1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/mac.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/signalvar.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 #include <sys/syslog.h> 54 #include <sys/systm.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/in_var.h> 67 #include <netinet/ip.h> 68 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip_options.h> 72 #include <netinet/ip6.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/in6_pcb.h> 75 #include <netinet6/ip6_var.h> 76 #include <netinet6/nd6.h> 77 #include <netinet/tcp.h> 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet6/tcp6_var.h> 83 #include <netinet/tcpip.h> 84 #ifdef TCPDEBUG 85 #include <netinet/tcp_debug.h> 86 #endif /* TCPDEBUG */ 87 88 #ifdef FAST_IPSEC 89 #include <netipsec/ipsec.h> 90 #include <netipsec/ipsec6.h> 91 #endif /*FAST_IPSEC*/ 92 93 #ifdef IPSEC 94 #include <netinet6/ipsec.h> 95 #include <netinet6/ipsec6.h> 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 static const int tcprexmtthresh = 3; 102 103 struct tcpstat tcpstat; 104 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107 static int log_in_vain = 0; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111 static int blackhole = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115 int tcp_delack_enabled = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120 #ifdef TCP_DROP_SYNFIN 121 static int drop_synfin = 0; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124 #endif 125 126 static int tcp_do_rfc3042 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130 static int tcp_do_rfc3390 = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135 static int tcp_insecure_rst = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 137 &tcp_insecure_rst, 0, 138 "Follow the old (insecure) criteria for accepting RST packets."); 139 140 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 141 "TCP Segment Reassembly Queue"); 142 143 static int tcp_reass_maxseg = 0; 144 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 145 &tcp_reass_maxseg, 0, 146 "Global maximum number of TCP Segments in Reassembly Queue"); 147 148 int tcp_reass_qsize = 0; 149 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 150 &tcp_reass_qsize, 0, 151 "Global number of TCP Segments currently in Reassembly Queue"); 152 153 static int tcp_reass_maxqlen = 48; 154 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 155 &tcp_reass_maxqlen, 0, 156 "Maximum number of TCP Segments per individual Reassembly Queue"); 157 158 static int tcp_reass_overflows = 0; 159 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 160 &tcp_reass_overflows, 0, 161 "Global number of TCP Segment Reassembly Queue Overflows"); 162 163 struct inpcbhead tcb; 164 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 165 struct inpcbinfo tcbinfo; 166 struct mtx *tcbinfo_mtx; 167 168 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 169 170 static void tcp_pulloutofband(struct socket *, 171 struct tcphdr *, struct mbuf *, int); 172 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 173 struct mbuf *); 174 static void tcp_xmit_timer(struct tcpcb *, int); 175 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 176 static int tcp_timewait(struct inpcb *, struct tcpopt *, 177 struct tcphdr *, struct mbuf *, int); 178 179 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 180 #ifdef INET6 181 #define ND6_HINT(tp) \ 182 do { \ 183 if ((tp) && (tp)->t_inpcb && \ 184 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 185 nd6_nud_hint(NULL, NULL, 0); \ 186 } while (0) 187 #else 188 #define ND6_HINT(tp) 189 #endif 190 191 /* 192 * Indicate whether this ack should be delayed. We can delay the ack if 193 * - there is no delayed ack timer in progress and 194 * - our last ack wasn't a 0-sized window. We never want to delay 195 * the ack that opens up a 0-sized window and 196 * - delayed acks are enabled or 197 * - this is a half-synchronized T/TCP connection. 198 */ 199 #define DELAY_ACK(tp) \ 200 ((!callout_active(tp->tt_delack) && \ 201 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 202 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 203 204 /* Initialize TCP reassembly queue */ 205 static void 206 tcp_reass_zone_change(void *tag) 207 { 208 209 tcp_reass_maxseg = nmbclusters / 16; 210 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 211 } 212 213 uma_zone_t tcp_reass_zone; 214 void 215 tcp_reass_init() 216 { 217 tcp_reass_maxseg = nmbclusters / 16; 218 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 219 &tcp_reass_maxseg); 220 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 221 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 222 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 223 EVENTHANDLER_REGISTER(nmbclusters_change, 224 tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY); 225 } 226 227 static int 228 tcp_reass(tp, th, tlenp, m) 229 register struct tcpcb *tp; 230 register struct tcphdr *th; 231 int *tlenp; 232 struct mbuf *m; 233 { 234 struct tseg_qent *q; 235 struct tseg_qent *p = NULL; 236 struct tseg_qent *nq; 237 struct tseg_qent *te = NULL; 238 struct socket *so = tp->t_inpcb->inp_socket; 239 int flags; 240 241 INP_LOCK_ASSERT(tp->t_inpcb); 242 243 /* 244 * XXX: tcp_reass() is rather inefficient with its data structures 245 * and should be rewritten (see NetBSD for optimizations). While 246 * doing that it should move to its own file tcp_reass.c. 247 */ 248 249 /* 250 * Call with th==NULL after become established to 251 * force pre-ESTABLISHED data up to user socket. 252 */ 253 if (th == NULL) 254 goto present; 255 256 /* 257 * Limit the number of segments in the reassembly queue to prevent 258 * holding on to too many segments (and thus running out of mbufs). 259 * Make sure to let the missing segment through which caused this 260 * queue. Always keep one global queue entry spare to be able to 261 * process the missing segment. 262 */ 263 if (th->th_seq != tp->rcv_nxt && 264 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 265 tp->t_segqlen >= tcp_reass_maxqlen)) { 266 tcp_reass_overflows++; 267 tcpstat.tcps_rcvmemdrop++; 268 m_freem(m); 269 *tlenp = 0; 270 return (0); 271 } 272 273 /* 274 * Allocate a new queue entry. If we can't, or hit the zone limit 275 * just drop the pkt. 276 */ 277 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 278 if (te == NULL) { 279 tcpstat.tcps_rcvmemdrop++; 280 m_freem(m); 281 *tlenp = 0; 282 return (0); 283 } 284 tp->t_segqlen++; 285 tcp_reass_qsize++; 286 287 /* 288 * Find a segment which begins after this one does. 289 */ 290 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 291 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 292 break; 293 p = q; 294 } 295 296 /* 297 * If there is a preceding segment, it may provide some of 298 * our data already. If so, drop the data from the incoming 299 * segment. If it provides all of our data, drop us. 300 */ 301 if (p != NULL) { 302 register int i; 303 /* conversion to int (in i) handles seq wraparound */ 304 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 305 if (i > 0) { 306 if (i >= *tlenp) { 307 tcpstat.tcps_rcvduppack++; 308 tcpstat.tcps_rcvdupbyte += *tlenp; 309 m_freem(m); 310 uma_zfree(tcp_reass_zone, te); 311 tp->t_segqlen--; 312 tcp_reass_qsize--; 313 /* 314 * Try to present any queued data 315 * at the left window edge to the user. 316 * This is needed after the 3-WHS 317 * completes. 318 */ 319 goto present; /* ??? */ 320 } 321 m_adj(m, i); 322 *tlenp -= i; 323 th->th_seq += i; 324 } 325 } 326 tcpstat.tcps_rcvoopack++; 327 tcpstat.tcps_rcvoobyte += *tlenp; 328 329 /* 330 * While we overlap succeeding segments trim them or, 331 * if they are completely covered, dequeue them. 332 */ 333 while (q) { 334 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 335 if (i <= 0) 336 break; 337 if (i < q->tqe_len) { 338 q->tqe_th->th_seq += i; 339 q->tqe_len -= i; 340 m_adj(q->tqe_m, i); 341 break; 342 } 343 344 nq = LIST_NEXT(q, tqe_q); 345 LIST_REMOVE(q, tqe_q); 346 m_freem(q->tqe_m); 347 uma_zfree(tcp_reass_zone, q); 348 tp->t_segqlen--; 349 tcp_reass_qsize--; 350 q = nq; 351 } 352 353 /* Insert the new segment queue entry into place. */ 354 te->tqe_m = m; 355 te->tqe_th = th; 356 te->tqe_len = *tlenp; 357 358 if (p == NULL) { 359 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 360 } else { 361 LIST_INSERT_AFTER(p, te, tqe_q); 362 } 363 364 present: 365 /* 366 * Present data to user, advancing rcv_nxt through 367 * completed sequence space. 368 */ 369 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 370 return (0); 371 q = LIST_FIRST(&tp->t_segq); 372 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 373 return (0); 374 SOCKBUF_LOCK(&so->so_rcv); 375 do { 376 tp->rcv_nxt += q->tqe_len; 377 flags = q->tqe_th->th_flags & TH_FIN; 378 nq = LIST_NEXT(q, tqe_q); 379 LIST_REMOVE(q, tqe_q); 380 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 381 m_freem(q->tqe_m); 382 else 383 sbappendstream_locked(&so->so_rcv, q->tqe_m); 384 uma_zfree(tcp_reass_zone, q); 385 tp->t_segqlen--; 386 tcp_reass_qsize--; 387 q = nq; 388 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 389 ND6_HINT(tp); 390 sorwakeup_locked(so); 391 return (flags); 392 } 393 394 /* 395 * TCP input routine, follows pages 65-76 of the 396 * protocol specification dated September, 1981 very closely. 397 */ 398 #ifdef INET6 399 int 400 tcp6_input(mp, offp, proto) 401 struct mbuf **mp; 402 int *offp, proto; 403 { 404 register struct mbuf *m = *mp; 405 struct in6_ifaddr *ia6; 406 407 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 408 409 /* 410 * draft-itojun-ipv6-tcp-to-anycast 411 * better place to put this in? 412 */ 413 ia6 = ip6_getdstifaddr(m); 414 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 415 struct ip6_hdr *ip6; 416 417 ip6 = mtod(m, struct ip6_hdr *); 418 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 419 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 420 return IPPROTO_DONE; 421 } 422 423 tcp_input(m, *offp); 424 return IPPROTO_DONE; 425 } 426 #endif 427 428 void 429 tcp_input(m, off0) 430 register struct mbuf *m; 431 int off0; 432 { 433 register struct tcphdr *th; 434 register struct ip *ip = NULL; 435 register struct ipovly *ipov; 436 register struct inpcb *inp = NULL; 437 u_char *optp = NULL; 438 int optlen = 0; 439 int len, tlen, off; 440 int drop_hdrlen; 441 register struct tcpcb *tp = 0; 442 register int thflags; 443 struct socket *so = 0; 444 int todrop, acked, ourfinisacked, needoutput = 0; 445 u_long tiwin; 446 struct tcpopt to; /* options in this segment */ 447 int headlocked = 0; 448 #ifdef IPFIREWALL_FORWARD 449 struct m_tag *fwd_tag; 450 #endif 451 int rstreason; /* For badport_bandlim accounting purposes */ 452 453 struct ip6_hdr *ip6 = NULL; 454 #ifdef INET6 455 int isipv6; 456 #else 457 const int isipv6 = 0; 458 #endif 459 460 #ifdef TCPDEBUG 461 /* 462 * The size of tcp_saveipgen must be the size of the max ip header, 463 * now IPv6. 464 */ 465 u_char tcp_saveipgen[40]; 466 struct tcphdr tcp_savetcp; 467 short ostate = 0; 468 #endif 469 470 #ifdef INET6 471 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 472 #endif 473 bzero((char *)&to, sizeof(to)); 474 475 tcpstat.tcps_rcvtotal++; 476 477 if (isipv6) { 478 #ifdef INET6 479 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 480 ip6 = mtod(m, struct ip6_hdr *); 481 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 482 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 483 tcpstat.tcps_rcvbadsum++; 484 goto drop; 485 } 486 th = (struct tcphdr *)((caddr_t)ip6 + off0); 487 488 /* 489 * Be proactive about unspecified IPv6 address in source. 490 * As we use all-zero to indicate unbounded/unconnected pcb, 491 * unspecified IPv6 address can be used to confuse us. 492 * 493 * Note that packets with unspecified IPv6 destination is 494 * already dropped in ip6_input. 