Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/netinet/tcp_input.c
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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: src/sys/netinet/tcp_input.c,v 1.252.2.21 2005/07/05 19:25:42 ps Exp $ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/mac.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/signalvar.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 #include <sys/syslog.h> 54 #include <sys/systm.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/in_var.h> 67 #include <netinet/ip.h> 68 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/nd6.h> 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet6/tcp6_var.h> 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif /* TCPDEBUG */ 86 87 #ifdef FAST_IPSEC 88 #include <netipsec/ipsec.h> 89 #include <netipsec/ipsec6.h> 90 #endif /*FAST_IPSEC*/ 91 92 #ifdef IPSEC 93 #include <netinet6/ipsec.h> 94 #include <netinet6/ipsec6.h> 95 #include <netkey/key.h> 96 #endif /*IPSEC*/ 97 98 #include <machine/in_cksum.h> 99 100 static const int tcprexmtthresh = 3; 101 tcp_cc tcp_ccgen; 102 103 struct tcpstat tcpstat; 104 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107 static int log_in_vain = 0; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111 static int blackhole = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115 int tcp_delack_enabled = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120 #ifdef TCP_DROP_SYNFIN 121 static int drop_synfin = 0; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124 #endif 125 126 static int tcp_do_rfc3042 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130 static int tcp_do_rfc3390 = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135 static int tcp_insecure_rst = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 137 &tcp_insecure_rst, 0, 138 "Follow the old (insecure) criteria for accepting RST packets."); 139 140 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 141 "TCP Segment Reassembly Queue"); 142 143 static int tcp_reass_maxseg = 0; 144 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 145 &tcp_reass_maxseg, 0, 146 "Global maximum number of TCP Segments in Reassembly Queue"); 147 148 int tcp_reass_qsize = 0; 149 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 150 &tcp_reass_qsize, 0, 151 "Global number of TCP Segments currently in Reassembly Queue"); 152 153 static int tcp_reass_maxqlen = 48; 154 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 155 &tcp_reass_maxqlen, 0, 156 "Maximum number of TCP Segments per individual Reassembly Queue"); 157 158 static int tcp_reass_overflows = 0; 159 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 160 &tcp_reass_overflows, 0, 161 "Global number of TCP Segment Reassembly Queue Overflows"); 162 163 struct inpcbhead tcb; 164 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 165 struct inpcbinfo tcbinfo; 166 struct mtx *tcbinfo_mtx; 167 168 static void tcp_dooptions(struct tcpcb *, struct tcpopt *, u_char *, 169 int, int, struct tcphdr *); 170 171 static void tcp_pulloutofband(struct socket *, 172 struct tcphdr *, struct mbuf *, int); 173 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 174 struct mbuf *); 175 static void tcp_xmit_timer(struct tcpcb *, int); 176 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 177 static int tcp_timewait(struct tcptw *, struct tcpopt *, 178 struct tcphdr *, struct mbuf *, int); 179 180 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 181 #ifdef INET6 182 #define ND6_HINT(tp) \ 183 do { \ 184 if ((tp) && (tp)->t_inpcb && \ 185 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 186 nd6_nud_hint(NULL, NULL, 0); \ 187 } while (0) 188 #else 189 #define ND6_HINT(tp) 190 #endif 191 192 /* 193 * Indicate whether this ack should be delayed. We can delay the ack if 194 * - there is no delayed ack timer in progress and 195 * - our last ack wasn't a 0-sized window. We never want to delay 196 * the ack that opens up a 0-sized window and 197 * - delayed acks are enabled or 198 * - this is a half-synchronized T/TCP connection. 199 */ 200 #define DELAY_ACK(tp) \ 201 ((!callout_active(tp->tt_delack) && \ 202 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 203 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 204 205 /* Initialize TCP reassembly queue */ 206 uma_zone_t tcp_reass_zone; 207 void 208 tcp_reass_init() 209 { 210 tcp_reass_maxseg = nmbclusters / 16; 211 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 212 &tcp_reass_maxseg); 213 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 214 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 215 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 216 } 217 218 static int 219 tcp_reass(tp, th, tlenp, m) 220 register struct tcpcb *tp; 221 register struct tcphdr *th; 222 int *tlenp; 223 struct mbuf *m; 224 { 225 struct tseg_qent *q; 226 struct tseg_qent *p = NULL; 227 struct tseg_qent *nq; 228 struct tseg_qent *te = NULL; 229 struct socket *so = tp->t_inpcb->inp_socket; 230 int flags; 231 232 INP_LOCK_ASSERT(tp->t_inpcb); 233 234 /* 235 * XXX: tcp_reass() is rather inefficient with its data structures 236 * and should be rewritten (see NetBSD for optimizations). While 237 * doing that it should move to its own file tcp_reass.c. 238 */ 239 240 /* 241 * Call with th==NULL after become established to 242 * force pre-ESTABLISHED data up to user socket. 243 */ 244 if (th == NULL) 245 goto present; 246 247 /* 248 * Limit the number of segments in the reassembly queue to prevent 249 * holding on to too many segments (and thus running out of mbufs). 250 * Make sure to let the missing segment through which caused this 251 * queue. Always keep one global queue entry spare to be able to 252 * process the missing segment. 253 */ 254 if (th->th_seq != tp->rcv_nxt && 255 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 256 tp->t_segqlen >= tcp_reass_maxqlen)) { 257 tcp_reass_overflows++; 258 tcpstat.tcps_rcvmemdrop++; 259 m_freem(m); 260 *tlenp = 0; 261 return (0); 262 } 263 264 /* 265 * Allocate a new queue entry. If we can't, or hit the zone limit 266 * just drop the pkt. 267 */ 268 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 269 if (te == NULL) { 270 tcpstat.tcps_rcvmemdrop++; 271 m_freem(m); 272 *tlenp = 0; 273 return (0); 274 } 275 tp->t_segqlen++; 276 tcp_reass_qsize++; 277 278 /* 279 * Find a segment which begins after this one does. 280 */ 281 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 282 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 283 break; 284 p = q; 285 } 286 287 /* 288 * If there is a preceding segment, it may provide some of 289 * our data already. If so, drop the data from the incoming 290 * segment. If it provides all of our data, drop us. 291 */ 292 if (p != NULL) { 293 register int i; 294 /* conversion to int (in i) handles seq wraparound */ 295 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 296 if (i > 0) { 297 if (i >= *tlenp) { 298 tcpstat.tcps_rcvduppack++; 299 tcpstat.tcps_rcvdupbyte += *tlenp; 300 m_freem(m); 301 uma_zfree(tcp_reass_zone, te); 302 tp->t_segqlen--; 303 tcp_reass_qsize--; 304 /* 305 * Try to present any queued data 306 * at the left window edge to the user. 307 * This is needed after the 3-WHS 308 * completes. 309 */ 310 goto present; /* ??? */ 311 } 312 m_adj(m, i); 313 *tlenp -= i; 314 th->th_seq += i; 315 } 316 } 317 tcpstat.tcps_rcvoopack++; 318 tcpstat.tcps_rcvoobyte += *tlenp; 319 320 /* 321 * While we overlap succeeding segments trim them or, 322 * if they are completely covered, dequeue them. 323 */ 324 while (q) { 325 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 326 if (i <= 0) 327 break; 328 if (i < q->tqe_len) { 329 q->tqe_th->th_seq += i; 330 q->tqe_len -= i; 331 m_adj(q->tqe_m, i); 332 break; 333 } 334 335 nq = LIST_NEXT(q, tqe_q); 336 LIST_REMOVE(q, tqe_q); 337 m_freem(q->tqe_m); 338 uma_zfree(tcp_reass_zone, q); 339 tp->t_segqlen--; 340 tcp_reass_qsize--; 341 q = nq; 342 } 343 344 /* Insert the new segment queue entry into place. */ 345 te->tqe_m = m; 346 te->tqe_th = th; 347 te->tqe_len = *tlenp; 348 349 if (p == NULL) { 350 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 351 } else { 352 LIST_INSERT_AFTER(p, te, tqe_q); 353 } 354 355 present: 356 /* 357 * Present data to user, advancing rcv_nxt through 358 * completed sequence space. 359 */ 360 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 361 return (0); 362 q = LIST_FIRST(&tp->t_segq); 363 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 364 return (0); 365 SOCKBUF_LOCK(&so->so_rcv); 366 do { 367 tp->rcv_nxt += q->tqe_len; 368 flags = q->tqe_th->th_flags & TH_FIN; 369 nq = LIST_NEXT(q, tqe_q); 370 LIST_REMOVE(q, tqe_q); 371 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 372 m_freem(q->tqe_m); 373 else 374 sbappendstream_locked(&so->so_rcv, q->tqe_m); 375 uma_zfree(tcp_reass_zone, q); 376 tp->t_segqlen--; 377 tcp_reass_qsize--; 378 q = nq; 379 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 380 ND6_HINT(tp); 381 sorwakeup_locked(so); 382 return (flags); 383 } 384 385 /* 386 * TCP input routine, follows pages 65-76 of the 387 * protocol specification dated September, 1981 very closely. 388 */ 389 #ifdef INET6 390 int 391 tcp6_input(mp, offp, proto) 392 struct mbuf **mp; 393 int *offp, proto; 394 { 395 register struct mbuf *m = *mp; 396 struct in6_ifaddr *ia6; 397 398 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 399 400 /* 401 * draft-itojun-ipv6-tcp-to-anycast 402 * better place to put this in? 403 */ 404 ia6 = ip6_getdstifaddr(m); 405 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 406 struct ip6_hdr *ip6; 407 408 ip6 = mtod(m, struct ip6_hdr *); 409 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 410 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 411 return IPPROTO_DONE; 412 } 413 414 tcp_input(m, *offp); 415 return IPPROTO_DONE; 416 } 417 #endif 418 419 void 420 tcp_input(m, off0) 421 register struct mbuf *m; 422 int off0; 423 { 424 register struct tcphdr *th; 425 register struct ip *ip = NULL; 426 register struct ipovly *ipov; 427 register struct inpcb *inp = NULL; 428 u_char *optp = NULL; 429 int optlen = 0; 430 int len, tlen, off; 431 int drop_hdrlen; 432 register struct tcpcb *tp = 0; 433 register int thflags; 434 struct socket *so = 0; 435 int todrop, acked, ourfinisacked, needoutput = 0; 436 u_long tiwin; 437 struct tcpopt to; /* options in this segment */ 438 struct rmxp_tao tao; /* our TAO cache entry */ 439 int headlocked = 0; 440 #ifdef IPFIREWALL_FORWARD 441 struct m_tag *fwd_tag; 442 #endif 443 int rstreason; /* For badport_bandlim accounting purposes */ 444 445 struct ip6_hdr *ip6 = NULL; 446 #ifdef INET6 447 int isipv6; 448 #else 449 const int isipv6 = 0; 450 #endif 451 452 #ifdef TCPDEBUG 453 /* 454 * The size of tcp_saveipgen must be the size of the max ip header, 455 * now IPv6. 456 */ 457 u_char tcp_saveipgen[40]; 458 struct tcphdr tcp_savetcp; 459 short ostate = 0; 460 #endif 461 462 #ifdef INET6 463 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 464 #endif 465 bzero(&tao, sizeof(tao)); 466 bzero((char *)&to, sizeof(to)); 467 468 tcpstat.tcps_rcvtotal++; 469 470 if (isipv6) { 471 #ifdef INET6 472 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 473 ip6 = mtod(m, struct ip6_hdr *); 474 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 475 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 476 tcpstat.tcps_rcvbadsum++; 477 goto drop; 478 } 479 th = (struct tcphdr *)((caddr_t)ip6 + off0); 480 481 /* 482 * Be proactive about unspecified IPv6 address in source. 483 * As we use all-zero to indicate unbounded/unconnected pcb, 484 * unspecified IPv6 address can be used to confuse us. 485 * 486 * Note that packets with unspecified IPv6 destination is 487 * already dropped in ip6_input. 