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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_autocorking;
283 extern int sysctl_tcp_invalid_ratelimit;
284 
285 extern atomic_long_t tcp_memory_allocated;
286 extern struct percpu_counter tcp_sockets_allocated;
287 extern int tcp_memory_pressure;
288 
289 /*
290  * The next routines deal with comparing 32 bit unsigned ints
291  * and worry about wraparound (automatic with unsigned arithmetic).
292  */
293 
294 static inline bool before(__u32 seq1, __u32 seq2)
295 {
296         return (__s32)(seq1-seq2) < 0;
297 }
298 #define after(seq2, seq1)       before(seq1, seq2)
299 
300 /* is s2<=s1<=s3 ? */
301 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
302 {
303         return seq3 - seq2 >= seq1 - seq2;
304 }
305 
306 static inline bool tcp_out_of_memory(struct sock *sk)
307 {
308         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
309             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
310                 return true;
311         return false;
312 }
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 /* syncookies: remember time of last synqueue overflow */
330 static inline void tcp_synq_overflow(struct sock *sk)
331 {
332         tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
333 }
334 
335 /* syncookies: no recent synqueue overflow on this listening socket? */
336 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
337 {
338         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
339         return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
340 }
341 
342 extern struct proto tcp_prot;
343 
344 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
345 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
346 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
347 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
348 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
349 
350 void tcp_tasklet_init(void);
351 
352 void tcp_v4_err(struct sk_buff *skb, u32);
353 
354 void tcp_shutdown(struct sock *sk, int how);
355 
356 void tcp_v4_early_demux(struct sk_buff *skb);
357 int tcp_v4_rcv(struct sk_buff *skb);
358 
359 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
360 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
361 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
362                  int flags);
363 void tcp_release_cb(struct sock *sk);
364 void tcp_wfree(struct sk_buff *skb);
365 void tcp_write_timer_handler(struct sock *sk);
366 void tcp_delack_timer_handler(struct sock *sk);
367 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
368 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
369                           const struct tcphdr *th, unsigned int len);
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(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(struct sock *sk, struct sk_buff *skb,
459                                   struct request_sock *req,
460                                   struct dst_entry *dst);
461 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
462 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
463 int tcp_connect(struct sock *sk);
464 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
465                                 struct request_sock *req,
466                                 struct tcp_fastopen_cookie *foc);
467 int tcp_disconnect(struct sock *sk, int flags);
468 
469 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
470 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
471 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
472 
473 /* From syncookies.c */
474 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
475                       u32 cookie);
476 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
477 #ifdef CONFIG_SYN_COOKIES
478 
479 /* Syncookies use a monotonic timer which increments every 60 seconds.
480  * This counter is used both as a hash input and partially encoded into
481  * the cookie value.  A cookie is only validated further if the delta
482  * between the current counter value and the encoded one is less than this,
483  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
484  * the counter advances immediately after a cookie is generated).
485  */
486 #define MAX_SYNCOOKIE_AGE 2
487 
488 static inline u32 tcp_cookie_time(void)
489 {
490         u64 val = get_jiffies_64();
491 
492         do_div(val, 60 * HZ);
493         return val;
494 }
495 
496 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
497                               u16 *mssp);
498 __u32 cookie_v4_init_sequence(struct sock *sk, const struct sk_buff *skb,
499                               __u16 *mss);
500 __u32 cookie_init_timestamp(struct request_sock *req);
501 bool cookie_timestamp_decode(struct tcp_options_received *opt);
502 bool cookie_ecn_ok(const struct tcp_options_received *opt,
503                    const struct net *net, const struct dst_entry *dst);
504 
505 /* From net/ipv6/syncookies.c */
506 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
507                       u32 cookie);
508 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
509 
510 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
511                               const struct tcphdr *th, u16 *mssp);
512 __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
513                               __u16 *mss);
514 #endif
515 /* tcp_output.c */
516 
517 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
518                                int nonagle);
519 bool tcp_may_send_now(struct sock *sk);
520 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
521 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
522 void tcp_retransmit_timer(struct sock *sk);
523 void tcp_xmit_retransmit_queue(struct sock *);
524 void tcp_simple_retransmit(struct sock *);
525 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
526 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
527 
528 void tcp_send_probe0(struct sock *);
529 void tcp_send_partial(struct sock *);
530 int tcp_write_wakeup(struct sock *);
531 void tcp_send_fin(struct sock *sk);
532 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
533 int tcp_send_synack(struct sock *);
534 void tcp_push_one(struct sock *, unsigned int mss_now);
535 void tcp_send_ack(struct sock *sk);
536 void tcp_send_delayed_ack(struct sock *sk);
537 void tcp_send_loss_probe(struct sock *sk);
538 bool tcp_schedule_loss_probe(struct sock *sk);
539 
540 /* tcp_input.c */
541 void tcp_resume_early_retransmit(struct sock *sk);
542 void tcp_rearm_rto(struct sock *sk);
543 void tcp_reset(struct sock *sk);
544 
545 /* tcp_timer.c */
546 void tcp_init_xmit_timers(struct sock *);
547 static inline void tcp_clear_xmit_timers(struct sock *sk)
548 {
549         inet_csk_clear_xmit_timers(sk);
550 }
551 
552 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
553 unsigned int tcp_current_mss(struct sock *sk);
554 
555 /* Bound MSS / TSO packet size with the half of the window */
556 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
557 {
558         int cutoff;
559 
560         /* When peer uses tiny windows, there is no use in packetizing
561          * to sub-MSS pieces for the sake of SWS or making sure there
562          * are enough packets in the pipe for fast recovery.
