2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Definitions for the TCP module.
8 * Version: @(#)tcp.h 1.0.5 05/23/93
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
13 * This program is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU General Public License
15 * as published by the Free Software Foundation; either version
16 * 2 of the License, or (at your option) any later version.
21 #define FASTRETRANS_DEBUG 1
23 #include <linux/list.h>
24 #include <linux/tcp.h>
25 #include <linux/bug.h>
26 #include <linux/slab.h>
27 #include <linux/cache.h>
28 #include <linux/percpu.h>
29 #include <linux/skbuff.h>
30 #include <linux/cryptohash.h>
31 #include <linux/kref.h>
32 #include <linux/ktime.h>
34 #include <net/inet_connection_sock.h>
35 #include <net/inet_timewait_sock.h>
36 #include <net/inet_hashtables.h>
37 #include <net/checksum.h>
38 #include <net/request_sock.h>
42 #include <net/tcp_states.h>
43 #include <net/inet_ecn.h>
46 #include <linux/seq_file.h>
47 #include <linux/memcontrol.h>
49 extern struct inet_hashinfo tcp_hashinfo;
51 extern struct percpu_counter tcp_orphan_count;
52 void tcp_time_wait(struct sock *sk, int state, int timeo);
54 #define MAX_TCP_HEADER (128 + MAX_HEADER)
55 #define MAX_TCP_OPTION_SPACE 40
58 * Never offer a window over 32767 without using window scaling. Some
59 * poor stacks do signed 16bit maths!
61 #define MAX_TCP_WINDOW 32767U
63 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
64 #define TCP_MIN_MSS 88U
66 /* The least MTU to use for probing */
67 #define TCP_BASE_MSS 1024
69 /* probing interval, default to 10 minutes as per RFC4821 */
70 #define TCP_PROBE_INTERVAL 600
72 /* Specify interval when tcp mtu probing will stop */
73 #define TCP_PROBE_THRESHOLD 8
75 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
76 #define TCP_FASTRETRANS_THRESH 3
78 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
79 #define TCP_MAX_QUICKACKS 16U
81 /* Maximal number of window scale according to RFC1323 */
82 #define TCP_MAX_WSCALE 14U
85 #define TCP_URG_VALID 0x0100
86 #define TCP_URG_NOTYET 0x0200
87 #define TCP_URG_READ 0x0400
89 #define TCP_RETR1 3 /*
90 * This is how many retries it does before it
91 * tries to figure out if the gateway is
92 * down. Minimal RFC value is 3; it corresponds
93 * to ~3sec-8min depending on RTO.
96 #define TCP_RETR2 15 /*
97 * This should take at least
98 * 90 minutes to time out.
99 * RFC1122 says that the limit is 100 sec.
100 * 15 is ~13-30min depending on RTO.
103 #define TCP_SYN_RETRIES 6 /* This is how many retries are done
104 * when active opening a connection.
105 * RFC1122 says the minimum retry MUST
106 * be at least 180secs. Nevertheless
107 * this value is corresponding to
108 * 63secs of retransmission with the
109 * current initial RTO.
112 #define TCP_SYNACK_RETRIES 5 /* This is how may retries are done
113 * when passive opening a connection.
114 * This is corresponding to 31secs of
115 * retransmission with the current
119 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
120 * state, about 60 seconds */
121 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
122 /* BSD style FIN_WAIT2 deadlock breaker.
123 * It used to be 3min, new value is 60sec,
124 * to combine FIN-WAIT-2 timeout with
128 #define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */
130 #define TCP_DELACK_MIN ((unsigned)(HZ/25)) /* minimal time to delay before sending an ACK */
131 #define TCP_ATO_MIN ((unsigned)(HZ/25))
133 #define TCP_DELACK_MIN 4U
134 #define TCP_ATO_MIN 4U
136 #define TCP_RTO_MAX ((unsigned)(120*HZ))
137 #define TCP_RTO_MIN ((unsigned)(HZ/5))
138 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ)) /* RFC6298 2.1 initial RTO value */
139 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
140 * used as a fallback RTO for the
141 * initial data transmission if no
142 * valid RTT sample has been acquired,
143 * most likely due to retrans in 3WHS.
146 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
147 * for local resources.
149 #define TCP_REO_TIMEOUT_MIN (2000) /* Min RACK reordering timeout in usec */
151 #define TCP_KEEPALIVE_TIME (120*60*HZ) /* two hours */
152 #define TCP_KEEPALIVE_PROBES 9 /* Max of 9 keepalive probes */
153 #define TCP_KEEPALIVE_INTVL (75*HZ)
155 #define MAX_TCP_KEEPIDLE 32767
156 #define MAX_TCP_KEEPINTVL 32767
157 #define MAX_TCP_KEEPCNT 127
158 #define MAX_TCP_SYNCNT 127
160 #define TCP_SYNQ_INTERVAL (HZ/5) /* Period of SYNACK timer */
162 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
163 #define TCP_PAWS_MSL 60 /* Per-host timestamps are invalidated
164 * after this time. It should be equal
165 * (or greater than) TCP_TIMEWAIT_LEN
166 * to provide reliability equal to one
167 * provided by timewait state.
169 #define TCP_PAWS_WINDOW 1 /* Replay window for per-host
170 * timestamps. It must be less than
171 * minimal timewait lifetime.
177 #define TCPOPT_NOP 1 /* Padding */
178 #define TCPOPT_EOL 0 /* End of options */
179 #define TCPOPT_MSS 2 /* Segment size negotiating */
180 #define TCPOPT_WINDOW 3 /* Window scaling */
181 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
182 #define TCPOPT_SACK 5 /* SACK Block */
183 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
184 #define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */
185 #define TCPOPT_FASTOPEN 34 /* Fast open (RFC7413) */
186 #define TCPOPT_EXP 254 /* Experimental */
187 /* Magic number to be after the option value for sharing TCP
188 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
190 #define TCPOPT_FASTOPEN_MAGIC 0xF989
196 #define TCPOLEN_MSS 4
197 #define TCPOLEN_WINDOW 3
198 #define TCPOLEN_SACK_PERM 2
199 #define TCPOLEN_TIMESTAMP 10
200 #define TCPOLEN_MD5SIG 18
201 #define TCPOLEN_FASTOPEN_BASE 2
202 #define TCPOLEN_EXP_FASTOPEN_BASE 4
204 /* But this is what stacks really send out. */
205 #define TCPOLEN_TSTAMP_ALIGNED 12
206 #define TCPOLEN_WSCALE_ALIGNED 4
207 #define TCPOLEN_SACKPERM_ALIGNED 4
208 #define TCPOLEN_SACK_BASE 2
209 #define TCPOLEN_SACK_BASE_ALIGNED 4
210 #define TCPOLEN_SACK_PERBLOCK 8
211 #define TCPOLEN_MD5SIG_ALIGNED 20
212 #define TCPOLEN_MSS_ALIGNED 4
214 /* Flags in tp->nonagle */
215 #define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
216 #define TCP_NAGLE_CORK 2 /* Socket is corked */
217 #define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */
219 /* TCP thin-stream limits */
220 #define TCP_THIN_LINEAR_RETRIES 6 /* After 6 linear retries, do exp. backoff */
222 /* TCP initial congestion window as per rfc6928 */
223 #define TCP_INIT_CWND 10
225 /* Bit Flags for sysctl_tcp_fastopen */
226 #define TFO_CLIENT_ENABLE 1
227 #define TFO_SERVER_ENABLE 2
228 #define TFO_CLIENT_NO_COOKIE 4 /* Data in SYN w/o cookie option */
230 /* Accept SYN data w/o any cookie option */
231 #define TFO_SERVER_COOKIE_NOT_REQD 0x200
233 /* Force enable TFO on all listeners, i.e., not requiring the
234 * TCP_FASTOPEN socket option.
