1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 85 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.31 2004/07/17 20:31:31 hsu Exp $ 86 */ 87 88 #include "opt_ipfw.h" /* for ipfw_fwd */ 89 #include "opt_inet6.h" 90 #include "opt_ipsec.h" 91 #include "opt_tcpdebug.h" 92 #include "opt_tcp_input.h" 93 94 #include <sys/param.h> 95 #include <sys/systm.h> 96 #include <sys/kernel.h> 97 #include <sys/sysctl.h> 98 #include <sys/malloc.h> 99 #include <sys/mbuf.h> 100 #include <sys/proc.h> /* for proc0 declaration */ 101 #include <sys/protosw.h> 102 #include <sys/socket.h> 103 #include <sys/socketvar.h> 104 #include <sys/syslog.h> 105 #include <sys/in_cksum.h> 106 107 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 108 #include <machine/stdarg.h> 109 110 #include <net/if.h> 111 #include <net/route.h> 112 113 #include <netinet/in.h> 114 #include <netinet/in_systm.h> 115 #include <netinet/ip.h> 116 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 117 #include <netinet/in_var.h> 118 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 119 #include <netinet/in_pcb.h> 120 #include <netinet/ip_var.h> 121 #include <netinet/ip6.h> 122 #include <netinet/icmp6.h> 123 #include <netinet6/nd6.h> 124 #include <netinet6/ip6_var.h> 125 #include <netinet6/in6_pcb.h> 126 #include <netinet/tcp.h> 127 #include <netinet/tcp_fsm.h> 128 #include <netinet/tcp_seq.h> 129 #include <netinet/tcp_timer.h> 130 #include <netinet/tcp_var.h> 131 #include <netinet6/tcp6_var.h> 132 #include <netinet/tcpip.h> 133 134 #ifdef TCPDEBUG 135 #include <netinet/tcp_debug.h> 136 137 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 138 struct tcphdr tcp_savetcp; 139 #endif 140 141 #ifdef FAST_IPSEC 142 #include <netipsec/ipsec.h> 143 #include <netipsec/ipsec6.h> 144 #endif 145 146 #ifdef IPSEC 147 #include <netinet6/ipsec.h> 148 #include <netinet6/ipsec6.h> 149 #include <netproto/key/key.h> 150 #endif 151 152 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 153 154 static const int tcprexmtthresh = 3; 155 tcp_cc tcp_ccgen; 156 static int log_in_vain = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 158 &log_in_vain, 0, "Log all incoming TCP connections"); 159 160 static int blackhole = 0; 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 162 &blackhole, 0, "Do not send RST when dropping refused connections"); 163 164 int tcp_delack_enabled = 1; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 166 &tcp_delack_enabled, 0, 167 "Delay ACK to try and piggyback it onto a data packet"); 168 169 #ifdef TCP_DROP_SYNFIN 170 static int drop_synfin = 0; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 172 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 173 #endif 174 175 static int tcp_do_limitedtransmit = 1; 176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 177 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 178 179 static int tcp_do_early_retransmit = 0; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 181 &tcp_do_early_retransmit, 0, "Early retransmit"); 182 183 static int tcp_do_rfc3390 = 1; 184 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 185 &tcp_do_rfc3390, 0, 186 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 187 188 static int tcp_do_eifel_detect = 1; 189 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 190 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 191 192 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 193 "TCP Segment Reassembly Queue"); 194 195 int tcp_reass_maxseg = 0; 196 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 197 &tcp_reass_maxseg, 0, 198 "Global maximum number of TCP Segments in Reassembly Queue"); 199 200 int tcp_reass_qsize = 0; 201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 202 &tcp_reass_qsize, 0, 203 "Global number of TCP Segments currently in Reassembly Queue"); 204 205 static int tcp_reass_overflows = 0; 206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 207 &tcp_reass_overflows, 0, 208 "Global number of TCP Segment Reassembly Queue Overflows"); 209 210 struct inpcbinfo tcbinfo[MAXCPU]; 211 212 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 213 static void tcp_pulloutofband(struct socket *, 214 struct tcphdr *, struct mbuf *, int); 215 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 216 struct mbuf *); 217 static void tcp_xmit_timer(struct tcpcb *, int); 218 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 219 220 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 221 #ifdef INET6 222 #define ND6_HINT(tp) \ 223 do { \ 224 if ((tp) && (tp)->t_inpcb && \ 225 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 226 (tp)->t_inpcb->in6p_route.ro_rt) \ 227 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 228 } while (0) 229 #else 230 #define ND6_HINT(tp) 231 #endif 232 233 /* 234 * Indicate whether this ack should be delayed. We can delay the ack if 235 * - delayed acks are enabled and 236 * - there is no delayed ack timer in progress and 237 * - our last ack wasn't a 0-sized window. We never want to delay 238 * the ack that opens up a 0-sized window. 239 */ 240 #define DELAY_ACK(tp) \ 241 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 242 (tp->t_flags & TF_RXWIN0SENT) == 0) 243 244 static int 245 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 246 { 247 struct tseg_qent *q; 248 struct tseg_qent *p = NULL; 249 struct tseg_qent *nq; 250 struct tseg_qent *te; 251 struct socket *so = tp->t_inpcb->inp_socket; 252 int flags; 253 254 /* 255 * Call with th==0 after become established to 256 * force pre-ESTABLISHED data up to user socket. 257 */ 258 if (th == 0) 259 goto present; 260 261 /* 262 * Limit the number of segments in the reassembly queue to prevent 263 * holding on to too many segments (and thus running out of mbufs). 264 * Make sure to let the missing segment through which caused this 265 * queue. Always keep one global queue entry spare to be able to 266 * process the missing segment. 267 */ 268 if (th->th_seq != tp->rcv_nxt && 269 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 270 tcp_reass_overflows++; 271 tcpstat.tcps_rcvmemdrop++; 272 m_freem(m); 273 return (0); 274 } 275 276 /* Allocate a new queue entry. */ 277 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 278 M_INTWAIT | M_NULLOK); 279 if (te == NULL) { 280 tcpstat.tcps_rcvmemdrop++; 281 m_freem(m); 282 return (0); 283 } 284 tcp_reass_qsize++; 285 286 /* 287 * Find a segment which begins after this one does. 288 */ 289 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 290 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 291 break; 292 p = q; 293 } 294 295 /* 296 * If there is a preceding segment, it may provide some of 297 * our data already. If so, drop the data from the incoming 298 * segment. If it provides all of our data, drop us. 299 */ 300 if (p != NULL) { 301 int i; 302 /* conversion to int (in i) handles seq wraparound */ 303 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 304 if (i > 0) { 305 if (i >= *tlenp) { 306 tcpstat.tcps_rcvduppack++; 307 tcpstat.tcps_rcvdupbyte += *tlenp; 308 m_freem(m); 309 free(te, M_TSEGQ); 310 tcp_reass_qsize--; 311 /* 312 * Try to present any queued data 313 * at the left window edge to the user. 314 * This is needed after the 3-WHS 315 * completes. 316 */ 317 goto present; /* ??? */ 318 } 319 m_adj(m, i); 320 *tlenp -= i; 321 th->th_seq += i; 322 } 323 } 324 tcpstat.tcps_rcvoopack++; 325 tcpstat.tcps_rcvoobyte += *tlenp; 326 327 /* 328 * While we overlap succeeding segments trim them or, 329 * if they are completely covered, dequeue them. 330 */ 331 while (q) { 332 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 333 if (i <= 0) 334 break; 335 if (i < q->tqe_len) { 336 q->tqe_th->th_seq += i; 337 q->tqe_len -= i; 338 m_adj(q->tqe_m, i); 339 break; 340 } 341 342 nq = LIST_NEXT(q, tqe_q); 343 LIST_REMOVE(q, tqe_q); 344 m_freem(q->tqe_m); 345 free(q, M_TSEGQ); 346 tcp_reass_qsize--; 347 q = nq; 348 } 349 350 /* Insert the new segment queue entry into place. */ 351 te->tqe_m = m; 352 te->tqe_th = th; 353 te->tqe_len = *tlenp; 354 355 if (p == NULL) { 356 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 357 } else { 358 LIST_INSERT_AFTER(p, te, tqe_q); 359 } 360 361 present: 362 /* 363 * Present data to user, advancing rcv_nxt through 364 * completed sequence space. 365 */ 366 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 367 return (0); 368 q = LIST_FIRST(&tp->t_segq); 369 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 370 return (0); 371 do { 372 tp->rcv_nxt += q->tqe_len; 373 flags = q->tqe_th->th_flags & TH_FIN; 374 nq = LIST_NEXT(q, tqe_q); 375 LIST_REMOVE(q, tqe_q); 376 if (so->so_state & SS_CANTRCVMORE) 377 m_freem(q->tqe_m); 378 else 379 sbappend(&so->so_rcv, q->tqe_m); 380 free(q, M_TSEGQ); 381 tcp_reass_qsize--; 382 q = nq; 383 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 384 ND6_HINT(tp); 385 sorwakeup(so); 386 return (flags); 387 } 388 389 /* 390 * TCP input routine, follows pages 65-76 of the 391 * protocol specification dated September, 1981 very closely. 392 */ 393 #ifdef INET6 394 int 395 tcp6_input(struct mbuf **mp, int *offp, int proto) 396 { 397 struct mbuf *m = *mp; 398 struct in6_ifaddr *ia6; 399 400 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 401 402 /* 403 * draft-itojun-ipv6-tcp-to-anycast 404 * better place to put this in? 405 */ 406 ia6 = ip6_getdstifaddr(m); 407 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 408 struct ip6_hdr *ip6; 409 410 ip6 = mtod(m, struct ip6_hdr *); 411 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 412 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 413 return (IPPROTO_DONE); 414 } 415 416 tcp_input(m, *offp, proto); 417 return (IPPROTO_DONE); 418 } 419 #endif 420 421 void 422 tcp_input(struct mbuf *m, ...) 423 { 424 __va_list ap; 425 int off0, proto; 426 struct tcphdr *th; 427 struct ip *ip = NULL; 428 struct ipovly *ipov; 429 struct inpcb *inp = NULL; 430 u_char *optp = NULL; 431 int optlen = 0; 432 int len, tlen, off; 433 int drop_hdrlen; 434 struct tcpcb *tp = NULL; 435 int thflags; 436 struct socket *so = 0; 437 int todrop, acked, ourfinisacked, needoutput = 0; 438 u_long tiwin; 439 struct tcpopt to; /* options in this segment */ 440 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 441 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 442 struct sockaddr_in *next_hop = NULL; 443 int rstreason; /* For badport_bandlim accounting purposes */ 444 int cpu; 445 struct ip6_hdr *ip6 = NULL; 446 #ifdef INET6 447 boolean_t isipv6; 448 #else 449 const boolean_t isipv6 = FALSE; 450 #endif 451 #ifdef TCPDEBUG 452 short ostate = 0; 453 #endif 454 455 __va_start(ap, m); 456 off0 = __va_arg(ap, int); 457 proto = __va_arg(ap, int); 458 __va_end(ap); 459 460 tcpstat.tcps_rcvtotal++; 461 462 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */ 463 while (m->m_type == MT_TAG) { 464 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 465 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 466 m = m->m_next; 467 } 468 469 #ifdef INET6 470 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 471 #endif 472 473 if (isipv6) { 474 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 475 ip6 = mtod(m, struct ip6_hdr *); 476 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 477 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 478 tcpstat.tcps_rcvbadsum++; 479 goto drop; 480 } 481 th = (struct tcphdr *)((caddr_t)ip6 + off0); 482 483 /* 484 * Be proactive about unspecified IPv6 address in source. 