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) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.68 2008/08/22 09:14:17 sephe Exp $ 69 */ 70 71 #include "opt_ipfw.h" /* for ipfw_fwd */ 72 #include "opt_inet6.h" 73 #include "opt_ipsec.h" 74 #include "opt_tcpdebug.h" 75 #include "opt_tcp_input.h" 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/sysctl.h> 81 #include <sys/malloc.h> 82 #include <sys/mbuf.h> 83 #include <sys/proc.h> /* for proc0 declaration */ 84 #include <sys/protosw.h> 85 #include <sys/socket.h> 86 #include <sys/socketvar.h> 87 #include <sys/syslog.h> 88 #include <sys/in_cksum.h> 89 90 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 91 #include <machine/stdarg.h> 92 93 #include <net/if.h> 94 #include <net/route.h> 95 96 #include <netinet/in.h> 97 #include <netinet/in_systm.h> 98 #include <netinet/ip.h> 99 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 100 #include <netinet/in_var.h> 101 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip6.h> 105 #include <netinet/icmp6.h> 106 #include <netinet6/nd6.h> 107 #include <netinet6/ip6_var.h> 108 #include <netinet6/in6_pcb.h> 109 #include <netinet/tcp.h> 110 #include <netinet/tcp_fsm.h> 111 #include <netinet/tcp_seq.h> 112 #include <netinet/tcp_timer.h> 113 #include <netinet/tcp_timer2.h> 114 #include <netinet/tcp_var.h> 115 #include <netinet6/tcp6_var.h> 116 #include <netinet/tcpip.h> 117 118 #ifdef TCPDEBUG 119 #include <netinet/tcp_debug.h> 120 121 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 122 struct tcphdr tcp_savetcp; 123 #endif 124 125 #ifdef FAST_IPSEC 126 #include <netproto/ipsec/ipsec.h> 127 #include <netproto/ipsec/ipsec6.h> 128 #endif 129 130 #ifdef IPSEC 131 #include <netinet6/ipsec.h> 132 #include <netinet6/ipsec6.h> 133 #include <netproto/key/key.h> 134 #endif 135 136 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 137 138 tcp_cc tcp_ccgen; 139 static int log_in_vain = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 141 &log_in_vain, 0, "Log all incoming TCP connections"); 142 143 static int blackhole = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 145 &blackhole, 0, "Do not send RST when dropping refused connections"); 146 147 int tcp_delack_enabled = 1; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 149 &tcp_delack_enabled, 0, 150 "Delay ACK to try and piggyback it onto a data packet"); 151 152 #ifdef TCP_DROP_SYNFIN 153 static int drop_synfin = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 156 #endif 157 158 static int tcp_do_limitedtransmit = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 161 162 static int tcp_do_early_retransmit = 1; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 164 &tcp_do_early_retransmit, 0, "Early retransmit"); 165 166 int tcp_aggregate_acks = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 169 170 int tcp_do_rfc3390 = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 172 &tcp_do_rfc3390, 0, 173 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 174 175 static int tcp_do_eifel_detect = 1; 176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 177 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 178 179 static int tcp_do_abc = 1; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 181 &tcp_do_abc, 0, 182 "TCP Appropriate Byte Counting (RFC 3465)"); 183 184 /* 185 * Define as tunable for easy testing with SACK on and off. 186 * Warning: do not change setting in the middle of an existing active TCP flow, 187 * else strange things might happen to that flow. 188 */ 189 int tcp_do_sack = 1; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 191 &tcp_do_sack, 0, "Enable SACK Algorithms"); 192 193 int tcp_do_smartsack = 1; 194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 195 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 196 197 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 198 "TCP Segment Reassembly Queue"); 199 200 int tcp_reass_maxseg = 0; 201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 202 &tcp_reass_maxseg, 0, 203 "Global maximum number of TCP Segments in Reassembly Queue"); 204 205 int tcp_reass_qsize = 0; 206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 207 &tcp_reass_qsize, 0, 208 "Global number of TCP Segments currently in Reassembly Queue"); 209 210 static int tcp_reass_overflows = 0; 211 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 212 &tcp_reass_overflows, 0, 213 "Global number of TCP Segment Reassembly Queue Overflows"); 214 215 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 216 static void tcp_pulloutofband(struct socket *, 217 struct tcphdr *, struct mbuf *, int); 218 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 219 struct mbuf *); 220 static void tcp_xmit_timer(struct tcpcb *, int); 221 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 222 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 223 224 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 225 #ifdef INET6 226 #define ND6_HINT(tp) \ 227 do { \ 228 if ((tp) && (tp)->t_inpcb && \ 229 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 230 (tp)->t_inpcb->in6p_route.ro_rt) \ 231 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 232 } while (0) 233 #else 234 #define ND6_HINT(tp) 235 #endif 236 237 /* 238 * Indicate whether this ack should be delayed. We can delay the ack if 239 * - delayed acks are enabled and 240 * - there is no delayed ack timer in progress and 241 * - our last ack wasn't a 0-sized window. We never want to delay 242 * the ack that opens up a 0-sized window. 243 */ 244 #define DELAY_ACK(tp) \ 245 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 246 !(tp->t_flags & TF_RXWIN0SENT)) 247 248 #define acceptable_window_update(tp, th, tiwin) \ 249 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 250 (tp->snd_wl1 == th->th_seq && \ 251 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 252 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 253 254 static int 255 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 256 { 257 struct tseg_qent *q; 258 struct tseg_qent *p = NULL; 259 struct tseg_qent *te; 260 struct socket *so = tp->t_inpcb->inp_socket; 261 int flags; 262 263 /* 264 * Call with th == NULL after become established to 265 * force pre-ESTABLISHED data up to user socket. 266 */ 267 if (th == NULL) 268 goto present; 269 270 /* 271 * Limit the number of segments in the reassembly queue to prevent 272 * holding on to too many segments (and thus running out of mbufs). 273 * Make sure to let the missing segment through which caused this 274 * queue. Always keep one global queue entry spare to be able to 275 * process the missing segment. 276 */ 277 if (th->th_seq != tp->rcv_nxt && 278 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 279 tcp_reass_overflows++; 280 tcpstat.tcps_rcvmemdrop++; 281 m_freem(m); 282 /* no SACK block to report */ 283 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 284 return (0); 285 } 286 287 /* Allocate a new queue entry. */ 288 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 289 M_INTWAIT | M_NULLOK); 290 if (te == NULL) { 291 tcpstat.tcps_rcvmemdrop++; 292 m_freem(m); 293 /* no SACK block to report */ 294 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 295 return (0); 296 } 297 tcp_reass_qsize++; 298 299 /* 300 * Find a segment which begins after this one does. 301 */ 302 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 303 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 304 break; 305 p = q; 306 } 307 308 /* 309 * If there is a preceding segment, it may provide some of 310 * our data already. If so, drop the data from the incoming 311 * segment. If it provides all of our data, drop us. 312 */ 313 if (p != NULL) { 314 tcp_seq_diff_t i; 315 316 /* conversion to int (in i) handles seq wraparound */ 317 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 318 if (i > 0) { /* overlaps preceding segment */ 319 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 320 /* enclosing block starts w/ preceding segment */ 321 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 322 if (i >= *tlenp) { 323 /* preceding encloses incoming segment */ 324 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 325 p->tqe_len; 326 tcpstat.tcps_rcvduppack++; 327 tcpstat.tcps_rcvdupbyte += *tlenp; 328 m_freem(m); 329 kfree(te, M_TSEGQ); 330 tcp_reass_qsize--; 331 /* 332 * Try to present any queued data 333 * at the left window edge to the user. 334 * This is needed after the 3-WHS 335 * completes. 336 */ 337 goto present; /* ??? */ 338 } 339 m_adj(m, i); 340 *tlenp -= i; 341 th->th_seq += i; 342 /* incoming segment end is enclosing block end */ 343 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 344 ((th->th_flags & TH_FIN) != 0); 345 /* trim end of reported D-SACK block */ 346 tp->reportblk.rblk_end = th->th_seq; 347 } 348 } 349 tcpstat.tcps_rcvoopack++; 350 tcpstat.tcps_rcvoobyte += *tlenp; 351 352 /* 353 * While we overlap succeeding segments trim them or, 354 * if they are completely covered, dequeue them. 355 */ 356 while (q) { 357 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 358 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 359 struct tseg_qent *nq; 360 361 if (i <= 0) 362 break; 363 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 364 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 365 tp->encloseblk = tp->reportblk; 366 /* report trailing duplicate D-SACK segment */ 367 tp->reportblk.rblk_start = q->tqe_th->th_seq; 368 } 369 if ((tp->t_flags & TF_ENCLOSESEG) && 370 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 371 /* extend enclosing block if one exists */ 372 tp->encloseblk.rblk_end = qend; 373 } 374 if (i < q->tqe_len) { 375 q->tqe_th->th_seq += i; 376 q->tqe_len -= i; 377 m_adj(q->tqe_m, i); 378 break; 379 } 380 381 nq = LIST_NEXT(q, tqe_q); 382 LIST_REMOVE(q, tqe_q); 383 m_freem(q->tqe_m); 384 kfree(q, M_TSEGQ); 385 tcp_reass_qsize--; 386 q = nq; 387 } 388 389 /* Insert the new segment queue entry into place. */ 390 te->tqe_m = m; 391 te->tqe_th = th; 392 te->tqe_len = *tlenp; 393 394 /* check if can coalesce with following segment */ 395 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 396 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 397 398 te->tqe_len += q->tqe_len; 399 if (q->tqe_th->th_flags & TH_FIN) 400 te->tqe_th->th_flags |= TH_FIN; 401 m_cat(te->tqe_m, q->tqe_m); 402 tp->encloseblk.rblk_end = tend; 403 /* 404 * When not reporting a duplicate segment, use 405 * the larger enclosing block as the SACK block. 406 */ 407 if (!(tp->t_flags & TF_DUPSEG)) 408 tp->reportblk.rblk_end = tend; 409 LIST_REMOVE(q, tqe_q); 410 kfree(q, M_TSEGQ); 411 tcp_reass_qsize--; 412 } 413 414 if (p == NULL) { 415 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 416 } else { 417 /* check if can coalesce with preceding segment */ 418 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 419 p->tqe_len += te->tqe_len; 420 m_cat(p->tqe_m, te->tqe_m); 421 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 422 /* 423 * When not reporting a duplicate segment, use 424 * the larger enclosing block as the SACK block. 425 */ 426 if (!(tp->t_flags & TF_DUPSEG)) 427 tp->reportblk.rblk_start = p->tqe_th->th_seq; 428 kfree(te, M_TSEGQ); 429 tcp_reass_qsize--; 430 } else 431 LIST_INSERT_AFTER(p, te, tqe_q); 432 } 433 434 present: 435 /* 436 * Present data to user, advancing rcv_nxt through 437 * completed sequence space. 438 */ 439 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 440 return (0); 441 q = LIST_FIRST(&tp->t_segq); 442 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 443 return (0); 444 tp->rcv_nxt += q->tqe_len; 445 if (!(tp->t_flags & TF_DUPSEG)) { 446 /* no SACK block to report since ACK advanced */ 447 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 448 } 449 /* no enclosing block to report since ACK advanced */ 450 tp->t_flags &= ~TF_ENCLOSESEG; 451 flags = q->tqe_th->th_flags & TH_FIN; 452 LIST_REMOVE(q, tqe_q); 453 KASSERT(LIST_EMPTY(&tp->t_segq) || 454 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 455 ("segment not coalesced")); 456 if (so->so_state & SS_CANTRCVMORE) 457 m_freem(q->tqe_m); 458 else 459 ssb_appendstream(&so->so_rcv, q->tqe_m); 460 kfree(q, M_TSEGQ); 461 tcp_reass_qsize--; 462 ND6_HINT(tp); 463 sorwakeup(so); 464 return (flags); 465 } 466 467 /* 468 * TCP input routine, follows pages 65-76 of the 469 * protocol specification dated September, 1981 very closely. 