495 */ 496 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 497 /* XXX stat */ 498 goto drop; 499 } 500 #else 501 th = NULL; /* XXX: avoid compiler warning */ 502 #endif 503 } else { 504 /* 505 * Get IP and TCP header together in first mbuf. 506 * Note: IP leaves IP header in first mbuf. 507 */ 508 if (off0 > sizeof (struct ip)) { 509 ip_stripoptions(m, (struct mbuf *)0); 510 off0 = sizeof(struct ip); 511 } 512 if (m->m_len < sizeof (struct tcpiphdr)) { 513 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 514 tcpstat.tcps_rcvshort++; 515 return; 516 } 517 } 518 ip = mtod(m, struct ip *); 519 ipov = (struct ipovly *)ip; 520 th = (struct tcphdr *)((caddr_t)ip + off0); 521 tlen = ip->ip_len; 522 523 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 524 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 525 th->th_sum = m->m_pkthdr.csum_data; 526 else 527 th->th_sum = in_pseudo(ip->ip_src.s_addr, 528 ip->ip_dst.s_addr, 529 htonl(m->m_pkthdr.csum_data + 530 ip->ip_len + 531 IPPROTO_TCP)); 532 th->th_sum ^= 0xffff; 533 #ifdef TCPDEBUG 534 ipov->ih_len = (u_short)tlen; 535 ipov->ih_len = htons(ipov->ih_len); 536 #endif 537 } else { 538 /* 539 * Checksum extended TCP header and data. 540 */ 541 len = sizeof (struct ip) + tlen; 542 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 543 ipov->ih_len = (u_short)tlen; 544 ipov->ih_len = htons(ipov->ih_len); 545 th->th_sum = in_cksum(m, len); 546 } 547 if (th->th_sum) { 548 tcpstat.tcps_rcvbadsum++; 549 goto drop; 550 } 551 #ifdef INET6 552 /* Re-initialization for later version check */ 553 ip->ip_v = IPVERSION; 554 #endif 555 } 556 557 /* 558 * Check that TCP offset makes sense, 559 * pull out TCP options and adjust length. XXX 560 */ 561 off = th->th_off << 2; 562 if (off < sizeof (struct tcphdr) || off > tlen) { 563 tcpstat.tcps_rcvbadoff++; 564 goto drop; 565 } 566 tlen -= off; /* tlen is used instead of ti->ti_len */ 567 if (off > sizeof (struct tcphdr)) { 568 if (isipv6) { 569 #ifdef INET6 570 IP6_EXTHDR_CHECK(m, off0, off, ); 571 ip6 = mtod(m, struct ip6_hdr *); 572 th = (struct tcphdr *)((caddr_t)ip6 + off0); 573 #endif 574 } else { 575 if (m->m_len < sizeof(struct ip) + off) { 576 if ((m = m_pullup(m, sizeof (struct ip) + off)) 577 == 0) { 578 tcpstat.tcps_rcvshort++; 579 return; 580 } 581 ip = mtod(m, struct ip *); 582 ipov = (struct ipovly *)ip; 583 th = (struct tcphdr *)((caddr_t)ip + off0); 584 } 585 } 586 optlen = off - sizeof (struct tcphdr); 587 optp = (u_char *)(th + 1); 588 } 589 thflags = th->th_flags; 590 591 #ifdef TCP_DROP_SYNFIN 592 /* 593 * If the drop_synfin option is enabled, drop all packets with 594 * both the SYN and FIN bits set. This prevents e.g. nmap from 595 * identifying the TCP/IP stack. 596 * 597 * This is a violation of the TCP specification. 598 */ 599 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 600 goto drop; 601 #endif 602 603 /* 604 * Convert TCP protocol specific fields to host format. 605 */ 606 th->th_seq = ntohl(th->th_seq); 607 th->th_ack = ntohl(th->th_ack); 608 th->th_win = ntohs(th->th_win); 609 th->th_urp = ntohs(th->th_urp); 610 611 /* 612 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 613 * until after ip6_savecontrol() is called and before other functions 614 * which don't want those proto headers. 615 * Because ip6_savecontrol() is going to parse the mbuf to 616 * search for data to be passed up to user-land, it wants mbuf 617 * parameters to be unchanged. 618 * XXX: the call of ip6_savecontrol() has been obsoleted based on 619 * latest version of the advanced API (20020110). 620 */ 621 drop_hdrlen = off0 + off; 622 623 /* 624 * Locate pcb for segment. 625 */ 626 INP_INFO_WLOCK(&tcbinfo); 627 headlocked = 1; 628 findpcb: 629 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 630 #ifdef IPFIREWALL_FORWARD 631 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 632 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 633 634 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 635 struct sockaddr_in *next_hop; 636 637 next_hop = (struct sockaddr_in *)(fwd_tag+1); 638 /* 639 * Transparently forwarded. Pretend to be the destination. 640 * already got one like this? 641 */ 642 inp = in_pcblookup_hash(&tcbinfo, 643 ip->ip_src, th->th_sport, 644 ip->ip_dst, th->th_dport, 645 0, m->m_pkthdr.rcvif); 646 if (!inp) { 647 /* It's new. Try to find the ambushing socket. */ 648 inp = in_pcblookup_hash(&tcbinfo, 649 ip->ip_src, th->th_sport, 650 next_hop->sin_addr, 651 next_hop->sin_port ? 652 ntohs(next_hop->sin_port) : 653 th->th_dport, 654 INPLOOKUP_WILDCARD, 655 m->m_pkthdr.rcvif); 656 } 657 /* Remove the tag from the packet. We don't need it anymore. */ 658 m_tag_delete(m, fwd_tag); 659 } else { 660 #endif /* IPFIREWALL_FORWARD */ 661 if (isipv6) { 662 #ifdef INET6 663 inp = in6_pcblookup_hash(&tcbinfo, 664 &ip6->ip6_src, th->th_sport, 665 &ip6->ip6_dst, th->th_dport, 666 INPLOOKUP_WILDCARD, 667 m->m_pkthdr.rcvif); 668 #endif 669 } else 670 inp = in_pcblookup_hash(&tcbinfo, 671 ip->ip_src, th->th_sport, 672 ip->ip_dst, th->th_dport, 673 INPLOOKUP_WILDCARD, 674 m->m_pkthdr.rcvif); 675 #ifdef IPFIREWALL_FORWARD 676 } 677 #endif /* IPFIREWALL_FORWARD */ 678 679 #if defined(IPSEC) || defined(FAST_IPSEC) 680 #ifdef INET6 681 if (isipv6) { 682 if (inp != NULL && ipsec6_in_reject(m, inp)) { 683 #ifdef IPSEC 684 ipsec6stat.in_polvio++; 685 #endif 686 goto drop; 687 } 688 } else 689 #endif /* INET6 */ 690 if (inp != NULL && ipsec4_in_reject(m, inp)) { 691 #ifdef IPSEC 692 ipsecstat.in_polvio++; 693 #endif 694 goto drop; 695 } 696 #endif /*IPSEC || FAST_IPSEC*/ 697 698 /* 699 * If the state is CLOSED (i.e., TCB does not exist) then 700 * all data in the incoming segment is discarded. 701 * If the TCB exists but is in CLOSED state, it is embryonic, 702 * but should either do a listen or a connect soon. 703 */ 704 if (inp == NULL) { 705 if (log_in_vain) { 706 #ifdef INET6 707 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 708 #else 709 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 710 #endif 711 712 if (isipv6) { 713 #ifdef INET6 714 strcpy(dbuf, "["); 715 strcpy(sbuf, "["); 716 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 717 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 718 strcat(dbuf, "]"); 719 strcat(sbuf, "]"); 720 #endif 721 } else { 722 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 723 strcpy(sbuf, inet_ntoa(ip->ip_src)); 724 } 725 switch (log_in_vain) { 726 case 1: 727 if ((thflags & TH_SYN) == 0) 728 break; 729 /* FALLTHROUGH */ 730 case 2: 731 log(LOG_INFO, 732 "Connection attempt to TCP %s:%d " 733 "from %s:%d flags:0x%02x\n", 734 dbuf, ntohs(th->th_dport), sbuf, 735 ntohs(th->th_sport), thflags); 736 break; 737 default: 738 break; 739 } 740 } 741 if (blackhole) { 742 switch (blackhole) { 743 case 1: 744 if (thflags & TH_SYN) 745 goto drop; 746 break; 747 case 2: 748 goto drop; 749 default: 750 goto drop; 751 } 752 } 753 rstreason = BANDLIM_RST_CLOSEDPORT; 754 goto dropwithreset; 755 } 756 INP_LOCK(inp); 757 758 /* Check the minimum TTL for socket. */ 759 if (inp->inp_ip_minttl != 0) { 760 #ifdef INET6 761 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 762 goto drop; 763 else 764 #endif 765 if (inp->inp_ip_minttl > ip->ip_ttl) 766 goto drop; 767 } 768 769 if (inp->inp_vflag & INP_TIMEWAIT) { 770 /* 771 * The only option of relevance is TOF_CC, and only if 772 * present in a SYN segment. See tcp_timewait(). 773 */ 774 if (thflags & TH_SYN) 775 tcp_dooptions(&to, optp, optlen, TO_SYN); 776 if (tcp_timewait(inp, &to, th, m, tlen)) 777 goto findpcb; 778 /* 779 * tcp_timewait unlocks inp. 780 */ 781 INP_INFO_WUNLOCK(&tcbinfo); 782 return; 783 } 784 tp = intotcpcb(inp); 785 if (tp == 0) { 786 INP_UNLOCK(inp); 787 rstreason = BANDLIM_RST_CLOSEDPORT; 788 goto dropwithreset; 789 } 790 if (tp->t_state == TCPS_CLOSED) 791 goto drop; 792 793 #ifdef MAC 794 INP_LOCK_ASSERT(inp); 795 if (mac_check_inpcb_deliver(inp, m)) 796 goto drop; 797 #endif 798 so = inp->inp_socket; 799 KASSERT(so != NULL, ("tcp_input: so == NULL")); 800 #ifdef TCPDEBUG 801 if (so->so_options & SO_DEBUG) { 802 ostate = tp->t_state; 803 if (isipv6) 804 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 805 else 806 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 807 tcp_savetcp = *th; 808 } 809 #endif 810 if (so->so_options & SO_ACCEPTCONN) { 811 struct in_conninfo inc; 812 813 bzero(&inc, sizeof(inc)); 814 #ifdef INET6 815 inc.inc_isipv6 = isipv6; 816 #endif 817 if (isipv6) { 818 inc.inc6_faddr = ip6->ip6_src; 819 inc.inc6_laddr = ip6->ip6_dst; 820 } else { 821 inc.inc_faddr = ip->ip_src; 822 inc.inc_laddr = ip->ip_dst; 823 } 824 inc.inc_fport = th->th_sport; 825 inc.inc_lport = th->th_dport; 826 827 /* 828 * If the state is LISTEN then ignore segment if it contains 829 * a RST. If the segment contains an ACK then it is bad and 830 * send a RST. If it does not contain a SYN then it is not 831 * interesting; drop it. 832 * 833 * If the state is SYN_RECEIVED (syncache) and seg contains 834 * an ACK, but not for our SYN/ACK, send a RST. If the seg 835 * contains a RST, check the sequence number to see if it 836 * is a valid reset segment. 837 */ 838 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 839 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 840 /* 841 * Parse the TCP options here because 842 * syncookies need access to the reflected 843 * timestamp. 844 */ 845 tcp_dooptions(&to, optp, optlen, 0); 846 if (!syncache_expand(&inc, &to, th, &so, m)) { 847 /* 848 * No syncache entry, or ACK was not 849 * for our SYN/ACK. Send a RST. 850 */ 851 tcpstat.tcps_badsyn++; 852 rstreason = BANDLIM_RST_OPENPORT; 853 goto dropwithreset; 854 } 855 if (so == NULL) { 856 /* 857 * Could not complete 3-way handshake, 858 * connection is being closed down, and 859 * syncache has free'd mbuf. 860 */ 861 INP_UNLOCK(inp); 862 INP_INFO_WUNLOCK(&tcbinfo); 863 return; 864 } 865 /* 866 * Socket is created in state SYN_RECEIVED. 867 * Continue processing segment. 868 */ 869 INP_UNLOCK(inp); 870 inp = sotoinpcb(so); 871 INP_LOCK(inp); 872 tp = intotcpcb(inp); 873 /* 874 * This is what would have happened in 875 * tcp_output() when the SYN,ACK was sent. 876 */ 877 tp->snd_up = tp->snd_una; 878 tp->snd_max = tp->snd_nxt = tp->iss + 1; 879 tp->last_ack_sent = tp->rcv_nxt; 880 goto after_listen; 881 } 882 if (thflags & TH_RST) { 883 syncache_chkrst(&inc, th); 884 goto drop; 885 } 886 if (thflags & TH_ACK) { 887 syncache_badack(&inc); 888 tcpstat.tcps_badsyn++; 889 rstreason = BANDLIM_RST_OPENPORT; 890 goto dropwithreset; 891 } 892 goto drop; 893 } 894 895 /* 896 * Segment's flags are (SYN) or (SYN|FIN). 897 */ 898 #ifdef INET6 899 /* 900 * If deprecated address is forbidden, 901 * we do not accept SYN to deprecated interface 902 * address to prevent any new inbound connection from 903 * getting established. 904 * When we do not accept SYN, we send a TCP RST, 905 * with deprecated source address (instead of dropping 906 * it). We compromise it as it is much better for peer 907 * to send a RST, and RST will be the final packet 908 * for the exchange. 909 * 910 * If we do not forbid deprecated addresses, we accept 911 * the SYN packet. RFC2462 does not suggest dropping 912 * SYN in this case. 913 * If we decipher RFC2462 5.5.4, it says like this: 914 * 1. use of deprecated addr with existing 915 * communication is okay - "SHOULD continue to be 916 * used" 917 * 2. use of it with new communication: 918 * (2a) "SHOULD NOT be used if alternate address 919 * with sufficient scope is available" 920 * (2b) nothing mentioned otherwise. 921 * Here we fall into (2b) case as we have no choice in 922 * our source address selection - we must obey the peer. 923 * 924 * The wording in RFC2462 is confusing, and there are 925 * multiple description text for deprecated address 926 * handling - worse, they are not exactly the same. 927 * I believe 5.5.4 is the best one, so we follow 5.5.4. 928 */ 929 if (isipv6 && !ip6_use_deprecated) { 930 struct in6_ifaddr *ia6; 931 932 if ((ia6 = ip6_getdstifaddr(m)) && 933 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 934 INP_UNLOCK(inp); 935 tp = NULL; 936 rstreason = BANDLIM_RST_OPENPORT; 937 goto dropwithreset; 938 } 939 } 940 #endif 941 /* 942 * If it is from this socket, drop it, it must be forged. 943 * Don't bother responding if the destination was a broadcast. 944 */ 945 if (th->th_dport == th->th_sport) { 946 if (isipv6) { 947 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 948 &ip6->ip6_src)) 949 goto drop; 950 } else { 951 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 952 goto drop; 953 } 954 } 955 /* 956 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 957 * 958 * Note that it is quite possible to receive unicast 959 * link-layer packets with a broadcast IP address. Use 960 * in_broadcast() to find them. 961 */ 962 if (m->m_flags & (M_BCAST|M_MCAST)) 963 goto drop; 964 if (isipv6) { 965 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 966 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 967 goto drop; 968 } else { 969 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 970 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 971 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 972 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 973 goto drop; 974 } 975 /* 976 * SYN appears to be valid; create compressed TCP state 977 * for syncache, or perform t/tcp connection. 