485 * As we use all-zero to indicate unbounded/unconnected pcb, 486 * unspecified IPv6 address can be used to confuse us. 487 * 488 * Note that packets with unspecified IPv6 destination is 489 * already dropped in ip6_input. 490 */ 491 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 492 /* XXX stat */ 493 goto drop; 494 } 495 } else { 496 /* 497 * Get IP and TCP header together in first mbuf. 498 * Note: IP leaves IP header in first mbuf. 499 */ 500 if (off0 > sizeof(struct ip)) { 501 ip_stripoptions(m); 502 off0 = sizeof(struct ip); 503 } 504 /* already checked and pulled up in ip_demux() */ 505 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 506 ("TCP header not in one mbuf")); 507 ip = mtod(m, struct ip *); 508 ipov = (struct ipovly *)ip; 509 th = (struct tcphdr *)((caddr_t)ip + off0); 510 tlen = ip->ip_len; 511 512 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 513 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 514 th->th_sum = m->m_pkthdr.csum_data; 515 else 516 th->th_sum = in_pseudo(ip->ip_src.s_addr, 517 ip->ip_dst.s_addr, 518 htonl(m->m_pkthdr.csum_data + 519 ip->ip_len + 520 IPPROTO_TCP)); 521 th->th_sum ^= 0xffff; 522 } else { 523 /* 524 * Checksum extended TCP header and data. 525 */ 526 len = sizeof(struct ip) + tlen; 527 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 528 ipov->ih_len = (u_short)tlen; 529 ipov->ih_len = htons(ipov->ih_len); 530 th->th_sum = in_cksum(m, len); 531 } 532 if (th->th_sum) { 533 tcpstat.tcps_rcvbadsum++; 534 goto drop; 535 } 536 #ifdef INET6 537 /* Re-initialization for later version check */ 538 ip->ip_v = IPVERSION; 539 #endif 540 } 541 542 /* 543 * Check that TCP offset makes sense, 544 * pull out TCP options and adjust length. XXX 545 */ 546 off = th->th_off << 2; 547 /* already checked and pulled up in ip_demux() */ 548 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 549 ("bad TCP data offset")); 550 tlen -= off; /* tlen is used instead of ti->ti_len */ 551 if (off > sizeof(struct tcphdr)) { 552 if (isipv6) { 553 IP6_EXTHDR_CHECK(m, off0, off, ); 554 ip6 = mtod(m, struct ip6_hdr *); 555 th = (struct tcphdr *)((caddr_t)ip6 + off0); 556 } else { 557 /* already pulled up in ip_demux() */ 558 KASSERT(m->m_len >= sizeof(struct ip) + off, 559 ("TCP header and options not in one mbuf")); 560 } 561 optlen = off - sizeof(struct tcphdr); 562 optp = (u_char *)(th + 1); 563 } 564 thflags = th->th_flags; 565 566 #ifdef TCP_DROP_SYNFIN 567 /* 568 * If the drop_synfin option is enabled, drop all packets with 569 * both the SYN and FIN bits set. This prevents e.g. nmap from 570 * identifying the TCP/IP stack. 571 * 572 * This is a violation of the TCP specification. 573 */ 574 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 575 goto drop; 576 #endif 577 578 /* 579 * Convert TCP protocol specific fields to host format. 580 */ 581 th->th_seq = ntohl(th->th_seq); 582 th->th_ack = ntohl(th->th_ack); 583 th->th_win = ntohs(th->th_win); 584 th->th_urp = ntohs(th->th_urp); 585 586 /* 587 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 588 * until after ip6_savecontrol() is called and before other functions 589 * which don't want those proto headers. 590 * Because ip6_savecontrol() is going to parse the mbuf to 591 * search for data to be passed up to user-land, it wants mbuf 592 * parameters to be unchanged. 593 * XXX: the call of ip6_savecontrol() has been obsoleted based on 594 * latest version of the advanced API (20020110). 595 */ 596 drop_hdrlen = off0 + off; 597 598 /* 599 * Locate pcb for segment. 600 */ 601 findpcb: 602 /* IPFIREWALL_FORWARD section */ 603 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 604 /* 605 * Transparently forwarded. Pretend to be the destination. 606 * already got one like this? 607 */ 608 cpu = mycpu->gd_cpuid; 609 inp = in_pcblookup_hash(&tcbinfo[cpu], 610 ip->ip_src, th->th_sport, 611 ip->ip_dst, th->th_dport, 612 0, m->m_pkthdr.rcvif); 613 if (!inp) { 614 /* 615 * It's new. Try to find the ambushing socket. 616 */ 617 618 /* 619 * The rest of the ipfw code stores the port in 620 * host order. XXX 621 * (The IP address is still in network order.) 622 */ 623 in_port_t dport = next_hop->sin_port ? 624 htons(next_hop->sin_port) : 625 th->th_dport; 626 627 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 628 next_hop->sin_addr.s_addr, dport); 629 inp = in_pcblookup_hash(&tcbinfo[cpu], 630 ip->ip_src, th->th_sport, 631 next_hop->sin_addr, dport, 632 1, m->m_pkthdr.rcvif); 633 } 634 } else { 635 if (isipv6) { 636 inp = in6_pcblookup_hash(&tcbinfo[0], 637 &ip6->ip6_src, th->th_sport, 638 &ip6->ip6_dst, th->th_dport, 639 1, m->m_pkthdr.rcvif); 640 } else { 641 cpu = mycpu->gd_cpuid; 642 inp = in_pcblookup_hash(&tcbinfo[cpu], 643 ip->ip_src, th->th_sport, 644 ip->ip_dst, th->th_dport, 645 1, m->m_pkthdr.rcvif); 646 } 647 } 648 649 #ifdef IPSEC 650 if (isipv6) { 651 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 652 ipsec6stat.in_polvio++; 653 goto drop; 654 } 655 } else { 656 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 657 ipsecstat.in_polvio++; 658 goto drop; 659 } 660 } 661 #endif 662 #ifdef FAST_IPSEC 663 if (isipv6) { 664 if (inp != NULL && ipsec6_in_reject(m, inp)) { 665 goto drop; 666 } 667 } else { 668 if (inp != NULL && ipsec4_in_reject(m, inp)) { 669 goto drop; 670 } 671 } 672 #endif 673 674 /* 675 * If the state is CLOSED (i.e., TCB does not exist) then 676 * all data in the incoming segment is discarded. 677 * If the TCB exists but is in CLOSED state, it is embryonic, 678 * but should either do a listen or a connect soon. 679 */ 680 if (inp == NULL) { 681 if (log_in_vain) { 682 #ifdef INET6 683 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 684 #else 685 char dbuf[4 * sizeof "123"], sbuf[4 * sizeof "123"]; 686 #endif 687 if (isipv6) { 688 strcpy(dbuf, "["); 689 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 690 strcat(dbuf, "]"); 691 strcpy(sbuf, "["); 692 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 693 strcat(sbuf, "]"); 694 } else { 695 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 696 strcpy(sbuf, inet_ntoa(ip->ip_src)); 697 } 698 switch (log_in_vain) { 699 case 1: 700 if ((thflags & TH_SYN) == 0) 701 break; 702 case 2: 703 log(LOG_INFO, 704 "Connection attempt to TCP %s:%d " 705 "from %s:%d flags:0x%02x\n", 706 dbuf, ntohs(th->th_dport), sbuf, 707 ntohs(th->th_sport), thflags); 708 break; 709 default: 710 break; 711 } 712 } 713 if (blackhole) { 714 switch (blackhole) { 715 case 1: 716 if (thflags & TH_SYN) 717 goto drop; 718 break; 719 case 2: 720 goto drop; 721 default: 722 goto drop; 723 } 724 } 725 rstreason = BANDLIM_RST_CLOSEDPORT; 726 goto dropwithreset; 727 } 728 tp = intotcpcb(inp); 729 if (tp == NULL) { 730 rstreason = BANDLIM_RST_CLOSEDPORT; 731 goto dropwithreset; 732 } 733 if (tp->t_state == TCPS_CLOSED) 734 goto drop; 735 736 /* Unscale the window into a 32-bit value. */ 737 if (!(thflags & TH_SYN)) 738 tiwin = th->th_win << tp->snd_scale; 739 else 740 tiwin = th->th_win; 741 742 so = inp->inp_socket; 743 744 #ifdef TCPDEBUG 745 if (so->so_options & SO_DEBUG) { 746 ostate = tp->t_state; 747 if (isipv6) 748 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 749 else 750 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 751 tcp_savetcp = *th; 752 } 753 #endif 754 755 bzero(&to, sizeof(to)); 756 757 if (so->so_options & SO_ACCEPTCONN) { 758 struct in_conninfo inc; 759 760 #ifdef INET6 761 inc.inc_isipv6 = (isipv6 == TRUE); 762 #endif 763 if (isipv6) { 764 inc.inc6_faddr = ip6->ip6_src; 765 inc.inc6_laddr = ip6->ip6_dst; 766 inc.inc6_route.ro_rt = NULL; /* XXX */ 767 } else { 768 inc.inc_faddr = ip->ip_src; 769 inc.inc_laddr = ip->ip_dst; 770 inc.inc_route.ro_rt = NULL; /* XXX */ 771 } 772 inc.inc_fport = th->th_sport; 773 inc.inc_lport = th->th_dport; 774 775 /* 776 * If the state is LISTEN then ignore segment if it contains 777 * a RST. If the segment contains an ACK then it is bad and 778 * send a RST. If it does not contain a SYN then it is not 779 * interesting; drop it. 780 * 781 * If the state is SYN_RECEIVED (syncache) and seg contains 782 * an ACK, but not for our SYN/ACK, send a RST. If the seg 783 * contains a RST, check the sequence number to see if it 784 * is a valid reset segment. 785 */ 786 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 787 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 788 if (!syncache_expand(&inc, th, &so, m)) { 789 /* 790 * No syncache entry, or ACK was not 791 * for our SYN/ACK. Send a RST. 792 */ 793 tcpstat.tcps_badsyn++; 794 rstreason = BANDLIM_RST_OPENPORT; 795 goto dropwithreset; 796 } 797 if (so == NULL) 798 /* 799 * Could not complete 3-way handshake, 800 * connection is being closed down, and 801 * syncache will free mbuf. 802 */ 803 return; 804 /* 805 * Socket is created in state SYN_RECEIVED. 806 * Continue processing segment. 807 */ 808 inp = sotoinpcb(so); 809 tp = intotcpcb(inp); 810 /* 811 * This is what would have happened in 812 * tcp_output() when the SYN,ACK was sent. 813 */ 814 tp->snd_up = tp->snd_una; 815 tp->snd_max = tp->snd_nxt = tp->iss + 1; 816 tp->last_ack_sent = tp->rcv_nxt; 817 /* 818 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 819 * until the _second_ ACK is received: 820 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 821 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 822 * move to ESTAB, set snd_wnd to tiwin. 823 */ 824 tp->snd_wnd = tiwin; /* unscaled */ 825 goto after_listen; 826 } 827 if (thflags & TH_RST) { 828 syncache_chkrst(&inc, th); 829 goto drop; 830 } 831 if (thflags & TH_ACK) { 832 syncache_badack(&inc); 833 tcpstat.tcps_badsyn++; 834 rstreason = BANDLIM_RST_OPENPORT; 835 goto dropwithreset; 836 } 837 goto drop; 838 } 839 840 /* 841 * Segment's flags are (SYN) or (SYN|FIN). 842 */ 843 #ifdef INET6 844 /* 845 * If deprecated address is forbidden, 846 * we do not accept SYN to deprecated interface 847 * address to prevent any new inbound connection from 848 * getting established. 