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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 
 35 #include <net/inet_connection_sock.h>
 36 #include <net/inet_timewait_sock.h>
 37 #include <net/inet_hashtables.h>
 38 #include <net/checksum.h>
 39 #include <net/request_sock.h>
 40 #include <net/sock.h>
 41 #include <net/snmp.h>
 42 #include <net/ip.h>
 43 #include <net/tcp_states.h>
 44 #include <net/inet_ecn.h>
 45 #include <net/dst.h>
 46 
 47 #include <linux/seq_file.h>
 48 #include <linux/memcontrol.h>
 49 
 50 extern struct inet_hashinfo tcp_hashinfo;
 51 
 52 extern struct percpu_counter tcp_orphan_count;
 53 void tcp_time_wait(struct sock *sk, int state, int timeo);
 54 
 55 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 56 #define MAX_TCP_OPTION_SPACE 40
 57 
 58 /* 
 59  * Never offer a window over 32767 without using window scaling. Some
 60  * poor stacks do signed 16bit maths! 
 61  */
 62 #define MAX_TCP_WINDOW          32767U
 63 
 64 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 65 #define TCP_MIN_MSS             88U
 66 
 67 /* The least MTU to use for probing */
 68 #define TCP_BASE_MSS            512
 69 
 70 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 71 #define TCP_FASTRETRANS_THRESH 3
 72 
 73 /* Maximal reordering. */
 74 #define TCP_MAX_REORDERING      127
 75 
 76 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 77 #define TCP_MAX_QUICKACKS       16U
 78 
 79 /* urg_data states */
 80 #define TCP_URG_VALID   0x0100
 81 #define TCP_URG_NOTYET  0x0200
 82 #define TCP_URG_READ    0x0400
 83 
 84 #define TCP_RETR1       3       /*
 85                                  * This is how many retries it does before it
 86                                  * tries to figure out if the gateway is
 87                                  * down. Minimal RFC value is 3; it corresponds
 88                                  * to ~3sec-8min depending on RTO.
 89                                  */
 90 
 91 #define TCP_RETR2       15      /*
 92                                  * This should take at least
 93                                  * 90 minutes to time out.
 94                                  * RFC1122 says that the limit is 100 sec.
 95                                  * 15 is ~13-30min depending on RTO.
 96                                  */
 97 
 98 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
 99                                  * when active opening a connection.
100                                  * RFC1122 says the minimum retry MUST
101                                  * be at least 180secs.  Nevertheless
102                                  * this value is corresponding to
103                                  * 63secs of retransmission with the
104                                  * current initial RTO.
105                                  */
106 
107 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
108                                  * when passive opening a connection.
109                                  * This is corresponding to 31secs of
110                                  * retransmission with the current
111                                  * initial RTO.
112                                  */
113 
114 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
115                                   * state, about 60 seconds     */
116 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
117                                  /* BSD style FIN_WAIT2 deadlock breaker.
118                                   * It used to be 3min, new value is 60sec,
119                                   * to combine FIN-WAIT-2 timeout with
120                                   * TIME-WAIT timer.
121                                   */
122 
123 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
124 #if HZ >= 100
125 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
126 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
127 #else
128 #define TCP_DELACK_MIN  4U
129 #define TCP_ATO_MIN     4U
130 #endif
131 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
132 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
133 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
134 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
135                                                  * used as a fallback RTO for the
136                                                  * initial data transmission if no
137                                                  * valid RTT sample has been acquired,
138                                                  * most likely due to retrans in 3WHS.
139                                                  */
140 
141 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
142                                                          * for local resources.
143                                                          */
144 
145 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
146 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
147 #define TCP_KEEPALIVE_INTVL     (75*HZ)
148 
149 #define MAX_TCP_KEEPIDLE        32767
150 #define MAX_TCP_KEEPINTVL       32767
151 #define MAX_TCP_KEEPCNT         127
152 #define MAX_TCP_SYNCNT          127
153 
154 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
155 
156 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
157 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
158                                          * after this time. It should be equal
159                                          * (or greater than) TCP_TIMEWAIT_LEN
160                                          * to provide reliability equal to one
161                                          * provided by timewait state.
162                                          */
163 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
164                                          * timestamps. It must be less than
165                                          * minimal timewait lifetime.
166                                          */
167 /*
168  *      TCP option
169  */
170  
171 #define TCPOPT_NOP              1       /* Padding */
172 #define TCPOPT_EOL              0       /* End of options */
173 #define TCPOPT_MSS              2       /* Segment size negotiating */
174 #define TCPOPT_WINDOW           3       /* Window scaling */
175 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
176 #define TCPOPT_SACK             5       /* SACK Block */
177 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
178 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
179 #define TCPOPT_EXP              254     /* Experimental */
180 /* Magic number to be after the option value for sharing TCP
181  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
182  */
183 #define TCPOPT_FASTOPEN_MAGIC   0xF989
184 
185 /*
186  *     TCP option lengths
187  */
188 
189 #define TCPOLEN_MSS            4
190 #define TCPOLEN_WINDOW         3
191 #define TCPOLEN_SACK_PERM      2
192 #define TCPOLEN_TIMESTAMP      10
193 #define TCPOLEN_MD5SIG         18
194 #define TCPOLEN_EXP_FASTOPEN_BASE  4
195 
196 /* But this is what stacks really send out. */
197 #define TCPOLEN_TSTAMP_ALIGNED          12
198 #define TCPOLEN_WSCALE_ALIGNED          4
199 #define TCPOLEN_SACKPERM_ALIGNED        4
200 #define TCPOLEN_SACK_BASE               2
201 #define TCPOLEN_SACK_BASE_ALIGNED       4
202 #define TCPOLEN_SACK_PERBLOCK           8
203 #define TCPOLEN_MD5SIG_ALIGNED          20
204 #define TCPOLEN_MSS_ALIGNED             4
205 
206 /* Flags in tp->nonagle */
207 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
208 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
209 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
210 
211 /* TCP thin-stream limits */
212 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
213 
214 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
215 #define TCP_INIT_CWND           10
216 
217 /* Bit Flags for sysctl_tcp_fastopen */
218 #define TFO_CLIENT_ENABLE       1
219 #define TFO_SERVER_ENABLE       2
220 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
221 
222 /* Process SYN data but skip cookie validation */
223 #define TFO_SERVER_COOKIE_NOT_CHKED     0x100
224 /* Accept SYN data w/o any cookie option */
225 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
226 
227 /* Force enable TFO on all listeners, i.e., not requiring the
228  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
229  */
230 #define TFO_SERVER_WO_SOCKOPT1  0x400
231 #define TFO_SERVER_WO_SOCKOPT2  0x800
232 /* Always create TFO child sockets on a TFO listener even when
233  * cookie/data not present. (For testing purpose!)
