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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 /* Process SYN data but skip cookie validation */
224 #define TFO_SERVER_COOKIE_NOT_CHKED     0x100
225 /* Accept SYN data w/o any cookie option */
226 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
227 
228 /* Force enable TFO on all listeners, i.e., not requiring the
229  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
230  */
231 #define TFO_SERVER_WO_SOCKOPT1  0x400
232 #define TFO_SERVER_WO_SOCKOPT2  0x800
233 /* Always create TFO child sockets on a TFO listener even when
234  * cookie/data not present. (For testing purpose!)
235  */
236 #define TFO_SERVER_ALWAYS       0x1000
237 
238 extern struct inet_timewait_death_row tcp_death_row;
239 
240 /* sysctl variables for tcp */
241 extern int sysctl_tcp_timestamps;
242 extern int sysctl_tcp_window_scaling;
243 extern int sysctl_tcp_sack;
244 extern int sysctl_tcp_fin_timeout;
245 extern int sysctl_tcp_keepalive_time;
246 extern int sysctl_tcp_keepalive_probes;
247 extern int sysctl_tcp_keepalive_intvl;
248 extern int sysctl_tcp_syn_retries;
249 extern int sysctl_tcp_synack_retries;
250 extern int sysctl_tcp_retries1;
251 extern int sysctl_tcp_retries2;
252 extern int sysctl_tcp_orphan_retries;
253 extern int sysctl_tcp_syncookies;
254 extern int sysctl_tcp_fastopen;
255 extern int sysctl_tcp_retrans_collapse;
256 extern int sysctl_tcp_stdurg;
257 extern int sysctl_tcp_rfc1337;
258 extern int sysctl_tcp_abort_on_overflow;
259 extern int sysctl_tcp_max_orphans;
260 extern int sysctl_tcp_fack;
261 extern int sysctl_tcp_reordering;
262 extern int sysctl_tcp_dsack;
263 extern long sysctl_tcp_mem[3];
264 extern int sysctl_tcp_wmem[3];
265 extern int sysctl_tcp_rmem[3];
266 extern int sysctl_tcp_app_win;
267 extern int sysctl_tcp_adv_win_scale;
268 extern int sysctl_tcp_tw_reuse;
269 extern int sysctl_tcp_frto;
270 extern int sysctl_tcp_low_latency;
271 extern int sysctl_tcp_dma_copybreak;
272 extern int sysctl_tcp_nometrics_save;
273 extern int sysctl_tcp_moderate_rcvbuf;
274 extern int sysctl_tcp_tso_win_divisor;
275 extern int sysctl_tcp_mtu_probing;
276 extern int sysctl_tcp_base_mss;
277 extern int sysctl_tcp_workaround_signed_windows;
278 extern int sysctl_tcp_slow_start_after_idle;
279 extern int sysctl_tcp_thin_linear_timeouts;
280 extern int sysctl_tcp_thin_dupack;
281 extern int sysctl_tcp_early_retrans;
282 extern int sysctl_tcp_limit_output_bytes;
283 extern int sysctl_tcp_challenge_ack_limit;
284 extern unsigned int sysctl_tcp_notsent_lowat;
285 extern int sysctl_tcp_min_tso_segs;
286 extern int sysctl_tcp_autocorking;
287 
288 extern atomic_long_t tcp_memory_allocated;
289 extern struct percpu_counter tcp_sockets_allocated;
290 extern int tcp_memory_pressure;
291 
292 /*
293  * The next routines deal with comparing 32 bit unsigned ints
294  * and worry about wraparound (automatic with unsigned arithmetic).
