1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_ipfw.h" /* for ipfw_fwd */ 36 #include "opt_inet.h" 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/kernel.h> 43 #include <sys/malloc.h> 44 #include <sys/mbuf.h> 45 #include <sys/proc.h> /* for proc0 declaration */ 46 #include <sys/protosw.h> 47 #include <sys/signalvar.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/sysctl.h> 51 #include <sys/syslog.h> 52 #include <sys/systm.h> 53 54 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 55 56 #include <vm/uma.h> 57 58 #include <net/if.h> 59 #include <net/route.h> 60 #include <net/vnet.h> 61 62 #define TCPSTATES /* for logging */ 63 64 #include <netinet/in.h> 65 #include <netinet/in_pcb.h> 66 #include <netinet/in_systm.h> 67 #include <netinet/in_var.h> 68 #include <netinet/ip.h> 69 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 70 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 71 #include <netinet/ip_var.h> 72 #include <netinet/ip_options.h> 73 #include <netinet/ip6.h> 74 #include <netinet/icmp6.h> 75 #include <netinet6/in6_pcb.h> 76 #include <netinet6/ip6_var.h> 77 #include <netinet6/nd6.h> 78 #include <netinet/tcp.h> 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet6/tcp6_var.h> 84 #include <netinet/tcpip.h> 85 #include <netinet/tcp_syncache.h> 86 #ifdef TCPDEBUG 87 #include <netinet/tcp_debug.h> 88 #endif /* TCPDEBUG */ 89 90 #ifdef IPSEC 91 #include <netipsec/ipsec.h> 92 #include <netipsec/ipsec6.h> 93 #endif /*IPSEC*/ 94 95 #include <machine/in_cksum.h> 96 97 #include <security/mac/mac_framework.h> 98 99 static const int tcprexmtthresh = 3; 100 101 VNET_DEFINE(struct tcpstat, tcpstat); 102 VNET_DEFINE(int, blackhole); 103 VNET_DEFINE(int, tcp_delack_enabled); 104 VNET_DEFINE(int, drop_synfin); 105 VNET_DEFINE(int, tcp_do_rfc3042); 106 VNET_DEFINE(int, tcp_do_rfc3390); 107 VNET_DEFINE(int, tcp_do_ecn); 108 VNET_DEFINE(int, tcp_ecn_maxretries); 109 VNET_DEFINE(int, tcp_insecure_rst); 110 VNET_DEFINE(int, tcp_do_autorcvbuf); 111 VNET_DEFINE(int, tcp_autorcvbuf_inc); 112 VNET_DEFINE(int, tcp_autorcvbuf_max); 113 VNET_DEFINE(int, tcp_do_rfc3465); 114 VNET_DEFINE(int, tcp_abc_l_var); 115 116 SYSCTL_VNET_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 117 &VNET_NAME(tcpstat), tcpstat, 118 "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 119 120 int tcp_log_in_vain = 0; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 122 &tcp_log_in_vain, 0, 123 "Log all incoming TCP segments to closed ports"); 124 125 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 126 &VNET_NAME(blackhole), 0, 127 "Do not send RST on segments to closed ports"); 128 129 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 130 &VNET_NAME(tcp_delack_enabled), 0, 131 "Delay ACK to try and piggyback it onto a data packet"); 132 133 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 134 &VNET_NAME(drop_synfin), 0, 135 "Drop TCP packets with SYN+FIN set"); 136 137 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 138 &VNET_NAME(tcp_do_rfc3042), 0, 139 "Enable RFC 3042 (Limited Transmit)"); 140 141 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 142 &VNET_NAME(tcp_do_rfc3390), 0, 143 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 144 145 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, 146 &VNET_NAME(tcp_do_rfc3465), 0, 147 "Enable RFC 3465 (Appropriate Byte Counting)"); 148 149 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW, 150 &VNET_NAME(tcp_abc_l_var), 2, 151 "Cap the max cwnd increment during slow-start to this number of segments"); 152 153 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 154 155 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW, 156 &VNET_NAME(tcp_do_ecn), 0, 157 "TCP ECN support"); 158 159 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW, 160 &VNET_NAME(tcp_ecn_maxretries), 0, 161 "Max retries before giving up on ECN"); 162 163 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 164 &VNET_NAME(tcp_insecure_rst), 0, 165 "Follow the old (insecure) criteria for accepting RST packets"); 166 167 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 168 &VNET_NAME(tcp_do_autorcvbuf), 0, 169 "Enable automatic receive buffer sizing"); 170 171 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 172 &VNET_NAME(tcp_autorcvbuf_inc), 0, 173 "Incrementor step size of automatic receive buffer"); 174 175 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 176 &VNET_NAME(tcp_autorcvbuf_max), 0, 177 "Max size of automatic receive buffer"); 178 179 int tcp_read_locking = 1; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, read_locking, CTLFLAG_RW, 181 &tcp_read_locking, 0, "Enable read locking strategy"); 182 183 int tcp_rlock_atfirst; 184 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rlock_atfirst, CTLFLAG_RD, 185 &tcp_rlock_atfirst, 0, ""); 186 187 int tcp_wlock_atfirst; 188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_wlock_atfirst, CTLFLAG_RD, 189 &tcp_wlock_atfirst, 0, ""); 190 191 int tcp_wlock_upgraded; 192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, wlock_upgraded, CTLFLAG_RD, 193 &tcp_wlock_upgraded, 0, ""); 194 195 int tcp_wlock_relocked; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, wlock_relocked, CTLFLAG_RD, 197 &tcp_wlock_relocked, 0, ""); 198 199 int tcp_wlock_looped; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, wlock_looped, CTLFLAG_RD, 201 &tcp_wlock_looped, 0, ""); 202 203 VNET_DEFINE(struct inpcbhead, tcb); 204 VNET_DEFINE(struct inpcbinfo, tcbinfo); 205 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 206 207 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 208 static void tcp_do_segment(struct mbuf *, struct tcphdr *, 209 struct socket *, struct tcpcb *, int, int, uint8_t, 210 int); 211 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 212 struct tcpcb *, int, int); 213 static void tcp_pulloutofband(struct socket *, 214 struct tcphdr *, struct mbuf *, int); 215 static void tcp_xmit_timer(struct tcpcb *, int); 216 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 217 static void inline 218 tcp_congestion_exp(struct tcpcb *); 219 220 /* 221 * Kernel module interface for updating tcpstat. The argument is an index 222 * into tcpstat treated as an array of u_long. While this encodes the 223 * general layout of tcpstat into the caller, it doesn't encode its location, 224 * so that future changes to add, for example, per-CPU stats support won't 225 * cause binary compatibility problems for kernel modules. 226 */ 227 void 228 kmod_tcpstat_inc(int statnum) 229 { 230 231 (*((u_long *)&V_tcpstat + statnum))++; 232 } 233 234 static void inline 235 tcp_congestion_exp(struct tcpcb *tp) 236 { 237 u_int win; 238 239 win = min(tp->snd_wnd, tp->snd_cwnd) / 240 2 / tp->t_maxseg; 241 if (win < 2) 242 win = 2; 243 tp->snd_ssthresh = win * tp->t_maxseg; 244 ENTER_FASTRECOVERY(tp); 245 tp->snd_recover = tp->snd_max; 246 if (tp->t_flags & TF_ECN_PERMIT) 247 tp->t_flags |= TF_ECN_SND_CWR; 248 } 249 250 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 251 #ifdef INET6 252 #define ND6_HINT(tp) \ 253 do { \ 254 if ((tp) && (tp)->t_inpcb && \ 255 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 256 nd6_nud_hint(NULL, NULL, 0); \ 257 } while (0) 258 #else 259 #define ND6_HINT(tp) 260 #endif 261 262 /* 263 * Indicate whether this ack should be delayed. We can delay the ack if 264 * - there is no delayed ack timer in progress and 265 * - our last ack wasn't a 0-sized window. We never want to delay 266 * the ack that opens up a 0-sized window and 267 * - delayed acks are enabled or 268 * - this is a half-synchronized T/TCP connection. 269 */ 270 #define DELAY_ACK(tp) \ 271 ((!tcp_timer_active(tp, TT_DELACK) && \ 272 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 273 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 274 275 /* 276 * TCP input handling is split into multiple parts: 277 * tcp6_input is a thin wrapper around tcp_input for the extended 278 * ip6_protox[] call format in ip6_input 279 * tcp_input handles primary segment validation, inpcb lookup and 280 * SYN processing on listen sockets 281 * tcp_do_segment processes the ACK and text of the segment for 282 * establishing, established and closing connections 283 */ 284 #ifdef INET6 285 int 286 tcp6_input(struct mbuf **mp, int *offp, int proto) 287 { 288 struct mbuf *m = *mp; 289 struct in6_ifaddr *ia6; 290 291 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 292 293 /* 294 * draft-itojun-ipv6-tcp-to-anycast 295 * better place to put this in? 296 */ 297 ia6 = ip6_getdstifaddr(m); 298 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 299 struct ip6_hdr *ip6; 300 301 ifa_free(&ia6->ia_ifa); 302 ip6 = mtod(m, struct ip6_hdr *); 303 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 304 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 305 return IPPROTO_DONE; 306 } 307 308 tcp_input(m, *offp); 309 return IPPROTO_DONE; 310 } 311 #endif 312 313 void 314 tcp_input(struct mbuf *m, int off0) 315 { 316 struct tcphdr *th; 317 struct ip *ip = NULL; 318 struct ipovly *ipov; 319 struct inpcb *inp = NULL; 320 struct tcpcb *tp = NULL; 321 struct socket *so = NULL; 322 u_char *optp = NULL; 323 int optlen = 0; 324 int len, tlen, off; 325 int drop_hdrlen; 326 int thflags; 327 int rstreason = 0; /* For badport_bandlim accounting purposes */ 328 uint8_t iptos; 329 #ifdef IPFIREWALL_FORWARD 330 struct m_tag *fwd_tag; 331 #endif 332 #ifdef INET6 333 struct ip6_hdr *ip6 = NULL; 334 int isipv6; 335 #else 336 const void *ip6 = NULL; 337 const int isipv6 = 0; 338 #endif 339 struct tcpopt to; /* options in this segment */ 340 char *s = NULL; /* address and port logging */ 341 int ti_locked; 342 #define TI_UNLOCKED 1 343 #define TI_RLOCKED 2 344 #define TI_WLOCKED 3 345 346 #ifdef TCPDEBUG 347 /* 348 * The size of tcp_saveipgen must be the size of the max ip header, 349 * now IPv6. 350 */ 351 u_char tcp_saveipgen[IP6_HDR_LEN]; 352 struct tcphdr tcp_savetcp; 353 short ostate = 0; 354 #endif 355 356 #ifdef INET6 357 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 358 #endif 359 360 to.to_flags = 0; 361 TCPSTAT_INC(tcps_rcvtotal); 362 363 if (isipv6) { 364 #ifdef INET6 365 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 366 ip6 = mtod(m, struct ip6_hdr *); 367 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 368 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 369 TCPSTAT_INC(tcps_rcvbadsum); 370 goto drop; 371 } 372 th = (struct tcphdr *)((caddr_t)ip6 + off0); 373 374 /* 375 * Be proactive about unspecified IPv6 address in source. 376 * As we use all-zero to indicate unbounded/unconnected pcb, 377 * unspecified IPv6 address can be used to confuse us. 378 * 379 * Note that packets with unspecified IPv6 destination is 380 * already dropped in ip6_input. 381 */ 382 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 383 /* XXX stat */ 384 goto drop; 385 } 386 #else 387 th = NULL; /* XXX: Avoid compiler warning. */ 388 #endif 389 } else { 390 /* 391 * Get IP and TCP header together in first mbuf. 392 * Note: IP leaves IP header in first mbuf. 393 */ 394 if (off0 > sizeof (struct ip)) { 395 ip_stripoptions(m, (struct mbuf *)0); 396 off0 = sizeof(struct ip); 397 } 398 if (m->m_len < sizeof (struct tcpiphdr)) { 399 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 400 == NULL) { 401 TCPSTAT_INC(tcps_rcvshort); 402 return; 403 } 404 } 405 ip = mtod(m, struct ip *); 406 ipov = (struct ipovly *)ip; 407 th = (struct tcphdr *)((caddr_t)ip + off0); 408 tlen = ip->ip_len; 409 410 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 411 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 412 th->th_sum = m->m_pkthdr.csum_data; 413 else 414 th->th_sum = in_pseudo(ip->ip_src.s_addr, 415 ip->ip_dst.s_addr, 416 htonl(m->m_pkthdr.csum_data + 417 ip->ip_len + 418 IPPROTO_TCP)); 419 th->th_sum ^= 0xffff; 420 #ifdef TCPDEBUG 421 ipov->ih_len = (u_short)tlen; 422 ipov->ih_len = htons(ipov->ih_len); 423 #endif 424 } else { 425 /* 426 * Checksum extended TCP header and data. 427 */ 428 len = sizeof (struct ip) + tlen; 429 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 430 ipov->ih_len = (u_short)tlen; 431 ipov->ih_len = htons(ipov->ih_len); 432 th->th_sum = in_cksum(m, len); 433 } 434 if (th->th_sum) { 435 TCPSTAT_INC(tcps_rcvbadsum); 436 goto drop; 437 } 438 /* Re-initialization for later version check */ 439 ip->ip_v = IPVERSION; 440 } 441 442 #ifdef INET6 443 if (isipv6) 444 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 445 else 446 #endif 447 iptos = ip->ip_tos; 448 449 /* 450 * Check that TCP offset makes sense, 451 * pull out TCP options and adjust length. XXX 452 */ 453 off = th->th_off << 2; 454 if (off < sizeof (struct tcphdr) || off > tlen) { 455 TCPSTAT_INC(tcps_rcvbadoff); 456 goto drop; 457 } 458 tlen -= off; /* tlen is used instead of ti->ti_len */ 459 if (off > sizeof (struct tcphdr)) { 460 if (isipv6) { 461 #ifdef INET6 462 IP6_EXTHDR_CHECK(m, off0, off, ); 463 ip6 = mtod(m, struct ip6_hdr *); 464 th = (struct tcphdr *)((caddr_t)ip6 + off0); 465 #endif 466 } else { 467 if (m->m_len < sizeof(struct ip) + off) { 468 if ((m = m_pullup(m, sizeof (struct ip) + off)) 469 == NULL) { 470 TCPSTAT_INC(tcps_rcvshort); 471 return; 472 } 473 ip = mtod(m, struct ip *); 474 ipov = (struct ipovly *)ip; 475 th = (struct tcphdr *)((caddr_t)ip + off0); 476 } 477 } 478 optlen = off - sizeof (struct tcphdr); 479 optp = (u_char *)(th + 1); 480 } 481 thflags = th->th_flags; 482 483 /* 484 * Convert TCP protocol specific fields to host format. 485 */ 486 th->th_seq = ntohl(th->th_seq); 487 th->th_ack = ntohl(th->th_ack); 488 th->th_win = ntohs(th->th_win); 489 th->th_urp = ntohs(th->th_urp); 490 491 /* 492 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 493 */ 494 drop_hdrlen = off0 + off; 495 496 /* 497 * Locate pcb for segment, which requires a lock on tcbinfo. 