236 #define TFO_SERVER_WO_SOCKOPT1 0x400
239 /* sysctl variables for tcp */
240 extern int sysctl_tcp_fastopen;
241 extern int sysctl_tcp_retrans_collapse;
242 extern int sysctl_tcp_stdurg;
243 extern int sysctl_tcp_rfc1337;
244 extern int sysctl_tcp_abort_on_overflow;
245 extern int sysctl_tcp_max_orphans;
246 extern int sysctl_tcp_fack;
247 extern int sysctl_tcp_reordering;
248 extern int sysctl_tcp_max_reordering;
249 extern int sysctl_tcp_dsack;
250 extern long sysctl_tcp_mem[3];
251 extern int sysctl_tcp_wmem[3];
252 extern int sysctl_tcp_rmem[3];
253 extern int sysctl_tcp_app_win;
254 extern int sysctl_tcp_adv_win_scale;
255 extern int sysctl_tcp_frto;
256 extern int sysctl_tcp_low_latency;
257 extern int sysctl_tcp_nometrics_save;
258 extern int sysctl_tcp_moderate_rcvbuf;
259 extern int sysctl_tcp_tso_win_divisor;
260 extern int sysctl_tcp_workaround_signed_windows;
261 extern int sysctl_tcp_slow_start_after_idle;
262 extern int sysctl_tcp_thin_linear_timeouts;
263 extern int sysctl_tcp_thin_dupack;
264 extern int sysctl_tcp_early_retrans;
265 extern int sysctl_tcp_recovery;
266 #define TCP_RACK_LOSS_DETECTION 0x1 /* Use RACK to detect losses */
268 extern int sysctl_tcp_limit_output_bytes;
269 extern int sysctl_tcp_challenge_ack_limit;
270 extern int sysctl_tcp_min_tso_segs;
271 extern int sysctl_tcp_min_rtt_wlen;
272 extern int sysctl_tcp_autocorking;
273 extern int sysctl_tcp_invalid_ratelimit;
274 extern int sysctl_tcp_pacing_ss_ratio;
275 extern int sysctl_tcp_pacing_ca_ratio;
277 extern atomic_long_t tcp_memory_allocated;
278 extern struct percpu_counter tcp_sockets_allocated;
279 extern unsigned long tcp_memory_pressure;
281 /* optimized version of sk_under_memory_pressure() for TCP sockets */
282 static inline bool tcp_under_memory_pressure(const struct sock *sk)
284 if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
285 mem_cgroup_under_socket_pressure(sk->sk_memcg))
288 return tcp_memory_pressure;
291 * The next routines deal with comparing 32 bit unsigned ints
292 * and worry about wraparound (automatic with unsigned arithmetic).
295 static inline bool before(__u32 seq1, __u32 seq2)
297 return (__s32)(seq1-seq2) < 0;
299 #define after(seq2, seq1) before(seq1, seq2)
301 /* is s2<=s1<=s3 ? */
302 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
304 return seq3 - seq2 >= seq1 - seq2;
307 static inline bool tcp_out_of_memory(struct sock *sk)
309 if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
310 sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
315 void sk_forced_mem_schedule(struct sock *sk, int size);
317 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
319 struct percpu_counter *ocp = sk->sk_prot->orphan_count;
320 int orphans = percpu_counter_read_positive(ocp);
322 if (orphans << shift > sysctl_tcp_max_orphans) {
323 orphans = percpu_counter_sum_positive(ocp);
324 if (orphans << shift > sysctl_tcp_max_orphans)
330 bool tcp_check_oom(struct sock *sk, int shift);
333 extern struct proto tcp_prot;
335 #define TCP_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.tcp_statistics, field)
336 #define __TCP_INC_STATS(net, field) __SNMP_INC_STATS((net)->mib.tcp_statistics, field)
337 #define TCP_DEC_STATS(net, field) SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
338 #define TCP_ADD_STATS(net, field, val) SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
340 void tcp_tasklet_init(void);
342 void tcp_v4_err(struct sk_buff *skb, u32);
344 void tcp_shutdown(struct sock *sk, int how);
346 void tcp_v4_early_demux(struct sk_buff *skb);
347 int tcp_v4_rcv(struct sk_buff *skb);
349 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
350 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
351 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
353 void tcp_release_cb(struct sock *sk);
354 void tcp_wfree(struct sk_buff *skb);
355 void tcp_write_timer_handler(struct sock *sk);
356 void tcp_delack_timer_handler(struct sock *sk);
357 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
358 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
359 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
360 const struct tcphdr *th, unsigned int len);
361 void tcp_rcv_space_adjust(struct sock *sk);
362 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
363 void tcp_twsk_destructor(struct sock *sk);
364 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
365 struct pipe_inode_info *pipe, size_t len,
368 static inline void tcp_dec_quickack_mode(struct sock *sk,
369 const unsigned int pkts)
371 struct inet_connection_sock *icsk = inet_csk(sk);
373 if (icsk->icsk_ack.quick) {
374 if (pkts >= icsk->icsk_ack.quick) {
375 icsk->icsk_ack.quick = 0;
376 /* Leaving quickack mode we deflate ATO. */
377 icsk->icsk_ack.ato = TCP_ATO_MIN;
379 icsk->icsk_ack.quick -= pkts;
384 #define TCP_ECN_QUEUE_CWR 2
385 #define TCP_ECN_DEMAND_CWR 4
386 #define TCP_ECN_SEEN 8
396 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
398 const struct tcphdr *th);
399 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
400 struct request_sock *req, bool fastopen);
401 int tcp_child_process(struct sock *parent, struct sock *child,
402 struct sk_buff *skb);
403 void tcp_enter_loss(struct sock *sk);
404 void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag);
405 void tcp_clear_retrans(struct tcp_sock *tp);
406 void tcp_update_metrics(struct sock *sk);
407 void tcp_init_metrics(struct sock *sk);
408 void tcp_metrics_init(void);
409 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
410 void tcp_disable_fack(struct tcp_sock *tp);
411 void tcp_close(struct sock *sk, long timeout);
412 void tcp_init_sock(struct sock *sk);
413 unsigned int tcp_poll(struct file *file, struct socket *sock,
414 struct poll_table_struct *wait);
415 int tcp_getsockopt(struct sock *sk, int level, int optname,
416 char __user *optval, int __user *optlen);
417 int tcp_setsockopt(struct sock *sk, int level, int optname,
418 char __user *optval, unsigned int optlen);
419 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
420 char __user *optval, int __user *optlen);
421 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
422 char __user *optval, unsigned int optlen);
423 void tcp_set_keepalive(struct sock *sk, int val);
424 void tcp_syn_ack_timeout(const struct request_sock *req);
425 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
426 int flags, int *addr_len);
427 void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
428 struct tcp_options_received *opt_rx,
429 int estab, struct tcp_fastopen_cookie *foc);
430 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
433 * TCP v4 functions exported for the inet6 API
436 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
437 void tcp_v4_mtu_reduced(struct sock *sk);
438 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
439 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
440 struct sock *tcp_create_openreq_child(const struct sock *sk,
441 struct request_sock *req,
442 struct sk_buff *skb);
443 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
444 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
445 struct request_sock *req,
446 struct dst_entry *dst,
447 struct request_sock *req_unhash,
449 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
