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Linux/include/net/tcp.h

  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              Definitions for the TCP module.
  7  *
  8  * Version:     @(#)tcp.h       1.0.5   05/23/93
  9  *
 10  * Authors:     Ross Biro
 11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  *
 13  *              This program is free software; you can redistribute it and/or
 14  *              modify it under the terms of the GNU General Public License
 15  *              as published by the Free Software Foundation; either version
 16  *              2 of the License, or (at your option) any later version.
 17  */
 18 #ifndef _TCP_H
 19 #define _TCP_H
 20 
 21 #define FASTRETRANS_DEBUG 1
 22 
 23 #include <linux/list.h>
 24 #include <linux/tcp.h>
 25 #include <linux/bug.h>
 26 #include <linux/slab.h>
 27 #include <linux/cache.h>
 28 #include <linux/percpu.h>
 29 #include <linux/skbuff.h>
 30 #include <linux/dmaengine.h>
 31 #include <linux/crypto.h>
 32 #include <linux/cryptohash.h>
 33 #include <linux/kref.h>
 34 #include <linux/ktime.h>
 35 
 36 #include <net/inet_connection_sock.h>
 37 #include <net/inet_timewait_sock.h>
 38 #include <net/inet_hashtables.h>
 39 #include <net/checksum.h>
 40 #include <net/request_sock.h>
 41 #include <net/sock.h>
 42 #include <net/snmp.h>
 43 #include <net/ip.h>
 44 #include <net/tcp_states.h>
 45 #include <net/inet_ecn.h>
 46 #include <net/dst.h>
 47 
 48 #include <linux/seq_file.h>
 49 #include <linux/memcontrol.h>
 50 
 51 extern struct inet_hashinfo tcp_hashinfo;
 52 
 53 extern struct percpu_counter tcp_orphan_count;
 54 void tcp_time_wait(struct sock *sk, int state, int timeo);
 55 
 56 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 57 #define MAX_TCP_OPTION_SPACE 40
 58 
 59 /* 
 60  * Never offer a window over 32767 without using window scaling. Some
 61  * poor stacks do signed 16bit maths! 
 62  */
 63 #define MAX_TCP_WINDOW          32767U
 64 
 65 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 66 #define TCP_MIN_MSS             88U
 67 
 68 /* The least MTU to use for probing */
 69 #define TCP_BASE_MSS            512
 70 
 71 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 72 #define TCP_FASTRETRANS_THRESH 3
 73 
 74 /* Maximal reordering. */
 75 #define TCP_MAX_REORDERING      127
 76 
 77 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 78 #define TCP_MAX_QUICKACKS       16U
 79 
 80 /* urg_data states */
 81 #define TCP_URG_VALID   0x0100
 82 #define TCP_URG_NOTYET  0x0200
 83 #define TCP_URG_READ    0x0400
 84 
 85 #define TCP_RETR1       3       /*
 86                                  * This is how many retries it does before it
 87                                  * tries to figure out if the gateway is
 88                                  * down. Minimal RFC value is 3; it corresponds
 89                                  * to ~3sec-8min depending on RTO.
 90                                  */
 91 
 92 #define TCP_RETR2       15      /*
 93                                  * This should take at least
 94                                  * 90 minutes to time out.
 95                                  * RFC1122 says that the limit is 100 sec.
 96                                  * 15 is ~13-30min depending on RTO.
 97                                  */
 98 
 99 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
100                                  * when active opening a connection.
101                                  * RFC1122 says the minimum retry MUST
102                                  * be at least 180secs.  Nevertheless
103                                  * this value is corresponding to
104                                  * 63secs of retransmission with the
105                                  * current initial RTO.
106                                  */
107 
108 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
109                                  * when passive opening a connection.
110                                  * This is corresponding to 31secs of
111                                  * retransmission with the current
112                                  * initial RTO.
113                                  */
114 
115 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
116                                   * state, about 60 seconds     */
117 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
118                                  /* BSD style FIN_WAIT2 deadlock breaker.
119                                   * It used to be 3min, new value is 60sec,
120                                   * to combine FIN-WAIT-2 timeout with
121                                   * TIME-WAIT timer.
122                                   */
123 
124 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
125 #if HZ >= 100
126 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
127 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
128 #else
129 #define TCP_DELACK_MIN  4U
130 #define TCP_ATO_MIN     4U
131 #endif
132 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
133 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
134 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
135 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
136                                                  * used as a fallback RTO for the
137                                                  * initial data transmission if no
138                                                  * valid RTT sample has been acquired,
139                                                  * most likely due to retrans in 3WHS.
140                                                  */
141 
142 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
143                                                          * for local resources.
144                                                          */
145 
146 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
147 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
148 #define TCP_KEEPALIVE_INTVL     (75*HZ)
149 
150 #define MAX_TCP_KEEPIDLE        32767
151 #define MAX_TCP_KEEPINTVL       32767
152 #define MAX_TCP_KEEPCNT         127
153 #define MAX_TCP_SYNCNT          127
154 
155 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
156 
157 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
158 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
159                                          * after this time. It should be equal
160                                          * (or greater than) TCP_TIMEWAIT_LEN
161                                          * to provide reliability equal to one
162                                          * provided by timewait state.
163                                          */
164 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
165                                          * timestamps. It must be less than
166                                          * minimal timewait lifetime.