563          *
564          * On the other hand, for extremely large MSS devices, handling
565          * smaller than MSS windows in this way does make sense.
566          */
567         if (tp->max_window >= 512)
568                 cutoff = (tp->max_window >> 1);
569         else
570                 cutoff = tp->max_window;
571 
572         if (cutoff && pktsize > cutoff)
573                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
574         else
575                 return pktsize;
576 }
577 
578 /* tcp.c */
579 void tcp_get_info(struct sock *, struct tcp_info *);
580 
581 /* Read 'sendfile()'-style from a TCP socket */
582 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
583                                 unsigned int, size_t);
584 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
585                   sk_read_actor_t recv_actor);
586 
587 void tcp_initialize_rcv_mss(struct sock *sk);
588 
589 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
590 int tcp_mss_to_mtu(struct sock *sk, int mss);
591 void tcp_mtup_init(struct sock *sk);
592 void tcp_init_buffer_space(struct sock *sk);
593 
594 static inline void tcp_bound_rto(const struct sock *sk)
595 {
596         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
597                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
598 }
599 
600 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
601 {
602         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
603 }
604 
605 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
606 {
607         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
608                                ntohl(TCP_FLAG_ACK) |
609                                snd_wnd);
610 }
611 
612 static inline void tcp_fast_path_on(struct tcp_sock *tp)
613 {
614         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
615 }
616 
617 static inline void tcp_fast_path_check(struct sock *sk)
618 {
619         struct tcp_sock *tp = tcp_sk(sk);
620 
621         if (skb_queue_empty(&tp->out_of_order_queue) &&
622             tp->rcv_wnd &&
623             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
624             !tp->urg_data)
625                 tcp_fast_path_on(tp);
626 }
627 
628 /* Compute the actual rto_min value */
629 static inline u32 tcp_rto_min(struct sock *sk)
630 {
631         const struct dst_entry *dst = __sk_dst_get(sk);
632         u32 rto_min = TCP_RTO_MIN;
633 
634         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
635                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
636         return rto_min;
637 }
638 
639 static inline u32 tcp_rto_min_us(struct sock *sk)
640 {
641         return jiffies_to_usecs(tcp_rto_min(sk));
642 }
643 
644 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
645 {
646         return dst_metric_locked(dst, RTAX_CC_ALGO);
647 }
648 
649 /* Compute the actual receive window we are currently advertising.
650  * Rcv_nxt can be after the window if our peer push more data
651  * than the offered window.
652  */
653 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
654 {
655         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
656 
657         if (win < 0)
658                 win = 0;
659         return (u32) win;
660 }
661 
662 /* Choose a new window, without checks for shrinking, and without
663  * scaling applied to the result.  The caller does these things
664  * if necessary.  This is a "raw" window selection.
665  */
666 u32 __tcp_select_window(struct sock *sk);
667 
668 void tcp_send_window_probe(struct sock *sk);
669 
670 /* TCP timestamps are only 32-bits, this causes a slight
671  * complication on 64-bit systems since we store a snapshot
672  * of jiffies in the buffer control blocks below.  We decided
673  * to use only the low 32-bits of jiffies and hide the ugly
674  * casts with the following macro.
675  */
676 #define tcp_time_stamp          ((__u32)(jiffies))
677 
678 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
679 {
680         return skb->skb_mstamp.stamp_jiffies;
681 }
682 
683 
684 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
685 
686 #define TCPHDR_FIN 0x01
687 #define TCPHDR_SYN 0x02
688 #define TCPHDR_RST 0x04
689 #define TCPHDR_PSH 0x08
690 #define TCPHDR_ACK 0x10
691 #define TCPHDR_URG 0x20
692 #define TCPHDR_ECE 0x40
693 #define TCPHDR_CWR 0x80
694 
695 /* This is what the send packet queuing engine uses to pass
696  * TCP per-packet control information to the transmission code.
697  * We also store the host-order sequence numbers in here too.
698  * This is 44 bytes if IPV6 is enabled.