488 */ 489 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 490 /* XXX stat */ 491 goto drop; 492 } 493 #else 494 th = NULL; /* XXX: avoid compiler warning */ 495 #endif 496 } else { 497 /* 498 * Get IP and TCP header together in first mbuf. 499 * Note: IP leaves IP header in first mbuf. 500 */ 501 if (off0 > sizeof (struct ip)) { 502 ip_stripoptions(m, (struct mbuf *)0); 503 off0 = sizeof(struct ip); 504 } 505 if (m->m_len < sizeof (struct tcpiphdr)) { 506 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 507 tcpstat.tcps_rcvshort++; 508 return; 509 } 510 } 511 ip = mtod(m, struct ip *); 512 ipov = (struct ipovly *)ip; 513 th = (struct tcphdr *)((caddr_t)ip + off0); 514 tlen = ip->ip_len; 515 516 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 517 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 518 th->th_sum = m->m_pkthdr.csum_data; 519 else 520 th->th_sum = in_pseudo(ip->ip_src.s_addr, 521 ip->ip_dst.s_addr, 522 htonl(m->m_pkthdr.csum_data + 523 ip->ip_len + 524 IPPROTO_TCP)); 525 th->th_sum ^= 0xffff; 526 #ifdef TCPDEBUG 527 ipov->ih_len = (u_short)tlen; 528 ipov->ih_len = htons(ipov->ih_len); 529 #endif 530 } else { 531 /* 532 * Checksum extended TCP header and data. 533 */ 534 len = sizeof (struct ip) + tlen; 535 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 536 ipov->ih_len = (u_short)tlen; 537 ipov->ih_len = htons(ipov->ih_len); 538 th->th_sum = in_cksum(m, len); 539 } 540 if (th->th_sum) { 541 tcpstat.tcps_rcvbadsum++; 542 goto drop; 543 } 544 #ifdef INET6 545 /* Re-initialization for later version check */ 546 ip->ip_v = IPVERSION; 547 #endif 548 } 549 550 /* 551 * Check that TCP offset makes sense, 552 * pull out TCP options and adjust length. XXX 553 */ 554 off = th->th_off << 2; 555 if (off < sizeof (struct tcphdr) || off > tlen) { 556 tcpstat.tcps_rcvbadoff++; 557 goto drop; 558 } 559 tlen -= off; /* tlen is used instead of ti->ti_len */ 560 if (off > sizeof (struct tcphdr)) { 561 if (isipv6) { 562 #ifdef INET6 563 IP6_EXTHDR_CHECK(m, off0, off, ); 564 ip6 = mtod(m, struct ip6_hdr *); 565 th = (struct tcphdr *)((caddr_t)ip6 + off0); 566 #endif 567 } else { 568 if (m->m_len < sizeof(struct ip) + off) { 569 if ((m = m_pullup(m, sizeof (struct ip) + off)) 570 == 0) { 571 tcpstat.tcps_rcvshort++; 572 return; 573 } 574 ip = mtod(m, struct ip *); 575 ipov = (struct ipovly *)ip; 576 th = (struct tcphdr *)((caddr_t)ip + off0); 577 } 578 } 579 optlen = off - sizeof (struct tcphdr); 580 optp = (u_char *)(th + 1); 581 } 582 thflags = th->th_flags; 583 584 #ifdef TCP_DROP_SYNFIN 585 /* 586 * If the drop_synfin option is enabled, drop all packets with 587 * both the SYN and FIN bits set. This prevents e.g. nmap from 588 * identifying the TCP/IP stack. 589 * 590 * This is a violation of the TCP specification. 591 */ 592 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 593 goto drop; 594 #endif 595 596 /* 597 * Convert TCP protocol specific fields to host format. 598 */ 599 th->th_seq = ntohl(th->th_seq); 600 th->th_ack = ntohl(th->th_ack); 601 th->th_win = ntohs(th->th_win); 602 th->th_urp = ntohs(th->th_urp); 603 604 /* 605 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 606 * until after ip6_savecontrol() is called and before other functions 607 * which don't want those proto headers. 608 * Because ip6_savecontrol() is going to parse the mbuf to 609 * search for data to be passed up to user-land, it wants mbuf 610 * parameters to be unchanged. 611 * XXX: the call of ip6_savecontrol() has been obsoleted based on 612 * latest version of the advanced API (20020110). 613 */ 614 drop_hdrlen = off0 + off; 615 616 /* 617 * Locate pcb for segment. 618 */ 619 INP_INFO_WLOCK(&tcbinfo); 620 headlocked = 1; 621 findpcb: 622 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 623 #ifdef IPFIREWALL_FORWARD 624 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 625 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 626 627 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 628 struct sockaddr_in *next_hop; 629 630 next_hop = (struct sockaddr_in *)(fwd_tag+1); 631 /* 632 * Transparently forwarded. Pretend to be the destination. 633 * already got one like this? 634 */ 635 inp = in_pcblookup_hash(&tcbinfo, 636 ip->ip_src, th->th_sport, 637 ip->ip_dst, th->th_dport, 638 0, m->m_pkthdr.rcvif); 639 if (!inp) { 640 /* It's new. Try to find the ambushing socket. */ 641 inp = in_pcblookup_hash(&tcbinfo, 642 ip->ip_src, th->th_sport, 643 next_hop->sin_addr, 644 next_hop->sin_port ? 645 ntohs(next_hop->sin_port) : 646 th->th_dport, 647 1, m->m_pkthdr.rcvif); 648 } 649 /* Remove the tag from the packet. We don't need it anymore. */ 650 m_tag_delete(m, fwd_tag); 651 } else { 652 #endif /* IPFIREWALL_FORWARD */ 653 if (isipv6) { 654 #ifdef INET6 655 inp = in6_pcblookup_hash(&tcbinfo, 656 &ip6->ip6_src, th->th_sport, 657 &ip6->ip6_dst, th->th_dport, 658 1, m->m_pkthdr.rcvif); 659 #endif 660 } else 661 inp = in_pcblookup_hash(&tcbinfo, 662 ip->ip_src, th->th_sport, 663 ip->ip_dst, th->th_dport, 664 1, m->m_pkthdr.rcvif); 665 #ifdef IPFIREWALL_FORWARD 666 } 667 #endif /* IPFIREWALL_FORWARD */ 668 669 #if defined(IPSEC) || defined(FAST_IPSEC) 670 #ifdef INET6 671 if (isipv6) { 672 if (inp != NULL && ipsec6_in_reject(m, inp)) { 673 #ifdef IPSEC 674 ipsec6stat.in_polvio++; 675 #endif 676 goto drop; 677 } 678 } else 679 #endif /* INET6 */ 680 if (inp != NULL && ipsec4_in_reject(m, inp)) { 681 #ifdef IPSEC 682 ipsecstat.in_polvio++; 683 #endif 684 goto drop; 685 } 686 #endif /*IPSEC || FAST_IPSEC*/ 687 688 /* 689 * If the state is CLOSED (i.e., TCB does not exist) then 690 * all data in the incoming segment is discarded. 691 * If the TCB exists but is in CLOSED state, it is embryonic, 692 * but should either do a listen or a connect soon. 693 */ 694 if (inp == NULL) { 695 if (log_in_vain) { 696 #ifdef INET6 697 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 698 #else 699 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 700 #endif 701 702 if (isipv6) { 703 #ifdef INET6 704 strcpy(dbuf, "["); 705 strcpy(sbuf, "["); 706 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 707 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 708 strcat(dbuf, "]"); 709 strcat(sbuf, "]"); 710 #endif 711 } else { 712 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 713 strcpy(sbuf, inet_ntoa(ip->ip_src)); 714 } 715 switch (log_in_vain) { 716 case 1: 717 if ((thflags & TH_SYN) == 0) 718 break; 719 /* FALLTHROUGH */ 720 case 2: 721 log(LOG_INFO, 722 "Connection attempt to TCP %s:%d " 723 "from %s:%d flags:0x%02x\n", 724 dbuf, ntohs(th->th_dport), sbuf, 725 ntohs(th->th_sport), thflags); 726 break; 727 default: 728 break; 729 } 730 } 731 if (blackhole) { 732 switch (blackhole) { 733 case 1: 734 if (thflags & TH_SYN) 735 goto drop; 736 break; 737 case 2: 738 goto drop; 739 default: 740 goto drop; 741 } 742 } 743 rstreason = BANDLIM_RST_CLOSEDPORT; 744 goto dropwithreset; 745 } 746 INP_LOCK(inp); 747 if (inp->inp_vflag & INP_TIMEWAIT) { 748 /* 749 * The only option of relevance is TOF_CC, and only if 750 * present in a SYN segment. See tcp_timewait(). 751 */ 752 if (thflags & TH_SYN) 753 tcp_dooptions((struct tcpcb *)NULL, &to, optp, optlen, 1, th); 754 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 755 &to, th, m, tlen)) 756 goto findpcb; 757 /* 758 * tcp_timewait unlocks inp. 759 */ 760 INP_INFO_WUNLOCK(&tcbinfo); 761 return; 762 } 763 tp = intotcpcb(inp); 764 if (tp == 0) { 765 INP_UNLOCK(inp); 766 rstreason = BANDLIM_RST_CLOSEDPORT; 767 goto dropwithreset; 768 } 769 if (tp->t_state == TCPS_CLOSED) 770 goto drop; 771 772 /* Unscale the window into a 32-bit value. */ 773 if ((thflags & TH_SYN) == 0) 774 tiwin = th->th_win << tp->snd_scale; 775 else 776 tiwin = th->th_win; 777 778 #ifdef MAC 779 INP_LOCK_ASSERT(inp); 780 if (mac_check_inpcb_deliver(inp, m)) 781 goto drop; 782 #endif 783 so = inp->inp_socket; 784 #ifdef TCPDEBUG 785 if (so->so_options & SO_DEBUG) { 786 ostate = tp->t_state; 787 if (isipv6) 788 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 789 else 790 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 791 tcp_savetcp = *th; 792 } 793 #endif 794 if (so->so_options & SO_ACCEPTCONN) { 795 struct in_conninfo inc; 796 797 #ifdef INET6 798 inc.inc_isipv6 = isipv6; 799 #endif 800 if (isipv6) { 801 inc.inc6_faddr = ip6->ip6_src; 802 inc.inc6_laddr = ip6->ip6_dst; 803 } else { 804 inc.inc_faddr = ip->ip_src; 805 inc.inc_laddr = ip->ip_dst; 806 } 807 inc.inc_fport = th->th_sport; 808 inc.inc_lport = th->th_dport; 809 810 /* 811 * If the state is LISTEN then ignore segment if it contains 812 * a RST. If the segment contains an ACK then it is bad and 813 * send a RST. If it does not contain a SYN then it is not 814 * interesting; drop it. 815 * 816 * If the state is SYN_RECEIVED (syncache) and seg contains 817 * an ACK, but not for our SYN/ACK, send a RST. If the seg 818 * contains a RST, check the sequence number to see if it 819 * is a valid reset segment. 820 */ 821 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 822 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 823 if (!syncache_expand(&inc, th, &so, m)) { 824 /* 825 * No syncache entry, or ACK was not 826 * for our SYN/ACK. Send a RST. 827 */ 828 tcpstat.tcps_badsyn++; 829 rstreason = BANDLIM_RST_OPENPORT; 830 goto dropwithreset; 831 } 832 if (so == NULL) { 833 /* 834 * Could not complete 3-way handshake, 835 * connection is being closed down, and 836 * syncache will free mbuf. 837 */ 838 INP_UNLOCK(inp); 839 INP_INFO_WUNLOCK(&tcbinfo); 840 return; 841 } 842 /* 843 * Socket is created in state SYN_RECEIVED. 844 * Continue processing segment. 845 */ 846 INP_UNLOCK(inp); 847 inp = sotoinpcb(so); 848 INP_LOCK(inp); 849 tp = intotcpcb(inp); 850 /* 851 * This is what would have happened in 852 * tcp_output() when the SYN,ACK was sent. 853 */ 854 tp->snd_up = tp->snd_una; 855 tp->snd_max = tp->snd_nxt = tp->iss + 1; 856 tp->last_ack_sent = tp->rcv_nxt; 857 /* 858 * RFC1323: The window in SYN & SYN/ACK 859 * segments is never scaled. 860 */ 861 tp->snd_wnd = tiwin; /* unscaled */ 862 goto after_listen; 863 } 864 if (thflags & TH_RST) { 865 syncache_chkrst(&inc, th); 866 goto drop; 867 } 868 if (thflags & TH_ACK) { 869 syncache_badack(&inc); 870 tcpstat.tcps_badsyn++; 871 rstreason = BANDLIM_RST_OPENPORT; 872 goto dropwithreset; 873 } 874 goto drop; 875 } 876 877 /* 878 * Segment's flags are (SYN) or (SYN|FIN). 879 */ 880 #ifdef INET6 881 /* 882 * If deprecated address is forbidden, 883 * we do not accept SYN to deprecated interface 884 * address to prevent any new inbound connection from 885 * getting established. 886 * When we do not accept SYN, we send a TCP RST, 887 * with deprecated source address (instead of dropping 888 * it). We compromise it as it is much better for peer 889 * to send a RST, and RST will be the final packet 890 * for the exchange. 891 * 892 * If we do not forbid deprecated addresses, we accept 893 * the SYN packet. RFC2462 does not suggest dropping 894 * SYN in this case. 895 * If we decipher RFC2462 5.5.4, it says like this: 896 * 1. use of deprecated addr with existing 897 * communication is okay - "SHOULD continue to be 898 * used" 899 * 2. use of it with new communication: 900 * (2a) "SHOULD NOT be used if alternate address 901 * with sufficient scope is available" 902 * (2b) nothing mentioned otherwise. 903 * Here we fall into (2b) case as we have no choice in 904 * our source address selection - we must obey the peer. 905 * 906 * The wording in RFC2462 is confusing, and there are 907 * multiple description text for deprecated address 908 * handling - worse, they are not exactly the same. 909 * I believe 5.5.4 is the best one, so we follow 5.5.4. 910 */ 911 if (isipv6 && !ip6_use_deprecated) { 912 struct in6_ifaddr *ia6; 913 914 if ((ia6 = ip6_getdstifaddr(m)) && 915 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 916 INP_UNLOCK(inp); 917 tp = NULL; 918 rstreason = BANDLIM_RST_OPENPORT; 919 goto dropwithreset; 920 } 921 } 922 #endif 923 /* 924 * If it is from this socket, drop it, it must be forged. 925 * Don't bother responding if the destination was a broadcast. 926 */ 927 if (th->th_dport == th->th_sport) { 928 if (isipv6) { 929 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 930 &ip6->ip6_src)) 931 goto drop; 932 } else { 933 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 934 goto drop; 935 } 936 } 937 /* 938 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 939 * 940 * Note that it is quite possible to receive unicast 941 * link-layer packets with a broadcast IP address. Use 942 * in_broadcast() to find them. 943 */ 944 if (m->m_flags & (M_BCAST|M_MCAST)) 945 goto drop; 946 if (isipv6) { 947 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 948 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 949 goto drop; 950 } else { 951 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 952 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 953 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 954 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 955 goto drop; 956 } 957 /* 958 * SYN appears to be valid; create compressed TCP state 959 * for syncache, or perform t/tcp connection. 960 */ 961 if (so->so_qlen <= so->so_qlimit) { 962 #ifdef TCPDEBUG 963 if (so->so_options & SO_DEBUG) 964 tcp_trace(TA_INPUT, ostate, tp, 965 (void *)tcp_saveipgen, &tcp_savetcp, 0); 966 #endif 967 tcp_dooptions(tp, &to, optp, optlen, 1, th); 968 if (!syncache_add(&inc, &to, th, &so, m)) 969 goto drop; 970 if (so == NULL) { 971 /* 972 * Entry added to syncache, mbuf used to 973 * send SYN,ACK packet. 974 */ 975 KASSERT(headlocked, ("headlocked")); 976 INP_UNLOCK(inp); 977 INP_INFO_WUNLOCK(&tcbinfo); 978 return; 979 } 980 /* 981 * Segment passed TAO tests. 