Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_input.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
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 * $FreeBSD: releng/5.4/sys/netinet/tcp_input.c 147668 2005-06-29 21:41:03Z simon $ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/mac.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/signalvar.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 #include <sys/syslog.h> 54 #include <sys/systm.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/in_var.h> 67 #include <netinet/ip.h> 68 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/nd6.h> 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet6/tcp6_var.h> 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif /* TCPDEBUG */ 86 87 #ifdef FAST_IPSEC 88 #include <netipsec/ipsec.h> 89 #include <netipsec/ipsec6.h> 90 #endif /*FAST_IPSEC*/ 91 92 #ifdef IPSEC 93 #include <netinet6/ipsec.h> 94 #include <netinet6/ipsec6.h> 95 #include <netkey/key.h> 96 #endif /*IPSEC*/ 97 98 #include <machine/in_cksum.h> 99 100 static const int tcprexmtthresh = 3; 101 tcp_cc tcp_ccgen; 102 103 struct tcpstat tcpstat; 104 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107 static int log_in_vain = 0; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111 static int blackhole = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115 int tcp_delack_enabled = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120 #ifdef TCP_DROP_SYNFIN 121 static int drop_synfin = 0; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124 #endif 125 126 static int tcp_do_rfc3042 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130 static int tcp_do_rfc3390 = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135 static int tcp_insecure_rst = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 137 &tcp_insecure_rst, 0, 138 "Follow the old (insecure) criteria for accepting RST packets."); 139 140 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 141 "TCP Segment Reassembly Queue"); 142 143 static int tcp_reass_maxseg = 0; 144 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 145 &tcp_reass_maxseg, 0, 146 "Global maximum number of TCP Segments in Reassembly Queue"); 147 148 int tcp_reass_qsize = 0; 149 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 150 &tcp_reass_qsize, 0, 151 "Global number of TCP Segments currently in Reassembly Queue"); 152 153 static int tcp_reass_maxqlen = 48; 154 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 155 &tcp_reass_maxqlen, 0, 156 "Maximum number of TCP Segments per individual Reassembly Queue"); 157 158 static int tcp_reass_overflows = 0; 159 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 160 &tcp_reass_overflows, 0, 161 "Global number of TCP Segment Reassembly Queue Overflows"); 162 163 struct inpcbhead tcb; 164 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 165 struct inpcbinfo tcbinfo; 166 struct mtx *tcbinfo_mtx; 167 168 static void tcp_dooptions(struct tcpcb *, struct tcpopt *, u_char *, 169 int, int, struct tcphdr *); 170 171 static void tcp_pulloutofband(struct socket *, 172 struct tcphdr *, struct mbuf *, int); 173 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 174 struct mbuf *); 175 static void tcp_xmit_timer(struct tcpcb *, int); 176 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 177 static int tcp_timewait(struct tcptw *, struct tcpopt *, 178 struct tcphdr *, struct mbuf *, int); 179 180 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 181 #ifdef INET6 182 #define ND6_HINT(tp) \ 183 do { \ 184 if ((tp) && (tp)->t_inpcb && \ 185 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 186 nd6_nud_hint(NULL, NULL, 0); \ 187 } while (0) 188 #else 189 #define ND6_HINT(tp) 190 #endif 191 192 /* 193 * Indicate whether this ack should be delayed. We can delay the ack if 194 * - there is no delayed ack timer in progress and 195 * - our last ack wasn't a 0-sized window. We never want to delay 196 * the ack that opens up a 0-sized window and 197 * - delayed acks are enabled or 198 * - this is a half-synchronized T/TCP connection. 199 */ 200 #define DELAY_ACK(tp) \ 201 ((!callout_active(tp->tt_delack) && \ 202 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 203 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 204 205 /* Initialize TCP reassembly queue */ 206 uma_zone_t tcp_reass_zone; 207 void 208 tcp_reass_init() 209 { 210 tcp_reass_maxseg = nmbclusters / 16; 211 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 212 &tcp_reass_maxseg); 213 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 214 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 215 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 216 } 217 218 static int 219 tcp_reass(tp, th, tlenp, m) 220 register struct tcpcb *tp; 221 register struct tcphdr *th; 222 int *tlenp; 223 struct mbuf *m; 224 { 225 struct tseg_qent *q; 226 struct tseg_qent *p = NULL; 227 struct tseg_qent *nq; 228 struct tseg_qent *te = NULL; 229 struct socket *so = tp->t_inpcb->inp_socket; 230 int flags; 231 232 INP_LOCK_ASSERT(tp->t_inpcb); 233 234 /* 235 * XXX: tcp_reass() is rather inefficient with its data structures 236 * and should be rewritten (see NetBSD for optimizations). While 237 * doing that it should move to its own file tcp_reass.c. 238 */ 239 240 /* 241 * Call with th==NULL after become established to 242 * force pre-ESTABLISHED data up to user socket. 243 */ 244 if (th == NULL) 245 goto present; 246 247 /* 248 * Limit the number of segments in the reassembly queue to prevent 249 * holding on to too many segments (and thus running out of mbufs). 250 * Make sure to let the missing segment through which caused this 251 * queue. Always keep one global queue entry spare to be able to 252 * process the missing segment. 253 */ 254 if (th->th_seq != tp->rcv_nxt && 255 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 256 tp->t_segqlen >= tcp_reass_maxqlen)) { 257 tcp_reass_overflows++; 258 tcpstat.tcps_rcvmemdrop++; 259 m_freem(m); 260 return (0); 261 } 262 263 /* 264 * Allocate a new queue entry. If we can't, or hit the zone limit 265 * just drop the pkt. 266 */ 267 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 268 if (te == NULL) { 269 tcpstat.tcps_rcvmemdrop++; 270 m_freem(m); 271 return (0); 272 } 273 tp->t_segqlen++; 274 tcp_reass_qsize++; 275 276 /* 277 * Find a segment which begins after this one does. 278 */ 279 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 280 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 281 break; 282 p = q; 283 } 284 285 /* 286 * If there is a preceding segment, it may provide some of 287 * our data already. If so, drop the data from the incoming 288 * segment. If it provides all of our data, drop us. 289 */ 290 if (p != NULL) { 291 register int i; 292 /* conversion to int (in i) handles seq wraparound */ 293 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 294 if (i > 0) { 295 if (i >= *tlenp) { 296 tcpstat.tcps_rcvduppack++; 297 tcpstat.tcps_rcvdupbyte += *tlenp; 298 m_freem(m); 299 uma_zfree(tcp_reass_zone, te); 300 tp->t_segqlen--; 301 tcp_reass_qsize--; 302 /* 303 * Try to present any queued data 304 * at the left window edge to the user. 305 * This is needed after the 3-WHS 306 * completes. 307 */ 308 goto present; /* ??? */ 309 } 310 m_adj(m, i); 311 *tlenp -= i; 312 th->th_seq += i; 313 } 314 } 315 tcpstat.tcps_rcvoopack++; 316 tcpstat.tcps_rcvoobyte += *tlenp; 317 318 /* 319 * While we overlap succeeding segments trim them or, 320 * if they are completely covered, dequeue them. 321 */ 322 while (q) { 323 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 324 if (i <= 0) 325 break; 326 if (i < q->tqe_len) { 327 q->tqe_th->th_seq += i; 328 q->tqe_len -= i; 329 m_adj(q->tqe_m, i); 330 break; 331 } 332 333 nq = LIST_NEXT(q, tqe_q); 334 LIST_REMOVE(q, tqe_q); 335 m_freem(q->tqe_m); 336 uma_zfree(tcp_reass_zone, q); 337 tp->t_segqlen--; 338 tcp_reass_qsize--; 339 q = nq; 340 } 341 342 /* Insert the new segment queue entry into place. */ 343 te->tqe_m = m; 344 te->tqe_th = th; 345 te->tqe_len = *tlenp; 346 347 if (p == NULL) { 348 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 349 } else { 350 LIST_INSERT_AFTER(p, te, tqe_q); 351 } 352 353 present: 354 /* 355 * Present data to user, advancing rcv_nxt through 356 * completed sequence space. 357 */ 358 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 359 return (0); 360 q = LIST_FIRST(&tp->t_segq); 361 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 362 return (0); 363 SOCKBUF_LOCK(&so->so_rcv); 364 do { 365 tp->rcv_nxt += q->tqe_len; 366 flags = q->tqe_th->th_flags & TH_FIN; 367 nq = LIST_NEXT(q, tqe_q); 368 LIST_REMOVE(q, tqe_q); 369 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 370 m_freem(q->tqe_m); 371 else 372 sbappendstream_locked(&so->so_rcv, q->tqe_m); 373 uma_zfree(tcp_reass_zone, q); 374 tp->t_segqlen--; 375 tcp_reass_qsize--; 376 q = nq; 377 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 378 ND6_HINT(tp); 379 sorwakeup_locked(so); 380 return (flags); 381 } 382 383 /* 384 * TCP input routine, follows pages 65-76 of the 385 * protocol specification dated September, 1981 very closely. 386 */ 387 #ifdef INET6 388 int 389 tcp6_input(mp, offp, proto) 390 struct mbuf **mp; 391 int *offp, proto; 392 { 393 register struct mbuf *m = *mp; 394 struct in6_ifaddr *ia6; 395 396 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 397 398 /* 399 * draft-itojun-ipv6-tcp-to-anycast 400 * better place to put this in? 401 */ 402 ia6 = ip6_getdstifaddr(m); 403 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 404 struct ip6_hdr *ip6; 405 406 ip6 = mtod(m, struct ip6_hdr *); 407 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 408 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 409 return IPPROTO_DONE; 410 } 411 412 tcp_input(m, *offp); 413 return IPPROTO_DONE; 414 } 415 #endif 416 417 void 418 tcp_input(m, off0) 419 register struct mbuf *m; 420 int off0; 421 { 422 register struct tcphdr *th; 423 register struct ip *ip = NULL; 424 register struct ipovly *ipov; 425 register struct inpcb *inp = NULL; 426 u_char *optp = NULL; 427 int optlen = 0; 428 int len, tlen, off; 429 int drop_hdrlen; 430 register struct tcpcb *tp = 0; 431 register int thflags; 432 struct socket *so = 0; 433 int todrop, acked, ourfinisacked, needoutput = 0; 434 u_long tiwin; 435 struct tcpopt to; /* options in this segment */ 436 struct rmxp_tao tao; /* our TAO cache entry */ 437 int headlocked = 0; 438 #ifdef IPFIREWALL_FORWARD 439 struct m_tag *fwd_tag; 440 #endif 441 int rstreason; /* For badport_bandlim accounting purposes */ 442 443 struct ip6_hdr *ip6 = NULL; 444 #ifdef INET6 445 int isipv6; 446 #else 447 const int isipv6 = 0; 448 #endif 449 450 #ifdef TCPDEBUG 451 /* 452 * The size of tcp_saveipgen must be the size of the max ip header, 453 * now IPv6. 454 */ 455 u_char tcp_saveipgen[40]; 456 struct tcphdr tcp_savetcp; 457 short ostate = 0; 458 #endif 459 460 #ifdef INET6 461 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 462 #endif 463 bzero(&tao, sizeof(tao)); 464 bzero((char *)&to, sizeof(to)); 465 466 tcpstat.tcps_rcvtotal++; 467 468 if (isipv6) { 469 #ifdef INET6 470 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 471 ip6 = mtod(m, struct ip6_hdr *); 472 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 473 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 474 tcpstat.tcps_rcvbadsum++; 475 goto drop; 476 } 477 th = (struct tcphdr *)((caddr_t)ip6 + off0); 478 479 /* 480 * Be proactive about unspecified IPv6 address in source. 481 * As we use all-zero to indicate unbounded/unconnected pcb, 482 * unspecified IPv6 address can be used to confuse us. 483 * 484 * Note that packets with unspecified IPv6 destination is 485 * already dropped in ip6_input. 