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 1.30 2004/07/08 22:07:35 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 #ifdef TCPDEBUG 134 #include <netinet/tcp_debug.h> 135 136 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 137 struct tcphdr tcp_savetcp; 138 #endif /* TCPDEBUG */ 139 140 #ifdef FAST_IPSEC 141 #include <netipsec/ipsec.h> 142 #include <netipsec/ipsec6.h> 143 #endif 144 145 #ifdef IPSEC 146 #include <netinet6/ipsec.h> 147 #include <netinet6/ipsec6.h> 148 #include <netproto/key/key.h> 149 #endif /*IPSEC*/ 150 151 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 152 153 static const int tcprexmtthresh = 3; 154 tcp_cc tcp_ccgen; 155 static int log_in_vain = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 157 &log_in_vain, 0, "Log all incoming TCP connections"); 158 159 static int blackhole = 0; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 161 &blackhole, 0, "Do not send RST when dropping refused connections"); 162 163 int tcp_delack_enabled = 1; 164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 165 &tcp_delack_enabled, 0, 166 "Delay ACK to try and piggyback it onto a data packet"); 167 168 #ifdef TCP_DROP_SYNFIN 169 static int drop_synfin = 0; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 171 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 172 #endif 173 174 static int tcp_do_limitedtransmit = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 176 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 177 178 static int tcp_do_early_retransmit = 0; 179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 180 &tcp_do_early_retransmit, 0, "Early retransmit"); 181 182 static int tcp_do_rfc3390 = 1; 183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 184 &tcp_do_rfc3390, 0, 185 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 186 187 static int tcp_do_eifel_detect = 1; 188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 189 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 190 191 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 192 "TCP Segment Reassembly Queue"); 193 194 int tcp_reass_maxseg = 0; 195 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 196 &tcp_reass_maxseg, 0, 197 "Global maximum number of TCP Segments in Reassembly Queue"); 198 199 int tcp_reass_qsize = 0; 200 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 201 &tcp_reass_qsize, 0, 202 "Global number of TCP Segments currently in Reassembly Queue"); 203 204 static int tcp_reass_overflows = 0; 205 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 206 &tcp_reass_overflows, 0, 207 "Global number of TCP Segment Reassembly Queue Overflows"); 208 209 struct inpcbinfo tcbinfo[MAXCPU]; 210 211 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 212 static void tcp_pulloutofband(struct socket *, 213 struct tcphdr *, struct mbuf *, int); 214 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 215 struct mbuf *); 216 static void tcp_xmit_timer(struct tcpcb *, int); 217 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 218 219 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 220 #ifdef INET6 221 #define ND6_HINT(tp) \ 222 do { \ 223 if ((tp) && (tp)->t_inpcb && \ 224 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 225 (tp)->t_inpcb->in6p_route.ro_rt) \ 226 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 227 } while (0) 228 #else 229 #define ND6_HINT(tp) 230 #endif 231 232 /* 233 * Indicate whether this ack should be delayed. We can delay the ack if 234 * - delayed acks are enabled and 235 * - there is no delayed ack timer in progress and 236 * - our last ack wasn't a 0-sized window. We never want to delay 237 * the ack that opens up a 0-sized window. 238 */ 239 #define DELAY_ACK(tp) \ 240 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 241 (tp->t_flags & TF_RXWIN0SENT) == 0) 242 243 static int 244 tcp_reass(tp, th, tlenp, m) 245 struct tcpcb *tp; 246 struct tcphdr *th; 247 int *tlenp; 248 struct mbuf *m; 249 { 250 struct tseg_qent *q; 251 struct tseg_qent *p = NULL; 252 struct tseg_qent *nq; 253 struct tseg_qent *te; 254 struct socket *so = tp->t_inpcb->inp_socket; 255 int flags; 256 257 /* 258 * Call with th==0 after become established to 259 * force pre-ESTABLISHED data up to user socket. 260 */ 261 if (th == 0) 262 goto present; 263 264 /* 265 * Limit the number of segments in the reassembly queue to prevent 266 * holding on to too many segments (and thus running out of mbufs). 267 * Make sure to let the missing segment through which caused this 268 * queue. Always keep one global queue entry spare to be able to 269 * process the missing segment. 270 */ 271 if (th->th_seq != tp->rcv_nxt && 272 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 273 tcp_reass_overflows++; 274 tcpstat.tcps_rcvmemdrop++; 275 m_freem(m); 276 return (0); 277 } 278 279 /* Allocate a new queue entry. */ 280 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 281 M_INTWAIT | M_NULLOK); 282 if (te == NULL) { 283 tcpstat.tcps_rcvmemdrop++; 284 m_freem(m); 285 return (0); 286 } 287 tcp_reass_qsize++; 288 289 /* 290 * Find a segment which begins after this one does. 291 */ 292 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 293 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 294 break; 295 p = q; 296 } 297 298 /* 299 * If there is a preceding segment, it may provide some of 300 * our data already. If so, drop the data from the incoming 301 * segment. If it provides all of our data, drop us. 302 */ 303 if (p != NULL) { 304 int i; 305 /* conversion to int (in i) handles seq wraparound */ 306 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 307 if (i > 0) { 308 if (i >= *tlenp) { 309 tcpstat.tcps_rcvduppack++; 310 tcpstat.tcps_rcvdupbyte += *tlenp; 311 m_freem(m); 312 free(te, M_TSEGQ); 313 tcp_reass_qsize--; 314 /* 315 * Try to present any queued data 316 * at the left window edge to the user. 317 * This is needed after the 3-WHS 318 * completes. 319 */ 320 goto present; /* ??? */ 321 } 322 m_adj(m, i); 323 *tlenp -= i; 324 th->th_seq += i; 325 } 326 } 327 tcpstat.tcps_rcvoopack++; 328 tcpstat.tcps_rcvoobyte += *tlenp; 329 330 /* 331 * While we overlap succeeding segments trim them or, 332 * if they are completely covered, dequeue them. 333 */ 334 while (q) { 335 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 336 if (i <= 0) 337 break; 338 if (i < q->tqe_len) { 339 q->tqe_th->th_seq += i; 340 q->tqe_len -= i; 341 m_adj(q->tqe_m, i); 342 break; 343 } 344 345 nq = LIST_NEXT(q, tqe_q); 346 LIST_REMOVE(q, tqe_q); 347 m_freem(q->tqe_m); 348 free(q, M_TSEGQ); 349 tcp_reass_qsize--; 350 q = nq; 351 } 352 353 /* Insert the new segment queue entry into place. */ 354 te->tqe_m = m; 355 te->tqe_th = th; 356 te->tqe_len = *tlenp; 357 358 if (p == NULL) { 359 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 360 } else { 361 LIST_INSERT_AFTER(p, te, tqe_q); 362 } 363 364 present: 365 /* 366 * Present data to user, advancing rcv_nxt through 367 * completed sequence space. 368 */ 369 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 370 return (0); 371 q = LIST_FIRST(&tp->t_segq); 372 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 373 return (0); 374 do { 375 tp->rcv_nxt += q->tqe_len; 376 flags = q->tqe_th->th_flags & TH_FIN; 377 nq = LIST_NEXT(q, tqe_q); 378 LIST_REMOVE(q, tqe_q); 379 if (so->so_state & SS_CANTRCVMORE) 380 m_freem(q->tqe_m); 381 else 382 sbappend(&so->so_rcv, q->tqe_m); 383 free(q, M_TSEGQ); 384 tcp_reass_qsize--; 385 q = nq; 386 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 387 ND6_HINT(tp); 388 sorwakeup(so); 389 return (flags); 390 } 391 392 /* 393 * TCP input routine, follows pages 65-76 of the 394 * protocol specification dated September, 1981 very closely. 395 */ 396 #ifdef INET6 397 int 398 tcp6_input(mp, offp, proto) 399 struct mbuf **mp; 400 int *offp, proto; 401 { 402 struct mbuf *m = *mp; 403 struct in6_ifaddr *ia6; 404 405 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 406 407 /* 408 * draft-itojun-ipv6-tcp-to-anycast 409 * better place to put this in? 410 */ 411 ia6 = ip6_getdstifaddr(m); 412 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 413 struct ip6_hdr *ip6; 414 415 ip6 = mtod(m, struct ip6_hdr *); 416 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 417 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 418 return (IPPROTO_DONE); 419 } 420 421 tcp_input(m, *offp, proto); 422 return (IPPROTO_DONE); 423 } 424 #endif 425 426 void 427 tcp_input(struct mbuf *m, ...) 428 { 429 __va_list ap; 430 int off0, proto; 431 struct tcphdr *th; 432 struct ip *ip = NULL; 433 struct ipovly *ipov; 434 struct inpcb *inp = NULL; 435 u_char *optp = NULL; 436 int optlen = 0; 437 int len, tlen, off; 438 int drop_hdrlen; 439 struct tcpcb *tp = NULL; 440 int thflags; 441 struct socket *so = 0; 442 int todrop, acked, ourfinisacked, needoutput = 0; 443 u_long tiwin; 444 struct tcpopt to; /* options in this segment */ 445 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 446 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 447 struct sockaddr_in *next_hop = NULL; 448 int rstreason; /* For badport_bandlim accounting purposes */ 449 int cpu; 450 struct ip6_hdr *ip6 = NULL; 451 #ifdef INET6 452 boolean_t isipv6; 453 #else 454 const boolean_t isipv6 = FALSE; 455 #endif 456 #ifdef TCPDEBUG 457 short ostate = 0; 458 #endif 459 460 __va_start(ap, m); 461 off0 = __va_arg(ap, int); 462 proto = __va_arg(ap, int); 463 __va_end(ap); 464 465 tcpstat.tcps_rcvtotal++; 466 467 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */ 468 while (m->m_type == MT_TAG) { 469 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 470 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 471 m = m->m_next; 472 } 473 474 #ifdef INET6 475 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 476 #endif 477 478 if (isipv6) { 479 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 480 ip6 = mtod(m, struct ip6_hdr *); 481 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 482 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 483 tcpstat.tcps_rcvbadsum++; 484 goto drop; 485 } 486 th = (struct tcphdr *)((caddr_t)ip6 + off0); 487 488 /* 489 * Be proactive about unspecified IPv6 address in source. 490 * As we use all-zero to indicate unbounded/unconnected pcb, 491 * unspecified IPv6 address can be used to confuse us. 492 * 493 * Note that packets with unspecified IPv6 destination is 494 * already dropped in ip6_input. 