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 * $FreeBSD$ 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> /* required for icmp_var.h */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip_options.h> 72 #include <netinet/ip6.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/in6_pcb.h> 75 #include <netinet6/ip6_var.h> 76 #include <netinet6/nd6.h> 77 #include <netinet/tcp.h> 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet6/tcp6_var.h> 83 #include <netinet/tcpip.h> 84 #ifdef TCPDEBUG 85 #include <netinet/tcp_debug.h> 86 #endif /* TCPDEBUG */ 87 88 #ifdef FAST_IPSEC 89 #include <netipsec/ipsec.h> 90 #include <netipsec/ipsec6.h> 91 #endif /*FAST_IPSEC*/ 92 93 #ifdef IPSEC 94 #include <netinet6/ipsec.h> 95 #include <netinet6/ipsec6.h> 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 static const int tcprexmtthresh = 3; 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 tcpopt *, u_char *, int, int); 169 170 static void tcp_pulloutofband(struct socket *, 171 struct tcphdr *, struct mbuf *, int); 172 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 173 struct mbuf *); 174 static void tcp_xmit_timer(struct tcpcb *, int); 175 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 176 static int tcp_timewait(struct inpcb *, struct tcpopt *, 177 struct tcphdr *, struct mbuf *, int); 178 179 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 180 #ifdef INET6 181 #define ND6_HINT(tp) \ 182 do { \ 183 if ((tp) && (tp)->t_inpcb && \ 184 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 185 nd6_nud_hint(NULL, NULL, 0); \ 186 } while (0) 187 #else 188 #define ND6_HINT(tp) 189 #endif 190 191 /* 192 * Indicate whether this ack should be delayed. We can delay the ack if 193 * - there is no delayed ack timer in progress and 194 * - our last ack wasn't a 0-sized window. We never want to delay 195 * the ack that opens up a 0-sized window and 196 * - delayed acks are enabled or 197 * - this is a half-synchronized T/TCP connection. 198 */ 199 #define DELAY_ACK(tp) \ 200 ((!callout_active(tp->tt_delack) && \ 201 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 202 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 203 204 /* Initialize TCP reassembly queue */ 205 static void 206 tcp_reass_zone_change(void *tag) 207 { 208 209 tcp_reass_maxseg = nmbclusters / 16; 210 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 211 } 212 213 uma_zone_t tcp_reass_zone; 214 void 215 tcp_reass_init() 216 { 217 tcp_reass_maxseg = nmbclusters / 16; 218 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 219 &tcp_reass_maxseg); 220 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 221 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 222 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 223 EVENTHANDLER_REGISTER(nmbclusters_change, 224 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 225 } 226 227 static int 228 tcp_reass(tp, th, tlenp, m) 229 register struct tcpcb *tp; 230 register struct tcphdr *th; 231 int *tlenp; 232 struct mbuf *m; 233 { 234 struct tseg_qent *q; 235 struct tseg_qent *p = NULL; 236 struct tseg_qent *nq; 237 struct tseg_qent *te = NULL; 238 struct socket *so = tp->t_inpcb->inp_socket; 239 int flags; 240 241 INP_LOCK_ASSERT(tp->t_inpcb); 242 243 /* 244 * XXX: tcp_reass() is rather inefficient with its data structures 245 * and should be rewritten (see NetBSD for optimizations). While 246 * doing that it should move to its own file tcp_reass.c. 247 */ 248 249 /* 250 * Call with th==NULL after become established to 251 * force pre-ESTABLISHED data up to user socket. 252 */ 253 if (th == NULL) 254 goto present; 255 256 /* 257 * Limit the number of segments in the reassembly queue to prevent 258 * holding on to too many segments (and thus running out of mbufs). 259 * Make sure to let the missing segment through which caused this 260 * queue. Always keep one global queue entry spare to be able to 261 * process the missing segment. 262 */ 263 if (th->th_seq != tp->rcv_nxt && 264 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 265 tp->t_segqlen >= tcp_reass_maxqlen)) { 266 tcp_reass_overflows++; 267 tcpstat.tcps_rcvmemdrop++; 268 m_freem(m); 269 *tlenp = 0; 270 return (0); 271 } 272 273 /* 274 * Allocate a new queue entry. If we can't, or hit the zone limit 275 * just drop the pkt. 276 */ 277 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 278 if (te == NULL) { 279 tcpstat.tcps_rcvmemdrop++; 280 m_freem(m); 281 *tlenp = 0; 282 return (0); 283 } 284 tp->t_segqlen++; 285 tcp_reass_qsize++; 286 287 /* 288 * Find a segment which begins after this one does. 289 */ 290 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 291 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 292 break; 293 p = q; 294 } 295 296 /* 297 * If there is a preceding segment, it may provide some of 298 * our data already. If so, drop the data from the incoming 299 * segment. If it provides all of our data, drop us. 300 */ 301 if (p != NULL) { 302 register int i; 303 /* conversion to int (in i) handles seq wraparound */ 304 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 305 if (i > 0) { 306 if (i >= *tlenp) { 307 tcpstat.tcps_rcvduppack++; 308 tcpstat.tcps_rcvdupbyte += *tlenp; 309 m_freem(m); 310 uma_zfree(tcp_reass_zone, te); 311 tp->t_segqlen--; 312 tcp_reass_qsize--; 313 /* 314 * Try to present any queued data 315 * at the left window edge to the user. 316 * This is needed after the 3-WHS 317 * completes. 318 */ 319 goto present; /* ??? */ 320 } 321 m_adj(m, i); 322 *tlenp -= i; 323 th->th_seq += i; 324 } 325 } 326 tcpstat.tcps_rcvoopack++; 327 tcpstat.tcps_rcvoobyte += *tlenp; 328 329 /* 330 * While we overlap succeeding segments trim them or, 331 * if they are completely covered, dequeue them. 332 */ 333 while (q) { 334 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 335 if (i <= 0) 336 break; 337 if (i < q->tqe_len) { 338 q->tqe_th->th_seq += i; 339 q->tqe_len -= i; 340 m_adj(q->tqe_m, i); 341 break; 342 } 343 344 nq = LIST_NEXT(q, tqe_q); 345 LIST_REMOVE(q, tqe_q); 346 m_freem(q->tqe_m); 347 uma_zfree(tcp_reass_zone, q); 348 tp->t_segqlen--; 349 tcp_reass_qsize--; 350 q = nq; 351 } 352 353 /* Insert the new segment queue entry into place. */ 354 te->tqe_m = m; 355 te->tqe_th = th; 356 te->tqe_len = *tlenp; 357 358 if (p == NULL) { 359 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 360 } else { 361 LIST_INSERT_AFTER(p, te, tqe_q); 362 } 363 364 present: 365 /* 366 * Present data to user, advancing rcv_nxt through 367 * completed sequence space. 368 */ 369 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 370 return (0); 371 q = LIST_FIRST(&tp->t_segq); 372 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 373 return (0); 374 SOCKBUF_LOCK(&so->so_rcv); 375 do { 376 tp->rcv_nxt += q->tqe_len; 377 flags = q->tqe_th->th_flags & TH_FIN; 378 nq = LIST_NEXT(q, tqe_q); 379 LIST_REMOVE(q, tqe_q); 380 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 381 m_freem(q->tqe_m); 382 else 383 sbappendstream_locked(&so->so_rcv, q->tqe_m); 384 uma_zfree(tcp_reass_zone, q); 385 tp->t_segqlen--; 386 tcp_reass_qsize--; 387 q = nq; 388 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 389 ND6_HINT(tp); 390 sorwakeup_locked(so); 391 return (flags); 392 } 393 394 /* 395 * TCP input routine, follows pages 65-76 of the 396 * protocol specification dated September, 1981 very closely. 397 */ 398 #ifdef INET6 399 int 400 tcp6_input(mp, offp, proto) 401 struct mbuf **mp; 402 int *offp, proto; 403 { 404 register struct mbuf *m = *mp; 405 struct in6_ifaddr *ia6; 406 407 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 408 409 /* 410 * draft-itojun-ipv6-tcp-to-anycast 411 * better place to put this in? 412 */ 413 ia6 = ip6_getdstifaddr(m); 414 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 415 struct ip6_hdr *ip6; 416 417 ip6 = mtod(m, struct ip6_hdr *); 418 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 419 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 420 return IPPROTO_DONE; 421 } 422 423 tcp_input(m, *offp); 424 return IPPROTO_DONE; 425 } 426 #endif 427 428 void 429 tcp_input(m, off0) 430 register struct mbuf *m; 431 int off0; 432 { 433 register struct tcphdr *th; 434 register struct ip *ip = NULL; 435 register struct ipovly *ipov; 436 register struct inpcb *inp = NULL; 437 u_char *optp = NULL; 438 int optlen = 0; 439 int len, tlen, off; 440 int drop_hdrlen; 441 register struct tcpcb *tp = 0; 442 register int thflags; 443 struct socket *so = 0; 444 int todrop, acked, ourfinisacked, needoutput = 0; 445 u_long tiwin; 446 struct tcpopt to; /* options in this segment */ 447 int headlocked = 0; 448 #ifdef IPFIREWALL_FORWARD 449 struct m_tag *fwd_tag; 450 #endif 451 int rstreason; /* For badport_bandlim accounting purposes */ 452 453 struct ip6_hdr *ip6 = NULL; 454 #ifdef INET6 455 int isipv6; 456 #else 457 const int isipv6 = 0; 458 #endif 459 460 #ifdef TCPDEBUG 461 /* 462 * The size of tcp_saveipgen must be the size of the max ip header, 463 * now IPv6. 464 */ 465 u_char tcp_saveipgen[40]; 466 struct tcphdr tcp_savetcp; 467 short ostate = 0; 468 #endif 469 470 #ifdef INET6 471 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 472 #endif 473 bzero((char *)&to, sizeof(to)); 474 475 tcpstat.tcps_rcvtotal++; 476 477 if (isipv6) { 478 #ifdef INET6 479 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 480 ip6 = mtod(m, struct ip6_hdr *); 481 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 482 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 483 tcpstat.tcps_rcvbadsum++; 484 goto drop; 485 } 486 th = (struct tcphdr *)((caddr_t)ip6 + off0); 487 488 /* 489 * Be proactive about unspecified IPv6 address in source. 490 * As we use all-zero to indicate unbounded/unconnected pcb, 491 * unspecified IPv6 address can be used to confuse us. 492 * 493 * Note that packets with unspecified IPv6 destination is 494 * already dropped in ip6_input. 495 */ 496 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 497 /* XXX stat */ 498 goto drop; 499 } 500 #else 501 th = NULL; /* XXX: avoid compiler warning */ 502 #endif 503 } else { 504 /* 505 * Get IP and TCP header together in first mbuf. 506 * Note: IP leaves IP header in first mbuf. 507 */ 508 if (off0 > sizeof (struct ip)) { 509 ip_stripoptions(m, (struct mbuf *)0); 510 off0 = sizeof(struct ip); 511 } 512 if (m->m_len < sizeof (struct tcpiphdr)) { 513 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 514 tcpstat.tcps_rcvshort++; 515 return; 516 } 517 } 518 ip = mtod(m, struct ip *); 519 ipov = (struct ipovly *)ip; 520 th = (struct tcphdr *)((caddr_t)ip + off0); 521 tlen = ip->ip_len; 522 523 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 524 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 525 th->th_sum = m->m_pkthdr.csum_data; 526 else 527 th->th_sum = in_pseudo(ip->ip_src.s_addr, 528 ip->ip_dst.s_addr, 529 htonl(m->m_pkthdr.csum_data + 530 ip->ip_len + 531 IPPROTO_TCP)); 532 th->th_sum ^= 0xffff; 533 #ifdef TCPDEBUG 534 ipov->ih_len = (u_short)tlen; 535 ipov->ih_len = htons(ipov->ih_len); 536 #endif 537 } else { 538 /* 539 * Checksum extended TCP header and data. 540 */ 541 len = sizeof (struct ip) + tlen; 542 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 543 ipov->ih_len = (u_short)tlen; 544 ipov->ih_len = htons(ipov->ih_len); 545 th->th_sum = in_cksum(m, len); 546 } 547 if (th->th_sum) { 548 tcpstat.tcps_rcvbadsum++; 549 goto drop; 550 } 551 #ifdef INET6 552 /* Re-initialization for later version check */ 553 ip->ip_v = IPVERSION; 554 #endif 555 } 556 557 /* 558 * Check that TCP offset makes sense, 559 * pull out TCP options and adjust length. XXX 560 */ 561 off = th->th_off << 2; 562 if (off < sizeof (struct tcphdr) || off > tlen) { 563 tcpstat.tcps_rcvbadoff++; 564 goto drop; 565 } 566 tlen -= off; /* tlen is used instead of ti->ti_len */ 567 if (off > sizeof (struct tcphdr)) { 568 if (isipv6) { 569 #ifdef INET6 570 IP6_EXTHDR_CHECK(m, off0, off, ); 571 ip6 = mtod(m, struct ip6_hdr *); 572 th = (struct tcphdr *)((caddr_t)ip6 + off0); 573 #endif 574 } else { 575 if (m->m_len < sizeof(struct ip) + off) { 576 if ((m = m_pullup(m, sizeof (struct ip) + off)) 577 == 0) { 578 tcpstat.tcps_rcvshort++; 579 return; 580 } 581 ip = mtod(m, struct ip *); 582 ipov = (struct ipovly *)ip; 583 th = (struct tcphdr *)((caddr_t)ip + off0); 584 } 585 } 586 optlen = off - sizeof (struct tcphdr); 587 optp = (u_char *)(th + 1); 588 } 589 thflags = th->th_flags; 590 591 #ifdef TCP_DROP_SYNFIN 592 /* 593 * If the drop_synfin option is enabled, drop all packets with 594 * both the SYN and FIN bits set. This prevents e.g. nmap from 595 * identifying the TCP/IP stack. 