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 1.62 2005/08/29 10:24:10 demizu 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 int tcp_aggregate_acks = 1; 183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 184 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 185 186 int tcp_do_rfc3390 = 1; 187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 188 &tcp_do_rfc3390, 0, 189 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 190 191 static int tcp_do_eifel_detect = 1; 192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 193 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 194 195 static int tcp_do_abc = 1; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 197 &tcp_do_abc, 0, 198 "TCP Appropriate Byte Counting (RFC 3465)"); 199 200 /* 201 * Define as tunable for easy testing with SACK on and off. 202 * Warning: do not change setting in the middle of an existing active TCP flow, 203 * else strange things might happen to that flow. 204 */ 205 int tcp_do_sack = 1; 206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 207 &tcp_do_sack, 0, "Enable SACK Algorithms"); 208 209 int tcp_do_smartsack = 1; 210 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 211 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 212 213 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 214 "TCP Segment Reassembly Queue"); 215 216 int tcp_reass_maxseg = 0; 217 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 218 &tcp_reass_maxseg, 0, 219 "Global maximum number of TCP Segments in Reassembly Queue"); 220 221 int tcp_reass_qsize = 0; 222 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 223 &tcp_reass_qsize, 0, 224 "Global number of TCP Segments currently in Reassembly Queue"); 225 226 static int tcp_reass_overflows = 0; 227 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 228 &tcp_reass_overflows, 0, 229 "Global number of TCP Segment Reassembly Queue Overflows"); 230 231 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 232 static void tcp_pulloutofband(struct socket *, 233 struct tcphdr *, struct mbuf *, int); 234 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 235 struct mbuf *); 236 static void tcp_xmit_timer(struct tcpcb *, int); 237 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 238 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 239 240 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 241 #ifdef INET6 242 #define ND6_HINT(tp) \ 243 do { \ 244 if ((tp) && (tp)->t_inpcb && \ 245 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 246 (tp)->t_inpcb->in6p_route.ro_rt) \ 247 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 248 } while (0) 249 #else 250 #define ND6_HINT(tp) 251 #endif 252 253 /* 254 * Indicate whether this ack should be delayed. We can delay the ack if 255 * - delayed acks are enabled and 256 * - there is no delayed ack timer in progress and 257 * - our last ack wasn't a 0-sized window. We never want to delay 258 * the ack that opens up a 0-sized window. 259 */ 260 #define DELAY_ACK(tp) \ 261 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 262 !(tp->t_flags & TF_RXWIN0SENT)) 263 264 #define acceptable_window_update(tp, th, tiwin) \ 265 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 266 (tp->snd_wl1 == th->th_seq && \ 267 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 268 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 269 270 static int 271 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 272 { 273 struct tseg_qent *q; 274 struct tseg_qent *p = NULL; 275 struct tseg_qent *te; 276 struct socket *so = tp->t_inpcb->inp_socket; 277 int flags; 278 279 /* 280 * Call with th == NULL after become established to 281 * force pre-ESTABLISHED data up to user socket. 282 */ 283 if (th == NULL) 284 goto present; 285 286 /* 287 * Limit the number of segments in the reassembly queue to prevent 288 * holding on to too many segments (and thus running out of mbufs). 289 * Make sure to let the missing segment through which caused this 290 * queue. Always keep one global queue entry spare to be able to 291 * process the missing segment. 292 */ 293 if (th->th_seq != tp->rcv_nxt && 294 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 295 tcp_reass_overflows++; 296 tcpstat.tcps_rcvmemdrop++; 297 m_freem(m); 298 /* no SACK block to report */ 299 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 300 return (0); 301 } 302 303 /* Allocate a new queue entry. */ 304 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 305 M_INTWAIT | M_NULLOK); 306 if (te == NULL) { 307 tcpstat.tcps_rcvmemdrop++; 308 m_freem(m); 309 /* no SACK block to report */ 310 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 311 return (0); 312 } 313 tcp_reass_qsize++; 314 315 /* 316 * Find a segment which begins after this one does. 317 */ 318 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 319 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 320 break; 321 p = q; 322 } 323 324 /* 325 * If there is a preceding segment, it may provide some of 326 * our data already. If so, drop the data from the incoming 327 * segment. If it provides all of our data, drop us. 328 */ 329 if (p != NULL) { 330 tcp_seq_diff_t i; 331 332 /* conversion to int (in i) handles seq wraparound */ 333 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 334 if (i > 0) { /* overlaps preceding segment */ 335 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 336 /* enclosing block starts w/ preceding segment */ 337 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 338 if (i >= *tlenp) { 339 /* preceding encloses incoming segment */ 340 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 341 p->tqe_len; 342 tcpstat.tcps_rcvduppack++; 343 tcpstat.tcps_rcvdupbyte += *tlenp; 344 m_freem(m); 345 free(te, M_TSEGQ); 346 tcp_reass_qsize--; 347 /* 348 * Try to present any queued data 349 * at the left window edge to the user. 350 * This is needed after the 3-WHS 351 * completes. 352 */ 353 goto present; /* ??? */ 354 } 355 m_adj(m, i); 356 *tlenp -= i; 357 th->th_seq += i; 358 /* incoming segment end is enclosing block end */ 359 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 360 ((th->th_flags & TH_FIN) != 0); 361 /* trim end of reported D-SACK block */ 362 tp->reportblk.rblk_end = th->th_seq; 363 } 364 } 365 tcpstat.tcps_rcvoopack++; 366 tcpstat.tcps_rcvoobyte += *tlenp; 367 368 /* 369 * While we overlap succeeding segments trim them or, 370 * if they are completely covered, dequeue them. 371 */ 372 while (q) { 373 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 374 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 375 struct tseg_qent *nq; 376 377 if (i <= 0) 378 break; 379 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 380 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 381 tp->encloseblk = tp->reportblk; 382 /* report trailing duplicate D-SACK segment */ 383 tp->reportblk.rblk_start = q->tqe_th->th_seq; 384 } 385 if ((tp->t_flags & TF_ENCLOSESEG) && 386 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 387 /* extend enclosing block if one exists */ 388 tp->encloseblk.rblk_end = qend; 389 } 390 if (i < q->tqe_len) { 391 q->tqe_th->th_seq += i; 392 q->tqe_len -= i; 393 m_adj(q->tqe_m, i); 394 break; 395 } 396 397 nq = LIST_NEXT(q, tqe_q); 398 LIST_REMOVE(q, tqe_q); 399 m_freem(q->tqe_m); 400 free(q, M_TSEGQ); 401 tcp_reass_qsize--; 402 q = nq; 403 } 404 405 /* Insert the new segment queue entry into place. */ 406 te->tqe_m = m; 407 te->tqe_th = th; 408 te->tqe_len = *tlenp; 409 410 /* check if can coalesce with following segment */ 411 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 412 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 413 414 te->tqe_len += q->tqe_len; 415 if (q->tqe_th->th_flags & TH_FIN) 416 te->tqe_th->th_flags |= TH_FIN; 417 m_cat(te->tqe_m, q->tqe_m); 418 tp->encloseblk.rblk_end = tend; 419 /* 420 * When not reporting a duplicate segment, use 421 * the larger enclosing block as the SACK block. 422 */ 423 if (!(tp->t_flags & TF_DUPSEG)) 424 tp->reportblk.rblk_end = tend; 425 LIST_REMOVE(q, tqe_q); 426 free(q, M_TSEGQ); 427 tcp_reass_qsize--; 428 } 429 430 if (p == NULL) { 431 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 432 } else { 433 /* check if can coalesce with preceding segment */ 434 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 435 p->tqe_len += te->tqe_len; 436 m_cat(p->tqe_m, te->tqe_m); 437 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 438 /* 439 * When not reporting a duplicate segment, use 440 * the larger enclosing block as the SACK block. 441 */ 442 if (!