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/crypto.h>
31 #include <linux/cryptohash.h>
32 #include <linux/kref.h>
33 #include <linux/ktime.h>
35 #include <net/inet_connection_sock.h>
36 #include <net/inet_timewait_sock.h>
37 #include <net/inet_hashtables.h>
38 #include <net/checksum.h>
39 #include <net/request_sock.h>
43 #include <net/tcp_states.h>
44 #include <net/inet_ecn.h>
47 #include <linux/seq_file.h>
48 #include <linux/memcontrol.h>
50 extern struct inet_hashinfo tcp_hashinfo;
52 extern struct percpu_counter tcp_orphan_count;
53 void tcp_time_wait(struct sock *sk, int state, int timeo);
55 #define MAX_TCP_HEADER (128 + MAX_HEADER)
56 #define MAX_TCP_OPTION_SPACE 40
59 * Never offer a window over 32767 without using window scaling. Some
60 * poor stacks do signed 16bit maths!
62 #define MAX_TCP_WINDOW 32767U
64 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
65 #define TCP_MIN_MSS 88U
67 /* The least MTU to use for probing */
68 #define TCP_BASE_MSS 1024
70 /* probing interval, default to 10 minutes as per RFC4821 */
71 #define TCP_PROBE_INTERVAL 600
73 /* Specify interval when tcp mtu probing will stop */
74 #define TCP_PROBE_THRESHOLD 8
76 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
77 #define TCP_FASTRETRANS_THRESH 3
79 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
80 #define TCP_MAX_QUICKACKS 16U
83 #define TCP_URG_VALID 0x0100
84 #define TCP_URG_NOTYET 0x0200
85 #define TCP_URG_READ 0x0400
87 #define TCP_RETR1 3 /*
88 * This is how many retries it does before it
89 * tries to figure out if the gateway is
90 * down. Minimal RFC value is 3; it corresponds
91 * to ~3sec-8min depending on RTO.
94 #define TCP_RETR2 15 /*
95 * This should take at least
96 * 90 minutes to time out.
97 * RFC1122 says that the limit is 100 sec.
98 * 15 is ~13-30min depending on RTO.
101 #define TCP_SYN_RETRIES 6 /* This is how many retries are done
102 * when active opening a connection.
103 * RFC1122 says the minimum retry MUST
104 * be at least 180secs. Nevertheless
105 * this value is corresponding to
106 * 63secs of retransmission with the
107 * current initial RTO.
110 #define TCP_SYNACK_RETRIES 5 /* This is how may retries are done
111 * when passive opening a connection.
112 * This is corresponding to 31secs of
113 * retransmission with the current
117 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
118 * state, about 60 seconds */
119 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
120 /* BSD style FIN_WAIT2 deadlock breaker.
121 * It used to be 3min, new value is 60sec,
122 * to combine FIN-WAIT-2 timeout with
126 #define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */
128 #define TCP_DELACK_MIN ((unsigned)(HZ/25)) /* minimal time to delay before sending an ACK */
129 #define TCP_ATO_MIN ((unsigned)(HZ/25))
131 #define TCP_DELACK_MIN 4U
132 #define TCP_ATO_MIN 4U
134 #define TCP_RTO_MAX ((unsigned)(120*HZ))
135 #define TCP_RTO_MIN ((unsigned)(HZ/5))
136 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ)) /* RFC6298 2.1 initial RTO value */
137 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
138 * used as a fallback RTO for the
139 * initial data transmission if no
140 * valid RTT sample has been acquired,
141 * most likely due to retrans in 3WHS.
144 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
145 * for local resources.
148 #define TCP_KEEPALIVE_TIME (120*60*HZ) /* two hours */
149 #define TCP_KEEPALIVE_PROBES 9 /* Max of 9 keepalive probes */
150 #define TCP_KEEPALIVE_INTVL (75*HZ)
152 #define MAX_TCP_KEEPIDLE 32767
153 #define MAX_TCP_KEEPINTVL 32767
154 #define MAX_TCP_KEEPCNT 127
155 #define MAX_TCP_SYNCNT 127
157 #define TCP_SYNQ_INTERVAL (HZ/5) /* Period of SYNACK timer */
159 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
160 #define TCP_PAWS_MSL 60 /* Per-host timestamps are invalidated
161 * after this time. It should be equal
162 * (or greater than) TCP_TIMEWAIT_LEN
163 * to provide reliability equal to one
164 * provided by timewait state.
166 #define TCP_PAWS_WINDOW 1 /* Replay window for per-host
167 * timestamps. It must be less than
168 * minimal timewait lifetime.
