Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
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.
6 : *
7 : * Implementation of the Transmission Control Protocol(TCP).
8 : *
9 : * Authors: Ross Biro
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>
20 : */
21 :
22 : /*
23 : * Changes: Pedro Roque : Retransmit queue handled by TCP.
24 : * : Fragmentation on mtu decrease
25 : * : Segment collapse on retransmit
26 : * : AF independence
27 : *
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
35 : *
36 : */
37 :
38 : #define pr_fmt(fmt) "TCP: " fmt
39 :
40 : #include <net/tcp.h>
41 : #include <net/mptcp.h>
42 :
43 : #include <linux/compiler.h>
44 : #include <linux/gfp.h>
45 : #include <linux/module.h>
46 : #include <linux/static_key.h>
47 :
48 : #include <trace/events/tcp.h>
49 :
50 : /* Refresh clocks of a TCP socket,
51 : * ensuring monotically increasing values.
52 : */
53 1062 : void tcp_mstamp_refresh(struct tcp_sock *tp)
54 : {
55 640 : u64 val = tcp_clock_ns();
56 :
57 1062 : tp->tcp_clock_cache = val;
58 422 : tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
59 640 : }
60 :
61 : static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
62 : int push_one, gfp_t gfp);
63 :
64 : /* Account for new data that has been sent to the network. */
65 364 : static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
66 : {
67 364 : struct inet_connection_sock *icsk = inet_csk(sk);
68 364 : struct tcp_sock *tp = tcp_sk(sk);
69 364 : unsigned int prior_packets = tp->packets_out;
70 :
71 364 : WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
72 :
73 364 : __skb_unlink(skb, &sk->sk_write_queue);
74 364 : tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
75 :
76 364 : if (tp->highest_sack == NULL)
77 234 : tp->highest_sack = skb;
78 :
79 364 : tp->packets_out += tcp_skb_pcount(skb);
80 364 : if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
81 234 : tcp_rearm_rto(sk);
82 :
83 364 : NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
84 : tcp_skb_pcount(skb));
85 364 : }
86 :
87 : /* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
88 : * window scaling factor due to loss of precision.
89 : * If window has been shrunk, what should we make? It is not clear at all.
90 : * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
91 : * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
92 : * invalid. OK, let's make this for now:
93 : */
94 62 : static inline __u32 tcp_acceptable_seq(const struct sock *sk)
95 : {
96 62 : const struct tcp_sock *tp = tcp_sk(sk);
97 :
98 62 : if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
99 0 : (tp->rx_opt.wscale_ok &&
100 0 : ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
101 : return tp->snd_nxt;
102 : else
103 0 : return tcp_wnd_end(tp);
104 : }
105 :
106 : /* Calculate mss to advertise in SYN segment.
107 : * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
108 : *
109 : * 1. It is independent of path mtu.
110 : * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
111 : * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
112 : * attached devices, because some buggy hosts are confused by
113 : * large MSS.
114 : * 4. We do not make 3, we advertise MSS, calculated from first
115 : * hop device mtu, but allow to raise it to ip_rt_min_advmss.
116 : * This may be overridden via information stored in routing table.
117 : * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
118 : * probably even Jumbo".
119 : */
120 0 : static __u16 tcp_advertise_mss(struct sock *sk)
121 : {
122 0 : struct tcp_sock *tp = tcp_sk(sk);
123 0 : const struct dst_entry *dst = __sk_dst_get(sk);
124 0 : int mss = tp->advmss;
125 :
126 0 : if (dst) {
127 0 : unsigned int metric = dst_metric_advmss(dst);
128 :
129 0 : if (metric < mss) {
130 0 : mss = metric;
131 0 : tp->advmss = mss;
132 : }
133 : }
134 :
135 0 : return (__u16)mss;
136 : }
137 :
138 : /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
139 : * This is the first part of cwnd validation mechanism.
140 : */
141 4 : void tcp_cwnd_restart(struct sock *sk, s32 delta)
142 : {
143 4 : struct tcp_sock *tp = tcp_sk(sk);
144 4 : u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
145 4 : u32 cwnd = tp->snd_cwnd;
146 :
147 4 : tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
148 :
149 4 : tp->snd_ssthresh = tcp_current_ssthresh(sk);
150 4 : restart_cwnd = min(restart_cwnd, cwnd);
151 :
152 4 : while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
153 0 : cwnd >>= 1;
154 4 : tp->snd_cwnd = max(cwnd, restart_cwnd);
155 4 : tp->snd_cwnd_stamp = tcp_jiffies32;
156 4 : tp->snd_cwnd_used = 0;
157 4 : }
158 :
159 : /* Congestion state accounting after a packet has been sent. */
160 361 : static void tcp_event_data_sent(struct tcp_sock *tp,
161 : struct sock *sk)
162 : {
163 361 : struct inet_connection_sock *icsk = inet_csk(sk);
164 361 : const u32 now = tcp_jiffies32;
165 :
166 361 : if (tcp_packets_in_flight(tp) == 0)
167 231 : tcp_ca_event(sk, CA_EVENT_TX_START);
168 :
169 : /* If this is the first data packet sent in response to the
170 : * previous received data,
171 : * and it is a reply for ato after last received packet,
172 : * increase pingpong count.
173 : */
174 361 : if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) &&
175 16 : (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
176 15 : inet_csk_inc_pingpong_cnt(sk);
177 :
178 361 : tp->lsndtime = now;
179 361 : }
180 :
181 : /* Account for an ACK we sent. */
182 426 : static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
183 : u32 rcv_nxt)
184 : {
185 426 : struct tcp_sock *tp = tcp_sk(sk);
186 :
187 426 : if (unlikely(tp->compressed_ack)) {
188 0 : NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
189 : tp->compressed_ack);
190 0 : tp->compressed_ack = 0;
191 0 : if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
192 0 : __sock_put(sk);
193 : }
194 :
195 426 : if (unlikely(rcv_nxt != tp->rcv_nxt))
196 : return; /* Special ACK sent by DCTCP to reflect ECN */
197 426 : tcp_dec_quickack_mode(sk, pkts);
198 426 : inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
199 : }
200 :
201 : /* Determine a window scaling and initial window to offer.
202 : * Based on the assumption that the given amount of space
203 : * will be offered. Store the results in the tp structure.
204 : * NOTE: for smooth operation initial space offering should
205 : * be a multiple of mss if possible. We assume here that mss >= 1.
206 : * This MUST be enforced by all callers.
207 : */
208 4 : void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
209 : __u32 *rcv_wnd, __u32 *window_clamp,
210 : int wscale_ok, __u8 *rcv_wscale,
211 : __u32 init_rcv_wnd)
212 : {
213 4 : unsigned int space = (__space < 0 ? 0 : __space);
214 :
215 : /* If no clamp set the clamp to the max possible scaled window */
216 4 : if (*window_clamp == 0)
217 4 : (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
218 4 : space = min(*window_clamp, space);
219 :
220 : /* Quantize space offering to a multiple of mss if possible. */
221 4 : if (space > mss)
222 4 : space = rounddown(space, mss);
223 :
224 : /* NOTE: offering an initial window larger than 32767
225 : * will break some buggy TCP stacks. If the admin tells us
226 : * it is likely we could be speaking with such a buggy stack
227 : * we will truncate our initial window offering to 32K-1
228 : * unless the remote has sent us a window scaling option,
229 : * which we interpret as a sign the remote TCP is not
230 : * misinterpreting the window field as a signed quantity.
231 : */
232 4 : if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
233 0 : (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
234 : else
235 4 : (*rcv_wnd) = min_t(u32, space, U16_MAX);
236 :
237 4 : if (init_rcv_wnd)
238 0 : *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
239 :
240 4 : *rcv_wscale = 0;
241 4 : if (wscale_ok) {
242 : /* Set window scaling on max possible window */
243 0 : space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
244 0 : space = max_t(u32, space, sysctl_rmem_max);
245 0 : space = min_t(u32, space, *window_clamp);
246 0 : *rcv_wscale = clamp_t(int, ilog2(space) - 15,
247 : 0, TCP_MAX_WSCALE);
248 : }
249 : /* Set the clamp no higher than max representable value */
250 4 : (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
251 4 : }
252 : EXPORT_SYMBOL(tcp_select_initial_window);
253 :
254 : /* Chose a new window to advertise, update state in tcp_sock for the
255 : * socket, and return result with RFC1323 scaling applied. The return
256 : * value can be stuffed directly into th->window for an outgoing
257 : * frame.
258 : */
259 426 : static u16 tcp_select_window(struct sock *sk)
260 : {
261 426 : struct tcp_sock *tp = tcp_sk(sk);
262 426 : u32 old_win = tp->rcv_wnd;
263 426 : u32 cur_win = tcp_receive_window(tp);
264 426 : u32 new_win = __tcp_select_window(sk);
265 :
266 : /* Never shrink the offered window */
267 426 : if (new_win < cur_win) {
268 : /* Danger Will Robinson!
269 : * Don't update rcv_wup/rcv_wnd here or else
270 : * we will not be able to advertise a zero
271 : * window in time. --DaveM
272 : *
273 : * Relax Will Robinson.
274 : */
275 9 : if (new_win == 0)
276 9 : NET_INC_STATS(sock_net(sk),
277 : LINUX_MIB_TCPWANTZEROWINDOWADV);
278 9 : new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
279 : }
280 426 : tp->rcv_wnd = new_win;
281 426 : tp->rcv_wup = tp->rcv_nxt;
282 :
283 : /* Make sure we do not exceed the maximum possible
284 : * scaled window.
285 : */
286 426 : if (!tp->rx_opt.rcv_wscale &&
287 426 : sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
288 0 : new_win = min(new_win, MAX_TCP_WINDOW);
289 : else
290 426 : new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
291 :
292 : /* RFC1323 scaling applied */
293 426 : new_win >>= tp->rx_opt.rcv_wscale;
294 :
295 : /* If we advertise zero window, disable fast path. */
296 426 : if (new_win == 0) {
297 0 : tp->pred_flags = 0;
298 0 : if (old_win)
299 0 : NET_INC_STATS(sock_net(sk),
300 : LINUX_MIB_TCPTOZEROWINDOWADV);
301 426 : } else if (old_win == 0) {
302 426 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
303 : }
304 :
305 426 : return new_win;
306 : }
307 :
308 : /* Packet ECN state for a SYN-ACK */
309 0 : static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
310 : {
311 0 : const struct tcp_sock *tp = tcp_sk(sk);
312 :
313 0 : TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
314 0 : if (!(tp->ecn_flags & TCP_ECN_OK))
315 0 : TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
316 0 : else if (tcp_ca_needs_ecn(sk) ||
317 0 : tcp_bpf_ca_needs_ecn(sk))
318 0 : INET_ECN_xmit(sk);
319 0 : }
320 :
321 : /* Packet ECN state for a SYN. */
322 0 : static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
323 : {
324 0 : struct tcp_sock *tp = tcp_sk(sk);
325 0 : bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
326 0 : bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
327 0 : tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
328 :
329 0 : if (!use_ecn) {
330 0 : const struct dst_entry *dst = __sk_dst_get(sk);
331 :
332 0 : if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
333 0 : use_ecn = true;
334 : }
335 :
336 0 : tp->ecn_flags = 0;
337 :
338 0 : if (use_ecn) {
339 0 : TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
340 0 : tp->ecn_flags = TCP_ECN_OK;
341 0 : if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
342 0 : INET_ECN_xmit(sk);
343 : }
344 0 : }
345 :
346 0 : static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
347 : {
348 0 : if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
349 : /* tp->ecn_flags are cleared at a later point in time when
350 : * SYN ACK is ultimatively being received.
351 : */
352 0 : TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
353 : }
354 :
355 : static void
356 4 : tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
357 : {
358 4 : if (inet_rsk(req)->ecn_ok)
359 0 : th->ece = 1;
360 : }
361 :
362 : /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
363 : * be sent.
364 : */
365 426 : static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
366 : struct tcphdr *th, int tcp_header_len)
367 : {
368 426 : struct tcp_sock *tp = tcp_sk(sk);
369 :
370 426 : if (tp->ecn_flags & TCP_ECN_OK) {
371 : /* Not-retransmitted data segment: set ECT and inject CWR. */
372 0 : if (skb->len != tcp_header_len &&
373 0 : !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
374 0 : INET_ECN_xmit(sk);
375 0 : if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
376 0 : tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
377 0 : th->cwr = 1;
378 0 : skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
379 : }
380 0 : } else if (!tcp_ca_needs_ecn(sk)) {
381 : /* ACK or retransmitted segment: clear ECT|CE */
382 0 : INET_ECN_dontxmit(sk);
383 : }
384 0 : if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
385 0 : th->ece = 1;
386 : }
387 426 : }
388 :
389 : /* Constructs common control bits of non-data skb. If SYN/FIN is present,
390 : * auto increment end seqno.
391 : */
392 65 : static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
393 : {
394 65 : skb->ip_summed = CHECKSUM_PARTIAL;
395 :
396 65 : TCP_SKB_CB(skb)->tcp_flags = flags;
397 65 : TCP_SKB_CB(skb)->sacked = 0;
398 :
399 65 : tcp_skb_pcount_set(skb, 1);
400 :
401 65 : TCP_SKB_CB(skb)->seq = seq;
402 65 : if (flags & (TCPHDR_SYN | TCPHDR_FIN))
403 3 : seq++;
404 65 : TCP_SKB_CB(skb)->end_seq = seq;
405 : }
406 :
407 792 : static inline bool tcp_urg_mode(const struct tcp_sock *tp)
408 : {
409 792 : return tp->snd_una != tp->snd_up;
410 : }
411 :
412 : #define OPTION_SACK_ADVERTISE (1 << 0)
413 : #define OPTION_TS (1 << 1)
414 : #define OPTION_MD5 (1 << 2)
415 : #define OPTION_WSCALE (1 << 3)
416 : #define OPTION_FAST_OPEN_COOKIE (1 << 8)
417 : #define OPTION_SMC (1 << 9)
418 : #define OPTION_MPTCP (1 << 10)
419 :
420 430 : static void smc_options_write(__be32 *ptr, u16 *options)
421 : {
422 : #if IS_ENABLED(CONFIG_SMC)
423 : if (static_branch_unlikely(&tcp_have_smc)) {
424 : if (unlikely(OPTION_SMC & *options)) {
425 : *ptr++ = htonl((TCPOPT_NOP << 24) |
426 : (TCPOPT_NOP << 16) |
427 : (TCPOPT_EXP << 8) |
428 : (TCPOLEN_EXP_SMC_BASE));
429 : *ptr++ = htonl(TCPOPT_SMC_MAGIC);
430 : }
431 : }
432 : #endif
433 430 : }
434 :
435 : struct tcp_out_options {
436 : u16 options; /* bit field of OPTION_* */
437 : u16 mss; /* 0 to disable */
438 : u8 ws; /* window scale, 0 to disable */
439 : u8 num_sack_blocks; /* number of SACK blocks to include */
440 : u8 hash_size; /* bytes in hash_location */
441 : u8 bpf_opt_len; /* length of BPF hdr option */
442 : __u8 *hash_location; /* temporary pointer, overloaded */
443 : __u32 tsval, tsecr; /* need to include OPTION_TS */
444 : struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
445 : struct mptcp_out_options mptcp;
446 : };
447 :
448 430 : static void mptcp_options_write(__be32 *ptr, const struct tcp_sock *tp,
449 : struct tcp_out_options *opts)
450 : {
451 : #if IS_ENABLED(CONFIG_MPTCP)
452 : if (unlikely(OPTION_MPTCP & opts->options))
453 : mptcp_write_options(ptr, tp, &opts->mptcp);
454 : #endif
455 430 : }
456 :
457 : #ifdef CONFIG_CGROUP_BPF
458 : static int bpf_skops_write_hdr_opt_arg0(struct sk_buff *skb,
459 : enum tcp_synack_type synack_type)
460 : {
461 : if (unlikely(!skb))
462 : return BPF_WRITE_HDR_TCP_CURRENT_MSS;
463 :
464 : if (unlikely(synack_type == TCP_SYNACK_COOKIE))
465 : return BPF_WRITE_HDR_TCP_SYNACK_COOKIE;
466 :
467 : return 0;
468 : }
469 :
470 : /* req, syn_skb and synack_type are used when writing synack */
471 : static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
472 : struct request_sock *req,
473 : struct sk_buff *syn_skb,
474 : enum tcp_synack_type synack_type,
475 : struct tcp_out_options *opts,
476 : unsigned int *remaining)
477 : {
478 : struct bpf_sock_ops_kern sock_ops;
479 : int err;
480 :
481 : if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
482 : BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) ||
483 : !*remaining)
484 : return;
485 :
486 : /* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
487 :
488 : /* init sock_ops */
489 : memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
490 :
491 : sock_ops.op = BPF_SOCK_OPS_HDR_OPT_LEN_CB;
492 :
493 : if (req) {
494 : /* The listen "sk" cannot be passed here because
495 : * it is not locked. It would not make too much
496 : * sense to do bpf_setsockopt(listen_sk) based
497 : * on individual connection request also.
498 : *
499 : * Thus, "req" is passed here and the cgroup-bpf-progs
500 : * of the listen "sk" will be run.
501 : *
502 : * "req" is also used here for fastopen even the "sk" here is
503 : * a fullsock "child" sk. It is to keep the behavior
504 : * consistent between fastopen and non-fastopen on
505 : * the bpf programming side.
506 : */
507 : sock_ops.sk = (struct sock *)req;
508 : sock_ops.syn_skb = syn_skb;
509 : } else {
510 : sock_owned_by_me(sk);
511 :
512 : sock_ops.is_fullsock = 1;
513 : sock_ops.sk = sk;
514 : }
515 :
516 : sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
517 : sock_ops.remaining_opt_len = *remaining;
518 : /* tcp_current_mss() does not pass a skb */
519 : if (skb)
520 : bpf_skops_init_skb(&sock_ops, skb, 0);
521 :
522 : err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
523 :
524 : if (err || sock_ops.remaining_opt_len == *remaining)
525 : return;
526 :
527 : opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len;
528 : /* round up to 4 bytes */
529 : opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3;
530 :
531 : *remaining -= opts->bpf_opt_len;
532 : }
533 :
534 : static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
535 : struct request_sock *req,
536 : struct sk_buff *syn_skb,
537 : enum tcp_synack_type synack_type,
538 : struct tcp_out_options *opts)
539 : {
540 : u8 first_opt_off, nr_written, max_opt_len = opts->bpf_opt_len;
541 : struct bpf_sock_ops_kern sock_ops;
542 : int err;
543 :
544 : if (likely(!max_opt_len))
545 : return;
546 :
547 : memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
548 :
549 : sock_ops.op = BPF_SOCK_OPS_WRITE_HDR_OPT_CB;
550 :
551 : if (req) {
552 : sock_ops.sk = (struct sock *)req;
553 : sock_ops.syn_skb = syn_skb;
554 : } else {
555 : sock_owned_by_me(sk);
556 :
557 : sock_ops.is_fullsock = 1;
558 : sock_ops.sk = sk;
559 : }
560 :
561 : sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
562 : sock_ops.remaining_opt_len = max_opt_len;
563 : first_opt_off = tcp_hdrlen(skb) - max_opt_len;
564 : bpf_skops_init_skb(&sock_ops, skb, first_opt_off);
565 :
566 : err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
567 :
568 : if (err)
569 : nr_written = 0;
570 : else
571 : nr_written = max_opt_len - sock_ops.remaining_opt_len;
572 :
573 : if (nr_written < max_opt_len)
574 : memset(skb->data + first_opt_off + nr_written, TCPOPT_NOP,
575 : max_opt_len - nr_written);
576 : }
577 : #else
578 4 : static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
579 : struct request_sock *req,
580 : struct sk_buff *syn_skb,
581 : enum tcp_synack_type synack_type,
582 : struct tcp_out_options *opts,
583 : unsigned int *remaining)
584 : {
585 4 : }
586 :
587 430 : static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
588 : struct request_sock *req,
589 : struct sk_buff *syn_skb,
590 : enum tcp_synack_type synack_type,
591 : struct tcp_out_options *opts)
592 : {
593 430 : }
594 : #endif
595 :
596 : /* Write previously computed TCP options to the packet.