495 */ 496 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 497 /* XXX stat */ 498 goto drop; 499 } 500 } else { 501 /* 502 * Get IP and TCP header together in first mbuf. 503 * Note: IP leaves IP header in first mbuf. 504 */ 505 if (off0 > sizeof(struct ip)) { 506 ip_stripoptions(m); 507 off0 = sizeof(struct ip); 508 } 509 /* already checked and pulled up in ip_demux() */ 510 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 511 ("TCP header not in one mbuf")); 512 ip = mtod(m, struct ip *); 513 ipov = (struct ipovly *)ip; 514 th = (struct tcphdr *)((caddr_t)ip + off0); 515 tlen = ip->ip_len; 516 517 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 518 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 519 th->th_sum = m->m_pkthdr.csum_data; 520 else 521 th->th_sum = in_pseudo(ip->ip_src.s_addr, 522 ip->ip_dst.s_addr, 523 htonl(m->m_pkthdr.csum_data + 524 ip->ip_len + 525 IPPROTO_TCP)); 526 th->th_sum ^= 0xffff; 527 } else { 528 /* 529 * Checksum extended TCP header and data. 530 */ 531 len = sizeof(struct ip) + tlen; 532 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 533 ipov->ih_len = (u_short)tlen; 534 ipov->ih_len = htons(ipov->ih_len); 535 th->th_sum = in_cksum(m, len); 536 } 537 if (th->th_sum) { 538 tcpstat.tcps_rcvbadsum++; 539 goto drop; 540 } 541 #ifdef INET6 542 /* Re-initialization for later version check */ 543 ip->ip_v = IPVERSION; 544 #endif 545 } 546 547 /* 548 * Check that TCP offset makes sense, 549 * pull out TCP options and adjust length. XXX 550 */ 551 off = th->th_off << 2; 552 /* already checked and pulled up in ip_demux() */ 553 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 554 ("bad TCP data offset")); 555 tlen -= off; /* tlen is used instead of ti->ti_len */ 556 if (off > sizeof(struct tcphdr)) { 557 if (isipv6) { 558 IP6_EXTHDR_CHECK(m, off0, off, ); 559 ip6 = mtod(m, struct ip6_hdr *); 560 th = (struct tcphdr *)((caddr_t)ip6 + off0); 561 } else { 562 /* already pulled up in ip_demux() */ 563 KASSERT(m->m_len >= sizeof(struct ip) + off, 564 ("TCP header and options not in one mbuf")); 565 } 566 optlen = off - sizeof(struct tcphdr); 567 optp = (u_char *)(th + 1); 568 } 569 thflags = th->th_flags; 570 571 #ifdef TCP_DROP_SYNFIN 572 /* 573 * If the drop_synfin option is enabled, drop all packets with 574 * both the SYN and FIN bits set. This prevents e.g. nmap from 575 * identifying the TCP/IP stack. 576 * 577 * This is a violation of the TCP specification. 578 */ 579 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 580 goto drop; 581 #endif 582 583 /* 584 * Convert TCP protocol specific fields to host format. 585 */ 586 th->th_seq = ntohl(th->th_seq); 587 th->th_ack = ntohl(th->th_ack); 588 th->th_win = ntohs(th->th_win); 589 th->th_urp = ntohs(th->th_urp); 590 591 /* 592 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 593 * until after ip6_savecontrol() is called and before other functions 594 * which don't want those proto headers. 595 * Because ip6_savecontrol() is going to parse the mbuf to 596 * search for data to be passed up to user-land, it wants mbuf 597 * parameters to be unchanged. 598 * XXX: the call of ip6_savecontrol() has been obsoleted based on 599 * latest version of the advanced API (20020110). 600 */ 601 drop_hdrlen = off0 + off; 602 603 /* 604 * Locate pcb for segment. 605 */ 606 findpcb: 607 /* IPFIREWALL_FORWARD section */ 608 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 609 /* 610 * Transparently forwarded. Pretend to be the destination. 611 * already got one like this? 612 */ 613 cpu = mycpu->gd_cpuid; 614 inp = in_pcblookup_hash(&tcbinfo[cpu], 615 ip->ip_src, th->th_sport, 616 ip->ip_dst, th->th_dport, 617 0, m->m_pkthdr.rcvif); 618 if (!inp) { 619 /* 620 * It's new. Try to find the ambushing socket. 621 */ 622 623 /* 624 * The rest of the ipfw code stores the port in 625 * host order. XXX 626 * (The IP address is still in network order.) 627 */ 628 in_port_t dport = next_hop->sin_port ? 629 htons(next_hop->sin_port) : 630 th->th_dport; 631 632 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 633 next_hop->sin_addr.s_addr, dport); 634 inp = in_pcblookup_hash(&tcbinfo[cpu], 635 ip->ip_src, th->th_sport, 636 next_hop->sin_addr, dport, 637 1, m->m_pkthdr.rcvif); 638 } 639 } else { 640 if (isipv6) { 641 inp = in6_pcblookup_hash(&tcbinfo[0], 642 &ip6->ip6_src, th->th_sport, 643 &ip6->ip6_dst, th->th_dport, 644 1, m->m_pkthdr.rcvif); 645 } else { 646 cpu = mycpu->gd_cpuid; 647 inp = in_pcblookup_hash(&tcbinfo[cpu], 648 ip->ip_src, th->th_sport, 649 ip->ip_dst, th->th_dport, 650 1, m->m_pkthdr.rcvif); 651 } 652 } 653 654 #ifdef IPSEC 655 if (isipv6) { 656 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 657 ipsec6stat.in_polvio++; 658 goto drop; 659 } 660 } else { 661 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 662 ipsecstat.in_polvio++; 663 goto drop; 664 } 665 } 666 #endif 667 #ifdef FAST_IPSEC 668 if (isipv6) { 669 if (inp != NULL && ipsec6_in_reject(m, inp)) { 670 goto drop; 671 } 672 } else { 673 if (inp != NULL && ipsec4_in_reject(m, inp)) { 674 goto drop; 675 } 676 } 677 #endif 678 679 /* 680 * If the state is CLOSED (i.e., TCB does not exist) then 681 * all data in the incoming segment is discarded. 682 * If the TCB exists but is in CLOSED state, it is embryonic, 683 * but should either do a listen or a connect soon. 684 */ 685 if (inp == NULL) { 686 if (log_in_vain) { 687 #ifdef INET6 688 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 689 #else 690 char dbuf[4 * sizeof "123"], sbuf[4 * sizeof "123"]; 691 #endif 692 if (isipv6) { 693 strcpy(dbuf, "["); 694 strcpy(sbuf, "["); 695 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 696 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 697 strcat(dbuf, "]"); 698 strcat(sbuf, "]"); 699 } else { 700 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 701 strcpy(sbuf, inet_ntoa(ip->ip_src)); 702 } 703 switch (log_in_vain) { 704 case 1: 705 if ((thflags & TH_SYN) == 0) 706 break; 707 case 2: 708 log(LOG_INFO, 709 "Connection attempt to TCP %s:%d " 710 "from %s:%d flags:0x%02x\n", 711 dbuf, ntohs(th->th_dport), sbuf, 712 ntohs(th->th_sport), thflags); 713 break; 714 default: 715 break; 716 } 717 } 718 if (blackhole) { 719 switch (blackhole) { 720 case 1: 721 if (thflags & TH_SYN) 722 goto drop; 723 break; 724 case 2: 725 goto drop; 726 default: 727 goto drop; 728 } 729 } 730 rstreason = BANDLIM_RST_CLOSEDPORT; 731 goto dropwithreset; 732 } 733 tp = intotcpcb(inp); 734 if (tp == NULL) { 735 rstreason = BANDLIM_RST_CLOSEDPORT; 736 goto dropwithreset; 737 } 738 if (tp->t_state == TCPS_CLOSED) 739 goto drop; 740 741 /* Unscale the window into a 32-bit value. */ 742 if ((thflags & TH_SYN) == 0) 743 tiwin = th->th_win << tp->snd_scale; 744 else 745 tiwin = th->th_win; 746 747 so = inp->inp_socket; 748 749 #ifdef TCPDEBUG 750 if (so->so_options & SO_DEBUG) { 751 ostate = tp->t_state; 752 if (isipv6) 753 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 754 else 755 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 756 tcp_savetcp = *th; 757 } 758 #endif 759 760 bzero((char *)&to, sizeof(to)); 761 762 if (so->so_options & SO_ACCEPTCONN) { 763 struct in_conninfo inc; 764 765 #ifdef INET6 766 inc.inc_isipv6 = (isipv6 == TRUE); 767 #endif 768 if (isipv6) { 769 inc.inc6_faddr = ip6->ip6_src; 770 inc.inc6_laddr = ip6->ip6_dst; 771 inc.inc6_route.ro_rt = NULL; /* XXX */ 772 } else { 773 inc.inc_faddr = ip->ip_src; 774 inc.inc_laddr = ip->ip_dst; 775 inc.inc_route.ro_rt = NULL; /* XXX */ 776 } 777 inc.inc_fport = th->th_sport; 778 inc.inc_lport = th->th_dport; 779 780 /* 781 * If the state is LISTEN then ignore segment if it contains 782 * a RST. If the segment contains an ACK then it is bad and 783 * send a RST. If it does not contain a SYN then it is not 784 * interesting; drop it. 785 * 786 * If the state is SYN_RECEIVED (syncache) and seg contains 787 * an ACK, but not for our SYN/ACK, send a RST. If the seg 788 * contains a RST, check the sequence number to see if it 789 * is a valid reset segment. 790 */ 791 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 792 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 793 if (!syncache_expand(&inc, th, &so, m)) { 794 /* 795 * No syncache entry, or ACK was not 796 * for our SYN/ACK. Send a RST. 797 */ 798 tcpstat.tcps_badsyn++; 799 rstreason = BANDLIM_RST_OPENPORT; 800 goto dropwithreset; 801 } 802 if (so == NULL) 803 /* 804 * Could not complete 3-way handshake, 805 * connection is being closed down, and 806 * syncache will free mbuf. 807 */ 808 return; 809 /* 810 * Socket is created in state SYN_RECEIVED. 811 * Continue processing segment. 812 */ 813 inp = sotoinpcb(so); 814 tp = intotcpcb(inp); 815 /* 816 * This is what would have happened in 817 * tcp_output() when the SYN,ACK was sent. 818 */ 819 tp->snd_up = tp->snd_una; 820 tp->snd_max = tp->snd_nxt = tp->iss + 1; 821 tp->last_ack_sent = tp->rcv_nxt; 822 /* 823 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 824 * until the _second_ ACK is received: 825 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 826 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 827 * move to ESTAB, set snd_wnd to tiwin. 828 */ 829 tp->snd_wnd = tiwin; /* unscaled */ 830 goto after_listen; 831 } 832 if (thflags & TH_RST) { 833 syncache_chkrst(&inc, th); 834 goto drop; 835 } 836 if (thflags & TH_ACK) { 837 syncache_badack(&inc); 838 tcpstat.tcps_badsyn++; 839 rstreason = BANDLIM_RST_OPENPORT; 840 goto dropwithreset; 841 } 842 goto drop; 843 } 844 845 /* 846 * Segment's flags are (SYN) or (SYN|FIN). 847 */ 848 #ifdef INET6 849 /* 850 * If deprecated address is forbidden, 851 * we do not accept SYN to deprecated interface 852 * address to prevent any new inbound connection from 853 * getting established. 854 * When we do not accept SYN, we send a TCP RST, 855 * with deprecated source address (instead of dropping 856 * it). We compromise it as it is much better for peer 857 * to send a RST, and RST will be the final packet 858 * for the exchange. 859 * 860 * If we do not forbid deprecated addresses, we accept 861 * the SYN packet. RFC2462 does not suggest dropping 862 * SYN in this case. 863 * If we decipher RFC2462 5.5.4, it says like this: 864 * 1. use of deprecated addr with existing 865 * communication is okay - "SHOULD continue to be 866 * used" 867 * 2. use of it with new communication: 868 * (2a) "SHOULD NOT be used if alternate address 869 * with sufficient scope is available" 870 * (2b) nothing mentioned otherwise. 871 * Here we fall into (2b) case as we have no choice in 872 * our source address selection - we must obey the peer. 873 * 874 * The wording in RFC2462 is confusing, and there are 875 * multiple description text for deprecated address 876 * handling - worse, they are not exactly the same. 877 * I believe 5.5.4 is the best one, so we follow 5.5.4. 