849 * When we do not accept SYN, we send a TCP RST, 850 * with deprecated source address (instead of dropping 851 * it). We compromise it as it is much better for peer 852 * to send a RST, and RST will be the final packet 853 * for the exchange. 854 * 855 * If we do not forbid deprecated addresses, we accept 856 * the SYN packet. RFC2462 does not suggest dropping 857 * SYN in this case. 858 * If we decipher RFC2462 5.5.4, it says like this: 859 * 1. use of deprecated addr with existing 860 * communication is okay - "SHOULD continue to be 861 * used" 862 * 2. use of it with new communication: 863 * (2a) "SHOULD NOT be used if alternate address 864 * with sufficient scope is available" 865 * (2b) nothing mentioned otherwise. 866 * Here we fall into (2b) case as we have no choice in 867 * our source address selection - we must obey the peer. 868 * 869 * The wording in RFC2462 is confusing, and there are 870 * multiple description text for deprecated address 871 * handling - worse, they are not exactly the same. 872 * I believe 5.5.4 is the best one, so we follow 5.5.4. 873 */ 874 if (isipv6 && !ip6_use_deprecated) { 875 struct in6_ifaddr *ia6; 876 877 if ((ia6 = ip6_getdstifaddr(m)) && 878 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 879 tp = NULL; 880 rstreason = BANDLIM_RST_OPENPORT; 881 goto dropwithreset; 882 } 883 } 884 #endif 885 /* 886 * If it is from this socket, drop it, it must be forged. 887 * Don't bother responding if the destination was a broadcast. 888 */ 889 if (th->th_dport == th->th_sport) { 890 if (isipv6) { 891 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 892 &ip6->ip6_src)) 893 goto drop; 894 } else { 895 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 896 goto drop; 897 } 898 } 899 /* 900 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 901 * 902 * Note that it is quite possible to receive unicast 903 * link-layer packets with a broadcast IP address. Use 904 * in_broadcast() to find them. 905 */ 906 if (m->m_flags & (M_BCAST|M_MCAST)) 907 goto drop; 908 if (isipv6) { 909 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 910 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 911 goto drop; 912 } else { 913 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 914 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 915 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 916 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 917 goto drop; 918 } 919 /* 920 * SYN appears to be valid; create compressed TCP state 921 * for syncache, or perform t/tcp connection. 922 */ 923 if (so->so_qlen <= so->so_qlimit) { 924 tcp_dooptions(&to, optp, optlen, TRUE); 925 if (!syncache_add(&inc, &to, th, &so, m)) 926 goto drop; 927 if (so == NULL) 928 /* 929 * Entry added to syncache, mbuf used to 930 * send SYN,ACK packet. 931 */ 932 return; 933 /* 934 * Segment passed TAO tests. 935 */ 936 inp = sotoinpcb(so); 937 tp = intotcpcb(inp); 938 tp->snd_wnd = tiwin; 939 tp->t_starttime = ticks; 940 tp->t_state = TCPS_ESTABLISHED; 941 942 /* 943 * If there is a FIN, or if there is data and the 944 * connection is local, then delay SYN,ACK(SYN) in 945 * the hope of piggy-backing it on a response 946 * segment. Otherwise must send ACK now in case 947 * the other side is slow starting. 948 */ 949 if (DELAY_ACK(tp) && 950 ((thflags & TH_FIN) || 951 (tlen != 0 && 952 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 953 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 954 callout_reset(tp->tt_delack, tcp_delacktime, 955 tcp_timer_delack, tp); 956 tp->t_flags |= TF_NEEDSYN; 957 } else 958 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 959 960 tcpstat.tcps_connects++; 961 soisconnected(so); 962 goto trimthenstep6; 963 } 964 goto drop; 965 } 966 after_listen: 967 968 /* XXX temp debugging */ 969 /* should not happen - syncache should pick up these connections */ 970 if (tp->t_state == TCPS_LISTEN) 971 panic("tcp_input: TCPS_LISTEN"); 972 973 /* 974 * Segment received on connection. 975 * Reset idle time and keep-alive timer. 976 */ 977 tp->t_rcvtime = ticks; 978 if (TCPS_HAVEESTABLISHED(tp->t_state)) 979 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 980 981 /* 982 * Process options. 983 * XXX this is tradtitional behavior, may need to be cleaned up. 984 */ 985 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 986 if (thflags & TH_SYN) { 987 if (to.to_flags & TOF_SCALE) { 988 tp->t_flags |= TF_RCVD_SCALE; 989 tp->requested_s_scale = to.to_requested_s_scale; 990 } 991 if (to.to_flags & TOF_TS) { 992 tp->t_flags |= TF_RCVD_TSTMP; 993 tp->ts_recent = to.to_tsval; 994 tp->ts_recent_age = ticks; 995 } 996 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 997 tp->t_flags |= TF_RCVD_CC; 998 if (to.to_flags & TOF_MSS) 999 tcp_mss(tp, to.to_mss); 1000 } 1001 1002 /* 1003 * Header prediction: check for the two common cases 1004 * of a uni-directional data xfer. If the packet has 1005 * no control flags, is in-sequence, the window didn't 1006 * change and we're not retransmitting, it's a 1007 * candidate. If the length is zero and the ack moved 1008 * forward, we're the sender side of the xfer. Just 1009 * free the data acked & wake any higher level process 1010 * that was blocked waiting for space. If the length 1011 * is non-zero and the ack didn't move, we're the 1012 * receiver side. If we're getting packets in-order 1013 * (the reassembly queue is empty), add the data to 1014 * the socket buffer and note that we need a delayed ack. 1015 * Make sure that the hidden state-flags are also off. 1016 * Since we check for TCPS_ESTABLISHED above, it can only 1017 * be TH_NEEDSYN. 1018 */ 1019 if (tp->t_state == TCPS_ESTABLISHED && 1020 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1021 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1022 ((to.to_flags & TOF_TS) == 0 || 1023 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1024 /* 1025 * Using the CC option is compulsory if once started: 1026 * the segment is OK if no T/TCP was negotiated or 1027 * if the segment has a CC option equal to CCrecv 1028 */ 1029 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1030 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1031 th->th_seq == tp->rcv_nxt && 1032 tiwin && tiwin == tp->snd_wnd && 1033 tp->snd_nxt == tp->snd_max) { 1034 1035 /* 1036 * If last ACK falls within this segment's sequence numbers, 1037 * record the timestamp. 1038 * NOTE that the test is modified according to the latest 1039 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1040 */ 1041 if ((to.to_flags & TOF_TS) != 0 && 1042 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1043 tp->ts_recent_age = ticks; 1044 tp->ts_recent = to.to_tsval; 1045 } 1046 1047 if (tlen == 0) { 1048 if (SEQ_GT(th->th_ack, tp->snd_una) && 1049 SEQ_LEQ(th->th_ack, tp->snd_max) && 1050 tp->snd_cwnd >= tp->snd_wnd && 1051 !IN_FASTRECOVERY(tp)) { 1052 /* 1053 * this is a pure ack for outstanding data. 1054 */ 1055 ++tcpstat.tcps_predack; 1056 /* 1057 * "bad retransmit" recovery 1058 * 1059 * If Eifel detection applies, then 1060 * it is deterministic, so use it 1061 * unconditionally over the old heuristic. 1062 * Otherwise, fall back to the old heuristic. 1063 */ 1064 if (tcp_do_eifel_detect && 1065 (to.to_flags & TOF_TS) && to.to_tsecr && 1066 (tp->t_flags & TF_FIRSTACCACK)) { 1067 /* Eifel detection applicable. */ 1068 if (to.to_tsecr < tp->t_rexmtTS) { 1069 tcp_revert_congestion_state(tp); 1070 ++tcpstat.tcps_eifeldetected; 1071 } 1072 } else if (tp->t_rxtshift == 1 && 1073 ticks < tp->t_badrxtwin) { 1074 tcp_revert_congestion_state(tp); 1075 ++tcpstat.tcps_rttdetected; 1076 } 1077 tp->t_flags &= ~(TF_FIRSTACCACK | 1078 TF_FASTREXMT | TF_EARLYREXMT); 1079 /* 1080 * Recalculate the retransmit timer / rtt. 1081 * 1082 * Some machines (certain windows boxes) 1083 * send broken timestamp replies during the 1084 * SYN+ACK phase, ignore timestamps of 0. 1085 */ 1086 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1087 tcp_xmit_timer(tp, 1088 ticks - to.to_tsecr + 1); 1089 } else if (tp->t_rtttime && 1090 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1091 tcp_xmit_timer(tp, 1092 ticks - tp->t_rtttime); 1093 } 1094 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1095 acked = th->th_ack - tp->snd_una; 1096 tcpstat.tcps_rcvackpack++; 1097 tcpstat.tcps_rcvackbyte += acked; 1098 sbdrop(&so->so_snd, acked); 1099 tp->snd_recover = th->th_ack - 1; 1100 tp->snd_una = th->th_ack; 1101 tp->t_dupacks = 0; 1102 m_freem(m); 1103 ND6_HINT(tp); /* some progress has been done */ 1104 1105 /* 1106 * If all outstanding data are acked, stop 1107 * retransmit timer, otherwise restart timer 1108 * using current (possibly backed-off) value. 1109 * If process is waiting for space, 1110 * wakeup/selwakeup/signal. If data 1111 * are ready to send, let tcp_output 1112 * decide between more output or persist. 1113 */ 1114 if (tp->snd_una == tp->snd_max) 1115 callout_stop(tp->tt_rexmt); 1116 else if (!callout_active(tp->tt_persist)) 1117 callout_reset(tp->tt_rexmt, 1118 tp->t_rxtcur, 1119 tcp_timer_rexmt, tp); 1120 1121 sowwakeup(so); 1122 if (so->so_snd.sb_cc) 1123 (void) tcp_output(tp); 1124 return; 1125 } 1126 } else if (th->th_ack == tp->snd_una && 1127 LIST_EMPTY(&tp->t_segq) && 1128 tlen <= sbspace(&so->so_rcv)) { 1129 /* 1130 * this is a pure, in-sequence data packet 1131 * with nothing on the reassembly queue and 1132 * we have enough buffer space to take it. 1133 */ 1134 ++tcpstat.tcps_preddat; 1135 tp->rcv_nxt += tlen; 1136 tcpstat.tcps_rcvpack++; 1137 tcpstat.tcps_rcvbyte += tlen; 1138 ND6_HINT(tp); /* some progress has been done */ 1139 /* 1140 * Add data to socket buffer. 1141 */ 1142 if (so->so_state & SS_CANTRCVMORE) { 1143 m_freem(m); 1144 } else { 1145 m_adj(m, drop_hdrlen); /* delayed header drop */ 1146 sbappend(&so->so_rcv, m); 1147 } 1148 sorwakeup(so); 1149 if (DELAY_ACK(tp)) { 1150 callout_reset(tp->tt_delack, tcp_delacktime, 1151 tcp_timer_delack, tp); 1152 } else { 1153 tp->t_flags |= TF_ACKNOW; 1154 tcp_output(tp); 1155 } 1156 return; 1157 } 1158 } 1159 1160 /* 1161 * Calculate amount of space in receive window, 1162 * and then do TCP input processing. 1163 * Receive window is amount of space in rcv queue, 1164 * but not less than advertised window. 1165 */ 1166 { int win; 1167 1168 win = sbspace(&so->so_rcv); 1169 if (win < 0) 1170 win = 0; 1171 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1172 } 1173 1174 switch (tp->t_state) { 1175 1176 /* 1177 * If the state is SYN_RECEIVED: 1178 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1179 */ 1180 case TCPS_SYN_RECEIVED: 1181 if ((thflags & TH_ACK) && 1182 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1183 SEQ_GT(th->th_ack, tp->snd_max))) { 1184 rstreason = BANDLIM_RST_OPENPORT; 1185 goto dropwithreset; 1186 } 1187 break; 1188 1189 /* 1190 * If the state is SYN_SENT: 1191 * if seg contains an ACK, but not for our SYN, drop the input. 