1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 85 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.49 2004/12/29 05:44:43 hsu Exp $ 86 */ 87 88 #include "opt_ipfw.h" /* for ipfw_fwd */ 89 #include "opt_inet6.h" 90 #include "opt_ipsec.h" 91 #include "opt_tcpdebug.h" 92 #include "opt_tcp_input.h" 93 94 #include <sys/param.h> 95 #include <sys/systm.h> 96 #include <sys/kernel.h> 97 #include <sys/sysctl.h> 98 #include <sys/malloc.h> 99 #include <sys/mbuf.h> 100 #include <sys/proc.h> /* for proc0 declaration */ 101 #include <sys/protosw.h> 102 #include <sys/socket.h> 103 #include <sys/socketvar.h> 104 #include <sys/syslog.h> 105 #include <sys/in_cksum.h> 106 107 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 108 #include <machine/stdarg.h> 109 110 #include <net/if.h> 111 #include <net/route.h> 112 113 #include <netinet/in.h> 114 #include <netinet/in_systm.h> 115 #include <netinet/ip.h> 116 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 117 #include <netinet/in_var.h> 118 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 119 #include <netinet/in_pcb.h> 120 #include <netinet/ip_var.h> 121 #include <netinet/ip6.h> 122 #include <netinet/icmp6.h> 123 #include <netinet6/nd6.h> 124 #include <netinet6/ip6_var.h> 125 #include <netinet6/in6_pcb.h> 126 #include <netinet/tcp.h> 127 #include <netinet/tcp_fsm.h> 128 #include <netinet/tcp_seq.h> 129 #include <netinet/tcp_timer.h> 130 #include <netinet/tcp_var.h> 131 #include <netinet6/tcp6_var.h> 132 #include <netinet/tcpip.h> 133 134 #ifdef TCPDEBUG 135 #include <netinet/tcp_debug.h> 136 137 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 138 struct tcphdr tcp_savetcp; 139 #endif 140 141 #ifdef FAST_IPSEC 142 #include <netproto/ipsec/ipsec.h> 143 #include <netproto/ipsec/ipsec6.h> 144 #endif 145 146 #ifdef IPSEC 147 #include <netinet6/ipsec.h> 148 #include <netinet6/ipsec6.h> 149 #include <netproto/key/key.h> 150 #endif 151 152 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 153 154 tcp_cc tcp_ccgen; 155 static int log_in_vain = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 157 &log_in_vain, 0, "Log all incoming TCP connections"); 158 159 static int blackhole = 0; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 161 &blackhole, 0, "Do not send RST when dropping refused connections"); 162 163 int tcp_delack_enabled = 1; 164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 165 &tcp_delack_enabled, 0, 166 "Delay ACK to try and piggyback it onto a data packet"); 167 168 #ifdef TCP_DROP_SYNFIN 169 static int drop_synfin = 0; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 171 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 172 #endif 173 174 static int tcp_do_limitedtransmit = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 176 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 177 178 static int tcp_do_early_retransmit = 1; 179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 180 &tcp_do_early_retransmit, 0, "Early retransmit"); 181 182 static int tcp_do_rfc3390 = 1; 183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 184 &tcp_do_rfc3390, 0, 185 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 186 187 static int tcp_do_eifel_detect = 1; 188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 189 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 190 191 /* 192 * Define as tunable for easy testing with SACK on and off. 193 * Warning: do not change setting in the middle of an existing active TCP flow, 194 * else strange things might happen to that flow. 195 */ 196 int tcp_do_sack = 1; 197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 198 &tcp_do_sack, 0, "Enable SACK Algorithms"); 199 200 int tcp_do_smartsack = 1; 201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 202 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 203 204 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 205 "TCP Segment Reassembly Queue"); 206 207 int tcp_reass_maxseg = 0; 208 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 209 &tcp_reass_maxseg, 0, 210 "Global maximum number of TCP Segments in Reassembly Queue"); 211 212 int tcp_reass_qsize = 0; 213 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 214 &tcp_reass_qsize, 0, 215 "Global number of TCP Segments currently in Reassembly Queue"); 216 217 static int tcp_reass_overflows = 0; 218 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 219 &tcp_reass_overflows, 0, 220 "Global number of TCP Segment Reassembly Queue Overflows"); 221 222 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 223 static void tcp_pulloutofband(struct socket *, 224 struct tcphdr *, struct mbuf *, int); 225 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 226 struct mbuf *); 227 static void tcp_xmit_timer(struct tcpcb *, int); 228 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 229 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 230 231 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 232 #ifdef INET6 233 #define ND6_HINT(tp) \ 234 do { \ 235 if ((tp) && (tp)->t_inpcb && \ 236 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 237 (tp)->t_inpcb->in6p_route.ro_rt) \ 238 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 239 } while (0) 240 #else 241 #define ND6_HINT(tp) 242 #endif 243 244 /* 245 * Indicate whether this ack should be delayed. We can delay the ack if 246 * - delayed acks are enabled and 247 * - there is no delayed ack timer in progress and 248 * - our last ack wasn't a 0-sized window. We never want to delay 249 * the ack that opens up a 0-sized window. 250 */ 251 #define DELAY_ACK(tp) \ 252 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 253 !(tp->t_flags & TF_RXWIN0SENT)) 254 255 #define acceptable_window_update(tp, th, tiwin) \ 256 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 257 (tp->snd_wl1 == th->th_seq && \ 258 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 259 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 260 261 static int 262 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 263 { 264 struct tseg_qent *q; 265 struct tseg_qent *p = NULL; 266 struct tseg_qent *te; 267 struct socket *so = tp->t_inpcb->inp_socket; 268 int flags; 269 270 /* 271 * Call with th == NULL after become established to 272 * force pre-ESTABLISHED data up to user socket. 273 */ 274 if (th == NULL) 275 goto present; 276 277 /* 278 * Limit the number of segments in the reassembly queue to prevent 279 * holding on to too many segments (and thus running out of mbufs). 280 * Make sure to let the missing segment through which caused this 281 * queue. Always keep one global queue entry spare to be able to 282 * process the missing segment. 283 */ 284 if (th->th_seq != tp->rcv_nxt && 285 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 286 tcp_reass_overflows++; 287 tcpstat.tcps_rcvmemdrop++; 288 m_freem(m); 289 /* no SACK block to report */ 290 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 291 return (0); 292 } 293 294 /* Allocate a new queue entry. */ 295 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 296 M_INTWAIT | M_NULLOK); 297 if (te == NULL) { 298 tcpstat.tcps_rcvmemdrop++; 299 m_freem(m); 300 /* no SACK block to report */ 301 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 302 return (0); 303 } 304 tcp_reass_qsize++; 305 306 /* 307 * Find a segment which begins after this one does. 308 */ 309 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 310 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 311 break; 312 p = q; 313 } 314 315 /* 316 * If there is a preceding segment, it may provide some of 317 * our data already. If so, drop the data from the incoming 318 * segment. If it provides all of our data, drop us. 319 */ 320 if (p != NULL) { 321 int i; 322 323 /* conversion to int (in i) handles seq wraparound */ 324 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 325 if (i > 0) { /* overlaps preceding segment */ 326 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 327 /* enclosing block starts w/ preceding segment */ 328 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 329 if (i >= *tlenp) { 330 /* preceding encloses incoming segment */ 331 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 332 p->tqe_len; 333 tcpstat.tcps_rcvduppack++; 334 tcpstat.tcps_rcvdupbyte += *tlenp; 335 m_freem(m); 336 free(te, M_TSEGQ); 337 tcp_reass_qsize--; 338 /* 339 * Try to present any queued data 340 * at the left window edge to the user. 341 * This is needed after the 3-WHS 342 * completes. 343 */ 344 goto present; /* ??? */ 345 } 346 m_adj(m, i); 347 *tlenp -= i; 348 th->th_seq += i; 349 /* incoming segment end is enclosing block end */ 350 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 351 ((th->th_flags & TH_FIN) != 0); 352 /* trim end of reported D-SACK block */ 353 tp->reportblk.rblk_end = th->th_seq; 354 } 355 } 356 tcpstat.tcps_rcvoopack++; 357 tcpstat.tcps_rcvoobyte += *tlenp; 358 359 /* 360 * While we overlap succeeding segments trim them or, 361 * if they are completely covered, dequeue them. 362 */ 363 while (q) { 364 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 365 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 366 struct tseg_qent *nq; 367 368 if (i <= 0) 369 break; 370 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 371 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 372 tp->encloseblk = tp->reportblk; 373 /* report trailing duplicate D-SACK segment */ 374 tp->reportblk.rblk_start = q->tqe_th->th_seq; 375 } 376 if ((tp->t_flags & TF_ENCLOSESEG) && 377 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 378 /* extend enclosing block if one exists */ 379 tp->encloseblk.rblk_end = qend; 380 } 381 if (i < q->tqe_len) { 382 q->tqe_th->th_seq += i; 383 q->tqe_len -= i; 384 m_adj(q->tqe_m, i); 385 break; 386 } 387 388 nq = LIST_NEXT(q, tqe_q); 389 LIST_REMOVE(q, tqe_q); 390 m_freem(q->tqe_m); 391 free(q, M_TSEGQ); 392 tcp_reass_qsize--; 393 q = nq; 394 } 395 396 /* Insert the new segment queue entry into place. */ 397 te->tqe_m = m; 398 te->tqe_th = th; 399 te->tqe_len = *tlenp; 400 401 /* check if can coalesce with following segment */ 402 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 403 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 404 405 te->tqe_len += q->tqe_len; 406 if (q->tqe_th->th_flags & TH_FIN) 407 te->tqe_th->th_flags |= TH_FIN; 408 m_cat(te->tqe_m, q->tqe_m); 409 tp->encloseblk.rblk_end = tend; 410 /* 411 * When not reporting a duplicate segment, use 412 * the larger enclosing block as the SACK block. 413 */ 414 if (!(tp->t_flags & TF_DUPSEG)) 415 tp->reportblk.rblk_end = tend; 416 LIST_REMOVE(q, tqe_q); 417 free(q, M_TSEGQ); 418 tcp_reass_qsize--; 419 } 420 421 if (p == NULL) { 422 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 423 } else { 424 /* check if can coalesce with preceding segment */ 425 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 426 p->tqe_len += te->tqe_len; 427 m_cat(p->tqe_m, te->tqe_m); 428 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 429 /* 430 * When not reporting a duplicate segment, use 431 * the larger enclosing block as the SACK block. 432 */ 433 if (!(tp->t_flags & TF_DUPSEG)) 434 tp->reportblk.rblk_start = p->tqe_th->th_seq; 435 free(te, M_TSEGQ); 436 tcp_reass_qsize--; 437 } else 438 LIST_INSERT_AFTER(p, te, tqe_q); 439 } 440 441 present: 442 /* 443 * Present data to user, advancing rcv_nxt through 444 * completed sequence space. 445 */ 446 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 447 return (0); 448 q = LIST_FIRST(&tp->t_segq); 449 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 450 return (0); 451 tp->rcv_nxt += q->tqe_len; 452 if (!