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Linux/include/net/tcp.h

  1 /*
  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.
  5  *
  6  *              Definitions for the TCP module.
  7  *
  8  * Version:     @(#)tcp.h       1.0.5   05/23/93
  9  *
 10  * Authors:     Ross Biro
 11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  *
 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.
 17  */
 18 #ifndef _TCP_H
 19 #define _TCP_H
 20 
 21 #define FASTRETRANS_DEBUG 1
 22 
 23 #include <linux/list.h>
 24 #include <linux/tcp.h>
 25 #include <linux/bug.h>
 26 #include <linux/slab.h>
 27 #include <linux/cache.h>
 28 #include <linux/percpu.h>
 29 #include <linux/skbuff.h>
 30 #include <linux/cryptohash.h>
 31 #include <linux/kref.h>
 32 #include <linux/ktime.h>
 33 
 34 #include <net/inet_connection_sock.h>
 35 #include <net/inet_timewait_sock.h>
 36 #include <net/inet_hashtables.h>
 37 #include <net/checksum.h>
 38 #include <net/request_sock.h>
 39 #include <net/sock.h>
 40 #include <net/snmp.h>
 41 #include <net/ip.h>
 42 #include <net/tcp_states.h>
 43 #include <net/inet_ecn.h>
 44 #include <net/dst.h>
 45 
 46 #include <linux/seq_file.h>
 47 #include <linux/memcontrol.h>
 48 
 49 extern struct inet_hashinfo tcp_hashinfo;
 50 
 51 extern struct percpu_counter tcp_orphan_count;
 52 void tcp_time_wait(struct sock *sk, int state, int timeo);
 53 
 54 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 55 #define MAX_TCP_OPTION_SPACE 40
 56 
 57 /*
 58  * Never offer a window over 32767 without using window scaling. Some
 59  * poor stacks do signed 16bit maths!
 60  */
 61 #define MAX_TCP_WINDOW          32767U
 62 
 63 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 64 #define TCP_MIN_MSS             88U
 65 
 66 /* The least MTU to use for probing */
 67 #define TCP_BASE_MSS            1024
 68 
 69 /* probing interval, default to 10 minutes as per RFC4821 */
 70 #define TCP_PROBE_INTERVAL      600
 71 
 72 /* Specify interval when tcp mtu probing will stop */
 73 #define TCP_PROBE_THRESHOLD     8
 74 
 75 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 76 #define TCP_FASTRETRANS_THRESH 3
 77 
 78 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 79 #define TCP_MAX_QUICKACKS       16U
 80 
 81 /* urg_data states */
 82 #define TCP_URG_VALID   0x0100
 83 #define TCP_URG_NOTYET  0x0200
 84 #define TCP_URG_READ    0x0400
 85 
 86 #define TCP_RETR1       3       /*
 87                                  * This is how many retries it does before it
 88                                  * tries to figure out if the gateway is
 89                                  * down. Minimal RFC value is 3; it corresponds
 90                                  * to ~3sec-8min depending on RTO.
 91                                  */
 92 
 93 #define TCP_RETR2       15      /*
 94                                  * This should take at least
 95                                  * 90 minutes to time out.
 96                                  * RFC1122 says that the limit is 100 sec.
 97                                  * 15 is ~13-30min depending on RTO.
 98                                  */
 99 
100 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
101                                  * when active opening a connection.
102                                  * RFC1122 says the minimum retry MUST
103                                  * be at least 180secs.  Nevertheless
104                                  * this value is corresponding to
105                                  * 63secs of retransmission with the
106                                  * current initial RTO.
107                                  */
108 
109 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
110                                  * when passive opening a connection.
111                                  * This is corresponding to 31secs of
112                                  * retransmission with the current
113                                  * initial RTO.
114                                  */
115 
116 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
117                                   * state, about 60 seconds     */
118 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
119                                  /* BSD style FIN_WAIT2 deadlock breaker.
120                                   * It used to be 3min, new value is 60sec,
121                                   * to combine FIN-WAIT-2 timeout with
122                                   * TIME-WAIT timer.
123                                   */
124 
125 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
126 #if HZ >= 100
127 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
128 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
129 #else
130 #define TCP_DELACK_MIN  4U
131 #define TCP_ATO_MIN     4U
132 #endif
133 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
134 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
135 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
136 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
137                                                  * used as a fallback RTO for the
138                                                  * initial data transmission if no
139                                                  * valid RTT sample has been acquired,
140                                                  * most likely due to retrans in 3WHS.
141                                                  */
142 
143 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
144                                                          * for local resources.
145                                                          */
146 
147 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
148 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
149 #define TCP_KEEPALIVE_INTVL     (75*HZ)
150 
151 #define MAX_TCP_KEEPIDLE        32767
152 #define MAX_TCP_KEEPINTVL       32767
153 #define MAX_TCP_KEEPCNT         127
154 #define MAX_TCP_SYNCNT          127
155 
156 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
157 
158 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
159 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
160                                          * after this time. It should be equal
161                                          * (or greater than) TCP_TIMEWAIT_LEN
162                                          * to provide reliability equal to one
163                                          * provided by timewait state.
164                                          */
165 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
166                                          * timestamps. It must be less than
167                                          * minimal timewait lifetime.
168                                          */
169 /*
170  *      TCP option
171  */
172 
173 #define TCPOPT_NOP              1       /* Padding */
174 #define TCPOPT_EOL              0       /* End of options */
175 #define TCPOPT_MSS              2       /* Segment size negotiating */
176 #define TCPOPT_WINDOW           3       /* Window scaling */
177 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
178 #define TCPOPT_SACK             5       /* SACK Block */
179 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
180 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
181 #define TCPOPT_FASTOPEN         34      /* Fast open (RFC7413) */
182 #define TCPOPT_EXP              254     /* Experimental */
183 /* Magic number to be after the option value for sharing TCP
184  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
185  */
186 #define TCPOPT_FASTOPEN_MAGIC   0xF989
187 
188 /*
189  *     TCP option lengths
190  */
191 
192 #define TCPOLEN_MSS            4
193 #define TCPOLEN_WINDOW         3
194 #define TCPOLEN_SACK_PERM      2
195 #define TCPOLEN_TIMESTAMP      10
196 #define TCPOLEN_MD5SIG         18
197 #define TCPOLEN_FASTOPEN_BASE  2
198 #define TCPOLEN_EXP_FASTOPEN_BASE  4
199 
200 /* But this is what stacks really send out. */
201 #define TCPOLEN_TSTAMP_ALIGNED          12
202 #define TCPOLEN_WSCALE_ALIGNED          4
203 #define TCPOLEN_SACKPERM_ALIGNED        4
204 #define TCPOLEN_SACK_BASE               2
205 #define TCPOLEN_SACK_BASE_ALIGNED       4
206 #define TCPOLEN_SACK_PERBLOCK           8
207 #define TCPOLEN_MD5SIG_ALIGNED          20
208 #define TCPOLEN_MSS_ALIGNED             4
209 
210 /* Flags in tp->nonagle */
211 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
212 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
213 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
214 
215 /* TCP thin-stream limits */
216 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
217 
218 /* TCP initial congestion window as per rfc6928 */
219 #define TCP_INIT_CWND           10
220 
221 /* Bit Flags for sysctl_tcp_fastopen */
222 #define TFO_CLIENT_ENABLE       1
223 #define TFO_SERVER_ENABLE       2
224 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
225 
226 /* Accept SYN data w/o any cookie option */
227 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
228 
229 /* Force enable TFO on all listeners, i.e., not requiring the
230  * TCP_FASTOPEN socket option.