470 */ 471 #ifdef INET6 472 int 473 tcp6_input(struct mbuf **mp, int *offp, int proto) 474 { 475 struct mbuf *m = *mp; 476 struct in6_ifaddr *ia6; 477 478 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 479 480 /* 481 * draft-itojun-ipv6-tcp-to-anycast 482 * better place to put this in? 483 */ 484 ia6 = ip6_getdstifaddr(m); 485 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 486 struct ip6_hdr *ip6; 487 488 ip6 = mtod(m, struct ip6_hdr *); 489 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 490 offsetof(struct ip6_hdr, ip6_dst)); 491 return (IPPROTO_DONE); 492 } 493 494 tcp_input(m, *offp, proto); 495 return (IPPROTO_DONE); 496 } 497 #endif 498 499 void 500 tcp_input(struct mbuf *m, ...) 501 { 502 __va_list ap; 503 int off0, proto; 504 struct tcphdr *th; 505 struct ip *ip = NULL; 506 struct ipovly *ipov; 507 struct inpcb *inp = NULL; 508 u_char *optp = NULL; 509 int optlen = 0; 510 int len, tlen, off; 511 int drop_hdrlen; 512 struct tcpcb *tp = NULL; 513 int thflags; 514 struct socket *so = 0; 515 int todrop, acked; 516 boolean_t ourfinisacked, needoutput = FALSE; 517 u_long tiwin; 518 int recvwin; 519 struct tcpopt to; /* options in this segment */ 520 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 521 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 522 struct sockaddr_in *next_hop = NULL; 523 int rstreason; /* For badport_bandlim accounting purposes */ 524 int cpu; 525 struct ip6_hdr *ip6 = NULL; 526 #ifdef INET6 527 boolean_t isipv6; 528 #else 529 const boolean_t isipv6 = FALSE; 530 #endif 531 #ifdef TCPDEBUG 532 short ostate = 0; 533 #endif 534 535 __va_start(ap, m); 536 off0 = __va_arg(ap, int); 537 proto = __va_arg(ap, int); 538 __va_end(ap); 539 540 tcpstat.tcps_rcvtotal++; 541 542 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 543 struct m_tag *mtag; 544 545 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 546 KKASSERT(mtag != NULL); 547 next_hop = m_tag_data(mtag); 548 } 549 550 #ifdef INET6 551 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 552 #endif 553 554 if (isipv6) { 555 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 556 ip6 = mtod(m, struct ip6_hdr *); 557 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 558 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 559 tcpstat.tcps_rcvbadsum++; 560 goto drop; 561 } 562 th = (struct tcphdr *)((caddr_t)ip6 + off0); 563 564 /* 565 * Be proactive about unspecified IPv6 address in source. 566 * As we use all-zero to indicate unbounded/unconnected pcb, 567 * unspecified IPv6 address can be used to confuse us. 568 * 569 * Note that packets with unspecified IPv6 destination is 570 * already dropped in ip6_input. 571 */ 572 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 573 /* XXX stat */ 574 goto drop; 575 } 576 } else { 577 /* 578 * Get IP and TCP header together in first mbuf. 579 * Note: IP leaves IP header in first mbuf. 580 */ 581 if (off0 > sizeof(struct ip)) { 582 ip_stripoptions(m); 583 off0 = sizeof(struct ip); 584 } 585 /* already checked and pulled up in ip_demux() */ 586 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 587 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 588 ip = mtod(m, struct ip *); 589 ipov = (struct ipovly *)ip; 590 th = (struct tcphdr *)((caddr_t)ip + off0); 591 tlen = ip->ip_len; 592 593 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 594 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 595 th->th_sum = m->m_pkthdr.csum_data; 596 else 597 th->th_sum = in_pseudo(ip->ip_src.s_addr, 598 ip->ip_dst.s_addr, 599 htonl(m->m_pkthdr.csum_data + 600 ip->ip_len + 601 IPPROTO_TCP)); 602 th->th_sum ^= 0xffff; 603 } else { 604 /* 605 * Checksum extended TCP header and data. 606 */ 607 len = sizeof(struct ip) + tlen; 608 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 609 ipov->ih_len = (u_short)tlen; 610 ipov->ih_len = htons(ipov->ih_len); 611 th->th_sum = in_cksum(m, len); 612 } 613 if (th->th_sum) { 614 tcpstat.tcps_rcvbadsum++; 615 goto drop; 616 } 617 #ifdef INET6 618 /* Re-initialization for later version check */ 619 ip->ip_v = IPVERSION; 620 #endif 621 } 622 623 /* 624 * Check that TCP offset makes sense, 625 * pull out TCP options and adjust length. XXX 626 */ 627 off = th->th_off << 2; 628 /* already checked and pulled up in ip_demux() */ 629 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 630 ("bad TCP data offset %d (tlen %d)", off, tlen)); 631 tlen -= off; /* tlen is used instead of ti->ti_len */ 632 if (off > sizeof(struct tcphdr)) { 633 if (isipv6) { 634 IP6_EXTHDR_CHECK(m, off0, off, ); 635 ip6 = mtod(m, struct ip6_hdr *); 636 th = (struct tcphdr *)((caddr_t)ip6 + off0); 637 } else { 638 /* already pulled up in ip_demux() */ 639 KASSERT(m->m_len >= sizeof(struct ip) + off, 640 ("TCP header and options not in one mbuf: " 641 "m_len %d, off %d", m->m_len, off)); 642 } 643 optlen = off - sizeof(struct tcphdr); 644 optp = (u_char *)(th + 1); 645 } 646 thflags = th->th_flags; 647 648 #ifdef TCP_DROP_SYNFIN 649 /* 650 * If the drop_synfin option is enabled, drop all packets with 651 * both the SYN and FIN bits set. This prevents e.g. nmap from 652 * identifying the TCP/IP stack. 653 * 654 * This is a violation of the TCP specification. 655 */ 656 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 657 goto drop; 658 #endif 659 660 /* 661 * Convert TCP protocol specific fields to host format. 662 */ 663 th->th_seq = ntohl(th->th_seq); 664 th->th_ack = ntohl(th->th_ack); 665 th->th_win = ntohs(th->th_win); 666 th->th_urp = ntohs(th->th_urp); 667 668 /* 669 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 670 * until after ip6_savecontrol() is called and before other functions 671 * which don't want those proto headers. 672 * Because ip6_savecontrol() is going to parse the mbuf to 673 * search for data to be passed up to user-land, it wants mbuf 674 * parameters to be unchanged. 675 * XXX: the call of ip6_savecontrol() has been obsoleted based on 676 * latest version of the advanced API (20020110). 677 */ 678 drop_hdrlen = off0 + off; 679 680 /* 681 * Locate pcb for segment. 682 */ 683 findpcb: 684 /* IPFIREWALL_FORWARD section */ 685 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 686 /* 687 * Transparently forwarded. Pretend to be the destination. 688 * already got one like this? 689 */ 690 cpu = mycpu->gd_cpuid; 691 inp = in_pcblookup_hash(&tcbinfo[cpu], 692 ip->ip_src, th->th_sport, 693 ip->ip_dst, th->th_dport, 694 0, m->m_pkthdr.rcvif); 695 if (!inp) { 696 /* 697 * It's new. Try to find the ambushing socket. 698 */ 699 700 /* 701 * The rest of the ipfw code stores the port in 702 * host order. XXX 703 * (The IP address is still in network order.) 704 */ 705 in_port_t dport = next_hop->sin_port ? 706 htons(next_hop->sin_port) : 707 th->th_dport; 708 709 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 710 next_hop->sin_addr.s_addr, dport); 711 inp = in_pcblookup_hash(&tcbinfo[cpu], 712 ip->ip_src, th->th_sport, 713 next_hop->sin_addr, dport, 714 1, m->m_pkthdr.rcvif); 715 } 716 } else { 717 if (isipv6) { 718 inp = in6_pcblookup_hash(&tcbinfo[0], 719 &ip6->ip6_src, th->th_sport, 720 &ip6->ip6_dst, th->th_dport, 721 1, m->m_pkthdr.rcvif); 722 } else { 723 cpu = mycpu->gd_cpuid; 724 inp = in_pcblookup_hash(&tcbinfo[cpu], 725 ip->ip_src, th->th_sport, 726 ip->ip_dst, th->th_dport, 727 1, m->m_pkthdr.rcvif); 728 } 729 } 730 731 /* 732 * If the state is CLOSED (i.e., TCB does not exist) then 733 * all data in the incoming segment is discarded. 734 * If the TCB exists but is in CLOSED state, it is embryonic, 735 * but should either do a listen or a connect soon. 736 */ 737 if (inp == NULL) { 738 if (log_in_vain) { 739 #ifdef INET6 740 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 741 #else 742 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 743 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 744 #endif 745 if (isipv6) { 746 strcpy(dbuf, "["); 747 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 748 strcat(dbuf, "]"); 749 strcpy(sbuf, "["); 750 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 751 strcat(sbuf, "]"); 752 } else { 753 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 754 strcpy(sbuf, inet_ntoa(ip->ip_src)); 755 } 756 switch (log_in_vain) { 757 case 1: 758 if (!(thflags & TH_SYN)) 759 break; 760 case 2: 761 log(LOG_INFO, 762 "Connection attempt to TCP %s:%d " 763 "from %s:%d flags:0x%02x\n", 764 dbuf, ntohs(th->th_dport), sbuf, 765 ntohs(th->th_sport), thflags); 766 break; 767 default: 768 break; 769 } 770 } 771 if (blackhole) { 772 switch (blackhole) { 773 case 1: 774 if (thflags & TH_SYN) 775 goto drop; 776 break; 777 case 2: 778 goto drop; 779 default: 780 goto drop; 781 } 782 } 783 rstreason = BANDLIM_RST_CLOSEDPORT; 784 goto dropwithreset; 785 } 786 787 #ifdef IPSEC 788 if (isipv6) { 789 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 790 ipsec6stat.in_polvio++; 791 goto drop; 792 } 793 } else { 794 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 795 ipsecstat.in_polvio++; 796 goto drop; 797 } 798 } 799 #endif 800 #ifdef FAST_IPSEC 801 if (isipv6) { 802 if (ipsec6_in_reject(m, inp)) 803 goto drop; 804 } else { 805 if (ipsec4_in_reject(m, inp)) 806 goto drop; 807 } 808 #endif 809 /* Check the minimum TTL for socket. */ 810 #ifdef INET6 811 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 812 goto drop; 813 #endif 814 815 tp = intotcpcb(inp); 816 if (tp == NULL) { 817 rstreason = BANDLIM_RST_CLOSEDPORT; 818 goto dropwithreset; 819 } 820 if (tp->t_state <= TCPS_CLOSED) 821 goto drop; 822 823 /* Unscale the window into a 32-bit value. */ 824 if (!(thflags & TH_SYN)) 825 tiwin = th->th_win << tp->snd_scale; 826 else 827 tiwin = th->th_win; 828 829 so = inp->inp_socket; 830 831 #ifdef TCPDEBUG 832 if (so->so_options & SO_DEBUG) { 833 ostate = tp->t_state; 834 if (isipv6) 835 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 836 else 837 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 838 tcp_savetcp = *th; 839 } 840 #endif 841 842 bzero(&to, sizeof to); 843 844 if (so->so_options & SO_ACCEPTCONN) { 845 struct in_conninfo inc; 846 847 #ifdef INET6 848 inc.inc_isipv6 = (isipv6 == TRUE); 849 #endif 850 if (isipv6) { 851 inc.inc6_faddr = ip6->ip6_src; 852 inc.inc6_laddr = ip6->ip6_dst; 853 inc.inc6_route.ro_rt = NULL; /* XXX */ 854 } else { 855 inc.inc_faddr = ip->ip_src; 856 inc.inc_laddr = ip->ip_dst; 857 inc.inc_route.ro_rt = NULL; /* XXX */ 858 } 859 inc.inc_fport = th->th_sport; 860 inc.inc_lport = th->th_dport; 861 862 /* 863 * If the state is LISTEN then ignore segment if it contains 864 * a RST. If the segment contains an ACK then it is bad and 865 * send a RST. If it does not contain a SYN then it is not 866 * interesting; drop it. 867 * 868 * If the state is SYN_RECEIVED (syncache) and seg contains 869 * an ACK, but not for our SYN/ACK, send a RST. If the seg 870 * contains a RST, check the sequence number to see if it 871 * is a valid reset segment. 872 */ 873 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 874 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 875 if (!syncache_expand(&inc, th, &so, m)) { 876 /* 877 * No syncache entry, or ACK was not 878 * for our SYN/ACK. Send a RST. 879 */ 880 tcpstat.tcps_badsyn++; 881 rstreason = BANDLIM_RST_OPENPORT; 882 goto dropwithreset; 883 } 884 if (so == NULL) 885 /* 886 * Could not complete 3-way handshake, 887 * connection is being closed down, and 888 * syncache will free mbuf. 889 */ 890 return; 891 /* 892 * Socket is created in state SYN_RECEIVED. 893 * Continue processing segment. 894 */ 895 inp = so->so_pcb; 896 tp = intotcpcb(inp); 897 /* 898 * This is what would have happened in 899 * tcp_output() when the SYN,ACK was sent. 900 */ 901 tp->snd_up = tp->snd_una; 902 tp->snd_max = tp->snd_nxt = tp->iss + 1; 903 tp->last_ack_sent = tp->rcv_nxt; 904 /* 905 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 906 * until the _second_ ACK is received: 907 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 908 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 909 * move to ESTAB, set snd_wnd to tiwin. 