597 : *
598 : * Beware: Something in the Internet is very sensitive to the ordering of
599 : * TCP options, we learned this through the hard way, so be careful here.
600 : * Luckily we can at least blame others for their non-compliance but from
601 : * inter-operability perspective it seems that we're somewhat stuck with
602 : * the ordering which we have been using if we want to keep working with
603 : * those broken things (not that it currently hurts anybody as there isn't
604 : * particular reason why the ordering would need to be changed).
605 : *
606 : * At least SACK_PERM as the first option is known to lead to a disaster
607 : * (but it may well be that other scenarios fail similarly).
608 : */
609 430 : static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
610 : struct tcp_out_options *opts)
611 : {
612 430 : u16 options = opts->options; /* mungable copy */
613 :
614 430 : if (unlikely(OPTION_MD5 & options)) {
615 0 : *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
616 : (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
617 : /* overload cookie hash location */
618 0 : opts->hash_location = (__u8 *)ptr;
619 0 : ptr += 4;
620 : }
621 :
622 430 : if (unlikely(opts->mss)) {
623 4 : *ptr++ = htonl((TCPOPT_MSS << 24) |
624 : (TCPOLEN_MSS << 16) |
625 : opts->mss);
626 : }
627 :
628 430 : if (likely(OPTION_TS & options)) {
629 0 : if (unlikely(OPTION_SACK_ADVERTISE & options)) {
630 0 : *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
631 : (TCPOLEN_SACK_PERM << 16) |
632 : (TCPOPT_TIMESTAMP << 8) |
633 : TCPOLEN_TIMESTAMP);
634 0 : options &= ~OPTION_SACK_ADVERTISE;
635 : } else {
636 0 : *ptr++ = htonl((TCPOPT_NOP << 24) |
637 : (TCPOPT_NOP << 16) |
638 : (TCPOPT_TIMESTAMP << 8) |
639 : TCPOLEN_TIMESTAMP);
640 : }
641 0 : *ptr++ = htonl(opts->tsval);
642 0 : *ptr++ = htonl(opts->tsecr);
643 : }
644 :
645 430 : if (unlikely(OPTION_SACK_ADVERTISE & options)) {
646 0 : *ptr++ = htonl((TCPOPT_NOP << 24) |
647 : (TCPOPT_NOP << 16) |
648 : (TCPOPT_SACK_PERM << 8) |
649 : TCPOLEN_SACK_PERM);
650 : }
651 :
652 430 : if (unlikely(OPTION_WSCALE & options)) {
653 0 : *ptr++ = htonl((TCPOPT_NOP << 24) |
654 : (TCPOPT_WINDOW << 16) |
655 : (TCPOLEN_WINDOW << 8) |
656 : opts->ws);
657 : }
658 :
659 430 : if (unlikely(opts->num_sack_blocks)) {
660 0 : struct tcp_sack_block *sp = tp->rx_opt.dsack ?
661 0 : tp->duplicate_sack : tp->selective_acks;
662 0 : int this_sack;
663 :
664 0 : *ptr++ = htonl((TCPOPT_NOP << 24) |
665 : (TCPOPT_NOP << 16) |
666 : (TCPOPT_SACK << 8) |
667 : (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
668 : TCPOLEN_SACK_PERBLOCK)));
669 :
670 0 : for (this_sack = 0; this_sack < opts->num_sack_blocks;
671 0 : ++this_sack) {
672 0 : *ptr++ = htonl(sp[this_sack].start_seq);
673 0 : *ptr++ = htonl(sp[this_sack].end_seq);
674 : }
675 :
676 0 : tp->rx_opt.dsack = 0;
677 : }
678 :
679 430 : if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
680 0 : struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
681 0 : u8 *p = (u8 *)ptr;
682 0 : u32 len; /* Fast Open option length */
683 :
684 0 : if (foc->exp) {
685 0 : len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
686 0 : *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
687 : TCPOPT_FASTOPEN_MAGIC);
688 0 : p += TCPOLEN_EXP_FASTOPEN_BASE;
689 : } else {
690 0 : len = TCPOLEN_FASTOPEN_BASE + foc->len;
691 0 : *p++ = TCPOPT_FASTOPEN;
692 0 : *p++ = len;
693 : }
694 :
695 0 : memcpy(p, foc->val, foc->len);
696 0 : if ((len & 3) == 2) {
697 0 : p[foc->len] = TCPOPT_NOP;
698 0 : p[foc->len + 1] = TCPOPT_NOP;
699 : }
700 0 : ptr += (len + 3) >> 2;
701 : }
702 :
703 430 : smc_options_write(ptr, &options);
704 :
705 430 : mptcp_options_write(ptr, tp, opts);
706 430 : }
707 :
708 0 : static void smc_set_option(const struct tcp_sock *tp,
709 : struct tcp_out_options *opts,
710 : unsigned int *remaining)
711 : {
712 : #if IS_ENABLED(CONFIG_SMC)
713 : if (static_branch_unlikely(&tcp_have_smc)) {
714 : if (tp->syn_smc) {
715 : if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
716 : opts->options |= OPTION_SMC;
717 : *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
718 : }
719 : }
720 : }
721 : #endif
722 0 : }
723 :
724 4 : static void smc_set_option_cond(const struct tcp_sock *tp,
725 : const struct inet_request_sock *ireq,
726 : struct tcp_out_options *opts,
727 : unsigned int *remaining)
728 : {
729 : #if IS_ENABLED(CONFIG_SMC)
730 : if (static_branch_unlikely(&tcp_have_smc)) {
731 : if (tp->syn_smc && ireq->smc_ok) {
732 : if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
733 : opts->options |= OPTION_SMC;
734 : *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
735 : }
736 : }
737 : }
738 : #endif
739 4 : }
740 :
741 4 : static void mptcp_set_option_cond(const struct request_sock *req,
742 : struct tcp_out_options *opts,
743 : unsigned int *remaining)
744 : {
745 4 : if (rsk_is_mptcp(req)) {
746 : unsigned int size;
747 :
748 : if (mptcp_synack_options(req, &size, &opts->mptcp)) {
749 : if (*remaining >= size) {
750 : opts->options |= OPTION_MPTCP;
751 : *remaining -= size;
752 : }
753 : }
754 : }
755 : }
756 :
757 : /* Compute TCP options for SYN packets. This is not the final
758 : * network wire format yet.
759 : */
760 0 : static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
761 : struct tcp_out_options *opts,
762 : struct tcp_md5sig_key **md5)
763 : {
764 0 : struct tcp_sock *tp = tcp_sk(sk);
765 0 : unsigned int remaining = MAX_TCP_OPTION_SPACE;
766 0 : struct tcp_fastopen_request *fastopen = tp->fastopen_req;
767 :
768 0 : *md5 = NULL;
769 : #ifdef CONFIG_TCP_MD5SIG
770 : if (static_branch_unlikely(&tcp_md5_needed) &&
771 : rcu_access_pointer(tp->md5sig_info)) {
772 : *md5 = tp->af_specific->md5_lookup(sk, sk);
773 : if (*md5) {
774 : opts->options |= OPTION_MD5;
775 : remaining -= TCPOLEN_MD5SIG_ALIGNED;
776 : }
777 : }
778 : #endif
779 :
780 : /* We always get an MSS option. The option bytes which will be seen in
781 : * normal data packets should timestamps be used, must be in the MSS
782 : * advertised. But we subtract them from tp->mss_cache so that
783 : * calculations in tcp_sendmsg are simpler etc. So account for this
784 : * fact here if necessary. If we don't do this correctly, as a
785 : * receiver we won't recognize data packets as being full sized when we
786 : * should, and thus we won't abide by the delayed ACK rules correctly.
787 : * SACKs don't matter, we never delay an ACK when we have any of those
788 : * going out. */
789 0 : opts->mss = tcp_advertise_mss(sk);
790 0 : remaining -= TCPOLEN_MSS_ALIGNED;
791 :
792 0 : if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
793 0 : opts->options |= OPTION_TS;
794 0 : opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
795 0 : opts->tsecr = tp->rx_opt.ts_recent;
796 0 : remaining -= TCPOLEN_TSTAMP_ALIGNED;
797 : }
798 0 : if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
799 0 : opts->ws = tp->rx_opt.rcv_wscale;
800 0 : opts->options |= OPTION_WSCALE;
801 0 : remaining -= TCPOLEN_WSCALE_ALIGNED;
802 : }
803 0 : if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
804 0 : opts->options |= OPTION_SACK_ADVERTISE;
805 0 : if (unlikely(!(OPTION_TS & opts->options)))
806 0 : remaining -= TCPOLEN_SACKPERM_ALIGNED;
807 : }
808 :
809 0 : if (fastopen && fastopen->cookie.len >= 0) {
810 0 : u32 need = fastopen->cookie.len;
811 :
812 0 : need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
813 : TCPOLEN_FASTOPEN_BASE;
814 0 : need = (need + 3) & ~3U; /* Align to 32 bits */
815 0 : if (remaining >= need) {
816 0 : opts->options |= OPTION_FAST_OPEN_COOKIE;
817 0 : opts->fastopen_cookie = &fastopen->cookie;
818 0 : remaining -= need;
819 0 : tp->syn_fastopen = 1;
820 0 : tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
821 : }
822 : }
823 :
824 0 : smc_set_option(tp, opts, &remaining);
825 :
826 0 : if (sk_is_mptcp(sk)) {
827 : unsigned int size;
828 :
829 : if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
830 : opts->options |= OPTION_MPTCP;
831 : remaining -= size;
832 : }
833 : }
834 :
835 0 : bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
836 :
837 0 : return MAX_TCP_OPTION_SPACE - remaining;
838 : }
839 :
840 : /* Set up TCP options for SYN-ACKs. */
841 4 : static unsigned int tcp_synack_options(const struct sock *sk,
842 : struct request_sock *req,
843 : unsigned int mss, struct sk_buff *skb,
844 : struct tcp_out_options *opts,
845 : const struct tcp_md5sig_key *md5,
846 : struct tcp_fastopen_cookie *foc,
847 : enum tcp_synack_type synack_type,
848 : struct sk_buff *syn_skb)
849 : {
850 4 : struct inet_request_sock *ireq = inet_rsk(req);
851 4 : unsigned int remaining = MAX_TCP_OPTION_SPACE;
852 :
853 : #ifdef CONFIG_TCP_MD5SIG
854 : if (md5) {
855 : opts->options |= OPTION_MD5;
856 : remaining -= TCPOLEN_MD5SIG_ALIGNED;
857 :
858 : /* We can't fit any SACK blocks in a packet with MD5 + TS
859 : * options. There was discussion about disabling SACK
860 : * rather than TS in order to fit in better with old,
861 : * buggy kernels, but that was deemed to be unnecessary.
862 : */
863 : if (synack_type != TCP_SYNACK_COOKIE)
864 : ireq->tstamp_ok &= !ireq->sack_ok;
865 : }
866 : #endif
867 :
868 : /* We always send an MSS option. */
869 4 : opts->mss = mss;
870 4 : remaining -= TCPOLEN_MSS_ALIGNED;
871 :
872 4 : if (likely(ireq->wscale_ok)) {
873 0 : opts->ws = ireq->rcv_wscale;
874 0 : opts->options |= OPTION_WSCALE;
875 0 : remaining -= TCPOLEN_WSCALE_ALIGNED;
876 : }
877 4 : if (likely(ireq->tstamp_ok)) {
878 0 : opts->options |= OPTION_TS;
879 0 : opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
880 0 : opts->tsecr = req->ts_recent;
881 0 : remaining -= TCPOLEN_TSTAMP_ALIGNED;
882 : }
883 4 : if (likely(ireq->sack_ok)) {
884 0 : opts->options |= OPTION_SACK_ADVERTISE;
885 0 : if (unlikely(!ireq->tstamp_ok))
886 0 : remaining -= TCPOLEN_SACKPERM_ALIGNED;
887 : }
888 4 : if (foc != NULL && foc->len >= 0) {
889 0 : u32 need = foc->len;
890 :
891 0 : need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
892 : TCPOLEN_FASTOPEN_BASE;
893 0 : need = (need + 3) & ~3U; /* Align to 32 bits */
894 0 : if (remaining >= need) {
895 0 : opts->options |= OPTION_FAST_OPEN_COOKIE;
896 0 : opts->fastopen_cookie = foc;
897 0 : remaining -= need;
898 : }
899 : }
900 :
901 4 : mptcp_set_option_cond(req, opts, &remaining);
902 :
903 4 : smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
904 :
905 4 : bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
906 : synack_type, opts, &remaining);
907 :
908 4 : return MAX_TCP_OPTION_SPACE - remaining;
909 : }
910 :
911 : /* Compute TCP options for ESTABLISHED sockets. This is not the
912 : * final wire format yet.
913 : */
914 922 : static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
915 : struct tcp_out_options *opts,
916 : struct tcp_md5sig_key **md5)
917 : {
918 922 : struct tcp_sock *tp = tcp_sk(sk);
919 922 : unsigned int size = 0;
920 922 : unsigned int eff_sacks;
921 :
922 922 : opts->options = 0;
923 :
924 922 : *md5 = NULL;
925 : #ifdef CONFIG_TCP_MD5SIG
926 : if (static_branch_unlikely(&tcp_md5_needed) &&
927 : rcu_access_pointer(tp->md5sig_info)) {
928 : *md5 = tp->af_specific->md5_lookup(sk, sk);
929 : if (*md5) {
930 : opts->options |= OPTION_MD5;
931 : size += TCPOLEN_MD5SIG_ALIGNED;
932 : }
933 : }
934 : #endif
935 :
936 922 : if (likely(tp->rx_opt.tstamp_ok)) {
937 0 : opts->options |= OPTION_TS;
938 0 : opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
939 0 : opts->tsecr = tp->rx_opt.ts_recent;
940 0 : size += TCPOLEN_TSTAMP_ALIGNED;
941 : }
942 :
943 : /* MPTCP options have precedence over SACK for the limited TCP
944 : * option space because a MPTCP connection would be forced to
945 : * fall back to regular TCP if a required multipath option is
946 : * missing. SACK still gets a chance to use whatever space is
947 : * left.
948 : */
949 922 : if (sk_is_mptcp(sk)) {
950 : unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
951 : unsigned int opt_size = 0;
952 :
953 : if (mptcp_established_options(sk, skb, &opt_size, remaining,
954 : &opts->mptcp)) {
955 : opts->options |= OPTION_MPTCP;
956 : size += opt_size;
957 : }
958 : }
959 :
960 922 : eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
961 922 : if (unlikely(eff_sacks)) {
962 0 : const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
963 0 : if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
964 : TCPOLEN_SACK_PERBLOCK))
965 : return size;
966 :
967 0 : opts->num_sack_blocks =
968 0 : min_t(unsigned int, eff_sacks,
969 : (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
970 : TCPOLEN_SACK_PERBLOCK);
971 :
972 0 : size += TCPOLEN_SACK_BASE_ALIGNED +
973 0 : opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
974 : }
975 :
976 922 : if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,
977 : BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) {
978 : unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
979 :
980 : bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
981 :
982 : size = MAX_TCP_OPTION_SPACE - remaining;
983 : }
984 :
985 922 : return size;
986 : }
987 :
988 :
989 : /* TCP SMALL QUEUES (TSQ)
990 : *
991 : * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
992 : * to reduce RTT and bufferbloat.
993 : * We do this using a special skb destructor (tcp_wfree).
994 : *
995 : * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
996 : * needs to be reallocated in a driver.
997 : * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
998 : *
999 : * Since transmit from skb destructor is forbidden, we use a tasklet
1000 : * to process all sockets that eventually need to send more skbs.
1001 : * We use one tasklet per cpu, with its own queue of sockets.
1002 : */
1003 : struct tsq_tasklet {
1004 : struct tasklet_struct tasklet;
1005 : struct list_head head; /* queue of tcp sockets */
1006 : };
1007 : static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
1008 :
1009 58 : static void tcp_tsq_write(struct sock *sk)
1010 : {
1011 58 : if ((1 << sk->sk_state) &
1012 : (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
1013 : TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
1014 58 : struct tcp_sock *tp = tcp_sk(sk);
1015 :
1016 58 : if (tp->lost_out > tp->retrans_out &&
1017 0 : tp->snd_cwnd > tcp_packets_in_flight(tp)) {
1018 0 : tcp_mstamp_refresh(tp);
1019 0 : tcp_xmit_retransmit_queue(sk);
1020 : }
1021 :
1022 58 : tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
1023 : 0, GFP_ATOMIC);
1024 : }
1025 58 : }
1026 :
1027 58 : static void tcp_tsq_handler(struct sock *sk)
1028 : {
1029 58 : bh_lock_sock(sk);
1030 58 : if (!sock_owned_by_user(sk))
1031 18 : tcp_tsq_write(sk);
1032 40 : else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
1033 40 : sock_hold(sk);
1034 58 : bh_unlock_sock(sk);
1035 58 : }
1036 : /*
1037 : * One tasklet per cpu tries to send more skbs.
1038 : * We run in tasklet context but need to disable irqs when
1039 : * transferring tsq->head because tcp_wfree() might
1040 : * interrupt us (non NAPI drivers)
1041 : */
1042 58 : static void tcp_tasklet_func(struct tasklet_struct *t)
1043 : {
1044 58 : struct tsq_tasklet *tsq = from_tasklet(tsq, t, tasklet);
1045 58 : LIST_HEAD(list);
1046 58 : unsigned long flags;
1047 58 : struct list_head *q, *n;
1048 58 : struct tcp_sock *tp;
1049 58 : struct sock *sk;
1050 :
1051 116 : local_irq_save(flags);
1052 58 : list_splice_init(&tsq->head, &list);
1053 58 : local_irq_restore(flags);
1054 :
1055 116 : list_for_each_safe(q, n, &list) {
1056 58 : tp = list_entry(q, struct tcp_sock, tsq_node);
1057 58 : list_del(&tp->tsq_node);
1058 :
1059 58 : sk = (struct sock *)tp;
1060 58 : smp_mb__before_atomic();
1061 58 : clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
1062 :
1063 58 : tcp_tsq_handler(sk);
1064 58 : sk_free(sk);
1065 : }
1066 58 : }
1067 :
1068 : #define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
1069 : TCPF_WRITE_TIMER_DEFERRED | \
1070 : TCPF_DELACK_TIMER_DEFERRED | \
1071 : TCPF_MTU_REDUCED_DEFERRED)
1072 : /**
1073 : * tcp_release_cb - tcp release_sock() callback
1074 : * @sk: socket
1075 : *
1076 : * called from release_sock() to perform protocol dependent
1077 : * actions before socket release.