(tp->t_flags & TF_DUPSEG)) { 453 /* no SACK block to report since ACK advanced */ 454 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 455 } 456 /* no enclosing block to report since ACK advanced */ 457 tp->t_flags &= ~TF_ENCLOSESEG; 458 flags = q->tqe_th->th_flags & TH_FIN; 459 LIST_REMOVE(q, tqe_q); 460 KASSERT(LIST_EMPTY(&tp->t_segq) || 461 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 462 ("segment not coalesced")); 463 if (so->so_state & SS_CANTRCVMORE) 464 m_freem(q->tqe_m); 465 else 466 sbappendstream(&so->so_rcv, q->tqe_m); 467 free(q, M_TSEGQ); 468 tcp_reass_qsize--; 469 ND6_HINT(tp); 470 sorwakeup(so); 471 return (flags); 472 } 473 474 /* 475 * TCP input routine, follows pages 65-76 of the 476 * protocol specification dated September, 1981 very closely. 477 */ 478 #ifdef INET6 479 int 480 tcp6_input(struct mbuf **mp, int *offp, int proto) 481 { 482 struct mbuf *m = *mp; 483 struct in6_ifaddr *ia6; 484 485 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 486 487 /* 488 * draft-itojun-ipv6-tcp-to-anycast 489 * better place to put this in? 490 */ 491 ia6 = ip6_getdstifaddr(m); 492 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 493 struct ip6_hdr *ip6; 494 495 ip6 = mtod(m, struct ip6_hdr *); 496 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 497 offsetof(struct ip6_hdr, ip6_dst)); 498 return (IPPROTO_DONE); 499 } 500 501 tcp_input(m, *offp, proto); 502 return (IPPROTO_DONE); 503 } 504 #endif 505 506 void 507 tcp_input(struct mbuf *m, ...) 508 { 509 __va_list ap; 510 int off0, proto; 511 struct tcphdr *th; 512 struct ip *ip = NULL; 513 struct ipovly *ipov; 514 struct inpcb *inp = NULL; 515 u_char *optp = NULL; 516 int optlen = 0; 517 int len, tlen, off; 518 int drop_hdrlen; 519 struct tcpcb *tp = NULL; 520 int thflags; 521 struct socket *so = 0; 522 int todrop, acked; 523 boolean_t ourfinisacked, needoutput = FALSE; 524 u_long tiwin; 525 int recvwin; 526 struct tcpopt to; /* options in this segment */ 527 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 528 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 529 struct sockaddr_in *next_hop = NULL; 530 int rstreason; /* For badport_bandlim accounting purposes */ 531 int cpu; 532 struct ip6_hdr *ip6 = NULL; 533 #ifdef INET6 534 boolean_t isipv6; 535 #else 536 const boolean_t isipv6 = FALSE; 537 #endif 538 #ifdef TCPDEBUG 539 short ostate = 0; 540 #endif 541 542 __va_start(ap, m); 543 off0 = __va_arg(ap, int); 544 proto = __va_arg(ap, int); 545 __va_end(ap); 546 547 tcpstat.tcps_rcvtotal++; 548 549 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */ 550 while (m->m_type == MT_TAG) { 551 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 552 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 553 m = m->m_next; 554 } 555 556 #ifdef INET6 557 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 558 #endif 559 560 if (isipv6) { 561 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 562 ip6 = mtod(m, struct ip6_hdr *); 563 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 564 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 565 tcpstat.tcps_rcvbadsum++; 566 goto drop; 567 } 568 th = (struct tcphdr *)((caddr_t)ip6 + off0); 569 570 /* 571 * Be proactive about unspecified IPv6 address in source. 572 * As we use all-zero to indicate unbounded/unconnected pcb, 573 * unspecified IPv6 address can be used to confuse us. 574 * 575 * Note that packets with unspecified IPv6 destination is 576 * already dropped in ip6_input. 577 */ 578 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 579 /* XXX stat */ 580 goto drop; 581 } 582 } else { 583 /* 584 * Get IP and TCP header together in first mbuf. 585 * Note: IP leaves IP header in first mbuf. 586 */ 587 if (off0 > sizeof(struct ip)) { 588 ip_stripoptions(m); 589 off0 = sizeof(struct ip); 590 } 591 /* already checked and pulled up in ip_demux() */ 592 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 593 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 594 ip = mtod(m, struct ip *); 595 ipov = (struct ipovly *)ip; 596 th = (struct tcphdr *)((caddr_t)ip + off0); 597 tlen = ip->ip_len; 598 599 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 600 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 601 th->th_sum = m->m_pkthdr.csum_data; 602 else 603 th->th_sum = in_pseudo(ip->ip_src.s_addr, 604 ip->ip_dst.s_addr, 605 htonl(m->m_pkthdr.csum_data + 606 ip->ip_len + 607 IPPROTO_TCP)); 608 th->th_sum ^= 0xffff; 609 } else { 610 /* 611 * Checksum extended TCP header and data. 612 */ 613 len = sizeof(struct ip) + tlen; 614 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 615 ipov->ih_len = (u_short)tlen; 616 ipov->ih_len = htons(ipov->ih_len); 617 th->th_sum = in_cksum(m, len); 618 } 619 if (th->th_sum) { 620 tcpstat.tcps_rcvbadsum++; 621 goto drop; 622 } 623 #ifdef INET6 624 /* Re-initialization for later version check */ 625 ip->ip_v = IPVERSION; 626 #endif 627 } 628 629 /* 630 * Check that TCP offset makes sense, 631 * pull out TCP options and adjust length. XXX 632 */ 633 off = th->th_off << 2; 634 /* already checked and pulled up in ip_demux() */ 635 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 636 ("bad TCP data offset %d (tlen %d)", off, tlen)); 637 tlen -= off; /* tlen is used instead of ti->ti_len */ 638 if (off > sizeof(struct tcphdr)) { 639 if (isipv6) { 640 IP6_EXTHDR_CHECK(m, off0, off, ); 641 ip6 = mtod(m, struct ip6_hdr *); 642 th = (struct tcphdr *)((caddr_t)ip6 + off0); 643 } else { 644 /* already pulled up in ip_demux() */ 645 KASSERT(m->m_len >= sizeof(struct ip) + off, 646 ("TCP header and options not in one mbuf: " 647 "m_len %d, off %d", m->m_len, off)); 648 } 649 optlen = off - sizeof(struct tcphdr); 650 optp = (u_char *)(th + 1); 651 } 652 thflags = th->th_flags; 653 654 #ifdef TCP_DROP_SYNFIN 655 /* 656 * If the drop_synfin option is enabled, drop all packets with 657 * both the SYN and FIN bits set. This prevents e.g. nmap from 658 * identifying the TCP/IP stack. 659 * 660 * This is a violation of the TCP specification. 661 */ 662 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 663 goto drop; 664 #endif 665 666 /* 667 * Convert TCP protocol specific fields to host format. 668 */ 669 th->th_seq = ntohl(th->th_seq); 670 th->th_ack = ntohl(th->th_ack); 671 th->th_win = ntohs(th->th_win); 672 th->th_urp = ntohs(th->th_urp); 673 674 /* 675 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 676 * until after ip6_savecontrol() is called and before other functions 677 * which don't want those proto headers. 678 * Because ip6_savecontrol() is going to parse the mbuf to 679 * search for data to be passed up to user-land, it wants mbuf 680 * parameters to be unchanged. 681 * XXX: the call of ip6_savecontrol() has been obsoleted based on 682 * latest version of the advanced API (20020110). 683 */ 684 drop_hdrlen = off0 + off; 685 686 /* 687 * Locate pcb for segment. 688 */ 689 findpcb: 690 /* IPFIREWALL_FORWARD section */ 691 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 692 /* 693 * Transparently forwarded. Pretend to be the destination. 694 * already got one like this? 695 */ 696 cpu = mycpu->gd_cpuid; 697 inp = in_pcblookup_hash(&tcbinfo[cpu], 698 ip->ip_src, th->th_sport, 699 ip->ip_dst, th->th_dport, 700 0, m->m_pkthdr.rcvif); 701 if (!inp) { 702 /* 703 * It's new. Try to find the ambushing socket. 704 */ 705 706 /* 707 * The rest of the ipfw code stores the port in 708 * host order. XXX 709 * (The IP address is still in network order.) 710 */ 711 in_port_t dport = next_hop->sin_port ? 712 htons(next_hop->sin_port) : 713 th->th_dport; 714 715 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 716 next_hop->sin_addr.s_addr, dport); 717 inp = in_pcblookup_hash(&tcbinfo[cpu], 718 ip->ip_src, th->th_sport, 719 next_hop->sin_addr, dport, 720 1, m->m_pkthdr.rcvif); 721 } 722 } else { 723 if (isipv6) { 724 inp = in6_pcblookup_hash(&tcbinfo[0], 725 &ip6->ip6_src, th->th_sport, 726 &ip6->ip6_dst, th->th_dport, 727 1, m->m_pkthdr.rcvif); 728 } else { 729 cpu = mycpu->gd_cpuid; 730 inp = in_pcblookup_hash(&tcbinfo[cpu], 731 ip->ip_src, th->th_sport, 732 ip->ip_dst, th->th_dport, 733 1, m->m_pkthdr.rcvif); 734 } 735 } 736 737 /* 738 * If the state is CLOSED (i.e., TCB does not exist) then 739 * all data in the incoming segment is discarded. 740 * If the TCB exists but is in CLOSED state, it is embryonic, 741 * but should either do a listen or a connect soon. 742 */ 743 if (inp == NULL) { 744 if (log_in_vain) { 745 #ifdef INET6 746 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 747 #else 748 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 749 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 750 #endif 751 if (isipv6) { 752 strcpy(dbuf, "["); 753 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 754 strcat(dbuf, "]"); 755 strcpy(sbuf, "["); 756 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 757 strcat(sbuf, "]"); 758 } else { 759 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 760 strcpy(sbuf, inet_ntoa(ip->ip_src)); 761 } 762 switch (log_in_vain) { 763 case 1: 764 if (!(thflags & TH_SYN)) 765 break; 766 case 2: 767 log(LOG_INFO, 768 "Connection attempt to TCP %s:%d " 769 "from %s:%d flags:0x%02x\n", 770 dbuf, ntohs(th->th_dport), sbuf, 771 ntohs(th->th_sport), thflags); 772 break; 773 default: 774 break; 775 } 776 } 777 if (blackhole) { 778 switch (blackhole) { 779 case 1: 780 if (thflags & TH_SYN) 781 goto drop; 782 break; 783 case 2: 784 goto drop; 785 default: 786 goto drop; 787 } 788 } 789 rstreason = BANDLIM_RST_CLOSEDPORT; 790 goto dropwithreset; 791 } 792 793 #ifdef IPSEC 794 if (isipv6) { 795 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 796 ipsec6stat.in_polvio++; 797 goto drop; 798 } 799 } else { 800 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 801 ipsecstat.in_polvio++; 802 goto drop; 803 } 804 } 805 #endif 806 #ifdef FAST_IPSEC 807 if (isipv6) { 808 if (ipsec6_in_reject(m, inp)) 809 goto drop; 810 } else { 811 if (ipsec4_in_reject(m, inp)) 812 goto drop; 813 } 814 #endif 815 816 tp = intotcpcb(inp); 817 if (tp == NULL) { 818 rstreason = BANDLIM_RST_CLOSEDPORT; 819 goto dropwithreset; 820 } 821 if (tp->t_state <= TCPS_CLOSED) 822 goto drop; 823 824 /* Unscale the window into a 32-bit value. */ 825 if (!(thflags & TH_SYN)) 826 tiwin = th->th_win << tp->snd_scale; 827 else 828 tiwin = th->th_win; 829 830 so = inp->inp_socket; 831 832 #ifdef TCPDEBUG 833 if (so->so_options & SO_DEBUG) { 834 ostate = tp->t_state; 835 if (isipv6) 836 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 837 else 838 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 839 tcp_savetcp = *th; 840 } 841 #endif 842 843 bzero(&to, sizeof to); 844 845 if (so->so_options & SO_ACCEPTCONN) { 846 struct in_conninfo inc; 847 848 #ifdef INET6 849 inc.inc_isipv6 = (isipv6 == TRUE); 850 #endif 851 if (isipv6) { 852 inc.inc6_faddr = ip6->ip6_src; 853 inc.inc6_laddr = ip6->ip6_dst; 854 inc.inc6_route.ro_rt = NULL; /* XXX */ 855 } else { 856 inc.inc_faddr = ip->ip_src; 857 inc.inc_laddr = ip->ip_dst; 858 inc.inc_route.ro_rt = NULL; /* XXX */ 859 } 860 inc.inc_fport = th->th_sport; 861 inc.inc_lport = th->th_dport; 862 863 /* 864 * If the state is LISTEN then ignore segment if it contains 865 * a RST. If the segment contains an ACK then it is bad and 866 * send a RST. If it does not contain a SYN then it is not 867 * interesting; drop it. 868 * 869 * If the state is SYN_RECEIVED (syncache) and seg contains 870 * an ACK, but not for our SYN/ACK, send a RST. If the seg 871 * contains a RST, check the sequence number to see if it 872 * is a valid reset segment. 873 */ 874 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 875 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 876 if (!syncache_expand(&inc, th, &so, m)) { 877 /* 878 * No syncache entry, or ACK was not 879 * for our SYN/ACK. Send a RST. 880 */ 881 tcpstat.tcps_badsyn++; 882 rstreason = BANDLIM_RST_OPENPORT; 883 goto dropwithreset; 884 } 885 if (so == NULL) 886 /* 887 * Could not complete 3-way handshake, 888 * connection is being closed down, and 889 * syncache will free mbuf. 890 */ 891 return; 892 /* 893 * Socket is created in state SYN_RECEIVED. 