486 */ 487 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 488 /* XXX stat */ 489 goto drop; 490 } 491 #else 492 th = NULL; /* XXX: avoid compiler warning */ 493 #endif 494 } else { 495 /* 496 * Get IP and TCP header together in first mbuf. 497 * Note: IP leaves IP header in first mbuf. 498 */ 499 if (off0 > sizeof (struct ip)) { 500 ip_stripoptions(m, (struct mbuf *)0); 501 off0 = sizeof(struct ip); 502 } 503 if (m->m_len < sizeof (struct tcpiphdr)) { 504 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 505 tcpstat.tcps_rcvshort++; 506 return; 507 } 508 } 509 ip = mtod(m, struct ip *); 510 ipov = (struct ipovly *)ip; 511 th = (struct tcphdr *)((caddr_t)ip + off0); 512 tlen = ip->ip_len; 513 514 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 515 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 516 th->th_sum = m->m_pkthdr.csum_data; 517 else 518 th->th_sum = in_pseudo(ip->ip_src.s_addr, 519 ip->ip_dst.s_addr, 520 htonl(m->m_pkthdr.csum_data + 521 ip->ip_len + 522 IPPROTO_TCP)); 523 th->th_sum ^= 0xffff; 524 #ifdef TCPDEBUG 525 ipov->ih_len = (u_short)tlen; 526 ipov->ih_len = htons(ipov->ih_len); 527 #endif 528 } else { 529 /* 530 * Checksum extended TCP header and data. 531 */ 532 len = sizeof (struct ip) + tlen; 533 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 534 ipov->ih_len = (u_short)tlen; 535 ipov->ih_len = htons(ipov->ih_len); 536 th->th_sum = in_cksum(m, len); 537 } 538 if (th->th_sum) { 539 tcpstat.tcps_rcvbadsum++; 540 goto drop; 541 } 542 #ifdef INET6 543 /* Re-initialization for later version check */ 544 ip->ip_v = IPVERSION; 545 #endif 546 } 547 548 /* 549 * Check that TCP offset makes sense, 550 * pull out TCP options and adjust length. XXX 551 */ 552 off = th->th_off << 2; 553 if (off < sizeof (struct tcphdr) || off > tlen) { 554 tcpstat.tcps_rcvbadoff++; 555 goto drop; 556 } 557 tlen -= off; /* tlen is used instead of ti->ti_len */ 558 if (off > sizeof (struct tcphdr)) { 559 if (isipv6) { 560 #ifdef INET6 561 IP6_EXTHDR_CHECK(m, off0, off, ); 562 ip6 = mtod(m, struct ip6_hdr *); 563 th = (struct tcphdr *)((caddr_t)ip6 + off0); 564 #endif 565 } else { 566 if (m->m_len < sizeof(struct ip) + off) { 567 if ((m = m_pullup(m, sizeof (struct ip) + off)) 568 == 0) { 569 tcpstat.tcps_rcvshort++; 570 return; 571 } 572 ip = mtod(m, struct ip *); 573 ipov = (struct ipovly *)ip; 574 th = (struct tcphdr *)((caddr_t)ip + off0); 575 } 576 } 577 optlen = off - sizeof (struct tcphdr); 578 optp = (u_char *)(th + 1); 579 } 580 thflags = th->th_flags; 581 582 #ifdef TCP_DROP_SYNFIN 583 /* 584 * If the drop_synfin option is enabled, drop all packets with 585 * both the SYN and FIN bits set. This prevents e.g. nmap from 586 * identifying the TCP/IP stack. 587 * 588 * This is a violation of the TCP specification. 589 */ 590 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 591 goto drop; 592 #endif 593 594 /* 595 * Convert TCP protocol specific fields to host format. 596 */ 597 th->th_seq = ntohl(th->th_seq); 598 th->th_ack = ntohl(th->th_ack); 599 th->th_win = ntohs(th->th_win); 600 th->th_urp = ntohs(th->th_urp); 601 602 /* 603 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 604 * until after ip6_savecontrol() is called and before other functions 605 * which don't want those proto headers. 606 * Because ip6_savecontrol() is going to parse the mbuf to 607 * search for data to be passed up to user-land, it wants mbuf 608 * parameters to be unchanged. 609 * XXX: the call of ip6_savecontrol() has been obsoleted based on 610 * latest version of the advanced API (20020110). 611 */ 612 drop_hdrlen = off0 + off; 613 614 /* 615 * Locate pcb for segment. 616 */ 617 INP_INFO_WLOCK(&tcbinfo); 618 headlocked = 1; 619 findpcb: 620 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 621 #ifdef IPFIREWALL_FORWARD 622 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 623 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 624 625 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 626 struct sockaddr_in *next_hop; 627 628 next_hop = (struct sockaddr_in *)(fwd_tag+1); 629 /* 630 * Transparently forwarded. Pretend to be the destination. 631 * already got one like this? 632 */ 633 inp = in_pcblookup_hash(&tcbinfo, 634 ip->ip_src, th->th_sport, 635 ip->ip_dst, th->th_dport, 636 0, m->m_pkthdr.rcvif); 637 if (!inp) { 638 /* It's new. Try to find the ambushing socket. */ 639 inp = in_pcblookup_hash(&tcbinfo, 640 ip->ip_src, th->th_sport, 641 next_hop->sin_addr, 642 next_hop->sin_port ? 643 ntohs(next_hop->sin_port) : 644 th->th_dport, 645 1, m->m_pkthdr.rcvif); 646 } 647 /* Remove the tag from the packet. We don't need it anymore. */ 648 m_tag_delete(m, fwd_tag); 649 } else { 650 #endif /* IPFIREWALL_FORWARD */ 651 if (isipv6) { 652 #ifdef INET6 653 inp = in6_pcblookup_hash(&tcbinfo, 654 &ip6->ip6_src, th->th_sport, 655 &ip6->ip6_dst, th->th_dport, 656 1, m->m_pkthdr.rcvif); 657 #endif 658 } else 659 inp = in_pcblookup_hash(&tcbinfo, 660 ip->ip_src, th->th_sport, 661 ip->ip_dst, th->th_dport, 662 1, m->m_pkthdr.rcvif); 663 #ifdef IPFIREWALL_FORWARD 664 } 665 #endif /* IPFIREWALL_FORWARD */ 666 667 #if defined(IPSEC) || defined(FAST_IPSEC) 668 #ifdef INET6 669 if (isipv6) { 670 if (inp != NULL && ipsec6_in_reject(m, inp)) { 671 #ifdef IPSEC 672 ipsec6stat.in_polvio++; 673 #endif 674 goto drop; 675 } 676 } else 677 #endif /* INET6 */ 678 if (inp != NULL && ipsec4_in_reject(m, inp)) { 679 #ifdef IPSEC 680 ipsecstat.in_polvio++; 681 #endif 682 goto drop; 683 } 684 #endif /*IPSEC || FAST_IPSEC*/ 685 686 /* 687 * If the state is CLOSED (i.e., TCB does not exist) then 688 * all data in the incoming segment is discarded. 689 * If the TCB exists but is in CLOSED state, it is embryonic, 690 * but should either do a listen or a connect soon. 691 */ 692 if (inp == NULL) { 693 if (log_in_vain) { 694 #ifdef INET6 695 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 696 #else 697 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 698 #endif 699 700 if (isipv6) { 701 #ifdef INET6 702 strcpy(dbuf, "["); 703 strcpy(sbuf, "["); 704 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 705 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 706 strcat(dbuf, "]"); 707 strcat(sbuf, "]"); 708 #endif 709 } else { 710 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 711 strcpy(sbuf, inet_ntoa(ip->ip_src)); 712 } 713 switch (log_in_vain) { 714 case 1: 715 if ((thflags & TH_SYN) == 0) 716 break; 717 /* FALLTHROUGH */ 718 case 2: 719 log(LOG_INFO, 720 "Connection attempt to TCP %s:%d " 721 "from %s:%d flags:0x%02x\n", 722 dbuf, ntohs(th->th_dport), sbuf, 723 ntohs(th->th_sport), thflags); 724 break; 725 default: 726 break; 727 } 728 } 729 if (blackhole) { 730 switch (blackhole) { 731 case 1: 732 if (thflags & TH_SYN) 733 goto drop; 734 break; 735 case 2: 736 goto drop; 737 default: 738 goto drop; 739 } 740 } 741 rstreason = BANDLIM_RST_CLOSEDPORT; 742 goto dropwithreset; 743 } 744 INP_LOCK(inp); 745 if (inp->inp_vflag & INP_TIMEWAIT) { 746 /* 747 * The only option of relevance is TOF_CC, and only if 748 * present in a SYN segment. See tcp_timewait(). 749 */ 750 if (thflags & TH_SYN) 751 tcp_dooptions((struct tcpcb *)NULL, &to, optp, optlen, 1, th); 752 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 753 &to, th, m, tlen)) 754 goto findpcb; 755 /* 756 * tcp_timewait unlocks inp. 757 */ 758 INP_INFO_WUNLOCK(&tcbinfo); 759 return; 760 } 761 tp = intotcpcb(inp); 762 if (tp == 0) { 763 INP_UNLOCK(inp); 764 rstreason = BANDLIM_RST_CLOSEDPORT; 765 goto dropwithreset; 766 } 767 if (tp->t_state == TCPS_CLOSED) 768 goto drop; 769 770 /* Unscale the window into a 32-bit value. */ 771 if ((thflags & TH_SYN) == 0) 772 tiwin = th->th_win << tp->snd_scale; 773 else 774 tiwin = th->th_win; 775 776 #ifdef MAC 777 INP_LOCK_ASSERT(inp); 778 if (mac_check_inpcb_deliver(inp, m)) 779 goto drop; 780 #endif 781 so = inp->inp_socket; 782 #ifdef TCPDEBUG 783 if (so->so_options & SO_DEBUG) { 784 ostate = tp->t_state; 785 if (isipv6) 786 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 787 else 788 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 789 tcp_savetcp = *th; 790 } 791 #endif 792 if (so->so_options & SO_ACCEPTCONN) { 793 struct in_conninfo inc; 794 795 #ifdef INET6 796 inc.inc_isipv6 = isipv6; 797 #endif 798 if (isipv6) { 799 inc.inc6_faddr = ip6->ip6_src; 800 inc.inc6_laddr = ip6->ip6_dst; 801 } else { 802 inc.inc_faddr = ip->ip_src; 803 inc.inc_laddr = ip->ip_dst; 804 } 805 inc.inc_fport = th->th_sport; 806 inc.inc_lport = th->th_dport; 807 808 /* 809 * If the state is LISTEN then ignore segment if it contains 810 * a RST. If the segment contains an ACK then it is bad and 811 * send a RST. If it does not contain a SYN then it is not 812 * interesting; drop it. 813 * 814 * If the state is SYN_RECEIVED (syncache) and seg contains 815 * an ACK, but not for our SYN/ACK, send a RST. If the seg 816 * contains a RST, check the sequence number to see if it 817 * is a valid reset segment. 818 */ 819 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 820 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 821 if (!syncache_expand(&inc, th, &so, m)) { 822 /* 823 * No syncache entry, or ACK was not 824 * for our SYN/ACK. Send a RST. 825 */ 826 tcpstat.tcps_badsyn++; 827 rstreason = BANDLIM_RST_OPENPORT; 828 goto dropwithreset; 829 } 830 if (so == NULL) { 831 /* 832 * Could not complete 3-way handshake, 833 * connection is being closed down, and 834 * syncache will free mbuf. 835 */ 836 INP_UNLOCK(inp); 837 INP_INFO_WUNLOCK(&tcbinfo); 838 return; 839 } 840 /* 841 * Socket is created in state SYN_RECEIVED. 842 * Continue processing segment. 843 */ 844 INP_UNLOCK(inp); 845 inp = sotoinpcb(so); 846 INP_LOCK(inp); 847 tp = intotcpcb(inp); 848 /* 849 * This is what would have happened in 850 * tcp_output() when the SYN,ACK was sent. 851 */ 852 tp->snd_up = tp->snd_una; 853 tp->snd_max = tp->snd_nxt = tp->iss + 1; 854 tp->last_ack_sent = tp->rcv_nxt; 855 /* 856 * RFC1323: The window in SYN & SYN/ACK 857 * segments is never scaled. 858 */ 859 tp->snd_wnd = tiwin; /* unscaled */ 860 goto after_listen; 861 } 862 if (thflags & TH_RST) { 863 syncache_chkrst(&inc, th); 864 goto drop; 865 } 866 if (thflags & TH_ACK) { 867 syncache_badack(&inc); 868 tcpstat.tcps_badsyn++; 869 rstreason = BANDLIM_RST_OPENPORT; 870 goto dropwithreset; 871 } 872 goto drop; 873 } 874 875 /* 876 * Segment's flags are (SYN) or (SYN|FIN). 877 */ 878 #ifdef INET6 879 /* 880 * If deprecated address is forbidden, 881 * we do not accept SYN to deprecated interface 882 * address to prevent any new inbound connection from 883 * getting established. 884 * When we do not accept SYN, we send a TCP RST, 885 * with deprecated source address (instead of dropping 886 * it). We compromise it as it is much better for peer 887 * to send a RST, and RST will be the final packet 888 * for the exchange. 889 * 890 * If we do not forbid deprecated addresses, we accept 891 * the SYN packet. RFC2462 does not suggest dropping 892 * SYN in this case. 893 * If we decipher RFC2462 5.5.4, it says like this: 894 * 1. use of deprecated addr with existing 895 * communication is okay - "SHOULD continue to be 896 * used" 897 * 2. use of it with new communication: 898 * (2a) "SHOULD NOT be used if alternate address 899 * with sufficient scope is available" 900 * (2b) nothing mentioned otherwise. 901 * Here we fall into (2b) case as we have no choice in 902 * our source address selection - we must obey the peer. 903 * 904 * The wording in RFC2462 is confusing, and there are 905 * multiple description text for deprecated address 906 * handling - worse, they are not exactly the same. 907 * I believe 5.5.4 is the best one, so we follow 5.5.4. 908 */ 909 if (isipv6 && !ip6_use_deprecated) { 910 struct in6_ifaddr *ia6; 911 912 if ((ia6 = ip6_getdstifaddr(m)) && 913 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 914 INP_UNLOCK(inp); 915 tp = NULL; 916 rstreason = BANDLIM_RST_OPENPORT; 917 goto dropwithreset; 918 } 919 } 920 #endif 921 /* 922 * If it is from this socket, drop it, it must be forged. 923 * Don't bother responding if the destination was a broadcast. 924 */ 925 if (th->th_dport == th->th_sport) { 926 if (isipv6) { 927 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 928 &ip6->ip6_src)) 929 goto drop; 930 } else { 931 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 932 goto drop; 933 } 934 } 935 /* 936 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 937 * 938 * Note that it is quite possible to receive unicast 939 * link-layer packets with a broadcast IP address. Use 940 * in_broadcast() to find them. 941 */ 942 if (m->m_flags & (M_BCAST|M_MCAST)) 943 goto drop; 944 if (isipv6) { 945 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 946 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 947 goto drop; 948 } else { 949 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 950 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 951 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 952 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 953 goto drop; 954 } 955 /* 956 * SYN appears to be valid; create compressed TCP state 957 * for syncache, or perform t/tcp connection. 958 */ 959 if (so->so_qlen <= so->so_qlimit) { 960 #ifdef TCPDEBUG 961 if (so->so_options & SO_DEBUG) 962 tcp_trace(TA_INPUT, ostate, tp, 963 (void *)tcp_saveipgen, &tcp_savetcp, 0); 964 #endif 965 tcp_dooptions(tp, &to, optp, optlen, 1, th); 966 if (!syncache_add(&inc, &to, th, &so, m)) 967 goto drop; 968 if (so == NULL) { 969 /* 970 * Entry added to syncache, mbuf used to 971 * send SYN,ACK packet. 