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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/dmaengine.h>
 31 #include <linux/crypto.h>
 32 #include <linux/cryptohash.h>
 33 #include <linux/kref.h>
 34 #include <linux/ktime.h>
 35 
 36 #include <net/inet_connection_sock.h>
 37 #include <net/inet_timewait_sock.h>
 38 #include <net/inet_hashtables.h>
 39 #include <net/checksum.h>
 40 #include <net/request_sock.h>
 41 #include <net/sock.h>
 42 #include <net/snmp.h>
 43 #include <net/ip.h>
 44 #include <net/tcp_states.h>
 45 #include <net/inet_ecn.h>
 46 #include <net/dst.h>
 47 
 48 #include <linux/seq_file.h>
 49 #include <linux/memcontrol.h>
 50 
 51 extern struct inet_hashinfo tcp_hashinfo;
 52 
 53 extern struct percpu_counter tcp_orphan_count;
 54 void tcp_time_wait(struct sock *sk, int state, int timeo);
 55 
 56 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 57 #define MAX_TCP_OPTION_SPACE 40
 58 
 59 /* 
 60  * Never offer a window over 32767 without using window scaling. Some
 61  * poor stacks do signed 16bit maths! 
 62  */
 63 #define MAX_TCP_WINDOW          32767U
 64 
 65 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 66 #define TCP_MIN_MSS             88U
 67 
 68 /* The least MTU to use for probing */
 69 #define TCP_BASE_MSS            512
 70 
 71 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 72 #define TCP_FASTRETRANS_THRESH 3
 73 
 74 /* Maximal reordering. */
 75 #define TCP_MAX_REORDERING      127
 76 
 77 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 78 #define TCP_MAX_QUICKACKS       16U
 79 
 80 /* urg_data states */
 81 #define TCP_URG_VALID   0x0100
 82 #define TCP_URG_NOTYET  0x0200
 83 #define TCP_URG_READ    0x0400
 84 
 85 #define TCP_RETR1       3       /*
 86                                  * This is how many retries it does before it
 87                                  * tries to figure out if the gateway is
 88                                  * down. Minimal RFC value is 3; it corresponds
 89                                  * to ~3sec-8min depending on RTO.
 90                                  */
 91 
 92 #define TCP_RETR2       15      /*
 93                                  * This should take at least
 94                                  * 90 minutes to time out.
 95                                  * RFC1122 says that the limit is 100 sec.
 96                                  * 15 is ~13-30min depending on RTO.
 97                                  */
 98 
 99 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
100                                  * when active opening a connection.
101                                  * RFC1122 says the minimum retry MUST
102                                  * be at least 180secs.  Nevertheless
103                                  * this value is corresponding to
104                                  * 63secs of retransmission with the
105                                  * current initial RTO.
106                                  */
107 
108 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
109                                  * when passive opening a connection.
110                                  * This is corresponding to 31secs of
111                                  * retransmission with the current
112                                  * initial RTO.
113                                  */
114 
115 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
116                                   * state, about 60 seconds     */
117 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
118                                  /* BSD style FIN_WAIT2 deadlock breaker.
119                                   * It used to be 3min, new value is 60sec,
120                                   * to combine FIN-WAIT-2 timeout with
121                                   * TIME-WAIT timer.
122                                   */
123 
124 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
125 #if HZ >= 100
126 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
127 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
128 #else
129 #define TCP_DELACK_MIN  4U
130 #define TCP_ATO_MIN     4U
131 #endif
132 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
133 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
134 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
135 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
136                                                  * used as a fallback RTO for the
137                                                  * initial data transmission if no
138                                                  * valid RTT sample has been acquired,
139                                                  * most likely due to retrans in 3WHS.
140                                                  */
141 
142 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
143                                                          * for local resources.
144                                                          */
145 
146 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
147 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
148 #define TCP_KEEPALIVE_INTVL     (75*HZ)
149 
150 #define MAX_TCP_KEEPIDLE        32767
151 #define MAX_TCP_KEEPINTVL       32767
152 #define MAX_TCP_KEEPCNT         127
153 #define MAX_TCP_SYNCNT          127
154 
155 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
156 
157 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
158 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
159                                          * after this time. It should be equal
160                                          * (or greater than) TCP_TIMEWAIT_LEN
161                                          * to provide reliability equal to one
162                                          * provided by timewait state.
163                                          */
164 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
165                                          * timestamps. It must be less than
166                                          * minimal timewait lifetime.