878 */ 879 if (isipv6 && !ip6_use_deprecated) { 880 struct in6_ifaddr *ia6; 881 882 if ((ia6 = ip6_getdstifaddr(m)) && 883 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 884 tp = NULL; 885 rstreason = BANDLIM_RST_OPENPORT; 886 goto dropwithreset; 887 } 888 } 889 #endif 890 /* 891 * If it is from this socket, drop it, it must be forged. 892 * Don't bother responding if the destination was a broadcast. 893 */ 894 if (th->th_dport == th->th_sport) { 895 if (isipv6) { 896 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 897 &ip6->ip6_src)) 898 goto drop; 899 } else { 900 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 901 goto drop; 902 } 903 } 904 /* 905 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 906 * 907 * Note that it is quite possible to receive unicast 908 * link-layer packets with a broadcast IP address. Use 909 * in_broadcast() to find them. 910 */ 911 if (m->m_flags & (M_BCAST|M_MCAST)) 912 goto drop; 913 if (isipv6) { 914 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 915 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 916 goto drop; 917 } else { 918 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 919 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 920 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 921 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 922 goto drop; 923 } 924 /* 925 * SYN appears to be valid; create compressed TCP state 926 * for syncache, or perform t/tcp connection. 927 */ 928 if (so->so_qlen <= so->so_qlimit) { 929 tcp_dooptions(&to, optp, optlen, 1); 930 if (!syncache_add(&inc, &to, th, &so, m)) 931 goto drop; 932 if (so == NULL) 933 /* 934 * Entry added to syncache, mbuf used to 935 * send SYN,ACK packet. 936 */ 937 return; 938 /* 939 * Segment passed TAO tests. 940 */ 941 inp = sotoinpcb(so); 942 tp = intotcpcb(inp); 943 tp->snd_wnd = tiwin; 944 tp->t_starttime = ticks; 945 tp->t_state = TCPS_ESTABLISHED; 946 947 /* 948 * If there is a FIN, or if there is data and the 949 * connection is local, then delay SYN,ACK(SYN) in 950 * the hope of piggy-backing it on a response 951 * segment. Otherwise must send ACK now in case 952 * the other side is slow starting. 953 */ 954 if (DELAY_ACK(tp) && 955 ((thflags & TH_FIN) || 956 (tlen != 0 && 957 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 958 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 959 callout_reset(tp->tt_delack, tcp_delacktime, 960 tcp_timer_delack, tp); 961 tp->t_flags |= TF_NEEDSYN; 962 } else 963 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 964 965 tcpstat.tcps_connects++; 966 soisconnected(so); 967 goto trimthenstep6; 968 } 969 goto drop; 970 } 971 after_listen: 972 973 /* XXX temp debugging */ 974 /* should not happen - syncache should pick up these connections */ 975 if (tp->t_state == TCPS_LISTEN) 976 panic("tcp_input: TCPS_LISTEN"); 977 978 /* 979 * Segment received on connection. 980 * Reset idle time and keep-alive timer. 981 */ 982 tp->t_rcvtime = ticks; 983 if (TCPS_HAVEESTABLISHED(tp->t_state)) 984 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 985 986 /* 987 * Process options. 988 * XXX this is tradtitional behavior, may need to be cleaned up. 989 */ 990 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 991 if (thflags & TH_SYN) { 992 if (to.to_flags & TOF_SCALE) { 993 tp->t_flags |= TF_RCVD_SCALE; 994 tp->requested_s_scale = to.to_requested_s_scale; 995 } 996 if (to.to_flags & TOF_TS) { 997 tp->t_flags |= TF_RCVD_TSTMP; 998 tp->ts_recent = to.to_tsval; 999 tp->ts_recent_age = ticks; 1000 } 1001 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 1002 tp->t_flags |= TF_RCVD_CC; 1003 if (to.to_flags & TOF_MSS) 1004 tcp_mss(tp, to.to_mss); 1005 } 1006 1007 /* 1008 * Header prediction: check for the two common cases 1009 * of a uni-directional data xfer. If the packet has 1010 * no control flags, is in-sequence, the window didn't 1011 * change and we're not retransmitting, it's a 1012 * candidate. If the length is zero and the ack moved 1013 * forward, we're the sender side of the xfer. Just 1014 * free the data acked & wake any higher level process 1015 * that was blocked waiting for space. If the length 1016 * is non-zero and the ack didn't move, we're the 1017 * receiver side. If we're getting packets in-order 1018 * (the reassembly queue is empty), add the data to 1019 * the socket buffer and note that we need a delayed ack. 1020 * Make sure that the hidden state-flags are also off. 1021 * Since we check for TCPS_ESTABLISHED above, it can only 1022 * be TH_NEEDSYN. 1023 */ 1024 if (tp->t_state == TCPS_ESTABLISHED && 1025 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1026 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1027 ((to.to_flags & TOF_TS) == 0 || 1028 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1029 /* 1030 * Using the CC option is compulsory if once started: 1031 * the segment is OK if no T/TCP was negotiated or 1032 * if the segment has a CC option equal to CCrecv 1033 */ 1034 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1035 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 1036 th->th_seq == tp->rcv_nxt && 1037 tiwin && tiwin == tp->snd_wnd && 1038 tp->snd_nxt == tp->snd_max) { 1039 1040 /* 1041 * If last ACK falls within this segment's sequence numbers, 1042 * record the timestamp. 1043 * NOTE that the test is modified according to the latest 1044 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1045 */ 1046 if ((to.to_flags & TOF_TS) != 0 && 1047 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1048 tp->ts_recent_age = ticks; 1049 tp->ts_recent = to.to_tsval; 1050 } 1051 1052 if (tlen == 0) { 1053 if (SEQ_GT(th->th_ack, tp->snd_una) && 1054 SEQ_LEQ(th->th_ack, tp->snd_max) && 1055 tp->snd_cwnd >= tp->snd_wnd && 1056 ((!tcp_do_newreno && 1057 tp->t_dupacks < tcprexmtthresh) || 1058 (tcp_do_newreno && !IN_FASTRECOVERY(tp)))) { 1059 /* 1060 * this is a pure ack for outstanding data. 1061 */ 1062 ++tcpstat.tcps_predack; 1063 /* 1064 * "bad retransmit" recovery 1065 * 1066 * If Eifel detection applies, then 1067 * it is deterministic, so use it 1068 * unconditionally over the old heuristic. 1069 * Otherwise, fall back to the old heuristic. 1070 */ 1071 if (tcp_do_eifel_detect && 1072 (to.to_flags & TOF_TS) && to.to_tsecr && 1073 (tp->t_flags & TF_FIRSTACCACK)) { 1074 /* Eifel detection applicable. */ 1075 if (to.to_tsecr < tp->t_rexmtTS) { 1076 tcp_revert_congestion_state(tp); 1077 ++tcpstat.tcps_eifeldetected; 1078 } 1079 } else if (tp->t_rxtshift == 1 && 1080 ticks < tp->t_badrxtwin) { 1081 tcp_revert_congestion_state(tp); 1082 ++tcpstat.tcps_rttdetected; 1083 } 1084 tp->t_flags &= ~(TF_FIRSTACCACK | 1085 TF_FASTREXMT | TF_EARLYREXMT); 1086 /* 1087 * Recalculate the retransmit timer / rtt. 1088 * 1089 * Some machines (certain windows boxes) 1090 * send broken timestamp replies during the 1091 * SYN+ACK phase, ignore timestamps of 0. 1092 */ 1093 if ((to.to_flags & TOF_TS) != 0 && 1094 to.to_tsecr) { 1095 tcp_xmit_timer(tp, 1096 ticks - to.to_tsecr + 1); 1097 } else if (tp->t_rtttime && 1098 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1099 tcp_xmit_timer(tp, 1100 ticks - tp->t_rtttime); 1101 } 1102 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1103 acked = th->th_ack - tp->snd_una; 1104 tcpstat.tcps_rcvackpack++; 1105 tcpstat.tcps_rcvackbyte += acked; 1106 sbdrop(&so->so_snd, acked); 1107 tp->snd_recover = th->th_ack - 1; 1108 tp->snd_una = th->th_ack; 1109 tp->t_dupacks = 0; 1110 m_freem(m); 1111 ND6_HINT(tp); /* some progress has been done */ 1112 1113 /* 1114 * If all outstanding data are acked, stop 1115 * retransmit timer, otherwise restart timer 1116 * using current (possibly backed-off) value. 1117 * If process is waiting for space, 1118 * wakeup/selwakeup/signal. If data 1119 * are ready to send, let tcp_output 1120 * decide between more output or persist. 1121 */ 1122 if (tp->snd_una == tp->snd_max) 1123 callout_stop(tp->tt_rexmt); 1124 else if (!callout_active(tp->tt_persist)) 1125 callout_reset(tp->tt_rexmt, 1126 tp->t_rxtcur, 1127 tcp_timer_rexmt, tp); 1128 1129 sowwakeup(so); 1130 if (so->so_snd.sb_cc) 1131 (void) tcp_output(tp); 1132 return; 1133 } 1134 } else if (th->th_ack == tp->snd_una && 1135 LIST_EMPTY(&tp->t_segq) && 1136 tlen <= sbspace(&so->so_rcv)) { 1137 /* 1138 * this is a pure, in-sequence data packet 1139 * with nothing on the reassembly queue and 1140 * we have enough buffer space to take it. 1141 */ 1142 ++tcpstat.tcps_preddat; 1143 tp->rcv_nxt += tlen; 1144 tcpstat.tcps_rcvpack++; 1145 tcpstat.tcps_rcvbyte += tlen; 1146 ND6_HINT(tp); /* some progress has been done */ 1147 /* 1148 * Add data to socket buffer. 1149 */ 1150 if (so->so_state & SS_CANTRCVMORE) { 1151 m_freem(m); 1152 } else { 1153 m_adj(m, drop_hdrlen); /* delayed header drop */ 1154 sbappend(&so->so_rcv, m); 1155 } 1156 sorwakeup(so); 1157 if (DELAY_ACK(tp)) { 1158 callout_reset(tp->tt_delack, tcp_delacktime, 1159 tcp_timer_delack, tp); 1160 } else { 1161 tp->t_flags |= TF_ACKNOW; 1162 tcp_output(tp); 1163 } 1164 return; 1165 } 1166 } 1167 1168 /* 1169 * Calculate amount of space in receive window, 1170 * and then do TCP input processing. 1171 * Receive window is amount of space in rcv queue, 1172 * but not less than advertised window. 1173 */ 1174 { int win; 1175 1176 win = sbspace(&so->so_rcv); 1177 if (win < 0) 1178 win = 0; 1179 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1180 } 1181 1182 switch (tp->t_state) { 1183 1184 /* 1185 * If the state is SYN_RECEIVED: 1186 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1187 */ 1188 case TCPS_SYN_RECEIVED: 1189 if ((thflags & TH_ACK) && 1190 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1191 SEQ_GT(th->th_ack, tp->snd_max))) { 1192 rstreason = BANDLIM_RST_OPENPORT; 1193 goto dropwithreset; 1194 } 1195 break; 1196 1197 /* 1198 * If the state is SYN_SENT: 1199 * if seg contains an ACK, but not for our SYN, drop the input. 1200 * if seg contains a RST, then drop the connection. 