450 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
451 int tcp_connect(struct sock *sk);
452 enum tcp_synack_type {
457 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
458 struct request_sock *req,
459 struct tcp_fastopen_cookie *foc,
460 enum tcp_synack_type synack_type);
461 int tcp_disconnect(struct sock *sk, int flags);
463 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
464 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
465 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
467 /* From syncookies.c */
468 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
469 struct request_sock *req,
470 struct dst_entry *dst, u32 tsoff);
471 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
473 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
474 #ifdef CONFIG_SYN_COOKIES
476 /* Syncookies use a monotonic timer which increments every 60 seconds.
477 * This counter is used both as a hash input and partially encoded into
478 * the cookie value. A cookie is only validated further if the delta
479 * between the current counter value and the encoded one is less than this,
480 * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
481 * the counter advances immediately after a cookie is generated).
483 #define MAX_SYNCOOKIE_AGE 2
484 #define TCP_SYNCOOKIE_PERIOD (60 * HZ)
485 #define TCP_SYNCOOKIE_VALID (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
487 /* syncookies: remember time of last synqueue overflow
488 * But do not dirty this field too often (once per second is enough)
489 * It is racy as we do not hold a lock, but race is very minor.
491 static inline void tcp_synq_overflow(const struct sock *sk)
493 unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
494 unsigned long now = jiffies;
496 if (time_after(now, last_overflow + HZ))
497 tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
500 /* syncookies: no recent synqueue overflow on this listening socket? */
501 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
503 unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
505 return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
508 static inline u32 tcp_cookie_time(void)
510 u64 val = get_jiffies_64();
512 do_div(val, TCP_SYNCOOKIE_PERIOD);
516 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
518 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
519 u64 cookie_init_timestamp(struct request_sock *req);
520 bool cookie_timestamp_decode(const struct net *net,
521 struct tcp_options_received *opt);
522 bool cookie_ecn_ok(const struct tcp_options_received *opt,
523 const struct net *net, const struct dst_entry *dst);
525 /* From net/ipv6/syncookies.c */
526 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
528 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
530 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
531 const struct tcphdr *th, u16 *mssp);
532 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
536 u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
538 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
540 bool tcp_may_send_now(struct sock *sk);
541 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
542 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
543 void tcp_retransmit_timer(struct sock *sk);
544 void tcp_xmit_retransmit_queue(struct sock *);
545 void tcp_simple_retransmit(struct sock *);
546 void tcp_enter_recovery(struct sock *sk, bool ece_ack);
547 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
548 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
550 void tcp_send_probe0(struct sock *);
551 void tcp_send_partial(struct sock *);
552 int tcp_write_wakeup(struct sock *, int mib);
553 void tcp_send_fin(struct sock *sk);
554 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
555 int tcp_send_synack(struct sock *);
556 void tcp_push_one(struct sock *, unsigned int mss_now);
557 void tcp_send_ack(struct sock *sk);
558 void tcp_send_delayed_ack(struct sock *sk);
559 void tcp_send_loss_probe(struct sock *sk);
560 bool tcp_schedule_loss_probe(struct sock *sk);
561 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
562 const struct sk_buff *next_skb);
565 void tcp_rearm_rto(struct sock *sk);
566 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
567 void tcp_reset(struct sock *sk);
568 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
569 void tcp_fin(struct sock *sk);
572 void tcp_init_xmit_timers(struct sock *);
573 static inline void tcp_clear_xmit_timers(struct sock *sk)
575 hrtimer_cancel(&tcp_sk(sk)->pacing_timer);
576 inet_csk_clear_xmit_timers(sk);
579 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
580 unsigned int tcp_current_mss(struct sock *sk);
582 /* Bound MSS / TSO packet size with the half of the window */
583 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
587 /* When peer uses tiny windows, there is no use in packetizing
588 * to sub-MSS pieces for the sake of SWS or making sure there
589 * are enough packets in the pipe for fast recovery.
591 * On the other hand, for extremely large MSS devices, handling
592 * smaller than MSS windows in this way does make sense.
594 if (tp->max_window > TCP_MSS_DEFAULT)
595 cutoff = (tp->max_window >> 1);
597 cutoff = tp->max_window;
599 if (cutoff && pktsize > cutoff)
600 return max_t(int, cutoff, 68U - tp->tcp_header_len);
606 void tcp_get_info(struct sock *, struct tcp_info *);
608 /* Read 'sendfile()'-style from a TCP socket */
609 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
610 sk_read_actor_t recv_actor);
612 void tcp_initialize_rcv_mss(struct sock *sk);
614 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
615 int tcp_mss_to_mtu(struct sock *sk, int mss);
616 void tcp_mtup_init(struct sock *sk);
617 void tcp_init_buffer_space(struct sock *sk);
619 static inline void tcp_bound_rto(const struct sock *sk)
621 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
622 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
625 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
627 return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
630 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
632 tp->pred_flags = htonl((tp->tcp_header_len << 26) |
633 ntohl(TCP_FLAG_ACK) |
637 static inline void tcp_fast_path_on(struct tcp_sock *tp)
639 __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
642 static inline void tcp_fast_path_check(struct sock *sk)
644 struct tcp_sock *tp = tcp_sk(sk);
646 if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
648 atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
650 tcp_fast_path_on(tp);
653 /* Compute the actual rto_min value */
654 static inline u32 tcp_rto_min(struct sock *sk)
656 const struct dst_entry *dst = __sk_dst_get(sk);
657 u32 rto_min = TCP_RTO_MIN;
659 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
660 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
664 static inline u32 tcp_rto_min_us(struct sock *sk)
666 return jiffies_to_usecs(tcp_rto_min(sk));
669 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
671 return dst_metric_locked(dst, RTAX_CC_ALGO);
674 /* Minimum RTT in usec. ~0 means not available. */
675 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
677 return minmax_get(&tp->rtt_min);
680 /* Compute the actual receive window we are currently advertising.