167                                          */
168 /*
169  *      TCP option
170  */
171  
172 #define TCPOPT_NOP              1       /* Padding */
173 #define TCPOPT_EOL              0       /* End of options */
174 #define TCPOPT_MSS              2       /* Segment size negotiating */
175 #define TCPOPT_WINDOW           3       /* Window scaling */
176 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
177 #define TCPOPT_SACK             5       /* SACK Block */
178 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
179 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
180 #define TCPOPT_EXP              254     /* Experimental */
181 /* Magic number to be after the option value for sharing TCP
182  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
183  */
184 #define TCPOPT_FASTOPEN_MAGIC   0xF989
185 
186 /*
187  *     TCP option lengths
188  */
189 
190 #define TCPOLEN_MSS            4
191 #define TCPOLEN_WINDOW         3
192 #define TCPOLEN_SACK_PERM      2
193 #define TCPOLEN_TIMESTAMP      10
194 #define TCPOLEN_MD5SIG         18
195 #define TCPOLEN_EXP_FASTOPEN_BASE  4
196 
197 /* But this is what stacks really send out. */
198 #define TCPOLEN_TSTAMP_ALIGNED          12
199 #define TCPOLEN_WSCALE_ALIGNED          4
200 #define TCPOLEN_SACKPERM_ALIGNED        4
201 #define TCPOLEN_SACK_BASE               2
202 #define TCPOLEN_SACK_BASE_ALIGNED       4
203 #define TCPOLEN_SACK_PERBLOCK           8
204 #define TCPOLEN_MD5SIG_ALIGNED          20
205 #define TCPOLEN_MSS_ALIGNED             4
206 
207 /* Flags in tp->nonagle */
208 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
209 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
210 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
211 
212 /* TCP thin-stream limits */
213 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
214 
215 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
216 #define TCP_INIT_CWND           10
217 
218 /* Bit Flags for sysctl_tcp_fastopen */
219 #define TFO_CLIENT_ENABLE       1
220 #define TFO_SERVER_ENABLE       2
221 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
222 
223 /* Accept SYN data w/o any cookie option */
224 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
225 
226 /* Force enable TFO on all listeners, i.e., not requiring the
227  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
228  */
229 #define TFO_SERVER_WO_SOCKOPT1  0x400
230 #define TFO_SERVER_WO_SOCKOPT2  0x800
231 
232 extern struct inet_timewait_death_row tcp_death_row;
233 
234 /* sysctl variables for tcp */
235 extern int sysctl_tcp_timestamps;
236 extern int sysctl_tcp_window_scaling;
237 extern int sysctl_tcp_sack;
238 extern int sysctl_tcp_fin_timeout;
239 extern int sysctl_tcp_keepalive_time;
240 extern int sysctl_tcp_keepalive_probes;
241 extern int sysctl_tcp_keepalive_intvl;
242 extern int sysctl_tcp_syn_retries;
243 extern int sysctl_tcp_synack_retries;
244 extern int sysctl_tcp_retries1;
245 extern int sysctl_tcp_retries2;
246 extern int sysctl_tcp_orphan_retries;
247 extern int sysctl_tcp_syncookies;
248 extern int sysctl_tcp_fastopen;
249 extern int sysctl_tcp_retrans_collapse;
250 extern int sysctl_tcp_stdurg;
251 extern int sysctl_tcp_rfc1337;
252 extern int sysctl_tcp_abort_on_overflow;
253 extern int sysctl_tcp_max_orphans;
254 extern int sysctl_tcp_fack;
255 extern int sysctl_tcp_reordering;
256 extern int sysctl_tcp_dsack;
257 extern long sysctl_tcp_mem[3];
258 extern int sysctl_tcp_wmem[3];
259 extern int sysctl_tcp_rmem[3];
260 extern int sysctl_tcp_app_win;
261 extern int sysctl_tcp_adv_win_scale;
262 extern int sysctl_tcp_tw_reuse;
263 extern int sysctl_tcp_frto;
264 extern int sysctl_tcp_low_latency;
265 extern int sysctl_tcp_dma_copybreak;
266 extern int sysctl_tcp_nometrics_save;
267 extern int sysctl_tcp_moderate_rcvbuf;
268 extern int sysctl_tcp_tso_win_divisor;
269 extern int sysctl_tcp_mtu_probing;
270 extern int sysctl_tcp_base_mss;
271 extern int sysctl_tcp_workaround_signed_windows;
272 extern int sysctl_tcp_slow_start_after_idle;
273 extern int sysctl_tcp_thin_linear_timeouts;
274 extern int sysctl_tcp_thin_dupack;
275 extern int sysctl_tcp_early_retrans;
276 extern int sysctl_tcp_limit_output_bytes;
277 extern int sysctl_tcp_challenge_ack_limit;
278 extern unsigned int sysctl_tcp_notsent_lowat;
279 extern int sysctl_tcp_min_tso_segs;
280 extern int sysctl_tcp_autocorking;
281 
282 extern atomic_long_t tcp_memory_allocated;
283 extern struct percpu_counter tcp_sockets_allocated;
284 extern int tcp_memory_pressure;
285 
286 /*
287  * The next routines deal with comparing 32 bit unsigned ints
288  * and worry about wraparound (automatic with unsigned arithmetic).
289  */
290 
291 static inline bool before(__u32 seq1, __u32 seq2)
292 {
293         return (__s32)(seq1-seq2) < 0;
294 }
295 #define after(seq2, seq1)       before(seq1, seq2)
296 
297 /* is s2<=s1<=s3 ? */
298 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
299 {
300         return seq3 - seq2 >= seq1 - seq2;
301 }
302 
303 static inline bool tcp_out_of_memory(struct sock *sk)
304 {
305         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
306             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
307                 return true;
308         return false;
309 }
310 
311 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
312 {
313         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
314         int orphans = percpu_counter_read_positive(ocp);
315 
316         if (orphans << shift > sysctl_tcp_max_orphans) {
317                 orphans = percpu_counter_sum_positive(ocp);
318                 if (orphans << shift > sysctl_tcp_max_orphans)
319                         return true;
320         }
321         return false;
322 }
323 
324 bool tcp_check_oom(struct sock *sk, int shift);
325 
326 /* syncookies: remember time of last synqueue overflow */
327 static inline void tcp_synq_overflow(struct sock *sk)
328 {
329         tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
330 }
331 
332 /* syncookies: no recent synqueue overflow on this listening socket? */
333 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
334 {
335         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
336         return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
337 }
338 
339 extern struct proto tcp_prot;
340 
341 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
342 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
343 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
344 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
345 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
346 
347 void tcp_tasklet_init(void);
348 
349 void tcp_v4_err(struct sk_buff *skb, u32);
350 
351 void tcp_shutdown(struct sock *sk, int how);
352 
353 void tcp_v4_early_demux(struct sk_buff *skb);
354 int tcp_v4_rcv(struct sk_buff *skb);
355 
356 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
357 int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
358                 size_t size);
359 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
360                  int flags);
361 void tcp_release_cb(struct sock *sk);
362 void tcp_wfree(struct sk_buff *skb);
363 void tcp_write_timer_handler(struct sock *sk);
364 void tcp_delack_timer_handler(struct sock *sk);
365 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
366 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
367                           const struct tcphdr *th, unsigned int len);
368 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
369                          const struct tcphdr *th, unsigned int len);
370 void tcp_rcv_space_adjust(struct sock *sk);
371 void tcp_cleanup_rbuf(struct sock *sk, int copied);
372 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
373 void tcp_twsk_destructor(struct sock *sk);
374 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
375                         struct pipe_inode_info *pipe, size_t len,
376                         unsigned int flags);
377 
378 static inline void tcp_dec_quickack_mode(struct sock *sk,
379                                          const unsigned int pkts)
380 {
381         struct inet_connection_sock *icsk = inet_csk(sk);
382 
383         if (icsk->icsk_ack.quick) {
384                 if (pkts >= icsk->icsk_ack.quick) {