167                                          */
168 /*
169  *      TCP option
170  */
171  
172 #define TCPOPT_NOP              1       /* Padding */
173 #define TCPOPT_EOL              0       /* End of options */
174 #define TCPOPT_MSS              2       /* Segment size negotiating */
175 #define TCPOPT_WINDOW           3       /* Window scaling */
176 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
177 #define TCPOPT_SACK             5       /* SACK Block */
178 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
179 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
180 #define TCPOPT_EXP              254     /* Experimental */
181 /* Magic number to be after the option value for sharing TCP
182  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
183  */
184 #define TCPOPT_FASTOPEN_MAGIC   0xF989
185 
186 /*
187  *     TCP option lengths
188  */
189 
190 #define TCPOLEN_MSS            4
191 #define TCPOLEN_WINDOW         3
192 #define TCPOLEN_SACK_PERM      2
193 #define TCPOLEN_TIMESTAMP      10
194 #define TCPOLEN_MD5SIG         18
195 #define TCPOLEN_EXP_FASTOPEN_BASE  4
196 
197 /* But this is what stacks really send out. */
198 #define TCPOLEN_TSTAMP_ALIGNED          12
199 #define TCPOLEN_WSCALE_ALIGNED          4
200 #define TCPOLEN_SACKPERM_ALIGNED        4
201 #define TCPOLEN_SACK_BASE               2
202 #define TCPOLEN_SACK_BASE_ALIGNED       4
203 #define TCPOLEN_SACK_PERBLOCK           8
204 #define TCPOLEN_MD5SIG_ALIGNED          20
205 #define TCPOLEN_MSS_ALIGNED             4
206 
207 /* Flags in tp->nonagle */
208 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
209 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
210 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
211 
212 /* TCP thin-stream limits */
213 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
214 
215 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
216 #define TCP_INIT_CWND           10
217 
218 /* Bit Flags for sysctl_tcp_fastopen */
219 #define TFO_CLIENT_ENABLE       1
220 #define TFO_SERVER_ENABLE       2
221 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
222 
223 /* Accept SYN data w/o any cookie option */
224 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
225 
226 /* Force enable TFO on all listeners, i.e., not requiring the
227  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
228  */
229 #define TFO_SERVER_WO_SOCKOPT1  0x400
230 #define TFO_SERVER_WO_SOCKOPT2  0x800
231 
232 extern struct inet_timewait_death_row tcp_death_row;
233 
234 /* sysctl variables for tcp */
235 extern int sysctl_tcp_timestamps;
236 extern int sysctl_tcp_window_scaling;
237 extern int sysctl_tcp_sack;
238 extern int sysctl_tcp_fin_timeout;
239 extern int sysctl_tcp_keepalive_time;
240 extern int sysctl_tcp_keepalive_probes;
241 extern int sysctl_tcp_keepalive_intvl;
242 extern int sysctl_tcp_syn_retries;
243 extern int sysctl_tcp_synack_retries;
244 extern int sysctl_tcp_retries1;
245 extern int sysctl_tcp_retries2;
246 extern int sysctl_tcp_orphan_retries;
247 extern int sysctl_tcp_syncookies;
248 extern int sysctl_tcp_fastopen;
249 extern int sysctl_tcp_retrans_collapse;
250 extern int sysctl_tcp_stdurg;
251 extern int sysctl_tcp_rfc1337;
252 extern int sysctl_tcp_abort_on_overflow;
253 extern int sysctl_tcp_max_orphans;
254 extern int sysctl_tcp_fack;
255 extern int sysctl_tcp_reordering;
256 extern int sysctl_tcp_dsack;
257 extern long sysctl_tcp_mem[3];
258 extern int sysctl_tcp_wmem[3];
259 extern int sysctl_tcp_rmem[3];
260 extern int sysctl_tcp_app_win;
261 extern int sysctl_tcp_adv_win_scale;
262 extern int sysctl_tcp_tw_reuse;
263 extern int sysctl_tcp_frto;
264 extern int sysctl_tcp_low_latency;
265 extern int sysctl_tcp_dma_copybreak;
266 extern int sysctl_tcp_nometrics_save;
267 extern int sysctl_tcp_moderate_rcvbuf;
268 extern int sysctl_tcp_tso_win_divisor;
269 extern int sysctl_tcp_mtu_probing;
270 extern int sysctl_tcp_base_mss;
271 extern int sysctl_tcp_workaround_signed_windows;
272 extern int sysctl_tcp_slow_start_after_idle;
273 extern int sysctl_tcp_thin_linear_timeouts;
274 extern int sysctl_tcp_thin_dupack;
275 extern int sysctl_tcp_early_retrans;
276 extern int sysctl_tcp_limit_output_bytes;
277 extern int sysctl_tcp_challenge_ack_limit;
278 extern unsigned int sysctl_tcp_notsent_lowat;
279 extern int sysctl_tcp_min_tso_segs;
280 extern int sysctl_tcp_autocorking;
281 
282 extern atomic_long_t tcp_memory_allocated;
283 extern struct percpu_counter tcp_sockets_allocated;
284 extern int tcp_memory_pressure;
285 
286 /*
287  * The next routines deal with comparing 32 bit unsigned ints
288  * and worry about wraparound (automatic with unsigned arithmetic).
289  */
290 
291 static inline bool before(__u32 seq1, __u32 seq2)
292 {
293         return (__s32)(seq1-seq2) < 0;
294 }
295 #define after(seq2, seq1)       before(seq1, seq2)
296 
297 /* is s2<=s1<=s3 ? */
298 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
299 {
300         return seq3 - seq2 >= seq1 - seq2;
301 }
302 
303 static inline bool tcp_out_of_memory(struct sock *sk)
304 {
305         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
306             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
307                 return true;
308         return false;
309 }
310 
311 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
312 {
313         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
314         int orphans = percpu_counter_read_positive(ocp);
315 
316         if (orphans << shift > sysctl_tcp_max_orphans) {
317                 orphans = percpu_counter_sum_positive(ocp);
318                 if (orphans << shift > sysctl_tcp_max_orphans)
319                         return true;
320         }
321         return false;
322 }
323 
324 bool tcp_check_oom(struct sock *sk, int shift);
325 
326 /* syncookies: remember time of last synqueue overflow */
327 static inline void tcp_synq_overflow(struct sock *sk)
328 {
329         tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
330 }
331 
332 /* syncookies: no recent synqueue overflow on this listening socket? */
333 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
334 {
335         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
336         return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
337 }
338 
339 extern struct proto tcp_prot;
340 
341 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
342 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
343 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
344 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
345 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
346 
347 void tcp_tasklet_init(void);
348 
349 void tcp_v4_err(struct sk_buff *skb, u32);
350 
351 void tcp_shutdown(struct sock *sk, int how);
352 
353 void tcp_v4_early_demux(struct sk_buff *skb);
354 int tcp_v4_rcv(struct sk_buff *skb);
355 
356 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
357 int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
358                 size_t size);
359 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
360                  int flags);
361 void tcp_release_cb(struct sock *sk);
362 void tcp_wfree(struct sk_buff *skb);
363 void tcp_write_timer_handler(struct sock *sk);
364 void tcp_delack_timer_handler(struct sock *sk);
365 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
366 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
367                           const struct tcphdr *th, unsigned int len);
368 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
369                          const struct tcphdr *th, unsigned int len);
370 void tcp_rcv_space_adjust(struct sock *sk);
371 void tcp_cleanup_rbuf(struct sock *sk, int copied);
372 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
373 void tcp_twsk_destructor(struct sock *sk);
374 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
375                         struct pipe_inode_info *pipe, size_t len,
376                         unsigned int flags);
377 
378 static inline void tcp_dec_quickack_mode(struct sock *sk,
379                                          const unsigned int pkts)
380 {
381         struct inet_connection_sock *icsk = inet_csk(sk);
382 
383         if (icsk->icsk_ack.quick) {
384                 if (pkts >= icsk->icsk_ack.quick) {
385                         icsk->icsk_ack.quick = 0;
386                         /* Leaving quickack mode we deflate ATO. */
387                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
388                 } else
389                         icsk->icsk_ack.quick -= pkts;
390         }
391 }
392 
393 #define TCP_ECN_OK              1
394 #define TCP_ECN_QUEUE_CWR       2
395 #define TCP_ECN_DEMAND_CWR      4
396 #define TCP_ECN_SEEN            8
397 
398 enum tcp_tw_status {
399         TCP_TW_SUCCESS = 0,
400         TCP_TW_RST = 1,
401         TCP_TW_ACK = 2,
402         TCP_TW_SYN = 3
403 };
404 
405 
406 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
407                                               struct sk_buff *skb,
408                                               const struct tcphdr *th);
409 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
410                            struct request_sock *req, struct request_sock **prev,
411                            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(struct sock *sk, struct request_sock *req);
439 int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
440                 size_t len, int nonblock, 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 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
453 struct sock *tcp_create_openreq_child(struct sock *sk,
454                                       struct request_sock *req,
455                                       struct sk_buff *skb);
456 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
457                                   struct request_sock *req,
458                                   struct dst_entry *dst);
459 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
460 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
461 int tcp_connect(struct sock *sk);
462 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
463                                 struct request_sock *req,
464                                 struct tcp_fastopen_cookie *foc);
465 int tcp_disconnect(struct sock *sk, int flags);
466 
467 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
468 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
469 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
470 
471 /* From syncookies.c */
472 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
473                       u32 cookie);
474 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
475                              struct ip_options *opt);
476 #ifdef CONFIG_SYN_COOKIES
477 
478 /* Syncookies use a monotonic timer which increments every 60 seconds.