596 * 597 * This is a violation of the TCP specification. 598 */ 599 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 600 goto drop; 601 #endif 602 603 /* 604 * Convert TCP protocol specific fields to host format. 605 */ 606 th->th_seq = ntohl(th->th_seq); 607 th->th_ack = ntohl(th->th_ack); 608 th->th_win = ntohs(th->th_win); 609 th->th_urp = ntohs(th->th_urp); 610 611 /* 612 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 613 * until after ip6_savecontrol() is called and before other functions 614 * which don't want those proto headers. 615 * Because ip6_savecontrol() is going to parse the mbuf to 616 * search for data to be passed up to user-land, it wants mbuf 617 * parameters to be unchanged. 618 * XXX: the call of ip6_savecontrol() has been obsoleted based on 619 * latest version of the advanced API (20020110). 620 */ 621 drop_hdrlen = off0 + off; 622 623 /* 624 * Locate pcb for segment. 625 */ 626 INP_INFO_WLOCK(&tcbinfo); 627 headlocked = 1; 628 findpcb: 629 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 630 #ifdef IPFIREWALL_FORWARD 631 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 632 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 633 634 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 635 struct sockaddr_in *next_hop; 636 637 next_hop = (struct sockaddr_in *)(fwd_tag+1); 638 /* 639 * Transparently forwarded. Pretend to be the destination. 640 * already got one like this? 641 */ 642 inp = in_pcblookup_hash(&tcbinfo, 643 ip->ip_src, th->th_sport, 644 ip->ip_dst, th->th_dport, 645 0, m->m_pkthdr.rcvif); 646 if (!inp) { 647 /* It's new. Try to find the ambushing socket. */ 648 inp = in_pcblookup_hash(&tcbinfo, 649 ip->ip_src, th->th_sport, 650 next_hop->sin_addr, 651 next_hop->sin_port ? 652 ntohs(next_hop->sin_port) : 653 th->th_dport, 654 INPLOOKUP_WILDCARD, 655 m->m_pkthdr.rcvif); 656 } 657 /* Remove the tag from the packet. We don't need it anymore. */ 658 m_tag_delete(m, fwd_tag); 659 } else { 660 #endif /* IPFIREWALL_FORWARD */ 661 if (isipv6) { 662 #ifdef INET6 663 inp = in6_pcblookup_hash(&tcbinfo, 664 &ip6->ip6_src, th->th_sport, 665 &ip6->ip6_dst, th->th_dport, 666 INPLOOKUP_WILDCARD, 667 m->m_pkthdr.rcvif); 668 #endif 669 } else 670 inp = in_pcblookup_hash(&tcbinfo, 671 ip->ip_src, th->th_sport, 672 ip->ip_dst, th->th_dport, 673 INPLOOKUP_WILDCARD, 674 m->m_pkthdr.rcvif); 675 #ifdef IPFIREWALL_FORWARD 676 } 677 #endif /* IPFIREWALL_FORWARD */ 678 679 #if defined(IPSEC) || defined(FAST_IPSEC) 680 #ifdef INET6 681 if (isipv6) { 682 if (inp != NULL && ipsec6_in_reject(m, inp)) { 683 #ifdef IPSEC 684 ipsec6stat.in_polvio++; 685 #endif 686 goto drop; 687 } 688 } else 689 #endif /* INET6 */ 690 if (inp != NULL && ipsec4_in_reject(m, inp)) { 691 #ifdef IPSEC 692 ipsecstat.in_polvio++; 693 #endif 694 goto drop; 695 } 696 #endif /*IPSEC || FAST_IPSEC*/ 697 698 /* 699 * If the state is CLOSED (i.e., TCB does not exist) then 700 * all data in the incoming segment is discarded. 701 * If the TCB exists but is in CLOSED state, it is embryonic, 702 * but should either do a listen or a connect soon. 703 */ 704 if (inp == NULL) { 705 if (log_in_vain) { 706 #ifdef INET6 707 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 708 #else 709 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 710 #endif 711 712 if (isipv6) { 713 #ifdef INET6 714 strcpy(dbuf, "["); 715 strcpy(sbuf, "["); 716 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 717 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 718 strcat(dbuf, "]"); 719 strcat(sbuf, "]"); 720 #endif 721 } else { 722 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 723 strcpy(sbuf, inet_ntoa(ip->ip_src)); 724 } 725 switch (log_in_vain) { 726 case 1: 727 if ((thflags & TH_SYN) == 0) 728 break; 729 /* FALLTHROUGH */ 730 case 2: 731 log(LOG_INFO, 732 "Connection attempt to TCP %s:%d " 733 "from %s:%d flags:0x%02x\n", 734 dbuf, ntohs(th->th_dport), sbuf, 735 ntohs(th->th_sport), thflags); 736 break; 737 default: 738 break; 739 } 740 } 741 if (blackhole) { 742 switch (blackhole) { 743 case 1: 744 if (thflags & TH_SYN) 745 goto drop; 746 break; 747 case 2: 748 goto drop; 749 default: 750 goto drop; 751 } 752 } 753 rstreason = BANDLIM_RST_CLOSEDPORT; 754 goto dropwithreset; 755 } 756 INP_LOCK(inp); 757 758 /* Check the minimum TTL for socket. */ 759 if (inp->inp_ip_minttl != 0) { 760 #ifdef INET6 761 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 762 goto drop; 763 else 764 #endif 765 if (inp->inp_ip_minttl > ip->ip_ttl) 766 goto drop; 767 } 768 769 if (inp->inp_vflag & INP_TIMEWAIT) { 770 /* 771 * The only option of relevance is TOF_CC, and only if 772 * present in a SYN segment. See tcp_timewait(). 773 */ 774 if (thflags & TH_SYN) 775 tcp_dooptions(&to, optp, optlen, TO_SYN); 776 if (tcp_timewait(inp, &to, th, m, tlen)) 777 goto findpcb; 778 /* 779 * tcp_timewait unlocks inp. 780 */ 781 INP_INFO_WUNLOCK(&tcbinfo); 782 return; 783 } 784 tp = intotcpcb(inp); 785 if (tp == 0) { 786 INP_UNLOCK(inp); 787 rstreason = BANDLIM_RST_CLOSEDPORT; 788 goto dropwithreset; 789 } 790 if (tp->t_state == TCPS_CLOSED) 791 goto drop; 792 793 #ifdef MAC 794 INP_LOCK_ASSERT(inp); 795 if (mac_check_inpcb_deliver(inp, m)) 796 goto drop; 797 #endif 798 so = inp->inp_socket; 799 KASSERT(so != NULL, ("tcp_input: so == NULL")); 800 #ifdef TCPDEBUG 801 if (so->so_options & SO_DEBUG) { 802 ostate = tp->t_state; 803 if (isipv6) 804 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 805 else 806 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 807 tcp_savetcp = *th; 808 } 809 #endif 810 if (so->so_options & SO_ACCEPTCONN) { 811 struct in_conninfo inc; 812 813 bzero(&inc, sizeof(inc)); 814 #ifdef INET6 815 inc.inc_isipv6 = isipv6; 816 #endif 817 if (isipv6) { 818 inc.inc6_faddr = ip6->ip6_src; 819 inc.inc6_laddr = ip6->ip6_dst; 820 } else { 821 inc.inc_faddr = ip->ip_src; 822 inc.inc_laddr = ip->ip_dst; 823 } 824 inc.inc_fport = th->th_sport; 825 inc.inc_lport = th->th_dport; 826 827 /* 828 * If the state is LISTEN then ignore segment if it contains 829 * a RST. If the segment contains an ACK then it is bad and 830 * send a RST. If it does not contain a SYN then it is not 831 * interesting; drop it. 832 * 833 * If the state is SYN_RECEIVED (syncache) and seg contains 834 * an ACK, but not for our SYN/ACK, send a RST. If the seg 835 * contains a RST, check the sequence number to see if it 836 * is a valid reset segment. 837 */ 838 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 839 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 840 if (!syncache_expand(&inc, th, &so, m)) { 841 /* 842 * No syncache entry, or ACK was not 843 * for our SYN/ACK. Send a RST. 844 */ 845 tcpstat.tcps_badsyn++; 846 rstreason = BANDLIM_RST_OPENPORT; 847 goto dropwithreset; 848 } 849 if (so == NULL) { 850 /* 851 * Could not complete 3-way handshake, 852 * connection is being closed down, and 853 * syncache has free'd mbuf. 854 */ 855 INP_UNLOCK(inp); 856 INP_INFO_WUNLOCK(&tcbinfo); 857 return; 858 } 859 /* 860 * Socket is created in state SYN_RECEIVED. 861 * Continue processing segment. 862 */ 863 INP_UNLOCK(inp); 864 inp = sotoinpcb(so); 865 INP_LOCK(inp); 866 tp = intotcpcb(inp); 867 /* 868 * This is what would have happened in 869 * tcp_output() when the SYN,ACK was sent. 870 */ 871 tp->snd_up = tp->snd_una; 872 tp->snd_max = tp->snd_nxt = tp->iss + 1; 873 tp->last_ack_sent = tp->rcv_nxt; 874 goto after_listen; 875 } 876 if (thflags & TH_RST) { 877 syncache_chkrst(&inc, th); 878 goto drop; 879 } 880 if (thflags & TH_ACK) { 881 syncache_badack(&inc); 882 tcpstat.tcps_badsyn++; 883 rstreason = BANDLIM_RST_OPENPORT; 884 goto dropwithreset; 885 } 886 goto drop; 887 } 888 889 /* 890 * Segment's flags are (SYN) or (SYN|FIN). 891 */ 892 #ifdef INET6 893 /* 894 * If deprecated address is forbidden, 895 * we do not accept SYN to deprecated interface 896 * address to prevent any new inbound connection from 897 * getting established. 898 * When we do not accept SYN, we send a TCP RST, 899 * with deprecated source address (instead of dropping 900 * it). We compromise it as it is much better for peer 901 * to send a RST, and RST will be the final packet 902 * for the exchange. 903 * 904 * If we do not forbid deprecated addresses, we accept 905 * the SYN packet. RFC2462 does not suggest dropping 906 * SYN in this case. 907 * If we decipher RFC2462 5.5.4, it says like this: 908 * 1. use of deprecated addr with existing 909 * communication is okay - "SHOULD continue to be 910 * used" 911 * 2. use of it with new communication: 912 * (2a) "SHOULD NOT be used if alternate address 913 * with sufficient scope is available" 914 * (2b) nothing mentioned otherwise. 915 * Here we fall into (2b) case as we have no choice in 916 * our source address selection - we must obey the peer. 917 * 918 * The wording in RFC2462 is confusing, and there are 919 * multiple description text for deprecated address 920 * handling - worse, they are not exactly the same. 921 * I believe 5.5.4 is the best one, so we follow 5.5.4. 922 */ 923 if (isipv6 && !ip6_use_deprecated) { 924 struct in6_ifaddr *ia6; 925 926 if ((ia6 = ip6_getdstifaddr(m)) && 927 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 928 INP_UNLOCK(inp); 929 tp = NULL; 930 rstreason = BANDLIM_RST_OPENPORT; 931 goto dropwithreset; 932 } 933 } 934 #endif 935 /* 936 * If it is from this socket, drop it, it must be forged. 937 * Don't bother responding if the destination was a broadcast. 938 */ 939 if (th->th_dport == th->th_sport) { 940 if (isipv6) { 941 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 942 &ip6->ip6_src)) 943 goto drop; 944 } else { 945 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 946 goto drop; 947 } 948 } 949 /* 950 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 951 * 952 * Note that it is quite possible to receive unicast 953 * link-layer packets with a broadcast IP address. Use 954 * in_broadcast() to find them. 955 */ 956 if (m->m_flags & (M_BCAST|M_MCAST)) 957 goto drop; 958 if (isipv6) { 959 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 960 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 961 goto drop; 962 } else { 963 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 964 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 965 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 966 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 967 goto drop; 968 } 969 /* 970 * SYN appears to be valid; create compressed TCP state 971 * for syncache, or perform t/tcp connection. 972 */ 973 if (so->so_qlen <= so->so_qlimit) { 974 #ifdef TCPDEBUG 975 if (so->so_options & SO_DEBUG) 976 tcp_trace(TA_INPUT, ostate, tp, 977 (void *)tcp_saveipgen, &tcp_savetcp, 0); 978 #endif 979 tcp_dooptions(&to, optp, optlen, TO_SYN); 980 if (!syncache_add(&inc, &to, th, inp, &so, m)) 981 goto drop; /* XXX: does not happen */ 982 if (so == NULL) { 983 /* 984 * Entry added to syncache, mbuf used to 985 * send SYN,ACK packet. Everything unlocked 986 * already. 987 */ 988 return; 989 } 990 panic("T/TCP not supported at the moment"); 991 #if 0 /* T/TCP */ 992 /* 993 * Segment passed TAO tests. 994 * XXX: Can't happen at the moment. 995 */ 996 INP_UNLOCK(inp); 997 inp = sotoinpcb(so); 998 INP_LOCK(inp); 999 tp = intotcpcb(inp); 1000 tp->t_starttime = ticks; 1001 tp->t_state = TCPS_ESTABLISHED; 1002 1003 /* 1004 * T/TCP logic: 1005 * If there is a FIN or if there is data, then 1006 * delay SYN,ACK(SYN) in the hope of piggy-backing 1007 * it on a response segment. Otherwise must send 1008 * ACK now in case the other side is slow starting. 