231  */
232 #define TFO_SERVER_WO_SOCKOPT1  0x400
233 
234 extern struct inet_timewait_death_row tcp_death_row;
235 
236 /* sysctl variables for tcp */
237 extern int sysctl_tcp_timestamps;
238 extern int sysctl_tcp_window_scaling;
239 extern int sysctl_tcp_sack;
240 extern int sysctl_tcp_fastopen;
241 extern int sysctl_tcp_retrans_collapse;
242 extern int sysctl_tcp_stdurg;
243 extern int sysctl_tcp_rfc1337;
244 extern int sysctl_tcp_abort_on_overflow;
245 extern int sysctl_tcp_max_orphans;
246 extern int sysctl_tcp_fack;
247 extern int sysctl_tcp_reordering;
248 extern int sysctl_tcp_max_reordering;
249 extern int sysctl_tcp_dsack;
250 extern long sysctl_tcp_mem[3];
251 extern int sysctl_tcp_wmem[3];
252 extern int sysctl_tcp_rmem[3];
253 extern int sysctl_tcp_app_win;
254 extern int sysctl_tcp_adv_win_scale;
255 extern int sysctl_tcp_frto;
256 extern int sysctl_tcp_low_latency;
257 extern int sysctl_tcp_nometrics_save;
258 extern int sysctl_tcp_moderate_rcvbuf;
259 extern int sysctl_tcp_tso_win_divisor;
260 extern int sysctl_tcp_workaround_signed_windows;
261 extern int sysctl_tcp_slow_start_after_idle;
262 extern int sysctl_tcp_thin_linear_timeouts;
263 extern int sysctl_tcp_thin_dupack;
264 extern int sysctl_tcp_early_retrans;
265 extern int sysctl_tcp_limit_output_bytes;
266 extern int sysctl_tcp_challenge_ack_limit;
267 extern int sysctl_tcp_min_tso_segs;
268 extern int sysctl_tcp_min_rtt_wlen;
269 extern int sysctl_tcp_autocorking;
270 extern int sysctl_tcp_invalid_ratelimit;
271 extern int sysctl_tcp_pacing_ss_ratio;
272 extern int sysctl_tcp_pacing_ca_ratio;
273 
274 extern atomic_long_t tcp_memory_allocated;
275 extern struct percpu_counter tcp_sockets_allocated;
276 extern int tcp_memory_pressure;
277 
278 /* optimized version of sk_under_memory_pressure() for TCP sockets */
279 static inline bool tcp_under_memory_pressure(const struct sock *sk)
280 {
281         if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
282             mem_cgroup_under_socket_pressure(sk->sk_memcg))
283                 return true;
284 
285         return tcp_memory_pressure;
286 }
287 /*
288  * The next routines deal with comparing 32 bit unsigned ints
289  * and worry about wraparound (automatic with unsigned arithmetic).
290  */
291 
292 static inline bool before(__u32 seq1, __u32 seq2)
293 {
294         return (__s32)(seq1-seq2) < 0;
295 }
296 #define after(seq2, seq1)       before(seq1, seq2)
297 
298 /* is s2<=s1<=s3 ? */
299 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
300 {
301         return seq3 - seq2 >= seq1 - seq2;
302 }
303 
304 static inline bool tcp_out_of_memory(struct sock *sk)
305 {
306         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
307             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
308                 return true;
309         return false;
310 }
311 
312 void sk_forced_mem_schedule(struct sock *sk, int size);
313 
314 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
315 {
316         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
317         int orphans = percpu_counter_read_positive(ocp);
318 
319         if (orphans << shift > sysctl_tcp_max_orphans) {
320                 orphans = percpu_counter_sum_positive(ocp);
321                 if (orphans << shift > sysctl_tcp_max_orphans)
322                         return true;
323         }
324         return false;
325 }
326 
327 bool tcp_check_oom(struct sock *sk, int shift);
328 
329 
330 extern struct proto tcp_prot;
331 
332 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
333 #define __TCP_INC_STATS(net, field)     __SNMP_INC_STATS((net)->mib.tcp_statistics, field)
334 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
335 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
336 
337 void tcp_tasklet_init(void);
338 
339 void tcp_v4_err(struct sk_buff *skb, u32);
340 
341 void tcp_shutdown(struct sock *sk, int how);
342 
343 void tcp_v4_early_demux(struct sk_buff *skb);
344 int tcp_v4_rcv(struct sk_buff *skb);
345 
346 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
347 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
348 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
349                  int flags);
350 void tcp_release_cb(struct sock *sk);
351 void tcp_wfree(struct sk_buff *skb);
352 void tcp_write_timer_handler(struct sock *sk);
353 void tcp_delack_timer_handler(struct sock *sk);
354 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
355 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
356 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
357                          const struct tcphdr *th, unsigned int len);
358 void tcp_rcv_space_adjust(struct sock *sk);
359 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
360 void tcp_twsk_destructor(struct sock *sk);
361 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
362                         struct pipe_inode_info *pipe, size_t len,
363                         unsigned int flags);
364 
365 static inline void tcp_dec_quickack_mode(struct sock *sk,
366                                          const unsigned int pkts)
367 {
368         struct inet_connection_sock *icsk = inet_csk(sk);
369 
370         if (icsk->icsk_ack.quick) {
371                 if (pkts >= icsk->icsk_ack.quick) {
372                         icsk->icsk_ack.quick = 0;
373                         /* Leaving quickack mode we deflate ATO. */
374                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
375                 } else
376                         icsk->icsk_ack.quick -= pkts;
377         }
378 }
379 
380 #define TCP_ECN_OK              1
381 #define TCP_ECN_QUEUE_CWR       2
382 #define TCP_ECN_DEMAND_CWR      4
383 #define TCP_ECN_SEEN            8
384 
385 enum tcp_tw_status {
386         TCP_TW_SUCCESS = 0,
387         TCP_TW_RST = 1,
388         TCP_TW_ACK = 2,
389         TCP_TW_SYN = 3
390 };
391 
392 
393 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
394                                               struct sk_buff *skb,
395                                               const struct tcphdr *th);
396 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
397                            struct request_sock *req, bool fastopen);
398 int tcp_child_process(struct sock *parent, struct sock *child,
399                       struct sk_buff *skb);
400 void tcp_enter_loss(struct sock *sk);
401 void tcp_clear_retrans(struct tcp_sock *tp);
402 void tcp_update_metrics(struct sock *sk);
403 void tcp_init_metrics(struct sock *sk);
404 void tcp_metrics_init(void);
405 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
406                         bool paws_check, bool timestamps);
407 bool tcp_remember_stamp(struct sock *sk);
408 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
409 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
410 void tcp_disable_fack(struct tcp_sock *tp);
411 void tcp_close(struct sock *sk, long timeout);
412 void tcp_init_sock(struct sock *sk);
413 unsigned int tcp_poll(struct file *file, struct socket *sock,
414                       struct poll_table_struct *wait);
415 int tcp_getsockopt(struct sock *sk, int level, int optname,
416                    char __user *optval, int __user *optlen);
417 int tcp_setsockopt(struct sock *sk, int level, int optname,
418                    char __user *optval, unsigned int optlen);
419 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
420                           char __user *optval, int __user *optlen);
421 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
422                           char __user *optval, unsigned int optlen);
423 void tcp_set_keepalive(struct sock *sk, int val);
424 void tcp_syn_ack_timeout(const struct request_sock *req);
425 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
426                 int flags, int *addr_len);
427 void tcp_parse_options(const struct sk_buff *skb,
428                        struct tcp_options_received *opt_rx,
429                        int estab, struct tcp_fastopen_cookie *foc);
430 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
431 
432 /*
433  *      TCP v4 functions exported for the inet6 API
434  */
435 
436 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
437 void tcp_v4_mtu_reduced(struct sock *sk);
438 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
439 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
440 struct sock *tcp_create_openreq_child(const struct sock *sk,
441                                       struct request_sock *req,
442                                       struct sk_buff *skb);
443 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
444 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
445                                   struct request_sock *req,
446                                   struct dst_entry *dst,
447                                   struct request_sock *req_unhash,
448                                   bool *own_req);
449 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
450 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
451 int tcp_connect(struct sock *sk);
452 enum tcp_synack_type {
453         TCP_SYNACK_NORMAL,
454         TCP_SYNACK_FASTOPEN,
455         TCP_SYNACK_COOKIE,
456 };
457 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
458                                 struct request_sock *req,
459                                 struct tcp_fastopen_cookie *foc,
460                                 enum tcp_synack_type synack_type);
461 int tcp_disconnect(struct sock *sk, int flags);
462 
463 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
464 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
465 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
466 
467 /* From syncookies.c */
468 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
469                                  struct request_sock *req,
470                                  struct dst_entry *dst);
471 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
472                       u32 cookie);
473 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
474 #ifdef CONFIG_SYN_COOKIES
475 
476 /* Syncookies use a monotonic timer which increments every 60 seconds.
