Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/netinet/tcp_input.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_ipfw.h" /* for ipfw_fwd */ 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 #include "opt_tcp_sack.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/mac.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/signalvar.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 #include <sys/syslog.h> 54 #include <sys/systm.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/in_var.h> 67 #include <netinet/ip.h> 68 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 69 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 70 #include <netinet/ip_var.h> 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/nd6.h> 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet6/tcp6_var.h> 82 #include <netinet/tcpip.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif /* TCPDEBUG */ 86 87 #ifdef FAST_IPSEC 88 #include <netipsec/ipsec.h> 89 #include <netipsec/ipsec6.h> 90 #endif /*FAST_IPSEC*/ 91 92 #ifdef IPSEC 93 #include <netinet6/ipsec.h> 94 #include <netinet6/ipsec6.h> 95 #include <netkey/key.h> 96 #endif /*IPSEC*/ 97 98 #include <machine/in_cksum.h> 99 100 static const int tcprexmtthresh = 3; 101 tcp_cc tcp_ccgen; 102 103 struct tcpstat tcpstat; 104 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 105 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 106 107 static int log_in_vain = 0; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 109 &log_in_vain, 0, "Log all incoming TCP connections"); 110 111 static int blackhole = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 113 &blackhole, 0, "Do not send RST when dropping refused connections"); 114 115 int tcp_delack_enabled = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 117 &tcp_delack_enabled, 0, 118 "Delay ACK to try and piggyback it onto a data packet"); 119 120 #ifdef TCP_DROP_SYNFIN 121 static int drop_synfin = 0; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 123 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 124 #endif 125 126 static int tcp_do_rfc3042 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 128 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 129 130 static int tcp_do_rfc3390 = 1; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 132 &tcp_do_rfc3390, 0, 133 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 134 135 static int tcp_insecure_rst = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 137 &tcp_insecure_rst, 0, 138 "Follow the old (insecure) criteria for accepting RST packets."); 139 140 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 141 "TCP Segment Reassembly Queue"); 142 143 static int tcp_reass_maxseg = 0; 144 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN, 145 &tcp_reass_maxseg, 0, 146 "Global maximum number of TCP Segments in Reassembly Queue"); 147 148 int tcp_reass_qsize = 0; 149 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 150 &tcp_reass_qsize, 0, 151 "Global number of TCP Segments currently in Reassembly Queue"); 152 153 static int tcp_reass_maxqlen = 48; 154 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW, 155 &tcp_reass_maxqlen, 0, 156 "Maximum number of TCP Segments per individual Reassembly Queue"); 157 158 static int tcp_reass_overflows = 0; 159 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 160 &tcp_reass_overflows, 0, 161 "Global number of TCP Segment Reassembly Queue Overflows"); 162 163 struct inpcbhead tcb; 164 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 165 struct inpcbinfo tcbinfo; 166 struct mtx *tcbinfo_mtx; 167 168 static void tcp_dooptions(struct tcpcb *, struct tcpopt *, u_char *, 169 int, int, struct tcphdr *); 170 171 static void tcp_pulloutofband(struct socket *, 172 struct tcphdr *, struct mbuf *, int); 173 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 174 struct mbuf *); 175 static void tcp_xmit_timer(struct tcpcb *, int); 176 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 177 static int tcp_timewait(struct tcptw *, struct tcpopt *, 178 struct tcphdr *, struct mbuf *, int); 179 180 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 181 #ifdef INET6 182 #define ND6_HINT(tp) \ 183 do { \ 184 if ((tp) && (tp)->t_inpcb && \ 185 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 186 nd6_nud_hint(NULL, NULL, 0); \ 187 } while (0) 188 #else 189 #define ND6_HINT(tp) 190 #endif 191 192 /* 193 * Indicate whether this ack should be delayed. We can delay the ack if 194 * - there is no delayed ack timer in progress and 195 * - our last ack wasn't a 0-sized window. We never want to delay 196 * the ack that opens up a 0-sized window and 197 * - delayed acks are enabled or 198 * - this is a half-synchronized T/TCP connection. 199 */ 200 #define DELAY_ACK(tp) \ 201 ((!callout_active(tp->tt_delack) && \ 202 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 203 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 204 205 /* Initialize TCP reassembly queue */ 206 uma_zone_t tcp_reass_zone; 207 void 208 tcp_reass_init() 209 { 210 tcp_reass_maxseg = nmbclusters / 16; 211 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments", 212 &tcp_reass_maxseg); 213 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent), 214 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 215 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg); 216 } 217 218 static int 219 tcp_reass(tp, th, tlenp, m) 220 register struct tcpcb *tp; 221 register struct tcphdr *th; 222 int *tlenp; 223 struct mbuf *m; 224 { 225 struct tseg_qent *q; 226 struct tseg_qent *p = NULL; 227 struct tseg_qent *nq; 228 struct tseg_qent *te = NULL; 229 struct socket *so = tp->t_inpcb->inp_socket; 230 int flags; 231 232 INP_LOCK_ASSERT(tp->t_inpcb); 233 234 /* 235 * XXX: tcp_reass() is rather inefficient with its data structures 236 * and should be rewritten (see NetBSD for optimizations). While 237 * doing that it should move to its own file tcp_reass.c. 238 */ 239 240 /* 241 * Call with th==NULL after become established to 242 * force pre-ESTABLISHED data up to user socket. 243 */ 244 if (th == NULL) 245 goto present; 246 247 /* 248 * Limit the number of segments in the reassembly queue to prevent 249 * holding on to too many segments (and thus running out of mbufs). 250 * Make sure to let the missing segment through which caused this 251 * queue. Always keep one global queue entry spare to be able to 252 * process the missing segment. 253 */ 254 if (th->th_seq != tp->rcv_nxt && 255 (tcp_reass_qsize + 1 >= tcp_reass_maxseg || 256 tp->t_segqlen >= tcp_reass_maxqlen)) { 257 tcp_reass_overflows++; 258 tcpstat.tcps_rcvmemdrop++; 259 m_freem(m); 260 *tlenp = 0; 261 return (0); 262 } 263 264 /* 265 * Allocate a new queue entry. If we can't, or hit the zone limit 266 * just drop the pkt. 267 */ 268 te = uma_zalloc(tcp_reass_zone, M_NOWAIT); 269 if (te == NULL) { 270 tcpstat.tcps_rcvmemdrop++; 271 m_freem(m); 272 *tlenp = 0; 273 return (0); 274 } 275 tp->t_segqlen++; 276 tcp_reass_qsize++; 277 278 /* 279 * Find a segment which begins after this one does. 280 */ 281 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 282 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 283 break; 284 p = q; 285 } 286 287 /* 288 * If there is a preceding segment, it may provide some of 289 * our data already. If so, drop the data from the incoming 290 * segment. If it provides all of our data, drop us. 291 */ 292 if (p != NULL) { 293 register int i; 294 /* conversion to int (in i) handles seq wraparound */ 295 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 296 if (i > 0) { 297 if (i >= *tlenp) { 298 tcpstat.tcps_rcvduppack++; 299 tcpstat.tcps_rcvdupbyte += *tlenp; 300 m_freem(m); 301 uma_zfree(tcp_reass_zone, te); 302 tp->t_segqlen--; 303 tcp_reass_qsize--; 304 /* 305 * Try to present any queued data 306 * at the left window edge to the user. 307 * This is needed after the 3-WHS 308 * completes. 309 */ 310 goto present; /* ??? */ 311 } 312 m_adj(m, i); 313 *tlenp -= i; 314 th->th_seq += i; 315 } 316 } 317 tcpstat.tcps_rcvoopack++; 318 tcpstat.tcps_rcvoobyte += *tlenp; 319 320 /* 321 * While we overlap succeeding segments trim them or, 322 * if they are completely covered, dequeue them. 323 */ 324 while (q) { 325 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 326 if (i <= 0) 327 break; 328 if (i < q->tqe_len) { 329 q->tqe_th->th_seq += i; 330 q->tqe_len -= i; 331 m_adj(q->tqe_m, i); 332 break; 333 } 334 335 nq = LIST_NEXT(q, tqe_q); 336 LIST_REMOVE(q, tqe_q); 337 m_freem(q->tqe_m); 338 uma_zfree(tcp_reass_zone, q); 339 tp->t_segqlen--; 340 tcp_reass_qsize--; 341 q = nq; 342 } 343 344 /* Insert the new segment queue entry into place. */ 345 te->tqe_m = m; 346 te->tqe_th = th; 347 te->tqe_len = *tlenp; 348 349 if (p == NULL) { 350 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 351 } else { 352 LIST_INSERT_AFTER(p, te, tqe_q); 353 } 354 355 present: 356 /* 357 * Present data to user, advancing rcv_nxt through 358 * completed sequence space. 359 */ 360 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 361 return (0); 362 q = LIST_FIRST(&tp->t_segq); 363 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 364 return (0); 365 SOCKBUF_LOCK(&so->so_rcv); 366 do { 367 tp->rcv_nxt += q->tqe_len; 368 flags = q->tqe_th->th_flags & TH_FIN; 369 nq = LIST_NEXT(q, tqe_q); 370 LIST_REMOVE(q, tqe_q); 371 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 372 m_freem(q->tqe_m); 373 else 374 sbappendstream_locked(&so->so_rcv, q->tqe_m); 375 uma_zfree(tcp_reass_zone, q); 376 tp->t_segqlen--; 377 tcp_reass_qsize--; 378 q = nq; 379 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 380 ND6_HINT(tp); 381 sorwakeup_locked(so); 382 return (flags); 383 } 384 385 /* 386 * TCP input routine, follows pages 65-76 of the 387 * protocol specification dated September, 1981 very closely. 388 */ 389 #ifdef INET6 390 int 391 tcp6_input(mp, offp, proto) 392 struct mbuf **mp; 393 int *offp, proto; 394 { 395 register struct mbuf *m = *mp; 396 struct in6_ifaddr *ia6; 397 398 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 399 400 /* 401 * draft-itojun-ipv6-tcp-to-anycast 402 * better place to put this in? 403 */ 404 ia6 = ip6_getdstifaddr(m); 405 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 406 struct ip6_hdr *ip6; 407 408 ip6 = mtod(m, struct ip6_hdr *); 409 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 410 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 411 return IPPROTO_DONE; 412 } 413 414 tcp_input(m, *offp); 415 return IPPROTO_DONE; 416 } 417 #endif 418 419 void 420 tcp_input(m, off0) 421 register struct mbuf *m; 422 int off0; 423 { 424 register struct tcphdr *th; 425 register struct ip *ip = NULL; 426 register struct ipovly *ipov; 427 register struct inpcb *inp = NULL; 428 u_char *optp = NULL; 429 int optlen = 0; 430 int len, tlen, off; 431 int drop_hdrlen; 432 register struct tcpcb *tp = 0; 433 register int thflags; 434 struct socket *so = 0; 435 int todrop, acked, ourfinisacked, needoutput = 0; 436 u_long tiwin; 437 struct tcpopt to; /* options in this segment */ 438 struct rmxp_tao tao; /* our TAO cache entry */ 439 int headlocked = 0; 440 #ifdef IPFIREWALL_FORWARD 441 struct m_tag *fwd_tag; 442 #endif 443 int rstreason; /* For badport_bandlim accounting purposes */ 444 445 struct ip6_hdr *ip6 = NULL; 446 #ifdef INET6 447 int isipv6; 448 #else 449 const int isipv6 = 0; 450 #endif 451 452 #ifdef TCPDEBUG 453 /* 454 * The size of tcp_saveipgen must be the size of the max ip header, 455 * now IPv6. 456 */ 457 u_char tcp_saveipgen[40]; 458 struct tcphdr tcp_savetcp; 459 short ostate = 0; 460 #endif 461 462 #ifdef INET6 463 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 464 #endif 465 bzero(&tao, sizeof(tao)); 466 bzero((char *)&to, sizeof(to)); 467 468 tcpstat.tcps_rcvtotal++; 469 470 if (isipv6) { 471 #ifdef INET6 472 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 473 ip6 = mtod(m, struct ip6_hdr *); 474 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 475 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 476 tcpstat.tcps_rcvbadsum++; 477 goto drop; 478 } 479 th = (struct tcphdr *)((caddr_t)ip6 + off0); 480 481 /* 482 * Be proactive about unspecified IPv6 address in source. 483 * As we use all-zero to indicate unbounded/unconnected pcb, 484 * unspecified IPv6 address can be used to confuse us. 485 * 486 * Note that packets with unspecified IPv6 destination is 487 * already dropped in ip6_input. 