978 */ 979 if (so->so_qlen <= so->so_qlimit) { 980 #ifdef TCPDEBUG 981 if (so->so_options & SO_DEBUG) 982 tcp_trace(TA_INPUT, ostate, tp, 983 (void *)tcp_saveipgen, &tcp_savetcp, 0); 984 #endif 985 tcp_dooptions(&to, optp, optlen, TO_SYN); 986 if (!syncache_add(&inc, &to, th, inp, &so, m)) 987 goto drop; /* XXX: does not happen */ 988 if (so == NULL) { 989 /* 990 * Entry added to syncache, mbuf used to 991 * send SYN,ACK packet. Everything unlocked 992 * already. 993 */ 994 return; 995 } 996 panic("T/TCP not supported at the moment"); 997 #if 0 /* T/TCP */ 998 /* 999 * Segment passed TAO tests. 1000 * XXX: Can't happen at the moment. 1001 */ 1002 INP_UNLOCK(inp); 1003 inp = sotoinpcb(so); 1004 INP_LOCK(inp); 1005 tp = intotcpcb(inp); 1006 tp->t_starttime = ticks; 1007 tp->t_state = TCPS_ESTABLISHED; 1008 1009 /* 1010 * T/TCP logic: 1011 * If there is a FIN or if there is data, then 1012 * delay SYN,ACK(SYN) in the hope of piggy-backing 1013 * it on a response segment. Otherwise must send 1014 * ACK now in case the other side is slow starting. 1015 */ 1016 if (thflags & TH_FIN || tlen != 0) 1017 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1018 else 1019 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1020 tiwin = th->th_win << tp->snd_scale; 1021 tcpstat.tcps_connects++; 1022 soisconnected(so); 1023 goto trimthenstep6; 1024 #endif /* T/TCP */ 1025 } 1026 goto drop; 1027 } 1028 after_listen: 1029 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1030 INP_LOCK_ASSERT(inp); 1031 1032 /* Syncache takes care of sockets in the listen state. */ 1033 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN")); 1034 1035 /* 1036 * This is the second part of the MSS DoS prevention code (after 1037 * minmss on the sending side) and it deals with too many too small 1038 * tcp packets in a too short timeframe (1 second). 1039 * 1040 * For every full second we count the number of received packets 1041 * and bytes. If we get a lot of packets per second for this connection 1042 * (tcp_minmssoverload) we take a closer look at it and compute the 1043 * average packet size for the past second. If that is less than 1044 * tcp_minmss we get too many packets with very small payload which 1045 * is not good and burdens our system (and every packet generates 1046 * a wakeup to the process connected to our socket). We can reasonable 1047 * expect this to be small packet DoS attack to exhaust our CPU 1048 * cycles. 1049 * 1050 * Care has to be taken for the minimum packet overload value. This 1051 * value defines the minimum number of packets per second before we 1052 * start to worry. This must not be too low to avoid killing for 1053 * example interactive connections with many small packets like 1054 * telnet or SSH. 1055 * 1056 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables 1057 * this check. 1058 * 1059 * Account for packet if payload packet, skip over ACK, etc. 1060 */ 1061 if (tcp_minmss && tcp_minmssoverload && 1062 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1063 if ((unsigned int)(tp->rcv_second - ticks) < hz) { 1064 tp->rcv_pps++; 1065 tp->rcv_byps += tlen + off; 1066 if (tp->rcv_pps > tcp_minmssoverload) { 1067 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1068 printf("too many small tcp packets from " 1069 "%s:%u, av. %lubyte/packet, " 1070 "dropping connection\n", 1071 #ifdef INET6 1072 isipv6 ? 1073 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1074 #endif 1075 inet_ntoa(inp->inp_inc.inc_faddr), 1076 inp->inp_inc.inc_fport, 1077 tp->rcv_byps / tp->rcv_pps); 1078 KASSERT(headlocked, ("tcp_input: " 1079 "after_listen: tcp_drop: head " 1080 "not locked")); 1081 tp = tcp_drop(tp, ECONNRESET); 1082 tcpstat.tcps_minmssdrops++; 1083 goto drop; 1084 } 1085 } 1086 } else { 1087 tp->rcv_second = ticks + hz; 1088 tp->rcv_pps = 1; 1089 tp->rcv_byps = tlen + off; 1090 } 1091 } 1092 1093 /* 1094 * Segment received on connection. 1095 * Reset idle time and keep-alive timer. 1096 */ 1097 tp->t_rcvtime = ticks; 1098 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1099 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1100 1101 /* 1102 * Unscale the window into a 32-bit value. 1103 * This value is bogus for the TCPS_SYN_SENT state 1104 * and is overwritten later. 1105 */ 1106 tiwin = th->th_win << tp->snd_scale; 1107 1108 /* 1109 * Parse options on any incoming segment. 1110 */ 1111 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) ? TO_SYN : 0); 1112 1113 /* 1114 * If echoed timestamp is later than the current time, 1115 * fall back to non RFC1323 RTT calculation. Normalize 1116 * timestamp if syncookies were used when this connection 1117 * was established. 1118 */ 1119 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1120 to.to_tsecr =- tp->ts_offset; 1121 if (TSTMP_GT(to.to_tsecr, ticks)) 1122 to.to_tsecr = 0; 1123 } 1124 1125 /* 1126 * Process options only when we get SYN/ACK back. The SYN case 1127 * for incoming connections is handled in tcp_syncache. 1128 * XXX this is traditional behavior, may need to be cleaned up. 1129 */ 1130 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1131 if ((to.to_flags & TOF_SCALE) && 1132 (tp->t_flags & TF_REQ_SCALE)) { 1133 tp->t_flags |= TF_RCVD_SCALE; 1134 tp->snd_scale = to.to_requested_s_scale; 1135 tp->snd_wnd = th->th_win << tp->snd_scale; 1136 tiwin = tp->snd_wnd; 1137 } 1138 if (to.to_flags & TOF_TS) { 1139 tp->t_flags |= TF_RCVD_TSTMP; 1140 tp->ts_recent = to.to_tsval; 1141 tp->ts_recent_age = ticks; 1142 } 1143 if (to.to_flags & TOF_MSS) 1144 tcp_mss(tp, to.to_mss); 1145 if (tp->sack_enable) { 1146 if (!(to.to_flags & TOF_SACK)) 1147 tp->sack_enable = 0; 1148 else 1149 tp->t_flags |= TF_SACK_PERMIT; 1150 } 1151 1152 } 1153 1154 /* 1155 * Header prediction: check for the two common cases 1156 * of a uni-directional data xfer. If the packet has 1157 * no control flags, is in-sequence, the window didn't 1158 * change and we're not retransmitting, it's a 1159 * candidate. If the length is zero and the ack moved 1160 * forward, we're the sender side of the xfer. Just 1161 * free the data acked & wake any higher level process 1162 * that was blocked waiting for space. If the length 1163 * is non-zero and the ack didn't move, we're the 1164 * receiver side. If we're getting packets in-order 1165 * (the reassembly queue is empty), add the data to 1166 * the socket buffer and note that we need a delayed ack. 1167 * Make sure that the hidden state-flags are also off. 1168 * Since we check for TCPS_ESTABLISHED above, it can only 1169 * be TH_NEEDSYN. 1170 */ 1171 if (tp->t_state == TCPS_ESTABLISHED && 1172 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1173 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1174 ((to.to_flags & TOF_TS) == 0 || 1175 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1176 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && 1177 tp->snd_nxt == tp->snd_max) { 1178 1179 /* 1180 * If last ACK falls within this segment's sequence numbers, 1181 * record the timestamp. 1182 * NOTE that the test is modified according to the latest 1183 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1184 */ 1185 if ((to.to_flags & TOF_TS) != 0 && 1186 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1187 tp->ts_recent_age = ticks; 1188 tp->ts_recent = to.to_tsval; 1189 } 1190 1191 if (tlen == 0) { 1192 if (SEQ_GT(th->th_ack, tp->snd_una) && 1193 SEQ_LEQ(th->th_ack, tp->snd_max) && 1194 tp->snd_cwnd >= tp->snd_wnd && 1195 ((!tcp_do_newreno && !tp->sack_enable && 1196 tp->t_dupacks < tcprexmtthresh) || 1197 ((tcp_do_newreno || tp->sack_enable) && 1198 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0 && 1199 TAILQ_EMPTY(&tp->snd_holes)))) { 1200 KASSERT(headlocked, ("headlocked")); 1201 INP_INFO_WUNLOCK(&tcbinfo); 1202 headlocked = 0; 1203 /* 1204 * this is a pure ack for outstanding data. 1205 */ 1206 ++tcpstat.tcps_predack; 1207 /* 1208 * "bad retransmit" recovery 1209 */ 1210 if (tp->t_rxtshift == 1 && 1211 ticks < tp->t_badrxtwin) { 1212 ++tcpstat.tcps_sndrexmitbad; 1213 tp->snd_cwnd = tp->snd_cwnd_prev; 1214 tp->snd_ssthresh = 1215 tp->snd_ssthresh_prev; 1216 tp->snd_recover = tp->snd_recover_prev; 1217 if (tp->t_flags & TF_WASFRECOVERY) 1218 ENTER_FASTRECOVERY(tp); 1219 tp->snd_nxt = tp->snd_max; 1220 tp->t_badrxtwin = 0; 1221 } 1222 1223 /* 1224 * Recalculate the transmit timer / rtt. 1225 * 1226 * Some boxes send broken timestamp replies 1227 * during the SYN+ACK phase, ignore 1228 * timestamps of 0 or we could calculate a 1229 * huge RTT and blow up the retransmit timer. 1230 */ 1231 if ((to.to_flags & TOF_TS) != 0 && 1232 to.to_tsecr) { 1233 if (!tp->t_rttlow || 1234 tp->t_rttlow > ticks - to.to_tsecr) 1235 tp->t_rttlow = ticks - to.to_tsecr; 1236 tcp_xmit_timer(tp, 1237 ticks - to.to_tsecr + 1); 1238 } else if (tp->t_rtttime && 1239 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1240 if (!tp->t_rttlow || 1241 tp->t_rttlow > ticks - tp->t_rtttime) 1242 tp->t_rttlow = ticks - tp->t_rtttime; 1243 tcp_xmit_timer(tp, 1244 ticks - tp->t_rtttime); 1245 } 1246 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1247 acked = th->th_ack - tp->snd_una; 1248 tcpstat.tcps_rcvackpack++; 1249 tcpstat.tcps_rcvackbyte += acked; 1250 sbdrop(&so->so_snd, acked); 1251 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1252 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1253 tp->snd_recover = th->th_ack - 1; 1254 tp->snd_una = th->th_ack; 1255 /* 1256 * pull snd_wl2 up to prevent seq wrap relative 1257 * to th_ack. 1258 */ 1259 tp->snd_wl2 = th->th_ack; 1260 tp->t_dupacks = 0; 1261 m_freem(m); 1262 ND6_HINT(tp); /* some progress has been done */ 1263 1264 /* 1265 * If all outstanding data are acked, stop 1266 * retransmit timer, otherwise restart timer 1267 * using current (possibly backed-off) value. 1268 * If process is waiting for space, 1269 * wakeup/selwakeup/signal. If data 1270 * are ready to send, let tcp_output 1271 * decide between more output or persist. 1272 1273 #ifdef TCPDEBUG 1274 if (so->so_options & SO_DEBUG) 1275 tcp_trace(TA_INPUT, ostate, tp, 1276 (void *)tcp_saveipgen, 1277 &tcp_savetcp, 0); 1278 #endif 1279 */ 1280 if (tp->snd_una == tp->snd_max) 1281 callout_stop(tp->tt_rexmt); 1282 else if (!callout_active(tp->tt_persist)) 1283 callout_reset(tp->tt_rexmt, 1284 tp->t_rxtcur, 1285 tcp_timer_rexmt, tp); 1286 1287 sowwakeup(so); 1288 if (so->so_snd.sb_cc) 1289 (void) tcp_output(tp); 1290 goto check_delack; 1291 } 1292 } else if (th->th_ack == tp->snd_una && 1293 LIST_EMPTY(&tp->t_segq) && 1294 tlen <= sbspace(&so->so_rcv)) { 1295 KASSERT(headlocked, ("headlocked")); 1296 INP_INFO_WUNLOCK(&tcbinfo); 1297 headlocked = 0; 1298 /* 1299 * this is a pure, in-sequence data packet 1300 * with nothing on the reassembly queue and 1301 * we have enough buffer space to take it. 1302 */ 1303 /* Clean receiver SACK report if present */ 1304 if (tp->sack_enable && tp->rcv_numsacks) 1305 tcp_clean_sackreport(tp); 1306 ++tcpstat.tcps_preddat; 1307 tp->rcv_nxt += tlen; 1308 /* 1309 * Pull snd_wl1 up to prevent seq wrap relative to 1310 * th_seq. 1311 */ 1312 tp->snd_wl1 = th->th_seq; 1313 /* 1314 * Pull rcv_up up to prevent seq wrap relative to 1315 * rcv_nxt. 1316 */ 1317 tp->rcv_up = tp->rcv_nxt; 1318 tcpstat.tcps_rcvpack++; 1319 tcpstat.tcps_rcvbyte += tlen; 1320 ND6_HINT(tp); /* some progress has been done */ 1321 /* 1322 #ifdef TCPDEBUG 1323 if (so->so_options & SO_DEBUG) 1324 tcp_trace(TA_INPUT, ostate, tp, 1325 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1326 #endif 1327 * Add data to socket buffer. 1328 */ 1329 SOCKBUF_LOCK(&so->so_rcv); 1330 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1331 m_freem(m); 1332 } else { 1333 m_adj(m, drop_hdrlen); /* delayed header drop */ 1334 sbappendstream_locked(&so->so_rcv, m); 1335 } 1336 sorwakeup_locked(so); 1337 if (DELAY_ACK(tp)) { 1338 tp->t_flags |= TF_DELACK; 1339 } else { 1340 tp->t_flags |= TF_ACKNOW; 1341 tcp_output(tp); 1342 } 1343 goto check_delack; 1344 } 1345 } 1346 1347 /* 1348 * Calculate amount of space in receive window, 1349 * and then do TCP input processing. 