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/tcp_ecn.h>
42 #include <net/mptcp.h>
43 #include <net/proto_memory.h>
44 #include <net/psp.h>
45
46 #include <linux/compiler.h>
47 #include <linux/gfp.h>
48 #include <linux/module.h>
49 #include <linux/static_key.h>
50 #include <linux/skbuff_ref.h>
51
52 #include <trace/events/tcp.h>
53
54 /* Refresh clocks of a TCP socket,
55 * ensuring monotically increasing values.
56 */
tcp_mstamp_refresh(struct tcp_sock * tp)57 void tcp_mstamp_refresh(struct tcp_sock *tp)
58 {
59 u64 val = tcp_clock_ns();
60
61 tp->tcp_clock_cache = val;
62 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
63 }
64
65 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
66 int push_one, gfp_t gfp);
67
68 /* Account for new data that has been sent to the network. */
tcp_event_new_data_sent(struct sock * sk,struct sk_buff * skb)69 static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
70 {
71 struct inet_connection_sock *icsk = inet_csk(sk);
72 struct tcp_sock *tp = tcp_sk(sk);
73 unsigned int prior_packets = tp->packets_out;
74
75 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
76
77 __skb_unlink(skb, &sk->sk_write_queue);
78 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
79
80 if (tp->highest_sack == NULL)
81 tp->highest_sack = skb;
82
83 tp->packets_out += tcp_skb_pcount(skb);
84 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
85 tcp_rearm_rto(sk);
86
87 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
88 tcp_skb_pcount(skb));
89 tcp_check_space(sk);
90 }
91
92 /* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
93 * window scaling factor due to loss of precision.
94 * If window has been shrunk, what should we make? It is not clear at all.
95 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
96 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
97 * invalid. OK, let's make this for now:
98 */
tcp_acceptable_seq(const struct sock * sk)99 static inline __u32 tcp_acceptable_seq(const struct sock *sk)
100 {
101 const struct tcp_sock *tp = tcp_sk(sk);
102
103 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
104 (tp->rx_opt.wscale_ok &&
105 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
106 return tp->snd_nxt;
107 else
108 return tcp_wnd_end(tp);
109 }
110
111 /* Calculate mss to advertise in SYN segment.
112 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
113 *
114 * 1. It is independent of path mtu.
115 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
116 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
117 * attached devices, because some buggy hosts are confused by
118 * large MSS.
119 * 4. We do not make 3, we advertise MSS, calculated from first
120 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
121 * This may be overridden via information stored in routing table.
122 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
123 * probably even Jumbo".
124 */
tcp_advertise_mss(struct sock * sk)125 static __u16 tcp_advertise_mss(struct sock *sk)
126 {
127 struct tcp_sock *tp = tcp_sk(sk);
128 const struct dst_entry *dst = __sk_dst_get(sk);
129 int mss = tp->advmss;
130
131 if (dst) {
132 unsigned int metric = dst_metric_advmss(dst);
133
134 if (metric < mss) {
135 mss = metric;
136 tp->advmss = mss;
137 }
138 }
139
140 return (__u16)mss;
141 }
142
143 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
144 * This is the first part of cwnd validation mechanism.
145 */
tcp_cwnd_restart(struct sock * sk,s32 delta)146 void tcp_cwnd_restart(struct sock *sk, s32 delta)
147 {
148 struct tcp_sock *tp = tcp_sk(sk);
149 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
150 u32 cwnd = tcp_snd_cwnd(tp);
151
152 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
153
154 tp->snd_ssthresh = tcp_current_ssthresh(sk);
155 restart_cwnd = min(restart_cwnd, cwnd);
156
157 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
158 cwnd >>= 1;
159 tcp_snd_cwnd_set(tp, max(cwnd, restart_cwnd));
160 tp->snd_cwnd_stamp = tcp_jiffies32;
161 tp->snd_cwnd_used = 0;
162 }
163
164 /* Congestion state accounting after a packet has been sent. */
tcp_event_data_sent(struct tcp_sock * tp,struct sock * sk)165 static void tcp_event_data_sent(struct tcp_sock *tp,
166 struct sock *sk)
167 {
168 struct inet_connection_sock *icsk = inet_csk(sk);
169 const u32 now = tcp_jiffies32;
170
171 if (tcp_packets_in_flight(tp) == 0)
172 tcp_ca_event(sk, CA_EVENT_TX_START);
173
174 tp->lsndtime = now;
175
176 /* If it is a reply for ato after last received
177 * packet, increase pingpong count.
178 */
179 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
180 inet_csk_inc_pingpong_cnt(sk);
181 }
182
183 /* Account for an ACK we sent. */
tcp_event_ack_sent(struct sock * sk,u32 rcv_nxt)184 static inline void tcp_event_ack_sent(struct sock *sk, u32 rcv_nxt)
185 {
186 struct tcp_sock *tp = tcp_sk(sk);
187
188 if (unlikely(tp->compressed_ack)) {
189 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
190 tp->compressed_ack);
191 tp->compressed_ack = 0;
192 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
193 __sock_put(sk);
194 }
195
196 if (unlikely(rcv_nxt != tp->rcv_nxt))
197 return; /* Special ACK sent by DCTCP to reflect ECN */
198 tcp_dec_quickack_mode(sk);
199 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
200 }
201
202 /* Determine a window scaling and initial window to offer.
203 * Based on the assumption that the given amount of space
204 * will be offered. Store the results in the tp structure.
205 * NOTE: for smooth operation initial space offering should
206 * be a multiple of mss if possible. We assume here that mss >= 1.
207 * This MUST be enforced by all callers.
208 */
tcp_select_initial_window(const struct sock * sk,int __space,__u32 mss,__u32 * rcv_wnd,__u32 * __window_clamp,int wscale_ok,__u8 * rcv_wscale,__u32 init_rcv_wnd)209 void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
210 __u32 *rcv_wnd, __u32 *__window_clamp,
211 int wscale_ok, __u8 *rcv_wscale,
212 __u32 init_rcv_wnd)
213 {
214 unsigned int space = (__space < 0 ? 0 : __space);
215 u32 window_clamp = READ_ONCE(*__window_clamp);
216
217 /* If no clamp set the clamp to the max possible scaled window */
218 if (window_clamp == 0)
219 window_clamp = (U16_MAX << TCP_MAX_WSCALE);
220 space = min(window_clamp, space);
221
222 /* Quantize space offering to a multiple of mss if possible. */
223 if (space > mss)
224 space = rounddown(space, mss);
225
226 /* NOTE: offering an initial window larger than 32767
227 * will break some buggy TCP stacks. If the admin tells us
228 * it is likely we could be speaking with such a buggy stack
229 * we will truncate our initial window offering to 32K-1
230 * unless the remote has sent us a window scaling option,
231 * which we interpret as a sign the remote TCP is not
232 * misinterpreting the window field as a signed quantity.
233 */
234 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows))
235 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
236 else
237 (*rcv_wnd) = space;
238
239 if (init_rcv_wnd)
240 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
241
242 *rcv_wscale = 0;
243 if (wscale_ok) {
244 /* Set window scaling on max possible window */
245 space = max_t(u32, space, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));
246 space = max_t(u32, space, READ_ONCE(sysctl_rmem_max));
247 space = min_t(u32, space, window_clamp);
248 *rcv_wscale = clamp_t(int, ilog2(space) - 15,
249 0, TCP_MAX_WSCALE);
250 }
251 /* Set the clamp no higher than max representable value */
252 WRITE_ONCE(*__window_clamp,
253 min_t(__u32, U16_MAX << (*rcv_wscale), window_clamp));
254 }
255 EXPORT_IPV6_MOD(tcp_select_initial_window);
256
257 /* Chose a new window to advertise, update state in tcp_sock for the
258 * socket, and return result with RFC1323 scaling applied. The return
259 * value can be stuffed directly into th->window for an outgoing
260 * frame.
261 */
tcp_select_window(struct sock * sk)262 static u16 tcp_select_window(struct sock *sk)
263 {
264 struct tcp_sock *tp = tcp_sk(sk);
265 struct net *net = sock_net(sk);
266 u32 old_win = tp->rcv_wnd;
267 u32 cur_win, new_win;
268
269 /* Make the window 0 if we failed to queue the data because we
270 * are out of memory.
271 */
272 if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) {
273 tp->pred_flags = 0;
274 tp->rcv_wnd = 0;
275 tp->rcv_wup = tp->rcv_nxt;
276 return 0;
277 }
278
279 cur_win = tcp_receive_window(tp);
280 new_win = __tcp_select_window(sk);
281 if (new_win < cur_win) {
282 /* Danger Will Robinson!
283 * Don't update rcv_wup/rcv_wnd here or else
284 * we will not be able to advertise a zero
285 * window in time. --DaveM
286 *
287 * Relax Will Robinson.
288 */
289 if (!READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) || !tp->rx_opt.rcv_wscale) {
290 /* Never shrink the offered window */
291 if (new_win == 0)
292 NET_INC_STATS(net, LINUX_MIB_TCPWANTZEROWINDOWADV);
293 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
294 }
295 }
296
297 tp->rcv_wnd = new_win;
298 tp->rcv_wup = tp->rcv_nxt;
299
300 /* Make sure we do not exceed the maximum possible
301 * scaled window.
302 */
303 if (!tp->rx_opt.rcv_wscale &&
304 READ_ONCE(net->ipv4.sysctl_tcp_workaround_signed_windows))
305 new_win = min(new_win, MAX_TCP_WINDOW);
306 else
307 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
308
309 /* RFC1323 scaling applied */
310 new_win >>= tp->rx_opt.rcv_wscale;
311
312 /* If we advertise zero window, disable fast path. */
313 if (new_win == 0) {
314 tp->pred_flags = 0;
315 if (old_win)
316 NET_INC_STATS(net, LINUX_MIB_TCPTOZEROWINDOWADV);
317 } else if (old_win == 0) {
318 NET_INC_STATS(net, LINUX_MIB_TCPFROMZEROWINDOWADV);
319 }
320
321 return new_win;
322 }
323
324 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
325 * be sent.
326 */
tcp_ecn_send(struct sock * sk,struct sk_buff * skb,struct tcphdr * th,int tcp_header_len)327 static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
328 struct tcphdr *th, int tcp_header_len)
329 {
330 struct tcp_sock *tp = tcp_sk(sk);
331
332 if (!tcp_ecn_mode_any(tp))
333 return;
334
335 if (tcp_ecn_mode_accecn(tp)) {
336 if (!tcp_accecn_ace_fail_recv(tp))
337 INET_ECN_xmit(sk);
338 tcp_accecn_set_ace(tp, skb, th);
339 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ACCECN;
340 } else {
341 /* Not-retransmitted data segment: set ECT and inject CWR. */
342 if (skb->len != tcp_header_len &&
343 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
344 INET_ECN_xmit(sk);
345 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
346 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
347 th->cwr = 1;
348 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
349 }
350 } else if (!tcp_ca_needs_ecn(sk)) {
351 /* ACK or retransmitted segment: clear ECT|CE */
352 INET_ECN_dontxmit(sk);
353 }
354 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
355 th->ece = 1;
356 }
357 }
358
359 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
360 * auto increment end seqno.
361 */
tcp_init_nondata_skb(struct sk_buff * skb,struct sock * sk,u32 seq,u16 flags)362 static void tcp_init_nondata_skb(struct sk_buff *skb, struct sock *sk,
363 u32 seq, u16 flags)
364 {
365 skb->ip_summed = CHECKSUM_PARTIAL;
366
367 TCP_SKB_CB(skb)->tcp_flags = flags;
368
369 tcp_skb_pcount_set(skb, 1);
370 psp_enqueue_set_decrypted(sk, skb);
371
372 TCP_SKB_CB(skb)->seq = seq;
373 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
374 seq++;
375 TCP_SKB_CB(skb)->end_seq = seq;
376 }
377
tcp_urg_mode(const struct tcp_sock * tp)378 static inline bool tcp_urg_mode(const struct tcp_sock *tp)
379 {
380 return tp->snd_una != tp->snd_up;
381 }
382
383 #define OPTION_SACK_ADVERTISE BIT(0)
384 #define OPTION_TS BIT(1)
385 #define OPTION_MD5 BIT(2)
386 #define OPTION_WSCALE BIT(3)
387 #define OPTION_FAST_OPEN_COOKIE BIT(8)
388 #define OPTION_SMC BIT(9)
389 #define OPTION_MPTCP BIT(10)
390 #define OPTION_AO BIT(11)
391 #define OPTION_ACCECN BIT(12)
392
smc_options_write(__be32 * ptr,u16 * options)393 static void smc_options_write(__be32 *ptr, u16 *options)
394 {
395 #if IS_ENABLED(CONFIG_SMC)
396 if (static_branch_unlikely(&tcp_have_smc)) {
397 if (unlikely(OPTION_SMC & *options)) {
398 *ptr++ = htonl((TCPOPT_NOP << 24) |
399 (TCPOPT_NOP << 16) |
400 (TCPOPT_EXP << 8) |
401 (TCPOLEN_EXP_SMC_BASE));
402 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
403 }
404 }
405 #endif
406 }
407
408 struct tcp_out_options {
409 u16 options; /* bit field of OPTION_* */
410 u16 mss; /* 0 to disable */
411 u8 ws; /* window scale, 0 to disable */
412 u8 num_sack_blocks; /* number of SACK blocks to include */
413 u8 num_accecn_fields:7, /* number of AccECN fields needed */
414 use_synack_ecn_bytes:1; /* Use synack_ecn_bytes or not */
415 u8 hash_size; /* bytes in hash_location */
416 u8 bpf_opt_len; /* length of BPF hdr option */
417 __u8 *hash_location; /* temporary pointer, overloaded */
418 __u32 tsval, tsecr; /* need to include OPTION_TS */
419 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
420 struct mptcp_out_options mptcp;
421 };
422
mptcp_options_write(struct tcphdr * th,__be32 * ptr,struct tcp_sock * tp,struct tcp_out_options * opts)423 static void mptcp_options_write(struct tcphdr *th, __be32 *ptr,
424 struct tcp_sock *tp,
425 struct tcp_out_options *opts)
426 {
427 #if IS_ENABLED(CONFIG_MPTCP)
428 if (unlikely(OPTION_MPTCP & opts->options))
429 mptcp_write_options(th, ptr, tp, &opts->mptcp);
430 #endif
431 }
432
433 #ifdef CONFIG_CGROUP_BPF
bpf_skops_write_hdr_opt_arg0(struct sk_buff * skb,enum tcp_synack_type synack_type)434 static int bpf_skops_write_hdr_opt_arg0(struct sk_buff *skb,
435 enum tcp_synack_type synack_type)
436 {
437 if (unlikely(!skb))
438 return BPF_WRITE_HDR_TCP_CURRENT_MSS;
439
440 if (unlikely(synack_type == TCP_SYNACK_COOKIE))
441 return BPF_WRITE_HDR_TCP_SYNACK_COOKIE;
442
443 return 0;
444 }
445
446 /* req, syn_skb and synack_type are used when writing synack */
bpf_skops_hdr_opt_len(struct sock * sk,struct sk_buff * skb,struct request_sock * req,struct sk_buff * syn_skb,enum tcp_synack_type synack_type,struct tcp_out_options * opts,unsigned int * remaining)447 static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
448 struct request_sock *req,
449 struct sk_buff *syn_skb,
450 enum tcp_synack_type synack_type,
451 struct tcp_out_options *opts,
452 unsigned int *remaining)
453 {
454 struct bpf_sock_ops_kern sock_ops;
455 int err;
456
457 if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
458 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) ||
459 !*remaining)
460 return;
461
462 /* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
463
464 /* init sock_ops */
465 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
466
467 sock_ops.op = BPF_SOCK_OPS_HDR_OPT_LEN_CB;
468
469 if (req) {
470 /* The listen "sk" cannot be passed here because
471 * it is not locked. It would not make too much
472 * sense to do bpf_setsockopt(listen_sk) based
473 * on individual connection request also.
474 *
475 * Thus, "req" is passed here and the cgroup-bpf-progs
476 * of the listen "sk" will be run.
477 *
478 * "req" is also used here for fastopen even the "sk" here is
479 * a fullsock "child" sk. It is to keep the behavior
480 * consistent between fastopen and non-fastopen on
481 * the bpf programming side.
482 */
483 sock_ops.sk = (struct sock *)req;
484 sock_ops.syn_skb = syn_skb;
485 } else {
486 sock_owned_by_me(sk);
487
488 sock_ops.is_fullsock = 1;
489 sock_ops.is_locked_tcp_sock = 1;
490 sock_ops.sk = sk;
491 }
492
493 sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
494 sock_ops.remaining_opt_len = *remaining;
495 /* tcp_current_mss() does not pass a skb */
496 if (skb)
497 bpf_skops_init_skb(&sock_ops, skb, 0);
498
499 err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
500
501 if (err || sock_ops.remaining_opt_len == *remaining)
502 return;
503
504 opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len;
505 /* round up to 4 bytes */
506 opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3;
507
508 *remaining -= opts->bpf_opt_len;
509 }
510
bpf_skops_write_hdr_opt(struct sock * sk,struct sk_buff * skb,struct request_sock * req,struct sk_buff * syn_skb,enum tcp_synack_type synack_type,struct tcp_out_options * opts)511 static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
512 struct request_sock *req,
513 struct sk_buff *syn_skb,
514 enum tcp_synack_type synack_type,
515 struct tcp_out_options *opts)
516 {
517 u8 first_opt_off, nr_written, max_opt_len = opts->bpf_opt_len;
518 struct bpf_sock_ops_kern sock_ops;
519 int err;
520
521 if (likely(!max_opt_len))
522 return;
523
524 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
525
526 sock_ops.op = BPF_SOCK_OPS_WRITE_HDR_OPT_CB;
527
528 if (req) {
529 sock_ops.sk = (struct sock *)req;
530 sock_ops.syn_skb = syn_skb;
531 } else {
532 sock_owned_by_me(sk);
533
534 sock_ops.is_fullsock = 1;
535 sock_ops.is_locked_tcp_sock = 1;
536 sock_ops.sk = sk;
537 }
538
539 sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
540 sock_ops.remaining_opt_len = max_opt_len;
541 first_opt_off = tcp_hdrlen(skb) - max_opt_len;
542 bpf_skops_init_skb(&sock_ops, skb, first_opt_off);
543
544 err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
545
546 if (err)
547 nr_written = 0;
548 else
549 nr_written = max_opt_len - sock_ops.remaining_opt_len;
550
551 if (nr_written < max_opt_len)
552 memset(skb->data + first_opt_off + nr_written, TCPOPT_NOP,
553 max_opt_len - nr_written);
554 }
555 #else
bpf_skops_hdr_opt_len(struct sock * sk,struct sk_buff * skb,struct request_sock * req,struct sk_buff * syn_skb,enum tcp_synack_type synack_type,struct tcp_out_options * opts,unsigned int * remaining)556 static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
557 struct request_sock *req,
558 struct sk_buff *syn_skb,
559 enum tcp_synack_type synack_type,
560 struct tcp_out_options *opts,
561 unsigned int *remaining)
562 {
563 }
564
bpf_skops_write_hdr_opt(struct sock * sk,struct sk_buff * skb,struct request_sock * req,struct sk_buff * syn_skb,enum tcp_synack_type synack_type,struct tcp_out_options * opts)565 static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
566 struct request_sock *req,
567 struct sk_buff *syn_skb,
568 enum tcp_synack_type synack_type,
569 struct tcp_out_options *opts)
570 {
571 }
572 #endif
573
process_tcp_ao_options(struct tcp_sock * tp,const struct tcp_request_sock * tcprsk,struct tcp_out_options * opts,struct tcp_key * key,__be32 * ptr)574 static __be32 *process_tcp_ao_options(struct tcp_sock *tp,
575 const struct tcp_request_sock *tcprsk,
576 struct tcp_out_options *opts,
577 struct tcp_key *key, __be32 *ptr)
578 {
579 #ifdef CONFIG_TCP_AO
580 u8 maclen = tcp_ao_maclen(key->ao_key);
581
582 if (tcprsk) {
583 u8 aolen = maclen + sizeof(struct tcp_ao_hdr);
584
585 *ptr++ = htonl((TCPOPT_AO << 24) | (aolen << 16) |
586 (tcprsk->ao_keyid << 8) |
587 (tcprsk->ao_rcv_next));
588 } else {
589 struct tcp_ao_key *rnext_key;
590 struct tcp_ao_info *ao_info;
591
592 ao_info = rcu_dereference_check(tp->ao_info,
593 lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
594 rnext_key = READ_ONCE(ao_info->rnext_key);
595 if (WARN_ON_ONCE(!rnext_key))
596 return ptr;
597 *ptr++ = htonl((TCPOPT_AO << 24) |
598 (tcp_ao_len(key->ao_key) << 16) |
599 (key->ao_key->sndid << 8) |
600 (rnext_key->rcvid));
601 }
602 opts->hash_location = (__u8 *)ptr;
603 ptr += maclen / sizeof(*ptr);
604 if (unlikely(maclen % sizeof(*ptr))) {
605 memset(ptr, TCPOPT_NOP, sizeof(*ptr));
606 ptr++;
607 }
608 #endif
609 return ptr;
610 }
611
612 /* Initial values for AccECN option, ordered is based on ECN field bits
613 * similar to received_ecn_bytes. Used for SYN/ACK AccECN option.
