1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/mac.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/signalvar.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 #include <sys/syslog.h> 54 #include <sys/systm.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/in_var.h> 67 #include <netinet/ip.h> 68 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip_options.h> 72 #include <netinet/ip6.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/in6_pcb.h> 75 #include <netinet6/ip6_var.h> 76 #include <netinet6/nd6.h> 77 #include <netinet/tcp.h> 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet6/tcp6_var.h> 83 #include <netinet/tcpip.h> 84 #ifdef TCPDEBUG 85 #include <netinet/tcp_debug.h> 86 #endif /* TCPDEBUG */ 87 88 #ifdef FAST_IPSEC 89 #include <netipsec/ipsec.h> 90 #include <netipsec/ipsec6.h> 91 #endif /*FAST_IPSEC*/ 92 93 #ifdef IPSEC 94 #include <netinet6/ipsec.h> 95 #include <netinet6/ipsec6.h> 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 static const int tcprexmtthresh = 3; 102 103 struct tcpstat tcpstat; 104 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107 static int log_in_vain = 0; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111 static int blackhole = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115 int tcp_delack_enabled = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120 #ifdef TCP_DROP_SYNFIN 121 static int drop_synfin = 0; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124 #endif 125 126 static int tcp_do_rfc3042 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130 static int tcp_do_rfc3390 = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135 static int tcp_insecure_rst = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 137 &tcp_insecure_rst, 0, 138 "Follow the old (insecure) criteria for accepting RST packets."); 139 140 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 141 "TCP Segment Reassembly Queue"); 142 143 static int tcp_reass_maxseg = 0; 144 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 145 &tcp_reass_maxseg, 0, 146 "Global maximum number of TCP Segments in Reassembly Queue"); 147 148 int tcp_reass_qsize = 0; 149 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 150 &tcp_reass_qsize, 0, 151 "Global number of TCP Segments currently in Reassembly Queue"); 152 153 static int tcp_reass_maxqlen = 48; 154 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 155 &tcp_reass_maxqlen, 0, 156 "Maximum number of TCP Segments per individual Reassembly Queue"); 157 158 static int tcp_reass_overflows = 0; 159 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 160 &tcp_reass_overflows, 0, 161 "Global number of TCP Segment Reassembly Queue Overflows"); 162 163 struct inpcbhead tcb; 164 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 165 struct inpcbinfo tcbinfo; 166 struct mtx *tcbinfo_mtx; 167 168 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 169 170 static void tcp_pulloutofband(struct socket *, 171 struct tcphdr *, struct mbuf *, int); 172 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 173 struct mbuf *); 174 static void tcp_xmit_timer(struct tcpcb *, int); 175 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 176 static int tcp_timewait(struct tcptw *, struct tcpopt *, 177 struct tcphdr *, struct mbuf *, int); 178 179 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 180 #ifdef INET6 181 #define ND6_HINT(tp) \ 182 do { \ 183 if ((tp) && (tp)->t_inpcb && \ 184 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 185 nd6_nud_hint(NULL, NULL, 0); \ 186 } while (0) 187 #else 188 #define ND6_HINT(tp) 189 #endif 190 191 /* 192 * Indicate whether this ack should be delayed. We can delay the ack if 193 * - there is no delayed ack timer in progress and 194 * - our last ack wasn't a 0-sized window. We never want to delay 195 * the ack that opens up a 0-sized window and 196 * - delayed acks are enabled or 197 * - this is a half-synchronized T/TCP connection. 198 */ 199 #define DELAY_ACK(tp) \ 200 ((!callout_active(tp->tt_delack) && \ 201 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 202 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 203 204 /* Initialize TCP reassembly queue */ 205 uma_zone_t tcp_reass_zone; 206 void 207 tcp_reass_init() 208 { 209 tcp_reass_maxseg = nmbclusters / 16; 210 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 211 &tcp_reass_maxseg); 212 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 213 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 214 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 215 } 216 217 static int 218 tcp_reass(tp, th, tlenp, m) 219 register struct tcpcb *tp; 220 register struct tcphdr *th; 221 int *tlenp; 222 struct mbuf *m; 223 { 224 struct tseg_qent *q; 225 struct tseg_qent *p = NULL; 226 struct tseg_qent *nq; 227 struct tseg_qent *te = NULL; 228 struct socket *so = tp->t_inpcb->inp_socket; 229 int flags; 230 231 INP_LOCK_ASSERT(tp->t_inpcb); 232 233 /* 234 * XXX: tcp_reass() is rather inefficient with its data structures 235 * and should be rewritten (see NetBSD for optimizations). While 236 * doing that it should move to its own file tcp_reass.c. 237 */ 238 239 /* 240 * Call with th==NULL after become established to 241 * force pre-ESTABLISHED data up to user socket. 242 */ 243 if (th == NULL) 244 goto present; 245 246 /* 247 * Limit the number of segments in the reassembly queue to prevent 248 * holding on to too many segments (and thus running out of mbufs). 249 * Make sure to let the missing segment through which caused this 250 * queue. Always keep one global queue entry spare to be able to 251 * process the missing segment. 252 */ 253 if (th->th_seq != tp->rcv_nxt && 254 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 255 tp->t_segqlen >= tcp_reass_maxqlen)) { 256 tcp_reass_overflows++; 257 tcpstat.tcps_rcvmemdrop++; 258 m_freem(m); 259 *tlenp = 0; 260 return (0); 261 } 262 263 /* 264 * Allocate a new queue entry. If we can't, or hit the zone limit 265 * just drop the pkt. 266 */ 267 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 268 if (te == NULL) { 269 tcpstat.tcps_rcvmemdrop++; 270 m_freem(m); 271 *tlenp = 0; 272 return (0); 273 } 274 tp->t_segqlen++; 275 tcp_reass_qsize++; 276 277 /* 278 * Find a segment which begins after this one does. 279 */ 280 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 281 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 282 break; 283 p = q; 284 } 285 286 /* 287 * If there is a preceding segment, it may provide some of 288 * our data already. If so, drop the data from the incoming 289 * segment. If it provides all of our data, drop us. 290 */ 291 if (p != NULL) { 292 register int i; 293 /* conversion to int (in i) handles seq wraparound */ 294 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 295 if (i > 0) { 296 if (i >= *tlenp) { 297 tcpstat.tcps_rcvduppack++; 298 tcpstat.tcps_rcvdupbyte += *tlenp; 299 m_freem(m); 300 uma_zfree(tcp_reass_zone, te); 301 tp->t_segqlen--; 302 tcp_reass_qsize--; 303 /* 304 * Try to present any queued data 305 * at the left window edge to the user. 306 * This is needed after the 3-WHS 307 * completes. 308 */ 309 goto present; /* ??? */ 310 } 311 m_adj(m, i); 312 *tlenp -= i; 313 th->th_seq += i; 314 } 315 } 316 tcpstat.tcps_rcvoopack++; 317 tcpstat.tcps_rcvoobyte += *tlenp; 318 319 /* 320 * While we overlap succeeding segments trim them or, 321 * if they are completely covered, dequeue them. 322 */ 323 while (q) { 324 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 325 if (i <= 0) 326 break; 327 if (i < q->tqe_len) { 328 q->tqe_th->th_seq += i; 329 q->tqe_len -= i; 330 m_adj(q->tqe_m, i); 331 break; 332 } 333 334 nq = LIST_NEXT(q, tqe_q); 335 LIST_REMOVE(q, tqe_q); 336 m_freem(q->tqe_m); 337 uma_zfree(tcp_reass_zone, q); 338 tp->t_segqlen--; 339 tcp_reass_qsize--; 340 q = nq; 341 } 342 343 /* Insert the new segment queue entry into place. */ 344 te->tqe_m = m; 345 te->tqe_th = th; 346 te->tqe_len = *tlenp; 347 348 if (p == NULL) { 349 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 350 } else { 351 LIST_INSERT_AFTER(p, te, tqe_q); 352 } 353 354 present: 355 /* 356 * Present data to user, advancing rcv_nxt through 357 * completed sequence space. 358 */ 359 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 360 return (0); 361 q = LIST_FIRST(&tp->t_segq); 362 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 363 return (0); 364 SOCKBUF_LOCK(&so->so_rcv); 365 do { 366 tp->rcv_nxt += q->tqe_len; 367 flags = q->tqe_th->th_flags & TH_FIN; 368 nq = LIST_NEXT(q, tqe_q); 369 LIST_REMOVE(q, tqe_q); 370 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 371 m_freem(q->tqe_m); 372 else 373 sbappendstream_locked(&so->so_rcv, q->tqe_m); 374 uma_zfree(tcp_reass_zone, q); 375 tp->t_segqlen--; 376 tcp_reass_qsize--; 377 q = nq; 378 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 379 ND6_HINT(tp); 380 sorwakeup_locked(so); 381 return (flags); 382 } 383 384 /* 385 * TCP input routine, follows pages 65-76 of the 386 * protocol specification dated September, 1981 very closely. 387 */ 388 #ifdef INET6 389 int 390 tcp6_input(mp, offp, proto) 391 struct mbuf **mp; 392 int *offp, proto; 393 { 394 register struct mbuf *m = *mp; 395 struct in6_ifaddr *ia6; 396 397 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 398 399 /* 400 * draft-itojun-ipv6-tcp-to-anycast 401 * better place to put this in? 402 */ 403 ia6 = ip6_getdstifaddr(m); 404 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 405 struct ip6_hdr *ip6; 406 407 ip6 = mtod(m, struct ip6_hdr *); 408 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 409 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 410 return IPPROTO_DONE; 411 } 412 413 tcp_input(m, *offp); 414 return IPPROTO_DONE; 415 } 416 #endif 417 418 void 419 tcp_input(m, off0) 420 register struct mbuf *m; 421 int off0; 422 { 423 register struct tcphdr *th; 424 register struct ip *ip = NULL; 425 register struct ipovly *ipov; 426 register struct inpcb *inp = NULL; 427 u_char *optp = NULL; 428 int optlen = 0; 429 int len, tlen, off; 430 int drop_hdrlen; 431 register struct tcpcb *tp = 0; 432 register int thflags; 433 struct socket *so = 0; 434 int todrop, acked, ourfinisacked, needoutput = 0; 435 u_long tiwin; 436 struct tcpopt to; /* options in this segment */ 437 int headlocked = 0; 438 #ifdef IPFIREWALL_FORWARD 439 struct m_tag *fwd_tag; 440 #endif 441 int rstreason; /* For badport_bandlim accounting purposes */ 442 443 struct ip6_hdr *ip6 = NULL; 444 #ifdef INET6 445 int isipv6; 446 #else 447 const int isipv6 = 0; 448 #endif 449 450 #ifdef TCPDEBUG 451 /* 452 * The size of tcp_saveipgen must be the size of the max ip header, 453 * now IPv6. 454 */ 455 u_char tcp_saveipgen[40]; 456 struct tcphdr tcp_savetcp; 457 short ostate = 0; 458 #endif 459 460 #ifdef INET6 461 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 462 #endif 463 bzero((char *)&to, sizeof(to)); 464 465 tcpstat.tcps_rcvtotal++; 466 467 if (isipv6) { 468 #ifdef INET6 469 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 470 ip6 = mtod(m, struct ip6_hdr *); 471 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 472 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 473 tcpstat.tcps_rcvbadsum++; 474 goto drop; 475 } 476 th = (struct tcphdr *)((caddr_t)ip6 + off0); 477 478 /* 479 * Be proactive about unspecified IPv6 address in source. 480 * As we use all-zero to indicate unbounded/unconnected pcb, 481 * unspecified IPv6 address can be used to confuse us. 482 * 483 * Note that packets with unspecified IPv6 destination is 484 * already dropped in ip6_input. 