1 // SPDX-License-Identifier: GPL-2.0-only
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>
23 * Changes: Pedro Roque : Retransmit queue handled by TCP.
24 * : Fragmentation on mtu decrease
25 * : Segment collapse on retransmit
28 * Linus Torvalds : send_delayed_ack
29 * David S. Miller : Charge memory using the right skb
30 * during syn/ack processing.
31 * David S. Miller : Output engine completely rewritten.
32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
33 * Cacophonix Gaul : draft-minshall-nagle-01
34 * J Hadi Salim : ECN support
38 #define pr_fmt(fmt) "TCP: " fmt
41 #include <net/mptcp.h>
43 #include <linux/compiler.h>
44 #include <linux/gfp.h>
45 #include <linux/module.h>
46 #include <linux/static_key.h>
48 #include <trace/events/tcp.h>
50 /* Refresh clocks of a TCP socket,
51 * ensuring monotically increasing values.
53 void tcp_mstamp_refresh(struct tcp_sock
*tp
)
55 u64 val
= tcp_clock_ns();
57 tp
->tcp_clock_cache
= val
;
58 tp
->tcp_mstamp
= div_u64(val
, NSEC_PER_USEC
);
61 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
62 int push_one
, gfp_t gfp
);
64 /* Account for new data that has been sent to the network. */
65 static void tcp_event_new_data_sent(struct sock
*sk
, struct sk_buff
*skb
)
67 struct inet_connection_sock
*icsk
= inet_csk(sk
);
68 struct tcp_sock
*tp
= tcp_sk(sk
);
69 unsigned int prior_packets
= tp
->packets_out
;
71 WRITE_ONCE(tp
->snd_nxt
, TCP_SKB_CB(skb
)->end_seq
);
73 __skb_unlink(skb
, &sk
->sk_write_queue
);
74 tcp_rbtree_insert(&sk
->tcp_rtx_queue
, skb
);
76 if (tp
->highest_sack
== NULL
)
77 tp
->highest_sack
= skb
;
79 tp
->packets_out
+= tcp_skb_pcount(skb
);
80 if (!prior_packets
|| icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
83 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
,
88 /* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
89 * window scaling factor due to loss of precision.
90 * If window has been shrunk, what should we make? It is not clear at all.
91 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
92 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
93 * invalid. OK, let's make this for now:
95 static inline __u32
tcp_acceptable_seq(const struct sock
*sk
)
97 const struct tcp_sock
*tp
= tcp_sk(sk
);
99 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
) ||
100 (tp
->rx_opt
.wscale_ok
&&
101 ((tp
->snd_nxt
- tcp_wnd_end(tp
)) < (1 << tp
->rx_opt
.rcv_wscale
))))
104 return tcp_wnd_end(tp
);
107 /* Calculate mss to advertise in SYN segment.
108 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
110 * 1. It is independent of path mtu.
111 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
112 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
113 * attached devices, because some buggy hosts are confused by
115 * 4. We do not make 3, we advertise MSS, calculated from first
116 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
117 * This may be overridden via information stored in routing table.
118 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
119 * probably even Jumbo".
121 static __u16
tcp_advertise_mss(struct sock
*sk
)
123 struct tcp_sock
*tp
= tcp_sk(sk
);
124 const struct dst_entry
*dst
= __sk_dst_get(sk
);
125 int mss
= tp
->advmss
;
128 unsigned int metric
= dst_metric_advmss(dst
);
139 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
140 * This is the first part of cwnd validation mechanism.
142 void tcp_cwnd_restart(struct sock
*sk
, s32 delta
)
144 struct tcp_sock
*tp
= tcp_sk(sk
);
145 u32 restart_cwnd
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
146 u32 cwnd
= tcp_snd_cwnd(tp
);
148 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
150 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
151 restart_cwnd
= min(restart_cwnd
, cwnd
);
153 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
155 tcp_snd_cwnd_set(tp
, max(cwnd
, restart_cwnd
));
156 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
157 tp
->snd_cwnd_used
= 0;
160 /* Congestion state accounting after a packet has been sent. */
161 static void tcp_event_data_sent(struct tcp_sock
*tp
,
164 struct inet_connection_sock
*icsk
= inet_csk(sk
);
165 const u32 now
= tcp_jiffies32
;
167 if (tcp_packets_in_flight(tp
) == 0)
168 tcp_ca_event(sk
, CA_EVENT_TX_START
);
172 /* If it is a reply for ato after last received
173 * packet, increase pingpong count.
175 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
176 inet_csk_inc_pingpong_cnt(sk
);
179 /* Account for an ACK we sent. */
180 static inline void tcp_event_ack_sent(struct sock
*sk
, u32 rcv_nxt
)
182 struct tcp_sock
*tp
= tcp_sk(sk
);
184 if (unlikely(tp
->compressed_ack
)) {
185 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPACKCOMPRESSED
,
187 tp
->compressed_ack
= 0;
188 if (hrtimer_try_to_cancel(&tp
->compressed_ack_timer
) == 1)
192 if (unlikely(rcv_nxt
!= tp
->rcv_nxt
))
193 return; /* Special ACK sent by DCTCP to reflect ECN */
194 tcp_dec_quickack_mode(sk
);
195 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
198 /* Determine a window scaling and initial window to offer.
199 * Based on the assumption that the given amount of space
200 * will be offered. Store the results in the tp structure.
201 * NOTE: for smooth operation initial space offering should
202 * be a multiple of mss if possible. We assume here that mss >= 1.
203 * This MUST be enforced by all callers.
205 void tcp_select_initial_window(const struct sock
*sk
, int __space
, __u32 mss
,
206 __u32
*rcv_wnd
, __u32
*window_clamp
,
207 int wscale_ok
, __u8
*rcv_wscale
,
210 unsigned int space
= (__space
< 0 ? 0 : __space
);
212 /* If no clamp set the clamp to the max possible scaled window */
213 if (*window_clamp
== 0)
214 (*window_clamp
) = (U16_MAX
<< TCP_MAX_WSCALE
);
215 space
= min(*window_clamp
, space
);
217 /* Quantize space offering to a multiple of mss if possible. */
219 space
= rounddown(space
, mss
);
221 /* NOTE: offering an initial window larger than 32767
222 * will break some buggy TCP stacks. If the admin tells us
223 * it is likely we could be speaking with such a buggy stack
224 * we will truncate our initial window offering to 32K-1
225 * unless the remote has sent us a window scaling option,
226 * which we interpret as a sign the remote TCP is not
227 * misinterpreting the window field as a signed quantity.
229 if (READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_workaround_signed_windows
))
230 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
232 (*rcv_wnd
) = min_t(u32
, space
, U16_MAX
);
235 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
239 /* Set window scaling on max possible window */
240 space
= max_t(u32
, space
, READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_rmem
[2]));
241 space
= max_t(u32
, space
, READ_ONCE(sysctl_rmem_max
));
242 space
= min_t(u32
, space
, *window_clamp
);
243 *rcv_wscale
= clamp_t(int, ilog2(space
) - 15,
246 /* Set the clamp no higher than max representable value */
247 (*window_clamp
) = min_t(__u32
, U16_MAX
<< (*rcv_wscale
), *window_clamp
);
249 EXPORT_SYMBOL(tcp_select_initial_window
);
251 /* Chose a new window to advertise, update state in tcp_sock for the
252 * socket, and return result with RFC1323 scaling applied. The return
253 * value can be stuffed directly into th->window for an outgoing
256 static u16
tcp_select_window(struct sock
*sk
)
258 struct tcp_sock
*tp
= tcp_sk(sk
);
259 struct net
*net
= sock_net(sk
);
260 u32 old_win
= tp
->rcv_wnd
;
261 u32 cur_win
, new_win
;
263 /* Make the window 0 if we failed to queue the data because we
264 * are out of memory. The window is temporary, so we don't store
267 if (unlikely(inet_csk(sk
)->icsk_ack
.pending
& ICSK_ACK_NOMEM
))
270 cur_win
= tcp_receive_window(tp
);
271 new_win
= __tcp_select_window(sk
);
272 if (new_win
< cur_win
) {
273 /* Danger Will Robinson!
274 * Don't update rcv_wup/rcv_wnd here or else
275 * we will not be able to advertise a zero
276 * window in time. --DaveM
278 * Relax Will Robinson.
280 if (!READ_ONCE(net
->ipv4
.sysctl_tcp_shrink_window
) || !tp
->rx_opt
.rcv_wscale
) {
281 /* Never shrink the offered window */
283 NET_INC_STATS(net
, LINUX_MIB_TCPWANTZEROWINDOWADV
);
284 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
288 tp
->rcv_wnd
= new_win
;
289 tp
->rcv_wup
= tp
->rcv_nxt
;
291 /* Make sure we do not exceed the maximum possible
294 if (!tp
->rx_opt
.rcv_wscale
&&
295 READ_ONCE(net
->ipv4
.sysctl_tcp_workaround_signed_windows
))
296 new_win
= min(new_win
, MAX_TCP_WINDOW
);
298 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
300 /* RFC1323 scaling applied */
301 new_win
>>= tp
->rx_opt
.rcv_wscale
;
303 /* If we advertise zero window, disable fast path. */
307 NET_INC_STATS(net
, LINUX_MIB_TCPTOZEROWINDOWADV
);
308 } else if (old_win
== 0) {
309 NET_INC_STATS(net
, LINUX_MIB_TCPFROMZEROWINDOWADV
);
315 /* Packet ECN state for a SYN-ACK */
316 static void tcp_ecn_send_synack(struct sock
*sk
, struct sk_buff
*skb
)
318 const struct tcp_sock
*tp
= tcp_sk(sk
);
320 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
321 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
322 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
323 else if (tcp_ca_needs_ecn(sk
) ||
324 tcp_bpf_ca_needs_ecn(sk
))
328 /* Packet ECN state for a SYN. */
329 static void tcp_ecn_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
331 struct tcp_sock
*tp
= tcp_sk(sk
);
332 bool bpf_needs_ecn
= tcp_bpf_ca_needs_ecn(sk
);
333 bool use_ecn
= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_ecn
) == 1 ||
334 tcp_ca_needs_ecn(sk
) || bpf_needs_ecn
;
337 const struct dst_entry
*dst
= __sk_dst_get(sk
);
339 if (dst
&& dst_feature(dst
, RTAX_FEATURE_ECN
))
346 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
347 tp
->ecn_flags
= TCP_ECN_OK
;
348 if (tcp_ca_needs_ecn(sk
) || bpf_needs_ecn
)
353 static void tcp_ecn_clear_syn(struct sock
*sk
, struct sk_buff
*skb
)
355 if (READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_ecn_fallback
))
356 /* tp->ecn_flags are cleared at a later point in time when
357 * SYN ACK is ultimatively being received.
359 TCP_SKB_CB(skb
)->tcp_flags
&= ~(TCPHDR_ECE
| TCPHDR_CWR
);
363 tcp_ecn_make_synack(const struct request_sock
*req
, struct tcphdr
*th
)
365 if (inet_rsk(req
)->ecn_ok
)
369 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
372 static void tcp_ecn_send(struct sock
*sk
, struct sk_buff
*skb
,
373 struct tcphdr
*th
, int tcp_header_len
)
375 struct tcp_sock
*tp
= tcp_sk(sk
);
377 if (tp
->ecn_flags
& TCP_ECN_OK
) {
378 /* Not-retransmitted data segment: set ECT and inject CWR. */
379 if (skb
->len
!= tcp_header_len
&&
380 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
382 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
383 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
385 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
387 } else if (!tcp_ca_needs_ecn(sk
)) {
388 /* ACK or retransmitted segment: clear ECT|CE */
389 INET_ECN_dontxmit(sk
);
391 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
396 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
397 * auto increment end seqno.
399 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
401 skb
->ip_summed
= CHECKSUM_PARTIAL
;
403 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
405 tcp_skb_pcount_set(skb
, 1);
407 TCP_SKB_CB(skb
)->seq
= seq
;
408 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
410 TCP_SKB_CB(skb
)->end_seq
= seq
;
413 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
415 return tp
->snd_una
!= tp
->snd_up
;
418 #define OPTION_SACK_ADVERTISE BIT(0)
419 #define OPTION_TS BIT(1)
420 #define OPTION_MD5 BIT(2)
421 #define OPTION_WSCALE BIT(3)
422 #define OPTION_FAST_OPEN_COOKIE BIT(8)
423 #define OPTION_SMC BIT(9)
424 #define OPTION_MPTCP BIT(10)
425 #define OPTION_AO BIT(11)
427 static void smc_options_write(__be32
*ptr
, u16
*options
)
429 #if IS_ENABLED(CONFIG_SMC)
430 if (static_branch_unlikely(&tcp_have_smc
)) {
431 if (unlikely(OPTION_SMC
& *options
)) {
432 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
435 (TCPOLEN_EXP_SMC_BASE
));
436 *ptr
++ = htonl(TCPOPT_SMC_MAGIC
);
442 struct tcp_out_options
{
443 u16 options
; /* bit field of OPTION_* */
444 u16 mss
; /* 0 to disable */
445 u8 ws
; /* window scale, 0 to disable */
446 u8 num_sack_blocks
; /* number of SACK blocks to include */
447 u8 hash_size
; /* bytes in hash_location */
448 u8 bpf_opt_len
; /* length of BPF hdr option */
449 __u8
*hash_location
; /* temporary pointer, overloaded */
450 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
451 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
452 struct mptcp_out_options mptcp
;
455 static void mptcp_options_write(struct tcphdr
*th
, __be32
*ptr
,
457 struct tcp_out_options
*opts
)
459 #if IS_ENABLED(CONFIG_MPTCP)
460 if (unlikely(OPTION_MPTCP
& opts
->options
))
461 mptcp_write_options(th
, ptr
, tp
, &opts
->mptcp
);
465 #ifdef CONFIG_CGROUP_BPF
466 static int bpf_skops_write_hdr_opt_arg0(struct sk_buff
*skb
,
467 enum tcp_synack_type synack_type
)
470 return BPF_WRITE_HDR_TCP_CURRENT_MSS
;
472 if (unlikely(synack_type
== TCP_SYNACK_COOKIE
))
473 return BPF_WRITE_HDR_TCP_SYNACK_COOKIE
;
478 /* req, syn_skb and synack_type are used when writing synack */
479 static void bpf_skops_hdr_opt_len(struct sock
*sk
, struct sk_buff
*skb
,
480 struct request_sock
*req
,
481 struct sk_buff
*syn_skb
,
482 enum tcp_synack_type synack_type
,
483 struct tcp_out_options
*opts
,
484 unsigned int *remaining
)
486 struct bpf_sock_ops_kern sock_ops
;
489 if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk
),
490 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG
)) ||
494 /* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
497 memset(&sock_ops
, 0, offsetof(struct bpf_sock_ops_kern
, temp
));
499 sock_ops
.op
= BPF_SOCK_OPS_HDR_OPT_LEN_CB
;
502 /* The listen "sk" cannot be passed here because
503 * it is not locked. It would not make too much
504 * sense to do bpf_setsockopt(listen_sk) based
505 * on individual connection request also.
507 * Thus, "req" is passed here and the cgroup-bpf-progs
508 * of the listen "sk" will be run.
510 * "req" is also used here for fastopen even the "sk" here is
511 * a fullsock "child" sk. It is to keep the behavior
512 * consistent between fastopen and non-fastopen on
513 * the bpf programming side.
515 sock_ops
.sk
= (struct sock
*)req
;
516 sock_ops
.syn_skb
= syn_skb
;
518 sock_owned_by_me(sk
);
520 sock_ops
.is_fullsock
= 1;
524 sock_ops
.args
[0] = bpf_skops_write_hdr_opt_arg0(skb
, synack_type
);
525 sock_ops
.remaining_opt_len
= *remaining
;
526 /* tcp_current_mss() does not pass a skb */
528 bpf_skops_init_skb(&sock_ops
, skb
, 0);
530 err
= BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops
, sk
);
532 if (err
|| sock_ops
.remaining_opt_len
== *remaining
)
535 opts
->bpf_opt_len
= *remaining
- sock_ops
.remaining_opt_len
;
536 /* round up to 4 bytes */
537 opts
->bpf_opt_len
= (opts
->bpf_opt_len
+ 3) & ~3;
539 *remaining
-= opts
->bpf_opt_len
;
542 static void bpf_skops_write_hdr_opt(struct sock
*sk
, struct sk_buff
*skb
,
543 struct request_sock
*req
,
544 struct sk_buff
*syn_skb
,
545 enum tcp_synack_type synack_type
,
546 struct tcp_out_options
*opts
)
548 u8 first_opt_off
, nr_written
, max_opt_len
= opts
->bpf_opt_len
;
549 struct bpf_sock_ops_kern sock_ops
;
552 if (likely(!max_opt_len
))
555 memset(&sock_ops
, 0, offsetof(struct bpf_sock_ops_kern
, temp
));
557 sock_ops
.op
= BPF_SOCK_OPS_WRITE_HDR_OPT_CB
;
560 sock_ops
.sk
= (struct sock
*)req
;
561 sock_ops
.syn_skb
= syn_skb
;
563 sock_owned_by_me(sk
);
565 sock_ops
.is_fullsock
= 1;
569 sock_ops
.args
[0] = bpf_skops_write_hdr_opt_arg0(skb
, synack_type
);
570 sock_ops
.remaining_opt_len
= max_opt_len
;
571 first_opt_off
= tcp_hdrlen(skb
) - max_opt_len
;
572 bpf_skops_init_skb(&sock_ops
, skb
, first_opt_off
);
574 err
= BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops
, sk
);
579 nr_written
= max_opt_len
- sock_ops
.remaining_opt_len
;
581 if (nr_written
< max_opt_len
)
582 memset(skb
->data
+ first_opt_off
+ nr_written
, TCPOPT_NOP
,
583 max_opt_len
- nr_written
);
586 static void bpf_skops_hdr_opt_len(struct sock
*sk
, struct sk_buff
*skb
,
587 struct request_sock
*req
,
588 struct sk_buff
*syn_skb
,
589 enum tcp_synack_type synack_type
,
590 struct tcp_out_options
*opts
,
591 unsigned int *remaining
)
595 static void bpf_skops_write_hdr_opt(struct sock
*sk
, struct sk_buff
*skb
,
596 struct request_sock
*req
,
597 struct sk_buff
*syn_skb
,
598 enum tcp_synack_type synack_type
,
599 struct tcp_out_options
*opts
)
604 static __be32
*process_tcp_ao_options(struct tcp_sock
*tp
,
605 const struct tcp_request_sock
*tcprsk
,
606 struct tcp_out_options
*opts
,
607 struct tcp_key
*key
, __be32
*ptr
)
610 u8 maclen
= tcp_ao_maclen(key
->ao_key
);
613 u8 aolen
= maclen
+ sizeof(struct tcp_ao_hdr
);
615 *ptr
++ = htonl((TCPOPT_AO
<< 24) | (aolen
<< 16) |
616 (tcprsk
->ao_keyid
<< 8) |
617 (tcprsk
->ao_rcv_next
));
619 struct tcp_ao_key
*rnext_key
;
620 struct tcp_ao_info
*ao_info
;
622 ao_info
= rcu_dereference_check(tp
->ao_info
,
623 lockdep_sock_is_held(&tp
->inet_conn
.icsk_inet
.sk
));
624 rnext_key
= READ_ONCE(ao_info
->rnext_key
);
625 if (WARN_ON_ONCE(!rnext_key
))
627 *ptr
++ = htonl((TCPOPT_AO
<< 24) |
628 (tcp_ao_len(key
->ao_key
) << 16) |
629 (key
->ao_key
->sndid
<< 8) |
632 opts
->hash_location
= (__u8
*)ptr
;
633 ptr
+= maclen
/ sizeof(*ptr
);
634 if (unlikely(maclen
% sizeof(*ptr
))) {
635 memset(ptr
, TCPOPT_NOP
, sizeof(*ptr
));
642 /* Write previously computed TCP options to the packet.