295  */
296 
297 static inline bool before(__u32 seq1, __u32 seq2)
298 {
299         return (__s32)(seq1-seq2) < 0;
300 }
301 #define after(seq2, seq1)       before(seq1, seq2)
302 
303 /* is s2<=s1<=s3 ? */
304 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
305 {
306         return seq3 - seq2 >= seq1 - seq2;
307 }
308 
309 static inline bool tcp_out_of_memory(struct sock *sk)
310 {
311         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
312             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
313                 return true;
314         return false;
315 }
316 
317 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
318 {
319         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
320         int orphans = percpu_counter_read_positive(ocp);
321 
322         if (orphans << shift > sysctl_tcp_max_orphans) {
323                 orphans = percpu_counter_sum_positive(ocp);
324                 if (orphans << shift > sysctl_tcp_max_orphans)
325                         return true;
326         }
327         return false;
328 }
329 
330 bool tcp_check_oom(struct sock *sk, int shift);
331 
332 /* syncookies: remember time of last synqueue overflow */
333 static inline void tcp_synq_overflow(struct sock *sk)
334 {
335         tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
336 }
337 
338 /* syncookies: no recent synqueue overflow on this listening socket? */
339 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
340 {
341         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
342         return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
343 }
344 
345 extern struct proto tcp_prot;
346 
347 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
348 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
349 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
350 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
351 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
352 
353 void tcp_tasklet_init(void);
354 
355 void tcp_v4_err(struct sk_buff *skb, u32);
356 
357 void tcp_shutdown(struct sock *sk, int how);
358 
359 void tcp_v4_early_demux(struct sk_buff *skb);
360 int tcp_v4_rcv(struct sk_buff *skb);
361 
362 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
363 int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
364                 size_t size);
365 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
366                  int flags);
367 void tcp_release_cb(struct sock *sk);
368 void tcp_wfree(struct sk_buff *skb);
369 void tcp_write_timer_handler(struct sock *sk);
370 void tcp_delack_timer_handler(struct sock *sk);
371 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
372 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
373                           const struct tcphdr *th, unsigned int len);
374 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
375                          const struct tcphdr *th, unsigned int len);
376 void tcp_rcv_space_adjust(struct sock *sk);
377 void tcp_cleanup_rbuf(struct sock *sk, int copied);
378 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
379 void tcp_twsk_destructor(struct sock *sk);
380 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
381                         struct pipe_inode_info *pipe, size_t len,
382                         unsigned int flags);
383 
384 static inline void tcp_dec_quickack_mode(struct sock *sk,
385                                          const unsigned int pkts)
386 {
387         struct inet_connection_sock *icsk = inet_csk(sk);
388 
389         if (icsk->icsk_ack.quick) {
390                 if (pkts >= icsk->icsk_ack.quick) {
391                         icsk->icsk_ack.quick = 0;
392                         /* Leaving quickack mode we deflate ATO. */
393                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
394                 } else
395                         icsk->icsk_ack.quick -= pkts;
396         }
397 }
398 
399 #define TCP_ECN_OK              1
400 #define TCP_ECN_QUEUE_CWR       2
401 #define TCP_ECN_DEMAND_CWR      4
402 #define TCP_ECN_SEEN            8
403 
404 enum tcp_tw_status {
405         TCP_TW_SUCCESS = 0,
406         TCP_TW_RST = 1,
407         TCP_TW_ACK = 2,
408         TCP_TW_SYN = 3
409 };
410 
411 
412 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
413                                               struct sk_buff *skb,
414                                               const struct tcphdr *th);
415 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
416                            struct request_sock *req, struct request_sock **prev,
417                            bool fastopen);
418 int tcp_child_process(struct sock *parent, struct sock *child,
419                       struct sk_buff *skb);
420 void tcp_enter_loss(struct sock *sk, int how);
421 void tcp_clear_retrans(struct tcp_sock *tp);
422 void tcp_update_metrics(struct sock *sk);
423 void tcp_init_metrics(struct sock *sk);
424 void tcp_metrics_init(void);
425 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
426                         bool paws_check);
427 bool tcp_remember_stamp(struct sock *sk);
428 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
429 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
430 void tcp_disable_fack(struct tcp_sock *tp);
431 void tcp_close(struct sock *sk, long timeout);
432 void tcp_init_sock(struct sock *sk);
433 unsigned int tcp_poll(struct file *file, struct socket *sock,
434                       struct poll_table_struct *wait);
435 int tcp_getsockopt(struct sock *sk, int level, int optname,
436                    char __user *optval, int __user *optlen);
437 int tcp_setsockopt(struct sock *sk, int level, int optname,
438                    char __user *optval, unsigned int optlen);
439 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
440                           char __user *optval, int __user *optlen);
441 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
442                           char __user *optval, unsigned int optlen);
443 void tcp_set_keepalive(struct sock *sk, int val);
444 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
445 int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
446                 size_t len, int nonblock, int flags, int *addr_len);
447 void tcp_parse_options(const struct sk_buff *skb,
448                        struct tcp_options_received *opt_rx,
449                        int estab, struct tcp_fastopen_cookie *foc);
450 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
451 
452 /*
453  *      TCP v4 functions exported for the inet6 API
454  */
455 
456 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
457 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
458 struct sock *tcp_create_openreq_child(struct sock *sk,
459                                       struct request_sock *req,
460                                       struct sk_buff *skb);
461 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
462                                   struct request_sock *req,
463                                   struct dst_entry *dst);
464 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
465 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
466 int tcp_connect(struct sock *sk);
467 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
468                                 struct request_sock *req,
469                                 struct tcp_fastopen_cookie *foc);
470 int tcp_disconnect(struct sock *sk, int flags);
471 
472 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
473 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
474 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
475 
476 /* From syncookies.c */
477 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
478                       u32 cookie);
479 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
480                              struct ip_options *opt);
481 #ifdef CONFIG_SYN_COOKIES
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 usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
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 static inline u32 tcp_rto_min_us(struct sock *sk)
661 {
662         return jiffies_to_usecs(tcp_rto_min(sk));
663 }
664 
665 /* Compute the actual receive window we are currently advertising.