614 */
615 static const u32 synack_ecn_bytes[3] = { 0, 0, 0 };
616
617 /* Write previously computed TCP options to the packet.
618 *
619 * Beware: Something in the Internet is very sensitive to the ordering of
620 * TCP options, we learned this through the hard way, so be careful here.
621 * Luckily we can at least blame others for their non-compliance but from
622 * inter-operability perspective it seems that we're somewhat stuck with
623 * the ordering which we have been using if we want to keep working with
624 * those broken things (not that it currently hurts anybody as there isn't
625 * particular reason why the ordering would need to be changed).
626 *
627 * At least SACK_PERM as the first option is known to lead to a disaster
628 * (but it may well be that other scenarios fail similarly).
629 */
tcp_options_write(struct tcphdr * th,struct tcp_sock * tp,const struct tcp_request_sock * tcprsk,struct tcp_out_options * opts,struct tcp_key * key)630 static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
631 const struct tcp_request_sock *tcprsk,
632 struct tcp_out_options *opts,
633 struct tcp_key *key)
634 {
635 u8 leftover_highbyte = TCPOPT_NOP; /* replace 1st NOP if avail */
636 u8 leftover_lowbyte = TCPOPT_NOP; /* replace 2nd NOP in succession */
637 __be32 *ptr = (__be32 *)(th + 1);
638 u16 options = opts->options; /* mungable copy */
639
640 if (tcp_key_is_md5(key)) {
641 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
642 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
643 /* overload cookie hash location */
644 opts->hash_location = (__u8 *)ptr;
645 ptr += 4;
646 } else if (tcp_key_is_ao(key)) {
647 ptr = process_tcp_ao_options(tp, tcprsk, opts, key, ptr);
648 }
649 if (unlikely(opts->mss)) {
650 *ptr++ = htonl((TCPOPT_MSS << 24) |
651 (TCPOLEN_MSS << 16) |
652 opts->mss);
653 }
654
655 if (likely(OPTION_TS & options)) {
656 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
657 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
658 (TCPOLEN_SACK_PERM << 16) |
659 (TCPOPT_TIMESTAMP << 8) |
660 TCPOLEN_TIMESTAMP);
661 options &= ~OPTION_SACK_ADVERTISE;
662 } else {
663 *ptr++ = htonl((TCPOPT_NOP << 24) |
664 (TCPOPT_NOP << 16) |
665 (TCPOPT_TIMESTAMP << 8) |
666 TCPOLEN_TIMESTAMP);
667 }
668 *ptr++ = htonl(opts->tsval);
669 *ptr++ = htonl(opts->tsecr);
670 }
671
672 if (OPTION_ACCECN & options) {
673 const u32 *ecn_bytes = opts->use_synack_ecn_bytes ?
674 synack_ecn_bytes :
675 tp->received_ecn_bytes;
676 const u8 ect0_idx = INET_ECN_ECT_0 - 1;
677 const u8 ect1_idx = INET_ECN_ECT_1 - 1;
678 const u8 ce_idx = INET_ECN_CE - 1;
679 u32 e0b;
680 u32 e1b;
681 u32 ceb;
682 u8 len;
683
684 e0b = ecn_bytes[ect0_idx] + TCP_ACCECN_E0B_INIT_OFFSET;
685 e1b = ecn_bytes[ect1_idx] + TCP_ACCECN_E1B_INIT_OFFSET;
686 ceb = ecn_bytes[ce_idx] + TCP_ACCECN_CEB_INIT_OFFSET;
687 len = TCPOLEN_ACCECN_BASE +
688 opts->num_accecn_fields * TCPOLEN_ACCECN_PERFIELD;
689
690 if (opts->num_accecn_fields == 2) {
691 *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) |
692 ((e1b >> 8) & 0xffff));
693 *ptr++ = htonl(((e1b & 0xff) << 24) |
694 (ceb & 0xffffff));
695 } else if (opts->num_accecn_fields == 1) {
696 *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) |
697 ((e1b >> 8) & 0xffff));
698 leftover_highbyte = e1b & 0xff;
699 leftover_lowbyte = TCPOPT_NOP;
700 } else if (opts->num_accecn_fields == 0) {
701 leftover_highbyte = TCPOPT_ACCECN1;
702 leftover_lowbyte = len;
703 } else if (opts->num_accecn_fields == 3) {
704 *ptr++ = htonl((TCPOPT_ACCECN1 << 24) | (len << 16) |
705 ((e1b >> 8) & 0xffff));
706 *ptr++ = htonl(((e1b & 0xff) << 24) |
707 (ceb & 0xffffff));
708 *ptr++ = htonl(((e0b & 0xffffff) << 8) |
709 TCPOPT_NOP);
710 }
711 if (tp) {
712 tp->accecn_minlen = 0;
713 tp->accecn_opt_tstamp = tp->tcp_mstamp;
714 if (tp->accecn_opt_demand)
715 tp->accecn_opt_demand--;
716 }
717 }
718
719 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
720 *ptr++ = htonl((leftover_highbyte << 24) |
721 (leftover_lowbyte << 16) |
722 (TCPOPT_SACK_PERM << 8) |
723 TCPOLEN_SACK_PERM);
724 leftover_highbyte = TCPOPT_NOP;
725 leftover_lowbyte = TCPOPT_NOP;
726 }
727
728 if (unlikely(OPTION_WSCALE & options)) {
729 u8 highbyte = TCPOPT_NOP;
730
731 /* Do not split the leftover 2-byte to fit into a single
732 * NOP, i.e., replace this NOP only when 1 byte is leftover
733 * within leftover_highbyte.
734 */
735 if (unlikely(leftover_highbyte != TCPOPT_NOP &&
736 leftover_lowbyte == TCPOPT_NOP)) {
737 highbyte = leftover_highbyte;
738 leftover_highbyte = TCPOPT_NOP;
739 }
740 *ptr++ = htonl((highbyte << 24) |
741 (TCPOPT_WINDOW << 16) |
742 (TCPOLEN_WINDOW << 8) |
743 opts->ws);
744 }
745
746 if (unlikely(opts->num_sack_blocks)) {
747 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
748 tp->duplicate_sack : tp->selective_acks;
749 int this_sack;
750
751 *ptr++ = htonl((leftover_highbyte << 24) |
752 (leftover_lowbyte << 16) |
753 (TCPOPT_SACK << 8) |
754 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
755 TCPOLEN_SACK_PERBLOCK)));
756 leftover_highbyte = TCPOPT_NOP;
757 leftover_lowbyte = TCPOPT_NOP;
758
759 for (this_sack = 0; this_sack < opts->num_sack_blocks;
760 ++this_sack) {
761 *ptr++ = htonl(sp[this_sack].start_seq);
762 *ptr++ = htonl(sp[this_sack].end_seq);
763 }
764
765 tp->rx_opt.dsack = 0;
766 } else if (unlikely(leftover_highbyte != TCPOPT_NOP ||
767 leftover_lowbyte != TCPOPT_NOP)) {
768 *ptr++ = htonl((leftover_highbyte << 24) |
769 (leftover_lowbyte << 16) |
770 (TCPOPT_NOP << 8) |
771 TCPOPT_NOP);
772 leftover_highbyte = TCPOPT_NOP;
773 leftover_lowbyte = TCPOPT_NOP;
774 }
775
776 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
777 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
778 u8 *p = (u8 *)ptr;
779 u32 len; /* Fast Open option length */
780
781 if (foc->exp) {
782 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
783 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
784 TCPOPT_FASTOPEN_MAGIC);
785 p += TCPOLEN_EXP_FASTOPEN_BASE;
786 } else {
787 len = TCPOLEN_FASTOPEN_BASE + foc->len;
788 *p++ = TCPOPT_FASTOPEN;
789 *p++ = len;
790 }
791
792 memcpy(p, foc->val, foc->len);
793 if ((len & 3) == 2) {
794 p[foc->len] = TCPOPT_NOP;
795 p[foc->len + 1] = TCPOPT_NOP;
796 }
797 ptr += (len + 3) >> 2;
798 }
799
800 smc_options_write(ptr, &options);
801
802 mptcp_options_write(th, ptr, tp, opts);
803 }
804
smc_set_option(const struct tcp_sock * tp,struct tcp_out_options * opts,unsigned int * remaining)805 static void smc_set_option(const struct tcp_sock *tp,
806 struct tcp_out_options *opts,
807 unsigned int *remaining)
808 {
809 #if IS_ENABLED(CONFIG_SMC)
810 if (static_branch_unlikely(&tcp_have_smc)) {
811 if (tp->syn_smc) {
812 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
813 opts->options |= OPTION_SMC;
814 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
815 }
816 }
817 }
818 #endif
819 }
820
smc_set_option_cond(const struct tcp_sock * tp,const struct inet_request_sock * ireq,struct tcp_out_options * opts,unsigned int * remaining)821 static void smc_set_option_cond(const struct tcp_sock *tp,
822 const struct inet_request_sock *ireq,
823 struct tcp_out_options *opts,
824 unsigned int *remaining)
825 {
826 #if IS_ENABLED(CONFIG_SMC)
827 if (static_branch_unlikely(&tcp_have_smc)) {
828 if (tp->syn_smc && ireq->smc_ok) {
829 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
830 opts->options |= OPTION_SMC;
831 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
832 }
833 }
834 }
835 #endif
836 }
837
mptcp_set_option_cond(const struct request_sock * req,struct tcp_out_options * opts,unsigned int * remaining)838 static void mptcp_set_option_cond(const struct request_sock *req,
839 struct tcp_out_options *opts,
840 unsigned int *remaining)
841 {
842 if (rsk_is_mptcp(req)) {
843 unsigned int size;
844
845 if (mptcp_synack_options(req, &size, &opts->mptcp)) {
846 if (*remaining >= size) {
847 opts->options |= OPTION_MPTCP;
848 *remaining -= size;
849 }
850 }
851 }
852 }
853
tcp_synack_options_combine_saving(struct tcp_out_options * opts)854 static u32 tcp_synack_options_combine_saving(struct tcp_out_options *opts)
855 {
856 /* How much there's room for combining with the alignment padding? */
857 if ((opts->options & (OPTION_SACK_ADVERTISE | OPTION_TS)) ==
858 OPTION_SACK_ADVERTISE)
859 return 2;
860 else if (opts->options & OPTION_WSCALE)
861 return 1;
862 return 0;
863 }
864
865 /* Calculates how long AccECN option will fit to @remaining option space.
866 *
867 * AccECN option can sometimes replace NOPs used for alignment of other
868 * TCP options (up to @max_combine_saving available).
869 *
870 * Only solutions with at least @required AccECN fields are accepted.
871 *
872 * Returns: The size of the AccECN option excluding space repurposed from
873 * the alignment of the other options.
874 */
tcp_options_fit_accecn(struct tcp_out_options * opts,int required,int remaining)875 static int tcp_options_fit_accecn(struct tcp_out_options *opts, int required,
876 int remaining)
877 {
878 int size = TCP_ACCECN_MAXSIZE;
879 int sack_blocks_reduce = 0;
880 int max_combine_saving;
881 int rem = remaining;
882 int align_size;
883
884 if (opts->use_synack_ecn_bytes)
885 max_combine_saving = tcp_synack_options_combine_saving(opts);
886 else
887 max_combine_saving = opts->num_sack_blocks > 0 ? 2 : 0;
888 opts->num_accecn_fields = TCP_ACCECN_NUMFIELDS;
889 while (opts->num_accecn_fields >= required) {
890 /* Pad to dword if cannot combine */
891 if ((size & 0x3) > max_combine_saving)
892 align_size = ALIGN(size, 4);
893 else
894 align_size = ALIGN_DOWN(size, 4);
895
896 if (rem >= align_size) {
897 size = align_size;
898 break;
899 } else if (opts->num_accecn_fields == required &&
900 opts->num_sack_blocks > 2 &&
901 required > 0) {
902 /* Try to fit the option by removing one SACK block */
903 opts->num_sack_blocks--;
904 sack_blocks_reduce++;
905 rem = rem + TCPOLEN_SACK_PERBLOCK;
906
907 opts->num_accecn_fields = TCP_ACCECN_NUMFIELDS;
908 size = TCP_ACCECN_MAXSIZE;
909 continue;
910 }
911
912 opts->num_accecn_fields--;
913 size -= TCPOLEN_ACCECN_PERFIELD;
914 }
915 if (sack_blocks_reduce > 0) {
916 if (opts->num_accecn_fields >= required)
917 size -= sack_blocks_reduce * TCPOLEN_SACK_PERBLOCK;
918 else
919 opts->num_sack_blocks += sack_blocks_reduce;
920 }
921 if (opts->num_accecn_fields < required)
922 return 0;
923
924 opts->options |= OPTION_ACCECN;
925 return size;
926 }
927
928 /* Compute TCP options for SYN packets. This is not the final
929 * network wire format yet.
930 */
tcp_syn_options(struct sock * sk,struct sk_buff * skb,struct tcp_out_options * opts,struct tcp_key * key)931 static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
932 struct tcp_out_options *opts,
933 struct tcp_key *key)
934 {
935 struct tcp_sock *tp = tcp_sk(sk);
936 unsigned int remaining = MAX_TCP_OPTION_SPACE;
937 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
938 bool timestamps;
939
940 /* Better than switch (key.type) as it has static branches */
941 if (tcp_key_is_md5(key)) {
942 timestamps = false;
943 opts->options |= OPTION_MD5;
944 remaining -= TCPOLEN_MD5SIG_ALIGNED;
945 } else {
946 timestamps = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps);
947 if (tcp_key_is_ao(key)) {
948 opts->options |= OPTION_AO;
949 remaining -= tcp_ao_len_aligned(key->ao_key);
950 }
951 }
952
953 /* We always get an MSS option. The option bytes which will be seen in
954 * normal data packets should timestamps be used, must be in the MSS
955 * advertised. But we subtract them from tp->mss_cache so that
956 * calculations in tcp_sendmsg are simpler etc. So account for this
957 * fact here if necessary. If we don't do this correctly, as a
958 * receiver we won't recognize data packets as being full sized when we
959 * should, and thus we won't abide by the delayed ACK rules correctly.
960 * SACKs don't matter, we never delay an ACK when we have any of those
961 * going out. */
962 opts->mss = tcp_advertise_mss(sk);
963 remaining -= TCPOLEN_MSS_ALIGNED;
964
965 if (likely(timestamps)) {
966 opts->options |= OPTION_TS;
967 opts->tsval = tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb) + tp->tsoffset;
968 opts->tsecr = tp->rx_opt.ts_recent;
969 remaining -= TCPOLEN_TSTAMP_ALIGNED;
970 }
971 if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling))) {
972 opts->ws = tp->rx_opt.rcv_wscale;
973 opts->options |= OPTION_WSCALE;
974 remaining -= TCPOLEN_WSCALE_ALIGNED;
975 }
976 if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_sack))) {
977 opts->options |= OPTION_SACK_ADVERTISE;
978 if (unlikely(!(OPTION_TS & opts->options)))
979 remaining -= TCPOLEN_SACKPERM_ALIGNED;
980 }
981
982 if (fastopen && fastopen->cookie.len >= 0) {
983 u32 need = fastopen->cookie.len;
984
985 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
986 TCPOLEN_FASTOPEN_BASE;
987 need = (need + 3) & ~3U; /* Align to 32 bits */
988 if (remaining >= need) {
989 opts->options |= OPTION_FAST_OPEN_COOKIE;
990 opts->fastopen_cookie = &fastopen->cookie;
991 remaining -= need;
992 tp->syn_fastopen = 1;
993 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
994 }
995 }
996
997 smc_set_option(tp, opts, &remaining);
998
999 if (sk_is_mptcp(sk)) {
1000 unsigned int size;
1001
1002 if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
1003 if (remaining >= size) {
1004 opts->options |= OPTION_MPTCP;
1005 remaining -= size;
1006 }
1007 }
1008 }
1009
1010 /* Simultaneous open SYN/ACK needs AccECN option but not SYN.
1011 * It is attempted to negotiate the use of AccECN also on the first
1012 * retransmitted SYN, as mentioned in "3.1.4.1. Retransmitted SYNs"
1013 * of AccECN draft.
1014 */
1015 if (unlikely((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) &&
1016 tcp_ecn_mode_accecn(tp) &&
1017 inet_csk(sk)->icsk_retransmits < 2 &&
1018 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) &&
1019 remaining >= TCPOLEN_ACCECN_BASE)) {
1020 opts->use_synack_ecn_bytes = 1;
1021 remaining -= tcp_options_fit_accecn(opts, 0, remaining);
1022 }
1023
1024 bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
1025
1026 return MAX_TCP_OPTION_SPACE - remaining;
1027 }
1028
1029 /* Set up TCP options for SYN-ACKs. */
tcp_synack_options(const struct sock * sk,struct request_sock * req,unsigned int mss,struct sk_buff * skb,struct tcp_out_options * opts,const struct tcp_key * key,struct tcp_fastopen_cookie * foc,enum tcp_synack_type synack_type,struct sk_buff * syn_skb)1030 static unsigned int tcp_synack_options(const struct sock *sk,
1031 struct request_sock *req,
1032 unsigned int mss, struct sk_buff *skb,
1033 struct tcp_out_options *opts,
1034 const struct tcp_key *key,
1035 struct tcp_fastopen_cookie *foc,
1036 enum tcp_synack_type synack_type,
1037 struct sk_buff *syn_skb)
1038 {
1039 struct inet_request_sock *ireq = inet_rsk(req);
1040 unsigned int remaining = MAX_TCP_OPTION_SPACE;
1041 struct tcp_request_sock *treq = tcp_rsk(req);
1042
1043 if (tcp_key_is_md5(key)) {
1044 opts->options |= OPTION_MD5;
1045 remaining -= TCPOLEN_MD5SIG_ALIGNED;
1046
1047 /* We can't fit any SACK blocks in a packet with MD5 + TS
1048 * options. There was discussion about disabling SACK
1049 * rather than TS in order to fit in better with old,
1050 * buggy kernels, but that was deemed to be unnecessary.
1051 */
1052 if (synack_type != TCP_SYNACK_COOKIE)
1053 ireq->tstamp_ok &= !ireq->sack_ok;
1054 } else if (tcp_key_is_ao(key)) {
1055 opts->options |= OPTION_AO;
1056 remaining -= tcp_ao_len_aligned(key->ao_key);
1057 ireq->tstamp_ok &= !ireq->sack_ok;
1058 }
1059
1060 /* We always send an MSS option. */
1061 opts->mss = mss;
1062 remaining -= TCPOLEN_MSS_ALIGNED;
1063
1064 if (likely(ireq->wscale_ok)) {
1065 opts->ws = ireq->rcv_wscale;
1066 opts->options |= OPTION_WSCALE;
1067 remaining -= TCPOLEN_WSCALE_ALIGNED;
1068 }
1069 if (likely(ireq->tstamp_ok)) {
1070 opts->options |= OPTION_TS;
1071 opts->tsval = tcp_skb_timestamp_ts(tcp_rsk(req)->req_usec_ts, skb) +
1072 tcp_rsk(req)->ts_off;
1073 if (!tcp_rsk(req)->snt_tsval_first) {
1074 if (!opts->tsval)
1075 opts->tsval = ~0U;
1076 tcp_rsk(req)->snt_tsval_first = opts->tsval;
1077 }
1078 WRITE_ONCE(tcp_rsk(req)->snt_tsval_last, opts->tsval);
1079 opts->tsecr = req->ts_recent;
1080 remaining -= TCPOLEN_TSTAMP_ALIGNED;
1081 }
1082 if (likely(ireq->sack_ok)) {
1083 opts->options |= OPTION_SACK_ADVERTISE;
1084 if (unlikely(!ireq->tstamp_ok))
1085 remaining -= TCPOLEN_SACKPERM_ALIGNED;
1086 }
1087 if (foc != NULL && foc->len >= 0) {
1088 u32 need = foc->len;
1089
1090 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
1091 TCPOLEN_FASTOPEN_BASE;
1092 need = (need + 3) & ~3U; /* Align to 32 bits */
1093 if (remaining >= need) {
1094 opts->options |= OPTION_FAST_OPEN_COOKIE;
1095 opts->fastopen_cookie = foc;
1096 remaining -= need;
1097 }
1098 }
1099
1100 mptcp_set_option_cond(req, opts, &remaining);
1101
1102 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
1103
1104 if (treq->accecn_ok &&
1105 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) &&
1106 req->num_timeout < 1 && remaining >= TCPOLEN_ACCECN_BASE) {
1107 opts->use_synack_ecn_bytes = 1;
1108 remaining -= tcp_options_fit_accecn(opts, 0, remaining);
1109 }
1110
1111 bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
1112 synack_type, opts, &remaining);
1113
1114 return MAX_TCP_OPTION_SPACE - remaining;
1115 }
1116
1117 /* Compute TCP options for ESTABLISHED sockets. This is not the
1118 * final wire format yet.