1192 * if seg contains a RST, then drop the connection. 1193 * if seg does not contain SYN, then drop it. 1194 * Otherwise this is an acceptable SYN segment 1195 * initialize tp->rcv_nxt and tp->irs 1196 * if seg contains ack then advance tp->snd_una 1197 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1198 * arrange for segment to be acked (eventually) 1199 * continue processing rest of data/controls, beginning with URG 1200 */ 1201 case TCPS_SYN_SENT: 1202 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1203 taop = &tao_noncached; 1204 bzero(taop, sizeof(*taop)); 1205 } 1206 1207 if ((thflags & TH_ACK) && 1208 (SEQ_LEQ(th->th_ack, tp->iss) || 1209 SEQ_GT(th->th_ack, tp->snd_max))) { 1210 /* 1211 * If we have a cached CCsent for the remote host, 1212 * hence we haven't just crashed and restarted, 1213 * do not send a RST. This may be a retransmission 1214 * from the other side after our earlier ACK was lost. 1215 * Our new SYN, when it arrives, will serve as the 1216 * needed ACK. 1217 */ 1218 if (taop->tao_ccsent != 0) 1219 goto drop; 1220 else { 1221 rstreason = BANDLIM_UNLIMITED; 1222 goto dropwithreset; 1223 } 1224 } 1225 if (thflags & TH_RST) { 1226 if (thflags & TH_ACK) 1227 tp = tcp_drop(tp, ECONNREFUSED); 1228 goto drop; 1229 } 1230 if ((thflags & TH_SYN) == 0) 1231 goto drop; 1232 tp->snd_wnd = th->th_win; /* initial send window */ 1233 tp->cc_recv = to.to_cc; /* foreign CC */ 1234 1235 tp->irs = th->th_seq; 1236 tcp_rcvseqinit(tp); 1237 if (thflags & TH_ACK) { 1238 /* 1239 * Our SYN was acked. If segment contains CC.ECHO 1240 * option, check it to make sure this segment really 1241 * matches our SYN. If not, just drop it as old 1242 * duplicate, but send an RST if we're still playing 1243 * by the old rules. If no CC.ECHO option, make sure 1244 * we don't get fooled into using T/TCP. 1245 */ 1246 if (to.to_flags & TOF_CCECHO) { 1247 if (tp->cc_send != to.to_ccecho) { 1248 if (taop->tao_ccsent != 0) 1249 goto drop; 1250 else { 1251 rstreason = BANDLIM_UNLIMITED; 1252 goto dropwithreset; 1253 } 1254 } 1255 } else 1256 tp->t_flags &= ~TF_RCVD_CC; 1257 tcpstat.tcps_connects++; 1258 soisconnected(so); 1259 /* Do window scaling on this connection? */ 1260 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1261 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1262 tp->snd_scale = tp->requested_s_scale; 1263 tp->rcv_scale = tp->request_r_scale; 1264 } 1265 /* Segment is acceptable, update cache if undefined. */ 1266 if (taop->tao_ccsent == 0) 1267 taop->tao_ccsent = to.to_ccecho; 1268 1269 tp->rcv_adv += tp->rcv_wnd; 1270 tp->snd_una++; /* SYN is acked */ 1271 /* 1272 * If there's data, delay ACK; if there's also a FIN 1273 * ACKNOW will be turned on later. 1274 */ 1275 if (DELAY_ACK(tp) && tlen != 0) 1276 callout_reset(tp->tt_delack, tcp_delacktime, 1277 tcp_timer_delack, tp); 1278 else 1279 tp->t_flags |= TF_ACKNOW; 1280 /* 1281 * Received <SYN,ACK> in SYN_SENT[*] state. 1282 * Transitions: 1283 * SYN_SENT --> ESTABLISHED 1284 * SYN_SENT* --> FIN_WAIT_1 1285 */ 1286 tp->t_starttime = ticks; 1287 if (tp->t_flags & TF_NEEDFIN) { 1288 tp->t_state = TCPS_FIN_WAIT_1; 1289 tp->t_flags &= ~TF_NEEDFIN; 1290 thflags &= ~TH_SYN; 1291 } else { 1292 tp->t_state = TCPS_ESTABLISHED; 1293 callout_reset(tp->tt_keep, tcp_keepidle, 1294 tcp_timer_keep, tp); 1295 } 1296 } else { 1297 /* 1298 * Received initial SYN in SYN-SENT[*] state => 1299 * simultaneous open. If segment contains CC option 1300 * and there is a cached CC, apply TAO test. 1301 * If it succeeds, connection is * half-synchronized. 1302 * Otherwise, do 3-way handshake: 1303 * SYN-SENT -> SYN-RECEIVED 1304 * SYN-SENT* -> SYN-RECEIVED* 1305 * If there was no CC option, clear cached CC value. 1306 */ 1307 tp->t_flags |= TF_ACKNOW; 1308 callout_stop(tp->tt_rexmt); 1309 if (to.to_flags & TOF_CC) { 1310 if (taop->tao_cc != 0 && 1311 CC_GT(to.to_cc, taop->tao_cc)) { 1312 /* 1313 * update cache and make transition: 1314 * SYN-SENT -> ESTABLISHED* 1315 * SYN-SENT* -> FIN-WAIT-1* 1316 */ 1317 taop->tao_cc = to.to_cc; 1318 tp->t_starttime = ticks; 1319 if (tp->t_flags & TF_NEEDFIN) { 1320 tp->t_state = TCPS_FIN_WAIT_1; 1321 tp->t_flags &= ~TF_NEEDFIN; 1322 } else { 1323 tp->t_state = TCPS_ESTABLISHED; 1324 callout_reset(tp->tt_keep, 1325 tcp_keepidle, 1326 tcp_timer_keep, 1327 tp); 1328 } 1329 tp->t_flags |= TF_NEEDSYN; 1330 } else 1331 tp->t_state = TCPS_SYN_RECEIVED; 1332 } else { 1333 /* CC.NEW or no option => invalidate cache */ 1334 taop->tao_cc = 0; 1335 tp->t_state = TCPS_SYN_RECEIVED; 1336 } 1337 } 1338 1339 trimthenstep6: 1340 /* 1341 * Advance th->th_seq to correspond to first data byte. 1342 * If data, trim to stay within window, 1343 * dropping FIN if necessary. 1344 */ 1345 th->th_seq++; 1346 if (tlen > tp->rcv_wnd) { 1347 todrop = tlen - tp->rcv_wnd; 1348 m_adj(m, -todrop); 1349 tlen = tp->rcv_wnd; 1350 thflags &= ~TH_FIN; 1351 tcpstat.tcps_rcvpackafterwin++; 1352 tcpstat.tcps_rcvbyteafterwin += todrop; 1353 } 1354 tp->snd_wl1 = th->th_seq - 1; 1355 tp->rcv_up = th->th_seq; 1356 /* 1357 * Client side of transaction: already sent SYN and data. 1358 * If the remote host used T/TCP to validate the SYN, 1359 * our data will be ACK'd; if so, enter normal data segment 1360 * processing in the middle of step 5, ack processing. 1361 * Otherwise, goto step 6. 1362 */ 1363 if (thflags & TH_ACK) 1364 goto process_ACK; 1365 1366 goto step6; 1367 1368 /* 1369 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1370 * if segment contains a SYN and CC [not CC.NEW] option: 1371 * if state == TIME_WAIT and connection duration > MSL, 1372 * drop packet and send RST; 1373 * 1374 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1375 * ack the FIN (and data) in retransmission queue. 1376 * Complete close and delete TCPCB. Then reprocess 1377 * segment, hoping to find new TCPCB in LISTEN state; 1378 * 1379 * else must be old SYN; drop it. 1380 * else do normal processing. 1381 */ 1382 case TCPS_LAST_ACK: 1383 case TCPS_CLOSING: 1384 case TCPS_TIME_WAIT: 1385 if ((thflags & TH_SYN) && 1386 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1387 if (tp->t_state == TCPS_TIME_WAIT && 1388 (ticks - tp->t_starttime) > tcp_msl) { 1389 rstreason = BANDLIM_UNLIMITED; 1390 goto dropwithreset; 1391 } 1392 if (CC_GT(to.to_cc, tp->cc_recv)) { 1393 tp = tcp_close(tp); 1394 goto findpcb; 1395 } 1396 else 1397 goto drop; 1398 } 1399 break; /* continue normal processing */ 1400 } 1401 1402 /* 1403 * States other than LISTEN or SYN_SENT. 1404 * First check the RST flag and sequence number since reset segments 1405 * are exempt from the timestamp and connection count tests. This 1406 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1407 * below which allowed reset segments in half the sequence space 1408 * to fall though and be processed (which gives forged reset 1409 * segments with a random sequence number a 50 percent chance of 1410 * killing a connection). 1411 * Then check timestamp, if present. 1412 * Then check the connection count, if present. 1413 * Then check that at least some bytes of segment are within 1414 * receive window. If segment begins before rcv_nxt, 1415 * drop leading data (and SYN); if nothing left, just ack. 1416 * 1417 * 1418 * If the RST bit is set, check the sequence number to see 1419 * if this is a valid reset segment. 1420 * RFC 793 page 37: 1421 * In all states except SYN-SENT, all reset (RST) segments 1422 * are validated by checking their SEQ-fields. A reset is 1423 * valid if its sequence number is in the window. 1424 * Note: this does not take into account delayed ACKs, so 1425 * we should test against last_ack_sent instead of rcv_nxt. 1426 * The sequence number in the reset segment is normally an 1427 * echo of our outgoing acknowlegement numbers, but some hosts 1428 * send a reset with the sequence number at the rightmost edge 1429 * of our receive window, and we have to handle this case. 1430 * If we have multiple segments in flight, the intial reset 1431 * segment sequence numbers will be to the left of last_ack_sent, 1432 * but they will eventually catch up. 1433 * In any case, it never made sense to trim reset segments to 1434 * fit the receive window since RFC 1122 says: 1435 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1436 * 1437 * A TCP SHOULD allow a received RST segment to include data. 1438 * 1439 * DISCUSSION 1440 * It has been suggested that a RST segment could contain 1441 * ASCII text that encoded and explained the cause of the 1442 * RST. No standard has yet been established for such 1443 * data. 1444 * 1445 * If the reset segment passes the sequence number test examine 1446 * the state: 1447 * SYN_RECEIVED STATE: 1448 * If passive open, return to LISTEN state. 1449 * If active open, inform user that connection was refused. 1450 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1451 * Inform user that connection was reset, and close tcb. 1452 * CLOSING, LAST_ACK STATES: 1453 * Close the tcb. 1454 * TIME_WAIT STATE: 1455 * Drop the segment - see Stevens, vol. 2, p. 964 and 1456 * RFC 1337. 1457 */ 1458 if (thflags & TH_RST) { 1459 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1460 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1461 switch (tp->t_state) { 1462 1463 case TCPS_SYN_RECEIVED: 1464 so->so_error = ECONNREFUSED; 1465 goto close; 1466 1467 case TCPS_ESTABLISHED: 1468 case TCPS_FIN_WAIT_1: 1469 case TCPS_FIN_WAIT_2: 1470 case TCPS_CLOSE_WAIT: 1471 so->so_error = ECONNRESET; 1472 close: 1473 tp->t_state = TCPS_CLOSED; 1474 tcpstat.tcps_drops++; 1475 tp = tcp_close(tp); 1476 break; 1477 1478 case TCPS_CLOSING: 1479 case TCPS_LAST_ACK: 1480 tp = tcp_close(tp); 1481 break; 1482 1483 case TCPS_TIME_WAIT: 1484 break; 1485 } 1486 } 1487 goto drop; 1488 } 1489 1490 /* 1491 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1492 * and it's less than ts_recent, drop it. 1493 */ 1494 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1495 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1496 1497 /* Check to see if ts_recent is over 24 days old. */ 1498 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1499 /* 1500 * Invalidate ts_recent. If this segment updates 1501 * ts_recent, the age will be reset later and ts_recent 1502 * will get a valid value. If it does not, setting 1503 * ts_recent to zero will at least satisfy the 1504 * requirement that zero be placed in the timestamp 1505 * echo reply when ts_recent isn't valid. The 1506 * age isn't reset until we get a valid ts_recent 1507 * because we don't want out-of-order segments to be 1508 * dropped when ts_recent is old. 1509 */ 1510 tp->ts_recent = 0; 1511 } else { 1512 tcpstat.tcps_rcvduppack++; 1513 tcpstat.tcps_rcvdupbyte += tlen; 1514 tcpstat.tcps_pawsdrop++; 1515 if (tlen) 1516 goto dropafterack; 1517 goto drop; 1518 } 1519 } 1520 1521 /* 1522 * T/TCP mechanism 1523 * If T/TCP was negotiated and the segment doesn't have CC, 1524 * or if its CC is wrong then drop the segment. 