479  * This counter is used both as a hash input and partially encoded into
480  * the cookie value.  A cookie is only validated further if the delta
481  * between the current counter value and the encoded one is less than this,
482  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
483  * the counter advances immediately after a cookie is generated).
484  */
485 #define MAX_SYNCOOKIE_AGE 2
486 
487 static inline u32 tcp_cookie_time(void)
488 {
489         u64 val = get_jiffies_64();
490 
491         do_div(val, 60 * HZ);
492         return val;
493 }
494 
495 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
496                               u16 *mssp);
497 __u32 cookie_v4_init_sequence(struct sock *sk, const struct sk_buff *skb,
498                               __u16 *mss);
499 #endif
500 
501 __u32 cookie_init_timestamp(struct request_sock *req);
502 bool cookie_check_timestamp(struct tcp_options_received *opt, struct net *net,
503                             bool *ecn_ok);
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 #ifdef CONFIG_SYN_COOKIES
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 bool tcp_syn_flood_action(struct sock *sk, const struct sk_buff *skb,
535                           const char *proto);
536 void tcp_push_one(struct sock *, unsigned int mss_now);
537 void tcp_send_ack(struct sock *sk);
538 void tcp_send_delayed_ack(struct sock *sk);
539 void tcp_send_loss_probe(struct sock *sk);
540 bool tcp_schedule_loss_probe(struct sock *sk);
541 
542 /* tcp_input.c */
543 void tcp_resume_early_retransmit(struct sock *sk);
544 void tcp_rearm_rto(struct sock *sk);
545 void tcp_reset(struct sock *sk);
546 
547 /* tcp_timer.c */
548 void tcp_init_xmit_timers(struct sock *);
549 static inline void tcp_clear_xmit_timers(struct sock *sk)
550 {
551         inet_csk_clear_xmit_timers(sk);
552 }
553 
554 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
555 unsigned int tcp_current_mss(struct sock *sk);
556 
557 /* Bound MSS / TSO packet size with the half of the window */
558 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
559 {
560         int cutoff;
561 
562         /* When peer uses tiny windows, there is no use in packetizing
563          * to sub-MSS pieces for the sake of SWS or making sure there
564          * are enough packets in the pipe for fast recovery.
565          *
566          * On the other hand, for extremely large MSS devices, handling
567          * smaller than MSS windows in this way does make sense.
568          */
569         if (tp->max_window >= 512)
570                 cutoff = (tp->max_window >> 1);
571         else
572                 cutoff = tp->max_window;
573 
574         if (cutoff && pktsize > cutoff)
575                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
576         else
577                 return pktsize;
578 }
579 
580 /* tcp.c */
581 void tcp_get_info(const struct sock *, struct tcp_info *);
582 
583 /* Read 'sendfile()'-style from a TCP socket */
584 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
585                                 unsigned int, size_t);
586 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
587                   sk_read_actor_t recv_actor);
588 
589 void tcp_initialize_rcv_mss(struct sock *sk);
590 
591 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
592 int tcp_mss_to_mtu(struct sock *sk, int mss);
593 void tcp_mtup_init(struct sock *sk);
594 void tcp_init_buffer_space(struct sock *sk);
595 
596 static inline void tcp_bound_rto(const struct sock *sk)
597 {
598         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
599                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
600 }
601 
602 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
603 {
604         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
605 }
606 
607 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
608 {
609         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
610                                ntohl(TCP_FLAG_ACK) |
611                                snd_wnd);
612 }
613 
614 static inline void tcp_fast_path_on(struct tcp_sock *tp)
615 {
616         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
617 }
618 
619 static inline void tcp_fast_path_check(struct sock *sk)
620 {
621         struct tcp_sock *tp = tcp_sk(sk);
622 
623         if (skb_queue_empty(&tp->out_of_order_queue) &&
624             tp->rcv_wnd &&
625             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
626             !tp->urg_data)
627                 tcp_fast_path_on(tp);
628 }
629 
630 /* Compute the actual rto_min value */
631 static inline u32 tcp_rto_min(struct sock *sk)
632 {
633         const struct dst_entry *dst = __sk_dst_get(sk);
634         u32 rto_min = TCP_RTO_MIN;
635 
636         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
637                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
638         return rto_min;
639 }
640 
641 static inline u32 tcp_rto_min_us(struct sock *sk)
642 {
643         return jiffies_to_usecs(tcp_rto_min(sk));
644 }
645 
646 /* Compute the actual receive window we are currently advertising.
647  * Rcv_nxt can be after the window if our peer push more data
648  * than the offered window.