1119 */
tcp_established_options(struct sock * sk,struct sk_buff * skb,struct tcp_out_options * opts,struct tcp_key * key)1120 static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
1121 struct tcp_out_options *opts,
1122 struct tcp_key *key)
1123 {
1124 struct tcp_sock *tp = tcp_sk(sk);
1125 unsigned int size = 0;
1126 unsigned int eff_sacks;
1127
1128 opts->options = 0;
1129
1130 /* Better than switch (key.type) as it has static branches */
1131 if (tcp_key_is_md5(key)) {
1132 opts->options |= OPTION_MD5;
1133 size += TCPOLEN_MD5SIG_ALIGNED;
1134 } else if (tcp_key_is_ao(key)) {
1135 opts->options |= OPTION_AO;
1136 size += tcp_ao_len_aligned(key->ao_key);
1137 }
1138
1139 if (likely(tp->rx_opt.tstamp_ok)) {
1140 opts->options |= OPTION_TS;
1141 opts->tsval = skb ? tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb) +
1142 tp->tsoffset : 0;
1143 opts->tsecr = tp->rx_opt.ts_recent;
1144 size += TCPOLEN_TSTAMP_ALIGNED;
1145 }
1146
1147 /* MPTCP options have precedence over SACK for the limited TCP
1148 * option space because a MPTCP connection would be forced to
1149 * fall back to regular TCP if a required multipath option is
1150 * missing. SACK still gets a chance to use whatever space is
1151 * left.
1152 */
1153 if (sk_is_mptcp(sk)) {
1154 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1155 unsigned int opt_size = 0;
1156
1157 if (mptcp_established_options(sk, skb, &opt_size, remaining,
1158 &opts->mptcp)) {
1159 opts->options |= OPTION_MPTCP;
1160 size += opt_size;
1161 }
1162 }
1163
1164 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
1165 if (unlikely(eff_sacks)) {
1166 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1167 if (likely(remaining >= TCPOLEN_SACK_BASE_ALIGNED +
1168 TCPOLEN_SACK_PERBLOCK)) {
1169 opts->num_sack_blocks =
1170 min_t(unsigned int, eff_sacks,
1171 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
1172 TCPOLEN_SACK_PERBLOCK);
1173
1174 size += TCPOLEN_SACK_BASE_ALIGNED +
1175 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
1176 } else {
1177 opts->num_sack_blocks = 0;
1178 }
1179 } else {
1180 opts->num_sack_blocks = 0;
1181 }
1182
1183 if (tcp_ecn_mode_accecn(tp)) {
1184 int ecn_opt = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option);
1185
1186 if (ecn_opt && tp->saw_accecn_opt && !tcp_accecn_opt_fail_send(tp) &&
1187 (ecn_opt >= TCP_ACCECN_OPTION_FULL || tp->accecn_opt_demand ||
1188 tcp_accecn_option_beacon_check(sk))) {
1189 opts->use_synack_ecn_bytes = 0;
1190 size += tcp_options_fit_accecn(opts, tp->accecn_minlen,
1191 MAX_TCP_OPTION_SPACE - size);
1192 }
1193 }
1194
1195 if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,
1196 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) {
1197 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1198
1199 bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
1200
1201 size = MAX_TCP_OPTION_SPACE - remaining;
1202 }
1203
1204 return size;
1205 }
1206
1207
1208 /* TCP SMALL QUEUES (TSQ)
1209 *
1210 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
1211 * to reduce RTT and bufferbloat.
1212 * We do this using a special skb destructor (tcp_wfree).
1213 *
1214 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
1215 * needs to be reallocated in a driver.
1216 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
1217 *
1218 * Since transmit from skb destructor is forbidden, we use a BH work item
1219 * to process all sockets that eventually need to send more skbs.
1220 * We use one work item per cpu, with its own queue of sockets.
1221 */
1222 struct tsq_work {
1223 struct work_struct work;
1224 struct list_head head; /* queue of tcp sockets */
1225 };
1226 static DEFINE_PER_CPU(struct tsq_work, tsq_work);
1227
tcp_tsq_write(struct sock * sk)1228 static void tcp_tsq_write(struct sock *sk)
1229 {
1230 if ((1 << sk->sk_state) &
1231 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
1232 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
1233 struct tcp_sock *tp = tcp_sk(sk);
1234
1235 if (tp->lost_out > tp->retrans_out &&
1236 tcp_snd_cwnd(tp) > tcp_packets_in_flight(tp)) {
1237 tcp_mstamp_refresh(tp);
1238 tcp_xmit_retransmit_queue(sk);
1239 }
1240
1241 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
1242 0, GFP_ATOMIC);
1243 }
1244 }
1245
tcp_tsq_handler(struct sock * sk)1246 static void tcp_tsq_handler(struct sock *sk)
1247 {
1248 bh_lock_sock(sk);
1249 if (!sock_owned_by_user(sk))
1250 tcp_tsq_write(sk);
1251 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
1252 sock_hold(sk);
1253 bh_unlock_sock(sk);
1254 }
1255 /*
1256 * One work item per cpu tries to send more skbs.
1257 * We run in BH context but need to disable irqs when
1258 * transferring tsq->head because tcp_wfree() might
1259 * interrupt us (non NAPI drivers)
1260 */
tcp_tsq_workfn(struct work_struct * work)1261 static void tcp_tsq_workfn(struct work_struct *work)
1262 {
1263 struct tsq_work *tsq = container_of(work, struct tsq_work, work);
1264 LIST_HEAD(list);
1265 unsigned long flags;
1266 struct list_head *q, *n;
1267 struct tcp_sock *tp;
1268 struct sock *sk;
1269
1270 local_irq_save(flags);
1271 list_splice_init(&tsq->head, &list);
1272 local_irq_restore(flags);
1273
1274 list_for_each_safe(q, n, &list) {
1275 tp = list_entry(q, struct tcp_sock, tsq_node);
1276 list_del(&tp->tsq_node);
1277
1278 sk = (struct sock *)tp;
1279 smp_mb__before_atomic();
1280 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
1281
1282 tcp_tsq_handler(sk);
1283 sk_free(sk);
1284 }
1285 }
1286
1287 #define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
1288 TCPF_WRITE_TIMER_DEFERRED | \
1289 TCPF_DELACK_TIMER_DEFERRED | \
1290 TCPF_MTU_REDUCED_DEFERRED | \
1291 TCPF_ACK_DEFERRED)
1292 /**
1293 * tcp_release_cb - tcp release_sock() callback
1294 * @sk: socket
1295 *
1296 * called from release_sock() to perform protocol dependent
1297 * actions before socket release.
1298 */
tcp_release_cb(struct sock * sk)1299 void tcp_release_cb(struct sock *sk)
1300 {
1301 unsigned long flags = smp_load_acquire(&sk->sk_tsq_flags);
1302 unsigned long nflags;
1303
1304 /* perform an atomic operation only if at least one flag is set */
1305 do {
1306 if (!(flags & TCP_DEFERRED_ALL))
1307 return;
1308 nflags = flags & ~TCP_DEFERRED_ALL;
1309 } while (!try_cmpxchg(&sk->sk_tsq_flags, &flags, nflags));
1310
1311 if (flags & TCPF_TSQ_DEFERRED) {
1312 tcp_tsq_write(sk);
1313 __sock_put(sk);
1314 }
1315
1316 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
1317 tcp_write_timer_handler(sk);
1318 __sock_put(sk);
1319 }
1320 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
1321 tcp_delack_timer_handler(sk);
1322 __sock_put(sk);
1323 }
1324 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
1325 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
1326 __sock_put(sk);
1327 }
1328 if ((flags & TCPF_ACK_DEFERRED) && inet_csk_ack_scheduled(sk))
1329 tcp_send_ack(sk);
1330 }
1331 EXPORT_IPV6_MOD(tcp_release_cb);
1332
tcp_tsq_work_init(void)1333 void __init tcp_tsq_work_init(void)
1334 {
1335 int i;
1336
1337 for_each_possible_cpu(i) {
1338 struct tsq_work *tsq = &per_cpu(tsq_work, i);
1339
1340 INIT_LIST_HEAD(&tsq->head);
1341 INIT_WORK(&tsq->work, tcp_tsq_workfn);
1342 }
1343 }
1344
1345 /*
1346 * Write buffer destructor automatically called from kfree_skb.
1347 * We can't xmit new skbs from this context, as we might already
1348 * hold qdisc lock.
1349 */
tcp_wfree(struct sk_buff * skb)1350 void tcp_wfree(struct sk_buff *skb)
1351 {
1352 struct sock *sk = skb->sk;
1353 struct tcp_sock *tp = tcp_sk(sk);
1354 unsigned long flags, nval, oval;
1355 struct tsq_work *tsq;
1356 bool empty;
1357
1358 /* Keep one reference on sk_wmem_alloc.
1359 * Will be released by sk_free() from here or tcp_tsq_workfn()
1360 */
1361 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
1362
1363 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
1364 * Wait until our queues (qdisc + devices) are drained.
1365 * This gives :
1366 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
1367 * - chance for incoming ACK (processed by another cpu maybe)
1368 * to migrate this flow (skb->ooo_okay will be eventually set)
1369 */
1370 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
1371 goto out;
1372
1373 oval = smp_load_acquire(&sk->sk_tsq_flags);
1374 do {
1375 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
1376 goto out;
1377
1378 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
1379 } while (!try_cmpxchg(&sk->sk_tsq_flags, &oval, nval));
1380
1381 /* queue this socket to BH workqueue */
1382 local_irq_save(flags);
1383 tsq = this_cpu_ptr(&tsq_work);
1384 empty = list_empty(&tsq->head);
1385 list_add(&tp->tsq_node, &tsq->head);
1386 if (empty)
1387 queue_work(system_bh_wq, &tsq->work);
1388 local_irq_restore(flags);
1389 return;
1390 out:
1391 sk_free(sk);
1392 }
1393
1394 /* Note: Called under soft irq.
1395 * We can call TCP stack right away, unless socket is owned by user.
1396 */
tcp_pace_kick(struct hrtimer * timer)1397 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
1398 {
1399 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
1400 struct sock *sk = (struct sock *)tp;
1401
1402 tcp_tsq_handler(sk);
1403 sock_put(sk);
1404
1405 return HRTIMER_NORESTART;
1406 }
1407
tcp_update_skb_after_send(struct sock * sk,struct sk_buff * skb,u64 prior_wstamp)1408 static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
1409 u64 prior_wstamp)
1410 {
1411 struct tcp_sock *tp = tcp_sk(sk);
1412
1413 if (sk->sk_pacing_status != SK_PACING_NONE) {
1414 unsigned long rate = READ_ONCE(sk->sk_pacing_rate);
1415
1416 /* Original sch_fq does not pace first 10 MSS
1417 * Note that tp->data_segs_out overflows after 2^32 packets,
1418 * this is a minor annoyance.
1419 */
1420 if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
1421 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
1422 u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
1423
1424 /* take into account OS jitter */
1425 len_ns -= min_t(u64, len_ns / 2, credit);
1426 tp->tcp_wstamp_ns += len_ns;
1427 }
1428 }
1429 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1430 }
1431
1432 INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1433 INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1434 INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
1435
1436 /* This routine actually transmits TCP packets queued in by
1437 * tcp_do_sendmsg(). This is used by both the initial
1438 * transmission and possible later retransmissions.
1439 * All SKB's seen here are completely headerless. It is our
1440 * job to build the TCP header, and pass the packet down to
1441 * IP so it can do the same plus pass the packet off to the
1442 * device.
1443 *
1444 * We are working here with either a clone of the original
1445 * SKB, or a fresh unique copy made by the retransmit engine.
1446 */
__tcp_transmit_skb(struct sock * sk,struct sk_buff * skb,int clone_it,gfp_t gfp_mask,u32 rcv_nxt)1447 static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1448 int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1449 {
1450 const struct inet_connection_sock *icsk = inet_csk(sk);
1451 struct inet_sock *inet;
1452 struct tcp_sock *tp;
1453 struct tcp_skb_cb *tcb;
1454 struct tcp_out_options opts;
1455 unsigned int tcp_options_size, tcp_header_size;
1456 struct sk_buff *oskb = NULL;
1457 struct tcp_key key;
1458 struct tcphdr *th;
1459 u64 prior_wstamp;
1460 int err;
1461
1462 BUG_ON(!skb || !tcp_skb_pcount(skb));
1463 tp = tcp_sk(sk);
1464 prior_wstamp = tp->tcp_wstamp_ns;
1465 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1466 skb_set_delivery_time(skb, tp->tcp_wstamp_ns, SKB_CLOCK_MONOTONIC);
1467 if (clone_it) {
1468 oskb = skb;
1469
1470 tcp_skb_tsorted_save(oskb) {
1471 if (unlikely(skb_cloned(oskb)))
1472 skb = pskb_copy(oskb, gfp_mask);
1473 else
1474 skb = skb_clone(oskb, gfp_mask);
1475 } tcp_skb_tsorted_restore(oskb);
1476
1477 if (unlikely(!skb))
1478 return -ENOBUFS;
1479 /* retransmit skbs might have a non zero value in skb->dev
1480 * because skb->dev is aliased with skb->rbnode.rb_left
1481 */
1482 skb->dev = NULL;
1483 }
1484
1485 inet = inet_sk(sk);
1486 tcb = TCP_SKB_CB(skb);
1487 memset(&opts, 0, sizeof(opts));
1488
1489 tcp_get_current_key(sk, &key);
1490 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1491 tcp_options_size = tcp_syn_options(sk, skb, &opts, &key);
1492 } else {
1493 tcp_options_size = tcp_established_options(sk, skb, &opts, &key);
1494 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1495 * at receiver : This slightly improve GRO performance.
1496 * Note that we do not force the PSH flag for non GSO packets,
1497 * because they might be sent under high congestion events,
1498 * and in this case it is better to delay the delivery of 1-MSS
1499 * packets and thus the corresponding ACK packet that would
1500 * release the following packet.
1501 */
1502 if (tcp_skb_pcount(skb) > 1)
1503 tcb->tcp_flags |= TCPHDR_PSH;
1504 }
1505 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1506
1507 /* We set skb->ooo_okay to one if this packet can select
1508 * a different TX queue than prior packets of this flow,
1509 * to avoid self inflicted reorders.
1510 * The 'other' queue decision is based on current cpu number
1511 * if XPS is enabled, or sk->sk_txhash otherwise.
1512 * We can switch to another (and better) queue if:
1513 * 1) No packet with payload is in qdisc/device queues.
1514 * Delays in TX completion can defeat the test
1515 * even if packets were already sent.
1516 * 2) Or rtx queue is empty.
1517 * This mitigates above case if ACK packets for
1518 * all prior packets were already processed.
1519 */
1520 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1) ||
1521 tcp_rtx_queue_empty(sk);
1522
1523 /* If we had to use memory reserve to allocate this skb,
1524 * this might cause drops if packet is looped back :
1525 * Other socket might not have SOCK_MEMALLOC.
1526 * Packets not looped back do not care about pfmemalloc.
1527 */
1528 skb->pfmemalloc = 0;
1529
1530 skb_push(skb, tcp_header_size);
1531 skb_reset_transport_header(skb);
1532
1533 skb_orphan(skb);
1534 skb->sk = sk;
1535 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1536 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1537
1538 skb_set_dst_pending_confirm(skb, READ_ONCE(sk->sk_dst_pending_confirm));
1539
1540 /* Build TCP header and checksum it. */
1541 th = (struct tcphdr *)skb->data;
1542 th->source = inet->inet_sport;
1543 th->dest = inet->inet_dport;
1544 th->seq = htonl(tcb->seq);
1545 th->ack_seq = htonl(rcv_nxt);
1546 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1547 (tcb->tcp_flags & TCPHDR_FLAGS_MASK));
1548
1549 th->check = 0;
1550 th->urg_ptr = 0;
1551
1552 /* The urg_mode check is necessary during a below snd_una win probe */
1553 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1554 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1555 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1556 th->urg = 1;
1557 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1558 th->urg_ptr = htons(0xFFFF);
1559 th->urg = 1;
1560 }
1561 }
1562
1563 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1564 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1565 th->window = htons(tcp_select_window(sk));
1566 tcp_ecn_send(sk, skb, th, tcp_header_size);
1567 } else {
1568 /* RFC1323: The window in SYN & SYN/ACK segments
1569 * is never scaled.
1570 */
1571 th->window = htons(min(tp->rcv_wnd, 65535U));
1572 }
1573
1574 tcp_options_write(th, tp, NULL, &opts, &key);
1575
1576 if (tcp_key_is_md5(&key)) {
1577 #ifdef CONFIG_TCP_MD5SIG
1578 /* Calculate the MD5 hash, as we have all we need now */
1579 sk_gso_disable(sk);
1580 tp->af_specific->calc_md5_hash(opts.hash_location,
1581 key.md5_key, sk, skb);
1582 #endif
1583 } else if (tcp_key_is_ao(&key)) {
1584 int err;
1585
1586 err = tcp_ao_transmit_skb(sk, skb, key.ao_key, th,
1587 opts.hash_location);
1588 if (err) {
1589 sk_skb_reason_drop(sk, skb, SKB_DROP_REASON_NOT_SPECIFIED);
1590 return -ENOMEM;
1591 }
1592 }
1593
1594 /* BPF prog is the last one writing header option */
1595 bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);
1596
1597 INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
1598 tcp_v6_send_check, tcp_v4_send_check,
1599 sk, skb);
1600
1601 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1602 tcp_event_ack_sent(sk, rcv_nxt);
1603
1604 if (skb->len != tcp_header_size) {
1605 tcp_event_data_sent(tp, sk);
1606 tp->data_segs_out += tcp_skb_pcount(skb);
1607 tp->bytes_sent += skb->len - tcp_header_size;
1608 }
1609
1610 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1611 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1612 tcp_skb_pcount(skb));
1613
1614 tp->segs_out += tcp_skb_pcount(skb);
1615 skb_set_hash_from_sk(skb, sk);
1616 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1617 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1618 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1619
1620 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1621
1622 /* Cleanup our debris for IP stacks */
1623 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1624 sizeof(struct inet6_skb_parm)));
1625
1626 tcp_add_tx_delay(skb, tp);
1627
1628 err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit,
1629 inet6_csk_xmit, ip_queue_xmit,
1630 sk, skb, &inet->cork.fl);
1631
1632 if (unlikely(err > 0)) {
1633 tcp_enter_cwr(sk);
1634 err = net_xmit_eval(err);
1635 }
1636 if (!err && oskb) {
1637 tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1638 tcp_rate_skb_sent(sk, oskb);
1639 }
1640 return err;
1641 }
1642
tcp_transmit_skb(struct sock * sk,struct sk_buff * skb,int clone_it,gfp_t gfp_mask)1643 static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1644 gfp_t gfp_mask)
1645 {
1646 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1647 tcp_sk(sk)->rcv_nxt);
1648 }
1649
1650 /* This routine just queues the buffer for sending.
1651 *
1652 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1653 * otherwise socket can stall.
1654 */
tcp_queue_skb(struct sock * sk,struct sk_buff * skb)1655 static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1656 {
1657 struct tcp_sock *tp = tcp_sk(sk);
1658
1659 /* Advance write_seq and place onto the write_queue. */
1660 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1661 __skb_header_release(skb);
1662 psp_enqueue_set_decrypted(sk, skb);
1663 tcp_add_write_queue_tail(sk, skb);
1664 sk_wmem_queued_add(sk, skb->truesize);
1665 sk_mem_charge(sk, skb->truesize);
1666 }
1667
1668 /* Initialize TSO segments for a packet. */
tcp_set_skb_tso_segs(struct sk_buff * skb,unsigned int mss_now)1669 static int tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1670 {
1671 int tso_segs;
1672
1673 if (skb->len <= mss_now) {
1674 /* Avoid the costly divide in the normal
1675 * non-TSO case.