234  */
235 #define TFO_SERVER_ALWAYS       0x1000
236 
237 extern struct inet_timewait_death_row tcp_death_row;
238 
239 /* sysctl variables for tcp */
240 extern int sysctl_tcp_timestamps;
241 extern int sysctl_tcp_window_scaling;
242 extern int sysctl_tcp_sack;
243 extern int sysctl_tcp_fin_timeout;
244 extern int sysctl_tcp_keepalive_time;
245 extern int sysctl_tcp_keepalive_probes;
246 extern int sysctl_tcp_keepalive_intvl;
247 extern int sysctl_tcp_syn_retries;
248 extern int sysctl_tcp_synack_retries;
249 extern int sysctl_tcp_retries1;
250 extern int sysctl_tcp_retries2;
251 extern int sysctl_tcp_orphan_retries;
252 extern int sysctl_tcp_syncookies;
253 extern int sysctl_tcp_fastopen;
254 extern int sysctl_tcp_retrans_collapse;
255 extern int sysctl_tcp_stdurg;
256 extern int sysctl_tcp_rfc1337;
257 extern int sysctl_tcp_abort_on_overflow;
258 extern int sysctl_tcp_max_orphans;
259 extern int sysctl_tcp_fack;
260 extern int sysctl_tcp_reordering;
261 extern int sysctl_tcp_dsack;
262 extern long sysctl_tcp_mem[3];
263 extern int sysctl_tcp_wmem[3];
264 extern int sysctl_tcp_rmem[3];
265 extern int sysctl_tcp_app_win;
266 extern int sysctl_tcp_adv_win_scale;
267 extern int sysctl_tcp_tw_reuse;
268 extern int sysctl_tcp_frto;
269 extern int sysctl_tcp_low_latency;
270 extern int sysctl_tcp_dma_copybreak;
271 extern int sysctl_tcp_nometrics_save;
272 extern int sysctl_tcp_moderate_rcvbuf;
273 extern int sysctl_tcp_tso_win_divisor;
274 extern int sysctl_tcp_mtu_probing;
275 extern int sysctl_tcp_base_mss;
276 extern int sysctl_tcp_workaround_signed_windows;
277 extern int sysctl_tcp_slow_start_after_idle;
278 extern int sysctl_tcp_thin_linear_timeouts;
279 extern int sysctl_tcp_thin_dupack;
280 extern int sysctl_tcp_early_retrans;
281 extern int sysctl_tcp_limit_output_bytes;
282 extern int sysctl_tcp_challenge_ack_limit;
283 extern unsigned int sysctl_tcp_notsent_lowat;
284 extern int sysctl_tcp_min_tso_segs;
285 extern int sysctl_tcp_autocorking;
286 
287 extern atomic_long_t tcp_memory_allocated;
288 extern struct percpu_counter tcp_sockets_allocated;
289 extern int tcp_memory_pressure;
290 
291 /*
292  * The next routines deal with comparing 32 bit unsigned ints
293  * and worry about wraparound (automatic with unsigned arithmetic).
294  */
295 
296 static inline bool before(__u32 seq1, __u32 seq2)
297 {
298         return (__s32)(seq1-seq2) < 0;
299 }
300 #define after(seq2, seq1)       before(seq1, seq2)
301 
302 /* is s2<=s1<=s3 ? */
303 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
304 {
305         return seq3 - seq2 >= seq1 - seq2;
306 }
307 
308 static inline bool tcp_out_of_memory(struct sock *sk)
309 {
310         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
311             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
312                 return true;
313         return false;
314 }
315 
316 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
317 {
318         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
319         int orphans = percpu_counter_read_positive(ocp);
320 
321         if (orphans << shift > sysctl_tcp_max_orphans) {
322                 orphans = percpu_counter_sum_positive(ocp);
323                 if (orphans << shift > sysctl_tcp_max_orphans)
324                         return true;
325         }
326         return false;
327 }
328 
329 bool tcp_check_oom(struct sock *sk, int shift);
330 
331 /* syncookies: remember time of last synqueue overflow */
332 static inline void tcp_synq_overflow(struct sock *sk)
333 {
334         tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
335 }
336 
337 /* syncookies: no recent synqueue overflow on this listening socket? */
338 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
339 {
340         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
341         return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
342 }
343 
344 extern struct proto tcp_prot;
345 
346 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
347 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
348 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
349 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
350 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
351 
352 void tcp_tasklet_init(void);
353 
354 void tcp_v4_err(struct sk_buff *skb, u32);
355 
356 void tcp_shutdown(struct sock *sk, int how);
357 
358 void tcp_v4_early_demux(struct sk_buff *skb);
359 int tcp_v4_rcv(struct sk_buff *skb);
360 
361 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
362 int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
363                 size_t size);
364 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
365                  int flags);
366 void tcp_release_cb(struct sock *sk);
367 void tcp_wfree(struct sk_buff *skb);
368 void tcp_write_timer_handler(struct sock *sk);
369 void tcp_delack_timer_handler(struct sock *sk);
370 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
371 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
372                           const struct tcphdr *th, unsigned int len);
373 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
374                          const struct tcphdr *th, unsigned int len);
375 void tcp_rcv_space_adjust(struct sock *sk);
376 void tcp_cleanup_rbuf(struct sock *sk, int copied);
377 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
378 void tcp_twsk_destructor(struct sock *sk);
379 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
380                         struct pipe_inode_info *pipe, size_t len,
381                         unsigned int flags);
382 
383 static inline void tcp_dec_quickack_mode(struct sock *sk,
384                                          const unsigned int pkts)
385 {
386         struct inet_connection_sock *icsk = inet_csk(sk);
387 
388         if (icsk->icsk_ack.quick) {
389                 if (pkts >= icsk->icsk_ack.quick) {
390                         icsk->icsk_ack.quick = 0;
391                         /* Leaving quickack mode we deflate ATO. */
392                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
393                 } else
394                         icsk->icsk_ack.quick -= pkts;
395         }
396 }
397 
398 #define TCP_ECN_OK              1
399 #define TCP_ECN_QUEUE_CWR       2
400 #define TCP_ECN_DEMAND_CWR      4
401 #define TCP_ECN_SEEN            8
402 
403 enum tcp_tw_status {
404         TCP_TW_SUCCESS = 0,
405         TCP_TW_RST = 1,
406         TCP_TW_ACK = 2,
407         TCP_TW_SYN = 3
408 };
409 
410 
411 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
412                                               struct sk_buff *skb,
413                                               const struct tcphdr *th);
414 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
415                            struct request_sock *req, struct request_sock **prev,
416                            bool fastopen);
417 int tcp_child_process(struct sock *parent, struct sock *child,
418                       struct sk_buff *skb);
419 void tcp_enter_loss(struct sock *sk, int how);
420 void tcp_clear_retrans(struct tcp_sock *tp);
