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TOMOYO Linux Cross Reference
Linux/include/net/tcp.h

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  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              Definitions for the TCP module.
  7  *
  8  * Version:     @(#)tcp.h       1.0.5   05/23/93
  9  *
 10  * Authors:     Ross Biro
 11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  *
 13  *              This program is free software; you can redistribute it and/or
 14  *              modify it under the terms of the GNU General Public License
 15  *              as published by the Free Software Foundation; either version
 16  *              2 of the License, or (at your option) any later version.
 17  */
 18 #ifndef _TCP_H
 19 #define _TCP_H
 20 
 21 #define FASTRETRANS_DEBUG 1
 22 
 23 #include <linux/list.h>
 24 #include <linux/tcp.h>
 25 #include <linux/bug.h>
 26 #include <linux/slab.h>
 27 #include <linux/cache.h>
 28 #include <linux/percpu.h>
 29 #include <linux/skbuff.h>
 30 #include <linux/cryptohash.h>
 31 #include <linux/kref.h>
 32 #include <linux/ktime.h>
 33 
 34 #include <net/inet_connection_sock.h>
 35 #include <net/inet_timewait_sock.h>
 36 #include <net/inet_hashtables.h>
 37 #include <net/checksum.h>
 38 #include <net/request_sock.h>
 39 #include <net/sock.h>
 40 #include <net/snmp.h>
 41 #include <net/ip.h>
 42 #include <net/tcp_states.h>
 43 #include <net/inet_ecn.h>
 44 #include <net/dst.h>
 45 
 46 #include <linux/seq_file.h>
 47 #include <linux/memcontrol.h>
 48 
 49 #include <linux/bpf.h>
 50 #include <linux/filter.h>
 51 #include <linux/bpf-cgroup.h>
 52 
 53 extern struct inet_hashinfo tcp_hashinfo;
 54 
 55 extern struct percpu_counter tcp_orphan_count;
 56 void tcp_time_wait(struct sock *sk, int state, int timeo);
 57 
 58 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 59 #define MAX_TCP_OPTION_SPACE 40
 60 
 61 /*
 62  * Never offer a window over 32767 without using window scaling. Some
 63  * poor stacks do signed 16bit maths!
 64  */
 65 #define MAX_TCP_WINDOW          32767U
 66 
 67 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 68 #define TCP_MIN_MSS             88U
 69 
 70 /* The least MTU to use for probing */
 71 #define TCP_BASE_MSS            1024
 72 
 73 /* probing interval, default to 10 minutes as per RFC4821 */
 74 #define TCP_PROBE_INTERVAL      600
 75 
 76 /* Specify interval when tcp mtu probing will stop */
 77 #define TCP_PROBE_THRESHOLD     8
 78 
 79 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 80 #define TCP_FASTRETRANS_THRESH 3
 81 
 82 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 83 #define TCP_MAX_QUICKACKS       16U
 84 
 85 /* Maximal number of window scale according to RFC1323 */
 86 #define TCP_MAX_WSCALE          14U
 87 
 88 /* urg_data states */
 89 #define TCP_URG_VALID   0x0100
 90 #define TCP_URG_NOTYET  0x0200
 91 #define TCP_URG_READ    0x0400
 92 
 93 #define TCP_RETR1       3       /*
 94                                  * This is how many retries it does before it
 95                                  * tries to figure out if the gateway is
 96                                  * down. Minimal RFC value is 3; it corresponds
 97                                  * to ~3sec-8min depending on RTO.
 98                                  */
 99 
100 #define TCP_RETR2       15      /*
101                                  * This should take at least
102                                  * 90 minutes to time out.
103                                  * RFC1122 says that the limit is 100 sec.
104                                  * 15 is ~13-30min depending on RTO.
105                                  */
106 
107 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
108                                  * when active opening a connection.
109                                  * RFC1122 says the minimum retry MUST
110                                  * be at least 180secs.  Nevertheless
111                                  * this value is corresponding to
112                                  * 63secs of retransmission with the
113                                  * current initial RTO.
114                                  */
115 
116 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
117                                  * when passive opening a connection.
118                                  * This is corresponding to 31secs of
119                                  * retransmission with the current
120                                  * initial RTO.
121                                  */
122 
123 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
124                                   * state, about 60 seconds     */
125 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
126                                  /* BSD style FIN_WAIT2 deadlock breaker.
127                                   * It used to be 3min, new value is 60sec,
128                                   * to combine FIN-WAIT-2 timeout with
129                                   * TIME-WAIT timer.
130                                   */
131 
132 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
133 #if HZ >= 100
134 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
135 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
136 #else
137 #define TCP_DELACK_MIN  4U
138 #define TCP_ATO_MIN     4U
139 #endif
140 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
141 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
142 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
143 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
144                                                  * used as a fallback RTO for the
145                                                  * initial data transmission if no
146                                                  * valid RTT sample has been acquired,
147                                                  * most likely due to retrans in 3WHS.
148                                                  */
149 
150 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
151                                                          * for local resources.
152                                                          */
153 #define TCP_REO_TIMEOUT_MIN     (2000) /* Min RACK reordering timeout in usec */
154 
155 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
156 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
157 #define TCP_KEEPALIVE_INTVL     (75*HZ)
158 
159 #define MAX_TCP_KEEPIDLE        32767
160 #define MAX_TCP_KEEPINTVL       32767
161 #define MAX_TCP_KEEPCNT         127
162 #define MAX_TCP_SYNCNT          127
163 
164 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
165 
166 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
167 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
168                                          * after this time. It should be equal
169                                          * (or greater than) TCP_TIMEWAIT_LEN
170                                          * to provide reliability equal to one
171                                          * provided by timewait state.
172                                          */
173 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
174                                          * timestamps. It must be less than
175                                          * minimal timewait lifetime.
176                                          */
177 /*
178  *      TCP option
179  */
180 
181 #define TCPOPT_NOP              1       /* Padding */
182 #define TCPOPT_EOL              0       /* End of options */
183 #define TCPOPT_MSS              2       /* Segment size negotiating */
184 #define TCPOPT_WINDOW           3       /* Window scaling */
185 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
186 #define TCPOPT_SACK             5       /* SACK Block */
187 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
188 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
189 #define TCPOPT_FASTOPEN         34      /* Fast open (RFC7413) */
190 #define TCPOPT_EXP              254     /* Experimental */
191 /* Magic number to be after the option value for sharing TCP
192  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
193  */
194 #define TCPOPT_FASTOPEN_MAGIC   0xF989
195 
196 /*
197  *     TCP option lengths
198  */
199 
200 #define TCPOLEN_MSS            4
201 #define TCPOLEN_WINDOW         3
202 #define TCPOLEN_SACK_PERM      2
203 #define TCPOLEN_TIMESTAMP      10
204 #define TCPOLEN_MD5SIG         18
205 #define TCPOLEN_FASTOPEN_BASE  2
206 #define TCPOLEN_EXP_FASTOPEN_BASE  4
207 
208 /* But this is what stacks really send out. */
209 #define TCPOLEN_TSTAMP_ALIGNED          12
210 #define TCPOLEN_WSCALE_ALIGNED          4
211 #define TCPOLEN_SACKPERM_ALIGNED        4
212 #define TCPOLEN_SACK_BASE               2
213 #define TCPOLEN_SACK_BASE_ALIGNED       4
214 #define TCPOLEN_SACK_PERBLOCK           8
215 #define TCPOLEN_MD5SIG_ALIGNED          20
216 #define TCPOLEN_MSS_ALIGNED             4
217 
218 /* Flags in tp->nonagle */
219 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
220 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
221 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
222 
223 /* TCP thin-stream limits */
224 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
225 
226 /* TCP initial congestion window as per rfc6928 */
227 #define TCP_INIT_CWND           10
228 
229 /* Bit Flags for sysctl_tcp_fastopen */
230 #define TFO_CLIENT_ENABLE       1
231 #define TFO_SERVER_ENABLE       2
232 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
233 
234 /* Accept SYN data w/o any cookie option */
235 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
236 
237 /* Force enable TFO on all listeners, i.e., not requiring the
238  * TCP_FASTOPEN socket option.