1201 * if seg does not contain SYN, then drop it. 1202 * Otherwise this is an acceptable SYN segment 1203 * initialize tp->rcv_nxt and tp->irs 1204 * if seg contains ack then advance tp->snd_una 1205 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1206 * arrange for segment to be acked (eventually) 1207 * continue processing rest of data/controls, beginning with URG 1208 */ 1209 case TCPS_SYN_SENT: 1210 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1211 taop = &tao_noncached; 1212 bzero(taop, sizeof(*taop)); 1213 } 1214 1215 if ((thflags & TH_ACK) && 1216 (SEQ_LEQ(th->th_ack, tp->iss) || 1217 SEQ_GT(th->th_ack, tp->snd_max))) { 1218 /* 1219 * If we have a cached CCsent for the remote host, 1220 * hence we haven't just crashed and restarted, 1221 * do not send a RST. This may be a retransmission 1222 * from the other side after our earlier ACK was lost. 1223 * Our new SYN, when it arrives, will serve as the 1224 * needed ACK. 1225 */ 1226 if (taop->tao_ccsent != 0) 1227 goto drop; 1228 else { 1229 rstreason = BANDLIM_UNLIMITED; 1230 goto dropwithreset; 1231 } 1232 } 1233 if (thflags & TH_RST) { 1234 if (thflags & TH_ACK) 1235 tp = tcp_drop(tp, ECONNREFUSED); 1236 goto drop; 1237 } 1238 if ((thflags & TH_SYN) == 0) 1239 goto drop; 1240 tp->snd_wnd = th->th_win; /* initial send window */ 1241 tp->cc_recv = to.to_cc; /* foreign CC */ 1242 1243 tp->irs = th->th_seq; 1244 tcp_rcvseqinit(tp); 1245 if (thflags & TH_ACK) { 1246 /* 1247 * Our SYN was acked. If segment contains CC.ECHO 1248 * option, check it to make sure this segment really 1249 * matches our SYN. If not, just drop it as old 1250 * duplicate, but send an RST if we're still playing 1251 * by the old rules. If no CC.ECHO option, make sure 1252 * we don't get fooled into using T/TCP. 1253 */ 1254 if (to.to_flags & TOF_CCECHO) { 1255 if (tp->cc_send != to.to_ccecho) { 1256 if (taop->tao_ccsent != 0) 1257 goto drop; 1258 else { 1259 rstreason = BANDLIM_UNLIMITED; 1260 goto dropwithreset; 1261 } 1262 } 1263 } else 1264 tp->t_flags &= ~TF_RCVD_CC; 1265 tcpstat.tcps_connects++; 1266 soisconnected(so); 1267 /* Do window scaling on this connection? */ 1268 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1269 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1270 tp->snd_scale = tp->requested_s_scale; 1271 tp->rcv_scale = tp->request_r_scale; 1272 } 1273 /* Segment is acceptable, update cache if undefined. */ 1274 if (taop->tao_ccsent == 0) 1275 taop->tao_ccsent = to.to_ccecho; 1276 1277 tp->rcv_adv += tp->rcv_wnd; 1278 tp->snd_una++; /* SYN is acked */ 1279 /* 1280 * If there's data, delay ACK; if there's also a FIN 1281 * ACKNOW will be turned on later. 1282 */ 1283 if (DELAY_ACK(tp) && tlen != 0) 1284 callout_reset(tp->tt_delack, tcp_delacktime, 1285 tcp_timer_delack, tp); 1286 else 1287 tp->t_flags |= TF_ACKNOW; 1288 /* 1289 * Received <SYN,ACK> in SYN_SENT[*] state. 1290 * Transitions: 1291 * SYN_SENT --> ESTABLISHED 1292 * SYN_SENT* --> FIN_WAIT_1 1293 */ 1294 tp->t_starttime = ticks; 1295 if (tp->t_flags & TF_NEEDFIN) { 1296 tp->t_state = TCPS_FIN_WAIT_1; 1297 tp->t_flags &= ~TF_NEEDFIN; 1298 thflags &= ~TH_SYN; 1299 } else { 1300 tp->t_state = TCPS_ESTABLISHED; 1301 callout_reset(tp->tt_keep, tcp_keepidle, 1302 tcp_timer_keep, tp); 1303 } 1304 } else { 1305 /* 1306 * Received initial SYN in SYN-SENT[*] state => 1307 * simultaneous open. If segment contains CC option 1308 * and there is a cached CC, apply TAO test. 1309 * If it succeeds, connection is * half-synchronized. 1310 * Otherwise, do 3-way handshake: 1311 * SYN-SENT -> SYN-RECEIVED 1312 * SYN-SENT* -> SYN-RECEIVED* 1313 * If there was no CC option, clear cached CC value. 1314 */ 1315 tp->t_flags |= TF_ACKNOW; 1316 callout_stop(tp->tt_rexmt); 1317 if (to.to_flags & TOF_CC) { 1318 if (taop->tao_cc != 0 && 1319 CC_GT(to.to_cc, taop->tao_cc)) { 1320 /* 1321 * update cache and make transition: 1322 * SYN-SENT -> ESTABLISHED* 1323 * SYN-SENT* -> FIN-WAIT-1* 1324 */ 1325 taop->tao_cc = to.to_cc; 1326 tp->t_starttime = ticks; 1327 if (tp->t_flags & TF_NEEDFIN) { 1328 tp->t_state = TCPS_FIN_WAIT_1; 1329 tp->t_flags &= ~TF_NEEDFIN; 1330 } else { 1331 tp->t_state = TCPS_ESTABLISHED; 1332 callout_reset(tp->tt_keep, 1333 tcp_keepidle, 1334 tcp_timer_keep, 1335 tp); 1336 } 1337 tp->t_flags |= TF_NEEDSYN; 1338 } else 1339 tp->t_state = TCPS_SYN_RECEIVED; 1340 } else { 1341 /* CC.NEW or no option => invalidate cache */ 1342 taop->tao_cc = 0; 1343 tp->t_state = TCPS_SYN_RECEIVED; 1344 } 1345 } 1346 1347 trimthenstep6: 1348 /* 1349 * Advance th->th_seq to correspond to first data byte. 1350 * If data, trim to stay within window, 1351 * dropping FIN if necessary. 1352 */ 1353 th->th_seq++; 1354 if (tlen > tp->rcv_wnd) { 1355 todrop = tlen - tp->rcv_wnd; 1356 m_adj(m, -todrop); 1357 tlen = tp->rcv_wnd; 1358 thflags &= ~TH_FIN; 1359 tcpstat.tcps_rcvpackafterwin++; 1360 tcpstat.tcps_rcvbyteafterwin += todrop; 1361 } 1362 tp->snd_wl1 = th->th_seq - 1; 1363 tp->rcv_up = th->th_seq; 1364 /* 1365 * Client side of transaction: already sent SYN and data. 1366 * If the remote host used T/TCP to validate the SYN, 1367 * our data will be ACK'd; if so, enter normal data segment 1368 * processing in the middle of step 5, ack processing. 1369 * Otherwise, goto step 6. 1370 */ 1371 if (thflags & TH_ACK) 1372 goto process_ACK; 1373 1374 goto step6; 1375 1376 /* 1377 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1378 * if segment contains a SYN and CC [not CC.NEW] option: 1379 * if state == TIME_WAIT and connection duration > MSL, 1380 * drop packet and send RST; 1381 * 1382 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1383 * ack the FIN (and data) in retransmission queue. 1384 * Complete close and delete TCPCB. Then reprocess 1385 * segment, hoping to find new TCPCB in LISTEN state; 1386 * 1387 * else must be old SYN; drop it. 1388 * else do normal processing. 1389 */ 1390 case TCPS_LAST_ACK: 1391 case TCPS_CLOSING: 1392 case TCPS_TIME_WAIT: 1393 if ((thflags & TH_SYN) && 1394 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1395 if (tp->t_state == TCPS_TIME_WAIT && 1396 (ticks - tp->t_starttime) > tcp_msl) { 1397 rstreason = BANDLIM_UNLIMITED; 1398 goto dropwithreset; 1399 } 1400 if (CC_GT(to.to_cc, tp->cc_recv)) { 1401 tp = tcp_close(tp); 1402 goto findpcb; 1403 } 1404 else 1405 goto drop; 1406 } 1407 break; /* continue normal processing */ 1408 } 1409 1410 /* 1411 * States other than LISTEN or SYN_SENT. 1412 * First check the RST flag and sequence number since reset segments 1413 * are exempt from the timestamp and connection count tests. This 1414 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1415 * below which allowed reset segments in half the sequence space 1416 * to fall though and be processed (which gives forged reset 1417 * segments with a random sequence number a 50 percent chance of 1418 * killing a connection). 1419 * Then check timestamp, if present. 1420 * Then check the connection count, if present. 1421 * Then check that at least some bytes of segment are within 1422 * receive window. If segment begins before rcv_nxt, 1423 * drop leading data (and SYN); if nothing left, just ack. 1424 * 1425 * 1426 * If the RST bit is set, check the sequence number to see 1427 * if this is a valid reset segment. 1428 * RFC 793 page 37: 1429 * In all states except SYN-SENT, all reset (RST) segments 1430 * are validated by checking their SEQ-fields. A reset is 1431 * valid if its sequence number is in the window. 1432 * Note: this does not take into account delayed ACKs, so 1433 * we should test against last_ack_sent instead of rcv_nxt. 1434 * The sequence number in the reset segment is normally an 1435 * echo of our outgoing acknowlegement numbers, but some hosts 1436 * send a reset with the sequence number at the rightmost edge 1437 * of our receive window, and we have to handle this case. 1438 * If we have multiple segments in flight, the intial reset 1439 * segment sequence numbers will be to the left of last_ack_sent, 1440 * but they will eventually catch up. 1441 * In any case, it never made sense to trim reset segments to 1442 * fit the receive window since RFC 1122 says: 1443 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1444 * 1445 * A TCP SHOULD allow a received RST segment to include data. 1446 * 1447 * DISCUSSION 1448 * It has been suggested that a RST segment could contain 1449 * ASCII text that encoded and explained the cause of the 1450 * RST. No standard has yet been established for such 1451 * data. 1452 * 1453 * If the reset segment passes the sequence number test examine 1454 * the state: 1455 * SYN_RECEIVED STATE: 1456 * If passive open, return to LISTEN state. 1457 * If active open, inform user that connection was refused. 1458 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1459 * Inform user that connection was reset, and close tcb. 1460 * CLOSING, LAST_ACK STATES: 1461 * Close the tcb. 1462 * TIME_WAIT STATE: 1463 * Drop the segment - see Stevens, vol. 2, p. 964 and 1464 * RFC 1337. 1465 */ 1466 if (thflags & TH_RST) { 1467 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1468 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1469 switch (tp->t_state) { 1470 1471 case TCPS_SYN_RECEIVED: 1472 so->so_error = ECONNREFUSED; 1473 goto close; 1474 1475 case TCPS_ESTABLISHED: 1476 case TCPS_FIN_WAIT_1: 1477 case TCPS_FIN_WAIT_2: 1478 case TCPS_CLOSE_WAIT: 1479 so->so_error = ECONNRESET; 1480 close: 1481 tp->t_state = TCPS_CLOSED; 1482 tcpstat.tcps_drops++; 1483 tp = tcp_close(tp); 1484 break; 1485 1486 case TCPS_CLOSING: 1487 case TCPS_LAST_ACK: 1488 tp = tcp_close(tp); 1489 break; 1490 1491 case TCPS_TIME_WAIT: 1492 break; 1493 } 1494 } 1495 goto drop; 1496 } 1497 1498 /* 1499 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1500 * and it's less than ts_recent, drop it. 1501 */ 1502 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1503 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1504 1505 /* Check to see if ts_recent is over 24 days old. */ 1506 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1507 /* 1508 * Invalidate ts_recent. If this segment updates 1509 * ts_recent, the age will be reset later and ts_recent 1510 * will get a valid value. If it does not, setting 1511 * ts_recent to zero will at least satisfy the 1512 * requirement that zero be placed in the timestamp 1513 * echo reply when ts_recent isn't valid. The 1514 * age isn't reset until we get a valid ts_recent 1515 * because we don't want out-of-order segments to be 1516 * dropped when ts_recent is old. 1517 */ 1518 tp->ts_recent = 0; 1519 } else { 1520 tcpstat.tcps_rcvduppack++; 1521 tcpstat.tcps_rcvdupbyte += tlen; 1522 tcpstat.tcps_pawsdrop++; 1523 if (tlen) 1524 goto dropafterack; 1525 goto drop; 1526 } 1527 } 1528 1529 /* 1530 * T/TCP mechanism 1531 * If T/TCP was negotiated and the segment doesn't have CC, 1532 * or if its CC is wrong then drop the segment. 1533 * RST segments do not have to comply with this. 1534 */ 1535 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1536 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1537 goto dropafterack; 1538 1539 /* 1540 * In the SYN-RECEIVED state, validate that the packet belongs to 1541 * this connection before trimming the data to fit the receive 1542 * window. Check the sequence number versus IRS since we know 1543 * the sequence numbers haven't wrapped. This is a partial fix 1544 * for the "LAND" DoS attack. 