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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/crypto.h>
 31 #include <linux/cryptohash.h>
 32 #include <linux/kref.h>
 33 #include <linux/ktime.h>
 34 
 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>
 40 #include <net/sock.h>
 41 #include <net/snmp.h>
 42 #include <net/ip.h>
 43 #include <net/tcp_states.h>
 44 #include <net/inet_ecn.h>
 45 #include <net/dst.h>
 46 
 47 #include <linux/seq_file.h>
 48 #include <linux/memcontrol.h>
 49 
 50 extern struct inet_hashinfo tcp_hashinfo;
 51 
 52 extern struct percpu_counter tcp_orphan_count;
 53 void tcp_time_wait(struct sock *sk, int state, int timeo);
 54 
 55 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 56 #define MAX_TCP_OPTION_SPACE 40
 57 
 58 /*
 59  * Never offer a window over 32767 without using window scaling. Some
 60  * poor stacks do signed 16bit maths!
 61  */
 62 #define MAX_TCP_WINDOW          32767U
 63 
 64 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 65 #define TCP_MIN_MSS             88U
 66 
 67 /* The least MTU to use for probing */
 68 #define TCP_BASE_MSS            1024
 69 
 70 /* probing interval, default to 10 minutes as per RFC4821 */
 71 #define TCP_PROBE_INTERVAL      600
 72 
 73 /* Specify interval when tcp mtu probing will stop */
 74 #define TCP_PROBE_THRESHOLD     8
 75 
 76 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 77 #define TCP_FASTRETRANS_THRESH 3
 78 
 79 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 80 #define TCP_MAX_QUICKACKS       16U
 81 
 82 /* urg_data states */
 83 #define TCP_URG_VALID   0x0100
 84 #define TCP_URG_NOTYET  0x0200
 85 #define TCP_URG_READ    0x0400
 86 
 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.
 92                                  */
 93 
 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.
 99                                  */
100 
101 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
102                                  * when active opening a connection.
103                                  * RFC1122 says the minimum retry MUST
104                                  * be at least 180secs.  Nevertheless
105                                  * this value is corresponding to
106                                  * 63secs of retransmission with the
107                                  * current initial RTO.
108                                  */
109 
110 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
111                                  * when passive opening a connection.
112                                  * This is corresponding to 31secs of
113                                  * retransmission with the current
114                                  * initial RTO.
115                                  */
116 
117 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
118                                   * state, about 60 seconds     */
119 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
120                                  /* BSD style FIN_WAIT2 deadlock breaker.
121                                   * It used to be 3min, new value is 60sec,
122                                   * to combine FIN-WAIT-2 timeout with
123                                   * TIME-WAIT timer.
124                                   */
125 
126 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
127 #if HZ >= 100
128 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
129 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
130 #else
131 #define TCP_DELACK_MIN  4U
132 #define TCP_ATO_MIN     4U
133 #endif
134 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
135 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
136 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
137 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
138                                                  * used as a fallback RTO for the
139                                                  * initial data transmission if no
140                                                  * valid RTT sample has been acquired,
141                                                  * most likely due to retrans in 3WHS.
142                                                  */
143 
144 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
145                                                          * for local resources.
146                                                          */
147 
148 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
149 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
150 #define TCP_KEEPALIVE_INTVL     (75*HZ)
151 
152 #define MAX_TCP_KEEPIDLE        32767
153 #define MAX_TCP_KEEPINTVL       32767
154 #define MAX_TCP_KEEPCNT         127
155 #define MAX_TCP_SYNCNT          127
156 
157 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
158 
159 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
160 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
161                                          * after this time. It should be equal
162                                          * (or greater than) TCP_TIMEWAIT_LEN
163                                          * to provide reliability equal to one
164                                          * provided by timewait state.
165                                          */
166 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
167                                          * timestamps. It must be less than
168                                          * minimal timewait lifetime.
169                                          */
170 /*
171  *      TCP option
172  */
173 
174 #define TCPOPT_NOP              1       /* Padding */
175 #define TCPOPT_EOL              0       /* End of options */
176 #define TCPOPT_MSS              2       /* Segment size negotiating */
177 #define TCPOPT_WINDOW           3       /* Window scaling */
178 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
179 #define TCPOPT_SACK             5       /* SACK Block */
180 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
181 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
182 #define TCPOPT_FASTOPEN         34      /* Fast open (RFC7413) */
183 #define TCPOPT_EXP              254     /* Experimental */
184 /* Magic number to be after the option value for sharing TCP
185  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
186  */
187 #define TCPOPT_FASTOPEN_MAGIC   0xF989
188 
189 /*
190  *     TCP option lengths
191  */
192 
193 #define TCPOLEN_MSS            4
194 #define TCPOLEN_WINDOW         3
195 #define TCPOLEN_SACK_PERM      2
196 #define TCPOLEN_TIMESTAMP      10
197 #define TCPOLEN_MD5SIG         18
198 #define TCPOLEN_FASTOPEN_BASE  2
199 #define TCPOLEN_EXP_FASTOPEN_BASE  4
200 
201 /* But this is what stacks really send out. */
202 #define TCPOLEN_TSTAMP_ALIGNED          12
203 #define TCPOLEN_WSCALE_ALIGNED          4
204 #define TCPOLEN_SACKPERM_ALIGNED        4
205 #define TCPOLEN_SACK_BASE               2
206 #define TCPOLEN_SACK_BASE_ALIGNED       4
207 #define TCPOLEN_SACK_PERBLOCK           8
208 #define TCPOLEN_MD5SIG_ALIGNED          20
209 #define TCPOLEN_MSS_ALIGNED             4
210 
211 /* Flags in tp->nonagle */
212 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
213 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
214 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
215 
216 /* TCP thin-stream limits */
217 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
218 
219 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
220 #define TCP_INIT_CWND           10
221 
222 /* Bit Flags for sysctl_tcp_fastopen */
223 #define TFO_CLIENT_ENABLE       1
224 #define TFO_SERVER_ENABLE       2
225 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
226 
227 /* Accept SYN data w/o any cookie option */
228 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
229 
230 /* Force enable TFO on all listeners, i.e., not requiring the
231  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
232  */
233 #define TFO_SERVER_WO_SOCKOPT1  0x400
234 #define TFO_SERVER_WO_SOCKOPT2  0x800
235 
236 extern struct inet_timewait_death_row tcp_death_row;
237 
238 /* sysctl variables for tcp */
239 extern int sysctl_tcp_timestamps;
240 extern int sysctl_tcp_window_scaling;
241 extern int sysctl_tcp_sack;
242 extern int sysctl_tcp_fin_timeout;
243 extern int sysctl_tcp_keepalive_time;
244 extern int sysctl_tcp_keepalive_probes;
245 extern int sysctl_tcp_keepalive_intvl;
246 extern int sysctl_tcp_syn_retries;
247 extern int sysctl_tcp_synack_retries;
248 extern int sysctl_tcp_retries1;
249 extern int sysctl_tcp_retries2;
250 extern int sysctl_tcp_orphan_retries;
251 extern int sysctl_tcp_syncookies;
252 extern int sysctl_tcp_fastopen;
253 extern int sysctl_tcp_retrans_collapse;
254 extern int sysctl_tcp_stdurg;
255 extern int sysctl_tcp_rfc1337;
256 extern int sysctl_tcp_abort_on_overflow;
257 extern int sysctl_tcp_max_orphans;
258 extern int sysctl_tcp_fack;
259 extern int sysctl_tcp_reordering;
260 extern int sysctl_tcp_max_reordering;
261 extern int sysctl_tcp_dsack;
262 extern long sysctl_tcp_mem[3];
263 extern int sysctl_tcp_wmem[3];
264 extern int sysctl_tcp_rmem[3];
265 extern int sysctl_tcp_app_win;
266 extern int sysctl_tcp_adv_win_scale;