488 */ 489 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 490 /* XXX stat */ 491 goto drop; 492 } 493 #else 494 th = NULL; /* XXX: avoid compiler warning */ 495 #endif 496 } else { 497 /* 498 * Get IP and TCP header together in first mbuf. 499 * Note: IP leaves IP header in first mbuf. 500 */ 501 if (off0 > sizeof (struct ip)) { 502 ip_stripoptions(m, (struct mbuf *)0); 503 off0 = sizeof(struct ip); 504 } 505 if (m->m_len < sizeof (struct tcpiphdr)) { 506 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 507 tcpstat.tcps_rcvshort++; 508 return; 509 } 510 } 511 ip = mtod(m, struct ip *); 512 ipov = (struct ipovly *)ip; 513 th = (struct tcphdr *)((caddr_t)ip + off0); 514 tlen = ip->ip_len; 515 516 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 517 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 518 th->th_sum = m->m_pkthdr.csum_data; 519 else 520 th->th_sum = in_pseudo(ip->ip_src.s_addr, 521 ip->ip_dst.s_addr, 522 htonl(m->m_pkthdr.csum_data + 523 ip->ip_len + 524 IPPROTO_TCP)); 525 th->th_sum ^= 0xffff; 526 #ifdef TCPDEBUG 527 ipov->ih_len = (u_short)tlen; 528 ipov->ih_len = htons(ipov->ih_len); 529 #endif 530 } else { 531 /* 532 * Checksum extended TCP header and data. 533 */ 534 len = sizeof (struct ip) + tlen; 535 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 536 ipov->ih_len = (u_short)tlen; 537 ipov->ih_len = htons(ipov->ih_len); 538 th->th_sum = in_cksum(m, len); 539 } 540 if (th->th_sum) { 541 tcpstat.tcps_rcvbadsum++; 542 goto drop; 543 } 544 #ifdef INET6 545 /* Re-initialization for later version check */ 546 ip->ip_v = IPVERSION; 547 #endif 548 } 549 550 /* 551 * Check that TCP offset makes sense, 552 * pull out TCP options and adjust length. XXX 553 */ 554 off = th->th_off << 2; 555 if (off < sizeof (struct tcphdr) || off > tlen) { 556 tcpstat.tcps_rcvbadoff++; 557 goto drop; 558 } 559 tlen -= off; /* tlen is used instead of ti->ti_len */ 560 if (off > sizeof (struct tcphdr)) { 561 if (isipv6) { 562 #ifdef INET6 563 IP6_EXTHDR_CHECK(m, off0, off, ); 564 ip6 = mtod(m, struct ip6_hdr *); 565 th = (struct tcphdr *)((caddr_t)ip6 + off0); 566 #endif 567 } else { 568 if (m->m_len < sizeof(struct ip) + off) { 569 if ((m = m_pullup(m, sizeof (struct ip) + off)) 570 == 0) { 571 tcpstat.tcps_rcvshort++; 572 return; 573 } 574 ip = mtod(m, struct ip *); 575 ipov = (struct ipovly *)ip; 576 th = (struct tcphdr *)((caddr_t)ip + off0); 577 } 578 } 579 optlen = off - sizeof (struct tcphdr); 580 optp = (u_char *)(th + 1); 581 } 582 thflags = th->th_flags; 583 584 #ifdef TCP_DROP_SYNFIN 585 /* 586 * If the drop_synfin option is enabled, drop all packets with 587 * both the SYN and FIN bits set. This prevents e.g. nmap from 588 * identifying the TCP/IP stack. 589 * 590 * This is a violation of the TCP specification. 591 */ 592 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 593 goto drop; 594 #endif 595 596 /* 597 * Convert TCP protocol specific fields to host format. 598 */ 599 th->th_seq = ntohl(th->th_seq); 600 th->th_ack = ntohl(th->th_ack); 601 th->th_win = ntohs(th->th_win); 602 th->th_urp = ntohs(th->th_urp); 603 604 /* 605 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 606 * until after ip6_savecontrol() is called and before other functions 607 * which don't want those proto headers. 608 * Because ip6_savecontrol() is going to parse the mbuf to 609 * search for data to be passed up to user-land, it wants mbuf 610 * parameters to be unchanged. 611 * XXX: the call of ip6_savecontrol() has been obsoleted based on 612 * latest version of the advanced API (20020110). 613 */ 614 drop_hdrlen = off0 + off; 615 616 /* 617 * Locate pcb for segment. 618 */ 619 INP_INFO_WLOCK(&tcbinfo); 620 headlocked = 1; 621 findpcb: 622 KASSERT(headlocked, ("tcp_input: findpcb: head not locked")); 623 #ifdef IPFIREWALL_FORWARD 624 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */ 625 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 626 627 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 628 struct sockaddr_in *next_hop; 629 630 next_hop = (struct sockaddr_in *)(fwd_tag+1); 631 /* 632 * Transparently forwarded. Pretend to be the destination. 633 * already got one like this? 634 */ 635 inp = in_pcblookup_hash(&tcbinfo, 636 ip->ip_src, th->th_sport, 637 ip->ip_dst, th->th_dport, 638 0, m->m_pkthdr.rcvif); 639 if (!inp) { 640 /* It's new. Try to find the ambushing socket. */ 641 inp = in_pcblookup_hash(&tcbinfo, 642 ip->ip_src, th->th_sport, 643 next_hop->sin_addr, 644 next_hop->sin_port ? 645 ntohs(next_hop->sin_port) : 646 th->th_dport, 647 1, m->m_pkthdr.rcvif); 648 } 649 /* Remove the tag from the packet. We don't need it anymore. */ 650 m_tag_delete(m, fwd_tag); 651 } else { 652 #endif /* IPFIREWALL_FORWARD */ 653 if (isipv6) { 654 #ifdef INET6 655 inp = in6_pcblookup_hash(&tcbinfo, 656 &ip6->ip6_src, th->th_sport, 657 &ip6->ip6_dst, th->th_dport, 658 1, m->m_pkthdr.rcvif); 659 #endif 660 } else 661 inp = in_pcblookup_hash(&tcbinfo, 662 ip->ip_src, th->th_sport, 663 ip->ip_dst, th->th_dport, 664 1, m->m_pkthdr.rcvif); 665 #ifdef IPFIREWALL_FORWARD 666 } 667 #endif /* IPFIREWALL_FORWARD */ 668 669 #if defined(IPSEC) || defined(FAST_IPSEC) 670 #ifdef INET6 671 if (isipv6) { 672 if (inp != NULL && ipsec6_in_reject(m, inp)) { 673 #ifdef IPSEC 674 ipsec6stat.in_polvio++; 675 #endif 676 goto drop; 677 } 678 } else 679 #endif /* INET6 */ 680 if (inp != NULL && ipsec4_in_reject(m, inp)) { 681 #ifdef IPSEC 682 ipsecstat.in_polvio++; 683 #endif 684 goto drop; 685 } 686 #endif /*IPSEC || FAST_IPSEC*/ 687 688 /* 689 * If the state is CLOSED (i.e., TCB does not exist) then 690 * all data in the incoming segment is discarded. 691 * If the TCB exists but is in CLOSED state, it is embryonic, 692 * but should either do a listen or a connect soon. 693 */ 694 if (inp == NULL) { 695 if (log_in_vain) { 696 #ifdef INET6 697 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 698 #else 699 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 700 #endif 701 702 if (isipv6) { 703 #ifdef INET6 704 strcpy(dbuf, "["); 705 strcpy(sbuf, "["); 706 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 707 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 708 strcat(dbuf, "]"); 709 strcat(sbuf, "]"); 710 #endif 711 } else { 712 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 713 strcpy(sbuf, inet_ntoa(ip->ip_src)); 714 } 715 switch (log_in_vain) { 716 case 1: 717 if ((thflags & TH_SYN) == 0) 718 break; 719 /* FALLTHROUGH */ 720 case 2: 721 log(LOG_INFO, 722 "Connection attempt to TCP %s:%d " 723 "from %s:%d flags:0x%02x\n", 724 dbuf, ntohs(th->th_dport), sbuf, 725 ntohs(th->th_sport), thflags); 726 break; 727 default: 728 break; 729 } 730 } 731 if (blackhole) { 732 switch (blackhole) { 733 case 1: 734 if (thflags & TH_SYN) 735 goto drop; 736 break; 737 case 2: 738 goto drop; 739 default: 740 goto drop; 741 } 742 } 743 rstreason = BANDLIM_RST_CLOSEDPORT; 744 goto dropwithreset; 745 } 746 INP_LOCK(inp); 747 if (inp->inp_vflag & INP_TIMEWAIT) { 748 /* 749 * The only option of relevance is TOF_CC, and only if 750 * present in a SYN segment. See tcp_timewait(). 751 */ 752 if (thflags & TH_SYN) 753 tcp_dooptions((struct tcpcb *)NULL, &to, optp, optlen, 1, th); 754 if (tcp_timewait((struct tcptw *)inp->inp_ppcb, 755 &to, th, m, tlen)) 756 goto findpcb; 757 /* 758 * tcp_timewait unlocks inp. 759 */ 760 INP_INFO_WUNLOCK(&tcbinfo); 761 return; 762 } 763 tp = intotcpcb(inp); 764 if (tp == 0) { 765 INP_UNLOCK(inp); 766 rstreason = BANDLIM_RST_CLOSEDPORT; 767 goto dropwithreset; 768 } 769 if (tp->t_state == TCPS_CLOSED) 770 goto drop; 771 772 /* Unscale the window into a 32-bit value. */ 773 if ((thflags & TH_SYN) == 0) 774 tiwin = th->th_win << tp->snd_scale; 775 else 776 tiwin = th->th_win; 777 778 #ifdef MAC 779 INP_LOCK_ASSERT(inp); 780 if (mac_check_inpcb_deliver(inp, m)) 781 goto drop; 782 #endif 783 so = inp->inp_socket; 784 #ifdef TCPDEBUG 785 if (so->so_options & SO_DEBUG) { 786 ostate = tp->t_state; 787 if (isipv6) 788 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 789 else 790 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 791 tcp_savetcp = *th; 792 } 793 #endif 794 if (so->so_options & SO_ACCEPTCONN) { 795 struct in_conninfo inc; 796 797 #ifdef INET6 798 inc.inc_isipv6 = isipv6; 799 #endif 800 if (isipv6) { 801 inc.inc6_faddr = ip6->ip6_src; 802 inc.inc6_laddr = ip6->ip6_dst; 803 } else { 804 inc.inc_faddr = ip->ip_src; 805 inc.inc_laddr = ip->ip_dst; 806 } 807 inc.inc_fport = th->th_sport; 808 inc.inc_lport = th->th_dport; 809 810 /* 811 * If the state is LISTEN then ignore segment if it contains 812 * a RST. If the segment contains an ACK then it is bad and 813 * send a RST. If it does not contain a SYN then it is not 814 * interesting; drop it. 815 * 816 * If the state is SYN_RECEIVED (syncache) and seg contains 817 * an ACK, but not for our SYN/ACK, send a RST. If the seg 818 * contains a RST, check the sequence number to see if it 819 * is a valid reset segment. 820 */ 821 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 822 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 823 if (!syncache_expand(&inc, th, &so, m)) { 824 /* 825 * No syncache entry, or ACK was not 826 * for our SYN/ACK. Send a RST. 827 */ 828 tcpstat.tcps_badsyn++; 829 rstreason = BANDLIM_RST_OPENPORT; 830 goto dropwithreset; 831 } 832 if (so == NULL) { 833 /* 834 * Could not complete 3-way handshake, 835 * connection is being closed down, and 836 * syncache will free mbuf. 837 */ 838 INP_UNLOCK(inp); 839 INP_INFO_WUNLOCK(&tcbinfo); 840 return; 841 } 842 /* 843 * Socket is created in state SYN_RECEIVED. 844 * Continue processing segment. 845 */ 846 INP_UNLOCK(inp); 847 inp = sotoinpcb(so); 848 INP_LOCK(inp); 849 tp = intotcpcb(inp); 850 /* 851 * This is what would have happened in 852 * tcp_output() when the SYN,ACK was sent. 853 */ 854 tp->snd_up = tp->snd_una; 855 tp->snd_max = tp->snd_nxt = tp->iss + 1; 856 tp->last_ack_sent = tp->rcv_nxt; 857 /* 858 * RFC1323: The window in SYN & SYN/ACK 859 * segments is never scaled. 860 */ 861 tp->snd_wnd = tiwin; /* unscaled */ 862 goto after_listen; 863 } 864 if (thflags & TH_RST) { 865 syncache_chkrst(&inc, th); 866 goto drop; 867 } 868 if (thflags & TH_ACK) { 869 syncache_badack(&inc); 870 tcpstat.tcps_badsyn++; 871 rstreason = BANDLIM_RST_OPENPORT; 872 goto dropwithreset; 873 } 874 goto drop; 875 } 876 877 /* 878 * Segment's flags are (SYN) or (SYN|FIN). 879 */ 880 #ifdef INET6 881 /* 882 * If deprecated address is forbidden, 883 * we do not accept SYN to deprecated interface 884 * address to prevent any new inbound connection from 885 * getting established. 886 * When we do not accept SYN, we send a TCP RST, 887 * with deprecated source address (instead of dropping 888 * it). We compromise it as it is much better for peer 889 * to send a RST, and RST will be the final packet 890 * for the exchange. 891 * 892 * If we do not forbid deprecated addresses, we accept 893 * the SYN packet. RFC2462 does not suggest dropping 894 * SYN in this case. 895 * If we decipher RFC2462 5.5.4, it says like this: 896 * 1. use of deprecated addr with existing 897 * communication is okay - "SHOULD continue to be 898 * used" 899 * 2. use of it with new communication: 900 * (2a) "SHOULD NOT be used if alternate address 901 * with sufficient scope is available" 902 * (2b) nothing mentioned otherwise. 903 * Here we fall into (2b) case as we have no choice in 904 * our source address selection - we must obey the peer. 905 * 906 * The wording in RFC2462 is confusing, and there are 907 * multiple description text for deprecated address 908 * handling - worse, they are not exactly the same. 909 * I believe 5.5.4 is the best one, so we follow 5.5.4. 910 */ 911 if (isipv6 && !ip6_use_deprecated) { 912 struct in6_ifaddr *ia6; 913 914 if ((ia6 = ip6_getdstifaddr(m)) && 915 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 916 INP_UNLOCK(inp); 917 tp = NULL; 918 rstreason = BANDLIM_RST_OPENPORT; 919 goto dropwithreset; 920 } 921 } 922 #endif 923 /* 924 * If it is from this socket, drop it, it must be forged. 925 * Don't bother responding if the destination was a broadcast. 926 */ 927 if (th->th_dport == th->th_sport) { 928 if (isipv6) { 929 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 930 &ip6->ip6_src)) 931 goto drop; 932 } else { 933 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 934 goto drop; 935 } 936 } 937 /* 938 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 939 * 940 * Note that it is quite possible to receive unicast 941 * link-layer packets with a broadcast IP address. Use 942 * in_broadcast() to find them. 943 */ 944 if (m->m_flags & (M_BCAST|M_MCAST)) 945 goto drop; 946 if (isipv6) { 947 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 948 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 949 goto drop; 950 } else { 951 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 952 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 953 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 954 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 955 goto drop; 956 } 957 /* 958 * SYN appears to be valid; create compressed TCP state 959 * for syncache, or perform t/tcp connection. 960 */ 961 if (so->so_qlen <= so->so_qlimit) { 962 #ifdef TCPDEBUG 963 if (so->so_options & SO_DEBUG) 964 tcp_trace(TA_INPUT, ostate, tp, 965 (void *)tcp_saveipgen, &tcp_savetcp, 0); 966 #endif 967 tcp_dooptions(tp, &to, optp, optlen, 1, th); 968 if (!syncache_add(&inc, &to, th, &so, m)) 969 goto drop; 970 if (so == NULL) { 971 /* 972 * Entry added to syncache, mbuf used to 973 * send SYN,ACK packet. 