1545 */ 1546 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1547 rstreason = BANDLIM_RST_OPENPORT; 1548 goto dropwithreset; 1549 } 1550 1551 todrop = tp->rcv_nxt - th->th_seq; 1552 if (todrop > 0) { 1553 if (thflags & TH_SYN) { 1554 thflags &= ~TH_SYN; 1555 th->th_seq++; 1556 if (th->th_urp > 1) 1557 th->th_urp--; 1558 else 1559 thflags &= ~TH_URG; 1560 todrop--; 1561 } 1562 /* 1563 * Following if statement from Stevens, vol. 2, p. 960. 1564 */ 1565 if (todrop > tlen 1566 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1567 /* 1568 * Any valid FIN must be to the left of the window. 1569 * At this point the FIN must be a duplicate or out 1570 * of sequence; drop it. 1571 */ 1572 thflags &= ~TH_FIN; 1573 1574 /* 1575 * Send an ACK to resynchronize and drop any data. 1576 * But keep on processing for RST or ACK. 1577 */ 1578 tp->t_flags |= TF_ACKNOW; 1579 todrop = tlen; 1580 tcpstat.tcps_rcvduppack++; 1581 tcpstat.tcps_rcvdupbyte += todrop; 1582 } else { 1583 tcpstat.tcps_rcvpartduppack++; 1584 tcpstat.tcps_rcvpartdupbyte += todrop; 1585 } 1586 drop_hdrlen += todrop; /* drop from the top afterwards */ 1587 th->th_seq += todrop; 1588 tlen -= todrop; 1589 if (th->th_urp > todrop) 1590 th->th_urp -= todrop; 1591 else { 1592 thflags &= ~TH_URG; 1593 th->th_urp = 0; 1594 } 1595 } 1596 1597 /* 1598 * If new data are received on a connection after the 1599 * user processes are gone, then RST the other end. 1600 */ 1601 if ((so->so_state & SS_NOFDREF) && 1602 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1603 tp = tcp_close(tp); 1604 tcpstat.tcps_rcvafterclose++; 1605 rstreason = BANDLIM_UNLIMITED; 1606 goto dropwithreset; 1607 } 1608 1609 /* 1610 * If segment ends after window, drop trailing data 1611 * (and PUSH and FIN); if nothing left, just ACK. 1612 */ 1613 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1614 if (todrop > 0) { 1615 tcpstat.tcps_rcvpackafterwin++; 1616 if (todrop >= tlen) { 1617 tcpstat.tcps_rcvbyteafterwin += tlen; 1618 /* 1619 * If a new connection request is received 1620 * while in TIME_WAIT, drop the old connection 1621 * and start over if the sequence numbers 1622 * are above the previous ones. 1623 */ 1624 if (thflags & TH_SYN && 1625 tp->t_state == TCPS_TIME_WAIT && 1626 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1627 tp = tcp_close(tp); 1628 goto findpcb; 1629 } 1630 /* 1631 * If window is closed can only take segments at 1632 * window edge, and have to drop data and PUSH from 1633 * incoming segments. Continue processing, but 1634 * remember to ack. Otherwise, drop segment 1635 * and ack. 1636 */ 1637 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1638 tp->t_flags |= TF_ACKNOW; 1639 tcpstat.tcps_rcvwinprobe++; 1640 } else 1641 goto dropafterack; 1642 } else 1643 tcpstat.tcps_rcvbyteafterwin += todrop; 1644 m_adj(m, -todrop); 1645 tlen -= todrop; 1646 thflags &= ~(TH_PUSH|TH_FIN); 1647 } 1648 1649 /* 1650 * If last ACK falls within this segment's sequence numbers, 1651 * record its timestamp. 1652 * NOTE that the test is modified according to the latest 1653 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1654 */ 1655 if ((to.to_flags & TOF_TS) != 0 && 1656 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1657 tp->ts_recent_age = ticks; 1658 tp->ts_recent = to.to_tsval; 1659 } 1660 1661 /* 1662 * If a SYN is in the window, then this is an 1663 * error and we send an RST and drop the connection. 1664 */ 1665 if (thflags & TH_SYN) { 1666 tp = tcp_drop(tp, ECONNRESET); 1667 rstreason = BANDLIM_UNLIMITED; 1668 goto dropwithreset; 1669 } 1670 1671 /* 1672 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1673 * flag is on (half-synchronized state), then queue data for 1674 * later processing; else drop segment and return. 1675 */ 1676 if ((thflags & TH_ACK) == 0) { 1677 if (tp->t_state == TCPS_SYN_RECEIVED || 1678 (tp->t_flags & TF_NEEDSYN)) 1679 goto step6; 1680 else 1681 goto drop; 1682 } 1683 1684 /* 1685 * Ack processing. 1686 */ 1687 switch (tp->t_state) { 1688 1689 /* 1690 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1691 * ESTABLISHED state and continue processing. 1692 * The ACK was checked above. 1693 */ 1694 case TCPS_SYN_RECEIVED: 1695 1696 tcpstat.tcps_connects++; 1697 soisconnected(so); 1698 /* Do window scaling? */ 1699 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1700 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1701 tp->snd_scale = tp->requested_s_scale; 1702 tp->rcv_scale = tp->request_r_scale; 1703 } 1704 /* 1705 * Upon successful completion of 3-way handshake, 1706 * update cache.CC if it was undefined, pass any queued 1707 * data to the user, and advance state appropriately. 1708 */ 1709 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1710 taop->tao_cc == 0) 1711 taop->tao_cc = tp->cc_recv; 1712 1713 /* 1714 * Make transitions: 1715 * SYN-RECEIVED -> ESTABLISHED 1716 * SYN-RECEIVED* -> FIN-WAIT-1 1717 */ 1718 tp->t_starttime = ticks; 1719 if (tp->t_flags & TF_NEEDFIN) { 1720 tp->t_state = TCPS_FIN_WAIT_1; 1721 tp->t_flags &= ~TF_NEEDFIN; 1722 } else { 1723 tp->t_state = TCPS_ESTABLISHED; 1724 callout_reset(tp->tt_keep, tcp_keepidle, 1725 tcp_timer_keep, tp); 1726 } 1727 /* 1728 * If segment contains data or ACK, will call tcp_reass() 1729 * later; if not, do so now to pass queued data to user. 1730 */ 1731 if (tlen == 0 && (thflags & TH_FIN) == 0) 1732 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1733 (struct mbuf *)0); 1734 tp->snd_wl1 = th->th_seq - 1; 1735 /* fall into ... */ 1736 1737 /* 1738 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1739 * ACKs. If the ack is in the range 1740 * tp->snd_una < th->th_ack <= tp->snd_max 1741 * then advance tp->snd_una to th->th_ack and drop 1742 * data from the retransmission queue. If this ACK reflects 1743 * more up to date window information we update our window information. 1744 */ 1745 case TCPS_ESTABLISHED: 1746 case TCPS_FIN_WAIT_1: 1747 case TCPS_FIN_WAIT_2: 1748 case TCPS_CLOSE_WAIT: 1749 case TCPS_CLOSING: 1750 case TCPS_LAST_ACK: 1751 case TCPS_TIME_WAIT: 1752 1753 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1754 if (tlen == 0 && tiwin == tp->snd_wnd) { 1755 tcpstat.tcps_rcvdupack++; 1756 /* 1757 * If we have outstanding data (other than 1758 * a window probe), this is a completely 1759 * duplicate ack (ie, window info didn't 1760 * change), the ack is the biggest we've 1761 * seen and we've seen exactly our rexmt 1762 * threshhold of them, assume a packet 1763 * has been dropped and retransmit it. 1764 * Kludge snd_nxt & the congestion 1765 * window so we send only this one 1766 * packet. 1767 * 1768 * We know we're losing at the current 1769 * window size so do congestion avoidance 1770 * (set ssthresh to half the current window 1771 * and pull our congestion window back to 1772 * the new ssthresh). 1773 * 1774 * Dup acks mean that packets have left the 1775 * network (they're now cached at the receiver) 1776 * so bump cwnd by the amount in the receiver 1777 * to keep a constant cwnd packets in the 1778 * network. 1779 */ 1780 if (!callout_active(tp->tt_rexmt) || 1781 th->th_ack != tp->snd_una) 1782 tp->t_dupacks = 0; 1783 else if (++tp->t_dupacks > tcprexmtthresh || 1784 (tcp_do_newreno && 1785 IN_FASTRECOVERY(tp))) { 1786 tp->snd_cwnd += tp->t_maxseg; 1787 (void) tcp_output(tp); 1788 goto drop; 1789 } else if (tp->t_dupacks == tcprexmtthresh) { 1790 tcp_seq onxt; 1791 u_int win; 1792 1793 if (tcp_do_newreno && 1794 SEQ_LEQ(th->th_ack, 1795 tp->snd_recover)) { 1796 tp->t_dupacks = 0; 1797 break; 1798 } 1799 fastretransmit: 1800 if (tcp_do_eifel_detect && 1801 (tp->t_flags & TF_RCVD_TSTMP)) { 1802 tcp_save_congestion_state(tp); 1803 tp->t_flags |= TF_FASTREXMT; 1804 } 1805 win = min(tp->snd_wnd, tp->snd_cwnd) / 1806 2 / tp->t_maxseg; 1807 if (win < 2) 1808 win = 2; 1809 tp->snd_ssthresh = win * tp->t_maxseg; 1810 ENTER_FASTRECOVERY(tp); 1811 tp->snd_recover = tp->snd_max; 1812 callout_stop(tp->tt_rexmt); 1813 tp->t_rtttime = 0; 1814 onxt = tp->snd_nxt; 1815 tp->snd_nxt = th->th_ack; 1816 tp->snd_cwnd = tp->t_maxseg; 1817 (void) tcp_output(tp); 1818 ++tcpstat.tcps_sndfastrexmit; 1819 KASSERT(tp->snd_limited <= 2, 1820 ("tp->snd_limited too big")); 1821 tp->snd_cwnd = tp->snd_ssthresh + 1822 (tp->t_maxseg * 1823 (tp->t_dupacks - tp->snd_limited)); 1824 if (SEQ_GT(onxt, tp->snd_nxt)) 1825 tp->snd_nxt = onxt; 1826 goto drop; 1827 } else if (tcp_do_limitedtransmit) { 1828 u_long oldcwnd = tp->snd_cwnd; 1829 tcp_seq oldsndmax = tp->snd_max; 1830 /* outstanding data */ 1831 uint32_t ownd = 1832 tp->snd_max - tp->snd_una; 1833 u_int sent; 1834 1835 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1836 1837 KASSERT(tp->t_dupacks == 1 || 1838 tp->t_dupacks == 2, 1839 ("dupacks not 1 or 2")); 1840 if (tp->t_dupacks == 1) 1841 tp->snd_limited = 0; 1842 tp->snd_cwnd = ownd + 1843 (tp->t_dupacks - tp->snd_limited) * 1844 tp->t_maxseg; 1845 (void) tcp_output(tp); 1846 tp->snd_cwnd = oldcwnd; 1847 sent = tp->snd_max - oldsndmax; 1848 if (sent > tp->t_maxseg) { 1849 KASSERT((tp->t_dupacks == 2 && 1850 tp->snd_limited == 0) || 1851 (sent == tp->t_maxseg + 1 && 1852 tp->t_flags & TF_SENTFIN), 1853 ("sent too much")); 1854 KASSERT(sent <= 1855 tp->t_maxseg * 2, 1856 ("sent too many segments")); 1857 tp->snd_limited = 2; 1858 tcpstat.tcps_sndlimited += 2; 1859 } else if (sent > 0) { 1860 ++tp->snd_limited; 1861 ++tcpstat.tcps_sndlimited; 1862 } else if (tcp_do_early_retransmit && 1863 (tcp_do_eifel_detect && 1864 (tp->t_flags & TF_RCVD_TSTMP)) && 1865 tcp_do_newreno && 1866 tp->t_dupacks + 1 >= 1867 iceildiv(ownd, tp->t_maxseg)) { 1868 ++tcpstat.tcps_sndearlyrexmit; 1869 tp->t_flags |= TF_EARLYREXMT; 1870 goto fastretransmit; 1871 } 1872 goto drop; 1873 } 1874 } else 1875 tp->t_dupacks = 0; 1876 break; 1877 } 1878 1879 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1880 1881 /* 1882 * If the congestion window was inflated to account 1883 * for the other side's cached packets, retract it. 1884 */ 1885 if (tcp_do_newreno) { 1886 if (IN_FASTRECOVERY(tp)) { 1887 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1888 tcp_newreno_partial_ack(tp, th); 1889 } else { 1890 /* 1891 * Window inflation should have left us 1892 * with approximately snd_ssthresh 1893 * outstanding data. 1894 * But in case we would be inclined to 1895 * send a burst, better to do it via 1896 * the slow start mechanism. 1897 */ 1898 if (SEQ_GT(th->th_ack + 1899 tp->snd_ssthresh, 1900 tp->snd_max)) 1901 tp->snd_cwnd = tp->snd_max - 1902 th->th_ack + 1903 tp->t_maxseg; 1904 else 1905 tp->snd_cwnd = tp->snd_ssthresh; 1906 } 1907 } 1908 } else { 1909 if (tp->t_dupacks >= tcprexmtthresh && 1910 tp->snd_cwnd > tp->snd_ssthresh) 1911 tp->snd_cwnd = tp->snd_ssthresh; 1912 } 1913 tp->t_dupacks = 0; 1914 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1915 /* 1916 * Detected optimistic ACK attack. 1917 * Force slow-start to de-synchronize attack. 