239  */
240 #define TFO_SERVER_WO_SOCKOPT1  0x400
241 
242 
243 /* sysctl variables for tcp */
244 extern int sysctl_tcp_fastopen;
245 extern int sysctl_tcp_retrans_collapse;
246 extern int sysctl_tcp_stdurg;
247 extern int sysctl_tcp_rfc1337;
248 extern int sysctl_tcp_abort_on_overflow;
249 extern int sysctl_tcp_max_orphans;
250 extern int sysctl_tcp_fack;
251 extern int sysctl_tcp_reordering;
252 extern int sysctl_tcp_max_reordering;
253 extern int sysctl_tcp_dsack;
254 extern long sysctl_tcp_mem[3];
255 extern int sysctl_tcp_wmem[3];
256 extern int sysctl_tcp_rmem[3];
257 extern int sysctl_tcp_app_win;
258 extern int sysctl_tcp_adv_win_scale;
259 extern int sysctl_tcp_frto;
260 extern int sysctl_tcp_low_latency;
261 extern int sysctl_tcp_nometrics_save;
262 extern int sysctl_tcp_moderate_rcvbuf;
263 extern int sysctl_tcp_tso_win_divisor;
264 extern int sysctl_tcp_workaround_signed_windows;
265 extern int sysctl_tcp_slow_start_after_idle;
266 extern int sysctl_tcp_thin_linear_timeouts;
267 extern int sysctl_tcp_thin_dupack;
268 extern int sysctl_tcp_early_retrans;
269 extern int sysctl_tcp_recovery;
270 #define TCP_RACK_LOSS_DETECTION  0x1 /* Use RACK to detect losses */
271 
272 extern int sysctl_tcp_limit_output_bytes;
273 extern int sysctl_tcp_challenge_ack_limit;
274 extern int sysctl_tcp_min_tso_segs;
275 extern int sysctl_tcp_min_rtt_wlen;
276 extern int sysctl_tcp_autocorking;
277 extern int sysctl_tcp_invalid_ratelimit;
278 extern int sysctl_tcp_pacing_ss_ratio;
279 extern int sysctl_tcp_pacing_ca_ratio;
280 
281 extern atomic_long_t tcp_memory_allocated;
282 extern struct percpu_counter tcp_sockets_allocated;
283 extern unsigned long tcp_memory_pressure;
284 
285 /* optimized version of sk_under_memory_pressure() for TCP sockets */
286 static inline bool tcp_under_memory_pressure(const struct sock *sk)
287 {
288         if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
289             mem_cgroup_under_socket_pressure(sk->sk_memcg))
290                 return true;
291 
292         return tcp_memory_pressure;
293 }
294 /*
295  * The next routines deal with comparing 32 bit unsigned ints
296  * and worry about wraparound (automatic with unsigned arithmetic).
297  */
298 
299 static inline bool before(__u32 seq1, __u32 seq2)
300 {
301         return (__s32)(seq1-seq2) < 0;
302 }
303 #define after(seq2, seq1)       before(seq1, seq2)
304 
305 /* is s2<=s1<=s3 ? */
306 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
307 {
308         return seq3 - seq2 >= seq1 - seq2;
309 }
310 
311 static inline bool tcp_out_of_memory(struct sock *sk)
312 {
313         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
314             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
315                 return true;
316         return false;
317 }
318 
319 void sk_forced_mem_schedule(struct sock *sk, int size);
320 
321 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
322 {
323         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
324         int orphans = percpu_counter_read_positive(ocp);
325 
326         if (orphans << shift > sysctl_tcp_max_orphans) {
327                 orphans = percpu_counter_sum_positive(ocp);
328                 if (orphans << shift > sysctl_tcp_max_orphans)
329                         return true;
330         }
331         return false;
332 }
333 
334 bool tcp_check_oom(struct sock *sk, int shift);
335 
336 
337 extern struct proto tcp_prot;
338 
339 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
340 #define __TCP_INC_STATS(net, field)     __SNMP_INC_STATS((net)->mib.tcp_statistics, field)
341 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
342 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
343 
344 void tcp_tasklet_init(void);
345 
346 void tcp_v4_err(struct sk_buff *skb, u32);
347 
348 void tcp_shutdown(struct sock *sk, int how);
349 
350 int tcp_v4_early_demux(struct sk_buff *skb);
351 int tcp_v4_rcv(struct sk_buff *skb);
352 
353 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
354 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
355 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
356                  int flags);
357 ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
358                  size_t size, int flags);
359 void tcp_release_cb(struct sock *sk);
360 void tcp_wfree(struct sk_buff *skb);
361 void tcp_write_timer_handler(struct sock *sk);
362 void tcp_delack_timer_handler(struct sock *sk);
363 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
364 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
365 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
366                          const struct tcphdr *th, unsigned int len);
367 void tcp_rcv_space_adjust(struct sock *sk);
368 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
369 void tcp_twsk_destructor(struct sock *sk);
370 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
371                         struct pipe_inode_info *pipe, size_t len,
372                         unsigned int flags);
373 
374 static inline void tcp_dec_quickack_mode(struct sock *sk,
375                                          const unsigned int pkts)
376 {
377         struct inet_connection_sock *icsk = inet_csk(sk);
378 
379         if (icsk->icsk_ack.quick) {
380                 if (pkts >= icsk->icsk_ack.quick) {
381                         icsk->icsk_ack.quick = 0;
382                         /* Leaving quickack mode we deflate ATO. */
383                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
384                 } else
385                         icsk->icsk_ack.quick -= pkts;
386         }
387 }
388 
389 #define TCP_ECN_OK              1
390 #define TCP_ECN_QUEUE_CWR       2
391 #define TCP_ECN_DEMAND_CWR      4
392 #define TCP_ECN_SEEN            8
393 
394 enum tcp_tw_status {
395         TCP_TW_SUCCESS = 0,
396         TCP_TW_RST = 1,
397         TCP_TW_ACK = 2,
398         TCP_TW_SYN = 3
399 };
400 
401 
402 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
403                                               struct sk_buff *skb,
404                                               const struct tcphdr *th);
405 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
406                            struct request_sock *req, bool fastopen);
407 int tcp_child_process(struct sock *parent, struct sock *child,
408                       struct sk_buff *skb);
409 void tcp_enter_loss(struct sock *sk);
410 void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag);
411 void tcp_clear_retrans(struct tcp_sock *tp);
412 void tcp_update_metrics(struct sock *sk);
413 void tcp_init_metrics(struct sock *sk);
414 void tcp_metrics_init(void);
415 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
416 void tcp_disable_fack(struct tcp_sock *tp);
417 void tcp_close(struct sock *sk, long timeout);
418 void tcp_init_sock(struct sock *sk);
419 unsigned int tcp_poll(struct file *file, struct socket *sock,
420                       struct poll_table_struct *wait);
421 int tcp_getsockopt(struct sock *sk, int level, int optname,
422                    char __user *optval, int __user *optlen);
423 int tcp_setsockopt(struct sock *sk, int level, int optname,
424                    char __user *optval, unsigned int optlen);
425 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
426                           char __user *optval, int __user *optlen);
427 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
428                           char __user *optval, unsigned int optlen);
429 void tcp_set_keepalive(struct sock *sk, int val);
430 void tcp_syn_ack_timeout(const struct request_sock *req);
431 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
432                 int flags, int *addr_len);
433 void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
434                        struct tcp_options_received *opt_rx,
435                        int estab, struct tcp_fastopen_cookie *foc);
436 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
437 
438 /*
439  *      TCP v4 functions exported for the inet6 API
440  */
441 
442 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
443 void tcp_v4_mtu_reduced(struct sock *sk);
444 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
445 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
446 struct sock *tcp_create_openreq_child(const struct sock *sk,
447                                       struct request_sock *req,
448                                       struct sk_buff *skb);
449 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
450 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
451                                   struct request_sock *req,
452                                   struct dst_entry *dst,
453                                   struct request_sock *req_unhash,
454                                   bool *own_req);
455 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
456 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
457 int tcp_connect(struct sock *sk);
458 enum tcp_synack_type {
459         TCP_SYNACK_NORMAL,
460         TCP_SYNACK_FASTOPEN,
461         TCP_SYNACK_COOKIE,
462 };
463 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
464                                 struct request_sock *req,
465                                 struct tcp_fastopen_cookie *foc,
466                                 enum tcp_synack_type synack_type);
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 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
475                                  struct request_sock *req,
476                                  struct dst_entry *dst, u32 tsoff);
477 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
478                       u32 cookie);
479 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
480 #ifdef CONFIG_SYN_COOKIES
481 
482 /* Syncookies use a monotonic timer which increments every 60 seconds.