681 * Rcv_nxt can be after the window if our peer push more data
682 * than the offered window.
684 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
686 s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
693 /* Choose a new window, without checks for shrinking, and without
694 * scaling applied to the result. The caller does these things
695 * if necessary. This is a "raw" window selection.
697 u32 __tcp_select_window(struct sock *sk);
699 void tcp_send_window_probe(struct sock *sk);
701 /* TCP uses 32bit jiffies to save some space.
702 * Note that this is different from tcp_time_stamp, which
703 * historically has been the same until linux-4.13.
705 #define tcp_jiffies32 ((u32)jiffies)
708 * Deliver a 32bit value for TCP timestamp option (RFC 7323)
709 * It is no longer tied to jiffies, but to 1 ms clock.
710 * Note: double check if you want to use tcp_jiffies32 instead of this.
712 #define TCP_TS_HZ 1000
714 static inline u64 tcp_clock_ns(void)
716 return local_clock();
719 static inline u64 tcp_clock_us(void)
721 return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
724 /* This should only be used in contexts where tp->tcp_mstamp is up to date */
725 static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
727 return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);
730 /* Could use tcp_clock_us() / 1000, but this version uses a single divide */
731 static inline u32 tcp_time_stamp_raw(void)
733 return div_u64(tcp_clock_ns(), NSEC_PER_SEC / TCP_TS_HZ);
737 /* Refresh 1us clock of a TCP socket,
738 * ensuring monotically increasing values.
740 static inline void tcp_mstamp_refresh(struct tcp_sock *tp)
742 u64 val = tcp_clock_us();
744 if (val > tp->tcp_mstamp)
745 tp->tcp_mstamp = val;
748 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
750 return max_t(s64, t1 - t0, 0);
753 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
755 return div_u64(skb->skb_mstamp, USEC_PER_SEC / TCP_TS_HZ);
759 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
761 #define TCPHDR_FIN 0x01
762 #define TCPHDR_SYN 0x02
763 #define TCPHDR_RST 0x04
764 #define TCPHDR_PSH 0x08
765 #define TCPHDR_ACK 0x10
766 #define TCPHDR_URG 0x20
767 #define TCPHDR_ECE 0x40
768 #define TCPHDR_CWR 0x80
770 #define TCPHDR_SYN_ECN (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
772 /* This is what the send packet queuing engine uses to pass
773 * TCP per-packet control information to the transmission code.
774 * We also store the host-order sequence numbers in here too.
775 * This is 44 bytes if IPV6 is enabled.
776 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
779 __u32 seq; /* Starting sequence number */
780 __u32 end_seq; /* SEQ + FIN + SYN + datalen */
782 /* Note : tcp_tw_isn is used in input path only
783 * (isn chosen by tcp_timewait_state_process())
785 * tcp_gso_segs/size are used in write queue only,
786 * cf tcp_skb_pcount()/tcp_skb_mss()
794 __u8 tcp_flags; /* TCP header flags. (tcp[13]) */
796 __u8 sacked; /* State flags for SACK/FACK. */
797 #define TCPCB_SACKED_ACKED 0x01 /* SKB ACK'd by a SACK block */
798 #define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */
799 #define TCPCB_LOST 0x04 /* SKB is lost */
800 #define TCPCB_TAGBITS 0x07 /* All tag bits */
801 #define TCPCB_REPAIRED 0x10 /* SKB repaired (no skb_mstamp) */
802 #define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */
803 #define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
806 __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */
807 __u8 txstamp_ack:1, /* Record TX timestamp for ack? */
808 eor:1, /* Is skb MSG_EOR marked? */
810 __u32 ack_seq; /* Sequence number ACK'd */
813 /* There is space for up to 24 bytes */
814 __u32 in_flight:30,/* Bytes in flight at transmit */
815 is_app_limited:1, /* cwnd not fully used? */
817 /* pkts S/ACKed so far upon tx of skb, incl retrans: */
819 /* start of send pipeline phase */
821 /* when we reached the "delivered" count */
822 u64 delivered_mstamp;
823 } tx; /* only used for outgoing skbs */
825 struct inet_skb_parm h4;
826 #if IS_ENABLED(CONFIG_IPV6)
827 struct inet6_skb_parm h6;
829 } header; /* For incoming skbs */
833 #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
836 #if IS_ENABLED(CONFIG_IPV6)
837 /* This is the variant of inet6_iif() that must be used by TCP,
838 * as TCP moves IP6CB into a different location in skb->cb[]
840 static inline int tcp_v6_iif(const struct sk_buff *skb)
842 bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
844 return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
848 /* TCP_SKB_CB reference means this can not be used from early demux */
849 static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
851 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
852 if (!net->ipv4.sysctl_tcp_l3mdev_accept &&
853 skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
859 /* Due to TSO, an SKB can be composed of multiple actual
860 * packets. To keep these tracked properly, we use this.
862 static inline int tcp_skb_pcount(const struct sk_buff *skb)
864 return TCP_SKB_CB(skb)->tcp_gso_segs;
867 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
869 TCP_SKB_CB(skb)->tcp_gso_segs = segs;
872 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
874 TCP_SKB_CB(skb)->tcp_gso_segs += segs;
877 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
878 static inline int tcp_skb_mss(const struct sk_buff *skb)
880 return TCP_SKB_CB(skb)->tcp_gso_size;
883 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
885 return likely(!TCP_SKB_CB(skb)->eor);
888 /* Events passed to congestion control interface */
890 CA_EVENT_TX_START, /* first transmit when no packets in flight */
891 CA_EVENT_CWND_RESTART, /* congestion window restart */
892 CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */
893 CA_EVENT_LOSS, /* loss timeout */
894 CA_EVENT_ECN_NO_CE, /* ECT set, but not CE marked */
895 CA_EVENT_ECN_IS_CE, /* received CE marked IP packet */
896 CA_EVENT_DELAYED_ACK, /* Delayed ack is sent */
897 CA_EVENT_NON_DELAYED_ACK,
900 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
901 enum tcp_ca_ack_event_flags {
902 CA_ACK_SLOWPATH = (1 << 0), /* In slow path processing */
903 CA_ACK_WIN_UPDATE = (1 << 1), /* ACK updated window */
904 CA_ACK_ECE = (1 << 2), /* ECE bit is set on ack */
908 * Interface for adding new TCP congestion control handlers
910 #define TCP_CA_NAME_MAX 16
911 #define TCP_CA_MAX 128
912 #define TCP_CA_BUF_MAX (TCP_CA_NAME_MAX*TCP_CA_MAX)
914 #define TCP_CA_UNSPEC 0
916 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
917 #define TCP_CONG_NON_RESTRICTED 0x1
918 /* Requires ECN/ECT set on all packets */
919 #define TCP_CONG_NEEDS_ECN 0x2
929 /* A rate sample measures the number of (original/retransmitted) data
930 * packets delivered "delivered" over an interval of time "interval_us".