1918 */ 1919 tp->snd_cwnd = tp->t_maxseg; 1920 1921 tcpstat.tcps_rcvacktoomuch++; 1922 goto dropafterack; 1923 } 1924 /* 1925 * If we reach this point, ACK is not a duplicate, 1926 * i.e., it ACKs something we sent. 1927 */ 1928 if (tp->t_flags & TF_NEEDSYN) { 1929 /* 1930 * T/TCP: Connection was half-synchronized, and our 1931 * SYN has been ACK'd (so connection is now fully 1932 * synchronized). Go to non-starred state, 1933 * increment snd_una for ACK of SYN, and check if 1934 * we can do window scaling. 1935 */ 1936 tp->t_flags &= ~TF_NEEDSYN; 1937 tp->snd_una++; 1938 /* Do window scaling? */ 1939 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1940 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1941 tp->snd_scale = tp->requested_s_scale; 1942 tp->rcv_scale = tp->request_r_scale; 1943 } 1944 } 1945 1946 process_ACK: 1947 acked = th->th_ack - tp->snd_una; 1948 tcpstat.tcps_rcvackpack++; 1949 tcpstat.tcps_rcvackbyte += acked; 1950 1951 /* 1952 * If we just performed our first retransmit, and the ACK 1953 * arrives within our recovery window, then it was a mistake 1954 * to do the retransmit in the first place. Recover our 1955 * original cwnd and ssthresh, and proceed to transmit where 1956 * we left off. 1957 */ 1958 if (tcp_do_eifel_detect && acked && 1959 (to.to_flags & TOF_TS) && to.to_tsecr && 1960 (tp->t_flags & TF_FIRSTACCACK)) { 1961 /* Eifel detection applicable. */ 1962 if (to.to_tsecr < tp->t_rexmtTS) { 1963 ++tcpstat.tcps_eifeldetected; 1964 tcp_revert_congestion_state(tp); 1965 if (tp->t_rxtshift == 1 && 1966 ticks >= tp->t_badrxtwin) 1967 ++tcpstat.tcps_rttcantdetect; 1968 } 1969 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1970 tcp_revert_congestion_state(tp); 1971 ++tcpstat.tcps_rttdetected; 1972 } 1973 1974 /* 1975 * If we have a timestamp reply, update smoothed 1976 * round trip time. If no timestamp is present but 1977 * transmit timer is running and timed sequence 1978 * number was acked, update smoothed round trip time. 1979 * Since we now have an rtt measurement, cancel the 1980 * timer backoff (cf., Phil Karn's retransmit alg.). 1981 * Recompute the initial retransmit timer. 1982 * 1983 * Some machines (certain windows boxes) send broken 1984 * timestamp replies during the SYN+ACK phase, ignore 1985 * timestamps of 0. 1986 */ 1987 if ((to.to_flags & TOF_TS) != 0 && 1988 to.to_tsecr) { 1989 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1990 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1991 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1992 } 1993 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1994 1995 /* 1996 * If all outstanding data is acked, stop retransmit 1997 * timer and remember to restart (more output or persist). 1998 * If there is more data to be acked, restart retransmit 1999 * timer, using current (possibly backed-off) value. 2000 */ 2001 if (th->th_ack == tp->snd_max) { 2002 callout_stop(tp->tt_rexmt); 2003 needoutput = 1; 2004 } else if (!callout_active(tp->tt_persist)) 2005 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2006 tcp_timer_rexmt, tp); 2007 2008 /* 2009 * If no data (only SYN) was ACK'd, 2010 * skip rest of ACK processing. 2011 */ 2012 if (acked == 0) 2013 goto step6; 2014 2015 /* Stop looking for an acceptable ACK since one was received. */ 2016 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2017 2018 /* 2019 * When new data is acked, open the congestion window. 2020 * If the window gives us less than ssthresh packets 2021 * in flight, open exponentially (maxseg per packet). 2022 * Otherwise open linearly: maxseg per window 2023 * (maxseg^2 / cwnd per packet). 2024 */ 2025 if (!tcp_do_newreno || !IN_FASTRECOVERY(tp)) { 2026 u_int cw = tp->snd_cwnd; 2027 u_int incr = tp->t_maxseg; 2028 if (cw > tp->snd_ssthresh) 2029 incr = incr * incr / cw; 2030 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2031 } 2032 if (acked > so->so_snd.sb_cc) { 2033 tp->snd_wnd -= so->so_snd.sb_cc; 2034 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2035 ourfinisacked = 1; 2036 } else { 2037 sbdrop(&so->so_snd, acked); 2038 tp->snd_wnd -= acked; 2039 ourfinisacked = 0; 2040 } 2041 sowwakeup(so); 2042 if (tcp_do_newreno) { 2043 if (IN_FASTRECOVERY(tp)) { 2044 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) 2045 EXIT_FASTRECOVERY(tp); 2046 } else { 2047 tp->snd_recover = th->th_ack - 1; 2048 } 2049 } 2050 tp->snd_una = th->th_ack; 2051 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2052 tp->snd_nxt = tp->snd_una; 2053 2054 switch (tp->t_state) { 2055 2056 /* 2057 * In FIN_WAIT_1 STATE in addition to the processing 2058 * for the ESTABLISHED state if our FIN is now acknowledged 2059 * then enter FIN_WAIT_2. 2060 */ 2061 case TCPS_FIN_WAIT_1: 2062 if (ourfinisacked) { 2063 /* 2064 * If we can't receive any more 2065 * data, then closing user can proceed. 2066 * Starting the timer is contrary to the 2067 * specification, but if we don't get a FIN 2068 * we'll hang forever. 2069 */ 2070 if (so->so_state & SS_CANTRCVMORE) { 2071 soisdisconnected(so); 2072 callout_reset(tp->tt_2msl, tcp_maxidle, 2073 tcp_timer_2msl, tp); 2074 } 2075 tp->t_state = TCPS_FIN_WAIT_2; 2076 } 2077 break; 2078 2079 /* 2080 * In CLOSING STATE in addition to the processing for 2081 * the ESTABLISHED state if the ACK acknowledges our FIN 2082 * then enter the TIME-WAIT state, otherwise ignore 2083 * the segment. 2084 */ 2085 case TCPS_CLOSING: 2086 if (ourfinisacked) { 2087 tp->t_state = TCPS_TIME_WAIT; 2088 tcp_canceltimers(tp); 2089 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2090 if (tp->cc_recv != 0 && 2091 (ticks - tp->t_starttime) < tcp_msl) 2092 callout_reset(tp->tt_2msl, 2093 tp->t_rxtcur * 2094 TCPTV_TWTRUNC, 2095 tcp_timer_2msl, tp); 2096 else 2097 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2098 tcp_timer_2msl, tp); 2099 soisdisconnected(so); 2100 } 2101 break; 2102 2103 /* 2104 * In LAST_ACK, we may still be waiting for data to drain 2105 * and/or to be acked, as well as for the ack of our FIN. 2106 * If our FIN is now acknowledged, delete the TCB, 2107 * enter the closed state and return. 2108 */ 2109 case TCPS_LAST_ACK: 2110 if (ourfinisacked) { 2111 tp = tcp_close(tp); 2112 goto drop; 2113 } 2114 break; 2115 2116 /* 2117 * In TIME_WAIT state the only thing that should arrive 2118 * is a retransmission of the remote FIN. Acknowledge 2119 * it and restart the finack timer. 2120 */ 2121 case TCPS_TIME_WAIT: 2122 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2123 tcp_timer_2msl, tp); 2124 goto dropafterack; 2125 } 2126 } 2127 2128 step6: 2129 /* 2130 * Update window information. 2131 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2132 */ 2133 if ((thflags & TH_ACK) && 2134 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2135 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2136 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2137 /* keep track of pure window updates */ 2138 if (tlen == 0 && 2139 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2140 tcpstat.tcps_rcvwinupd++; 2141 tp->snd_wnd = tiwin; 2142 tp->snd_wl1 = th->th_seq; 2143 tp->snd_wl2 = th->th_ack; 2144 if (tp->snd_wnd > tp->max_sndwnd) 2145 tp->max_sndwnd = tp->snd_wnd; 2146 needoutput = 1; 2147 } 2148 2149 /* 2150 * Process segments with URG. 2151 */ 2152 if ((thflags & TH_URG) && th->th_urp && 2153 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2154 /* 2155 * This is a kludge, but if we receive and accept 2156 * random urgent pointers, we'll crash in 2157 * soreceive. It's hard to imagine someone 2158 * actually wanting to send this much urgent data. 2159 */ 2160 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2161 th->th_urp = 0; /* XXX */ 2162 thflags &= ~TH_URG; /* XXX */ 2163 goto dodata; /* XXX */ 2164 } 2165 /* 2166 * If this segment advances the known urgent pointer, 2167 * then mark the data stream. This should not happen 2168 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2169 * a FIN has been received from the remote side. 2170 * In these states we ignore the URG. 2171 * 2172 * According to RFC961 (Assigned Protocols), 2173 * the urgent pointer points to the last octet 2174 * of urgent data. We continue, however, 2175 * to consider it to indicate the first octet 2176 * of data past the urgent section as the original 2177 * spec states (in one of two places). 2178 */ 2179 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2180 tp->rcv_up = th->th_seq + th->th_urp; 2181 so->so_oobmark = so->so_rcv.sb_cc + 2182 (tp->rcv_up - tp->rcv_nxt) - 1; 2183 if (so->so_oobmark == 0) 2184 so->so_state |= SS_RCVATMARK; 2185 sohasoutofband(so); 2186 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2187 } 2188 /* 2189 * Remove out of band data so doesn't get presented to user. 2190 * This can happen independent of advancing the URG pointer, 2191 * but if two URG's are pending at once, some out-of-band 2192 * data may creep in... ick. 2193 */ 2194 if (th->th_urp <= (u_long)tlen 2195 #ifdef SO_OOBINLINE 2196 && (so->so_options & SO_OOBINLINE) == 0 2197 #endif 2198 ) 2199 tcp_pulloutofband(so, th, m, 2200 drop_hdrlen); /* hdr drop is delayed */ 2201 } else { 2202 /* 2203 * If no out of band data is expected, 2204 * pull receive urgent pointer along 2205 * with the receive window. 2206 */ 2207 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2208 tp->rcv_up = tp->rcv_nxt; 2209 } 2210 dodata: /* XXX */ 2211 2212 /* 2213 * Process the segment text, merging it into the TCP sequencing queue, 2214 * and arranging for acknowledgment of receipt if necessary. 2215 * This process logically involves adjusting tp->rcv_wnd as data 2216 * is presented to the user (this happens in tcp_usrreq.c, 2217 * case PRU_RCVD). If a FIN has already been received on this 2218 * connection then we just ignore the text. 2219 */ 2220 if ((tlen || (thflags & TH_FIN)) && 2221 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2222 m_adj(m, drop_hdrlen); /* delayed header drop */ 2223 /* 2224 * Insert segment which includes th into TCP reassembly queue 2225 * with control block tp. Set thflags to whether reassembly now 2226 * includes a segment with FIN. This handles the common case 2227 * inline (segment is the next to be received on an established 2228 * connection, and the queue is empty), avoiding linkage into 2229 * and removal from the queue and repetition of various 2230 * conversions. 2231 * Set DELACK for segments received in order, but ack 2232 * immediately when segments are out of order (so 2233 * fast retransmit can work). 