1676 */
1677 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1678 tcp_skb_pcount_set(skb, 1);
1679 return 1;
1680 }
1681 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1682 tso_segs = DIV_ROUND_UP(skb->len, mss_now);
1683 tcp_skb_pcount_set(skb, tso_segs);
1684 return tso_segs;
1685 }
1686
1687 /* Pcount in the middle of the write queue got changed, we need to do various
1688 * tweaks to fix counters
1689 */
tcp_adjust_pcount(struct sock * sk,const struct sk_buff * skb,int decr)1690 static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1691 {
1692 struct tcp_sock *tp = tcp_sk(sk);
1693
1694 tp->packets_out -= decr;
1695
1696 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1697 tp->sacked_out -= decr;
1698 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1699 tp->retrans_out -= decr;
1700 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1701 tp->lost_out -= decr;
1702
1703 /* Reno case is special. Sigh... */
1704 if (tcp_is_reno(tp) && decr > 0)
1705 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1706
1707 tcp_verify_left_out(tp);
1708 }
1709
tcp_has_tx_tstamp(const struct sk_buff * skb)1710 static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1711 {
1712 return TCP_SKB_CB(skb)->txstamp_ack ||
1713 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1714 }
1715
tcp_fragment_tstamp(struct sk_buff * skb,struct sk_buff * skb2)1716 static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1717 {
1718 struct skb_shared_info *shinfo = skb_shinfo(skb);
1719
1720 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1721 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1722 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1723 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1724
1725 shinfo->tx_flags &= ~tsflags;
1726 shinfo2->tx_flags |= tsflags;
1727 swap(shinfo->tskey, shinfo2->tskey);
1728 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1729 TCP_SKB_CB(skb)->txstamp_ack = 0;
1730 }
1731 }
1732
tcp_skb_fragment_eor(struct sk_buff * skb,struct sk_buff * skb2)1733 static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1734 {
1735 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1736 TCP_SKB_CB(skb)->eor = 0;
1737 }
1738
1739 /* Insert buff after skb on the write or rtx queue of sk. */
tcp_insert_write_queue_after(struct sk_buff * skb,struct sk_buff * buff,struct sock * sk,enum tcp_queue tcp_queue)1740 static void tcp_insert_write_queue_after(struct sk_buff *skb,
1741 struct sk_buff *buff,
1742 struct sock *sk,
1743 enum tcp_queue tcp_queue)
1744 {
1745 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1746 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1747 else
1748 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1749 }
1750
1751 /* Function to create two new TCP segments. Shrinks the given segment
1752 * to the specified size and appends a new segment with the rest of the
1753 * packet to the list. This won't be called frequently, I hope.
1754 * Remember, these are still headerless SKBs at this point.
1755 */
tcp_fragment(struct sock * sk,enum tcp_queue tcp_queue,struct sk_buff * skb,u32 len,unsigned int mss_now,gfp_t gfp)1756 int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1757 struct sk_buff *skb, u32 len,
1758 unsigned int mss_now, gfp_t gfp)
1759 {
1760 struct tcp_sock *tp = tcp_sk(sk);
1761 struct sk_buff *buff;
1762 int old_factor;
1763 long limit;
1764 u16 flags;
1765 int nlen;
1766
1767 if (WARN_ON(len > skb->len))
1768 return -EINVAL;
1769
1770 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb));
1771
1772 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1773 * We need some allowance to not penalize applications setting small
1774 * SO_SNDBUF values.
1775 * Also allow first and last skb in retransmit queue to be split.
1776 */
1777 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_LEGACY_MAX_SIZE);
1778 if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1779 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1780 skb != tcp_rtx_queue_head(sk) &&
1781 skb != tcp_rtx_queue_tail(sk))) {
1782 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1783 return -ENOMEM;
1784 }
1785
1786 if (skb_unclone_keeptruesize(skb, gfp))
1787 return -ENOMEM;
1788
1789 /* Get a new skb... force flag on. */
1790 buff = tcp_stream_alloc_skb(sk, gfp, true);
1791 if (!buff)
1792 return -ENOMEM; /* We'll just try again later. */
1793 skb_copy_decrypted(buff, skb);
1794 mptcp_skb_ext_copy(buff, skb);
1795
1796 sk_wmem_queued_add(sk, buff->truesize);
1797 sk_mem_charge(sk, buff->truesize);
1798 nlen = skb->len - len;
1799 buff->truesize += nlen;
1800 skb->truesize -= nlen;
1801
1802 /* Correct the sequence numbers. */
1803 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1804 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1805 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1806
1807 /* PSH and FIN should only be set in the second packet. */
1808 flags = TCP_SKB_CB(skb)->tcp_flags;
1809 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1810 TCP_SKB_CB(buff)->tcp_flags = flags;
1811 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1812 tcp_skb_fragment_eor(skb, buff);
1813
1814 skb_split(skb, buff, len);
1815
1816 skb_set_delivery_time(buff, skb->tstamp, SKB_CLOCK_MONOTONIC);
1817 tcp_fragment_tstamp(skb, buff);
1818
1819 old_factor = tcp_skb_pcount(skb);
1820
1821 /* Fix up tso_factor for both original and new SKB. */
1822 tcp_set_skb_tso_segs(skb, mss_now);
1823 tcp_set_skb_tso_segs(buff, mss_now);
1824
1825 /* Update delivered info for the new segment */
1826 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1827
1828 /* If this packet has been sent out already, we must
1829 * adjust the various packet counters.
1830 */
1831 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1832 int diff = old_factor - tcp_skb_pcount(skb) -
1833 tcp_skb_pcount(buff);
1834
1835 if (diff)
1836 tcp_adjust_pcount(sk, skb, diff);
1837 }
1838
1839 /* Link BUFF into the send queue. */
1840 __skb_header_release(buff);
1841 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1842 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1843 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1844
1845 return 0;
1846 }
1847
1848 /* This is similar to __pskb_pull_tail(). The difference is that pulled
1849 * data is not copied, but immediately discarded.
1850 */
__pskb_trim_head(struct sk_buff * skb,int len)1851 static int __pskb_trim_head(struct sk_buff *skb, int len)
1852 {
1853 struct skb_shared_info *shinfo;
1854 int i, k, eat;
1855
1856 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb));
1857 eat = len;
1858 k = 0;
1859 shinfo = skb_shinfo(skb);
1860 for (i = 0; i < shinfo->nr_frags; i++) {
1861 int size = skb_frag_size(&shinfo->frags[i]);
1862
1863 if (size <= eat) {
1864 skb_frag_unref(skb, i);
1865 eat -= size;
1866 } else {
1867 shinfo->frags[k] = shinfo->frags[i];
1868 if (eat) {
1869 skb_frag_off_add(&shinfo->frags[k], eat);
1870 skb_frag_size_sub(&shinfo->frags[k], eat);
1871 eat = 0;
1872 }
1873 k++;
1874 }
1875 }
1876 shinfo->nr_frags = k;
1877
1878 skb->data_len -= len;
1879 skb->len = skb->data_len;
1880 return len;
1881 }
1882
1883 /* Remove acked data from a packet in the transmit queue. */
tcp_trim_head(struct sock * sk,struct sk_buff * skb,u32 len)1884 int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1885 {
1886 u32 delta_truesize;
1887
1888 if (skb_unclone_keeptruesize(skb, GFP_ATOMIC))
1889 return -ENOMEM;
1890
1891 delta_truesize = __pskb_trim_head(skb, len);
1892
1893 TCP_SKB_CB(skb)->seq += len;
1894
1895 skb->truesize -= delta_truesize;
1896 sk_wmem_queued_add(sk, -delta_truesize);
1897 if (!skb_zcopy_pure(skb))
1898 sk_mem_uncharge(sk, delta_truesize);
1899
1900 /* Any change of skb->len requires recalculation of tso factor. */
1901 if (tcp_skb_pcount(skb) > 1)
1902 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1903
1904 return 0;
1905 }
1906
1907 /* Calculate MSS not accounting any TCP options. */
__tcp_mtu_to_mss(struct sock * sk,int pmtu)1908 static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1909 {
1910 const struct tcp_sock *tp = tcp_sk(sk);
1911 const struct inet_connection_sock *icsk = inet_csk(sk);
1912 int mss_now;
1913
1914 /* Calculate base mss without TCP options:
1915 It is MMS_S - sizeof(tcphdr) of rfc1122
1916 */
1917 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1918
1919 /* Clamp it (mss_clamp does not include tcp options) */
1920 if (mss_now > tp->rx_opt.mss_clamp)
1921 mss_now = tp->rx_opt.mss_clamp;
1922
1923 /* Now subtract optional transport overhead */
1924 mss_now -= icsk->icsk_ext_hdr_len;
1925
1926 /* Then reserve room for full set of TCP options and 8 bytes of data */
1927 mss_now = max(mss_now,
1928 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss));
1929 return mss_now;
1930 }
1931
1932 /* Calculate MSS. Not accounting for SACKs here. */
tcp_mtu_to_mss(struct sock * sk,int pmtu)1933 int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1934 {
1935 /* Subtract TCP options size, not including SACKs */
1936 return __tcp_mtu_to_mss(sk, pmtu) -
1937 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1938 }
1939 EXPORT_IPV6_MOD(tcp_mtu_to_mss);
1940
1941 /* Inverse of above */
tcp_mss_to_mtu(struct sock * sk,int mss)1942 int tcp_mss_to_mtu(struct sock *sk, int mss)
1943 {
1944 const struct tcp_sock *tp = tcp_sk(sk);
1945 const struct inet_connection_sock *icsk = inet_csk(sk);
1946
1947 return mss +
1948 tp->tcp_header_len +
1949 icsk->icsk_ext_hdr_len +
1950 icsk->icsk_af_ops->net_header_len;
1951 }
1952 EXPORT_SYMBOL(tcp_mss_to_mtu);
1953
1954 /* MTU probing init per socket */
tcp_mtup_init(struct sock * sk)1955 void tcp_mtup_init(struct sock *sk)
1956 {
1957 struct tcp_sock *tp = tcp_sk(sk);
1958 struct inet_connection_sock *icsk = inet_csk(sk);
1959 struct net *net = sock_net(sk);
1960
1961 icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1;
1962 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1963 icsk->icsk_af_ops->net_header_len;
1964 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, READ_ONCE(net->ipv4.sysctl_tcp_base_mss));
1965 icsk->icsk_mtup.probe_size = 0;
1966 if (icsk->icsk_mtup.enabled)
1967 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1968 }
1969
1970 /* This function synchronize snd mss to current pmtu/exthdr set.
1971
1972 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1973 for TCP options, but includes only bare TCP header.
1974
1975 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1976 It is minimum of user_mss and mss received with SYN.
1977 It also does not include TCP options.
1978
1979 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1980
1981 tp->mss_cache is current effective sending mss, including
1982 all tcp options except for SACKs. It is evaluated,
1983 taking into account current pmtu, but never exceeds
1984 tp->rx_opt.mss_clamp.
1985
1986 NOTE1. rfc1122 clearly states that advertised MSS
1987 DOES NOT include either tcp or ip options.
1988
1989 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1990 are READ ONLY outside this function. --ANK (980731)
1991 */
tcp_sync_mss(struct sock * sk,u32 pmtu)1992 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1993 {
1994 struct tcp_sock *tp = tcp_sk(sk);
1995 struct inet_connection_sock *icsk = inet_csk(sk);
1996 int mss_now;
1997
1998 if (icsk->icsk_mtup.search_high > pmtu)
1999 icsk->icsk_mtup.search_high = pmtu;
2000
2001 mss_now = tcp_mtu_to_mss(sk, pmtu);
2002 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
2003
2004 /* And store cached results */
2005 icsk->icsk_pmtu_cookie = pmtu;
2006 if (icsk->icsk_mtup.enabled)
2007 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
2008 tp->mss_cache = mss_now;
2009
2010 return mss_now;
2011 }
2012 EXPORT_IPV6_MOD(tcp_sync_mss);
2013
2014 /* Compute the current effective MSS, taking SACKs and IP options,
2015 * and even PMTU discovery events into account.
2016 */
tcp_current_mss(struct sock * sk)2017 unsigned int tcp_current_mss(struct sock *sk)
2018 {
2019 const struct tcp_sock *tp = tcp_sk(sk);
2020 const struct dst_entry *dst = __sk_dst_get(sk);
2021 u32 mss_now;
2022 unsigned int header_len;
2023 struct tcp_out_options opts;
2024 struct tcp_key key;
2025
2026 mss_now = tp->mss_cache;
2027
2028 if (dst) {
2029 u32 mtu = dst_mtu(dst);
2030 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
2031 mss_now = tcp_sync_mss(sk, mtu);
2032 }
2033 tcp_get_current_key(sk, &key);
2034 header_len = tcp_established_options(sk, NULL, &opts, &key) +
2035 sizeof(struct tcphdr);
2036 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
2037 * some common options. If this is an odd packet (because we have SACK
2038 * blocks etc) then our calculated header_len will be different, and
2039 * we have to adjust mss_now correspondingly */
2040 if (header_len != tp->tcp_header_len) {
2041 int delta = (int) header_len - tp->tcp_header_len;
2042 mss_now -= delta;
2043 }
2044
2045 return mss_now;
2046 }
2047
2048 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
2049 * As additional protections, we do not touch cwnd in retransmission phases,
2050 * and if application hit its sndbuf limit recently.
2051 */
tcp_cwnd_application_limited(struct sock * sk)2052 static void tcp_cwnd_application_limited(struct sock *sk)
2053 {
2054 struct tcp_sock *tp = tcp_sk(sk);
2055
2056 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
2057 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
2058 /* Limited by application or receiver window. */
2059 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
2060 u32 win_used = max(tp->snd_cwnd_used, init_win);
2061 if (win_used < tcp_snd_cwnd(tp)) {
2062 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2063 tcp_snd_cwnd_set(tp, (tcp_snd_cwnd(tp) + win_used) >> 1);
2064 }
2065 tp->snd_cwnd_used = 0;
2066 }
2067 tp->snd_cwnd_stamp = tcp_jiffies32;
2068 }
2069
tcp_cwnd_validate(struct sock * sk,bool is_cwnd_limited)2070 static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
2071 {
2072 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2073 struct tcp_sock *tp = tcp_sk(sk);
2074
2075 /* Track the strongest available signal of the degree to which the cwnd
2076 * is fully utilized. If cwnd-limited then remember that fact for the
2077 * current window. If not cwnd-limited then track the maximum number of
2078 * outstanding packets in the current window. (If cwnd-limited then we
2079 * chose to not update tp->max_packets_out to avoid an extra else
2080 * clause with no functional impact.)
2081 */
2082 if (!before(tp->snd_una, tp->cwnd_usage_seq) ||
2083 is_cwnd_limited ||
2084 (!tp->is_cwnd_limited &&
2085 tp->packets_out > tp->max_packets_out)) {
2086 tp->is_cwnd_limited = is_cwnd_limited;
2087 tp->max_packets_out = tp->packets_out;
2088 tp->cwnd_usage_seq = tp->snd_nxt;
2089 }
2090
2091 if (tcp_is_cwnd_limited(sk)) {
2092 /* Network is feed fully. */
2093 tp->snd_cwnd_used = 0;
2094 tp->snd_cwnd_stamp = tcp_jiffies32;
2095 } else {
2096 /* Network starves. */
2097 if (tp->packets_out > tp->snd_cwnd_used)
2098 tp->snd_cwnd_used = tp->packets_out;
2099
2100 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) &&
2101 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
2102 !ca_ops->cong_control)
2103 tcp_cwnd_application_limited(sk);
2104
2105 /* The following conditions together indicate the starvation
2106 * is caused by insufficient sender buffer:
2107 * 1) just sent some data (see tcp_write_xmit)
2108 * 2) not cwnd limited (this else condition)
2109 * 3) no more data to send (tcp_write_queue_empty())
2110 * 4) application is hitting buffer limit (SOCK_NOSPACE)
2111 */
2112 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
2113 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
2114 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
2115 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
2116 }
2117 }
2118
2119 /* Minshall's variant of the Nagle send check. */
tcp_minshall_check(const struct tcp_sock * tp)2120 static bool tcp_minshall_check(const struct tcp_sock *tp)
2121 {
2122 return after(tp->snd_sml, tp->snd_una) &&
2123 !after(tp->snd_sml, tp->snd_nxt);
2124 }
2125
2126 /* Update snd_sml if this skb is under mss
2127 * Note that a TSO packet might end with a sub-mss segment
2128 * The test is really :
2129 * if ((skb->len % mss) != 0)
2130 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
2131 * But we can avoid doing the divide again given we already have
2132 * skb_pcount = skb->len / mss_now
2133 */
tcp_minshall_update(struct tcp_sock * tp,unsigned int mss_now,const struct sk_buff * skb)2134 static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
2135 const struct sk_buff *skb)
2136 {
2137 if (skb->len < tcp_skb_pcount(skb) * mss_now)
2138 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
2139 }
2140
2141 /* Return false, if packet can be sent now without violation Nagle's rules:
2142 * 1. It is full sized. (provided by caller in %partial bool)
2143 * 2. Or it contains FIN. (already checked by caller)
2144 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
2145 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
2146 * With Minshall's modification: all sent small packets are ACKed.
2147 */
tcp_nagle_check(bool partial,const struct tcp_sock * tp,int nonagle)2148 static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
2149 int nonagle)
2150 {
2151 return partial &&
2152 ((nonagle & TCP_NAGLE_CORK) ||
2153 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
2154 }
2155
2156 /* Return how many segs we'd like on a TSO packet,
2157 * depending on current pacing rate, and how close the peer is.
2158 *
2159 * Rationale is:
2160 * - For close peers, we rather send bigger packets to reduce
2161 * cpu costs, because occasional losses will be repaired fast.
2162 * - For long distance/rtt flows, we would like to get ACK clocking
2163 * with 1 ACK per ms.
2164 *
2165 * Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting
2166 * in bigger TSO bursts. We we cut the RTT-based allowance in half
2167 * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance
2168 * is below 1500 bytes after 6 * ~500 usec = 3ms.
2169 */
tcp_tso_autosize(const struct sock * sk,unsigned int mss_now,int min_tso_segs)2170 static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
2171 int min_tso_segs)
2172 {
2173 unsigned long bytes;
2174 u32 r;
2175
2176 bytes = READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift);
2177
2178 r = tcp_min_rtt(tcp_sk(sk)) >> READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log);
2179 if (r < BITS_PER_TYPE(sk->sk_gso_max_size))
2180 bytes += sk->sk_gso_max_size >> r;
2181
2182 bytes = min_t(unsigned long, bytes, sk->sk_gso_max_size);
2183
2184 return max_t(u32, bytes / mss_now, min_tso_segs);
2185 }
2186
2187 /* Return the number of segments we want in the skb we are transmitting.
2188 * See if congestion control module wants to decide; otherwise, autosize.
2189 */
tcp_tso_segs(struct sock * sk,unsigned int mss_now)2190 static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
2191 {
2192 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2193 u32 min_tso, tso_segs;
2194
2195 min_tso = ca_ops->min_tso_segs ?
2196 ca_ops->min_tso_segs(sk) :
2197 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
2198
2199 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
2200 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
2201 }
2202
2203 /* Returns the portion of skb which can be sent right away */
tcp_mss_split_point(const struct sock * sk,const struct sk_buff * skb,unsigned int mss_now,unsigned int max_segs,int nonagle)2204 static unsigned int tcp_mss_split_point(const struct sock *sk,
2205 const struct sk_buff *skb,
2206 unsigned int mss_now,
2207 unsigned int max_segs,
2208 int nonagle)
2209 {
2210 const struct tcp_sock *tp = tcp_sk(sk);
2211 u32 partial, needed, window, max_len;
2212
2213 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2214 max_len = mss_now * max_segs;
2215
2216 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
2217 return max_len;
2218
2219 needed = min(skb->len, window);
2220
2221 if (max_len <= needed)
2222 return max_len;
2223
2224 partial = needed % mss_now;
2225 /* If last segment is not a full MSS, check if Nagle rules allow us
2226 * to include this last segment in this skb.
2227 * Otherwise, we'll split the skb at last MSS boundary
2228 */
2229 if (tcp_nagle_check(partial != 0, tp, nonagle))
2230 return needed - partial;
2231
2232 return needed;
2233 }
2234
2235 /* Can at least one segment of SKB be sent right now, according to the
2236 * congestion window rules? If so, return how many segments are allowed.
2237 */
tcp_cwnd_test(const struct tcp_sock * tp)2238 static u32 tcp_cwnd_test(const struct tcp_sock *tp)
2239 {
2240 u32 in_flight, cwnd, halfcwnd;
2241
2242 in_flight = tcp_packets_in_flight(tp);
2243 cwnd = tcp_snd_cwnd(tp);
2244 if (in_flight >= cwnd)
2245 return 0;
2246
2247 /* For better scheduling, ensure we have at least
2248 * 2 GSO packets in flight.
2249 */
2250 halfcwnd = max(cwnd >> 1, 1U);
2251 return min(halfcwnd, cwnd - in_flight);
2252 }
2253
2254 /* Initialize TSO state of a skb.
2255 * This must be invoked the first time we consider transmitting
2256 * SKB onto the wire.
2257 */
tcp_init_tso_segs(struct sk_buff * skb,unsigned int mss_now)2258 static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
2259 {
2260 int tso_segs = tcp_skb_pcount(skb);
2261
2262 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now))
2263 return tcp_set_skb_tso_segs(skb, mss_now);
2264
2265 return tso_segs;
2266 }
2267
2268
2269 /* Return true if the Nagle test allows this packet to be
2270 * sent now.