485 */ 486 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 487 /* XXX stat */ 488 goto drop; 489 } 490 #else 491 th = NULL; /* XXX: avoid compiler warning */ 492 #endif 493 } else { 494 /* 495 * Get IP and TCP header together in first mbuf. 496 * Note: IP leaves IP header in first mbuf. 497 */ 498 if (off0 > sizeof (struct ip)) { 499 ip_stripoptions(m, (struct mbuf *)0); 500 off0 = sizeof(struct ip); 501 } 502 if (m->m_len < sizeof (struct tcpiphdr)) { 503 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 504 tcpstat.tcps_rcvshort++; 505 return; 506 } 507 } 508 ip = mtod(m, struct ip *); 509 ipov = (struct ipovly *)ip; 510 th = (struct tcphdr *)((caddr_t)ip + off0); 511 tlen = ip->ip_len; 512 513 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 514 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 515 th->th_sum = m->m_pkthdr.csum_data; 516 else 517 th->th_sum = in_pseudo(ip->ip_src.s_addr, 518 ip->ip_dst.s_addr, 519 htonl(m->m_pkthdr.csum_data + 520 ip->ip_len + 521 IPPROTO_TCP)); 522 th->th_sum ^= 0xffff; 523 #ifdef TCPDEBUG 524 ipov->ih_len = (u_short)tlen; 525 ipov->ih_len = htons(ipov->ih_len); 526 #endif 527 } else { 528 /* 529 * Checksum extended TCP header and data. 530 */ 531 len = sizeof (struct ip) + tlen; 532 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 533 ipov->ih_len = (u_short)tlen; 534 ipov->ih_len = htons(ipov->ih_len); 535 th->th_sum = in_cksum(m, len); 536 } 537 if (th->th_sum) { 538 tcpstat.tcps_rcvbadsum++; 539 goto drop; 540 } 541 #ifdef INET6 542 /* Re-initialization for later version check */ 543 ip->ip_v = IPVERSION; 544 #endif 545 } 546 547 /* 548 * Check that TCP offset makes sense, 549 * pull out TCP options and adjust length. XXX 550 */ 551 off = th->th_off << 2; 552 if (off < sizeof (struct tcphdr) || off > tlen) { 553 tcpstat.tcps_rcvbadoff++; 554 goto drop; 555 } 556 tlen -= off; /* tlen is used instead of ti->ti_len */ 557 if (off > sizeof (struct tcphdr)) { 558 if (isipv6) { 559 #ifdef INET6 560 IP6_EXTHDR_CHECK(m, off0, off, ); 561 ip6 = mtod(m, struct ip6_hdr *); 562 th = (struct tcphdr *)((caddr_t)ip6 + off0); 563 #endif 564 } else { 565 if (m->m_len < sizeof(struct ip) + off) { 566 if ((m = m_pullup(m, sizeof (struct ip) + off)) 567 == 0) { 568 tcpstat.tcps_rcvshort++; 569 return; 570 } 571 ip = mtod(m, struct ip *); 572 ipov = (struct ipovly *)ip; 573 th = (struct tcphdr *)((caddr_t)ip + off0); 574 } 575 } 576 optlen = off - sizeof (struct tcphdr); 577 optp = (u_char *)(th + 1); 578 } 579 thflags = th->th_flags; 580 581 #ifdef TCP_DROP_SYNFIN 582 /* 583 * If the drop_synfin option is enabled, drop all packets with 584 * both the SYN and FIN bits set. This prevents e.g. nmap from 585 * identifying the TCP/IP stack. 586 * 587 * This is a violation of the TCP specification. 588 */ 589 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 590 goto drop; 591 #endif 592 593 /* 594 * Convert TCP protocol specific fields to host format. 595 */ 596 th->th_seq = ntohl(th->th_seq); 597 th->th_ack = ntohl(th->th_ack); 598 th->th_win = ntohs(th->th_win); 599 th->th_urp = ntohs(th->th_urp); 600 601 /* 602 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 603 * until after ip6_savecontrol() is called and before other functions 604 * which don't want those proto headers. 605 * Because ip6_savecontrol() is going to parse the mbuf to 606 * search for data to be passed up to user-land, it wants mbuf 607 * parameters to be unchanged. 608 * XXX: the call of ip6_savecontrol() has been obsoleted based on 609 * latest version of the advanced API (20020110). 610 */ 611 drop_hdrlen = off0 + off; 612 613 /* 614 * Locate pcb for segment. 615 */ 616 INP_INFO_WLOCK(&tcbinfo); 617 headlocked = 1; 618 findpcb: 619 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 620 #ifdef IPFIREWALL_FORWARD 621 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 622 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 623 624 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 625 struct sockaddr_in *next_hop; 626 627 next_hop = (struct sockaddr_in *)(fwd_tag+1); 628 /* 629 * Transparently forwarded. Pretend to be the destination. 630 * already got one like this? 631 */ 632 inp = in_pcblookup_hash(&tcbinfo, 633 ip->ip_src, th->th_sport, 634 ip->ip_dst, th->th_dport, 635 0, m->m_pkthdr.rcvif); 636 if (!inp) { 637 /* It's new. Try to find the ambushing socket. */ 638 inp = in_pcblookup_hash(&tcbinfo, 639 ip->ip_src, th->th_sport, 640 next_hop->sin_addr, 641 next_hop->sin_port ? 642 ntohs(next_hop->sin_port) : 643 th->th_dport, 644 1, m->m_pkthdr.rcvif); 645 } 646 /* Remove the tag from the packet. We don't need it anymore. */ 647 m_tag_delete(m, fwd_tag); 648 } else { 649 #endif /* IPFIREWALL_FORWARD */ 650 if (isipv6) { 651 #ifdef INET6 652 inp = in6_pcblookup_hash(&tcbinfo, 653 &ip6->ip6_src, th->th_sport, 654 &ip6->ip6_dst, th->th_dport, 655 1, m->m_pkthdr.rcvif); 656 #endif 657 } else 658 inp = in_pcblookup_hash(&tcbinfo, 659 ip->ip_src, th->th_sport, 660 ip->ip_dst, th->th_dport, 661 1, m->m_pkthdr.rcvif); 662 #ifdef IPFIREWALL_FORWARD 663 } 664 #endif /* IPFIREWALL_FORWARD */ 665 666 #if defined(IPSEC) || defined(FAST_IPSEC) 667 #ifdef INET6 668 if (isipv6) { 669 if (inp != NULL && ipsec6_in_reject(m, inp)) { 670 #ifdef IPSEC 671 ipsec6stat.in_polvio++; 672 #endif 673 goto drop; 674 } 675 } else 676 #endif /* INET6 */ 677 if (inp != NULL && ipsec4_in_reject(m, inp)) { 678 #ifdef IPSEC 679 ipsecstat.in_polvio++; 680 #endif 681 goto drop; 682 } 683 #endif /*IPSEC || FAST_IPSEC*/ 684 685 /* 686 * If the state is CLOSED (i.e., TCB does not exist) then 687 * all data in the incoming segment is discarded. 688 * If the TCB exists but is in CLOSED state, it is embryonic, 689 * but should either do a listen or a connect soon. 690 */ 691 if (inp == NULL) { 692 if (log_in_vain) { 693 #ifdef INET6 694 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 695 #else 696 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 697 #endif 698 699 if (isipv6) { 700 #ifdef INET6 701 strcpy(dbuf, "["); 702 strcpy(sbuf, "["); 703 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 704 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 705 strcat(dbuf, "]"); 706 strcat(sbuf, "]"); 707 #endif 708 } else { 709 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 710 strcpy(sbuf, inet_ntoa(ip->ip_src)); 711 } 712 switch (log_in_vain) { 713 case 1: 714 if ((thflags & TH_SYN) == 0) 715 break; 716 /* FALLTHROUGH */ 717 case 2: 718 log(LOG_INFO, 719 "Connection attempt to TCP %s:%d " 720 "from %s:%d flags:0x%02x\n", 721 dbuf, ntohs(th->th_dport), sbuf, 722 ntohs(th->th_sport), thflags); 723 break; 724 default: 725 break; 726 } 727 } 728 if (blackhole) { 729 switch (blackhole) { 730 case 1: 731 if (thflags & TH_SYN) 732 goto drop; 733 break; 734 case 2: 735 goto drop; 736 default: 737 goto drop; 738 } 739 } 740 rstreason = BANDLIM_RST_CLOSEDPORT; 741 goto dropwithreset; 742 } 743 INP_LOCK(inp); 744 745 /* Check the minimum TTL for socket. */ 746 if (inp->inp_ip_minttl != 0) { 747 #ifdef INET6 748 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 749 goto drop; 750 else 751 #endif 752 if (inp->inp_ip_minttl > ip->ip_ttl) 753 goto drop; 754 } 755 756 if (inp->inp_vflag & INP_TIMEWAIT) { 757 /* 758 * The only option of relevance is TOF_CC, and only if 759 * present in a SYN segment. See tcp_timewait(). 760 */ 761 if (thflags & TH_SYN) 762 tcp_dooptions(&to, optp, optlen, 1); 763 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 764 &to, th, m, tlen)) 765 goto findpcb; 766 /* 767 * tcp_timewait unlocks inp. 768 */ 769 INP_INFO_WUNLOCK(&tcbinfo); 770 return; 771 } 772 tp = intotcpcb(inp); 773 if (tp == 0) { 774 INP_UNLOCK(inp); 775 rstreason = BANDLIM_RST_CLOSEDPORT; 776 goto dropwithreset; 777 } 778 if (tp->t_state == TCPS_CLOSED) 779 goto drop; 780 781 #ifdef MAC 782 INP_LOCK_ASSERT(inp); 783 if (mac_check_inpcb_deliver(inp, m)) 784 goto drop; 785 #endif 786 so = inp->inp_socket; 787 #ifdef TCPDEBUG 788 if (so->so_options & SO_DEBUG) { 789 ostate = tp->t_state; 790 if (isipv6) 791 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 792 else 793 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 794 tcp_savetcp = *th; 795 } 796 #endif 797 if (so->so_options & SO_ACCEPTCONN) { 798 struct in_conninfo inc; 799 800 #ifdef INET6 801 inc.inc_isipv6 = isipv6; 802 #endif 803 if (isipv6) { 804 inc.inc6_faddr = ip6->ip6_src; 805 inc.inc6_laddr = ip6->ip6_dst; 806 } else { 807 inc.inc_faddr = ip->ip_src; 808 inc.inc_laddr = ip->ip_dst; 809 } 810 inc.inc_fport = th->th_sport; 811 inc.inc_lport = th->th_dport; 812 813 /* 814 * If the state is LISTEN then ignore segment if it contains 815 * a RST. If the segment contains an ACK then it is bad and 816 * send a RST. If it does not contain a SYN then it is not 817 * interesting; drop it. 818 * 819 * If the state is SYN_RECEIVED (syncache) and seg contains 820 * an ACK, but not for our SYN/ACK, send a RST. If the seg 821 * contains a RST, check the sequence number to see if it 822 * is a valid reset segment. 823 */ 824 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 825 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 826 if (!syncache_expand(&inc, th, &so, m)) { 827 /* 828 * No syncache entry, or ACK was not 829 * for our SYN/ACK. Send a RST. 830 */ 831 tcpstat.tcps_badsyn++; 832 rstreason = BANDLIM_RST_OPENPORT; 833 goto dropwithreset; 834 } 835 if (so == NULL) { 836 /* 837 * Could not complete 3-way handshake, 838 * connection is being closed down, and 839 * syncache has free'd mbuf. 840 */ 841 INP_UNLOCK(inp); 842 INP_INFO_WUNLOCK(&tcbinfo); 843 return; 844 } 845 /* 846 * Socket is created in state SYN_RECEIVED. 847 * Continue processing segment. 848 */ 849 INP_UNLOCK(inp); 850 inp = sotoinpcb(so); 851 INP_LOCK(inp); 852 tp = intotcpcb(inp); 853 /* 854 * This is what would have happened in 855 * tcp_output() when the SYN,ACK was sent. 856 */ 857 tp->snd_up = tp->snd_una; 858 tp->snd_max = tp->snd_nxt = tp->iss + 1; 859 tp->last_ack_sent = tp->rcv_nxt; 860 goto after_listen; 861 } 862 if (thflags & TH_RST) { 863 syncache_chkrst(&inc, th); 864 goto drop; 865 } 866 if (thflags & TH_ACK) { 867 syncache_badack(&inc); 868 tcpstat.tcps_badsyn++; 869 rstreason = BANDLIM_RST_OPENPORT; 870 goto dropwithreset; 871 } 872 goto drop; 873 } 874 875 /* 876 * Segment's flags are (SYN) or (SYN|FIN). 877 */ 878 #ifdef INET6 879 /* 880 * If deprecated address is forbidden, 881 * we do not accept SYN to deprecated interface 882 * address to prevent any new inbound connection from 883 * getting established. 884 * When we do not accept SYN, we send a TCP RST, 885 * with deprecated source address (instead of dropping 886 * it). We compromise it as it is much better for peer 887 * to send a RST, and RST will be the final packet 888 * for the exchange. 889 * 890 * If we do not forbid deprecated addresses, we accept 891 * the SYN packet. RFC2462 does not suggest dropping 892 * SYN in this case. 893 * If we decipher RFC2462 5.5.4, it says like this: 894 * 1. use of deprecated addr with existing 895 * communication is okay - "SHOULD continue to be 896 * used" 897 * 2. use of it with new communication: 898 * (2a) "SHOULD NOT be used if alternate address 899 * with sufficient scope is available" 900 * (2b) nothing mentioned otherwise. 901 * Here we fall into (2b) case as we have no choice in 902 * our source address selection - we must obey the peer. 903 * 904 * The wording in RFC2462 is confusing, and there are 905 * multiple description text for deprecated address 906 * handling - worse, they are not exactly the same. 907 * I believe 5.5.4 is the best one, so we follow 5.5.4. 908 */ 909 if (isipv6 && !ip6_use_deprecated) { 910 struct in6_ifaddr *ia6; 911 912 if ((ia6 = ip6_getdstifaddr(m)) && 913 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 914 INP_UNLOCK(inp); 915 tp = NULL; 916 rstreason = BANDLIM_RST_OPENPORT; 917 goto dropwithreset; 918 } 919 } 920 #endif 921 /* 922 * If it is from this socket, drop it, it must be forged. 923 * Don't bother responding if the destination was a broadcast. 924 */ 925 if (th->th_dport == th->th_sport) { 926 if (isipv6) { 927 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 928 &ip6->ip6_src)) 929 goto drop; 930 } else { 931 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 932 goto drop; 933 } 934 } 935 /* 936 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 937 * 938 * Note that it is quite possible to receive unicast 939 * link-layer packets with a broadcast IP address. Use 940 * in_broadcast() to find them. 941 */ 942 if (m->m_flags & (M_BCAST|M_MCAST)) 943 goto drop; 944 if (isipv6) { 945 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 946 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 947 goto drop; 948 } else { 949 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 950 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 951 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 952 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 953 goto drop; 954 } 955 /* 956 * SYN appears to be valid; create compressed TCP state 957 * for syncache, or perform t/tcp connection. 