tcp_input.c revision 196019
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: head/sys/netinet/tcp_input.c 196019 2009-08-01 19:26:27Z rwatson $"); 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 99static const int tcprexmtthresh = 3; 100 101VNET_DEFINE(struct tcpstat, tcpstat); 102VNET_DEFINE(int, blackhole); 103VNET_DEFINE(int, tcp_delack_enabled); 104VNET_DEFINE(int, drop_synfin); 105VNET_DEFINE(int, tcp_do_rfc3042); 106VNET_DEFINE(int, tcp_do_rfc3390); 107VNET_DEFINE(int, tcp_do_ecn); 108VNET_DEFINE(int, tcp_ecn_maxretries); 109VNET_DEFINE(int, tcp_insecure_rst); 110VNET_DEFINE(int, tcp_do_autorcvbuf); 111VNET_DEFINE(int, tcp_autorcvbuf_inc); 112VNET_DEFINE(int, tcp_autorcvbuf_max); 113VNET_DEFINE(int, tcp_do_rfc3465); 114VNET_DEFINE(int, tcp_abc_l_var); 115 116SYSCTL_VNET_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 117 &VNET_NAME(tcpstat), tcpstat, 118 "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 119 120int tcp_log_in_vain = 0; 121SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 122 &tcp_log_in_vain, 0, 123 "Log all incoming TCP segments to closed ports"); 124 125SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 126 &VNET_NAME(blackhole), 0, 127 "Do not send RST on segments to closed ports"); 128 129SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 130 &VNET_NAME(tcp_delack_enabled), 0, 131 "Delay ACK to try and piggyback it onto a data packet"); 132 133SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 134 &VNET_NAME(drop_synfin), 0, 135 "Drop TCP packets with SYN+FIN set"); 136 137SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 138 &VNET_NAME(tcp_do_rfc3042), 0, 139 "Enable RFC 3042 (Limited Transmit)"); 140 141SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 142 &VNET_NAME(tcp_do_rfc3390), 0, 143 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 144 145SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, 146 &VNET_NAME(tcp_do_rfc3465), 0, 147 "Enable RFC 3465 (Appropriate Byte Counting)"); 148 149SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW, 150 &VNET_NAME(tcp_abc_l_var), 2, 151 "Cap the max cwnd increment during slow-start to this number of segments"); 152 153SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 154 155SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW, 156 &VNET_NAME(tcp_do_ecn), 0, 157 "TCP ECN support"); 158 159SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW, 160 &VNET_NAME(tcp_ecn_maxretries), 0, 161 "Max retries before giving up on ECN"); 162 163SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 164 &VNET_NAME(tcp_insecure_rst), 0, 165 "Follow the old (insecure) criteria for accepting RST packets"); 166 167SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 168 &VNET_NAME(tcp_do_autorcvbuf), 0, 169 "Enable automatic receive buffer sizing"); 170 171SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 172 &VNET_NAME(tcp_autorcvbuf_inc), 0, 173 "Incrementor step size of automatic receive buffer"); 174 175SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 176 &VNET_NAME(tcp_autorcvbuf_max), 0, 177 "Max size of automatic receive buffer"); 178 179int tcp_read_locking = 1; 180SYSCTL_INT(_net_inet_tcp, OID_AUTO, read_locking, CTLFLAG_RW, 181 &tcp_read_locking, 0, "Enable read locking strategy"); 182 183int tcp_rlock_atfirst; 184SYSCTL_INT(_net_inet_tcp, OID_AUTO, rlock_atfirst, CTLFLAG_RD, 185 &tcp_rlock_atfirst, 0, ""); 186 187int tcp_wlock_atfirst; 188SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_wlock_atfirst, CTLFLAG_RD, 189 &tcp_wlock_atfirst, 0, ""); 190 191int tcp_wlock_upgraded; 192SYSCTL_INT(_net_inet_tcp, OID_AUTO, wlock_upgraded, CTLFLAG_RD, 193 &tcp_wlock_upgraded, 0, ""); 194 195int tcp_wlock_relocked; 196SYSCTL_INT(_net_inet_tcp, OID_AUTO, wlock_relocked, CTLFLAG_RD, 197 &tcp_wlock_relocked, 0, ""); 198 199int tcp_wlock_looped; 200SYSCTL_INT(_net_inet_tcp, OID_AUTO, wlock_looped, CTLFLAG_RD, 201 &tcp_wlock_looped, 0, ""); 202 203VNET_DEFINE(struct inpcbhead, tcb); 204VNET_DEFINE(struct inpcbinfo, tcbinfo); 205#define tcb6 tcb /* for KAME src sync over BSD*'s */ 206 207static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 208static void tcp_do_segment(struct mbuf *, struct tcphdr *, 209 struct socket *, struct tcpcb *, int, int, uint8_t, 210 int); 211static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 212 struct tcpcb *, int, int); 213static void tcp_pulloutofband(struct socket *, 214 struct tcphdr *, struct mbuf *, int); 215static void tcp_xmit_timer(struct tcpcb *, int); 216static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 217static void inline 218 tcp_congestion_exp(struct tcpcb *); 219 220static void inline 221tcp_congestion_exp(struct tcpcb *tp) 222{ 223 u_int win; 224 225 win = min(tp->snd_wnd, tp->snd_cwnd) / 226 2 / tp->t_maxseg; 227 if (win < 2) 228 win = 2; 229 tp->snd_ssthresh = win * tp->t_maxseg; 230 ENTER_FASTRECOVERY(tp); 231 tp->snd_recover = tp->snd_max; 232 if (tp->t_flags & TF_ECN_PERMIT) 233 tp->t_flags |= TF_ECN_SND_CWR; 234} 235 236/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 237#ifdef INET6 238#define ND6_HINT(tp) \ 239do { \ 240 if ((tp) && (tp)->t_inpcb && \ 241 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 242 nd6_nud_hint(NULL, NULL, 0); \ 243} while (0) 244#else 245#define ND6_HINT(tp) 246#endif 247 248/* 249 * Indicate whether this ack should be delayed. We can delay the ack if 250 * - there is no delayed ack timer in progress and 251 * - our last ack wasn't a 0-sized window. We never want to delay 252 * the ack that opens up a 0-sized window and 253 * - delayed acks are enabled or 254 * - this is a half-synchronized T/TCP connection. 255 */ 256#define DELAY_ACK(tp) \ 257 ((!tcp_timer_active(tp, TT_DELACK) && \ 258 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 259 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 260 261/* 262 * TCP input handling is split into multiple parts: 263 * tcp6_input is a thin wrapper around tcp_input for the extended 264 * ip6_protox[] call format in ip6_input 265 * tcp_input handles primary segment validation, inpcb lookup and 266 * SYN processing on listen sockets 267 * tcp_do_segment processes the ACK and text of the segment for 268 * establishing, established and closing connections 269 */ 270#ifdef INET6 271int 272tcp6_input(struct mbuf **mp, int *offp, int proto) 273{ 274 struct mbuf *m = *mp; 275 struct in6_ifaddr *ia6; 276 277 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 278 279 /* 280 * draft-itojun-ipv6-tcp-to-anycast 281 * better place to put this in? 282 */ 283 ia6 = ip6_getdstifaddr(m); 284 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 285 struct ip6_hdr *ip6; 286 287 ifa_free(&ia6->ia_ifa); 288 ip6 = mtod(m, struct ip6_hdr *); 289 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 290 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 291 return IPPROTO_DONE; 292 } 293 294 tcp_input(m, *offp); 295 return IPPROTO_DONE; 296} 297#endif 298 299void 300tcp_input(struct mbuf *m, int off0) 301{ 302 struct tcphdr *th; 303 struct ip *ip = NULL; 304 struct ipovly *ipov; 305 struct inpcb *inp = NULL; 306 struct tcpcb *tp = NULL; 307 struct socket *so = NULL; 308 u_char *optp = NULL; 309 int optlen = 0; 310 int len, tlen, off; 311 int drop_hdrlen; 312 int thflags; 313 int rstreason = 0; /* For badport_bandlim accounting purposes */ 314 uint8_t iptos; 315#ifdef IPFIREWALL_FORWARD 316 struct m_tag *fwd_tag; 317#endif 318#ifdef INET6 319 struct ip6_hdr *ip6 = NULL; 320 int isipv6; 321#else 322 const void *ip6 = NULL; 323 const int isipv6 = 0; 324#endif 325 struct tcpopt to; /* options in this segment */ 326 char *s = NULL; /* address and port logging */ 327 int ti_locked; 328#define TI_UNLOCKED 1 329#define TI_RLOCKED 2 330#define TI_WLOCKED 3 331 332#ifdef TCPDEBUG 333 /* 334 * The size of tcp_saveipgen must be the size of the max ip header, 335 * now IPv6. 336 */ 337 u_char tcp_saveipgen[IP6_HDR_LEN]; 338 struct tcphdr tcp_savetcp; 339 short ostate = 0; 340#endif 341 342#ifdef INET6 343 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 344#endif 345 346 to.to_flags = 0; 347 TCPSTAT_INC(tcps_rcvtotal); 348 349 if (isipv6) { 350#ifdef INET6 351 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 352 ip6 = mtod(m, struct ip6_hdr *); 353 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 354 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 355 TCPSTAT_INC(tcps_rcvbadsum); 356 goto drop; 357 } 358 th = (struct tcphdr *)((caddr_t)ip6 + off0); 359 360 /* 361 * Be proactive about unspecified IPv6 address in source. 362 * As we use all-zero to indicate unbounded/unconnected pcb, 363 * unspecified IPv6 address can be used to confuse us. 364 * 365 * Note that packets with unspecified IPv6 destination is 366 * already dropped in ip6_input. 367 */ 368 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 369 /* XXX stat */ 370 goto drop; 371 } 372#else 373 th = NULL; /* XXX: Avoid compiler warning. */ 374#endif 375 } else { 376 /* 377 * Get IP and TCP header together in first mbuf. 378 * Note: IP leaves IP header in first mbuf. 379 */ 380 if (off0 > sizeof (struct ip)) { 381 ip_stripoptions(m, (struct mbuf *)0); 382 off0 = sizeof(struct ip); 383 } 384 if (m->m_len < sizeof (struct tcpiphdr)) { 385 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 386 == NULL) { 387 TCPSTAT_INC(tcps_rcvshort); 388 return; 389 } 390 } 391 ip = mtod(m, struct ip *); 392 ipov = (struct ipovly *)ip; 393 th = (struct tcphdr *)((caddr_t)ip + off0); 394 tlen = ip->ip_len; 395 396 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 397 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 398 th->th_sum = m->m_pkthdr.csum_data; 399 else 400 th->th_sum = in_pseudo(ip->ip_src.s_addr, 401 ip->ip_dst.s_addr, 402 htonl(m->m_pkthdr.csum_data + 403 ip->ip_len + 404 IPPROTO_TCP)); 405 th->th_sum ^= 0xffff; 406#ifdef TCPDEBUG 407 ipov->ih_len = (u_short)tlen; 408 ipov->ih_len = htons(ipov->ih_len); 409#endif 410 } else { 411 /* 412 * Checksum extended TCP header and data. 413 */ 414 len = sizeof (struct ip) + tlen; 415 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 416 ipov->ih_len = (u_short)tlen; 417 ipov->ih_len = htons(ipov->ih_len); 418 th->th_sum = in_cksum(m, len); 419 } 420 if (th->th_sum) { 421 TCPSTAT_INC(tcps_rcvbadsum); 422 goto drop; 423 } 424 /* Re-initialization for later version check */ 425 ip->ip_v = IPVERSION; 426 } 427 428#ifdef INET6 429 if (isipv6) 430 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 431 else 432#endif 433 iptos = ip->ip_tos; 434 435 /* 436 * Check that TCP offset makes sense, 437 * pull out TCP options and adjust length. XXX 438 */ 439 off = th->th_off << 2; 440 if (off < sizeof (struct tcphdr) || off > tlen) { 441 TCPSTAT_INC(tcps_rcvbadoff); 442 goto drop; 443 } 444 tlen -= off; /* tlen is used instead of ti->ti_len */ 445 if (off > sizeof (struct tcphdr)) { 446 if (isipv6) { 447#ifdef INET6 448 IP6_EXTHDR_CHECK(m, off0, off, ); 449 ip6 = mtod(m, struct ip6_hdr *); 450 th = (struct tcphdr *)((caddr_t)ip6 + off0); 451#endif 452 } else { 453 if (m->m_len < sizeof(struct ip) + off) { 454 if ((m = m_pullup(m, sizeof (struct ip) + off)) 455 == NULL) { 456 TCPSTAT_INC(tcps_rcvshort); 457 return; 458 } 459 ip = mtod(m, struct ip *); 460 ipov = (struct ipovly *)ip; 461 th = (struct tcphdr *)((caddr_t)ip + off0); 462 } 463 } 464 optlen = off - sizeof (struct tcphdr); 465 optp = (u_char *)(th + 1); 466 } 467 thflags = th->th_flags; 468 469 /* 470 * Convert TCP protocol specific fields to host format. 471 */ 472 th->th_seq = ntohl(th->th_seq); 473 th->th_ack = ntohl(th->th_ack); 474 th->th_win = ntohs(th->th_win); 475 th->th_urp = ntohs(th->th_urp); 476 477 /* 478 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 479 */ 480 drop_hdrlen = off0 + off; 481 482 /* 483 * Locate pcb for segment, which requires a lock on tcbinfo. 484 * Optimisticaly acquire a global read lock rather than a write lock 485 * unless header flags necessarily imply a state change. There are 486 * two cases where we might discover later we need a write lock 487 * despite the flags: ACKs moving a connection out of the syncache, 488 * and ACKs for a connection in TIMEWAIT. 489 */ 490 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 491 tcp_read_locking == 0) { 492 INP_INFO_WLOCK(&V_tcbinfo); 493 ti_locked = TI_WLOCKED; 494 tcp_wlock_atfirst++; 495 } else { 496 INP_INFO_RLOCK(&V_tcbinfo); 497 ti_locked = TI_RLOCKED; 498 tcp_rlock_atfirst++; 499 } 500 501findpcb: 502#ifdef INVARIANTS 503 if (ti_locked == TI_RLOCKED) 504 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 505 else if (ti_locked == TI_WLOCKED) 506 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 507 else 508 panic("%s: findpcb ti_locked %d\n", __func__, ti_locked); 509#endif 510 511#ifdef IPFIREWALL_FORWARD 512 /* 513 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 514 */ 515 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 516 517 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 518 struct sockaddr_in *next_hop; 519 520 next_hop = (struct sockaddr_in *)(fwd_tag+1); 521 /* 522 * Transparently forwarded. Pretend to be the destination. 523 * already got one like this? 524 */ 525 inp = in_pcblookup_hash(&V_tcbinfo, 526 ip->ip_src, th->th_sport, 527 ip->ip_dst, th->th_dport, 528 0, m->m_pkthdr.rcvif); 529 if (!inp) { 530 /* It's new. Try to find the ambushing socket. */ 531 inp = in_pcblookup_hash(&V_tcbinfo, 532 ip->ip_src, th->th_sport, 533 next_hop->sin_addr, 534 next_hop->sin_port ? 