477  * This counter is used both as a hash input and partially encoded into
478  * the cookie value.  A cookie is only validated further if the delta
479  * between the current counter value and the encoded one is less than this,
480  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
481  * the counter advances immediately after a cookie is generated).
482  */
483 #define MAX_SYNCOOKIE_AGE       2
484 #define TCP_SYNCOOKIE_PERIOD    (60 * HZ)
485 #define TCP_SYNCOOKIE_VALID     (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
486 
487 /* syncookies: remember time of last synqueue overflow
488  * But do not dirty this field too often (once per second is enough)
489  * It is racy as we do not hold a lock, but race is very minor.
490  */
491 static inline void tcp_synq_overflow(const struct sock *sk)
492 {
493         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
494         unsigned long now = jiffies;
495 
496         if (time_after(now, last_overflow + HZ))
497                 tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
498 }
499 
500 /* syncookies: no recent synqueue overflow on this listening socket? */
501 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
502 {
503         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
504 
505         return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
506 }
507 
508 static inline u32 tcp_cookie_time(void)
509 {
510         u64 val = get_jiffies_64();
511 
512         do_div(val, TCP_SYNCOOKIE_PERIOD);
513         return val;
514 }
515 
516 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
517                               u16 *mssp);
518 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
519 __u32 cookie_init_timestamp(struct request_sock *req);
520 bool cookie_timestamp_decode(struct tcp_options_received *opt);
521 bool cookie_ecn_ok(const struct tcp_options_received *opt,
522                    const struct net *net, const struct dst_entry *dst);
523 
524 /* From net/ipv6/syncookies.c */
525 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
526                       u32 cookie);
527 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
528 
529 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
530                               const struct tcphdr *th, u16 *mssp);
531 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
532 #endif
533 /* tcp_output.c */
534 
535 u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
536                      int min_tso_segs);
537 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
538                                int nonagle);
539 bool tcp_may_send_now(struct sock *sk);
540 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
541 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
542 void tcp_retransmit_timer(struct sock *sk);
543 void tcp_xmit_retransmit_queue(struct sock *);
544 void tcp_simple_retransmit(struct sock *);
545 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
546 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
547 
548 void tcp_send_probe0(struct sock *);
549 void tcp_send_partial(struct sock *);
550 int tcp_write_wakeup(struct sock *, int mib);
551 void tcp_send_fin(struct sock *sk);
552 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
553 int tcp_send_synack(struct sock *);
554 void tcp_push_one(struct sock *, unsigned int mss_now);
555 void tcp_send_ack(struct sock *sk);
556 void tcp_send_delayed_ack(struct sock *sk);
557 void tcp_send_loss_probe(struct sock *sk);
558 bool tcp_schedule_loss_probe(struct sock *sk);
559 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
560                              const struct sk_buff *next_skb);
561 
562 /* tcp_input.c */
563 void tcp_resume_early_retransmit(struct sock *sk);
564 void tcp_rearm_rto(struct sock *sk);
565 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
566 void tcp_reset(struct sock *sk);
567 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
568 void tcp_fin(struct sock *sk);
569 
570 /* tcp_timer.c */
571 void tcp_init_xmit_timers(struct sock *);
572 static inline void tcp_clear_xmit_timers(struct sock *sk)
573 {
574         inet_csk_clear_xmit_timers(sk);
575 }
576 
577 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
578 unsigned int tcp_current_mss(struct sock *sk);
579 
580 /* Bound MSS / TSO packet size with the half of the window */
581 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
582 {
583         int cutoff;
584 
585         /* When peer uses tiny windows, there is no use in packetizing
586          * to sub-MSS pieces for the sake of SWS or making sure there
587          * are enough packets in the pipe for fast recovery.
588          *
589          * On the other hand, for extremely large MSS devices, handling
590          * smaller than MSS windows in this way does make sense.
591          */
592         if (tp->max_window > TCP_MSS_DEFAULT)
593                 cutoff = (tp->max_window >> 1);
594         else
595                 cutoff = tp->max_window;
596 
597         if (cutoff && pktsize > cutoff)
598                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
599         else
600                 return pktsize;
601 }
602 
603 /* tcp.c */
604 void tcp_get_info(struct sock *, struct tcp_info *);
605 
606 /* Read 'sendfile()'-style from a TCP socket */
607 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
608                   sk_read_actor_t recv_actor);
609 
610 void tcp_initialize_rcv_mss(struct sock *sk);
611 
612 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
613 int tcp_mss_to_mtu(struct sock *sk, int mss);
614 void tcp_mtup_init(struct sock *sk);
615 void tcp_init_buffer_space(struct sock *sk);
616 
617 static inline void tcp_bound_rto(const struct sock *sk)
618 {
619         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
620                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
621 }
622 
623 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
624 {
625         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
626 }
627 
628 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
629 {
630         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
631                                ntohl(TCP_FLAG_ACK) |
632                                snd_wnd);
633 }
634 
635 static inline void tcp_fast_path_on(struct tcp_sock *tp)
636 {
637         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
638 }
639 
640 static inline void tcp_fast_path_check(struct sock *sk)
641 {
642         struct tcp_sock *tp = tcp_sk(sk);
643 
644         if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
645             tp->rcv_wnd &&
646             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
647             !tp->urg_data)
648                 tcp_fast_path_on(tp);
649 }
650 
651 /* Compute the actual rto_min value */
652 static inline u32 tcp_rto_min(struct sock *sk)
653 {
654         const struct dst_entry *dst = __sk_dst_get(sk);
655         u32 rto_min = TCP_RTO_MIN;
656 
657         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
658                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
659         return rto_min;
660 }
661 
662 static inline u32 tcp_rto_min_us(struct sock *sk)
663 {
664         return jiffies_to_usecs(tcp_rto_min(sk));
665 }
666 
667 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
668 {
669         return dst_metric_locked(dst, RTAX_CC_ALGO);
670 }
671 
672 /* Minimum RTT in usec. ~0 means not available. */
673 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
674 {
675         return minmax_get(&tp->rtt_min);
676 }
677 
678 /* Compute the actual receive window we are currently advertising.
679  * Rcv_nxt can be after the window if our peer push more data
680  * than the offered window.
681  */
682 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
683 {
684         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
685 
686         if (win < 0)
687                 win = 0;
688         return (u32) win;
689 }
690 
691 /* Choose a new window, without checks for shrinking, and without
692  * scaling applied to the result.  The caller does these things
693  * if necessary.  This is a "raw" window selection.
694  */
695 u32 __tcp_select_window(struct sock *sk);
696 
697 void tcp_send_window_probe(struct sock *sk);
698 
699 /* TCP timestamps are only 32-bits, this causes a slight
700  * complication on 64-bit systems since we store a snapshot
701  * of jiffies in the buffer control blocks below.  We decided
702  * to use only the low 32-bits of jiffies and hide the ugly
703  * casts with the following macro.