644 * Beware: Something in the Internet is very sensitive to the ordering of
645 * TCP options, we learned this through the hard way, so be careful here.
646 * Luckily we can at least blame others for their non-compliance but from
647 * inter-operability perspective it seems that we're somewhat stuck with
648 * the ordering which we have been using if we want to keep working with
649 * those broken things (not that it currently hurts anybody as there isn't
650 * particular reason why the ordering would need to be changed).
652 * At least SACK_PERM as the first option is known to lead to a disaster
653 * (but it may well be that other scenarios fail similarly).
655 static void tcp_options_write(struct tcphdr
*th
, struct tcp_sock
*tp
,
656 const struct tcp_request_sock
*tcprsk
,
657 struct tcp_out_options
*opts
,
660 __be32
*ptr
= (__be32
*)(th
+ 1);
661 u16 options
= opts
->options
; /* mungable copy */
663 if (tcp_key_is_md5(key
)) {
664 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
665 (TCPOPT_MD5SIG
<< 8) | TCPOLEN_MD5SIG
);
666 /* overload cookie hash location */
667 opts
->hash_location
= (__u8
*)ptr
;
669 } else if (tcp_key_is_ao(key
)) {
670 ptr
= process_tcp_ao_options(tp
, tcprsk
, opts
, key
, ptr
);
672 if (unlikely(opts
->mss
)) {
673 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
674 (TCPOLEN_MSS
<< 16) |
678 if (likely(OPTION_TS
& options
)) {
679 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
680 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
681 (TCPOLEN_SACK_PERM
<< 16) |
682 (TCPOPT_TIMESTAMP
<< 8) |
684 options
&= ~OPTION_SACK_ADVERTISE
;
686 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
688 (TCPOPT_TIMESTAMP
<< 8) |
691 *ptr
++ = htonl(opts
->tsval
);
692 *ptr
++ = htonl(opts
->tsecr
);
695 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
696 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
698 (TCPOPT_SACK_PERM
<< 8) |
702 if (unlikely(OPTION_WSCALE
& options
)) {
703 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
704 (TCPOPT_WINDOW
<< 16) |
705 (TCPOLEN_WINDOW
<< 8) |
709 if (unlikely(opts
->num_sack_blocks
)) {
710 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
711 tp
->duplicate_sack
: tp
->selective_acks
;
714 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
717 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
718 TCPOLEN_SACK_PERBLOCK
)));
720 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
722 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
723 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
726 tp
->rx_opt
.dsack
= 0;
729 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
730 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
732 u32 len
; /* Fast Open option length */
735 len
= TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
;
736 *ptr
= htonl((TCPOPT_EXP
<< 24) | (len
<< 16) |
737 TCPOPT_FASTOPEN_MAGIC
);
738 p
+= TCPOLEN_EXP_FASTOPEN_BASE
;
740 len
= TCPOLEN_FASTOPEN_BASE
+ foc
->len
;
741 *p
++ = TCPOPT_FASTOPEN
;
745 memcpy(p
, foc
->val
, foc
->len
);
746 if ((len
& 3) == 2) {
747 p
[foc
->len
] = TCPOPT_NOP
;
748 p
[foc
->len
+ 1] = TCPOPT_NOP
;
750 ptr
+= (len
+ 3) >> 2;
753 smc_options_write(ptr
, &options
);
755 mptcp_options_write(th
, ptr
, tp
, opts
);
758 static void smc_set_option(const struct tcp_sock
*tp
,
759 struct tcp_out_options
*opts
,
760 unsigned int *remaining
)
762 #if IS_ENABLED(CONFIG_SMC)
763 if (static_branch_unlikely(&tcp_have_smc
)) {
765 if (*remaining
>= TCPOLEN_EXP_SMC_BASE_ALIGNED
) {
766 opts
->options
|= OPTION_SMC
;
767 *remaining
-= TCPOLEN_EXP_SMC_BASE_ALIGNED
;
774 static void smc_set_option_cond(const struct tcp_sock
*tp
,
775 const struct inet_request_sock
*ireq
,
776 struct tcp_out_options
*opts
,
777 unsigned int *remaining
)
779 #if IS_ENABLED(CONFIG_SMC)
780 if (static_branch_unlikely(&tcp_have_smc
)) {
781 if (tp
->syn_smc
&& ireq
->smc_ok
) {
782 if (*remaining
>= TCPOLEN_EXP_SMC_BASE_ALIGNED
) {
783 opts
->options
|= OPTION_SMC
;
784 *remaining
-= TCPOLEN_EXP_SMC_BASE_ALIGNED
;
791 static void mptcp_set_option_cond(const struct request_sock
*req
,
792 struct tcp_out_options
*opts
,
793 unsigned int *remaining
)
795 if (rsk_is_mptcp(req
)) {
798 if (mptcp_synack_options(req
, &size
, &opts
->mptcp
)) {
799 if (*remaining
>= size
) {
800 opts
->options
|= OPTION_MPTCP
;
807 /* Compute TCP options for SYN packets. This is not the final
808 * network wire format yet.
810 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
811 struct tcp_out_options
*opts
,
814 struct tcp_sock
*tp
= tcp_sk(sk
);
815 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
816 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
819 /* Better than switch (key.type) as it has static branches */
820 if (tcp_key_is_md5(key
)) {
822 opts
->options
|= OPTION_MD5
;
823 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
825 timestamps
= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_timestamps
);
826 if (tcp_key_is_ao(key
)) {
827 opts
->options
|= OPTION_AO
;
828 remaining
-= tcp_ao_len_aligned(key
->ao_key
);
832 /* We always get an MSS option. The option bytes which will be seen in
833 * normal data packets should timestamps be used, must be in the MSS
834 * advertised. But we subtract them from tp->mss_cache so that
835 * calculations in tcp_sendmsg are simpler etc. So account for this
836 * fact here if necessary. If we don't do this correctly, as a
837 * receiver we won't recognize data packets as being full sized when we
838 * should, and thus we won't abide by the delayed ACK rules correctly.
839 * SACKs don't matter, we never delay an ACK when we have any of those
841 opts
->mss
= tcp_advertise_mss(sk
);
842 remaining
-= TCPOLEN_MSS_ALIGNED
;
844 if (likely(timestamps
)) {
845 opts
->options
|= OPTION_TS
;
846 opts
->tsval
= tcp_skb_timestamp_ts(tp
->tcp_usec_ts
, skb
) + tp
->tsoffset
;
847 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
848 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
850 if (likely(READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_window_scaling
))) {
851 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
852 opts
->options
|= OPTION_WSCALE
;
853 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
855 if (likely(READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_sack
))) {
856 opts
->options
|= OPTION_SACK_ADVERTISE
;
857 if (unlikely(!(OPTION_TS
& opts
->options
)))
858 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
861 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
862 u32 need
= fastopen
->cookie
.len
;
864 need
+= fastopen
->cookie
.exp
? TCPOLEN_EXP_FASTOPEN_BASE
:
865 TCPOLEN_FASTOPEN_BASE
;
866 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
867 if (remaining
>= need
) {
868 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
869 opts
->fastopen_cookie
= &fastopen
->cookie
;
871 tp
->syn_fastopen
= 1;
872 tp
->syn_fastopen_exp
= fastopen
->cookie
.exp
? 1 : 0;
876 smc_set_option(tp
, opts
, &remaining
);
878 if (sk_is_mptcp(sk
)) {
881 if (mptcp_syn_options(sk
, skb
, &size
, &opts
->mptcp
)) {
882 opts
->options
|= OPTION_MPTCP
;
887 bpf_skops_hdr_opt_len(sk
, skb
, NULL
, NULL
, 0, opts
, &remaining
);
889 return MAX_TCP_OPTION_SPACE
- remaining
;
892 /* Set up TCP options for SYN-ACKs. */
893 static unsigned int tcp_synack_options(const struct sock
*sk
,
894 struct request_sock
*req
,
895 unsigned int mss
, struct sk_buff
*skb
,
896 struct tcp_out_options
*opts
,
897 const struct tcp_key
*key
,
898 struct tcp_fastopen_cookie
*foc
,
899 enum tcp_synack_type synack_type
,
900 struct sk_buff
*syn_skb
)
902 struct inet_request_sock
*ireq
= inet_rsk(req
);
903 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
905 if (tcp_key_is_md5(key
)) {
906 opts
->options
|= OPTION_MD5
;
907 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
909 /* We can't fit any SACK blocks in a packet with MD5 + TS
910 * options. There was discussion about disabling SACK
911 * rather than TS in order to fit in better with old,
912 * buggy kernels, but that was deemed to be unnecessary.
914 if (synack_type
!= TCP_SYNACK_COOKIE
)
915 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
916 } else if (tcp_key_is_ao(key
)) {
917 opts
->options
|= OPTION_AO
;
918 remaining
-= tcp_ao_len_aligned(key
->ao_key
);
919 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
922 /* We always send an MSS option. */
924 remaining
-= TCPOLEN_MSS_ALIGNED
;
926 if (likely(ireq
->wscale_ok
)) {
927 opts
->ws
= ireq
->rcv_wscale
;
928 opts
->options
|= OPTION_WSCALE
;
929 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
931 if (likely(ireq
->tstamp_ok
)) {
932 opts
->options
|= OPTION_TS
;
933 opts
->tsval
= tcp_skb_timestamp_ts(tcp_rsk(req
)->req_usec_ts
, skb
) +
934 tcp_rsk(req
)->ts_off
;
935 opts
->tsecr
= READ_ONCE(req
->ts_recent
);
936 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
938 if (likely(ireq
->sack_ok
)) {
939 opts
->options
|= OPTION_SACK_ADVERTISE
;
940 if (unlikely(!ireq
->tstamp_ok
))
941 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
943 if (foc
!= NULL
&& foc
->len
>= 0) {
946 need
+= foc
->exp
? TCPOLEN_EXP_FASTOPEN_BASE
:
947 TCPOLEN_FASTOPEN_BASE
;
948 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
949 if (remaining
>= need
) {
950 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
951 opts
->fastopen_cookie
= foc
;
956 mptcp_set_option_cond(req
, opts
, &remaining
);
958 smc_set_option_cond(tcp_sk(sk
), ireq
, opts
, &remaining
);
960 bpf_skops_hdr_opt_len((struct sock
*)sk
, skb
, req
, syn_skb
,
961 synack_type
, opts
, &remaining
);
963 return MAX_TCP_OPTION_SPACE
- remaining
;
966 /* Compute TCP options for ESTABLISHED sockets. This is not the
967 * final wire format yet.
969 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
970 struct tcp_out_options
*opts
,
973 struct tcp_sock
*tp
= tcp_sk(sk
);
974 unsigned int size
= 0;
975 unsigned int eff_sacks
;
979 /* Better than switch (key.type) as it has static branches */
980 if (tcp_key_is_md5(key
)) {
981 opts
->options
|= OPTION_MD5
;
982 size
+= TCPOLEN_MD5SIG_ALIGNED
;
983 } else if (tcp_key_is_ao(key
)) {
984 opts
->options
|= OPTION_AO
;
985 size
+= tcp_ao_len_aligned(key
->ao_key
);
988 if (likely(tp
->rx_opt
.tstamp_ok
)) {
989 opts
->options
|= OPTION_TS
;
990 opts
->tsval
= skb
? tcp_skb_timestamp_ts(tp
->tcp_usec_ts
, skb
) +
992 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
993 size
+= TCPOLEN_TSTAMP_ALIGNED
;
996 /* MPTCP options have precedence over SACK for the limited TCP
997 * option space because a MPTCP connection would be forced to
998 * fall back to regular TCP if a required multipath option is
999 * missing. SACK still gets a chance to use whatever space is
1002 if (sk_is_mptcp(sk
)) {
1003 unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
1004 unsigned int opt_size
= 0;
1006 if (mptcp_established_options(sk
, skb
, &opt_size
, remaining
,
1008 opts
->options
|= OPTION_MPTCP
;
1013 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
1014 if (unlikely(eff_sacks
)) {
1015 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
1016 if (unlikely(remaining
< TCPOLEN_SACK_BASE_ALIGNED
+
1017 TCPOLEN_SACK_PERBLOCK
))
1020 opts
->num_sack_blocks
=
1021 min_t(unsigned int, eff_sacks
,
1022 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
1023 TCPOLEN_SACK_PERBLOCK
);
1025 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
1026 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
1029 if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp
,
1030 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG
))) {
1031 unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
1033 bpf_skops_hdr_opt_len(sk
, skb
, NULL
, NULL
, 0, opts
, &remaining
);
1035 size
= MAX_TCP_OPTION_SPACE
- remaining
;
1042 /* TCP SMALL QUEUES (TSQ)
1044 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
1045 * to reduce RTT and bufferbloat.
1046 * We do this using a special skb destructor (tcp_wfree).
1048 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
1049 * needs to be reallocated in a driver.
1050 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
1052 * Since transmit from skb destructor is forbidden, we use a tasklet
1053 * to process all sockets that eventually need to send more skbs.
1054 * We use one tasklet per cpu, with its own queue of sockets.
1056 struct tsq_tasklet
{
1057 struct tasklet_struct tasklet
;
1058 struct list_head head
; /* queue of tcp sockets */
1060 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
1062 static void tcp_tsq_write(struct sock
*sk
)
1064 if ((1 << sk
->sk_state
) &
1065 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
1066 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
)) {
1067 struct tcp_sock
*tp
= tcp_sk(sk
);
1069 if (tp
->lost_out
> tp
->retrans_out
&&
1070 tcp_snd_cwnd(tp
) > tcp_packets_in_flight(tp
)) {
1071 tcp_mstamp_refresh(tp
);
1072 tcp_xmit_retransmit_queue(sk
);
1075 tcp_write_xmit(sk
, tcp_current_mss(sk
), tp
->nonagle
,
1080 static void tcp_tsq_handler(struct sock
*sk
)
1083 if (!sock_owned_by_user(sk
))
1085 else if (!test_and_set_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
))
1090 * One tasklet per cpu tries to send more skbs.
1091 * We run in tasklet context but need to disable irqs when
1092 * transferring tsq->head because tcp_wfree() might
1093 * interrupt us (non NAPI drivers)
1095 static void tcp_tasklet_func(struct tasklet_struct
*t
)
1097 struct tsq_tasklet
*tsq
= from_tasklet(tsq
, t
, tasklet
);
1099 unsigned long flags
;
1100 struct list_head
*q
, *n
;
1101 struct tcp_sock
*tp
;
1104 local_irq_save(flags
);
1105 list_splice_init(&tsq
->head
, &list
);
1106 local_irq_restore(flags
);
1108 list_for_each_safe(q
, n
, &list
) {
1109 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
1110 list_del(&tp
->tsq_node
);
1112 sk
= (struct sock
*)tp
;
1113 smp_mb__before_atomic();
1114 clear_bit(TSQ_QUEUED
, &sk
->sk_tsq_flags
);
1116 tcp_tsq_handler(sk
);
1121 #define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
1122 TCPF_WRITE_TIMER_DEFERRED | \
1123 TCPF_DELACK_TIMER_DEFERRED | \
1124 TCPF_MTU_REDUCED_DEFERRED | \
1127 * tcp_release_cb - tcp release_sock() callback
1130 * called from release_sock() to perform protocol dependent
1131 * actions before socket release.