1009 */ 1010 if (thflags & TH_FIN || tlen != 0) 1011 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1012 else 1013 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1014 tiwin = th->th_win << tp->snd_scale; 1015 tcpstat.tcps_connects++; 1016 soisconnected(so); 1017 goto trimthenstep6; 1018 #endif /* T/TCP */ 1019 } 1020 goto drop; 1021 } 1022 after_listen: 1023 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1024 INP_LOCK_ASSERT(inp); 1025 1026 /* Syncache takes care of sockets in the listen state. */ 1027 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1028 1029 /* 1030 * This is the second part of the MSS DoS prevention code (after 1031 * minmss on the sending side) and it deals with too many too small 1032 * tcp packets in a too short timeframe (1 second). 1033 * 1034 * For every full second we count the number of received packets 1035 * and bytes. If we get a lot of packets per second for this connection 1036 * (tcp_minmssoverload) we take a closer look at it and compute the 1037 * average packet size for the past second. If that is less than 1038 * tcp_minmss we get too many packets with very small payload which 1039 * is not good and burdens our system (and every packet generates 1040 * a wakeup to the process connected to our socket). We can reasonable 1041 * expect this to be small packet DoS attack to exhaust our CPU 1042 * cycles. 1043 * 1044 * Care has to be taken for the minimum packet overload value. This 1045 * value defines the minimum number of packets per second before we 1046 * start to worry. This must not be too low to avoid killing for 1047 * example interactive connections with many small packets like 1048 * telnet or SSH. 1049 * 1050 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1051 * this check. 1052 * 1053 * Account for packet if payload packet, skip over ACK, etc. 1054 */ 1055 if (tcp_minmss && tcp_minmssoverload && 1056 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1057 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1058 tp->rcv_pps++; 1059 tp->rcv_byps += tlen + off; 1060 if (tp->rcv_pps > tcp_minmssoverload) { 1061 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1062 printf("too many small tcp packets from " 1063 "%s:%u, av. %lubyte/packet, " 1064 "dropping connection\n", 1065 #ifdef INET6 1066 isipv6 ? 1067 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1068 #endif 1069 inet_ntoa(inp->inp_inc.inc_faddr), 1070 inp->inp_inc.inc_fport, 1071 tp->rcv_byps / tp->rcv_pps); 1072 KASSERT(headlocked, ("tcp_input: " 1073 "after_listen: tcp_drop: head " 1074 "not locked")); 1075 tp = tcp_drop(tp, ECONNRESET); 1076 tcpstat.tcps_minmssdrops++; 1077 goto drop; 1078 } 1079 } 1080 } else { 1081 tp->rcv_second = ticks + hz; 1082 tp->rcv_pps = 1; 1083 tp->rcv_byps = tlen + off; 1084 } 1085 } 1086 1087 /* 1088 * Segment received on connection. 1089 * Reset idle time and keep-alive timer. 1090 */ 1091 tp->t_rcvtime = ticks; 1092 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1093 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1094 1095 /* 1096 * Unscale the window into a 32-bit value. 1097 * This value is bogus for the TCPS_SYN_SENT state 1098 * and is overwritten later. 1099 */ 1100 tiwin = th->th_win << tp->snd_scale; 1101 1102 /* 1103 * Parse options on any incoming segment. 1104 */ 1105 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) ? TO_SYN : 0); 1106 1107 /* 1108 * If echoed timestamp is later than the current time, 1109 * fall back to non RFC1323 RTT calculation. 1110 */ 1111 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 1112 TSTMP_GT(to.to_tsecr, ticks)) 1113 to.to_tsecr = 0; 1114 1115 /* 1116 * Process options only when we get SYN/ACK back. The SYN case 1117 * for incoming connections is handled in tcp_syncache. 1118 * XXX this is traditional behavior, may need to be cleaned up. 1119 */ 1120 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1121 if ((to.to_flags & TOF_SCALE) && 1122 (tp->t_flags & TF_REQ_SCALE)) { 1123 tp->t_flags |= TF_RCVD_SCALE; 1124 tp->snd_scale = to.to_requested_s_scale; 1125 tp->snd_wnd = th->th_win << tp->snd_scale; 1126 tiwin = tp->snd_wnd; 1127 } 1128 if (to.to_flags & TOF_TS) { 1129 tp->t_flags |= TF_RCVD_TSTMP; 1130 tp->ts_recent = to.to_tsval; 1131 tp->ts_recent_age = ticks; 1132 } 1133 if (to.to_flags & TOF_MSS) 1134 tcp_mss(tp, to.to_mss); 1135 if (tp->sack_enable) { 1136 if (!(to.to_flags & TOF_SACK)) 1137 tp->sack_enable = 0; 1138 else 1139 tp->t_flags |= TF_SACK_PERMIT; 1140 } 1141 1142 } 1143 1144 /* 1145 * Header prediction: check for the two common cases 1146 * of a uni-directional data xfer. If the packet has 1147 * no control flags, is in-sequence, the window didn't 1148 * change and we're not retransmitting, it's a 1149 * candidate. If the length is zero and the ack moved 1150 * forward, we're the sender side of the xfer. Just 1151 * free the data acked & wake any higher level process 1152 * that was blocked waiting for space. If the length 1153 * is non-zero and the ack didn't move, we're the 1154 * receiver side. If we're getting packets in-order 1155 * (the reassembly queue is empty), add the data to 1156 * the socket buffer and note that we need a delayed ack. 1157 * Make sure that the hidden state-flags are also off. 1158 * Since we check for TCPS_ESTABLISHED above, it can only 1159 * be TH_NEEDSYN. 1160 */ 1161 if (tp->t_state == TCPS_ESTABLISHED && 1162 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1163 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1164 ((to.to_flags & TOF_TS) == 0 || 1165 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1166 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1167 tp->snd_nxt == tp->snd_max) { 1168 1169 /* 1170 * If last ACK falls within this segment's sequence numbers, 1171 * record the timestamp. 1172 * NOTE that the test is modified according to the latest 1173 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1174 */ 1175 if ((to.to_flags & TOF_TS) != 0 && 1176 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1177 tp->ts_recent_age = ticks; 1178 tp->ts_recent = to.to_tsval; 1179 } 1180 1181 if (tlen == 0) { 1182 if (SEQ_GT(th->th_ack, tp->snd_una) && 1183 SEQ_LEQ(th->th_ack, tp->snd_max) && 1184 tp->snd_cwnd >= tp->snd_wnd && 1185 ((!tcp_do_newreno && !tp->sack_enable && 1186 tp->t_dupacks < tcprexmtthresh) || 1187 ((tcp_do_newreno || tp->sack_enable) && 1188 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1189 TAILQ_EMPTY(&tp->snd_holes)))) { 1190 KASSERT(headlocked, ("headlocked")); 1191 INP_INFO_WUNLOCK(&tcbinfo); 1192 headlocked = 0; 1193 /* 1194 * this is a pure ack for outstanding data. 1195 */ 1196 ++tcpstat.tcps_predack; 1197 /* 1198 * "bad retransmit" recovery 1199 */ 1200 if (tp->t_rxtshift == 1 && 1201 ticks < tp->t_badrxtwin) { 1202 ++tcpstat.tcps_sndrexmitbad; 1203 tp->snd_cwnd = tp->snd_cwnd_prev; 1204 tp->snd_ssthresh = 1205 tp->snd_ssthresh_prev; 1206 tp->snd_recover = tp->snd_recover_prev; 1207 if (tp->t_flags & TF_WASFRECOVERY) 1208 ENTER_FASTRECOVERY(tp); 1209 tp->snd_nxt = tp->snd_max; 1210 tp->t_badrxtwin = 0; 1211 } 1212 1213 /* 1214 * Recalculate the transmit timer / rtt. 1215 * 1216 * Some boxes send broken timestamp replies 1217 * during the SYN+ACK phase, ignore 1218 * timestamps of 0 or we could calculate a 1219 * huge RTT and blow up the retransmit timer. 1220 */ 1221 if ((to.to_flags & TOF_TS) != 0 && 1222 to.to_tsecr) { 1223 if (!tp->t_rttlow || 1224 tp->t_rttlow > ticks - to.to_tsecr) 1225 tp->t_rttlow = ticks - to.to_tsecr; 1226 tcp_xmit_timer(tp, 1227 ticks - to.to_tsecr + 1); 1228 } else if (tp->t_rtttime && 1229 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1230 if (!tp->t_rttlow || 1231 tp->t_rttlow > ticks - tp->t_rtttime) 1232 tp->t_rttlow = ticks - tp->t_rtttime; 1233 tcp_xmit_timer(tp, 1234 ticks - tp->t_rtttime); 1235 } 1236 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1237 acked = th->th_ack - tp->snd_una; 1238 tcpstat.tcps_rcvackpack++; 1239 tcpstat.tcps_rcvackbyte += acked; 1240 sbdrop(&so->so_snd, acked); 1241 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1242 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1243 tp->snd_recover = th->th_ack - 1; 1244 tp->snd_una = th->th_ack; 1245 /* 1246 * pull snd_wl2 up to prevent seq wrap relative 1247 * to th_ack. 1248 */ 1249 tp->snd_wl2 = th->th_ack; 1250 tp->t_dupacks = 0; 1251 m_freem(m); 1252 ND6_HINT(tp); /* some progress has been done */ 1253 1254 /* 1255 * If all outstanding data are acked, stop 1256 * retransmit timer, otherwise restart timer 1257 * using current (possibly backed-off) value. 1258 * If process is waiting for space, 1259 * wakeup/selwakeup/signal. If data 1260 * are ready to send, let tcp_output 1261 * decide between more output or persist. 1262 1263 #ifdef TCPDEBUG 1264 if (so->so_options & SO_DEBUG) 1265 tcp_trace(TA_INPUT, ostate, tp, 1266 (void *)tcp_saveipgen, 1267 &tcp_savetcp, 0); 1268 #endif 1269 */ 1270 if (tp->snd_una == tp->snd_max) 1271 callout_stop(tp->tt_rexmt); 1272 else if (!callout_active(tp->tt_persist)) 1273 callout_reset(tp->tt_rexmt, 1274 tp->t_rxtcur, 1275 tcp_timer_rexmt, tp); 1276 1277 sowwakeup(so); 1278 if (so->so_snd.sb_cc) 1279 (void) tcp_output(tp); 1280 goto check_delack; 1281 } 1282 } else if (th->th_ack == tp->snd_una && 1283 LIST_EMPTY(&tp->t_segq) && 1284 tlen <= sbspace(&so->so_rcv)) { 1285 KASSERT(headlocked, ("headlocked")); 1286 INP_INFO_WUNLOCK(&tcbinfo); 1287 headlocked = 0; 1288 /* 1289 * this is a pure, in-sequence data packet 1290 * with nothing on the reassembly queue and 1291 * we have enough buffer space to take it. 1292 */ 1293 /* Clean receiver SACK report if present */ 1294 if (tp->sack_enable && tp->rcv_numsacks) 1295 tcp_clean_sackreport(tp); 1296 ++tcpstat.tcps_preddat; 1297 tp->rcv_nxt += tlen; 1298 /* 1299 * Pull snd_wl1 up to prevent seq wrap relative to 1300 * th_seq. 1301 */ 1302 tp->snd_wl1 = th->th_seq; 1303 /* 1304 * Pull rcv_up up to prevent seq wrap relative to 1305 * rcv_nxt. 1306 */ 1307 tp->rcv_up = tp->rcv_nxt; 1308 tcpstat.tcps_rcvpack++; 1309 tcpstat.tcps_rcvbyte += tlen; 1310 ND6_HINT(tp); /* some progress has been done */ 1311 /* 1312 #ifdef TCPDEBUG 1313 if (so->so_options & SO_DEBUG) 1314 tcp_trace(TA_INPUT, ostate, tp, 1315 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1316 #endif 1317 * Add data to socket buffer. 1318 */ 1319 SOCKBUF_LOCK(&so->so_rcv); 1320 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1321 m_freem(m); 1322 } else { 1323 m_adj(m, drop_hdrlen); /* delayed header drop */ 1324 sbappendstream_locked(&so->so_rcv, m); 1325 } 1326 sorwakeup_locked(so); 1327 if (DELAY_ACK(tp)) { 1328 tp->t_flags |= TF_DELACK; 1329 } else { 1330 tp->t_flags |= TF_ACKNOW; 1331 tcp_output(tp); 1332 } 1333 goto check_delack; 1334 } 1335 } 1336 1337 /* 1338 * Calculate amount of space in receive window, 1339 * and then do TCP input processing. 1340 * Receive window is amount of space in rcv queue, 1341 * but not less than advertised window. 1342 */ 1343 { int win; 1344 1345 win = sbspace(&so->so_rcv); 1346 if (win < 0) 1347 win = 0; 1348 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1349 } 1350 1351 switch (tp->t_state) { 1352 1353 /* 1354 * If the state is SYN_RECEIVED: 1355 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1356 */ 1357 case TCPS_SYN_RECEIVED: 1358 if ((thflags & TH_ACK) && 1359 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1360 SEQ_GT(th->th_ack, tp->snd_max))) { 1361 rstreason = BANDLIM_RST_OPENPORT; 1362 goto dropwithreset; 1363 } 1364 break; 1365 1366 /* 1367 * If the state is SYN_SENT: 1368 * if seg contains an ACK, but not for our SYN, drop the input. 1369 * if seg contains a RST, then drop the connection. 