699  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
700  */
701 struct tcp_skb_cb {
702         __u32           seq;            /* Starting sequence number     */
703         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
704         union {
705                 /* Note : tcp_tw_isn is used in input path only
706                  *        (isn chosen by tcp_timewait_state_process())
707                  *
708                  *        tcp_gso_segs is used in write queue only,
709                  *        cf tcp_skb_pcount()
710                  */
711                 __u32           tcp_tw_isn;
712                 __u32           tcp_gso_segs;
713         };
714         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
715 
716         __u8            sacked;         /* State flags for SACK/FACK.   */
717 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
718 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
719 #define TCPCB_LOST              0x04    /* SKB is lost                  */
720 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
721 #define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
722 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
723 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
724                                 TCPCB_REPAIRED)
725 
726         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
727         /* 1 byte hole */
728         __u32           ack_seq;        /* Sequence number ACK'd        */
729         union {
730                 struct inet_skb_parm    h4;
731 #if IS_ENABLED(CONFIG_IPV6)
732                 struct inet6_skb_parm   h6;
733 #endif
734         } header;       /* For incoming frames          */
735 };
736 
737 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
738 
739 
740 #if IS_ENABLED(CONFIG_IPV6)
741 /* This is the variant of inet6_iif() that must be used by TCP,
742  * as TCP moves IP6CB into a different location in skb->cb[]
743  */
744 static inline int tcp_v6_iif(const struct sk_buff *skb)
745 {
746         return TCP_SKB_CB(skb)->header.h6.iif;
747 }
748 #endif
749 
750 /* Due to TSO, an SKB can be composed of multiple actual
751  * packets.  To keep these tracked properly, we use this.
752  */
753 static inline int tcp_skb_pcount(const struct sk_buff *skb)
754 {
755         return TCP_SKB_CB(skb)->tcp_gso_segs;
756 }
757 
758 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
759 {
760         TCP_SKB_CB(skb)->tcp_gso_segs = segs;
761 }
762 
763 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
764 {
765         TCP_SKB_CB(skb)->tcp_gso_segs += segs;
766 }
767 
768 /* This is valid iff tcp_skb_pcount() > 1. */
769 static inline int tcp_skb_mss(const struct sk_buff *skb)
770 {
771         return skb_shinfo(skb)->gso_size;
772 }
773 
774 /* Events passed to congestion control interface */
775 enum tcp_ca_event {
776         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
777         CA_EVENT_CWND_RESTART,  /* congestion window restart */
778         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
779         CA_EVENT_LOSS,          /* loss timeout */
780         CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
781         CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
782         CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
783         CA_EVENT_NON_DELAYED_ACK,
784 };
785 
786 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
787 enum tcp_ca_ack_event_flags {
788         CA_ACK_SLOWPATH         = (1 << 0),     /* In slow path processing */
789         CA_ACK_WIN_UPDATE       = (1 << 1),     /* ACK updated window */
790         CA_ACK_ECE              = (1 << 2),     /* ECE bit is set on ack */
791 };
792 
793 /*
794  * Interface for adding new TCP congestion control handlers
795  */
796 #define TCP_CA_NAME_MAX 16
797 #define TCP_CA_MAX      128
798 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
799 
800 #define TCP_CA_UNSPEC   0
801 
802 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
803 #define TCP_CONG_NON_RESTRICTED 0x1
804 /* Requires ECN/ECT set on all packets */
805 #define TCP_CONG_NEEDS_ECN      0x2
806 
807 union tcp_cc_info;
808 
809 struct tcp_congestion_ops {
810         struct list_head        list;
811         u32 key;
812         u32 flags;
813 
814         /* initialize private data (optional) */
815         void (*init)(struct sock *sk);
816         /* cleanup private data  (optional) */
817         void (*release)(struct sock *sk);
818 
819         /* return slow start threshold (required) */
820         u32 (*ssthresh)(struct sock *sk);
821         /* do new cwnd calculation (required) */
822         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
823         /* call before changing ca_state (optional) */
824         void (*set_state)(struct sock *sk, u8 new_state);
825         /* call when cwnd event occurs (optional) */
826         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
827         /* call when ack arrives (optional) */
828         void (*in_ack_event)(struct sock *sk, u32 flags);
829         /* new value of cwnd after loss (optional) */
830         u32  (*undo_cwnd)(struct sock *sk);
831         /* hook for packet ack accounting (optional) */
832         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
833         /* get info for inet_diag (optional) */
834         size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
835                            union tcp_cc_info *info);
836 
837         char            name[TCP_CA_NAME_MAX];
838         struct module   *owner;
839 };
840 
841 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
842 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
843 
844 void tcp_assign_congestion_control(struct sock *sk);
845 void tcp_init_congestion_control(struct sock *sk);
846 void tcp_cleanup_congestion_control(struct sock *sk);
847 int tcp_set_default_congestion_control(const char *name);
848 void tcp_get_default_congestion_control(char *name);
849 void tcp_get_available_congestion_control(char *buf, size_t len);
850 void tcp_get_allowed_congestion_control(char *buf, size_t len);
851 int tcp_set_allowed_congestion_control(char *allowed);
852 int tcp_set_congestion_control(struct sock *sk, const char *name);
853 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
854 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
855 
856 u32 tcp_reno_ssthresh(struct sock *sk);
857 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
858 extern struct tcp_congestion_ops tcp_reno;
859 
860 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
861 u32 tcp_ca_get_key_by_name(const char *name);
862 #ifdef CONFIG_INET
863 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
864 #else
865 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
866 {
867         return NULL;
868 }
869 #endif
870 
871 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
872 {
873         const struct inet_connection_sock *icsk = inet_csk(sk);
874 
875         return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
876 }
877 
878 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
879 {
880         struct inet_connection_sock *icsk = inet_csk(sk);
881 
882         if (icsk->icsk_ca_ops->set_state)
883                 icsk->icsk_ca_ops->set_state(sk, ca_state);
884         icsk->icsk_ca_state = ca_state;
885 }
886 
887 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
888 {
889         const struct inet_connection_sock *icsk = inet_csk(sk);
890 
891         if (icsk->icsk_ca_ops->cwnd_event)
892                 icsk->icsk_ca_ops->cwnd_event(sk, event);
893 }
894 
895 /* These functions determine how the current flow behaves in respect of SACK
896  * handling. SACK is negotiated with the peer, and therefore it can vary
897  * between different flows.