421 void tcp_update_metrics(struct sock *sk);
422 void tcp_init_metrics(struct sock *sk);
423 void tcp_metrics_init(void);
424 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
425                         bool paws_check);
426 bool tcp_remember_stamp(struct sock *sk);
427 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
428 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
429 void tcp_disable_fack(struct tcp_sock *tp);
430 void tcp_close(struct sock *sk, long timeout);
431 void tcp_init_sock(struct sock *sk);
432 unsigned int tcp_poll(struct file *file, struct socket *sock,
433                       struct poll_table_struct *wait);
434 int tcp_getsockopt(struct sock *sk, int level, int optname,
435                    char __user *optval, int __user *optlen);
436 int tcp_setsockopt(struct sock *sk, int level, int optname,
437                    char __user *optval, unsigned int optlen);
438 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
439                           char __user *optval, int __user *optlen);
440 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
441                           char __user *optval, unsigned int optlen);
442 void tcp_set_keepalive(struct sock *sk, int val);
443 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
444 int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
445                 size_t len, int nonblock, int flags, int *addr_len);
446 void tcp_parse_options(const struct sk_buff *skb,
447                        struct tcp_options_received *opt_rx,
448                        int estab, struct tcp_fastopen_cookie *foc);
449 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
450 
451 /*
452  *      TCP v4 functions exported for the inet6 API
453  */
454 
455 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
456 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
457 struct sock *tcp_create_openreq_child(struct sock *sk,
458                                       struct request_sock *req,
459                                       struct sk_buff *skb);
460 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
461                                   struct request_sock *req,
462                                   struct dst_entry *dst);
463 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
464 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
465 int tcp_connect(struct sock *sk);
466 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
467                                 struct request_sock *req,
468                                 struct tcp_fastopen_cookie *foc);
469 int tcp_disconnect(struct sock *sk, int flags);
470 
471 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
472 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
473 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
474 
475 /* From syncookies.c */
476 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
477                       u32 cookie);
478 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
479                              struct ip_options *opt);
480 #ifdef CONFIG_SYN_COOKIES
481 #include <linux/ktime.h>
482 
483 /* Syncookies use a monotonic timer which increments every 60 seconds.
484  * This counter is used both as a hash input and partially encoded into
485  * the cookie value.  A cookie is only validated further if the delta
486  * between the current counter value and the encoded one is less than this,
487  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
488  * the counter advances immediately after a cookie is generated).
489  */
490 #define MAX_SYNCOOKIE_AGE 2
491 
492 static inline u32 tcp_cookie_time(void)
493 {
494         u64 val = get_jiffies_64();
495 
496         do_div(val, 60 * HZ);
497         return val;
498 }
499 
500 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
501                               u16 *mssp);
502 __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mss);
503 #else
504 static inline __u32 cookie_v4_init_sequence(struct sock *sk,
505                                             struct sk_buff *skb,
506                                             __u16 *mss)
507 {
508         return 0;
509 }
510 #endif
511 
512 __u32 cookie_init_timestamp(struct request_sock *req);
513 bool cookie_check_timestamp(struct tcp_options_received *opt, struct net *net,
514                             bool *ecn_ok);
515 
516 /* From net/ipv6/syncookies.c */
517 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
518                       u32 cookie);
519 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
520 #ifdef CONFIG_SYN_COOKIES
521 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
522                               const struct tcphdr *th, u16 *mssp);
523 __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
524                               __u16 *mss);
525 #else
526 static inline __u32 cookie_v6_init_sequence(struct sock *sk,
527                                             struct sk_buff *skb,
528                                             __u16 *mss)
529 {
530         return 0;
531 }
532 #endif
533 /* tcp_output.c */
534 
535 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
536                                int nonagle);
537 bool tcp_may_send_now(struct sock *sk);
538 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
539 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
540 void tcp_retransmit_timer(struct sock *sk);
541 void tcp_xmit_retransmit_queue(struct sock *);
542 void tcp_simple_retransmit(struct sock *);
543 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
544 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);
545 
546 void tcp_send_probe0(struct sock *);
547 void tcp_send_partial(struct sock *);
548 int tcp_write_wakeup(struct sock *);
549 void tcp_send_fin(struct sock *sk);
550 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
551 int tcp_send_synack(struct sock *);
552 bool tcp_syn_flood_action(struct sock *sk, const struct sk_buff *skb,
553                           const char *proto);
554 void tcp_push_one(struct sock *, unsigned int mss_now);
555 void tcp_send_ack(struct sock *sk);
556 void tcp_send_delayed_ack(struct sock *sk);
557 void tcp_send_loss_probe(struct sock *sk);
558 bool tcp_schedule_loss_probe(struct sock *sk);
559 
560 /* tcp_input.c */
561 void tcp_cwnd_application_limited(struct sock *sk);
562 void tcp_resume_early_retransmit(struct sock *sk);
563 void tcp_rearm_rto(struct sock *sk);
564 void tcp_reset(struct sock *sk);
565 
566 /* tcp_timer.c */
567 void tcp_init_xmit_timers(struct sock *);
568 static inline void tcp_clear_xmit_timers(struct sock *sk)
569 {
570         inet_csk_clear_xmit_timers(sk);
571 }
572 
573 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
574 unsigned int tcp_current_mss(struct sock *sk);
575 
576 /* Bound MSS / TSO packet size with the half of the window */
577 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
578 {
579         int cutoff;
580 
581         /* When peer uses tiny windows, there is no use in packetizing
582          * to sub-MSS pieces for the sake of SWS or making sure there
583          * are enough packets in the pipe for fast recovery.