2271 */
tcp_nagle_test(const struct tcp_sock * tp,const struct sk_buff * skb,unsigned int cur_mss,int nonagle)2272 static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
2273 unsigned int cur_mss, int nonagle)
2274 {
2275 /* Nagle rule does not apply to frames, which sit in the middle of the
2276 * write_queue (they have no chances to get new data).
2277 *
2278 * This is implemented in the callers, where they modify the 'nonagle'
2279 * argument based upon the location of SKB in the send queue.
2280 */
2281 if (nonagle & TCP_NAGLE_PUSH)
2282 return true;
2283
2284 /* Don't use the nagle rule for urgent data (or for the final FIN). */
2285 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
2286 return true;
2287
2288 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
2289 return true;
2290
2291 return false;
2292 }
2293
2294 /* Does at least the first segment of SKB fit into the send window? */
tcp_snd_wnd_test(const struct tcp_sock * tp,const struct sk_buff * skb,unsigned int cur_mss)2295 static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
2296 const struct sk_buff *skb,
2297 unsigned int cur_mss)
2298 {
2299 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2300
2301 if (skb->len > cur_mss)
2302 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
2303
2304 return !after(end_seq, tcp_wnd_end(tp));
2305 }
2306
2307 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
2308 * which is put after SKB on the list. It is very much like
2309 * tcp_fragment() except that it may make several kinds of assumptions
2310 * in order to speed up the splitting operation. In particular, we
2311 * know that all the data is in scatter-gather pages, and that the
2312 * packet has never been sent out before (and thus is not cloned).
2313 */
tso_fragment(struct sock * sk,struct sk_buff * skb,unsigned int len,unsigned int mss_now,gfp_t gfp)2314 static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
2315 unsigned int mss_now, gfp_t gfp)
2316 {
2317 int nlen = skb->len - len;
2318 struct sk_buff *buff;
2319 u16 flags;
2320
2321 /* All of a TSO frame must be composed of paged data. */
2322 DEBUG_NET_WARN_ON_ONCE(skb->len != skb->data_len);
2323
2324 buff = tcp_stream_alloc_skb(sk, gfp, true);
2325 if (unlikely(!buff))
2326 return -ENOMEM;
2327 skb_copy_decrypted(buff, skb);
2328 mptcp_skb_ext_copy(buff, skb);
2329
2330 sk_wmem_queued_add(sk, buff->truesize);
2331 sk_mem_charge(sk, buff->truesize);
2332 buff->truesize += nlen;
2333 skb->truesize -= nlen;
2334
2335 /* Correct the sequence numbers. */
2336 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
2337 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
2338 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
2339
2340 /* PSH and FIN should only be set in the second packet. */
2341 flags = TCP_SKB_CB(skb)->tcp_flags;
2342 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
2343 TCP_SKB_CB(buff)->tcp_flags = flags;
2344
2345 tcp_skb_fragment_eor(skb, buff);
2346
2347 skb_split(skb, buff, len);
2348 tcp_fragment_tstamp(skb, buff);
2349
2350 /* Fix up tso_factor for both original and new SKB. */
2351 tcp_set_skb_tso_segs(skb, mss_now);
2352 tcp_set_skb_tso_segs(buff, mss_now);
2353
2354 /* Link BUFF into the send queue. */
2355 __skb_header_release(buff);
2356 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
2357
2358 return 0;
2359 }
2360
2361 /* Try to defer sending, if possible, in order to minimize the amount
2362 * of TSO splitting we do. View it as a kind of TSO Nagle test.
2363 *
2364 * This algorithm is from John Heffner.
2365 */
tcp_tso_should_defer(struct sock * sk,struct sk_buff * skb,bool * is_cwnd_limited,bool * is_rwnd_limited,u32 max_segs)2366 static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
2367 bool *is_cwnd_limited,
2368 bool *is_rwnd_limited,
2369 u32 max_segs)
2370 {
2371 const struct inet_connection_sock *icsk = inet_csk(sk);
2372 u32 send_win, cong_win, limit, in_flight, threshold;
2373 u64 srtt_in_ns, expected_ack, how_far_is_the_ack;
2374 struct tcp_sock *tp = tcp_sk(sk);
2375 struct sk_buff *head;
2376 int win_divisor;
2377 s64 delta;
2378
2379 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
2380 goto send_now;
2381
2382 /* Avoid bursty behavior by allowing defer
2383 * only if the last write was recent (1 ms).
2384 * Note that tp->tcp_wstamp_ns can be in the future if we have
2385 * packets waiting in a qdisc or device for EDT delivery.
2386 */
2387 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
2388 if (delta > 0)
2389 goto send_now;
2390
2391 in_flight = tcp_packets_in_flight(tp);
2392
2393 BUG_ON(tcp_skb_pcount(skb) <= 1);
2394 BUG_ON(tcp_snd_cwnd(tp) <= in_flight);
2395
2396 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2397
2398 /* From in_flight test above, we know that cwnd > in_flight. */
2399 cong_win = (tcp_snd_cwnd(tp) - in_flight) * tp->mss_cache;
2400
2401 limit = min(send_win, cong_win);
2402
2403 /* If a full-sized TSO skb can be sent, do it. */
2404 if (limit >= max_segs * tp->mss_cache)
2405 goto send_now;
2406
2407 /* Middle in queue won't get any more data, full sendable already? */
2408 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
2409 goto send_now;
2410
2411 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
2412 if (win_divisor) {
2413 u32 chunk = min(tp->snd_wnd, tcp_snd_cwnd(tp) * tp->mss_cache);
2414
2415 /* If at least some fraction of a window is available,
2416 * just use it.
2417 */
2418 chunk /= win_divisor;
2419 if (limit >= chunk)
2420 goto send_now;
2421 } else {
2422 /* Different approach, try not to defer past a single
2423 * ACK. Receiver should ACK every other full sized
2424 * frame, so if we have space for more than 3 frames
2425 * then send now.
2426 */
2427 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
2428 goto send_now;
2429 }
2430
2431 /* TODO : use tsorted_sent_queue ? */
2432 head = tcp_rtx_queue_head(sk);
2433 if (!head)
2434 goto send_now;
2435
2436 srtt_in_ns = (u64)(NSEC_PER_USEC >> 3) * tp->srtt_us;
2437 /* When is the ACK expected ? */
2438 expected_ack = head->tstamp + srtt_in_ns;
2439 /* How far from now is the ACK expected ? */
2440 how_far_is_the_ack = expected_ack - tp->tcp_clock_cache;
2441
2442 /* If next ACK is likely to come too late,
2443 * ie in more than min(1ms, half srtt), do not defer.
2444 */
2445 threshold = min(srtt_in_ns >> 1, NSEC_PER_MSEC);
2446
2447 if ((s64)(how_far_is_the_ack - threshold) > 0)
2448 goto send_now;
2449
2450 /* Ok, it looks like it is advisable to defer.
2451 * Three cases are tracked :
2452 * 1) We are cwnd-limited
2453 * 2) We are rwnd-limited
2454 * 3) We are application limited.
2455 */
2456 if (cong_win < send_win) {
2457 if (cong_win <= skb->len) {
2458 *is_cwnd_limited = true;
2459 return true;
2460 }
2461 } else {
2462 if (send_win <= skb->len) {
2463 *is_rwnd_limited = true;
2464 return true;
2465 }
2466 }
2467
2468 /* If this packet won't get more data, do not wait. */
2469 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2470 TCP_SKB_CB(skb)->eor)
2471 goto send_now;
2472
2473 return true;
2474
2475 send_now:
2476 return false;
2477 }
2478
tcp_mtu_check_reprobe(struct sock * sk)2479 static inline void tcp_mtu_check_reprobe(struct sock *sk)
2480 {
2481 struct inet_connection_sock *icsk = inet_csk(sk);
2482 struct tcp_sock *tp = tcp_sk(sk);
2483 struct net *net = sock_net(sk);
2484 u32 interval;
2485 s32 delta;
2486
2487 interval = READ_ONCE(net->ipv4.sysctl_tcp_probe_interval);
2488 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2489 if (unlikely(delta >= interval * HZ)) {
2490 int mss = tcp_current_mss(sk);
2491
2492 /* Update current search range */
2493 icsk->icsk_mtup.probe_size = 0;
2494 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2495 sizeof(struct tcphdr) +
2496 icsk->icsk_af_ops->net_header_len;
2497 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2498
2499 /* Update probe time stamp */
2500 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2501 }
2502 }
2503
tcp_can_coalesce_send_queue_head(struct sock * sk,int len)2504 static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2505 {
2506 struct sk_buff *skb, *next;
2507
2508 skb = tcp_send_head(sk);
2509 tcp_for_write_queue_from_safe(skb, next, sk) {
2510 if (len <= skb->len)
2511 break;
2512
2513 if (tcp_has_tx_tstamp(skb) || !tcp_skb_can_collapse(skb, next))
2514 return false;
2515
2516 len -= skb->len;
2517 }
2518
2519 return true;
2520 }
2521
tcp_clone_payload(struct sock * sk,struct sk_buff * to,int probe_size)2522 static int tcp_clone_payload(struct sock *sk, struct sk_buff *to,
2523 int probe_size)
2524 {
2525 skb_frag_t *lastfrag = NULL, *fragto = skb_shinfo(to)->frags;
2526 int i, todo, len = 0, nr_frags = 0;
2527 const struct sk_buff *skb;
2528
2529 if (!sk_wmem_schedule(sk, to->truesize + probe_size))
2530 return -ENOMEM;
2531
2532 skb_queue_walk(&sk->sk_write_queue, skb) {
2533 const skb_frag_t *fragfrom = skb_shinfo(skb)->frags;
2534
2535 if (skb_headlen(skb))
2536 return -EINVAL;
2537
2538 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, fragfrom++) {
2539 if (len >= probe_size)
2540 goto commit;
2541 todo = min_t(int, skb_frag_size(fragfrom),
2542 probe_size - len);
2543 len += todo;
2544 if (lastfrag &&
2545 skb_frag_page(fragfrom) == skb_frag_page(lastfrag) &&
2546 skb_frag_off(fragfrom) == skb_frag_off(lastfrag) +
2547 skb_frag_size(lastfrag)) {
2548 skb_frag_size_add(lastfrag, todo);
2549 continue;
2550 }
2551 if (unlikely(nr_frags == MAX_SKB_FRAGS))
2552 return -E2BIG;
2553 skb_frag_page_copy(fragto, fragfrom);
2554 skb_frag_off_copy(fragto, fragfrom);
2555 skb_frag_size_set(fragto, todo);
2556 nr_frags++;
2557 lastfrag = fragto++;
2558 }
2559 }
2560 commit:
2561 WARN_ON_ONCE(len != probe_size);
2562 for (i = 0; i < nr_frags; i++)
2563 skb_frag_ref(to, i);
2564
2565 skb_shinfo(to)->nr_frags = nr_frags;
2566 to->truesize += probe_size;
2567 to->len += probe_size;
2568 to->data_len += probe_size;
2569 __skb_header_release(to);
2570 return 0;
2571 }
2572
2573 /* tcp_mtu_probe() and tcp_grow_skb() can both eat an skb (src) if
2574 * all its payload was moved to another one (dst).
2575 * Make sure to transfer tcp_flags, eor, and tstamp.
2576 */
tcp_eat_one_skb(struct sock * sk,struct sk_buff * dst,struct sk_buff * src)2577 static void tcp_eat_one_skb(struct sock *sk,
2578 struct sk_buff *dst,
2579 struct sk_buff *src)
2580 {
2581 TCP_SKB_CB(dst)->tcp_flags |= TCP_SKB_CB(src)->tcp_flags;
2582 TCP_SKB_CB(dst)->eor = TCP_SKB_CB(src)->eor;
2583 tcp_skb_collapse_tstamp(dst, src);
2584 tcp_unlink_write_queue(src, sk);
2585 tcp_wmem_free_skb(sk, src);
2586 }
2587
2588 /* Create a new MTU probe if we are ready.
2589 * MTU probe is regularly attempting to increase the path MTU by
2590 * deliberately sending larger packets. This discovers routing
2591 * changes resulting in larger path MTUs.
2592 *
2593 * Returns 0 if we should wait to probe (no cwnd available),
2594 * 1 if a probe was sent,
2595 * -1 otherwise
2596 */
tcp_mtu_probe(struct sock * sk)2597 static int tcp_mtu_probe(struct sock *sk)
2598 {
2599 struct inet_connection_sock *icsk = inet_csk(sk);
2600 struct tcp_sock *tp = tcp_sk(sk);
2601 struct sk_buff *skb, *nskb, *next;
2602 struct net *net = sock_net(sk);
2603 int probe_size;
2604 int size_needed;
2605 int copy, len;
2606 int mss_now;
2607 int interval;
2608
2609 /* Not currently probing/verifying,
2610 * not in recovery,
2611 * have enough cwnd, and
2612 * not SACKing (the variable headers throw things off)
2613 */
2614 if (likely(!icsk->icsk_mtup.enabled ||
2615 icsk->icsk_mtup.probe_size ||
2616 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2617 tcp_snd_cwnd(tp) < 11 ||
2618 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2619 return -1;
2620
2621 /* Use binary search for probe_size between tcp_mss_base,
2622 * and current mss_clamp. if (search_high - search_low)
2623 * smaller than a threshold, backoff from probing.
2624 */
2625 mss_now = tcp_current_mss(sk);
2626 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2627 icsk->icsk_mtup.search_low) >> 1);
2628 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2629 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2630 /* When misfortune happens, we are reprobing actively,
2631 * and then reprobe timer has expired. We stick with current
2632 * probing process by not resetting search range to its orignal.
2633 */
2634 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2635 interval < READ_ONCE(net->ipv4.sysctl_tcp_probe_threshold)) {
2636 /* Check whether enough time has elaplased for
2637 * another round of probing.
2638 */
2639 tcp_mtu_check_reprobe(sk);
2640 return -1;
2641 }
2642
2643 /* Have enough data in the send queue to probe? */
2644 if (tp->write_seq - tp->snd_nxt < size_needed)
2645 return -1;
2646
2647 if (tp->snd_wnd < size_needed)
2648 return -1;
2649 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2650 return 0;
2651
2652 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2653 if (tcp_packets_in_flight(tp) + 2 > tcp_snd_cwnd(tp)) {
2654 if (!tcp_packets_in_flight(tp))
2655 return -1;
2656 else
2657 return 0;
2658 }
2659
2660 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2661 return -1;
2662
2663 /* We're allowed to probe. Build it now. */
2664 nskb = tcp_stream_alloc_skb(sk, GFP_ATOMIC, false);
2665 if (!nskb)
2666 return -1;
2667
2668 /* build the payload, and be prepared to abort if this fails. */
2669 if (tcp_clone_payload(sk, nskb, probe_size)) {
2670 tcp_skb_tsorted_anchor_cleanup(nskb);
2671 consume_skb(nskb);
2672 return -1;
2673 }
2674 sk_wmem_queued_add(sk, nskb->truesize);
2675 sk_mem_charge(sk, nskb->truesize);
2676
2677 skb = tcp_send_head(sk);
2678 skb_copy_decrypted(nskb, skb);
2679 mptcp_skb_ext_copy(nskb, skb);
2680
2681 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2682 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2683 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2684
2685 tcp_insert_write_queue_before(nskb, skb, sk);
2686 tcp_highest_sack_replace(sk, skb, nskb);
2687
2688 len = 0;
2689 tcp_for_write_queue_from_safe(skb, next, sk) {
2690 copy = min_t(int, skb->len, probe_size - len);
2691
2692 if (skb->len <= copy) {
2693 tcp_eat_one_skb(sk, nskb, skb);
2694 } else {
2695 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2696 ~(TCPHDR_FIN|TCPHDR_PSH);
2697 __pskb_trim_head(skb, copy);
2698 tcp_set_skb_tso_segs(skb, mss_now);
2699 TCP_SKB_CB(skb)->seq += copy;
2700 }
2701
2702 len += copy;
2703
2704 if (len >= probe_size)
2705 break;
2706 }
2707 tcp_init_tso_segs(nskb, nskb->len);
2708
2709 /* We're ready to send. If this fails, the probe will
2710 * be resegmented into mss-sized pieces by tcp_write_xmit().
2711 */
2712 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2713 /* Decrement cwnd here because we are sending
2714 * effectively two packets. */
2715 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - 1);
2716 tcp_event_new_data_sent(sk, nskb);
2717
2718 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2719 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2720 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2721
2722 return 1;
2723 }
2724
2725 return -1;
2726 }
2727
tcp_pacing_check(struct sock * sk)2728 static bool tcp_pacing_check(struct sock *sk)
2729 {
2730 struct tcp_sock *tp = tcp_sk(sk);
2731
2732 if (!tcp_needs_internal_pacing(sk))
2733 return false;
2734
2735 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2736 return false;
2737
2738 if (!hrtimer_is_queued(&tp->pacing_timer)) {
2739 hrtimer_start(&tp->pacing_timer,
2740 ns_to_ktime(tp->tcp_wstamp_ns),
2741 HRTIMER_MODE_ABS_PINNED_SOFT);
2742 sock_hold(sk);
2743 }
2744 return true;
2745 }
2746
tcp_rtx_queue_empty_or_single_skb(const struct sock * sk)2747 static bool tcp_rtx_queue_empty_or_single_skb(const struct sock *sk)
2748 {
2749 const struct rb_node *node = sk->tcp_rtx_queue.rb_node;
2750
2751 /* No skb in the rtx queue. */
2752 if (!node)
2753 return true;
2754
2755 /* Only one skb in rtx queue. */
2756 return !node->rb_left && !node->rb_right;
2757 }
2758
2759 /* TCP Small Queues :
2760 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2761 * (These limits are doubled for retransmits)
2762 * This allows for :
2763 * - better RTT estimation and ACK scheduling
2764 * - faster recovery
2765 * - high rates
2766 * Alas, some drivers / subsystems require a fair amount
2767 * of queued bytes to ensure line rate.
2768 * One example is wifi aggregation (802.11 AMPDU)
2769 */
tcp_small_queue_check(struct sock * sk,const struct sk_buff * skb,unsigned int factor)2770 static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2771 unsigned int factor)
2772 {
2773 unsigned long limit;
2774
2775 limit = max_t(unsigned long,
2776 2 * skb->truesize,
2777 READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift));
2778 limit = min_t(unsigned long, limit,
2779 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes));
2780 limit <<= factor;
2781
2782 if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2783 tcp_sk(sk)->tcp_tx_delay) {
2784 u64 extra_bytes = (u64)READ_ONCE(sk->sk_pacing_rate) *
2785 tcp_sk(sk)->tcp_tx_delay;
2786
2787 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2788 * approximate our needs assuming an ~100% skb->truesize overhead.
2789 * USEC_PER_SEC is approximated by 2^20.
2790 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2791 */
2792 extra_bytes >>= (20 - 1);
2793 limit += extra_bytes;
2794 }
2795 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2796 /* Always send skb if rtx queue is empty or has one skb.
2797 * No need to wait for TX completion to call us back,
2798 * after softirq schedule.
2799 * This helps when TX completions are delayed too much.
2800 */
2801 if (tcp_rtx_queue_empty_or_single_skb(sk))
2802 return false;
2803
2804 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2805 /* It is possible TX completion already happened
2806 * before we set TSQ_THROTTLED, so we must
2807 * test again the condition.
2808 */
2809 smp_mb__after_atomic();
2810 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2811 return true;
2812 }
2813 return false;
2814 }
2815
tcp_chrono_set(struct tcp_sock * tp,const enum tcp_chrono new)2816 static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2817 {
2818 const u32 now = tcp_jiffies32;
2819 enum tcp_chrono old = tp->chrono_type;
2820
2821 if (old > TCP_CHRONO_UNSPEC)
2822 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2823 tp->chrono_start = now;
2824 tp->chrono_type = new;
2825 }
2826
tcp_chrono_start(struct sock * sk,const enum tcp_chrono type)2827 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2828 {
2829 struct tcp_sock *tp = tcp_sk(sk);
2830
2831 /* If there are multiple conditions worthy of tracking in a
2832 * chronograph then the highest priority enum takes precedence
2833 * over the other conditions. So that if something "more interesting"
2834 * starts happening, stop the previous chrono and start a new one.
2835 */
2836 if (type > tp->chrono_type)
2837 tcp_chrono_set(tp, type);
2838 }
2839
tcp_chrono_stop(struct sock * sk,const enum tcp_chrono type)2840 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2841 {
2842 struct tcp_sock *tp = tcp_sk(sk);
2843
2844
2845 /* There are multiple conditions worthy of tracking in a
2846 * chronograph, so that the highest priority enum takes
2847 * precedence over the other conditions (see tcp_chrono_start).
2848 * If a condition stops, we only stop chrono tracking if
2849 * it's the "most interesting" or current chrono we are
2850 * tracking and starts busy chrono if we have pending data.
2851 */
2852 if (tcp_rtx_and_write_queues_empty(sk))
2853 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2854 else if (type == tp->chrono_type)
2855 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2856 }
2857
2858 /* First skb in the write queue is smaller than ideal packet size.
2859 * Check if we can move payload from the second skb in the queue.