498 * Optimisticaly acquire a global read lock rather than a write lock 499 * unless header flags necessarily imply a state change. There are 500 * two cases where we might discover later we need a write lock 501 * despite the flags: ACKs moving a connection out of the syncache, 502 * and ACKs for a connection in TIMEWAIT. 503 */ 504 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 505 tcp_read_locking == 0) { 506 INP_INFO_WLOCK(&V_tcbinfo); 507 ti_locked = TI_WLOCKED; 508 tcp_wlock_atfirst++; 509 } else { 510 INP_INFO_RLOCK(&V_tcbinfo); 511 ti_locked = TI_RLOCKED; 512 tcp_rlock_atfirst++; 513 } 514 515 findpcb: 516 #ifdef INVARIANTS 517 if (ti_locked == TI_RLOCKED) 518 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 519 else if (ti_locked == TI_WLOCKED) 520 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 521 else 522 panic("%s: findpcb ti_locked %d\n", __func__, ti_locked); 523 #endif 524 525 #ifdef IPFIREWALL_FORWARD 526 /* 527 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 528 */ 529 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 530 531 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 532 struct sockaddr_in *next_hop; 533 534 next_hop = (struct sockaddr_in *)(fwd_tag+1); 535 /* 536 * Transparently forwarded. Pretend to be the destination. 537 * already got one like this? 538 */ 539 inp = in_pcblookup_hash(&V_tcbinfo, 540 ip->ip_src, th->th_sport, 541 ip->ip_dst, th->th_dport, 542 0, m->m_pkthdr.rcvif); 543 if (!inp) { 544 /* It's new. Try to find the ambushing socket. */ 545 inp = in_pcblookup_hash(&V_tcbinfo, 546 ip->ip_src, th->th_sport, 547 next_hop->sin_addr, 548 next_hop->sin_port ? 549 ntohs(next_hop->sin_port) : 550 th->th_dport, 551 INPLOOKUP_WILDCARD, 552 m->m_pkthdr.rcvif); 553 } 554 /* Remove the tag from the packet. We don't need it anymore. */ 555 m_tag_delete(m, fwd_tag); 556 } else 557 #endif /* IPFIREWALL_FORWARD */ 558 { 559 if (isipv6) { 560 #ifdef INET6 561 inp = in6_pcblookup_hash(&V_tcbinfo, 562 &ip6->ip6_src, th->th_sport, 563 &ip6->ip6_dst, th->th_dport, 564 INPLOOKUP_WILDCARD, 565 m->m_pkthdr.rcvif); 566 #endif 567 } else 568 inp = in_pcblookup_hash(&V_tcbinfo, 569 ip->ip_src, th->th_sport, 570 ip->ip_dst, th->th_dport, 571 INPLOOKUP_WILDCARD, 572 m->m_pkthdr.rcvif); 573 } 574 575 /* 576 * If the INPCB does not exist then all data in the incoming 577 * segment is discarded and an appropriate RST is sent back. 578 * XXX MRT Send RST using which routing table? 579 */ 580 if (inp == NULL) { 581 /* 582 * Log communication attempts to ports that are not 583 * in use. 584 */ 585 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 586 tcp_log_in_vain == 2) { 587 if ((s = tcp_log_addrs(NULL, th, (void *)ip, ip6))) 588 log(LOG_INFO, "%s; %s: Connection attempt " 589 "to closed port\n", s, __func__); 590 } 591 /* 592 * When blackholing do not respond with a RST but 593 * completely ignore the segment and drop it. 594 */ 595 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 596 V_blackhole == 2) 597 goto dropunlock; 598 599 rstreason = BANDLIM_RST_CLOSEDPORT; 600 goto dropwithreset; 601 } 602 INP_WLOCK(inp); 603 if (!(inp->inp_flags & INP_HW_FLOWID) 604 && (m->m_flags & M_FLOWID) 605 && ((inp->inp_socket == NULL) 606 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) { 607 inp->inp_flags |= INP_HW_FLOWID; 608 inp->inp_flags &= ~INP_SW_FLOWID; 609 inp->inp_flowid = m->m_pkthdr.flowid; 610 } 611 #ifdef IPSEC 612 #ifdef INET6 613 if (isipv6 && ipsec6_in_reject(m, inp)) { 614 V_ipsec6stat.in_polvio++; 615 goto dropunlock; 616 } else 617 #endif /* INET6 */ 618 if (ipsec4_in_reject(m, inp) != 0) { 619 V_ipsec4stat.in_polvio++; 620 goto dropunlock; 621 } 622 #endif /* IPSEC */ 623 624 /* 625 * Check the minimum TTL for socket. 626 */ 627 if (inp->inp_ip_minttl != 0) { 628 #ifdef INET6 629 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 630 goto dropunlock; 631 else 632 #endif 633 if (inp->inp_ip_minttl > ip->ip_ttl) 634 goto dropunlock; 635 } 636 637 /* 638 * A previous connection in TIMEWAIT state is supposed to catch stray 639 * or duplicate segments arriving late. If this segment was a 640 * legitimate new connection attempt the old INPCB gets removed and 641 * we can try again to find a listening socket. 642 * 643 * At this point, due to earlier optimism, we may hold a read lock on 644 * the inpcbinfo, rather than a write lock. If so, we need to 645 * upgrade, or if that fails, acquire a reference on the inpcb, drop 646 * all locks, acquire a global write lock, and then re-acquire the 647 * inpcb lock. We may at that point discover that another thread has 648 * tried to free the inpcb, in which case we need to loop back and 649 * try to find a new inpcb to deliver to. 650 */ 651 if (inp->inp_flags & INP_TIMEWAIT) { 652 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 653 ("%s: INP_TIMEWAIT ti_locked %d", __func__, ti_locked)); 654 655 if (ti_locked == TI_RLOCKED) { 656 if (rw_try_upgrade(&V_tcbinfo.ipi_lock) == 0) { 657 in_pcbref(inp); 658 INP_WUNLOCK(inp); 659 INP_INFO_RUNLOCK(&V_tcbinfo); 660 INP_INFO_WLOCK(&V_tcbinfo); 661 ti_locked = TI_WLOCKED; 662 INP_WLOCK(inp); 663 if (in_pcbrele(inp)) { 664 tcp_wlock_looped++; 665 inp = NULL; 666 goto findpcb; 667 } 668 tcp_wlock_relocked++; 669 } else { 670 ti_locked = TI_WLOCKED; 671 tcp_wlock_upgraded++; 672 } 673 } 674 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 675 676 if (thflags & TH_SYN) 677 tcp_dooptions(&to, optp, optlen, TO_SYN); 678 /* 679 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 680 */ 681 if (tcp_twcheck(inp, &to, th, m, tlen)) 682 goto findpcb; 683 INP_INFO_WUNLOCK(&V_tcbinfo); 684 return; 685 } 686 /* 687 * The TCPCB may no longer exist if the connection is winding 688 * down or it is in the CLOSED state. Either way we drop the 689 * segment and send an appropriate response. 690 */ 691 tp = intotcpcb(inp); 692 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 693 rstreason = BANDLIM_RST_CLOSEDPORT; 694 goto dropwithreset; 695 } 696 697 /* 698 * We've identified a valid inpcb, but it could be that we need an 699 * inpcbinfo write lock and have only a read lock. In this case, 700 * attempt to upgrade/relock using the same strategy as the TIMEWAIT 701 * case above. 702 */ 703 if (tp->t_state != TCPS_ESTABLISHED || 704 (thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 705 tcp_read_locking == 0) { 706 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 707 ("%s: upgrade check ti_locked %d", __func__, ti_locked)); 708 709 if (ti_locked == TI_RLOCKED) { 710 if (rw_try_upgrade(&V_tcbinfo.ipi_lock) == 0) { 711 in_pcbref(inp); 712 INP_WUNLOCK(inp); 713 INP_INFO_RUNLOCK(&V_tcbinfo); 714 INP_INFO_WLOCK(&V_tcbinfo); 715 ti_locked = TI_WLOCKED; 716 INP_WLOCK(inp); 717 if (in_pcbrele(inp)) { 718 tcp_wlock_looped++; 719 inp = NULL; 720 goto findpcb; 721 } 722 tcp_wlock_relocked++; 723 } else { 724 ti_locked = TI_WLOCKED; 725 tcp_wlock_upgraded++; 726 } 727 } 728 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 729 } 730 731 #ifdef MAC 732 INP_WLOCK_ASSERT(inp); 733 if (mac_inpcb_check_deliver(inp, m)) 734 goto dropunlock; 735 #endif 736 so = inp->inp_socket; 737 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 738 #ifdef TCPDEBUG 739 if (so->so_options & SO_DEBUG) { 740 ostate = tp->t_state; 741 if (isipv6) { 742 #ifdef INET6 743 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 744 #endif 745 } else 746 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 747 tcp_savetcp = *th; 748 } 749 #endif 750 /* 751 * When the socket is accepting connections (the INPCB is in LISTEN 752 * state) we look into the SYN cache if this is a new connection 753 * attempt or the completion of a previous one. 754 */ 755 if (so->so_options & SO_ACCEPTCONN) { 756 struct in_conninfo inc; 757 758 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 759 "tp not listening", __func__)); 760 761 bzero(&inc, sizeof(inc)); 762 #ifdef INET6 763 if (isipv6) { 764 inc.inc_flags |= INC_ISIPV6; 765 inc.inc6_faddr = ip6->ip6_src; 766 inc.inc6_laddr = ip6->ip6_dst; 767 } else 768 #endif 769 { 770 inc.inc_faddr = ip->ip_src; 771 inc.inc_laddr = ip->ip_dst; 772 } 773 inc.inc_fport = th->th_sport; 774 inc.inc_lport = th->th_dport; 775 inc.inc_fibnum = so->so_fibnum; 776 777 /* 778 * Check for an existing connection attempt in syncache if 779 * the flag is only ACK. A successful lookup creates a new 780 * socket appended to the listen queue in SYN_RECEIVED state. 781 */ 782 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 783 /* 784 * Parse the TCP options here because 785 * syncookies need access to the reflected 786 * timestamp. 787 */ 788 tcp_dooptions(&to, optp, optlen, 0); 789 /* 790 * NB: syncache_expand() doesn't unlock 791 * inp and tcpinfo locks. 792 */ 793 if (!syncache_expand(&inc, &to, th, &so, m)) { 794 /* 795 * No syncache entry or ACK was not 796 * for our SYN/ACK. Send a RST. 797 * NB: syncache did its own logging 798 * of the failure cause. 799 */ 800 rstreason = BANDLIM_RST_OPENPORT; 801 goto dropwithreset; 802 } 803 if (so == NULL) { 804 /* 805 * We completed the 3-way handshake 806 * but could not allocate a socket 807 * either due to memory shortage, 808 * listen queue length limits or 809 * global socket limits. Send RST 810 * or wait and have the remote end 811 * retransmit the ACK for another 812 * try. 813 */ 814 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 815 log(LOG_DEBUG, "%s; %s: Listen socket: " 816 "Socket allocation failed due to " 817 "limits or memory shortage, %s\n", 818 s, __func__, 819 V_tcp_sc_rst_sock_fail ? 820 "sending RST" : "try again"); 821 if (V_tcp_sc_rst_sock_fail) { 822 rstreason = BANDLIM_UNLIMITED; 823 goto dropwithreset; 824 } else 825 goto dropunlock; 826 } 827 /* 828 * Socket is created in state SYN_RECEIVED. 829 * Unlock the listen socket, lock the newly 830 * created socket and update the tp variable. 831 */ 832 INP_WUNLOCK(inp); /* listen socket */ 833 inp = sotoinpcb(so); 834 INP_WLOCK(inp); /* new connection */ 835 tp = intotcpcb(inp); 836 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 837 ("%s: ", __func__)); 838 /* 839 * Process the segment and the data it 840 * contains. tcp_do_segment() consumes 841 * the mbuf chain and unlocks the inpcb. 842 */ 843 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 844 iptos, ti_locked); 845 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 846 return; 847 } 848 /* 849 * Segment flag validation for new connection attempts: 850 * 851 * Our (SYN|ACK) response was rejected. 852 * Check with syncache and remove entry to prevent 853 * retransmits. 854 * 855 * NB: syncache_chkrst does its own logging of failure 856 * causes. 857 */ 858 if (thflags & TH_RST) { 859 syncache_chkrst(&inc, th); 860 goto dropunlock; 861 } 862 /* 863 * We can't do anything without SYN. 864 */ 865 if ((thflags & TH_SYN) == 0) { 866 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 867 log(LOG_DEBUG, "%s; %s: Listen socket: " 868 "SYN is missing, segment ignored\n", 869 s, __func__); 870 TCPSTAT_INC(tcps_badsyn); 871 goto dropunlock; 872 } 873 /* 874 * (SYN|ACK) is bogus on a listen socket. 875 */ 876 if (thflags & TH_ACK) { 877 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 878 log(LOG_DEBUG, "%s; %s: Listen socket: " 879 "SYN|ACK invalid, segment rejected\n", 880 s, __func__); 881 syncache_badack(&inc); /* XXX: Not needed! */ 882 TCPSTAT_INC(tcps_badsyn); 883 rstreason = BANDLIM_RST_OPENPORT; 884 goto dropwithreset; 885 } 886 /* 887 * If the drop_synfin option is enabled, drop all 888 * segments with both the SYN and FIN bits set. 889 * This prevents e.g. nmap from identifying the 890 * TCP/IP stack. 891 * XXX: Poor reasoning. nmap has other methods 892 * and is constantly refining its stack detection 893 * strategies. 894 * XXX: This is a violation of the TCP specification 895 * and was used by RFC1644. 896 */ 897 if ((thflags & TH_FIN) && V_drop_synfin) { 898 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 899 log(LOG_DEBUG, "%s; %s: Listen socket: " 900 "SYN|FIN segment ignored (based on " 901 "sysctl setting)\n", s, __func__); 902 TCPSTAT_INC(tcps_badsyn); 903 goto dropunlock; 904 } 905 /* 906 * Segment's flags are (SYN) or (SYN|FIN). 907 * 908 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 909 * as they do not affect the state of the TCP FSM. 910 * The data pointed to by TH_URG and th_urp is ignored. 911 */ 912 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 913 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 914 KASSERT(thflags & (TH_SYN), 915 ("%s: Listen socket: TH_SYN not set", __func__)); 916 #ifdef INET6 917 /* 918 * If deprecated address is forbidden, 919 * we do not accept SYN to deprecated interface 920 * address to prevent any new inbound connection from 921 * getting established. 922 * When we do not accept SYN, we send a TCP RST, 923 * with deprecated source address (instead of dropping 924 * it). We compromise it as it is much better for peer 925 * to send a RST, and RST will be the final packet 926 * for the exchange. 927 * 928 * If we do not forbid deprecated addresses, we accept 929 * the SYN packet. RFC2462 does not suggest dropping 930 * SYN in this case. 931 * If we decipher RFC2462 5.5.4, it says like this: 932 * 1. use of deprecated addr with existing 933 * communication is okay - "SHOULD continue to be 934 * used" 935 * 2. use of it with new communication: 936 * (2a) "SHOULD NOT be used if alternate address 937 * with sufficient scope is available" 938 * (2b) nothing mentioned otherwise. 