1 // SPDX-License-Identifier: GPL-2.0
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
7 * Implementation of the Transmission Control Protocol(TCP).
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 * Florian La Roche, <flla@stud.uni-sb.de>
14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 * Matthew Dillon, <dillon@apollo.west.oic.com>
18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 * Jorge Cwik, <jorge@laser.satlink.net>
24 * Pedro Roque : Fast Retransmit/Recovery.
26 * Retransmit queue handled by TCP.
27 * Better retransmit timer handling.
28 * New congestion avoidance.
32 * Eric : Fast Retransmit.
33 * Randy Scott : MSS option defines.
34 * Eric Schenk : Fixes to slow start algorithm.
35 * Eric Schenk : Yet another double ACK bug.
36 * Eric Schenk : Delayed ACK bug fixes.
37 * Eric Schenk : Floyd style fast retrans war avoidance.
38 * David S. Miller : Don't allow zero congestion window.
39 * Eric Schenk : Fix retransmitter so that it sends
40 * next packet on ack of previous packet.
41 * Andi Kleen : Moved open_request checking here
42 * and process RSTs for open_requests.
43 * Andi Kleen : Better prune_queue, and other fixes.
44 * Andrey Savochkin: Fix RTT measurements in the presence of
46 * Andrey Savochkin: Check sequence numbers correctly when
47 * removing SACKs due to in sequence incoming
49 * Andi Kleen: Make sure we never ack data there is not
50 * enough room for. Also make this condition
51 * a fatal error if it might still happen.
52 * Andi Kleen: Add tcp_measure_rcv_mss to make
53 * connections with MSS<min(MTU,ann. MSS)
54 * work without delayed acks.
55 * Andi Kleen: Process packets with PSH set in the
57 * J Hadi Salim: ECN support
60 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
61 * engine. Lots of bugs are found.
62 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
65 #define pr_fmt(fmt) "TCP: " fmt
68 #include <linux/slab.h>
69 #include <linux/module.h>
70 #include <linux/sysctl.h>
71 #include <linux/kernel.h>
72 #include <linux/prefetch.h>
75 #include <net/inet_common.h>
76 #include <linux/ipsec.h>
77 #include <asm/unaligned.h>
78 #include <linux/errqueue.h>
79 #include <trace/events/tcp.h>
80 #include <linux/jump_label_ratelimit.h>
81 #include <net/busy_poll.h>
82 #include <net/mptcp.h>
84 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
86 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
87 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
88 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
89 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
90 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
91 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
92 #define FLAG_ECE 0x40 /* ECE in this ACK */
93 #define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
94 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
95 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
96 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
97 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
98 #define FLAG_SET_XMIT_TIMER 0x1000 /* Set TLP or RTO timer */
99 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
100 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
101 #define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */
102 #define FLAG_ACK_MAYBE_DELAYED 0x10000 /* Likely a delayed ACK */
103 #define FLAG_DSACK_TLP 0x20000 /* DSACK for tail loss probe */
105 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
106 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
107 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE|FLAG_DSACKING_ACK)
108 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
110 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
111 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
113 #define REXMIT_NONE 0 /* no loss recovery to do */
114 #define REXMIT_LOST 1 /* retransmit packets marked lost */
115 #define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
117 #if IS_ENABLED(CONFIG_TLS_DEVICE)
118 static DEFINE_STATIC_KEY_DEFERRED_FALSE(clean_acked_data_enabled
, HZ
);
120 void clean_acked_data_enable(struct inet_connection_sock
*icsk
,
121 void (*cad
)(struct sock
*sk
, u32 ack_seq
))
123 icsk
->icsk_clean_acked
= cad
;
124 static_branch_deferred_inc(&clean_acked_data_enabled
);
126 EXPORT_SYMBOL_GPL(clean_acked_data_enable
);
128 void clean_acked_data_disable(struct inet_connection_sock
*icsk
)
130 static_branch_slow_dec_deferred(&clean_acked_data_enabled
);
131 icsk
->icsk_clean_acked
= NULL
;
133 EXPORT_SYMBOL_GPL(clean_acked_data_disable
);
135 void clean_acked_data_flush(void)
137 static_key_deferred_flush(&clean_acked_data_enabled
);
139 EXPORT_SYMBOL_GPL(clean_acked_data_flush
);
142 #ifdef CONFIG_CGROUP_BPF
143 static void bpf_skops_parse_hdr(struct sock
*sk
, struct sk_buff
*skb
)
145 bool unknown_opt
= tcp_sk(sk
)->rx_opt
.saw_unknown
&&
146 BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk
),
147 BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG
);
148 bool parse_all_opt
= BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk
),
149 BPF_SOCK_OPS_PARSE_ALL_HDR_OPT_CB_FLAG
);
150 struct bpf_sock_ops_kern sock_ops
;
152 if (likely(!unknown_opt
&& !parse_all_opt
))
155 /* The skb will be handled in the
156 * bpf_skops_established() or
157 * bpf_skops_write_hdr_opt().
159 switch (sk
->sk_state
) {
166 sock_owned_by_me(sk
);
168 memset(&sock_ops
, 0, offsetof(struct bpf_sock_ops_kern
, temp
));
169 sock_ops
.op
= BPF_SOCK_OPS_PARSE_HDR_OPT_CB
;
170 sock_ops
.is_fullsock
= 1;
172 bpf_skops_init_skb(&sock_ops
, skb
, tcp_hdrlen(skb
));
174 BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops
);
177 static void bpf_skops_established(struct sock
*sk
, int bpf_op
,
180 struct bpf_sock_ops_kern sock_ops
;
182 sock_owned_by_me(sk
);
184 memset(&sock_ops
, 0, offsetof(struct bpf_sock_ops_kern
, temp
));
185 sock_ops
.op
= bpf_op
;
186 sock_ops
.is_fullsock
= 1;
188 /* sk with TCP_REPAIR_ON does not have skb in tcp_finish_connect */
190 bpf_skops_init_skb(&sock_ops
, skb
, tcp_hdrlen(skb
));
192 BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops
);
195 static void bpf_skops_parse_hdr(struct sock
*sk
, struct sk_buff
*skb
)
199 static void bpf_skops_established(struct sock
*sk
, int bpf_op
,
205 static void tcp_gro_dev_warn(struct sock
*sk
, const struct sk_buff
*skb
,
208 static bool __once __read_mostly
;
211 struct net_device
*dev
;
216 dev
= dev_get_by_index_rcu(sock_net(sk
), skb
->skb_iif
);
217 if (!dev
|| len
>= dev
->mtu
)
218 pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
219 dev
? dev
->name
: "Unknown driver");
224 /* Adapt the MSS value used to make delayed ack decision to the
227 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
229 struct inet_connection_sock
*icsk
= inet_csk(sk
);
230 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
233 icsk
->icsk_ack
.last_seg_size
= 0;
235 /* skb->len may jitter because of SACKs, even if peer
236 * sends good full-sized frames.
238 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
239 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
240 /* Note: divides are still a bit expensive.
241 * For the moment, only adjust scaling_ratio
242 * when we update icsk_ack.rcv_mss.
244 if (unlikely(len
!= icsk
->icsk_ack
.rcv_mss
)) {
245 u64 val
= (u64
)skb
->len
<< TCP_RMEM_TO_WIN_SCALE
;
247 do_div(val
, skb
->truesize
);
248 tcp_sk(sk
)->scaling_ratio
= val
? val
: 1;
250 icsk
->icsk_ack
.rcv_mss
= min_t(unsigned int, len
,
252 /* Account for possibly-removed options */
253 if (unlikely(len
> icsk
->icsk_ack
.rcv_mss
+
254 MAX_TCP_OPTION_SPACE
))
255 tcp_gro_dev_warn(sk
, skb
, len
);
256 /* If the skb has a len of exactly 1*MSS and has the PSH bit
257 * set then it is likely the end of an application write. So
258 * more data may not be arriving soon, and yet the data sender
259 * may be waiting for an ACK if cwnd-bound or using TX zero
260 * copy. So we set ICSK_ACK_PUSHED here so that
261 * tcp_cleanup_rbuf() will send an ACK immediately if the app
262 * reads all of the data and is not ping-pong. If len > MSS
263 * then this logic does not matter (and does not hurt) because
264 * tcp_cleanup_rbuf() will always ACK immediately if the app
265 * reads data and there is more than an MSS of unACKed data.
267 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_PSH
)
268 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
270 /* Otherwise, we make more careful check taking into account,
271 * that SACKs block is variable.
273 * "len" is invariant segment length, including TCP header.
275 len
+= skb
->data
- skb_transport_header(skb
);
276 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
277 /* If PSH is not set, packet should be
278 * full sized, provided peer TCP is not badly broken.
279 * This observation (if it is correct 8)) allows
280 * to handle super-low mtu links fairly.
282 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
283 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
284 /* Subtract also invariant (if peer is RFC compliant),
285 * tcp header plus fixed timestamp option length.
286 * Resulting "len" is MSS free of SACK jitter.
288 len
-= tcp_sk(sk
)->tcp_header_len
;
289 icsk
->icsk_ack
.last_seg_size
= len
;
291 icsk
->icsk_ack
.rcv_mss
= len
;
295 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
296 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
297 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
301 static void tcp_incr_quickack(struct sock
*sk
, unsigned int max_quickacks
)
303 struct inet_connection_sock
*icsk
= inet_csk(sk
);
304 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
308 quickacks
= min(quickacks
, max_quickacks
);
309 if (quickacks
> icsk
->icsk_ack
.quick
)
310 icsk
->icsk_ack
.quick
= quickacks
;
313 static void tcp_enter_quickack_mode(struct sock
*sk
, unsigned int max_quickacks
)
315 struct inet_connection_sock
*icsk
= inet_csk(sk
);
317 tcp_incr_quickack(sk
, max_quickacks
);
318 inet_csk_exit_pingpong_mode(sk
);
319 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
322 /* Send ACKs quickly, if "quick" count is not exhausted
323 * and the session is not interactive.
326 static bool tcp_in_quickack_mode(struct sock
*sk
)
328 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
329 const struct dst_entry
*dst
= __sk_dst_get(sk
);
331 return (dst
&& dst_metric(dst
, RTAX_QUICKACK
)) ||
332 (icsk
->icsk_ack
.quick
&& !inet_csk_in_pingpong_mode(sk
));
335 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
337 if (tp
->ecn_flags
& TCP_ECN_OK
)
338 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
341 static void tcp_ecn_accept_cwr(struct sock
*sk
, const struct sk_buff
*skb
)
343 if (tcp_hdr(skb
)->cwr
) {
344 tcp_sk(sk
)->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
346 /* If the sender is telling us it has entered CWR, then its
347 * cwnd may be very low (even just 1 packet), so we should ACK
350 if (TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
)
351 inet_csk(sk
)->icsk_ack
.pending
|= ICSK_ACK_NOW
;
355 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
357 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
360 static void __tcp_ecn_check_ce(struct sock
*sk
, const struct sk_buff
*skb
)
362 struct tcp_sock
*tp
= tcp_sk(sk
);
364 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
365 case INET_ECN_NOT_ECT
:
366 /* Funny extension: if ECT is not set on a segment,
367 * and we already seen ECT on a previous segment,
368 * it is probably a retransmit.
370 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
371 tcp_enter_quickack_mode(sk
, 2);
374 if (tcp_ca_needs_ecn(sk
))
375 tcp_ca_event(sk
, CA_EVENT_ECN_IS_CE
);
377 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
378 /* Better not delay acks, sender can have a very low cwnd */
379 tcp_enter_quickack_mode(sk
, 2);
380 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
382 tp
->ecn_flags
|= TCP_ECN_SEEN
;
385 if (tcp_ca_needs_ecn(sk
))
386 tcp_ca_event(sk
, CA_EVENT_ECN_NO_CE
);
387 tp
->ecn_flags
|= TCP_ECN_SEEN
;
392 static void tcp_ecn_check_ce(struct sock
*sk
, const struct sk_buff
*skb
)
394 if (tcp_sk(sk
)->ecn_flags
& TCP_ECN_OK
)
395 __tcp_ecn_check_ce(sk
, skb
);
398 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
400 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
401 tp
->ecn_flags
&= ~TCP_ECN_OK
;
404 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
406 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
407 tp
->ecn_flags
&= ~TCP_ECN_OK
;
410 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
412 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
417 /* Buffer size and advertised window tuning.
419 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
422 static void tcp_sndbuf_expand(struct sock
*sk
)
424 const struct tcp_sock
*tp
= tcp_sk(sk
);
425 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
429 /* Worst case is non GSO/TSO : each frame consumes one skb
430 * and skb->head is kmalloced using power of two area of memory
432 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
434 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
436 per_mss
= roundup_pow_of_two(per_mss
) +
437 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
439 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tcp_snd_cwnd(tp
));
440 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
442 /* Fast Recovery (RFC 5681 3.2) :
443 * Cubic needs 1.7 factor, rounded to 2 to include
444 * extra cushion (application might react slowly to EPOLLOUT)
446 sndmem
= ca_ops
->sndbuf_expand
? ca_ops
->sndbuf_expand(sk
) : 2;
447 sndmem
*= nr_segs
* per_mss
;
449 if (sk
->sk_sndbuf
< sndmem
)
450 WRITE_ONCE(sk
->sk_sndbuf
,
451 min(sndmem
, READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_wmem
[2])));
454 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
456 * All tcp_full_space() is split to two parts: "network" buffer, allocated
457 * forward and advertised in receiver window (tp->rcv_wnd) and
458 * "application buffer", required to isolate scheduling/application
459 * latencies from network.
460 * window_clamp is maximal advertised window. It can be less than
461 * tcp_full_space(), in this case tcp_full_space() - window_clamp
462 * is reserved for "application" buffer. The less window_clamp is
463 * the smoother our behaviour from viewpoint of network, but the lower
464 * throughput and the higher sensitivity of the connection to losses. 8)
466 * rcv_ssthresh is more strict window_clamp used at "slow start"
467 * phase to predict further behaviour of this connection.
468 * It is used for two goals:
469 * - to enforce header prediction at sender, even when application
470 * requires some significant "application buffer". It is check #1.
471 * - to prevent pruning of receive queue because of misprediction
472 * of receiver window. Check #2.
474 * The scheme does not work when sender sends good segments opening
475 * window and then starts to feed us spaghetti. But it should work
476 * in common situations. Otherwise, we have to rely on queue collapsing.
479 /* Slow part of check#2. */
480 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
,
481 unsigned int skbtruesize
)
483 const struct tcp_sock
*tp
= tcp_sk(sk
);
485 int truesize
= tcp_win_from_space(sk
, skbtruesize
) >> 1;
486 int window
= tcp_win_from_space(sk
, READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_rmem
[2])) >> 1;
488 while (tp
->rcv_ssthresh
<= window
) {
489 if (truesize
<= skb
->len
)
490 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
498 /* Even if skb appears to have a bad len/truesize ratio, TCP coalescing
499 * can play nice with us, as sk_buff and skb->head might be either
500 * freed or shared with up to MAX_SKB_FRAGS segments.
501 * Only give a boost to drivers using page frag(s) to hold the frame(s),
502 * and if no payload was pulled in skb->head before reaching us.
504 static u32
truesize_adjust(bool adjust
, const struct sk_buff
*skb
)
506 u32 truesize
= skb
->truesize
;
508 if (adjust
&& !skb_headlen(skb
)) {
509 truesize
-= SKB_TRUESIZE(skb_end_offset(skb
));
510 /* paranoid check, some drivers might be buggy */
511 if (unlikely((int)truesize
< (int)skb
->len
))
512 truesize
= skb
->truesize
;
517 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
,
520 struct tcp_sock
*tp
= tcp_sk(sk
);
523 room
= min_t(int, tp
->window_clamp
, tcp_space(sk
)) - tp
->rcv_ssthresh
;
529 if (!tcp_under_memory_pressure(sk
)) {
530 unsigned int truesize
= truesize_adjust(adjust
, skb
);
533 /* Check #2. Increase window, if skb with such overhead
534 * will fit to rcvbuf in future.
536 if (tcp_win_from_space(sk
, truesize
) <= skb
->len
)
537 incr
= 2 * tp
->advmss
;
539 incr
= __tcp_grow_window(sk
, skb
, truesize
);
542 incr
= max_t(int, incr
, 2 * skb
->len
);
543 tp
->rcv_ssthresh
+= min(room
, incr
);
544 inet_csk(sk
)->icsk_ack
.quick
|= 1;
548 * Adjust rcv_ssthresh according to reserved mem
550 tcp_adjust_rcv_ssthresh(sk
);
554 /* 3. Try to fixup all. It is made immediately after connection enters
557 static void tcp_init_buffer_space(struct sock
*sk
)
559 int tcp_app_win
= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_app_win
);
560 struct tcp_sock
*tp
= tcp_sk(sk
);
563 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
564 tcp_sndbuf_expand(sk
);
566 tcp_mstamp_refresh(tp
);
567 tp
->rcvq_space
.time
= tp
->tcp_mstamp
;
568 tp
->rcvq_space
.seq
= tp
->copied_seq
;
570 maxwin
= tcp_full_space(sk
);
572 if (tp
->window_clamp
>= maxwin
) {
573 tp
->window_clamp
= maxwin
;
575 if (tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
576 tp
->window_clamp
= max(maxwin
-
577 (maxwin
>> tcp_app_win
),
581 /* Force reservation of one segment. */
583 tp
->window_clamp
> 2 * tp
->advmss
&&
584 tp
->window_clamp
+ tp
->advmss
> maxwin
)
585 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
587 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
588 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
589 tp
->rcvq_space
.space
= min3(tp
->rcv_ssthresh
, tp
->rcv_wnd
,
590 (u32
)TCP_INIT_CWND
* tp
->advmss
);
593 /* 4. Recalculate window clamp after socket hit its memory bounds. */
594 static void tcp_clamp_window(struct sock
*sk
)
596 struct tcp_sock
*tp
= tcp_sk(sk
);
597 struct inet_connection_sock
*icsk
= inet_csk(sk
);
598 struct net
*net
= sock_net(sk
);
601 icsk
->icsk_ack
.quick
= 0;
602 rmem2
= READ_ONCE(net
->ipv4
.sysctl_tcp_rmem
[2]);
604 if (sk
->sk_rcvbuf
< rmem2
&&
605 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
606 !tcp_under_memory_pressure(sk
) &&
607 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
608 WRITE_ONCE(sk
->sk_rcvbuf
,
609 min(atomic_read(&sk
->sk_rmem_alloc
), rmem2
));
611 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
612 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
615 /* Initialize RCV_MSS value.
616 * RCV_MSS is an our guess about MSS used by the peer.
617 * We haven't any direct information about the MSS.
618 * It's better to underestimate the RCV_MSS rather than overestimate.
619 * Overestimations make us ACKing less frequently than needed.
620 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
622 void tcp_initialize_rcv_mss(struct sock
*sk
)
624 const struct tcp_sock
*tp
= tcp_sk(sk
);
625 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
627 hint
= min(hint
, tp
->rcv_wnd
/ 2);
628 hint
= min(hint
, TCP_MSS_DEFAULT
);
629 hint
= max(hint
, TCP_MIN_MSS
);
631 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
633 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
635 /* Receiver "autotuning" code.
637 * The algorithm for RTT estimation w/o timestamps is based on
638 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
639 * <https://public.lanl.gov/radiant/pubs.html#DRS>
641 * More detail on this code can be found at
642 * <http://staff.psc.edu/jheffner/>,
643 * though this reference is out of date. A new paper
646 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
648 u32 new_sample
= tp
->rcv_rtt_est
.rtt_us
;
651 if (new_sample
!= 0) {
652 /* If we sample in larger samples in the non-timestamp
653 * case, we could grossly overestimate the RTT especially
654 * with chatty applications or bulk transfer apps which
655 * are stalled on filesystem I/O.
657 * Also, since we are only going for a minimum in the
658 * non-timestamp case, we do not smooth things out
659 * else with timestamps disabled convergence takes too
663 m
-= (new_sample
>> 3);
671 /* No previous measure. */
675 tp
->rcv_rtt_est
.rtt_us
= new_sample
;
678 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
682 if (tp
->rcv_rtt_est
.time
== 0)
684 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
686 delta_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, tp
->rcv_rtt_est
.time
);
689 tcp_rcv_rtt_update(tp
, delta_us
, 1);
692 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
693 tp
->rcv_rtt_est
.time
= tp
->tcp_mstamp
;
696 static s32
tcp_rtt_tsopt_us(const struct tcp_sock
*tp
)
700 delta
= tcp_time_stamp_ts(tp
) - tp
->rx_opt
.rcv_tsecr
;
704 if (likely(delta
< INT_MAX
/ (USEC_PER_SEC
/ TCP_TS_HZ
))) {
707 delta_us
= delta
* (USEC_PER_SEC
/ TCP_TS_HZ
);
713 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
714 const struct sk_buff
*skb
)
716 struct tcp_sock
*tp
= tcp_sk(sk
);
718 if (tp
->rx_opt
.rcv_tsecr
== tp
->rcv_rtt_last_tsecr
)
720 tp
->rcv_rtt_last_tsecr
= tp
->rx_opt
.rcv_tsecr
;
722 if (TCP_SKB_CB(skb
)->end_seq
-
723 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
) {
724 s32 delta
= tcp_rtt_tsopt_us(tp
);
727 tcp_rcv_rtt_update(tp
, delta
, 0);
732 * This function should be called every time data is copied to user space.
733 * It calculates the appropriate TCP receive buffer space.
735 void tcp_rcv_space_adjust(struct sock
*sk
)
737 struct tcp_sock
*tp
= tcp_sk(sk
);
741 trace_tcp_rcv_space_adjust(sk
);
743 tcp_mstamp_refresh(tp
);
744 time
= tcp_stamp_us_delta(tp
->tcp_mstamp
, tp
->rcvq_space
.time
);
745 if (time
< (tp
->rcv_rtt_est
.rtt_us
>> 3) || tp
->rcv_rtt_est
.rtt_us
== 0)
748 /* Number of bytes copied to user in last RTT */
749 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
750 if (copied
<= tp
->rcvq_space
.space
)
754 * copied = bytes received in previous RTT, our base window
755 * To cope with packet losses, we need a 2x factor
756 * To cope with slow start, and sender growing its cwin by 100 %
757 * every RTT, we need a 4x factor, because the ACK we are sending
758 * now is for the next RTT, not the current one :
759 * <prev RTT . ><current RTT .. ><next RTT .... >
762 if (READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_moderate_rcvbuf
) &&
763 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
767 /* minimal window to cope with packet losses, assuming
768 * steady state. Add some cushion because of small variations.
770 rcvwin
= ((u64
)copied
<< 1) + 16 * tp
->advmss
;
772 /* Accommodate for sender rate increase (eg. slow start) */
773 grow
= rcvwin
* (copied
- tp
->rcvq_space
.space
);
774 do_div(grow
, tp
->rcvq_space
.space
);
775 rcvwin
+= (grow
<< 1);
777 rcvbuf
= min_t(u64
, tcp_space_from_win(sk
, rcvwin
),
778 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_rmem
[2]));
779 if (rcvbuf
> sk
->sk_rcvbuf
) {
780 WRITE_ONCE(sk
->sk_rcvbuf
, rcvbuf
);
782 /* Make the window clamp follow along. */
783 tp
->window_clamp
= tcp_win_from_space(sk
, rcvbuf
);
786 tp
->rcvq_space
.space
= copied
;
789 tp
->rcvq_space
.seq
= tp
->copied_seq
;
790 tp
->rcvq_space
.time
= tp
->tcp_mstamp
;
793 static void tcp_save_lrcv_flowlabel(struct sock
*sk
, const struct sk_buff
*skb
)
795 #if IS_ENABLED(CONFIG_IPV6)
796 struct inet_connection_sock
*icsk
= inet_csk(sk
);
798 if (skb
->protocol
== htons(ETH_P_IPV6
))
799 icsk
->icsk_ack
.lrcv_flowlabel
= ntohl(ip6_flowlabel(ipv6_hdr(skb
)));
803 /* There is something which you must keep in mind when you analyze the
804 * behavior of the tp->ato delayed ack timeout interval. When a
805 * connection starts up, we want to ack as quickly as possible. The
806 * problem is that "good" TCP's do slow start at the beginning of data
807 * transmission. The means that until we send the first few ACK's the
808 * sender will sit on his end and only queue most of his data, because
809 * he can only send snd_cwnd unacked packets at any given time. For
810 * each ACK we send, he increments snd_cwnd and transmits more of his
813 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
815 struct tcp_sock
*tp
= tcp_sk(sk
);
816 struct inet_connection_sock
*icsk
= inet_csk(sk
);
819 inet_csk_schedule_ack(sk
);
821 tcp_measure_rcv_mss(sk
, skb
);
823 tcp_rcv_rtt_measure(tp
);
827 if (!icsk
->icsk_ack
.ato
) {
828 /* The _first_ data packet received, initialize
829 * delayed ACK engine.
831 tcp_incr_quickack(sk
, TCP_MAX_QUICKACKS
);
832 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
834 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
836 if (m
<= TCP_ATO_MIN
/ 2) {
837 /* The fastest case is the first. */
838 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
839 } else if (m
< icsk
->icsk_ack
.ato
) {
840 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
841 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
842 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
843 } else if (m
> icsk
->icsk_rto
) {
844 /* Too long gap. Apparently sender failed to
845 * restart window, so that we send ACKs quickly.
847 tcp_incr_quickack(sk
, TCP_MAX_QUICKACKS
);
850 icsk
->icsk_ack
.lrcvtime
= now
;
851 tcp_save_lrcv_flowlabel(sk
, skb
);
853 tcp_ecn_check_ce(sk
, skb
);
856 tcp_grow_window(sk
, skb
, true);
859 /* Called to compute a smoothed rtt estimate. The data fed to this
860 * routine either comes from timestamps, or from segments that were
861 * known _not_ to have been retransmitted [see Karn/Partridge
862 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
863 * piece by Van Jacobson.
864 * NOTE: the next three routines used to be one big routine.
865 * To save cycles in the RFC 1323 implementation it was better to break
866 * it up into three procedures. -- erics
868 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
870 struct tcp_sock
*tp
= tcp_sk(sk
);
871 long m
= mrtt_us
; /* RTT */
872 u32 srtt
= tp
->srtt_us
;
874 /* The following amusing code comes from Jacobson's
875 * article in SIGCOMM '88. Note that rtt and mdev
876 * are scaled versions of rtt and mean deviation.
877 * This is designed to be as fast as possible
878 * m stands for "measurement".
