= 0;
1906 tp
->undo_retrans
= -1;
1907 tp
->fackets_out
= 0;
1911 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1913 tp
->undo_marker
= tp
->snd_una
;
1914 /* Retransmission still in flight may cause DSACKs later. */
1915 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1918 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1919 * and reset tags completely, otherwise preserve SACKs. If receiver
1920 * dropped its ofo queue, we will know this due to reneging detection.
1922 void tcp_enter_loss(struct sock
*sk
)
1924 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1925 struct tcp_sock
*tp
= tcp_sk(sk
);
1926 struct sk_buff
*skb
;
1927 bool new_recovery
= false;
1928 bool is_reneg
; /* is receiver reneging on SACKs? */
1930 /* Reduce ssthresh if it has not yet been made inside this window. */
1931 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1932 !after(tp
->high_seq
, tp
->snd_una
) ||
1933 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1934 new_recovery
= true;
1935 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1936 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1937 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1941 tp
->snd_cwnd_cnt
= 0;
1942 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1944 tp
->retrans_out
= 0;
1947 if (tcp_is_reno(tp
))
1948 tcp_reset_reno_sack(tp
);
1950 skb
= tcp_write_queue_head(sk
);
1951 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1953 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1955 tp
->fackets_out
= 0;
1957 tcp_clear_all_retrans_hints(tp
);
1959 tcp_for_write_queue(skb
, sk
) {
1960 if (skb
== tcp_send_head(sk
))
1963 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1964 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || is_reneg
) {
1965 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1966 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1967 tp
->lost_out
+= tcp_skb_pcount(skb
);
1968 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1971 tcp_verify_left_out(tp
);
1973 /* Timeout in disordered state after receiving substantial DUPACKs
1974 * suggests that the degree of reordering is over-estimated.
1976 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1977 tp
->sacked_out
>= sysctl_tcp_reordering
)
1978 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1979 sysctl_tcp_reordering
);
1980 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1981 tp
->high_seq
= tp
->snd_nxt
;
1982 tcp_ecn_queue_cwr(tp
);
1984 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1985 * loss recovery is underway except recurring timeout(s) on
1986 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1988 tp
->frto
= sysctl_tcp_frto
&&
1989 (new_recovery
|| icsk
->icsk_retransmits
) &&
1990 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1993 /* If ACK arrived pointing to a remembered SACK, it means that our
1994 * remembered SACKs do not reflect real state of receiver i.e.
1995 * receiver _host_ is heavily congested (or buggy).
1997 * To avoid big spurious retransmission bursts due to transient SACK
1998 * scoreboard oddities that look like reneging, we give the receiver a
1999 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2000 * restore sanity to the SACK scoreboard. If the apparent reneging
2001 * persists until this RTO then we'll clear the SACK scoreboard.
2003 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2005 if (flag
& FLAG_SACK_RENEGING
) {
2006 struct tcp_sock
*tp
= tcp_sk(sk
);
2007 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2008 msecs_to_jiffies(10));
2010 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2011 delay
, TCP_RTO_MAX
);
2017 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2019 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2022 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2023 * counter when SACK is enabled (without SACK, sacked_out is used for
2026 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2027 * segments up to the highest received SACK block so far and holes in
2030 * With reordering, holes may still be in flight, so RFC3517 recovery
2031 * uses pure sacked_out (total number of SACKed segments) even though
2032 * it violates the RFC that uses duplicate ACKs, often these are equal
2033 * but when e.g. out-of-window ACKs or packet duplication occurs,
2034 * they differ. Since neither occurs due to loss, TCP should really
2037 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2039 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2042 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2044 struct tcp_sock
*tp
= tcp_sk(sk
);
2045 unsigned long delay
;
2047 /* Delay early retransmit and entering fast recovery for
2048 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2049 * available, or RTO is scheduled to fire first.
2051 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
2052 (flag
& FLAG_ECE
) || !tp
->srtt_us
)
2055 delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 5),
2056 msecs_to_jiffies(2));
2058 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2061 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2066 /* Linux NewReno/SACK/FACK/ECN state machine.
2067 * --------------------------------------
2069 * "Open" Normal state, no dubious events, fast path.
2070 * "Disorder" In all the respects it is "Open",
2071 * but requires a bit more attention. It is entered when
2072 * we see some SACKs or dupacks. It is split of "Open"
2073 * mainly to move some processing from fast path to slow one.
2074 * "CWR" CWND was reduced due to some Congestion Notification event.
2075 * It can be ECN, ICMP source quench, local device congestion.
2076 * "Recovery" CWND was reduced, we are fast-retransmitting.
2077 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2079 * tcp_fastretrans_alert() is entered:
2080 * - each incoming ACK, if state is not "Open"
2081 * - when arrived ACK is unusual, namely:
2086 * Counting packets in flight is pretty simple.
2088 * in_flight = packets_out - left_out + retrans_out
2090 * packets_out is SND.NXT-SND.UNA counted in packets.
2092 * retrans_out is number of retransmitted segments.
2094 * left_out is number of segments left network, but not ACKed yet.
2096 * left_out = sacked_out + lost_out
2098 * sacked_out: Packets, which arrived to receiver out of order
2099 * and hence not ACKed. With SACKs this number is simply
2100 * amount of SACKed data. Even without SACKs
2101 * it is easy to give pretty reliable estimate of this number,
2102 * counting duplicate ACKs.
2104 * lost_out: Packets lost by network. TCP has no explicit
2105 * "loss notification" feedback from network (for now).
2106 * It means that this number can be only _guessed_.
2107 * Actually, it is the heuristics to predict lossage that
2108 * distinguishes different algorithms.
2110 * F.e. after RTO, when all the queue is considered as lost,
2111 * lost_out = packets_out and in_flight = retrans_out.
2113 * Essentially, we have now two algorithms counting
2116 * FACK: It is the simplest heuristics. As soon as we decided
2117 * that something is lost, we decide that _all_ not SACKed
2118 * packets until the most forward SACK are lost. I.e.
2119 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2120 * It is absolutely correct estimate, if network does not reorder
2121 * packets. And it loses any connection to reality when reordering
2122 * takes place. We use FACK by default until reordering
2123 * is suspected on the path to this destination.
2125 * NewReno: when Recovery is entered, we assume that one segment
2126 * is lost (classic Reno). While we are in Recovery and
2127 * a partial ACK arrives, we assume that one more packet
2128 * is lost (NewReno). This heuristics are the same in NewReno
2131 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2132 * deflation etc. CWND is real congestion window, never inflated, changes
2133 * only according to classic VJ rules.
2135 * Really tricky (and requiring careful tuning) part of algorithm
2136 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2137 * The first determines the moment _when_ we should reduce CWND and,
2138 * hence, slow down forward transmission. In fact, it determines the moment
2139 * when we decide that hole is caused by loss, rather than by a reorder.
2141 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2142 * holes, caused by lost packets.
2144 * And the most logically complicated part of algorithm is undo
2145 * heuristics. We detect false retransmits due to both too early
2146 * fast retransmit (reordering) and underestimated RTO, analyzing
2147 * timestamps and D-SACKs. When we detect that some segments were
2148 * retransmitted by mistake and CWND reduction was wrong, we undo
2149 * window reduction and abort recovery phase. This logic is hidden
2150 * inside several functions named tcp_try_undo_<something>.
2153 /* This function decides, when we should leave Disordered state
2154 * and enter Recovery phase, reducing congestion window.
2156 * Main question: may we further continue forward transmission
2157 * with the same cwnd?
2159 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2161 struct tcp_sock
*tp
= tcp_sk(sk
);
2164 /* Trick#1: The loss is proven. */
2168 /* Not-A-Trick#2 : Classic rule... */
2169 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2172 /* Trick#4: It is still not OK... But will it be useful to delay
2175 packets_out
= tp
->packets_out
;
2176 if (packets_out
<= tp
->reordering
&&
2177 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2178 !tcp_may_send_now(sk
)) {
2179 /* We have nothing to send. This connection is limited
2180 * either by receiver window or by application.
2185 /* If a thin stream is detected, retransmit after first
2186 * received dupack. Employ only if SACK is supported in order
2187 * to avoid possible corner-case series of spurious retransmissions
2188 * Use only if there are no unsent data.
2190 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2191 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2192 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2195 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2196 * retransmissions due to small network reorderings, we implement
2197 * Mitigation A.3 in the RFC and delay the retransmission for a short
2198 * interval if appropriate.
2200 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2201 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2202 !tcp_may_send_now(sk
))
2203 return !tcp_pause_early_retransmit(sk
, flag
);
2208 /* Detect loss in event "A" above by marking head of queue up as lost.
2209 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2210 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2211 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2212 * the maximum SACKed segments to pass before reaching this limit.
2214 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2216 struct tcp_sock
*tp
= tcp_sk(sk
);
2217 struct sk_buff
*skb
;
2221 /* Use SACK to deduce losses of new sequences sent during recovery */
2222 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2224 WARN_ON(packets
> tp
->packets_out
);
2225 if (tp
->lost_skb_hint
) {
2226 skb
= tp
->lost_skb_hint
;
2227 cnt
= tp
->lost_cnt_hint
;
2228 /* Head already handled? */
2229 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2232 skb
= tcp_write_queue_head(sk
);
2236 tcp_for_write_queue_from(skb
, sk
) {
2237 if (skb
== tcp_send_head(sk
))
2239 /* TODO: do this better */
2240 /* this is not the most efficient way to do this... */
2241 tp
->lost_skb_hint
= skb
;
2242 tp
->lost_cnt_hint
= cnt
;
2244 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2248 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2249 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2250 cnt
+= tcp_skb_pcount(skb
);
2252 if (cnt
> packets
) {
2253 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2254 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2255 (oldcnt
>= packets
))
2258 mss
= skb_shinfo(skb
)->gso_size
;
2259 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
,
2266 tcp_skb_mark_lost(tp
, skb
);
2271 tcp_verify_left_out(tp
);
2274 /* Account newly detected lost packet(s) */
2276 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2278 struct tcp_sock
*tp
= tcp_sk(sk
);
2280 if (tcp_is_reno(tp
)) {
2281 tcp_mark_head_lost(sk
, 1, 1);
2282 } else if (tcp_is_fack(tp
)) {
2283 int lost
= tp
->fackets_out
- tp
->reordering
;
2286 tcp_mark_head_lost(sk
, lost
, 0);
2288 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2289 if (sacked_upto
>= 0)
2290 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2291 else if (fast_rexmit
)
2292 tcp_mark_head_lost(sk
, 1, 1);
2296 /* CWND moderation, preventing bursts due to too big ACKs
2297 * in dubious situations.
2299 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2301 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2302 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2303 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2306 /* Nothing was retransmitted or returned timestamp is less
2307 * than timestamp of the first retransmission.
2309 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2311 return !tp
->retrans_stamp
||
2312 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2313 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2316 /* Undo procedures. */
2318 #if FASTRETRANS_DEBUG > 1
2319 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2321 struct tcp_sock
*tp
= tcp_sk(sk
);
2322 struct inet_sock
*inet
= inet_sk(sk
);
2324 if (sk
->sk_family
== AF_INET
) {
2325 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2327 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2328 tp
->snd_cwnd
, tcp_left_out(tp
),
2329 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2332 #if IS_ENABLED(CONFIG_IPV6)
2333 else if (sk
->sk_family
== AF_INET6
) {
2334 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2335 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2337 &np
->daddr
, ntohs(inet
->inet_dport
),
2338 tp
->snd_cwnd
, tcp_left_out(tp
),
2339 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2345 #define DBGUNDO(x...) do { } while (0)
2348 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2350 struct tcp_sock
*tp
= tcp_sk(sk
);
2353 struct sk_buff
*skb
;
2355 tcp_for_write_queue(skb
, sk
) {
2356 if (skb
== tcp_send_head(sk
))
2358 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2361 tcp_clear_all_retrans_hints(tp
);
2364 if (tp
->prior_ssthresh
) {
2365 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2367 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2368 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2370 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2372 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2373 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2374 tcp_ecn_withdraw_cwr(tp
);
2377 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2379 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2380 tp
->undo_marker
= 0;
2383 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2385 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2388 /* People celebrate: "We love our President!" */
2389 static bool tcp_try_undo_recovery(struct sock
*sk
)
2391 struct tcp_sock
*tp
= tcp_sk(sk
);
2393 if (tcp_may_undo(tp
)) {
2396 /* Happy end! We did not retransmit anything
2397 * or our original transmission succeeded.