894 * Continue processing segment. 895 */ 896 inp = sotoinpcb(so); 897 tp = intotcpcb(inp); 898 /* 899 * This is what would have happened in 900 * tcp_output() when the SYN,ACK was sent. 901 */ 902 tp->snd_up = tp->snd_una; 903 tp->snd_max = tp->snd_nxt = tp->iss + 1; 904 tp->last_ack_sent = tp->rcv_nxt; 905 /* 906 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 907 * until the _second_ ACK is received: 908 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 909 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 910 * move to ESTAB, set snd_wnd to tiwin. 911 */ 912 tp->snd_wnd = tiwin; /* unscaled */ 913 goto after_listen; 914 } 915 if (thflags & TH_RST) { 916 syncache_chkrst(&inc, th); 917 goto drop; 918 } 919 if (thflags & TH_ACK) { 920 syncache_badack(&inc); 921 tcpstat.tcps_badsyn++; 922 rstreason = BANDLIM_RST_OPENPORT; 923 goto dropwithreset; 924 } 925 goto drop; 926 } 927 928 /* 929 * Segment's flags are (SYN) or (SYN | FIN). 930 */ 931 #ifdef INET6 932 /* 933 * If deprecated address is forbidden, 934 * we do not accept SYN to deprecated interface 935 * address to prevent any new inbound connection from 936 * getting established. 937 * When we do not accept SYN, we send a TCP RST, 938 * with deprecated source address (instead of dropping 939 * it). We compromise it as it is much better for peer 940 * to send a RST, and RST will be the final packet 941 * for the exchange. 942 * 943 * If we do not forbid deprecated addresses, we accept 944 * the SYN packet. RFC2462 does not suggest dropping 945 * SYN in this case. 946 * If we decipher RFC2462 5.5.4, it says like this: 947 * 1. use of deprecated addr with existing 948 * communication is okay - "SHOULD continue to be 949 * used" 950 * 2. use of it with new communication: 951 * (2a) "SHOULD NOT be used if alternate address 952 * with sufficient scope is available" 953 * (2b) nothing mentioned otherwise. 954 * Here we fall into (2b) case as we have no choice in 955 * our source address selection - we must obey the peer. 956 * 957 * The wording in RFC2462 is confusing, and there are 958 * multiple description text for deprecated address 959 * handling - worse, they are not exactly the same. 960 * I believe 5.5.4 is the best one, so we follow 5.5.4. 961 */ 962 if (isipv6 && !ip6_use_deprecated) { 963 struct in6_ifaddr *ia6; 964 965 if ((ia6 = ip6_getdstifaddr(m)) && 966 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 967 tp = NULL; 968 rstreason = BANDLIM_RST_OPENPORT; 969 goto dropwithreset; 970 } 971 } 972 #endif 973 /* 974 * If it is from this socket, drop it, it must be forged. 975 * Don't bother responding if the destination was a broadcast. 976 */ 977 if (th->th_dport == th->th_sport) { 978 if (isipv6) { 979 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 980 &ip6->ip6_src)) 981 goto drop; 982 } else { 983 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 984 goto drop; 985 } 986 } 987 /* 988 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 989 * 990 * Note that it is quite possible to receive unicast 991 * link-layer packets with a broadcast IP address. Use 992 * in_broadcast() to find them. 993 */ 994 if (m->m_flags & (M_BCAST | M_MCAST)) 995 goto drop; 996 if (isipv6) { 997 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 998 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 999 goto drop; 1000 } else { 1001 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1002 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1003 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1004 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1005 goto drop; 1006 } 1007 /* 1008 * SYN appears to be valid; create compressed TCP state 1009 * for syncache, or perform t/tcp connection. 1010 */ 1011 if (so->so_qlen <= so->so_qlimit) { 1012 tcp_dooptions(&to, optp, optlen, TRUE); 1013 if (!syncache_add(&inc, &to, th, &so, m)) 1014 goto drop; 1015 if (so == NULL) 1016 /* 1017 * Entry added to syncache, mbuf used to 1018 * send SYN,ACK packet. 1019 */ 1020 return; 1021 /* 1022 * Segment passed TAO tests. 1023 */ 1024 inp = sotoinpcb(so); 1025 tp = intotcpcb(inp); 1026 tp->snd_wnd = tiwin; 1027 tp->t_starttime = ticks; 1028 tp->t_state = TCPS_ESTABLISHED; 1029 1030 /* 1031 * If there is a FIN, or if there is data and the 1032 * connection is local, then delay SYN,ACK(SYN) in 1033 * the hope of piggy-backing it on a response 1034 * segment. Otherwise must send ACK now in case 1035 * the other side is slow starting. 1036 */ 1037 if (DELAY_ACK(tp) && 1038 ((thflags & TH_FIN) || 1039 (tlen != 0 && 1040 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1041 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1042 callout_reset(tp->tt_delack, tcp_delacktime, 1043 tcp_timer_delack, tp); 1044 tp->t_flags |= TF_NEEDSYN; 1045 } else 1046 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1047 1048 tcpstat.tcps_connects++; 1049 soisconnected(so); 1050 goto trimthenstep6; 1051 } 1052 goto drop; 1053 } 1054 after_listen: 1055 1056 /* should not happen - syncache should pick up these connections */ 1057 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1058 1059 /* 1060 * Segment received on connection. 1061 * Reset idle time and keep-alive timer. 1062 */ 1063 tp->t_rcvtime = ticks; 1064 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1065 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1066 1067 /* 1068 * Process options. 1069 * XXX this is tradtitional behavior, may need to be cleaned up. 1070 */ 1071 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1072 if (thflags & TH_SYN) { 1073 if (to.to_flags & TOF_SCALE) { 1074 tp->t_flags |= TF_RCVD_SCALE; 1075 tp->requested_s_scale = to.to_requested_s_scale; 1076 } 1077 if (to.to_flags & TOF_TS) { 1078 tp->t_flags |= TF_RCVD_TSTMP; 1079 tp->ts_recent = to.to_tsval; 1080 tp->ts_recent_age = ticks; 1081 } 1082 if (to.to_flags & (TOF_CC | TOF_CCNEW)) 1083 tp->t_flags |= TF_RCVD_CC; 1084 if (to.to_flags & TOF_MSS) 1085 tcp_mss(tp, to.to_mss); 1086 /* 1087 * Only set the TF_SACK_PERMITTED per-connection flag 1088 * if we got a SACK_PERMITTED option from the other side 1089 * and the global tcp_do_sack variable is true. 1090 */ 1091 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1092 tp->t_flags |= TF_SACK_PERMITTED; 1093 } 1094 1095 /* 1096 * Header prediction: check for the two common cases 1097 * of a uni-directional data xfer. If the packet has 1098 * no control flags, is in-sequence, the window didn't 1099 * change and we're not retransmitting, it's a 1100 * candidate. If the length is zero and the ack moved 1101 * forward, we're the sender side of the xfer. Just 1102 * free the data acked & wake any higher level process 1103 * that was blocked waiting for space. If the length 1104 * is non-zero and the ack didn't move, we're the 1105 * receiver side. If we're getting packets in-order 1106 * (the reassembly queue is empty), add the data to 1107 * the socket buffer and note that we need a delayed ack. 1108 * Make sure that the hidden state-flags are also off. 1109 * Since we check for TCPS_ESTABLISHED above, it can only 1110 * be TH_NEEDSYN. 1111 */ 1112 if (tp->t_state == TCPS_ESTABLISHED && 1113 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1114 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1115 (!(to.to_flags & TOF_TS) || 1116 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1117 /* 1118 * Using the CC option is compulsory if once started: 1119 * the segment is OK if no T/TCP was negotiated or 1120 * if the segment has a CC option equal to CCrecv 1121 */ 1122 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1123 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) && 1124 th->th_seq == tp->rcv_nxt && 1125 tp->snd_nxt == tp->snd_max) { 1126 1127 /* 1128 * If last ACK falls within this segment's sequence numbers, 1129 * record the timestamp. 1130 * NOTE that the test is modified according to the latest 1131 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1132 */ 1133 if ((to.to_flags & TOF_TS) && 1134 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1135 tp->ts_recent_age = ticks; 1136 tp->ts_recent = to.to_tsval; 1137 } 1138 1139 if (tlen == 0) { 1140 if (SEQ_GT(th->th_ack, tp->snd_una) && 1141 SEQ_LEQ(th->th_ack, tp->snd_max) && 1142 tp->snd_cwnd >= tp->snd_wnd && 1143 !IN_FASTRECOVERY(tp)) { 1144 /* 1145 * this is a pure ack for outstanding data. 1146 */ 1147 ++tcpstat.tcps_predack; 1148 /* 1149 * "bad retransmit" recovery 1150 * 1151 * If Eifel detection applies, then 1152 * it is deterministic, so use it 1153 * unconditionally over the old heuristic. 1154 * Otherwise, fall back to the old heuristic. 1155 */ 1156 if (tcp_do_eifel_detect && 1157 (to.to_flags & TOF_TS) && to.to_tsecr && 1158 (tp->t_flags & TF_FIRSTACCACK)) { 1159 /* Eifel detection applicable. */ 1160 if (to.to_tsecr < tp->t_rexmtTS) { 1161 tcp_revert_congestion_state(tp); 1162 ++tcpstat.tcps_eifeldetected; 1163 } 1164 } else if (tp->t_rxtshift == 1 && 1165 ticks < tp->t_badrxtwin) { 1166 tcp_revert_congestion_state(tp); 1167 ++tcpstat.tcps_rttdetected; 1168 } 1169 tp->t_flags &= ~(TF_FIRSTACCACK | 1170 TF_FASTREXMT | TF_EARLYREXMT); 1171 /* 1172 * Recalculate the retransmit timer / rtt. 1173 * 1174 * Some machines (certain windows boxes) 1175 * send broken timestamp replies during the 1176 * SYN+ACK phase, ignore timestamps of 0. 1177 */ 1178 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1179 tcp_xmit_timer(tp, 1180 ticks - to.to_tsecr + 1); 1181 } else if (tp->t_rtttime && 1182 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1183 tcp_xmit_timer(tp, 1184 ticks - tp->t_rtttime); 1185 } 1186 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1187 acked = th->th_ack - tp->snd_una; 1188 tcpstat.tcps_rcvackpack++; 1189 tcpstat.tcps_rcvackbyte += acked; 1190 sbdrop(&so->so_snd, acked); 1191 tp->snd_recover = th->th_ack - 1; 1192 tp->snd_una = th->th_ack; 1193 tp->t_dupacks = 0; 1194 /* 1195 * Update window information. 1196 */ 1197 if (tiwin != tp->snd_wnd && 1198 acceptable_window_update(tp, th, tiwin)) { 1199 /* keep track of pure window updates */ 1200 if (tp->snd_wl2 == th->th_ack && 1201 tiwin > tp->snd_wnd) 1202 tcpstat.tcps_rcvwinupd++; 1203 tp->snd_wnd = tiwin; 1204 tp->snd_wl1 = th->th_seq; 1205 tp->snd_wl2 = th->th_ack; 1206 if (tp->snd_wnd > tp->max_sndwnd) 1207 tp->max_sndwnd = tp->snd_wnd; 1208 } 1209 m_freem(m); 1210 ND6_HINT(tp); /* some progress has been done */ 1211 /* 1212 * If all outstanding data are acked, stop 1213 * retransmit timer, otherwise restart timer 1214 * using current (possibly backed-off) value. 1215 * If process is waiting for space, 1216 * wakeup/selwakeup/signal. If data 1217 * are ready to send, let tcp_output 1218 * decide between more output or persist. 1219 */ 1220 if (tp->snd_una == tp->snd_max) 1221 callout_stop(tp->tt_rexmt); 1222 else if (!callout_active(tp->tt_persist)) 1223 callout_reset(tp->tt_rexmt, 1224 tp->t_rxtcur, 1225 tcp_timer_rexmt, tp); 1226 1227 sowwakeup(so); 1228 if (so->so_snd.sb_cc) 1229 tcp_output(tp); 1230 return; 1231 } 1232 } else if (tiwin == tp->snd_wnd && 1233 th->th_ack == tp->snd_una && 1234 LIST_EMPTY(&tp->t_segq) && 1235 tlen <= sbspace(&so->so_rcv)) { 1236 /* 1237 * this is a pure, in-sequence data packet 1238 * with nothing on the reassembly queue and 1239 * we have enough buffer space to take it. 1240 */ 1241 ++tcpstat.tcps_preddat; 1242 tp->rcv_nxt += tlen; 1243 tcpstat.tcps_rcvpack++; 1244 tcpstat.tcps_rcvbyte += tlen; 1245 ND6_HINT(tp); /* some progress has been done */ 1246 /* 1247 * Add data to socket buffer. 