267 extern int sysctl_tcp_tw_reuse;
268 extern int sysctl_tcp_frto;
269 extern int sysctl_tcp_low_latency;
270 extern int sysctl_tcp_nometrics_save;
271 extern int sysctl_tcp_moderate_rcvbuf;
272 extern int sysctl_tcp_tso_win_divisor;
273 extern int sysctl_tcp_workaround_signed_windows;
274 extern int sysctl_tcp_slow_start_after_idle;
275 extern int sysctl_tcp_thin_linear_timeouts;
276 extern int sysctl_tcp_thin_dupack;
277 extern int sysctl_tcp_early_retrans;
278 extern int sysctl_tcp_limit_output_bytes;
279 extern int sysctl_tcp_challenge_ack_limit;
280 extern unsigned int sysctl_tcp_notsent_lowat;
281 extern int sysctl_tcp_min_tso_segs;
282 extern int sysctl_tcp_min_rtt_wlen;
283 extern int sysctl_tcp_autocorking;
284 extern int sysctl_tcp_invalid_ratelimit;
285 extern int sysctl_tcp_pacing_ss_ratio;
286 extern int sysctl_tcp_pacing_ca_ratio;
287 
288 extern atomic_long_t tcp_memory_allocated;
289 extern struct percpu_counter tcp_sockets_allocated;
290 extern int tcp_memory_pressure;
291 
292 /* optimized version of sk_under_memory_pressure() for TCP sockets */
293 static inline bool tcp_under_memory_pressure(const struct sock *sk)
294 {
295         if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
296                 return !!sk->sk_cgrp->memory_pressure;
297 
298         return tcp_memory_pressure;
299 }
300 /*
301  * The next routines deal with comparing 32 bit unsigned ints
302  * and worry about wraparound (automatic with unsigned arithmetic).
303  */
304 
305 static inline bool before(__u32 seq1, __u32 seq2)
306 {
307         return (__s32)(seq1-seq2) < 0;
308 }
309 #define after(seq2, seq1)       before(seq1, seq2)
310 
311 /* is s2<=s1<=s3 ? */
312 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
313 {
314         return seq3 - seq2 >= seq1 - seq2;
315 }
316 
317 static inline bool tcp_out_of_memory(struct sock *sk)
318 {
319         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
320             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
321                 return true;
322         return false;
323 }
324 
325 void sk_forced_mem_schedule(struct sock *sk, int size);
326 
327 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
328 {
329         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
330         int orphans = percpu_counter_read_positive(ocp);
331 
332         if (orphans << shift > sysctl_tcp_max_orphans) {
333                 orphans = percpu_counter_sum_positive(ocp);
334                 if (orphans << shift > sysctl_tcp_max_orphans)
335                         return true;
336         }
337         return false;
338 }
339 
340 bool tcp_check_oom(struct sock *sk, int shift);
341 
342 
343 extern struct proto tcp_prot;
344 
345 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
346 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
347 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
348 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
349 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
350 
351 void tcp_tasklet_init(void);
352 
353 void tcp_v4_err(struct sk_buff *skb, u32);
354 
355 void tcp_shutdown(struct sock *sk, int how);
356 
357 void tcp_v4_early_demux(struct sk_buff *skb);
358 int tcp_v4_rcv(struct sk_buff *skb);
359 
360 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
361 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
362 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
363                  int flags);
364 void tcp_release_cb(struct sock *sk);
365 void tcp_wfree(struct sk_buff *skb);
366 void tcp_write_timer_handler(struct sock *sk);
367 void tcp_delack_timer_handler(struct sock *sk);
368 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
369 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
370 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
371                          const struct tcphdr *th, unsigned int len);
372 void tcp_rcv_space_adjust(struct sock *sk);
373 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
374 void tcp_twsk_destructor(struct sock *sk);
375 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
376                         struct pipe_inode_info *pipe, size_t len,
377                         unsigned int flags);
378 
379 static inline void tcp_dec_quickack_mode(struct sock *sk,
380                                          const unsigned int pkts)
381 {
382         struct inet_connection_sock *icsk = inet_csk(sk);
383 
384         if (icsk->icsk_ack.quick) {
385                 if (pkts >= icsk->icsk_ack.quick) {
386                         icsk->icsk_ack.quick = 0;
387                         /* Leaving quickack mode we deflate ATO. */
388                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
389                 } else
390                         icsk->icsk_ack.quick -= pkts;
391         }
392 }
393 
394 #define TCP_ECN_OK              1
395 #define TCP_ECN_QUEUE_CWR       2
396 #define TCP_ECN_DEMAND_CWR      4
397 #define TCP_ECN_SEEN            8
398 
399 enum tcp_tw_status {
400         TCP_TW_SUCCESS = 0,
401         TCP_TW_RST = 1,
402         TCP_TW_ACK = 2,
403         TCP_TW_SYN = 3
404 };
405 
406 
407 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
408                                               struct sk_buff *skb,
409                                               const struct tcphdr *th);
410 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
411                            struct request_sock *req, bool fastopen);
412 int tcp_child_process(struct sock *parent, struct sock *child,
413                       struct sk_buff *skb);
414 void tcp_enter_loss(struct sock *sk);
415 void tcp_clear_retrans(struct tcp_sock *tp);
416 void tcp_update_metrics(struct sock *sk);
417 void tcp_init_metrics(struct sock *sk);
418 void tcp_metrics_init(void);
419 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
420                         bool paws_check, bool timestamps);
421 bool tcp_remember_stamp(struct sock *sk);
422 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
423 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
424 void tcp_disable_fack(struct tcp_sock *tp);
425 void tcp_close(struct sock *sk, long timeout);
426 void tcp_init_sock(struct sock *sk);
427 unsigned int tcp_poll(struct file *file, struct socket *sock,
428                       struct poll_table_struct *wait);
429 int tcp_getsockopt(struct sock *sk, int level, int optname,
430                    char __user *optval, int __user *optlen);
431 int tcp_setsockopt(struct sock *sk, int level, int optname,
432                    char __user *optval, unsigned int optlen);
433 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
434                           char __user *optval, int __user *optlen);
435 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
436                           char __user *optval, unsigned int optlen);
437 void tcp_set_keepalive(struct sock *sk, int val);
438 void tcp_syn_ack_timeout(const struct request_sock *req);
439 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
440                 int flags, int *addr_len);
441 void tcp_parse_options(const struct sk_buff *skb,
442                        struct tcp_options_received *opt_rx,
443                        int estab, struct tcp_fastopen_cookie *foc);
444 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
445 
446 /*
447  *      TCP v4 functions exported for the inet6 API
448  */
449 
450 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
451 void tcp_v4_mtu_reduced(struct sock *sk);
452 void tcp_req_err(struct sock *sk, u32 seq);
453 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
454 struct sock *tcp_create_openreq_child(const struct sock *sk,
455                                       struct request_sock *req,
456                                       struct sk_buff *skb);
457 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
458 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
459                                   struct request_sock *req,
460                                   struct dst_entry *dst,
461                                   struct request_sock *req_unhash,
462                                   bool *own_req);
463 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
464 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
465 int tcp_connect(struct sock *sk);
466 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
467                                 struct request_sock *req,
468                                 struct tcp_fastopen_cookie *foc,
469                                 bool attach_req);
470 int tcp_disconnect(struct sock *sk, int flags);
471 
472 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
473 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
474 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
475 
476 /* From syncookies.c */
477 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
478                                  struct request_sock *req,
479                                  struct dst_entry *dst);
480 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
481                       u32 cookie);
482 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
483 #ifdef CONFIG_SYN_COOKIES
484 
485 /* Syncookies use a monotonic timer which increments every 60 seconds.