1370 * if seg does not contain SYN, then drop it. 1371 * Otherwise this is an acceptable SYN segment 1372 * initialize tp->rcv_nxt and tp->irs 1373 * if seg contains ack then advance tp->snd_una 1374 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1375 * arrange for segment to be acked (eventually) 1376 * continue processing rest of data/controls, beginning with URG 1377 */ 1378 case TCPS_SYN_SENT: 1379 if ((thflags & TH_ACK) && 1380 (SEQ_LEQ(th->th_ack, tp->iss) || 1381 SEQ_GT(th->th_ack, tp->snd_max))) { 1382 rstreason = BANDLIM_UNLIMITED; 1383 goto dropwithreset; 1384 } 1385 if (thflags & TH_RST) { 1386 if (thflags & TH_ACK) { 1387 KASSERT(headlocked, ("tcp_input: after_listen" 1388 ": tcp_drop.2: head not locked")); 1389 tp = tcp_drop(tp, ECONNREFUSED); 1390 } 1391 goto drop; 1392 } 1393 if ((thflags & TH_SYN) == 0) 1394 goto drop; 1395 1396 /* Initial send window, already scaled. */ 1397 tp->snd_wnd = th->th_win; 1398 1399 tp->irs = th->th_seq; 1400 tcp_rcvseqinit(tp); 1401 if (thflags & TH_ACK) { 1402 tcpstat.tcps_connects++; 1403 soisconnected(so); 1404 #ifdef MAC 1405 SOCK_LOCK(so); 1406 mac_set_socket_peer_from_mbuf(m, so); 1407 SOCK_UNLOCK(so); 1408 #endif 1409 /* Do window scaling on this connection? */ 1410 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1411 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1412 tp->rcv_scale = tp->request_r_scale; 1413 } 1414 tp->rcv_adv += tp->rcv_wnd; 1415 tp->snd_una++; /* SYN is acked */ 1416 /* 1417 * If there's data, delay ACK; if there's also a FIN 1418 * ACKNOW will be turned on later. 1419 */ 1420 if (DELAY_ACK(tp) && tlen != 0) 1421 callout_reset(tp->tt_delack, tcp_delacktime, 1422 tcp_timer_delack, tp); 1423 else 1424 tp->t_flags |= TF_ACKNOW; 1425 /* 1426 * Received <SYN,ACK> in SYN_SENT[*] state. 1427 * Transitions: 1428 * SYN_SENT --> ESTABLISHED 1429 * SYN_SENT* --> FIN_WAIT_1 1430 */ 1431 tp->t_starttime = ticks; 1432 if (tp->t_flags & TF_NEEDFIN) { 1433 tp->t_state = TCPS_FIN_WAIT_1; 1434 tp->t_flags &= ~TF_NEEDFIN; 1435 thflags &= ~TH_SYN; 1436 } else { 1437 tp->t_state = TCPS_ESTABLISHED; 1438 callout_reset(tp->tt_keep, tcp_keepidle, 1439 tcp_timer_keep, tp); 1440 } 1441 } else { 1442 /* 1443 * Received initial SYN in SYN-SENT[*] state => 1444 * simultaneous open. If segment contains CC option 1445 * and there is a cached CC, apply TAO test. 1446 * If it succeeds, connection is * half-synchronized. 1447 * Otherwise, do 3-way handshake: 1448 * SYN-SENT -> SYN-RECEIVED 1449 * SYN-SENT* -> SYN-RECEIVED* 1450 * If there was no CC option, clear cached CC value. 1451 */ 1452 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1453 callout_stop(tp->tt_rexmt); 1454 tp->t_state = TCPS_SYN_RECEIVED; 1455 } 1456 1457 #if 0 /* T/TCP */ 1458 trimthenstep6: 1459 #endif 1460 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1461 "locked")); 1462 INP_LOCK_ASSERT(inp); 1463 1464 /* 1465 * Advance th->th_seq to correspond to first data byte. 1466 * If data, trim to stay within window, 1467 * dropping FIN if necessary. 1468 */ 1469 th->th_seq++; 1470 if (tlen > tp->rcv_wnd) { 1471 todrop = tlen - tp->rcv_wnd; 1472 m_adj(m, -todrop); 1473 tlen = tp->rcv_wnd; 1474 thflags &= ~TH_FIN; 1475 tcpstat.tcps_rcvpackafterwin++; 1476 tcpstat.tcps_rcvbyteafterwin += todrop; 1477 } 1478 tp->snd_wl1 = th->th_seq - 1; 1479 tp->rcv_up = th->th_seq; 1480 /* 1481 * Client side of transaction: already sent SYN and data. 1482 * If the remote host used T/TCP to validate the SYN, 1483 * our data will be ACK'd; if so, enter normal data segment 1484 * processing in the middle of step 5, ack processing. 1485 * Otherwise, goto step 6. 1486 */ 1487 if (thflags & TH_ACK) 1488 goto process_ACK; 1489 1490 goto step6; 1491 1492 /* 1493 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1494 * do normal processing. 1495 * 1496 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1497 */ 1498 case TCPS_LAST_ACK: 1499 case TCPS_CLOSING: 1500 case TCPS_TIME_WAIT: 1501 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1502 break; /* continue normal processing */ 1503 } 1504 1505 /* 1506 * States other than LISTEN or SYN_SENT. 1507 * First check the RST flag and sequence number since reset segments 1508 * are exempt from the timestamp and connection count tests. This 1509 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1510 * below which allowed reset segments in half the sequence space 1511 * to fall though and be processed (which gives forged reset 1512 * segments with a random sequence number a 50 percent chance of 1513 * killing a connection). 1514 * Then check timestamp, if present. 1515 * Then check the connection count, if present. 1516 * Then check that at least some bytes of segment are within 1517 * receive window. If segment begins before rcv_nxt, 1518 * drop leading data (and SYN); if nothing left, just ack. 1519 * 1520 * 1521 * If the RST bit is set, check the sequence number to see 1522 * if this is a valid reset segment. 1523 * RFC 793 page 37: 1524 * In all states except SYN-SENT, all reset (RST) segments 1525 * are validated by checking their SEQ-fields. A reset is 1526 * valid if its sequence number is in the window. 1527 * Note: this does not take into account delayed ACKs, so 1528 * we should test against last_ack_sent instead of rcv_nxt. 1529 * The sequence number in the reset segment is normally an 1530 * echo of our outgoing acknowlegement numbers, but some hosts 1531 * send a reset with the sequence number at the rightmost edge 1532 * of our receive window, and we have to handle this case. 1533 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1534 * that brute force RST attacks are possible. To combat this, 1535 * we use a much stricter check while in the ESTABLISHED state, 1536 * only accepting RSTs where the sequence number is equal to 1537 * last_ack_sent. In all other states (the states in which a 1538 * RST is more likely), the more permissive check is used. 1539 * If we have multiple segments in flight, the intial reset 1540 * segment sequence numbers will be to the left of last_ack_sent, 1541 * but they will eventually catch up. 1542 * In any case, it never made sense to trim reset segments to 1543 * fit the receive window since RFC 1122 says: 1544 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1545 * 1546 * A TCP SHOULD allow a received RST segment to include data. 1547 * 1548 * DISCUSSION 1549 * It has been suggested that a RST segment could contain 1550 * ASCII text that encoded and explained the cause of the 1551 * RST. No standard has yet been established for such 1552 * data. 1553 * 1554 * If the reset segment passes the sequence number test examine 1555 * the state: 1556 * SYN_RECEIVED STATE: 1557 * If passive open, return to LISTEN state. 1558 * If active open, inform user that connection was refused. 1559 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1560 * Inform user that connection was reset, and close tcb. 1561 * CLOSING, LAST_ACK STATES: 1562 * Close the tcb. 1563 * TIME_WAIT STATE: 1564 * Drop the segment - see Stevens, vol. 2, p. 964 and 1565 * RFC 1337. 1566 */ 1567 if (thflags & TH_RST) { 1568 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1569 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1570 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1571 switch (tp->t_state) { 1572 1573 case TCPS_SYN_RECEIVED: 1574 so->so_error = ECONNREFUSED; 1575 goto close; 1576 1577 case TCPS_ESTABLISHED: 1578 if (tp->last_ack_sent != th->th_seq && 1579 tcp_insecure_rst == 0) { 1580 tcpstat.tcps_badrst++; 1581 goto drop; 1582 } 1583 case TCPS_FIN_WAIT_1: 1584 case TCPS_FIN_WAIT_2: 1585 case TCPS_CLOSE_WAIT: 1586 so->so_error = ECONNRESET; 1587 close: 1588 tp->t_state = TCPS_CLOSED; 1589 tcpstat.tcps_drops++; 1590 KASSERT(headlocked, ("tcp_input: " 1591 "trimthenstep6: tcp_close: head not " 1592 "locked")); 1593 tp = tcp_close(tp); 1594 break; 1595 1596 case TCPS_CLOSING: 1597 case TCPS_LAST_ACK: 1598 KASSERT(headlocked, ("trimthenstep6: " 1599 "tcp_close.2: head not locked")); 1600 tp = tcp_close(tp); 1601 break; 1602 1603 case TCPS_TIME_WAIT: 1604 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1605 ("timewait")); 1606 break; 1607 } 1608 } 1609 goto drop; 1610 } 1611 1612 /* 1613 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1614 * and it's less than ts_recent, drop it. 1615 */ 1616 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1617 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1618 1619 /* Check to see if ts_recent is over 24 days old. */ 1620 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1621 /* 1622 * Invalidate ts_recent. If this segment updates 1623 * ts_recent, the age will be reset later and ts_recent 1624 * will get a valid value. If it does not, setting 1625 * ts_recent to zero will at least satisfy the 1626 * requirement that zero be placed in the timestamp 1627 * echo reply when ts_recent isn't valid. The 1628 * age isn't reset until we get a valid ts_recent 1629 * because we don't want out-of-order segments to be 1630 * dropped when ts_recent is old. 1631 */ 1632 tp->ts_recent = 0; 1633 } else { 1634 tcpstat.tcps_rcvduppack++; 1635 tcpstat.tcps_rcvdupbyte += tlen; 1636 tcpstat.tcps_pawsdrop++; 1637 if (tlen) 1638 goto dropafterack; 1639 goto drop; 1640 } 1641 } 1642 1643 /* 1644 * In the SYN-RECEIVED state, validate that the packet belongs to 1645 * this connection before trimming the data to fit the receive 1646 * window. Check the sequence number versus IRS since we know 1647 * the sequence numbers haven't wrapped. This is a partial fix 1648 * for the "LAND" DoS attack. 1649 */ 1650 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1651 rstreason = BANDLIM_RST_OPENPORT; 1652 goto dropwithreset; 1653 } 1654 1655 todrop = tp->rcv_nxt - th->th_seq; 1656 if (todrop > 0) { 1657 if (thflags & TH_SYN) { 1658 thflags &= ~TH_SYN; 1659 th->th_seq++; 1660 if (th->th_urp > 1) 1661 th->th_urp--; 1662 else 1663 thflags &= ~TH_URG; 1664 todrop--; 1665 } 1666 /* 1667 * Following if statement from Stevens, vol. 2, p. 960. 1668 */ 1669 if (todrop > tlen 1670 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1671 /* 1672 * Any valid FIN must be to the left of the window. 1673 * At this point the FIN must be a duplicate or out 1674 * of sequence; drop it. 1675 */ 1676 thflags &= ~TH_FIN; 1677 1678 /* 1679 * Send an ACK to resynchronize and drop any data. 1680 * But keep on processing for RST or ACK. 1681 */ 1682 tp->t_flags |= TF_ACKNOW; 1683 todrop = tlen; 1684 tcpstat.tcps_rcvduppack++; 1685 tcpstat.tcps_rcvdupbyte += todrop; 1686 } else { 1687 tcpstat.tcps_rcvpartduppack++; 1688 tcpstat.tcps_rcvpartdupbyte += todrop; 1689 } 1690 drop_hdrlen += todrop; /* drop from the top afterwards */ 1691 th->th_seq += todrop; 1692 tlen -= todrop; 1693 if (th->th_urp > todrop) 1694 th->th_urp -= todrop; 1695 else { 1696 thflags &= ~TH_URG; 1697 th->th_urp = 0; 1698 } 1699 } 1700 1701 /* 1702 * If new data are received on a connection after the 1703 * user processes are gone, then RST the other end. 1704 */ 1705 if ((so->so_state & SS_NOFDREF) && 1706 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1707 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1708 "locked")); 1709 tp = tcp_close(tp); 1710 tcpstat.tcps_rcvafterclose++; 1711 rstreason = BANDLIM_UNLIMITED; 1712 goto dropwithreset; 1713 } 1714 1715 /* 1716 * If segment ends after window, drop trailing data 1717 * (and PUSH and FIN); if nothing left, just ACK. 1718 */ 1719 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1720 if (todrop > 0) { 1721 tcpstat.tcps_rcvpackafterwin++; 1722 if (todrop >= tlen) { 1723 tcpstat.tcps_rcvbyteafterwin += tlen; 1724 /* 1725 * If a new connection request is received 1726 * while in TIME_WAIT, drop the old connection 1727 * and start over if the sequence numbers 1728 * are above the previous ones. 1729 */ 1730 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1731 if (thflags & TH_SYN && 1732 tp->t_state == TCPS_TIME_WAIT && 1733 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1734 KASSERT(headlocked, ("trimthenstep6: " 1735 "tcp_close.4: head not locked")); 1736 tp = tcp_close(tp); 1737 goto findpcb; 1738 } 1739 /* 1740 * If window is closed can only take segments at 1741 * window edge, and have to drop data and PUSH from 1742 * incoming segments. Continue processing, but 1743 * remember to ack. Otherwise, drop segment 1744 * and ack. 1745 */ 1746 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1747 tp->t_flags |= TF_ACKNOW; 1748 tcpstat.tcps_rcvwinprobe++; 1749 } else 1750 goto dropafterack; 1751 } else 1752 tcpstat.tcps_rcvbyteafterwin += todrop; 1753 m_adj(m, -todrop); 1754 tlen -= todrop; 1755 thflags &= ~(TH_PUSH|TH_FIN); 1756 } 1757 1758 /* 1759 * If last ACK falls within this segment's sequence numbers, 1760 * record its timestamp. 