535 ntohs(next_hop->sin_port) : 536 th->th_dport, 537 INPLOOKUP_WILDCARD, 538 m->m_pkthdr.rcvif); 539 } 540 /* Remove the tag from the packet. We don't need it anymore. */ 541 m_tag_delete(m, fwd_tag); 542 } else 543#endif /* IPFIREWALL_FORWARD */ 544 { 545 if (isipv6) { 546#ifdef INET6 547 inp = in6_pcblookup_hash(&V_tcbinfo, 548 &ip6->ip6_src, th->th_sport, 549 &ip6->ip6_dst, th->th_dport, 550 INPLOOKUP_WILDCARD, 551 m->m_pkthdr.rcvif); 552#endif 553 } else 554 inp = in_pcblookup_hash(&V_tcbinfo, 555 ip->ip_src, th->th_sport, 556 ip->ip_dst, th->th_dport, 557 INPLOOKUP_WILDCARD, 558 m->m_pkthdr.rcvif); 559 } 560 561 /* 562 * If the INPCB does not exist then all data in the incoming 563 * segment is discarded and an appropriate RST is sent back. 564 * XXX MRT Send RST using which routing table? 565 */ 566 if (inp == NULL) { 567 /* 568 * Log communication attempts to ports that are not 569 * in use. 570 */ 571 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 572 tcp_log_in_vain == 2) { 573 if ((s = tcp_log_addrs(NULL, th, (void *)ip, ip6))) 574 log(LOG_INFO, "%s; %s: Connection attempt " 575 "to closed port\n", s, __func__); 576 } 577 /* 578 * When blackholing do not respond with a RST but 579 * completely ignore the segment and drop it. 580 */ 581 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 582 V_blackhole == 2) 583 goto dropunlock; 584 585 rstreason = BANDLIM_RST_CLOSEDPORT; 586 goto dropwithreset; 587 } 588 INP_WLOCK(inp); 589 if (!(inp->inp_flags & INP_HW_FLOWID) 590 && (m->m_flags & M_FLOWID) 591 && ((inp->inp_socket == NULL) 592 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) { 593 inp->inp_flags |= INP_HW_FLOWID; 594 inp->inp_flags &= ~INP_SW_FLOWID; 595 inp->inp_flowid = m->m_pkthdr.flowid; 596 } 597#ifdef IPSEC 598#ifdef INET6 599 if (isipv6 && ipsec6_in_reject(m, inp)) { 600 V_ipsec6stat.in_polvio++; 601 goto dropunlock; 602 } else 603#endif /* INET6 */ 604 if (ipsec4_in_reject(m, inp) != 0) { 605 V_ipsec4stat.in_polvio++; 606 goto dropunlock; 607 } 608#endif /* IPSEC */ 609 610 /* 611 * Check the minimum TTL for socket. 612 */ 613 if (inp->inp_ip_minttl != 0) { 614#ifdef INET6 615 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 616 goto dropunlock; 617 else 618#endif 619 if (inp->inp_ip_minttl > ip->ip_ttl) 620 goto dropunlock; 621 } 622 623 /* 624 * A previous connection in TIMEWAIT state is supposed to catch stray 625 * or duplicate segments arriving late. If this segment was a 626 * legitimate new connection attempt the old INPCB gets removed and 627 * we can try again to find a listening socket. 628 * 629 * At this point, due to earlier optimism, we may hold a read lock on 630 * the inpcbinfo, rather than a write lock. If so, we need to 631 * upgrade, or if that fails, acquire a reference on the inpcb, drop 632 * all locks, acquire a global write lock, and then re-acquire the 633 * inpcb lock. We may at that point discover that another thread has 634 * tried to free the inpcb, in which case we need to loop back and 635 * try to find a new inpcb to deliver to. 636 */ 637 if (inp->inp_flags & INP_TIMEWAIT) { 638 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 639 ("%s: INP_TIMEWAIT ti_locked %d", __func__, ti_locked)); 640 641 if (ti_locked == TI_RLOCKED) { 642 if (rw_try_upgrade(&V_tcbinfo.ipi_lock) == 0) { 643 in_pcbref(inp); 644 INP_WUNLOCK(inp); 645 INP_INFO_RUNLOCK(&V_tcbinfo); 646 INP_INFO_WLOCK(&V_tcbinfo); 647 ti_locked = TI_WLOCKED; 648 INP_WLOCK(inp); 649 if (in_pcbrele(inp)) { 650 tcp_wlock_looped++; 651 inp = NULL; 652 goto findpcb; 653 } 654 tcp_wlock_relocked++; 655 } else { 656 ti_locked = TI_WLOCKED; 657 tcp_wlock_upgraded++; 658 } 659 } 660 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 661 662 if (thflags & TH_SYN) 663 tcp_dooptions(&to, optp, optlen, TO_SYN); 664 /* 665 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 666 */ 667 if (tcp_twcheck(inp, &to, th, m, tlen)) 668 goto findpcb; 669 INP_INFO_WUNLOCK(&V_tcbinfo); 670 return; 671 } 672 /* 673 * The TCPCB may no longer exist if the connection is winding 674 * down or it is in the CLOSED state. Either way we drop the 675 * segment and send an appropriate response. 676 */ 677 tp = intotcpcb(inp); 678 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 679 rstreason = BANDLIM_RST_CLOSEDPORT; 680 goto dropwithreset; 681 } 682 683 /* 684 * We've identified a valid inpcb, but it could be that we need an 685 * inpcbinfo write lock and have only a read lock. In this case, 686 * attempt to upgrade/relock using the same strategy as the TIMEWAIT 687 * case above. 688 */ 689 if (tp->t_state != TCPS_ESTABLISHED || 690 (thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 691 tcp_read_locking == 0) { 692 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 693 ("%s: upgrade check ti_locked %d", __func__, ti_locked)); 694 695 if (ti_locked == TI_RLOCKED) { 696 if (rw_try_upgrade(&V_tcbinfo.ipi_lock) == 0) { 697 in_pcbref(inp); 698 INP_WUNLOCK(inp); 699 INP_INFO_RUNLOCK(&V_tcbinfo); 700 INP_INFO_WLOCK(&V_tcbinfo); 701 ti_locked = TI_WLOCKED; 702 INP_WLOCK(inp); 703 if (in_pcbrele(inp)) { 704 tcp_wlock_looped++; 705 inp = NULL; 706 goto findpcb; 707 } 708 tcp_wlock_relocked++; 709 } else { 710 ti_locked = TI_WLOCKED; 711 tcp_wlock_upgraded++; 712 } 713 } 714 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 715 } 716 717#ifdef MAC 718 INP_WLOCK_ASSERT(inp); 719 if (mac_inpcb_check_deliver(inp, m)) 720 goto dropunlock; 721#endif 722 so = inp->inp_socket; 723 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 724#ifdef TCPDEBUG 725 if (so->so_options & SO_DEBUG) { 726 ostate = tp->t_state; 727 if (isipv6) { 728#ifdef INET6 729 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 730#endif 731 } else 732 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 733 tcp_savetcp = *th; 734 } 735#endif 736 /* 737 * When the socket is accepting connections (the INPCB is in LISTEN 738 * state) we look into the SYN cache if this is a new connection 739 * attempt or the completion of a previous one. 740 */ 741 if (so->so_options & SO_ACCEPTCONN) { 742 struct in_conninfo inc; 743 744 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 745 "tp not listening", __func__)); 746 747 bzero(&inc, sizeof(inc)); 748#ifdef INET6 749 if (isipv6) { 750 inc.inc_flags |= INC_ISIPV6; 751 inc.inc6_faddr = ip6->ip6_src; 752 inc.inc6_laddr = ip6->ip6_dst; 753 } else 754#endif 755 { 756 inc.inc_faddr = ip->ip_src; 757 inc.inc_laddr = ip->ip_dst; 758 } 759 inc.inc_fport = th->th_sport; 760 inc.inc_lport = th->th_dport; 761 inc.inc_fibnum = so->so_fibnum; 762 763 /* 764 * Check for an existing connection attempt in syncache if 765 * the flag is only ACK. A successful lookup creates a new 766 * socket appended to the listen queue in SYN_RECEIVED state. 767 */ 768 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 769 /* 770 * Parse the TCP options here because 771 * syncookies need access to the reflected 772 * timestamp. 773 */ 774 tcp_dooptions(&to, optp, optlen, 0); 775 /* 776 * NB: syncache_expand() doesn't unlock 777 * inp and tcpinfo locks. 778 */ 779 if (!syncache_expand(&inc, &to, th, &so, m)) { 780 /* 781 * No syncache entry or ACK was not 782 * for our SYN/ACK. Send a RST. 783 * NB: syncache did its own logging 784 * of the failure cause. 785 */ 786 rstreason = BANDLIM_RST_OPENPORT; 787 goto dropwithreset; 788 } 789 if (so == NULL) { 790 /* 791 * We completed the 3-way handshake 792 * but could not allocate a socket 793 * either due to memory shortage, 794 * listen queue length limits or 795 * global socket limits. Send RST 796 * or wait and have the remote end 797 * retransmit the ACK for another 798 * try. 799 */ 800 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 801 log(LOG_DEBUG, "%s; %s: Listen socket: " 802 "Socket allocation failed due to " 803 "limits or memory shortage, %s\n", 804 s, __func__, 805 V_tcp_sc_rst_sock_fail ? 806 "sending RST" : "try again"); 807 if (V_tcp_sc_rst_sock_fail) { 808 rstreason = BANDLIM_UNLIMITED; 809 goto dropwithreset; 810 } else 811 goto dropunlock; 812 } 813 /* 814 * Socket is created in state SYN_RECEIVED. 815 * Unlock the listen socket, lock the newly 816 * created socket and update the tp variable. 817 */ 818 INP_WUNLOCK(inp); /* listen socket */ 819 inp = sotoinpcb(so); 820 INP_WLOCK(inp); /* new connection */ 821 tp = intotcpcb(inp); 822 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 823 ("%s: ", __func__)); 824 /* 825 * Process the segment and the data it 826 * contains. tcp_do_segment() consumes 827 * the mbuf chain and unlocks the inpcb. 828 */ 829 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 830 iptos, ti_locked); 831 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 832 return; 833 } 834 /* 835 * Segment flag validation for new connection attempts: 836 * 837 * Our (SYN|ACK) response was rejected. 838 * Check with syncache and remove entry to prevent 839 * retransmits. 840 * 841 * NB: syncache_chkrst does its own logging of failure 842 * causes. 843 */ 844 if (thflags & TH_RST) { 845 syncache_chkrst(&inc, th); 846 goto dropunlock; 847 } 848 /* 849 * We can't do anything without SYN. 850 */ 851 if ((thflags & TH_SYN) == 0) { 852 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 853 log(LOG_DEBUG, "%s; %s: Listen socket: " 854 "SYN is missing, segment ignored\n", 855 s, __func__); 856 TCPSTAT_INC(tcps_badsyn); 857 goto dropunlock; 858 } 859 /* 860 * (SYN|ACK) is bogus on a listen socket. 861 */ 862 if (thflags & TH_ACK) { 863 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 864 log(LOG_DEBUG, "%s; %s: Listen socket: " 865 "SYN|ACK invalid, segment rejected\n", 866 s, __func__); 867 syncache_badack(&inc); /* XXX: Not needed! */ 868 TCPSTAT_INC(tcps_badsyn); 869 rstreason = BANDLIM_RST_OPENPORT; 870 goto dropwithreset; 871 } 872 /* 873 * If the drop_synfin option is enabled, drop all 874 * segments with both the SYN and FIN bits set. 875 * This prevents e.g. nmap from identifying the 876 * TCP/IP stack. 877 * XXX: Poor reasoning. nmap has other methods 878 * and is constantly refining its stack detection 879 * strategies. 880 * XXX: This is a violation of the TCP specification 881 * and was used by RFC1644. 882 */ 883 if ((thflags & TH_FIN) && V_drop_synfin) { 884 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 885 log(LOG_DEBUG, "%s; %s: Listen socket: " 886 "SYN|FIN segment ignored (based on " 887 "sysctl setting)\n", s, __func__); 888 TCPSTAT_INC(tcps_badsyn); 889 goto dropunlock; 890 } 891 /* 892 * Segment's flags are (SYN) or (SYN|FIN). 893 * 894 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 895 * as they do not affect the state of the TCP FSM. 896 * The data pointed to by TH_URG and th_urp is ignored. 897 */ 898 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 899 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 900 KASSERT(thflags & (TH_SYN), 901 ("%s: Listen socket: TH_SYN not set", __func__)); 902#ifdef INET6 903 /* 904 * If deprecated address is forbidden, 905 * we do not accept SYN to deprecated interface 906 * address to prevent any new inbound connection from 907 * getting established. 908 * When we do not accept SYN, we send a TCP RST, 909 * with deprecated source address (instead of dropping 910 * it). We compromise it as it is much better for peer 911 * to send a RST, and RST will be the final packet 912 * for the exchange. 913 * 914 * If we do not forbid deprecated addresses, we accept 915 * the SYN packet. RFC2462 does not suggest dropping 916 * SYN in this case. 917 * If we decipher RFC2462 5.5.4, it says like this: 918 * 1. use of deprecated addr with existing 919 * communication is okay - "SHOULD continue to be 920 * used" 921 * 2. use of it with new communication: 922 * (2a) "SHOULD NOT be used if alternate address 923 * with sufficient scope is available" 924 * (2b) nothing mentioned otherwise. 925 * Here we fall into (2b) case as we have no choice in 926 * our source address selection - we must obey the peer. 927 * 928 * The wording in RFC2462 is confusing, and there are 929 * multiple description text for deprecated address 930 * handling - worse, they are not exactly the same. 931 * I believe 5.5.4 is the best one, so we follow 5.5.4. 932 */ 933 if (isipv6 && !V_ip6_use_deprecated) { 934 struct in6_ifaddr *ia6; 935 936 ia6 = ip6_getdstifaddr(m); 937 if (ia6 != NULL && 938 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 939 ifa_free(&ia6->ia_ifa); 940 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 941 log(LOG_DEBUG, "%s; %s: Listen socket: " 942 "Connection attempt to deprecated " 943 "IPv6 address rejected\n", 944 s, __func__); 945 rstreason = BANDLIM_RST_OPENPORT; 946 goto dropwithreset; 947 } 948 ifa_free(&ia6->ia_ifa); 949 } 950#endif 951 /* 952 * Basic sanity checks on incoming SYN requests: 953 * Don't respond if the destination is a link layer 954 * broadcast according to RFC1122 4.2.3.10, p. 104. 955 * If it is from this socket it must be forged. 956 * Don't respond if the source or destination is a 957 * global or subnet broad- or multicast address. 