931 * The tcp_rate.c code fills in the rate sample, and congestion
932 * control modules that define a cong_control function to run at the end
933 * of ACK processing can optionally chose to consult this sample when
934 * setting cwnd and pacing rate.
935 * A sample is invalid if "delivered" or "interval_us" is negative.
938 u64 prior_mstamp; /* starting timestamp for interval */
939 u32 prior_delivered; /* tp->delivered at "prior_mstamp" */
940 s32 delivered; /* number of packets delivered over interval */
941 long interval_us; /* time for tp->delivered to incr "delivered" */
942 long rtt_us; /* RTT of last (S)ACKed packet (or -1) */
943 int losses; /* number of packets marked lost upon ACK */
944 u32 acked_sacked; /* number of packets newly (S)ACKed upon ACK */
945 u32 prior_in_flight; /* in flight before this ACK */
946 bool is_app_limited; /* is sample from packet with bubble in pipe? */
947 bool is_retrans; /* is sample from retransmission? */
950 struct tcp_congestion_ops {
951 struct list_head list;
955 /* initialize private data (optional) */
956 void (*init)(struct sock *sk);
957 /* cleanup private data (optional) */
958 void (*release)(struct sock *sk);
960 /* return slow start threshold (required) */
961 u32 (*ssthresh)(struct sock *sk);
962 /* do new cwnd calculation (required) */
963 void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
964 /* call before changing ca_state (optional) */
965 void (*set_state)(struct sock *sk, u8 new_state);
966 /* call when cwnd event occurs (optional) */
967 void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
968 /* call when ack arrives (optional) */
969 void (*in_ack_event)(struct sock *sk, u32 flags);
970 /* new value of cwnd after loss (required) */
971 u32 (*undo_cwnd)(struct sock *sk);
972 /* hook for packet ack accounting (optional) */
973 void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
974 /* suggest number of segments for each skb to transmit (optional) */
975 u32 (*tso_segs_goal)(struct sock *sk);
976 /* returns the multiplier used in tcp_sndbuf_expand (optional) */
977 u32 (*sndbuf_expand)(struct sock *sk);
978 /* call when packets are delivered to update cwnd and pacing rate,
979 * after all the ca_state processing. (optional)
981 void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
982 /* get info for inet_diag (optional) */
983 size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
984 union tcp_cc_info *info);
986 char name[TCP_CA_NAME_MAX];
987 struct module *owner;
990 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
991 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
993 void tcp_assign_congestion_control(struct sock *sk);
994 void tcp_init_congestion_control(struct sock *sk);
995 void tcp_cleanup_congestion_control(struct sock *sk);
996 int tcp_set_default_congestion_control(const char *name);
997 void tcp_get_default_congestion_control(char *name);
998 void tcp_get_available_congestion_control(char *buf, size_t len);
999 void tcp_get_allowed_congestion_control(char *buf, size_t len);
1000 int tcp_set_allowed_congestion_control(char *allowed);
1001 int tcp_set_congestion_control(struct sock *sk, const char *name);
1002 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
1003 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
1005 u32 tcp_reno_ssthresh(struct sock *sk);
1006 u32 tcp_reno_undo_cwnd(struct sock *sk);
1007 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
1008 extern struct tcp_congestion_ops tcp_reno;
1010 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
1011 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
1013 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
1015 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
1021 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
1023 const struct inet_connection_sock *icsk = inet_csk(sk);
1025 return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
1028 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
1030 struct inet_connection_sock *icsk = inet_csk(sk);
1032 if (icsk->icsk_ca_ops->set_state)
1033 icsk->icsk_ca_ops->set_state(sk, ca_state);
1034 icsk->icsk_ca_state = ca_state;
1037 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
1039 const struct inet_connection_sock *icsk = inet_csk(sk);
1041 if (icsk->icsk_ca_ops->cwnd_event)
1042 icsk->icsk_ca_ops->cwnd_event(sk, event);
1045 /* From tcp_rate.c */
1046 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
1047 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
1048 struct rate_sample *rs);
1049 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
1050 struct rate_sample *rs);
1051 void tcp_rate_check_app_limited(struct sock *sk);
1053 /* These functions determine how the current flow behaves in respect of SACK
1054 * handling. SACK is negotiated with the peer, and therefore it can vary
1055 * between different flows.
1057 * tcp_is_sack - SACK enabled
1058 * tcp_is_reno - No SACK
1059 * tcp_is_fack - FACK enabled, implies SACK enabled
1061 static inline int tcp_is_sack(const struct tcp_sock *tp)
1063 return tp->rx_opt.sack_ok;
1066 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1068 return !tcp_is_sack(tp);
1071 static inline bool tcp_is_fack(const struct tcp_sock *tp)
1073 return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
1076 static inline void tcp_enable_fack(struct tcp_sock *tp)
1078 tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
1081 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1083 return tp->sacked_out + tp->lost_out;
1086 /* This determines how many packets are "in the network" to the best
1087 * of our knowledge. In many cases it is conservative, but where
1088 * detailed information is available from the receiver (via SACK
1089 * blocks etc.) we can make more aggressive calculations.
1091 * Use this for decisions involving congestion control, use just
1092 * tp->packets_out to determine if the send queue is empty or not.
1094 * Read this equation as:
1096 * "Packets sent once on transmission queue" MINUS
1097 * "Packets left network, but not honestly ACKed yet" PLUS
1098 * "Packets fast retransmitted"
1100 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1102 return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1105 #define TCP_INFINITE_SSTHRESH 0x7fffffff
1107 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1109 return tp->snd_cwnd < tp->snd_ssthresh;
1112 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1114 return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1117 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1119 return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1120 (1 << inet_csk(sk)->icsk_ca_state);
1123 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1124 * The exception is cwnd reduction phase, when cwnd is decreasing towards
1127 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1129 const struct tcp_sock *tp = tcp_sk(sk);
1131 if (tcp_in_cwnd_reduction(sk))
1132 return tp->snd_ssthresh;
1134 return max(tp->snd_ssthresh,
1135 ((tp->snd_cwnd >> 1) +
1136 (tp->snd_cwnd >> 2)));
1139 /* Use define here intentionally to get WARN_ON location shown at the caller */
1140 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1142 void tcp_enter_cwr(struct sock *sk);
1143 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1145 /* The maximum number of MSS of available cwnd for which TSO defers
1146 * sending if not using sysctl_tcp_tso_win_divisor.
