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/dmaengine.h>
31 #include <linux/crypto.h>
32 #include <linux/cryptohash.h>
33 #include <linux/kref.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 extern 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 /* Offer an initial receive window of 10 mss. */
65 #define TCP_DEFAULT_INIT_RCVWND 10
67 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
68 #define TCP_MIN_MSS 88U
70 /* The least MTU to use for probing */
71 #define TCP_BASE_MSS 512
73 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
74 #define TCP_FASTRETRANS_THRESH 3
76 /* Maximal reordering. */
77 #define TCP_MAX_REORDERING 127
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 5 /* number of times to retry active opening a
102 * connection: ~180sec is RFC minimum */
104 #define TCP_SYNACK_RETRIES 5 /* number of times to retry passive opening a
105 * connection: ~180sec is RFC minimum */
107 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
108 * state, about 60 seconds */
109 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
110 /* BSD style FIN_WAIT2 deadlock breaker.
111 * It used to be 3min, new value is 60sec,
112 * to combine FIN-WAIT-2 timeout with
116 #define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */
118 #define TCP_DELACK_MIN ((unsigned)(HZ/25)) /* minimal time to delay before sending an ACK */
119 #define TCP_ATO_MIN ((unsigned)(HZ/25))
121 #define TCP_DELACK_MIN 4U
122 #define TCP_ATO_MIN 4U
124 #define TCP_RTO_MAX ((unsigned)(120*HZ))
125 #define TCP_RTO_MIN ((unsigned)(HZ/5))
126 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ)) /* RFC6298 2.1 initial RTO value */
127 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
128 * used as a fallback RTO for the
129 * initial data transmission if no
130 * valid RTT sample has been acquired,
131 * most likely due to retrans in 3WHS.
134 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
135 * for local resources.
138 #define TCP_KEEPALIVE_TIME (120*60*HZ) /* two hours */
139 #define TCP_KEEPALIVE_PROBES 9 /* Max of 9 keepalive probes */
140 #define TCP_KEEPALIVE_INTVL (75*HZ)
142 #define MAX_TCP_KEEPIDLE 32767
143 #define MAX_TCP_KEEPINTVL 32767
144 #define MAX_TCP_KEEPCNT 127
145 #define MAX_TCP_SYNCNT 127
147 #define TCP_SYNQ_INTERVAL (HZ/5) /* Period of SYNACK timer */
149 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
150 #define TCP_PAWS_MSL 60 /* Per-host timestamps are invalidated
151 * after this time. It should be equal
152 * (or greater than) TCP_TIMEWAIT_LEN
153 * to provide reliability equal to one
154 * provided by timewait state.
156 #define TCP_PAWS_WINDOW 1 /* Replay window for per-host
157 * timestamps. It must be less than
158 * minimal timewait lifetime.
164 #define TCPOPT_NOP 1 /* Padding */
165 #define TCPOPT_EOL 0 /* End of options */
166 #define TCPOPT_MSS 2 /* Segment size negotiating */
167 #define TCPOPT_WINDOW 3 /* Window scaling */
168 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
169 #define TCPOPT_SACK 5 /* SACK Block */
170 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
171 #define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */
172 #define TCPOPT_COOKIE 253 /* Cookie extension (experimental) */
178 #define TCPOLEN_MSS 4
179 #define TCPOLEN_WINDOW 3
180 #define TCPOLEN_SACK_PERM 2
181 #define TCPOLEN_TIMESTAMP 10
182 #define TCPOLEN_MD5SIG 18
183 #define TCPOLEN_COOKIE_BASE 2 /* Cookie-less header extension */
184 #define TCPOLEN_COOKIE_PAIR 3 /* Cookie pair header extension */
185 #define TCPOLEN_COOKIE_MIN (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MIN)
186 #define TCPOLEN_COOKIE_MAX (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MAX)
188 /* But this is what stacks really send out. */
189 #define TCPOLEN_TSTAMP_ALIGNED 12
190 #define TCPOLEN_WSCALE_ALIGNED 4
191 #define TCPOLEN_SACKPERM_ALIGNED 4
192 #define TCPOLEN_SACK_BASE 2
193 #define TCPOLEN_SACK_BASE_ALIGNED 4
194 #define TCPOLEN_SACK_PERBLOCK 8
195 #define TCPOLEN_MD5SIG_ALIGNED 20
196 #define TCPOLEN_MSS_ALIGNED 4
198 /* Flags in tp->nonagle */
199 #define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */
200 #define TCP_NAGLE_CORK 2 /* Socket is corked */
201 #define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */
203 /* TCP thin-stream limits */
204 #define TCP_THIN_LINEAR_RETRIES 6 /* After 6 linear retries, do exp. backoff */
206 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
207 #define TCP_INIT_CWND 10
209 extern struct inet_timewait_death_row tcp_death_row;
211 /* sysctl variables for tcp */
212 extern int sysctl_tcp_timestamps;
213 extern int sysctl_tcp_window_scaling;
214 extern int sysctl_tcp_sack;
215 extern int sysctl_tcp_fin_timeout;
216 extern int sysctl_tcp_keepalive_time;
217 extern int sysctl_tcp_keepalive_probes;
218 extern int sysctl_tcp_keepalive_intvl;
219 extern int sysctl_tcp_syn_retries;
220 extern int sysctl_tcp_synack_retries;
221 extern int sysctl_tcp_retries1;
222 extern int sysctl_tcp_retries2;
223 extern int sysctl_tcp_orphan_retries;
224 extern int sysctl_tcp_syncookies;
225 extern int sysctl_tcp_retrans_collapse;
226 extern int sysctl_tcp_stdurg;
227 extern int sysctl_tcp_rfc1337;
228 extern int sysctl_tcp_abort_on_overflow;
229 extern int sysctl_tcp_max_orphans;
230 extern int sysctl_tcp_fack;
231 extern int sysctl_tcp_reordering;
232 extern int sysctl_tcp_ecn;
233 extern int sysctl_tcp_dsack;
234 extern int sysctl_tcp_wmem[3];
235 extern int sysctl_tcp_rmem[3];
236 extern int sysctl_tcp_app_win;
237 extern int sysctl_tcp_adv_win_scale;
238 extern int sysctl_tcp_tw_reuse;
239 extern int sysctl_tcp_frto;
240 extern int sysctl_tcp_frto_response;
241 extern int sysctl_tcp_low_latency;
242 extern int sysctl_tcp_dma_copybreak;
243 extern int sysctl_tcp_nometrics_save;
244 extern int sysctl_tcp_moderate_rcvbuf;