(tp->t_flags & TF_DUPSEG)) 443 tp->reportblk.rblk_start = p->tqe_th->th_seq; 444 free(te, M_TSEGQ); 445 tcp_reass_qsize--; 446 } else 447 LIST_INSERT_AFTER(p, te, tqe_q); 448 } 449 450 present: 451 /* 452 * Present data to user, advancing rcv_nxt through 453 * completed sequence space. 454 */ 455 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 456 return (0); 457 q = LIST_FIRST(&tp->t_segq); 458 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 459 return (0); 460 tp->rcv_nxt += q->tqe_len; 461 if (!(tp->t_flags & TF_DUPSEG)) { 462 /* no SACK block to report since ACK advanced */ 463 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 464 } 465 /* no enclosing block to report since ACK advanced */ 466 tp->t_flags &= ~TF_ENCLOSESEG; 467 flags = q->tqe_th->th_flags & TH_FIN; 468 LIST_REMOVE(q, tqe_q); 469 KASSERT(LIST_EMPTY(&tp->t_segq) || 470 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 471 ("segment not coalesced")); 472 if (so->so_state & SS_CANTRCVMORE) 473 m_freem(q->tqe_m); 474 else 475 sbappendstream(&so->so_rcv, q->tqe_m); 476 free(q, M_TSEGQ); 477 tcp_reass_qsize--; 478 ND6_HINT(tp); 479 sorwakeup(so); 480 return (flags); 481 } 482 483 /* 484 * TCP input routine, follows pages 65-76 of the 485 * protocol specification dated September, 1981 very closely. 486 */ 487 #ifdef INET6 488 int 489 tcp6_input(struct mbuf **mp, int *offp, int proto) 490 { 491 struct mbuf *m = *mp; 492 struct in6_ifaddr *ia6; 493 494 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 495 496 /* 497 * draft-itojun-ipv6-tcp-to-anycast 498 * better place to put this in? 499 */ 500 ia6 = ip6_getdstifaddr(m); 501 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 502 struct ip6_hdr *ip6; 503 504 ip6 = mtod(m, struct ip6_hdr *); 505 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 506 offsetof(struct ip6_hdr, ip6_dst)); 507 return (IPPROTO_DONE); 508 } 509 510 tcp_input(m, *offp, proto); 511 return (IPPROTO_DONE); 512 } 513 #endif 514 515 void 516 tcp_input(struct mbuf *m, ...) 517 { 518 __va_list ap; 519 int off0, proto; 520 struct tcphdr *th; 521 struct ip *ip = NULL; 522 struct ipovly *ipov; 523 struct inpcb *inp = NULL; 524 u_char *optp = NULL; 525 int optlen = 0; 526 int len, tlen, off; 527 int drop_hdrlen; 528 struct tcpcb *tp = NULL; 529 int thflags; 530 struct socket *so = 0; 531 int todrop, acked; 532 boolean_t ourfinisacked, needoutput = FALSE; 533 u_long tiwin; 534 int recvwin; 535 struct tcpopt to; /* options in this segment */ 536 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 537 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 538 struct sockaddr_in *next_hop = NULL; 539 int rstreason; /* For badport_bandlim accounting purposes */ 540 int cpu; 541 struct ip6_hdr *ip6 = NULL; 542 #ifdef INET6 543 boolean_t isipv6; 544 #else 545 const boolean_t isipv6 = FALSE; 546 #endif 547 #ifdef TCPDEBUG 548 short ostate = 0; 549 #endif 550 551 __va_start(ap, m); 552 off0 = __va_arg(ap, int); 553 proto = __va_arg(ap, int); 554 __va_end(ap); 555 556 tcpstat.tcps_rcvtotal++; 557 558 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */ 559 while (m->m_type == MT_TAG) { 560 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 561 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 562 m = m->m_next; 563 } 564 565 #ifdef INET6 566 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 567 #endif 568 569 if (isipv6) { 570 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 571 ip6 = mtod(m, struct ip6_hdr *); 572 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 573 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 574 tcpstat.tcps_rcvbadsum++; 575 goto drop; 576 } 577 th = (struct tcphdr *)((caddr_t)ip6 + off0); 578 579 /* 580 * Be proactive about unspecified IPv6 address in source. 581 * As we use all-zero to indicate unbounded/unconnected pcb, 582 * unspecified IPv6 address can be used to confuse us. 583 * 584 * Note that packets with unspecified IPv6 destination is 585 * already dropped in ip6_input. 586 */ 587 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 588 /* XXX stat */ 589 goto drop; 590 } 591 } else { 592 /* 593 * Get IP and TCP header together in first mbuf. 594 * Note: IP leaves IP header in first mbuf. 595 */ 596 if (off0 > sizeof(struct ip)) { 597 ip_stripoptions(m); 598 off0 = sizeof(struct ip); 599 } 600 /* already checked and pulled up in ip_demux() */ 601 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 602 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 603 ip = mtod(m, struct ip *); 604 ipov = (struct ipovly *)ip; 605 th = (struct tcphdr *)((caddr_t)ip + off0); 606 tlen = ip->ip_len; 607 608 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 609 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 610 th->th_sum = m->m_pkthdr.csum_data; 611 else 612 th->th_sum = in_pseudo(ip->ip_src.s_addr, 613 ip->ip_dst.s_addr, 614 htonl(m->m_pkthdr.csum_data + 615 ip->ip_len + 616 IPPROTO_TCP)); 617 th->th_sum ^= 0xffff; 618 } else { 619 /* 620 * Checksum extended TCP header and data. 621 */ 622 len = sizeof(struct ip) + tlen; 623 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 624 ipov->ih_len = (u_short)tlen; 625 ipov->ih_len = htons(ipov->ih_len); 626 th->th_sum = in_cksum(m, len); 627 } 628 if (th->th_sum) { 629 tcpstat.tcps_rcvbadsum++; 630 goto drop; 631 } 632 #ifdef INET6 633 /* Re-initialization for later version check */ 634 ip->ip_v = IPVERSION; 635 #endif 636 } 637 638 /* 639 * Check that TCP offset makes sense, 640 * pull out TCP options and adjust length. XXX 641 */ 642 off = th->th_off << 2; 643 /* already checked and pulled up in ip_demux() */ 644 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 645 ("bad TCP data offset %d (tlen %d)", off, tlen)); 646 tlen -= off; /* tlen is used instead of ti->ti_len */ 647 if (off > sizeof(struct tcphdr)) { 648 if (isipv6) { 649 IP6_EXTHDR_CHECK(m, off0, off, ); 650 ip6 = mtod(m, struct ip6_hdr *); 651 th = (struct tcphdr *)((caddr_t)ip6 + off0); 652 } else { 653 /* already pulled up in ip_demux() */ 654 KASSERT(m->m_len >= sizeof(struct ip) + off, 655 ("TCP header and options not in one mbuf: " 656 "m_len %d, off %d", m->m_len, off)); 657 } 658 optlen = off - sizeof(struct tcphdr); 659 optp = (u_char *)(th + 1); 660 } 661 thflags = th->th_flags; 662 663 #ifdef TCP_DROP_SYNFIN 664 /* 665 * If the drop_synfin option is enabled, drop all packets with 666 * both the SYN and FIN bits set. This prevents e.g. nmap from 667 * identifying the TCP/IP stack. 668 * 669 * This is a violation of the TCP specification. 670 */ 671 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 672 goto drop; 673 #endif 674 675 /* 676 * Convert TCP protocol specific fields to host format. 677 */ 678 th->th_seq = ntohl(th->th_seq); 679 th->th_ack = ntohl(th->th_ack); 680 th->th_win = ntohs(th->th_win); 681 th->th_urp = ntohs(th->th_urp); 682 683 /* 684 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 685 * until after ip6_savecontrol() is called and before other functions 686 * which don't want those proto headers. 687 * Because ip6_savecontrol() is going to parse the mbuf to 688 * search for data to be passed up to user-land, it wants mbuf 689 * parameters to be unchanged. 690 * XXX: the call of ip6_savecontrol() has been obsoleted based on 691 * latest version of the advanced API (20020110). 692 */ 693 drop_hdrlen = off0 + off; 694 695 /* 696 * Locate pcb for segment. 697 */ 698 findpcb: 699 /* IPFIREWALL_FORWARD section */ 700 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 701 /* 702 * Transparently forwarded. Pretend to be the destination. 703 * already got one like this? 704 */ 705 cpu = mycpu->gd_cpuid; 706 inp = in_pcblookup_hash(&tcbinfo[cpu], 707 ip->ip_src, th->th_sport, 708 ip->ip_dst, th->th_dport, 709 0, m->m_pkthdr.rcvif); 710 if (!inp) { 711 /* 712 * It's new. Try to find the ambushing socket. 713 */ 714 715 /* 716 * The rest of the ipfw code stores the port in 717 * host order. XXX 718 * (The IP address is still in network order.) 719 */ 720 in_port_t dport = next_hop->sin_port ? 721 htons(next_hop->sin_port) : 722 th->th_dport; 723 724 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 725 next_hop->sin_addr.s_addr, dport); 726 inp = in_pcblookup_hash(&tcbinfo[cpu], 727 ip->ip_src, th->th_sport, 728 next_hop->sin_addr, dport, 729 1, m->m_pkthdr.rcvif); 730 } 731 } else { 732 if (isipv6) { 733 inp = in6_pcblookup_hash(&tcbinfo[0], 734 &ip6->ip6_src, th->th_sport, 735 &ip6->ip6_dst, th->th_dport, 736 1, m->m_pkthdr.rcvif); 737 } else { 738 cpu = mycpu->gd_cpuid; 739 inp = in_pcblookup_hash(&tcbinfo[cpu], 740 ip->ip_src, th->th_sport, 741 ip->ip_dst, th->th_dport, 742 1, m->m_pkthdr.rcvif); 743 } 744 } 745 746 /* 747 * If the state is CLOSED (i.e., TCB does not exist) then 748 * all data in the incoming segment is discarded. 