483  * This counter is used both as a hash input and partially encoded into
484  * the cookie value.  A cookie is only validated further if the delta
485  * between the current counter value and the encoded one is less than this,
486  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
487  * the counter advances immediately after a cookie is generated).
488  */
489 #define MAX_SYNCOOKIE_AGE       2
490 #define TCP_SYNCOOKIE_PERIOD    (60 * HZ)
491 #define TCP_SYNCOOKIE_VALID     (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
492 
493 /* syncookies: remember time of last synqueue overflow
494  * But do not dirty this field too often (once per second is enough)
495  * It is racy as we do not hold a lock, but race is very minor.
496  */
497 static inline void tcp_synq_overflow(const struct sock *sk)
498 {
499         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
500         unsigned long now = jiffies;
501 
502         if (time_after(now, last_overflow + HZ))
503                 tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
504 }
505 
506 /* syncookies: no recent synqueue overflow on this listening socket? */
507 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
508 {
509         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
510 
511         return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
512 }
513 
514 static inline u32 tcp_cookie_time(void)
515 {
516         u64 val = get_jiffies_64();
517 
518         do_div(val, TCP_SYNCOOKIE_PERIOD);
519         return val;
520 }
521 
522 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
523                               u16 *mssp);
524 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
525 u64 cookie_init_timestamp(struct request_sock *req);
526 bool cookie_timestamp_decode(const struct net *net,
527                              struct tcp_options_received *opt);
528 bool cookie_ecn_ok(const struct tcp_options_received *opt,
529                    const struct net *net, const struct dst_entry *dst);
530 
531 /* From net/ipv6/syncookies.c */
532 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
533                       u32 cookie);
534 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
535 
536 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
537                               const struct tcphdr *th, u16 *mssp);
538 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
539 #endif
540 /* tcp_output.c */
541 
542 u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
543                      int min_tso_segs);
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 *sk, struct sk_buff *skb, int segs);
548 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
549 void tcp_retransmit_timer(struct sock *sk);
550 void tcp_xmit_retransmit_queue(struct sock *);
551 void tcp_simple_retransmit(struct sock *);
552 void tcp_enter_recovery(struct sock *sk, bool ece_ack);
553 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
554 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
555 
556 void tcp_send_probe0(struct sock *);
557 void tcp_send_partial(struct sock *);
558 int tcp_write_wakeup(struct sock *, int mib);
559 void tcp_send_fin(struct sock *sk);
560 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
561 int tcp_send_synack(struct sock *);
562 void tcp_push_one(struct sock *, unsigned int mss_now);
563 void tcp_send_ack(struct sock *sk);
564 void tcp_send_delayed_ack(struct sock *sk);
565 void tcp_send_loss_probe(struct sock *sk);
566 bool tcp_schedule_loss_probe(struct sock *sk);
567 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
568                              const struct sk_buff *next_skb);
569 
570 /* tcp_input.c */
571 void tcp_rearm_rto(struct sock *sk);
572 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
573 void tcp_reset(struct sock *sk);
574 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
575 void tcp_fin(struct sock *sk);
576 
577 /* tcp_timer.c */
578 void tcp_init_xmit_timers(struct sock *);
579 static inline void tcp_clear_xmit_timers(struct sock *sk)
580 {
581         hrtimer_cancel(&tcp_sk(sk)->pacing_timer);
582         inet_csk_clear_xmit_timers(sk);
583 }
584 
585 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
586 unsigned int tcp_current_mss(struct sock *sk);
587 
588 /* Bound MSS / TSO packet size with the half of the window */
589 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
590 {
591         int cutoff;
592 
593         /* When peer uses tiny windows, there is no use in packetizing
594          * to sub-MSS pieces for the sake of SWS or making sure there
595          * are enough packets in the pipe for fast recovery.
596          *
597          * On the other hand, for extremely large MSS devices, handling
598          * smaller than MSS windows in this way does make sense.
599          */
600         if (tp->max_window > TCP_MSS_DEFAULT)
601                 cutoff = (tp->max_window >> 1);
602         else
603                 cutoff = tp->max_window;
604 
605         if (cutoff && pktsize > cutoff)
606                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
607         else
608                 return pktsize;
609 }
610 
611 /* tcp.c */
612 void tcp_get_info(struct sock *, struct tcp_info *);
613 
614 /* Read 'sendfile()'-style from a TCP socket */
615 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
616                   sk_read_actor_t recv_actor);
617 
618 void tcp_initialize_rcv_mss(struct sock *sk);
619 
620 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
621 int tcp_mss_to_mtu(struct sock *sk, int mss);
622 void tcp_mtup_init(struct sock *sk);
623 void tcp_init_buffer_space(struct sock *sk);
624 
625 static inline void tcp_bound_rto(const struct sock *sk)
626 {
627         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
628                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
629 }
630 
631 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
632 {
633         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
634 }
635 
636 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
637 {
638         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
639                                ntohl(TCP_FLAG_ACK) |
640                                snd_wnd);
641 }
642 
643 static inline void tcp_fast_path_on(struct tcp_sock *tp)
644 {
645         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
646 }
647 
648 static inline void tcp_fast_path_check(struct sock *sk)
649 {
650         struct tcp_sock *tp = tcp_sk(sk);
651 
652         if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
653             tp->rcv_wnd &&
654             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
655             !tp->urg_data)
656                 tcp_fast_path_on(tp);
657 }
658 
659 /* Compute the actual rto_min value */
660 static inline u32 tcp_rto_min(struct sock *sk)
661 {
662         const struct dst_entry *dst = __sk_dst_get(sk);
663         u32 rto_min = TCP_RTO_MIN;
664 
665         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
666                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
667         return rto_min;
668 }
669 
670 static inline u32 tcp_rto_min_us(struct sock *sk)
671 {
672         return jiffies_to_usecs(tcp_rto_min(sk));
673 }
674 
675 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
676 {
677         return dst_metric_locked(dst, RTAX_CC_ALGO);
678 }
679 
680 /* Minimum RTT in usec. ~0 means not available. */
681 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
682 {
683         return minmax_get(&tp->rtt_min);
684 }
685 
686 /* Compute the actual receive window we are currently advertising.
687  * Rcv_nxt can be after the window if our peer push more data
688  * than the offered window.
689  */
690 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
691 {
692         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
693 
694         if (win < 0)
695                 win = 0;
696         return (u32) win;
697 }
698 
699 /* Choose a new window, without checks for shrinking, and without
700  * scaling applied to the result.  The caller does these things
701  * if necessary.  This is a "raw" window selection.
702  */
703 u32 __tcp_select_window(struct sock *sk);
704 
705 void tcp_send_window_probe(struct sock *sk);
706 
707 /* TCP uses 32bit jiffies to save some space.
708  * Note that this is different from tcp_time_stamp, which
709  * historically has been the same until linux-4.13.
710  */
711 #define tcp_jiffies32 ((u32)jiffies)
712 
713 /*
714  * Deliver a 32bit value for TCP timestamp option (RFC 7323)
715  * It is no longer tied to jiffies, but to 1 ms clock.
716  * Note: double check if you want to use tcp_jiffies32 instead of this.
717  */
718 #define TCP_TS_HZ       1000
719 
720 static inline u64 tcp_clock_ns(void)
721 {
722         return local_clock();
723 }
724 
725 static inline u64 tcp_clock_us(void)
726 {
727         return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
728 }
729 
730 /* This should only be used in contexts where tp->tcp_mstamp is up to date */
731 static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
732 {
733         return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);
734 }
735 
736 /* Could use tcp_clock_us() / 1000, but this version uses a single divide */
737 static inline u32 tcp_time_stamp_raw(void)
738 {
739         return div_u64(tcp_clock_ns(), NSEC_PER_SEC / TCP_TS_HZ);
740 }
741 
742 
743 /* Refresh 1us clock of a TCP socket,
744  * ensuring monotically increasing values.