958 */ 959 if (so->so_qlen <= so->so_qlimit) { 960 #ifdef TCPDEBUG 961 if (so->so_options & SO_DEBUG) 962 tcp_trace(TA_INPUT, ostate, tp, 963 (void *)tcp_saveipgen, &tcp_savetcp, 0); 964 #endif 965 tcp_dooptions(&to, optp, optlen, 1); 966 if (!syncache_add(&inc, &to, th, &so, m)) 967 goto drop; 968 if (so == NULL) { 969 /* 970 * Entry added to syncache, mbuf used to 971 * send SYN,ACK packet. 972 */ 973 KASSERT(headlocked, ("headlocked")); 974 INP_UNLOCK(inp); 975 INP_INFO_WUNLOCK(&tcbinfo); 976 return; 977 } 978 /* 979 * Segment passed TAO tests. 980 * XXX: Can't happen at the moment. 981 */ 982 INP_UNLOCK(inp); 983 inp = sotoinpcb(so); 984 INP_LOCK(inp); 985 tp = intotcpcb(inp); 986 tp->t_starttime = ticks; 987 tp->t_state = TCPS_ESTABLISHED; 988 989 /* 990 * T/TCP logic: 991 * If there is a FIN or if there is data, then 992 * delay SYN,ACK(SYN) in the hope of piggy-backing 993 * it on a response segment. Otherwise must send 994 * ACK now in case the other side is slow starting. 995 */ 996 if (thflags & TH_FIN || tlen != 0) 997 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 998 else 999 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1000 tiwin = th->th_win << tp->snd_scale; 1001 tcpstat.tcps_connects++; 1002 soisconnected(so); 1003 goto trimthenstep6; 1004 } 1005 goto drop; 1006 } 1007 after_listen: 1008 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1009 INP_LOCK_ASSERT(inp); 1010 1011 /* Syncache takes care of sockets in the listen state. */ 1012 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1013 1014 /* 1015 * This is the second part of the MSS DoS prevention code (after 1016 * minmss on the sending side) and it deals with too many too small 1017 * tcp packets in a too short timeframe (1 second). 1018 * 1019 * For every full second we count the number of received packets 1020 * and bytes. If we get a lot of packets per second for this connection 1021 * (tcp_minmssoverload) we take a closer look at it and compute the 1022 * average packet size for the past second. If that is less than 1023 * tcp_minmss we get too many packets with very small payload which 1024 * is not good and burdens our system (and every packet generates 1025 * a wakeup to the process connected to our socket). We can reasonable 1026 * expect this to be small packet DoS attack to exhaust our CPU 1027 * cycles. 1028 * 1029 * Care has to be taken for the minimum packet overload value. This 1030 * value defines the minimum number of packets per second before we 1031 * start to worry. This must not be too low to avoid killing for 1032 * example interactive connections with many small packets like 1033 * telnet or SSH. 1034 * 1035 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1036 * this check. 1037 * 1038 * Account for packet if payload packet, skip over ACK, etc. 1039 */ 1040 if (tcp_minmss && tcp_minmssoverload && 1041 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1042 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1043 tp->rcv_pps++; 1044 tp->rcv_byps += tlen + off; 1045 if (tp->rcv_pps > tcp_minmssoverload) { 1046 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1047 printf("too many small tcp packets from " 1048 "%s:%u, av. %lubyte/packet, " 1049 "dropping connection\n", 1050 #ifdef INET6 1051 isipv6 ? 1052 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1053 #endif 1054 inet_ntoa(inp->inp_inc.inc_faddr), 1055 inp->inp_inc.inc_fport, 1056 tp->rcv_byps / tp->rcv_pps); 1057 KASSERT(headlocked, ("tcp_input: " 1058 "after_listen: tcp_drop: head " 1059 "not locked")); 1060 tp = tcp_drop(tp, ECONNRESET); 1061 tcpstat.tcps_minmssdrops++; 1062 goto drop; 1063 } 1064 } 1065 } else { 1066 tp->rcv_second = ticks + hz; 1067 tp->rcv_pps = 1; 1068 tp->rcv_byps = tlen + off; 1069 } 1070 } 1071 1072 /* 1073 * Segment received on connection. 1074 * Reset idle time and keep-alive timer. 1075 */ 1076 tp->t_rcvtime = ticks; 1077 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1078 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1079 1080 /* 1081 * Unscale the window into a 32-bit value. 1082 * This value is bogus for the TCPS_SYN_SENT state 1083 * and is overwritten later. 1084 */ 1085 tiwin = th->th_win << tp->snd_scale; 1086 1087 /* 1088 * Process options only when we get SYN/ACK back. The SYN case 1089 * for incoming connections is handled in tcp_syncache. 1090 * XXX this is traditional behavior, may need to be cleaned up. 1091 */ 1092 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 1093 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1094 if ((to.to_flags & TOF_SCALE) && 1095 (tp->t_flags & TF_REQ_SCALE)) { 1096 tp->t_flags |= TF_RCVD_SCALE; 1097 tp->snd_scale = to.to_requested_s_scale; 1098 tp->snd_wnd = th->th_win << tp->snd_scale; 1099 tiwin = tp->snd_wnd; 1100 } 1101 if (to.to_flags & TOF_TS) { 1102 tp->t_flags |= TF_RCVD_TSTMP; 1103 tp->ts_recent = to.to_tsval; 1104 tp->ts_recent_age = ticks; 1105 } 1106 if (to.to_flags & TOF_MSS) 1107 tcp_mss(tp, to.to_mss); 1108 if (tp->sack_enable) { 1109 if (!(to.to_flags & TOF_SACK)) 1110 tp->sack_enable = 0; 1111 else 1112 tp->t_flags |= TF_SACK_PERMIT; 1113 } 1114 1115 } 1116 1117 /* 1118 * Header prediction: check for the two common cases 1119 * of a uni-directional data xfer. If the packet has 1120 * no control flags, is in-sequence, the window didn't 1121 * change and we're not retransmitting, it's a 1122 * candidate. If the length is zero and the ack moved 1123 * forward, we're the sender side of the xfer. Just 1124 * free the data acked & wake any higher level process 1125 * that was blocked waiting for space. If the length 1126 * is non-zero and the ack didn't move, we're the 1127 * receiver side. If we're getting packets in-order 1128 * (the reassembly queue is empty), add the data to 1129 * the socket buffer and note that we need a delayed ack. 1130 * Make sure that the hidden state-flags are also off. 1131 * Since we check for TCPS_ESTABLISHED above, it can only 1132 * be TH_NEEDSYN. 1133 */ 1134 if (tp->t_state == TCPS_ESTABLISHED && 1135 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1136 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1137 ((to.to_flags & TOF_TS) == 0 || 1138 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1139 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1140 tp->snd_nxt == tp->snd_max) { 1141 1142 /* 1143 * If last ACK falls within this segment's sequence numbers, 1144 * record the timestamp. 1145 * NOTE that the test is modified according to the latest 1146 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1147 */ 1148 if ((to.to_flags & TOF_TS) != 0 && 1149 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1150 tp->ts_recent_age = ticks; 1151 tp->ts_recent = to.to_tsval; 1152 } 1153 1154 if (tlen == 0) { 1155 if (SEQ_GT(th->th_ack, tp->snd_una) && 1156 SEQ_LEQ(th->th_ack, tp->snd_max) && 1157 tp->snd_cwnd >= tp->snd_wnd && 1158 ((!tcp_do_newreno && !tp->sack_enable && 1159 tp->t_dupacks < tcprexmtthresh) || 1160 ((tcp_do_newreno || tp->sack_enable) && 1161 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1162 TAILQ_EMPTY(&tp->snd_holes)))) { 1163 KASSERT(headlocked, ("headlocked")); 1164 INP_INFO_WUNLOCK(&tcbinfo); 1165 headlocked = 0; 1166 /* 1167 * this is a pure ack for outstanding data. 1168 */ 1169 ++tcpstat.tcps_predack; 1170 /* 1171 * "bad retransmit" recovery 1172 */ 1173 if (tp->t_rxtshift == 1 && 1174 ticks < tp->t_badrxtwin) { 1175 ++tcpstat.tcps_sndrexmitbad; 1176 tp->snd_cwnd = tp->snd_cwnd_prev; 1177 tp->snd_ssthresh = 1178 tp->snd_ssthresh_prev; 1179 tp->snd_recover = tp->snd_recover_prev; 1180 if (tp->t_flags & TF_WASFRECOVERY) 1181 ENTER_FASTRECOVERY(tp); 1182 tp->snd_nxt = tp->snd_max; 1183 tp->t_badrxtwin = 0; 1184 } 1185 1186 /* 1187 * Recalculate the transmit timer / rtt. 1188 * 1189 * Some boxes send broken timestamp replies 1190 * during the SYN+ACK phase, ignore 1191 * timestamps of 0 or we could calculate a 1192 * huge RTT and blow up the retransmit timer. 1193 */ 1194 if ((to.to_flags & TOF_TS) != 0 && 1195 to.to_tsecr) { 1196 if (!tp->t_rttlow || 1197 tp->t_rttlow > ticks - to.to_tsecr) 1198 tp->t_rttlow = ticks - to.to_tsecr; 1199 tcp_xmit_timer(tp, 1200 ticks - to.to_tsecr + 1); 1201 } else if (tp->t_rtttime && 1202 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1203 if (!tp->t_rttlow || 1204 tp->t_rttlow > ticks - tp->t_rtttime) 1205 tp->t_rttlow = ticks - tp->t_rtttime; 1206 tcp_xmit_timer(tp, 1207 ticks - tp->t_rtttime); 1208 } 1209 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1210 acked = th->th_ack - tp->snd_una; 1211 tcpstat.tcps_rcvackpack++; 1212 tcpstat.tcps_rcvackbyte += acked; 1213 sbdrop(&so->so_snd, acked); 1214 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1215 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1216 tp->snd_recover = th->th_ack - 1; 1217 tp->snd_una = th->th_ack; 1218 /* 1219 * pull snd_wl2 up to prevent seq wrap relative 1220 * to th_ack. 1221 */ 1222 tp->snd_wl2 = th->th_ack; 1223 tp->t_dupacks = 0; 1224 m_freem(m); 1225 ND6_HINT(tp); /* some progress has been done */ 1226 1227 /* 1228 * If all outstanding data are acked, stop 1229 * retransmit timer, otherwise restart timer 1230 * using current (possibly backed-off) value. 1231 * If process is waiting for space, 1232 * wakeup/selwakeup/signal. If data 1233 * are ready to send, let tcp_output 1234 * decide between more output or persist. 1235 1236 #ifdef TCPDEBUG 1237 if (so->so_options & SO_DEBUG) 1238 tcp_trace(TA_INPUT, ostate, tp, 1239 (void *)tcp_saveipgen, 1240 &tcp_savetcp, 0); 1241 #endif 1242 */ 1243 if (tp->snd_una == tp->snd_max) 1244 callout_stop(tp->tt_rexmt); 1245 else if (!callout_active(tp->tt_persist)) 1246 callout_reset(tp->tt_rexmt, 1247 tp->t_rxtcur, 1248 tcp_timer_rexmt, tp); 1249 1250 sowwakeup(so); 1251 if (so->so_snd.sb_cc) 1252 (void) tcp_output(tp); 1253 goto check_delack; 1254 } 1255 } else if (th->th_ack == tp->snd_una && 1256 LIST_EMPTY(&tp->t_segq) && 1257 tlen <= sbspace(&so->so_rcv)) { 1258 KASSERT(headlocked, ("headlocked")); 1259 INP_INFO_WUNLOCK(&tcbinfo); 1260 headlocked = 0; 1261 /* 1262 * this is a pure, in-sequence data packet 1263 * with nothing on the reassembly queue and 1264 * we have enough buffer space to take it. 1265 */ 1266 /* Clean receiver SACK report if present */ 1267 if (tp->sack_enable && tp->rcv_numsacks) 1268 tcp_clean_sackreport(tp); 1269 ++tcpstat.tcps_preddat; 1270 tp->rcv_nxt += tlen; 1271 /* 1272 * Pull snd_wl1 up to prevent seq wrap relative to 1273 * th_seq. 1274 */ 1275 tp->snd_wl1 = th->th_seq; 1276 /* 1277 * Pull rcv_up up to prevent seq wrap relative to 1278 * rcv_nxt. 1279 */ 1280 tp->rcv_up = tp->rcv_nxt; 1281 tcpstat.tcps_rcvpack++; 1282 tcpstat.tcps_rcvbyte += tlen; 1283 ND6_HINT(tp); /* some progress has been done */ 1284 /* 1285 #ifdef TCPDEBUG 1286 if (so->so_options & SO_DEBUG) 1287 tcp_trace(TA_INPUT, ostate, tp, 1288 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1289 #endif 1290 * Add data to socket buffer. 1291 */ 1292 SOCKBUF_LOCK(&so->so_rcv); 1293 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1294 m_freem(m); 1295 } else { 1296 m_adj(m, drop_hdrlen); /* delayed header drop */ 1297 sbappendstream_locked(&so->so_rcv, m); 1298 } 1299 sorwakeup_locked(so); 1300 if (DELAY_ACK(tp)) { 1301 tp->t_flags |= TF_DELACK; 1302 } else { 1303 tp->t_flags |= TF_ACKNOW; 1304 tcp_output(tp); 1305 } 1306 goto check_delack; 1307 } 1308 } 1309 1310 /* 1311 * Calculate amount of space in receive window, 1312 * and then do TCP input processing. 1313 * Receive window is amount of space in rcv queue, 1314 * but not less than advertised window. 