910 */ 911 tp->snd_wnd = tiwin; /* unscaled */ 912 goto after_listen; 913 } 914 if (thflags & TH_RST) { 915 syncache_chkrst(&inc, th); 916 goto drop; 917 } 918 if (thflags & TH_ACK) { 919 syncache_badack(&inc); 920 tcpstat.tcps_badsyn++; 921 rstreason = BANDLIM_RST_OPENPORT; 922 goto dropwithreset; 923 } 924 goto drop; 925 } 926 927 /* 928 * Segment's flags are (SYN) or (SYN | FIN). 929 */ 930 #ifdef INET6 931 /* 932 * If deprecated address is forbidden, 933 * we do not accept SYN to deprecated interface 934 * address to prevent any new inbound connection from 935 * getting established. 936 * When we do not accept SYN, we send a TCP RST, 937 * with deprecated source address (instead of dropping 938 * it). We compromise it as it is much better for peer 939 * to send a RST, and RST will be the final packet 940 * for the exchange. 941 * 942 * If we do not forbid deprecated addresses, we accept 943 * the SYN packet. RFC2462 does not suggest dropping 944 * SYN in this case. 945 * If we decipher RFC2462 5.5.4, it says like this: 946 * 1. use of deprecated addr with existing 947 * communication is okay - "SHOULD continue to be 948 * used" 949 * 2. use of it with new communication: 950 * (2a) "SHOULD NOT be used if alternate address 951 * with sufficient scope is available" 952 * (2b) nothing mentioned otherwise. 953 * Here we fall into (2b) case as we have no choice in 954 * our source address selection - we must obey the peer. 955 * 956 * The wording in RFC2462 is confusing, and there are 957 * multiple description text for deprecated address 958 * handling - worse, they are not exactly the same. 959 * I believe 5.5.4 is the best one, so we follow 5.5.4. 960 */ 961 if (isipv6 && !ip6_use_deprecated) { 962 struct in6_ifaddr *ia6; 963 964 if ((ia6 = ip6_getdstifaddr(m)) && 965 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 966 tp = NULL; 967 rstreason = BANDLIM_RST_OPENPORT; 968 goto dropwithreset; 969 } 970 } 971 #endif 972 /* 973 * If it is from this socket, drop it, it must be forged. 974 * Don't bother responding if the destination was a broadcast. 975 */ 976 if (th->th_dport == th->th_sport) { 977 if (isipv6) { 978 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 979 &ip6->ip6_src)) 980 goto drop; 981 } else { 982 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 983 goto drop; 984 } 985 } 986 /* 987 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 988 * 989 * Note that it is quite possible to receive unicast 990 * link-layer packets with a broadcast IP address. Use 991 * in_broadcast() to find them. 992 */ 993 if (m->m_flags & (M_BCAST | M_MCAST)) 994 goto drop; 995 if (isipv6) { 996 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 997 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 998 goto drop; 999 } else { 1000 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1001 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1002 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1003 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1004 goto drop; 1005 } 1006 /* 1007 * SYN appears to be valid; create compressed TCP state 1008 * for syncache, or perform t/tcp connection. 1009 */ 1010 if (so->so_qlen <= so->so_qlimit) { 1011 tcp_dooptions(&to, optp, optlen, TRUE); 1012 if (!syncache_add(&inc, &to, th, &so, m)) 1013 goto drop; 1014 if (so == NULL) 1015 /* 1016 * Entry added to syncache, mbuf used to 1017 * send SYN,ACK packet. 1018 */ 1019 return; 1020 /* 1021 * Segment passed TAO tests. 1022 */ 1023 inp = so->so_pcb; 1024 tp = intotcpcb(inp); 1025 tp->snd_wnd = tiwin; 1026 tp->t_starttime = ticks; 1027 tp->t_state = TCPS_ESTABLISHED; 1028 1029 /* 1030 * If there is a FIN, or if there is data and the 1031 * connection is local, then delay SYN,ACK(SYN) in 1032 * the hope of piggy-backing it on a response 1033 * segment. Otherwise must send ACK now in case 1034 * the other side is slow starting. 1035 */ 1036 if (DELAY_ACK(tp) && 1037 ((thflags & TH_FIN) || 1038 (tlen != 0 && 1039 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1040 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1041 tcp_callout_reset(tp, tp->tt_delack, 1042 tcp_delacktime, tcp_timer_delack); 1043 tp->t_flags |= TF_NEEDSYN; 1044 } else { 1045 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1046 } 1047 1048 tcpstat.tcps_connects++; 1049 soisconnected(so); 1050 goto trimthenstep6; 1051 } 1052 goto drop; 1053 } 1054 after_listen: 1055 1056 /* should not happen - syncache should pick up these connections */ 1057 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1058 1059 /* 1060 * Segment received on connection. 1061 * Reset idle time and keep-alive timer. 1062 */ 1063 tp->t_rcvtime = ticks; 1064 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 1065 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1066 tcp_timer_keep); 1067 } 1068 1069 /* 1070 * Process options. 1071 * XXX this is tradtitional behavior, may need to be cleaned up. 1072 */ 1073 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1074 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1075 if (to.to_flags & TOF_SCALE) { 1076 tp->t_flags |= TF_RCVD_SCALE; 1077 tp->requested_s_scale = to.to_requested_s_scale; 1078 } 1079 if (to.to_flags & TOF_TS) { 1080 tp->t_flags |= TF_RCVD_TSTMP; 1081 tp->ts_recent = to.to_tsval; 1082 tp->ts_recent_age = ticks; 1083 } 1084 if (to.to_flags & (TOF_CC | TOF_CCNEW)) 1085 tp->t_flags |= TF_RCVD_CC; 1086 if (to.to_flags & TOF_MSS) 1087 tcp_mss(tp, to.to_mss); 1088 /* 1089 * Only set the TF_SACK_PERMITTED per-connection flag 1090 * if we got a SACK_PERMITTED option from the other side 1091 * and the global tcp_do_sack variable is true. 1092 */ 1093 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1094 tp->t_flags |= TF_SACK_PERMITTED; 1095 } 1096 1097 /* 1098 * Header prediction: check for the two common cases 1099 * of a uni-directional data xfer. If the packet has 1100 * no control flags, is in-sequence, the window didn't 1101 * change and we're not retransmitting, it's a 1102 * candidate. If the length is zero and the ack moved 1103 * forward, we're the sender side of the xfer. Just 1104 * free the data acked & wake any higher level process 1105 * that was blocked waiting for space. If the length 1106 * is non-zero and the ack didn't move, we're the 1107 * receiver side. If we're getting packets in-order 1108 * (the reassembly queue is empty), add the data to 1109 * the socket buffer and note that we need a delayed ack. 1110 * Make sure that the hidden state-flags are also off. 1111 * Since we check for TCPS_ESTABLISHED above, it can only 1112 * be TH_NEEDSYN. 1113 */ 1114 if (tp->t_state == TCPS_ESTABLISHED && 1115 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1116 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1117 (!(to.to_flags & TOF_TS) || 1118 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1119 /* 1120 * Using the CC option is compulsory if once started: 1121 * the segment is OK if no T/TCP was negotiated or 1122 * if the segment has a CC option equal to CCrecv 1123 */ 1124 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1125 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) && 1126 th->th_seq == tp->rcv_nxt && 1127 tp->snd_nxt == tp->snd_max) { 1128 1129 /* 1130 * If last ACK falls within this segment's sequence numbers, 1131 * record the timestamp. 1132 * NOTE that the test is modified according to the latest 1133 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1134 */ 1135 if ((to.to_flags & TOF_TS) && 1136 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1137 tp->ts_recent_age = ticks; 1138 tp->ts_recent = to.to_tsval; 1139 } 1140 1141 if (tlen == 0) { 1142 if (SEQ_GT(th->th_ack, tp->snd_una) && 1143 SEQ_LEQ(th->th_ack, tp->snd_max) && 1144 tp->snd_cwnd >= tp->snd_wnd && 1145 !IN_FASTRECOVERY(tp)) { 1146 /* 1147 * This is a pure ack for outstanding data. 1148 */ 1149 ++tcpstat.tcps_predack; 1150 /* 1151 * "bad retransmit" recovery 1152 * 1153 * If Eifel detection applies, then 1154 * it is deterministic, so use it 1155 * unconditionally over the old heuristic. 1156 * Otherwise, fall back to the old heuristic. 1157 */ 1158 if (tcp_do_eifel_detect && 1159 (to.to_flags & TOF_TS) && to.to_tsecr && 1160 (tp->t_flags & TF_FIRSTACCACK)) { 1161 /* Eifel detection applicable. */ 1162 if (to.to_tsecr < tp->t_rexmtTS) { 1163 tcp_revert_congestion_state(tp); 1164 ++tcpstat.tcps_eifeldetected; 1165 } 1166 } else if (tp->t_rxtshift == 1 && 1167 ticks < tp->t_badrxtwin) { 1168 tcp_revert_congestion_state(tp); 1169 ++tcpstat.tcps_rttdetected; 1170 } 1171 tp->t_flags &= ~(TF_FIRSTACCACK | 1172 TF_FASTREXMT | TF_EARLYREXMT); 1173 /* 1174 * Recalculate the retransmit timer / rtt. 1175 * 1176 * Some machines (certain windows boxes) 1177 * send broken timestamp replies during the 1178 * SYN+ACK phase, ignore timestamps of 0. 1179 */ 1180 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1181 tcp_xmit_timer(tp, 1182 ticks - to.to_tsecr + 1); 1183 } else if (tp->t_rtttime && 1184 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1185 tcp_xmit_timer(tp, 1186 ticks - tp->t_rtttime); 1187 } 1188 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1189 acked = th->th_ack - tp->snd_una; 1190 tcpstat.tcps_rcvackpack++; 1191 tcpstat.tcps_rcvackbyte += acked; 1192 sbdrop(&so->so_snd.sb, acked); 1193 tp->snd_recover = th->th_ack - 1; 1194 tp->snd_una = th->th_ack; 1195 tp->t_dupacks = 0; 1196 /* 1197 * Update window information. 1198 */ 1199 if (tiwin != tp->snd_wnd && 1200 acceptable_window_update(tp, th, tiwin)) { 1201 /* keep track of pure window updates */ 1202 if (tp->snd_wl2 == th->th_ack && 1203 tiwin > tp->snd_wnd) 1204 tcpstat.tcps_rcvwinupd++; 1205 tp->snd_wnd = tiwin; 1206 tp->snd_wl1 = th->th_seq; 1207 tp->snd_wl2 = th->th_ack; 1208 if (tp->snd_wnd > tp->max_sndwnd) 1209 tp->max_sndwnd = tp->snd_wnd; 1210 } 1211 m_freem(m); 1212 ND6_HINT(tp); /* some progress has been done */ 1213 /* 1214 * If all outstanding data are acked, stop 1215 * retransmit timer, otherwise restart timer 1216 * using current (possibly backed-off) value. 1217 * If process is waiting for space, 1218 * wakeup/selwakeup/signal. If data 1219 * are ready to send, let tcp_output 1220 * decide between more output or persist. 1221 */ 1222 if (tp->snd_una == tp->snd_max) { 1223 tcp_callout_stop(tp, tp->tt_rexmt); 1224 } else if (!tcp_callout_active(tp, 1225 tp->tt_persist)) { 1226 tcp_callout_reset(tp, tp->tt_rexmt, 1227 tp->t_rxtcur, tcp_timer_rexmt); 1228 } 1229 sowwakeup(so); 1230 if (so->so_snd.ssb_cc > 0) 1231 tcp_output(tp); 1232 return; 1233 } 1234 } else if (tiwin == tp->snd_wnd && 1235 th->th_ack == tp->snd_una && 1236 LIST_EMPTY(&tp->t_segq) && 1237 tlen <= ssb_space(&so->so_rcv)) { 1238 /* 1239 * This is a pure, in-sequence data packet 1240 * with nothing on the reassembly queue and 1241 * we have enough buffer space to take it. 1242 */ 1243 ++tcpstat.tcps_preddat; 1244 tp->rcv_nxt += tlen; 1245 tcpstat.tcps_rcvpack++; 1246 tcpstat.tcps_rcvbyte += tlen; 1247 ND6_HINT(tp); /* some progress has been done */ 1248 /* 1249 * Add data to socket buffer. 1250 */ 1251 if (so->so_state & SS_CANTRCVMORE) { 1252 m_freem(m); 1253 } else { 1254 m_adj(m, drop_hdrlen); /* delayed header drop */ 1255 ssb_appendstream(&so->so_rcv, m); 1256 } 1257 sorwakeup(so); 1258 /* 1259 * This code is responsible for most of the ACKs 1260 * the TCP stack sends back after receiving a data 1261 * packet. Note that the DELAY_ACK check fails if 1262 * the delack timer is already running, which results 1263 * in an ack being sent every other packet (which is 1264 * what we want). 