174 #define TCPOPT_NOP 1 /* Padding */
175 #define TCPOPT_EOL 0 /* End of options */
176 #define TCPOPT_MSS 2 /* Segment size negotiating */
177 #define TCPOPT_WINDOW 3 /* Window scaling */
178 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
179 #define TCPOPT_SACK 5 /* SACK Block */
180 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
181 #define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */
182 #define TCPOPT_FASTOPEN 34 /* Fast open (RFC7413) */
183 #define TCPOPT_EXP 254 /* Experimental */
184 /* Magic number to be after the option value for sharing TCP
185 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
187 #define TCPOPT_FASTOPEN_MAGIC 0xF989
193 #define TCPOLEN_MSS 4
194 #define TCPOLEN_WINDOW 3
195 #define TCPOLEN_SACK_PERM 2
196 #define TCPOLEN_TIMESTAMP 10
197 #define TCPOLEN_MD5SIG 18
198 #define TCPOLEN_FASTOPEN_BASE 2
199 #define TCPOLEN_EXP_FASTOPEN_BASE 4
201 /* But this is what stacks really send out. */
202 #define TCPOLEN_TSTAMP_ALIGNED 12
203 #define TCPOLEN_WSCALE_ALIGNED 4
204 #define TCPOLEN_SACKPERM_ALIGNED 4
205 #define TCPOLEN_SACK_BASE 2
206 #define TCPOLEN_SACK_BASE_ALIGNED 4
207 #define TCPOLEN_SACK_PERBLOCK 8
208 #define TCPOLEN_MD5SIG_ALIGNED 20
209 #define TCPOLEN_MSS_ALIGNED 4
211 /* Flags in tp->nonagle */
212 #define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
213 #define TCP_NAGLE_CORK 2 /* Socket is corked */
214 #define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */
216 /* TCP thin-stream limits */
217 #define TCP_THIN_LINEAR_RETRIES 6 /* After 6 linear retries, do exp. backoff */
219 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
220 #define TCP_INIT_CWND 10
222 /* Bit Flags for sysctl_tcp_fastopen */
223 #define TFO_CLIENT_ENABLE 1
224 #define TFO_SERVER_ENABLE 2
225 #define TFO_CLIENT_NO_COOKIE 4 /* Data in SYN w/o cookie option */
227 /* Accept SYN data w/o any cookie option */
228 #define TFO_SERVER_COOKIE_NOT_REQD 0x200
230 /* Force enable TFO on all listeners, i.e., not requiring the
231 * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
233 #define TFO_SERVER_WO_SOCKOPT1 0x400
234 #define TFO_SERVER_WO_SOCKOPT2 0x800
236 extern struct inet_timewait_death_row tcp_death_row;
238 /* sysctl variables for tcp */
239 extern int sysctl_tcp_timestamps;
240 extern int sysctl_tcp_window_scaling;
241 extern int sysctl_tcp_sack;
242 extern int sysctl_tcp_fin_timeout;
243 extern int sysctl_tcp_keepalive_intvl;
244 extern int sysctl_tcp_syn_retries;
245 extern int sysctl_tcp_synack_retries;
246 extern int sysctl_tcp_retries1;
247 extern int sysctl_tcp_retries2;
248 extern int sysctl_tcp_orphan_retries;
249 extern int sysctl_tcp_syncookies;
250 extern int sysctl_tcp_fastopen;
251 extern int sysctl_tcp_retrans_collapse;
252 extern int sysctl_tcp_stdurg;
253 extern int sysctl_tcp_rfc1337;
254 extern int sysctl_tcp_abort_on_overflow;
255 extern int sysctl_tcp_max_orphans;
256 extern int sysctl_tcp_fack;
257 extern int sysctl_tcp_reordering;
258 extern int sysctl_tcp_max_reordering;
259 extern int sysctl_tcp_dsack;
260 extern long sysctl_tcp_mem[3];
261 extern int sysctl_tcp_wmem[3];
262 extern int sysctl_tcp_rmem[3];
263 extern int sysctl_tcp_app_win;
264 extern int sysctl_tcp_adv_win_scale;
265 extern int sysctl_tcp_tw_reuse;
266 extern int sysctl_tcp_frto;
267 extern int sysctl_tcp_low_latency;
268 extern int sysctl_tcp_nometrics_save;
269 extern int sysctl_tcp_moderate_rcvbuf;
270 extern int sysctl_tcp_tso_win_divisor;
271 extern int sysctl_tcp_workaround_signed_windows;
272 extern int sysctl_tcp_slow_start_after_idle;
273 extern int sysctl_tcp_thin_linear_timeouts;
274 extern int sysctl_tcp_thin_dupack;
275 extern int sysctl_tcp_early_retrans;
276 extern int sysctl_tcp_limit_output_bytes;
277 extern int sysctl_tcp_challenge_ack_limit;
278 extern unsigned int sysctl_tcp_notsent_lowat;
279 extern int sysctl_tcp_min_tso_segs;
280 extern int sysctl_tcp_min_rtt_wlen;
281 extern int sysctl_tcp_autocorking;
282 extern int sysctl_tcp_invalid_ratelimit;
283 extern int sysctl_tcp_pacing_ss_ratio;
284 extern int sysctl_tcp_pacing_ca_ratio;
286 extern atomic_long_t tcp_memory_allocated;
287 extern struct percpu_counter tcp_sockets_allocated;
288 extern int tcp_memory_pressure;
290 /* optimized version of sk_under_memory_pressure() for TCP sockets */
291 static inline bool tcp_under_memory_pressure(const struct sock *sk)
293 if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
294 return !!sk->sk_cgrp->memory_pressure;
296 return tcp_memory_pressure;
299 * The next routines deal with comparing 32 bit unsigned ints
300 * and worry about wraparound (automatic with unsigned arithmetic).