245 extern int sysctl_tcp_tso_win_divisor;
246 extern int sysctl_tcp_abc;
247 extern int sysctl_tcp_mtu_probing;
248 extern int sysctl_tcp_base_mss;
249 extern int sysctl_tcp_workaround_signed_windows;
250 extern int sysctl_tcp_slow_start_after_idle;
251 extern int sysctl_tcp_max_ssthresh;
252 extern int sysctl_tcp_cookie_size;
253 extern int sysctl_tcp_thin_linear_timeouts;
254 extern int sysctl_tcp_thin_dupack;
255 extern int sysctl_tcp_early_retrans;
257 extern atomic_long_t tcp_memory_allocated;
258 extern struct percpu_counter tcp_sockets_allocated;
259 extern int tcp_memory_pressure;
262 * The next routines deal with comparing 32 bit unsigned ints
263 * and worry about wraparound (automatic with unsigned arithmetic).
266 static inline bool before(__u32 seq1, __u32 seq2)
268 return (__s32)(seq1-seq2) < 0;
270 #define after(seq2, seq1) before(seq1, seq2)
272 /* is s2<=s1<=s3 ? */
273 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
275 return seq3 - seq2 >= seq1 - seq2;
278 static inline bool tcp_out_of_memory(struct sock *sk)
280 if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
281 sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
286 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
288 struct percpu_counter *ocp = sk->sk_prot->orphan_count;
289 int orphans = percpu_counter_read_positive(ocp);
291 if (orphans << shift > sysctl_tcp_max_orphans) {
292 orphans = percpu_counter_sum_positive(ocp);
293 if (orphans << shift > sysctl_tcp_max_orphans)
299 extern bool tcp_check_oom(struct sock *sk, int shift);
301 /* syncookies: remember time of last synqueue overflow */
302 static inline void tcp_synq_overflow(struct sock *sk)
304 tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
307 /* syncookies: no recent synqueue overflow on this listening socket? */
308 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
310 unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
311 return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
314 extern struct proto tcp_prot;
316 #define TCP_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.tcp_statistics, field)
317 #define TCP_INC_STATS_BH(net, field) SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
318 #define TCP_DEC_STATS(net, field) SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
319 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
320 #define TCP_ADD_STATS(net, field, val) SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
322 extern void tcp_init_mem(struct net *net);
324 extern void tcp_v4_err(struct sk_buff *skb, u32);
326 extern void tcp_shutdown (struct sock *sk, int how);
328 extern void tcp_v4_early_demux(struct sk_buff *skb);
329 extern int tcp_v4_rcv(struct sk_buff *skb);
331 extern struct inet_peer *tcp_v4_get_peer(struct sock *sk);
332 extern int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
333 extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
335 extern int tcp_sendpage(struct sock *sk, struct page *page, int offset,
336 size_t size, int flags);
337 extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
338 extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
339 const struct tcphdr *th, unsigned int len);
340 extern int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
341 const struct tcphdr *th, unsigned int len);
342 extern void tcp_rcv_space_adjust(struct sock *sk);
343 extern void tcp_cleanup_rbuf(struct sock *sk, int copied);
344 extern int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
345 extern void tcp_twsk_destructor(struct sock *sk);
346 extern ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
347 struct pipe_inode_info *pipe, size_t len,
350 static inline void tcp_dec_quickack_mode(struct sock *sk,
351 const unsigned int pkts)
353 struct inet_connection_sock *icsk = inet_csk(sk);
355 if (icsk->icsk_ack.quick) {
356 if (pkts >= icsk->icsk_ack.quick) {
357 icsk->icsk_ack.quick = 0;
358 /* Leaving quickack mode we deflate ATO. */
359 icsk->icsk_ack.ato = TCP_ATO_MIN;
361 icsk->icsk_ack.quick -= pkts;
366 #define TCP_ECN_QUEUE_CWR 2
367 #define TCP_ECN_DEMAND_CWR 4
368 #define TCP_ECN_SEEN 8
378 extern enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
380 const struct tcphdr *th);
381 extern struct sock * tcp_check_req(struct sock *sk,struct sk_buff *skb,
382 struct request_sock *req,
383 struct request_sock **prev);
384 extern int tcp_child_process(struct sock *parent, struct sock *child,
385 struct sk_buff *skb);
386 extern bool tcp_use_frto(struct sock *sk);
387 extern void tcp_enter_frto(struct sock *sk);
388 extern void tcp_enter_loss(struct sock *sk, int how);
389 extern void tcp_clear_retrans(struct tcp_sock *tp);
390 extern void tcp_update_metrics(struct sock *sk);
391 extern void tcp_init_metrics(struct sock *sk);
392 extern bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
393 extern void tcp_disable_fack(struct tcp_sock *tp);
394 extern void tcp_close(struct sock *sk, long timeout);
395 extern void tcp_init_sock(struct sock *sk);
396 extern unsigned int tcp_poll(struct file * file, struct socket *sock,
397 struct poll_table_struct *wait);
398 extern int tcp_getsockopt(struct sock *sk, int level, int optname,
399 char __user *optval, int __user *optlen);
400 extern int tcp_setsockopt(struct sock *sk, int level, int optname,
401 char __user *optval, unsigned int optlen);
402 extern int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
403 char __user *optval, int __user *optlen);
404 extern int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
405 char __user *optval, unsigned int optlen);
406 extern void tcp_set_keepalive(struct sock *sk, int val);
407 extern void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
408 extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
409 size_t len, int nonblock, int flags, int *addr_len);