1265 * 1266 * We then further aggregate acks by not actually 1267 * sending one until the protocol thread has completed 1268 * processing the current backlog of packets. This 1269 * does not delay the ack any further, but allows us 1270 * to take advantage of the packet aggregation that 1271 * high speed NICs do (usually blocks of 8-10 packets) 1272 * to send a single ack rather then four or five acks, 1273 * greatly reducing the ack rate, the return channel 1274 * bandwidth, and the protocol overhead on both ends. 1275 * 1276 * Since this also has the effect of slowing down 1277 * the exponential slow-start ramp-up, systems with 1278 * very large bandwidth-delay products might want 1279 * to turn the feature off. 1280 */ 1281 if (DELAY_ACK(tp)) { 1282 tcp_callout_reset(tp, tp->tt_delack, 1283 tcp_delacktime, tcp_timer_delack); 1284 } else if (tcp_aggregate_acks) { 1285 tp->t_flags |= TF_ACKNOW; 1286 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1287 tp->t_flags |= TF_ONOUTPUTQ; 1288 tp->tt_cpu = mycpu->gd_cpuid; 1289 TAILQ_INSERT_TAIL( 1290 &tcpcbackq[tp->tt_cpu], 1291 tp, t_outputq); 1292 } 1293 } else { 1294 tp->t_flags |= TF_ACKNOW; 1295 tcp_output(tp); 1296 } 1297 return; 1298 } 1299 } 1300 1301 /* 1302 * Calculate amount of space in receive window, 1303 * and then do TCP input processing. 1304 * Receive window is amount of space in rcv queue, 1305 * but not less than advertised window. 1306 */ 1307 recvwin = ssb_space(&so->so_rcv); 1308 if (recvwin < 0) 1309 recvwin = 0; 1310 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1311 1312 switch (tp->t_state) { 1313 /* 1314 * If the state is SYN_RECEIVED: 1315 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1316 */ 1317 case TCPS_SYN_RECEIVED: 1318 if ((thflags & TH_ACK) && 1319 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1320 SEQ_GT(th->th_ack, tp->snd_max))) { 1321 rstreason = BANDLIM_RST_OPENPORT; 1322 goto dropwithreset; 1323 } 1324 break; 1325 1326 /* 1327 * If the state is SYN_SENT: 1328 * if seg contains an ACK, but not for our SYN, drop the input. 1329 * if seg contains a RST, then drop the connection. 1330 * if seg does not contain SYN, then drop it. 1331 * Otherwise this is an acceptable SYN segment 1332 * initialize tp->rcv_nxt and tp->irs 1333 * if seg contains ack then advance tp->snd_una 1334 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1335 * arrange for segment to be acked (eventually) 1336 * continue processing rest of data/controls, beginning with URG 1337 */ 1338 case TCPS_SYN_SENT: 1339 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1340 taop = &tao_noncached; 1341 bzero(taop, sizeof *taop); 1342 } 1343 1344 if ((thflags & TH_ACK) && 1345 (SEQ_LEQ(th->th_ack, tp->iss) || 1346 SEQ_GT(th->th_ack, tp->snd_max))) { 1347 /* 1348 * If we have a cached CCsent for the remote host, 1349 * hence we haven't just crashed and restarted, 1350 * do not send a RST. This may be a retransmission 1351 * from the other side after our earlier ACK was lost. 1352 * Our new SYN, when it arrives, will serve as the 1353 * needed ACK. 1354 */ 1355 if (taop->tao_ccsent != 0) 1356 goto drop; 1357 else { 1358 rstreason = BANDLIM_UNLIMITED; 1359 goto dropwithreset; 1360 } 1361 } 1362 if (thflags & TH_RST) { 1363 if (thflags & TH_ACK) 1364 tp = tcp_drop(tp, ECONNREFUSED); 1365 goto drop; 1366 } 1367 if (!(thflags & TH_SYN)) 1368 goto drop; 1369 tp->snd_wnd = th->th_win; /* initial send window */ 1370 tp->cc_recv = to.to_cc; /* foreign CC */ 1371 1372 tp->irs = th->th_seq; 1373 tcp_rcvseqinit(tp); 1374 if (thflags & TH_ACK) { 1375 /* 1376 * Our SYN was acked. If segment contains CC.ECHO 1377 * option, check it to make sure this segment really 1378 * matches our SYN. If not, just drop it as old 1379 * duplicate, but send an RST if we're still playing 1380 * by the old rules. If no CC.ECHO option, make sure 1381 * we don't get fooled into using T/TCP. 1382 */ 1383 if (to.to_flags & TOF_CCECHO) { 1384 if (tp->cc_send != to.to_ccecho) { 1385 if (taop->tao_ccsent != 0) 1386 goto drop; 1387 else { 1388 rstreason = BANDLIM_UNLIMITED; 1389 goto dropwithreset; 1390 } 1391 } 1392 } else 1393 tp->t_flags &= ~TF_RCVD_CC; 1394 tcpstat.tcps_connects++; 1395 soisconnected(so); 1396 /* Do window scaling on this connection? */ 1397 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1398 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1399 tp->snd_scale = tp->requested_s_scale; 1400 tp->rcv_scale = tp->request_r_scale; 1401 } 1402 /* Segment is acceptable, update cache if undefined. */ 1403 if (taop->tao_ccsent == 0) 1404 taop->tao_ccsent = to.to_ccecho; 1405 1406 tp->rcv_adv += tp->rcv_wnd; 1407 tp->snd_una++; /* SYN is acked */ 1408 tcp_callout_stop(tp, tp->tt_rexmt); 1409 /* 1410 * If there's data, delay ACK; if there's also a FIN 1411 * ACKNOW will be turned on later. 1412 */ 1413 if (DELAY_ACK(tp) && tlen != 0) { 1414 tcp_callout_reset(tp, tp->tt_delack, 1415 tcp_delacktime, tcp_timer_delack); 1416 } else { 1417 tp->t_flags |= TF_ACKNOW; 1418 } 1419 /* 1420 * Received <SYN,ACK> in SYN_SENT[*] state. 1421 * Transitions: 1422 * SYN_SENT --> ESTABLISHED 1423 * SYN_SENT* --> FIN_WAIT_1 1424 */ 1425 tp->t_starttime = ticks; 1426 if (tp->t_flags & TF_NEEDFIN) { 1427 tp->t_state = TCPS_FIN_WAIT_1; 1428 tp->t_flags &= ~TF_NEEDFIN; 1429 thflags &= ~TH_SYN; 1430 } else { 1431 tp->t_state = TCPS_ESTABLISHED; 1432 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1433 tcp_timer_keep); 1434 } 1435 } else { 1436 /* 1437 * Received initial SYN in SYN-SENT[*] state => 1438 * simultaneous open. If segment contains CC option 1439 * and there is a cached CC, apply TAO test. 1440 * If it succeeds, connection is * half-synchronized. 1441 * Otherwise, do 3-way handshake: 1442 * SYN-SENT -> SYN-RECEIVED 1443 * SYN-SENT* -> SYN-RECEIVED* 1444 * If there was no CC option, clear cached CC value. 1445 */ 1446 tp->t_flags |= TF_ACKNOW; 1447 tcp_callout_stop(tp, tp->tt_rexmt); 1448 if (to.to_flags & TOF_CC) { 1449 if (taop->tao_cc != 0 && 1450 CC_GT(to.to_cc, taop->tao_cc)) { 1451 /* 1452 * update cache and make transition: 1453 * SYN-SENT -> ESTABLISHED* 1454 * SYN-SENT* -> FIN-WAIT-1* 1455 */ 1456 taop->tao_cc = to.to_cc; 1457 tp->t_starttime = ticks; 1458 if (tp->t_flags & TF_NEEDFIN) { 1459 tp->t_state = TCPS_FIN_WAIT_1; 1460 tp->t_flags &= ~TF_NEEDFIN; 1461 } else { 1462 tp->t_state = TCPS_ESTABLISHED; 1463 tcp_callout_reset(tp, 1464 tp->tt_keep, tcp_keepidle, 1465 tcp_timer_keep); 1466 } 1467 tp->t_flags |= TF_NEEDSYN; 1468 } else 1469 tp->t_state = TCPS_SYN_RECEIVED; 1470 } else { 1471 /* CC.NEW or no option => invalidate cache */ 1472 taop->tao_cc = 0; 1473 tp->t_state = TCPS_SYN_RECEIVED; 1474 } 1475 } 1476 1477 trimthenstep6: 1478 /* 1479 * Advance th->th_seq to correspond to first data byte. 1480 * If data, trim to stay within window, 1481 * dropping FIN if necessary. 1482 */ 1483 th->th_seq++; 1484 if (tlen > tp->rcv_wnd) { 1485 todrop = tlen - tp->rcv_wnd; 1486 m_adj(m, -todrop); 1487 tlen = tp->rcv_wnd; 1488 thflags &= ~TH_FIN; 1489 tcpstat.tcps_rcvpackafterwin++; 1490 tcpstat.tcps_rcvbyteafterwin += todrop; 1491 } 1492 tp->snd_wl1 = th->th_seq - 1; 1493 tp->rcv_up = th->th_seq; 1494 /* 1495 * Client side of transaction: already sent SYN and data. 1496 * If the remote host used T/TCP to validate the SYN, 1497 * our data will be ACK'd; if so, enter normal data segment 1498 * processing in the middle of step 5, ack processing. 1499 * Otherwise, goto step 6. 1500 */ 1501 if (thflags & TH_ACK) 1502 goto process_ACK; 1503 1504 goto step6; 1505 1506 /* 1507 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1508 * if segment contains a SYN and CC [not CC.NEW] option: 1509 * if state == TIME_WAIT and connection duration > MSL, 1510 * drop packet and send RST; 1511 * 1512 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1513 * ack the FIN (and data) in retransmission queue. 1514 * Complete close and delete TCPCB. Then reprocess 1515 * segment, hoping to find new TCPCB in LISTEN state; 1516 * 1517 * else must be old SYN; drop it. 1518 * else do normal processing. 1519 */ 1520 case TCPS_LAST_ACK: 1521 case TCPS_CLOSING: 1522 case TCPS_TIME_WAIT: 1523 if ((thflags & TH_SYN) && 1524 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1525 if (tp->t_state == TCPS_TIME_WAIT && 1526 (ticks - tp->t_starttime) > tcp_msl) { 1527 rstreason = BANDLIM_UNLIMITED; 1528 goto dropwithreset; 1529 } 1530 if (CC_GT(to.to_cc, tp->cc_recv)) { 1531 tp = tcp_close(tp); 1532 goto findpcb; 1533 } 1534 else 1535 goto drop; 1536 } 1537 break; /* continue normal processing */ 1538 } 1539 1540 /* 1541 * States other than LISTEN or SYN_SENT. 1542 * First check the RST flag and sequence number since reset segments 1543 * are exempt from the timestamp and connection count tests. This 1544 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1545 * below which allowed reset segments in half the sequence space 1546 * to fall though and be processed (which gives forged reset 1547 * segments with a random sequence number a 50 percent chance of 1548 * killing a connection). 1549 * Then check timestamp, if present. 1550 * Then check the connection count, if present. 1551 * Then check that at least some bytes of segment are within 1552 * receive window. If segment begins before rcv_nxt, 1553 * drop leading data (and SYN); if nothing left, just ack. 1554 * 1555 * 1556 * If the RST bit is set, check the sequence number to see 1557 * if this is a valid reset segment. 1558 * RFC 793 page 37: 1559 * In all states except SYN-SENT, all reset (RST) segments 1560 * are validated by checking their SEQ-fields. A reset is 1561 * valid if its sequence number is in the window. 1562 * Note: this does not take into account delayed ACKs, so 1563 * we should test against last_ack_sent instead of rcv_nxt. 1564 * The sequence number in the reset segment is normally an 1565 * echo of our outgoing acknowledgement numbers, but some hosts 1566 * send a reset with the sequence number at the rightmost edge 1567 * of our receive window, and we have to handle this case. 1568 * If we have multiple segments in flight, the intial reset 1569 * segment sequence numbers will be to the left of last_ack_sent, 1570 * but they will eventually catch up. 1571 * In any case, it never made sense to trim reset segments to 1572 * fit the receive window since RFC 1122 says: 1573 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1574 * 1575 * A TCP SHOULD allow a received RST segment to include data. 1576 * 1577 * DISCUSSION 1578 * It has been suggested that a RST segment could contain 1579 * ASCII text that encoded and explained the cause of the 1580 * RST. No standard has yet been established for such 1581 * data. 1582 * 1583 * If the reset segment passes the sequence number test examine 1584 * the state: 1585 * SYN_RECEIVED STATE: 1586 * If passive open, return to LISTEN state. 1587 * If active open, inform user that connection was refused. 1588 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1589 * Inform user that connection was reset, and close tcb. 1590 * CLOSING, LAST_ACK STATES: 1591 * Close the tcb. 1592 * TIME_WAIT STATE: 1593 * Drop the segment - see Stevens, vol. 2, p. 964 and 1594 * RFC 1337. 1595 */ 1596 if (thflags & TH_RST) { 1597 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1598 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1599 switch (tp->t_state) { 1600 1601 case TCPS_SYN_RECEIVED: 1602 so->so_error = ECONNREFUSED; 1603 goto close; 1604 1605 case TCPS_ESTABLISHED: 1606 case TCPS_FIN_WAIT_1: 1607 case TCPS_FIN_WAIT_2: 1608 case TCPS_CLOSE_WAIT: 1609 so->so_error = ECONNRESET; 1610 close: 1611 tp->t_state = TCPS_CLOSED; 1612 tcpstat.tcps_drops++; 1613 tp = tcp_close(tp); 1614 break; 1615 1616 case TCPS_CLOSING: 1617 case TCPS_LAST_ACK: 1618 tp = tcp_close(tp); 1619 break; 1620 1621 case TCPS_TIME_WAIT: 1622 break; 1623 } 1624 } 1625 goto drop; 1626 } 1627 1628 /* 1629 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1630 * and it's less than ts_recent, drop it. 1631 */ 1632 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1633 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1634 1635 /* Check to see if ts_recent is over 24 days old. */ 1636 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1637 /* 1638 * Invalidate ts_recent. If this segment updates 1639 * ts_recent, the age will be reset later and ts_recent 1640 * will get a valid value. If it does not, setting 1641 * ts_recent to zero will at least satisfy the 1642 * requirement that zero be placed in the timestamp 1643 * echo reply when ts_recent isn't valid. The 1644 * age isn't reset until we get a valid ts_recent 1645 * because we don't want out-of-order segments to be 1646 * dropped when ts_recent is old. 1647 */ 1648 tp->ts_recent = 0; 1649 } else { 1650 tcpstat.tcps_rcvduppack++; 1651 tcpstat.tcps_rcvdupbyte += tlen; 1652 tcpstat.tcps_pawsdrop++; 1653 if (tlen) 1654 goto dropafterack; 1655 goto drop; 1656 } 1657 } 1658 1659 /* 1660 * T/TCP mechanism 1661 * If T/TCP was negotiated and the segment doesn't have CC, 1662 * or if its CC is wrong then drop the segment. 