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