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> /* for ICMP_BANDLIM */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/nd6.h> 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet6/tcp6_var.h> 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif /* TCPDEBUG */ 86 87 #ifdef FAST_IPSEC 88 #include <netipsec/ipsec.h> 89 #include <netipsec/ipsec6.h> 90 #endif /*FAST_IPSEC*/ 91 92 #ifdef IPSEC 93 #include <netinet6/ipsec.h> 94 #include <netinet6/ipsec6.h> 95 #include <netkey/key.h> 96 #endif /*IPSEC*/ 97 98 #include <machine/in_cksum.h> 99 100 static const int tcprexmtthresh = 3; 101 102 struct tcpstat tcpstat; 103 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 104 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 105 106 static int log_in_vain = 0; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 108 &log_in_vain, 0, "Log all incoming TCP connections"); 109 110 static int blackhole = 0; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 112 &blackhole, 0, "Do not send RST when dropping refused connections"); 113 114 int tcp_delack_enabled = 1; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 116 &tcp_delack_enabled, 0, 117 "Delay ACK to try and piggyback it onto a data packet"); 118 119 #ifdef TCP_DROP_SYNFIN 120 static int drop_synfin = 0; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 122 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 123 #endif 124 125 static int tcp_do_rfc3042 = 1; 126 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 127 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 128 129 static int tcp_do_rfc3390 = 1; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 131 &tcp_do_rfc3390, 0, 132 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 133 134 static int tcp_insecure_rst = 0; 135 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 136 &tcp_insecure_rst, 0, 137 "Follow the old (insecure) criteria for accepting RST packets."); 138 139 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 140 "TCP Segment Reassembly Queue"); 141 142 static int tcp_reass_maxseg = 0; 143 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 144 &tcp_reass_maxseg, 0, 145 "Global maximum number of TCP Segments in Reassembly Queue"); 146 147 int tcp_reass_qsize = 0; 148 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 149 &tcp_reass_qsize, 0, 150 "Global number of TCP Segments currently in Reassembly Queue"); 151 152 static int tcp_reass_maxqlen = 48; 153 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 154 &tcp_reass_maxqlen, 0, 155 "Maximum number of TCP Segments per individual Reassembly Queue"); 156 157 static int tcp_reass_overflows = 0; 158 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 159 &tcp_reass_overflows, 0, 160 "Global number of TCP Segment Reassembly Queue Overflows"); 161 162 struct inpcbhead tcb; 163 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 164 struct inpcbinfo tcbinfo; 165 struct mtx *tcbinfo_mtx; 166 167 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 168 169 static void tcp_pulloutofband(struct socket *, 170 struct tcphdr *, struct mbuf *, int); 171 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 172 struct mbuf *); 173 static void tcp_xmit_timer(struct tcpcb *, int); 174 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 175 static int tcp_timewait(struct tcptw *, struct tcpopt *, 176 struct tcphdr *, struct mbuf *, int); 177 178 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 179 #ifdef INET6 180 #define ND6_HINT(tp) \ 181 do { \ 182 if ((tp) && (tp)->t_inpcb && \ 183 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 184 nd6_nud_hint(NULL, NULL, 0); \ 185 } while (0) 186 #else 187 #define ND6_HINT(tp) 188 #endif 189 190 /* 191 * Indicate whether this ack should be delayed. We can delay the ack if 192 * - there is no delayed ack timer in progress and 193 * - our last ack wasn't a 0-sized window. We never want to delay 194 * the ack that opens up a 0-sized window and 195 * - delayed acks are enabled or 196 * - this is a half-synchronized T/TCP connection. 197 */ 198 #define DELAY_ACK(tp) \ 199 ((!callout_active(tp->tt_delack) && \ 200 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 201 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 202 203 /* Initialize TCP reassembly queue */ 204 uma_zone_t tcp_reass_zone; 205 void 206 tcp_reass_init() 207 { 208 tcp_reass_maxseg = nmbclusters / 16; 209 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 210 &tcp_reass_maxseg); 211 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 212 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 213 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 214 } 215 216 static int 217 tcp_reass(tp, th, tlenp, m) 218 register struct tcpcb *tp; 219 register struct tcphdr *th; 220 int *tlenp; 221 struct mbuf *m; 222 { 223 struct tseg_qent *q; 224 struct tseg_qent *p = NULL; 225 struct tseg_qent *nq; 226 struct tseg_qent *te = NULL; 227 struct socket *so = tp->t_inpcb->inp_socket; 228 int flags; 229 230 INP_LOCK_ASSERT(tp->t_inpcb); 231 232 /* 233 * XXX: tcp_reass() is rather inefficient with its data structures 234 * and should be rewritten (see NetBSD for optimizations). While 235 * doing that it should move to its own file tcp_reass.c. 236 */ 237 238 /* 239 * Call with th==NULL after become established to 240 * force pre-ESTABLISHED data up to user socket. 241 */ 242 if (th == NULL) 243 goto present; 244 245 /* 246 * Limit the number of segments in the reassembly queue to prevent 247 * holding on to too many segments (and thus running out of mbufs). 248 * Make sure to let the missing segment through which caused this 249 * queue. Always keep one global queue entry spare to be able to 250 * process the missing segment. 251 */ 252 if (th->th_seq != tp->rcv_nxt && 253 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 254 tp->t_segqlen >= tcp_reass_maxqlen)) { 255 tcp_reass_overflows++; 256 tcpstat.tcps_rcvmemdrop++; 257 m_freem(m); 258 *tlenp = 0; 259 return (0); 260 } 261 262 /* 263 * Allocate a new queue entry. If we can't, or hit the zone limit 264 * just drop the pkt. 265 */ 266 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 267 if (te == NULL) { 268 tcpstat.tcps_rcvmemdrop++; 269 m_freem(m); 270 *tlenp = 0; 271 return (0); 272 } 273 tp->t_segqlen++; 274 tcp_reass_qsize++; 275 276 /* 277 * Find a segment which begins after this one does. 278 */ 279 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 280 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 281 break; 282 p = q; 283 } 284 285 /* 286 * If there is a preceding segment, it may provide some of 287 * our data already. If so, drop the data from the incoming 288 * segment. If it provides all of our data, drop us. 289 */ 290 if (p != NULL) { 291 register int i; 292 /* conversion to int (in i) handles seq wraparound */ 293 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 294 if (i > 0) { 295 if (i >= *tlenp) { 296 tcpstat.tcps_rcvduppack++; 297 tcpstat.tcps_rcvdupbyte += *tlenp; 298 m_freem(m); 299 uma_zfree(tcp_reass_zone, te); 300 tp->t_segqlen--; 301 tcp_reass_qsize--; 302 /* 303 * Try to present any queued data 304 * at the left window edge to the user. 305 * This is needed after the 3-WHS 306 * completes. 307 */ 308 goto present; /* ??? */ 309 } 310 m_adj(m, i); 311 *tlenp -= i; 312 th->th_seq += i; 313 } 314 } 315 tcpstat.tcps_rcvoopack++; 316 tcpstat.tcps_rcvoobyte += *tlenp; 317 318 /* 319 * While we overlap succeeding segments trim them or, 320 * if they are completely covered, dequeue them. 321 */ 322 while (q) { 323 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 324 if (i <= 0) 325 break; 326 if (i < q->tqe_len) { 327 q->tqe_th->th_seq += i; 328 q->tqe_len -= i; 329 m_adj(q->tqe_m, i); 330 break; 331 } 332 333 nq = LIST_NEXT(q, tqe_q); 334 LIST_REMOVE(q, tqe_q); 335 m_freem(q->tqe_m); 336 uma_zfree(tcp_reass_zone, q); 337 tp->t_segqlen--; 338 tcp_reass_qsize--; 339 q = nq; 340 } 341 342 /* Insert the new segment queue entry into place. */ 343 te->tqe_m = m; 344 te->tqe_th = th; 345 te->tqe_len = *tlenp; 346 347 if (p == NULL) { 348 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 349 } else { 350 LIST_INSERT_AFTER(p, te, tqe_q); 351 } 352 353 present: 354 /* 355 * Present data to user, advancing rcv_nxt through 356 * completed sequence space. 357 */ 358 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 359 return (0); 360 q = LIST_FIRST(&tp->t_segq); 361 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 362 return (0); 363 SOCKBUF_LOCK(&so->so_rcv); 364 do { 365 tp->rcv_nxt += q->tqe_len; 366 flags = q->tqe_th->th_flags & TH_FIN; 367 nq = LIST_NEXT(q, tqe_q); 368 LIST_REMOVE(q, tqe_q); 369 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 370 m_freem(q->tqe_m); 371 else 372 sbappendstream_locked(&so->so_rcv, q->tqe_m); 373 uma_zfree(tcp_reass_zone, q); 374 tp->t_segqlen--; 375 tcp_reass_qsize--; 376 q = nq; 377 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 378 ND6_HINT(tp); 379 sorwakeup_locked(so); 380 return (flags); 381 } 382 383 /* 384 * TCP input routine, follows pages 65-76 of the 385 * protocol specification dated September, 1981 very closely. 386 */ 387 #ifdef INET6 388 int 389 tcp6_input(mp, offp, proto) 390 struct mbuf **mp; 391 int *offp, proto; 392 { 393 register struct mbuf *m = *mp; 394 struct in6_ifaddr *ia6; 395 396 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 397 398 /* 399 * draft-itojun-ipv6-tcp-to-anycast 400 * better place to put this in? 401 */ 402 ia6 = ip6_getdstifaddr(m); 403 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 404 struct ip6_hdr *ip6; 405 406 ip6 = mtod(m, struct ip6_hdr *); 407 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 408 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 409 return IPPROTO_DONE; 410 } 411 412 tcp_input(m, *offp); 413 return IPPROTO_DONE; 414 } 415 #endif 416 417 void 418 tcp_input(m, off0) 419 register struct mbuf *m; 420 int off0; 421 { 422 register struct tcphdr *th; 423 register struct ip *ip = NULL; 424 register struct ipovly *ipov; 425 register struct inpcb *inp = NULL; 426 u_char *optp = NULL; 427 int optlen = 0; 428 int len, tlen, off; 429 int drop_hdrlen; 430 register struct tcpcb *tp = 0; 431 register int thflags; 432 struct socket *so = 0; 433 int todrop, acked, ourfinisacked, needoutput = 0; 434 u_long tiwin; 435 struct tcpopt to; /* options in this segment */ 436 int headlocked = 0; 437 #ifdef IPFIREWALL_FORWARD 438 struct m_tag *fwd_tag; 439 #endif 440 int rstreason; /* For badport_bandlim accounting purposes */ 441 442 struct ip6_hdr *ip6 = NULL; 443 #ifdef INET6 444 int isipv6; 445 #else 446 const int isipv6 = 0; 447 #endif 448 449 #ifdef TCPDEBUG 450 /* 451 * The size of tcp_saveipgen must be the size of the max ip header, 452 * now IPv6. 453 */ 454 u_char tcp_saveipgen[40]; 455 struct tcphdr tcp_savetcp; 456 short ostate = 0; 457 #endif 458 459 #ifdef INET6 460 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 461 #endif 462 bzero((char *)&to, sizeof(to)); 463 464 tcpstat.tcps_rcvtotal++; 465 466 if (isipv6) { 467 #ifdef INET6 468 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 469 ip6 = mtod(m, struct ip6_hdr *); 470 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 471 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 472 tcpstat.tcps_rcvbadsum++; 473 goto drop; 474 } 475 th = (struct tcphdr *)((caddr_t)ip6 + off0); 476 477 /* 478 * Be proactive about unspecified IPv6 address in source. 479 * As we use all-zero to indicate unbounded/unconnected pcb, 480 * unspecified IPv6 address can be used to confuse us. 481 * 482 * Note that packets with unspecified IPv6 destination is 483 * already dropped in ip6_input. 