1663 * RST segments do not have to comply with this. 1664 */ 1665 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1666 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1667 goto dropafterack; 1668 1669 /* 1670 * In the SYN-RECEIVED state, validate that the packet belongs to 1671 * this connection before trimming the data to fit the receive 1672 * window. Check the sequence number versus IRS since we know 1673 * the sequence numbers haven't wrapped. This is a partial fix 1674 * for the "LAND" DoS attack. 1675 */ 1676 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1677 rstreason = BANDLIM_RST_OPENPORT; 1678 goto dropwithreset; 1679 } 1680 1681 todrop = tp->rcv_nxt - th->th_seq; 1682 if (todrop > 0) { 1683 if (TCP_DO_SACK(tp)) { 1684 /* Report duplicate segment at head of packet. */ 1685 tp->reportblk.rblk_start = th->th_seq; 1686 tp->reportblk.rblk_end = th->th_seq + tlen; 1687 if (thflags & TH_FIN) 1688 ++tp->reportblk.rblk_end; 1689 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1690 tp->reportblk.rblk_end = tp->rcv_nxt; 1691 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1692 } 1693 if (thflags & TH_SYN) { 1694 thflags &= ~TH_SYN; 1695 th->th_seq++; 1696 if (th->th_urp > 1) 1697 th->th_urp--; 1698 else 1699 thflags &= ~TH_URG; 1700 todrop--; 1701 } 1702 /* 1703 * Following if statement from Stevens, vol. 2, p. 960. 1704 */ 1705 if (todrop > tlen || 1706 (todrop == tlen && !(thflags & TH_FIN))) { 1707 /* 1708 * Any valid FIN must be to the left of the window. 1709 * At this point the FIN must be a duplicate or out 1710 * of sequence; drop it. 1711 */ 1712 thflags &= ~TH_FIN; 1713 1714 /* 1715 * Send an ACK to resynchronize and drop any data. 1716 * But keep on processing for RST or ACK. 1717 */ 1718 tp->t_flags |= TF_ACKNOW; 1719 todrop = tlen; 1720 tcpstat.tcps_rcvduppack++; 1721 tcpstat.tcps_rcvdupbyte += todrop; 1722 } else { 1723 tcpstat.tcps_rcvpartduppack++; 1724 tcpstat.tcps_rcvpartdupbyte += todrop; 1725 } 1726 drop_hdrlen += todrop; /* drop from the top afterwards */ 1727 th->th_seq += todrop; 1728 tlen -= todrop; 1729 if (th->th_urp > todrop) 1730 th->th_urp -= todrop; 1731 else { 1732 thflags &= ~TH_URG; 1733 th->th_urp = 0; 1734 } 1735 } 1736 1737 /* 1738 * If new data are received on a connection after the 1739 * user processes are gone, then RST the other end. 1740 */ 1741 if ((so->so_state & SS_NOFDREF) && 1742 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1743 tp = tcp_close(tp); 1744 tcpstat.tcps_rcvafterclose++; 1745 rstreason = BANDLIM_UNLIMITED; 1746 goto dropwithreset; 1747 } 1748 1749 /* 1750 * If segment ends after window, drop trailing data 1751 * (and PUSH and FIN); if nothing left, just ACK. 1752 */ 1753 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1754 if (todrop > 0) { 1755 tcpstat.tcps_rcvpackafterwin++; 1756 if (todrop >= tlen) { 1757 tcpstat.tcps_rcvbyteafterwin += tlen; 1758 /* 1759 * If a new connection request is received 1760 * while in TIME_WAIT, drop the old connection 1761 * and start over if the sequence numbers 1762 * are above the previous ones. 1763 */ 1764 if (thflags & TH_SYN && 1765 tp->t_state == TCPS_TIME_WAIT && 1766 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1767 tp = tcp_close(tp); 1768 goto findpcb; 1769 } 1770 /* 1771 * If window is closed can only take segments at 1772 * window edge, and have to drop data and PUSH from 1773 * incoming segments. Continue processing, but 1774 * remember to ack. Otherwise, drop segment 1775 * and ack. 1776 */ 1777 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1778 tp->t_flags |= TF_ACKNOW; 1779 tcpstat.tcps_rcvwinprobe++; 1780 } else 1781 goto dropafterack; 1782 } else 1783 tcpstat.tcps_rcvbyteafterwin += todrop; 1784 m_adj(m, -todrop); 1785 tlen -= todrop; 1786 thflags &= ~(TH_PUSH | TH_FIN); 1787 } 1788 1789 /* 1790 * If last ACK falls within this segment's sequence numbers, 1791 * record its timestamp. 1792 * NOTE: 1793 * 1) That the test incorporates suggestions from the latest 1794 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1795 * 2) That updating only on newer timestamps interferes with 1796 * our earlier PAWS tests, so this check should be solely 1797 * predicated on the sequence space of this segment. 1798 * 3) That we modify the segment boundary check to be 1799 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1800 * instead of RFC1323's 1801 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1802 * This modified check allows us to overcome RFC1323's 1803 * limitations as described in Stevens TCP/IP Illustrated 1804 * Vol. 2 p.869. In such cases, we can still calculate the 1805 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1806 */ 1807 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1808 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1809 + ((thflags & TH_SYN) != 0) 1810 + ((thflags & TH_FIN) != 0)))) { 1811 tp->ts_recent_age = ticks; 1812 tp->ts_recent = to.to_tsval; 1813 } 1814 1815 /* 1816 * If a SYN is in the window, then this is an 1817 * error and we send an RST and drop the connection. 1818 */ 1819 if (thflags & TH_SYN) { 1820 tp = tcp_drop(tp, ECONNRESET); 1821 rstreason = BANDLIM_UNLIMITED; 1822 goto dropwithreset; 1823 } 1824 1825 /* 1826 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1827 * flag is on (half-synchronized state), then queue data for 1828 * later processing; else drop segment and return. 1829 */ 1830 if (!(thflags & TH_ACK)) { 1831 if (tp->t_state == TCPS_SYN_RECEIVED || 1832 (tp->t_flags & TF_NEEDSYN)) 1833 goto step6; 1834 else 1835 goto drop; 1836 } 1837 1838 /* 1839 * Ack processing. 1840 */ 1841 switch (tp->t_state) { 1842 /* 1843 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1844 * ESTABLISHED state and continue processing. 1845 * The ACK was checked above. 1846 */ 1847 case TCPS_SYN_RECEIVED: 1848 1849 tcpstat.tcps_connects++; 1850 soisconnected(so); 1851 /* Do window scaling? */ 1852 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1853 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1854 tp->snd_scale = tp->requested_s_scale; 1855 tp->rcv_scale = tp->request_r_scale; 1856 } 1857 /* 1858 * Upon successful completion of 3-way handshake, 1859 * update cache.CC if it was undefined, pass any queued 1860 * data to the user, and advance state appropriately. 1861 */ 1862 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1863 taop->tao_cc == 0) 1864 taop->tao_cc = tp->cc_recv; 1865 1866 /* 1867 * Make transitions: 1868 * SYN-RECEIVED -> ESTABLISHED 1869 * SYN-RECEIVED* -> FIN-WAIT-1 1870 */ 1871 tp->t_starttime = ticks; 1872 if (tp->t_flags & TF_NEEDFIN) { 1873 tp->t_state = TCPS_FIN_WAIT_1; 1874 tp->t_flags &= ~TF_NEEDFIN; 1875 } else { 1876 tp->t_state = TCPS_ESTABLISHED; 1877 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1878 tcp_timer_keep); 1879 } 1880 /* 1881 * If segment contains data or ACK, will call tcp_reass() 1882 * later; if not, do so now to pass queued data to user. 1883 */ 1884 if (tlen == 0 && !(thflags & TH_FIN)) 1885 tcp_reass(tp, NULL, NULL, NULL); 1886 /* fall into ... */ 1887 1888 /* 1889 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1890 * ACKs. If the ack is in the range 1891 * tp->snd_una < th->th_ack <= tp->snd_max 1892 * then advance tp->snd_una to th->th_ack and drop 1893 * data from the retransmission queue. If this ACK reflects 1894 * more up to date window information we update our window information. 1895 */ 1896 case TCPS_ESTABLISHED: 1897 case TCPS_FIN_WAIT_1: 1898 case TCPS_FIN_WAIT_2: 1899 case TCPS_CLOSE_WAIT: 1900 case TCPS_CLOSING: 1901 case TCPS_LAST_ACK: 1902 case TCPS_TIME_WAIT: 1903 1904 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1905 if (TCP_DO_SACK(tp)) 1906 tcp_sack_update_scoreboard(tp, &to); 1907 if (tlen != 0 || tiwin != tp->snd_wnd) { 1908 tp->t_dupacks = 0; 1909 break; 1910 } 1911 tcpstat.tcps_rcvdupack++; 1912 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1913 th->th_ack != tp->snd_una) { 1914 tp->t_dupacks = 0; 1915 break; 1916 } 1917 /* 1918 * We have outstanding data (other than 1919 * a window probe), this is a completely 1920 * duplicate ack (ie, window info didn't 1921 * change), the ack is the biggest we've 1922 * seen and we've seen exactly our rexmt 1923 * threshhold of them, so assume a packet 1924 * has been dropped and retransmit it. 1925 * Kludge snd_nxt & the congestion 1926 * window so we send only this one 1927 * packet. 1928 */ 1929 if (IN_FASTRECOVERY(tp)) { 1930 if (TCP_DO_SACK(tp)) { 1931 /* No artifical cwnd inflation. */ 1932 tcp_sack_rexmt(tp, th); 1933 } else { 1934 /* 1935 * Dup acks mean that packets 1936 * have left the network 1937 * (they're now cached at the 1938 * receiver) so bump cwnd by 1939 * the amount in the receiver 1940 * to keep a constant cwnd 1941 * packets in the network. 1942 */ 1943 tp->snd_cwnd += tp->t_maxseg; 1944 tcp_output(tp); 1945 } 1946 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1947 tp->t_dupacks = 0; 1948 break; 1949 } else if (++tp->t_dupacks == tcprexmtthresh) { 1950 tcp_seq old_snd_nxt; 1951 u_int win; 1952 1953 fastretransmit: 1954 if (tcp_do_eifel_detect && 1955 (tp->t_flags & TF_RCVD_TSTMP)) { 1956 tcp_save_congestion_state(tp); 1957 tp->t_flags |= TF_FASTREXMT; 1958 } 1959 /* 1960 * We know we're losing at the current 1961 * window size, so do congestion avoidance: 1962 * set ssthresh to half the current window 1963 * and pull our congestion window back to the 1964 * new ssthresh. 1965 */ 1966 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1967 tp->t_maxseg; 1968 if (win < 2) 1969 win = 2; 1970 tp->snd_ssthresh = win * tp->t_maxseg; 1971 ENTER_FASTRECOVERY(tp); 1972 tp->snd_recover = tp->snd_max; 1973 tcp_callout_stop(tp, tp->tt_rexmt); 1974 tp->t_rtttime = 0; 1975 old_snd_nxt = tp->snd_nxt; 1976 tp->snd_nxt = th->th_ack; 1977 tp->snd_cwnd = tp->t_maxseg; 1978 tcp_output(tp); 1979 ++tcpstat.tcps_sndfastrexmit; 1980 tp->snd_cwnd = tp->snd_ssthresh; 1981 tp->rexmt_high = tp->snd_nxt; 1982 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1983 tp->snd_nxt = old_snd_nxt; 1984 KASSERT(tp->snd_limited <= 2, 1985 ("tp->snd_limited too big")); 1986 if (TCP_DO_SACK(tp)) 1987 tcp_sack_rexmt(tp, th); 1988 else 1989 tp->snd_cwnd += tp->t_maxseg * 1990 (tp->t_dupacks - tp->snd_limited); 1991 } else if (tcp_do_limitedtransmit) { 1992 u_long oldcwnd = tp->snd_cwnd; 1993 tcp_seq oldsndmax = tp->snd_max; 1994 tcp_seq oldsndnxt = tp->snd_nxt; 1995 /* outstanding data */ 1996 uint32_t ownd = tp->snd_max - tp->snd_una; 1997 u_int sent; 1998 1999 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2000 2001 KASSERT(tp->t_dupacks == 1 || 2002 tp->t_dupacks == 2, 2003 ("dupacks not 1 or 2")); 2004 if (tp->t_dupacks == 1) 2005 tp->snd_limited = 0; 2006 tp->snd_nxt = tp->snd_max; 2007 tp->snd_cwnd = ownd + 2008 (tp->t_dupacks - tp->snd_limited) * 2009 tp->t_maxseg; 2010 tcp_output(tp); 2011 2012 /* 2013 * Other acks may have been processed, 2014 * snd_nxt cannot be reset to a value less 2015 * then snd_una. 2016 */ 2017 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2018 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2019 tp->snd_nxt = oldsndnxt; 2020 else 2021 tp->snd_nxt = tp->snd_una; 2022 } 2023 tp->snd_cwnd = oldcwnd; 2024 sent = tp->snd_max - oldsndmax; 2025 if (sent > tp->t_maxseg) { 2026 KASSERT((tp->t_dupacks == 2 && 2027 tp->snd_limited == 0) || 2028 (sent == tp->t_maxseg + 1 && 2029 tp->t_flags & TF_SENTFIN), 2030 ("sent too much")); 2031 KASSERT(sent <= tp->t_maxseg * 2, 2032 ("sent too many segments")); 2033 tp->snd_limited = 2; 2034 tcpstat.tcps_sndlimited += 2; 2035 } else if (sent > 0) { 2036 ++tp->snd_limited; 2037 ++tcpstat.tcps_sndlimited; 2038 } else if (tcp_do_early_retransmit && 2039 (tcp_do_eifel_detect && 2040 (tp->t_flags & TF_RCVD_TSTMP)) && 2041 ownd < 4 * tp->t_maxseg && 2042 tp->t_dupacks + 1 >= 2043 iceildiv(ownd, tp->t_maxseg) && 2044 (!TCP_DO_SACK(tp) || 2045 ownd <= tp->t_maxseg || 2046 tcp_sack_has_sacked(&tp->scb, 2047 ownd - tp->t_maxseg))) { 2048 ++tcpstat.tcps_sndearlyrexmit; 2049 tp->t_flags |= TF_EARLYREXMT; 2050 goto fastretransmit; 2051 } 2052 } 2053 goto drop; 2054 } 2055 2056 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2057 tp->t_dupacks = 0; 2058 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2059 /* 2060 * Detected optimistic ACK attack. 