584          *
585          * On the other hand, for extremely large MSS devices, handling
586          * smaller than MSS windows in this way does make sense.
587          */
588         if (tp->max_window >= 512)
589                 cutoff = (tp->max_window >> 1);
590         else
591                 cutoff = tp->max_window;
592 
593         if (cutoff && pktsize > cutoff)
594                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
595         else
596                 return pktsize;
597 }
598 
599 /* tcp.c */
600 void tcp_get_info(const struct sock *, struct tcp_info *);
601 
602 /* Read 'sendfile()'-style from a TCP socket */
603 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
604                                 unsigned int, size_t);
605 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
606                   sk_read_actor_t recv_actor);
607 
608 void tcp_initialize_rcv_mss(struct sock *sk);
609 
610 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
611 int tcp_mss_to_mtu(struct sock *sk, int mss);
612 void tcp_mtup_init(struct sock *sk);
613 void tcp_init_buffer_space(struct sock *sk);
614 
615 static inline void tcp_bound_rto(const struct sock *sk)
616 {
617         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
618                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
619 }
620 
621 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
622 {
623         return (tp->srtt >> 3) + tp->rttvar;
624 }
625 
626 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
627 {
628         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
629                                ntohl(TCP_FLAG_ACK) |
630                                snd_wnd);
631 }
632 
633 static inline void tcp_fast_path_on(struct tcp_sock *tp)
634 {
635         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
636 }
637 
638 static inline void tcp_fast_path_check(struct sock *sk)
639 {
640         struct tcp_sock *tp = tcp_sk(sk);
641 
642         if (skb_queue_empty(&tp->out_of_order_queue) &&
643             tp->rcv_wnd &&
644             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
645             !tp->urg_data)
646                 tcp_fast_path_on(tp);
647 }
648 
649 /* Compute the actual rto_min value */
650 static inline u32 tcp_rto_min(struct sock *sk)
651 {
652         const struct dst_entry *dst = __sk_dst_get(sk);
653         u32 rto_min = TCP_RTO_MIN;
654 
655         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
656                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
657         return rto_min;
658 }
659 
660 /* Compute the actual receive window we are currently advertising.
661  * Rcv_nxt can be after the window if our peer push more data
662  * than the offered window.
663  */
664 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
665 {
666         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
667 
668         if (win < 0)
669                 win = 0;
670         return (u32) win;
671 }
672 
673 /* Choose a new window, without checks for shrinking, and without
674  * scaling applied to the result.  The caller does these things
675  * if necessary.  This is a "raw" window selection.
676  */
677 u32 __tcp_select_window(struct sock *sk);
678 
679 void tcp_send_window_probe(struct sock *sk);
680 
681 /* TCP timestamps are only 32-bits, this causes a slight
682  * complication on 64-bit systems since we store a snapshot
683  * of jiffies in the buffer control blocks below.  We decided
684  * to use only the low 32-bits of jiffies and hide the ugly
685  * casts with the following macro.
686  */
687 #define tcp_time_stamp          ((__u32)(jiffies))
688 
689 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
690 
691 #define TCPHDR_FIN 0x01
692 #define TCPHDR_SYN 0x02
693 #define TCPHDR_RST 0x04
694 #define TCPHDR_PSH 0x08
695 #define TCPHDR_ACK 0x10
696 #define TCPHDR_URG 0x20
697 #define TCPHDR_ECE 0x40
698 #define TCPHDR_CWR 0x80
699 
700 /* This is what the send packet queuing engine uses to pass
701  * TCP per-packet control information to the transmission code.
702  * We also store the host-order sequence numbers in here too.
703  * This is 44 bytes if IPV6 is enabled.
704  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
705  */
706 struct tcp_skb_cb {
707         union {
708                 struct inet_skb_parm    h4;
709 #if IS_ENABLED(CONFIG_IPV6)
710                 struct inet6_skb_parm   h6;
711 #endif
712         } header;       /* For incoming frames          */
713         __u32           seq;            /* Starting sequence number     */
714         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
715         __u32           when;           /* used to compute rtt's        */
716         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
717 
718         __u8            sacked;         /* State flags for SACK/FACK.   */
719 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
720 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
721 #define TCPCB_LOST              0x04    /* SKB is lost                  */
722 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
723 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
724 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
725 
726         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
727         /* 1 byte hole */
728         __u32           ack_seq;        /* Sequence number ACK'd        */
729 };
730 
731 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
732 
733 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
734  *
735  * If we receive a SYN packet with these bits set, it means a network is
736  * playing bad games with TOS bits. In order to avoid possible false congestion
737  * notifications, we disable TCP ECN negociation.
738  */
739 static inline void
740 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
741                 struct net *net)
742 {
743         const struct tcphdr *th = tcp_hdr(skb);
744 
745         if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr &&
746             INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
747                 inet_rsk(req)->ecn_ok = 1;
748 }
749 
750 /* Due to TSO, an SKB can be composed of multiple actual
751  * packets.  To keep these tracked properly, we use this.