1133 void tcp_release_cb(struct sock
*sk
)
1135 unsigned long flags
= smp_load_acquire(&sk
->sk_tsq_flags
);
1136 unsigned long nflags
;
1138 /* perform an atomic operation only if at least one flag is set */
1140 if (!(flags
& TCP_DEFERRED_ALL
))
1142 nflags
= flags
& ~TCP_DEFERRED_ALL
;
1143 } while (!try_cmpxchg(&sk
->sk_tsq_flags
, &flags
, nflags
));
1145 if (flags
& TCPF_TSQ_DEFERRED
) {
1150 if (flags
& TCPF_WRITE_TIMER_DEFERRED
) {
1151 tcp_write_timer_handler(sk
);
1154 if (flags
& TCPF_DELACK_TIMER_DEFERRED
) {
1155 tcp_delack_timer_handler(sk
);
1158 if (flags
& TCPF_MTU_REDUCED_DEFERRED
) {
1159 inet_csk(sk
)->icsk_af_ops
->mtu_reduced(sk
);
1162 if ((flags
& TCPF_ACK_DEFERRED
) && inet_csk_ack_scheduled(sk
))
1165 EXPORT_SYMBOL(tcp_release_cb
);
1167 void __init
tcp_tasklet_init(void)
1171 for_each_possible_cpu(i
) {
1172 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
1174 INIT_LIST_HEAD(&tsq
->head
);
1175 tasklet_setup(&tsq
->tasklet
, tcp_tasklet_func
);
1180 * Write buffer destructor automatically called from kfree_skb.
1181 * We can't xmit new skbs from this context, as we might already
1184 void tcp_wfree(struct sk_buff
*skb
)
1186 struct sock
*sk
= skb
->sk
;
1187 struct tcp_sock
*tp
= tcp_sk(sk
);
1188 unsigned long flags
, nval
, oval
;
1189 struct tsq_tasklet
*tsq
;
1192 /* Keep one reference on sk_wmem_alloc.
1193 * Will be released by sk_free() from here or tcp_tasklet_func()
1195 WARN_ON(refcount_sub_and_test(skb
->truesize
- 1, &sk
->sk_wmem_alloc
));
1197 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
1198 * Wait until our queues (qdisc + devices) are drained.
1200 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
1201 * - chance for incoming ACK (processed by another cpu maybe)
1202 * to migrate this flow (skb->ooo_okay will be eventually set)
1204 if (refcount_read(&sk
->sk_wmem_alloc
) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current
)
1207 oval
= smp_load_acquire(&sk
->sk_tsq_flags
);
1209 if (!(oval
& TSQF_THROTTLED
) || (oval
& TSQF_QUEUED
))
1212 nval
= (oval
& ~TSQF_THROTTLED
) | TSQF_QUEUED
;
1213 } while (!try_cmpxchg(&sk
->sk_tsq_flags
, &oval
, nval
));
1215 /* queue this socket to tasklet queue */
1216 local_irq_save(flags
);
1217 tsq
= this_cpu_ptr(&tsq_tasklet
);
1218 empty
= list_empty(&tsq
->head
);
1219 list_add(&tp
->tsq_node
, &tsq
->head
);
1221 tasklet_schedule(&tsq
->tasklet
);
1222 local_irq_restore(flags
);
1228 /* Note: Called under soft irq.
1229 * We can call TCP stack right away, unless socket is owned by user.
1231 enum hrtimer_restart
tcp_pace_kick(struct hrtimer
*timer
)
1233 struct tcp_sock
*tp
= container_of(timer
, struct tcp_sock
, pacing_timer
);
1234 struct sock
*sk
= (struct sock
*)tp
;
1236 tcp_tsq_handler(sk
);
1239 return HRTIMER_NORESTART
;
1242 static void tcp_update_skb_after_send(struct sock
*sk
, struct sk_buff
*skb
,
1245 struct tcp_sock
*tp
= tcp_sk(sk
);
1247 if (sk
->sk_pacing_status
!= SK_PACING_NONE
) {
1248 unsigned long rate
= READ_ONCE(sk
->sk_pacing_rate
);
1250 /* Original sch_fq does not pace first 10 MSS
1251 * Note that tp->data_segs_out overflows after 2^32 packets,
1252 * this is a minor annoyance.
1254 if (rate
!= ~0UL && rate
&& tp
->data_segs_out
>= 10) {
1255 u64 len_ns
= div64_ul((u64
)skb
->len
* NSEC_PER_SEC
, rate
);
1256 u64 credit
= tp
->tcp_wstamp_ns
- prior_wstamp
;
1258 /* take into account OS jitter */
1259 len_ns
-= min_t(u64
, len_ns
/ 2, credit
);
1260 tp
->tcp_wstamp_ns
+= len_ns
;
1263 list_move_tail(&skb
->tcp_tsorted_anchor
, &tp
->tsorted_sent_queue
);
1266 INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock
*sk
, struct sk_buff
*skb
, struct flowi
*fl
));
1267 INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock
*sk
, struct sk_buff
*skb
, struct flowi
*fl
));
1268 INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock
*sk
, struct sk_buff
*skb
));
1270 /* This routine actually transmits TCP packets queued in by
1271 * tcp_do_sendmsg(). This is used by both the initial
1272 * transmission and possible later retransmissions.
1273 * All SKB's seen here are completely headerless. It is our
1274 * job to build the TCP header, and pass the packet down to
1275 * IP so it can do the same plus pass the packet off to the
1278 * We are working here with either a clone of the original
1279 * SKB, or a fresh unique copy made by the retransmit engine.
1281 static int __tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
,
1282 int clone_it
, gfp_t gfp_mask
, u32 rcv_nxt
)
1284 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1285 struct inet_sock
*inet
;
1286 struct tcp_sock
*tp
;
1287 struct tcp_skb_cb
*tcb
;
1288 struct tcp_out_options opts
;
1289 unsigned int tcp_options_size
, tcp_header_size
;
1290 struct sk_buff
*oskb
= NULL
;
1296 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
1298 prior_wstamp
= tp
->tcp_wstamp_ns
;
1299 tp
->tcp_wstamp_ns
= max(tp
->tcp_wstamp_ns
, tp
->tcp_clock_cache
);
1300 skb_set_delivery_time(skb
, tp
->tcp_wstamp_ns
, true);
1304 tcp_skb_tsorted_save(oskb
) {
1305 if (unlikely(skb_cloned(oskb
)))
1306 skb
= pskb_copy(oskb
, gfp_mask
);
1308 skb
= skb_clone(oskb
, gfp_mask
);
1309 } tcp_skb_tsorted_restore(oskb
);
1313 /* retransmit skbs might have a non zero value in skb->dev
1314 * because skb->dev is aliased with skb->rbnode.rb_left
1320 tcb
= TCP_SKB_CB(skb
);
1321 memset(&opts
, 0, sizeof(opts
));
1323 tcp_get_current_key(sk
, &key
);
1324 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
)) {
1325 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &key
);
1327 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
, &key
);
1328 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1329 * at receiver : This slightly improve GRO performance.
1330 * Note that we do not force the PSH flag for non GSO packets,
1331 * because they might be sent under high congestion events,
1332 * and in this case it is better to delay the delivery of 1-MSS
1333 * packets and thus the corresponding ACK packet that would
1334 * release the following packet.
1336 if (tcp_skb_pcount(skb
) > 1)
1337 tcb
->tcp_flags
|= TCPHDR_PSH
;
1339 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
1341 /* We set skb->ooo_okay to one if this packet can select
1342 * a different TX queue than prior packets of this flow,
1343 * to avoid self inflicted reorders.
1344 * The 'other' queue decision is based on current cpu number
1345 * if XPS is enabled, or sk->sk_txhash otherwise.
1346 * We can switch to another (and better) queue if:
1347 * 1) No packet with payload is in qdisc/device queues.
1348 * Delays in TX completion can defeat the test
1349 * even if packets were already sent.
1350 * 2) Or rtx queue is empty.
1351 * This mitigates above case if ACK packets for
1352 * all prior packets were already processed.
1354 skb
->ooo_okay
= sk_wmem_alloc_get(sk
) < SKB_TRUESIZE(1) ||
1355 tcp_rtx_queue_empty(sk
);
1357 /* If we had to use memory reserve to allocate this skb,
1358 * this might cause drops if packet is looped back :
1359 * Other socket might not have SOCK_MEMALLOC.
1360 * Packets not looped back do not care about pfmemalloc.
1362 skb
->pfmemalloc
= 0;
1364 skb_push(skb
, tcp_header_size
);
1365 skb_reset_transport_header(skb
);
1369 skb
->destructor
= skb_is_tcp_pure_ack(skb
) ? __sock_wfree
: tcp_wfree
;
1370 refcount_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
1372 skb_set_dst_pending_confirm(skb
, READ_ONCE(sk
->sk_dst_pending_confirm
));
1374 /* Build TCP header and checksum it. */
1375 th
= (struct tcphdr
*)skb
->data
;
1376 th
->source
= inet
->inet_sport
;
1377 th
->dest
= inet
->inet_dport
;
1378 th
->seq
= htonl(tcb
->seq
);
1379 th
->ack_seq
= htonl(rcv_nxt
);
1380 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
1386 /* The urg_mode check is necessary during a below snd_una win probe */
1387 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
1388 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
1389 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
1391 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
1392 th
->urg_ptr
= htons(0xFFFF);
1397 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
1398 if (likely(!(tcb
->tcp_flags
& TCPHDR_SYN
))) {
1399 th
->window
= htons(tcp_select_window(sk
));
1400 tcp_ecn_send(sk
, skb
, th
, tcp_header_size
);
1402 /* RFC1323: The window in SYN & SYN/ACK segments
1405 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
1408 tcp_options_write(th
, tp
, NULL
, &opts
, &key
);
1410 if (tcp_key_is_md5(&key
)) {
1411 #ifdef CONFIG_TCP_MD5SIG
1412 /* Calculate the MD5 hash, as we have all we need now */
1414 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
1415 key
.md5_key
, sk
, skb
);
1417 } else if (tcp_key_is_ao(&key
)) {
1420 err
= tcp_ao_transmit_skb(sk
, skb
, key
.ao_key
, th
,
1421 opts
.hash_location
);
1423 kfree_skb_reason(skb
, SKB_DROP_REASON_NOT_SPECIFIED
);
1428 /* BPF prog is the last one writing header option */
1429 bpf_skops_write_hdr_opt(sk
, skb
, NULL
, NULL
, 0, &opts
);
1431 INDIRECT_CALL_INET(icsk
->icsk_af_ops
->send_check
,
1432 tcp_v6_send_check
, tcp_v4_send_check
,
1435 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
1436 tcp_event_ack_sent(sk
, rcv_nxt
);
1438 if (skb
->len
!= tcp_header_size
) {
1439 tcp_event_data_sent(tp
, sk
);
1440 tp
->data_segs_out
+= tcp_skb_pcount(skb
);
1441 tp
->bytes_sent
+= skb
->len
- tcp_header_size
;
1444 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
1445 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
1446 tcp_skb_pcount(skb
));
1448 tp
->segs_out
+= tcp_skb_pcount(skb
);
1449 skb_set_hash_from_sk(skb
, sk
);
1450 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1451 skb_shinfo(skb
)->gso_segs
= tcp_skb_pcount(skb
);
1452 skb_shinfo(skb
)->gso_size
= tcp_skb_mss(skb
);
1454 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1456 /* Cleanup our debris for IP stacks */
1457 memset(skb
->cb
, 0, max(sizeof(struct inet_skb_parm
),
1458 sizeof(struct inet6_skb_parm
)));
1460 tcp_add_tx_delay(skb
, tp
);
1462 err
= INDIRECT_CALL_INET(icsk
->icsk_af_ops
->queue_xmit
,
1463 inet6_csk_xmit
, ip_queue_xmit
,
1464 sk
, skb
, &inet
->cork
.fl
);
1466 if (unlikely(err
> 0)) {
1468 err
= net_xmit_eval(err
);
1471 tcp_update_skb_after_send(sk
, oskb
, prior_wstamp
);
1472 tcp_rate_skb_sent(sk
, oskb
);
1477 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
1480 return __tcp_transmit_skb(sk
, skb
, clone_it
, gfp_mask
,
1481 tcp_sk(sk
)->rcv_nxt
);
1484 /* This routine just queues the buffer for sending.
1486 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1487 * otherwise socket can stall.
1489 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
1491 struct tcp_sock
*tp
= tcp_sk(sk
);
1493 /* Advance write_seq and place onto the write_queue. */
1494 WRITE_ONCE(tp
->write_seq
, TCP_SKB_CB(skb
)->end_seq
);
1495 __skb_header_release(skb
);
1496 tcp_add_write_queue_tail(sk
, skb
);
1497 sk_wmem_queued_add(sk
, skb
->truesize
);
1498 sk_mem_charge(sk
, skb
->truesize
);
1501 /* Initialize TSO segments for a packet. */
1502 static void tcp_set_skb_tso_segs(struct sk_buff
*skb
, unsigned int mss_now
)
1504 if (skb
->len
<= mss_now
) {
1505 /* Avoid the costly divide in the normal
1508 tcp_skb_pcount_set(skb
, 1);
1509 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1511 tcp_skb_pcount_set(skb
, DIV_ROUND_UP(skb
->len
, mss_now
));
1512 TCP_SKB_CB(skb
)->tcp_gso_size
= mss_now
;
1516 /* Pcount in the middle of the write queue got changed, we need to do various
1517 * tweaks to fix counters
1519 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1521 struct tcp_sock
*tp
= tcp_sk(sk
);
1523 tp
->packets_out
-= decr
;
1525 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1526 tp
->sacked_out
-= decr
;
1527 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1528 tp
->retrans_out
-= decr
;
1529 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1530 tp
->lost_out
-= decr
;
1532 /* Reno case is special. Sigh... */
1533 if (tcp_is_reno(tp
) && decr
> 0)
1534 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1536 if (tp
->lost_skb_hint
&&
1537 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1538 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
1539 tp
->lost_cnt_hint
-= decr
;
1541 tcp_verify_left_out(tp
);
1544 static bool tcp_has_tx_tstamp(const struct sk_buff
*skb
)
1546 return TCP_SKB_CB(skb
)->txstamp_ack
||
1547 (skb_shinfo(skb
)->tx_flags
& SKBTX_ANY_TSTAMP
);
1550 static void tcp_fragment_tstamp(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1552 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1554 if (unlikely(tcp_has_tx_tstamp(skb
)) &&
1555 !before(shinfo
->tskey
, TCP_SKB_CB(skb2
)->seq
)) {
1556 struct skb_shared_info
*shinfo2
= skb_shinfo(skb2
);
1557 u8 tsflags
= shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
1559 shinfo
->tx_flags
&= ~tsflags
;
1560 shinfo2
->tx_flags
|= tsflags
;
1561 swap(shinfo
->tskey
, shinfo2
->tskey
);
1562 TCP_SKB_CB(skb2
)->txstamp_ack
= TCP_SKB_CB(skb
)->txstamp_ack
;
1563 TCP_SKB_CB(skb
)->txstamp_ack
= 0;
1567 static void tcp_skb_fragment_eor(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1569 TCP_SKB_CB(skb2
)->eor
= TCP_SKB_CB(skb
)->eor
;
1570 TCP_SKB_CB(skb
)->eor
= 0;
1573 /* Insert buff after skb on the write or rtx queue of sk. */
1574 static void tcp_insert_write_queue_after(struct sk_buff
*skb
,
1575 struct sk_buff
*buff
,
1577 enum tcp_queue tcp_queue
)
1579 if (tcp_queue
== TCP_FRAG_IN_WRITE_QUEUE
)
1580 __skb_queue_after(&sk
->sk_write_queue
, skb
, buff
);
1582 tcp_rbtree_insert(&sk
->tcp_rtx_queue
, buff
);
1585 /* Function to create two new TCP segments. Shrinks the given segment
1586 * to the specified size and appends a new segment with the rest of the
1587 * packet to the list. This won't be called frequently, I hope.
1588 * Remember, these are still headerless SKBs at this point.
1590 int tcp_fragment(struct sock
*sk
, enum tcp_queue tcp_queue
,
1591 struct sk_buff
*skb
, u32 len
,
1592 unsigned int mss_now
, gfp_t gfp
)
1594 struct tcp_sock
*tp
= tcp_sk(sk
);
1595 struct sk_buff
*buff
;
1601 if (WARN_ON(len
> skb
->len
))
1604 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb
));
1606 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1607 * We need some allowance to not penalize applications setting small
1609 * Also allow first and last skb in retransmit queue to be split.
1611 limit
= sk
->sk_sndbuf
+ 2 * SKB_TRUESIZE(GSO_LEGACY_MAX_SIZE
);
1612 if (unlikely((sk
->sk_wmem_queued
>> 1) > limit
&&
1613 tcp_queue
!= TCP_FRAG_IN_WRITE_QUEUE
&&
1614 skb
!= tcp_rtx_queue_head(sk
) &&
1615 skb
!= tcp_rtx_queue_tail(sk
))) {
1616 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPWQUEUETOOBIG
);
1620 if (skb_unclone_keeptruesize(skb
, gfp
))
1623 /* Get a new skb... force flag on. */
1624 buff
= tcp_stream_alloc_skb(sk
, gfp
, true);
1626 return -ENOMEM
; /* We'll just try again later. */
1627 skb_copy_decrypted(buff
, skb
);
1628 mptcp_skb_ext_copy(buff
, skb
);
1630 sk_wmem_queued_add(sk
, buff
->truesize
);
1631 sk_mem_charge(sk
, buff
->truesize
);
1632 nlen
= skb
->len
- len
;
1633 buff
->truesize
+= nlen
;
1634 skb
->truesize
-= nlen
;
1636 /* Correct the sequence numbers. */
1637 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1638 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1639 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1641 /* PSH and FIN should only be set in the second packet. */
1642 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1643 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1644 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1645 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1646 tcp_skb_fragment_eor(skb
, buff
);
1648 skb_split(skb
, buff
, len
);
1650 skb_set_delivery_time(buff
, skb
->tstamp
, true);
1651 tcp_fragment_tstamp(skb
, buff
);
1653 old_factor
= tcp_skb_pcount(skb
);
1655 /* Fix up tso_factor for both original and new SKB. */
1656 tcp_set_skb_tso_segs(skb
, mss_now
);
1657 tcp_set_skb_tso_segs(buff
, mss_now
);
1659 /* Update delivered info for the new segment */
1660 TCP_SKB_CB(buff
)->tx
= TCP_SKB_CB(skb
)->tx
;
1662 /* If this packet has been sent out already, we must
1663 * adjust the various packet counters.