303 static inline bool before(__u32 seq1, __u32 seq2)
305 return (__s32)(seq1-seq2) < 0;
307 #define after(seq2, seq1) before(seq1, seq2)
309 /* is s2<=s1<=s3 ? */
310 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
312 return seq3 - seq2 >= seq1 - seq2;
315 static inline bool tcp_out_of_memory(struct sock *sk)
317 if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
318 sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
323 void sk_forced_mem_schedule(struct sock *sk, int size);
325 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
327 struct percpu_counter *ocp = sk->sk_prot->orphan_count;
328 int orphans = percpu_counter_read_positive(ocp);
330 if (orphans << shift > sysctl_tcp_max_orphans) {
331 orphans = percpu_counter_sum_positive(ocp);
332 if (orphans << shift > sysctl_tcp_max_orphans)
338 bool tcp_check_oom(struct sock *sk, int shift);
341 extern struct proto tcp_prot;
343 #define TCP_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.tcp_statistics, field)
344 #define TCP_INC_STATS_BH(net, field) SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
345 #define TCP_DEC_STATS(net, field) SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
346 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
347 #define TCP_ADD_STATS(net, field, val) SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
349 void tcp_tasklet_init(void);
351 void tcp_v4_err(struct sk_buff *skb, u32);
353 void tcp_shutdown(struct sock *sk, int how);
355 void tcp_v4_early_demux(struct sk_buff *skb);
356 int tcp_v4_rcv(struct sk_buff *skb);
358 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
359 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
360 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
362 void tcp_release_cb(struct sock *sk);
363 void tcp_wfree(struct sk_buff *skb);
364 void tcp_write_timer_handler(struct sock *sk);
365 void tcp_delack_timer_handler(struct sock *sk);
366 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
367 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
368 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
369 const struct tcphdr *th, unsigned int len);
370 void tcp_rcv_space_adjust(struct sock *sk);
371 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
372 void tcp_twsk_destructor(struct sock *sk);
373 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
374 struct pipe_inode_info *pipe, size_t len,
377 static inline void tcp_dec_quickack_mode(struct sock *sk,
378 const unsigned int pkts)
380 struct inet_connection_sock *icsk = inet_csk(sk);
382 if (icsk->icsk_ack.quick) {
383 if (pkts >= icsk->icsk_ack.quick) {
384 icsk->icsk_ack.quick = 0;
385 /* Leaving quickack mode we deflate ATO. */
386 icsk->icsk_ack.ato = TCP_ATO_MIN;
388 icsk->icsk_ack.quick -= pkts;
393 #define TCP_ECN_QUEUE_CWR 2
394 #define TCP_ECN_DEMAND_CWR 4
395 #define TCP_ECN_SEEN 8
405 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
407 const struct tcphdr *th);
408 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
409 struct request_sock *req, bool fastopen);
410 int tcp_child_process(struct sock *parent, struct sock *child,
411 struct sk_buff *skb);
412 void tcp_enter_loss(struct sock *sk);
413 void tcp_clear_retrans(struct tcp_sock *tp);
414 void tcp_update_metrics(struct sock *sk);
415 void tcp_init_metrics(struct sock *sk);
416 void tcp_metrics_init(void);
417 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
418 bool paws_check, bool timestamps);
419 bool tcp_remember_stamp(struct sock *sk);
420 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
421 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
422 void tcp_disable_fack(struct tcp_sock *tp);
423 void tcp_close(struct sock *sk, long timeout);
424 void tcp_init_sock(struct sock *sk);
425 unsigned int tcp_poll(struct file *file, struct socket *sock,
426 struct poll_table_struct *wait);
427 int tcp_getsockopt(struct sock *sk, int level, int optname,
428 char __user *optval, int __user *optlen);
429 int tcp_setsockopt(struct sock *sk, int level, int optname,
430 char __user *optval, unsigned int optlen);
431 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
432 char __user *optval, int __user *optlen);
433 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
434 char __user *optval, unsigned int optlen);
435 void tcp_set_keepalive(struct sock *sk, int val);
436 void tcp_syn_ack_timeout(const struct request_sock *req);
437 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
438 int flags, int *addr_len);
439 void tcp_parse_options(const struct sk_buff *skb,
440 struct tcp_options_received *opt_rx,
441 int estab, struct tcp_fastopen_cookie *foc);
442 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
445 * TCP v4 functions exported for the inet6 API
448 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
449 void tcp_v4_mtu_reduced(struct sock *sk);
450 void tcp_req_err(struct sock *sk, u32 seq);
451 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
452 struct sock *tcp_create_openreq_child(const struct sock *sk,
453 struct request_sock *req,
454 struct sk_buff *skb);
455 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
456 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
457 struct request_sock *req,
458 struct dst_entry *dst,
459 struct request_sock *req_unhash,
461 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
462 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
463 int tcp_connect(struct sock *sk);
464 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
465 struct request_sock *req,
466 struct tcp_fastopen_cookie *foc,
468 int tcp_disconnect(struct sock *sk, int flags);
470 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
471 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
472 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
474 /* From syncookies.c */
475 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
476 struct request_sock *req,
477 struct dst_entry *dst);
478 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
480 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
481 #ifdef CONFIG_SYN_COOKIES
483 /* Syncookies use a monotonic timer which increments every 60 seconds.
484 * This counter is used both as a hash input and partially encoded into
485 * the cookie value. A cookie is only validated further if the delta
486 * between the current counter value and the encoded one is less than this,
487 * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
488 * the counter advances immediately after a cookie is generated).
490 #define MAX_SYNCOOKIE_AGE 2
491 #define TCP_SYNCOOKIE_PERIOD (60 * HZ)
492 #define TCP_SYNCOOKIE_VALID (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
494 /* syncookies: remember time of last synqueue overflow
495 * But do not dirty this field too often (once per second is enough)
496 * It is racy as we do not hold a lock, but race is very minor.