484 */ 485 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 486 /* XXX stat */ 487 goto drop; 488 } 489 #else 490 th = NULL; /* XXX: avoid compiler warning */ 491 #endif 492 } else { 493 /* 494 * Get IP and TCP header together in first mbuf. 495 * Note: IP leaves IP header in first mbuf. 496 */ 497 if (off0 > sizeof (struct ip)) { 498 ip_stripoptions(m, (struct mbuf *)0); 499 off0 = sizeof(struct ip); 500 } 501 if (m->m_len < sizeof (struct tcpiphdr)) { 502 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 503 tcpstat.tcps_rcvshort++; 504 return; 505 } 506 } 507 ip = mtod(m, struct ip *); 508 ipov = (struct ipovly *)ip; 509 th = (struct tcphdr *)((caddr_t)ip + off0); 510 tlen = ip->ip_len; 511 512 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 513 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 514 th->th_sum = m->m_pkthdr.csum_data; 515 else 516 th->th_sum = in_pseudo(ip->ip_src.s_addr, 517 ip->ip_dst.s_addr, 518 htonl(m->m_pkthdr.csum_data + 519 ip->ip_len + 520 IPPROTO_TCP)); 521 th->th_sum ^= 0xffff; 522 #ifdef TCPDEBUG 523 ipov->ih_len = (u_short)tlen; 524 ipov->ih_len = htons(ipov->ih_len); 525 #endif 526 } else { 527 /* 528 * Checksum extended TCP header and data. 529 */ 530 len = sizeof (struct ip) + tlen; 531 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 532 ipov->ih_len = (u_short)tlen; 533 ipov->ih_len = htons(ipov->ih_len); 534 th->th_sum = in_cksum(m, len); 535 } 536 if (th->th_sum) { 537 tcpstat.tcps_rcvbadsum++; 538 goto drop; 539 } 540 #ifdef INET6 541 /* Re-initialization for later version check */ 542 ip->ip_v = IPVERSION; 543 #endif 544 } 545 546 /* 547 * Check that TCP offset makes sense, 548 * pull out TCP options and adjust length. XXX 549 */ 550 off = th->th_off << 2; 551 if (off < sizeof (struct tcphdr) || off > tlen) { 552 tcpstat.tcps_rcvbadoff++; 553 goto drop; 554 } 555 tlen -= off; /* tlen is used instead of ti->ti_len */ 556 if (off > sizeof (struct tcphdr)) { 557 if (isipv6) { 558 #ifdef INET6 559 IP6_EXTHDR_CHECK(m, off0, off, ); 560 ip6 = mtod(m, struct ip6_hdr *); 561 th = (struct tcphdr *)((caddr_t)ip6 + off0); 562 #endif 563 } else { 564 if (m->m_len < sizeof(struct ip) + off) { 565 if ((m = m_pullup(m, sizeof (struct ip) + off)) 566 == 0) { 567 tcpstat.tcps_rcvshort++; 568 return; 569 } 570 ip = mtod(m, struct ip *); 571 ipov = (struct ipovly *)ip; 572 th = (struct tcphdr *)((caddr_t)ip + off0); 573 } 574 } 575 optlen = off - sizeof (struct tcphdr); 576 optp = (u_char *)(th + 1); 577 } 578 thflags = th->th_flags; 579 580 #ifdef TCP_DROP_SYNFIN 581 /* 582 * If the drop_synfin option is enabled, drop all packets with 583 * both the SYN and FIN bits set. This prevents e.g. nmap from 584 * identifying the TCP/IP stack. 585 * 586 * This is a violation of the TCP specification. 587 */ 588 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 589 goto drop; 590 #endif 591 592 /* 593 * Convert TCP protocol specific fields to host format. 594 */ 595 th->th_seq = ntohl(th->th_seq); 596 th->th_ack = ntohl(th->th_ack); 597 th->th_win = ntohs(th->th_win); 598 th->th_urp = ntohs(th->th_urp); 599 600 /* 601 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 602 * until after ip6_savecontrol() is called and before other functions 603 * which don't want those proto headers. 604 * Because ip6_savecontrol() is going to parse the mbuf to 605 * search for data to be passed up to user-land, it wants mbuf 606 * parameters to be unchanged. 607 * XXX: the call of ip6_savecontrol() has been obsoleted based on 608 * latest version of the advanced API (20020110). 609 */ 610 drop_hdrlen = off0 + off; 611 612 /* 613 * Locate pcb for segment. 614 */ 615 INP_INFO_WLOCK(&tcbinfo); 616 headlocked = 1; 617 findpcb: 618 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 619 #ifdef IPFIREWALL_FORWARD 620 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 621 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 622 623 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 624 struct sockaddr_in *next_hop; 625 626 next_hop = (struct sockaddr_in *)(fwd_tag+1); 627 /* 628 * Transparently forwarded. Pretend to be the destination. 629 * already got one like this? 630 */ 631 inp = in_pcblookup_hash(&tcbinfo, 632 ip->ip_src, th->th_sport, 633 ip->ip_dst, th->th_dport, 634 0, m->m_pkthdr.rcvif); 635 if (!inp) { 636 /* It's new. Try to find the ambushing socket. */ 637 inp = in_pcblookup_hash(&tcbinfo, 638 ip->ip_src, th->th_sport, 639 next_hop->sin_addr, 640 next_hop->sin_port ? 641 ntohs(next_hop->sin_port) : 642 th->th_dport, 643 1, m->m_pkthdr.rcvif); 644 } 645 /* Remove the tag from the packet. We don't need it anymore. */ 646 m_tag_delete(m, fwd_tag); 647 } else { 648 #endif /* IPFIREWALL_FORWARD */ 649 if (isipv6) { 650 #ifdef INET6 651 inp = in6_pcblookup_hash(&tcbinfo, 652 &ip6->ip6_src, th->th_sport, 653 &ip6->ip6_dst, th->th_dport, 654 1, m->m_pkthdr.rcvif); 655 #endif 656 } else 657 inp = in_pcblookup_hash(&tcbinfo, 658 ip->ip_src, th->th_sport, 659 ip->ip_dst, th->th_dport, 660 1, m->m_pkthdr.rcvif); 661 #ifdef IPFIREWALL_FORWARD 662 } 663 #endif /* IPFIREWALL_FORWARD */ 664 665 #if defined(IPSEC) || defined(FAST_IPSEC) 666 #ifdef INET6 667 if (isipv6) { 668 if (inp != NULL && ipsec6_in_reject(m, inp)) { 669 #ifdef IPSEC 670 ipsec6stat.in_polvio++; 671 #endif 672 goto drop; 673 } 674 } else 675 #endif /* INET6 */ 676 if (inp != NULL && ipsec4_in_reject(m, inp)) { 677 #ifdef IPSEC 678 ipsecstat.in_polvio++; 679 #endif 680 goto drop; 681 } 682 #endif /*IPSEC || FAST_IPSEC*/ 683 684 /* 685 * If the state is CLOSED (i.e., TCB does not exist) then 686 * all data in the incoming segment is discarded. 687 * If the TCB exists but is in CLOSED state, it is embryonic, 688 * but should either do a listen or a connect soon. 689 */ 690 if (inp == NULL) { 691 if (log_in_vain) { 692 #ifdef INET6 693 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 694 #else 695 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 696 #endif 697 698 if (isipv6) { 699 #ifdef INET6 700 strcpy(dbuf, "["); 701 strcpy(sbuf, "["); 702 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 703 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 704 strcat(dbuf, "]"); 705 strcat(sbuf, "]"); 706 #endif 707 } else { 708 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 709 strcpy(sbuf, inet_ntoa(ip->ip_src)); 710 } 711 switch (log_in_vain) { 712 case 1: 713 if ((thflags & TH_SYN) == 0) 714 break; 715 /* FALLTHROUGH */ 716 case 2: 717 log(LOG_INFO, 718 "Connection attempt to TCP %s:%d " 719 "from %s:%d flags:0x%02x\n", 720 dbuf, ntohs(th->th_dport), sbuf, 721 ntohs(th->th_sport), thflags); 722 break; 723 default: 724 break; 725 } 726 } 727 if (blackhole) { 728 switch (blackhole) { 729 case 1: 730 if (thflags & TH_SYN) 731 goto drop; 732 break; 733 case 2: 734 goto drop; 735 default: 736 goto drop; 737 } 738 } 739 rstreason = BANDLIM_RST_CLOSEDPORT; 740 goto dropwithreset; 741 } 742 INP_LOCK(inp); 743 744 /* Check the minimum TTL for socket. */ 745 if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl) 746 goto drop; 747 748 if (inp->inp_vflag & INP_TIMEWAIT) { 749 /* 750 * The only option of relevance is TOF_CC, and only if 751 * present in a SYN segment. See tcp_timewait(). 752 */ 753 if (thflags & TH_SYN) 754 tcp_dooptions(&to, optp, optlen, 1); 755 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 756 &to, th, m, tlen)) 757 goto findpcb; 758 /* 759 * tcp_timewait unlocks inp. 760 */ 761 INP_INFO_WUNLOCK(&tcbinfo); 762 return; 763 } 764 tp = intotcpcb(inp); 765 if (tp == 0) { 766 INP_UNLOCK(inp); 767 rstreason = BANDLIM_RST_CLOSEDPORT; 768 goto dropwithreset; 769 } 770 if (tp->t_state == TCPS_CLOSED) 771 goto drop; 772 773 /* Unscale the window into a 32-bit value. */ 774 if ((thflags & TH_SYN) == 0) 775 tiwin = th->th_win << tp->snd_scale; 776 else 777 tiwin = th->th_win; 778 779 #ifdef MAC 780 INP_LOCK_ASSERT(inp); 781 if (mac_check_inpcb_deliver(inp, m)) 782 goto drop; 783 #endif 784 so = inp->inp_socket; 785 #ifdef TCPDEBUG 786 if (so->so_options & SO_DEBUG) { 787 ostate = tp->t_state; 788 if (isipv6) 789 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 790 else 791 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 792 tcp_savetcp = *th; 793 } 794 #endif 795 if (so->so_options & SO_ACCEPTCONN) { 796 struct in_conninfo inc; 797 798 #ifdef INET6 799 inc.inc_isipv6 = isipv6; 800 #endif 801 if (isipv6) { 802 inc.inc6_faddr = ip6->ip6_src; 803 inc.inc6_laddr = ip6->ip6_dst; 804 } else { 805 inc.inc_faddr = ip->ip_src; 806 inc.inc_laddr = ip->ip_dst; 807 } 808 inc.inc_fport = th->th_sport; 809 inc.inc_lport = th->th_dport; 810 811 /* 812 * If the state is LISTEN then ignore segment if it contains 813 * a RST. If the segment contains an ACK then it is bad and 814 * send a RST. If it does not contain a SYN then it is not 815 * interesting; drop it. 816 * 817 * If the state is SYN_RECEIVED (syncache) and seg contains 818 * an ACK, but not for our SYN/ACK, send a RST. If the seg 819 * contains a RST, check the sequence number to see if it 820 * is a valid reset segment. 821 */ 822 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 823 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 824 if (!syncache_expand(&inc, th, &so, m)) { 825 /* 826 * No syncache entry, or ACK was not 827 * for our SYN/ACK. Send a RST. 828 */ 829 tcpstat.tcps_badsyn++; 830 rstreason = BANDLIM_RST_OPENPORT; 831 goto dropwithreset; 832 } 833 if (so == NULL) { 834 /* 835 * Could not complete 3-way handshake, 836 * connection is being closed down, and 837 * syncache will free mbuf. 838 */ 839 INP_UNLOCK(inp); 840 INP_INFO_WUNLOCK(&tcbinfo); 841 return; 842 } 843 /* 844 * Socket is created in state SYN_RECEIVED. 845 * Continue processing segment. 846 */ 847 INP_UNLOCK(inp); 848 inp = sotoinpcb(so); 849 INP_LOCK(inp); 850 tp = intotcpcb(inp); 851 /* 852 * This is what would have happened in 853 * tcp_output() when the SYN,ACK was sent. 854 */ 855 tp->snd_up = tp->snd_una; 856 tp->snd_max = tp->snd_nxt = tp->iss + 1; 857 tp->last_ack_sent = tp->rcv_nxt; 858 /* 859 * RFC1323: The window in SYN & SYN/ACK 860 * segments is never scaled. 861 */ 862 tp->snd_wnd = tiwin; /* unscaled */ 863 goto after_listen; 864 } 865 if (thflags & TH_RST) { 866 syncache_chkrst(&inc, th); 867 goto drop; 868 } 869 if (thflags & TH_ACK) { 870 syncache_badack(&inc); 871 tcpstat.tcps_badsyn++; 872 rstreason = BANDLIM_RST_OPENPORT; 873 goto dropwithreset; 874 } 875 goto drop; 876 } 877 878 /* 879 * Segment's flags are (SYN) or (SYN|FIN). 880 */ 881 #ifdef INET6 882 /* 883 * If deprecated address is forbidden, 884 * we do not accept SYN to deprecated interface 885 * address to prevent any new inbound connection from 886 * getting established. 887 * When we do not accept SYN, we send a TCP RST, 888 * with deprecated source address (instead of dropping 889 * it). We compromise it as it is much better for peer 890 * to send a RST, and RST will be the final packet 891 * for the exchange. 892 * 893 * If we do not forbid deprecated addresses, we accept 894 * the SYN packet. RFC2462 does not suggest dropping 895 * SYN in this case. 896 * If we decipher RFC2462 5.5.4, it says like this: 897 * 1. use of deprecated addr with existing 898 * communication is okay - "SHOULD continue to be 899 * used" 900 * 2. use of it with new communication: 901 * (2a) "SHOULD NOT be used if alternate address 902 * with sufficient scope is available" 903 * (2b) nothing mentioned otherwise. 904 * Here we fall into (2b) case as we have no choice in 905 * our source address selection - we must obey the peer. 906 * 907 * The wording in RFC2462 is confusing, and there are 908 * multiple description text for deprecated address 909 * handling - worse, they are not exactly the same. 910 * I believe 5.5.4 is the best one, so we follow 5.5.4. 911 */ 912 if (isipv6 && !ip6_use_deprecated) { 913 struct in6_ifaddr *ia6; 914 915 if ((ia6 = ip6_getdstifaddr(m)) && 916 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 917 INP_UNLOCK(inp); 918 tp = NULL; 919 rstreason = BANDLIM_RST_OPENPORT; 920 goto dropwithreset; 921 } 922 } 923 #endif 924 /* 925 * If it is from this socket, drop it, it must be forged. 926 * Don't bother responding if the destination was a broadcast. 