1525 * RST segments do not have to comply with this. 1526 */ 1527 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1528 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1529 goto dropafterack; 1530 1531 /* 1532 * In the SYN-RECEIVED state, validate that the packet belongs to 1533 * this connection before trimming the data to fit the receive 1534 * window. Check the sequence number versus IRS since we know 1535 * the sequence numbers haven't wrapped. This is a partial fix 1536 * for the "LAND" DoS attack. 1537 */ 1538 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1539 rstreason = BANDLIM_RST_OPENPORT; 1540 goto dropwithreset; 1541 } 1542 1543 todrop = tp->rcv_nxt - th->th_seq; 1544 if (todrop > 0) { 1545 if (thflags & TH_SYN) { 1546 thflags &= ~TH_SYN; 1547 th->th_seq++; 1548 if (th->th_urp > 1) 1549 th->th_urp--; 1550 else 1551 thflags &= ~TH_URG; 1552 todrop--; 1553 } 1554 /* 1555 * Following if statement from Stevens, vol. 2, p. 960. 1556 */ 1557 if (todrop > tlen 1558 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1559 /* 1560 * Any valid FIN must be to the left of the window. 1561 * At this point the FIN must be a duplicate or out 1562 * of sequence; drop it. 1563 */ 1564 thflags &= ~TH_FIN; 1565 1566 /* 1567 * Send an ACK to resynchronize and drop any data. 1568 * But keep on processing for RST or ACK. 1569 */ 1570 tp->t_flags |= TF_ACKNOW; 1571 todrop = tlen; 1572 tcpstat.tcps_rcvduppack++; 1573 tcpstat.tcps_rcvdupbyte += todrop; 1574 } else { 1575 tcpstat.tcps_rcvpartduppack++; 1576 tcpstat.tcps_rcvpartdupbyte += todrop; 1577 } 1578 drop_hdrlen += todrop; /* drop from the top afterwards */ 1579 th->th_seq += todrop; 1580 tlen -= todrop; 1581 if (th->th_urp > todrop) 1582 th->th_urp -= todrop; 1583 else { 1584 thflags &= ~TH_URG; 1585 th->th_urp = 0; 1586 } 1587 } 1588 1589 /* 1590 * If new data are received on a connection after the 1591 * user processes are gone, then RST the other end. 1592 */ 1593 if ((so->so_state & SS_NOFDREF) && 1594 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1595 tp = tcp_close(tp); 1596 tcpstat.tcps_rcvafterclose++; 1597 rstreason = BANDLIM_UNLIMITED; 1598 goto dropwithreset; 1599 } 1600 1601 /* 1602 * If segment ends after window, drop trailing data 1603 * (and PUSH and FIN); if nothing left, just ACK. 1604 */ 1605 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1606 if (todrop > 0) { 1607 tcpstat.tcps_rcvpackafterwin++; 1608 if (todrop >= tlen) { 1609 tcpstat.tcps_rcvbyteafterwin += tlen; 1610 /* 1611 * If a new connection request is received 1612 * while in TIME_WAIT, drop the old connection 1613 * and start over if the sequence numbers 1614 * are above the previous ones. 1615 */ 1616 if (thflags & TH_SYN && 1617 tp->t_state == TCPS_TIME_WAIT && 1618 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1619 tp = tcp_close(tp); 1620 goto findpcb; 1621 } 1622 /* 1623 * If window is closed can only take segments at 1624 * window edge, and have to drop data and PUSH from 1625 * incoming segments. Continue processing, but 1626 * remember to ack. Otherwise, drop segment 1627 * and ack. 1628 */ 1629 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1630 tp->t_flags |= TF_ACKNOW; 1631 tcpstat.tcps_rcvwinprobe++; 1632 } else 1633 goto dropafterack; 1634 } else 1635 tcpstat.tcps_rcvbyteafterwin += todrop; 1636 m_adj(m, -todrop); 1637 tlen -= todrop; 1638 thflags &= ~(TH_PUSH|TH_FIN); 1639 } 1640 1641 /* 1642 * If last ACK falls within this segment's sequence numbers, 1643 * record its timestamp. 1644 * NOTE that the test is modified according to the latest 1645 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1646 */ 1647 if ((to.to_flags & TOF_TS) != 0 && 1648 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1649 tp->ts_recent_age = ticks; 1650 tp->ts_recent = to.to_tsval; 1651 } 1652 1653 /* 1654 * If a SYN is in the window, then this is an 1655 * error and we send an RST and drop the connection. 1656 */ 1657 if (thflags & TH_SYN) { 1658 tp = tcp_drop(tp, ECONNRESET); 1659 rstreason = BANDLIM_UNLIMITED; 1660 goto dropwithreset; 1661 } 1662 1663 /* 1664 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1665 * flag is on (half-synchronized state), then queue data for 1666 * later processing; else drop segment and return. 1667 */ 1668 if ((thflags & TH_ACK) == 0) { 1669 if (tp->t_state == TCPS_SYN_RECEIVED || 1670 (tp->t_flags & TF_NEEDSYN)) 1671 goto step6; 1672 else 1673 goto drop; 1674 } 1675 1676 /* 1677 * Ack processing. 1678 */ 1679 switch (tp->t_state) { 1680 1681 /* 1682 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1683 * ESTABLISHED state and continue processing. 1684 * The ACK was checked above. 1685 */ 1686 case TCPS_SYN_RECEIVED: 1687 1688 tcpstat.tcps_connects++; 1689 soisconnected(so); 1690 /* Do window scaling? */ 1691 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1692 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1693 tp->snd_scale = tp->requested_s_scale; 1694 tp->rcv_scale = tp->request_r_scale; 1695 } 1696 /* 1697 * Upon successful completion of 3-way handshake, 1698 * update cache.CC if it was undefined, pass any queued 1699 * data to the user, and advance state appropriately. 1700 */ 1701 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1702 taop->tao_cc == 0) 1703 taop->tao_cc = tp->cc_recv; 1704 1705 /* 1706 * Make transitions: 1707 * SYN-RECEIVED -> ESTABLISHED 1708 * SYN-RECEIVED* -> FIN-WAIT-1 1709 */ 1710 tp->t_starttime = ticks; 1711 if (tp->t_flags & TF_NEEDFIN) { 1712 tp->t_state = TCPS_FIN_WAIT_1; 1713 tp->t_flags &= ~TF_NEEDFIN; 1714 } else { 1715 tp->t_state = TCPS_ESTABLISHED; 1716 callout_reset(tp->tt_keep, tcp_keepidle, 1717 tcp_timer_keep, tp); 1718 } 1719 /* 1720 * If segment contains data or ACK, will call tcp_reass() 1721 * later; if not, do so now to pass queued data to user. 1722 */ 1723 if (tlen == 0 && (thflags & TH_FIN) == 0) 1724 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1725 (struct mbuf *)0); 1726 tp->snd_wl1 = th->th_seq - 1; 1727 /* fall into ... */ 1728 1729 /* 1730 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1731 * ACKs. If the ack is in the range 1732 * tp->snd_una < th->th_ack <= tp->snd_max 1733 * then advance tp->snd_una to th->th_ack and drop 1734 * data from the retransmission queue. If this ACK reflects 1735 * more up to date window information we update our window information. 1736 */ 1737 case TCPS_ESTABLISHED: 1738 case TCPS_FIN_WAIT_1: 1739 case TCPS_FIN_WAIT_2: 1740 case TCPS_CLOSE_WAIT: 1741 case TCPS_CLOSING: 1742 case TCPS_LAST_ACK: 1743 case TCPS_TIME_WAIT: 1744 1745 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1746 if (tlen != 0 || tiwin != tp->snd_wnd) { 1747 tp->t_dupacks = 0; 1748 break; 1749 } 1750 tcpstat.tcps_rcvdupack++; 1751 /* 1752 * If we have outstanding data (other than 1753 * a window probe), this is a completely 1754 * duplicate ack (ie, window info didn't 1755 * change), the ack is the biggest we've 1756 * seen and we've seen exactly our rexmt 1757 * threshhold of them, assume a packet 1758 * has been dropped and retransmit it. 1759 * Kludge snd_nxt & the congestion 1760 * window so we send only this one 1761 * packet. 1762 * 1763 * We know we're losing at the current 1764 * window size so do congestion avoidance 1765 * (set ssthresh to half the current window 1766 * and pull our congestion window back to 1767 * the new ssthresh). 1768 * 1769 * Dup acks mean that packets have left the 1770 * network (they're now cached at the receiver) 1771 * so bump cwnd by the amount in the receiver 1772 * to keep a constant cwnd packets in the 1773 * network. 1774 */ 1775 if (!callout_active(tp->tt_rexmt) || 1776 th->th_ack != tp->snd_una) { 1777 tp->t_dupacks = 0; 1778 break; 1779 } 1780 if (IN_FASTRECOVERY(tp)) { 1781 tp->snd_cwnd += tp->t_maxseg; 1782 (void) tcp_output(tp); 1783 } else if (++tp->t_dupacks == tcprexmtthresh) { 1784 tcp_seq onxt; 1785 u_int win; 1786 1787 if (SEQ_LEQ(th->th_ack, tp->snd_recover)) { 1788 tp->t_dupacks = 0; 1789 break; 1790 } 1791 fastretransmit: 1792 if (tcp_do_eifel_detect && 1793 (tp->t_flags & TF_RCVD_TSTMP)) { 1794 tcp_save_congestion_state(tp); 1795 tp->t_flags |= TF_FASTREXMT; 1796 } 1797 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1798 tp->t_maxseg; 1799 if (win < 2) 1800 win = 2; 1801 tp->snd_ssthresh = win * tp->t_maxseg; 1802 ENTER_FASTRECOVERY(tp); 1803 tp->snd_recover = tp->snd_max; 1804 callout_stop(tp->tt_rexmt); 1805 tp->t_rtttime = 0; 1806 onxt = tp->snd_nxt; 1807 tp->snd_nxt = th->th_ack; 1808 tp->snd_cwnd = tp->t_maxseg; 1809 (void) tcp_output(tp); 1810 ++tcpstat.tcps_sndfastrexmit; 1811 KASSERT(tp->snd_limited <= 2, 1812 ("tp->snd_limited too big")); 1813 tp->snd_cwnd = tp->snd_ssthresh + 1814 (tp->t_maxseg * 1815 (tp->t_dupacks - tp->snd_limited)); 1816 if (SEQ_GT(onxt, tp->snd_nxt)) 1817 tp->snd_nxt = onxt; 1818 } else if (tcp_do_limitedtransmit) { 1819 u_long oldcwnd = tp->snd_cwnd; 1820 tcp_seq oldsndmax = tp->snd_max; 1821 /* outstanding data */ 1822 uint32_t ownd = tp->snd_max - tp->snd_una; 1823 u_int sent; 1824 1825 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1826 1827 KASSERT(tp->t_dupacks == 1 || 1828 tp->t_dupacks == 2, 1829 ("dupacks not 1 or 2")); 1830 if (tp->t_dupacks == 1) 1831 tp->snd_limited = 0; 1832 tp->snd_cwnd = ownd + 1833 (tp->t_dupacks - tp->snd_limited) * 1834 tp->t_maxseg; 1835 (void) tcp_output(tp); 1836 tp->snd_cwnd = oldcwnd; 1837 sent = tp->snd_max - oldsndmax; 1838 if (sent > tp->t_maxseg) { 1839 KASSERT((tp->t_dupacks == 2 && 1840 tp->snd_limited == 0) || 1841 (sent == tp->t_maxseg + 1 && 1842 tp->t_flags & TF_SENTFIN), 1843 ("sent too much")); 1844 KASSERT(sent <= tp->t_maxseg * 2, 1845 ("sent too many segments")); 1846 tp->snd_limited = 2; 1847 tcpstat.tcps_sndlimited += 2; 1848 } else if (sent > 0) { 1849 ++tp->snd_limited; 1850 ++tcpstat.tcps_sndlimited; 1851 } else if (tcp_do_early_retransmit && 1852 (tcp_do_eifel_detect && 1853 (tp->t_flags & TF_RCVD_TSTMP)) && 1854 tp->t_dupacks + 1 >= 1855 iceildiv(ownd, tp->t_maxseg)) { 1856 ++tcpstat.tcps_sndearlyrexmit; 1857 tp->t_flags |= TF_EARLYREXMT; 1858 goto fastretransmit; 1859 } 1860 } 1861 goto drop; 1862 } 1863 1864 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1865 1866 /* 1867 * If the congestion window was inflated to account 1868 * for the other side's cached packets, retract it. 1869 */ 1870 if (IN_FASTRECOVERY(tp)) { 1871 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1872 tcp_newreno_partial_ack(tp, th); 1873 } else { 1874 /* 1875 * Window inflation should have left us 1876 * with approximately snd_ssthresh 1877 * outstanding data. 1878 * But in case we would be inclined to 1879 * send a burst, better to do it via 1880 * the slow start mechanism. 