880 * On a 1990 paper the rto value is changed to:
881 * RTO = rtt + 4 * mdev
883 * Funny. This algorithm seems to be very broken.
884 * These formulae increase RTO, when it should be decreased, increase
885 * too slowly, when it should be increased quickly, decrease too quickly
886 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
887 * does not matter how to _calculate_ it. Seems, it was trap
888 * that VJ failed to avoid. 8)
891 m
-= (srtt
>> 3); /* m is now error in rtt est */
892 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
894 m
= -m
; /* m is now abs(error) */
895 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
896 /* This is similar to one of Eifel findings.
897 * Eifel blocks mdev updates when rtt decreases.
898 * This solution is a bit different: we use finer gain
899 * for mdev in this case (alpha*beta).
900 * Like Eifel it also prevents growth of rto,
901 * but also it limits too fast rto decreases,
902 * happening in pure Eifel.
907 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
909 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
910 if (tp
->mdev_us
> tp
->mdev_max_us
) {
911 tp
->mdev_max_us
= tp
->mdev_us
;
912 if (tp
->mdev_max_us
> tp
->rttvar_us
)
913 tp
->rttvar_us
= tp
->mdev_max_us
;
915 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
916 if (tp
->mdev_max_us
< tp
->rttvar_us
)
917 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
918 tp
->rtt_seq
= tp
->snd_nxt
;
919 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
924 /* no previous measure. */
925 srtt
= m
<< 3; /* take the measured time to be rtt */
926 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
927 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
928 tp
->mdev_max_us
= tp
->rttvar_us
;
929 tp
->rtt_seq
= tp
->snd_nxt
;
933 tp
->srtt_us
= max(1U, srtt
);
936 static void tcp_update_pacing_rate(struct sock
*sk
)
938 const struct tcp_sock
*tp
= tcp_sk(sk
);
941 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
942 rate
= (u64
)tp
->mss_cache
* ((USEC_PER_SEC
/ 100) << 3);
944 /* current rate is (cwnd * mss) / srtt
945 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
946 * In Congestion Avoidance phase, set it to 120 % the current rate.
948 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
949 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
950 * end of slow start and should slow down.
952 if (tcp_snd_cwnd(tp
) < tp
->snd_ssthresh
/ 2)
953 rate
*= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_pacing_ss_ratio
);
955 rate
*= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_pacing_ca_ratio
);
957 rate
*= max(tcp_snd_cwnd(tp
), tp
->packets_out
);
959 if (likely(tp
->srtt_us
))
960 do_div(rate
, tp
->srtt_us
);
962 /* WRITE_ONCE() is needed because sch_fq fetches sk_pacing_rate
963 * without any lock. We want to make sure compiler wont store
964 * intermediate values in this location.
966 WRITE_ONCE(sk
->sk_pacing_rate
,
967 min_t(u64
, rate
, READ_ONCE(sk
->sk_max_pacing_rate
)));
970 /* Calculate rto without backoff. This is the second half of Van Jacobson's
971 * routine referred to above.
973 static void tcp_set_rto(struct sock
*sk
)
975 const struct tcp_sock
*tp
= tcp_sk(sk
);
976 /* Old crap is replaced with new one. 8)
979 * 1. If rtt variance happened to be less 50msec, it is hallucination.
980 * It cannot be less due to utterly erratic ACK generation made
981 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
982 * to do with delayed acks, because at cwnd>2 true delack timeout
983 * is invisible. Actually, Linux-2.4 also generates erratic
984 * ACKs in some circumstances.
986 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
988 /* 2. Fixups made earlier cannot be right.
989 * If we do not estimate RTO correctly without them,
990 * all the algo is pure shit and should be replaced
991 * with correct one. It is exactly, which we pretend to do.
994 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
995 * guarantees that rto is higher.
1000 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
1002 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
1005 cwnd
= TCP_INIT_CWND
;
1006 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
1009 struct tcp_sacktag_state
{
1010 /* Timestamps for earliest and latest never-retransmitted segment
1011 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1012 * but congestion control should still get an accurate delay signal.
1019 unsigned int mss_now
;
1020 struct rate_sample
*rate
;
1023 /* Take a notice that peer is sending D-SACKs. Skip update of data delivery
1024 * and spurious retransmission information if this DSACK is unlikely caused by
1026 * - DSACKed sequence range is larger than maximum receiver's window.
1027 * - Total no. of DSACKed segments exceed the total no. of retransmitted segs.
1029 static u32
tcp_dsack_seen(struct tcp_sock
*tp
, u32 start_seq
,
1030 u32 end_seq
, struct tcp_sacktag_state
*state
)
1032 u32 seq_len
, dup_segs
= 1;
1034 if (!before(start_seq
, end_seq
))
1037 seq_len
= end_seq
- start_seq
;
1038 /* Dubious DSACK: DSACKed range greater than maximum advertised rwnd */
1039 if (seq_len
> tp
->max_window
)
1041 if (seq_len
> tp
->mss_cache
)
1042 dup_segs
= DIV_ROUND_UP(seq_len
, tp
->mss_cache
);
1043 else if (tp
->tlp_high_seq
&& tp
->tlp_high_seq
== end_seq
)
1044 state
->flag
|= FLAG_DSACK_TLP
;
1046 tp
->dsack_dups
+= dup_segs
;
1047 /* Skip the DSACK if dup segs weren't retransmitted by sender */
1048 if (tp
->dsack_dups
> tp
->total_retrans
)
1051 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
1052 /* We increase the RACK ordering window in rounds where we receive
1053 * DSACKs that may have been due to reordering causing RACK to trigger
1054 * a spurious fast recovery. Thus RACK ignores DSACKs that happen
1055 * without having seen reordering, or that match TLP probes (TLP
1056 * is timer-driven, not triggered by RACK).
1058 if (tp
->reord_seen
&& !(state
->flag
& FLAG_DSACK_TLP
))
1059 tp
->rack
.dsack_seen
= 1;
1061 state
->flag
|= FLAG_DSACKING_ACK
;
1062 /* A spurious retransmission is delivered */
1063 state
->sack_delivered
+= dup_segs
;
1068 /* It's reordering when higher sequence was delivered (i.e. sacked) before
1069 * some lower never-retransmitted sequence ("low_seq"). The maximum reordering
1070 * distance is approximated in full-mss packet distance ("reordering").
1072 static void tcp_check_sack_reordering(struct sock
*sk
, const u32 low_seq
,
1075 struct tcp_sock
*tp
= tcp_sk(sk
);
1076 const u32 mss
= tp
->mss_cache
;
1079 fack
= tcp_highest_sack_seq(tp
);
1080 if (!before(low_seq
, fack
))
1083 metric
= fack
- low_seq
;
1084 if ((metric
> tp
->reordering
* mss
) && mss
) {
1085 #if FASTRETRANS_DEBUG > 1
1086 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
1087 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
1091 tp
->undo_marker
? tp
->undo_retrans
: 0);
1093 tp
->reordering
= min_t(u32
, (metric
+ mss
- 1) / mss
,
1094 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_max_reordering
));
1097 /* This exciting event is worth to be remembered. 8) */
1099 NET_INC_STATS(sock_net(sk
),
1100 ts
? LINUX_MIB_TCPTSREORDER
: LINUX_MIB_TCPSACKREORDER
);
1103 /* This must be called before lost_out or retrans_out are updated
1104 * on a new loss, because we want to know if all skbs previously
1105 * known to be lost have already been retransmitted, indicating
1106 * that this newly lost skb is our next skb to retransmit.
1108 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1110 if ((!tp
->retransmit_skb_hint
&& tp
->retrans_out
>= tp
->lost_out
) ||
1111 (tp
->retransmit_skb_hint
&&
1112 before(TCP_SKB_CB(skb
)->seq
,
1113 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
)))
1114 tp
->retransmit_skb_hint
= skb
;
1117 /* Sum the number of packets on the wire we have marked as lost, and
1118 * notify the congestion control module that the given skb was marked lost.
1120 static void tcp_notify_skb_loss_event(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
1122 tp
->lost
+= tcp_skb_pcount(skb
);
1125 void tcp_mark_skb_lost(struct sock
*sk
, struct sk_buff
*skb
)
1127 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1128 struct tcp_sock
*tp
= tcp_sk(sk
);
1130 if (sacked
& TCPCB_SACKED_ACKED
)
1133 tcp_verify_retransmit_hint(tp
, skb
);
1134 if (sacked
& TCPCB_LOST
) {
1135 if (sacked
& TCPCB_SACKED_RETRANS
) {
1136 /* Account for retransmits that are lost again */
1137 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1138 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1139 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
,
1140 tcp_skb_pcount(skb
));
1141 tcp_notify_skb_loss_event(tp
, skb
);
1144 tp
->lost_out
+= tcp_skb_pcount(skb
);
1145 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1146 tcp_notify_skb_loss_event(tp
, skb
);
1150 /* Updates the delivered and delivered_ce counts */
1151 static void tcp_count_delivered(struct tcp_sock
*tp
, u32 delivered
,
1154 tp
->delivered
+= delivered
;
1156 tp
->delivered_ce
+= delivered
;
1159 /* This procedure tags the retransmission queue when SACKs arrive.
1161 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1162 * Packets in queue with these bits set are counted in variables
1163 * sacked_out, retrans_out and lost_out, correspondingly.
1165 * Valid combinations are:
1166 * Tag InFlight Description
1167 * 0 1 - orig segment is in flight.
1168 * S 0 - nothing flies, orig reached receiver.
1169 * L 0 - nothing flies, orig lost by net.
1170 * R 2 - both orig and retransmit are in flight.
1171 * L|R 1 - orig is lost, retransmit is in flight.
1172 * S|R 1 - orig reached receiver, retrans is still in flight.
1173 * (L|S|R is logically valid, it could occur when L|R is sacked,
1174 * but it is equivalent to plain S and code short-curcuits it to S.
1175 * L|S is logically invalid, it would mean -1 packet in flight 8))
1177 * These 6 states form finite state machine, controlled by the following events:
1178 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1179 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1180 * 3. Loss detection event of two flavors:
1181 * A. Scoreboard estimator decided the packet is lost.
1182 * A'. Reno "three dupacks" marks head of queue lost.
1183 * B. SACK arrives sacking SND.NXT at the moment, when the
1184 * segment was retransmitted.
1185 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1187 * It is pleasant to note, that state diagram turns out to be commutative,
1188 * so that we are allowed not to be bothered by order of our actions,
1189 * when multiple events arrive simultaneously. (see the function below).
1191 * Reordering detection.
1192 * --------------------
1193 * Reordering metric is maximal distance, which a packet can be displaced
1194 * in packet stream. With SACKs we can estimate it:
1196 * 1. SACK fills old hole and the corresponding segment was not
1197 * ever retransmitted -> reordering. Alas, we cannot use it
1198 * when segment was retransmitted.
1199 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1200 * for retransmitted and already SACKed segment -> reordering..
1201 * Both of these heuristics are not used in Loss state, when we cannot
1202 * account for retransmits accurately.
1204 * SACK block validation.
1205 * ----------------------
1207 * SACK block range validation checks that the received SACK block fits to
1208 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1209 * Note that SND.UNA is not included to the range though being valid because
1210 * it means that the receiver is rather inconsistent with itself reporting
1211 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1212 * perfectly valid, however, in light of RFC2018 which explicitly states
1213 * that "SACK block MUST reflect the newest segment. Even if the newest
1214 * segment is going to be discarded ...", not that it looks very clever
1215 * in case of head skb. Due to potentional receiver driven attacks, we
1216 * choose to avoid immediate execution of a walk in write queue due to
1217 * reneging and defer head skb's loss recovery to standard loss recovery
1218 * procedure that will eventually trigger (nothing forbids us doing this).
1220 * Implements also blockage to start_seq wrap-around. Problem lies in the
1221 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1222 * there's no guarantee that it will be before snd_nxt (n). The problem
1223 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1226 * <- outs wnd -> <- wrapzone ->
1227 * u e n u_w e_w s n_w
1229 * |<------------+------+----- TCP seqno space --------------+---------->|
1230 * ...-- <2^31 ->| |<--------...
1231 * ...---- >2^31 ------>| |<--------...
1233 * Current code wouldn't be vulnerable but it's better still to discard such
1234 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1235 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1236 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1237 * equal to the ideal case (infinite seqno space without wrap caused issues).
1239 * With D-SACK the lower bound is extended to cover sequence space below
1240 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1241 * again, D-SACK block must not to go across snd_una (for the same reason as
1242 * for the normal SACK blocks, explained above). But there all simplicity
1243 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1244 * fully below undo_marker they do not affect behavior in anyway and can
1245 * therefore be safely ignored. In rare cases (which are more or less
1246 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1247 * fragmentation and packet reordering past skb's retransmission. To consider
1248 * them correctly, the acceptable range must be extended even more though
1249 * the exact amount is rather hard to quantify. However, tp->max_window can
1250 * be used as an exaggerated estimate.
1252 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
1253 u32 start_seq
, u32 end_seq
)
1255 /* Too far in future, or reversed (interpretation is ambiguous) */
1256 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1259 /* Nasty start_seq wrap-around check (see comments above) */
1260 if (!before(start_seq
, tp
->snd_nxt
))
1263 /* In outstanding window? ...This is valid exit for D-SACKs too.
1264 * start_seq == snd_una is non-sensical (see comments above)
1266 if (after(start_seq
, tp
->snd_una
))
1269 if (!is_dsack
|| !tp
->undo_marker
)
1272 /* ...Then it's D-SACK, and must reside below snd_una completely */
1273 if (after(end_seq
, tp
->snd_una
))
1276 if (!before(start_seq
, tp
->undo_marker
))
1280 if (!after(end_seq
, tp
->undo_marker
))
1283 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1284 * start_seq < undo_marker and end_seq >= undo_marker.
1286 return !before(start_seq
, end_seq
- tp
->max_window
);
1289 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1290 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1291 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1293 struct tcp_sock
*tp
= tcp_sk(sk
);
1294 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1295 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1298 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1299 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1300 } else if (num_sacks
> 1) {
1301 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1302 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1304 if (after(end_seq_0
, end_seq_1
) || before(start_seq_0
, start_seq_1
))
1306 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKOFORECV
);
1311 dup_segs
= tcp_dsack_seen(tp
, start_seq_0
, end_seq_0
, state
);
1312 if (!dup_segs
) { /* Skip dubious DSACK */
1313 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKIGNOREDDUBIOUS
);
1317 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKRECVSEGS
, dup_segs
);
1319 /* D-SACK for already forgotten data... Do dumb counting. */
1320 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1321 !after(end_seq_0
, prior_snd_una
) &&
1322 after(end_seq_0
, tp
->undo_marker
))
1323 tp
->undo_retrans
= max_t(int, 0, tp
->undo_retrans
- dup_segs
);
1328 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1329 * the incoming SACK may not exactly match but we can find smaller MSS
1330 * aligned portion of it that matches. Therefore we might need to fragment
1331 * which may fail and creates some hassle (caller must handle error case
1334 * FIXME: this could be merged to shift decision code
1336 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1337 u32 start_seq
, u32 end_seq
)
1341 unsigned int pkt_len
;
1344 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1345 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1347 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1348 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1349 mss
= tcp_skb_mss(skb
);
1350 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1353 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1357 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1362 /* Round if necessary so that SACKs cover only full MSSes
1363 * and/or the remaining small portion (if present)
1365 if (pkt_len
> mss
) {
1366 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1367 if (!in_sack
&& new_len
< pkt_len
)
1372 if (pkt_len
>= skb
->len
&& !in_sack
)
1375 err
= tcp_fragment(sk
, TCP_FRAG_IN_RTX_QUEUE
, skb
,
1376 pkt_len
, mss
, GFP_ATOMIC
);
1384 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1385 static u8
tcp_sacktag_one(struct sock
*sk
,
1386 struct tcp_sacktag_state
*state
, u8 sacked
,
1387 u32 start_seq
, u32 end_seq
,
1388 int dup_sack
, int pcount
,
1391 struct tcp_sock
*tp
= tcp_sk(sk
);
1393 /* Account D-SACK for retransmitted packet. */
1394 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1395 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1396 after(end_seq
, tp
->undo_marker
))
1397 tp
->undo_retrans
= max_t(int, 0, tp
->undo_retrans
- pcount
);
1398 if ((sacked
& TCPCB_SACKED_ACKED
) &&
1399 before(start_seq
, state
->reord
))
1400 state
->reord
= start_seq
;
1403 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1404 if (!after(end_seq
, tp
->snd_una
))
1407 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1408 tcp_rack_advance(tp
, sacked
, end_seq
, xmit_time
);
1410 if (sacked
& TCPCB_SACKED_RETRANS
) {
1411 /* If the segment is not tagged as lost,
1412 * we do not clear RETRANS, believing
1413 * that retransmission is still in flight.
1415 if (sacked
& TCPCB_LOST
) {
1416 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1417 tp
->lost_out
-= pcount
;
1418 tp
->retrans_out
-= pcount
;
1421 if (!(sacked
& TCPCB_RETRANS
)) {
1422 /* New sack for not retransmitted frame,
1423 * which was in hole. It is reordering.
1425 if (before(start_seq
,
1426 tcp_highest_sack_seq(tp
)) &&
1427 before(start_seq
, state
->reord
))
1428 state
->reord
= start_seq
;
1430 if (!after(end_seq
, tp
->high_seq
))
1431 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1432 if (state
->first_sackt
== 0)
1433 state
->first_sackt
= xmit_time
;
1434 state
->last_sackt
= xmit_time
;
1437 if (sacked
& TCPCB_LOST
) {
1438 sacked
&= ~TCPCB_LOST
;
1439 tp
->lost_out
-= pcount
;
1443 sacked
|= TCPCB_SACKED_ACKED
;
1444 state
->flag
|= FLAG_DATA_SACKED
;
1445 tp
->sacked_out
+= pcount
;
1446 /* Out-of-order packets delivered */
1447 state
->sack_delivered
+= pcount
;
1449 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1450 if (tp
->lost_skb_hint
&&
1451 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1452 tp
->lost_cnt_hint
+= pcount
;
1455 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1456 * frames and clear it. undo_retrans is decreased above, L|R frames
1457 * are accounted above as well.
1459 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1460 sacked
&= ~TCPCB_SACKED_RETRANS
;
1461 tp
->retrans_out
-= pcount
;
1467 /* Shift newly-SACKed bytes from this skb to the immediately previous
1468 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1470 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*prev
,
1471 struct sk_buff
*skb
,
1472 struct tcp_sacktag_state
*state
,
1473 unsigned int pcount
, int shifted
, int mss
,
1476 struct tcp_sock
*tp
= tcp_sk(sk
);
1477 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1478 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1482 /* Adjust counters and hints for the newly sacked sequence
1483 * range but discard the return value since prev is already
1484 * marked. We must tag the range first because the seq
1485 * advancement below implicitly advances
1486 * tcp_highest_sack_seq() when skb is highest_sack.
1488 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1489 start_seq
, end_seq
, dup_sack
, pcount
,
1490 tcp_skb_timestamp_us(skb
));
1491 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1493 if (skb
== tp
->lost_skb_hint
)
1494 tp
->lost_cnt_hint
+= pcount
;
1496 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1497 TCP_SKB_CB(skb
)->seq
+= shifted
;
1499 tcp_skb_pcount_add(prev
, pcount
);
1500 WARN_ON_ONCE(tcp_skb_pcount(skb
) < pcount
);
1501 tcp_skb_pcount_add(skb
, -pcount
);
1503 /* When we're adding to gso_segs == 1, gso_size will be zero,
1504 * in theory this shouldn't be necessary but as long as DSACK
1505 * code can come after this skb later on it's better to keep
1506 * setting gso_size to something.
1508 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1509 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1511 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1512 if (tcp_skb_pcount(skb
) <= 1)
1513 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1515 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1516 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1519 BUG_ON(!tcp_skb_pcount(skb
));
1520 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1524 /* Whole SKB was eaten :-) */
1526 if (skb
== tp
->retransmit_skb_hint
)
1527 tp
->retransmit_skb_hint
= prev
;
1528 if (skb
== tp
->lost_skb_hint
) {
1529 tp
->lost_skb_hint
= prev
;
1530 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1533 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1534 TCP_SKB_CB(prev
)->eor
= TCP_SKB_CB(skb
)->eor
;
1535 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1536 TCP_SKB_CB(prev
)->end_seq
++;
1538 if (skb
== tcp_highest_sack(sk
))
1539 tcp_advance_highest_sack(sk
, skb
);
1541 tcp_skb_collapse_tstamp(prev
, skb
);
1542 if (unlikely(TCP_SKB_CB(prev
)->tx
.delivered_mstamp
))
1543 TCP_SKB_CB(prev
)->tx
.delivered_mstamp
= 0;
1545 tcp_rtx_queue_unlink_and_free(skb
, sk
);
1547 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1552 /* I wish gso_size would have a bit more sane initialization than
1553 * something-or-zero which complicates things
1555 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1557 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1560 /* Shifting pages past head area doesn't work */
1561 static int skb_can_shift(const struct sk_buff
*skb
)
1563 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1566 int tcp_skb_shift(struct sk_buff
*to
, struct sk_buff
*from
,
1567 int pcount
, int shiftlen
)
1569 /* TCP min gso_size is 8 bytes (TCP_MIN_GSO_SIZE)
1570 * Since TCP_SKB_CB(skb)->tcp_gso_segs is 16 bits, we need
1571 * to make sure not storing more than 65535 * 8 bytes per skb,
1572 * even if current MSS is bigger.
1574 if (unlikely(to
->len
+ shiftlen
>= 65535 * TCP_MIN_GSO_SIZE
))
1576 if (unlikely(tcp_skb_pcount(to
) + pcount
> 65535))
1578 return skb_shift(to
, from
, shiftlen
);
1581 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1584 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1585 struct tcp_sacktag_state
*state
,
1586 u32 start_seq
, u32 end_seq
,
1589 struct tcp_sock
*tp
= tcp_sk(sk
);
1590 struct sk_buff
*prev
;
1596 /* Normally R but no L won't result in plain S */
1598 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1600 if (!skb_can_shift(skb
))
1602 /* This frame is about to be dropped (was ACKed). */
1603 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1606 /* Can only happen with delayed DSACK + discard craziness */
1607 prev
= skb_rb_prev(skb
);
1611 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1614 if (!tcp_skb_can_collapse(prev
, skb
))
1617 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1618 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1622 pcount
= tcp_skb_pcount(skb
);
1623 mss
= tcp_skb_seglen(skb
);
1625 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1626 * drop this restriction as unnecessary
1628 if (mss
!= tcp_skb_seglen(prev
))
1631 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1633 /* CHECKME: This is non-MSS split case only?, this will
1634 * cause skipped skbs due to advancing loop btw, original
1635 * has that feature too
1637 if (tcp_skb_pcount(skb
) <= 1)
1640 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1642 /* TODO: head merge to next could be attempted here
1643 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1644 * though it might not be worth of the additional hassle
1646 * ...we can probably just fallback to what was done
1647 * previously. We could try merging non-SACKed ones
1648 * as well but it probably isn't going to buy off
1649 * because later SACKs might again split them, and
1650 * it would make skb timestamp tracking considerably
1656 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1658 BUG_ON(len
> skb
->len
);
1660 /* MSS boundaries should be honoured or else pcount will
1661 * severely break even though it makes things bit trickier.
1662 * Optimize common case to avoid most of the divides
1664 mss
= tcp_skb_mss(skb
);
1666 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1667 * drop this restriction as unnecessary
1669 if (mss
!= tcp_skb_seglen(prev
))
1674 } else if (len
< mss
) {
1682 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1683 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1686 if (!tcp_skb_shift(prev
, skb
, pcount
, len
))
1688 if (!tcp_shifted_skb(sk
, prev
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1691 /* Hole filled allows collapsing with the next as well, this is very
1692 * useful when hole on every nth skb pattern happens
1694 skb
= skb_rb_next(prev
);
1698 if (!skb_can_shift(skb
) ||
1699 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1700 (mss
!= tcp_skb_seglen(skb
)))
1703 if (!tcp_skb_can_collapse(prev
, skb
))
1706 pcount
= tcp_skb_pcount(skb
);
1707 if (tcp_skb_shift(prev
, skb
, pcount
, len
))
1708 tcp_shifted_skb(sk
, prev
, skb
, state
, pcount
,
1718 NET_INC_STATS(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1722 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1723 struct tcp_sack_block
*next_dup
,
1724 struct tcp_sacktag_state
*state
,
1725 u32 start_seq
, u32 end_seq
,
1728 struct tcp_sock
*tp
= tcp_sk(sk
);
1729 struct sk_buff
*tmp
;
1731 skb_rbtree_walk_from(skb
) {
1733 bool dup_sack
= dup_sack_in
;
1735 /* queue is in-order => we can short-circuit the walk early */
1736 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1740 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1741 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1742 next_dup
->start_seq
,
1748 /* skb reference here is a bit tricky to get right, since
1749 * shifting can eat and free both this skb and the next,
1750 * so not even _safe variant of the loop is enough.
1753 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1754 start_seq
, end_seq
, dup_sack
);
1763 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1769 if (unlikely(in_sack
< 0))
1773 TCP_SKB_CB(skb
)->sacked
=
1776 TCP_SKB_CB(skb
)->sacked
,
1777 TCP_SKB_CB(skb
)->seq
,
1778 TCP_SKB_CB(skb
)->end_seq
,
1780 tcp_skb_pcount(skb
),
1781 tcp_skb_timestamp_us(skb
));
1782 tcp_rate_skb_delivered(sk
, skb
, state
->rate
);
1783 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1784 list_del_init(&skb
->tcp_tsorted_anchor
);
1786 if (!before(TCP_SKB_CB(skb
)->seq
,
1787 tcp_highest_sack_seq(tp
)))
1788 tcp_advance_highest_sack(sk
, skb
);
1794 static struct sk_buff
*tcp_sacktag_bsearch(struct sock
*sk
, u32 seq
)
1796 struct rb_node
*parent
, **p
= &sk
->tcp_rtx_queue
.rb_node
;
1797 struct sk_buff
*skb
;
1801 skb
= rb_to_skb(parent
);
1802 if (before(seq
, TCP_SKB_CB(skb
)->seq
)) {
1803 p
= &parent
->rb_left
;
1806 if (!before(seq
, TCP_SKB_CB(skb
)->end_seq
)) {
1807 p
= &parent
->rb_right
;
1815 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1818 if (skb
&& after(TCP_SKB_CB(skb
)->seq
, skip_to_seq
))
1821 return tcp_sacktag_bsearch(sk
, skip_to_seq
);
1824 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1826 struct tcp_sack_block
*next_dup
,
1827 struct tcp_sacktag_state
*state
,
1833 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1834 skb
= tcp_sacktag_skip(skb
, sk
, next_dup
->start_seq
);
1835 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1836 next_dup
->start_seq
, next_dup
->end_seq
,
1843 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1845 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1849 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1850 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1852 struct tcp_sock
*tp
= tcp_sk(sk
);
1853 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1854 TCP_SKB_CB(ack_skb
)->sacked
);
1855 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1856 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1857 struct tcp_sack_block
*cache
;
1858 struct sk_buff
*skb
;
1859 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1861 bool found_dup_sack
= false;
1863 int first_sack_index
;
1866 state
->reord
= tp
->snd_nxt
;
1868 if (!tp
->sacked_out
)
1869 tcp_highest_sack_reset(sk
);
1871 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1872 num_sacks
, prior_snd_una
, state
);
1874 /* Eliminate too old ACKs, but take into
1875 * account more or less fresh ones, they can
1876 * contain valid SACK info.