898  *
899  * tcp_is_sack - SACK enabled
900  * tcp_is_reno - No SACK
901  * tcp_is_fack - FACK enabled, implies SACK enabled
902  */
903 static inline int tcp_is_sack(const struct tcp_sock *tp)
904 {
905         return tp->rx_opt.sack_ok;
906 }
907 
908 static inline bool tcp_is_reno(const struct tcp_sock *tp)
909 {
910         return !tcp_is_sack(tp);
911 }
912 
913 static inline bool tcp_is_fack(const struct tcp_sock *tp)
914 {
915         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
916 }
917 
918 static inline void tcp_enable_fack(struct tcp_sock *tp)
919 {
920         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
921 }
922 
923 /* TCP early-retransmit (ER) is similar to but more conservative than
924  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
925  */
926 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
927 {
928         tp->do_early_retrans = sysctl_tcp_early_retrans &&
929                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
930                 sysctl_tcp_reordering == 3;
931 }
932 
933 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
934 {
935         tp->do_early_retrans = 0;
936 }
937 
938 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
939 {
940         return tp->sacked_out + tp->lost_out;
941 }
942 
943 /* This determines how many packets are "in the network" to the best
944  * of our knowledge.  In many cases it is conservative, but where
945  * detailed information is available from the receiver (via SACK
946  * blocks etc.) we can make more aggressive calculations.
947  *
948  * Use this for decisions involving congestion control, use just
949  * tp->packets_out to determine if the send queue is empty or not.
950  *
951  * Read this equation as:
952  *
953  *      "Packets sent once on transmission queue" MINUS
954  *      "Packets left network, but not honestly ACKed yet" PLUS
955  *      "Packets fast retransmitted"
956  */
957 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
958 {
959         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
960 }
961 
962 #define TCP_INFINITE_SSTHRESH   0x7fffffff
963 
964 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
965 {
966         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
967 }
968 
969 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
970 {
971         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
972                (1 << inet_csk(sk)->icsk_ca_state);
973 }
974 
975 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
976  * The exception is cwnd reduction phase, when cwnd is decreasing towards
977  * ssthresh.
978  */
979 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
980 {
981         const struct tcp_sock *tp = tcp_sk(sk);
982 
983         if (tcp_in_cwnd_reduction(sk))
984                 return tp->snd_ssthresh;
985         else
986                 return max(tp->snd_ssthresh,
987                            ((tp->snd_cwnd >> 1) +
988                             (tp->snd_cwnd >> 2)));
989 }
990 
991 /* Use define here intentionally to get WARN_ON location shown at the caller */
992 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
993 
994 void tcp_enter_cwr(struct sock *sk);
995 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
996 
997 /* The maximum number of MSS of available cwnd for which TSO defers
998  * sending if not using sysctl_tcp_tso_win_divisor.
999  */
1000 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1001 {
1002         return 3;
1003 }
1004 
1005 /* Slow start with delack produces 3 packets of burst, so that
1006  * it is safe "de facto".  This will be the default - same as
1007  * the default reordering threshold - but if reordering increases,
1008  * we must be able to allow cwnd to burst at least this much in order
1009  * to not pull it back when holes are filled.
1010  */
1011 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
1012 {
1013         return tp->reordering;
1014 }
1015 
1016 /* Returns end sequence number of the receiver's advertised window */
1017 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1018 {
1019         return tp->snd_una + tp->snd_wnd;
1020 }
1021 
1022 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1023  * flexible approach. The RFC suggests cwnd should not be raised unless
1024  * it was fully used previously. And that's exactly what we do in
1025  * congestion avoidance mode. But in slow start we allow cwnd to grow
1026  * as long as the application has used half the cwnd.
1027  * Example :
1028  *    cwnd is 10 (IW10), but application sends 9 frames.
1029  *    We allow cwnd to reach 18 when all frames are ACKed.
1030  * This check is safe because it's as aggressive as slow start which already
1031  * risks 100% overshoot. The advantage is that we discourage application to
1032  * either send more filler packets or data to artificially blow up the cwnd
1033  * usage, and allow application-limited process to probe bw more aggressively.