486  * This counter is used both as a hash input and partially encoded into
487  * the cookie value.  A cookie is only validated further if the delta
488  * between the current counter value and the encoded one is less than this,
489  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
490  * the counter advances immediately after a cookie is generated).
491  */
492 #define MAX_SYNCOOKIE_AGE       2
493 #define TCP_SYNCOOKIE_PERIOD    (60 * HZ)
494 #define TCP_SYNCOOKIE_VALID     (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
495 
496 /* syncookies: remember time of last synqueue overflow
497  * But do not dirty this field too often (once per second is enough)
498  * It is racy as we do not hold a lock, but race is very minor.
499  */
500 static inline void tcp_synq_overflow(const struct sock *sk)
501 {
502         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
503         unsigned long now = jiffies;
504 
505         if (time_after(now, last_overflow + HZ))
506                 tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
507 }
508 
509 /* syncookies: no recent synqueue overflow on this listening socket? */
510 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
511 {
512         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
513 
514         return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
515 }
516 
517 static inline u32 tcp_cookie_time(void)
518 {
519         u64 val = get_jiffies_64();
520 
521         do_div(val, TCP_SYNCOOKIE_PERIOD);
522         return val;
523 }
524 
525 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
526                               u16 *mssp);
527 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
528 __u32 cookie_init_timestamp(struct request_sock *req);
529 bool cookie_timestamp_decode(struct tcp_options_received *opt);
530 bool cookie_ecn_ok(const struct tcp_options_received *opt,
531                    const struct net *net, const struct dst_entry *dst);
532 
533 /* From net/ipv6/syncookies.c */
534 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
535                       u32 cookie);
536 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
537 
538 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
539                               const struct tcphdr *th, u16 *mssp);
540 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
541 #endif
542 /* tcp_output.c */
543 
544 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
545                                int nonagle);
546 bool tcp_may_send_now(struct sock *sk);
547 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
548 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
549 void tcp_retransmit_timer(struct sock *sk);
550 void tcp_xmit_retransmit_queue(struct sock *);
551 void tcp_simple_retransmit(struct sock *);
552 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
553 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
554 
555 void tcp_send_probe0(struct sock *);
556 void tcp_send_partial(struct sock *);
557 int tcp_write_wakeup(struct sock *, int mib);
558 void tcp_send_fin(struct sock *sk);
559 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
560 int tcp_send_synack(struct sock *);
561 void tcp_push_one(struct sock *, unsigned int mss_now);
562 void tcp_send_ack(struct sock *sk);
563 void tcp_send_delayed_ack(struct sock *sk);
564 void tcp_send_loss_probe(struct sock *sk);
565 bool tcp_schedule_loss_probe(struct sock *sk);
566 
567 /* tcp_input.c */
568 void tcp_resume_early_retransmit(struct sock *sk);
569 void tcp_rearm_rto(struct sock *sk);
570 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
571 void tcp_reset(struct sock *sk);
572 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
573 
574 /* tcp_timer.c */
575 void tcp_init_xmit_timers(struct sock *);
576 static inline void tcp_clear_xmit_timers(struct sock *sk)
577 {
578         inet_csk_clear_xmit_timers(sk);
579 }
580 
581 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
582 unsigned int tcp_current_mss(struct sock *sk);
583 
584 /* Bound MSS / TSO packet size with the half of the window */
585 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
586 {
587         int cutoff;
588 
589         /* When peer uses tiny windows, there is no use in packetizing
590          * to sub-MSS pieces for the sake of SWS or making sure there
591          * are enough packets in the pipe for fast recovery.
592          *
593          * On the other hand, for extremely large MSS devices, handling
594          * smaller than MSS windows in this way does make sense.
595          */
596         if (tp->max_window >= 512)
597                 cutoff = (tp->max_window >> 1);
598         else
599                 cutoff = tp->max_window;
600 
601         if (cutoff && pktsize > cutoff)
602                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
603         else
604                 return pktsize;
605 }
606 
607 /* tcp.c */
608 void tcp_get_info(struct sock *, struct tcp_info *);
609 
610 /* Read 'sendfile()'-style from a TCP socket */
611 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
612                                 unsigned int, size_t);
613 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
614                   sk_read_actor_t recv_actor);
615 
616 void tcp_initialize_rcv_mss(struct sock *sk);
617 
618 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
619 int tcp_mss_to_mtu(struct sock *sk, int mss);
620 void tcp_mtup_init(struct sock *sk);
621 void tcp_init_buffer_space(struct sock *sk);
622 
623 static inline void tcp_bound_rto(const struct sock *sk)
624 {
625         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
626                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
627 }
628 
629 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
630 {
631         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
632 }
633 
634 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
635 {
636         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
637                                ntohl(TCP_FLAG_ACK) |
638                                snd_wnd);
639 }
640 
641 static inline void tcp_fast_path_on(struct tcp_sock *tp)
642 {
643         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
644 }
645 
646 static inline void tcp_fast_path_check(struct sock *sk)
647 {
648         struct tcp_sock *tp = tcp_sk(sk);
649 
650         if (skb_queue_empty(&tp->out_of_order_queue) &&
651             tp->rcv_wnd &&
652             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
653             !tp->urg_data)
654                 tcp_fast_path_on(tp);
655 }
656 
657 /* Compute the actual rto_min value */
658 static inline u32 tcp_rto_min(struct sock *sk)
659 {
660         const struct dst_entry *dst = __sk_dst_get(sk);
661         u32 rto_min = TCP_RTO_MIN;
662 
663         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
664                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
665         return rto_min;
666 }
667 
668 static inline u32 tcp_rto_min_us(struct sock *sk)
669 {
670         return jiffies_to_usecs(tcp_rto_min(sk));
671 }
672 
673 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
674 {
675         return dst_metric_locked(dst, RTAX_CC_ALGO);
676 }
677 
678 /* Minimum RTT in usec. ~0 means not available. */
679 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
680 {
681         return tp->rtt_min[0].rtt;
682 }
683 
684 /* Compute the actual receive window we are currently advertising.