649  */
650 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
651 {
652         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
653 
654         if (win < 0)
655                 win = 0;
656         return (u32) win;
657 }
658 
659 /* Choose a new window, without checks for shrinking, and without
660  * scaling applied to the result.  The caller does these things
661  * if necessary.  This is a "raw" window selection.
662  */
663 u32 __tcp_select_window(struct sock *sk);
664 
665 void tcp_send_window_probe(struct sock *sk);
666 
667 /* TCP timestamps are only 32-bits, this causes a slight
668  * complication on 64-bit systems since we store a snapshot
669  * of jiffies in the buffer control blocks below.  We decided
670  * to use only the low 32-bits of jiffies and hide the ugly
671  * casts with the following macro.
672  */
673 #define tcp_time_stamp          ((__u32)(jiffies))
674 
675 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
676 
677 #define TCPHDR_FIN 0x01
678 #define TCPHDR_SYN 0x02
679 #define TCPHDR_RST 0x04
680 #define TCPHDR_PSH 0x08
681 #define TCPHDR_ACK 0x10
682 #define TCPHDR_URG 0x20
683 #define TCPHDR_ECE 0x40
684 #define TCPHDR_CWR 0x80
685 
686 /* This is what the send packet queuing engine uses to pass
687  * TCP per-packet control information to the transmission code.
688  * We also store the host-order sequence numbers in here too.
689  * This is 44 bytes if IPV6 is enabled.
690  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
691  */
692 struct tcp_skb_cb {
693         union {
694                 struct inet_skb_parm    h4;
695 #if IS_ENABLED(CONFIG_IPV6)
696                 struct inet6_skb_parm   h6;
697 #endif
698         } header;       /* For incoming frames          */
699         __u32           seq;            /* Starting sequence number     */
700         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
701         __u32           when;           /* used to compute rtt's        */
702         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
703 
704         __u8            sacked;         /* State flags for SACK/FACK.   */
705 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
706 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
707 #define TCPCB_LOST              0x04    /* SKB is lost                  */
708 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
709 #define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
710 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
711 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
712                                 TCPCB_REPAIRED)
713 
714         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
715         /* 1 byte hole */
716         __u32           ack_seq;        /* Sequence number ACK'd        */
717 };
718 
719 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
720 
721 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
722  *
723  * If we receive a SYN packet with these bits set, it means a network is
724  * playing bad games with TOS bits. In order to avoid possible false congestion
725  * notifications, we disable TCP ECN negociation.
726  */
727 static inline void
728 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
729                 struct net *net)
730 {
731         const struct tcphdr *th = tcp_hdr(skb);
732 
733         if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr &&
734             INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
735                 inet_rsk(req)->ecn_ok = 1;
736 }
737 
738 /* Due to TSO, an SKB can be composed of multiple actual
739  * packets.  To keep these tracked properly, we use this.
740  */
741 static inline int tcp_skb_pcount(const struct sk_buff *skb)
742 {
743         return skb_shinfo(skb)->gso_segs;
744 }
745 
746 /* This is valid iff tcp_skb_pcount() > 1. */
747 static inline int tcp_skb_mss(const struct sk_buff *skb)
748 {
749         return skb_shinfo(skb)->gso_size;
750 }
751 
752 /* Events passed to congestion control interface */
753 enum tcp_ca_event {
754         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
755         CA_EVENT_CWND_RESTART,  /* congestion window restart */
756         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
757         CA_EVENT_LOSS,          /* loss timeout */
758         CA_EVENT_FAST_ACK,      /* in sequence ack */
759         CA_EVENT_SLOW_ACK,      /* other ack */
760 };
761 
762 /*
763  * Interface for adding new TCP congestion control handlers
764  */
765 #define TCP_CA_NAME_MAX 16
766 #define TCP_CA_MAX      128
767 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
768 
769 #define TCP_CONG_NON_RESTRICTED 0x1
770 
771 struct tcp_congestion_ops {
772         struct list_head        list;
773         unsigned long flags;
774 
775         /* initialize private data (optional) */
776         void (*init)(struct sock *sk);
777         /* cleanup private data  (optional) */
778         void (*release)(struct sock *sk);
779 
780         /* return slow start threshold (required) */
781         u32 (*ssthresh)(struct sock *sk);
782         /* do new cwnd calculation (required) */
783         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
784         /* call before changing ca_state (optional) */
785         void (*set_state)(struct sock *sk, u8 new_state);
786         /* call when cwnd event occurs (optional) */
787         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
788         /* new value of cwnd after loss (optional) */
789         u32  (*undo_cwnd)(struct sock *sk);
790         /* hook for packet ack accounting (optional) */
791         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
792         /* get info for inet_diag (optional) */
793         void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
794 
795         char            name[TCP_CA_NAME_MAX];
796         struct module   *owner;
797 };
798 
799 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
800 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
801 
802 void tcp_init_congestion_control(struct sock *sk);
803 void tcp_cleanup_congestion_control(struct sock *sk);
804 int tcp_set_default_congestion_control(const char *name);
805 void tcp_get_default_congestion_control(char *name);
806 void tcp_get_available_congestion_control(char *buf, size_t len);
807 void tcp_get_allowed_congestion_control(char *buf, size_t len);
808 int tcp_set_allowed_congestion_control(char *allowed);
809 int tcp_set_congestion_control(struct sock *sk, const char *name);
810 int tcp_slow_start(struct tcp_sock *tp, u32 acked);
811 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
812 
813 extern struct tcp_congestion_ops tcp_init_congestion_ops;
814 u32 tcp_reno_ssthresh(struct sock *sk);
815 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
816 extern struct tcp_congestion_ops tcp_reno;
817 
818 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
819 {
820         struct inet_connection_sock *icsk = inet_csk(sk);
821 
822         if (icsk->icsk_ca_ops->set_state)
823                 icsk->icsk_ca_ops->set_state(sk, ca_state);
824         icsk->icsk_ca_state = ca_state;
825 }
826 
827 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
828 {
829         const struct inet_connection_sock *icsk = inet_csk(sk);
830 
831         if (icsk->icsk_ca_ops->cwnd_event)
832                 icsk->icsk_ca_ops->cwnd_event(sk, event);
833 }
834 
835 /* These functions determine how the current flow behaves in respect of SACK
836  * handling. SACK is negotiated with the peer, and therefore it can vary
837  * between different flows.
