1 /* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * Definitions for the TCP module. 7 * 8 * Version: @(#)tcp.h 1.0.5 05/23/93 9 * 10 * Authors: Ross Biro 11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * 13 * This program is free software; you can redistribute it and/or 14 * modify it under the terms of the GNU General Public License 15 * as published by the Free Software Foundation; either version 16 * 2 of the License, or (at your option) any later version. 17 */ 18 #ifndef _TCP_H 19 #define _TCP_H 20 21 #define FASTRETRANS_DEBUG 1 22 23 #include <linux/list.h> 24 #include <linux/tcp.h> 25 #include <linux/bug.h> 26 #include <linux/slab.h> 27 #include <linux/cache.h> 28 #include <linux/percpu.h> 29 #include <linux/skbuff.h> 30 #include <linux/dmaengine.h> 31 #include <linux/crypto.h> 32 #include <linux/cryptohash.h> 33 #include <linux/kref.h> 34 35 #include <net/inet_connection_sock.h> 36 #include <net/inet_timewait_sock.h> 37 #include <net/inet_hashtables.h> 38 #include <net/checksum.h> 39 #include <net/request_sock.h> 40 #include <net/sock.h> 41 #include <net/snmp.h> 42 #include <net/ip.h> 43 #include <net/tcp_states.h> 44 #include <net/inet_ecn.h> 45 #include <net/dst.h> 46 47 #include <linux/seq_file.h> 48 #include <linux/memcontrol.h> 49 50 extern struct inet_hashinfo tcp_hashinfo; 51 52 extern struct percpu_counter tcp_orphan_count; 53 extern void tcp_time_wait(struct sock *sk, int state, int timeo); 54 55 #define MAX_TCP_HEADER (128 + MAX_HEADER) 56 #define MAX_TCP_OPTION_SPACE 40 57 58 /* 59 * Never offer a window over 32767 without using window scaling. Some 60 * poor stacks do signed 16bit maths! 61 */ 62 #define MAX_TCP_WINDOW 32767U 63 64 /* Offer an initial receive window of 10 mss. */ 65 #define TCP_DEFAULT_INIT_RCVWND 10 66 67 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */ 68 #define TCP_MIN_MSS 88U 69 70 /* The least MTU to use for probing */ 71 #define TCP_BASE_MSS 512 72 73 /* After receiving this amount of duplicate ACKs fast retransmit starts. */ 74 #define TCP_FASTRETRANS_THRESH 3 75 76 /* Maximal reordering. */ 77 #define TCP_MAX_REORDERING 127 78 79 /* Maximal number of ACKs sent quickly to accelerate slow-start. */ 80 #define TCP_MAX_QUICKACKS 16U 81 82 /* urg_data states */ 83 #define TCP_URG_VALID 0x0100 84 #define TCP_URG_NOTYET 0x0200 85 #define TCP_URG_READ 0x0400 86 87 #define TCP_RETR1 3 /* 88 * This is how many retries it does before it 89 * tries to figure out if the gateway is 90 * down. Minimal RFC value is 3; it corresponds 91 * to ~3sec-8min depending on RTO. 92 */ 93 94 #define TCP_RETR2 15 /* 95 * This should take at least 96 * 90 minutes to time out. 97 * RFC1122 says that the limit is 100 sec. 98 * 15 is ~13-30min depending on RTO. 99 */ 100 101 #define TCP_SYN_RETRIES 6 /* This is how many retries are done 102 * when active opening a connection. 103 * RFC1122 says the minimum retry MUST 104 * be at least 180secs. Nevertheless 105 * this value is corresponding to 106 * 63secs of retransmission with the 107 * current initial RTO. 108 */ 109 110 #define TCP_SYNACK_RETRIES 5 /* This is how may retries are done 111 * when passive opening a connection. 112 * This is corresponding to 31secs of 113 * retransmission with the current 114 * initial RTO. 115 */ 116 117 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT 118 * state, about 60 seconds */ 119 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN 120 /* BSD style FIN_WAIT2 deadlock breaker. 121 * It used to be 3min, new value is 60sec, 122 * to combine FIN-WAIT-2 timeout with 123 * TIME-WAIT timer. 124 */ 125 126 #define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */ 127 #if HZ >= 100 128 #define TCP_DELACK_MIN ((unsigned)(HZ/25)) /* minimal time to delay before sending an ACK */ 129 #define TCP_ATO_MIN ((unsigned)(HZ/25)) 130 #else 131 #define TCP_DELACK_MIN 4U 132 #define TCP_ATO_MIN 4U 133 #endif 134 #define TCP_RTO_MAX ((unsigned)(120*HZ)) 135 #define TCP_RTO_MIN ((unsigned)(HZ/5)) 136 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ)) /* RFC6298 2.1 initial RTO value */ 137 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now 138 * used as a fallback RTO for the 139 * initial data transmission if no 140 * valid RTT sample has been acquired, 141 * most likely due to retrans in 3WHS. 142 */ 143 144 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes 145 * for local resources. 146 */ 147 148 #define TCP_KEEPALIVE_TIME (120*60*HZ) /* two hours */ 149 #define TCP_KEEPALIVE_PROBES 9 /* Max of 9 keepalive probes */ 150 #define TCP_KEEPALIVE_INTVL (75*HZ) 151 152 #define MAX_TCP_KEEPIDLE 32767 153 #define MAX_TCP_KEEPINTVL 32767 154 #define MAX_TCP_KEEPCNT 127 155 #define MAX_TCP_SYNCNT 127 156 157 #define TCP_SYNQ_INTERVAL (HZ/5) /* Period of SYNACK timer */ 158 159 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24) 160 #define TCP_PAWS_MSL 60 /* Per-host timestamps are invalidated 161 * after this time. It should be equal 162 * (or greater than) TCP_TIMEWAIT_LEN 163 * to provide reliability equal to one 164 * provided by timewait state. 165 */ 166 #define TCP_PAWS_WINDOW 1 /* Replay window for per-host 167 * timestamps. It must be less than 168 * minimal timewait lifetime. 169 */ 170 /* 171 * TCP option 172 */ 173 174 #define TCPOPT_NOP 1 /* Padding */ 175 #define TCPOPT_EOL 0 /* End of options */ 176 #define TCPOPT_MSS 2 /* Segment size negotiating */ 177 #define TCPOPT_WINDOW 3 /* Window scaling */ 178 #define TCPOPT_SACK_PERM 4 /* SACK Permitted */ 179 #define TCPOPT_SACK 5 /* SACK Block */ 180 #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */ 181 #define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */ 182 #define TCPOPT_COOKIE 253 /* Cookie extension (experimental) */ 183 #define TCPOPT_EXP 254 /* Experimental */ 184 /* Magic number to be after the option value for sharing TCP 185 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt 186 */ 187 #define TCPOPT_FASTOPEN_MAGIC 0xF989 188 189 /* 190 * TCP option lengths 191 */ 192 193 #define TCPOLEN_MSS 4 194 #define TCPOLEN_WINDOW 3 195 #define TCPOLEN_SACK_PERM 2 196 #define TCPOLEN_TIMESTAMP 10 197 #define TCPOLEN_MD5SIG 18 198 #define TCPOLEN_EXP_FASTOPEN_BASE 4 199 #define TCPOLEN_COOKIE_BASE 2 /* Cookie-less header extension */ 200 #define TCPOLEN_COOKIE_PAIR 3 /* Cookie pair header extension */ 201 #define TCPOLEN_COOKIE_MIN (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MIN) 202 #define TCPOLEN_COOKIE_MAX (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MAX) 203 204 /* But this is what stacks really send out. */ 205 #define TCPOLEN_TSTAMP_ALIGNED 12 206 #define TCPOLEN_WSCALE_ALIGNED 4 207 #define TCPOLEN_SACKPERM_ALIGNED 4 208 #define TCPOLEN_SACK_BASE 2 209 #define TCPOLEN_SACK_BASE_ALIGNED 4 210 #define TCPOLEN_SACK_PERBLOCK 8 211 #define TCPOLEN_MD5SIG_ALIGNED 20 212 #define TCPOLEN_MSS_ALIGNED 4 213 214 /* Flags in tp->nonagle */ 215 #define TCP_NAGLE_OFF 1 /* Nagle's algo is disabled */ 216 #define TCP_NAGLE_CORK 2 /* Socket is corked */ 217 #define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */ 218 219 /* TCP thin-stream limits */ 220 #define TCP_THIN_LINEAR_RETRIES 6 /* After 6 linear retries, do exp. backoff */ 221 222 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */ 223 #define TCP_INIT_CWND 10 224 225 /* Bit Flags for sysctl_tcp_fastopen */ 226 #define TFO_CLIENT_ENABLE 1 227 #define TFO_SERVER_ENABLE 2 228 #define TFO_CLIENT_NO_COOKIE 4 /* Data in SYN w/o cookie option */ 229 230 /* Process SYN data but skip cookie validation */ 231 #define TFO_SERVER_COOKIE_NOT_CHKED 0x100 232 /* Accept SYN data w/o any cookie option */ 233 #define TFO_SERVER_COOKIE_NOT_REQD 0x200 234 235 /* Force enable TFO on all listeners, i.e., not requiring the 236 * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen. 237 */ 238 #define TFO_SERVER_WO_SOCKOPT1 0x400 239 #define TFO_SERVER_WO_SOCKOPT2 0x800 240 /* Always create TFO child sockets on a TFO listener even when 241 * cookie/data not present. (For testing purpose!) 