1315 */ 1316 { int win; 1317 1318 win = sbspace(&so->so_rcv); 1319 if (win < 0) 1320 win = 0; 1321 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1322 } 1323 1324 switch (tp->t_state) { 1325 1326 /* 1327 * If the state is SYN_RECEIVED: 1328 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1329 */ 1330 case TCPS_SYN_RECEIVED: 1331 if ((thflags & TH_ACK) && 1332 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1333 SEQ_GT(th->th_ack, tp->snd_max))) { 1334 rstreason = BANDLIM_RST_OPENPORT; 1335 goto dropwithreset; 1336 } 1337 break; 1338 1339 /* 1340 * If the state is SYN_SENT: 1341 * if seg contains an ACK, but not for our SYN, drop the input. 1342 * if seg contains a RST, then drop the connection. 1343 * if seg does not contain SYN, then drop it. 1344 * Otherwise this is an acceptable SYN segment 1345 * initialize tp->rcv_nxt and tp->irs 1346 * if seg contains ack then advance tp->snd_una 1347 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1348 * arrange for segment to be acked (eventually) 1349 * continue processing rest of data/controls, beginning with URG 1350 */ 1351 case TCPS_SYN_SENT: 1352 if ((thflags & TH_ACK) && 1353 (SEQ_LEQ(th->th_ack, tp->iss) || 1354 SEQ_GT(th->th_ack, tp->snd_max))) { 1355 rstreason = BANDLIM_UNLIMITED; 1356 goto dropwithreset; 1357 } 1358 if (thflags & TH_RST) { 1359 if (thflags & TH_ACK) { 1360 KASSERT(headlocked, ("tcp_input: after_listen" 1361 ": tcp_drop.2: head not locked")); 1362 tp = tcp_drop(tp, ECONNREFUSED); 1363 } 1364 goto drop; 1365 } 1366 if ((thflags & TH_SYN) == 0) 1367 goto drop; 1368 1369 /* Initial send window, already scaled. */ 1370 tp->snd_wnd = th->th_win; 1371 1372 tp->irs = th->th_seq; 1373 tcp_rcvseqinit(tp); 1374 if (thflags & TH_ACK) { 1375 tcpstat.tcps_connects++; 1376 soisconnected(so); 1377 #ifdef MAC 1378 SOCK_LOCK(so); 1379 mac_set_socket_peer_from_mbuf(m, so); 1380 SOCK_UNLOCK(so); 1381 #endif 1382 /* Do window scaling on this connection? */ 1383 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1384 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1385 tp->rcv_scale = tp->request_r_scale; 1386 } 1387 tp->rcv_adv += tp->rcv_wnd; 1388 tp->snd_una++; /* SYN is acked */ 1389 /* 1390 * If there's data, delay ACK; if there's also a FIN 1391 * ACKNOW will be turned on later. 1392 */ 1393 if (DELAY_ACK(tp) && tlen != 0) 1394 callout_reset(tp->tt_delack, tcp_delacktime, 1395 tcp_timer_delack, tp); 1396 else 1397 tp->t_flags |= TF_ACKNOW; 1398 /* 1399 * Received <SYN,ACK> in SYN_SENT[*] state. 1400 * Transitions: 1401 * SYN_SENT --> ESTABLISHED 1402 * SYN_SENT* --> FIN_WAIT_1 1403 */ 1404 tp->t_starttime = ticks; 1405 if (tp->t_flags & TF_NEEDFIN) { 1406 tp->t_state = TCPS_FIN_WAIT_1; 1407 tp->t_flags &= ~TF_NEEDFIN; 1408 thflags &= ~TH_SYN; 1409 } else { 1410 tp->t_state = TCPS_ESTABLISHED; 1411 callout_reset(tp->tt_keep, tcp_keepidle, 1412 tcp_timer_keep, tp); 1413 } 1414 } else { 1415 /* 1416 * Received initial SYN in SYN-SENT[*] state => 1417 * simultaneous open. If segment contains CC option 1418 * and there is a cached CC, apply TAO test. 1419 * If it succeeds, connection is * half-synchronized. 1420 * Otherwise, do 3-way handshake: 1421 * SYN-SENT -> SYN-RECEIVED 1422 * SYN-SENT* -> SYN-RECEIVED* 1423 * If there was no CC option, clear cached CC value. 1424 */ 1425 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1426 callout_stop(tp->tt_rexmt); 1427 tp->t_state = TCPS_SYN_RECEIVED; 1428 } 1429 1430 trimthenstep6: 1431 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1432 "locked")); 1433 INP_LOCK_ASSERT(inp); 1434 1435 /* 1436 * Advance th->th_seq to correspond to first data byte. 1437 * If data, trim to stay within window, 1438 * dropping FIN if necessary. 1439 */ 1440 th->th_seq++; 1441 if (tlen > tp->rcv_wnd) { 1442 todrop = tlen - tp->rcv_wnd; 1443 m_adj(m, -todrop); 1444 tlen = tp->rcv_wnd; 1445 thflags &= ~TH_FIN; 1446 tcpstat.tcps_rcvpackafterwin++; 1447 tcpstat.tcps_rcvbyteafterwin += todrop; 1448 } 1449 tp->snd_wl1 = th->th_seq - 1; 1450 tp->rcv_up = th->th_seq; 1451 /* 1452 * Client side of transaction: already sent SYN and data. 1453 * If the remote host used T/TCP to validate the SYN, 1454 * our data will be ACK'd; if so, enter normal data segment 1455 * processing in the middle of step 5, ack processing. 1456 * Otherwise, goto step 6. 1457 */ 1458 if (thflags & TH_ACK) 1459 goto process_ACK; 1460 1461 goto step6; 1462 1463 /* 1464 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1465 * do normal processing. 1466 * 1467 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1468 */ 1469 case TCPS_LAST_ACK: 1470 case TCPS_CLOSING: 1471 case TCPS_TIME_WAIT: 1472 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1473 break; /* continue normal processing */ 1474 } 1475 1476 /* 1477 * States other than LISTEN or SYN_SENT. 1478 * First check the RST flag and sequence number since reset segments 1479 * are exempt from the timestamp and connection count tests. This 1480 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1481 * below which allowed reset segments in half the sequence space 1482 * to fall though and be processed (which gives forged reset 1483 * segments with a random sequence number a 50 percent chance of 1484 * killing a connection). 1485 * Then check timestamp, if present. 1486 * Then check the connection count, if present. 1487 * Then check that at least some bytes of segment are within 1488 * receive window. If segment begins before rcv_nxt, 1489 * drop leading data (and SYN); if nothing left, just ack. 1490 * 1491 * 1492 * If the RST bit is set, check the sequence number to see 1493 * if this is a valid reset segment. 1494 * RFC 793 page 37: 1495 * In all states except SYN-SENT, all reset (RST) segments 1496 * are validated by checking their SEQ-fields. A reset is 1497 * valid if its sequence number is in the window. 1498 * Note: this does not take into account delayed ACKs, so 1499 * we should test against last_ack_sent instead of rcv_nxt. 1500 * The sequence number in the reset segment is normally an 1501 * echo of our outgoing acknowlegement numbers, but some hosts 1502 * send a reset with the sequence number at the rightmost edge 1503 * of our receive window, and we have to handle this case. 1504 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1505 * that brute force RST attacks are possible. To combat this, 1506 * we use a much stricter check while in the ESTABLISHED state, 1507 * only accepting RSTs where the sequence number is equal to 1508 * last_ack_sent. In all other states (the states in which a 1509 * RST is more likely), the more permissive check is used. 1510 * If we have multiple segments in flight, the intial reset 1511 * segment sequence numbers will be to the left of last_ack_sent, 1512 * but they will eventually catch up. 1513 * In any case, it never made sense to trim reset segments to 1514 * fit the receive window since RFC 1122 says: 1515 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1516 * 1517 * A TCP SHOULD allow a received RST segment to include data. 1518 * 1519 * DISCUSSION 1520 * It has been suggested that a RST segment could contain 1521 * ASCII text that encoded and explained the cause of the 1522 * RST. No standard has yet been established for such 1523 * data. 1524 * 1525 * If the reset segment passes the sequence number test examine 1526 * the state: 1527 * SYN_RECEIVED STATE: 1528 * If passive open, return to LISTEN state. 1529 * If active open, inform user that connection was refused. 1530 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1531 * Inform user that connection was reset, and close tcb. 1532 * CLOSING, LAST_ACK STATES: 1533 * Close the tcb. 1534 * TIME_WAIT STATE: 1535 * Drop the segment - see Stevens, vol. 2, p. 964 and 1536 * RFC 1337. 1537 */ 1538 if (thflags & TH_RST) { 1539 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1540 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1541 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1542 switch (tp->t_state) { 1543 1544 case TCPS_SYN_RECEIVED: 1545 so->so_error = ECONNREFUSED; 1546 goto close; 1547 1548 case TCPS_ESTABLISHED: 1549 if (tp->last_ack_sent != th->th_seq && 1550 tcp_insecure_rst == 0) { 1551 tcpstat.tcps_badrst++; 1552 goto drop; 1553 } 1554 case TCPS_FIN_WAIT_1: 1555 case TCPS_FIN_WAIT_2: 1556 case TCPS_CLOSE_WAIT: 1557 so->so_error = ECONNRESET; 1558 close: 1559 tp->t_state = TCPS_CLOSED; 1560 tcpstat.tcps_drops++; 1561 KASSERT(headlocked, ("tcp_input: " 1562 "trimthenstep6: tcp_close: head not " 1563 "locked")); 1564 tp = tcp_close(tp); 1565 break; 1566 1567 case TCPS_CLOSING: 1568 case TCPS_LAST_ACK: 1569 KASSERT(headlocked, ("trimthenstep6: " 1570 "tcp_close.2: head not locked")); 1571 tp = tcp_close(tp); 1572 break; 1573 1574 case TCPS_TIME_WAIT: 1575 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1576 ("timewait")); 1577 break; 1578 } 1579 } 1580 goto drop; 1581 } 1582 1583 /* 1584 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1585 * and it's less than ts_recent, drop it. 1586 */ 1587 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1588 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1589 1590 /* Check to see if ts_recent is over 24 days old. */ 1591 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1592 /* 1593 * Invalidate ts_recent. If this segment updates 1594 * ts_recent, the age will be reset later and ts_recent 1595 * will get a valid value. If it does not, setting 1596 * ts_recent to zero will at least satisfy the 1597 * requirement that zero be placed in the timestamp 1598 * echo reply when ts_recent isn't valid. The 1599 * age isn't reset until we get a valid ts_recent 1600 * because we don't want out-of-order segments to be 1601 * dropped when ts_recent is old. 1602 */ 1603 tp->ts_recent = 0; 1604 } else { 1605 tcpstat.tcps_rcvduppack++; 1606 tcpstat.tcps_rcvdupbyte += tlen; 1607 tcpstat.tcps_pawsdrop++; 1608 if (tlen) 1609 goto dropafterack; 1610 goto drop; 1611 } 1612 } 1613 1614 /* 1615 * In the SYN-RECEIVED state, validate that the packet belongs to 1616 * this connection before trimming the data to fit the receive 1617 * window. Check the sequence number versus IRS since we know 1618 * the sequence numbers haven't wrapped. This is a partial fix 1619 * for the "LAND" DoS attack. 1620 */ 1621 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1622 rstreason = BANDLIM_RST_OPENPORT; 1623 goto dropwithreset; 1624 } 1625 1626 todrop = tp->rcv_nxt - th->th_seq; 1627 if (todrop > 0) { 1628 if (thflags & TH_SYN) { 1629 thflags &= ~TH_SYN; 1630 th->th_seq++; 1631 if (th->th_urp > 1) 1632 th->th_urp--; 1633 else 1634 thflags &= ~TH_URG; 1635 todrop--; 1636 } 1637 /* 1638 * Following if statement from Stevens, vol. 2, p. 960. 1639 */ 1640 if (todrop > tlen 1641 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1642 /* 1643 * Any valid FIN must be to the left of the window. 1644 * At this point the FIN must be a duplicate or out 1645 * of sequence; drop it. 1646 */ 1647 thflags &= ~TH_FIN; 1648 1649 /* 1650 * Send an ACK to resynchronize and drop any data. 1651 * But keep on processing for RST or ACK. 1652 */ 1653 tp->t_flags |= TF_ACKNOW; 1654 todrop = tlen; 1655 tcpstat.tcps_rcvduppack++; 1656 tcpstat.tcps_rcvdupbyte += todrop; 1657 } else { 1658 tcpstat.tcps_rcvpartduppack++; 1659 tcpstat.tcps_rcvpartdupbyte += todrop; 1660 } 1661 drop_hdrlen += todrop; /* drop from the top afterwards */ 1662 th->th_seq += todrop; 1663 tlen -= todrop; 1664 if (th->th_urp > todrop) 1665 th->th_urp -= todrop; 1666 else { 1667 thflags &= ~TH_URG; 1668 th->th_urp = 0; 1669 } 1670 } 1671 1672 /* 1673 * If new data are received on a connection after the 1674 * user processes are gone, then RST the other end. 1675 */ 1676 if ((so->so_state & SS_NOFDREF) && 1677 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1678 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1679 "locked")); 1680 tp = tcp_close(tp); 1681 tcpstat.tcps_rcvafterclose++; 1682 rstreason = BANDLIM_UNLIMITED; 1683 goto dropwithreset; 1684 } 1685 1686 /* 1687 * If segment ends after window, drop trailing data 1688 * (and PUSH and FIN); if nothing left, just ACK. 1689 */ 1690 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1691 if (todrop > 0) { 1692 tcpstat.tcps_rcvpackafterwin++; 1693 if (todrop >= tlen) { 1694 tcpstat.tcps_rcvbyteafterwin += tlen; 1695 /* 1696 * If a new connection request is received 1697 * while in TIME_WAIT, drop the old connection 1698 * and start over if the sequence numbers 1699 * are above the previous ones. 1700 */ 1701 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1702 if (thflags & TH_SYN && 1703 tp->t_state == TCPS_TIME_WAIT && 1704 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1705 KASSERT(headlocked, ("trimthenstep6: " 1706 "tcp_close.4: head not locked")); 1707 tp = tcp_close(tp); 1708 goto findpcb; 1709 } 1710 /* 1711 * If window is closed can only take segments at 1712 * window edge, and have to drop data and PUSH from 1713 * incoming segments. Continue processing, but 1714 * remember to ack. Otherwise, drop segment 1715 * and ack. 1716 */ 1717 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1718 tp->t_flags |= TF_ACKNOW; 1719 tcpstat.tcps_rcvwinprobe++; 1720 } else 1721 goto dropafterack; 1722 } else 1723 tcpstat.tcps_rcvbyteafterwin += todrop; 1724 m_adj(m, -todrop); 1725 tlen -= todrop; 1726 thflags &= ~(TH_PUSH|TH_FIN); 1727 } 1728 1729 /* 1730 * If last ACK falls within this segment's sequence numbers, 1731 * record its timestamp. 