498 static inline void tcp_synq_overflow(const struct sock *sk)
500 unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
501 unsigned long now = jiffies;
503 if (time_after(now, last_overflow + HZ))
504 tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
507 /* syncookies: no recent synqueue overflow on this listening socket? */
508 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
510 unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
512 return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
515 static inline u32 tcp_cookie_time(void)
517 u64 val = get_jiffies_64();
519 do_div(val, TCP_SYNCOOKIE_PERIOD);
523 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
525 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
526 __u32 cookie_init_timestamp(struct request_sock *req);
527 bool cookie_timestamp_decode(struct tcp_options_received *opt);
528 bool cookie_ecn_ok(const struct tcp_options_received *opt,
529 const struct net *net, const struct dst_entry *dst);
531 /* From net/ipv6/syncookies.c */
532 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
534 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
536 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
537 const struct tcphdr *th, u16 *mssp);
538 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
542 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
544 bool tcp_may_send_now(struct sock *sk);
545 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
546 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
547 void tcp_retransmit_timer(struct sock *sk);
548 void tcp_xmit_retransmit_queue(struct sock *);
549 void tcp_simple_retransmit(struct sock *);
550 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
551 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
553 void tcp_send_probe0(struct sock *);
554 void tcp_send_partial(struct sock *);
555 int tcp_write_wakeup(struct sock *, int mib);
556 void tcp_send_fin(struct sock *sk);
557 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
558 int tcp_send_synack(struct sock *);
559 void tcp_push_one(struct sock *, unsigned int mss_now);
560 void tcp_send_ack(struct sock *sk);
561 void tcp_send_delayed_ack(struct sock *sk);
562 void tcp_send_loss_probe(struct sock *sk);
563 bool tcp_schedule_loss_probe(struct sock *sk);
566 void tcp_resume_early_retransmit(struct sock *sk);
567 void tcp_rearm_rto(struct sock *sk);
568 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
569 void tcp_reset(struct sock *sk);
570 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
573 void tcp_init_xmit_timers(struct sock *);
574 static inline void tcp_clear_xmit_timers(struct sock *sk)
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 >= 512)
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 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
610 unsigned int, size_t);
611 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
612 sk_read_actor_t recv_actor);
614 void tcp_initialize_rcv_mss(struct sock *sk);
616 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
617 int tcp_mss_to_mtu(struct sock *sk, int mss);
618 void tcp_mtup_init(struct sock *sk);
619 void tcp_init_buffer_space(struct sock *sk);
621 static inline void tcp_bound_rto(const struct sock *sk)
623 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
624 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
627 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
629 return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
632 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
634 tp->pred_flags = htonl((tp->tcp_header_len << 26) |
635 ntohl(TCP_FLAG_ACK) |
639 static inline void tcp_fast_path_on(struct tcp_sock *tp)
641 __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
644 static inline void tcp_fast_path_check(struct sock *sk)
646 struct tcp_sock *tp = tcp_sk(sk);
648 if (skb_queue_empty(&tp->out_of_order_queue) &&
650 atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
652 tcp_fast_path_on(tp);
655 /* Compute the actual rto_min value */
656 static inline u32 tcp_rto_min(struct sock *sk)
658 const struct dst_entry *dst = __sk_dst_get(sk);
659 u32 rto_min = TCP_RTO_MIN;
661 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
662 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
666 static inline u32 tcp_rto_min_us(struct sock *sk)
668 return jiffies_to_usecs(tcp_rto_min(sk));
671 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
673 return dst_metric_locked(dst, RTAX_CC_ALGO);
676 /* Minimum RTT in usec. ~0 means not available. */
677 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
679 return tp->rtt_min[0].rtt;
682 /* Compute the actual receive window we are currently advertising.
683 * Rcv_nxt can be after the window if our peer push more data
684 * than the offered window.
686 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
688 s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
695 /* Choose a new window, without checks for shrinking, and without
696 * scaling applied to the result. The caller does these things
697 * if necessary. This is a "raw" window selection.
699 u32 __tcp_select_window(struct sock *sk);
701 void tcp_send_window_probe(struct sock *sk);
703 /* TCP timestamps are only 32-bits, this causes a slight
704 * complication on 64-bit systems since we store a snapshot
705 * of jiffies in the buffer control blocks below. We decided
706 * to use only the low 32-bits of jiffies and hide the ugly
707 * casts with the following macro.
709 #define tcp_time_stamp ((__u32)(jiffies))
711 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
713 return skb->skb_mstamp.stamp_jiffies;
717 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
719 #define TCPHDR_FIN 0x01
720 #define TCPHDR_SYN 0x02
721 #define TCPHDR_RST 0x04
722 #define TCPHDR_PSH 0x08
723 #define TCPHDR_ACK 0x10
724 #define TCPHDR_URG 0x20
725 #define TCPHDR_ECE 0x40
726 #define TCPHDR_CWR 0x80
728 #define TCPHDR_SYN_ECN (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
730 /* This is what the send packet queuing engine uses to pass
731 * TCP per-packet control information to the transmission code.
732 * We also store the host-order sequence numbers in here too.
733 * This is 44 bytes if IPV6 is enabled.
734 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
737 __u32 seq; /* Starting sequence number */
738 __u32 end_seq; /* SEQ + FIN + SYN + datalen */
740 /* Note : tcp_tw_isn is used in input path only
741 * (isn chosen by tcp_timewait_state_process())
743 * tcp_gso_segs/size are used in write queue only,
744 * cf tcp_skb_pcount()/tcp_skb_mss()
752 __u8 tcp_flags; /* TCP header flags. (tcp[13]) */
754 __u8 sacked; /* State flags for SACK/FACK. */
755 #define TCPCB_SACKED_ACKED 0x01 /* SKB ACK'd by a SACK block */
756 #define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */
757 #define TCPCB_LOST 0x04 /* SKB is lost */
758 #define TCPCB_TAGBITS 0x07 /* All tag bits */
759 #define TCPCB_REPAIRED 0x10 /* SKB repaired (no skb_mstamp) */
760 #define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */
761 #define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
764 __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */
766 __u32 ack_seq; /* Sequence number ACK'd */
768 struct inet_skb_parm h4;
769 #if IS_ENABLED(CONFIG_IPV6)
770 struct inet6_skb_parm h6;
772 } header; /* For incoming frames */
775 #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
778 #if IS_ENABLED(CONFIG_IPV6)
779 /* This is the variant of inet6_iif() that must be used by TCP,
780 * as TCP moves IP6CB into a different location in skb->cb[]
782 static inline int tcp_v6_iif(const struct sk_buff *skb)
784 return TCP_SKB_CB(skb)->header.h6.iif;
788 /* Due to TSO, an SKB can be composed of multiple actual
789 * packets. To keep these tracked properly, we use this.