1148 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1153 /* Returns end sequence number of the receiver's advertised window */
1154 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1156 return tp->snd_una + tp->snd_wnd;
1159 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1160 * flexible approach. The RFC suggests cwnd should not be raised unless
1161 * it was fully used previously. And that's exactly what we do in
1162 * congestion avoidance mode. But in slow start we allow cwnd to grow
1163 * as long as the application has used half the cwnd.
1165 * cwnd is 10 (IW10), but application sends 9 frames.
1166 * We allow cwnd to reach 18 when all frames are ACKed.
1167 * This check is safe because it's as aggressive as slow start which already
1168 * risks 100% overshoot. The advantage is that we discourage application to
1169 * either send more filler packets or data to artificially blow up the cwnd
1170 * usage, and allow application-limited process to probe bw more aggressively.
1172 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1174 const struct tcp_sock *tp = tcp_sk(sk);
1176 /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1177 if (tcp_in_slow_start(tp))
1178 return tp->snd_cwnd < 2 * tp->max_packets_out;
1180 return tp->is_cwnd_limited;
1183 /* Something is really bad, we could not queue an additional packet,
1184 * because qdisc is full or receiver sent a 0 window.
1185 * We do not want to add fuel to the fire, or abort too early,
1186 * so make sure the timer we arm now is at least 200ms in the future,
1187 * regardless of current icsk_rto value (as it could be ~2ms)
1189 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1191 return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1194 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1195 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1196 unsigned long max_when)
1198 u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1200 return (unsigned long)min_t(u64, when, max_when);
1203 static inline void tcp_check_probe_timer(struct sock *sk)
1205 if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1206 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1207 tcp_probe0_base(sk), TCP_RTO_MAX);
1210 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1215 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1221 * Calculate(/check) TCP checksum
1223 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1224 __be32 daddr, __wsum base)
1226 return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1229 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1231 return __skb_checksum_complete(skb);
1234 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1236 return !skb_csum_unnecessary(skb) &&
1237 __tcp_checksum_complete(skb);
1240 /* Prequeue for VJ style copy to user, combined with checksumming. */
1242 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1244 tp->ucopy.task = NULL;
1246 tp->ucopy.memory = 0;
1247 skb_queue_head_init(&tp->ucopy.prequeue);
1250 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1251 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
1252 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1257 static const char *statename[]={
1258 "Unused","Established","Syn Sent","Syn Recv",
1259 "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1260 "Close Wait","Last ACK","Listen","Closing"
1263 void tcp_set_state(struct sock *sk, int state);
1265 void tcp_done(struct sock *sk);
1267 int tcp_abort(struct sock *sk, int err);
1269 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1272 rx_opt->num_sacks = 0;
1275 u32 tcp_default_init_rwnd(u32 mss);
1276 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1278 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1280 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1281 struct tcp_sock *tp = tcp_sk(sk);
1284 if (!sysctl_tcp_slow_start_after_idle || tp->packets_out ||
1285 ca_ops->cong_control)
1287 delta = tcp_jiffies32 - tp->lsndtime;
1288 if (delta > inet_csk(sk)->icsk_rto)
1289 tcp_cwnd_restart(sk, delta);
1292 /* Determine a window scaling and initial window to offer. */
1293 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1294 __u32 *window_clamp, int wscale_ok,
1295 __u8 *rcv_wscale, __u32 init_rcv_wnd);
1297 static inline int tcp_win_from_space(int space)
1299 int tcp_adv_win_scale = sysctl_tcp_adv_win_scale;
1301 return tcp_adv_win_scale <= 0 ?
1302 (space>>(-tcp_adv_win_scale)) :
1303 space - (space>>tcp_adv_win_scale);
1306 /* Note: caller must be prepared to deal with negative returns */
1307 static inline int tcp_space(const struct sock *sk)
1309 return tcp_win_from_space(sk->sk_rcvbuf -
1310 atomic_read(&sk->sk_rmem_alloc));
1313 static inline int tcp_full_space(const struct sock *sk)
1315 return tcp_win_from_space(sk->sk_rcvbuf);
1318 extern void tcp_openreq_init_rwin(struct request_sock *req,
1319 const struct sock *sk_listener,
1320 const struct dst_entry *dst);
1322 void tcp_enter_memory_pressure(struct sock *sk);
1323 void tcp_leave_memory_pressure(struct sock *sk);
1325 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1327 struct net *net = sock_net((struct sock *)tp);
1329 return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
1332 static inline int keepalive_time_when(const struct tcp_sock *tp)
1334 struct net *net = sock_net((struct sock *)tp);
1336 return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1339 static inline int keepalive_probes(const struct tcp_sock *tp)
1341 struct net *net = sock_net((struct sock *)tp);
1343 return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1346 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1348 const struct inet_connection_sock *icsk = &tp->inet_conn;
1350 return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime,
1351 tcp_jiffies32 - tp->rcv_tstamp);
1354 static inline int tcp_fin_time(const struct sock *sk)
1356 int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
1357 const int rto = inet_csk(sk)->icsk_rto;
1359 if (fin_timeout < (rto << 2) - (rto >> 1))
1360 fin_timeout = (rto << 2) - (rto >> 1);
1365 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1368 if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1370 if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1373 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1374 * then following tcp messages have valid values. Ignore 0 value,
1375 * or else 'negative' tsval might forbid us to accept their packets.
1377 if (!rx_opt->ts_recent)
1382 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1385 if (tcp_paws_check(rx_opt, 0))
1388 /* RST segments are not recommended to carry timestamp,
1389 and, if they do, it is recommended to ignore PAWS because
1390 "their cleanup function should take precedence over timestamps."
1391 Certainly, it is mistake. It is necessary to understand the reasons
1392 of this constraint to relax it: if peer reboots, clock may go
1393 out-of-sync and half-open connections will not be reset.
1394 Actually, the problem would be not existing if all
1395 the implementations followed draft about maintaining clock
1396 via reboots. Linux-2.2 DOES NOT!