242 */ 243 #define TFO_SERVER_ALWAYS 0x1000 244 245 extern struct inet_timewait_death_row tcp_death_row; 246 247 /* sysctl variables for tcp */ 248 extern int sysctl_tcp_timestamps; 249 extern int sysctl_tcp_window_scaling; 250 extern int sysctl_tcp_sack; 251 extern int sysctl_tcp_fin_timeout; 252 extern int sysctl_tcp_keepalive_time; 253 extern int sysctl_tcp_keepalive_probes; 254 extern int sysctl_tcp_keepalive_intvl; 255 extern int sysctl_tcp_syn_retries; 256 extern int sysctl_tcp_synack_retries; 257 extern int sysctl_tcp_retries1; 258 extern int sysctl_tcp_retries2; 259 extern int sysctl_tcp_orphan_retries; 260 extern int sysctl_tcp_syncookies; 261 extern int sysctl_tcp_fastopen; 262 extern int sysctl_tcp_retrans_collapse; 263 extern int sysctl_tcp_stdurg; 264 extern int sysctl_tcp_rfc1337; 265 extern int sysctl_tcp_abort_on_overflow; 266 extern int sysctl_tcp_max_orphans; 267 extern int sysctl_tcp_fack; 268 extern int sysctl_tcp_reordering; 269 extern int sysctl_tcp_ecn; 270 extern int sysctl_tcp_dsack; 271 extern int sysctl_tcp_wmem[3]; 272 extern int sysctl_tcp_rmem[3]; 273 extern int sysctl_tcp_app_win; 274 extern int sysctl_tcp_adv_win_scale; 275 extern int sysctl_tcp_tw_reuse; 276 extern int sysctl_tcp_frto; 277 extern int sysctl_tcp_frto_response; 278 extern int sysctl_tcp_low_latency; 279 extern int sysctl_tcp_dma_copybreak; 280 extern int sysctl_tcp_nometrics_save; 281 extern int sysctl_tcp_moderate_rcvbuf; 282 extern int sysctl_tcp_tso_win_divisor; 283 extern int sysctl_tcp_abc; 284 extern int sysctl_tcp_mtu_probing; 285 extern int sysctl_tcp_base_mss; 286 extern int sysctl_tcp_workaround_signed_windows; 287 extern int sysctl_tcp_slow_start_after_idle; 288 extern int sysctl_tcp_max_ssthresh; 289 extern int sysctl_tcp_cookie_size; 290 extern int sysctl_tcp_thin_linear_timeouts; 291 extern int sysctl_tcp_thin_dupack; 292 extern int sysctl_tcp_early_retrans; 293 extern int sysctl_tcp_limit_output_bytes; 294 extern int sysctl_tcp_challenge_ack_limit; 295 296 extern atomic_long_t tcp_memory_allocated; 297 extern struct percpu_counter tcp_sockets_allocated; 298 extern int tcp_memory_pressure; 299 300 /* 301 * The next routines deal with comparing 32 bit unsigned ints 302 * and worry about wraparound (automatic with unsigned arithmetic). 303 */ 304 305 static inline bool before(__u32 seq1, __u32 seq2) 306 { 307 return (__s32)(seq1-seq2) < 0; 308 } 309 #define after(seq2, seq1) before(seq1, seq2) 310 311 /* is s2<=s1<=s3 ? */ 312 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3) 313 { 314 return seq3 - seq2 >= seq1 - seq2; 315 } 316 317 static inline bool tcp_out_of_memory(struct sock *sk) 318 { 319 if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF && 320 sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2)) 321 return true; 322 return false; 323 } 324 325 static inline bool tcp_too_many_orphans(struct sock *sk, int shift) 326 { 327 struct percpu_counter *ocp = sk->sk_prot->orphan_count; 328 int orphans = percpu_counter_read_positive(ocp); 329 330 if (orphans << shift > sysctl_tcp_max_orphans) { 331 orphans = percpu_counter_sum_positive(ocp); 332 if (orphans << shift > sysctl_tcp_max_orphans) 333 return true; 334 } 335 return false; 336 } 337 338 extern bool tcp_check_oom(struct sock *sk, int shift); 339 340 /* syncookies: remember time of last synqueue overflow */ 341 static inline void tcp_synq_overflow(struct sock *sk) 342 { 343 tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies; 344 } 345 346 /* syncookies: no recent synqueue overflow on this listening socket? */ 347 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk) 348 { 349 unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; 350 return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK); 351 } 352 353 extern struct proto tcp_prot; 354 355 #define TCP_INC_STATS(net, field) SNMP_INC_STATS((net)->mib.tcp_statistics, field) 356 #define TCP_INC_STATS_BH(net, field) SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field) 357 #define TCP_DEC_STATS(net, field) SNMP_DEC_STATS((net)->mib.tcp_statistics, field) 358 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val) 359 #define TCP_ADD_STATS(net, field, val) SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val) 360 361 extern void tcp_init_mem(struct net *net); 362 363 extern void tcp_tasklet_init(void); 364 365 extern void tcp_v4_err(struct sk_buff *skb, u32); 366 367 extern void tcp_shutdown (struct sock *sk, int how); 368 369 extern void tcp_v4_early_demux(struct sk_buff *skb); 370 extern int tcp_v4_rcv(struct sk_buff *skb); 371 372 extern int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw); 373 extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 374 size_t size); 375 extern int tcp_sendpage(struct sock *sk, struct page *page, int offset, 376 size_t size, int flags); 377 extern void tcp_release_cb(struct sock *sk); 378 extern void tcp_write_timer_handler(struct sock *sk); 379 extern void tcp_delack_timer_handler(struct sock *sk); 380 extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg); 381 extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 382 const struct tcphdr *th, unsigned int len); 383 extern int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 384 const struct tcphdr *th, unsigned int len); 385 extern void tcp_rcv_space_adjust(struct sock *sk); 386 extern void tcp_cleanup_rbuf(struct sock *sk, int copied); 387 extern int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp); 388 extern void tcp_twsk_destructor(struct sock *sk); 389 extern ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos, 390 struct pipe_inode_info *pipe, size_t len, 391 unsigned int flags); 392 393 static inline void tcp_dec_quickack_mode(struct sock *sk, 394 const unsigned int pkts) 395 { 396 struct inet_connection_sock *icsk = inet_csk(sk); 397 398 if (icsk->icsk_ack.quick) { 399 if (pkts >= icsk->icsk_ack.quick) { 400 icsk->icsk_ack.quick = 0; 401 /* Leaving quickack mode we deflate ATO. */ 402 icsk->icsk_ack.ato = TCP_ATO_MIN; 403 } else 404 icsk->icsk_ack.quick -= pkts; 405 } 406 } 407 408 #define TCP_ECN_OK 1 409 #define TCP_ECN_QUEUE_CWR 2 410 #define TCP_ECN_DEMAND_CWR 4 411 #define TCP_ECN_SEEN 8 412 413 enum tcp_tw_status { 414 TCP_TW_SUCCESS = 0, 415 TCP_TW_RST = 1, 416 TCP_TW_ACK = 2, 417 TCP_TW_SYN = 3 418 }; 419 420 421 extern enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw, 422 struct sk_buff *skb, 423 const struct tcphdr *th); 424 extern struct sock * tcp_check_req(struct sock *sk,struct sk_buff *skb, 425 struct request_sock *req, 426 struct request_sock **prev, 427 bool fastopen); 428 extern int tcp_child_process(struct sock *parent, struct sock *child, 429 struct sk_buff *skb); 430 extern bool tcp_use_frto(struct sock *sk); 431 extern void tcp_enter_frto(struct sock *sk); 432 extern void tcp_enter_loss(struct sock *sk, int how); 433 extern void tcp_clear_retrans(struct tcp_sock *tp); 434 extern void tcp_update_metrics(struct sock *sk); 435 extern void tcp_init_metrics(struct sock *sk); 436 extern void tcp_metrics_init(void); 437 extern bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst, bool paws_check); 438 extern bool tcp_remember_stamp(struct sock *sk); 439 extern bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw); 440 extern void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst); 441 extern void tcp_disable_fack(struct tcp_sock *tp); 442 extern void tcp_close(struct sock *sk, long timeout); 443 extern void tcp_init_sock(struct sock *sk); 444 extern unsigned int tcp_poll(struct file * file, struct socket *sock, 445 struct poll_table_struct *wait); 446 extern int tcp_getsockopt(struct sock *sk, int level, int optname, 447 char __user *optval, int __user *optlen); 448 extern int tcp_setsockopt(struct sock *sk, int level, int optname, 449 char __user *optval, unsigned int optlen); 450 extern int compat_tcp_getsockopt(struct sock *sk, int level, int optname, 451 char __user *optval, int __user *optlen); 452 extern int compat_tcp_setsockopt(struct sock *sk, int level, int optname, 453 char __user *optval, unsigned int optlen); 454 extern void tcp_set_keepalive(struct sock *sk, int val); 455 extern void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req); 456 extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 457 size_t len, int nonblock, int flags, int *addr_len); 458 extern void tcp_parse_options(const struct sk_buff *skb, 459 struct tcp_options_received *opt_rx, const u8 **hvpp, 460 int estab, struct tcp_fastopen_cookie *foc); 461 extern const u8 *tcp_parse_md5sig_option(const struct tcphdr *th); 462 463 /* 464 * TCP v4 functions exported for the inet6 API 465 */ 466 467 extern void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb); 468 extern int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb); 469 extern struct sock * tcp_create_openreq_child(struct sock *sk, 470 struct request_sock *req, 471 struct sk_buff *skb); 472 extern struct sock * tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb, 473 struct request_sock *req, 474 struct dst_entry *dst); 475 extern int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb); 476 extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, 477 int addr_len); 478 extern int tcp_connect(struct sock *sk); 479 extern struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst, 480 struct request_sock *req, 481 struct request_values *rvp, 482 struct tcp_fastopen_cookie *foc); 483 extern int tcp_disconnect(struct sock *sk, int flags); 484 485 void tcp_connect_init(struct sock *sk); 486 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb); 487 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size); 488 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb); 489 490 /* From syncookies.c */ 491 extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS]; 492 extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, 493 struct ip_options *opt); 494 #ifdef CONFIG_SYN_COOKIES 495 extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, 496 __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 extern __u32 cookie_init_timestamp(struct request_sock *req); 507 extern bool cookie_check_timestamp(struct tcp_options_received *opt, bool *); 508 509 /* From net/ipv6/syncookies.c */ 510 extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb); 511 #ifdef CONFIG_SYN_COOKIES 512 extern __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb, 513 __u16 *mss); 514 #else 515 static inline __u32 cookie_v6_init_sequence(struct sock *sk, 516 struct sk_buff *skb, 517 __u16 *mss) 518 { 519 return 0; 520 } 521 #endif 522 /* tcp_output.c */ 523 524 extern void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, 525 int nonagle); 526 extern bool tcp_may_send_now(struct sock *sk); 527 extern int __tcp_retransmit_skb(struct sock *, struct sk_buff *); 528 extern int tcp_retransmit_skb(struct sock *, struct sk_buff *); 529 extern void tcp_retransmit_timer(struct sock *sk); 530 extern void tcp_xmit_retransmit_queue(struct sock *); 531 extern void tcp_simple_retransmit(struct sock *); 532 extern int tcp_trim_head(struct sock *, struct sk_buff *, u32); 533 extern int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int); 534 535 extern void tcp_send_probe0(struct sock *); 536 extern void tcp_send_partial(struct sock *); 537 extern int tcp_write_wakeup(struct sock *); 538 extern void tcp_send_fin(struct sock *sk); 539 extern void tcp_send_active_reset(struct sock *sk, gfp_t priority); 540 extern int tcp_send_synack(struct sock *); 541 extern bool tcp_syn_flood_action(struct sock *sk, 542 const struct sk_buff *skb, 543 const char *proto); 544 extern void tcp_push_one(struct sock *, unsigned int mss_now); 545 extern void tcp_send_ack(struct sock *sk); 546 extern void tcp_send_delayed_ack(struct sock *sk); 547 548 /* tcp_input.c */ 549 extern void tcp_cwnd_application_limited(struct sock *sk); 550 extern void tcp_resume_early_retransmit(struct sock *sk); 551 extern void tcp_rearm_rto(struct sock *sk); 552 extern void tcp_reset(struct sock *sk); 553 554 /* tcp_timer.c */ 555 extern void tcp_init_xmit_timers(struct sock *); 556 static inline void tcp_clear_xmit_timers(struct sock *sk) 557 { 558 inet_csk_clear_xmit_timers(sk); 559 } 560 561 extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu); 562 extern unsigned int tcp_current_mss(struct sock *sk); 563 564 /* Bound MSS / TSO packet size with the half of the window */ 565 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize) 566 { 567 int cutoff; 568 569 /* When peer uses tiny windows, there is no use in packetizing 570 * to sub-MSS pieces for the sake of SWS or making sure there 571 * are enough packets in the pipe for fast recovery. 572 * 573 * On the other hand, for extremely large MSS devices, handling 574 * smaller than MSS windows in this way does make sense. 