410 extern void tcp_parse_options(const struct sk_buff *skb,
411 struct tcp_options_received *opt_rx, const u8 **hvpp,
413 extern const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
416 * TCP v4 functions exported for the inet6 API
419 extern void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
420 extern int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
421 extern struct sock * tcp_create_openreq_child(struct sock *sk,
422 struct request_sock *req,
423 struct sk_buff *skb);
424 extern struct sock * tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
425 struct request_sock *req,
426 struct dst_entry *dst);
427 extern int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
428 extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
430 extern int tcp_connect(struct sock *sk);
431 extern struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
432 struct request_sock *req,
433 struct request_values *rvp);
434 extern int tcp_disconnect(struct sock *sk, int flags);
436 void tcp_connect_init(struct sock *sk);
437 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
438 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
440 /* From syncookies.c */
441 extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
442 extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
443 struct ip_options *opt);
444 #ifdef CONFIG_SYN_COOKIES
445 extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb,
448 static inline __u32 cookie_v4_init_sequence(struct sock *sk,
456 extern __u32 cookie_init_timestamp(struct request_sock *req);
457 extern bool cookie_check_timestamp(struct tcp_options_received *opt, bool *);
459 /* From net/ipv6/syncookies.c */
460 extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
461 #ifdef CONFIG_SYN_COOKIES
462 extern __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
465 static inline __u32 cookie_v6_init_sequence(struct sock *sk,
474 extern void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
476 extern bool tcp_may_send_now(struct sock *sk);
477 extern int tcp_retransmit_skb(struct sock *, struct sk_buff *);
478 extern void tcp_retransmit_timer(struct sock *sk);
479 extern void tcp_xmit_retransmit_queue(struct sock *);
480 extern void tcp_simple_retransmit(struct sock *);
481 extern int tcp_trim_head(struct sock *, struct sk_buff *, u32);
482 extern int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);
484 extern void tcp_send_probe0(struct sock *);
485 extern void tcp_send_partial(struct sock *);
486 extern int tcp_write_wakeup(struct sock *);
487 extern void tcp_send_fin(struct sock *sk);
488 extern void tcp_send_active_reset(struct sock *sk, gfp_t priority);
489 extern int tcp_send_synack(struct sock *);
490 extern bool tcp_syn_flood_action(struct sock *sk,
491 const struct sk_buff *skb,
493 extern void tcp_push_one(struct sock *, unsigned int mss_now);
494 extern void tcp_send_ack(struct sock *sk);
495 extern void tcp_send_delayed_ack(struct sock *sk);
498 extern void tcp_cwnd_application_limited(struct sock *sk);
499 extern void tcp_resume_early_retransmit(struct sock *sk);
500 extern void tcp_rearm_rto(struct sock *sk);
503 extern void tcp_init_xmit_timers(struct sock *);
504 static inline void tcp_clear_xmit_timers(struct sock *sk)
506 inet_csk_clear_xmit_timers(sk);
509 extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
510 extern unsigned int tcp_current_mss(struct sock *sk);
512 /* Bound MSS / TSO packet size with the half of the window */
513 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
517 /* When peer uses tiny windows, there is no use in packetizing
518 * to sub-MSS pieces for the sake of SWS or making sure there
519 * are enough packets in the pipe for fast recovery.
521 * On the other hand, for extremely large MSS devices, handling
522 * smaller than MSS windows in this way does make sense.
524 if (tp->max_window >= 512)
525 cutoff = (tp->max_window >> 1);
527 cutoff = tp->max_window;
529 if (cutoff && pktsize > cutoff)
530 return max_t(int, cutoff, 68U - tp->tcp_header_len);
536 extern void tcp_get_info(const struct sock *, struct tcp_info *);
538 /* Read 'sendfile()'-style from a TCP socket */
539 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
540 unsigned int, size_t);
541 extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
542 sk_read_actor_t recv_actor);
544 extern void tcp_initialize_rcv_mss(struct sock *sk);
546 extern int tcp_mtu_to_mss(struct sock *sk, int pmtu);
547 extern int tcp_mss_to_mtu(struct sock *sk, int mss);
548 extern void tcp_mtup_init(struct sock *sk);
549 extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt);
551 static inline void tcp_bound_rto(const struct sock *sk)
553 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
554 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
557 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
559 return (tp->srtt >> 3) + tp->rttvar;
562 extern void tcp_set_rto(struct sock *sk);
564 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
566 tp->pred_flags = htonl((tp->tcp_header_len << 26) |
567 ntohl(TCP_FLAG_ACK) |
571 static inline void tcp_fast_path_on(struct tcp_sock *tp)
573 __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
576 static inline void tcp_fast_path_check(struct sock *sk)
578 struct tcp_sock *tp = tcp_sk(sk);
580 if (skb_queue_empty(&tp->out_of_order_queue) &&
582 atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
584 tcp_fast_path_on(tp);
587 /* Compute the actual rto_min value */
588 static inline u32 tcp_rto_min(struct sock *sk)
590 const struct dst_entry *dst = __sk_dst_get(sk);
591 u32 rto_min = TCP_RTO_MIN;
593 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
594 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
598 /* Compute the actual receive window we are currently advertising.