958 * Note that it is quite possible to receive unicast 959 * link-layer packets with a broadcast IP address. Use 960 * in_broadcast() to find them. 961 */ 962 if (m->m_flags & (M_BCAST|M_MCAST)) { 963 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 964 log(LOG_DEBUG, "%s; %s: Listen socket: " 965 "Connection attempt from broad- or multicast " 966 "link layer address ignored\n", s, __func__); 967 goto dropunlock; 968 } 969 if (isipv6) { 970#ifdef INET6 971 if (th->th_dport == th->th_sport && 972 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 973 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 974 log(LOG_DEBUG, "%s; %s: Listen socket: " 975 "Connection attempt to/from self " 976 "ignored\n", s, __func__); 977 goto dropunlock; 978 } 979 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 980 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 981 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 982 log(LOG_DEBUG, "%s; %s: Listen socket: " 983 "Connection attempt from/to multicast " 984 "address ignored\n", s, __func__); 985 goto dropunlock; 986 } 987#endif 988 } else { 989 if (th->th_dport == th->th_sport && 990 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 991 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 992 log(LOG_DEBUG, "%s; %s: Listen socket: " 993 "Connection attempt from/to self " 994 "ignored\n", s, __func__); 995 goto dropunlock; 996 } 997 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 998 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 999 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1000 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1001 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1002 log(LOG_DEBUG, "%s; %s: Listen socket: " 1003 "Connection attempt from/to broad- " 1004 "or multicast address ignored\n", 1005 s, __func__); 1006 goto dropunlock; 1007 } 1008 } 1009 /* 1010 * SYN appears to be valid. Create compressed TCP state 1011 * for syncache. 1012 */ 1013#ifdef TCPDEBUG 1014 if (so->so_options & SO_DEBUG) 1015 tcp_trace(TA_INPUT, ostate, tp, 1016 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1017#endif 1018 tcp_dooptions(&to, optp, optlen, TO_SYN); 1019 syncache_add(&inc, &to, th, inp, &so, m); 1020 /* 1021 * Entry added to syncache and mbuf consumed. 1022 * Everything already unlocked by syncache_add(). 1023 */ 1024 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1025 return; 1026 } 1027 1028 /* 1029 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1030 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1031 * the inpcb, and unlocks pcbinfo. 1032 */ 1033 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1034 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1035 return; 1036 1037dropwithreset: 1038 if (ti_locked == TI_RLOCKED) 1039 INP_INFO_RUNLOCK(&V_tcbinfo); 1040 else if (ti_locked == TI_WLOCKED) 1041 INP_INFO_WUNLOCK(&V_tcbinfo); 1042 else 1043 panic("%s: dropwithreset ti_locked %d", __func__, ti_locked); 1044 ti_locked = TI_UNLOCKED; 1045 1046 if (inp != NULL) { 1047 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1048 INP_WUNLOCK(inp); 1049 } else 1050 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1051 m = NULL; /* mbuf chain got consumed. */ 1052 goto drop; 1053 1054dropunlock: 1055 if (ti_locked == TI_RLOCKED) 1056 INP_INFO_RUNLOCK(&V_tcbinfo); 1057 else if (ti_locked == TI_WLOCKED) 1058 INP_INFO_WUNLOCK(&V_tcbinfo); 1059 else 1060 panic("%s: dropunlock ti_locked %d", __func__, ti_locked); 1061 ti_locked = TI_UNLOCKED; 1062 1063 if (inp != NULL) 1064 INP_WUNLOCK(inp); 1065 1066drop: 1067 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1068 if (s != NULL) 1069 free(s, M_TCPLOG); 1070 if (m != NULL) 1071 m_freem(m); 1072} 1073 1074static void 1075tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1076 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1077 int ti_locked) 1078{ 1079 int thflags, acked, ourfinisacked, needoutput = 0; 1080 int rstreason, todrop, win; 1081 u_long tiwin; 1082 struct tcpopt to; 1083 1084#ifdef TCPDEBUG 1085 /* 1086 * The size of tcp_saveipgen must be the size of the max ip header, 1087 * now IPv6. 1088 */ 1089 u_char tcp_saveipgen[IP6_HDR_LEN]; 1090 struct tcphdr tcp_savetcp; 1091 short ostate = 0; 1092#endif 1093 thflags = th->th_flags; 1094 1095 /* 1096 * If this is either a state-changing packet or current state isn't 1097 * established, we require a write lock on tcbinfo. Otherwise, we 1098 * allow either a read lock or a write lock, as we may have acquired 1099 * a write lock due to a race. 1100 * 1101 * Require a global write lock for SYN/FIN/RST segments or 1102 * non-established connections; otherwise accept either a read or 1103 * write lock, as we may have conservatively acquired a write lock in 1104 * certain cases in tcp_input() (is this still true?). Currently we 1105 * will never enter with no lock, so we try to drop it quickly in the 1106 * common pure ack/pure data cases. 1107 */ 1108 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1109 tp->t_state != TCPS_ESTABLISHED) { 1110 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for " 1111 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1112 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1113 } else { 1114#ifdef INVARIANTS 1115 if (ti_locked == TI_RLOCKED) 1116 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1117 else if (ti_locked == TI_WLOCKED) 1118 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1119 else 1120 panic("%s: ti_locked %d for EST", __func__, 1121 ti_locked); 1122#endif 1123 } 1124 INP_WLOCK_ASSERT(tp->t_inpcb); 1125 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1126 __func__)); 1127 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1128 __func__)); 1129 1130 /* 1131 * Segment received on connection. 1132 * Reset idle time and keep-alive timer. 1133 * XXX: This should be done after segment 1134 * validation to ignore broken/spoofed segs. 1135 */ 1136 tp->t_rcvtime = ticks; 1137 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1138 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 1139 1140 /* 1141 * Unscale the window into a 32-bit value. 1142 * For the SYN_SENT state the scale is zero. 1143 */ 1144 tiwin = th->th_win << tp->snd_scale; 1145 1146 /* 1147 * TCP ECN processing. 1148 */ 1149 if (tp->t_flags & TF_ECN_PERMIT) { 1150 switch (iptos & IPTOS_ECN_MASK) { 1151 case IPTOS_ECN_CE: 1152 tp->t_flags |= TF_ECN_SND_ECE; 1153 TCPSTAT_INC(tcps_ecn_ce); 1154 break; 1155 case IPTOS_ECN_ECT0: 1156 TCPSTAT_INC(tcps_ecn_ect0); 1157 break; 1158 case IPTOS_ECN_ECT1: 1159 TCPSTAT_INC(tcps_ecn_ect1); 1160 break; 1161 } 1162 1163 if (thflags & TH_CWR) 1164 tp->t_flags &= ~TF_ECN_SND_ECE; 1165 1166 /* 1167 * Congestion experienced. 1168 * Ignore if we are already trying to recover. 1169 */ 1170 if ((thflags & TH_ECE) && 1171 SEQ_LEQ(th->th_ack, tp->snd_recover)) { 1172 TCPSTAT_INC(tcps_ecn_rcwnd); 1173 tcp_congestion_exp(tp); 1174 } 1175 } 1176 1177 /* 1178 * Parse options on any incoming segment. 1179 */ 1180 tcp_dooptions(&to, (u_char *)(th + 1), 1181 (th->th_off << 2) - sizeof(struct tcphdr), 1182 (thflags & TH_SYN) ? TO_SYN : 0); 1183 1184 /* 1185 * If echoed timestamp is later than the current time, 1186 * fall back to non RFC1323 RTT calculation. Normalize 1187 * timestamp if syncookies were used when this connection 1188 * was established. 1189 */ 1190 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1191 to.to_tsecr -= tp->ts_offset; 1192 if (TSTMP_GT(to.to_tsecr, ticks)) 1193 to.to_tsecr = 0; 1194 } 1195 1196 /* 1197 * Process options only when we get SYN/ACK back. The SYN case 1198 * for incoming connections is handled in tcp_syncache. 1199 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1200 * or <SYN,ACK>) segment itself is never scaled. 1201 * XXX this is traditional behavior, may need to be cleaned up. 1202 */ 1203 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1204 if ((to.to_flags & TOF_SCALE) && 1205 (tp->t_flags & TF_REQ_SCALE)) { 1206 tp->t_flags |= TF_RCVD_SCALE; 1207 tp->snd_scale = to.to_wscale; 1208 } 1209 /* 1210 * Initial send window. It will be updated with 1211 * the next incoming segment to the scaled value. 1212 */ 1213 tp->snd_wnd = th->th_win; 1214 if (to.to_flags & TOF_TS) { 1215 tp->t_flags |= TF_RCVD_TSTMP; 1216 tp->ts_recent = to.to_tsval; 1217 tp->ts_recent_age = ticks; 1218 } 1219 if (to.to_flags & TOF_MSS) 1220 tcp_mss(tp, to.to_mss); 1221 if ((tp->t_flags & TF_SACK_PERMIT) && 1222 (to.to_flags & TOF_SACKPERM) == 0) 1223 tp->t_flags &= ~TF_SACK_PERMIT; 1224 } 1225 1226 /* 1227 * Header prediction: check for the two common cases 1228 * of a uni-directional data xfer. If the packet has 1229 * no control flags, is in-sequence, the window didn't 1230 * change and we're not retransmitting, it's a 1231 * candidate. If the length is zero and the ack moved 1232 * forward, we're the sender side of the xfer. Just 1233 * free the data acked & wake any higher level process 1234 * that was blocked waiting for space. If the length 1235 * is non-zero and the ack didn't move, we're the 1236 * receiver side. If we're getting packets in-order 1237 * (the reassembly queue is empty), add the data to 1238 * the socket buffer and note that we need a delayed ack. 1239 * Make sure that the hidden state-flags are also off. 1240 * Since we check for TCPS_ESTABLISHED first, it can only 1241 * be TH_NEEDSYN. 1242 */ 1243 if (tp->t_state == TCPS_ESTABLISHED && 1244 th->th_seq == tp->rcv_nxt && 1245 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1246 tp->snd_nxt == tp->snd_max && 1247 tiwin && tiwin == tp->snd_wnd && 1248 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1249 LIST_EMPTY(&tp->t_segq) && 1250 ((to.to_flags & TOF_TS) == 0 || 1251 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1252 1253 /* 1254 * If last ACK falls within this segment's sequence numbers, 1255 * record the timestamp. 1256 * NOTE that the test is modified according to the latest 1257 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1258 */ 1259 if ((to.to_flags & TOF_TS) != 0 && 1260 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1261 tp->ts_recent_age = ticks; 1262 tp->ts_recent = to.to_tsval; 1263 } 1264 1265 if (tlen == 0) { 1266 if (SEQ_GT(th->th_ack, tp->snd_una) && 1267 SEQ_LEQ(th->th_ack, tp->snd_max) && 1268 tp->snd_cwnd >= tp->snd_wnd && 1269 ((!V_tcp_do_newreno && 1270 !(tp->t_flags & TF_SACK_PERMIT) && 1271 tp->t_dupacks < tcprexmtthresh) || 1272 ((V_tcp_do_newreno || 1273 (tp->t_flags & TF_SACK_PERMIT)) && 1274 !IN_FASTRECOVERY(tp) && 1275 (to.to_flags & TOF_SACK) == 0 && 1276 TAILQ_EMPTY(&tp->snd_holes)))) { 1277 /* 1278 * This is a pure ack for outstanding data. 1279 */ 1280 if (ti_locked == TI_RLOCKED) 1281 INP_INFO_RUNLOCK(&V_tcbinfo); 1282 else if (ti_locked == TI_WLOCKED) 1283 INP_INFO_WUNLOCK(&V_tcbinfo); 1284 else 1285 panic("%s: ti_locked %d on pure ACK", 1286 __func__, ti_locked); 1287 ti_locked = TI_UNLOCKED; 1288 1289 TCPSTAT_INC(tcps_predack); 1290 1291 /* 1292 * "bad retransmit" recovery. 1293 */ 1294 if (tp->t_rxtshift == 1 && 1295 (int)(ticks - tp->t_badrxtwin) < 0) { 1296 TCPSTAT_INC(tcps_sndrexmitbad); 1297 tp->snd_cwnd = tp->snd_cwnd_prev; 1298 tp->snd_ssthresh = 1299 tp->snd_ssthresh_prev; 1300 tp->snd_recover = tp->snd_recover_prev; 1301 if (tp->t_flags & TF_WASFRECOVERY) 1302 ENTER_FASTRECOVERY(tp); 1303 tp->snd_nxt = tp->snd_max; 1304 tp->t_badrxtwin = 0; 1305 } 1306 1307 /* 1308 * Recalculate the transmit timer / rtt. 1309 * 1310 * Some boxes send broken timestamp replies 1311 * during the SYN+ACK phase, ignore 1312 * timestamps of 0 or we could calculate a 1313 * huge RTT and blow up the retransmit timer. 1314 */ 1315 if ((to.to_flags & TOF_TS) != 0 && 1316 to.to_tsecr) { 1317 if (!tp->t_rttlow || 1318 tp->t_rttlow > ticks - to.to_tsecr) 1319 tp->t_rttlow = ticks - to.to_tsecr; 1320 tcp_xmit_timer(tp, 1321 ticks - to.to_tsecr + 1); 1322 } else if (tp->t_rtttime && 1323 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1324 if (!tp->t_rttlow || 1325 tp->t_rttlow > ticks - tp->t_rtttime) 1326 tp->t_rttlow = ticks - tp->t_rtttime; 1327 tcp_xmit_timer(tp, 1328 ticks - tp->t_rtttime); 1329 } 1330 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1331 acked = th->th_ack - tp->snd_una; 1332 TCPSTAT_INC(tcps_rcvackpack); 1333 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1334 sbdrop(&so->so_snd, acked); 1335 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1336 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1337 tp->snd_recover = th->th_ack - 1; 1338 tp->snd_una = th->th_ack; 1339 /* 1340 * Pull snd_wl2 up to prevent seq wrap relative 1341 * to th_ack. 1342 */ 1343 tp->snd_wl2 = th->th_ack; 1344 tp->t_dupacks = 0; 1345 m_freem(m); 1346 ND6_HINT(tp); /* Some progress has been made. */ 1347 1348 /* 1349 * If all outstanding data are acked, stop 1350 * retransmit timer, otherwise restart timer 1351 * using current (possibly backed-off) value. 1352 * If process is waiting for space, 1353 * wakeup/selwakeup/signal. If data 1354 * are ready to send, let tcp_output 1355 * decide between more output or persist. 