749 * If the TCB exists but is in CLOSED state, it is embryonic, 750 * but should either do a listen or a connect soon. 751 */ 752 if (inp == NULL) { 753 if (log_in_vain) { 754 #ifdef INET6 755 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 756 #else 757 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 758 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 759 #endif 760 if (isipv6) { 761 strcpy(dbuf, "["); 762 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 763 strcat(dbuf, "]"); 764 strcpy(sbuf, "["); 765 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 766 strcat(sbuf, "]"); 767 } else { 768 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 769 strcpy(sbuf, inet_ntoa(ip->ip_src)); 770 } 771 switch (log_in_vain) { 772 case 1: 773 if (!(thflags & TH_SYN)) 774 break; 775 case 2: 776 log(LOG_INFO, 777 "Connection attempt to TCP %s:%d " 778 "from %s:%d flags:0x%02x\n", 779 dbuf, ntohs(th->th_dport), sbuf, 780 ntohs(th->th_sport), thflags); 781 break; 782 default: 783 break; 784 } 785 } 786 if (blackhole) { 787 switch (blackhole) { 788 case 1: 789 if (thflags & TH_SYN) 790 goto drop; 791 break; 792 case 2: 793 goto drop; 794 default: 795 goto drop; 796 } 797 } 798 rstreason = BANDLIM_RST_CLOSEDPORT; 799 goto dropwithreset; 800 } 801 802 #ifdef IPSEC 803 if (isipv6) { 804 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 805 ipsec6stat.in_polvio++; 806 goto drop; 807 } 808 } else { 809 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 810 ipsecstat.in_polvio++; 811 goto drop; 812 } 813 } 814 #endif 815 #ifdef FAST_IPSEC 816 if (isipv6) { 817 if (ipsec6_in_reject(m, inp)) 818 goto drop; 819 } else { 820 if (ipsec4_in_reject(m, inp)) 821 goto drop; 822 } 823 #endif 824 825 tp = intotcpcb(inp); 826 if (tp == NULL) { 827 rstreason = BANDLIM_RST_CLOSEDPORT; 828 goto dropwithreset; 829 } 830 if (tp->t_state <= TCPS_CLOSED) 831 goto drop; 832 833 /* Unscale the window into a 32-bit value. */ 834 if (!(thflags & TH_SYN)) 835 tiwin = th->th_win << tp->snd_scale; 836 else 837 tiwin = th->th_win; 838 839 so = inp->inp_socket; 840 841 #ifdef TCPDEBUG 842 if (so->so_options & SO_DEBUG) { 843 ostate = tp->t_state; 844 if (isipv6) 845 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 846 else 847 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 848 tcp_savetcp = *th; 849 } 850 #endif 851 852 bzero(&to, sizeof to); 853 854 if (so->so_options & SO_ACCEPTCONN) { 855 struct in_conninfo inc; 856 857 #ifdef INET6 858 inc.inc_isipv6 = (isipv6 == TRUE); 859 #endif 860 if (isipv6) { 861 inc.inc6_faddr = ip6->ip6_src; 862 inc.inc6_laddr = ip6->ip6_dst; 863 inc.inc6_route.ro_rt = NULL; /* XXX */ 864 } else { 865 inc.inc_faddr = ip->ip_src; 866 inc.inc_laddr = ip->ip_dst; 867 inc.inc_route.ro_rt = NULL; /* XXX */ 868 } 869 inc.inc_fport = th->th_sport; 870 inc.inc_lport = th->th_dport; 871 872 /* 873 * If the state is LISTEN then ignore segment if it contains 874 * a RST. If the segment contains an ACK then it is bad and 875 * send a RST. If it does not contain a SYN then it is not 876 * interesting; drop it. 877 * 878 * If the state is SYN_RECEIVED (syncache) and seg contains 879 * an ACK, but not for our SYN/ACK, send a RST. If the seg 880 * contains a RST, check the sequence number to see if it 881 * is a valid reset segment. 882 */ 883 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 884 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 885 if (!syncache_expand(&inc, th, &so, m)) { 886 /* 887 * No syncache entry, or ACK was not 888 * for our SYN/ACK. Send a RST. 889 */ 890 tcpstat.tcps_badsyn++; 891 rstreason = BANDLIM_RST_OPENPORT; 892 goto dropwithreset; 893 } 894 if (so == NULL) 895 /* 896 * Could not complete 3-way handshake, 897 * connection is being closed down, and 898 * syncache will free mbuf. 899 */ 900 return; 901 /* 902 * Socket is created in state SYN_RECEIVED. 903 * Continue processing segment. 904 */ 905 inp = so->so_pcb; 906 tp = intotcpcb(inp); 907 /* 908 * This is what would have happened in 909 * tcp_output() when the SYN,ACK was sent. 910 */ 911 tp->snd_up = tp->snd_una; 912 tp->snd_max = tp->snd_nxt = tp->iss + 1; 913 tp->last_ack_sent = tp->rcv_nxt; 914 /* 915 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 916 * until the _second_ ACK is received: 917 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 918 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 919 * move to ESTAB, set snd_wnd to tiwin. 920 */ 921 tp->snd_wnd = tiwin; /* unscaled */ 922 goto after_listen; 923 } 924 if (thflags & TH_RST) { 925 syncache_chkrst(&inc, th); 926 goto drop; 927 } 928 if (thflags & TH_ACK) { 929 syncache_badack(&inc); 930 tcpstat.tcps_badsyn++; 931 rstreason = BANDLIM_RST_OPENPORT; 932 goto dropwithreset; 933 } 934 goto drop; 935 } 936 937 /* 938 * Segment's flags are (SYN) or (SYN | FIN). 939 */ 940 #ifdef INET6 941 /* 942 * If deprecated address is forbidden, 943 * we do not accept SYN to deprecated interface 944 * address to prevent any new inbound connection from 945 * getting established. 946 * When we do not accept SYN, we send a TCP RST, 947 * with deprecated source address (instead of dropping 948 * it). We compromise it as it is much better for peer 949 * to send a RST, and RST will be the final packet 950 * for the exchange. 951 * 952 * If we do not forbid deprecated addresses, we accept 953 * the SYN packet. RFC2462 does not suggest dropping 954 * SYN in this case. 955 * If we decipher RFC2462 5.5.4, it says like this: 956 * 1. use of deprecated addr with existing 957 * communication is okay - "SHOULD continue to be 958 * used" 959 * 2. use of it with new communication: 960 * (2a) "SHOULD NOT be used if alternate address 961 * with sufficient scope is available" 962 * (2b) nothing mentioned otherwise. 963 * Here we fall into (2b) case as we have no choice in 964 * our source address selection - we must obey the peer. 965 * 966 * The wording in RFC2462 is confusing, and there are 967 * multiple description text for deprecated address 968 * handling - worse, they are not exactly the same. 969 * I believe 5.5.4 is the best one, so we follow 5.5.4. 970 */ 971 if (isipv6 && !ip6_use_deprecated) { 972 struct in6_ifaddr *ia6; 973 974 if ((ia6 = ip6_getdstifaddr(m)) && 975 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 976 tp = NULL; 977 rstreason = BANDLIM_RST_OPENPORT; 978 goto dropwithreset; 979 } 980 } 981 #endif 982 /* 983 * If it is from this socket, drop it, it must be forged. 984 * Don't bother responding if the destination was a broadcast. 985 */ 986 if (th->th_dport == th->th_sport) { 987 if (isipv6) { 988 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 989 &ip6->ip6_src)) 990 goto drop; 991 } else { 992 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 993 goto drop; 994 } 995 } 996 /* 997 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 998 * 999 * Note that it is quite possible to receive unicast 1000 * link-layer packets with a broadcast IP address. Use 1001 * in_broadcast() to find them. 1002 */ 1003 if (m->m_flags & (M_BCAST | M_MCAST)) 1004 goto drop; 1005 if (isipv6) { 1006 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1007 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1008 goto drop; 1009 } else { 1010 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1011 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1012 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1013 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1014 goto drop; 1015 } 1016 /* 1017 * SYN appears to be valid; create compressed TCP state 1018 * for syncache, or perform t/tcp connection. 1019 */ 1020 if (so->so_qlen <= so->so_qlimit) { 1021 tcp_dooptions(&to, optp, optlen, TRUE); 1022 if (!syncache_add(&inc, &to, th, &so, m)) 1023 goto drop; 1024 if (so == NULL) 1025 /* 1026 * Entry added to syncache, mbuf used to 1027 * send SYN,ACK packet. 1028 */ 1029 return; 1030 /* 1031 * Segment passed TAO tests. 1032 */ 1033 inp = so->so_pcb; 1034 tp = intotcpcb(inp); 1035 tp->snd_wnd = tiwin; 1036 tp->t_starttime = ticks; 1037 tp->t_state = TCPS_ESTABLISHED; 1038 1039 /* 1040 * If there is a FIN, or if there is data and the 1041 * connection is local, then delay SYN,ACK(SYN) in 1042 * the hope of piggy-backing it on a response 1043 * segment. Otherwise must send ACK now in case 1044 * the other side is slow starting. 