2234 */ 2235 if (th->th_seq == tp->rcv_nxt && 2236 LIST_EMPTY(&tp->t_segq) && 2237 TCPS_HAVEESTABLISHED(tp->t_state)) { 2238 if (DELAY_ACK(tp)) 2239 callout_reset(tp->tt_delack, tcp_delacktime, 2240 tcp_timer_delack, tp); 2241 else 2242 tp->t_flags |= TF_ACKNOW; 2243 tp->rcv_nxt += tlen; 2244 thflags = th->th_flags & TH_FIN; 2245 tcpstat.tcps_rcvpack++; 2246 tcpstat.tcps_rcvbyte += tlen; 2247 ND6_HINT(tp); 2248 if (so->so_state & SS_CANTRCVMORE) 2249 m_freem(m); 2250 else 2251 sbappend(&so->so_rcv, m); 2252 sorwakeup(so); 2253 } else { 2254 thflags = tcp_reass(tp, th, &tlen, m); 2255 tp->t_flags |= TF_ACKNOW; 2256 } 2257 2258 /* 2259 * Note the amount of data that peer has sent into 2260 * our window, in order to estimate the sender's 2261 * buffer size. 2262 */ 2263 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2264 } else { 2265 m_freem(m); 2266 thflags &= ~TH_FIN; 2267 } 2268 2269 /* 2270 * If FIN is received ACK the FIN and let the user know 2271 * that the connection is closing. 2272 */ 2273 if (thflags & TH_FIN) { 2274 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2275 socantrcvmore(so); 2276 /* 2277 * If connection is half-synchronized 2278 * (ie NEEDSYN flag on) then delay ACK, 2279 * so it may be piggybacked when SYN is sent. 2280 * Otherwise, since we received a FIN then no 2281 * more input can be expected, send ACK now. 2282 */ 2283 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2284 callout_reset(tp->tt_delack, tcp_delacktime, 2285 tcp_timer_delack, tp); 2286 else 2287 tp->t_flags |= TF_ACKNOW; 2288 tp->rcv_nxt++; 2289 } 2290 switch (tp->t_state) { 2291 2292 /* 2293 * In SYN_RECEIVED and ESTABLISHED STATES 2294 * enter the CLOSE_WAIT state. 2295 */ 2296 case TCPS_SYN_RECEIVED: 2297 tp->t_starttime = ticks; 2298 /*FALLTHROUGH*/ 2299 case TCPS_ESTABLISHED: 2300 tp->t_state = TCPS_CLOSE_WAIT; 2301 break; 2302 2303 /* 2304 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2305 * enter the CLOSING state. 2306 */ 2307 case TCPS_FIN_WAIT_1: 2308 tp->t_state = TCPS_CLOSING; 2309 break; 2310 2311 /* 2312 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2313 * starting the time-wait timer, turning off the other 2314 * standard timers. 2315 */ 2316 case TCPS_FIN_WAIT_2: 2317 tp->t_state = TCPS_TIME_WAIT; 2318 tcp_canceltimers(tp); 2319 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2320 if (tp->cc_recv != 0 && 2321 (ticks - tp->t_starttime) < tcp_msl) { 2322 callout_reset(tp->tt_2msl, 2323 tp->t_rxtcur * TCPTV_TWTRUNC, 2324 tcp_timer_2msl, tp); 2325 /* For transaction client, force ACK now. */ 2326 tp->t_flags |= TF_ACKNOW; 2327 } 2328 else 2329 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2330 tcp_timer_2msl, tp); 2331 soisdisconnected(so); 2332 break; 2333 2334 /* 2335 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2336 */ 2337 case TCPS_TIME_WAIT: 2338 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2339 tcp_timer_2msl, tp); 2340 break; 2341 } 2342 } 2343 #ifdef TCPDEBUG 2344 if (so->so_options & SO_DEBUG) 2345 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2346 &tcp_savetcp, 0); 2347 #endif 2348 2349 /* 2350 * Return any desired output. 2351 */ 2352 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2353 (void) tcp_output(tp); 2354 return; 2355 2356 dropafterack: 2357 /* 2358 * Generate an ACK dropping incoming segment if it occupies 2359 * sequence space, where the ACK reflects our state. 2360 * 2361 * We can now skip the test for the RST flag since all 2362 * paths to this code happen after packets containing 2363 * RST have been dropped. 2364 * 2365 * In the SYN-RECEIVED state, don't send an ACK unless the 2366 * segment we received passes the SYN-RECEIVED ACK test. 2367 * If it fails send a RST. This breaks the loop in the 2368 * "LAND" DoS attack, and also prevents an ACK storm 2369 * between two listening ports that have been sent forged 2370 * SYN segments, each with the source address of the other. 2371 */ 2372 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2373 (SEQ_GT(tp->snd_una, th->th_ack) || 2374 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2375 rstreason = BANDLIM_RST_OPENPORT; 2376 goto dropwithreset; 2377 } 2378 #ifdef TCPDEBUG 2379 if (so->so_options & SO_DEBUG) 2380 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2381 &tcp_savetcp, 0); 2382 #endif 2383 m_freem(m); 2384 tp->t_flags |= TF_ACKNOW; 2385 (void) tcp_output(tp); 2386 return; 2387 2388 dropwithreset: 2389 /* 2390 * Generate a RST, dropping incoming segment. 2391 * Make ACK acceptable to originator of segment. 2392 * Don't bother to respond if destination was broadcast/multicast. 2393 */ 2394 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2395 goto drop; 2396 if (isipv6) { 2397 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2398 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2399 goto drop; 2400 } else { 2401 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2402 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2403 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2404 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2405 goto drop; 2406 } 2407 /* IPv6 anycast check is done at tcp6_input() */ 2408 2409 /* 2410 * Perform bandwidth limiting. 2411 */ 2412 #ifdef ICMP_BANDLIM 2413 if (badport_bandlim(rstreason) < 0) 2414 goto drop; 2415 #endif 2416 2417 #ifdef TCPDEBUG 2418 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2419 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2420 &tcp_savetcp, 0); 2421 #endif 2422 if (thflags & TH_ACK) 2423 /* mtod() below is safe as long as hdr dropping is delayed */ 2424 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2425 TH_RST); 2426 else { 2427 if (thflags & TH_SYN) 2428 tlen++; 2429 /* mtod() below is safe as long as hdr dropping is delayed */ 2430 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2431 (tcp_seq)0, TH_RST|TH_ACK); 2432 } 2433 return; 2434 2435 drop: 2436 /* 2437 * Drop space held by incoming segment and return. 2438 */ 2439 #ifdef TCPDEBUG 2440 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2441 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2442 &tcp_savetcp, 0); 2443 #endif 2444 m_freem(m); 2445 return; 2446 } 2447 2448 /* 2449 * Parse TCP options and place in tcpopt. 2450 */ 2451 static void 2452 tcp_dooptions(to, cp, cnt, is_syn) 2453 struct tcpopt *to; 2454 u_char *cp; 2455 int cnt; 2456 { 2457 int opt, optlen; 2458 2459 to->to_flags = 0; 2460 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2461 opt = cp[0]; 2462 if (opt == TCPOPT_EOL) 2463 break; 2464 if (opt == TCPOPT_NOP) 2465 optlen = 1; 2466 else { 2467 if (cnt < 2) 2468 break; 2469 optlen = cp[1]; 2470 if (optlen < 2 || optlen > cnt) 2471 break; 2472 } 2473 switch (opt) { 2474 case TCPOPT_MAXSEG: 2475 if (optlen != TCPOLEN_MAXSEG) 2476 continue; 2477 if (!is_syn) 2478 continue; 2479 to->to_flags |= TOF_MSS; 2480 bcopy((char *)cp + 2, 2481 (char *)&to->to_mss, sizeof(to->to_mss)); 2482 to->to_mss = ntohs(to->to_mss); 2483 break; 2484 case TCPOPT_WINDOW: 2485 if (optlen != TCPOLEN_WINDOW) 2486 continue; 2487 if (! is_syn) 2488 continue; 2489 to->to_flags |= TOF_SCALE; 2490 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2491 break; 2492 case TCPOPT_TIMESTAMP: 2493 if (optlen != TCPOLEN_TIMESTAMP) 2494 continue; 2495 to->to_flags |= TOF_TS; 2496 bcopy((char *)cp + 2, 2497 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2498 to->to_tsval = ntohl(to->to_tsval); 2499 bcopy((char *)cp + 6, 2500 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2501 to->to_tsecr = ntohl(to->to_tsecr); 2502 break; 2503 case TCPOPT_CC: 2504 if (optlen != TCPOLEN_CC) 2505 continue; 2506 to->to_flags |= TOF_CC; 2507 bcopy((char *)cp + 2, 2508 (char *)&to->to_cc, sizeof(to->to_cc)); 2509 to->to_cc = ntohl(to->to_cc); 2510 break; 2511 case TCPOPT_CCNEW: 2512 if (optlen != TCPOLEN_CC) 2513 continue; 2514 if (!is_syn) 2515 continue; 2516 to->to_flags |= TOF_CCNEW; 2517 bcopy((char *)cp + 2, 2518 (char *)&to->to_cc, sizeof(to->to_cc)); 2519 to->to_cc = ntohl(to->to_cc); 2520 break; 2521 case TCPOPT_CCECHO: 2522 if (optlen != TCPOLEN_CC) 2523 continue; 2524 if (!is_syn) 2525 continue; 2526 to->to_flags |= TOF_CCECHO; 2527 bcopy((char *)cp + 2, 2528 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2529 to->to_ccecho = ntohl(to->to_ccecho); 2530 break; 2531 default: 2532 continue; 2533 } 2534 } 2535 } 2536 2537 /* 2538 * Pull out of band byte out of a segment so 2539 * it doesn't appear in the user's data queue. 2540 * It is still reflected in the segment length for 2541 * sequencing purposes. 2542 */ 2543 static void 2544 tcp_pulloutofband(so, th, m, off) 2545 struct socket *so; 2546 struct tcphdr *th; 2547 struct mbuf *m; 2548 int off; /* delayed to be droped hdrlen */ 2549 { 2550 int cnt = off + th->th_urp - 1; 2551 2552 while (cnt >= 0) { 2553 if (m->m_len > cnt) { 2554 char *cp = mtod(m, caddr_t) + cnt; 2555 struct tcpcb *tp = sototcpcb(so); 2556 2557 tp->t_iobc = *cp; 2558 tp->t_oobflags |= TCPOOB_HAVEDATA; 2559 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2560 m->m_len--; 2561 if (m->m_flags & M_PKTHDR) 2562 m->m_pkthdr.len--; 2563 return; 2564 } 2565 cnt -= m->m_len; 2566 m = m->m_next; 2567 if (m == 0) 2568 break; 2569 } 2570 panic("tcp_pulloutofband"); 2571 } 2572 2573 /* 2574 * Collect new round-trip time estimate 2575 * and update averages and current timeout. 2576 */ 2577 static void 2578 tcp_xmit_timer(tp, rtt) 2579 struct tcpcb *tp; 2580 int rtt; 2581 { 2582 int delta; 2583 2584 tcpstat.tcps_rttupdated++; 2585 tp->t_rttupdated++; 2586 if (tp->t_srtt != 0) { 2587 /* 2588 * srtt is stored as fixed point with 5 bits after the 2589 * binary point (i.e., scaled by 8). The following magic 2590 * is equivalent to the smoothing algorithm in rfc793 with 2591 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2592 * point). Adjust rtt to origin 0. 2593 */ 2594 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2595 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2596 2597 if ((tp->t_srtt += delta) <= 0) 2598 tp->t_srtt = 1; 2599 2600 /* 2601 * We accumulate a smoothed rtt variance (actually, a 2602 * smoothed mean difference), then set the retransmit 2603 * timer to smoothed rtt + 4 times the smoothed variance. 2604 * rttvar is stored as fixed point with 4 bits after the 2605 * binary point (scaled by 16). The following is 2606 * equivalent to rfc793 smoothing with an alpha of .75 2607 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2608 * rfc793's wired-in beta. 2609 */ 2610 if (delta < 0) 2611 delta = -delta; 2612 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2613 if ((tp->t_rttvar += delta) <= 0) 2614 tp->t_rttvar = 1; 2615 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2616 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2617 } else { 2618 /* 2619 * No rtt measurement yet - use the unsmoothed rtt. 2620 * Set the variance to half the rtt (so our first 2621 * retransmit happens at 3*rtt). 