1356 */ 1357#ifdef TCPDEBUG 1358 if (so->so_options & SO_DEBUG) 1359 tcp_trace(TA_INPUT, ostate, tp, 1360 (void *)tcp_saveipgen, 1361 &tcp_savetcp, 0); 1362#endif 1363 if (tp->snd_una == tp->snd_max) 1364 tcp_timer_activate(tp, TT_REXMT, 0); 1365 else if (!tcp_timer_active(tp, TT_PERSIST)) 1366 tcp_timer_activate(tp, TT_REXMT, 1367 tp->t_rxtcur); 1368 sowwakeup(so); 1369 if (so->so_snd.sb_cc) 1370 (void) tcp_output(tp); 1371 goto check_delack; 1372 } 1373 } else if (th->th_ack == tp->snd_una && 1374 tlen <= sbspace(&so->so_rcv)) { 1375 int newsize = 0; /* automatic sockbuf scaling */ 1376 1377 /* 1378 * This is a pure, in-sequence data packet with 1379 * nothing on the reassembly queue and we have enough 1380 * buffer space to take it. 1381 */ 1382 if (ti_locked == TI_RLOCKED) 1383 INP_INFO_RUNLOCK(&V_tcbinfo); 1384 else if (ti_locked == TI_WLOCKED) 1385 INP_INFO_WUNLOCK(&V_tcbinfo); 1386 else 1387 panic("%s: ti_locked %d on pure data " 1388 "segment", __func__, ti_locked); 1389 ti_locked = TI_UNLOCKED; 1390 1391 /* Clean receiver SACK report if present */ 1392 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1393 tcp_clean_sackreport(tp); 1394 TCPSTAT_INC(tcps_preddat); 1395 tp->rcv_nxt += tlen; 1396 /* 1397 * Pull snd_wl1 up to prevent seq wrap relative to 1398 * th_seq. 1399 */ 1400 tp->snd_wl1 = th->th_seq; 1401 /* 1402 * Pull rcv_up up to prevent seq wrap relative to 1403 * rcv_nxt. 1404 */ 1405 tp->rcv_up = tp->rcv_nxt; 1406 TCPSTAT_INC(tcps_rcvpack); 1407 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1408 ND6_HINT(tp); /* Some progress has been made */ 1409#ifdef TCPDEBUG 1410 if (so->so_options & SO_DEBUG) 1411 tcp_trace(TA_INPUT, ostate, tp, 1412 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1413#endif 1414 /* 1415 * Automatic sizing of receive socket buffer. Often the send 1416 * buffer size is not optimally adjusted to the actual network 1417 * conditions at hand (delay bandwidth product). Setting the 1418 * buffer size too small limits throughput on links with high 1419 * bandwidth and high delay (eg. trans-continental/oceanic links). 1420 * 1421 * On the receive side the socket buffer memory is only rarely 1422 * used to any significant extent. This allows us to be much 1423 * more aggressive in scaling the receive socket buffer. For 1424 * the case that the buffer space is actually used to a large 1425 * extent and we run out of kernel memory we can simply drop 1426 * the new segments; TCP on the sender will just retransmit it 1427 * later. Setting the buffer size too big may only consume too 1428 * much kernel memory if the application doesn't read() from 1429 * the socket or packet loss or reordering makes use of the 1430 * reassembly queue. 1431 * 1432 * The criteria to step up the receive buffer one notch are: 1433 * 1. the number of bytes received during the time it takes 1434 * one timestamp to be reflected back to us (the RTT); 1435 * 2. received bytes per RTT is within seven eighth of the 1436 * current socket buffer size; 1437 * 3. receive buffer size has not hit maximal automatic size; 1438 * 1439 * This algorithm does one step per RTT at most and only if 1440 * we receive a bulk stream w/o packet losses or reorderings. 1441 * Shrinking the buffer during idle times is not necessary as 1442 * it doesn't consume any memory when idle. 1443 * 1444 * TODO: Only step up if the application is actually serving 1445 * the buffer to better manage the socket buffer resources. 1446 */ 1447 if (V_tcp_do_autorcvbuf && 1448 to.to_tsecr && 1449 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1450 if (to.to_tsecr > tp->rfbuf_ts && 1451 to.to_tsecr - tp->rfbuf_ts < hz) { 1452 if (tp->rfbuf_cnt > 1453 (so->so_rcv.sb_hiwat / 8 * 7) && 1454 so->so_rcv.sb_hiwat < 1455 V_tcp_autorcvbuf_max) { 1456 newsize = 1457 min(so->so_rcv.sb_hiwat + 1458 V_tcp_autorcvbuf_inc, 1459 V_tcp_autorcvbuf_max); 1460 } 1461 /* Start over with next RTT. */ 1462 tp->rfbuf_ts = 0; 1463 tp->rfbuf_cnt = 0; 1464 } else 1465 tp->rfbuf_cnt += tlen; /* add up */ 1466 } 1467 1468 /* Add data to socket buffer. */ 1469 SOCKBUF_LOCK(&so->so_rcv); 1470 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1471 m_freem(m); 1472 } else { 1473 /* 1474 * Set new socket buffer size. 1475 * Give up when limit is reached. 1476 */ 1477 if (newsize) 1478 if (!sbreserve_locked(&so->so_rcv, 1479 newsize, so, NULL)) 1480 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1481 m_adj(m, drop_hdrlen); /* delayed header drop */ 1482 sbappendstream_locked(&so->so_rcv, m); 1483 } 1484 /* NB: sorwakeup_locked() does an implicit unlock. */ 1485 sorwakeup_locked(so); 1486 if (DELAY_ACK(tp)) { 1487 tp->t_flags |= TF_DELACK; 1488 } else { 1489 tp->t_flags |= TF_ACKNOW; 1490 tcp_output(tp); 1491 } 1492 goto check_delack; 1493 } 1494 } 1495 1496 /* 1497 * Calculate amount of space in receive window, 1498 * and then do TCP input processing. 1499 * Receive window is amount of space in rcv queue, 1500 * but not less than advertised window. 1501 */ 1502 win = sbspace(&so->so_rcv); 1503 if (win < 0) 1504 win = 0; 1505 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1506 1507 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1508 tp->rfbuf_ts = 0; 1509 tp->rfbuf_cnt = 0; 1510 1511 switch (tp->t_state) { 1512 1513 /* 1514 * If the state is SYN_RECEIVED: 1515 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1516 */ 1517 case TCPS_SYN_RECEIVED: 1518 if ((thflags & TH_ACK) && 1519 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1520 SEQ_GT(th->th_ack, tp->snd_max))) { 1521 rstreason = BANDLIM_RST_OPENPORT; 1522 goto dropwithreset; 1523 } 1524 break; 1525 1526 /* 1527 * If the state is SYN_SENT: 1528 * if seg contains an ACK, but not for our SYN, drop the input. 1529 * if seg contains a RST, then drop the connection. 1530 * if seg does not contain SYN, then drop it. 1531 * Otherwise this is an acceptable SYN segment 1532 * initialize tp->rcv_nxt and tp->irs 1533 * if seg contains ack then advance tp->snd_una 1534 * if seg contains an ECE and ECN support is enabled, the stream 1535 * is ECN capable. 1536 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1537 * arrange for segment to be acked (eventually) 1538 * continue processing rest of data/controls, beginning with URG 1539 */ 1540 case TCPS_SYN_SENT: 1541 if ((thflags & TH_ACK) && 1542 (SEQ_LEQ(th->th_ack, tp->iss) || 1543 SEQ_GT(th->th_ack, tp->snd_max))) { 1544 rstreason = BANDLIM_UNLIMITED; 1545 goto dropwithreset; 1546 } 1547 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) 1548 tp = tcp_drop(tp, ECONNREFUSED); 1549 if (thflags & TH_RST) 1550 goto drop; 1551 if (!(thflags & TH_SYN)) 1552 goto drop; 1553 1554 tp->irs = th->th_seq; 1555 tcp_rcvseqinit(tp); 1556 if (thflags & TH_ACK) { 1557 TCPSTAT_INC(tcps_connects); 1558 soisconnected(so); 1559#ifdef MAC 1560 mac_socketpeer_set_from_mbuf(m, so); 1561#endif 1562 /* Do window scaling on this connection? */ 1563 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1564 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1565 tp->rcv_scale = tp->request_r_scale; 1566 } 1567 tp->rcv_adv += tp->rcv_wnd; 1568 tp->snd_una++; /* SYN is acked */ 1569 /* 1570 * If there's data, delay ACK; if there's also a FIN 1571 * ACKNOW will be turned on later. 1572 */ 1573 if (DELAY_ACK(tp) && tlen != 0) 1574 tcp_timer_activate(tp, TT_DELACK, 1575 tcp_delacktime); 1576 else 1577 tp->t_flags |= TF_ACKNOW; 1578 1579 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 1580 tp->t_flags |= TF_ECN_PERMIT; 1581 TCPSTAT_INC(tcps_ecn_shs); 1582 } 1583 1584 /* 1585 * Received <SYN,ACK> in SYN_SENT[*] state. 1586 * Transitions: 1587 * SYN_SENT --> ESTABLISHED 1588 * SYN_SENT* --> FIN_WAIT_1 1589 */ 1590 tp->t_starttime = ticks; 1591 if (tp->t_flags & TF_NEEDFIN) { 1592 tp->t_state = TCPS_FIN_WAIT_1; 1593 tp->t_flags &= ~TF_NEEDFIN; 1594 thflags &= ~TH_SYN; 1595 } else { 1596 tp->t_state = TCPS_ESTABLISHED; 1597 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 1598 } 1599 } else { 1600 /* 1601 * Received initial SYN in SYN-SENT[*] state => 1602 * simultaneous open. If segment contains CC option 1603 * and there is a cached CC, apply TAO test. 1604 * If it succeeds, connection is * half-synchronized. 1605 * Otherwise, do 3-way handshake: 1606 * SYN-SENT -> SYN-RECEIVED 1607 * SYN-SENT* -> SYN-RECEIVED* 1608 * If there was no CC option, clear cached CC value. 1609 */ 1610 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1611 tcp_timer_activate(tp, TT_REXMT, 0); 1612 tp->t_state = TCPS_SYN_RECEIVED; 1613 } 1614 1615 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: " 1616 "ti_locked %d", __func__, ti_locked)); 1617 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1618 INP_WLOCK_ASSERT(tp->t_inpcb); 1619 1620 /* 1621 * Advance th->th_seq to correspond to first data byte. 1622 * If data, trim to stay within window, 1623 * dropping FIN if necessary. 1624 */ 1625 th->th_seq++; 1626 if (tlen > tp->rcv_wnd) { 1627 todrop = tlen - tp->rcv_wnd; 1628 m_adj(m, -todrop); 1629 tlen = tp->rcv_wnd; 1630 thflags &= ~TH_FIN; 1631 TCPSTAT_INC(tcps_rcvpackafterwin); 1632 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 1633 } 1634 tp->snd_wl1 = th->th_seq - 1; 1635 tp->rcv_up = th->th_seq; 1636 /* 1637 * Client side of transaction: already sent SYN and data. 1638 * If the remote host used T/TCP to validate the SYN, 1639 * our data will be ACK'd; if so, enter normal data segment 1640 * processing in the middle of step 5, ack processing. 1641 * Otherwise, goto step 6. 1642 */ 1643 if (thflags & TH_ACK) 1644 goto process_ACK; 1645 1646 goto step6; 1647 1648 /* 1649 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1650 * do normal processing. 1651 * 1652 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1653 */ 1654 case TCPS_LAST_ACK: 1655 case TCPS_CLOSING: 1656 break; /* continue normal processing */ 1657 } 1658 1659 /* 1660 * States other than LISTEN or SYN_SENT. 1661 * First check the RST flag and sequence number since reset segments 1662 * are exempt from the timestamp and connection count tests. This 1663 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1664 * below which allowed reset segments in half the sequence space 1665 * to fall though and be processed (which gives forged reset 1666 * segments with a random sequence number a 50 percent chance of 1667 * killing a connection). 1668 * Then check timestamp, if present. 1669 * Then check the connection count, if present. 1670 * Then check that at least some bytes of segment are within 1671 * receive window. If segment begins before rcv_nxt, 1672 * drop leading data (and SYN); if nothing left, just ack. 1673 * 1674 * 1675 * If the RST bit is set, check the sequence number to see 1676 * if this is a valid reset segment. 1677 * RFC 793 page 37: 1678 * In all states except SYN-SENT, all reset (RST) segments 1679 * are validated by checking their SEQ-fields. A reset is 1680 * valid if its sequence number is in the window. 1681 * Note: this does not take into account delayed ACKs, so 1682 * we should test against last_ack_sent instead of rcv_nxt. 1683 * The sequence number in the reset segment is normally an 1684 * echo of our outgoing acknowlegement numbers, but some hosts 1685 * send a reset with the sequence number at the rightmost edge 1686 * of our receive window, and we have to handle this case. 1687 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1688 * that brute force RST attacks are possible. To combat this, 1689 * we use a much stricter check while in the ESTABLISHED state, 1690 * only accepting RSTs where the sequence number is equal to 1691 * last_ack_sent. In all other states (the states in which a 1692 * RST is more likely), the more permissive check is used. 1693 * If we have multiple segments in flight, the initial reset 1694 * segment sequence numbers will be to the left of last_ack_sent, 1695 * but they will eventually catch up. 1696 * In any case, it never made sense to trim reset segments to 1697 * fit the receive window since RFC 1122 says: 1698 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1699 * 1700 * A TCP SHOULD allow a received RST segment to include data. 1701 * 1702 * DISCUSSION 1703 * It has been suggested that a RST segment could contain 1704 * ASCII text that encoded and explained the cause of the 1705 * RST. No standard has yet been established for such 1706 * data. 1707 * 1708 * If the reset segment passes the sequence number test examine 1709 * the state: 1710 * SYN_RECEIVED STATE: 1711 * If passive open, return to LISTEN state. 1712 * If active open, inform user that connection was refused. 1713 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1714 * Inform user that connection was reset, and close tcb. 1715 * CLOSING, LAST_ACK STATES: 1716 * Close the tcb. 1717 * TIME_WAIT STATE: 1718 * Drop the segment - see Stevens, vol. 2, p. 964 and 1719 * RFC 1337. 