1045 */ 1046 if (DELAY_ACK(tp) && 1047 ((thflags & TH_FIN) || 1048 (tlen != 0 && 1049 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1050 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1051 callout_reset(tp->tt_delack, tcp_delacktime, 1052 tcp_timer_delack, tp); 1053 tp->t_flags |= TF_NEEDSYN; 1054 } else 1055 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1056 1057 tcpstat.tcps_connects++; 1058 soisconnected(so); 1059 goto trimthenstep6; 1060 } 1061 goto drop; 1062 } 1063 after_listen: 1064 1065 /* should not happen - syncache should pick up these connections */ 1066 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1067 1068 /* 1069 * Segment received on connection. 1070 * Reset idle time and keep-alive timer. 1071 */ 1072 tp->t_rcvtime = ticks; 1073 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1074 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 1075 1076 /* 1077 * Process options. 1078 * XXX this is tradtitional behavior, may need to be cleaned up. 1079 */ 1080 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1081 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1082 if (to.to_flags & TOF_SCALE) { 1083 tp->t_flags |= TF_RCVD_SCALE; 1084 tp->requested_s_scale = to.to_requested_s_scale; 1085 } 1086 if (to.to_flags & TOF_TS) { 1087 tp->t_flags |= TF_RCVD_TSTMP; 1088 tp->ts_recent = to.to_tsval; 1089 tp->ts_recent_age = ticks; 1090 } 1091 if (to.to_flags & (TOF_CC | TOF_CCNEW)) 1092 tp->t_flags |= TF_RCVD_CC; 1093 if (to.to_flags & TOF_MSS) 1094 tcp_mss(tp, to.to_mss); 1095 /* 1096 * Only set the TF_SACK_PERMITTED per-connection flag 1097 * if we got a SACK_PERMITTED option from the other side 1098 * and the global tcp_do_sack variable is true. 1099 */ 1100 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1101 tp->t_flags |= TF_SACK_PERMITTED; 1102 } 1103 1104 /* 1105 * Header prediction: check for the two common cases 1106 * of a uni-directional data xfer. If the packet has 1107 * no control flags, is in-sequence, the window didn't 1108 * change and we're not retransmitting, it's a 1109 * candidate. If the length is zero and the ack moved 1110 * forward, we're the sender side of the xfer. Just 1111 * free the data acked & wake any higher level process 1112 * that was blocked waiting for space. If the length 1113 * is non-zero and the ack didn't move, we're the 1114 * receiver side. If we're getting packets in-order 1115 * (the reassembly queue is empty), add the data to 1116 * the socket buffer and note that we need a delayed ack. 1117 * Make sure that the hidden state-flags are also off. 1118 * Since we check for TCPS_ESTABLISHED above, it can only 1119 * be TH_NEEDSYN. 1120 */ 1121 if (tp->t_state == TCPS_ESTABLISHED && 1122 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1123 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1124 (!(to.to_flags & TOF_TS) || 1125 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1126 /* 1127 * Using the CC option is compulsory if once started: 1128 * the segment is OK if no T/TCP was negotiated or 1129 * if the segment has a CC option equal to CCrecv 1130 */ 1131 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1132 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) && 1133 th->th_seq == tp->rcv_nxt && 1134 tp->snd_nxt == tp->snd_max) { 1135 1136 /* 1137 * If last ACK falls within this segment's sequence numbers, 1138 * record the timestamp. 1139 * NOTE that the test is modified according to the latest 1140 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1141 */ 1142 if ((to.to_flags & TOF_TS) && 1143 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1144 tp->ts_recent_age = ticks; 1145 tp->ts_recent = to.to_tsval; 1146 } 1147 1148 if (tlen == 0) { 1149 if (SEQ_GT(th->th_ack, tp->snd_una) && 1150 SEQ_LEQ(th->th_ack, tp->snd_max) && 1151 tp->snd_cwnd >= tp->snd_wnd && 1152 !IN_FASTRECOVERY(tp)) { 1153 /* 1154 * This is a pure ack for outstanding data. 1155 */ 1156 ++tcpstat.tcps_predack; 1157 /* 1158 * "bad retransmit" recovery 1159 * 1160 * If Eifel detection applies, then 1161 * it is deterministic, so use it 1162 * unconditionally over the old heuristic. 1163 * Otherwise, fall back to the old heuristic. 1164 */ 1165 if (tcp_do_eifel_detect && 1166 (to.to_flags & TOF_TS) && to.to_tsecr && 1167 (tp->t_flags & TF_FIRSTACCACK)) { 1168 /* Eifel detection applicable. */ 1169 if (to.to_tsecr < tp->t_rexmtTS) { 1170 tcp_revert_congestion_state(tp); 1171 ++tcpstat.tcps_eifeldetected; 1172 } 1173 } else if (tp->t_rxtshift == 1 && 1174 ticks < tp->t_badrxtwin) { 1175 tcp_revert_congestion_state(tp); 1176 ++tcpstat.tcps_rttdetected; 1177 } 1178 tp->t_flags &= ~(TF_FIRSTACCACK | 1179 TF_FASTREXMT | TF_EARLYREXMT); 1180 /* 1181 * Recalculate the retransmit timer / rtt. 1182 * 1183 * Some machines (certain windows boxes) 1184 * send broken timestamp replies during the 1185 * SYN+ACK phase, ignore timestamps of 0. 1186 */ 1187 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1188 tcp_xmit_timer(tp, 1189 ticks - to.to_tsecr + 1); 1190 } else if (tp->t_rtttime && 1191 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1192 tcp_xmit_timer(tp, 1193 ticks - tp->t_rtttime); 1194 } 1195 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1196 acked = th->th_ack - tp->snd_una; 1197 tcpstat.tcps_rcvackpack++; 1198 tcpstat.tcps_rcvackbyte += acked; 1199 sbdrop(&so->so_snd, acked); 1200 tp->snd_recover = th->th_ack - 1; 1201 tp->snd_una = th->th_ack; 1202 tp->t_dupacks = 0; 1203 /* 1204 * Update window information. 1205 */ 1206 if (tiwin != tp->snd_wnd && 1207 acceptable_window_update(tp, th, tiwin)) { 1208 /* keep track of pure window updates */ 1209 if (tp->snd_wl2 == th->th_ack && 1210 tiwin > tp->snd_wnd) 1211 tcpstat.tcps_rcvwinupd++; 1212 tp->snd_wnd = tiwin; 1213 tp->snd_wl1 = th->th_seq; 1214 tp->snd_wl2 = th->th_ack; 1215 if (tp->snd_wnd > tp->max_sndwnd) 1216 tp->max_sndwnd = tp->snd_wnd; 1217 } 1218 m_freem(m); 1219 ND6_HINT(tp); /* some progress has been done */ 1220 /* 1221 * If all outstanding data are acked, stop 1222 * retransmit timer, otherwise restart timer 1223 * using current (possibly backed-off) value. 1224 * If process is waiting for space, 1225 * wakeup/selwakeup/signal. If data 1226 * are ready to send, let tcp_output 1227 * decide between more output or persist. 1228 */ 1229 if (tp->snd_una == tp->snd_max) 1230 callout_stop(tp->tt_rexmt); 1231 else if (!callout_active(tp->tt_persist)) 1232 callout_reset(tp->tt_rexmt, 1233 tp->t_rxtcur, 1234 tcp_timer_rexmt, tp); 1235 sowwakeup(so); 1236 if (so->so_snd.sb_cc > 0) 1237 tcp_output(tp); 1238 return; 1239 } 1240 } else if (tiwin == tp->snd_wnd && 1241 th->th_ack == tp->snd_una && 1242 LIST_EMPTY(&tp->t_segq) && 1243 tlen <= sbspace(&so->so_rcv)) { 1244 /* 1245 * This is a pure, in-sequence data packet 1246 * with nothing on the reassembly queue and 1247 * we have enough buffer space to take it. 1248 */ 1249 ++tcpstat.tcps_preddat; 1250 tp->rcv_nxt += tlen; 1251 tcpstat.tcps_rcvpack++; 1252 tcpstat.tcps_rcvbyte += tlen; 1253 ND6_HINT(tp); /* some progress has been done */ 1254 /* 1255 * Add data to socket buffer. 1256 */ 1257 if (so->so_state & SS_CANTRCVMORE) { 1258 m_freem(m); 1259 } else { 1260 m_adj(m, drop_hdrlen); /* delayed header drop */ 1261 sbappendstream(&so->so_rcv, m); 1262 } 1263 sorwakeup(so); 1264 /* 1265 * This code is responsible for most of the ACKs 1266 * the TCP stack sends back after receiving a data 1267 * packet. Note that the DELAY_ACK check fails if 1268 * the delack timer is already running, which results 1269 * in an ack being sent every other packet (which is 1270 * what we want). 1271 * 1272 * We then further aggregate acks by not actually 1273 * sending one until the protocol thread has completed 1274 * processing the current backlog of packets. This 1275 * does not delay the ack any further, but allows us 1276 * to take advantage of the packet aggregation that 1277 * high speed NICs do (usually blocks of 8-10 packets) 1278 * to send a single ack rather then four or five acks, 1279 * greatly reducing the ack rate, the return channel 1280 * bandwidth, and the protocol overhead on both ends. 1281 * 1282 * Since this also has the effect of slowing down 1283 * the exponential slow-start ramp-up, systems with 1284 * very large bandwidth-delay products might want 1285 * to turn the feature off. 1286 */ 1287 if (DELAY_ACK(tp)) { 1288 callout_reset(tp->tt_delack, tcp_delacktime, 1289 tcp_timer_delack, tp); 1290 } else if (tcp_aggregate_acks) { 1291 tp->t_flags |= TF_ACKNOW; 1292 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1293 tp->t_flags |= TF_ONOUTPUTQ; 1294 tp->tt_cpu = mycpu->gd_cpuid; 1295 TAILQ_INSERT_TAIL( 1296 &tcpcbackq[tp->tt_cpu], 1297 tp, t_outputq); 1298 } 1299 } else { 1300 tp->t_flags |= TF_ACKNOW; 1301 tcp_output(tp); 1302 } 1303 return; 1304 } 1305 } 1306 1307 /* 1308 * Calculate amount of space in receive window, 1309 * and then do TCP input processing. 