599 * Rcv_nxt can be after the window if our peer push more data
600 * than the offered window.
602 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
604 s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
611 /* Choose a new window, without checks for shrinking, and without
612 * scaling applied to the result. The caller does these things
613 * if necessary. This is a "raw" window selection.
615 extern u32 __tcp_select_window(struct sock *sk);
617 void tcp_send_window_probe(struct sock *sk);
619 /* TCP timestamps are only 32-bits, this causes a slight
620 * complication on 64-bit systems since we store a snapshot
621 * of jiffies in the buffer control blocks below. We decided
622 * to use only the low 32-bits of jiffies and hide the ugly
623 * casts with the following macro.
625 #define tcp_time_stamp ((__u32)(jiffies))
627 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
629 #define TCPHDR_FIN 0x01
630 #define TCPHDR_SYN 0x02
631 #define TCPHDR_RST 0x04
632 #define TCPHDR_PSH 0x08
633 #define TCPHDR_ACK 0x10
634 #define TCPHDR_URG 0x20
635 #define TCPHDR_ECE 0x40
636 #define TCPHDR_CWR 0x80
638 /* This is what the send packet queuing engine uses to pass
639 * TCP per-packet control information to the transmission code.
640 * We also store the host-order sequence numbers in here too.
641 * This is 44 bytes if IPV6 is enabled.
642 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
646 struct inet_skb_parm h4;
647 #if IS_ENABLED(CONFIG_IPV6)
648 struct inet6_skb_parm h6;
650 } header; /* For incoming frames */
651 __u32 seq; /* Starting sequence number */
652 __u32 end_seq; /* SEQ + FIN + SYN + datalen */
653 __u32 when; /* used to compute rtt's */
654 __u8 tcp_flags; /* TCP header flags. (tcp[13]) */
656 __u8 sacked; /* State flags for SACK/FACK. */
657 #define TCPCB_SACKED_ACKED 0x01 /* SKB ACK'd by a SACK block */
658 #define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */
659 #define TCPCB_LOST 0x04 /* SKB is lost */
660 #define TCPCB_TAGBITS 0x07 /* All tag bits */
661 #define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */
662 #define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
664 __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */
666 __u32 ack_seq; /* Sequence number ACK'd */
669 #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
671 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
673 * If we receive a SYN packet with these bits set, it means a network is
674 * playing bad games with TOS bits. In order to avoid possible false congestion
675 * notifications, we disable TCP ECN negociation.
678 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb)
680 const struct tcphdr *th = tcp_hdr(skb);
682 if (sysctl_tcp_ecn && th->ece && th->cwr &&
683 INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
684 inet_rsk(req)->ecn_ok = 1;
687 /* Due to TSO, an SKB can be composed of multiple actual
688 * packets. To keep these tracked properly, we use this.
690 static inline int tcp_skb_pcount(const struct sk_buff *skb)
692 return skb_shinfo(skb)->gso_segs;
695 /* This is valid iff tcp_skb_pcount() > 1. */
696 static inline int tcp_skb_mss(const struct sk_buff *skb)
698 return skb_shinfo(skb)->gso_size;
701 /* Events passed to congestion control interface */
703 CA_EVENT_TX_START, /* first transmit when no packets in flight */
704 CA_EVENT_CWND_RESTART, /* congestion window restart */
705 CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */
706 CA_EVENT_FRTO, /* fast recovery timeout */
707 CA_EVENT_LOSS, /* loss timeout */
708 CA_EVENT_FAST_ACK, /* in sequence ack */
709 CA_EVENT_SLOW_ACK, /* other ack */
713 * Interface for adding new TCP congestion control handlers
715 #define TCP_CA_NAME_MAX 16
716 #define TCP_CA_MAX 128
717 #define TCP_CA_BUF_MAX (TCP_CA_NAME_MAX*TCP_CA_MAX)
719 #define TCP_CONG_NON_RESTRICTED 0x1
720 #define TCP_CONG_RTT_STAMP 0x2
722 struct tcp_congestion_ops {
723 struct list_head list;
726 /* initialize private data (optional) */
727 void (*init)(struct sock *sk);
728 /* cleanup private data (optional) */
729 void (*release)(struct sock *sk);
731 /* return slow start threshold (required) */
732 u32 (*ssthresh)(struct sock *sk);
733 /* lower bound for congestion window (optional) */
734 u32 (*min_cwnd)(const struct sock *sk);
735 /* do new cwnd calculation (required) */
736 void (*cong_avoid)(struct sock *sk, u32 ack, u32 in_flight);
737 /* call before changing ca_state (optional) */
738 void (*set_state)(struct sock *sk, u8 new_state);
739 /* call when cwnd event occurs (optional) */
740 void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
741 /* new value of cwnd after loss (optional) */
742 u32 (*undo_cwnd)(struct sock *sk);
743 /* hook for packet ack accounting (optional) */
744 void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
745 /* get info for inet_diag (optional) */
746 void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
748 char name[TCP_CA_NAME_MAX];
749 struct module *owner;
752 extern int tcp_register_congestion_control(struct tcp_congestion_ops *type);
753 extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
755 extern void tcp_init_congestion_control(struct sock *sk);
756 extern void tcp_cleanup_congestion_control(struct sock *sk);
757 extern int tcp_set_default_congestion_control(const char *name);
758 extern void tcp_get_default_congestion_control(char *name);
759 extern void tcp_get_available_congestion_control(char *buf, size_t len);
760 extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
761 extern int tcp_set_allowed_congestion_control(char *allowed);
762 extern int tcp_set_congestion_control(struct sock *sk, const char *name);
763 extern void tcp_slow_start(struct tcp_sock *tp);
764 extern void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
766 extern struct tcp_congestion_ops tcp_init_congestion_ops;
767 extern u32 tcp_reno_ssthresh(struct sock *sk);
768 extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight);
769 extern u32 tcp_reno_min_cwnd(const struct sock *sk);
770 extern struct tcp_congestion_ops tcp_reno;
772 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
774 struct inet_connection_sock *icsk = inet_csk(sk);
776 if (icsk->icsk_ca_ops->set_state)
777 icsk->icsk_ca_ops->set_state(sk, ca_state);
778 icsk->icsk_ca_state = ca_state;
781 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
783 const struct inet_connection_sock *icsk = inet_csk(sk);
785 if (icsk->icsk_ca_ops->cwnd_event)
786 icsk->icsk_ca_ops->cwnd_event(sk, event);
789 /* These functions determine how the current flow behaves in respect of SACK
790 * handling. SACK is negotiated with the peer, and therefore it can vary
791 * between different flows.