927 */ 928 if (th->th_dport == th->th_sport) { 929 if (isipv6) { 930 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 931 &ip6->ip6_src)) 932 goto drop; 933 } else { 934 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 935 goto drop; 936 } 937 } 938 /* 939 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 940 * 941 * Note that it is quite possible to receive unicast 942 * link-layer packets with a broadcast IP address. Use 943 * in_broadcast() to find them. 944 */ 945 if (m->m_flags & (M_BCAST|M_MCAST)) 946 goto drop; 947 if (isipv6) { 948 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 949 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 950 goto drop; 951 } else { 952 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 953 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 954 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 955 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 956 goto drop; 957 } 958 /* 959 * SYN appears to be valid; create compressed TCP state 960 * for syncache, or perform t/tcp connection. 961 */ 962 if (so->so_qlen <= so->so_qlimit) { 963 #ifdef TCPDEBUG 964 if (so->so_options & SO_DEBUG) 965 tcp_trace(TA_INPUT, ostate, tp, 966 (void *)tcp_saveipgen, &tcp_savetcp, 0); 967 #endif 968 tcp_dooptions(&to, optp, optlen, 1); 969 if (!syncache_add(&inc, &to, th, &so, m)) 970 goto drop; 971 if (so == NULL) { 972 /* 973 * Entry added to syncache, mbuf used to 974 * send SYN,ACK packet. 975 */ 976 KASSERT(headlocked, ("headlocked")); 977 INP_UNLOCK(inp); 978 INP_INFO_WUNLOCK(&tcbinfo); 979 return; 980 } 981 /* 982 * Segment passed TAO tests. 983 */ 984 INP_UNLOCK(inp); 985 inp = sotoinpcb(so); 986 INP_LOCK(inp); 987 tp = intotcpcb(inp); 988 tp->snd_wnd = tiwin; 989 tp->t_starttime = ticks; 990 tp->t_state = TCPS_ESTABLISHED; 991 992 /* 993 * T/TCP logic: 994 * If there is a FIN or if there is data, then 995 * delay SYN,ACK(SYN) in the hope of piggy-backing 996 * it on a response segment. Otherwise must send 997 * ACK now in case the other side is slow starting. 998 */ 999 if (thflags & TH_FIN || tlen != 0) 1000 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1001 else 1002 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1003 tcpstat.tcps_connects++; 1004 soisconnected(so); 1005 goto trimthenstep6; 1006 } 1007 goto drop; 1008 } 1009 after_listen: 1010 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1011 INP_LOCK_ASSERT(inp); 1012 1013 /* Syncache takes care of sockets in the listen state. */ 1014 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1015 1016 /* 1017 * This is the second part of the MSS DoS prevention code (after 1018 * minmss on the sending side) and it deals with too many too small 1019 * tcp packets in a too short timeframe (1 second). 1020 * 1021 * For every full second we count the number of received packets 1022 * and bytes. If we get a lot of packets per second for this connection 1023 * (tcp_minmssoverload) we take a closer look at it and compute the 1024 * average packet size for the past second. If that is less than 1025 * tcp_minmss we get too many packets with very small payload which 1026 * is not good and burdens our system (and every packet generates 1027 * a wakeup to the process connected to our socket). We can reasonable 1028 * expect this to be small packet DoS attack to exhaust our CPU 1029 * cycles. 1030 * 1031 * Care has to be taken for the minimum packet overload value. This 1032 * value defines the minimum number of packets per second before we 1033 * start to worry. This must not be too low to avoid killing for 1034 * example interactive connections with many small packets like 1035 * telnet or SSH. 1036 * 1037 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1038 * this check. 1039 * 1040 * Account for packet if payload packet, skip over ACK, etc. 1041 */ 1042 if (tcp_minmss && tcp_minmssoverload && 1043 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1044 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1045 tp->rcv_pps++; 1046 tp->rcv_byps += tlen + off; 1047 if (tp->rcv_pps > tcp_minmssoverload) { 1048 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1049 printf("too many small tcp packets from " 1050 "%s:%u, av. %lubyte/packet, " 1051 "dropping connection\n", 1052 #ifdef INET6 1053 isipv6 ? 1054 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1055 #endif 1056 inet_ntoa(inp->inp_inc.inc_faddr), 1057 inp->inp_inc.inc_fport, 1058 tp->rcv_byps / tp->rcv_pps); 1059 KASSERT(headlocked, ("tcp_input: " 1060 "after_listen: tcp_drop: head " 1061 "not locked")); 1062 tp = tcp_drop(tp, ECONNRESET); 1063 tcpstat.tcps_minmssdrops++; 1064 goto drop; 1065 } 1066 } 1067 } else { 1068 tp->rcv_second = ticks + hz; 1069 tp->rcv_pps = 1; 1070 tp->rcv_byps = tlen + off; 1071 } 1072 } 1073 1074 /* 1075 * Segment received on connection. 1076 * Reset idle time and keep-alive timer. 1077 */ 1078 tp->t_rcvtime = ticks; 1079 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1080 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1081 1082 /* 1083 * Process options only when we get SYN/ACK back. The SYN case 1084 * for incoming connections is handled in tcp_syncache. 1085 * XXX this is traditional behavior, may need to be cleaned up. 1086 */ 1087 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1088 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1089 if (to.to_flags & TOF_SCALE) { 1090 tp->t_flags |= TF_RCVD_SCALE; 1091 tp->requested_s_scale = to.to_requested_s_scale; 1092 } 1093 if (to.to_flags & TOF_TS) { 1094 tp->t_flags |= TF_RCVD_TSTMP; 1095 tp->ts_recent = to.to_tsval; 1096 tp->ts_recent_age = ticks; 1097 } 1098 if (to.to_flags & TOF_MSS) 1099 tcp_mss(tp, to.to_mss); 1100 if (tp->sack_enable) { 1101 if (!(to.to_flags & TOF_SACK)) 1102 tp->sack_enable = 0; 1103 else 1104 tp->t_flags |= TF_SACK_PERMIT; 1105 } 1106 1107 } 1108 1109 /* 1110 * Header prediction: check for the two common cases 1111 * of a uni-directional data xfer. If the packet has 1112 * no control flags, is in-sequence, the window didn't 1113 * change and we're not retransmitting, it's a 1114 * candidate. If the length is zero and the ack moved 1115 * forward, we're the sender side of the xfer. Just 1116 * free the data acked & wake any higher level process 1117 * that was blocked waiting for space. If the length 1118 * is non-zero and the ack didn't move, we're the 1119 * receiver side. If we're getting packets in-order 1120 * (the reassembly queue is empty), add the data to 1121 * the socket buffer and note that we need a delayed ack. 1122 * Make sure that the hidden state-flags are also off. 1123 * Since we check for TCPS_ESTABLISHED above, it can only 1124 * be TH_NEEDSYN. 1125 */ 1126 if (tp->t_state == TCPS_ESTABLISHED && 1127 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1128 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1129 ((to.to_flags & TOF_TS) == 0 || 1130 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1131 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1132 tp->snd_nxt == tp->snd_max) { 1133 1134 /* 1135 * If last ACK falls within this segment's sequence numbers, 1136 * record the timestamp. 1137 * NOTE that the test is modified according to the latest 1138 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1139 */ 1140 if ((to.to_flags & TOF_TS) != 0 && 1141 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1142 tp->ts_recent_age = ticks; 1143 tp->ts_recent = to.to_tsval; 1144 } 1145 1146 if (tlen == 0) { 1147 if (SEQ_GT(th->th_ack, tp->snd_una) && 1148 SEQ_LEQ(th->th_ack, tp->snd_max) && 1149 tp->snd_cwnd >= tp->snd_wnd && 1150 ((!tcp_do_newreno && !tp->sack_enable && 1151 tp->t_dupacks < tcprexmtthresh) || 1152 ((tcp_do_newreno || tp->sack_enable) && 1153 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1154 TAILQ_EMPTY(&tp->snd_holes)))) { 1155 KASSERT(headlocked, ("headlocked")); 1156 INP_INFO_WUNLOCK(&tcbinfo); 1157 headlocked = 0; 1158 /* 1159 * this is a pure ack for outstanding data. 1160 */ 1161 ++tcpstat.tcps_predack; 1162 /* 1163 * "bad retransmit" recovery 1164 */ 1165 if (tp->t_rxtshift == 1 && 1166 ticks < tp->t_badrxtwin) { 1167 ++tcpstat.tcps_sndrexmitbad; 1168 tp->snd_cwnd = tp->snd_cwnd_prev; 1169 tp->snd_ssthresh = 1170 tp->snd_ssthresh_prev; 1171 tp->snd_recover = tp->snd_recover_prev; 1172 if (tp->t_flags & TF_WASFRECOVERY) 1173 ENTER_FASTRECOVERY(tp); 1174 tp->snd_nxt = tp->snd_max; 1175 tp->t_badrxtwin = 0; 1176 } 1177 1178 /* 1179 * Recalculate the transmit timer / rtt. 1180 * 1181 * Some boxes send broken timestamp replies 1182 * during the SYN+ACK phase, ignore 1183 * timestamps of 0 or we could calculate a 1184 * huge RTT and blow up the retransmit timer. 1185 */ 1186 if ((to.to_flags & TOF_TS) != 0 && 1187 to.to_tsecr) { 1188 tcp_xmit_timer(tp, 1189 ticks - to.to_tsecr + 1); 1190 } else if (tp->t_rtttime && 1191 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1192 tcp_xmit_timer(tp, 1193 ticks - tp->t_rtttime); 1194 } 1195 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1196 acked = th->th_ack - tp->snd_una; 1197 tcpstat.tcps_rcvackpack++; 1198 tcpstat.tcps_rcvackbyte += acked; 1199 sbdrop(&so->so_snd, acked); 1200 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1201 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1202 tp->snd_recover = th->th_ack - 1; 1203 tp->snd_una = th->th_ack; 1204 /* 1205 * pull snd_wl2 up to prevent seq wrap relative 1206 * to th_ack. 1207 */ 1208 tp->snd_wl2 = th->th_ack; 1209 tp->t_dupacks = 0; 1210 m_freem(m); 1211 ND6_HINT(tp); /* some progress has been done */ 1212 1213 /* 1214 * If all outstanding data are acked, stop 1215 * retransmit timer, otherwise restart timer 1216 * using current (possibly backed-off) value. 1217 * If process is waiting for space, 1218 * wakeup/selwakeup/signal. If data 1219 * are ready to send, let tcp_output 1220 * decide between more output or persist. 1221 1222 #ifdef TCPDEBUG 1223 if (so->so_options & SO_DEBUG) 1224 tcp_trace(TA_INPUT, ostate, tp, 1225 (void *)tcp_saveipgen, 1226 &tcp_savetcp, 0); 1227 #endif 1228 */ 1229 if (tp->snd_una == tp->snd_max) 1230 callout_stop(tp->tt_rexmt); 1231 else if (!callout_active(tp->tt_persist)) 1232 callout_reset(tp->tt_rexmt, 1233 tp->t_rxtcur, 1234 tcp_timer_rexmt, tp); 1235 1236 sowwakeup(so); 1237 if (so->so_snd.sb_cc) 1238 (void) tcp_output(tp); 1239 goto check_delack; 1240 } 1241 } else if (th->th_ack == tp->snd_una && 1242 LIST_EMPTY(&tp->t_segq) && 1243 tlen <= sbspace(&so->so_rcv)) { 1244 KASSERT(headlocked, ("headlocked")); 1245 INP_INFO_WUNLOCK(&tcbinfo); 1246 headlocked = 0; 1247 /* 1248 * this is a pure, in-sequence data packet 1249 * with nothing on the reassembly queue and 1250 * we have enough buffer space to take it. 1251 */ 1252 /* Clean receiver SACK report if present */ 1253 if (tp->sack_enable && tp->rcv_numsacks) 1254 tcp_clean_sackreport(tp); 1255 ++tcpstat.tcps_preddat; 1256 tp->rcv_nxt += tlen; 1257 /* 1258 * Pull snd_wl1 up to prevent seq wrap relative to 1259 * th_seq. 1260 */ 1261 tp->snd_wl1 = th->th_seq; 1262 /* 1263 * Pull rcv_up up to prevent seq wrap relative to 1264 * rcv_nxt. 1265 */ 1266 tp->rcv_up = tp->rcv_nxt; 1267 tcpstat.tcps_rcvpack++; 1268 tcpstat.tcps_rcvbyte += tlen; 1269 ND6_HINT(tp); /* some progress has been done */ 1270 /* 1271 #ifdef TCPDEBUG 1272 if (so->so_options & SO_DEBUG) 1273 tcp_trace(TA_INPUT, ostate, tp, 1274 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1275 #endif 1276 * Add data to socket buffer. 1277 */ 1278 SOCKBUF_LOCK(&so->so_rcv); 1279 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1280 m_freem(m); 1281 } else { 1282 m_adj(m, drop_hdrlen); /* delayed header drop */ 1283 sbappendstream_locked(&so->so_rcv, m); 1284 } 1285 sorwakeup_locked(so); 1286 if (DELAY_ACK(tp)) { 1287 tp->t_flags |= TF_DELACK; 1288 } else { 1289 tp->t_flags |= TF_ACKNOW; 1290 tcp_output(tp); 1291 } 1292 goto check_delack; 1293 } 1294 } 1295 1296 /* 1297 * Calculate amount of space in receive window, 1298 * and then do TCP input processing. 1299 * Receive window is amount of space in rcv queue, 1300 * but not less than advertised window. 1301 */ 1302 { int win; 1303 1304 win = sbspace(&so->so_rcv); 1305 if (win < 0) 1306 win = 0; 1307 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1308 } 1309 1310 switch (tp->t_state) { 1311 1312 /* 1313 * If the state is SYN_RECEIVED: 1314 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1315 */ 1316 case TCPS_SYN_RECEIVED: 1317 if ((thflags & TH_ACK) && 1318 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1319 SEQ_GT(th->th_ack, tp->snd_max))) { 1320 rstreason = BANDLIM_RST_OPENPORT; 1321 goto dropwithreset; 1322 } 1323 break; 1324 1325 /* 1326 * If the state is SYN_SENT: 1327 * if seg contains an ACK, but not for our SYN, drop the input. 