1761 * NOTE: 1762 * 1) That the test incorporates suggestions from the latest 1763 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1764 * 2) That updating only on newer timestamps interferes with 1765 * our earlier PAWS tests, so this check should be solely 1766 * predicated on the sequence space of this segment. 1767 * 3) That we modify the segment boundary check to be 1768 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1769 * instead of RFC1323's 1770 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1771 * This modified check allows us to overcome RFC1323's 1772 * limitations as described in Stevens TCP/IP Illustrated 1773 * Vol. 2 p.869. In such cases, we can still calculate the 1774 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1775 */ 1776 if ((to.to_flags & TOF_TS) != 0 && 1777 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1778 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1779 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1780 tp->ts_recent_age = ticks; 1781 tp->ts_recent = to.to_tsval; 1782 } 1783 1784 /* 1785 * If a SYN is in the window, then this is an 1786 * error and we send an RST and drop the connection. 1787 */ 1788 if (thflags & TH_SYN) { 1789 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1790 "head not locked")); 1791 tp = tcp_drop(tp, ECONNRESET); 1792 rstreason = BANDLIM_UNLIMITED; 1793 goto drop; 1794 } 1795 1796 /* 1797 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1798 * flag is on (half-synchronized state), then queue data for 1799 * later processing; else drop segment and return. 1800 */ 1801 if ((thflags & TH_ACK) == 0) { 1802 if (tp->t_state == TCPS_SYN_RECEIVED || 1803 (tp->t_flags & TF_NEEDSYN)) 1804 goto step6; 1805 else if (tp->t_flags & TF_ACKNOW) 1806 goto dropafterack; 1807 else 1808 goto drop; 1809 } 1810 1811 /* 1812 * Ack processing. 1813 */ 1814 switch (tp->t_state) { 1815 1816 /* 1817 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1818 * ESTABLISHED state and continue processing. 1819 * The ACK was checked above. 1820 */ 1821 case TCPS_SYN_RECEIVED: 1822 1823 tcpstat.tcps_connects++; 1824 soisconnected(so); 1825 /* Do window scaling? */ 1826 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1827 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1828 tp->rcv_scale = tp->request_r_scale; 1829 tp->snd_wnd = tiwin; 1830 } 1831 /* 1832 * Make transitions: 1833 * SYN-RECEIVED -> ESTABLISHED 1834 * SYN-RECEIVED* -> FIN-WAIT-1 1835 */ 1836 tp->t_starttime = ticks; 1837 if (tp->t_flags & TF_NEEDFIN) { 1838 tp->t_state = TCPS_FIN_WAIT_1; 1839 tp->t_flags &= ~TF_NEEDFIN; 1840 } else { 1841 tp->t_state = TCPS_ESTABLISHED; 1842 callout_reset(tp->tt_keep, tcp_keepidle, 1843 tcp_timer_keep, tp); 1844 } 1845 /* 1846 * If segment contains data or ACK, will call tcp_reass() 1847 * later; if not, do so now to pass queued data to user. 1848 */ 1849 if (tlen == 0 && (thflags & TH_FIN) == 0) 1850 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1851 (struct mbuf *)0); 1852 tp->snd_wl1 = th->th_seq - 1; 1853 /* FALLTHROUGH */ 1854 1855 /* 1856 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1857 * ACKs. If the ack is in the range 1858 * tp->snd_una < th->th_ack <= tp->snd_max 1859 * then advance tp->snd_una to th->th_ack and drop 1860 * data from the retransmission queue. If this ACK reflects 1861 * more up to date window information we update our window information. 1862 */ 1863 case TCPS_ESTABLISHED: 1864 case TCPS_FIN_WAIT_1: 1865 case TCPS_FIN_WAIT_2: 1866 case TCPS_CLOSE_WAIT: 1867 case TCPS_CLOSING: 1868 case TCPS_LAST_ACK: 1869 case TCPS_TIME_WAIT: 1870 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1871 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1872 tcpstat.tcps_rcvacktoomuch++; 1873 goto dropafterack; 1874 } 1875 if (tp->sack_enable && 1876 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1877 tcp_sack_doack(tp, &to, th->th_ack); 1878 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1879 if (tlen == 0 && tiwin == tp->snd_wnd) { 1880 tcpstat.tcps_rcvdupack++; 1881 /* 1882 * If we have outstanding data (other than 1883 * a window probe), this is a completely 1884 * duplicate ack (ie, window info didn't 1885 * change), the ack is the biggest we've 1886 * seen and we've seen exactly our rexmt 1887 * threshhold of them, assume a packet 1888 * has been dropped and retransmit it. 1889 * Kludge snd_nxt & the congestion 1890 * window so we send only this one 1891 * packet. 1892 * 1893 * We know we're losing at the current 1894 * window size so do congestion avoidance 1895 * (set ssthresh to half the current window 1896 * and pull our congestion window back to 1897 * the new ssthresh). 1898 * 1899 * Dup acks mean that packets have left the 1900 * network (they're now cached at the receiver) 1901 * so bump cwnd by the amount in the receiver 1902 * to keep a constant cwnd packets in the 1903 * network. 1904 */ 1905 if (!callout_active(tp->tt_rexmt) || 1906 th->th_ack != tp->snd_una) 1907 tp->t_dupacks = 0; 1908 else if (++tp->t_dupacks > tcprexmtthresh || 1909 ((tcp_do_newreno || tp->sack_enable) && 1910 IN_FASTRECOVERY(tp))) { 1911 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1912 int awnd; 1913 1914 /* 1915 * Compute the amount of data in flight first. 1916 * We can inject new data into the pipe iff 1917 * we have less than 1/2 the original window's 1918 * worth of data in flight. 1919 */ 1920 awnd = (tp->snd_nxt - tp->snd_fack) + 1921 tp->sackhint.sack_bytes_rexmit; 1922 if (awnd < tp->snd_ssthresh) { 1923 tp->snd_cwnd += tp->t_maxseg; 1924 if (tp->snd_cwnd > tp->snd_ssthresh) 1925 tp->snd_cwnd = tp->snd_ssthresh; 1926 } 1927 } else 1928 tp->snd_cwnd += tp->t_maxseg; 1929 (void) tcp_output(tp); 1930 goto drop; 1931 } else if (tp->t_dupacks == tcprexmtthresh) { 1932 tcp_seq onxt = tp->snd_nxt; 1933 u_int win; 1934 1935 /* 1936 * If we're doing sack, check to 1937 * see if we're already in sack 1938 * recovery. If we're not doing sack, 1939 * check to see if we're in newreno 1940 * recovery. 1941 */ 1942 if (tp->sack_enable) { 1943 if (IN_FASTRECOVERY(tp)) { 1944 tp->t_dupacks = 0; 1945 break; 1946 } 1947 } else if (tcp_do_newreno) { 1948 if (SEQ_LEQ(th->th_ack, 1949 tp->snd_recover)) { 1950 tp->t_dupacks = 0; 1951 break; 1952 } 1953 } 1954 win = min(tp->snd_wnd, tp->snd_cwnd) / 1955 2 / tp->t_maxseg; 1956 if (win < 2) 1957 win = 2; 1958 tp->snd_ssthresh = win * tp->t_maxseg; 1959 ENTER_FASTRECOVERY(tp); 1960 tp->snd_recover = tp->snd_max; 1961 callout_stop(tp->tt_rexmt); 1962 tp->t_rtttime = 0; 1963 if (tp->sack_enable) { 1964 tcpstat.tcps_sack_recovery_episode++; 1965 tp->sack_newdata = tp->snd_nxt; 1966 tp->snd_cwnd = tp->t_maxseg; 1967 (void) tcp_output(tp); 1968 goto drop; 1969 } 1970 tp->snd_nxt = th->th_ack; 1971 tp->snd_cwnd = tp->t_maxseg; 1972 (void) tcp_output(tp); 1973 KASSERT(tp->snd_limited <= 2, 1974 ("tp->snd_limited too big")); 1975 tp->snd_cwnd = tp->snd_ssthresh + 1976 tp->t_maxseg * 1977 (tp->t_dupacks - tp->snd_limited); 1978 if (SEQ_GT(onxt, tp->snd_nxt)) 1979 tp->snd_nxt = onxt; 1980 goto drop; 1981 } else if (tcp_do_rfc3042) { 1982 u_long oldcwnd = tp->snd_cwnd; 1983 tcp_seq oldsndmax = tp->snd_max; 1984 u_int sent; 1985 1986 KASSERT(tp->t_dupacks == 1 || 1987 tp->t_dupacks == 2, 1988 ("dupacks not 1 or 2")); 1989 if (tp->t_dupacks == 1) 1990 tp->snd_limited = 0; 1991 tp->snd_cwnd = 1992 (tp->snd_nxt - tp->snd_una) + 1993 (tp->t_dupacks - tp->snd_limited) * 1994 tp->t_maxseg; 1995 (void) tcp_output(tp); 1996 sent = tp->snd_max - oldsndmax; 1997 if (sent > tp->t_maxseg) { 1998 KASSERT((tp->t_dupacks == 2 && 1999 tp->snd_limited == 0) || 2000 (sent == tp->t_maxseg + 1 && 2001 tp->t_flags & TF_SENTFIN), 2002 ("sent too much")); 2003 tp->snd_limited = 2; 2004 } else if (sent > 0) 2005 ++tp->snd_limited; 2006 tp->snd_cwnd = oldcwnd; 2007 goto drop; 2008 } 2009 } else 2010 tp->t_dupacks = 0; 2011 break; 2012 } 2013 2014 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2015 2016 /* 2017 * If the congestion window was inflated to account 2018 * for the other side's cached packets, retract it. 2019 */ 2020 if (tcp_do_newreno || tp->sack_enable) { 2021 if (IN_FASTRECOVERY(tp)) { 2022 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2023 if (tp->sack_enable) 2024 tcp_sack_partialack(tp, th); 2025 else 2026 tcp_newreno_partial_ack(tp, th); 2027 } else { 2028 /* 2029 * Out of fast recovery. 2030 * Window inflation should have left us 2031 * with approximately snd_ssthresh 2032 * outstanding data. 2033 * But in case we would be inclined to 2034 * send a burst, better to do it via 2035 * the slow start mechanism. 2036 */ 2037 if (SEQ_GT(th->th_ack + 2038 tp->snd_ssthresh, 2039 tp->snd_max)) 2040 tp->snd_cwnd = tp->snd_max - 2041 th->th_ack + 2042 tp->t_maxseg; 2043 else 2044 tp->snd_cwnd = tp->snd_ssthresh; 2045 } 2046 } 2047 } else { 2048 if (tp->t_dupacks >= tcprexmtthresh && 2049 tp->snd_cwnd > tp->snd_ssthresh) 2050 tp->snd_cwnd = tp->snd_ssthresh; 2051 } 2052 tp->t_dupacks = 0; 2053 /* 2054 * If we reach this point, ACK is not a duplicate, 2055 * i.e., it ACKs something we sent. 2056 */ 2057 if (tp->t_flags & TF_NEEDSYN) { 2058 /* 2059 * T/TCP: Connection was half-synchronized, and our 2060 * SYN has been ACK'd (so connection is now fully 2061 * synchronized). Go to non-starred state, 2062 * increment snd_una for ACK of SYN, and check if 2063 * we can do window scaling. 2064 */ 2065 tp->t_flags &= ~TF_NEEDSYN; 2066 tp->snd_una++; 2067 /* Do window scaling? */ 2068 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2069 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2070 tp->rcv_scale = tp->request_r_scale; 2071 /* Send window already scaled. */ 2072 } 2073 } 2074 2075 process_ACK: 2076 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2077 "locked")); 2078 INP_LOCK_ASSERT(inp); 2079 2080 acked = th->th_ack - tp->snd_una; 2081 tcpstat.tcps_rcvackpack++; 2082 tcpstat.tcps_rcvackbyte += acked; 2083 2084 /* 2085 * If we just performed our first retransmit, and the ACK 2086 * arrives within our recovery window, then it was a mistake 2087 * to do the retransmit in the first place. Recover our 2088 * original cwnd and ssthresh, and proceed to transmit where 2089 * we left off. 2090 */ 2091 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2092 ++tcpstat.tcps_sndrexmitbad; 2093 tp->snd_cwnd = tp->snd_cwnd_prev; 2094 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2095 tp->snd_recover = tp->snd_recover_prev; 2096 if (tp->t_flags & TF_WASFRECOVERY) 2097 ENTER_FASTRECOVERY(tp); 2098 tp->snd_nxt = tp->snd_max; 2099 tp->t_badrxtwin = 0; /* XXX probably not required */ 2100 } 2101 2102 /* 2103 * If we have a timestamp reply, update smoothed 2104 * round trip time. If no timestamp is present but 2105 * transmit timer is running and timed sequence 2106 * number was acked, update smoothed round trip time. 2107 * Since we now have an rtt measurement, cancel the 2108 * timer backoff (cf., Phil Karn's retransmit alg.). 2109 * Recompute the initial retransmit timer. 2110 * 2111 * Some boxes send broken timestamp replies 2112 * during the SYN+ACK phase, ignore 2113 * timestamps of 0 or we could calculate a 2114 * huge RTT and blow up the retransmit timer. 2115 */ 2116 if ((to.to_flags & TOF_TS) != 0 && 2117 to.to_tsecr) { 2118 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2119 tp->t_rttlow = ticks - to.to_tsecr; 2120 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2121 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2122 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2123 tp->t_rttlow = ticks - tp->t_rtttime; 2124 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2125 } 2126 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2127 2128 /* 2129 * If all outstanding data is acked, stop retransmit 2130 * timer and remember to restart (more output or persist). 