666  * Rcv_nxt can be after the window if our peer push more data
667  * than the offered window.
668  */
669 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
670 {
671         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
672 
673         if (win < 0)
674                 win = 0;
675         return (u32) win;
676 }
677 
678 /* Choose a new window, without checks for shrinking, and without
679  * scaling applied to the result.  The caller does these things
680  * if necessary.  This is a "raw" window selection.
681  */
682 u32 __tcp_select_window(struct sock *sk);
683 
684 void tcp_send_window_probe(struct sock *sk);
685 
686 /* TCP timestamps are only 32-bits, this causes a slight
687  * complication on 64-bit systems since we store a snapshot
688  * of jiffies in the buffer control blocks below.  We decided
689  * to use only the low 32-bits of jiffies and hide the ugly
690  * casts with the following macro.
691  */
692 #define tcp_time_stamp          ((__u32)(jiffies))
693 
694 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
695 
696 #define TCPHDR_FIN 0x01
697 #define TCPHDR_SYN 0x02
698 #define TCPHDR_RST 0x04
699 #define TCPHDR_PSH 0x08
700 #define TCPHDR_ACK 0x10
701 #define TCPHDR_URG 0x20
702 #define TCPHDR_ECE 0x40
703 #define TCPHDR_CWR 0x80
704 
705 /* This is what the send packet queuing engine uses to pass
706  * TCP per-packet control information to the transmission code.
707  * We also store the host-order sequence numbers in here too.
708  * This is 44 bytes if IPV6 is enabled.
709  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
710  */
711 struct tcp_skb_cb {
712         union {
713                 struct inet_skb_parm    h4;
714 #if IS_ENABLED(CONFIG_IPV6)
715                 struct inet6_skb_parm   h6;
716 #endif
717         } header;       /* For incoming frames          */
718         __u32           seq;            /* Starting sequence number     */
719         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
720         __u32           when;           /* used to compute rtt's        */
721         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
722 
723         __u8            sacked;         /* State flags for SACK/FACK.   */
724 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
725 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
726 #define TCPCB_LOST              0x04    /* SKB is lost                  */
727 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
728 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
729 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
730 
731         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
732         /* 1 byte hole */
733         __u32           ack_seq;        /* Sequence number ACK'd        */
734 };
735 
736 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
737 
738 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
739  *
740  * If we receive a SYN packet with these bits set, it means a network is
741  * playing bad games with TOS bits. In order to avoid possible false congestion
742  * notifications, we disable TCP ECN negociation.
743  */
744 static inline void
745 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
746                 struct net *net)
747 {
748         const struct tcphdr *th = tcp_hdr(skb);
749 
750         if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr &&
751             INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
752                 inet_rsk(req)->ecn_ok = 1;
753 }
754 
755 /* Due to TSO, an SKB can be composed of multiple actual
756  * packets.  To keep these tracked properly, we use this.
757  */
758 static inline int tcp_skb_pcount(const struct sk_buff *skb)
759 {
760         return skb_shinfo(skb)->gso_segs;
761 }
762 
763 /* This is valid iff tcp_skb_pcount() > 1. */
764 static inline int tcp_skb_mss(const struct sk_buff *skb)
765 {
766         return skb_shinfo(skb)->gso_size;
767 }
768 
769 /* Events passed to congestion control interface */
770 enum tcp_ca_event {
771         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
772         CA_EVENT_CWND_RESTART,  /* congestion window restart */
773         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
774         CA_EVENT_LOSS,          /* loss timeout */
775         CA_EVENT_FAST_ACK,      /* in sequence ack */
776         CA_EVENT_SLOW_ACK,      /* other ack */
777 };
778 
779 /*
780  * Interface for adding new TCP congestion control handlers
781  */
782 #define TCP_CA_NAME_MAX 16
783 #define TCP_CA_MAX      128
784 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
785 
786 #define TCP_CONG_NON_RESTRICTED 0x1
787 
788 struct tcp_congestion_ops {
789         struct list_head        list;
790         unsigned long flags;
791 
792         /* initialize private data (optional) */
793         void (*init)(struct sock *sk);
794         /* cleanup private data  (optional) */
795         void (*release)(struct sock *sk);
796 
797         /* return slow start threshold (required) */
798         u32 (*ssthresh)(struct sock *sk);
799         /* do new cwnd calculation (required) */
800         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
801         /* call before changing ca_state (optional) */
802         void (*set_state)(struct sock *sk, u8 new_state);
803         /* call when cwnd event occurs (optional) */
804         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
805         /* new value of cwnd after loss (optional) */