1665 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1666 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1667 tcp_skb_pcount(buff
);
1670 tcp_adjust_pcount(sk
, skb
, diff
);
1673 /* Link BUFF into the send queue. */
1674 __skb_header_release(buff
);
1675 tcp_insert_write_queue_after(skb
, buff
, sk
, tcp_queue
);
1676 if (tcp_queue
== TCP_FRAG_IN_RTX_QUEUE
)
1677 list_add(&buff
->tcp_tsorted_anchor
, &skb
->tcp_tsorted_anchor
);
1682 /* This is similar to __pskb_pull_tail(). The difference is that pulled
1683 * data is not copied, but immediately discarded.
1685 static int __pskb_trim_head(struct sk_buff
*skb
, int len
)
1687 struct skb_shared_info
*shinfo
;
1690 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb
));
1693 shinfo
= skb_shinfo(skb
);
1694 for (i
= 0; i
< shinfo
->nr_frags
; i
++) {
1695 int size
= skb_frag_size(&shinfo
->frags
[i
]);
1698 skb_frag_unref(skb
, i
);
1701 shinfo
->frags
[k
] = shinfo
->frags
[i
];
1703 skb_frag_off_add(&shinfo
->frags
[k
], eat
);
1704 skb_frag_size_sub(&shinfo
->frags
[k
], eat
);
1710 shinfo
->nr_frags
= k
;
1712 skb
->data_len
-= len
;
1713 skb
->len
= skb
->data_len
;
1717 /* Remove acked data from a packet in the transmit queue. */
1718 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1722 if (skb_unclone_keeptruesize(skb
, GFP_ATOMIC
))
1725 delta_truesize
= __pskb_trim_head(skb
, len
);
1727 TCP_SKB_CB(skb
)->seq
+= len
;
1729 skb
->truesize
-= delta_truesize
;
1730 sk_wmem_queued_add(sk
, -delta_truesize
);
1731 if (!skb_zcopy_pure(skb
))
1732 sk_mem_uncharge(sk
, delta_truesize
);
1734 /* Any change of skb->len requires recalculation of tso factor. */
1735 if (tcp_skb_pcount(skb
) > 1)
1736 tcp_set_skb_tso_segs(skb
, tcp_skb_mss(skb
));
1741 /* Calculate MSS not accounting any TCP options. */
1742 static inline int __tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1744 const struct tcp_sock
*tp
= tcp_sk(sk
);
1745 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1748 /* Calculate base mss without TCP options:
1749 It is MMS_S - sizeof(tcphdr) of rfc1122
1751 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1753 /* Clamp it (mss_clamp does not include tcp options) */
1754 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1755 mss_now
= tp
->rx_opt
.mss_clamp
;
1757 /* Now subtract optional transport overhead */
1758 mss_now
-= icsk
->icsk_ext_hdr_len
;
1760 /* Then reserve room for full set of TCP options and 8 bytes of data */
1761 mss_now
= max(mss_now
,
1762 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_min_snd_mss
));
1766 /* Calculate MSS. Not accounting for SACKs here. */
1767 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1769 /* Subtract TCP options size, not including SACKs */
1770 return __tcp_mtu_to_mss(sk
, pmtu
) -
1771 (tcp_sk(sk
)->tcp_header_len
- sizeof(struct tcphdr
));
1773 EXPORT_SYMBOL(tcp_mtu_to_mss
);
1775 /* Inverse of above */
1776 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1778 const struct tcp_sock
*tp
= tcp_sk(sk
);
1779 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1782 tp
->tcp_header_len
+
1783 icsk
->icsk_ext_hdr_len
+
1784 icsk
->icsk_af_ops
->net_header_len
;
1786 EXPORT_SYMBOL(tcp_mss_to_mtu
);
1788 /* MTU probing init per socket */
1789 void tcp_mtup_init(struct sock
*sk
)
1791 struct tcp_sock
*tp
= tcp_sk(sk
);
1792 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1793 struct net
*net
= sock_net(sk
);
1795 icsk
->icsk_mtup
.enabled
= READ_ONCE(net
->ipv4
.sysctl_tcp_mtu_probing
) > 1;
1796 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1797 icsk
->icsk_af_ops
->net_header_len
;
1798 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, READ_ONCE(net
->ipv4
.sysctl_tcp_base_mss
));
1799 icsk
->icsk_mtup
.probe_size
= 0;
1800 if (icsk
->icsk_mtup
.enabled
)
1801 icsk
->icsk_mtup
.probe_timestamp
= tcp_jiffies32
;
1803 EXPORT_SYMBOL(tcp_mtup_init
);
1805 /* This function synchronize snd mss to current pmtu/exthdr set.
1807 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1808 for TCP options, but includes only bare TCP header.
1810 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1811 It is minimum of user_mss and mss received with SYN.
1812 It also does not include TCP options.
1814 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1816 tp->mss_cache is current effective sending mss, including
1817 all tcp options except for SACKs. It is evaluated,
1818 taking into account current pmtu, but never exceeds
1819 tp->rx_opt.mss_clamp.
1821 NOTE1. rfc1122 clearly states that advertised MSS
1822 DOES NOT include either tcp or ip options.
1824 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1825 are READ ONLY outside this function. --ANK (980731)
1827 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1829 struct tcp_sock
*tp
= tcp_sk(sk
);
1830 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1833 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1834 icsk
->icsk_mtup
.search_high
= pmtu
;
1836 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1837 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1839 /* And store cached results */
1840 icsk
->icsk_pmtu_cookie
= pmtu
;
1841 if (icsk
->icsk_mtup
.enabled
)
1842 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1843 tp
->mss_cache
= mss_now
;
1847 EXPORT_SYMBOL(tcp_sync_mss
);
1849 /* Compute the current effective MSS, taking SACKs and IP options,
1850 * and even PMTU discovery events into account.
1852 unsigned int tcp_current_mss(struct sock
*sk
)
1854 const struct tcp_sock
*tp
= tcp_sk(sk
);
1855 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1857 unsigned int header_len
;
1858 struct tcp_out_options opts
;
1861 mss_now
= tp
->mss_cache
;
1864 u32 mtu
= dst_mtu(dst
);
1865 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1866 mss_now
= tcp_sync_mss(sk
, mtu
);
1868 tcp_get_current_key(sk
, &key
);
1869 header_len
= tcp_established_options(sk
, NULL
, &opts
, &key
) +
1870 sizeof(struct tcphdr
);
1871 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1872 * some common options. If this is an odd packet (because we have SACK
1873 * blocks etc) then our calculated header_len will be different, and
1874 * we have to adjust mss_now correspondingly */
1875 if (header_len
!= tp
->tcp_header_len
) {
1876 int delta
= (int) header_len
- tp
->tcp_header_len
;
1883 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1884 * As additional protections, we do not touch cwnd in retransmission phases,
1885 * and if application hit its sndbuf limit recently.
1887 static void tcp_cwnd_application_limited(struct sock
*sk
)
1889 struct tcp_sock
*tp
= tcp_sk(sk
);
1891 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
1892 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
1893 /* Limited by application or receiver window. */
1894 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
1895 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
1896 if (win_used
< tcp_snd_cwnd(tp
)) {
1897 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1898 tcp_snd_cwnd_set(tp
, (tcp_snd_cwnd(tp
) + win_used
) >> 1);
1900 tp
->snd_cwnd_used
= 0;
1902 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
1905 static void tcp_cwnd_validate(struct sock
*sk
, bool is_cwnd_limited
)
1907 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1908 struct tcp_sock
*tp
= tcp_sk(sk
);
1910 /* Track the strongest available signal of the degree to which the cwnd
1911 * is fully utilized. If cwnd-limited then remember that fact for the
1912 * current window. If not cwnd-limited then track the maximum number of
1913 * outstanding packets in the current window. (If cwnd-limited then we
1914 * chose to not update tp->max_packets_out to avoid an extra else
1915 * clause with no functional impact.)
1917 if (!before(tp
->snd_una
, tp
->cwnd_usage_seq
) ||
1919 (!tp
->is_cwnd_limited
&&
1920 tp
->packets_out
> tp
->max_packets_out
)) {
1921 tp
->is_cwnd_limited
= is_cwnd_limited
;
1922 tp
->max_packets_out
= tp
->packets_out
;
1923 tp
->cwnd_usage_seq
= tp
->snd_nxt
;
1926 if (tcp_is_cwnd_limited(sk
)) {
1927 /* Network is feed fully. */
1928 tp
->snd_cwnd_used
= 0;
1929 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
1931 /* Network starves. */
1932 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1933 tp
->snd_cwnd_used
= tp
->packets_out
;
1935 if (READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_slow_start_after_idle
) &&
1936 (s32
)(tcp_jiffies32
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
&&
1937 !ca_ops
->cong_control
)
1938 tcp_cwnd_application_limited(sk
);
1940 /* The following conditions together indicate the starvation
1941 * is caused by insufficient sender buffer:
1942 * 1) just sent some data (see tcp_write_xmit)
1943 * 2) not cwnd limited (this else condition)
1944 * 3) no more data to send (tcp_write_queue_empty())
1945 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1947 if (tcp_write_queue_empty(sk
) && sk
->sk_socket
&&
1948 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
) &&
1949 (1 << sk
->sk_state
) & (TCPF_ESTABLISHED
| TCPF_CLOSE_WAIT
))
1950 tcp_chrono_start(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
1954 /* Minshall's variant of the Nagle send check. */
1955 static bool tcp_minshall_check(const struct tcp_sock
*tp
)
1957 return after(tp
->snd_sml
, tp
->snd_una
) &&
1958 !after(tp
->snd_sml
, tp
->snd_nxt
);
1961 /* Update snd_sml if this skb is under mss
1962 * Note that a TSO packet might end with a sub-mss segment
1963 * The test is really :
1964 * if ((skb->len % mss) != 0)
1965 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1966 * But we can avoid doing the divide again given we already have
1967 * skb_pcount = skb->len / mss_now
1969 static void tcp_minshall_update(struct tcp_sock
*tp
, unsigned int mss_now
,
1970 const struct sk_buff
*skb
)
1972 if (skb
->len
< tcp_skb_pcount(skb
) * mss_now
)
1973 tp
->snd_sml
= TCP_SKB_CB(skb
)->end_seq
;
1976 /* Return false, if packet can be sent now without violation Nagle's rules:
1977 * 1. It is full sized. (provided by caller in %partial bool)
1978 * 2. Or it contains FIN. (already checked by caller)
1979 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1980 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1981 * With Minshall's modification: all sent small packets are ACKed.
1983 static bool tcp_nagle_check(bool partial
, const struct tcp_sock
*tp
,
1987 ((nonagle
& TCP_NAGLE_CORK
) ||
1988 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1991 /* Return how many segs we'd like on a TSO packet,
1992 * depending on current pacing rate, and how close the peer is.
1995 * - For close peers, we rather send bigger packets to reduce
1996 * cpu costs, because occasional losses will be repaired fast.
1997 * - For long distance/rtt flows, we would like to get ACK clocking
1998 * with 1 ACK per ms.
2000 * Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting
2001 * in bigger TSO bursts. We we cut the RTT-based allowance in half
2002 * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance
2003 * is below 1500 bytes after 6 * ~500 usec = 3ms.
2005 static u32
tcp_tso_autosize(const struct sock
*sk
, unsigned int mss_now
,
2008 unsigned long bytes
;
2011 bytes
= READ_ONCE(sk
->sk_pacing_rate
) >> READ_ONCE(sk
->sk_pacing_shift
);
2013 r
= tcp_min_rtt(tcp_sk(sk
)) >> READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_tso_rtt_log
);
2014 if (r
< BITS_PER_TYPE(sk
->sk_gso_max_size
))
2015 bytes
+= sk
->sk_gso_max_size
>> r
;
2017 bytes
= min_t(unsigned long, bytes
, sk
->sk_gso_max_size
);
2019 return max_t(u32
, bytes
/ mss_now
, min_tso_segs
);
2022 /* Return the number of segments we want in the skb we are transmitting.
2023 * See if congestion control module wants to decide; otherwise, autosize.
2025 static u32
tcp_tso_segs(struct sock
*sk
, unsigned int mss_now
)
2027 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2028 u32 min_tso
, tso_segs
;
2030 min_tso
= ca_ops
->min_tso_segs
?
2031 ca_ops
->min_tso_segs(sk
) :
2032 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_min_tso_segs
);
2034 tso_segs
= tcp_tso_autosize(sk
, mss_now
, min_tso
);
2035 return min_t(u32
, tso_segs
, sk
->sk_gso_max_segs
);
2038 /* Returns the portion of skb which can be sent right away */
2039 static unsigned int tcp_mss_split_point(const struct sock
*sk
,
2040 const struct sk_buff
*skb
,
2041 unsigned int mss_now
,
2042 unsigned int max_segs
,
2045 const struct tcp_sock
*tp
= tcp_sk(sk
);
2046 u32 partial
, needed
, window
, max_len
;
2048 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
2049 max_len
= mss_now
* max_segs
;
2051 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
2054 needed
= min(skb
->len
, window
);
2056 if (max_len
<= needed
)
2059 partial
= needed
% mss_now
;
2060 /* If last segment is not a full MSS, check if Nagle rules allow us
2061 * to include this last segment in this skb.
2062 * Otherwise, we'll split the skb at last MSS boundary
2064 if (tcp_nagle_check(partial
!= 0, tp
, nonagle
))
2065 return needed
- partial
;
2070 /* Can at least one segment of SKB be sent right now, according to the
2071 * congestion window rules? If so, return how many segments are allowed.
2073 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
2074 const struct sk_buff
*skb
)
2076 u32 in_flight
, cwnd
, halfcwnd
;
2078 /* Don't be strict about the congestion window for the final FIN. */
2079 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
2080 tcp_skb_pcount(skb
) == 1)
2083 in_flight
= tcp_packets_in_flight(tp
);
2084 cwnd
= tcp_snd_cwnd(tp
);
2085 if (in_flight
>= cwnd
)
2088 /* For better scheduling, ensure we have at least
2089 * 2 GSO packets in flight.
2091 halfcwnd
= max(cwnd
>> 1, 1U);
2092 return min(halfcwnd
, cwnd
- in_flight
);
2095 /* Initialize TSO state of a skb.
2096 * This must be invoked the first time we consider transmitting
2097 * SKB onto the wire.
2099 static int tcp_init_tso_segs(struct sk_buff
*skb
, unsigned int mss_now
)
2101 int tso_segs
= tcp_skb_pcount(skb
);
2103 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
2104 tcp_set_skb_tso_segs(skb
, mss_now
);
2105 tso_segs
= tcp_skb_pcount(skb
);
2111 /* Return true if the Nagle test allows this packet to be
2114 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
2115 unsigned int cur_mss
, int nonagle
)
2117 /* Nagle rule does not apply to frames, which sit in the middle of the
2118 * write_queue (they have no chances to get new data).
2120 * This is implemented in the callers, where they modify the 'nonagle'
2121 * argument based upon the location of SKB in the send queue.
2123 if (nonagle
& TCP_NAGLE_PUSH
)
2126 /* Don't use the nagle rule for urgent data (or for the final FIN). */
2127 if (tcp_urg_mode(tp
) || (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
2130 if (!tcp_nagle_check(skb
->len
< cur_mss
, tp
, nonagle
))
2136 /* Does at least the first segment of SKB fit into the send window? */
2137 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
2138 const struct sk_buff
*skb
,
2139 unsigned int cur_mss
)
2141 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
2143 if (skb
->len
> cur_mss
)
2144 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
2146 return !after(end_seq
, tcp_wnd_end(tp
));
2149 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
2150 * which is put after SKB on the list. It is very much like
2151 * tcp_fragment() except that it may make several kinds of assumptions
2152 * in order to speed up the splitting operation. In particular, we
2153 * know that all the data is in scatter-gather pages, and that the
2154 * packet has never been sent out before (and thus is not cloned).
2156 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
2157 unsigned int mss_now
, gfp_t gfp
)
2159 int nlen
= skb
->len
- len
;
2160 struct sk_buff
*buff
;
2163 /* All of a TSO frame must be composed of paged data. */
2164 DEBUG_NET_WARN_ON_ONCE(skb
->len
!= skb
->data_len
);
2166 buff
= tcp_stream_alloc_skb(sk
, gfp
, true);
2167 if (unlikely(!buff
))
2169 skb_copy_decrypted(buff
, skb
);
2170 mptcp_skb_ext_copy(buff
, skb
);
2172 sk_wmem_queued_add(sk
, buff
->truesize
);
2173 sk_mem_charge(sk
, buff
->truesize
);
2174 buff
->truesize
+= nlen
;
2175 skb
->truesize
-= nlen
;
2177 /* Correct the sequence numbers. */
2178 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
2179 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
2180 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
2182 /* PSH and FIN should only be set in the second packet. */
2183 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
2184 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
2185 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
2187 tcp_skb_fragment_eor(skb
, buff
);
2189 skb_split(skb
, buff
, len
);
2190 tcp_fragment_tstamp(skb
, buff
);
2192 /* Fix up tso_factor for both original and new SKB. */
2193 tcp_set_skb_tso_segs(skb
, mss_now
);
2194 tcp_set_skb_tso_segs(buff
, mss_now
);
2196 /* Link BUFF into the send queue. */
2197 __skb_header_release(buff
);
2198 tcp_insert_write_queue_after(skb
, buff
, sk
, TCP_FRAG_IN_WRITE_QUEUE
);
2203 /* Try to defer sending, if possible, in order to minimize the amount
2204 * of TSO splitting we do. View it as a kind of TSO Nagle test.
2206 * This algorithm is from John Heffner.
2208 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
,
2209 bool *is_cwnd_limited
,
2210 bool *is_rwnd_limited
,
2213 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2214 u32 send_win
, cong_win
, limit
, in_flight
;
2215 struct tcp_sock
*tp
= tcp_sk(sk
);
2216 struct sk_buff
*head
;
2220 if (icsk
->icsk_ca_state
>= TCP_CA_Recovery
)
2223 /* Avoid bursty behavior by allowing defer
2224 * only if the last write was recent (1 ms).