752  */
753 static inline int tcp_skb_pcount(const struct sk_buff *skb)
754 {
755         return skb_shinfo(skb)->gso_segs;
756 }
757 
758 /* This is valid iff tcp_skb_pcount() > 1. */
759 static inline int tcp_skb_mss(const struct sk_buff *skb)
760 {
761         return skb_shinfo(skb)->gso_size;
762 }
763 
764 /* Events passed to congestion control interface */
765 enum tcp_ca_event {
766         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
767         CA_EVENT_CWND_RESTART,  /* congestion window restart */
768         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
769         CA_EVENT_LOSS,          /* loss timeout */
770         CA_EVENT_FAST_ACK,      /* in sequence ack */
771         CA_EVENT_SLOW_ACK,      /* other ack */
772 };
773 
774 /*
775  * Interface for adding new TCP congestion control handlers
776  */
777 #define TCP_CA_NAME_MAX 16
778 #define TCP_CA_MAX      128
779 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
780 
781 #define TCP_CONG_NON_RESTRICTED 0x1
782 #define TCP_CONG_RTT_STAMP      0x2
783 
784 struct tcp_congestion_ops {
785         struct list_head        list;
786         unsigned long flags;
787 
788         /* initialize private data (optional) */
789         void (*init)(struct sock *sk);
790         /* cleanup private data  (optional) */
791         void (*release)(struct sock *sk);
792 
793         /* return slow start threshold (required) */
794         u32 (*ssthresh)(struct sock *sk);
795         /* lower bound for congestion window (optional) */
796         u32 (*min_cwnd)(const struct sock *sk);
797         /* do new cwnd calculation (required) */
798         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
799         /* call before changing ca_state (optional) */
800         void (*set_state)(struct sock *sk, u8 new_state);
801         /* call when cwnd event occurs (optional) */
802         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
803         /* new value of cwnd after loss (optional) */
804         u32  (*undo_cwnd)(struct sock *sk);
805         /* hook for packet ack accounting (optional) */
806         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
807         /* get info for inet_diag (optional) */
808         void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
809 
810         char            name[TCP_CA_NAME_MAX];
811         struct module   *owner;
812 };
813 
814 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
815 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
816 
817 void tcp_init_congestion_control(struct sock *sk);
818 void tcp_cleanup_congestion_control(struct sock *sk);
819 int tcp_set_default_congestion_control(const char *name);
820 void tcp_get_default_congestion_control(char *name);
821 void tcp_get_available_congestion_control(char *buf, size_t len);
822 void tcp_get_allowed_congestion_control(char *buf, size_t len);
823 int tcp_set_allowed_congestion_control(char *allowed);
824 int tcp_set_congestion_control(struct sock *sk, const char *name);
825 int tcp_slow_start(struct tcp_sock *tp, u32 acked);
826 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
827 
828 extern struct tcp_congestion_ops tcp_init_congestion_ops;
829 u32 tcp_reno_ssthresh(struct sock *sk);
830 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
831 u32 tcp_reno_min_cwnd(const struct sock *sk);
832 extern struct tcp_congestion_ops tcp_reno;
833 
834 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
835 {
836         struct inet_connection_sock *icsk = inet_csk(sk);
837 
838         if (icsk->icsk_ca_ops->set_state)
839                 icsk->icsk_ca_ops->set_state(sk, ca_state);
840         icsk->icsk_ca_state = ca_state;
841 }
842 
843 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
844 {
845         const struct inet_connection_sock *icsk = inet_csk(sk);
846 
847         if (icsk->icsk_ca_ops->cwnd_event)
848                 icsk->icsk_ca_ops->cwnd_event(sk, event);
849 }
850 
851 /* These functions determine how the current flow behaves in respect of SACK
852  * handling. SACK is negotiated with the peer, and therefore it can vary
853  * between different flows.
854  *
855  * tcp_is_sack - SACK enabled
856  * tcp_is_reno - No SACK
857  * tcp_is_fack - FACK enabled, implies SACK enabled
858  */
859 static inline int tcp_is_sack(const struct tcp_sock *tp)
860 {
861         return tp->rx_opt.sack_ok;
862 }
863 
864 static inline bool tcp_is_reno(const struct tcp_sock *tp)
865 {
866         return !tcp_is_sack(tp);
867 }
868 
869 static inline bool tcp_is_fack(const struct tcp_sock *tp)
870 {
871         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
872 }
873 
874 static inline void tcp_enable_fack(struct tcp_sock *tp)
875 {
876         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
877 }
878 
879 /* TCP early-retransmit (ER) is similar to but more conservative than
880  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
881  */
882 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
883 {
884         tp->do_early_retrans = sysctl_tcp_early_retrans &&
885                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
886                 sysctl_tcp_reordering == 3;
887 }
888 
889 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
890 {
891         tp->do_early_retrans = 0;
892 }
893 
894 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
895 {
896         return tp->sacked_out + tp->lost_out;
897 }
898 
899 /* This determines how many packets are "in the network" to the best
900  * of our knowledge.  In many cases it is conservative, but where
901  * detailed information is available from the receiver (via SACK
902  * blocks etc.) we can make more aggressive calculations.
903  *
904  * Use this for decisions involving congestion control, use just
905  * tp->packets_out to determine if the send queue is empty or not.
906  *
907  * Read this equation as:
908  *
909  *      "Packets sent once on transmission queue" MINUS
910  *      "Packets left network, but not honestly ACKed yet" PLUS
911  *      "Packets fast retransmitted"
912  */
913 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
914 {
915         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
916 }
917 
918 #define TCP_INFINITE_SSTHRESH   0x7fffffff
919 
920 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
921 {
922         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
923 }
924 
925 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
926 {
927         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
928                (1 << inet_csk(sk)->icsk_ca_state);
929 }
930 
931 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
932  * The exception is cwnd reduction phase, when cwnd is decreasing towards
933  * ssthresh.
934  */
935 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
936 {
937         const struct tcp_sock *tp = tcp_sk(sk);
938 
939         if (tcp_in_cwnd_reduction(sk))
940                 return tp->snd_ssthresh;
941         else
942                 return max(tp->snd_ssthresh,
943                            ((tp->snd_cwnd >> 1) +
944                             (tp->snd_cwnd >> 2)));
945 }
946 
947 /* Use define here intentionally to get WARN_ON location shown at the caller */
948 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
949 
950 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
951 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
952 
953 /* The maximum number of MSS of available cwnd for which TSO defers
954  * sending if not using sysctl_tcp_tso_win_divisor.
955  */
956 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
957 {
958         return 3;
959 }
960 
961 /* Slow start with delack produces 3 packets of burst, so that
962  * it is safe "de facto".  This will be the default - same as
963  * the default reordering threshold - but if reordering increases,
964  * we must be able to allow cwnd to burst at least this much in order
965  * to not pull it back when holes are filled.