972 */ 973 KASSERT(headlocked, ("headlocked")); 974 INP_UNLOCK(inp); 975 INP_INFO_WUNLOCK(&tcbinfo); 976 return; 977 } 978 /* 979 * Segment passed TAO tests. 980 */ 981 INP_UNLOCK(inp); 982 inp = sotoinpcb(so); 983 INP_LOCK(inp); 984 tp = intotcpcb(inp); 985 tp->snd_wnd = tiwin; 986 tp->t_starttime = ticks; 987 tp->t_state = TCPS_ESTABLISHED; 988 989 /* 990 * T/TCP logic: 991 * If there is a FIN or if there is data, then 992 * delay SYN,ACK(SYN) in the hope of piggy-backing 993 * it on a response segment. Otherwise must send 994 * ACK now in case the other side is slow starting. 995 */ 996 if (thflags & TH_FIN || tlen != 0) 997 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 998 else 999 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1000 tcpstat.tcps_connects++; 1001 soisconnected(so); 1002 goto trimthenstep6; 1003 } 1004 goto drop; 1005 } 1006 after_listen: 1007 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1008 INP_LOCK_ASSERT(inp); 1009 1010 /* XXX temp debugging */ 1011 /* should not happen - syncache should pick up these connections */ 1012 if (tp->t_state == TCPS_LISTEN) 1013 panic("tcp_input: TCPS_LISTEN"); 1014 1015 /* 1016 * This is the second part of the MSS DoS prevention code (after 1017 * minmss on the sending side) and it deals with too many too small 1018 * tcp packets in a too short timeframe (1 second). 1019 * 1020 * For every full second we count the number of received packets 1021 * and bytes. If we get a lot of packets per second for this connection 1022 * (tcp_minmssoverload) we take a closer look at it and compute the 1023 * average packet size for the past second. If that is less than 1024 * tcp_minmss we get too many packets with very small payload which 1025 * is not good and burdens our system (and every packet generates 1026 * a wakeup to the process connected to our socket). We can reasonable 1027 * expect this to be small packet DoS attack to exhaust our CPU 1028 * cycles. 1029 * 1030 * Care has to be taken for the minimum packet overload value. This 1031 * value defines the minimum number of packets per second before we 1032 * start to worry. This must not be too low to avoid killing for 1033 * example interactive connections with many small packets like 1034 * telnet or SSH. 1035 * 1036 * Setting either tcp_minmssoverload or tcp_minmss to "" disables 1037 * this check. 1038 * 1039 * Account for packet if payload packet, skip over ACK, etc. 1040 */ 1041 if (tcp_minmss && tcp_minmssoverload && 1042 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1043 if (tp->rcv_second > ticks) { 1044 tp->rcv_pps++; 1045 tp->rcv_byps += tlen + off; 1046 if (tp->rcv_pps > tcp_minmssoverload) { 1047 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1048 printf("too many small tcp packets from " 1049 "%s:%u, av. %lubyte/packet, " 1050 "dropping connection\n", 1051 #ifdef INET6 1052 isipv6 ? 1053 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1054 #endif 1055 inet_ntoa(inp->inp_inc.inc_faddr), 1056 inp->inp_inc.inc_fport, 1057 tp->rcv_byps / tp->rcv_pps); 1058 tp = tcp_drop(tp, ECONNRESET); 1059 tcpstat.tcps_minmssdrops++; 1060 goto drop; 1061 } 1062 } 1063 } else { 1064 tp->rcv_second = ticks + hz; 1065 tp->rcv_pps = 1; 1066 tp->rcv_byps = tlen + off; 1067 } 1068 } 1069 1070 /* 1071 * Segment received on connection. 1072 * Reset idle time and keep-alive timer. 1073 */ 1074 tp->t_rcvtime = ticks; 1075 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1076 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1077 1078 /* 1079 * Process options only when we get SYN/ACK back. The SYN case 1080 * for incoming connections is handled in tcp_syncache. 1081 * XXX this is traditional behavior, may need to be cleaned up. 1082 */ 1083 tcp_dooptions(tp, &to, optp, optlen, thflags & TH_SYN, th); 1084 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1085 if (to.to_flags & TOF_SCALE) { 1086 tp->t_flags |= TF_RCVD_SCALE; 1087 tp->requested_s_scale = to.to_requested_s_scale; 1088 } 1089 if (to.to_flags & TOF_TS) { 1090 tp->t_flags |= TF_RCVD_TSTMP; 1091 tp->ts_recent = to.to_tsval; 1092 tp->ts_recent_age = ticks; 1093 } 1094 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1095 tp->t_flags |= TF_RCVD_CC; 1096 if (to.to_flags & TOF_MSS) 1097 tcp_mss(tp, to.to_mss); 1098 if (tp->sack_enable) { 1099 if (!(to.to_flags & TOF_SACK)) 1100 tp->sack_enable = 0; 1101 else 1102 tp->t_flags |= TF_SACK_PERMIT; 1103 } 1104 1105 } 1106 1107 if (tp->sack_enable) { 1108 /* Delete stale (cumulatively acked) SACK holes */ 1109 tcp_del_sackholes(tp, th); 1110 } 1111 1112 /* 1113 * Header prediction: check for the two common cases 1114 * of a uni-directional data xfer. If the packet has 1115 * no control flags, is in-sequence, the window didn't 1116 * change and we're not retransmitting, it's a 1117 * candidate. If the length is zero and the ack moved 1118 * forward, we're the sender side of the xfer. Just 1119 * free the data acked & wake any higher level process 1120 * that was blocked waiting for space. If the length 1121 * is non-zero and the ack didn't move, we're the 1122 * receiver side. If we're getting packets in-order 1123 * (the reassembly queue is empty), add the data to 1124 * the socket buffer and note that we need a delayed ack. 1125 * Make sure that the hidden state-flags are also off. 1126 * Since we check for TCPS_ESTABLISHED above, it can only 1127 * be TH_NEEDSYN. 1128 */ 1129 if (tp->t_state == TCPS_ESTABLISHED && 1130 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1131 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1132 ((to.to_flags & TOF_TS) == 0 || 1133 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1134 /* 1135 * Using the CC option is compulsory if once started: 1136 * the segment is OK if no T/TCP was negotiated or 1137 * if the segment has a CC option equal to CCrecv 1138 */ 1139 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1140 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1141 th->th_seq == tp->rcv_nxt && 1142 tiwin && tiwin == tp->snd_wnd && 1143 tp->snd_nxt == tp->snd_max) { 1144 1145 /* 1146 * If last ACK falls within this segment's sequence numbers, 1147 * record the timestamp. 1148 * NOTE that the test is modified according to the latest 1149 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1150 */ 1151 if ((to.to_flags & TOF_TS) != 0 && 1152 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1153 tp->ts_recent_age = ticks; 1154 tp->ts_recent = to.to_tsval; 1155 } 1156 1157 if (tlen == 0) { 1158 if (SEQ_GT(th->th_ack, tp->snd_una) && 1159 SEQ_LEQ(th->th_ack, tp->snd_max) && 1160 tp->snd_cwnd >= tp->snd_wnd && 1161 ((!tcp_do_newreno && !tp->sack_enable && 1162 tp->t_dupacks < tcprexmtthresh) || 1163 ((tcp_do_newreno || tp->sack_enable) && 1164 !IN_FASTRECOVERY(tp)))) { 1165 KASSERT(headlocked, ("headlocked")); 1166 INP_INFO_WUNLOCK(&tcbinfo); 1167 headlocked = 0; 1168 /* 1169 * this is a pure ack for outstanding data. 1170 */ 1171 ++tcpstat.tcps_predack; 1172 /* 1173 * "bad retransmit" recovery 1174 */ 1175 if (tp->t_rxtshift == 1 && 1176 ticks < tp->t_badrxtwin) { 1177 ++tcpstat.tcps_sndrexmitbad; 1178 tp->snd_cwnd = tp->snd_cwnd_prev; 1179 tp->snd_ssthresh = 1180 tp->snd_ssthresh_prev; 1181 tp->snd_recover = tp->snd_recover_prev; 1182 if (tp->t_flags & TF_WASFRECOVERY) 1183 ENTER_FASTRECOVERY(tp); 1184 tp->snd_nxt = tp->snd_max; 1185 tp->t_badrxtwin = 0; 1186 } 1187 1188 /* 1189 * Recalculate the transmit timer / rtt. 1190 * 1191 * Some boxes send broken timestamp replies 1192 * during the SYN+ACK phase, ignore 1193 * timestamps of 0 or we could calculate a 1194 * huge RTT and blow up the retransmit timer. 1195 */ 1196 if ((to.to_flags & TOF_TS) != 0 && 1197 to.to_tsecr) { 1198 tcp_xmit_timer(tp, 1199 ticks - to.to_tsecr + 1); 1200 } else if (tp->t_rtttime && 1201 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1202 tcp_xmit_timer(tp, 1203 ticks - tp->t_rtttime); 1204 } 1205 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1206 acked = th->th_ack - tp->snd_una; 1207 tcpstat.tcps_rcvackpack++; 1208 tcpstat.tcps_rcvackbyte += acked; 1209 sbdrop(&so->so_snd, acked); 1210 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1211 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1212 tp->snd_recover = th->th_ack - 1; 1213 tp->snd_una = th->th_ack; 1214 /* 1215 * pull snd_wl2 up to prevent seq wrap relative 1216 * to th_ack. 1217 */ 1218 tp->snd_wl2 = th->th_ack; 1219 tp->t_dupacks = 0; 1220 m_freem(m); 1221 ND6_HINT(tp); /* some progress has been done */ 1222 1223 /* 1224 * If all outstanding data are acked, stop 1225 * retransmit timer, otherwise restart timer 1226 * using current (possibly backed-off) value. 1227 * If process is waiting for space, 1228 * wakeup/selwakeup/signal. If data 1229 * are ready to send, let tcp_output 1230 * decide between more output or persist. 1231 1232 #ifdef TCPDEBUG 1233 if (so->so_options & SO_DEBUG) 1234 tcp_trace(TA_INPUT, ostate, tp, 1235 (void *)tcp_saveipgen, 1236 &tcp_savetcp, 0); 1237 #endif 1238 */ 1239 if (tp->snd_una == tp->snd_max) 1240 callout_stop(tp->tt_rexmt); 1241 else if (!callout_active(tp->tt_persist)) 1242 callout_reset(tp->tt_rexmt, 1243 tp->t_rxtcur, 1244 tcp_timer_rexmt, tp); 1245 1246 sowwakeup(so); 1247 if (so->so_snd.sb_cc) 1248 (void) tcp_output(tp); 1249 goto check_delack; 1250 } 1251 } else if (th->th_ack == tp->snd_una && 1252 LIST_EMPTY(&tp->t_segq) && 1253 tlen <= sbspace(&so->so_rcv)) { 1254 KASSERT(headlocked, ("headlocked")); 1255 INP_INFO_WUNLOCK(&tcbinfo); 1256 headlocked = 0; 1257 /* 1258 * this is a pure, in-sequence data packet 1259 * with nothing on the reassembly queue and 1260 * we have enough buffer space to take it. 1261 */ 1262 /* Clean receiver SACK report if present */ 1263 if (tp->sack_enable && tp->rcv_numsacks) 1264 tcp_clean_sackreport(tp); 1265 ++tcpstat.tcps_preddat; 1266 tp->rcv_nxt += tlen; 1267 /* 1268 * Pull snd_wl1 up to prevent seq wrap relative to 1269 * th_seq. 1270 */ 1271 tp->snd_wl1 = th->th_seq; 1272 /* 1273 * Pull rcv_up up to prevent seq wrap relative to 1274 * rcv_nxt. 1275 */ 1276 tp->rcv_up = tp->rcv_nxt; 1277 tcpstat.tcps_rcvpack++; 1278 tcpstat.tcps_rcvbyte += tlen; 1279 ND6_HINT(tp); /* some progress has been done */ 1280 /* 1281 #ifdef TCPDEBUG 1282 if (so->so_options & SO_DEBUG) 1283 tcp_trace(TA_INPUT, ostate, tp, 1284 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1285 #endif 1286 * Add data to socket buffer. 1287 */ 1288 SOCKBUF_LOCK(&so->so_rcv); 1289 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1290 m_freem(m); 1291 } else { 1292 m_adj(m, drop_hdrlen); /* delayed header drop */ 1293 sbappendstream_locked(&so->so_rcv, m); 1294 } 1295 sorwakeup_locked(so); 1296 if (DELAY_ACK(tp)) { 1297 tp->t_flags |= TF_DELACK; 1298 } else { 1299 tp->t_flags |= TF_ACKNOW; 1300 tcp_output(tp); 1301 } 1302 goto check_delack; 1303 } 1304 } 1305 1306 /* 1307 * Calculate amount of space in receive window, 1308 * and then do TCP input processing. 1309 * Receive window is amount of space in rcv queue, 1310 * but not less than advertised window. 1311 */ 1312 { int win; 1313 1314 win = sbspace(&so->so_rcv); 1315 if (win < 0) 1316 win = 0; 1317 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1318 } 1319 1320 switch (tp->t_state) { 1321 1322 /* 1323 * If the state is SYN_RECEIVED: 1324 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1325 */ 1326 case TCPS_SYN_RECEIVED: 1327 if ((thflags & TH_ACK) && 1328 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1329 SEQ_GT(th->th_ack, tp->snd_max))) { 1330 rstreason = BANDLIM_RST_OPENPORT; 1331 goto dropwithreset; 1332 } 1333 break; 1334 1335 /* 1336 * If the state is SYN_SENT: 1337 * if seg contains an ACK, but not for our SYN, drop the input. 1338 * if seg contains a RST, then drop the connection. 