1878 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1881 if (!tp
->packets_out
)
1885 first_sack_index
= 0;
1886 for (i
= 0; i
< num_sacks
; i
++) {
1887 bool dup_sack
= !i
&& found_dup_sack
;
1889 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1890 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1892 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1893 sp
[used_sacks
].start_seq
,
1894 sp
[used_sacks
].end_seq
)) {
1898 if (!tp
->undo_marker
)
1899 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1901 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1903 /* Don't count olds caused by ACK reordering */
1904 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1905 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1907 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1910 NET_INC_STATS(sock_net(sk
), mib_idx
);
1912 first_sack_index
= -1;
1916 /* Ignore very old stuff early */
1917 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
)) {
1919 first_sack_index
= -1;
1926 /* order SACK blocks to allow in order walk of the retrans queue */
1927 for (i
= used_sacks
- 1; i
> 0; i
--) {
1928 for (j
= 0; j
< i
; j
++) {
1929 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1930 swap(sp
[j
], sp
[j
+ 1]);
1932 /* Track where the first SACK block goes to */
1933 if (j
== first_sack_index
)
1934 first_sack_index
= j
+ 1;
1939 state
->mss_now
= tcp_current_mss(sk
);
1943 if (!tp
->sacked_out
) {
1944 /* It's already past, so skip checking against it */
1945 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1947 cache
= tp
->recv_sack_cache
;
1948 /* Skip empty blocks in at head of the cache */
1949 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1954 while (i
< used_sacks
) {
1955 u32 start_seq
= sp
[i
].start_seq
;
1956 u32 end_seq
= sp
[i
].end_seq
;
1957 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1958 struct tcp_sack_block
*next_dup
= NULL
;
1960 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1961 next_dup
= &sp
[i
+ 1];
1963 /* Skip too early cached blocks */
1964 while (tcp_sack_cache_ok(tp
, cache
) &&
1965 !before(start_seq
, cache
->end_seq
))
1968 /* Can skip some work by looking recv_sack_cache? */
1969 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1970 after(end_seq
, cache
->start_seq
)) {
1973 if (before(start_seq
, cache
->start_seq
)) {
1974 skb
= tcp_sacktag_skip(skb
, sk
, start_seq
);
1975 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1982 /* Rest of the block already fully processed? */
1983 if (!after(end_seq
, cache
->end_seq
))
1986 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1990 /* ...tail remains todo... */
1991 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1992 /* ...but better entrypoint exists! */
1993 skb
= tcp_highest_sack(sk
);
2000 skb
= tcp_sacktag_skip(skb
, sk
, cache
->end_seq
);
2001 /* Check overlap against next cached too (past this one already) */
2006 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
2007 skb
= tcp_highest_sack(sk
);
2011 skb
= tcp_sacktag_skip(skb
, sk
, start_seq
);
2014 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
2015 start_seq
, end_seq
, dup_sack
);
2021 /* Clear the head of the cache sack blocks so we can skip it next time */
2022 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
2023 tp
->recv_sack_cache
[i
].start_seq
= 0;
2024 tp
->recv_sack_cache
[i
].end_seq
= 0;
2026 for (j
= 0; j
< used_sacks
; j
++)
2027 tp
->recv_sack_cache
[i
++] = sp
[j
];
2029 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
|| tp
->undo_marker
)
2030 tcp_check_sack_reordering(sk
, state
->reord
, 0);
2032 tcp_verify_left_out(tp
);
2035 #if FASTRETRANS_DEBUG > 0
2036 WARN_ON((int)tp
->sacked_out
< 0);
2037 WARN_ON((int)tp
->lost_out
< 0);
2038 WARN_ON((int)tp
->retrans_out
< 0);
2039 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
2044 /* Limits sacked_out so that sum with lost_out isn't ever larger than
2045 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
2047 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
2051 holes
= max(tp
->lost_out
, 1U);
2052 holes
= min(holes
, tp
->packets_out
);
2054 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
2055 tp
->sacked_out
= tp
->packets_out
- holes
;
2061 /* If we receive more dupacks than we expected counting segments
2062 * in assumption of absent reordering, interpret this as reordering.
2063 * The only another reason could be bug in receiver TCP.
2065 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
2067 struct tcp_sock
*tp
= tcp_sk(sk
);
2069 if (!tcp_limit_reno_sacked(tp
))
2072 tp
->reordering
= min_t(u32
, tp
->packets_out
+ addend
,
2073 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_max_reordering
));
2075 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRENOREORDER
);
2078 /* Emulate SACKs for SACKless connection: account for a new dupack. */
2080 static void tcp_add_reno_sack(struct sock
*sk
, int num_dupack
, bool ece_ack
)
2083 struct tcp_sock
*tp
= tcp_sk(sk
);
2084 u32 prior_sacked
= tp
->sacked_out
;
2087 tp
->sacked_out
+= num_dupack
;
2088 tcp_check_reno_reordering(sk
, 0);
2089 delivered
= tp
->sacked_out
- prior_sacked
;
2091 tcp_count_delivered(tp
, delivered
, ece_ack
);
2092 tcp_verify_left_out(tp
);
2096 /* Account for ACK, ACKing some data in Reno Recovery phase. */
2098 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
, bool ece_ack
)
2100 struct tcp_sock
*tp
= tcp_sk(sk
);
2103 /* One ACK acked hole. The rest eat duplicate ACKs. */
2104 tcp_count_delivered(tp
, max_t(int, acked
- tp
->sacked_out
, 1),
2106 if (acked
- 1 >= tp
->sacked_out
)
2109 tp
->sacked_out
-= acked
- 1;
2111 tcp_check_reno_reordering(sk
, acked
);
2112 tcp_verify_left_out(tp
);
2115 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
2120 void tcp_clear_retrans(struct tcp_sock
*tp
)
2122 tp
->retrans_out
= 0;
2124 tp
->undo_marker
= 0;
2125 tp
->undo_retrans
= -1;
2129 tp
->total_rto_recoveries
= 0;
2130 tp
->total_rto_time
= 0;
2133 static inline void tcp_init_undo(struct tcp_sock
*tp
)
2135 tp
->undo_marker
= tp
->snd_una
;
2136 /* Retransmission still in flight may cause DSACKs later. */
2137 tp
->undo_retrans
= tp
->retrans_out
? : -1;
2140 static bool tcp_is_rack(const struct sock
*sk
)
2142 return READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_recovery
) &
2143 TCP_RACK_LOSS_DETECTION
;
2146 /* If we detect SACK reneging, forget all SACK information
2147 * and reset tags completely, otherwise preserve SACKs. If receiver
2148 * dropped its ofo queue, we will know this due to reneging detection.
2150 static void tcp_timeout_mark_lost(struct sock
*sk
)
2152 struct tcp_sock
*tp
= tcp_sk(sk
);
2153 struct sk_buff
*skb
, *head
;
2154 bool is_reneg
; /* is receiver reneging on SACKs? */
2156 head
= tcp_rtx_queue_head(sk
);
2157 is_reneg
= head
&& (TCP_SKB_CB(head
)->sacked
& TCPCB_SACKED_ACKED
);
2159 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2161 /* Mark SACK reneging until we recover from this loss event. */
2162 tp
->is_sack_reneg
= 1;
2163 } else if (tcp_is_reno(tp
)) {
2164 tcp_reset_reno_sack(tp
);
2168 skb_rbtree_walk_from(skb
) {
2170 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2171 else if (tcp_is_rack(sk
) && skb
!= head
&&
2172 tcp_rack_skb_timeout(tp
, skb
, 0) > 0)
2173 continue; /* Don't mark recently sent ones lost yet */
2174 tcp_mark_skb_lost(sk
, skb
);
2176 tcp_verify_left_out(tp
);
2177 tcp_clear_all_retrans_hints(tp
);
2180 /* Enter Loss state. */
2181 void tcp_enter_loss(struct sock
*sk
)
2183 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2184 struct tcp_sock
*tp
= tcp_sk(sk
);
2185 struct net
*net
= sock_net(sk
);
2186 bool new_recovery
= icsk
->icsk_ca_state
< TCP_CA_Recovery
;
2189 tcp_timeout_mark_lost(sk
);
2191 /* Reduce ssthresh if it has not yet been made inside this window. */
2192 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
2193 !after(tp
->high_seq
, tp
->snd_una
) ||
2194 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2195 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2196 tp
->prior_cwnd
= tcp_snd_cwnd(tp
);
2197 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2198 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2201 tcp_snd_cwnd_set(tp
, tcp_packets_in_flight(tp
) + 1);
2202 tp
->snd_cwnd_cnt
= 0;
2203 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2205 /* Timeout in disordered state after receiving substantial DUPACKs
2206 * suggests that the degree of reordering is over-estimated.
2208 reordering
= READ_ONCE(net
->ipv4
.sysctl_tcp_reordering
);
2209 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
2210 tp
->sacked_out
>= reordering
)
2211 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2214 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2215 tp
->high_seq
= tp
->snd_nxt
;
2216 tcp_ecn_queue_cwr(tp
);
2218 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
2219 * loss recovery is underway except recurring timeout(s) on
2220 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
2222 tp
->frto
= READ_ONCE(net
->ipv4
.sysctl_tcp_frto
) &&
2223 (new_recovery
|| icsk
->icsk_retransmits
) &&
2224 !inet_csk(sk
)->icsk_mtup
.probe_size
;
2227 /* If ACK arrived pointing to a remembered SACK, it means that our
2228 * remembered SACKs do not reflect real state of receiver i.e.
2229 * receiver _host_ is heavily congested (or buggy).
2231 * To avoid big spurious retransmission bursts due to transient SACK
2232 * scoreboard oddities that look like reneging, we give the receiver a
2233 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2234 * restore sanity to the SACK scoreboard. If the apparent reneging
2235 * persists until this RTO then we'll clear the SACK scoreboard.
2237 static bool tcp_check_sack_reneging(struct sock
*sk
, int *ack_flag
)
2239 if (*ack_flag
& FLAG_SACK_RENEGING
&&
2240 *ack_flag
& FLAG_SND_UNA_ADVANCED
) {
2241 struct tcp_sock
*tp
= tcp_sk(sk
);
2242 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2243 msecs_to_jiffies(10));
2245 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2246 delay
, TCP_RTO_MAX
);
2247 *ack_flag
&= ~FLAG_SET_XMIT_TIMER
;
2253 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2254 * counter when SACK is enabled (without SACK, sacked_out is used for
2257 * With reordering, holes may still be in flight, so RFC3517 recovery
2258 * uses pure sacked_out (total number of SACKed segments) even though
2259 * it violates the RFC that uses duplicate ACKs, often these are equal
2260 * but when e.g. out-of-window ACKs or packet duplication occurs,
2261 * they differ. Since neither occurs due to loss, TCP should really
2264 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2266 return tp
->sacked_out
+ 1;
2269 /* Linux NewReno/SACK/ECN state machine.
2270 * --------------------------------------
2272 * "Open" Normal state, no dubious events, fast path.
2273 * "Disorder" In all the respects it is "Open",
2274 * but requires a bit more attention. It is entered when
2275 * we see some SACKs or dupacks. It is split of "Open"
2276 * mainly to move some processing from fast path to slow one.
2277 * "CWR" CWND was reduced due to some Congestion Notification event.
2278 * It can be ECN, ICMP source quench, local device congestion.
2279 * "Recovery" CWND was reduced, we are fast-retransmitting.
2280 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2282 * tcp_fastretrans_alert() is entered:
2283 * - each incoming ACK, if state is not "Open"
2284 * - when arrived ACK is unusual, namely:
2289 * Counting packets in flight is pretty simple.
2291 * in_flight = packets_out - left_out + retrans_out
2293 * packets_out is SND.NXT-SND.UNA counted in packets.
2295 * retrans_out is number of retransmitted segments.
2297 * left_out is number of segments left network, but not ACKed yet.
2299 * left_out = sacked_out + lost_out
2301 * sacked_out: Packets, which arrived to receiver out of order
2302 * and hence not ACKed. With SACKs this number is simply
2303 * amount of SACKed data. Even without SACKs
2304 * it is easy to give pretty reliable estimate of this number,
2305 * counting duplicate ACKs.
2307 * lost_out: Packets lost by network. TCP has no explicit
2308 * "loss notification" feedback from network (for now).
2309 * It means that this number can be only _guessed_.
2310 * Actually, it is the heuristics to predict lossage that
2311 * distinguishes different algorithms.
2313 * F.e. after RTO, when all the queue is considered as lost,
2314 * lost_out = packets_out and in_flight = retrans_out.
2316 * Essentially, we have now a few algorithms detecting
2319 * If the receiver supports SACK:
2321 * RFC6675/3517: It is the conventional algorithm. A packet is
2322 * considered lost if the number of higher sequence packets
2323 * SACKed is greater than or equal the DUPACK thoreshold
2324 * (reordering). This is implemented in tcp_mark_head_lost and
2325 * tcp_update_scoreboard.
2327 * RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
2328 * (2017-) that checks timing instead of counting DUPACKs.
2329 * Essentially a packet is considered lost if it's not S/ACKed
2330 * after RTT + reordering_window, where both metrics are
2331 * dynamically measured and adjusted. This is implemented in
2332 * tcp_rack_mark_lost.
2334 * If the receiver does not support SACK:
2336 * NewReno (RFC6582): in Recovery we assume that one segment
2337 * is lost (classic Reno). While we are in Recovery and
2338 * a partial ACK arrives, we assume that one more packet
2339 * is lost (NewReno). This heuristics are the same in NewReno
2342 * Really tricky (and requiring careful tuning) part of algorithm
2343 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2344 * The first determines the moment _when_ we should reduce CWND and,
2345 * hence, slow down forward transmission. In fact, it determines the moment
2346 * when we decide that hole is caused by loss, rather than by a reorder.
2348 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2349 * holes, caused by lost packets.
2351 * And the most logically complicated part of algorithm is undo
2352 * heuristics. We detect false retransmits due to both too early
2353 * fast retransmit (reordering) and underestimated RTO, analyzing
2354 * timestamps and D-SACKs. When we detect that some segments were
2355 * retransmitted by mistake and CWND reduction was wrong, we undo
2356 * window reduction and abort recovery phase. This logic is hidden
2357 * inside several functions named tcp_try_undo_<something>.
2360 /* This function decides, when we should leave Disordered state
2361 * and enter Recovery phase, reducing congestion window.
2363 * Main question: may we further continue forward transmission
2364 * with the same cwnd?
2366 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2368 struct tcp_sock
*tp
= tcp_sk(sk
);
2370 /* Trick#1: The loss is proven. */
2374 /* Not-A-Trick#2 : Classic rule... */
2375 if (!tcp_is_rack(sk
) && tcp_dupack_heuristics(tp
) > tp
->reordering
)
2381 /* Detect loss in event "A" above by marking head of queue up as lost.
2382 * For RFC3517 SACK, a segment is considered lost if it
2383 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2384 * the maximum SACKed segments to pass before reaching this limit.
2386 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2388 struct tcp_sock
*tp
= tcp_sk(sk
);
2389 struct sk_buff
*skb
;
2391 /* Use SACK to deduce losses of new sequences sent during recovery */
2392 const u32 loss_high
= tp
->snd_nxt
;
2394 WARN_ON(packets
> tp
->packets_out
);
2395 skb
= tp
->lost_skb_hint
;
2397 /* Head already handled? */
2398 if (mark_head
&& after(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
))
2400 cnt
= tp
->lost_cnt_hint
;
2402 skb
= tcp_rtx_queue_head(sk
);
2406 skb_rbtree_walk_from(skb
) {
2407 /* TODO: do this better */
2408 /* this is not the most efficient way to do this... */
2409 tp
->lost_skb_hint
= skb
;
2410 tp
->lost_cnt_hint
= cnt
;
2412 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2415 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2416 cnt
+= tcp_skb_pcount(skb
);
2421 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
))
2422 tcp_mark_skb_lost(sk
, skb
);
2427 tcp_verify_left_out(tp
);
2430 /* Account newly detected lost packet(s) */
2432 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2434 struct tcp_sock
*tp
= tcp_sk(sk
);
2436 if (tcp_is_sack(tp
)) {
2437 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2438 if (sacked_upto
>= 0)
2439 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2440 else if (fast_rexmit
)
2441 tcp_mark_head_lost(sk
, 1, 1);
2445 static bool tcp_tsopt_ecr_before(const struct tcp_sock
*tp
, u32 when
)
2447 return tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2448 before(tp
->rx_opt
.rcv_tsecr
, when
);
2451 /* skb is spurious retransmitted if the returned timestamp echo
2452 * reply is prior to the skb transmission time
2454 static bool tcp_skb_spurious_retrans(const struct tcp_sock
*tp
,
2455 const struct sk_buff
*skb
)
2457 return (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
) &&
2458 tcp_tsopt_ecr_before(tp
, tcp_skb_timestamp_ts(tp
->tcp_usec_ts
, skb
));
2461 /* Nothing was retransmitted or returned timestamp is less
2462 * than timestamp of the first retransmission.
2464 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2466 return tp
->retrans_stamp
&&
2467 tcp_tsopt_ecr_before(tp
, tp
->retrans_stamp
);
2470 /* Undo procedures. */
2472 /* We can clear retrans_stamp when there are no retransmissions in the
2473 * window. It would seem that it is trivially available for us in
2474 * tp->retrans_out, however, that kind of assumptions doesn't consider
2475 * what will happen if errors occur when sending retransmission for the
2476 * second time. ...It could the that such segment has only
2477 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2478 * the head skb is enough except for some reneging corner cases that
2479 * are not worth the effort.
2481 * Main reason for all this complexity is the fact that connection dying
2482 * time now depends on the validity of the retrans_stamp, in particular,
2483 * that successive retransmissions of a segment must not advance
2484 * retrans_stamp under any conditions.
2486 static bool tcp_any_retrans_done(const struct sock
*sk
)
2488 const struct tcp_sock
*tp
= tcp_sk(sk
);
2489 struct sk_buff
*skb
;
2491 if (tp
->retrans_out
)
2494 skb
= tcp_rtx_queue_head(sk
);
2495 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2501 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2503 #if FASTRETRANS_DEBUG > 1
2504 struct tcp_sock
*tp
= tcp_sk(sk
);
2505 struct inet_sock
*inet
= inet_sk(sk
);
2507 if (sk
->sk_family
== AF_INET
) {
2508 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2510 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2511 tcp_snd_cwnd(tp
), tcp_left_out(tp
),
2512 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2515 #if IS_ENABLED(CONFIG_IPV6)
2516 else if (sk
->sk_family
== AF_INET6
) {
2517 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2519 &sk
->sk_v6_daddr
, ntohs(inet
->inet_dport
),
2520 tcp_snd_cwnd(tp
), tcp_left_out(tp
),
2521 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2528 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2530 struct tcp_sock
*tp
= tcp_sk(sk
);
2533 struct sk_buff
*skb
;
2535 skb_rbtree_walk(skb
, &sk
->tcp_rtx_queue
) {
2536 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2539 tcp_clear_all_retrans_hints(tp
);
2542 if (tp
->prior_ssthresh
) {
2543 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2545 tcp_snd_cwnd_set(tp
, icsk
->icsk_ca_ops
->undo_cwnd(sk
));
2547 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2548 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2549 tcp_ecn_withdraw_cwr(tp
);
2552 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2553 tp
->undo_marker
= 0;
2554 tp
->rack
.advanced
= 1; /* Force RACK to re-exam losses */
2557 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2559 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2562 static bool tcp_is_non_sack_preventing_reopen(struct sock
*sk
)
2564 struct tcp_sock
*tp
= tcp_sk(sk
);
2566 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2567 /* Hold old state until something *above* high_seq
2568 * is ACKed. For Reno it is MUST to prevent false
2569 * fast retransmits (RFC2582). SACK TCP is safe. */
2570 if (!tcp_any_retrans_done(sk
))
2571 tp
->retrans_stamp
= 0;
2577 /* People celebrate: "We love our President!" */
2578 static bool tcp_try_undo_recovery(struct sock
*sk
)
2580 struct tcp_sock
*tp
= tcp_sk(sk
);
2582 if (tcp_may_undo(tp
)) {
2585 /* Happy end! We did not retransmit anything
2586 * or our original transmission succeeded.
2588 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2589 tcp_undo_cwnd_reduction(sk
, false);
2590 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2591 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2593 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2595 NET_INC_STATS(sock_net(sk
), mib_idx
);
2596 } else if (tp
->rack
.reo_wnd_persist
) {
2597 tp
->rack
.reo_wnd_persist
--;
2599 if (tcp_is_non_sack_preventing_reopen(sk
))
2601 tcp_set_ca_state(sk
, TCP_CA_Open
);
2602 tp
->is_sack_reneg
= 0;
2606 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2607 static bool tcp_try_undo_dsack(struct sock
*sk
)
2609 struct tcp_sock
*tp
= tcp_sk(sk
);
2611 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2612 tp
->rack
.reo_wnd_persist
= min(TCP_RACK_RECOVERY_THRESH
,
2613 tp
->rack
.reo_wnd_persist
+ 1);
2614 DBGUNDO(sk
, "D-SACK");
2615 tcp_undo_cwnd_reduction(sk
, false);
2616 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2622 /* Undo during loss recovery after partial ACK or using F-RTO. */
2623 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2625 struct tcp_sock
*tp
= tcp_sk(sk
);
2627 if (frto_undo
|| tcp_may_undo(tp
)) {
2628 tcp_undo_cwnd_reduction(sk
, true);
2630 DBGUNDO(sk
, "partial loss");
2631 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2633 NET_INC_STATS(sock_net(sk
),
2634 LINUX_MIB_TCPSPURIOUSRTOS
);
2635 inet_csk(sk
)->icsk_retransmits
= 0;
2636 if (tcp_is_non_sack_preventing_reopen(sk
))
2638 if (frto_undo
|| tcp_is_sack(tp
)) {
2639 tcp_set_ca_state(sk
, TCP_CA_Open
);
2640 tp
->is_sack_reneg
= 0;
2647 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2648 * It computes the number of packets to send (sndcnt) based on packets newly
2650 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2651 * cwnd reductions across a full RTT.
2652 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2653 * But when SND_UNA is acked without further losses,
2654 * slow starts cwnd up to ssthresh to speed up the recovery.
2656 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2658 struct tcp_sock
*tp
= tcp_sk(sk
);
2660 tp
->high_seq
= tp
->snd_nxt
;
2661 tp
->tlp_high_seq
= 0;
2662 tp
->snd_cwnd_cnt
= 0;
2663 tp
->prior_cwnd
= tcp_snd_cwnd(tp
);
2664 tp
->prr_delivered
= 0;
2666 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2667 tcp_ecn_queue_cwr(tp
);
2670 void tcp_cwnd_reduction(struct sock
*sk
, int newly_acked_sacked
, int newly_lost
, int flag
)
2672 struct tcp_sock
*tp
= tcp_sk(sk
);
2674 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2676 if (newly_acked_sacked
<= 0 || WARN_ON_ONCE(!tp
->prior_cwnd
))
2679 tp
->prr_delivered
+= newly_acked_sacked
;
2681 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2683 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2685 sndcnt
= max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2686 newly_acked_sacked
);
2687 if (flag
& FLAG_SND_UNA_ADVANCED
&& !newly_lost
)
2689 sndcnt
= min(delta
, sndcnt
);
2691 /* Force a fast retransmit upon entering fast recovery */
2692 sndcnt
= max(sndcnt
, (tp
->prr_out
? 0 : 1));
2693 tcp_snd_cwnd_set(tp
, tcp_packets_in_flight(tp
) + sndcnt
);
2696 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2698 struct tcp_sock
*tp
= tcp_sk(sk
);
2700 if (inet_csk(sk
)->icsk_ca_ops
->cong_control
)
2703 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2704 if (tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
&&
2705 (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
|| tp
->undo_marker
)) {
2706 tcp_snd_cwnd_set(tp
, tp
->snd_ssthresh
);
2707 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2709 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2712 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2713 void tcp_enter_cwr(struct sock
*sk
)
2715 struct tcp_sock
*tp
= tcp_sk(sk
);
2717 tp
->prior_ssthresh
= 0;
2718 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2719 tp
->undo_marker
= 0;
2720 tcp_init_cwnd_reduction(sk
);
2721 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2724 EXPORT_SYMBOL(tcp_enter_cwr
);
2726 static void tcp_try_keep_open(struct sock
*sk
)
2728 struct tcp_sock
*tp
= tcp_sk(sk
);
2729 int state
= TCP_CA_Open
;
2731 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2732 state
= TCP_CA_Disorder
;
2734 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2735 tcp_set_ca_state(sk
, state
);
2736 tp
->high_seq
= tp
->snd_nxt
;
2740 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2742 struct tcp_sock
*tp
= tcp_sk(sk
);
2744 tcp_verify_left_out(tp
);
2746 if (!tcp_any_retrans_done(sk
))
2747 tp
->retrans_stamp
= 0;
2749 if (flag
& FLAG_ECE
)
2752 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2753 tcp_try_keep_open(sk
);
2757 static void tcp_mtup_probe_failed(struct sock
*sk
)
2759 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2761 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2762 icsk
->icsk_mtup
.probe_size
= 0;
2763 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPFAIL
);
2766 static void tcp_mtup_probe_success(struct sock
*sk
)
2768 struct tcp_sock
*tp
= tcp_sk(sk
);
2769 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2772 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2774 val
= (u64
)tcp_snd_cwnd(tp
) * tcp_mss_to_mtu(sk
, tp
->mss_cache
);
2775 do_div(val
, icsk
->icsk_mtup
.probe_size
);
2776 DEBUG_NET_WARN_ON_ONCE((u32
)val
!= val
);
2777 tcp_snd_cwnd_set(tp
, max_t(u32
, 1U, val
));
2779 tp
->snd_cwnd_cnt
= 0;
2780 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
2781 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2783 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2784 icsk
->icsk_mtup
.probe_size
= 0;
2785 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2786 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPMTUPSUCCESS
);
2789 /* Do a simple retransmit without using the backoff mechanisms in
2790 * tcp_timer. This is used for path mtu discovery.