793 * tcp_is_sack - SACK enabled
794 * tcp_is_reno - No SACK
795 * tcp_is_fack - FACK enabled, implies SACK enabled
797 static inline int tcp_is_sack(const struct tcp_sock *tp)
799 return tp->rx_opt.sack_ok;
802 static inline bool tcp_is_reno(const struct tcp_sock *tp)
804 return !tcp_is_sack(tp);
807 static inline bool tcp_is_fack(const struct tcp_sock *tp)
809 return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
812 static inline void tcp_enable_fack(struct tcp_sock *tp)
814 tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
817 /* TCP early-retransmit (ER) is similar to but more conservative than
818 * the thin-dupack feature. Enable ER only if thin-dupack is disabled.
820 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
822 tp->do_early_retrans = sysctl_tcp_early_retrans &&
823 !sysctl_tcp_thin_dupack && sysctl_tcp_reordering == 3;
824 tp->early_retrans_delayed = 0;
827 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
829 tp->do_early_retrans = 0;
832 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
834 return tp->sacked_out + tp->lost_out;
837 /* This determines how many packets are "in the network" to the best
838 * of our knowledge. In many cases it is conservative, but where
839 * detailed information is available from the receiver (via SACK
840 * blocks etc.) we can make more aggressive calculations.
842 * Use this for decisions involving congestion control, use just
843 * tp->packets_out to determine if the send queue is empty or not.
845 * Read this equation as:
847 * "Packets sent once on transmission queue" MINUS
848 * "Packets left network, but not honestly ACKed yet" PLUS
849 * "Packets fast retransmitted"
851 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
853 return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
856 #define TCP_INFINITE_SSTHRESH 0x7fffffff
858 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
860 return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
863 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
864 * The exception is rate halving phase, when cwnd is decreasing towards
867 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
869 const struct tcp_sock *tp = tcp_sk(sk);
871 if ((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_CWR | TCPF_CA_Recovery))
872 return tp->snd_ssthresh;
874 return max(tp->snd_ssthresh,
875 ((tp->snd_cwnd >> 1) +
876 (tp->snd_cwnd >> 2)));
879 /* Use define here intentionally to get WARN_ON location shown at the caller */
880 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
882 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
883 extern __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
885 /* The maximum number of MSS of available cwnd for which TSO defers
886 * sending if not using sysctl_tcp_tso_win_divisor.
888 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
893 /* Slow start with delack produces 3 packets of burst, so that
894 * it is safe "de facto". This will be the default - same as
895 * the default reordering threshold - but if reordering increases,
896 * we must be able to allow cwnd to burst at least this much in order
897 * to not pull it back when holes are filled.
899 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
901 return tp->reordering;
904 /* Returns end sequence number of the receiver's advertised window */
905 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
907 return tp->snd_una + tp->snd_wnd;
909 extern bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
911 static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss,
912 const struct sk_buff *skb)
915 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
918 static inline void tcp_check_probe_timer(struct sock *sk)
920 const struct tcp_sock *tp = tcp_sk(sk);
921 const struct inet_connection_sock *icsk = inet_csk(sk);
923 if (!tp->packets_out && !icsk->icsk_pending)
924 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
925 icsk->icsk_rto, TCP_RTO_MAX);
928 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
933 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
939 * Calculate(/check) TCP checksum
941 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
942 __be32 daddr, __wsum base)
944 return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
947 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
949 return __skb_checksum_complete(skb);
952 static inline bool tcp_checksum_complete(struct sk_buff *skb)
954 return !skb_csum_unnecessary(skb) &&
955 __tcp_checksum_complete(skb);
958 /* Prequeue for VJ style copy to user, combined with checksumming. */
960 static inline void tcp_prequeue_init(struct tcp_sock *tp)
962 tp->ucopy.task = NULL;
964 tp->ucopy.memory = 0;
965 skb_queue_head_init(&tp->ucopy.prequeue);
966 #ifdef CONFIG_NET_DMA
967 tp->ucopy.dma_chan = NULL;
968 tp->ucopy.wakeup = 0;
969 tp->ucopy.pinned_list = NULL;
970 tp->ucopy.dma_cookie = 0;
974 /* Packet is added to VJ-style prequeue for processing in process
975 * context, if a reader task is waiting. Apparently, this exciting
976 * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93)
977 * failed somewhere. Latency? Burstiness? Well, at least now we will
978 * see, why it failed. 8)8) --ANK
980 * NOTE: is this not too big to inline?