2225 * Note that tp->tcp_wstamp_ns can be in the future if we have
2226 * packets waiting in a qdisc or device for EDT delivery.
2228 delta
= tp
->tcp_clock_cache
- tp
->tcp_wstamp_ns
- NSEC_PER_MSEC
;
2232 in_flight
= tcp_packets_in_flight(tp
);
2234 BUG_ON(tcp_skb_pcount(skb
) <= 1);
2235 BUG_ON(tcp_snd_cwnd(tp
) <= in_flight
);
2237 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
2239 /* From in_flight test above, we know that cwnd > in_flight. */
2240 cong_win
= (tcp_snd_cwnd(tp
) - in_flight
) * tp
->mss_cache
;
2242 limit
= min(send_win
, cong_win
);
2244 /* If a full-sized TSO skb can be sent, do it. */
2245 if (limit
>= max_segs
* tp
->mss_cache
)
2248 /* Middle in queue won't get any more data, full sendable already? */
2249 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
2252 win_divisor
= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_tso_win_divisor
);
2254 u32 chunk
= min(tp
->snd_wnd
, tcp_snd_cwnd(tp
) * tp
->mss_cache
);
2256 /* If at least some fraction of a window is available,
2259 chunk
/= win_divisor
;
2263 /* Different approach, try not to defer past a single
2264 * ACK. Receiver should ACK every other full sized
2265 * frame, so if we have space for more than 3 frames
2268 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
2272 /* TODO : use tsorted_sent_queue ? */
2273 head
= tcp_rtx_queue_head(sk
);
2276 delta
= tp
->tcp_clock_cache
- head
->tstamp
;
2277 /* If next ACK is likely to come too late (half srtt), do not defer */
2278 if ((s64
)(delta
- (u64
)NSEC_PER_USEC
* (tp
->srtt_us
>> 4)) < 0)
2281 /* Ok, it looks like it is advisable to defer.
2282 * Three cases are tracked :
2283 * 1) We are cwnd-limited
2284 * 2) We are rwnd-limited
2285 * 3) We are application limited.
2287 if (cong_win
< send_win
) {
2288 if (cong_win
<= skb
->len
) {
2289 *is_cwnd_limited
= true;
2293 if (send_win
<= skb
->len
) {
2294 *is_rwnd_limited
= true;
2299 /* If this packet won't get more data, do not wait. */
2300 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) ||
2301 TCP_SKB_CB(skb
)->eor
)
2310 static inline void tcp_mtu_check_reprobe(struct sock
*sk
)
2312 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2313 struct tcp_sock
*tp
= tcp_sk(sk
);
2314 struct net
*net
= sock_net(sk
);
2318 interval
= READ_ONCE(net
->ipv4
.sysctl_tcp_probe_interval
);
2319 delta
= tcp_jiffies32
- icsk
->icsk_mtup
.probe_timestamp
;
2320 if (unlikely(delta
>= interval
* HZ
)) {
2321 int mss
= tcp_current_mss(sk
);
2323 /* Update current search range */
2324 icsk
->icsk_mtup
.probe_size
= 0;
2325 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+
2326 sizeof(struct tcphdr
) +
2327 icsk
->icsk_af_ops
->net_header_len
;
2328 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, mss
);
2330 /* Update probe time stamp */
2331 icsk
->icsk_mtup
.probe_timestamp
= tcp_jiffies32
;
2335 static bool tcp_can_coalesce_send_queue_head(struct sock
*sk
, int len
)
2337 struct sk_buff
*skb
, *next
;
2339 skb
= tcp_send_head(sk
);
2340 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
2341 if (len
<= skb
->len
)
2344 if (unlikely(TCP_SKB_CB(skb
)->eor
) ||
2345 tcp_has_tx_tstamp(skb
) ||
2346 !skb_pure_zcopy_same(skb
, next
))
2355 static int tcp_clone_payload(struct sock
*sk
, struct sk_buff
*to
,
2358 skb_frag_t
*lastfrag
= NULL
, *fragto
= skb_shinfo(to
)->frags
;
2359 int i
, todo
, len
= 0, nr_frags
= 0;
2360 const struct sk_buff
*skb
;
2362 if (!sk_wmem_schedule(sk
, to
->truesize
+ probe_size
))
2365 skb_queue_walk(&sk
->sk_write_queue
, skb
) {
2366 const skb_frag_t
*fragfrom
= skb_shinfo(skb
)->frags
;
2368 if (skb_headlen(skb
))
2371 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++, fragfrom
++) {
2372 if (len
>= probe_size
)
2374 todo
= min_t(int, skb_frag_size(fragfrom
),
2378 skb_frag_page(fragfrom
) == skb_frag_page(lastfrag
) &&
2379 skb_frag_off(fragfrom
) == skb_frag_off(lastfrag
) +
2380 skb_frag_size(lastfrag
)) {
2381 skb_frag_size_add(lastfrag
, todo
);
2384 if (unlikely(nr_frags
== MAX_SKB_FRAGS
))
2386 skb_frag_page_copy(fragto
, fragfrom
);
2387 skb_frag_off_copy(fragto
, fragfrom
);
2388 skb_frag_size_set(fragto
, todo
);
2390 lastfrag
= fragto
++;
2394 WARN_ON_ONCE(len
!= probe_size
);
2395 for (i
= 0; i
< nr_frags
; i
++)
2396 skb_frag_ref(to
, i
);
2398 skb_shinfo(to
)->nr_frags
= nr_frags
;
2399 to
->truesize
+= probe_size
;
2400 to
->len
+= probe_size
;
2401 to
->data_len
+= probe_size
;
2402 __skb_header_release(to
);
2406 /* Create a new MTU probe if we are ready.
2407 * MTU probe is regularly attempting to increase the path MTU by
2408 * deliberately sending larger packets. This discovers routing
2409 * changes resulting in larger path MTUs.
2411 * Returns 0 if we should wait to probe (no cwnd available),
2412 * 1 if a probe was sent,
2415 static int tcp_mtu_probe(struct sock
*sk
)
2417 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2418 struct tcp_sock
*tp
= tcp_sk(sk
);
2419 struct sk_buff
*skb
, *nskb
, *next
;
2420 struct net
*net
= sock_net(sk
);
2427 /* Not currently probing/verifying,
2429 * have enough cwnd, and
2430 * not SACKing (the variable headers throw things off)
2432 if (likely(!icsk
->icsk_mtup
.enabled
||
2433 icsk
->icsk_mtup
.probe_size
||
2434 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
2435 tcp_snd_cwnd(tp
) < 11 ||
2436 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
))
2439 /* Use binary search for probe_size between tcp_mss_base,
2440 * and current mss_clamp. if (search_high - search_low)
2441 * smaller than a threshold, backoff from probing.
2443 mss_now
= tcp_current_mss(sk
);
2444 probe_size
= tcp_mtu_to_mss(sk
, (icsk
->icsk_mtup
.search_high
+
2445 icsk
->icsk_mtup
.search_low
) >> 1);
2446 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
2447 interval
= icsk
->icsk_mtup
.search_high
- icsk
->icsk_mtup
.search_low
;
2448 /* When misfortune happens, we are reprobing actively,
2449 * and then reprobe timer has expired. We stick with current
2450 * probing process by not resetting search range to its orignal.
2452 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
) ||
2453 interval
< READ_ONCE(net
->ipv4
.sysctl_tcp_probe_threshold
)) {
2454 /* Check whether enough time has elaplased for
2455 * another round of probing.
2457 tcp_mtu_check_reprobe(sk
);
2461 /* Have enough data in the send queue to probe? */
2462 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
2465 if (tp
->snd_wnd
< size_needed
)
2467 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
2470 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2471 if (tcp_packets_in_flight(tp
) + 2 > tcp_snd_cwnd(tp
)) {
2472 if (!tcp_packets_in_flight(tp
))
2478 if (!tcp_can_coalesce_send_queue_head(sk
, probe_size
))
2481 /* We're allowed to probe. Build it now. */
2482 nskb
= tcp_stream_alloc_skb(sk
, GFP_ATOMIC
, false);
2486 /* build the payload, and be prepared to abort if this fails. */
2487 if (tcp_clone_payload(sk
, nskb
, probe_size
)) {
2488 tcp_skb_tsorted_anchor_cleanup(nskb
);
2492 sk_wmem_queued_add(sk
, nskb
->truesize
);
2493 sk_mem_charge(sk
, nskb
->truesize
);
2495 skb
= tcp_send_head(sk
);
2496 skb_copy_decrypted(nskb
, skb
);
2497 mptcp_skb_ext_copy(nskb
, skb
);
2499 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
2500 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
2501 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
2503 tcp_insert_write_queue_before(nskb
, skb
, sk
);
2504 tcp_highest_sack_replace(sk
, skb
, nskb
);
2507 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
2508 copy
= min_t(int, skb
->len
, probe_size
- len
);
2510 if (skb
->len
<= copy
) {
2511 /* We've eaten all the data from this skb.
2513 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
2514 /* If this is the last SKB we copy and eor is set
2515 * we need to propagate it to the new skb.
2517 TCP_SKB_CB(nskb
)->eor
= TCP_SKB_CB(skb
)->eor
;
2518 tcp_skb_collapse_tstamp(nskb
, skb
);
2519 tcp_unlink_write_queue(skb
, sk
);
2520 tcp_wmem_free_skb(sk
, skb
);
2522 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
2523 ~(TCPHDR_FIN
|TCPHDR_PSH
);
2524 __pskb_trim_head(skb
, copy
);
2525 tcp_set_skb_tso_segs(skb
, mss_now
);
2526 TCP_SKB_CB(skb
)->seq
+= copy
;
2531 if (len
>= probe_size
)
2534 tcp_init_tso_segs(nskb
, nskb
->len
);
2536 /* We're ready to send. If this fails, the probe will
2537 * be resegmented into mss-sized pieces by tcp_write_xmit().
2539 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
2540 /* Decrement cwnd here because we are sending
2541 * effectively two packets. */
2542 tcp_snd_cwnd_set(tp
, tcp_snd_cwnd(tp
) - 1);
2543 tcp_event_new_data_sent(sk
, nskb
);
2545 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
2546 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
2547 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
2555 static bool tcp_pacing_check(struct sock
*sk
)
2557 struct tcp_sock
*tp
= tcp_sk(sk
);
2559 if (!tcp_needs_internal_pacing(sk
))
2562 if (tp
->tcp_wstamp_ns
<= tp
->tcp_clock_cache
)
2565 if (!hrtimer_is_queued(&tp
->pacing_timer
)) {
2566 hrtimer_start(&tp
->pacing_timer
,
2567 ns_to_ktime(tp
->tcp_wstamp_ns
),
2568 HRTIMER_MODE_ABS_PINNED_SOFT
);
2574 static bool tcp_rtx_queue_empty_or_single_skb(const struct sock
*sk
)
2576 const struct rb_node
*node
= sk
->tcp_rtx_queue
.rb_node
;
2578 /* No skb in the rtx queue. */
2582 /* Only one skb in rtx queue. */
2583 return !node
->rb_left
&& !node
->rb_right
;
2586 /* TCP Small Queues :
2587 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2588 * (These limits are doubled for retransmits)
2590 * - better RTT estimation and ACK scheduling
2593 * Alas, some drivers / subsystems require a fair amount
2594 * of queued bytes to ensure line rate.
2595 * One example is wifi aggregation (802.11 AMPDU)
2597 static bool tcp_small_queue_check(struct sock
*sk
, const struct sk_buff
*skb
,
2598 unsigned int factor
)
2600 unsigned long limit
;
2602 limit
= max_t(unsigned long,
2604 READ_ONCE(sk
->sk_pacing_rate
) >> READ_ONCE(sk
->sk_pacing_shift
));
2605 if (sk
->sk_pacing_status
== SK_PACING_NONE
)
2606 limit
= min_t(unsigned long, limit
,
2607 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_limit_output_bytes
));
2610 if (static_branch_unlikely(&tcp_tx_delay_enabled
) &&
2611 tcp_sk(sk
)->tcp_tx_delay
) {
2612 u64 extra_bytes
= (u64
)READ_ONCE(sk
->sk_pacing_rate
) *
2613 tcp_sk(sk
)->tcp_tx_delay
;
2615 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2616 * approximate our needs assuming an ~100% skb->truesize overhead.
2617 * USEC_PER_SEC is approximated by 2^20.
2618 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2620 extra_bytes
>>= (20 - 1);
2621 limit
+= extra_bytes
;
2623 if (refcount_read(&sk
->sk_wmem_alloc
) > limit
) {
2624 /* Always send skb if rtx queue is empty or has one skb.
2625 * No need to wait for TX completion to call us back,
2626 * after softirq/tasklet schedule.
2627 * This helps when TX completions are delayed too much.
2629 if (tcp_rtx_queue_empty_or_single_skb(sk
))
2632 set_bit(TSQ_THROTTLED
, &sk
->sk_tsq_flags
);
2633 /* It is possible TX completion already happened
2634 * before we set TSQ_THROTTLED, so we must
2635 * test again the condition.
2637 smp_mb__after_atomic();
2638 if (refcount_read(&sk
->sk_wmem_alloc
) > limit
)
2644 static void tcp_chrono_set(struct tcp_sock
*tp
, const enum tcp_chrono
new)
2646 const u32 now
= tcp_jiffies32
;
2647 enum tcp_chrono old
= tp
->chrono_type
;
2649 if (old
> TCP_CHRONO_UNSPEC
)
2650 tp
->chrono_stat
[old
- 1] += now
- tp
->chrono_start
;
2651 tp
->chrono_start
= now
;
2652 tp
->chrono_type
= new;
2655 void tcp_chrono_start(struct sock
*sk
, const enum tcp_chrono type
)
2657 struct tcp_sock
*tp
= tcp_sk(sk
);
2659 /* If there are multiple conditions worthy of tracking in a
2660 * chronograph then the highest priority enum takes precedence
2661 * over the other conditions. So that if something "more interesting"
2662 * starts happening, stop the previous chrono and start a new one.
2664 if (type
> tp
->chrono_type
)
2665 tcp_chrono_set(tp
, type
);
2668 void tcp_chrono_stop(struct sock
*sk
, const enum tcp_chrono type
)
2670 struct tcp_sock
*tp
= tcp_sk(sk
);
2673 /* There are multiple conditions worthy of tracking in a
2674 * chronograph, so that the highest priority enum takes
2675 * precedence over the other conditions (see tcp_chrono_start).
2676 * If a condition stops, we only stop chrono tracking if
2677 * it's the "most interesting" or current chrono we are
2678 * tracking and starts busy chrono if we have pending data.
2680 if (tcp_rtx_and_write_queues_empty(sk
))
2681 tcp_chrono_set(tp
, TCP_CHRONO_UNSPEC
);
2682 else if (type
== tp
->chrono_type
)
2683 tcp_chrono_set(tp
, TCP_CHRONO_BUSY
);
2686 /* This routine writes packets to the network. It advances the
2687 * send_head. This happens as incoming acks open up the remote
2690 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2691 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2692 * account rare use of URG, this is not a big flaw.
2694 * Send at most one packet when push_one > 0. Temporarily ignore
2695 * cwnd limit to force at most one packet out when push_one == 2.
2697 * Returns true, if no segments are in flight and we have queued segments,
2698 * but cannot send anything now because of SWS or another problem.
2700 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
2701 int push_one
, gfp_t gfp
)
2703 struct tcp_sock
*tp
= tcp_sk(sk
);
2704 struct sk_buff
*skb
;
2705 unsigned int tso_segs
, sent_pkts
;
2708 bool is_cwnd_limited
= false, is_rwnd_limited
= false;
2713 tcp_mstamp_refresh(tp
);
2715 /* Do MTU probing. */
2716 result
= tcp_mtu_probe(sk
);
2719 } else if (result
> 0) {
2724 max_segs
= tcp_tso_segs(sk
, mss_now
);
2725 while ((skb
= tcp_send_head(sk
))) {
2728 if (unlikely(tp
->repair
) && tp
->repair_queue
== TCP_SEND_QUEUE
) {
2729 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2730 tp
->tcp_wstamp_ns
= tp
->tcp_clock_cache
;
2731 skb_set_delivery_time(skb
, tp
->tcp_wstamp_ns
, true);
2732 list_move_tail(&skb
->tcp_tsorted_anchor
, &tp
->tsorted_sent_queue
);
2733 tcp_init_tso_segs(skb
, mss_now
);
2734 goto repair
; /* Skip network transmission */
2737 if (tcp_pacing_check(sk
))
2740 tso_segs
= tcp_init_tso_segs(skb
, mss_now
);
2743 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
2746 /* Force out a loss probe pkt. */
2752 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
))) {
2753 is_rwnd_limited
= true;
2757 if (tso_segs
== 1) {
2758 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
2759 (tcp_skb_is_last(sk
, skb
) ?
2760 nonagle
: TCP_NAGLE_PUSH
))))
2764 tcp_tso_should_defer(sk
, skb
, &is_cwnd_limited
,
2765 &is_rwnd_limited
, max_segs
))
2770 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
2771 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
2777 if (skb
->len
> limit
&&
2778 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
2781 if (tcp_small_queue_check(sk
, skb
, 0))
2784 /* Argh, we hit an empty skb(), presumably a thread
2785 * is sleeping in sendmsg()/sk_stream_wait_memory().
2786 * We do not want to send a pure-ack packet and have
2787 * a strange looking rtx queue with empty packet(s).
2789 if (TCP_SKB_CB(skb
)->end_seq
== TCP_SKB_CB(skb
)->seq
)
2792 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
2796 /* Advance the send_head. This one is sent out.
2797 * This call will increment packets_out.