575 */ 576 if (tp->max_window >= 512) 577 cutoff = (tp->max_window >> 1); 578 else 579 cutoff = tp->max_window; 580 581 if (cutoff && pktsize > cutoff) 582 return max_t(int, cutoff, 68U - tp->tcp_header_len); 583 else 584 return pktsize; 585 } 586 587 /* tcp.c */ 588 extern void tcp_get_info(const struct sock *, struct tcp_info *); 589 590 /* Read 'sendfile()'-style from a TCP socket */ 591 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *, 592 unsigned int, size_t); 593 extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc, 594 sk_read_actor_t recv_actor); 595 596 extern void tcp_initialize_rcv_mss(struct sock *sk); 597 598 extern int tcp_mtu_to_mss(struct sock *sk, int pmtu); 599 extern int tcp_mss_to_mtu(struct sock *sk, int mss); 600 extern void tcp_mtup_init(struct sock *sk); 601 extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt); 602 extern void tcp_init_buffer_space(struct sock *sk); 603 604 static inline void tcp_bound_rto(const struct sock *sk) 605 { 606 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) 607 inet_csk(sk)->icsk_rto = TCP_RTO_MAX; 608 } 609 610 static inline u32 __tcp_set_rto(const struct tcp_sock *tp) 611 { 612 return (tp->srtt >> 3) + tp->rttvar; 613 } 614 615 extern void tcp_set_rto(struct sock *sk); 616 617 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd) 618 { 619 tp->pred_flags = htonl((tp->tcp_header_len << 26) | 620 ntohl(TCP_FLAG_ACK) | 621 snd_wnd); 622 } 623 624 static inline void tcp_fast_path_on(struct tcp_sock *tp) 625 { 626 __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale); 627 } 628 629 static inline void tcp_fast_path_check(struct sock *sk) 630 { 631 struct tcp_sock *tp = tcp_sk(sk); 632 633 if (skb_queue_empty(&tp->out_of_order_queue) && 634 tp->rcv_wnd && 635 atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf && 636 !tp->urg_data) 637 tcp_fast_path_on(tp); 638 } 639 640 /* Compute the actual rto_min value */ 641 static inline u32 tcp_rto_min(struct sock *sk) 642 { 643 const struct dst_entry *dst = __sk_dst_get(sk); 644 u32 rto_min = TCP_RTO_MIN; 645 646 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN)) 647 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN); 648 return rto_min; 649 } 650 651 /* Compute the actual receive window we are currently advertising. 652 * Rcv_nxt can be after the window if our peer push more data 653 * than the offered window. 654 */ 655 static inline u32 tcp_receive_window(const struct tcp_sock *tp) 656 { 657 s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt; 658 659 if (win < 0) 660 win = 0; 661 return (u32) win; 662 } 663 664 /* Choose a new window, without checks for shrinking, and without 665 * scaling applied to the result. The caller does these things 666 * if necessary. This is a "raw" window selection. 667 */ 668 extern u32 __tcp_select_window(struct sock *sk); 669 670 void tcp_send_window_probe(struct sock *sk); 671 672 /* TCP timestamps are only 32-bits, this causes a slight 673 * complication on 64-bit systems since we store a snapshot 674 * of jiffies in the buffer control blocks below. We decided 675 * to use only the low 32-bits of jiffies and hide the ugly 676 * casts with the following macro. 677 */ 678 #define tcp_time_stamp ((__u32)(jiffies)) 679 680 #define tcp_flag_byte(th) (((u_int8_t *)th)[13]) 681 682 #define TCPHDR_FIN 0x01 683 #define TCPHDR_SYN 0x02 684 #define TCPHDR_RST 0x04 685 #define TCPHDR_PSH 0x08 686 #define TCPHDR_ACK 0x10 687 #define TCPHDR_URG 0x20 688 #define TCPHDR_ECE 0x40 689 #define TCPHDR_CWR 0x80 690 691 /* This is what the send packet queuing engine uses to pass 692 * TCP per-packet control information to the transmission code. 693 * We also store the host-order sequence numbers in here too. 694 * This is 44 bytes if IPV6 is enabled. 695 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately. 696 */ 697 struct tcp_skb_cb { 698 union { 699 struct inet_skb_parm h4; 700 #if IS_ENABLED(CONFIG_IPV6) 701 struct inet6_skb_parm h6; 702 #endif 703 } header; /* For incoming frames */ 704 __u32 seq; /* Starting sequence number */ 705 __u32 end_seq; /* SEQ + FIN + SYN + datalen */ 706 __u32 when; /* used to compute rtt's */ 707 __u8 tcp_flags; /* TCP header flags. (tcp[13]) */ 708 709 __u8 sacked; /* State flags for SACK/FACK. */ 710 #define TCPCB_SACKED_ACKED 0x01 /* SKB ACK'd by a SACK block */ 711 #define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */ 712 #define TCPCB_LOST 0x04 /* SKB is lost */ 713 #define TCPCB_TAGBITS 0x07 /* All tag bits */ 714 #define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */ 715 #define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS) 716 717 __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */ 718 /* 1 byte hole */ 719 __u32 ack_seq; /* Sequence number ACK'd */ 720 }; 721 722 #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0])) 723 724 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set 725 * 726 * If we receive a SYN packet with these bits set, it means a network is 727 * playing bad games with TOS bits. In order to avoid possible false congestion 728 * notifications, we disable TCP ECN negociation. 729 */ 730 static inline void 731 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb) 732 { 733 const struct tcphdr *th = tcp_hdr(skb); 734 735 if (sysctl_tcp_ecn && th->ece && th->cwr && 736 INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield)) 737 inet_rsk(req)->ecn_ok = 1; 738 } 739 740 /* Due to TSO, an SKB can be composed of multiple actual 741 * packets. To keep these tracked properly, we use this. 742 */ 743 static inline int tcp_skb_pcount(const struct sk_buff *skb) 744 { 745 return skb_shinfo(skb)->gso_segs; 746 } 747 748 /* This is valid iff tcp_skb_pcount() > 1. */ 749 static inline int tcp_skb_mss(const struct sk_buff *skb) 750 { 751 return skb_shinfo(skb)->gso_size; 752 } 753 754 /* Events passed to congestion control interface */ 755 enum tcp_ca_event { 756 CA_EVENT_TX_START, /* first transmit when no packets in flight */ 757 CA_EVENT_CWND_RESTART, /* congestion window restart */ 758 CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */ 759 CA_EVENT_FRTO, /* fast recovery timeout */ 760 CA_EVENT_LOSS, /* loss timeout */ 761 CA_EVENT_FAST_ACK, /* in sequence ack */ 762 CA_EVENT_SLOW_ACK, /* other ack */ 763 }; 764 765 /* 766 * Interface for adding new TCP congestion control handlers 767 */ 768 #define TCP_CA_NAME_MAX 16 769 #define TCP_CA_MAX 128 770 #define TCP_CA_BUF_MAX (TCP_CA_NAME_MAX*TCP_CA_MAX) 771 772 #define TCP_CONG_NON_RESTRICTED 0x1 773 #define TCP_CONG_RTT_STAMP 0x2 774 775 struct tcp_congestion_ops { 776 struct list_head list; 777 unsigned long flags; 778 779 /* initialize private data (optional) */ 780 void (*init)(struct sock *sk); 781 /* cleanup private data (optional) */ 782 void (*release)(struct sock *sk); 783 784 /* return slow start threshold (required) */ 785 u32 (*ssthresh)(struct sock *sk); 786 /* lower bound for congestion window (optional) */ 787 u32 (*min_cwnd)(const struct sock *sk); 788 /* do new cwnd calculation (required) */ 789 void (*cong_avoid)(struct sock *sk, u32 ack, u32 in_flight); 790 /* call before changing ca_state (optional) */ 791 void (*set_state)(struct sock *sk, u8 new_state); 792 /* call when cwnd event occurs (optional) */ 793 void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev); 794 /* new value of cwnd after loss (optional) */ 795 u32 (*undo_cwnd)(struct sock *sk); 796 /* hook for packet ack accounting (optional) */ 797 void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us); 798 /* get info for inet_diag (optional) */ 799 void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb); 800 801 char name[TCP_CA_NAME_MAX]; 802 struct module *owner; 803 }; 804 805 extern int tcp_register_congestion_control(struct tcp_congestion_ops *type); 806 extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type); 807 808 