1339 * if seg does not contain SYN, then drop it. 1340 * Otherwise this is an acceptable SYN segment 1341 * initialize tp->rcv_nxt and tp->irs 1342 * if seg contains ack then advance tp->snd_una 1343 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1344 * arrange for segment to be acked (eventually) 1345 * continue processing rest of data/controls, beginning with URG 1346 */ 1347 case TCPS_SYN_SENT: 1348 if (tcp_do_rfc1644) 1349 tcp_hc_gettao(&inp->inp_inc, &tao); 1350 1351 if ((thflags & TH_ACK) && 1352 (SEQ_LEQ(th->th_ack, tp->iss) || 1353 SEQ_GT(th->th_ack, tp->snd_max))) { 1354 /* 1355 * If we have a cached CCsent for the remote host, 1356 * hence we haven't just crashed and restarted, 1357 * do not send a RST. This may be a retransmission 1358 * from the other side after our earlier ACK was lost. 1359 * Our new SYN, when it arrives, will serve as the 1360 * needed ACK. 1361 */ 1362 if (tao.tao_ccsent != 0) 1363 goto drop; 1364 else { 1365 rstreason = BANDLIM_UNLIMITED; 1366 goto dropwithreset; 1367 } 1368 } 1369 if (thflags & TH_RST) { 1370 if (thflags & TH_ACK) 1371 tp = tcp_drop(tp, ECONNREFUSED); 1372 goto drop; 1373 } 1374 if ((thflags & TH_SYN) == 0) 1375 goto drop; 1376 tp->snd_wnd = th->th_win; /* initial send window */ 1377 tp->cc_recv = to.to_cc; /* foreign CC */ 1378 1379 tp->irs = th->th_seq; 1380 tcp_rcvseqinit(tp); 1381 if (thflags & TH_ACK) { 1382 /* 1383 * Our SYN was acked. If segment contains CC.ECHO 1384 * option, check it to make sure this segment really 1385 * matches our SYN. If not, just drop it as old 1386 * duplicate, but send an RST if we're still playing 1387 * by the old rules. If no CC.ECHO option, make sure 1388 * we don't get fooled into using T/TCP. 1389 */ 1390 if (to.to_flags & TOF_CCECHO) { 1391 if (tp->cc_send != to.to_ccecho) { 1392 if (tao.tao_ccsent != 0) 1393 goto drop; 1394 else { 1395 rstreason = BANDLIM_UNLIMITED; 1396 goto dropwithreset; 1397 } 1398 } 1399 } else 1400 tp->t_flags &= ~TF_RCVD_CC; 1401 tcpstat.tcps_connects++; 1402 soisconnected(so); 1403 #ifdef MAC 1404 SOCK_LOCK(so); 1405 mac_set_socket_peer_from_mbuf(m, so); 1406 SOCK_UNLOCK(so); 1407 #endif 1408 /* Do window scaling on this connection? */ 1409 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1410 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1411 tp->snd_scale = tp->requested_s_scale; 1412 tp->rcv_scale = tp->request_r_scale; 1413 } 1414 /* Segment is acceptable, update cache if undefined. */ 1415 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1416 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1417 1418 tp->rcv_adv += tp->rcv_wnd; 1419 tp->snd_una++; /* SYN is acked */ 1420 /* 1421 * If there's data, delay ACK; if there's also a FIN 1422 * ACKNOW will be turned on later. 1423 */ 1424 if (DELAY_ACK(tp) && tlen != 0) 1425 callout_reset(tp->tt_delack, tcp_delacktime, 1426 tcp_timer_delack, tp); 1427 else 1428 tp->t_flags |= TF_ACKNOW; 1429 /* 1430 * Received <SYN,ACK> in SYN_SENT[*] state. 1431 * Transitions: 1432 * SYN_SENT --> ESTABLISHED 1433 * SYN_SENT* --> FIN_WAIT_1 1434 */ 1435 tp->t_starttime = ticks; 1436 if (tp->t_flags & TF_NEEDFIN) { 1437 tp->t_state = TCPS_FIN_WAIT_1; 1438 tp->t_flags &= ~TF_NEEDFIN; 1439 thflags &= ~TH_SYN; 1440 } else { 1441 tp->t_state = TCPS_ESTABLISHED; 1442 callout_reset(tp->tt_keep, tcp_keepidle, 1443 tcp_timer_keep, tp); 1444 } 1445 } else { 1446 /* 1447 * Received initial SYN in SYN-SENT[*] state => 1448 * simultaneous open. If segment contains CC option 1449 * and there is a cached CC, apply TAO test. 1450 * If it succeeds, connection is * half-synchronized. 1451 * Otherwise, do 3-way handshake: 1452 * SYN-SENT -> SYN-RECEIVED 1453 * SYN-SENT* -> SYN-RECEIVED* 1454 * If there was no CC option, clear cached CC value. 1455 */ 1456 tp->t_flags |= TF_ACKNOW; 1457 callout_stop(tp->tt_rexmt); 1458 if (to.to_flags & TOF_CC) { 1459 if (tao.tao_cc != 0 && 1460 CC_GT(to.to_cc, tao.tao_cc)) { 1461 /* 1462 * update cache and make transition: 1463 * SYN-SENT -> ESTABLISHED* 1464 * SYN-SENT* -> FIN-WAIT-1* 1465 */ 1466 tao.tao_cc = to.to_cc; 1467 tcp_hc_updatetao(&inp->inp_inc, 1468 TCP_HC_TAO_CC, to.to_cc, 0); 1469 tp->t_starttime = ticks; 1470 if (tp->t_flags & TF_NEEDFIN) { 1471 tp->t_state = TCPS_FIN_WAIT_1; 1472 tp->t_flags &= ~TF_NEEDFIN; 1473 } else { 1474 tp->t_state = TCPS_ESTABLISHED; 1475 callout_reset(tp->tt_keep, 1476 tcp_keepidle, 1477 tcp_timer_keep, 1478 tp); 1479 } 1480 tp->t_flags |= TF_NEEDSYN; 1481 } else 1482 tp->t_state = TCPS_SYN_RECEIVED; 1483 } else { 1484 if (tcp_do_rfc1644) { 1485 /* CC.NEW or no option => invalidate cache */ 1486 tao.tao_cc = 0; 1487 tcp_hc_updatetao(&inp->inp_inc, 1488 TCP_HC_TAO_CC, to.to_cc, 0); 1489 } 1490 tp->t_state = TCPS_SYN_RECEIVED; 1491 } 1492 } 1493 1494 trimthenstep6: 1495 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1496 "locked")); 1497 INP_LOCK_ASSERT(inp); 1498 1499 /* 1500 * Advance th->th_seq to correspond to first data byte. 1501 * If data, trim to stay within window, 1502 * dropping FIN if necessary. 1503 */ 1504 th->th_seq++; 1505 if (tlen > tp->rcv_wnd) { 1506 todrop = tlen - tp->rcv_wnd; 1507 m_adj(m, -todrop); 1508 tlen = tp->rcv_wnd; 1509 thflags &= ~TH_FIN; 1510 tcpstat.tcps_rcvpackafterwin++; 1511 tcpstat.tcps_rcvbyteafterwin += todrop; 1512 } 1513 tp->snd_wl1 = th->th_seq - 1; 1514 tp->rcv_up = th->th_seq; 1515 /* 1516 * Client side of transaction: already sent SYN and data. 1517 * If the remote host used T/TCP to validate the SYN, 1518 * our data will be ACK'd; if so, enter normal data segment 1519 * processing in the middle of step 5, ack processing. 1520 * Otherwise, goto step 6. 1521 */ 1522 if (thflags & TH_ACK) 1523 goto process_ACK; 1524 1525 goto step6; 1526 1527 /* 1528 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1529 * if segment contains a SYN and CC [not CC.NEW] option: 1530 * if state == TIME_WAIT and connection duration > MSL, 1531 * drop packet and send RST; 1532 * 1533 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1534 * ack the FIN (and data) in retransmission queue. 1535 * Complete close and delete TCPCB. Then reprocess 1536 * segment, hoping to find new TCPCB in LISTEN state; 1537 * 1538 * else must be old SYN; drop it. 1539 * else do normal processing. 1540 */ 1541 case TCPS_LAST_ACK: 1542 case TCPS_CLOSING: 1543 case TCPS_TIME_WAIT: 1544 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1545 if ((thflags & TH_SYN) && 1546 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1547 if (tp->t_state == TCPS_TIME_WAIT && 1548 (ticks - tp->t_starttime) > tcp_msl) { 1549 rstreason = BANDLIM_UNLIMITED; 1550 goto dropwithreset; 1551 } 1552 if (CC_GT(to.to_cc, tp->cc_recv)) { 1553 tp = tcp_close(tp); 1554 goto findpcb; 1555 } 1556 else 1557 goto drop; 1558 } 1559 break; /* continue normal processing */ 1560 } 1561 1562 /* 1563 * States other than LISTEN or SYN_SENT. 1564 * First check the RST flag and sequence number since reset segments 1565 * are exempt from the timestamp and connection count tests. This 1566 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1567 * below which allowed reset segments in half the sequence space 1568 * to fall though and be processed (which gives forged reset 1569 * segments with a random sequence number a 50 percent chance of 1570 * killing a connection). 1571 * Then check timestamp, if present. 1572 * Then check the connection count, if present. 1573 * Then check that at least some bytes of segment are within 1574 * receive window. If segment begins before rcv_nxt, 1575 * drop leading data (and SYN); if nothing left, just ack. 1576 * 1577 * 1578 * If the RST bit is set, check the sequence number to see 1579 * if this is a valid reset segment. 1580 * RFC 793 page 37: 1581 * In all states except SYN-SENT, all reset (RST) segments 1582 * are validated by checking their SEQ-fields. A reset is 1583 * valid if its sequence number is in the window. 1584 * Note: this does not take into account delayed ACKs, so 1585 * we should test against last_ack_sent instead of rcv_nxt. 1586 * The sequence number in the reset segment is normally an 1587 * echo of our outgoing acknowlegement numbers, but some hosts 1588 * send a reset with the sequence number at the rightmost edge 1589 * of our receive window, and we have to handle this case. 1590 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1591 * that brute force RST attacks are possible. To combat this, 1592 * we use a much stricter check while in the ESTABLISHED state, 1593 * only accepting RSTs where the sequence number is equal to 1594 * last_ack_sent. In all other states (the states in which a 1595 * RST is more likely), the more permissive check is used. 1596 * If we have multiple segments in flight, the intial reset 1597 * segment sequence numbers will be to the left of last_ack_sent, 1598 * but they will eventually catch up. 1599 * In any case, it never made sense to trim reset segments to 1600 * fit the receive window since RFC 1122 says: 1601 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1602 * 1603 * A TCP SHOULD allow a received RST segment to include data. 1604 * 1605 * DISCUSSION 1606 * It has been suggested that a RST segment could contain 1607 * ASCII text that encoded and explained the cause of the 1608 * RST. No standard has yet been established for such 1609 * data. 1610 * 1611 * If the reset segment passes the sequence number test examine 1612 * the state: 1613 * SYN_RECEIVED STATE: 1614 * If passive open, return to LISTEN state. 1615 * If active open, inform user that connection was refused. 1616 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1617 * Inform user that connection was reset, and close tcb. 1618 * CLOSING, LAST_ACK STATES: 1619 * Close the tcb. 1620 * TIME_WAIT STATE: 1621 * Drop the segment - see Stevens, vol. 2, p. 964 and 1622 * RFC 1337. 1623 */ 1624 if (thflags & TH_RST) { 1625 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1626 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1627 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1628 switch (tp->t_state) { 1629 1630 case TCPS_SYN_RECEIVED: 1631 so->so_error = ECONNREFUSED; 1632 goto close; 1633 1634 case TCPS_ESTABLISHED: 1635 if (tp->last_ack_sent != th->th_seq && 1636 tcp_insecure_rst == 0) { 1637 tcpstat.tcps_badrst++; 1638 goto drop; 1639 } 1640 case TCPS_FIN_WAIT_1: 1641 case TCPS_FIN_WAIT_2: 1642 case TCPS_CLOSE_WAIT: 1643 so->so_error = ECONNRESET; 1644 close: 1645 tp->t_state = TCPS_CLOSED; 1646 tcpstat.tcps_drops++; 1647 tp = tcp_close(tp); 1648 break; 1649 1650 case TCPS_CLOSING: 1651 case TCPS_LAST_ACK: 1652 tp = tcp_close(tp); 1653 break; 1654 1655 case TCPS_TIME_WAIT: 1656 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1657 ("timewait")); 1658 break; 1659 } 1660 } 1661 goto drop; 1662 } 1663 1664 /* 1665 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1666 * and it's less than ts_recent, drop it. 1667 */ 1668 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1669 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1670 1671 /* Check to see if ts_recent is over 24 days old. */ 1672 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1673 /* 1674 * Invalidate ts_recent. If this segment updates 1675 * ts_recent, the age will be reset later and ts_recent 1676 * will get a valid value. If it does not, setting 1677 * ts_recent to zero will at least satisfy the 1678 * requirement that zero be placed in the timestamp 1679 * echo reply when ts_recent isn't valid. The 1680 * age isn't reset until we get a valid ts_recent 1681 * because we don't want out-of-order segments to be 1682 * dropped when ts_recent is old. 1683 */ 1684 tp->ts_recent = 0; 1685 } else { 1686 tcpstat.tcps_rcvduppack++; 1687 tcpstat.tcps_rcvdupbyte += tlen; 1688 tcpstat.tcps_pawsdrop++; 1689 if (tlen) 1690 goto dropafterack; 1691 goto drop; 1692 } 1693 } 1694 1695 /* 1696 * T/TCP mechanism 1697 * If T/TCP was negotiated and the segment doesn't have CC, 1698 * or if its CC is wrong then drop the segment. 1699 * RST segments do not have to comply with this. 1700 */ 1701 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1702 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1703 goto dropafterack; 1704 1705 /* 1706 * In the SYN-RECEIVED state, validate that the packet belongs to 1707 * this connection before trimming the data to fit the receive 1708 * window. Check the sequence number versus IRS since we know 1709 * the sequence numbers haven't wrapped. This is a partial fix 1710 * for the "LAND" DoS attack. 1711 */ 1712 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1713 rstreason = BANDLIM_RST_OPENPORT; 1714 goto dropwithreset; 1715 } 1716 1717 todrop = tp->rcv_nxt - th->th_seq; 1718 if (todrop > 0) { 1719 if (thflags & TH_SYN) { 1720 thflags &= ~TH_SYN; 1721 th->th_seq++; 1722 if (th->th_urp > 1) 1723 th->th_urp--; 1724 else 1725 thflags &= ~TH_URG; 1726 todrop--; 1727 } 1728 /* 1729 * Following if statement from Stevens, vol. 2, p. 960. 1730 */ 1731 if (todrop > tlen 1732 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1733 /* 1734 * Any valid FIN must be to the left of the window. 