806         u32  (*undo_cwnd)(struct sock *sk);
807         /* hook for packet ack accounting (optional) */
808         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
809         /* get info for inet_diag (optional) */
810         void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
811 
812         char            name[TCP_CA_NAME_MAX];
813         struct module   *owner;
814 };
815 
816 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
817 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
818 
819 void tcp_init_congestion_control(struct sock *sk);
820 void tcp_cleanup_congestion_control(struct sock *sk);
821 int tcp_set_default_congestion_control(const char *name);
822 void tcp_get_default_congestion_control(char *name);
823 void tcp_get_available_congestion_control(char *buf, size_t len);
824 void tcp_get_allowed_congestion_control(char *buf, size_t len);
825 int tcp_set_allowed_congestion_control(char *allowed);
826 int tcp_set_congestion_control(struct sock *sk, const char *name);
827 int tcp_slow_start(struct tcp_sock *tp, u32 acked);
828 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
829 
830 extern struct tcp_congestion_ops tcp_init_congestion_ops;
831 u32 tcp_reno_ssthresh(struct sock *sk);
832 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
833 extern struct tcp_congestion_ops tcp_reno;
834 
835 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
836 {
837         struct inet_connection_sock *icsk = inet_csk(sk);
838 
839         if (icsk->icsk_ca_ops->set_state)
840                 icsk->icsk_ca_ops->set_state(sk, ca_state);
841         icsk->icsk_ca_state = ca_state;
842 }
843 
844 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
845 {
846         const struct inet_connection_sock *icsk = inet_csk(sk);
847 
848         if (icsk->icsk_ca_ops->cwnd_event)
849                 icsk->icsk_ca_ops->cwnd_event(sk, event);
850 }
851 
852 /* These functions determine how the current flow behaves in respect of SACK
853  * handling. SACK is negotiated with the peer, and therefore it can vary
854  * between different flows.
855  *
856  * tcp_is_sack - SACK enabled
857  * tcp_is_reno - No SACK
858  * tcp_is_fack - FACK enabled, implies SACK enabled
859  */
860 static inline int tcp_is_sack(const struct tcp_sock *tp)
861 {
862         return tp->rx_opt.sack_ok;
863 }
864 
865 static inline bool tcp_is_reno(const struct tcp_sock *tp)
866 {
867         return !tcp_is_sack(tp);
868 }
869 
870 static inline bool tcp_is_fack(const struct tcp_sock *tp)
871 {
872         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
873 }
874 
875 static inline void tcp_enable_fack(struct tcp_sock *tp)
876 {
877         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
878 }
879 
880 /* TCP early-retransmit (ER) is similar to but more conservative than
881  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
882  */
883 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
884 {
885         tp->do_early_retrans = sysctl_tcp_early_retrans &&
886                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
887                 sysctl_tcp_reordering == 3;
888 }
889 
890 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
891 {
892         tp->do_early_retrans = 0;
893 }
894 
895 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
896 {
897         return tp->sacked_out + tp->lost_out;
898 }
899 
900 /* This determines how many packets are "in the network" to the best
901  * of our knowledge.  In many cases it is conservative, but where
902  * detailed information is available from the receiver (via SACK
903  * blocks etc.) we can make more aggressive calculations.
904  *
905  * Use this for decisions involving congestion control, use just
906  * tp->packets_out to determine if the send queue is empty or not.
907  *
908  * Read this equation as:
909  *
910  *      "Packets sent once on transmission queue" MINUS
911  *      "Packets left network, but not honestly ACKed yet" PLUS
912  *      "Packets fast retransmitted"
913  */
914 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
915 {
916         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
917 }
918 
919 #define TCP_INFINITE_SSTHRESH   0x7fffffff
920 
921 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
922 {
923         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
924 }
925 
926 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
927 {
928         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
929                (1 << inet_csk(sk)->icsk_ca_state);
930 }
931 
932 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
933  * The exception is cwnd reduction phase, when cwnd is decreasing towards
934  * ssthresh.
935  */
936 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
937 {
938         const struct tcp_sock *tp = tcp_sk(sk);
939 
940         if (tcp_in_cwnd_reduction(sk))
941                 return tp->snd_ssthresh;
942         else
943                 return max(tp->snd_ssthresh,
944                            ((tp->snd_cwnd >> 1) +
945                             (tp->snd_cwnd >> 2)));
946 }
947 
948 /* Use define here intentionally to get WARN_ON location shown at the caller */
949 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
950 
951 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
952 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
953 
954 /* The maximum number of MSS of available cwnd for which TSO defers
955  * sending if not using sysctl_tcp_tso_win_divisor.