2791 * The socket is already locked here.
2793 void tcp_simple_retransmit(struct sock
*sk
)
2795 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2796 struct tcp_sock
*tp
= tcp_sk(sk
);
2797 struct sk_buff
*skb
;
2800 /* A fastopen SYN request is stored as two separate packets within
2801 * the retransmit queue, this is done by tcp_send_syn_data().
2802 * As a result simply checking the MSS of the frames in the queue
2803 * will not work for the SYN packet.
2805 * Us being here is an indication of a path MTU issue so we can
2806 * assume that the fastopen SYN was lost and just mark all the
2807 * frames in the retransmit queue as lost. We will use an MSS of
2808 * -1 to mark all frames as lost, otherwise compute the current MSS.
2810 if (tp
->syn_data
&& sk
->sk_state
== TCP_SYN_SENT
)
2813 mss
= tcp_current_mss(sk
);
2815 skb_rbtree_walk(skb
, &sk
->tcp_rtx_queue
) {
2816 if (tcp_skb_seglen(skb
) > mss
)
2817 tcp_mark_skb_lost(sk
, skb
);
2820 tcp_clear_retrans_hints_partial(tp
);
2825 if (tcp_is_reno(tp
))
2826 tcp_limit_reno_sacked(tp
);
2828 tcp_verify_left_out(tp
);
2830 /* Don't muck with the congestion window here.
2831 * Reason is that we do not increase amount of _data_
2832 * in network, but units changed and effective
2833 * cwnd/ssthresh really reduced now.
2835 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2836 tp
->high_seq
= tp
->snd_nxt
;
2837 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2838 tp
->prior_ssthresh
= 0;
2839 tp
->undo_marker
= 0;
2840 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2842 tcp_xmit_retransmit_queue(sk
);
2844 EXPORT_SYMBOL(tcp_simple_retransmit
);
2846 void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2848 struct tcp_sock
*tp
= tcp_sk(sk
);
2851 if (tcp_is_reno(tp
))
2852 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2854 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2856 NET_INC_STATS(sock_net(sk
), mib_idx
);
2858 tp
->prior_ssthresh
= 0;
2861 if (!tcp_in_cwnd_reduction(sk
)) {
2863 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2864 tcp_init_cwnd_reduction(sk
);
2866 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2869 static void tcp_update_rto_time(struct tcp_sock
*tp
)
2871 if (tp
->rto_stamp
) {
2872 tp
->total_rto_time
+= tcp_time_stamp_ms(tp
) - tp
->rto_stamp
;
2877 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2878 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2880 static void tcp_process_loss(struct sock
*sk
, int flag
, int num_dupack
,
2883 struct tcp_sock
*tp
= tcp_sk(sk
);
2884 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2886 if ((flag
& FLAG_SND_UNA_ADVANCED
|| rcu_access_pointer(tp
->fastopen_rsk
)) &&
2887 tcp_try_undo_loss(sk
, false))
2890 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2891 /* Step 3.b. A timeout is spurious if not all data are
2892 * lost, i.e., never-retransmitted data are (s)acked.
2894 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2895 tcp_try_undo_loss(sk
, true))
2898 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2899 if (flag
& FLAG_DATA_SACKED
|| num_dupack
)
2900 tp
->frto
= 0; /* Step 3.a. loss was real */
2901 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2902 tp
->high_seq
= tp
->snd_nxt
;
2903 /* Step 2.b. Try send new data (but deferred until cwnd
2904 * is updated in tcp_ack()). Otherwise fall back to
2905 * the conventional recovery.
2907 if (!tcp_write_queue_empty(sk
) &&
2908 after(tcp_wnd_end(tp
), tp
->snd_nxt
)) {
2909 *rexmit
= REXMIT_NEW
;
2917 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2918 tcp_try_undo_recovery(sk
);
2921 if (tcp_is_reno(tp
)) {
2922 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2923 * delivered. Lower inflight to clock out (re)transmissions.
2925 if (after(tp
->snd_nxt
, tp
->high_seq
) && num_dupack
)
2926 tcp_add_reno_sack(sk
, num_dupack
, flag
& FLAG_ECE
);
2927 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2928 tcp_reset_reno_sack(tp
);
2930 *rexmit
= REXMIT_LOST
;
2933 static bool tcp_force_fast_retransmit(struct sock
*sk
)
2935 struct tcp_sock
*tp
= tcp_sk(sk
);
2937 return after(tcp_highest_sack_seq(tp
),
2938 tp
->snd_una
+ tp
->reordering
* tp
->mss_cache
);
2941 /* Undo during fast recovery after partial ACK. */
2942 static bool tcp_try_undo_partial(struct sock
*sk
, u32 prior_snd_una
,
2945 struct tcp_sock
*tp
= tcp_sk(sk
);
2947 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2948 /* Plain luck! Hole if filled with delayed
2949 * packet, rather than with a retransmit. Check reordering.
2951 tcp_check_sack_reordering(sk
, prior_snd_una
, 1);
2953 /* We are getting evidence that the reordering degree is higher
2954 * than we realized. If there are no retransmits out then we
2955 * can undo. Otherwise we clock out new packets but do not
2956 * mark more packets lost or retransmit more.
2958 if (tp
->retrans_out
)
2961 if (!tcp_any_retrans_done(sk
))
2962 tp
->retrans_stamp
= 0;
2964 DBGUNDO(sk
, "partial recovery");
2965 tcp_undo_cwnd_reduction(sk
, true);
2966 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2967 tcp_try_keep_open(sk
);
2969 /* Partial ACK arrived. Force fast retransmit. */
2970 *do_lost
= tcp_force_fast_retransmit(sk
);
2975 static void tcp_identify_packet_loss(struct sock
*sk
, int *ack_flag
)
2977 struct tcp_sock
*tp
= tcp_sk(sk
);
2979 if (tcp_rtx_queue_empty(sk
))
2982 if (unlikely(tcp_is_reno(tp
))) {
2983 tcp_newreno_mark_lost(sk
, *ack_flag
& FLAG_SND_UNA_ADVANCED
);
2984 } else if (tcp_is_rack(sk
)) {
2985 u32 prior_retrans
= tp
->retrans_out
;
2987 if (tcp_rack_mark_lost(sk
))
2988 *ack_flag
&= ~FLAG_SET_XMIT_TIMER
;
2989 if (prior_retrans
> tp
->retrans_out
)
2990 *ack_flag
|= FLAG_LOST_RETRANS
;
2994 /* Process an event, which can update packets-in-flight not trivially.
2995 * Main goal of this function is to calculate new estimate for left_out,
2996 * taking into account both packets sitting in receiver's buffer and
2997 * packets lost by network.
2999 * Besides that it updates the congestion state when packet loss or ECN
3000 * is detected. But it does not reduce the cwnd, it is done by the
3001 * congestion control later.
3003 * It does _not_ decide what to send, it is made in function
3004 * tcp_xmit_retransmit_queue().
3006 static void tcp_fastretrans_alert(struct sock
*sk
, const u32 prior_snd_una
,
3007 int num_dupack
, int *ack_flag
, int *rexmit
)
3009 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3010 struct tcp_sock
*tp
= tcp_sk(sk
);
3011 int fast_rexmit
= 0, flag
= *ack_flag
;
3012 bool ece_ack
= flag
& FLAG_ECE
;
3013 bool do_lost
= num_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
3014 tcp_force_fast_retransmit(sk
));
3016 if (!tp
->packets_out
&& tp
->sacked_out
)
3019 /* Now state machine starts.
3020 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
3022 tp
->prior_ssthresh
= 0;
3024 /* B. In all the states check for reneging SACKs. */
3025 if (tcp_check_sack_reneging(sk
, ack_flag
))
3028 /* C. Check consistency of the current state. */
3029 tcp_verify_left_out(tp
);
3031 /* D. Check state exit conditions. State can be terminated
3032 * when high_seq is ACKed. */
3033 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
3034 WARN_ON(tp
->retrans_out
!= 0 && !tp
->syn_data
);
3035 tp
->retrans_stamp
= 0;
3036 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
3037 switch (icsk
->icsk_ca_state
) {
3039 /* CWR is to be held something *above* high_seq
3040 * is ACKed for CWR bit to reach receiver. */
3041 if (tp
->snd_una
!= tp
->high_seq
) {
3042 tcp_end_cwnd_reduction(sk
);
3043 tcp_set_ca_state(sk
, TCP_CA_Open
);
3047 case TCP_CA_Recovery
:
3048 if (tcp_is_reno(tp
))
3049 tcp_reset_reno_sack(tp
);
3050 if (tcp_try_undo_recovery(sk
))
3052 tcp_end_cwnd_reduction(sk
);
3057 /* E. Process state. */
3058 switch (icsk
->icsk_ca_state
) {
3059 case TCP_CA_Recovery
:
3060 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3061 if (tcp_is_reno(tp
))
3062 tcp_add_reno_sack(sk
, num_dupack
, ece_ack
);
3063 } else if (tcp_try_undo_partial(sk
, prior_snd_una
, &do_lost
))
3066 if (tcp_try_undo_dsack(sk
))
3067 tcp_try_keep_open(sk
);
3069 tcp_identify_packet_loss(sk
, ack_flag
);
3070 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
) {
3071 if (!tcp_time_to_recover(sk
, flag
))
3073 /* Undo reverts the recovery state. If loss is evident,
3074 * starts a new recovery (e.g. reordering then loss);
3076 tcp_enter_recovery(sk
, ece_ack
);
3080 tcp_process_loss(sk
, flag
, num_dupack
, rexmit
);
3081 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
3082 tcp_update_rto_time(tp
);
3083 tcp_identify_packet_loss(sk
, ack_flag
);
3084 if (!(icsk
->icsk_ca_state
== TCP_CA_Open
||
3085 (*ack_flag
& FLAG_LOST_RETRANS
)))
3087 /* Change state if cwnd is undone or retransmits are lost */
3090 if (tcp_is_reno(tp
)) {
3091 if (flag
& FLAG_SND_UNA_ADVANCED
)
3092 tcp_reset_reno_sack(tp
);
3093 tcp_add_reno_sack(sk
, num_dupack
, ece_ack
);
3096 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
3097 tcp_try_undo_dsack(sk
);
3099 tcp_identify_packet_loss(sk
, ack_flag
);
3100 if (!tcp_time_to_recover(sk
, flag
)) {
3101 tcp_try_to_open(sk
, flag
);
3105 /* MTU probe failure: don't reduce cwnd */
3106 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3107 icsk
->icsk_mtup
.probe_size
&&
3108 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3109 tcp_mtup_probe_failed(sk
);
3110 /* Restores the reduction we did in tcp_mtup_probe() */
3111 tcp_snd_cwnd_set(tp
, tcp_snd_cwnd(tp
) + 1);
3112 tcp_simple_retransmit(sk
);
3116 /* Otherwise enter Recovery state */
3117 tcp_enter_recovery(sk
, ece_ack
);
3121 if (!tcp_is_rack(sk
) && do_lost
)
3122 tcp_update_scoreboard(sk
, fast_rexmit
);
3123 *rexmit
= REXMIT_LOST
;
3126 static void tcp_update_rtt_min(struct sock
*sk
, u32 rtt_us
, const int flag
)
3128 u32 wlen
= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_min_rtt_wlen
) * HZ
;
3129 struct tcp_sock
*tp
= tcp_sk(sk
);
3131 if ((flag
& FLAG_ACK_MAYBE_DELAYED
) && rtt_us
> tcp_min_rtt(tp
)) {
3132 /* If the remote keeps returning delayed ACKs, eventually
3133 * the min filter would pick it up and overestimate the
3134 * prop. delay when it expires. Skip suspected delayed ACKs.
3138 minmax_running_min(&tp
->rtt_min
, wlen
, tcp_jiffies32
,
3139 rtt_us
? : jiffies_to_usecs(1));
3142 static bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3143 long seq_rtt_us
, long sack_rtt_us
,
3144 long ca_rtt_us
, struct rate_sample
*rs
)
3146 const struct tcp_sock
*tp
= tcp_sk(sk
);
3148 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
3149 * broken middle-boxes or peers may corrupt TS-ECR fields. But
3150 * Karn's algorithm forbids taking RTT if some retransmitted data
3151 * is acked (RFC6298).
3154 seq_rtt_us
= sack_rtt_us
;
3156 /* RTTM Rule: A TSecr value received in a segment is used to
3157 * update the averaged RTT measurement only if the segment
3158 * acknowledges some new data, i.e., only if it advances the
3159 * left edge of the send window.
3160 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3162 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&&
3163 tp
->rx_opt
.rcv_tsecr
&& flag
& FLAG_ACKED
)
3164 seq_rtt_us
= ca_rtt_us
= tcp_rtt_tsopt_us(tp
);
3166 rs
->rtt_us
= ca_rtt_us
; /* RTT of last (S)ACKed packet (or -1) */
3170 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
3171 * always taken together with ACK, SACK, or TS-opts. Any negative
3172 * values will be skipped with the seq_rtt_us < 0 check above.
3174 tcp_update_rtt_min(sk
, ca_rtt_us
, flag
);
3175 tcp_rtt_estimator(sk
, seq_rtt_us
);
3178 /* RFC6298: only reset backoff on valid RTT measurement. */
3179 inet_csk(sk
)->icsk_backoff
= 0;
3183 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
3184 void tcp_synack_rtt_meas(struct sock
*sk
, struct request_sock
*req
)
3186 struct rate_sample rs
;
3189 if (req
&& !req
->num_retrans
&& tcp_rsk(req
)->snt_synack
)
3190 rtt_us
= tcp_stamp_us_delta(tcp_clock_us(), tcp_rsk(req
)->snt_synack
);
3192 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, rtt_us
, -1L, rtt_us
, &rs
);
3196 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
3198 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3200 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
3201 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_jiffies32
;
3204 /* Restart timer after forward progress on connection.
3205 * RFC2988 recommends to restart timer to now+rto.
3207 void tcp_rearm_rto(struct sock
*sk
)
3209 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3210 struct tcp_sock
*tp
= tcp_sk(sk
);
3212 /* If the retrans timer is currently being used by Fast Open
3213 * for SYN-ACK retrans purpose, stay put.
3215 if (rcu_access_pointer(tp
->fastopen_rsk
))
3218 if (!tp
->packets_out
) {
3219 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3221 u32 rto
= inet_csk(sk
)->icsk_rto
;
3222 /* Offset the time elapsed after installing regular RTO */
3223 if (icsk
->icsk_pending
== ICSK_TIME_REO_TIMEOUT
||
3224 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
3225 s64 delta_us
= tcp_rto_delta_us(sk
);
3226 /* delta_us may not be positive if the socket is locked
3227 * when the retrans timer fires and is rescheduled.
3229 rto
= usecs_to_jiffies(max_t(int, delta_us
, 1));
3231 tcp_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
3236 /* Try to schedule a loss probe; if that doesn't work, then schedule an RTO. */
3237 static void tcp_set_xmit_timer(struct sock
*sk
)
3239 if (!tcp_schedule_loss_probe(sk
, true))
3243 /* If we get here, the whole TSO packet has not been acked. */
3244 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3246 struct tcp_sock
*tp
= tcp_sk(sk
);
3249 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3251 packets_acked
= tcp_skb_pcount(skb
);
3252 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3254 packets_acked
-= tcp_skb_pcount(skb
);
3256 if (packets_acked
) {
3257 BUG_ON(tcp_skb_pcount(skb
) == 0);
3258 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3261 return packets_acked
;
3264 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3265 const struct sk_buff
*ack_skb
, u32 prior_snd_una
)
3267 const struct skb_shared_info
*shinfo
;
3269 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3270 if (likely(!TCP_SKB_CB(skb
)->txstamp_ack
))
3273 shinfo
= skb_shinfo(skb
);
3274 if (!before(shinfo
->tskey
, prior_snd_una
) &&
3275 before(shinfo
->tskey
, tcp_sk(sk
)->snd_una
)) {
3276 tcp_skb_tsorted_save(skb
) {
3277 __skb_tstamp_tx(skb
, ack_skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3278 } tcp_skb_tsorted_restore(skb
);
3282 /* Remove acknowledged frames from the retransmission queue. If our packet
3283 * is before the ack sequence we can discard it as it's confirmed to have
3284 * arrived at the other end.
3286 static int tcp_clean_rtx_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
3287 u32 prior_fack
, u32 prior_snd_una
,
3288 struct tcp_sacktag_state
*sack
, bool ece_ack
)
3290 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3291 u64 first_ackt
, last_ackt
;
3292 struct tcp_sock
*tp
= tcp_sk(sk
);
3293 u32 prior_sacked
= tp
->sacked_out
;
3294 u32 reord
= tp
->snd_nxt
; /* lowest acked un-retx un-sacked seq */
3295 struct sk_buff
*skb
, *next
;
3296 bool fully_acked
= true;
3297 long sack_rtt_us
= -1L;
3298 long seq_rtt_us
= -1L;
3299 long ca_rtt_us
= -1L;
3306 for (skb
= skb_rb_first(&sk
->tcp_rtx_queue
); skb
; skb
= next
) {
3307 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3308 const u32 start_seq
= scb
->seq
;
3309 u8 sacked
= scb
->sacked
;
3312 /* Determine how many packets and what bytes were acked, tso and else */
3313 if (after(scb
->end_seq
, tp
->snd_una
)) {
3314 if (tcp_skb_pcount(skb
) == 1 ||
3315 !after(tp
->snd_una
, scb
->seq
))
3318 acked_pcount
= tcp_tso_acked(sk
, skb
);
3321 fully_acked
= false;
3323 acked_pcount
= tcp_skb_pcount(skb
);
3326 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3327 if (sacked
& TCPCB_SACKED_RETRANS
)
3328 tp
->retrans_out
-= acked_pcount
;
3329 flag
|= FLAG_RETRANS_DATA_ACKED
;
3330 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3331 last_ackt
= tcp_skb_timestamp_us(skb
);
3332 WARN_ON_ONCE(last_ackt
== 0);
3334 first_ackt
= last_ackt
;
3336 if (before(start_seq
, reord
))
3338 if (!after(scb
->end_seq
, tp
->high_seq
))
3339 flag
|= FLAG_ORIG_SACK_ACKED
;
3342 if (sacked
& TCPCB_SACKED_ACKED
) {
3343 tp
->sacked_out
-= acked_pcount
;
3344 } else if (tcp_is_sack(tp
)) {
3345 tcp_count_delivered(tp
, acked_pcount
, ece_ack
);
3346 if (!tcp_skb_spurious_retrans(tp
, skb
))
3347 tcp_rack_advance(tp
, sacked
, scb
->end_seq
,
3348 tcp_skb_timestamp_us(skb
));
3350 if (sacked
& TCPCB_LOST
)
3351 tp
->lost_out
-= acked_pcount
;
3353 tp
->packets_out
-= acked_pcount
;
3354 pkts_acked
+= acked_pcount
;
3355 tcp_rate_skb_delivered(sk
, skb
, sack
->rate
);
3357 /* Initial outgoing SYN's get put onto the write_queue
3358 * just like anything else we transmit. It is not
3359 * true data, and if we misinform our callers that
3360 * this ACK acks real data, we will erroneously exit
3361 * connection startup slow start one packet too
3362 * quickly. This is severely frowned upon behavior.
3364 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3365 flag
|= FLAG_DATA_ACKED
;
3367 flag
|= FLAG_SYN_ACKED
;
3368 tp
->retrans_stamp
= 0;
3374 tcp_ack_tstamp(sk
, skb
, ack_skb
, prior_snd_una
);
3376 next
= skb_rb_next(skb
);
3377 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3378 tp
->retransmit_skb_hint
= NULL
;
3379 if (unlikely(skb
== tp
->lost_skb_hint
))
3380 tp
->lost_skb_hint
= NULL
;
3381 tcp_highest_sack_replace(sk
, skb
, next
);
3382 tcp_rtx_queue_unlink_and_free(skb
, sk
);
3386 tcp_chrono_stop(sk
, TCP_CHRONO_BUSY
);
3388 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3389 tp
->snd_up
= tp
->snd_una
;
3392 tcp_ack_tstamp(sk
, skb
, ack_skb
, prior_snd_una
);
3393 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
3394 flag
|= FLAG_SACK_RENEGING
;
3397 if (likely(first_ackt
) && !(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3398 seq_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, first_ackt
);
3399 ca_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, last_ackt
);
3401 if (pkts_acked
== 1 && fully_acked
&& !prior_sacked
&&
3402 (tp
->snd_una
- prior_snd_una
) < tp
->mss_cache
&&
3403 sack
->rate
->prior_delivered
+ 1 == tp
->delivered
&&
3404 !(flag
& (FLAG_CA_ALERT
| FLAG_SYN_ACKED
))) {
3405 /* Conservatively mark a delayed ACK. It's typically
3406 * from a lone runt packet over the round trip to
3407 * a receiver w/o out-of-order or CE events.
3409 flag
|= FLAG_ACK_MAYBE_DELAYED
;
3412 if (sack
->first_sackt
) {
3413 sack_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, sack
->first_sackt
);
3414 ca_rtt_us
= tcp_stamp_us_delta(tp
->tcp_mstamp
, sack
->last_sackt
);
3416 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
,
3417 ca_rtt_us
, sack
->rate
);
3419 if (flag
& FLAG_ACKED
) {
3420 flag
|= FLAG_SET_XMIT_TIMER
; /* set TLP or RTO timer */
3421 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3422 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3423 tcp_mtup_probe_success(sk
);
3426 if (tcp_is_reno(tp
)) {
3427 tcp_remove_reno_sacks(sk
, pkts_acked
, ece_ack
);
3429 /* If any of the cumulatively ACKed segments was
3430 * retransmitted, non-SACK case cannot confirm that
3431 * progress was due to original transmission due to
3432 * lack of TCPCB_SACKED_ACKED bits even if some of
3433 * the packets may have been never retransmitted.
3435 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3436 flag
&= ~FLAG_ORIG_SACK_ACKED
;
3440 /* Non-retransmitted hole got filled? That's reordering */
3441 if (before(reord
, prior_fack
))
3442 tcp_check_sack_reordering(sk
, reord
, 0);
3444 delta
= prior_sacked
- tp
->sacked_out
;
3445 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3447 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3448 sack_rtt_us
> tcp_stamp_us_delta(tp
->tcp_mstamp
,
3449 tcp_skb_timestamp_us(skb
))) {
3450 /* Do not re-arm RTO if the sack RTT is measured from data sent
3451 * after when the head was last (re)transmitted. Otherwise the
3452 * timeout may continue to extend in loss recovery.
3454 flag
|= FLAG_SET_XMIT_TIMER
; /* set TLP or RTO timer */
3457 if (icsk
->icsk_ca_ops
->pkts_acked
) {
3458 struct ack_sample sample
= { .pkts_acked
= pkts_acked
,
3459 .rtt_us
= sack
->rate
->rtt_us
};
3461 sample
.in_flight
= tp
->mss_cache
*
3462 (tp
->delivered
- sack
->rate
->prior_delivered
);
3463 icsk
->icsk_ca_ops
->pkts_acked(sk
, &sample
);
3466 #if FASTRETRANS_DEBUG > 0
3467 WARN_ON((int)tp
->sacked_out
< 0);
3468 WARN_ON((int)tp
->lost_out
< 0);
3469 WARN_ON((int)tp
->retrans_out
< 0);
3470 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3471 icsk
= inet_csk(sk
);
3473 pr_debug("Leak l=%u %d\n",
3474 tp
->lost_out
, icsk
->icsk_ca_state
);
3477 if (tp
->sacked_out
) {
3478 pr_debug("Leak s=%u %d\n",
3479 tp
->sacked_out
, icsk
->icsk_ca_state
);
3482 if (tp
->retrans_out
) {
3483 pr_debug("Leak r=%u %d\n",
3484 tp
->retrans_out
, icsk
->icsk_ca_state
);
3485 tp
->retrans_out
= 0;
3492 static void tcp_ack_probe(struct sock
*sk
)
3494 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3495 struct sk_buff
*head
= tcp_send_head(sk
);
3496 const struct tcp_sock
*tp
= tcp_sk(sk
);
3498 /* Was it a usable window open? */
3501 if (!after(TCP_SKB_CB(head
)->end_seq
, tcp_wnd_end(tp
))) {
3502 icsk
->icsk_backoff
= 0;
3503 icsk
->icsk_probes_tstamp
= 0;
3504 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3505 /* Socket must be waked up by subsequent tcp_data_snd_check().
3506 * This function is not for random using!
3509 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3511 when
= tcp_clamp_probe0_to_user_timeout(sk
, when
);
3512 tcp_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
, when
, TCP_RTO_MAX
);
3516 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3518 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3519 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3522 /* Decide wheather to run the increase function of congestion control. */
3523 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3525 /* If reordering is high then always grow cwnd whenever data is
3526 * delivered regardless of its ordering. Otherwise stay conservative
3527 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3528 * new SACK or ECE mark may first advance cwnd here and later reduce
3529 * cwnd in tcp_fastretrans_alert() based on more states.
3531 if (tcp_sk(sk
)->reordering
>
3532 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_reordering
))
3533 return flag
& FLAG_FORWARD_PROGRESS
;
3535 return flag
& FLAG_DATA_ACKED
;
3538 /* The "ultimate" congestion control function that aims to replace the rigid
3539 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3540 * It's called toward the end of processing an ACK with precise rate
3541 * information. All transmission or retransmission are delayed afterwards.
3543 static void tcp_cong_control(struct sock
*sk
, u32 ack
, u32 acked_sacked
,
3544 int flag
, const struct rate_sample
*rs
)
3546 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3548 if (icsk
->icsk_ca_ops
->cong_control
) {
3549 icsk
->icsk_ca_ops
->cong_control(sk
, rs
);
3553 if (tcp_in_cwnd_reduction(sk
)) {
3554 /* Reduce cwnd if state mandates */
3555 tcp_cwnd_reduction(sk
, acked_sacked
, rs
->losses
, flag
);
3556 } else if (tcp_may_raise_cwnd(sk
, flag
)) {
3557 /* Advance cwnd if state allows */
3558 tcp_cong_avoid(sk
, ack
, acked_sacked
);
3560 tcp_update_pacing_rate(sk
);
3563 /* Check that window update is acceptable.