extern void tcp_init_congestion_control(struct sock *sk); 809 extern void tcp_cleanup_congestion_control(struct sock *sk); 810 extern int tcp_set_default_congestion_control(const char *name); 811 extern void tcp_get_default_congestion_control(char *name); 812 extern void tcp_get_available_congestion_control(char *buf, size_t len); 813 extern void tcp_get_allowed_congestion_control(char *buf, size_t len); 814 extern int tcp_set_allowed_congestion_control(char *allowed); 815 extern int tcp_set_congestion_control(struct sock *sk, const char *name); 816 extern void tcp_slow_start(struct tcp_sock *tp); 817 extern void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w); 818 819 extern struct tcp_congestion_ops tcp_init_congestion_ops; 820 extern u32 tcp_reno_ssthresh(struct sock *sk); 821 extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight); 822 extern u32 tcp_reno_min_cwnd(const struct sock *sk); 823 extern struct tcp_congestion_ops tcp_reno; 824 825 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state) 826 { 827 struct inet_connection_sock *icsk = inet_csk(sk); 828 829 if (icsk->icsk_ca_ops->set_state) 830 icsk->icsk_ca_ops->set_state(sk, ca_state); 831 icsk->icsk_ca_state = ca_state; 832 } 833 834 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event) 835 { 836 const struct inet_connection_sock *icsk = inet_csk(sk); 837 838 if (icsk->icsk_ca_ops->cwnd_event) 839 icsk->icsk_ca_ops->cwnd_event(sk, event); 840 } 841 842 /* These functions determine how the current flow behaves in respect of SACK 843 * handling. SACK is negotiated with the peer, and therefore it can vary 844 * between different flows. 845 * 846 * tcp_is_sack - SACK enabled 847 * tcp_is_reno - No SACK 848 * tcp_is_fack - FACK enabled, implies SACK enabled 849 */ 850 static inline int tcp_is_sack(const struct tcp_sock *tp) 851 { 852 return tp->rx_opt.sack_ok; 853 } 854 855 static inline bool tcp_is_reno(const struct tcp_sock *tp) 856 { 857 return !tcp_is_sack(tp); 858 } 859 860 static inline bool tcp_is_fack(const struct tcp_sock *tp) 861 { 862 return tp->rx_opt.sack_ok & TCP_FACK_ENABLED; 863 } 864 865 static inline void tcp_enable_fack(struct tcp_sock *tp) 866 { 867 tp->rx_opt.sack_ok |= TCP_FACK_ENABLED; 868 } 869 870 /* TCP early-retransmit (ER) is similar to but more conservative than 871 * the thin-dupack feature. Enable ER only if thin-dupack is disabled. 872 */ 873 static inline void tcp_enable_early_retrans(struct tcp_sock *tp) 874 { 875 tp->do_early_retrans = sysctl_tcp_early_retrans && 876 !sysctl_tcp_thin_dupack && sysctl_tcp_reordering == 3; 877 tp->early_retrans_delayed = 0; 878 } 879 880 static inline void tcp_disable_early_retrans(struct tcp_sock *tp) 881 { 882 tp->do_early_retrans = 0; 883 } 884 885 static inline unsigned int tcp_left_out(const struct tcp_sock *tp) 886 { 887 return tp->sacked_out + tp->lost_out; 888 } 889 890 /* This determines how many packets are "in the network" to the best 891 * of our knowledge. In many cases it is conservative, but where 892 * detailed information is available from the receiver (via SACK 893 * blocks etc.) we can make more aggressive calculations. 894 * 895 * Use this for decisions involving congestion control, use just 896 * tp->packets_out to determine if the send queue is empty or not. 897 * 898 * Read this equation as: 899 * 900 * "Packets sent once on transmission queue" MINUS 901 * "Packets left network, but not honestly ACKed yet" PLUS 902 * "Packets fast retransmitted" 903 */ 904 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp) 905 { 906 return tp->packets_out - tcp_left_out(tp) + tp->retrans_out; 907 } 908 909 #define TCP_INFINITE_SSTHRESH 0x7fffffff 910 911 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp) 912 { 913 return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH; 914 } 915 916 static inline bool tcp_in_cwnd_reduction(const struct sock *sk) 917 { 918 return (TCPF_CA_CWR | TCPF_CA_Recovery) & 919 (1 << inet_csk(sk)->icsk_ca_state); 920 } 921 922 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd. 923 * The exception is cwnd reduction phase, when cwnd is decreasing towards 924 * ssthresh. 925 */ 926 static inline __u32 tcp_current_ssthresh(const struct sock *sk) 927 { 928 const struct tcp_sock *tp = tcp_sk(sk); 929 930 if (tcp_in_cwnd_reduction(sk)) 931 return tp->snd_ssthresh; 932 else 933 return max(tp->snd_ssthresh, 934 ((tp->snd_cwnd >> 1) + 935 (tp->snd_cwnd >> 2))); 936 } 937 938 /* Use define here intentionally to get WARN_ON location shown at the caller */ 939 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out) 940 941 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh); 942 extern __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst); 943 944 /* The maximum number of MSS of available cwnd for which TSO defers 945 * sending if not using sysctl_tcp_tso_win_divisor. 946 */ 947 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp) 948 { 949 return 3; 950 } 951 952 /* Slow start with delack produces 3 packets of burst, so that 953 * it is safe "de facto". This will be the default - same as 954 * the default reordering threshold - but if reordering increases, 955 * we must be able to allow cwnd to burst at least this much in order 956 * to not pull it back when holes are filled. 957 */ 958 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp) 959 { 960 return tp->reordering; 961 } 962 963 /* Returns end sequence number of the receiver's advertised window */ 964 static inline u32 tcp_wnd_end(const struct tcp_sock *tp) 965 { 966 return tp->snd_una + tp->snd_wnd; 967 } 968 extern bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight); 969 970 static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss, 971 const struct sk_buff *skb) 972 { 973 if (skb->len < mss) 974 tp->snd_sml = TCP_SKB_CB(skb)->end_seq; 975 } 976 977 static inline void tcp_check_probe_timer(struct sock *sk) 978 { 979 const struct tcp_sock *tp = tcp_sk(sk); 980 const struct inet_connection_sock *icsk = inet_csk(sk); 981 982 if (!tp->packets_out && !icsk->icsk_pending) 983 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 984 icsk->icsk_rto, TCP_RTO_MAX); 985 } 986 987 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq) 988 { 989 tp->snd_wl1 = seq; 990 } 991 992 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq) 993 { 994 tp->snd_wl1 = seq; 995 } 996 997 /* 998 * Calculate(/check) TCP checksum 999 */ 1000 static inline __sum16 tcp_v4_check(int len, __be32 saddr, 1001 __be32 daddr, __wsum base) 1002 { 1003 return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base); 1004 } 1005 1006 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb) 1007 { 1008 return __skb_checksum_complete(skb); 1009 } 1010 1011 static inline bool tcp_checksum_complete(struct sk_buff *skb) 1012 { 1013 return !skb_csum_unnecessary(skb) && 1014 __tcp_checksum_complete(skb); 1015 } 1016 1017 /* Prequeue for VJ style copy to user, combined with checksumming. */ 1018 1019 static inline void tcp_prequeue_init(struct tcp_sock *tp) 1020 { 1021 tp->ucopy.task = NULL; 1022 tp->ucopy.len = 0; 1023 tp->ucopy.memory = 0; 1024 skb_queue_head_init(&tp->ucopy.prequeue); 1025 #ifdef CONFIG_NET_DMA 1026 tp->ucopy.dma_chan = NULL; 1027 tp->ucopy.wakeup = 0; 1028 tp->ucopy.pinned_list = NULL; 1029 tp->ucopy.dma_cookie = 0; 1030 #endif 1031 } 1032 1033 /* Packet is added to VJ-style prequeue for processing in process 1034 * context, if a reader task is waiting. Apparently, this exciting 1035 * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93) 1036 * failed somewhere. Latency? Burstiness? Well, at least now we will 1037 * see, why it failed. 