974 */ 975 KASSERT(headlocked, ("headlocked")); 976 INP_UNLOCK(inp); 977 INP_INFO_WUNLOCK(&tcbinfo); 978 return; 979 } 980 /* 981 * Segment passed TAO tests. 982 */ 983 INP_UNLOCK(inp); 984 inp = sotoinpcb(so); 985 INP_LOCK(inp); 986 tp = intotcpcb(inp); 987 tp->snd_wnd = tiwin; 988 tp->t_starttime = ticks; 989 tp->t_state = TCPS_ESTABLISHED; 990 991 /* 992 * T/TCP logic: 993 * If there is a FIN or if there is data, then 994 * delay SYN,ACK(SYN) in the hope of piggy-backing 995 * it on a response segment. Otherwise must send 996 * ACK now in case the other side is slow starting. 997 */ 998 if (thflags & TH_FIN || tlen != 0) 999 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 1000 else 1001 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1002 tcpstat.tcps_connects++; 1003 soisconnected(so); 1004 goto trimthenstep6; 1005 } 1006 goto drop; 1007 } 1008 after_listen: 1009 KASSERT(headlocked, ("tcp_input: after_listen: head not locked")); 1010 INP_LOCK_ASSERT(inp); 1011 1012 /* XXX temp debugging */ 1013 /* should not happen - syncache should pick up these connections */ 1014 if (tp->t_state == TCPS_LISTEN) 1015 panic("tcp_input: TCPS_LISTEN"); 1016 1017 /* 1018 * This is the second part of the MSS DoS prevention code (after 1019 * minmss on the sending side) and it deals with too many too small 1020 * tcp packets in a too short timeframe (1 second). 1021 * 1022 * For every full second we count the number of received packets 1023 * and bytes. If we get a lot of packets per second for this connection 1024 * (tcp_minmssoverload) we take a closer look at it and compute the 1025 * average packet size for the past second. If that is less than 1026 * tcp_minmss we get too many packets with very small payload which 1027 * is not good and burdens our system (and every packet generates 1028 * a wakeup to the process connected to our socket). We can reasonable 1029 * expect this to be small packet DoS attack to exhaust our CPU 1030 * cycles. 1031 * 1032 * Care has to be taken for the minimum packet overload value. This 1033 * value defines the minimum number of packets per second before we 1034 * start to worry. This must not be too low to avoid killing for 1035 * example interactive connections with many small packets like 1036 * telnet or SSH. 1037 * 1038 * Setting either tcp_minmssoverload or tcp_minmss to "" disables 1039 * this check. 1040 * 1041 * Account for packet if payload packet, skip over ACK, etc. 1042 */ 1043 if (tcp_minmss && tcp_minmssoverload && 1044 tp->t_state == TCPS_ESTABLISHED && tlen > 0) { 1045 if (tp->rcv_second > ticks) { 1046 tp->rcv_pps++; 1047 tp->rcv_byps += tlen + off; 1048 if (tp->rcv_pps > tcp_minmssoverload) { 1049 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) { 1050 printf("too many small tcp packets from " 1051 "%s:%u, av. %lubyte/packet, " 1052 "dropping connection\n", 1053 #ifdef INET6 1054 isipv6 ? 1055 ip6_sprintf(&inp->inp_inc.inc6_faddr) : 1056 #endif 1057 inet_ntoa(inp->inp_inc.inc_faddr), 1058 inp->inp_inc.inc_fport, 1059 tp->rcv_byps / tp->rcv_pps); 1060 KASSERT(headlocked, ("tcp_input: " 1061 "after_listen: tcp_drop: head " 1062 "not locked")); 1063 tp = tcp_drop(tp, ECONNRESET); 1064 tcpstat.tcps_minmssdrops++; 1065 goto drop; 1066 } 1067 } 1068 } else { 1069 tp->rcv_second = ticks + hz; 1070 tp->rcv_pps = 1; 1071 tp->rcv_byps = tlen + off; 1072 } 1073 } 1074 1075 /* 1076 * Segment received on connection. 1077 * Reset idle time and keep-alive timer. 1078 */ 1079 tp->t_rcvtime = ticks; 1080 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1081 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1082 1083 /* 1084 * Process options only when we get SYN/ACK back. The SYN case 1085 * for incoming connections is handled in tcp_syncache. 1086 * XXX this is traditional behavior, may need to be cleaned up. 1087 */ 1088 tcp_dooptions(tp, &to, optp, optlen, thflags & TH_SYN, th); 1089 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1090 if (to.to_flags & TOF_SCALE) { 1091 tp->t_flags |= TF_RCVD_SCALE; 1092 tp->requested_s_scale = to.to_requested_s_scale; 1093 } 1094 if (to.to_flags & TOF_TS) { 1095 tp->t_flags |= TF_RCVD_TSTMP; 1096 tp->ts_recent = to.to_tsval; 1097 tp->ts_recent_age = ticks; 1098 } 1099 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1100 tp->t_flags |= TF_RCVD_CC; 1101 if (to.to_flags & TOF_MSS) 1102 tcp_mss(tp, to.to_mss); 1103 if (tp->sack_enable) { 1104 if (!(to.to_flags & TOF_SACK)) 1105 tp->sack_enable = 0; 1106 else 1107 tp->t_flags |= TF_SACK_PERMIT; 1108 } 1109 1110 } 1111 1112 if (tp->sack_enable) { 1113 /* Delete stale (cumulatively acked) SACK holes */ 1114 tcp_del_sackholes(tp, th); 1115 } 1116 1117 /* 1118 * Header prediction: check for the two common cases 1119 * of a uni-directional data xfer. If the packet has 1120 * no control flags, is in-sequence, the window didn't 1121 * change and we're not retransmitting, it's a 1122 * candidate. If the length is zero and the ack moved 1123 * forward, we're the sender side of the xfer. Just 1124 * free the data acked & wake any higher level process 1125 * that was blocked waiting for space. If the length 1126 * is non-zero and the ack didn't move, we're the 1127 * receiver side. If we're getting packets in-order 1128 * (the reassembly queue is empty), add the data to 1129 * the socket buffer and note that we need a delayed ack. 1130 * Make sure that the hidden state-flags are also off. 1131 * Since we check for TCPS_ESTABLISHED above, it can only 1132 * be TH_NEEDSYN. 1133 */ 1134 if (tp->t_state == TCPS_ESTABLISHED && 1135 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1136 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1137 ((to.to_flags & TOF_TS) == 0 || 1138 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1139 /* 1140 * Using the CC option is compulsory if once started: 1141 * the segment is OK if no T/TCP was negotiated or 1142 * if the segment has a CC option equal to CCrecv 1143 */ 1144 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1145 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1146 th->th_seq == tp->rcv_nxt && 1147 tiwin && tiwin == tp->snd_wnd && 1148 tp->snd_nxt == tp->snd_max) { 1149 1150 /* 1151 * If last ACK falls within this segment's sequence numbers, 1152 * record the timestamp. 1153 * NOTE that the test is modified according to the latest 1154 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1155 */ 1156 if ((to.to_flags & TOF_TS) != 0 && 1157 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1158 tp->ts_recent_age = ticks; 1159 tp->ts_recent = to.to_tsval; 1160 } 1161 1162 if (tlen == 0) { 1163 if (SEQ_GT(th->th_ack, tp->snd_una) && 1164 SEQ_LEQ(th->th_ack, tp->snd_max) && 1165 tp->snd_cwnd >= tp->snd_wnd && 1166 ((!tcp_do_newreno && !tp->sack_enable && 1167 tp->t_dupacks < tcprexmtthresh) || 1168 ((tcp_do_newreno || tp->sack_enable) && 1169 !IN_FASTRECOVERY(tp)))) { 1170 KASSERT(headlocked, ("headlocked")); 1171 INP_INFO_WUNLOCK(&tcbinfo); 1172 headlocked = 0; 1173 /* 1174 * this is a pure ack for outstanding data. 1175 */ 1176 ++tcpstat.tcps_predack; 1177 /* 1178 * "bad retransmit" recovery 1179 */ 1180 if (tp->t_rxtshift == 1 && 1181 ticks < tp->t_badrxtwin) { 1182 ++tcpstat.tcps_sndrexmitbad; 1183 tp->snd_cwnd = tp->snd_cwnd_prev; 1184 tp->snd_ssthresh = 1185 tp->snd_ssthresh_prev; 1186 tp->snd_recover = tp->snd_recover_prev; 1187 if (tp->t_flags & TF_WASFRECOVERY) 1188 ENTER_FASTRECOVERY(tp); 1189 tp->snd_nxt = tp->snd_max; 1190 tp->t_badrxtwin = 0; 1191 } 1192 1193 /* 1194 * Recalculate the transmit timer / rtt. 1195 * 1196 * Some boxes send broken timestamp replies 1197 * during the SYN+ACK phase, ignore 1198 * timestamps of 0 or we could calculate a 1199 * huge RTT and blow up the retransmit timer. 1200 */ 1201 if ((to.to_flags & TOF_TS) != 0 && 1202 to.to_tsecr) { 1203 tcp_xmit_timer(tp, 1204 ticks - to.to_tsecr + 1); 1205 } else if (tp->t_rtttime && 1206 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1207 tcp_xmit_timer(tp, 1208 ticks - tp->t_rtttime); 1209 } 1210 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1211 acked = th->th_ack - tp->snd_una; 1212 tcpstat.tcps_rcvackpack++; 1213 tcpstat.tcps_rcvackbyte += acked; 1214 sbdrop(&so->so_snd, acked); 1215 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1216 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1217 tp->snd_recover = th->th_ack - 1; 1218 tp->snd_una = th->th_ack; 1219 /* 1220 * pull snd_wl2 up to prevent seq wrap relative 1221 * to th_ack. 1222 */ 1223 tp->snd_wl2 = th->th_ack; 1224 tp->t_dupacks = 0; 1225 m_freem(m); 1226 ND6_HINT(tp); /* some progress has been done */ 1227 1228 /* 1229 * If all outstanding data are acked, stop 1230 * retransmit timer, otherwise restart timer 1231 * using current (possibly backed-off) value. 1232 * If process is waiting for space, 1233 * wakeup/selwakeup/signal. If data 1234 * are ready to send, let tcp_output 1235 * decide between more output or persist. 1236 1237 #ifdef TCPDEBUG 1238 if (so->so_options & SO_DEBUG) 1239 tcp_trace(TA_INPUT, ostate, tp, 1240 (void *)tcp_saveipgen, 1241 &tcp_savetcp, 0); 1242 #endif 1243 */ 1244 if (tp->snd_una == tp->snd_max) 1245 callout_stop(tp->tt_rexmt); 1246 else if (!callout_active(tp->tt_persist)) 1247 callout_reset(tp->tt_rexmt, 1248 tp->t_rxtcur, 1249 tcp_timer_rexmt, tp); 1250 1251 sowwakeup(so); 1252 if (so->so_snd.sb_cc) 1253 (void) tcp_output(tp); 1254 goto check_delack; 1255 } 1256 } else if (th->th_ack == tp->snd_una && 1257 LIST_EMPTY(&tp->t_segq) && 1258 tlen <= sbspace(&so->so_rcv)) { 1259 KASSERT(headlocked, ("headlocked")); 1260 INP_INFO_WUNLOCK(&tcbinfo); 1261 headlocked = 0; 1262 /* 1263 * this is a pure, in-sequence data packet 1264 * with nothing on the reassembly queue and 1265 * we have enough buffer space to take it. 1266 */ 1267 /* Clean receiver SACK report if present */ 1268 if (tp->sack_enable && tp->rcv_numsacks) 1269 tcp_clean_sackreport(tp); 1270 ++tcpstat.tcps_preddat; 1271 tp->rcv_nxt += tlen; 1272 /* 1273 * Pull snd_wl1 up to prevent seq wrap relative to 1274 * th_seq. 1275 */ 1276 tp->snd_wl1 = th->th_seq; 1277 /* 1278 * Pull rcv_up up to prevent seq wrap relative to 1279 * rcv_nxt. 1280 */ 1281 tp->rcv_up = tp->rcv_nxt; 1282 tcpstat.tcps_rcvpack++; 1283 tcpstat.tcps_rcvbyte += tlen; 1284 ND6_HINT(tp); /* some progress has been done */ 1285 /* 1286 #ifdef TCPDEBUG 1287 if (so->so_options & SO_DEBUG) 1288 tcp_trace(TA_INPUT, ostate, tp, 1289 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1290 #endif 1291 * Add data to socket buffer. 1292 */ 1293 SOCKBUF_LOCK(&so->so_rcv); 1294 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1295 m_freem(m); 1296 } else { 1297 m_adj(m, drop_hdrlen); /* delayed header drop */ 1298 sbappendstream_locked(&so->so_rcv, m); 1299 } 1300 sorwakeup_locked(so); 1301 if (DELAY_ACK(tp)) { 1302 tp->t_flags |= TF_DELACK; 1303 } else { 1304 tp->t_flags |= TF_ACKNOW; 1305 tcp_output(tp); 1306 } 1307 goto check_delack; 1308 } 1309 } 1310 1311 /* 1312 * Calculate amount of space in receive window, 1313 * and then do TCP input processing. 1314 * Receive window is amount of space in rcv queue, 1315 * but not less than advertised window. 1316 */ 1317 { int win; 1318 1319 win = sbspace(&so->so_rcv); 1320 if (win < 0) 1321 win = 0; 1322 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1323 } 1324 1325 switch (tp->t_state) { 1326 1327 /* 1328 * If the state is SYN_RECEIVED: 1329 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1330 */ 1331 case TCPS_SYN_RECEIVED: 1332 if ((thflags & TH_ACK) && 1333 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1334 SEQ_GT(th->th_ack, tp->snd_max))) { 1335 rstreason = BANDLIM_RST_OPENPORT; 1336 goto dropwithreset; 1337 } 1338 break; 1339 1340 /* 1341 * If the state is SYN_SENT: 1342 * if seg contains an ACK, but not for our SYN, drop the input. 1343 * if seg contains a RST, then drop the connection. 