1350 * Receive window is amount of space in rcv queue, 1351 * but not less than advertised window. 1352 */ 1353 { int win; 1354 1355 win = sbspace(&so->so_rcv); 1356 if (win < 0) 1357 win = 0; 1358 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1359 } 1360 1361 switch (tp->t_state) { 1362 1363 /* 1364 * If the state is SYN_RECEIVED: 1365 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1366 */ 1367 case TCPS_SYN_RECEIVED: 1368 if ((thflags & TH_ACK) && 1369 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1370 SEQ_GT(th->th_ack, tp->snd_max))) { 1371 rstreason = BANDLIM_RST_OPENPORT; 1372 goto dropwithreset; 1373 } 1374 break; 1375 1376 /* 1377 * If the state is SYN_SENT: 1378 * if seg contains an ACK, but not for our SYN, drop the input. 1379 * if seg contains a RST, then drop the connection. 1380 * if seg does not contain SYN, then drop it. 1381 * Otherwise this is an acceptable SYN segment 1382 * initialize tp->rcv_nxt and tp->irs 1383 * if seg contains ack then advance tp->snd_una 1384 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1385 * arrange for segment to be acked (eventually) 1386 * continue processing rest of data/controls, beginning with URG 1387 */ 1388 case TCPS_SYN_SENT: 1389 if ((thflags & TH_ACK) && 1390 (SEQ_LEQ(th->th_ack, tp->iss) || 1391 SEQ_GT(th->th_ack, tp->snd_max))) { 1392 rstreason = BANDLIM_UNLIMITED; 1393 goto dropwithreset; 1394 } 1395 if (thflags & TH_RST) { 1396 if (thflags & TH_ACK) { 1397 KASSERT(headlocked, ("tcp_input: after_listen" 1398 ": tcp_drop.2: head not locked")); 1399 tp = tcp_drop(tp, ECONNREFUSED); 1400 } 1401 goto drop; 1402 } 1403 if ((thflags & TH_SYN) == 0) 1404 goto drop; 1405 1406 /* Initial send window, already scaled. */ 1407 tp->snd_wnd = th->th_win; 1408 1409 tp->irs = th->th_seq; 1410 tcp_rcvseqinit(tp); 1411 if (thflags & TH_ACK) { 1412 tcpstat.tcps_connects++; 1413 soisconnected(so); 1414 #ifdef MAC 1415 SOCK_LOCK(so); 1416 mac_set_socket_peer_from_mbuf(m, so); 1417 SOCK_UNLOCK(so); 1418 #endif 1419 /* Do window scaling on this connection? */ 1420 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1421 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1422 tp->rcv_scale = tp->request_r_scale; 1423 } 1424 tp->rcv_adv += tp->rcv_wnd; 1425 tp->snd_una++; /* SYN is acked */ 1426 /* 1427 * If there's data, delay ACK; if there's also a FIN 1428 * ACKNOW will be turned on later. 1429 */ 1430 if (DELAY_ACK(tp) && tlen != 0) 1431 callout_reset(tp->tt_delack, tcp_delacktime, 1432 tcp_timer_delack, tp); 1433 else 1434 tp->t_flags |= TF_ACKNOW; 1435 /* 1436 * Received <SYN,ACK> in SYN_SENT[*] state. 1437 * Transitions: 1438 * SYN_SENT --> ESTABLISHED 1439 * SYN_SENT* --> FIN_WAIT_1 1440 */ 1441 tp->t_starttime = ticks; 1442 if (tp->t_flags & TF_NEEDFIN) { 1443 tp->t_state = TCPS_FIN_WAIT_1; 1444 tp->t_flags &= ~TF_NEEDFIN; 1445 thflags &= ~TH_SYN; 1446 } else { 1447 tp->t_state = TCPS_ESTABLISHED; 1448 callout_reset(tp->tt_keep, tcp_keepidle, 1449 tcp_timer_keep, tp); 1450 } 1451 } else { 1452 /* 1453 * Received initial SYN in SYN-SENT[*] state => 1454 * simultaneous open. If segment contains CC option 1455 * and there is a cached CC, apply TAO test. 1456 * If it succeeds, connection is * half-synchronized. 1457 * Otherwise, do 3-way handshake: 1458 * SYN-SENT -> SYN-RECEIVED 1459 * SYN-SENT* -> SYN-RECEIVED* 1460 * If there was no CC option, clear cached CC value. 1461 */ 1462 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1463 callout_stop(tp->tt_rexmt); 1464 tp->t_state = TCPS_SYN_RECEIVED; 1465 } 1466 1467 #if 0 /* T/TCP */ 1468 trimthenstep6: 1469 #endif 1470 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1471 "locked")); 1472 INP_LOCK_ASSERT(inp); 1473 1474 /* 1475 * Advance th->th_seq to correspond to first data byte. 1476 * If data, trim to stay within window, 1477 * dropping FIN if necessary. 1478 */ 1479 th->th_seq++; 1480 if (tlen > tp->rcv_wnd) { 1481 todrop = tlen - tp->rcv_wnd; 1482 m_adj(m, -todrop); 1483 tlen = tp->rcv_wnd; 1484 thflags &= ~TH_FIN; 1485 tcpstat.tcps_rcvpackafterwin++; 1486 tcpstat.tcps_rcvbyteafterwin += todrop; 1487 } 1488 tp->snd_wl1 = th->th_seq - 1; 1489 tp->rcv_up = th->th_seq; 1490 /* 1491 * Client side of transaction: already sent SYN and data. 1492 * If the remote host used T/TCP to validate the SYN, 1493 * our data will be ACK'd; if so, enter normal data segment 1494 * processing in the middle of step 5, ack processing. 1495 * Otherwise, goto step 6. 1496 */ 1497 if (thflags & TH_ACK) 1498 goto process_ACK; 1499 1500 goto step6; 1501 1502 /* 1503 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1504 * do normal processing. 1505 * 1506 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1507 */ 1508 case TCPS_LAST_ACK: 1509 case TCPS_CLOSING: 1510 case TCPS_TIME_WAIT: 1511 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1512 break; /* continue normal processing */ 1513 } 1514 1515 /* 1516 * States other than LISTEN or SYN_SENT. 1517 * First check the RST flag and sequence number since reset segments 1518 * are exempt from the timestamp and connection count tests. This 1519 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1520 * below which allowed reset segments in half the sequence space 1521 * to fall though and be processed (which gives forged reset 1522 * segments with a random sequence number a 50 percent chance of 1523 * killing a connection). 1524 * Then check timestamp, if present. 1525 * Then check the connection count, if present. 1526 * Then check that at least some bytes of segment are within 1527 * receive window. If segment begins before rcv_nxt, 1528 * drop leading data (and SYN); if nothing left, just ack. 1529 * 1530 * 1531 * If the RST bit is set, check the sequence number to see 1532 * if this is a valid reset segment. 1533 * RFC 793 page 37: 1534 * In all states except SYN-SENT, all reset (RST) segments 1535 * are validated by checking their SEQ-fields. A reset is 1536 * valid if its sequence number is in the window. 1537 * Note: this does not take into account delayed ACKs, so 1538 * we should test against last_ack_sent instead of rcv_nxt. 1539 * The sequence number in the reset segment is normally an 1540 * echo of our outgoing acknowlegement numbers, but some hosts 1541 * send a reset with the sequence number at the rightmost edge 1542 * of our receive window, and we have to handle this case. 1543 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1544 * that brute force RST attacks are possible. To combat this, 1545 * we use a much stricter check while in the ESTABLISHED state, 1546 * only accepting RSTs where the sequence number is equal to 1547 * last_ack_sent. In all other states (the states in which a 1548 * RST is more likely), the more permissive check is used. 1549 * If we have multiple segments in flight, the intial reset 1550 * segment sequence numbers will be to the left of last_ack_sent, 1551 * but they will eventually catch up. 1552 * In any case, it never made sense to trim reset segments to 1553 * fit the receive window since RFC 1122 says: 1554 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1555 * 1556 * A TCP SHOULD allow a received RST segment to include data. 1557 * 1558 * DISCUSSION 1559 * It has been suggested that a RST segment could contain 1560 * ASCII text that encoded and explained the cause of the 1561 * RST. No standard has yet been established for such 1562 * data. 1563 * 1564 * If the reset segment passes the sequence number test examine 1565 * the state: 1566 * SYN_RECEIVED STATE: 1567 * If passive open, return to LISTEN state. 1568 * If active open, inform user that connection was refused. 1569 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1570 * Inform user that connection was reset, and close tcb. 1571 * CLOSING, LAST_ACK STATES: 1572 * Close the tcb. 1573 * TIME_WAIT STATE: 1574 * Drop the segment - see Stevens, vol. 2, p. 964 and 1575 * RFC 1337. 1576 */ 1577 if (thflags & TH_RST) { 1578 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1579 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1580 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1581 switch (tp->t_state) { 1582 1583 case TCPS_SYN_RECEIVED: 1584 so->so_error = ECONNREFUSED; 1585 goto close; 1586 1587 case TCPS_ESTABLISHED: 1588 if (tp->last_ack_sent != th->th_seq && 1589 tcp_insecure_rst == 0) { 1590 tcpstat.tcps_badrst++; 1591 goto drop; 1592 } 1593 case TCPS_FIN_WAIT_1: 1594 case TCPS_FIN_WAIT_2: 1595 case TCPS_CLOSE_WAIT: 1596 so->so_error = ECONNRESET; 1597 close: 1598 tp->t_state = TCPS_CLOSED; 1599 tcpstat.tcps_drops++; 1600 KASSERT(headlocked, ("tcp_input: " 1601 "trimthenstep6: tcp_close: head not " 1602 "locked")); 1603 tp = tcp_close(tp); 1604 break; 1605 1606 case TCPS_CLOSING: 1607 case TCPS_LAST_ACK: 1608 KASSERT(headlocked, ("trimthenstep6: " 1609 "tcp_close.2: head not locked")); 1610 tp = tcp_close(tp); 1611 break; 1612 1613 case TCPS_TIME_WAIT: 1614 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1615 ("timewait")); 1616 break; 1617 } 1618 } 1619 goto drop; 1620 } 1621 1622 /* 1623 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1624 * and it's less than ts_recent, drop it. 1625 */ 1626 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1627 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1628 1629 /* Check to see if ts_recent is over 24 days old. */ 1630 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1631 /* 1632 * Invalidate ts_recent. If this segment updates 1633 * ts_recent, the age will be reset later and ts_recent 1634 * will get a valid value. If it does not, setting 1635 * ts_recent to zero will at least satisfy the 1636 * requirement that zero be placed in the timestamp 1637 * echo reply when ts_recent isn't valid. The 1638 * age isn't reset until we get a valid ts_recent 1639 * because we don't want out-of-order segments to be 1640 * dropped when ts_recent is old. 1641 */ 1642 tp->ts_recent = 0; 1643 } else { 1644 tcpstat.tcps_rcvduppack++; 1645 tcpstat.tcps_rcvdupbyte += tlen; 1646 tcpstat.tcps_pawsdrop++; 1647 if (tlen) 1648 goto dropafterack; 1649 goto drop; 1650 } 1651 } 1652 1653 /* 1654 * In the SYN-RECEIVED state, validate that the packet belongs to 1655 * this connection before trimming the data to fit the receive 1656 * window. Check the sequence number versus IRS since we know 1657 * the sequence numbers haven't wrapped. This is a partial fix 1658 * for the "LAND" DoS attack. 1659 */ 1660 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1661 rstreason = BANDLIM_RST_OPENPORT; 1662 goto dropwithreset; 1663 } 1664 1665 todrop = tp->rcv_nxt - th->th_seq; 1666 if (todrop > 0) { 1667 if (thflags & TH_SYN) { 1668 thflags &= ~TH_SYN; 1669 th->th_seq++; 1670 if (th->th_urp > 1) 1671 th->th_urp--; 1672 else 1673 thflags &= ~TH_URG; 1674 todrop--; 1675 } 1676 /* 1677 * Following if statement from Stevens, vol. 2, p. 960. 1678 */ 1679 if (todrop > tlen 1680 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1681 /* 1682 * Any valid FIN must be to the left of the window. 