982 */ 983 INP_UNLOCK(inp); 984 inp = sotoinpcb(so); 985 INP_LOCK(inp); 986 tp = intotcpcb(inp); 987 tp->snd_wnd = tiwin; 988 tp->t_starttime = ticks; 989 tp->t_state = TCPS_ESTABLISHED; 990 991 /* 992 * T/TCP logic: 993 * If there is a FIN or if there is data, then 994 * delay SYN,ACK(SYN) in the hope of piggy-backing 995 * it on a response segment. Otherwise must send 996 * ACK now in case the other side is slow starting. 997 */ 998 if (thflags & TH_FIN || tlen != 0) 999 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1000 else 1001 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1002 tcpstat.tcps_connects++; 1003 soisconnected(so); 1004 goto trimthenstep6; 1005 } 1006 goto drop; 1007 } 1008 after_listen: 1009 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1010 INP_LOCK_ASSERT(inp); 1011 1012 /* XXX temp debugging */ 1013 /* should not happen - syncache should pick up these connections */ 1014 if (tp->t_state == TCPS_LISTEN) 1015 panic("tcp_input: TCPS_LISTEN"); 1016 1017 /* 1018 * This is the second part of the MSS DoS prevention code (after 1019 * minmss on the sending side) and it deals with too many too small 1020 * tcp packets in a too short timeframe (1 second). 1021 * 1022 * For every full second we count the number of received packets 1023 * and bytes. If we get a lot of packets per second for this connection 1024 * (tcp_minmssoverload) we take a closer look at it and compute the 1025 * average packet size for the past second. If that is less than 1026 * tcp_minmss we get too many packets with very small payload which 1027 * is not good and burdens our system (and every packet generates 1028 * a wakeup to the process connected to our socket). We can reasonable 1029 * expect this to be small packet DoS attack to exhaust our CPU 1030 * cycles. 1031 * 1032 * Care has to be taken for the minimum packet overload value. This 1033 * value defines the minimum number of packets per second before we 1034 * start to worry. This must not be too low to avoid killing for 1035 * example interactive connections with many small packets like 1036 * telnet or SSH. 1037 * 1038 * Setting either tcp_minmssoverload or tcp_minmss to "" disables 1039 * this check. 1040 * 1041 * Account for packet if payload packet, skip over ACK, etc. 1042 */ 1043 if (tcp_minmss && tcp_minmssoverload && 1044 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1045 if (tp->rcv_second > ticks) { 1046 tp->rcv_pps++; 1047 tp->rcv_byps += tlen + off; 1048 if (tp->rcv_pps > tcp_minmssoverload) { 1049 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1050 printf("too many small tcp packets from " 1051 "%s:%u, av. %lubyte/packet, " 1052 "dropping connection\n", 1053 #ifdef INET6 1054 isipv6 ? 1055 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1056 #endif 1057 inet_ntoa(inp->inp_inc.inc_faddr), 1058 inp->inp_inc.inc_fport, 1059 tp->rcv_byps / tp->rcv_pps); 1060 KASSERT(headlocked, ("tcp_input: " 1061 "after_listen: tcp_drop: head " 1062 "not locked")); 1063 tp = tcp_drop(tp, ECONNRESET); 1064 tcpstat.tcps_minmssdrops++; 1065 goto drop; 1066 } 1067 } 1068 } else { 1069 tp->rcv_second = ticks + hz; 1070 tp->rcv_pps = 1; 1071 tp->rcv_byps = tlen + off; 1072 } 1073 } 1074 1075 /* 1076 * Segment received on connection. 1077 * Reset idle time and keep-alive timer. 1078 */ 1079 tp->t_rcvtime = ticks; 1080 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1081 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1082 1083 /* 1084 * Process options only when we get SYN/ACK back. The SYN case 1085 * for incoming connections is handled in tcp_syncache. 1086 * XXX this is traditional behavior, may need to be cleaned up. 1087 */ 1088 tcp_dooptions(tp, &to, optp, optlen, thflags & TH_SYN, th); 1089 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1090 if (to.to_flags & TOF_SCALE) { 1091 tp->t_flags |= TF_RCVD_SCALE; 1092 tp->requested_s_scale = to.to_requested_s_scale; 1093 } 1094 if (to.to_flags & TOF_TS) { 1095 tp->t_flags |= TF_RCVD_TSTMP; 1096 tp->ts_recent = to.to_tsval; 1097 tp->ts_recent_age = ticks; 1098 } 1099 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1100 tp->t_flags |= TF_RCVD_CC; 1101 if (to.to_flags & TOF_MSS) 1102 tcp_mss(tp, to.to_mss); 1103 if (tp->sack_enable) { 1104 if (!(to.to_flags & TOF_SACK)) 1105 tp->sack_enable = 0; 1106 else 1107 tp->t_flags |= TF_SACK_PERMIT; 1108 } 1109 1110 } 1111 1112 if (tp->sack_enable) { 1113 /* Delete stale (cumulatively acked) SACK holes */ 1114 tcp_del_sackholes(tp, th); 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 /* 1140 * Using the CC option is compulsory if once started: 1141 * the segment is OK if no T/TCP was negotiated or 1142 * if the segment has a CC option equal to CCrecv 1143 */ 1144 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1145 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1146 th->th_seq == tp->rcv_nxt && 1147 tiwin && tiwin == tp->snd_wnd && 1148 tp->snd_nxt == tp->snd_max) { 1149 1150 /* 1151 * If last ACK falls within this segment's sequence numbers, 1152 * record the timestamp. 1153 * NOTE that the test is modified according to the latest 1154 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1155 */ 1156 if ((to.to_flags & TOF_TS) != 0 && 1157 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1158 tp->ts_recent_age = ticks; 1159 tp->ts_recent = to.to_tsval; 1160 } 1161 1162 if (tlen == 0) { 1163 if (SEQ_GT(th->th_ack, tp->snd_una) && 1164 SEQ_LEQ(th->th_ack, tp->snd_max) && 1165 tp->snd_cwnd >= tp->snd_wnd && 1166 ((!tcp_do_newreno && !tp->sack_enable && 1167 tp->t_dupacks < tcprexmtthresh) || 1168 ((tcp_do_newreno || tp->sack_enable) && 1169 !IN_FASTRECOVERY(tp)))) { 1170 KASSERT(headlocked, ("headlocked")); 1171 INP_INFO_WUNLOCK(&tcbinfo); 1172 headlocked = 0; 1173 /* 1174 * this is a pure ack for outstanding data. 1175 */ 1176 ++tcpstat.tcps_predack; 1177 /* 1178 * "bad retransmit" recovery 1179 */ 1180 if (tp->t_rxtshift == 1 && 1181 ticks < tp->t_badrxtwin) { 1182 ++tcpstat.tcps_sndrexmitbad; 1183 tp->snd_cwnd = tp->snd_cwnd_prev; 1184 tp->snd_ssthresh = 1185 tp->snd_ssthresh_prev; 1186 tp->snd_recover = tp->snd_recover_prev; 1187 if (tp->t_flags & TF_WASFRECOVERY) 1188 ENTER_FASTRECOVERY(tp); 1189 tp->snd_nxt = tp->snd_max; 1190 tp->t_badrxtwin = 0; 1191 } 1192 1193 /* 1194 * Recalculate the transmit timer / rtt. 1195 * 1196 * Some boxes send broken timestamp replies 1197 * during the SYN+ACK phase, ignore 1198 * timestamps of 0 or we could calculate a 1199 * huge RTT and blow up the retransmit timer. 1200 */ 1201 if ((to.to_flags & TOF_TS) != 0 && 1202 to.to_tsecr) { 1203 tcp_xmit_timer(tp, 1204 ticks - to.to_tsecr + 1); 1205 } else if (tp->t_rtttime && 1206 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1207 tcp_xmit_timer(tp, 1208 ticks - tp->t_rtttime); 1209 } 1210 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1211 acked = th->th_ack - tp->snd_una; 1212 tcpstat.tcps_rcvackpack++; 1213 tcpstat.tcps_rcvackbyte += acked; 1214 sbdrop(&so->so_snd, acked); 1215 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1216 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1217 tp->snd_recover = th->th_ack - 1; 1218 tp->snd_una = th->th_ack; 1219 /* 1220 * pull snd_wl2 up to prevent seq wrap relative 1221 * to th_ack. 1222 */ 1223 tp->snd_wl2 = th->th_ack; 1224 tp->t_dupacks = 0; 1225 m_freem(m); 1226 ND6_HINT(tp); /* some progress has been done */ 1227 1228 /* 1229 * If all outstanding data are acked, stop 1230 * retransmit timer, otherwise restart timer 1231 * using current (possibly backed-off) value. 1232 * If process is waiting for space, 1233 * wakeup/selwakeup/signal. If data 1234 * are ready to send, let tcp_output 1235 * decide between more output or persist. 1236 1237 #ifdef TCPDEBUG 1238 if (so->so_options & SO_DEBUG) 1239 tcp_trace(TA_INPUT, ostate, tp, 1240 (void *)tcp_saveipgen, 1241 &tcp_savetcp, 0); 1242 #endif 1243 */ 1244 if (tp->snd_una == tp->snd_max) 1245 callout_stop(tp->tt_rexmt); 1246 else if (!callout_active(tp->tt_persist)) 1247 callout_reset(tp->tt_rexmt, 1248 tp->t_rxtcur, 1249 tcp_timer_rexmt, tp); 1250 1251 sowwakeup(so); 1252 if (so->so_snd.sb_cc) 1253 (void) tcp_output(tp); 1254 goto check_delack; 1255 } 1256 } else if (th->th_ack == tp->snd_una && 1257 LIST_EMPTY(&tp->t_segq) && 1258 tlen <= sbspace(&so->so_rcv)) { 1259 KASSERT(headlocked, ("headlocked")); 1260 INP_INFO_WUNLOCK(&tcbinfo); 1261 headlocked = 0; 1262 /* 1263 * this is a pure, in-sequence data packet 1264 * with nothing on the reassembly queue and 1265 * we have enough buffer space to take it. 1266 */ 1267 /* Clean receiver SACK report if present */ 1268 if (tp->sack_enable && tp->rcv_numsacks) 1269 tcp_clean_sackreport(tp); 1270 ++tcpstat.tcps_preddat; 1271 tp->rcv_nxt += tlen; 1272 /* 1273 * Pull snd_wl1 up to prevent seq wrap relative to 1274 * th_seq. 1275 */ 1276 tp->snd_wl1 = th->th_seq; 1277 /* 1278 * Pull rcv_up up to prevent seq wrap relative to 1279 * rcv_nxt. 1280 */ 1281 tp->rcv_up = tp->rcv_nxt; 1282 tcpstat.tcps_rcvpack++; 1283 tcpstat.tcps_rcvbyte += tlen; 1284 ND6_HINT(tp); /* some progress has been done */ 1285 /* 1286 #ifdef TCPDEBUG 1287 if (so->so_options & SO_DEBUG) 1288 tcp_trace(TA_INPUT, ostate, tp, 1289 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1290 #endif 1291 * Add data to socket buffer. 1292 */ 1293 SOCKBUF_LOCK(&so->so_rcv); 1294 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1295 m_freem(m); 1296 } else { 1297 m_adj(m, drop_hdrlen); /* delayed header drop */ 1298 sbappendstream_locked(&so->so_rcv, m); 1299 } 1300 sorwakeup_locked(so); 1301 if (DELAY_ACK(tp)) { 1302 tp->t_flags |= TF_DELACK; 1303 } else { 1304 tp->t_flags |= TF_ACKNOW; 1305 tcp_output(tp); 1306 } 1307 goto check_delack; 1308 } 1309 } 1310 1311 /* 1312 * Calculate amount of space in receive window, 1313 * and then do TCP input processing. 1314 * Receive window is amount of space in rcv queue, 1315 * but not less than advertised window. 1316 */ 1317 { int win; 1318 1319 win = sbspace(&so->so_rcv); 1320 if (win < 0) 1321 win = 0; 1322 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1323 } 1324 1325 switch (tp->t_state) { 1326 1327 /* 1328 * If the state is SYN_RECEIVED: 1329 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1330 */ 1331 case TCPS_SYN_RECEIVED: 1332 if ((thflags & TH_ACK) && 1333 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1334 SEQ_GT(th->th_ack, tp->snd_max))) { 1335 rstreason = BANDLIM_RST_OPENPORT; 1336 goto dropwithreset; 1337 } 1338 break; 1339 1340 /* 1341 * If the state is SYN_SENT: 1342 * if seg contains an ACK, but not for our SYN, drop the input. 1343 * if seg contains a RST, then drop the connection. 1344 * if seg does not contain SYN, then drop it. 1345 * Otherwise this is an acceptable SYN segment 1346 * initialize tp->rcv_nxt and tp->irs 1347 * if seg contains ack then advance tp->snd_una 1348 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1349 * arrange for segment to be acked (eventually) 1350 * continue processing rest of data/controls, beginning with URG 1351 */ 1352 case TCPS_SYN_SENT: 1353 if (tcp_do_rfc1644) 1354 tcp_hc_gettao(&inp->inp_inc, &tao); 1355 1356 if ((thflags & TH_ACK) && 1357 (SEQ_LEQ(th->th_ack, tp->iss) || 1358 SEQ_GT(th->th_ack, tp->snd_max))) { 1359 /* 1360 * If we have a cached CCsent for the remote host, 1361 * hence we haven't just crashed and restarted, 1362 * do not send a RST. This may be a retransmission 1363 * from the other side after our earlier ACK was lost. 1364 * Our new SYN, when it arrives, will serve as the 1365 * needed ACK. 1366 */ 1367 if (tao.tao_ccsent != 0) 1368 goto drop; 1369 else { 1370 rstreason = BANDLIM_UNLIMITED; 1371 goto dropwithreset; 1372 } 1373 } 1374 if (thflags & TH_RST) { 1375 if (thflags & TH_ACK) { 1376 KASSERT(headlocked, ("tcp_input: after_listen" 1377 ": tcp_drop.2: head not locked")); 1378 tp = tcp_drop(tp, ECONNREFUSED); 1379 } 1380 goto drop; 1381 } 1382 if ((thflags & TH_SYN) == 0) 1383 goto drop; 1384 tp->snd_wnd = th->th_win; /* initial send window */ 1385 tp->cc_recv = to.to_cc; /* foreign CC */ 1386 1387 tp->irs = th->th_seq; 1388 tcp_rcvseqinit(tp); 1389 if (thflags & TH_ACK) { 1390 /* 1391 * Our SYN was acked. If segment contains CC.ECHO 1392 * option, check it to make sure this segment really 1393 * matches our SYN. If not, just drop it as old 1394 * duplicate, but send an RST if we're still playing 1395 * by the old rules. If no CC.ECHO option, make sure 1396 * we don't get fooled into using T/TCP. 1397 */ 1398 if (to.to_flags & TOF_CCECHO) { 1399 if (tp->cc_send != to.to_ccecho) { 1400 if (tao.tao_ccsent != 0) 1401 goto drop; 1402 else { 1403 rstreason = BANDLIM_UNLIMITED; 1404 goto dropwithreset; 1405 } 1406 } 1407 } else 1408 tp->t_flags &= ~TF_RCVD_CC; 1409 tcpstat.tcps_connects++; 1410 soisconnected(so); 1411 #ifdef MAC 1412 SOCK_LOCK(so); 1413 mac_set_socket_peer_from_mbuf(m, so); 1414 SOCK_UNLOCK(so); 1415 #endif 1416 /* Do window scaling on this connection? */ 1417 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1418 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1419 tp->snd_scale = tp->requested_s_scale; 1420 tp->rcv_scale = tp->request_r_scale; 1421 } 1422 /* Segment is acceptable, update cache if undefined. */ 1423 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1424 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1425 1426 tp->rcv_adv += tp->rcv_wnd; 1427 tp->snd_una++; /* SYN is acked */ 1428 /* 1429 * If there's data, delay ACK; if there's also a FIN 1430 * ACKNOW will be turned on later. 