1078 : */
1079 651 : void tcp_release_cb(struct sock *sk)
1080 : {
1081 651 : unsigned long flags, nflags;
1082 :
1083 : /* perform an atomic operation only if at least one flag is set */
1084 651 : do {
1085 651 : flags = sk->sk_tsq_flags;
1086 651 : if (!(flags & TCP_DEFERRED_ALL))
1087 : return;
1088 40 : nflags = flags & ~TCP_DEFERRED_ALL;
1089 40 : } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
1090 :
1091 40 : if (flags & TCPF_TSQ_DEFERRED) {
1092 40 : tcp_tsq_write(sk);
1093 40 : __sock_put(sk);
1094 : }
1095 : /* Here begins the tricky part :
1096 : * We are called from release_sock() with :
1097 : * 1) BH disabled
1098 : * 2) sk_lock.slock spinlock held
1099 : * 3) socket owned by us (sk->sk_lock.owned == 1)
1100 : *
1101 : * But following code is meant to be called from BH handlers,
1102 : * so we should keep BH disabled, but early release socket ownership
1103 : */
1104 40 : sock_release_ownership(sk);
1105 :
1106 40 : if (flags & TCPF_WRITE_TIMER_DEFERRED) {
1107 0 : tcp_write_timer_handler(sk);
1108 0 : __sock_put(sk);
1109 : }
1110 40 : if (flags & TCPF_DELACK_TIMER_DEFERRED) {
1111 0 : tcp_delack_timer_handler(sk);
1112 0 : __sock_put(sk);
1113 : }
1114 40 : if (flags & TCPF_MTU_REDUCED_DEFERRED) {
1115 0 : inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
1116 0 : __sock_put(sk);
1117 : }
1118 : }
1119 : EXPORT_SYMBOL(tcp_release_cb);
1120 :
1121 1 : void __init tcp_tasklet_init(void)
1122 : {
1123 1 : int i;
1124 :
1125 5 : for_each_possible_cpu(i) {
1126 4 : struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
1127 :
1128 4 : INIT_LIST_HEAD(&tsq->head);
1129 4 : tasklet_setup(&tsq->tasklet, tcp_tasklet_func);
1130 : }
1131 1 : }
1132 :
1133 : /*
1134 : * Write buffer destructor automatically called from kfree_skb.
1135 : * We can't xmit new skbs from this context, as we might already
1136 : * hold qdisc lock.
1137 : */
1138 364 : void tcp_wfree(struct sk_buff *skb)
1139 : {
1140 364 : struct sock *sk = skb->sk;
1141 364 : struct tcp_sock *tp = tcp_sk(sk);
1142 364 : unsigned long flags, nval, oval;
1143 :
1144 : /* Keep one reference on sk_wmem_alloc.
1145 : * Will be released by sk_free() from here or tcp_tasklet_func()
1146 : */
1147 364 : WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
1148 :
1149 : /* If this softirq is serviced by ksoftirqd, we are likely under stress.
1150 : * Wait until our queues (qdisc + devices) are drained.
1151 : * This gives :
1152 : * - less callbacks to tcp_write_xmit(), reducing stress (batches)
1153 : * - chance for incoming ACK (processed by another cpu maybe)
1154 : * to migrate this flow (skb->ooo_okay will be eventually set)
1155 : */
1156 403 : if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
1157 5 : goto out;
1158 :
1159 359 : for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
1160 359 : struct tsq_tasklet *tsq;
1161 359 : bool empty;
1162 :
1163 359 : if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
1164 301 : goto out;
1165 :
1166 58 : nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
1167 58 : nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
1168 58 : if (nval != oval)
1169 0 : continue;
1170 :
1171 : /* queue this socket to tasklet queue */
1172 116 : local_irq_save(flags);
1173 58 : tsq = this_cpu_ptr(&tsq_tasklet);
1174 58 : empty = list_empty(&tsq->head);
1175 58 : list_add(&tp->tsq_node, &tsq->head);
1176 58 : if (empty)
1177 58 : tasklet_schedule(&tsq->tasklet);
1178 58 : local_irq_restore(flags);
1179 : return;
1180 : }
1181 306 : out:
1182 306 : sk_free(sk);
1183 : }
1184 :
1185 : /* Note: Called under soft irq.
1186 : * We can call TCP stack right away, unless socket is owned by user.
1187 : */
1188 0 : enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
1189 : {
1190 0 : struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
1191 0 : struct sock *sk = (struct sock *)tp;
1192 :
1193 0 : tcp_tsq_handler(sk);
1194 0 : sock_put(sk);
1195 :
1196 0 : return HRTIMER_NORESTART;
1197 : }
1198 :
1199 364 : static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
1200 : u64 prior_wstamp)
1201 : {
1202 364 : struct tcp_sock *tp = tcp_sk(sk);
1203 :
1204 364 : if (sk->sk_pacing_status != SK_PACING_NONE) {
1205 0 : unsigned long rate = sk->sk_pacing_rate;
1206 :
1207 : /* Original sch_fq does not pace first 10 MSS
1208 : * Note that tp->data_segs_out overflows after 2^32 packets,
1209 : * this is a minor annoyance.
1210 : */
1211 0 : if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
1212 0 : u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
1213 0 : u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
1214 :
1215 : /* take into account OS jitter */
1216 0 : len_ns -= min_t(u64, len_ns / 2, credit);
1217 0 : tp->tcp_wstamp_ns += len_ns;
1218 : }
1219 : }
1220 364 : list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1221 364 : }
1222 :
1223 : INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1224 : INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1225 : INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
1226 :
1227 : /* This routine actually transmits TCP packets queued in by
1228 : * tcp_do_sendmsg(). This is used by both the initial
1229 : * transmission and possible later retransmissions.
1230 : * All SKB's seen here are completely headerless. It is our
1231 : * job to build the TCP header, and pass the packet down to
1232 : * IP so it can do the same plus pass the packet off to the
1233 : * device.
1234 : *
1235 : * We are working here with either a clone of the original
1236 : * SKB, or a fresh unique copy made by the retransmit engine.
1237 : */
1238 426 : static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1239 : int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1240 : {
1241 426 : const struct inet_connection_sock *icsk = inet_csk(sk);
1242 426 : struct inet_sock *inet;
1243 426 : struct tcp_sock *tp;
1244 426 : struct tcp_skb_cb *tcb;
1245 426 : struct tcp_out_options opts;
1246 426 : unsigned int tcp_options_size, tcp_header_size;
1247 426 : struct sk_buff *oskb = NULL;
1248 426 : struct tcp_md5sig_key *md5;
1249 426 : struct tcphdr *th;
1250 426 : u64 prior_wstamp;
1251 426 : int err;
1252 :
1253 426 : BUG_ON(!skb || !tcp_skb_pcount(skb));
1254 426 : tp = tcp_sk(sk);
1255 426 : prior_wstamp = tp->tcp_wstamp_ns;
1256 426 : tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1257 426 : skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
1258 426 : if (clone_it) {
1259 364 : TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
1260 364 : - tp->snd_una;
1261 364 : oskb = skb;
1262 :
1263 364 : tcp_skb_tsorted_save(oskb) {
1264 364 : if (unlikely(skb_cloned(oskb)))
1265 0 : skb = pskb_copy(oskb, gfp_mask);
1266 : else
1267 364 : skb = skb_clone(oskb, gfp_mask);
1268 364 : } tcp_skb_tsorted_restore(oskb);
1269 :
1270 364 : if (unlikely(!skb))
1271 : return -ENOBUFS;
1272 : /* retransmit skbs might have a non zero value in skb->dev
1273 : * because skb->dev is aliased with skb->rbnode.rb_left
1274 : */
1275 364 : skb->dev = NULL;
1276 : }
1277 :
1278 426 : inet = inet_sk(sk);
1279 426 : tcb = TCP_SKB_CB(skb);
1280 426 : memset(&opts, 0, sizeof(opts));
1281 :
1282 426 : if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1283 0 : tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
1284 : } else {
1285 426 : tcp_options_size = tcp_established_options(sk, skb, &opts,
1286 : &md5);
1287 : /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1288 : * at receiver : This slightly improve GRO performance.
1289 : * Note that we do not force the PSH flag for non GSO packets,
1290 : * because they might be sent under high congestion events,
1291 : * and in this case it is better to delay the delivery of 1-MSS
1292 : * packets and thus the corresponding ACK packet that would
1293 : * release the following packet.
1294 : */
1295 426 : if (tcp_skb_pcount(skb) > 1)
1296 0 : tcb->tcp_flags |= TCPHDR_PSH;
1297 : }
1298 426 : tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1299 :
1300 : /* if no packet is in qdisc/device queue, then allow XPS to select
1301 : * another queue. We can be called from tcp_tsq_handler()
1302 : * which holds one reference to sk.
1303 : *
1304 : * TODO: Ideally, in-flight pure ACK packets should not matter here.
1305 : * One way to get this would be to set skb->truesize = 2 on them.
1306 : */
1307 426 : skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1308 :
1309 : /* If we had to use memory reserve to allocate this skb,
1310 : * this might cause drops if packet is looped back :
1311 : * Other socket might not have SOCK_MEMALLOC.
1312 : * Packets not looped back do not care about pfmemalloc.
1313 : */
1314 426 : skb->pfmemalloc = 0;
1315 :
1316 426 : skb_push(skb, tcp_header_size);
1317 426 : skb_reset_transport_header(skb);
1318 :
1319 426 : skb_orphan(skb);
1320 426 : skb->sk = sk;
1321 426 : skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1322 426 : refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1323 :
1324 426 : skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
1325 :
1326 : /* Build TCP header and checksum it. */
1327 426 : th = (struct tcphdr *)skb->data;
1328 426 : th->source = inet->inet_sport;
1329 426 : th->dest = inet->inet_dport;
1330 426 : th->seq = htonl(tcb->seq);
1331 426 : th->ack_seq = htonl(rcv_nxt);
1332 426 : *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1333 : tcb->tcp_flags);
1334 :
1335 426 : th->check = 0;
1336 426 : th->urg_ptr = 0;
1337 :
1338 : /* The urg_mode check is necessary during a below snd_una win probe */
1339 426 : if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1340 0 : if (before(tp->snd_up, tcb->seq + 0x10000)) {
1341 0 : th->urg_ptr = htons(tp->snd_up - tcb->seq);
1342 0 : th->urg = 1;
1343 0 : } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1344 0 : th->urg_ptr = htons(0xFFFF);
1345 0 : th->urg = 1;
1346 : }
1347 : }
1348 :
1349 426 : skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1350 426 : if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1351 426 : th->window = htons(tcp_select_window(sk));
1352 426 : tcp_ecn_send(sk, skb, th, tcp_header_size);
1353 : } else {
1354 : /* RFC1323: The window in SYN & SYN/ACK segments
1355 : * is never scaled.
1356 : */
1357 0 : th->window = htons(min(tp->rcv_wnd, 65535U));
1358 : }
1359 :
1360 426 : tcp_options_write((__be32 *)(th + 1), tp, &opts);
1361 :
1362 : #ifdef CONFIG_TCP_MD5SIG
1363 : /* Calculate the MD5 hash, as we have all we need now */
1364 : if (md5) {
1365 : sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1366 : tp->af_specific->calc_md5_hash(opts.hash_location,
1367 : md5, sk, skb);
1368 : }
1369 : #endif
1370 :
1371 : /* BPF prog is the last one writing header option */
1372 426 : bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);
1373 :
1374 426 : INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
1375 : tcp_v6_send_check, tcp_v4_send_check,
1376 : sk, skb);
1377 :
1378 426 : if (likely(tcb->tcp_flags & TCPHDR_ACK))
1379 426 : tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt);
1380 :
1381 426 : if (skb->len != tcp_header_size) {
1382 361 : tcp_event_data_sent(tp, sk);
1383 361 : tp->data_segs_out += tcp_skb_pcount(skb);
1384 361 : tp->bytes_sent += skb->len - tcp_header_size;
1385 : }
1386 :
1387 426 : if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1388 426 : TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1389 : tcp_skb_pcount(skb));
1390 :
1391 426 : tp->segs_out += tcp_skb_pcount(skb);
1392 426 : skb_set_hash_from_sk(skb, sk);
1393 : /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1394 426 : skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1395 426 : skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1396 :
1397 : /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1398 :
1399 : /* Cleanup our debris for IP stacks */
1400 426 : memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1401 : sizeof(struct inet6_skb_parm)));
1402 :
1403 426 : tcp_add_tx_delay(skb, tp);
1404 :
1405 426 : err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit,
1406 : inet6_csk_xmit, ip_queue_xmit,
1407 : sk, skb, &inet->cork.fl);
1408 :
1409 426 : if (unlikely(err > 0)) {
1410 0 : tcp_enter_cwr(sk);
1411 0 : err = net_xmit_eval(err);
1412 : }
1413 426 : if (!err && oskb) {
1414 364 : tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1415 364 : tcp_rate_skb_sent(sk, oskb);
1416 : }
1417 : return err;
1418 : }
1419 :
1420 364 : static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1421 : gfp_t gfp_mask)
1422 : {
1423 364 : return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1424 364 : tcp_sk(sk)->rcv_nxt);
1425 : }
1426 :
1427 : /* This routine just queues the buffer for sending.
1428 : *
1429 : * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1430 : * otherwise socket can stall.
1431 : */
1432 3 : static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1433 : {
1434 3 : struct tcp_sock *tp = tcp_sk(sk);
1435 :
1436 : /* Advance write_seq and place onto the write_queue. */
1437 3 : WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1438 3 : __skb_header_release(skb);
1439 3 : tcp_add_write_queue_tail(sk, skb);
1440 3 : sk_wmem_queued_add(sk, skb->truesize);
1441 3 : sk_mem_charge(sk, skb->truesize);
1442 3 : }
1443 :
1444 : /* Initialize TSO segments for a packet. */
1445 361 : static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1446 : {
1447 0 : if (skb->len <= mss_now) {
1448 : /* Avoid the costly divide in the normal
1449 : * non-TSO case.
1450 : */
1451 361 : tcp_skb_pcount_set(skb, 1);
1452 361 : TCP_SKB_CB(skb)->tcp_gso_size = 0;
1453 : } else {
1454 0 : tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1455 0 : TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1456 : }
1457 0 : }
1458 :
1459 : /* Pcount in the middle of the write queue got changed, we need to do various
1460 : * tweaks to fix counters
1461 : */
1462 0 : static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1463 : {
1464 0 : struct tcp_sock *tp = tcp_sk(sk);
1465 :
1466 0 : tp->packets_out -= decr;
1467 :
1468 0 : if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1469 0 : tp->sacked_out -= decr;
1470 0 : if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1471 0 : tp->retrans_out -= decr;
1472 0 : if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1473 0 : tp->lost_out -= decr;
1474 :
1475 : /* Reno case is special. Sigh... */
1476 0 : if (tcp_is_reno(tp) && decr > 0)
1477 0 : tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1478 :
1479 0 : if (tp->lost_skb_hint &&
1480 0 : before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1481 0 : (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1482 0 : tp->lost_cnt_hint -= decr;
1483 :
1484 0 : tcp_verify_left_out(tp);
1485 0 : }
1486 :
1487 0 : static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1488 : {
1489 0 : return TCP_SKB_CB(skb)->txstamp_ack ||
1490 0 : (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1491 : }
1492 :
1493 0 : static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1494 : {
1495 0 : struct skb_shared_info *shinfo = skb_shinfo(skb);
1496 :
1497 0 : if (unlikely(tcp_has_tx_tstamp(skb)) &&
1498 0 : !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1499 0 : struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1500 0 : u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1501 :
1502 0 : shinfo->tx_flags &= ~tsflags;
1503 0 : shinfo2->tx_flags |= tsflags;
1504 0 : swap(shinfo->tskey, shinfo2->tskey);
1505 0 : TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1506 0 : TCP_SKB_CB(skb)->txstamp_ack = 0;
1507 : }
1508 0 : }
1509 :
1510 0 : static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1511 : {
1512 0 : TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1513 0 : TCP_SKB_CB(skb)->eor = 0;
1514 : }
1515 :
1516 : /* Insert buff after skb on the write or rtx queue of sk. */
1517 0 : static void tcp_insert_write_queue_after(struct sk_buff *skb,
1518 : struct sk_buff *buff,
1519 : struct sock *sk,
1520 : enum tcp_queue tcp_queue)
1521 : {
1522 0 : if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1523 0 : __skb_queue_after(&sk->sk_write_queue, skb, buff);
1524 : else
1525 0 : tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1526 0 : }
1527 :
1528 : /* Function to create two new TCP segments. Shrinks the given segment
1529 : * to the specified size and appends a new segment with the rest of the
1530 : * packet to the list. This won't be called frequently, I hope.
1531 : * Remember, these are still headerless SKBs at this point.
1532 : */
1533 0 : int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1534 : struct sk_buff *skb, u32 len,
1535 : unsigned int mss_now, gfp_t gfp)
1536 : {
1537 0 : struct tcp_sock *tp = tcp_sk(sk);
1538 0 : struct sk_buff *buff;
1539 0 : int nsize, old_factor;
1540 0 : long limit;
1541 0 : int nlen;
1542 0 : u8 flags;
1543 :
1544 0 : if (WARN_ON(len > skb->len))
1545 : return -EINVAL;
1546 :
1547 0 : nsize = skb_headlen(skb) - len;
1548 0 : if (nsize < 0)
1549 : nsize = 0;
1550 :
1551 : /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1552 : * We need some allowance to not penalize applications setting small
1553 : * SO_SNDBUF values.
1554 : * Also allow first and last skb in retransmit queue to be split.