1034  */
1035 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1036 {
1037         const struct tcp_sock *tp = tcp_sk(sk);
1038 
1039         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1040         if (tp->snd_cwnd <= tp->snd_ssthresh)
1041                 return tp->snd_cwnd < 2 * tp->max_packets_out;
1042 
1043         return tp->is_cwnd_limited;
1044 }
1045 
1046 static inline void tcp_check_probe_timer(struct sock *sk)
1047 {
1048         const struct tcp_sock *tp = tcp_sk(sk);
1049         const struct inet_connection_sock *icsk = inet_csk(sk);
1050 
1051         if (!tp->packets_out && !icsk->icsk_pending)
1052                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1053                                           icsk->icsk_rto, TCP_RTO_MAX);
1054 }
1055 
1056 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1057 {
1058         tp->snd_wl1 = seq;
1059 }
1060 
1061 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1062 {
1063         tp->snd_wl1 = seq;
1064 }
1065 
1066 /*
1067  * Calculate(/check) TCP checksum
1068  */
1069 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1070                                    __be32 daddr, __wsum base)
1071 {
1072         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1073 }
1074 
1075 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1076 {
1077         return __skb_checksum_complete(skb);
1078 }
1079 
1080 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1081 {
1082         return !skb_csum_unnecessary(skb) &&
1083                 __tcp_checksum_complete(skb);
1084 }
1085 
1086 /* Prequeue for VJ style copy to user, combined with checksumming. */
1087 
1088 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1089 {
1090         tp->ucopy.task = NULL;
1091         tp->ucopy.len = 0;
1092         tp->ucopy.memory = 0;
1093         skb_queue_head_init(&tp->ucopy.prequeue);
1094 }
1095 
1096 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1097 
1098 #undef STATE_TRACE
1099 
1100 #ifdef STATE_TRACE
1101 static const char *statename[]={
1102         "Unused","Established","Syn Sent","Syn Recv",
1103         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1104         "Close Wait","Last ACK","Listen","Closing"
1105 };
1106 #endif
1107 void tcp_set_state(struct sock *sk, int state);
1108 
1109 void tcp_done(struct sock *sk);
1110 
1111 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1112 {
1113         rx_opt->dsack = 0;
1114         rx_opt->num_sacks = 0;
1115 }
1116 
1117 u32 tcp_default_init_rwnd(u32 mss);
1118 
1119 /* Determine a window scaling and initial window to offer. */
1120 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1121                                __u32 *window_clamp, int wscale_ok,
1122                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1123 
1124 static inline int tcp_win_from_space(int space)
1125 {
1126         return sysctl_tcp_adv_win_scale<=0 ?
1127                 (space>>(-sysctl_tcp_adv_win_scale)) :
1128                 space - (space>>sysctl_tcp_adv_win_scale);
1129 }
1130 
1131 /* Note: caller must be prepared to deal with negative returns */
1132 static inline int tcp_space(const struct sock *sk)
1133 {
1134         return tcp_win_from_space(sk->sk_rcvbuf -
1135                                   atomic_read(&sk->sk_rmem_alloc));
1136 }
1137 
1138 static inline int tcp_full_space(const struct sock *sk)
1139 {
1140         return tcp_win_from_space(sk->sk_rcvbuf);
1141 }
1142 
1143 extern void tcp_openreq_init_rwin(struct request_sock *req,
1144                                   struct sock *sk, struct dst_entry *dst);
1145 
1146 void tcp_enter_memory_pressure(struct sock *sk);
1147 
1148 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1149 {
1150         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1151 }
1152 
1153 static inline int keepalive_time_when(const struct tcp_sock *tp)
1154 {
1155         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1156 }
1157 
1158 static inline int keepalive_probes(const struct tcp_sock *tp)
1159 {
1160         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1161 }
1162 
1163 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1164 {
1165         const struct inet_connection_sock *icsk = &tp->inet_conn;
1166 
1167         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1168                           tcp_time_stamp - tp->rcv_tstamp);
1169 }
1170 
1171 static inline int tcp_fin_time(const struct sock *sk)
1172 {
1173         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1174         const int rto = inet_csk(sk)->icsk_rto;
1175 
1176         if (fin_timeout < (rto << 2) - (rto >> 1))
1177                 fin_timeout = (rto << 2) - (rto >> 1);
1178 
1179         return fin_timeout;
1180 }
1181 
1182 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1183                                   int paws_win)
1184 {
1185         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1186                 return true;
1187         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1188                 return true;
1189         /*
1190          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1191          * then following tcp messages have valid values. Ignore 0 value,
1192          * or else 'negative' tsval might forbid us to accept their packets.
1193          */
1194         if (!rx_opt->ts_recent)
1195                 return true;
1196         return false;
1197 }
1198 
1199 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1200                                    int rst)
1201 {
1202         if (tcp_paws_check(rx_opt, 0))
1203                 return false;
1204 
1205         /* RST segments are not recommended to carry timestamp,
1206            and, if they do, it is recommended to ignore PAWS because
1207            "their cleanup function should take precedence over timestamps."
1208            Certainly, it is mistake. It is necessary to understand the reasons
1209            of this constraint to relax it: if peer reboots, clock may go
1210            out-of-sync and half-open connections will not be reset.