1735 * At this point the FIN must be a duplicate or out 1736 * of sequence; drop it. 1737 */ 1738 thflags &= ~TH_FIN; 1739 1740 /* 1741 * Send an ACK to resynchronize and drop any data. 1742 * But keep on processing for RST or ACK. 1743 */ 1744 tp->t_flags |= TF_ACKNOW; 1745 todrop = tlen; 1746 tcpstat.tcps_rcvduppack++; 1747 tcpstat.tcps_rcvdupbyte += todrop; 1748 } else { 1749 tcpstat.tcps_rcvpartduppack++; 1750 tcpstat.tcps_rcvpartdupbyte += todrop; 1751 } 1752 drop_hdrlen += todrop; /* drop from the top afterwards */ 1753 th->th_seq += todrop; 1754 tlen -= todrop; 1755 if (th->th_urp > todrop) 1756 th->th_urp -= todrop; 1757 else { 1758 thflags &= ~TH_URG; 1759 th->th_urp = 0; 1760 } 1761 } 1762 1763 /* 1764 * If new data are received on a connection after the 1765 * user processes are gone, then RST the other end. 1766 */ 1767 if ((so->so_state & SS_NOFDREF) && 1768 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1769 tp = tcp_close(tp); 1770 tcpstat.tcps_rcvafterclose++; 1771 rstreason = BANDLIM_UNLIMITED; 1772 goto dropwithreset; 1773 } 1774 1775 /* 1776 * If segment ends after window, drop trailing data 1777 * (and PUSH and FIN); if nothing left, just ACK. 1778 */ 1779 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1780 if (todrop > 0) { 1781 tcpstat.tcps_rcvpackafterwin++; 1782 if (todrop >= tlen) { 1783 tcpstat.tcps_rcvbyteafterwin += tlen; 1784 /* 1785 * If a new connection request is received 1786 * while in TIME_WAIT, drop the old connection 1787 * and start over if the sequence numbers 1788 * are above the previous ones. 1789 */ 1790 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1791 if (thflags & TH_SYN && 1792 tp->t_state == TCPS_TIME_WAIT && 1793 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1794 tp = tcp_close(tp); 1795 goto findpcb; 1796 } 1797 /* 1798 * If window is closed can only take segments at 1799 * window edge, and have to drop data and PUSH from 1800 * incoming segments. Continue processing, but 1801 * remember to ack. Otherwise, drop segment 1802 * and ack. 1803 */ 1804 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1805 tp->t_flags |= TF_ACKNOW; 1806 tcpstat.tcps_rcvwinprobe++; 1807 } else 1808 goto dropafterack; 1809 } else 1810 tcpstat.tcps_rcvbyteafterwin += todrop; 1811 m_adj(m, -todrop); 1812 tlen -= todrop; 1813 thflags &= ~(TH_PUSH|TH_FIN); 1814 } 1815 1816 /* 1817 * If last ACK falls within this segment's sequence numbers, 1818 * record its timestamp. 1819 * NOTE: 1820 * 1) That the test incorporates suggestions from the latest 1821 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1822 * 2) That updating only on newer timestamps interferes with 1823 * our earlier PAWS tests, so this check should be solely 1824 * predicated on the sequence space of this segment. 1825 * 3) That we modify the segment boundary check to be 1826 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1827 * instead of RFC1323's 1828 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1829 * This modified check allows us to overcome RFC1323's 1830 * limitations as described in Stevens TCP/IP Illustrated 1831 * Vol. 2 p.869. In such cases, we can still calculate the 1832 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1833 */ 1834 if ((to.to_flags & TOF_TS) != 0 && 1835 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1836 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1837 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1838 tp->ts_recent_age = ticks; 1839 tp->ts_recent = to.to_tsval; 1840 } 1841 1842 /* 1843 * If a SYN is in the window, then this is an 1844 * error and we send an RST and drop the connection. 1845 */ 1846 if (thflags & TH_SYN) { 1847 tp = tcp_drop(tp, ECONNRESET); 1848 rstreason = BANDLIM_UNLIMITED; 1849 goto drop; 1850 } 1851 1852 /* 1853 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1854 * flag is on (half-synchronized state), then queue data for 1855 * later processing; else drop segment and return. 1856 */ 1857 if ((thflags & TH_ACK) == 0) { 1858 if (tp->t_state == TCPS_SYN_RECEIVED || 1859 (tp->t_flags & TF_NEEDSYN)) 1860 goto step6; 1861 else 1862 goto drop; 1863 } 1864 1865 /* 1866 * Ack processing. 1867 */ 1868 switch (tp->t_state) { 1869 1870 /* 1871 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1872 * ESTABLISHED state and continue processing. 1873 * The ACK was checked above. 1874 */ 1875 case TCPS_SYN_RECEIVED: 1876 1877 tcpstat.tcps_connects++; 1878 soisconnected(so); 1879 /* Do window scaling? */ 1880 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1881 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1882 tp->snd_scale = tp->requested_s_scale; 1883 tp->rcv_scale = tp->request_r_scale; 1884 } 1885 /* 1886 * Upon successful completion of 3-way handshake, 1887 * update cache.CC, pass any queued data to the user, 1888 * and advance state appropriately. 1889 */ 1890 if (tcp_do_rfc1644) { 1891 tao.tao_cc = tp->cc_recv; 1892 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1893 tp->cc_recv, 0); 1894 } 1895 /* 1896 * Make transitions: 1897 * SYN-RECEIVED -> ESTABLISHED 1898 * SYN-RECEIVED* -> FIN-WAIT-1 1899 */ 1900 tp->t_starttime = ticks; 1901 if (tp->t_flags & TF_NEEDFIN) { 1902 tp->t_state = TCPS_FIN_WAIT_1; 1903 tp->t_flags &= ~TF_NEEDFIN; 1904 } else { 1905 tp->t_state = TCPS_ESTABLISHED; 1906 callout_reset(tp->tt_keep, tcp_keepidle, 1907 tcp_timer_keep, tp); 1908 } 1909 /* 1910 * If segment contains data or ACK, will call tcp_reass() 1911 * later; if not, do so now to pass queued data to user. 1912 */ 1913 if (tlen == 0 && (thflags & TH_FIN) == 0) 1914 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1915 (struct mbuf *)0); 1916 tp->snd_wl1 = th->th_seq - 1; 1917 /* FALLTHROUGH */ 1918 1919 /* 1920 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1921 * ACKs. If the ack is in the range 1922 * tp->snd_una < th->th_ack <= tp->snd_max 1923 * then advance tp->snd_una to th->th_ack and drop 1924 * data from the retransmission queue. If this ACK reflects 1925 * more up to date window information we update our window information. 1926 */ 1927 case TCPS_ESTABLISHED: 1928 case TCPS_FIN_WAIT_1: 1929 case TCPS_FIN_WAIT_2: 1930 case TCPS_CLOSE_WAIT: 1931 case TCPS_CLOSING: 1932 case TCPS_LAST_ACK: 1933 case TCPS_TIME_WAIT: 1934 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1935 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1936 if (tlen == 0 && tiwin == tp->snd_wnd) { 1937 tcpstat.tcps_rcvdupack++; 1938 /* 1939 * If we have outstanding data (other than 1940 * a window probe), this is a completely 1941 * duplicate ack (ie, window info didn't 1942 * change), the ack is the biggest we've 1943 * seen and we've seen exactly our rexmt 1944 * threshhold of them, assume a packet 1945 * has been dropped and retransmit it. 1946 * Kludge snd_nxt & the congestion 1947 * window so we send only this one 1948 * packet. 1949 * 1950 * We know we're losing at the current 1951 * window size so do congestion avoidance 1952 * (set ssthresh to half the current window 1953 * and pull our congestion window back to 1954 * the new ssthresh). 1955 * 1956 * Dup acks mean that packets have left the 1957 * network (they're now cached at the receiver) 1958 * so bump cwnd by the amount in the receiver 1959 * to keep a constant cwnd packets in the 1960 * network. 1961 */ 1962 if (!callout_active(tp->tt_rexmt) || 1963 th->th_ack != tp->snd_una) 1964 tp->t_dupacks = 0; 1965 else if (++tp->t_dupacks > tcprexmtthresh || 1966 ((tcp_do_newreno || tp->sack_enable) && 1967 IN_FASTRECOVERY(tp))) { 1968 tp->snd_cwnd += tp->t_maxseg; 1969 (void) tcp_output(tp); 1970 goto drop; 1971 } else if (tp->t_dupacks == tcprexmtthresh) { 1972 tcp_seq onxt = tp->snd_nxt; 1973 u_int win; 1974 1975 /* 1976 * If we're doing sack, check to 1977 * see if we're already in sack 1978 * recovery. If we're not doing sack, 1979 * check to see if we're in newreno 1980 * recovery. 1981 */ 1982 if (tp->sack_enable) { 1983 if (IN_FASTRECOVERY(tp)) { 1984 tp->t_dupacks = 0; 1985 break; 1986 } 1987 } else if (tcp_do_newreno) { 1988 if (SEQ_LEQ(th->th_ack, 1989 tp->snd_recover)) { 1990 tp->t_dupacks = 0; 1991 break; 1992 } 1993 } 1994 win = min(tp->snd_wnd, tp->snd_cwnd) / 1995 2 / tp->t_maxseg; 1996 if (win < 2) 1997 win = 2; 1998 tp->snd_ssthresh = win * tp->t_maxseg; 1999 ENTER_FASTRECOVERY(tp); 2000 tp->snd_recover = tp->snd_max; 2001 callout_stop(tp->tt_rexmt); 2002 tp->t_rtttime = 0; 2003 if (tp->sack_enable) { 2004 tcpstat.tcps_sack_recovery_episode++; 2005 tp->sack_newdata = tp->snd_nxt; 2006 tp->snd_cwnd = tp->t_maxseg; 2007 (void) tcp_output(tp); 2008 goto drop; 2009 } 2010 tp->snd_nxt = th->th_ack; 2011 tp->snd_cwnd = tp->t_maxseg; 2012 (void) tcp_output(tp); 2013 KASSERT(tp->snd_limited <= 2, 2014 ("tp->snd_limited too big")); 2015 tp->snd_cwnd = tp->snd_ssthresh + 2016 tp->t_maxseg * 2017 (tp->t_dupacks - tp->snd_limited); 2018 if (SEQ_GT(onxt, tp->snd_nxt)) 2019 tp->snd_nxt = onxt; 2020 goto drop; 2021 } else if (tcp_do_rfc3042) { 2022 u_long oldcwnd = tp->snd_cwnd; 2023 tcp_seq oldsndmax = tp->snd_max; 2024 u_int sent; 2025 2026 KASSERT(tp->t_dupacks == 1 || 2027 tp->t_dupacks == 2, 2028 ("dupacks not 1 or 2")); 2029 if (tp->t_dupacks == 1) 2030 tp->snd_limited = 0; 2031 tp->snd_cwnd = 2032 (tp->snd_nxt - tp->snd_una) + 2033 (tp->t_dupacks - tp->snd_limited) * 2034 tp->t_maxseg; 2035 (void) tcp_output(tp); 2036 sent = tp->snd_max - oldsndmax; 2037 if (sent > tp->t_maxseg) { 2038 KASSERT((tp->t_dupacks == 2 && 2039 tp->snd_limited == 0) || 2040 (sent == tp->t_maxseg + 1 && 2041 tp->t_flags & TF_SENTFIN), 2042 ("sent too much")); 2043 tp->snd_limited = 2; 2044 } else if (sent > 0) 2045 ++tp->snd_limited; 2046 tp->snd_cwnd = oldcwnd; 2047 goto drop; 2048 } 2049 } else 2050 tp->t_dupacks = 0; 2051 break; 2052 } 2053 2054 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2055 2056 /* 2057 * If the congestion window was inflated to account 2058 * for the other side's cached packets, retract it. 2059 */ 2060 if (tcp_do_newreno || tp->sack_enable) { 2061 if (IN_FASTRECOVERY(tp)) { 2062 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2063 if (tp->sack_enable) 2064 tcp_sack_partialack(tp, th); 2065 else 2066 tcp_newreno_partial_ack(tp, th); 2067 } else { 2068 /* 2069 * Out of fast recovery. 2070 * Window inflation should have left us 2071 * with approximately snd_ssthresh 2072 * outstanding data. 2073 * But in case we would be inclined to 2074 * send a burst, better to do it via 2075 * the slow start mechanism. 2076 */ 2077 if (SEQ_GT(th->th_ack + 2078 tp->snd_ssthresh, 2079 tp->snd_max)) 2080 tp->snd_cwnd = tp->snd_max - 2081 th->th_ack + 2082 tp->t_maxseg; 2083 else 2084 tp->snd_cwnd = tp->snd_ssthresh; 2085 } 2086 } 2087 } else { 2088 if (tp->t_dupacks >= tcprexmtthresh && 2089 tp->snd_cwnd > tp->snd_ssthresh) 2090 tp->snd_cwnd = tp->snd_ssthresh; 2091 } 2092 tp->t_dupacks = 0; 2093 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2094 tcpstat.tcps_rcvacktoomuch++; 2095 goto dropafterack; 2096 } 2097 /* 2098 * If we reach this point, ACK is not a duplicate, 2099 * i.e., it ACKs something we sent. 2100 */ 2101 if (tp->t_flags & TF_NEEDSYN) { 2102 /* 2103 * T/TCP: Connection was half-synchronized, and our 2104 * SYN has been ACK'd (so connection is now fully 2105 * synchronized). Go to non-starred state, 2106 * increment snd_una for ACK of SYN, and check if 2107 * we can do window scaling. 2108 */ 2109 tp->t_flags &= ~TF_NEEDSYN; 2110 tp->snd_una++; 2111 /* Do window scaling? */ 2112 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2113 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2114 tp->snd_scale = tp->requested_s_scale; 2115 tp->rcv_scale = tp->request_r_scale; 2116 } 2117 } 2118 2119 process_ACK: 2120 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2121 "locked")); 2122 INP_LOCK_ASSERT(inp); 2123 2124 acked = th->th_ack - tp->snd_una; 2125 tcpstat.tcps_rcvackpack++; 2126 tcpstat.tcps_rcvackbyte += acked; 2127 2128 /* 2129 * If we just performed our first retransmit, and the ACK 2130 * arrives within our recovery window, then it was a mistake 2131 * to do the retransmit in the first place. Recover our 2132 * original cwnd and ssthresh, and proceed to transmit where 2133 * we left off. 2134 */ 2135 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2136 ++tcpstat.tcps_sndrexmitbad; 2137 tp->snd_cwnd = tp->snd_cwnd_prev; 2138 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2139 tp->snd_recover = tp->snd_recover_prev; 2140 if (tp->t_flags & TF_WASFRECOVERY) 2141 ENTER_FASTRECOVERY(tp); 2142 tp->snd_nxt = tp->snd_max; 2143 tp->t_badrxtwin = 0; /* XXX probably not required */ 2144 } 2145 2146 /* 2147 * If we have a timestamp reply, update smoothed 2148 * round trip time. If no timestamp is present but 2149 * transmit timer is running and timed sequence 2150 * number was acked, update smoothed round trip time. 2151 * Since we now have an rtt measurement, cancel the 2152 * timer backoff (cf., Phil Karn's retransmit alg.). 2153 * Recompute the initial retransmit timer. 2154 * 2155 * Some boxes send broken timestamp replies 2156 * during the SYN+ACK phase, ignore 2157 * timestamps of 0 or we could calculate a 2158 * huge RTT and blow up the retransmit timer. 