1720 */ 1721 if (thflags & TH_RST) { 1722 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1723 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1724 switch (tp->t_state) { 1725 1726 case TCPS_SYN_RECEIVED: 1727 so->so_error = ECONNREFUSED; 1728 goto close; 1729 1730 case TCPS_ESTABLISHED: 1731 if (V_tcp_insecure_rst == 0 && 1732 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 1733 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 1734 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1735 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 1736 TCPSTAT_INC(tcps_badrst); 1737 goto drop; 1738 } 1739 /* FALLTHROUGH */ 1740 case TCPS_FIN_WAIT_1: 1741 case TCPS_FIN_WAIT_2: 1742 case TCPS_CLOSE_WAIT: 1743 so->so_error = ECONNRESET; 1744 close: 1745 KASSERT(ti_locked == TI_WLOCKED, 1746 ("tcp_do_segment: TH_RST 1 ti_locked %d", 1747 ti_locked)); 1748 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1749 1750 tp->t_state = TCPS_CLOSED; 1751 TCPSTAT_INC(tcps_drops); 1752 tp = tcp_close(tp); 1753 break; 1754 1755 case TCPS_CLOSING: 1756 case TCPS_LAST_ACK: 1757 KASSERT(ti_locked == TI_WLOCKED, 1758 ("tcp_do_segment: TH_RST 2 ti_locked %d", 1759 ti_locked)); 1760 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1761 1762 tp = tcp_close(tp); 1763 break; 1764 } 1765 } 1766 goto drop; 1767 } 1768 1769 /* 1770 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1771 * and it's less than ts_recent, drop it. 1772 */ 1773 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1774 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1775 1776 /* Check to see if ts_recent is over 24 days old. */ 1777 if (ticks - tp->ts_recent_age > TCP_PAWS_IDLE) { 1778 /* 1779 * Invalidate ts_recent. If this segment updates 1780 * ts_recent, the age will be reset later and ts_recent 1781 * will get a valid value. If it does not, setting 1782 * ts_recent to zero will at least satisfy the 1783 * requirement that zero be placed in the timestamp 1784 * echo reply when ts_recent isn't valid. The 1785 * age isn't reset until we get a valid ts_recent 1786 * because we don't want out-of-order segments to be 1787 * dropped when ts_recent is old. 1788 */ 1789 tp->ts_recent = 0; 1790 } else { 1791 TCPSTAT_INC(tcps_rcvduppack); 1792 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 1793 TCPSTAT_INC(tcps_pawsdrop); 1794 if (tlen) 1795 goto dropafterack; 1796 goto drop; 1797 } 1798 } 1799 1800 /* 1801 * In the SYN-RECEIVED state, validate that the packet belongs to 1802 * this connection before trimming the data to fit the receive 1803 * window. Check the sequence number versus IRS since we know 1804 * the sequence numbers haven't wrapped. This is a partial fix 1805 * for the "LAND" DoS attack. 1806 */ 1807 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1808 rstreason = BANDLIM_RST_OPENPORT; 1809 goto dropwithreset; 1810 } 1811 1812 todrop = tp->rcv_nxt - th->th_seq; 1813 if (todrop > 0) { 1814 /* 1815 * If this is a duplicate SYN for our current connection, 1816 * advance over it and pretend and it's not a SYN. 1817 */ 1818 if (thflags & TH_SYN && th->th_seq == tp->irs) { 1819 thflags &= ~TH_SYN; 1820 th->th_seq++; 1821 if (th->th_urp > 1) 1822 th->th_urp--; 1823 else 1824 thflags &= ~TH_URG; 1825 todrop--; 1826 } 1827 /* 1828 * Following if statement from Stevens, vol. 2, p. 960. 1829 */ 1830 if (todrop > tlen 1831 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1832 /* 1833 * Any valid FIN must be to the left of the window. 1834 * At this point the FIN must be a duplicate or out 1835 * of sequence; drop it. 1836 */ 1837 thflags &= ~TH_FIN; 1838 1839 /* 1840 * Send an ACK to resynchronize and drop any data. 1841 * But keep on processing for RST or ACK. 1842 */ 1843 tp->t_flags |= TF_ACKNOW; 1844 todrop = tlen; 1845 TCPSTAT_INC(tcps_rcvduppack); 1846 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 1847 } else { 1848 TCPSTAT_INC(tcps_rcvpartduppack); 1849 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 1850 } 1851 drop_hdrlen += todrop; /* drop from the top afterwards */ 1852 th->th_seq += todrop; 1853 tlen -= todrop; 1854 if (th->th_urp > todrop) 1855 th->th_urp -= todrop; 1856 else { 1857 thflags &= ~TH_URG; 1858 th->th_urp = 0; 1859 } 1860 } 1861 1862 /* 1863 * If new data are received on a connection after the 1864 * user processes are gone, then RST the other end. 1865 */ 1866 if ((so->so_state & SS_NOFDREF) && 1867 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1868 char *s; 1869 1870 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && " 1871 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 1872 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1873 1874 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { 1875 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket " 1876 "was closed, sending RST and removing tcpcb\n", 1877 s, __func__, tcpstates[tp->t_state], tlen); 1878 free(s, M_TCPLOG); 1879 } 1880 tp = tcp_close(tp); 1881 TCPSTAT_INC(tcps_rcvafterclose); 1882 rstreason = BANDLIM_UNLIMITED; 1883 goto dropwithreset; 1884 } 1885 1886 /* 1887 * If segment ends after window, drop trailing data 1888 * (and PUSH and FIN); if nothing left, just ACK. 1889 */ 1890 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1891 if (todrop > 0) { 1892 TCPSTAT_INC(tcps_rcvpackafterwin); 1893 if (todrop >= tlen) { 1894 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 1895 /* 1896 * If window is closed can only take segments at 1897 * window edge, and have to drop data and PUSH from 1898 * incoming segments. Continue processing, but 1899 * remember to ack. Otherwise, drop segment 1900 * and ack. 1901 */ 1902 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1903 tp->t_flags |= TF_ACKNOW; 1904 TCPSTAT_INC(tcps_rcvwinprobe); 1905 } else 1906 goto dropafterack; 1907 } else 1908 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 1909 m_adj(m, -todrop); 1910 tlen -= todrop; 1911 thflags &= ~(TH_PUSH|TH_FIN); 1912 } 1913 1914 /* 1915 * If last ACK falls within this segment's sequence numbers, 1916 * record its timestamp. 1917 * NOTE: 1918 * 1) That the test incorporates suggestions from the latest 1919 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1920 * 2) That updating only on newer timestamps interferes with 1921 * our earlier PAWS tests, so this check should be solely 1922 * predicated on the sequence space of this segment. 1923 * 3) That we modify the segment boundary check to be 1924 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1925 * instead of RFC1323's 1926 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1927 * This modified check allows us to overcome RFC1323's 1928 * limitations as described in Stevens TCP/IP Illustrated 1929 * Vol. 2 p.869. In such cases, we can still calculate the 1930 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1931 */ 1932 if ((to.to_flags & TOF_TS) != 0 && 1933 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1934 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1935 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1936 tp->ts_recent_age = ticks; 1937 tp->ts_recent = to.to_tsval; 1938 } 1939 1940 /* 1941 * If a SYN is in the window, then this is an 1942 * error and we send an RST and drop the connection. 1943 */ 1944 if (thflags & TH_SYN) { 1945 KASSERT(ti_locked == TI_WLOCKED, 1946 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 1947 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1948 1949 tp = tcp_drop(tp, ECONNRESET); 1950 rstreason = BANDLIM_UNLIMITED; 1951 goto drop; 1952 } 1953 1954 /* 1955 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1956 * flag is on (half-synchronized state), then queue data for 1957 * later processing; else drop segment and return. 1958 */ 1959 if ((thflags & TH_ACK) == 0) { 1960 if (tp->t_state == TCPS_SYN_RECEIVED || 1961 (tp->t_flags & TF_NEEDSYN)) 1962 goto step6; 1963 else if (tp->t_flags & TF_ACKNOW) 1964 goto dropafterack; 1965 else 1966 goto drop; 1967 } 1968 1969 /* 1970 * Ack processing. 1971 */ 1972 switch (tp->t_state) { 1973 1974 /* 1975 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1976 * ESTABLISHED state and continue processing. 1977 * The ACK was checked above. 1978 */ 1979 case TCPS_SYN_RECEIVED: 1980 1981 TCPSTAT_INC(tcps_connects); 1982 soisconnected(so); 1983 /* Do window scaling? */ 1984 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1985 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1986 tp->rcv_scale = tp->request_r_scale; 1987 tp->snd_wnd = tiwin; 1988 } 1989 /* 1990 * Make transitions: 1991 * SYN-RECEIVED -> ESTABLISHED 1992 * SYN-RECEIVED* -> FIN-WAIT-1 1993 */ 1994 tp->t_starttime = ticks; 1995 if (tp->t_flags & TF_NEEDFIN) { 1996 tp->t_state = TCPS_FIN_WAIT_1; 1997 tp->t_flags &= ~TF_NEEDFIN; 1998 } else { 1999 tp->t_state = TCPS_ESTABLISHED; 2000 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 2001 } 2002 /* 2003 * If segment contains data or ACK, will call tcp_reass() 2004 * later; if not, do so now to pass queued data to user. 2005 */ 2006 if (tlen == 0 && (thflags & TH_FIN) == 0) 2007 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2008 (struct mbuf *)0); 2009 tp->snd_wl1 = th->th_seq - 1; 2010 /* FALLTHROUGH */ 2011 2012 /* 2013 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2014 * ACKs. If the ack is in the range 2015 * tp->snd_una < th->th_ack <= tp->snd_max 2016 * then advance tp->snd_una to th->th_ack and drop 2017 * data from the retransmission queue. If this ACK reflects 2018 * more up to date window information we update our window information. 2019 */ 2020 case TCPS_ESTABLISHED: 2021 case TCPS_FIN_WAIT_1: 2022 case TCPS_FIN_WAIT_2: 2023 case TCPS_CLOSE_WAIT: 2024 case TCPS_CLOSING: 2025 case TCPS_LAST_ACK: 2026 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2027 TCPSTAT_INC(tcps_rcvacktoomuch); 2028 goto dropafterack; 2029 } 2030 if ((tp->t_flags & TF_SACK_PERMIT) && 2031 ((to.to_flags & TOF_SACK) || 2032 !TAILQ_EMPTY(&tp->snd_holes))) 2033 tcp_sack_doack(tp, &to, th->th_ack); 2034 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2035 if (tlen == 0 && tiwin == tp->snd_wnd) { 2036 TCPSTAT_INC(tcps_rcvdupack); 2037 /* 2038 * If we have outstanding data (other than 2039 * a window probe), this is a completely 2040 * duplicate ack (ie, window info didn't 2041 * change), the ack is the biggest we've 2042 * seen and we've seen exactly our rexmt 2043 * threshhold of them, assume a packet 2044 * has been dropped and retransmit it. 2045 * Kludge snd_nxt & the congestion 2046 * window so we send only this one 2047 * packet. 2048 * 2049 * We know we're losing at the current 2050 * window size so do congestion avoidance 2051 * (set ssthresh to half the current window 2052 * and pull our congestion window back to 2053 * the new ssthresh). 2054 * 2055 * Dup acks mean that packets have left the 2056 * network (they're now cached at the receiver) 2057 * so bump cwnd by the amount in the receiver 2058 * to keep a constant cwnd packets in the 2059 * network. 2060 * 2061 * When using TCP ECN, notify the peer that 2062 * we reduced the cwnd. 2063 */ 2064 if (!tcp_timer_active(tp, TT_REXMT) || 2065 th->th_ack != tp->snd_una) 2066 tp->t_dupacks = 0; 2067 else if (++tp->t_dupacks > tcprexmtthresh || 2068 ((V_tcp_do_newreno || 2069 (tp->t_flags & TF_SACK_PERMIT)) && 2070 IN_FASTRECOVERY(tp))) { 2071 if ((tp->t_flags & TF_SACK_PERMIT) && 2072 IN_FASTRECOVERY(tp)) { 2073 int awnd; 2074 2075 /* 2076 * Compute the amount of data in flight first. 2077 * We can inject new data into the pipe iff 2078 * we have less than 1/2 the original window's 2079 * worth of data in flight. 2080 */ 2081 awnd = (tp->snd_nxt - tp->snd_fack) + 2082 tp->sackhint.sack_bytes_rexmit; 2083 if (awnd < tp->snd_ssthresh) { 2084 tp->snd_cwnd += tp->t_maxseg; 2085 if (tp->snd_cwnd > tp->snd_ssthresh) 2086 tp->snd_cwnd = tp->snd_ssthresh; 2087 } 2088 } else 2089 tp->snd_cwnd += tp->t_maxseg; 2090 (void) tcp_output(tp); 2091 goto drop; 2092 } else if (tp->t_dupacks == tcprexmtthresh) { 2093 tcp_seq onxt = tp->snd_nxt; 2094 2095 /* 2096 * If we're doing sack, check to 2097 * see if we're already in sack 2098 * recovery. If we're not doing sack, 2099 * check to see if we're in newreno 2100 * recovery. 2101 */ 2102 if (tp->t_flags & TF_SACK_PERMIT) { 2103 if (IN_FASTRECOVERY(tp)) { 2104 tp->t_dupacks = 0; 2105 break; 2106 } 2107 } else if (V_tcp_do_newreno || 2108 V_tcp_do_ecn) { 2109 if (SEQ_LEQ(th->th_ack, 2110 tp->snd_recover)) { 2111 tp->t_dupacks = 0; 2112 break; 2113 } 2114 } 2115 tcp_congestion_exp(tp); 2116 tcp_timer_activate(tp, TT_REXMT, 0); 2117 tp->t_rtttime = 0; 2118 if (tp->t_flags & TF_SACK_PERMIT) { 2119 TCPSTAT_INC( 2120 tcps_sack_recovery_episode); 2121 tp->sack_newdata = tp->snd_nxt; 2122 tp->snd_cwnd = tp->t_maxseg; 2123 (void) tcp_output(tp); 2124 goto drop; 2125 } 2126 tp->snd_nxt = th->th_ack; 2127 tp->snd_cwnd = tp->t_maxseg; 2128 (void) tcp_output(tp); 2129 KASSERT(tp->snd_limited <= 2, 2130 ("%s: tp->snd_limited too big", 2131 __func__)); 2132 tp->snd_cwnd = tp->snd_ssthresh + 2133 tp->t_maxseg * 2134 (tp->t_dupacks - tp->snd_limited); 2135 if (SEQ_GT(onxt, tp->snd_nxt)) 2136 tp->snd_nxt = onxt; 2137 goto drop; 2138 } else if (V_tcp_do_rfc3042) { 2139 u_long oldcwnd = tp->snd_cwnd; 2140 tcp_seq oldsndmax = tp->snd_max; 2141 u_int sent; 2142 2143 KASSERT(tp->t_dupacks == 1 || 2144 tp->t_dupacks == 2, 2145 ("%s: dupacks not 1 or 2", 2146 __func__)); 2147 if (tp->t_dupacks == 1) 2148 tp->snd_limited = 0; 2149 tp->snd_cwnd = 2150 (tp->snd_nxt - tp->snd_una) + 2151 (tp->t_dupacks - tp->snd_limited) * 2152 tp->t_maxseg; 2153 (void) tcp_output(tp); 2154 sent = tp->snd_max - oldsndmax; 2155 if (sent > tp->t_maxseg) { 2156 KASSERT((tp->t_dupacks == 2 && 2157 tp->snd_limited == 0) || 2158 (sent == tp->t_maxseg + 1 && 2159 tp->t_flags & TF_SENTFIN), 2160 ("%s: sent too much", 2161 __func__)); 2162 tp->snd_limited = 2; 2163 } else if (sent > 0) 2164 ++tp->snd_limited; 2165 tp->snd_cwnd = oldcwnd; 2166 goto drop; 2167 } 2168 } else 2169 tp->t_dupacks = 0; 2170 break; 2171 } 2172 2173 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2174 ("%s: th_ack <= snd_una", __func__)); 2175 2176 /* 2177 * If the congestion window was inflated to account 2178 * for the other side's cached packets, retract it. 2179 */ 2180 if (V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) { 2181 if (IN_FASTRECOVERY(tp)) { 2182 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2183 if (tp->t_flags & TF_SACK_PERMIT) 2184 tcp_sack_partialack(tp, th); 2185 else 2186 tcp_newreno_partial_ack(tp, th); 2187 } else { 2188 /* 2189 * Out of fast recovery. 