1211            Actually, the problem would be not existing if all
1212            the implementations followed draft about maintaining clock
1213            via reboots. Linux-2.2 DOES NOT!
1214 
1215            However, we can relax time bounds for RST segments to MSL.
1216          */
1217         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1218                 return false;
1219         return true;
1220 }
1221 
1222 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1223                           int mib_idx, u32 *last_oow_ack_time);
1224 
1225 static inline void tcp_mib_init(struct net *net)
1226 {
1227         /* See RFC 2012 */
1228         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1229         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1230         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1231         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1232 }
1233 
1234 /* from STCP */
1235 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1236 {
1237         tp->lost_skb_hint = NULL;
1238 }
1239 
1240 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1241 {
1242         tcp_clear_retrans_hints_partial(tp);
1243         tp->retransmit_skb_hint = NULL;
1244 }
1245 
1246 /* MD5 Signature */
1247 struct crypto_hash;
1248 
1249 union tcp_md5_addr {
1250         struct in_addr  a4;
1251 #if IS_ENABLED(CONFIG_IPV6)
1252         struct in6_addr a6;
1253 #endif
1254 };
1255 
1256 /* - key database */
1257 struct tcp_md5sig_key {
1258         struct hlist_node       node;
1259         u8                      keylen;
1260         u8                      family; /* AF_INET or AF_INET6 */
1261         union tcp_md5_addr      addr;
1262         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1263         struct rcu_head         rcu;
1264 };
1265 
1266 /* - sock block */
1267 struct tcp_md5sig_info {
1268         struct hlist_head       head;
1269         struct rcu_head         rcu;
1270 };
1271 
1272 /* - pseudo header */
1273 struct tcp4_pseudohdr {
1274         __be32          saddr;
1275         __be32          daddr;
1276         __u8            pad;
1277         __u8            protocol;
1278         __be16          len;
1279 };
1280 
1281 struct tcp6_pseudohdr {
1282         struct in6_addr saddr;
1283         struct in6_addr daddr;
1284         __be32          len;
1285         __be32          protocol;       /* including padding */
1286 };
1287 
1288 union tcp_md5sum_block {
1289         struct tcp4_pseudohdr ip4;
1290 #if IS_ENABLED(CONFIG_IPV6)
1291         struct tcp6_pseudohdr ip6;
1292 #endif
1293 };
1294 
1295 /* - pool: digest algorithm, hash description and scratch buffer */
1296 struct tcp_md5sig_pool {
1297         struct hash_desc        md5_desc;
1298         union tcp_md5sum_block  md5_blk;
1299 };
1300 
1301 /* - functions */
1302 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1303                         const struct sock *sk, const struct sk_buff *skb);
1304 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1305                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1306 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1307                    int family);
1308 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1309                                          const struct sock *addr_sk);
1310 
1311 #ifdef CONFIG_TCP_MD5SIG
1312 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1313                                          const union tcp_md5_addr *addr,
1314                                          int family);
1315 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1316 #else
1317 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1318                                          const union tcp_md5_addr *addr,
1319                                          int family)
1320 {
1321         return NULL;
1322 }
1323 #define tcp_twsk_md5_key(twsk)  NULL
1324 #endif
1325 
1326 bool tcp_alloc_md5sig_pool(void);
1327 
1328 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1329 static inline void tcp_put_md5sig_pool(void)
1330 {
1331         local_bh_enable();
1332 }
1333 
1334 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1335 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1336                           unsigned int header_len);
1337 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1338                      const struct tcp_md5sig_key *key);
1339 
1340 /* From tcp_fastopen.c */
1341 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1342                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1343                             unsigned long *last_syn_loss);
1344 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1345                             struct tcp_fastopen_cookie *cookie, bool syn_lost,
1346                             u16 try_exp);
1347 struct tcp_fastopen_request {
1348         /* Fast Open cookie. Size 0 means a cookie request */
1349         struct tcp_fastopen_cookie      cookie;
1350         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1351         size_t                          size;
1352         int                             copied; /* queued in tcp_connect() */
1353 };
1354 void tcp_free_fastopen_req(struct tcp_sock *tp);
1355 
1356 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1357 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1358 bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1359                       struct request_sock *req,
1360                       struct tcp_fastopen_cookie *foc,
1361                       struct dst_entry *dst);
1362 void tcp_fastopen_init_key_once(bool publish);
1363 #define TCP_FASTOPEN_KEY_LENGTH 16
1364 
1365 /* Fastopen key context */
1366 struct tcp_fastopen_context {
1367         struct crypto_cipher    *tfm;
1368         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1369         struct rcu_head         rcu;
1370 };
1371 