3564 * The function assumes that snd_una<=ack<=snd_next.
3566 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3567 const u32 ack
, const u32 ack_seq
,
3570 return after(ack
, tp
->snd_una
) ||
3571 after(ack_seq
, tp
->snd_wl1
) ||
3572 (ack_seq
== tp
->snd_wl1
&& (nwin
> tp
->snd_wnd
|| !nwin
));
3575 static void tcp_snd_sne_update(struct tcp_sock
*tp
, u32 ack
)
3577 #ifdef CONFIG_TCP_AO
3578 struct tcp_ao_info
*ao
;
3580 if (!static_branch_unlikely(&tcp_ao_needed
.key
))
3583 ao
= rcu_dereference_protected(tp
->ao_info
,
3584 lockdep_sock_is_held((struct sock
*)tp
));
3585 if (ao
&& ack
< tp
->snd_una
)
3590 /* If we update tp->snd_una, also update tp->bytes_acked */
3591 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3593 u32 delta
= ack
- tp
->snd_una
;
3595 sock_owned_by_me((struct sock
*)tp
);
3596 tp
->bytes_acked
+= delta
;
3597 tcp_snd_sne_update(tp
, ack
);
3601 static void tcp_rcv_sne_update(struct tcp_sock
*tp
, u32 seq
)
3603 #ifdef CONFIG_TCP_AO
3604 struct tcp_ao_info
*ao
;
3606 if (!static_branch_unlikely(&tcp_ao_needed
.key
))
3609 ao
= rcu_dereference_protected(tp
->ao_info
,
3610 lockdep_sock_is_held((struct sock
*)tp
));
3611 if (ao
&& seq
< tp
->rcv_nxt
)
3616 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3617 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3619 u32 delta
= seq
- tp
->rcv_nxt
;
3621 sock_owned_by_me((struct sock
*)tp
);
3622 tp
->bytes_received
+= delta
;
3623 tcp_rcv_sne_update(tp
, seq
);
3624 WRITE_ONCE(tp
->rcv_nxt
, seq
);
3627 /* Update our send window.
3629 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3630 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3632 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3635 struct tcp_sock
*tp
= tcp_sk(sk
);
3637 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3639 if (likely(!tcp_hdr(skb
)->syn
))
3640 nwin
<<= tp
->rx_opt
.snd_wscale
;
3642 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3643 flag
|= FLAG_WIN_UPDATE
;
3644 tcp_update_wl(tp
, ack_seq
);
3646 if (tp
->snd_wnd
!= nwin
) {
3649 /* Note, it is the only place, where
3650 * fast path is recovered for sending TCP.
3653 tcp_fast_path_check(sk
);
3655 if (!tcp_write_queue_empty(sk
))
3656 tcp_slow_start_after_idle_check(sk
);
3658 if (nwin
> tp
->max_window
) {
3659 tp
->max_window
= nwin
;
3660 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3665 tcp_snd_una_update(tp
, ack
);
3670 static bool __tcp_oow_rate_limited(struct net
*net
, int mib_idx
,
3671 u32
*last_oow_ack_time
)
3673 /* Paired with the WRITE_ONCE() in this function. */
3674 u32 val
= READ_ONCE(*last_oow_ack_time
);
3677 s32 elapsed
= (s32
)(tcp_jiffies32
- val
);
3680 elapsed
< READ_ONCE(net
->ipv4
.sysctl_tcp_invalid_ratelimit
)) {
3681 NET_INC_STATS(net
, mib_idx
);
3682 return true; /* rate-limited: don't send yet! */
3686 /* Paired with the prior READ_ONCE() and with itself,
3687 * as we might be lockless.
3689 WRITE_ONCE(*last_oow_ack_time
, tcp_jiffies32
);
3691 return false; /* not rate-limited: go ahead, send dupack now! */
3694 /* Return true if we're currently rate-limiting out-of-window ACKs and
3695 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3696 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3697 * attacks that send repeated SYNs or ACKs for the same connection. To
3698 * do this, we do not send a duplicate SYNACK or ACK if the remote
3699 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3701 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3702 int mib_idx
, u32
*last_oow_ack_time
)
3704 /* Data packets without SYNs are not likely part of an ACK loop. */
3705 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3709 return __tcp_oow_rate_limited(net
, mib_idx
, last_oow_ack_time
);
3712 /* RFC 5961 7 [ACK Throttling] */
3713 static void tcp_send_challenge_ack(struct sock
*sk
)
3715 struct tcp_sock
*tp
= tcp_sk(sk
);
3716 struct net
*net
= sock_net(sk
);
3717 u32 count
, now
, ack_limit
;
3719 /* First check our per-socket dupack rate limit. */
3720 if (__tcp_oow_rate_limited(net
,
3721 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3722 &tp
->last_oow_ack_time
))
3725 ack_limit
= READ_ONCE(net
->ipv4
.sysctl_tcp_challenge_ack_limit
);
3726 if (ack_limit
== INT_MAX
)
3729 /* Then check host-wide RFC 5961 rate limit. */
3731 if (now
!= READ_ONCE(net
->ipv4
.tcp_challenge_timestamp
)) {
3732 u32 half
= (ack_limit
+ 1) >> 1;
3734 WRITE_ONCE(net
->ipv4
.tcp_challenge_timestamp
, now
);
3735 WRITE_ONCE(net
->ipv4
.tcp_challenge_count
,
3736 get_random_u32_inclusive(half
, ack_limit
+ half
- 1));
3738 count
= READ_ONCE(net
->ipv4
.tcp_challenge_count
);
3740 WRITE_ONCE(net
->ipv4
.tcp_challenge_count
, count
- 1);
3742 NET_INC_STATS(net
, LINUX_MIB_TCPCHALLENGEACK
);
3747 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3749 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3750 tp
->rx_opt
.ts_recent_stamp
= ktime_get_seconds();
3753 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3755 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3756 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3757 * extra check below makes sure this can only happen
3758 * for pure ACK frames. -DaveM
3760 * Not only, also it occurs for expired timestamps.
3763 if (tcp_paws_check(&tp
->rx_opt
, 0))
3764 tcp_store_ts_recent(tp
);
3768 /* This routine deals with acks during a TLP episode and ends an episode by
3769 * resetting tlp_high_seq. Ref: TLP algorithm in draft-ietf-tcpm-rack
3771 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3773 struct tcp_sock
*tp
= tcp_sk(sk
);
3775 if (before(ack
, tp
->tlp_high_seq
))
3778 if (!tp
->tlp_retrans
) {
3779 /* TLP of new data has been acknowledged */
3780 tp
->tlp_high_seq
= 0;
3781 } else if (flag
& FLAG_DSACK_TLP
) {
3782 /* This DSACK means original and TLP probe arrived; no loss */
3783 tp
->tlp_high_seq
= 0;
3784 } else if (after(ack
, tp
->tlp_high_seq
)) {
3785 /* ACK advances: there was a loss, so reduce cwnd. Reset
3786 * tlp_high_seq in tcp_init_cwnd_reduction()
3788 tcp_init_cwnd_reduction(sk
);
3789 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3790 tcp_end_cwnd_reduction(sk
);
3791 tcp_try_keep_open(sk
);
3792 NET_INC_STATS(sock_net(sk
),
3793 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3794 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3795 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3796 /* Pure dupack: original and TLP probe arrived; no loss */
3797 tp
->tlp_high_seq
= 0;
3801 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3803 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3805 if (icsk
->icsk_ca_ops
->in_ack_event
)
3806 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3809 /* Congestion control has updated the cwnd already. So if we're in
3810 * loss recovery then now we do any new sends (for FRTO) or
3811 * retransmits (for CA_Loss or CA_recovery) that make sense.
3813 static void tcp_xmit_recovery(struct sock
*sk
, int rexmit
)
3815 struct tcp_sock
*tp
= tcp_sk(sk
);
3817 if (rexmit
== REXMIT_NONE
|| sk
->sk_state
== TCP_SYN_SENT
)
3820 if (unlikely(rexmit
== REXMIT_NEW
)) {
3821 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
3823 if (after(tp
->snd_nxt
, tp
->high_seq
))
3827 tcp_xmit_retransmit_queue(sk
);
3830 /* Returns the number of packets newly acked or sacked by the current ACK */
3831 static u32
tcp_newly_delivered(struct sock
*sk
, u32 prior_delivered
, int flag
)
3833 const struct net
*net
= sock_net(sk
);
3834 struct tcp_sock
*tp
= tcp_sk(sk
);
3837 delivered
= tp
->delivered
- prior_delivered
;
3838 NET_ADD_STATS(net
, LINUX_MIB_TCPDELIVERED
, delivered
);
3839 if (flag
& FLAG_ECE
)
3840 NET_ADD_STATS(net
, LINUX_MIB_TCPDELIVEREDCE
, delivered
);
3845 /* This routine deals with incoming acks, but not outgoing ones. */
3846 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3848 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3849 struct tcp_sock
*tp
= tcp_sk(sk
);
3850 struct tcp_sacktag_state sack_state
;
3851 struct rate_sample rs
= { .prior_delivered
= 0 };
3852 u32 prior_snd_una
= tp
->snd_una
;
3853 bool is_sack_reneg
= tp
->is_sack_reneg
;
3854 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3855 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3857 int prior_packets
= tp
->packets_out
;
3858 u32 delivered
= tp
->delivered
;
3859 u32 lost
= tp
->lost
;
3860 int rexmit
= REXMIT_NONE
; /* Flag to (re)transmit to recover losses */
3863 sack_state
.first_sackt
= 0;
3864 sack_state
.rate
= &rs
;
3865 sack_state
.sack_delivered
= 0;
3867 /* We very likely will need to access rtx queue. */
3868 prefetch(sk
->tcp_rtx_queue
.rb_node
);
3870 /* If the ack is older than previous acks
3871 * then we can probably ignore it.
3873 if (before(ack
, prior_snd_una
)) {
3876 /* do not accept ACK for bytes we never sent. */
3877 max_window
= min_t(u64
, tp
->max_window
, tp
->bytes_acked
);
3878 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3879 if (before(ack
, prior_snd_una
- max_window
)) {
3880 if (!(flag
& FLAG_NO_CHALLENGE_ACK
))
3881 tcp_send_challenge_ack(sk
);
3882 return -SKB_DROP_REASON_TCP_TOO_OLD_ACK
;
3887 /* If the ack includes data we haven't sent yet, discard
3888 * this segment (RFC793 Section 3.9).
3890 if (after(ack
, tp
->snd_nxt
))
3891 return -SKB_DROP_REASON_TCP_ACK_UNSENT_DATA
;
3893 if (after(ack
, prior_snd_una
)) {
3894 flag
|= FLAG_SND_UNA_ADVANCED
;
3895 icsk
->icsk_retransmits
= 0;
3897 #if IS_ENABLED(CONFIG_TLS_DEVICE)
3898 if (static_branch_unlikely(&clean_acked_data_enabled
.key
))
3899 if (icsk
->icsk_clean_acked
)
3900 icsk
->icsk_clean_acked(sk
, ack
);
3904 prior_fack
= tcp_is_sack(tp
) ? tcp_highest_sack_seq(tp
) : tp
->snd_una
;
3905 rs
.prior_in_flight
= tcp_packets_in_flight(tp
);
3907 /* ts_recent update must be made after we are sure that the packet
3910 if (flag
& FLAG_UPDATE_TS_RECENT
)
3911 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3913 if ((flag
& (FLAG_SLOWPATH
| FLAG_SND_UNA_ADVANCED
)) ==
3914 FLAG_SND_UNA_ADVANCED
) {
3915 /* Window is constant, pure forward advance.
3916 * No more checks are required.
3917 * Note, we use the fact that SND.UNA>=SND.WL2.
3919 tcp_update_wl(tp
, ack_seq
);
3920 tcp_snd_una_update(tp
, ack
);
3921 flag
|= FLAG_WIN_UPDATE
;
3923 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3925 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3927 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3929 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3932 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3934 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3936 if (TCP_SKB_CB(skb
)->sacked
)
3937 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3940 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3942 ack_ev_flags
|= CA_ACK_ECE
;
3945 if (sack_state
.sack_delivered
)
3946 tcp_count_delivered(tp
, sack_state
.sack_delivered
,
3949 if (flag
& FLAG_WIN_UPDATE
)
3950 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3952 tcp_in_ack_event(sk
, ack_ev_flags
);
3955 /* This is a deviation from RFC3168 since it states that:
3956 * "When the TCP data sender is ready to set the CWR bit after reducing
3957 * the congestion window, it SHOULD set the CWR bit only on the first
3958 * new data packet that it transmits."
3959 * We accept CWR on pure ACKs to be more robust
3960 * with widely-deployed TCP implementations that do this.
3962 tcp_ecn_accept_cwr(sk
, skb
);
3964 /* We passed data and got it acked, remove any soft error
3965 * log. Something worked...
3967 WRITE_ONCE(sk
->sk_err_soft
, 0);
3968 icsk
->icsk_probes_out
= 0;
3969 tp
->rcv_tstamp
= tcp_jiffies32
;
3973 /* See if we can take anything off of the retransmit queue. */
3974 flag
|= tcp_clean_rtx_queue(sk
, skb
, prior_fack
, prior_snd_una
,
3975 &sack_state
, flag
& FLAG_ECE
);
3977 tcp_rack_update_reo_wnd(sk
, &rs
);
3979 if (tp
->tlp_high_seq
)
3980 tcp_process_tlp_ack(sk
, ack
, flag
);
3982 if (tcp_ack_is_dubious(sk
, flag
)) {
3983 if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3984 FLAG_NOT_DUP
| FLAG_DSACKING_ACK
))) {
3986 /* Consider if pure acks were aggregated in tcp_add_backlog() */
3987 if (!(flag
& FLAG_DATA
))
3988 num_dupack
= max_t(u16
, 1, skb_shinfo(skb
)->gso_segs
);
3990 tcp_fastretrans_alert(sk
, prior_snd_una
, num_dupack
, &flag
,
3994 /* If needed, reset TLP/RTO timer when RACK doesn't set. */
3995 if (flag
& FLAG_SET_XMIT_TIMER
)
3996 tcp_set_xmit_timer(sk
);
3998 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
4001 delivered
= tcp_newly_delivered(sk
, delivered
, flag
);
4002 lost
= tp
->lost
- lost
; /* freshly marked lost */
4003 rs
.is_ack_delayed
= !!(flag
& FLAG_ACK_MAYBE_DELAYED
);
4004 tcp_rate_gen(sk
, delivered
, lost
, is_sack_reneg
, sack_state
.rate
);
4005 tcp_cong_control(sk
, ack
, delivered
, flag
, sack_state
.rate
);
4006 tcp_xmit_recovery(sk
, rexmit
);
4010 /* If data was DSACKed, see if we can undo a cwnd reduction. */
4011 if (flag
& FLAG_DSACKING_ACK
) {
4012 tcp_fastretrans_alert(sk
, prior_snd_una
, num_dupack
, &flag
,
4014 tcp_newly_delivered(sk
, delivered
, flag
);
4016 /* If this ack opens up a zero window, clear backoff. It was
4017 * being used to time the probes, and is probably far higher than
4018 * it needs to be for normal retransmission.
4022 if (tp
->tlp_high_seq
)
4023 tcp_process_tlp_ack(sk
, ack
, flag
);
4027 /* If data was SACKed, tag it and see if we should send more data.
4028 * If data was DSACKed, see if we can undo a cwnd reduction.
4030 if (TCP_SKB_CB(skb
)->sacked
) {
4031 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
4033 tcp_fastretrans_alert(sk
, prior_snd_una
, num_dupack
, &flag
,
4035 tcp_newly_delivered(sk
, delivered
, flag
);
4036 tcp_xmit_recovery(sk
, rexmit
);
4042 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
4043 bool syn
, struct tcp_fastopen_cookie
*foc
,
4046 /* Valid only in SYN or SYN-ACK with an even length. */
4047 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
4050 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
4051 len
<= TCP_FASTOPEN_COOKIE_MAX
)
4052 memcpy(foc
->val
, cookie
, len
);
4059 static bool smc_parse_options(const struct tcphdr
*th
,
4060 struct tcp_options_received
*opt_rx
,
4061 const unsigned char *ptr
,
4064 #if IS_ENABLED(CONFIG_SMC)
4065 if (static_branch_unlikely(&tcp_have_smc
)) {
4066 if (th
->syn
&& !(opsize
& 1) &&
4067 opsize
>= TCPOLEN_EXP_SMC_BASE
&&
4068 get_unaligned_be32(ptr
) == TCPOPT_SMC_MAGIC
) {
4077 /* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
4080 u16
tcp_parse_mss_option(const struct tcphdr
*th
, u16 user_mss
)
4082 const unsigned char *ptr
= (const unsigned char *)(th
+ 1);
4083 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
4086 while (length
> 0) {
4087 int opcode
= *ptr
++;
4093 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
4100 if (opsize
< 2) /* "silly options" */
4102 if (opsize
> length
)
4103 return mss
; /* fail on partial options */
4104 if (opcode
== TCPOPT_MSS
&& opsize
== TCPOLEN_MSS
) {
4105 u16 in_mss
= get_unaligned_be16(ptr
);
4108 if (user_mss
&& user_mss
< in_mss
)
4119 EXPORT_SYMBOL_GPL(tcp_parse_mss_option
);
4121 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
4122 * But, this can also be called on packets in the established flow when
4123 * the fast version below fails.
4125 void tcp_parse_options(const struct net
*net
,
4126 const struct sk_buff
*skb
,
4127 struct tcp_options_received
*opt_rx
, int estab
,
4128 struct tcp_fastopen_cookie
*foc
)
4130 const unsigned char *ptr
;
4131 const struct tcphdr
*th
= tcp_hdr(skb
);
4132 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
4134 ptr
= (const unsigned char *)(th
+ 1);
4135 opt_rx
->saw_tstamp
= 0;
4136 opt_rx
->saw_unknown
= 0;
4138 while (length
> 0) {
4139 int opcode
= *ptr
++;
4145 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
4152 if (opsize
< 2) /* "silly options" */
4154 if (opsize
> length
)
4155 return; /* don't parse partial options */
4158 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
4159 u16 in_mss
= get_unaligned_be16(ptr
);
4161 if (opt_rx
->user_mss
&&
4162 opt_rx
->user_mss
< in_mss
)
4163 in_mss
= opt_rx
->user_mss
;
4164 opt_rx
->mss_clamp
= in_mss
;
4169 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
4170 !estab
&& READ_ONCE(net
->ipv4
.sysctl_tcp_window_scaling
)) {
4171 __u8 snd_wscale
= *(__u8
*)ptr
;
4172 opt_rx
->wscale_ok
= 1;
4173 if (snd_wscale
> TCP_MAX_WSCALE
) {
4174 net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n",
4178 snd_wscale
= TCP_MAX_WSCALE
;
4180 opt_rx
->snd_wscale
= snd_wscale
;
4183 case TCPOPT_TIMESTAMP
:
4184 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
4185 ((estab
&& opt_rx
->tstamp_ok
) ||
4186 (!estab
&& READ_ONCE(net
->ipv4
.sysctl_tcp_timestamps
)))) {
4187 opt_rx
->saw_tstamp
= 1;
4188 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
4189 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
4192 case TCPOPT_SACK_PERM
:
4193 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
4194 !estab
&& READ_ONCE(net
->ipv4
.sysctl_tcp_sack
)) {
4195 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
4196 tcp_sack_reset(opt_rx
);
4201 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
4202 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
4204 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
4207 #ifdef CONFIG_TCP_MD5SIG
4209 /* The MD5 Hash has already been
4210 * checked (see tcp_v{4,6}_rcv()).
4214 case TCPOPT_FASTOPEN
:
4215 tcp_parse_fastopen_option(
4216 opsize
- TCPOLEN_FASTOPEN_BASE
,
4217 ptr
, th
->syn
, foc
, false);
4221 /* Fast Open option shares code 254 using a
4222 * 16 bits magic number.
4224 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
4225 get_unaligned_be16(ptr
) ==
4226 TCPOPT_FASTOPEN_MAGIC
) {
4227 tcp_parse_fastopen_option(opsize
-
4228 TCPOLEN_EXP_FASTOPEN_BASE
,
4229 ptr
+ 2, th
->syn
, foc
, true);
4233 if (smc_parse_options(th
, opt_rx
, ptr
, opsize
))
4236 opt_rx
->saw_unknown
= 1;
4240 opt_rx
->saw_unknown
= 1;
4247 EXPORT_SYMBOL(tcp_parse_options
);
4249 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
4251 const __be32
*ptr
= (const __be32
*)(th
+ 1);
4253 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4254 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
4255 tp
->rx_opt
.saw_tstamp
= 1;
4257 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4260 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
4262 tp
->rx_opt
.rcv_tsecr
= 0;
4268 /* Fast parse options. This hopes to only see timestamps.
4269 * If it is wrong it falls back on tcp_parse_options().
4271 static bool tcp_fast_parse_options(const struct net
*net
,
4272 const struct sk_buff
*skb
,
4273 const struct tcphdr
*th
, struct tcp_sock
*tp
)
4275 /* In the spirit of fast parsing, compare doff directly to constant
4276 * values. Because equality is used, short doff can be ignored here.
4278 if (th
->doff
== (sizeof(*th
) / 4)) {
4279 tp
->rx_opt
.saw_tstamp
= 0;
4281 } else if (tp
->rx_opt
.tstamp_ok
&&
4282 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
4283 if (tcp_parse_aligned_timestamp(tp
, th
))
4287 tcp_parse_options(net
, skb
, &tp
->rx_opt
, 1, NULL
);
4288 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
4289 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
4294 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
4296 * Parse Signature options
4298 int tcp_do_parse_auth_options(const struct tcphdr
*th
,
4299 const u8
**md5_hash
, const u8
**ao_hash
)
4301 int length
= (th
->doff
<< 2) - sizeof(*th
);
4302 const u8
*ptr
= (const u8
*)(th
+ 1);
4303 unsigned int minlen
= TCPOLEN_MD5SIG
;
4305 if (IS_ENABLED(CONFIG_TCP_AO
))
4306 minlen
= sizeof(struct tcp_ao_hdr
) + 1;
4311 /* If not enough data remaining, we can short cut */
4312 while (length
>= minlen
) {
4313 int opcode
= *ptr
++;
4324 if (opsize
< 2 || opsize
> length
)
4326 if (opcode
== TCPOPT_MD5SIG
) {
4327 if (opsize
!= TCPOLEN_MD5SIG
)
4329 if (unlikely(*md5_hash
|| *ao_hash
))
4332 } else if (opcode
== TCPOPT_AO
) {
4333 if (opsize
<= sizeof(struct tcp_ao_hdr
))
4335 if (unlikely(*md5_hash
|| *ao_hash
))
4345 EXPORT_SYMBOL(tcp_do_parse_auth_options
);
4348 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4350 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4351 * it can pass through stack. So, the following predicate verifies that
4352 * this segment is not used for anything but congestion avoidance or
4353 * fast retransmit. Moreover, we even are able to eliminate most of such
4354 * second order effects, if we apply some small "replay" window (~RTO)
4355 * to timestamp space.
4357 * All these measures still do not guarantee that we reject wrapped ACKs
4358 * on networks with high bandwidth, when sequence space is recycled fastly,
4359 * but it guarantees that such events will be very rare and do not affect
4360 * connection seriously. This doesn't look nice, but alas, PAWS is really
4363 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4364 * states that events when retransmit arrives after original data are rare.
4365 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4366 * the biggest problem on large power networks even with minor reordering.
4367 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4368 * up to bandwidth of 18Gigabit/sec. 8) ]
4371 /* Estimates max number of increments of remote peer TSval in
4372 * a replay window (based on our current RTO estimation).
4374 static u32
tcp_tsval_replay(const struct sock
*sk
)
4376 /* If we use usec TS resolution,
4377 * then expect the remote peer to use the same resolution.
4379 if (tcp_sk(sk
)->tcp_usec_ts
)
4380 return inet_csk(sk
)->icsk_rto
* (USEC_PER_SEC
/ HZ
);
4382 /* RFC 7323 recommends a TSval clock between 1ms and 1sec.
4383 * We know that some OS (including old linux) can use 1200 Hz.
4385 return inet_csk(sk
)->icsk_rto
* 1200 / HZ
;
4388 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
4390 const struct tcp_sock
*tp
= tcp_sk(sk
);
4391 const struct tcphdr
*th
= tcp_hdr(skb
);
4392 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4393 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
4395 return /* 1. Pure ACK with correct sequence number. */
4396 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
4398 /* 2. ... and duplicate ACK. */
4399 ack
== tp
->snd_una
&&
4401 /* 3. ... and does not update window. */
4402 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
4404 /* 4. ... and sits in replay window. */
4405 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <=
4406 tcp_tsval_replay(sk
);
4409 static inline bool tcp_paws_discard(const struct sock
*sk
,
4410 const struct sk_buff
*skb
)
4412 const struct tcp_sock
*tp
= tcp_sk(sk
);
4414 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
4415 !tcp_disordered_ack(sk
, skb
);
4418 /* Check segment sequence number for validity.
4420 * Segment controls are considered valid, if the segment
4421 * fits to the window after truncation to the window. Acceptability
4422 * of data (and SYN, FIN, of course) is checked separately.
4423 * See tcp_data_queue(), for example.
4425 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4426 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4427 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4428 * (borrowed from freebsd)
4431 static enum skb_drop_reason
tcp_sequence(const struct tcp_sock
*tp
,
4432 u32 seq
, u32 end_seq
)
4434 if (before(end_seq
, tp
->rcv_wup
))
4435 return SKB_DROP_REASON_TCP_OLD_SEQUENCE
;
4437 if (after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4438 return SKB_DROP_REASON_TCP_INVALID_SEQUENCE
;
4440 return SKB_NOT_DROPPED_YET
;
4443 /* When we get a reset we do this. */
4444 void tcp_reset(struct sock
*sk
, struct sk_buff
*skb
)
4446 trace_tcp_receive_reset(sk
);
4448 /* mptcp can't tell us to ignore reset pkts,
4449 * so just ignore the return value of mptcp_incoming_options().
4451 if (sk_is_mptcp(sk
))
4452 mptcp_incoming_options(sk
, skb
);
4454 /* We want the right error as BSD sees it (and indeed as we do). */
4455 switch (sk
->sk_state
) {
4457 WRITE_ONCE(sk
->sk_err
, ECONNREFUSED
);
4459 case TCP_CLOSE_WAIT
:
4460 WRITE_ONCE(sk
->sk_err
, EPIPE
);
4465 WRITE_ONCE(sk
->sk_err
, ECONNRESET
);
4467 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4470 tcp_write_queue_purge(sk
);
4473 if (!sock_flag(sk
, SOCK_DEAD
))
4474 sk_error_report(sk
);
4478 * Process the FIN bit. This now behaves as it is supposed to work
4479 * and the FIN takes effect when it is validly part of sequence
4480 * space. Not before when we get holes.