2061 * Force slow-start to de-synchronize attack. 2062 */ 2063 tp->snd_cwnd = tp->t_maxseg; 2064 tp->snd_wacked = 0; 2065 2066 tcpstat.tcps_rcvacktoomuch++; 2067 goto dropafterack; 2068 } 2069 /* 2070 * If we reach this point, ACK is not a duplicate, 2071 * i.e., it ACKs something we sent. 2072 */ 2073 if (tp->t_flags & TF_NEEDSYN) { 2074 /* 2075 * T/TCP: Connection was half-synchronized, and our 2076 * SYN has been ACK'd (so connection is now fully 2077 * synchronized). Go to non-starred state, 2078 * increment snd_una for ACK of SYN, and check if 2079 * we can do window scaling. 2080 */ 2081 tp->t_flags &= ~TF_NEEDSYN; 2082 tp->snd_una++; 2083 /* Do window scaling? */ 2084 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2085 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2086 tp->snd_scale = tp->requested_s_scale; 2087 tp->rcv_scale = tp->request_r_scale; 2088 } 2089 } 2090 2091 process_ACK: 2092 acked = th->th_ack - tp->snd_una; 2093 tcpstat.tcps_rcvackpack++; 2094 tcpstat.tcps_rcvackbyte += acked; 2095 2096 if (tcp_do_eifel_detect && acked > 0 && 2097 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2098 (tp->t_flags & TF_FIRSTACCACK)) { 2099 /* Eifel detection applicable. */ 2100 if (to.to_tsecr < tp->t_rexmtTS) { 2101 ++tcpstat.tcps_eifeldetected; 2102 tcp_revert_congestion_state(tp); 2103 if (tp->t_rxtshift == 1 && 2104 ticks >= tp->t_badrxtwin) 2105 ++tcpstat.tcps_rttcantdetect; 2106 } 2107 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2108 /* 2109 * If we just performed our first retransmit, 2110 * and the ACK arrives within our recovery window, 2111 * then it was a mistake to do the retransmit 2112 * in the first place. Recover our original cwnd 2113 * and ssthresh, and proceed to transmit where we 2114 * left off. 2115 */ 2116 tcp_revert_congestion_state(tp); 2117 ++tcpstat.tcps_rttdetected; 2118 } 2119 2120 /* 2121 * If we have a timestamp reply, update smoothed 2122 * round trip time. If no timestamp is present but 2123 * transmit timer is running and timed sequence 2124 * number was acked, update smoothed round trip time. 2125 * Since we now have an rtt measurement, cancel the 2126 * timer backoff (cf., Phil Karn's retransmit alg.). 2127 * Recompute the initial retransmit timer. 2128 * 2129 * Some machines (certain windows boxes) send broken 2130 * timestamp replies during the SYN+ACK phase, ignore 2131 * timestamps of 0. 2132 */ 2133 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2134 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2135 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2136 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2137 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2138 2139 /* 2140 * If no data (only SYN) was ACK'd, 2141 * skip rest of ACK processing. 2142 */ 2143 if (acked == 0) 2144 goto step6; 2145 2146 /* Stop looking for an acceptable ACK since one was received. */ 2147 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2148 2149 if (acked > so->so_snd.ssb_cc) { 2150 tp->snd_wnd -= so->so_snd.ssb_cc; 2151 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2152 ourfinisacked = TRUE; 2153 } else { 2154 sbdrop(&so->so_snd.sb, acked); 2155 tp->snd_wnd -= acked; 2156 ourfinisacked = FALSE; 2157 } 2158 sowwakeup(so); 2159 2160 /* 2161 * Update window information. 2162 * Don't look at window if no ACK: 2163 * TAC's send garbage on first SYN. 2164 */ 2165 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2166 (tp->snd_wl1 == th->th_seq && 2167 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2168 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2169 /* keep track of pure window updates */ 2170 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2171 tiwin > tp->snd_wnd) 2172 tcpstat.tcps_rcvwinupd++; 2173 tp->snd_wnd = tiwin; 2174 tp->snd_wl1 = th->th_seq; 2175 tp->snd_wl2 = th->th_ack; 2176 if (tp->snd_wnd > tp->max_sndwnd) 2177 tp->max_sndwnd = tp->snd_wnd; 2178 needoutput = TRUE; 2179 } 2180 2181 tp->snd_una = th->th_ack; 2182 if (TCP_DO_SACK(tp)) 2183 tcp_sack_update_scoreboard(tp, &to); 2184 if (IN_FASTRECOVERY(tp)) { 2185 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2186 EXIT_FASTRECOVERY(tp); 2187 needoutput = TRUE; 2188 /* 2189 * If the congestion window was inflated 2190 * to account for the other side's 2191 * cached packets, retract it. 2192 */ 2193 if (!TCP_DO_SACK(tp)) 2194 tp->snd_cwnd = tp->snd_ssthresh; 2195 2196 /* 2197 * Window inflation should have left us 2198 * with approximately snd_ssthresh outstanding 2199 * data. But, in case we would be inclined 2200 * to send a burst, better do it using 2201 * slow start. 2202 */ 2203 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2204 tp->snd_max + 2 * tp->t_maxseg)) 2205 tp->snd_cwnd = 2206 (tp->snd_max - tp->snd_una) + 2207 2 * tp->t_maxseg; 2208 2209 tp->snd_wacked = 0; 2210 } else { 2211 if (TCP_DO_SACK(tp)) { 2212 tp->snd_max_rexmt = tp->snd_max; 2213 tcp_sack_rexmt(tp, th); 2214 } else { 2215 tcp_newreno_partial_ack(tp, th, acked); 2216 } 2217 needoutput = FALSE; 2218 } 2219 } else { 2220 /* 2221 * Open the congestion window. When in slow-start, 2222 * open exponentially: maxseg per packet. Otherwise, 2223 * open linearly: maxseg per window. 2224 */ 2225 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2226 u_int abc_sslimit = 2227 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2228 tp->t_maxseg : 2 * tp->t_maxseg); 2229 2230 /* slow-start */ 2231 tp->snd_cwnd += tcp_do_abc ? 2232 min(acked, abc_sslimit) : tp->t_maxseg; 2233 } else { 2234 /* linear increase */ 2235 tp->snd_wacked += tcp_do_abc ? acked : 2236 tp->t_maxseg; 2237 if (tp->snd_wacked >= tp->snd_cwnd) { 2238 tp->snd_wacked -= tp->snd_cwnd; 2239 tp->snd_cwnd += tp->t_maxseg; 2240 } 2241 } 2242 tp->snd_cwnd = min(tp->snd_cwnd, 2243 TCP_MAXWIN << tp->snd_scale); 2244 tp->snd_recover = th->th_ack - 1; 2245 } 2246 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2247 tp->snd_nxt = tp->snd_una; 2248 2249 /* 2250 * If all outstanding data is acked, stop retransmit 2251 * timer and remember to restart (more output or persist). 2252 * If there is more data to be acked, restart retransmit 2253 * timer, using current (possibly backed-off) value. 2254 */ 2255 if (th->th_ack == tp->snd_max) { 2256 tcp_callout_stop(tp, tp->tt_rexmt); 2257 needoutput = TRUE; 2258 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2259 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2260 tcp_timer_rexmt); 2261 } 2262 2263 switch (tp->t_state) { 2264 /* 2265 * In FIN_WAIT_1 STATE in addition to the processing 2266 * for the ESTABLISHED state if our FIN is now acknowledged 2267 * then enter FIN_WAIT_2. 2268 */ 2269 case TCPS_FIN_WAIT_1: 2270 if (ourfinisacked) { 2271 /* 2272 * If we can't receive any more 2273 * data, then closing user can proceed. 2274 * Starting the timer is contrary to the 2275 * specification, but if we don't get a FIN 2276 * we'll hang forever. 2277 */ 2278 if (so->so_state & SS_CANTRCVMORE) { 2279 soisdisconnected(so); 2280 tcp_callout_reset(tp, tp->tt_2msl, 2281 tcp_maxidle, tcp_timer_2msl); 2282 } 2283 tp->t_state = TCPS_FIN_WAIT_2; 2284 } 2285 break; 2286 2287 /* 2288 * In CLOSING STATE in addition to the processing for 2289 * the ESTABLISHED state if the ACK acknowledges our FIN 2290 * then enter the TIME-WAIT state, otherwise ignore 2291 * the segment. 2292 */ 2293 case TCPS_CLOSING: 2294 if (ourfinisacked) { 2295 tp->t_state = TCPS_TIME_WAIT; 2296 tcp_canceltimers(tp); 2297 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2298 if (tp->cc_recv != 0 && 2299 (ticks - tp->t_starttime) < tcp_msl) { 2300 tcp_callout_reset(tp, tp->tt_2msl, 2301 tp->t_rxtcur * TCPTV_TWTRUNC, 2302 tcp_timer_2msl); 2303 } else { 2304 tcp_callout_reset(tp, tp->tt_2msl, 2305 2 * tcp_msl, tcp_timer_2msl); 2306 } 2307 soisdisconnected(so); 2308 } 2309 break; 2310 2311 /* 2312 * In LAST_ACK, we may still be waiting for data to drain 2313 * and/or to be acked, as well as for the ack of our FIN. 2314 * If our FIN is now acknowledged, delete the TCB, 2315 * enter the closed state and return. 2316 */ 2317 case TCPS_LAST_ACK: 2318 if (ourfinisacked) { 2319 tp = tcp_close(tp); 2320 goto drop; 2321 } 2322 break; 2323 2324 /* 2325 * In TIME_WAIT state the only thing that should arrive 2326 * is a retransmission of the remote FIN. Acknowledge 2327 * it and restart the finack timer. 2328 */ 2329 case TCPS_TIME_WAIT: 2330 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2331 tcp_timer_2msl); 2332 goto dropafterack; 2333 } 2334 } 2335 2336 step6: 2337 /* 2338 * Update window information. 2339 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2340 */ 2341 if ((thflags & TH_ACK) && 2342 acceptable_window_update(tp, th, tiwin)) { 2343 /* keep track of pure window updates */ 2344 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2345 tiwin > tp->snd_wnd) 2346 tcpstat.tcps_rcvwinupd++; 2347 tp->snd_wnd = tiwin; 2348 tp->snd_wl1 = th->th_seq; 2349 tp->snd_wl2 = th->th_ack; 2350 if (tp->snd_wnd > tp->max_sndwnd) 2351 tp->max_sndwnd = tp->snd_wnd; 2352 needoutput = TRUE; 2353 } 2354 2355 /* 2356 * Process segments with URG. 2357 */ 2358 if ((thflags & TH_URG) && th->th_urp && 2359 !TCPS_HAVERCVDFIN(tp->t_state)) { 2360 /* 2361 * This is a kludge, but if we receive and accept 2362 * random urgent pointers, we'll crash in 2363 * soreceive. It's hard to imagine someone 2364 * actually wanting to send this much urgent data. 2365 */ 2366 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2367 th->th_urp = 0; /* XXX */ 2368 thflags &= ~TH_URG; /* XXX */ 2369 goto dodata; /* XXX */ 2370 } 2371 /* 2372 * If this segment advances the known urgent pointer, 2373 * then mark the data stream. This should not happen 2374 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2375 * a FIN has been received from the remote side. 2376 * In these states we ignore the URG. 2377 * 2378 * According to RFC961 (Assigned Protocols), 2379 * the urgent pointer points to the last octet 2380 * of urgent data. We continue, however, 2381 * to consider it to indicate the first octet 2382 * of data past the urgent section as the original 2383 * spec states (in one of two places). 2384 */ 2385 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2386 tp->rcv_up = th->th_seq + th->th_urp; 2387 so->so_oobmark = so->so_rcv.ssb_cc + 2388 (tp->rcv_up - tp->rcv_nxt) - 1; 2389 if (so->so_oobmark == 0) 2390 so->so_state |= SS_RCVATMARK; 2391 sohasoutofband(so); 2392 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2393 } 2394 /* 2395 * Remove out of band data so doesn't get presented to user. 2396 * This can happen independent of advancing the URG pointer, 2397 * but if two URG's are pending at once, some out-of-band 2398 * data may creep in... ick. 2399 */ 2400 if (th->th_urp <= (u_long)tlen && 2401 !(so->so_options & SO_OOBINLINE)) { 2402 /* hdr drop is delayed */ 2403 tcp_pulloutofband(so, th, m, drop_hdrlen); 2404 } 2405 } else { 2406 /* 2407 * If no out of band data is expected, 2408 * pull receive urgent pointer along 2409 * with the receive window. 2410 */ 2411 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2412 tp->rcv_up = tp->rcv_nxt; 2413 } 2414 2415 dodata: /* XXX */ 2416 /* 2417 * Process the segment text, merging it into the TCP sequencing queue, 2418 * and arranging for acknowledgment of receipt if necessary. 