1328 * if seg contains a RST, then drop the connection. 1329 * if seg does not contain SYN, then drop it. 1330 * Otherwise this is an acceptable SYN segment 1331 * initialize tp->rcv_nxt and tp->irs 1332 * if seg contains ack then advance tp->snd_una 1333 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1334 * arrange for segment to be acked (eventually) 1335 * continue processing rest of data/controls, beginning with URG 1336 */ 1337 case TCPS_SYN_SENT: 1338 if ((thflags & TH_ACK) && 1339 (SEQ_LEQ(th->th_ack, tp->iss) || 1340 SEQ_GT(th->th_ack, tp->snd_max))) { 1341 rstreason = BANDLIM_UNLIMITED; 1342 goto dropwithreset; 1343 } 1344 if (thflags & TH_RST) { 1345 if (thflags & TH_ACK) { 1346 KASSERT(headlocked, ("tcp_input: after_listen" 1347 ": tcp_drop.2: head not locked")); 1348 tp = tcp_drop(tp, ECONNREFUSED); 1349 } 1350 goto drop; 1351 } 1352 if ((thflags & TH_SYN) == 0) 1353 goto drop; 1354 tp->snd_wnd = th->th_win; /* initial send window */ 1355 1356 tp->irs = th->th_seq; 1357 tcp_rcvseqinit(tp); 1358 if (thflags & TH_ACK) { 1359 tcpstat.tcps_connects++; 1360 soisconnected(so); 1361 #ifdef MAC 1362 SOCK_LOCK(so); 1363 mac_set_socket_peer_from_mbuf(m, so); 1364 SOCK_UNLOCK(so); 1365 #endif 1366 /* Do window scaling on this connection? */ 1367 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1368 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1369 tp->snd_scale = tp->requested_s_scale; 1370 tp->rcv_scale = tp->request_r_scale; 1371 } 1372 tp->rcv_adv += tp->rcv_wnd; 1373 tp->snd_una++; /* SYN is acked */ 1374 /* 1375 * If there's data, delay ACK; if there's also a FIN 1376 * ACKNOW will be turned on later. 1377 */ 1378 if (DELAY_ACK(tp) && tlen != 0) 1379 callout_reset(tp->tt_delack, tcp_delacktime, 1380 tcp_timer_delack, tp); 1381 else 1382 tp->t_flags |= TF_ACKNOW; 1383 /* 1384 * Received <SYN,ACK> in SYN_SENT[*] state. 1385 * Transitions: 1386 * SYN_SENT --> ESTABLISHED 1387 * SYN_SENT* --> FIN_WAIT_1 1388 */ 1389 tp->t_starttime = ticks; 1390 if (tp->t_flags & TF_NEEDFIN) { 1391 tp->t_state = TCPS_FIN_WAIT_1; 1392 tp->t_flags &= ~TF_NEEDFIN; 1393 thflags &= ~TH_SYN; 1394 } else { 1395 tp->t_state = TCPS_ESTABLISHED; 1396 callout_reset(tp->tt_keep, tcp_keepidle, 1397 tcp_timer_keep, tp); 1398 } 1399 } else { 1400 /* 1401 * Received initial SYN in SYN-SENT[*] state => 1402 * simultaneous open. If segment contains CC option 1403 * and there is a cached CC, apply TAO test. 1404 * If it succeeds, connection is * half-synchronized. 1405 * Otherwise, do 3-way handshake: 1406 * SYN-SENT -> SYN-RECEIVED 1407 * SYN-SENT* -> SYN-RECEIVED* 1408 * If there was no CC option, clear cached CC value. 1409 */ 1410 tp->t_flags |= TF_ACKNOW; 1411 callout_stop(tp->tt_rexmt); 1412 tp->t_state = TCPS_SYN_RECEIVED; 1413 } 1414 1415 trimthenstep6: 1416 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1417 "locked")); 1418 INP_LOCK_ASSERT(inp); 1419 1420 /* 1421 * Advance th->th_seq to correspond to first data byte. 1422 * If data, trim to stay within window, 1423 * dropping FIN if necessary. 1424 */ 1425 th->th_seq++; 1426 if (tlen > tp->rcv_wnd) { 1427 todrop = tlen - tp->rcv_wnd; 1428 m_adj(m, -todrop); 1429 tlen = tp->rcv_wnd; 1430 thflags &= ~TH_FIN; 1431 tcpstat.tcps_rcvpackafterwin++; 1432 tcpstat.tcps_rcvbyteafterwin += todrop; 1433 } 1434 tp->snd_wl1 = th->th_seq - 1; 1435 tp->rcv_up = th->th_seq; 1436 /* 1437 * Client side of transaction: already sent SYN and data. 1438 * If the remote host used T/TCP to validate the SYN, 1439 * our data will be ACK'd; if so, enter normal data segment 1440 * processing in the middle of step 5, ack processing. 1441 * Otherwise, goto step 6. 1442 */ 1443 if (thflags & TH_ACK) 1444 goto process_ACK; 1445 1446 goto step6; 1447 1448 /* 1449 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1450 * do normal processing. 1451 * 1452 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1453 */ 1454 case TCPS_LAST_ACK: 1455 case TCPS_CLOSING: 1456 case TCPS_TIME_WAIT: 1457 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1458 break; /* continue normal processing */ 1459 } 1460 1461 /* 1462 * States other than LISTEN or SYN_SENT. 1463 * First check the RST flag and sequence number since reset segments 1464 * are exempt from the timestamp and connection count tests. This 1465 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1466 * below which allowed reset segments in half the sequence space 1467 * to fall though and be processed (which gives forged reset 1468 * segments with a random sequence number a 50 percent chance of 1469 * killing a connection). 1470 * Then check timestamp, if present. 1471 * Then check the connection count, if present. 1472 * Then check that at least some bytes of segment are within 1473 * receive window. If segment begins before rcv_nxt, 1474 * drop leading data (and SYN); if nothing left, just ack. 1475 * 1476 * 1477 * If the RST bit is set, check the sequence number to see 1478 * if this is a valid reset segment. 1479 * RFC 793 page 37: 1480 * In all states except SYN-SENT, all reset (RST) segments 1481 * are validated by checking their SEQ-fields. A reset is 1482 * valid if its sequence number is in the window. 1483 * Note: this does not take into account delayed ACKs, so 1484 * we should test against last_ack_sent instead of rcv_nxt. 1485 * The sequence number in the reset segment is normally an 1486 * echo of our outgoing acknowlegement numbers, but some hosts 1487 * send a reset with the sequence number at the rightmost edge 1488 * of our receive window, and we have to handle this case. 1489 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1490 * that brute force RST attacks are possible. To combat this, 1491 * we use a much stricter check while in the ESTABLISHED state, 1492 * only accepting RSTs where the sequence number is equal to 1493 * last_ack_sent. In all other states (the states in which a 1494 * RST is more likely), the more permissive check is used. 1495 * If we have multiple segments in flight, the intial reset 1496 * segment sequence numbers will be to the left of last_ack_sent, 1497 * but they will eventually catch up. 1498 * In any case, it never made sense to trim reset segments to 1499 * fit the receive window since RFC 1122 says: 1500 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1501 * 1502 * A TCP SHOULD allow a received RST segment to include data. 1503 * 1504 * DISCUSSION 1505 * It has been suggested that a RST segment could contain 1506 * ASCII text that encoded and explained the cause of the 1507 * RST. No standard has yet been established for such 1508 * data. 1509 * 1510 * If the reset segment passes the sequence number test examine 1511 * the state: 1512 * SYN_RECEIVED STATE: 1513 * If passive open, return to LISTEN state. 1514 * If active open, inform user that connection was refused. 1515 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1516 * Inform user that connection was reset, and close tcb. 1517 * CLOSING, LAST_ACK STATES: 1518 * Close the tcb. 1519 * TIME_WAIT STATE: 1520 * Drop the segment - see Stevens, vol. 2, p. 964 and 1521 * RFC 1337. 1522 */ 1523 if (thflags & TH_RST) { 1524 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1525 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1526 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1527 switch (tp->t_state) { 1528 1529 case TCPS_SYN_RECEIVED: 1530 so->so_error = ECONNREFUSED; 1531 goto close; 1532 1533 case TCPS_ESTABLISHED: 1534 if (tp->last_ack_sent != th->th_seq && 1535 tcp_insecure_rst == 0) { 1536 tcpstat.tcps_badrst++; 1537 goto drop; 1538 } 1539 case TCPS_FIN_WAIT_1: 1540 case TCPS_FIN_WAIT_2: 1541 case TCPS_CLOSE_WAIT: 1542 so->so_error = ECONNRESET; 1543 close: 1544 tp->t_state = TCPS_CLOSED; 1545 tcpstat.tcps_drops++; 1546 KASSERT(headlocked, ("tcp_input: " 1547 "trimthenstep6: tcp_close: head not " 1548 "locked")); 1549 tp = tcp_close(tp); 1550 break; 1551 1552 case TCPS_CLOSING: 1553 case TCPS_LAST_ACK: 1554 KASSERT(headlocked, ("trimthenstep6: " 1555 "tcp_close.2: head not locked")); 1556 tp = tcp_close(tp); 1557 break; 1558 1559 case TCPS_TIME_WAIT: 1560 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1561 ("timewait")); 1562 break; 1563 } 1564 } 1565 goto drop; 1566 } 1567 1568 /* 1569 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1570 * and it's less than ts_recent, drop it. 1571 */ 1572 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1573 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1574 1575 /* Check to see if ts_recent is over 24 days old. */ 1576 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1577 /* 1578 * Invalidate ts_recent. If this segment updates 1579 * ts_recent, the age will be reset later and ts_recent 1580 * will get a valid value. If it does not, setting 1581 * ts_recent to zero will at least satisfy the 1582 * requirement that zero be placed in the timestamp 1583 * echo reply when ts_recent isn't valid. The 1584 * age isn't reset until we get a valid ts_recent 1585 * because we don't want out-of-order segments to be 1586 * dropped when ts_recent is old. 1587 */ 1588 tp->ts_recent = 0; 1589 } else { 1590 tcpstat.tcps_rcvduppack++; 1591 tcpstat.tcps_rcvdupbyte += tlen; 1592 tcpstat.tcps_pawsdrop++; 1593 if (tlen) 1594 goto dropafterack; 1595 goto drop; 1596 } 1597 } 1598 1599 /* 1600 * In the SYN-RECEIVED state, validate that the packet belongs to 1601 * this connection before trimming the data to fit the receive 1602 * window. Check the sequence number versus IRS since we know 1603 * the sequence numbers haven't wrapped. This is a partial fix 1604 * for the "LAND" DoS attack. 1605 */ 1606 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1607 rstreason = BANDLIM_RST_OPENPORT; 1608 goto dropwithreset; 1609 } 1610 1611 todrop = tp->rcv_nxt - th->th_seq; 1612 if (todrop > 0) { 1613 if (thflags & TH_SYN) { 1614 thflags &= ~TH_SYN; 1615 th->th_seq++; 1616 if (th->th_urp > 1) 1617 th->th_urp--; 1618 else 1619 thflags &= ~TH_URG; 1620 todrop--; 1621 } 1622 /* 1623 * Following if statement from Stevens, vol. 2, p. 960. 1624 */ 1625 if (todrop > tlen 1626 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1627 /* 1628 * Any valid FIN must be to the left of the window. 1629 * At this point the FIN must be a duplicate or out 1630 * of sequence; drop it. 1631 */ 1632 thflags &= ~TH_FIN; 1633 1634 /* 1635 * Send an ACK to resynchronize and drop any data. 1636 * But keep on processing for RST or ACK. 1637 */ 1638 tp->t_flags |= TF_ACKNOW; 1639 todrop = tlen; 1640 tcpstat.tcps_rcvduppack++; 1641 tcpstat.tcps_rcvdupbyte += todrop; 1642 } else { 1643 tcpstat.tcps_rcvpartduppack++; 1644 tcpstat.tcps_rcvpartdupbyte += todrop; 1645 } 1646 drop_hdrlen += todrop; /* drop from the top afterwards */ 1647 th->th_seq += todrop; 1648 tlen -= todrop; 1649 if (th->th_urp > todrop) 1650 th->th_urp -= todrop; 1651 else { 1652 thflags &= ~TH_URG; 1653 th->th_urp = 0; 1654 } 1655 } 1656 1657 /* 1658 * If new data are received on a connection after the 1659 * user processes are gone, then RST the other end. 1660 */ 1661 if ((so->so_state & SS_NOFDREF) && 1662 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1663 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1664 "locked")); 1665 tp = tcp_close(tp); 1666 tcpstat.tcps_rcvafterclose++; 1667 rstreason = BANDLIM_UNLIMITED; 1668 goto dropwithreset; 1669 } 1670 1671 /* 1672 * If segment ends after window, drop trailing data 1673 * (and PUSH and FIN); if nothing left, just ACK. 1674 */ 1675 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1676 if (todrop > 0) { 1677 tcpstat.tcps_rcvpackafterwin++; 1678 if (todrop >= tlen) { 1679 tcpstat.tcps_rcvbyteafterwin += tlen; 1680 /* 1681 * If a new connection request is received 1682 * while in TIME_WAIT, drop the old connection 1683 * and start over if the sequence numbers 1684 * are above the previous ones. 1685 */ 1686 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1687 if (thflags & TH_SYN && 1688 tp->t_state == TCPS_TIME_WAIT && 1689 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1690 KASSERT(headlocked, ("trimthenstep6: " 1691 "tcp_close.4: head not locked")); 1692 tp = tcp_close(tp); 1693 goto findpcb; 1694 } 1695 /* 1696 * If window is closed can only take segments at 1697 * window edge, and have to drop data and PUSH from 1698 * incoming segments. Continue processing, but 1699 * remember to ack. Otherwise, drop segment 1700 * and ack. 1701 */ 1702 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1703 tp->t_flags |= TF_ACKNOW; 1704 tcpstat.tcps_rcvwinprobe++; 1705 } else 1706 goto dropafterack; 1707 } else 1708 tcpstat.tcps_rcvbyteafterwin += todrop; 1709 m_adj(m, -todrop); 1710 tlen -= todrop; 1711 thflags &= ~(TH_PUSH|TH_FIN); 1712 } 1713 1714 /* 1715 * If last ACK falls within this segment's sequence numbers, 1716 * record its timestamp. 