704  */
705 #define tcp_time_stamp          ((__u32)(jiffies))
706 
707 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
708 {
709         return skb->skb_mstamp.stamp_jiffies;
710 }
711 
712 
713 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
714 
715 #define TCPHDR_FIN 0x01
716 #define TCPHDR_SYN 0x02
717 #define TCPHDR_RST 0x04
718 #define TCPHDR_PSH 0x08
719 #define TCPHDR_ACK 0x10
720 #define TCPHDR_URG 0x20
721 #define TCPHDR_ECE 0x40
722 #define TCPHDR_CWR 0x80
723 
724 #define TCPHDR_SYN_ECN  (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
725 
726 /* This is what the send packet queuing engine uses to pass
727  * TCP per-packet control information to the transmission code.
728  * We also store the host-order sequence numbers in here too.
729  * This is 44 bytes if IPV6 is enabled.
730  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
731  */
732 struct tcp_skb_cb {
733         __u32           seq;            /* Starting sequence number     */
734         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
735         union {
736                 /* Note : tcp_tw_isn is used in input path only
737                  *        (isn chosen by tcp_timewait_state_process())
738                  *
739                  *        tcp_gso_segs/size are used in write queue only,
740                  *        cf tcp_skb_pcount()/tcp_skb_mss()
741                  */
742                 __u32           tcp_tw_isn;
743                 struct {
744                         u16     tcp_gso_segs;
745                         u16     tcp_gso_size;
746                 };
747         };
748         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
749 
750         __u8            sacked;         /* State flags for SACK/FACK.   */
751 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
752 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
753 #define TCPCB_LOST              0x04    /* SKB is lost                  */
754 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
755 #define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
756 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
757 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
758                                 TCPCB_REPAIRED)
759 
760         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
761         __u8            txstamp_ack:1,  /* Record TX timestamp for ack? */
762                         eor:1,          /* Is skb MSG_EOR marked? */
763                         unused:6;
764         __u32           ack_seq;        /* Sequence number ACK'd        */
765         union {
766                 struct {
767                         /* There is space for up to 24 bytes */
768                         __u32 in_flight:30,/* Bytes in flight at transmit */
769                               is_app_limited:1, /* cwnd not fully used? */
770                               unused:1;
771                         /* pkts S/ACKed so far upon tx of skb, incl retrans: */
772                         __u32 delivered;
773                         /* start of send pipeline phase */
774                         struct skb_mstamp first_tx_mstamp;
775                         /* when we reached the "delivered" count */
776                         struct skb_mstamp delivered_mstamp;
777                 } tx;   /* only used for outgoing skbs */
778                 union {
779                         struct inet_skb_parm    h4;
780 #if IS_ENABLED(CONFIG_IPV6)
781                         struct inet6_skb_parm   h6;
782 #endif
783                 } header;       /* For incoming skbs */
784         };
785 };
786 
787 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
788 
789 
790 #if IS_ENABLED(CONFIG_IPV6)
791 /* This is the variant of inet6_iif() that must be used by TCP,
792  * as TCP moves IP6CB into a different location in skb->cb[]
793  */
794 static inline int tcp_v6_iif(const struct sk_buff *skb)
795 {
796         bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
797 
798         return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
799 }
800 #endif
801 
802 /* TCP_SKB_CB reference means this can not be used from early demux */
803 static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
804 {
805 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
806         if (!net->ipv4.sysctl_tcp_l3mdev_accept &&
807             skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
808                 return true;
809 #endif
810         return false;
811 }
812 
813 /* Due to TSO, an SKB can be composed of multiple actual
814  * packets.  To keep these tracked properly, we use this.
815  */
816 static inline int tcp_skb_pcount(const struct sk_buff *skb)
817 {
818         return TCP_SKB_CB(skb)->tcp_gso_segs;
819 }
820 
821 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
822 {
823         TCP_SKB_CB(skb)->tcp_gso_segs = segs;
824 }
825 
826 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
827 {
828         TCP_SKB_CB(skb)->tcp_gso_segs += segs;
829 }
830 
831 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
832 static inline int tcp_skb_mss(const struct sk_buff *skb)
833 {
834         return TCP_SKB_CB(skb)->tcp_gso_size;
835 }
836 
837 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
838 {
839         return likely(!TCP_SKB_CB(skb)->eor);
840 }
841 
842 /* Events passed to congestion control interface */
843 enum tcp_ca_event {
844         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
845         CA_EVENT_CWND_RESTART,  /* congestion window restart */
846         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
847         CA_EVENT_LOSS,          /* loss timeout */
848         CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
849         CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
850         CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
851         CA_EVENT_NON_DELAYED_ACK,
852 };
853 
854 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
855 enum tcp_ca_ack_event_flags {
856         CA_ACK_SLOWPATH         = (1 << 0),     /* In slow path processing */
857         CA_ACK_WIN_UPDATE       = (1 << 1),     /* ACK updated window */
858         CA_ACK_ECE              = (1 << 2),     /* ECE bit is set on ack */
859 };
860 
861 /*
862  * Interface for adding new TCP congestion control handlers
863  */
864 #define TCP_CA_NAME_MAX 16
865 #define TCP_CA_MAX      128
866 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
867 
868 #define TCP_CA_UNSPEC   0
869 
870 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
871 #define TCP_CONG_NON_RESTRICTED 0x1
872 /* Requires ECN/ECT set on all packets */
873 #define TCP_CONG_NEEDS_ECN      0x2
874 
875 union tcp_cc_info;
876 
877 struct ack_sample {
878         u32 pkts_acked;
879         s32 rtt_us;
880         u32 in_flight;
881 };
882 
883 /* A rate sample measures the number of (original/retransmitted) data
884  * packets delivered "delivered" over an interval of time "interval_us".
885  * The tcp_rate.c code fills in the rate sample, and congestion
886  * control modules that define a cong_control function to run at the end
887  * of ACK processing can optionally chose to consult this sample when
888  * setting cwnd and pacing rate.
889  * A sample is invalid if "delivered" or "interval_us" is negative.