2399 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2400 tcp_undo_cwnd_reduction(sk
, false);
2401 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2402 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2404 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2406 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2408 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2409 /* Hold old state until something *above* high_seq
2410 * is ACKed. For Reno it is MUST to prevent false
2411 * fast retransmits (RFC2582). SACK TCP is safe. */
2412 tcp_moderate_cwnd(tp
);
2415 tcp_set_ca_state(sk
, TCP_CA_Open
);
2419 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2420 static bool tcp_try_undo_dsack(struct sock
*sk
)
2422 struct tcp_sock
*tp
= tcp_sk(sk
);
2424 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2425 DBGUNDO(sk
, "D-SACK");
2426 tcp_undo_cwnd_reduction(sk
, false);
2427 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2433 /* We can clear retrans_stamp when there are no retransmissions in the
2434 * window. It would seem that it is trivially available for us in
2435 * tp->retrans_out, however, that kind of assumptions doesn't consider
2436 * what will happen if errors occur when sending retransmission for the
2437 * second time. ...It could the that such segment has only
2438 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2439 * the head skb is enough except for some reneging corner cases that
2440 * are not worth the effort.
2442 * Main reason for all this complexity is the fact that connection dying
2443 * time now depends on the validity of the retrans_stamp, in particular,
2444 * that successive retransmissions of a segment must not advance
2445 * retrans_stamp under any conditions.
2447 static bool tcp_any_retrans_done(const struct sock
*sk
)
2449 const struct tcp_sock
*tp
= tcp_sk(sk
);
2450 struct sk_buff
*skb
;
2452 if (tp
->retrans_out
)
2455 skb
= tcp_write_queue_head(sk
);
2456 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2462 /* Undo during loss recovery after partial ACK or using F-RTO. */
2463 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2465 struct tcp_sock
*tp
= tcp_sk(sk
);
2467 if (frto_undo
|| tcp_may_undo(tp
)) {
2468 tcp_undo_cwnd_reduction(sk
, true);
2470 DBGUNDO(sk
, "partial loss");
2471 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2473 NET_INC_STATS_BH(sock_net(sk
),
2474 LINUX_MIB_TCPSPURIOUSRTOS
);
2475 inet_csk(sk
)->icsk_retransmits
= 0;
2476 if (frto_undo
|| tcp_is_sack(tp
))
2477 tcp_set_ca_state(sk
, TCP_CA_Open
);
2483 /* The cwnd reduction in CWR and Recovery use the PRR algorithm
2484 * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/
2485 * It computes the number of packets to send (sndcnt) based on packets newly
2487 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2488 * cwnd reductions across a full RTT.
2489 * 2) If packets in flight is lower than ssthresh (such as due to excess
2490 * losses and/or application stalls), do not perform any further cwnd
2491 * reductions, but instead slow start up to ssthresh.
2493 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2495 struct tcp_sock
*tp
= tcp_sk(sk
);
2497 tp
->high_seq
= tp
->snd_nxt
;
2498 tp
->tlp_high_seq
= 0;
2499 tp
->snd_cwnd_cnt
= 0;
2500 tp
->prior_cwnd
= tp
->snd_cwnd
;
2501 tp
->prr_delivered
= 0;
2503 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2504 tcp_ecn_queue_cwr(tp
);
2507 static void tcp_cwnd_reduction(struct sock
*sk
, const int prior_unsacked
,
2510 struct tcp_sock
*tp
= tcp_sk(sk
);
2512 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2513 int newly_acked_sacked
= prior_unsacked
-
2514 (tp
->packets_out
- tp
->sacked_out
);
2516 tp
->prr_delivered
+= newly_acked_sacked
;
2517 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
2518 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2520 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2522 sndcnt
= min_t(int, delta
,
2523 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2524 newly_acked_sacked
) + 1);
2527 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2528 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2531 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2533 struct tcp_sock
*tp
= tcp_sk(sk
);
2535 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2536 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2537 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2538 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2539 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2541 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2544 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2545 void tcp_enter_cwr(struct sock
*sk
)
2547 struct tcp_sock
*tp
= tcp_sk(sk
);
2549 tp
->prior_ssthresh
= 0;
2550 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2551 tp
->undo_marker
= 0;
2552 tcp_init_cwnd_reduction(sk
);
2553 tcp_set_ca_state(sk
, TCP_CA_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);
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 (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
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 (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2700 /* Step 3.b. A timeout is spurious if not all data are
2701 * lost, i.e., never-retransmitted data are (s)acked.
2703 if (tcp_try_undo_loss(sk
, flag
& FLAG_ORIG_SACK_ACKED
))
2706 if (after(tp
->snd_nxt
, tp
->high_seq
) &&
2707 (flag
& FLAG_DATA_SACKED
|| is_dupack
)) {
2708 tp
->frto
= 0; /* Loss was real: 2nd part of step 3.a */
2709 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2710 tp
->high_seq
= tp
->snd_nxt
;
2711 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
2713 if (after(tp
->snd_nxt
, tp
->high_seq
))
2714 return; /* Step 2.b */
2720 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2721 tcp_try_undo_recovery(sk
);
2724 if (tcp_is_reno(tp
)) {
2725 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2726 * delivered. Lower inflight to clock out (re)tranmissions.
2728 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2729 tcp_add_reno_sack(sk
);
2730 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2731 tcp_reset_reno_sack(tp
);
2733 if (tcp_try_undo_loss(sk
, false))
2735 tcp_xmit_retransmit_queue(sk
);
2738 /* Undo during fast recovery after partial ACK. */
2739 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
,
2740 const int prior_unsacked
)
2742 struct tcp_sock
*tp
= tcp_sk(sk
);
2744 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2745 /* Plain luck! Hole if filled with delayed
2746 * packet, rather than with a retransmit.
2748 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2750 /* We are getting evidence that the reordering degree is higher
2751 * than we realized. If there are no retransmits out then we
2752 * can undo. Otherwise we clock out new packets but do not
2753 * mark more packets lost or retransmit more.
2755 if (tp
->retrans_out
) {
2756 tcp_cwnd_reduction(sk
, prior_unsacked
, 0);
2760 if (!tcp_any_retrans_done(sk
))
2761 tp
->retrans_stamp
= 0;
2763 DBGUNDO(sk
, "partial recovery");
2764 tcp_undo_cwnd_reduction(sk
, true);
2765 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2766 tcp_try_keep_open(sk
);
2772 /* Process an event, which can update packets-in-flight not trivially.
2773 * Main goal of this function is to calculate new estimate for left_out,
2774 * taking into account both packets sitting in receiver's buffer and
2775 * packets lost by network.
2777 * Besides that it does CWND reduction, when packet loss is detected
2778 * and changes state of machine.
2780 * It does _not_ decide what to send, it is made in function
2781 * tcp_xmit_retransmit_queue().
2783 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2784 const int prior_unsacked
,
2785 bool is_dupack
, int flag
)
2787 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2788 struct tcp_sock
*tp
= tcp_sk(sk
);
2789 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2790 (tcp_fackets_out(tp
) > tp
->reordering
));
2791 int fast_rexmit
= 0;
2793 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2795 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2796 tp
->fackets_out
= 0;
2798 /* Now state machine starts.
2799 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2800 if (flag
& FLAG_ECE
)
2801 tp
->prior_ssthresh
= 0;
2803 /* B. In all the states check for reneging SACKs. */
2804 if (tcp_check_sack_reneging(sk
, flag
))
2807 /* C. Check consistency of the current state. */
2808 tcp_verify_left_out(tp
);
2810 /* D. Check state exit conditions. State can be terminated
2811 * when high_seq is ACKed. */
2812 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2813 WARN_ON(tp
->retrans_out
!= 0);
2814 tp
->retrans_stamp
= 0;
2815 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2816 switch (icsk
->icsk_ca_state
) {
2818 /* CWR is to be held something *above* high_seq
2819 * is ACKed for CWR bit to reach receiver. */
2820 if (tp
->snd_una
!= tp
->high_seq
) {
2821 tcp_end_cwnd_reduction(sk
);
2822 tcp_set_ca_state(sk
, TCP_CA_Open
);
2826 case TCP_CA_Recovery
:
2827 if (tcp_is_reno(tp
))
2828 tcp_reset_reno_sack(tp
);
2829 if (tcp_try_undo_recovery(sk
))
2831 tcp_end_cwnd_reduction(sk
);
2836 /* E. Process state. */
2837 switch (icsk
->icsk_ca_state
) {
2838 case TCP_CA_Recovery
:
2839 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2840 if (tcp_is_reno(tp
) && is_dupack
)
2841 tcp_add_reno_sack(sk
);
2843 if (tcp_try_undo_partial(sk
, acked
, prior_unsacked
))
2845 /* Partial ACK arrived. Force fast retransmit. */
2846 do_lost
= tcp_is_reno(tp
) ||
2847 tcp_fackets_out(tp
) > tp
->reordering
;
2849 if (tcp_try_undo_dsack(sk
)) {
2850 tcp_try_keep_open(sk
);
2855 tcp_process_loss(sk
, flag
, is_dupack
);
2856 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2858 /* Fall through to processing in Open state. */
2860 if (tcp_is_reno(tp
)) {
2861 if (flag
& FLAG_SND_UNA_ADVANCED
)
2862 tcp_reset_reno_sack(tp
);
2864 tcp_add_reno_sack(sk
);
2867 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2868 tcp_try_undo_dsack(sk
);
2870 if (!tcp_time_to_recover(sk
, flag
)) {
2871 tcp_try_to_open(sk
, flag
, prior_unsacked
);
2875 /* MTU probe failure: don't reduce cwnd */
2876 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2877 icsk
->icsk_mtup
.probe_size
&&
2878 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2879 tcp_mtup_probe_failed(sk
);
2880 /* Restores the reduction we did in tcp_mtup_probe() */
2882 tcp_simple_retransmit(sk
);
2886 /* Otherwise enter Recovery state */
2887 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2892 tcp_update_scoreboard(sk
, fast_rexmit
);
2893 tcp_cwnd_reduction(sk
, prior_unsacked
, fast_rexmit
);
2894 tcp_xmit_retransmit_queue(sk
);
2897 static inline bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2898 long seq_rtt_us
, long sack_rtt_us
)
2900 const struct tcp_sock
*tp
= tcp_sk(sk
);
2902 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2903 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2904 * Karn's algorithm forbids taking RTT if some retransmitted data
2905 * is acked (RFC6298).
2907 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2911 seq_rtt_us
= sack_rtt_us
;
2913 /* RTTM Rule: A TSecr value received in a segment is used to
2914 * update the averaged RTT measurement only if the segment
2915 * acknowledges some new data, i.e., only if it advances the
2916 * left edge of the send window.