8)8) --ANK 1038 * 1039 * NOTE: is this not too big to inline? 1040 */ 1041 static inline bool tcp_prequeue(struct sock *sk, struct sk_buff *skb) 1042 { 1043 struct tcp_sock *tp = tcp_sk(sk); 1044 1045 if (sysctl_tcp_low_latency || !tp->ucopy.task) 1046 return false; 1047 1048 __skb_queue_tail(&tp->ucopy.prequeue, skb); 1049 tp->ucopy.memory += skb->truesize; 1050 if (tp->ucopy.memory > sk->sk_rcvbuf) { 1051 struct sk_buff *skb1; 1052 1053 BUG_ON(sock_owned_by_user(sk)); 1054 1055 while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) { 1056 sk_backlog_rcv(sk, skb1); 1057 NET_INC_STATS_BH(sock_net(sk), 1058 LINUX_MIB_TCPPREQUEUEDROPPED); 1059 } 1060 1061 tp->ucopy.memory = 0; 1062 } else if (skb_queue_len(&tp->ucopy.prequeue) == 1) { 1063 wake_up_interruptible_sync_poll(sk_sleep(sk), 1064 POLLIN | POLLRDNORM | POLLRDBAND); 1065 if (!inet_csk_ack_scheduled(sk)) 1066 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 1067 (3 * tcp_rto_min(sk)) / 4, 1068 TCP_RTO_MAX); 1069 } 1070 return true; 1071 } 1072 1073 1074 #undef STATE_TRACE 1075 1076 #ifdef STATE_TRACE 1077 static const char *statename[]={ 1078 "Unused","Established","Syn Sent","Syn Recv", 1079 "Fin Wait 1","Fin Wait 2","Time Wait", "Close", 1080 "Close Wait","Last ACK","Listen","Closing" 1081 }; 1082 #endif 1083 extern void tcp_set_state(struct sock *sk, int state); 1084 1085 extern void tcp_done(struct sock *sk); 1086 1087 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt) 1088 { 1089 rx_opt->dsack = 0; 1090 rx_opt->num_sacks = 0; 1091 } 1092 1093 /* Determine a window scaling and initial window to offer. */ 1094 extern void tcp_select_initial_window(int __space, __u32 mss, 1095 __u32 *rcv_wnd, __u32 *window_clamp, 1096 int wscale_ok, __u8 *rcv_wscale, 1097 __u32 init_rcv_wnd); 1098 1099 static inline int tcp_win_from_space(int space) 1100 { 1101 return sysctl_tcp_adv_win_scale<=0 ? 1102 (space>>(-sysctl_tcp_adv_win_scale)) : 1103 space - (space>>sysctl_tcp_adv_win_scale); 1104 } 1105 1106 /* Note: caller must be prepared to deal with negative returns */ 1107 static inline int tcp_space(const struct sock *sk) 1108 { 1109 return tcp_win_from_space(sk->sk_rcvbuf - 1110 atomic_read(&sk->sk_rmem_alloc)); 1111 } 1112 1113 static inline int tcp_full_space(const struct sock *sk) 1114 { 1115 return tcp_win_from_space(sk->sk_rcvbuf); 1116 } 1117 1118 static inline void tcp_openreq_init(struct request_sock *req, 1119 struct tcp_options_received *rx_opt, 1120 struct sk_buff *skb) 1121 { 1122 struct inet_request_sock *ireq = inet_rsk(req); 1123 1124 req->rcv_wnd = 0; /* So that tcp_send_synack() knows! */ 1125 req->cookie_ts = 0; 1126 tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq; 1127 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 1128 tcp_rsk(req)->snt_synack = 0; 1129 req->mss = rx_opt->mss_clamp; 1130 req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0; 1131 ireq->tstamp_ok = rx_opt->tstamp_ok; 1132 ireq->sack_ok = rx_opt->sack_ok; 1133 ireq->snd_wscale = rx_opt->snd_wscale; 1134 ireq->wscale_ok = rx_opt->wscale_ok; 1135 ireq->acked = 0; 1136 ireq->ecn_ok = 0; 1137 ireq->rmt_port = tcp_hdr(skb)->source; 1138 ireq->loc_port = tcp_hdr(skb)->dest; 1139 } 1140 1141 /* Compute time elapsed between SYNACK and the ACK completing 3WHS */ 1142 static inline void tcp_synack_rtt_meas(struct sock *sk, 1143 struct request_sock *req) 1144 { 1145 if (tcp_rsk(req)->snt_synack) 1146 tcp_valid_rtt_meas(sk, 1147 tcp_time_stamp - tcp_rsk(req)->snt_synack); 1148 } 1149 1150 extern void tcp_enter_memory_pressure(struct sock *sk); 1151 1152 static inline int keepalive_intvl_when(const struct tcp_sock *tp) 1153 { 1154 return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl; 1155 } 1156 1157 static inline int keepalive_time_when(const struct tcp_sock *tp) 1158 { 1159 return tp->keepalive_time ? : sysctl_tcp_keepalive_time; 1160 } 1161 1162 static inline int keepalive_probes(const struct tcp_sock *tp) 1163 { 1164 return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes; 1165 } 1166 1167 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp) 1168 { 1169 const struct inet_connection_sock *icsk = &tp->inet_conn; 1170 1171 return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime, 1172 tcp_time_stamp - tp->rcv_tstamp); 1173 } 1174 1175 static inline int tcp_fin_time(const struct sock *sk) 1176 { 1177 int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout; 1178 const int rto = inet_csk(sk)->icsk_rto; 1179 1180 if (fin_timeout < (rto << 2) - (rto >> 1)) 1181 fin_timeout = (rto << 2) - (rto >> 1); 1182 1183 return fin_timeout; 1184 } 1185 1186 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt, 1187 int paws_win) 1188 { 1189 if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win) 1190 return true; 1191 if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)) 1192 return true; 1193 /* 1194 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0, 1195 * then following tcp messages have valid values. Ignore 0 value, 1196 * or else 'negative' tsval might forbid us to accept their packets. 1197 */ 1198 if (!rx_opt->ts_recent) 1199 return true; 1200 return false; 1201 } 1202 1203 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt, 1204 int rst) 1205 { 1206 if (tcp_paws_check(rx_opt, 0)) 1207 return false; 1208 1209 /* RST segments are not recommended to carry timestamp, 1210 and, if they do, it is recommended to ignore PAWS because 1211 "their cleanup function should take precedence over timestamps." 1212 Certainly, it is mistake. It is necessary to understand the reasons 1213 of this constraint to relax it: if peer reboots, clock may go 1214 out-of-sync and half-open connections will not be reset. 