685  * Rcv_nxt can be after the window if our peer push more data
686  * than the offered window.
687  */
688 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
689 {
690         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
691 
692         if (win < 0)
693                 win = 0;
694         return (u32) win;
695 }
696 
697 /* Choose a new window, without checks for shrinking, and without
698  * scaling applied to the result.  The caller does these things
699  * if necessary.  This is a "raw" window selection.
700  */
701 u32 __tcp_select_window(struct sock *sk);
702 
703 void tcp_send_window_probe(struct sock *sk);
704 
705 /* TCP timestamps are only 32-bits, this causes a slight
706  * complication on 64-bit systems since we store a snapshot
707  * of jiffies in the buffer control blocks below.  We decided
708  * to use only the low 32-bits of jiffies and hide the ugly
709  * casts with the following macro.
710  */
711 #define tcp_time_stamp          ((__u32)(jiffies))
712 
713 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
714 {
715         return skb->skb_mstamp.stamp_jiffies;
716 }
717 
718 
719 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
720 
721 #define TCPHDR_FIN 0x01
722 #define TCPHDR_SYN 0x02
723 #define TCPHDR_RST 0x04
724 #define TCPHDR_PSH 0x08
725 #define TCPHDR_ACK 0x10
726 #define TCPHDR_URG 0x20
727 #define TCPHDR_ECE 0x40
728 #define TCPHDR_CWR 0x80
729 
730 #define TCPHDR_SYN_ECN  (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
731 
732 /* This is what the send packet queuing engine uses to pass
733  * TCP per-packet control information to the transmission code.
734  * We also store the host-order sequence numbers in here too.
735  * This is 44 bytes if IPV6 is enabled.
736  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
737  */
738 struct tcp_skb_cb {
739         __u32           seq;            /* Starting sequence number     */
740         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
741         union {
742                 /* Note : tcp_tw_isn is used in input path only
743                  *        (isn chosen by tcp_timewait_state_process())
744                  *
745                  *        tcp_gso_segs/size are used in write queue only,
746                  *        cf tcp_skb_pcount()/tcp_skb_mss()
747                  */
748                 __u32           tcp_tw_isn;
749                 struct {
750                         u16     tcp_gso_segs;
751                         u16     tcp_gso_size;
752                 };
753         };
754         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
755 
756         __u8            sacked;         /* State flags for SACK/FACK.   */
757 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
758 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
759 #define TCPCB_LOST              0x04    /* SKB is lost                  */
760 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
761 #define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
762 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
763 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
764                                 TCPCB_REPAIRED)
765 
766         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
767         /* 1 byte hole */
768         __u32           ack_seq;        /* Sequence number ACK'd        */
769         union {
770                 struct inet_skb_parm    h4;
771 #if IS_ENABLED(CONFIG_IPV6)
772                 struct inet6_skb_parm   h6;
773 #endif
774         } header;       /* For incoming frames          */
775 };
776 
777 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
778 
779 
780 #if IS_ENABLED(CONFIG_IPV6)
781 /* This is the variant of inet6_iif() that must be used by TCP,
782  * as TCP moves IP6CB into a different location in skb->cb[]
783  */
784 static inline int tcp_v6_iif(const struct sk_buff *skb)
785 {
786         return TCP_SKB_CB(skb)->header.h6.iif;
787 }
788 #endif
789 
790 /* Due to TSO, an SKB can be composed of multiple actual
791  * packets.  To keep these tracked properly, we use this.
792  */
793 static inline int tcp_skb_pcount(const struct sk_buff *skb)
794 {
795         return TCP_SKB_CB(skb)->tcp_gso_segs;
796 }
797 
798 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
799 {
800         TCP_SKB_CB(skb)->tcp_gso_segs = segs;
801 }
802 
803 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
804 {
805         TCP_SKB_CB(skb)->tcp_gso_segs += segs;
806 }
807 
808 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
809 static inline int tcp_skb_mss(const struct sk_buff *skb)
810 {
811         return TCP_SKB_CB(skb)->tcp_gso_size;
812 }
813 
814 /* Events passed to congestion control interface */
815 enum tcp_ca_event {
816         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
817         CA_EVENT_CWND_RESTART,  /* congestion window restart */
818         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
819         CA_EVENT_LOSS,          /* loss timeout */
820         CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
821         CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
822         CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
823         CA_EVENT_NON_DELAYED_ACK,
824 };
825 
826 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
827 enum tcp_ca_ack_event_flags {
828         CA_ACK_SLOWPATH         = (1 << 0),     /* In slow path processing */
829         CA_ACK_WIN_UPDATE       = (1 << 1),     /* ACK updated window */
830         CA_ACK_ECE              = (1 << 2),     /* ECE bit is set on ack */
831 };
832 
833 /*
834  * Interface for adding new TCP congestion control handlers
835  */
836 #define TCP_CA_NAME_MAX 16
837 #define TCP_CA_MAX      128
838 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
839 
840 #define TCP_CA_UNSPEC   0
841 
842 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
843 #define TCP_CONG_NON_RESTRICTED 0x1
844 /* Requires ECN/ECT set on all packets */
845 #define TCP_CONG_NEEDS_ECN      0x2
846 
847 union tcp_cc_info;
848 
849 struct tcp_congestion_ops {
850         struct list_head        list;
851         u32 key;
852         u32 flags;
853 
854         /* initialize private data (optional) */
855         void (*init)(struct sock *sk);
856         /* cleanup private data  (optional) */
857         void (*release)(struct sock *sk);
858 
859         /* return slow start threshold (required) */
860         u32 (*ssthresh)(struct sock *sk);
861         /* do new cwnd calculation (required) */
862         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
863         /* call before changing ca_state (optional) */
864         void (*set_state)(struct sock *sk, u8 new_state);
865         /* call when cwnd event occurs (optional) */
866         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
867         /* call when ack arrives (optional) */
868         void (*in_ack_event)(struct sock *sk, u32 flags);
869         /* new value of cwnd after loss (optional) */
870         u32  (*undo_cwnd)(struct sock *sk);
871         /* hook for packet ack accounting (optional) */
872         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
873         /* get info for inet_diag (optional) */
874         size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
875                            union tcp_cc_info *info);
876 
877         char            name[TCP_CA_NAME_MAX];
878         struct module   *owner;
879 };
880 
881 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
882 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
883 
884 void tcp_assign_congestion_control(struct sock *sk);