1248 */ 1249 if (so->so_state & SS_CANTRCVMORE) { 1250 m_freem(m); 1251 } else { 1252 m_adj(m, drop_hdrlen); /* delayed header drop */ 1253 sbappendstream(&so->so_rcv, m); 1254 } 1255 sorwakeup(so); 1256 1257 /* 1258 * This code is responsible for most of the ACKs 1259 * the TCP stack sends back after receiving a data 1260 * packet. Note that the DELAY_ACK check fails if 1261 * the delack timer is already running, which results 1262 * in an ack being sent every other packet (which is 1263 * what we want). 1264 */ 1265 if (DELAY_ACK(tp)) { 1266 callout_reset(tp->tt_delack, tcp_delacktime, 1267 tcp_timer_delack, tp); 1268 } else { 1269 tp->t_flags |= TF_ACKNOW; 1270 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1271 tp->t_flags |= TF_ONOUTPUTQ; 1272 tp->tt_cpu = mycpu->gd_cpuid; 1273 TAILQ_INSERT_TAIL( 1274 &tcpcbackq[tp->tt_cpu], 1275 tp, t_outputq); 1276 } 1277 } 1278 return; 1279 } 1280 } 1281 1282 /* 1283 * Calculate amount of space in receive window, 1284 * and then do TCP input processing. 1285 * Receive window is amount of space in rcv queue, 1286 * but not less than advertised window. 1287 */ 1288 recvwin = sbspace(&so->so_rcv); 1289 if (recvwin < 0) 1290 recvwin = 0; 1291 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1292 1293 switch (tp->t_state) { 1294 /* 1295 * If the state is SYN_RECEIVED: 1296 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1297 */ 1298 case TCPS_SYN_RECEIVED: 1299 if ((thflags & TH_ACK) && 1300 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1301 SEQ_GT(th->th_ack, tp->snd_max))) { 1302 rstreason = BANDLIM_RST_OPENPORT; 1303 goto dropwithreset; 1304 } 1305 break; 1306 1307 /* 1308 * If the state is SYN_SENT: 1309 * if seg contains an ACK, but not for our SYN, drop the input. 1310 * if seg contains a RST, then drop the connection. 1311 * if seg does not contain SYN, then drop it. 1312 * Otherwise this is an acceptable SYN segment 1313 * initialize tp->rcv_nxt and tp->irs 1314 * if seg contains ack then advance tp->snd_una 1315 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1316 * arrange for segment to be acked (eventually) 1317 * continue processing rest of data/controls, beginning with URG 1318 */ 1319 case TCPS_SYN_SENT: 1320 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1321 taop = &tao_noncached; 1322 bzero(taop, sizeof *taop); 1323 } 1324 1325 if ((thflags & TH_ACK) && 1326 (SEQ_LEQ(th->th_ack, tp->iss) || 1327 SEQ_GT(th->th_ack, tp->snd_max))) { 1328 /* 1329 * If we have a cached CCsent for the remote host, 1330 * hence we haven't just crashed and restarted, 1331 * do not send a RST. This may be a retransmission 1332 * from the other side after our earlier ACK was lost. 1333 * Our new SYN, when it arrives, will serve as the 1334 * needed ACK. 1335 */ 1336 if (taop->tao_ccsent != 0) 1337 goto drop; 1338 else { 1339 rstreason = BANDLIM_UNLIMITED; 1340 goto dropwithreset; 1341 } 1342 } 1343 if (thflags & TH_RST) { 1344 if (thflags & TH_ACK) 1345 tp = tcp_drop(tp, ECONNREFUSED); 1346 goto drop; 1347 } 1348 if (!(thflags & TH_SYN)) 1349 goto drop; 1350 tp->snd_wnd = th->th_win; /* initial send window */ 1351 tp->cc_recv = to.to_cc; /* foreign CC */ 1352 1353 tp->irs = th->th_seq; 1354 tcp_rcvseqinit(tp); 1355 if (thflags & TH_ACK) { 1356 /* 1357 * Our SYN was acked. If segment contains CC.ECHO 1358 * option, check it to make sure this segment really 1359 * matches our SYN. If not, just drop it as old 1360 * duplicate, but send an RST if we're still playing 1361 * by the old rules. If no CC.ECHO option, make sure 1362 * we don't get fooled into using T/TCP. 1363 */ 1364 if (to.to_flags & TOF_CCECHO) { 1365 if (tp->cc_send != to.to_ccecho) { 1366 if (taop->tao_ccsent != 0) 1367 goto drop; 1368 else { 1369 rstreason = BANDLIM_UNLIMITED; 1370 goto dropwithreset; 1371 } 1372 } 1373 } else 1374 tp->t_flags &= ~TF_RCVD_CC; 1375 tcpstat.tcps_connects++; 1376 soisconnected(so); 1377 /* Do window scaling on this connection? */ 1378 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1379 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1380 tp->snd_scale = tp->requested_s_scale; 1381 tp->rcv_scale = tp->request_r_scale; 1382 } 1383 /* Segment is acceptable, update cache if undefined. */ 1384 if (taop->tao_ccsent == 0) 1385 taop->tao_ccsent = to.to_ccecho; 1386 1387 tp->rcv_adv += tp->rcv_wnd; 1388 tp->snd_una++; /* SYN is acked */ 1389 callout_stop(tp->tt_rexmt); 1390 /* 1391 * If there's data, delay ACK; if there's also a FIN 1392 * ACKNOW will be turned on later. 1393 */ 1394 if (DELAY_ACK(tp) && tlen != 0) 1395 callout_reset(tp->tt_delack, tcp_delacktime, 1396 tcp_timer_delack, tp); 1397 else 1398 tp->t_flags |= TF_ACKNOW; 1399 /* 1400 * Received <SYN,ACK> in SYN_SENT[*] state. 1401 * Transitions: 1402 * SYN_SENT --> ESTABLISHED 1403 * SYN_SENT* --> FIN_WAIT_1 1404 */ 1405 tp->t_starttime = ticks; 1406 if (tp->t_flags & TF_NEEDFIN) { 1407 tp->t_state = TCPS_FIN_WAIT_1; 1408 tp->t_flags &= ~TF_NEEDFIN; 1409 thflags &= ~TH_SYN; 1410 } else { 1411 tp->t_state = TCPS_ESTABLISHED; 1412 callout_reset(tp->tt_keep, tcp_keepidle, 1413 tcp_timer_keep, tp); 1414 } 1415 } else { 1416 /* 1417 * Received initial SYN in SYN-SENT[*] state => 1418 * simultaneous open. If segment contains CC option 1419 * and there is a cached CC, apply TAO test. 1420 * If it succeeds, connection is * half-synchronized. 1421 * Otherwise, do 3-way handshake: 1422 * SYN-SENT -> SYN-RECEIVED 1423 * SYN-SENT* -> SYN-RECEIVED* 1424 * If there was no CC option, clear cached CC value. 1425 */ 1426 tp->t_flags |= TF_ACKNOW; 1427 callout_stop(tp->tt_rexmt); 1428 if (to.to_flags & TOF_CC) { 1429 if (taop->tao_cc != 0 && 1430 CC_GT(to.to_cc, taop->tao_cc)) { 1431 /* 1432 * update cache and make transition: 1433 * SYN-SENT -> ESTABLISHED* 1434 * SYN-SENT* -> FIN-WAIT-1* 1435 */ 1436 taop->tao_cc = to.to_cc; 1437 tp->t_starttime = ticks; 1438 if (tp->t_flags & TF_NEEDFIN) { 1439 tp->t_state = TCPS_FIN_WAIT_1; 1440 tp->t_flags &= ~TF_NEEDFIN; 1441 } else { 1442 tp->t_state = TCPS_ESTABLISHED; 1443 callout_reset(tp->tt_keep, 1444 tcp_keepidle, 1445 tcp_timer_keep, 1446 tp); 1447 } 1448 tp->t_flags |= TF_NEEDSYN; 1449 } else 1450 tp->t_state = TCPS_SYN_RECEIVED; 1451 } else { 1452 /* CC.NEW or no option => invalidate cache */ 1453 taop->tao_cc = 0; 1454 tp->t_state = TCPS_SYN_RECEIVED; 1455 } 1456 } 1457 1458 trimthenstep6: 1459 /* 1460 * Advance th->th_seq to correspond to first data byte. 1461 * If data, trim to stay within window, 1462 * dropping FIN if necessary. 1463 */ 1464 th->th_seq++; 1465 if (tlen > tp->rcv_wnd) { 1466 todrop = tlen - tp->rcv_wnd; 1467 m_adj(m, -todrop); 1468 tlen = tp->rcv_wnd; 1469 thflags &= ~TH_FIN; 1470 tcpstat.tcps_rcvpackafterwin++; 1471 tcpstat.tcps_rcvbyteafterwin += todrop; 1472 } 1473 tp->snd_wl1 = th->th_seq - 1; 1474 tp->rcv_up = th->th_seq; 1475 /* 1476 * Client side of transaction: already sent SYN and data. 1477 * If the remote host used T/TCP to validate the SYN, 1478 * our data will be ACK'd; if so, enter normal data segment 1479 * processing in the middle of step 5, ack processing. 1480 * Otherwise, goto step 6. 1481 */ 1482 if (thflags & TH_ACK) 1483 goto process_ACK; 1484 1485 goto step6; 1486 1487 /* 1488 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1489 * if segment contains a SYN and CC [not CC.NEW] option: 1490 * if state == TIME_WAIT and connection duration > MSL, 1491 * drop packet and send RST; 1492 * 1493 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1494 * ack the FIN (and data) in retransmission queue. 1495 * Complete close and delete TCPCB. Then reprocess 1496 * segment, hoping to find new TCPCB in LISTEN state; 1497 * 1498 * else must be old SYN; drop it. 1499 * else do normal processing. 1500 */ 1501 case TCPS_LAST_ACK: 1502 case TCPS_CLOSING: 1503 case TCPS_TIME_WAIT: 1504 if ((thflags & TH_SYN) && 1505 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1506 if (tp->t_state == TCPS_TIME_WAIT && 1507 (ticks - tp->t_starttime) > tcp_msl) { 1508 rstreason = BANDLIM_UNLIMITED; 1509 goto dropwithreset; 1510 } 1511 if (CC_GT(to.to_cc, tp->cc_recv)) { 1512 tp = tcp_close(tp); 1513 goto findpcb; 1514 } 1515 else 1516 goto drop; 1517 } 1518 break; /* continue normal processing */ 1519 } 1520 1521 /* 1522 * States other than LISTEN or SYN_SENT. 1523 * First check the RST flag and sequence number since reset segments 1524 * are exempt from the timestamp and connection count tests. This 1525 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1526 * below which allowed reset segments in half the sequence space 1527 * to fall though and be processed (which gives forged reset 1528 * segments with a random sequence number a 50 percent chance of 1529 * killing a connection). 1530 * Then check timestamp, if present. 1531 * Then check the connection count, if present. 1532 * Then check that at least some bytes of segment are within 1533 * receive window. If segment begins before rcv_nxt, 1534 * drop leading data (and SYN); if nothing left, just ack. 1535 * 1536 * 1537 * If the RST bit is set, check the sequence number to see 1538 * if this is a valid reset segment. 1539 * RFC 793 page 37: 1540 * In all states except SYN-SENT, all reset (RST) segments 1541 * are validated by checking their SEQ-fields. A reset is 1542 * valid if its sequence number is in the window. 1543 * Note: this does not take into account delayed ACKs, so 1544 * we should test against last_ack_sent instead of rcv_nxt. 1545 * The sequence number in the reset segment is normally an 1546 * echo of our outgoing acknowledgement numbers, but some hosts 1547 * send a reset with the sequence number at the rightmost edge 1548 * of our receive window, and we have to handle this case. 1549 * If we have multiple segments in flight, the intial reset 1550 * segment sequence numbers will be to the left of last_ack_sent, 1551 * but they will eventually catch up. 1552 * In any case, it never made sense to trim reset segments to 1553 * fit the receive window since RFC 1122 says: 1554 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1555 * 1556 * A TCP SHOULD allow a received RST segment to include data. 1557 * 1558 * DISCUSSION 1559 * It has been suggested that a RST segment could contain 1560 * ASCII text that encoded and explained the cause of the 1561 * RST. No standard has yet been established for such 1562 * data. 1563 * 1564 * If the reset segment passes the sequence number test examine 1565 * the state: 1566 * SYN_RECEIVED STATE: 1567 * If passive open, return to LISTEN state. 1568 * If active open, inform user that connection was refused. 1569 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1570 * Inform user that connection was reset, and close tcb. 1571 * CLOSING, LAST_ACK STATES: 1572 * Close the tcb. 1573 * TIME_WAIT STATE: 1574 * Drop the segment - see Stevens, vol. 2, p. 964 and 1575 * RFC 1337. 1576 */ 1577 if (thflags & TH_RST) { 1578 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1579 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1580 switch (tp->t_state) { 1581 1582 case TCPS_SYN_RECEIVED: 1583 so->so_error = ECONNREFUSED; 1584 goto close; 1585 1586 case TCPS_ESTABLISHED: 1587 case TCPS_FIN_WAIT_1: 1588 case TCPS_FIN_WAIT_2: 1589 case TCPS_CLOSE_WAIT: 1590 so->so_error = ECONNRESET; 1591 close: 1592 tp->t_state = TCPS_CLOSED; 1593 tcpstat.tcps_drops++; 1594 tp = tcp_close(tp); 1595 break; 1596 1597 case TCPS_CLOSING: 1598 case TCPS_LAST_ACK: 1599 tp = tcp_close(tp); 1600 break; 1601 1602 case TCPS_TIME_WAIT: 1603 break; 1604 } 1605 } 1606 goto drop; 1607 } 1608 1609 /* 1610 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1611 * and it's less than ts_recent, drop it. 1612 */ 1613 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1614 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1615 1616 /* Check to see if ts_recent is over 24 days old. */ 1617 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1618 /* 1619 * Invalidate ts_recent. If this segment updates 1620 * ts_recent, the age will be reset later and ts_recent 1621 * will get a valid value. If it does not, setting 1622 * ts_recent to zero will at least satisfy the 1623 * requirement that zero be placed in the timestamp 1624 * echo reply when ts_recent isn't valid. The 1625 * age isn't reset until we get a valid ts_recent 1626 * because we don't want out-of-order segments to be 1627 * dropped when ts_recent is old. 1628 */ 1629 tp->ts_recent = 0; 1630 } else { 1631 tcpstat.tcps_rcvduppack++; 1632 tcpstat.tcps_rcvdupbyte += tlen; 1633 tcpstat.tcps_pawsdrop++; 1634 if (tlen) 1635 goto dropafterack; 1636 goto drop; 1637 } 1638 } 1639 1640 /* 1641 * T/TCP mechanism 1642 * If T/TCP was negotiated and the segment doesn't have CC, 1643 * or if its CC is wrong then drop the segment. 