1431 */ 1432 if (DELAY_ACK(tp) && tlen != 0) 1433 callout_reset(tp->tt_delack, tcp_delacktime, 1434 tcp_timer_delack, tp); 1435 else 1436 tp->t_flags |= TF_ACKNOW; 1437 /* 1438 * Received <SYN,ACK> in SYN_SENT[*] state. 1439 * Transitions: 1440 * SYN_SENT --> ESTABLISHED 1441 * SYN_SENT* --> FIN_WAIT_1 1442 */ 1443 tp->t_starttime = ticks; 1444 if (tp->t_flags & TF_NEEDFIN) { 1445 tp->t_state = TCPS_FIN_WAIT_1; 1446 tp->t_flags &= ~TF_NEEDFIN; 1447 thflags &= ~TH_SYN; 1448 } else { 1449 tp->t_state = TCPS_ESTABLISHED; 1450 callout_reset(tp->tt_keep, tcp_keepidle, 1451 tcp_timer_keep, tp); 1452 } 1453 } else { 1454 /* 1455 * Received initial SYN in SYN-SENT[*] state => 1456 * simultaneous open. If segment contains CC option 1457 * and there is a cached CC, apply TAO test. 1458 * If it succeeds, connection is * half-synchronized. 1459 * Otherwise, do 3-way handshake: 1460 * SYN-SENT -> SYN-RECEIVED 1461 * SYN-SENT* -> SYN-RECEIVED* 1462 * If there was no CC option, clear cached CC value. 1463 */ 1464 tp->t_flags |= TF_ACKNOW; 1465 callout_stop(tp->tt_rexmt); 1466 if (to.to_flags & TOF_CC) { 1467 if (tao.tao_cc != 0 && 1468 CC_GT(to.to_cc, tao.tao_cc)) { 1469 /* 1470 * update cache and make transition: 1471 * SYN-SENT -> ESTABLISHED* 1472 * SYN-SENT* -> FIN-WAIT-1* 1473 */ 1474 tao.tao_cc = to.to_cc; 1475 tcp_hc_updatetao(&inp->inp_inc, 1476 TCP_HC_TAO_CC, to.to_cc, 0); 1477 tp->t_starttime = ticks; 1478 if (tp->t_flags & TF_NEEDFIN) { 1479 tp->t_state = TCPS_FIN_WAIT_1; 1480 tp->t_flags &= ~TF_NEEDFIN; 1481 } else { 1482 tp->t_state = TCPS_ESTABLISHED; 1483 callout_reset(tp->tt_keep, 1484 tcp_keepidle, 1485 tcp_timer_keep, 1486 tp); 1487 } 1488 tp->t_flags |= TF_NEEDSYN; 1489 } else 1490 tp->t_state = TCPS_SYN_RECEIVED; 1491 } else { 1492 if (tcp_do_rfc1644) { 1493 /* CC.NEW or no option => invalidate cache */ 1494 tao.tao_cc = 0; 1495 tcp_hc_updatetao(&inp->inp_inc, 1496 TCP_HC_TAO_CC, to.to_cc, 0); 1497 } 1498 tp->t_state = TCPS_SYN_RECEIVED; 1499 } 1500 } 1501 1502 trimthenstep6: 1503 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1504 "locked")); 1505 INP_LOCK_ASSERT(inp); 1506 1507 /* 1508 * Advance th->th_seq to correspond to first data byte. 1509 * If data, trim to stay within window, 1510 * dropping FIN if necessary. 1511 */ 1512 th->th_seq++; 1513 if (tlen > tp->rcv_wnd) { 1514 todrop = tlen - tp->rcv_wnd; 1515 m_adj(m, -todrop); 1516 tlen = tp->rcv_wnd; 1517 thflags &= ~TH_FIN; 1518 tcpstat.tcps_rcvpackafterwin++; 1519 tcpstat.tcps_rcvbyteafterwin += todrop; 1520 } 1521 tp->snd_wl1 = th->th_seq - 1; 1522 tp->rcv_up = th->th_seq; 1523 /* 1524 * Client side of transaction: already sent SYN and data. 1525 * If the remote host used T/TCP to validate the SYN, 1526 * our data will be ACK'd; if so, enter normal data segment 1527 * processing in the middle of step 5, ack processing. 1528 * Otherwise, goto step 6. 1529 */ 1530 if (thflags & TH_ACK) 1531 goto process_ACK; 1532 1533 goto step6; 1534 1535 /* 1536 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1537 * if segment contains a SYN and CC [not CC.NEW] option: 1538 * if state == TIME_WAIT and connection duration > MSL, 1539 * drop packet and send RST; 1540 * 1541 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1542 * ack the FIN (and data) in retransmission queue. 1543 * Complete close and delete TCPCB. Then reprocess 1544 * segment, hoping to find new TCPCB in LISTEN state; 1545 * 1546 * else must be old SYN; drop it. 1547 * else do normal processing. 1548 */ 1549 case TCPS_LAST_ACK: 1550 case TCPS_CLOSING: 1551 case TCPS_TIME_WAIT: 1552 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1553 if ((thflags & TH_SYN) && 1554 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1555 if (tp->t_state == TCPS_TIME_WAIT && 1556 (ticks - tp->t_starttime) > tcp_msl) { 1557 rstreason = BANDLIM_UNLIMITED; 1558 goto dropwithreset; 1559 } 1560 if (CC_GT(to.to_cc, tp->cc_recv)) { 1561 tp = tcp_close(tp); 1562 goto findpcb; 1563 } 1564 else 1565 goto drop; 1566 } 1567 break; /* continue normal processing */ 1568 } 1569 1570 /* 1571 * States other than LISTEN or SYN_SENT. 1572 * First check the RST flag and sequence number since reset segments 1573 * are exempt from the timestamp and connection count tests. This 1574 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1575 * below which allowed reset segments in half the sequence space 1576 * to fall though and be processed (which gives forged reset 1577 * segments with a random sequence number a 50 percent chance of 1578 * killing a connection). 1579 * Then check timestamp, if present. 1580 * Then check the connection count, if present. 1581 * Then check that at least some bytes of segment are within 1582 * receive window. If segment begins before rcv_nxt, 1583 * drop leading data (and SYN); if nothing left, just ack. 1584 * 1585 * 1586 * If the RST bit is set, check the sequence number to see 1587 * if this is a valid reset segment. 1588 * RFC 793 page 37: 1589 * In all states except SYN-SENT, all reset (RST) segments 1590 * are validated by checking their SEQ-fields. A reset is 1591 * valid if its sequence number is in the window. 1592 * Note: this does not take into account delayed ACKs, so 1593 * we should test against last_ack_sent instead of rcv_nxt. 1594 * The sequence number in the reset segment is normally an 1595 * echo of our outgoing acknowlegement numbers, but some hosts 1596 * send a reset with the sequence number at the rightmost edge 1597 * of our receive window, and we have to handle this case. 1598 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1599 * that brute force RST attacks are possible. To combat this, 1600 * we use a much stricter check while in the ESTABLISHED state, 1601 * only accepting RSTs where the sequence number is equal to 1602 * last_ack_sent. In all other states (the states in which a 1603 * RST is more likely), the more permissive check is used. 1604 * If we have multiple segments in flight, the intial reset 1605 * segment sequence numbers will be to the left of last_ack_sent, 1606 * but they will eventually catch up. 1607 * In any case, it never made sense to trim reset segments to 1608 * fit the receive window since RFC 1122 says: 1609 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1610 * 1611 * A TCP SHOULD allow a received RST segment to include data. 1612 * 1613 * DISCUSSION 1614 * It has been suggested that a RST segment could contain 1615 * ASCII text that encoded and explained the cause of the 1616 * RST. No standard has yet been established for such 1617 * data. 1618 * 1619 * If the reset segment passes the sequence number test examine 1620 * the state: 1621 * SYN_RECEIVED STATE: 1622 * If passive open, return to LISTEN state. 1623 * If active open, inform user that connection was refused. 1624 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1625 * Inform user that connection was reset, and close tcb. 1626 * CLOSING, LAST_ACK STATES: 1627 * Close the tcb. 1628 * TIME_WAIT STATE: 1629 * Drop the segment - see Stevens, vol. 2, p. 964 and 1630 * RFC 1337. 1631 */ 1632 if (thflags & TH_RST) { 1633 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1634 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1635 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1636 switch (tp->t_state) { 1637 1638 case TCPS_SYN_RECEIVED: 1639 so->so_error = ECONNREFUSED; 1640 goto close; 1641 1642 case TCPS_ESTABLISHED: 1643 if (tp->last_ack_sent != th->th_seq && 1644 tcp_insecure_rst == 0) { 1645 tcpstat.tcps_badrst++; 1646 goto drop; 1647 } 1648 case TCPS_FIN_WAIT_1: 1649 case TCPS_FIN_WAIT_2: 1650 case TCPS_CLOSE_WAIT: 1651 so->so_error = ECONNRESET; 1652 close: 1653 tp->t_state = TCPS_CLOSED; 1654 tcpstat.tcps_drops++; 1655 KASSERT(headlocked, ("tcp_input: " 1656 "trimthenstep6: tcp_close: head not " 1657 "locked")); 1658 tp = tcp_close(tp); 1659 break; 1660 1661 case TCPS_CLOSING: 1662 case TCPS_LAST_ACK: 1663 KASSERT(headlocked, ("trimthenstep6: " 1664 "tcp_close.2: head not locked")); 1665 tp = tcp_close(tp); 1666 break; 1667 1668 case TCPS_TIME_WAIT: 1669 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1670 ("timewait")); 1671 break; 1672 } 1673 } 1674 goto drop; 1675 } 1676 1677 /* 1678 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1679 * and it's less than ts_recent, drop it. 1680 */ 1681 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1682 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1683 1684 /* Check to see if ts_recent is over 24 days old. */ 1685 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1686 /* 1687 * Invalidate ts_recent. If this segment updates 1688 * ts_recent, the age will be reset later and ts_recent 1689 * will get a valid value. If it does not, setting 1690 * ts_recent to zero will at least satisfy the 1691 * requirement that zero be placed in the timestamp 1692 * echo reply when ts_recent isn't valid. The 1693 * age isn't reset until we get a valid ts_recent 1694 * because we don't want out-of-order segments to be 1695 * dropped when ts_recent is old. 1696 */ 1697 tp->ts_recent = 0; 1698 } else { 1699 tcpstat.tcps_rcvduppack++; 1700 tcpstat.tcps_rcvdupbyte += tlen; 1701 tcpstat.tcps_pawsdrop++; 1702 if (tlen) 1703 goto dropafterack; 1704 goto drop; 1705 } 1706 } 1707 1708 /* 1709 * T/TCP mechanism 1710 * If T/TCP was negotiated and the segment doesn't have CC, 1711 * or if its CC is wrong then drop the segment. 1712 * RST segments do not have to comply with this. 1713 */ 1714 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1715 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1716 goto dropafterack; 1717 1718 /* 1719 * In the SYN-RECEIVED state, validate that the packet belongs to 1720 * this connection before trimming the data to fit the receive 1721 * window. Check the sequence number versus IRS since we know 1722 * the sequence numbers haven't wrapped. This is a partial fix 1723 * for the "LAND" DoS attack. 1724 */ 1725 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1726 rstreason = BANDLIM_RST_OPENPORT; 1727 goto dropwithreset; 1728 } 1729 1730 todrop = tp->rcv_nxt - th->th_seq; 1731 if (todrop > 0) { 1732 if (thflags & TH_SYN) { 1733 thflags &= ~TH_SYN; 1734 th->th_seq++; 1735 if (th->th_urp > 1) 1736 th->th_urp--; 1737 else 1738 thflags &= ~TH_URG; 1739 todrop--; 1740 } 1741 /* 1742 * Following if statement from Stevens, vol. 2, p. 960. 1743 */ 1744 if (todrop > tlen 1745 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1746 /* 1747 * Any valid FIN must be to the left of the window. 1748 * At this point the FIN must be a duplicate or out 1749 * of sequence; drop it. 1750 */ 1751 thflags &= ~TH_FIN; 1752 1753 /* 1754 * Send an ACK to resynchronize and drop any data. 1755 * But keep on processing for RST or ACK. 1756 */ 1757 tp->t_flags |= TF_ACKNOW; 1758 todrop = tlen; 1759 tcpstat.tcps_rcvduppack++; 1760 tcpstat.tcps_rcvdupbyte += todrop; 1761 } else { 1762 tcpstat.tcps_rcvpartduppack++; 1763 tcpstat.tcps_rcvpartdupbyte += todrop; 1764 } 1765 drop_hdrlen += todrop; /* drop from the top afterwards */ 1766 th->th_seq += todrop; 1767 tlen -= todrop; 1768 if (th->th_urp > todrop) 1769 th->th_urp -= todrop; 1770 else { 1771 thflags &= ~TH_URG; 1772 th->th_urp = 0; 1773 } 1774 } 1775 1776 /* 1777 * If new data are received on a connection after the 1778 * user processes are gone, then RST the other end. 1779 */ 1780 if ((so->so_state & SS_NOFDREF) && 1781 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1782 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1783 "locked")); 1784 tp = tcp_close(tp); 1785 tcpstat.tcps_rcvafterclose++; 1786 rstreason = BANDLIM_UNLIMITED; 1787 goto dropwithreset; 1788 } 1789 1790 /* 1791 * If segment ends after window, drop trailing data 1792 * (and PUSH and FIN); if nothing left, just ACK. 1793 */ 1794 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1795 if (todrop > 0) { 1796 tcpstat.tcps_rcvpackafterwin++; 1797 if (todrop >= tlen) { 1798 tcpstat.tcps_rcvbyteafterwin += tlen; 1799 /* 1800 * If a new connection request is received 1801 * while in TIME_WAIT, drop the old connection 1802 * and start over if the sequence numbers 1803 * are above the previous ones. 1804 */ 1805 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1806 if (thflags & TH_SYN && 1807 tp->t_state == TCPS_TIME_WAIT && 1808 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1809 KASSERT(headlocked, ("trimthenstep6: " 1810 "tcp_close.4: head not locked")); 1811 tp = tcp_close(tp); 1812 goto findpcb; 1813 } 1814 /* 1815 * If window is closed can only take segments at 1816 * window edge, and have to drop data and PUSH from 1817 * incoming segments. Continue processing, but 1818 * remember to ack. Otherwise, drop segment 1819 * and ack. 1820 */ 1821 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1822 tp->t_flags |= TF_ACKNOW; 1823 tcpstat.tcps_rcvwinprobe++; 1824 } else 1825 goto dropafterack; 1826 } else 1827 tcpstat.tcps_rcvbyteafterwin += todrop; 1828 m_adj(m, -todrop); 1829 tlen -= todrop; 1830 thflags &= ~(TH_PUSH|TH_FIN); 1831 } 1832 1833 /* 1834 * If last ACK falls within this segment's sequence numbers, 1835 * record its timestamp. 