2860 */
tcp_grow_skb(struct sock * sk,struct sk_buff * skb,int amount)2861 static void tcp_grow_skb(struct sock *sk, struct sk_buff *skb, int amount)
2862 {
2863 struct sk_buff *next_skb = skb->next;
2864 unsigned int nlen;
2865
2866 if (tcp_skb_is_last(sk, skb))
2867 return;
2868
2869 if (!tcp_skb_can_collapse(skb, next_skb))
2870 return;
2871
2872 nlen = min_t(u32, amount, next_skb->len);
2873 if (!nlen || !skb_shift(skb, next_skb, nlen))
2874 return;
2875
2876 TCP_SKB_CB(skb)->end_seq += nlen;
2877 TCP_SKB_CB(next_skb)->seq += nlen;
2878
2879 if (!next_skb->len) {
2880 /* In case FIN is set, we need to update end_seq */
2881 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2882
2883 tcp_eat_one_skb(sk, skb, next_skb);
2884 }
2885 }
2886
2887 /* This routine writes packets to the network. It advances the
2888 * send_head. This happens as incoming acks open up the remote
2889 * window for us.
2890 *
2891 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2892 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2893 * account rare use of URG, this is not a big flaw.
2894 *
2895 * Send at most one packet when push_one > 0. Temporarily ignore
2896 * cwnd limit to force at most one packet out when push_one == 2.
2897
2898 * Returns true, if no segments are in flight and we have queued segments,
2899 * but cannot send anything now because of SWS or another problem.
2900 */
tcp_write_xmit(struct sock * sk,unsigned int mss_now,int nonagle,int push_one,gfp_t gfp)2901 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2902 int push_one, gfp_t gfp)
2903 {
2904 struct tcp_sock *tp = tcp_sk(sk);
2905 struct sk_buff *skb;
2906 unsigned int tso_segs, sent_pkts;
2907 u32 cwnd_quota, max_segs;
2908 int result;
2909 bool is_cwnd_limited = false, is_rwnd_limited = false;
2910
2911 sent_pkts = 0;
2912
2913 tcp_mstamp_refresh(tp);
2914
2915 /* AccECN option beacon depends on mstamp, it may change mss */
2916 if (tcp_ecn_mode_accecn(tp) && tcp_accecn_option_beacon_check(sk))
2917 mss_now = tcp_current_mss(sk);
2918
2919 if (!push_one) {
2920 /* Do MTU probing. */
2921 result = tcp_mtu_probe(sk);
2922 if (!result) {
2923 return false;
2924 } else if (result > 0) {
2925 sent_pkts = 1;
2926 }
2927 }
2928
2929 max_segs = tcp_tso_segs(sk, mss_now);
2930 while ((skb = tcp_send_head(sk))) {
2931 unsigned int limit;
2932 int missing_bytes;
2933
2934 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2935 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2936 tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2937 skb_set_delivery_time(skb, tp->tcp_wstamp_ns, SKB_CLOCK_MONOTONIC);
2938 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2939 tcp_init_tso_segs(skb, mss_now);
2940 goto repair; /* Skip network transmission */
2941 }
2942
2943 if (tcp_pacing_check(sk))
2944 break;
2945
2946 cwnd_quota = tcp_cwnd_test(tp);
2947 if (!cwnd_quota) {
2948 if (push_one == 2)
2949 /* Force out a loss probe pkt. */
2950 cwnd_quota = 1;
2951 else
2952 break;
2953 }
2954 cwnd_quota = min(cwnd_quota, max_segs);
2955 missing_bytes = cwnd_quota * mss_now - skb->len;
2956 if (missing_bytes > 0)
2957 tcp_grow_skb(sk, skb, missing_bytes);
2958
2959 tso_segs = tcp_set_skb_tso_segs(skb, mss_now);
2960
2961 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2962 is_rwnd_limited = true;
2963 break;
2964 }
2965
2966 if (tso_segs == 1) {
2967 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2968 (tcp_skb_is_last(sk, skb) ?
2969 nonagle : TCP_NAGLE_PUSH))))
2970 break;
2971 } else {
2972 if (!push_one &&
2973 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2974 &is_rwnd_limited, max_segs))
2975 break;
2976 }
2977
2978 limit = mss_now;
2979 if (tso_segs > 1 && !tcp_urg_mode(tp))
2980 limit = tcp_mss_split_point(sk, skb, mss_now,
2981 cwnd_quota,
2982 nonagle);
2983
2984 if (skb->len > limit &&
2985 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2986 break;
2987
2988 if (tcp_small_queue_check(sk, skb, 0))
2989 break;
2990
2991 /* Argh, we hit an empty skb(), presumably a thread
2992 * is sleeping in sendmsg()/sk_stream_wait_memory().
2993 * We do not want to send a pure-ack packet and have
2994 * a strange looking rtx queue with empty packet(s).
2995 */
2996 if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
2997 break;
2998
2999 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
3000 break;
3001
3002 repair:
3003 /* Advance the send_head. This one is sent out.
3004 * This call will increment packets_out.
3005 */
3006 tcp_event_new_data_sent(sk, skb);
3007
3008 tcp_minshall_update(tp, mss_now, skb);
3009 sent_pkts += tcp_skb_pcount(skb);
3010
3011 if (push_one)
3012 break;
3013 }
3014
3015 if (is_rwnd_limited)
3016 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
3017 else
3018 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
3019
3020 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tcp_snd_cwnd(tp));
3021 if (likely(sent_pkts || is_cwnd_limited))
3022 tcp_cwnd_validate(sk, is_cwnd_limited);
3023
3024 if (likely(sent_pkts)) {
3025 if (tcp_in_cwnd_reduction(sk))
3026 tp->prr_out += sent_pkts;
3027
3028 /* Send one loss probe per tail loss episode. */
3029 if (push_one != 2)
3030 tcp_schedule_loss_probe(sk, false);
3031 return false;
3032 }
3033 return !tp->packets_out && !tcp_write_queue_empty(sk);
3034 }
3035
tcp_schedule_loss_probe(struct sock * sk,bool advancing_rto)3036 bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
3037 {
3038 struct inet_connection_sock *icsk = inet_csk(sk);
3039 struct tcp_sock *tp = tcp_sk(sk);
3040 u32 timeout, timeout_us, rto_delta_us;
3041 int early_retrans;
3042
3043 /* Don't do any loss probe on a Fast Open connection before 3WHS
3044 * finishes.
3045 */
3046 if (rcu_access_pointer(tp->fastopen_rsk))
3047 return false;
3048
3049 early_retrans = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_early_retrans);
3050 /* Schedule a loss probe in 2*RTT for SACK capable connections
3051 * not in loss recovery, that are either limited by cwnd or application.
3052 */
3053 if ((early_retrans != 3 && early_retrans != 4) ||
3054 !tp->packets_out || !tcp_is_sack(tp) ||
3055 (icsk->icsk_ca_state != TCP_CA_Open &&
3056 icsk->icsk_ca_state != TCP_CA_CWR))
3057 return false;
3058
3059 /* Probe timeout is 2*rtt. Add minimum RTO to account
3060 * for delayed ack when there's one outstanding packet. If no RTT
3061 * sample is available then probe after TCP_TIMEOUT_INIT.
3062 */
3063 if (tp->srtt_us) {
3064 timeout_us = tp->srtt_us >> 2;
3065 if (tp->packets_out == 1)
3066 timeout_us += tcp_rto_min_us(sk);
3067 else
3068 timeout_us += TCP_TIMEOUT_MIN_US;
3069 timeout = usecs_to_jiffies(timeout_us);
3070 } else {
3071 timeout = TCP_TIMEOUT_INIT;
3072 }
3073
3074 /* If the RTO formula yields an earlier time, then use that time. */
3075 rto_delta_us = advancing_rto ?
3076 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
3077 tcp_rto_delta_us(sk); /* How far in future is RTO? */
3078 if (rto_delta_us > 0)
3079 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
3080
3081 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, true);
3082 return true;
3083 }
3084
3085 /* Thanks to skb fast clones, we can detect if a prior transmit of
3086 * a packet is still in a qdisc or driver queue.
3087 * In this case, there is very little point doing a retransmit !
3088 */
skb_still_in_host_queue(struct sock * sk,const struct sk_buff * skb)3089 static bool skb_still_in_host_queue(struct sock *sk,
3090 const struct sk_buff *skb)
3091 {
3092 if (unlikely(skb_fclone_busy(sk, skb))) {
3093 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
3094 smp_mb__after_atomic();
3095 if (skb_fclone_busy(sk, skb)) {
3096 NET_INC_STATS(sock_net(sk),
3097 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
3098 return true;
3099 }
3100 }
3101 return false;
3102 }
3103
3104 /* When probe timeout (PTO) fires, try send a new segment if possible, else
3105 * retransmit the last segment.
3106 */
tcp_send_loss_probe(struct sock * sk)3107 void tcp_send_loss_probe(struct sock *sk)
3108 {
3109 struct tcp_sock *tp = tcp_sk(sk);
3110 struct sk_buff *skb;
3111 int pcount;
3112 int mss = tcp_current_mss(sk);
3113
3114 /* At most one outstanding TLP */
3115 if (tp->tlp_high_seq)
3116 goto rearm_timer;
3117
3118 tp->tlp_retrans = 0;
3119 skb = tcp_send_head(sk);
3120 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
3121 pcount = tp->packets_out;
3122 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
3123 if (tp->packets_out > pcount)
3124 goto probe_sent;
3125 goto rearm_timer;
3126 }
3127 skb = skb_rb_last(&sk->tcp_rtx_queue);
3128 if (unlikely(!skb)) {
3129 tcp_warn_once(sk, tp->packets_out, "invalid inflight: ");
3130 smp_store_release(&inet_csk(sk)->icsk_pending, 0);
3131 return;
3132 }
3133
3134 if (skb_still_in_host_queue(sk, skb))
3135 goto rearm_timer;
3136
3137 pcount = tcp_skb_pcount(skb);
3138 if (WARN_ON(!pcount))
3139 goto rearm_timer;
3140
3141 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
3142 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
3143 (pcount - 1) * mss, mss,
3144 GFP_ATOMIC)))
3145 goto rearm_timer;
3146 skb = skb_rb_next(skb);
3147 }
3148
3149 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
3150 goto rearm_timer;
3151
3152 if (__tcp_retransmit_skb(sk, skb, 1))
3153 goto rearm_timer;
3154
3155 tp->tlp_retrans = 1;
3156
3157 probe_sent:
3158 /* Record snd_nxt for loss detection. */
3159 tp->tlp_high_seq = tp->snd_nxt;
3160
3161 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
3162 /* Reset s.t. tcp_rearm_rto will restart timer from now */
3163 smp_store_release(&inet_csk(sk)->icsk_pending, 0);
3164 rearm_timer:
3165 tcp_rearm_rto(sk);
3166 }
3167
3168 /* Push out any pending frames which were held back due to
3169 * TCP_CORK or attempt at coalescing tiny packets.
3170 * The socket must be locked by the caller.
3171 */
__tcp_push_pending_frames(struct sock * sk,unsigned int cur_mss,int nonagle)3172 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
3173 int nonagle)
3174 {
3175 /* If we are closed, the bytes will have to remain here.
3176 * In time closedown will finish, we empty the write queue and
3177 * all will be happy.
3178 */
3179 if (unlikely(sk->sk_state == TCP_CLOSE))
3180 return;
3181
3182 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
3183 sk_gfp_mask(sk, GFP_ATOMIC)))
3184 tcp_check_probe_timer(sk);
3185 }
3186
3187 /* Send _single_ skb sitting at the send head. This function requires
3188 * true push pending frames to setup probe timer etc.
3189 */
tcp_push_one(struct sock * sk,unsigned int mss_now)3190 void tcp_push_one(struct sock *sk, unsigned int mss_now)
3191 {
3192 struct sk_buff *skb = tcp_send_head(sk);
3193
3194 BUG_ON(!skb || skb->len < mss_now);
3195
3196 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
3197 }
3198
3199 /* This function returns the amount that we can raise the
3200 * usable window based on the following constraints
3201 *
3202 * 1. The window can never be shrunk once it is offered (RFC 793)
3203 * 2. We limit memory per socket
3204 *
3205 * RFC 1122:
3206 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
3207 * RECV.NEXT + RCV.WIN fixed until:
3208 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
3209 *
3210 * i.e. don't raise the right edge of the window until you can raise
3211 * it at least MSS bytes.
3212 *
3213 * Unfortunately, the recommended algorithm breaks header prediction,
3214 * since header prediction assumes th->window stays fixed.
3215 *
3216 * Strictly speaking, keeping th->window fixed violates the receiver
3217 * side SWS prevention criteria. The problem is that under this rule
3218 * a stream of single byte packets will cause the right side of the
3219 * window to always advance by a single byte.
3220 *
3221 * Of course, if the sender implements sender side SWS prevention
3222 * then this will not be a problem.
3223 *
3224 * BSD seems to make the following compromise:
3225 *
3226 * If the free space is less than the 1/4 of the maximum
3227 * space available and the free space is less than 1/2 mss,
3228 * then set the window to 0.
3229 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
3230 * Otherwise, just prevent the window from shrinking
3231 * and from being larger than the largest representable value.
3232 *
3233 * This prevents incremental opening of the window in the regime
3234 * where TCP is limited by the speed of the reader side taking
3235 * data out of the TCP receive queue. It does nothing about
3236 * those cases where the window is constrained on the sender side
3237 * because the pipeline is full.
3238 *
3239 * BSD also seems to "accidentally" limit itself to windows that are a
3240 * multiple of MSS, at least until the free space gets quite small.
3241 * This would appear to be a side effect of the mbuf implementation.
3242 * Combining these two algorithms results in the observed behavior
3243 * of having a fixed window size at almost all times.
3244 *
3245 * Below we obtain similar behavior by forcing the offered window to
3246 * a multiple of the mss when it is feasible to do so.
3247 *
3248 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
3249 * Regular options like TIMESTAMP are taken into account.
3250 */
__tcp_select_window(struct sock * sk)3251 u32 __tcp_select_window(struct sock *sk)
3252 {
3253 struct inet_connection_sock *icsk = inet_csk(sk);
3254 struct tcp_sock *tp = tcp_sk(sk);
3255 struct net *net = sock_net(sk);
3256 /* MSS for the peer's data. Previous versions used mss_clamp
3257 * here. I don't know if the value based on our guesses
3258 * of peer's MSS is better for the performance. It's more correct
3259 * but may be worse for the performance because of rcv_mss
3260 * fluctuations. --SAW 1998/11/1
3261 */
3262 int mss = icsk->icsk_ack.rcv_mss;
3263 int free_space = tcp_space(sk);
3264 int allowed_space = tcp_full_space(sk);
3265 int full_space, window;
3266
3267 if (sk_is_mptcp(sk))
3268 mptcp_space(sk, &free_space, &allowed_space);
3269
3270 full_space = min_t(int, tp->window_clamp, allowed_space);
3271
3272 if (unlikely(mss > full_space)) {
3273 mss = full_space;
3274 if (mss <= 0)
3275 return 0;
3276 }
3277
3278 /* Only allow window shrink if the sysctl is enabled and we have
3279 * a non-zero scaling factor in effect.
3280 */
3281 if (READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) && tp->rx_opt.rcv_wscale)
3282 goto shrink_window_allowed;
3283
3284 /* do not allow window to shrink */
3285
3286 if (free_space < (full_space >> 1)) {
3287 icsk->icsk_ack.quick = 0;
3288
3289 if (tcp_under_memory_pressure(sk))
3290 tcp_adjust_rcv_ssthresh(sk);
3291
3292 /* free_space might become our new window, make sure we don't
3293 * increase it due to wscale.
3294 */
3295 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
3296
3297 /* if free space is less than mss estimate, or is below 1/16th
3298 * of the maximum allowed, try to move to zero-window, else
3299 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
3300 * new incoming data is dropped due to memory limits.
3301 * With large window, mss test triggers way too late in order
3302 * to announce zero window in time before rmem limit kicks in.
3303 */
3304 if (free_space < (allowed_space >> 4) || free_space < mss)
3305 return 0;
3306 }
3307
3308 if (free_space > tp->rcv_ssthresh)
3309 free_space = tp->rcv_ssthresh;
3310
3311 /* Don't do rounding if we are using window scaling, since the
3312 * scaled window will not line up with the MSS boundary anyway.
3313 */
3314 if (tp->rx_opt.rcv_wscale) {
3315 window = free_space;
3316
3317 /* Advertise enough space so that it won't get scaled away.
3318 * Import case: prevent zero window announcement if
3319 * 1<<rcv_wscale > mss.
3320 */
3321 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
3322 } else {
3323 window = tp->rcv_wnd;
3324 /* Get the largest window that is a nice multiple of mss.
3325 * Window clamp already applied above.
3326 * If our current window offering is within 1 mss of the
3327 * free space we just keep it. This prevents the divide
3328 * and multiply from happening most of the time.
3329 * We also don't do any window rounding when the free space
3330 * is too small.
3331 */
3332 if (window <= free_space - mss || window > free_space)
3333 window = rounddown(free_space, mss);
3334 else if (mss == full_space &&
3335 free_space > window + (full_space >> 1))
3336 window = free_space;
3337 }
3338
3339 return window;
3340
3341 shrink_window_allowed:
3342 /* new window should always be an exact multiple of scaling factor */
3343 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
3344
3345 if (free_space < (full_space >> 1)) {
3346 icsk->icsk_ack.quick = 0;
3347
3348 if (tcp_under_memory_pressure(sk))
3349 tcp_adjust_rcv_ssthresh(sk);
3350
3351 /* if free space is too low, return a zero window */
3352 if (free_space < (allowed_space >> 4) || free_space < mss ||
3353 free_space < (1 << tp->rx_opt.rcv_wscale))
3354 return 0;
3355 }
3356
3357 if (free_space > tp->rcv_ssthresh) {
3358 free_space = tp->rcv_ssthresh;
3359 /* new window should always be an exact multiple of scaling factor
3360 *
3361 * For this case, we ALIGN "up" (increase free_space) because
3362 * we know free_space is not zero here, it has been reduced from
3363 * the memory-based limit, and rcv_ssthresh is not a hard limit
3364 * (unlike sk_rcvbuf).
3365 */
3366 free_space = ALIGN(free_space, (1 << tp->rx_opt.rcv_wscale));
3367 }
3368
3369 return free_space;
3370 }
3371
tcp_skb_collapse_tstamp(struct sk_buff * skb,const struct sk_buff * next_skb)3372 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
3373 const struct sk_buff *next_skb)
3374 {
3375 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
3376 const struct skb_shared_info *next_shinfo =
3377 skb_shinfo(next_skb);
3378 struct skb_shared_info *shinfo = skb_shinfo(skb);
3379
3380 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
3381 shinfo->tskey = next_shinfo->tskey;
3382 TCP_SKB_CB(skb)->txstamp_ack |=
3383 TCP_SKB_CB(next_skb)->txstamp_ack;
3384 }
3385 }
3386
3387 /* Collapses two adjacent SKB's during retransmission. */
tcp_collapse_retrans(struct sock * sk,struct sk_buff * skb)3388 static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
3389 {
3390 struct tcp_sock *tp = tcp_sk(sk);
3391 struct sk_buff *next_skb = skb_rb_next(skb);
3392 int next_skb_size;
3393
3394 next_skb_size = next_skb->len;
3395
3396 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
3397
3398 if (next_skb_size && !tcp_skb_shift(skb, next_skb, 1, next_skb_size))
3399 return false;
3400
3401 tcp_highest_sack_replace(sk, next_skb, skb);
3402
3403 /* Update sequence range on original skb. */
3404 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
3405
3406 /* Merge over control information. This moves PSH/FIN etc. over */
3407 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
3408
3409 /* All done, get rid of second SKB and account for it so
3410 * packet counting does not break.
3411 */
3412 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
3413 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
3414
3415 /* changed transmit queue under us so clear hints */
3416 if (next_skb == tp->retransmit_skb_hint)
3417 tp->retransmit_skb_hint = skb;
3418
3419 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
3420
3421 tcp_skb_collapse_tstamp(skb, next_skb);
3422
3423 tcp_rtx_queue_unlink_and_free(next_skb, sk);
3424 return true;
3425 }
3426
3427 /* Check if coalescing SKBs is legal. */
tcp_can_collapse(const struct sock * sk,const struct sk_buff * skb)3428 static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
3429 {
3430 if (tcp_skb_pcount(skb) > 1)
3431 return false;
3432 if (skb_cloned(skb))
3433 return false;
3434 if (!skb_frags_readable(skb))
3435 return false;
3436 /* Some heuristics for collapsing over SACK'd could be invented */
3437 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
3438 return false;
3439
3440 return true;
3441 }
3442
3443 /* Collapse packets in the retransmit queue to make to create
3444 * less packets on the wire. This is only done on retransmission.