791 static inline int tcp_skb_pcount(const struct sk_buff *skb)
793 return TCP_SKB_CB(skb)->tcp_gso_segs;
796 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
798 TCP_SKB_CB(skb)->tcp_gso_segs = segs;
801 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
803 TCP_SKB_CB(skb)->tcp_gso_segs += segs;
806 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
807 static inline int tcp_skb_mss(const struct sk_buff *skb)
809 return TCP_SKB_CB(skb)->tcp_gso_size;
812 /* Events passed to congestion control interface */
814 CA_EVENT_TX_START, /* first transmit when no packets in flight */
815 CA_EVENT_CWND_RESTART, /* congestion window restart */
816 CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */
817 CA_EVENT_LOSS, /* loss timeout */
818 CA_EVENT_ECN_NO_CE, /* ECT set, but not CE marked */
819 CA_EVENT_ECN_IS_CE, /* received CE marked IP packet */
820 CA_EVENT_DELAYED_ACK, /* Delayed ack is sent */
821 CA_EVENT_NON_DELAYED_ACK,
824 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
825 enum tcp_ca_ack_event_flags {
826 CA_ACK_SLOWPATH = (1 << 0), /* In slow path processing */
827 CA_ACK_WIN_UPDATE = (1 << 1), /* ACK updated window */
828 CA_ACK_ECE = (1 << 2), /* ECE bit is set on ack */
832 * Interface for adding new TCP congestion control handlers
834 #define TCP_CA_NAME_MAX 16
835 #define TCP_CA_MAX 128
836 #define TCP_CA_BUF_MAX (TCP_CA_NAME_MAX*TCP_CA_MAX)
838 #define TCP_CA_UNSPEC 0
840 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
841 #define TCP_CONG_NON_RESTRICTED 0x1
842 /* Requires ECN/ECT set on all packets */
843 #define TCP_CONG_NEEDS_ECN 0x2
847 struct tcp_congestion_ops {
848 struct list_head list;
852 /* initialize private data (optional) */
853 void (*init)(struct sock *sk);
854 /* cleanup private data (optional) */
855 void (*release)(struct sock *sk);
857 /* return slow start threshold (required) */
858 u32 (*ssthresh)(struct sock *sk);
859 /* do new cwnd calculation (required) */
860 void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
861 /* call before changing ca_state (optional) */
862 void (*set_state)(struct sock *sk, u8 new_state);
863 /* call when cwnd event occurs (optional) */
864 void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
865 /* call when ack arrives (optional) */
866 void (*in_ack_event)(struct sock *sk, u32 flags);
867 /* new value of cwnd after loss (optional) */
868 u32 (*undo_cwnd)(struct sock *sk);
869 /* hook for packet ack accounting (optional) */
870 void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
871 /* get info for inet_diag (optional) */
872 size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
873 union tcp_cc_info *info);
875 char name[TCP_CA_NAME_MAX];
876 struct module *owner;
879 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
880 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
882 void tcp_assign_congestion_control(struct sock *sk);
883 void tcp_init_congestion_control(struct sock *sk);
884 void tcp_cleanup_congestion_control(struct sock *sk);
885 int tcp_set_default_congestion_control(const char *name);
886 void tcp_get_default_congestion_control(char *name);
887 void tcp_get_available_congestion_control(char *buf, size_t len);
888 void tcp_get_allowed_congestion_control(char *buf, size_t len);
889 int tcp_set_allowed_congestion_control(char *allowed);
890 int tcp_set_congestion_control(struct sock *sk, const char *name);
891 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
892 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
894 u32 tcp_reno_ssthresh(struct sock *sk);
895 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
896 extern struct tcp_congestion_ops tcp_reno;
898 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
899 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
901 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
903 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
909 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
911 const struct inet_connection_sock *icsk = inet_csk(sk);
913 return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
916 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
918 struct inet_connection_sock *icsk = inet_csk(sk);
920 if (icsk->icsk_ca_ops->set_state)
921 icsk->icsk_ca_ops->set_state(sk, ca_state);
922 icsk->icsk_ca_state = ca_state;
925 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
927 const struct inet_connection_sock *icsk = inet_csk(sk);
929 if (icsk->icsk_ca_ops->cwnd_event)
930 icsk->icsk_ca_ops->cwnd_event(sk, event);
933 /* These functions determine how the current flow behaves in respect of SACK
934 * handling. SACK is negotiated with the peer, and therefore it can vary
935 * between different flows.
937 * tcp_is_sack - SACK enabled
938 * tcp_is_reno - No SACK
939 * tcp_is_fack - FACK enabled, implies SACK enabled
941 static inline int tcp_is_sack(const struct tcp_sock *tp)
943 return tp->rx_opt.sack_ok;
946 static inline bool tcp_is_reno(const struct tcp_sock *tp)
948 return !tcp_is_sack(tp);
951 static inline bool tcp_is_fack(const struct tcp_sock *tp)
953 return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
956 static inline void tcp_enable_fack(struct tcp_sock *tp)
958 tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
961 /* TCP early-retransmit (ER) is similar to but more conservative than
962 * the thin-dupack feature. Enable ER only if thin-dupack is disabled.
964 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
966 tp->do_early_retrans = sysctl_tcp_early_retrans &&
967 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
968 sysctl_tcp_reordering == 3;
971 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
973 tp->do_early_retrans = 0;
976 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
978 return tp->sacked_out + tp->lost_out;
981 /* This determines how many packets are "in the network" to the best
982 * of our knowledge. In many cases it is conservative, but where
983 * detailed information is available from the receiver (via SACK
984 * blocks etc.) we can make more aggressive calculations.
986 * Use this for decisions involving congestion control, use just
987 * tp->packets_out to determine if the send queue is empty or not.
989 * Read this equation as:
991 * "Packets sent once on transmission queue" MINUS
992 * "Packets left network, but not honestly ACKed yet" PLUS
993 * "Packets fast retransmitted"
995 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
997 return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1000 #define TCP_INFINITE_SSTHRESH 0x7fffffff
1002 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1004 return tp->snd_cwnd < tp->snd_ssthresh;
1007 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1009 return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1012 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1014 return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1015 (1 << inet_csk(sk)->icsk_ca_state);
1018 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1019 * The exception is cwnd reduction phase, when cwnd is decreasing towards
1022 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1024 const struct tcp_sock *tp = tcp_sk(sk);
1026 if (tcp_in_cwnd_reduction(sk))
1027 return tp->snd_ssthresh;
1029 return max(tp->snd_ssthresh,
1030 ((tp->snd_cwnd >> 1) +
1031 (tp->snd_cwnd >> 2)));
1034 /* Use define here intentionally to get WARN_ON location shown at the caller */
1035 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1037 void tcp_enter_cwr(struct sock *sk);
1038 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1040 /* The maximum number of MSS of available cwnd for which TSO defers
1041 * sending if not using sysctl_tcp_tso_win_divisor.