1310 * Receive window is amount of space in rcv queue, 1311 * but not less than advertised window. 1312 */ 1313 recvwin = sbspace(&so->so_rcv); 1314 if (recvwin < 0) 1315 recvwin = 0; 1316 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1317 1318 switch (tp->t_state) { 1319 /* 1320 * If the state is SYN_RECEIVED: 1321 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1322 */ 1323 case TCPS_SYN_RECEIVED: 1324 if ((thflags & TH_ACK) && 1325 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1326 SEQ_GT(th->th_ack, tp->snd_max))) { 1327 rstreason = BANDLIM_RST_OPENPORT; 1328 goto dropwithreset; 1329 } 1330 break; 1331 1332 /* 1333 * If the state is SYN_SENT: 1334 * if seg contains an ACK, but not for our SYN, drop the input. 1335 * if seg contains a RST, then drop the connection. 1336 * if seg does not contain SYN, then drop it. 1337 * Otherwise this is an acceptable SYN segment 1338 * initialize tp->rcv_nxt and tp->irs 1339 * if seg contains ack then advance tp->snd_una 1340 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1341 * arrange for segment to be acked (eventually) 1342 * continue processing rest of data/controls, beginning with URG 1343 */ 1344 case TCPS_SYN_SENT: 1345 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1346 taop = &tao_noncached; 1347 bzero(taop, sizeof *taop); 1348 } 1349 1350 if ((thflags & TH_ACK) && 1351 (SEQ_LEQ(th->th_ack, tp->iss) || 1352 SEQ_GT(th->th_ack, tp->snd_max))) { 1353 /* 1354 * If we have a cached CCsent for the remote host, 1355 * hence we haven't just crashed and restarted, 1356 * do not send a RST. This may be a retransmission 1357 * from the other side after our earlier ACK was lost. 1358 * Our new SYN, when it arrives, will serve as the 1359 * needed ACK. 1360 */ 1361 if (taop->tao_ccsent != 0) 1362 goto drop; 1363 else { 1364 rstreason = BANDLIM_UNLIMITED; 1365 goto dropwithreset; 1366 } 1367 } 1368 if (thflags & TH_RST) { 1369 if (thflags & TH_ACK) 1370 tp = tcp_drop(tp, ECONNREFUSED); 1371 goto drop; 1372 } 1373 if (!(thflags & TH_SYN)) 1374 goto drop; 1375 tp->snd_wnd = th->th_win; /* initial send window */ 1376 tp->cc_recv = to.to_cc; /* foreign CC */ 1377 1378 tp->irs = th->th_seq; 1379 tcp_rcvseqinit(tp); 1380 if (thflags & TH_ACK) { 1381 /* 1382 * Our SYN was acked. If segment contains CC.ECHO 1383 * option, check it to make sure this segment really 1384 * matches our SYN. If not, just drop it as old 1385 * duplicate, but send an RST if we're still playing 1386 * by the old rules. If no CC.ECHO option, make sure 1387 * we don't get fooled into using T/TCP. 1388 */ 1389 if (to.to_flags & TOF_CCECHO) { 1390 if (tp->cc_send != to.to_ccecho) { 1391 if (taop->tao_ccsent != 0) 1392 goto drop; 1393 else { 1394 rstreason = BANDLIM_UNLIMITED; 1395 goto dropwithreset; 1396 } 1397 } 1398 } else 1399 tp->t_flags &= ~TF_RCVD_CC; 1400 tcpstat.tcps_connects++; 1401 soisconnected(so); 1402 /* Do window scaling on this connection? */ 1403 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1404 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1405 tp->snd_scale = tp->requested_s_scale; 1406 tp->rcv_scale = tp->request_r_scale; 1407 } 1408 /* Segment is acceptable, update cache if undefined. */ 1409 if (taop->tao_ccsent == 0) 1410 taop->tao_ccsent = to.to_ccecho; 1411 1412 tp->rcv_adv += tp->rcv_wnd; 1413 tp->snd_una++; /* SYN is acked */ 1414 callout_stop(tp->tt_rexmt); 1415 /* 1416 * If there's data, delay ACK; if there's also a FIN 1417 * ACKNOW will be turned on later. 1418 */ 1419 if (DELAY_ACK(tp) && tlen != 0) 1420 callout_reset(tp->tt_delack, tcp_delacktime, 1421 tcp_timer_delack, tp); 1422 else 1423 tp->t_flags |= TF_ACKNOW; 1424 /* 1425 * Received <SYN,ACK> in SYN_SENT[*] state. 1426 * Transitions: 1427 * SYN_SENT --> ESTABLISHED 1428 * SYN_SENT* --> FIN_WAIT_1 1429 */ 1430 tp->t_starttime = ticks; 1431 if (tp->t_flags & TF_NEEDFIN) { 1432 tp->t_state = TCPS_FIN_WAIT_1; 1433 tp->t_flags &= ~TF_NEEDFIN; 1434 thflags &= ~TH_SYN; 1435 } else { 1436 tp->t_state = TCPS_ESTABLISHED; 1437 callout_reset(tp->tt_keep, tcp_keepidle, 1438 tcp_timer_keep, tp); 1439 } 1440 } else { 1441 /* 1442 * Received initial SYN in SYN-SENT[*] state => 1443 * simultaneous open. If segment contains CC option 1444 * and there is a cached CC, apply TAO test. 1445 * If it succeeds, connection is * half-synchronized. 1446 * Otherwise, do 3-way handshake: 1447 * SYN-SENT -> SYN-RECEIVED 1448 * SYN-SENT* -> SYN-RECEIVED* 1449 * If there was no CC option, clear cached CC value. 1450 */ 1451 tp->t_flags |= TF_ACKNOW; 1452 callout_stop(tp->tt_rexmt); 1453 if (to.to_flags & TOF_CC) { 1454 if (taop->tao_cc != 0 && 1455 CC_GT(to.to_cc, taop->tao_cc)) { 1456 /* 1457 * update cache and make transition: 1458 * SYN-SENT -> ESTABLISHED* 1459 * SYN-SENT* -> FIN-WAIT-1* 1460 */ 1461 taop->tao_cc = to.to_cc; 1462 tp->t_starttime = ticks; 1463 if (tp->t_flags & TF_NEEDFIN) { 1464 tp->t_state = TCPS_FIN_WAIT_1; 1465 tp->t_flags &= ~TF_NEEDFIN; 1466 } else { 1467 tp->t_state = TCPS_ESTABLISHED; 1468 callout_reset(tp->tt_keep, 1469 tcp_keepidle, 1470 tcp_timer_keep, 1471 tp); 1472 } 1473 tp->t_flags |= TF_NEEDSYN; 1474 } else 1475 tp->t_state = TCPS_SYN_RECEIVED; 1476 } else { 1477 /* CC.NEW or no option => invalidate cache */ 1478 taop->tao_cc = 0; 1479 tp->t_state = TCPS_SYN_RECEIVED; 1480 } 1481 } 1482 1483 trimthenstep6: 1484 /* 1485 * Advance th->th_seq to correspond to first data byte. 1486 * If data, trim to stay within window, 1487 * dropping FIN if necessary. 1488 */ 1489 th->th_seq++; 1490 if (tlen > tp->rcv_wnd) { 1491 todrop = tlen - tp->rcv_wnd; 1492 m_adj(m, -todrop); 1493 tlen = tp->rcv_wnd; 1494 thflags &= ~TH_FIN; 1495 tcpstat.tcps_rcvpackafterwin++; 1496 tcpstat.tcps_rcvbyteafterwin += todrop; 1497 } 1498 tp->snd_wl1 = th->th_seq - 1; 1499 tp->rcv_up = th->th_seq; 1500 /* 1501 * Client side of transaction: already sent SYN and data. 1502 * If the remote host used T/TCP to validate the SYN, 1503 * our data will be ACK'd; if so, enter normal data segment 1504 * processing in the middle of step 5, ack processing. 1505 * Otherwise, goto step 6. 1506 */ 1507 if (thflags & TH_ACK) 1508 goto process_ACK; 1509 1510 goto step6; 1511 1512 /* 1513 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1514 * if segment contains a SYN and CC [not CC.NEW] option: 1515 * if state == TIME_WAIT and connection duration > MSL, 1516 * drop packet and send RST; 1517 * 1518 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1519 * ack the FIN (and data) in retransmission queue. 1520 * Complete close and delete TCPCB. Then reprocess 1521 * segment, hoping to find new TCPCB in LISTEN state; 1522 * 1523 * else must be old SYN; drop it. 1524 * else do normal processing. 1525 */ 1526 case TCPS_LAST_ACK: 1527 case TCPS_CLOSING: 1528 case TCPS_TIME_WAIT: 1529 if ((thflags & TH_SYN) && 1530 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1531 if (tp->t_state == TCPS_TIME_WAIT && 1532 (ticks - tp->t_starttime) > tcp_msl) { 1533 rstreason = BANDLIM_UNLIMITED; 1534 goto dropwithreset; 1535 } 1536 if (CC_GT(to.to_cc, tp->cc_recv)) { 1537 tp = tcp_close(tp); 1538 goto findpcb; 1539 } 1540 else 1541 goto drop; 1542 } 1543 break; /* continue normal processing */ 1544 } 1545 1546 /* 1547 * States other than LISTEN or SYN_SENT. 1548 * First check the RST flag and sequence number since reset segments 1549 * are exempt from the timestamp and connection count tests. This 1550 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1551 * below which allowed reset segments in half the sequence space 1552 * to fall though and be processed (which gives forged reset 1553 * segments with a random sequence number a 50 percent chance of 1554 * killing a connection). 1555 * Then check timestamp, if present. 1556 * Then check the connection count, if present. 1557 * Then check that at least some bytes of segment are within 1558 * receive window. If segment begins before rcv_nxt, 1559 * drop leading data (and SYN); if nothing left, just ack. 1560 * 1561 * 1562 * If the RST bit is set, check the sequence number to see 1563 * if this is a valid reset segment. 1564 * RFC 793 page 37: 1565 * In all states except SYN-SENT, all reset (RST) segments 1566 * are validated by checking their SEQ-fields. A reset is 1567 * valid if its sequence number is in the window. 