2190 * Window inflation should have left us 2191 * with approximately snd_ssthresh 2192 * outstanding data. 2193 * But in case we would be inclined to 2194 * send a burst, better to do it via 2195 * the slow start mechanism. 2196 */ 2197 if (SEQ_GT(th->th_ack + 2198 tp->snd_ssthresh, 2199 tp->snd_max)) 2200 tp->snd_cwnd = tp->snd_max - 2201 th->th_ack + 2202 tp->t_maxseg; 2203 else 2204 tp->snd_cwnd = tp->snd_ssthresh; 2205 } 2206 } 2207 } else { 2208 if (tp->t_dupacks >= tcprexmtthresh && 2209 tp->snd_cwnd > tp->snd_ssthresh) 2210 tp->snd_cwnd = tp->snd_ssthresh; 2211 } 2212 tp->t_dupacks = 0; 2213 /* 2214 * If we reach this point, ACK is not a duplicate, 2215 * i.e., it ACKs something we sent. 2216 */ 2217 if (tp->t_flags & TF_NEEDSYN) { 2218 /* 2219 * T/TCP: Connection was half-synchronized, and our 2220 * SYN has been ACK'd (so connection is now fully 2221 * synchronized). Go to non-starred state, 2222 * increment snd_una for ACK of SYN, and check if 2223 * we can do window scaling. 2224 */ 2225 tp->t_flags &= ~TF_NEEDSYN; 2226 tp->snd_una++; 2227 /* Do window scaling? */ 2228 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2229 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2230 tp->rcv_scale = tp->request_r_scale; 2231 /* Send window already scaled. */ 2232 } 2233 } 2234 2235process_ACK: 2236 INP_INFO_LOCK_ASSERT(&V_tcbinfo); 2237 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2238 ("tcp_input: process_ACK ti_locked %d", ti_locked)); 2239 INP_WLOCK_ASSERT(tp->t_inpcb); 2240 2241 acked = th->th_ack - tp->snd_una; 2242 TCPSTAT_INC(tcps_rcvackpack); 2243 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2244 2245 /* 2246 * If we just performed our first retransmit, and the ACK 2247 * arrives within our recovery window, then it was a mistake 2248 * to do the retransmit in the first place. Recover our 2249 * original cwnd and ssthresh, and proceed to transmit where 2250 * we left off. 2251 */ 2252 if (tp->t_rxtshift == 1 && (int)(ticks - tp->t_badrxtwin) < 0) { 2253 TCPSTAT_INC(tcps_sndrexmitbad); 2254 tp->snd_cwnd = tp->snd_cwnd_prev; 2255 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2256 tp->snd_recover = tp->snd_recover_prev; 2257 if (tp->t_flags & TF_WASFRECOVERY) 2258 ENTER_FASTRECOVERY(tp); 2259 tp->snd_nxt = tp->snd_max; 2260 tp->t_badrxtwin = 0; /* XXX probably not required */ 2261 } 2262 2263 /* 2264 * If we have a timestamp reply, update smoothed 2265 * round trip time. If no timestamp is present but 2266 * transmit timer is running and timed sequence 2267 * number was acked, update smoothed round trip time. 2268 * Since we now have an rtt measurement, cancel the 2269 * timer backoff (cf., Phil Karn's retransmit alg.). 2270 * Recompute the initial retransmit timer. 2271 * 2272 * Some boxes send broken timestamp replies 2273 * during the SYN+ACK phase, ignore 2274 * timestamps of 0 or we could calculate a 2275 * huge RTT and blow up the retransmit timer. 2276 */ 2277 if ((to.to_flags & TOF_TS) != 0 && 2278 to.to_tsecr) { 2279 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2280 tp->t_rttlow = ticks - to.to_tsecr; 2281 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2282 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2283 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2284 tp->t_rttlow = ticks - tp->t_rtttime; 2285 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2286 } 2287 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2288 2289 /* 2290 * If all outstanding data is acked, stop retransmit 2291 * timer and remember to restart (more output or persist). 2292 * If there is more data to be acked, restart retransmit 2293 * timer, using current (possibly backed-off) value. 2294 */ 2295 if (th->th_ack == tp->snd_max) { 2296 tcp_timer_activate(tp, TT_REXMT, 0); 2297 needoutput = 1; 2298 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2299 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2300 2301 /* 2302 * If no data (only SYN) was ACK'd, 2303 * skip rest of ACK processing. 2304 */ 2305 if (acked == 0) 2306 goto step6; 2307 2308 /* 2309 * When new data is acked, open the congestion window. 2310 * Method depends on which congestion control state we're 2311 * in (slow start or cong avoid) and if ABC (RFC 3465) is 2312 * enabled. 2313 * 2314 * slow start: cwnd <= ssthresh 2315 * cong avoid: cwnd > ssthresh 2316 * 2317 * slow start and ABC (RFC 3465): 2318 * Grow cwnd exponentially by the amount of data 2319 * ACKed capping the max increment per ACK to 2320 * (abc_l_var * maxseg) bytes. 2321 * 2322 * slow start without ABC (RFC 2581): 2323 * Grow cwnd exponentially by maxseg per ACK. 2324 * 2325 * cong avoid and ABC (RFC 3465): 2326 * Grow cwnd linearly by maxseg per RTT for each 2327 * cwnd worth of ACKed data. 2328 * 2329 * cong avoid without ABC (RFC 2581): 2330 * Grow cwnd linearly by approximately maxseg per RTT using 2331 * maxseg^2 / cwnd per ACK as the increment. 2332 * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to 2333 * avoid capping cwnd. 2334 */ 2335 if ((!V_tcp_do_newreno && !(tp->t_flags & TF_SACK_PERMIT)) || 2336 !IN_FASTRECOVERY(tp)) { 2337 u_int cw = tp->snd_cwnd; 2338 u_int incr = tp->t_maxseg; 2339 /* In congestion avoidance? */ 2340 if (cw > tp->snd_ssthresh) { 2341 if (V_tcp_do_rfc3465) { 2342 tp->t_bytes_acked += acked; 2343 if (tp->t_bytes_acked >= tp->snd_cwnd) 2344 tp->t_bytes_acked -= cw; 2345 else 2346 incr = 0; 2347 } 2348 else 2349 incr = max((incr * incr / cw), 1); 2350 /* 2351 * In slow-start with ABC enabled and no RTO in sight? 2352 * (Must not use abc_l_var > 1 if slow starting after an 2353 * RTO. On RTO, snd_nxt = snd_una, so the snd_nxt == 2354 * snd_max check is sufficient to handle this). 2355 */ 2356 } else if (V_tcp_do_rfc3465 && 2357 tp->snd_nxt == tp->snd_max) 2358 incr = min(acked, 2359 V_tcp_abc_l_var * tp->t_maxseg); 2360 /* ABC is on by default, so (incr == 0) frequently. */ 2361 if (incr > 0) 2362 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2363 } 2364 SOCKBUF_LOCK(&so->so_snd); 2365 if (acked > so->so_snd.sb_cc) { 2366 tp->snd_wnd -= so->so_snd.sb_cc; 2367 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2368 ourfinisacked = 1; 2369 } else { 2370 sbdrop_locked(&so->so_snd, acked); 2371 tp->snd_wnd -= acked; 2372 ourfinisacked = 0; 2373 } 2374 /* NB: sowwakeup_locked() does an implicit unlock. */ 2375 sowwakeup_locked(so); 2376 /* Detect una wraparound. */ 2377 if ((V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) && 2378 !IN_FASTRECOVERY(tp) && 2379 SEQ_GT(tp->snd_una, tp->snd_recover) && 2380 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2381 tp->snd_recover = th->th_ack - 1; 2382 if ((V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) && 2383 IN_FASTRECOVERY(tp) && 2384 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2385 EXIT_FASTRECOVERY(tp); 2386 tp->t_bytes_acked = 0; 2387 } 2388 tp->snd_una = th->th_ack; 2389 if (tp->t_flags & TF_SACK_PERMIT) { 2390 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2391 tp->snd_recover = tp->snd_una; 2392 } 2393 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2394 tp->snd_nxt = tp->snd_una; 2395 2396 switch (tp->t_state) { 2397 2398 /* 2399 * In FIN_WAIT_1 STATE in addition to the processing 2400 * for the ESTABLISHED state if our FIN is now acknowledged 2401 * then enter FIN_WAIT_2. 2402 */ 2403 case TCPS_FIN_WAIT_1: 2404 if (ourfinisacked) { 2405 /* 2406 * If we can't receive any more 2407 * data, then closing user can proceed. 2408 * Starting the timer is contrary to the 2409 * specification, but if we don't get a FIN 2410 * we'll hang forever. 2411 * 2412 * XXXjl: 2413 * we should release the tp also, and use a 2414 * compressed state. 2415 */ 2416 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2417 int timeout; 2418 2419 soisdisconnected(so); 2420 timeout = (tcp_fast_finwait2_recycle) ? 2421 tcp_finwait2_timeout : tcp_maxidle; 2422 tcp_timer_activate(tp, TT_2MSL, timeout); 2423 } 2424 tp->t_state = TCPS_FIN_WAIT_2; 2425 } 2426 break; 2427 2428 /* 2429 * In CLOSING STATE in addition to the processing for 2430 * the ESTABLISHED state if the ACK acknowledges our FIN 2431 * then enter the TIME-WAIT state, otherwise ignore 2432 * the segment. 2433 */ 2434 case TCPS_CLOSING: 2435 if (ourfinisacked) { 2436 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2437 tcp_twstart(tp); 2438 INP_INFO_WUNLOCK(&V_tcbinfo); 2439 m_freem(m); 2440 return; 2441 } 2442 break; 2443 2444 /* 2445 * In LAST_ACK, we may still be waiting for data to drain 2446 * and/or to be acked, as well as for the ack of our FIN. 2447 * If our FIN is now acknowledged, delete the TCB, 2448 * enter the closed state and return. 2449 */ 2450 case TCPS_LAST_ACK: 2451 if (ourfinisacked) { 2452 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2453 tp = tcp_close(tp); 2454 goto drop; 2455 } 2456 break; 2457 } 2458 } 2459 2460step6: 2461 INP_INFO_LOCK_ASSERT(&V_tcbinfo); 2462 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2463 ("tcp_do_segment: step6 ti_locked %d", ti_locked)); 2464 INP_WLOCK_ASSERT(tp->t_inpcb); 2465 2466 /* 2467 * Update window information. 2468 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2469 */ 2470 if ((thflags & TH_ACK) && 2471 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2472 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2473 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2474 /* keep track of pure window updates */ 2475 if (tlen == 0 && 2476 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2477 TCPSTAT_INC(tcps_rcvwinupd); 2478 tp->snd_wnd = tiwin; 2479 tp->snd_wl1 = th->th_seq; 2480 tp->snd_wl2 = th->th_ack; 2481 if (tp->snd_wnd > tp->max_sndwnd) 2482 tp->max_sndwnd = tp->snd_wnd; 2483 needoutput = 1; 2484 } 2485 2486 /* 2487 * Process segments with URG. 2488 */ 2489 if ((thflags & TH_URG) && th->th_urp && 2490 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2491 /* 2492 * This is a kludge, but if we receive and accept 2493 * random urgent pointers, we'll crash in 2494 * soreceive. It's hard to imagine someone 2495 * actually wanting to send this much urgent data. 2496 */ 2497 SOCKBUF_LOCK(&so->so_rcv); 2498 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2499 th->th_urp = 0; /* XXX */ 2500 thflags &= ~TH_URG; /* XXX */ 2501 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2502 goto dodata; /* XXX */ 2503 } 2504 /* 2505 * If this segment advances the known urgent pointer, 2506 * then mark the data stream. This should not happen 2507 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2508 * a FIN has been received from the remote side. 2509 * In these states we ignore the URG. 2510 * 2511 * According to RFC961 (Assigned Protocols), 2512 * the urgent pointer points to the last octet 2513 * of urgent data. We continue, however, 2514 * to consider it to indicate the first octet 2515 * of data past the urgent section as the original 2516 * spec states (in one of two places). 2517 */ 2518 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2519 tp->rcv_up = th->th_seq + th->th_urp; 2520 so->so_oobmark = so->so_rcv.sb_cc + 2521 (tp->rcv_up - tp->rcv_nxt) - 1; 2522 if (so->so_oobmark == 0) 2523 so->so_rcv.sb_state |= SBS_RCVATMARK; 2524 sohasoutofband(so); 2525 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2526 } 2527 SOCKBUF_UNLOCK(&so->so_rcv); 2528 /* 2529 * Remove out of band data so doesn't get presented to user. 2530 * This can happen independent of advancing the URG pointer, 2531 * but if two URG's are pending at once, some out-of-band 2532 * data may creep in... ick. 2533 */ 2534 if (th->th_urp <= (u_long)tlen && 2535 !(so->so_options & SO_OOBINLINE)) { 2536 /* hdr drop is delayed */ 2537 tcp_pulloutofband(so, th, m, drop_hdrlen); 2538 } 2539 } else { 2540 /* 2541 * If no out of band data is expected, 2542 * pull receive urgent pointer along 2543 * with the receive window. 2544 */ 2545 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2546 tp->rcv_up = tp->rcv_nxt; 2547 } 2548dodata: /* XXX */ 2549 INP_INFO_LOCK_ASSERT(&V_tcbinfo); 2550 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2551 ("tcp_do_segment: dodata ti_locked %d", ti_locked)); 2552 INP_WLOCK_ASSERT(tp->t_inpcb); 2553 2554 /* 2555 * Process the segment text, merging it into the TCP sequencing queue, 2556 * and arranging for acknowledgment of receipt if necessary. 2557 * This process logically involves adjusting tp->rcv_wnd as data 2558 * is presented to the user (this happens in tcp_usrreq.c, 2559 * case PRU_RCVD). If a FIN has already been received on this 2560 * connection then we just ignore the text. 2561 */ 2562 if ((tlen || (thflags & TH_FIN)) && 2563 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2564 tcp_seq save_start = th->th_seq; 2565 m_adj(m, drop_hdrlen); /* delayed header drop */ 2566 /* 2567 * Insert segment which includes th into TCP reassembly queue 2568 * with control block tp. Set thflags to whether reassembly now 2569 * includes a segment with FIN. This handles the common case 2570 * inline (segment is the next to be received on an established 2571 * connection, and the queue is empty), avoiding linkage into 2572 * and removal from the queue and repetition of various 2573 * conversions. 2574 * Set DELACK for segments received in order, but ack 2575 * immediately when segments are out of order (so 2576 * fast retransmit can work). 