838  *
839  * tcp_is_sack - SACK enabled
840  * tcp_is_reno - No SACK
841  * tcp_is_fack - FACK enabled, implies SACK enabled
842  */
843 static inline int tcp_is_sack(const struct tcp_sock *tp)
844 {
845         return tp->rx_opt.sack_ok;
846 }
847 
848 static inline bool tcp_is_reno(const struct tcp_sock *tp)
849 {
850         return !tcp_is_sack(tp);
851 }
852 
853 static inline bool tcp_is_fack(const struct tcp_sock *tp)
854 {
855         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
856 }
857 
858 static inline void tcp_enable_fack(struct tcp_sock *tp)
859 {
860         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
861 }
862 
863 /* TCP early-retransmit (ER) is similar to but more conservative than
864  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
865  */
866 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
867 {
868         tp->do_early_retrans = sysctl_tcp_early_retrans &&
869                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
870                 sysctl_tcp_reordering == 3;
871 }
872 
873 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
874 {
875         tp->do_early_retrans = 0;
876 }
877 
878 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
879 {
880         return tp->sacked_out + tp->lost_out;
881 }
882 
883 /* This determines how many packets are "in the network" to the best
884  * of our knowledge.  In many cases it is conservative, but where
885  * detailed information is available from the receiver (via SACK
886  * blocks etc.) we can make more aggressive calculations.
887  *
888  * Use this for decisions involving congestion control, use just
889  * tp->packets_out to determine if the send queue is empty or not.
890  *
891  * Read this equation as:
892  *
893  *      "Packets sent once on transmission queue" MINUS
894  *      "Packets left network, but not honestly ACKed yet" PLUS
895  *      "Packets fast retransmitted"
896  */
897 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
898 {
899         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
900 }
901 
902 #define TCP_INFINITE_SSTHRESH   0x7fffffff
903 
904 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
905 {
906         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
907 }
908 
909 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
910 {
911         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
912                (1 << inet_csk(sk)->icsk_ca_state);
913 }
914 
915 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
916  * The exception is cwnd reduction phase, when cwnd is decreasing towards
917  * ssthresh.
918  */
919 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
920 {
921         const struct tcp_sock *tp = tcp_sk(sk);
922 
923         if (tcp_in_cwnd_reduction(sk))
924                 return tp->snd_ssthresh;
925         else
926                 return max(tp->snd_ssthresh,
927                            ((tp->snd_cwnd >> 1) +
928                             (tp->snd_cwnd >> 2)));
929 }
930 
931 /* Use define here intentionally to get WARN_ON location shown at the caller */
932 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
933 
934 void tcp_enter_cwr(struct sock *sk);
935 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
936 
937 /* The maximum number of MSS of available cwnd for which TSO defers
938  * sending if not using sysctl_tcp_tso_win_divisor.
939  */
940 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
941 {
942         return 3;
943 }
944 
945 /* Slow start with delack produces 3 packets of burst, so that
946  * it is safe "de facto".  This will be the default - same as
947  * the default reordering threshold - but if reordering increases,
948  * we must be able to allow cwnd to burst at least this much in order
949  * to not pull it back when holes are filled.
950  */
951 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
952 {
953         return tp->reordering;
954 }
955 
956 /* Returns end sequence number of the receiver's advertised window */
957 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
958 {
959         return tp->snd_una + tp->snd_wnd;
960 }
961 
962 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
963  * flexible approach. The RFC suggests cwnd should not be raised unless
964  * it was fully used previously. And that's exactly what we do in
965  * congestion avoidance mode. But in slow start we allow cwnd to grow
966  * as long as the application has used half the cwnd.
967  * Example :
968  *    cwnd is 10 (IW10), but application sends 9 frames.
969  *    We allow cwnd to reach 18 when all frames are ACKed.
970  * This check is safe because it's as aggressive as slow start which already
971  * risks 100% overshoot. The advantage is that we discourage application to
972  * either send more filler packets or data to artificially blow up the cwnd
973  * usage, and allow application-limited process to probe bw more aggressively.
974  */
975 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
976 {
977         const struct tcp_sock *tp = tcp_sk(sk);
978 
979         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
980         if (tp->snd_cwnd <= tp->snd_ssthresh)
981                 return tp->snd_cwnd < 2 * tp->max_packets_out;
982 
983         return tp->is_cwnd_limited;
984 }
985 
986 static inline void tcp_check_probe_timer(struct sock *sk)
987 {
988         const struct tcp_sock *tp = tcp_sk(sk);
989         const struct inet_connection_sock *icsk = inet_csk(sk);
990 
991         if (!tp->packets_out && !icsk->icsk_pending)
992                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
993                                           icsk->icsk_rto, TCP_RTO_MAX);
994 }
995 
996 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
997 {
998         tp->snd_wl1 = seq;
999 }
1000 
1001 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1002 {
1003         tp->snd_wl1 = seq;
1004 }
1005 
1006 /*
1007  * Calculate(/check) TCP checksum
1008  */
1009 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1010                                    __be32 daddr, __wsum base)
1011 {
1012         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1013 }
1014 
1015 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1016 {
1017         return __skb_checksum_complete(skb);
1018 }
1019 
1020 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1021 {
1022         return !skb_csum_unnecessary(skb) &&
1023                 __tcp_checksum_complete(skb);
1024 }
1025 
1026 /* Prequeue for VJ style copy to user, combined with checksumming. */
1027 
1028 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1029 {
1030         tp->ucopy.task = NULL;
1031         tp->ucopy.len = 0;
1032         tp->ucopy.memory = 0;
1033         skb_queue_head_init(&tp->ucopy.prequeue);
1034 #ifdef CONFIG_NET_DMA
1035         tp->ucopy.dma_chan = NULL;
1036         tp->ucopy.wakeup = 0;
1037         tp->ucopy.pinned_list = NULL;
1038         tp->ucopy.dma_cookie = 0;
1039 #endif
1040 }
1041 
1042 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1043 
1044 #undef STATE_TRACE
1045 
1046 #ifdef STATE_TRACE
1047 static const char *statename[]={
1048         "Unused","Established","Syn Sent","Syn Recv",
1049         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1050         "Close Wait","Last ACK","Listen","Closing"
1051 };
1052 #endif
1053 void tcp_set_state(struct sock *sk, int state);
1054 
1055 void tcp_done(struct sock *sk);
1056 
1057 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1058 {
1059         rx_opt->dsack = 0;
1060         rx_opt->num_sacks = 0;
1061 }
1062 
1063 u32 tcp_default_init_rwnd(u32 mss);
1064 
1065 /* Determine a window scaling and initial window to offer. */
1066 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1067                                __u32 *window_clamp, int wscale_ok,
1068                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1069 
1070 static inline int tcp_win_from_space(int space)
1071 {
1072         return sysctl_tcp_adv_win_scale<=0 ?