1717 * NOTE: 1718 * 1) That the test incorporates suggestions from the latest 1719 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1720 * 2) That updating only on newer timestamps interferes with 1721 * our earlier PAWS tests, so this check should be solely 1722 * predicated on the sequence space of this segment. 1723 * 3) That we modify the segment boundary check to be 1724 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1725 * instead of RFC1323's 1726 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1727 * This modified check allows us to overcome RFC1323's 1728 * limitations as described in Stevens TCP/IP Illustrated 1729 * Vol. 2 p.869. In such cases, we can still calculate the 1730 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1731 */ 1732 if ((to.to_flags & TOF_TS) != 0 && 1733 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1734 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1735 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1736 tp->ts_recent_age = ticks; 1737 tp->ts_recent = to.to_tsval; 1738 } 1739 1740 /* 1741 * If a SYN is in the window, then this is an 1742 * error and we send an RST and drop the connection. 1743 */ 1744 if (thflags & TH_SYN) { 1745 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1746 "head not locked")); 1747 tp = tcp_drop(tp, ECONNRESET); 1748 rstreason = BANDLIM_UNLIMITED; 1749 goto drop; 1750 } 1751 1752 /* 1753 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1754 * flag is on (half-synchronized state), then queue data for 1755 * later processing; else drop segment and return. 1756 */ 1757 if ((thflags & TH_ACK) == 0) { 1758 if (tp->t_state == TCPS_SYN_RECEIVED || 1759 (tp->t_flags & TF_NEEDSYN)) 1760 goto step6; 1761 else 1762 goto drop; 1763 } 1764 1765 /* 1766 * Ack processing. 1767 */ 1768 switch (tp->t_state) { 1769 1770 /* 1771 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1772 * ESTABLISHED state and continue processing. 1773 * The ACK was checked above. 1774 */ 1775 case TCPS_SYN_RECEIVED: 1776 1777 tcpstat.tcps_connects++; 1778 soisconnected(so); 1779 /* Do window scaling? */ 1780 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1781 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1782 tp->snd_scale = tp->requested_s_scale; 1783 tp->rcv_scale = tp->request_r_scale; 1784 } 1785 /* 1786 * Make transitions: 1787 * SYN-RECEIVED -> ESTABLISHED 1788 * SYN-RECEIVED* -> FIN-WAIT-1 1789 */ 1790 tp->t_starttime = ticks; 1791 if (tp->t_flags & TF_NEEDFIN) { 1792 tp->t_state = TCPS_FIN_WAIT_1; 1793 tp->t_flags &= ~TF_NEEDFIN; 1794 } else { 1795 tp->t_state = TCPS_ESTABLISHED; 1796 callout_reset(tp->tt_keep, tcp_keepidle, 1797 tcp_timer_keep, tp); 1798 } 1799 /* 1800 * If segment contains data or ACK, will call tcp_reass() 1801 * later; if not, do so now to pass queued data to user. 1802 */ 1803 if (tlen == 0 && (thflags & TH_FIN) == 0) 1804 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1805 (struct mbuf *)0); 1806 tp->snd_wl1 = th->th_seq - 1; 1807 /* FALLTHROUGH */ 1808 1809 /* 1810 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1811 * ACKs. If the ack is in the range 1812 * tp->snd_una < th->th_ack <= tp->snd_max 1813 * then advance tp->snd_una to th->th_ack and drop 1814 * data from the retransmission queue. If this ACK reflects 1815 * more up to date window information we update our window information. 1816 */ 1817 case TCPS_ESTABLISHED: 1818 case TCPS_FIN_WAIT_1: 1819 case TCPS_FIN_WAIT_2: 1820 case TCPS_CLOSE_WAIT: 1821 case TCPS_CLOSING: 1822 case TCPS_LAST_ACK: 1823 case TCPS_TIME_WAIT: 1824 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1825 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1826 tcpstat.tcps_rcvacktoomuch++; 1827 goto dropafterack; 1828 } 1829 if (tp->sack_enable && 1830 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1831 tcp_sack_doack(tp, &to, th->th_ack); 1832 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1833 if (tlen == 0 && tiwin == tp->snd_wnd) { 1834 tcpstat.tcps_rcvdupack++; 1835 /* 1836 * If we have outstanding data (other than 1837 * a window probe), this is a completely 1838 * duplicate ack (ie, window info didn't 1839 * change), the ack is the biggest we've 1840 * seen and we've seen exactly our rexmt 1841 * threshhold of them, assume a packet 1842 * has been dropped and retransmit it. 1843 * Kludge snd_nxt & the congestion 1844 * window so we send only this one 1845 * packet. 1846 * 1847 * We know we're losing at the current 1848 * window size so do congestion avoidance 1849 * (set ssthresh to half the current window 1850 * and pull our congestion window back to 1851 * the new ssthresh). 1852 * 1853 * Dup acks mean that packets have left the 1854 * network (they're now cached at the receiver) 1855 * so bump cwnd by the amount in the receiver 1856 * to keep a constant cwnd packets in the 1857 * network. 1858 */ 1859 if (!callout_active(tp->tt_rexmt) || 1860 th->th_ack != tp->snd_una) 1861 tp->t_dupacks = 0; 1862 else if (++tp->t_dupacks > tcprexmtthresh || 1863 ((tcp_do_newreno || tp->sack_enable) && 1864 IN_FASTRECOVERY(tp))) { 1865 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1866 int awnd; 1867 1868 /* 1869 * Compute the amount of data in flight first. 1870 * We can inject new data into the pipe iff 1871 * we have less than 1/2 the original window's 1872 * worth of data in flight. 1873 */ 1874 awnd = (tp->snd_nxt - tp->snd_fack) + 1875 tp->sackhint.sack_bytes_rexmit; 1876 if (awnd < tp->snd_ssthresh) { 1877 tp->snd_cwnd += tp->t_maxseg; 1878 if (tp->snd_cwnd > tp->snd_ssthresh) 1879 tp->snd_cwnd = tp->snd_ssthresh; 1880 } 1881 } else 1882 tp->snd_cwnd += tp->t_maxseg; 1883 (void) tcp_output(tp); 1884 goto drop; 1885 } else if (tp->t_dupacks == tcprexmtthresh) { 1886 tcp_seq onxt = tp->snd_nxt; 1887 u_int win; 1888 1889 /* 1890 * If we're doing sack, check to 1891 * see if we're already in sack 1892 * recovery. If we're not doing sack, 1893 * check to see if we're in newreno 1894 * recovery. 1895 */ 1896 if (tp->sack_enable) { 1897 if (IN_FASTRECOVERY(tp)) { 1898 tp->t_dupacks = 0; 1899 break; 1900 } 1901 } else if (tcp_do_newreno) { 1902 if (SEQ_LEQ(th->th_ack, 1903 tp->snd_recover)) { 1904 tp->t_dupacks = 0; 1905 break; 1906 } 1907 } 1908 win = min(tp->snd_wnd, tp->snd_cwnd) / 1909 2 / tp->t_maxseg; 1910 if (win < 2) 1911 win = 2; 1912 tp->snd_ssthresh = win * tp->t_maxseg; 1913 ENTER_FASTRECOVERY(tp); 1914 tp->snd_recover = tp->snd_max; 1915 callout_stop(tp->tt_rexmt); 1916 tp->t_rtttime = 0; 1917 if (tp->sack_enable) { 1918 tcpstat.tcps_sack_recovery_episode++; 1919 tp->sack_newdata = tp->snd_nxt; 1920 tp->snd_cwnd = tp->t_maxseg; 1921 (void) tcp_output(tp); 1922 goto drop; 1923 } 1924 tp->snd_nxt = th->th_ack; 1925 tp->snd_cwnd = tp->t_maxseg; 1926 (void) tcp_output(tp); 1927 KASSERT(tp->snd_limited <= 2, 1928 ("tp->snd_limited too big")); 1929 tp->snd_cwnd = tp->snd_ssthresh + 1930 tp->t_maxseg * 1931 (tp->t_dupacks - tp->snd_limited); 1932 if (SEQ_GT(onxt, tp->snd_nxt)) 1933 tp->snd_nxt = onxt; 1934 goto drop; 1935 } else if (tcp_do_rfc3042) { 1936 u_long oldcwnd = tp->snd_cwnd; 1937 tcp_seq oldsndmax = tp->snd_max; 1938 u_int sent; 1939 1940 KASSERT(tp->t_dupacks == 1 || 1941 tp->t_dupacks == 2, 1942 ("dupacks not 1 or 2")); 1943 if (tp->t_dupacks == 1) 1944 tp->snd_limited = 0; 1945 tp->snd_cwnd = 1946 (tp->snd_nxt - tp->snd_una) + 1947 (tp->t_dupacks - tp->snd_limited) * 1948 tp->t_maxseg; 1949 (void) tcp_output(tp); 1950 sent = tp->snd_max - oldsndmax; 1951 if (sent > tp->t_maxseg) { 1952 KASSERT((tp->t_dupacks == 2 && 1953 tp->snd_limited == 0) || 1954 (sent == tp->t_maxseg + 1 && 1955 tp->t_flags & TF_SENTFIN), 1956 ("sent too much")); 1957 tp->snd_limited = 2; 1958 } else if (sent > 0) 1959 ++tp->snd_limited; 1960 tp->snd_cwnd = oldcwnd; 1961 goto drop; 1962 } 1963 } else 1964 tp->t_dupacks = 0; 1965 break; 1966 } 1967 1968 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1969 1970 /* 1971 * If the congestion window was inflated to account 1972 * for the other side's cached packets, retract it. 1973 */ 1974 if (tcp_do_newreno || tp->sack_enable) { 1975 if (IN_FASTRECOVERY(tp)) { 1976 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1977 if (tp->sack_enable) 1978 tcp_sack_partialack(tp, th); 1979 else 1980 tcp_newreno_partial_ack(tp, th); 1981 } else { 1982 /* 1983 * Out of fast recovery. 1984 * Window inflation should have left us 1985 * with approximately snd_ssthresh 1986 * outstanding data. 1987 * But in case we would be inclined to 1988 * send a burst, better to do it via 1989 * the slow start mechanism. 1990 */ 1991 if (SEQ_GT(th->th_ack + 1992 tp->snd_ssthresh, 1993 tp->snd_max)) 1994 tp->snd_cwnd = tp->snd_max - 1995 th->th_ack + 1996 tp->t_maxseg; 1997 else 1998 tp->snd_cwnd = tp->snd_ssthresh; 1999 } 2000 } 2001 } else { 2002 if (tp->t_dupacks >= tcprexmtthresh && 2003 tp->snd_cwnd > tp->snd_ssthresh) 2004 tp->snd_cwnd = tp->snd_ssthresh; 2005 } 2006 tp->t_dupacks = 0; 2007 /* 2008 * If we reach this point, ACK is not a duplicate, 2009 * i.e., it ACKs something we sent. 2010 */ 2011 if (tp->t_flags & TF_NEEDSYN) { 2012 /* 2013 * T/TCP: Connection was half-synchronized, and our 2014 * SYN has been ACK'd (so connection is now fully 2015 * synchronized). Go to non-starred state, 2016 * increment snd_una for ACK of SYN, and check if 2017 * we can do window scaling. 2018 */ 2019 tp->t_flags &= ~TF_NEEDSYN; 2020 tp->snd_una++; 2021 /* Do window scaling? */ 2022 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2023 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2024 tp->snd_scale = tp->requested_s_scale; 2025 tp->rcv_scale = tp->request_r_scale; 2026 } 2027 } 2028 2029 process_ACK: 2030 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2031 "locked")); 2032 INP_LOCK_ASSERT(inp); 2033 2034 acked = th->th_ack - tp->snd_una; 2035 tcpstat.tcps_rcvackpack++; 2036 tcpstat.tcps_rcvackbyte += acked; 2037 2038 /* 2039 * If we just performed our first retransmit, and the ACK 2040 * arrives within our recovery window, then it was a mistake 2041 * to do the retransmit in the first place. Recover our 2042 * original cwnd and ssthresh, and proceed to transmit where 2043 * we left off. 2044 */ 2045 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2046 ++tcpstat.tcps_sndrexmitbad; 2047 tp->snd_cwnd = tp->snd_cwnd_prev; 2048 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2049 tp->snd_recover = tp->snd_recover_prev; 2050 if (tp->t_flags & TF_WASFRECOVERY) 2051 ENTER_FASTRECOVERY(tp); 2052 tp->snd_nxt = tp->snd_max; 2053 tp->t_badrxtwin = 0; /* XXX probably not required */ 2054 } 2055 2056 /* 2057 * If we have a timestamp reply, update smoothed 2058 * round trip time. If no timestamp is present but 2059 * transmit timer is running and timed sequence 2060 * number was acked, update smoothed round trip time. 2061 * Since we now have an rtt measurement, cancel the 2062 * timer backoff (cf., Phil Karn's retransmit alg.). 2063 * Recompute the initial retransmit timer. 2064 * 2065 * Some boxes send broken timestamp replies 2066 * during the SYN+ACK phase, ignore 2067 * timestamps of 0 or we could calculate a 2068 * huge RTT and blow up the retransmit timer. 