385                         icsk->icsk_ack.quick = 0;
386                         /* Leaving quickack mode we deflate ATO. */
387                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
388                 } else
389                         icsk->icsk_ack.quick -= pkts;
390         }
391 }
392 
393 #define TCP_ECN_OK              1
394 #define TCP_ECN_QUEUE_CWR       2
395 #define TCP_ECN_DEMAND_CWR      4
396 #define TCP_ECN_SEEN            8
397 
398 enum tcp_tw_status {
399         TCP_TW_SUCCESS = 0,
400         TCP_TW_RST = 1,
401         TCP_TW_ACK = 2,
402         TCP_TW_SYN = 3
403 };
404 
405 
406 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
407                                               struct sk_buff *skb,
408                                               const struct tcphdr *th);
409 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
410                            struct request_sock *req, struct request_sock **prev,
411                            bool fastopen);
412 int tcp_child_process(struct sock *parent, struct sock *child,
413                       struct sk_buff *skb);
414 void tcp_enter_loss(struct sock *sk, int how);
415 void tcp_clear_retrans(struct tcp_sock *tp);
416 void tcp_update_metrics(struct sock *sk);
417 void tcp_init_metrics(struct sock *sk);
418 void tcp_metrics_init(void);
419 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
420                         bool paws_check);
421 bool tcp_remember_stamp(struct sock *sk);
422 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
423 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
424 void tcp_disable_fack(struct tcp_sock *tp);
425 void tcp_close(struct sock *sk, long timeout);
426 void tcp_init_sock(struct sock *sk);
427 unsigned int tcp_poll(struct file *file, struct socket *sock,
428                       struct poll_table_struct *wait);
429 int tcp_getsockopt(struct sock *sk, int level, int optname,
430                    char __user *optval, int __user *optlen);
431 int tcp_setsockopt(struct sock *sk, int level, int optname,
432                    char __user *optval, unsigned int optlen);
433 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
434                           char __user *optval, int __user *optlen);
435 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
436                           char __user *optval, unsigned int optlen);
437 void tcp_set_keepalive(struct sock *sk, int val);
438 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
439 int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
440                 size_t len, int nonblock, int flags, int *addr_len);
441 void tcp_parse_options(const struct sk_buff *skb,
442                        struct tcp_options_received *opt_rx,
443                        int estab, struct tcp_fastopen_cookie *foc);
444 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
445 
446 /*
447  *      TCP v4 functions exported for the inet6 API
448  */
449 
450 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
451 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
452 struct sock *tcp_create_openreq_child(struct sock *sk,
453                                       struct request_sock *req,
454                                       struct sk_buff *skb);
455 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
456                                   struct request_sock *req,
457                                   struct dst_entry *dst);
458 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
459 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
460 int tcp_connect(struct sock *sk);
461 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
462                                 struct request_sock *req,
463                                 struct tcp_fastopen_cookie *foc);
464 int tcp_disconnect(struct sock *sk, int flags);
465 
466 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
467 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
468 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
469 
470 /* From syncookies.c */
471 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
472                       u32 cookie);
473 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
474                              struct ip_options *opt);
475 #ifdef CONFIG_SYN_COOKIES
476 
477 /* Syncookies use a monotonic timer which increments every 60 seconds.
478  * This counter is used both as a hash input and partially encoded into
479  * the cookie value.  A cookie is only validated further if the delta
480  * between the current counter value and the encoded one is less than this,
481  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
482  * the counter advances immediately after a cookie is generated).
483  */
484 #define MAX_SYNCOOKIE_AGE 2
485 
486 static inline u32 tcp_cookie_time(void)
487 {
488         u64 val = get_jiffies_64();
489 
490         do_div(val, 60 * HZ);
491         return val;
492 }
493 
494 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
495                               u16 *mssp);
496 __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mss);
497 #else
498 static inline __u32 cookie_v4_init_sequence(struct sock *sk,
499                                             struct sk_buff *skb,
500                                             __u16 *mss)
501 {
502         return 0;
503 }
504 #endif
505 
506 __u32 cookie_init_timestamp(struct request_sock *req);
507 bool cookie_check_timestamp(struct tcp_options_received *opt, struct net *net,
508                             bool *ecn_ok);
509 
510 /* From net/ipv6/syncookies.c */
511 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
512                       u32 cookie);
513 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
514 #ifdef CONFIG_SYN_COOKIES
515 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
516                               const struct tcphdr *th, u16 *mssp);
517 __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
518                               __u16 *mss);
519 #else
520 static inline __u32 cookie_v6_init_sequence(struct sock *sk,
521                                             struct sk_buff *skb,
522                                             __u16 *mss)
523 {
524         return 0;
525 }
526 #endif
527 /* tcp_output.c */
528 
529 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
530                                int nonagle);
531 bool tcp_may_send_now(struct sock *sk);
532 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
533 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
534 void tcp_retransmit_timer(struct sock *sk);
535 void tcp_xmit_retransmit_queue(struct sock *);
536 void tcp_simple_retransmit(struct sock *);
537 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
538 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
539 
540 void tcp_send_probe0(struct sock *);
541 void tcp_send_partial(struct sock *);
542 int tcp_write_wakeup(struct sock *);
543 void tcp_send_fin(struct sock *sk);
544 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
545 int tcp_send_synack(struct sock *);
546 bool tcp_syn_flood_action(struct sock *sk, const struct sk_buff *skb,
547                           const char *proto);
548 void tcp_push_one(struct sock *, unsigned int mss_now);
549 void tcp_send_ack(struct sock *sk);
550 void tcp_send_delayed_ack(struct sock *sk);
551 void tcp_send_loss_probe(struct sock *sk);
552 bool tcp_schedule_loss_probe(struct sock *sk);
553 
554 /* tcp_input.c */
555 void tcp_resume_early_retransmit(struct sock *sk);
556 void tcp_rearm_rto(struct sock *sk);
557 void tcp_reset(struct sock *sk);
558 
559 /* tcp_timer.c */
560 void tcp_init_xmit_timers(struct sock *);
561 static inline void tcp_clear_xmit_timers(struct sock *sk)
562 {
563         inet_csk_clear_xmit_timers(sk);
564 }
565 
566 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
567 unsigned int tcp_current_mss(struct sock *sk);
568 
569 /* Bound MSS / TSO packet size with the half of the window */
570 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
571 {
572         int cutoff;
573 
574         /* When peer uses tiny windows, there is no use in packetizing
575          * to sub-MSS pieces for the sake of SWS or making sure there
576          * are enough packets in the pipe for fast recovery.