745  */
746 static inline void tcp_mstamp_refresh(struct tcp_sock *tp)
747 {
748         u64 val = tcp_clock_us();
749 
750         if (val > tp->tcp_mstamp)
751                 tp->tcp_mstamp = val;
752 }
753 
754 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
755 {
756         return max_t(s64, t1 - t0, 0);
757 }
758 
759 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
760 {
761         return div_u64(skb->skb_mstamp, USEC_PER_SEC / TCP_TS_HZ);
762 }
763 
764 
765 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
766 
767 #define TCPHDR_FIN 0x01
768 #define TCPHDR_SYN 0x02
769 #define TCPHDR_RST 0x04
770 #define TCPHDR_PSH 0x08
771 #define TCPHDR_ACK 0x10
772 #define TCPHDR_URG 0x20
773 #define TCPHDR_ECE 0x40
774 #define TCPHDR_CWR 0x80
775 
776 #define TCPHDR_SYN_ECN  (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
777 
778 /* This is what the send packet queuing engine uses to pass
779  * TCP per-packet control information to the transmission code.
780  * We also store the host-order sequence numbers in here too.
781  * This is 44 bytes if IPV6 is enabled.
782  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
783  */
784 struct tcp_skb_cb {
785         __u32           seq;            /* Starting sequence number     */
786         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
787         union {
788                 /* Note : tcp_tw_isn is used in input path only
789                  *        (isn chosen by tcp_timewait_state_process())
790                  *
791                  *        tcp_gso_segs/size are used in write queue only,
792                  *        cf tcp_skb_pcount()/tcp_skb_mss()
793                  */
794                 __u32           tcp_tw_isn;
795                 struct {
796                         u16     tcp_gso_segs;
797                         u16     tcp_gso_size;
798                 };
799         };
800         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
801 
802         __u8            sacked;         /* State flags for SACK/FACK.   */
803 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
804 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
805 #define TCPCB_LOST              0x04    /* SKB is lost                  */
806 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
807 #define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
808 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
809 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
810                                 TCPCB_REPAIRED)
811 
812         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
813         __u8            txstamp_ack:1,  /* Record TX timestamp for ack? */
814                         eor:1,          /* Is skb MSG_EOR marked? */
815                         unused:6;
816         __u32           ack_seq;        /* Sequence number ACK'd        */
817         union {
818                 struct {
819                         /* There is space for up to 24 bytes */
820                         __u32 in_flight:30,/* Bytes in flight at transmit */
821                               is_app_limited:1, /* cwnd not fully used? */
822                               unused:1;
823                         /* pkts S/ACKed so far upon tx of skb, incl retrans: */
824                         __u32 delivered;
825                         /* start of send pipeline phase */
826                         u64 first_tx_mstamp;
827                         /* when we reached the "delivered" count */
828                         u64 delivered_mstamp;
829                 } tx;   /* only used for outgoing skbs */
830                 union {
831                         struct inet_skb_parm    h4;
832 #if IS_ENABLED(CONFIG_IPV6)
833                         struct inet6_skb_parm   h6;
834 #endif
835                 } header;       /* For incoming skbs */
836         };
837 };
838 
839 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
840 
841 
842 #if IS_ENABLED(CONFIG_IPV6)
843 /* This is the variant of inet6_iif() that must be used by TCP,
844  * as TCP moves IP6CB into a different location in skb->cb[]
845  */
846 static inline int tcp_v6_iif(const struct sk_buff *skb)
847 {
848         bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
849 
850         return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
851 }
852 #endif
853 
854 /* TCP_SKB_CB reference means this can not be used from early demux */
855 static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
856 {
857 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
858         if (!net->ipv4.sysctl_tcp_l3mdev_accept &&
859             skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
860                 return true;
861 #endif
862         return false;
863 }
864 
865 /* Due to TSO, an SKB can be composed of multiple actual
866  * packets.  To keep these tracked properly, we use this.
867  */
868 static inline int tcp_skb_pcount(const struct sk_buff *skb)
869 {
870         return TCP_SKB_CB(skb)->tcp_gso_segs;
871 }
872 
873 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
874 {
875         TCP_SKB_CB(skb)->tcp_gso_segs = segs;
876 }
877 
878 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
879 {
880         TCP_SKB_CB(skb)->tcp_gso_segs += segs;
881 }
882 
883 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
884 static inline int tcp_skb_mss(const struct sk_buff *skb)
885 {
886         return TCP_SKB_CB(skb)->tcp_gso_size;
887 }
888 
889 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
890 {
891         return likely(!TCP_SKB_CB(skb)->eor);
892 }
893 
894 /* Events passed to congestion control interface */
895 enum tcp_ca_event {
896         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
897         CA_EVENT_CWND_RESTART,  /* congestion window restart */
898         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
899         CA_EVENT_LOSS,          /* loss timeout */
900         CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
901         CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
902         CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
903         CA_EVENT_NON_DELAYED_ACK,
904 };
905 
906 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
907 enum tcp_ca_ack_event_flags {
908         CA_ACK_SLOWPATH         = (1 << 0),     /* In slow path processing */
909         CA_ACK_WIN_UPDATE       = (1 << 1),     /* ACK updated window */
910         CA_ACK_ECE              = (1 << 2),     /* ECE bit is set on ack */
911 };
912 
913 /*
914  * Interface for adding new TCP congestion control handlers
915  */
916 #define TCP_CA_NAME_MAX 16
917 #define TCP_CA_MAX      128
918 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
919 
920 #define TCP_CA_UNSPEC   0
921 
922 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
923 #define TCP_CONG_NON_RESTRICTED 0x1
924 /* Requires ECN/ECT set on all packets */
925 #define TCP_CONG_NEEDS_ECN      0x2
926 
927 union tcp_cc_info;
928 
929 struct ack_sample {
930         u32 pkts_acked;
931         s32 rtt_us;
932         u32 in_flight;
933 };
934 
935 /* A rate sample measures the number of (original/retransmitted) data
936  * packets delivered "delivered" over an interval of time "interval_us".
937  * The tcp_rate.c code fills in the rate sample, and congestion
938  * control modules that define a cong_control function to run at the end
939  * of ACK processing can optionally chose to consult this sample when
940  * setting cwnd and pacing rate.
941  * A sample is invalid if "delivered" or "interval_us" is negative.
942  */
943 struct rate_sample {
944         u64  prior_mstamp; /* starting timestamp for interval */
945         u32  prior_delivered;   /* tp->delivered at "prior_mstamp" */
946         s32  delivered;         /* number of packets delivered over interval */
947         long interval_us;       /* time for tp->delivered to incr "delivered" */
948         long rtt_us;            /* RTT of last (S)ACKed packet (or -1) */
949         int  losses;            /* number of packets marked lost upon ACK */
950         u32  acked_sacked;      /* number of packets newly (S)ACKed upon ACK */
951         u32  prior_in_flight;   /* in flight before this ACK */
952         bool is_app_limited;    /* is sample from packet with bubble in pipe? */
953         bool is_retrans;        /* is sample from retransmission? */
954 };
955 
956 struct tcp_congestion_ops {
957         struct list_head        list;
958         u32 key;
959         u32 flags;
960 
961         /* initialize private data (optional) */
962         void (*init)(struct sock *sk);
963         /* cleanup private data  (optional) */
964         void (*release)(struct sock *sk);
965 
966         /* return slow start threshold (required) */
967         u32 (*ssthresh)(struct sock *sk);
968         /* do new cwnd calculation (required) */
969         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
970         /* call before changing ca_state (optional) */
971         void (*set_state)(struct sock *sk, u8 new_state);
972         /* call when cwnd event occurs (optional) */
973         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
974         /* call when ack arrives (optional) */
975         void (*in_ack_event)(struct sock *sk, u32 flags);
976         /* new value of cwnd after loss (required) */
977         u32  (*undo_cwnd)(struct sock *sk);
978         /* hook for packet ack accounting (optional) */
979         void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
980         /* suggest number of segments for each skb to transmit (optional) */
981         u32 (*tso_segs_goal)(struct sock *sk);
982         /* returns the multiplier used in tcp_sndbuf_expand (optional) */
983         u32 (*sndbuf_expand)(struct sock *sk);
984         /* call when packets are delivered to update cwnd and pacing rate,
985          * after all the ca_state processing. (optional)
986          */
987         void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
988         /* get info for inet_diag (optional) */
989         size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
990                            union tcp_cc_info *info);
991 
992         char            name[TCP_CA_NAME_MAX];
993         struct module   *owner;
994 };
995 
996 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
997 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
998 
999 void tcp_assign_congestion_control(struct sock *sk);
1000 void tcp_init_congestion_control(struct sock *sk);
1001 void tcp_cleanup_congestion_control(struct sock *sk);
1002 int tcp_set_default_congestion_control(const char *name);
1003 void tcp_get_default_congestion_control(char *name);
1004 void tcp_get_available_congestion_control(char *buf, size_t len);
1005 void tcp_get_allowed_congestion_control(char *buf, size_t len);
1006 int tcp_set_allowed_congestion_control(char *allowed);
1007 int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, bool reinit);
1008 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
1009 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
1010 
1011 u32 tcp_reno_ssthresh(struct sock *sk);
1012 u32 tcp_reno_undo_cwnd(struct sock *sk);
1013 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
1014 extern struct tcp_congestion_ops tcp_reno;
1015 
1016 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
1017 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
1018 #ifdef CONFIG_INET
1019 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
1020 #else
1021 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
1022 {
1023         return NULL;
1024 }
1025 #endif
1026 
1027 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
1028 {
1029         const struct inet_connection_sock *icsk = inet_csk(sk);
1030 
1031         return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
1032 }
1033 
1034 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
1035 {
1036         struct inet_connection_sock *icsk = inet_csk(sk);
1037 
1038         if (icsk->icsk_ca_ops->set_state)
1039                 icsk->icsk_ca_ops->set_state(sk, ca_state);
1040         icsk->icsk_ca_state = ca_state;
1041 }
1042 
1043 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
1044 {
1045         const struct inet_connection_sock *icsk = inet_csk(sk);
1046 
1047         if (icsk->icsk_ca_ops->cwnd_event)
1048                 icsk->icsk_ca_ops->cwnd_event(sk, event);
1049 }
1050 
1051 /* From tcp_rate.c */
1052 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
1053 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
1054                             struct rate_sample *rs);
1055 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
1056                   struct rate_sample *rs);
1057 void tcp_rate_check_app_limited(struct sock *sk);
1058 
1059 /* These functions determine how the current flow behaves in respect of SACK
1060  * handling. SACK is negotiated with the peer, and therefore it can vary
1061  * between different flows.