1344 * if seg does not contain SYN, then drop it. 1345 * Otherwise this is an acceptable SYN segment 1346 * initialize tp->rcv_nxt and tp->irs 1347 * if seg contains ack then advance tp->snd_una 1348 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1349 * arrange for segment to be acked (eventually) 1350 * continue processing rest of data/controls, beginning with URG 1351 */ 1352 case TCPS_SYN_SENT: 1353 if (tcp_do_rfc1644) 1354 tcp_hc_gettao(&inp->inp_inc, &tao); 1355 1356 if ((thflags & TH_ACK) && 1357 (SEQ_LEQ(th->th_ack, tp->iss) || 1358 SEQ_GT(th->th_ack, tp->snd_max))) { 1359 /* 1360 * If we have a cached CCsent for the remote host, 1361 * hence we haven't just crashed and restarted, 1362 * do not send a RST. This may be a retransmission 1363 * from the other side after our earlier ACK was lost. 1364 * Our new SYN, when it arrives, will serve as the 1365 * needed ACK. 1366 */ 1367 if (tao.tao_ccsent != 0) 1368 goto drop; 1369 else { 1370 rstreason = BANDLIM_UNLIMITED; 1371 goto dropwithreset; 1372 } 1373 } 1374 if (thflags & TH_RST) { 1375 if (thflags & TH_ACK) { 1376 KASSERT(headlocked, ("tcp_input: after_listen" 1377 ": tcp_drop.2: head not locked")); 1378 tp = tcp_drop(tp, ECONNREFUSED); 1379 } 1380 goto drop; 1381 } 1382 if ((thflags & TH_SYN) == 0) 1383 goto drop; 1384 tp->snd_wnd = th->th_win; /* initial send window */ 1385 tp->cc_recv = to.to_cc; /* foreign CC */ 1386 1387 tp->irs = th->th_seq; 1388 tcp_rcvseqinit(tp); 1389 if (thflags & TH_ACK) { 1390 /* 1391 * Our SYN was acked. If segment contains CC.ECHO 1392 * option, check it to make sure this segment really 1393 * matches our SYN. If not, just drop it as old 1394 * duplicate, but send an RST if we're still playing 1395 * by the old rules. If no CC.ECHO option, make sure 1396 * we don't get fooled into using T/TCP. 1397 */ 1398 if (to.to_flags & TOF_CCECHO) { 1399 if (tp->cc_send != to.to_ccecho) { 1400 if (tao.tao_ccsent != 0) 1401 goto drop; 1402 else { 1403 rstreason = BANDLIM_UNLIMITED; 1404 goto dropwithreset; 1405 } 1406 } 1407 } else 1408 tp->t_flags &= ~TF_RCVD_CC; 1409 tcpstat.tcps_connects++; 1410 soisconnected(so); 1411 #ifdef MAC 1412 SOCK_LOCK(so); 1413 mac_set_socket_peer_from_mbuf(m, so); 1414 SOCK_UNLOCK(so); 1415 #endif 1416 /* Do window scaling on this connection? */ 1417 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1418 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1419 tp->snd_scale = tp->requested_s_scale; 1420 tp->rcv_scale = tp->request_r_scale; 1421 } 1422 /* Segment is acceptable, update cache if undefined. */ 1423 if (tao.tao_ccsent == 0 && tcp_do_rfc1644) 1424 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CCSENT, to.to_ccecho, 0); 1425 1426 tp->rcv_adv += tp->rcv_wnd; 1427 tp->snd_una++; /* SYN is acked */ 1428 /* 1429 * If there's data, delay ACK; if there's also a FIN 1430 * ACKNOW will be turned on later. 1431 */ 1432 if (DELAY_ACK(tp) && tlen != 0) 1433 callout_reset(tp->tt_delack, tcp_delacktime, 1434 tcp_timer_delack, tp); 1435 else 1436 tp->t_flags |= TF_ACKNOW; 1437 /* 1438 * Received <SYN,ACK> in SYN_SENT[*] state. 1439 * Transitions: 1440 * SYN_SENT --> ESTABLISHED 1441 * SYN_SENT* --> FIN_WAIT_1 1442 */ 1443 tp->t_starttime = ticks; 1444 if (tp->t_flags & TF_NEEDFIN) { 1445 tp->t_state = TCPS_FIN_WAIT_1; 1446 tp->t_flags &= ~TF_NEEDFIN; 1447 thflags &= ~TH_SYN; 1448 } else { 1449 tp->t_state = TCPS_ESTABLISHED; 1450 callout_reset(tp->tt_keep, tcp_keepidle, 1451 tcp_timer_keep, tp); 1452 } 1453 } else { 1454 /* 1455 * Received initial SYN in SYN-SENT[*] state => 1456 * simultaneous open. If segment contains CC option 1457 * and there is a cached CC, apply TAO test. 1458 * If it succeeds, connection is * half-synchronized. 1459 * Otherwise, do 3-way handshake: 1460 * SYN-SENT -> SYN-RECEIVED 1461 * SYN-SENT* -> SYN-RECEIVED* 1462 * If there was no CC option, clear cached CC value. 1463 */ 1464 tp->t_flags |= TF_ACKNOW; 1465 callout_stop(tp->tt_rexmt); 1466 if (to.to_flags & TOF_CC) { 1467 if (tao.tao_cc != 0 && 1468 CC_GT(to.to_cc, tao.tao_cc)) { 1469 /* 1470 * update cache and make transition: 1471 * SYN-SENT -> ESTABLISHED* 1472 * SYN-SENT* -> FIN-WAIT-1* 1473 */ 1474 tao.tao_cc = to.to_cc; 1475 tcp_hc_updatetao(&inp->inp_inc, 1476 TCP_HC_TAO_CC, to.to_cc, 0); 1477 tp->t_starttime = ticks; 1478 if (tp->t_flags & TF_NEEDFIN) { 1479 tp->t_state = TCPS_FIN_WAIT_1; 1480 tp->t_flags &= ~TF_NEEDFIN; 1481 } else { 1482 tp->t_state = TCPS_ESTABLISHED; 1483 callout_reset(tp->tt_keep, 1484 tcp_keepidle, 1485 tcp_timer_keep, 1486 tp); 1487 } 1488 tp->t_flags |= TF_NEEDSYN; 1489 } else 1490 tp->t_state = TCPS_SYN_RECEIVED; 1491 } else { 1492 if (tcp_do_rfc1644) { 1493 /* CC.NEW or no option => invalidate cache */ 1494 tao.tao_cc = 0; 1495 tcp_hc_updatetao(&inp->inp_inc, 1496 TCP_HC_TAO_CC, to.to_cc, 0); 1497 } 1498 tp->t_state = TCPS_SYN_RECEIVED; 1499 } 1500 } 1501 1502 trimthenstep6: 1503 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not " 1504 "locked")); 1505 INP_LOCK_ASSERT(inp); 1506 1507 /* 1508 * Advance th->th_seq to correspond to first data byte. 1509 * If data, trim to stay within window, 1510 * dropping FIN if necessary. 1511 */ 1512 th->th_seq++; 1513 if (tlen > tp->rcv_wnd) { 1514 todrop = tlen - tp->rcv_wnd; 1515 m_adj(m, -todrop); 1516 tlen = tp->rcv_wnd; 1517 thflags &= ~TH_FIN; 1518 tcpstat.tcps_rcvpackafterwin++; 1519 tcpstat.tcps_rcvbyteafterwin += todrop; 1520 } 1521 tp->snd_wl1 = th->th_seq - 1; 1522 tp->rcv_up = th->th_seq; 1523 /* 1524 * Client side of transaction: already sent SYN and data. 1525 * If the remote host used T/TCP to validate the SYN, 1526 * our data will be ACK'd; if so, enter normal data segment 1527 * processing in the middle of step 5, ack processing. 1528 * Otherwise, goto step 6. 1529 */ 1530 if (thflags & TH_ACK) 1531 goto process_ACK; 1532 1533 goto step6; 1534 1535 /* 1536 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1537 * if segment contains a SYN and CC [not CC.NEW] option: 1538 * if state == TIME_WAIT and connection duration > MSL, 1539 * drop packet and send RST; 1540 * 1541 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1542 * ack the FIN (and data) in retransmission queue. 1543 * Complete close and delete TCPCB. Then reprocess 1544 * segment, hoping to find new TCPCB in LISTEN state; 1545 * 1546 * else must be old SYN; drop it. 1547 * else do normal processing. 1548 */ 1549 case TCPS_LAST_ACK: 1550 case TCPS_CLOSING: 1551 case TCPS_TIME_WAIT: 1552 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1553 if ((thflags & TH_SYN) && 1554 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1555 if (tp->t_state == TCPS_TIME_WAIT && 1556 (ticks - tp->t_starttime) > tcp_msl) { 1557 rstreason = BANDLIM_UNLIMITED; 1558 goto dropwithreset; 1559 } 1560 if (CC_GT(to.to_cc, tp->cc_recv)) { 1561 tp = tcp_close(tp); 1562 goto findpcb; 1563 } 1564 else 1565 goto drop; 1566 } 1567 break; /* continue normal processing */ 1568 } 1569 1570 /* 1571 * States other than LISTEN or SYN_SENT. 1572 * First check the RST flag and sequence number since reset segments 1573 * are exempt from the timestamp and connection count tests. This 1574 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1575 * below which allowed reset segments in half the sequence space 1576 * to fall though and be processed (which gives forged reset 1577 * segments with a random sequence number a 50 percent chance of 1578 * killing a connection). 1579 * Then check timestamp, if present. 1580 * Then check the connection count, if present. 1581 * Then check that at least some bytes of segment are within 1582 * receive window. If segment begins before rcv_nxt, 1583 * drop leading data (and SYN); if nothing left, just ack. 1584 * 1585 * 1586 * If the RST bit is set, check the sequence number to see 1587 * if this is a valid reset segment. 1588 * RFC 793 page 37: 1589 * In all states except SYN-SENT, all reset (RST) segments 1590 * are validated by checking their SEQ-fields. A reset is 1591 * valid if its sequence number is in the window. 1592 * Note: this does not take into account delayed ACKs, so 1593 * we should test against last_ack_sent instead of rcv_nxt. 1594 * The sequence number in the reset segment is normally an 1595 * echo of our outgoing acknowlegement numbers, but some hosts 1596 * send a reset with the sequence number at the rightmost edge 1597 * of our receive window, and we have to handle this case. 1598 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1599 * that brute force RST attacks are possible. To combat this, 1600 * we use a much stricter check while in the ESTABLISHED state, 1601 * only accepting RSTs where the sequence number is equal to 1602 * last_ack_sent. In all other states (the states in which a 1603 * RST is more likely), the more permissive check is used. 1604 * If we have multiple segments in flight, the intial reset 1605 * segment sequence numbers will be to the left of last_ack_sent, 1606 * but they will eventually catch up. 1607 * In any case, it never made sense to trim reset segments to 1608 * fit the receive window since RFC 1122 says: 1609 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1610 * 1611 * A TCP SHOULD allow a received RST segment to include data. 1612 * 1613 * DISCUSSION 1614 * It has been suggested that a RST segment could contain 1615 * ASCII text that encoded and explained the cause of the 1616 * RST. No standard has yet been established for such 1617 * data. 1618 * 1619 * If the reset segment passes the sequence number test examine 1620 * the state: 1621 * SYN_RECEIVED STATE: 1622 * If passive open, return to LISTEN state. 1623 * If active open, inform user that connection was refused. 1624 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1625 * Inform user that connection was reset, and close tcb. 1626 * CLOSING, LAST_ACK STATES: 1627 * Close the tcb. 1628 * TIME_WAIT STATE: 1629 * Drop the segment - see Stevens, vol. 2, p. 964 and 1630 * RFC 1337. 1631 */ 1632 if (thflags & TH_RST) { 1633 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1634 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 1635 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 1636 switch (tp->t_state) { 1637 1638 case TCPS_SYN_RECEIVED: 1639 so->so_error = ECONNREFUSED; 1640 goto close; 1641 1642 case TCPS_ESTABLISHED: 1643 if (tp->last_ack_sent != th->th_seq && 1644 tcp_insecure_rst == 0) { 1645 tcpstat.tcps_badrst++; 1646 goto drop; 1647 } 1648 case TCPS_FIN_WAIT_1: 1649 case TCPS_FIN_WAIT_2: 1650 case TCPS_CLOSE_WAIT: 1651 so->so_error = ECONNRESET; 1652 close: 1653 tp->t_state = TCPS_CLOSED; 1654 tcpstat.tcps_drops++; 1655 KASSERT(headlocked, ("tcp_input: " 1656 "trimthenstep6: tcp_close: head not " 1657 "locked")); 1658 tp = tcp_close(tp); 1659 break; 1660 1661 case TCPS_CLOSING: 1662 case TCPS_LAST_ACK: 1663 KASSERT(headlocked, ("trimthenstep6: " 1664 "tcp_close.2: head not locked")); 1665 tp = tcp_close(tp); 1666 break; 1667 1668 case TCPS_TIME_WAIT: 1669 KASSERT(tp->t_state != TCPS_TIME_WAIT, 1670 ("timewait")); 1671 break; 1672 } 1673 } 1674 goto drop; 1675 } 1676 1677 /* 1678 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1679 * and it's less than ts_recent, drop it. 1680 */ 1681 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1682 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1683 1684 /* Check to see if ts_recent is over 24 days old. */ 1685 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1686 /* 1687 * Invalidate ts_recent. If this segment updates 1688 * ts_recent, the age will be reset later and ts_recent 1689 * will get a valid value. If it does not, setting 1690 * ts_recent to zero will at least satisfy the 1691 * requirement that zero be placed in the timestamp 1692 * echo reply when ts_recent isn't valid. The 1693 * age isn't reset until we get a valid ts_recent 1694 * because we don't want out-of-order segments to be 1695 * dropped when ts_recent is old. 1696 */ 1697 tp->ts_recent = 0; 1698 } else { 1699 tcpstat.tcps_rcvduppack++; 1700 tcpstat.tcps_rcvdupbyte += tlen; 1701 tcpstat.tcps_pawsdrop++; 1702 if (tlen) 1703 goto dropafterack; 1704 goto drop; 1705 } 1706 } 1707 1708 /* 1709 * T/TCP mechanism 1710 * If T/TCP was negotiated and the segment doesn't have CC, 1711 * or if its CC is wrong then drop the segment. 1712 * RST segments do not have to comply with this. 1713 */ 1714 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1715 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1716 goto dropafterack; 1717 1718 /* 1719 * In the SYN-RECEIVED state, validate that the packet belongs to 1720 * this connection before trimming the data to fit the receive 1721 * window. Check the sequence number versus IRS since we know 1722 * the sequence numbers haven't wrapped. This is a partial fix 1723 * for the "LAND" DoS attack. 1724 */ 1725 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1726 rstreason = BANDLIM_RST_OPENPORT; 1727 goto dropwithreset; 1728 } 1729 1730 todrop = tp->rcv_nxt - th->th_seq; 1731 if (todrop > 0) { 1732 if (thflags & TH_SYN) { 1733 thflags &= ~TH_SYN; 1734 th->th_seq++; 1735 if (th->th_urp > 1) 1736 th->th_urp--; 1737 else 1738 thflags &= ~TH_URG; 1739 todrop--; 1740 } 1741 /* 1742 * Following if statement from Stevens, vol. 2, p. 960. 1743 */ 1744 if (todrop > tlen 1745 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1746 /* 1747 * Any valid FIN must be to the left of the window. 