2069 */ 2070 if ((to.to_flags & TOF_TS) != 0 && 2071 to.to_tsecr) { 2072 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2073 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2074 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2075 } 2076 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2077 2078 /* 2079 * If all outstanding data is acked, stop retransmit 2080 * timer and remember to restart (more output or persist). 2081 * If there is more data to be acked, restart retransmit 2082 * timer, using current (possibly backed-off) value. 2083 */ 2084 if (th->th_ack == tp->snd_max) { 2085 callout_stop(tp->tt_rexmt); 2086 needoutput = 1; 2087 } else if (!callout_active(tp->tt_persist)) 2088 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2089 tcp_timer_rexmt, tp); 2090 2091 /* 2092 * If no data (only SYN) was ACK'd, 2093 * skip rest of ACK processing. 2094 */ 2095 if (acked == 0) 2096 goto step6; 2097 2098 /* 2099 * When new data is acked, open the congestion window. 2100 * If the window gives us less than ssthresh packets 2101 * in flight, open exponentially (maxseg per packet). 2102 * Otherwise open linearly: maxseg per window 2103 * (maxseg^2 / cwnd per packet). 2104 */ 2105 if ((!tcp_do_newreno && !tp->sack_enable) || 2106 !IN_FASTRECOVERY(tp)) { 2107 register u_int cw = tp->snd_cwnd; 2108 register u_int incr = tp->t_maxseg; 2109 if (cw > tp->snd_ssthresh) 2110 incr = incr * incr / cw; 2111 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2112 } 2113 SOCKBUF_LOCK(&so->so_snd); 2114 if (acked > so->so_snd.sb_cc) { 2115 tp->snd_wnd -= so->so_snd.sb_cc; 2116 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2117 ourfinisacked = 1; 2118 } else { 2119 sbdrop_locked(&so->so_snd, acked); 2120 tp->snd_wnd -= acked; 2121 ourfinisacked = 0; 2122 } 2123 sowwakeup_locked(so); 2124 /* detect una wraparound */ 2125 if ((tcp_do_newreno || tp->sack_enable) && 2126 !IN_FASTRECOVERY(tp) && 2127 SEQ_GT(tp->snd_una, tp->snd_recover) && 2128 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2129 tp->snd_recover = th->th_ack - 1; 2130 if ((tcp_do_newreno || tp->sack_enable) && 2131 IN_FASTRECOVERY(tp) && 2132 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2133 EXIT_FASTRECOVERY(tp); 2134 tp->snd_una = th->th_ack; 2135 if (tp->sack_enable) { 2136 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2137 tp->snd_recover = tp->snd_una; 2138 } 2139 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2140 tp->snd_nxt = tp->snd_una; 2141 2142 switch (tp->t_state) { 2143 2144 /* 2145 * In FIN_WAIT_1 STATE in addition to the processing 2146 * for the ESTABLISHED state if our FIN is now acknowledged 2147 * then enter FIN_WAIT_2. 2148 */ 2149 case TCPS_FIN_WAIT_1: 2150 if (ourfinisacked) { 2151 /* 2152 * If we can't receive any more 2153 * data, then closing user can proceed. 2154 * Starting the timer is contrary to the 2155 * specification, but if we don't get a FIN 2156 * we'll hang forever. 2157 */ 2158 /* XXXjl 2159 * we should release the tp also, and use a 2160 * compressed state. 2161 */ 2162 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2163 soisdisconnected(so); 2164 callout_reset(tp->tt_2msl, tcp_maxidle, 2165 tcp_timer_2msl, tp); 2166 } 2167 tp->t_state = TCPS_FIN_WAIT_2; 2168 } 2169 break; 2170 2171 /* 2172 * In CLOSING STATE in addition to the processing for 2173 * the ESTABLISHED state if the ACK acknowledges our FIN 2174 * then enter the TIME-WAIT state, otherwise ignore 2175 * the segment. 2176 */ 2177 case TCPS_CLOSING: 2178 if (ourfinisacked) { 2179 KASSERT(headlocked, ("tcp_input: process_ACK: " 2180 "head not locked")); 2181 tcp_twstart(tp); 2182 INP_INFO_WUNLOCK(&tcbinfo); 2183 m_freem(m); 2184 return; 2185 } 2186 break; 2187 2188 /* 2189 * In LAST_ACK, we may still be waiting for data to drain 2190 * and/or to be acked, as well as for the ack of our FIN. 2191 * If our FIN is now acknowledged, delete the TCB, 2192 * enter the closed state and return. 2193 */ 2194 case TCPS_LAST_ACK: 2195 if (ourfinisacked) { 2196 KASSERT(headlocked, ("tcp_input: process_ACK:" 2197 " tcp_close: head not locked")); 2198 tp = tcp_close(tp); 2199 goto drop; 2200 } 2201 break; 2202 2203 /* 2204 * In TIME_WAIT state the only thing that should arrive 2205 * is a retransmission of the remote FIN. Acknowledge 2206 * it and restart the finack timer. 2207 */ 2208 case TCPS_TIME_WAIT: 2209 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2210 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2211 tcp_timer_2msl, tp); 2212 goto dropafterack; 2213 } 2214 } 2215 2216 step6: 2217 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2218 INP_LOCK_ASSERT(inp); 2219 2220 /* 2221 * Update window information. 2222 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2223 */ 2224 if ((thflags & TH_ACK) && 2225 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2226 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2227 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2228 /* keep track of pure window updates */ 2229 if (tlen == 0 && 2230 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2231 tcpstat.tcps_rcvwinupd++; 2232 tp->snd_wnd = tiwin; 2233 tp->snd_wl1 = th->th_seq; 2234 tp->snd_wl2 = th->th_ack; 2235 if (tp->snd_wnd > tp->max_sndwnd) 2236 tp->max_sndwnd = tp->snd_wnd; 2237 needoutput = 1; 2238 } 2239 2240 /* 2241 * Process segments with URG. 2242 */ 2243 if ((thflags & TH_URG) && th->th_urp && 2244 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2245 /* 2246 * This is a kludge, but if we receive and accept 2247 * random urgent pointers, we'll crash in 2248 * soreceive. It's hard to imagine someone 2249 * actually wanting to send this much urgent data. 2250 */ 2251 SOCKBUF_LOCK(&so->so_rcv); 2252 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2253 th->th_urp = 0; /* XXX */ 2254 thflags &= ~TH_URG; /* XXX */ 2255 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2256 goto dodata; /* XXX */ 2257 } 2258 /* 2259 * If this segment advances the known urgent pointer, 2260 * then mark the data stream. This should not happen 2261 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2262 * a FIN has been received from the remote side. 2263 * In these states we ignore the URG. 2264 * 2265 * According to RFC961 (Assigned Protocols), 2266 * the urgent pointer points to the last octet 2267 * of urgent data. We continue, however, 2268 * to consider it to indicate the first octet 2269 * of data past the urgent section as the original 2270 * spec states (in one of two places). 2271 */ 2272 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2273 tp->rcv_up = th->th_seq + th->th_urp; 2274 so->so_oobmark = so->so_rcv.sb_cc + 2275 (tp->rcv_up - tp->rcv_nxt) - 1; 2276 if (so->so_oobmark == 0) 2277 so->so_rcv.sb_state |= SBS_RCVATMARK; 2278 sohasoutofband(so); 2279 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2280 } 2281 SOCKBUF_UNLOCK(&so->so_rcv); 2282 /* 2283 * Remove out of band data so doesn't get presented to user. 2284 * This can happen independent of advancing the URG pointer, 2285 * but if two URG's are pending at once, some out-of-band 2286 * data may creep in... ick. 2287 */ 2288 if (th->th_urp <= (u_long)tlen && 2289 !(so->so_options & SO_OOBINLINE)) { 2290 /* hdr drop is delayed */ 2291 tcp_pulloutofband(so, th, m, drop_hdrlen); 2292 } 2293 } else { 2294 /* 2295 * If no out of band data is expected, 2296 * pull receive urgent pointer along 2297 * with the receive window. 2298 */ 2299 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2300 tp->rcv_up = tp->rcv_nxt; 2301 } 2302 dodata: /* XXX */ 2303 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2304 INP_LOCK_ASSERT(inp); 2305 2306 /* 2307 * Process the segment text, merging it into the TCP sequencing queue, 2308 * and arranging for acknowledgment of receipt if necessary. 2309 * This process logically involves adjusting tp->rcv_wnd as data 2310 * is presented to the user (this happens in tcp_usrreq.c, 2311 * case PRU_RCVD). If a FIN has already been received on this 2312 * connection then we just ignore the text. 2313 */ 2314 if ((tlen || (thflags & TH_FIN)) && 2315 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2316 tcp_seq save_start = th->th_seq; 2317 tcp_seq save_end = th->th_seq + tlen; 2318 m_adj(m, drop_hdrlen); /* delayed header drop */ 2319 /* 2320 * Insert segment which includes th into TCP reassembly queue 2321 * with control block tp. Set thflags to whether reassembly now 2322 * includes a segment with FIN. This handles the common case 2323 * inline (segment is the next to be received on an established 2324 * connection, and the queue is empty), avoiding linkage into 2325 * and removal from the queue and repetition of various 2326 * conversions. 2327 * Set DELACK for segments received in order, but ack 2328 * immediately when segments are out of order (so 2329 * fast retransmit can work). 2330 */ 2331 if (th->th_seq == tp->rcv_nxt && 2332 LIST_EMPTY(&tp->t_segq) && 2333 TCPS_HAVEESTABLISHED(tp->t_state)) { 2334 if (DELAY_ACK(tp)) 2335 tp->t_flags |= TF_DELACK; 2336 else 2337 tp->t_flags |= TF_ACKNOW; 2338 tp->rcv_nxt += tlen; 2339 thflags = th->th_flags & TH_FIN; 2340 tcpstat.tcps_rcvpack++; 2341 tcpstat.tcps_rcvbyte += tlen; 2342 ND6_HINT(tp); 2343 SOCKBUF_LOCK(&so->so_rcv); 2344 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2345 m_freem(m); 2346 else 2347 sbappendstream_locked(&so->so_rcv, m); 2348 sorwakeup_locked(so); 2349 } else { 2350 thflags = tcp_reass(tp, th, &tlen, m); 2351 tp->t_flags |= TF_ACKNOW; 2352 } 2353 if (tlen > 0 && tp->sack_enable) 2354 tcp_update_sack_list(tp, save_start, save_end); 2355 /* 2356 * Note the amount of data that peer has sent into 2357 * our window, in order to estimate the sender's 2358 * buffer size. 2359 */ 2360 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2361 } else { 2362 m_freem(m); 2363 thflags &= ~TH_FIN; 2364 } 2365 2366 /* 2367 * If FIN is received ACK the FIN and let the user know 2368 * that the connection is closing. 2369 */ 2370 if (thflags & TH_FIN) { 2371 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2372 socantrcvmore(so); 2373 /* 2374 * If connection is half-synchronized 2375 * (ie NEEDSYN flag on) then delay ACK, 2376 * so it may be piggybacked when SYN is sent. 2377 * Otherwise, since we received a FIN then no 2378 * more input can be expected, send ACK now. 2379 */ 2380 if (tp->t_flags & TF_NEEDSYN) 2381 tp->t_flags |= TF_DELACK; 2382 else 2383 tp->t_flags |= TF_ACKNOW; 2384 tp->rcv_nxt++; 2385 } 2386 switch (tp->t_state) { 2387 2388 /* 2389 * In SYN_RECEIVED and ESTABLISHED STATES 2390 * enter the CLOSE_WAIT state. 2391 */ 2392 case TCPS_SYN_RECEIVED: 2393 tp->t_starttime = ticks; 2394 /*FALLTHROUGH*/ 2395 case TCPS_ESTABLISHED: 2396 tp->t_state = TCPS_CLOSE_WAIT; 2397 break; 2398 2399 /* 2400 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2401 * enter the CLOSING state. 2402 */ 2403 case TCPS_FIN_WAIT_1: 2404 tp->t_state = TCPS_CLOSING; 2405 break; 2406 2407 /* 2408 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2409 * starting the time-wait timer, turning off the other 2410 * standard timers. 2411 */ 2412 case TCPS_FIN_WAIT_2: 2413 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2414 "TCP_FIN_WAIT_2: head not locked")); 2415 tcp_twstart(tp); 2416 INP_INFO_WUNLOCK(&tcbinfo); 2417 return; 2418 2419 /* 2420 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2421 */ 2422 case TCPS_TIME_WAIT: 2423 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2424 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2425 tcp_timer_2msl, tp); 2426 break; 2427 } 2428 } 2429 INP_INFO_WUNLOCK(&tcbinfo); 2430 headlocked = 0; 2431 #ifdef TCPDEBUG 2432 if (so->so_options & SO_DEBUG) 2433 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2434 &tcp_savetcp, 0); 2435 #endif 2436 2437 /* 2438 * Return any desired output. 