1062  *
1063  * tcp_is_sack - SACK enabled
1064  * tcp_is_reno - No SACK
1065  * tcp_is_fack - FACK enabled, implies SACK enabled
1066  */
1067 static inline int tcp_is_sack(const struct tcp_sock *tp)
1068 {
1069         return tp->rx_opt.sack_ok;
1070 }
1071 
1072 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1073 {
1074         return !tcp_is_sack(tp);
1075 }
1076 
1077 static inline bool tcp_is_fack(const struct tcp_sock *tp)
1078 {
1079         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
1080 }
1081 
1082 static inline void tcp_enable_fack(struct tcp_sock *tp)
1083 {
1084         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
1085 }
1086 
1087 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1088 {
1089         return tp->sacked_out + tp->lost_out;
1090 }
1091 
1092 /* This determines how many packets are "in the network" to the best
1093  * of our knowledge.  In many cases it is conservative, but where
1094  * detailed information is available from the receiver (via SACK
1095  * blocks etc.) we can make more aggressive calculations.
1096  *
1097  * Use this for decisions involving congestion control, use just
1098  * tp->packets_out to determine if the send queue is empty or not.
1099  *
1100  * Read this equation as:
1101  *
1102  *      "Packets sent once on transmission queue" MINUS
1103  *      "Packets left network, but not honestly ACKed yet" PLUS
1104  *      "Packets fast retransmitted"
1105  */
1106 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1107 {
1108         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1109 }
1110 
1111 #define TCP_INFINITE_SSTHRESH   0x7fffffff
1112 
1113 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1114 {
1115         return tp->snd_cwnd < tp->snd_ssthresh;
1116 }
1117 
1118 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1119 {
1120         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1121 }
1122 
1123 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1124 {
1125         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1126                (1 << inet_csk(sk)->icsk_ca_state);
1127 }
1128 
1129 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1130  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1131  * ssthresh.
1132  */
1133 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1134 {
1135         const struct tcp_sock *tp = tcp_sk(sk);
1136 
1137         if (tcp_in_cwnd_reduction(sk))
1138                 return tp->snd_ssthresh;
1139         else
1140                 return max(tp->snd_ssthresh,
1141                            ((tp->snd_cwnd >> 1) +
1142                             (tp->snd_cwnd >> 2)));
1143 }
1144 
1145 /* Use define here intentionally to get WARN_ON location shown at the caller */
1146 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1147 
1148 void tcp_enter_cwr(struct sock *sk);
1149 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1150 
1151 /* The maximum number of MSS of available cwnd for which TSO defers
1152  * sending if not using sysctl_tcp_tso_win_divisor.
1153  */
1154 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1155 {
1156         return 3;
1157 }
1158 
1159 /* Returns end sequence number of the receiver's advertised window */
1160 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1161 {
1162         return tp->snd_una + tp->snd_wnd;
1163 }
1164 
1165 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1166  * flexible approach. The RFC suggests cwnd should not be raised unless
1167  * it was fully used previously. And that's exactly what we do in
1168  * congestion avoidance mode. But in slow start we allow cwnd to grow
1169  * as long as the application has used half the cwnd.
1170  * Example :
1171  *    cwnd is 10 (IW10), but application sends 9 frames.
1172  *    We allow cwnd to reach 18 when all frames are ACKed.
1173  * This check is safe because it's as aggressive as slow start which already
1174  * risks 100% overshoot. The advantage is that we discourage application to
1175  * either send more filler packets or data to artificially blow up the cwnd
1176  * usage, and allow application-limited process to probe bw more aggressively.
1177  */
1178 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1179 {
1180         const struct tcp_sock *tp = tcp_sk(sk);
1181 
1182         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1183         if (tcp_in_slow_start(tp))
1184                 return tp->snd_cwnd < 2 * tp->max_packets_out;
1185 
1186         return tp->is_cwnd_limited;
1187 }
1188 
1189 /* Something is really bad, we could not queue an additional packet,
1190  * because qdisc is full or receiver sent a 0 window.
1191  * We do not want to add fuel to the fire, or abort too early,
1192  * so make sure the timer we arm now is at least 200ms in the future,
1193  * regardless of current icsk_rto value (as it could be ~2ms)
1194  */
1195 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1196 {
1197         return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1198 }
1199 
1200 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1201 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1202                                             unsigned long max_when)
1203 {
1204         u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1205 
1206         return (unsigned long)min_t(u64, when, max_when);
1207 }
1208 
1209 static inline void tcp_check_probe_timer(struct sock *sk)
1210 {
1211         if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1212                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1213                                           tcp_probe0_base(sk), TCP_RTO_MAX);
1214 }
1215 
1216 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1217 {
1218         tp->snd_wl1 = seq;
1219 }
1220 
1221 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1222 {
1223         tp->snd_wl1 = seq;
1224 }
1225 
1226 /*
1227  * Calculate(/check) TCP checksum
1228  */
1229 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1230                                    __be32 daddr, __wsum base)
1231 {
1232         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1233 }
1234 
1235 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1236 {
1237         return __skb_checksum_complete(skb);
1238 }
1239 
1240 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1241 {
1242         return !skb_csum_unnecessary(skb) &&
1243                 __tcp_checksum_complete(skb);
1244 }
1245 
1246 /* Prequeue for VJ style copy to user, combined with checksumming. */
1247 
1248 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1249 {
1250         tp->ucopy.task = NULL;
1251         tp->ucopy.len = 0;
1252         tp->ucopy.memory = 0;
1253         skb_queue_head_init(&tp->ucopy.prequeue);
1254 }
1255 
1256 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1257 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
1258 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1259 
1260 #undef STATE_TRACE
1261 
1262 #ifdef STATE_TRACE
1263 static const char *statename[]={
1264         "Unused","Established","Syn Sent","Syn Recv",
1265         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1266         "Close Wait","Last ACK","Listen","Closing"
1267 };
1268 #endif
1269 void tcp_set_state(struct sock *sk, int state);
1270 
1271 void tcp_done(struct sock *sk);
1272 
1273 int tcp_abort(struct sock *sk, int err);
1274 
1275 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1276 {
1277         rx_opt->dsack = 0;
1278         rx_opt->num_sacks = 0;
1279 }
1280 
1281 u32 tcp_default_init_rwnd(u32 mss);
1282 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1283 
1284 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1285 {
1286         const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1287         struct tcp_sock *tp = tcp_sk(sk);
1288         s32 delta;
1289 
1290         if (!sysctl_tcp_slow_start_after_idle || tp->packets_out ||
1291             ca_ops->cong_control)
1292                 return;
1293         delta = tcp_jiffies32 - tp->lsndtime;
1294         if (delta > inet_csk(sk)->icsk_rto)
1295                 tcp_cwnd_restart(sk, delta);
1296 }
1297 
1298 /* Determine a window scaling and initial window to offer. */
1299 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1300                                __u32 *window_clamp, int wscale_ok,
1301                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1302 
1303 static inline int tcp_win_from_space(int space)
1304 {
1305         int tcp_adv_win_scale = sysctl_tcp_adv_win_scale;
1306 
1307         return tcp_adv_win_scale <= 0 ?