956  */
957 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
958 {
959         return 3;
960 }
961 
962 /* Slow start with delack produces 3 packets of burst, so that
963  * it is safe "de facto".  This will be the default - same as
964  * the default reordering threshold - but if reordering increases,
965  * we must be able to allow cwnd to burst at least this much in order
966  * to not pull it back when holes are filled.
967  */
968 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
969 {
970         return tp->reordering;
971 }
972 
973 /* Returns end sequence number of the receiver's advertised window */
974 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
975 {
976         return tp->snd_una + tp->snd_wnd;
977 }
978 bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
979 
980 static inline void tcp_check_probe_timer(struct sock *sk)
981 {
982         const struct tcp_sock *tp = tcp_sk(sk);
983         const struct inet_connection_sock *icsk = inet_csk(sk);
984 
985         if (!tp->packets_out && !icsk->icsk_pending)
986                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
987                                           icsk->icsk_rto, TCP_RTO_MAX);
988 }
989 
990 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
991 {
992         tp->snd_wl1 = seq;
993 }
994 
995 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
996 {
997         tp->snd_wl1 = seq;
998 }
999 
1000 /*
1001  * Calculate(/check) TCP checksum
1002  */
1003 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1004                                    __be32 daddr, __wsum base)
1005 {
1006         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1007 }
1008 
1009 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1010 {
1011         return __skb_checksum_complete(skb);
1012 }
1013 
1014 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1015 {
1016         return !skb_csum_unnecessary(skb) &&
1017                 __tcp_checksum_complete(skb);
1018 }
1019 
1020 /* Prequeue for VJ style copy to user, combined with checksumming. */
1021 
1022 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1023 {
1024         tp->ucopy.task = NULL;
1025         tp->ucopy.len = 0;
1026         tp->ucopy.memory = 0;
1027         skb_queue_head_init(&tp->ucopy.prequeue);
1028 #ifdef CONFIG_NET_DMA
1029         tp->ucopy.dma_chan = NULL;
1030         tp->ucopy.wakeup = 0;
1031         tp->ucopy.pinned_list = NULL;
1032         tp->ucopy.dma_cookie = 0;
1033 #endif
1034 }
1035 
1036 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1037 
1038 #undef STATE_TRACE
1039 
1040 #ifdef STATE_TRACE
1041 static const char *statename[]={
1042         "Unused","Established","Syn Sent","Syn Recv",
1043         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1044         "Close Wait","Last ACK","Listen","Closing"
1045 };
1046 #endif
1047 void tcp_set_state(struct sock *sk, int state);
1048 
1049 void tcp_done(struct sock *sk);
1050 
1051 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1052 {
1053         rx_opt->dsack = 0;
1054         rx_opt->num_sacks = 0;
1055 }
1056 
1057 u32 tcp_default_init_rwnd(u32 mss);
1058 
1059 /* Determine a window scaling and initial window to offer. */
1060 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1061                                __u32 *window_clamp, int wscale_ok,
1062                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1063 
1064 static inline int tcp_win_from_space(int space)
1065 {
1066         return sysctl_tcp_adv_win_scale<=0 ?
1067                 (space>>(-sysctl_tcp_adv_win_scale)) :
1068                 space - (space>>sysctl_tcp_adv_win_scale);
1069 }
1070 
1071 /* Note: caller must be prepared to deal with negative returns */ 
1072 static inline int tcp_space(const struct sock *sk)
1073 {
1074         return tcp_win_from_space(sk->sk_rcvbuf -
1075                                   atomic_read(&sk->sk_rmem_alloc));
1076 } 
1077 
1078 static inline int tcp_full_space(const struct sock *sk)
1079 {
1080         return tcp_win_from_space(sk->sk_rcvbuf); 
1081 }
1082 
1083 static inline void tcp_openreq_init(struct request_sock *req,
1084                                     struct tcp_options_received *rx_opt,
1085                                     struct sk_buff *skb)
1086 {
1087         struct inet_request_sock *ireq = inet_rsk(req);
1088 
1089         req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
1090         req->cookie_ts = 0;
1091         tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1092         tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1093         tcp_rsk(req)->snt_synack = 0;
1094         req->mss = rx_opt->mss_clamp;
1095         req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1096         ireq->tstamp_ok = rx_opt->tstamp_ok;
1097         ireq->sack_ok = rx_opt->sack_ok;
1098         ireq->snd_wscale = rx_opt->snd_wscale;
1099         ireq->wscale_ok = rx_opt->wscale_ok;
1100         ireq->acked = 0;
1101         ireq->ecn_ok = 0;
1102         ireq->ir_rmt_port = tcp_hdr(skb)->source;
1103         ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
1104 }
1105 
1106 void tcp_enter_memory_pressure(struct sock *sk);
1107 
1108 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1109 {
1110         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1111 }
1112 
1113 static inline int keepalive_time_when(const struct tcp_sock *tp)
1114 {
1115         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1116 }
1117 
1118 static inline int keepalive_probes(const struct tcp_sock *tp)
1119 {
1120         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1121 }
1122 
1123 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1124 {
1125         const struct inet_connection_sock *icsk = &tp->inet_conn;
1126 
1127         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1128                           tcp_time_stamp - tp->rcv_tstamp);
1129 }
1130 
1131 static inline int tcp_fin_time(const struct sock *sk)
1132 {
1133         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1134         const int rto = inet_csk(sk)->icsk_rto;
1135 
1136         if (fin_timeout < (rto << 2) - (rto >> 1))
1137                 fin_timeout = (rto << 2) - (rto >> 1);
1138 
1139         return fin_timeout;
1140 }
1141 
1142 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1143                                   int paws_win)
1144 {
1145         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1146                 return true;
1147         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1148                 return true;
1149         /*
1150          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1151          * then following tcp messages have valid values. Ignore 0 value,
1152          * or else 'negative' tsval might forbid us to accept their packets.