1555 : */
1556 0 : limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_MAX_SIZE);
1557 0 : if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1558 : tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1559 : skb != tcp_rtx_queue_head(sk) &&
1560 : skb != tcp_rtx_queue_tail(sk))) {
1561 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1562 0 : return -ENOMEM;
1563 : }
1564 :
1565 0 : if (skb_unclone(skb, gfp))
1566 : return -ENOMEM;
1567 :
1568 : /* Get a new skb... force flag on. */
1569 0 : buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1570 0 : if (!buff)
1571 : return -ENOMEM; /* We'll just try again later. */
1572 0 : skb_copy_decrypted(buff, skb);
1573 0 : mptcp_skb_ext_copy(buff, skb);
1574 :
1575 0 : sk_wmem_queued_add(sk, buff->truesize);
1576 0 : sk_mem_charge(sk, buff->truesize);
1577 0 : nlen = skb->len - len - nsize;
1578 0 : buff->truesize += nlen;
1579 0 : skb->truesize -= nlen;
1580 :
1581 : /* Correct the sequence numbers. */
1582 0 : TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1583 0 : TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1584 0 : TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1585 :
1586 : /* PSH and FIN should only be set in the second packet. */
1587 0 : flags = TCP_SKB_CB(skb)->tcp_flags;
1588 0 : TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1589 0 : TCP_SKB_CB(buff)->tcp_flags = flags;
1590 0 : TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1591 0 : tcp_skb_fragment_eor(skb, buff);
1592 :
1593 0 : skb_split(skb, buff, len);
1594 :
1595 0 : buff->ip_summed = CHECKSUM_PARTIAL;
1596 :
1597 0 : buff->tstamp = skb->tstamp;
1598 0 : tcp_fragment_tstamp(skb, buff);
1599 :
1600 0 : old_factor = tcp_skb_pcount(skb);
1601 :
1602 : /* Fix up tso_factor for both original and new SKB. */
1603 0 : tcp_set_skb_tso_segs(skb, mss_now);
1604 0 : tcp_set_skb_tso_segs(buff, mss_now);
1605 :
1606 : /* Update delivered info for the new segment */
1607 0 : TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1608 :
1609 : /* If this packet has been sent out already, we must
1610 : * adjust the various packet counters.
1611 : */
1612 0 : if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1613 0 : int diff = old_factor - tcp_skb_pcount(skb) -
1614 0 : tcp_skb_pcount(buff);
1615 :
1616 0 : if (diff)
1617 0 : tcp_adjust_pcount(sk, skb, diff);
1618 : }
1619 :
1620 : /* Link BUFF into the send queue. */
1621 0 : __skb_header_release(buff);
1622 0 : tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1623 0 : if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1624 0 : list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1625 :
1626 : return 0;
1627 : }
1628 :
1629 : /* This is similar to __pskb_pull_tail(). The difference is that pulled
1630 : * data is not copied, but immediately discarded.
1631 : */
1632 0 : static int __pskb_trim_head(struct sk_buff *skb, int len)
1633 : {
1634 0 : struct skb_shared_info *shinfo;
1635 0 : int i, k, eat;
1636 :
1637 0 : eat = min_t(int, len, skb_headlen(skb));
1638 0 : if (eat) {
1639 0 : __skb_pull(skb, eat);
1640 0 : len -= eat;
1641 0 : if (!len)
1642 : return 0;
1643 : }
1644 0 : eat = len;
1645 0 : k = 0;
1646 0 : shinfo = skb_shinfo(skb);
1647 0 : for (i = 0; i < shinfo->nr_frags; i++) {
1648 0 : int size = skb_frag_size(&shinfo->frags[i]);
1649 :
1650 0 : if (size <= eat) {
1651 0 : skb_frag_unref(skb, i);
1652 0 : eat -= size;
1653 : } else {
1654 0 : shinfo->frags[k] = shinfo->frags[i];
1655 0 : if (eat) {
1656 0 : skb_frag_off_add(&shinfo->frags[k], eat);
1657 0 : skb_frag_size_sub(&shinfo->frags[k], eat);
1658 0 : eat = 0;
1659 : }
1660 0 : k++;
1661 : }
1662 : }
1663 0 : shinfo->nr_frags = k;
1664 :
1665 0 : skb->data_len -= len;
1666 0 : skb->len = skb->data_len;
1667 0 : return len;
1668 : }
1669 :
1670 : /* Remove acked data from a packet in the transmit queue. */
1671 0 : int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1672 : {
1673 0 : u32 delta_truesize;
1674 :
1675 0 : if (skb_unclone(skb, GFP_ATOMIC))
1676 : return -ENOMEM;
1677 :
1678 0 : delta_truesize = __pskb_trim_head(skb, len);
1679 :
1680 0 : TCP_SKB_CB(skb)->seq += len;
1681 0 : skb->ip_summed = CHECKSUM_PARTIAL;
1682 :
1683 0 : if (delta_truesize) {
1684 0 : skb->truesize -= delta_truesize;
1685 0 : sk_wmem_queued_add(sk, -delta_truesize);
1686 0 : sk_mem_uncharge(sk, delta_truesize);
1687 : }
1688 :
1689 : /* Any change of skb->len requires recalculation of tso factor. */
1690 0 : if (tcp_skb_pcount(skb) > 1)
1691 0 : tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1692 :
1693 : return 0;
1694 : }
1695 :
1696 : /* Calculate MSS not accounting any TCP options. */
1697 4 : static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1698 : {
1699 4 : const struct tcp_sock *tp = tcp_sk(sk);
1700 4 : const struct inet_connection_sock *icsk = inet_csk(sk);
1701 4 : int mss_now;
1702 :
1703 : /* Calculate base mss without TCP options:
1704 : It is MMS_S - sizeof(tcphdr) of rfc1122
1705 : */
1706 4 : mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1707 :
1708 : /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1709 4 : if (icsk->icsk_af_ops->net_frag_header_len) {
1710 0 : const struct dst_entry *dst = __sk_dst_get(sk);
1711 :
1712 0 : if (dst && dst_allfrag(dst))
1713 0 : mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1714 : }
1715 :
1716 : /* Clamp it (mss_clamp does not include tcp options) */
1717 4 : if (mss_now > tp->rx_opt.mss_clamp)
1718 : mss_now = tp->rx_opt.mss_clamp;
1719 :
1720 : /* Now subtract optional transport overhead */
1721 4 : mss_now -= icsk->icsk_ext_hdr_len;
1722 :
1723 : /* Then reserve room for full set of TCP options and 8 bytes of data */
1724 4 : mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);
1725 4 : return mss_now;
1726 : }
1727 :
1728 : /* Calculate MSS. Not accounting for SACKs here. */
1729 4 : int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1730 : {
1731 : /* Subtract TCP options size, not including SACKs */
1732 4 : return __tcp_mtu_to_mss(sk, pmtu) -
1733 4 : (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1734 : }
1735 :
1736 : /* Inverse of above */
1737 4 : int tcp_mss_to_mtu(struct sock *sk, int mss)
1738 : {
1739 4 : const struct tcp_sock *tp = tcp_sk(sk);
1740 4 : const struct inet_connection_sock *icsk = inet_csk(sk);
1741 4 : int mtu;
1742 :
1743 4 : mtu = mss +
1744 4 : tp->tcp_header_len +
1745 4 : icsk->icsk_ext_hdr_len +
1746 4 : icsk->icsk_af_ops->net_header_len;
1747 :
1748 : /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1749 4 : if (icsk->icsk_af_ops->net_frag_header_len) {
1750 0 : const struct dst_entry *dst = __sk_dst_get(sk);
1751 :
1752 0 : if (dst && dst_allfrag(dst))
1753 0 : mtu += icsk->icsk_af_ops->net_frag_header_len;
1754 : }
1755 4 : return mtu;
1756 : }
1757 : EXPORT_SYMBOL(tcp_mss_to_mtu);
1758 :
1759 : /* MTU probing init per socket */
1760 4 : void tcp_mtup_init(struct sock *sk)
1761 : {
1762 4 : struct tcp_sock *tp = tcp_sk(sk);
1763 4 : struct inet_connection_sock *icsk = inet_csk(sk);
1764 4 : struct net *net = sock_net(sk);
1765 :
1766 4 : icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
1767 4 : icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1768 4 : icsk->icsk_af_ops->net_header_len;
1769 4 : icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
1770 4 : icsk->icsk_mtup.probe_size = 0;
1771 4 : if (icsk->icsk_mtup.enabled)
1772 0 : icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1773 4 : }
1774 : EXPORT_SYMBOL(tcp_mtup_init);
1775 :
1776 : /* This function synchronize snd mss to current pmtu/exthdr set.
1777 :
1778 : tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1779 : for TCP options, but includes only bare TCP header.
1780 :
1781 : tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1782 : It is minimum of user_mss and mss received with SYN.
1783 : It also does not include TCP options.
1784 :
1785 : inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1786 :
1787 : tp->mss_cache is current effective sending mss, including
1788 : all tcp options except for SACKs. It is evaluated,
1789 : taking into account current pmtu, but never exceeds
1790 : tp->rx_opt.mss_clamp.
1791 :
1792 : NOTE1. rfc1122 clearly states that advertised MSS
1793 : DOES NOT include either tcp or ip options.
1794 :
1795 : NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1796 : are READ ONLY outside this function. --ANK (980731)
1797 : */
1798 4 : unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1799 : {
1800 4 : struct tcp_sock *tp = tcp_sk(sk);
1801 4 : struct inet_connection_sock *icsk = inet_csk(sk);
1802 4 : int mss_now;
1803 :
1804 4 : if (icsk->icsk_mtup.search_high > pmtu)
1805 0 : icsk->icsk_mtup.search_high = pmtu;
1806 :
1807 4 : mss_now = tcp_mtu_to_mss(sk, pmtu);
1808 4 : mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1809 :
1810 : /* And store cached results */
1811 4 : icsk->icsk_pmtu_cookie = pmtu;
1812 4 : if (icsk->icsk_mtup.enabled)
1813 0 : mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1814 4 : tp->mss_cache = mss_now;
1815 :
1816 4 : return mss_now;
1817 : }
1818 : EXPORT_SYMBOL(tcp_sync_mss);
1819 :
1820 : /* Compute the current effective MSS, taking SACKs and IP options,
1821 : * and even PMTU discovery events into account.
1822 : */
1823 496 : unsigned int tcp_current_mss(struct sock *sk)
1824 : {
1825 496 : const struct tcp_sock *tp = tcp_sk(sk);
1826 496 : const struct dst_entry *dst = __sk_dst_get(sk);
1827 496 : u32 mss_now;
1828 496 : unsigned int header_len;
1829 496 : struct tcp_out_options opts;
1830 496 : struct tcp_md5sig_key *md5;
1831 :
1832 496 : mss_now = tp->mss_cache;
1833 :
1834 496 : if (dst) {
1835 492 : u32 mtu = dst_mtu(dst);
1836 492 : if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1837 0 : mss_now = tcp_sync_mss(sk, mtu);
1838 : }
1839 :
1840 496 : header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1841 : sizeof(struct tcphdr);
1842 : /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1843 : * some common options. If this is an odd packet (because we have SACK
1844 : * blocks etc) then our calculated header_len will be different, and
1845 : * we have to adjust mss_now correspondingly */
1846 496 : if (header_len != tp->tcp_header_len) {
1847 0 : int delta = (int) header_len - tp->tcp_header_len;
1848 0 : mss_now -= delta;
1849 : }
1850 :
1851 496 : return mss_now;
1852 : }
1853 :
1854 : /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1855 : * As additional protections, we do not touch cwnd in retransmission phases,
1856 : * and if application hit its sndbuf limit recently.
1857 : */
1858 0 : static void tcp_cwnd_application_limited(struct sock *sk)
1859 : {
1860 0 : struct tcp_sock *tp = tcp_sk(sk);
1861 :
1862 0 : if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1863 0 : sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1864 : /* Limited by application or receiver window. */
1865 0 : u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1866 0 : u32 win_used = max(tp->snd_cwnd_used, init_win);
1867 0 : if (win_used < tp->snd_cwnd) {
1868 0 : tp->snd_ssthresh = tcp_current_ssthresh(sk);
1869 0 : tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
1870 : }
1871 0 : tp->snd_cwnd_used = 0;
1872 : }
1873 0 : tp->snd_cwnd_stamp = tcp_jiffies32;
1874 0 : }
1875 :
1876 364 : static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1877 : {
1878 364 : const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1879 364 : struct tcp_sock *tp = tcp_sk(sk);
1880 :
1881 : /* Track the maximum number of outstanding packets in each
1882 : * window, and remember whether we were cwnd-limited then.
1883 : */
1884 364 : if (!before(tp->snd_una, tp->max_packets_seq) ||
1885 126 : tp->packets_out > tp->max_packets_out ||
1886 : is_cwnd_limited) {
1887 343 : tp->max_packets_out = tp->packets_out;
1888 343 : tp->max_packets_seq = tp->snd_nxt;
1889 343 : tp->is_cwnd_limited = is_cwnd_limited;
1890 : }
1891 :
1892 728 : if (tcp_is_cwnd_limited(sk)) {
1893 : /* Network is feed fully. */
1894 0 : tp->snd_cwnd_used = 0;
1895 0 : tp->snd_cwnd_stamp = tcp_jiffies32;
1896 : } else {
1897 : /* Network starves. */
1898 364 : if (tp->packets_out > tp->snd_cwnd_used)
1899 11 : tp->snd_cwnd_used = tp->packets_out;
1900 :
1901 364 : if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
1902 364 : (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1903 0 : !ca_ops->cong_control)
1904 0 : tcp_cwnd_application_limited(sk);
1905 :
1906 : /* The following conditions together indicate the starvation
1907 : * is caused by insufficient sender buffer:
1908 : * 1) just sent some data (see tcp_write_xmit)
1909 : * 2) not cwnd limited (this else condition)
1910 : * 3) no more data to send (tcp_write_queue_empty())
1911 : * 4) application is hitting buffer limit (SOCK_NOSPACE)
1912 : */
1913 364 : if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1914 364 : test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1915 0 : (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1916 364 : tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1917 : }
1918 364 : }
1919 :
1920 : /* Minshall's variant of the Nagle send check. */
1921 2 : static bool tcp_minshall_check(const struct tcp_sock *tp)
1922 : {
1923 2 : return after(tp->snd_sml, tp->snd_una) &&
1924 2 : !after(tp->snd_sml, tp->snd_nxt);
1925 : }
1926 :
1927 : /* Update snd_sml if this skb is under mss
1928 : * Note that a TSO packet might end with a sub-mss segment
1929 : * The test is really :
1930 : * if ((skb->len % mss) != 0)
1931 : * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1932 : * But we can avoid doing the divide again given we already have
1933 : * skb_pcount = skb->len / mss_now
1934 : */
1935 364 : static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1936 : const struct sk_buff *skb)
1937 : {
1938 364 : if (skb->len < tcp_skb_pcount(skb) * mss_now)
1939 364 : tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1940 : }
1941 :
1942 : /* Return false, if packet can be sent now without violation Nagle's rules:
1943 : * 1. It is full sized. (provided by caller in %partial bool)
1944 : * 2. Or it contains FIN. (already checked by caller)
1945 : * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1946 : * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1947 : * With Minshall's modification: all sent small packets are ACKed.
1948 : */
1949 363 : static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1950 : int nonagle)
1951 : {
1952 363 : return partial &&
1953 363 : ((nonagle & TCP_NAGLE_CORK) ||
1954 42 : (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1955 : }
1956 :
1957 : /* Return how many segs we'd like on a TSO packet,
1958 : * to send one TSO packet per ms
1959 : */
1960 422 : static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
1961 : int min_tso_segs)
1962 : {
1963 422 : u32 bytes, segs;
1964 :
1965 422 : bytes = min_t(unsigned long,
1966 : sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift),
1967 : sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
1968 :
1969 : /* Goal is to send at least one packet per ms,
1970 : * not one big TSO packet every 100 ms.
1971 : * This preserves ACK clocking and is consistent
1972 : * with tcp_tso_should_defer() heuristic.
1973 : */
1974 422 : segs = max_t(u32, bytes / mss_now, min_tso_segs);
1975 :
1976 422 : return segs;
1977 : }
1978 :
1979 : /* Return the number of segments we want in the skb we are transmitting.
1980 : * See if congestion control module wants to decide; otherwise, autosize.
1981 : */
1982 422 : static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
1983 : {
1984 422 : const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1985 422 : u32 min_tso, tso_segs;
1986 :
1987 844 : min_tso = ca_ops->min_tso_segs ?
1988 422 : ca_ops->min_tso_segs(sk) :
1989 422 : sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
1990 :
1991 422 : tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
1992 422 : return min_t(u32, tso_segs, sk->sk_gso_max_segs);
1993 : }
1994 :
1995 : /* Returns the portion of skb which can be sent right away */
1996 0 : static unsigned int tcp_mss_split_point(const struct sock *sk,
1997 : const struct sk_buff *skb,
1998 : unsigned int mss_now,
1999 : unsigned int max_segs,
2000 : int nonagle)
2001 : {
2002 0 : const struct tcp_sock *tp = tcp_sk(sk);
2003 0 : u32 partial, needed, window, max_len;
2004 :
2005 0 : window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2006 0 : max_len = mss_now * max_segs;
2007 :
2008 0 : if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
2009 : return max_len;
2010 :
2011 0 : needed = min(skb->len, window);
2012 :
2013 0 : if (max_len <= needed)
2014 : return max_len;
2015 :
2016 0 : partial = needed % mss_now;
2017 : /* If last segment is not a full MSS, check if Nagle rules allow us
2018 : * to include this last segment in this skb.
2019 : * Otherwise, we'll split the skb at last MSS boundary
2020 : */
2021 0 : if (tcp_nagle_check(partial != 0, tp, nonagle))
2022 0 : return needed - partial;
2023 :
2024 : return needed;
2025 : }
2026 :
2027 : /* Can at least one segment of SKB be sent right now, according to the
2028 : * congestion window rules? If so, return how many segments are allowed.
2029 : */
2030 366 : static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
2031 : const struct sk_buff *skb)
2032 : {
2033 366 : u32 in_flight, cwnd, halfcwnd;
2034 :
2035 : /* Don't be strict about the congestion window for the final FIN. */
2036 366 : if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
2037 3 : tcp_skb_pcount(skb) == 1)
2038 : return 1;
2039 :
2040 363 : in_flight = tcp_packets_in_flight(tp);
2041 363 : cwnd = tp->snd_cwnd;
2042 363 : if (in_flight >= cwnd)
2043 : return 0;
2044 :
2045 : /* For better scheduling, ensure we have at least
2046 : * 2 GSO packets in flight.
2047 : */
2048 363 : halfcwnd = max(cwnd >> 1, 1U);
2049 363 : return min(halfcwnd, cwnd - in_flight);
2050 : }
2051 :
2052 : /* Initialize TSO state of a skb.
2053 : * This must be invoked the first time we consider transmitting
2054 : * SKB onto the wire.
2055 : */
2056 366 : static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
2057 : {
2058 366 : int tso_segs = tcp_skb_pcount(skb);
2059 :
2060 366 : if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
2061 361 : tcp_set_skb_tso_segs(skb, mss_now);
2062 361 : tso_segs = tcp_skb_pcount(skb);
2063 : }
2064 366 : return tso_segs;
2065 : }
2066 :
2067 :
2068 : /* Return true if the Nagle test allows this packet to be
2069 : * sent now.
2070 : */
2071 366 : static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
2072 : unsigned int cur_mss, int nonagle)
2073 : {
2074 : /* Nagle rule does not apply to frames, which sit in the middle of the
2075 : * write_queue (they have no chances to get new data).
2076 : *
2077 : * This is implemented in the callers, where they modify the 'nonagle'
2078 : * argument based upon the location of SKB in the send queue.