1215 Actually, the problem would be not existing if all 1216 the implementations followed draft about maintaining clock 1217 via reboots. Linux-2.2 DOES NOT! 1218 1219 However, we can relax time bounds for RST segments to MSL. 1220 */ 1221 if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL) 1222 return false; 1223 return true; 1224 } 1225 1226 static inline void tcp_mib_init(struct net *net) 1227 { 1228 /* See RFC 2012 */ 1229 TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1); 1230 TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ); 1231 TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ); 1232 TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1); 1233 } 1234 1235 /* from STCP */ 1236 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp) 1237 { 1238 tp->lost_skb_hint = NULL; 1239 tp->scoreboard_skb_hint = NULL; 1240 } 1241 1242 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp) 1243 { 1244 tcp_clear_retrans_hints_partial(tp); 1245 tp->retransmit_skb_hint = NULL; 1246 } 1247 1248 /* MD5 Signature */ 1249 struct crypto_hash; 1250 1251 union tcp_md5_addr { 1252 struct in_addr a4; 1253 #if IS_ENABLED(CONFIG_IPV6) 1254 struct in6_addr a6; 1255 #endif 1256 }; 1257 1258 /* - key database */ 1259 struct tcp_md5sig_key { 1260 struct hlist_node node; 1261 u8 keylen; 1262 u8 family; /* AF_INET or AF_INET6 */ 1263 union tcp_md5_addr addr; 1264 u8 key[TCP_MD5SIG_MAXKEYLEN]; 1265 struct rcu_head rcu; 1266 }; 1267 1268 /* - sock block */ 1269 struct tcp_md5sig_info { 1270 struct hlist_head head; 1271 struct rcu_head rcu; 1272 }; 1273 1274 /* - pseudo header */ 1275 struct tcp4_pseudohdr { 1276 __be32 saddr; 1277 __be32 daddr; 1278 __u8 pad; 1279 __u8 protocol; 1280 __be16 len; 1281 }; 1282 1283 struct tcp6_pseudohdr { 1284 struct in6_addr saddr; 1285 struct in6_addr daddr; 1286 __be32 len; 1287 __be32 protocol; /* including padding */ 1288 }; 1289 1290 union tcp_md5sum_block { 1291 struct tcp4_pseudohdr ip4; 1292 #if IS_ENABLED(CONFIG_IPV6) 1293 struct tcp6_pseudohdr ip6; 1294 #endif 1295 }; 1296 1297 /* - pool: digest algorithm, hash description and scratch buffer */ 1298 struct tcp_md5sig_pool { 1299 struct hash_desc md5_desc; 1300 union tcp_md5sum_block md5_blk; 1301 }; 1302 1303 /* - functions */ 1304 extern int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key, 1305 const struct sock *sk, 1306 const struct request_sock *req, 1307 const struct sk_buff *skb); 1308 extern int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr, 1309 int family, const u8 *newkey, 1310 u8 newkeylen, gfp_t gfp); 1311 extern int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, 1312 int family); 1313 extern struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk, 1314 struct sock *addr_sk); 1315 1316 #ifdef CONFIG_TCP_MD5SIG 1317 extern struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk, 1318 const union tcp_md5_addr *addr, int family); 1319 #define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key) 1320 #else 1321 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk, 1322 const union tcp_md5_addr *addr, 1323 int family) 1324 { 1325 return NULL; 1326 } 1327 #define tcp_twsk_md5_key(twsk) NULL 1328 #endif 1329 1330 extern struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *); 1331 extern void tcp_free_md5sig_pool(void); 1332 1333 extern struct tcp_md5sig_pool *tcp_get_md5sig_pool(void); 1334 extern void tcp_put_md5sig_pool(void); 1335 1336 extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *); 1337 extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *, 1338 unsigned int header_len); 1339 extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, 1340 const struct tcp_md5sig_key *key); 1341 1342 /* From tcp_fastopen.c */ 1343 extern void tcp_fastopen_cache_get(struct sock *sk, u16 *mss, 1344 struct tcp_fastopen_cookie *cookie, 1345 int *syn_loss, unsigned long *last_syn_loss); 1346 extern void tcp_fastopen_cache_set(struct sock *sk, u16 mss, 1347 struct tcp_fastopen_cookie *cookie, 1348 bool syn_lost); 1349 struct tcp_fastopen_request { 1350 /* Fast Open cookie. Size 0 means a cookie request */ 1351 struct tcp_fastopen_cookie cookie; 1352 struct msghdr *data; /* data in MSG_FASTOPEN */ 1353 u16 copied; /* queued in tcp_connect() */ 1354 }; 1355 void tcp_free_fastopen_req(struct tcp_sock *tp); 1356 1357 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx; 1358 int tcp_fastopen_reset_cipher(void *key, unsigned int len); 1359 void tcp_fastopen_cookie_gen(__be32 addr, struct tcp_fastopen_cookie *foc); 1360 1361 #define TCP_FASTOPEN_KEY_LENGTH 16 1362 1363 /* Fastopen key context */ 1364 struct tcp_fastopen_context { 1365 struct crypto_cipher __rcu *tfm; 1366 __u8 key[TCP_FASTOPEN_KEY_LENGTH]; 1367 struct rcu_head rcu; 1368 }; 1369 1370 /* write queue abstraction */ 1371 static inline void tcp_write_queue_purge(struct sock *sk) 1372 { 1373 struct sk_buff *skb; 1374 1375 while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) 1376 sk_wmem_free_skb(sk, skb); 1377 sk_mem_reclaim(sk); 1378 tcp_clear_all_retrans_hints(tcp_sk(sk)); 1379 } 1380 1381 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk) 1382 { 1383 return skb_peek(&sk->sk_write_queue); 1384 } 1385 1386 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk) 1387 { 1388 return skb_peek_tail(&sk->sk_write_queue); 1389 } 1390 1391 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk, 1392 const struct sk_buff *skb) 1393 { 1394 return skb_queue_next(&sk->sk_write_queue, skb); 1395 } 1396 1397 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk, 1398 const struct sk_buff *skb) 1399 { 1400 return skb_queue_prev(&sk->sk_write_queue, skb); 1401 } 1402 1403 #define tcp_for_write_queue(skb, sk) \ 1404 skb_queue_walk(&(sk)->sk_write_queue, skb) 1405 1406 #define tcp_for_write_queue_from(skb, sk) \ 1407 skb_queue_walk_from(&(sk)->sk_write_queue, skb) 1408 1409 #define tcp_for_write_queue_from_safe(skb, tmp, sk) \ 1410 skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp) 1411 1412 static inline struct sk_buff *tcp_send_head(const struct sock *sk) 1413 { 1414 return sk->sk_send_head; 1415 } 1416 1417 static inline bool tcp_skb_is_last(const struct sock *sk, 1418 const struct sk_buff *skb) 1419 { 1420 return skb_queue_is_last(&sk->sk_write_queue, skb); 1421 } 1422 1423 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb) 1424 { 1425 if (tcp_skb_is_last(sk, skb)) 1426 sk->sk_send_head = NULL; 1427 else 1428 sk->sk_send_head = tcp_write_queue_next(sk, skb); 1429 } 1430 1431 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked) 1432 { 1433 if (sk->sk_send_head == skb_unlinked) 1434 sk->sk_send_head = NULL; 1435 } 1436 1437 static inline void tcp_init_send_head(struct sock *sk) 1438 { 1439 sk->sk_send_head = NULL; 1440 } 1441 1442 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb) 1443 { 1444 __skb_queue_tail(&sk->sk_write_queue, skb); 1445 } 1446 1447 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb) 1448 { 1449 __tcp_add_write_queue_tail(sk, skb); 1450 1451 /* Queue it, remembering where we must start sending. */ 1452 if (sk->sk_send_head == NULL) { 1453 sk->sk_send_head = skb; 1454 1455 if (tcp_sk(sk)->highest_sack == NULL) 1456 tcp_sk(sk)->highest_sack = skb; 1457 } 1458 } 1459 1460 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb) 1461 { 1462 __skb_queue_head(&sk->sk_write_queue, skb); 1463 } 1464 1465 /* Insert buff after skb on the write queue of sk. */ 1466 static inline void tcp_insert_write_queue_after(struct sk_buff *skb, 1467 struct sk_buff *buff, 1468 struct sock *sk) 1469 { 1470 __skb_queue_after(&sk->sk_write_queue, skb, buff); 1471 } 1472 1473 /* Insert new before skb on the write queue of sk. */ 1474 static inline void tcp_insert_write_queue_before(struct sk_buff *new, 1475 struct sk_buff *skb, 1476 struct sock *sk) 1477 { 1478 __skb_queue_before(&sk->sk_write_queue, skb, new); 1479 1480 if (sk->sk_send_head == skb) 1481 sk->sk_send_head = new; 1482 } 1483 1484 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk) 1485 { 1486 __skb_unlink(skb, &sk->sk_write_queue); 1487 } 1488 1489 static inline bool tcp_write_queue_empty(struct sock *sk) 1490 { 1491 return skb_queue_empty(&sk->sk_write_queue); 1492 } 1493 1494 static inline void tcp_push_pending_frames(struct sock *sk) 1495 { 1496 if (tcp_send_head(sk)) { 1497 struct tcp_sock *tp = tcp_sk(sk); 1498 1499 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle); 1500 } 1501 } 1502 1503 /* Start sequence of the skb just after the highest skb with SACKed 1504 * bit, valid only if sacked_out > 0 or when the caller has ensured 1505 * validity by itself. 