885 void tcp_init_congestion_control(struct sock *sk);
886 void tcp_cleanup_congestion_control(struct sock *sk);
887 int tcp_set_default_congestion_control(const char *name);
888 void tcp_get_default_congestion_control(char *name);
889 void tcp_get_available_congestion_control(char *buf, size_t len);
890 void tcp_get_allowed_congestion_control(char *buf, size_t len);
891 int tcp_set_allowed_congestion_control(char *allowed);
892 int tcp_set_congestion_control(struct sock *sk, const char *name);
893 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
894 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
895 
896 u32 tcp_reno_ssthresh(struct sock *sk);
897 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
898 extern struct tcp_congestion_ops tcp_reno;
899 
900 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
901 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
902 #ifdef CONFIG_INET
903 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
904 #else
905 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
906 {
907         return NULL;
908 }
909 #endif
910 
911 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
912 {
913         const struct inet_connection_sock *icsk = inet_csk(sk);
914 
915         return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
916 }
917 
918 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
919 {
920         struct inet_connection_sock *icsk = inet_csk(sk);
921 
922         if (icsk->icsk_ca_ops->set_state)
923                 icsk->icsk_ca_ops->set_state(sk, ca_state);
924         icsk->icsk_ca_state = ca_state;
925 }
926 
927 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
928 {
929         const struct inet_connection_sock *icsk = inet_csk(sk);
930 
931         if (icsk->icsk_ca_ops->cwnd_event)
932                 icsk->icsk_ca_ops->cwnd_event(sk, event);
933 }
934 
935 /* These functions determine how the current flow behaves in respect of SACK
936  * handling. SACK is negotiated with the peer, and therefore it can vary
937  * between different flows.
938  *
939  * tcp_is_sack - SACK enabled
940  * tcp_is_reno - No SACK
941  * tcp_is_fack - FACK enabled, implies SACK enabled
942  */
943 static inline int tcp_is_sack(const struct tcp_sock *tp)
944 {
945         return tp->rx_opt.sack_ok;
946 }
947 
948 static inline bool tcp_is_reno(const struct tcp_sock *tp)
949 {
950         return !tcp_is_sack(tp);
951 }
952 
953 static inline bool tcp_is_fack(const struct tcp_sock *tp)
954 {
955         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
956 }
957 
958 static inline void tcp_enable_fack(struct tcp_sock *tp)
959 {
960         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
961 }
962 
963 /* TCP early-retransmit (ER) is similar to but more conservative than
964  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
965  */
966 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
967 {
968         tp->do_early_retrans = sysctl_tcp_early_retrans &&
969                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
970                 sysctl_tcp_reordering == 3;
971 }
972 
973 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
974 {
975         tp->do_early_retrans = 0;
976 }
977 
978 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
979 {
980         return tp->sacked_out + tp->lost_out;
981 }
982 
983 /* This determines how many packets are "in the network" to the best
984  * of our knowledge.  In many cases it is conservative, but where
985  * detailed information is available from the receiver (via SACK
986  * blocks etc.) we can make more aggressive calculations.
987  *
988  * Use this for decisions involving congestion control, use just
989  * tp->packets_out to determine if the send queue is empty or not.
990  *
991  * Read this equation as:
992  *
993  *      "Packets sent once on transmission queue" MINUS
994  *      "Packets left network, but not honestly ACKed yet" PLUS
995  *      "Packets fast retransmitted"
996  */
997 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
998 {
999         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1000 }
1001 
1002 #define TCP_INFINITE_SSTHRESH   0x7fffffff
1003 
1004 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1005 {
1006         return tp->snd_cwnd < tp->snd_ssthresh;
1007 }
1008 
1009 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1010 {
1011         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1012 }
1013 
1014 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1015 {
1016         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1017                (1 << inet_csk(sk)->icsk_ca_state);
1018 }
1019 
1020 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1021  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1022  * ssthresh.
1023  */
1024 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1025 {
1026         const struct tcp_sock *tp = tcp_sk(sk);
1027 
1028         if (tcp_in_cwnd_reduction(sk))
1029                 return tp->snd_ssthresh;
1030         else
1031                 return max(tp->snd_ssthresh,
1032                            ((tp->snd_cwnd >> 1) +
1033                             (tp->snd_cwnd >> 2)));
1034 }
1035 
1036 /* Use define here intentionally to get WARN_ON location shown at the caller */
1037 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1038 
1039 void tcp_enter_cwr(struct sock *sk);
1040 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1041 
1042 /* The maximum number of MSS of available cwnd for which TSO defers
1043  * sending if not using sysctl_tcp_tso_win_divisor.
1044  */
1045 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1046 {
1047         return 3;
1048 }
1049 
1050 /* Slow start with delack produces 3 packets of burst, so that
1051  * it is safe "de facto".  This will be the default - same as
1052  * the default reordering threshold - but if reordering increases,
1053  * we must be able to allow cwnd to burst at least this much in order
1054  * to not pull it back when holes are filled.
1055  */
1056 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
1057 {
1058         return tp->reordering;
1059 }
1060 
1061 /* Returns end sequence number of the receiver's advertised window */
1062 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1063 {
1064         return tp->snd_una + tp->snd_wnd;
1065 }
1066 
1067 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1068  * flexible approach. The RFC suggests cwnd should not be raised unless
1069  * it was fully used previously. And that's exactly what we do in
1070  * congestion avoidance mode. But in slow start we allow cwnd to grow
1071  * as long as the application has used half the cwnd.
1072  * Example :
1073  *    cwnd is 10 (IW10), but application sends 9 frames.
1074  *    We allow cwnd to reach 18 when all frames are ACKed.
1075  * This check is safe because it's as aggressive as slow start which already
1076  * risks 100% overshoot. The advantage is that we discourage application to
1077  * either send more filler packets or data to artificially blow up the cwnd
1078  * usage, and allow application-limited process to probe bw more aggressively.
1079  */
1080 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1081 {
1082         const struct tcp_sock *tp = tcp_sk(sk);
1083 
1084         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1085         if (tcp_in_slow_start(tp))
1086                 return tp->snd_cwnd < 2 * tp->max_packets_out;
1087 
1088         return tp->is_cwnd_limited;
1089 }
1090 
1091 /* Something is really bad, we could not queue an additional packet,
1092  * because qdisc is full or receiver sent a 0 window.