982 static inline bool tcp_prequeue(struct sock *sk, struct sk_buff *skb)
984 struct tcp_sock *tp = tcp_sk(sk);
986 if (sysctl_tcp_low_latency || !tp->ucopy.task)
989 __skb_queue_tail(&tp->ucopy.prequeue, skb);
990 tp->ucopy.memory += skb->truesize;
991 if (tp->ucopy.memory > sk->sk_rcvbuf) {
992 struct sk_buff *skb1;
994 BUG_ON(sock_owned_by_user(sk));
996 while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) {
997 sk_backlog_rcv(sk, skb1);
998 NET_INC_STATS_BH(sock_net(sk),
999 LINUX_MIB_TCPPREQUEUEDROPPED);
1002 tp->ucopy.memory = 0;
1003 } else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
1004 wake_up_interruptible_sync_poll(sk_sleep(sk),
1005 POLLIN | POLLRDNORM | POLLRDBAND);
1006 if (!inet_csk_ack_scheduled(sk))
1007 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
1008 (3 * tcp_rto_min(sk)) / 4,
1018 static const char *statename[]={
1019 "Unused","Established","Syn Sent","Syn Recv",
1020 "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1021 "Close Wait","Last ACK","Listen","Closing"
1024 extern void tcp_set_state(struct sock *sk, int state);
1026 extern void tcp_done(struct sock *sk);
1028 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1031 rx_opt->num_sacks = 0;
1034 /* Determine a window scaling and initial window to offer. */
1035 extern void tcp_select_initial_window(int __space, __u32 mss,
1036 __u32 *rcv_wnd, __u32 *window_clamp,
1037 int wscale_ok, __u8 *rcv_wscale,
1038 __u32 init_rcv_wnd);
1040 static inline int tcp_win_from_space(int space)
1042 return sysctl_tcp_adv_win_scale<=0 ?
1043 (space>>(-sysctl_tcp_adv_win_scale)) :
1044 space - (space>>sysctl_tcp_adv_win_scale);
1047 /* Note: caller must be prepared to deal with negative returns */
1048 static inline int tcp_space(const struct sock *sk)
1050 return tcp_win_from_space(sk->sk_rcvbuf -
1051 atomic_read(&sk->sk_rmem_alloc));
1054 static inline int tcp_full_space(const struct sock *sk)
1056 return tcp_win_from_space(sk->sk_rcvbuf);
1059 static inline void tcp_openreq_init(struct request_sock *req,
1060 struct tcp_options_received *rx_opt,
1061 struct sk_buff *skb)
1063 struct inet_request_sock *ireq = inet_rsk(req);
1065 req->rcv_wnd = 0; /* So that tcp_send_synack() knows! */
1067 tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1068 req->mss = rx_opt->mss_clamp;
1069 req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1070 ireq->tstamp_ok = rx_opt->tstamp_ok;
1071 ireq->sack_ok = rx_opt->sack_ok;
1072 ireq->snd_wscale = rx_opt->snd_wscale;
1073 ireq->wscale_ok = rx_opt->wscale_ok;
1076 ireq->rmt_port = tcp_hdr(skb)->source;
1077 ireq->loc_port = tcp_hdr(skb)->dest;
1080 extern void tcp_enter_memory_pressure(struct sock *sk);
1082 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1084 return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1087 static inline int keepalive_time_when(const struct tcp_sock *tp)
1089 return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1092 static inline int keepalive_probes(const struct tcp_sock *tp)
1094 return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1097 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1099 const struct inet_connection_sock *icsk = &tp->inet_conn;
1101 return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1102 tcp_time_stamp - tp->rcv_tstamp);
1105 static inline int tcp_fin_time(const struct sock *sk)
1107 int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1108 const int rto = inet_csk(sk)->icsk_rto;
1110 if (fin_timeout < (rto << 2) - (rto >> 1))
1111 fin_timeout = (rto << 2) - (rto >> 1);
1116 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1119 if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1121 if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1124 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1125 * then following tcp messages have valid values. Ignore 0 value,
1126 * or else 'negative' tsval might forbid us to accept their packets.
1128 if (!rx_opt->ts_recent)
1133 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1136 if (tcp_paws_check(rx_opt, 0))
1139 /* RST segments are not recommended to carry timestamp,
1140 and, if they do, it is recommended to ignore PAWS because
1141 "their cleanup function should take precedence over timestamps."
1142 Certainly, it is mistake. It is necessary to understand the reasons
1143 of this constraint to relax it: if peer reboots, clock may go
1144 out-of-sync and half-open connections will not be reset.
1145 Actually, the problem would be not existing if all
1146 the implementations followed draft about maintaining clock
1147 via reboots. Linux-2.2 DOES NOT!