2439 */ 2440 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2441 (void) tcp_output(tp); 2442 2443 check_delack: 2444 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2445 INP_LOCK_ASSERT(inp); 2446 if (tp->t_flags & TF_DELACK) { 2447 tp->t_flags &= ~TF_DELACK; 2448 callout_reset(tp->tt_delack, tcp_delacktime, 2449 tcp_timer_delack, tp); 2450 } 2451 INP_UNLOCK(inp); 2452 return; 2453 2454 dropafterack: 2455 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2456 /* 2457 * Generate an ACK dropping incoming segment if it occupies 2458 * sequence space, where the ACK reflects our state. 2459 * 2460 * We can now skip the test for the RST flag since all 2461 * paths to this code happen after packets containing 2462 * RST have been dropped. 2463 * 2464 * In the SYN-RECEIVED state, don't send an ACK unless the 2465 * segment we received passes the SYN-RECEIVED ACK test. 2466 * If it fails send a RST. This breaks the loop in the 2467 * "LAND" DoS attack, and also prevents an ACK storm 2468 * between two listening ports that have been sent forged 2469 * SYN segments, each with the source address of the other. 2470 */ 2471 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2472 (SEQ_GT(tp->snd_una, th->th_ack) || 2473 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2474 rstreason = BANDLIM_RST_OPENPORT; 2475 goto dropwithreset; 2476 } 2477 #ifdef TCPDEBUG 2478 if (so->so_options & SO_DEBUG) 2479 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2480 &tcp_savetcp, 0); 2481 #endif 2482 KASSERT(headlocked, ("headlocked should be 1")); 2483 INP_INFO_WUNLOCK(&tcbinfo); 2484 tp->t_flags |= TF_ACKNOW; 2485 (void) tcp_output(tp); 2486 INP_UNLOCK(inp); 2487 m_freem(m); 2488 return; 2489 2490 dropwithreset: 2491 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2492 /* 2493 * Generate a RST, dropping incoming segment. 2494 * Make ACK acceptable to originator of segment. 2495 * Don't bother to respond if destination was broadcast/multicast. 2496 */ 2497 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2498 goto drop; 2499 if (isipv6) { 2500 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2501 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2502 goto drop; 2503 } else { 2504 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2505 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2506 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2507 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2508 goto drop; 2509 } 2510 /* IPv6 anycast check is done at tcp6_input() */ 2511 2512 /* 2513 * Perform bandwidth limiting. 2514 */ 2515 if (badport_bandlim(rstreason) < 0) 2516 goto drop; 2517 2518 #ifdef TCPDEBUG 2519 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2520 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2521 &tcp_savetcp, 0); 2522 #endif 2523 2524 if (thflags & TH_ACK) 2525 /* mtod() below is safe as long as hdr dropping is delayed */ 2526 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2527 TH_RST); 2528 else { 2529 if (thflags & TH_SYN) 2530 tlen++; 2531 /* mtod() below is safe as long as hdr dropping is delayed */ 2532 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2533 (tcp_seq)0, TH_RST|TH_ACK); 2534 } 2535 2536 if (tp) 2537 INP_UNLOCK(inp); 2538 if (headlocked) 2539 INP_INFO_WUNLOCK(&tcbinfo); 2540 return; 2541 2542 drop: 2543 /* 2544 * Drop space held by incoming segment and return. 2545 */ 2546 #ifdef TCPDEBUG 2547 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2548 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2549 &tcp_savetcp, 0); 2550 #endif 2551 if (tp) 2552 INP_UNLOCK(inp); 2553 if (headlocked) 2554 INP_INFO_WUNLOCK(&tcbinfo); 2555 m_freem(m); 2556 return; 2557 } 2558 2559 /* 2560 * Parse TCP options and place in tcpopt. 2561 */ 2562 static void 2563 tcp_dooptions(to, cp, cnt, is_syn) 2564 struct tcpopt *to; 2565 u_char *cp; 2566 int cnt; 2567 int is_syn; 2568 { 2569 int opt, optlen; 2570 2571 to->to_flags = 0; 2572 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2573 opt = cp[0]; 2574 if (opt == TCPOPT_EOL) 2575 break; 2576 if (opt == TCPOPT_NOP) 2577 optlen = 1; 2578 else { 2579 if (cnt < 2) 2580 break; 2581 optlen = cp[1]; 2582 if (optlen < 2 || optlen > cnt) 2583 break; 2584 } 2585 switch (opt) { 2586 case TCPOPT_MAXSEG: 2587 if (optlen != TCPOLEN_MAXSEG) 2588 continue; 2589 if (!is_syn) 2590 continue; 2591 to->to_flags |= TOF_MSS; 2592 bcopy((char *)cp + 2, 2593 (char *)&to->to_mss, sizeof(to->to_mss)); 2594 to->to_mss = ntohs(to->to_mss); 2595 break; 2596 case TCPOPT_WINDOW: 2597 if (optlen != TCPOLEN_WINDOW) 2598 continue; 2599 if (! is_syn) 2600 continue; 2601 to->to_flags |= TOF_SCALE; 2602 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2603 break; 2604 case TCPOPT_TIMESTAMP: 2605 if (optlen != TCPOLEN_TIMESTAMP) 2606 continue; 2607 to->to_flags |= TOF_TS; 2608 bcopy((char *)cp + 2, 2609 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2610 to->to_tsval = ntohl(to->to_tsval); 2611 bcopy((char *)cp + 6, 2612 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2613 to->to_tsecr = ntohl(to->to_tsecr); 2614 /* 2615 * If echoed timestamp is later than the current time, 2616 * fall back to non RFC1323 RTT calculation. 2617 */ 2618 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2619 to->to_tsecr = 0; 2620 break; 2621 #ifdef TCP_SIGNATURE 2622 /* 2623 * XXX In order to reply to a host which has set the 2624 * TCP_SIGNATURE option in its initial SYN, we have to 2625 * record the fact that the option was observed here 2626 * for the syncache code to perform the correct response. 2627 */ 2628 case TCPOPT_SIGNATURE: 2629 if (optlen != TCPOLEN_SIGNATURE) 2630 continue; 2631 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2632 break; 2633 #endif 2634 case TCPOPT_SACK_PERMITTED: 2635 if (!tcp_do_sack || 2636 optlen != TCPOLEN_SACK_PERMITTED) 2637 continue; 2638 if (is_syn) { 2639 /* MUST only be set on SYN */ 2640 to->to_flags |= TOF_SACK; 2641 } 2642 break; 2643 case TCPOPT_SACK: 2644 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2645 continue; 2646 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2647 to->to_sacks = cp + 2; 2648 tcpstat.tcps_sack_rcv_blocks++; 2649 break; 2650 default: 2651 continue; 2652 } 2653 } 2654 } 2655 2656 /* 2657 * Pull out of band byte out of a segment so 2658 * it doesn't appear in the user's data queue. 2659 * It is still reflected in the segment length for 2660 * sequencing purposes. 2661 */ 2662 static void 2663 tcp_pulloutofband(so, th, m, off) 2664 struct socket *so; 2665 struct tcphdr *th; 2666 register struct mbuf *m; 2667 int off; /* delayed to be droped hdrlen */ 2668 { 2669 int cnt = off + th->th_urp - 1; 2670 2671 while (cnt >= 0) { 2672 if (m->m_len > cnt) { 2673 char *cp = mtod(m, caddr_t) + cnt; 2674 struct tcpcb *tp = sototcpcb(so); 2675 2676 tp->t_iobc = *cp; 2677 tp->t_oobflags |= TCPOOB_HAVEDATA; 2678 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2679 m->m_len--; 2680 if (m->m_flags & M_PKTHDR) 2681 m->m_pkthdr.len--; 2682 return; 2683 } 2684 cnt -= m->m_len; 2685 m = m->m_next; 2686 if (m == 0) 2687 break; 2688 } 2689 panic("tcp_pulloutofband"); 2690 } 2691 2692 /* 2693 * Collect new round-trip time estimate 2694 * and update averages and current timeout. 2695 */ 2696 static void 2697 tcp_xmit_timer(tp, rtt) 2698 register struct tcpcb *tp; 2699 int rtt; 2700 { 2701 register int delta; 2702 2703 INP_LOCK_ASSERT(tp->t_inpcb); 2704 2705 tcpstat.tcps_rttupdated++; 2706 tp->t_rttupdated++; 2707 if (tp->t_srtt != 0) { 2708 /* 2709 * srtt is stored as fixed point with 5 bits after the 2710 * binary point (i.e., scaled by 8). The following magic 2711 * is equivalent to the smoothing algorithm in rfc793 with 2712 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2713 * point). Adjust rtt to origin 0. 2714 */ 2715 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2716 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2717 2718 if ((tp->t_srtt += delta) <= 0) 2719 tp->t_srtt = 1; 2720 2721 /* 2722 * We accumulate a smoothed rtt variance (actually, a 2723 * smoothed mean difference), then set the retransmit 2724 * timer to smoothed rtt + 4 times the smoothed variance. 2725 * rttvar is stored as fixed point with 4 bits after the 2726 * binary point (scaled by 16). The following is 2727 * equivalent to rfc793 smoothing with an alpha of .75 2728 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2729 * rfc793's wired-in beta. 2730 */ 2731 if (delta < 0) 2732 delta = -delta; 2733 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2734 if ((tp->t_rttvar += delta) <= 0) 2735 tp->t_rttvar = 1; 2736 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2737 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2738 } else { 2739 /* 2740 * No rtt measurement yet - use the unsmoothed rtt. 2741 * Set the variance to half the rtt (so our first 2742 * retransmit happens at 3*rtt). 2743 */ 2744 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2745 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2746 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2747 } 2748 tp->t_rtttime = 0; 2749 tp->t_rxtshift = 0; 2750 2751 /* 2752 * the retransmit should happen at rtt + 4 * rttvar. 2753 * Because of the way we do the smoothing, srtt and rttvar 2754 * will each average +1/2 tick of bias. When we compute 2755 * the retransmit timer, we want 1/2 tick of rounding and 2756 * 1 extra tick because of +-1/2 tick uncertainty in the 2757 * firing of the timer. The bias will give us exactly the 2758 * 1.5 tick we need. But, because the bias is 2759 * statistical, we have to test that we don't drop below 2760 * the minimum feasible timer (which is 2 ticks). 2761 */ 2762 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2763 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2764 2765 /* 2766 * We received an ack for a packet that wasn't retransmitted; 2767 * it is probably safe to discard any error indications we've 2768 * received recently. This isn't quite right, but close enough 2769 * for now (a route might have failed after we sent a segment, 2770 * and the return path might not be symmetrical). 2771 */ 2772 tp->t_softerror = 0; 2773 } 2774 2775 /* 2776 * Determine a reasonable value for maxseg size. 2777 * If the route is known, check route for mtu. 2778 * If none, use an mss that can be handled on the outgoing 2779 * interface without forcing IP to fragment; if bigger than 2780 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2781 * to utilize large mbufs. If no route is found, route has no mtu, 2782 * or the destination isn't local, use a default, hopefully conservative 2783 * size (usually 512 or the default IP max size, but no more than the mtu 2784 * of the interface), as we can't discover anything about intervening 2785 * gateways or networks. We also initialize the congestion/slow start 2786 * window to be a single segment if the destination isn't local. 2787 * While looking at the routing entry, we also initialize other path-dependent 2788 * parameters from pre-set or cached values in the routing entry. 2789 * 2790 * Also take into account the space needed for options that we 2791 * send regularly. Make maxseg shorter by that amount to assure 2792 * that we can send maxseg amount of data even when the options 2793 * are present. Store the upper limit of the length of options plus 2794 * data in maxopd. 2795 * 2796 * 2797 * In case of T/TCP, we call this routine during implicit connection 2798 * setup as well (offer = -1), to initialize maxseg from the cached 2799 * MSS of our peer. 2800 * 2801 * NOTE that this routine is only called when we process an incoming 2802 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2803 */ 2804 void 2805 tcp_mss(tp, offer) 2806 struct tcpcb *tp; 2807 int offer; 2808 { 2809 int rtt, mss; 2810 u_long bufsize; 2811 u_long maxmtu; 2812 struct inpcb *inp = tp->t_inpcb; 2813 struct socket *so; 2814 struct hc_metrics_lite metrics; 2815 int origoffer = offer; 2816 #ifdef INET6 2817 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2818 size_t min_protoh = isipv6 ? 