1153          */
1154         if (!rx_opt->ts_recent)
1155                 return true;
1156         return false;
1157 }
1158 
1159 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1160                                    int rst)
1161 {
1162         if (tcp_paws_check(rx_opt, 0))
1163                 return false;
1164 
1165         /* RST segments are not recommended to carry timestamp,
1166            and, if they do, it is recommended to ignore PAWS because
1167            "their cleanup function should take precedence over timestamps."
1168            Certainly, it is mistake. It is necessary to understand the reasons
1169            of this constraint to relax it: if peer reboots, clock may go
1170            out-of-sync and half-open connections will not be reset.
1171            Actually, the problem would be not existing if all
1172            the implementations followed draft about maintaining clock
1173            via reboots. Linux-2.2 DOES NOT!
1174 
1175            However, we can relax time bounds for RST segments to MSL.
1176          */
1177         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1178                 return false;
1179         return true;
1180 }
1181 
1182 static inline void tcp_mib_init(struct net *net)
1183 {
1184         /* See RFC 2012 */
1185         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1186         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1187         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1188         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1189 }
1190 
1191 /* from STCP */
1192 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1193 {
1194         tp->lost_skb_hint = NULL;
1195 }
1196 
1197 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1198 {
1199         tcp_clear_retrans_hints_partial(tp);
1200         tp->retransmit_skb_hint = NULL;
1201 }
1202 
1203 /* MD5 Signature */
1204 struct crypto_hash;
1205 
1206 union tcp_md5_addr {
1207         struct in_addr  a4;
1208 #if IS_ENABLED(CONFIG_IPV6)
1209         struct in6_addr a6;
1210 #endif
1211 };
1212 
1213 /* - key database */
1214 struct tcp_md5sig_key {
1215         struct hlist_node       node;
1216         u8                      keylen;
1217         u8                      family; /* AF_INET or AF_INET6 */
1218         union tcp_md5_addr      addr;
1219         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1220         struct rcu_head         rcu;
1221 };
1222 
1223 /* - sock block */
1224 struct tcp_md5sig_info {
1225         struct hlist_head       head;
1226         struct rcu_head         rcu;
1227 };
1228 
1229 /* - pseudo header */
1230 struct tcp4_pseudohdr {
1231         __be32          saddr;
1232         __be32          daddr;
1233         __u8            pad;
1234         __u8            protocol;
1235         __be16          len;
1236 };
1237 
1238 struct tcp6_pseudohdr {
1239         struct in6_addr saddr;
1240         struct in6_addr daddr;
1241         __be32          len;
1242         __be32          protocol;       /* including padding */
1243 };
1244 
1245 union tcp_md5sum_block {
1246         struct tcp4_pseudohdr ip4;
1247 #if IS_ENABLED(CONFIG_IPV6)
1248         struct tcp6_pseudohdr ip6;
1249 #endif
1250 };
1251 
1252 /* - pool: digest algorithm, hash description and scratch buffer */
1253 struct tcp_md5sig_pool {
1254         struct hash_desc        md5_desc;
1255         union tcp_md5sum_block  md5_blk;
1256 };
1257 
1258 /* - functions */
1259 int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1260                         const struct sock *sk, const struct request_sock *req,
1261                         const struct sk_buff *skb);
1262 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1263                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1264 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1265                    int family);
1266 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1267                                          struct sock *addr_sk);
1268 
1269 #ifdef CONFIG_TCP_MD5SIG
1270 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1271                                          const union tcp_md5_addr *addr,
1272                                          int family);
1273 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1274 #else
1275 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1276                                          const union tcp_md5_addr *addr,
1277                                          int family)
1278 {
1279         return NULL;
1280 }
1281 #define tcp_twsk_md5_key(twsk)  NULL
1282 #endif
1283 
1284 bool tcp_alloc_md5sig_pool(void);
1285 
1286 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1287 static inline void tcp_put_md5sig_pool(void)
1288 {
1289         local_bh_enable();
1290 }
1291 
1292 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1293 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1294                           unsigned int header_len);
1295 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1296                      const struct tcp_md5sig_key *key);
1297 
1298 /* From tcp_fastopen.c */
1299 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1300                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1301                             unsigned long *last_syn_loss);
1302 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1303                             struct tcp_fastopen_cookie *cookie, bool syn_lost);
1304 struct tcp_fastopen_request {