2079 : */
2080 366 : if (nonagle & TCP_NAGLE_PUSH)
2081 : return true;
2082 :
2083 : /* Don't use the nagle rule for urgent data (or for the final FIN). */
2084 366 : if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
2085 : return true;
2086 :
2087 363 : if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
2088 361 : return true;
2089 :
2090 : return false;
2091 : }
2092 :
2093 : /* Does at least the first segment of SKB fit into the send window? */
2094 366 : static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
2095 : const struct sk_buff *skb,
2096 : unsigned int cur_mss)
2097 : {
2098 366 : u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2099 :
2100 366 : if (skb->len > cur_mss)
2101 0 : end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
2102 :
2103 366 : return !after(end_seq, tcp_wnd_end(tp));
2104 : }
2105 :
2106 : /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
2107 : * which is put after SKB on the list. It is very much like
2108 : * tcp_fragment() except that it may make several kinds of assumptions
2109 : * in order to speed up the splitting operation. In particular, we
2110 : * know that all the data is in scatter-gather pages, and that the
2111 : * packet has never been sent out before (and thus is not cloned).
2112 : */
2113 0 : static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
2114 : unsigned int mss_now, gfp_t gfp)
2115 : {
2116 0 : int nlen = skb->len - len;
2117 0 : struct sk_buff *buff;
2118 0 : u8 flags;
2119 :
2120 : /* All of a TSO frame must be composed of paged data. */
2121 0 : if (skb->len != skb->data_len)
2122 0 : return tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
2123 : skb, len, mss_now, gfp);
2124 :
2125 0 : buff = sk_stream_alloc_skb(sk, 0, gfp, true);
2126 0 : if (unlikely(!buff))
2127 : return -ENOMEM;
2128 0 : skb_copy_decrypted(buff, skb);
2129 0 : mptcp_skb_ext_copy(buff, skb);
2130 :
2131 0 : sk_wmem_queued_add(sk, buff->truesize);
2132 0 : sk_mem_charge(sk, buff->truesize);
2133 0 : buff->truesize += nlen;
2134 0 : skb->truesize -= nlen;
2135 :
2136 : /* Correct the sequence numbers. */
2137 0 : TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
2138 0 : TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
2139 0 : TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
2140 :
2141 : /* PSH and FIN should only be set in the second packet. */
2142 0 : flags = TCP_SKB_CB(skb)->tcp_flags;
2143 0 : TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
2144 0 : TCP_SKB_CB(buff)->tcp_flags = flags;
2145 :
2146 : /* This packet was never sent out yet, so no SACK bits. */
2147 0 : TCP_SKB_CB(buff)->sacked = 0;
2148 :
2149 0 : tcp_skb_fragment_eor(skb, buff);
2150 :
2151 0 : buff->ip_summed = CHECKSUM_PARTIAL;
2152 0 : skb_split(skb, buff, len);
2153 0 : tcp_fragment_tstamp(skb, buff);
2154 :
2155 : /* Fix up tso_factor for both original and new SKB. */
2156 0 : tcp_set_skb_tso_segs(skb, mss_now);
2157 0 : tcp_set_skb_tso_segs(buff, mss_now);
2158 :
2159 : /* Link BUFF into the send queue. */
2160 0 : __skb_header_release(buff);
2161 0 : tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
2162 :
2163 0 : return 0;
2164 : }
2165 :
2166 : /* Try to defer sending, if possible, in order to minimize the amount
2167 : * of TSO splitting we do. View it as a kind of TSO Nagle test.
2168 : *
2169 : * This algorithm is from John Heffner.
2170 : */
2171 0 : static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
2172 : bool *is_cwnd_limited,
2173 : bool *is_rwnd_limited,
2174 : u32 max_segs)
2175 : {
2176 0 : const struct inet_connection_sock *icsk = inet_csk(sk);
2177 0 : u32 send_win, cong_win, limit, in_flight;
2178 0 : struct tcp_sock *tp = tcp_sk(sk);
2179 0 : struct sk_buff *head;
2180 0 : int win_divisor;
2181 0 : s64 delta;
2182 :
2183 0 : if (icsk->icsk_ca_state >= TCP_CA_Recovery)
2184 0 : goto send_now;
2185 :
2186 : /* Avoid bursty behavior by allowing defer
2187 : * only if the last write was recent (1 ms).
2188 : * Note that tp->tcp_wstamp_ns can be in the future if we have
2189 : * packets waiting in a qdisc or device for EDT delivery.
2190 : */
2191 0 : delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
2192 0 : if (delta > 0)
2193 0 : goto send_now;
2194 :
2195 0 : in_flight = tcp_packets_in_flight(tp);
2196 :
2197 0 : BUG_ON(tcp_skb_pcount(skb) <= 1);
2198 0 : BUG_ON(tp->snd_cwnd <= in_flight);
2199 :
2200 0 : send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2201 :
2202 : /* From in_flight test above, we know that cwnd > in_flight. */
2203 0 : cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
2204 :
2205 0 : limit = min(send_win, cong_win);
2206 :
2207 : /* If a full-sized TSO skb can be sent, do it. */
2208 0 : if (limit >= max_segs * tp->mss_cache)
2209 0 : goto send_now;
2210 :
2211 : /* Middle in queue won't get any more data, full sendable already? */
2212 0 : if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
2213 0 : goto send_now;
2214 :
2215 0 : win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
2216 0 : if (win_divisor) {
2217 0 : u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
2218 :
2219 : /* If at least some fraction of a window is available,
2220 : * just use it.
2221 : */
2222 0 : chunk /= win_divisor;
2223 0 : if (limit >= chunk)
2224 0 : goto send_now;
2225 : } else {
2226 : /* Different approach, try not to defer past a single
2227 : * ACK. Receiver should ACK every other full sized
2228 : * frame, so if we have space for more than 3 frames
2229 : * then send now.
2230 : */
2231 0 : if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
2232 0 : goto send_now;
2233 : }
2234 :
2235 : /* TODO : use tsorted_sent_queue ? */
2236 0 : head = tcp_rtx_queue_head(sk);
2237 0 : if (!head)
2238 0 : goto send_now;
2239 0 : delta = tp->tcp_clock_cache - head->tstamp;
2240 : /* If next ACK is likely to come too late (half srtt), do not defer */
2241 0 : if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
2242 0 : goto send_now;
2243 :
2244 : /* Ok, it looks like it is advisable to defer.
2245 : * Three cases are tracked :
2246 : * 1) We are cwnd-limited
2247 : * 2) We are rwnd-limited
2248 : * 3) We are application limited.
2249 : */
2250 0 : if (cong_win < send_win) {
2251 0 : if (cong_win <= skb->len) {
2252 0 : *is_cwnd_limited = true;
2253 0 : return true;
2254 : }
2255 : } else {
2256 0 : if (send_win <= skb->len) {
2257 0 : *is_rwnd_limited = true;
2258 0 : return true;
2259 : }
2260 : }
2261 :
2262 : /* If this packet won't get more data, do not wait. */
2263 0 : if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2264 : TCP_SKB_CB(skb)->eor)
2265 0 : goto send_now;
2266 :
2267 : return true;
2268 :
2269 : send_now:
2270 : return false;
2271 : }
2272 :
2273 0 : static inline void tcp_mtu_check_reprobe(struct sock *sk)
2274 : {
2275 0 : struct inet_connection_sock *icsk = inet_csk(sk);
2276 0 : struct tcp_sock *tp = tcp_sk(sk);
2277 0 : struct net *net = sock_net(sk);
2278 0 : u32 interval;
2279 0 : s32 delta;
2280 :
2281 0 : interval = net->ipv4.sysctl_tcp_probe_interval;
2282 0 : delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2283 0 : if (unlikely(delta >= interval * HZ)) {
2284 0 : int mss = tcp_current_mss(sk);
2285 :
2286 : /* Update current search range */
2287 0 : icsk->icsk_mtup.probe_size = 0;
2288 0 : icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2289 0 : sizeof(struct tcphdr) +
2290 0 : icsk->icsk_af_ops->net_header_len;
2291 0 : icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2292 :
2293 : /* Update probe time stamp */
2294 0 : icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2295 : }
2296 0 : }
2297 :
2298 0 : static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2299 : {
2300 0 : struct sk_buff *skb, *next;
2301 :
2302 0 : skb = tcp_send_head(sk);
2303 0 : tcp_for_write_queue_from_safe(skb, next, sk) {
2304 0 : if (len <= skb->len)
2305 : break;
2306 :
2307 0 : if (unlikely(TCP_SKB_CB(skb)->eor) || tcp_has_tx_tstamp(skb))
2308 : return false;
2309 :
2310 0 : len -= skb->len;
2311 : }
2312 :
2313 : return true;
2314 : }
2315 :
2316 : /* Create a new MTU probe if we are ready.
2317 : * MTU probe is regularly attempting to increase the path MTU by
2318 : * deliberately sending larger packets. This discovers routing
2319 : * changes resulting in larger path MTUs.
2320 : *
2321 : * Returns 0 if we should wait to probe (no cwnd available),
2322 : * 1 if a probe was sent,
2323 : * -1 otherwise
2324 : */
2325 422 : static int tcp_mtu_probe(struct sock *sk)
2326 : {
2327 422 : struct inet_connection_sock *icsk = inet_csk(sk);
2328 422 : struct tcp_sock *tp = tcp_sk(sk);
2329 422 : struct sk_buff *skb, *nskb, *next;
2330 422 : struct net *net = sock_net(sk);
2331 422 : int probe_size;
2332 422 : int size_needed;
2333 422 : int copy, len;
2334 422 : int mss_now;
2335 422 : int interval;
2336 :
2337 : /* Not currently probing/verifying,
2338 : * not in recovery,
2339 : * have enough cwnd, and
2340 : * not SACKing (the variable headers throw things off)
2341 : */
2342 422 : if (likely(!icsk->icsk_mtup.enabled ||
2343 : icsk->icsk_mtup.probe_size ||
2344 : inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2345 : tp->snd_cwnd < 11 ||
2346 : tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2347 : return -1;
2348 :
2349 : /* Use binary search for probe_size between tcp_mss_base,
2350 : * and current mss_clamp. if (search_high - search_low)
2351 : * smaller than a threshold, backoff from probing.
2352 : */
2353 0 : mss_now = tcp_current_mss(sk);
2354 0 : probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2355 0 : icsk->icsk_mtup.search_low) >> 1);
2356 0 : size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2357 0 : interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2358 : /* When misfortune happens, we are reprobing actively,
2359 : * and then reprobe timer has expired. We stick with current
2360 : * probing process by not resetting search range to its orignal.
2361 : */
2362 0 : if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2363 0 : interval < net->ipv4.sysctl_tcp_probe_threshold) {
2364 : /* Check whether enough time has elaplased for
2365 : * another round of probing.
2366 : */
2367 0 : tcp_mtu_check_reprobe(sk);
2368 0 : return -1;
2369 : }
2370 :
2371 : /* Have enough data in the send queue to probe? */
2372 0 : if (tp->write_seq - tp->snd_nxt < size_needed)
2373 : return -1;
2374 :
2375 0 : if (tp->snd_wnd < size_needed)
2376 : return -1;
2377 0 : if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2378 : return 0;
2379 :
2380 : /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2381 0 : if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
2382 0 : if (!tcp_packets_in_flight(tp))
2383 : return -1;
2384 : else
2385 0 : return 0;
2386 : }
2387 :
2388 0 : if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2389 : return -1;
2390 :
2391 : /* We're allowed to probe. Build it now. */
2392 0 : nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2393 0 : if (!nskb)
2394 : return -1;
2395 0 : sk_wmem_queued_add(sk, nskb->truesize);
2396 0 : sk_mem_charge(sk, nskb->truesize);
2397 :
2398 0 : skb = tcp_send_head(sk);
2399 0 : skb_copy_decrypted(nskb, skb);
2400 0 : mptcp_skb_ext_copy(nskb, skb);
2401 :
2402 0 : TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2403 0 : TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2404 0 : TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2405 0 : TCP_SKB_CB(nskb)->sacked = 0;
2406 0 : nskb->csum = 0;
2407 0 : nskb->ip_summed = CHECKSUM_PARTIAL;
2408 :
2409 0 : tcp_insert_write_queue_before(nskb, skb, sk);
2410 0 : tcp_highest_sack_replace(sk, skb, nskb);
2411 :
2412 0 : len = 0;
2413 0 : tcp_for_write_queue_from_safe(skb, next, sk) {
2414 0 : copy = min_t(int, skb->len, probe_size - len);
2415 0 : skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2416 :
2417 0 : if (skb->len <= copy) {
2418 : /* We've eaten all the data from this skb.
2419 : * Throw it away. */
2420 0 : TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2421 : /* If this is the last SKB we copy and eor is set
2422 : * we need to propagate it to the new skb.
2423 : */
2424 0 : TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
2425 0 : tcp_skb_collapse_tstamp(nskb, skb);
2426 0 : tcp_unlink_write_queue(skb, sk);
2427 0 : sk_wmem_free_skb(sk, skb);
2428 : } else {
2429 0 : TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2430 : ~(TCPHDR_FIN|TCPHDR_PSH);
2431 0 : if (!skb_shinfo(skb)->nr_frags) {
2432 0 : skb_pull(skb, copy);
2433 : } else {
2434 0 : __pskb_trim_head(skb, copy);
2435 0 : tcp_set_skb_tso_segs(skb, mss_now);
2436 : }
2437 0 : TCP_SKB_CB(skb)->seq += copy;
2438 : }
2439 :
2440 0 : len += copy;
2441 :
2442 0 : if (len >= probe_size)
2443 : break;
2444 : }
2445 0 : tcp_init_tso_segs(nskb, nskb->len);
2446 :
2447 : /* We're ready to send. If this fails, the probe will
2448 : * be resegmented into mss-sized pieces by tcp_write_xmit().
2449 : */
2450 0 : if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2451 : /* Decrement cwnd here because we are sending
2452 : * effectively two packets. */
2453 0 : tp->snd_cwnd--;
2454 0 : tcp_event_new_data_sent(sk, nskb);
2455 :
2456 0 : icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2457 0 : tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2458 0 : tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2459 :
2460 0 : return 1;
2461 : }
2462 :
2463 : return -1;
2464 : }
2465 :
2466 366 : static bool tcp_pacing_check(struct sock *sk)
2467 : {
2468 366 : struct tcp_sock *tp = tcp_sk(sk);
2469 :
2470 366 : if (!tcp_needs_internal_pacing(sk))
2471 : return false;
2472 :
2473 0 : if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2474 : return false;
2475 :
2476 0 : if (!hrtimer_is_queued(&tp->pacing_timer)) {
2477 0 : hrtimer_start(&tp->pacing_timer,
2478 : ns_to_ktime(tp->tcp_wstamp_ns),
2479 : HRTIMER_MODE_ABS_PINNED_SOFT);
2480 0 : sock_hold(sk);
2481 : }
2482 : return true;
2483 : }
2484 :
2485 : /* TCP Small Queues :
2486 : * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2487 : * (These limits are doubled for retransmits)
2488 : * This allows for :
2489 : * - better RTT estimation and ACK scheduling
2490 : * - faster recovery
2491 : * - high rates
2492 : * Alas, some drivers / subsystems require a fair amount
2493 : * of queued bytes to ensure line rate.
2494 : * One example is wifi aggregation (802.11 AMPDU)
2495 : */
2496 364 : static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2497 : unsigned int factor)
2498 : {
2499 364 : unsigned long limit;
2500 :
2501 364 : limit = max_t(unsigned long,
2502 : 2 * skb->truesize,
2503 : sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift));
2504 364 : if (sk->sk_pacing_status == SK_PACING_NONE)
2505 364 : limit = min_t(unsigned long, limit,
2506 : sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
2507 364 : limit <<= factor;
2508 :
2509 364 : if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2510 0 : tcp_sk(sk)->tcp_tx_delay) {
2511 0 : u64 extra_bytes = (u64)sk->sk_pacing_rate * tcp_sk(sk)->tcp_tx_delay;
2512 :
2513 : /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2514 : * approximate our needs assuming an ~100% skb->truesize overhead.
2515 : * USEC_PER_SEC is approximated by 2^20.
2516 : * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2517 : */
2518 0 : extra_bytes >>= (20 - 1);
2519 0 : limit += extra_bytes;
2520 : }
2521 364 : if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2522 : /* Always send skb if rtx queue is empty.
2523 : * No need to wait for TX completion to call us back,
2524 : * after softirq/tasklet schedule.
2525 : * This helps when TX completions are delayed too much.
2526 : */
2527 0 : if (tcp_rtx_queue_empty(sk))
2528 : return false;
2529 :
2530 0 : set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2531 : /* It is possible TX completion already happened
2532 : * before we set TSQ_THROTTLED, so we must
2533 : * test again the condition.
2534 : */
2535 0 : smp_mb__after_atomic();
2536 0 : if (refcount_read(&sk->sk_wmem_alloc) > limit)
2537 0 : return true;
2538 : }
2539 : return false;
2540 : }
2541 :
2542 478 : static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2543 : {
2544 478 : const u32 now = tcp_jiffies32;
2545 478 : enum tcp_chrono old = tp->chrono_type;
2546 :
2547 478 : if (old > TCP_CHRONO_UNSPEC)
2548 234 : tp->chrono_stat[old - 1] += now - tp->chrono_start;
2549 478 : tp->chrono_start = now;
2550 478 : tp->chrono_type = new;
2551 478 : }
2552 :
2553 364 : void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2554 : {
2555 364 : struct tcp_sock *tp = tcp_sk(sk);
2556 :
2557 : /* If there are multiple conditions worthy of tracking in a
2558 : * chronograph then the highest priority enum takes precedence
2559 : * over the other conditions. So that if something "more interesting"
2560 : * starts happening, stop the previous chrono and start a new one.
2561 : */
2562 364 : if (type > tp->chrono_type)
2563 220 : tcp_chrono_set(tp, type);
2564 361 : }
2565 :
2566 660 : void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2567 : {
2568 660 : struct tcp_sock *tp = tcp_sk(sk);
2569 :
2570 :
2571 : /* There are multiple conditions worthy of tracking in a
2572 : * chronograph, so that the highest priority enum takes
2573 : * precedence over the other conditions (see tcp_chrono_start).
2574 : * If a condition stops, we only stop chrono tracking if
2575 : * it's the "most interesting" or current chrono we are
2576 : * tracking and starts busy chrono if we have pending data.
2577 : */
2578 918 : if (tcp_rtx_and_write_queues_empty(sk))
2579 244 : tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2580 416 : else if (type == tp->chrono_type)
2581 14 : tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2582 660 : }
2583 :
2584 : /* This routine writes packets to the network. It advances the
2585 : * send_head. This happens as incoming acks open up the remote
2586 : * window for us.
2587 : *
2588 : * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2589 : * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2590 : * account rare use of URG, this is not a big flaw.
2591 : *
2592 : * Send at most one packet when push_one > 0. Temporarily ignore
2593 : * cwnd limit to force at most one packet out when push_one == 2.
2594 :
2595 : * Returns true, if no segments are in flight and we have queued segments,
2596 : * but cannot send anything now because of SWS or another problem.