3445 */
tcp_retrans_try_collapse(struct sock * sk,struct sk_buff * to,int space)3446 static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
3447 int space)
3448 {
3449 struct tcp_sock *tp = tcp_sk(sk);
3450 struct sk_buff *skb = to, *tmp;
3451 bool first = true;
3452
3453 if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse))
3454 return;
3455 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3456 return;
3457
3458 skb_rbtree_walk_from_safe(skb, tmp) {
3459 if (!tcp_can_collapse(sk, skb))
3460 break;
3461
3462 if (!tcp_skb_can_collapse(to, skb))
3463 break;
3464
3465 space -= skb->len;
3466
3467 if (first) {
3468 first = false;
3469 continue;
3470 }
3471
3472 if (space < 0)
3473 break;
3474
3475 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
3476 break;
3477
3478 if (!tcp_collapse_retrans(sk, to))
3479 break;
3480 }
3481 }
3482
3483 /* This retransmits one SKB. Policy decisions and retransmit queue
3484 * state updates are done by the caller. Returns non-zero if an
3485 * error occurred which prevented the send.
3486 */
__tcp_retransmit_skb(struct sock * sk,struct sk_buff * skb,int segs)3487 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3488 {
3489 struct inet_connection_sock *icsk = inet_csk(sk);
3490 struct tcp_sock *tp = tcp_sk(sk);
3491 unsigned int cur_mss;
3492 int diff, len, err;
3493 int avail_wnd;
3494
3495 /* Inconclusive MTU probe */
3496 if (icsk->icsk_mtup.probe_size)
3497 icsk->icsk_mtup.probe_size = 0;
3498
3499 if (skb_still_in_host_queue(sk, skb)) {
3500 err = -EBUSY;
3501 goto out;
3502 }
3503
3504 start:
3505 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
3506 if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3507 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
3508 TCP_SKB_CB(skb)->seq++;
3509 goto start;
3510 }
3511 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
3512 WARN_ON_ONCE(1);
3513 err = -EINVAL;
3514 goto out;
3515 }
3516 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) {
3517 err = -ENOMEM;
3518 goto out;
3519 }
3520 }
3521
3522 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) {
3523 err = -EHOSTUNREACH; /* Routing failure or similar. */
3524 goto out;
3525 }
3526
3527 cur_mss = tcp_current_mss(sk);
3528 avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3529
3530 /* If receiver has shrunk his window, and skb is out of
3531 * new window, do not retransmit it. The exception is the
3532 * case, when window is shrunk to zero. In this case
3533 * our retransmit of one segment serves as a zero window probe.
3534 */
3535 if (avail_wnd <= 0) {
3536 if (TCP_SKB_CB(skb)->seq != tp->snd_una) {
3537 err = -EAGAIN;
3538 goto out;
3539 }
3540 avail_wnd = cur_mss;
3541 }
3542
3543 len = cur_mss * segs;
3544 if (len > avail_wnd) {
3545 len = rounddown(avail_wnd, cur_mss);
3546 if (!len)
3547 len = avail_wnd;
3548 }
3549 if (skb->len > len) {
3550 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
3551 cur_mss, GFP_ATOMIC)) {
3552 err = -ENOMEM; /* We'll try again later. */
3553 goto out;
3554 }
3555 } else {
3556 if (skb_unclone_keeptruesize(skb, GFP_ATOMIC)) {
3557 err = -ENOMEM;
3558 goto out;
3559 }
3560
3561 diff = tcp_skb_pcount(skb);
3562 tcp_set_skb_tso_segs(skb, cur_mss);
3563 diff -= tcp_skb_pcount(skb);
3564 if (diff)
3565 tcp_adjust_pcount(sk, skb, diff);
3566 avail_wnd = min_t(int, avail_wnd, cur_mss);
3567 if (skb->len < avail_wnd)
3568 tcp_retrans_try_collapse(sk, skb, avail_wnd);
3569 }
3570
3571 /* RFC3168, section 6.1.1.1. ECN fallback
3572 * As AccECN uses the same SYN flags (+ AE), this check covers both
3573 * cases.
3574 */
3575 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
3576 tcp_ecn_clear_syn(sk, skb);
3577
3578 /* Update global and local TCP statistics. */
3579 segs = tcp_skb_pcount(skb);
3580 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
3581 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3582 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3583 tp->total_retrans += segs;
3584 tp->bytes_retrans += skb->len;
3585
3586 /* make sure skb->data is aligned on arches that require it
3587 * and check if ack-trimming & collapsing extended the headroom
3588 * beyond what csum_start can cover.
3589 */
3590 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
3591 skb_headroom(skb) >= 0xFFFF)) {
3592 struct sk_buff *nskb;
3593
3594 tcp_skb_tsorted_save(skb) {
3595 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
3596 if (nskb) {
3597 nskb->dev = NULL;
3598 err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
3599 } else {
3600 err = -ENOBUFS;
3601 }
3602 } tcp_skb_tsorted_restore(skb);
3603
3604 if (!err) {
3605 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
3606 tcp_rate_skb_sent(sk, skb);
3607 }
3608 } else {
3609 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3610 }
3611
3612 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
3613 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
3614 TCP_SKB_CB(skb)->seq, segs, err);
3615
3616 if (unlikely(err) && err != -EBUSY)
3617 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
3618
3619 /* To avoid taking spuriously low RTT samples based on a timestamp
3620 * for a transmit that never happened, always mark EVER_RETRANS
3621 */
3622 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
3623
3624 out:
3625 trace_tcp_retransmit_skb(sk, skb, err);
3626 return err;
3627 }
3628
tcp_retransmit_skb(struct sock * sk,struct sk_buff * skb,int segs)3629 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3630 {
3631 struct tcp_sock *tp = tcp_sk(sk);
3632 int err = __tcp_retransmit_skb(sk, skb, segs);
3633
3634 if (err == 0) {
3635 #if FASTRETRANS_DEBUG > 0
3636 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3637 net_dbg_ratelimited("retrans_out leaked\n");
3638 }
3639 #endif
3640 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3641 tp->retrans_out += tcp_skb_pcount(skb);
3642 }
3643
3644 /* Save stamp of the first (attempted) retransmit. */
3645 if (!tp->retrans_stamp)
3646 tp->retrans_stamp = tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb);
3647
3648 if (tp->undo_retrans < 0)
3649 tp->undo_retrans = 0;
3650 tp->undo_retrans += tcp_skb_pcount(skb);
3651 return err;
3652 }
3653
3654 /* This gets called after a retransmit timeout, and the initially
3655 * retransmitted data is acknowledged. It tries to continue
3656 * resending the rest of the retransmit queue, until either
3657 * we've sent it all or the congestion window limit is reached.
3658 */
tcp_xmit_retransmit_queue(struct sock * sk)3659 void tcp_xmit_retransmit_queue(struct sock *sk)
3660 {
3661 const struct inet_connection_sock *icsk = inet_csk(sk);
3662 struct sk_buff *skb, *rtx_head, *hole = NULL;
3663 struct tcp_sock *tp = tcp_sk(sk);
3664 bool rearm_timer = false;
3665 u32 max_segs;
3666 int mib_idx;
3667
3668 if (!tp->packets_out)
3669 return;
3670
3671 rtx_head = tcp_rtx_queue_head(sk);
3672 skb = tp->retransmit_skb_hint ?: rtx_head;
3673 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3674 skb_rbtree_walk_from(skb) {
3675 __u8 sacked;
3676 int segs;
3677
3678 if (tcp_pacing_check(sk))
3679 break;
3680
3681 /* we could do better than to assign each time */
3682 if (!hole)
3683 tp->retransmit_skb_hint = skb;
3684
3685 segs = tcp_snd_cwnd(tp) - tcp_packets_in_flight(tp);
3686 if (segs <= 0)
3687 break;
3688 sacked = TCP_SKB_CB(skb)->sacked;
3689 /* In case tcp_shift_skb_data() have aggregated large skbs,
3690 * we need to make sure not sending too bigs TSO packets
3691 */
3692 segs = min_t(int, segs, max_segs);
3693
3694 if (tp->retrans_out >= tp->lost_out) {
3695 break;
3696 } else if (!(sacked & TCPCB_LOST)) {
3697 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3698 hole = skb;
3699 continue;
3700
3701 } else {
3702 if (icsk->icsk_ca_state != TCP_CA_Loss)
3703 mib_idx = LINUX_MIB_TCPFASTRETRANS;
3704 else
3705 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3706 }
3707
3708 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3709 continue;
3710
3711 if (tcp_small_queue_check(sk, skb, 1))
3712 break;
3713
3714 if (tcp_retransmit_skb(sk, skb, segs))
3715 break;
3716
3717 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3718
3719 if (tcp_in_cwnd_reduction(sk))
3720 tp->prr_out += tcp_skb_pcount(skb);
3721
3722 if (skb == rtx_head &&
3723 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3724 rearm_timer = true;
3725
3726 }
3727 if (rearm_timer)
3728 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3729 inet_csk(sk)->icsk_rto, true);
3730 }
3731
3732 /* We allow to exceed memory limits for FIN packets to expedite
3733 * connection tear down and (memory) recovery.
3734 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3735 * or even be forced to close flow without any FIN.
3736 * In general, we want to allow one skb per socket to avoid hangs
3737 * with edge trigger epoll()
3738 */
sk_forced_mem_schedule(struct sock * sk,int size)3739 void sk_forced_mem_schedule(struct sock *sk, int size)
3740 {
3741 int delta, amt;
3742
3743 delta = size - sk->sk_forward_alloc;
3744 if (delta <= 0)
3745 return;
3746 amt = sk_mem_pages(delta);
3747 sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
3748 sk_memory_allocated_add(sk, amt);
3749
3750 if (mem_cgroup_sk_enabled(sk))
3751 mem_cgroup_sk_charge(sk, amt, gfp_memcg_charge() | __GFP_NOFAIL);
3752 }
3753
3754 /* Send a FIN. The caller locks the socket for us.
3755 * We should try to send a FIN packet really hard, but eventually give up.
3756 */
tcp_send_fin(struct sock * sk)3757 void tcp_send_fin(struct sock *sk)
3758 {
3759 struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk);
3760 struct tcp_sock *tp = tcp_sk(sk);
3761
3762 /* Optimization, tack on the FIN if we have one skb in write queue and
3763 * this skb was not yet sent, or we are under memory pressure.
3764 * Note: in the latter case, FIN packet will be sent after a timeout,
3765 * as TCP stack thinks it has already been transmitted.
3766 */
3767 tskb = tail;
3768 if (!tskb && tcp_under_memory_pressure(sk))
3769 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3770
3771 if (tskb) {
3772 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3773 TCP_SKB_CB(tskb)->end_seq++;
3774 tp->write_seq++;
3775 if (!tail) {
3776 /* This means tskb was already sent.
3777 * Pretend we included the FIN on previous transmit.
3778 * We need to set tp->snd_nxt to the value it would have
3779 * if FIN had been sent. This is because retransmit path
3780 * does not change tp->snd_nxt.
3781 */
3782 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3783 return;
3784 }
3785 } else {
3786 skb = alloc_skb_fclone(MAX_TCP_HEADER,
3787 sk_gfp_mask(sk, GFP_ATOMIC |
3788 __GFP_NOWARN));
3789 if (unlikely(!skb))
3790 return;
3791
3792 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3793 skb_reserve(skb, MAX_TCP_HEADER);
3794 sk_forced_mem_schedule(sk, skb->truesize);
3795 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3796 tcp_init_nondata_skb(skb, sk, tp->write_seq,
3797 TCPHDR_ACK | TCPHDR_FIN);
3798 tcp_queue_skb(sk, skb);
3799 }
3800 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3801 }
3802
3803 /* We get here when a process closes a file descriptor (either due to
3804 * an explicit close() or as a byproduct of exit()'ing) and there
3805 * was unread data in the receive queue. This behavior is recommended
3806 * by RFC 2525, section 2.17. -DaveM
3807 */
tcp_send_active_reset(struct sock * sk,gfp_t priority,enum sk_rst_reason reason)3808 void tcp_send_active_reset(struct sock *sk, gfp_t priority,
3809 enum sk_rst_reason reason)
3810 {
3811 struct sk_buff *skb;
3812
3813 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3814
3815 /* NOTE: No TCP options attached and we never retransmit this. */
3816 skb = alloc_skb(MAX_TCP_HEADER, priority);
3817 if (!skb) {
3818 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3819 return;
3820 }
3821
3822 /* Reserve space for headers and prepare control bits. */
3823 skb_reserve(skb, MAX_TCP_HEADER);
3824 tcp_init_nondata_skb(skb, sk, tcp_acceptable_seq(sk),
3825 TCPHDR_ACK | TCPHDR_RST);
3826 tcp_mstamp_refresh(tcp_sk(sk));
3827 /* Send it off. */
3828 if (tcp_transmit_skb(sk, skb, 0, priority))
3829 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3830
3831 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3832 * skb here is different to the troublesome skb, so use NULL
3833 */
3834 trace_tcp_send_reset(sk, NULL, reason);
3835 }
3836
3837 /* Send a crossed SYN-ACK during socket establishment.
3838 * WARNING: This routine must only be called when we have already sent
3839 * a SYN packet that crossed the incoming SYN that caused this routine
3840 * to get called. If this assumption fails then the initial rcv_wnd
3841 * and rcv_wscale values will not be correct.
3842 */
tcp_send_synack(struct sock * sk)3843 int tcp_send_synack(struct sock *sk)
3844 {
3845 struct sk_buff *skb;
3846
3847 skb = tcp_rtx_queue_head(sk);
3848 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3849 pr_err("%s: wrong queue state\n", __func__);
3850 return -EFAULT;
3851 }
3852 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3853 if (skb_cloned(skb)) {
3854 struct sk_buff *nskb;
3855
3856 tcp_skb_tsorted_save(skb) {
3857 nskb = skb_copy(skb, GFP_ATOMIC);
3858 } tcp_skb_tsorted_restore(skb);
3859 if (!nskb)
3860 return -ENOMEM;
3861 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3862 tcp_highest_sack_replace(sk, skb, nskb);
3863 tcp_rtx_queue_unlink_and_free(skb, sk);
3864 __skb_header_release(nskb);
3865 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3866 sk_wmem_queued_add(sk, nskb->truesize);
3867 sk_mem_charge(sk, nskb->truesize);
3868 skb = nskb;
3869 }
3870
3871 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3872 tcp_ecn_send_synack(sk, skb);
3873 }
3874 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3875 }
3876
3877 /**
3878 * tcp_make_synack - Allocate one skb and build a SYNACK packet.
3879 * @sk: listener socket
3880 * @dst: dst entry attached to the SYNACK. It is consumed and caller
3881 * should not use it again.
3882 * @req: request_sock pointer
3883 * @foc: cookie for tcp fast open
3884 * @synack_type: Type of synack to prepare
3885 * @syn_skb: SYN packet just received. It could be NULL for rtx case.
3886 */
tcp_make_synack(const struct sock * sk,struct dst_entry * dst,struct request_sock * req,struct tcp_fastopen_cookie * foc,enum tcp_synack_type synack_type,struct sk_buff * syn_skb)3887 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3888 struct request_sock *req,
3889 struct tcp_fastopen_cookie *foc,
3890 enum tcp_synack_type synack_type,
3891 struct sk_buff *syn_skb)
3892 {
3893 struct inet_request_sock *ireq = inet_rsk(req);
3894 const struct tcp_sock *tp = tcp_sk(sk);
3895 struct tcp_out_options opts;
3896 struct tcp_key key = {};
3897 struct sk_buff *skb;
3898 int tcp_header_size;
3899 struct tcphdr *th;
3900 int mss;
3901 u64 now;
3902
3903 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3904 if (unlikely(!skb)) {
3905 dst_release(dst);
3906 return NULL;
3907 }
3908 /* Reserve space for headers. */
3909 skb_reserve(skb, MAX_TCP_HEADER);
3910
3911 switch (synack_type) {
3912 case TCP_SYNACK_NORMAL:
3913 skb_set_owner_edemux(skb, req_to_sk(req));
3914 break;
3915 case TCP_SYNACK_COOKIE:
3916 /* Under synflood, we do not attach skb to a socket,
3917 * to avoid false sharing.
3918 */
3919 break;
3920 case TCP_SYNACK_FASTOPEN:
3921 /* sk is a const pointer, because we want to express multiple
3922 * cpu might call us concurrently.
3923 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3924 */
3925 skb_set_owner_w(skb, (struct sock *)sk);
3926 break;
3927 }
3928 skb_dst_set(skb, dst);
3929
3930 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3931
3932 memset(&opts, 0, sizeof(opts));
3933 now = tcp_clock_ns();
3934 #ifdef CONFIG_SYN_COOKIES
3935 if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))
3936 skb_set_delivery_time(skb, cookie_init_timestamp(req, now),
3937 SKB_CLOCK_MONOTONIC);
3938 else
3939 #endif
3940 {
3941 skb_set_delivery_time(skb, now, SKB_CLOCK_MONOTONIC);
3942 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3943 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3944 }
3945
3946 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3947 rcu_read_lock();
3948 #endif
3949 if (tcp_rsk_used_ao(req)) {
3950 #ifdef CONFIG_TCP_AO
3951 struct tcp_ao_key *ao_key = NULL;
3952 u8 keyid = tcp_rsk(req)->ao_keyid;
3953 u8 rnext = tcp_rsk(req)->ao_rcv_next;
3954
3955 ao_key = tcp_sk(sk)->af_specific->ao_lookup(sk, req_to_sk(req),
3956 keyid, -1);
3957 /* If there is no matching key - avoid sending anything,
3958 * especially usigned segments. It could try harder and lookup
3959 * for another peer-matching key, but the peer has requested
3960 * ao_keyid (RFC5925 RNextKeyID), so let's keep it simple here.
3961 */
3962 if (unlikely(!ao_key)) {
3963 trace_tcp_ao_synack_no_key(sk, keyid, rnext);
3964 rcu_read_unlock();
3965 kfree_skb(skb);
3966 net_warn_ratelimited("TCP-AO: the keyid %u from SYN packet is not present - not sending SYNACK\n",
3967 keyid);
3968 return NULL;
3969 }
3970 key.ao_key = ao_key;
3971 key.type = TCP_KEY_AO;
3972 #endif
3973 } else {
3974 #ifdef CONFIG_TCP_MD5SIG
3975 key.md5_key = tcp_rsk(req)->af_specific->req_md5_lookup(sk,
3976 req_to_sk(req));
3977 if (key.md5_key)
3978 key.type = TCP_KEY_MD5;
3979 #endif
3980 }
3981 skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4);
3982 /* bpf program will be interested in the tcp_flags */
3983 TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;
3984 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts,
3985 &key, foc, synack_type, syn_skb)
3986 + sizeof(*th);
3987
3988 skb_push(skb, tcp_header_size);
3989 skb_reset_transport_header(skb);
3990
3991 th = (struct tcphdr *)skb->data;
3992 memset(th, 0, sizeof(struct tcphdr));
3993 th->syn = 1;
3994 th->ack = 1;
3995 tcp_ecn_make_synack(req, th);
3996 th->source = htons(ireq->ir_num);
3997 th->dest = ireq->ir_rmt_port;
3998 skb->mark = ireq->ir_mark;
3999 skb->ip_summed = CHECKSUM_PARTIAL;
4000 th->seq = htonl(tcp_rsk(req)->snt_isn);
4001 /* XXX data is queued and acked as is. No buffer/window check */
4002 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
4003
4004 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
4005 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
4006 tcp_options_write(th, NULL, tcp_rsk(req), &opts, &key);
4007 th->doff = (tcp_header_size >> 2);
4008 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
4009
4010 /* Okay, we have all we need - do the md5 hash if needed */
4011 if (tcp_key_is_md5(&key)) {
4012 #ifdef CONFIG_TCP_MD5SIG
4013 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
4014 key.md5_key, req_to_sk(req), skb);
4015 #endif
4016 } else if (tcp_key_is_ao(&key)) {
4017 #ifdef CONFIG_TCP_AO
4018 tcp_rsk(req)->af_specific->ao_synack_hash(opts.hash_location,
4019 key.ao_key, req, skb,
4020 opts.hash_location - (u8 *)th, 0);
4021 #endif
4022 }
4023 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
4024 rcu_read_unlock();
4025 #endif
4026
4027 bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb,
4028 synack_type, &opts);
4029
4030 skb_set_delivery_time(skb, now, SKB_CLOCK_MONOTONIC);
4031 tcp_add_tx_delay(skb, tp);
4032
4033 return skb;
4034 }
4035 EXPORT_IPV6_MOD(tcp_make_synack);
4036
tcp_ca_dst_init(struct sock * sk,const struct dst_entry * dst)4037 static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
4038 {
4039 struct inet_connection_sock *icsk = inet_csk(sk);
4040 const struct tcp_congestion_ops *ca;
4041 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
4042
4043 if (ca_key == TCP_CA_UNSPEC)
4044 return;
4045
4046 rcu_read_lock();
4047 ca = tcp_ca_find_key(ca_key);
4048 if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
4049 bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
4050 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
4051 icsk->icsk_ca_ops = ca;
4052 }
4053 rcu_read_unlock();
4054 }
4055
4056 /* Do all connect socket setups that can be done AF independent. */
tcp_connect_init(struct sock * sk)4057 static void tcp_connect_init(struct sock *sk)
4058 {
4059 const struct dst_entry *dst = __sk_dst_get(sk);
4060 struct tcp_sock *tp = tcp_sk(sk);
4061 __u8 rcv_wscale;
4062 u16 user_mss;
4063 u32 rcv_wnd;
4064
4065 /* We'll fix this up when we get a response from the other end.