1683 * At this point the FIN must be a duplicate or out 1684 * of sequence; drop it. 1685 */ 1686 thflags &= ~TH_FIN; 1687 1688 /* 1689 * Send an ACK to resynchronize and drop any data. 1690 * But keep on processing for RST or ACK. 1691 */ 1692 tp->t_flags |= TF_ACKNOW; 1693 todrop = tlen; 1694 tcpstat.tcps_rcvduppack++; 1695 tcpstat.tcps_rcvdupbyte += todrop; 1696 } else { 1697 tcpstat.tcps_rcvpartduppack++; 1698 tcpstat.tcps_rcvpartdupbyte += todrop; 1699 } 1700 drop_hdrlen += todrop; /* drop from the top afterwards */ 1701 th->th_seq += todrop; 1702 tlen -= todrop; 1703 if (th->th_urp > todrop) 1704 th->th_urp -= todrop; 1705 else { 1706 thflags &= ~TH_URG; 1707 th->th_urp = 0; 1708 } 1709 } 1710 1711 /* 1712 * If new data are received on a connection after the 1713 * user processes are gone, then RST the other end. 1714 */ 1715 if ((so->so_state & SS_NOFDREF) && 1716 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1717 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1718 "locked")); 1719 tp = tcp_close(tp); 1720 tcpstat.tcps_rcvafterclose++; 1721 rstreason = BANDLIM_UNLIMITED; 1722 goto dropwithreset; 1723 } 1724 1725 /* 1726 * If segment ends after window, drop trailing data 1727 * (and PUSH and FIN); if nothing left, just ACK. 1728 */ 1729 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1730 if (todrop > 0) { 1731 tcpstat.tcps_rcvpackafterwin++; 1732 if (todrop >= tlen) { 1733 tcpstat.tcps_rcvbyteafterwin += tlen; 1734 /* 1735 * If a new connection request is received 1736 * while in TIME_WAIT, drop the old connection 1737 * and start over if the sequence numbers 1738 * are above the previous ones. 1739 */ 1740 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1741 if (thflags & TH_SYN && 1742 tp->t_state == TCPS_TIME_WAIT && 1743 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1744 KASSERT(headlocked, ("trimthenstep6: " 1745 "tcp_close.4: head not locked")); 1746 tp = tcp_close(tp); 1747 goto findpcb; 1748 } 1749 /* 1750 * If window is closed can only take segments at 1751 * window edge, and have to drop data and PUSH from 1752 * incoming segments. Continue processing, but 1753 * remember to ack. Otherwise, drop segment 1754 * and ack. 1755 */ 1756 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1757 tp->t_flags |= TF_ACKNOW; 1758 tcpstat.tcps_rcvwinprobe++; 1759 } else 1760 goto dropafterack; 1761 } else 1762 tcpstat.tcps_rcvbyteafterwin += todrop; 1763 m_adj(m, -todrop); 1764 tlen -= todrop; 1765 thflags &= ~(TH_PUSH|TH_FIN); 1766 } 1767 1768 /* 1769 * If last ACK falls within this segment's sequence numbers, 1770 * record its timestamp. 1771 * NOTE: 1772 * 1) That the test incorporates suggestions from the latest 1773 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1774 * 2) That updating only on newer timestamps interferes with 1775 * our earlier PAWS tests, so this check should be solely 1776 * predicated on the sequence space of this segment. 1777 * 3) That we modify the segment boundary check to be 1778 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1779 * instead of RFC1323's 1780 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1781 * This modified check allows us to overcome RFC1323's 1782 * limitations as described in Stevens TCP/IP Illustrated 1783 * Vol. 2 p.869. In such cases, we can still calculate the 1784 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1785 */ 1786 if ((to.to_flags & TOF_TS) != 0 && 1787 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1788 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1789 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1790 tp->ts_recent_age = ticks; 1791 tp->ts_recent = to.to_tsval; 1792 } 1793 1794 /* 1795 * If a SYN is in the window, then this is an 1796 * error and we send an RST and drop the connection. 1797 */ 1798 if (thflags & TH_SYN) { 1799 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1800 "head not locked")); 1801 tp = tcp_drop(tp, ECONNRESET); 1802 rstreason = BANDLIM_UNLIMITED; 1803 goto drop; 1804 } 1805 1806 /* 1807 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1808 * flag is on (half-synchronized state), then queue data for 1809 * later processing; else drop segment and return. 1810 */ 1811 if ((thflags & TH_ACK) == 0) { 1812 if (tp->t_state == TCPS_SYN_RECEIVED || 1813 (tp->t_flags & TF_NEEDSYN)) 1814 goto step6; 1815 else if (tp->t_flags & TF_ACKNOW) 1816 goto dropafterack; 1817 else 1818 goto drop; 1819 } 1820 1821 /* 1822 * Ack processing. 1823 */ 1824 switch (tp->t_state) { 1825 1826 /* 1827 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1828 * ESTABLISHED state and continue processing. 1829 * The ACK was checked above. 1830 */ 1831 case TCPS_SYN_RECEIVED: 1832 1833 tcpstat.tcps_connects++; 1834 soisconnected(so); 1835 /* Do window scaling? */ 1836 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1837 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1838 tp->rcv_scale = tp->request_r_scale; 1839 tp->snd_wnd = tiwin; 1840 } 1841 /* 1842 * Make transitions: 1843 * SYN-RECEIVED -> ESTABLISHED 1844 * SYN-RECEIVED* -> FIN-WAIT-1 1845 */ 1846 tp->t_starttime = ticks; 1847 if (tp->t_flags & TF_NEEDFIN) { 1848 tp->t_state = TCPS_FIN_WAIT_1; 1849 tp->t_flags &= ~TF_NEEDFIN; 1850 } else { 1851 tp->t_state = TCPS_ESTABLISHED; 1852 callout_reset(tp->tt_keep, tcp_keepidle, 1853 tcp_timer_keep, tp); 1854 } 1855 /* 1856 * If segment contains data or ACK, will call tcp_reass() 1857 * later; if not, do so now to pass queued data to user. 1858 */ 1859 if (tlen == 0 && (thflags & TH_FIN) == 0) 1860 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1861 (struct mbuf *)0); 1862 tp->snd_wl1 = th->th_seq - 1; 1863 /* FALLTHROUGH */ 1864 1865 /* 1866 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1867 * ACKs. If the ack is in the range 1868 * tp->snd_una < th->th_ack <= tp->snd_max 1869 * then advance tp->snd_una to th->th_ack and drop 1870 * data from the retransmission queue. If this ACK reflects 1871 * more up to date window information we update our window information. 1872 */ 1873 case TCPS_ESTABLISHED: 1874 case TCPS_FIN_WAIT_1: 1875 case TCPS_FIN_WAIT_2: 1876 case TCPS_CLOSE_WAIT: 1877 case TCPS_CLOSING: 1878 case TCPS_LAST_ACK: 1879 case TCPS_TIME_WAIT: 1880 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1881 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1882 tcpstat.tcps_rcvacktoomuch++; 1883 goto dropafterack; 1884 } 1885 if (tp->sack_enable && 1886 (to.to_nsacks > 0 || !TAILQ_EMPTY(&tp->snd_holes))) 1887 tcp_sack_doack(tp, &to, th->th_ack); 1888 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1889 if (tlen == 0 && tiwin == tp->snd_wnd) { 1890 tcpstat.tcps_rcvdupack++; 1891 /* 1892 * If we have outstanding data (other than 1893 * a window probe), this is a completely 1894 * duplicate ack (ie, window info didn't 1895 * change), the ack is the biggest we've 1896 * seen and we've seen exactly our rexmt 1897 * threshhold of them, assume a packet 1898 * has been dropped and retransmit it. 1899 * Kludge snd_nxt & the congestion 1900 * window so we send only this one 1901 * packet. 1902 * 1903 * We know we're losing at the current 1904 * window size so do congestion avoidance 1905 * (set ssthresh to half the current window 1906 * and pull our congestion window back to 1907 * the new ssthresh). 1908 * 1909 * Dup acks mean that packets have left the 1910 * network (they're now cached at the receiver) 1911 * so bump cwnd by the amount in the receiver 1912 * to keep a constant cwnd packets in the 1913 * network. 1914 */ 1915 if (!callout_active(tp->tt_rexmt) || 1916 th->th_ack != tp->snd_una) 1917 tp->t_dupacks = 0; 1918 else if (++tp->t_dupacks > tcprexmtthresh || 1919 ((tcp_do_newreno || tp->sack_enable) && 1920 IN_FASTRECOVERY(tp))) { 1921 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1922 int awnd; 1923 1924 /* 1925 * Compute the amount of data in flight first. 1926 * We can inject new data into the pipe iff 1927 * we have less than 1/2 the original window's 1928 * worth of data in flight. 1929 */ 1930 awnd = (tp->snd_nxt - tp->snd_fack) + 1931 tp->sackhint.sack_bytes_rexmit; 1932 if (awnd < tp->snd_ssthresh) { 1933 tp->snd_cwnd += tp->t_maxseg; 1934 if (tp->snd_cwnd > tp->snd_ssthresh) 1935 tp->snd_cwnd = tp->snd_ssthresh; 1936 } 1937 } else 1938 tp->snd_cwnd += tp->t_maxseg; 1939 (void) tcp_output(tp); 1940 goto drop; 1941 } else if (tp->t_dupacks == tcprexmtthresh) { 1942 tcp_seq onxt = tp->snd_nxt; 1943 u_int win; 1944 1945 /* 1946 * If we're doing sack, check to 1947 * see if we're already in sack 1948 * recovery. If we're not doing sack, 1949 * check to see if we're in newreno 1950 * recovery. 1951 */ 1952 if (tp->sack_enable) { 1953 if (IN_FASTRECOVERY(tp)) { 1954 tp->t_dupacks = 0; 1955 break; 1956 } 1957 } else if (tcp_do_newreno) { 1958 if (SEQ_LEQ(th->th_ack, 1959 tp->snd_recover)) { 1960 tp->t_dupacks = 0; 1961 break; 1962 } 1963 } 1964 win = min(tp->snd_wnd, tp->snd_cwnd) / 1965 2 / tp->t_maxseg; 1966 if (win < 2) 1967 win = 2; 1968 tp->snd_ssthresh = win * tp->t_maxseg; 1969 ENTER_FASTRECOVERY(tp); 1970 tp->snd_recover = tp->snd_max; 1971 callout_stop(tp->tt_rexmt); 1972 tp->t_rtttime = 0; 1973 if (tp->sack_enable) { 1974 tcpstat.tcps_sack_recovery_episode++; 1975 tp->sack_newdata = tp->snd_nxt; 1976 tp->snd_cwnd = tp->t_maxseg; 1977 (void) tcp_output(tp); 1978 goto drop; 1979 } 1980 tp->snd_nxt = th->th_ack; 1981 tp->snd_cwnd = tp->t_maxseg; 1982 (void) tcp_output(tp); 1983 KASSERT(tp->snd_limited <= 2, 1984 ("tp->snd_limited too big")); 1985 tp->snd_cwnd = tp->snd_ssthresh + 1986 tp->t_maxseg * 1987 (tp->t_dupacks - tp->snd_limited); 1988 if (SEQ_GT(onxt, tp->snd_nxt)) 1989 tp->snd_nxt = onxt; 1990 goto drop; 1991 } else if (tcp_do_rfc3042) { 1992 u_long oldcwnd = tp->snd_cwnd; 1993 tcp_seq oldsndmax = tp->snd_max; 1994 u_int sent; 1995 1996 KASSERT(tp->t_dupacks == 1 || 1997 tp->t_dupacks == 2, 1998 ("dupacks not 1 or 2")); 1999 if (tp->t_dupacks == 1) 2000 tp->snd_limited = 0; 2001 tp->snd_cwnd = 2002 (tp->snd_nxt - tp->snd_una) + 2003 (tp->t_dupacks - tp->snd_limited) * 2004 tp->t_maxseg; 2005 (void) tcp_output(tp); 2006 sent = tp->snd_max - oldsndmax; 2007 if (sent > tp->t_maxseg) { 2008 KASSERT((tp->t_dupacks == 2 && 2009 tp->snd_limited == 0) || 2010 (sent == tp->t_maxseg + 1 && 2011 tp->t_flags & TF_SENTFIN), 2012 ("sent too much")); 2013 tp->snd_limited = 2; 2014 } else if (sent > 0) 2015 ++tp->snd_limited; 2016 tp->snd_cwnd = oldcwnd; 2017 goto drop; 2018 } 2019 } else 2020 tp->t_dupacks = 0; 2021 break; 2022 } 2023 2024 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2025 2026 /* 2027 * If the congestion window was inflated to account 2028 * for the other side's cached packets, retract it. 2029 */ 2030 if (tcp_do_newreno || tp->sack_enable) { 2031 if (IN_FASTRECOVERY(tp)) { 2032 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2033 if (tp->sack_enable) 2034 tcp_sack_partialack(tp, th); 2035 else 2036 tcp_newreno_partial_ack(tp, th); 2037 } else { 2038 /* 2039 * Out of fast recovery. 2040 * Window inflation should have left us 2041 * with approximately snd_ssthresh 2042 * outstanding data. 2043 * But in case we would be inclined to 2044 * send a burst, better to do it via 2045 * the slow start mechanism. 2046 */ 2047 if (SEQ_GT(th->th_ack + 2048 tp->snd_ssthresh, 2049 tp->snd_max)) 2050 tp->snd_cwnd = tp->snd_max - 2051 th->th_ack + 2052 tp->t_maxseg; 2053 else 2054 tp->snd_cwnd = tp->snd_ssthresh; 2055 } 2056 } 2057 } else { 2058 if (tp->t_dupacks >= tcprexmtthresh && 2059 tp->snd_cwnd > tp->snd_ssthresh) 2060 tp->snd_cwnd = tp->snd_ssthresh; 2061 } 2062 tp->t_dupacks = 0; 2063 /* 2064 * If we reach this point, ACK is not a duplicate, 2065 * i.e., it ACKs something we sent. 2066 */ 2067 if (tp->t_flags & TF_NEEDSYN) { 2068 /* 2069 * T/TCP: Connection was half-synchronized, and our 2070 * SYN has been ACK'd (so connection is now fully 2071 * synchronized). Go to non-starred state, 2072 * increment snd_una for ACK of SYN, and check if 2073 * we can do window scaling. 2074 */ 2075 tp->t_flags &= ~TF_NEEDSYN; 2076 tp->snd_una++; 2077 /* Do window scaling? */ 2078 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2079 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2080 tp->rcv_scale = tp->request_r_scale; 2081 /* Send window already scaled. */ 2082 } 2083 } 2084 2085 process_ACK: 2086 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2087 "locked")); 2088 INP_LOCK_ASSERT(inp); 2089 2090 acked = th->th_ack - tp->snd_una; 2091 tcpstat.tcps_rcvackpack++; 2092 tcpstat.tcps_rcvackbyte += acked; 2093 2094 /* 2095 * If we just performed our first retransmit, and the ACK 2096 * arrives within our recovery window, then it was a mistake 2097 * to do the retransmit in the first place. Recover our 2098 * original cwnd and ssthresh, and proceed to transmit where 2099 * we left off. 2100 */ 2101 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2102 ++tcpstat.tcps_sndrexmitbad; 2103 tp->snd_cwnd = tp->snd_cwnd_prev; 2104 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2105 tp->snd_recover = tp->snd_recover_prev; 2106 if (tp->t_flags & TF_WASFRECOVERY) 2107 ENTER_FASTRECOVERY(tp); 2108 tp->snd_nxt = tp->snd_max; 2109 tp->t_badrxtwin = 0; /* XXX probably not required */ 2110 } 2111 2112 /* 2113 * If we have a timestamp reply, update smoothed 2114 * round trip time. If no timestamp is present but 2115 * transmit timer is running and timed sequence 2116 * number was acked, update smoothed round trip time. 2117 * Since we now have an rtt measurement, cancel the 2118 * timer backoff (cf., Phil Karn's retransmit alg.). 