1149 However, we can relax time bounds for RST segments to MSL.
1151 if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1156 static inline void tcp_mib_init(struct net *net)
1159 TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1160 TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1161 TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1162 TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1166 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1168 tp->lost_skb_hint = NULL;
1169 tp->scoreboard_skb_hint = NULL;
1172 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1174 tcp_clear_retrans_hints_partial(tp);
1175 tp->retransmit_skb_hint = NULL;
1181 union tcp_md5_addr {
1183 #if IS_ENABLED(CONFIG_IPV6)
1188 /* - key database */
1189 struct tcp_md5sig_key {
1190 struct hlist_node node;
1192 u8 family; /* AF_INET or AF_INET6 */
1193 union tcp_md5_addr addr;
1194 u8 key[TCP_MD5SIG_MAXKEYLEN];
1195 struct rcu_head rcu;
1199 struct tcp_md5sig_info {
1200 struct hlist_head head;
1201 struct rcu_head rcu;
1204 /* - pseudo header */
1205 struct tcp4_pseudohdr {
1213 struct tcp6_pseudohdr {
1214 struct in6_addr saddr;
1215 struct in6_addr daddr;
1217 __be32 protocol; /* including padding */
1220 union tcp_md5sum_block {
1221 struct tcp4_pseudohdr ip4;
1222 #if IS_ENABLED(CONFIG_IPV6)
1223 struct tcp6_pseudohdr ip6;
1227 /* - pool: digest algorithm, hash description and scratch buffer */
1228 struct tcp_md5sig_pool {
1229 struct hash_desc md5_desc;
1230 union tcp_md5sum_block md5_blk;
1234 extern int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1235 const struct sock *sk,
1236 const struct request_sock *req,
1237 const struct sk_buff *skb);
1238 extern int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1239 int family, const u8 *newkey,
1240 u8 newkeylen, gfp_t gfp);
1241 extern int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1243 extern struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1244 struct sock *addr_sk);
1246 #ifdef CONFIG_TCP_MD5SIG
1247 extern struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1248 const union tcp_md5_addr *addr, int family);
1249 #define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key)
1251 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1252 const union tcp_md5_addr *addr,
1257 #define tcp_twsk_md5_key(twsk) NULL
1260 extern struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *);
1261 extern void tcp_free_md5sig_pool(void);
1263 extern struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1264 extern void tcp_put_md5sig_pool(void);
1266 extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1267 extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1268 unsigned int header_len);
1269 extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1270 const struct tcp_md5sig_key *key);
1272 /* write queue abstraction */
1273 static inline void tcp_write_queue_purge(struct sock *sk)
1275 struct sk_buff *skb;
1277 while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1278 sk_wmem_free_skb(sk, skb);
1280 tcp_clear_all_retrans_hints(tcp_sk(sk));
1283 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1285 return skb_peek(&sk->sk_write_queue);
1288 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1290 return skb_peek_tail(&sk->sk_write_queue);
1293 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1294 const struct sk_buff *skb)
1296 return skb_queue_next(&sk->sk_write_queue, skb);
1299 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1300 const struct sk_buff *skb)
1302 return skb_queue_prev(&sk->sk_write_queue, skb);
1305 #define tcp_for_write_queue(skb, sk) \
1306 skb_queue_walk(&(sk)->sk_write_queue, skb)
1308 #define tcp_for_write_queue_from(skb, sk) \
1309 skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1311 #define tcp_for_write_queue_from_safe(skb, tmp, sk) \
1312 skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1314 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1316 return sk->sk_send_head;
1319 static inline bool tcp_skb_is_last(const struct sock *sk,
1320 const struct sk_buff *skb)
1322 return skb_queue_is_last(&sk->sk_write_queue, skb);
1325 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1327 if (tcp_skb_is_last(sk, skb))
1328 sk->sk_send_head = NULL;
1330 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1333 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1335 if (sk->sk_send_head == skb_unlinked)
1336 sk->sk_send_head = NULL;
1339 static inline void tcp_init_send_head(struct sock *sk)
1341 sk->sk_send_head = NULL;
1344 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1346 __skb_queue_tail(&sk->sk_write_queue, skb);
1349 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1351 __tcp_add_write_queue_tail(sk, skb);
1353 /* Queue it, remembering where we must start sending. */
1354 if (sk->sk_send_head == NULL) {
1355 sk->sk_send_head = skb;
1357 if (tcp_sk(sk)->highest_sack == NULL)
1358 tcp_sk(sk)->highest_sack = skb;
1362 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1364 __skb_queue_head(&sk->sk_write_queue, skb);
1367 /* Insert buff after skb on the write queue of sk. */
1368 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1369 struct sk_buff *buff,
1372 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1375 /* Insert new before skb on the write queue of sk. */
1376 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1377 struct sk_buff *skb,
1380 __skb_queue_before(&sk->sk_write_queue, skb, new);
1382 if (sk->sk_send_head == skb)
1383 sk->sk_send_head = new;
1386 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1388 __skb_unlink(skb, &sk->sk_write_queue);
1391 static inline bool tcp_write_queue_empty(struct sock *sk)
1393 return skb_queue_empty(&sk->sk_write_queue);
1396 static inline void tcp_push_pending_frames(struct sock *sk)
1398 if (tcp_send_head(sk)) {
1399 struct tcp_sock *tp = tcp_sk(sk);
1401 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1405 /* Start sequence of the skb just after the highest skb with SACKed
1406 * bit, valid only if sacked_out > 0 or when the caller has ensured
1407 * validity by itself.
1409 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1411 if (!tp->sacked_out)
1414 if (tp->highest_sack == NULL)
1417 return TCP_SKB_CB(tp->highest_sack)->seq;
1420 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1422 tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1423 tcp_write_queue_next(sk, skb);
1426 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1428 return tcp_sk(sk)->highest_sack;
1431 static inline void tcp_highest_sack_reset(struct sock *sk)
1433 tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1436 /* Called when old skb is about to be deleted (to be combined with new skb) */
1437 static inline void tcp_highest_sack_combine(struct sock *sk,
1438 struct sk_buff *old,
1439 struct sk_buff *new)
1441 if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1442 tcp_sk(sk)->highest_sack = new;
1445 /* Determines whether this is a thin stream (which may suffer from
1446 * increased latency). Used to trigger latency-reducing mechanisms.