1881 */ 1882 if (SEQ_GT(th->th_ack + tp->snd_ssthresh, 1883 tp->snd_max)) 1884 tp->snd_cwnd = tp->snd_max - 1885 th->th_ack + tp->t_maxseg; 1886 else 1887 tp->snd_cwnd = tp->snd_ssthresh; 1888 } 1889 } 1890 tp->t_dupacks = 0; 1891 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1892 /* 1893 * Detected optimistic ACK attack. 1894 * Force slow-start to de-synchronize attack. 1895 */ 1896 tp->snd_cwnd = tp->t_maxseg; 1897 1898 tcpstat.tcps_rcvacktoomuch++; 1899 goto dropafterack; 1900 } 1901 /* 1902 * If we reach this point, ACK is not a duplicate, 1903 * i.e., it ACKs something we sent. 1904 */ 1905 if (tp->t_flags & TF_NEEDSYN) { 1906 /* 1907 * T/TCP: Connection was half-synchronized, and our 1908 * SYN has been ACK'd (so connection is now fully 1909 * synchronized). Go to non-starred state, 1910 * increment snd_una for ACK of SYN, and check if 1911 * we can do window scaling. 1912 */ 1913 tp->t_flags &= ~TF_NEEDSYN; 1914 tp->snd_una++; 1915 /* Do window scaling? */ 1916 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1917 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1918 tp->snd_scale = tp->requested_s_scale; 1919 tp->rcv_scale = tp->request_r_scale; 1920 } 1921 } 1922 1923 process_ACK: 1924 acked = th->th_ack - tp->snd_una; 1925 tcpstat.tcps_rcvackpack++; 1926 tcpstat.tcps_rcvackbyte += acked; 1927 1928 /* 1929 * If we just performed our first retransmit, and the ACK 1930 * arrives within our recovery window, then it was a mistake 1931 * to do the retransmit in the first place. Recover our 1932 * original cwnd and ssthresh, and proceed to transmit where 1933 * we left off. 1934 */ 1935 if (tcp_do_eifel_detect && acked && 1936 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 1937 (tp->t_flags & TF_FIRSTACCACK)) { 1938 /* Eifel detection applicable. */ 1939 if (to.to_tsecr < tp->t_rexmtTS) { 1940 ++tcpstat.tcps_eifeldetected; 1941 tcp_revert_congestion_state(tp); 1942 if (tp->t_rxtshift == 1 && 1943 ticks >= tp->t_badrxtwin) 1944 ++tcpstat.tcps_rttcantdetect; 1945 } 1946 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1947 tcp_revert_congestion_state(tp); 1948 ++tcpstat.tcps_rttdetected; 1949 } 1950 1951 /* 1952 * If we have a timestamp reply, update smoothed 1953 * round trip time. If no timestamp is present but 1954 * transmit timer is running and timed sequence 1955 * number was acked, update smoothed round trip time. 1956 * Since we now have an rtt measurement, cancel the 1957 * timer backoff (cf., Phil Karn's retransmit alg.). 1958 * Recompute the initial retransmit timer. 1959 * 1960 * Some machines (certain windows boxes) send broken 1961 * timestamp replies during the SYN+ACK phase, ignore 1962 * timestamps of 0. 1963 */ 1964 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 1965 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1966 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 1967 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1968 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1969 1970 /* 1971 * If all outstanding data is acked, stop retransmit 1972 * timer and remember to restart (more output or persist). 1973 * If there is more data to be acked, restart retransmit 1974 * timer, using current (possibly backed-off) value. 1975 */ 1976 if (th->th_ack == tp->snd_max) { 1977 callout_stop(tp->tt_rexmt); 1978 needoutput = 1; 1979 } else if (!callout_active(tp->tt_persist)) 1980 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1981 tcp_timer_rexmt, tp); 1982 1983 /* 1984 * If no data (only SYN) was ACK'd, 1985 * skip rest of ACK processing. 1986 */ 1987 if (acked == 0) 1988 goto step6; 1989 1990 /* Stop looking for an acceptable ACK since one was received. */ 1991 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 1992 1993 /* 1994 * When new data is acked, open the congestion window. 1995 * If the window gives us less than ssthresh packets 1996 * in flight, open exponentially (maxseg per packet). 1997 * Otherwise open linearly: maxseg per window 1998 * (maxseg^2 / cwnd per packet). 1999 */ 2000 if (!IN_FASTRECOVERY(tp)) { 2001 u_int cw = tp->snd_cwnd; 2002 u_int incr = tp->t_maxseg; 2003 2004 if (cw > tp->snd_ssthresh) 2005 incr = incr * incr / cw; 2006 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2007 } 2008 if (acked > so->so_snd.sb_cc) { 2009 tp->snd_wnd -= so->so_snd.sb_cc; 2010 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2011 ourfinisacked = 1; 2012 } else { 2013 sbdrop(&so->so_snd, acked); 2014 tp->snd_wnd -= acked; 2015 ourfinisacked = 0; 2016 } 2017 sowwakeup(so); 2018 if (IN_FASTRECOVERY(tp)) { 2019 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) 2020 EXIT_FASTRECOVERY(tp); 2021 } else { 2022 tp->snd_recover = th->th_ack - 1; 2023 } 2024 tp->snd_una = th->th_ack; 2025 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2026 tp->snd_nxt = tp->snd_una; 2027 2028 switch (tp->t_state) { 2029 2030 /* 2031 * In FIN_WAIT_1 STATE in addition to the processing 2032 * for the ESTABLISHED state if our FIN is now acknowledged 2033 * then enter FIN_WAIT_2. 2034 */ 2035 case TCPS_FIN_WAIT_1: 2036 if (ourfinisacked) { 2037 /* 2038 * If we can't receive any more 2039 * data, then closing user can proceed. 2040 * Starting the timer is contrary to the 2041 * specification, but if we don't get a FIN 2042 * we'll hang forever. 2043 */ 2044 if (so->so_state & SS_CANTRCVMORE) { 2045 soisdisconnected(so); 2046 callout_reset(tp->tt_2msl, tcp_maxidle, 2047 tcp_timer_2msl, tp); 2048 } 2049 tp->t_state = TCPS_FIN_WAIT_2; 2050 } 2051 break; 2052 2053 /* 2054 * In CLOSING STATE in addition to the processing for 2055 * the ESTABLISHED state if the ACK acknowledges our FIN 2056 * then enter the TIME-WAIT state, otherwise ignore 2057 * the segment. 2058 */ 2059 case TCPS_CLOSING: 2060 if (ourfinisacked) { 2061 tp->t_state = TCPS_TIME_WAIT; 2062 tcp_canceltimers(tp); 2063 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2064 if (tp->cc_recv != 0 && 2065 (ticks - tp->t_starttime) < tcp_msl) 2066 callout_reset(tp->tt_2msl, 2067 tp->t_rxtcur * 2068 TCPTV_TWTRUNC, 2069 tcp_timer_2msl, tp); 2070 else 2071 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2072 tcp_timer_2msl, tp); 2073 soisdisconnected(so); 2074 } 2075 break; 2076 2077 /* 2078 * In LAST_ACK, we may still be waiting for data to drain 2079 * and/or to be acked, as well as for the ack of our FIN. 2080 * If our FIN is now acknowledged, delete the TCB, 2081 * enter the closed state and return. 2082 */ 2083 case TCPS_LAST_ACK: 2084 if (ourfinisacked) { 2085 tp = tcp_close(tp); 2086 goto drop; 2087 } 2088 break; 2089 2090 /* 2091 * In TIME_WAIT state the only thing that should arrive 2092 * is a retransmission of the remote FIN. Acknowledge 2093 * it and restart the finack timer. 2094 */ 2095 case TCPS_TIME_WAIT: 2096 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2097 tcp_timer_2msl, tp); 2098 goto dropafterack; 2099 } 2100 } 2101 2102 step6: 2103 /* 2104 * Update window information. 2105 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2106 */ 2107 if ((thflags & TH_ACK) && 2108 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2109 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2110 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2111 /* keep track of pure window updates */ 2112 if (tlen == 0 && 2113 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2114 tcpstat.tcps_rcvwinupd++; 2115 tp->snd_wnd = tiwin; 2116 tp->snd_wl1 = th->th_seq; 2117 tp->snd_wl2 = th->th_ack; 2118 if (tp->snd_wnd > tp->max_sndwnd) 2119 tp->max_sndwnd = tp->snd_wnd; 2120 needoutput = 1; 2121 } 2122 2123 /* 2124 * Process segments with URG. 2125 */ 2126 if ((thflags & TH_URG) && th->th_urp && 2127 !TCPS_HAVERCVDFIN(tp->t_state)) { 2128 /* 2129 * This is a kludge, but if we receive and accept 2130 * random urgent pointers, we'll crash in 2131 * soreceive. It's hard to imagine someone 2132 * actually wanting to send this much urgent data. 2133 */ 2134 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2135 th->th_urp = 0; /* XXX */ 2136 thflags &= ~TH_URG; /* XXX */ 2137 goto dodata; /* XXX */ 2138 } 2139 /* 2140 * If this segment advances the known urgent pointer, 2141 * then mark the data stream. This should not happen 2142 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2143 * a FIN has been received from the remote side. 2144 * In these states we ignore the URG. 2145 * 2146 * According to RFC961 (Assigned Protocols), 2147 * the urgent pointer points to the last octet 2148 * of urgent data. We continue, however, 2149 * to consider it to indicate the first octet 2150 * of data past the urgent section as the original 2151 * spec states (in one of two places). 2152 */ 2153 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2154 tp->rcv_up = th->th_seq + th->th_urp; 2155 so->so_oobmark = so->so_rcv.sb_cc + 2156 (tp->rcv_up - tp->rcv_nxt) - 1; 2157 if (so->so_oobmark == 0) 2158 so->so_state |= SS_RCVATMARK; 2159 sohasoutofband(so); 2160 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2161 } 2162 /* 2163 * Remove out of band data so doesn't get presented to user. 2164 * This can happen independent of advancing the URG pointer, 2165 * but if two URG's are pending at once, some out-of-band 2166 * data may creep in... ick. 2167 */ 2168 if (th->th_urp <= (u_long)tlen 2169 #ifdef SO_OOBINLINE 2170 && (so->so_options & SO_OOBINLINE) == 0 2171 #endif 2172 ) 2173 tcp_pulloutofband(so, th, m, 2174 drop_hdrlen); /* hdr drop is delayed */ 2175 } else { 2176 /* 2177 * If no out of band data is expected, 2178 * pull receive urgent pointer along 2179 * with the receive window. 2180 */ 2181 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2182 tp->rcv_up = tp->rcv_nxt; 2183 } 2184 dodata: /* XXX */ 2185 2186 /* 2187 * Process the segment text, merging it into the TCP sequencing queue, 2188 * and arranging for acknowledgment of receipt if necessary. 2189 * This process logically involves adjusting tp->rcv_wnd as data 2190 * is presented to the user (this happens in tcp_usrreq.c, 2191 * case PRU_RCVD). If a FIN has already been received on this 2192 * connection then we just ignore the text. 2193 */ 2194 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2195 m_adj(m, drop_hdrlen); /* delayed header drop */ 2196 /* 2197 * Insert segment which includes th into TCP reassembly queue 2198 * with control block tp. Set thflags to whether reassembly now 2199 * includes a segment with FIN. This handles the common case 2200 * inline (segment is the next to be received on an established 2201 * connection, and the queue is empty), avoiding linkage into 2202 * and removal from the queue and repetition of various 2203 * conversions. 