1732 * NOTE: 1733 * 1) That the test incorporates suggestions from the latest 1734 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1735 * 2) That updating only on newer timestamps interferes with 1736 * our earlier PAWS tests, so this check should be solely 1737 * predicated on the sequence space of this segment. 1738 * 3) That we modify the segment boundary check to be 1739 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1740 * instead of RFC1323's 1741 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1742 * This modified check allows us to overcome RFC1323's 1743 * limitations as described in Stevens TCP/IP Illustrated 1744 * Vol. 2 p.869. In such cases, we can still calculate the 1745 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1746 */ 1747 if ((to.to_flags & TOF_TS) != 0 && 1748 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1749 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1750 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1751 tp->ts_recent_age = ticks; 1752 tp->ts_recent = to.to_tsval; 1753 } 1754 1755 /* 1756 * If a SYN is in the window, then this is an 1757 * error and we send an RST and drop the connection. 1758 */ 1759 if (thflags & TH_SYN) { 1760 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1761 "head not locked")); 1762 tp = tcp_drop(tp, ECONNRESET); 1763 rstreason = BANDLIM_UNLIMITED; 1764 goto drop; 1765 } 1766 1767 /* 1768 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1769 * flag is on (half-synchronized state), then queue data for 1770 * later processing; else drop segment and return. 1771 */ 1772 if ((thflags & TH_ACK) == 0) { 1773 if (tp->t_state == TCPS_SYN_RECEIVED || 1774 (tp->t_flags & TF_NEEDSYN)) 1775 goto step6; 1776 else 1777 goto drop; 1778 } 1779 1780 /* 1781 * Ack processing. 1782 */ 1783 switch (tp->t_state) { 1784 1785 /* 1786 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1787 * ESTABLISHED state and continue processing. 1788 * The ACK was checked above. 1789 */ 1790 case TCPS_SYN_RECEIVED: 1791 1792 tcpstat.tcps_connects++; 1793 soisconnected(so); 1794 /* Do window scaling? */ 1795 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1796 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1797 tp->rcv_scale = tp->request_r_scale; 1798 tp->snd_wnd = tiwin; 1799 } 1800 /* 1801 * Make transitions: 1802 * SYN-RECEIVED -> ESTABLISHED 1803 * SYN-RECEIVED* -> FIN-WAIT-1 1804 */ 1805 tp->t_starttime = ticks; 1806 if (tp->t_flags & TF_NEEDFIN) { 1807 tp->t_state = TCPS_FIN_WAIT_1; 1808 tp->t_flags &= ~TF_NEEDFIN; 1809 } else { 1810 tp->t_state = TCPS_ESTABLISHED; 1811 callout_reset(tp->tt_keep, tcp_keepidle, 1812 tcp_timer_keep, tp); 1813 } 1814 /* 1815 * If segment contains data or ACK, will call tcp_reass() 1816 * later; if not, do so now to pass queued data to user. 1817 */ 1818 if (tlen == 0 && (thflags & TH_FIN) == 0) 1819 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1820 (struct mbuf *)0); 1821 tp->snd_wl1 = th->th_seq - 1; 1822 /* FALLTHROUGH */ 1823 1824 /* 1825 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1826 * ACKs. If the ack is in the range 1827 * tp->snd_una < th->th_ack <= tp->snd_max 1828 * then advance tp->snd_una to th->th_ack and drop 1829 * data from the retransmission queue. If this ACK reflects 1830 * more up to date window information we update our window information. 1831 */ 1832 case TCPS_ESTABLISHED: 1833 case TCPS_FIN_WAIT_1: 1834 case TCPS_FIN_WAIT_2: 1835 case TCPS_CLOSE_WAIT: 1836 case TCPS_CLOSING: 1837 case TCPS_LAST_ACK: 1838 case TCPS_TIME_WAIT: 1839 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1840 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1841 tcpstat.tcps_rcvacktoomuch++; 1842 goto dropafterack; 1843 } 1844 if (tp->sack_enable && 1845 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1846 tcp_sack_doack(tp, &to, th->th_ack); 1847 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1848 if (tlen == 0 && tiwin == tp->snd_wnd) { 1849 tcpstat.tcps_rcvdupack++; 1850 /* 1851 * If we have outstanding data (other than 1852 * a window probe), this is a completely 1853 * duplicate ack (ie, window info didn't 1854 * change), the ack is the biggest we've 1855 * seen and we've seen exactly our rexmt 1856 * threshhold of them, assume a packet 1857 * has been dropped and retransmit it. 1858 * Kludge snd_nxt & the congestion 1859 * window so we send only this one 1860 * packet. 1861 * 1862 * We know we're losing at the current 1863 * window size so do congestion avoidance 1864 * (set ssthresh to half the current window 1865 * and pull our congestion window back to 1866 * the new ssthresh). 1867 * 1868 * Dup acks mean that packets have left the 1869 * network (they're now cached at the receiver) 1870 * so bump cwnd by the amount in the receiver 1871 * to keep a constant cwnd packets in the 1872 * network. 1873 */ 1874 if (!callout_active(tp->tt_rexmt) || 1875 th->th_ack != tp->snd_una) 1876 tp->t_dupacks = 0; 1877 else if (++tp->t_dupacks > tcprexmtthresh || 1878 ((tcp_do_newreno || tp->sack_enable) && 1879 IN_FASTRECOVERY(tp))) { 1880 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1881 int awnd; 1882 1883 /* 1884 * Compute the amount of data in flight first. 1885 * We can inject new data into the pipe iff 1886 * we have less than 1/2 the original window's 1887 * worth of data in flight. 1888 */ 1889 awnd = (tp->snd_nxt - tp->snd_fack) + 1890 tp->sackhint.sack_bytes_rexmit; 1891 if (awnd < tp->snd_ssthresh) { 1892 tp->snd_cwnd += tp->t_maxseg; 1893 if (tp->snd_cwnd > tp->snd_ssthresh) 1894 tp->snd_cwnd = tp->snd_ssthresh; 1895 } 1896 } else 1897 tp->snd_cwnd += tp->t_maxseg; 1898 (void) tcp_output(tp); 1899 goto drop; 1900 } else if (tp->t_dupacks == tcprexmtthresh) { 1901 tcp_seq onxt = tp->snd_nxt; 1902 u_int win; 1903 1904 /* 1905 * If we're doing sack, check to 1906 * see if we're already in sack 1907 * recovery. If we're not doing sack, 1908 * check to see if we're in newreno 1909 * recovery. 1910 */ 1911 if (tp->sack_enable) { 1912 if (IN_FASTRECOVERY(tp)) { 1913 tp->t_dupacks = 0; 1914 break; 1915 } 1916 } else if (tcp_do_newreno) { 1917 if (SEQ_LEQ(th->th_ack, 1918 tp->snd_recover)) { 1919 tp->t_dupacks = 0; 1920 break; 1921 } 1922 } 1923 win = min(tp->snd_wnd, tp->snd_cwnd) / 1924 2 / tp->t_maxseg; 1925 if (win < 2) 1926 win = 2; 1927 tp->snd_ssthresh = win * tp->t_maxseg; 1928 ENTER_FASTRECOVERY(tp); 1929 tp->snd_recover = tp->snd_max; 1930 callout_stop(tp->tt_rexmt); 1931 tp->t_rtttime = 0; 1932 if (tp->sack_enable) { 1933 tcpstat.tcps_sack_recovery_episode++; 1934 tp->sack_newdata = tp->snd_nxt; 1935 tp->snd_cwnd = tp->t_maxseg; 1936 (void) tcp_output(tp); 1937 goto drop; 1938 } 1939 tp->snd_nxt = th->th_ack; 1940 tp->snd_cwnd = tp->t_maxseg; 1941 (void) tcp_output(tp); 1942 KASSERT(tp->snd_limited <= 2, 1943 ("tp->snd_limited too big")); 1944 tp->snd_cwnd = tp->snd_ssthresh + 1945 tp->t_maxseg * 1946 (tp->t_dupacks - tp->snd_limited); 1947 if (SEQ_GT(onxt, tp->snd_nxt)) 1948 tp->snd_nxt = onxt; 1949 goto drop; 1950 } else if (tcp_do_rfc3042) { 1951 u_long oldcwnd = tp->snd_cwnd; 1952 tcp_seq oldsndmax = tp->snd_max; 1953 u_int sent; 1954 1955 KASSERT(tp->t_dupacks == 1 || 1956 tp->t_dupacks == 2, 1957 ("dupacks not 1 or 2")); 1958 if (tp->t_dupacks == 1) 1959 tp->snd_limited = 0; 1960 tp->snd_cwnd = 1961 (tp->snd_nxt - tp->snd_una) + 1962 (tp->t_dupacks - tp->snd_limited) * 1963 tp->t_maxseg; 1964 (void) tcp_output(tp); 1965 sent = tp->snd_max - oldsndmax; 1966 if (sent > tp->t_maxseg) { 1967 KASSERT((tp->t_dupacks == 2 && 1968 tp->snd_limited == 0) || 1969 (sent == tp->t_maxseg + 1 && 1970 tp->t_flags & TF_SENTFIN), 1971 ("sent too much")); 1972 tp->snd_limited = 2; 1973 } else if (sent > 0) 1974 ++tp->snd_limited; 1975 tp->snd_cwnd = oldcwnd; 1976 goto drop; 1977 } 1978 } else 1979 tp->t_dupacks = 0; 1980 break; 1981 } 1982 1983 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1984 1985 /* 1986 * If the congestion window was inflated to account 1987 * for the other side's cached packets, retract it. 1988 */ 1989 if (tcp_do_newreno || tp->sack_enable) { 1990 if (IN_FASTRECOVERY(tp)) { 1991 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1992 if (tp->sack_enable) 1993 tcp_sack_partialack(tp, th); 1994 else 1995 tcp_newreno_partial_ack(tp, th); 1996 } else { 1997 /* 1998 * Out of fast recovery. 1999 * Window inflation should have left us 2000 * with approximately snd_ssthresh 2001 * outstanding data. 2002 * But in case we would be inclined to 2003 * send a burst, better to do it via 2004 * the slow start mechanism. 2005 */ 2006 if (SEQ_GT(th->th_ack + 2007 tp->snd_ssthresh, 2008 tp->snd_max)) 2009 tp->snd_cwnd = tp->snd_max - 2010 th->th_ack + 2011 tp->t_maxseg; 2012 else 2013 tp->snd_cwnd = tp->snd_ssthresh; 2014 } 2015 } 2016 } else { 2017 if (tp->t_dupacks >= tcprexmtthresh && 2018 tp->snd_cwnd > tp->snd_ssthresh) 2019 tp->snd_cwnd = tp->snd_ssthresh; 2020 } 2021 tp->t_dupacks = 0; 2022 /* 2023 * If we reach this point, ACK is not a duplicate, 2024 * i.e., it ACKs something we sent. 2025 */ 2026 if (tp->t_flags & TF_NEEDSYN) { 2027 /* 2028 * T/TCP: Connection was half-synchronized, and our 2029 * SYN has been ACK'd (so connection is now fully 2030 * synchronized). Go to non-starred state, 2031 * increment snd_una for ACK of SYN, and check if 2032 * we can do window scaling. 2033 */ 2034 tp->t_flags &= ~TF_NEEDSYN; 2035 tp->snd_una++; 2036 /* Do window scaling? */ 2037 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2038 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2039 tp->rcv_scale = tp->request_r_scale; 2040 /* Send window already scaled. */ 2041 } 2042 } 2043 2044 process_ACK: 2045 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2046 "locked")); 2047 INP_LOCK_ASSERT(inp); 2048 2049 acked = th->th_ack - tp->snd_una; 2050 tcpstat.tcps_rcvackpack++; 2051 tcpstat.tcps_rcvackbyte += acked; 2052 2053 /* 2054 * If we just performed our first retransmit, and the ACK 2055 * arrives within our recovery window, then it was a mistake 2056 * to do the retransmit in the first place. Recover our 2057 * original cwnd and ssthresh, and proceed to transmit where 2058 * we left off. 2059 */ 2060 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2061 ++tcpstat.tcps_sndrexmitbad; 2062 tp->snd_cwnd = tp->snd_cwnd_prev; 2063 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2064 tp->snd_recover = tp->snd_recover_prev; 2065 if (tp->t_flags & TF_WASFRECOVERY) 2066 ENTER_FASTRECOVERY(tp); 2067 tp->snd_nxt = tp->snd_max; 2068 tp->t_badrxtwin = 0; /* XXX probably not required */ 2069 } 2070 2071 /* 2072 * If we have a timestamp reply, update smoothed 2073 * round trip time. If no timestamp is present but 2074 * transmit timer is running and timed sequence 2075 * number was acked, update smoothed round trip time. 2076 * Since we now have an rtt measurement, cancel the 2077 * timer backoff (cf., Phil Karn's retransmit alg.). 2078 * Recompute the initial retransmit timer. 2079 * 2080 * Some boxes send broken timestamp replies 2081 * during the SYN+ACK phase, ignore 2082 * timestamps of 0 or we could calculate a 2083 * huge RTT and blow up the retransmit timer. 