966  */
967 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
968 {
969         return tp->reordering;
970 }
971 
972 /* Returns end sequence number of the receiver's advertised window */
973 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
974 {
975         return tp->snd_una + tp->snd_wnd;
976 }
977 bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
978 
979 static inline void tcp_check_probe_timer(struct sock *sk)
980 {
981         const struct tcp_sock *tp = tcp_sk(sk);
982         const struct inet_connection_sock *icsk = inet_csk(sk);
983 
984         if (!tp->packets_out && !icsk->icsk_pending)
985                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
986                                           icsk->icsk_rto, TCP_RTO_MAX);
987 }
988 
989 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
990 {
991         tp->snd_wl1 = seq;
992 }
993 
994 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
995 {
996         tp->snd_wl1 = seq;
997 }
998 
999 /*
1000  * Calculate(/check) TCP checksum
1001  */
1002 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1003                                    __be32 daddr, __wsum base)
1004 {
1005         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1006 }
1007 
1008 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1009 {
1010         return __skb_checksum_complete(skb);
1011 }
1012 
1013 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1014 {
1015         return !skb_csum_unnecessary(skb) &&
1016                 __tcp_checksum_complete(skb);
1017 }
1018 
1019 /* Prequeue for VJ style copy to user, combined with checksumming. */
1020 
1021 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1022 {
1023         tp->ucopy.task = NULL;
1024         tp->ucopy.len = 0;
1025         tp->ucopy.memory = 0;
1026         skb_queue_head_init(&tp->ucopy.prequeue);
1027 #ifdef CONFIG_NET_DMA
1028         tp->ucopy.dma_chan = NULL;
1029         tp->ucopy.wakeup = 0;
1030         tp->ucopy.pinned_list = NULL;
1031         tp->ucopy.dma_cookie = 0;
1032 #endif
1033 }
1034 
1035 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1036 
1037 #undef STATE_TRACE
1038 
1039 #ifdef STATE_TRACE
1040 static const char *statename[]={
1041         "Unused","Established","Syn Sent","Syn Recv",
1042         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1043         "Close Wait","Last ACK","Listen","Closing"
1044 };
1045 #endif
1046 void tcp_set_state(struct sock *sk, int state);
1047 
1048 void tcp_done(struct sock *sk);
1049 
1050 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1051 {
1052         rx_opt->dsack = 0;
1053         rx_opt->num_sacks = 0;
1054 }
1055 
1056 u32 tcp_default_init_rwnd(u32 mss);
1057 
1058 /* Determine a window scaling and initial window to offer. */
1059 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1060                                __u32 *window_clamp, int wscale_ok,
1061                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1062 
1063 static inline int tcp_win_from_space(int space)
1064 {
1065         return sysctl_tcp_adv_win_scale<=0 ?
1066                 (space>>(-sysctl_tcp_adv_win_scale)) :
1067                 space - (space>>sysctl_tcp_adv_win_scale);
1068 }
1069 
1070 /* Note: caller must be prepared to deal with negative returns */ 
1071 static inline int tcp_space(const struct sock *sk)
1072 {
1073         return tcp_win_from_space(sk->sk_rcvbuf -
1074                                   atomic_read(&sk->sk_rmem_alloc));
1075 } 
1076 
1077 static inline int tcp_full_space(const struct sock *sk)
1078 {
1079         return tcp_win_from_space(sk->sk_rcvbuf); 
1080 }
1081 
1082 static inline void tcp_openreq_init(struct request_sock *req,
1083                                     struct tcp_options_received *rx_opt,
1084                                     struct sk_buff *skb)
1085 {
1086         struct inet_request_sock *ireq = inet_rsk(req);
1087 
1088         req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
1089         req->cookie_ts = 0;
1090         tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1091         tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1092         tcp_rsk(req)->snt_synack = 0;
1093         req->mss = rx_opt->mss_clamp;
1094         req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1095         ireq->tstamp_ok = rx_opt->tstamp_ok;
1096         ireq->sack_ok = rx_opt->sack_ok;
1097         ireq->snd_wscale = rx_opt->snd_wscale;
1098         ireq->wscale_ok = rx_opt->wscale_ok;
1099         ireq->acked = 0;
1100         ireq->ecn_ok = 0;
1101         ireq->ir_rmt_port = tcp_hdr(skb)->source;
1102         ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
1103 }
1104 
1105 void tcp_enter_memory_pressure(struct sock *sk);
1106 
1107 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1108 {
1109         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1110 }
1111 
1112 static inline int keepalive_time_when(const struct tcp_sock *tp)
1113 {
1114         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1115 }
1116 
1117 static inline int keepalive_probes(const struct tcp_sock *tp)
1118 {
1119         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1120 }
1121 
1122 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1123 {
1124         const struct inet_connection_sock *icsk = &tp->inet_conn;
1125 
1126         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1127                           tcp_time_stamp - tp->rcv_tstamp);
1128 }
1129 
1130 static inline int tcp_fin_time(const struct sock *sk)
1131 {
1132         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1133         const int rto = inet_csk(sk)->icsk_rto;
1134 
1135         if (fin_timeout < (rto << 2) - (rto >> 1))
1136                 fin_timeout = (rto << 2) - (rto >> 1);
1137 
1138         return fin_timeout;
1139 }
1140 
1141 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1142                                   int paws_win)
1143 {
1144         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1145                 return true;
1146         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1147                 return true;
1148         /*
1149          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1150          * then following tcp messages have valid values. Ignore 0 value,
1151          * or else 'negative' tsval might forbid us to accept their packets.
1152          */
1153         if (!rx_opt->ts_recent)
1154                 return true;
1155         return false;
1156 }
1157 
1158 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1159                                    int rst)
1160 {
1161         if (tcp_paws_check(rx_opt, 0))
1162                 return false;
1163 
1164         /* RST segments are not recommended to carry timestamp,
1165            and, if they do, it is recommended to ignore PAWS because
1166            "their cleanup function should take precedence over timestamps."
1167            Certainly, it is mistake. It is necessary to understand the reasons
1168            of this constraint to relax it: if peer reboots, clock may go
1169            out-of-sync and half-open connections will not be reset.
1170            Actually, the problem would be not existing if all
1171            the implementations followed draft about maintaining clock
1172            via reboots. Linux-2.2 DOES NOT!