1398 However, we can relax time bounds for RST segments to MSL.
1400 if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1405 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1406 int mib_idx, u32 *last_oow_ack_time);
1408 static inline void tcp_mib_init(struct net *net)
1411 TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1412 TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1413 TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1414 TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1418 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1420 tp->lost_skb_hint = NULL;
1423 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1425 tcp_clear_retrans_hints_partial(tp);
1426 tp->retransmit_skb_hint = NULL;
1429 union tcp_md5_addr {
1431 #if IS_ENABLED(CONFIG_IPV6)
1436 /* - key database */
1437 struct tcp_md5sig_key {
1438 struct hlist_node node;
1440 u8 family; /* AF_INET or AF_INET6 */
1441 union tcp_md5_addr addr;
1442 u8 key[TCP_MD5SIG_MAXKEYLEN];
1443 struct rcu_head rcu;
1447 struct tcp_md5sig_info {
1448 struct hlist_head head;
1449 struct rcu_head rcu;
1452 /* - pseudo header */
1453 struct tcp4_pseudohdr {
1461 struct tcp6_pseudohdr {
1462 struct in6_addr saddr;
1463 struct in6_addr daddr;
1465 __be32 protocol; /* including padding */
1468 union tcp_md5sum_block {
1469 struct tcp4_pseudohdr ip4;
1470 #if IS_ENABLED(CONFIG_IPV6)
1471 struct tcp6_pseudohdr ip6;
1475 /* - pool: digest algorithm, hash description and scratch buffer */
1476 struct tcp_md5sig_pool {
1477 struct ahash_request *md5_req;
1482 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1483 const struct sock *sk, const struct sk_buff *skb);
1484 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1485 int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1486 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1488 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1489 const struct sock *addr_sk);
1491 #ifdef CONFIG_TCP_MD5SIG
1492 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1493 const union tcp_md5_addr *addr,
1495 #define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key)
1497 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1498 const union tcp_md5_addr *addr,
1503 #define tcp_twsk_md5_key(twsk) NULL
1506 bool tcp_alloc_md5sig_pool(void);
1508 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1509 static inline void tcp_put_md5sig_pool(void)
1514 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1515 unsigned int header_len);
1516 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1517 const struct tcp_md5sig_key *key);
1519 /* From tcp_fastopen.c */
1520 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1521 struct tcp_fastopen_cookie *cookie, int *syn_loss,
1522 unsigned long *last_syn_loss);
1523 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1524 struct tcp_fastopen_cookie *cookie, bool syn_lost,
1526 struct tcp_fastopen_request {
1527 /* Fast Open cookie. Size 0 means a cookie request */
1528 struct tcp_fastopen_cookie cookie;
1529 struct msghdr *data; /* data in MSG_FASTOPEN */
1531 int copied; /* queued in tcp_connect() */
1533 void tcp_free_fastopen_req(struct tcp_sock *tp);
1535 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1536 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1537 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1538 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1539 struct request_sock *req,
1540 struct tcp_fastopen_cookie *foc,
1541 struct dst_entry *dst);
1542 void tcp_fastopen_init_key_once(bool publish);
1543 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
1544 struct tcp_fastopen_cookie *cookie);
1545 bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
1546 #define TCP_FASTOPEN_KEY_LENGTH 16
1548 /* Fastopen key context */
1549 struct tcp_fastopen_context {
1550 struct crypto_cipher *tfm;
1551 __u8 key[TCP_FASTOPEN_KEY_LENGTH];
1552 struct rcu_head rcu;
1555 extern unsigned int sysctl_tcp_fastopen_blackhole_timeout;
1556 void tcp_fastopen_active_disable(struct sock *sk);
1557 bool tcp_fastopen_active_should_disable(struct sock *sk);
1558 void tcp_fastopen_active_disable_ofo_check(struct sock *sk);
1559 void tcp_fastopen_active_timeout_reset(void);
1561 /* Latencies incurred by various limits for a sender. They are
1562 * chronograph-like stats that are mutually exclusive.
1566 TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1567 TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
1568 TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
1572 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
1573 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
1575 /* write queue abstraction */
1576 static inline void tcp_write_queue_purge(struct sock *sk)
1578 struct sk_buff *skb;
1580 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1581 while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1582 sk_wmem_free_skb(sk, skb);
1584 tcp_clear_all_retrans_hints(tcp_sk(sk));
1587 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1589 return skb_peek(&sk->sk_write_queue);
1592 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1594 return skb_peek_tail(&sk->sk_write_queue);
1597 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1598 const struct sk_buff *skb)
1600 return skb_queue_next(&sk->sk_write_queue, skb);
1603 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1604 const struct sk_buff *skb)
1606 return skb_queue_prev(&sk->sk_write_queue, skb);
1609 #define tcp_for_write_queue(skb, sk) \
1610 skb_queue_walk(&(sk)->sk_write_queue, skb)
1612 #define tcp_for_write_queue_from(skb, sk) \
1613 skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1615 #define tcp_for_write_queue_from_safe(skb, tmp, sk) \
1616 skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1618 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1620 return sk->sk_send_head;
1623 static inline bool tcp_skb_is_last(const struct sock *sk,
1624 const struct sk_buff *skb)
1626 return skb_queue_is_last(&sk->sk_write_queue, skb);
1629 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1631 if (tcp_skb_is_last(sk, skb))
1632 sk->sk_send_head = NULL;
1634 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1637 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1639 if (sk->sk_send_head == skb_unlinked) {
1640 sk->sk_send_head = NULL;
1641 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1643 if (tcp_sk(sk)->highest_sack == skb_unlinked)
1644 tcp_sk(sk)->highest_sack = NULL;
1647 static inline void tcp_init_send_head(struct sock *sk)
1649 sk->sk_send_head = NULL;
1652 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1654 __skb_queue_tail(&sk->sk_write_queue, skb);
1657 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1659 __tcp_add_write_queue_tail(sk, skb);
1661 /* Queue it, remembering where we must start sending. */
1662 if (sk->sk_send_head == NULL) {
1663 sk->sk_send_head = skb;
1664 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
1666 if (tcp_sk(sk)->highest_sack == NULL)
1667 tcp_sk(sk)->highest_sack = skb;
1671 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1673 __skb_queue_head(&sk->sk_write_queue, skb);
1676 /* Insert buff after skb on the write queue of sk. */
1677 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1678 struct sk_buff *buff,
1681 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1684 /* Insert new before skb on the write queue of sk. */
1685 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1686 struct sk_buff *skb,
1689 __skb_queue_before(&sk->sk_write_queue, skb, new);
1691 if (sk->sk_send_head == skb)
1692 sk->sk_send_head = new;
1695 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1697 __skb_unlink(skb, &sk->sk_write_queue);
1700 static inline bool tcp_write_queue_empty(struct sock *sk)
1702 return skb_queue_empty(&sk->sk_write_queue);
1705 static inline void tcp_push_pending_frames(struct sock *sk)
1707 if (tcp_send_head(sk)) {
1708 struct tcp_sock *tp = tcp_sk(sk);
1710 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1714 /* Start sequence of the skb just after the highest skb with SACKed
1715 * bit, valid only if sacked_out > 0 or when the caller has ensured
1716 * validity by itself.