1372 /* write queue abstraction */
1373 static inline void tcp_write_queue_purge(struct sock *sk)
1374 {
1375         struct sk_buff *skb;
1376 
1377         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1378                 sk_wmem_free_skb(sk, skb);
1379         sk_mem_reclaim(sk);
1380         tcp_clear_all_retrans_hints(tcp_sk(sk));
1381 }
1382 
1383 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1384 {
1385         return skb_peek(&sk->sk_write_queue);
1386 }
1387 
1388 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1389 {
1390         return skb_peek_tail(&sk->sk_write_queue);
1391 }
1392 
1393 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1394                                                    const struct sk_buff *skb)
1395 {
1396         return skb_queue_next(&sk->sk_write_queue, skb);
1397 }
1398 
1399 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1400                                                    const struct sk_buff *skb)
1401 {
1402         return skb_queue_prev(&sk->sk_write_queue, skb);
1403 }
1404 
1405 #define tcp_for_write_queue(skb, sk)                                    \
1406         skb_queue_walk(&(sk)->sk_write_queue, skb)
1407 
1408 #define tcp_for_write_queue_from(skb, sk)                               \
1409         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1410 
1411 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1412         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1413 
1414 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1415 {
1416         return sk->sk_send_head;
1417 }
1418 
1419 static inline bool tcp_skb_is_last(const struct sock *sk,
1420                                    const struct sk_buff *skb)
1421 {
1422         return skb_queue_is_last(&sk->sk_write_queue, skb);
1423 }
1424 
1425 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1426 {
1427         if (tcp_skb_is_last(sk, skb))
1428                 sk->sk_send_head = NULL;
1429         else
1430                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1431 }
1432 
1433 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1434 {
1435         if (sk->sk_send_head == skb_unlinked)
1436                 sk->sk_send_head = NULL;
1437 }
1438 
1439 static inline void tcp_init_send_head(struct sock *sk)
1440 {
1441         sk->sk_send_head = NULL;
1442 }
1443 
1444 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1445 {
1446         __skb_queue_tail(&sk->sk_write_queue, skb);
1447 }
1448 
1449 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1450 {
1451         __tcp_add_write_queue_tail(sk, skb);
1452 
1453         /* Queue it, remembering where we must start sending. */
1454         if (sk->sk_send_head == NULL) {
1455                 sk->sk_send_head = skb;
1456 
1457                 if (tcp_sk(sk)->highest_sack == NULL)
1458                         tcp_sk(sk)->highest_sack = skb;
1459         }
1460 }
1461 
1462 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1463 {
1464         __skb_queue_head(&sk->sk_write_queue, skb);
1465 }
1466 
1467 /* Insert buff after skb on the write queue of sk.  */
1468 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1469                                                 struct sk_buff *buff,
1470                                                 struct sock *sk)
1471 {
1472         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1473 }
1474 
1475 /* Insert new before skb on the write queue of sk.  */
1476 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1477                                                   struct sk_buff *skb,
1478                                                   struct sock *sk)
1479 {
1480         __skb_queue_before(&sk->sk_write_queue, skb, new);
1481 
1482         if (sk->sk_send_head == skb)
1483                 sk->sk_send_head = new;
1484 }
1485 
1486 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1487 {
1488         __skb_unlink(skb, &sk->sk_write_queue);
1489 }
1490 
1491 static inline bool tcp_write_queue_empty(struct sock *sk)
1492 {
1493         return skb_queue_empty(&sk->sk_write_queue);
1494 }
1495 
1496 static inline void tcp_push_pending_frames(struct sock *sk)
1497 {
1498         if (tcp_send_head(sk)) {
1499                 struct tcp_sock *tp = tcp_sk(sk);
1500 
1501                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1502         }
1503 }
1504 
1505 /* Start sequence of the skb just after the highest skb with SACKed
1506  * bit, valid only if sacked_out > 0 or when the caller has ensured
1507  * validity by itself.
1508  */
1509 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1510 {
1511         if (!tp->sacked_out)
1512                 return tp->snd_una;
1513 
1514         if (tp->highest_sack == NULL)
1515                 return tp->snd_nxt;
1516 
1517         return TCP_SKB_CB(tp->highest_sack)->seq;
1518 }
1519 
1520 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1521 {
1522         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1523                                                 tcp_write_queue_next(sk, skb);
1524 }
1525 
1526 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1527 {
1528         return tcp_sk(sk)->highest_sack;
1529 }
1530 
1531 static inline void tcp_highest_sack_reset(struct sock *sk)
1532 {
1533         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1534 }
1535 
1536 /* Called when old skb is about to be deleted (to be combined with new skb) */
1537 static inline void tcp_highest_sack_combine(struct sock *sk,
1538                                             struct sk_buff *old,
1539                                             struct sk_buff *new)
1540 {
1541         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1542                 tcp_sk(sk)->highest_sack = new;
1543 }
1544 
1545 /* Determines whether this is a thin stream (which may suffer from
1546  * increased latency). Used to trigger latency-reducing mechanisms.