2917 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2919 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2921 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
2926 tcp_rtt_estimator(sk
, seq_rtt_us
);
2929 /* RFC6298: only reset backoff on valid RTT measurement. */
2930 inet_csk(sk
)->icsk_backoff
= 0;
2934 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2935 static void tcp_synack_rtt_meas(struct sock
*sk
, const u32 synack_stamp
)
2937 struct tcp_sock
*tp
= tcp_sk(sk
);
2938 long seq_rtt_us
= -1L;
2940 if (synack_stamp
&& !tp
->total_retrans
)
2941 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- synack_stamp
);
2943 /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
2944 * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
2947 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, seq_rtt_us
, -1L);
2950 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2952 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2954 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2955 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2958 /* Restart timer after forward progress on connection.
2959 * RFC2988 recommends to restart timer to now+rto.
2961 void tcp_rearm_rto(struct sock
*sk
)
2963 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2964 struct tcp_sock
*tp
= tcp_sk(sk
);
2966 /* If the retrans timer is currently being used by Fast Open
2967 * for SYN-ACK retrans purpose, stay put.
2969 if (tp
->fastopen_rsk
)
2972 if (!tp
->packets_out
) {
2973 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2975 u32 rto
= inet_csk(sk
)->icsk_rto
;
2976 /* Offset the time elapsed after installing regular RTO */
2977 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
2978 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
2979 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
2980 const u32 rto_time_stamp
=
2981 tcp_skb_timestamp(skb
) + rto
;
2982 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
2983 /* delta may not be positive if the socket is locked
2984 * when the retrans timer fires and is rescheduled.
2989 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
2994 /* This function is called when the delayed ER timer fires. TCP enters
2995 * fast recovery and performs fast-retransmit.
2997 void tcp_resume_early_retransmit(struct sock
*sk
)
2999 struct tcp_sock
*tp
= tcp_sk(sk
);
3003 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3004 if (!tp
->do_early_retrans
)
3007 tcp_enter_recovery(sk
, false);
3008 tcp_update_scoreboard(sk
, 1);
3009 tcp_xmit_retransmit_queue(sk
);
3012 /* If we get here, the whole TSO packet has not been acked. */
3013 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3015 struct tcp_sock
*tp
= tcp_sk(sk
);
3018 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3020 packets_acked
= tcp_skb_pcount(skb
);
3021 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3023 packets_acked
-= tcp_skb_pcount(skb
);
3025 if (packets_acked
) {
3026 BUG_ON(tcp_skb_pcount(skb
) == 0);
3027 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3030 return packets_acked
;
3033 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3036 const struct skb_shared_info
*shinfo
;
3038 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3039 if (likely(!(sk
->sk_tsflags
& SOF_TIMESTAMPING_TX_ACK
)))
3042 shinfo
= skb_shinfo(skb
);
3043 if ((shinfo
->tx_flags
& SKBTX_ACK_TSTAMP
) &&
3044 between(shinfo
->tskey
, prior_snd_una
, tcp_sk(sk
)->snd_una
- 1))
3045 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3048 /* Remove acknowledged frames from the retransmission queue. If our packet
3049 * is before the ack sequence we can discard it as it's confirmed to have
3050 * arrived at the other end.
3052 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3053 u32 prior_snd_una
, long sack_rtt_us
)
3055 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3056 struct skb_mstamp first_ackt
, last_ackt
, now
;
3057 struct tcp_sock
*tp
= tcp_sk(sk
);
3058 u32 prior_sacked
= tp
->sacked_out
;
3059 u32 reord
= tp
->packets_out
;
3060 bool fully_acked
= true;
3061 long ca_seq_rtt_us
= -1L;
3062 long seq_rtt_us
= -1L;
3063 struct sk_buff
*skb
;
3070 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3071 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3072 u8 sacked
= scb
->sacked
;
3075 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3077 /* Determine how many packets and what bytes were acked, tso and else */
3078 if (after(scb
->end_seq
, tp
->snd_una
)) {
3079 if (tcp_skb_pcount(skb
) == 1 ||
3080 !after(tp
->snd_una
, scb
->seq
))
3083 acked_pcount
= tcp_tso_acked(sk
, skb
);
3087 fully_acked
= false;
3089 /* Speedup tcp_unlink_write_queue() and next loop */
3090 prefetchw(skb
->next
);
3091 acked_pcount
= tcp_skb_pcount(skb
);
3094 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3095 if (sacked
& TCPCB_SACKED_RETRANS
)
3096 tp
->retrans_out
-= acked_pcount
;
3097 flag
|= FLAG_RETRANS_DATA_ACKED
;
3099 last_ackt
= skb
->skb_mstamp
;
3100 WARN_ON_ONCE(last_ackt
.v64
== 0);
3101 if (!first_ackt
.v64
)
3102 first_ackt
= last_ackt
;
3104 if (!(sacked
& TCPCB_SACKED_ACKED
))
3105 reord
= min(pkts_acked
, reord
);
3106 if (!after(scb
->end_seq
, tp
->high_seq
))
3107 flag
|= FLAG_ORIG_SACK_ACKED
;
3110 if (sacked
& TCPCB_SACKED_ACKED
)
3111 tp
->sacked_out
-= acked_pcount
;
3112 if (sacked
& TCPCB_LOST
)
3113 tp
->lost_out
-= acked_pcount
;
3115 tp
->packets_out
-= acked_pcount
;
3116 pkts_acked
+= acked_pcount
;
3118 /* Initial outgoing SYN's get put onto the write_queue
3119 * just like anything else we transmit. It is not
3120 * true data, and if we misinform our callers that
3121 * this ACK acks real data, we will erroneously exit
3122 * connection startup slow start one packet too
3123 * quickly. This is severely frowned upon behavior.
3125 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3126 flag
|= FLAG_DATA_ACKED
;
3128 flag
|= FLAG_SYN_ACKED
;
3129 tp
->retrans_stamp
= 0;
3135 tcp_unlink_write_queue(skb
, sk
);
3136 sk_wmem_free_skb(sk
, skb
);
3137 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3138 tp
->retransmit_skb_hint
= NULL
;
3139 if (unlikely(skb
== tp
->lost_skb_hint
))
3140 tp
->lost_skb_hint
= NULL
;
3143 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3144 tp
->snd_up
= tp
->snd_una
;
3146 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3147 flag
|= FLAG_SACK_RENEGING
;
3149 skb_mstamp_get(&now
);
3150 if (likely(first_ackt
.v64
)) {
3151 seq_rtt_us
= skb_mstamp_us_delta(&now
, &first_ackt
);
3152 ca_seq_rtt_us
= skb_mstamp_us_delta(&now
, &last_ackt
);
3155 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
);
3157 if (flag
& FLAG_ACKED
) {
3158 const struct tcp_congestion_ops
*ca_ops
3159 = inet_csk(sk
)->icsk_ca_ops
;
3162 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3163 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3164 tcp_mtup_probe_success(sk
);
3167 if (tcp_is_reno(tp
)) {
3168 tcp_remove_reno_sacks(sk
, pkts_acked
);
3172 /* Non-retransmitted hole got filled? That's reordering */
3173 if (reord
< prior_fackets
)
3174 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3176 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3177 prior_sacked
- tp
->sacked_out
;
3178 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3181 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3183 if (ca_ops
->pkts_acked
)
3184 ca_ops
->pkts_acked(sk
, pkts_acked
, ca_seq_rtt_us
);
3186 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3187 sack_rtt_us
> skb_mstamp_us_delta(&now
, &skb
->skb_mstamp
)) {
3188 /* Do not re-arm RTO if the sack RTT is measured from data sent
3189 * after when the head was last (re)transmitted. Otherwise the
3190 * timeout may continue to extend in loss recovery.
3195 #if FASTRETRANS_DEBUG > 0
3196 WARN_ON((int)tp
->sacked_out
< 0);
3197 WARN_ON((int)tp
->lost_out
< 0);
3198 WARN_ON((int)tp
->retrans_out
< 0);
3199 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3200 icsk
= inet_csk(sk
);
3202 pr_debug("Leak l=%u %d\n",
3203 tp
->lost_out
, icsk
->icsk_ca_state
);
3206 if (tp
->sacked_out
) {
3207 pr_debug("Leak s=%u %d\n",
3208 tp
->sacked_out
, icsk
->icsk_ca_state
);
3211 if (tp
->retrans_out
) {
3212 pr_debug("Leak r=%u %d\n",
3213 tp
->retrans_out
, icsk
->icsk_ca_state
);
3214 tp
->retrans_out
= 0;
3221 static void tcp_ack_probe(struct sock
*sk
)
3223 const struct tcp_sock
*tp
= tcp_sk(sk
);
3224 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3226 /* Was it a usable window open? */
3228 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3229 icsk
->icsk_backoff
= 0;
3230 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3231 /* Socket must be waked up by subsequent tcp_data_snd_check().
3232 * This function is not for random using!
3235 unsigned long when
= inet_csk_rto_backoff(icsk
, TCP_RTO_MAX
);
3237 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3242 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3244 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3245 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3248 /* Decide wheather to run the increase function of congestion control. */
3249 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3251 if (tcp_in_cwnd_reduction(sk
))
3254 /* If reordering is high then always grow cwnd whenever data is
3255 * delivered regardless of its ordering. Otherwise stay conservative
3256 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3257 * new SACK or ECE mark may first advance cwnd here and later reduce
3258 * cwnd in tcp_fastretrans_alert() based on more states.
3260 if (tcp_sk(sk
)->reordering
> sysctl_tcp_reordering
)
3261 return flag
& FLAG_FORWARD_PROGRESS
;
3263 return flag
& FLAG_DATA_ACKED
;
3266 /* Check that window update is acceptable.
3267 * The function assumes that snd_una<=ack<=snd_next.
3269 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3270 const u32 ack
, const u32 ack_seq
,
3273 return after(ack
, tp
->snd_una
) ||
3274 after(ack_seq
, tp
->snd_wl1
) ||
3275 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3278 /* Update our send window.
3280 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3281 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3283 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3286 struct tcp_sock
*tp
= tcp_sk(sk
);
3288 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3290 if (likely(!tcp_hdr(skb
)->syn
))
3291 nwin
<<= tp
->rx_opt
.snd_wscale
;
3293 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3294 flag
|= FLAG_WIN_UPDATE
;
3295 tcp_update_wl(tp
, ack_seq
);
3297 if (tp
->snd_wnd
!= nwin
) {
3300 /* Note, it is the only place, where
3301 * fast path is recovered for sending TCP.
3304 tcp_fast_path_check(sk
);
3306 if (nwin
> tp
->max_window
) {
3307 tp
->max_window
= nwin
;
3308 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3318 /* RFC 5961 7 [ACK Throttling] */
3319 static void tcp_send_challenge_ack(struct sock
*sk
)
3321 /* unprotected vars, we dont care of overwrites */
3322 static u32 challenge_timestamp
;
3323 static unsigned int challenge_count
;
3324 u32 now
= jiffies
/ HZ
;
3326 if (now
!= challenge_timestamp
) {
3327 challenge_timestamp
= now
;
3328 challenge_count
= 0;
3330 if (++challenge_count
<= sysctl_tcp_challenge_ack_limit
) {
3331 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3336 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3338 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3339 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3342 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3344 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3345 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3346 * extra check below makes sure this can only happen
3347 * for pure ACK frames. -DaveM
3349 * Not only, also it occurs for expired timestamps.
3352 if (tcp_paws_check(&tp
->rx_opt
, 0))
3353 tcp_store_ts_recent(tp
);
3357 /* This routine deals with acks during a TLP episode.
3358 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3360 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3362 struct tcp_sock
*tp
= tcp_sk(sk
);
3363 bool is_tlp_dupack
= (ack
== tp
->tlp_high_seq
) &&
3364 !(flag
& (FLAG_SND_UNA_ADVANCED
|
3365 FLAG_NOT_DUP
| FLAG_DATA_SACKED
));
3367 /* Mark the end of TLP episode on receiving TLP dupack or when
3368 * ack is after tlp_high_seq.