1043 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1048 /* Slow start with delack produces 3 packets of burst, so that
1049 * it is safe "de facto". This will be the default - same as
1050 * the default reordering threshold - but if reordering increases,
1051 * we must be able to allow cwnd to burst at least this much in order
1052 * to not pull it back when holes are filled.
1054 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
1056 return tp->reordering;
1059 /* Returns end sequence number of the receiver's advertised window */
1060 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1062 return tp->snd_una + tp->snd_wnd;
1065 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1066 * flexible approach. The RFC suggests cwnd should not be raised unless
1067 * it was fully used previously. And that's exactly what we do in
1068 * congestion avoidance mode. But in slow start we allow cwnd to grow
1069 * as long as the application has used half the cwnd.
1071 * cwnd is 10 (IW10), but application sends 9 frames.
1072 * We allow cwnd to reach 18 when all frames are ACKed.
1073 * This check is safe because it's as aggressive as slow start which already
1074 * risks 100% overshoot. The advantage is that we discourage application to
1075 * either send more filler packets or data to artificially blow up the cwnd
1076 * usage, and allow application-limited process to probe bw more aggressively.
1078 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1080 const struct tcp_sock *tp = tcp_sk(sk);
1082 /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1083 if (tcp_in_slow_start(tp))
1084 return tp->snd_cwnd < 2 * tp->max_packets_out;
1086 return tp->is_cwnd_limited;
1089 /* Something is really bad, we could not queue an additional packet,
1090 * because qdisc is full or receiver sent a 0 window.
1091 * We do not want to add fuel to the fire, or abort too early,
1092 * so make sure the timer we arm now is at least 200ms in the future,
1093 * regardless of current icsk_rto value (as it could be ~2ms)
1095 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1097 return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1100 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1101 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1102 unsigned long max_when)
1104 u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1106 return (unsigned long)min_t(u64, when, max_when);
1109 static inline void tcp_check_probe_timer(struct sock *sk)
1111 if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1112 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1113 tcp_probe0_base(sk), TCP_RTO_MAX);
1116 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1121 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1127 * Calculate(/check) TCP checksum
1129 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1130 __be32 daddr, __wsum base)
1132 return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1135 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1137 return __skb_checksum_complete(skb);
1140 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1142 return !skb_csum_unnecessary(skb) &&
1143 __tcp_checksum_complete(skb);
1146 /* Prequeue for VJ style copy to user, combined with checksumming. */
1148 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1150 tp->ucopy.task = NULL;
1152 tp->ucopy.memory = 0;
1153 skb_queue_head_init(&tp->ucopy.prequeue);
1156 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1161 static const char *statename[]={
1162 "Unused","Established","Syn Sent","Syn Recv",
1163 "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1164 "Close Wait","Last ACK","Listen","Closing"
1167 void tcp_set_state(struct sock *sk, int state);
1169 void tcp_done(struct sock *sk);
1171 int tcp_abort(struct sock *sk, int err);
1173 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1176 rx_opt->num_sacks = 0;
1179 u32 tcp_default_init_rwnd(u32 mss);
1180 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1182 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1184 struct tcp_sock *tp = tcp_sk(sk);
1187 if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
1189 delta = tcp_time_stamp - tp->lsndtime;
1190 if (delta > inet_csk(sk)->icsk_rto)
1191 tcp_cwnd_restart(sk, delta);
1194 /* Determine a window scaling and initial window to offer. */
1195 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1196 __u32 *window_clamp, int wscale_ok,
1197 __u8 *rcv_wscale, __u32 init_rcv_wnd);
1199 static inline int tcp_win_from_space(int space)
1201 return sysctl_tcp_adv_win_scale<=0 ?
1202 (space>>(-sysctl_tcp_adv_win_scale)) :
1203 space - (space>>sysctl_tcp_adv_win_scale);
1206 /* Note: caller must be prepared to deal with negative returns */
1207 static inline int tcp_space(const struct sock *sk)
1209 return tcp_win_from_space(sk->sk_rcvbuf -
1210 atomic_read(&sk->sk_rmem_alloc));
1213 static inline int tcp_full_space(const struct sock *sk)
1215 return tcp_win_from_space(sk->sk_rcvbuf);
1218 extern void tcp_openreq_init_rwin(struct request_sock *req,
1219 const struct sock *sk_listener,
1220 const struct dst_entry *dst);
1222 void tcp_enter_memory_pressure(struct sock *sk);
1224 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1226 return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1229 static inline int keepalive_time_when(const struct tcp_sock *tp)
1231 struct net *net = sock_net((struct sock *)tp);
1233 return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1236 static inline int keepalive_probes(const struct tcp_sock *tp)
1238 struct net *net = sock_net((struct sock *)tp);
1240 return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1243 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1245 const struct inet_connection_sock *icsk = &tp->inet_conn;
1247 return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1248 tcp_time_stamp - tp->rcv_tstamp);
1251 static inline int tcp_fin_time(const struct sock *sk)
1253 int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1254 const int rto = inet_csk(sk)->icsk_rto;
1256 if (fin_timeout < (rto << 2) - (rto >> 1))
1257 fin_timeout = (rto << 2) - (rto >> 1);
1262 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1265 if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1267 if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1270 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1271 * then following tcp messages have valid values. Ignore 0 value,
1272 * or else 'negative' tsval might forbid us to accept their packets.
1274 if (!rx_opt->ts_recent)
1279 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1282 if (tcp_paws_check(rx_opt, 0))
1285 /* RST segments are not recommended to carry timestamp,
1286 and, if they do, it is recommended to ignore PAWS because
1287 "their cleanup function should take precedence over timestamps."
1288 Certainly, it is mistake. It is necessary to understand the reasons
1289 of this constraint to relax it: if peer reboots, clock may go
1290 out-of-sync and half-open connections will not be reset.
1291 Actually, the problem would be not existing if all
1292 the implementations followed draft about maintaining clock
1293 via reboots. Linux-2.2 DOES NOT!