939 * Here we fall into (2b) case as we have no choice in 940 * our source address selection - we must obey the peer. 941 * 942 * The wording in RFC2462 is confusing, and there are 943 * multiple description text for deprecated address 944 * handling - worse, they are not exactly the same. 945 * I believe 5.5.4 is the best one, so we follow 5.5.4. 946 */ 947 if (isipv6 && !V_ip6_use_deprecated) { 948 struct in6_ifaddr *ia6; 949 950 ia6 = ip6_getdstifaddr(m); 951 if (ia6 != NULL && 952 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 953 ifa_free(&ia6->ia_ifa); 954 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 955 log(LOG_DEBUG, "%s; %s: Listen socket: " 956 "Connection attempt to deprecated " 957 "IPv6 address rejected\n", 958 s, __func__); 959 rstreason = BANDLIM_RST_OPENPORT; 960 goto dropwithreset; 961 } 962 ifa_free(&ia6->ia_ifa); 963 } 964 #endif 965 /* 966 * Basic sanity checks on incoming SYN requests: 967 * Don't respond if the destination is a link layer 968 * broadcast according to RFC1122 4.2.3.10, p. 104. 969 * If it is from this socket it must be forged. 970 * Don't respond if the source or destination is a 971 * global or subnet broad- or multicast address. 972 * Note that it is quite possible to receive unicast 973 * link-layer packets with a broadcast IP address. Use 974 * in_broadcast() to find them. 975 */ 976 if (m->m_flags & (M_BCAST|M_MCAST)) { 977 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 978 log(LOG_DEBUG, "%s; %s: Listen socket: " 979 "Connection attempt from broad- or multicast " 980 "link layer address ignored\n", s, __func__); 981 goto dropunlock; 982 } 983 if (isipv6) { 984 #ifdef INET6 985 if (th->th_dport == th->th_sport && 986 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 987 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 988 log(LOG_DEBUG, "%s; %s: Listen socket: " 989 "Connection attempt to/from self " 990 "ignored\n", s, __func__); 991 goto dropunlock; 992 } 993 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 994 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 995 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 996 log(LOG_DEBUG, "%s; %s: Listen socket: " 997 "Connection attempt from/to multicast " 998 "address ignored\n", s, __func__); 999 goto dropunlock; 1000 } 1001 #endif 1002 } else { 1003 if (th->th_dport == th->th_sport && 1004 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1005 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1006 log(LOG_DEBUG, "%s; %s: Listen socket: " 1007 "Connection attempt from/to self " 1008 "ignored\n", s, __func__); 1009 goto dropunlock; 1010 } 1011 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1012 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1013 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1014 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1015 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1016 log(LOG_DEBUG, "%s; %s: Listen socket: " 1017 "Connection attempt from/to broad- " 1018 "or multicast address ignored\n", 1019 s, __func__); 1020 goto dropunlock; 1021 } 1022 } 1023 /* 1024 * SYN appears to be valid. Create compressed TCP state 1025 * for syncache. 1026 */ 1027 #ifdef TCPDEBUG 1028 if (so->so_options & SO_DEBUG) 1029 tcp_trace(TA_INPUT, ostate, tp, 1030 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1031 #endif 1032 tcp_dooptions(&to, optp, optlen, TO_SYN); 1033 syncache_add(&inc, &to, th, inp, &so, m); 1034 /* 1035 * Entry added to syncache and mbuf consumed. 1036 * Everything already unlocked by syncache_add(). 1037 */ 1038 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1039 return; 1040 } 1041 1042 /* 1043 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1044 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1045 * the inpcb, and unlocks pcbinfo. 1046 */ 1047 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1048 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1049 return; 1050 1051 dropwithreset: 1052 if (ti_locked == TI_RLOCKED) 1053 INP_INFO_RUNLOCK(&V_tcbinfo); 1054 else if (ti_locked == TI_WLOCKED) 1055 INP_INFO_WUNLOCK(&V_tcbinfo); 1056 else 1057 panic("%s: dropwithreset ti_locked %d", __func__, ti_locked); 1058 ti_locked = TI_UNLOCKED; 1059 1060 if (inp != NULL) { 1061 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1062 INP_WUNLOCK(inp); 1063 } else 1064 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1065 m = NULL; /* mbuf chain got consumed. */ 1066 goto drop; 1067 1068 dropunlock: 1069 if (ti_locked == TI_RLOCKED) 1070 INP_INFO_RUNLOCK(&V_tcbinfo); 1071 else if (ti_locked == TI_WLOCKED) 1072 INP_INFO_WUNLOCK(&V_tcbinfo); 1073 else 1074 panic("%s: dropunlock ti_locked %d", __func__, ti_locked); 1075 ti_locked = TI_UNLOCKED; 1076 1077 if (inp != NULL) 1078 INP_WUNLOCK(inp); 1079 1080 drop: 1081 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1082 if (s != NULL) 1083 free(s, M_TCPLOG); 1084 if (m != NULL) 1085 m_freem(m); 1086 } 1087 1088 static void 1089 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1090 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1091 int ti_locked) 1092 { 1093 int thflags, acked, ourfinisacked, needoutput = 0; 1094 int rstreason, todrop, win; 1095 u_long tiwin; 1096 struct tcpopt to; 1097 1098 #ifdef TCPDEBUG 1099 /* 1100 * The size of tcp_saveipgen must be the size of the max ip header, 1101 * now IPv6. 1102 */ 1103 u_char tcp_saveipgen[IP6_HDR_LEN]; 1104 struct tcphdr tcp_savetcp; 1105 short ostate = 0; 1106 #endif 1107 thflags = th->th_flags; 1108 1109 /* 1110 * If this is either a state-changing packet or current state isn't 1111 * established, we require a write lock on tcbinfo. Otherwise, we 1112 * allow either a read lock or a write lock, as we may have acquired 1113 * a write lock due to a race. 1114 * 1115 * Require a global write lock for SYN/FIN/RST segments or 1116 * non-established connections; otherwise accept either a read or 1117 * write lock, as we may have conservatively acquired a write lock in 1118 * certain cases in tcp_input() (is this still true?). Currently we 1119 * will never enter with no lock, so we try to drop it quickly in the 1120 * common pure ack/pure data cases. 1121 */ 1122 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1123 tp->t_state != TCPS_ESTABLISHED) { 1124 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for " 1125 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1126 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1127 } else { 1128 #ifdef INVARIANTS 1129 if (ti_locked == TI_RLOCKED) 1130 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1131 else if (ti_locked == TI_WLOCKED) 1132 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1133 else 1134 panic("%s: ti_locked %d for EST", __func__, 1135 ti_locked); 1136 #endif 1137 } 1138 INP_WLOCK_ASSERT(tp->t_inpcb); 1139 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1140 __func__)); 1141 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1142 __func__)); 1143 1144 /* 1145 * Segment received on connection. 1146 * Reset idle time and keep-alive timer. 1147 * XXX: This should be done after segment 1148 * validation to ignore broken/spoofed segs. 1149 */ 1150 tp->t_rcvtime = ticks; 1151 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1152 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 1153 1154 /* 1155 * Unscale the window into a 32-bit value. 1156 * For the SYN_SENT state the scale is zero. 1157 */ 1158 tiwin = th->th_win << tp->snd_scale; 1159 1160 /* 1161 * TCP ECN processing. 1162 */ 1163 if (tp->t_flags & TF_ECN_PERMIT) { 1164 switch (iptos & IPTOS_ECN_MASK) { 1165 case IPTOS_ECN_CE: 1166 tp->t_flags |= TF_ECN_SND_ECE; 1167 TCPSTAT_INC(tcps_ecn_ce); 1168 break; 1169 case IPTOS_ECN_ECT0: 1170 TCPSTAT_INC(tcps_ecn_ect0); 1171 break; 1172 case IPTOS_ECN_ECT1: 1173 TCPSTAT_INC(tcps_ecn_ect1); 1174 break; 1175 } 1176 1177 if (thflags & TH_CWR) 1178 tp->t_flags &= ~TF_ECN_SND_ECE; 1179 1180 /* 1181 * Congestion experienced. 1182 * Ignore if we are already trying to recover. 1183 */ 1184 if ((thflags & TH_ECE) && 1185 SEQ_LEQ(th->th_ack, tp->snd_recover)) { 1186 TCPSTAT_INC(tcps_ecn_rcwnd); 1187 tcp_congestion_exp(tp); 1188 } 1189 } 1190 1191 /* 1192 * Parse options on any incoming segment. 1193 */ 1194 tcp_dooptions(&to, (u_char *)(th + 1), 1195 (th->th_off << 2) - sizeof(struct tcphdr), 1196 (thflags & TH_SYN) ? TO_SYN : 0); 1197 1198 /* 1199 * If echoed timestamp is later than the current time, 1200 * fall back to non RFC1323 RTT calculation. Normalize 1201 * timestamp if syncookies were used when this connection 1202 * was established. 1203 */ 1204 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1205 to.to_tsecr -= tp->ts_offset; 1206 if (TSTMP_GT(to.to_tsecr, ticks)) 1207 to.to_tsecr = 0; 1208 } 1209 1210 /* 1211 * Process options only when we get SYN/ACK back. The SYN case 1212 * for incoming connections is handled in tcp_syncache. 1213 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1214 * or <SYN,ACK>) segment itself is never scaled. 1215 * XXX this is traditional behavior, may need to be cleaned up. 1216 */ 1217 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1218 if ((to.to_flags & TOF_SCALE) && 1219 (tp->t_flags & TF_REQ_SCALE)) { 1220 tp->t_flags |= TF_RCVD_SCALE; 1221 tp->snd_scale = to.to_wscale; 1222 } 1223 /* 1224 * Initial send window. It will be updated with 1225 * the next incoming segment to the scaled value. 1226 */ 1227 tp->snd_wnd = th->th_win; 1228 if (to.to_flags & TOF_TS) { 1229 tp->t_flags |= TF_RCVD_TSTMP; 1230 tp->ts_recent = to.to_tsval; 1231 tp->ts_recent_age = ticks; 1232 } 1233 if (to.to_flags & TOF_MSS) 1234 tcp_mss(tp, to.to_mss); 1235 if ((tp->t_flags & TF_SACK_PERMIT) && 1236 (to.to_flags & TOF_SACKPERM) == 0) 1237 tp->t_flags &= ~TF_SACK_PERMIT; 1238 } 1239 1240 /* 1241 * Header prediction: check for the two common cases 1242 * of a uni-directional data xfer. If the packet has 1243 * no control flags, is in-sequence, the window didn't 1244 * change and we're not retransmitting, it's a 1245 * candidate. If the length is zero and the ack moved 1246 * forward, we're the sender side of the xfer. Just 1247 * free the data acked & wake any higher level process 1248 * that was blocked waiting for space. If the length 1249 * is non-zero and the ack didn't move, we're the 1250 * receiver side. If we're getting packets in-order 1251 * (the reassembly queue is empty), add the data to 1252 * the socket buffer and note that we need a delayed ack. 1253 * Make sure that the hidden state-flags are also off. 1254 * Since we check for TCPS_ESTABLISHED first, it can only 1255 * be TH_NEEDSYN. 1256 */ 1257 if (tp->t_state == TCPS_ESTABLISHED && 1258 th->th_seq == tp->rcv_nxt && 1259 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1260 tp->snd_nxt == tp->snd_max && 1261 tiwin && tiwin == tp->snd_wnd && 1262 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1263 LIST_EMPTY(&tp->t_segq) && 1264 ((to.to_flags & TOF_TS) == 0 || 1265 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1266 1267 /* 1268 * If last ACK falls within this segment's sequence numbers, 1269 * record the timestamp. 1270 * NOTE that the test is modified according to the latest 1271 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1272 */ 1273 if ((to.to_flags & TOF_TS) != 0 && 1274 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1275 tp->ts_recent_age = ticks; 1276 tp->ts_recent = to.to_tsval; 1277 } 1278 1279 if (tlen == 0) { 1280 if (SEQ_GT(th->th_ack, tp->snd_una) && 1281 SEQ_LEQ(th->th_ack, tp->snd_max) && 1282 tp->snd_cwnd >= tp->snd_wnd && 1283 ((!V_tcp_do_newreno && 1284 !(tp->t_flags & TF_SACK_PERMIT) && 1285 tp->t_dupacks < tcprexmtthresh) || 1286 ((V_tcp_do_newreno || 1287 (tp->t_flags & TF_SACK_PERMIT)) && 1288 !IN_FASTRECOVERY(tp) && 1289 (to.to_flags & TOF_SACK) == 0 && 1290 TAILQ_EMPTY(&tp->snd_holes)))) { 1291 /* 1292 * This is a pure ack for outstanding data. 1293 */ 1294 if (ti_locked == TI_RLOCKED) 1295 INP_INFO_RUNLOCK(&V_tcbinfo); 1296 else if (ti_locked == TI_WLOCKED) 1297 INP_INFO_WUNLOCK(&V_tcbinfo); 1298 else 1299 panic("%s: ti_locked %d on pure ACK", 1300 __func__, ti_locked); 1301 ti_locked = TI_UNLOCKED; 1302 1303 TCPSTAT_INC(tcps_predack); 1304 1305 /* 1306 * "bad retransmit" recovery. 1307 */ 1308 if (tp->t_rxtshift == 1 && 1309 (int)(ticks - tp->t_badrxtwin) < 0) { 1310 TCPSTAT_INC(tcps_sndrexmitbad); 1311 tp->snd_cwnd = tp->snd_cwnd_prev; 1312 tp->snd_ssthresh = 1313 tp->snd_ssthresh_prev; 1314 tp->snd_recover = tp->snd_recover_prev; 1315 if (tp->t_flags & TF_WASFRECOVERY) 1316 ENTER_FASTRECOVERY(tp); 1317 tp->snd_nxt = tp->snd_max; 1318 tp->t_badrxtwin = 0; 1319 } 1320 1321 /* 1322 * Recalculate the transmit timer / rtt. 1323 * 1324 * Some boxes send broken timestamp replies 1325 * during the SYN+ACK phase, ignore 1326 * timestamps of 0 or we could calculate a 1327 * huge RTT and blow up the retransmit timer. 1328 */ 1329 if ((to.to_flags & TOF_TS) != 0 && 1330 to.to_tsecr) { 1331 if (!tp->t_rttlow || 1332 tp->t_rttlow > ticks - to.to_tsecr) 1333 tp->t_rttlow = ticks - to.to_tsecr; 1334 tcp_xmit_timer(tp, 1335 ticks - to.to_tsecr + 1); 1336 } else if (tp->t_rtttime && 1337 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1338 if (!tp->t_rttlow || 1339 tp->t_rttlow > ticks - tp->t_rtttime) 1340 tp->t_rttlow = ticks - tp->t_rtttime; 1341 tcp_xmit_timer(tp, 1342 ticks - tp->t_rtttime); 1343 } 1344 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1345 acked = th->th_ack - tp->snd_una; 1346 TCPSTAT_INC(tcps_rcvackpack); 1347 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1348 sbdrop(&so->so_snd, acked); 1349 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1350 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1351 tp->snd_recover = th->th_ack - 1; 1352 tp->snd_una = th->th_ack; 1353 /* 1354 * Pull snd_wl2 up to prevent seq wrap relative 1355 * to th_ack. 1356 */ 1357 tp->snd_wl2 = th->th_ack; 1358 tp->t_dupacks = 0; 1359 m_freem(m); 1360 ND6_HINT(tp); /* Some progress has been made. */ 1361 1362 /* 1363 * If all outstanding data are acked, stop 1364 * retransmit timer, otherwise restart timer 1365 * using current (possibly backed-off) value. 