2622 */ 2623 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2624 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2625 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2626 } 2627 tp->t_rtttime = 0; 2628 tp->t_rxtshift = 0; 2629 2630 /* 2631 * the retransmit should happen at rtt + 4 * rttvar. 2632 * Because of the way we do the smoothing, srtt and rttvar 2633 * will each average +1/2 tick of bias. When we compute 2634 * the retransmit timer, we want 1/2 tick of rounding and 2635 * 1 extra tick because of +-1/2 tick uncertainty in the 2636 * firing of the timer. The bias will give us exactly the 2637 * 1.5 tick we need. But, because the bias is 2638 * statistical, we have to test that we don't drop below 2639 * the minimum feasible timer (which is 2 ticks). 2640 */ 2641 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2642 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2643 2644 /* 2645 * We received an ack for a packet that wasn't retransmitted; 2646 * it is probably safe to discard any error indications we've 2647 * received recently. This isn't quite right, but close enough 2648 * for now (a route might have failed after we sent a segment, 2649 * and the return path might not be symmetrical). 2650 */ 2651 tp->t_softerror = 0; 2652 } 2653 2654 /* 2655 * Determine a reasonable value for maxseg size. 2656 * If the route is known, check route for mtu. 2657 * If none, use an mss that can be handled on the outgoing 2658 * interface without forcing IP to fragment; if bigger than 2659 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2660 * to utilize large mbufs. If no route is found, route has no mtu, 2661 * or the destination isn't local, use a default, hopefully conservative 2662 * size (usually 512 or the default IP max size, but no more than the mtu 2663 * of the interface), as we can't discover anything about intervening 2664 * gateways or networks. We also initialize the congestion/slow start 2665 * window to be a single segment if the destination isn't local. 2666 * While looking at the routing entry, we also initialize other path-dependent 2667 * parameters from pre-set or cached values in the routing entry. 2668 * 2669 * Also take into account the space needed for options that we 2670 * send regularly. Make maxseg shorter by that amount to assure 2671 * that we can send maxseg amount of data even when the options 2672 * are present. Store the upper limit of the length of options plus 2673 * data in maxopd. 2674 * 2675 * NOTE that this routine is only called when we process an incoming 2676 * segment, for outgoing segments only tcp_mssopt is called. 2677 * 2678 * In case of T/TCP, we call this routine during implicit connection 2679 * setup as well (offer = -1), to initialize maxseg from the cached 2680 * MSS of our peer. 2681 */ 2682 void 2683 tcp_mss(tp, offer) 2684 struct tcpcb *tp; 2685 int offer; 2686 { 2687 struct rtentry *rt; 2688 struct ifnet *ifp; 2689 int rtt, mss; 2690 u_long bufsize; 2691 struct inpcb *inp = tp->t_inpcb; 2692 struct socket *so; 2693 struct rmxp_tao *taop; 2694 int origoffer = offer; 2695 #ifdef INET6 2696 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2697 size_t min_protoh = isipv6 ? 2698 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2699 sizeof(struct tcpiphdr); 2700 #else 2701 const boolean_t isipv6 = FALSE; 2702 const size_t min_protoh = sizeof(struct tcpiphdr); 2703 #endif 2704 2705 if (isipv6) 2706 rt = tcp_rtlookup6(&inp->inp_inc); 2707 else 2708 rt = tcp_rtlookup(&inp->inp_inc); 2709 if (rt == NULL) { 2710 tp->t_maxopd = tp->t_maxseg = 2711 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2712 return; 2713 } 2714 ifp = rt->rt_ifp; 2715 so = inp->inp_socket; 2716 2717 taop = rmx_taop(rt->rt_rmx); 2718 /* 2719 * Offer == -1 means that we didn't receive SYN yet, 2720 * use cached value in that case; 2721 */ 2722 if (offer == -1) 2723 offer = taop->tao_mssopt; 2724 /* 2725 * Offer == 0 means that there was no MSS on the SYN segment, 2726 * in this case we use tcp_mssdflt. 2727 */ 2728 if (offer == 0) 2729 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2730 else 2731 /* 2732 * Sanity check: make sure that maxopd will be large 2733 * enough to allow some data on segments even is the 2734 * all the option space is used (40bytes). Otherwise 2735 * funny things may happen in tcp_output. 2736 */ 2737 offer = max(offer, 64); 2738 taop->tao_mssopt = offer; 2739 2740 /* 2741 * While we're here, check if there's an initial rtt 2742 * or rttvar. Convert from the route-table units 2743 * to scaled multiples of the slow timeout timer. 2744 */ 2745 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2746 /* 2747 * XXX the lock bit for RTT indicates that the value 2748 * is also a minimum value; this is subject to time. 2749 */ 2750 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2751 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2752 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2753 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2754 tcpstat.tcps_usedrtt++; 2755 if (rt->rt_rmx.rmx_rttvar) { 2756 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2757 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2758 tcpstat.tcps_usedrttvar++; 2759 } else { 2760 /* default variation is +- 1 rtt */ 2761 tp->t_rttvar = 2762 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2763 } 2764 TCPT_RANGESET(tp->t_rxtcur, 2765 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2766 tp->t_rttmin, TCPTV_REXMTMAX); 2767 } 2768 /* 2769 * if there's an mtu associated with the route, use it 2770 * else, use the link mtu. 2771 */ 2772 if (rt->rt_rmx.rmx_mtu) 2773 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2774 else { 2775 if (isipv6) { 2776 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2777 min_protoh; 2778 if (!in6_localaddr(&inp->in6p_faddr)) 2779 mss = min(mss, tcp_v6mssdflt); 2780 } else { 2781 mss = ifp->if_mtu - min_protoh; 2782 if (!in_localaddr(inp->inp_faddr)) 2783 mss = min(mss, tcp_mssdflt); 2784 } 2785 } 2786 mss = min(mss, offer); 2787 /* 2788 * maxopd stores the maximum length of data AND options 2789 * in a segment; maxseg is the amount of data in a normal 2790 * segment. We need to store this value (maxopd) apart 2791 * from maxseg, because now every segment carries options 2792 * and thus we normally have somewhat less data in segments. 2793 */ 2794 tp->t_maxopd = mss; 2795 2796 /* 2797 * In case of T/TCP, origoffer==-1 indicates, that no segments 2798 * were received yet. In this case we just guess, otherwise 2799 * we do the same as before T/TCP. 2800 */ 2801 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2802 (origoffer == -1 || 2803 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2804 mss -= TCPOLEN_TSTAMP_APPA; 2805 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2806 (origoffer == -1 || 2807 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2808 mss -= TCPOLEN_CC_APPA; 2809 2810 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2811 if (mss > MCLBYTES) 2812 mss &= ~(MCLBYTES-1); 2813 #else 2814 if (mss > MCLBYTES) 2815 mss = mss / MCLBYTES * MCLBYTES; 2816 #endif 2817 /* 2818 * If there's a pipesize, change the socket buffer 2819 * to that size. Make the socket buffers an integral 2820 * number of mss units; if the mss is larger than 2821 * the socket buffer, decrease the mss. 2822 */ 2823 #ifdef RTV_SPIPE 2824 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2825 #endif 2826 bufsize = so->so_snd.sb_hiwat; 2827 if (bufsize < mss) 2828 mss = bufsize; 2829 else { 2830 bufsize = roundup(bufsize, mss); 2831 if (bufsize > sb_max) 2832 bufsize = sb_max; 2833 if (bufsize > so->so_snd.sb_hiwat) 2834 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2835 } 2836 tp->t_maxseg = mss; 2837 2838 #ifdef RTV_RPIPE 2839 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2840 #endif 2841 bufsize = so->so_rcv.sb_hiwat; 2842 if (bufsize > mss) { 2843 bufsize = roundup(bufsize, mss); 2844 if (bufsize > sb_max) 2845 bufsize = sb_max; 2846 if (bufsize > so->so_rcv.sb_hiwat) 2847 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2848 } 2849 2850 /* 2851 * Set the slow-start flight size depending on whether this 2852 * is a local network or not. 2853 */ 2854 if (tcp_do_rfc3390) 2855 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2856 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2857 (!isipv6 && in_localaddr(inp->inp_faddr))) 2858 tp->snd_cwnd = mss * ss_fltsz_local; 2859 else 2860 tp->snd_cwnd = mss * ss_fltsz; 2861 2862 if (rt->rt_rmx.rmx_ssthresh) { 2863 /* 2864 * There's some sort of gateway or interface 2865 * buffer limit on the path. Use this to set 2866 * the slow start threshhold, but set the 2867 * threshold to no less than 2*mss. 2868 */ 2869 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2870 tcpstat.tcps_usedssthresh++; 2871 } 2872 } 2873 2874 /* 2875 * Determine the MSS option to send on an outgoing SYN. 2876 */ 2877 int 2878 tcp_mssopt(tp) 2879 struct tcpcb *tp; 2880 { 2881 struct rtentry *rt; 2882 #ifdef INET6 2883 boolean_t isipv6 = 2884 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2885 int min_protoh = isipv6 ? 2886 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2887 sizeof(struct tcpiphdr); 2888 #else 2889 const boolean_t isipv6 = FALSE; 2890 const size_t min_protoh = sizeof(struct tcpiphdr); 2891 #endif 2892 2893 if (isipv6) 2894 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2895 else 2896 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2897 if (rt == NULL) 2898 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2899 2900 return (rt->rt_ifp->if_mtu - min_protoh); 2901 } 2902 2903 2904 /* 2905 * When a partial ack arrives, force the retransmission of the 2906 * next unacknowledged segment. Do not clear tp->t_dupacks. 2907 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2908 * be started again. 2909 */ 2910 static void 2911 tcp_newreno_partial_ack(tp, th) 2912 struct tcpcb *tp; 2913 struct tcphdr *th; 2914 { 2915 tcp_seq onxt = tp->snd_nxt; 2916 u_long ocwnd = tp->snd_cwnd; 2917 2918 callout_stop(tp->tt_rexmt); 2919 tp->t_rtttime = 0; 2920 tp->snd_nxt = th->th_ack; 2921 /* 2922 * Set snd_cwnd to one segment beyond acknowledged offset 2923 * (tp->snd_una has not yet been updated when this function is called.) 2924 */ 2925 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2926 tp->t_flags |= TF_ACKNOW; 2927 (void) tcp_output(tp); 2928 tp->snd_cwnd = ocwnd; 2929 if (SEQ_GT(onxt, tp->snd_nxt)) 2930 tp->snd_nxt = onxt; 2931 /* 2932 * Partial window deflation. Relies on fact that tp->snd_una 2933 * not updated yet. 2934 */ 2935 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2936 } 2937