2119 * Recompute the initial retransmit timer. 2120 * 2121 * Some boxes send broken timestamp replies 2122 * during the SYN+ACK phase, ignore 2123 * timestamps of 0 or we could calculate a 2124 * huge RTT and blow up the retransmit timer. 2125 */ 2126 if ((to.to_flags & TOF_TS) != 0 && 2127 to.to_tsecr) { 2128 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 2129 tp->t_rttlow = ticks - to.to_tsecr; 2130 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2131 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2132 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2133 tp->t_rttlow = ticks - tp->t_rtttime; 2134 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2135 } 2136 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2137 2138 /* 2139 * If all outstanding data is acked, stop retransmit 2140 * timer and remember to restart (more output or persist). 2141 * If there is more data to be acked, restart retransmit 2142 * timer, using current (possibly backed-off) value. 2143 */ 2144 if (th->th_ack == tp->snd_max) { 2145 callout_stop(tp->tt_rexmt); 2146 needoutput = 1; 2147 } else if (!callout_active(tp->tt_persist)) 2148 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2149 tcp_timer_rexmt, tp); 2150 2151 /* 2152 * If no data (only SYN) was ACK'd, 2153 * skip rest of ACK processing. 2154 */ 2155 if (acked == 0) 2156 goto step6; 2157 2158 /* 2159 * When new data is acked, open the congestion window. 2160 * If the window gives us less than ssthresh packets 2161 * in flight, open exponentially (maxseg per packet). 2162 * Otherwise open linearly: maxseg per window 2163 * (maxseg^2 / cwnd per packet). 2164 */ 2165 if ((!tcp_do_newreno && !tp->sack_enable) || 2166 !IN_FASTRECOVERY(tp)) { 2167 register u_int cw = tp->snd_cwnd; 2168 register u_int incr = tp->t_maxseg; 2169 if (cw > tp->snd_ssthresh) 2170 incr = incr * incr / cw; 2171 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2172 } 2173 SOCKBUF_LOCK(&so->so_snd); 2174 if (acked > so->so_snd.sb_cc) { 2175 tp->snd_wnd -= so->so_snd.sb_cc; 2176 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2177 ourfinisacked = 1; 2178 } else { 2179 sbdrop_locked(&so->so_snd, acked); 2180 tp->snd_wnd -= acked; 2181 ourfinisacked = 0; 2182 } 2183 sowwakeup_locked(so); 2184 /* detect una wraparound */ 2185 if ((tcp_do_newreno || tp->sack_enable) && 2186 !IN_FASTRECOVERY(tp) && 2187 SEQ_GT(tp->snd_una, tp->snd_recover) && 2188 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2189 tp->snd_recover = th->th_ack - 1; 2190 if ((tcp_do_newreno || tp->sack_enable) && 2191 IN_FASTRECOVERY(tp) && 2192 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2193 EXIT_FASTRECOVERY(tp); 2194 tp->snd_una = th->th_ack; 2195 if (tp->sack_enable) { 2196 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2197 tp->snd_recover = tp->snd_una; 2198 } 2199 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2200 tp->snd_nxt = tp->snd_una; 2201 2202 switch (tp->t_state) { 2203 2204 /* 2205 * In FIN_WAIT_1 STATE in addition to the processing 2206 * for the ESTABLISHED state if our FIN is now acknowledged 2207 * then enter FIN_WAIT_2. 2208 */ 2209 case TCPS_FIN_WAIT_1: 2210 if (ourfinisacked) { 2211 /* 2212 * If we can't receive any more 2213 * data, then closing user can proceed. 2214 * Starting the timer is contrary to the 2215 * specification, but if we don't get a FIN 2216 * we'll hang forever. 2217 */ 2218 /* XXXjl 2219 * we should release the tp also, and use a 2220 * compressed state. 2221 */ 2222 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2223 soisdisconnected(so); 2224 callout_reset(tp->tt_2msl, tcp_maxidle, 2225 tcp_timer_2msl, tp); 2226 } 2227 tp->t_state = TCPS_FIN_WAIT_2; 2228 } 2229 break; 2230 2231 /* 2232 * In CLOSING STATE in addition to the processing for 2233 * the ESTABLISHED state if the ACK acknowledges our FIN 2234 * then enter the TIME-WAIT state, otherwise ignore 2235 * the segment. 2236 */ 2237 case TCPS_CLOSING: 2238 if (ourfinisacked) { 2239 KASSERT(headlocked, ("tcp_input: process_ACK: " 2240 "head not locked")); 2241 tcp_twstart(tp); 2242 INP_INFO_WUNLOCK(&tcbinfo); 2243 m_freem(m); 2244 return; 2245 } 2246 break; 2247 2248 /* 2249 * In LAST_ACK, we may still be waiting for data to drain 2250 * and/or to be acked, as well as for the ack of our FIN. 2251 * If our FIN is now acknowledged, delete the TCB, 2252 * enter the closed state and return. 2253 */ 2254 case TCPS_LAST_ACK: 2255 if (ourfinisacked) { 2256 KASSERT(headlocked, ("tcp_input: process_ACK:" 2257 " tcp_close: head not locked")); 2258 tp = tcp_close(tp); 2259 goto drop; 2260 } 2261 break; 2262 2263 /* 2264 * In TIME_WAIT state the only thing that should arrive 2265 * is a retransmission of the remote FIN. Acknowledge 2266 * it and restart the finack timer. 2267 */ 2268 case TCPS_TIME_WAIT: 2269 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2270 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2271 tcp_timer_2msl, tp); 2272 goto dropafterack; 2273 } 2274 } 2275 2276 step6: 2277 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2278 INP_LOCK_ASSERT(inp); 2279 2280 /* 2281 * Update window information. 2282 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2283 */ 2284 if ((thflags & TH_ACK) && 2285 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2286 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2287 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2288 /* keep track of pure window updates */ 2289 if (tlen == 0 && 2290 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2291 tcpstat.tcps_rcvwinupd++; 2292 tp->snd_wnd = tiwin; 2293 tp->snd_wl1 = th->th_seq; 2294 tp->snd_wl2 = th->th_ack; 2295 if (tp->snd_wnd > tp->max_sndwnd) 2296 tp->max_sndwnd = tp->snd_wnd; 2297 needoutput = 1; 2298 } 2299 2300 /* 2301 * Process segments with URG. 2302 */ 2303 if ((thflags & TH_URG) && th->th_urp && 2304 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2305 /* 2306 * This is a kludge, but if we receive and accept 2307 * random urgent pointers, we'll crash in 2308 * soreceive. It's hard to imagine someone 2309 * actually wanting to send this much urgent data. 2310 */ 2311 SOCKBUF_LOCK(&so->so_rcv); 2312 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2313 th->th_urp = 0; /* XXX */ 2314 thflags &= ~TH_URG; /* XXX */ 2315 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2316 goto dodata; /* XXX */ 2317 } 2318 /* 2319 * If this segment advances the known urgent pointer, 2320 * then mark the data stream. This should not happen 2321 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2322 * a FIN has been received from the remote side. 2323 * In these states we ignore the URG. 2324 * 2325 * According to RFC961 (Assigned Protocols), 2326 * the urgent pointer points to the last octet 2327 * of urgent data. We continue, however, 2328 * to consider it to indicate the first octet 2329 * of data past the urgent section as the original 2330 * spec states (in one of two places). 2331 */ 2332 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2333 tp->rcv_up = th->th_seq + th->th_urp; 2334 so->so_oobmark = so->so_rcv.sb_cc + 2335 (tp->rcv_up - tp->rcv_nxt) - 1; 2336 if (so->so_oobmark == 0) 2337 so->so_rcv.sb_state |= SBS_RCVATMARK; 2338 sohasoutofband(so); 2339 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2340 } 2341 SOCKBUF_UNLOCK(&so->so_rcv); 2342 /* 2343 * Remove out of band data so doesn't get presented to user. 2344 * This can happen independent of advancing the URG pointer, 2345 * but if two URG's are pending at once, some out-of-band 2346 * data may creep in... ick. 2347 */ 2348 if (th->th_urp <= (u_long)tlen && 2349 !(so->so_options & SO_OOBINLINE)) { 2350 /* hdr drop is delayed */ 2351 tcp_pulloutofband(so, th, m, drop_hdrlen); 2352 } 2353 } else { 2354 /* 2355 * If no out of band data is expected, 2356 * pull receive urgent pointer along 2357 * with the receive window. 2358 */ 2359 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2360 tp->rcv_up = tp->rcv_nxt; 2361 } 2362 dodata: /* XXX */ 2363 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2364 INP_LOCK_ASSERT(inp); 2365 2366 /* 2367 * Process the segment text, merging it into the TCP sequencing queue, 2368 * and arranging for acknowledgment of receipt if necessary. 2369 * This process logically involves adjusting tp->rcv_wnd as data 2370 * is presented to the user (this happens in tcp_usrreq.c, 2371 * case PRU_RCVD). If a FIN has already been received on this 2372 * connection then we just ignore the text. 2373 */ 2374 if ((tlen || (thflags & TH_FIN)) && 2375 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2376 tcp_seq save_start = th->th_seq; 2377 tcp_seq save_end = th->th_seq + tlen; 2378 m_adj(m, drop_hdrlen); /* delayed header drop */ 2379 /* 2380 * Insert segment which includes th into TCP reassembly queue 2381 * with control block tp. Set thflags to whether reassembly now 2382 * includes a segment with FIN. This handles the common case 2383 * inline (segment is the next to be received on an established 2384 * connection, and the queue is empty), avoiding linkage into 2385 * and removal from the queue and repetition of various 2386 * conversions. 2387 * Set DELACK for segments received in order, but ack 2388 * immediately when segments are out of order (so 2389 * fast retransmit can work). 2390 */ 2391 if (th->th_seq == tp->rcv_nxt && 2392 LIST_EMPTY(&tp->t_segq) && 2393 TCPS_HAVEESTABLISHED(tp->t_state)) { 2394 if (DELAY_ACK(tp)) 2395 tp->t_flags |= TF_DELACK; 2396 else 2397 tp->t_flags |= TF_ACKNOW; 2398 tp->rcv_nxt += tlen; 2399 thflags = th->th_flags & TH_FIN; 2400 tcpstat.tcps_rcvpack++; 2401 tcpstat.tcps_rcvbyte += tlen; 2402 ND6_HINT(tp); 2403 SOCKBUF_LOCK(&so->so_rcv); 2404 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2405 m_freem(m); 2406 else 2407 sbappendstream_locked(&so->so_rcv, m); 2408 sorwakeup_locked(so); 2409 } else { 2410 thflags = tcp_reass(tp, th, &tlen, m); 2411 tp->t_flags |= TF_ACKNOW; 2412 } 2413 if (tlen > 0 && tp->sack_enable) 2414 tcp_update_sack_list(tp, save_start, save_end); 2415 /* 2416 * Note the amount of data that peer has sent into 2417 * our window, in order to estimate the sender's 2418 * buffer size. 2419 */ 2420 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2421 } else { 2422 m_freem(m); 2423 thflags &= ~TH_FIN; 2424 } 2425 2426 /* 2427 * If FIN is received ACK the FIN and let the user know 2428 * that the connection is closing. 2429 */ 2430 if (thflags & TH_FIN) { 2431 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2432 socantrcvmore(so); 2433 /* 2434 * If connection is half-synchronized 2435 * (ie NEEDSYN flag on) then delay ACK, 2436 * so it may be piggybacked when SYN is sent. 2437 * Otherwise, since we received a FIN then no 2438 * more input can be expected, send ACK now. 2439 */ 2440 if (tp->t_flags & TF_NEEDSYN) 2441 tp->t_flags |= TF_DELACK; 2442 else 2443 tp->t_flags |= TF_ACKNOW; 2444 tp->rcv_nxt++; 2445 } 2446 switch (tp->t_state) { 2447 2448 /* 2449 * In SYN_RECEIVED and ESTABLISHED STATES 2450 * enter the CLOSE_WAIT state. 2451 */ 2452 case TCPS_SYN_RECEIVED: 2453 tp->t_starttime = ticks; 2454 /*FALLTHROUGH*/ 2455 case TCPS_ESTABLISHED: 2456 tp->t_state = TCPS_CLOSE_WAIT; 2457 break; 2458 2459 /* 2460 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2461 * enter the CLOSING state. 2462 */ 2463 case TCPS_FIN_WAIT_1: 2464 tp->t_state = TCPS_CLOSING; 2465 break; 2466 2467 /* 2468 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2469 * starting the time-wait timer, turning off the other 2470 * standard timers. 2471 */ 2472 case TCPS_FIN_WAIT_2: 2473 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2474 "TCP_FIN_WAIT_2: head not locked")); 2475 tcp_twstart(tp); 2476 INP_INFO_WUNLOCK(&tcbinfo); 2477 return; 2478 2479 /* 2480 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2481 */ 2482 case TCPS_TIME_WAIT: 2483 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2484 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2485 tcp_timer_2msl, tp); 2486 break; 2487 } 2488 } 2489 INP_INFO_WUNLOCK(&tcbinfo); 2490 headlocked = 0; 2491 #ifdef TCPDEBUG 2492 if (so->so_options & SO_DEBUG) 2493 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2494 &tcp_savetcp, 0); 2495 #endif 2496 2497 /* 2498 * Return any desired output. 