890  */
891 struct rate_sample {
892         struct  skb_mstamp prior_mstamp; /* starting timestamp for interval */
893         u32  prior_delivered;   /* tp->delivered at "prior_mstamp" */
894         s32  delivered;         /* number of packets delivered over interval */
895         long interval_us;       /* time for tp->delivered to incr "delivered" */
896         long rtt_us;            /* RTT of last (S)ACKed packet (or -1) */
897         int  losses;            /* number of packets marked lost upon ACK */
898         u32  acked_sacked;      /* number of packets newly (S)ACKed upon ACK */
899         u32  prior_in_flight;   /* in flight before this ACK */
900         bool is_app_limited;    /* is sample from packet with bubble in pipe? */
901         bool is_retrans;        /* is sample from retransmission? */
902 };
903 
904 struct tcp_congestion_ops {
905         struct list_head        list;
906         u32 key;
907         u32 flags;
908 
909         /* initialize private data (optional) */
910         void (*init)(struct sock *sk);
911         /* cleanup private data  (optional) */
912         void (*release)(struct sock *sk);
913 
914         /* return slow start threshold (required) */
915         u32 (*ssthresh)(struct sock *sk);
916         /* do new cwnd calculation (required) */
917         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
918         /* call before changing ca_state (optional) */
919         void (*set_state)(struct sock *sk, u8 new_state);
920         /* call when cwnd event occurs (optional) */
921         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
922         /* call when ack arrives (optional) */
923         void (*in_ack_event)(struct sock *sk, u32 flags);
924         /* new value of cwnd after loss (optional) */
925         u32  (*undo_cwnd)(struct sock *sk);
926         /* hook for packet ack accounting (optional) */
927         void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
928         /* suggest number of segments for each skb to transmit (optional) */
929         u32 (*tso_segs_goal)(struct sock *sk);
930         /* returns the multiplier used in tcp_sndbuf_expand (optional) */
931         u32 (*sndbuf_expand)(struct sock *sk);
932         /* call when packets are delivered to update cwnd and pacing rate,
933          * after all the ca_state processing. (optional)
934          */
935         void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
936         /* get info for inet_diag (optional) */
937         size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
938                            union tcp_cc_info *info);
939 
940         char            name[TCP_CA_NAME_MAX];
941         struct module   *owner;
942 };
943 
944 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
945 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
946 
947 void tcp_assign_congestion_control(struct sock *sk);
948 void tcp_init_congestion_control(struct sock *sk);
949 void tcp_cleanup_congestion_control(struct sock *sk);
950 int tcp_set_default_congestion_control(const char *name);
951 void tcp_get_default_congestion_control(char *name);
952 void tcp_get_available_congestion_control(char *buf, size_t len);
953 void tcp_get_allowed_congestion_control(char *buf, size_t len);
954 int tcp_set_allowed_congestion_control(char *allowed);
955 int tcp_set_congestion_control(struct sock *sk, const char *name);
956 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
957 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
958 
959 u32 tcp_reno_ssthresh(struct sock *sk);
960 u32 tcp_reno_undo_cwnd(struct sock *sk);
961 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
962 extern struct tcp_congestion_ops tcp_reno;
963 
964 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
965 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
966 #ifdef CONFIG_INET
967 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
968 #else
969 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
970 {
971         return NULL;
972 }
973 #endif
974 
975 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
976 {
977         const struct inet_connection_sock *icsk = inet_csk(sk);
978 
979         return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
980 }
981 
982 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
983 {
984         struct inet_connection_sock *icsk = inet_csk(sk);
985 
986         if (icsk->icsk_ca_ops->set_state)
987                 icsk->icsk_ca_ops->set_state(sk, ca_state);
988         icsk->icsk_ca_state = ca_state;
989 }
990 
991 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
992 {
993         const struct inet_connection_sock *icsk = inet_csk(sk);
994 
995         if (icsk->icsk_ca_ops->cwnd_event)
996                 icsk->icsk_ca_ops->cwnd_event(sk, event);
997 }
998 
999 /* From tcp_rate.c */
1000 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
1001 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
1002                             struct rate_sample *rs);
1003 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
1004                   struct skb_mstamp *now, struct rate_sample *rs);
1005 void tcp_rate_check_app_limited(struct sock *sk);
1006 
1007 /* These functions determine how the current flow behaves in respect of SACK
1008  * handling. SACK is negotiated with the peer, and therefore it can vary
1009  * between different flows.
1010  *
1011  * tcp_is_sack - SACK enabled
1012  * tcp_is_reno - No SACK
1013  * tcp_is_fack - FACK enabled, implies SACK enabled
1014  */
1015 static inline int tcp_is_sack(const struct tcp_sock *tp)
1016 {
1017         return tp->rx_opt.sack_ok;
1018 }
1019 
1020 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1021 {
1022         return !tcp_is_sack(tp);
1023 }
1024 
1025 static inline bool tcp_is_fack(const struct tcp_sock *tp)
1026 {
1027         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
1028 }
1029 
1030 static inline void tcp_enable_fack(struct tcp_sock *tp)
1031 {
1032         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
1033 }
1034 
1035 /* TCP early-retransmit (ER) is similar to but more conservative than
1036  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
1037  */
1038 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
1039 {
1040         struct net *net = sock_net((struct sock *)tp);
1041 
1042         tp->do_early_retrans = sysctl_tcp_early_retrans &&
1043                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
1044                 net->ipv4.sysctl_tcp_reordering == 3;
1045 }
1046 
1047 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
1048 {
1049         tp->do_early_retrans = 0;
1050 }
1051 
1052 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1053 {
1054         return tp->sacked_out + tp->lost_out;
1055 }
1056 
1057 /* This determines how many packets are "in the network" to the best
1058  * of our knowledge.  In many cases it is conservative, but where
1059  * detailed information is available from the receiver (via SACK
1060  * blocks etc.) we can make more aggressive calculations.
1061  *
1062  * Use this for decisions involving congestion control, use just
1063  * tp->packets_out to determine if the send queue is empty or not.
1064  *
1065  * Read this equation as:
1066  *
1067  *      "Packets sent once on transmission queue" MINUS
1068  *      "Packets left network, but not honestly ACKed yet" PLUS
1069  *      "Packets fast retransmitted"
1070  */
1071 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1072 {
1073         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1074 }
1075 
1076 #define TCP_INFINITE_SSTHRESH   0x7fffffff
1077 
1078 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1079 {
1080         return tp->snd_cwnd < tp->snd_ssthresh;
1081 }
1082 
1083 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1084 {
1085         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1086 }
1087 
1088 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1089 {
1090         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1091                (1 << inet_csk(sk)->icsk_ca_state);
1092 }
1093 
1094 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1095  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1096  * ssthresh.
1097  */
1098 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1099 {
1100         const struct tcp_sock *tp = tcp_sk(sk);
1101 
1102         if (tcp_in_cwnd_reduction(sk))
1103                 return tp->snd_ssthresh;
1104         else
1105                 return max(tp->snd_ssthresh,
1106                            ((tp->snd_cwnd >> 1) +
1107                             (tp->snd_cwnd >> 2)));
1108 }
1109 
1110 /* Use define here intentionally to get WARN_ON location shown at the caller */
1111 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1112 
1113 void tcp_enter_cwr(struct sock *sk);
1114 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1115 
1116 /* The maximum number of MSS of available cwnd for which TSO defers
1117  * sending if not using sysctl_tcp_tso_win_divisor.
1118  */
1119 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1120 {
1121         return 3;
1122 }
1123 
1124 /* Returns end sequence number of the receiver's advertised window */
1125 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1126 {
1127         return tp->snd_una + tp->snd_wnd;
1128 }
1129 
1130 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1131  * flexible approach. The RFC suggests cwnd should not be raised unless
1132  * it was fully used previously. And that's exactly what we do in
1133  * congestion avoidance mode. But in slow start we allow cwnd to grow
1134  * as long as the application has used half the cwnd.
1135  * Example :
1136  *    cwnd is 10 (IW10), but application sends 9 frames.
1137  *    We allow cwnd to reach 18 when all frames are ACKed.
1138  * This check is safe because it's as aggressive as slow start which already
1139  * risks 100% overshoot. The advantage is that we discourage application to
1140  * either send more filler packets or data to artificially blow up the cwnd
1141  * usage, and allow application-limited process to probe bw more aggressively.
1142  */
1143 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1144 {
1145         const struct tcp_sock *tp = tcp_sk(sk);
1146 
1147         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1148         if (tcp_in_slow_start(tp))
1149                 return tp->snd_cwnd < 2 * tp->max_packets_out;
1150 
1151         return tp->is_cwnd_limited;
1152 }
1153 
1154 /* Something is really bad, we could not queue an additional packet,
1155  * because qdisc is full or receiver sent a 0 window.