1836 * NOTE: 1837 * 1) That the test incorporates suggestions from the latest 1838 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1839 * 2) That updating only on newer timestamps interferes with 1840 * our earlier PAWS tests, so this check should be solely 1841 * predicated on the sequence space of this segment. 1842 * 3) That we modify the segment boundary check to be 1843 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1844 * instead of RFC1323's 1845 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1846 * This modified check allows us to overcome RFC1323's 1847 * limitations as described in Stevens TCP/IP Illustrated 1848 * Vol. 2 p.869. In such cases, we can still calculate the 1849 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1850 */ 1851 if ((to.to_flags & TOF_TS) != 0 && 1852 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1853 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1854 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1855 tp->ts_recent_age = ticks; 1856 tp->ts_recent = to.to_tsval; 1857 } 1858 1859 /* 1860 * If a SYN is in the window, then this is an 1861 * error and we send an RST and drop the connection. 1862 */ 1863 if (thflags & TH_SYN) { 1864 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1865 "head not locked")); 1866 tp = tcp_drop(tp, ECONNRESET); 1867 rstreason = BANDLIM_UNLIMITED; 1868 goto drop; 1869 } 1870 1871 /* 1872 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1873 * flag is on (half-synchronized state), then queue data for 1874 * later processing; else drop segment and return. 1875 */ 1876 if ((thflags & TH_ACK) == 0) { 1877 if (tp->t_state == TCPS_SYN_RECEIVED || 1878 (tp->t_flags & TF_NEEDSYN)) 1879 goto step6; 1880 else 1881 goto drop; 1882 } 1883 1884 /* 1885 * Ack processing. 1886 */ 1887 switch (tp->t_state) { 1888 1889 /* 1890 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1891 * ESTABLISHED state and continue processing. 1892 * The ACK was checked above. 1893 */ 1894 case TCPS_SYN_RECEIVED: 1895 1896 tcpstat.tcps_connects++; 1897 soisconnected(so); 1898 /* Do window scaling? */ 1899 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1900 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1901 tp->snd_scale = tp->requested_s_scale; 1902 tp->rcv_scale = tp->request_r_scale; 1903 } 1904 /* 1905 * Upon successful completion of 3-way handshake, 1906 * update cache.CC, pass any queued data to the user, 1907 * and advance state appropriately. 1908 */ 1909 if (tcp_do_rfc1644) { 1910 tao.tao_cc = tp->cc_recv; 1911 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1912 tp->cc_recv, 0); 1913 } 1914 /* 1915 * Make transitions: 1916 * SYN-RECEIVED -> ESTABLISHED 1917 * SYN-RECEIVED* -> FIN-WAIT-1 1918 */ 1919 tp->t_starttime = ticks; 1920 if (tp->t_flags & TF_NEEDFIN) { 1921 tp->t_state = TCPS_FIN_WAIT_1; 1922 tp->t_flags &= ~TF_NEEDFIN; 1923 } else { 1924 tp->t_state = TCPS_ESTABLISHED; 1925 callout_reset(tp->tt_keep, tcp_keepidle, 1926 tcp_timer_keep, tp); 1927 } 1928 /* 1929 * If segment contains data or ACK, will call tcp_reass() 1930 * later; if not, do so now to pass queued data to user. 1931 */ 1932 if (tlen == 0 && (thflags & TH_FIN) == 0) 1933 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1934 (struct mbuf *)0); 1935 tp->snd_wl1 = th->th_seq - 1; 1936 /* FALLTHROUGH */ 1937 1938 /* 1939 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1940 * ACKs. If the ack is in the range 1941 * tp->snd_una < th->th_ack <= tp->snd_max 1942 * then advance tp->snd_una to th->th_ack and drop 1943 * data from the retransmission queue. If this ACK reflects 1944 * more up to date window information we update our window information. 1945 */ 1946 case TCPS_ESTABLISHED: 1947 case TCPS_FIN_WAIT_1: 1948 case TCPS_FIN_WAIT_2: 1949 case TCPS_CLOSE_WAIT: 1950 case TCPS_CLOSING: 1951 case TCPS_LAST_ACK: 1952 case TCPS_TIME_WAIT: 1953 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1954 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1955 if (tlen == 0 && tiwin == tp->snd_wnd) { 1956 tcpstat.tcps_rcvdupack++; 1957 /* 1958 * If we have outstanding data (other than 1959 * a window probe), this is a completely 1960 * duplicate ack (ie, window info didn't 1961 * change), the ack is the biggest we've 1962 * seen and we've seen exactly our rexmt 1963 * threshhold of them, assume a packet 1964 * has been dropped and retransmit it. 1965 * Kludge snd_nxt & the congestion 1966 * window so we send only this one 1967 * packet. 1968 * 1969 * We know we're losing at the current 1970 * window size so do congestion avoidance 1971 * (set ssthresh to half the current window 1972 * and pull our congestion window back to 1973 * the new ssthresh). 1974 * 1975 * Dup acks mean that packets have left the 1976 * network (they're now cached at the receiver) 1977 * so bump cwnd by the amount in the receiver 1978 * to keep a constant cwnd packets in the 1979 * network. 1980 */ 1981 if (!callout_active(tp->tt_rexmt) || 1982 th->th_ack != tp->snd_una) 1983 tp->t_dupacks = 0; 1984 else if (++tp->t_dupacks > tcprexmtthresh || 1985 ((tcp_do_newreno || tp->sack_enable) && 1986 IN_FASTRECOVERY(tp))) { 1987 1988 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1989 int data_in_pipe; 1990 int sacked, lost_not_rexmitted; 1991 1992 /* 1993 * Compute the amount of data in flight first. 1994 * We can inject new data into the pipe iff 1995 * we have less than 1/2 the original window's 1996 * worth of data in flight. 1997 */ 1998 sacked = tcp_sacked_bytes(tp, &lost_not_rexmitted); 1999 data_in_pipe = (tp->snd_nxt - tp->snd_una) - 2000 (sacked + lost_not_rexmitted); 2001 if (data_in_pipe < tp->snd_ssthresh) { 2002 tp->snd_cwnd += tp->t_maxseg; 2003 if (tp->snd_cwnd > tp->snd_ssthresh) 2004 tp->snd_cwnd = tp->snd_ssthresh; 2005 } 2006 } else 2007 tp->snd_cwnd += tp->t_maxseg; 2008 (void) tcp_output(tp); 2009 goto drop; 2010 } else if (tp->t_dupacks == tcprexmtthresh) { 2011 tcp_seq onxt = tp->snd_nxt; 2012 u_int win; 2013 2014 /* 2015 * If we're doing sack, check to 2016 * see if we're already in sack 2017 * recovery. If we're not doing sack, 2018 * check to see if we're in newreno 2019 * recovery. 2020 */ 2021 if (tp->sack_enable) { 2022 if (IN_FASTRECOVERY(tp)) { 2023 tp->t_dupacks = 0; 2024 break; 2025 } 2026 } else if (tcp_do_newreno) { 2027 if (SEQ_LEQ(th->th_ack, 2028 tp->snd_recover)) { 2029 tp->t_dupacks = 0; 2030 break; 2031 } 2032 } 2033 win = min(tp->snd_wnd, tp->snd_cwnd) / 2034 2 / tp->t_maxseg; 2035 if (win < 2) 2036 win = 2; 2037 tp->snd_ssthresh = win * tp->t_maxseg; 2038 ENTER_FASTRECOVERY(tp); 2039 tp->snd_recover = tp->snd_max; 2040 callout_stop(tp->tt_rexmt); 2041 tp->t_rtttime = 0; 2042 if (tp->sack_enable) { 2043 tcpstat.tcps_sack_recovery_episode++; 2044 tp->sack_newdata = tp->snd_nxt; 2045 tp->snd_cwnd = tp->t_maxseg; 2046 (void) tcp_output(tp); 2047 goto drop; 2048 } 2049 tp->snd_nxt = th->th_ack; 2050 tp->snd_cwnd = tp->t_maxseg; 2051 (void) tcp_output(tp); 2052 KASSERT(tp->snd_limited <= 2, 2053 ("tp->snd_limited too big")); 2054 tp->snd_cwnd = tp->snd_ssthresh + 2055 tp->t_maxseg * 2056 (tp->t_dupacks - tp->snd_limited); 2057 if (SEQ_GT(onxt, tp->snd_nxt)) 2058 tp->snd_nxt = onxt; 2059 goto drop; 2060 } else if (tcp_do_rfc3042) { 2061 u_long oldcwnd = tp->snd_cwnd; 2062 tcp_seq oldsndmax = tp->snd_max; 2063 u_int sent; 2064 2065 KASSERT(tp->t_dupacks == 1 || 2066 tp->t_dupacks == 2, 2067 ("dupacks not 1 or 2")); 2068 if (tp->t_dupacks == 1) 2069 tp->snd_limited = 0; 2070 tp->snd_cwnd = 2071 (tp->snd_nxt - tp->snd_una) + 2072 (tp->t_dupacks - tp->snd_limited) * 2073 tp->t_maxseg; 2074 (void) tcp_output(tp); 2075 sent = tp->snd_max - oldsndmax; 2076 if (sent > tp->t_maxseg) { 2077 KASSERT((tp->t_dupacks == 2 && 2078 tp->snd_limited == 0) || 2079 (sent == tp->t_maxseg + 1 && 2080 tp->t_flags & TF_SENTFIN), 2081 ("sent too much")); 2082 tp->snd_limited = 2; 2083 } else if (sent > 0) 2084 ++tp->snd_limited; 2085 tp->snd_cwnd = oldcwnd; 2086 goto drop; 2087 } 2088 } else 2089 tp->t_dupacks = 0; 2090 break; 2091 } 2092 2093 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2094 2095 /* 2096 * If the congestion window was inflated to account 2097 * for the other side's cached packets, retract it. 2098 */ 2099 if (tcp_do_newreno || tp->sack_enable) { 2100 if (IN_FASTRECOVERY(tp)) { 2101 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2102 if (tp->sack_enable) 2103 tcp_sack_partialack(tp, th); 2104 else 2105 tcp_newreno_partial_ack(tp, th); 2106 } else { 2107 /* 2108 * Out of fast recovery. 2109 * Window inflation should have left us 2110 * with approximately snd_ssthresh 2111 * outstanding data. 2112 * But in case we would be inclined to 2113 * send a burst, better to do it via 2114 * the slow start mechanism. 2115 */ 2116 if (SEQ_GT(th->th_ack + 2117 tp->snd_ssthresh, 2118 tp->snd_max)) 2119 tp->snd_cwnd = tp->snd_max - 2120 th->th_ack + 2121 tp->t_maxseg; 2122 else 2123 tp->snd_cwnd = tp->snd_ssthresh; 2124 } 2125 } 2126 } else { 2127 if (tp->t_dupacks >= tcprexmtthresh && 2128 tp->snd_cwnd > tp->snd_ssthresh) 2129 tp->snd_cwnd = tp->snd_ssthresh; 2130 } 2131 tp->t_dupacks = 0; 2132 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2133 tcpstat.tcps_rcvacktoomuch++; 2134 goto dropafterack; 2135 } 2136 /* 2137 * If we reach this point, ACK is not a duplicate, 2138 * i.e., it ACKs something we sent. 2139 */ 2140 if (tp->t_flags & TF_NEEDSYN) { 2141 /* 2142 * T/TCP: Connection was half-synchronized, and our 2143 * SYN has been ACK'd (so connection is now fully 2144 * synchronized). Go to non-starred state, 2145 * increment snd_una for ACK of SYN, and check if 2146 * we can do window scaling. 2147 */ 2148 tp->t_flags &= ~TF_NEEDSYN; 2149 tp->snd_una++; 2150 /* Do window scaling? */ 2151 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2152 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2153 tp->snd_scale = tp->requested_s_scale; 2154 tp->rcv_scale = tp->request_r_scale; 2155 } 2156 } 2157 2158 process_ACK: 2159 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2160 "locked")); 2161 INP_LOCK_ASSERT(inp); 2162 2163 acked = th->th_ack - tp->snd_una; 2164 tcpstat.tcps_rcvackpack++; 2165 tcpstat.tcps_rcvackbyte += acked; 2166 2167 /* 2168 * If we just performed our first retransmit, and the ACK 2169 * arrives within our recovery window, then it was a mistake 2170 * to do the retransmit in the first place. Recover our 2171 * original cwnd and ssthresh, and proceed to transmit where 2172 * we left off. 2173 */ 2174 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2175 ++tcpstat.tcps_sndrexmitbad; 2176 tp->snd_cwnd = tp->snd_cwnd_prev; 2177 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2178 tp->snd_recover = tp->snd_recover_prev; 2179 if (tp->t_flags & TF_WASFRECOVERY) 2180 ENTER_FASTRECOVERY(tp); 2181 tp->snd_nxt = tp->snd_max; 2182 tp->t_badrxtwin = 0; /* XXX probably not required */ 2183 } 2184 2185 /* 2186 * If we have a timestamp reply, update smoothed 2187 * round trip time. If no timestamp is present but 2188 * transmit timer is running and timed sequence 2189 * number was acked, update smoothed round trip time. 2190 * Since we now have an rtt measurement, cancel the 2191 * timer backoff (cf., Phil Karn's retransmit alg.). 2192 * Recompute the initial retransmit timer. 2193 * 2194 * Some boxes send broken timestamp replies 2195 * during the SYN+ACK phase, ignore 2196 * timestamps of 0 or we could calculate a 2197 * huge RTT and blow up the retransmit timer. 