3370 if (is_tlp_dupack
) {
3371 tp
->tlp_high_seq
= 0;
3375 if (after(ack
, tp
->tlp_high_seq
)) {
3376 tp
->tlp_high_seq
= 0;
3377 /* Don't reduce cwnd if DSACK arrives for TLP retrans. */
3378 if (!(flag
& FLAG_DSACKING_ACK
)) {
3379 tcp_init_cwnd_reduction(sk
);
3380 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3381 tcp_end_cwnd_reduction(sk
);
3382 tcp_try_keep_open(sk
);
3383 NET_INC_STATS_BH(sock_net(sk
),
3384 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3389 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3391 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3393 if (icsk
->icsk_ca_ops
->in_ack_event
)
3394 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3397 /* This routine deals with incoming acks, but not outgoing ones. */
3398 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3400 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3401 struct tcp_sock
*tp
= tcp_sk(sk
);
3402 u32 prior_snd_una
= tp
->snd_una
;
3403 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3404 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3405 bool is_dupack
= false;
3407 int prior_packets
= tp
->packets_out
;
3408 const int prior_unsacked
= tp
->packets_out
- tp
->sacked_out
;
3409 int acked
= 0; /* Number of packets newly acked */
3410 long sack_rtt_us
= -1L;
3412 /* We very likely will need to access write queue head. */
3413 prefetchw(sk
->sk_write_queue
.next
);
3415 /* If the ack is older than previous acks
3416 * then we can probably ignore it.
3418 if (before(ack
, prior_snd_una
)) {
3419 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3420 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3421 tcp_send_challenge_ack(sk
);
3427 /* If the ack includes data we haven't sent yet, discard
3428 * this segment (RFC793 Section 3.9).
3430 if (after(ack
, tp
->snd_nxt
))
3433 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3434 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3437 if (after(ack
, prior_snd_una
)) {
3438 flag
|= FLAG_SND_UNA_ADVANCED
;
3439 icsk
->icsk_retransmits
= 0;
3442 prior_fackets
= tp
->fackets_out
;
3444 /* ts_recent update must be made after we are sure that the packet
3447 if (flag
& FLAG_UPDATE_TS_RECENT
)
3448 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3450 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3451 /* Window is constant, pure forward advance.
3452 * No more checks are required.
3453 * Note, we use the fact that SND.UNA>=SND.WL2.
3455 tcp_update_wl(tp
, ack_seq
);
3457 flag
|= FLAG_WIN_UPDATE
;
3459 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3461 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3463 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3465 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3468 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3470 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3472 if (TCP_SKB_CB(skb
)->sacked
)
3473 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3476 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3478 ack_ev_flags
|= CA_ACK_ECE
;
3481 if (flag
& FLAG_WIN_UPDATE
)
3482 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3484 tcp_in_ack_event(sk
, ack_ev_flags
);
3487 /* We passed data and got it acked, remove any soft error
3488 * log. Something worked...
3490 sk
->sk_err_soft
= 0;
3491 icsk
->icsk_probes_out
= 0;
3492 tp
->rcv_tstamp
= tcp_time_stamp
;
3496 /* See if we can take anything off of the retransmit queue. */
3497 acked
= tp
->packets_out
;
3498 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
,
3500 acked
-= tp
->packets_out
;
3502 /* Advance cwnd if state allows */
3503 if (tcp_may_raise_cwnd(sk
, flag
))
3504 tcp_cong_avoid(sk
, ack
, acked
);
3506 if (tcp_ack_is_dubious(sk
, flag
)) {
3507 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3508 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3511 if (tp
->tlp_high_seq
)
3512 tcp_process_tlp_ack(sk
, ack
, flag
);
3514 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3515 struct dst_entry
*dst
= __sk_dst_get(sk
);
3520 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3521 tcp_schedule_loss_probe(sk
);
3522 tcp_update_pacing_rate(sk
);
3526 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3527 if (flag
& FLAG_DSACKING_ACK
)
3528 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3530 /* If this ack opens up a zero window, clear backoff. It was
3531 * being used to time the probes, and is probably far higher than
3532 * it needs to be for normal retransmission.
3534 if (tcp_send_head(sk
))
3537 if (tp
->tlp_high_seq
)
3538 tcp_process_tlp_ack(sk
, ack
, flag
);
3542 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3546 /* If data was SACKed, tag it and see if we should send more data.
3547 * If data was DSACKed, see if we can undo a cwnd reduction.
3549 if (TCP_SKB_CB(skb
)->sacked
) {
3550 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3552 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3556 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3560 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3561 * But, this can also be called on packets in the established flow when
3562 * the fast version below fails.
3564 void tcp_parse_options(const struct sk_buff
*skb
,
3565 struct tcp_options_received
*opt_rx
, int estab
,
3566 struct tcp_fastopen_cookie
*foc
)
3568 const unsigned char *ptr
;
3569 const struct tcphdr
*th
= tcp_hdr(skb
);
3570 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3572 ptr
= (const unsigned char *)(th
+ 1);
3573 opt_rx
->saw_tstamp
= 0;
3575 while (length
> 0) {
3576 int opcode
= *ptr
++;
3582 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3587 if (opsize
< 2) /* "silly options" */
3589 if (opsize
> length
)
3590 return; /* don't parse partial options */
3593 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3594 u16 in_mss
= get_unaligned_be16(ptr
);
3596 if (opt_rx
->user_mss
&&
3597 opt_rx
->user_mss
< in_mss
)
3598 in_mss
= opt_rx
->user_mss
;
3599 opt_rx
->mss_clamp
= in_mss
;
3604 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3605 !estab
&& sysctl_tcp_window_scaling
) {
3606 __u8 snd_wscale
= *(__u8
*)ptr
;
3607 opt_rx
->wscale_ok
= 1;
3608 if (snd_wscale
> 14) {
3609 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3614 opt_rx
->snd_wscale
= snd_wscale
;
3617 case TCPOPT_TIMESTAMP
:
3618 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3619 ((estab
&& opt_rx
->tstamp_ok
) ||
3620 (!estab
&& sysctl_tcp_timestamps
))) {
3621 opt_rx
->saw_tstamp
= 1;
3622 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3623 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3626 case TCPOPT_SACK_PERM
:
3627 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3628 !estab
&& sysctl_tcp_sack
) {
3629 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3630 tcp_sack_reset(opt_rx
);
3635 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3636 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3638 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3641 #ifdef CONFIG_TCP_MD5SIG
3644 * The MD5 Hash has already been
3645 * checked (see tcp_v{4,6}_do_rcv()).
3650 /* Fast Open option shares code 254 using a
3651 * 16 bits magic number. It's valid only in
3652 * SYN or SYN-ACK with an even size.
3654 if (opsize
< TCPOLEN_EXP_FASTOPEN_BASE
||
3655 get_unaligned_be16(ptr
) != TCPOPT_FASTOPEN_MAGIC
||
3656 foc
== NULL
|| !th
->syn
|| (opsize
& 1))
3658 foc
->len
= opsize
- TCPOLEN_EXP_FASTOPEN_BASE
;
3659 if (foc
->len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3660 foc
->len
<= TCP_FASTOPEN_COOKIE_MAX
)
3661 memcpy(foc
->val
, ptr
+ 2, foc
->len
);
3662 else if (foc
->len
!= 0)
3672 EXPORT_SYMBOL(tcp_parse_options
);
3674 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3676 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3678 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3679 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3680 tp
->rx_opt
.saw_tstamp
= 1;
3682 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3685 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3687 tp
->rx_opt
.rcv_tsecr
= 0;
3693 /* Fast parse options. This hopes to only see timestamps.
3694 * If it is wrong it falls back on tcp_parse_options().
3696 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3697 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3699 /* In the spirit of fast parsing, compare doff directly to constant
3700 * values. Because equality is used, short doff can be ignored here.
3702 if (th
->doff
== (sizeof(*th
) / 4)) {
3703 tp
->rx_opt
.saw_tstamp
= 0;
3705 } else if (tp
->rx_opt
.tstamp_ok
&&
3706 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3707 if (tcp_parse_aligned_timestamp(tp
, th
))
3711 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3712 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3713 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3718 #ifdef CONFIG_TCP_MD5SIG
3720 * Parse MD5 Signature option
3722 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3724 int length
= (th
->doff
<< 2) - sizeof(*th
);
3725 const u8
*ptr
= (const u8
*)(th
+ 1);
3727 /* If the TCP option is too short, we can short cut */
3728 if (length
< TCPOLEN_MD5SIG
)
3731 while (length
> 0) {
3732 int opcode
= *ptr
++;
3743 if (opsize
< 2 || opsize
> length
)
3745 if (opcode
== TCPOPT_MD5SIG
)
3746 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3753 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3756 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3758 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3759 * it can pass through stack. So, the following predicate verifies that
3760 * this segment is not used for anything but congestion avoidance or
3761 * fast retransmit. Moreover, we even are able to eliminate most of such
3762 * second order effects, if we apply some small "replay" window (~RTO)
3763 * to timestamp space.
3765 * All these measures still do not guarantee that we reject wrapped ACKs
3766 * on networks with high bandwidth, when sequence space is recycled fastly,
3767 * but it guarantees that such events will be very rare and do not affect
3768 * connection seriously. This doesn't look nice, but alas, PAWS is really
3771 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3772 * states that events when retransmit arrives after original data are rare.
3773 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3774 * the biggest problem on large power networks even with minor reordering.
3775 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3776 * up to bandwidth of 18Gigabit/sec. 8) ]
3779 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3781 const struct tcp_sock
*tp
= tcp_sk(sk
);
3782 const struct tcphdr
*th
= tcp_hdr(skb
);
3783 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3784 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3786 return (/* 1. Pure ACK with correct sequence number. */
3787 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3789 /* 2. ... and duplicate ACK. */
3790 ack
== tp
->snd_una
&&
3792 /* 3. ... and does not update window. */
3793 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3795 /* 4. ... and sits in replay window. */
3796 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3799 static inline bool tcp_paws_discard(const struct sock
*sk
,
3800 const struct sk_buff
*skb
)
3802 const struct tcp_sock
*tp
= tcp_sk(sk
);
3804 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3805 !tcp_disordered_ack(sk
, skb
);
3808 /* Check segment sequence number for validity.
3810 * Segment controls are considered valid, if the segment
3811 * fits to the window after truncation to the window. Acceptability
3812 * of data (and SYN, FIN, of course) is checked separately.
3813 * See tcp_data_queue(), for example.
3815 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3816 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3817 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3818 * (borrowed from freebsd)
3821 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3823 return !before(end_seq
, tp
->rcv_wup
) &&
3824 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3827 /* When we get a reset we do this. */
3828 void tcp_reset(struct sock
*sk
)
3830 /* We want the right error as BSD sees it (and indeed as we do). */
3831 switch (sk
->sk_state
) {
3833 sk
->sk_err
= ECONNREFUSED
;
3835 case TCP_CLOSE_WAIT
:
3841 sk
->sk_err
= ECONNRESET
;
3843 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3846 if (!sock_flag(sk
, SOCK_DEAD
))
3847 sk
->sk_error_report(sk
);
3853 * Process the FIN bit. This now behaves as it is supposed to work
3854 * and the FIN takes effect when it is validly part of sequence
3855 * space. Not before when we get holes.