1748 * At this point the FIN must be a duplicate or out 1749 * of sequence; drop it. 1750 */ 1751 thflags &= ~TH_FIN; 1752 1753 /* 1754 * Send an ACK to resynchronize and drop any data. 1755 * But keep on processing for RST or ACK. 1756 */ 1757 tp->t_flags |= TF_ACKNOW; 1758 todrop = tlen; 1759 tcpstat.tcps_rcvduppack++; 1760 tcpstat.tcps_rcvdupbyte += todrop; 1761 } else { 1762 tcpstat.tcps_rcvpartduppack++; 1763 tcpstat.tcps_rcvpartdupbyte += todrop; 1764 } 1765 drop_hdrlen += todrop; /* drop from the top afterwards */ 1766 th->th_seq += todrop; 1767 tlen -= todrop; 1768 if (th->th_urp > todrop) 1769 th->th_urp -= todrop; 1770 else { 1771 thflags &= ~TH_URG; 1772 th->th_urp = 0; 1773 } 1774 } 1775 1776 /* 1777 * If new data are received on a connection after the 1778 * user processes are gone, then RST the other end. 1779 */ 1780 if ((so->so_state & SS_NOFDREF) && 1781 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1782 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not " 1783 "locked")); 1784 tp = tcp_close(tp); 1785 tcpstat.tcps_rcvafterclose++; 1786 rstreason = BANDLIM_UNLIMITED; 1787 goto dropwithreset; 1788 } 1789 1790 /* 1791 * If segment ends after window, drop trailing data 1792 * (and PUSH and FIN); if nothing left, just ACK. 1793 */ 1794 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1795 if (todrop > 0) { 1796 tcpstat.tcps_rcvpackafterwin++; 1797 if (todrop >= tlen) { 1798 tcpstat.tcps_rcvbyteafterwin += tlen; 1799 /* 1800 * If a new connection request is received 1801 * while in TIME_WAIT, drop the old connection 1802 * and start over if the sequence numbers 1803 * are above the previous ones. 1804 */ 1805 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1806 if (thflags & TH_SYN && 1807 tp->t_state == TCPS_TIME_WAIT && 1808 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1809 KASSERT(headlocked, ("trimthenstep6: " 1810 "tcp_close.4: head not locked")); 1811 tp = tcp_close(tp); 1812 goto findpcb; 1813 } 1814 /* 1815 * If window is closed can only take segments at 1816 * window edge, and have to drop data and PUSH from 1817 * incoming segments. Continue processing, but 1818 * remember to ack. Otherwise, drop segment 1819 * and ack. 1820 */ 1821 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1822 tp->t_flags |= TF_ACKNOW; 1823 tcpstat.tcps_rcvwinprobe++; 1824 } else 1825 goto dropafterack; 1826 } else 1827 tcpstat.tcps_rcvbyteafterwin += todrop; 1828 m_adj(m, -todrop); 1829 tlen -= todrop; 1830 thflags &= ~(TH_PUSH|TH_FIN); 1831 } 1832 1833 /* 1834 * If last ACK falls within this segment's sequence numbers, 1835 * record its timestamp. 1836 * NOTE: 1837 * 1) That the test incorporates suggestions from the latest 1838 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1839 * 2) That updating only on newer timestamps interferes with 1840 * our earlier PAWS tests, so this check should be solely 1841 * predicated on the sequence space of this segment. 1842 * 3) That we modify the segment boundary check to be 1843 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1844 * instead of RFC1323's 1845 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1846 * This modified check allows us to overcome RFC1323's 1847 * limitations as described in Stevens TCP/IP Illustrated 1848 * Vol. 2 p.869. In such cases, we can still calculate the 1849 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1850 */ 1851 if ((to.to_flags & TOF_TS) != 0 && 1852 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1853 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1854 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1855 tp->ts_recent_age = ticks; 1856 tp->ts_recent = to.to_tsval; 1857 } 1858 1859 /* 1860 * If a SYN is in the window, then this is an 1861 * error and we send an RST and drop the connection. 1862 */ 1863 if (thflags & TH_SYN) { 1864 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: " 1865 "head not locked")); 1866 tp = tcp_drop(tp, ECONNRESET); 1867 rstreason = BANDLIM_UNLIMITED; 1868 goto drop; 1869 } 1870 1871 /* 1872 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1873 * flag is on (half-synchronized state), then queue data for 1874 * later processing; else drop segment and return. 1875 */ 1876 if ((thflags & TH_ACK) == 0) { 1877 if (tp->t_state == TCPS_SYN_RECEIVED || 1878 (tp->t_flags & TF_NEEDSYN)) 1879 goto step6; 1880 else if (tp->t_flags & TF_ACKNOW) 1881 goto dropafterack; 1882 else 1883 goto drop; 1884 } 1885 1886 /* 1887 * Ack processing. 1888 */ 1889 switch (tp->t_state) { 1890 1891 /* 1892 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1893 * ESTABLISHED state and continue processing. 1894 * The ACK was checked above. 1895 */ 1896 case TCPS_SYN_RECEIVED: 1897 1898 tcpstat.tcps_connects++; 1899 soisconnected(so); 1900 /* Do window scaling? */ 1901 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1902 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1903 tp->snd_scale = tp->requested_s_scale; 1904 tp->rcv_scale = tp->request_r_scale; 1905 } 1906 /* 1907 * Upon successful completion of 3-way handshake, 1908 * update cache.CC, pass any queued data to the user, 1909 * and advance state appropriately. 1910 */ 1911 if (tcp_do_rfc1644) { 1912 tao.tao_cc = tp->cc_recv; 1913 tcp_hc_updatetao(&inp->inp_inc, TCP_HC_TAO_CC, 1914 tp->cc_recv, 0); 1915 } 1916 /* 1917 * Make transitions: 1918 * SYN-RECEIVED -> ESTABLISHED 1919 * SYN-RECEIVED* -> FIN-WAIT-1 1920 */ 1921 tp->t_starttime = ticks; 1922 if (tp->t_flags & TF_NEEDFIN) { 1923 tp->t_state = TCPS_FIN_WAIT_1; 1924 tp->t_flags &= ~TF_NEEDFIN; 1925 } else { 1926 tp->t_state = TCPS_ESTABLISHED; 1927 callout_reset(tp->tt_keep, tcp_keepidle, 1928 tcp_timer_keep, tp); 1929 } 1930 /* 1931 * If segment contains data or ACK, will call tcp_reass() 1932 * later; if not, do so now to pass queued data to user. 1933 */ 1934 if (tlen == 0 && (thflags & TH_FIN) == 0) 1935 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1936 (struct mbuf *)0); 1937 tp->snd_wl1 = th->th_seq - 1; 1938 /* FALLTHROUGH */ 1939 1940 /* 1941 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1942 * ACKs. If the ack is in the range 1943 * tp->snd_una < th->th_ack <= tp->snd_max 1944 * then advance tp->snd_una to th->th_ack and drop 1945 * data from the retransmission queue. If this ACK reflects 1946 * more up to date window information we update our window information. 1947 */ 1948 case TCPS_ESTABLISHED: 1949 case TCPS_FIN_WAIT_1: 1950 case TCPS_FIN_WAIT_2: 1951 case TCPS_CLOSE_WAIT: 1952 case TCPS_CLOSING: 1953 case TCPS_LAST_ACK: 1954 case TCPS_TIME_WAIT: 1955 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 1956 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1957 if (tlen == 0 && tiwin == tp->snd_wnd) { 1958 tcpstat.tcps_rcvdupack++; 1959 /* 1960 * If we have outstanding data (other than 1961 * a window probe), this is a completely 1962 * duplicate ack (ie, window info didn't 1963 * change), the ack is the biggest we've 1964 * seen and we've seen exactly our rexmt 1965 * threshhold of them, assume a packet 1966 * has been dropped and retransmit it. 1967 * Kludge snd_nxt & the congestion 1968 * window so we send only this one 1969 * packet. 1970 * 1971 * We know we're losing at the current 1972 * window size so do congestion avoidance 1973 * (set ssthresh to half the current window 1974 * and pull our congestion window back to 1975 * the new ssthresh). 1976 * 1977 * Dup acks mean that packets have left the 1978 * network (they're now cached at the receiver) 1979 * so bump cwnd by the amount in the receiver 1980 * to keep a constant cwnd packets in the 1981 * network. 1982 */ 1983 if (!callout_active(tp->tt_rexmt) || 1984 th->th_ack != tp->snd_una) 1985 tp->t_dupacks = 0; 1986 else if (++tp->t_dupacks > tcprexmtthresh || 1987 ((tcp_do_newreno || tp->sack_enable) && 1988 IN_FASTRECOVERY(tp))) { 1989 1990 if (tp->sack_enable && IN_FASTRECOVERY(tp)) { 1991 int data_in_pipe; 1992 int sacked, lost_not_rexmitted; 1993 1994 /* 1995 * Compute the amount of data in flight first. 1996 * We can inject new data into the pipe iff 1997 * we have less than 1/2 the original window's 1998 * worth of data in flight. 1999 */ 2000 sacked = tcp_sacked_bytes(tp, &lost_not_rexmitted); 2001 data_in_pipe = (tp->snd_nxt - tp->snd_una) - 2002 (sacked + lost_not_rexmitted); 2003 if (data_in_pipe < tp->snd_ssthresh) { 2004 tp->snd_cwnd += tp->t_maxseg; 2005 if (tp->snd_cwnd > tp->snd_ssthresh) 2006 tp->snd_cwnd = tp->snd_ssthresh; 2007 } 2008 } else 2009 tp->snd_cwnd += tp->t_maxseg; 2010 (void) tcp_output(tp); 2011 goto drop; 2012 } else if (tp->t_dupacks == tcprexmtthresh) { 2013 tcp_seq onxt = tp->snd_nxt; 2014 u_int win; 2015 2016 /* 2017 * If we're doing sack, check to 2018 * see if we're already in sack 2019 * recovery. If we're not doing sack, 2020 * check to see if we're in newreno 2021 * recovery. 2022 */ 2023 if (tp->sack_enable) { 2024 if (IN_FASTRECOVERY(tp)) { 2025 tp->t_dupacks = 0; 2026 break; 2027 } 2028 } else if (tcp_do_newreno) { 2029 if (SEQ_LEQ(th->th_ack, 2030 tp->snd_recover)) { 2031 tp->t_dupacks = 0; 2032 break; 2033 } 2034 } 2035 win = min(tp->snd_wnd, tp->snd_cwnd) / 2036 2 / tp->t_maxseg; 2037 if (win < 2) 2038 win = 2; 2039 tp->snd_ssthresh = win * tp->t_maxseg; 2040 ENTER_FASTRECOVERY(tp); 2041 tp->snd_recover = tp->snd_max; 2042 callout_stop(tp->tt_rexmt); 2043 tp->t_rtttime = 0; 2044 if (tp->sack_enable) { 2045 tcpstat.tcps_sack_recovery_episode++; 2046 tp->sack_newdata = tp->snd_nxt; 2047 tp->snd_cwnd = tp->t_maxseg; 2048 (void) tcp_output(tp); 2049 goto drop; 2050 } 2051 tp->snd_nxt = th->th_ack; 2052 tp->snd_cwnd = tp->t_maxseg; 2053 (void) tcp_output(tp); 2054 KASSERT(tp->snd_limited <= 2, 2055 ("tp->snd_limited too big")); 2056 tp->snd_cwnd = tp->snd_ssthresh + 2057 tp->t_maxseg * 2058 (tp->t_dupacks - tp->snd_limited); 2059 if (SEQ_GT(onxt, tp->snd_nxt)) 2060 tp->snd_nxt = onxt; 2061 goto drop; 2062 } else if (tcp_do_rfc3042) { 2063 u_long oldcwnd = tp->snd_cwnd; 2064 tcp_seq oldsndmax = tp->snd_max; 2065 u_int sent; 2066 2067 KASSERT(tp->t_dupacks == 1 || 2068 tp->t_dupacks == 2, 2069 ("dupacks not 1 or 2")); 2070 if (tp->t_dupacks == 1) 2071 tp->snd_limited = 0; 2072 tp->snd_cwnd = 2073 (tp->snd_nxt - tp->snd_una) + 2074 (tp->t_dupacks - tp->snd_limited) * 2075 tp->t_maxseg; 2076 (void) tcp_output(tp); 2077 sent = tp->snd_max - oldsndmax; 2078 if (sent > tp->t_maxseg) { 2079 KASSERT((tp->t_dupacks == 2 && 2080 tp->snd_limited == 0) || 2081 (sent == tp->t_maxseg + 1 && 2082 tp->t_flags & TF_SENTFIN), 2083 ("sent too much")); 2084 tp->snd_limited = 2; 2085 } else if (sent > 0) 2086 ++tp->snd_limited; 2087 tp->snd_cwnd = oldcwnd; 2088 goto drop; 2089 } 2090 } else 2091 tp->t_dupacks = 0; 2092 break; 2093 } 2094 2095 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2096 2097 /* 2098 * If the congestion window was inflated to account 2099 * for the other side's cached packets, retract it. 2100 */ 2101 if (tcp_do_newreno || tp->sack_enable) { 2102 if (IN_FASTRECOVERY(tp)) { 2103 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2104 if (tp->sack_enable) 2105 tcp_sack_partialack(tp, th); 2106 else 2107 tcp_newreno_partial_ack(tp, th); 2108 } else { 2109 /* 2110 * Out of fast recovery. 2111 * Window inflation should have left us 2112 * with approximately snd_ssthresh 2113 * outstanding data. 2114 * But in case we would be inclined to 2115 * send a burst, better to do it via 2116 * the slow start mechanism. 2117 */ 2118 if (SEQ_GT(th->th_ack + 2119 tp->snd_ssthresh, 2120 tp->snd_max)) 2121 tp->snd_cwnd = tp->snd_max - 2122 th->th_ack + 2123 tp->t_maxseg; 2124 else 2125 tp->snd_cwnd = tp->snd_ssthresh; 2126 } 2127 } 2128 } else { 2129 if (tp->t_dupacks >= tcprexmtthresh && 2130 tp->snd_cwnd > tp->snd_ssthresh) 2131 tp->snd_cwnd = tp->snd_ssthresh; 2132 } 2133 tp->t_dupacks = 0; 2134 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2135 tcpstat.tcps_rcvacktoomuch++; 2136 goto dropafterack; 2137 } 2138 /* 2139 * If we reach this point, ACK is not a duplicate, 2140 * i.e., it ACKs something we sent. 2141 */ 2142 if (tp->t_flags & TF_NEEDSYN) { 2143 /* 2144 * T/TCP: Connection was half-synchronized, and our 2145 * SYN has been ACK'd (so connection is now fully 2146 * synchronized). Go to non-starred state, 2147 * increment snd_una for ACK of SYN, and check if 2148 * we can do window scaling. 2149 */ 2150 tp->t_flags &= ~TF_NEEDSYN; 2151 tp->snd_una++; 2152 /* Do window scaling? */ 2153 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2154 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2155 tp->snd_scale = tp->requested_s_scale; 2156 tp->rcv_scale = tp->request_r_scale; 2157 } 2158 } 2159 2160 process_ACK: 2161 KASSERT(headlocked, ("tcp_input: process_ACK: head not " 2162 "locked")); 2163 INP_LOCK_ASSERT(inp); 2164 2165 acked = th->th_ack - tp->snd_una; 2166 tcpstat.tcps_rcvackpack++; 2167 tcpstat.tcps_rcvackbyte += acked; 2168 2169 /* 2170 * If we just performed our first retransmit, and the ACK 2171 * arrives within our recovery window, then it was a mistake 2172 * to do the retransmit in the first place. Recover our 2173 * original cwnd and ssthresh, and proceed to transmit where 2174 * we left off. 2175 */ 2176 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2177 ++tcpstat.tcps_sndrexmitbad; 2178 tp->snd_cwnd = tp->snd_cwnd_prev; 2179 tp->snd_ssthresh = tp->snd_ssthresh_prev; 2180 tp->snd_recover = tp->snd_recover_prev; 2181 if (tp->t_flags & TF_WASFRECOVERY) 2182 ENTER_FASTRECOVERY(tp); 2183 tp->snd_nxt = tp->snd_max; 2184 tp->t_badrxtwin = 0; /* XXX probably not required */ 2185 } 2186 2187 /* 2188 * If we have a timestamp reply, update smoothed 2189 * round trip time. If no timestamp is present but 2190 * transmit timer is running and timed sequence 2191 * number was acked, update smoothed round trip time. 2192 * Since we now have an rtt measurement, cancel the 2193 * timer backoff (cf., Phil Karn's retransmit alg.). 