2799 tcp_event_new_data_sent(sk
, skb
);
2801 tcp_minshall_update(tp
, mss_now
, skb
);
2802 sent_pkts
+= tcp_skb_pcount(skb
);
2808 if (is_rwnd_limited
)
2809 tcp_chrono_start(sk
, TCP_CHRONO_RWND_LIMITED
);
2811 tcp_chrono_stop(sk
, TCP_CHRONO_RWND_LIMITED
);
2813 is_cwnd_limited
|= (tcp_packets_in_flight(tp
) >= tcp_snd_cwnd(tp
));
2814 if (likely(sent_pkts
|| is_cwnd_limited
))
2815 tcp_cwnd_validate(sk
, is_cwnd_limited
);
2817 if (likely(sent_pkts
)) {
2818 if (tcp_in_cwnd_reduction(sk
))
2819 tp
->prr_out
+= sent_pkts
;
2821 /* Send one loss probe per tail loss episode. */
2823 tcp_schedule_loss_probe(sk
, false);
2826 return !tp
->packets_out
&& !tcp_write_queue_empty(sk
);
2829 bool tcp_schedule_loss_probe(struct sock
*sk
, bool advancing_rto
)
2831 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2832 struct tcp_sock
*tp
= tcp_sk(sk
);
2833 u32 timeout
, timeout_us
, rto_delta_us
;
2836 /* Don't do any loss probe on a Fast Open connection before 3WHS
2839 if (rcu_access_pointer(tp
->fastopen_rsk
))
2842 early_retrans
= READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_early_retrans
);
2843 /* Schedule a loss probe in 2*RTT for SACK capable connections
2844 * not in loss recovery, that are either limited by cwnd or application.
2846 if ((early_retrans
!= 3 && early_retrans
!= 4) ||
2847 !tp
->packets_out
|| !tcp_is_sack(tp
) ||
2848 (icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2849 icsk
->icsk_ca_state
!= TCP_CA_CWR
))
2852 /* Probe timeout is 2*rtt. Add minimum RTO to account
2853 * for delayed ack when there's one outstanding packet. If no RTT
2854 * sample is available then probe after TCP_TIMEOUT_INIT.
2857 timeout_us
= tp
->srtt_us
>> 2;
2858 if (tp
->packets_out
== 1)
2859 timeout_us
+= tcp_rto_min_us(sk
);
2861 timeout_us
+= TCP_TIMEOUT_MIN_US
;
2862 timeout
= usecs_to_jiffies(timeout_us
);
2864 timeout
= TCP_TIMEOUT_INIT
;
2867 /* If the RTO formula yields an earlier time, then use that time. */
2868 rto_delta_us
= advancing_rto
?
2869 jiffies_to_usecs(inet_csk(sk
)->icsk_rto
) :
2870 tcp_rto_delta_us(sk
); /* How far in future is RTO? */
2871 if (rto_delta_us
> 0)
2872 timeout
= min_t(u32
, timeout
, usecs_to_jiffies(rto_delta_us
));
2874 tcp_reset_xmit_timer(sk
, ICSK_TIME_LOSS_PROBE
, timeout
, TCP_RTO_MAX
);
2878 /* Thanks to skb fast clones, we can detect if a prior transmit of
2879 * a packet is still in a qdisc or driver queue.
2880 * In this case, there is very little point doing a retransmit !
2882 static bool skb_still_in_host_queue(struct sock
*sk
,
2883 const struct sk_buff
*skb
)
2885 if (unlikely(skb_fclone_busy(sk
, skb
))) {
2886 set_bit(TSQ_THROTTLED
, &sk
->sk_tsq_flags
);
2887 smp_mb__after_atomic();
2888 if (skb_fclone_busy(sk
, skb
)) {
2889 NET_INC_STATS(sock_net(sk
),
2890 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES
);
2897 /* When probe timeout (PTO) fires, try send a new segment if possible, else
2898 * retransmit the last segment.
2900 void tcp_send_loss_probe(struct sock
*sk
)
2902 struct tcp_sock
*tp
= tcp_sk(sk
);
2903 struct sk_buff
*skb
;
2905 int mss
= tcp_current_mss(sk
);
2907 /* At most one outstanding TLP */
2908 if (tp
->tlp_high_seq
)
2911 tp
->tlp_retrans
= 0;
2912 skb
= tcp_send_head(sk
);
2913 if (skb
&& tcp_snd_wnd_test(tp
, skb
, mss
)) {
2914 pcount
= tp
->packets_out
;
2915 tcp_write_xmit(sk
, mss
, TCP_NAGLE_OFF
, 2, GFP_ATOMIC
);
2916 if (tp
->packets_out
> pcount
)
2920 skb
= skb_rb_last(&sk
->tcp_rtx_queue
);
2921 if (unlikely(!skb
)) {
2922 WARN_ONCE(tp
->packets_out
,
2923 "invalid inflight: %u state %u cwnd %u mss %d\n",
2924 tp
->packets_out
, sk
->sk_state
, tcp_snd_cwnd(tp
), mss
);
2925 inet_csk(sk
)->icsk_pending
= 0;
2929 if (skb_still_in_host_queue(sk
, skb
))
2932 pcount
= tcp_skb_pcount(skb
);
2933 if (WARN_ON(!pcount
))
2936 if ((pcount
> 1) && (skb
->len
> (pcount
- 1) * mss
)) {
2937 if (unlikely(tcp_fragment(sk
, TCP_FRAG_IN_RTX_QUEUE
, skb
,
2938 (pcount
- 1) * mss
, mss
,
2941 skb
= skb_rb_next(skb
);
2944 if (WARN_ON(!skb
|| !tcp_skb_pcount(skb
)))
2947 if (__tcp_retransmit_skb(sk
, skb
, 1))
2950 tp
->tlp_retrans
= 1;
2953 /* Record snd_nxt for loss detection. */
2954 tp
->tlp_high_seq
= tp
->snd_nxt
;
2956 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSPROBES
);
2957 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2958 inet_csk(sk
)->icsk_pending
= 0;
2963 /* Push out any pending frames which were held back due to
2964 * TCP_CORK or attempt at coalescing tiny packets.
2965 * The socket must be locked by the caller.
2967 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2970 /* If we are closed, the bytes will have to remain here.
2971 * In time closedown will finish, we empty the write queue and
2972 * all will be happy.
2974 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2977 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2978 sk_gfp_mask(sk
, GFP_ATOMIC
)))
2979 tcp_check_probe_timer(sk
);
2982 /* Send _single_ skb sitting at the send head. This function requires
2983 * true push pending frames to setup probe timer etc.
2985 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2987 struct sk_buff
*skb
= tcp_send_head(sk
);
2989 BUG_ON(!skb
|| skb
->len
< mss_now
);
2991 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2994 /* This function returns the amount that we can raise the
2995 * usable window based on the following constraints
2997 * 1. The window can never be shrunk once it is offered (RFC 793)
2998 * 2. We limit memory per socket
3001 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
3002 * RECV.NEXT + RCV.WIN fixed until:
3003 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
3005 * i.e. don't raise the right edge of the window until you can raise
3006 * it at least MSS bytes.
3008 * Unfortunately, the recommended algorithm breaks header prediction,
3009 * since header prediction assumes th->window stays fixed.
3011 * Strictly speaking, keeping th->window fixed violates the receiver
3012 * side SWS prevention criteria. The problem is that under this rule
3013 * a stream of single byte packets will cause the right side of the
3014 * window to always advance by a single byte.
3016 * Of course, if the sender implements sender side SWS prevention
3017 * then this will not be a problem.
3019 * BSD seems to make the following compromise:
3021 * If the free space is less than the 1/4 of the maximum
3022 * space available and the free space is less than 1/2 mss,
3023 * then set the window to 0.
3024 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
3025 * Otherwise, just prevent the window from shrinking
3026 * and from being larger than the largest representable value.
3028 * This prevents incremental opening of the window in the regime
3029 * where TCP is limited by the speed of the reader side taking
3030 * data out of the TCP receive queue. It does nothing about
3031 * those cases where the window is constrained on the sender side
3032 * because the pipeline is full.
3034 * BSD also seems to "accidentally" limit itself to windows that are a
3035 * multiple of MSS, at least until the free space gets quite small.
3036 * This would appear to be a side effect of the mbuf implementation.
3037 * Combining these two algorithms results in the observed behavior
3038 * of having a fixed window size at almost all times.
3040 * Below we obtain similar behavior by forcing the offered window to
3041 * a multiple of the mss when it is feasible to do so.
3043 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
3044 * Regular options like TIMESTAMP are taken into account.
3046 u32
__tcp_select_window(struct sock
*sk
)
3048 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3049 struct tcp_sock
*tp
= tcp_sk(sk
);
3050 struct net
*net
= sock_net(sk
);
3051 /* MSS for the peer's data. Previous versions used mss_clamp
3052 * here. I don't know if the value based on our guesses
3053 * of peer's MSS is better for the performance. It's more correct
3054 * but may be worse for the performance because of rcv_mss
3055 * fluctuations. --SAW 1998/11/1
3057 int mss
= icsk
->icsk_ack
.rcv_mss
;
3058 int free_space
= tcp_space(sk
);
3059 int allowed_space
= tcp_full_space(sk
);
3060 int full_space
, window
;
3062 if (sk_is_mptcp(sk
))
3063 mptcp_space(sk
, &free_space
, &allowed_space
);
3065 full_space
= min_t(int, tp
->window_clamp
, allowed_space
);
3067 if (unlikely(mss
> full_space
)) {
3073 /* Only allow window shrink if the sysctl is enabled and we have
3074 * a non-zero scaling factor in effect.
3076 if (READ_ONCE(net
->ipv4
.sysctl_tcp_shrink_window
) && tp
->rx_opt
.rcv_wscale
)
3077 goto shrink_window_allowed
;
3079 /* do not allow window to shrink */
3081 if (free_space
< (full_space
>> 1)) {
3082 icsk
->icsk_ack
.quick
= 0;
3084 if (tcp_under_memory_pressure(sk
))
3085 tcp_adjust_rcv_ssthresh(sk
);
3087 /* free_space might become our new window, make sure we don't
3088 * increase it due to wscale.
3090 free_space
= round_down(free_space
, 1 << tp
->rx_opt
.rcv_wscale
);
3092 /* if free space is less than mss estimate, or is below 1/16th
3093 * of the maximum allowed, try to move to zero-window, else
3094 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
3095 * new incoming data is dropped due to memory limits.
3096 * With large window, mss test triggers way too late in order
3097 * to announce zero window in time before rmem limit kicks in.
3099 if (free_space
< (allowed_space
>> 4) || free_space
< mss
)
3103 if (free_space
> tp
->rcv_ssthresh
)
3104 free_space
= tp
->rcv_ssthresh
;
3106 /* Don't do rounding if we are using window scaling, since the
3107 * scaled window will not line up with the MSS boundary anyway.
3109 if (tp
->rx_opt
.rcv_wscale
) {
3110 window
= free_space
;
3112 /* Advertise enough space so that it won't get scaled away.
3113 * Import case: prevent zero window announcement if
3114 * 1<<rcv_wscale > mss.
3116 window
= ALIGN(window
, (1 << tp
->rx_opt
.rcv_wscale
));
3118 window
= tp
->rcv_wnd
;
3119 /* Get the largest window that is a nice multiple of mss.
3120 * Window clamp already applied above.
3121 * If our current window offering is within 1 mss of the
3122 * free space we just keep it. This prevents the divide
3123 * and multiply from happening most of the time.
3124 * We also don't do any window rounding when the free space
3127 if (window
<= free_space
- mss
|| window
> free_space
)
3128 window
= rounddown(free_space
, mss
);
3129 else if (mss
== full_space
&&
3130 free_space
> window
+ (full_space
>> 1))
3131 window
= free_space
;
3136 shrink_window_allowed
:
3137 /* new window should always be an exact multiple of scaling factor */
3138 free_space
= round_down(free_space
, 1 << tp
->rx_opt
.rcv_wscale
);
3140 if (free_space
< (full_space
>> 1)) {
3141 icsk
->icsk_ack
.quick
= 0;
3143 if (tcp_under_memory_pressure(sk
))
3144 tcp_adjust_rcv_ssthresh(sk
);
3146 /* if free space is too low, return a zero window */
3147 if (free_space
< (allowed_space
>> 4) || free_space
< mss
||
3148 free_space
< (1 << tp
->rx_opt
.rcv_wscale
))
3152 if (free_space
> tp
->rcv_ssthresh
) {
3153 free_space
= tp
->rcv_ssthresh
;
3154 /* new window should always be an exact multiple of scaling factor
3156 * For this case, we ALIGN "up" (increase free_space) because
3157 * we know free_space is not zero here, it has been reduced from
3158 * the memory-based limit, and rcv_ssthresh is not a hard limit
3159 * (unlike sk_rcvbuf).
3161 free_space
= ALIGN(free_space
, (1 << tp
->rx_opt
.rcv_wscale
));
3167 void tcp_skb_collapse_tstamp(struct sk_buff
*skb
,
3168 const struct sk_buff
*next_skb
)
3170 if (unlikely(tcp_has_tx_tstamp(next_skb
))) {
3171 const struct skb_shared_info
*next_shinfo
=
3172 skb_shinfo(next_skb
);
3173 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
3175 shinfo
->tx_flags
|= next_shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
3176 shinfo
->tskey
= next_shinfo
->tskey
;
3177 TCP_SKB_CB(skb
)->txstamp_ack
|=
3178 TCP_SKB_CB(next_skb
)->txstamp_ack
;
3182 /* Collapses two adjacent SKB's during retransmission. */
3183 static bool tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
3185 struct tcp_sock
*tp
= tcp_sk(sk
);
3186 struct sk_buff
*next_skb
= skb_rb_next(skb
);
3189 next_skb_size
= next_skb
->len
;
3191 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
3193 if (next_skb_size
&& !tcp_skb_shift(skb
, next_skb
, 1, next_skb_size
))
3196 tcp_highest_sack_replace(sk
, next_skb
, skb
);
3198 /* Update sequence range on original skb. */
3199 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
3201 /* Merge over control information. This moves PSH/FIN etc. over */
3202 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
3204 /* All done, get rid of second SKB and account for it so
3205 * packet counting does not break.
3207 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
3208 TCP_SKB_CB(skb
)->eor
= TCP_SKB_CB(next_skb
)->eor
;
3210 /* changed transmit queue under us so clear hints */
3211 tcp_clear_retrans_hints_partial(tp
);
3212 if (next_skb
== tp
->retransmit_skb_hint
)
3213 tp
->retransmit_skb_hint
= skb
;
3215 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
3217 tcp_skb_collapse_tstamp(skb
, next_skb
);
3219 tcp_rtx_queue_unlink_and_free(next_skb
, sk
);
3223 /* Check if coalescing SKBs is legal. */
3224 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
3226 if (tcp_skb_pcount(skb
) > 1)
3228 if (skb_cloned(skb
))
3230 /* Some heuristics for collapsing over SACK'd could be invented */
3231 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
3237 /* Collapse packets in the retransmit queue to make to create
3238 * less packets on the wire. This is only done on retransmission.
3240 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
3243 struct tcp_sock
*tp
= tcp_sk(sk
);
3244 struct sk_buff
*skb
= to
, *tmp
;
3247 if (!READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_retrans_collapse
))
3249 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
3252 skb_rbtree_walk_from_safe(skb
, tmp
) {
3253 if (!tcp_can_collapse(sk
, skb
))
3256 if (!tcp_skb_can_collapse(to
, skb
))
3269 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
3272 if (!tcp_collapse_retrans(sk
, to
))
3277 /* This retransmits one SKB. Policy decisions and retransmit queue
3278 * state updates are done by the caller. Returns non-zero if an
3279 * error occurred which prevented the send.
3281 int __tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int segs
)
3283 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3284 struct tcp_sock
*tp
= tcp_sk(sk
);
3285 unsigned int cur_mss
;
3289 /* Inconclusive MTU probe */
3290 if (icsk
->icsk_mtup
.probe_size
)
3291 icsk
->icsk_mtup
.probe_size
= 0;
3293 if (skb_still_in_host_queue(sk
, skb
))
3297 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
3298 if (unlikely(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
3299 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_SYN
;
3300 TCP_SKB_CB(skb
)->seq
++;
3303 if (unlikely(before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))) {
3307 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3311 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
3312 return -EHOSTUNREACH
; /* Routing failure or similar. */
3314 cur_mss
= tcp_current_mss(sk
);
3315 avail_wnd
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3317 /* If receiver has shrunk his window, and skb is out of
3318 * new window, do not retransmit it. The exception is the
3319 * case, when window is shrunk to zero. In this case
3320 * our retransmit of one segment serves as a zero window probe.
3322 if (avail_wnd
<= 0) {
3323 if (TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
3325 avail_wnd
= cur_mss
;
3328 len
= cur_mss
* segs
;
3329 if (len
> avail_wnd
) {
3330 len
= rounddown(avail_wnd
, cur_mss
);
3334 if (skb
->len
> len
) {
3335 if (tcp_fragment(sk
, TCP_FRAG_IN_RTX_QUEUE
, skb
, len
,
3336 cur_mss
, GFP_ATOMIC
))
3337 return -ENOMEM
; /* We'll try again later. */
3339 if (skb_unclone_keeptruesize(skb
, GFP_ATOMIC
))
3342 diff
= tcp_skb_pcount(skb
);
3343 tcp_set_skb_tso_segs(skb
, cur_mss
);
3344 diff
-= tcp_skb_pcount(skb
);
3346 tcp_adjust_pcount(sk
, skb
, diff
);
3347 avail_wnd
= min_t(int, avail_wnd
, cur_mss
);
3348 if (skb
->len
< avail_wnd
)
3349 tcp_retrans_try_collapse(sk
, skb
, avail_wnd
);
3352 /* RFC3168, section 6.1.1.1. ECN fallback */
3353 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN_ECN
) == TCPHDR_SYN_ECN
)
3354 tcp_ecn_clear_syn(sk
, skb
);
3356 /* Update global and local TCP statistics. */
3357 segs
= tcp_skb_pcount(skb
);
3358 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
, segs
);
3359 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
3360 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
3361 tp
->total_retrans
+= segs
;
3362 tp
->bytes_retrans
+= skb
->len
;
3364 /* make sure skb->data is aligned on arches that require it
3365 * and check if ack-trimming & collapsing extended the headroom
3366 * beyond what csum_start can cover.