1718 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1720 if (!tp->sacked_out)
1723 if (tp->highest_sack == NULL)
1726 return TCP_SKB_CB(tp->highest_sack)->seq;
1729 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1731 tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1732 tcp_write_queue_next(sk, skb);
1735 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1737 return tcp_sk(sk)->highest_sack;
1740 static inline void tcp_highest_sack_reset(struct sock *sk)
1742 tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1745 /* Called when old skb is about to be deleted (to be combined with new skb) */
1746 static inline void tcp_highest_sack_combine(struct sock *sk,
1747 struct sk_buff *old,
1748 struct sk_buff *new)
1750 if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1751 tcp_sk(sk)->highest_sack = new;
1754 /* This helper checks if socket has IP_TRANSPARENT set */
1755 static inline bool inet_sk_transparent(const struct sock *sk)
1757 switch (sk->sk_state) {
1759 return inet_twsk(sk)->tw_transparent;
1760 case TCP_NEW_SYN_RECV:
1761 return inet_rsk(inet_reqsk(sk))->no_srccheck;
1763 return inet_sk(sk)->transparent;
1766 /* Determines whether this is a thin stream (which may suffer from
1767 * increased latency). Used to trigger latency-reducing mechanisms.
1769 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1771 return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1775 enum tcp_seq_states {
1776 TCP_SEQ_STATE_LISTENING,
1777 TCP_SEQ_STATE_ESTABLISHED,
1780 int tcp_seq_open(struct inode *inode, struct file *file);
1782 struct tcp_seq_afinfo {
1785 const struct file_operations *seq_fops;
1786 struct seq_operations seq_ops;
1789 struct tcp_iter_state {
1790 struct seq_net_private p;
1792 enum tcp_seq_states state;
1793 struct sock *syn_wait_sk;
1794 int bucket, offset, sbucket, num;
1798 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1799 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1801 extern struct request_sock_ops tcp_request_sock_ops;
1802 extern struct request_sock_ops tcp6_request_sock_ops;
1804 void tcp_v4_destroy_sock(struct sock *sk);
1806 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1807 netdev_features_t features);
1808 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1809 int tcp_gro_complete(struct sk_buff *skb);
1811 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1813 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1815 struct net *net = sock_net((struct sock *)tp);
1816 return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
1819 static inline bool tcp_stream_memory_free(const struct sock *sk)
1821 const struct tcp_sock *tp = tcp_sk(sk);
1822 u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1824 return notsent_bytes < tcp_notsent_lowat(tp);
1827 #ifdef CONFIG_PROC_FS
1828 int tcp4_proc_init(void);
1829 void tcp4_proc_exit(void);
1832 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1833 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1834 const struct tcp_request_sock_ops *af_ops,
1835 struct sock *sk, struct sk_buff *skb);
1837 /* TCP af-specific functions */
1838 struct tcp_sock_af_ops {
1839 #ifdef CONFIG_TCP_MD5SIG
1840 struct tcp_md5sig_key *(*md5_lookup) (const struct sock *sk,
1841 const struct sock *addr_sk);
1842 int (*calc_md5_hash)(char *location,
1843 const struct tcp_md5sig_key *md5,
1844 const struct sock *sk,
1845 const struct sk_buff *skb);
1846 int (*md5_parse)(struct sock *sk,
1847 char __user *optval,
1852 struct tcp_request_sock_ops {
1854 #ifdef CONFIG_TCP_MD5SIG
1855 struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1856 const struct sock *addr_sk);
1857 int (*calc_md5_hash) (char *location,
1858 const struct tcp_md5sig_key *md5,
1859 const struct sock *sk,
1860 const struct sk_buff *skb);
1862 void (*init_req)(struct request_sock *req,
1863 const struct sock *sk_listener,
1864 struct sk_buff *skb);
1865 #ifdef CONFIG_SYN_COOKIES
1866 __u32 (*cookie_init_seq)(const struct sk_buff *skb,
1869 struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1870 const struct request_sock *req);
1871 u32 (*init_seq)(const struct sk_buff *skb);
1872 u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
1873 int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1874 struct flowi *fl, struct request_sock *req,
1875 struct tcp_fastopen_cookie *foc,
1876 enum tcp_synack_type synack_type);
1879 #ifdef CONFIG_SYN_COOKIES
1880 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1881 const struct sock *sk, struct sk_buff *skb,
1884 tcp_synq_overflow(sk);
1885 __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1886 return ops->cookie_init_seq(skb, mss);
1889 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1890 const struct sock *sk, struct sk_buff *skb,
1897 int tcpv4_offload_init(void);
1899 void tcp_v4_init(void);
1900 void tcp_init(void);
1902 /* tcp_recovery.c */
1903 extern void tcp_rack_mark_lost(struct sock *sk);
1904 extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
1906 extern void tcp_rack_reo_timeout(struct sock *sk);
1909 * Save and compile IPv4 options, return a pointer to it
1911 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1913 const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1914 struct ip_options_rcu *dopt = NULL;
1917 int opt_size = sizeof(*dopt) + opt->optlen;
1919 dopt = kmalloc(opt_size, GFP_ATOMIC);
1920 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1928 /* locally generated TCP pure ACKs have skb->truesize == 2
1929 * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1930 * This is much faster than dissecting the packet to find out.
1931 * (Think of GRE encapsulations, IPv4, IPv6, ...)
1933 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1935 return skb->truesize == 2;
1938 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1943 static inline int tcp_inq(struct sock *sk)
1945 struct tcp_sock *tp = tcp_sk(sk);
1948 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
1950 } else if (sock_flag(sk, SOCK_URGINLINE) ||
1952 before(tp->urg_seq, tp->copied_seq) ||
1953 !before(tp->urg_seq, tp->rcv_nxt)) {
1955 answ = tp->rcv_nxt - tp->copied_seq;
1957 /* Subtract 1, if FIN was received */
1958 if (answ && sock_flag(sk, SOCK_DONE))
1961 answ = tp->urg_seq - tp->copied_seq;
1967 int tcp_peek_len(struct socket *sock);
1969 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
1973 segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
1974 tp->segs_in += segs_in;
1975 if (skb->len > tcp_hdrlen(skb))
1976 tp->data_segs_in += segs_in;
1980 * TCP listen path runs lockless.
1981 * We forced "struct sock" to be const qualified to make sure
1982 * we don't modify one of its field by mistake.
1983 * Here, we increment sk_drops which is an atomic_t, so we can safely
1984 * make sock writable again.
1986 static inline void tcp_listendrop(const struct sock *sk)
1988 atomic_inc(&((struct sock *)sk)->sk_drops);
1989 __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
1992 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);