2194 * Recompute the initial retransmit timer. 2195 * 2196 * Some boxes send broken timestamp replies 2197 * during the SYN+ACK phase, ignore 2198 * timestamps of 0 or we could calculate a 2199 * huge RTT and blow up the retransmit timer. 2200 */ 2201 if ((to.to_flags & TOF_TS) != 0 && 2202 to.to_tsecr) { 2203 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2204 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2205 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2206 } 2207 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2208 2209 /* 2210 * If all outstanding data is acked, stop retransmit 2211 * timer and remember to restart (more output or persist). 2212 * If there is more data to be acked, restart retransmit 2213 * timer, using current (possibly backed-off) value. 2214 */ 2215 if (th->th_ack == tp->snd_max) { 2216 callout_stop(tp->tt_rexmt); 2217 needoutput = 1; 2218 } else if (!callout_active(tp->tt_persist)) 2219 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2220 tcp_timer_rexmt, tp); 2221 2222 /* 2223 * If no data (only SYN) was ACK'd, 2224 * skip rest of ACK processing. 2225 */ 2226 if (acked == 0) 2227 goto step6; 2228 2229 /* 2230 * When new data is acked, open the congestion window. 2231 * If the window gives us less than ssthresh packets 2232 * in flight, open exponentially (maxseg per packet). 2233 * Otherwise open linearly: maxseg per window 2234 * (maxseg^2 / cwnd per packet). 2235 */ 2236 if ((!tcp_do_newreno && !tp->sack_enable) || 2237 !IN_FASTRECOVERY(tp)) { 2238 register u_int cw = tp->snd_cwnd; 2239 register u_int incr = tp->t_maxseg; 2240 if (cw > tp->snd_ssthresh) 2241 incr = incr * incr / cw; 2242 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2243 } 2244 SOCKBUF_LOCK(&so->so_snd); 2245 if (acked > so->so_snd.sb_cc) { 2246 tp->snd_wnd -= so->so_snd.sb_cc; 2247 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2248 ourfinisacked = 1; 2249 } else { 2250 sbdrop_locked(&so->so_snd, acked); 2251 tp->snd_wnd -= acked; 2252 ourfinisacked = 0; 2253 } 2254 sowwakeup_locked(so); 2255 /* detect una wraparound */ 2256 if ((tcp_do_newreno || tp->sack_enable) && 2257 !IN_FASTRECOVERY(tp) && 2258 SEQ_GT(tp->snd_una, tp->snd_recover) && 2259 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2260 tp->snd_recover = th->th_ack - 1; 2261 if ((tcp_do_newreno || tp->sack_enable) && 2262 IN_FASTRECOVERY(tp) && 2263 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2264 EXIT_FASTRECOVERY(tp); 2265 tp->snd_una = th->th_ack; 2266 if (tp->sack_enable) { 2267 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2268 tp->snd_recover = tp->snd_una; 2269 } 2270 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2271 tp->snd_nxt = tp->snd_una; 2272 2273 switch (tp->t_state) { 2274 2275 /* 2276 * In FIN_WAIT_1 STATE in addition to the processing 2277 * for the ESTABLISHED state if our FIN is now acknowledged 2278 * then enter FIN_WAIT_2. 2279 */ 2280 case TCPS_FIN_WAIT_1: 2281 if (ourfinisacked) { 2282 /* 2283 * If we can't receive any more 2284 * data, then closing user can proceed. 2285 * Starting the timer is contrary to the 2286 * specification, but if we don't get a FIN 2287 * we'll hang forever. 2288 */ 2289 /* XXXjl 2290 * we should release the tp also, and use a 2291 * compressed state. 2292 */ 2293 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2294 soisdisconnected(so); 2295 callout_reset(tp->tt_2msl, tcp_maxidle, 2296 tcp_timer_2msl, tp); 2297 } 2298 tp->t_state = TCPS_FIN_WAIT_2; 2299 } 2300 break; 2301 2302 /* 2303 * In CLOSING STATE in addition to the processing for 2304 * the ESTABLISHED state if the ACK acknowledges our FIN 2305 * then enter the TIME-WAIT state, otherwise ignore 2306 * the segment. 2307 */ 2308 case TCPS_CLOSING: 2309 if (ourfinisacked) { 2310 KASSERT(headlocked, ("tcp_input: process_ACK: " 2311 "head not locked")); 2312 tcp_twstart(tp); 2313 INP_INFO_WUNLOCK(&tcbinfo); 2314 m_freem(m); 2315 return; 2316 } 2317 break; 2318 2319 /* 2320 * In LAST_ACK, we may still be waiting for data to drain 2321 * and/or to be acked, as well as for the ack of our FIN. 2322 * If our FIN is now acknowledged, delete the TCB, 2323 * enter the closed state and return. 2324 */ 2325 case TCPS_LAST_ACK: 2326 if (ourfinisacked) { 2327 KASSERT(headlocked, ("tcp_input: process_ACK:" 2328 " tcp_close: head not locked")); 2329 tp = tcp_close(tp); 2330 goto drop; 2331 } 2332 break; 2333 2334 /* 2335 * In TIME_WAIT state the only thing that should arrive 2336 * is a retransmission of the remote FIN. Acknowledge 2337 * it and restart the finack timer. 2338 */ 2339 case TCPS_TIME_WAIT: 2340 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2341 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2342 tcp_timer_2msl, tp); 2343 goto dropafterack; 2344 } 2345 } 2346 2347 step6: 2348 KASSERT(headlocked, ("tcp_input: step6: head not locked")); 2349 INP_LOCK_ASSERT(inp); 2350 2351 /* 2352 * Update window information. 2353 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2354 */ 2355 if ((thflags & TH_ACK) && 2356 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2357 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2358 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2359 /* keep track of pure window updates */ 2360 if (tlen == 0 && 2361 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2362 tcpstat.tcps_rcvwinupd++; 2363 tp->snd_wnd = tiwin; 2364 tp->snd_wl1 = th->th_seq; 2365 tp->snd_wl2 = th->th_ack; 2366 if (tp->snd_wnd > tp->max_sndwnd) 2367 tp->max_sndwnd = tp->snd_wnd; 2368 needoutput = 1; 2369 } 2370 2371 /* 2372 * Process segments with URG. 2373 */ 2374 if ((thflags & TH_URG) && th->th_urp && 2375 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2376 /* 2377 * This is a kludge, but if we receive and accept 2378 * random urgent pointers, we'll crash in 2379 * soreceive. It's hard to imagine someone 2380 * actually wanting to send this much urgent data. 2381 */ 2382 SOCKBUF_LOCK(&so->so_rcv); 2383 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2384 th->th_urp = 0; /* XXX */ 2385 thflags &= ~TH_URG; /* XXX */ 2386 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2387 goto dodata; /* XXX */ 2388 } 2389 /* 2390 * If this segment advances the known urgent pointer, 2391 * then mark the data stream. This should not happen 2392 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2393 * a FIN has been received from the remote side. 2394 * In these states we ignore the URG. 2395 * 2396 * According to RFC961 (Assigned Protocols), 2397 * the urgent pointer points to the last octet 2398 * of urgent data. We continue, however, 2399 * to consider it to indicate the first octet 2400 * of data past the urgent section as the original 2401 * spec states (in one of two places). 2402 */ 2403 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2404 tp->rcv_up = th->th_seq + th->th_urp; 2405 so->so_oobmark = so->so_rcv.sb_cc + 2406 (tp->rcv_up - tp->rcv_nxt) - 1; 2407 if (so->so_oobmark == 0) 2408 so->so_rcv.sb_state |= SBS_RCVATMARK; 2409 sohasoutofband(so); 2410 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2411 } 2412 SOCKBUF_UNLOCK(&so->so_rcv); 2413 /* 2414 * Remove out of band data so doesn't get presented to user. 2415 * This can happen independent of advancing the URG pointer, 2416 * but if two URG's are pending at once, some out-of-band 2417 * data may creep in... ick. 2418 */ 2419 if (th->th_urp <= (u_long)tlen && 2420 !(so->so_options & SO_OOBINLINE)) { 2421 /* hdr drop is delayed */ 2422 tcp_pulloutofband(so, th, m, drop_hdrlen); 2423 } 2424 } else { 2425 /* 2426 * If no out of band data is expected, 2427 * pull receive urgent pointer along 2428 * with the receive window. 2429 */ 2430 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2431 tp->rcv_up = tp->rcv_nxt; 2432 } 2433 dodata: /* XXX */ 2434 KASSERT(headlocked, ("tcp_input: dodata: head not locked")); 2435 INP_LOCK_ASSERT(inp); 2436 2437 /* 2438 * Process the segment text, merging it into the TCP sequencing queue, 2439 * and arranging for acknowledgment of receipt if necessary. 2440 * This process logically involves adjusting tp->rcv_wnd as data 2441 * is presented to the user (this happens in tcp_usrreq.c, 2442 * case PRU_RCVD). If a FIN has already been received on this 2443 * connection then we just ignore the text. 2444 */ 2445 if ((tlen || (thflags & TH_FIN)) && 2446 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2447 tcp_seq save_start = th->th_seq; 2448 tcp_seq save_end = th->th_seq + tlen; 2449 m_adj(m, drop_hdrlen); /* delayed header drop */ 2450 /* 2451 * Insert segment which includes th into TCP reassembly queue 2452 * with control block tp. Set thflags to whether reassembly now 2453 * includes a segment with FIN. This handles the common case 2454 * inline (segment is the next to be received on an established 2455 * connection, and the queue is empty), avoiding linkage into 2456 * and removal from the queue and repetition of various 2457 * conversions. 2458 * Set DELACK for segments received in order, but ack 2459 * immediately when segments are out of order (so 2460 * fast retransmit can work). 2461 */ 2462 if (th->th_seq == tp->rcv_nxt && 2463 LIST_EMPTY(&tp->t_segq) && 2464 TCPS_HAVEESTABLISHED(tp->t_state)) { 2465 if (DELAY_ACK(tp)) 2466 tp->t_flags |= TF_DELACK; 2467 else 2468 tp->t_flags |= TF_ACKNOW; 2469 tp->rcv_nxt += tlen; 2470 thflags = th->th_flags & TH_FIN; 2471 tcpstat.tcps_rcvpack++; 2472 tcpstat.tcps_rcvbyte += tlen; 2473 ND6_HINT(tp); 2474 SOCKBUF_LOCK(&so->so_rcv); 2475 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2476 m_freem(m); 2477 else 2478 sbappendstream_locked(&so->so_rcv, m); 2479 sorwakeup_locked(so); 2480 } else { 2481 thflags = tcp_reass(tp, th, &tlen, m); 2482 tp->t_flags |= TF_ACKNOW; 2483 } 2484 if (tlen > 0 && tp->sack_enable) 2485 tcp_update_sack_list(tp, save_start, save_end); 2486 /* 2487 * Note the amount of data that peer has sent into 2488 * our window, in order to estimate the sender's 2489 * buffer size. 2490 */ 2491 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2492 } else { 2493 m_freem(m); 2494 thflags &= ~TH_FIN; 2495 } 2496 2497 /* 2498 * If FIN is received ACK the FIN and let the user know 2499 * that the connection is closing. 2500 */ 2501 if (thflags & TH_FIN) { 2502 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2503 socantrcvmore(so); 2504 /* 2505 * If connection is half-synchronized 2506 * (ie NEEDSYN flag on) then delay ACK, 2507 * so it may be piggybacked when SYN is sent. 2508 * Otherwise, since we received a FIN then no 2509 * more input can be expected, send ACK now. 2510 */ 2511 if (tp->t_flags & TF_NEEDSYN) 2512 tp->t_flags |= TF_DELACK; 2513 else 2514 tp->t_flags |= TF_ACKNOW; 2515 tp->rcv_nxt++; 2516 } 2517 switch (tp->t_state) { 2518 2519 /* 2520 * In SYN_RECEIVED and ESTABLISHED STATES 2521 * enter the CLOSE_WAIT state. 2522 */ 2523 case TCPS_SYN_RECEIVED: 2524 tp->t_starttime = ticks; 2525 /*FALLTHROUGH*/ 2526 case TCPS_ESTABLISHED: 2527 tp->t_state = TCPS_CLOSE_WAIT; 2528 break; 2529 2530 /* 2531 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2532 * enter the CLOSING state. 2533 */ 2534 case TCPS_FIN_WAIT_1: 2535 tp->t_state = TCPS_CLOSING; 2536 break; 2537 2538 /* 2539 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2540 * starting the time-wait timer, turning off the other 2541 * standard timers. 2542 */ 2543 case TCPS_FIN_WAIT_2: 2544 KASSERT(headlocked == 1, ("tcp_input: dodata: " 2545 "TCP_FIN_WAIT_2: head not locked")); 2546 tcp_twstart(tp); 2547 INP_INFO_WUNLOCK(&tcbinfo); 2548 return; 2549 2550 /* 2551 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2552 */ 2553 case TCPS_TIME_WAIT: 2554 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait")); 2555 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2556 tcp_timer_2msl, tp); 2557 break; 2558 } 2559 } 2560 INP_INFO_WUNLOCK(&tcbinfo); 2561 headlocked = 0; 2562 #ifdef TCPDEBUG 2563 if (so->so_options & SO_DEBUG) 2564 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2565 &tcp_savetcp, 0); 2566 #endif 2567 2568 /* 2569 * Return any desired output. 2570 */ 2571 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2572 (void) tcp_output(tp); 2573 2574 check_delack: 2575 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked")); 2576 INP_LOCK_ASSERT(inp); 2577 if (tp->t_flags & TF_DELACK) { 2578 tp->t_flags &= ~TF_DELACK; 2579 callout_reset(tp->tt_delack, tcp_delacktime, 2580 tcp_timer_delack, tp); 2581 } 2582 INP_UNLOCK(inp); 2583 return; 2584 2585 dropafterack: 2586 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked")); 2587 /* 2588 * Generate an ACK dropping incoming segment if it occupies 2589 * sequence space, where the ACK reflects our state. 