1366 * If process is waiting for space, 1367 * wakeup/selwakeup/signal. If data 1368 * are ready to send, let tcp_output 1369 * decide between more output or persist. 1370 */ 1371 #ifdef TCPDEBUG 1372 if (so->so_options & SO_DEBUG) 1373 tcp_trace(TA_INPUT, ostate, tp, 1374 (void *)tcp_saveipgen, 1375 &tcp_savetcp, 0); 1376 #endif 1377 if (tp->snd_una == tp->snd_max) 1378 tcp_timer_activate(tp, TT_REXMT, 0); 1379 else if (!tcp_timer_active(tp, TT_PERSIST)) 1380 tcp_timer_activate(tp, TT_REXMT, 1381 tp->t_rxtcur); 1382 sowwakeup(so); 1383 if (so->so_snd.sb_cc) 1384 (void) tcp_output(tp); 1385 goto check_delack; 1386 } 1387 } else if (th->th_ack == tp->snd_una && 1388 tlen <= sbspace(&so->so_rcv)) { 1389 int newsize = 0; /* automatic sockbuf scaling */ 1390 1391 /* 1392 * This is a pure, in-sequence data packet with 1393 * nothing on the reassembly queue and we have enough 1394 * buffer space to take it. 1395 */ 1396 if (ti_locked == TI_RLOCKED) 1397 INP_INFO_RUNLOCK(&V_tcbinfo); 1398 else if (ti_locked == TI_WLOCKED) 1399 INP_INFO_WUNLOCK(&V_tcbinfo); 1400 else 1401 panic("%s: ti_locked %d on pure data " 1402 "segment", __func__, ti_locked); 1403 ti_locked = TI_UNLOCKED; 1404 1405 /* Clean receiver SACK report if present */ 1406 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1407 tcp_clean_sackreport(tp); 1408 TCPSTAT_INC(tcps_preddat); 1409 tp->rcv_nxt += tlen; 1410 /* 1411 * Pull snd_wl1 up to prevent seq wrap relative to 1412 * th_seq. 1413 */ 1414 tp->snd_wl1 = th->th_seq; 1415 /* 1416 * Pull rcv_up up to prevent seq wrap relative to 1417 * rcv_nxt. 1418 */ 1419 tp->rcv_up = tp->rcv_nxt; 1420 TCPSTAT_INC(tcps_rcvpack); 1421 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1422 ND6_HINT(tp); /* Some progress has been made */ 1423 #ifdef TCPDEBUG 1424 if (so->so_options & SO_DEBUG) 1425 tcp_trace(TA_INPUT, ostate, tp, 1426 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1427 #endif 1428 /* 1429 * Automatic sizing of receive socket buffer. Often the send 1430 * buffer size is not optimally adjusted to the actual network 1431 * conditions at hand (delay bandwidth product). Setting the 1432 * buffer size too small limits throughput on links with high 1433 * bandwidth and high delay (eg. trans-continental/oceanic links). 1434 * 1435 * On the receive side the socket buffer memory is only rarely 1436 * used to any significant extent. This allows us to be much 1437 * more aggressive in scaling the receive socket buffer. For 1438 * the case that the buffer space is actually used to a large 1439 * extent and we run out of kernel memory we can simply drop 1440 * the new segments; TCP on the sender will just retransmit it 1441 * later. Setting the buffer size too big may only consume too 1442 * much kernel memory if the application doesn't read() from 1443 * the socket or packet loss or reordering makes use of the 1444 * reassembly queue. 1445 * 1446 * The criteria to step up the receive buffer one notch are: 1447 * 1. the number of bytes received during the time it takes 1448 * one timestamp to be reflected back to us (the RTT); 1449 * 2. received bytes per RTT is within seven eighth of the 1450 * current socket buffer size; 1451 * 3. receive buffer size has not hit maximal automatic size; 1452 * 1453 * This algorithm does one step per RTT at most and only if 1454 * we receive a bulk stream w/o packet losses or reorderings. 1455 * Shrinking the buffer during idle times is not necessary as 1456 * it doesn't consume any memory when idle. 1457 * 1458 * TODO: Only step up if the application is actually serving 1459 * the buffer to better manage the socket buffer resources. 1460 */ 1461 if (V_tcp_do_autorcvbuf && 1462 to.to_tsecr && 1463 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1464 if (to.to_tsecr > tp->rfbuf_ts && 1465 to.to_tsecr - tp->rfbuf_ts < hz) { 1466 if (tp->rfbuf_cnt > 1467 (so->so_rcv.sb_hiwat / 8 * 7) && 1468 so->so_rcv.sb_hiwat < 1469 V_tcp_autorcvbuf_max) { 1470 newsize = 1471 min(so->so_rcv.sb_hiwat + 1472 V_tcp_autorcvbuf_inc, 1473 V_tcp_autorcvbuf_max); 1474 } 1475 /* Start over with next RTT. */ 1476 tp->rfbuf_ts = 0; 1477 tp->rfbuf_cnt = 0; 1478 } else 1479 tp->rfbuf_cnt += tlen; /* add up */ 1480 } 1481 1482 /* Add data to socket buffer. */ 1483 SOCKBUF_LOCK(&so->so_rcv); 1484 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1485 m_freem(m); 1486 } else { 1487 /* 1488 * Set new socket buffer size. 1489 * Give up when limit is reached. 1490 */ 1491 if (newsize) 1492 if (!sbreserve_locked(&so->so_rcv, 1493 newsize, so, NULL)) 1494 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1495 m_adj(m, drop_hdrlen); /* delayed header drop */ 1496 sbappendstream_locked(&so->so_rcv, m); 1497 } 1498 /* NB: sorwakeup_locked() does an implicit unlock. */ 1499 sorwakeup_locked(so); 1500 if (DELAY_ACK(tp)) { 1501 tp->t_flags |= TF_DELACK; 1502 } else { 1503 tp->t_flags |= TF_ACKNOW; 1504 tcp_output(tp); 1505 } 1506 goto check_delack; 1507 } 1508 } 1509 1510 /* 1511 * Calculate amount of space in receive window, 1512 * and then do TCP input processing. 1513 * Receive window is amount of space in rcv queue, 1514 * but not less than advertised window. 1515 */ 1516 win = sbspace(&so->so_rcv); 1517 if (win < 0) 1518 win = 0; 1519 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1520 1521 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1522 tp->rfbuf_ts = 0; 1523 tp->rfbuf_cnt = 0; 1524 1525 switch (tp->t_state) { 1526 1527 /* 1528 * If the state is SYN_RECEIVED: 1529 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1530 */ 1531 case TCPS_SYN_RECEIVED: 1532 if ((thflags & TH_ACK) && 1533 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1534 SEQ_GT(th->th_ack, tp->snd_max))) { 1535 rstreason = BANDLIM_RST_OPENPORT; 1536 goto dropwithreset; 1537 } 1538 break; 1539 1540 /* 1541 * If the state is SYN_SENT: 1542 * if seg contains an ACK, but not for our SYN, drop the input. 1543 * if seg contains a RST, then drop the connection. 1544 * if seg does not contain SYN, then drop it. 1545 * Otherwise this is an acceptable SYN segment 1546 * initialize tp->rcv_nxt and tp->irs 1547 * if seg contains ack then advance tp->snd_una 1548 * if seg contains an ECE and ECN support is enabled, the stream 1549 * is ECN capable. 1550 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1551 * arrange for segment to be acked (eventually) 1552 * continue processing rest of data/controls, beginning with URG 1553 */ 1554 case TCPS_SYN_SENT: 1555 if ((thflags & TH_ACK) && 1556 (SEQ_LEQ(th->th_ack, tp->iss) || 1557 SEQ_GT(th->th_ack, tp->snd_max))) { 1558 rstreason = BANDLIM_UNLIMITED; 1559 goto dropwithreset; 1560 } 1561 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) 1562 tp = tcp_drop(tp, ECONNREFUSED); 1563 if (thflags & TH_RST) 1564 goto drop; 1565 if (!(thflags & TH_SYN)) 1566 goto drop; 1567 1568 tp->irs = th->th_seq; 1569 tcp_rcvseqinit(tp); 1570 if (thflags & TH_ACK) { 1571 TCPSTAT_INC(tcps_connects); 1572 soisconnected(so); 1573 #ifdef MAC 1574 mac_socketpeer_set_from_mbuf(m, so); 1575 #endif 1576 /* Do window scaling on this connection? */ 1577 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1578 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1579 tp->rcv_scale = tp->request_r_scale; 1580 } 1581 tp->rcv_adv += tp->rcv_wnd; 1582 tp->snd_una++; /* SYN is acked */ 1583 /* 1584 * If there's data, delay ACK; if there's also a FIN 1585 * ACKNOW will be turned on later. 1586 */ 1587 if (DELAY_ACK(tp) && tlen != 0) 1588 tcp_timer_activate(tp, TT_DELACK, 1589 tcp_delacktime); 1590 else 1591 tp->t_flags |= TF_ACKNOW; 1592 1593 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 1594 tp->t_flags |= TF_ECN_PERMIT; 1595 TCPSTAT_INC(tcps_ecn_shs); 1596 } 1597 1598 /* 1599 * Received <SYN,ACK> in SYN_SENT[*] state. 1600 * Transitions: 1601 * SYN_SENT --> ESTABLISHED 1602 * SYN_SENT* --> FIN_WAIT_1 1603 */ 1604 tp->t_starttime = ticks; 1605 if (tp->t_flags & TF_NEEDFIN) { 1606 tp->t_state = TCPS_FIN_WAIT_1; 1607 tp->t_flags &= ~TF_NEEDFIN; 1608 thflags &= ~TH_SYN; 1609 } else { 1610 tp->t_state = TCPS_ESTABLISHED; 1611 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 1612 } 1613 } else { 1614 /* 1615 * Received initial SYN in SYN-SENT[*] state => 1616 * simultaneous open. If segment contains CC option 1617 * and there is a cached CC, apply TAO test. 1618 * If it succeeds, connection is * half-synchronized. 1619 * Otherwise, do 3-way handshake: 1620 * SYN-SENT -> SYN-RECEIVED 1621 * SYN-SENT* -> SYN-RECEIVED* 1622 * If there was no CC option, clear cached CC value. 1623 */ 1624 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1625 tcp_timer_activate(tp, TT_REXMT, 0); 1626 tp->t_state = TCPS_SYN_RECEIVED; 1627 } 1628 1629 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: " 1630 "ti_locked %d", __func__, ti_locked)); 1631 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1632 INP_WLOCK_ASSERT(tp->t_inpcb); 1633 1634 /* 1635 * Advance th->th_seq to correspond to first data byte. 1636 * If data, trim to stay within window, 1637 * dropping FIN if necessary. 1638 */ 1639 th->th_seq++; 1640 if (tlen > tp->rcv_wnd) { 1641 todrop = tlen - tp->rcv_wnd; 1642 m_adj(m, -todrop); 1643 tlen = tp->rcv_wnd; 1644 thflags &= ~TH_FIN; 1645 TCPSTAT_INC(tcps_rcvpackafterwin); 1646 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 1647 } 1648 tp->snd_wl1 = th->th_seq - 1; 1649 tp->rcv_up = th->th_seq; 1650 /* 1651 * Client side of transaction: already sent SYN and data. 1652 * If the remote host used T/TCP to validate the SYN, 1653 * our data will be ACK'd; if so, enter normal data segment 1654 * processing in the middle of step 5, ack processing. 1655 * Otherwise, goto step 6. 1656 */ 1657 if (thflags & TH_ACK) 1658 goto process_ACK; 1659 1660 goto step6; 1661 1662 /* 1663 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1664 * do normal processing. 1665 * 1666 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1667 */ 1668 case TCPS_LAST_ACK: 1669 case TCPS_CLOSING: 1670 break; /* continue normal processing */ 1671 } 1672 1673 /* 1674 * States other than LISTEN or SYN_SENT. 1675 * First check the RST flag and sequence number since reset segments 1676 * are exempt from the timestamp and connection count tests. This 1677 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1678 * below which allowed reset segments in half the sequence space 1679 * to fall though and be processed (which gives forged reset 1680 * segments with a random sequence number a 50 percent chance of 1681 * killing a connection). 1682 * Then check timestamp, if present. 1683 * Then check the connection count, if present. 1684 * Then check that at least some bytes of segment are within 1685 * receive window. If segment begins before rcv_nxt, 1686 * drop leading data (and SYN); if nothing left, just ack. 1687 * 1688 * 1689 * If the RST bit is set, check the sequence number to see 1690 * if this is a valid reset segment. 1691 * RFC 793 page 37: 1692 * In all states except SYN-SENT, all reset (RST) segments 1693 * are validated by checking their SEQ-fields. A reset is 1694 * valid if its sequence number is in the window. 1695 * Note: this does not take into account delayed ACKs, so 1696 * we should test against last_ack_sent instead of rcv_nxt. 1697 * The sequence number in the reset segment is normally an 1698 * echo of our outgoing acknowlegement numbers, but some hosts 1699 * send a reset with the sequence number at the rightmost edge 1700 * of our receive window, and we have to handle this case. 1701 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1702 * that brute force RST attacks are possible. To combat this, 1703 * we use a much stricter check while in the ESTABLISHED state, 1704 * only accepting RSTs where the sequence number is equal to 1705 * last_ack_sent. In all other states (the states in which a 1706 * RST is more likely), the more permissive check is used. 1707 * If we have multiple segments in flight, the initial reset 1708 * segment sequence numbers will be to the left of last_ack_sent, 1709 * but they will eventually catch up. 1710 * In any case, it never made sense to trim reset segments to 1711 * fit the receive window since RFC 1122 says: 1712 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1713 * 1714 * A TCP SHOULD allow a received RST segment to include data. 1715 * 1716 * DISCUSSION 1717 * It has been suggested that a RST segment could contain 1718 * ASCII text that encoded and explained the cause of the 1719 * RST. No standard has yet been established for such 1720 * data. 1721 * 1722 * If the reset segment passes the sequence number test examine 1723 * the state: 1724 * SYN_RECEIVED STATE: 1725 * If passive open, return to LISTEN state. 1726 * If active open, inform user that connection was refused. 1727 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1728 * Inform user that connection was reset, and close tcb. 1729 * CLOSING, LAST_ACK STATES: 1730 * Close the tcb. 1731 * TIME_WAIT STATE: 1732 * Drop the segment - see Stevens, vol. 2, p. 964 and 1733 * RFC 1337. 