1295 However, we can relax time bounds for RST segments to MSL.
1297 if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1302 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1303 int mib_idx, u32 *last_oow_ack_time);
1305 static inline void tcp_mib_init(struct net *net)
1308 TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1309 TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1310 TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1311 TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1315 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1317 tp->lost_skb_hint = NULL;
1320 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1322 tcp_clear_retrans_hints_partial(tp);
1323 tp->retransmit_skb_hint = NULL;
1329 union tcp_md5_addr {
1331 #if IS_ENABLED(CONFIG_IPV6)
1336 /* - key database */
1337 struct tcp_md5sig_key {
1338 struct hlist_node node;
1340 u8 family; /* AF_INET or AF_INET6 */
1341 union tcp_md5_addr addr;
1342 u8 key[TCP_MD5SIG_MAXKEYLEN];
1343 struct rcu_head rcu;
1347 struct tcp_md5sig_info {
1348 struct hlist_head head;
1349 struct rcu_head rcu;
1352 /* - pseudo header */
1353 struct tcp4_pseudohdr {
1361 struct tcp6_pseudohdr {
1362 struct in6_addr saddr;
1363 struct in6_addr daddr;
1365 __be32 protocol; /* including padding */
1368 union tcp_md5sum_block {
1369 struct tcp4_pseudohdr ip4;
1370 #if IS_ENABLED(CONFIG_IPV6)
1371 struct tcp6_pseudohdr ip6;
1375 /* - pool: digest algorithm, hash description and scratch buffer */
1376 struct tcp_md5sig_pool {
1377 struct hash_desc md5_desc;
1378 union tcp_md5sum_block md5_blk;
1382 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1383 const struct sock *sk, const struct sk_buff *skb);
1384 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1385 int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1386 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1388 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1389 const struct sock *addr_sk);
1391 #ifdef CONFIG_TCP_MD5SIG
1392 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1393 const union tcp_md5_addr *addr,
1395 #define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key)
1397 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1398 const union tcp_md5_addr *addr,
1403 #define tcp_twsk_md5_key(twsk) NULL
1406 bool tcp_alloc_md5sig_pool(void);
1408 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1409 static inline void tcp_put_md5sig_pool(void)
1414 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1415 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1416 unsigned int header_len);
1417 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1418 const struct tcp_md5sig_key *key);
1420 /* From tcp_fastopen.c */
1421 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1422 struct tcp_fastopen_cookie *cookie, int *syn_loss,
1423 unsigned long *last_syn_loss);
1424 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1425 struct tcp_fastopen_cookie *cookie, bool syn_lost,
1427 struct tcp_fastopen_request {
1428 /* Fast Open cookie. Size 0 means a cookie request */
1429 struct tcp_fastopen_cookie cookie;
1430 struct msghdr *data; /* data in MSG_FASTOPEN */
1432 int copied; /* queued in tcp_connect() */
1434 void tcp_free_fastopen_req(struct tcp_sock *tp);
1436 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1437 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1438 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1439 struct request_sock *req,
1440 struct tcp_fastopen_cookie *foc,
1441 struct dst_entry *dst);
1442 void tcp_fastopen_init_key_once(bool publish);
1443 #define TCP_FASTOPEN_KEY_LENGTH 16
1445 /* Fastopen key context */
1446 struct tcp_fastopen_context {
1447 struct crypto_cipher *tfm;
1448 __u8 key[TCP_FASTOPEN_KEY_LENGTH];
1449 struct rcu_head rcu;
1452 /* write queue abstraction */
1453 static inline void tcp_write_queue_purge(struct sock *sk)
1455 struct sk_buff *skb;
1457 while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1458 sk_wmem_free_skb(sk, skb);
1460 tcp_clear_all_retrans_hints(tcp_sk(sk));
1463 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1465 return skb_peek(&sk->sk_write_queue);
1468 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1470 return skb_peek_tail(&sk->sk_write_queue);
1473 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1474 const struct sk_buff *skb)
1476 return skb_queue_next(&sk->sk_write_queue, skb);
1479 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1480 const struct sk_buff *skb)
1482 return skb_queue_prev(&sk->sk_write_queue, skb);
1485 #define tcp_for_write_queue(skb, sk) \
1486 skb_queue_walk(&(sk)->sk_write_queue, skb)
1488 #define tcp_for_write_queue_from(skb, sk) \
1489 skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1491 #define tcp_for_write_queue_from_safe(skb, tmp, sk) \
1492 skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1494 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1496 return sk->sk_send_head;
1499 static inline bool tcp_skb_is_last(const struct sock *sk,
1500 const struct sk_buff *skb)
1502 return skb_queue_is_last(&sk->sk_write_queue, skb);
1505 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1507 if (tcp_skb_is_last(sk, skb))
1508 sk->sk_send_head = NULL;
1510 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1513 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1515 if (sk->sk_send_head == skb_unlinked)
1516 sk->sk_send_head = NULL;
1519 static inline void tcp_init_send_head(struct sock *sk)
1521 sk->sk_send_head = NULL;
1524 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1526 __skb_queue_tail(&sk->sk_write_queue, skb);
1529 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1531 __tcp_add_write_queue_tail(sk, skb);
1533 /* Queue it, remembering where we must start sending. */
1534 if (sk->sk_send_head == NULL) {
1535 sk->sk_send_head = skb;
1537 if (tcp_sk(sk)->highest_sack == NULL)
1538 tcp_sk(sk)->highest_sack = skb;
1542 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1544 __skb_queue_head(&sk->sk_write_queue, skb);
1547 /* Insert buff after skb on the write queue of sk. */
1548 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1549 struct sk_buff *buff,
1552 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1555 /* Insert new before skb on the write queue of sk. */
1556 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1557 struct sk_buff *skb,
1560 __skb_queue_before(&sk->sk_write_queue, skb, new);
1562 if (sk->sk_send_head == skb)
1563 sk->sk_send_head = new;
1566 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1568 __skb_unlink(skb, &sk->sk_write_queue);
1571 static inline bool tcp_write_queue_empty(struct sock *sk)
1573 return skb_queue_empty(&sk->sk_write_queue);
1576 static inline void tcp_push_pending_frames(struct sock *sk)
1578 if (tcp_send_head(sk)) {
1579 struct tcp_sock *tp = tcp_sk(sk);
1581 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1585 /* Start sequence of the skb just after the highest skb with SACKed
1586 * bit, valid only if sacked_out > 0 or when the caller has ensured
1587 * validity by itself.