2084 */ 2085 if ((to.to_flags & TOF_TS) != 0 && 2086 to.to_tsecr) { 2087 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2088 tp->t_rttlow = ticks - to.to_tsecr; 2089 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2090 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2091 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2092 tp->t_rttlow = ticks - tp->t_rtttime; 2093 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2094 } 2095 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2096 2097 /* 2098 * If all outstanding data is acked, stop retransmit 2099 * timer and remember to restart (more output or persist). 2100 * If there is more data to be acked, restart retransmit 2101 * timer, using current (possibly backed-off) value. 2102 */ 2103 if (th->th_ack == tp->snd_max) { 2104 callout_stop(tp->tt_rexmt); 2105 needoutput = 1; 2106 } else if (!callout_active(tp->tt_persist)) 2107 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2108 tcp_timer_rexmt, tp); 2109 2110 /* 2111 * If no data (only SYN) was ACK'd, 2112 * skip rest of ACK processing. 2113 */ 2114 if (acked == 0) 2115 goto step6; 2116 2117 /* 2118 * When new data is acked, open the congestion window. 2119 * If the window gives us less than ssthresh packets 2120 * in flight, open exponentially (maxseg per packet). 2121 * Otherwise open linearly: maxseg per window 2122 * (maxseg^2 / cwnd per packet). 2123 */ 2124 if ((!tcp_do_newreno && !tp->sack_enable) || 2125 !IN_FASTRECOVERY(tp)) { 2126 register u_int cw = tp->snd_cwnd; 2127 register u_int incr = tp->t_maxseg; 2128 if (cw > tp->snd_ssthresh) 2129 incr = incr * incr / cw; 2130 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2131 } 2132 SOCKBUF_LOCK(&so->so_snd); 2133 if (acked > so->so_snd.sb_cc) { 2134 tp->snd_wnd -= so->so_snd.sb_cc; 2135 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2136 ourfinisacked = 1; 2137 } else { 2138 sbdrop_locked(&so->so_snd, acked); 2139 tp->snd_wnd -= acked; 2140 ourfinisacked = 0; 2141 } 2142 sowwakeup_locked(so); 2143 /* detect una wraparound */ 2144 if ((tcp_do_newreno || tp->sack_enable) && 2145 !IN_FASTRECOVERY(tp) && 2146 SEQ_GT(tp->snd_una, tp->snd_recover) && 2147 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2148 tp->snd_recover = th->th_ack - 1; 2149 if ((tcp_do_newreno || tp->sack_enable) && 2150 IN_FASTRECOVERY(tp) && 2151 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2152 EXIT_FASTRECOVERY(tp); 2153 tp->snd_una = th->th_ack; 2154 if (tp->sack_enable) { 2155 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2156 tp->snd_recover = tp->snd_una; 2157 } 2158 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2159 tp->snd_nxt = tp->snd_una; 2160 2161 switch (tp->t_state) { 2162 2163 /* 2164 * In FIN_WAIT_1 STATE in addition to the processing 2165 * for the ESTABLISHED state if our FIN is now acknowledged 2166 * then enter FIN_WAIT_2. 2167 */ 2168 case TCPS_FIN_WAIT_1: 2169 if (ourfinisacked) { 2170 /* 2171 * If we can't receive any more 2172 * data, then closing user can proceed. 2173 * Starting the timer is contrary to the 2174 * specification, but if we don't get a FIN 2175 * we'll hang forever. 2176 */ 2177 /* XXXjl 2178 * we should release the tp also, and use a 2179 * compressed state. 2180 */ 2181 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2182 soisdisconnected(so); 2183 callout_reset(tp->tt_2msl, tcp_maxidle, 2184 tcp_timer_2msl, tp); 2185 } 2186 tp->t_state = TCPS_FIN_WAIT_2; 2187 } 2188 break; 2189 2190 /* 2191 * In CLOSING STATE in addition to the processing for 2192 * the ESTABLISHED state if the ACK acknowledges our FIN 2193 * then enter the TIME-WAIT state, otherwise ignore 2194 * the segment. 2195 */ 2196 case TCPS_CLOSING: 2197 if (ourfinisacked) { 2198 KASSERT(headlocked, ("tcp_input: process_ACK: " 2199 "head not locked")); 2200 tcp_twstart(tp); 2201 INP_INFO_WUNLOCK(&tcbinfo); 2202 m_freem(m); 2203 return; 2204 } 2205 break; 2206 2207 /* 2208 * In LAST_ACK, we may still be waiting for data to drain 2209 * and/or to be acked, as well as for the ack of our FIN. 2210 * If our FIN is now acknowledged, delete the TCB, 2211 * enter the closed state and return. 2212 */ 2213 case TCPS_LAST_ACK: 2214 if (ourfinisacked) { 2215 KASSERT(headlocked, ("tcp_input: process_ACK:" 2216 " tcp_close: head not locked")); 2217 tp = tcp_close(tp); 2218 goto drop; 2219 } 2220 break; 2221 2222 /* 2223 * In TIME_WAIT state the only thing that should arrive 2224 * is a retransmission of the remote FIN. Acknowledge 2225 * it and restart the finack timer. 2226 */ 2227 case TCPS_TIME_WAIT: 2228 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2229 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2230 tcp_timer_2msl, tp); 2231 goto dropafterack; 2232 } 2233 } 2234 2235 step6: 2236 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2237 INP_LOCK_ASSERT(inp); 2238 2239 /* 2240 * Update window information. 2241 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2242 */ 2243 if ((thflags & TH_ACK) && 2244 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2245 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2246 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2247 /* keep track of pure window updates */ 2248 if (tlen == 0 && 2249 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2250 tcpstat.tcps_rcvwinupd++; 2251 tp->snd_wnd = tiwin; 2252 tp->snd_wl1 = th->th_seq; 2253 tp->snd_wl2 = th->th_ack; 2254 if (tp->snd_wnd > tp->max_sndwnd) 2255 tp->max_sndwnd = tp->snd_wnd; 2256 needoutput = 1; 2257 } 2258 2259 /* 2260 * Process segments with URG. 2261 */ 2262 if ((thflags & TH_URG) && th->th_urp && 2263 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2264 /* 2265 * This is a kludge, but if we receive and accept 2266 * random urgent pointers, we'll crash in 2267 * soreceive. It's hard to imagine someone 2268 * actually wanting to send this much urgent data. 2269 */ 2270 SOCKBUF_LOCK(&so->so_rcv); 2271 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2272 th->th_urp = 0; /* XXX */ 2273 thflags &= ~TH_URG; /* XXX */ 2274 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2275 goto dodata; /* XXX */ 2276 } 2277 /* 2278 * If this segment advances the known urgent pointer, 2279 * then mark the data stream. This should not happen 2280 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2281 * a FIN has been received from the remote side. 2282 * In these states we ignore the URG. 2283 * 2284 * According to RFC961 (Assigned Protocols), 2285 * the urgent pointer points to the last octet 2286 * of urgent data. We continue, however, 2287 * to consider it to indicate the first octet 2288 * of data past the urgent section as the original 2289 * spec states (in one of two places). 2290 */ 2291 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2292 tp->rcv_up = th->th_seq + th->th_urp; 2293 so->so_oobmark = so->so_rcv.sb_cc + 2294 (tp->rcv_up - tp->rcv_nxt) - 1; 2295 if (so->so_oobmark == 0) 2296 so->so_rcv.sb_state |= SBS_RCVATMARK; 2297 sohasoutofband(so); 2298 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2299 } 2300 SOCKBUF_UNLOCK(&so->so_rcv); 2301 /* 2302 * Remove out of band data so doesn't get presented to user. 2303 * This can happen independent of advancing the URG pointer, 2304 * but if two URG's are pending at once, some out-of-band 2305 * data may creep in... ick. 2306 */ 2307 if (th->th_urp <= (u_long)tlen && 2308 !(so->so_options & SO_OOBINLINE)) { 2309 /* hdr drop is delayed */ 2310 tcp_pulloutofband(so, th, m, drop_hdrlen); 2311 } 2312 } else { 2313 /* 2314 * If no out of band data is expected, 2315 * pull receive urgent pointer along 2316 * with the receive window. 2317 */ 2318 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2319 tp->rcv_up = tp->rcv_nxt; 2320 } 2321 dodata: /* XXX */ 2322 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2323 INP_LOCK_ASSERT(inp); 2324 2325 /* 2326 * Process the segment text, merging it into the TCP sequencing queue, 2327 * and arranging for acknowledgment of receipt if necessary. 2328 * This process logically involves adjusting tp->rcv_wnd as data 2329 * is presented to the user (this happens in tcp_usrreq.c, 2330 * case PRU_RCVD). If a FIN has already been received on this 2331 * connection then we just ignore the text. 2332 */ 2333 if ((tlen || (thflags & TH_FIN)) && 2334 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2335 tcp_seq save_start = th->th_seq; 2336 tcp_seq save_end = th->th_seq + tlen; 2337 m_adj(m, drop_hdrlen); /* delayed header drop */ 2338 /* 2339 * Insert segment which includes th into TCP reassembly queue 2340 * with control block tp. Set thflags to whether reassembly now 2341 * includes a segment with FIN. This handles the common case 2342 * inline (segment is the next to be received on an established 2343 * connection, and the queue is empty), avoiding linkage into 2344 * and removal from the queue and repetition of various 2345 * conversions. 2346 * Set DELACK for segments received in order, but ack 2347 * immediately when segments are out of order (so 2348 * fast retransmit can work). 2349 */ 2350 if (th->th_seq == tp->rcv_nxt && 2351 LIST_EMPTY(&tp->t_segq) && 2352 TCPS_HAVEESTABLISHED(tp->t_state)) { 2353 if (DELAY_ACK(tp)) 2354 tp->t_flags |= TF_DELACK; 2355 else 2356 tp->t_flags |= TF_ACKNOW; 2357 tp->rcv_nxt += tlen; 2358 thflags = th->th_flags & TH_FIN; 2359 tcpstat.tcps_rcvpack++; 2360 tcpstat.tcps_rcvbyte += tlen; 2361 ND6_HINT(tp); 2362 SOCKBUF_LOCK(&so->so_rcv); 2363 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2364 m_freem(m); 2365 else 2366 sbappendstream_locked(&so->so_rcv, m); 2367 sorwakeup_locked(so); 2368 } else { 2369 thflags = tcp_reass(tp, th, &tlen, m); 2370 tp->t_flags |= TF_ACKNOW; 2371 } 2372 if (tlen > 0 && tp->sack_enable) 2373 tcp_update_sack_list(tp, save_start, save_end); 2374 /* 2375 * Note the amount of data that peer has sent into 2376 * our window, in order to estimate the sender's 2377 * buffer size. 2378 */ 2379 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2380 } else { 2381 m_freem(m); 2382 thflags &= ~TH_FIN; 2383 } 2384 2385 /* 2386 * If FIN is received ACK the FIN and let the user know 2387 * that the connection is closing. 2388 */ 2389 if (thflags & TH_FIN) { 2390 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2391 socantrcvmore(so); 2392 /* 2393 * If connection is half-synchronized 2394 * (ie NEEDSYN flag on) then delay ACK, 2395 * so it may be piggybacked when SYN is sent. 2396 * Otherwise, since we received a FIN then no 2397 * more input can be expected, send ACK now. 2398 */ 2399 if (tp->t_flags & TF_NEEDSYN) 2400 tp->t_flags |= TF_DELACK; 2401 else 2402 tp->t_flags |= TF_ACKNOW; 2403 tp->rcv_nxt++; 2404 } 2405 switch (tp->t_state) { 2406 2407 /* 2408 * In SYN_RECEIVED and ESTABLISHED STATES 2409 * enter the CLOSE_WAIT state. 2410 */ 2411 case TCPS_SYN_RECEIVED: 2412 tp->t_starttime = ticks; 2413 /*FALLTHROUGH*/ 2414 case TCPS_ESTABLISHED: 2415 tp->t_state = TCPS_CLOSE_WAIT; 2416 break; 2417 2418 /* 2419 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2420 * enter the CLOSING state. 2421 */ 2422 case TCPS_FIN_WAIT_1: 2423 tp->t_state = TCPS_CLOSING; 2424 break; 2425 2426 /* 2427 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2428 * starting the time-wait timer, turning off the other 2429 * standard timers. 2430 */ 2431 case TCPS_FIN_WAIT_2: 2432 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2433 "TCP_FIN_WAIT_2: head not locked")); 2434 tcp_twstart(tp); 2435 INP_INFO_WUNLOCK(&tcbinfo); 2436 return; 2437 2438 /* 2439 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2440 */ 2441 case TCPS_TIME_WAIT: 2442 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2443 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2444 tcp_timer_2msl, tp); 2445 break; 2446 } 2447 } 2448 INP_INFO_WUNLOCK(&tcbinfo); 2449 headlocked = 0; 2450 #ifdef TCPDEBUG 2451 if (so->so_options & SO_DEBUG) 2452 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2453 &tcp_savetcp, 0); 2454 #endif 2455 2456 /* 2457 * Return any desired output. 