1734 */ 1735 if (thflags & TH_RST) { 1736 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1737 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1738 switch (tp->t_state) { 1739 1740 case TCPS_SYN_RECEIVED: 1741 so->so_error = ECONNREFUSED; 1742 goto close; 1743 1744 case TCPS_ESTABLISHED: 1745 if (V_tcp_insecure_rst == 0 && 1746 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 1747 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 1748 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1749 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 1750 TCPSTAT_INC(tcps_badrst); 1751 goto drop; 1752 } 1753 /* FALLTHROUGH */ 1754 case TCPS_FIN_WAIT_1: 1755 case TCPS_FIN_WAIT_2: 1756 case TCPS_CLOSE_WAIT: 1757 so->so_error = ECONNRESET; 1758 close: 1759 KASSERT(ti_locked == TI_WLOCKED, 1760 ("tcp_do_segment: TH_RST 1 ti_locked %d", 1761 ti_locked)); 1762 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1763 1764 tp->t_state = TCPS_CLOSED; 1765 TCPSTAT_INC(tcps_drops); 1766 tp = tcp_close(tp); 1767 break; 1768 1769 case TCPS_CLOSING: 1770 case TCPS_LAST_ACK: 1771 KASSERT(ti_locked == TI_WLOCKED, 1772 ("tcp_do_segment: TH_RST 2 ti_locked %d", 1773 ti_locked)); 1774 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1775 1776 tp = tcp_close(tp); 1777 break; 1778 } 1779 } 1780 goto drop; 1781 } 1782 1783 /* 1784 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1785 * and it's less than ts_recent, drop it. 1786 */ 1787 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1788 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1789 1790 /* Check to see if ts_recent is over 24 days old. */ 1791 if (ticks - tp->ts_recent_age > TCP_PAWS_IDLE) { 1792 /* 1793 * Invalidate ts_recent. If this segment updates 1794 * ts_recent, the age will be reset later and ts_recent 1795 * will get a valid value. If it does not, setting 1796 * ts_recent to zero will at least satisfy the 1797 * requirement that zero be placed in the timestamp 1798 * echo reply when ts_recent isn't valid. The 1799 * age isn't reset until we get a valid ts_recent 1800 * because we don't want out-of-order segments to be 1801 * dropped when ts_recent is old. 1802 */ 1803 tp->ts_recent = 0; 1804 } else { 1805 TCPSTAT_INC(tcps_rcvduppack); 1806 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 1807 TCPSTAT_INC(tcps_pawsdrop); 1808 if (tlen) 1809 goto dropafterack; 1810 goto drop; 1811 } 1812 } 1813 1814 /* 1815 * In the SYN-RECEIVED state, validate that the packet belongs to 1816 * this connection before trimming the data to fit the receive 1817 * window. Check the sequence number versus IRS since we know 1818 * the sequence numbers haven't wrapped. This is a partial fix 1819 * for the "LAND" DoS attack. 1820 */ 1821 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1822 rstreason = BANDLIM_RST_OPENPORT; 1823 goto dropwithreset; 1824 } 1825 1826 todrop = tp->rcv_nxt - th->th_seq; 1827 if (todrop > 0) { 1828 /* 1829 * If this is a duplicate SYN for our current connection, 1830 * advance over it and pretend and it's not a SYN. 1831 */ 1832 if (thflags & TH_SYN && th->th_seq == tp->irs) { 1833 thflags &= ~TH_SYN; 1834 th->th_seq++; 1835 if (th->th_urp > 1) 1836 th->th_urp--; 1837 else 1838 thflags &= ~TH_URG; 1839 todrop--; 1840 } 1841 /* 1842 * Following if statement from Stevens, vol. 2, p. 960. 1843 */ 1844 if (todrop > tlen 1845 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1846 /* 1847 * Any valid FIN must be to the left of the window. 1848 * At this point the FIN must be a duplicate or out 1849 * of sequence; drop it. 1850 */ 1851 thflags &= ~TH_FIN; 1852 1853 /* 1854 * Send an ACK to resynchronize and drop any data. 1855 * But keep on processing for RST or ACK. 1856 */ 1857 tp->t_flags |= TF_ACKNOW; 1858 todrop = tlen; 1859 TCPSTAT_INC(tcps_rcvduppack); 1860 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 1861 } else { 1862 TCPSTAT_INC(tcps_rcvpartduppack); 1863 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 1864 } 1865 drop_hdrlen += todrop; /* drop from the top afterwards */ 1866 th->th_seq += todrop; 1867 tlen -= todrop; 1868 if (th->th_urp > todrop) 1869 th->th_urp -= todrop; 1870 else { 1871 thflags &= ~TH_URG; 1872 th->th_urp = 0; 1873 } 1874 } 1875 1876 /* 1877 * If new data are received on a connection after the 1878 * user processes are gone, then RST the other end. 1879 */ 1880 if ((so->so_state & SS_NOFDREF) && 1881 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1882 char *s; 1883 1884 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && " 1885 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 1886 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1887 1888 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { 1889 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket " 1890 "was closed, sending RST and removing tcpcb\n", 1891 s, __func__, tcpstates[tp->t_state], tlen); 1892 free(s, M_TCPLOG); 1893 } 1894 tp = tcp_close(tp); 1895 TCPSTAT_INC(tcps_rcvafterclose); 1896 rstreason = BANDLIM_UNLIMITED; 1897 goto dropwithreset; 1898 } 1899 1900 /* 1901 * If segment ends after window, drop trailing data 1902 * (and PUSH and FIN); if nothing left, just ACK. 1903 */ 1904 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1905 if (todrop > 0) { 1906 TCPSTAT_INC(tcps_rcvpackafterwin); 1907 if (todrop >= tlen) { 1908 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 1909 /* 1910 * If window is closed can only take segments at 1911 * window edge, and have to drop data and PUSH from 1912 * incoming segments. Continue processing, but 1913 * remember to ack. Otherwise, drop segment 1914 * and ack. 1915 */ 1916 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1917 tp->t_flags |= TF_ACKNOW; 1918 TCPSTAT_INC(tcps_rcvwinprobe); 1919 } else 1920 goto dropafterack; 1921 } else 1922 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 1923 m_adj(m, -todrop); 1924 tlen -= todrop; 1925 thflags &= ~(TH_PUSH|TH_FIN); 1926 } 1927 1928 /* 1929 * If last ACK falls within this segment's sequence numbers, 1930 * record its timestamp. 1931 * NOTE: 1932 * 1) That the test incorporates suggestions from the latest 1933 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1934 * 2) That updating only on newer timestamps interferes with 1935 * our earlier PAWS tests, so this check should be solely 1936 * predicated on the sequence space of this segment. 1937 * 3) That we modify the segment boundary check to be 1938 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1939 * instead of RFC1323's 1940 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1941 * This modified check allows us to overcome RFC1323's 1942 * limitations as described in Stevens TCP/IP Illustrated 1943 * Vol. 2 p.869. In such cases, we can still calculate the 1944 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1945 */ 1946 if ((to.to_flags & TOF_TS) != 0 && 1947 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1948 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1949 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1950 tp->ts_recent_age = ticks; 1951 tp->ts_recent = to.to_tsval; 1952 } 1953 1954 /* 1955 * If a SYN is in the window, then this is an 1956 * error and we send an RST and drop the connection. 1957 */ 1958 if (thflags & TH_SYN) { 1959 KASSERT(ti_locked == TI_WLOCKED, 1960 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 1961 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1962 1963 tp = tcp_drop(tp, ECONNRESET); 1964 rstreason = BANDLIM_UNLIMITED; 1965 goto drop; 1966 } 1967 1968 /* 1969 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1970 * flag is on (half-synchronized state), then queue data for 1971 * later processing; else drop segment and return. 1972 */ 1973 if ((thflags & TH_ACK) == 0) { 1974 if (tp->t_state == TCPS_SYN_RECEIVED || 1975 (tp->t_flags & TF_NEEDSYN)) 1976 goto step6; 1977 else if (tp->t_flags & TF_ACKNOW) 1978 goto dropafterack; 1979 else 1980 goto drop; 1981 } 1982 1983 /* 1984 * Ack processing. 1985 */ 1986 switch (tp->t_state) { 1987 1988 /* 1989 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1990 * ESTABLISHED state and continue processing. 1991 * The ACK was checked above. 1992 */ 1993 case TCPS_SYN_RECEIVED: 1994 1995 TCPSTAT_INC(tcps_connects); 1996 soisconnected(so); 1997 /* Do window scaling? */ 1998 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1999 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2000 tp->rcv_scale = tp->request_r_scale; 2001 tp->snd_wnd = tiwin; 2002 } 2003 /* 2004 * Make transitions: 2005 * SYN-RECEIVED -> ESTABLISHED 2006 * SYN-RECEIVED* -> FIN-WAIT-1 2007 */ 2008 tp->t_starttime = ticks; 2009 if (tp->t_flags & TF_NEEDFIN) { 2010 tp->t_state = TCPS_FIN_WAIT_1; 2011 tp->t_flags &= ~TF_NEEDFIN; 2012 } else { 2013 tp->t_state = TCPS_ESTABLISHED; 2014 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 2015 } 2016 /* 2017 * If segment contains data or ACK, will call tcp_reass() 2018 * later; if not, do so now to pass queued data to user. 2019 */ 2020 if (tlen == 0 && (thflags & TH_FIN) == 0) 2021 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2022 (struct mbuf *)0); 2023 tp->snd_wl1 = th->th_seq - 1; 2024 /* FALLTHROUGH */ 2025 2026 /* 2027 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2028 * ACKs. If the ack is in the range 2029 * tp->snd_una < th->th_ack <= tp->snd_max 2030 * then advance tp->snd_una to th->th_ack and drop 2031 * data from the retransmission queue. If this ACK reflects 2032 * more up to date window information we update our window information. 2033 */ 2034 case TCPS_ESTABLISHED: 2035 case TCPS_FIN_WAIT_1: 2036 case TCPS_FIN_WAIT_2: 2037 case TCPS_CLOSE_WAIT: 2038 case TCPS_CLOSING: 2039 case TCPS_LAST_ACK: 2040 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2041 TCPSTAT_INC(tcps_rcvacktoomuch); 2042 goto dropafterack; 2043 } 2044 if ((tp->t_flags & TF_SACK_PERMIT) && 2045 ((to.to_flags & TOF_SACK) || 2046 !TAILQ_EMPTY(&tp->snd_holes))) 2047 tcp_sack_doack(tp, &to, th->th_ack); 2048 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2049 if (tlen == 0 && tiwin == tp->snd_wnd) { 2050 TCPSTAT_INC(tcps_rcvdupack); 2051 /* 2052 * If we have outstanding data (other than 2053 * a window probe), this is a completely 2054 * duplicate ack (ie, window info didn't 2055 * change), the ack is the biggest we've 2056 * seen and we've seen exactly our rexmt 2057 * threshhold of them, assume a packet 2058 * has been dropped and retransmit it. 2059 * Kludge snd_nxt & the congestion 2060 * window so we send only this one 2061 * packet. 2062 * 2063 * We know we're losing at the current 2064 * window size so do congestion avoidance 2065 * (set ssthresh to half the current window 2066 * and pull our congestion window back to 2067 * the new ssthresh). 2068 * 2069 * Dup acks mean that packets have left the 2070 * network (they're now cached at the receiver) 2071 * so bump cwnd by the amount in the receiver 2072 * to keep a constant cwnd packets in the 2073 * network. 2074 * 2075 * When using TCP ECN, notify the peer that 2076 * we reduced the cwnd. 2077 */ 2078 if (!tcp_timer_active(tp, TT_REXMT) || 2079 th->th_ack != tp->snd_una) 2080 tp->t_dupacks = 0; 2081 else if (++tp->t_dupacks > tcprexmtthresh || 2082 ((V_tcp_do_newreno || 2083 (tp->t_flags & TF_SACK_PERMIT)) && 2084 IN_FASTRECOVERY(tp))) { 2085 if ((tp->t_flags & TF_SACK_PERMIT) && 2086 IN_FASTRECOVERY(tp)) { 2087 int awnd; 2088 2089 /* 2090 * Compute the amount of data in flight first. 2091 * We can inject new data into the pipe iff 2092 * we have less than 1/2 the original window's 2093 * worth of data in flight. 2094 */ 2095 awnd = (tp->snd_nxt - tp->snd_fack) + 2096 tp->sackhint.sack_bytes_rexmit; 2097 if (awnd < tp->snd_ssthresh) { 2098 tp->snd_cwnd += tp->t_maxseg; 2099 if (tp->snd_cwnd > tp->snd_ssthresh) 2100 tp->snd_cwnd = tp->snd_ssthresh; 2101 } 2102 } else 2103 tp->snd_cwnd += tp->t_maxseg; 2104 (void) tcp_output(tp); 2105 goto drop; 2106 } else if (tp->t_dupacks == tcprexmtthresh) { 2107 tcp_seq onxt = tp->snd_nxt; 2108 2109 /* 2110 * If we're doing sack, check to 2111 * see if we're already in sack 2112 * recovery. If we're not doing sack, 2113 * check to see if we're in newreno 2114 * recovery. 2115 */ 2116 if (tp->t_flags & TF_SACK_PERMIT) { 2117 if (IN_FASTRECOVERY(tp)) { 2118 tp->t_dupacks = 0; 2119 break; 2120 } 2121 } else if (V_tcp_do_newreno || 2122 V_tcp_do_ecn) { 2123 if (SEQ_LEQ(th->th_ack, 2124 tp->snd_recover)) { 2125 tp->t_dupacks = 0; 2126 break; 2127 } 2128 } 2129 tcp_congestion_exp(tp); 2130 tcp_timer_activate(tp, TT_REXMT, 0); 2131 tp->t_rtttime = 0; 2132 if (tp->t_flags & TF_SACK_PERMIT) { 2133 TCPSTAT_INC( 2134 tcps_sack_recovery_episode); 2135 tp->sack_newdata = tp->snd_nxt; 2136 tp->snd_cwnd = tp->t_maxseg; 2137 (void) tcp_output(tp); 2138 goto drop; 2139 } 2140 tp->snd_nxt = th->th_ack; 2141 tp->snd_cwnd = tp->t_maxseg; 2142 (void) tcp_output(tp); 2143 KASSERT(tp->snd_limited <= 2, 2144 ("%s: tp->snd_limited too big", 2145 __func__)); 2146 tp->snd_cwnd = tp->snd_ssthresh + 2147 tp->t_maxseg * 2148 (tp->t_dupacks - tp->snd_limited); 2149 if (SEQ_GT(onxt, tp->snd_nxt)) 2150 tp->snd_nxt = onxt; 2151 goto drop; 2152 } else if (V_tcp_do_rfc3042) { 2153 u_long oldcwnd = tp->snd_cwnd; 2154 tcp_seq oldsndmax = tp->snd_max; 2155 u_int sent; 2156 2157 KASSERT(tp->t_dupacks == 1 || 2158 tp->t_dupacks == 2, 2159 ("%s: dupacks not 1 or 2", 2160 __func__)); 2161 if (tp->t_dupacks == 1) 2162 tp->snd_limited = 0; 2163 tp->snd_cwnd = 2164 (tp->snd_nxt - tp->snd_una) + 2165 (tp->t_dupacks - tp->snd_limited) * 2166 tp->t_maxseg; 2167 (void) tcp_output(tp); 2168 sent = tp->snd_max - oldsndmax; 2169 if (sent > tp->t_maxseg) { 2170 KASSERT((tp->t_dupacks == 2 && 2171 tp->snd_limited == 0) || 2172 (sent == tp->t_maxseg + 1 && 2173 tp->t_flags & TF_SENTFIN), 2174 ("%s: sent too much", 2175 __func__)); 2176 tp->snd_limited = 2; 2177 } else if (sent > 0) 2178 ++tp->snd_limited; 2179 tp->snd_cwnd = oldcwnd; 2180 goto drop; 2181 } 2182 } else 2183 tp->t_dupacks = 0; 2184 break; 2185 } 2186 2187 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2188 ("%s: th_ack <= snd_una", __func__)); 2189 2190 /* 2191 * If the congestion window was inflated to account 2192 * for the other side's cached packets, retract it. 2193 */ 2194 if (V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) { 2195 if (IN_FASTRECOVERY(tp)) { 2196 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2197 if (tp->t_flags & TF_SACK_PERMIT) 2198 tcp_sack_partialack(tp, th); 2199 else 2200 tcp_newreno_partial_ack(tp, th); 2201 } else { 2202 /* 2203 * Out of fast recovery. 