3368 if (unlikely((NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3)) ||
3369 skb_headroom(skb
) >= 0xFFFF)) {
3370 struct sk_buff
*nskb
;
3372 tcp_skb_tsorted_save(skb
) {
3373 nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
, GFP_ATOMIC
);
3376 err
= tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
);
3380 } tcp_skb_tsorted_restore(skb
);
3383 tcp_update_skb_after_send(sk
, skb
, tp
->tcp_wstamp_ns
);
3384 tcp_rate_skb_sent(sk
, skb
);
3387 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3390 /* To avoid taking spuriously low RTT samples based on a timestamp
3391 * for a transmit that never happened, always mark EVER_RETRANS
3393 TCP_SKB_CB(skb
)->sacked
|= TCPCB_EVER_RETRANS
;
3395 if (BPF_SOCK_OPS_TEST_FLAG(tp
, BPF_SOCK_OPS_RETRANS_CB_FLAG
))
3396 tcp_call_bpf_3arg(sk
, BPF_SOCK_OPS_RETRANS_CB
,
3397 TCP_SKB_CB(skb
)->seq
, segs
, err
);
3400 trace_tcp_retransmit_skb(sk
, skb
);
3401 } else if (err
!= -EBUSY
) {
3402 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
, segs
);
3407 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int segs
)
3409 struct tcp_sock
*tp
= tcp_sk(sk
);
3410 int err
= __tcp_retransmit_skb(sk
, skb
, segs
);
3413 #if FASTRETRANS_DEBUG > 0
3414 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
3415 net_dbg_ratelimited("retrans_out leaked\n");
3418 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
3419 tp
->retrans_out
+= tcp_skb_pcount(skb
);
3422 /* Save stamp of the first (attempted) retransmit. */
3423 if (!tp
->retrans_stamp
)
3424 tp
->retrans_stamp
= tcp_skb_timestamp_ts(tp
->tcp_usec_ts
, skb
);
3426 if (tp
->undo_retrans
< 0)
3427 tp
->undo_retrans
= 0;
3428 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
3432 /* This gets called after a retransmit timeout, and the initially
3433 * retransmitted data is acknowledged. It tries to continue
3434 * resending the rest of the retransmit queue, until either
3435 * we've sent it all or the congestion window limit is reached.
3437 void tcp_xmit_retransmit_queue(struct sock
*sk
)
3439 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3440 struct sk_buff
*skb
, *rtx_head
, *hole
= NULL
;
3441 struct tcp_sock
*tp
= tcp_sk(sk
);
3442 bool rearm_timer
= false;
3446 if (!tp
->packets_out
)
3449 rtx_head
= tcp_rtx_queue_head(sk
);
3450 skb
= tp
->retransmit_skb_hint
?: rtx_head
;
3451 max_segs
= tcp_tso_segs(sk
, tcp_current_mss(sk
));
3452 skb_rbtree_walk_from(skb
) {
3456 if (tcp_pacing_check(sk
))
3459 /* we could do better than to assign each time */
3461 tp
->retransmit_skb_hint
= skb
;
3463 segs
= tcp_snd_cwnd(tp
) - tcp_packets_in_flight(tp
);
3466 sacked
= TCP_SKB_CB(skb
)->sacked
;
3467 /* In case tcp_shift_skb_data() have aggregated large skbs,
3468 * we need to make sure not sending too bigs TSO packets
3470 segs
= min_t(int, segs
, max_segs
);
3472 if (tp
->retrans_out
>= tp
->lost_out
) {
3474 } else if (!(sacked
& TCPCB_LOST
)) {
3475 if (!hole
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
3480 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
3481 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
3483 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
3486 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
3489 if (tcp_small_queue_check(sk
, skb
, 1))
3492 if (tcp_retransmit_skb(sk
, skb
, segs
))
3495 NET_ADD_STATS(sock_net(sk
), mib_idx
, tcp_skb_pcount(skb
));
3497 if (tcp_in_cwnd_reduction(sk
))
3498 tp
->prr_out
+= tcp_skb_pcount(skb
);
3500 if (skb
== rtx_head
&&
3501 icsk
->icsk_pending
!= ICSK_TIME_REO_TIMEOUT
)
3506 tcp_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3507 inet_csk(sk
)->icsk_rto
,
3511 /* We allow to exceed memory limits for FIN packets to expedite
3512 * connection tear down and (memory) recovery.
3513 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3514 * or even be forced to close flow without any FIN.
3515 * In general, we want to allow one skb per socket to avoid hangs
3516 * with edge trigger epoll()
3518 void sk_forced_mem_schedule(struct sock
*sk
, int size
)
3522 delta
= size
- sk
->sk_forward_alloc
;
3525 amt
= sk_mem_pages(delta
);
3526 sk_forward_alloc_add(sk
, amt
<< PAGE_SHIFT
);
3527 sk_memory_allocated_add(sk
, amt
);
3529 if (mem_cgroup_sockets_enabled
&& sk
->sk_memcg
)
3530 mem_cgroup_charge_skmem(sk
->sk_memcg
, amt
,
3531 gfp_memcg_charge() | __GFP_NOFAIL
);
3534 /* Send a FIN. The caller locks the socket for us.
3535 * We should try to send a FIN packet really hard, but eventually give up.
3537 void tcp_send_fin(struct sock
*sk
)
3539 struct sk_buff
*skb
, *tskb
, *tail
= tcp_write_queue_tail(sk
);
3540 struct tcp_sock
*tp
= tcp_sk(sk
);
3542 /* Optimization, tack on the FIN if we have one skb in write queue and
3543 * this skb was not yet sent, or we are under memory pressure.
3544 * Note: in the latter case, FIN packet will be sent after a timeout,
3545 * as TCP stack thinks it has already been transmitted.
3548 if (!tskb
&& tcp_under_memory_pressure(sk
))
3549 tskb
= skb_rb_last(&sk
->tcp_rtx_queue
);
3552 TCP_SKB_CB(tskb
)->tcp_flags
|= TCPHDR_FIN
;
3553 TCP_SKB_CB(tskb
)->end_seq
++;
3556 /* This means tskb was already sent.
3557 * Pretend we included the FIN on previous transmit.
3558 * We need to set tp->snd_nxt to the value it would have
3559 * if FIN had been sent. This is because retransmit path
3560 * does not change tp->snd_nxt.
3562 WRITE_ONCE(tp
->snd_nxt
, tp
->snd_nxt
+ 1);
3566 skb
= alloc_skb_fclone(MAX_TCP_HEADER
,
3567 sk_gfp_mask(sk
, GFP_ATOMIC
|
3572 INIT_LIST_HEAD(&skb
->tcp_tsorted_anchor
);
3573 skb_reserve(skb
, MAX_TCP_HEADER
);
3574 sk_forced_mem_schedule(sk
, skb
->truesize
);
3575 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3576 tcp_init_nondata_skb(skb
, tp
->write_seq
,
3577 TCPHDR_ACK
| TCPHDR_FIN
);
3578 tcp_queue_skb(sk
, skb
);
3580 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
), TCP_NAGLE_OFF
);
3583 /* We get here when a process closes a file descriptor (either due to
3584 * an explicit close() or as a byproduct of exit()'ing) and there
3585 * was unread data in the receive queue. This behavior is recommended
3586 * by RFC 2525, section 2.17. -DaveM
3588 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
3590 struct sk_buff
*skb
;
3592 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
3594 /* NOTE: No TCP options attached and we never retransmit this. */
3595 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
3597 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
3601 /* Reserve space for headers and prepare control bits. */
3602 skb_reserve(skb
, MAX_TCP_HEADER
);
3603 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
3604 TCPHDR_ACK
| TCPHDR_RST
);
3605 tcp_mstamp_refresh(tcp_sk(sk
));
3607 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
3608 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
3610 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3611 * skb here is different to the troublesome skb, so use NULL
3613 trace_tcp_send_reset(sk
, NULL
);
3616 /* Send a crossed SYN-ACK during socket establishment.
3617 * WARNING: This routine must only be called when we have already sent
3618 * a SYN packet that crossed the incoming SYN that caused this routine
3619 * to get called. If this assumption fails then the initial rcv_wnd
3620 * and rcv_wscale values will not be correct.
3622 int tcp_send_synack(struct sock
*sk
)
3624 struct sk_buff
*skb
;
3626 skb
= tcp_rtx_queue_head(sk
);
3627 if (!skb
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
3628 pr_err("%s: wrong queue state\n", __func__
);
3631 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
3632 if (skb_cloned(skb
)) {
3633 struct sk_buff
*nskb
;
3635 tcp_skb_tsorted_save(skb
) {
3636 nskb
= skb_copy(skb
, GFP_ATOMIC
);
3637 } tcp_skb_tsorted_restore(skb
);
3640 INIT_LIST_HEAD(&nskb
->tcp_tsorted_anchor
);
3641 tcp_highest_sack_replace(sk
, skb
, nskb
);
3642 tcp_rtx_queue_unlink_and_free(skb
, sk
);
3643 __skb_header_release(nskb
);
3644 tcp_rbtree_insert(&sk
->tcp_rtx_queue
, nskb
);
3645 sk_wmem_queued_add(sk
, nskb
->truesize
);
3646 sk_mem_charge(sk
, nskb
->truesize
);
3650 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
3651 tcp_ecn_send_synack(sk
, skb
);
3653 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3657 * tcp_make_synack - Allocate one skb and build a SYNACK packet.
3658 * @sk: listener socket
3659 * @dst: dst entry attached to the SYNACK. It is consumed and caller
3660 * should not use it again.
3661 * @req: request_sock pointer
3662 * @foc: cookie for tcp fast open
3663 * @synack_type: Type of synack to prepare
3664 * @syn_skb: SYN packet just received. It could be NULL for rtx case.
3666 struct sk_buff
*tcp_make_synack(const struct sock
*sk
, struct dst_entry
*dst
,
3667 struct request_sock
*req
,
3668 struct tcp_fastopen_cookie
*foc
,
3669 enum tcp_synack_type synack_type
,
3670 struct sk_buff
*syn_skb
)
3672 struct inet_request_sock
*ireq
= inet_rsk(req
);
3673 const struct tcp_sock
*tp
= tcp_sk(sk
);
3674 struct tcp_out_options opts
;
3675 struct tcp_key key
= {};
3676 struct sk_buff
*skb
;
3677 int tcp_header_size
;
3682 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
3683 if (unlikely(!skb
)) {
3687 /* Reserve space for headers. */
3688 skb_reserve(skb
, MAX_TCP_HEADER
);
3690 switch (synack_type
) {
3691 case TCP_SYNACK_NORMAL
:
3692 skb_set_owner_w(skb
, req_to_sk(req
));
3694 case TCP_SYNACK_COOKIE
:
3695 /* Under synflood, we do not attach skb to a socket,
3696 * to avoid false sharing.
3699 case TCP_SYNACK_FASTOPEN
:
3700 /* sk is a const pointer, because we want to express multiple
3701 * cpu might call us concurrently.
3702 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3704 skb_set_owner_w(skb
, (struct sock
*)sk
);
3707 skb_dst_set(skb
, dst
);
3709 mss
= tcp_mss_clamp(tp
, dst_metric_advmss(dst
));
3711 memset(&opts
, 0, sizeof(opts
));
3712 now
= tcp_clock_ns();
3713 #ifdef CONFIG_SYN_COOKIES
3714 if (unlikely(synack_type
== TCP_SYNACK_COOKIE
&& ireq
->tstamp_ok
))
3715 skb_set_delivery_time(skb
, cookie_init_timestamp(req
, now
),
3720 skb_set_delivery_time(skb
, now
, true);
3721 if (!tcp_rsk(req
)->snt_synack
) /* Timestamp first SYNACK */
3722 tcp_rsk(req
)->snt_synack
= tcp_skb_timestamp_us(skb
);
3725 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3728 if (tcp_rsk_used_ao(req
)) {
3729 #ifdef CONFIG_TCP_AO
3730 struct tcp_ao_key
*ao_key
= NULL
;
3731 u8 keyid
= tcp_rsk(req
)->ao_keyid
;
3733 ao_key
= tcp_sk(sk
)->af_specific
->ao_lookup(sk
, req_to_sk(req
),
3735 /* If there is no matching key - avoid sending anything,
3736 * especially usigned segments. It could try harder and lookup
3737 * for another peer-matching key, but the peer has requested
3738 * ao_keyid (RFC5925 RNextKeyID), so let's keep it simple here.
3740 if (unlikely(!ao_key
)) {
3743 net_warn_ratelimited("TCP-AO: the keyid %u from SYN packet is not present - not sending SYNACK\n",
3747 key
.ao_key
= ao_key
;
3748 key
.type
= TCP_KEY_AO
;
3751 #ifdef CONFIG_TCP_MD5SIG
3752 key
.md5_key
= tcp_rsk(req
)->af_specific
->req_md5_lookup(sk
,
3755 key
.type
= TCP_KEY_MD5
;
3758 skb_set_hash(skb
, READ_ONCE(tcp_rsk(req
)->txhash
), PKT_HASH_TYPE_L4
);
3759 /* bpf program will be interested in the tcp_flags */
3760 TCP_SKB_CB(skb
)->tcp_flags
= TCPHDR_SYN
| TCPHDR_ACK
;
3761 tcp_header_size
= tcp_synack_options(sk
, req
, mss
, skb
, &opts
,
3762 &key
, foc
, synack_type
, syn_skb
)
3765 skb_push(skb
, tcp_header_size
);
3766 skb_reset_transport_header(skb
);
3768 th
= (struct tcphdr
*)skb
->data
;
3769 memset(th
, 0, sizeof(struct tcphdr
));
3772 tcp_ecn_make_synack(req
, th
);
3773 th
->source
= htons(ireq
->ir_num
);
3774 th
->dest
= ireq
->ir_rmt_port
;
3775 skb
->mark
= ireq
->ir_mark
;
3776 skb
->ip_summed
= CHECKSUM_PARTIAL
;
3777 th
->seq
= htonl(tcp_rsk(req
)->snt_isn
);
3778 /* XXX data is queued and acked as is. No buffer/window check */
3779 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_nxt
);
3781 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3782 th
->window
= htons(min(req
->rsk_rcv_wnd
, 65535U));
3783 tcp_options_write(th
, NULL
, tcp_rsk(req
), &opts
, &key
);
3784 th
->doff
= (tcp_header_size
>> 2);
3785 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
3787 /* Okay, we have all we need - do the md5 hash if needed */
3788 if (tcp_key_is_md5(&key
)) {
3789 #ifdef CONFIG_TCP_MD5SIG
3790 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
3791 key
.md5_key
, req_to_sk(req
), skb
);
3793 } else if (tcp_key_is_ao(&key
)) {
3794 #ifdef CONFIG_TCP_AO
3795 tcp_rsk(req
)->af_specific
->ao_synack_hash(opts
.hash_location
,
3796 key
.ao_key
, req
, skb
,
3797 opts
.hash_location
- (u8
*)th
, 0);
3800 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3804 bpf_skops_write_hdr_opt((struct sock
*)sk
, skb
, req
, syn_skb
,
3805 synack_type
, &opts
);
3807 skb_set_delivery_time(skb
, now
, true);
3808 tcp_add_tx_delay(skb
, tp
);
3812 EXPORT_SYMBOL(tcp_make_synack
);
3814 static void tcp_ca_dst_init(struct sock
*sk
, const struct dst_entry
*dst
)
3816 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3817 const struct tcp_congestion_ops
*ca
;
3818 u32 ca_key
= dst_metric(dst
, RTAX_CC_ALGO
);
3820 if (ca_key
== TCP_CA_UNSPEC
)
3824 ca
= tcp_ca_find_key(ca_key
);
3825 if (likely(ca
&& bpf_try_module_get(ca
, ca
->owner
))) {
3826 bpf_module_put(icsk
->icsk_ca_ops
, icsk
->icsk_ca_ops
->owner
);
3827 icsk
->icsk_ca_dst_locked
= tcp_ca_dst_locked(dst
);
3828 icsk
->icsk_ca_ops
= ca
;
3833 /* Do all connect socket setups that can be done AF independent. */
3834 static void tcp_connect_init(struct sock
*sk
)
3836 const struct dst_entry
*dst
= __sk_dst_get(sk
);
3837 struct tcp_sock
*tp
= tcp_sk(sk
);
3841 /* We'll fix this up when we get a response from the other end.