2198 */ 2199 if ((to.to_flags & TOF_TS) != 0 && 2200 to.to_tsecr) { 2201 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2202 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2203 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2204 } 2205 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2206 2207 /* 2208 * If all outstanding data is acked, stop retransmit 2209 * timer and remember to restart (more output or persist). 2210 * If there is more data to be acked, restart retransmit 2211 * timer, using current (possibly backed-off) value. 2212 */ 2213 if (th->th_ack == tp->snd_max) { 2214 callout_stop(tp->tt_rexmt); 2215 needoutput = 1; 2216 } else if (!callout_active(tp->tt_persist)) 2217 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2218 tcp_timer_rexmt, tp); 2219 2220 /* 2221 * If no data (only SYN) was ACK'd, 2222 * skip rest of ACK processing. 2223 */ 2224 if (acked == 0) 2225 goto step6; 2226 2227 /* 2228 * When new data is acked, open the congestion window. 2229 * If the window gives us less than ssthresh packets 2230 * in flight, open exponentially (maxseg per packet). 2231 * Otherwise open linearly: maxseg per window 2232 * (maxseg^2 / cwnd per packet). 2233 */ 2234 if ((!tcp_do_newreno && !tp->sack_enable) || 2235 !IN_FASTRECOVERY(tp)) { 2236 register u_int cw = tp->snd_cwnd; 2237 register u_int incr = tp->t_maxseg; 2238 if (cw > tp->snd_ssthresh) 2239 incr = incr * incr / cw; 2240 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2241 } 2242 SOCKBUF_LOCK(&so->so_snd); 2243 if (acked > so->so_snd.sb_cc) { 2244 tp->snd_wnd -= so->so_snd.sb_cc; 2245 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2246 ourfinisacked = 1; 2247 } else { 2248 sbdrop_locked(&so->so_snd, acked); 2249 tp->snd_wnd -= acked; 2250 ourfinisacked = 0; 2251 } 2252 sowwakeup_locked(so); 2253 /* detect una wraparound */ 2254 if ((tcp_do_newreno || tp->sack_enable) && 2255 !IN_FASTRECOVERY(tp) && 2256 SEQ_GT(tp->snd_una, tp->snd_recover) && 2257 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2258 tp->snd_recover = th->th_ack - 1; 2259 if ((tcp_do_newreno || tp->sack_enable) && 2260 IN_FASTRECOVERY(tp) && 2261 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2262 EXIT_FASTRECOVERY(tp); 2263 tp->snd_una = th->th_ack; 2264 if (tp->sack_enable) { 2265 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2266 tp->snd_recover = tp->snd_una; 2267 } 2268 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2269 tp->snd_nxt = tp->snd_una; 2270 2271 switch (tp->t_state) { 2272 2273 /* 2274 * In FIN_WAIT_1 STATE in addition to the processing 2275 * for the ESTABLISHED state if our FIN is now acknowledged 2276 * then enter FIN_WAIT_2. 2277 */ 2278 case TCPS_FIN_WAIT_1: 2279 if (ourfinisacked) { 2280 /* 2281 * If we can't receive any more 2282 * data, then closing user can proceed. 2283 * Starting the timer is contrary to the 2284 * specification, but if we don't get a FIN 2285 * we'll hang forever. 2286 */ 2287 /* XXXjl 2288 * we should release the tp also, and use a 2289 * compressed state. 2290 */ 2291 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2292 soisdisconnected(so); 2293 callout_reset(tp->tt_2msl, tcp_maxidle, 2294 tcp_timer_2msl, tp); 2295 } 2296 tp->t_state = TCPS_FIN_WAIT_2; 2297 } 2298 break; 2299 2300 /* 2301 * In CLOSING STATE in addition to the processing for 2302 * the ESTABLISHED state if the ACK acknowledges our FIN 2303 * then enter the TIME-WAIT state, otherwise ignore 2304 * the segment. 2305 */ 2306 case TCPS_CLOSING: 2307 if (ourfinisacked) { 2308 KASSERT(headlocked, ("tcp_input: process_ACK: " 2309 "head not locked")); 2310 tcp_twstart(tp); 2311 INP_INFO_WUNLOCK(&tcbinfo); 2312 m_freem(m); 2313 return; 2314 } 2315 break; 2316 2317 /* 2318 * In LAST_ACK, we may still be waiting for data to drain 2319 * and/or to be acked, as well as for the ack of our FIN. 2320 * If our FIN is now acknowledged, delete the TCB, 2321 * enter the closed state and return. 2322 */ 2323 case TCPS_LAST_ACK: 2324 if (ourfinisacked) { 2325 KASSERT(headlocked, ("tcp_input: process_ACK:" 2326 " tcp_close: head not locked")); 2327 tp = tcp_close(tp); 2328 goto drop; 2329 } 2330 break; 2331 2332 /* 2333 * In TIME_WAIT state the only thing that should arrive 2334 * is a retransmission of the remote FIN. Acknowledge 2335 * it and restart the finack timer. 2336 */ 2337 case TCPS_TIME_WAIT: 2338 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2339 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2340 tcp_timer_2msl, tp); 2341 goto dropafterack; 2342 } 2343 } 2344 2345 step6: 2346 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2347 INP_LOCK_ASSERT(inp); 2348 2349 /* 2350 * Update window information. 2351 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2352 */ 2353 if ((thflags & TH_ACK) && 2354 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2355 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2356 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2357 /* keep track of pure window updates */ 2358 if (tlen == 0 && 2359 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2360 tcpstat.tcps_rcvwinupd++; 2361 tp->snd_wnd = tiwin; 2362 tp->snd_wl1 = th->th_seq; 2363 tp->snd_wl2 = th->th_ack; 2364 if (tp->snd_wnd > tp->max_sndwnd) 2365 tp->max_sndwnd = tp->snd_wnd; 2366 needoutput = 1; 2367 } 2368 2369 /* 2370 * Process segments with URG. 2371 */ 2372 if ((thflags & TH_URG) && th->th_urp && 2373 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2374 /* 2375 * This is a kludge, but if we receive and accept 2376 * random urgent pointers, we'll crash in 2377 * soreceive. It's hard to imagine someone 2378 * actually wanting to send this much urgent data. 2379 */ 2380 SOCKBUF_LOCK(&so->so_rcv); 2381 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2382 th->th_urp = 0; /* XXX */ 2383 thflags &= ~TH_URG; /* XXX */ 2384 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2385 goto dodata; /* XXX */ 2386 } 2387 /* 2388 * If this segment advances the known urgent pointer, 2389 * then mark the data stream. This should not happen 2390 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2391 * a FIN has been received from the remote side. 2392 * In these states we ignore the URG. 2393 * 2394 * According to RFC961 (Assigned Protocols), 2395 * the urgent pointer points to the last octet 2396 * of urgent data. We continue, however, 2397 * to consider it to indicate the first octet 2398 * of data past the urgent section as the original 2399 * spec states (in one of two places). 2400 */ 2401 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2402 tp->rcv_up = th->th_seq + th->th_urp; 2403 so->so_oobmark = so->so_rcv.sb_cc + 2404 (tp->rcv_up - tp->rcv_nxt) - 1; 2405 if (so->so_oobmark == 0) 2406 so->so_rcv.sb_state |= SBS_RCVATMARK; 2407 sohasoutofband(so); 2408 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2409 } 2410 SOCKBUF_UNLOCK(&so->so_rcv); 2411 /* 2412 * Remove out of band data so doesn't get presented to user. 2413 * This can happen independent of advancing the URG pointer, 2414 * but if two URG's are pending at once, some out-of-band 2415 * data may creep in... ick. 2416 */ 2417 if (th->th_urp <= (u_long)tlen && 2418 !(so->so_options & SO_OOBINLINE)) { 2419 /* hdr drop is delayed */ 2420 tcp_pulloutofband(so, th, m, drop_hdrlen); 2421 } 2422 } else { 2423 /* 2424 * If no out of band data is expected, 2425 * pull receive urgent pointer along 2426 * with the receive window. 2427 */ 2428 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2429 tp->rcv_up = tp->rcv_nxt; 2430 } 2431 dodata: /* XXX */ 2432 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2433 INP_LOCK_ASSERT(inp); 2434 2435 /* 2436 * Process the segment text, merging it into the TCP sequencing queue, 2437 * and arranging for acknowledgment of receipt if necessary. 2438 * This process logically involves adjusting tp->rcv_wnd as data 2439 * is presented to the user (this happens in tcp_usrreq.c, 2440 * case PRU_RCVD). If a FIN has already been received on this 2441 * connection then we just ignore the text. 2442 */ 2443 if ((tlen || (thflags & TH_FIN)) && 2444 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2445 tcp_seq save_start = th->th_seq; 2446 tcp_seq save_end = th->th_seq + tlen; 2447 m_adj(m, drop_hdrlen); /* delayed header drop */ 2448 /* 2449 * Insert segment which includes th into TCP reassembly queue 2450 * with control block tp. Set thflags to whether reassembly now 2451 * includes a segment with FIN. This handles the common case 2452 * inline (segment is the next to be received on an established 2453 * connection, and the queue is empty), avoiding linkage into 2454 * and removal from the queue and repetition of various 2455 * conversions. 2456 * Set DELACK for segments received in order, but ack 2457 * immediately when segments are out of order (so 2458 * fast retransmit can work). 2459 */ 2460 if (th->th_seq == tp->rcv_nxt && 2461 LIST_EMPTY(&tp->t_segq) && 2462 TCPS_HAVEESTABLISHED(tp->t_state)) { 2463 if (DELAY_ACK(tp)) 2464 tp->t_flags |= TF_DELACK; 2465 else 2466 tp->t_flags |= TF_ACKNOW; 2467 tp->rcv_nxt += tlen; 2468 thflags = th->th_flags & TH_FIN; 2469 tcpstat.tcps_rcvpack++; 2470 tcpstat.tcps_rcvbyte += tlen; 2471 ND6_HINT(tp); 2472 SOCKBUF_LOCK(&so->so_rcv); 2473 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2474 m_freem(m); 2475 else 2476 sbappendstream_locked(&so->so_rcv, m); 2477 sorwakeup_locked(so); 2478 } else { 2479 thflags = tcp_reass(tp, th, &tlen, m); 2480 tp->t_flags |= TF_ACKNOW; 2481 } 2482 if (tlen > 0 && tp->sack_enable) 2483 tcp_update_sack_list(tp, save_start, save_end); 2484 /* 2485 * Note the amount of data that peer has sent into 2486 * our window, in order to estimate the sender's 2487 * buffer size. 2488 */ 2489 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2490 } else { 2491 m_freem(m); 2492 thflags &= ~TH_FIN; 2493 } 2494 2495 /* 2496 * If FIN is received ACK the FIN and let the user know 2497 * that the connection is closing. 2498 */ 2499 if (thflags & TH_FIN) { 2500 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2501 socantrcvmore(so); 2502 /* 2503 * If connection is half-synchronized 2504 * (ie NEEDSYN flag on) then delay ACK, 2505 * so it may be piggybacked when SYN is sent. 2506 * Otherwise, since we received a FIN then no 2507 * more input can be expected, send ACK now. 2508 */ 2509 if (tp->t_flags & TF_NEEDSYN) 2510 tp->t_flags |= TF_DELACK; 2511 else 2512 tp->t_flags |= TF_ACKNOW; 2513 tp->rcv_nxt++; 2514 } 2515 switch (tp->t_state) { 2516 2517 /* 2518 * In SYN_RECEIVED and ESTABLISHED STATES 2519 * enter the CLOSE_WAIT state. 2520 */ 2521 case TCPS_SYN_RECEIVED: 2522 tp->t_starttime = ticks; 2523 /*FALLTHROUGH*/ 2524 case TCPS_ESTABLISHED: 2525 tp->t_state = TCPS_CLOSE_WAIT; 2526 break; 2527 2528 /* 2529 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2530 * enter the CLOSING state. 2531 */ 2532 case TCPS_FIN_WAIT_1: 2533 tp->t_state = TCPS_CLOSING; 2534 break; 2535 2536 /* 2537 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2538 * starting the time-wait timer, turning off the other 2539 * standard timers. 2540 */ 2541 case TCPS_FIN_WAIT_2: 2542 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2543 "TCP_FIN_WAIT_2: head not locked")); 2544 tcp_twstart(tp); 2545 INP_INFO_WUNLOCK(&tcbinfo); 2546 return; 2547 2548 /* 2549 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2550 */ 2551 case TCPS_TIME_WAIT: 2552 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2553 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2554 tcp_timer_2msl, tp); 2555 break; 2556 } 2557 } 2558 INP_INFO_WUNLOCK(&tcbinfo); 2559 headlocked = 0; 2560 #ifdef TCPDEBUG 2561 if (so->so_options & SO_DEBUG) 2562 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2563 &tcp_savetcp, 0); 2564 #endif 2565 2566 /* 2567 * Return any desired output. 2568 */ 2569 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2570 (void) tcp_output(tp); 2571 2572 check_delack: 2573 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2574 INP_LOCK_ASSERT(inp); 2575 if (tp->t_flags & TF_DELACK) { 2576 tp->t_flags &= ~TF_DELACK; 2577 callout_reset(tp->tt_delack, tcp_delacktime, 2578 tcp_timer_delack, tp); 2579 } 2580 INP_UNLOCK(inp); 2581 return; 2582 2583 dropafterack: 2584 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2585 /* 2586 * Generate an ACK dropping incoming segment if it occupies 2587 * sequence space, where the ACK reflects our state. 2588 * 2589 * We can now skip the test for the RST flag since all 2590 * paths to this code happen after packets containing 2591 * RST have been dropped. 