2204 * Window inflation should have left us 2205 * with approximately snd_ssthresh 2206 * outstanding data. 2207 * But in case we would be inclined to 2208 * send a burst, better to do it via 2209 * the slow start mechanism. 2210 */ 2211 if (SEQ_GT(th->th_ack + 2212 tp->snd_ssthresh, 2213 tp->snd_max)) 2214 tp->snd_cwnd = tp->snd_max - 2215 th->th_ack + 2216 tp->t_maxseg; 2217 else 2218 tp->snd_cwnd = tp->snd_ssthresh; 2219 } 2220 } 2221 } else { 2222 if (tp->t_dupacks >= tcprexmtthresh && 2223 tp->snd_cwnd > tp->snd_ssthresh) 2224 tp->snd_cwnd = tp->snd_ssthresh; 2225 } 2226 tp->t_dupacks = 0; 2227 /* 2228 * If we reach this point, ACK is not a duplicate, 2229 * i.e., it ACKs something we sent. 2230 */ 2231 if (tp->t_flags & TF_NEEDSYN) { 2232 /* 2233 * T/TCP: Connection was half-synchronized, and our 2234 * SYN has been ACK'd (so connection is now fully 2235 * synchronized). Go to non-starred state, 2236 * increment snd_una for ACK of SYN, and check if 2237 * we can do window scaling. 2238 */ 2239 tp->t_flags &= ~TF_NEEDSYN; 2240 tp->snd_una++; 2241 /* Do window scaling? */ 2242 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2243 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2244 tp->rcv_scale = tp->request_r_scale; 2245 /* Send window already scaled. */ 2246 } 2247 } 2248 2249 process_ACK: 2250 INP_INFO_LOCK_ASSERT(&V_tcbinfo); 2251 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2252 ("tcp_input: process_ACK ti_locked %d", ti_locked)); 2253 INP_WLOCK_ASSERT(tp->t_inpcb); 2254 2255 acked = th->th_ack - tp->snd_una; 2256 TCPSTAT_INC(tcps_rcvackpack); 2257 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2258 2259 /* 2260 * If we just performed our first retransmit, and the ACK 2261 * arrives within our recovery window, then it was a mistake 2262 * to do the retransmit in the first place. Recover our 2263 * original cwnd and ssthresh, and proceed to transmit where 2264 * we left off. 2265 */ 2266 if (tp->t_rxtshift == 1 && (int)(ticks - tp->t_badrxtwin) < 0) { 2267 TCPSTAT_INC(tcps_sndrexmitbad); 2268 tp->snd_cwnd = tp->snd_cwnd_prev; 2269 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2270 tp->snd_recover = tp->snd_recover_prev; 2271 if (tp->t_flags & TF_WASFRECOVERY) 2272 ENTER_FASTRECOVERY(tp); 2273 tp->snd_nxt = tp->snd_max; 2274 tp->t_badrxtwin = 0; /* XXX probably not required */ 2275 } 2276 2277 /* 2278 * If we have a timestamp reply, update smoothed 2279 * round trip time. If no timestamp is present but 2280 * transmit timer is running and timed sequence 2281 * number was acked, update smoothed round trip time. 2282 * Since we now have an rtt measurement, cancel the 2283 * timer backoff (cf., Phil Karn's retransmit alg.). 2284 * Recompute the initial retransmit timer. 2285 * 2286 * Some boxes send broken timestamp replies 2287 * during the SYN+ACK phase, ignore 2288 * timestamps of 0 or we could calculate a 2289 * huge RTT and blow up the retransmit timer. 2290 */ 2291 if ((to.to_flags & TOF_TS) != 0 && 2292 to.to_tsecr) { 2293 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2294 tp->t_rttlow = ticks - to.to_tsecr; 2295 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2296 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2297 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2298 tp->t_rttlow = ticks - tp->t_rtttime; 2299 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2300 } 2301 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2302 2303 /* 2304 * If all outstanding data is acked, stop retransmit 2305 * timer and remember to restart (more output or persist). 2306 * If there is more data to be acked, restart retransmit 2307 * timer, using current (possibly backed-off) value. 2308 */ 2309 if (th->th_ack == tp->snd_max) { 2310 tcp_timer_activate(tp, TT_REXMT, 0); 2311 needoutput = 1; 2312 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2313 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2314 2315 /* 2316 * If no data (only SYN) was ACK'd, 2317 * skip rest of ACK processing. 2318 */ 2319 if (acked == 0) 2320 goto step6; 2321 2322 /* 2323 * When new data is acked, open the congestion window. 2324 * Method depends on which congestion control state we're 2325 * in (slow start or cong avoid) and if ABC (RFC 3465) is 2326 * enabled. 2327 * 2328 * slow start: cwnd <= ssthresh 2329 * cong avoid: cwnd > ssthresh 2330 * 2331 * slow start and ABC (RFC 3465): 2332 * Grow cwnd exponentially by the amount of data 2333 * ACKed capping the max increment per ACK to 2334 * (abc_l_var * maxseg) bytes. 2335 * 2336 * slow start without ABC (RFC 2581): 2337 * Grow cwnd exponentially by maxseg per ACK. 2338 * 2339 * cong avoid and ABC (RFC 3465): 2340 * Grow cwnd linearly by maxseg per RTT for each 2341 * cwnd worth of ACKed data. 2342 * 2343 * cong avoid without ABC (RFC 2581): 2344 * Grow cwnd linearly by approximately maxseg per RTT using 2345 * maxseg^2 / cwnd per ACK as the increment. 2346 * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to 2347 * avoid capping cwnd. 2348 */ 2349 if ((!V_tcp_do_newreno && !(tp->t_flags & TF_SACK_PERMIT)) || 2350 !IN_FASTRECOVERY(tp)) { 2351 u_int cw = tp->snd_cwnd; 2352 u_int incr = tp->t_maxseg; 2353 /* In congestion avoidance? */ 2354 if (cw > tp->snd_ssthresh) { 2355 if (V_tcp_do_rfc3465) { 2356 tp->t_bytes_acked += acked; 2357 if (tp->t_bytes_acked >= tp->snd_cwnd) 2358 tp->t_bytes_acked -= cw; 2359 else 2360 incr = 0; 2361 } 2362 else 2363 incr = max((incr * incr / cw), 1); 2364 /* 2365 * In slow-start with ABC enabled and no RTO in sight? 2366 * (Must not use abc_l_var > 1 if slow starting after an 2367 * RTO. On RTO, snd_nxt = snd_una, so the snd_nxt == 2368 * snd_max check is sufficient to handle this). 2369 */ 2370 } else if (V_tcp_do_rfc3465 && 2371 tp->snd_nxt == tp->snd_max) 2372 incr = min(acked, 2373 V_tcp_abc_l_var * tp->t_maxseg); 2374 /* ABC is on by default, so (incr == 0) frequently. */ 2375 if (incr > 0) 2376 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2377 } 2378 SOCKBUF_LOCK(&so->so_snd); 2379 if (acked > so->so_snd.sb_cc) { 2380 tp->snd_wnd -= so->so_snd.sb_cc; 2381 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2382 ourfinisacked = 1; 2383 } else { 2384 sbdrop_locked(&so->so_snd, acked); 2385 tp->snd_wnd -= acked; 2386 ourfinisacked = 0; 2387 } 2388 /* NB: sowwakeup_locked() does an implicit unlock. */ 2389 sowwakeup_locked(so); 2390 /* Detect una wraparound. */ 2391 if ((V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) && 2392 !IN_FASTRECOVERY(tp) && 2393 SEQ_GT(tp->snd_una, tp->snd_recover) && 2394 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2395 tp->snd_recover = th->th_ack - 1; 2396 if ((V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) && 2397 IN_FASTRECOVERY(tp) && 2398 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2399 EXIT_FASTRECOVERY(tp); 2400 tp->t_bytes_acked = 0; 2401 } 2402 tp->snd_una = th->th_ack; 2403 if (tp->t_flags & TF_SACK_PERMIT) { 2404 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2405 tp->snd_recover = tp->snd_una; 2406 } 2407 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2408 tp->snd_nxt = tp->snd_una; 2409 2410 switch (tp->t_state) { 2411 2412 /* 2413 * In FIN_WAIT_1 STATE in addition to the processing 2414 * for the ESTABLISHED state if our FIN is now acknowledged 2415 * then enter FIN_WAIT_2. 2416 */ 2417 case TCPS_FIN_WAIT_1: 2418 if (ourfinisacked) { 2419 /* 2420 * If we can't receive any more 2421 * data, then closing user can proceed. 2422 * Starting the timer is contrary to the 2423 * specification, but if we don't get a FIN 2424 * we'll hang forever. 2425 * 2426 * XXXjl: 2427 * we should release the tp also, and use a 2428 * compressed state. 2429 */ 2430 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2431 int timeout; 2432 2433 soisdisconnected(so); 2434 timeout = (tcp_fast_finwait2_recycle) ? 2435 tcp_finwait2_timeout : tcp_maxidle; 2436 tcp_timer_activate(tp, TT_2MSL, timeout); 2437 } 2438 tp->t_state = TCPS_FIN_WAIT_2; 2439 } 2440 break; 2441 2442 /* 2443 * In CLOSING STATE in addition to the processing for 2444 * the ESTABLISHED state if the ACK acknowledges our FIN 2445 * then enter the TIME-WAIT state, otherwise ignore 2446 * the segment. 2447 */ 2448 case TCPS_CLOSING: 2449 if (ourfinisacked) { 2450 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2451 tcp_twstart(tp); 2452 INP_INFO_WUNLOCK(&V_tcbinfo); 2453 m_freem(m); 2454 return; 2455 } 2456 break; 2457 2458 /* 2459 * In LAST_ACK, we may still be waiting for data to drain 2460 * and/or to be acked, as well as for the ack of our FIN. 2461 * If our FIN is now acknowledged, delete the TCB, 2462 * enter the closed state and return. 2463 */ 2464 case TCPS_LAST_ACK: 2465 if (ourfinisacked) { 2466 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2467 tp = tcp_close(tp); 2468 goto drop; 2469 } 2470 break; 2471 } 2472 } 2473 2474 step6: 2475 INP_INFO_LOCK_ASSERT(&V_tcbinfo); 2476 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2477 ("tcp_do_segment: step6 ti_locked %d", ti_locked)); 2478 INP_WLOCK_ASSERT(tp->t_inpcb); 2479 2480 /* 2481 * Update window information. 2482 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2483 */ 2484 if ((thflags & TH_ACK) && 2485 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2486 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2487 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2488 /* keep track of pure window updates */ 2489 if (tlen == 0 && 2490 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2491 TCPSTAT_INC(tcps_rcvwinupd); 2492 tp->snd_wnd = tiwin; 2493 tp->snd_wl1 = th->th_seq; 2494 tp->snd_wl2 = th->th_ack; 2495 if (tp->snd_wnd > tp->max_sndwnd) 2496 tp->max_sndwnd = tp->snd_wnd; 2497 needoutput = 1; 2498 } 2499 2500 /* 2501 * Process segments with URG. 2502 */ 2503 if ((thflags & TH_URG) && th->th_urp && 2504 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2505 /* 2506 * This is a kludge, but if we receive and accept 2507 * random urgent pointers, we'll crash in 2508 * soreceive. It's hard to imagine someone 2509 * actually wanting to send this much urgent data. 2510 */ 2511 SOCKBUF_LOCK(&so->so_rcv); 2512 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2513 th->th_urp = 0; /* XXX */ 2514 thflags &= ~TH_URG; /* XXX */ 2515 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2516 goto dodata; /* XXX */ 2517 } 2518 /* 2519 * If this segment advances the known urgent pointer, 2520 * then mark the data stream. This should not happen 2521 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2522 * a FIN has been received from the remote side. 2523 * In these states we ignore the URG. 2524 * 2525 * According to RFC961 (Assigned Protocols), 2526 * the urgent pointer points to the last octet 2527 * of urgent data. We continue, however, 2528 * to consider it to indicate the first octet 2529 * of data past the urgent section as the original 2530 * spec states (in one of two places). 2531 */ 2532 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2533 tp->rcv_up = th->th_seq + th->th_urp; 2534 so->so_oobmark = so->so_rcv.sb_cc + 2535 (tp->rcv_up - tp->rcv_nxt) - 1; 2536 if (so->so_oobmark == 0) 2537 so->so_rcv.sb_state |= SBS_RCVATMARK; 2538 sohasoutofband(so); 2539 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2540 } 2541 SOCKBUF_UNLOCK(&so->so_rcv); 2542 /* 2543 * Remove out of band data so doesn't get presented to user. 2544 * This can happen independent of advancing the URG pointer, 2545 * but if two URG's are pending at once, some out-of-band 2546 * data may creep in... ick. 2547 */ 2548 if (th->th_urp <= (u_long)tlen && 2549 !(so->so_options & SO_OOBINLINE)) { 2550 /* hdr drop is delayed */ 2551 tcp_pulloutofband(so, th, m, drop_hdrlen); 2552 } 2553 } else { 2554 /* 2555 * If no out of band data is expected, 2556 * pull receive urgent pointer along 2557 * with the receive window. 2558 */ 2559 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2560 tp->rcv_up = tp->rcv_nxt; 2561 } 2562 dodata: /* XXX */ 2563 INP_INFO_LOCK_ASSERT(&V_tcbinfo); 2564 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2565 ("tcp_do_segment: dodata ti_locked %d", ti_locked)); 2566 INP_WLOCK_ASSERT(tp->t_inpcb); 2567 2568 /* 2569 * Process the segment text, merging it into the TCP sequencing queue, 2570 * and arranging for acknowledgment of receipt if necessary. 2571 * This process logically involves adjusting tp->rcv_wnd as data 2572 * is presented to the user (this happens in tcp_usrreq.c, 2573 * case PRU_RCVD). If a FIN has already been received on this 2574 * connection then we just ignore the text. 2575 */ 2576 if ((tlen || (thflags & TH_FIN)) && 2577 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2578 tcp_seq save_start = th->th_seq; 2579 m_adj(m, drop_hdrlen); /* delayed header drop */ 2580 /* 2581 * Insert segment which includes th into TCP reassembly queue 2582 * with control block tp. Set thflags to whether reassembly now 2583 * includes a segment with FIN. This handles the common case 2584 * inline (segment is the next to be received on an established 2585 * connection, and the queue is empty), avoiding linkage into 2586 * and removal from the queue and repetition of various 2587 * conversions. 