1093  * We do not want to add fuel to the fire, or abort too early,
1094  * so make sure the timer we arm now is at least 200ms in the future,
1095  * regardless of current icsk_rto value (as it could be ~2ms)
1096  */
1097 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1098 {
1099         return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1100 }
1101 
1102 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1103 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1104                                             unsigned long max_when)
1105 {
1106         u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1107 
1108         return (unsigned long)min_t(u64, when, max_when);
1109 }
1110 
1111 static inline void tcp_check_probe_timer(struct sock *sk)
1112 {
1113         if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1114                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1115                                           tcp_probe0_base(sk), TCP_RTO_MAX);
1116 }
1117 
1118 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1119 {
1120         tp->snd_wl1 = seq;
1121 }
1122 
1123 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1124 {
1125         tp->snd_wl1 = seq;
1126 }
1127 
1128 /*
1129  * Calculate(/check) TCP checksum
1130  */
1131 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1132                                    __be32 daddr, __wsum base)
1133 {
1134         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1135 }
1136 
1137 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1138 {
1139         return __skb_checksum_complete(skb);
1140 }
1141 
1142 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1143 {
1144         return !skb_csum_unnecessary(skb) &&
1145                 __tcp_checksum_complete(skb);
1146 }
1147 
1148 /* Prequeue for VJ style copy to user, combined with checksumming. */
1149 
1150 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1151 {
1152         tp->ucopy.task = NULL;
1153         tp->ucopy.len = 0;
1154         tp->ucopy.memory = 0;
1155         skb_queue_head_init(&tp->ucopy.prequeue);
1156 }
1157 
1158 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1159 
1160 #undef STATE_TRACE
1161 
1162 #ifdef STATE_TRACE
1163 static const char *statename[]={
1164         "Unused","Established","Syn Sent","Syn Recv",
1165         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1166         "Close Wait","Last ACK","Listen","Closing"
1167 };
1168 #endif
1169 void tcp_set_state(struct sock *sk, int state);
1170 
1171 void tcp_done(struct sock *sk);
1172 
1173 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1174 {
1175         rx_opt->dsack = 0;
1176         rx_opt->num_sacks = 0;
1177 }
1178 
1179 u32 tcp_default_init_rwnd(u32 mss);
1180 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1181 
1182 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1183 {
1184         struct tcp_sock *tp = tcp_sk(sk);
1185         s32 delta;
1186 
1187         if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
1188                 return;
1189         delta = tcp_time_stamp - tp->lsndtime;
1190         if (delta > inet_csk(sk)->icsk_rto)
1191                 tcp_cwnd_restart(sk, delta);
1192 }
1193 
1194 /* Determine a window scaling and initial window to offer. */
1195 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1196                                __u32 *window_clamp, int wscale_ok,
1197                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1198 
1199 static inline int tcp_win_from_space(int space)
1200 {
1201         return sysctl_tcp_adv_win_scale<=0 ?
1202                 (space>>(-sysctl_tcp_adv_win_scale)) :
1203                 space - (space>>sysctl_tcp_adv_win_scale);
1204 }
1205 
1206 /* Note: caller must be prepared to deal with negative returns */
1207 static inline int tcp_space(const struct sock *sk)
1208 {
1209         return tcp_win_from_space(sk->sk_rcvbuf -
1210                                   atomic_read(&sk->sk_rmem_alloc));
1211 }
1212 
1213 static inline int tcp_full_space(const struct sock *sk)
1214 {
1215         return tcp_win_from_space(sk->sk_rcvbuf);
1216 }
1217 
1218 extern void tcp_openreq_init_rwin(struct request_sock *req,
1219                                   const struct sock *sk_listener,
1220                                   const struct dst_entry *dst);
1221 
1222 void tcp_enter_memory_pressure(struct sock *sk);
1223 
1224 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1225 {
1226         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1227 }
1228 
1229 static inline int keepalive_time_when(const struct tcp_sock *tp)
1230 {
1231         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1232 }
1233 
1234 static inline int keepalive_probes(const struct tcp_sock *tp)
1235 {
1236         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1237 }
1238 
1239 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1240 {
1241         const struct inet_connection_sock *icsk = &tp->inet_conn;
1242 
1243         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1244                           tcp_time_stamp - tp->rcv_tstamp);
1245 }
1246 
1247 static inline int tcp_fin_time(const struct sock *sk)
1248 {
1249         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1250         const int rto = inet_csk(sk)->icsk_rto;
1251 
1252         if (fin_timeout < (rto << 2) - (rto >> 1))
1253                 fin_timeout = (rto << 2) - (rto >> 1);
1254 
1255         return fin_timeout;
1256 }
1257 
1258 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1259                                   int paws_win)
1260 {
1261         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1262                 return true;
1263         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1264                 return true;
1265         /*
1266          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1267          * then following tcp messages have valid values. Ignore 0 value,
1268          * or else 'negative' tsval might forbid us to accept their packets.
1269          */
1270         if (!rx_opt->ts_recent)
1271                 return true;
1272         return false;
1273 }
1274 
1275 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1276                                    int rst)
1277 {
1278         if (tcp_paws_check(rx_opt, 0))
1279                 return false;
1280 
1281         /* RST segments are not recommended to carry timestamp,
1282            and, if they do, it is recommended to ignore PAWS because
1283            "their cleanup function should take precedence over timestamps."
1284            Certainly, it is mistake. It is necessary to understand the reasons
1285            of this constraint to relax it: if peer reboots, clock may go
1286            out-of-sync and half-open connections will not be reset.
1287            Actually, the problem would be not existing if all
1288            the implementations followed draft about maintaining clock
1289            via reboots. Linux-2.2 DOES NOT!