1305         /* Fast Open cookie. Size 0 means a cookie request */
1306         struct tcp_fastopen_cookie      cookie;
1307         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1308         size_t                          size;
1309         int                             copied; /* queued in tcp_connect() */
1310 };
1311 void tcp_free_fastopen_req(struct tcp_sock *tp);
1312 
1313 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1314 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1315 void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
1316                              struct tcp_fastopen_cookie *foc);
1317 void tcp_fastopen_init_key_once(bool publish);
1318 #define TCP_FASTOPEN_KEY_LENGTH 16
1319 
1320 /* Fastopen key context */
1321 struct tcp_fastopen_context {
1322         struct crypto_cipher    *tfm;
1323         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1324         struct rcu_head         rcu;
1325 };
1326 
1327 /* write queue abstraction */
1328 static inline void tcp_write_queue_purge(struct sock *sk)
1329 {
1330         struct sk_buff *skb;
1331 
1332         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1333                 sk_wmem_free_skb(sk, skb);
1334         sk_mem_reclaim(sk);
1335         tcp_clear_all_retrans_hints(tcp_sk(sk));
1336 }
1337 
1338 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1339 {
1340         return skb_peek(&sk->sk_write_queue);
1341 }
1342 
1343 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1344 {
1345         return skb_peek_tail(&sk->sk_write_queue);
1346 }
1347 
1348 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1349                                                    const struct sk_buff *skb)
1350 {
1351         return skb_queue_next(&sk->sk_write_queue, skb);
1352 }
1353 
1354 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1355                                                    const struct sk_buff *skb)
1356 {
1357         return skb_queue_prev(&sk->sk_write_queue, skb);
1358 }
1359 
1360 #define tcp_for_write_queue(skb, sk)                                    \
1361         skb_queue_walk(&(sk)->sk_write_queue, skb)
1362 
1363 #define tcp_for_write_queue_from(skb, sk)                               \
1364         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1365 
1366 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1367         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1368 
1369 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1370 {
1371         return sk->sk_send_head;
1372 }
1373 
1374 static inline bool tcp_skb_is_last(const struct sock *sk,
1375                                    const struct sk_buff *skb)
1376 {
1377         return skb_queue_is_last(&sk->sk_write_queue, skb);
1378 }
1379 
1380 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1381 {
1382         if (tcp_skb_is_last(sk, skb))
1383                 sk->sk_send_head = NULL;
1384         else
1385                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1386 }
1387 
1388 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1389 {
1390         if (sk->sk_send_head == skb_unlinked)
1391                 sk->sk_send_head = NULL;
1392 }
1393 
1394 static inline void tcp_init_send_head(struct sock *sk)
1395 {
1396         sk->sk_send_head = NULL;
1397 }
1398 
1399 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1400 {
1401         __skb_queue_tail(&sk->sk_write_queue, skb);
1402 }
1403 
1404 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1405 {
1406         __tcp_add_write_queue_tail(sk, skb);
1407 
1408         /* Queue it, remembering where we must start sending. */
1409         if (sk->sk_send_head == NULL) {
1410                 sk->sk_send_head = skb;
1411 
1412                 if (tcp_sk(sk)->highest_sack == NULL)
1413                         tcp_sk(sk)->highest_sack = skb;
1414         }
1415 }
1416 
1417 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1418 {
1419         __skb_queue_head(&sk->sk_write_queue, skb);
1420 }
1421 
1422 /* Insert buff after skb on the write queue of sk.  */
1423 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1424                                                 struct sk_buff *buff,
1425                                                 struct sock *sk)
1426 {
1427         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1428 }
1429 
1430 /* Insert new before skb on the write queue of sk.  */
1431 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1432                                                   struct sk_buff *skb,
1433                                                   struct sock *sk)
1434 {
1435         __skb_queue_before(&sk->sk_write_queue, skb, new);
1436 
1437         if (sk->sk_send_head == skb)
1438                 sk->sk_send_head = new;
1439 }
1440 
1441 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1442 {
1443         __skb_unlink(skb, &sk->sk_write_queue);
1444 }
1445 
1446 static inline bool tcp_write_queue_empty(struct sock *sk)
1447 {
1448         return skb_queue_empty(&sk->sk_write_queue);
1449 }
1450 
1451 static inline void tcp_push_pending_frames(struct sock *sk)
1452 {
1453         if (tcp_send_head(sk)) {
1454                 struct tcp_sock *tp = tcp_sk(sk);
1455 
1456                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1457         }
1458 }
1459 
1460 /* Start sequence of the skb just after the highest skb with SACKed
1461  * bit, valid only if sacked_out > 0 or when the caller has ensured
1462  * validity by itself.