1073                 (space>>(-sysctl_tcp_adv_win_scale)) :
1074                 space - (space>>sysctl_tcp_adv_win_scale);
1075 }
1076 
1077 /* Note: caller must be prepared to deal with negative returns */ 
1078 static inline int tcp_space(const struct sock *sk)
1079 {
1080         return tcp_win_from_space(sk->sk_rcvbuf -
1081                                   atomic_read(&sk->sk_rmem_alloc));
1082 } 
1083 
1084 static inline int tcp_full_space(const struct sock *sk)
1085 {
1086         return tcp_win_from_space(sk->sk_rcvbuf); 
1087 }
1088 
1089 static inline void tcp_openreq_init(struct request_sock *req,
1090                                     struct tcp_options_received *rx_opt,
1091                                     struct sk_buff *skb, struct sock *sk)
1092 {
1093         struct inet_request_sock *ireq = inet_rsk(req);
1094 
1095         req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
1096         req->cookie_ts = 0;
1097         tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1098         tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1099         tcp_rsk(req)->snt_synack = tcp_time_stamp;
1100         req->mss = rx_opt->mss_clamp;
1101         req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1102         ireq->tstamp_ok = rx_opt->tstamp_ok;
1103         ireq->sack_ok = rx_opt->sack_ok;
1104         ireq->snd_wscale = rx_opt->snd_wscale;
1105         ireq->wscale_ok = rx_opt->wscale_ok;
1106         ireq->acked = 0;
1107         ireq->ecn_ok = 0;
1108         ireq->ir_rmt_port = tcp_hdr(skb)->source;
1109         ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
1110         ireq->ir_mark = inet_request_mark(sk, skb);
1111 }
1112 
1113 extern void tcp_openreq_init_rwin(struct request_sock *req,
1114                                   struct sock *sk, struct dst_entry *dst);
1115 
1116 void tcp_enter_memory_pressure(struct sock *sk);
1117 
1118 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1119 {
1120         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1121 }
1122 
1123 static inline int keepalive_time_when(const struct tcp_sock *tp)
1124 {
1125         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1126 }
1127 
1128 static inline int keepalive_probes(const struct tcp_sock *tp)
1129 {
1130         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1131 }
1132 
1133 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1134 {
1135         const struct inet_connection_sock *icsk = &tp->inet_conn;
1136 
1137         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1138                           tcp_time_stamp - tp->rcv_tstamp);
1139 }
1140 
1141 static inline int tcp_fin_time(const struct sock *sk)
1142 {
1143         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1144         const int rto = inet_csk(sk)->icsk_rto;
1145 
1146         if (fin_timeout < (rto << 2) - (rto >> 1))
1147                 fin_timeout = (rto << 2) - (rto >> 1);
1148 
1149         return fin_timeout;
1150 }
1151 
1152 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1153                                   int paws_win)
1154 {
1155         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1156                 return true;
1157         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1158                 return true;
1159         /*
1160          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1161          * then following tcp messages have valid values. Ignore 0 value,
1162          * or else 'negative' tsval might forbid us to accept their packets.
1163          */
1164         if (!rx_opt->ts_recent)
1165                 return true;
1166         return false;
1167 }
1168 
1169 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1170                                    int rst)
1171 {
1172         if (tcp_paws_check(rx_opt, 0))
1173                 return false;
1174 
1175         /* RST segments are not recommended to carry timestamp,
1176            and, if they do, it is recommended to ignore PAWS because
1177            "their cleanup function should take precedence over timestamps."
1178            Certainly, it is mistake. It is necessary to understand the reasons
1179            of this constraint to relax it: if peer reboots, clock may go
1180            out-of-sync and half-open connections will not be reset.
1181            Actually, the problem would be not existing if all
1182            the implementations followed draft about maintaining clock
1183            via reboots. Linux-2.2 DOES NOT!