577          *
578          * On the other hand, for extremely large MSS devices, handling
579          * smaller than MSS windows in this way does make sense.
580          */
581         if (tp->max_window >= 512)
582                 cutoff = (tp->max_window >> 1);
583         else
584                 cutoff = tp->max_window;
585 
586         if (cutoff && pktsize > cutoff)
587                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
588         else
589                 return pktsize;
590 }
591 
592 /* tcp.c */
593 void tcp_get_info(const struct sock *, struct tcp_info *);
594 
595 /* Read 'sendfile()'-style from a TCP socket */
596 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
597                                 unsigned int, size_t);
598 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
599                   sk_read_actor_t recv_actor);
600 
601 void tcp_initialize_rcv_mss(struct sock *sk);
602 
603 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
604 int tcp_mss_to_mtu(struct sock *sk, int mss);
605 void tcp_mtup_init(struct sock *sk);
606 void tcp_init_buffer_space(struct sock *sk);
607 
608 static inline void tcp_bound_rto(const struct sock *sk)
609 {
610         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
611                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
612 }
613 
614 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
615 {
616         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
617 }
618 
619 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
620 {
621         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
622                                ntohl(TCP_FLAG_ACK) |
623                                snd_wnd);
624 }
625 
626 static inline void tcp_fast_path_on(struct tcp_sock *tp)
627 {
628         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
629 }
630 
631 static inline void tcp_fast_path_check(struct sock *sk)
632 {
633         struct tcp_sock *tp = tcp_sk(sk);
634 
635         if (skb_queue_empty(&tp->out_of_order_queue) &&
636             tp->rcv_wnd &&
637             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
638             !tp->urg_data)
639                 tcp_fast_path_on(tp);
640 }
641 
642 /* Compute the actual rto_min value */
643 static inline u32 tcp_rto_min(struct sock *sk)
644 {
645         const struct dst_entry *dst = __sk_dst_get(sk);
646         u32 rto_min = TCP_RTO_MIN;
647 
648         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
649                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
650         return rto_min;
651 }
652 
653 static inline u32 tcp_rto_min_us(struct sock *sk)
654 {
655         return jiffies_to_usecs(tcp_rto_min(sk));
656 }
657 
658 /* Compute the actual receive window we are currently advertising.
659  * Rcv_nxt can be after the window if our peer push more data
660  * than the offered window.
661  */
662 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
663 {
664         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
665 
666         if (win < 0)
667                 win = 0;
668         return (u32) win;
669 }
670 
671 /* Choose a new window, without checks for shrinking, and without
672  * scaling applied to the result.  The caller does these things
673  * if necessary.  This is a "raw" window selection.
674  */
675 u32 __tcp_select_window(struct sock *sk);
676 
677 void tcp_send_window_probe(struct sock *sk);
678 
679 /* TCP timestamps are only 32-bits, this causes a slight
680  * complication on 64-bit systems since we store a snapshot
681  * of jiffies in the buffer control blocks below.  We decided
682  * to use only the low 32-bits of jiffies and hide the ugly
683  * casts with the following macro.
684  */
685 #define tcp_time_stamp          ((__u32)(jiffies))
686 
687 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
688 
689 #define TCPHDR_FIN 0x01
690 #define TCPHDR_SYN 0x02
691 #define TCPHDR_RST 0x04
692 #define TCPHDR_PSH 0x08
693 #define TCPHDR_ACK 0x10
694 #define TCPHDR_URG 0x20
695 #define TCPHDR_ECE 0x40
696 #define TCPHDR_CWR 0x80
697 
698 /* This is what the send packet queuing engine uses to pass
699  * TCP per-packet control information to the transmission code.
700  * We also store the host-order sequence numbers in here too.
701  * This is 44 bytes if IPV6 is enabled.
702  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
703  */
704 struct tcp_skb_cb {
705         union {
706                 struct inet_skb_parm    h4;
707 #if IS_ENABLED(CONFIG_IPV6)
708                 struct inet6_skb_parm   h6;
709 #endif
710         } header;       /* For incoming frames          */
711         __u32           seq;            /* Starting sequence number     */
712         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
713         __u32           when;           /* used to compute rtt's        */
714         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
715 
716         __u8            sacked;         /* State flags for SACK/FACK.   */
717 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
718 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
719 #define TCPCB_LOST              0x04    /* SKB is lost                  */
720 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
721 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
722 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
723 
724         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
725         /* 1 byte hole */
726         __u32           ack_seq;        /* Sequence number ACK'd        */
727 };
728 
729 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
730 
731 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
732  *
733  * If we receive a SYN packet with these bits set, it means a network is
734  * playing bad games with TOS bits. In order to avoid possible false congestion
735  * notifications, we disable TCP ECN negociation.
736  */
737 static inline void
738 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
739                 struct net *net)
740 {
741         const struct tcphdr *th = tcp_hdr(skb);
742 
743         if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr &&
744             INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
745                 inet_rsk(req)->ecn_ok = 1;
746 }
747 
748 /* Due to TSO, an SKB can be composed of multiple actual
749  * packets.  To keep these tracked properly, we use this.