2499 */ 2500 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2501 (void) tcp_output(tp); 2502 2503 check_delack: 2504 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2505 INP_LOCK_ASSERT(inp); 2506 if (tp->t_flags & TF_DELACK) { 2507 tp->t_flags &= ~TF_DELACK; 2508 callout_reset(tp->tt_delack, tcp_delacktime, 2509 tcp_timer_delack, tp); 2510 } 2511 INP_UNLOCK(inp); 2512 return; 2513 2514 dropafterack: 2515 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2516 /* 2517 * Generate an ACK dropping incoming segment if it occupies 2518 * sequence space, where the ACK reflects our state. 2519 * 2520 * We can now skip the test for the RST flag since all 2521 * paths to this code happen after packets containing 2522 * RST have been dropped. 2523 * 2524 * In the SYN-RECEIVED state, don't send an ACK unless the 2525 * segment we received passes the SYN-RECEIVED ACK test. 2526 * If it fails send a RST. This breaks the loop in the 2527 * "LAND" DoS attack, and also prevents an ACK storm 2528 * between two listening ports that have been sent forged 2529 * SYN segments, each with the source address of the other. 2530 */ 2531 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2532 (SEQ_GT(tp->snd_una, th->th_ack) || 2533 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2534 rstreason = BANDLIM_RST_OPENPORT; 2535 goto dropwithreset; 2536 } 2537 #ifdef TCPDEBUG 2538 if (so->so_options & SO_DEBUG) 2539 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2540 &tcp_savetcp, 0); 2541 #endif 2542 KASSERT(headlocked, ("headlocked should be 1")); 2543 INP_INFO_WUNLOCK(&tcbinfo); 2544 tp->t_flags |= TF_ACKNOW; 2545 (void) tcp_output(tp); 2546 INP_UNLOCK(inp); 2547 m_freem(m); 2548 return; 2549 2550 dropwithreset: 2551 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2552 /* 2553 * Generate a RST, dropping incoming segment. 2554 * Make ACK acceptable to originator of segment. 2555 * Don't bother to respond if destination was broadcast/multicast. 2556 */ 2557 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2558 goto drop; 2559 if (isipv6) { 2560 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2561 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2562 goto drop; 2563 } else { 2564 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2565 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2566 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2567 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2568 goto drop; 2569 } 2570 /* IPv6 anycast check is done at tcp6_input() */ 2571 2572 /* 2573 * Perform bandwidth limiting. 2574 */ 2575 if (badport_bandlim(rstreason) < 0) 2576 goto drop; 2577 2578 #ifdef TCPDEBUG 2579 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2580 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2581 &tcp_savetcp, 0); 2582 #endif 2583 2584 if (thflags & TH_ACK) 2585 /* mtod() below is safe as long as hdr dropping is delayed */ 2586 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2587 TH_RST); 2588 else { 2589 if (thflags & TH_SYN) 2590 tlen++; 2591 /* mtod() below is safe as long as hdr dropping is delayed */ 2592 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2593 (tcp_seq)0, TH_RST|TH_ACK); 2594 } 2595 2596 if (tp != NULL) 2597 INP_UNLOCK(inp); 2598 if (headlocked) 2599 INP_INFO_WUNLOCK(&tcbinfo); 2600 return; 2601 2602 drop: 2603 /* 2604 * Drop space held by incoming segment and return. 2605 */ 2606 #ifdef TCPDEBUG 2607 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2608 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2609 &tcp_savetcp, 0); 2610 #endif 2611 if (tp != NULL) 2612 INP_UNLOCK(inp); 2613 if (headlocked) 2614 INP_INFO_WUNLOCK(&tcbinfo); 2615 m_freem(m); 2616 return; 2617 } 2618 2619 /* 2620 * Parse TCP options and place in tcpopt. 2621 */ 2622 static void 2623 tcp_dooptions(to, cp, cnt, flags) 2624 struct tcpopt *to; 2625 u_char *cp; 2626 int cnt; 2627 int flags; 2628 { 2629 int opt, optlen; 2630 2631 to->to_flags = 0; 2632 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2633 opt = cp[0]; 2634 if (opt == TCPOPT_EOL) 2635 break; 2636 if (opt == TCPOPT_NOP) 2637 optlen = 1; 2638 else { 2639 if (cnt < 2) 2640 break; 2641 optlen = cp[1]; 2642 if (optlen < 2 || optlen > cnt) 2643 break; 2644 } 2645 switch (opt) { 2646 case TCPOPT_MAXSEG: 2647 if (optlen != TCPOLEN_MAXSEG) 2648 continue; 2649 if (!(flags & TO_SYN)) 2650 continue; 2651 to->to_flags |= TOF_MSS; 2652 bcopy((char *)cp + 2, 2653 (char *)&to->to_mss, sizeof(to->to_mss)); 2654 to->to_mss = ntohs(to->to_mss); 2655 break; 2656 case TCPOPT_WINDOW: 2657 if (optlen != TCPOLEN_WINDOW) 2658 continue; 2659 if (!(flags & TO_SYN)) 2660 continue; 2661 to->to_flags |= TOF_SCALE; 2662 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2663 break; 2664 case TCPOPT_TIMESTAMP: 2665 if (optlen != TCPOLEN_TIMESTAMP) 2666 continue; 2667 to->to_flags |= TOF_TS; 2668 bcopy((char *)cp + 2, 2669 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2670 to->to_tsval = ntohl(to->to_tsval); 2671 bcopy((char *)cp + 6, 2672 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2673 to->to_tsecr = ntohl(to->to_tsecr); 2674 break; 2675 #ifdef TCP_SIGNATURE 2676 /* 2677 * XXX In order to reply to a host which has set the 2678 * TCP_SIGNATURE option in its initial SYN, we have to 2679 * record the fact that the option was observed here 2680 * for the syncache code to perform the correct response. 2681 */ 2682 case TCPOPT_SIGNATURE: 2683 if (optlen != TCPOLEN_SIGNATURE) 2684 continue; 2685 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2686 break; 2687 #endif 2688 case TCPOPT_SACK_PERMITTED: 2689 if (optlen != TCPOLEN_SACK_PERMITTED) 2690 continue; 2691 if (!(flags & TO_SYN)) 2692 continue; 2693 if (!tcp_do_sack) 2694 continue; 2695 to->to_flags |= TOF_SACK; 2696 break; 2697 case TCPOPT_SACK: 2698 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2699 continue; 2700 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2701 to->to_sacks = cp + 2; 2702 tcpstat.tcps_sack_rcv_blocks++; 2703 break; 2704 default: 2705 continue; 2706 } 2707 } 2708 } 2709 2710 /* 2711 * Pull out of band byte out of a segment so 2712 * it doesn't appear in the user's data queue. 2713 * It is still reflected in the segment length for 2714 * sequencing purposes. 2715 */ 2716 static void 2717 tcp_pulloutofband(so, th, m, off) 2718 struct socket *so; 2719 struct tcphdr *th; 2720 register struct mbuf *m; 2721 int off; /* delayed to be droped hdrlen */ 2722 { 2723 int cnt = off + th->th_urp - 1; 2724 2725 while (cnt >= 0) { 2726 if (m->m_len > cnt) { 2727 char *cp = mtod(m, caddr_t) + cnt; 2728 struct tcpcb *tp = sototcpcb(so); 2729 2730 tp->t_iobc = *cp; 2731 tp->t_oobflags |= TCPOOB_HAVEDATA; 2732 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2733 m->m_len--; 2734 if (m->m_flags & M_PKTHDR) 2735 m->m_pkthdr.len--; 2736 return; 2737 } 2738 cnt -= m->m_len; 2739 m = m->m_next; 2740 if (m == 0) 2741 break; 2742 } 2743 panic("tcp_pulloutofband"); 2744 } 2745 2746 /* 2747 * Collect new round-trip time estimate 2748 * and update averages and current timeout. 2749 */ 2750 static void 2751 tcp_xmit_timer(tp, rtt) 2752 register struct tcpcb *tp; 2753 int rtt; 2754 { 2755 register int delta; 2756 2757 INP_LOCK_ASSERT(tp->t_inpcb); 2758 2759 tcpstat.tcps_rttupdated++; 2760 tp->t_rttupdated++; 2761 if (tp->t_srtt != 0) { 2762 /* 2763 * srtt is stored as fixed point with 5 bits after the 2764 * binary point (i.e., scaled by 8). The following magic 2765 * is equivalent to the smoothing algorithm in rfc793 with 2766 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2767 * point). Adjust rtt to origin 0. 2768 */ 2769 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2770 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2771 2772 if ((tp->t_srtt += delta) <= 0) 2773 tp->t_srtt = 1; 2774 2775 /* 2776 * We accumulate a smoothed rtt variance (actually, a 2777 * smoothed mean difference), then set the retransmit 2778 * timer to smoothed rtt + 4 times the smoothed variance. 2779 * rttvar is stored as fixed point with 4 bits after the 2780 * binary point (scaled by 16). The following is 2781 * equivalent to rfc793 smoothing with an alpha of .75 2782 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2783 * rfc793's wired-in beta. 2784 */ 2785 if (delta < 0) 2786 delta = -delta; 2787 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2788 if ((tp->t_rttvar += delta) <= 0) 2789 tp->t_rttvar = 1; 2790 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2791 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2792 } else { 2793 /* 2794 * No rtt measurement yet - use the unsmoothed rtt. 2795 * Set the variance to half the rtt (so our first 2796 * retransmit happens at 3*rtt). 2797 */ 2798 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2799 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2800 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2801 } 2802 tp->t_rtttime = 0; 2803 tp->t_rxtshift = 0; 2804 2805 /* 2806 * the retransmit should happen at rtt + 4 * rttvar. 2807 * Because of the way we do the smoothing, srtt and rttvar 2808 * will each average +1/2 tick of bias. When we compute 2809 * the retransmit timer, we want 1/2 tick of rounding and 2810 * 1 extra tick because of +-1/2 tick uncertainty in the 2811 * firing of the timer. The bias will give us exactly the 2812 * 1.5 tick we need. But, because the bias is 2813 * statistical, we have to test that we don't drop below 2814 * the minimum feasible timer (which is 2 ticks). 2815 */ 2816 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2817 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2818 2819 /* 2820 * We received an ack for a packet that wasn't retransmitted; 2821 * it is probably safe to discard any error indications we've 2822 * received recently. This isn't quite right, but close enough 2823 * for now (a route might have failed after we sent a segment, 2824 * and the return path might not be symmetrical). 2825 */ 2826 tp->t_softerror = 0; 2827 } 2828 2829 /* 2830 * Determine a reasonable value for maxseg size. 2831 * If the route is known, check route for mtu. 2832 * If none, use an mss that can be handled on the outgoing 2833 * interface without forcing IP to fragment; if bigger than 2834 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2835 * to utilize large mbufs. If no route is found, route has no mtu, 2836 * or the destination isn't local, use a default, hopefully conservative 2837 * size (usually 512 or the default IP max size, but no more than the mtu 2838 * of the interface), as we can't discover anything about intervening 2839 * gateways or networks. We also initialize the congestion/slow start 2840 * window to be a single segment if the destination isn't local. 2841 * While looking at the routing entry, we also initialize other path-dependent 2842 * parameters from pre-set or cached values in the routing entry. 2843 * 2844 * Also take into account the space needed for options that we 2845 * send regularly. Make maxseg shorter by that amount to assure 2846 * that we can send maxseg amount of data even when the options 2847 * are present. Store the upper limit of the length of options plus 2848 * data in maxopd. 2849 * 2850 * 2851 * In case of T/TCP, we call this routine during implicit connection 2852 * setup as well (offer = -1), to initialize maxseg from the cached 2853 * MSS of our peer. 2854 * 2855 * NOTE that this routine is only called when we process an incoming 2856 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2857 */ 2858 void 2859 tcp_mss(tp, offer) 2860 struct tcpcb *tp; 2861 int offer; 2862 { 2863 int rtt, mss; 2864 u_long bufsize; 2865 u_long maxmtu; 2866 struct inpcb *inp = tp->t_inpcb; 2867 struct socket *so; 2868 struct hc_metrics_lite metrics; 2869 int origoffer = offer; 2870 int mtuflags = 0; 2871 #ifdef INET6 2872 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2873 size_t min_protoh = isipv6 ? 2874 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2875 sizeof (struct tcpiphdr); 2876 #else 2877 const size_t min_protoh = sizeof(struct tcpiphdr); 2878 #endif 2879 2880 /* initialize */ 2881 #ifdef INET6 2882 if (isipv6) { 2883 maxmtu = tcp_maxmtu6(&inp->inp_inc, &mtuflags); 2884 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2885 } else 2886 #endif 2887 { 2888 maxmtu = tcp_maxmtu(&inp->inp_inc, &mtuflags); 2889 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2890 } 2891 so = inp->inp_socket; 2892 2893 /* 2894 * no route to sender, stay with default mss and return 2895 */ 2896 if (maxmtu == 0) 2897 return; 2898 2899 /* what have we got? */ 2900 switch (offer) { 2901 case 0: 2902 /* 2903 * Offer == 0 means that there was no MSS on the SYN 2904 * segment, in this case we use tcp_mssdflt. 