2458 */ 2459 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2460 (void) tcp_output(tp); 2461 2462 check_delack: 2463 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2464 INP_LOCK_ASSERT(inp); 2465 if (tp->t_flags & TF_DELACK) { 2466 tp->t_flags &= ~TF_DELACK; 2467 callout_reset(tp->tt_delack, tcp_delacktime, 2468 tcp_timer_delack, tp); 2469 } 2470 INP_UNLOCK(inp); 2471 return; 2472 2473 dropafterack: 2474 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2475 /* 2476 * Generate an ACK dropping incoming segment if it occupies 2477 * sequence space, where the ACK reflects our state. 2478 * 2479 * We can now skip the test for the RST flag since all 2480 * paths to this code happen after packets containing 2481 * RST have been dropped. 2482 * 2483 * In the SYN-RECEIVED state, don't send an ACK unless the 2484 * segment we received passes the SYN-RECEIVED ACK test. 2485 * If it fails send a RST. This breaks the loop in the 2486 * "LAND" DoS attack, and also prevents an ACK storm 2487 * between two listening ports that have been sent forged 2488 * SYN segments, each with the source address of the other. 2489 */ 2490 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2491 (SEQ_GT(tp->snd_una, th->th_ack) || 2492 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2493 rstreason = BANDLIM_RST_OPENPORT; 2494 goto dropwithreset; 2495 } 2496 #ifdef TCPDEBUG 2497 if (so->so_options & SO_DEBUG) 2498 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2499 &tcp_savetcp, 0); 2500 #endif 2501 KASSERT(headlocked, ("headlocked should be 1")); 2502 INP_INFO_WUNLOCK(&tcbinfo); 2503 tp->t_flags |= TF_ACKNOW; 2504 (void) tcp_output(tp); 2505 INP_UNLOCK(inp); 2506 m_freem(m); 2507 return; 2508 2509 dropwithreset: 2510 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2511 /* 2512 * Generate a RST, dropping incoming segment. 2513 * Make ACK acceptable to originator of segment. 2514 * Don't bother to respond if destination was broadcast/multicast. 2515 */ 2516 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2517 goto drop; 2518 if (isipv6) { 2519 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2520 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2521 goto drop; 2522 } else { 2523 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2524 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2525 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2526 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2527 goto drop; 2528 } 2529 /* IPv6 anycast check is done at tcp6_input() */ 2530 2531 /* 2532 * Perform bandwidth limiting. 2533 */ 2534 if (badport_bandlim(rstreason) < 0) 2535 goto drop; 2536 2537 #ifdef TCPDEBUG 2538 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2539 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2540 &tcp_savetcp, 0); 2541 #endif 2542 2543 if (thflags & TH_ACK) 2544 /* mtod() below is safe as long as hdr dropping is delayed */ 2545 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2546 TH_RST); 2547 else { 2548 if (thflags & TH_SYN) 2549 tlen++; 2550 /* mtod() below is safe as long as hdr dropping is delayed */ 2551 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2552 (tcp_seq)0, TH_RST|TH_ACK); 2553 } 2554 2555 if (tp) 2556 INP_UNLOCK(inp); 2557 if (headlocked) 2558 INP_INFO_WUNLOCK(&tcbinfo); 2559 return; 2560 2561 drop: 2562 /* 2563 * Drop space held by incoming segment and return. 2564 */ 2565 #ifdef TCPDEBUG 2566 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2567 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2568 &tcp_savetcp, 0); 2569 #endif 2570 if (tp) 2571 INP_UNLOCK(inp); 2572 if (headlocked) 2573 INP_INFO_WUNLOCK(&tcbinfo); 2574 m_freem(m); 2575 return; 2576 } 2577 2578 /* 2579 * Parse TCP options and place in tcpopt. 2580 */ 2581 static void 2582 tcp_dooptions(to, cp, cnt, is_syn) 2583 struct tcpopt *to; 2584 u_char *cp; 2585 int cnt; 2586 int is_syn; 2587 { 2588 int opt, optlen; 2589 2590 to->to_flags = 0; 2591 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2592 opt = cp[0]; 2593 if (opt == TCPOPT_EOL) 2594 break; 2595 if (opt == TCPOPT_NOP) 2596 optlen = 1; 2597 else { 2598 if (cnt < 2) 2599 break; 2600 optlen = cp[1]; 2601 if (optlen < 2 || optlen > cnt) 2602 break; 2603 } 2604 switch (opt) { 2605 case TCPOPT_MAXSEG: 2606 if (optlen != TCPOLEN_MAXSEG) 2607 continue; 2608 if (!is_syn) 2609 continue; 2610 to->to_flags |= TOF_MSS; 2611 bcopy((char *)cp + 2, 2612 (char *)&to->to_mss, sizeof(to->to_mss)); 2613 to->to_mss = ntohs(to->to_mss); 2614 break; 2615 case TCPOPT_WINDOW: 2616 if (optlen != TCPOLEN_WINDOW) 2617 continue; 2618 if (! is_syn) 2619 continue; 2620 to->to_flags |= TOF_SCALE; 2621 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2622 break; 2623 case TCPOPT_TIMESTAMP: 2624 if (optlen != TCPOLEN_TIMESTAMP) 2625 continue; 2626 to->to_flags |= TOF_TS; 2627 bcopy((char *)cp + 2, 2628 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2629 to->to_tsval = ntohl(to->to_tsval); 2630 bcopy((char *)cp + 6, 2631 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2632 to->to_tsecr = ntohl(to->to_tsecr); 2633 /* 2634 * If echoed timestamp is later than the current time, 2635 * fall back to non RFC1323 RTT calculation. 2636 */ 2637 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2638 to->to_tsecr = 0; 2639 break; 2640 #ifdef TCP_SIGNATURE 2641 /* 2642 * XXX In order to reply to a host which has set the 2643 * TCP_SIGNATURE option in its initial SYN, we have to 2644 * record the fact that the option was observed here 2645 * for the syncache code to perform the correct response. 2646 */ 2647 case TCPOPT_SIGNATURE: 2648 if (optlen != TCPOLEN_SIGNATURE) 2649 continue; 2650 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2651 break; 2652 #endif 2653 case TCPOPT_SACK_PERMITTED: 2654 if (!tcp_do_sack || 2655 optlen != TCPOLEN_SACK_PERMITTED) 2656 continue; 2657 if (is_syn) { 2658 /* MUST only be set on SYN */ 2659 to->to_flags |= TOF_SACK; 2660 } 2661 break; 2662 case TCPOPT_SACK: 2663 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2664 continue; 2665 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2666 to->to_sacks = cp + 2; 2667 tcpstat.tcps_sack_rcv_blocks++; 2668 break; 2669 default: 2670 continue; 2671 } 2672 } 2673 } 2674 2675 /* 2676 * Pull out of band byte out of a segment so 2677 * it doesn't appear in the user's data queue. 2678 * It is still reflected in the segment length for 2679 * sequencing purposes. 2680 */ 2681 static void 2682 tcp_pulloutofband(so, th, m, off) 2683 struct socket *so; 2684 struct tcphdr *th; 2685 register struct mbuf *m; 2686 int off; /* delayed to be droped hdrlen */ 2687 { 2688 int cnt = off + th->th_urp - 1; 2689 2690 while (cnt >= 0) { 2691 if (m->m_len > cnt) { 2692 char *cp = mtod(m, caddr_t) + cnt; 2693 struct tcpcb *tp = sototcpcb(so); 2694 2695 tp->t_iobc = *cp; 2696 tp->t_oobflags |= TCPOOB_HAVEDATA; 2697 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2698 m->m_len--; 2699 if (m->m_flags & M_PKTHDR) 2700 m->m_pkthdr.len--; 2701 return; 2702 } 2703 cnt -= m->m_len; 2704 m = m->m_next; 2705 if (m == 0) 2706 break; 2707 } 2708 panic("tcp_pulloutofband"); 2709 } 2710 2711 /* 2712 * Collect new round-trip time estimate 2713 * and update averages and current timeout. 2714 */ 2715 static void 2716 tcp_xmit_timer(tp, rtt) 2717 register struct tcpcb *tp; 2718 int rtt; 2719 { 2720 register int delta; 2721 2722 INP_LOCK_ASSERT(tp->t_inpcb); 2723 2724 tcpstat.tcps_rttupdated++; 2725 tp->t_rttupdated++; 2726 if (tp->t_srtt != 0) { 2727 /* 2728 * srtt is stored as fixed point with 5 bits after the 2729 * binary point (i.e., scaled by 8). The following magic 2730 * is equivalent to the smoothing algorithm in rfc793 with 2731 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2732 * point). Adjust rtt to origin 0. 2733 */ 2734 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2735 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2736 2737 if ((tp->t_srtt += delta) <= 0) 2738 tp->t_srtt = 1; 2739 2740 /* 2741 * We accumulate a smoothed rtt variance (actually, a 2742 * smoothed mean difference), then set the retransmit 2743 * timer to smoothed rtt + 4 times the smoothed variance. 2744 * rttvar is stored as fixed point with 4 bits after the 2745 * binary point (scaled by 16). The following is 2746 * equivalent to rfc793 smoothing with an alpha of .75 2747 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2748 * rfc793's wired-in beta. 2749 */ 2750 if (delta < 0) 2751 delta = -delta; 2752 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2753 if ((tp->t_rttvar += delta) <= 0) 2754 tp->t_rttvar = 1; 2755 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2756 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2757 } else { 2758 /* 2759 * No rtt measurement yet - use the unsmoothed rtt. 2760 * Set the variance to half the rtt (so our first 2761 * retransmit happens at 3*rtt). 2762 */ 2763 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2764 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2765 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2766 } 2767 tp->t_rtttime = 0; 2768 tp->t_rxtshift = 0; 2769 2770 /* 2771 * the retransmit should happen at rtt + 4 * rttvar. 2772 * Because of the way we do the smoothing, srtt and rttvar 2773 * will each average +1/2 tick of bias. When we compute 2774 * the retransmit timer, we want 1/2 tick of rounding and 2775 * 1 extra tick because of +-1/2 tick uncertainty in the 2776 * firing of the timer. The bias will give us exactly the 2777 * 1.5 tick we need. But, because the bias is 2778 * statistical, we have to test that we don't drop below 2779 * the minimum feasible timer (which is 2 ticks). 2780 */ 2781 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2782 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2783 2784 /* 2785 * We received an ack for a packet that wasn't retransmitted; 2786 * it is probably safe to discard any error indications we've 2787 * received recently. This isn't quite right, but close enough 2788 * for now (a route might have failed after we sent a segment, 2789 * and the return path might not be symmetrical). 2790 */ 2791 tp->t_softerror = 0; 2792 } 2793 2794 /* 2795 * Determine a reasonable value for maxseg size. 2796 * If the route is known, check route for mtu. 2797 * If none, use an mss that can be handled on the outgoing 2798 * interface without forcing IP to fragment; if bigger than 2799 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2800 * to utilize large mbufs. If no route is found, route has no mtu, 2801 * or the destination isn't local, use a default, hopefully conservative 2802 * size (usually 512 or the default IP max size, but no more than the mtu 2803 * of the interface), as we can't discover anything about intervening 2804 * gateways or networks. We also initialize the congestion/slow start 2805 * window to be a single segment if the destination isn't local. 2806 * While looking at the routing entry, we also initialize other path-dependent 2807 * parameters from pre-set or cached values in the routing entry. 2808 * 2809 * Also take into account the space needed for options that we 2810 * send regularly. Make maxseg shorter by that amount to assure 2811 * that we can send maxseg amount of data even when the options 2812 * are present. Store the upper limit of the length of options plus 2813 * data in maxopd. 2814 * 2815 * 2816 * In case of T/TCP, we call this routine during implicit connection 2817 * setup as well (offer = -1), to initialize maxseg from the cached 2818 * MSS of our peer. 2819 * 2820 * NOTE that this routine is only called when we process an incoming 2821 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2822 */ 2823 void 2824 tcp_mss(tp, offer) 2825 struct tcpcb *tp; 2826 int offer; 2827 { 2828 int rtt, mss; 2829 u_long bufsize; 2830 u_long maxmtu; 2831 struct inpcb *inp = tp->t_inpcb; 2832 struct socket *so; 2833 struct hc_metrics_lite metrics; 2834 int origoffer = offer; 2835 #ifdef INET6 2836 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2837 size_t min_protoh = isipv6 ? 