2588 * Set DELACK for segments received in order, but ack 2589 * immediately when segments are out of order (so 2590 * fast retransmit can work). 2591 */ 2592 if (th->th_seq == tp->rcv_nxt && 2593 LIST_EMPTY(&tp->t_segq) && 2594 TCPS_HAVEESTABLISHED(tp->t_state)) { 2595 if (DELAY_ACK(tp)) 2596 tp->t_flags |= TF_DELACK; 2597 else 2598 tp->t_flags |= TF_ACKNOW; 2599 tp->rcv_nxt += tlen; 2600 thflags = th->th_flags & TH_FIN; 2601 TCPSTAT_INC(tcps_rcvpack); 2602 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2603 ND6_HINT(tp); 2604 SOCKBUF_LOCK(&so->so_rcv); 2605 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2606 m_freem(m); 2607 else 2608 sbappendstream_locked(&so->so_rcv, m); 2609 /* NB: sorwakeup_locked() does an implicit unlock. */ 2610 sorwakeup_locked(so); 2611 } else { 2612 /* 2613 * XXX: Due to the header drop above "th" is 2614 * theoretically invalid by now. Fortunately 2615 * m_adj() doesn't actually frees any mbufs 2616 * when trimming from the head. 2617 */ 2618 thflags = tcp_reass(tp, th, &tlen, m); 2619 tp->t_flags |= TF_ACKNOW; 2620 } 2621 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2622 tcp_update_sack_list(tp, save_start, save_start + tlen); 2623 #if 0 2624 /* 2625 * Note the amount of data that peer has sent into 2626 * our window, in order to estimate the sender's 2627 * buffer size. 2628 * XXX: Unused. 2629 */ 2630 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2631 #endif 2632 } else { 2633 m_freem(m); 2634 thflags &= ~TH_FIN; 2635 } 2636 2637 /* 2638 * If FIN is received ACK the FIN and let the user know 2639 * that the connection is closing. 2640 */ 2641 if (thflags & TH_FIN) { 2642 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2643 socantrcvmore(so); 2644 /* 2645 * If connection is half-synchronized 2646 * (ie NEEDSYN flag on) then delay ACK, 2647 * so it may be piggybacked when SYN is sent. 2648 * Otherwise, since we received a FIN then no 2649 * more input can be expected, send ACK now. 2650 */ 2651 if (tp->t_flags & TF_NEEDSYN) 2652 tp->t_flags |= TF_DELACK; 2653 else 2654 tp->t_flags |= TF_ACKNOW; 2655 tp->rcv_nxt++; 2656 } 2657 switch (tp->t_state) { 2658 2659 /* 2660 * In SYN_RECEIVED and ESTABLISHED STATES 2661 * enter the CLOSE_WAIT state. 2662 */ 2663 case TCPS_SYN_RECEIVED: 2664 tp->t_starttime = ticks; 2665 /* FALLTHROUGH */ 2666 case TCPS_ESTABLISHED: 2667 tp->t_state = TCPS_CLOSE_WAIT; 2668 break; 2669 2670 /* 2671 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2672 * enter the CLOSING state. 2673 */ 2674 case TCPS_FIN_WAIT_1: 2675 tp->t_state = TCPS_CLOSING; 2676 break; 2677 2678 /* 2679 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2680 * starting the time-wait timer, turning off the other 2681 * standard timers. 2682 */ 2683 case TCPS_FIN_WAIT_2: 2684 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2685 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata " 2686 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 2687 ti_locked)); 2688 2689 tcp_twstart(tp); 2690 INP_INFO_WUNLOCK(&V_tcbinfo); 2691 return; 2692 } 2693 } 2694 if (ti_locked == TI_RLOCKED) 2695 INP_INFO_RUNLOCK(&V_tcbinfo); 2696 else if (ti_locked == TI_WLOCKED) 2697 INP_INFO_WUNLOCK(&V_tcbinfo); 2698 else 2699 panic("%s: dodata epilogue ti_locked %d", __func__, 2700 ti_locked); 2701 ti_locked = TI_UNLOCKED; 2702 2703 #ifdef TCPDEBUG 2704 if (so->so_options & SO_DEBUG) 2705 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2706 &tcp_savetcp, 0); 2707 #endif 2708 2709 /* 2710 * Return any desired output. 2711 */ 2712 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2713 (void) tcp_output(tp); 2714 2715 check_delack: 2716 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 2717 __func__, ti_locked)); 2718 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 2719 INP_WLOCK_ASSERT(tp->t_inpcb); 2720 2721 if (tp->t_flags & TF_DELACK) { 2722 tp->t_flags &= ~TF_DELACK; 2723 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 2724 } 2725 INP_WUNLOCK(tp->t_inpcb); 2726 return; 2727 2728 dropafterack: 2729 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2730 ("tcp_do_segment: dropafterack ti_locked %d", ti_locked)); 2731 2732 /* 2733 * Generate an ACK dropping incoming segment if it occupies 2734 * sequence space, where the ACK reflects our state. 2735 * 2736 * We can now skip the test for the RST flag since all 2737 * paths to this code happen after packets containing 2738 * RST have been dropped. 2739 * 2740 * In the SYN-RECEIVED state, don't send an ACK unless the 2741 * segment we received passes the SYN-RECEIVED ACK test. 2742 * If it fails send a RST. This breaks the loop in the 2743 * "LAND" DoS attack, and also prevents an ACK storm 2744 * between two listening ports that have been sent forged 2745 * SYN segments, each with the source address of the other. 2746 */ 2747 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2748 (SEQ_GT(tp->snd_una, th->th_ack) || 2749 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2750 rstreason = BANDLIM_RST_OPENPORT; 2751 goto dropwithreset; 2752 } 2753 #ifdef TCPDEBUG 2754 if (so->so_options & SO_DEBUG) 2755 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2756 &tcp_savetcp, 0); 2757 #endif 2758 if (ti_locked == TI_RLOCKED) 2759 INP_INFO_RUNLOCK(&V_tcbinfo); 2760 else if (ti_locked == TI_WLOCKED) 2761 INP_INFO_WUNLOCK(&V_tcbinfo); 2762 else 2763 panic("%s: dropafterack epilogue ti_locked %d", __func__, 2764 ti_locked); 2765 ti_locked = TI_UNLOCKED; 2766 2767 tp->t_flags |= TF_ACKNOW; 2768 (void) tcp_output(tp); 2769 INP_WUNLOCK(tp->t_inpcb); 2770 m_freem(m); 2771 return; 2772 2773 dropwithreset: 2774 if (ti_locked == TI_RLOCKED) 2775 INP_INFO_RUNLOCK(&V_tcbinfo); 2776 else if (ti_locked == TI_WLOCKED) 2777 INP_INFO_WUNLOCK(&V_tcbinfo); 2778 else 2779 panic("%s: dropwithreset ti_locked %d", __func__, ti_locked); 2780 ti_locked = TI_UNLOCKED; 2781 2782 if (tp != NULL) { 2783 tcp_dropwithreset(m, th, tp, tlen, rstreason); 2784 INP_WUNLOCK(tp->t_inpcb); 2785 } else 2786 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 2787 return; 2788 2789 drop: 2790 if (ti_locked == TI_RLOCKED) 2791 INP_INFO_RUNLOCK(&V_tcbinfo); 2792 else if (ti_locked == TI_WLOCKED) 2793 INP_INFO_WUNLOCK(&V_tcbinfo); 2794 #ifdef INVARIANTS 2795 else 2796 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 2797 #endif 2798 ti_locked = TI_UNLOCKED; 2799 2800 /* 2801 * Drop space held by incoming segment and return. 2802 */ 2803 #ifdef TCPDEBUG 2804 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2805 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2806 &tcp_savetcp, 0); 2807 #endif 2808 if (tp != NULL) 2809 INP_WUNLOCK(tp->t_inpcb); 2810 m_freem(m); 2811 } 2812 2813 /* 2814 * Issue RST and make ACK acceptable to originator of segment. 2815 * The mbuf must still include the original packet header. 2816 * tp may be NULL. 2817 */ 2818 static void 2819 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 2820 int tlen, int rstreason) 2821 { 2822 struct ip *ip; 2823 #ifdef INET6 2824 struct ip6_hdr *ip6; 2825 #endif 2826 2827 if (tp != NULL) { 2828 INP_WLOCK_ASSERT(tp->t_inpcb); 2829 } 2830 2831 /* Don't bother if destination was broadcast/multicast. */ 2832 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2833 goto drop; 2834 #ifdef INET6 2835 if (mtod(m, struct ip *)->ip_v == 6) { 2836 ip6 = mtod(m, struct ip6_hdr *); 2837 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2838 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2839 goto drop; 2840 /* IPv6 anycast check is done at tcp6_input() */ 2841 } else 2842 #endif 2843 { 2844 ip = mtod(m, struct ip *); 2845 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2846 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2847 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2848 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2849 goto drop; 2850 } 2851 2852 /* Perform bandwidth limiting. */ 2853 if (badport_bandlim(rstreason) < 0) 2854 goto drop; 2855 2856 /* tcp_respond consumes the mbuf chain. */ 2857 if (th->th_flags & TH_ACK) { 2858 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 2859 th->th_ack, TH_RST); 2860 } else { 2861 if (th->th_flags & TH_SYN) 2862 tlen++; 2863 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2864 (tcp_seq)0, TH_RST|TH_ACK); 2865 } 2866 return; 2867 drop: 2868 m_freem(m); 2869 } 2870 2871 /* 2872 * Parse TCP options and place in tcpopt. 2873 */ 2874 static void 2875 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 2876 { 2877 int opt, optlen; 2878 2879 to->to_flags = 0; 2880 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2881 opt = cp[0]; 2882 if (opt == TCPOPT_EOL) 2883 break; 2884 if (opt == TCPOPT_NOP) 2885 optlen = 1; 2886 else { 2887 if (cnt < 2) 2888 break; 2889 optlen = cp[1]; 2890 if (optlen < 2 || optlen > cnt) 2891 break; 2892 } 2893 switch (opt) { 2894 case TCPOPT_MAXSEG: 2895 if (optlen != TCPOLEN_MAXSEG) 2896 continue; 2897 if (!(flags & TO_SYN)) 2898 continue; 2899 to->to_flags |= TOF_MSS; 2900 bcopy((char *)cp + 2, 2901 (char *)&to->to_mss, sizeof(to->to_mss)); 2902 to->to_mss = ntohs(to->to_mss); 2903 break; 2904 case TCPOPT_WINDOW: 2905 if (optlen != TCPOLEN_WINDOW) 2906 continue; 2907 if (!(flags & TO_SYN)) 2908 continue; 2909 to->to_flags |= TOF_SCALE; 2910 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 2911 break; 2912 case TCPOPT_TIMESTAMP: 2913 if (optlen != TCPOLEN_TIMESTAMP) 2914 continue; 2915 to->to_flags |= TOF_TS; 2916 bcopy((char *)cp + 2, 2917 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2918 to->to_tsval = ntohl(to->to_tsval); 2919 bcopy((char *)cp + 6, 2920 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2921 to->to_tsecr = ntohl(to->to_tsecr); 2922 break; 2923 #ifdef TCP_SIGNATURE 2924 /* 2925 * XXX In order to reply to a host which has set the 2926 * TCP_SIGNATURE option in its initial SYN, we have to 2927 * record the fact that the option was observed here 2928 * for the syncache code to perform the correct response. 2929 */ 2930 case TCPOPT_SIGNATURE: 2931 if (optlen != TCPOLEN_SIGNATURE) 2932 continue; 2933 to->to_flags |= TOF_SIGNATURE; 2934 to->to_signature = cp + 2; 2935 break; 2936 #endif 2937 case TCPOPT_SACK_PERMITTED: 2938 if (optlen != TCPOLEN_SACK_PERMITTED) 2939 continue; 2940 if (!(flags & TO_SYN)) 2941 continue; 2942 if (!V_tcp_do_sack) 2943 continue; 2944 to->to_flags |= TOF_SACKPERM; 2945 break; 2946 case TCPOPT_SACK: 2947 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2948 continue; 2949 if (flags & TO_SYN) 2950 continue; 2951 to->to_flags |= TOF_SACK; 2952 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2953 to->to_sacks = cp + 2; 2954 TCPSTAT_INC(tcps_sack_rcv_blocks); 2955 break; 2956 default: 2957 continue; 2958 } 2959 } 2960 } 2961 2962 /* 2963 * Pull out of band byte out of a segment so 2964 * it doesn't appear in the user's data queue. 2965 * It is still reflected in the segment length for 2966 * sequencing purposes. 2967 */ 2968 static void 2969 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 2970 int off) 2971 { 2972 int cnt = off + th->th_urp - 1; 2973 2974 while (cnt >= 0) { 2975 if (m->m_len > cnt) { 2976 char *cp = mtod(m, caddr_t) + cnt; 2977 struct tcpcb *tp = sototcpcb(so); 2978 2979 INP_WLOCK_ASSERT(tp->t_inpcb); 2980 2981 tp->t_iobc = *cp; 2982 tp->t_oobflags |= TCPOOB_HAVEDATA; 2983 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2984 m->m_len--; 2985 if (m->m_flags & M_PKTHDR) 2986 m->m_pkthdr.len--; 2987 return; 2988 } 2989 cnt -= m->m_len; 2990 m = m->m_next; 2991 if (m == NULL) 2992 break; 2993 } 2994 panic("tcp_pulloutofband"); 2995 } 2996 2997 /* 2998 * Collect new round-trip time estimate 2999 * and update averages and current timeout. 3000 */ 3001 static void 3002 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3003 { 3004 int delta; 3005 3006 INP_WLOCK_ASSERT(tp->t_inpcb); 3007 3008 TCPSTAT_INC(tcps_rttupdated); 3009 tp->t_rttupdated++; 3010 if (tp->t_srtt != 0) { 3011 /* 3012 * srtt is stored as fixed point with 5 bits after the 3013 * binary point (i.e., scaled by 8). The following magic 3014 * is equivalent to the smoothing algorithm in rfc793 with 3015 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3016 * point). Adjust rtt to origin 0. 3017 */ 3018 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3019 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3020 3021 if ((tp->t_srtt += delta) <= 0) 3022 tp->t_srtt = 1; 3023 3024 /* 3025 * We accumulate a smoothed rtt variance (actually, a 3026 * smoothed mean difference), then set the retransmit 3027 * timer to smoothed rtt + 4 times the smoothed variance. 3028 * rttvar is stored as fixed point with 4 bits after the 3029 * binary point (scaled by 16). The following is 3030 * equivalent to rfc793 smoothing with an alpha of .75 3031 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3032 * rfc793's wired-in beta. 3033 */ 3034 if (delta < 0) 3035 delta = -delta; 3036 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3037 if ((tp->t_rttvar += delta) <= 0) 3038 tp->t_rttvar = 1; 3039 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3040 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3041 } else { 3042 /* 3043 * No rtt measurement yet - use the unsmoothed rtt. 3044 * Set the variance to half the rtt (so our first 3045 * retransmit happens at 3*rtt). 