1463  */
1464 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1465 {
1466         if (!tp->sacked_out)
1467                 return tp->snd_una;
1468 
1469         if (tp->highest_sack == NULL)
1470                 return tp->snd_nxt;
1471 
1472         return TCP_SKB_CB(tp->highest_sack)->seq;
1473 }
1474 
1475 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1476 {
1477         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1478                                                 tcp_write_queue_next(sk, skb);
1479 }
1480 
1481 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1482 {
1483         return tcp_sk(sk)->highest_sack;
1484 }
1485 
1486 static inline void tcp_highest_sack_reset(struct sock *sk)
1487 {
1488         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1489 }
1490 
1491 /* Called when old skb is about to be deleted (to be combined with new skb) */
1492 static inline void tcp_highest_sack_combine(struct sock *sk,
1493                                             struct sk_buff *old,
1494                                             struct sk_buff *new)
1495 {
1496         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1497                 tcp_sk(sk)->highest_sack = new;
1498 }
1499 
1500 /* Determines whether this is a thin stream (which may suffer from
1501  * increased latency). Used to trigger latency-reducing mechanisms.
1502  */
1503 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1504 {
1505         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1506 }
1507 
1508 /* /proc */
1509 enum tcp_seq_states {
1510         TCP_SEQ_STATE_LISTENING,
1511         TCP_SEQ_STATE_OPENREQ,
1512         TCP_SEQ_STATE_ESTABLISHED,
1513 };
1514 
1515 int tcp_seq_open(struct inode *inode, struct file *file);
1516 
1517 struct tcp_seq_afinfo {
1518         char                            *name;
1519         sa_family_t                     family;
1520         const struct file_operations    *seq_fops;
1521         struct seq_operations           seq_ops;
1522 };
1523 
1524 struct tcp_iter_state {
1525         struct seq_net_private  p;
1526         sa_family_t             family;
1527         enum tcp_seq_states     state;
1528         struct sock             *syn_wait_sk;
1529         int                     bucket, offset, sbucket, num;
1530         kuid_t                  uid;
1531         loff_t                  last_pos;
1532 };
1533 
1534 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1535 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1536 
1537 extern struct request_sock_ops tcp_request_sock_ops;
1538 extern struct request_sock_ops tcp6_request_sock_ops;
1539 
1540 void tcp_v4_destroy_sock(struct sock *sk);
1541 
1542 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1543                                 netdev_features_t features);
1544 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1545 int tcp_gro_complete(struct sk_buff *skb);
1546 
1547 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1548 
1549 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1550 {
1551         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1552 }
1553 
1554 static inline bool tcp_stream_memory_free(const struct sock *sk)
1555 {
1556         const struct tcp_sock *tp = tcp_sk(sk);
1557         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1558 
1559         return notsent_bytes < tcp_notsent_lowat(tp);
1560 }
1561 
1562 #ifdef CONFIG_PROC_FS
1563 int tcp4_proc_init(void);
1564 void tcp4_proc_exit(void);
1565 #endif
1566 
1567 /* TCP af-specific functions */
1568 struct tcp_sock_af_ops {
1569 #ifdef CONFIG_TCP_MD5SIG
1570         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1571                                                 struct sock *addr_sk);
1572         int                     (*calc_md5_hash) (char *location,
1573                                                   struct tcp_md5sig_key *md5,
1574                                                   const struct sock *sk,
1575                                                   const struct request_sock *req,
1576                                                   const struct sk_buff *skb);
1577         int                     (*md5_parse) (struct sock *sk,
1578                                               char __user *optval,
1579                                               int optlen);
1580 #endif
1581 };
1582 
1583 struct tcp_request_sock_ops {
1584 #ifdef CONFIG_TCP_MD5SIG
1585         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1586                                                 struct request_sock *req);
1587         int                     (*calc_md5_hash) (char *location,
1588                                                   struct tcp_md5sig_key *md5,
1589                                                   const struct sock *sk,
1590                                                   const struct request_sock *req,
1591                                                   const struct sk_buff *skb);
1592 #endif
1593 };
1594 
1595 int tcpv4_offload_init(void);
1596 
1597 void tcp_v4_init(void);
1598 void tcp_init(void);
1599 
1600 #endif  /* _TCP_H */
1601 

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