1644 * RST segments do not have to comply with this. 1645 */ 1646 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1647 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1648 goto dropafterack; 1649 1650 /* 1651 * In the SYN-RECEIVED state, validate that the packet belongs to 1652 * this connection before trimming the data to fit the receive 1653 * window. Check the sequence number versus IRS since we know 1654 * the sequence numbers haven't wrapped. This is a partial fix 1655 * for the "LAND" DoS attack. 1656 */ 1657 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1658 rstreason = BANDLIM_RST_OPENPORT; 1659 goto dropwithreset; 1660 } 1661 1662 todrop = tp->rcv_nxt - th->th_seq; 1663 if (todrop > 0) { 1664 if (TCP_DO_SACK(tp)) { 1665 /* Report duplicate segment at head of packet. */ 1666 tp->reportblk.rblk_start = th->th_seq; 1667 tp->reportblk.rblk_end = th->th_seq + tlen; 1668 if (thflags & TH_FIN) 1669 ++tp->reportblk.rblk_end; 1670 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1671 tp->reportblk.rblk_end = tp->rcv_nxt; 1672 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1673 } 1674 if (thflags & TH_SYN) { 1675 thflags &= ~TH_SYN; 1676 th->th_seq++; 1677 if (th->th_urp > 1) 1678 th->th_urp--; 1679 else 1680 thflags &= ~TH_URG; 1681 todrop--; 1682 } 1683 /* 1684 * Following if statement from Stevens, vol. 2, p. 960. 1685 */ 1686 if (todrop > tlen || 1687 (todrop == tlen && !(thflags & TH_FIN))) { 1688 /* 1689 * Any valid FIN must be to the left of the window. 1690 * At this point the FIN must be a duplicate or out 1691 * of sequence; drop it. 1692 */ 1693 thflags &= ~TH_FIN; 1694 1695 /* 1696 * Send an ACK to resynchronize and drop any data. 1697 * But keep on processing for RST or ACK. 1698 */ 1699 tp->t_flags |= TF_ACKNOW; 1700 todrop = tlen; 1701 tcpstat.tcps_rcvduppack++; 1702 tcpstat.tcps_rcvdupbyte += todrop; 1703 } else { 1704 tcpstat.tcps_rcvpartduppack++; 1705 tcpstat.tcps_rcvpartdupbyte += todrop; 1706 } 1707 drop_hdrlen += todrop; /* drop from the top afterwards */ 1708 th->th_seq += todrop; 1709 tlen -= todrop; 1710 if (th->th_urp > todrop) 1711 th->th_urp -= todrop; 1712 else { 1713 thflags &= ~TH_URG; 1714 th->th_urp = 0; 1715 } 1716 } 1717 1718 /* 1719 * If new data are received on a connection after the 1720 * user processes are gone, then RST the other end. 1721 */ 1722 if ((so->so_state & SS_NOFDREF) && 1723 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1724 tp = tcp_close(tp); 1725 tcpstat.tcps_rcvafterclose++; 1726 rstreason = BANDLIM_UNLIMITED; 1727 goto dropwithreset; 1728 } 1729 1730 /* 1731 * If segment ends after window, drop trailing data 1732 * (and PUSH and FIN); if nothing left, just ACK. 1733 */ 1734 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1735 if (todrop > 0) { 1736 tcpstat.tcps_rcvpackafterwin++; 1737 if (todrop >= tlen) { 1738 tcpstat.tcps_rcvbyteafterwin += tlen; 1739 /* 1740 * If a new connection request is received 1741 * while in TIME_WAIT, drop the old connection 1742 * and start over if the sequence numbers 1743 * are above the previous ones. 1744 */ 1745 if (thflags & TH_SYN && 1746 tp->t_state == TCPS_TIME_WAIT && 1747 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1748 tp = tcp_close(tp); 1749 goto findpcb; 1750 } 1751 /* 1752 * If window is closed can only take segments at 1753 * window edge, and have to drop data and PUSH from 1754 * incoming segments. Continue processing, but 1755 * remember to ack. Otherwise, drop segment 1756 * and ack. 1757 */ 1758 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1759 tp->t_flags |= TF_ACKNOW; 1760 tcpstat.tcps_rcvwinprobe++; 1761 } else 1762 goto dropafterack; 1763 } else 1764 tcpstat.tcps_rcvbyteafterwin += todrop; 1765 m_adj(m, -todrop); 1766 tlen -= todrop; 1767 thflags &= ~(TH_PUSH | TH_FIN); 1768 } 1769 1770 /* 1771 * If last ACK falls within this segment's sequence numbers, 1772 * record its timestamp. 1773 * NOTE that the test is modified according to the latest 1774 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1775 */ 1776 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1777 tp->ts_recent_age = ticks; 1778 tp->ts_recent = to.to_tsval; 1779 } 1780 1781 /* 1782 * If a SYN is in the window, then this is an 1783 * error and we send an RST and drop the connection. 1784 */ 1785 if (thflags & TH_SYN) { 1786 tp = tcp_drop(tp, ECONNRESET); 1787 rstreason = BANDLIM_UNLIMITED; 1788 goto dropwithreset; 1789 } 1790 1791 /* 1792 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1793 * flag is on (half-synchronized state), then queue data for 1794 * later processing; else drop segment and return. 1795 */ 1796 if (!(thflags & TH_ACK)) { 1797 if (tp->t_state == TCPS_SYN_RECEIVED || 1798 (tp->t_flags & TF_NEEDSYN)) 1799 goto step6; 1800 else 1801 goto drop; 1802 } 1803 1804 /* 1805 * Ack processing. 1806 */ 1807 switch (tp->t_state) { 1808 /* 1809 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1810 * ESTABLISHED state and continue processing. 1811 * The ACK was checked above. 1812 */ 1813 case TCPS_SYN_RECEIVED: 1814 1815 tcpstat.tcps_connects++; 1816 soisconnected(so); 1817 /* Do window scaling? */ 1818 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1819 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1820 tp->snd_scale = tp->requested_s_scale; 1821 tp->rcv_scale = tp->request_r_scale; 1822 } 1823 /* 1824 * Upon successful completion of 3-way handshake, 1825 * update cache.CC if it was undefined, pass any queued 1826 * data to the user, and advance state appropriately. 1827 */ 1828 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1829 taop->tao_cc == 0) 1830 taop->tao_cc = tp->cc_recv; 1831 1832 /* 1833 * Make transitions: 1834 * SYN-RECEIVED -> ESTABLISHED 1835 * SYN-RECEIVED* -> FIN-WAIT-1 1836 */ 1837 tp->t_starttime = ticks; 1838 if (tp->t_flags & TF_NEEDFIN) { 1839 tp->t_state = TCPS_FIN_WAIT_1; 1840 tp->t_flags &= ~TF_NEEDFIN; 1841 } else { 1842 tp->t_state = TCPS_ESTABLISHED; 1843 callout_reset(tp->tt_keep, tcp_keepidle, 1844 tcp_timer_keep, tp); 1845 } 1846 /* 1847 * If segment contains data or ACK, will call tcp_reass() 1848 * later; if not, do so now to pass queued data to user. 1849 */ 1850 if (tlen == 0 && !(thflags & TH_FIN)) 1851 tcp_reass(tp, NULL, NULL, NULL); 1852 /* fall into ... */ 1853 1854 /* 1855 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1856 * ACKs. If the ack is in the range 1857 * tp->snd_una < th->th_ack <= tp->snd_max 1858 * then advance tp->snd_una to th->th_ack and drop 1859 * data from the retransmission queue. If this ACK reflects 1860 * more up to date window information we update our window information. 1861 */ 1862 case TCPS_ESTABLISHED: 1863 case TCPS_FIN_WAIT_1: 1864 case TCPS_FIN_WAIT_2: 1865 case TCPS_CLOSE_WAIT: 1866 case TCPS_CLOSING: 1867 case TCPS_LAST_ACK: 1868 case TCPS_TIME_WAIT: 1869 1870 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1871 if (TCP_DO_SACK(tp)) 1872 tcp_sack_update_scoreboard(tp, &to); 1873 if (tlen != 0 || tiwin != tp->snd_wnd) { 1874 tp->t_dupacks = 0; 1875 break; 1876 } 1877 tcpstat.tcps_rcvdupack++; 1878 if (!callout_active(tp->tt_rexmt) || 1879 th->th_ack != tp->snd_una) { 1880 tp->t_dupacks = 0; 1881 break; 1882 } 1883 /* 1884 * We have outstanding data (other than 1885 * a window probe), this is a completely 1886 * duplicate ack (ie, window info didn't 1887 * change), the ack is the biggest we've 1888 * seen and we've seen exactly our rexmt 1889 * threshhold of them, so assume a packet 1890 * has been dropped and retransmit it. 1891 * Kludge snd_nxt & the congestion 1892 * window so we send only this one 1893 * packet. 1894 */ 1895 if (IN_FASTRECOVERY(tp)) { 1896 if (TCP_DO_SACK(tp)) { 1897 /* No artifical cwnd inflation. */ 1898 tcp_sack_rexmt(tp, th); 1899 } else { 1900 /* 1901 * Dup acks mean that packets 1902 * have left the network 1903 * (they're now cached at the 1904 * receiver) so bump cwnd by 1905 * the amount in the receiver 1906 * to keep a constant cwnd 1907 * packets in the network. 1908 */ 1909 tp->snd_cwnd += tp->t_maxseg; 1910 tcp_output(tp); 1911 } 1912 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1913 tp->t_dupacks = 0; 1914 break; 1915 } else if (++tp->t_dupacks == tcprexmtthresh) { 1916 tcp_seq old_snd_nxt; 1917 u_int win; 1918 1919 fastretransmit: 1920 if (tcp_do_eifel_detect && 1921 (tp->t_flags & TF_RCVD_TSTMP)) { 1922 tcp_save_congestion_state(tp); 1923 tp->t_flags |= TF_FASTREXMT; 1924 } 1925 /* 1926 * We know we're losing at the current 1927 * window size, so do congestion avoidance: 1928 * set ssthresh to half the current window 1929 * and pull our congestion window back to the 1930 * new ssthresh. 1931 */ 1932 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1933 tp->t_maxseg; 1934 if (win < 2) 1935 win = 2; 1936 tp->snd_ssthresh = win * tp->t_maxseg; 1937 ENTER_FASTRECOVERY(tp); 1938 tp->snd_recover = tp->snd_max; 1939 callout_stop(tp->tt_rexmt); 1940 tp->t_rtttime = 0; 1941 old_snd_nxt = tp->snd_nxt; 1942 tp->snd_nxt = th->th_ack; 1943 tp->snd_cwnd = tp->t_maxseg; 1944 tcp_output(tp); 1945 ++tcpstat.tcps_sndfastrexmit; 1946 tp->snd_cwnd = tp->snd_ssthresh; 1947 tp->rexmt_high = tp->snd_nxt; 1948 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1949 tp->snd_nxt = old_snd_nxt; 1950 KASSERT(tp->snd_limited <= 2, 1951 ("tp->snd_limited too big")); 1952 if (TCP_DO_SACK(tp)) 1953 tcp_sack_rexmt(tp, th); 1954 else 1955 tp->snd_cwnd += tp->t_maxseg * 1956 (tp->t_dupacks - tp->snd_limited); 1957 } else if (tcp_do_limitedtransmit) { 1958 u_long oldcwnd = tp->snd_cwnd; 1959 tcp_seq oldsndmax = tp->snd_max; 1960 /* outstanding data */ 1961 uint32_t ownd = tp->snd_max - tp->snd_una; 1962 u_int sent; 1963 1964 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 1965 1966 KASSERT(tp->t_dupacks == 1 || 1967 tp->t_dupacks == 2, 1968 ("dupacks not 1 or 2")); 1969 if (tp->t_dupacks == 1) 1970 tp->snd_limited = 0; 1971 tp->snd_cwnd = ownd + 1972 (tp->t_dupacks - tp->snd_limited) * 1973 tp->t_maxseg; 1974 tcp_output(tp); 1975 tp->snd_cwnd = oldcwnd; 1976 sent = tp->snd_max - oldsndmax; 1977 if (sent > tp->t_maxseg) { 1978 KASSERT((tp->t_dupacks == 2 && 1979 tp->snd_limited == 0) || 1980 (sent == tp->t_maxseg + 1 && 1981 tp->t_flags & TF_SENTFIN), 1982 ("sent too much")); 1983 KASSERT(sent <= tp->t_maxseg * 2, 1984 ("sent too many segments")); 1985 tp->snd_limited = 2; 1986 tcpstat.tcps_sndlimited += 2; 1987 } else if (sent > 0) { 1988 ++tp->snd_limited; 1989 ++tcpstat.tcps_sndlimited; 1990 } else if (tcp_do_early_retransmit && 1991 (tcp_do_eifel_detect && 1992 (tp->t_flags & TF_RCVD_TSTMP)) && 1993 ownd < 4 * tp->t_maxseg && 1994 tp->t_dupacks + 1 >= 1995 iceildiv(ownd, tp->t_maxseg) && 1996 (!TCP_DO_SACK(tp) || 1997 ownd <= tp->t_maxseg || 1998 tcp_sack_has_sacked(&tp->scb, 1999 ownd - tp->t_maxseg))) { 2000 ++tcpstat.tcps_sndearlyrexmit; 2001 tp->t_flags |= TF_EARLYREXMT; 2002 goto fastretransmit; 2003 } 2004 } 2005 goto drop; 2006 } 2007 2008 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2009 tp->t_dupacks = 0; 2010 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2011 /* 2012 * Detected optimistic ACK attack. 