750  */
751 static inline int tcp_skb_pcount(const struct sk_buff *skb)
752 {
753         return skb_shinfo(skb)->gso_segs;
754 }
755 
756 /* This is valid iff tcp_skb_pcount() > 1. */
757 static inline int tcp_skb_mss(const struct sk_buff *skb)
758 {
759         return skb_shinfo(skb)->gso_size;
760 }
761 
762 /* Events passed to congestion control interface */
763 enum tcp_ca_event {
764         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
765         CA_EVENT_CWND_RESTART,  /* congestion window restart */
766         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
767         CA_EVENT_LOSS,          /* loss timeout */
768         CA_EVENT_FAST_ACK,      /* in sequence ack */
769         CA_EVENT_SLOW_ACK,      /* other ack */
770 };
771 
772 /*
773  * Interface for adding new TCP congestion control handlers
774  */
775 #define TCP_CA_NAME_MAX 16
776 #define TCP_CA_MAX      128
777 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
778 
779 #define TCP_CONG_NON_RESTRICTED 0x1
780 
781 struct tcp_congestion_ops {
782         struct list_head        list;
783         unsigned long flags;
784 
785         /* initialize private data (optional) */
786         void (*init)(struct sock *sk);
787         /* cleanup private data  (optional) */
788         void (*release)(struct sock *sk);
789 
790         /* return slow start threshold (required) */
791         u32 (*ssthresh)(struct sock *sk);
792         /* do new cwnd calculation (required) */
793         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
794         /* call before changing ca_state (optional) */
795         void (*set_state)(struct sock *sk, u8 new_state);
796         /* call when cwnd event occurs (optional) */
797         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
798         /* new value of cwnd after loss (optional) */
799         u32  (*undo_cwnd)(struct sock *sk);
800         /* hook for packet ack accounting (optional) */
801         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
802         /* get info for inet_diag (optional) */
803         void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
804 
805         char            name[TCP_CA_NAME_MAX];
806         struct module   *owner;
807 };
808 
809 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
810 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
811 
812 void tcp_init_congestion_control(struct sock *sk);
813 void tcp_cleanup_congestion_control(struct sock *sk);
814 int tcp_set_default_congestion_control(const char *name);
815 void tcp_get_default_congestion_control(char *name);
816 void tcp_get_available_congestion_control(char *buf, size_t len);
817 void tcp_get_allowed_congestion_control(char *buf, size_t len);
818 int tcp_set_allowed_congestion_control(char *allowed);
819 int tcp_set_congestion_control(struct sock *sk, const char *name);
820 int tcp_slow_start(struct tcp_sock *tp, u32 acked);
821 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
822 
823 extern struct tcp_congestion_ops tcp_init_congestion_ops;
824 u32 tcp_reno_ssthresh(struct sock *sk);
825 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
826 extern struct tcp_congestion_ops tcp_reno;
827 
828 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
829 {
830         struct inet_connection_sock *icsk = inet_csk(sk);
831 
832         if (icsk->icsk_ca_ops->set_state)
833                 icsk->icsk_ca_ops->set_state(sk, ca_state);
834         icsk->icsk_ca_state = ca_state;
835 }
836 
837 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
838 {
839         const struct inet_connection_sock *icsk = inet_csk(sk);
840 
841         if (icsk->icsk_ca_ops->cwnd_event)
842                 icsk->icsk_ca_ops->cwnd_event(sk, event);
843 }
844 
845 /* These functions determine how the current flow behaves in respect of SACK
846  * handling. SACK is negotiated with the peer, and therefore it can vary
847  * between different flows.
848  *
849  * tcp_is_sack - SACK enabled
850  * tcp_is_reno - No SACK
851  * tcp_is_fack - FACK enabled, implies SACK enabled
852  */
853 static inline int tcp_is_sack(const struct tcp_sock *tp)
854 {
855         return tp->rx_opt.sack_ok;
856 }
857 
858 static inline bool tcp_is_reno(const struct tcp_sock *tp)
859 {
860         return !tcp_is_sack(tp);
861 }
862 
863 static inline bool tcp_is_fack(const struct tcp_sock *tp)
864 {
865         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
866 }
867 
868 static inline void tcp_enable_fack(struct tcp_sock *tp)
869 {
870         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
871 }
872 
873 /* TCP early-retransmit (ER) is similar to but more conservative than
874  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
875  */
876 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
877 {
878         tp->do_early_retrans = sysctl_tcp_early_retrans &&
879                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
880                 sysctl_tcp_reordering == 3;
881 }
882 
883 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
884 {
885         tp->do_early_retrans = 0;
886 }
887 
888 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
889 {
890         return tp->sacked_out + tp->lost_out;
891 }
892 
893 /* This determines how many packets are "in the network" to the best
894  * of our knowledge.  In many cases it is conservative, but where
895  * detailed information is available from the receiver (via SACK
896  * blocks etc.) we can make more aggressive calculations.
897  *
898  * Use this for decisions involving congestion control, use just
899  * tp->packets_out to determine if the send queue is empty or not.
900  *
901  * Read this equation as:
902  *
903  *      "Packets sent once on transmission queue" MINUS
904  *      "Packets left network, but not honestly ACKed yet" PLUS
905  *      "Packets fast retransmitted"
906  */
907 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
908 {
909         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
910 }
911 
912 #define TCP_INFINITE_SSTHRESH   0x7fffffff
913 
914 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
915 {
916         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
917 }
918 
919 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
920 {
921         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
922                (1 << inet_csk(sk)->icsk_ca_state);
923 }
924 
925 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
926  * The exception is cwnd reduction phase, when cwnd is decreasing towards
927  * ssthresh.
928  */
929 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
930 {
931         const struct tcp_sock *tp = tcp_sk(sk);
932 
933         if (tcp_in_cwnd_reduction(sk))
934                 return tp->snd_ssthresh;
935         else
936                 return max(tp->snd_ssthresh,
937                            ((tp->snd_cwnd >> 1) +
938                             (tp->snd_cwnd >> 2)));
939 }
940 
941 /* Use define here intentionally to get WARN_ON location shown at the caller */
942 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
943 
944 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
945 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
946 
947 /* The maximum number of MSS of available cwnd for which TSO defers
948  * sending if not using sysctl_tcp_tso_win_divisor.
949  */
950 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
951 {
952         return 3;
953 }
954 
955 /* Slow start with delack produces 3 packets of burst, so that
956  * it is safe "de facto".  This will be the default - same as
957  * the default reordering threshold - but if reordering increases,
958  * we must be able to allow cwnd to burst at least this much in order
959  * to not pull it back when holes are filled.
960  */
961 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
962 {
963         return tp->reordering;
964 }
965 
966 /* Returns end sequence number of the receiver's advertised window */
967 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
968 {
969         return tp->snd_una + tp->snd_wnd;
970 }
971 
972 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
973  * flexible approach. The RFC suggests cwnd should not be raised unless
974  * it was fully used previously. And that's exactly what we do in
975  * congestion avoidance mode. But in slow start we allow cwnd to grow
976  * as long as the application has used half the cwnd.
977  * Example :
978  *    cwnd is 10 (IW10), but application sends 9 frames.
979  *    We allow cwnd to reach 18 when all frames are ACKed.