3857 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3858 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3861 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3862 * close and we go into CLOSING (and later onto TIME-WAIT)
3864 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3866 static void tcp_fin(struct sock
*sk
)
3868 struct tcp_sock
*tp
= tcp_sk(sk
);
3869 const struct dst_entry
*dst
;
3871 inet_csk_schedule_ack(sk
);
3873 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3874 sock_set_flag(sk
, SOCK_DONE
);
3876 switch (sk
->sk_state
) {
3878 case TCP_ESTABLISHED
:
3879 /* Move to CLOSE_WAIT */
3880 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3881 dst
= __sk_dst_get(sk
);
3882 if (!dst
|| !dst_metric(dst
, RTAX_QUICKACK
))
3883 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3886 case TCP_CLOSE_WAIT
:
3888 /* Received a retransmission of the FIN, do
3893 /* RFC793: Remain in the LAST-ACK state. */
3897 /* This case occurs when a simultaneous close
3898 * happens, we must ack the received FIN and
3899 * enter the CLOSING state.
3902 tcp_set_state(sk
, TCP_CLOSING
);
3905 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3907 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3910 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3911 * cases we should never reach this piece of code.
3913 pr_err("%s: Impossible, sk->sk_state=%d\n",
3914 __func__
, sk
->sk_state
);
3918 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3919 * Probably, we should reset in this case. For now drop them.
3921 __skb_queue_purge(&tp
->out_of_order_queue
);
3922 if (tcp_is_sack(tp
))
3923 tcp_sack_reset(&tp
->rx_opt
);
3926 if (!sock_flag(sk
, SOCK_DEAD
)) {
3927 sk
->sk_state_change(sk
);
3929 /* Do not send POLL_HUP for half duplex close. */
3930 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3931 sk
->sk_state
== TCP_CLOSE
)
3932 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
3934 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
3938 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
3941 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3942 if (before(seq
, sp
->start_seq
))
3943 sp
->start_seq
= seq
;
3944 if (after(end_seq
, sp
->end_seq
))
3945 sp
->end_seq
= end_seq
;
3951 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
3953 struct tcp_sock
*tp
= tcp_sk(sk
);
3955 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3958 if (before(seq
, tp
->rcv_nxt
))
3959 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
3961 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
3963 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3965 tp
->rx_opt
.dsack
= 1;
3966 tp
->duplicate_sack
[0].start_seq
= seq
;
3967 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3971 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
3973 struct tcp_sock
*tp
= tcp_sk(sk
);
3975 if (!tp
->rx_opt
.dsack
)
3976 tcp_dsack_set(sk
, seq
, end_seq
);
3978 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3981 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
3983 struct tcp_sock
*tp
= tcp_sk(sk
);
3985 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3986 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3987 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
3988 tcp_enter_quickack_mode(sk
);
3990 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3991 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3993 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3994 end_seq
= tp
->rcv_nxt
;
3995 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4002 /* These routines update the SACK block as out-of-order packets arrive or
4003 * in-order packets close up the sequence space.
4005 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4008 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4009 struct tcp_sack_block
*swalk
= sp
+ 1;
4011 /* See if the recent change to the first SACK eats into
4012 * or hits the sequence space of other SACK blocks, if so coalesce.
4014 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4015 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4018 /* Zap SWALK, by moving every further SACK up by one slot.
4019 * Decrease num_sacks.
4021 tp
->rx_opt
.num_sacks
--;
4022 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4026 this_sack
++, swalk
++;
4030 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4032 struct tcp_sock
*tp
= tcp_sk(sk
);
4033 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4034 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4040 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4041 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4042 /* Rotate this_sack to the first one. */
4043 for (; this_sack
> 0; this_sack
--, sp
--)
4044 swap(*sp
, *(sp
- 1));
4046 tcp_sack_maybe_coalesce(tp
);
4051 /* Could not find an adjacent existing SACK, build a new one,
4052 * put it at the front, and shift everyone else down. We
4053 * always know there is at least one SACK present already here.
4055 * If the sack array is full, forget about the last one.
4057 if (this_sack
>= TCP_NUM_SACKS
) {
4059 tp
->rx_opt
.num_sacks
--;
4062 for (; this_sack
> 0; this_sack
--, sp
--)
4066 /* Build the new head SACK, and we're done. */
4067 sp
->start_seq
= seq
;
4068 sp
->end_seq
= end_seq
;
4069 tp
->rx_opt
.num_sacks
++;
4072 /* RCV.NXT advances, some SACKs should be eaten. */
4074 static void tcp_sack_remove(struct tcp_sock
*tp
)
4076 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4077 int num_sacks
= tp
->rx_opt
.num_sacks
;
4080 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4081 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4082 tp
->rx_opt
.num_sacks
= 0;
4086 for (this_sack
= 0; this_sack
< num_sacks
;) {
4087 /* Check if the start of the sack is covered by RCV.NXT. */
4088 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4091 /* RCV.NXT must cover all the block! */
4092 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4094 /* Zap this SACK, by moving forward any other SACKS. */
4095 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4096 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4103 tp
->rx_opt
.num_sacks
= num_sacks
;
4107 * tcp_try_coalesce - try to merge skb to prior one
4110 * @from: buffer to add in queue
4111 * @fragstolen: pointer to boolean
4113 * Before queueing skb @from after @to, try to merge them
4114 * to reduce overall memory use and queue lengths, if cost is small.
4115 * Packets in ofo or receive queues can stay a long time.
4116 * Better try to coalesce them right now to avoid future collapses.
4117 * Returns true if caller should free @from instead of queueing it
4119 static bool tcp_try_coalesce(struct sock
*sk
,
4121 struct sk_buff
*from
,
4126 *fragstolen
= false;
4128 /* Its possible this segment overlaps with prior segment in queue */
4129 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4132 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4135 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4136 sk_mem_charge(sk
, delta
);
4137 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4138 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4139 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4140 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4144 /* This one checks to see if we can put data from the
4145 * out_of_order queue into the receive_queue.
4147 static void tcp_ofo_queue(struct sock
*sk
)
4149 struct tcp_sock
*tp
= tcp_sk(sk
);
4150 __u32 dsack_high
= tp
->rcv_nxt
;
4151 struct sk_buff
*skb
, *tail
;
4152 bool fragstolen
, eaten
;
4154 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4155 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4158 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4159 __u32 dsack
= dsack_high
;
4160 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4161 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4162 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4165 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4166 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4167 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4171 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4172 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4173 TCP_SKB_CB(skb
)->end_seq
);
4175 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4176 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4177 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4179 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4180 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4183 kfree_skb_partial(skb
, fragstolen
);
4187 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4188 static int tcp_prune_queue(struct sock
*sk
);
4190 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4193 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4194 !sk_rmem_schedule(sk
, skb
, size
)) {
4196 if (tcp_prune_queue(sk
) < 0)
4199 if (!sk_rmem_schedule(sk
, skb
, size
)) {
4200 if (!tcp_prune_ofo_queue(sk
))
4203 if (!sk_rmem_schedule(sk
, skb
, size
))
4210 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4212 struct tcp_sock
*tp
= tcp_sk(sk
);
4213 struct sk_buff
*skb1
;
4216 tcp_ecn_check_ce(tp
, skb
);
4218 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4219 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4224 /* Disable header prediction. */
4226 inet_csk_schedule_ack(sk
);
4228 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4229 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4230 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4232 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4234 /* Initial out of order segment, build 1 SACK. */
4235 if (tcp_is_sack(tp
)) {
4236 tp
->rx_opt
.num_sacks
= 1;
4237 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4238 tp
->selective_acks
[0].end_seq
=
4239 TCP_SKB_CB(skb
)->end_seq
;
4241 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4245 seq
= TCP_SKB_CB(skb
)->seq
;
4246 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4248 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4251 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4252 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4254 tcp_grow_window(sk
, skb
);
4255 kfree_skb_partial(skb
, fragstolen
);
4259 if (!tp
->rx_opt
.num_sacks
||
4260 tp
->selective_acks
[0].end_seq
!= seq
)
4263 /* Common case: data arrive in order after hole. */
4264 tp
->selective_acks
[0].end_seq
= end_seq
;
4268 /* Find place to insert this segment. */
4270 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4272 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4276 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4279 /* Do skb overlap to previous one? */
4280 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4281 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4282 /* All the bits are present. Drop. */
4283 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4286 tcp_dsack_set(sk
, seq
, end_seq
);
4289 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4290 /* Partial overlap. */
4291 tcp_dsack_set(sk
, seq
,
4292 TCP_SKB_CB(skb1
)->end_seq
);
4294 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4298 skb1
= skb_queue_prev(
4299 &tp
->out_of_order_queue
,
4304 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4306 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4308 /* And clean segments covered by new one as whole. */
4309 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4310 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4312 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4314 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4315 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4319 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4320 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4321 TCP_SKB_CB(skb1
)->end_seq
);
4322 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4327 if (tcp_is_sack(tp
))
4328 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4331 tcp_grow_window(sk
, skb
);
4332 skb_set_owner_r(skb
, sk
);
4336 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4340 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4342 __skb_pull(skb
, hdrlen
);
4344 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4345 tcp_sk(sk
)->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4347 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4348 skb_set_owner_r(skb
, sk
);
4353 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4355 struct sk_buff
*skb
;
4361 skb
= alloc_skb(size
, sk
->sk_allocation
);
4365 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4368 if (memcpy_fromiovec(skb_put(skb
, size
), msg
->msg_iov
, size
))
4371 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4372 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4373 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4375 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4376 WARN_ON_ONCE(fragstolen
); /* should not happen */
4387 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4389 struct tcp_sock
*tp
= tcp_sk(sk
);
4391 bool fragstolen
= false;
4393 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4397 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4399 tcp_ecn_accept_cwr(tp
, skb
);
4401 tp
->rx_opt
.dsack
= 0;
4403 /* Queue data for delivery to the user.
4404 * Packets in sequence go to the receive queue.
4405 * Out of sequence packets to the out_of_order_queue.
4407 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4408 if (tcp_receive_window(tp
) == 0)
4411 /* Ok. In sequence. In window. */
4412 if (tp
->ucopy
.task
== current
&&
4413 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4414 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4415 int chunk
= min_t(unsigned int, skb
->len
,
4418 __set_current_state(TASK_RUNNING
);
4421 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4422 tp
->ucopy
.len
-= chunk
;
4423 tp
->copied_seq
+= chunk
;
4424 eaten
= (chunk
== skb
->len
);
4425 tcp_rcv_space_adjust(sk
);
4433 tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4436 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4438 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4440 tcp_event_data_recv(sk
, skb
);
4441 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4444 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4447 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4448 * gap in queue is filled.
4450 if (skb_queue_empty(&tp
->out_of_order_queue
))
4451 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4454 if (tp
->rx_opt
.num_sacks
)
4455 tcp_sack_remove(tp
);
4457 tcp_fast_path_check(sk
);
4460 kfree_skb_partial(skb
, fragstolen
);
4461 if (!sock_flag(sk
, SOCK_DEAD
))
4462 sk
->sk_data_ready(sk
);
4466 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4467 /* A retransmit, 2nd most common case. Force an immediate ack. */
4468 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4469 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4472 tcp_enter_quickack_mode(sk
);
4473 inet_csk_schedule_ack(sk
);
4479 /* Out of window. F.e. zero window probe. */
4480 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4483 tcp_enter_quickack_mode(sk
);
4485 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4486 /* Partial packet, seq < rcv_next < end_seq */
4487 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4488 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4489 TCP_SKB_CB(skb
)->end_seq
);
4491 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4493 /* If window is closed, drop tail of packet. But after
4494 * remembering D-SACK for its head made in previous line.
4496 if (!tcp_receive_window(tp
))
4501 tcp_data_queue_ofo(sk
, skb
);
4504 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4505 struct sk_buff_head
*list
)
4507 struct sk_buff
*next
= NULL
;
4509 if (!skb_queue_is_last(list
, skb
))
4510 next
= skb_queue_next(list
, skb
);
4512 __skb_unlink(skb
, list
);
4514 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4519 /* Collapse contiguous sequence of skbs head..tail with
4520 * sequence numbers start..end.