2131 * If there is more data to be acked, restart retransmit 2132 * timer, using current (possibly backed-off) value. 2133 */ 2134 if (th->th_ack == tp->snd_max) { 2135 callout_stop(tp->tt_rexmt); 2136 needoutput = 1; 2137 } else if (!callout_active(tp->tt_persist)) 2138 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2139 tcp_timer_rexmt, tp); 2140 2141 /* 2142 * If no data (only SYN) was ACK'd, 2143 * skip rest of ACK processing. 2144 */ 2145 if (acked == 0) 2146 goto step6; 2147 2148 /* 2149 * When new data is acked, open the congestion window. 2150 * If the window gives us less than ssthresh packets 2151 * in flight, open exponentially (maxseg per packet). 2152 * Otherwise open linearly: maxseg per window 2153 * (maxseg^2 / cwnd per packet). 2154 */ 2155 if ((!tcp_do_newreno && !tp->sack_enable) || 2156 !IN_FASTRECOVERY(tp)) { 2157 register u_int cw = tp->snd_cwnd; 2158 register u_int incr = tp->t_maxseg; 2159 if (cw > tp->snd_ssthresh) 2160 incr = incr * incr / cw; 2161 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2162 } 2163 SOCKBUF_LOCK(&so->so_snd); 2164 if (acked > so->so_snd.sb_cc) { 2165 tp->snd_wnd -= so->so_snd.sb_cc; 2166 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2167 ourfinisacked = 1; 2168 } else { 2169 sbdrop_locked(&so->so_snd, acked); 2170 tp->snd_wnd -= acked; 2171 ourfinisacked = 0; 2172 } 2173 sowwakeup_locked(so); 2174 /* detect una wraparound */ 2175 if ((tcp_do_newreno || tp->sack_enable) && 2176 !IN_FASTRECOVERY(tp) && 2177 SEQ_GT(tp->snd_una, tp->snd_recover) && 2178 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2179 tp->snd_recover = th->th_ack - 1; 2180 if ((tcp_do_newreno || tp->sack_enable) && 2181 IN_FASTRECOVERY(tp) && 2182 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2183 EXIT_FASTRECOVERY(tp); 2184 tp->snd_una = th->th_ack; 2185 if (tp->sack_enable) { 2186 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2187 tp->snd_recover = tp->snd_una; 2188 } 2189 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2190 tp->snd_nxt = tp->snd_una; 2191 2192 switch (tp->t_state) { 2193 2194 /* 2195 * In FIN_WAIT_1 STATE in addition to the processing 2196 * for the ESTABLISHED state if our FIN is now acknowledged 2197 * then enter FIN_WAIT_2. 2198 */ 2199 case TCPS_FIN_WAIT_1: 2200 if (ourfinisacked) { 2201 /* 2202 * If we can't receive any more 2203 * data, then closing user can proceed. 2204 * Starting the timer is contrary to the 2205 * specification, but if we don't get a FIN 2206 * we'll hang forever. 2207 */ 2208 /* XXXjl 2209 * we should release the tp also, and use a 2210 * compressed state. 2211 */ 2212 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2213 soisdisconnected(so); 2214 callout_reset(tp->tt_2msl, tcp_maxidle, 2215 tcp_timer_2msl, tp); 2216 } 2217 tp->t_state = TCPS_FIN_WAIT_2; 2218 } 2219 break; 2220 2221 /* 2222 * In CLOSING STATE in addition to the processing for 2223 * the ESTABLISHED state if the ACK acknowledges our FIN 2224 * then enter the TIME-WAIT state, otherwise ignore 2225 * the segment. 2226 */ 2227 case TCPS_CLOSING: 2228 if (ourfinisacked) { 2229 KASSERT(headlocked, ("tcp_input: process_ACK: " 2230 "head not locked")); 2231 tcp_twstart(tp); 2232 INP_INFO_WUNLOCK(&tcbinfo); 2233 m_freem(m); 2234 return; 2235 } 2236 break; 2237 2238 /* 2239 * In LAST_ACK, we may still be waiting for data to drain 2240 * and/or to be acked, as well as for the ack of our FIN. 2241 * If our FIN is now acknowledged, delete the TCB, 2242 * enter the closed state and return. 2243 */ 2244 case TCPS_LAST_ACK: 2245 if (ourfinisacked) { 2246 KASSERT(headlocked, ("tcp_input: process_ACK:" 2247 " tcp_close: head not locked")); 2248 tp = tcp_close(tp); 2249 goto drop; 2250 } 2251 break; 2252 2253 /* 2254 * In TIME_WAIT state the only thing that should arrive 2255 * is a retransmission of the remote FIN. Acknowledge 2256 * it and restart the finack timer. 2257 */ 2258 case TCPS_TIME_WAIT: 2259 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2260 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2261 tcp_timer_2msl, tp); 2262 goto dropafterack; 2263 } 2264 } 2265 2266 step6: 2267 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2268 INP_LOCK_ASSERT(inp); 2269 2270 /* 2271 * Update window information. 2272 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2273 */ 2274 if ((thflags & TH_ACK) && 2275 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2276 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2277 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2278 /* keep track of pure window updates */ 2279 if (tlen == 0 && 2280 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2281 tcpstat.tcps_rcvwinupd++; 2282 tp->snd_wnd = tiwin; 2283 tp->snd_wl1 = th->th_seq; 2284 tp->snd_wl2 = th->th_ack; 2285 if (tp->snd_wnd > tp->max_sndwnd) 2286 tp->max_sndwnd = tp->snd_wnd; 2287 needoutput = 1; 2288 } 2289 2290 /* 2291 * Process segments with URG. 2292 */ 2293 if ((thflags & TH_URG) && th->th_urp && 2294 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2295 /* 2296 * This is a kludge, but if we receive and accept 2297 * random urgent pointers, we'll crash in 2298 * soreceive. It's hard to imagine someone 2299 * actually wanting to send this much urgent data. 2300 */ 2301 SOCKBUF_LOCK(&so->so_rcv); 2302 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2303 th->th_urp = 0; /* XXX */ 2304 thflags &= ~TH_URG; /* XXX */ 2305 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2306 goto dodata; /* XXX */ 2307 } 2308 /* 2309 * If this segment advances the known urgent pointer, 2310 * then mark the data stream. This should not happen 2311 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2312 * a FIN has been received from the remote side. 2313 * In these states we ignore the URG. 2314 * 2315 * According to RFC961 (Assigned Protocols), 2316 * the urgent pointer points to the last octet 2317 * of urgent data. We continue, however, 2318 * to consider it to indicate the first octet 2319 * of data past the urgent section as the original 2320 * spec states (in one of two places). 2321 */ 2322 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2323 tp->rcv_up = th->th_seq + th->th_urp; 2324 so->so_oobmark = so->so_rcv.sb_cc + 2325 (tp->rcv_up - tp->rcv_nxt) - 1; 2326 if (so->so_oobmark == 0) 2327 so->so_rcv.sb_state |= SBS_RCVATMARK; 2328 sohasoutofband(so); 2329 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2330 } 2331 SOCKBUF_UNLOCK(&so->so_rcv); 2332 /* 2333 * Remove out of band data so doesn't get presented to user. 2334 * This can happen independent of advancing the URG pointer, 2335 * but if two URG's are pending at once, some out-of-band 2336 * data may creep in... ick. 2337 */ 2338 if (th->th_urp <= (u_long)tlen && 2339 !(so->so_options & SO_OOBINLINE)) { 2340 /* hdr drop is delayed */ 2341 tcp_pulloutofband(so, th, m, drop_hdrlen); 2342 } 2343 } else { 2344 /* 2345 * If no out of band data is expected, 2346 * pull receive urgent pointer along 2347 * with the receive window. 2348 */ 2349 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2350 tp->rcv_up = tp->rcv_nxt; 2351 } 2352 dodata: /* XXX */ 2353 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2354 INP_LOCK_ASSERT(inp); 2355 2356 /* 2357 * Process the segment text, merging it into the TCP sequencing queue, 2358 * and arranging for acknowledgment of receipt if necessary. 2359 * This process logically involves adjusting tp->rcv_wnd as data 2360 * is presented to the user (this happens in tcp_usrreq.c, 2361 * case PRU_RCVD). If a FIN has already been received on this 2362 * connection then we just ignore the text. 2363 */ 2364 if ((tlen || (thflags & TH_FIN)) && 2365 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2366 tcp_seq save_start = th->th_seq; 2367 tcp_seq save_end = th->th_seq + tlen; 2368 m_adj(m, drop_hdrlen); /* delayed header drop */ 2369 /* 2370 * Insert segment which includes th into TCP reassembly queue 2371 * with control block tp. Set thflags to whether reassembly now 2372 * includes a segment with FIN. This handles the common case 2373 * inline (segment is the next to be received on an established 2374 * connection, and the queue is empty), avoiding linkage into 2375 * and removal from the queue and repetition of various 2376 * conversions. 2377 * Set DELACK for segments received in order, but ack 2378 * immediately when segments are out of order (so 2379 * fast retransmit can work). 2380 */ 2381 if (th->th_seq == tp->rcv_nxt && 2382 LIST_EMPTY(&tp->t_segq) && 2383 TCPS_HAVEESTABLISHED(tp->t_state)) { 2384 if (DELAY_ACK(tp)) 2385 tp->t_flags |= TF_DELACK; 2386 else 2387 tp->t_flags |= TF_ACKNOW; 2388 tp->rcv_nxt += tlen; 2389 thflags = th->th_flags & TH_FIN; 2390 tcpstat.tcps_rcvpack++; 2391 tcpstat.tcps_rcvbyte += tlen; 2392 ND6_HINT(tp); 2393 SOCKBUF_LOCK(&so->so_rcv); 2394 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2395 m_freem(m); 2396 else 2397 sbappendstream_locked(&so->so_rcv, m); 2398 sorwakeup_locked(so); 2399 } else { 2400 thflags = tcp_reass(tp, th, &tlen, m); 2401 tp->t_flags |= TF_ACKNOW; 2402 } 2403 if (tlen > 0 && tp->sack_enable) 2404 tcp_update_sack_list(tp, save_start, save_end); 2405 /* 2406 * Note the amount of data that peer has sent into 2407 * our window, in order to estimate the sender's 2408 * buffer size. 2409 */ 2410 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2411 } else { 2412 m_freem(m); 2413 thflags &= ~TH_FIN; 2414 } 2415 2416 /* 2417 * If FIN is received ACK the FIN and let the user know 2418 * that the connection is closing. 2419 */ 2420 if (thflags & TH_FIN) { 2421 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2422 socantrcvmore(so); 2423 /* 2424 * If connection is half-synchronized 2425 * (ie NEEDSYN flag on) then delay ACK, 2426 * so it may be piggybacked when SYN is sent. 2427 * Otherwise, since we received a FIN then no 2428 * more input can be expected, send ACK now. 2429 */ 2430 if (tp->t_flags & TF_NEEDSYN) 2431 tp->t_flags |= TF_DELACK; 2432 else 2433 tp->t_flags |= TF_ACKNOW; 2434 tp->rcv_nxt++; 2435 } 2436 switch (tp->t_state) { 2437 2438 /* 2439 * In SYN_RECEIVED and ESTABLISHED STATES 2440 * enter the CLOSE_WAIT state. 2441 */ 2442 case TCPS_SYN_RECEIVED: 2443 tp->t_starttime = ticks; 2444 /*FALLTHROUGH*/ 2445 case TCPS_ESTABLISHED: 2446 tp->t_state = TCPS_CLOSE_WAIT; 2447 break; 2448 2449 /* 2450 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2451 * enter the CLOSING state. 2452 */ 2453 case TCPS_FIN_WAIT_1: 2454 tp->t_state = TCPS_CLOSING; 2455 break; 2456 2457 /* 2458 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2459 * starting the time-wait timer, turning off the other 2460 * standard timers. 2461 */ 2462 case TCPS_FIN_WAIT_2: 2463 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2464 "TCP_FIN_WAIT_2: head not locked")); 2465 tcp_twstart(tp); 2466 INP_INFO_WUNLOCK(&tcbinfo); 2467 return; 2468 2469 /* 2470 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2471 */ 2472 case TCPS_TIME_WAIT: 2473 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2474 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2475 tcp_timer_2msl, tp); 2476 break; 2477 } 2478 } 2479 INP_INFO_WUNLOCK(&tcbinfo); 2480 headlocked = 0; 2481 #ifdef TCPDEBUG 2482 if (so->so_options & SO_DEBUG) 2483 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2484 &tcp_savetcp, 0); 2485 #endif 2486 2487 /* 2488 * Return any desired output. 2489 */ 2490 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2491 (void) tcp_output(tp); 2492 2493 check_delack: 2494 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2495 INP_LOCK_ASSERT(inp); 2496 if (tp->t_flags & TF_DELACK) { 2497 tp->t_flags &= ~TF_DELACK; 2498 callout_reset(tp->tt_delack, tcp_delacktime, 2499 tcp_timer_delack, tp); 2500 } 2501 INP_UNLOCK(inp); 2502 return; 2503 2504 dropafterack: 2505 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2506 /* 2507 * Generate an ACK dropping incoming segment if it occupies 2508 * sequence space, where the ACK reflects our state. 