980  * This check is safe because it's as aggressive as slow start which already
981  * risks 100% overshoot. The advantage is that we discourage application to
982  * either send more filler packets or data to artificially blow up the cwnd
983  * usage, and allow application-limited process to probe bw more aggressively.
984  */
985 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
986 {
987         const struct tcp_sock *tp = tcp_sk(sk);
988 
989         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
990         if (tp->snd_cwnd <= tp->snd_ssthresh)
991                 return tp->snd_cwnd < 2 * tp->max_packets_out;
992 
993         return tp->is_cwnd_limited;
994 }
995 
996 static inline void tcp_check_probe_timer(struct sock *sk)
997 {
998         const struct tcp_sock *tp = tcp_sk(sk);
999         const struct inet_connection_sock *icsk = inet_csk(sk);
1000 
1001         if (!tp->packets_out && !icsk->icsk_pending)
1002                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1003                                           icsk->icsk_rto, TCP_RTO_MAX);
1004 }
1005 
1006 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1007 {
1008         tp->snd_wl1 = seq;
1009 }
1010 
1011 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1012 {
1013         tp->snd_wl1 = seq;
1014 }
1015 
1016 /*
1017  * Calculate(/check) TCP checksum
1018  */
1019 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1020                                    __be32 daddr, __wsum base)
1021 {
1022         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1023 }
1024 
1025 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1026 {
1027         return __skb_checksum_complete(skb);
1028 }
1029 
1030 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1031 {
1032         return !skb_csum_unnecessary(skb) &&
1033                 __tcp_checksum_complete(skb);
1034 }
1035 
1036 /* Prequeue for VJ style copy to user, combined with checksumming. */
1037 
1038 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1039 {
1040         tp->ucopy.task = NULL;
1041         tp->ucopy.len = 0;
1042         tp->ucopy.memory = 0;
1043         skb_queue_head_init(&tp->ucopy.prequeue);
1044 #ifdef CONFIG_NET_DMA
1045         tp->ucopy.dma_chan = NULL;
1046         tp->ucopy.wakeup = 0;
1047         tp->ucopy.pinned_list = NULL;
1048         tp->ucopy.dma_cookie = 0;
1049 #endif
1050 }
1051 
1052 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1053 
1054 #undef STATE_TRACE
1055 
1056 #ifdef STATE_TRACE
1057 static const char *statename[]={
1058         "Unused","Established","Syn Sent","Syn Recv",
1059         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1060         "Close Wait","Last ACK","Listen","Closing"
1061 };
1062 #endif
1063 void tcp_set_state(struct sock *sk, int state);
1064 
1065 void tcp_done(struct sock *sk);
1066 
1067 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1068 {
1069         rx_opt->dsack = 0;
1070         rx_opt->num_sacks = 0;
1071 }
1072 
1073 u32 tcp_default_init_rwnd(u32 mss);
1074 
1075 /* Determine a window scaling and initial window to offer. */
1076 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1077                                __u32 *window_clamp, int wscale_ok,
1078                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1079 
1080 static inline int tcp_win_from_space(int space)
1081 {
1082         return sysctl_tcp_adv_win_scale<=0 ?
1083                 (space>>(-sysctl_tcp_adv_win_scale)) :
1084                 space - (space>>sysctl_tcp_adv_win_scale);
1085 }
1086 
1087 /* Note: caller must be prepared to deal with negative returns */ 
1088 static inline int tcp_space(const struct sock *sk)
1089 {
1090         return tcp_win_from_space(sk->sk_rcvbuf -
1091                                   atomic_read(&sk->sk_rmem_alloc));
1092 } 
1093 
1094 static inline int tcp_full_space(const struct sock *sk)
1095 {
1096         return tcp_win_from_space(sk->sk_rcvbuf); 
1097 }
1098 
1099 static inline void tcp_openreq_init(struct request_sock *req,
1100                                     struct tcp_options_received *rx_opt,
1101                                     struct sk_buff *skb)
1102 {
1103         struct inet_request_sock *ireq = inet_rsk(req);
1104 
1105         req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
1106         req->cookie_ts = 0;
1107         tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1108         tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1109         tcp_rsk(req)->snt_synack = 0;
1110         req->mss = rx_opt->mss_clamp;
1111         req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1112         ireq->tstamp_ok = rx_opt->tstamp_ok;
1113         ireq->sack_ok = rx_opt->sack_ok;
1114         ireq->snd_wscale = rx_opt->snd_wscale;
1115         ireq->wscale_ok = rx_opt->wscale_ok;
1116         ireq->acked = 0;
1117         ireq->ecn_ok = 0;
1118         ireq->ir_rmt_port = tcp_hdr(skb)->source;
1119         ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
1120 }
1121 
1122 extern void tcp_openreq_init_rwin(struct request_sock *req,
1123                                   struct sock *sk, struct dst_entry *dst);
1124 
1125 void tcp_enter_memory_pressure(struct sock *sk);
1126 
1127 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1128 {
1129         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1130 }
1131 
1132 static inline int keepalive_time_when(const struct tcp_sock *tp)
1133 {
1134         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1135 }
1136 
1137 static inline int keepalive_probes(const struct tcp_sock *tp)
1138 {
1139         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1140 }
1141 
1142 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1143 {
1144         const struct inet_connection_sock *icsk = &tp->inet_conn;
1145 
1146         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1147                           tcp_time_stamp - tp->rcv_tstamp);
1148 }
1149 
1150 static inline int tcp_fin_time(const struct sock *sk)
1151 {
1152         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1153         const int rto = inet_csk(sk)->icsk_rto;
1154 
1155         if (fin_timeout < (rto << 2) - (rto >> 1))
1156                 fin_timeout = (rto << 2) - (rto >> 1);
1157 
1158         return fin_timeout;
1159 }
1160 
1161 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1162                                   int paws_win)
1163 {
1164         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1165                 return true;
1166         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1167                 return true;
1168         /*
1169          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1170          * then following tcp messages have valid values. Ignore 0 value,
1171          * or else 'negative' tsval might forbid us to accept their packets.
1172          */
1173         if (!rx_opt->ts_recent)
1174                 return true;
1175         return false;
1176 }
1177 
1178 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1179                                    int rst)
1180 {
1181         if (tcp_paws_check(rx_opt, 0))
1182                 return false;
1183 
1184         /* RST segments are not recommended to carry timestamp,
1185            and, if they do, it is recommended to ignore PAWS because
1186            "their cleanup function should take precedence over timestamps."