3046 */ 3047 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3048 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3049 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3050 } 3051 tp->t_rtttime = 0; 3052 tp->t_rxtshift = 0; 3053 3054 /* 3055 * the retransmit should happen at rtt + 4 * rttvar. 3056 * Because of the way we do the smoothing, srtt and rttvar 3057 * will each average +1/2 tick of bias. When we compute 3058 * the retransmit timer, we want 1/2 tick of rounding and 3059 * 1 extra tick because of +-1/2 tick uncertainty in the 3060 * firing of the timer. The bias will give us exactly the 3061 * 1.5 tick we need. But, because the bias is 3062 * statistical, we have to test that we don't drop below 3063 * the minimum feasible timer (which is 2 ticks). 3064 */ 3065 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3066 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3067 3068 /* 3069 * We received an ack for a packet that wasn't retransmitted; 3070 * it is probably safe to discard any error indications we've 3071 * received recently. This isn't quite right, but close enough 3072 * for now (a route might have failed after we sent a segment, 3073 * and the return path might not be symmetrical). 3074 */ 3075 tp->t_softerror = 0; 3076 } 3077 3078 /* 3079 * Determine a reasonable value for maxseg size. 3080 * If the route is known, check route for mtu. 3081 * If none, use an mss that can be handled on the outgoing 3082 * interface without forcing IP to fragment; if bigger than 3083 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 3084 * to utilize large mbufs. If no route is found, route has no mtu, 3085 * or the destination isn't local, use a default, hopefully conservative 3086 * size (usually 512 or the default IP max size, but no more than the mtu 3087 * of the interface), as we can't discover anything about intervening 3088 * gateways or networks. We also initialize the congestion/slow start 3089 * window to be a single segment if the destination isn't local. 3090 * While looking at the routing entry, we also initialize other path-dependent 3091 * parameters from pre-set or cached values in the routing entry. 3092 * 3093 * Also take into account the space needed for options that we 3094 * send regularly. Make maxseg shorter by that amount to assure 3095 * that we can send maxseg amount of data even when the options 3096 * are present. Store the upper limit of the length of options plus 3097 * data in maxopd. 3098 * 3099 * In case of T/TCP, we call this routine during implicit connection 3100 * setup as well (offer = -1), to initialize maxseg from the cached 3101 * MSS of our peer. 3102 * 3103 * NOTE that this routine is only called when we process an incoming 3104 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 3105 */ 3106 void 3107 tcp_mss_update(struct tcpcb *tp, int offer, 3108 struct hc_metrics_lite *metricptr, int *mtuflags) 3109 { 3110 int mss; 3111 u_long maxmtu; 3112 struct inpcb *inp = tp->t_inpcb; 3113 struct hc_metrics_lite metrics; 3114 int origoffer = offer; 3115 #ifdef INET6 3116 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3117 size_t min_protoh = isipv6 ? 3118 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3119 sizeof (struct tcpiphdr); 3120 #else 3121 const size_t min_protoh = sizeof(struct tcpiphdr); 3122 #endif 3123 3124 INP_WLOCK_ASSERT(tp->t_inpcb); 3125 3126 /* Initialize. */ 3127 #ifdef INET6 3128 if (isipv6) { 3129 maxmtu = tcp_maxmtu6(&inp->inp_inc, mtuflags); 3130 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; 3131 } else 3132 #endif 3133 { 3134 maxmtu = tcp_maxmtu(&inp->inp_inc, mtuflags); 3135 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; 3136 } 3137 3138 /* 3139 * No route to sender, stay with default mss and return. 3140 */ 3141 if (maxmtu == 0) { 3142 /* 3143 * In case we return early we need to initialize metrics 3144 * to a defined state as tcp_hc_get() would do for us 3145 * if there was no cache hit. 3146 */ 3147 if (metricptr != NULL) 3148 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3149 return; 3150 } 3151 3152 /* What have we got? */ 3153 switch (offer) { 3154 case 0: 3155 /* 3156 * Offer == 0 means that there was no MSS on the SYN 3157 * segment, in this case we use tcp_mssdflt as 3158 * already assigned to t_maxopd above. 3159 */ 3160 offer = tp->t_maxopd; 3161 break; 3162 3163 case -1: 3164 /* 3165 * Offer == -1 means that we didn't receive SYN yet. 3166 */ 3167 /* FALLTHROUGH */ 3168 3169 default: 3170 /* 3171 * Prevent DoS attack with too small MSS. Round up 3172 * to at least minmss. 3173 */ 3174 offer = max(offer, V_tcp_minmss); 3175 } 3176 3177 /* 3178 * rmx information is now retrieved from tcp_hostcache. 3179 */ 3180 tcp_hc_get(&inp->inp_inc, &metrics); 3181 if (metricptr != NULL) 3182 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3183 3184 /* 3185 * If there's a discovered mtu int tcp hostcache, use it 3186 * else, use the link mtu. 3187 */ 3188 if (metrics.rmx_mtu) 3189 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3190 else { 3191 #ifdef INET6 3192 if (isipv6) { 3193 mss = maxmtu - min_protoh; 3194 if (!V_path_mtu_discovery && 3195 !in6_localaddr(&inp->in6p_faddr)) 3196 mss = min(mss, V_tcp_v6mssdflt); 3197 } else 3198 #endif 3199 { 3200 mss = maxmtu - min_protoh; 3201 if (!V_path_mtu_discovery && 3202 !in_localaddr(inp->inp_faddr)) 3203 mss = min(mss, V_tcp_mssdflt); 3204 } 3205 /* 3206 * XXX - The above conditional (mss = maxmtu - min_protoh) 3207 * probably violates the TCP spec. 3208 * The problem is that, since we don't know the 3209 * other end's MSS, we are supposed to use a conservative 3210 * default. But, if we do that, then MTU discovery will 3211 * never actually take place, because the conservative 3212 * default is much less than the MTUs typically seen 3213 * on the Internet today. For the moment, we'll sweep 3214 * this under the carpet. 3215 * 3216 * The conservative default might not actually be a problem 3217 * if the only case this occurs is when sending an initial 3218 * SYN with options and data to a host we've never talked 3219 * to before. Then, they will reply with an MSS value which 3220 * will get recorded and the new parameters should get 3221 * recomputed. For Further Study. 3222 */ 3223 } 3224 mss = min(mss, offer); 3225 3226 /* 3227 * Sanity check: make sure that maxopd will be large 3228 * enough to allow some data on segments even if the 3229 * all the option space is used (40bytes). Otherwise 3230 * funny things may happen in tcp_output. 3231 */ 3232 mss = max(mss, 64); 3233 3234 /* 3235 * maxopd stores the maximum length of data AND options 3236 * in a segment; maxseg is the amount of data in a normal 3237 * segment. We need to store this value (maxopd) apart 3238 * from maxseg, because now every segment carries options 3239 * and thus we normally have somewhat less data in segments. 3240 */ 3241 tp->t_maxopd = mss; 3242 3243 /* 3244 * origoffer==-1 indicates that no segments were received yet. 3245 * In this case we just guess. 3246 */ 3247 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3248 (origoffer == -1 || 3249 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3250 mss -= TCPOLEN_TSTAMP_APPA; 3251 3252 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3253 if (mss > MCLBYTES) 3254 mss &= ~(MCLBYTES-1); 3255 #else 3256 if (mss > MCLBYTES) 3257 mss = mss / MCLBYTES * MCLBYTES; 3258 #endif 3259 tp->t_maxseg = mss; 3260 } 3261 3262 void 3263 tcp_mss(struct tcpcb *tp, int offer) 3264 { 3265 int rtt, mss; 3266 u_long bufsize; 3267 struct inpcb *inp; 3268 struct socket *so; 3269 struct hc_metrics_lite metrics; 3270 int mtuflags = 0; 3271 #ifdef INET6 3272 int isipv6; 3273 #endif 3274 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3275 3276 tcp_mss_update(tp, offer, &metrics, &mtuflags); 3277 3278 mss = tp->t_maxseg; 3279 inp = tp->t_inpcb; 3280 #ifdef INET6 3281 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3282 #endif 3283 3284 /* 3285 * If there's a pipesize, change the socket buffer to that size, 3286 * don't change if sb_hiwat is different than default (then it 3287 * has been changed on purpose with setsockopt). 3288 * Make the socket buffers an integral number of mss units; 3289 * if the mss is larger than the socket buffer, decrease the mss. 3290 */ 3291 so = inp->inp_socket; 3292 SOCKBUF_LOCK(&so->so_snd); 3293 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3294 bufsize = metrics.rmx_sendpipe; 3295 else 3296 bufsize = so->so_snd.sb_hiwat; 3297 if (bufsize < mss) 3298 mss = bufsize; 3299 else { 3300 bufsize = roundup(bufsize, mss); 3301 if (bufsize > sb_max) 3302 bufsize = sb_max; 3303 if (bufsize > so->so_snd.sb_hiwat) 3304 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3305 } 3306 SOCKBUF_UNLOCK(&so->so_snd); 3307 tp->t_maxseg = mss; 3308 3309 SOCKBUF_LOCK(&so->so_rcv); 3310 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3311 bufsize = metrics.rmx_recvpipe; 3312 else 3313 bufsize = so->so_rcv.sb_hiwat; 3314 if (bufsize > mss) { 3315 bufsize = roundup(bufsize, mss); 3316 if (bufsize > sb_max) 3317 bufsize = sb_max; 3318 if (bufsize > so->so_rcv.sb_hiwat) 3319 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3320 } 3321 SOCKBUF_UNLOCK(&so->so_rcv); 3322 /* 3323 * While we're here, check the others too. 3324 */ 3325 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3326 tp->t_srtt = rtt; 3327 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3328 TCPSTAT_INC(tcps_usedrtt); 3329 if (metrics.rmx_rttvar) { 3330 tp->t_rttvar = metrics.rmx_rttvar; 3331 TCPSTAT_INC(tcps_usedrttvar); 3332 } else { 3333 /* default variation is +- 1 rtt */ 3334 tp->t_rttvar = 3335 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3336 } 3337 TCPT_RANGESET(tp->t_rxtcur, 3338 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3339 tp->t_rttmin, TCPTV_REXMTMAX); 3340 } 3341 if (metrics.rmx_ssthresh) { 3342 /* 3343 * There's some sort of gateway or interface 3344 * buffer limit on the path. Use this to set 3345 * the slow start threshhold, but set the 3346 * threshold to no less than 2*mss. 3347 */ 3348 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3349 TCPSTAT_INC(tcps_usedssthresh); 3350 } 3351 if (metrics.rmx_bandwidth) 3352 tp->snd_bandwidth = metrics.rmx_bandwidth; 3353 3354 /* 3355 * Set the slow-start flight size depending on whether this 3356 * is a local network or not. 3357 * 3358 * Extend this so we cache the cwnd too and retrieve it here. 3359 * Make cwnd even bigger than RFC3390 suggests but only if we 3360 * have previous experience with the remote host. Be careful 3361 * not make cwnd bigger than remote receive window or our own 3362 * send socket buffer. Maybe put some additional upper bound 3363 * on the retrieved cwnd. Should do incremental updates to 3364 * hostcache when cwnd collapses so next connection doesn't 3365 * overloads the path again. 3366 * 3367 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3368 * We currently check only in syncache_socket for that. 3369 */ 3370 #define TCP_METRICS_CWND 3371 #ifdef TCP_METRICS_CWND 3372 if (metrics.rmx_cwnd) 3373 tp->snd_cwnd = max(mss, 3374 min(metrics.rmx_cwnd / 2, 3375 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3376 else 3377 #endif 3378 if (V_tcp_do_rfc3390) 3379 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3380 #ifdef INET6 3381 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3382 (!isipv6 && in_localaddr(inp->inp_faddr))) 3383 #else 3384 else if (in_localaddr(inp->inp_faddr)) 3385 #endif 3386 tp->snd_cwnd = mss * V_ss_fltsz_local; 3387 else 3388 tp->snd_cwnd = mss * V_ss_fltsz; 3389 3390 /* Check the interface for TSO capabilities. */ 3391 if (mtuflags & CSUM_TSO) 3392 tp->t_flags |= TF_TSO; 3393 } 3394 3395 /* 3396 * Determine the MSS option to send on an outgoing SYN. 3397 */ 3398 int 3399 tcp_mssopt(struct in_conninfo *inc) 3400 { 3401 int mss = 0; 3402 u_long maxmtu = 0; 3403 u_long thcmtu = 0; 3404 size_t min_protoh; 3405 3406 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3407 3408 #ifdef INET6 3409 if (inc->inc_flags & INC_ISIPV6) { 3410 mss = V_tcp_v6mssdflt; 3411 maxmtu = tcp_maxmtu6(inc, NULL); 3412 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3413 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3414 } else 3415 #endif 3416 { 3417 mss = V_tcp_mssdflt; 3418 maxmtu = tcp_maxmtu(inc, NULL); 3419 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3420 min_protoh = sizeof(struct tcpiphdr); 3421 } 3422 if (maxmtu && thcmtu) 3423 mss = min(maxmtu, thcmtu) - min_protoh; 3424 else if (maxmtu || thcmtu) 3425 mss = max(maxmtu, thcmtu) - min_protoh; 3426 3427 return (mss); 3428 } 3429 3430 3431 /* 3432 * On a partial ack arrives, force the retransmission of the 3433 * next unacknowledged segment. Do not clear tp->t_dupacks. 3434 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3435 * be started again. 3436 */ 3437 static void 3438 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3439 { 3440 tcp_seq onxt = tp->snd_nxt; 3441 u_long ocwnd = tp->snd_cwnd; 3442 3443 INP_WLOCK_ASSERT(tp->t_inpcb); 3444 3445 tcp_timer_activate(tp, TT_REXMT, 0); 3446 tp->t_rtttime = 0; 3447 tp->snd_nxt = th->th_ack; 3448 /* 3449 * Set snd_cwnd to one segment beyond acknowledged offset. 3450 * (tp->snd_una has not yet been updated when this function is called.) 3451 */ 3452 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3453 tp->t_flags |= TF_ACKNOW; 3454 (void) tcp_output(tp); 3455 tp->snd_cwnd = ocwnd; 3456 if (SEQ_GT(onxt, tp->snd_nxt)) 3457 tp->snd_nxt = onxt; 3458 /* 3459 * Partial window deflation. Relies on fact that tp->snd_una 3460 * not updated yet. 3461 */ 3462 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3463 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3464 else 3465 tp->snd_cwnd = 0; 3466 tp->snd_cwnd += tp->t_maxseg; 3467 } 3468