2509 * 2510 * We can now skip the test for the RST flag since all 2511 * paths to this code happen after packets containing 2512 * RST have been dropped. 2513 * 2514 * In the SYN-RECEIVED state, don't send an ACK unless the 2515 * segment we received passes the SYN-RECEIVED ACK test. 2516 * If it fails send a RST. This breaks the loop in the 2517 * "LAND" DoS attack, and also prevents an ACK storm 2518 * between two listening ports that have been sent forged 2519 * SYN segments, each with the source address of the other. 2520 */ 2521 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2522 (SEQ_GT(tp->snd_una, th->th_ack) || 2523 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2524 rstreason = BANDLIM_RST_OPENPORT; 2525 goto dropwithreset; 2526 } 2527 #ifdef TCPDEBUG 2528 if (so->so_options & SO_DEBUG) 2529 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2530 &tcp_savetcp, 0); 2531 #endif 2532 KASSERT(headlocked, ("headlocked should be 1")); 2533 INP_INFO_WUNLOCK(&tcbinfo); 2534 tp->t_flags |= TF_ACKNOW; 2535 (void) tcp_output(tp); 2536 INP_UNLOCK(inp); 2537 m_freem(m); 2538 return; 2539 2540 dropwithreset: 2541 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2542 /* 2543 * Generate a RST, dropping incoming segment. 2544 * Make ACK acceptable to originator of segment. 2545 * Don't bother to respond if destination was broadcast/multicast. 2546 */ 2547 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2548 goto drop; 2549 if (isipv6) { 2550 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2551 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2552 goto drop; 2553 } else { 2554 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2555 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2556 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2557 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2558 goto drop; 2559 } 2560 /* IPv6 anycast check is done at tcp6_input() */ 2561 2562 /* 2563 * Perform bandwidth limiting. 2564 */ 2565 if (badport_bandlim(rstreason) < 0) 2566 goto drop; 2567 2568 #ifdef TCPDEBUG 2569 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2570 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2571 &tcp_savetcp, 0); 2572 #endif 2573 2574 if (thflags & TH_ACK) 2575 /* mtod() below is safe as long as hdr dropping is delayed */ 2576 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2577 TH_RST); 2578 else { 2579 if (thflags & TH_SYN) 2580 tlen++; 2581 /* mtod() below is safe as long as hdr dropping is delayed */ 2582 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2583 (tcp_seq)0, TH_RST|TH_ACK); 2584 } 2585 2586 if (tp != NULL) 2587 INP_UNLOCK(inp); 2588 if (headlocked) 2589 INP_INFO_WUNLOCK(&tcbinfo); 2590 return; 2591 2592 drop: 2593 /* 2594 * Drop space held by incoming segment and return. 2595 */ 2596 #ifdef TCPDEBUG 2597 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2598 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2599 &tcp_savetcp, 0); 2600 #endif 2601 if (tp != NULL) 2602 INP_UNLOCK(inp); 2603 if (headlocked) 2604 INP_INFO_WUNLOCK(&tcbinfo); 2605 m_freem(m); 2606 return; 2607 } 2608 2609 /* 2610 * Parse TCP options and place in tcpopt. 2611 */ 2612 static void 2613 tcp_dooptions(to, cp, cnt, flags) 2614 struct tcpopt *to; 2615 u_char *cp; 2616 int cnt; 2617 int flags; 2618 { 2619 int opt, optlen; 2620 2621 to->to_flags = 0; 2622 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2623 opt = cp[0]; 2624 if (opt == TCPOPT_EOL) 2625 break; 2626 if (opt == TCPOPT_NOP) 2627 optlen = 1; 2628 else { 2629 if (cnt < 2) 2630 break; 2631 optlen = cp[1]; 2632 if (optlen < 2 || optlen > cnt) 2633 break; 2634 } 2635 switch (opt) { 2636 case TCPOPT_MAXSEG: 2637 if (optlen != TCPOLEN_MAXSEG) 2638 continue; 2639 if (!(flags & TO_SYN)) 2640 continue; 2641 to->to_flags |= TOF_MSS; 2642 bcopy((char *)cp + 2, 2643 (char *)&to->to_mss, sizeof(to->to_mss)); 2644 to->to_mss = ntohs(to->to_mss); 2645 break; 2646 case TCPOPT_WINDOW: 2647 if (optlen != TCPOLEN_WINDOW) 2648 continue; 2649 if (!(flags & TO_SYN)) 2650 continue; 2651 to->to_flags |= TOF_SCALE; 2652 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2653 break; 2654 case TCPOPT_TIMESTAMP: 2655 if (optlen != TCPOLEN_TIMESTAMP) 2656 continue; 2657 to->to_flags |= TOF_TS; 2658 bcopy((char *)cp + 2, 2659 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2660 to->to_tsval = ntohl(to->to_tsval); 2661 bcopy((char *)cp + 6, 2662 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2663 to->to_tsecr = ntohl(to->to_tsecr); 2664 break; 2665 #ifdef TCP_SIGNATURE 2666 /* 2667 * XXX In order to reply to a host which has set the 2668 * TCP_SIGNATURE option in its initial SYN, we have to 2669 * record the fact that the option was observed here 2670 * for the syncache code to perform the correct response. 2671 */ 2672 case TCPOPT_SIGNATURE: 2673 if (optlen != TCPOLEN_SIGNATURE) 2674 continue; 2675 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2676 break; 2677 #endif 2678 case TCPOPT_SACK_PERMITTED: 2679 if (optlen != TCPOLEN_SACK_PERMITTED) 2680 continue; 2681 if (!(flags & TO_SYN)) 2682 continue; 2683 if (!tcp_do_sack) 2684 continue; 2685 to->to_flags |= TOF_SACK; 2686 break; 2687 case TCPOPT_SACK: 2688 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2689 continue; 2690 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2691 to->to_sacks = cp + 2; 2692 tcpstat.tcps_sack_rcv_blocks++; 2693 break; 2694 default: 2695 continue; 2696 } 2697 } 2698 } 2699 2700 /* 2701 * Pull out of band byte out of a segment so 2702 * it doesn't appear in the user's data queue. 2703 * It is still reflected in the segment length for 2704 * sequencing purposes. 2705 */ 2706 static void 2707 tcp_pulloutofband(so, th, m, off) 2708 struct socket *so; 2709 struct tcphdr *th; 2710 register struct mbuf *m; 2711 int off; /* delayed to be droped hdrlen */ 2712 { 2713 int cnt = off + th->th_urp - 1; 2714 2715 while (cnt >= 0) { 2716 if (m->m_len > cnt) { 2717 char *cp = mtod(m, caddr_t) + cnt; 2718 struct tcpcb *tp = sototcpcb(so); 2719 2720 tp->t_iobc = *cp; 2721 tp->t_oobflags |= TCPOOB_HAVEDATA; 2722 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2723 m->m_len--; 2724 if (m->m_flags & M_PKTHDR) 2725 m->m_pkthdr.len--; 2726 return; 2727 } 2728 cnt -= m->m_len; 2729 m = m->m_next; 2730 if (m == 0) 2731 break; 2732 } 2733 panic("tcp_pulloutofband"); 2734 } 2735 2736 /* 2737 * Collect new round-trip time estimate 2738 * and update averages and current timeout. 2739 */ 2740 static void 2741 tcp_xmit_timer(tp, rtt) 2742 register struct tcpcb *tp; 2743 int rtt; 2744 { 2745 register int delta; 2746 2747 INP_LOCK_ASSERT(tp->t_inpcb); 2748 2749 tcpstat.tcps_rttupdated++; 2750 tp->t_rttupdated++; 2751 if (tp->t_srtt != 0) { 2752 /* 2753 * srtt is stored as fixed point with 5 bits after the 2754 * binary point (i.e., scaled by 8). The following magic 2755 * is equivalent to the smoothing algorithm in rfc793 with 2756 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2757 * point). Adjust rtt to origin 0. 2758 */ 2759 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2760 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2761 2762 if ((tp->t_srtt += delta) <= 0) 2763 tp->t_srtt = 1; 2764 2765 /* 2766 * We accumulate a smoothed rtt variance (actually, a 2767 * smoothed mean difference), then set the retransmit 2768 * timer to smoothed rtt + 4 times the smoothed variance. 2769 * rttvar is stored as fixed point with 4 bits after the 2770 * binary point (scaled by 16). The following is 2771 * equivalent to rfc793 smoothing with an alpha of .75 2772 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2773 * rfc793's wired-in beta. 2774 */ 2775 if (delta < 0) 2776 delta = -delta; 2777 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2778 if ((tp->t_rttvar += delta) <= 0) 2779 tp->t_rttvar = 1; 2780 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2781 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2782 } else { 2783 /* 2784 * No rtt measurement yet - use the unsmoothed rtt. 2785 * Set the variance to half the rtt (so our first 2786 * retransmit happens at 3*rtt). 2787 */ 2788 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2789 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2790 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2791 } 2792 tp->t_rtttime = 0; 2793 tp->t_rxtshift = 0; 2794 2795 /* 2796 * the retransmit should happen at rtt + 4 * rttvar. 2797 * Because of the way we do the smoothing, srtt and rttvar 2798 * will each average +1/2 tick of bias. When we compute 2799 * the retransmit timer, we want 1/2 tick of rounding and 2800 * 1 extra tick because of +-1/2 tick uncertainty in the 2801 * firing of the timer. The bias will give us exactly the 2802 * 1.5 tick we need. But, because the bias is 2803 * statistical, we have to test that we don't drop below 2804 * the minimum feasible timer (which is 2 ticks). 2805 */ 2806 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2807 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2808 2809 /* 2810 * We received an ack for a packet that wasn't retransmitted; 2811 * it is probably safe to discard any error indications we've 2812 * received recently. This isn't quite right, but close enough 2813 * for now (a route might have failed after we sent a segment, 2814 * and the return path might not be symmetrical). 2815 */ 2816 tp->t_softerror = 0; 2817 } 2818 2819 /* 2820 * Determine a reasonable value for maxseg size. 2821 * If the route is known, check route for mtu. 2822 * If none, use an mss that can be handled on the outgoing 2823 * interface without forcing IP to fragment; if bigger than 2824 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2825 * to utilize large mbufs. If no route is found, route has no mtu, 2826 * or the destination isn't local, use a default, hopefully conservative 2827 * size (usually 512 or the default IP max size, but no more than the mtu 2828 * of the interface), as we can't discover anything about intervening 2829 * gateways or networks. We also initialize the congestion/slow start 2830 * window to be a single segment if the destination isn't local. 2831 * While looking at the routing entry, we also initialize other path-dependent 2832 * parameters from pre-set or cached values in the routing entry. 2833 * 2834 * Also take into account the space needed for options that we 2835 * send regularly. Make maxseg shorter by that amount to assure 2836 * that we can send maxseg amount of data even when the options 2837 * are present. Store the upper limit of the length of options plus 2838 * data in maxopd. 2839 * 2840 * 2841 * In case of T/TCP, we call this routine during implicit connection 2842 * setup as well (offer = -1), to initialize maxseg from the cached 2843 * MSS of our peer. 2844 * 2845 * NOTE that this routine is only called when we process an incoming 2846 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2847 */ 2848 void 2849 tcp_mss(tp, offer) 2850 struct tcpcb *tp; 2851 int offer; 2852 { 2853 int rtt, mss; 2854 u_long bufsize; 2855 u_long maxmtu; 2856 struct inpcb *inp = tp->t_inpcb; 2857 struct socket *so; 2858 struct hc_metrics_lite metrics; 2859 int origoffer = offer; 2860 #ifdef INET6 2861 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2862 size_t min_protoh = isipv6 ? 2863 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2864 sizeof (struct tcpiphdr); 2865 #else 2866 const size_t min_protoh = sizeof(struct tcpiphdr); 2867 #endif 2868 2869 /* initialize */ 2870 #ifdef INET6 2871 if (isipv6) { 2872 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2873 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2874 } else 2875 #endif 2876 { 2877 maxmtu = tcp_maxmtu(&inp->inp_inc); 2878 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2879 } 2880 so = inp->inp_socket; 2881 2882 /* 2883 * no route to sender, stay with default mss and return 2884 */ 2885 if (maxmtu == 0) 2886 return; 2887 2888 /* what have we got? */ 2889 switch (offer) { 2890 case 0: 2891 /* 2892 * Offer == 0 means that there was no MSS on the SYN 2893 * segment, in this case we use tcp_mssdflt. 