2905 */ 2906 offer = 2907 #ifdef INET6 2908 isipv6 ? tcp_v6mssdflt : 2909 #endif 2910 tcp_mssdflt; 2911 break; 2912 2913 case -1: 2914 /* 2915 * Offer == -1 means that we didn't receive SYN yet. 2916 */ 2917 /* FALLTHROUGH */ 2918 2919 default: 2920 /* 2921 * Prevent DoS attack with too small MSS. Round up 2922 * to at least minmss. 2923 */ 2924 offer = max(offer, tcp_minmss); 2925 /* 2926 * Sanity check: make sure that maxopd will be large 2927 * enough to allow some data on segments even if the 2928 * all the option space is used (40bytes). Otherwise 2929 * funny things may happen in tcp_output. 2930 */ 2931 offer = max(offer, 64); 2932 } 2933 2934 /* 2935 * rmx information is now retrieved from tcp_hostcache 2936 */ 2937 tcp_hc_get(&inp->inp_inc, &metrics); 2938 2939 /* 2940 * if there's a discovered mtu int tcp hostcache, use it 2941 * else, use the link mtu. 2942 */ 2943 if (metrics.rmx_mtu) 2944 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2945 else { 2946 #ifdef INET6 2947 if (isipv6) { 2948 mss = maxmtu - min_protoh; 2949 if (!path_mtu_discovery && 2950 !in6_localaddr(&inp->in6p_faddr)) 2951 mss = min(mss, tcp_v6mssdflt); 2952 } else 2953 #endif 2954 { 2955 mss = maxmtu - min_protoh; 2956 if (!path_mtu_discovery && 2957 !in_localaddr(inp->inp_faddr)) 2958 mss = min(mss, tcp_mssdflt); 2959 } 2960 } 2961 mss = min(mss, offer); 2962 2963 /* 2964 * maxopd stores the maximum length of data AND options 2965 * in a segment; maxseg is the amount of data in a normal 2966 * segment. We need to store this value (maxopd) apart 2967 * from maxseg, because now every segment carries options 2968 * and thus we normally have somewhat less data in segments. 2969 */ 2970 tp->t_maxopd = mss; 2971 2972 /* 2973 * origoffer==-1 indicates, that no segments were received yet. 2974 * In this case we just guess. 2975 */ 2976 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2977 (origoffer == -1 || 2978 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2979 mss -= TCPOLEN_TSTAMP_APPA; 2980 tp->t_maxseg = mss; 2981 2982 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2983 if (mss > MCLBYTES) 2984 mss &= ~(MCLBYTES-1); 2985 #else 2986 if (mss > MCLBYTES) 2987 mss = mss / MCLBYTES * MCLBYTES; 2988 #endif 2989 tp->t_maxseg = mss; 2990 2991 /* 2992 * If there's a pipesize, change the socket buffer to that size, 2993 * don't change if sb_hiwat is different than default (then it 2994 * has been changed on purpose with setsockopt). 2995 * Make the socket buffers an integral number of mss units; 2996 * if the mss is larger than the socket buffer, decrease the mss. 2997 */ 2998 SOCKBUF_LOCK(&so->so_snd); 2999 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3000 bufsize = metrics.rmx_sendpipe; 3001 else 3002 bufsize = so->so_snd.sb_hiwat; 3003 if (bufsize < mss) 3004 mss = bufsize; 3005 else { 3006 bufsize = roundup(bufsize, mss); 3007 if (bufsize > sb_max) 3008 bufsize = sb_max; 3009 if (bufsize > so->so_snd.sb_hiwat) 3010 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3011 } 3012 SOCKBUF_UNLOCK(&so->so_snd); 3013 tp->t_maxseg = mss; 3014 3015 SOCKBUF_LOCK(&so->so_rcv); 3016 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3017 bufsize = metrics.rmx_recvpipe; 3018 else 3019 bufsize = so->so_rcv.sb_hiwat; 3020 if (bufsize > mss) { 3021 bufsize = roundup(bufsize, mss); 3022 if (bufsize > sb_max) 3023 bufsize = sb_max; 3024 if (bufsize > so->so_rcv.sb_hiwat) 3025 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3026 } 3027 SOCKBUF_UNLOCK(&so->so_rcv); 3028 /* 3029 * While we're here, check the others too 3030 */ 3031 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3032 tp->t_srtt = rtt; 3033 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3034 tcpstat.tcps_usedrtt++; 3035 if (metrics.rmx_rttvar) { 3036 tp->t_rttvar = metrics.rmx_rttvar; 3037 tcpstat.tcps_usedrttvar++; 3038 } else { 3039 /* default variation is +- 1 rtt */ 3040 tp->t_rttvar = 3041 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3042 } 3043 TCPT_RANGESET(tp->t_rxtcur, 3044 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3045 tp->t_rttmin, TCPTV_REXMTMAX); 3046 } 3047 if (metrics.rmx_ssthresh) { 3048 /* 3049 * There's some sort of gateway or interface 3050 * buffer limit on the path. Use this to set 3051 * the slow start threshhold, but set the 3052 * threshold to no less than 2*mss. 3053 */ 3054 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3055 tcpstat.tcps_usedssthresh++; 3056 } 3057 if (metrics.rmx_bandwidth) 3058 tp->snd_bandwidth = metrics.rmx_bandwidth; 3059 3060 /* 3061 * Set the slow-start flight size depending on whether this 3062 * is a local network or not. 3063 * 3064 * Extend this so we cache the cwnd too and retrieve it here. 3065 * Make cwnd even bigger than RFC3390 suggests but only if we 3066 * have previous experience with the remote host. Be careful 3067 * not make cwnd bigger than remote receive window or our own 3068 * send socket buffer. Maybe put some additional upper bound 3069 * on the retrieved cwnd. Should do incremental updates to 3070 * hostcache when cwnd collapses so next connection doesn't 3071 * overloads the path again. 3072 * 3073 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3074 * We currently check only in syncache_socket for that. 3075 */ 3076 #define TCP_METRICS_CWND 3077 #ifdef TCP_METRICS_CWND 3078 if (metrics.rmx_cwnd) 3079 tp->snd_cwnd = max(mss, 3080 min(metrics.rmx_cwnd / 2, 3081 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3082 else 3083 #endif 3084 if (tcp_do_rfc3390) 3085 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3086 #ifdef INET6 3087 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3088 (!isipv6 && in_localaddr(inp->inp_faddr))) 3089 #else 3090 else if (in_localaddr(inp->inp_faddr)) 3091 #endif 3092 tp->snd_cwnd = mss * ss_fltsz_local; 3093 else 3094 tp->snd_cwnd = mss * ss_fltsz; 3095 3096 /* Check the interface for TSO capabilities. */ 3097 if (mtuflags & CSUM_TSO) 3098 tp->t_flags |= TF_TSO; 3099 } 3100 3101 /* 3102 * Determine the MSS option to send on an outgoing SYN. 3103 */ 3104 int 3105 tcp_mssopt(inc) 3106 struct in_conninfo *inc; 3107 { 3108 int mss = 0; 3109 u_long maxmtu = 0; 3110 u_long thcmtu = 0; 3111 size_t min_protoh; 3112 #ifdef INET6 3113 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3114 #endif 3115 3116 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3117 3118 #ifdef INET6 3119 if (isipv6) { 3120 mss = tcp_v6mssdflt; 3121 maxmtu = tcp_maxmtu6(inc, NULL); 3122 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3123 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3124 } else 3125 #endif 3126 { 3127 mss = tcp_mssdflt; 3128 maxmtu = tcp_maxmtu(inc, NULL); 3129 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3130 min_protoh = sizeof(struct tcpiphdr); 3131 } 3132 if (maxmtu && thcmtu) 3133 mss = min(maxmtu, thcmtu) - min_protoh; 3134 else if (maxmtu || thcmtu) 3135 mss = max(maxmtu, thcmtu) - min_protoh; 3136 3137 return (mss); 3138 } 3139 3140 3141 /* 3142 * On a partial ack arrives, force the retransmission of the 3143 * next unacknowledged segment. Do not clear tp->t_dupacks. 3144 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3145 * be started again. 3146 */ 3147 static void 3148 tcp_newreno_partial_ack(tp, th) 3149 struct tcpcb *tp; 3150 struct tcphdr *th; 3151 { 3152 tcp_seq onxt = tp->snd_nxt; 3153 u_long ocwnd = tp->snd_cwnd; 3154 3155 callout_stop(tp->tt_rexmt); 3156 tp->t_rtttime = 0; 3157 tp->snd_nxt = th->th_ack; 3158 /* 3159 * Set snd_cwnd to one segment beyond acknowledged offset. 3160 * (tp->snd_una has not yet been updated when this function is called.) 3161 */ 3162 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3163 tp->t_flags |= TF_ACKNOW; 3164 (void) tcp_output(tp); 3165 tp->snd_cwnd = ocwnd; 3166 if (SEQ_GT(onxt, tp->snd_nxt)) 3167 tp->snd_nxt = onxt; 3168 /* 3169 * Partial window deflation. Relies on fact that tp->snd_una 3170 * not updated yet. 3171 */ 3172 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3173 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3174 else 3175 tp->snd_cwnd = 0; 3176 tp->snd_cwnd += tp->t_maxseg; 3177 } 3178 3179 /* 3180 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3181 * looking for a pcb in the listen state. Returns 0 otherwise. 3182 */ 3183 static int 3184 tcp_timewait(inp, to, th, m, tlen) 3185 struct inpcb *inp; 3186 struct tcpopt *to; 3187 struct tcphdr *th; 3188 struct mbuf *m; 3189 int tlen; 3190 { 3191 struct tcptw *tw; 3192 int thflags; 3193 tcp_seq seq; 3194 #ifdef INET6 3195 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3196 #else 3197 const int isipv6 = 0; 3198 #endif 3199 3200 /* tcbinfo lock required for tcp_twclose(), tcp_timer_2msl_reset(). */ 3201 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3202 INP_LOCK_ASSERT(inp); 3203 3204 /* 3205 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 3206 * still present. This is undesirable, but temporarily necessary 3207 * until we work out how to handle inpcb's who's timewait state has 3208 * been removed. 3209 */ 3210 tw = intotw(inp); 3211 if (tw == NULL) 3212 goto drop; 3213 3214 thflags = th->th_flags; 3215 3216 /* 3217 * NOTE: for FIN_WAIT_2 (to be added later), 3218 * must validate sequence number before accepting RST 3219 */ 3220 3221 /* 3222 * If the segment contains RST: 3223 * Drop the segment - see Stevens, vol. 2, p. 964 and 3224 * RFC 1337. 3225 */ 3226 if (thflags & TH_RST) 3227 goto drop; 3228 3229 #if 0 3230 /* PAWS not needed at the moment */ 3231 /* 3232 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3233 * and it's less than ts_recent, drop it. 3234 */ 3235 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3236 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3237 if ((thflags & TH_ACK) == 0) 3238 goto drop; 3239 goto ack; 3240 } 3241 /* 3242 * ts_recent is never updated because we never accept new segments. 3243 */ 3244 #endif 3245 3246 /* 3247 * If a new connection request is received 3248 * while in TIME_WAIT, drop the old connection 3249 * and start over if the sequence numbers 3250 * are above the previous ones. 3251 */ 3252 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3253 tcp_twclose(tw, 0); 3254 return (1); 3255 } 3256 3257 /* 3258 * Drop the the segment if it does not contain an ACK. 3259 */ 3260 if ((thflags & TH_ACK) == 0) 3261 goto drop; 3262 3263 /* 3264 * Reset the 2MSL timer if this is a duplicate FIN. 3265 */ 3266 if (thflags & TH_FIN) { 3267 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3268 if (seq + 1 == tw->rcv_nxt) 3269 tcp_timer_2msl_reset(tw, 1); 3270 } 3271 3272 /* 3273 * Acknowledge the segment if it has data or is not a duplicate ACK. 3274 */ 3275 if (thflags != TH_ACK || tlen != 0 || 3276 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3277 tcp_twrespond(tw, TH_ACK); 3278 goto drop; 3279 3280 /* 3281 * Generate a RST, dropping incoming segment. 3282 * Make ACK acceptable to originator of segment. 3283 * Don't bother to respond if destination was broadcast/multicast. 3284 */ 3285 if (m->m_flags & (M_BCAST|M_MCAST)) 3286 goto drop; 3287 if (isipv6) { 3288 struct ip6_hdr *ip6; 3289 3290 /* IPv6 anycast check is done at tcp6_input() */ 3291 ip6 = mtod(m, struct ip6_hdr *); 3292 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3293 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3294 goto drop; 3295 } else { 3296 struct ip *ip; 3297 3298 ip = mtod(m, struct ip *); 3299 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3300 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3301 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3302 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3303 goto drop; 3304 } 3305 if (thflags & TH_ACK) { 3306 tcp_respond(NULL, 3307 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3308 } else { 3309 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3310 tcp_respond(NULL, 3311 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3312 } 3313 INP_UNLOCK(inp); 3314 return (0); 3315 3316 drop: 3317 INP_UNLOCK(inp); 3318 m_freem(m); 3319 return (0); 3320 } 3321