1290 
1291            However, we can relax time bounds for RST segments to MSL.
1292          */
1293         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1294                 return false;
1295         return true;
1296 }
1297 
1298 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1299                           int mib_idx, u32 *last_oow_ack_time);
1300 
1301 static inline void tcp_mib_init(struct net *net)
1302 {
1303         /* See RFC 2012 */
1304         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1305         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1306         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1307         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1308 }
1309 
1310 /* from STCP */
1311 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1312 {
1313         tp->lost_skb_hint = NULL;
1314 }
1315 
1316 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1317 {
1318         tcp_clear_retrans_hints_partial(tp);
1319         tp->retransmit_skb_hint = NULL;
1320 }
1321 
1322 /* MD5 Signature */
1323 struct crypto_hash;
1324 
1325 union tcp_md5_addr {
1326         struct in_addr  a4;
1327 #if IS_ENABLED(CONFIG_IPV6)
1328         struct in6_addr a6;
1329 #endif
1330 };
1331 
1332 /* - key database */
1333 struct tcp_md5sig_key {
1334         struct hlist_node       node;
1335         u8                      keylen;
1336         u8                      family; /* AF_INET or AF_INET6 */
1337         union tcp_md5_addr      addr;
1338         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1339         struct rcu_head         rcu;
1340 };
1341 
1342 /* - sock block */
1343 struct tcp_md5sig_info {
1344         struct hlist_head       head;
1345         struct rcu_head         rcu;
1346 };
1347 
1348 /* - pseudo header */
1349 struct tcp4_pseudohdr {
1350         __be32          saddr;
1351         __be32          daddr;
1352         __u8            pad;
1353         __u8            protocol;
1354         __be16          len;
1355 };
1356 
1357 struct tcp6_pseudohdr {
1358         struct in6_addr saddr;
1359         struct in6_addr daddr;
1360         __be32          len;
1361         __be32          protocol;       /* including padding */
1362 };
1363 
1364 union tcp_md5sum_block {
1365         struct tcp4_pseudohdr ip4;
1366 #if IS_ENABLED(CONFIG_IPV6)
1367         struct tcp6_pseudohdr ip6;
1368 #endif
1369 };
1370 
1371 /* - pool: digest algorithm, hash description and scratch buffer */
1372 struct tcp_md5sig_pool {
1373         struct hash_desc        md5_desc;
1374         union tcp_md5sum_block  md5_blk;
1375 };
1376 
1377 /* - functions */
1378 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1379                         const struct sock *sk, const struct sk_buff *skb);
1380 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1381                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1382 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1383                    int family);
1384 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1385                                          const struct sock *addr_sk);
1386 
1387 #ifdef CONFIG_TCP_MD5SIG
1388 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1389                                          const union tcp_md5_addr *addr,
1390                                          int family);
1391 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1392 #else
1393 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1394                                          const union tcp_md5_addr *addr,
1395                                          int family)
1396 {
1397         return NULL;
1398 }
1399 #define tcp_twsk_md5_key(twsk)  NULL
1400 #endif
1401 
1402 bool tcp_alloc_md5sig_pool(void);
1403 
1404 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1405 static inline void tcp_put_md5sig_pool(void)
1406 {
1407         local_bh_enable();
1408 }
1409 
1410 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1411 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1412                           unsigned int header_len);
1413 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1414                      const struct tcp_md5sig_key *key);
1415 
1416 /* From tcp_fastopen.c */
1417 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1418                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1419                             unsigned long *last_syn_loss);
1420 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1421                             struct tcp_fastopen_cookie *cookie, bool syn_lost,
1422                             u16 try_exp);
1423 struct tcp_fastopen_request {
1424         /* Fast Open cookie. Size 0 means a cookie request */
1425         struct tcp_fastopen_cookie      cookie;
1426         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1427         size_t                          size;
1428         int                             copied; /* queued in tcp_connect() */
1429 };
1430 void tcp_free_fastopen_req(struct tcp_sock *tp);
1431 
1432 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1433 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1434 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1435                               struct request_sock *req,
1436                               struct tcp_fastopen_cookie *foc,
1437                               struct dst_entry *dst);
1438 void tcp_fastopen_init_key_once(bool publish);
1439 #define TCP_FASTOPEN_KEY_LENGTH 16
1440 
1441 /* Fastopen key context */
1442 struct tcp_fastopen_context {
1443         struct crypto_cipher    *tfm;
1444         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1445         struct rcu_head         rcu;
1446 };
1447 
1448 /* write queue abstraction */
1449 static inline void tcp_write_queue_purge(struct sock *sk)
1450 {
1451         struct sk_buff *skb;
1452 
1453         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1454                 sk_wmem_free_skb(sk, skb);
1455         sk_mem_reclaim(sk);
1456         tcp_clear_all_retrans_hints(tcp_sk(sk));
1457 }
1458 
1459 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1460 {
1461         return skb_peek(&sk->sk_write_queue);
1462 }
1463 
1464 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1465 {
1466         return skb_peek_tail(&sk->sk_write_queue);
1467 }
1468 
1469 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1470                                                    const struct sk_buff *skb)
1471 {
1472         return skb_queue_next(&sk->sk_write_queue, skb);
1473 }
1474 
1475 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1476                                                    const struct sk_buff *skb)
1477 {
1478         return skb_queue_prev(&sk->sk_write_queue, skb);
1479 }
1480 
1481 #define tcp_for_write_queue(skb, sk)                                    \
1482         skb_queue_walk(&(sk)->sk_write_queue, skb)
1483 
1484 #define tcp_for_write_queue_from(skb, sk)                               \
1485         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1486 
1487 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1488         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1489 
1490 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1491 {
1492         return sk->sk_send_head;
1493 }
1494 
1495 static inline bool tcp_skb_is_last(const struct sock *sk,
1496                                    const struct sk_buff *skb)
1497 {
1498         return skb_queue_is_last(&sk->sk_write_queue, skb);
1499 }
1500 
1501 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1502 {
1503         if (tcp_skb_is_last(sk, skb))
1504                 sk->sk_send_head = NULL;
1505         else
1506                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1507 }
1508 
1509 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1510 {
1511         if (sk->sk_send_head == skb_unlinked)
1512                 sk->sk_send_head = NULL;
1513 }
1514 
1515 static inline void tcp_init_send_head(struct sock *sk)
1516 {
1517         sk->sk_send_head = NULL;
1518 }
1519 
1520 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1521 {
1522         __skb_queue_tail(&sk->sk_write_queue, skb);
1523 }
1524 
1525 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1526 {
1527         __tcp_add_write_queue_tail(sk, skb);
1528 
1529         /* Queue it, remembering where we must start sending. */
1530         if (sk->sk_send_head == NULL) {
1531                 sk->sk_send_head = skb;
1532 
1533                 if (tcp_sk(sk)->highest_sack == NULL)
1534                         tcp_sk(sk)->highest_sack = skb;
1535         }
1536 }
1537 
1538 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1539 {
1540         __skb_queue_head(&sk->sk_write_queue, skb);
1541 }
1542 
1543 /* Insert buff after skb on the write queue of sk.  */
1544 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1545                                                 struct sk_buff *buff,
1546                                                 struct sock *sk)
1547 {
1548         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1549 }
1550 
1551 /* Insert new before skb on the write queue of sk.  */
1552 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1553                                                   struct sk_buff *skb,
1554                                                   struct sock *sk)
1555 {
1556         __skb_queue_before(&sk->sk_write_queue, skb, new);
1557 
1558         if (sk->sk_send_head == skb)
1559                 sk->sk_send_head = new;
1560 }
1561 
1562 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1563 {
1564         __skb_unlink(skb, &sk->sk_write_queue);
1565 }
1566 
1567 static inline bool tcp_write_queue_empty(struct sock *sk)
1568 {
1569         return skb_queue_empty(&sk->sk_write_queue);
1570 }
1571 
1572 static inline void tcp_push_pending_frames(struct sock *sk)
1573 {
1574         if (tcp_send_head(sk)) {
1575                 struct tcp_sock *tp = tcp_sk(sk);
1576 
1577                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1578         }
1579 }
1580 
1581 /* Start sequence of the skb just after the highest skb with SACKed
1582  * bit, valid only if sacked_out > 0 or when the caller has ensured
1583  * validity by itself.