4522 * If tail is NULL, this means until the end of the list.
4524 * Segments with FIN/SYN are not collapsed (only because this
4528 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4529 struct sk_buff
*head
, struct sk_buff
*tail
,
4532 struct sk_buff
*skb
, *n
;
4535 /* First, check that queue is collapsible and find
4536 * the point where collapsing can be useful. */
4540 skb_queue_walk_from_safe(list
, skb
, n
) {
4543 /* No new bits? It is possible on ofo queue. */
4544 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4545 skb
= tcp_collapse_one(sk
, skb
, list
);
4551 /* The first skb to collapse is:
4553 * - bloated or contains data before "start" or
4554 * overlaps to the next one.
4556 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4557 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4558 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4559 end_of_skbs
= false;
4563 if (!skb_queue_is_last(list
, skb
)) {
4564 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4566 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4567 end_of_skbs
= false;
4572 /* Decided to skip this, advance start seq. */
4573 start
= TCP_SKB_CB(skb
)->end_seq
;
4576 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4579 while (before(start
, end
)) {
4580 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4581 struct sk_buff
*nskb
;
4583 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4587 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4588 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4589 __skb_queue_before(list
, skb
, nskb
);
4590 skb_set_owner_r(nskb
, sk
);
4592 /* Copy data, releasing collapsed skbs. */
4594 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4595 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4599 size
= min(copy
, size
);
4600 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4602 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4606 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4607 skb
= tcp_collapse_one(sk
, skb
, list
);
4610 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4617 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4618 * and tcp_collapse() them until all the queue is collapsed.
4620 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4622 struct tcp_sock
*tp
= tcp_sk(sk
);
4623 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4624 struct sk_buff
*head
;
4630 start
= TCP_SKB_CB(skb
)->seq
;
4631 end
= TCP_SKB_CB(skb
)->end_seq
;
4635 struct sk_buff
*next
= NULL
;
4637 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4638 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4641 /* Segment is terminated when we see gap or when
4642 * we are at the end of all the queue. */
4644 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4645 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4646 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4647 head
, skb
, start
, end
);
4651 /* Start new segment */
4652 start
= TCP_SKB_CB(skb
)->seq
;
4653 end
= TCP_SKB_CB(skb
)->end_seq
;
4655 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4656 start
= TCP_SKB_CB(skb
)->seq
;
4657 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4658 end
= TCP_SKB_CB(skb
)->end_seq
;
4664 * Purge the out-of-order queue.
4665 * Return true if queue was pruned.
4667 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4669 struct tcp_sock
*tp
= tcp_sk(sk
);
4672 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4673 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4674 __skb_queue_purge(&tp
->out_of_order_queue
);
4676 /* Reset SACK state. A conforming SACK implementation will
4677 * do the same at a timeout based retransmit. When a connection
4678 * is in a sad state like this, we care only about integrity
4679 * of the connection not performance.
4681 if (tp
->rx_opt
.sack_ok
)
4682 tcp_sack_reset(&tp
->rx_opt
);
4689 /* Reduce allocated memory if we can, trying to get
4690 * the socket within its memory limits again.
4692 * Return less than zero if we should start dropping frames
4693 * until the socket owning process reads some of the data
4694 * to stabilize the situation.
4696 static int tcp_prune_queue(struct sock
*sk
)
4698 struct tcp_sock
*tp
= tcp_sk(sk
);
4700 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4702 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4704 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4705 tcp_clamp_window(sk
);
4706 else if (sk_under_memory_pressure(sk
))
4707 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4709 tcp_collapse_ofo_queue(sk
);
4710 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4711 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4712 skb_peek(&sk
->sk_receive_queue
),
4714 tp
->copied_seq
, tp
->rcv_nxt
);
4717 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4720 /* Collapsing did not help, destructive actions follow.
4721 * This must not ever occur. */
4723 tcp_prune_ofo_queue(sk
);
4725 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4728 /* If we are really being abused, tell the caller to silently
4729 * drop receive data on the floor. It will get retransmitted
4730 * and hopefully then we'll have sufficient space.
4732 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4734 /* Massive buffer overcommit. */
4739 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4741 const struct tcp_sock
*tp
= tcp_sk(sk
);
4743 /* If the user specified a specific send buffer setting, do
4746 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4749 /* If we are under global TCP memory pressure, do not expand. */
4750 if (sk_under_memory_pressure(sk
))
4753 /* If we are under soft global TCP memory pressure, do not expand. */
4754 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4757 /* If we filled the congestion window, do not expand. */
4758 if (tp
->packets_out
>= tp
->snd_cwnd
)
4764 /* When incoming ACK allowed to free some skb from write_queue,
4765 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4766 * on the exit from tcp input handler.
4768 * PROBLEM: sndbuf expansion does not work well with largesend.
4770 static void tcp_new_space(struct sock
*sk
)
4772 struct tcp_sock
*tp
= tcp_sk(sk
);
4774 if (tcp_should_expand_sndbuf(sk
)) {
4775 tcp_sndbuf_expand(sk
);
4776 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4779 sk
->sk_write_space(sk
);
4782 static void tcp_check_space(struct sock
*sk
)
4784 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4785 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4786 if (sk
->sk_socket
&&
4787 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4792 static inline void tcp_data_snd_check(struct sock
*sk
)
4794 tcp_push_pending_frames(sk
);
4795 tcp_check_space(sk
);
4799 * Check if sending an ack is needed.
4801 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4803 struct tcp_sock
*tp
= tcp_sk(sk
);
4805 /* More than one full frame received... */
4806 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4807 /* ... and right edge of window advances far enough.
4808 * (tcp_recvmsg() will send ACK otherwise). Or...
4810 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4811 /* We ACK each frame or... */
4812 tcp_in_quickack_mode(sk
) ||
4813 /* We have out of order data. */
4814 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4815 /* Then ack it now */
4818 /* Else, send delayed ack. */
4819 tcp_send_delayed_ack(sk
);
4823 static inline void tcp_ack_snd_check(struct sock
*sk
)
4825 if (!inet_csk_ack_scheduled(sk
)) {
4826 /* We sent a data segment already. */
4829 __tcp_ack_snd_check(sk
, 1);
4833 * This routine is only called when we have urgent data
4834 * signaled. Its the 'slow' part of tcp_urg. It could be
4835 * moved inline now as tcp_urg is only called from one
4836 * place. We handle URGent data wrong. We have to - as
4837 * BSD still doesn't use the correction from RFC961.
4838 * For 1003.1g we should support a new option TCP_STDURG to permit
4839 * either form (or just set the sysctl tcp_stdurg).
4842 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
4844 struct tcp_sock
*tp
= tcp_sk(sk
);
4845 u32 ptr
= ntohs(th
->urg_ptr
);
4847 if (ptr
&& !sysctl_tcp_stdurg
)
4849 ptr
+= ntohl(th
->seq
);
4851 /* Ignore urgent data that we've already seen and read. */
4852 if (after(tp
->copied_seq
, ptr
))
4855 /* Do not replay urg ptr.
4857 * NOTE: interesting situation not covered by specs.
4858 * Misbehaving sender may send urg ptr, pointing to segment,
4859 * which we already have in ofo queue. We are not able to fetch
4860 * such data and will stay in TCP_URG_NOTYET until will be eaten
4861 * by recvmsg(). Seems, we are not obliged to handle such wicked
4862 * situations. But it is worth to think about possibility of some
4863 * DoSes using some hypothetical application level deadlock.
4865 if (before(ptr
, tp
->rcv_nxt
))
4868 /* Do we already have a newer (or duplicate) urgent pointer? */
4869 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4872 /* Tell the world about our new urgent pointer. */
4875 /* We may be adding urgent data when the last byte read was
4876 * urgent. To do this requires some care. We cannot just ignore
4877 * tp->copied_seq since we would read the last urgent byte again
4878 * as data, nor can we alter copied_seq until this data arrives
4879 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4881 * NOTE. Double Dutch. Rendering to plain English: author of comment
4882 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4883 * and expect that both A and B disappear from stream. This is _wrong_.
4884 * Though this happens in BSD with high probability, this is occasional.
4885 * Any application relying on this is buggy. Note also, that fix "works"
4886 * only in this artificial test. Insert some normal data between A and B and we will
4887 * decline of BSD again. Verdict: it is better to remove to trap
4890 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4891 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4892 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4894 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4895 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4900 tp
->urg_data
= TCP_URG_NOTYET
;
4903 /* Disable header prediction. */
4907 /* This is the 'fast' part of urgent handling. */
4908 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
4910 struct tcp_sock
*tp
= tcp_sk(sk
);
4912 /* Check if we get a new urgent pointer - normally not. */
4914 tcp_check_urg(sk
, th
);
4916 /* Do we wait for any urgent data? - normally not... */
4917 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4918 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4921 /* Is the urgent pointer pointing into this packet? */
4922 if (ptr
< skb
->len
) {
4924 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4926 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4927 if (!sock_flag(sk
, SOCK_DEAD
))
4928 sk
->sk_data_ready(sk
);
4933 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4935 struct tcp_sock
*tp
= tcp_sk(sk
);
4936 int chunk
= skb
->len
- hlen
;
4940 if (skb_csum_unnecessary(skb
))
4941 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4943 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4947 tp
->ucopy
.len
-= chunk
;
4948 tp
->copied_seq
+= chunk
;
4949 tcp_rcv_space_adjust(sk
);
4956 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
4957 struct sk_buff
*skb
)
4961 if (sock_owned_by_user(sk
)) {
4963 result
= __tcp_checksum_complete(skb
);
4966 result
= __tcp_checksum_complete(skb
);
4971 static inline bool tcp_checksum_complete_user(struct sock
*sk
,
4972 struct sk_buff
*skb
)
4974 return !skb_csum_unnecessary(skb
) &&
4975 __tcp_checksum_complete_user(sk
, skb
);
4978 /* Does PAWS and seqno based validation of an incoming segment, flags will
4979 * play significant role here.
4981 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
4982 const struct tcphdr
*th
, int syn_inerr
)
4984 struct tcp_sock
*tp
= tcp_sk(sk
);
4986 /* RFC1323: H1. Apply PAWS check first. */
4987 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4988 tcp_paws_discard(sk
, skb
)) {
4990 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
4991 tcp_send_dupack(sk
, skb
);
4994 /* Reset is accepted even if it did not pass PAWS. */
4997 /* Step 1: check sequence number */
4998 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4999 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5000 * (RST) segments are validated by checking their SEQ-fields."
5001 * And page 69: "If an incoming segment is not acceptable,
5002 * an acknowledgment should be sent in reply (unless the RST
5003 * bit is set, if so drop the segment and return)".
5008 tcp_send_dupack(sk
, skb
);
5013 /* Step 2: check RST bit */
5016 * If sequence number exactly matches RCV.NXT, then
5017 * RESET the connection
5019 * Send a challenge ACK
5021 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
)
5024 tcp_send_challenge_ack(sk
);
5028 /* step 3: check security and precedence [ignored] */
5030 /* step 4: Check for a SYN
5031 * RFC 5691 4.2 : Send a challenge ack
5036 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5037 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5038 tcp_send_challenge_ack(sk
);
5050 * TCP receive function for the ESTABLISHED state.
5052 * It is split into a fast path and a slow path. The fast path is
5054 * - A zero window was announced from us - zero window probing
5055 * is only handled properly in the slow path.
5056 * - Out of order segments arrived.
5057 * - Urgent data is expected.