1184 
1185            However, we can relax time bounds for RST segments to MSL.
1186          */
1187         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1188                 return false;
1189         return true;
1190 }
1191 
1192 static inline void tcp_mib_init(struct net *net)
1193 {
1194         /* See RFC 2012 */
1195         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1196         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1197         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1198         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1199 }
1200 
1201 /* from STCP */
1202 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1203 {
1204         tp->lost_skb_hint = NULL;
1205 }
1206 
1207 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1208 {
1209         tcp_clear_retrans_hints_partial(tp);
1210         tp->retransmit_skb_hint = NULL;
1211 }
1212 
1213 /* MD5 Signature */
1214 struct crypto_hash;
1215 
1216 union tcp_md5_addr {
1217         struct in_addr  a4;
1218 #if IS_ENABLED(CONFIG_IPV6)
1219         struct in6_addr a6;
1220 #endif
1221 };
1222 
1223 /* - key database */
1224 struct tcp_md5sig_key {
1225         struct hlist_node       node;
1226         u8                      keylen;
1227         u8                      family; /* AF_INET or AF_INET6 */
1228         union tcp_md5_addr      addr;
1229         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1230         struct rcu_head         rcu;
1231 };
1232 
1233 /* - sock block */
1234 struct tcp_md5sig_info {
1235         struct hlist_head       head;
1236         struct rcu_head         rcu;
1237 };
1238 
1239 /* - pseudo header */
1240 struct tcp4_pseudohdr {
1241         __be32          saddr;
1242         __be32          daddr;
1243         __u8            pad;
1244         __u8            protocol;
1245         __be16          len;
1246 };
1247 
1248 struct tcp6_pseudohdr {
1249         struct in6_addr saddr;
1250         struct in6_addr daddr;
1251         __be32          len;
1252         __be32          protocol;       /* including padding */
1253 };
1254 
1255 union tcp_md5sum_block {
1256         struct tcp4_pseudohdr ip4;
1257 #if IS_ENABLED(CONFIG_IPV6)
1258         struct tcp6_pseudohdr ip6;
1259 #endif
1260 };
1261 
1262 /* - pool: digest algorithm, hash description and scratch buffer */
1263 struct tcp_md5sig_pool {
1264         struct hash_desc        md5_desc;
1265         union tcp_md5sum_block  md5_blk;
1266 };
1267 
1268 /* - functions */
1269 int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1270                         const struct sock *sk, const struct request_sock *req,
1271                         const struct sk_buff *skb);
1272 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1273                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1274 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1275                    int family);
1276 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1277                                          struct sock *addr_sk);
1278 
1279 #ifdef CONFIG_TCP_MD5SIG
1280 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1281                                          const union tcp_md5_addr *addr,
1282                                          int family);
1283 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1284 #else
1285 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1286                                          const union tcp_md5_addr *addr,
1287                                          int family)
1288 {
1289         return NULL;
1290 }
1291 #define tcp_twsk_md5_key(twsk)  NULL
1292 #endif
1293 
1294 bool tcp_alloc_md5sig_pool(void);
1295 
1296 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1297 static inline void tcp_put_md5sig_pool(void)
1298 {
1299         local_bh_enable();
1300 }
1301 
1302 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1303 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1304                           unsigned int header_len);
1305 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1306                      const struct tcp_md5sig_key *key);
1307 
1308 /* From tcp_fastopen.c */
1309 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1310                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1311                             unsigned long *last_syn_loss);
1312 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1313                             struct tcp_fastopen_cookie *cookie, bool syn_lost);
1314 struct tcp_fastopen_request {
1315         /* Fast Open cookie. Size 0 means a cookie request */
1316         struct tcp_fastopen_cookie      cookie;
1317         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1318         size_t                          size;
1319         int                             copied; /* queued in tcp_connect() */
1320 };
1321 void tcp_free_fastopen_req(struct tcp_sock *tp);
1322 
1323 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1324 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1325 bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1326                       struct request_sock *req,
1327                       struct tcp_fastopen_cookie *foc,
1328                       struct dst_entry *dst);
1329 void tcp_fastopen_init_key_once(bool publish);
1330 #define TCP_FASTOPEN_KEY_LENGTH 16
1331 
1332 /* Fastopen key context */
1333 struct tcp_fastopen_context {
1334         struct crypto_cipher    *tfm;
1335         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1336         struct rcu_head         rcu;
1337 };
1338 
1339 /* write queue abstraction */
1340 static inline void tcp_write_queue_purge(struct sock *sk)
1341 {
1342         struct sk_buff *skb;
1343 
1344         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1345                 sk_wmem_free_skb(sk, skb);
1346         sk_mem_reclaim(sk);
1347         tcp_clear_all_retrans_hints(tcp_sk(sk));
1348 }
1349 
1350 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1351 {
1352         return skb_peek(&sk->sk_write_queue);
1353 }
1354 
1355 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1356 {
1357         return skb_peek_tail(&sk->sk_write_queue);
1358 }
1359 
1360 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1361                                                    const struct sk_buff *skb)
1362 {
1363         return skb_queue_next(&sk->sk_write_queue, skb);
1364 }
1365 
1366 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1367                                                    const struct sk_buff *skb)
1368 {
1369         return skb_queue_prev(&sk->sk_write_queue, skb);
1370 }
1371 
1372 #define tcp_for_write_queue(skb, sk)                                    \
1373         skb_queue_walk(&(sk)->sk_write_queue, skb)
1374 
1375 #define tcp_for_write_queue_from(skb, sk)                               \
1376         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1377 
1378 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1379         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1380 
1381 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1382 {
1383         return sk->sk_send_head;
1384 }
1385 
1386 static inline bool tcp_skb_is_last(const struct sock *sk,
1387                                    const struct sk_buff *skb)
1388 {
1389         return skb_queue_is_last(&sk->sk_write_queue, skb);
1390 }
1391 
1392 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1393 {
1394         if (tcp_skb_is_last(sk, skb))
1395                 sk->sk_send_head = NULL;
1396         else
1397                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1398 }
1399 
1400 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1401 {
1402         if (sk->sk_send_head == skb_unlinked)
1403                 sk->sk_send_head = NULL;
1404 }
1405 
1406 static inline void tcp_init_send_head(struct sock *sk)
1407 {
1408         sk->sk_send_head = NULL;
1409 }
1410 
1411 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1412 {
1413         __skb_queue_tail(&sk->sk_write_queue, skb);
1414 }
1415 
1416 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1417 {
1418         __tcp_add_write_queue_tail(sk, skb);
1419 
1420         /* Queue it, remembering where we must start sending. */
1421         if (sk->sk_send_head == NULL) {
1422                 sk->sk_send_head = skb;
1423 
1424                 if (tcp_sk(sk)->highest_sack == NULL)
1425                         tcp_sk(sk)->highest_sack = skb;
1426         }
1427 }
1428 
1429 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1430 {
1431         __skb_queue_head(&sk->sk_write_queue, skb);
1432 }
1433 
1434 /* Insert buff after skb on the write queue of sk.  */
1435 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1436                                                 struct sk_buff *buff,
1437                                                 struct sock *sk)
1438 {
1439         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1440 }
1441 
1442 /* Insert new before skb on the write queue of sk.  */
1443 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1444                                                   struct sk_buff *skb,
1445                                                   struct sock *sk)
1446 {
1447         __skb_queue_before(&sk->sk_write_queue, skb, new);
1448 
1449         if (sk->sk_send_head == skb)
1450                 sk->sk_send_head = new;
1451 }
1452 
1453 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1454 {
1455         __skb_unlink(skb, &sk->sk_write_queue);
1456 }
1457 
1458 static inline bool tcp_write_queue_empty(struct sock *sk)
1459 {
1460         return skb_queue_empty(&sk->sk_write_queue);
1461 }
1462 
1463 static inline void tcp_push_pending_frames(struct sock *sk)
1464 {
1465         if (tcp_send_head(sk)) {
1466                 struct tcp_sock *tp = tcp_sk(sk);
1467 
1468                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1469         }
1470 }
1471 
1472 /* Start sequence of the skb just after the highest skb with SACKed
1473  * bit, valid only if sacked_out > 0 or when the caller has ensured
1474  * validity by itself.