1547  */
1548 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1549 {
1550         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1551 }
1552 
1553 /* /proc */
1554 enum tcp_seq_states {
1555         TCP_SEQ_STATE_LISTENING,
1556         TCP_SEQ_STATE_OPENREQ,
1557         TCP_SEQ_STATE_ESTABLISHED,
1558 };
1559 
1560 int tcp_seq_open(struct inode *inode, struct file *file);
1561 
1562 struct tcp_seq_afinfo {
1563         char                            *name;
1564         sa_family_t                     family;
1565         const struct file_operations    *seq_fops;
1566         struct seq_operations           seq_ops;
1567 };
1568 
1569 struct tcp_iter_state {
1570         struct seq_net_private  p;
1571         sa_family_t             family;
1572         enum tcp_seq_states     state;
1573         struct sock             *syn_wait_sk;
1574         int                     bucket, offset, sbucket, num;
1575         kuid_t                  uid;
1576         loff_t                  last_pos;
1577 };
1578 
1579 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1580 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1581 
1582 extern struct request_sock_ops tcp_request_sock_ops;
1583 extern struct request_sock_ops tcp6_request_sock_ops;
1584 
1585 void tcp_v4_destroy_sock(struct sock *sk);
1586 
1587 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1588                                 netdev_features_t features);
1589 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1590 int tcp_gro_complete(struct sk_buff *skb);
1591 
1592 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1593 
1594 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1595 {
1596         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1597 }
1598 
1599 static inline bool tcp_stream_memory_free(const struct sock *sk)
1600 {
1601         const struct tcp_sock *tp = tcp_sk(sk);
1602         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1603 
1604         return notsent_bytes < tcp_notsent_lowat(tp);
1605 }
1606 
1607 #ifdef CONFIG_PROC_FS
1608 int tcp4_proc_init(void);
1609 void tcp4_proc_exit(void);
1610 #endif
1611 
1612 int tcp_rtx_synack(struct sock *sk, struct request_sock *req);
1613 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1614                      const struct tcp_request_sock_ops *af_ops,
1615                      struct sock *sk, struct sk_buff *skb);
1616 
1617 /* TCP af-specific functions */
1618 struct tcp_sock_af_ops {
1619 #ifdef CONFIG_TCP_MD5SIG
1620         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1621                                                 const struct sock *addr_sk);
1622         int             (*calc_md5_hash)(char *location,
1623                                          const struct tcp_md5sig_key *md5,
1624                                          const struct sock *sk,
1625                                          const struct sk_buff *skb);
1626         int             (*md5_parse)(struct sock *sk,
1627                                      char __user *optval,
1628                                      int optlen);
1629 #endif
1630 };
1631 
1632 struct tcp_request_sock_ops {
1633         u16 mss_clamp;
1634 #ifdef CONFIG_TCP_MD5SIG
1635         struct tcp_md5sig_key *(*req_md5_lookup)(struct sock *sk,
1636                                                  const struct sock *addr_sk);
1637         int             (*calc_md5_hash) (char *location,
1638                                           const struct tcp_md5sig_key *md5,
1639                                           const struct sock *sk,
1640                                           const struct sk_buff *skb);
1641 #endif
1642         void (*init_req)(struct request_sock *req, struct sock *sk,
1643                          struct sk_buff *skb);
1644 #ifdef CONFIG_SYN_COOKIES
1645         __u32 (*cookie_init_seq)(struct sock *sk, const struct sk_buff *skb,
1646                                  __u16 *mss);
1647 #endif
1648         struct dst_entry *(*route_req)(struct sock *sk, struct flowi *fl,
1649                                        const struct request_sock *req,
1650                                        bool *strict);
1651         __u32 (*init_seq)(const struct sk_buff *skb);
1652         int (*send_synack)(struct sock *sk, struct dst_entry *dst,
1653                            struct flowi *fl, struct request_sock *req,
1654                            u16 queue_mapping, struct tcp_fastopen_cookie *foc);
1655         void (*queue_hash_add)(struct sock *sk, struct request_sock *req,
1656                                const unsigned long timeout);
1657 };
1658 
1659 #ifdef CONFIG_SYN_COOKIES
1660 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1661                                          struct sock *sk, struct sk_buff *skb,
1662                                          __u16 *mss)
1663 {
1664         return ops->cookie_init_seq(sk, skb, mss);
1665 }
1666 #else
1667 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1668                                          struct sock *sk, struct sk_buff *skb,
1669                                          __u16 *mss)
1670 {
1671         return 0;
1672 }
1673 #endif
1674 
1675 int tcpv4_offload_init(void);
1676 
1677 void tcp_v4_init(void);
1678 void tcp_init(void);
1679 
1680 /*
1681  * Save and compile IPv4 options, return a pointer to it
1682  */
1683 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1684 {
1685         const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1686         struct ip_options_rcu *dopt = NULL;
1687 
1688         if (opt->optlen) {
1689                 int opt_size = sizeof(*dopt) + opt->optlen;
1690 
1691                 dopt = kmalloc(opt_size, GFP_ATOMIC);
1692                 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1693                         kfree(dopt);
1694                         dopt = NULL;
1695                 }
1696         }
1697         return dopt;
1698 }
1699 
1700 /* locally generated TCP pure ACKs have skb->truesize == 2
1701  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1702  * This is much faster than dissecting the packet to find out.
1703  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1704  */
1705 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1706 {
1707         return skb->truesize == 2;
1708 }
1709 
1710 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1711 {
1712         skb->truesize = 2;
1713 }
1714 
1715 #endif  /* _TCP_H */
1716 

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