2013 * Force slow-start to de-synchronize attack. 2014 */ 2015 tp->snd_cwnd = tp->t_maxseg; 2016 2017 tcpstat.tcps_rcvacktoomuch++; 2018 goto dropafterack; 2019 } 2020 /* 2021 * If we reach this point, ACK is not a duplicate, 2022 * i.e., it ACKs something we sent. 2023 */ 2024 if (tp->t_flags & TF_NEEDSYN) { 2025 /* 2026 * T/TCP: Connection was half-synchronized, and our 2027 * SYN has been ACK'd (so connection is now fully 2028 * synchronized). Go to non-starred state, 2029 * increment snd_una for ACK of SYN, and check if 2030 * we can do window scaling. 2031 */ 2032 tp->t_flags &= ~TF_NEEDSYN; 2033 tp->snd_una++; 2034 /* Do window scaling? */ 2035 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2036 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2037 tp->snd_scale = tp->requested_s_scale; 2038 tp->rcv_scale = tp->request_r_scale; 2039 } 2040 } 2041 2042 process_ACK: 2043 acked = th->th_ack - tp->snd_una; 2044 tcpstat.tcps_rcvackpack++; 2045 tcpstat.tcps_rcvackbyte += acked; 2046 2047 if (tcp_do_eifel_detect && acked > 0 && 2048 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2049 (tp->t_flags & TF_FIRSTACCACK)) { 2050 /* Eifel detection applicable. */ 2051 if (to.to_tsecr < tp->t_rexmtTS) { 2052 ++tcpstat.tcps_eifeldetected; 2053 tcp_revert_congestion_state(tp); 2054 if (tp->t_rxtshift == 1 && 2055 ticks >= tp->t_badrxtwin) 2056 ++tcpstat.tcps_rttcantdetect; 2057 } 2058 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2059 /* 2060 * If we just performed our first retransmit, 2061 * and the ACK arrives within our recovery window, 2062 * then it was a mistake to do the retransmit 2063 * in the first place. Recover our original cwnd 2064 * and ssthresh, and proceed to transmit where we 2065 * left off. 2066 */ 2067 tcp_revert_congestion_state(tp); 2068 ++tcpstat.tcps_rttdetected; 2069 } 2070 2071 /* 2072 * If we have a timestamp reply, update smoothed 2073 * round trip time. If no timestamp is present but 2074 * transmit timer is running and timed sequence 2075 * number was acked, update smoothed round trip time. 2076 * Since we now have an rtt measurement, cancel the 2077 * timer backoff (cf., Phil Karn's retransmit alg.). 2078 * Recompute the initial retransmit timer. 2079 * 2080 * Some machines (certain windows boxes) send broken 2081 * timestamp replies during the SYN+ACK phase, ignore 2082 * timestamps of 0. 2083 */ 2084 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2085 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2086 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2087 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2088 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2089 2090 /* 2091 * If no data (only SYN) was ACK'd, 2092 * skip rest of ACK processing. 2093 */ 2094 if (acked == 0) 2095 goto step6; 2096 2097 /* Stop looking for an acceptable ACK since one was received. */ 2098 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2099 2100 if (acked > so->so_snd.sb_cc) { 2101 tp->snd_wnd -= so->so_snd.sb_cc; 2102 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2103 ourfinisacked = TRUE; 2104 } else { 2105 sbdrop(&so->so_snd, acked); 2106 tp->snd_wnd -= acked; 2107 ourfinisacked = FALSE; 2108 } 2109 sowwakeup(so); 2110 2111 /* 2112 * Update window information. 2113 * Don't look at window if no ACK: 2114 * TAC's send garbage on first SYN. 2115 */ 2116 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2117 (tp->snd_wl1 == th->th_seq && 2118 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2119 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2120 /* keep track of pure window updates */ 2121 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2122 tiwin > tp->snd_wnd) 2123 tcpstat.tcps_rcvwinupd++; 2124 tp->snd_wnd = tiwin; 2125 tp->snd_wl1 = th->th_seq; 2126 tp->snd_wl2 = th->th_ack; 2127 if (tp->snd_wnd > tp->max_sndwnd) 2128 tp->max_sndwnd = tp->snd_wnd; 2129 needoutput = TRUE; 2130 } 2131 2132 tp->snd_una = th->th_ack; 2133 if (TCP_DO_SACK(tp)) 2134 tcp_sack_update_scoreboard(tp, &to); 2135 if (IN_FASTRECOVERY(tp)) { 2136 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2137 EXIT_FASTRECOVERY(tp); 2138 needoutput = TRUE; 2139 /* 2140 * If the congestion window was inflated 2141 * to account for the other side's 2142 * cached packets, retract it. 2143 * 2144 * Window inflation should have left us 2145 * with approximately snd_ssthresh outstanding 2146 * data. But, in case we would be inclined 2147 * to send a burst, better do it using 2148 * slow start. 2149 */ 2150 if (!TCP_DO_SACK(tp)) 2151 tp->snd_cwnd = tp->snd_ssthresh; 2152 2153 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2154 tp->snd_max + 2 * tp->t_maxseg)) 2155 tp->snd_cwnd = 2156 (tp->snd_max - tp->snd_una) + 2157 2 * tp->t_maxseg; 2158 } else { 2159 if (TCP_DO_SACK(tp)) { 2160 tp->snd_max_rexmt = tp->snd_max; 2161 tcp_sack_rexmt(tp, th); 2162 } else { 2163 tcp_newreno_partial_ack(tp, th, acked); 2164 } 2165 needoutput = FALSE; 2166 } 2167 } else { 2168 /* 2169 * When new data is acked, open the congestion window. 2170 * If the window gives us less than ssthresh packets 2171 * in flight, open exponentially (maxseg per packet). 2172 * Otherwise open linearly: maxseg per window 2173 * (maxseg^2 / cwnd per packet). 2174 */ 2175 u_int cw = tp->snd_cwnd; 2176 u_int incr; 2177 2178 if (cw > tp->snd_ssthresh) 2179 incr = tp->t_maxseg * tp->t_maxseg / cw; 2180 else 2181 incr = tp->t_maxseg; 2182 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2183 tp->snd_recover = th->th_ack - 1; 2184 } 2185 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2186 tp->snd_nxt = tp->snd_una; 2187 2188 /* 2189 * If all outstanding data is acked, stop retransmit 2190 * timer and remember to restart (more output or persist). 2191 * If there is more data to be acked, restart retransmit 2192 * timer, using current (possibly backed-off) value. 2193 */ 2194 if (th->th_ack == tp->snd_max) { 2195 callout_stop(tp->tt_rexmt); 2196 needoutput = TRUE; 2197 } else if (!callout_active(tp->tt_persist)) 2198 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2199 tcp_timer_rexmt, tp); 2200 2201 switch (tp->t_state) { 2202 /* 2203 * In FIN_WAIT_1 STATE in addition to the processing 2204 * for the ESTABLISHED state if our FIN is now acknowledged 2205 * then enter FIN_WAIT_2. 2206 */ 2207 case TCPS_FIN_WAIT_1: 2208 if (ourfinisacked) { 2209 /* 2210 * If we can't receive any more 2211 * data, then closing user can proceed. 2212 * Starting the timer is contrary to the 2213 * specification, but if we don't get a FIN 2214 * we'll hang forever. 2215 */ 2216 if (so->so_state & SS_CANTRCVMORE) { 2217 soisdisconnected(so); 2218 callout_reset(tp->tt_2msl, tcp_maxidle, 2219 tcp_timer_2msl, tp); 2220 } 2221 tp->t_state = TCPS_FIN_WAIT_2; 2222 } 2223 break; 2224 2225 /* 2226 * In CLOSING STATE in addition to the processing for 2227 * the ESTABLISHED state if the ACK acknowledges our FIN 2228 * then enter the TIME-WAIT state, otherwise ignore 2229 * the segment. 2230 */ 2231 case TCPS_CLOSING: 2232 if (ourfinisacked) { 2233 tp->t_state = TCPS_TIME_WAIT; 2234 tcp_canceltimers(tp); 2235 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2236 if (tp->cc_recv != 0 && 2237 (ticks - tp->t_starttime) < tcp_msl) 2238 callout_reset(tp->tt_2msl, 2239 tp->t_rxtcur * TCPTV_TWTRUNC, 2240 tcp_timer_2msl, tp); 2241 else 2242 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2243 tcp_timer_2msl, tp); 2244 soisdisconnected(so); 2245 } 2246 break; 2247 2248 /* 2249 * In LAST_ACK, we may still be waiting for data to drain 2250 * and/or to be acked, as well as for the ack of our FIN. 2251 * If our FIN is now acknowledged, delete the TCB, 2252 * enter the closed state and return. 2253 */ 2254 case TCPS_LAST_ACK: 2255 if (ourfinisacked) { 2256 tp = tcp_close(tp); 2257 goto drop; 2258 } 2259 break; 2260 2261 /* 2262 * In TIME_WAIT state the only thing that should arrive 2263 * is a retransmission of the remote FIN. Acknowledge 2264 * it and restart the finack timer. 2265 */ 2266 case TCPS_TIME_WAIT: 2267 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2268 tcp_timer_2msl, tp); 2269 goto dropafterack; 2270 } 2271 } 2272 2273 step6: 2274 /* 2275 * Update window information. 2276 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2277 */ 2278 if ((thflags & TH_ACK) && 2279 acceptable_window_update(tp, th, tiwin)) { 2280 /* keep track of pure window updates */ 2281 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2282 tiwin > tp->snd_wnd) 2283 tcpstat.tcps_rcvwinupd++; 2284 tp->snd_wnd = tiwin; 2285 tp->snd_wl1 = th->th_seq; 2286 tp->snd_wl2 = th->th_ack; 2287 if (tp->snd_wnd > tp->max_sndwnd) 2288 tp->max_sndwnd = tp->snd_wnd; 2289 needoutput = TRUE; 2290 } 2291 2292 /* 2293 * Process segments with URG. 2294 */ 2295 if ((thflags & TH_URG) && th->th_urp && 2296 !TCPS_HAVERCVDFIN(tp->t_state)) { 2297 /* 2298 * This is a kludge, but if we receive and accept 2299 * random urgent pointers, we'll crash in 2300 * soreceive. It's hard to imagine someone 2301 * actually wanting to send this much urgent data. 2302 */ 2303 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2304 th->th_urp = 0; /* XXX */ 2305 thflags &= ~TH_URG; /* XXX */ 2306 goto dodata; /* XXX */ 2307 } 2308 /* 2309 * If this segment advances the known urgent pointer, 2310 * then mark the data stream. This should not happen 2311 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2312 * a FIN has been received from the remote side. 2313 * In these states we ignore the URG. 2314 * 2315 * According to RFC961 (Assigned Protocols), 2316 * the urgent pointer points to the last octet 2317 * of urgent data. We continue, however, 2318 * to consider it to indicate the first octet 2319 * of data past the urgent section as the original 2320 * spec states (in one of two places). 2321 */ 2322 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2323 tp->rcv_up = th->th_seq + th->th_urp; 2324 so->so_oobmark = so->so_rcv.sb_cc + 2325 (tp->rcv_up - tp->rcv_nxt) - 1; 2326 if (so->so_oobmark == 0) 2327 so->so_state |= SS_RCVATMARK; 2328 sohasoutofband(so); 2329 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2330 } 2331 /* 2332 * Remove out of band data so doesn't get presented to user. 2333 * This can happen independent of advancing the URG pointer, 2334 * but if two URG's are pending at once, some out-of-band 2335 * data may creep in... ick. 2336 */ 2337 if (th->th_urp <= (u_long)tlen && 2338 !(so->so_options & SO_OOBINLINE)) { 2339 /* hdr drop is delayed */ 2340 tcp_pulloutofband(so, th, m, drop_hdrlen); 2341 } 2342 } else { 2343 /* 2344 * If no out of band data is expected, 2345 * pull receive urgent pointer along 2346 * with the receive window. 2347 */ 2348 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2349 tp->rcv_up = tp->rcv_nxt; 2350 } 2351 2352 dodata: /* XXX */ 2353 /* 2354 * Process the segment text, merging it into the TCP sequencing queue, 2355 * and arranging for acknowledgment of receipt if necessary. 2356 * This process logically involves adjusting tp->rcv_wnd as data 2357 * is presented to the user (this happens in tcp_usrreq.c, 2358 * case PRU_RCVD). If a FIN has already been received on this 2359 * connection then we just ignore the text. 2360 */ 2361 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2362 m_adj(m, drop_hdrlen); /* delayed header drop */ 2363 /* 2364 * Insert segment which includes th into TCP reassembly queue 2365 * with control block tp. Set thflags to whether reassembly now 2366 * includes a segment with FIN. This handles the common case 2367 * inline (segment is the next to be received on an established 2368 * connection, and the queue is empty), avoiding linkage into 2369 * and removal from the queue and repetition of various 2370 * conversions. 