4482 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4483 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4486 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4487 * close and we go into CLOSING (and later onto TIME-WAIT)
4489 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4491 void tcp_fin(struct sock
*sk
)
4493 struct tcp_sock
*tp
= tcp_sk(sk
);
4495 inet_csk_schedule_ack(sk
);
4497 WRITE_ONCE(sk
->sk_shutdown
, sk
->sk_shutdown
| RCV_SHUTDOWN
);
4498 sock_set_flag(sk
, SOCK_DONE
);
4500 switch (sk
->sk_state
) {
4502 case TCP_ESTABLISHED
:
4503 /* Move to CLOSE_WAIT */
4504 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4505 inet_csk_enter_pingpong_mode(sk
);
4508 case TCP_CLOSE_WAIT
:
4510 /* Received a retransmission of the FIN, do
4515 /* RFC793: Remain in the LAST-ACK state. */
4519 /* This case occurs when a simultaneous close
4520 * happens, we must ack the received FIN and
4521 * enter the CLOSING state.
4524 tcp_set_state(sk
, TCP_CLOSING
);
4527 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4529 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4532 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4533 * cases we should never reach this piece of code.
4535 pr_err("%s: Impossible, sk->sk_state=%d\n",
4536 __func__
, sk
->sk_state
);
4540 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4541 * Probably, we should reset in this case. For now drop them.
4543 skb_rbtree_purge(&tp
->out_of_order_queue
);
4544 if (tcp_is_sack(tp
))
4545 tcp_sack_reset(&tp
->rx_opt
);
4547 if (!sock_flag(sk
, SOCK_DEAD
)) {
4548 sk
->sk_state_change(sk
);
4550 /* Do not send POLL_HUP for half duplex close. */
4551 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4552 sk
->sk_state
== TCP_CLOSE
)
4553 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4555 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4559 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4562 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4563 if (before(seq
, sp
->start_seq
))
4564 sp
->start_seq
= seq
;
4565 if (after(end_seq
, sp
->end_seq
))
4566 sp
->end_seq
= end_seq
;
4572 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4574 struct tcp_sock
*tp
= tcp_sk(sk
);
4576 if (tcp_is_sack(tp
) && READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_dsack
)) {
4579 if (before(seq
, tp
->rcv_nxt
))
4580 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4582 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4584 NET_INC_STATS(sock_net(sk
), mib_idx
);
4586 tp
->rx_opt
.dsack
= 1;
4587 tp
->duplicate_sack
[0].start_seq
= seq
;
4588 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4592 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4594 struct tcp_sock
*tp
= tcp_sk(sk
);
4596 if (!tp
->rx_opt
.dsack
)
4597 tcp_dsack_set(sk
, seq
, end_seq
);
4599 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4602 static void tcp_rcv_spurious_retrans(struct sock
*sk
, const struct sk_buff
*skb
)
4604 /* When the ACK path fails or drops most ACKs, the sender would
4605 * timeout and spuriously retransmit the same segment repeatedly.
4606 * If it seems our ACKs are not reaching the other side,
4607 * based on receiving a duplicate data segment with new flowlabel
4608 * (suggesting the sender suffered an RTO), and we are not already
4609 * repathing due to our own RTO, then rehash the socket to repath our
4612 #if IS_ENABLED(CONFIG_IPV6)
4613 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
&&
4614 skb
->protocol
== htons(ETH_P_IPV6
) &&
4615 (tcp_sk(sk
)->inet_conn
.icsk_ack
.lrcv_flowlabel
!=
4616 ntohl(ip6_flowlabel(ipv6_hdr(skb
)))) &&
4617 sk_rethink_txhash(sk
))
4618 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPDUPLICATEDATAREHASH
);
4620 /* Save last flowlabel after a spurious retrans. */
4621 tcp_save_lrcv_flowlabel(sk
, skb
);
4625 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4627 struct tcp_sock
*tp
= tcp_sk(sk
);
4629 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4630 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4631 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4632 tcp_enter_quickack_mode(sk
, TCP_MAX_QUICKACKS
);
4634 if (tcp_is_sack(tp
) && READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_dsack
)) {
4635 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4637 tcp_rcv_spurious_retrans(sk
, skb
);
4638 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4639 end_seq
= tp
->rcv_nxt
;
4640 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4647 /* These routines update the SACK block as out-of-order packets arrive or
4648 * in-order packets close up the sequence space.
4650 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4653 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4654 struct tcp_sack_block
*swalk
= sp
+ 1;
4656 /* See if the recent change to the first SACK eats into
4657 * or hits the sequence space of other SACK blocks, if so coalesce.
4659 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4660 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4663 /* Zap SWALK, by moving every further SACK up by one slot.
4664 * Decrease num_sacks.
4666 tp
->rx_opt
.num_sacks
--;
4667 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4676 void tcp_sack_compress_send_ack(struct sock
*sk
)
4678 struct tcp_sock
*tp
= tcp_sk(sk
);
4680 if (!tp
->compressed_ack
)
4683 if (hrtimer_try_to_cancel(&tp
->compressed_ack_timer
) == 1)
4686 /* Since we have to send one ack finally,
4687 * substract one from tp->compressed_ack to keep
4688 * LINUX_MIB_TCPACKCOMPRESSED accurate.
4690 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPACKCOMPRESSED
,
4691 tp
->compressed_ack
- 1);
4693 tp
->compressed_ack
= 0;
4697 /* Reasonable amount of sack blocks included in TCP SACK option
4698 * The max is 4, but this becomes 3 if TCP timestamps are there.
4699 * Given that SACK packets might be lost, be conservative and use 2.
4701 #define TCP_SACK_BLOCKS_EXPECTED 2
4703 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4705 struct tcp_sock
*tp
= tcp_sk(sk
);
4706 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4707 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4713 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4714 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4715 if (this_sack
>= TCP_SACK_BLOCKS_EXPECTED
)
4716 tcp_sack_compress_send_ack(sk
);
4717 /* Rotate this_sack to the first one. */
4718 for (; this_sack
> 0; this_sack
--, sp
--)
4719 swap(*sp
, *(sp
- 1));
4721 tcp_sack_maybe_coalesce(tp
);
4726 if (this_sack
>= TCP_SACK_BLOCKS_EXPECTED
)
4727 tcp_sack_compress_send_ack(sk
);
4729 /* Could not find an adjacent existing SACK, build a new one,
4730 * put it at the front, and shift everyone else down. We
4731 * always know there is at least one SACK present already here.
4733 * If the sack array is full, forget about the last one.
4735 if (this_sack
>= TCP_NUM_SACKS
) {
4737 tp
->rx_opt
.num_sacks
--;
4740 for (; this_sack
> 0; this_sack
--, sp
--)
4744 /* Build the new head SACK, and we're done. */
4745 sp
->start_seq
= seq
;
4746 sp
->end_seq
= end_seq
;
4747 tp
->rx_opt
.num_sacks
++;
4750 /* RCV.NXT advances, some SACKs should be eaten. */
4752 static void tcp_sack_remove(struct tcp_sock
*tp
)
4754 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4755 int num_sacks
= tp
->rx_opt
.num_sacks
;
4758 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4759 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4760 tp
->rx_opt
.num_sacks
= 0;
4764 for (this_sack
= 0; this_sack
< num_sacks
;) {
4765 /* Check if the start of the sack is covered by RCV.NXT. */
4766 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4769 /* RCV.NXT must cover all the block! */
4770 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4772 /* Zap this SACK, by moving forward any other SACKS. */
4773 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4774 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4781 tp
->rx_opt
.num_sacks
= num_sacks
;
4785 * tcp_try_coalesce - try to merge skb to prior one
4788 * @from: buffer to add in queue
4789 * @fragstolen: pointer to boolean
4791 * Before queueing skb @from after @to, try to merge them
4792 * to reduce overall memory use and queue lengths, if cost is small.
4793 * Packets in ofo or receive queues can stay a long time.
4794 * Better try to coalesce them right now to avoid future collapses.
4795 * Returns true if caller should free @from instead of queueing it
4797 static bool tcp_try_coalesce(struct sock
*sk
,
4799 struct sk_buff
*from
,
4804 *fragstolen
= false;
4806 /* Its possible this segment overlaps with prior segment in queue */
4807 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4810 if (!mptcp_skb_can_collapse(to
, from
))
4813 #ifdef CONFIG_TLS_DEVICE
4814 if (from
->decrypted
!= to
->decrypted
)
4818 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4821 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4822 sk_mem_charge(sk
, delta
);
4823 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4824 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4825 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4826 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4828 if (TCP_SKB_CB(from
)->has_rxtstamp
) {
4829 TCP_SKB_CB(to
)->has_rxtstamp
= true;
4830 to
->tstamp
= from
->tstamp
;
4831 skb_hwtstamps(to
)->hwtstamp
= skb_hwtstamps(from
)->hwtstamp
;
4837 static bool tcp_ooo_try_coalesce(struct sock
*sk
,
4839 struct sk_buff
*from
,
4842 bool res
= tcp_try_coalesce(sk
, to
, from
, fragstolen
);
4844 /* In case tcp_drop_reason() is called later, update to->gso_segs */
4846 u32 gso_segs
= max_t(u16
, 1, skb_shinfo(to
)->gso_segs
) +
4847 max_t(u16
, 1, skb_shinfo(from
)->gso_segs
);
4849 skb_shinfo(to
)->gso_segs
= min_t(u32
, gso_segs
, 0xFFFF);
4854 static void tcp_drop_reason(struct sock
*sk
, struct sk_buff
*skb
,
4855 enum skb_drop_reason reason
)
4857 sk_drops_add(sk
, skb
);
4858 kfree_skb_reason(skb
, reason
);
4861 /* This one checks to see if we can put data from the
4862 * out_of_order queue into the receive_queue.
4864 static void tcp_ofo_queue(struct sock
*sk
)
4866 struct tcp_sock
*tp
= tcp_sk(sk
);
4867 __u32 dsack_high
= tp
->rcv_nxt
;
4868 bool fin
, fragstolen
, eaten
;
4869 struct sk_buff
*skb
, *tail
;
4872 p
= rb_first(&tp
->out_of_order_queue
);
4875 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4878 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4879 __u32 dsack
= dsack_high
;
4880 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4881 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4882 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4885 rb_erase(&skb
->rbnode
, &tp
->out_of_order_queue
);
4887 if (unlikely(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))) {
4888 tcp_drop_reason(sk
, skb
, SKB_DROP_REASON_TCP_OFO_DROP
);
4892 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4893 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4894 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4895 fin
= TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
;
4897 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4899 kfree_skb_partial(skb
, fragstolen
);
4901 if (unlikely(fin
)) {
4903 /* tcp_fin() purges tp->out_of_order_queue,
4904 * so we must end this loop right now.
4911 static bool tcp_prune_ofo_queue(struct sock
*sk
, const struct sk_buff
*in_skb
);
4912 static int tcp_prune_queue(struct sock
*sk
, const struct sk_buff
*in_skb
);
4914 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4917 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4918 !sk_rmem_schedule(sk
, skb
, size
)) {
4920 if (tcp_prune_queue(sk
, skb
) < 0)
4923 while (!sk_rmem_schedule(sk
, skb
, size
)) {
4924 if (!tcp_prune_ofo_queue(sk
, skb
))
4931 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4933 struct tcp_sock
*tp
= tcp_sk(sk
);
4934 struct rb_node
**p
, *parent
;
4935 struct sk_buff
*skb1
;
4939 tcp_save_lrcv_flowlabel(sk
, skb
);
4940 tcp_ecn_check_ce(sk
, skb
);
4942 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4943 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4944 sk
->sk_data_ready(sk
);
4945 tcp_drop_reason(sk
, skb
, SKB_DROP_REASON_PROTO_MEM
);
4949 /* Disable header prediction. */
4951 inet_csk_schedule_ack(sk
);
4953 tp
->rcv_ooopack
+= max_t(u16
, 1, skb_shinfo(skb
)->gso_segs
);
4954 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4955 seq
= TCP_SKB_CB(skb
)->seq
;
4956 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4958 p
= &tp
->out_of_order_queue
.rb_node
;
4959 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
4960 /* Initial out of order segment, build 1 SACK. */
4961 if (tcp_is_sack(tp
)) {
4962 tp
->rx_opt
.num_sacks
= 1;
4963 tp
->selective_acks
[0].start_seq
= seq
;
4964 tp
->selective_acks
[0].end_seq
= end_seq
;
4966 rb_link_node(&skb
->rbnode
, NULL
, p
);
4967 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
4968 tp
->ooo_last_skb
= skb
;
4972 /* In the typical case, we are adding an skb to the end of the list.
4973 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4975 if (tcp_ooo_try_coalesce(sk
, tp
->ooo_last_skb
,
4976 skb
, &fragstolen
)) {
4978 /* For non sack flows, do not grow window to force DUPACK
4979 * and trigger fast retransmit.
4981 if (tcp_is_sack(tp
))
4982 tcp_grow_window(sk
, skb
, true);
4983 kfree_skb_partial(skb
, fragstolen
);
4987 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4988 if (!before(seq
, TCP_SKB_CB(tp
->ooo_last_skb
)->end_seq
)) {
4989 parent
= &tp
->ooo_last_skb
->rbnode
;
4990 p
= &parent
->rb_right
;
4994 /* Find place to insert this segment. Handle overlaps on the way. */
4998 skb1
= rb_to_skb(parent
);
4999 if (before(seq
, TCP_SKB_CB(skb1
)->seq
)) {
5000 p
= &parent
->rb_left
;
5003 if (before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
5004 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
5005 /* All the bits are present. Drop. */
5006 NET_INC_STATS(sock_net(sk
),
5007 LINUX_MIB_TCPOFOMERGE
);
5008 tcp_drop_reason(sk
, skb
,
5009 SKB_DROP_REASON_TCP_OFOMERGE
);
5011 tcp_dsack_set(sk
, seq
, end_seq
);
5014 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
5015 /* Partial overlap. */
5016 tcp_dsack_set(sk
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
5018 /* skb's seq == skb1's seq and skb covers skb1.
5019 * Replace skb1 with skb.
5021 rb_replace_node(&skb1
->rbnode
, &skb
->rbnode
,
5022 &tp
->out_of_order_queue
);
5023 tcp_dsack_extend(sk
,
5024 TCP_SKB_CB(skb1
)->seq
,
5025 TCP_SKB_CB(skb1
)->end_seq
);
5026 NET_INC_STATS(sock_net(sk
),
5027 LINUX_MIB_TCPOFOMERGE
);
5028 tcp_drop_reason(sk
, skb1
,
5029 SKB_DROP_REASON_TCP_OFOMERGE
);
5032 } else if (tcp_ooo_try_coalesce(sk
, skb1
,
5033 skb
, &fragstolen
)) {
5036 p
= &parent
->rb_right
;
5039 /* Insert segment into RB tree. */
5040 rb_link_node(&skb
->rbnode
, parent
, p
);
5041 rb_insert_color(&skb
->rbnode
, &tp
->out_of_order_queue
);
5044 /* Remove other segments covered by skb. */
5045 while ((skb1
= skb_rb_next(skb
)) != NULL
) {
5046 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
5048 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
5049 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
5053 rb_erase(&skb1
->rbnode
, &tp
->out_of_order_queue
);
5054 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
5055 TCP_SKB_CB(skb1
)->end_seq
);
5056 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
5057 tcp_drop_reason(sk
, skb1
, SKB_DROP_REASON_TCP_OFOMERGE
);
5059 /* If there is no skb after us, we are the last_skb ! */
5061 tp
->ooo_last_skb
= skb
;
5064 if (tcp_is_sack(tp
))
5065 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
5068 /* For non sack flows, do not grow window to force DUPACK
5069 * and trigger fast retransmit.
5071 if (tcp_is_sack(tp
))
5072 tcp_grow_window(sk
, skb
, false);
5074 skb_set_owner_r(skb
, sk
);
5078 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
,
5082 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
5085 tcp_try_coalesce(sk
, tail
,
5086 skb
, fragstolen
)) ? 1 : 0;
5087 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
5089 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
5090 skb_set_owner_r(skb
, sk
);
5095 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
5097 struct sk_buff
*skb
;
5105 if (size
> PAGE_SIZE
) {
5106 int npages
= min_t(size_t, size
>> PAGE_SHIFT
, MAX_SKB_FRAGS
);
5108 data_len
= npages
<< PAGE_SHIFT
;
5109 size
= data_len
+ (size
& ~PAGE_MASK
);
5111 skb
= alloc_skb_with_frags(size
- data_len
, data_len
,
5112 PAGE_ALLOC_COSTLY_ORDER
,
5113 &err
, sk
->sk_allocation
);
5117 skb_put(skb
, size
- data_len
);
5118 skb
->data_len
= data_len
;
5121 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
)) {
5122 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVQDROP
);
5126 err
= skb_copy_datagram_from_iter(skb
, 0, &msg
->msg_iter
, size
);
5130 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
5131 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
5132 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
5134 if (tcp_queue_rcv(sk
, skb
, &fragstolen
)) {
5135 WARN_ON_ONCE(fragstolen
); /* should not happen */
5147 void tcp_data_ready(struct sock
*sk
)
5149 if (tcp_epollin_ready(sk
, sk
->sk_rcvlowat
) || sock_flag(sk
, SOCK_DONE
))
5150 sk
->sk_data_ready(sk
);
5153 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
5155 struct tcp_sock
*tp
= tcp_sk(sk
);
5156 enum skb_drop_reason reason
;
5160 /* If a subflow has been reset, the packet should not continue
5161 * to be processed, drop the packet.
5163 if (sk_is_mptcp(sk
) && !mptcp_incoming_options(sk
, skb
)) {
5168 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
) {
5173 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
5175 reason
= SKB_DROP_REASON_NOT_SPECIFIED
;
5176 tp
->rx_opt
.dsack
= 0;
5178 /* Queue data for delivery to the user.
5179 * Packets in sequence go to the receive queue.
5180 * Out of sequence packets to the out_of_order_queue.
5182 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
5183 if (tcp_receive_window(tp
) == 0) {
5184 reason
= SKB_DROP_REASON_TCP_ZEROWINDOW
;
5185 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPZEROWINDOWDROP
);
5189 /* Ok. In sequence. In window. */
5191 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
)) {
5192 /* TODO: maybe ratelimit these WIN 0 ACK ? */
5193 inet_csk(sk
)->icsk_ack
.pending
|=
5194 (ICSK_ACK_NOMEM
| ICSK_ACK_NOW
);
5195 inet_csk_schedule_ack(sk
);
5196 sk
->sk_data_ready(sk
);
5198 if (skb_queue_len(&sk
->sk_receive_queue
)) {
5199 reason
= SKB_DROP_REASON_PROTO_MEM
;
5200 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVQDROP
);
5203 sk_forced_mem_schedule(sk
, skb
->truesize
);
5206 eaten
= tcp_queue_rcv(sk
, skb
, &fragstolen
);
5208 tcp_event_data_recv(sk
, skb
);
5209 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
5212 if (!RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
5215 /* RFC5681. 4.2. SHOULD send immediate ACK, when
5216 * gap in queue is filled.
5218 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
5219 inet_csk(sk
)->icsk_ack
.pending
|= ICSK_ACK_NOW
;
5222 if (tp
->rx_opt
.num_sacks
)
5223 tcp_sack_remove(tp
);
5225 tcp_fast_path_check(sk
);
5228 kfree_skb_partial(skb
, fragstolen
);
5229 if (!sock_flag(sk
, SOCK_DEAD
))
5234 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
5235 tcp_rcv_spurious_retrans(sk
, skb
);
5236 /* A retransmit, 2nd most common case. Force an immediate ack. */
5237 reason
= SKB_DROP_REASON_TCP_OLD_DATA
;
5238 NET_INC_STATS(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
5239 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
5242 tcp_enter_quickack_mode(sk
, TCP_MAX_QUICKACKS
);
5243 inet_csk_schedule_ack(sk
);
5245 tcp_drop_reason(sk
, skb
, reason
);
5249 /* Out of window. F.e. zero window probe. */
5250 if (!before(TCP_SKB_CB(skb
)->seq
,
5251 tp
->rcv_nxt
+ tcp_receive_window(tp
))) {
5252 reason
= SKB_DROP_REASON_TCP_OVERWINDOW
;
5256 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5257 /* Partial packet, seq < rcv_next < end_seq */
5258 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
5260 /* If window is closed, drop tail of packet. But after
5261 * remembering D-SACK for its head made in previous line.
5263 if (!tcp_receive_window(tp
)) {
5264 reason
= SKB_DROP_REASON_TCP_ZEROWINDOW
;
5265 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPZEROWINDOWDROP
);
5271 tcp_data_queue_ofo(sk
, skb
);
5274 static struct sk_buff
*tcp_skb_next(struct sk_buff
*skb
, struct sk_buff_head
*list
)
5277 return !skb_queue_is_last(list
, skb
) ? skb
->next
: NULL
;
5279 return skb_rb_next(skb
);
5282 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
5283 struct sk_buff_head
*list
,
5284 struct rb_root
*root
)
5286 struct sk_buff
*next
= tcp_skb_next(skb
, list
);
5289 __skb_unlink(skb
, list
);
5291 rb_erase(&skb
->rbnode
, root
);
5294 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
5299 /* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
5300 void tcp_rbtree_insert(struct rb_root
*root
, struct sk_buff
*skb
)
5302 struct rb_node
**p
= &root
->rb_node
;
5303 struct rb_node
*parent
= NULL
;
5304 struct sk_buff
*skb1
;
5308 skb1
= rb_to_skb(parent
);
5309 if (before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb1
)->seq
))
5310 p
= &parent
->rb_left
;
5312 p
= &parent
->rb_right
;
5314 rb_link_node(&skb
->rbnode
, parent
, p
);
5315 rb_insert_color(&skb
->rbnode
, root
);
5318 /* Collapse contiguous sequence of skbs head..tail with
5319 * sequence numbers start..end.
5321 * If tail is NULL, this means until the end of the queue.
5323 * Segments with FIN/SYN are not collapsed (only because this
5327 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
, struct rb_root
*root
,
5328 struct sk_buff
*head
, struct sk_buff
*tail
, u32 start
, u32 end
)
5330 struct sk_buff
*skb
= head
, *n
;
5331 struct sk_buff_head tmp
;
5334 /* First, check that queue is collapsible and find
5335 * the point where collapsing can be useful.
5338 for (end_of_skbs
= true; skb
!= NULL
&& skb
!= tail
; skb
= n
) {
5339 n
= tcp_skb_next(skb
, list
);
5341 /* No new bits? It is possible on ofo queue. */
5342 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
5343 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
5349 /* The first skb to collapse is:
5351 * - bloated or contains data before "start" or
5352 * overlaps to the next one and mptcp allow collapsing.
5354 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
5355 (tcp_win_from_space(sk
, skb
->truesize
) > skb
->len
||
5356 before(TCP_SKB_CB(skb
)->seq
, start
))) {
5357 end_of_skbs
= false;
5361 if (n
&& n
!= tail
&& mptcp_skb_can_collapse(skb
, n
) &&
5362 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(n
)->seq
) {
5363 end_of_skbs
= false;
5367 /* Decided to skip this, advance start seq. */
5368 start
= TCP_SKB_CB(skb
)->end_seq
;
5371 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
5374 __skb_queue_head_init(&tmp
);
5376 while (before(start
, end
)) {
5377 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
5378 struct sk_buff
*nskb
;
5380 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
5384 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
5385 #ifdef CONFIG_TLS_DEVICE
5386 nskb
->decrypted
= skb
->decrypted
;
5388 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
5390 __skb_queue_before(list
, skb
, nskb
);
5392 __skb_queue_tail(&tmp
, nskb
); /* defer rbtree insertion */
5393 skb_set_owner_r(nskb
, sk
);
5394 mptcp_skb_ext_move(nskb
, skb
);
5396 /* Copy data, releasing collapsed skbs. */
5398 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
5399 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
5403 size
= min(copy
, size
);
5404 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
5406 TCP_SKB_CB(nskb
)->end_seq
+= size
;
5410 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
5411 skb
= tcp_collapse_one(sk
, skb
, list
, root
);
5414 !mptcp_skb_can_collapse(nskb
, skb
) ||
5415 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
5417 #ifdef CONFIG_TLS_DEVICE
5418 if (skb
->decrypted
!= nskb
->decrypted
)
5425 skb_queue_walk_safe(&tmp
, skb
, n
)
5426 tcp_rbtree_insert(root
, skb
);
5429 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
5430 * and tcp_collapse() them until all the queue is collapsed.
5432 static void tcp_collapse_ofo_queue(struct sock
*sk
)
5434 struct tcp_sock
*tp
= tcp_sk(sk
);
5435 u32 range_truesize
, sum_tiny
= 0;
5436 struct sk_buff
*skb
, *head
;
5439 skb
= skb_rb_first(&tp
->out_of_order_queue
);
5442 tp
->ooo_last_skb
= skb_rb_last(&tp
->out_of_order_queue
);
5445 start
= TCP_SKB_CB(skb
)->seq
;
5446 end
= TCP_SKB_CB(skb
)->end_seq
;
5447 range_truesize
= skb
->truesize
;
5449 for (head
= skb
;;) {
5450 skb
= skb_rb_next(skb
);
5452 /* Range is terminated when we see a gap or when
5453 * we are at the queue end.
5456 after(TCP_SKB_CB(skb
)->seq
, end
) ||
5457 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
5458 /* Do not attempt collapsing tiny skbs */
5459 if (range_truesize
!= head
->truesize
||
5460 end
- start
>= SKB_WITH_OVERHEAD(PAGE_SIZE
)) {
5461 tcp_collapse(sk
, NULL
, &tp
->out_of_order_queue
,
5462 head
, skb
, start
, end
);
5464 sum_tiny
+= range_truesize
;
5465 if (sum_tiny
> sk
->sk_rcvbuf
>> 3)
5471 range_truesize
+= skb
->truesize
;
5472 if (unlikely(before(TCP_SKB_CB(skb
)->seq
, start
)))
5473 start
= TCP_SKB_CB(skb
)->seq
;
5474 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
5475 end
= TCP_SKB_CB(skb
)->end_seq
;
5480 * Clean the out-of-order queue to make room.