4066 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
4067 */
4068 tp->tcp_header_len = sizeof(struct tcphdr);
4069 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps))
4070 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
4071
4072 tcp_ao_connect_init(sk);
4073
4074 /* If user gave his TCP_MAXSEG, record it to clamp */
4075 user_mss = READ_ONCE(tp->rx_opt.user_mss);
4076 if (user_mss)
4077 tp->rx_opt.mss_clamp = user_mss;
4078 tp->max_window = 0;
4079 tcp_mtup_init(sk);
4080 tcp_sync_mss(sk, dst_mtu(dst));
4081
4082 tcp_ca_dst_init(sk, dst);
4083
4084 if (!tp->window_clamp)
4085 WRITE_ONCE(tp->window_clamp, dst_metric(dst, RTAX_WINDOW));
4086 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
4087
4088 tcp_initialize_rcv_mss(sk);
4089
4090 /* limit the window selection if the user enforce a smaller rx buffer */
4091 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
4092 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
4093 WRITE_ONCE(tp->window_clamp, tcp_full_space(sk));
4094
4095 rcv_wnd = tcp_rwnd_init_bpf(sk);
4096 if (rcv_wnd == 0)
4097 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
4098
4099 tcp_select_initial_window(sk, tcp_full_space(sk),
4100 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
4101 &tp->rcv_wnd,
4102 &tp->window_clamp,
4103 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling),
4104 &rcv_wscale,
4105 rcv_wnd);
4106
4107 tp->rx_opt.rcv_wscale = rcv_wscale;
4108 tp->rcv_ssthresh = tp->rcv_wnd;
4109
4110 WRITE_ONCE(sk->sk_err, 0);
4111 sock_reset_flag(sk, SOCK_DONE);
4112 tp->snd_wnd = 0;
4113 tcp_init_wl(tp, 0);
4114 tcp_write_queue_purge(sk);
4115 tp->snd_una = tp->write_seq;
4116 tp->snd_sml = tp->write_seq;
4117 tp->snd_up = tp->write_seq;
4118 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
4119
4120 if (likely(!tp->repair))
4121 tp->rcv_nxt = 0;
4122 else
4123 tp->rcv_tstamp = tcp_jiffies32;
4124 tp->rcv_wup = tp->rcv_nxt;
4125 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
4126
4127 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
4128 WRITE_ONCE(inet_csk(sk)->icsk_retransmits, 0);
4129 tcp_clear_retrans(tp);
4130 }
4131
tcp_connect_queue_skb(struct sock * sk,struct sk_buff * skb)4132 static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
4133 {
4134 struct tcp_sock *tp = tcp_sk(sk);
4135 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
4136
4137 tcb->end_seq += skb->len;
4138 __skb_header_release(skb);
4139 sk_wmem_queued_add(sk, skb->truesize);
4140 sk_mem_charge(sk, skb->truesize);
4141 WRITE_ONCE(tp->write_seq, tcb->end_seq);
4142 tp->packets_out += tcp_skb_pcount(skb);
4143 }
4144
4145 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
4146 * queue a data-only packet after the regular SYN, such that regular SYNs
4147 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
4148 * only the SYN sequence, the data are retransmitted in the first ACK.
4149 * If cookie is not cached or other error occurs, falls back to send a
4150 * regular SYN with Fast Open cookie request option.
4151 */
tcp_send_syn_data(struct sock * sk,struct sk_buff * syn)4152 static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
4153 {
4154 struct inet_connection_sock *icsk = inet_csk(sk);
4155 struct tcp_sock *tp = tcp_sk(sk);
4156 struct tcp_fastopen_request *fo = tp->fastopen_req;
4157 struct page_frag *pfrag = sk_page_frag(sk);
4158 struct sk_buff *syn_data;
4159 int space, err = 0;
4160
4161 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
4162 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
4163 goto fallback;
4164
4165 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
4166 * user-MSS. Reserve maximum option space for middleboxes that add
4167 * private TCP options. The cost is reduced data space in SYN :(
4168 */
4169 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
4170 /* Sync mss_cache after updating the mss_clamp */
4171 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4172
4173 space = __tcp_mtu_to_mss(sk, icsk->icsk_pmtu_cookie) -
4174 MAX_TCP_OPTION_SPACE;
4175
4176 space = min_t(size_t, space, fo->size);
4177
4178 if (space &&
4179 !skb_page_frag_refill(min_t(size_t, space, PAGE_SIZE),
4180 pfrag, sk->sk_allocation))
4181 goto fallback;
4182 syn_data = tcp_stream_alloc_skb(sk, sk->sk_allocation, false);
4183 if (!syn_data)
4184 goto fallback;
4185 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
4186 if (space) {
4187 space = min_t(size_t, space, pfrag->size - pfrag->offset);
4188 space = tcp_wmem_schedule(sk, space);
4189 }
4190 if (space) {
4191 space = copy_page_from_iter(pfrag->page, pfrag->offset,
4192 space, &fo->data->msg_iter);
4193 if (unlikely(!space)) {
4194 tcp_skb_tsorted_anchor_cleanup(syn_data);
4195 kfree_skb(syn_data);
4196 goto fallback;
4197 }
4198 skb_fill_page_desc(syn_data, 0, pfrag->page,
4199 pfrag->offset, space);
4200 page_ref_inc(pfrag->page);
4201 pfrag->offset += space;
4202 skb_len_add(syn_data, space);
4203 skb_zcopy_set(syn_data, fo->uarg, NULL);
4204 }
4205 /* No more data pending in inet_wait_for_connect() */
4206 if (space == fo->size)
4207 fo->data = NULL;
4208 fo->copied = space;
4209
4210 tcp_connect_queue_skb(sk, syn_data);
4211 if (syn_data->len)
4212 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
4213
4214 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
4215
4216 skb_set_delivery_time(syn, syn_data->skb_mstamp_ns, SKB_CLOCK_MONOTONIC);
4217
4218 /* Now full SYN+DATA was cloned and sent (or not),
4219 * remove the SYN from the original skb (syn_data)
4220 * we keep in write queue in case of a retransmit, as we
4221 * also have the SYN packet (with no data) in the same queue.
4222 */
4223 TCP_SKB_CB(syn_data)->seq++;
4224 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
4225 if (!err) {
4226 tp->syn_data = (fo->copied > 0);
4227 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
4228 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
4229 goto done;
4230 }
4231
4232 /* data was not sent, put it in write_queue */
4233 __skb_queue_tail(&sk->sk_write_queue, syn_data);
4234 tp->packets_out -= tcp_skb_pcount(syn_data);
4235
4236 fallback:
4237 /* Send a regular SYN with Fast Open cookie request option */
4238 if (fo->cookie.len > 0)
4239 fo->cookie.len = 0;
4240 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
4241 if (err)
4242 tp->syn_fastopen = 0;
4243 done:
4244 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
4245 return err;
4246 }
4247
4248 /* Build a SYN and send it off. */
tcp_connect(struct sock * sk)4249 int tcp_connect(struct sock *sk)
4250 {
4251 struct tcp_sock *tp = tcp_sk(sk);
4252 struct sk_buff *buff;
4253 int err;
4254
4255 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
4256
4257 #if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
4258 /* Has to be checked late, after setting daddr/saddr/ops.
4259 * Return error if the peer has both a md5 and a tcp-ao key
4260 * configured as this is ambiguous.
4261 */
4262 if (unlikely(rcu_dereference_protected(tp->md5sig_info,
4263 lockdep_sock_is_held(sk)))) {
4264 bool needs_ao = !!tp->af_specific->ao_lookup(sk, sk, -1, -1);
4265 bool needs_md5 = !!tp->af_specific->md5_lookup(sk, sk);
4266 struct tcp_ao_info *ao_info;
4267
4268 ao_info = rcu_dereference_check(tp->ao_info,
4269 lockdep_sock_is_held(sk));
4270 if (ao_info) {
4271 /* This is an extra check: tcp_ao_required() in
4272 * tcp_v{4,6}_parse_md5_keys() should prevent adding
4273 * md5 keys on ao_required socket.
4274 */
4275 needs_ao |= ao_info->ao_required;
4276 WARN_ON_ONCE(ao_info->ao_required && needs_md5);
4277 }
4278 if (needs_md5 && needs_ao)
4279 return -EKEYREJECTED;
4280
4281 /* If we have a matching md5 key and no matching tcp-ao key
4282 * then free up ao_info if allocated.
4283 */
4284 if (needs_md5) {
4285 tcp_ao_destroy_sock(sk, false);
4286 } else if (needs_ao) {
4287 tcp_clear_md5_list(sk);
4288 kfree(rcu_replace_pointer(tp->md5sig_info, NULL,
4289 lockdep_sock_is_held(sk)));
4290 }
4291 }
4292 #endif
4293 #ifdef CONFIG_TCP_AO
4294 if (unlikely(rcu_dereference_protected(tp->ao_info,
4295 lockdep_sock_is_held(sk)))) {
4296 /* Don't allow connecting if ao is configured but no
4297 * matching key is found.
4298 */
4299 if (!tp->af_specific->ao_lookup(sk, sk, -1, -1))
4300 return -EKEYREJECTED;
4301 }
4302 #endif
4303
4304 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
4305 return -EHOSTUNREACH; /* Routing failure or similar. */
4306
4307 tcp_connect_init(sk);
4308
4309 if (unlikely(tp->repair)) {
4310 tcp_finish_connect(sk, NULL);
4311 return 0;
4312 }
4313
4314 buff = tcp_stream_alloc_skb(sk, sk->sk_allocation, true);
4315 if (unlikely(!buff))
4316 return -ENOBUFS;
4317
4318 /* SYN eats a sequence byte, write_seq updated by
4319 * tcp_connect_queue_skb().
4320 */
4321 tcp_init_nondata_skb(buff, sk, tp->write_seq, TCPHDR_SYN);
4322 tcp_mstamp_refresh(tp);
4323 tp->retrans_stamp = tcp_time_stamp_ts(tp);
4324 tcp_connect_queue_skb(sk, buff);
4325 tcp_ecn_send_syn(sk, buff);
4326 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
4327
4328 /* Send off SYN; include data in Fast Open. */
4329 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
4330 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
4331 if (err == -ECONNREFUSED)
4332 return err;
4333
4334 /* We change tp->snd_nxt after the tcp_transmit_skb() call
4335 * in order to make this packet get counted in tcpOutSegs.
4336 */
4337 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
4338 tp->pushed_seq = tp->write_seq;
4339 buff = tcp_send_head(sk);
4340 if (unlikely(buff)) {
4341 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
4342 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
4343 }
4344 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
4345
4346 /* Timer for repeating the SYN until an answer. */
4347 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
4348 inet_csk(sk)->icsk_rto, false);
4349 return 0;
4350 }
4351 EXPORT_SYMBOL(tcp_connect);
4352
tcp_delack_max(const struct sock * sk)4353 u32 tcp_delack_max(const struct sock *sk)
4354 {
4355 u32 delack_from_rto_min = max(tcp_rto_min(sk), 2) - 1;
4356
4357 return min(READ_ONCE(inet_csk(sk)->icsk_delack_max), delack_from_rto_min);
4358 }
4359
4360 /* Send out a delayed ack, the caller does the policy checking
4361 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
4362 * for details.
4363 */
tcp_send_delayed_ack(struct sock * sk)4364 void tcp_send_delayed_ack(struct sock *sk)
4365 {
4366 struct inet_connection_sock *icsk = inet_csk(sk);
4367 int ato = icsk->icsk_ack.ato;
4368 unsigned long timeout;
4369
4370 if (ato > TCP_DELACK_MIN) {
4371 const struct tcp_sock *tp = tcp_sk(sk);
4372 int max_ato = HZ / 2;
4373
4374 if (inet_csk_in_pingpong_mode(sk) ||
4375 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
4376 max_ato = TCP_DELACK_MAX;
4377
4378 /* Slow path, intersegment interval is "high". */
4379
4380 /* If some rtt estimate is known, use it to bound delayed ack.
4381 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
4382 * directly.
4383 */
4384 if (tp->srtt_us) {
4385 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
4386 TCP_DELACK_MIN);
4387
4388 if (rtt < max_ato)
4389 max_ato = rtt;
4390 }
4391
4392 ato = min(ato, max_ato);
4393 }
4394
4395 ato = min_t(u32, ato, tcp_delack_max(sk));
4396
4397 /* Stay within the limit we were given */
4398 timeout = jiffies + ato;
4399
4400 /* Use new timeout only if there wasn't a older one earlier. */
4401 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
4402 /* If delack timer is about to expire, send ACK now. */
4403 if (time_before_eq(icsk_delack_timeout(icsk), jiffies + (ato >> 2))) {
4404 tcp_send_ack(sk);
4405 return;
4406 }
4407
4408 if (!time_before(timeout, icsk_delack_timeout(icsk)))
4409 timeout = icsk_delack_timeout(icsk);
4410 }
4411 smp_store_release(&icsk->icsk_ack.pending,
4412 icsk->icsk_ack.pending | ICSK_ACK_SCHED | ICSK_ACK_TIMER);
4413 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
4414 }
4415
4416 /* This routine sends an ack and also updates the window. */
__tcp_send_ack(struct sock * sk,u32 rcv_nxt,u16 flags)4417 void __tcp_send_ack(struct sock *sk, u32 rcv_nxt, u16 flags)
4418 {
4419 struct sk_buff *buff;
4420
4421 /* If we have been reset, we may not send again. */
4422 if (sk->sk_state == TCP_CLOSE)
4423 return;
4424
4425 /* We are not putting this on the write queue, so
4426 * tcp_transmit_skb() will set the ownership to this
4427 * sock.
4428 */
4429 buff = alloc_skb(MAX_TCP_HEADER,
4430 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4431 if (unlikely(!buff)) {
4432 struct inet_connection_sock *icsk = inet_csk(sk);
4433 unsigned long delay;
4434
4435 delay = TCP_DELACK_MAX << icsk->icsk_ack.retry;
4436 if (delay < tcp_rto_max(sk))
4437 icsk->icsk_ack.retry++;
4438 inet_csk_schedule_ack(sk);
4439 icsk->icsk_ack.ato = TCP_ATO_MIN;
4440 tcp_reset_xmit_timer(sk, ICSK_TIME_DACK, delay, false);
4441 return;
4442 }
4443
4444 /* Reserve space for headers and prepare control bits. */
4445 skb_reserve(buff, MAX_TCP_HEADER);
4446 tcp_init_nondata_skb(buff, sk,
4447 tcp_acceptable_seq(sk), TCPHDR_ACK | flags);
4448
4449 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
4450 * too much.
4451 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
4452 */
4453 skb_set_tcp_pure_ack(buff);
4454
4455 /* Send it off, this clears delayed acks for us. */
4456 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
4457 }
4458 EXPORT_SYMBOL_GPL(__tcp_send_ack);
4459
tcp_send_ack(struct sock * sk)4460 void tcp_send_ack(struct sock *sk)
4461 {
4462 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt, 0);
4463 }
4464
4465 /* This routine sends a packet with an out of date sequence
4466 * number. It assumes the other end will try to ack it.
4467 *
4468 * Question: what should we make while urgent mode?
4469 * 4.4BSD forces sending single byte of data. We cannot send
4470 * out of window data, because we have SND.NXT==SND.MAX...
4471 *
4472 * Current solution: to send TWO zero-length segments in urgent mode:
4473 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
4474 * out-of-date with SND.UNA-1 to probe window.
4475 */
tcp_xmit_probe_skb(struct sock * sk,int urgent,int mib)4476 static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
4477 {
4478 struct tcp_sock *tp = tcp_sk(sk);
4479 struct sk_buff *skb;
4480
4481 /* We don't queue it, tcp_transmit_skb() sets ownership. */
4482 skb = alloc_skb(MAX_TCP_HEADER,
4483 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4484 if (!skb)
4485 return -1;
4486
4487 /* Reserve space for headers and set control bits. */
4488 skb_reserve(skb, MAX_TCP_HEADER);
4489 /* Use a previous sequence. This should cause the other
4490 * end to send an ack. Don't queue or clone SKB, just
4491 * send it.
4492 */
4493 tcp_init_nondata_skb(skb, sk, tp->snd_una - !urgent, TCPHDR_ACK);
4494 NET_INC_STATS(sock_net(sk), mib);
4495 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
4496 }
4497
4498 /* Called from setsockopt( ... TCP_REPAIR ) */
tcp_send_window_probe(struct sock * sk)4499 void tcp_send_window_probe(struct sock *sk)
4500 {
4501 if (sk->sk_state == TCP_ESTABLISHED) {
4502 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
4503 tcp_mstamp_refresh(tcp_sk(sk));
4504 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
4505 }
4506 }
4507
4508 /* Initiate keepalive or window probe from timer. */
tcp_write_wakeup(struct sock * sk,int mib)4509 int tcp_write_wakeup(struct sock *sk, int mib)
4510 {
4511 struct tcp_sock *tp = tcp_sk(sk);
4512 struct sk_buff *skb;
4513
4514 if (sk->sk_state == TCP_CLOSE)
4515 return -1;
4516
4517 skb = tcp_send_head(sk);
4518 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
4519 int err;
4520 unsigned int mss = tcp_current_mss(sk);
4521 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
4522
4523 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
4524 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
4525
4526 /* We are probing the opening of a window
4527 * but the window size is != 0
4528 * must have been a result SWS avoidance ( sender )
4529 */
4530 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
4531 skb->len > mss) {
4532 seg_size = min(seg_size, mss);
4533 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4534 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
4535 skb, seg_size, mss, GFP_ATOMIC))
4536 return -1;
4537 } else if (!tcp_skb_pcount(skb))
4538 tcp_set_skb_tso_segs(skb, mss);
4539
4540 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4541 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
4542 if (!err)
4543 tcp_event_new_data_sent(sk, skb);
4544 return err;
4545 } else {
4546 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
4547 tcp_xmit_probe_skb(sk, 1, mib);
4548 return tcp_xmit_probe_skb(sk, 0, mib);
4549 }
4550 }
4551
4552 /* A window probe timeout has occurred. If window is not closed send
4553 * a partial packet else a zero probe.
4554 */
tcp_send_probe0(struct sock * sk)4555 void tcp_send_probe0(struct sock *sk)
4556 {
4557 struct inet_connection_sock *icsk = inet_csk(sk);
4558 struct tcp_sock *tp = tcp_sk(sk);
4559 struct net *net = sock_net(sk);
4560 unsigned long timeout;
4561 int err;
4562
4563 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
4564
4565 if (tp->packets_out || tcp_write_queue_empty(sk)) {
4566 /* Cancel probe timer, if it is not required. */
4567 WRITE_ONCE(icsk->icsk_probes_out, 0);
4568 icsk->icsk_backoff = 0;
4569 icsk->icsk_probes_tstamp = 0;
4570 return;
4571 }
4572
4573 WRITE_ONCE(icsk->icsk_probes_out, icsk->icsk_probes_out + 1);
4574 if (err <= 0) {
4575 if (icsk->icsk_backoff < READ_ONCE(net->ipv4.sysctl_tcp_retries2))
4576 icsk->icsk_backoff++;
4577 timeout = tcp_probe0_when(sk, tcp_rto_max(sk));
4578 } else {
4579 /* If packet was not sent due to local congestion,
4580 * Let senders fight for local resources conservatively.
4581 */
4582 timeout = TCP_RESOURCE_PROBE_INTERVAL;
4583 }
4584
4585 timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout);
4586 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, true);
4587 }
4588
tcp_rtx_synack(const struct sock * sk,struct request_sock * req)4589 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
4590 {
4591 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
4592 struct flowi fl;
4593 int res;
4594
4595 /* Paired with WRITE_ONCE() in sock_setsockopt() */
4596 if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED)
4597 WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash());
4598 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
4599 NULL);
4600 if (!res) {
4601 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
4602 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
4603 if (unlikely(tcp_passive_fastopen(sk))) {
4604 /* sk has const attribute because listeners are lockless.
4605 * However in this case, we are dealing with a passive fastopen
4606 * socket thus we can change total_retrans value.
4607 */
4608 tcp_sk_rw(sk)->total_retrans++;
4609 }
4610 trace_tcp_retransmit_synack(sk, req);
4611 WRITE_ONCE(req->num_retrans, req->num_retrans + 1);
4612 }
4613 return res;
4614 }
4615 EXPORT_IPV6_MOD(tcp_rtx_synack);
4616