2204 * Set DELACK for segments received in order, but ack 2205 * immediately when segments are out of order (so 2206 * fast retransmit can work). 2207 */ 2208 if (th->th_seq == tp->rcv_nxt && 2209 LIST_EMPTY(&tp->t_segq) && 2210 TCPS_HAVEESTABLISHED(tp->t_state)) { 2211 if (DELAY_ACK(tp)) 2212 callout_reset(tp->tt_delack, tcp_delacktime, 2213 tcp_timer_delack, tp); 2214 else 2215 tp->t_flags |= TF_ACKNOW; 2216 tp->rcv_nxt += tlen; 2217 thflags = th->th_flags & TH_FIN; 2218 tcpstat.tcps_rcvpack++; 2219 tcpstat.tcps_rcvbyte += tlen; 2220 ND6_HINT(tp); 2221 if (so->so_state & SS_CANTRCVMORE) 2222 m_freem(m); 2223 else 2224 sbappend(&so->so_rcv, m); 2225 sorwakeup(so); 2226 } else { 2227 thflags = tcp_reass(tp, th, &tlen, m); 2228 tp->t_flags |= TF_ACKNOW; 2229 } 2230 2231 /* 2232 * Note the amount of data that peer has sent into 2233 * our window, in order to estimate the sender's 2234 * buffer size. 2235 */ 2236 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2237 } else { 2238 m_freem(m); 2239 thflags &= ~TH_FIN; 2240 } 2241 2242 /* 2243 * If FIN is received ACK the FIN and let the user know 2244 * that the connection is closing. 2245 */ 2246 if (thflags & TH_FIN) { 2247 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2248 socantrcvmore(so); 2249 /* 2250 * If connection is half-synchronized 2251 * (ie NEEDSYN flag on) then delay ACK, 2252 * so it may be piggybacked when SYN is sent. 2253 * Otherwise, since we received a FIN then no 2254 * more input can be expected, send ACK now. 2255 */ 2256 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2257 callout_reset(tp->tt_delack, tcp_delacktime, 2258 tcp_timer_delack, tp); 2259 else 2260 tp->t_flags |= TF_ACKNOW; 2261 tp->rcv_nxt++; 2262 } 2263 switch (tp->t_state) { 2264 2265 /* 2266 * In SYN_RECEIVED and ESTABLISHED STATES 2267 * enter the CLOSE_WAIT state. 2268 */ 2269 case TCPS_SYN_RECEIVED: 2270 tp->t_starttime = ticks; 2271 /*FALLTHROUGH*/ 2272 case TCPS_ESTABLISHED: 2273 tp->t_state = TCPS_CLOSE_WAIT; 2274 break; 2275 2276 /* 2277 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2278 * enter the CLOSING state. 2279 */ 2280 case TCPS_FIN_WAIT_1: 2281 tp->t_state = TCPS_CLOSING; 2282 break; 2283 2284 /* 2285 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2286 * starting the time-wait timer, turning off the other 2287 * standard timers. 2288 */ 2289 case TCPS_FIN_WAIT_2: 2290 tp->t_state = TCPS_TIME_WAIT; 2291 tcp_canceltimers(tp); 2292 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2293 if (tp->cc_recv != 0 && 2294 (ticks - tp->t_starttime) < tcp_msl) { 2295 callout_reset(tp->tt_2msl, 2296 tp->t_rxtcur * TCPTV_TWTRUNC, 2297 tcp_timer_2msl, tp); 2298 /* For transaction client, force ACK now. */ 2299 tp->t_flags |= TF_ACKNOW; 2300 } 2301 else 2302 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2303 tcp_timer_2msl, tp); 2304 soisdisconnected(so); 2305 break; 2306 2307 /* 2308 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2309 */ 2310 case TCPS_TIME_WAIT: 2311 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2312 tcp_timer_2msl, tp); 2313 break; 2314 } 2315 } 2316 #ifdef TCPDEBUG 2317 if (so->so_options & SO_DEBUG) 2318 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2319 &tcp_savetcp, 0); 2320 #endif 2321 2322 /* 2323 * Return any desired output. 2324 */ 2325 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2326 (void) tcp_output(tp); 2327 return; 2328 2329 dropafterack: 2330 /* 2331 * Generate an ACK dropping incoming segment if it occupies 2332 * sequence space, where the ACK reflects our state. 2333 * 2334 * We can now skip the test for the RST flag since all 2335 * paths to this code happen after packets containing 2336 * RST have been dropped. 2337 * 2338 * In the SYN-RECEIVED state, don't send an ACK unless the 2339 * segment we received passes the SYN-RECEIVED ACK test. 2340 * If it fails send a RST. This breaks the loop in the 2341 * "LAND" DoS attack, and also prevents an ACK storm 2342 * between two listening ports that have been sent forged 2343 * SYN segments, each with the source address of the other. 2344 */ 2345 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2346 (SEQ_GT(tp->snd_una, th->th_ack) || 2347 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2348 rstreason = BANDLIM_RST_OPENPORT; 2349 goto dropwithreset; 2350 } 2351 #ifdef TCPDEBUG 2352 if (so->so_options & SO_DEBUG) 2353 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2354 &tcp_savetcp, 0); 2355 #endif 2356 m_freem(m); 2357 tp->t_flags |= TF_ACKNOW; 2358 (void) tcp_output(tp); 2359 return; 2360 2361 dropwithreset: 2362 /* 2363 * Generate a RST, dropping incoming segment. 2364 * Make ACK acceptable to originator of segment. 2365 * Don't bother to respond if destination was broadcast/multicast. 2366 */ 2367 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2368 goto drop; 2369 if (isipv6) { 2370 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2371 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2372 goto drop; 2373 } else { 2374 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2375 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2376 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2377 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2378 goto drop; 2379 } 2380 /* IPv6 anycast check is done at tcp6_input() */ 2381 2382 /* 2383 * Perform bandwidth limiting. 2384 */ 2385 #ifdef ICMP_BANDLIM 2386 if (badport_bandlim(rstreason) < 0) 2387 goto drop; 2388 #endif 2389 2390 #ifdef TCPDEBUG 2391 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2392 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2393 &tcp_savetcp, 0); 2394 #endif 2395 if (thflags & TH_ACK) 2396 /* mtod() below is safe as long as hdr dropping is delayed */ 2397 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2398 TH_RST); 2399 else { 2400 if (thflags & TH_SYN) 2401 tlen++; 2402 /* mtod() below is safe as long as hdr dropping is delayed */ 2403 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2404 (tcp_seq)0, TH_RST|TH_ACK); 2405 } 2406 return; 2407 2408 drop: 2409 /* 2410 * Drop space held by incoming segment and return. 2411 */ 2412 #ifdef TCPDEBUG 2413 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2414 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2415 &tcp_savetcp, 0); 2416 #endif 2417 m_freem(m); 2418 return; 2419 } 2420 2421 /* 2422 * Parse TCP options and place in tcpopt. 2423 */ 2424 static void 2425 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2426 { 2427 int opt, optlen; 2428 2429 to->to_flags = 0; 2430 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2431 opt = cp[0]; 2432 if (opt == TCPOPT_EOL) 2433 break; 2434 if (opt == TCPOPT_NOP) 2435 optlen = 1; 2436 else { 2437 if (cnt < 2) 2438 break; 2439 optlen = cp[1]; 2440 if (optlen < 2 || optlen > cnt) 2441 break; 2442 } 2443 switch (opt) { 2444 case TCPOPT_MAXSEG: 2445 if (optlen != TCPOLEN_MAXSEG) 2446 continue; 2447 if (!is_syn) 2448 continue; 2449 to->to_flags |= TOF_MSS; 2450 bcopy(cp + 2, &to->to_mss, sizeof(to->to_mss)); 2451 to->to_mss = ntohs(to->to_mss); 2452 break; 2453 case TCPOPT_WINDOW: 2454 if (optlen != TCPOLEN_WINDOW) 2455 continue; 2456 if (!is_syn) 2457 continue; 2458 to->to_flags |= TOF_SCALE; 2459 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2460 break; 2461 case TCPOPT_TIMESTAMP: 2462 if (optlen != TCPOLEN_TIMESTAMP) 2463 continue; 2464 to->to_flags |= TOF_TS; 2465 bcopy(cp + 2, &to->to_tsval, sizeof(to->to_tsval)); 2466 to->to_tsval = ntohl(to->to_tsval); 2467 bcopy(cp + 6, &to->to_tsecr, sizeof(to->to_tsecr)); 2468 to->to_tsecr = ntohl(to->to_tsecr); 2469 break; 2470 case TCPOPT_CC: 2471 if (optlen != TCPOLEN_CC) 2472 continue; 2473 to->to_flags |= TOF_CC; 2474 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc)); 2475 to->to_cc = ntohl(to->to_cc); 2476 break; 2477 case TCPOPT_CCNEW: 2478 if (optlen != TCPOLEN_CC) 2479 continue; 2480 if (!is_syn) 2481 continue; 2482 to->to_flags |= TOF_CCNEW; 2483 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc)); 2484 to->to_cc = ntohl(to->to_cc); 2485 break; 2486 case TCPOPT_CCECHO: 2487 if (optlen != TCPOLEN_CC) 2488 continue; 2489 if (!is_syn) 2490 continue; 2491 to->to_flags |= TOF_CCECHO; 2492 bcopy(cp + 2, &to->to_ccecho, sizeof(to->to_ccecho)); 2493 to->to_ccecho = ntohl(to->to_ccecho); 2494 break; 2495 default: 2496 continue; 2497 } 2498 } 2499 } 2500 2501 /* 2502 * Pull out of band byte out of a segment so 2503 * it doesn't appear in the user's data queue. 2504 * It is still reflected in the segment length for 2505 * sequencing purposes. 2506 * "off" is the delayed to be dropped hdrlen. 2507 */ 2508 static void 2509 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2510 { 2511 int cnt = off + th->th_urp - 1; 2512 2513 while (cnt >= 0) { 2514 if (m->m_len > cnt) { 2515 char *cp = mtod(m, caddr_t) + cnt; 2516 struct tcpcb *tp = sototcpcb(so); 2517 2518 tp->t_iobc = *cp; 2519 tp->t_oobflags |= TCPOOB_HAVEDATA; 2520 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2521 m->m_len--; 2522 if (m->m_flags & M_PKTHDR) 2523 m->m_pkthdr.len--; 2524 return; 2525 } 2526 cnt -= m->m_len; 2527 m = m->m_next; 2528 if (m == 0) 2529 break; 2530 } 2531 panic("tcp_pulloutofband"); 2532 } 2533 2534 /* 2535 * Collect new round-trip time estimate 2536 * and update averages and current timeout. 2537 */ 2538 static void 2539 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2540 { 2541 int delta; 2542 2543 tcpstat.tcps_rttupdated++; 2544 tp->t_rttupdated++; 2545 if (tp->t_srtt != 0) { 2546 /* 2547 * srtt is stored as fixed point with 5 bits after the 2548 * binary point (i.e., scaled by 8). The following magic 2549 * is equivalent to the smoothing algorithm in rfc793 with 2550 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2551 * point). Adjust rtt to origin 0. 2552 */ 2553 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2554 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2555 2556 if ((tp->t_srtt += delta) <= 0) 2557 tp->t_srtt = 1; 2558 2559 /* 2560 * We accumulate a smoothed rtt variance (actually, a 2561 * smoothed mean difference), then set the retransmit 2562 * timer to smoothed rtt + 4 times the smoothed variance. 2563 * rttvar is stored as fixed point with 4 bits after the 2564 * binary point (scaled by 16). The following is 2565 * equivalent to rfc793 smoothing with an alpha of .75 2566 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2567 * rfc793's wired-in beta. 2568 */ 2569 if (delta < 0) 2570 delta = -delta; 2571 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2572 if ((tp->t_rttvar += delta) <= 0) 2573 tp->t_rttvar = 1; 2574 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2575 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2576 } else { 2577 /* 2578 * No rtt measurement yet - use the unsmoothed rtt. 2579 * Set the variance to half the rtt (so our first 2580 * retransmit happens at 3*rtt). 