2592 * 2593 * In the SYN-RECEIVED state, don't send an ACK unless the 2594 * segment we received passes the SYN-RECEIVED ACK test. 2595 * If it fails send a RST. This breaks the loop in the 2596 * "LAND" DoS attack, and also prevents an ACK storm 2597 * between two listening ports that have been sent forged 2598 * SYN segments, each with the source address of the other. 2599 */ 2600 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2601 (SEQ_GT(tp->snd_una, th->th_ack) || 2602 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2603 rstreason = BANDLIM_RST_OPENPORT; 2604 goto dropwithreset; 2605 } 2606 #ifdef TCPDEBUG 2607 if (so->so_options & SO_DEBUG) 2608 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2609 &tcp_savetcp, 0); 2610 #endif 2611 KASSERT(headlocked, ("headlocked should be 1")); 2612 INP_INFO_WUNLOCK(&tcbinfo); 2613 tp->t_flags |= TF_ACKNOW; 2614 (void) tcp_output(tp); 2615 INP_UNLOCK(inp); 2616 m_freem(m); 2617 return; 2618 2619 dropwithreset: 2620 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2621 /* 2622 * Generate a RST, dropping incoming segment. 2623 * Make ACK acceptable to originator of segment. 2624 * Don't bother to respond if destination was broadcast/multicast. 2625 */ 2626 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2627 goto drop; 2628 if (isipv6) { 2629 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2630 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2631 goto drop; 2632 } else { 2633 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2634 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2635 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2636 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2637 goto drop; 2638 } 2639 /* IPv6 anycast check is done at tcp6_input() */ 2640 2641 /* 2642 * Perform bandwidth limiting. 2643 */ 2644 if (badport_bandlim(rstreason) < 0) 2645 goto drop; 2646 2647 #ifdef TCPDEBUG 2648 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2649 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2650 &tcp_savetcp, 0); 2651 #endif 2652 2653 if (thflags & TH_ACK) 2654 /* mtod() below is safe as long as hdr dropping is delayed */ 2655 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2656 TH_RST); 2657 else { 2658 if (thflags & TH_SYN) 2659 tlen++; 2660 /* mtod() below is safe as long as hdr dropping is delayed */ 2661 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2662 (tcp_seq)0, TH_RST|TH_ACK); 2663 } 2664 2665 if (tp) 2666 INP_UNLOCK(inp); 2667 if (headlocked) 2668 INP_INFO_WUNLOCK(&tcbinfo); 2669 return; 2670 2671 drop: 2672 /* 2673 * Drop space held by incoming segment and return. 2674 */ 2675 #ifdef TCPDEBUG 2676 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2677 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2678 &tcp_savetcp, 0); 2679 #endif 2680 if (tp) 2681 INP_UNLOCK(inp); 2682 if (headlocked) 2683 INP_INFO_WUNLOCK(&tcbinfo); 2684 m_freem(m); 2685 return; 2686 } 2687 2688 /* 2689 * Parse TCP options and place in tcpopt. 2690 */ 2691 static void 2692 tcp_dooptions(tp, to, cp, cnt, is_syn, th) 2693 struct tcpcb *tp; 2694 struct tcpopt *to; 2695 u_char *cp; 2696 int cnt; 2697 int is_syn; 2698 struct tcphdr *th; 2699 { 2700 int opt, optlen; 2701 2702 to->to_flags = 0; 2703 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2704 opt = cp[0]; 2705 if (opt == TCPOPT_EOL) 2706 break; 2707 if (opt == TCPOPT_NOP) 2708 optlen = 1; 2709 else { 2710 if (cnt < 2) 2711 break; 2712 optlen = cp[1]; 2713 if (optlen < 2 || optlen > cnt) 2714 break; 2715 } 2716 switch (opt) { 2717 case TCPOPT_MAXSEG: 2718 if (optlen != TCPOLEN_MAXSEG) 2719 continue; 2720 if (!is_syn) 2721 continue; 2722 to->to_flags |= TOF_MSS; 2723 bcopy((char *)cp + 2, 2724 (char *)&to->to_mss, sizeof(to->to_mss)); 2725 to->to_mss = ntohs(to->to_mss); 2726 break; 2727 case TCPOPT_WINDOW: 2728 if (optlen != TCPOLEN_WINDOW) 2729 continue; 2730 if (! is_syn) 2731 continue; 2732 to->to_flags |= TOF_SCALE; 2733 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2734 break; 2735 case TCPOPT_TIMESTAMP: 2736 if (optlen != TCPOLEN_TIMESTAMP) 2737 continue; 2738 to->to_flags |= TOF_TS; 2739 bcopy((char *)cp + 2, 2740 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2741 to->to_tsval = ntohl(to->to_tsval); 2742 bcopy((char *)cp + 6, 2743 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2744 to->to_tsecr = ntohl(to->to_tsecr); 2745 /* 2746 * If echoed timestamp is later than the current time, 2747 * fall back to non RFC1323 RTT calculation. 2748 */ 2749 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2750 to->to_tsecr = 0; 2751 break; 2752 case TCPOPT_CC: 2753 if (optlen != TCPOLEN_CC) 2754 continue; 2755 to->to_flags |= TOF_CC; 2756 bcopy((char *)cp + 2, 2757 (char *)&to->to_cc, sizeof(to->to_cc)); 2758 to->to_cc = ntohl(to->to_cc); 2759 break; 2760 case TCPOPT_CCNEW: 2761 if (optlen != TCPOLEN_CC) 2762 continue; 2763 if (!is_syn) 2764 continue; 2765 to->to_flags |= TOF_CCNEW; 2766 bcopy((char *)cp + 2, 2767 (char *)&to->to_cc, sizeof(to->to_cc)); 2768 to->to_cc = ntohl(to->to_cc); 2769 break; 2770 case TCPOPT_CCECHO: 2771 if (optlen != TCPOLEN_CC) 2772 continue; 2773 if (!is_syn) 2774 continue; 2775 to->to_flags |= TOF_CCECHO; 2776 bcopy((char *)cp + 2, 2777 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2778 to->to_ccecho = ntohl(to->to_ccecho); 2779 break; 2780 #ifdef TCP_SIGNATURE 2781 /* 2782 * XXX In order to reply to a host which has set the 2783 * TCP_SIGNATURE option in its initial SYN, we have to 2784 * record the fact that the option was observed here 2785 * for the syncache code to perform the correct response. 2786 */ 2787 case TCPOPT_SIGNATURE: 2788 if (optlen != TCPOLEN_SIGNATURE) 2789 continue; 2790 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2791 break; 2792 #endif 2793 case TCPOPT_SACK_PERMITTED: 2794 if (!tcp_do_sack || 2795 optlen != TCPOLEN_SACK_PERMITTED) 2796 continue; 2797 if (is_syn) { 2798 /* MUST only be set on SYN */ 2799 to->to_flags |= TOF_SACK; 2800 } 2801 break; 2802 2803 case TCPOPT_SACK: 2804 if (!tp || tcp_sack_option(tp, th, cp, optlen)) 2805 continue; 2806 break; 2807 default: 2808 continue; 2809 } 2810 } 2811 } 2812 2813 /* 2814 * Pull out of band byte out of a segment so 2815 * it doesn't appear in the user's data queue. 2816 * It is still reflected in the segment length for 2817 * sequencing purposes. 2818 */ 2819 static void 2820 tcp_pulloutofband(so, th, m, off) 2821 struct socket *so; 2822 struct tcphdr *th; 2823 register struct mbuf *m; 2824 int off; /* delayed to be droped hdrlen */ 2825 { 2826 int cnt = off + th->th_urp - 1; 2827 2828 while (cnt >= 0) { 2829 if (m->m_len > cnt) { 2830 char *cp = mtod(m, caddr_t) + cnt; 2831 struct tcpcb *tp = sototcpcb(so); 2832 2833 tp->t_iobc = *cp; 2834 tp->t_oobflags |= TCPOOB_HAVEDATA; 2835 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2836 m->m_len--; 2837 if (m->m_flags & M_PKTHDR) 2838 m->m_pkthdr.len--; 2839 return; 2840 } 2841 cnt -= m->m_len; 2842 m = m->m_next; 2843 if (m == 0) 2844 break; 2845 } 2846 panic("tcp_pulloutofband"); 2847 } 2848 2849 /* 2850 * Collect new round-trip time estimate 2851 * and update averages and current timeout. 2852 */ 2853 static void 2854 tcp_xmit_timer(tp, rtt) 2855 register struct tcpcb *tp; 2856 int rtt; 2857 { 2858 register int delta; 2859 2860 INP_LOCK_ASSERT(tp->t_inpcb); 2861 2862 tcpstat.tcps_rttupdated++; 2863 tp->t_rttupdated++; 2864 if (tp->t_srtt != 0) { 2865 /* 2866 * srtt is stored as fixed point with 5 bits after the 2867 * binary point (i.e., scaled by 8). The following magic 2868 * is equivalent to the smoothing algorithm in rfc793 with 2869 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2870 * point). Adjust rtt to origin 0. 2871 */ 2872 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2873 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2874 2875 if ((tp->t_srtt += delta) <= 0) 2876 tp->t_srtt = 1; 2877 2878 /* 2879 * We accumulate a smoothed rtt variance (actually, a 2880 * smoothed mean difference), then set the retransmit 2881 * timer to smoothed rtt + 4 times the smoothed variance. 2882 * rttvar is stored as fixed point with 4 bits after the 2883 * binary point (scaled by 16). The following is 2884 * equivalent to rfc793 smoothing with an alpha of .75 2885 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2886 * rfc793's wired-in beta. 2887 */ 2888 if (delta < 0) 2889 delta = -delta; 2890 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2891 if ((tp->t_rttvar += delta) <= 0) 2892 tp->t_rttvar = 1; 2893 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2894 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2895 } else { 2896 /* 2897 * No rtt measurement yet - use the unsmoothed rtt. 2898 * Set the variance to half the rtt (so our first 2899 * retransmit happens at 3*rtt). 2900 */ 2901 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2902 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2903 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2904 } 2905 tp->t_rtttime = 0; 2906 tp->t_rxtshift = 0; 2907 2908 /* 2909 * the retransmit should happen at rtt + 4 * rttvar. 2910 * Because of the way we do the smoothing, srtt and rttvar 2911 * will each average +1/2 tick of bias. When we compute 2912 * the retransmit timer, we want 1/2 tick of rounding and 2913 * 1 extra tick because of +-1/2 tick uncertainty in the 2914 * firing of the timer. The bias will give us exactly the 2915 * 1.5 tick we need. But, because the bias is 2916 * statistical, we have to test that we don't drop below 2917 * the minimum feasible timer (which is 2 ticks). 2918 */ 2919 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2920 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2921 2922 /* 2923 * We received an ack for a packet that wasn't retransmitted; 2924 * it is probably safe to discard any error indications we've 2925 * received recently. This isn't quite right, but close enough 2926 * for now (a route might have failed after we sent a segment, 2927 * and the return path might not be symmetrical). 2928 */ 2929 tp->t_softerror = 0; 2930 } 2931 2932 /* 2933 * Determine a reasonable value for maxseg size. 2934 * If the route is known, check route for mtu. 2935 * If none, use an mss that can be handled on the outgoing 2936 * interface without forcing IP to fragment; if bigger than 2937 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2938 * to utilize large mbufs. If no route is found, route has no mtu, 2939 * or the destination isn't local, use a default, hopefully conservative 2940 * size (usually 512 or the default IP max size, but no more than the mtu 2941 * of the interface), as we can't discover anything about intervening 2942 * gateways or networks. We also initialize the congestion/slow start 2943 * window to be a single segment if the destination isn't local. 2944 * While looking at the routing entry, we also initialize other path-dependent 2945 * parameters from pre-set or cached values in the routing entry. 2946 * 2947 * Also take into account the space needed for options that we 2948 * send regularly. Make maxseg shorter by that amount to assure 2949 * that we can send maxseg amount of data even when the options 2950 * are present. Store the upper limit of the length of options plus 2951 * data in maxopd. 2952 * 2953 * 2954 * In case of T/TCP, we call this routine during implicit connection 2955 * setup as well (offer = -1), to initialize maxseg from the cached 2956 * MSS of our peer. 2957 * 2958 * NOTE that this routine is only called when we process an incoming 2959 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2960 */ 2961 void 2962 tcp_mss(tp, offer) 2963 struct tcpcb *tp; 2964 int offer; 2965 { 2966 int rtt, mss; 2967 u_long bufsize; 2968 u_long maxmtu; 2969 struct inpcb *inp = tp->t_inpcb; 2970 struct socket *so; 2971 struct hc_metrics_lite metrics; 2972 struct rmxp_tao tao; 2973 int origoffer = offer; 2974 #ifdef INET6 2975 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2976 size_t min_protoh = isipv6 ? 2977 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2978 sizeof (struct tcpiphdr); 2979 #else 2980 const size_t min_protoh = sizeof(struct tcpiphdr); 2981 #endif 2982 bzero(&tao, sizeof(tao)); 2983 2984 /* initialize */ 2985 #ifdef INET6 2986 if (isipv6) { 2987 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2988 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2989 } else 2990 #endif 2991 { 2992 maxmtu = tcp_maxmtu(&inp->inp_inc); 2993 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2994 } 2995 so = inp->inp_socket; 2996 2997 /* 2998 * no route to sender, stay with default mss and return 2999 */ 3000 if (maxmtu == 0) 3001 return; 3002 3003 /* what have we got? */ 3004 switch (offer) { 3005 case 0: 3006 /* 3007 * Offer == 0 means that there was no MSS on the SYN 3008 * segment, in this case we use tcp_mssdflt. 