2577 */ 2578 if (th->th_seq == tp->rcv_nxt && 2579 LIST_EMPTY(&tp->t_segq) && 2580 TCPS_HAVEESTABLISHED(tp->t_state)) { 2581 if (DELAY_ACK(tp)) 2582 tp->t_flags |= TF_DELACK; 2583 else 2584 tp->t_flags |= TF_ACKNOW; 2585 tp->rcv_nxt += tlen; 2586 thflags = th->th_flags & TH_FIN; 2587 TCPSTAT_INC(tcps_rcvpack); 2588 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2589 ND6_HINT(tp); 2590 SOCKBUF_LOCK(&so->so_rcv); 2591 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2592 m_freem(m); 2593 else 2594 sbappendstream_locked(&so->so_rcv, m); 2595 /* NB: sorwakeup_locked() does an implicit unlock. */ 2596 sorwakeup_locked(so); 2597 } else { 2598 /* 2599 * XXX: Due to the header drop above "th" is 2600 * theoretically invalid by now. Fortunately 2601 * m_adj() doesn't actually frees any mbufs 2602 * when trimming from the head. 2603 */ 2604 thflags = tcp_reass(tp, th, &tlen, m); 2605 tp->t_flags |= TF_ACKNOW; 2606 } 2607 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2608 tcp_update_sack_list(tp, save_start, save_start + tlen); 2609#if 0 2610 /* 2611 * Note the amount of data that peer has sent into 2612 * our window, in order to estimate the sender's 2613 * buffer size. 2614 * XXX: Unused. 2615 */ 2616 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2617#endif 2618 } else { 2619 m_freem(m); 2620 thflags &= ~TH_FIN; 2621 } 2622 2623 /* 2624 * If FIN is received ACK the FIN and let the user know 2625 * that the connection is closing. 2626 */ 2627 if (thflags & TH_FIN) { 2628 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2629 socantrcvmore(so); 2630 /* 2631 * If connection is half-synchronized 2632 * (ie NEEDSYN flag on) then delay ACK, 2633 * so it may be piggybacked when SYN is sent. 2634 * Otherwise, since we received a FIN then no 2635 * more input can be expected, send ACK now. 2636 */ 2637 if (tp->t_flags & TF_NEEDSYN) 2638 tp->t_flags |= TF_DELACK; 2639 else 2640 tp->t_flags |= TF_ACKNOW; 2641 tp->rcv_nxt++; 2642 } 2643 switch (tp->t_state) { 2644 2645 /* 2646 * In SYN_RECEIVED and ESTABLISHED STATES 2647 * enter the CLOSE_WAIT state. 2648 */ 2649 case TCPS_SYN_RECEIVED: 2650 tp->t_starttime = ticks; 2651 /* FALLTHROUGH */ 2652 case TCPS_ESTABLISHED: 2653 tp->t_state = TCPS_CLOSE_WAIT; 2654 break; 2655 2656 /* 2657 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2658 * enter the CLOSING state. 2659 */ 2660 case TCPS_FIN_WAIT_1: 2661 tp->t_state = TCPS_CLOSING; 2662 break; 2663 2664 /* 2665 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2666 * starting the time-wait timer, turning off the other 2667 * standard timers. 2668 */ 2669 case TCPS_FIN_WAIT_2: 2670 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2671 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata " 2672 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 2673 ti_locked)); 2674 2675 tcp_twstart(tp); 2676 INP_INFO_WUNLOCK(&V_tcbinfo); 2677 return; 2678 } 2679 } 2680 if (ti_locked == TI_RLOCKED) 2681 INP_INFO_RUNLOCK(&V_tcbinfo); 2682 else if (ti_locked == TI_WLOCKED) 2683 INP_INFO_WUNLOCK(&V_tcbinfo); 2684 else 2685 panic("%s: dodata epilogue ti_locked %d", __func__, 2686 ti_locked); 2687 ti_locked = TI_UNLOCKED; 2688 2689#ifdef TCPDEBUG 2690 if (so->so_options & SO_DEBUG) 2691 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2692 &tcp_savetcp, 0); 2693#endif 2694 2695 /* 2696 * Return any desired output. 2697 */ 2698 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2699 (void) tcp_output(tp); 2700 2701check_delack: 2702 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 2703 __func__, ti_locked)); 2704 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 2705 INP_WLOCK_ASSERT(tp->t_inpcb); 2706 2707 if (tp->t_flags & TF_DELACK) { 2708 tp->t_flags &= ~TF_DELACK; 2709 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 2710 } 2711 INP_WUNLOCK(tp->t_inpcb); 2712 return; 2713 2714dropafterack: 2715 KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED, 2716 ("tcp_do_segment: dropafterack ti_locked %d", ti_locked)); 2717 2718 /* 2719 * Generate an ACK dropping incoming segment if it occupies 2720 * sequence space, where the ACK reflects our state. 2721 * 2722 * We can now skip the test for the RST flag since all 2723 * paths to this code happen after packets containing 2724 * RST have been dropped. 2725 * 2726 * In the SYN-RECEIVED state, don't send an ACK unless the 2727 * segment we received passes the SYN-RECEIVED ACK test. 2728 * If it fails send a RST. This breaks the loop in the 2729 * "LAND" DoS attack, and also prevents an ACK storm 2730 * between two listening ports that have been sent forged 2731 * SYN segments, each with the source address of the other. 2732 */ 2733 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2734 (SEQ_GT(tp->snd_una, th->th_ack) || 2735 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2736 rstreason = BANDLIM_RST_OPENPORT; 2737 goto dropwithreset; 2738 } 2739#ifdef TCPDEBUG 2740 if (so->so_options & SO_DEBUG) 2741 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2742 &tcp_savetcp, 0); 2743#endif 2744 if (ti_locked == TI_RLOCKED) 2745 INP_INFO_RUNLOCK(&V_tcbinfo); 2746 else if (ti_locked == TI_WLOCKED) 2747 INP_INFO_WUNLOCK(&V_tcbinfo); 2748 else 2749 panic("%s: dropafterack epilogue ti_locked %d", __func__, 2750 ti_locked); 2751 ti_locked = TI_UNLOCKED; 2752 2753 tp->t_flags |= TF_ACKNOW; 2754 (void) tcp_output(tp); 2755 INP_WUNLOCK(tp->t_inpcb); 2756 m_freem(m); 2757 return; 2758 2759dropwithreset: 2760 if (ti_locked == TI_RLOCKED) 2761 INP_INFO_RUNLOCK(&V_tcbinfo); 2762 else if (ti_locked == TI_WLOCKED) 2763 INP_INFO_WUNLOCK(&V_tcbinfo); 2764 else 2765 panic("%s: dropwithreset ti_locked %d", __func__, ti_locked); 2766 ti_locked = TI_UNLOCKED; 2767 2768 if (tp != NULL) { 2769 tcp_dropwithreset(m, th, tp, tlen, rstreason); 2770 INP_WUNLOCK(tp->t_inpcb); 2771 } else 2772 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 2773 return; 2774 2775drop: 2776 if (ti_locked == TI_RLOCKED) 2777 INP_INFO_RUNLOCK(&V_tcbinfo); 2778 else if (ti_locked == TI_WLOCKED) 2779 INP_INFO_WUNLOCK(&V_tcbinfo); 2780#ifdef INVARIANTS 2781 else 2782 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 2783#endif 2784 ti_locked = TI_UNLOCKED; 2785 2786 /* 2787 * Drop space held by incoming segment and return. 2788 */ 2789#ifdef TCPDEBUG 2790 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2791 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2792 &tcp_savetcp, 0); 2793#endif 2794 if (tp != NULL) 2795 INP_WUNLOCK(tp->t_inpcb); 2796 m_freem(m); 2797} 2798 2799/* 2800 * Issue RST and make ACK acceptable to originator of segment. 2801 * The mbuf must still include the original packet header. 2802 * tp may be NULL. 2803 */ 2804static void 2805tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 2806 int tlen, int rstreason) 2807{ 2808 struct ip *ip; 2809#ifdef INET6 2810 struct ip6_hdr *ip6; 2811#endif 2812 2813 if (tp != NULL) { 2814 INP_WLOCK_ASSERT(tp->t_inpcb); 2815 } 2816 2817 /* Don't bother if destination was broadcast/multicast. */ 2818 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2819 goto drop; 2820#ifdef INET6 2821 if (mtod(m, struct ip *)->ip_v == 6) { 2822 ip6 = mtod(m, struct ip6_hdr *); 2823 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2824 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2825 goto drop; 2826 /* IPv6 anycast check is done at tcp6_input() */ 2827 } else 2828#endif 2829 { 2830 ip = mtod(m, struct ip *); 2831 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2832 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2833 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2834 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2835 goto drop; 2836 } 2837 2838 /* Perform bandwidth limiting. */ 2839 if (badport_bandlim(rstreason) < 0) 2840 goto drop; 2841 2842 /* tcp_respond consumes the mbuf chain. */ 2843 if (th->th_flags & TH_ACK) { 2844 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 2845 th->th_ack, TH_RST); 2846 } else { 2847 if (th->th_flags & TH_SYN) 2848 tlen++; 2849 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2850 (tcp_seq)0, TH_RST|TH_ACK); 2851 } 2852 return; 2853drop: 2854 m_freem(m); 2855} 2856 2857/* 2858 * Parse TCP options and place in tcpopt. 2859 */ 2860static void 2861tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 2862{ 2863 int opt, optlen; 2864 2865 to->to_flags = 0; 2866 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2867 opt = cp[0]; 2868 if (opt == TCPOPT_EOL) 2869 break; 2870 if (opt == TCPOPT_NOP) 2871 optlen = 1; 2872 else { 2873 if (cnt < 2) 2874 break; 2875 optlen = cp[1]; 2876 if (optlen < 2 || optlen > cnt) 2877 break; 2878 } 2879 switch (opt) { 2880 case TCPOPT_MAXSEG: 2881 if (optlen != TCPOLEN_MAXSEG) 2882 continue; 2883 if (!(flags & TO_SYN)) 2884 continue; 2885 to->to_flags |= TOF_MSS; 2886 bcopy((char *)cp + 2, 2887 (char *)&to->to_mss, sizeof(to->to_mss)); 2888 to->to_mss = ntohs(to->to_mss); 2889 break; 2890 case TCPOPT_WINDOW: 2891 if (optlen != TCPOLEN_WINDOW) 2892 continue; 2893 if (!(flags & TO_SYN)) 2894 continue; 2895 to->to_flags |= TOF_SCALE; 2896 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 2897 break; 2898 case TCPOPT_TIMESTAMP: 2899 if (optlen != TCPOLEN_TIMESTAMP) 2900 continue; 2901 to->to_flags |= TOF_TS; 2902 bcopy((char *)cp + 2, 2903 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2904 to->to_tsval = ntohl(to->to_tsval); 2905 bcopy((char *)cp + 6, 2906 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2907 to->to_tsecr = ntohl(to->to_tsecr); 2908 break; 2909#ifdef TCP_SIGNATURE 2910 /* 2911 * XXX In order to reply to a host which has set the 2912 * TCP_SIGNATURE option in its initial SYN, we have to 2913 * record the fact that the option was observed here 2914 * for the syncache code to perform the correct response. 2915 */ 2916 case TCPOPT_SIGNATURE: 2917 if (optlen != TCPOLEN_SIGNATURE) 2918 continue; 2919 to->to_flags |= TOF_SIGNATURE; 2920 to->to_signature = cp + 2; 2921 break; 2922#endif 2923 case TCPOPT_SACK_PERMITTED: 2924 if (optlen != TCPOLEN_SACK_PERMITTED) 2925 continue; 2926 if (!(flags & TO_SYN)) 2927 continue; 2928 if (!V_tcp_do_sack) 2929 continue; 2930 to->to_flags |= TOF_SACKPERM; 2931 break; 2932 case TCPOPT_SACK: 2933 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2934 continue; 2935 if (flags & TO_SYN) 2936 continue; 2937 to->to_flags |= TOF_SACK; 2938 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2939 to->to_sacks = cp + 2; 2940 TCPSTAT_INC(tcps_sack_rcv_blocks); 2941 break; 2942 default: 2943 continue; 2944 } 2945 } 2946} 2947 2948/* 2949 * Pull out of band byte out of a segment so 2950 * it doesn't appear in the user's data queue. 2951 * It is still reflected in the segment length for 2952 * sequencing purposes. 2953 */ 2954static void 2955tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 2956 int off) 2957{ 2958 int cnt = off + th->th_urp - 1; 2959 2960 while (cnt >= 0) { 2961 if (m->m_len > cnt) { 2962 char *cp = mtod(m, caddr_t) + cnt; 2963 struct tcpcb *tp = sototcpcb(so); 2964 2965 INP_WLOCK_ASSERT(tp->t_inpcb); 2966 2967 tp->t_iobc = *cp; 2968 tp->t_oobflags |= TCPOOB_HAVEDATA; 2969 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2970 m->m_len--; 2971 if (m->m_flags & M_PKTHDR) 2972 m->m_pkthdr.len--; 2973 return; 2974 } 2975 cnt -= m->m_len; 2976 m = m->m_next; 2977 if (m == NULL) 2978 break; 2979 } 2980 panic("tcp_pulloutofband"); 2981} 2982 2983/* 2984 * Collect new round-trip time estimate 2985 * and update averages and current timeout. 2986 */ 2987static void 2988tcp_xmit_timer(struct tcpcb *tp, int rtt) 2989{ 2990 int delta; 2991 2992 INP_WLOCK_ASSERT(tp->t_inpcb); 2993 2994 TCPSTAT_INC(tcps_rttupdated); 2995 tp->t_rttupdated++; 2996 if (tp->t_srtt != 0) { 2997 /* 2998 * srtt is stored as fixed point with 5 bits after the 2999 * binary point (i.e., scaled by 8). The following magic 3000 * is equivalent to the smoothing algorithm in rfc793 with 3001 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3002 * point). Adjust rtt to origin 0. 3003 */ 3004 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3005 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3006 3007 if ((tp->t_srtt += delta) <= 0) 3008 tp->t_srtt = 1; 3009 3010 /* 3011 * We accumulate a smoothed rtt variance (actually, a 3012 * smoothed mean difference), then set the retransmit 3013 * timer to smoothed rtt + 4 times the smoothed variance. 3014 * rttvar is stored as fixed point with 4 bits after the 3015 * binary point (scaled by 16). The following is 3016 * equivalent to rfc793 smoothing with an alpha of .75 3017 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3018 * rfc793's wired-in beta. 3019 */ 3020 if (delta < 0) 3021 delta = -delta; 3022 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3023 if ((tp->t_rttvar += delta) <= 0) 3024 tp->t_rttvar = 1; 3025 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3026 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3027 } else { 3028 /* 3029 * No rtt measurement yet - use the unsmoothed rtt. 3030 * Set the variance to half the rtt (so our first 3031 * retransmit happens at 3*rtt). 3032 */ 3033 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3034 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3035 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3036 } 3037 tp->t_rtttime = 0; 3038 tp->t_rxtshift = 0; 3039 3040 /* 3041 * the retransmit should happen at rtt + 4 * rttvar. 