1187            Certainly, it is mistake. It is necessary to understand the reasons
1188            of this constraint to relax it: if peer reboots, clock may go
1189            out-of-sync and half-open connections will not be reset.
1190            Actually, the problem would be not existing if all
1191            the implementations followed draft about maintaining clock
1192            via reboots. Linux-2.2 DOES NOT!
1193 
1194            However, we can relax time bounds for RST segments to MSL.
1195          */
1196         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1197                 return false;
1198         return true;
1199 }
1200 
1201 static inline void tcp_mib_init(struct net *net)
1202 {
1203         /* See RFC 2012 */
1204         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1205         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1206         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1207         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1208 }
1209 
1210 /* from STCP */
1211 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1212 {
1213         tp->lost_skb_hint = NULL;
1214 }
1215 
1216 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1217 {
1218         tcp_clear_retrans_hints_partial(tp);
1219         tp->retransmit_skb_hint = NULL;
1220 }
1221 
1222 /* MD5 Signature */
1223 struct crypto_hash;
1224 
1225 union tcp_md5_addr {
1226         struct in_addr  a4;
1227 #if IS_ENABLED(CONFIG_IPV6)
1228         struct in6_addr a6;
1229 #endif
1230 };
1231 
1232 /* - key database */
1233 struct tcp_md5sig_key {
1234         struct hlist_node       node;
1235         u8                      keylen;
1236         u8                      family; /* AF_INET or AF_INET6 */
1237         union tcp_md5_addr      addr;
1238         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1239         struct rcu_head         rcu;
1240 };
1241 
1242 /* - sock block */
1243 struct tcp_md5sig_info {
1244         struct hlist_head       head;
1245         struct rcu_head         rcu;
1246 };
1247 
1248 /* - pseudo header */
1249 struct tcp4_pseudohdr {
1250         __be32          saddr;
1251         __be32          daddr;
1252         __u8            pad;
1253         __u8            protocol;
1254         __be16          len;
1255 };
1256 
1257 struct tcp6_pseudohdr {
1258         struct in6_addr saddr;
1259         struct in6_addr daddr;
1260         __be32          len;
1261         __be32          protocol;       /* including padding */
1262 };
1263 
1264 union tcp_md5sum_block {
1265         struct tcp4_pseudohdr ip4;
1266 #if IS_ENABLED(CONFIG_IPV6)
1267         struct tcp6_pseudohdr ip6;
1268 #endif
1269 };
1270 
1271 /* - pool: digest algorithm, hash description and scratch buffer */
1272 struct tcp_md5sig_pool {
1273         struct hash_desc        md5_desc;
1274         union tcp_md5sum_block  md5_blk;
1275 };
1276 
1277 /* - functions */
1278 int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1279                         const struct sock *sk, const struct request_sock *req,
1280                         const struct sk_buff *skb);
1281 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1282                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1283 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1284                    int family);
1285 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1286                                          struct sock *addr_sk);
1287 
1288 #ifdef CONFIG_TCP_MD5SIG
1289 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1290                                          const union tcp_md5_addr *addr,
1291                                          int family);
1292 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1293 #else
1294 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1295                                          const union tcp_md5_addr *addr,
1296                                          int family)
1297 {
1298         return NULL;
1299 }
1300 #define tcp_twsk_md5_key(twsk)  NULL
1301 #endif
1302 
1303 bool tcp_alloc_md5sig_pool(void);
1304 
1305 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1306 static inline void tcp_put_md5sig_pool(void)
1307 {
1308         local_bh_enable();
1309 }
1310 
1311 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1312 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1313                           unsigned int header_len);
1314 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1315                      const struct tcp_md5sig_key *key);
1316 
1317 /* From tcp_fastopen.c */
1318 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1319                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1320                             unsigned long *last_syn_loss);
1321 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1322                             struct tcp_fastopen_cookie *cookie, bool syn_lost);
1323 struct tcp_fastopen_request {
1324         /* Fast Open cookie. Size 0 means a cookie request */
1325         struct tcp_fastopen_cookie      cookie;
1326         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1327         size_t                          size;
1328         int                             copied; /* queued in tcp_connect() */
1329 };
1330 void tcp_free_fastopen_req(struct tcp_sock *tp);
1331 
1332 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1333 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1334 bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1335                       struct request_sock *req,
1336                       struct tcp_fastopen_cookie *foc,
1337                       struct dst_entry *dst);
1338 void tcp_fastopen_init_key_once(bool publish);
1339 #define TCP_FASTOPEN_KEY_LENGTH 16
1340 
1341 /* Fastopen key context */
1342 struct tcp_fastopen_context {
1343         struct crypto_cipher    *tfm;
1344         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1345         struct rcu_head         rcu;
1346 };
1347 
1348 /* write queue abstraction */
1349 static inline void tcp_write_queue_purge(struct sock *sk)
1350 {
1351         struct sk_buff *skb;
1352 
1353         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1354                 sk_wmem_free_skb(sk, skb);
1355         sk_mem_reclaim(sk);
1356         tcp_clear_all_retrans_hints(tcp_sk(sk));
1357 }
1358 
1359 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1360 {
1361         return skb_peek(&sk->sk_write_queue);
1362 }
1363 
1364 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1365 {
1366         return skb_peek_tail(&sk->sk_write_queue);
1367 }
1368 
1369 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1370                                                    const struct sk_buff *skb)
1371 {
1372         return skb_queue_next(&sk->sk_write_queue, skb);
1373 }
1374 
1375 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1376                                                    const struct sk_buff *skb)
1377 {
1378         return skb_queue_prev(&sk->sk_write_queue, skb);
1379 }
1380 
1381 #define tcp_for_write_queue(skb, sk)                                    \
1382         skb_queue_walk(&(sk)->sk_write_queue, skb)
1383 
1384 #define tcp_for_write_queue_from(skb, sk)                               \
1385         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1386 
1387 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1388         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1389 
1390 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1391 {
1392         return sk->sk_send_head;
1393 }
1394 
1395 static inline bool tcp_skb_is_last(const struct sock *sk,
1396                                    const struct sk_buff *skb)
1397 {
1398         return skb_queue_is_last(&sk->sk_write_queue, skb);
1399 }
1400 
1401 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1402 {