1448 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1450 return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1454 enum tcp_seq_states {
1455 TCP_SEQ_STATE_LISTENING,
1456 TCP_SEQ_STATE_OPENREQ,
1457 TCP_SEQ_STATE_ESTABLISHED,
1458 TCP_SEQ_STATE_TIME_WAIT,
1461 int tcp_seq_open(struct inode *inode, struct file *file);
1463 struct tcp_seq_afinfo {
1466 const struct file_operations *seq_fops;
1467 struct seq_operations seq_ops;
1470 struct tcp_iter_state {
1471 struct seq_net_private p;
1473 enum tcp_seq_states state;
1474 struct sock *syn_wait_sk;
1475 int bucket, offset, sbucket, num, uid;
1479 extern int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1480 extern void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1482 extern struct request_sock_ops tcp_request_sock_ops;
1483 extern struct request_sock_ops tcp6_request_sock_ops;
1485 extern void tcp_v4_destroy_sock(struct sock *sk);
1487 extern int tcp_v4_gso_send_check(struct sk_buff *skb);
1488 extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
1489 netdev_features_t features);
1490 extern struct sk_buff **tcp_gro_receive(struct sk_buff **head,
1491 struct sk_buff *skb);
1492 extern struct sk_buff **tcp4_gro_receive(struct sk_buff **head,
1493 struct sk_buff *skb);
1494 extern int tcp_gro_complete(struct sk_buff *skb);
1495 extern int tcp4_gro_complete(struct sk_buff *skb);
1497 #ifdef CONFIG_PROC_FS
1498 extern int tcp4_proc_init(void);
1499 extern void tcp4_proc_exit(void);
1502 /* TCP af-specific functions */
1503 struct tcp_sock_af_ops {
1504 #ifdef CONFIG_TCP_MD5SIG
1505 struct tcp_md5sig_key *(*md5_lookup) (struct sock *sk,
1506 struct sock *addr_sk);
1507 int (*calc_md5_hash) (char *location,
1508 struct tcp_md5sig_key *md5,
1509 const struct sock *sk,
1510 const struct request_sock *req,
1511 const struct sk_buff *skb);
1512 int (*md5_parse) (struct sock *sk,
1513 char __user *optval,
1518 struct tcp_request_sock_ops {
1519 #ifdef CONFIG_TCP_MD5SIG
1520 struct tcp_md5sig_key *(*md5_lookup) (struct sock *sk,
1521 struct request_sock *req);
1522 int (*calc_md5_hash) (char *location,
1523 struct tcp_md5sig_key *md5,
1524 const struct sock *sk,
1525 const struct request_sock *req,
1526 const struct sk_buff *skb);
1530 /* Using SHA1 for now, define some constants.
1532 #define COOKIE_DIGEST_WORDS (SHA_DIGEST_WORDS)
1533 #define COOKIE_MESSAGE_WORDS (SHA_MESSAGE_BYTES / 4)
1534 #define COOKIE_WORKSPACE_WORDS (COOKIE_DIGEST_WORDS + COOKIE_MESSAGE_WORDS)
1536 extern int tcp_cookie_generator(u32 *bakery);
1539 * struct tcp_cookie_values - each socket needs extra space for the
1540 * cookies, together with (optional) space for any SYN data.
1542 * A tcp_sock contains a pointer to the current value, and this is
1543 * cloned to the tcp_timewait_sock.
1545 * @cookie_pair: variable data from the option exchange.
1547 * @cookie_desired: user specified tcpct_cookie_desired. Zero
1548 * indicates default (sysctl_tcp_cookie_size).
1549 * After cookie sent, remembers size of cookie.
1550 * Range 0, TCP_COOKIE_MIN to TCP_COOKIE_MAX.
1552 * @s_data_desired: user specified tcpct_s_data_desired. When the
1553 * constant payload is specified (@s_data_constant),
1554 * holds its length instead.
1555 * Range 0 to TCP_MSS_DESIRED.
1557 * @s_data_payload: constant data that is to be included in the
1558 * payload of SYN or SYNACK segments when the
1559 * cookie option is present.
1561 struct tcp_cookie_values {
1563 u8 cookie_pair[TCP_COOKIE_PAIR_SIZE];
1564 u8 cookie_pair_size;
1566 u16 s_data_desired:11,
1571 u8 s_data_payload[0];
1574 static inline void tcp_cookie_values_release(struct kref *kref)
1576 kfree(container_of(kref, struct tcp_cookie_values, kref));
1579 /* The length of constant payload data. Note that s_data_desired is
1580 * overloaded, depending on s_data_constant: either the length of constant
1581 * data (returned here) or the limit on variable data.
1583 static inline int tcp_s_data_size(const struct tcp_sock *tp)
1585 return (tp->cookie_values != NULL && tp->cookie_values->s_data_constant)
1586 ? tp->cookie_values->s_data_desired
1591 * struct tcp_extend_values - tcp_ipv?.c to tcp_output.c workspace.
1593 * As tcp_request_sock has already been extended in other places, the
1594 * only remaining method is to pass stack values along as function
1595 * parameters. These parameters are not needed after sending SYNACK.
1597 * @cookie_bakery: cryptographic secret and message workspace.
1599 * @cookie_plus: bytes in authenticator/cookie option, copied from
1600 * struct tcp_options_received (above).
1602 struct tcp_extend_values {
1603 struct request_values rv;
1604 u32 cookie_bakery[COOKIE_WORKSPACE_WORDS];
1610 static inline struct tcp_extend_values *tcp_xv(struct request_values *rvp)
1612 return (struct tcp_extend_values *)rvp;
1615 extern void tcp_v4_init(void);
1616 extern void tcp_init(void);