2597 : */
2598 422 : static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2599 : int push_one, gfp_t gfp)
2600 : {
2601 422 : struct tcp_sock *tp = tcp_sk(sk);
2602 422 : struct sk_buff *skb;
2603 422 : unsigned int tso_segs, sent_pkts;
2604 422 : int cwnd_quota;
2605 422 : int result;
2606 422 : bool is_cwnd_limited = false, is_rwnd_limited = false;
2607 422 : u32 max_segs;
2608 :
2609 422 : sent_pkts = 0;
2610 :
2611 422 : tcp_mstamp_refresh(tp);
2612 422 : if (!push_one) {
2613 : /* Do MTU probing. */
2614 422 : result = tcp_mtu_probe(sk);
2615 422 : if (!result) {
2616 : return false;
2617 422 : } else if (result > 0) {
2618 0 : sent_pkts = 1;
2619 : }
2620 : }
2621 :
2622 422 : max_segs = tcp_tso_segs(sk, mss_now);
2623 786 : while ((skb = tcp_send_head(sk))) {
2624 366 : unsigned int limit;
2625 :
2626 366 : if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2627 : /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2628 0 : skb->skb_mstamp_ns = tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2629 0 : list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2630 0 : tcp_init_tso_segs(skb, mss_now);
2631 0 : goto repair; /* Skip network transmission */
2632 : }
2633 :
2634 366 : if (tcp_pacing_check(sk))
2635 : break;
2636 :
2637 366 : tso_segs = tcp_init_tso_segs(skb, mss_now);
2638 366 : BUG_ON(!tso_segs);
2639 :
2640 366 : cwnd_quota = tcp_cwnd_test(tp, skb);
2641 366 : if (!cwnd_quota) {
2642 0 : if (push_one == 2)
2643 : /* Force out a loss probe pkt. */
2644 : cwnd_quota = 1;
2645 : else
2646 : break;
2647 : }
2648 :
2649 366 : if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2650 0 : is_rwnd_limited = true;
2651 0 : break;
2652 : }
2653 :
2654 366 : if (tso_segs == 1) {
2655 366 : if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2656 : (tcp_skb_is_last(sk, skb) ?
2657 : nonagle : TCP_NAGLE_PUSH))))
2658 : break;
2659 : } else {
2660 0 : if (!push_one &&
2661 0 : tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2662 : &is_rwnd_limited, max_segs))
2663 : break;
2664 : }
2665 :
2666 364 : limit = mss_now;
2667 364 : if (tso_segs > 1 && !tcp_urg_mode(tp))
2668 0 : limit = tcp_mss_split_point(sk, skb, mss_now,
2669 0 : min_t(unsigned int,
2670 : cwnd_quota,
2671 : max_segs),
2672 : nonagle);
2673 :
2674 364 : if (skb->len > limit &&
2675 0 : unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2676 : break;
2677 :
2678 364 : if (tcp_small_queue_check(sk, skb, 0))
2679 : break;
2680 :
2681 : /* Argh, we hit an empty skb(), presumably a thread
2682 : * is sleeping in sendmsg()/sk_stream_wait_memory().
2683 : * We do not want to send a pure-ack packet and have
2684 : * a strange looking rtx queue with empty packet(s).
2685 : */
2686 364 : if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
2687 : break;
2688 :
2689 364 : if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2690 : break;
2691 :
2692 364 : repair:
2693 : /* Advance the send_head. This one is sent out.
2694 : * This call will increment packets_out.
2695 : */
2696 364 : tcp_event_new_data_sent(sk, skb);
2697 :
2698 364 : tcp_minshall_update(tp, mss_now, skb);
2699 364 : sent_pkts += tcp_skb_pcount(skb);
2700 :
2701 364 : if (push_one)
2702 : break;
2703 : }
2704 :
2705 422 : if (is_rwnd_limited)
2706 0 : tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2707 : else
2708 422 : tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2709 :
2710 422 : is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2711 422 : if (likely(sent_pkts || is_cwnd_limited))
2712 364 : tcp_cwnd_validate(sk, is_cwnd_limited);
2713 :
2714 422 : if (likely(sent_pkts)) {
2715 364 : if (tcp_in_cwnd_reduction(sk))
2716 0 : tp->prr_out += sent_pkts;
2717 :
2718 : /* Send one loss probe per tail loss episode. */
2719 364 : if (push_one != 2)
2720 364 : tcp_schedule_loss_probe(sk, false);
2721 364 : return false;
2722 : }
2723 78 : return !tp->packets_out && !tcp_write_queue_empty(sk);
2724 : }
2725 :
2726 715 : bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2727 : {
2728 715 : struct inet_connection_sock *icsk = inet_csk(sk);
2729 715 : struct tcp_sock *tp = tcp_sk(sk);
2730 715 : u32 timeout, rto_delta_us;
2731 715 : int early_retrans;
2732 :
2733 : /* Don't do any loss probe on a Fast Open connection before 3WHS
2734 : * finishes.
2735 : */
2736 715 : if (rcu_access_pointer(tp->fastopen_rsk))
2737 : return false;
2738 :
2739 715 : early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
2740 : /* Schedule a loss probe in 2*RTT for SACK capable connections
2741 : * not in loss recovery, that are either limited by cwnd or application.
2742 : */
2743 715 : if ((early_retrans != 3 && early_retrans != 4) ||
2744 715 : !tp->packets_out || !tcp_is_sack(tp) ||
2745 0 : (icsk->icsk_ca_state != TCP_CA_Open &&
2746 : icsk->icsk_ca_state != TCP_CA_CWR))
2747 : return false;
2748 :
2749 : /* Probe timeout is 2*rtt. Add minimum RTO to account
2750 : * for delayed ack when there's one outstanding packet. If no RTT
2751 : * sample is available then probe after TCP_TIMEOUT_INIT.
2752 : */
2753 0 : if (tp->srtt_us) {
2754 0 : timeout = usecs_to_jiffies(tp->srtt_us >> 2);
2755 0 : if (tp->packets_out == 1)
2756 0 : timeout += TCP_RTO_MIN;
2757 : else
2758 0 : timeout += TCP_TIMEOUT_MIN;
2759 : } else {
2760 : timeout = TCP_TIMEOUT_INIT;
2761 : }
2762 :
2763 : /* If the RTO formula yields an earlier time, then use that time. */
2764 0 : rto_delta_us = advancing_rto ?
2765 0 : jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2766 0 : tcp_rto_delta_us(sk); /* How far in future is RTO? */
2767 0 : if (rto_delta_us > 0)
2768 0 : timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2769 :
2770 0 : tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, TCP_RTO_MAX);
2771 0 : return true;
2772 : }
2773 :
2774 : /* Thanks to skb fast clones, we can detect if a prior transmit of
2775 : * a packet is still in a qdisc or driver queue.
2776 : * In this case, there is very little point doing a retransmit !
2777 : */
2778 0 : static bool skb_still_in_host_queue(const struct sock *sk,
2779 : const struct sk_buff *skb)
2780 : {
2781 0 : if (unlikely(skb_fclone_busy(sk, skb))) {
2782 0 : NET_INC_STATS(sock_net(sk),
2783 : LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2784 0 : return true;
2785 : }
2786 : return false;
2787 : }
2788 :
2789 : /* When probe timeout (PTO) fires, try send a new segment if possible, else
2790 : * retransmit the last segment.
2791 : */
2792 0 : void tcp_send_loss_probe(struct sock *sk)
2793 : {
2794 0 : struct tcp_sock *tp = tcp_sk(sk);
2795 0 : struct sk_buff *skb;
2796 0 : int pcount;
2797 0 : int mss = tcp_current_mss(sk);
2798 :
2799 : /* At most one outstanding TLP */
2800 0 : if (tp->tlp_high_seq)
2801 0 : goto rearm_timer;
2802 :
2803 0 : tp->tlp_retrans = 0;
2804 0 : skb = tcp_send_head(sk);
2805 0 : if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2806 0 : pcount = tp->packets_out;
2807 0 : tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2808 0 : if (tp->packets_out > pcount)
2809 0 : goto probe_sent;
2810 0 : goto rearm_timer;
2811 : }
2812 0 : skb = skb_rb_last(&sk->tcp_rtx_queue);
2813 0 : if (unlikely(!skb)) {
2814 0 : WARN_ONCE(tp->packets_out,
2815 : "invalid inflight: %u state %u cwnd %u mss %d\n",
2816 : tp->packets_out, sk->sk_state, tp->snd_cwnd, mss);
2817 0 : inet_csk(sk)->icsk_pending = 0;
2818 0 : return;
2819 : }
2820 :
2821 0 : if (skb_still_in_host_queue(sk, skb))
2822 0 : goto rearm_timer;
2823 :
2824 0 : pcount = tcp_skb_pcount(skb);
2825 0 : if (WARN_ON(!pcount))
2826 0 : goto rearm_timer;
2827 :
2828 0 : if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2829 0 : if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2830 : (pcount - 1) * mss, mss,
2831 : GFP_ATOMIC)))
2832 0 : goto rearm_timer;
2833 0 : skb = skb_rb_next(skb);
2834 : }
2835 :
2836 0 : if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2837 0 : goto rearm_timer;
2838 :
2839 0 : if (__tcp_retransmit_skb(sk, skb, 1))
2840 0 : goto rearm_timer;
2841 :
2842 0 : tp->tlp_retrans = 1;
2843 :
2844 0 : probe_sent:
2845 : /* Record snd_nxt for loss detection. */
2846 0 : tp->tlp_high_seq = tp->snd_nxt;
2847 :
2848 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2849 : /* Reset s.t. tcp_rearm_rto will restart timer from now */
2850 0 : inet_csk(sk)->icsk_pending = 0;
2851 0 : rearm_timer:
2852 0 : tcp_rearm_rto(sk);
2853 : }
2854 :
2855 : /* Push out any pending frames which were held back due to
2856 : * TCP_CORK or attempt at coalescing tiny packets.
2857 : * The socket must be locked by the caller.
2858 : */
2859 364 : void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2860 : int nonagle)
2861 : {
2862 : /* If we are closed, the bytes will have to remain here.
2863 : * In time closedown will finish, we empty the write queue and
2864 : * all will be happy.
2865 : */
2866 364 : if (unlikely(sk->sk_state == TCP_CLOSE))
2867 : return;
2868 :
2869 364 : if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2870 : sk_gfp_mask(sk, GFP_ATOMIC)))
2871 0 : tcp_check_probe_timer(sk);
2872 : }
2873 :
2874 : /* Send _single_ skb sitting at the send head. This function requires
2875 : * true push pending frames to setup probe timer etc.
2876 : */
2877 0 : void tcp_push_one(struct sock *sk, unsigned int mss_now)
2878 : {
2879 0 : struct sk_buff *skb = tcp_send_head(sk);
2880 :
2881 0 : BUG_ON(!skb || skb->len < mss_now);
2882 :
2883 0 : tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2884 0 : }
2885 :
2886 : /* This function returns the amount that we can raise the
2887 : * usable window based on the following constraints
2888 : *
2889 : * 1. The window can never be shrunk once it is offered (RFC 793)
2890 : * 2. We limit memory per socket
2891 : *
2892 : * RFC 1122:
2893 : * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2894 : * RECV.NEXT + RCV.WIN fixed until:
2895 : * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2896 : *
2897 : * i.e. don't raise the right edge of the window until you can raise
2898 : * it at least MSS bytes.
2899 : *
2900 : * Unfortunately, the recommended algorithm breaks header prediction,
2901 : * since header prediction assumes th->window stays fixed.
2902 : *
2903 : * Strictly speaking, keeping th->window fixed violates the receiver
2904 : * side SWS prevention criteria. The problem is that under this rule
2905 : * a stream of single byte packets will cause the right side of the
2906 : * window to always advance by a single byte.
2907 : *
2908 : * Of course, if the sender implements sender side SWS prevention
2909 : * then this will not be a problem.
2910 : *
2911 : * BSD seems to make the following compromise:
2912 : *
2913 : * If the free space is less than the 1/4 of the maximum
2914 : * space available and the free space is less than 1/2 mss,
2915 : * then set the window to 0.
2916 : * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2917 : * Otherwise, just prevent the window from shrinking
2918 : * and from being larger than the largest representable value.
2919 : *
2920 : * This prevents incremental opening of the window in the regime
2921 : * where TCP is limited by the speed of the reader side taking
2922 : * data out of the TCP receive queue. It does nothing about
2923 : * those cases where the window is constrained on the sender side
2924 : * because the pipeline is full.
2925 : *
2926 : * BSD also seems to "accidentally" limit itself to windows that are a
2927 : * multiple of MSS, at least until the free space gets quite small.
2928 : * This would appear to be a side effect of the mbuf implementation.
2929 : * Combining these two algorithms results in the observed behavior
2930 : * of having a fixed window size at almost all times.
2931 : *
2932 : * Below we obtain similar behavior by forcing the offered window to
2933 : * a multiple of the mss when it is feasible to do so.
2934 : *
2935 : * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2936 : * Regular options like TIMESTAMP are taken into account.
2937 : */
2938 464 : u32 __tcp_select_window(struct sock *sk)
2939 : {
2940 464 : struct inet_connection_sock *icsk = inet_csk(sk);
2941 464 : struct tcp_sock *tp = tcp_sk(sk);
2942 : /* MSS for the peer's data. Previous versions used mss_clamp
2943 : * here. I don't know if the value based on our guesses
2944 : * of peer's MSS is better for the performance. It's more correct
2945 : * but may be worse for the performance because of rcv_mss
2946 : * fluctuations. --SAW 1998/11/1
2947 : */
2948 464 : int mss = icsk->icsk_ack.rcv_mss;
2949 464 : int free_space = tcp_space(sk);
2950 464 : int allowed_space = tcp_full_space(sk);
2951 464 : int full_space, window;
2952 :
2953 464 : if (sk_is_mptcp(sk))
2954 464 : mptcp_space(sk, &free_space, &allowed_space);
2955 :
2956 464 : full_space = min_t(int, tp->window_clamp, allowed_space);
2957 :
2958 464 : if (unlikely(mss > full_space)) {
2959 0 : mss = full_space;
2960 0 : if (mss <= 0)
2961 : return 0;
2962 : }
2963 464 : if (free_space < (full_space >> 1)) {
2964 1 : icsk->icsk_ack.quick = 0;
2965 :
2966 1 : if (tcp_under_memory_pressure(sk))
2967 0 : tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2968 : 4U * tp->advmss);
2969 :
2970 : /* free_space might become our new window, make sure we don't
2971 : * increase it due to wscale.
2972 : */
2973 1 : free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2974 :
2975 : /* if free space is less than mss estimate, or is below 1/16th
2976 : * of the maximum allowed, try to move to zero-window, else
2977 : * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2978 : * new incoming data is dropped due to memory limits.
2979 : * With large window, mss test triggers way too late in order
2980 : * to announce zero window in time before rmem limit kicks in.
2981 : */
2982 1 : if (free_space < (allowed_space >> 4) || free_space < mss)
2983 : return 0;
2984 : }
2985 :
2986 464 : if (free_space > tp->rcv_ssthresh)
2987 454 : free_space = tp->rcv_ssthresh;
2988 :
2989 : /* Don't do rounding if we are using window scaling, since the
2990 : * scaled window will not line up with the MSS boundary anyway.
2991 : */
2992 464 : if (tp->rx_opt.rcv_wscale) {
2993 0 : window = free_space;
2994 :
2995 : /* Advertise enough space so that it won't get scaled away.
2996 : * Import case: prevent zero window announcement if
2997 : * 1<<rcv_wscale > mss.
2998 : */
2999 0 : window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
3000 : } else {
3001 464 : window = tp->rcv_wnd;
3002 : /* Get the largest window that is a nice multiple of mss.
3003 : * Window clamp already applied above.
3004 : * If our current window offering is within 1 mss of the
3005 : * free space we just keep it. This prevents the divide
3006 : * and multiply from happening most of the time.
3007 : * We also don't do any window rounding when the free space
3008 : * is too small.
3009 : */
3010 464 : if (window <= free_space - mss || window > free_space)
3011 42 : window = rounddown(free_space, mss);
3012 422 : else if (mss == full_space &&
3013 0 : free_space > window + (full_space >> 1))
3014 0 : window = free_space;
3015 : }
3016 :
3017 464 : return window;
3018 : }
3019 :
3020 0 : void tcp_skb_collapse_tstamp(struct sk_buff *skb,
3021 : const struct sk_buff *next_skb)
3022 : {
3023 0 : if (unlikely(tcp_has_tx_tstamp(next_skb))) {
3024 0 : const struct skb_shared_info *next_shinfo =
3025 0 : skb_shinfo(next_skb);
3026 0 : struct skb_shared_info *shinfo = skb_shinfo(skb);
3027 :
3028 0 : shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
3029 0 : shinfo->tskey = next_shinfo->tskey;
3030 0 : TCP_SKB_CB(skb)->txstamp_ack |=
3031 0 : TCP_SKB_CB(next_skb)->txstamp_ack;
3032 : }
3033 0 : }
3034 :
3035 : /* Collapses two adjacent SKB's during retransmission. */
3036 0 : static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
3037 : {
3038 0 : struct tcp_sock *tp = tcp_sk(sk);
3039 0 : struct sk_buff *next_skb = skb_rb_next(skb);
3040 0 : int next_skb_size;
3041 :
3042 0 : next_skb_size = next_skb->len;
3043 :
3044 0 : BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
3045 :
3046 0 : if (next_skb_size) {
3047 0 : if (next_skb_size <= skb_availroom(skb))
3048 0 : skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
3049 : next_skb_size);
3050 0 : else if (!tcp_skb_shift(skb, next_skb, 1, next_skb_size))
3051 : return false;
3052 : }
3053 0 : tcp_highest_sack_replace(sk, next_skb, skb);
3054 :
3055 : /* Update sequence range on original skb. */
3056 0 : TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
3057 :
3058 : /* Merge over control information. This moves PSH/FIN etc. over */
3059 0 : TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
3060 :
3061 : /* All done, get rid of second SKB and account for it so
3062 : * packet counting does not break.
3063 : */
3064 0 : TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
3065 0 : TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
3066 :
3067 : /* changed transmit queue under us so clear hints */
3068 0 : tcp_clear_retrans_hints_partial(tp);
3069 0 : if (next_skb == tp->retransmit_skb_hint)
3070 0 : tp->retransmit_skb_hint = skb;
3071 :
3072 0 : tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
3073 :
3074 0 : tcp_skb_collapse_tstamp(skb, next_skb);
3075 :
3076 0 : tcp_rtx_queue_unlink_and_free(next_skb, sk);
3077 0 : return true;
3078 : }
3079 :
3080 : /* Check if coalescing SKBs is legal. */
3081 0 : static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
3082 : {
3083 0 : if (tcp_skb_pcount(skb) > 1)
3084 : return false;
3085 0 : if (skb_cloned(skb))
3086 : return false;
3087 : /* Some heuristics for collapsing over SACK'd could be invented */
3088 0 : if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
3089 : return false;
3090 :
3091 : return true;
3092 : }
3093 :
3094 : /* Collapse packets in the retransmit queue to make to create
3095 : * less packets on the wire. This is only done on retransmission.