1568 * Note: this does not take into account delayed ACKs, so 1569 * we should test against last_ack_sent instead of rcv_nxt. 1570 * The sequence number in the reset segment is normally an 1571 * echo of our outgoing acknowledgement numbers, but some hosts 1572 * send a reset with the sequence number at the rightmost edge 1573 * of our receive window, and we have to handle this case. 1574 * If we have multiple segments in flight, the intial reset 1575 * segment sequence numbers will be to the left of last_ack_sent, 1576 * but they will eventually catch up. 1577 * In any case, it never made sense to trim reset segments to 1578 * fit the receive window since RFC 1122 says: 1579 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1580 * 1581 * A TCP SHOULD allow a received RST segment to include data. 1582 * 1583 * DISCUSSION 1584 * It has been suggested that a RST segment could contain 1585 * ASCII text that encoded and explained the cause of the 1586 * RST. No standard has yet been established for such 1587 * data. 1588 * 1589 * If the reset segment passes the sequence number test examine 1590 * the state: 1591 * SYN_RECEIVED STATE: 1592 * If passive open, return to LISTEN state. 1593 * If active open, inform user that connection was refused. 1594 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1595 * Inform user that connection was reset, and close tcb. 1596 * CLOSING, LAST_ACK STATES: 1597 * Close the tcb. 1598 * TIME_WAIT STATE: 1599 * Drop the segment - see Stevens, vol. 2, p. 964 and 1600 * RFC 1337. 1601 */ 1602 if (thflags & TH_RST) { 1603 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1604 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1605 switch (tp->t_state) { 1606 1607 case TCPS_SYN_RECEIVED: 1608 so->so_error = ECONNREFUSED; 1609 goto close; 1610 1611 case TCPS_ESTABLISHED: 1612 case TCPS_FIN_WAIT_1: 1613 case TCPS_FIN_WAIT_2: 1614 case TCPS_CLOSE_WAIT: 1615 so->so_error = ECONNRESET; 1616 close: 1617 tp->t_state = TCPS_CLOSED; 1618 tcpstat.tcps_drops++; 1619 tp = tcp_close(tp); 1620 break; 1621 1622 case TCPS_CLOSING: 1623 case TCPS_LAST_ACK: 1624 tp = tcp_close(tp); 1625 break; 1626 1627 case TCPS_TIME_WAIT: 1628 break; 1629 } 1630 } 1631 goto drop; 1632 } 1633 1634 /* 1635 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1636 * and it's less than ts_recent, drop it. 1637 */ 1638 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1639 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1640 1641 /* Check to see if ts_recent is over 24 days old. */ 1642 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1643 /* 1644 * Invalidate ts_recent. If this segment updates 1645 * ts_recent, the age will be reset later and ts_recent 1646 * will get a valid value. If it does not, setting 1647 * ts_recent to zero will at least satisfy the 1648 * requirement that zero be placed in the timestamp 1649 * echo reply when ts_recent isn't valid. The 1650 * age isn't reset until we get a valid ts_recent 1651 * because we don't want out-of-order segments to be 1652 * dropped when ts_recent is old. 1653 */ 1654 tp->ts_recent = 0; 1655 } else { 1656 tcpstat.tcps_rcvduppack++; 1657 tcpstat.tcps_rcvdupbyte += tlen; 1658 tcpstat.tcps_pawsdrop++; 1659 if (tlen) 1660 goto dropafterack; 1661 goto drop; 1662 } 1663 } 1664 1665 /* 1666 * T/TCP mechanism 1667 * If T/TCP was negotiated and the segment doesn't have CC, 1668 * or if its CC is wrong then drop the segment. 1669 * RST segments do not have to comply with this. 1670 */ 1671 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1672 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1673 goto dropafterack; 1674 1675 /* 1676 * In the SYN-RECEIVED state, validate that the packet belongs to 1677 * this connection before trimming the data to fit the receive 1678 * window. Check the sequence number versus IRS since we know 1679 * the sequence numbers haven't wrapped. This is a partial fix 1680 * for the "LAND" DoS attack. 1681 */ 1682 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1683 rstreason = BANDLIM_RST_OPENPORT; 1684 goto dropwithreset; 1685 } 1686 1687 todrop = tp->rcv_nxt - th->th_seq; 1688 if (todrop > 0) { 1689 if (TCP_DO_SACK(tp)) { 1690 /* Report duplicate segment at head of packet. */ 1691 tp->reportblk.rblk_start = th->th_seq; 1692 tp->reportblk.rblk_end = th->th_seq + tlen; 1693 if (thflags & TH_FIN) 1694 ++tp->reportblk.rblk_end; 1695 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1696 tp->reportblk.rblk_end = tp->rcv_nxt; 1697 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1698 } 1699 if (thflags & TH_SYN) { 1700 thflags &= ~TH_SYN; 1701 th->th_seq++; 1702 if (th->th_urp > 1) 1703 th->th_urp--; 1704 else 1705 thflags &= ~TH_URG; 1706 todrop--; 1707 } 1708 /* 1709 * Following if statement from Stevens, vol. 2, p. 960. 1710 */ 1711 if (todrop > tlen || 1712 (todrop == tlen && !(thflags & TH_FIN))) { 1713 /* 1714 * Any valid FIN must be to the left of the window. 1715 * At this point the FIN must be a duplicate or out 1716 * of sequence; drop it. 1717 */ 1718 thflags &= ~TH_FIN; 1719 1720 /* 1721 * Send an ACK to resynchronize and drop any data. 1722 * But keep on processing for RST or ACK. 1723 */ 1724 tp->t_flags |= TF_ACKNOW; 1725 todrop = tlen; 1726 tcpstat.tcps_rcvduppack++; 1727 tcpstat.tcps_rcvdupbyte += todrop; 1728 } else { 1729 tcpstat.tcps_rcvpartduppack++; 1730 tcpstat.tcps_rcvpartdupbyte += todrop; 1731 } 1732 drop_hdrlen += todrop; /* drop from the top afterwards */ 1733 th->th_seq += todrop; 1734 tlen -= todrop; 1735 if (th->th_urp > todrop) 1736 th->th_urp -= todrop; 1737 else { 1738 thflags &= ~TH_URG; 1739 th->th_urp = 0; 1740 } 1741 } 1742 1743 /* 1744 * If new data are received on a connection after the 1745 * user processes are gone, then RST the other end. 1746 */ 1747 if ((so->so_state & SS_NOFDREF) && 1748 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1749 tp = tcp_close(tp); 1750 tcpstat.tcps_rcvafterclose++; 1751 rstreason = BANDLIM_UNLIMITED; 1752 goto dropwithreset; 1753 } 1754 1755 /* 1756 * If segment ends after window, drop trailing data 1757 * (and PUSH and FIN); if nothing left, just ACK. 1758 */ 1759 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1760 if (todrop > 0) { 1761 tcpstat.tcps_rcvpackafterwin++; 1762 if (todrop >= tlen) { 1763 tcpstat.tcps_rcvbyteafterwin += tlen; 1764 /* 1765 * If a new connection request is received 1766 * while in TIME_WAIT, drop the old connection 1767 * and start over if the sequence numbers 1768 * are above the previous ones. 1769 */ 1770 if (thflags & TH_SYN && 1771 tp->t_state == TCPS_TIME_WAIT && 1772 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1773 tp = tcp_close(tp); 1774 goto findpcb; 1775 } 1776 /* 1777 * If window is closed can only take segments at 1778 * window edge, and have to drop data and PUSH from 1779 * incoming segments. Continue processing, but 1780 * remember to ack. Otherwise, drop segment 1781 * and ack. 1782 */ 1783 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1784 tp->t_flags |= TF_ACKNOW; 1785 tcpstat.tcps_rcvwinprobe++; 1786 } else 1787 goto dropafterack; 1788 } else 1789 tcpstat.tcps_rcvbyteafterwin += todrop; 1790 m_adj(m, -todrop); 1791 tlen -= todrop; 1792 thflags &= ~(TH_PUSH | TH_FIN); 1793 } 1794 1795 /* 1796 * If last ACK falls within this segment's sequence numbers, 1797 * record its timestamp. 1798 * NOTE: 1799 * 1) That the test incorporates suggestions from the latest 1800 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1801 * 2) That updating only on newer timestamps interferes with 1802 * our earlier PAWS tests, so this check should be solely 1803 * predicated on the sequence space of this segment. 1804 * 3) That we modify the segment boundary check to be 1805 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1806 * instead of RFC1323's 1807 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1808 * This modified check allows us to overcome RFC1323's 1809 * limitations as described in Stevens TCP/IP Illustrated 1810 * Vol. 2 p.869. In such cases, we can still calculate the 1811 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1812 */ 1813 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1814 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1815 + ((thflags & TH_SYN) != 0) 1816 + ((thflags & TH_FIN) != 0)))) { 1817 tp->ts_recent_age = ticks; 1818 tp->ts_recent = to.to_tsval; 1819 } 1820 1821 /* 1822 * If a SYN is in the window, then this is an 1823 * error and we send an RST and drop the connection. 1824 */ 1825 if (thflags & TH_SYN) { 1826 tp = tcp_drop(tp, ECONNRESET); 1827 rstreason = BANDLIM_UNLIMITED; 1828 goto dropwithreset; 1829 } 1830 1831 /* 1832 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1833 * flag is on (half-synchronized state), then queue data for 1834 * later processing; else drop segment and return. 1835 */ 1836 if (!(thflags & TH_ACK)) { 1837 if (tp->t_state == TCPS_SYN_RECEIVED || 1838 (tp->t_flags & TF_NEEDSYN)) 1839 goto step6; 1840 else 1841 goto drop; 1842 } 1843 1844 /* 1845 * Ack processing. 