3009 */ 3010 offer = 3011 #ifdef INET6 3012 isipv6 ? tcp_v6mssdflt : 3013 #endif 3014 tcp_mssdflt; 3015 break; 3016 3017 case -1: 3018 /* 3019 * Offer == -1 means that we didn't receive SYN yet, 3020 * use cached value in that case; 3021 */ 3022 if (tcp_do_rfc1644) 3023 tcp_hc_gettao(&inp->inp_inc, &tao); 3024 if (tao.tao_mssopt != 0) 3025 offer = tao.tao_mssopt; 3026 /* FALLTHROUGH */ 3027 3028 default: 3029 /* 3030 * Prevent DoS attack with too small MSS. Round up 3031 * to at least minmss. 3032 */ 3033 offer = max(offer, tcp_minmss); 3034 /* 3035 * Sanity check: make sure that maxopd will be large 3036 * enough to allow some data on segments even if the 3037 * all the option space is used (40bytes). Otherwise 3038 * funny things may happen in tcp_output. 3039 */ 3040 offer = max(offer, 64); 3041 if (tcp_do_rfc1644) 3042 tcp_hc_updatetao(&inp->inp_inc, 3043 TCP_HC_TAO_MSSOPT, 0, offer); 3044 } 3045 3046 /* 3047 * rmx information is now retrieved from tcp_hostcache 3048 */ 3049 tcp_hc_get(&inp->inp_inc, &metrics); 3050 3051 /* 3052 * if there's a discovered mtu int tcp hostcache, use it 3053 * else, use the link mtu. 3054 */ 3055 if (metrics.rmx_mtu) 3056 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3057 else { 3058 #ifdef INET6 3059 if (isipv6) { 3060 mss = maxmtu - min_protoh; 3061 if (!path_mtu_discovery && 3062 !in6_localaddr(&inp->in6p_faddr)) 3063 mss = min(mss, tcp_v6mssdflt); 3064 } else 3065 #endif 3066 { 3067 mss = maxmtu - min_protoh; 3068 if (!path_mtu_discovery && 3069 !in_localaddr(inp->inp_faddr)) 3070 mss = min(mss, tcp_mssdflt); 3071 } 3072 } 3073 mss = min(mss, offer); 3074 3075 /* 3076 * maxopd stores the maximum length of data AND options 3077 * in a segment; maxseg is the amount of data in a normal 3078 * segment. We need to store this value (maxopd) apart 3079 * from maxseg, because now every segment carries options 3080 * and thus we normally have somewhat less data in segments. 3081 */ 3082 tp->t_maxopd = mss; 3083 3084 /* 3085 * In case of T/TCP, origoffer==-1 indicates, that no segments 3086 * were received yet. In this case we just guess, otherwise 3087 * we do the same as before T/TCP. 3088 */ 3089 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3090 (origoffer == -1 || 3091 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3092 mss -= TCPOLEN_TSTAMP_APPA; 3093 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 3094 (origoffer == -1 || 3095 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3096 mss -= TCPOLEN_CC_APPA; 3097 tp->t_maxseg = mss; 3098 3099 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3100 if (mss > MCLBYTES) 3101 mss &= ~(MCLBYTES-1); 3102 #else 3103 if (mss > MCLBYTES) 3104 mss = mss / MCLBYTES * MCLBYTES; 3105 #endif 3106 tp->t_maxseg = mss; 3107 3108 /* 3109 * If there's a pipesize, change the socket buffer to that size, 3110 * don't change if sb_hiwat is different than default (then it 3111 * has been changed on purpose with setsockopt). 3112 * Make the socket buffers an integral number of mss units; 3113 * if the mss is larger than the socket buffer, decrease the mss. 3114 */ 3115 SOCKBUF_LOCK(&so->so_snd); 3116 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3117 bufsize = metrics.rmx_sendpipe; 3118 else 3119 bufsize = so->so_snd.sb_hiwat; 3120 if (bufsize < mss) 3121 mss = bufsize; 3122 else { 3123 bufsize = roundup(bufsize, mss); 3124 if (bufsize > sb_max) 3125 bufsize = sb_max; 3126 if (bufsize > so->so_snd.sb_hiwat) 3127 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3128 } 3129 SOCKBUF_UNLOCK(&so->so_snd); 3130 tp->t_maxseg = mss; 3131 3132 SOCKBUF_LOCK(&so->so_rcv); 3133 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3134 bufsize = metrics.rmx_recvpipe; 3135 else 3136 bufsize = so->so_rcv.sb_hiwat; 3137 if (bufsize > mss) { 3138 bufsize = roundup(bufsize, mss); 3139 if (bufsize > sb_max) 3140 bufsize = sb_max; 3141 if (bufsize > so->so_rcv.sb_hiwat) 3142 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3143 } 3144 SOCKBUF_UNLOCK(&so->so_rcv); 3145 /* 3146 * While we're here, check the others too 3147 */ 3148 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3149 tp->t_srtt = rtt; 3150 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3151 tcpstat.tcps_usedrtt++; 3152 if (metrics.rmx_rttvar) { 3153 tp->t_rttvar = metrics.rmx_rttvar; 3154 tcpstat.tcps_usedrttvar++; 3155 } else { 3156 /* default variation is +- 1 rtt */ 3157 tp->t_rttvar = 3158 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3159 } 3160 TCPT_RANGESET(tp->t_rxtcur, 3161 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3162 tp->t_rttmin, TCPTV_REXMTMAX); 3163 } 3164 if (metrics.rmx_ssthresh) { 3165 /* 3166 * There's some sort of gateway or interface 3167 * buffer limit on the path. Use this to set 3168 * the slow start threshhold, but set the 3169 * threshold to no less than 2*mss. 3170 */ 3171 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3172 tcpstat.tcps_usedssthresh++; 3173 } 3174 if (metrics.rmx_bandwidth) 3175 tp->snd_bandwidth = metrics.rmx_bandwidth; 3176 3177 /* 3178 * Set the slow-start flight size depending on whether this 3179 * is a local network or not. 3180 * 3181 * Extend this so we cache the cwnd too and retrieve it here. 3182 * Make cwnd even bigger than RFC3390 suggests but only if we 3183 * have previous experience with the remote host. Be careful 3184 * not make cwnd bigger than remote receive window or our own 3185 * send socket buffer. Maybe put some additional upper bound 3186 * on the retrieved cwnd. Should do incremental updates to 3187 * hostcache when cwnd collapses so next connection doesn't 3188 * overloads the path again. 3189 * 3190 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3191 * We currently check only in syncache_socket for that. 3192 */ 3193 #define TCP_METRICS_CWND 3194 #ifdef TCP_METRICS_CWND 3195 if (metrics.rmx_cwnd) 3196 tp->snd_cwnd = max(mss, 3197 min(metrics.rmx_cwnd / 2, 3198 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3199 else 3200 #endif 3201 if (tcp_do_rfc3390) 3202 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3203 #ifdef INET6 3204 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3205 (!isipv6 && in_localaddr(inp->inp_faddr))) 3206 #else 3207 else if (in_localaddr(inp->inp_faddr)) 3208 #endif 3209 tp->snd_cwnd = mss * ss_fltsz_local; 3210 else 3211 tp->snd_cwnd = mss * ss_fltsz; 3212 } 3213 3214 /* 3215 * Determine the MSS option to send on an outgoing SYN. 3216 */ 3217 int 3218 tcp_mssopt(inc) 3219 struct in_conninfo *inc; 3220 { 3221 int mss = 0; 3222 u_long maxmtu = 0; 3223 u_long thcmtu = 0; 3224 size_t min_protoh; 3225 #ifdef INET6 3226 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3227 #endif 3228 3229 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3230 3231 #ifdef INET6 3232 if (isipv6) { 3233 mss = tcp_v6mssdflt; 3234 maxmtu = tcp_maxmtu6(inc); 3235 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3236 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3237 } else 3238 #endif 3239 { 3240 mss = tcp_mssdflt; 3241 maxmtu = tcp_maxmtu(inc); 3242 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3243 min_protoh = sizeof(struct tcpiphdr); 3244 } 3245 if (maxmtu && thcmtu) 3246 mss = min(maxmtu, thcmtu) - min_protoh; 3247 else if (maxmtu || thcmtu) 3248 mss = max(maxmtu, thcmtu) - min_protoh; 3249 3250 return (mss); 3251 } 3252 3253 3254 /* 3255 * On a partial ack arrives, force the retransmission of the 3256 * next unacknowledged segment. Do not clear tp->t_dupacks. 3257 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3258 * be started again. 3259 */ 3260 static void 3261 tcp_newreno_partial_ack(tp, th) 3262 struct tcpcb *tp; 3263 struct tcphdr *th; 3264 { 3265 tcp_seq onxt = tp->snd_nxt; 3266 u_long ocwnd = tp->snd_cwnd; 3267 3268 callout_stop(tp->tt_rexmt); 3269 tp->t_rtttime = 0; 3270 tp->snd_nxt = th->th_ack; 3271 /* 3272 * Set snd_cwnd to one segment beyond acknowledged offset. 3273 * (tp->snd_una has not yet been updated when this function is called.) 3274 */ 3275 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3276 tp->t_flags |= TF_ACKNOW; 3277 (void) tcp_output(tp); 3278 tp->snd_cwnd = ocwnd; 3279 if (SEQ_GT(onxt, tp->snd_nxt)) 3280 tp->snd_nxt = onxt; 3281 /* 3282 * Partial window deflation. Relies on fact that tp->snd_una 3283 * not updated yet. 3284 */ 3285 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3286 } 3287 3288 /* 3289 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3290 * looking for a pcb in the listen state. Returns 0 otherwise. 3291 */ 3292 static int 3293 tcp_timewait(tw, to, th, m, tlen) 3294 struct tcptw *tw; 3295 struct tcpopt *to; 3296 struct tcphdr *th; 3297 struct mbuf *m; 3298 int tlen; 3299 { 3300 int thflags; 3301 tcp_seq seq; 3302 #ifdef INET6 3303 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3304 #else 3305 const int isipv6 = 0; 3306 #endif 3307 3308 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3309 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3310 INP_LOCK_ASSERT(tw->tw_inpcb); 3311 3312 thflags = th->th_flags; 3313 3314 /* 3315 * NOTE: for FIN_WAIT_2 (to be added later), 3316 * must validate sequence number before accepting RST 3317 */ 3318 3319 /* 3320 * If the segment contains RST: 3321 * Drop the segment - see Stevens, vol. 2, p. 964 and 3322 * RFC 1337. 3323 */ 3324 if (thflags & TH_RST) 3325 goto drop; 3326 3327 /* 3328 * If segment contains a SYN and CC [not CC.NEW] option: 3329 * if connection duration > MSL, drop packet and send RST; 3330 * 3331 * if SEG.CC > CCrecv then is new SYN. 3332 * Complete close and delete TCPCB. Then reprocess 3333 * segment, hoping to find new TCPCB in LISTEN state; 3334 * 3335 * else must be old SYN; drop it. 3336 * else do normal processing. 3337 */ 3338 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3339 if ((ticks - tw->t_starttime) > tcp_msl) 3340 goto reset; 3341 if (CC_GT(to->to_cc, tw->cc_recv)) { 3342 (void) tcp_twclose(tw, 0); 3343 return (1); 3344 } 3345 goto drop; 3346 } 3347 3348 #if 0 3349 /* PAWS not needed at the moment */ 3350 /* 3351 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3352 * and it's less than ts_recent, drop it. 3353 */ 3354 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3355 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3356 if ((thflags & TH_ACK) == 0) 3357 goto drop; 3358 goto ack; 3359 } 3360 /* 3361 * ts_recent is never updated because we never accept new segments. 3362 */ 3363 #endif 3364 3365 /* 3366 * If a new connection request is received 3367 * while in TIME_WAIT, drop the old connection 3368 * and start over if the sequence numbers 3369 * are above the previous ones. 3370 */ 3371 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3372 (void) tcp_twclose(tw, 0); 3373 return (1); 3374 } 3375 3376 /* 3377 * Drop the the segment if it does not contain an ACK. 3378 */ 3379 if ((thflags & TH_ACK) == 0) 3380 goto drop; 3381 3382 /* 3383 * Reset the 2MSL timer if this is a duplicate FIN. 3384 */ 3385 if (thflags & TH_FIN) { 3386 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3387 if (seq + 1 == tw->rcv_nxt) 3388 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3389 } 3390 3391 /* 3392 * Acknowledge the segment if it has data or is not a duplicate ACK. 3393 */ 3394 if (thflags != TH_ACK || tlen != 0 || 3395 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3396 tcp_twrespond(tw, TH_ACK); 3397 goto drop; 3398 3399 reset: 3400 /* 3401 * Generate a RST, dropping incoming segment. 3402 * Make ACK acceptable to originator of segment. 3403 * Don't bother to respond if destination was broadcast/multicast. 3404 */ 3405 if (m->m_flags & (M_BCAST|M_MCAST)) 3406 goto drop; 3407 if (isipv6) { 3408 struct ip6_hdr *ip6; 3409 3410 /* IPv6 anycast check is done at tcp6_input() */ 3411 ip6 = mtod(m, struct ip6_hdr *); 3412 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3413 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3414 goto drop; 3415 } else { 3416 struct ip *ip; 3417 3418 ip = mtod(m, struct ip *); 3419 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3420 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3421 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3422 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3423 goto drop; 3424 } 3425 if (thflags & TH_ACK) { 3426 tcp_respond(NULL, 3427 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3428 } else { 3429 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3430 tcp_respond(NULL, 3431 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3432 } 3433 INP_UNLOCK(tw->tw_inpcb); 3434 return (0); 3435 3436 drop: 3437 INP_UNLOCK(tw->tw_inpcb); 3438 m_freem(m); 3439 return (0); 3440 }
Cache object: 25a8db9b5ceacc63ef0b77310111785b
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