1589 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1591 if (!tp->sacked_out)
1594 if (tp->highest_sack == NULL)
1597 return TCP_SKB_CB(tp->highest_sack)->seq;
1600 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1602 tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1603 tcp_write_queue_next(sk, skb);
1606 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1608 return tcp_sk(sk)->highest_sack;
1611 static inline void tcp_highest_sack_reset(struct sock *sk)
1613 tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1616 /* Called when old skb is about to be deleted (to be combined with new skb) */
1617 static inline void tcp_highest_sack_combine(struct sock *sk,
1618 struct sk_buff *old,
1619 struct sk_buff *new)
1621 if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1622 tcp_sk(sk)->highest_sack = new;
1625 /* This helper checks if socket has IP_TRANSPARENT set */
1626 static inline bool inet_sk_transparent(const struct sock *sk)
1628 switch (sk->sk_state) {
1630 return inet_twsk(sk)->tw_transparent;
1631 case TCP_NEW_SYN_RECV:
1632 return inet_rsk(inet_reqsk(sk))->no_srccheck;
1634 return inet_sk(sk)->transparent;
1637 /* Determines whether this is a thin stream (which may suffer from
1638 * increased latency). Used to trigger latency-reducing mechanisms.
1640 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1642 return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1646 enum tcp_seq_states {
1647 TCP_SEQ_STATE_LISTENING,
1648 TCP_SEQ_STATE_ESTABLISHED,
1651 int tcp_seq_open(struct inode *inode, struct file *file);
1653 struct tcp_seq_afinfo {
1656 const struct file_operations *seq_fops;
1657 struct seq_operations seq_ops;
1660 struct tcp_iter_state {
1661 struct seq_net_private p;
1663 enum tcp_seq_states state;
1664 struct sock *syn_wait_sk;
1665 int bucket, offset, sbucket, num;
1669 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1670 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1672 extern struct request_sock_ops tcp_request_sock_ops;
1673 extern struct request_sock_ops tcp6_request_sock_ops;
1675 void tcp_v4_destroy_sock(struct sock *sk);
1677 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1678 netdev_features_t features);
1679 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1680 int tcp_gro_complete(struct sk_buff *skb);
1682 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1684 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1686 return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1689 static inline bool tcp_stream_memory_free(const struct sock *sk)
1691 const struct tcp_sock *tp = tcp_sk(sk);
1692 u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1694 return notsent_bytes < tcp_notsent_lowat(tp);
1697 #ifdef CONFIG_PROC_FS
1698 int tcp4_proc_init(void);
1699 void tcp4_proc_exit(void);
1702 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1703 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1704 const struct tcp_request_sock_ops *af_ops,
1705 struct sock *sk, struct sk_buff *skb);
1707 /* TCP af-specific functions */
1708 struct tcp_sock_af_ops {
1709 #ifdef CONFIG_TCP_MD5SIG
1710 struct tcp_md5sig_key *(*md5_lookup) (const struct sock *sk,
1711 const struct sock *addr_sk);
1712 int (*calc_md5_hash)(char *location,
1713 const struct tcp_md5sig_key *md5,
1714 const struct sock *sk,
1715 const struct sk_buff *skb);
1716 int (*md5_parse)(struct sock *sk,
1717 char __user *optval,
1722 struct tcp_request_sock_ops {
1724 #ifdef CONFIG_TCP_MD5SIG
1725 struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1726 const struct sock *addr_sk);
1727 int (*calc_md5_hash) (char *location,
1728 const struct tcp_md5sig_key *md5,
1729 const struct sock *sk,
1730 const struct sk_buff *skb);
1732 void (*init_req)(struct request_sock *req,
1733 const struct sock *sk_listener,
1734 struct sk_buff *skb);
1735 #ifdef CONFIG_SYN_COOKIES
1736 __u32 (*cookie_init_seq)(const struct sk_buff *skb,
1739 struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1740 const struct request_sock *req,
1742 __u32 (*init_seq)(const struct sk_buff *skb);
1743 int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1744 struct flowi *fl, struct request_sock *req,
1745 struct tcp_fastopen_cookie *foc,
1749 #ifdef CONFIG_SYN_COOKIES
1750 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1751 const struct sock *sk, struct sk_buff *skb,
1754 tcp_synq_overflow(sk);
1755 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1756 return ops->cookie_init_seq(skb, mss);
1759 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1760 const struct sock *sk, struct sk_buff *skb,
1767 int tcpv4_offload_init(void);
1769 void tcp_v4_init(void);
1770 void tcp_init(void);
1772 /* tcp_recovery.c */
1774 /* Flags to enable various loss recovery features. See below */
1775 extern int sysctl_tcp_recovery;
1777 /* Use TCP RACK to detect (some) tail and retransmit losses */
1778 #define TCP_RACK_LOST_RETRANS 0x1
1780 extern int tcp_rack_mark_lost(struct sock *sk);
1782 extern void tcp_rack_advance(struct tcp_sock *tp,
1783 const struct skb_mstamp *xmit_time, u8 sacked);
1786 * Save and compile IPv4 options, return a pointer to it
1788 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1790 const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1791 struct ip_options_rcu *dopt = NULL;
1794 int opt_size = sizeof(*dopt) + opt->optlen;
1796 dopt = kmalloc(opt_size, GFP_ATOMIC);
1797 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1805 /* locally generated TCP pure ACKs have skb->truesize == 2
1806 * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1807 * This is much faster than dissecting the packet to find out.
1808 * (Think of GRE encapsulations, IPv4, IPv6, ...)
1810 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1812 return skb->truesize == 2;
1815 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)