1506 */ 1507 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp) 1508 { 1509 if (!tp->sacked_out) 1510 return tp->snd_una; 1511 1512 if (tp->highest_sack == NULL) 1513 return tp->snd_nxt; 1514 1515 return TCP_SKB_CB(tp->highest_sack)->seq; 1516 } 1517 1518 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb) 1519 { 1520 tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL : 1521 tcp_write_queue_next(sk, skb); 1522 } 1523 1524 static inline struct sk_buff *tcp_highest_sack(struct sock *sk) 1525 { 1526 return tcp_sk(sk)->highest_sack; 1527 } 1528 1529 static inline void tcp_highest_sack_reset(struct sock *sk) 1530 { 1531 tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk); 1532 } 1533 1534 /* Called when old skb is about to be deleted (to be combined with new skb) */ 1535 static inline void tcp_highest_sack_combine(struct sock *sk, 1536 struct sk_buff *old, 1537 struct sk_buff *new) 1538 { 1539 if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack)) 1540 tcp_sk(sk)->highest_sack = new; 1541 } 1542 1543 /* Determines whether this is a thin stream (which may suffer from 1544 * increased latency). Used to trigger latency-reducing mechanisms. 1545 */ 1546 static inline bool tcp_stream_is_thin(struct tcp_sock *tp) 1547 { 1548 return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp); 1549 } 1550 1551 /* /proc */ 1552 enum tcp_seq_states { 1553 TCP_SEQ_STATE_LISTENING, 1554 TCP_SEQ_STATE_OPENREQ, 1555 TCP_SEQ_STATE_ESTABLISHED, 1556 TCP_SEQ_STATE_TIME_WAIT, 1557 }; 1558 1559 int tcp_seq_open(struct inode *inode, struct file *file); 1560 1561 struct tcp_seq_afinfo { 1562 char *name; 1563 sa_family_t family; 1564 const struct file_operations *seq_fops; 1565 struct seq_operations seq_ops; 1566 }; 1567 1568 struct tcp_iter_state { 1569 struct seq_net_private p; 1570 sa_family_t family; 1571 enum tcp_seq_states state; 1572 struct sock *syn_wait_sk; 1573 int bucket, offset, sbucket, num; 1574 kuid_t uid; 1575 loff_t last_pos; 1576 }; 1577 1578 extern int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo); 1579 extern void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo); 1580 1581 extern struct request_sock_ops tcp_request_sock_ops; 1582 extern struct request_sock_ops tcp6_request_sock_ops; 1583 1584 extern void tcp_v4_destroy_sock(struct sock *sk); 1585 1586 extern int tcp_v4_gso_send_check(struct sk_buff *skb); 1587 extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb, 1588 netdev_features_t features); 1589 extern struct sk_buff **tcp_gro_receive(struct sk_buff **head, 1590 struct sk_buff *skb); 1591 extern struct sk_buff **tcp4_gro_receive(struct sk_buff **head, 1592 struct sk_buff *skb); 1593 extern int tcp_gro_complete(struct sk_buff *skb); 1594 extern int tcp4_gro_complete(struct sk_buff *skb); 1595 1596 #ifdef CONFIG_PROC_FS 1597 extern int tcp4_proc_init(void); 1598 extern void tcp4_proc_exit(void); 1599 #endif 1600 1601 /* TCP af-specific functions */ 1602 struct tcp_sock_af_ops { 1603 #ifdef CONFIG_TCP_MD5SIG 1604 struct tcp_md5sig_key *(*md5_lookup) (struct sock *sk, 1605 struct sock *addr_sk); 1606 int (*calc_md5_hash) (char *location, 1607 struct tcp_md5sig_key *md5, 1608 const struct sock *sk, 1609 const struct request_sock *req, 1610 const struct sk_buff *skb); 1611 int (*md5_parse) (struct sock *sk, 1612 char __user *optval, 1613 int optlen); 1614 #endif 1615 }; 1616 1617 struct tcp_request_sock_ops { 1618 #ifdef CONFIG_TCP_MD5SIG 1619 struct tcp_md5sig_key *(*md5_lookup) (struct sock *sk, 1620 struct request_sock *req); 1621 int (*calc_md5_hash) (char *location, 1622 struct tcp_md5sig_key *md5, 1623 const struct sock *sk, 1624 const struct request_sock *req, 1625 const struct sk_buff *skb); 1626 #endif 1627 }; 1628 1629 /* Using SHA1 for now, define some constants. 1630 */ 1631 #define COOKIE_DIGEST_WORDS (SHA_DIGEST_WORDS) 1632 #define COOKIE_MESSAGE_WORDS (SHA_MESSAGE_BYTES / 4) 1633 #define COOKIE_WORKSPACE_WORDS (COOKIE_DIGEST_WORDS + COOKIE_MESSAGE_WORDS) 1634 1635 extern int tcp_cookie_generator(u32 *bakery); 1636 1637 /** 1638 * struct tcp_cookie_values - each socket needs extra space for the 1639 * cookies, together with (optional) space for any SYN data. 1640 * 1641 * A tcp_sock contains a pointer to the current value, and this is 1642 * cloned to the tcp_timewait_sock. 1643 * 1644 * @cookie_pair: variable data from the option exchange. 1645 * 1646 * @cookie_desired: user specified tcpct_cookie_desired. Zero 1647 * indicates default (sysctl_tcp_cookie_size). 1648 * After cookie sent, remembers size of cookie. 1649 * Range 0, TCP_COOKIE_MIN to TCP_COOKIE_MAX. 1650 * 1651 * @s_data_desired: user specified tcpct_s_data_desired. When the 1652 * constant payload is specified (@s_data_constant), 1653 * holds its length instead. 1654 * Range 0 to TCP_MSS_DESIRED. 1655 * 1656 * @s_data_payload: constant data that is to be included in the 1657 * payload of SYN or SYNACK segments when the 1658 * cookie option is present. 1659 */ 1660 struct tcp_cookie_values { 1661 struct kref kref; 1662 u8 cookie_pair[TCP_COOKIE_PAIR_SIZE]; 1663 u8 cookie_pair_size; 1664 u8 cookie_desired; 1665 u16 s_data_desired:11, 1666 s_data_constant:1, 1667 s_data_in:1, 1668 s_data_out:1, 1669 s_data_unused:2; 1670 u8 s_data_payload[0]; 1671 }; 1672 1673 static inline void tcp_cookie_values_release(struct kref *kref) 1674 { 1675 kfree(container_of(kref, struct tcp_cookie_values, kref)); 1676 } 1677 1678 /* The length of constant payload data. Note that s_data_desired is 1679 * overloaded, depending on s_data_constant: either the length of constant 1680 * data (returned here) or the limit on variable data. 1681 */ 1682 static inline int tcp_s_data_size(const struct tcp_sock *tp) 1683 { 1684 return (tp->cookie_values != NULL && tp->cookie_values->s_data_constant) 1685 ? tp->cookie_values->s_data_desired 1686 : 0; 1687 } 1688 1689 /** 1690 * struct tcp_extend_values - tcp_ipv?.c to tcp_output.c workspace. 1691 * 1692 * As tcp_request_sock has already been extended in other places, the 1693 * only remaining method is to pass stack values along as function 1694 * parameters. These parameters are not needed after sending SYNACK. 1695 * 1696 * @cookie_bakery: cryptographic secret and message workspace. 1697 * 1698 * @cookie_plus: bytes in authenticator/cookie option, copied from 1699 * struct tcp_options_received (above). 1700 */ 1701 struct tcp_extend_values { 1702 struct request_values rv; 1703 u32 cookie_bakery[COOKIE_WORKSPACE_WORDS]; 1704 u8 cookie_plus:6, 1705 cookie_out_never:1, 1706 cookie_in_always:1; 1707 }; 1708 1709 static inline struct tcp_extend_values *tcp_xv(struct request_values *rvp) 1710 { 1711 return (struct tcp_extend_values *)rvp; 1712 } 1713 1714 extern void tcp_v4_init(void); 1715 extern void tcp_init(void); 1716 1717 #endif /* _TCP_H */ 1718