3842 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3844 tp
->tcp_header_len
= sizeof(struct tcphdr
);
3845 if (READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_timestamps
))
3846 tp
->tcp_header_len
+= TCPOLEN_TSTAMP_ALIGNED
;
3848 tcp_ao_connect_init(sk
);
3850 /* If user gave his TCP_MAXSEG, record it to clamp */
3851 if (tp
->rx_opt
.user_mss
)
3852 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
3855 tcp_sync_mss(sk
, dst_mtu(dst
));
3857 tcp_ca_dst_init(sk
, dst
);
3859 if (!tp
->window_clamp
)
3860 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
3861 tp
->advmss
= tcp_mss_clamp(tp
, dst_metric_advmss(dst
));
3863 tcp_initialize_rcv_mss(sk
);
3865 /* limit the window selection if the user enforce a smaller rx buffer */
3866 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
3867 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
3868 tp
->window_clamp
= tcp_full_space(sk
);
3870 rcv_wnd
= tcp_rwnd_init_bpf(sk
);
3872 rcv_wnd
= dst_metric(dst
, RTAX_INITRWND
);
3874 tcp_select_initial_window(sk
, tcp_full_space(sk
),
3875 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
3878 READ_ONCE(sock_net(sk
)->ipv4
.sysctl_tcp_window_scaling
),
3882 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
3883 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
3885 WRITE_ONCE(sk
->sk_err
, 0);
3886 sock_reset_flag(sk
, SOCK_DONE
);
3889 tcp_write_queue_purge(sk
);
3890 tp
->snd_una
= tp
->write_seq
;
3891 tp
->snd_sml
= tp
->write_seq
;
3892 tp
->snd_up
= tp
->write_seq
;
3893 WRITE_ONCE(tp
->snd_nxt
, tp
->write_seq
);
3895 if (likely(!tp
->repair
))
3898 tp
->rcv_tstamp
= tcp_jiffies32
;
3899 tp
->rcv_wup
= tp
->rcv_nxt
;
3900 WRITE_ONCE(tp
->copied_seq
, tp
->rcv_nxt
);
3902 inet_csk(sk
)->icsk_rto
= tcp_timeout_init(sk
);
3903 inet_csk(sk
)->icsk_retransmits
= 0;
3904 tcp_clear_retrans(tp
);
3907 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
3909 struct tcp_sock
*tp
= tcp_sk(sk
);
3910 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
3912 tcb
->end_seq
+= skb
->len
;
3913 __skb_header_release(skb
);
3914 sk_wmem_queued_add(sk
, skb
->truesize
);
3915 sk_mem_charge(sk
, skb
->truesize
);
3916 WRITE_ONCE(tp
->write_seq
, tcb
->end_seq
);
3917 tp
->packets_out
+= tcp_skb_pcount(skb
);
3920 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
3921 * queue a data-only packet after the regular SYN, such that regular SYNs
3922 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3923 * only the SYN sequence, the data are retransmitted in the first ACK.
3924 * If cookie is not cached or other error occurs, falls back to send a
3925 * regular SYN with Fast Open cookie request option.
3927 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
3929 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3930 struct tcp_sock
*tp
= tcp_sk(sk
);
3931 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
3932 struct page_frag
*pfrag
= sk_page_frag(sk
);
3933 struct sk_buff
*syn_data
;
3936 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
3937 if (!tcp_fastopen_cookie_check(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
))
3940 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3941 * user-MSS. Reserve maximum option space for middleboxes that add
3942 * private TCP options. The cost is reduced data space in SYN :(
3944 tp
->rx_opt
.mss_clamp
= tcp_mss_clamp(tp
, tp
->rx_opt
.mss_clamp
);
3945 /* Sync mss_cache after updating the mss_clamp */
3946 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
3948 space
= __tcp_mtu_to_mss(sk
, icsk
->icsk_pmtu_cookie
) -
3949 MAX_TCP_OPTION_SPACE
;
3951 space
= min_t(size_t, space
, fo
->size
);
3954 !skb_page_frag_refill(min_t(size_t, space
, PAGE_SIZE
),
3955 pfrag
, sk
->sk_allocation
))
3957 syn_data
= tcp_stream_alloc_skb(sk
, sk
->sk_allocation
, false);
3960 memcpy(syn_data
->cb
, syn
->cb
, sizeof(syn
->cb
));
3962 space
= min_t(size_t, space
, pfrag
->size
- pfrag
->offset
);
3963 space
= tcp_wmem_schedule(sk
, space
);
3966 space
= copy_page_from_iter(pfrag
->page
, pfrag
->offset
,
3967 space
, &fo
->data
->msg_iter
);
3968 if (unlikely(!space
)) {
3969 tcp_skb_tsorted_anchor_cleanup(syn_data
);
3970 kfree_skb(syn_data
);
3973 skb_fill_page_desc(syn_data
, 0, pfrag
->page
,
3974 pfrag
->offset
, space
);
3975 page_ref_inc(pfrag
->page
);
3976 pfrag
->offset
+= space
;
3977 skb_len_add(syn_data
, space
);
3978 skb_zcopy_set(syn_data
, fo
->uarg
, NULL
);
3980 /* No more data pending in inet_wait_for_connect() */
3981 if (space
== fo
->size
)
3985 tcp_connect_queue_skb(sk
, syn_data
);
3987 tcp_chrono_start(sk
, TCP_CHRONO_BUSY
);
3989 err
= tcp_transmit_skb(sk
, syn_data
, 1, sk
->sk_allocation
);
3991 skb_set_delivery_time(syn
, syn_data
->skb_mstamp_ns
, true);
3993 /* Now full SYN+DATA was cloned and sent (or not),
3994 * remove the SYN from the original skb (syn_data)
3995 * we keep in write queue in case of a retransmit, as we
3996 * also have the SYN packet (with no data) in the same queue.
3998 TCP_SKB_CB(syn_data
)->seq
++;
3999 TCP_SKB_CB(syn_data
)->tcp_flags
= TCPHDR_ACK
| TCPHDR_PSH
;
4001 tp
->syn_data
= (fo
->copied
> 0);
4002 tcp_rbtree_insert(&sk
->tcp_rtx_queue
, syn_data
);
4003 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
);
4007 /* data was not sent, put it in write_queue */
4008 __skb_queue_tail(&sk
->sk_write_queue
, syn_data
);
4009 tp
->packets_out
-= tcp_skb_pcount(syn_data
);
4012 /* Send a regular SYN with Fast Open cookie request option */
4013 if (fo
->cookie
.len
> 0)
4015 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
4017 tp
->syn_fastopen
= 0;
4019 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
4023 /* Build a SYN and send it off. */
4024 int tcp_connect(struct sock
*sk
)
4026 struct tcp_sock
*tp
= tcp_sk(sk
);
4027 struct sk_buff
*buff
;
4030 tcp_call_bpf(sk
, BPF_SOCK_OPS_TCP_CONNECT_CB
, 0, NULL
);
4032 #if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
4033 /* Has to be checked late, after setting daddr/saddr/ops.
4034 * Return error if the peer has both a md5 and a tcp-ao key
4035 * configured as this is ambiguous.
4037 if (unlikely(rcu_dereference_protected(tp
->md5sig_info
,
4038 lockdep_sock_is_held(sk
)))) {
4039 bool needs_ao
= !!tp
->af_specific
->ao_lookup(sk
, sk
, -1, -1);
4040 bool needs_md5
= !!tp
->af_specific
->md5_lookup(sk
, sk
);
4041 struct tcp_ao_info
*ao_info
;
4043 ao_info
= rcu_dereference_check(tp
->ao_info
,
4044 lockdep_sock_is_held(sk
));
4046 /* This is an extra check: tcp_ao_required() in
4047 * tcp_v{4,6}_parse_md5_keys() should prevent adding
4048 * md5 keys on ao_required socket.
4050 needs_ao
|= ao_info
->ao_required
;
4051 WARN_ON_ONCE(ao_info
->ao_required
&& needs_md5
);
4053 if (needs_md5
&& needs_ao
)
4054 return -EKEYREJECTED
;
4056 /* If we have a matching md5 key and no matching tcp-ao key
4057 * then free up ao_info if allocated.
4060 tcp_ao_destroy_sock(sk
, false);
4061 } else if (needs_ao
) {
4062 tcp_clear_md5_list(sk
);
4063 kfree(rcu_replace_pointer(tp
->md5sig_info
, NULL
,
4064 lockdep_sock_is_held(sk
)));
4068 #ifdef CONFIG_TCP_AO
4069 if (unlikely(rcu_dereference_protected(tp
->ao_info
,
4070 lockdep_sock_is_held(sk
)))) {
4071 /* Don't allow connecting if ao is configured but no
4072 * matching key is found.
4074 if (!tp
->af_specific
->ao_lookup(sk
, sk
, -1, -1))
4075 return -EKEYREJECTED
;
4079 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
4080 return -EHOSTUNREACH
; /* Routing failure or similar. */
4082 tcp_connect_init(sk
);
4084 if (unlikely(tp
->repair
)) {
4085 tcp_finish_connect(sk
, NULL
);
4089 buff
= tcp_stream_alloc_skb(sk
, sk
->sk_allocation
, true);
4090 if (unlikely(!buff
))
4093 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
4094 tcp_mstamp_refresh(tp
);
4095 tp
->retrans_stamp
= tcp_time_stamp_ts(tp
);
4096 tcp_connect_queue_skb(sk
, buff
);
4097 tcp_ecn_send_syn(sk
, buff
);
4098 tcp_rbtree_insert(&sk
->tcp_rtx_queue
, buff
);
4100 /* Send off SYN; include data in Fast Open. */
4101 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
4102 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
4103 if (err
== -ECONNREFUSED
)
4106 /* We change tp->snd_nxt after the tcp_transmit_skb() call
4107 * in order to make this packet get counted in tcpOutSegs.
4109 WRITE_ONCE(tp
->snd_nxt
, tp
->write_seq
);
4110 tp
->pushed_seq
= tp
->write_seq
;
4111 buff
= tcp_send_head(sk
);
4112 if (unlikely(buff
)) {
4113 WRITE_ONCE(tp
->snd_nxt
, TCP_SKB_CB(buff
)->seq
);
4114 tp
->pushed_seq
= TCP_SKB_CB(buff
)->seq
;
4116 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
4118 /* Timer for repeating the SYN until an answer. */
4119 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
4120 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
4123 EXPORT_SYMBOL(tcp_connect
);
4125 u32
tcp_delack_max(const struct sock
*sk
)
4127 const struct dst_entry
*dst
= __sk_dst_get(sk
);
4128 u32 delack_max
= inet_csk(sk
)->icsk_delack_max
;
4130 if (dst
&& dst_metric_locked(dst
, RTAX_RTO_MIN
)) {
4131 u32 rto_min
= dst_metric_rtt(dst
, RTAX_RTO_MIN
);
4132 u32 delack_from_rto_min
= max_t(int, 1, rto_min
- 1);
4134 delack_max
= min_t(u32
, delack_max
, delack_from_rto_min
);
4139 /* Send out a delayed ack, the caller does the policy checking
4140 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
4143 void tcp_send_delayed_ack(struct sock
*sk
)
4145 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4146 int ato
= icsk
->icsk_ack
.ato
;
4147 unsigned long timeout
;
4149 if (ato
> TCP_DELACK_MIN
) {
4150 const struct tcp_sock
*tp
= tcp_sk(sk
);
4151 int max_ato
= HZ
/ 2;
4153 if (inet_csk_in_pingpong_mode(sk
) ||
4154 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
4155 max_ato
= TCP_DELACK_MAX
;
4157 /* Slow path, intersegment interval is "high". */
4159 /* If some rtt estimate is known, use it to bound delayed ack.
4160 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
4164 int rtt
= max_t(int, usecs_to_jiffies(tp
->srtt_us
>> 3),
4171 ato
= min(ato
, max_ato
);
4174 ato
= min_t(u32
, ato
, tcp_delack_max(sk
));
4176 /* Stay within the limit we were given */
4177 timeout
= jiffies
+ ato
;
4179 /* Use new timeout only if there wasn't a older one earlier. */
4180 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
4181 /* If delack timer is about to expire, send ACK now. */
4182 if (time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
4187 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
4188 timeout
= icsk
->icsk_ack
.timeout
;
4190 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
4191 icsk
->icsk_ack
.timeout
= timeout
;
4192 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
4195 /* This routine sends an ack and also updates the window. */
4196 void __tcp_send_ack(struct sock
*sk
, u32 rcv_nxt
)
4198 struct sk_buff
*buff
;
4200 /* If we have been reset, we may not send again. */
4201 if (sk
->sk_state
== TCP_CLOSE
)
4204 /* We are not putting this on the write queue, so
4205 * tcp_transmit_skb() will set the ownership to this
4208 buff
= alloc_skb(MAX_TCP_HEADER
,
4209 sk_gfp_mask(sk
, GFP_ATOMIC
| __GFP_NOWARN
));
4210 if (unlikely(!buff
)) {
4211 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4212 unsigned long delay
;
4214 delay
= TCP_DELACK_MAX
<< icsk
->icsk_ack
.retry
;
4215 if (delay
< TCP_RTO_MAX
)
4216 icsk
->icsk_ack
.retry
++;
4217 inet_csk_schedule_ack(sk
);
4218 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4219 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
, delay
, TCP_RTO_MAX
);
4223 /* Reserve space for headers and prepare control bits. */
4224 skb_reserve(buff
, MAX_TCP_HEADER
);
4225 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
4227 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
4229 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
4231 skb_set_tcp_pure_ack(buff
);
4233 /* Send it off, this clears delayed acks for us. */
4234 __tcp_transmit_skb(sk
, buff
, 0, (__force gfp_t
)0, rcv_nxt
);
4236 EXPORT_SYMBOL_GPL(__tcp_send_ack
);
4238 void tcp_send_ack(struct sock
*sk
)
4240 __tcp_send_ack(sk
, tcp_sk(sk
)->rcv_nxt
);
4243 /* This routine sends a packet with an out of date sequence
4244 * number. It assumes the other end will try to ack it.
4246 * Question: what should we make while urgent mode?
4247 * 4.4BSD forces sending single byte of data. We cannot send
4248 * out of window data, because we have SND.NXT==SND.MAX...
4250 * Current solution: to send TWO zero-length segments in urgent mode:
4251 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
4252 * out-of-date with SND.UNA-1 to probe window.
4254 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
, int mib
)
4256 struct tcp_sock
*tp
= tcp_sk(sk
);
4257 struct sk_buff
*skb
;
4259 /* We don't queue it, tcp_transmit_skb() sets ownership. */
4260 skb
= alloc_skb(MAX_TCP_HEADER
,
4261 sk_gfp_mask(sk
, GFP_ATOMIC
| __GFP_NOWARN
));
4265 /* Reserve space for headers and set control bits. */
4266 skb_reserve(skb
, MAX_TCP_HEADER
);
4267 /* Use a previous sequence. This should cause the other
4268 * end to send an ack. Don't queue or clone SKB, just
4271 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
4272 NET_INC_STATS(sock_net(sk
), mib
);
4273 return tcp_transmit_skb(sk
, skb
, 0, (__force gfp_t
)0);
4276 /* Called from setsockopt( ... TCP_REPAIR ) */
4277 void tcp_send_window_probe(struct sock
*sk
)
4279 if (sk
->sk_state
== TCP_ESTABLISHED
) {
4280 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
4281 tcp_mstamp_refresh(tcp_sk(sk
));
4282 tcp_xmit_probe_skb(sk
, 0, LINUX_MIB_TCPWINPROBE
);
4286 /* Initiate keepalive or window probe from timer. */
4287 int tcp_write_wakeup(struct sock
*sk
, int mib
)
4289 struct tcp_sock
*tp
= tcp_sk(sk
);
4290 struct sk_buff
*skb
;
4292 if (sk
->sk_state
== TCP_CLOSE
)
4295 skb
= tcp_send_head(sk
);
4296 if (skb
&& before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
4298 unsigned int mss
= tcp_current_mss(sk
);
4299 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
4301 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
4302 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
4304 /* We are probing the opening of a window
4305 * but the window size is != 0
4306 * must have been a result SWS avoidance ( sender )
4308 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
4310 seg_size
= min(seg_size
, mss
);
4311 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
4312 if (tcp_fragment(sk
, TCP_FRAG_IN_WRITE_QUEUE
,
4313 skb
, seg_size
, mss
, GFP_ATOMIC
))
4315 } else if (!tcp_skb_pcount(skb
))
4316 tcp_set_skb_tso_segs(skb
, mss
);
4318 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
4319 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
4321 tcp_event_new_data_sent(sk
, skb
);
4324 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
4325 tcp_xmit_probe_skb(sk
, 1, mib
);
4326 return tcp_xmit_probe_skb(sk
, 0, mib
);
4330 /* A window probe timeout has occurred. If window is not closed send
4331 * a partial packet else a zero probe.
4333 void tcp_send_probe0(struct sock
*sk
)
4335 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4336 struct tcp_sock
*tp
= tcp_sk(sk
);
4337 struct net
*net
= sock_net(sk
);
4338 unsigned long timeout
;
4341 err
= tcp_write_wakeup(sk
, LINUX_MIB_TCPWINPROBE
);
4343 if (tp
->packets_out
|| tcp_write_queue_empty(sk
)) {
4344 /* Cancel probe timer, if it is not required. */
4345 icsk
->icsk_probes_out
= 0;
4346 icsk
->icsk_backoff
= 0;
4347 icsk
->icsk_probes_tstamp
= 0;
4351 icsk
->icsk_probes_out
++;
4353 if (icsk
->icsk_backoff
< READ_ONCE(net
->ipv4
.sysctl_tcp_retries2
))
4354 icsk
->icsk_backoff
++;
4355 timeout
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
4357 /* If packet was not sent due to local congestion,
4358 * Let senders fight for local resources conservatively.
4360 timeout
= TCP_RESOURCE_PROBE_INTERVAL
;
4363 timeout
= tcp_clamp_probe0_to_user_timeout(sk
, timeout
);
4364 tcp_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
, timeout
, TCP_RTO_MAX
);
4367 int tcp_rtx_synack(const struct sock
*sk
, struct request_sock
*req
)
4369 const struct tcp_request_sock_ops
*af_ops
= tcp_rsk(req
)->af_specific
;
4373 /* Paired with WRITE_ONCE() in sock_setsockopt() */
4374 if (READ_ONCE(sk
->sk_txrehash
) == SOCK_TXREHASH_ENABLED
)
4375 WRITE_ONCE(tcp_rsk(req
)->txhash
, net_tx_rndhash());
4376 res
= af_ops
->send_synack(sk
, NULL
, &fl
, req
, NULL
, TCP_SYNACK_NORMAL
,
4379 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
4380 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
4381 if (unlikely(tcp_passive_fastopen(sk
))) {
4382 /* sk has const attribute because listeners are lockless.
4383 * However in this case, we are dealing with a passive fastopen
4384 * socket thus we can change total_retrans value.
4386 tcp_sk_rw(sk
)->total_retrans
++;
4388 trace_tcp_retransmit_synack(sk
, req
);
4392 EXPORT_SYMBOL(tcp_rtx_synack
);