2419 * This process logically involves adjusting tp->rcv_wnd as data 2420 * is presented to the user (this happens in tcp_usrreq.c, 2421 * case PRU_RCVD). If a FIN has already been received on this 2422 * connection then we just ignore the text. 2423 */ 2424 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2425 m_adj(m, drop_hdrlen); /* delayed header drop */ 2426 /* 2427 * Insert segment which includes th into TCP reassembly queue 2428 * with control block tp. Set thflags to whether reassembly now 2429 * includes a segment with FIN. This handles the common case 2430 * inline (segment is the next to be received on an established 2431 * connection, and the queue is empty), avoiding linkage into 2432 * and removal from the queue and repetition of various 2433 * conversions. 2434 * Set DELACK for segments received in order, but ack 2435 * immediately when segments are out of order (so 2436 * fast retransmit can work). 2437 */ 2438 if (th->th_seq == tp->rcv_nxt && 2439 LIST_EMPTY(&tp->t_segq) && 2440 TCPS_HAVEESTABLISHED(tp->t_state)) { 2441 if (DELAY_ACK(tp)) { 2442 tcp_callout_reset(tp, tp->tt_delack, 2443 tcp_delacktime, tcp_timer_delack); 2444 } else { 2445 tp->t_flags |= TF_ACKNOW; 2446 } 2447 tp->rcv_nxt += tlen; 2448 thflags = th->th_flags & TH_FIN; 2449 tcpstat.tcps_rcvpack++; 2450 tcpstat.tcps_rcvbyte += tlen; 2451 ND6_HINT(tp); 2452 if (so->so_state & SS_CANTRCVMORE) 2453 m_freem(m); 2454 else 2455 ssb_appendstream(&so->so_rcv, m); 2456 sorwakeup(so); 2457 } else { 2458 if (!(tp->t_flags & TF_DUPSEG)) { 2459 /* Initialize SACK report block. */ 2460 tp->reportblk.rblk_start = th->th_seq; 2461 tp->reportblk.rblk_end = th->th_seq + tlen + 2462 ((thflags & TH_FIN) != 0); 2463 } 2464 thflags = tcp_reass(tp, th, &tlen, m); 2465 tp->t_flags |= TF_ACKNOW; 2466 } 2467 2468 /* 2469 * Note the amount of data that peer has sent into 2470 * our window, in order to estimate the sender's 2471 * buffer size. 2472 */ 2473 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2474 } else { 2475 m_freem(m); 2476 thflags &= ~TH_FIN; 2477 } 2478 2479 /* 2480 * If FIN is received ACK the FIN and let the user know 2481 * that the connection is closing. 2482 */ 2483 if (thflags & TH_FIN) { 2484 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2485 socantrcvmore(so); 2486 /* 2487 * If connection is half-synchronized 2488 * (ie NEEDSYN flag on) then delay ACK, 2489 * so it may be piggybacked when SYN is sent. 2490 * Otherwise, since we received a FIN then no 2491 * more input can be expected, send ACK now. 2492 */ 2493 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2494 tcp_callout_reset(tp, tp->tt_delack, 2495 tcp_delacktime, tcp_timer_delack); 2496 } else { 2497 tp->t_flags |= TF_ACKNOW; 2498 } 2499 tp->rcv_nxt++; 2500 } 2501 2502 switch (tp->t_state) { 2503 /* 2504 * In SYN_RECEIVED and ESTABLISHED STATES 2505 * enter the CLOSE_WAIT state. 2506 */ 2507 case TCPS_SYN_RECEIVED: 2508 tp->t_starttime = ticks; 2509 /*FALLTHROUGH*/ 2510 case TCPS_ESTABLISHED: 2511 tp->t_state = TCPS_CLOSE_WAIT; 2512 break; 2513 2514 /* 2515 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2516 * enter the CLOSING state. 2517 */ 2518 case TCPS_FIN_WAIT_1: 2519 tp->t_state = TCPS_CLOSING; 2520 break; 2521 2522 /* 2523 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2524 * starting the time-wait timer, turning off the other 2525 * standard timers. 2526 */ 2527 case TCPS_FIN_WAIT_2: 2528 tp->t_state = TCPS_TIME_WAIT; 2529 tcp_canceltimers(tp); 2530 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2531 if (tp->cc_recv != 0 && 2532 (ticks - tp->t_starttime) < tcp_msl) { 2533 tcp_callout_reset(tp, tp->tt_2msl, 2534 tp->t_rxtcur * TCPTV_TWTRUNC, 2535 tcp_timer_2msl); 2536 /* For transaction client, force ACK now. */ 2537 tp->t_flags |= TF_ACKNOW; 2538 } else { 2539 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2540 tcp_timer_2msl); 2541 } 2542 soisdisconnected(so); 2543 break; 2544 2545 /* 2546 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2547 */ 2548 case TCPS_TIME_WAIT: 2549 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2550 tcp_timer_2msl); 2551 break; 2552 } 2553 } 2554 2555 #ifdef TCPDEBUG 2556 if (so->so_options & SO_DEBUG) 2557 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2558 #endif 2559 2560 /* 2561 * Return any desired output. 2562 */ 2563 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2564 tcp_output(tp); 2565 return; 2566 2567 dropafterack: 2568 /* 2569 * Generate an ACK dropping incoming segment if it occupies 2570 * sequence space, where the ACK reflects our state. 2571 * 2572 * We can now skip the test for the RST flag since all 2573 * paths to this code happen after packets containing 2574 * RST have been dropped. 2575 * 2576 * In the SYN-RECEIVED state, don't send an ACK unless the 2577 * segment we received passes the SYN-RECEIVED ACK test. 2578 * If it fails send a RST. This breaks the loop in the 2579 * "LAND" DoS attack, and also prevents an ACK storm 2580 * between two listening ports that have been sent forged 2581 * SYN segments, each with the source address of the other. 2582 */ 2583 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2584 (SEQ_GT(tp->snd_una, th->th_ack) || 2585 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2586 rstreason = BANDLIM_RST_OPENPORT; 2587 goto dropwithreset; 2588 } 2589 #ifdef TCPDEBUG 2590 if (so->so_options & SO_DEBUG) 2591 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2592 #endif 2593 m_freem(m); 2594 tp->t_flags |= TF_ACKNOW; 2595 tcp_output(tp); 2596 return; 2597 2598 dropwithreset: 2599 /* 2600 * Generate a RST, dropping incoming segment. 2601 * Make ACK acceptable to originator of segment. 2602 * Don't bother to respond if destination was broadcast/multicast. 2603 */ 2604 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2605 goto drop; 2606 if (isipv6) { 2607 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2608 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2609 goto drop; 2610 } else { 2611 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2612 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2613 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2614 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2615 goto drop; 2616 } 2617 /* IPv6 anycast check is done at tcp6_input() */ 2618 2619 /* 2620 * Perform bandwidth limiting. 2621 */ 2622 #ifdef ICMP_BANDLIM 2623 if (badport_bandlim(rstreason) < 0) 2624 goto drop; 2625 #endif 2626 2627 #ifdef TCPDEBUG 2628 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2629 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2630 #endif 2631 if (thflags & TH_ACK) 2632 /* mtod() below is safe as long as hdr dropping is delayed */ 2633 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2634 TH_RST); 2635 else { 2636 if (thflags & TH_SYN) 2637 tlen++; 2638 /* mtod() below is safe as long as hdr dropping is delayed */ 2639 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2640 (tcp_seq)0, TH_RST | TH_ACK); 2641 } 2642 return; 2643 2644 drop: 2645 /* 2646 * Drop space held by incoming segment and return. 2647 */ 2648 #ifdef TCPDEBUG 2649 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2650 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2651 #endif 2652 m_freem(m); 2653 return; 2654 } 2655 2656 /* 2657 * Parse TCP options and place in tcpopt. 2658 */ 2659 static void 2660 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2661 { 2662 int opt, optlen, i; 2663 2664 to->to_flags = 0; 2665 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2666 opt = cp[0]; 2667 if (opt == TCPOPT_EOL) 2668 break; 2669 if (opt == TCPOPT_NOP) 2670 optlen = 1; 2671 else { 2672 if (cnt < 2) 2673 break; 2674 optlen = cp[1]; 2675 if (optlen < 2 || optlen > cnt) 2676 break; 2677 } 2678 switch (opt) { 2679 case TCPOPT_MAXSEG: 2680 if (optlen != TCPOLEN_MAXSEG) 2681 continue; 2682 if (!is_syn) 2683 continue; 2684 to->to_flags |= TOF_MSS; 2685 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2686 to->to_mss = ntohs(to->to_mss); 2687 break; 2688 case TCPOPT_WINDOW: 2689 if (optlen != TCPOLEN_WINDOW) 2690 continue; 2691 if (!is_syn) 2692 continue; 2693 to->to_flags |= TOF_SCALE; 2694 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2695 break; 2696 case TCPOPT_TIMESTAMP: 2697 if (optlen != TCPOLEN_TIMESTAMP) 2698 continue; 2699 to->to_flags |= TOF_TS; 2700 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2701 to->to_tsval = ntohl(to->to_tsval); 2702 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2703 to->to_tsecr = ntohl(to->to_tsecr); 2704 /* 2705 * If echoed timestamp is later than the current time, 2706 * fall back to non RFC1323 RTT calculation. 2707 */ 2708 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2709 to->to_tsecr = 0; 2710 break; 2711 case TCPOPT_CC: 2712 if (optlen != TCPOLEN_CC) 2713 continue; 2714 to->to_flags |= TOF_CC; 2715 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2716 to->to_cc = ntohl(to->to_cc); 2717 break; 2718 case TCPOPT_CCNEW: 2719 if (optlen != TCPOLEN_CC) 2720 continue; 2721 if (!is_syn) 2722 continue; 2723 to->to_flags |= TOF_CCNEW; 2724 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2725 to->to_cc = ntohl(to->to_cc); 2726 break; 2727 case TCPOPT_CCECHO: 2728 if (optlen != TCPOLEN_CC) 2729 continue; 2730 if (!is_syn) 2731 continue; 2732 to->to_flags |= TOF_CCECHO; 2733 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho); 2734 to->to_ccecho = ntohl(to->to_ccecho); 2735 break; 2736 case TCPOPT_SACK_PERMITTED: 2737 if (optlen != TCPOLEN_SACK_PERMITTED) 2738 continue; 2739 if (!is_syn) 2740 continue; 2741 to->to_flags |= TOF_SACK_PERMITTED; 2742 break; 2743 case TCPOPT_SACK: 2744 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2745 continue; 2746 to->to_nsackblocks = (optlen - 2) / 8; 2747 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2748 to->to_flags |= TOF_SACK; 2749 for (i = 0; i < to->to_nsackblocks; i++) { 2750 struct raw_sackblock *r = &to->to_sackblocks[i]; 2751 2752 r->rblk_start = ntohl(r->rblk_start); 2753 r->rblk_end = ntohl(r->rblk_end); 2754 } 2755 break; 2756 default: 2757 continue; 2758 } 2759 } 2760 } 2761 2762 /* 2763 * Pull out of band byte out of a segment so 2764 * it doesn't appear in the user's data queue. 2765 * It is still reflected in the segment length for 2766 * sequencing purposes. 2767 * "off" is the delayed to be dropped hdrlen. 2768 */ 2769 static void 2770 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2771 { 2772 int cnt = off + th->th_urp - 1; 2773 2774 while (cnt >= 0) { 2775 if (m->m_len > cnt) { 2776 char *cp = mtod(m, caddr_t) + cnt; 2777 struct tcpcb *tp = sototcpcb(so); 2778 2779 tp->t_iobc = *cp; 2780 tp->t_oobflags |= TCPOOB_HAVEDATA; 2781 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2782 m->m_len--; 2783 if (m->m_flags & M_PKTHDR) 2784 m->m_pkthdr.len--; 2785 return; 2786 } 2787 cnt -= m->m_len; 2788 m = m->m_next; 2789 if (m == 0) 2790 break; 2791 } 2792 panic("tcp_pulloutofband"); 2793 } 2794 2795 /* 2796 * Collect new round-trip time estimate 2797 * and update averages and current timeout. 2798 */ 2799 static void 2800 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2801 { 2802 int delta; 2803 2804 tcpstat.tcps_rttupdated++; 2805 tp->t_rttupdated++; 2806 if (tp->t_srtt != 0) { 2807 /* 2808 * srtt is stored as fixed point with 5 bits after the 2809 * binary point (i.e., scaled by 8). The following magic 2810 * is equivalent to the smoothing algorithm in rfc793 with 2811 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2812 * point). Adjust rtt to origin 0. 2813 */ 2814 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2815 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2816 2817 if ((tp->t_srtt += delta) <= 0) 2818 tp->t_srtt = 1; 2819 2820 /* 2821 * We accumulate a smoothed rtt variance (actually, a 2822 * smoothed mean difference), then set the retransmit 2823 * timer to smoothed rtt + 4 times the smoothed variance. 2824 * rttvar is stored as fixed point with 4 bits after the 2825 * binary point (scaled by 16). The following is 2826 * equivalent to rfc793 smoothing with an alpha of .75 2827 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2828 * rfc793's wired-in beta. 2829 */ 2830 if (delta < 0) 2831 delta = -delta; 2832 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2833 if ((tp->t_rttvar += delta) <= 0) 2834 tp->t_rttvar = 1; 2835 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2836 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2837 } else { 2838 /* 2839 * No rtt measurement yet - use the unsmoothed rtt. 2840 * Set the variance to half the rtt (so our first 2841 * retransmit happens at 3*rtt). 