2590 * 2591 * We can now skip the test for the RST flag since all 2592 * paths to this code happen after packets containing 2593 * RST have been dropped. 2594 * 2595 * In the SYN-RECEIVED state, don't send an ACK unless the 2596 * segment we received passes the SYN-RECEIVED ACK test. 2597 * If it fails send a RST. This breaks the loop in the 2598 * "LAND" DoS attack, and also prevents an ACK storm 2599 * between two listening ports that have been sent forged 2600 * SYN segments, each with the source address of the other. 2601 */ 2602 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2603 (SEQ_GT(tp->snd_una, th->th_ack) || 2604 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2605 rstreason = BANDLIM_RST_OPENPORT; 2606 goto dropwithreset; 2607 } 2608 #ifdef TCPDEBUG 2609 if (so->so_options & SO_DEBUG) 2610 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2611 &tcp_savetcp, 0); 2612 #endif 2613 KASSERT(headlocked, ("headlocked should be 1")); 2614 INP_INFO_WUNLOCK(&tcbinfo); 2615 tp->t_flags |= TF_ACKNOW; 2616 (void) tcp_output(tp); 2617 INP_UNLOCK(inp); 2618 m_freem(m); 2619 return; 2620 2621 dropwithreset: 2622 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked")); 2623 /* 2624 * Generate a RST, dropping incoming segment. 2625 * Make ACK acceptable to originator of segment. 2626 * Don't bother to respond if destination was broadcast/multicast. 2627 */ 2628 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2629 goto drop; 2630 if (isipv6) { 2631 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2632 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2633 goto drop; 2634 } else { 2635 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2636 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2637 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2638 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2639 goto drop; 2640 } 2641 /* IPv6 anycast check is done at tcp6_input() */ 2642 2643 /* 2644 * Perform bandwidth limiting. 2645 */ 2646 if (badport_bandlim(rstreason) < 0) 2647 goto drop; 2648 2649 #ifdef TCPDEBUG 2650 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2651 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2652 &tcp_savetcp, 0); 2653 #endif 2654 2655 if (thflags & TH_ACK) 2656 /* mtod() below is safe as long as hdr dropping is delayed */ 2657 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2658 TH_RST); 2659 else { 2660 if (thflags & TH_SYN) 2661 tlen++; 2662 /* mtod() below is safe as long as hdr dropping is delayed */ 2663 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2664 (tcp_seq)0, TH_RST|TH_ACK); 2665 } 2666 2667 if (tp) 2668 INP_UNLOCK(inp); 2669 if (headlocked) 2670 INP_INFO_WUNLOCK(&tcbinfo); 2671 return; 2672 2673 drop: 2674 /* 2675 * Drop space held by incoming segment and return. 2676 */ 2677 #ifdef TCPDEBUG 2678 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2679 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2680 &tcp_savetcp, 0); 2681 #endif 2682 if (tp) 2683 INP_UNLOCK(inp); 2684 if (headlocked) 2685 INP_INFO_WUNLOCK(&tcbinfo); 2686 m_freem(m); 2687 return; 2688 } 2689 2690 /* 2691 * Parse TCP options and place in tcpopt. 2692 */ 2693 static void 2694 tcp_dooptions(tp, to, cp, cnt, is_syn, th) 2695 struct tcpcb *tp; 2696 struct tcpopt *to; 2697 u_char *cp; 2698 int cnt; 2699 int is_syn; 2700 struct tcphdr *th; 2701 { 2702 int opt, optlen; 2703 2704 to->to_flags = 0; 2705 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2706 opt = cp[0]; 2707 if (opt == TCPOPT_EOL) 2708 break; 2709 if (opt == TCPOPT_NOP) 2710 optlen = 1; 2711 else { 2712 if (cnt < 2) 2713 break; 2714 optlen = cp[1]; 2715 if (optlen < 2 || optlen > cnt) 2716 break; 2717 } 2718 switch (opt) { 2719 case TCPOPT_MAXSEG: 2720 if (optlen != TCPOLEN_MAXSEG) 2721 continue; 2722 if (!is_syn) 2723 continue; 2724 to->to_flags |= TOF_MSS; 2725 bcopy((char *)cp + 2, 2726 (char *)&to->to_mss, sizeof(to->to_mss)); 2727 to->to_mss = ntohs(to->to_mss); 2728 break; 2729 case TCPOPT_WINDOW: 2730 if (optlen != TCPOLEN_WINDOW) 2731 continue; 2732 if (! is_syn) 2733 continue; 2734 to->to_flags |= TOF_SCALE; 2735 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2736 break; 2737 case TCPOPT_TIMESTAMP: 2738 if (optlen != TCPOLEN_TIMESTAMP) 2739 continue; 2740 to->to_flags |= TOF_TS; 2741 bcopy((char *)cp + 2, 2742 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2743 to->to_tsval = ntohl(to->to_tsval); 2744 bcopy((char *)cp + 6, 2745 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2746 to->to_tsecr = ntohl(to->to_tsecr); 2747 /* 2748 * If echoed timestamp is later than the current time, 2749 * fall back to non RFC1323 RTT calculation. 2750 */ 2751 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks)) 2752 to->to_tsecr = 0; 2753 break; 2754 case TCPOPT_CC: 2755 if (optlen != TCPOLEN_CC) 2756 continue; 2757 to->to_flags |= TOF_CC; 2758 bcopy((char *)cp + 2, 2759 (char *)&to->to_cc, sizeof(to->to_cc)); 2760 to->to_cc = ntohl(to->to_cc); 2761 break; 2762 case TCPOPT_CCNEW: 2763 if (optlen != TCPOLEN_CC) 2764 continue; 2765 if (!is_syn) 2766 continue; 2767 to->to_flags |= TOF_CCNEW; 2768 bcopy((char *)cp + 2, 2769 (char *)&to->to_cc, sizeof(to->to_cc)); 2770 to->to_cc = ntohl(to->to_cc); 2771 break; 2772 case TCPOPT_CCECHO: 2773 if (optlen != TCPOLEN_CC) 2774 continue; 2775 if (!is_syn) 2776 continue; 2777 to->to_flags |= TOF_CCECHO; 2778 bcopy((char *)cp + 2, 2779 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2780 to->to_ccecho = ntohl(to->to_ccecho); 2781 break; 2782 #ifdef TCP_SIGNATURE 2783 /* 2784 * XXX In order to reply to a host which has set the 2785 * TCP_SIGNATURE option in its initial SYN, we have to 2786 * record the fact that the option was observed here 2787 * for the syncache code to perform the correct response. 2788 */ 2789 case TCPOPT_SIGNATURE: 2790 if (optlen != TCPOLEN_SIGNATURE) 2791 continue; 2792 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2793 break; 2794 #endif 2795 case TCPOPT_SACK_PERMITTED: 2796 if (!tcp_do_sack || 2797 optlen != TCPOLEN_SACK_PERMITTED) 2798 continue; 2799 if (is_syn) { 2800 /* MUST only be set on SYN */ 2801 to->to_flags |= TOF_SACK; 2802 } 2803 break; 2804 2805 case TCPOPT_SACK: 2806 if (!tp || tcp_sack_option(tp, th, cp, optlen)) 2807 continue; 2808 break; 2809 default: 2810 continue; 2811 } 2812 } 2813 } 2814 2815 /* 2816 * Pull out of band byte out of a segment so 2817 * it doesn't appear in the user's data queue. 2818 * It is still reflected in the segment length for 2819 * sequencing purposes. 2820 */ 2821 static void 2822 tcp_pulloutofband(so, th, m, off) 2823 struct socket *so; 2824 struct tcphdr *th; 2825 register struct mbuf *m; 2826 int off; /* delayed to be droped hdrlen */ 2827 { 2828 int cnt = off + th->th_urp - 1; 2829 2830 while (cnt >= 0) { 2831 if (m->m_len > cnt) { 2832 char *cp = mtod(m, caddr_t) + cnt; 2833 struct tcpcb *tp = sototcpcb(so); 2834 2835 tp->t_iobc = *cp; 2836 tp->t_oobflags |= TCPOOB_HAVEDATA; 2837 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2838 m->m_len--; 2839 if (m->m_flags & M_PKTHDR) 2840 m->m_pkthdr.len--; 2841 return; 2842 } 2843 cnt -= m->m_len; 2844 m = m->m_next; 2845 if (m == 0) 2846 break; 2847 } 2848 panic("tcp_pulloutofband"); 2849 } 2850 2851 /* 2852 * Collect new round-trip time estimate 2853 * and update averages and current timeout. 2854 */ 2855 static void 2856 tcp_xmit_timer(tp, rtt) 2857 register struct tcpcb *tp; 2858 int rtt; 2859 { 2860 register int delta; 2861 2862 INP_LOCK_ASSERT(tp->t_inpcb); 2863 2864 tcpstat.tcps_rttupdated++; 2865 tp->t_rttupdated++; 2866 if (tp->t_srtt != 0) { 2867 /* 2868 * srtt is stored as fixed point with 5 bits after the 2869 * binary point (i.e., scaled by 8). The following magic 2870 * is equivalent to the smoothing algorithm in rfc793 with 2871 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2872 * point). Adjust rtt to origin 0. 2873 */ 2874 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2875 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2876 2877 if ((tp->t_srtt += delta) <= 0) 2878 tp->t_srtt = 1; 2879 2880 /* 2881 * We accumulate a smoothed rtt variance (actually, a 2882 * smoothed mean difference), then set the retransmit 2883 * timer to smoothed rtt + 4 times the smoothed variance. 2884 * rttvar is stored as fixed point with 4 bits after the 2885 * binary point (scaled by 16). The following is 2886 * equivalent to rfc793 smoothing with an alpha of .75 2887 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2888 * rfc793's wired-in beta. 2889 */ 2890 if (delta < 0) 2891 delta = -delta; 2892 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2893 if ((tp->t_rttvar += delta) <= 0) 2894 tp->t_rttvar = 1; 2895 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2896 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2897 } else { 2898 /* 2899 * No rtt measurement yet - use the unsmoothed rtt. 2900 * Set the variance to half the rtt (so our first 2901 * retransmit happens at 3*rtt). 2902 */ 2903 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2904 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2905 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2906 } 2907 tp->t_rtttime = 0; 2908 tp->t_rxtshift = 0; 2909 2910 /* 2911 * the retransmit should happen at rtt + 4 * rttvar. 2912 * Because of the way we do the smoothing, srtt and rttvar 2913 * will each average +1/2 tick of bias. When we compute 2914 * the retransmit timer, we want 1/2 tick of rounding and 2915 * 1 extra tick because of +-1/2 tick uncertainty in the 2916 * firing of the timer. The bias will give us exactly the 2917 * 1.5 tick we need. But, because the bias is 2918 * statistical, we have to test that we don't drop below 2919 * the minimum feasible timer (which is 2 ticks). 2920 */ 2921 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2922 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2923 2924 /* 2925 * We received an ack for a packet that wasn't retransmitted; 2926 * it is probably safe to discard any error indications we've 2927 * received recently. This isn't quite right, but close enough 2928 * for now (a route might have failed after we sent a segment, 2929 * and the return path might not be symmetrical). 2930 */ 2931 tp->t_softerror = 0; 2932 } 2933 2934 /* 2935 * Determine a reasonable value for maxseg size. 2936 * If the route is known, check route for mtu. 2937 * If none, use an mss that can be handled on the outgoing 2938 * interface without forcing IP to fragment; if bigger than 2939 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2940 * to utilize large mbufs. If no route is found, route has no mtu, 2941 * or the destination isn't local, use a default, hopefully conservative 2942 * size (usually 512 or the default IP max size, but no more than the mtu 2943 * of the interface), as we can't discover anything about intervening 2944 * gateways or networks. We also initialize the congestion/slow start 2945 * window to be a single segment if the destination isn't local. 2946 * While looking at the routing entry, we also initialize other path-dependent 2947 * parameters from pre-set or cached values in the routing entry. 2948 * 2949 * Also take into account the space needed for options that we 2950 * send regularly. Make maxseg shorter by that amount to assure 2951 * that we can send maxseg amount of data even when the options 2952 * are present. Store the upper limit of the length of options plus 2953 * data in maxopd. 2954 * 2955 * 2956 * In case of T/TCP, we call this routine during implicit connection 2957 * setup as well (offer = -1), to initialize maxseg from the cached 2958 * MSS of our peer. 2959 * 2960 * NOTE that this routine is only called when we process an incoming 2961 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2962 */ 2963 void 2964 tcp_mss(tp, offer) 2965 struct tcpcb *tp; 2966 int offer; 2967 { 2968 int rtt, mss; 2969 u_long bufsize; 2970 u_long maxmtu; 2971 struct inpcb *inp = tp->t_inpcb; 2972 struct socket *so; 2973 struct hc_metrics_lite metrics; 2974 struct rmxp_tao tao; 2975 int origoffer = offer; 2976 #ifdef INET6 2977 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2978 size_t min_protoh = isipv6 ? 2979 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2980 sizeof (struct tcpiphdr); 2981 #else 2982 const size_t min_protoh = sizeof(struct tcpiphdr); 2983 #endif 2984 bzero(&tao, sizeof(tao)); 2985 2986 /* initialize */ 2987 #ifdef INET6 2988 if (isipv6) { 2989 maxmtu = tcp_maxmtu6(&inp->inp_inc); 2990 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2991 } else 2992 #endif 2993 { 2994 maxmtu = tcp_maxmtu(&inp->inp_inc); 2995 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2996 } 2997 so = inp->inp_socket; 2998 2999 /* 3000 * no route to sender, stay with default mss and return 3001 */ 3002 if (maxmtu == 0) 3003 return; 3004 3005 /* what have we got? */ 3006 switch (offer) { 3007 case 0: 3008 /* 3009 * Offer == 0 means that there was no MSS on the SYN 3010 * segment, in this case we use tcp_mssdflt. 