1308                 (space>>(-tcp_adv_win_scale)) :
1309                 space - (space>>tcp_adv_win_scale);
1310 }
1311 
1312 /* Note: caller must be prepared to deal with negative returns */
1313 static inline int tcp_space(const struct sock *sk)
1314 {
1315         return tcp_win_from_space(sk->sk_rcvbuf -
1316                                   atomic_read(&sk->sk_rmem_alloc));
1317 }
1318 
1319 static inline int tcp_full_space(const struct sock *sk)
1320 {
1321         return tcp_win_from_space(sk->sk_rcvbuf);
1322 }
1323 
1324 extern void tcp_openreq_init_rwin(struct request_sock *req,
1325                                   const struct sock *sk_listener,
1326                                   const struct dst_entry *dst);
1327 
1328 void tcp_enter_memory_pressure(struct sock *sk);
1329 void tcp_leave_memory_pressure(struct sock *sk);
1330 
1331 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1332 {
1333         struct net *net = sock_net((struct sock *)tp);
1334 
1335         return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
1336 }
1337 
1338 static inline int keepalive_time_when(const struct tcp_sock *tp)
1339 {
1340         struct net *net = sock_net((struct sock *)tp);
1341 
1342         return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1343 }
1344 
1345 static inline int keepalive_probes(const struct tcp_sock *tp)
1346 {
1347         struct net *net = sock_net((struct sock *)tp);
1348 
1349         return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1350 }
1351 
1352 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1353 {
1354         const struct inet_connection_sock *icsk = &tp->inet_conn;
1355 
1356         return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime,
1357                           tcp_jiffies32 - tp->rcv_tstamp);
1358 }
1359 
1360 static inline int tcp_fin_time(const struct sock *sk)
1361 {
1362         int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
1363         const int rto = inet_csk(sk)->icsk_rto;
1364 
1365         if (fin_timeout < (rto << 2) - (rto >> 1))
1366                 fin_timeout = (rto << 2) - (rto >> 1);
1367 
1368         return fin_timeout;
1369 }
1370 
1371 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1372                                   int paws_win)
1373 {
1374         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1375                 return true;
1376         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1377                 return true;
1378         /*
1379          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1380          * then following tcp messages have valid values. Ignore 0 value,
1381          * or else 'negative' tsval might forbid us to accept their packets.
1382          */
1383         if (!rx_opt->ts_recent)
1384                 return true;
1385         return false;
1386 }
1387 
1388 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1389                                    int rst)
1390 {
1391         if (tcp_paws_check(rx_opt, 0))
1392                 return false;
1393 
1394         /* RST segments are not recommended to carry timestamp,
1395            and, if they do, it is recommended to ignore PAWS because
1396            "their cleanup function should take precedence over timestamps."
1397            Certainly, it is mistake. It is necessary to understand the reasons
1398            of this constraint to relax it: if peer reboots, clock may go
1399            out-of-sync and half-open connections will not be reset.
1400            Actually, the problem would be not existing if all
1401            the implementations followed draft about maintaining clock
1402            via reboots. Linux-2.2 DOES NOT!
1403 
1404            However, we can relax time bounds for RST segments to MSL.
1405          */
1406         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1407                 return false;
1408         return true;
1409 }
1410 
1411 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1412                           int mib_idx, u32 *last_oow_ack_time);
1413 
1414 static inline void tcp_mib_init(struct net *net)
1415 {
1416         /* See RFC 2012 */
1417         TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1418         TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1419         TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1420         TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1421 }
1422 
1423 /* from STCP */
1424 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1425 {
1426         tp->lost_skb_hint = NULL;
1427 }
1428 
1429 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1430 {
1431         tcp_clear_retrans_hints_partial(tp);
1432         tp->retransmit_skb_hint = NULL;
1433 }
1434 
1435 union tcp_md5_addr {
1436         struct in_addr  a4;
1437 #if IS_ENABLED(CONFIG_IPV6)
1438         struct in6_addr a6;
1439 #endif
1440 };
1441 
1442 /* - key database */
1443 struct tcp_md5sig_key {
1444         struct hlist_node       node;
1445         u8                      keylen;
1446         u8                      family; /* AF_INET or AF_INET6 */
1447         union tcp_md5_addr      addr;
1448         u8                      prefixlen;
1449         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1450         struct rcu_head         rcu;
1451 };
1452 
1453 /* - sock block */
1454 struct tcp_md5sig_info {
1455         struct hlist_head       head;
1456         struct rcu_head         rcu;
1457 };
1458 
1459 /* - pseudo header */
1460 struct tcp4_pseudohdr {
1461         __be32          saddr;
1462         __be32          daddr;
1463         __u8            pad;
1464         __u8            protocol;
1465         __be16          len;
1466 };
1467 
1468 struct tcp6_pseudohdr {
1469         struct in6_addr saddr;
1470         struct in6_addr daddr;
1471         __be32          len;
1472         __be32          protocol;       /* including padding */
1473 };
1474 
1475 union tcp_md5sum_block {
1476         struct tcp4_pseudohdr ip4;
1477 #if IS_ENABLED(CONFIG_IPV6)
1478         struct tcp6_pseudohdr ip6;
1479 #endif
1480 };
1481 
1482 /* - pool: digest algorithm, hash description and scratch buffer */
1483 struct tcp_md5sig_pool {
1484         struct ahash_request    *md5_req;
1485         void                    *scratch;
1486 };
1487 
1488 /* - functions */
1489 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1490                         const struct sock *sk, const struct sk_buff *skb);
1491 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1492                    int family, u8 prefixlen, const u8 *newkey, u8 newkeylen,
1493                    gfp_t gfp);
1494 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1495                    int family, u8 prefixlen);
1496 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1497                                          const struct sock *addr_sk);
1498 
1499 #ifdef CONFIG_TCP_MD5SIG
1500 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1501                                          const union tcp_md5_addr *addr,
1502                                          int family);
1503 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1504 #else
1505 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1506                                          const union tcp_md5_addr *addr,
1507                                          int family)
1508 {
1509         return NULL;
1510 }
1511 #define tcp_twsk_md5_key(twsk)  NULL
1512 #endif
1513 
1514 bool tcp_alloc_md5sig_pool(void);
1515 
1516 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1517 static inline void tcp_put_md5sig_pool(void)
1518 {
1519         local_bh_enable();
1520 }
1521 
1522 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1523                           unsigned int header_len);
1524 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1525                      const struct tcp_md5sig_key *key);
1526 
1527 /* From tcp_fastopen.c */
1528 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1529                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1530                             unsigned long *last_syn_loss);
1531 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1532                             struct tcp_fastopen_cookie *cookie, bool syn_lost,
1533                             u16 try_exp);
1534 struct tcp_fastopen_request {
1535         /* Fast Open cookie. Size 0 means a cookie request */
1536         struct tcp_fastopen_cookie      cookie;
1537         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1538         size_t                          size;
1539         int                             copied; /* queued in tcp_connect() */
1540 };
1541 void tcp_free_fastopen_req(struct tcp_sock *tp);
1542 
1543 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1544 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1545 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1546 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1547                               struct request_sock *req,
1548                               struct tcp_fastopen_cookie *foc,
1549                               struct dst_entry *dst);
1550 void tcp_fastopen_init_key_once(bool publish);
1551 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
1552                              struct tcp_fastopen_cookie *cookie);
1553 bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
1554 #define TCP_FASTOPEN_KEY_LENGTH 16
1555 
1556 /* Fastopen key context */
1557 struct tcp_fastopen_context {
1558         struct crypto_cipher    *tfm;
1559         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1560         struct rcu_head         rcu;
1561 };
1562 
1563 extern unsigned int sysctl_tcp_fastopen_blackhole_timeout;
1564 void tcp_fastopen_active_disable(struct sock *sk);
1565 bool tcp_fastopen_active_should_disable(struct sock *sk);
1566 void tcp_fastopen_active_disable_ofo_check(struct sock *sk);
1567 void tcp_fastopen_active_timeout_reset(void);
1568 
1569 /* Latencies incurred by various limits for a sender. They are
1570  * chronograph-like stats that are mutually exclusive.