1846 */ 1847 switch (tp->t_state) { 1848 /* 1849 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1850 * ESTABLISHED state and continue processing. 1851 * The ACK was checked above. 1852 */ 1853 case TCPS_SYN_RECEIVED: 1854 1855 tcpstat.tcps_connects++; 1856 soisconnected(so); 1857 /* Do window scaling? */ 1858 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1859 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1860 tp->snd_scale = tp->requested_s_scale; 1861 tp->rcv_scale = tp->request_r_scale; 1862 } 1863 /* 1864 * Upon successful completion of 3-way handshake, 1865 * update cache.CC if it was undefined, pass any queued 1866 * data to the user, and advance state appropriately. 1867 */ 1868 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1869 taop->tao_cc == 0) 1870 taop->tao_cc = tp->cc_recv; 1871 1872 /* 1873 * Make transitions: 1874 * SYN-RECEIVED -> ESTABLISHED 1875 * SYN-RECEIVED* -> FIN-WAIT-1 1876 */ 1877 tp->t_starttime = ticks; 1878 if (tp->t_flags & TF_NEEDFIN) { 1879 tp->t_state = TCPS_FIN_WAIT_1; 1880 tp->t_flags &= ~TF_NEEDFIN; 1881 } else { 1882 tp->t_state = TCPS_ESTABLISHED; 1883 callout_reset(tp->tt_keep, tcp_keepidle, 1884 tcp_timer_keep, tp); 1885 } 1886 /* 1887 * If segment contains data or ACK, will call tcp_reass() 1888 * later; if not, do so now to pass queued data to user. 1889 */ 1890 if (tlen == 0 && !(thflags & TH_FIN)) 1891 tcp_reass(tp, NULL, NULL, NULL); 1892 /* fall into ... */ 1893 1894 /* 1895 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1896 * ACKs. If the ack is in the range 1897 * tp->snd_una < th->th_ack <= tp->snd_max 1898 * then advance tp->snd_una to th->th_ack and drop 1899 * data from the retransmission queue. If this ACK reflects 1900 * more up to date window information we update our window information. 1901 */ 1902 case TCPS_ESTABLISHED: 1903 case TCPS_FIN_WAIT_1: 1904 case TCPS_FIN_WAIT_2: 1905 case TCPS_CLOSE_WAIT: 1906 case TCPS_CLOSING: 1907 case TCPS_LAST_ACK: 1908 case TCPS_TIME_WAIT: 1909 1910 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1911 if (TCP_DO_SACK(tp)) 1912 tcp_sack_update_scoreboard(tp, &to); 1913 if (tlen != 0 || tiwin != tp->snd_wnd) { 1914 tp->t_dupacks = 0; 1915 break; 1916 } 1917 tcpstat.tcps_rcvdupack++; 1918 if (!callout_active(tp->tt_rexmt) || 1919 th->th_ack != tp->snd_una) { 1920 tp->t_dupacks = 0; 1921 break; 1922 } 1923 /* 1924 * We have outstanding data (other than 1925 * a window probe), this is a completely 1926 * duplicate ack (ie, window info didn't 1927 * change), the ack is the biggest we've 1928 * seen and we've seen exactly our rexmt 1929 * threshhold of them, so assume a packet 1930 * has been dropped and retransmit it. 1931 * Kludge snd_nxt & the congestion 1932 * window so we send only this one 1933 * packet. 1934 */ 1935 if (IN_FASTRECOVERY(tp)) { 1936 if (TCP_DO_SACK(tp)) { 1937 /* No artifical cwnd inflation. */ 1938 tcp_sack_rexmt(tp, th); 1939 } else { 1940 /* 1941 * Dup acks mean that packets 1942 * have left the network 1943 * (they're now cached at the 1944 * receiver) so bump cwnd by 1945 * the amount in the receiver 1946 * to keep a constant cwnd 1947 * packets in the network. 1948 */ 1949 tp->snd_cwnd += tp->t_maxseg; 1950 tcp_output(tp); 1951 } 1952 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1953 tp->t_dupacks = 0; 1954 break; 1955 } else if (++tp->t_dupacks == tcprexmtthresh) { 1956 tcp_seq old_snd_nxt; 1957 u_int win; 1958 1959 fastretransmit: 1960 if (tcp_do_eifel_detect && 1961 (tp->t_flags & TF_RCVD_TSTMP)) { 1962 tcp_save_congestion_state(tp); 1963 tp->t_flags |= TF_FASTREXMT; 1964 } 1965 /* 1966 * We know we're losing at the current 1967 * window size, so do congestion avoidance: 1968 * set ssthresh to half the current window 1969 * and pull our congestion window back to the 1970 * new ssthresh. 1971 */ 1972 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1973 tp->t_maxseg; 1974 if (win < 2) 1975 win = 2; 1976 tp->snd_ssthresh = win * tp->t_maxseg; 1977 ENTER_FASTRECOVERY(tp); 1978 tp->snd_recover = tp->snd_max; 1979 callout_stop(tp->tt_rexmt); 1980 tp->t_rtttime = 0; 1981 old_snd_nxt = tp->snd_nxt; 1982 tp->snd_nxt = th->th_ack; 1983 tp->snd_cwnd = tp->t_maxseg; 1984 tcp_output(tp); 1985 ++tcpstat.tcps_sndfastrexmit; 1986 tp->snd_cwnd = tp->snd_ssthresh; 1987 tp->rexmt_high = tp->snd_nxt; 1988 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1989 tp->snd_nxt = old_snd_nxt; 1990 KASSERT(tp->snd_limited <= 2, 1991 ("tp->snd_limited too big")); 1992 if (TCP_DO_SACK(tp)) 1993 tcp_sack_rexmt(tp, th); 1994 else 1995 tp->snd_cwnd += tp->t_maxseg * 1996 (tp->t_dupacks - tp->snd_limited); 1997 } else if (tcp_do_limitedtransmit) { 1998 u_long oldcwnd = tp->snd_cwnd; 1999 tcp_seq oldsndmax = tp->snd_max; 2000 tcp_seq oldsndnxt = tp->snd_nxt; 2001 /* outstanding data */ 2002 uint32_t ownd = tp->snd_max - tp->snd_una; 2003 u_int sent; 2004 2005 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2006 2007 KASSERT(tp->t_dupacks == 1 || 2008 tp->t_dupacks == 2, 2009 ("dupacks not 1 or 2")); 2010 if (tp->t_dupacks == 1) 2011 tp->snd_limited = 0; 2012 tp->snd_nxt = tp->snd_max; 2013 tp->snd_cwnd = ownd + 2014 (tp->t_dupacks - tp->snd_limited) * 2015 tp->t_maxseg; 2016 tcp_output(tp); 2017 if (SEQ_LT(oldsndnxt, oldsndmax)) 2018 tp->snd_nxt = oldsndnxt; 2019 tp->snd_cwnd = oldcwnd; 2020 sent = tp->snd_max - oldsndmax; 2021 if (sent > tp->t_maxseg) { 2022 KASSERT((tp->t_dupacks == 2 && 2023 tp->snd_limited == 0) || 2024 (sent == tp->t_maxseg + 1 && 2025 tp->t_flags & TF_SENTFIN), 2026 ("sent too much")); 2027 KASSERT(sent <= tp->t_maxseg * 2, 2028 ("sent too many segments")); 2029 tp->snd_limited = 2; 2030 tcpstat.tcps_sndlimited += 2; 2031 } else if (sent > 0) { 2032 ++tp->snd_limited; 2033 ++tcpstat.tcps_sndlimited; 2034 } else if (tcp_do_early_retransmit && 2035 (tcp_do_eifel_detect && 2036 (tp->t_flags & TF_RCVD_TSTMP)) && 2037 ownd < 4 * tp->t_maxseg && 2038 tp->t_dupacks + 1 >= 2039 iceildiv(ownd, tp->t_maxseg) && 2040 (!TCP_DO_SACK(tp) || 2041 ownd <= tp->t_maxseg || 2042 tcp_sack_has_sacked(&tp->scb, 2043 ownd - tp->t_maxseg))) { 2044 ++tcpstat.tcps_sndearlyrexmit; 2045 tp->t_flags |= TF_EARLYREXMT; 2046 goto fastretransmit; 2047 } 2048 } 2049 goto drop; 2050 } 2051 2052 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2053 tp->t_dupacks = 0; 2054 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2055 /* 2056 * Detected optimistic ACK attack. 2057 * Force slow-start to de-synchronize attack. 2058 */ 2059 tp->snd_cwnd = tp->t_maxseg; 2060 tp->snd_wacked = 0; 2061 2062 tcpstat.tcps_rcvacktoomuch++; 2063 goto dropafterack; 2064 } 2065 /* 2066 * If we reach this point, ACK is not a duplicate, 2067 * i.e., it ACKs something we sent. 2068 */ 2069 if (tp->t_flags & TF_NEEDSYN) { 2070 /* 2071 * T/TCP: Connection was half-synchronized, and our 2072 * SYN has been ACK'd (so connection is now fully 2073 * synchronized). Go to non-starred state, 2074 * increment snd_una for ACK of SYN, and check if 2075 * we can do window scaling. 2076 */ 2077 tp->t_flags &= ~TF_NEEDSYN; 2078 tp->snd_una++; 2079 /* Do window scaling? */ 2080 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2081 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2082 tp->snd_scale = tp->requested_s_scale; 2083 tp->rcv_scale = tp->request_r_scale; 2084 } 2085 } 2086 2087 process_ACK: 2088 acked = th->th_ack - tp->snd_una; 2089 tcpstat.tcps_rcvackpack++; 2090 tcpstat.tcps_rcvackbyte += acked; 2091 2092 if (tcp_do_eifel_detect && acked > 0 && 2093 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2094 (tp->t_flags & TF_FIRSTACCACK)) { 2095 /* Eifel detection applicable. */ 2096 if (to.to_tsecr < tp->t_rexmtTS) { 2097 ++tcpstat.tcps_eifeldetected; 2098 tcp_revert_congestion_state(tp); 2099 if (tp->t_rxtshift == 1 && 2100 ticks >= tp->t_badrxtwin) 2101 ++tcpstat.tcps_rttcantdetect; 2102 } 2103 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2104 /* 2105 * If we just performed our first retransmit, 2106 * and the ACK arrives within our recovery window, 2107 * then it was a mistake to do the retransmit 2108 * in the first place. Recover our original cwnd 2109 * and ssthresh, and proceed to transmit where we 2110 * left off. 2111 */ 2112 tcp_revert_congestion_state(tp); 2113 ++tcpstat.tcps_rttdetected; 2114 } 2115 2116 /* 2117 * If we have a timestamp reply, update smoothed 2118 * round trip time. If no timestamp is present but 2119 * transmit timer is running and timed sequence 2120 * number was acked, update smoothed round trip time. 2121 * Since we now have an rtt measurement, cancel the 2122 * timer backoff (cf., Phil Karn's retransmit alg.). 