3042 * Because of the way we do the smoothing, srtt and rttvar 3043 * will each average +1/2 tick of bias. When we compute 3044 * the retransmit timer, we want 1/2 tick of rounding and 3045 * 1 extra tick because of +-1/2 tick uncertainty in the 3046 * firing of the timer. The bias will give us exactly the 3047 * 1.5 tick we need. But, because the bias is 3048 * statistical, we have to test that we don't drop below 3049 * the minimum feasible timer (which is 2 ticks). 3050 */ 3051 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3052 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3053 3054 /* 3055 * We received an ack for a packet that wasn't retransmitted; 3056 * it is probably safe to discard any error indications we've 3057 * received recently. This isn't quite right, but close enough 3058 * for now (a route might have failed after we sent a segment, 3059 * and the return path might not be symmetrical). 3060 */ 3061 tp->t_softerror = 0; 3062} 3063 3064/* 3065 * Determine a reasonable value for maxseg size. 3066 * If the route is known, check route for mtu. 3067 * If none, use an mss that can be handled on the outgoing 3068 * interface without forcing IP to fragment; if bigger than 3069 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 3070 * to utilize large mbufs. If no route is found, route has no mtu, 3071 * or the destination isn't local, use a default, hopefully conservative 3072 * size (usually 512 or the default IP max size, but no more than the mtu 3073 * of the interface), as we can't discover anything about intervening 3074 * gateways or networks. We also initialize the congestion/slow start 3075 * window to be a single segment if the destination isn't local. 3076 * While looking at the routing entry, we also initialize other path-dependent 3077 * parameters from pre-set or cached values in the routing entry. 3078 * 3079 * Also take into account the space needed for options that we 3080 * send regularly. Make maxseg shorter by that amount to assure 3081 * that we can send maxseg amount of data even when the options 3082 * are present. Store the upper limit of the length of options plus 3083 * data in maxopd. 3084 * 3085 * In case of T/TCP, we call this routine during implicit connection 3086 * setup as well (offer = -1), to initialize maxseg from the cached 3087 * MSS of our peer. 3088 * 3089 * NOTE that this routine is only called when we process an incoming 3090 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 3091 */ 3092void 3093tcp_mss_update(struct tcpcb *tp, int offer, 3094 struct hc_metrics_lite *metricptr, int *mtuflags) 3095{ 3096 int mss; 3097 u_long maxmtu; 3098 struct inpcb *inp = tp->t_inpcb; 3099 struct hc_metrics_lite metrics; 3100 int origoffer = offer; 3101#ifdef INET6 3102 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3103 size_t min_protoh = isipv6 ? 3104 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3105 sizeof (struct tcpiphdr); 3106#else 3107 const size_t min_protoh = sizeof(struct tcpiphdr); 3108#endif 3109 3110 INP_WLOCK_ASSERT(tp->t_inpcb); 3111 3112 /* Initialize. */ 3113#ifdef INET6 3114 if (isipv6) { 3115 maxmtu = tcp_maxmtu6(&inp->inp_inc, mtuflags); 3116 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; 3117 } else 3118#endif 3119 { 3120 maxmtu = tcp_maxmtu(&inp->inp_inc, mtuflags); 3121 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; 3122 } 3123 3124 /* 3125 * No route to sender, stay with default mss and return. 3126 */ 3127 if (maxmtu == 0) { 3128 /* 3129 * In case we return early we need to initialize metrics 3130 * to a defined state as tcp_hc_get() would do for us 3131 * if there was no cache hit. 3132 */ 3133 if (metricptr != NULL) 3134 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3135 return; 3136 } 3137 3138 /* What have we got? */ 3139 switch (offer) { 3140 case 0: 3141 /* 3142 * Offer == 0 means that there was no MSS on the SYN 3143 * segment, in this case we use tcp_mssdflt as 3144 * already assigned to t_maxopd above. 3145 */ 3146 offer = tp->t_maxopd; 3147 break; 3148 3149 case -1: 3150 /* 3151 * Offer == -1 means that we didn't receive SYN yet. 3152 */ 3153 /* FALLTHROUGH */ 3154 3155 default: 3156 /* 3157 * Prevent DoS attack with too small MSS. Round up 3158 * to at least minmss. 3159 */ 3160 offer = max(offer, V_tcp_minmss); 3161 } 3162 3163 /* 3164 * rmx information is now retrieved from tcp_hostcache. 3165 */ 3166 tcp_hc_get(&inp->inp_inc, &metrics); 3167 if (metricptr != NULL) 3168 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3169 3170 /* 3171 * If there's a discovered mtu int tcp hostcache, use it 3172 * else, use the link mtu. 3173 */ 3174 if (metrics.rmx_mtu) 3175 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3176 else { 3177#ifdef INET6 3178 if (isipv6) { 3179 mss = maxmtu - min_protoh; 3180 if (!V_path_mtu_discovery && 3181 !in6_localaddr(&inp->in6p_faddr)) 3182 mss = min(mss, V_tcp_v6mssdflt); 3183 } else 3184#endif 3185 { 3186 mss = maxmtu - min_protoh; 3187 if (!V_path_mtu_discovery && 3188 !in_localaddr(inp->inp_faddr)) 3189 mss = min(mss, V_tcp_mssdflt); 3190 } 3191 /* 3192 * XXX - The above conditional (mss = maxmtu - min_protoh) 3193 * probably violates the TCP spec. 3194 * The problem is that, since we don't know the 3195 * other end's MSS, we are supposed to use a conservative 3196 * default. But, if we do that, then MTU discovery will 3197 * never actually take place, because the conservative 3198 * default is much less than the MTUs typically seen 3199 * on the Internet today. For the moment, we'll sweep 3200 * this under the carpet. 3201 * 3202 * The conservative default might not actually be a problem 3203 * if the only case this occurs is when sending an initial 3204 * SYN with options and data to a host we've never talked 3205 * to before. Then, they will reply with an MSS value which 3206 * will get recorded and the new parameters should get 3207 * recomputed. For Further Study. 3208 */ 3209 } 3210 mss = min(mss, offer); 3211 3212 /* 3213 * Sanity check: make sure that maxopd will be large 3214 * enough to allow some data on segments even if the 3215 * all the option space is used (40bytes). Otherwise 3216 * funny things may happen in tcp_output. 3217 */ 3218 mss = max(mss, 64); 3219 3220 /* 3221 * maxopd stores the maximum length of data AND options 3222 * in a segment; maxseg is the amount of data in a normal 3223 * segment. We need to store this value (maxopd) apart 3224 * from maxseg, because now every segment carries options 3225 * and thus we normally have somewhat less data in segments. 3226 */ 3227 tp->t_maxopd = mss; 3228 3229 /* 3230 * origoffer==-1 indicates that no segments were received yet. 3231 * In this case we just guess. 3232 */ 3233 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3234 (origoffer == -1 || 3235 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3236 mss -= TCPOLEN_TSTAMP_APPA; 3237 3238#if (MCLBYTES & (MCLBYTES - 1)) == 0 3239 if (mss > MCLBYTES) 3240 mss &= ~(MCLBYTES-1); 3241#else 3242 if (mss > MCLBYTES) 3243 mss = mss / MCLBYTES * MCLBYTES; 3244#endif 3245 tp->t_maxseg = mss; 3246} 3247 3248void 3249tcp_mss(struct tcpcb *tp, int offer) 3250{ 3251 int rtt, mss; 3252 u_long bufsize; 3253 struct inpcb *inp; 3254 struct socket *so; 3255 struct hc_metrics_lite metrics; 3256 int mtuflags = 0; 3257#ifdef INET6 3258 int isipv6; 3259#endif 3260 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3261 3262 tcp_mss_update(tp, offer, &metrics, &mtuflags); 3263 3264 mss = tp->t_maxseg; 3265 inp = tp->t_inpcb; 3266#ifdef INET6 3267 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3268#endif 3269 3270 /* 3271 * If there's a pipesize, change the socket buffer to that size, 3272 * don't change if sb_hiwat is different than default (then it 3273 * has been changed on purpose with setsockopt). 3274 * Make the socket buffers an integral number of mss units; 3275 * if the mss is larger than the socket buffer, decrease the mss. 3276 */ 3277 so = inp->inp_socket; 3278 SOCKBUF_LOCK(&so->so_snd); 3279 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3280 bufsize = metrics.rmx_sendpipe; 3281 else 3282 bufsize = so->so_snd.sb_hiwat; 3283 if (bufsize < mss) 3284 mss = bufsize; 3285 else { 3286 bufsize = roundup(bufsize, mss); 3287 if (bufsize > sb_max) 3288 bufsize = sb_max; 3289 if (bufsize > so->so_snd.sb_hiwat) 3290 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3291 } 3292 SOCKBUF_UNLOCK(&so->so_snd); 3293 tp->t_maxseg = mss; 3294 3295 SOCKBUF_LOCK(&so->so_rcv); 3296 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3297 bufsize = metrics.rmx_recvpipe; 3298 else 3299 bufsize = so->so_rcv.sb_hiwat; 3300 if (bufsize > mss) { 3301 bufsize = roundup(bufsize, mss); 3302 if (bufsize > sb_max) 3303 bufsize = sb_max; 3304 if (bufsize > so->so_rcv.sb_hiwat) 3305 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3306 } 3307 SOCKBUF_UNLOCK(&so->so_rcv); 3308 /* 3309 * While we're here, check the others too. 3310 */ 3311 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3312 tp->t_srtt = rtt; 3313 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3314 TCPSTAT_INC(tcps_usedrtt); 3315 if (metrics.rmx_rttvar) { 3316 tp->t_rttvar = metrics.rmx_rttvar; 3317 TCPSTAT_INC(tcps_usedrttvar); 3318 } else { 3319 /* default variation is +- 1 rtt */ 3320 tp->t_rttvar = 3321 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3322 } 3323 TCPT_RANGESET(tp->t_rxtcur, 3324 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3325 tp->t_rttmin, TCPTV_REXMTMAX); 3326 } 3327 if (metrics.rmx_ssthresh) { 3328 /* 3329 * There's some sort of gateway or interface 3330 * buffer limit on the path. Use this to set 3331 * the slow start threshhold, but set the 3332 * threshold to no less than 2*mss. 3333 */ 3334 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3335 TCPSTAT_INC(tcps_usedssthresh); 3336 } 3337 if (metrics.rmx_bandwidth) 3338 tp->snd_bandwidth = metrics.rmx_bandwidth; 3339 3340 /* 3341 * Set the slow-start flight size depending on whether this 3342 * is a local network or not. 3343 * 3344 * Extend this so we cache the cwnd too and retrieve it here. 3345 * Make cwnd even bigger than RFC3390 suggests but only if we 3346 * have previous experience with the remote host. Be careful 3347 * not make cwnd bigger than remote receive window or our own 3348 * send socket buffer. Maybe put some additional upper bound 3349 * on the retrieved cwnd. Should do incremental updates to 3350 * hostcache when cwnd collapses so next connection doesn't 3351 * overloads the path again. 3352 * 3353 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3354 * We currently check only in syncache_socket for that. 3355 */ 3356#define TCP_METRICS_CWND 3357#ifdef TCP_METRICS_CWND 3358 if (metrics.rmx_cwnd) 3359 tp->snd_cwnd = max(mss, 3360 min(metrics.rmx_cwnd / 2, 3361 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3362 else 3363#endif 3364 if (V_tcp_do_rfc3390) 3365 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3366#ifdef INET6 3367 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3368 (!isipv6 && in_localaddr(inp->inp_faddr))) 3369#else 3370 else if (in_localaddr(inp->inp_faddr)) 3371#endif 3372 tp->snd_cwnd = mss * V_ss_fltsz_local; 3373 else 3374 tp->snd_cwnd = mss * V_ss_fltsz; 3375 3376 /* Check the interface for TSO capabilities. */ 3377 if (mtuflags & CSUM_TSO) 3378 tp->t_flags |= TF_TSO; 3379} 3380 3381/* 3382 * Determine the MSS option to send on an outgoing SYN. 3383 */ 3384int 3385tcp_mssopt(struct in_conninfo *inc) 3386{ 3387 int mss = 0; 3388 u_long maxmtu = 0; 3389 u_long thcmtu = 0; 3390 size_t min_protoh; 3391 3392 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3393 3394#ifdef INET6 3395 if (inc->inc_flags & INC_ISIPV6) { 3396 mss = V_tcp_v6mssdflt; 3397 maxmtu = tcp_maxmtu6(inc, NULL); 3398 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3399 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3400 } else 3401#endif 3402 { 3403 mss = V_tcp_mssdflt; 3404 maxmtu = tcp_maxmtu(inc, NULL); 3405 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3406 min_protoh = sizeof(struct tcpiphdr); 3407 } 3408 if (maxmtu && thcmtu) 3409 mss = min(maxmtu, thcmtu) - min_protoh; 3410 else if (maxmtu || thcmtu) 3411 mss = max(maxmtu, thcmtu) - min_protoh; 3412 3413 return (mss); 3414} 3415 3416 3417/* 3418 * On a partial ack arrives, force the retransmission of the 3419 * next unacknowledged segment. Do not clear tp->t_dupacks. 3420 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3421 * be started again. 3422 */ 3423static void 3424tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3425{ 3426 tcp_seq onxt = tp->snd_nxt; 3427 u_long ocwnd = tp->snd_cwnd; 3428 3429 INP_WLOCK_ASSERT(tp->t_inpcb); 3430 3431 tcp_timer_activate(tp, TT_REXMT, 0); 3432 tp->t_rtttime = 0; 3433 tp->snd_nxt = th->th_ack; 3434 /* 3435 * Set snd_cwnd to one segment beyond acknowledged offset. 3436 * (tp->snd_una has not yet been updated when this function is called.) 3437 */ 3438 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3439 tp->t_flags |= TF_ACKNOW; 3440 (void) tcp_output(tp); 3441 tp->snd_cwnd = ocwnd; 3442 if (SEQ_GT(onxt, tp->snd_nxt)) 3443 tp->snd_nxt = onxt; 3444 /* 3445 * Partial window deflation. Relies on fact that tp->snd_una 3446 * not updated yet. 3447 */ 3448 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3449 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3450 else 3451 tp->snd_cwnd = 0; 3452 tp->snd_cwnd += tp->t_maxseg; 3453} 3454