3096 : */
3097 0 : static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
3098 : int space)
3099 : {
3100 0 : struct tcp_sock *tp = tcp_sk(sk);
3101 0 : struct sk_buff *skb = to, *tmp;
3102 0 : bool first = true;
3103 :
3104 0 : if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
3105 : return;
3106 0 : if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3107 : return;
3108 :
3109 0 : skb_rbtree_walk_from_safe(skb, tmp) {
3110 0 : if (!tcp_can_collapse(sk, skb))
3111 : break;
3112 :
3113 0 : if (!tcp_skb_can_collapse(to, skb))
3114 : break;
3115 :
3116 0 : space -= skb->len;
3117 :
3118 0 : if (first) {
3119 0 : first = false;
3120 0 : continue;
3121 : }
3122 :
3123 0 : if (space < 0)
3124 : break;
3125 :
3126 0 : if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
3127 : break;
3128 :
3129 0 : if (!tcp_collapse_retrans(sk, to))
3130 : break;
3131 : }
3132 : }
3133 :
3134 : /* This retransmits one SKB. Policy decisions and retransmit queue
3135 : * state updates are done by the caller. Returns non-zero if an
3136 : * error occurred which prevented the send.
3137 : */
3138 0 : int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3139 : {
3140 0 : struct inet_connection_sock *icsk = inet_csk(sk);
3141 0 : struct tcp_sock *tp = tcp_sk(sk);
3142 0 : unsigned int cur_mss;
3143 0 : int diff, len, err;
3144 :
3145 :
3146 : /* Inconclusive MTU probe */
3147 0 : if (icsk->icsk_mtup.probe_size)
3148 0 : icsk->icsk_mtup.probe_size = 0;
3149 :
3150 : /* Do not sent more than we queued. 1/4 is reserved for possible
3151 : * copying overhead: fragmentation, tunneling, mangling etc.
3152 : */
3153 0 : if (refcount_read(&sk->sk_wmem_alloc) >
3154 0 : min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
3155 : sk->sk_sndbuf))
3156 : return -EAGAIN;
3157 :
3158 0 : if (skb_still_in_host_queue(sk, skb))
3159 : return -EBUSY;
3160 :
3161 0 : if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
3162 0 : if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
3163 0 : WARN_ON_ONCE(1);
3164 0 : return -EINVAL;
3165 : }
3166 0 : if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3167 : return -ENOMEM;
3168 : }
3169 :
3170 0 : if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3171 : return -EHOSTUNREACH; /* Routing failure or similar. */
3172 :
3173 0 : cur_mss = tcp_current_mss(sk);
3174 :
3175 : /* If receiver has shrunk his window, and skb is out of
3176 : * new window, do not retransmit it. The exception is the
3177 : * case, when window is shrunk to zero. In this case
3178 : * our retransmit serves as a zero window probe.
3179 : */
3180 0 : if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
3181 : TCP_SKB_CB(skb)->seq != tp->snd_una)
3182 : return -EAGAIN;
3183 :
3184 0 : len = cur_mss * segs;
3185 0 : if (skb->len > len) {
3186 0 : if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
3187 : cur_mss, GFP_ATOMIC))
3188 : return -ENOMEM; /* We'll try again later. */
3189 : } else {
3190 0 : if (skb_unclone(skb, GFP_ATOMIC))
3191 : return -ENOMEM;
3192 :
3193 0 : diff = tcp_skb_pcount(skb);
3194 0 : tcp_set_skb_tso_segs(skb, cur_mss);
3195 0 : diff -= tcp_skb_pcount(skb);
3196 0 : if (diff)
3197 0 : tcp_adjust_pcount(sk, skb, diff);
3198 0 : if (skb->len < cur_mss)
3199 0 : tcp_retrans_try_collapse(sk, skb, cur_mss);
3200 : }
3201 :
3202 : /* RFC3168, section 6.1.1.1. ECN fallback */
3203 0 : if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
3204 0 : tcp_ecn_clear_syn(sk, skb);
3205 :
3206 : /* Update global and local TCP statistics. */
3207 0 : segs = tcp_skb_pcount(skb);
3208 0 : TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
3209 0 : if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3210 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3211 0 : tp->total_retrans += segs;
3212 0 : tp->bytes_retrans += skb->len;
3213 :
3214 : /* make sure skb->data is aligned on arches that require it
3215 : * and check if ack-trimming & collapsing extended the headroom
3216 : * beyond what csum_start can cover.
3217 : */
3218 0 : if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
3219 : skb_headroom(skb) >= 0xFFFF)) {
3220 0 : struct sk_buff *nskb;
3221 :
3222 0 : tcp_skb_tsorted_save(skb) {
3223 0 : nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
3224 0 : if (nskb) {
3225 0 : nskb->dev = NULL;
3226 0 : err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
3227 : } else {
3228 : err = -ENOBUFS;
3229 : }
3230 0 : } tcp_skb_tsorted_restore(skb);
3231 :
3232 0 : if (!err) {
3233 0 : tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
3234 0 : tcp_rate_skb_sent(sk, skb);
3235 : }
3236 : } else {
3237 0 : err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3238 : }
3239 :
3240 : /* To avoid taking spuriously low RTT samples based on a timestamp
3241 : * for a transmit that never happened, always mark EVER_RETRANS
3242 : */
3243 0 : TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
3244 :
3245 0 : if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
3246 0 : tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
3247 : TCP_SKB_CB(skb)->seq, segs, err);
3248 :
3249 0 : if (likely(!err)) {
3250 0 : trace_tcp_retransmit_skb(sk, skb);
3251 0 : } else if (err != -EBUSY) {
3252 0 : NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
3253 : }
3254 : return err;
3255 : }
3256 :
3257 0 : int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3258 : {
3259 0 : struct tcp_sock *tp = tcp_sk(sk);
3260 0 : int err = __tcp_retransmit_skb(sk, skb, segs);
3261 :
3262 0 : if (err == 0) {
3263 : #if FASTRETRANS_DEBUG > 0
3264 0 : if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3265 0 : net_dbg_ratelimited("retrans_out leaked\n");
3266 : }
3267 : #endif
3268 0 : TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3269 0 : tp->retrans_out += tcp_skb_pcount(skb);
3270 : }
3271 :
3272 : /* Save stamp of the first (attempted) retransmit. */
3273 0 : if (!tp->retrans_stamp)
3274 0 : tp->retrans_stamp = tcp_skb_timestamp(skb);
3275 :
3276 0 : if (tp->undo_retrans < 0)
3277 0 : tp->undo_retrans = 0;
3278 0 : tp->undo_retrans += tcp_skb_pcount(skb);
3279 0 : return err;
3280 : }
3281 :
3282 : /* This gets called after a retransmit timeout, and the initially
3283 : * retransmitted data is acknowledged. It tries to continue
3284 : * resending the rest of the retransmit queue, until either
3285 : * we've sent it all or the congestion window limit is reached.
3286 : */
3287 0 : void tcp_xmit_retransmit_queue(struct sock *sk)
3288 : {
3289 0 : const struct inet_connection_sock *icsk = inet_csk(sk);
3290 0 : struct sk_buff *skb, *rtx_head, *hole = NULL;
3291 0 : struct tcp_sock *tp = tcp_sk(sk);
3292 0 : bool rearm_timer = false;
3293 0 : u32 max_segs;
3294 0 : int mib_idx;
3295 :
3296 0 : if (!tp->packets_out)
3297 : return;
3298 :
3299 0 : rtx_head = tcp_rtx_queue_head(sk);
3300 0 : skb = tp->retransmit_skb_hint ?: rtx_head;
3301 0 : max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3302 0 : skb_rbtree_walk_from(skb) {
3303 0 : __u8 sacked;
3304 0 : int segs;
3305 :
3306 0 : if (tcp_pacing_check(sk))
3307 : break;
3308 :
3309 : /* we could do better than to assign each time */
3310 0 : if (!hole)
3311 0 : tp->retransmit_skb_hint = skb;
3312 :
3313 0 : segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
3314 0 : if (segs <= 0)
3315 : break;
3316 0 : sacked = TCP_SKB_CB(skb)->sacked;
3317 : /* In case tcp_shift_skb_data() have aggregated large skbs,
3318 : * we need to make sure not sending too bigs TSO packets
3319 : */
3320 0 : segs = min_t(int, segs, max_segs);
3321 :
3322 0 : if (tp->retrans_out >= tp->lost_out) {
3323 : break;
3324 0 : } else if (!(sacked & TCPCB_LOST)) {
3325 0 : if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3326 0 : hole = skb;
3327 0 : continue;
3328 :
3329 : } else {
3330 0 : if (icsk->icsk_ca_state != TCP_CA_Loss)
3331 : mib_idx = LINUX_MIB_TCPFASTRETRANS;
3332 : else
3333 0 : mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3334 : }
3335 :
3336 0 : if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3337 0 : continue;
3338 :
3339 0 : if (tcp_small_queue_check(sk, skb, 1))
3340 : break;
3341 :
3342 0 : if (tcp_retransmit_skb(sk, skb, segs))
3343 : break;
3344 :
3345 0 : NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3346 :
3347 0 : if (tcp_in_cwnd_reduction(sk))
3348 0 : tp->prr_out += tcp_skb_pcount(skb);
3349 :
3350 0 : if (skb == rtx_head &&
3351 0 : icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3352 0 : rearm_timer = true;
3353 :
3354 : }
3355 0 : if (rearm_timer)
3356 0 : tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3357 0 : inet_csk(sk)->icsk_rto,
3358 : TCP_RTO_MAX);
3359 : }
3360 :
3361 : /* We allow to exceed memory limits for FIN packets to expedite
3362 : * connection tear down and (memory) recovery.
3363 : * Otherwise tcp_send_fin() could be tempted to either delay FIN
3364 : * or even be forced to close flow without any FIN.
3365 : * In general, we want to allow one skb per socket to avoid hangs
3366 : * with edge trigger epoll()
3367 : */
3368 228 : void sk_forced_mem_schedule(struct sock *sk, int size)
3369 : {
3370 228 : int amt;
3371 :
3372 228 : if (size <= sk->sk_forward_alloc)
3373 : return;
3374 11 : amt = sk_mem_pages(size);
3375 11 : sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3376 11 : sk_memory_allocated_add(sk, amt);
3377 :
3378 11 : if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3379 : mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3380 : }
3381 :
3382 : /* Send a FIN. The caller locks the socket for us.
3383 : * We should try to send a FIN packet really hard, but eventually give up.
3384 : */
3385 3 : void tcp_send_fin(struct sock *sk)
3386 : {
3387 3 : struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk);
3388 0 : struct tcp_sock *tp = tcp_sk(sk);
3389 :
3390 : /* Optimization, tack on the FIN if we have one skb in write queue and
3391 : * this skb was not yet sent, or we are under memory pressure.
3392 : * Note: in the latter case, FIN packet will be sent after a timeout,
3393 : * as TCP stack thinks it has already been transmitted.
3394 : */
3395 3 : tskb = tail;
3396 3 : if (!tskb && tcp_under_memory_pressure(sk))
3397 0 : tskb = skb_rb_last(&sk->tcp_rtx_queue);
3398 :
3399 3 : if (tskb) {
3400 0 : TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3401 0 : TCP_SKB_CB(tskb)->end_seq++;
3402 0 : tp->write_seq++;
3403 0 : if (!tail) {
3404 : /* This means tskb was already sent.
3405 : * Pretend we included the FIN on previous transmit.
3406 : * We need to set tp->snd_nxt to the value it would have
3407 : * if FIN had been sent. This is because retransmit path
3408 : * does not change tp->snd_nxt.
3409 : */
3410 0 : WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3411 0 : return;
3412 : }
3413 : } else {
3414 3 : skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
3415 3 : if (unlikely(!skb))
3416 : return;
3417 :
3418 3 : INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3419 3 : skb_reserve(skb, MAX_TCP_HEADER);
3420 3 : sk_forced_mem_schedule(sk, skb->truesize);
3421 : /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3422 3 : tcp_init_nondata_skb(skb, tp->write_seq,
3423 : TCPHDR_ACK | TCPHDR_FIN);
3424 3 : tcp_queue_skb(sk, skb);
3425 : }
3426 3 : __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3427 : }
3428 :
3429 : /* We get here when a process closes a file descriptor (either due to
3430 : * an explicit close() or as a byproduct of exit()'ing) and there
3431 : * was unread data in the receive queue. This behavior is recommended
3432 : * by RFC 2525, section 2.17. -DaveM
3433 : */
3434 0 : void tcp_send_active_reset(struct sock *sk, gfp_t priority)
3435 : {
3436 0 : struct sk_buff *skb;
3437 :
3438 0 : TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3439 :
3440 : /* NOTE: No TCP options attached and we never retransmit this. */
3441 0 : skb = alloc_skb(MAX_TCP_HEADER, priority);
3442 0 : if (!skb) {
3443 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3444 0 : return;
3445 : }
3446 :
3447 : /* Reserve space for headers and prepare control bits. */
3448 0 : skb_reserve(skb, MAX_TCP_HEADER);
3449 0 : tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3450 : TCPHDR_ACK | TCPHDR_RST);
3451 0 : tcp_mstamp_refresh(tcp_sk(sk));
3452 : /* Send it off. */
3453 0 : if (tcp_transmit_skb(sk, skb, 0, priority))
3454 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3455 :
3456 : /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3457 : * skb here is different to the troublesome skb, so use NULL
3458 : */
3459 0 : trace_tcp_send_reset(sk, NULL);
3460 : }
3461 :
3462 : /* Send a crossed SYN-ACK during socket establishment.
3463 : * WARNING: This routine must only be called when we have already sent
3464 : * a SYN packet that crossed the incoming SYN that caused this routine
3465 : * to get called. If this assumption fails then the initial rcv_wnd
3466 : * and rcv_wscale values will not be correct.
3467 : */
3468 0 : int tcp_send_synack(struct sock *sk)
3469 : {
3470 0 : struct sk_buff *skb;
3471 :
3472 0 : skb = tcp_rtx_queue_head(sk);
3473 0 : if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3474 0 : pr_err("%s: wrong queue state\n", __func__);
3475 0 : return -EFAULT;
3476 : }
3477 0 : if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3478 0 : if (skb_cloned(skb)) {
3479 0 : struct sk_buff *nskb;
3480 :
3481 0 : tcp_skb_tsorted_save(skb) {
3482 0 : nskb = skb_copy(skb, GFP_ATOMIC);
3483 0 : } tcp_skb_tsorted_restore(skb);
3484 0 : if (!nskb)
3485 : return -ENOMEM;
3486 0 : INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3487 0 : tcp_highest_sack_replace(sk, skb, nskb);
3488 0 : tcp_rtx_queue_unlink_and_free(skb, sk);
3489 0 : __skb_header_release(nskb);
3490 0 : tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3491 0 : sk_wmem_queued_add(sk, nskb->truesize);
3492 0 : sk_mem_charge(sk, nskb->truesize);
3493 : skb = nskb;
3494 : }
3495 :
3496 0 : TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3497 0 : tcp_ecn_send_synack(sk, skb);
3498 : }
3499 0 : return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3500 : }
3501 :
3502 : /**
3503 : * tcp_make_synack - Allocate one skb and build a SYNACK packet.
3504 : * @sk: listener socket
3505 : * @dst: dst entry attached to the SYNACK. It is consumed and caller
3506 : * should not use it again.
3507 : * @req: request_sock pointer
3508 : * @foc: cookie for tcp fast open
3509 : * @synack_type: Type of synack to prepare
3510 : * @syn_skb: SYN packet just received. It could be NULL for rtx case.
3511 : */
3512 4 : struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3513 : struct request_sock *req,
3514 : struct tcp_fastopen_cookie *foc,
3515 : enum tcp_synack_type synack_type,
3516 : struct sk_buff *syn_skb)
3517 : {
3518 4 : struct inet_request_sock *ireq = inet_rsk(req);
3519 4 : const struct tcp_sock *tp = tcp_sk(sk);
3520 4 : struct tcp_md5sig_key *md5 = NULL;
3521 4 : struct tcp_out_options opts;
3522 4 : struct sk_buff *skb;
3523 4 : int tcp_header_size;
3524 4 : struct tcphdr *th;
3525 4 : int mss;
3526 4 : u64 now;
3527 :
3528 4 : skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3529 4 : if (unlikely(!skb)) {
3530 0 : dst_release(dst);
3531 0 : return NULL;
3532 : }
3533 : /* Reserve space for headers. */
3534 4 : skb_reserve(skb, MAX_TCP_HEADER);
3535 :
3536 4 : switch (synack_type) {
3537 : case TCP_SYNACK_NORMAL:
3538 4 : skb_set_owner_w(skb, req_to_sk(req));
3539 4 : break;
3540 : case TCP_SYNACK_COOKIE:
3541 : /* Under synflood, we do not attach skb to a socket,
3542 : * to avoid false sharing.
3543 : */
3544 : break;
3545 0 : case TCP_SYNACK_FASTOPEN:
3546 : /* sk is a const pointer, because we want to express multiple
3547 : * cpu might call us concurrently.
3548 : * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3549 : */
3550 0 : skb_set_owner_w(skb, (struct sock *)sk);
3551 0 : break;
3552 : }
3553 4 : skb_dst_set(skb, dst);
3554 :
3555 4 : mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3556 :
3557 4 : memset(&opts, 0, sizeof(opts));
3558 4 : now = tcp_clock_ns();
3559 : #ifdef CONFIG_SYN_COOKIES
3560 : if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))
3561 : skb->skb_mstamp_ns = cookie_init_timestamp(req, now);
3562 : else
3563 : #endif
3564 : {
3565 4 : skb->skb_mstamp_ns = now;
3566 4 : if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3567 4 : tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3568 : }
3569 :
3570 : #ifdef CONFIG_TCP_MD5SIG
3571 : rcu_read_lock();
3572 : md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
3573 : #endif
3574 4 : skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3575 : /* bpf program will be interested in the tcp_flags */
3576 4 : TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;
3577 4 : tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
3578 : foc, synack_type,
3579 4 : syn_skb) + sizeof(*th);
3580 :
3581 4 : skb_push(skb, tcp_header_size);
3582 4 : skb_reset_transport_header(skb);
3583 :
3584 4 : th = (struct tcphdr *)skb->data;
3585 4 : memset(th, 0, sizeof(struct tcphdr));
3586 4 : th->syn = 1;
3587 4 : th->ack = 1;
3588 4 : tcp_ecn_make_synack(req, th);
3589 4 : th->source = htons(ireq->ir_num);
3590 4 : th->dest = ireq->ir_rmt_port;
3591 4 : skb->mark = ireq->ir_mark;
3592 4 : skb->ip_summed = CHECKSUM_PARTIAL;
3593 4 : th->seq = htonl(tcp_rsk(req)->snt_isn);
3594 : /* XXX data is queued and acked as is. No buffer/window check */
3595 4 : th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3596 :
3597 : /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3598 4 : th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3599 4 : tcp_options_write((__be32 *)(th + 1), NULL, &opts);
3600 4 : th->doff = (tcp_header_size >> 2);
3601 4 : __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3602 :
3603 : #ifdef CONFIG_TCP_MD5SIG
3604 : /* Okay, we have all we need - do the md5 hash if needed */
3605 : if (md5)
3606 : tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3607 : md5, req_to_sk(req), skb);
3608 : rcu_read_unlock();
3609 : #endif
3610 :
3611 4 : bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb,
3612 : synack_type, &opts);
3613 :
3614 4 : skb->skb_mstamp_ns = now;
3615 4 : tcp_add_tx_delay(skb, tp);
3616 :
3617 4 : return skb;
3618 : }
3619 : EXPORT_SYMBOL(tcp_make_synack);
3620 :
3621 0 : static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3622 : {
3623 0 : struct inet_connection_sock *icsk = inet_csk(sk);
3624 0 : const struct tcp_congestion_ops *ca;
3625 0 : u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3626 :
3627 0 : if (ca_key == TCP_CA_UNSPEC)
3628 : return;
3629 :
3630 0 : rcu_read_lock();
3631 0 : ca = tcp_ca_find_key(ca_key);
3632 0 : if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
3633 0 : bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
3634 0 : icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3635 0 : icsk->icsk_ca_ops = ca;
3636 : }
3637 0 : rcu_read_unlock();
3638 : }
3639 :
3640 : /* Do all connect socket setups that can be done AF independent. */
3641 0 : static void tcp_connect_init(struct sock *sk)
3642 : {
3643 0 : const struct dst_entry *dst = __sk_dst_get(sk);
3644 0 : struct tcp_sock *tp = tcp_sk(sk);
3645 0 : __u8 rcv_wscale;
3646 0 : u32 rcv_wnd;
3647 :
3648 : /* We'll fix this up when we get a response from the other end.
