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