1571  */
1572 enum tcp_chrono {
1573         TCP_CHRONO_UNSPEC,
1574         TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1575         TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
1576         TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
1577         __TCP_CHRONO_MAX,
1578 };
1579 
1580 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
1581 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
1582 
1583 /* write queue abstraction */
1584 static inline void tcp_write_queue_purge(struct sock *sk)
1585 {
1586         struct sk_buff *skb;
1587 
1588         tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1589         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1590                 sk_wmem_free_skb(sk, skb);
1591         sk_mem_reclaim(sk);
1592         tcp_clear_all_retrans_hints(tcp_sk(sk));
1593 }
1594 
1595 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1596 {
1597         return skb_peek(&sk->sk_write_queue);
1598 }
1599 
1600 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1601 {
1602         return skb_peek_tail(&sk->sk_write_queue);
1603 }
1604 
1605 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1606                                                    const struct sk_buff *skb)
1607 {
1608         return skb_queue_next(&sk->sk_write_queue, skb);
1609 }
1610 
1611 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1612                                                    const struct sk_buff *skb)
1613 {
1614         return skb_queue_prev(&sk->sk_write_queue, skb);
1615 }
1616 
1617 #define tcp_for_write_queue(skb, sk)                                    \
1618         skb_queue_walk(&(sk)->sk_write_queue, skb)
1619 
1620 #define tcp_for_write_queue_from(skb, sk)                               \
1621         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1622 
1623 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1624         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1625 
1626 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1627 {
1628         return sk->sk_send_head;
1629 }
1630 
1631 static inline bool tcp_skb_is_last(const struct sock *sk,
1632                                    const struct sk_buff *skb)
1633 {
1634         return skb_queue_is_last(&sk->sk_write_queue, skb);
1635 }
1636 
1637 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1638 {
1639         if (tcp_skb_is_last(sk, skb))
1640                 sk->sk_send_head = NULL;
1641         else
1642                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1643 }
1644 
1645 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1646 {
1647         if (sk->sk_send_head == skb_unlinked) {
1648                 sk->sk_send_head = NULL;
1649                 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1650         }
1651         if (tcp_sk(sk)->highest_sack == skb_unlinked)
1652                 tcp_sk(sk)->highest_sack = NULL;
1653 }
1654 
1655 static inline void tcp_init_send_head(struct sock *sk)
1656 {
1657         sk->sk_send_head = NULL;
1658 }
1659 
1660 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1661 {
1662         __skb_queue_tail(&sk->sk_write_queue, skb);
1663 }
1664 
1665 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1666 {
1667         __tcp_add_write_queue_tail(sk, skb);
1668 
1669         /* Queue it, remembering where we must start sending. */
1670         if (sk->sk_send_head == NULL) {
1671                 sk->sk_send_head = skb;
1672                 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
1673 
1674                 if (tcp_sk(sk)->highest_sack == NULL)
1675                         tcp_sk(sk)->highest_sack = skb;
1676         }
1677 }
1678 
1679 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1680 {
1681         __skb_queue_head(&sk->sk_write_queue, skb);
1682 }
1683 
1684 /* Insert buff after skb on the write queue of sk.  */
1685 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1686                                                 struct sk_buff *buff,
1687                                                 struct sock *sk)
1688 {
1689         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1690 }
1691 
1692 /* Insert new before skb on the write queue of sk.  */
1693 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1694                                                   struct sk_buff *skb,
1695                                                   struct sock *sk)
1696 {
1697         __skb_queue_before(&sk->sk_write_queue, skb, new);
1698 
1699         if (sk->sk_send_head == skb)
1700                 sk->sk_send_head = new;
1701 }
1702 
1703 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1704 {
1705         __skb_unlink(skb, &sk->sk_write_queue);
1706 }
1707 
1708 static inline bool tcp_write_queue_empty(struct sock *sk)
1709 {
1710         return skb_queue_empty(&sk->sk_write_queue);
1711 }
1712 
1713 static inline void tcp_push_pending_frames(struct sock *sk)
1714 {
1715         if (tcp_send_head(sk)) {
1716                 struct tcp_sock *tp = tcp_sk(sk);
1717 
1718                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1719         }
1720 }
1721 
1722 /* Start sequence of the skb just after the highest skb with SACKed
1723  * bit, valid only if sacked_out > 0 or when the caller has ensured
1724  * validity by itself.
1725  */
1726 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1727 {
1728         if (!tp->sacked_out)
1729                 return tp->snd_una;
1730 
1731         if (tp->highest_sack == NULL)
1732                 return tp->snd_nxt;
1733 
1734         return TCP_SKB_CB(tp->highest_sack)->seq;
1735 }
1736 
1737 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1738 {
1739         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1740                                                 tcp_write_queue_next(sk, skb);
1741 }
1742 
1743 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1744 {
1745         return tcp_sk(sk)->highest_sack;
1746 }
1747 
1748 static inline void tcp_highest_sack_reset(struct sock *sk)
1749 {
1750         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1751 }
1752 
1753 /* Called when old skb is about to be deleted and replaced by new skb */
1754 static inline void tcp_highest_sack_replace(struct sock *sk,
1755                                             struct sk_buff *old,
1756                                             struct sk_buff *new)
1757 {
1758         if (old == tcp_highest_sack(sk))
1759                 tcp_sk(sk)->highest_sack = new;
1760 }
1761 
1762 /* This helper checks if socket has IP_TRANSPARENT set */
1763 static inline bool inet_sk_transparent(const struct sock *sk)
1764 {
1765         switch (sk->sk_state) {
1766         case TCP_TIME_WAIT:
1767                 return inet_twsk(sk)->tw_transparent;
1768         case TCP_NEW_SYN_RECV:
1769                 return inet_rsk(inet_reqsk(sk))->no_srccheck;
1770         }
1771         return inet_sk(sk)->transparent;
1772 }
1773 
1774 /* Determines whether this is a thin stream (which may suffer from
1775  * increased latency). Used to trigger latency-reducing mechanisms.