1156  * We do not want to add fuel to the fire, or abort too early,
1157  * so make sure the timer we arm now is at least 200ms in the future,
1158  * regardless of current icsk_rto value (as it could be ~2ms)
1159  */
1160 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1161 {
1162         return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1163 }
1164 
1165 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1166 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1167                                             unsigned long max_when)
1168 {
1169         u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1170 
1171         return (unsigned long)min_t(u64, when, max_when);
1172 }
1173 
1174 static inline void tcp_check_probe_timer(struct sock *sk)
1175 {
1176         if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1177                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1178                                           tcp_probe0_base(sk), TCP_RTO_MAX);
1179 }
1180 
1181 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1182 {
1183         tp->snd_wl1 = seq;
1184 }
1185 
1186 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1187 {
1188         tp->snd_wl1 = seq;
1189 }
1190 
1191 /*
1192  * Calculate(/check) TCP checksum
1193  */
1194 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1195                                    __be32 daddr, __wsum base)
1196 {
1197         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1198 }
1199 
1200 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1201 {
1202         return __skb_checksum_complete(skb);
1203 }
1204 
1205 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1206 {
1207         return !skb_csum_unnecessary(skb) &&
1208                 __tcp_checksum_complete(skb);
1209 }
1210 
1211 /* Prequeue for VJ style copy to user, combined with checksumming. */
1212 
1213 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1214 {
1215         tp->ucopy.task = NULL;
1216         tp->ucopy.len = 0;
1217         tp->ucopy.memory = 0;
1218         skb_queue_head_init(&tp->ucopy.prequeue);
1219 }
1220 
1221 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1222 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
1223 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1224 
1225 #undef STATE_TRACE
1226 
1227 #ifdef STATE_TRACE
1228 static const char *statename[]={
1229         "Unused","Established","Syn Sent","Syn Recv",
1230         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1231         "Close Wait","Last ACK","Listen","Closing"
1232 };
1233 #endif
1234 void tcp_set_state(struct sock *sk, int state);
1235 
1236 void tcp_done(struct sock *sk);
1237 
1238 int tcp_abort(struct sock *sk, int err);
1239 
1240 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1241 {
1242         rx_opt->dsack = 0;
1243         rx_opt->num_sacks = 0;
1244 }
1245 
1246 u32 tcp_default_init_rwnd(u32 mss);
1247 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1248 
1249 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1250 {
1251         struct tcp_sock *tp = tcp_sk(sk);
1252         s32 delta;
1253 
1254         if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
1255                 return;
1256         delta = tcp_time_stamp - tp->lsndtime;
1257         if (delta > inet_csk(sk)->icsk_rto)
1258                 tcp_cwnd_restart(sk, delta);
1259 }
1260 
1261 /* Determine a window scaling and initial window to offer. */
1262 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1263                                __u32 *window_clamp, int wscale_ok,
1264                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1265 
1266 static inline int tcp_win_from_space(int space)
1267 {
1268         return sysctl_tcp_adv_win_scale<=0 ?
1269                 (space>>(-sysctl_tcp_adv_win_scale)) :
1270                 space - (space>>sysctl_tcp_adv_win_scale);
1271 }
1272 
1273 /* Note: caller must be prepared to deal with negative returns */
1274 static inline int tcp_space(const struct sock *sk)
1275 {
1276         return tcp_win_from_space(sk->sk_rcvbuf -
1277                                   atomic_read(&sk->sk_rmem_alloc));
1278 }
1279 
1280 static inline int tcp_full_space(const struct sock *sk)
1281 {
1282         return tcp_win_from_space(sk->sk_rcvbuf);
1283 }
1284 
1285 extern void tcp_openreq_init_rwin(struct request_sock *req,
1286                                   const struct sock *sk_listener,
1287                                   const struct dst_entry *dst);
1288 
1289 void tcp_enter_memory_pressure(struct sock *sk);
1290 
1291 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1292 {
1293         struct net *net = sock_net((struct sock *)tp);
1294 
1295         return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
1296 }
1297 
1298 static inline int keepalive_time_when(const struct tcp_sock *tp)
1299 {
1300         struct net *net = sock_net((struct sock *)tp);
1301 
1302         return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1303 }
1304 
1305 static inline int keepalive_probes(const struct tcp_sock *tp)
1306 {
1307         struct net *net = sock_net((struct sock *)tp);
1308 
1309         return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1310 }
1311 
1312 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1313 {
1314         const struct inet_connection_sock *icsk = &tp->inet_conn;
1315 
1316         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1317                           tcp_time_stamp - tp->rcv_tstamp);
1318 }
1319 
1320 static inline int tcp_fin_time(const struct sock *sk)
1321 {
1322         int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
1323         const int rto = inet_csk(sk)->icsk_rto;
1324 
1325         if (fin_timeout < (rto << 2) - (rto >> 1))
1326                 fin_timeout = (rto << 2) - (rto >> 1);
1327 
1328         return fin_timeout;
1329 }
1330 
1331 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1332                                   int paws_win)
1333 {
1334         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1335                 return true;
1336         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1337                 return true;
1338         /*
1339          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1340          * then following tcp messages have valid values. Ignore 0 value,
1341          * or else 'negative' tsval might forbid us to accept their packets.
1342          */
1343         if (!rx_opt->ts_recent)
1344                 return true;
1345         return false;
1346 }
1347 
1348 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1349                                    int rst)
1350 {
1351         if (tcp_paws_check(rx_opt, 0))
1352                 return false;
1353 
1354         /* RST segments are not recommended to carry timestamp,
1355            and, if they do, it is recommended to ignore PAWS because
1356            "their cleanup function should take precedence over timestamps."
1357            Certainly, it is mistake. It is necessary to understand the reasons
1358            of this constraint to relax it: if peer reboots, clock may go
1359            out-of-sync and half-open connections will not be reset.
1360            Actually, the problem would be not existing if all
1361            the implementations followed draft about maintaining clock
1362            via reboots. Linux-2.2 DOES NOT!
1363 
1364            However, we can relax time bounds for RST segments to MSL.
1365          */
1366         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1367                 return false;
1368         return true;
1369 }
1370 
1371 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1372                           int mib_idx, u32 *last_oow_ack_time);
1373 
1374 static inline void tcp_mib_init(struct net *net)
1375 {
1376         /* See RFC 2012 */
1377         TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1378         TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1379         TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1380         TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1381 }
1382 
1383 /* from STCP */
1384 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1385 {
1386         tp->lost_skb_hint = NULL;
1387 }
1388 
1389 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1390 {
1391         tcp_clear_retrans_hints_partial(tp);
1392         tp->retransmit_skb_hint = NULL;
1393 }
1394 
1395 union tcp_md5_addr {
1396         struct in_addr  a4;
1397 #if IS_ENABLED(CONFIG_IPV6)
1398         struct in6_addr a6;
1399 #endif
1400 };
1401 
1402 /* - key database */
1403 struct tcp_md5sig_key {
1404         struct hlist_node       node;
1405         u8                      keylen;
1406         u8                      family; /* AF_INET or AF_INET6 */
1407         union tcp_md5_addr      addr;
1408         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1409         struct rcu_head         rcu;
1410 };
1411 
1412 /* - sock block */
1413 struct tcp_md5sig_info {
1414         struct hlist_head       head;
1415         struct rcu_head         rcu;
1416 };
1417 
1418 /* - pseudo header */
1419 struct tcp4_pseudohdr {
1420         __be32          saddr;
1421         __be32          daddr;
1422         __u8            pad;
1423         __u8            protocol;
1424         __be16          len;
1425 };
1426 
1427 struct tcp6_pseudohdr {
1428         struct in6_addr saddr;
1429         struct in6_addr daddr;
1430         __be32          len;
1431         __be32          protocol;       /* including padding */
1432 };
1433 
1434 union tcp_md5sum_block {
1435         struct tcp4_pseudohdr ip4;
1436 #if IS_ENABLED(CONFIG_IPV6)
1437         struct tcp6_pseudohdr ip6;
1438 #endif
1439 };
1440 
1441 /* - pool: digest algorithm, hash description and scratch buffer */
1442 struct tcp_md5sig_pool {
1443         struct ahash_request    *md5_req;
1444         void                    *scratch;
1445 };
1446 
1447 /* - functions */
1448 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1449                         const struct sock *sk, const struct sk_buff *skb);
1450 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1451                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1452 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1453                    int family);
1454 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1455                                          const struct sock *addr_sk);
1456 
1457 #ifdef CONFIG_TCP_MD5SIG
1458 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1459                                          const union tcp_md5_addr *addr,
1460                                          int family);
1461 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1462 #else
1463 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1464                                          const union tcp_md5_addr *addr,
1465                                          int family)
1466 {
1467         return NULL;
1468 }
1469 #define tcp_twsk_md5_key(twsk)  NULL
1470 #endif
1471 
1472 bool tcp_alloc_md5sig_pool(void);
1473 
1474 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1475 static inline void tcp_put_md5sig_pool(void)
1476 {
1477         local_bh_enable();
1478 }
1479 
1480 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1481                           unsigned int header_len);
1482 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1483                      const struct tcp_md5sig_key *key);
1484 
1485 /* From tcp_fastopen.c */
1486 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1487                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1488                             unsigned long *last_syn_loss);
1489 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1490                             struct tcp_fastopen_cookie *cookie, bool syn_lost,
1491                             u16 try_exp);
1492 struct tcp_fastopen_request {
1493         /* Fast Open cookie. Size 0 means a cookie request */
1494         struct tcp_fastopen_cookie      cookie;
1495         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1496         size_t                          size;
1497         int                             copied; /* queued in tcp_connect() */
1498 };
1499 void tcp_free_fastopen_req(struct tcp_sock *tp);
1500 
1501 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1502 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1503 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1504 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1505                               struct request_sock *req,
1506                               struct tcp_fastopen_cookie *foc,
1507                               struct dst_entry *dst);
1508 void tcp_fastopen_init_key_once(bool publish);
1509 #define TCP_FASTOPEN_KEY_LENGTH 16
1510 
1511 /* Fastopen key context */
1512 struct tcp_fastopen_context {
1513         struct crypto_cipher    *tfm;
1514         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1515         struct rcu_head         rcu;
1516 };
1517 
1518 /* Latencies incurred by various limits for a sender. They are
1519  * chronograph-like stats that are mutually exclusive.