1403         if (tcp_skb_is_last(sk, skb))
1404                 sk->sk_send_head = NULL;
1405         else
1406                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1407 }
1408 
1409 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1410 {
1411         if (sk->sk_send_head == skb_unlinked)
1412                 sk->sk_send_head = NULL;
1413 }
1414 
1415 static inline void tcp_init_send_head(struct sock *sk)
1416 {
1417         sk->sk_send_head = NULL;
1418 }
1419 
1420 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1421 {
1422         __skb_queue_tail(&sk->sk_write_queue, skb);
1423 }
1424 
1425 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1426 {
1427         __tcp_add_write_queue_tail(sk, skb);
1428 
1429         /* Queue it, remembering where we must start sending. */
1430         if (sk->sk_send_head == NULL) {
1431                 sk->sk_send_head = skb;
1432 
1433                 if (tcp_sk(sk)->highest_sack == NULL)
1434                         tcp_sk(sk)->highest_sack = skb;
1435         }
1436 }
1437 
1438 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1439 {
1440         __skb_queue_head(&sk->sk_write_queue, skb);
1441 }
1442 
1443 /* Insert buff after skb on the write queue of sk.  */
1444 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1445                                                 struct sk_buff *buff,
1446                                                 struct sock *sk)
1447 {
1448         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1449 }
1450 
1451 /* Insert new before skb on the write queue of sk.  */
1452 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1453                                                   struct sk_buff *skb,
1454                                                   struct sock *sk)
1455 {
1456         __skb_queue_before(&sk->sk_write_queue, skb, new);
1457 
1458         if (sk->sk_send_head == skb)
1459                 sk->sk_send_head = new;
1460 }
1461 
1462 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1463 {
1464         __skb_unlink(skb, &sk->sk_write_queue);
1465 }
1466 
1467 static inline bool tcp_write_queue_empty(struct sock *sk)
1468 {
1469         return skb_queue_empty(&sk->sk_write_queue);
1470 }
1471 
1472 static inline void tcp_push_pending_frames(struct sock *sk)
1473 {
1474         if (tcp_send_head(sk)) {
1475                 struct tcp_sock *tp = tcp_sk(sk);
1476 
1477                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1478         }
1479 }
1480 
1481 /* Start sequence of the skb just after the highest skb with SACKed
1482  * bit, valid only if sacked_out > 0 or when the caller has ensured
1483  * validity by itself.
1484  */
1485 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1486 {
1487         if (!tp->sacked_out)
1488                 return tp->snd_una;
1489 
1490         if (tp->highest_sack == NULL)
1491                 return tp->snd_nxt;
1492 
1493         return TCP_SKB_CB(tp->highest_sack)->seq;
1494 }
1495 
1496 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1497 {
1498         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1499                                                 tcp_write_queue_next(sk, skb);
1500 }
1501 
1502 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1503 {
1504         return tcp_sk(sk)->highest_sack;
1505 }
1506 
1507 static inline void tcp_highest_sack_reset(struct sock *sk)
1508 {
1509         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1510 }
1511 
1512 /* Called when old skb is about to be deleted (to be combined with new skb) */
1513 static inline void tcp_highest_sack_combine(struct sock *sk,
1514                                             struct sk_buff *old,
1515                                             struct sk_buff *new)
1516 {
1517         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1518                 tcp_sk(sk)->highest_sack = new;
1519 }
1520 
1521 /* Determines whether this is a thin stream (which may suffer from
1522  * increased latency). Used to trigger latency-reducing mechanisms.
1523  */
1524 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1525 {
1526         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1527 }
1528 
1529 /* /proc */
1530 enum tcp_seq_states {
1531         TCP_SEQ_STATE_LISTENING,
1532         TCP_SEQ_STATE_OPENREQ,
1533         TCP_SEQ_STATE_ESTABLISHED,
1534 };
1535 
1536 int tcp_seq_open(struct inode *inode, struct file *file);
1537 
1538 struct tcp_seq_afinfo {
1539         char                            *name;
1540         sa_family_t                     family;
1541         const struct file_operations    *seq_fops;
1542         struct seq_operations           seq_ops;
1543 };
1544 
1545 struct tcp_iter_state {
1546         struct seq_net_private  p;
1547         sa_family_t             family;
1548         enum tcp_seq_states     state;
1549         struct sock             *syn_wait_sk;
1550         int                     bucket, offset, sbucket, num;
1551         kuid_t                  uid;
1552         loff_t                  last_pos;
1553 };
1554 
1555 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1556 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1557 
1558 extern struct request_sock_ops tcp_request_sock_ops;
1559 extern struct request_sock_ops tcp6_request_sock_ops;
1560 
1561 void tcp_v4_destroy_sock(struct sock *sk);
1562 
1563 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1564                                 netdev_features_t features);
1565 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1566 int tcp_gro_complete(struct sk_buff *skb);
1567 
1568 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1569 
1570 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1571 {
1572         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1573 }
1574 
1575 static inline bool tcp_stream_memory_free(const struct sock *sk)
1576 {
1577         const struct tcp_sock *tp = tcp_sk(sk);
1578         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1579 
1580         return notsent_bytes < tcp_notsent_lowat(tp);
1581 }
1582 
1583 #ifdef CONFIG_PROC_FS
1584 int tcp4_proc_init(void);
1585 void tcp4_proc_exit(void);
1586 #endif
1587 
1588 /* TCP af-specific functions */
1589 struct tcp_sock_af_ops {
1590 #ifdef CONFIG_TCP_MD5SIG
1591         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1592                                                 struct sock *addr_sk);
1593         int                     (*calc_md5_hash) (char *location,
1594                                                   struct tcp_md5sig_key *md5,
1595                                                   const struct sock *sk,
1596                                                   const struct request_sock *req,
1597                                                   const struct sk_buff *skb);
1598         int                     (*md5_parse) (struct sock *sk,
1599                                               char __user *optval,
1600                                               int optlen);
1601 #endif
1602 };
1603 
1604 struct tcp_request_sock_ops {
1605 #ifdef CONFIG_TCP_MD5SIG
1606         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1607                                                 struct request_sock *req);
1608         int                     (*calc_md5_hash) (char *location,
1609                                                   struct tcp_md5sig_key *md5,
1610                                                   const struct sock *sk,
1611                                                   const struct request_sock *req,
1612                                                   const struct sk_buff *skb);
1613 #endif
1614 };
1615 
1616 int tcpv4_offload_init(void);
1617 
1618 void tcp_v4_init(void);
1619 void tcp_init(void);
1620 
1621 #endif  /* _TCP_H */
1622 

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