1173 
1174            However, we can relax time bounds for RST segments to MSL.
1175          */
1176         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1177                 return false;
1178         return true;
1179 }
1180 
1181 static inline void tcp_mib_init(struct net *net)
1182 {
1183         /* See RFC 2012 */
1184         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1185         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1186         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1187         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1188 }
1189 
1190 /* from STCP */
1191 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1192 {
1193         tp->lost_skb_hint = NULL;
1194 }
1195 
1196 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1197 {
1198         tcp_clear_retrans_hints_partial(tp);
1199         tp->retransmit_skb_hint = NULL;
1200 }
1201 
1202 /* MD5 Signature */
1203 struct crypto_hash;
1204 
1205 union tcp_md5_addr {
1206         struct in_addr  a4;
1207 #if IS_ENABLED(CONFIG_IPV6)
1208         struct in6_addr a6;
1209 #endif
1210 };
1211 
1212 /* - key database */
1213 struct tcp_md5sig_key {
1214         struct hlist_node       node;
1215         u8                      keylen;
1216         u8                      family; /* AF_INET or AF_INET6 */
1217         union tcp_md5_addr      addr;
1218         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1219         struct rcu_head         rcu;
1220 };
1221 
1222 /* - sock block */
1223 struct tcp_md5sig_info {
1224         struct hlist_head       head;
1225         struct rcu_head         rcu;
1226 };
1227 
1228 /* - pseudo header */
1229 struct tcp4_pseudohdr {
1230         __be32          saddr;
1231         __be32          daddr;
1232         __u8            pad;
1233         __u8            protocol;
1234         __be16          len;
1235 };
1236 
1237 struct tcp6_pseudohdr {
1238         struct in6_addr saddr;
1239         struct in6_addr daddr;
1240         __be32          len;
1241         __be32          protocol;       /* including padding */
1242 };
1243 
1244 union tcp_md5sum_block {
1245         struct tcp4_pseudohdr ip4;
1246 #if IS_ENABLED(CONFIG_IPV6)
1247         struct tcp6_pseudohdr ip6;
1248 #endif
1249 };
1250 
1251 /* - pool: digest algorithm, hash description and scratch buffer */
1252 struct tcp_md5sig_pool {
1253         struct hash_desc        md5_desc;
1254         union tcp_md5sum_block  md5_blk;
1255 };
1256 
1257 /* - functions */
1258 int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1259                         const struct sock *sk, const struct request_sock *req,
1260                         const struct sk_buff *skb);
1261 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1262                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1263 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1264                    int family);
1265 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1266                                          struct sock *addr_sk);
1267 
1268 #ifdef CONFIG_TCP_MD5SIG
1269 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1270                                          const union tcp_md5_addr *addr,
1271                                          int family);
1272 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1273 #else
1274 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1275                                          const union tcp_md5_addr *addr,
1276                                          int family)
1277 {
1278         return NULL;
1279 }
1280 #define tcp_twsk_md5_key(twsk)  NULL
1281 #endif
1282 
1283 bool tcp_alloc_md5sig_pool(void);
1284 
1285 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1286 static inline void tcp_put_md5sig_pool(void)
1287 {
1288         local_bh_enable();
1289 }
1290 
1291 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1292 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1293                           unsigned int header_len);
1294 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1295                      const struct tcp_md5sig_key *key);
1296 
1297 /* From tcp_fastopen.c */
1298 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1299                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1300                             unsigned long *last_syn_loss);
1301 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1302                             struct tcp_fastopen_cookie *cookie, bool syn_lost);
1303 struct tcp_fastopen_request {
1304         /* Fast Open cookie. Size 0 means a cookie request */
1305         struct tcp_fastopen_cookie      cookie;
1306         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1307         size_t                          size;
1308         int                             copied; /* queued in tcp_connect() */
1309 };
1310 void tcp_free_fastopen_req(struct tcp_sock *tp);
1311 
1312 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1313 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1314 void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
1315                              struct tcp_fastopen_cookie *foc);
1316 void tcp_fastopen_init_key_once(bool publish);
1317 #define TCP_FASTOPEN_KEY_LENGTH 16
1318 
1319 /* Fastopen key context */
1320 struct tcp_fastopen_context {
1321         struct crypto_cipher    *tfm;
1322         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1323         struct rcu_head         rcu;
1324 };
1325 
1326 /* write queue abstraction */
1327 static inline void tcp_write_queue_purge(struct sock *sk)
1328 {
1329         struct sk_buff *skb;
1330 
1331         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1332                 sk_wmem_free_skb(sk, skb);
1333         sk_mem_reclaim(sk);
1334         tcp_clear_all_retrans_hints(tcp_sk(sk));
1335 }
1336 
1337 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1338 {
1339         return skb_peek(&sk->sk_write_queue);
1340 }
1341 
1342 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1343 {
1344         return skb_peek_tail(&sk->sk_write_queue);
1345 }
1346 
1347 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1348                                                    const struct sk_buff *skb)
1349 {
1350         return skb_queue_next(&sk->sk_write_queue, skb);
1351 }
1352 
1353 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1354                                                    const struct sk_buff *skb)
1355 {
1356         return skb_queue_prev(&sk->sk_write_queue, skb);
1357 }
1358 
1359 #define tcp_for_write_queue(skb, sk)                                    \
1360         skb_queue_walk(&(sk)->sk_write_queue, skb)
1361 
1362 #define tcp_for_write_queue_from(skb, sk)                               \
1363         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1364 
1365 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1366         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1367 
1368 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1369 {
1370         return sk->sk_send_head;
1371 }
1372 
1373 static inline bool tcp_skb_is_last(const struct sock *sk,
1374                                    const struct sk_buff *skb)
1375 {
1376         return skb_queue_is_last(&sk->sk_write_queue, skb);
1377 }
1378 
1379 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1380 {
1381         if (tcp_skb_is_last(sk, skb))
1382                 sk->sk_send_head = NULL;
1383         else
1384                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1385 }
1386 
1387 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1388 {