1776  */
1777 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1778 {
1779         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1780 }
1781 
1782 /* /proc */
1783 enum tcp_seq_states {
1784         TCP_SEQ_STATE_LISTENING,
1785         TCP_SEQ_STATE_ESTABLISHED,
1786 };
1787 
1788 int tcp_seq_open(struct inode *inode, struct file *file);
1789 
1790 struct tcp_seq_afinfo {
1791         char                            *name;
1792         sa_family_t                     family;
1793         const struct file_operations    *seq_fops;
1794         struct seq_operations           seq_ops;
1795 };
1796 
1797 struct tcp_iter_state {
1798         struct seq_net_private  p;
1799         sa_family_t             family;
1800         enum tcp_seq_states     state;
1801         struct sock             *syn_wait_sk;
1802         int                     bucket, offset, sbucket, num;
1803         loff_t                  last_pos;
1804 };
1805 
1806 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1807 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1808 
1809 extern struct request_sock_ops tcp_request_sock_ops;
1810 extern struct request_sock_ops tcp6_request_sock_ops;
1811 
1812 void tcp_v4_destroy_sock(struct sock *sk);
1813 
1814 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1815                                 netdev_features_t features);
1816 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1817 int tcp_gro_complete(struct sk_buff *skb);
1818 
1819 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1820 
1821 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1822 {
1823         struct net *net = sock_net((struct sock *)tp);
1824         return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
1825 }
1826 
1827 static inline bool tcp_stream_memory_free(const struct sock *sk)
1828 {
1829         const struct tcp_sock *tp = tcp_sk(sk);
1830         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1831 
1832         return notsent_bytes < tcp_notsent_lowat(tp);
1833 }
1834 
1835 #ifdef CONFIG_PROC_FS
1836 int tcp4_proc_init(void);
1837 void tcp4_proc_exit(void);
1838 #endif
1839 
1840 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1841 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1842                      const struct tcp_request_sock_ops *af_ops,
1843                      struct sock *sk, struct sk_buff *skb);
1844 
1845 /* TCP af-specific functions */
1846 struct tcp_sock_af_ops {
1847 #ifdef CONFIG_TCP_MD5SIG
1848         struct tcp_md5sig_key   *(*md5_lookup) (const struct sock *sk,
1849                                                 const struct sock *addr_sk);
1850         int             (*calc_md5_hash)(char *location,
1851                                          const struct tcp_md5sig_key *md5,
1852                                          const struct sock *sk,
1853                                          const struct sk_buff *skb);
1854         int             (*md5_parse)(struct sock *sk,
1855                                      int optname,
1856                                      char __user *optval,
1857                                      int optlen);
1858 #endif
1859 };
1860 
1861 struct tcp_request_sock_ops {
1862         u16 mss_clamp;
1863 #ifdef CONFIG_TCP_MD5SIG
1864         struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1865                                                  const struct sock *addr_sk);
1866         int             (*calc_md5_hash) (char *location,
1867                                           const struct tcp_md5sig_key *md5,
1868                                           const struct sock *sk,
1869                                           const struct sk_buff *skb);
1870 #endif
1871         void (*init_req)(struct request_sock *req,
1872                          const struct sock *sk_listener,
1873                          struct sk_buff *skb);
1874 #ifdef CONFIG_SYN_COOKIES
1875         __u32 (*cookie_init_seq)(const struct sk_buff *skb,
1876                                  __u16 *mss);
1877 #endif
1878         struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1879                                        const struct request_sock *req);
1880         u32 (*init_seq)(const struct sk_buff *skb);
1881         u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
1882         int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1883                            struct flowi *fl, struct request_sock *req,
1884                            struct tcp_fastopen_cookie *foc,
1885                            enum tcp_synack_type synack_type);
1886 };
1887 
1888 #ifdef CONFIG_SYN_COOKIES
1889 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1890                                          const struct sock *sk, struct sk_buff *skb,
1891                                          __u16 *mss)
1892 {
1893         tcp_synq_overflow(sk);
1894         __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1895         return ops->cookie_init_seq(skb, mss);
1896 }
1897 #else
1898 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1899                                          const struct sock *sk, struct sk_buff *skb,
1900                                          __u16 *mss)
1901 {
1902         return 0;
1903 }
1904 #endif
1905 
1906 int tcpv4_offload_init(void);
1907 
1908 void tcp_v4_init(void);
1909 void tcp_init(void);
1910 
1911 /* tcp_recovery.c */
1912 extern void tcp_rack_mark_lost(struct sock *sk);
1913 extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
1914                              u64 xmit_time);
1915 extern void tcp_rack_reo_timeout(struct sock *sk);
1916 
1917 /* At how many usecs into the future should the RTO fire? */
1918 static inline s64 tcp_rto_delta_us(const struct sock *sk)
1919 {
1920         const struct sk_buff *skb = tcp_write_queue_head(sk);
1921         u32 rto = inet_csk(sk)->icsk_rto;
1922         u64 rto_time_stamp_us = skb->skb_mstamp + jiffies_to_usecs(rto);
1923 
1924         return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
1925 }
1926 
1927 /*
1928  * Save and compile IPv4 options, return a pointer to it
1929  */
1930 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1931 {
1932         const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1933         struct ip_options_rcu *dopt = NULL;
1934 
1935         if (opt->optlen) {
1936                 int opt_size = sizeof(*dopt) + opt->optlen;
1937 
1938                 dopt = kmalloc(opt_size, GFP_ATOMIC);
1939                 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1940                         kfree(dopt);
1941                         dopt = NULL;
1942                 }
1943         }
1944         return dopt;
1945 }
1946 
1947 /* locally generated TCP pure ACKs have skb->truesize == 2
1948  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1949  * This is much faster than dissecting the packet to find out.
1950  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1951  */
1952 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1953 {
1954         return skb->truesize == 2;
1955 }
1956 
1957 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1958 {
1959         skb->truesize = 2;
1960 }
1961 
1962 static inline int tcp_inq(struct sock *sk)
1963 {
1964         struct tcp_sock *tp = tcp_sk(sk);
1965         int answ;
1966 
1967         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
1968                 answ = 0;
1969         } else if (sock_flag(sk, SOCK_URGINLINE) ||
1970                    !tp->urg_data ||
1971                    before(tp->urg_seq, tp->copied_seq) ||
1972                    !before(tp->urg_seq, tp->rcv_nxt)) {
1973 
1974                 answ = tp->rcv_nxt - tp->copied_seq;
1975 
1976                 /* Subtract 1, if FIN was received */
1977                 if (answ && sock_flag(sk, SOCK_DONE))
1978                         answ--;
1979         } else {
1980                 answ = tp->urg_seq - tp->copied_seq;
1981         }
1982 
1983         return answ;
1984 }
1985 
1986 int tcp_peek_len(struct socket *sock);
1987 
1988 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
1989 {
1990         u16 segs_in;
1991 
1992         segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
1993         tp->segs_in += segs_in;
1994         if (skb->len > tcp_hdrlen(skb))
1995                 tp->data_segs_in += segs_in;
1996 }
1997 
1998 /*
1999  * TCP listen path runs lockless.
2000  * We forced "struct sock" to be const qualified to make sure
2001  * we don't modify one of its field by mistake.
2002  * Here, we increment sk_drops which is an atomic_t, so we can safely
2003  * make sock writable again.
2004  */
2005 static inline void tcp_listendrop(const struct sock *sk)
2006 {
2007         atomic_inc(&((struct sock *)sk)->sk_drops);
2008         __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
2009 }
2010 
2011 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);
2012 
2013 /*
2014  * Interface for adding Upper Level Protocols over TCP
2015  */
2016 
2017 #define TCP_ULP_NAME_MAX        16
2018 #define TCP_ULP_MAX             128
2019 #define TCP_ULP_BUF_MAX         (TCP_ULP_NAME_MAX*TCP_ULP_MAX)
2020 
2021 struct tcp_ulp_ops {
2022         struct list_head        list;
2023 
2024         /* initialize ulp */
2025         int (*init)(struct sock *sk);
2026         /* cleanup ulp */
2027         void (*release)(struct sock *sk);
2028 
2029         char            name[TCP_ULP_NAME_MAX];
2030         struct module   *owner;
2031 };
2032 int tcp_register_ulp(struct tcp_ulp_ops *type);
2033 void tcp_unregister_ulp(struct tcp_ulp_ops *type);
2034 int tcp_set_ulp(struct sock *sk, const char *name);
2035 void tcp_get_available_ulp(char *buf, size_t len);
2036 void tcp_cleanup_ulp(struct sock *sk);
2037 
2038 /* Call BPF_SOCK_OPS program that returns an int. If the return value
2039  * is < 0, then the BPF op failed (for example if the loaded BPF
2040  * program does not support the chosen operation or there is no BPF
2041  * program loaded).
2042  */
2043 #ifdef CONFIG_BPF
2044 static inline int tcp_call_bpf(struct sock *sk, int op)
2045 {
2046         struct bpf_sock_ops_kern sock_ops;
2047         int ret;
2048 
2049         if (sk_fullsock(sk))
2050                 sock_owned_by_me(sk);
2051 
2052         memset(&sock_ops, 0, sizeof(sock_ops));
2053         sock_ops.sk = sk;
2054         sock_ops.op = op;
2055 
2056         ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
2057         if (ret == 0)
2058                 ret = sock_ops.reply;
2059         else
2060                 ret = -1;
2061         return ret;
2062 }
2063 #else
2064 static inline int tcp_call_bpf(struct sock *sk, int op)
2065 {
2066         return -EPERM;
2067 }
2068 #endif
2069 
2070 static inline u32 tcp_timeout_init(struct sock *sk)
2071 {
2072         int timeout;
2073 
2074         timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT);
2075 
2076         if (timeout <= 0)
2077                 timeout = TCP_TIMEOUT_INIT;
2078         return timeout;
2079 }
2080 
2081 static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
2082 {
2083         int rwnd;
2084 
2085         rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT);
2086 
2087         if (rwnd < 0)
2088                 rwnd = 0;
2089         return rwnd;
2090 }
2091 
2092 static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
2093 {
2094         return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN) == 1);
2095 }
2096 #endif  /* _TCP_H */
2097 

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