3011 */ 3012 offer = 3013 #ifdef INET6 3014 isipv6 ? tcp_v6mssdflt : 3015 #endif 3016 tcp_mssdflt; 3017 break; 3018 3019 case -1: 3020 /* 3021 * Offer == -1 means that we didn't receive SYN yet, 3022 * use cached value in that case; 3023 */ 3024 if (tcp_do_rfc1644) 3025 tcp_hc_gettao(&inp->inp_inc, &tao); 3026 if (tao.tao_mssopt != 0) 3027 offer = tao.tao_mssopt; 3028 /* FALLTHROUGH */ 3029 3030 default: 3031 /* 3032 * Prevent DoS attack with too small MSS. Round up 3033 * to at least minmss. 3034 */ 3035 offer = max(offer, tcp_minmss); 3036 /* 3037 * Sanity check: make sure that maxopd will be large 3038 * enough to allow some data on segments even if the 3039 * all the option space is used (40bytes). Otherwise 3040 * funny things may happen in tcp_output. 3041 */ 3042 offer = max(offer, 64); 3043 if (tcp_do_rfc1644) 3044 tcp_hc_updatetao(&inp->inp_inc, 3045 TCP_HC_TAO_MSSOPT, 0, offer); 3046 } 3047 3048 /* 3049 * rmx information is now retrieved from tcp_hostcache 3050 */ 3051 tcp_hc_get(&inp->inp_inc, &metrics); 3052 3053 /* 3054 * if there's a discovered mtu int tcp hostcache, use it 3055 * else, use the link mtu. 3056 */ 3057 if (metrics.rmx_mtu) 3058 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3059 else { 3060 #ifdef INET6 3061 if (isipv6) { 3062 mss = maxmtu - min_protoh; 3063 if (!path_mtu_discovery && 3064 !in6_localaddr(&inp->in6p_faddr)) 3065 mss = min(mss, tcp_v6mssdflt); 3066 } else 3067 #endif 3068 { 3069 mss = maxmtu - min_protoh; 3070 if (!path_mtu_discovery && 3071 !in_localaddr(inp->inp_faddr)) 3072 mss = min(mss, tcp_mssdflt); 3073 } 3074 } 3075 mss = min(mss, offer); 3076 3077 /* 3078 * maxopd stores the maximum length of data AND options 3079 * in a segment; maxseg is the amount of data in a normal 3080 * segment. We need to store this value (maxopd) apart 3081 * from maxseg, because now every segment carries options 3082 * and thus we normally have somewhat less data in segments. 3083 */ 3084 tp->t_maxopd = mss; 3085 3086 /* 3087 * In case of T/TCP, origoffer==-1 indicates, that no segments 3088 * were received yet. In this case we just guess, otherwise 3089 * we do the same as before T/TCP. 3090 */ 3091 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3092 (origoffer == -1 || 3093 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3094 mss -= TCPOLEN_TSTAMP_APPA; 3095 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 3096 (origoffer == -1 || 3097 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3098 mss -= TCPOLEN_CC_APPA; 3099 tp->t_maxseg = mss; 3100 3101 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3102 if (mss > MCLBYTES) 3103 mss &= ~(MCLBYTES-1); 3104 #else 3105 if (mss > MCLBYTES) 3106 mss = mss / MCLBYTES * MCLBYTES; 3107 #endif 3108 tp->t_maxseg = mss; 3109 3110 /* 3111 * If there's a pipesize, change the socket buffer to that size, 3112 * don't change if sb_hiwat is different than default (then it 3113 * has been changed on purpose with setsockopt). 3114 * Make the socket buffers an integral number of mss units; 3115 * if the mss is larger than the socket buffer, decrease the mss. 3116 */ 3117 SOCKBUF_LOCK(&so->so_snd); 3118 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 3119 bufsize = metrics.rmx_sendpipe; 3120 else 3121 bufsize = so->so_snd.sb_hiwat; 3122 if (bufsize < mss) 3123 mss = bufsize; 3124 else { 3125 bufsize = roundup(bufsize, mss); 3126 if (bufsize > sb_max) 3127 bufsize = sb_max; 3128 if (bufsize > so->so_snd.sb_hiwat) 3129 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3130 } 3131 SOCKBUF_UNLOCK(&so->so_snd); 3132 tp->t_maxseg = mss; 3133 3134 SOCKBUF_LOCK(&so->so_rcv); 3135 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 3136 bufsize = metrics.rmx_recvpipe; 3137 else 3138 bufsize = so->so_rcv.sb_hiwat; 3139 if (bufsize > mss) { 3140 bufsize = roundup(bufsize, mss); 3141 if (bufsize > sb_max) 3142 bufsize = sb_max; 3143 if (bufsize > so->so_rcv.sb_hiwat) 3144 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3145 } 3146 SOCKBUF_UNLOCK(&so->so_rcv); 3147 /* 3148 * While we're here, check the others too 3149 */ 3150 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 3151 tp->t_srtt = rtt; 3152 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3153 tcpstat.tcps_usedrtt++; 3154 if (metrics.rmx_rttvar) { 3155 tp->t_rttvar = metrics.rmx_rttvar; 3156 tcpstat.tcps_usedrttvar++; 3157 } else { 3158 /* default variation is +- 1 rtt */ 3159 tp->t_rttvar = 3160 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3161 } 3162 TCPT_RANGESET(tp->t_rxtcur, 3163 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3164 tp->t_rttmin, TCPTV_REXMTMAX); 3165 } 3166 if (metrics.rmx_ssthresh) { 3167 /* 3168 * There's some sort of gateway or interface 3169 * buffer limit on the path. Use this to set 3170 * the slow start threshhold, but set the 3171 * threshold to no less than 2*mss. 3172 */ 3173 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 3174 tcpstat.tcps_usedssthresh++; 3175 } 3176 if (metrics.rmx_bandwidth) 3177 tp->snd_bandwidth = metrics.rmx_bandwidth; 3178 3179 /* 3180 * Set the slow-start flight size depending on whether this 3181 * is a local network or not. 3182 * 3183 * Extend this so we cache the cwnd too and retrieve it here. 3184 * Make cwnd even bigger than RFC3390 suggests but only if we 3185 * have previous experience with the remote host. Be careful 3186 * not make cwnd bigger than remote receive window or our own 3187 * send socket buffer. Maybe put some additional upper bound 3188 * on the retrieved cwnd. Should do incremental updates to 3189 * hostcache when cwnd collapses so next connection doesn't 3190 * overloads the path again. 3191 * 3192 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 3193 * We currently check only in syncache_socket for that. 3194 */ 3195 #define TCP_METRICS_CWND 3196 #ifdef TCP_METRICS_CWND 3197 if (metrics.rmx_cwnd) 3198 tp->snd_cwnd = max(mss, 3199 min(metrics.rmx_cwnd / 2, 3200 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 3201 else 3202 #endif 3203 if (tcp_do_rfc3390) 3204 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3205 #ifdef INET6 3206 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3207 (!isipv6 && in_localaddr(inp->inp_faddr))) 3208 #else 3209 else if (in_localaddr(inp->inp_faddr)) 3210 #endif 3211 tp->snd_cwnd = mss * ss_fltsz_local; 3212 else 3213 tp->snd_cwnd = mss * ss_fltsz; 3214 } 3215 3216 /* 3217 * Determine the MSS option to send on an outgoing SYN. 3218 */ 3219 int 3220 tcp_mssopt(inc) 3221 struct in_conninfo *inc; 3222 { 3223 int mss = 0; 3224 u_long maxmtu = 0; 3225 u_long thcmtu = 0; 3226 size_t min_protoh; 3227 #ifdef INET6 3228 int isipv6 = inc->inc_isipv6 ? 1 : 0; 3229 #endif 3230 3231 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3232 3233 #ifdef INET6 3234 if (isipv6) { 3235 mss = tcp_v6mssdflt; 3236 maxmtu = tcp_maxmtu6(inc); 3237 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3238 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3239 } else 3240 #endif 3241 { 3242 mss = tcp_mssdflt; 3243 maxmtu = tcp_maxmtu(inc); 3244 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3245 min_protoh = sizeof(struct tcpiphdr); 3246 } 3247 if (maxmtu && thcmtu) 3248 mss = min(maxmtu, thcmtu) - min_protoh; 3249 else if (maxmtu || thcmtu) 3250 mss = max(maxmtu, thcmtu) - min_protoh; 3251 3252 return (mss); 3253 } 3254 3255 3256 /* 3257 * On a partial ack arrives, force the retransmission of the 3258 * next unacknowledged segment. Do not clear tp->t_dupacks. 3259 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3260 * be started again. 3261 */ 3262 static void 3263 tcp_newreno_partial_ack(tp, th) 3264 struct tcpcb *tp; 3265 struct tcphdr *th; 3266 { 3267 tcp_seq onxt = tp->snd_nxt; 3268 u_long ocwnd = tp->snd_cwnd; 3269 3270 callout_stop(tp->tt_rexmt); 3271 tp->t_rtttime = 0; 3272 tp->snd_nxt = th->th_ack; 3273 /* 3274 * Set snd_cwnd to one segment beyond acknowledged offset. 3275 * (tp->snd_una has not yet been updated when this function is called.) 3276 */ 3277 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3278 tp->t_flags |= TF_ACKNOW; 3279 (void) tcp_output(tp); 3280 tp->snd_cwnd = ocwnd; 3281 if (SEQ_GT(onxt, tp->snd_nxt)) 3282 tp->snd_nxt = onxt; 3283 /* 3284 * Partial window deflation. Relies on fact that tp->snd_una 3285 * not updated yet. 3286 */ 3287 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 3288 } 3289 3290 /* 3291 * Returns 1 if the TIME_WAIT state was killed and we should start over, 3292 * looking for a pcb in the listen state. Returns 0 otherwise. 3293 */ 3294 static int 3295 tcp_timewait(tw, to, th, m, tlen) 3296 struct tcptw *tw; 3297 struct tcpopt *to; 3298 struct tcphdr *th; 3299 struct mbuf *m; 3300 int tlen; 3301 { 3302 int thflags; 3303 tcp_seq seq; 3304 #ifdef INET6 3305 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 3306 #else 3307 const int isipv6 = 0; 3308 #endif 3309 3310 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */ 3311 INP_INFO_WLOCK_ASSERT(&tcbinfo); 3312 INP_LOCK_ASSERT(tw->tw_inpcb); 3313 3314 thflags = th->th_flags; 3315 3316 /* 3317 * NOTE: for FIN_WAIT_2 (to be added later), 3318 * must validate sequence number before accepting RST 3319 */ 3320 3321 /* 3322 * If the segment contains RST: 3323 * Drop the segment - see Stevens, vol. 2, p. 964 and 3324 * RFC 1337. 3325 */ 3326 if (thflags & TH_RST) 3327 goto drop; 3328 3329 /* 3330 * If segment contains a SYN and CC [not CC.NEW] option: 3331 * if connection duration > MSL, drop packet and send RST; 3332 * 3333 * if SEG.CC > CCrecv then is new SYN. 3334 * Complete close and delete TCPCB. Then reprocess 3335 * segment, hoping to find new TCPCB in LISTEN state; 3336 * 3337 * else must be old SYN; drop it. 3338 * else do normal processing. 3339 */ 3340 if ((thflags & TH_SYN) && (to->to_flags & TOF_CC) && tw->cc_recv != 0) { 3341 if ((ticks - tw->t_starttime) > tcp_msl) 3342 goto reset; 3343 if (CC_GT(to->to_cc, tw->cc_recv)) { 3344 (void) tcp_twclose(tw, 0); 3345 return (1); 3346 } 3347 goto drop; 3348 } 3349 3350 #if 0 3351 /* PAWS not needed at the moment */ 3352 /* 3353 * RFC 1323 PAWS: If we have a timestamp reply on this segment 3354 * and it's less than ts_recent, drop it. 3355 */ 3356 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 3357 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 3358 if ((thflags & TH_ACK) == 0) 3359 goto drop; 3360 goto ack; 3361 } 3362 /* 3363 * ts_recent is never updated because we never accept new segments. 3364 */ 3365 #endif 3366 3367 /* 3368 * If a new connection request is received 3369 * while in TIME_WAIT, drop the old connection 3370 * and start over if the sequence numbers 3371 * are above the previous ones. 3372 */ 3373 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 3374 (void) tcp_twclose(tw, 0); 3375 return (1); 3376 } 3377 3378 /* 3379 * Drop the the segment if it does not contain an ACK. 3380 */ 3381 if ((thflags & TH_ACK) == 0) 3382 goto drop; 3383 3384 /* 3385 * Reset the 2MSL timer if this is a duplicate FIN. 3386 */ 3387 if (thflags & TH_FIN) { 3388 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 3389 if (seq + 1 == tw->rcv_nxt) 3390 tcp_timer_2msl_reset(tw, 2 * tcp_msl); 3391 } 3392 3393 /* 3394 * Acknowledge the segment if it has data or is not a duplicate ACK. 3395 */ 3396 if (thflags != TH_ACK || tlen != 0 || 3397 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 3398 tcp_twrespond(tw, TH_ACK); 3399 goto drop; 3400 3401 reset: 3402 /* 3403 * Generate a RST, dropping incoming segment. 3404 * Make ACK acceptable to originator of segment. 3405 * Don't bother to respond if destination was broadcast/multicast. 3406 */ 3407 if (m->m_flags & (M_BCAST|M_MCAST)) 3408 goto drop; 3409 if (isipv6) { 3410 struct ip6_hdr *ip6; 3411 3412 /* IPv6 anycast check is done at tcp6_input() */ 3413 ip6 = mtod(m, struct ip6_hdr *); 3414 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3415 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3416 goto drop; 3417 } else { 3418 struct ip *ip; 3419 3420 ip = mtod(m, struct ip *); 3421 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3422 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3423 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3424 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3425 goto drop; 3426 } 3427 if (thflags & TH_ACK) { 3428 tcp_respond(NULL, 3429 mtod(m, void *), th, m, 0, th->th_ack, TH_RST); 3430 } else { 3431 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0); 3432 tcp_respond(NULL, 3433 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK); 3434 } 3435 INP_UNLOCK(tw->tw_inpcb); 3436 return (0); 3437 3438 drop: 3439 INP_UNLOCK(tw->tw_inpcb); 3440 m_freem(m); 3441 return (0); 3442 }
Cache object: 479de24ff11daf00e65b5ba2d2ff3bc8
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