2819 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2820 sizeof (struct tcpiphdr); 2821 #else 2822 const size_t min_protoh = sizeof(struct tcpiphdr); 2823 #endif 2824 2825 /* initialize */ 2826 #ifdef INET6 2827 if (isipv6) { 2828 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2829 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2830 } else 2831 #endif 2832 { 2833 maxmtu = tcp_maxmtu(&inp->inp_inc); 2834 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2835 } 2836 so = inp->inp_socket; 2837 2838 /* 2839 * no route to sender, stay with default mss and return 2840 */ 2841 if (maxmtu == 0) 2842 return; 2843 2844 /* what have we got? */ 2845 switch (offer) { 2846 case 0: 2847 /* 2848 * Offer == 0 means that there was no MSS on the SYN 2849 * segment, in this case we use tcp_mssdflt. 2850 */ 2851 offer = 2852 #ifdef INET6 2853 isipv6 ? tcp_v6mssdflt : 2854 #endif 2855 tcp_mssdflt; 2856 break; 2857 2858 case -1: 2859 /* 2860 * Offer == -1 means that we didn't receive SYN yet. 2861 */ 2862 /* FALLTHROUGH */ 2863 2864 default: 2865 /* 2866 * Prevent DoS attack with too small MSS. Round up 2867 * to at least minmss. 2868 */ 2869 offer = max(offer, tcp_minmss); 2870 /* 2871 * Sanity check: make sure that maxopd will be large 2872 * enough to allow some data on segments even if the 2873 * all the option space is used (40bytes). Otherwise 2874 * funny things may happen in tcp_output. 2875 */ 2876 offer = max(offer, 64); 2877 } 2878 2879 /* 2880 * rmx information is now retrieved from tcp_hostcache 2881 */ 2882 tcp_hc_get(&inp->inp_inc, &metrics); 2883 2884 /* 2885 * if there's a discovered mtu int tcp hostcache, use it 2886 * else, use the link mtu. 2887 */ 2888 if (metrics.rmx_mtu) 2889 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2890 else { 2891 #ifdef INET6 2892 if (isipv6) { 2893 mss = maxmtu - min_protoh; 2894 if (!path_mtu_discovery && 2895 !in6_localaddr(&inp->in6p_faddr)) 2896 mss = min(mss, tcp_v6mssdflt); 2897 } else 2898 #endif 2899 { 2900 mss = maxmtu - min_protoh; 2901 if (!path_mtu_discovery && 2902 !in_localaddr(inp->inp_faddr)) 2903 mss = min(mss, tcp_mssdflt); 2904 } 2905 } 2906 mss = min(mss, offer); 2907 2908 /* 2909 * maxopd stores the maximum length of data AND options 2910 * in a segment; maxseg is the amount of data in a normal 2911 * segment. We need to store this value (maxopd) apart 2912 * from maxseg, because now every segment carries options 2913 * and thus we normally have somewhat less data in segments. 2914 */ 2915 tp->t_maxopd = mss; 2916 2917 /* 2918 * origoffer==-1 indicates, that no segments were received yet. 2919 * In this case we just guess. 2920 */ 2921 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2922 (origoffer == -1 || 2923 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2924 mss -= TCPOLEN_TSTAMP_APPA; 2925 tp->t_maxseg = mss; 2926 2927 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2928 if (mss > MCLBYTES) 2929 mss &= ~(MCLBYTES-1); 2930 #else 2931 if (mss > MCLBYTES) 2932 mss = mss / MCLBYTES * MCLBYTES; 2933 #endif 2934 tp->t_maxseg = mss; 2935 2936 /* 2937 * If there's a pipesize, change the socket buffer to that size, 2938 * don't change if sb_hiwat is different than default (then it 2939 * has been changed on purpose with setsockopt). 2940 * Make the socket buffers an integral number of mss units; 2941 * if the mss is larger than the socket buffer, decrease the mss. 2942 */ 2943 SOCKBUF_LOCK(&so->so_snd); 2944 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2945 bufsize = metrics.rmx_sendpipe; 2946 else 2947 bufsize = so->so_snd.sb_hiwat; 2948 if (bufsize < mss) 2949 mss = bufsize; 2950 else { 2951 bufsize = roundup(bufsize, mss); 2952 if (bufsize > sb_max) 2953 bufsize = sb_max; 2954 if (bufsize > so->so_snd.sb_hiwat) 2955 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 2956 } 2957 SOCKBUF_UNLOCK(&so->so_snd); 2958 tp->t_maxseg = mss; 2959 2960 SOCKBUF_LOCK(&so->so_rcv); 2961 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2962 bufsize = metrics.rmx_recvpipe; 2963 else 2964 bufsize = so->so_rcv.sb_hiwat; 2965 if (bufsize > mss) { 2966 bufsize = roundup(bufsize, mss); 2967 if (bufsize > sb_max) 2968 bufsize = sb_max; 2969 if (bufsize > so->so_rcv.sb_hiwat) 2970 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 2971 } 2972 SOCKBUF_UNLOCK(&so->so_rcv); 2973 /* 2974 * While we're here, check the others too 2975 */ 2976 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2977 tp->t_srtt = rtt; 2978 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2979 tcpstat.tcps_usedrtt++; 2980 if (metrics.rmx_rttvar) { 2981 tp->t_rttvar = metrics.rmx_rttvar; 2982 tcpstat.tcps_usedrttvar++; 2983 } else { 2984 /* default variation is +- 1 rtt */ 2985 tp->t_rttvar = 2986 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2987 } 2988 TCPT_RANGESET(tp->t_rxtcur, 2989 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2990 tp->t_rttmin, TCPTV_REXMTMAX); 2991 } 2992 if (metrics.rmx_ssthresh) { 2993 /* 2994 * There's some sort of gateway or interface 2995 * buffer limit on the path. Use this to set 2996 * the slow start threshhold, but set the 2997 * threshold to no less than 2*mss. 2998 */ 2999 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3000 tcpstat.tcps_usedssthresh++; 3001 } 3002 if (metrics.rmx_bandwidth) 3003 tp->snd_bandwidth = metrics.rmx_bandwidth; 3004 3005 /* 3006 * Set the slow-start flight size depending on whether this 3007 * is a local network or not. 3008 * 3009 * Extend this so we cache the cwnd too and retrieve it here. 3010 * Make cwnd even bigger than RFC3390 suggests but only if we 3011 * have previous experience with the remote host. Be careful 3012 * not make cwnd bigger than remote receive window or our own 3013 * send socket buffer. Maybe put some additional upper bound 3014 * on the retrieved cwnd. Should do incremental updates to 3015 * hostcache when cwnd collapses so next connection doesn't 3016 * overloads the path again. 3017 * 3018 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3019 * We currently check only in syncache_socket for that. 3020 */ 3021 #define TCP_METRICS_CWND 3022 #ifdef TCP_METRICS_CWND 3023 if (metrics.rmx_cwnd) 3024 tp->snd_cwnd = max(mss, 3025 min(metrics.rmx_cwnd / 2, 3026 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3027 else 3028 #endif 3029 if (tcp_do_rfc3390) 3030 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3031 #ifdef INET6 3032 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3033 (!isipv6 && in_localaddr(inp->inp_faddr))) 3034 #else 3035 else if (in_localaddr(inp->inp_faddr)) 3036 #endif 3037 tp->snd_cwnd = mss * ss_fltsz_local; 3038 else 3039 tp->snd_cwnd = mss * ss_fltsz; 3040 } 3041 3042 /* 3043 * Determine the MSS option to send on an outgoing SYN. 3044 */ 3045 int 3046 tcp_mssopt(inc) 3047 struct in_conninfo *inc; 3048 { 3049 int mss = 0; 3050 u_long maxmtu = 0; 3051 u_long thcmtu = 0; 3052 size_t min_protoh; 3053 #ifdef INET6 3054 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3055 #endif 3056 3057 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3058 3059 #ifdef INET6 3060 if (isipv6) { 3061 mss = tcp_v6mssdflt; 3062 maxmtu = tcp_maxmtu6(inc); 3063 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3064 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3065 } else 3066 #endif 3067 { 3068 mss = tcp_mssdflt; 3069 maxmtu = tcp_maxmtu(inc); 3070 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3071 min_protoh = sizeof(struct tcpiphdr); 3072 } 3073 if (maxmtu && thcmtu) 3074 mss = min(maxmtu, thcmtu) - min_protoh; 3075 else if (maxmtu || thcmtu) 3076 mss = max(maxmtu, thcmtu) - min_protoh; 3077 3078 return (mss); 3079 } 3080 3081 3082 /* 3083 * On a partial ack arrives, force the retransmission of the 3084 * next unacknowledged segment. Do not clear tp->t_dupacks. 3085 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3086 * be started again. 3087 */ 3088 static void 3089 tcp_newreno_partial_ack(tp, th) 3090 struct tcpcb *tp; 3091 struct tcphdr *th; 3092 { 3093 tcp_seq onxt = tp->snd_nxt; 3094 u_long ocwnd = tp->snd_cwnd; 3095 3096 callout_stop(tp->tt_rexmt); 3097 tp->t_rtttime = 0; 3098 tp->snd_nxt = th->th_ack; 3099 /* 3100 * Set snd_cwnd to one segment beyond acknowledged offset. 3101 * (tp->snd_una has not yet been updated when this function is called.) 3102 */ 3103 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3104 tp->t_flags |= TF_ACKNOW; 3105 (void) tcp_output(tp); 3106 tp->snd_cwnd = ocwnd; 3107 if (SEQ_GT(onxt, tp->snd_nxt)) 3108 tp->snd_nxt = onxt; 3109 /* 3110 * Partial window deflation. Relies on fact that tp->snd_una 3111 * not updated yet. 3112 */ 3113 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3114 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3115 else 3116 tp->snd_cwnd = 0; 3117 tp->snd_cwnd += tp->t_maxseg; 3118 } 3119 3120 /* 3121 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3122 * looking for a pcb in the listen state. Returns 0 otherwise. 3123 */ 3124 static int 3125 tcp_timewait(tw, to, th, m, tlen) 3126 struct tcptw *tw; 3127 struct tcpopt *to; 3128 struct tcphdr *th; 3129 struct mbuf *m; 3130 int tlen; 3131 { 3132 int thflags; 3133 tcp_seq seq; 3134 #ifdef INET6 3135 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3136 #else 3137 const int isipv6 = 0; 3138 #endif 3139 3140 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3141 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3142 INP_LOCK_ASSERT(tw->tw_inpcb); 3143 3144 thflags = th->th_flags; 3145 3146 /* 3147 * NOTE: for FIN_WAIT_2 (to be added later), 3148 * must validate sequence number before accepting RST 3149 */ 3150 3151 /* 3152 * If the segment contains RST: 3153 * Drop the segment - see Stevens, vol. 2, p. 964 and 3154 * RFC 1337. 3155 */ 3156 if (thflags & TH_RST) 3157 goto drop; 3158 3159 #if 0 3160 /* PAWS not needed at the moment */ 3161 /* 3162 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3163 * and it's less than ts_recent, drop it. 3164 */ 3165 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3166 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3167 if ((thflags & TH_ACK) == 0) 3168 goto drop; 3169 goto ack; 3170 } 3171 /* 3172 * ts_recent is never updated because we never accept new segments. 3173 */ 3174 #endif 3175 3176 /* 3177 * If a new connection request is received 3178 * while in TIME_WAIT, drop the old connection 3179 * and start over if the sequence numbers 3180 * are above the previous ones. 3181 */ 3182 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3183 (void) tcp_twclose(tw, 0); 3184 return (1); 3185 } 3186 3187 /* 3188 * Drop the the segment if it does not contain an ACK. 3189 */ 3190 if ((thflags & TH_ACK) == 0) 3191 goto drop; 3192 3193 /* 3194 * Reset the 2MSL timer if this is a duplicate FIN. 3195 */ 3196 if (thflags & TH_FIN) { 3197 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3198 if (seq + 1 == tw->rcv_nxt) 3199 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3200 } 3201 3202 /* 3203 * Acknowledge the segment if it has data or is not a duplicate ACK. 3204 */ 3205 if (thflags != TH_ACK || tlen != 0 || 3206 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3207 tcp_twrespond(tw, TH_ACK); 3208 goto drop; 3209 3210 /* 3211 * Generate a RST, dropping incoming segment. 3212 * Make ACK acceptable to originator of segment. 3213 * Don't bother to respond if destination was broadcast/multicast. 3214 */ 3215 if (m->m_flags & (M_BCAST|M_MCAST)) 3216 goto drop; 3217 if (isipv6) { 3218 struct ip6_hdr *ip6; 3219 3220 /* IPv6 anycast check is done at tcp6_input() */ 3221 ip6 = mtod(m, struct ip6_hdr *); 3222 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3223 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3224 goto drop; 3225 } else { 3226 struct ip *ip; 3227 3228 ip = mtod(m, struct ip *); 3229 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3230 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3231 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3232 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3233 goto drop; 3234 } 3235 if (thflags & TH_ACK) { 3236 tcp_respond(NULL, 3237 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3238 } else { 3239 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3240 tcp_respond(NULL, 3241 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3242 } 3243 INP_UNLOCK(tw->tw_inpcb); 3244 return (0); 3245 3246 drop: 3247 INP_UNLOCK(tw->tw_inpcb); 3248 m_freem(m); 3249 return (0); 3250 } 3251