5481 * We drop high sequences packets to :
5482 * 1) Let a chance for holes to be filled.
5483 * This means we do not drop packets from ooo queue if their sequence
5484 * is before incoming packet sequence.
5485 * 2) not add too big latencies if thousands of packets sit there.
5486 * (But if application shrinks SO_RCVBUF, we could still end up
5487 * freeing whole queue here)
5488 * 3) Drop at least 12.5 % of sk_rcvbuf to avoid malicious attacks.
5490 * Return true if queue has shrunk.
5492 static bool tcp_prune_ofo_queue(struct sock
*sk
, const struct sk_buff
*in_skb
)
5494 struct tcp_sock
*tp
= tcp_sk(sk
);
5495 struct rb_node
*node
, *prev
;
5496 bool pruned
= false;
5499 if (RB_EMPTY_ROOT(&tp
->out_of_order_queue
))
5502 goal
= sk
->sk_rcvbuf
>> 3;
5503 node
= &tp
->ooo_last_skb
->rbnode
;
5506 struct sk_buff
*skb
= rb_to_skb(node
);
5508 /* If incoming skb would land last in ofo queue, stop pruning. */
5509 if (after(TCP_SKB_CB(in_skb
)->seq
, TCP_SKB_CB(skb
)->seq
))
5512 prev
= rb_prev(node
);
5513 rb_erase(node
, &tp
->out_of_order_queue
);
5514 goal
-= skb
->truesize
;
5515 tcp_drop_reason(sk
, skb
, SKB_DROP_REASON_TCP_OFO_QUEUE_PRUNE
);
5516 tp
->ooo_last_skb
= rb_to_skb(prev
);
5517 if (!prev
|| goal
<= 0) {
5518 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
&&
5519 !tcp_under_memory_pressure(sk
))
5521 goal
= sk
->sk_rcvbuf
>> 3;
5527 NET_INC_STATS(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
5528 /* Reset SACK state. A conforming SACK implementation will
5529 * do the same at a timeout based retransmit. When a connection
5530 * is in a sad state like this, we care only about integrity
5531 * of the connection not performance.
5533 if (tp
->rx_opt
.sack_ok
)
5534 tcp_sack_reset(&tp
->rx_opt
);
5539 /* Reduce allocated memory if we can, trying to get
5540 * the socket within its memory limits again.
5542 * Return less than zero if we should start dropping frames
5543 * until the socket owning process reads some of the data
5544 * to stabilize the situation.
5546 static int tcp_prune_queue(struct sock
*sk
, const struct sk_buff
*in_skb
)
5548 struct tcp_sock
*tp
= tcp_sk(sk
);
5550 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
5552 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
5553 tcp_clamp_window(sk
);
5554 else if (tcp_under_memory_pressure(sk
))
5555 tcp_adjust_rcv_ssthresh(sk
);
5557 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5560 tcp_collapse_ofo_queue(sk
);
5561 if (!skb_queue_empty(&sk
->sk_receive_queue
))
5562 tcp_collapse(sk
, &sk
->sk_receive_queue
, NULL
,
5563 skb_peek(&sk
->sk_receive_queue
),
5565 tp
->copied_seq
, tp
->rcv_nxt
);
5567 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5570 /* Collapsing did not help, destructive actions follow.
5571 * This must not ever occur. */
5573 tcp_prune_ofo_queue(sk
, in_skb
);
5575 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5578 /* If we are really being abused, tell the caller to silently
5579 * drop receive data on the floor. It will get retransmitted
5580 * and hopefully then we'll have sufficient space.
5582 NET_INC_STATS(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
5584 /* Massive buffer overcommit. */
5589 static bool tcp_should_expand_sndbuf(struct sock
*sk
)
5591 const struct tcp_sock
*tp
= tcp_sk(sk
);
5593 /* If the user specified a specific send buffer setting, do
5596 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
5599 /* If we are under global TCP memory pressure, do not expand. */
5600 if (tcp_under_memory_pressure(sk
)) {
5601 int unused_mem
= sk_unused_reserved_mem(sk
);
5603 /* Adjust sndbuf according to reserved mem. But make sure
5604 * it never goes below SOCK_MIN_SNDBUF.
5605 * See sk_stream_moderate_sndbuf() for more details.
5607 if (unused_mem
> SOCK_MIN_SNDBUF
)
5608 WRITE_ONCE(sk
->sk_sndbuf
, unused_mem
);
5613 /* If we are under soft global TCP memory pressure, do not expand. */
5614 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
5617 /* If we filled the congestion window, do not expand. */
5618 if (tcp_packets_in_flight(tp
) >= tcp_snd_cwnd(tp
))
5624 static void tcp_new_space(struct sock
*sk
)
5626 struct tcp_sock
*tp
= tcp_sk(sk
);
5628 if (tcp_should_expand_sndbuf(sk
)) {
5629 tcp_sndbuf_expand(sk
);
5630 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
5633 INDIRECT_CALL_1(sk
->sk_write_space
, sk_stream_write_space
, sk
);
5636 /* Caller made space either from:
5637 * 1) Freeing skbs in rtx queues (after tp->snd_una has advanced)
5638 * 2) Sent skbs from output queue (and thus advancing tp->snd_nxt)
5640 * We might be able to generate EPOLLOUT to the application if:
5641 * 1) Space consumed in output/rtx queues is below sk->sk_sndbuf/2
5642 * 2) notsent amount (tp->write_seq - tp->snd_nxt) became
5643 * small enough that tcp_stream_memory_free() decides it
5644 * is time to generate EPOLLOUT.
5646 void tcp_check_space(struct sock
*sk
)
5648 /* pairs with tcp_poll() */
5650 if (sk
->sk_socket
&&
5651 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
5653 if (!test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
5654 tcp_chrono_stop(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
5658 static inline void tcp_data_snd_check(struct sock
*sk
)
5660 tcp_push_pending_frames(sk
);
5661 tcp_check_space(sk
);
5665 * Check if sending an ack is needed.
5667 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5669 struct tcp_sock
*tp
= tcp_sk(sk
);
5670 unsigned long rtt
, delay
;
5672 /* More than one full frame received... */
5673 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5674 /* ... and right edge of window advances far enough.
5675 * (tcp_recvmsg() will send ACK otherwise).
5676 * If application uses SO_RCVLOWAT, we want send ack now if
5677 * we have not received enough bytes to satisfy the condition.
5679 (tp
->rcv_nxt
- tp
->copied_seq
< sk
->sk_rcvlowat
||
5680 __tcp_select_window(sk
) >= tp
->rcv_wnd
)) ||
5681 /* We ACK each frame or... */
5682 tcp_in_quickack_mode(sk
) ||
5683 /* Protocol state mandates a one-time immediate ACK */
5684 inet_csk(sk
)->icsk_ack
.pending
& ICSK_ACK_NOW
) {
5685 /* If we are running from __release_sock() in user context,
5686 * Defer the ack until tcp_release_cb().
5688 if (sock_owned_by_user_nocheck(sk
) &&
5689 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_backlog_ack_defer
)) {
5690 set_bit(TCP_ACK_DEFERRED
, &sk
->sk_tsq_flags
);
5698 if (!ofo_possible
|| RB_EMPTY_ROOT(&tp
->out_of_order_queue
)) {
5699 tcp_send_delayed_ack(sk
);
5703 if (!tcp_is_sack(tp
) ||
5704 tp
->compressed_ack
>= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_comp_sack_nr
))
5707 if (tp
->compressed_ack_rcv_nxt
!= tp
->rcv_nxt
) {
5708 tp
->compressed_ack_rcv_nxt
= tp
->rcv_nxt
;
5709 tp
->dup_ack_counter
= 0;
5711 if (tp
->dup_ack_counter
< TCP_FASTRETRANS_THRESH
) {
5712 tp
->dup_ack_counter
++;
5715 tp
->compressed_ack
++;
5716 if (hrtimer_is_queued(&tp
->compressed_ack_timer
))
5719 /* compress ack timer : 5 % of rtt, but no more than tcp_comp_sack_delay_ns */
5721 rtt
= tp
->rcv_rtt_est
.rtt_us
;
5722 if (tp
->srtt_us
&& tp
->srtt_us
< rtt
)
5725 delay
= min_t(unsigned long,
5726 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_comp_sack_delay_ns
),
5727 rtt
* (NSEC_PER_USEC
>> 3)/20);
5729 hrtimer_start_range_ns(&tp
->compressed_ack_timer
, ns_to_ktime(delay
),
5730 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_comp_sack_slack_ns
),
5731 HRTIMER_MODE_REL_PINNED_SOFT
);
5734 static inline void tcp_ack_snd_check(struct sock
*sk
)
5736 if (!inet_csk_ack_scheduled(sk
)) {
5737 /* We sent a data segment already. */
5740 __tcp_ack_snd_check(sk
, 1);
5744 * This routine is only called when we have urgent data
5745 * signaled. Its the 'slow' part of tcp_urg. It could be
5746 * moved inline now as tcp_urg is only called from one
5747 * place. We handle URGent data wrong. We have to - as
5748 * BSD still doesn't use the correction from RFC961.
5749 * For 1003.1g we should support a new option TCP_STDURG to permit
5750 * either form (or just set the sysctl tcp_stdurg).
5753 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5755 struct tcp_sock
*tp
= tcp_sk(sk
);
5756 u32 ptr
= ntohs(th
->urg_ptr
);
5758 if (ptr
&& !READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_stdurg
))
5760 ptr
+= ntohl(th
->seq
);
5762 /* Ignore urgent data that we've already seen and read. */
5763 if (after(tp
->copied_seq
, ptr
))
5766 /* Do not replay urg ptr.
5768 * NOTE: interesting situation not covered by specs.
5769 * Misbehaving sender may send urg ptr, pointing to segment,
5770 * which we already have in ofo queue. We are not able to fetch
5771 * such data and will stay in TCP_URG_NOTYET until will be eaten
5772 * by recvmsg(). Seems, we are not obliged to handle such wicked
5773 * situations. But it is worth to think about possibility of some
5774 * DoSes using some hypothetical application level deadlock.
5776 if (before(ptr
, tp
->rcv_nxt
))
5779 /* Do we already have a newer (or duplicate) urgent pointer? */
5780 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5783 /* Tell the world about our new urgent pointer. */
5786 /* We may be adding urgent data when the last byte read was
5787 * urgent. To do this requires some care. We cannot just ignore
5788 * tp->copied_seq since we would read the last urgent byte again
5789 * as data, nor can we alter copied_seq until this data arrives
5790 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5792 * NOTE. Double Dutch. Rendering to plain English: author of comment
5793 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5794 * and expect that both A and B disappear from stream. This is _wrong_.
5795 * Though this happens in BSD with high probability, this is occasional.
5796 * Any application relying on this is buggy. Note also, that fix "works"
5797 * only in this artificial test. Insert some normal data between A and B and we will
5798 * decline of BSD again. Verdict: it is better to remove to trap
5801 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5802 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5803 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5805 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5806 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5811 WRITE_ONCE(tp
->urg_data
, TCP_URG_NOTYET
);
5812 WRITE_ONCE(tp
->urg_seq
, ptr
);
5814 /* Disable header prediction. */
5818 /* This is the 'fast' part of urgent handling. */
5819 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5821 struct tcp_sock
*tp
= tcp_sk(sk
);
5823 /* Check if we get a new urgent pointer - normally not. */
5824 if (unlikely(th
->urg
))
5825 tcp_check_urg(sk
, th
);
5827 /* Do we wait for any urgent data? - normally not... */
5828 if (unlikely(tp
->urg_data
== TCP_URG_NOTYET
)) {
5829 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5832 /* Is the urgent pointer pointing into this packet? */
5833 if (ptr
< skb
->len
) {
5835 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5837 WRITE_ONCE(tp
->urg_data
, TCP_URG_VALID
| tmp
);
5838 if (!sock_flag(sk
, SOCK_DEAD
))
5839 sk
->sk_data_ready(sk
);
5844 /* Accept RST for rcv_nxt - 1 after a FIN.
5845 * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
5846 * FIN is sent followed by a RST packet. The RST is sent with the same
5847 * sequence number as the FIN, and thus according to RFC 5961 a challenge
5848 * ACK should be sent. However, Mac OSX rate limits replies to challenge
5849 * ACKs on the closed socket. In addition middleboxes can drop either the
5850 * challenge ACK or a subsequent RST.
5852 static bool tcp_reset_check(const struct sock
*sk
, const struct sk_buff
*skb
)
5854 const struct tcp_sock
*tp
= tcp_sk(sk
);
5856 return unlikely(TCP_SKB_CB(skb
)->seq
== (tp
->rcv_nxt
- 1) &&
5857 (1 << sk
->sk_state
) & (TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
|
5861 /* Does PAWS and seqno based validation of an incoming segment, flags will
5862 * play significant role here.
5864 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5865 const struct tcphdr
*th
, int syn_inerr
)
5867 struct tcp_sock
*tp
= tcp_sk(sk
);
5870 /* RFC1323: H1. Apply PAWS check first. */
5871 if (tcp_fast_parse_options(sock_net(sk
), skb
, th
, tp
) &&
5872 tp
->rx_opt
.saw_tstamp
&&
5873 tcp_paws_discard(sk
, skb
)) {
5875 if (unlikely(th
->syn
))
5877 NET_INC_STATS(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5878 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5879 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5880 &tp
->last_oow_ack_time
))
5881 tcp_send_dupack(sk
, skb
);
5882 SKB_DR_SET(reason
, TCP_RFC7323_PAWS
);
5885 /* Reset is accepted even if it did not pass PAWS. */
5888 /* Step 1: check sequence number */
5889 reason
= tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
5891 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5892 * (RST) segments are validated by checking their SEQ-fields."
5893 * And page 69: "If an incoming segment is not acceptable,
5894 * an acknowledgment should be sent in reply (unless the RST
5895 * bit is set, if so drop the segment and return)".
5900 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5901 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5902 &tp
->last_oow_ack_time
))
5903 tcp_send_dupack(sk
, skb
);
5904 } else if (tcp_reset_check(sk
, skb
)) {
5910 /* Step 2: check RST bit */
5912 /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
5913 * FIN and SACK too if available):
5914 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
5915 * the right-most SACK block,
5917 * RESET the connection
5919 * Send a challenge ACK
5921 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
||
5922 tcp_reset_check(sk
, skb
))
5925 if (tcp_is_sack(tp
) && tp
->rx_opt
.num_sacks
> 0) {
5926 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
5927 int max_sack
= sp
[0].end_seq
;
5930 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;
5932 max_sack
= after(sp
[this_sack
].end_seq
,
5934 sp
[this_sack
].end_seq
: max_sack
;
5937 if (TCP_SKB_CB(skb
)->seq
== max_sack
)
5941 /* Disable TFO if RST is out-of-order
5942 * and no data has been received
5943 * for current active TFO socket
5945 if (tp
->syn_fastopen
&& !tp
->data_segs_in
&&
5946 sk
->sk_state
== TCP_ESTABLISHED
)
5947 tcp_fastopen_active_disable(sk
);
5948 tcp_send_challenge_ack(sk
);
5949 SKB_DR_SET(reason
, TCP_RESET
);
5953 /* step 3: check security and precedence [ignored] */
5955 /* step 4: Check for a SYN
5956 * RFC 5961 4.2 : Send a challenge ack
5961 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
5962 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5963 tcp_send_challenge_ack(sk
);
5964 SKB_DR_SET(reason
, TCP_INVALID_SYN
);
5968 bpf_skops_parse_hdr(sk
, skb
);
5973 tcp_drop_reason(sk
, skb
, reason
);
5983 * TCP receive function for the ESTABLISHED state.
5985 * It is split into a fast path and a slow path. The fast path is
5987 * - A zero window was announced from us - zero window probing
5988 * is only handled properly in the slow path.
5989 * - Out of order segments arrived.
5990 * - Urgent data is expected.
5991 * - There is no buffer space left
5992 * - Unexpected TCP flags/window values/header lengths are received
5993 * (detected by checking the TCP header against pred_flags)
5994 * - Data is sent in both directions. Fast path only supports pure senders
5995 * or pure receivers (this means either the sequence number or the ack
5996 * value must stay constant)
5997 * - Unexpected TCP option.
5999 * When these conditions are not satisfied it drops into a standard
6000 * receive procedure patterned after RFC793 to handle all cases.
6001 * The first three cases are guaranteed by proper pred_flags setting,
6002 * the rest is checked inline. Fast processing is turned on in
6003 * tcp_data_queue when everything is OK.
6005 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
)
6007 enum skb_drop_reason reason
= SKB_DROP_REASON_NOT_SPECIFIED
;
6008 const struct tcphdr
*th
= (const struct tcphdr
*)skb
->data
;
6009 struct tcp_sock
*tp
= tcp_sk(sk
);
6010 unsigned int len
= skb
->len
;
6012 /* TCP congestion window tracking */
6013 trace_tcp_probe(sk
, skb
);
6015 tcp_mstamp_refresh(tp
);
6016 if (unlikely(!rcu_access_pointer(sk
->sk_rx_dst
)))
6017 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
6019 * Header prediction.
6020 * The code loosely follows the one in the famous
6021 * "30 instruction TCP receive" Van Jacobson mail.
6023 * Van's trick is to deposit buffers into socket queue
6024 * on a device interrupt, to call tcp_recv function
6025 * on the receive process context and checksum and copy
6026 * the buffer to user space. smart...
6028 * Our current scheme is not silly either but we take the
6029 * extra cost of the net_bh soft interrupt processing...
6030 * We do checksum and copy also but from device to kernel.
6033 tp
->rx_opt
.saw_tstamp
= 0;
6035 /* pred_flags is 0xS?10 << 16 + snd_wnd
6036 * if header_prediction is to be made
6037 * 'S' will always be tp->tcp_header_len >> 2
6038 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
6039 * turn it off (when there are holes in the receive
6040 * space for instance)
6041 * PSH flag is ignored.
6044 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
6045 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
6046 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
6047 int tcp_header_len
= tp
->tcp_header_len
;
6049 /* Timestamp header prediction: tcp_header_len
6050 * is automatically equal to th->doff*4 due to pred_flags
6054 /* Check timestamp */
6055 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
6056 /* No? Slow path! */
6057 if (!tcp_parse_aligned_timestamp(tp
, th
))
6060 /* If PAWS failed, check it more carefully in slow path */
6061 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
6064 /* DO NOT update ts_recent here, if checksum fails
6065 * and timestamp was corrupted part, it will result
6066 * in a hung connection since we will drop all
6067 * future packets due to the PAWS test.
6071 if (len
<= tcp_header_len
) {
6072 /* Bulk data transfer: sender */
6073 if (len
== tcp_header_len
) {
6074 /* Predicted packet is in window by definition.
6075 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
6076 * Hence, check seq<=rcv_wup reduces to:
6078 if (tcp_header_len
==
6079 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
6080 tp
->rcv_nxt
== tp
->rcv_wup
)
6081 tcp_store_ts_recent(tp
);
6083 /* We know that such packets are checksummed
6086 tcp_ack(sk
, skb
, 0);
6088 tcp_data_snd_check(sk
);
6089 /* When receiving pure ack in fast path, update
6090 * last ts ecr directly instead of calling
6091 * tcp_rcv_rtt_measure_ts()
6093 tp
->rcv_rtt_last_tsecr
= tp
->rx_opt
.rcv_tsecr
;
6095 } else { /* Header too small */
6096 reason
= SKB_DROP_REASON_PKT_TOO_SMALL
;
6097 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
6102 bool fragstolen
= false;
6104 if (tcp_checksum_complete(skb
))
6107 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
6110 /* Predicted packet is in window by definition.
6111 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
6112 * Hence, check seq<=rcv_wup reduces to:
6114 if (tcp_header_len
==
6115 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
6116 tp
->rcv_nxt
== tp
->rcv_wup
)
6117 tcp_store_ts_recent(tp
);
6119 tcp_rcv_rtt_measure_ts(sk
, skb
);
6121 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
6123 /* Bulk data transfer: receiver */
6125 __skb_pull(skb
, tcp_header_len
);
6126 eaten
= tcp_queue_rcv(sk
, skb
, &fragstolen
);
6128 tcp_event_data_recv(sk
, skb
);
6130 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
6131 /* Well, only one small jumplet in fast path... */
6132 tcp_ack(sk
, skb
, FLAG_DATA
);
6133 tcp_data_snd_check(sk
);
6134 if (!inet_csk_ack_scheduled(sk
))
6137 tcp_update_wl(tp
, TCP_SKB_CB(skb
)->seq
);
6140 __tcp_ack_snd_check(sk
, 0);
6143 kfree_skb_partial(skb
, fragstolen
);
6150 if (len
< (th
->doff
<< 2) || tcp_checksum_complete(skb
))
6153 if (!th
->ack
&& !th
->rst
&& !th
->syn
) {
6154 reason
= SKB_DROP_REASON_TCP_FLAGS
;
6159 * Standard slow path.
6162 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
6166 reason
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
);
6167 if ((int)reason
< 0) {
6171 tcp_rcv_rtt_measure_ts(sk
, skb
);
6173 /* Process urgent data. */
6174 tcp_urg(sk
, skb
, th
);
6176 /* step 7: process the segment text */
6177 tcp_data_queue(sk
, skb
);
6179 tcp_data_snd_check(sk
);
6180 tcp_ack_snd_check(sk
);
6184 reason
= SKB_DROP_REASON_TCP_CSUM
;
6185 trace_tcp_bad_csum(skb
);
6186 TCP_INC_STATS(sock_net(sk
), TCP_MIB_CSUMERRORS
);
6187 TCP_INC_STATS(sock_net(sk
), TCP_MIB_INERRS
);
6190 tcp_drop_reason(sk
, skb
, reason
);
6192 EXPORT_SYMBOL(tcp_rcv_established
);
6194 void tcp_init_transfer(struct sock
*sk
, int bpf_op
, struct sk_buff
*skb
)
6196 struct inet_connection_sock
*icsk
= inet_csk(sk
);
6197 struct tcp_sock
*tp
= tcp_sk(sk
);
6200 icsk
->icsk_af_ops
->rebuild_header(sk
);
6201 tcp_init_metrics(sk
);
6203 /* Initialize the congestion window to start the transfer.
6204 * Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
6205 * retransmitted. In light of RFC6298 more aggressive 1sec
6206 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
6207 * retransmission has occurred.
6209 if (tp
->total_retrans
> 1 && tp
->undo_marker
)
6210 tcp_snd_cwnd_set(tp
, 1);
6212 tcp_snd_cwnd_set(tp
, tcp_init_cwnd(tp
, __sk_dst_get(sk
)));
6213 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
6215 bpf_skops_established(sk
, bpf_op
, skb
);
6216 /* Initialize congestion control unless BPF initialized it already: */
6217 if (!icsk
->icsk_ca_initialized
)
6218 tcp_init_congestion_control(sk
);
6219 tcp_init_buffer_space(sk
);
6222 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
6224 struct tcp_sock
*tp
= tcp_sk(sk
);
6225 struct inet_connection_sock
*icsk
= inet_csk(sk
);
6227 tcp_ao_finish_connect(sk
, skb
);
6228 tcp_set_state(sk
, TCP_ESTABLISHED
);
6229 icsk
->icsk_ack
.lrcvtime
= tcp_jiffies32
;
6232 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
6233 security_inet_conn_established(sk
, skb
);
6234 sk_mark_napi_id(sk
, skb
);
6237 tcp_init_transfer(sk
, BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB
, skb
);
6239 /* Prevent spurious tcp_cwnd_restart() on first data
6242 tp
->lsndtime
= tcp_jiffies32
;
6244 if (sock_flag(sk
, SOCK_KEEPOPEN
))
6245 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
6247 if (!tp
->rx_opt
.snd_wscale
)
6248 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
6253 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
6254 struct tcp_fastopen_cookie
*cookie
)
6256 struct tcp_sock
*tp
= tcp_sk(sk
);
6257 struct sk_buff
*data
= tp
->syn_data
? tcp_rtx_queue_head(sk
) : NULL
;
6258 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
6259 bool syn_drop
= false;
6261 if (mss
== tp
->rx_opt
.user_mss
) {
6262 struct tcp_options_received opt
;
6264 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
6265 tcp_clear_options(&opt
);
6266 opt
.user_mss
= opt
.mss_clamp
= 0;
6267 tcp_parse_options(sock_net(sk
), synack
, &opt
, 0, NULL
);
6268 mss
= opt
.mss_clamp
;
6271 if (!tp
->syn_fastopen
) {
6272 /* Ignore an unsolicited cookie */
6274 } else if (tp
->total_retrans
) {
6275 /* SYN timed out and the SYN-ACK neither has a cookie nor
6276 * acknowledges data. Presumably the remote received only
6277 * the retransmitted (regular) SYNs: either the original
6278 * SYN-data or the corresponding SYN-ACK was dropped.
6280 syn_drop
= (cookie
->len
< 0 && data
);
6281 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
6282 /* We requested a cookie but didn't get it. If we did not use
6283 * the (old) exp opt format then try so next time (try_exp=1).
6284 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
6286 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
6289 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
6291 if (data
) { /* Retransmit unacked data in SYN */
6292 if (tp
->total_retrans
)
6293 tp
->fastopen_client_fail
= TFO_SYN_RETRANSMITTED
;
6295 tp
->fastopen_client_fail
= TFO_DATA_NOT_ACKED
;
6296 skb_rbtree_walk_from(data
)
6297 tcp_mark_skb_lost(sk
, data
);
6298 tcp_xmit_retransmit_queue(sk
);
6299 NET_INC_STATS(sock_net(sk
),
6300 LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
6303 tp
->syn_data_acked
= tp
->syn_data
;
6304 if (tp
->syn_data_acked
) {
6305 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
6306 /* SYN-data is counted as two separate packets in tcp_ack() */
6307 if (tp
->delivered
> 1)
6311 tcp_fastopen_add_skb(sk
, synack
);
6316 static void smc_check_reset_syn(struct tcp_sock
*tp
)
6318 #if IS_ENABLED(CONFIG_SMC)
6319 if (static_branch_unlikely(&tcp_have_smc
)) {
6320 if (tp
->syn_smc
&& !tp
->rx_opt
.smc_ok
)
6326 static void tcp_try_undo_spurious_syn(struct sock
*sk
)
6328 struct tcp_sock
*tp
= tcp_sk(sk
);
6331 /* undo_marker is set when SYN or SYNACK times out. The timeout is
6332 * spurious if the ACK's timestamp option echo value matches the
6333 * original SYN timestamp.