1520  */
1521 enum tcp_chrono {
1522         TCP_CHRONO_UNSPEC,
1523         TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1524         TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
1525         TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
1526         __TCP_CHRONO_MAX,
1527 };
1528 
1529 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
1530 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
1531 
1532 /* write queue abstraction */
1533 static inline void tcp_write_queue_purge(struct sock *sk)
1534 {
1535         struct sk_buff *skb;
1536 
1537         tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1538         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1539                 sk_wmem_free_skb(sk, skb);
1540         sk_mem_reclaim(sk);
1541         tcp_clear_all_retrans_hints(tcp_sk(sk));
1542 }
1543 
1544 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1545 {
1546         return skb_peek(&sk->sk_write_queue);
1547 }
1548 
1549 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1550 {
1551         return skb_peek_tail(&sk->sk_write_queue);
1552 }
1553 
1554 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1555                                                    const struct sk_buff *skb)
1556 {
1557         return skb_queue_next(&sk->sk_write_queue, skb);
1558 }
1559 
1560 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1561                                                    const struct sk_buff *skb)
1562 {
1563         return skb_queue_prev(&sk->sk_write_queue, skb);
1564 }
1565 
1566 #define tcp_for_write_queue(skb, sk)                                    \
1567         skb_queue_walk(&(sk)->sk_write_queue, skb)
1568 
1569 #define tcp_for_write_queue_from(skb, sk)                               \
1570         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1571 
1572 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1573         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1574 
1575 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1576 {
1577         return sk->sk_send_head;
1578 }
1579 
1580 static inline bool tcp_skb_is_last(const struct sock *sk,
1581                                    const struct sk_buff *skb)
1582 {
1583         return skb_queue_is_last(&sk->sk_write_queue, skb);
1584 }
1585 
1586 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1587 {
1588         if (tcp_skb_is_last(sk, skb))
1589                 sk->sk_send_head = NULL;
1590         else
1591                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1592 }
1593 
1594 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1595 {
1596         if (sk->sk_send_head == skb_unlinked) {
1597                 sk->sk_send_head = NULL;
1598                 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1599         }
1600         if (tcp_sk(sk)->highest_sack == skb_unlinked)
1601                 tcp_sk(sk)->highest_sack = NULL;
1602 }
1603 
1604 static inline void tcp_init_send_head(struct sock *sk)
1605 {
1606         sk->sk_send_head = NULL;
1607 }
1608 
1609 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1610 {
1611         __skb_queue_tail(&sk->sk_write_queue, skb);
1612 }
1613 
1614 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1615 {
1616         __tcp_add_write_queue_tail(sk, skb);
1617 
1618         /* Queue it, remembering where we must start sending. */
1619         if (sk->sk_send_head == NULL) {
1620                 sk->sk_send_head = skb;
1621                 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
1622 
1623                 if (tcp_sk(sk)->highest_sack == NULL)
1624                         tcp_sk(sk)->highest_sack = skb;
1625         }
1626 }
1627 
1628 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1629 {
1630         __skb_queue_head(&sk->sk_write_queue, skb);
1631 }
1632 
1633 /* Insert buff after skb on the write queue of sk.  */
1634 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1635                                                 struct sk_buff *buff,
1636                                                 struct sock *sk)
1637 {
1638         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1639 }
1640 
1641 /* Insert new before skb on the write queue of sk.  */
1642 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1643                                                   struct sk_buff *skb,
1644                                                   struct sock *sk)
1645 {
1646         __skb_queue_before(&sk->sk_write_queue, skb, new);
1647 
1648         if (sk->sk_send_head == skb)
1649                 sk->sk_send_head = new;
1650 }
1651 
1652 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1653 {
1654         __skb_unlink(skb, &sk->sk_write_queue);
1655 }
1656 
1657 static inline bool tcp_write_queue_empty(struct sock *sk)
1658 {
1659         return skb_queue_empty(&sk->sk_write_queue);
1660 }
1661 
1662 static inline void tcp_push_pending_frames(struct sock *sk)
1663 {
1664         if (tcp_send_head(sk)) {
1665                 struct tcp_sock *tp = tcp_sk(sk);
1666 
1667                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1668         }
1669 }
1670 
1671 /* Start sequence of the skb just after the highest skb with SACKed
1672  * bit, valid only if sacked_out > 0 or when the caller has ensured
1673  * validity by itself.
1674  */
1675 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1676 {
1677         if (!tp->sacked_out)
1678                 return tp->snd_una;
1679 
1680         if (tp->highest_sack == NULL)
1681                 return tp->snd_nxt;
1682 
1683         return TCP_SKB_CB(tp->highest_sack)->seq;
1684 }
1685 
1686 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1687 {
1688         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1689                                                 tcp_write_queue_next(sk, skb);
1690 }
1691 
1692 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1693 {
1694         return tcp_sk(sk)->highest_sack;
1695 }
1696 
1697 static inline void tcp_highest_sack_reset(struct sock *sk)
1698 {
1699         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1700 }
1701 
1702 /* Called when old skb is about to be deleted (to be combined with new skb) */
1703 static inline void tcp_highest_sack_combine(struct sock *sk,
1704                                             struct sk_buff *old,
1705                                             struct sk_buff *new)
1706 {
1707         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1708                 tcp_sk(sk)->highest_sack = new;
1709 }
1710 
1711 /* This helper checks if socket has IP_TRANSPARENT set */
1712 static inline bool inet_sk_transparent(const struct sock *sk)
1713 {
1714         switch (sk->sk_state) {
1715         case TCP_TIME_WAIT:
1716                 return inet_twsk(sk)->tw_transparent;
1717         case TCP_NEW_SYN_RECV:
1718                 return inet_rsk(inet_reqsk(sk))->no_srccheck;
1719         }
1720         return inet_sk(sk)->transparent;
1721 }
1722 
1723 /* Determines whether this is a thin stream (which may suffer from
1724  * increased latency). Used to trigger latency-reducing mechanisms.