2159 */ 2160 if ((to.to_flags & TOF_TS) != 0 && 2161 to.to_tsecr) { 2162 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2163 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2164 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2165 } 2166 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2167 2168 /* 2169 * If all outstanding data is acked, stop retransmit 2170 * timer and remember to restart (more output or persist). 2171 * If there is more data to be acked, restart retransmit 2172 * timer, using current (possibly backed-off) value. 2173 */ 2174 if (th->th_ack == tp->snd_max) { 2175 callout_stop(tp->tt_rexmt); 2176 needoutput = 1; 2177 } else if (!callout_active(tp->tt_persist)) 2178 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2179 tcp_timer_rexmt, tp); 2180 2181 /* 2182 * If no data (only SYN) was ACK'd, 2183 * skip rest of ACK processing. 2184 */ 2185 if (acked == 0) 2186 goto step6; 2187 2188 /* 2189 * When new data is acked, open the congestion window. 2190 * If the window gives us less than ssthresh packets 2191 * in flight, open exponentially (maxseg per packet). 2192 * Otherwise open linearly: maxseg per window 2193 * (maxseg^2 / cwnd per packet). 2194 */ 2195 if ((!tcp_do_newreno && !tp->sack_enable) || 2196 !IN_FASTRECOVERY(tp)) { 2197 register u_int cw = tp->snd_cwnd; 2198 register u_int incr = tp->t_maxseg; 2199 if (cw > tp->snd_ssthresh) 2200 incr = incr * incr / cw; 2201 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2202 } 2203 SOCKBUF_LOCK(&so->so_snd); 2204 if (acked > so->so_snd.sb_cc) { 2205 tp->snd_wnd -= so->so_snd.sb_cc; 2206 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2207 ourfinisacked = 1; 2208 } else { 2209 sbdrop_locked(&so->so_snd, acked); 2210 tp->snd_wnd -= acked; 2211 ourfinisacked = 0; 2212 } 2213 sowwakeup_locked(so); 2214 /* detect una wraparound */ 2215 if ((tcp_do_newreno || tp->sack_enable) && 2216 !IN_FASTRECOVERY(tp) && 2217 SEQ_GT(tp->snd_una, tp->snd_recover) && 2218 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2219 tp->snd_recover = th->th_ack - 1; 2220 if ((tcp_do_newreno || tp->sack_enable) && 2221 IN_FASTRECOVERY(tp) && 2222 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2223 EXIT_FASTRECOVERY(tp); 2224 tp->snd_una = th->th_ack; 2225 if (tp->sack_enable) { 2226 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2227 tp->snd_recover = tp->snd_una; 2228 } 2229 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2230 tp->snd_nxt = tp->snd_una; 2231 2232 switch (tp->t_state) { 2233 2234 /* 2235 * In FIN_WAIT_1 STATE in addition to the processing 2236 * for the ESTABLISHED state if our FIN is now acknowledged 2237 * then enter FIN_WAIT_2. 2238 */ 2239 case TCPS_FIN_WAIT_1: 2240 if (ourfinisacked) { 2241 /* 2242 * If we can't receive any more 2243 * data, then closing user can proceed. 2244 * Starting the timer is contrary to the 2245 * specification, but if we don't get a FIN 2246 * we'll hang forever. 2247 */ 2248 /* XXXjl 2249 * we should release the tp also, and use a 2250 * compressed state. 2251 */ 2252 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2253 soisdisconnected(so); 2254 callout_reset(tp->tt_2msl, tcp_maxidle, 2255 tcp_timer_2msl, tp); 2256 } 2257 tp->t_state = TCPS_FIN_WAIT_2; 2258 } 2259 break; 2260 2261 /* 2262 * In CLOSING STATE in addition to the processing for 2263 * the ESTABLISHED state if the ACK acknowledges our FIN 2264 * then enter the TIME-WAIT state, otherwise ignore 2265 * the segment. 2266 */ 2267 case TCPS_CLOSING: 2268 if (ourfinisacked) { 2269 KASSERT(headlocked, ("tcp_input: process_ACK: " 2270 "head not locked")); 2271 tcp_twstart(tp); 2272 INP_INFO_WUNLOCK(&tcbinfo); 2273 m_freem(m); 2274 return; 2275 } 2276 break; 2277 2278 /* 2279 * In LAST_ACK, we may still be waiting for data to drain 2280 * and/or to be acked, as well as for the ack of our FIN. 2281 * If our FIN is now acknowledged, delete the TCB, 2282 * enter the closed state and return. 2283 */ 2284 case TCPS_LAST_ACK: 2285 if (ourfinisacked) { 2286 tp = tcp_close(tp); 2287 goto drop; 2288 } 2289 break; 2290 2291 /* 2292 * In TIME_WAIT state the only thing that should arrive 2293 * is a retransmission of the remote FIN. Acknowledge 2294 * it and restart the finack timer. 2295 */ 2296 case TCPS_TIME_WAIT: 2297 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2298 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2299 tcp_timer_2msl, tp); 2300 goto dropafterack; 2301 } 2302 } 2303 2304 step6: 2305 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2306 INP_LOCK_ASSERT(inp); 2307 2308 /* 2309 * Update window information. 2310 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2311 */ 2312 if ((thflags & TH_ACK) && 2313 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2314 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2315 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2316 /* keep track of pure window updates */ 2317 if (tlen == 0 && 2318 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2319 tcpstat.tcps_rcvwinupd++; 2320 tp->snd_wnd = tiwin; 2321 tp->snd_wl1 = th->th_seq; 2322 tp->snd_wl2 = th->th_ack; 2323 if (tp->snd_wnd > tp->max_sndwnd) 2324 tp->max_sndwnd = tp->snd_wnd; 2325 needoutput = 1; 2326 } 2327 2328 /* 2329 * Process segments with URG. 2330 */ 2331 if ((thflags & TH_URG) && th->th_urp && 2332 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2333 /* 2334 * This is a kludge, but if we receive and accept 2335 * random urgent pointers, we'll crash in 2336 * soreceive. It's hard to imagine someone 2337 * actually wanting to send this much urgent data. 2338 */ 2339 SOCKBUF_LOCK(&so->so_rcv); 2340 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2341 th->th_urp = 0; /* XXX */ 2342 thflags &= ~TH_URG; /* XXX */ 2343 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2344 goto dodata; /* XXX */ 2345 } 2346 /* 2347 * If this segment advances the known urgent pointer, 2348 * then mark the data stream. This should not happen 2349 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2350 * a FIN has been received from the remote side. 2351 * In these states we ignore the URG. 2352 * 2353 * According to RFC961 (Assigned Protocols), 2354 * the urgent pointer points to the last octet 2355 * of urgent data. We continue, however, 2356 * to consider it to indicate the first octet 2357 * of data past the urgent section as the original 2358 * spec states (in one of two places). 2359 */ 2360 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2361 tp->rcv_up = th->th_seq + th->th_urp; 2362 so->so_oobmark = so->so_rcv.sb_cc + 2363 (tp->rcv_up - tp->rcv_nxt) - 1; 2364 if (so->so_oobmark == 0) 2365 so->so_rcv.sb_state |= SBS_RCVATMARK; 2366 sohasoutofband(so); 2367 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2368 } 2369 SOCKBUF_UNLOCK(&so->so_rcv); 2370 /* 2371 * Remove out of band data so doesn't get presented to user. 2372 * This can happen independent of advancing the URG pointer, 2373 * but if two URG's are pending at once, some out-of-band 2374 * data may creep in... ick. 2375 */ 2376 if (th->th_urp <= (u_long)tlen && 2377 !(so->so_options & SO_OOBINLINE)) { 2378 /* hdr drop is delayed */ 2379 tcp_pulloutofband(so, th, m, drop_hdrlen); 2380 } 2381 } else { 2382 /* 2383 * If no out of band data is expected, 2384 * pull receive urgent pointer along 2385 * with the receive window. 2386 */ 2387 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2388 tp->rcv_up = tp->rcv_nxt; 2389 } 2390 dodata: /* XXX */ 2391 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2392 INP_LOCK_ASSERT(inp); 2393 2394 /* 2395 * Process the segment text, merging it into the TCP sequencing queue, 2396 * and arranging for acknowledgment of receipt if necessary. 2397 * This process logically involves adjusting tp->rcv_wnd as data 2398 * is presented to the user (this happens in tcp_usrreq.c, 2399 * case PRU_RCVD). If a FIN has already been received on this 2400 * connection then we just ignore the text. 2401 */ 2402 if ((tlen || (thflags & TH_FIN)) && 2403 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2404 m_adj(m, drop_hdrlen); /* delayed header drop */ 2405 /* 2406 * Insert segment which includes th into TCP reassembly queue 2407 * with control block tp. Set thflags to whether reassembly now 2408 * includes a segment with FIN. This handles the common case 2409 * inline (segment is the next to be received on an established 2410 * connection, and the queue is empty), avoiding linkage into 2411 * and removal from the queue and repetition of various 2412 * conversions. 2413 * Set DELACK for segments received in order, but ack 2414 * immediately when segments are out of order (so 2415 * fast retransmit can work). 2416 */ 2417 if (th->th_seq == tp->rcv_nxt && 2418 LIST_EMPTY(&tp->t_segq) && 2419 TCPS_HAVEESTABLISHED(tp->t_state)) { 2420 if (DELAY_ACK(tp)) 2421 tp->t_flags |= TF_DELACK; 2422 else 2423 tp->t_flags |= TF_ACKNOW; 2424 tp->rcv_nxt += tlen; 2425 thflags = th->th_flags & TH_FIN; 2426 tcpstat.tcps_rcvpack++; 2427 tcpstat.tcps_rcvbyte += tlen; 2428 ND6_HINT(tp); 2429 SOCKBUF_LOCK(&so->so_rcv); 2430 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2431 m_freem(m); 2432 else 2433 sbappendstream_locked(&so->so_rcv, m); 2434 sorwakeup_locked(so); 2435 } else { 2436 thflags = tcp_reass(tp, th, &tlen, m); 2437 tp->t_flags |= TF_ACKNOW; 2438 } 2439 if (tp->sack_enable) 2440 tcp_update_sack_list(tp, th->th_seq, th->th_seq + tlen); 2441 /* 2442 * Note the amount of data that peer has sent into 2443 * our window, in order to estimate the sender's 2444 * buffer size. 2445 */ 2446 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2447 } else { 2448 m_freem(m); 2449 thflags &= ~TH_FIN; 2450 } 2451 2452 /* 2453 * If FIN is received ACK the FIN and let the user know 2454 * that the connection is closing. 2455 */ 2456 if (thflags & TH_FIN) { 2457 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2458 socantrcvmore(so); 2459 /* 2460 * If connection is half-synchronized 2461 * (ie NEEDSYN flag on) then delay ACK, 2462 * so it may be piggybacked when SYN is sent. 2463 * Otherwise, since we received a FIN then no 2464 * more input can be expected, send ACK now. 2465 */ 2466 if (tp->t_flags & TF_NEEDSYN) 2467 tp->t_flags |= TF_DELACK; 2468 else 2469 tp->t_flags |= TF_ACKNOW; 2470 tp->rcv_nxt++; 2471 } 2472 switch (tp->t_state) { 2473 2474 /* 2475 * In SYN_RECEIVED and ESTABLISHED STATES 2476 * enter the CLOSE_WAIT state. 2477 */ 2478 case TCPS_SYN_RECEIVED: 2479 tp->t_starttime = ticks; 2480 /*FALLTHROUGH*/ 2481 case TCPS_ESTABLISHED: 2482 tp->t_state = TCPS_CLOSE_WAIT; 2483 break; 2484 2485 /* 2486 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2487 * enter the CLOSING state. 2488 */ 2489 case TCPS_FIN_WAIT_1: 2490 tp->t_state = TCPS_CLOSING; 2491 break; 2492 2493 /* 2494 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2495 * starting the time-wait timer, turning off the other 2496 * standard timers. 2497 */ 2498 case TCPS_FIN_WAIT_2: 2499 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2500 "TCP_FIN_WAIT_2: head not locked")); 2501 tcp_twstart(tp); 2502 INP_INFO_WUNLOCK(&tcbinfo); 2503 return; 2504 2505 /* 2506 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2507 */ 2508 case TCPS_TIME_WAIT: 2509 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2510 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2511 tcp_timer_2msl, tp); 2512 break; 2513 } 2514 } 2515 INP_INFO_WUNLOCK(&tcbinfo); 2516 headlocked = 0; 2517 #ifdef TCPDEBUG 2518 if (so->so_options & SO_DEBUG) 2519 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2520 &tcp_savetcp, 0); 2521 #endif 2522 2523 /* 2524 * Return any desired output. 2525 */ 2526 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2527 (void) tcp_output(tp); 2528 2529 check_delack: 2530 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2531 INP_LOCK_ASSERT(inp); 2532 if (tp->t_flags & TF_DELACK) { 2533 tp->t_flags &= ~TF_DELACK; 2534 callout_reset(tp->tt_delack, tcp_delacktime, 2535 tcp_timer_delack, tp); 2536 } 2537 INP_UNLOCK(inp); 2538 return; 2539 2540 dropafterack: 2541 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2542 /* 2543 * Generate an ACK dropping incoming segment if it occupies 2544 * sequence space, where the ACK reflects our state. 2545 * 2546 * We can now skip the test for the RST flag since all 2547 * paths to this code happen after packets containing 2548 * RST have been dropped. 2549 * 2550 * In the SYN-RECEIVED state, don't send an ACK unless the 2551 * segment we received passes the SYN-RECEIVED ACK test. 2552 * If it fails send a RST. This breaks the loop in the 2553 * "LAND" DoS attack, and also prevents an ACK storm 2554 * between two listening ports that have been sent forged 2555 * SYN segments, each with the source address of the other. 