5058 * - There is no buffer space left
5059 * - Unexpected TCP flags/window values/header lengths are received
5060 * (detected by checking the TCP header against pred_flags)
5061 * - Data is sent in both directions. Fast path only supports pure senders
5062 * or pure receivers (this means either the sequence number or the ack
5063 * value must stay constant)
5064 * - Unexpected TCP option.
5066 * When these conditions are not satisfied it drops into a standard
5067 * receive procedure patterned after RFC793 to handle all cases.
5068 * The first three cases are guaranteed by proper pred_flags setting,
5069 * the rest is checked inline. Fast processing is turned on in
5070 * tcp_data_queue when everything is OK.
5072 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5073 const struct tcphdr
*th
, unsigned int len
)
5075 struct tcp_sock
*tp
= tcp_sk(sk
);
5077 if (unlikely(sk
->sk_rx_dst
== NULL
))
5078 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5080 * Header prediction.
5081 * The code loosely follows the one in the famous
5082 * "30 instruction TCP receive" Van Jacobson mail.
5084 * Van's trick is to deposit buffers into socket queue
5085 * on a device interrupt, to call tcp_recv function
5086 * on the receive process context and checksum and copy
5087 * the buffer to user space. smart...
5089 * Our current scheme is not silly either but we take the
5090 * extra cost of the net_bh soft interrupt processing...
5091 * We do checksum and copy also but from device to kernel.
5094 tp
->rx_opt
.saw_tstamp
= 0;
5096 /* pred_flags is 0xS?10 << 16 + snd_wnd
5097 * if header_prediction is to be made
5098 * 'S' will always be tp->tcp_header_len >> 2
5099 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5100 * turn it off (when there are holes in the receive
5101 * space for instance)
5102 * PSH flag is ignored.
5105 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5106 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5107 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5108 int tcp_header_len
= tp
->tcp_header_len
;
5110 /* Timestamp header prediction: tcp_header_len
5111 * is automatically equal to th->doff*4 due to pred_flags
5115 /* Check timestamp */
5116 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5117 /* No? Slow path! */
5118 if (!tcp_parse_aligned_timestamp(tp
, th
))
5121 /* If PAWS failed, check it more carefully in slow path */
5122 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5125 /* DO NOT update ts_recent here, if checksum fails
5126 * and timestamp was corrupted part, it will result
5127 * in a hung connection since we will drop all
5128 * future packets due to the PAWS test.
5132 if (len
<= tcp_header_len
) {
5133 /* Bulk data transfer: sender */
5134 if (len
== tcp_header_len
) {
5135 /* Predicted packet is in window by definition.
5136 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5137 * Hence, check seq<=rcv_wup reduces to:
5139 if (tcp_header_len
==
5140 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5141 tp
->rcv_nxt
== tp
->rcv_wup
)
5142 tcp_store_ts_recent(tp
);
5144 /* We know that such packets are checksummed
5147 tcp_ack(sk
, skb
, 0);
5149 tcp_data_snd_check(sk
);
5151 } else { /* Header too small */
5152 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5157 bool fragstolen
= false;
5159 if (tp
->ucopy
.task
== current
&&
5160 tp
->copied_seq
== tp
->rcv_nxt
&&
5161 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5162 sock_owned_by_user(sk
)) {
5163 __set_current_state(TASK_RUNNING
);
5165 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5166 /* Predicted packet is in window by definition.
5167 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5168 * Hence, check seq<=rcv_wup reduces to:
5170 if (tcp_header_len
==
5171 (sizeof(struct tcphdr
) +
5172 TCPOLEN_TSTAMP_ALIGNED
) &&
5173 tp
->rcv_nxt
== tp
->rcv_wup
)
5174 tcp_store_ts_recent(tp
);
5176 tcp_rcv_rtt_measure_ts(sk
, skb
);
5178 __skb_pull(skb
, tcp_header_len
);
5179 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5180 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5185 if (tcp_checksum_complete_user(sk
, skb
))
5188 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5191 /* Predicted packet is in window by definition.
5192 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5193 * Hence, check seq<=rcv_wup reduces to:
5195 if (tcp_header_len
==
5196 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5197 tp
->rcv_nxt
== tp
->rcv_wup
)
5198 tcp_store_ts_recent(tp
);
5200 tcp_rcv_rtt_measure_ts(sk
, skb
);
5202 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5204 /* Bulk data transfer: receiver */
5205 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5209 tcp_event_data_recv(sk
, skb
);
5211 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5212 /* Well, only one small jumplet in fast path... */
5213 tcp_ack(sk
, skb
, FLAG_DATA
);
5214 tcp_data_snd_check(sk
);
5215 if (!inet_csk_ack_scheduled(sk
))
5219 __tcp_ack_snd_check(sk
, 0);
5222 kfree_skb_partial(skb
, fragstolen
);
5223 sk
->sk_data_ready(sk
);
5229 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5232 if (!th
->ack
&& !th
->rst
)
5236 * Standard slow path.
5239 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5243 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5246 tcp_rcv_rtt_measure_ts(sk
, skb
);
5248 /* Process urgent data. */
5249 tcp_urg(sk
, skb
, th
);
5251 /* step 7: process the segment text */
5252 tcp_data_queue(sk
, skb
);
5254 tcp_data_snd_check(sk
);
5255 tcp_ack_snd_check(sk
);
5259 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5260 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5265 EXPORT_SYMBOL(tcp_rcv_established
);
5267 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5269 struct tcp_sock
*tp
= tcp_sk(sk
);
5270 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5272 tcp_set_state(sk
, TCP_ESTABLISHED
);
5275 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5276 security_inet_conn_established(sk
, skb
);
5279 /* Make sure socket is routed, for correct metrics. */
5280 icsk
->icsk_af_ops
->rebuild_header(sk
);
5282 tcp_init_metrics(sk
);
5284 tcp_init_congestion_control(sk
);
5286 /* Prevent spurious tcp_cwnd_restart() on first data
5289 tp
->lsndtime
= tcp_time_stamp
;
5291 tcp_init_buffer_space(sk
);
5293 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5294 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5296 if (!tp
->rx_opt
.snd_wscale
)
5297 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5301 if (!sock_flag(sk
, SOCK_DEAD
)) {
5302 sk
->sk_state_change(sk
);
5303 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5307 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5308 struct tcp_fastopen_cookie
*cookie
)
5310 struct tcp_sock
*tp
= tcp_sk(sk
);
5311 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5312 u16 mss
= tp
->rx_opt
.mss_clamp
;
5315 if (mss
== tp
->rx_opt
.user_mss
) {
5316 struct tcp_options_received opt
;
5318 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5319 tcp_clear_options(&opt
);
5320 opt
.user_mss
= opt
.mss_clamp
= 0;
5321 tcp_parse_options(synack
, &opt
, 0, NULL
);
5322 mss
= opt
.mss_clamp
;
5325 if (!tp
->syn_fastopen
) /* Ignore an unsolicited cookie */
5328 /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
5329 * the remote receives only the retransmitted (regular) SYNs: either
5330 * the original SYN-data or the corresponding SYN-ACK is lost.
5332 syn_drop
= (cookie
->len
<= 0 && data
&& tp
->total_retrans
);
5334 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
);
5336 if (data
) { /* Retransmit unacked data in SYN */
5337 tcp_for_write_queue_from(data
, sk
) {
5338 if (data
== tcp_send_head(sk
) ||
5339 __tcp_retransmit_skb(sk
, data
))
5343 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5346 tp
->syn_data_acked
= tp
->syn_data
;
5347 if (tp
->syn_data_acked
)
5348 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
5352 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5353 const struct tcphdr
*th
, unsigned int len
)
5355 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5356 struct tcp_sock
*tp
= tcp_sk(sk
);
5357 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5358 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5360 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5361 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5362 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5366 * "If the state is SYN-SENT then
5367 * first check the ACK bit
5368 * If the ACK bit is set
5369 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5370 * a reset (unless the RST bit is set, if so drop
5371 * the segment and return)"
5373 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5374 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5375 goto reset_and_undo
;
5377 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5378 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5380 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5381 goto reset_and_undo
;
5384 /* Now ACK is acceptable.
5386 * "If the RST bit is set
5387 * If the ACK was acceptable then signal the user "error:
5388 * connection reset", drop the segment, enter CLOSED state,
5389 * delete TCB, and return."
5398 * "fifth, if neither of the SYN or RST bits is set then
5399 * drop the segment and return."
5405 goto discard_and_undo
;
5408 * "If the SYN bit is on ...
5409 * are acceptable then ...
5410 * (our SYN has been ACKed), change the connection
5411 * state to ESTABLISHED..."
5414 tcp_ecn_rcv_synack(tp
, th
);
5416 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5417 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5419 /* Ok.. it's good. Set up sequence numbers and
5420 * move to established.
5422 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5423 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5425 /* RFC1323: The window in SYN & SYN/ACK segments is
5428 tp
->snd_wnd
= ntohs(th
->window
);
5430 if (!tp
->rx_opt
.wscale_ok
) {
5431 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5432 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5435 if (tp
->rx_opt
.saw_tstamp
) {
5436 tp
->rx_opt
.tstamp_ok
= 1;
5437 tp
->tcp_header_len
=
5438 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5439 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5440 tcp_store_ts_recent(tp
);
5442 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5445 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5446 tcp_enable_fack(tp
);
5449 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5450 tcp_initialize_rcv_mss(sk
);
5452 /* Remember, tcp_poll() does not lock socket!
5453 * Change state from SYN-SENT only after copied_seq
5454 * is initialized. */
5455 tp
->copied_seq
= tp
->rcv_nxt
;
5459 tcp_finish_connect(sk
, skb
);
5461 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5462 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5465 if (sk
->sk_write_pending
||
5466 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5467 icsk
->icsk_ack
.pingpong
) {
5468 /* Save one ACK. Data will be ready after
5469 * several ticks, if write_pending is set.
5471 * It may be deleted, but with this feature tcpdumps
5472 * look so _wonderfully_ clever, that I was not able
5473 * to stand against the temptation 8) --ANK
5475 inet_csk_schedule_ack(sk
);
5476 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5477 tcp_enter_quickack_mode(sk
);
5478 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5479 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5490 /* No ACK in the segment */
5494 * "If the RST bit is set
5496 * Otherwise (no ACK) drop the segment and return."
5499 goto discard_and_undo
;
5503 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5504 tcp_paws_reject(&tp
->rx_opt
, 0))
5505 goto discard_and_undo
;
5508 /* We see SYN without ACK. It is attempt of
5509 * simultaneous connect with crossed SYNs.
5510 * Particularly, it can be connect to self.
5512 tcp_set_state(sk
, TCP_SYN_RECV
);
5514 if (tp
->rx_opt
.saw_tstamp
) {
5515 tp
->rx_opt
.tstamp_ok
= 1;
5516 tcp_store_ts_recent(tp
);
5517 tp
->tcp_header_len
=
5518 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5520 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5523 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5524 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5526 /* RFC1323: The window in SYN & SYN/ACK segments is
5529 tp
->snd_wnd
= ntohs(th
->window
);
5530 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5531 tp
->max_window
= tp
->snd_wnd
;
5533 tcp_ecn_rcv_syn(tp
, th
);
5536 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5537 tcp_initialize_rcv_mss(sk
);
5539 tcp_send_synack(sk
);
5541 /* Note, we could accept data and URG from this segment.
5542 * There are no obstacles to make this (except that we must
5543 * either change tcp_recvmsg() to prevent it from returning data
5544 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5546 * However, if we ignore data in ACKless segments sometimes,
5547 * we have no reasons to accept it sometimes.
5548 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5549 * is not flawless. So, discard packet for sanity.
5550 * Uncomment this return to process the data.