3649 : * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3650 : */
3651 0 : tp->tcp_header_len = sizeof(struct tcphdr);
3652 0 : if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
3653 0 : tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3654 :
3655 : #ifdef CONFIG_TCP_MD5SIG
3656 : if (tp->af_specific->md5_lookup(sk, sk))
3657 : tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
3658 : #endif
3659 :
3660 : /* If user gave his TCP_MAXSEG, record it to clamp */
3661 0 : if (tp->rx_opt.user_mss)
3662 0 : tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3663 0 : tp->max_window = 0;
3664 0 : tcp_mtup_init(sk);
3665 0 : tcp_sync_mss(sk, dst_mtu(dst));
3666 :
3667 0 : tcp_ca_dst_init(sk, dst);
3668 :
3669 0 : if (!tp->window_clamp)
3670 0 : tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3671 0 : tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3672 :
3673 0 : tcp_initialize_rcv_mss(sk);
3674 :
3675 : /* limit the window selection if the user enforce a smaller rx buffer */
3676 0 : if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3677 0 : (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3678 0 : tp->window_clamp = tcp_full_space(sk);
3679 :
3680 0 : rcv_wnd = tcp_rwnd_init_bpf(sk);
3681 0 : if (rcv_wnd == 0)
3682 0 : rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3683 :
3684 0 : tcp_select_initial_window(sk, tcp_full_space(sk),
3685 0 : tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3686 0 : &tp->rcv_wnd,
3687 0 : &tp->window_clamp,
3688 0 : sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3689 : &rcv_wscale,
3690 : rcv_wnd);
3691 :
3692 0 : tp->rx_opt.rcv_wscale = rcv_wscale;
3693 0 : tp->rcv_ssthresh = tp->rcv_wnd;
3694 :
3695 0 : sk->sk_err = 0;
3696 0 : sock_reset_flag(sk, SOCK_DONE);
3697 0 : tp->snd_wnd = 0;
3698 0 : tcp_init_wl(tp, 0);
3699 0 : tcp_write_queue_purge(sk);
3700 0 : tp->snd_una = tp->write_seq;
3701 0 : tp->snd_sml = tp->write_seq;
3702 0 : tp->snd_up = tp->write_seq;
3703 0 : WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3704 :
3705 0 : if (likely(!tp->repair))
3706 0 : tp->rcv_nxt = 0;
3707 : else
3708 0 : tp->rcv_tstamp = tcp_jiffies32;
3709 0 : tp->rcv_wup = tp->rcv_nxt;
3710 0 : WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
3711 :
3712 0 : inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3713 0 : inet_csk(sk)->icsk_retransmits = 0;
3714 0 : tcp_clear_retrans(tp);
3715 0 : }
3716 :
3717 0 : static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3718 : {
3719 0 : struct tcp_sock *tp = tcp_sk(sk);
3720 0 : struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3721 :
3722 0 : tcb->end_seq += skb->len;
3723 0 : __skb_header_release(skb);
3724 0 : sk_wmem_queued_add(sk, skb->truesize);
3725 0 : sk_mem_charge(sk, skb->truesize);
3726 0 : WRITE_ONCE(tp->write_seq, tcb->end_seq);
3727 0 : tp->packets_out += tcp_skb_pcount(skb);
3728 0 : }
3729 :
3730 : /* Build and send a SYN with data and (cached) Fast Open cookie. However,
3731 : * queue a data-only packet after the regular SYN, such that regular SYNs
3732 : * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3733 : * only the SYN sequence, the data are retransmitted in the first ACK.
3734 : * If cookie is not cached or other error occurs, falls back to send a
3735 : * regular SYN with Fast Open cookie request option.
3736 : */
3737 0 : static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3738 : {
3739 0 : struct tcp_sock *tp = tcp_sk(sk);
3740 0 : struct tcp_fastopen_request *fo = tp->fastopen_req;
3741 0 : int space, err = 0;
3742 0 : struct sk_buff *syn_data;
3743 :
3744 0 : tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3745 0 : if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3746 0 : goto fallback;
3747 :
3748 : /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3749 : * user-MSS. Reserve maximum option space for middleboxes that add
3750 : * private TCP options. The cost is reduced data space in SYN :(
3751 : */
3752 0 : tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3753 :
3754 0 : space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3755 : MAX_TCP_OPTION_SPACE;
3756 :
3757 0 : space = min_t(size_t, space, fo->size);
3758 :
3759 : /* limit to order-0 allocations */
3760 0 : space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
3761 :
3762 0 : syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3763 0 : if (!syn_data)
3764 0 : goto fallback;
3765 0 : syn_data->ip_summed = CHECKSUM_PARTIAL;
3766 0 : memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3767 0 : if (space) {
3768 0 : int copied = copy_from_iter(skb_put(syn_data, space), space,
3769 0 : &fo->data->msg_iter);
3770 0 : if (unlikely(!copied)) {
3771 0 : tcp_skb_tsorted_anchor_cleanup(syn_data);
3772 0 : kfree_skb(syn_data);
3773 0 : goto fallback;
3774 : }
3775 0 : if (copied != space) {
3776 0 : skb_trim(syn_data, copied);
3777 0 : space = copied;
3778 : }
3779 0 : skb_zcopy_set(syn_data, fo->uarg, NULL);
3780 : }
3781 : /* No more data pending in inet_wait_for_connect() */
3782 0 : if (space == fo->size)
3783 0 : fo->data = NULL;
3784 0 : fo->copied = space;
3785 :
3786 0 : tcp_connect_queue_skb(sk, syn_data);
3787 0 : if (syn_data->len)
3788 0 : tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3789 :
3790 0 : err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3791 :
3792 0 : syn->skb_mstamp_ns = syn_data->skb_mstamp_ns;
3793 :
3794 : /* Now full SYN+DATA was cloned and sent (or not),
3795 : * remove the SYN from the original skb (syn_data)
3796 : * we keep in write queue in case of a retransmit, as we
3797 : * also have the SYN packet (with no data) in the same queue.
3798 : */
3799 0 : TCP_SKB_CB(syn_data)->seq++;
3800 0 : TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3801 0 : if (!err) {
3802 0 : tp->syn_data = (fo->copied > 0);
3803 0 : tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
3804 0 : NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3805 0 : goto done;
3806 : }
3807 :
3808 : /* data was not sent, put it in write_queue */
3809 0 : __skb_queue_tail(&sk->sk_write_queue, syn_data);
3810 0 : tp->packets_out -= tcp_skb_pcount(syn_data);
3811 :
3812 0 : fallback:
3813 : /* Send a regular SYN with Fast Open cookie request option */
3814 0 : if (fo->cookie.len > 0)
3815 0 : fo->cookie.len = 0;
3816 0 : err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3817 0 : if (err)
3818 0 : tp->syn_fastopen = 0;
3819 0 : done:
3820 0 : fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3821 0 : return err;
3822 : }
3823 :
3824 : /* Build a SYN and send it off. */
3825 0 : int tcp_connect(struct sock *sk)
3826 : {
3827 0 : struct tcp_sock *tp = tcp_sk(sk);
3828 0 : struct sk_buff *buff;
3829 0 : int err;
3830 :
3831 0 : tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
3832 :
3833 0 : if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3834 : return -EHOSTUNREACH; /* Routing failure or similar. */
3835 :
3836 0 : tcp_connect_init(sk);
3837 :
3838 0 : if (unlikely(tp->repair)) {
3839 0 : tcp_finish_connect(sk, NULL);
3840 0 : return 0;
3841 : }
3842 :
3843 0 : buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3844 0 : if (unlikely(!buff))
3845 : return -ENOBUFS;
3846 :
3847 0 : tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3848 0 : tcp_mstamp_refresh(tp);
3849 0 : tp->retrans_stamp = tcp_time_stamp(tp);
3850 0 : tcp_connect_queue_skb(sk, buff);
3851 0 : tcp_ecn_send_syn(sk, buff);
3852 0 : tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
3853 :
3854 : /* Send off SYN; include data in Fast Open. */
3855 0 : err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3856 0 : tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3857 0 : if (err == -ECONNREFUSED)
3858 : return err;
3859 :
3860 : /* We change tp->snd_nxt after the tcp_transmit_skb() call
3861 : * in order to make this packet get counted in tcpOutSegs.
3862 : */
3863 0 : WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3864 0 : tp->pushed_seq = tp->write_seq;
3865 0 : buff = tcp_send_head(sk);
3866 0 : if (unlikely(buff)) {
3867 0 : WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
3868 0 : tp->pushed_seq = TCP_SKB_CB(buff)->seq;
3869 : }
3870 0 : TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3871 :
3872 : /* Timer for repeating the SYN until an answer. */
3873 0 : inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3874 0 : inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3875 0 : return 0;
3876 : }
3877 : EXPORT_SYMBOL(tcp_connect);
3878 :
3879 : /* Send out a delayed ack, the caller does the policy checking
3880 : * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3881 : * for details.
3882 : */
3883 14 : void tcp_send_delayed_ack(struct sock *sk)
3884 : {
3885 14 : struct inet_connection_sock *icsk = inet_csk(sk);
3886 14 : int ato = icsk->icsk_ack.ato;
3887 14 : unsigned long timeout;
3888 :
3889 14 : if (ato > TCP_DELACK_MIN) {
3890 1 : const struct tcp_sock *tp = tcp_sk(sk);
3891 1 : int max_ato = HZ / 2;
3892 :
3893 1 : if (inet_csk_in_pingpong_mode(sk) ||
3894 0 : (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3895 1 : max_ato = TCP_DELACK_MAX;
3896 :
3897 : /* Slow path, intersegment interval is "high". */
3898 :
3899 : /* If some rtt estimate is known, use it to bound delayed ack.
3900 : * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3901 : * directly.
3902 : */
3903 1 : if (tp->srtt_us) {
3904 1 : int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3905 : TCP_DELACK_MIN);
3906 :
3907 1 : if (rtt < max_ato)
3908 : max_ato = rtt;
3909 : }
3910 :
3911 1 : ato = min(ato, max_ato);
3912 : }
3913 :
3914 14 : ato = min_t(u32, ato, inet_csk(sk)->icsk_delack_max);
3915 :
3916 : /* Stay within the limit we were given */
3917 14 : timeout = jiffies + ato;
3918 :
3919 : /* Use new timeout only if there wasn't a older one earlier. */
3920 14 : if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3921 : /* If delack timer is about to expire, send ACK now. */
3922 2 : if (time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3923 0 : tcp_send_ack(sk);
3924 0 : return;
3925 : }
3926 :
3927 2 : if (!time_before(timeout, icsk->icsk_ack.timeout))
3928 2 : timeout = icsk->icsk_ack.timeout;
3929 : }
3930 14 : icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3931 14 : icsk->icsk_ack.timeout = timeout;
3932 14 : sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3933 : }
3934 :
3935 : /* This routine sends an ack and also updates the window. */
3936 62 : void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
3937 : {
3938 62 : struct sk_buff *buff;
3939 :
3940 : /* If we have been reset, we may not send again. */
3941 62 : if (sk->sk_state == TCP_CLOSE)
3942 : return;
3943 :
3944 : /* We are not putting this on the write queue, so
3945 : * tcp_transmit_skb() will set the ownership to this
3946 : * sock.
3947 : */
3948 62 : buff = alloc_skb(MAX_TCP_HEADER,
3949 : sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3950 62 : if (unlikely(!buff)) {
3951 0 : struct inet_connection_sock *icsk = inet_csk(sk);
3952 0 : unsigned long delay;
3953 :
3954 0 : delay = TCP_DELACK_MAX << icsk->icsk_ack.retry;
3955 0 : if (delay < TCP_RTO_MAX)
3956 0 : icsk->icsk_ack.retry++;
3957 0 : inet_csk_schedule_ack(sk);
3958 0 : icsk->icsk_ack.ato = TCP_ATO_MIN;
3959 0 : inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, delay, TCP_RTO_MAX);
3960 0 : return;
3961 : }
3962 :
3963 : /* Reserve space for headers and prepare control bits. */
3964 62 : skb_reserve(buff, MAX_TCP_HEADER);
3965 62 : tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3966 :
3967 : /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3968 : * too much.
3969 : * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3970 : */
3971 62 : skb_set_tcp_pure_ack(buff);
3972 :
3973 : /* Send it off, this clears delayed acks for us. */
3974 62 : __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
3975 : }
3976 : EXPORT_SYMBOL_GPL(__tcp_send_ack);
3977 :
3978 62 : void tcp_send_ack(struct sock *sk)
3979 : {
3980 62 : __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
3981 62 : }
3982 :
3983 : /* This routine sends a packet with an out of date sequence
3984 : * number. It assumes the other end will try to ack it.
3985 : *
3986 : * Question: what should we make while urgent mode?
3987 : * 4.4BSD forces sending single byte of data. We cannot send
3988 : * out of window data, because we have SND.NXT==SND.MAX...
3989 : *
3990 : * Current solution: to send TWO zero-length segments in urgent mode:
3991 : * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3992 : * out-of-date with SND.UNA-1 to probe window.
3993 : */
3994 0 : static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
3995 : {
3996 0 : struct tcp_sock *tp = tcp_sk(sk);
3997 0 : struct sk_buff *skb;
3998 :
3999 : /* We don't queue it, tcp_transmit_skb() sets ownership. */
4000 0 : skb = alloc_skb(MAX_TCP_HEADER,
4001 : sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4002 0 : if (!skb)
4003 : return -1;
4004 :
4005 : /* Reserve space for headers and set control bits. */
4006 0 : skb_reserve(skb, MAX_TCP_HEADER);
4007 : /* Use a previous sequence. This should cause the other
4008 : * end to send an ack. Don't queue or clone SKB, just
4009 : * send it.
4010 : */
4011 0 : tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
4012 0 : NET_INC_STATS(sock_net(sk), mib);
4013 0 : return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
4014 : }
4015 :
4016 : /* Called from setsockopt( ... TCP_REPAIR ) */
4017 0 : void tcp_send_window_probe(struct sock *sk)
4018 : {
4019 0 : if (sk->sk_state == TCP_ESTABLISHED) {
4020 0 : tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
4021 0 : tcp_mstamp_refresh(tcp_sk(sk));
4022 0 : tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
4023 : }
4024 0 : }
4025 :
4026 : /* Initiate keepalive or window probe from timer. */
4027 0 : int tcp_write_wakeup(struct sock *sk, int mib)
4028 : {
4029 0 : struct tcp_sock *tp = tcp_sk(sk);
4030 0 : struct sk_buff *skb;
4031 :
4032 0 : if (sk->sk_state == TCP_CLOSE)
4033 : return -1;
4034 :
4035 0 : skb = tcp_send_head(sk);
4036 0 : if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
4037 0 : int err;
4038 0 : unsigned int mss = tcp_current_mss(sk);
4039 0 : unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
4040 :
4041 0 : if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
4042 0 : tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
4043 :
4044 : /* We are probing the opening of a window
4045 : * but the window size is != 0
4046 : * must have been a result SWS avoidance ( sender )
4047 : */
4048 0 : if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
4049 0 : skb->len > mss) {
4050 0 : seg_size = min(seg_size, mss);
4051 0 : TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4052 0 : if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
4053 : skb, seg_size, mss, GFP_ATOMIC))
4054 : return -1;
4055 0 : } else if (!tcp_skb_pcount(skb))
4056 0 : tcp_set_skb_tso_segs(skb, mss);
4057 :
4058 0 : TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4059 0 : err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
4060 0 : if (!err)
4061 0 : tcp_event_new_data_sent(sk, skb);
4062 0 : return err;
4063 : } else {
4064 0 : if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
4065 0 : tcp_xmit_probe_skb(sk, 1, mib);
4066 0 : return tcp_xmit_probe_skb(sk, 0, mib);
4067 : }
4068 : }
4069 :
4070 : /* A window probe timeout has occurred. If window is not closed send
4071 : * a partial packet else a zero probe.
4072 : */
4073 0 : void tcp_send_probe0(struct sock *sk)
4074 : {
4075 0 : struct inet_connection_sock *icsk = inet_csk(sk);
4076 0 : struct tcp_sock *tp = tcp_sk(sk);
4077 0 : struct net *net = sock_net(sk);
4078 0 : unsigned long timeout;
4079 0 : int err;
4080 :
4081 0 : err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
4082 :
4083 0 : if (tp->packets_out || tcp_write_queue_empty(sk)) {
4084 : /* Cancel probe timer, if it is not required. */
4085 0 : icsk->icsk_probes_out = 0;
4086 0 : icsk->icsk_backoff = 0;
4087 0 : icsk->icsk_probes_tstamp = 0;
4088 0 : return;
4089 : }
4090 :
4091 0 : icsk->icsk_probes_out++;
4092 0 : if (err <= 0) {
4093 0 : if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
4094 0 : icsk->icsk_backoff++;
4095 0 : timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
4096 : } else {
4097 : /* If packet was not sent due to local congestion,
4098 : * Let senders fight for local resources conservatively.
4099 : */
4100 : timeout = TCP_RESOURCE_PROBE_INTERVAL;
4101 : }
4102 :
4103 0 : timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout);
4104 0 : tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX);
4105 : }
4106 :
4107 0 : int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
4108 : {
4109 0 : const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
4110 0 : struct flowi fl;
4111 0 : int res;
4112 :
4113 0 : tcp_rsk(req)->txhash = net_tx_rndhash();
4114 0 : res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
4115 : NULL);
4116 0 : if (!res) {
4117 0 : __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
4118 0 : __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
4119 0 : if (unlikely(tcp_passive_fastopen(sk)))
4120 0 : tcp_sk(sk)->total_retrans++;
4121 0 : trace_tcp_retransmit_synack(sk, req);
4122 : }
4123 0 : return res;
4124 : }
4125 : EXPORT_SYMBOL(tcp_rtx_synack);
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