2556 */ 2557 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2558 (SEQ_GT(tp->snd_una, th->th_ack) || 2559 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2560 rstreason = BANDLIM_RST_OPENPORT; 2561 goto dropwithreset; 2562 } 2563 #ifdef TCPDEBUG 2564 if (so->so_options & SO_DEBUG) 2565 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2566 &tcp_savetcp, 0); 2567 #endif 2568 KASSERT(headlocked, ("headlocked should be 1")); 2569 INP_INFO_WUNLOCK(&tcbinfo); 2570 tp->t_flags |= TF_ACKNOW; 2571 (void) tcp_output(tp); 2572 INP_UNLOCK(inp); 2573 m_freem(m); 2574 return; 2575 2576 dropwithreset: 2577 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2578 /* 2579 * Generate a RST, dropping incoming segment. 2580 * Make ACK acceptable to originator of segment. 2581 * Don't bother to respond if destination was broadcast/multicast. 2582 */ 2583 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2584 goto drop; 2585 if (isipv6) { 2586 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2587 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2588 goto drop; 2589 } else { 2590 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2591 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2592 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2593 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2594 goto drop; 2595 } 2596 /* IPv6 anycast check is done at tcp6_input() */ 2597 2598 /* 2599 * Perform bandwidth limiting. 2600 */ 2601 if (badport_bandlim(rstreason) < 0) 2602 goto drop; 2603 2604 #ifdef TCPDEBUG 2605 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2606 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2607 &tcp_savetcp, 0); 2608 #endif 2609 2610 if (thflags & TH_ACK) 2611 /* mtod() below is safe as long as hdr dropping is delayed */ 2612 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2613 TH_RST); 2614 else { 2615 if (thflags & TH_SYN) 2616 tlen++; 2617 /* mtod() below is safe as long as hdr dropping is delayed */ 2618 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2619 (tcp_seq)0, TH_RST|TH_ACK); 2620 } 2621 2622 if (tp) 2623 INP_UNLOCK(inp); 2624 if (headlocked) 2625 INP_INFO_WUNLOCK(&tcbinfo); 2626 return; 2627 2628 drop: 2629 /* 2630 * Drop space held by incoming segment and return. 2631 */ 2632 #ifdef TCPDEBUG 2633 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2634 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2635 &tcp_savetcp, 0); 2636 #endif 2637 if (tp) 2638 INP_UNLOCK(inp); 2639 if (headlocked) 2640 INP_INFO_WUNLOCK(&tcbinfo); 2641 m_freem(m); 2642 return; 2643 } 2644 2645 /* 2646 * Parse TCP options and place in tcpopt. 2647 */ 2648 static void 2649 tcp_dooptions(tp, to, cp, cnt, is_syn, th) 2650 struct tcpcb *tp; 2651 struct tcpopt *to; 2652 u_char *cp; 2653 int cnt; 2654 int is_syn; 2655 struct tcphdr *th; 2656 { 2657 int opt, optlen; 2658 2659 to->to_flags = 0; 2660 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2661 opt = cp[0]; 2662 if (opt == TCPOPT_EOL) 2663 break; 2664 if (opt == TCPOPT_NOP) 2665 optlen = 1; 2666 else { 2667 if (cnt < 2) 2668 break; 2669 optlen = cp[1]; 2670 if (optlen < 2 || optlen > cnt) 2671 break; 2672 } 2673 switch (opt) { 2674 case TCPOPT_MAXSEG: 2675 if (optlen != TCPOLEN_MAXSEG) 2676 continue; 2677 if (!is_syn) 2678 continue; 2679 to->to_flags |= TOF_MSS; 2680 bcopy((char *)cp + 2, 2681 (char *)&to->to_mss, sizeof(to->to_mss)); 2682 to->to_mss = ntohs(to->to_mss); 2683 break; 2684 case TCPOPT_WINDOW: 2685 if (optlen != TCPOLEN_WINDOW) 2686 continue; 2687 if (! is_syn) 2688 continue; 2689 to->to_flags |= TOF_SCALE; 2690 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2691 break; 2692 case TCPOPT_TIMESTAMP: 2693 if (optlen != TCPOLEN_TIMESTAMP) 2694 continue; 2695 to->to_flags |= TOF_TS; 2696 bcopy((char *)cp + 2, 2697 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2698 to->to_tsval = ntohl(to->to_tsval); 2699 bcopy((char *)cp + 6, 2700 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2701 to->to_tsecr = ntohl(to->to_tsecr); 2702 /* 2703 * If echoed timestamp is later than the current time, 2704 * fall back to non RFC1323 RTT calculation. 2705 */ 2706 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2707 to->to_tsecr = 0; 2708 break; 2709 case TCPOPT_CC: 2710 if (optlen != TCPOLEN_CC) 2711 continue; 2712 to->to_flags |= TOF_CC; 2713 bcopy((char *)cp + 2, 2714 (char *)&to->to_cc, sizeof(to->to_cc)); 2715 to->to_cc = ntohl(to->to_cc); 2716 break; 2717 case TCPOPT_CCNEW: 2718 if (optlen != TCPOLEN_CC) 2719 continue; 2720 if (!is_syn) 2721 continue; 2722 to->to_flags |= TOF_CCNEW; 2723 bcopy((char *)cp + 2, 2724 (char *)&to->to_cc, sizeof(to->to_cc)); 2725 to->to_cc = ntohl(to->to_cc); 2726 break; 2727 case TCPOPT_CCECHO: 2728 if (optlen != TCPOLEN_CC) 2729 continue; 2730 if (!is_syn) 2731 continue; 2732 to->to_flags |= TOF_CCECHO; 2733 bcopy((char *)cp + 2, 2734 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2735 to->to_ccecho = ntohl(to->to_ccecho); 2736 break; 2737 #ifdef TCP_SIGNATURE 2738 /* 2739 * XXX In order to reply to a host which has set the 2740 * TCP_SIGNATURE option in its initial SYN, we have to 2741 * record the fact that the option was observed here 2742 * for the syncache code to perform the correct response. 2743 */ 2744 case TCPOPT_SIGNATURE: 2745 if (optlen != TCPOLEN_SIGNATURE) 2746 continue; 2747 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2748 break; 2749 #endif 2750 case TCPOPT_SACK_PERMITTED: 2751 if (!tcp_do_sack || 2752 optlen != TCPOLEN_SACK_PERMITTED) 2753 continue; 2754 if (is_syn) { 2755 /* MUST only be set on SYN */ 2756 to->to_flags |= TOF_SACK; 2757 } 2758 break; 2759 2760 case TCPOPT_SACK: 2761 if (!tp || tcp_sack_option(tp, th, cp, optlen)) 2762 continue; 2763 break; 2764 default: 2765 continue; 2766 } 2767 } 2768 } 2769 2770 /* 2771 * Pull out of band byte out of a segment so 2772 * it doesn't appear in the user's data queue. 2773 * It is still reflected in the segment length for 2774 * sequencing purposes. 2775 */ 2776 static void 2777 tcp_pulloutofband(so, th, m, off) 2778 struct socket *so; 2779 struct tcphdr *th; 2780 register struct mbuf *m; 2781 int off; /* delayed to be droped hdrlen */ 2782 { 2783 int cnt = off + th->th_urp - 1; 2784 2785 while (cnt >= 0) { 2786 if (m->m_len > cnt) { 2787 char *cp = mtod(m, caddr_t) + cnt; 2788 struct tcpcb *tp = sototcpcb(so); 2789 2790 tp->t_iobc = *cp; 2791 tp->t_oobflags |= TCPOOB_HAVEDATA; 2792 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2793 m->m_len--; 2794 if (m->m_flags & M_PKTHDR) 2795 m->m_pkthdr.len--; 2796 return; 2797 } 2798 cnt -= m->m_len; 2799 m = m->m_next; 2800 if (m == 0) 2801 break; 2802 } 2803 panic("tcp_pulloutofband"); 2804 } 2805 2806 /* 2807 * Collect new round-trip time estimate 2808 * and update averages and current timeout. 2809 */ 2810 static void 2811 tcp_xmit_timer(tp, rtt) 2812 register struct tcpcb *tp; 2813 int rtt; 2814 { 2815 register int delta; 2816 2817 INP_LOCK_ASSERT(tp->t_inpcb); 2818 2819 tcpstat.tcps_rttupdated++; 2820 tp->t_rttupdated++; 2821 if (tp->t_srtt != 0) { 2822 /* 2823 * srtt is stored as fixed point with 5 bits after the 2824 * binary point (i.e., scaled by 8). The following magic 2825 * is equivalent to the smoothing algorithm in rfc793 with 2826 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2827 * point). Adjust rtt to origin 0. 2828 */ 2829 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2830 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2831 2832 if ((tp->t_srtt += delta) <= 0) 2833 tp->t_srtt = 1; 2834 2835 /* 2836 * We accumulate a smoothed rtt variance (actually, a 2837 * smoothed mean difference), then set the retransmit 2838 * timer to smoothed rtt + 4 times the smoothed variance. 2839 * rttvar is stored as fixed point with 4 bits after the 2840 * binary point (scaled by 16). The following is 2841 * equivalent to rfc793 smoothing with an alpha of .75 2842 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2843 * rfc793's wired-in beta. 2844 */ 2845 if (delta < 0) 2846 delta = -delta; 2847 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2848 if ((tp->t_rttvar += delta) <= 0) 2849 tp->t_rttvar = 1; 2850 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2851 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2852 } else { 2853 /* 2854 * No rtt measurement yet - use the unsmoothed rtt. 2855 * Set the variance to half the rtt (so our first 2856 * retransmit happens at 3*rtt). 2857 */ 2858 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2859 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2860 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2861 } 2862 tp->t_rtttime = 0; 2863 tp->t_rxtshift = 0; 2864 2865 /* 2866 * the retransmit should happen at rtt + 4 * rttvar. 2867 * Because of the way we do the smoothing, srtt and rttvar 2868 * will each average +1/2 tick of bias. When we compute 2869 * the retransmit timer, we want 1/2 tick of rounding and 2870 * 1 extra tick because of +-1/2 tick uncertainty in the 2871 * firing of the timer. The bias will give us exactly the 2872 * 1.5 tick we need. But, because the bias is 2873 * statistical, we have to test that we don't drop below 2874 * the minimum feasible timer (which is 2 ticks). 2875 */ 2876 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2877 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2878 2879 /* 2880 * We received an ack for a packet that wasn't retransmitted; 2881 * it is probably safe to discard any error indications we've 2882 * received recently. This isn't quite right, but close enough 2883 * for now (a route might have failed after we sent a segment, 2884 * and the return path might not be symmetrical). 2885 */ 2886 tp->t_softerror = 0; 2887 } 2888 2889 /* 2890 * Determine a reasonable value for maxseg size. 2891 * If the route is known, check route for mtu. 2892 * If none, use an mss that can be handled on the outgoing 2893 * interface without forcing IP to fragment; if bigger than 2894 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2895 * to utilize large mbufs. If no route is found, route has no mtu, 2896 * or the destination isn't local, use a default, hopefully conservative 2897 * size (usually 512 or the default IP max size, but no more than the mtu 2898 * of the interface), as we can't discover anything about intervening 2899 * gateways or networks. We also initialize the congestion/slow start 2900 * window to be a single segment if the destination isn't local. 2901 * While looking at the routing entry, we also initialize other path-dependent 2902 * parameters from pre-set or cached values in the routing entry. 2903 * 2904 * Also take into account the space needed for options that we 2905 * send regularly. Make maxseg shorter by that amount to assure 2906 * that we can send maxseg amount of data even when the options 2907 * are present. Store the upper limit of the length of options plus 2908 * data in maxopd. 2909 * 2910 * 2911 * In case of T/TCP, we call this routine during implicit connection 2912 * setup as well (offer = -1), to initialize maxseg from the cached 2913 * MSS of our peer. 2914 * 2915 * NOTE that this routine is only called when we process an incoming 2916 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2917 */ 2918 void 2919 tcp_mss(tp, offer) 2920 struct tcpcb *tp; 2921 int offer; 2922 { 2923 int rtt, mss; 2924 u_long bufsize; 2925 u_long maxmtu; 2926 struct inpcb *inp = tp->t_inpcb; 2927 struct socket *so; 2928 struct hc_metrics_lite metrics; 2929 struct rmxp_tao tao; 2930 int origoffer = offer; 2931 #ifdef INET6 2932 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2933 size_t min_protoh = isipv6 ? 2934 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2935 sizeof (struct tcpiphdr); 2936 #else 2937 const size_t min_protoh = sizeof(struct tcpiphdr); 2938 #endif 2939 bzero(&tao, sizeof(tao)); 2940 2941 /* initialize */ 2942 #ifdef INET6 2943 if (isipv6) { 2944 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2945 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2946 } else 2947 #endif 2948 { 2949 maxmtu = tcp_maxmtu(&inp->inp_inc); 2950 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2951 } 2952 so = inp->inp_socket; 2953 2954 /* 2955 * no route to sender, stay with default mss and return 2956 */ 2957 if (maxmtu == 0) 2958 return; 2959 2960 /* what have we got? */ 2961 switch (offer) { 2962 case 0: 2963 /* 2964 * Offer == 0 means that there was no MSS on the SYN 2965 * segment, in this case we use tcp_mssdflt. 