2371 * Set DELACK for segments received in order, but ack 2372 * immediately when segments are out of order (so 2373 * fast retransmit can work). 2374 */ 2375 if (th->th_seq == tp->rcv_nxt && 2376 LIST_EMPTY(&tp->t_segq) && 2377 TCPS_HAVEESTABLISHED(tp->t_state)) { 2378 if (DELAY_ACK(tp)) 2379 callout_reset(tp->tt_delack, tcp_delacktime, 2380 tcp_timer_delack, tp); 2381 else 2382 tp->t_flags |= TF_ACKNOW; 2383 tp->rcv_nxt += tlen; 2384 thflags = th->th_flags & TH_FIN; 2385 tcpstat.tcps_rcvpack++; 2386 tcpstat.tcps_rcvbyte += tlen; 2387 ND6_HINT(tp); 2388 if (so->so_state & SS_CANTRCVMORE) 2389 m_freem(m); 2390 else 2391 sbappendstream(&so->so_rcv, m); 2392 sorwakeup(so); 2393 } else { 2394 if (!(tp->t_flags & TF_DUPSEG)) { 2395 /* Initialize SACK report block. */ 2396 tp->reportblk.rblk_start = th->th_seq; 2397 tp->reportblk.rblk_end = th->th_seq + tlen + 2398 ((thflags & TH_FIN) != 0); 2399 } 2400 thflags = tcp_reass(tp, th, &tlen, m); 2401 tp->t_flags |= TF_ACKNOW; 2402 } 2403 2404 /* 2405 * Note the amount of data that peer has sent into 2406 * our window, in order to estimate the sender's 2407 * buffer size. 2408 */ 2409 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2410 } else { 2411 m_freem(m); 2412 thflags &= ~TH_FIN; 2413 } 2414 2415 /* 2416 * If FIN is received ACK the FIN and let the user know 2417 * that the connection is closing. 2418 */ 2419 if (thflags & TH_FIN) { 2420 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2421 socantrcvmore(so); 2422 /* 2423 * If connection is half-synchronized 2424 * (ie NEEDSYN flag on) then delay ACK, 2425 * so it may be piggybacked when SYN is sent. 2426 * Otherwise, since we received a FIN then no 2427 * more input can be expected, send ACK now. 2428 */ 2429 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2430 callout_reset(tp->tt_delack, tcp_delacktime, 2431 tcp_timer_delack, tp); 2432 else 2433 tp->t_flags |= TF_ACKNOW; 2434 tp->rcv_nxt++; 2435 } 2436 2437 switch (tp->t_state) { 2438 /* 2439 * In SYN_RECEIVED and ESTABLISHED STATES 2440 * enter the CLOSE_WAIT state. 2441 */ 2442 case TCPS_SYN_RECEIVED: 2443 tp->t_starttime = ticks; 2444 /*FALLTHROUGH*/ 2445 case TCPS_ESTABLISHED: 2446 tp->t_state = TCPS_CLOSE_WAIT; 2447 break; 2448 2449 /* 2450 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2451 * enter the CLOSING state. 2452 */ 2453 case TCPS_FIN_WAIT_1: 2454 tp->t_state = TCPS_CLOSING; 2455 break; 2456 2457 /* 2458 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2459 * starting the time-wait timer, turning off the other 2460 * standard timers. 2461 */ 2462 case TCPS_FIN_WAIT_2: 2463 tp->t_state = TCPS_TIME_WAIT; 2464 tcp_canceltimers(tp); 2465 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2466 if (tp->cc_recv != 0 && 2467 (ticks - tp->t_starttime) < tcp_msl) { 2468 callout_reset(tp->tt_2msl, 2469 tp->t_rxtcur * TCPTV_TWTRUNC, 2470 tcp_timer_2msl, tp); 2471 /* For transaction client, force ACK now. */ 2472 tp->t_flags |= TF_ACKNOW; 2473 } 2474 else 2475 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2476 tcp_timer_2msl, tp); 2477 soisdisconnected(so); 2478 break; 2479 2480 /* 2481 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2482 */ 2483 case TCPS_TIME_WAIT: 2484 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2485 tcp_timer_2msl, tp); 2486 break; 2487 } 2488 } 2489 2490 #ifdef TCPDEBUG 2491 if (so->so_options & SO_DEBUG) 2492 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2493 #endif 2494 2495 /* 2496 * Return any desired output. 2497 */ 2498 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2499 tcp_output(tp); 2500 return; 2501 2502 dropafterack: 2503 /* 2504 * Generate an ACK dropping incoming segment if it occupies 2505 * sequence space, where the ACK reflects our state. 2506 * 2507 * We can now skip the test for the RST flag since all 2508 * paths to this code happen after packets containing 2509 * RST have been dropped. 2510 * 2511 * In the SYN-RECEIVED state, don't send an ACK unless the 2512 * segment we received passes the SYN-RECEIVED ACK test. 2513 * If it fails send a RST. This breaks the loop in the 2514 * "LAND" DoS attack, and also prevents an ACK storm 2515 * between two listening ports that have been sent forged 2516 * SYN segments, each with the source address of the other. 2517 */ 2518 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2519 (SEQ_GT(tp->snd_una, th->th_ack) || 2520 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2521 rstreason = BANDLIM_RST_OPENPORT; 2522 goto dropwithreset; 2523 } 2524 #ifdef TCPDEBUG 2525 if (so->so_options & SO_DEBUG) 2526 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2527 #endif 2528 m_freem(m); 2529 tp->t_flags |= TF_ACKNOW; 2530 tcp_output(tp); 2531 return; 2532 2533 dropwithreset: 2534 /* 2535 * Generate a RST, dropping incoming segment. 2536 * Make ACK acceptable to originator of segment. 2537 * Don't bother to respond if destination was broadcast/multicast. 2538 */ 2539 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2540 goto drop; 2541 if (isipv6) { 2542 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2543 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2544 goto drop; 2545 } else { 2546 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2547 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2548 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2549 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2550 goto drop; 2551 } 2552 /* IPv6 anycast check is done at tcp6_input() */ 2553 2554 /* 2555 * Perform bandwidth limiting. 2556 */ 2557 #ifdef ICMP_BANDLIM 2558 if (badport_bandlim(rstreason) < 0) 2559 goto drop; 2560 #endif 2561 2562 #ifdef TCPDEBUG 2563 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2564 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2565 #endif 2566 if (thflags & TH_ACK) 2567 /* mtod() below is safe as long as hdr dropping is delayed */ 2568 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2569 TH_RST); 2570 else { 2571 if (thflags & TH_SYN) 2572 tlen++; 2573 /* mtod() below is safe as long as hdr dropping is delayed */ 2574 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2575 (tcp_seq)0, TH_RST | TH_ACK); 2576 } 2577 return; 2578 2579 drop: 2580 /* 2581 * Drop space held by incoming segment and return. 2582 */ 2583 #ifdef TCPDEBUG 2584 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2585 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2586 #endif 2587 m_freem(m); 2588 return; 2589 } 2590 2591 /* 2592 * Parse TCP options and place in tcpopt. 2593 */ 2594 static void 2595 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2596 { 2597 int opt, optlen, i; 2598 2599 to->to_flags = 0; 2600 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2601 opt = cp[0]; 2602 if (opt == TCPOPT_EOL) 2603 break; 2604 if (opt == TCPOPT_NOP) 2605 optlen = 1; 2606 else { 2607 if (cnt < 2) 2608 break; 2609 optlen = cp[1]; 2610 if (optlen < 2 || optlen > cnt) 2611 break; 2612 } 2613 switch (opt) { 2614 case TCPOPT_MAXSEG: 2615 if (optlen != TCPOLEN_MAXSEG) 2616 continue; 2617 if (!is_syn) 2618 continue; 2619 to->to_flags |= TOF_MSS; 2620 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2621 to->to_mss = ntohs(to->to_mss); 2622 break; 2623 case TCPOPT_WINDOW: 2624 if (optlen != TCPOLEN_WINDOW) 2625 continue; 2626 if (!is_syn) 2627 continue; 2628 to->to_flags |= TOF_SCALE; 2629 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2630 break; 2631 case TCPOPT_TIMESTAMP: 2632 if (optlen != TCPOLEN_TIMESTAMP) 2633 continue; 2634 to->to_flags |= TOF_TS; 2635 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2636 to->to_tsval = ntohl(to->to_tsval); 2637 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2638 to->to_tsecr = ntohl(to->to_tsecr); 2639 break; 2640 case TCPOPT_CC: 2641 if (optlen != TCPOLEN_CC) 2642 continue; 2643 to->to_flags |= TOF_CC; 2644 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2645 to->to_cc = ntohl(to->to_cc); 2646 break; 2647 case TCPOPT_CCNEW: 2648 if (optlen != TCPOLEN_CC) 2649 continue; 2650 if (!is_syn) 2651 continue; 2652 to->to_flags |= TOF_CCNEW; 2653 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2654 to->to_cc = ntohl(to->to_cc); 2655 break; 2656 case TCPOPT_CCECHO: 2657 if (optlen != TCPOLEN_CC) 2658 continue; 2659 if (!is_syn) 2660 continue; 2661 to->to_flags |= TOF_CCECHO; 2662 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho); 2663 to->to_ccecho = ntohl(to->to_ccecho); 2664 break; 2665 case TCPOPT_SACK_PERMITTED: 2666 if (optlen != TCPOLEN_SACK_PERMITTED) 2667 continue; 2668 if (!is_syn) 2669 continue; 2670 to->to_flags |= TOF_SACK_PERMITTED; 2671 break; 2672 case TCPOPT_SACK: 2673 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2674 continue; 2675 to->to_nsackblocks = (optlen - 2) / 8; 2676 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2677 to->to_flags |= TOF_SACK; 2678 for (i = 0; i < to->to_nsackblocks; i++) { 2679 struct raw_sackblock *r = &to->to_sackblocks[i]; 2680 2681 r->rblk_start = ntohl(r->rblk_start); 2682 r->rblk_end = ntohl(r->rblk_end); 2683 } 2684 break; 2685 default: 2686 continue; 2687 } 2688 } 2689 } 2690 2691 /* 2692 * Pull out of band byte out of a segment so 2693 * it doesn't appear in the user's data queue. 2694 * It is still reflected in the segment length for 2695 * sequencing purposes. 2696 * "off" is the delayed to be dropped hdrlen. 2697 */ 2698 static void 2699 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2700 { 2701 int cnt = off + th->th_urp - 1; 2702 2703 while (cnt >= 0) { 2704 if (m->m_len > cnt) { 2705 char *cp = mtod(m, caddr_t) + cnt; 2706 struct tcpcb *tp = sototcpcb(so); 2707 2708 tp->t_iobc = *cp; 2709 tp->t_oobflags |= TCPOOB_HAVEDATA; 2710 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2711 m->m_len--; 2712 if (m->m_flags & M_PKTHDR) 2713 m->m_pkthdr.len--; 2714 return; 2715 } 2716 cnt -= m->m_len; 2717 m = m->m_next; 2718 if (m == 0) 2719 break; 2720 } 2721 panic("tcp_pulloutofband"); 2722 } 2723 2724 /* 2725 * Collect new round-trip time estimate 2726 * and update averages and current timeout. 2727 */ 2728 static void 2729 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2730 { 2731 int delta; 2732 2733 tcpstat.tcps_rttupdated++; 2734 tp->t_rttupdated++; 2735 if (tp->t_srtt != 0) { 2736 /* 2737 * srtt is stored as fixed point with 5 bits after the 2738 * binary point (i.e., scaled by 8). The following magic 2739 * is equivalent to the smoothing algorithm in rfc793 with 2740 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2741 * point). Adjust rtt to origin 0. 2742 */ 2743 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2744 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2745 2746 if ((tp->t_srtt += delta) <= 0) 2747 tp->t_srtt = 1; 2748 2749 /* 2750 * We accumulate a smoothed rtt variance (actually, a 2751 * smoothed mean difference), then set the retransmit 2752 * timer to smoothed rtt + 4 times the smoothed variance. 2753 * rttvar is stored as fixed point with 4 bits after the 2754 * binary point (scaled by 16). The following is 2755 * equivalent to rfc793 smoothing with an alpha of .75 2756 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2757 * rfc793's wired-in beta. 2758 */ 2759 if (delta < 0) 2760 delta = -delta; 2761 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2762 if ((tp->t_rttvar += delta) <= 0) 2763 tp->t_rttvar = 1; 2764 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2765 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2766 } else { 2767 /* 2768 * No rtt measurement yet - use the unsmoothed rtt. 2769 * Set the variance to half the rtt (so our first 2770 * retransmit happens at 3*rtt). 2771 */ 2772 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2773 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2774 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2775 } 2776 tp->t_rtttime = 0; 2777 tp->t_rxtshift = 0; 2778 2779 /* 2780 * the retransmit should happen at rtt + 4 * rttvar. 