2838 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2839 sizeof (struct tcpiphdr); 2840 #else 2841 const size_t min_protoh = sizeof(struct tcpiphdr); 2842 #endif 2843 2844 /* initialize */ 2845 #ifdef INET6 2846 if (isipv6) { 2847 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2848 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2849 } else 2850 #endif 2851 { 2852 maxmtu = tcp_maxmtu(&inp->inp_inc); 2853 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2854 } 2855 so = inp->inp_socket; 2856 2857 /* 2858 * no route to sender, stay with default mss and return 2859 */ 2860 if (maxmtu == 0) 2861 return; 2862 2863 /* what have we got? */ 2864 switch (offer) { 2865 case 0: 2866 /* 2867 * Offer == 0 means that there was no MSS on the SYN 2868 * segment, in this case we use tcp_mssdflt. 2869 */ 2870 offer = 2871 #ifdef INET6 2872 isipv6 ? tcp_v6mssdflt : 2873 #endif 2874 tcp_mssdflt; 2875 break; 2876 2877 case -1: 2878 /* 2879 * Offer == -1 means that we didn't receive SYN yet. 2880 */ 2881 /* FALLTHROUGH */ 2882 2883 default: 2884 /* 2885 * Prevent DoS attack with too small MSS. Round up 2886 * to at least minmss. 2887 */ 2888 offer = max(offer, tcp_minmss); 2889 /* 2890 * Sanity check: make sure that maxopd will be large 2891 * enough to allow some data on segments even if the 2892 * all the option space is used (40bytes). Otherwise 2893 * funny things may happen in tcp_output. 2894 */ 2895 offer = max(offer, 64); 2896 } 2897 2898 /* 2899 * rmx information is now retrieved from tcp_hostcache 2900 */ 2901 tcp_hc_get(&inp->inp_inc, &metrics); 2902 2903 /* 2904 * if there's a discovered mtu int tcp hostcache, use it 2905 * else, use the link mtu. 2906 */ 2907 if (metrics.rmx_mtu) 2908 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2909 else { 2910 #ifdef INET6 2911 if (isipv6) { 2912 mss = maxmtu - min_protoh; 2913 if (!path_mtu_discovery && 2914 !in6_localaddr(&inp->in6p_faddr)) 2915 mss = min(mss, tcp_v6mssdflt); 2916 } else 2917 #endif 2918 { 2919 mss = maxmtu - min_protoh; 2920 if (!path_mtu_discovery && 2921 !in_localaddr(inp->inp_faddr)) 2922 mss = min(mss, tcp_mssdflt); 2923 } 2924 } 2925 mss = min(mss, offer); 2926 2927 /* 2928 * maxopd stores the maximum length of data AND options 2929 * in a segment; maxseg is the amount of data in a normal 2930 * segment. We need to store this value (maxopd) apart 2931 * from maxseg, because now every segment carries options 2932 * and thus we normally have somewhat less data in segments. 2933 */ 2934 tp->t_maxopd = mss; 2935 2936 /* 2937 * origoffer==-1 indicates, that no segments were received yet. 2938 * In this case we just guess. 2939 */ 2940 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2941 (origoffer == -1 || 2942 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2943 mss -= TCPOLEN_TSTAMP_APPA; 2944 tp->t_maxseg = mss; 2945 2946 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2947 if (mss > MCLBYTES) 2948 mss &= ~(MCLBYTES-1); 2949 #else 2950 if (mss > MCLBYTES) 2951 mss = mss / MCLBYTES * MCLBYTES; 2952 #endif 2953 tp->t_maxseg = mss; 2954 2955 /* 2956 * If there's a pipesize, change the socket buffer to that size, 2957 * don't change if sb_hiwat is different than default (then it 2958 * has been changed on purpose with setsockopt). 2959 * Make the socket buffers an integral number of mss units; 2960 * if the mss is larger than the socket buffer, decrease the mss. 2961 */ 2962 SOCKBUF_LOCK(&so->so_snd); 2963 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2964 bufsize = metrics.rmx_sendpipe; 2965 else 2966 bufsize = so->so_snd.sb_hiwat; 2967 if (bufsize < mss) 2968 mss = bufsize; 2969 else { 2970 bufsize = roundup(bufsize, mss); 2971 if (bufsize > sb_max) 2972 bufsize = sb_max; 2973 if (bufsize > so->so_snd.sb_hiwat) 2974 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 2975 } 2976 SOCKBUF_UNLOCK(&so->so_snd); 2977 tp->t_maxseg = mss; 2978 2979 SOCKBUF_LOCK(&so->so_rcv); 2980 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2981 bufsize = metrics.rmx_recvpipe; 2982 else 2983 bufsize = so->so_rcv.sb_hiwat; 2984 if (bufsize > mss) { 2985 bufsize = roundup(bufsize, mss); 2986 if (bufsize > sb_max) 2987 bufsize = sb_max; 2988 if (bufsize > so->so_rcv.sb_hiwat) 2989 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 2990 } 2991 SOCKBUF_UNLOCK(&so->so_rcv); 2992 /* 2993 * While we're here, check the others too 2994 */ 2995 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2996 tp->t_srtt = rtt; 2997 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2998 tcpstat.tcps_usedrtt++; 2999 if (metrics.rmx_rttvar) { 3000 tp->t_rttvar = metrics.rmx_rttvar; 3001 tcpstat.tcps_usedrttvar++; 3002 } else { 3003 /* default variation is +- 1 rtt */ 3004 tp->t_rttvar = 3005 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3006 } 3007 TCPT_RANGESET(tp->t_rxtcur, 3008 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3009 tp->t_rttmin, TCPTV_REXMTMAX); 3010 } 3011 if (metrics.rmx_ssthresh) { 3012 /* 3013 * There's some sort of gateway or interface 3014 * buffer limit on the path. Use this to set 3015 * the slow start threshhold, but set the 3016 * threshold to no less than 2*mss. 3017 */ 3018 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3019 tcpstat.tcps_usedssthresh++; 3020 } 3021 if (metrics.rmx_bandwidth) 3022 tp->snd_bandwidth = metrics.rmx_bandwidth; 3023 3024 /* 3025 * Set the slow-start flight size depending on whether this 3026 * is a local network or not. 3027 * 3028 * Extend this so we cache the cwnd too and retrieve it here. 3029 * Make cwnd even bigger than RFC3390 suggests but only if we 3030 * have previous experience with the remote host. Be careful 3031 * not make cwnd bigger than remote receive window or our own 3032 * send socket buffer. Maybe put some additional upper bound 3033 * on the retrieved cwnd. Should do incremental updates to 3034 * hostcache when cwnd collapses so next connection doesn't 3035 * overloads the path again. 3036 * 3037 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3038 * We currently check only in syncache_socket for that. 3039 */ 3040 #define TCP_METRICS_CWND 3041 #ifdef TCP_METRICS_CWND 3042 if (metrics.rmx_cwnd) 3043 tp->snd_cwnd = max(mss, 3044 min(metrics.rmx_cwnd / 2, 3045 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3046 else 3047 #endif 3048 if (tcp_do_rfc3390) 3049 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3050 #ifdef INET6 3051 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3052 (!isipv6 && in_localaddr(inp->inp_faddr))) 3053 #else 3054 else if (in_localaddr(inp->inp_faddr)) 3055 #endif 3056 tp->snd_cwnd = mss * ss_fltsz_local; 3057 else 3058 tp->snd_cwnd = mss * ss_fltsz; 3059 } 3060 3061 /* 3062 * Determine the MSS option to send on an outgoing SYN. 3063 */ 3064 int 3065 tcp_mssopt(inc) 3066 struct in_conninfo *inc; 3067 { 3068 int mss = 0; 3069 u_long maxmtu = 0; 3070 u_long thcmtu = 0; 3071 size_t min_protoh; 3072 #ifdef INET6 3073 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3074 #endif 3075 3076 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3077 3078 #ifdef INET6 3079 if (isipv6) { 3080 mss = tcp_v6mssdflt; 3081 maxmtu = tcp_maxmtu6(inc); 3082 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3083 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3084 } else 3085 #endif 3086 { 3087 mss = tcp_mssdflt; 3088 maxmtu = tcp_maxmtu(inc); 3089 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3090 min_protoh = sizeof(struct tcpiphdr); 3091 } 3092 if (maxmtu && thcmtu) 3093 mss = min(maxmtu, thcmtu) - min_protoh; 3094 else if (maxmtu || thcmtu) 3095 mss = max(maxmtu, thcmtu) - min_protoh; 3096 3097 return (mss); 3098 } 3099 3100 3101 /* 3102 * On a partial ack arrives, force the retransmission of the 3103 * next unacknowledged segment. Do not clear tp->t_dupacks. 3104 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3105 * be started again. 3106 */ 3107 static void 3108 tcp_newreno_partial_ack(tp, th) 3109 struct tcpcb *tp; 3110 struct tcphdr *th; 3111 { 3112 tcp_seq onxt = tp->snd_nxt; 3113 u_long ocwnd = tp->snd_cwnd; 3114 3115 callout_stop(tp->tt_rexmt); 3116 tp->t_rtttime = 0; 3117 tp->snd_nxt = th->th_ack; 3118 /* 3119 * Set snd_cwnd to one segment beyond acknowledged offset. 3120 * (tp->snd_una has not yet been updated when this function is called.) 3121 */ 3122 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3123 tp->t_flags |= TF_ACKNOW; 3124 (void) tcp_output(tp); 3125 tp->snd_cwnd = ocwnd; 3126 if (SEQ_GT(onxt, tp->snd_nxt)) 3127 tp->snd_nxt = onxt; 3128 /* 3129 * Partial window deflation. Relies on fact that tp->snd_una 3130 * not updated yet. 3131 */ 3132 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3133 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3134 else 3135 tp->snd_cwnd = 0; 3136 tp->snd_cwnd += tp->t_maxseg; 3137 } 3138 3139 /* 3140 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3141 * looking for a pcb in the listen state. Returns 0 otherwise. 3142 */ 3143 static int 3144 tcp_timewait(tw, to, th, m, tlen) 3145 struct tcptw *tw; 3146 struct tcpopt *to; 3147 struct tcphdr *th; 3148 struct mbuf *m; 3149 int tlen; 3150 { 3151 int thflags; 3152 tcp_seq seq; 3153 #ifdef INET6 3154 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3155 #else 3156 const int isipv6 = 0; 3157 #endif 3158 3159 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3160 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3161 INP_LOCK_ASSERT(tw->tw_inpcb); 3162 3163 thflags = th->th_flags; 3164 3165 /* 3166 * NOTE: for FIN_WAIT_2 (to be added later), 3167 * must validate sequence number before accepting RST 3168 */ 3169 3170 /* 3171 * If the segment contains RST: 3172 * Drop the segment - see Stevens, vol. 2, p. 964 and 3173 * RFC 1337. 3174 */ 3175 if (thflags & TH_RST) 3176 goto drop; 3177 3178 #if 0 3179 /* PAWS not needed at the moment */ 3180 /* 3181 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3182 * and it's less than ts_recent, drop it. 3183 */ 3184 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3185 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3186 if ((thflags & TH_ACK) == 0) 3187 goto drop; 3188 goto ack; 3189 } 3190 /* 3191 * ts_recent is never updated because we never accept new segments. 3192 */ 3193 #endif 3194 3195 /* 3196 * If a new connection request is received 3197 * while in TIME_WAIT, drop the old connection 3198 * and start over if the sequence numbers 3199 * are above the previous ones. 3200 */ 3201 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3202 (void) tcp_twclose(tw, 0); 3203 return (1); 3204 } 3205 3206 /* 3207 * Drop the the segment if it does not contain an ACK. 3208 */ 3209 if ((thflags & TH_ACK) == 0) 3210 goto drop; 3211 3212 /* 3213 * Reset the 2MSL timer if this is a duplicate FIN. 3214 */ 3215 if (thflags & TH_FIN) { 3216 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3217 if (seq + 1 == tw->rcv_nxt) 3218 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3219 } 3220 3221 /* 3222 * Acknowledge the segment if it has data or is not a duplicate ACK. 3223 */ 3224 if (thflags != TH_ACK || tlen != 0 || 3225 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3226 tcp_twrespond(tw, TH_ACK); 3227 goto drop; 3228 3229 /* 3230 * Generate a RST, dropping incoming segment. 3231 * Make ACK acceptable to originator of segment. 3232 * Don't bother to respond if destination was broadcast/multicast. 3233 */ 3234 if (m->m_flags & (M_BCAST|M_MCAST)) 3235 goto drop; 3236 if (isipv6) { 3237 struct ip6_hdr *ip6; 3238 3239 /* IPv6 anycast check is done at tcp6_input() */ 3240 ip6 = mtod(m, struct ip6_hdr *); 3241 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3242 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3243 goto drop; 3244 } else { 3245 struct ip *ip; 3246 3247 ip = mtod(m, struct ip *); 3248 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3249 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3250 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3251 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3252 goto drop; 3253 } 3254 if (thflags & TH_ACK) { 3255 tcp_respond(NULL, 3256 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3257 } else { 3258 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3259 tcp_respond(NULL, 3260 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3261 } 3262 INP_UNLOCK(tw->tw_inpcb); 3263 return (0); 3264 3265 drop: 3266 INP_UNLOCK(tw->tw_inpcb); 3267 m_freem(m); 3268 return (0); 3269 } 3270