2966 */ 2967 offer = 2968 #ifdef INET6 2969 isipv6 ? tcp_v6mssdflt : 2970 #endif 2971 tcp_mssdflt; 2972 break; 2973 2974 case -1: 2975 /* 2976 * Offer == -1 means that we didn't receive SYN yet, 2977 * use cached value in that case; 2978 */ 2979 if (tcp_do_rfc1644) 2980 tcp_hc_gettao(&inp->inp_inc, &tao); 2981 if (tao.tao_mssopt != 0) 2982 offer = tao.tao_mssopt; 2983 /* FALLTHROUGH */ 2984 2985 default: 2986 /* 2987 * Prevent DoS attack with too small MSS. Round up 2988 * to at least minmss. 2989 */ 2990 offer = max(offer, tcp_minmss); 2991 /* 2992 * Sanity check: make sure that maxopd will be large 2993 * enough to allow some data on segments even if the 2994 * all the option space is used (40bytes). Otherwise 2995 * funny things may happen in tcp_output. 2996 */ 2997 offer = max(offer, 64); 2998 if (tcp_do_rfc1644) 2999 tcp_hc_updatetao(&inp->inp_inc, 3000 TCP_HC_TAO_MSSOPT, 0, offer); 3001 } 3002 3003 /* 3004 * rmx information is now retrieved from tcp_hostcache 3005 */ 3006 tcp_hc_get(&inp->inp_inc, &metrics); 3007 3008 /* 3009 * if there's a discovered mtu int tcp hostcache, use it 3010 * else, use the link mtu. 3011 */ 3012 if (metrics.rmx_mtu) 3013 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3014 else { 3015 #ifdef INET6 3016 if (isipv6) { 3017 mss = maxmtu - min_protoh; 3018 if (!path_mtu_discovery && 3019 !in6_localaddr(&inp->in6p_faddr)) 3020 mss = min(mss, tcp_v6mssdflt); 3021 } else 3022 #endif 3023 { 3024 mss = maxmtu - min_protoh; 3025 if (!path_mtu_discovery && 3026 !in_localaddr(inp->inp_faddr)) 3027 mss = min(mss, tcp_mssdflt); 3028 } 3029 } 3030 mss = min(mss, offer); 3031 3032 /* 3033 * maxopd stores the maximum length of data AND options 3034 * in a segment; maxseg is the amount of data in a normal 3035 * segment. We need to store this value (maxopd) apart 3036 * from maxseg, because now every segment carries options 3037 * and thus we normally have somewhat less data in segments. 3038 */ 3039 tp->t_maxopd = mss; 3040 3041 /* 3042 * In case of T/TCP, origoffer==-1 indicates, that no segments 3043 * were received yet. In this case we just guess, otherwise 3044 * we do the same as before T/TCP. 3045 */ 3046 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3047 (origoffer == -1 || 3048 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3049 mss -= TCPOLEN_TSTAMP_APPA; 3050 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 3051 (origoffer == -1 || 3052 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3053 mss -= TCPOLEN_CC_APPA; 3054 tp->t_maxseg = mss; 3055 3056 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3057 if (mss > MCLBYTES) 3058 mss &= ~(MCLBYTES-1); 3059 #else 3060 if (mss > MCLBYTES) 3061 mss = mss / MCLBYTES * MCLBYTES; 3062 #endif 3063 tp->t_maxseg = mss; 3064 3065 /* 3066 * If there's a pipesize, change the socket buffer to that size, 3067 * don't change if sb_hiwat is different than default (then it 3068 * has been changed on purpose with setsockopt). 3069 * Make the socket buffers an integral number of mss units; 3070 * if the mss is larger than the socket buffer, decrease the mss. 3071 */ 3072 SOCKBUF_LOCK(&so->so_snd); 3073 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3074 bufsize = metrics.rmx_sendpipe; 3075 else 3076 bufsize = so->so_snd.sb_hiwat; 3077 if (bufsize < mss) 3078 mss = bufsize; 3079 else { 3080 bufsize = roundup(bufsize, mss); 3081 if (bufsize > sb_max) 3082 bufsize = sb_max; 3083 if (bufsize > so->so_snd.sb_hiwat) 3084 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3085 } 3086 SOCKBUF_UNLOCK(&so->so_snd); 3087 tp->t_maxseg = mss; 3088 3089 SOCKBUF_LOCK(&so->so_rcv); 3090 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3091 bufsize = metrics.rmx_recvpipe; 3092 else 3093 bufsize = so->so_rcv.sb_hiwat; 3094 if (bufsize > mss) { 3095 bufsize = roundup(bufsize, mss); 3096 if (bufsize > sb_max) 3097 bufsize = sb_max; 3098 if (bufsize > so->so_rcv.sb_hiwat) 3099 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3100 } 3101 SOCKBUF_UNLOCK(&so->so_rcv); 3102 /* 3103 * While we're here, check the others too 3104 */ 3105 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3106 tp->t_srtt = rtt; 3107 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3108 tcpstat.tcps_usedrtt++; 3109 if (metrics.rmx_rttvar) { 3110 tp->t_rttvar = metrics.rmx_rttvar; 3111 tcpstat.tcps_usedrttvar++; 3112 } else { 3113 /* default variation is +- 1 rtt */ 3114 tp->t_rttvar = 3115 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3116 } 3117 TCPT_RANGESET(tp->t_rxtcur, 3118 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3119 tp->t_rttmin, TCPTV_REXMTMAX); 3120 } 3121 if (metrics.rmx_ssthresh) { 3122 /* 3123 * There's some sort of gateway or interface 3124 * buffer limit on the path. Use this to set 3125 * the slow start threshhold, but set the 3126 * threshold to no less than 2*mss. 3127 */ 3128 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3129 tcpstat.tcps_usedssthresh++; 3130 } 3131 if (metrics.rmx_bandwidth) 3132 tp->snd_bandwidth = metrics.rmx_bandwidth; 3133 3134 /* 3135 * Set the slow-start flight size depending on whether this 3136 * is a local network or not. 3137 * 3138 * Extend this so we cache the cwnd too and retrieve it here. 3139 * Make cwnd even bigger than RFC3390 suggests but only if we 3140 * have previous experience with the remote host. Be careful 3141 * not make cwnd bigger than remote receive window or our own 3142 * send socket buffer. Maybe put some additional upper bound 3143 * on the retrieved cwnd. Should do incremental updates to 3144 * hostcache when cwnd collapses so next connection doesn't 3145 * overloads the path again. 3146 * 3147 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3148 * We currently check only in syncache_socket for that. 3149 */ 3150 #define TCP_METRICS_CWND 3151 #ifdef TCP_METRICS_CWND 3152 if (metrics.rmx_cwnd) 3153 tp->snd_cwnd = max(mss, 3154 min(metrics.rmx_cwnd / 2, 3155 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3156 else 3157 #endif 3158 if (tcp_do_rfc3390) 3159 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3160 #ifdef INET6 3161 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3162 (!isipv6 && in_localaddr(inp->inp_faddr))) 3163 #else 3164 else if (in_localaddr(inp->inp_faddr)) 3165 #endif 3166 tp->snd_cwnd = mss * ss_fltsz_local; 3167 else 3168 tp->snd_cwnd = mss * ss_fltsz; 3169 } 3170 3171 /* 3172 * Determine the MSS option to send on an outgoing SYN. 3173 */ 3174 int 3175 tcp_mssopt(inc) 3176 struct in_conninfo *inc; 3177 { 3178 int mss = 0; 3179 u_long maxmtu = 0; 3180 u_long thcmtu = 0; 3181 size_t min_protoh; 3182 #ifdef INET6 3183 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3184 #endif 3185 3186 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3187 3188 #ifdef INET6 3189 if (isipv6) { 3190 mss = tcp_v6mssdflt; 3191 maxmtu = tcp_maxmtu6(inc); 3192 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3193 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3194 } else 3195 #endif 3196 { 3197 mss = tcp_mssdflt; 3198 maxmtu = tcp_maxmtu(inc); 3199 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3200 min_protoh = sizeof(struct tcpiphdr); 3201 } 3202 if (maxmtu && thcmtu) 3203 mss = min(maxmtu, thcmtu) - min_protoh; 3204 else if (maxmtu || thcmtu) 3205 mss = max(maxmtu, thcmtu) - min_protoh; 3206 3207 return (mss); 3208 } 3209 3210 3211 /* 3212 * On a partial ack arrives, force the retransmission of the 3213 * next unacknowledged segment. Do not clear tp->t_dupacks. 3214 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3215 * be started again. 3216 */ 3217 static void 3218 tcp_newreno_partial_ack(tp, th) 3219 struct tcpcb *tp; 3220 struct tcphdr *th; 3221 { 3222 tcp_seq onxt = tp->snd_nxt; 3223 u_long ocwnd = tp->snd_cwnd; 3224 3225 callout_stop(tp->tt_rexmt); 3226 tp->t_rtttime = 0; 3227 tp->snd_nxt = th->th_ack; 3228 /* 3229 * Set snd_cwnd to one segment beyond acknowledged offset. 3230 * (tp->snd_una has not yet been updated when this function is called.) 3231 */ 3232 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3233 tp->t_flags |= TF_ACKNOW; 3234 (void) tcp_output(tp); 3235 tp->snd_cwnd = ocwnd; 3236 if (SEQ_GT(onxt, tp->snd_nxt)) 3237 tp->snd_nxt = onxt; 3238 /* 3239 * Partial window deflation. Relies on fact that tp->snd_una 3240 * not updated yet. 3241 */ 3242 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3243 } 3244 3245 /* 3246 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3247 * looking for a pcb in the listen state. Returns 0 otherwise. 3248 */ 3249 static int 3250 tcp_timewait(tw, to, th, m, tlen) 3251 struct tcptw *tw; 3252 struct tcpopt *to; 3253 struct tcphdr *th; 3254 struct mbuf *m; 3255 int tlen; 3256 { 3257 int thflags; 3258 tcp_seq seq; 3259 #ifdef INET6 3260 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3261 #else 3262 const int isipv6 = 0; 3263 #endif 3264 3265 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3266 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3267 INP_LOCK_ASSERT(tw->tw_inpcb); 3268 3269 thflags = th->th_flags; 3270 3271 /* 3272 * NOTE: for FIN_WAIT_2 (to be added later), 3273 * must validate sequence number before accepting RST 3274 */ 3275 3276 /* 3277 * If the segment contains RST: 3278 * Drop the segment - see Stevens, vol. 2, p. 964 and 3279 * RFC 1337. 3280 */ 3281 if (thflags & TH_RST) 3282 goto drop; 3283 3284 /* 3285 * If segment contains a SYN and CC [not CC.NEW] option: 3286 * if connection duration > MSL, drop packet and send RST; 3287 * 3288 * if SEG.CC > CCrecv then is new SYN. 3289 * Complete close and delete TCPCB. Then reprocess 3290 * segment, hoping to find new TCPCB in LISTEN state; 3291 * 3292 * else must be old SYN; drop it. 3293 * else do normal processing. 3294 */ 3295 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3296 if ((ticks - tw->t_starttime) > tcp_msl) 3297 goto reset; 3298 if (CC_GT(to->to_cc, tw->cc_recv)) { 3299 (void) tcp_twclose(tw, 0); 3300 return (1); 3301 } 3302 goto drop; 3303 } 3304 3305 #if 0 3306 /* PAWS not needed at the moment */ 3307 /* 3308 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3309 * and it's less than ts_recent, drop it. 3310 */ 3311 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3312 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3313 if ((thflags & TH_ACK) == 0) 3314 goto drop; 3315 goto ack; 3316 } 3317 /* 3318 * ts_recent is never updated because we never accept new segments. 3319 */ 3320 #endif 3321 3322 /* 3323 * If a new connection request is received 3324 * while in TIME_WAIT, drop the old connection 3325 * and start over if the sequence numbers 3326 * are above the previous ones. 3327 */ 3328 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3329 (void) tcp_twclose(tw, 0); 3330 return (1); 3331 } 3332 3333 /* 3334 * Drop the the segment if it does not contain an ACK. 3335 */ 3336 if ((thflags & TH_ACK) == 0) 3337 goto drop; 3338 3339 /* 3340 * Reset the 2MSL timer if this is a duplicate FIN. 3341 */ 3342 if (thflags & TH_FIN) { 3343 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3344 if (seq + 1 == tw->rcv_nxt) 3345 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3346 } 3347 3348 /* 3349 * Acknowledge the segment if it has data or is not a duplicate ACK. 3350 */ 3351 if (thflags != TH_ACK || tlen != 0 || 3352 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3353 tcp_twrespond(tw, TH_ACK); 3354 goto drop; 3355 3356 reset: 3357 /* 3358 * Generate a RST, dropping incoming segment. 3359 * Make ACK acceptable to originator of segment. 3360 * Don't bother to respond if destination was broadcast/multicast. 3361 */ 3362 if (m->m_flags & (M_BCAST|M_MCAST)) 3363 goto drop; 3364 if (isipv6) { 3365 struct ip6_hdr *ip6; 3366 3367 /* IPv6 anycast check is done at tcp6_input() */ 3368 ip6 = mtod(m, struct ip6_hdr *); 3369 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3370 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3371 goto drop; 3372 } else { 3373 struct ip *ip; 3374 3375 ip = mtod(m, struct ip *); 3376 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3377 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3378 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3379 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3380 goto drop; 3381 } 3382 if (thflags & TH_ACK) { 3383 tcp_respond(NULL, 3384 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3385 } else { 3386 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3387 tcp_respond(NULL, 3388 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3389 } 3390 INP_UNLOCK(tw->tw_inpcb); 3391 return (0); 3392 3393 drop: 3394 INP_UNLOCK(tw->tw_inpcb); 3395 m_freem(m); 3396 return (0); 3397 }
Cache object: e5cde52d3f600a0a31d4936449e24f10
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]