6335 syn_stamp
= tp
->retrans_stamp
;
6336 if (tp
->undo_marker
&& syn_stamp
&& tp
->rx_opt
.saw_tstamp
&&
6337 syn_stamp
== tp
->rx_opt
.rcv_tsecr
)
6338 tp
->undo_marker
= 0;
6341 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
6342 const struct tcphdr
*th
)
6344 struct inet_connection_sock
*icsk
= inet_csk(sk
);
6345 struct tcp_sock
*tp
= tcp_sk(sk
);
6346 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6347 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
6351 tcp_parse_options(sock_net(sk
), skb
, &tp
->rx_opt
, 0, &foc
);
6352 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
6353 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
6357 * "If the state is SYN-SENT then
6358 * first check the ACK bit
6359 * If the ACK bit is set
6360 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
6361 * a reset (unless the RST bit is set, if so drop
6362 * the segment and return)"
6364 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
6365 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
6366 /* Previous FIN/ACK or RST/ACK might be ignored. */
6367 if (icsk
->icsk_retransmits
== 0)
6368 inet_csk_reset_xmit_timer(sk
,
6370 TCP_TIMEOUT_MIN
, TCP_RTO_MAX
);
6371 goto reset_and_undo
;
6374 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
6375 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
6376 tcp_time_stamp_ts(tp
))) {
6377 NET_INC_STATS(sock_net(sk
),
6378 LINUX_MIB_PAWSACTIVEREJECTED
);
6379 goto reset_and_undo
;
6382 /* Now ACK is acceptable.
6384 * "If the RST bit is set
6385 * If the ACK was acceptable then signal the user "error:
6386 * connection reset", drop the segment, enter CLOSED state,
6387 * delete TCB, and return."
6398 * "fifth, if neither of the SYN or RST bits is set then
6399 * drop the segment and return."
6405 SKB_DR_SET(reason
, TCP_FLAGS
);
6406 goto discard_and_undo
;
6409 * "If the SYN bit is on ...
6410 * are acceptable then ...
6411 * (our SYN has been ACKed), change the connection
6412 * state to ESTABLISHED..."
6415 tcp_ecn_rcv_synack(tp
, th
);
6417 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
6418 tcp_try_undo_spurious_syn(sk
);
6419 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
6421 /* Ok.. it's good. Set up sequence numbers and
6422 * move to established.
6424 WRITE_ONCE(tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
+ 1);
6425 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
6427 /* RFC1323: The window in SYN & SYN/ACK segments is
6430 tp
->snd_wnd
= ntohs(th
->window
);
6432 if (!tp
->rx_opt
.wscale_ok
) {
6433 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
6434 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
6437 if (tp
->rx_opt
.saw_tstamp
) {
6438 tp
->rx_opt
.tstamp_ok
= 1;
6439 tp
->tcp_header_len
=
6440 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
6441 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
6442 tcp_store_ts_recent(tp
);
6444 tp
->tcp_header_len
= sizeof(struct tcphdr
);
6447 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
6448 tcp_initialize_rcv_mss(sk
);
6450 /* Remember, tcp_poll() does not lock socket!
6451 * Change state from SYN-SENT only after copied_seq
6452 * is initialized. */
6453 WRITE_ONCE(tp
->copied_seq
, tp
->rcv_nxt
);
6455 smc_check_reset_syn(tp
);
6459 tcp_finish_connect(sk
, skb
);
6461 fastopen_fail
= (tp
->syn_fastopen
|| tp
->syn_data
) &&
6462 tcp_rcv_fastopen_synack(sk
, skb
, &foc
);
6464 if (!sock_flag(sk
, SOCK_DEAD
)) {
6465 sk
->sk_state_change(sk
);
6466 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
6470 if (sk
->sk_write_pending
||
6471 READ_ONCE(icsk
->icsk_accept_queue
.rskq_defer_accept
) ||
6472 inet_csk_in_pingpong_mode(sk
)) {
6473 /* Save one ACK. Data will be ready after
6474 * several ticks, if write_pending is set.
6476 * It may be deleted, but with this feature tcpdumps
6477 * look so _wonderfully_ clever, that I was not able
6478 * to stand against the temptation 8) --ANK
6480 inet_csk_schedule_ack(sk
);
6481 tcp_enter_quickack_mode(sk
, TCP_MAX_QUICKACKS
);
6482 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
6483 TCP_DELACK_MAX
, TCP_RTO_MAX
);
6490 /* No ACK in the segment */
6494 * "If the RST bit is set
6496 * Otherwise (no ACK) drop the segment and return."
6498 SKB_DR_SET(reason
, TCP_RESET
);
6499 goto discard_and_undo
;
6503 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
6504 tcp_paws_reject(&tp
->rx_opt
, 0)) {
6505 SKB_DR_SET(reason
, TCP_RFC7323_PAWS
);
6506 goto discard_and_undo
;
6509 /* We see SYN without ACK. It is attempt of
6510 * simultaneous connect with crossed SYNs.
6511 * Particularly, it can be connect to self.
6513 #ifdef CONFIG_TCP_AO
6514 struct tcp_ao_info
*ao
;
6516 ao
= rcu_dereference_protected(tp
->ao_info
,
6517 lockdep_sock_is_held(sk
));
6519 WRITE_ONCE(ao
->risn
, th
->seq
);
6523 tcp_set_state(sk
, TCP_SYN_RECV
);
6525 if (tp
->rx_opt
.saw_tstamp
) {
6526 tp
->rx_opt
.tstamp_ok
= 1;
6527 tcp_store_ts_recent(tp
);
6528 tp
->tcp_header_len
=
6529 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
6531 tp
->tcp_header_len
= sizeof(struct tcphdr
);
6534 WRITE_ONCE(tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
+ 1);
6535 WRITE_ONCE(tp
->copied_seq
, tp
->rcv_nxt
);
6536 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
6538 /* RFC1323: The window in SYN & SYN/ACK segments is
6541 tp
->snd_wnd
= ntohs(th
->window
);
6542 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
6543 tp
->max_window
= tp
->snd_wnd
;
6545 tcp_ecn_rcv_syn(tp
, th
);
6548 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
6549 tcp_initialize_rcv_mss(sk
);
6551 tcp_send_synack(sk
);
6553 /* Note, we could accept data and URG from this segment.
6554 * There are no obstacles to make this (except that we must
6555 * either change tcp_recvmsg() to prevent it from returning data
6556 * before 3WHS completes per RFC793, or employ TCP Fast Open).
6558 * However, if we ignore data in ACKless segments sometimes,
6559 * we have no reasons to accept it sometimes.
6560 * Also, seems the code doing it in step6 of tcp_rcv_state_process
6561 * is not flawless. So, discard packet for sanity.
6562 * Uncomment this return to process the data.
6569 /* "fifth, if neither of the SYN or RST bits is set then
6570 * drop the segment and return."
6574 tcp_clear_options(&tp
->rx_opt
);
6575 tp
->rx_opt
.mss_clamp
= saved_clamp
;
6576 tcp_drop_reason(sk
, skb
, reason
);
6580 tcp_clear_options(&tp
->rx_opt
);
6581 tp
->rx_opt
.mss_clamp
= saved_clamp
;
6585 static void tcp_rcv_synrecv_state_fastopen(struct sock
*sk
)
6587 struct tcp_sock
*tp
= tcp_sk(sk
);
6588 struct request_sock
*req
;
6590 /* If we are still handling the SYNACK RTO, see if timestamp ECR allows
6591 * undo. If peer SACKs triggered fast recovery, we can't undo here.
6593 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
&& !tp
->packets_out
)
6594 tcp_try_undo_recovery(sk
);
6596 /* Reset rtx states to prevent spurious retransmits_timed_out() */
6597 tcp_update_rto_time(tp
);
6598 tp
->retrans_stamp
= 0;
6599 inet_csk(sk
)->icsk_retransmits
= 0;
6601 /* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
6602 * we no longer need req so release it.
6604 req
= rcu_dereference_protected(tp
->fastopen_rsk
,
6605 lockdep_sock_is_held(sk
));
6606 reqsk_fastopen_remove(sk
, req
, false);
6608 /* Re-arm the timer because data may have been sent out.
6609 * This is similar to the regular data transmission case
6610 * when new data has just been ack'ed.
6612 * (TFO) - we could try to be more aggressive and
6613 * retransmitting any data sooner based on when they
6620 * This function implements the receiving procedure of RFC 793 for
6621 * all states except ESTABLISHED and TIME_WAIT.
6622 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
6623 * address independent.
6626 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
)
6628 struct tcp_sock
*tp
= tcp_sk(sk
);
6629 struct inet_connection_sock
*icsk
= inet_csk(sk
);
6630 const struct tcphdr
*th
= tcp_hdr(skb
);
6631 struct request_sock
*req
;
6636 switch (sk
->sk_state
) {
6638 SKB_DR_SET(reason
, TCP_CLOSE
);
6646 SKB_DR_SET(reason
, TCP_RESET
);
6651 SKB_DR_SET(reason
, TCP_FLAGS
);
6654 /* It is possible that we process SYN packets from backlog,
6655 * so we need to make sure to disable BH and RCU right there.
6659 acceptable
= icsk
->icsk_af_ops
->conn_request(sk
, skb
) >= 0;
6668 SKB_DR_SET(reason
, TCP_FLAGS
);
6672 tp
->rx_opt
.saw_tstamp
= 0;
6673 tcp_mstamp_refresh(tp
);
6674 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
);
6678 /* Do step6 onward by hand. */
6679 tcp_urg(sk
, skb
, th
);
6681 tcp_data_snd_check(sk
);
6685 tcp_mstamp_refresh(tp
);
6686 tp
->rx_opt
.saw_tstamp
= 0;
6687 req
= rcu_dereference_protected(tp
->fastopen_rsk
,
6688 lockdep_sock_is_held(sk
));
6692 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
6693 sk
->sk_state
!= TCP_FIN_WAIT1
);
6695 if (!tcp_check_req(sk
, skb
, req
, true, &req_stolen
)) {
6696 SKB_DR_SET(reason
, TCP_FASTOPEN
);
6701 if (!th
->ack
&& !th
->rst
&& !th
->syn
) {
6702 SKB_DR_SET(reason
, TCP_FLAGS
);
6705 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
6708 /* step 5: check the ACK field */
6709 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
6710 FLAG_UPDATE_TS_RECENT
|
6711 FLAG_NO_CHALLENGE_ACK
) > 0;
6714 if (sk
->sk_state
== TCP_SYN_RECV
)
6715 return 1; /* send one RST */
6716 tcp_send_challenge_ack(sk
);
6717 SKB_DR_SET(reason
, TCP_OLD_ACK
);
6720 switch (sk
->sk_state
) {
6722 tp
->delivered
++; /* SYN-ACK delivery isn't tracked in tcp_ack */
6724 tcp_synack_rtt_meas(sk
, req
);
6727 tcp_rcv_synrecv_state_fastopen(sk
);
6729 tcp_try_undo_spurious_syn(sk
);
6730 tp
->retrans_stamp
= 0;
6731 tcp_init_transfer(sk
, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB
,
6733 WRITE_ONCE(tp
->copied_seq
, tp
->rcv_nxt
);
6735 tcp_ao_established(sk
);
6737 tcp_set_state(sk
, TCP_ESTABLISHED
);
6738 sk
->sk_state_change(sk
);
6740 /* Note, that this wakeup is only for marginal crossed SYN case.
6741 * Passively open sockets are not waked up, because
6742 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
6745 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
6747 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
6748 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
6749 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
6751 if (tp
->rx_opt
.tstamp_ok
)
6752 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
6754 if (!inet_csk(sk
)->icsk_ca_ops
->cong_control
)
6755 tcp_update_pacing_rate(sk
);
6757 /* Prevent spurious tcp_cwnd_restart() on first data packet */
6758 tp
->lsndtime
= tcp_jiffies32
;
6760 tcp_initialize_rcv_mss(sk
);
6761 tcp_fast_path_on(tp
);
6764 case TCP_FIN_WAIT1
: {
6768 tcp_rcv_synrecv_state_fastopen(sk
);
6770 if (tp
->snd_una
!= tp
->write_seq
)
6773 tcp_set_state(sk
, TCP_FIN_WAIT2
);
6774 WRITE_ONCE(sk
->sk_shutdown
, sk
->sk_shutdown
| SEND_SHUTDOWN
);
6778 if (!sock_flag(sk
, SOCK_DEAD
)) {
6779 /* Wake up lingering close() */
6780 sk
->sk_state_change(sk
);
6784 if (READ_ONCE(tp
->linger2
) < 0) {
6786 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6789 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6790 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6791 /* Receive out of order FIN after close() */
6792 if (tp
->syn_fastopen
&& th
->fin
)
6793 tcp_fastopen_active_disable(sk
);
6795 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6799 tmo
= tcp_fin_time(sk
);
6800 if (tmo
> TCP_TIMEWAIT_LEN
) {
6801 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
6802 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
6803 /* Bad case. We could lose such FIN otherwise.
6804 * It is not a big problem, but it looks confusing
6805 * and not so rare event. We still can lose it now,
6806 * if it spins in bh_lock_sock(), but it is really
6809 inet_csk_reset_keepalive_timer(sk
, tmo
);
6811 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
6818 if (tp
->snd_una
== tp
->write_seq
) {
6819 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
6825 if (tp
->snd_una
== tp
->write_seq
) {
6826 tcp_update_metrics(sk
);
6833 /* step 6: check the URG bit */
6834 tcp_urg(sk
, skb
, th
);
6836 /* step 7: process the segment text */
6837 switch (sk
->sk_state
) {
6838 case TCP_CLOSE_WAIT
:
6841 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
6842 /* If a subflow has been reset, the packet should not
6843 * continue to be processed, drop the packet.
6845 if (sk_is_mptcp(sk
) && !mptcp_incoming_options(sk
, skb
))
6852 /* RFC 793 says to queue data in these states,
6853 * RFC 1122 says we MUST send a reset.
6854 * BSD 4.4 also does reset.
6856 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
6857 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6858 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6859 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6865 case TCP_ESTABLISHED
:
6866 tcp_data_queue(sk
, skb
);
6871 /* tcp_data could move socket to TIME-WAIT */
6872 if (sk
->sk_state
!= TCP_CLOSE
) {
6873 tcp_data_snd_check(sk
);
6874 tcp_ack_snd_check(sk
);
6879 tcp_drop_reason(sk
, skb
, reason
);
6887 EXPORT_SYMBOL(tcp_rcv_state_process
);
6889 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
6891 struct inet_request_sock
*ireq
= inet_rsk(req
);
6893 if (family
== AF_INET
)
6894 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6895 &ireq
->ir_rmt_addr
, port
);
6896 #if IS_ENABLED(CONFIG_IPV6)
6897 else if (family
== AF_INET6
)
6898 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6899 &ireq
->ir_v6_rmt_addr
, port
);
6903 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6905 * If we receive a SYN packet with these bits set, it means a
6906 * network is playing bad games with TOS bits. In order to
6907 * avoid possible false congestion notifications, we disable
6908 * TCP ECN negotiation.
6910 * Exception: tcp_ca wants ECN. This is required for DCTCP
6911 * congestion control: Linux DCTCP asserts ECT on all packets,
6912 * including SYN, which is most optimal solution; however,
6913 * others, such as FreeBSD do not.
6915 * Exception: At least one of the reserved bits of the TCP header (th->res1) is
6916 * set, indicating the use of a future TCP extension (such as AccECN). See
6917 * RFC8311 §4.3 which updates RFC3168 to allow the development of such
6920 static void tcp_ecn_create_request(struct request_sock
*req
,
6921 const struct sk_buff
*skb
,
6922 const struct sock
*listen_sk
,
6923 const struct dst_entry
*dst
)
6925 const struct tcphdr
*th
= tcp_hdr(skb
);
6926 const struct net
*net
= sock_net(listen_sk
);
6927 bool th_ecn
= th
->ece
&& th
->cwr
;
6934 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
6935 ecn_ok_dst
= dst_feature(dst
, DST_FEATURE_ECN_MASK
);
6936 ecn_ok
= READ_ONCE(net
->ipv4
.sysctl_tcp_ecn
) || ecn_ok_dst
;
6938 if (((!ect
|| th
->res1
) && ecn_ok
) || tcp_ca_needs_ecn(listen_sk
) ||
6939 (ecn_ok_dst
& DST_FEATURE_ECN_CA
) ||
6940 tcp_bpf_ca_needs_ecn((struct sock
*)req
))
6941 inet_rsk(req
)->ecn_ok
= 1;
6944 static void tcp_openreq_init(struct request_sock
*req
,
6945 const struct tcp_options_received
*rx_opt
,
6946 struct sk_buff
*skb
, const struct sock
*sk
)
6948 struct inet_request_sock
*ireq
= inet_rsk(req
);
6950 req
->rsk_rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6951 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6952 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6953 tcp_rsk(req
)->snt_synack
= 0;
6954 tcp_rsk(req
)->last_oow_ack_time
= 0;
6955 req
->mss
= rx_opt
->mss_clamp
;
6956 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6957 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6958 ireq
->sack_ok
= rx_opt
->sack_ok
;
6959 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6960 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6963 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6964 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6965 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6966 #if IS_ENABLED(CONFIG_SMC)
6967 ireq
->smc_ok
= rx_opt
->smc_ok
&& !(tcp_sk(sk
)->smc_hs_congested
&&
6968 tcp_sk(sk
)->smc_hs_congested(sk
));
6972 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6973 struct sock
*sk_listener
,
6974 bool attach_listener
)
6976 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
,
6980 struct inet_request_sock
*ireq
= inet_rsk(req
);
6982 ireq
->ireq_opt
= NULL
;
6983 #if IS_ENABLED(CONFIG_IPV6)
6984 ireq
->pktopts
= NULL
;
6986 atomic64_set(&ireq
->ir_cookie
, 0);
6987 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6988 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6989 ireq
->ireq_family
= sk_listener
->sk_family
;
6990 req
->timeout
= TCP_TIMEOUT_INIT
;
6995 EXPORT_SYMBOL(inet_reqsk_alloc
);
6998 * Return true if a syncookie should be sent
7000 static bool tcp_syn_flood_action(const struct sock
*sk
, const char *proto
)
7002 struct request_sock_queue
*queue
= &inet_csk(sk
)->icsk_accept_queue
;
7003 const char *msg
= "Dropping request";
7004 struct net
*net
= sock_net(sk
);
7005 bool want_cookie
= false;
7008 syncookies
= READ_ONCE(net
->ipv4
.sysctl_tcp_syncookies
);
7010 #ifdef CONFIG_SYN_COOKIES
7012 msg
= "Sending cookies";
7014 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
7017 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
7019 if (!READ_ONCE(queue
->synflood_warned
) && syncookies
!= 2 &&
7020 xchg(&queue
->synflood_warned
, 1) == 0) {
7021 if (IS_ENABLED(CONFIG_IPV6
) && sk
->sk_family
== AF_INET6
) {
7022 net_info_ratelimited("%s: Possible SYN flooding on port [%pI6c]:%u. %s.\n",
7023 proto
, inet6_rcv_saddr(sk
),
7026 net_info_ratelimited("%s: Possible SYN flooding on port %pI4:%u. %s.\n",
7027 proto
, &sk
->sk_rcv_saddr
,
7035 static void tcp_reqsk_record_syn(const struct sock
*sk
,
7036 struct request_sock
*req
,
7037 const struct sk_buff
*skb
)
7039 if (tcp_sk(sk
)->save_syn
) {
7040 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
7041 struct saved_syn
*saved_syn
;
7045 if (tcp_sk(sk
)->save_syn
== 2) { /* Save full header. */
7046 base
= skb_mac_header(skb
);
7047 mac_hdrlen
= skb_mac_header_len(skb
);
7050 base
= skb_network_header(skb
);
7054 saved_syn
= kmalloc(struct_size(saved_syn
, data
, len
),
7057 saved_syn
->mac_hdrlen
= mac_hdrlen
;
7058 saved_syn
->network_hdrlen
= skb_network_header_len(skb
);
7059 saved_syn
->tcp_hdrlen
= tcp_hdrlen(skb
);
7060 memcpy(saved_syn
->data
, base
, len
);
7061 req
->saved_syn
= saved_syn
;
7066 /* If a SYN cookie is required and supported, returns a clamped MSS value to be
7067 * used for SYN cookie generation.
7069 u16
tcp_get_syncookie_mss(struct request_sock_ops
*rsk_ops
,
7070 const struct tcp_request_sock_ops
*af_ops
,
7071 struct sock
*sk
, struct tcphdr
*th
)
7073 struct tcp_sock
*tp
= tcp_sk(sk
);
7076 if (READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_syncookies
) != 2 &&
7077 !inet_csk_reqsk_queue_is_full(sk
))
7080 if (!tcp_syn_flood_action(sk
, rsk_ops
->slab_name
))
7083 if (sk_acceptq_is_full(sk
)) {
7084 NET_INC_STATS(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
7088 mss
= tcp_parse_mss_option(th
, tp
->rx_opt
.user_mss
);
7090 mss
= af_ops
->mss_clamp
;
7094 EXPORT_SYMBOL_GPL(tcp_get_syncookie_mss
);
7096 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
7097 const struct tcp_request_sock_ops
*af_ops
,
7098 struct sock
*sk
, struct sk_buff
*skb
)
7100 struct tcp_fastopen_cookie foc
= { .len
= -1 };
7101 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
7102 struct tcp_options_received tmp_opt
;
7103 struct tcp_sock
*tp
= tcp_sk(sk
);
7104 struct net
*net
= sock_net(sk
);
7105 struct sock
*fastopen_sk
= NULL
;
7106 struct request_sock
*req
;
7107 bool want_cookie
= false;
7108 struct dst_entry
*dst
;
7112 #ifdef CONFIG_TCP_AO
7113 const struct tcp_ao_hdr
*aoh
;
7116 syncookies
= READ_ONCE(net
->ipv4
.sysctl_tcp_syncookies
);
7118 /* TW buckets are converted to open requests without
7119 * limitations, they conserve resources and peer is
7120 * evidently real one.
7122 if ((syncookies
== 2 || inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
7123 want_cookie
= tcp_syn_flood_action(sk
, rsk_ops
->slab_name
);
7128 if (sk_acceptq_is_full(sk
)) {
7129 NET_INC_STATS(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
7133 req
= inet_reqsk_alloc(rsk_ops
, sk
, !want_cookie
);
7137 req
->syncookie
= want_cookie
;
7138 tcp_rsk(req
)->af_specific
= af_ops
;
7139 tcp_rsk(req
)->ts_off
= 0;
7140 tcp_rsk(req
)->req_usec_ts
= false;
7141 #if IS_ENABLED(CONFIG_MPTCP)
7142 tcp_rsk(req
)->is_mptcp
= 0;
7145 tcp_clear_options(&tmp_opt
);
7146 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
7147 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
7148 tcp_parse_options(sock_net(sk
), skb
, &tmp_opt
, 0,
7149 want_cookie
? NULL
: &foc
);
7151 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
7152 tcp_clear_options(&tmp_opt
);
7154 if (IS_ENABLED(CONFIG_SMC
) && want_cookie
)
7157 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
7158 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
7159 inet_rsk(req
)->no_srccheck
= inet_test_bit(TRANSPARENT
, sk
);
7161 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
7162 inet_rsk(req
)->ir_iif
= inet_request_bound_dev_if(sk
, skb
);
7164 dst
= af_ops
->route_req(sk
, skb
, &fl
, req
);
7168 if (tmp_opt
.tstamp_ok
) {
7169 tcp_rsk(req
)->req_usec_ts
= dst_tcp_usec_ts(dst
);
7170 tcp_rsk(req
)->ts_off
= af_ops
->init_ts_off(net
, skb
);
7172 if (!want_cookie
&& !isn
) {
7173 int max_syn_backlog
= READ_ONCE(net
->ipv4
.sysctl_max_syn_backlog
);
7175 /* Kill the following clause, if you dislike this way. */
7177 (max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
7178 (max_syn_backlog
>> 2)) &&
7179 !tcp_peer_is_proven(req
, dst
)) {
7180 /* Without syncookies last quarter of
7181 * backlog is filled with destinations,
7182 * proven to be alive.
7183 * It means that we continue to communicate
7184 * to destinations, already remembered
7185 * to the moment of synflood.
7187 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
7189 goto drop_and_release
;
7192 isn
= af_ops
->init_seq(skb
);
7195 tcp_ecn_create_request(req
, skb
, sk
, dst
);
7198 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
7199 if (!tmp_opt
.tstamp_ok
)
7200 inet_rsk(req
)->ecn_ok
= 0;
7203 #ifdef CONFIG_TCP_AO
7204 if (tcp_parse_auth_options(tcp_hdr(skb
), NULL
, &aoh
))
7205 goto drop_and_release
; /* Invalid TCP options */
7207 tcp_rsk(req
)->used_tcp_ao
= true;
7208 tcp_rsk(req
)->ao_rcv_next
= aoh
->keyid
;
7209 tcp_rsk(req
)->ao_keyid
= aoh
->rnext_keyid
;
7212 tcp_rsk(req
)->used_tcp_ao
= false;
7215 tcp_rsk(req
)->snt_isn
= isn
;
7216 tcp_rsk(req
)->txhash
= net_tx_rndhash();
7217 tcp_rsk(req
)->syn_tos
= TCP_SKB_CB(skb
)->ip_dsfield
;
7218 tcp_openreq_init_rwin(req
, sk
, dst
);
7219 sk_rx_queue_set(req_to_sk(req
), skb
);
7221 tcp_reqsk_record_syn(sk
, req
, skb
);
7222 fastopen_sk
= tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
7225 af_ops
->send_synack(fastopen_sk
, dst
, &fl
, req
,
7226 &foc
, TCP_SYNACK_FASTOPEN
, skb
);
7227 /* Add the child socket directly into the accept queue */
7228 if (!inet_csk_reqsk_queue_add(sk
, req
, fastopen_sk
)) {
7229 reqsk_fastopen_remove(fastopen_sk
, req
, false);
7230 bh_unlock_sock(fastopen_sk
);
7231 sock_put(fastopen_sk
);
7234 sk
->sk_data_ready(sk
);
7235 bh_unlock_sock(fastopen_sk
);
7236 sock_put(fastopen_sk
);
7238 tcp_rsk(req
)->tfo_listener
= false;
7240 req
->timeout
= tcp_timeout_init((struct sock
*)req
);
7241 inet_csk_reqsk_queue_hash_add(sk
, req
, req
->timeout
);
7243 af_ops
->send_synack(sk
, dst
, &fl
, req
, &foc
,
7244 !want_cookie
? TCP_SYNACK_NORMAL
:
7263 EXPORT_SYMBOL(tcp_conn_request
);