1584  */
1585 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1586 {
1587         if (!tp->sacked_out)
1588                 return tp->snd_una;
1589 
1590         if (tp->highest_sack == NULL)
1591                 return tp->snd_nxt;
1592 
1593         return TCP_SKB_CB(tp->highest_sack)->seq;
1594 }
1595 
1596 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1597 {
1598         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1599                                                 tcp_write_queue_next(sk, skb);
1600 }
1601 
1602 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1603 {
1604         return tcp_sk(sk)->highest_sack;
1605 }
1606 
1607 static inline void tcp_highest_sack_reset(struct sock *sk)
1608 {
1609         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1610 }
1611 
1612 /* Called when old skb is about to be deleted (to be combined with new skb) */
1613 static inline void tcp_highest_sack_combine(struct sock *sk,
1614                                             struct sk_buff *old,
1615                                             struct sk_buff *new)
1616 {
1617         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1618                 tcp_sk(sk)->highest_sack = new;
1619 }
1620 
1621 /* Determines whether this is a thin stream (which may suffer from
1622  * increased latency). Used to trigger latency-reducing mechanisms.
1623  */
1624 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1625 {
1626         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1627 }
1628 
1629 /* /proc */
1630 enum tcp_seq_states {
1631         TCP_SEQ_STATE_LISTENING,
1632         TCP_SEQ_STATE_ESTABLISHED,
1633 };
1634 
1635 int tcp_seq_open(struct inode *inode, struct file *file);
1636 
1637 struct tcp_seq_afinfo {
1638         char                            *name;
1639         sa_family_t                     family;
1640         const struct file_operations    *seq_fops;
1641         struct seq_operations           seq_ops;
1642 };
1643 
1644 struct tcp_iter_state {
1645         struct seq_net_private  p;
1646         sa_family_t             family;
1647         enum tcp_seq_states     state;
1648         struct sock             *syn_wait_sk;
1649         int                     bucket, offset, sbucket, num;
1650         loff_t                  last_pos;
1651 };
1652 
1653 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1654 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1655 
1656 extern struct request_sock_ops tcp_request_sock_ops;
1657 extern struct request_sock_ops tcp6_request_sock_ops;
1658 
1659 void tcp_v4_destroy_sock(struct sock *sk);
1660 
1661 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1662                                 netdev_features_t features);
1663 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1664 int tcp_gro_complete(struct sk_buff *skb);
1665 
1666 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1667 
1668 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1669 {
1670         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1671 }
1672 
1673 static inline bool tcp_stream_memory_free(const struct sock *sk)
1674 {
1675         const struct tcp_sock *tp = tcp_sk(sk);
1676         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1677 
1678         return notsent_bytes < tcp_notsent_lowat(tp);
1679 }
1680 
1681 #ifdef CONFIG_PROC_FS
1682 int tcp4_proc_init(void);
1683 void tcp4_proc_exit(void);
1684 #endif
1685 
1686 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1687 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1688                      const struct tcp_request_sock_ops *af_ops,
1689                      struct sock *sk, struct sk_buff *skb);
1690 
1691 /* TCP af-specific functions */
1692 struct tcp_sock_af_ops {
1693 #ifdef CONFIG_TCP_MD5SIG
1694         struct tcp_md5sig_key   *(*md5_lookup) (const struct sock *sk,
1695                                                 const struct sock *addr_sk);
1696         int             (*calc_md5_hash)(char *location,
1697                                          const struct tcp_md5sig_key *md5,
1698                                          const struct sock *sk,
1699                                          const struct sk_buff *skb);
1700         int             (*md5_parse)(struct sock *sk,
1701                                      char __user *optval,
1702                                      int optlen);
1703 #endif
1704 };
1705 
1706 struct tcp_request_sock_ops {
1707         u16 mss_clamp;
1708 #ifdef CONFIG_TCP_MD5SIG
1709         struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1710                                                  const struct sock *addr_sk);
1711         int             (*calc_md5_hash) (char *location,
1712                                           const struct tcp_md5sig_key *md5,
1713                                           const struct sock *sk,
1714                                           const struct sk_buff *skb);
1715 #endif
1716         void (*init_req)(struct request_sock *req,
1717                          const struct sock *sk_listener,
1718                          struct sk_buff *skb);
1719 #ifdef CONFIG_SYN_COOKIES
1720         __u32 (*cookie_init_seq)(const struct sk_buff *skb,
1721                                  __u16 *mss);
1722 #endif
1723         struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1724                                        const struct request_sock *req,
1725                                        bool *strict);
1726         __u32 (*init_seq)(const struct sk_buff *skb);
1727         int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1728                            struct flowi *fl, struct request_sock *req,
1729                            struct tcp_fastopen_cookie *foc,
1730                            bool attach_req);
1731 };
1732 
1733 #ifdef CONFIG_SYN_COOKIES
1734 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1735                                          const struct sock *sk, struct sk_buff *skb,
1736                                          __u16 *mss)
1737 {
1738         tcp_synq_overflow(sk);
1739         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1740         return ops->cookie_init_seq(skb, mss);
1741 }
1742 #else
1743 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1744                                          const struct sock *sk, struct sk_buff *skb,
1745                                          __u16 *mss)
1746 {
1747         return 0;
1748 }
1749 #endif
1750 
1751 int tcpv4_offload_init(void);
1752 
1753 void tcp_v4_init(void);
1754 void tcp_init(void);
1755 
1756 /* tcp_recovery.c */
1757 
1758 /* Flags to enable various loss recovery features. See below */
1759 extern int sysctl_tcp_recovery;
1760 
1761 /* Use TCP RACK to detect (some) tail and retransmit losses */
1762 #define TCP_RACK_LOST_RETRANS  0x1
1763 
1764 extern int tcp_rack_mark_lost(struct sock *sk);
1765 
1766 extern void tcp_rack_advance(struct tcp_sock *tp,
1767                              const struct skb_mstamp *xmit_time, u8 sacked);
1768 
1769 /*
1770  * Save and compile IPv4 options, return a pointer to it
1771  */
1772 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1773 {
1774         const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1775         struct ip_options_rcu *dopt = NULL;
1776 
1777         if (opt->optlen) {
1778                 int opt_size = sizeof(*dopt) + opt->optlen;
1779 
1780                 dopt = kmalloc(opt_size, GFP_ATOMIC);
1781                 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1782                         kfree(dopt);
1783                         dopt = NULL;
1784                 }
1785         }
1786         return dopt;
1787 }
1788 
1789 /* locally generated TCP pure ACKs have skb->truesize == 2
1790  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1791  * This is much faster than dissecting the packet to find out.
1792  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1793  */
1794 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1795 {
1796         return skb->truesize == 2;
1797 }
1798 
1799 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1800 {
1801         skb->truesize = 2;
1802 }
1803 
1804 #endif  /* _TCP_H */
1805 

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