1725  */
1726 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1727 {
1728         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1729 }
1730 
1731 /* /proc */
1732 enum tcp_seq_states {
1733         TCP_SEQ_STATE_LISTENING,
1734         TCP_SEQ_STATE_ESTABLISHED,
1735 };
1736 
1737 int tcp_seq_open(struct inode *inode, struct file *file);
1738 
1739 struct tcp_seq_afinfo {
1740         char                            *name;
1741         sa_family_t                     family;
1742         const struct file_operations    *seq_fops;
1743         struct seq_operations           seq_ops;
1744 };
1745 
1746 struct tcp_iter_state {
1747         struct seq_net_private  p;
1748         sa_family_t             family;
1749         enum tcp_seq_states     state;
1750         struct sock             *syn_wait_sk;
1751         int                     bucket, offset, sbucket, num;
1752         loff_t                  last_pos;
1753 };
1754 
1755 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1756 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1757 
1758 extern struct request_sock_ops tcp_request_sock_ops;
1759 extern struct request_sock_ops tcp6_request_sock_ops;
1760 
1761 void tcp_v4_destroy_sock(struct sock *sk);
1762 
1763 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1764                                 netdev_features_t features);
1765 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1766 int tcp_gro_complete(struct sk_buff *skb);
1767 
1768 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1769 
1770 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1771 {
1772         struct net *net = sock_net((struct sock *)tp);
1773         return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
1774 }
1775 
1776 static inline bool tcp_stream_memory_free(const struct sock *sk)
1777 {
1778         const struct tcp_sock *tp = tcp_sk(sk);
1779         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1780 
1781         return notsent_bytes < tcp_notsent_lowat(tp);
1782 }
1783 
1784 #ifdef CONFIG_PROC_FS
1785 int tcp4_proc_init(void);
1786 void tcp4_proc_exit(void);
1787 #endif
1788 
1789 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1790 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1791                      const struct tcp_request_sock_ops *af_ops,
1792                      struct sock *sk, struct sk_buff *skb);
1793 
1794 /* TCP af-specific functions */
1795 struct tcp_sock_af_ops {
1796 #ifdef CONFIG_TCP_MD5SIG
1797         struct tcp_md5sig_key   *(*md5_lookup) (const struct sock *sk,
1798                                                 const struct sock *addr_sk);
1799         int             (*calc_md5_hash)(char *location,
1800                                          const struct tcp_md5sig_key *md5,
1801                                          const struct sock *sk,
1802                                          const struct sk_buff *skb);
1803         int             (*md5_parse)(struct sock *sk,
1804                                      char __user *optval,
1805                                      int optlen);
1806 #endif
1807 };
1808 
1809 struct tcp_request_sock_ops {
1810         u16 mss_clamp;
1811 #ifdef CONFIG_TCP_MD5SIG
1812         struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1813                                                  const struct sock *addr_sk);
1814         int             (*calc_md5_hash) (char *location,
1815                                           const struct tcp_md5sig_key *md5,
1816                                           const struct sock *sk,
1817                                           const struct sk_buff *skb);
1818 #endif
1819         void (*init_req)(struct request_sock *req,
1820                          const struct sock *sk_listener,
1821                          struct sk_buff *skb);
1822 #ifdef CONFIG_SYN_COOKIES
1823         __u32 (*cookie_init_seq)(const struct sk_buff *skb,
1824                                  __u16 *mss);
1825 #endif
1826         struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1827                                        const struct request_sock *req,
1828                                        bool *strict);
1829         __u32 (*init_seq)(const struct sk_buff *skb, u32 *tsoff);
1830         int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1831                            struct flowi *fl, struct request_sock *req,
1832                            struct tcp_fastopen_cookie *foc,
1833                            enum tcp_synack_type synack_type);
1834 };
1835 
1836 #ifdef CONFIG_SYN_COOKIES
1837 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1838                                          const struct sock *sk, struct sk_buff *skb,
1839                                          __u16 *mss)
1840 {
1841         tcp_synq_overflow(sk);
1842         __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1843         return ops->cookie_init_seq(skb, mss);
1844 }
1845 #else
1846 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1847                                          const struct sock *sk, struct sk_buff *skb,
1848                                          __u16 *mss)
1849 {
1850         return 0;
1851 }
1852 #endif
1853 
1854 int tcpv4_offload_init(void);
1855 
1856 void tcp_v4_init(void);
1857 void tcp_init(void);
1858 
1859 /* tcp_recovery.c */
1860 
1861 /* Flags to enable various loss recovery features. See below */
1862 extern int sysctl_tcp_recovery;
1863 
1864 /* Use TCP RACK to detect (some) tail and retransmit losses */
1865 #define TCP_RACK_LOST_RETRANS  0x1
1866 
1867 extern int tcp_rack_mark_lost(struct sock *sk);
1868 
1869 extern void tcp_rack_advance(struct tcp_sock *tp,
1870                              const struct skb_mstamp *xmit_time, u8 sacked);
1871 
1872 /*
1873  * Save and compile IPv4 options, return a pointer to it
1874  */
1875 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1876 {
1877         const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1878         struct ip_options_rcu *dopt = NULL;
1879 
1880         if (opt->optlen) {
1881                 int opt_size = sizeof(*dopt) + opt->optlen;
1882 
1883                 dopt = kmalloc(opt_size, GFP_ATOMIC);
1884                 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1885                         kfree(dopt);
1886                         dopt = NULL;
1887                 }
1888         }
1889         return dopt;
1890 }
1891 
1892 /* locally generated TCP pure ACKs have skb->truesize == 2
1893  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1894  * This is much faster than dissecting the packet to find out.
1895  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1896  */
1897 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1898 {
1899         return skb->truesize == 2;
1900 }
1901 
1902 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1903 {
1904         skb->truesize = 2;
1905 }
1906 
1907 static inline int tcp_inq(struct sock *sk)
1908 {
1909         struct tcp_sock *tp = tcp_sk(sk);
1910         int answ;
1911 
1912         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
1913                 answ = 0;
1914         } else if (sock_flag(sk, SOCK_URGINLINE) ||
1915                    !tp->urg_data ||
1916                    before(tp->urg_seq, tp->copied_seq) ||
1917                    !before(tp->urg_seq, tp->rcv_nxt)) {
1918 
1919                 answ = tp->rcv_nxt - tp->copied_seq;
1920 
1921                 /* Subtract 1, if FIN was received */
1922                 if (answ && sock_flag(sk, SOCK_DONE))
1923                         answ--;
1924         } else {
1925                 answ = tp->urg_seq - tp->copied_seq;
1926         }
1927 
1928         return answ;
1929 }
1930 
1931 int tcp_peek_len(struct socket *sock);
1932 
1933 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
1934 {
1935         u16 segs_in;
1936 
1937         segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
1938         tp->segs_in += segs_in;
1939         if (skb->len > tcp_hdrlen(skb))
1940                 tp->data_segs_in += segs_in;
1941 }
1942 
1943 /*
1944  * TCP listen path runs lockless.
1945  * We forced "struct sock" to be const qualified to make sure
1946  * we don't modify one of its field by mistake.
1947  * Here, we increment sk_drops which is an atomic_t, so we can safely
1948  * make sock writable again.
1949  */
1950 static inline void tcp_listendrop(const struct sock *sk)
1951 {
1952         atomic_inc(&((struct sock *)sk)->sk_drops);
1953         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
1954 }
1955 
1956 #endif  /* _TCP_H */
1957 

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