2842 */ 2843 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2844 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2845 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2846 } 2847 tp->t_rtttime = 0; 2848 tp->t_rxtshift = 0; 2849 2850 /* 2851 * the retransmit should happen at rtt + 4 * rttvar. 2852 * Because of the way we do the smoothing, srtt and rttvar 2853 * will each average +1/2 tick of bias. When we compute 2854 * the retransmit timer, we want 1/2 tick of rounding and 2855 * 1 extra tick because of +-1/2 tick uncertainty in the 2856 * firing of the timer. The bias will give us exactly the 2857 * 1.5 tick we need. But, because the bias is 2858 * statistical, we have to test that we don't drop below 2859 * the minimum feasible timer (which is 2 ticks). 2860 */ 2861 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2862 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2863 2864 /* 2865 * We received an ack for a packet that wasn't retransmitted; 2866 * it is probably safe to discard any error indications we've 2867 * received recently. This isn't quite right, but close enough 2868 * for now (a route might have failed after we sent a segment, 2869 * and the return path might not be symmetrical). 2870 */ 2871 tp->t_softerror = 0; 2872 } 2873 2874 /* 2875 * Determine a reasonable value for maxseg size. 2876 * If the route is known, check route for mtu. 2877 * If none, use an mss that can be handled on the outgoing 2878 * interface without forcing IP to fragment; if bigger than 2879 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2880 * to utilize large mbufs. If no route is found, route has no mtu, 2881 * or the destination isn't local, use a default, hopefully conservative 2882 * size (usually 512 or the default IP max size, but no more than the mtu 2883 * of the interface), as we can't discover anything about intervening 2884 * gateways or networks. We also initialize the congestion/slow start 2885 * window to be a single segment if the destination isn't local. 2886 * While looking at the routing entry, we also initialize other path-dependent 2887 * parameters from pre-set or cached values in the routing entry. 2888 * 2889 * Also take into account the space needed for options that we 2890 * send regularly. Make maxseg shorter by that amount to assure 2891 * that we can send maxseg amount of data even when the options 2892 * are present. Store the upper limit of the length of options plus 2893 * data in maxopd. 2894 * 2895 * NOTE that this routine is only called when we process an incoming 2896 * segment, for outgoing segments only tcp_mssopt is called. 2897 * 2898 * In case of T/TCP, we call this routine during implicit connection 2899 * setup as well (offer = -1), to initialize maxseg from the cached 2900 * MSS of our peer. 2901 */ 2902 void 2903 tcp_mss(struct tcpcb *tp, int offer) 2904 { 2905 struct rtentry *rt; 2906 struct ifnet *ifp; 2907 int rtt, mss; 2908 u_long bufsize; 2909 struct inpcb *inp = tp->t_inpcb; 2910 struct socket *so; 2911 struct rmxp_tao *taop; 2912 int origoffer = offer; 2913 #ifdef INET6 2914 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2915 size_t min_protoh = isipv6 ? 2916 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2917 sizeof(struct tcpiphdr); 2918 #else 2919 const boolean_t isipv6 = FALSE; 2920 const size_t min_protoh = sizeof(struct tcpiphdr); 2921 #endif 2922 2923 if (isipv6) 2924 rt = tcp_rtlookup6(&inp->inp_inc); 2925 else 2926 rt = tcp_rtlookup(&inp->inp_inc); 2927 if (rt == NULL) { 2928 tp->t_maxopd = tp->t_maxseg = 2929 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2930 return; 2931 } 2932 ifp = rt->rt_ifp; 2933 so = inp->inp_socket; 2934 2935 taop = rmx_taop(rt->rt_rmx); 2936 /* 2937 * Offer == -1 means that we didn't receive SYN yet, 2938 * use cached value in that case; 2939 */ 2940 if (offer == -1) 2941 offer = taop->tao_mssopt; 2942 /* 2943 * Offer == 0 means that there was no MSS on the SYN segment, 2944 * in this case we use tcp_mssdflt. 2945 */ 2946 if (offer == 0) 2947 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2948 else 2949 /* 2950 * Sanity check: make sure that maxopd will be large 2951 * enough to allow some data on segments even is the 2952 * all the option space is used (40bytes). Otherwise 2953 * funny things may happen in tcp_output. 2954 */ 2955 offer = max(offer, 64); 2956 taop->tao_mssopt = offer; 2957 2958 /* 2959 * While we're here, check if there's an initial rtt 2960 * or rttvar. Convert from the route-table units 2961 * to scaled multiples of the slow timeout timer. 2962 */ 2963 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2964 /* 2965 * XXX the lock bit for RTT indicates that the value 2966 * is also a minimum value; this is subject to time. 2967 */ 2968 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2969 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2970 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2971 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2972 tcpstat.tcps_usedrtt++; 2973 if (rt->rt_rmx.rmx_rttvar) { 2974 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2975 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2976 tcpstat.tcps_usedrttvar++; 2977 } else { 2978 /* default variation is +- 1 rtt */ 2979 tp->t_rttvar = 2980 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2981 } 2982 TCPT_RANGESET(tp->t_rxtcur, 2983 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2984 tp->t_rttmin, TCPTV_REXMTMAX); 2985 } 2986 /* 2987 * if there's an mtu associated with the route, use it 2988 * else, use the link mtu. 2989 */ 2990 if (rt->rt_rmx.rmx_mtu) 2991 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2992 else { 2993 if (isipv6) { 2994 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2995 if (!in6_localaddr(&inp->in6p_faddr)) 2996 mss = min(mss, tcp_v6mssdflt); 2997 } else { 2998 mss = ifp->if_mtu - min_protoh; 2999 if (!in_localaddr(inp->inp_faddr)) 3000 mss = min(mss, tcp_mssdflt); 3001 } 3002 } 3003 mss = min(mss, offer); 3004 /* 3005 * maxopd stores the maximum length of data AND options 3006 * in a segment; maxseg is the amount of data in a normal 3007 * segment. We need to store this value (maxopd) apart 3008 * from maxseg, because now every segment carries options 3009 * and thus we normally have somewhat less data in segments. 3010 */ 3011 tp->t_maxopd = mss; 3012 3013 /* 3014 * In case of T/TCP, origoffer==-1 indicates, that no segments 3015 * were received yet. In this case we just guess, otherwise 3016 * we do the same as before T/TCP. 3017 */ 3018 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3019 (origoffer == -1 || 3020 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3021 mss -= TCPOLEN_TSTAMP_APPA; 3022 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 3023 (origoffer == -1 || 3024 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3025 mss -= TCPOLEN_CC_APPA; 3026 3027 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3028 if (mss > MCLBYTES) 3029 mss &= ~(MCLBYTES-1); 3030 #else 3031 if (mss > MCLBYTES) 3032 mss = mss / MCLBYTES * MCLBYTES; 3033 #endif 3034 /* 3035 * If there's a pipesize, change the socket buffer 3036 * to that size. Make the socket buffers an integral 3037 * number of mss units; if the mss is larger than 3038 * the socket buffer, decrease the mss. 3039 */ 3040 #ifdef RTV_SPIPE 3041 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3042 #endif 3043 bufsize = so->so_snd.ssb_hiwat; 3044 if (bufsize < mss) 3045 mss = bufsize; 3046 else { 3047 bufsize = roundup(bufsize, mss); 3048 if (bufsize > sb_max) 3049 bufsize = sb_max; 3050 if (bufsize > so->so_snd.ssb_hiwat) 3051 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3052 } 3053 tp->t_maxseg = mss; 3054 3055 #ifdef RTV_RPIPE 3056 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3057 #endif 3058 bufsize = so->so_rcv.ssb_hiwat; 3059 if (bufsize > mss) { 3060 bufsize = roundup(bufsize, mss); 3061 if (bufsize > sb_max) 3062 bufsize = sb_max; 3063 if (bufsize > so->so_rcv.ssb_hiwat) 3064 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3065 } 3066 3067 /* 3068 * Set the slow-start flight size depending on whether this 3069 * is a local network or not. 3070 */ 3071 if (tcp_do_rfc3390) 3072 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3073 else 3074 tp->snd_cwnd = mss; 3075 3076 if (rt->rt_rmx.rmx_ssthresh) { 3077 /* 3078 * There's some sort of gateway or interface 3079 * buffer limit on the path. Use this to set 3080 * the slow start threshhold, but set the 3081 * threshold to no less than 2*mss. 3082 */ 3083 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3084 tcpstat.tcps_usedssthresh++; 3085 } 3086 } 3087 3088 /* 3089 * Determine the MSS option to send on an outgoing SYN. 3090 */ 3091 int 3092 tcp_mssopt(struct tcpcb *tp) 3093 { 3094 struct rtentry *rt; 3095 #ifdef INET6 3096 boolean_t isipv6 = 3097 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3098 int min_protoh = isipv6 ? 3099 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3100 sizeof(struct tcpiphdr); 3101 #else 3102 const boolean_t isipv6 = FALSE; 3103 const size_t min_protoh = sizeof(struct tcpiphdr); 3104 #endif 3105 3106 if (isipv6) 3107 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3108 else 3109 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3110 if (rt == NULL) 3111 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3112 3113 return (rt->rt_ifp->if_mtu - min_protoh); 3114 } 3115 3116 /* 3117 * When a partial ack arrives, force the retransmission of the 3118 * next unacknowledged segment. Do not exit Fast Recovery. 3119 * 3120 * Implement the Slow-but-Steady variant of NewReno by restarting the 3121 * the retransmission timer. Turn it off here so it can be restarted 3122 * later in tcp_output(). 3123 */ 3124 static void 3125 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3126 { 3127 tcp_seq old_snd_nxt = tp->snd_nxt; 3128 u_long ocwnd = tp->snd_cwnd; 3129 3130 tcp_callout_stop(tp, tp->tt_rexmt); 3131 tp->t_rtttime = 0; 3132 tp->snd_nxt = th->th_ack; 3133 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3134 tp->snd_cwnd = tp->t_maxseg; 3135 tp->t_flags |= TF_ACKNOW; 3136 tcp_output(tp); 3137 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3138 tp->snd_nxt = old_snd_nxt; 3139 /* partial window deflation */ 3140 if (ocwnd > acked) 3141 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3142 else 3143 tp->snd_cwnd = tp->t_maxseg; 3144 } 3145 3146 /* 3147 * In contrast to the Slow-but-Steady NewReno variant, 3148 * we do not reset the retransmission timer for SACK retransmissions, 3149 * except when retransmitting snd_una. 3150 */ 3151 static void 3152 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3153 { 3154 uint32_t pipe, seglen; 3155 tcp_seq nextrexmt; 3156 boolean_t lostdup; 3157 tcp_seq old_snd_nxt = tp->snd_nxt; 3158 u_long ocwnd = tp->snd_cwnd; 3159 int nseg = 0; /* consecutive new segments */ 3160 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3161 3162 tp->t_rtttime = 0; 3163 pipe = tcp_sack_compute_pipe(tp); 3164 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3165 (!tcp_do_smartsack || nseg < MAXBURST) && 3166 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3167 uint32_t sent; 3168 tcp_seq old_snd_max; 3169 int error; 3170 3171 if (nextrexmt == tp->snd_max) 3172 ++nseg; 3173 tp->snd_nxt = nextrexmt; 3174 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3175 old_snd_max = tp->snd_max; 3176 if (nextrexmt == tp->snd_una) 3177 tcp_callout_stop(tp, tp->tt_rexmt); 3178 error = tcp_output(tp); 3179 if (error != 0) 3180 break; 3181 sent = tp->snd_nxt - nextrexmt; 3182 if (sent <= 0) 3183 break; 3184 if (!lostdup) 3185 pipe += sent; 3186 tcpstat.tcps_sndsackpack++; 3187 tcpstat.tcps_sndsackbyte += sent; 3188 if (SEQ_LT(nextrexmt, old_snd_max) && 3189 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3190 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3191 } 3192 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3193 tp->snd_nxt = old_snd_nxt; 3194 tp->snd_cwnd = ocwnd; 3195 } 3196