1389         if (sk->sk_send_head == skb_unlinked)
1390                 sk->sk_send_head = NULL;
1391 }
1392 
1393 static inline void tcp_init_send_head(struct sock *sk)
1394 {
1395         sk->sk_send_head = NULL;
1396 }
1397 
1398 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1399 {
1400         __skb_queue_tail(&sk->sk_write_queue, skb);
1401 }
1402 
1403 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1404 {
1405         __tcp_add_write_queue_tail(sk, skb);
1406 
1407         /* Queue it, remembering where we must start sending. */
1408         if (sk->sk_send_head == NULL) {
1409                 sk->sk_send_head = skb;
1410 
1411                 if (tcp_sk(sk)->highest_sack == NULL)
1412                         tcp_sk(sk)->highest_sack = skb;
1413         }
1414 }
1415 
1416 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1417 {
1418         __skb_queue_head(&sk->sk_write_queue, skb);
1419 }
1420 
1421 /* Insert buff after skb on the write queue of sk.  */
1422 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1423                                                 struct sk_buff *buff,
1424                                                 struct sock *sk)
1425 {
1426         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1427 }
1428 
1429 /* Insert new before skb on the write queue of sk.  */
1430 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1431                                                   struct sk_buff *skb,
1432                                                   struct sock *sk)
1433 {
1434         __skb_queue_before(&sk->sk_write_queue, skb, new);
1435 
1436         if (sk->sk_send_head == skb)
1437                 sk->sk_send_head = new;
1438 }
1439 
1440 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1441 {
1442         __skb_unlink(skb, &sk->sk_write_queue);
1443 }
1444 
1445 static inline bool tcp_write_queue_empty(struct sock *sk)
1446 {
1447         return skb_queue_empty(&sk->sk_write_queue);
1448 }
1449 
1450 static inline void tcp_push_pending_frames(struct sock *sk)
1451 {
1452         if (tcp_send_head(sk)) {
1453                 struct tcp_sock *tp = tcp_sk(sk);
1454 
1455                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1456         }
1457 }
1458 
1459 /* Start sequence of the skb just after the highest skb with SACKed
1460  * bit, valid only if sacked_out > 0 or when the caller has ensured
1461  * validity by itself.
1462  */
1463 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1464 {
1465         if (!tp->sacked_out)
1466                 return tp->snd_una;
1467 
1468         if (tp->highest_sack == NULL)
1469                 return tp->snd_nxt;
1470 
1471         return TCP_SKB_CB(tp->highest_sack)->seq;
1472 }
1473 
1474 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1475 {
1476         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1477                                                 tcp_write_queue_next(sk, skb);
1478 }
1479 
1480 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1481 {
1482         return tcp_sk(sk)->highest_sack;
1483 }
1484 
1485 static inline void tcp_highest_sack_reset(struct sock *sk)
1486 {
1487         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1488 }
1489 
1490 /* Called when old skb is about to be deleted (to be combined with new skb) */
1491 static inline void tcp_highest_sack_combine(struct sock *sk,
1492                                             struct sk_buff *old,
1493                                             struct sk_buff *new)
1494 {
1495         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1496                 tcp_sk(sk)->highest_sack = new;
1497 }
1498 
1499 /* Determines whether this is a thin stream (which may suffer from
1500  * increased latency). Used to trigger latency-reducing mechanisms.
1501  */
1502 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1503 {
1504         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1505 }
1506 
1507 /* /proc */
1508 enum tcp_seq_states {
1509         TCP_SEQ_STATE_LISTENING,
1510         TCP_SEQ_STATE_OPENREQ,
1511         TCP_SEQ_STATE_ESTABLISHED,
1512 };
1513 
1514 int tcp_seq_open(struct inode *inode, struct file *file);
1515 
1516 struct tcp_seq_afinfo {
1517         char                            *name;
1518         sa_family_t                     family;
1519         const struct file_operations    *seq_fops;
1520         struct seq_operations           seq_ops;
1521 };
1522 
1523 struct tcp_iter_state {
1524         struct seq_net_private  p;
1525         sa_family_t             family;
1526         enum tcp_seq_states     state;
1527         struct sock             *syn_wait_sk;
1528         int                     bucket, offset, sbucket, num;
1529         kuid_t                  uid;
1530         loff_t                  last_pos;
1531 };
1532 
1533 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1534 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1535 
1536 extern struct request_sock_ops tcp_request_sock_ops;
1537 extern struct request_sock_ops tcp6_request_sock_ops;
1538 
1539 void tcp_v4_destroy_sock(struct sock *sk);
1540 
1541 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1542                                 netdev_features_t features);
1543 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1544 int tcp_gro_complete(struct sk_buff *skb);
1545 
1546 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1547 
1548 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1549 {
1550         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1551 }
1552 
1553 static inline bool tcp_stream_memory_free(const struct sock *sk)
1554 {
1555         const struct tcp_sock *tp = tcp_sk(sk);
1556         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1557 
1558         return notsent_bytes < tcp_notsent_lowat(tp);
1559 }
1560 
1561 #ifdef CONFIG_PROC_FS
1562 int tcp4_proc_init(void);
1563 void tcp4_proc_exit(void);
1564 #endif
1565 
1566 /* TCP af-specific functions */
1567 struct tcp_sock_af_ops {
1568 #ifdef CONFIG_TCP_MD5SIG
1569         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1570                                                 struct sock *addr_sk);
1571         int                     (*calc_md5_hash) (char *location,
1572                                                   struct tcp_md5sig_key *md5,
1573                                                   const struct sock *sk,
1574                                                   const struct request_sock *req,
1575                                                   const struct sk_buff *skb);
1576         int                     (*md5_parse) (struct sock *sk,
1577                                               char __user *optval,
1578                                               int optlen);
1579 #endif
1580 };
1581 
1582 struct tcp_request_sock_ops {
1583 #ifdef CONFIG_TCP_MD5SIG
1584         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1585                                                 struct request_sock *req);
1586         int                     (*calc_md5_hash) (char *location,
1587                                                   struct tcp_md5sig_key *md5,
1588                                                   const struct sock *sk,
1589                                                   const struct request_sock *req,
1590                                                   const struct sk_buff *skb);
1591 #endif
1592 };
1593 
1594 int tcpv4_offload_init(void);
1595 
1596 void tcp_v4_init(void);
1597 void tcp_init(void);
1598 
1599 #endif  /* _TCP_H */
1600 

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