2894 */ 2895 offer = 2896 #ifdef INET6 2897 isipv6 ? tcp_v6mssdflt : 2898 #endif 2899 tcp_mssdflt; 2900 break; 2901 2902 case -1: 2903 /* 2904 * Offer == -1 means that we didn't receive SYN yet. 2905 */ 2906 /* FALLTHROUGH */ 2907 2908 default: 2909 /* 2910 * Prevent DoS attack with too small MSS. Round up 2911 * to at least minmss. 2912 */ 2913 offer = max(offer, tcp_minmss); 2914 /* 2915 * Sanity check: make sure that maxopd will be large 2916 * enough to allow some data on segments even if the 2917 * all the option space is used (40bytes). Otherwise 2918 * funny things may happen in tcp_output. 2919 */ 2920 offer = max(offer, 64); 2921 } 2922 2923 /* 2924 * rmx information is now retrieved from tcp_hostcache 2925 */ 2926 tcp_hc_get(&inp->inp_inc, &metrics); 2927 2928 /* 2929 * if there's a discovered mtu int tcp hostcache, use it 2930 * else, use the link mtu. 2931 */ 2932 if (metrics.rmx_mtu) 2933 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2934 else { 2935 #ifdef INET6 2936 if (isipv6) { 2937 mss = maxmtu - min_protoh; 2938 if (!path_mtu_discovery && 2939 !in6_localaddr(&inp->in6p_faddr)) 2940 mss = min(mss, tcp_v6mssdflt); 2941 } else 2942 #endif 2943 { 2944 mss = maxmtu - min_protoh; 2945 if (!path_mtu_discovery && 2946 !in_localaddr(inp->inp_faddr)) 2947 mss = min(mss, tcp_mssdflt); 2948 } 2949 } 2950 mss = min(mss, offer); 2951 2952 /* 2953 * maxopd stores the maximum length of data AND options 2954 * in a segment; maxseg is the amount of data in a normal 2955 * segment. We need to store this value (maxopd) apart 2956 * from maxseg, because now every segment carries options 2957 * and thus we normally have somewhat less data in segments. 2958 */ 2959 tp->t_maxopd = mss; 2960 2961 /* 2962 * origoffer==-1 indicates, that no segments were received yet. 2963 * In this case we just guess. 2964 */ 2965 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2966 (origoffer == -1 || 2967 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2968 mss -= TCPOLEN_TSTAMP_APPA; 2969 tp->t_maxseg = mss; 2970 2971 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2972 if (mss > MCLBYTES) 2973 mss &= ~(MCLBYTES-1); 2974 #else 2975 if (mss > MCLBYTES) 2976 mss = mss / MCLBYTES * MCLBYTES; 2977 #endif 2978 tp->t_maxseg = mss; 2979 2980 /* 2981 * If there's a pipesize, change the socket buffer to that size, 2982 * don't change if sb_hiwat is different than default (then it 2983 * has been changed on purpose with setsockopt). 2984 * Make the socket buffers an integral number of mss units; 2985 * if the mss is larger than the socket buffer, decrease the mss. 2986 */ 2987 SOCKBUF_LOCK(&so->so_snd); 2988 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2989 bufsize = metrics.rmx_sendpipe; 2990 else 2991 bufsize = so->so_snd.sb_hiwat; 2992 if (bufsize < mss) 2993 mss = bufsize; 2994 else { 2995 bufsize = roundup(bufsize, mss); 2996 if (bufsize > sb_max) 2997 bufsize = sb_max; 2998 if (bufsize > so->so_snd.sb_hiwat) 2999 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3000 } 3001 SOCKBUF_UNLOCK(&so->so_snd); 3002 tp->t_maxseg = mss; 3003 3004 SOCKBUF_LOCK(&so->so_rcv); 3005 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3006 bufsize = metrics.rmx_recvpipe; 3007 else 3008 bufsize = so->so_rcv.sb_hiwat; 3009 if (bufsize > mss) { 3010 bufsize = roundup(bufsize, mss); 3011 if (bufsize > sb_max) 3012 bufsize = sb_max; 3013 if (bufsize > so->so_rcv.sb_hiwat) 3014 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3015 } 3016 SOCKBUF_UNLOCK(&so->so_rcv); 3017 /* 3018 * While we're here, check the others too 3019 */ 3020 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3021 tp->t_srtt = rtt; 3022 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3023 tcpstat.tcps_usedrtt++; 3024 if (metrics.rmx_rttvar) { 3025 tp->t_rttvar = metrics.rmx_rttvar; 3026 tcpstat.tcps_usedrttvar++; 3027 } else { 3028 /* default variation is +- 1 rtt */ 3029 tp->t_rttvar = 3030 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3031 } 3032 TCPT_RANGESET(tp->t_rxtcur, 3033 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3034 tp->t_rttmin, TCPTV_REXMTMAX); 3035 } 3036 if (metrics.rmx_ssthresh) { 3037 /* 3038 * There's some sort of gateway or interface 3039 * buffer limit on the path. Use this to set 3040 * the slow start threshhold, but set the 3041 * threshold to no less than 2*mss. 3042 */ 3043 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3044 tcpstat.tcps_usedssthresh++; 3045 } 3046 if (metrics.rmx_bandwidth) 3047 tp->snd_bandwidth = metrics.rmx_bandwidth; 3048 3049 /* 3050 * Set the slow-start flight size depending on whether this 3051 * is a local network or not. 3052 * 3053 * Extend this so we cache the cwnd too and retrieve it here. 3054 * Make cwnd even bigger than RFC3390 suggests but only if we 3055 * have previous experience with the remote host. Be careful 3056 * not make cwnd bigger than remote receive window or our own 3057 * send socket buffer. Maybe put some additional upper bound 3058 * on the retrieved cwnd. Should do incremental updates to 3059 * hostcache when cwnd collapses so next connection doesn't 3060 * overloads the path again. 3061 * 3062 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3063 * We currently check only in syncache_socket for that. 3064 */ 3065 #define TCP_METRICS_CWND 3066 #ifdef TCP_METRICS_CWND 3067 if (metrics.rmx_cwnd) 3068 tp->snd_cwnd = max(mss, 3069 min(metrics.rmx_cwnd / 2, 3070 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3071 else 3072 #endif 3073 if (tcp_do_rfc3390) 3074 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3075 #ifdef INET6 3076 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3077 (!isipv6 && in_localaddr(inp->inp_faddr))) 3078 #else 3079 else if (in_localaddr(inp->inp_faddr)) 3080 #endif 3081 tp->snd_cwnd = mss * ss_fltsz_local; 3082 else 3083 tp->snd_cwnd = mss * ss_fltsz; 3084 } 3085 3086 /* 3087 * Determine the MSS option to send on an outgoing SYN. 3088 */ 3089 int 3090 tcp_mssopt(inc) 3091 struct in_conninfo *inc; 3092 { 3093 int mss = 0; 3094 u_long maxmtu = 0; 3095 u_long thcmtu = 0; 3096 size_t min_protoh; 3097 #ifdef INET6 3098 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3099 #endif 3100 3101 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3102 3103 #ifdef INET6 3104 if (isipv6) { 3105 mss = tcp_v6mssdflt; 3106 maxmtu = tcp_maxmtu6(inc); 3107 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3108 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3109 } else 3110 #endif 3111 { 3112 mss = tcp_mssdflt; 3113 maxmtu = tcp_maxmtu(inc); 3114 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3115 min_protoh = sizeof(struct tcpiphdr); 3116 } 3117 if (maxmtu && thcmtu) 3118 mss = min(maxmtu, thcmtu) - min_protoh; 3119 else if (maxmtu || thcmtu) 3120 mss = max(maxmtu, thcmtu) - min_protoh; 3121 3122 return (mss); 3123 } 3124 3125 3126 /* 3127 * On a partial ack arrives, force the retransmission of the 3128 * next unacknowledged segment. Do not clear tp->t_dupacks. 3129 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3130 * be started again. 3131 */ 3132 static void 3133 tcp_newreno_partial_ack(tp, th) 3134 struct tcpcb *tp; 3135 struct tcphdr *th; 3136 { 3137 tcp_seq onxt = tp->snd_nxt; 3138 u_long ocwnd = tp->snd_cwnd; 3139 3140 callout_stop(tp->tt_rexmt); 3141 tp->t_rtttime = 0; 3142 tp->snd_nxt = th->th_ack; 3143 /* 3144 * Set snd_cwnd to one segment beyond acknowledged offset. 3145 * (tp->snd_una has not yet been updated when this function is called.) 3146 */ 3147 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3148 tp->t_flags |= TF_ACKNOW; 3149 (void) tcp_output(tp); 3150 tp->snd_cwnd = ocwnd; 3151 if (SEQ_GT(onxt, tp->snd_nxt)) 3152 tp->snd_nxt = onxt; 3153 /* 3154 * Partial window deflation. Relies on fact that tp->snd_una 3155 * not updated yet. 3156 */ 3157 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3158 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3159 else 3160 tp->snd_cwnd = 0; 3161 tp->snd_cwnd += tp->t_maxseg; 3162 } 3163 3164 /* 3165 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3166 * looking for a pcb in the listen state. Returns 0 otherwise. 3167 */ 3168 static int 3169 tcp_timewait(inp, to, th, m, tlen) 3170 struct inpcb *inp; 3171 struct tcpopt *to; 3172 struct tcphdr *th; 3173 struct mbuf *m; 3174 int tlen; 3175 { 3176 struct tcptw *tw; 3177 int thflags; 3178 tcp_seq seq; 3179 #ifdef INET6 3180 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3181 #else 3182 const int isipv6 = 0; 3183 #endif 3184 3185 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3186 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3187 INP_LOCK_ASSERT(inp); 3188 3189 /* 3190 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 3191 * still present. This is undesirable, but temporarily necessary 3192 * until we work out how to handle inpcb's who's timewait state has 3193 * been removed. 3194 */ 3195 tw = intotw(inp); 3196 if (tw == NULL) 3197 goto drop; 3198 3199 thflags = th->th_flags; 3200 3201 /* 3202 * NOTE: for FIN_WAIT_2 (to be added later), 3203 * must validate sequence number before accepting RST 3204 */ 3205 3206 /* 3207 * If the segment contains RST: 3208 * Drop the segment - see Stevens, vol. 2, p. 964 and 3209 * RFC 1337. 3210 */ 3211 if (thflags & TH_RST) 3212 goto drop; 3213 3214 #if 0 3215 /* PAWS not needed at the moment */ 3216 /* 3217 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3218 * and it's less than ts_recent, drop it. 3219 */ 3220 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3221 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3222 if ((thflags & TH_ACK) == 0) 3223 goto drop; 3224 goto ack; 3225 } 3226 /* 3227 * ts_recent is never updated because we never accept new segments. 3228 */ 3229 #endif 3230 3231 /* 3232 * If a new connection request is received 3233 * while in TIME_WAIT, drop the old connection 3234 * and start over if the sequence numbers 3235 * are above the previous ones. 3236 */ 3237 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3238 tcp_twclose(tw, 0); 3239 return (1); 3240 } 3241 3242 /* 3243 * Drop the the segment if it does not contain an ACK. 3244 */ 3245 if ((thflags & TH_ACK) == 0) 3246 goto drop; 3247 3248 /* 3249 * Reset the 2MSL timer if this is a duplicate FIN. 3250 */ 3251 if (thflags & TH_FIN) { 3252 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3253 if (seq + 1 == tw->rcv_nxt) 3254 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3255 } 3256 3257 /* 3258 * Acknowledge the segment if it has data or is not a duplicate ACK. 3259 */ 3260 if (thflags != TH_ACK || tlen != 0 || 3261 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3262 tcp_twrespond(tw, TH_ACK); 3263 goto drop; 3264 3265 /* 3266 * Generate a RST, dropping incoming segment. 3267 * Make ACK acceptable to originator of segment. 3268 * Don't bother to respond if destination was broadcast/multicast. 3269 */ 3270 if (m->m_flags & (M_BCAST|M_MCAST)) 3271 goto drop; 3272 if (isipv6) { 3273 struct ip6_hdr *ip6; 3274 3275 /* IPv6 anycast check is done at tcp6_input() */ 3276 ip6 = mtod(m, struct ip6_hdr *); 3277 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3278 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3279 goto drop; 3280 } else { 3281 struct ip *ip; 3282 3283 ip = mtod(m, struct ip *); 3284 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3285 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3286 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3287 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3288 goto drop; 3289 } 3290 if (thflags & TH_ACK) { 3291 tcp_respond(NULL, 3292 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3293 } else { 3294 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3295 tcp_respond(NULL, 3296 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3297 } 3298 INP_UNLOCK(inp); 3299 return (0); 3300 3301 drop: 3302 INP_UNLOCK(inp); 3303 m_freem(m); 3304 return (0); 3305 } 3306