5557 /* "fifth, if neither of the SYN or RST bits is set then
5558 * drop the segment and return."
5562 tcp_clear_options(&tp
->rx_opt
);
5563 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5567 tcp_clear_options(&tp
->rx_opt
);
5568 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5573 * This function implements the receiving procedure of RFC 793 for
5574 * all states except ESTABLISHED and TIME_WAIT.
5575 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5576 * address independent.
5579 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5580 const struct tcphdr
*th
, unsigned int len
)
5582 struct tcp_sock
*tp
= tcp_sk(sk
);
5583 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5584 struct request_sock
*req
;
5589 tp
->rx_opt
.saw_tstamp
= 0;
5591 switch (sk
->sk_state
) {
5605 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5608 /* Now we have several options: In theory there is
5609 * nothing else in the frame. KA9Q has an option to
5610 * send data with the syn, BSD accepts data with the
5611 * syn up to the [to be] advertised window and
5612 * Solaris 2.1 gives you a protocol error. For now
5613 * we just ignore it, that fits the spec precisely
5614 * and avoids incompatibilities. It would be nice in
5615 * future to drop through and process the data.
5617 * Now that TTCP is starting to be used we ought to
5619 * But, this leaves one open to an easy denial of
5620 * service attack, and SYN cookies can't defend
5621 * against this problem. So, we drop the data
5622 * in the interest of security over speed unless
5623 * it's still in use.
5631 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5635 /* Do step6 onward by hand. */
5636 tcp_urg(sk
, skb
, th
);
5638 tcp_data_snd_check(sk
);
5642 req
= tp
->fastopen_rsk
;
5644 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5645 sk
->sk_state
!= TCP_FIN_WAIT1
);
5647 if (tcp_check_req(sk
, skb
, req
, NULL
, true) == NULL
)
5651 if (!th
->ack
&& !th
->rst
)
5654 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5657 /* step 5: check the ACK field */
5658 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5659 FLAG_UPDATE_TS_RECENT
) > 0;
5661 switch (sk
->sk_state
) {
5666 /* Once we leave TCP_SYN_RECV, we no longer need req
5670 synack_stamp
= tcp_rsk(req
)->snt_synack
;
5671 tp
->total_retrans
= req
->num_retrans
;
5672 reqsk_fastopen_remove(sk
, req
, false);
5674 synack_stamp
= tp
->lsndtime
;
5675 /* Make sure socket is routed, for correct metrics. */
5676 icsk
->icsk_af_ops
->rebuild_header(sk
);
5677 tcp_init_congestion_control(sk
);
5680 tp
->copied_seq
= tp
->rcv_nxt
;
5681 tcp_init_buffer_space(sk
);
5684 tcp_set_state(sk
, TCP_ESTABLISHED
);
5685 sk
->sk_state_change(sk
);
5687 /* Note, that this wakeup is only for marginal crossed SYN case.
5688 * Passively open sockets are not waked up, because
5689 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5692 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5694 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5695 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5696 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5697 tcp_synack_rtt_meas(sk
, synack_stamp
);
5699 if (tp
->rx_opt
.tstamp_ok
)
5700 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5703 /* Re-arm the timer because data may have been sent out.
5704 * This is similar to the regular data transmission case
5705 * when new data has just been ack'ed.
5707 * (TFO) - we could try to be more aggressive and
5708 * retransmitting any data sooner based on when they
5713 tcp_init_metrics(sk
);
5715 tcp_update_pacing_rate(sk
);
5717 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5718 tp
->lsndtime
= tcp_time_stamp
;
5720 tcp_initialize_rcv_mss(sk
);
5721 tcp_fast_path_on(tp
);
5724 case TCP_FIN_WAIT1
: {
5725 struct dst_entry
*dst
;
5728 /* If we enter the TCP_FIN_WAIT1 state and we are a
5729 * Fast Open socket and this is the first acceptable
5730 * ACK we have received, this would have acknowledged
5731 * our SYNACK so stop the SYNACK timer.
5734 /* Return RST if ack_seq is invalid.
5735 * Note that RFC793 only says to generate a
5736 * DUPACK for it but for TCP Fast Open it seems
5737 * better to treat this case like TCP_SYN_RECV
5742 /* We no longer need the request sock. */
5743 reqsk_fastopen_remove(sk
, req
, false);
5746 if (tp
->snd_una
!= tp
->write_seq
)
5749 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5750 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5752 dst
= __sk_dst_get(sk
);
5756 if (!sock_flag(sk
, SOCK_DEAD
)) {
5757 /* Wake up lingering close() */
5758 sk
->sk_state_change(sk
);
5762 if (tp
->linger2
< 0 ||
5763 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5764 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5766 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5770 tmo
= tcp_fin_time(sk
);
5771 if (tmo
> TCP_TIMEWAIT_LEN
) {
5772 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5773 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5774 /* Bad case. We could lose such FIN otherwise.
5775 * It is not a big problem, but it looks confusing
5776 * and not so rare event. We still can lose it now,
5777 * if it spins in bh_lock_sock(), but it is really
5780 inet_csk_reset_keepalive_timer(sk
, tmo
);
5782 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5789 if (tp
->snd_una
== tp
->write_seq
) {
5790 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5796 if (tp
->snd_una
== tp
->write_seq
) {
5797 tcp_update_metrics(sk
);
5804 /* step 6: check the URG bit */
5805 tcp_urg(sk
, skb
, th
);
5807 /* step 7: process the segment text */
5808 switch (sk
->sk_state
) {
5809 case TCP_CLOSE_WAIT
:
5812 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5816 /* RFC 793 says to queue data in these states,
5817 * RFC 1122 says we MUST send a reset.
5818 * BSD 4.4 also does reset.
5820 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5821 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5822 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5823 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5829 case TCP_ESTABLISHED
:
5830 tcp_data_queue(sk
, skb
);
5835 /* tcp_data could move socket to TIME-WAIT */
5836 if (sk
->sk_state
!= TCP_CLOSE
) {
5837 tcp_data_snd_check(sk
);
5838 tcp_ack_snd_check(sk
);
5847 EXPORT_SYMBOL(tcp_rcv_state_process
);
5849 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
5851 struct inet_request_sock
*ireq
= inet_rsk(req
);
5853 if (family
== AF_INET
)
5854 LIMIT_NETDEBUG(KERN_DEBUG
pr_fmt("drop open request from %pI4/%u\n"),
5855 &ireq
->ir_rmt_addr
, port
);
5856 #if IS_ENABLED(CONFIG_IPV6)
5857 else if (family
== AF_INET6
)
5858 LIMIT_NETDEBUG(KERN_DEBUG
pr_fmt("drop open request from %pI6/%u\n"),
5859 &ireq
->ir_v6_rmt_addr
, port
);
5863 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
5865 * If we receive a SYN packet with these bits set, it means a
5866 * network is playing bad games with TOS bits. In order to
5867 * avoid possible false congestion notifications, we disable
5868 * TCP ECN negociation.
5870 * Exception: tcp_ca wants ECN. This is required for DCTCP
5871 * congestion control; it requires setting ECT on all packets,
5872 * including SYN. We inverse the test in this case: If our
5873 * local socket wants ECN, but peer only set ece/cwr (but not
5874 * ECT in IP header) its probably a non-DCTCP aware sender.
5876 static void tcp_ecn_create_request(struct request_sock
*req
,
5877 const struct sk_buff
*skb
,
5878 const struct sock
*listen_sk
)
5880 const struct tcphdr
*th
= tcp_hdr(skb
);
5881 const struct net
*net
= sock_net(listen_sk
);
5882 bool th_ecn
= th
->ece
&& th
->cwr
;
5888 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
5889 need_ecn
= tcp_ca_needs_ecn(listen_sk
);
5891 if (!ect
&& !need_ecn
&& net
->ipv4
.sysctl_tcp_ecn
)
5892 inet_rsk(req
)->ecn_ok
= 1;
5893 else if (ect
&& need_ecn
)
5894 inet_rsk(req
)->ecn_ok
= 1;
5897 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
5898 const struct tcp_request_sock_ops
*af_ops
,
5899 struct sock
*sk
, struct sk_buff
*skb
)
5901 struct tcp_options_received tmp_opt
;
5902 struct request_sock
*req
;
5903 struct tcp_sock
*tp
= tcp_sk(sk
);
5904 struct dst_entry
*dst
= NULL
;
5905 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
5906 bool want_cookie
= false, fastopen
;
5908 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5912 /* TW buckets are converted to open requests without
5913 * limitations, they conserve resources and peer is
5914 * evidently real one.
5916 if ((sysctl_tcp_syncookies
== 2 ||
5917 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
5918 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
5924 /* Accept backlog is full. If we have already queued enough
5925 * of warm entries in syn queue, drop request. It is better than
5926 * clogging syn queue with openreqs with exponentially increasing
5929 if (sk_acceptq_is_full(sk
) && inet_csk_reqsk_queue_young(sk
) > 1) {
5930 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
5934 req
= inet_reqsk_alloc(rsk_ops
);
5938 tcp_rsk(req
)->af_specific
= af_ops
;
5940 tcp_clear_options(&tmp_opt
);
5941 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
5942 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
5943 tcp_parse_options(skb
, &tmp_opt
, 0, want_cookie
? NULL
: &foc
);
5945 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
5946 tcp_clear_options(&tmp_opt
);
5948 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
5949 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
5951 af_ops
->init_req(req
, sk
, skb
);
5953 if (security_inet_conn_request(sk
, skb
, req
))
5956 if (!want_cookie
|| tmp_opt
.tstamp_ok
)
5957 tcp_ecn_create_request(req
, skb
, sk
);
5960 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
5961 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
5963 /* VJ's idea. We save last timestamp seen
5964 * from the destination in peer table, when entering
5965 * state TIME-WAIT, and check against it before
5966 * accepting new connection request.
5968 * If "isn" is not zero, this request hit alive
5969 * timewait bucket, so that all the necessary checks
5970 * are made in the function processing timewait state.
5972 if (tcp_death_row
.sysctl_tw_recycle
) {
5975 dst
= af_ops
->route_req(sk
, &fl
, req
, &strict
);
5977 if (dst
&& strict
&&
5978 !tcp_peer_is_proven(req
, dst
, true,
5979 tmp_opt
.saw_tstamp
)) {
5980 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSPASSIVEREJECTED
);
5981 goto drop_and_release
;
5984 /* Kill the following clause, if you dislike this way. */
5985 else if (!sysctl_tcp_syncookies
&&
5986 (sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
5987 (sysctl_max_syn_backlog
>> 2)) &&
5988 !tcp_peer_is_proven(req
, dst
, false,
5989 tmp_opt
.saw_tstamp
)) {
5990 /* Without syncookies last quarter of
5991 * backlog is filled with destinations,
5992 * proven to be alive.
5993 * It means that we continue to communicate
5994 * to destinations, already remembered
5995 * to the moment of synflood.
5997 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
5999 goto drop_and_release
;
6002 isn
= af_ops
->init_seq(skb
);
6005 dst
= af_ops
->route_req(sk
, &fl
, req
, NULL
);
6010 tcp_rsk(req
)->snt_isn
= isn
;
6011 tcp_openreq_init_rwin(req
, sk
, dst
);
6012 fastopen
= !want_cookie
&&
6013 tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6014 err
= af_ops
->send_synack(sk
, dst
, &fl
, req
,
6015 skb_get_queue_mapping(skb
), &foc
);
6017 if (err
|| want_cookie
)
6020 tcp_rsk(req
)->listener
= NULL
;
6021 af_ops
->queue_hash_add(sk
, req
, TCP_TIMEOUT_INIT
);
6031 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENDROPS
);
6034 EXPORT_SYMBOL(tcp_conn_request
);