1475  */
1476 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1477 {
1478         if (!tp->sacked_out)
1479                 return tp->snd_una;
1480 
1481         if (tp->highest_sack == NULL)
1482                 return tp->snd_nxt;
1483 
1484         return TCP_SKB_CB(tp->highest_sack)->seq;
1485 }
1486 
1487 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1488 {
1489         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1490                                                 tcp_write_queue_next(sk, skb);
1491 }
1492 
1493 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1494 {
1495         return tcp_sk(sk)->highest_sack;
1496 }
1497 
1498 static inline void tcp_highest_sack_reset(struct sock *sk)
1499 {
1500         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1501 }
1502 
1503 /* Called when old skb is about to be deleted (to be combined with new skb) */
1504 static inline void tcp_highest_sack_combine(struct sock *sk,
1505                                             struct sk_buff *old,
1506                                             struct sk_buff *new)
1507 {
1508         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1509                 tcp_sk(sk)->highest_sack = new;
1510 }
1511 
1512 /* Determines whether this is a thin stream (which may suffer from
1513  * increased latency). Used to trigger latency-reducing mechanisms.
1514  */
1515 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1516 {
1517         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1518 }
1519 
1520 /* /proc */
1521 enum tcp_seq_states {
1522         TCP_SEQ_STATE_LISTENING,
1523         TCP_SEQ_STATE_OPENREQ,
1524         TCP_SEQ_STATE_ESTABLISHED,
1525 };
1526 
1527 int tcp_seq_open(struct inode *inode, struct file *file);
1528 
1529 struct tcp_seq_afinfo {
1530         char                            *name;
1531         sa_family_t                     family;
1532         const struct file_operations    *seq_fops;
1533         struct seq_operations           seq_ops;
1534 };
1535 
1536 struct tcp_iter_state {
1537         struct seq_net_private  p;
1538         sa_family_t             family;
1539         enum tcp_seq_states     state;
1540         struct sock             *syn_wait_sk;
1541         int                     bucket, offset, sbucket, num;
1542         kuid_t                  uid;
1543         loff_t                  last_pos;
1544 };
1545 
1546 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1547 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1548 
1549 extern struct request_sock_ops tcp_request_sock_ops;
1550 extern struct request_sock_ops tcp6_request_sock_ops;
1551 
1552 void tcp_v4_destroy_sock(struct sock *sk);
1553 
1554 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1555                                 netdev_features_t features);
1556 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1557 int tcp_gro_complete(struct sk_buff *skb);
1558 
1559 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1560 
1561 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1562 {
1563         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1564 }
1565 
1566 static inline bool tcp_stream_memory_free(const struct sock *sk)
1567 {
1568         const struct tcp_sock *tp = tcp_sk(sk);
1569         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1570 
1571         return notsent_bytes < tcp_notsent_lowat(tp);
1572 }
1573 
1574 #ifdef CONFIG_PROC_FS
1575 int tcp4_proc_init(void);
1576 void tcp4_proc_exit(void);
1577 #endif
1578 
1579 int tcp_rtx_synack(struct sock *sk, struct request_sock *req);
1580 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1581                      const struct tcp_request_sock_ops *af_ops,
1582                      struct sock *sk, struct sk_buff *skb);
1583 
1584 /* TCP af-specific functions */
1585 struct tcp_sock_af_ops {
1586 #ifdef CONFIG_TCP_MD5SIG
1587         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1588                                                 struct sock *addr_sk);
1589         int                     (*calc_md5_hash) (char *location,
1590                                                   struct tcp_md5sig_key *md5,
1591                                                   const struct sock *sk,
1592                                                   const struct request_sock *req,
1593                                                   const struct sk_buff *skb);
1594         int                     (*md5_parse) (struct sock *sk,
1595                                               char __user *optval,
1596                                               int optlen);
1597 #endif
1598 };
1599 
1600 struct tcp_request_sock_ops {
1601         u16 mss_clamp;
1602 #ifdef CONFIG_TCP_MD5SIG
1603         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1604                                                 struct request_sock *req);
1605         int                     (*calc_md5_hash) (char *location,
1606                                                   struct tcp_md5sig_key *md5,
1607                                                   const struct sock *sk,
1608                                                   const struct request_sock *req,
1609                                                   const struct sk_buff *skb);
1610 #endif
1611         void (*init_req)(struct request_sock *req, struct sock *sk,
1612                          struct sk_buff *skb);
1613 #ifdef CONFIG_SYN_COOKIES
1614         __u32 (*cookie_init_seq)(struct sock *sk, const struct sk_buff *skb,
1615                                  __u16 *mss);
1616 #endif
1617         struct dst_entry *(*route_req)(struct sock *sk, struct flowi *fl,
1618                                        const struct request_sock *req,
1619                                        bool *strict);
1620         __u32 (*init_seq)(const struct sk_buff *skb);
1621         int (*send_synack)(struct sock *sk, struct dst_entry *dst,
1622                            struct flowi *fl, struct request_sock *req,
1623                            u16 queue_mapping, struct tcp_fastopen_cookie *foc);
1624         void (*queue_hash_add)(struct sock *sk, struct request_sock *req,
1625                                const unsigned long timeout);
1626 };
1627 
1628 #ifdef CONFIG_SYN_COOKIES
1629 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1630                                          struct sock *sk, struct sk_buff *skb,
1631                                          __u16 *mss)
1632 {
1633         return ops->cookie_init_seq(sk, skb, mss);
1634 }
1635 #else
1636 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1637                                          struct sock *sk, struct sk_buff *skb,
1638                                          __u16 *mss)
1639 {
1640         return 0;
1641 }
1642 #endif
1643 
1644 int tcpv4_offload_init(void);
1645 
1646 void tcp_v4_init(void);
1647 void tcp_init(void);
1648 
1649 #endif  /* _TCP_H */
1650 

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