2581 */ 2582 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2583 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2584 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2585 } 2586 tp->t_rtttime = 0; 2587 tp->t_rxtshift = 0; 2588 2589 /* 2590 * the retransmit should happen at rtt + 4 * rttvar. 2591 * Because of the way we do the smoothing, srtt and rttvar 2592 * will each average +1/2 tick of bias. When we compute 2593 * the retransmit timer, we want 1/2 tick of rounding and 2594 * 1 extra tick because of +-1/2 tick uncertainty in the 2595 * firing of the timer. The bias will give us exactly the 2596 * 1.5 tick we need. But, because the bias is 2597 * statistical, we have to test that we don't drop below 2598 * the minimum feasible timer (which is 2 ticks). 2599 */ 2600 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2601 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2602 2603 /* 2604 * We received an ack for a packet that wasn't retransmitted; 2605 * it is probably safe to discard any error indications we've 2606 * received recently. This isn't quite right, but close enough 2607 * for now (a route might have failed after we sent a segment, 2608 * and the return path might not be symmetrical). 2609 */ 2610 tp->t_softerror = 0; 2611 } 2612 2613 /* 2614 * Determine a reasonable value for maxseg size. 2615 * If the route is known, check route for mtu. 2616 * If none, use an mss that can be handled on the outgoing 2617 * interface without forcing IP to fragment; if bigger than 2618 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2619 * to utilize large mbufs. If no route is found, route has no mtu, 2620 * or the destination isn't local, use a default, hopefully conservative 2621 * size (usually 512 or the default IP max size, but no more than the mtu 2622 * of the interface), as we can't discover anything about intervening 2623 * gateways or networks. We also initialize the congestion/slow start 2624 * window to be a single segment if the destination isn't local. 2625 * While looking at the routing entry, we also initialize other path-dependent 2626 * parameters from pre-set or cached values in the routing entry. 2627 * 2628 * Also take into account the space needed for options that we 2629 * send regularly. Make maxseg shorter by that amount to assure 2630 * that we can send maxseg amount of data even when the options 2631 * are present. Store the upper limit of the length of options plus 2632 * data in maxopd. 2633 * 2634 * NOTE that this routine is only called when we process an incoming 2635 * segment, for outgoing segments only tcp_mssopt is called. 2636 * 2637 * In case of T/TCP, we call this routine during implicit connection 2638 * setup as well (offer = -1), to initialize maxseg from the cached 2639 * MSS of our peer. 2640 */ 2641 void 2642 tcp_mss(struct tcpcb *tp, int offer) 2643 { 2644 struct rtentry *rt; 2645 struct ifnet *ifp; 2646 int rtt, mss; 2647 u_long bufsize; 2648 struct inpcb *inp = tp->t_inpcb; 2649 struct socket *so; 2650 struct rmxp_tao *taop; 2651 int origoffer = offer; 2652 #ifdef INET6 2653 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2654 size_t min_protoh = isipv6 ? 2655 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2656 sizeof(struct tcpiphdr); 2657 #else 2658 const boolean_t isipv6 = FALSE; 2659 const size_t min_protoh = sizeof(struct tcpiphdr); 2660 #endif 2661 2662 if (isipv6) 2663 rt = tcp_rtlookup6(&inp->inp_inc); 2664 else 2665 rt = tcp_rtlookup(&inp->inp_inc); 2666 if (rt == NULL) { 2667 tp->t_maxopd = tp->t_maxseg = 2668 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2669 return; 2670 } 2671 ifp = rt->rt_ifp; 2672 so = inp->inp_socket; 2673 2674 taop = rmx_taop(rt->rt_rmx); 2675 /* 2676 * Offer == -1 means that we didn't receive SYN yet, 2677 * use cached value in that case; 2678 */ 2679 if (offer == -1) 2680 offer = taop->tao_mssopt; 2681 /* 2682 * Offer == 0 means that there was no MSS on the SYN segment, 2683 * in this case we use tcp_mssdflt. 2684 */ 2685 if (offer == 0) 2686 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2687 else 2688 /* 2689 * Sanity check: make sure that maxopd will be large 2690 * enough to allow some data on segments even is the 2691 * all the option space is used (40bytes). Otherwise 2692 * funny things may happen in tcp_output. 2693 */ 2694 offer = max(offer, 64); 2695 taop->tao_mssopt = offer; 2696 2697 /* 2698 * While we're here, check if there's an initial rtt 2699 * or rttvar. Convert from the route-table units 2700 * to scaled multiples of the slow timeout timer. 2701 */ 2702 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2703 /* 2704 * XXX the lock bit for RTT indicates that the value 2705 * is also a minimum value; this is subject to time. 2706 */ 2707 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2708 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2709 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2710 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2711 tcpstat.tcps_usedrtt++; 2712 if (rt->rt_rmx.rmx_rttvar) { 2713 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2714 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2715 tcpstat.tcps_usedrttvar++; 2716 } else { 2717 /* default variation is +- 1 rtt */ 2718 tp->t_rttvar = 2719 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2720 } 2721 TCPT_RANGESET(tp->t_rxtcur, 2722 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2723 tp->t_rttmin, TCPTV_REXMTMAX); 2724 } 2725 /* 2726 * if there's an mtu associated with the route, use it 2727 * else, use the link mtu. 2728 */ 2729 if (rt->rt_rmx.rmx_mtu) 2730 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2731 else { 2732 if (isipv6) { 2733 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2734 min_protoh; 2735 if (!in6_localaddr(&inp->in6p_faddr)) 2736 mss = min(mss, tcp_v6mssdflt); 2737 } else { 2738 mss = ifp->if_mtu - min_protoh; 2739 if (!in_localaddr(inp->inp_faddr)) 2740 mss = min(mss, tcp_mssdflt); 2741 } 2742 } 2743 mss = min(mss, offer); 2744 /* 2745 * maxopd stores the maximum length of data AND options 2746 * in a segment; maxseg is the amount of data in a normal 2747 * segment. We need to store this value (maxopd) apart 2748 * from maxseg, because now every segment carries options 2749 * and thus we normally have somewhat less data in segments. 2750 */ 2751 tp->t_maxopd = mss; 2752 2753 /* 2754 * In case of T/TCP, origoffer==-1 indicates, that no segments 2755 * were received yet. In this case we just guess, otherwise 2756 * we do the same as before T/TCP. 2757 */ 2758 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2759 (origoffer == -1 || 2760 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2761 mss -= TCPOLEN_TSTAMP_APPA; 2762 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2763 (origoffer == -1 || 2764 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2765 mss -= TCPOLEN_CC_APPA; 2766 2767 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2768 if (mss > MCLBYTES) 2769 mss &= ~(MCLBYTES-1); 2770 #else 2771 if (mss > MCLBYTES) 2772 mss = mss / MCLBYTES * MCLBYTES; 2773 #endif 2774 /* 2775 * If there's a pipesize, change the socket buffer 2776 * to that size. Make the socket buffers an integral 2777 * number of mss units; if the mss is larger than 2778 * the socket buffer, decrease the mss. 2779 */ 2780 #ifdef RTV_SPIPE 2781 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2782 #endif 2783 bufsize = so->so_snd.sb_hiwat; 2784 if (bufsize < mss) 2785 mss = bufsize; 2786 else { 2787 bufsize = roundup(bufsize, mss); 2788 if (bufsize > sb_max) 2789 bufsize = sb_max; 2790 if (bufsize > so->so_snd.sb_hiwat) 2791 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2792 } 2793 tp->t_maxseg = mss; 2794 2795 #ifdef RTV_RPIPE 2796 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2797 #endif 2798 bufsize = so->so_rcv.sb_hiwat; 2799 if (bufsize > mss) { 2800 bufsize = roundup(bufsize, mss); 2801 if (bufsize > sb_max) 2802 bufsize = sb_max; 2803 if (bufsize > so->so_rcv.sb_hiwat) 2804 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2805 } 2806 2807 /* 2808 * Set the slow-start flight size depending on whether this 2809 * is a local network or not. 2810 */ 2811 if (tcp_do_rfc3390) 2812 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2813 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2814 (!isipv6 && in_localaddr(inp->inp_faddr))) 2815 tp->snd_cwnd = mss * ss_fltsz_local; 2816 else 2817 tp->snd_cwnd = mss * ss_fltsz; 2818 2819 if (rt->rt_rmx.rmx_ssthresh) { 2820 /* 2821 * There's some sort of gateway or interface 2822 * buffer limit on the path. Use this to set 2823 * the slow start threshhold, but set the 2824 * threshold to no less than 2*mss. 2825 */ 2826 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2827 tcpstat.tcps_usedssthresh++; 2828 } 2829 } 2830 2831 /* 2832 * Determine the MSS option to send on an outgoing SYN. 2833 */ 2834 int 2835 tcp_mssopt(struct tcpcb *tp) 2836 { 2837 struct rtentry *rt; 2838 #ifdef INET6 2839 boolean_t isipv6 = 2840 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2841 int min_protoh = isipv6 ? 2842 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2843 sizeof(struct tcpiphdr); 2844 #else 2845 const boolean_t isipv6 = FALSE; 2846 const size_t min_protoh = sizeof(struct tcpiphdr); 2847 #endif 2848 2849 if (isipv6) 2850 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2851 else 2852 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2853 if (rt == NULL) 2854 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2855 2856 return (rt->rt_ifp->if_mtu - min_protoh); 2857 } 2858 2859 2860 /* 2861 * When a partial ack arrives, force the retransmission of the 2862 * next unacknowledged segment. Do not clear tp->t_dupacks. 2863 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2864 * be started again. 2865 */ 2866 static void 2867 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 2868 { 2869 tcp_seq onxt = tp->snd_nxt; 2870 u_long ocwnd = tp->snd_cwnd; 2871 2872 callout_stop(tp->tt_rexmt); 2873 tp->t_rtttime = 0; 2874 tp->snd_nxt = th->th_ack; 2875 /* 2876 * Set snd_cwnd to one segment beyond acknowledged offset 2877 * (tp->snd_una has not yet been updated when this function is called.) 2878 */ 2879 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2880 tp->t_flags |= TF_ACKNOW; 2881 (void) tcp_output(tp); 2882 tp->snd_cwnd = ocwnd; 2883 if (SEQ_GT(onxt, tp->snd_nxt)) 2884 tp->snd_nxt = onxt; 2885 /* 2886 * Partial window deflation. Relies on fact that tp->snd_una 2887 * not updated yet. 2888 */ 2889 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2890 } 2891