2781 * Because of the way we do the smoothing, srtt and rttvar 2782 * will each average +1/2 tick of bias. When we compute 2783 * the retransmit timer, we want 1/2 tick of rounding and 2784 * 1 extra tick because of +-1/2 tick uncertainty in the 2785 * firing of the timer. The bias will give us exactly the 2786 * 1.5 tick we need. But, because the bias is 2787 * statistical, we have to test that we don't drop below 2788 * the minimum feasible timer (which is 2 ticks). 2789 */ 2790 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2791 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2792 2793 /* 2794 * We received an ack for a packet that wasn't retransmitted; 2795 * it is probably safe to discard any error indications we've 2796 * received recently. This isn't quite right, but close enough 2797 * for now (a route might have failed after we sent a segment, 2798 * and the return path might not be symmetrical). 2799 */ 2800 tp->t_softerror = 0; 2801 } 2802 2803 /* 2804 * Determine a reasonable value for maxseg size. 2805 * If the route is known, check route for mtu. 2806 * If none, use an mss that can be handled on the outgoing 2807 * interface without forcing IP to fragment; if bigger than 2808 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2809 * to utilize large mbufs. If no route is found, route has no mtu, 2810 * or the destination isn't local, use a default, hopefully conservative 2811 * size (usually 512 or the default IP max size, but no more than the mtu 2812 * of the interface), as we can't discover anything about intervening 2813 * gateways or networks. We also initialize the congestion/slow start 2814 * window to be a single segment if the destination isn't local. 2815 * While looking at the routing entry, we also initialize other path-dependent 2816 * parameters from pre-set or cached values in the routing entry. 2817 * 2818 * Also take into account the space needed for options that we 2819 * send regularly. Make maxseg shorter by that amount to assure 2820 * that we can send maxseg amount of data even when the options 2821 * are present. Store the upper limit of the length of options plus 2822 * data in maxopd. 2823 * 2824 * NOTE that this routine is only called when we process an incoming 2825 * segment, for outgoing segments only tcp_mssopt is called. 2826 * 2827 * In case of T/TCP, we call this routine during implicit connection 2828 * setup as well (offer = -1), to initialize maxseg from the cached 2829 * MSS of our peer. 2830 */ 2831 void 2832 tcp_mss(struct tcpcb *tp, int offer) 2833 { 2834 struct rtentry *rt; 2835 struct ifnet *ifp; 2836 int rtt, mss; 2837 u_long bufsize; 2838 struct inpcb *inp = tp->t_inpcb; 2839 struct socket *so; 2840 struct rmxp_tao *taop; 2841 int origoffer = offer; 2842 #ifdef INET6 2843 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2844 size_t min_protoh = isipv6 ? 2845 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2846 sizeof(struct tcpiphdr); 2847 #else 2848 const boolean_t isipv6 = FALSE; 2849 const size_t min_protoh = sizeof(struct tcpiphdr); 2850 #endif 2851 2852 if (isipv6) 2853 rt = tcp_rtlookup6(&inp->inp_inc); 2854 else 2855 rt = tcp_rtlookup(&inp->inp_inc); 2856 if (rt == NULL) { 2857 tp->t_maxopd = tp->t_maxseg = 2858 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2859 return; 2860 } 2861 ifp = rt->rt_ifp; 2862 so = inp->inp_socket; 2863 2864 taop = rmx_taop(rt->rt_rmx); 2865 /* 2866 * Offer == -1 means that we didn't receive SYN yet, 2867 * use cached value in that case; 2868 */ 2869 if (offer == -1) 2870 offer = taop->tao_mssopt; 2871 /* 2872 * Offer == 0 means that there was no MSS on the SYN segment, 2873 * in this case we use tcp_mssdflt. 2874 */ 2875 if (offer == 0) 2876 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2877 else 2878 /* 2879 * Sanity check: make sure that maxopd will be large 2880 * enough to allow some data on segments even is the 2881 * all the option space is used (40bytes). Otherwise 2882 * funny things may happen in tcp_output. 2883 */ 2884 offer = max(offer, 64); 2885 taop->tao_mssopt = offer; 2886 2887 /* 2888 * While we're here, check if there's an initial rtt 2889 * or rttvar. Convert from the route-table units 2890 * to scaled multiples of the slow timeout timer. 2891 */ 2892 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2893 /* 2894 * XXX the lock bit for RTT indicates that the value 2895 * is also a minimum value; this is subject to time. 2896 */ 2897 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2898 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2899 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2900 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2901 tcpstat.tcps_usedrtt++; 2902 if (rt->rt_rmx.rmx_rttvar) { 2903 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2904 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2905 tcpstat.tcps_usedrttvar++; 2906 } else { 2907 /* default variation is +- 1 rtt */ 2908 tp->t_rttvar = 2909 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2910 } 2911 TCPT_RANGESET(tp->t_rxtcur, 2912 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2913 tp->t_rttmin, TCPTV_REXMTMAX); 2914 } 2915 /* 2916 * if there's an mtu associated with the route, use it 2917 * else, use the link mtu. 2918 */ 2919 if (rt->rt_rmx.rmx_mtu) 2920 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2921 else { 2922 if (isipv6) { 2923 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2924 min_protoh; 2925 if (!in6_localaddr(&inp->in6p_faddr)) 2926 mss = min(mss, tcp_v6mssdflt); 2927 } else { 2928 mss = ifp->if_mtu - min_protoh; 2929 if (!in_localaddr(inp->inp_faddr)) 2930 mss = min(mss, tcp_mssdflt); 2931 } 2932 } 2933 mss = min(mss, offer); 2934 /* 2935 * maxopd stores the maximum length of data AND options 2936 * in a segment; maxseg is the amount of data in a normal 2937 * segment. We need to store this value (maxopd) apart 2938 * from maxseg, because now every segment carries options 2939 * and thus we normally have somewhat less data in segments. 2940 */ 2941 tp->t_maxopd = mss; 2942 2943 /* 2944 * In case of T/TCP, origoffer==-1 indicates, that no segments 2945 * were received yet. In this case we just guess, otherwise 2946 * we do the same as before T/TCP. 2947 */ 2948 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2949 (origoffer == -1 || 2950 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2951 mss -= TCPOLEN_TSTAMP_APPA; 2952 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 2953 (origoffer == -1 || 2954 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2955 mss -= TCPOLEN_CC_APPA; 2956 2957 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2958 if (mss > MCLBYTES) 2959 mss &= ~(MCLBYTES-1); 2960 #else 2961 if (mss > MCLBYTES) 2962 mss = mss / MCLBYTES * MCLBYTES; 2963 #endif 2964 /* 2965 * If there's a pipesize, change the socket buffer 2966 * to that size. Make the socket buffers an integral 2967 * number of mss units; if the mss is larger than 2968 * the socket buffer, decrease the mss. 2969 */ 2970 #ifdef RTV_SPIPE 2971 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2972 #endif 2973 bufsize = so->so_snd.sb_hiwat; 2974 if (bufsize < mss) 2975 mss = bufsize; 2976 else { 2977 bufsize = roundup(bufsize, mss); 2978 if (bufsize > sb_max) 2979 bufsize = sb_max; 2980 if (bufsize > so->so_snd.sb_hiwat) 2981 sbreserve(&so->so_snd, bufsize, so, NULL); 2982 } 2983 tp->t_maxseg = mss; 2984 2985 #ifdef RTV_RPIPE 2986 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2987 #endif 2988 bufsize = so->so_rcv.sb_hiwat; 2989 if (bufsize > mss) { 2990 bufsize = roundup(bufsize, mss); 2991 if (bufsize > sb_max) 2992 bufsize = sb_max; 2993 if (bufsize > so->so_rcv.sb_hiwat) 2994 sbreserve(&so->so_rcv, bufsize, so, NULL); 2995 } 2996 2997 /* 2998 * Set the slow-start flight size depending on whether this 2999 * is a local network or not. 3000 */ 3001 if (tcp_do_rfc3390) 3002 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3003 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 3004 (!isipv6 && in_localaddr(inp->inp_faddr))) 3005 tp->snd_cwnd = mss * ss_fltsz_local; 3006 else 3007 tp->snd_cwnd = mss * ss_fltsz; 3008 3009 if (rt->rt_rmx.rmx_ssthresh) { 3010 /* 3011 * There's some sort of gateway or interface 3012 * buffer limit on the path. Use this to set 3013 * the slow start threshhold, but set the 3014 * threshold to no less than 2*mss. 3015 */ 3016 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3017 tcpstat.tcps_usedssthresh++; 3018 } 3019 } 3020 3021 /* 3022 * Determine the MSS option to send on an outgoing SYN. 3023 */ 3024 int 3025 tcp_mssopt(struct tcpcb *tp) 3026 { 3027 struct rtentry *rt; 3028 #ifdef INET6 3029 boolean_t isipv6 = 3030 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3031 int min_protoh = isipv6 ? 3032 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3033 sizeof(struct tcpiphdr); 3034 #else 3035 const boolean_t isipv6 = FALSE; 3036 const size_t min_protoh = sizeof(struct tcpiphdr); 3037 #endif 3038 3039 if (isipv6) 3040 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3041 else 3042 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3043 if (rt == NULL) 3044 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3045 3046 return (rt->rt_ifp->if_mtu - min_protoh); 3047 } 3048 3049 /* 3050 * When a partial ack arrives, force the retransmission of the 3051 * next unacknowledged segment. Do not exit Fast Recovery. 3052 * 3053 * Implement the Slow-but-Steady variant of NewReno by restarting the 3054 * the retransmission timer. Turn it off here so it can be restarted 3055 * later in tcp_output(). 3056 */ 3057 static void 3058 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3059 { 3060 tcp_seq old_snd_nxt = tp->snd_nxt; 3061 u_long ocwnd = tp->snd_cwnd; 3062 3063 callout_stop(tp->tt_rexmt); 3064 tp->t_rtttime = 0; 3065 tp->snd_nxt = th->th_ack; 3066 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3067 tp->snd_cwnd = tp->t_maxseg; 3068 tp->t_flags |= TF_ACKNOW; 3069 tcp_output(tp); 3070 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3071 tp->snd_nxt = old_snd_nxt; 3072 /* partial window deflation */ 3073 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3074 } 3075 3076 /* 3077 * In contrast to the Slow-but-Steady NewReno variant, 3078 * we do not reset the retransmission timer for SACK retransmissions, 3079 * except when retransmitting snd_una. 3080 */ 3081 static void 3082 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3083 { 3084 uint32_t pipe, seglen; 3085 tcp_seq nextrexmt; 3086 boolean_t lostdup; 3087 tcp_seq old_snd_nxt = tp->snd_nxt; 3088 u_long ocwnd = tp->snd_cwnd; 3089 int nseg = 0; /* consecutive new segments */ 3090 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3091 3092 tp->t_rtttime = 0; 3093 pipe = tcp_sack_compute_pipe(tp); 3094 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3095 (!tcp_do_smartsack || nseg < MAXBURST) && 3096 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3097 uint32_t sent; 3098 tcp_seq old_snd_max; 3099 int error; 3100 3101 if (nextrexmt == tp->snd_max) ++nseg; 3102 tp->snd_nxt = nextrexmt; 3103 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3104 old_snd_max = tp->snd_max; 3105 if (nextrexmt == tp->snd_una) 3106 callout_stop(tp->tt_rexmt); 3107 error = tcp_output(tp); 3108 if (error != 0) 3109 break; 3110 sent = tp->snd_nxt - nextrexmt; 3111 if (sent <= 0) 3112 break; 3113 if (!lostdup) 3114 pipe += sent; 3115 tcpstat.tcps_sndsackpack++; 3116 tcpstat.tcps_sndsackbyte += sent; 3117 if (SEQ_LT(nextrexmt, old_snd_max) && 3118 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3119 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3120 } 3121 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3122 tp->snd_nxt = old_snd_nxt; 3123 tp->snd_cwnd = ocwnd; 3124 } 3125