2123 * Recompute the initial retransmit timer. 2124 * 2125 * Some machines (certain windows boxes) send broken 2126 * timestamp replies during the SYN+ACK phase, ignore 2127 * timestamps of 0. 2128 */ 2129 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2130 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2131 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2132 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2133 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2134 2135 /* 2136 * If no data (only SYN) was ACK'd, 2137 * skip rest of ACK processing. 2138 */ 2139 if (acked == 0) 2140 goto step6; 2141 2142 /* Stop looking for an acceptable ACK since one was received. */ 2143 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2144 2145 if (acked > so->so_snd.sb_cc) { 2146 tp->snd_wnd -= so->so_snd.sb_cc; 2147 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 2148 ourfinisacked = TRUE; 2149 } else { 2150 sbdrop(&so->so_snd, acked); 2151 tp->snd_wnd -= acked; 2152 ourfinisacked = FALSE; 2153 } 2154 sowwakeup(so); 2155 2156 /* 2157 * Update window information. 2158 * Don't look at window if no ACK: 2159 * TAC's send garbage on first SYN. 2160 */ 2161 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2162 (tp->snd_wl1 == th->th_seq && 2163 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2164 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2165 /* keep track of pure window updates */ 2166 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2167 tiwin > tp->snd_wnd) 2168 tcpstat.tcps_rcvwinupd++; 2169 tp->snd_wnd = tiwin; 2170 tp->snd_wl1 = th->th_seq; 2171 tp->snd_wl2 = th->th_ack; 2172 if (tp->snd_wnd > tp->max_sndwnd) 2173 tp->max_sndwnd = tp->snd_wnd; 2174 needoutput = TRUE; 2175 } 2176 2177 tp->snd_una = th->th_ack; 2178 if (TCP_DO_SACK(tp)) 2179 tcp_sack_update_scoreboard(tp, &to); 2180 if (IN_FASTRECOVERY(tp)) { 2181 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2182 EXIT_FASTRECOVERY(tp); 2183 needoutput = TRUE; 2184 /* 2185 * If the congestion window was inflated 2186 * to account for the other side's 2187 * cached packets, retract it. 2188 */ 2189 if (!TCP_DO_SACK(tp)) 2190 tp->snd_cwnd = tp->snd_ssthresh; 2191 2192 /* 2193 * Window inflation should have left us 2194 * with approximately snd_ssthresh outstanding 2195 * data. But, in case we would be inclined 2196 * to send a burst, better do it using 2197 * slow start. 2198 */ 2199 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2200 tp->snd_max + 2 * tp->t_maxseg)) 2201 tp->snd_cwnd = 2202 (tp->snd_max - tp->snd_una) + 2203 2 * tp->t_maxseg; 2204 2205 tp->snd_wacked = 0; 2206 } else { 2207 if (TCP_DO_SACK(tp)) { 2208 tp->snd_max_rexmt = tp->snd_max; 2209 tcp_sack_rexmt(tp, th); 2210 } else { 2211 tcp_newreno_partial_ack(tp, th, acked); 2212 } 2213 needoutput = FALSE; 2214 } 2215 } else { 2216 /* 2217 * Open the congestion window. When in slow-start, 2218 * open exponentially: maxseg per packet. Otherwise, 2219 * open linearly: maxseg per window. 2220 */ 2221 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2222 u_int abc_sslimit = 2223 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2224 tp->t_maxseg : 2 * tp->t_maxseg); 2225 2226 /* slow-start */ 2227 tp->snd_cwnd += tcp_do_abc ? 2228 min(acked, abc_sslimit) : tp->t_maxseg; 2229 } else { 2230 /* linear increase */ 2231 tp->snd_wacked += tcp_do_abc ? acked : 2232 tp->t_maxseg; 2233 if (tp->snd_wacked >= tp->snd_cwnd) { 2234 tp->snd_wacked -= tp->snd_cwnd; 2235 tp->snd_cwnd += tp->t_maxseg; 2236 } 2237 } 2238 tp->snd_cwnd = min(tp->snd_cwnd, 2239 TCP_MAXWIN << tp->snd_scale); 2240 tp->snd_recover = th->th_ack - 1; 2241 } 2242 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2243 tp->snd_nxt = tp->snd_una; 2244 2245 /* 2246 * If all outstanding data is acked, stop retransmit 2247 * timer and remember to restart (more output or persist). 2248 * If there is more data to be acked, restart retransmit 2249 * timer, using current (possibly backed-off) value. 2250 */ 2251 if (th->th_ack == tp->snd_max) { 2252 callout_stop(tp->tt_rexmt); 2253 needoutput = TRUE; 2254 } else if (!callout_active(tp->tt_persist)) 2255 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 2256 tcp_timer_rexmt, tp); 2257 2258 switch (tp->t_state) { 2259 /* 2260 * In FIN_WAIT_1 STATE in addition to the processing 2261 * for the ESTABLISHED state if our FIN is now acknowledged 2262 * then enter FIN_WAIT_2. 2263 */ 2264 case TCPS_FIN_WAIT_1: 2265 if (ourfinisacked) { 2266 /* 2267 * If we can't receive any more 2268 * data, then closing user can proceed. 2269 * Starting the timer is contrary to the 2270 * specification, but if we don't get a FIN 2271 * we'll hang forever. 2272 */ 2273 if (so->so_state & SS_CANTRCVMORE) { 2274 soisdisconnected(so); 2275 callout_reset(tp->tt_2msl, tcp_maxidle, 2276 tcp_timer_2msl, tp); 2277 } 2278 tp->t_state = TCPS_FIN_WAIT_2; 2279 } 2280 break; 2281 2282 /* 2283 * In CLOSING STATE in addition to the processing for 2284 * the ESTABLISHED state if the ACK acknowledges our FIN 2285 * then enter the TIME-WAIT state, otherwise ignore 2286 * the segment. 2287 */ 2288 case TCPS_CLOSING: 2289 if (ourfinisacked) { 2290 tp->t_state = TCPS_TIME_WAIT; 2291 tcp_canceltimers(tp); 2292 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2293 if (tp->cc_recv != 0 && 2294 (ticks - tp->t_starttime) < tcp_msl) 2295 callout_reset(tp->tt_2msl, 2296 tp->t_rxtcur * TCPTV_TWTRUNC, 2297 tcp_timer_2msl, tp); 2298 else 2299 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2300 tcp_timer_2msl, tp); 2301 soisdisconnected(so); 2302 } 2303 break; 2304 2305 /* 2306 * In LAST_ACK, we may still be waiting for data to drain 2307 * and/or to be acked, as well as for the ack of our FIN. 2308 * If our FIN is now acknowledged, delete the TCB, 2309 * enter the closed state and return. 2310 */ 2311 case TCPS_LAST_ACK: 2312 if (ourfinisacked) { 2313 tp = tcp_close(tp); 2314 goto drop; 2315 } 2316 break; 2317 2318 /* 2319 * In TIME_WAIT state the only thing that should arrive 2320 * is a retransmission of the remote FIN. Acknowledge 2321 * it and restart the finack timer. 2322 */ 2323 case TCPS_TIME_WAIT: 2324 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2325 tcp_timer_2msl, tp); 2326 goto dropafterack; 2327 } 2328 } 2329 2330 step6: 2331 /* 2332 * Update window information. 2333 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2334 */ 2335 if ((thflags & TH_ACK) && 2336 acceptable_window_update(tp, th, tiwin)) { 2337 /* keep track of pure window updates */ 2338 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2339 tiwin > tp->snd_wnd) 2340 tcpstat.tcps_rcvwinupd++; 2341 tp->snd_wnd = tiwin; 2342 tp->snd_wl1 = th->th_seq; 2343 tp->snd_wl2 = th->th_ack; 2344 if (tp->snd_wnd > tp->max_sndwnd) 2345 tp->max_sndwnd = tp->snd_wnd; 2346 needoutput = TRUE; 2347 } 2348 2349 /* 2350 * Process segments with URG. 2351 */ 2352 if ((thflags & TH_URG) && th->th_urp && 2353 !TCPS_HAVERCVDFIN(tp->t_state)) { 2354 /* 2355 * This is a kludge, but if we receive and accept 2356 * random urgent pointers, we'll crash in 2357 * soreceive. It's hard to imagine someone 2358 * actually wanting to send this much urgent data. 2359 */ 2360 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2361 th->th_urp = 0; /* XXX */ 2362 thflags &= ~TH_URG; /* XXX */ 2363 goto dodata; /* XXX */ 2364 } 2365 /* 2366 * If this segment advances the known urgent pointer, 2367 * then mark the data stream. This should not happen 2368 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2369 * a FIN has been received from the remote side. 2370 * In these states we ignore the URG. 2371 * 2372 * According to RFC961 (Assigned Protocols), 2373 * the urgent pointer points to the last octet 2374 * of urgent data. We continue, however, 2375 * to consider it to indicate the first octet 2376 * of data past the urgent section as the original 2377 * spec states (in one of two places). 2378 */ 2379 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2380 tp->rcv_up = th->th_seq + th->th_urp; 2381 so->so_oobmark = so->so_rcv.sb_cc + 2382 (tp->rcv_up - tp->rcv_nxt) - 1; 2383 if (so->so_oobmark == 0) 2384 so->so_state |= SS_RCVATMARK; 2385 sohasoutofband(so); 2386 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2387 } 2388 /* 2389 * Remove out of band data so doesn't get presented to user. 2390 * This can happen independent of advancing the URG pointer, 2391 * but if two URG's are pending at once, some out-of-band 2392 * data may creep in... ick. 2393 */ 2394 if (th->th_urp <= (u_long)tlen && 2395 !(so->so_options & SO_OOBINLINE)) { 2396 /* hdr drop is delayed */ 2397 tcp_pulloutofband(so, th, m, drop_hdrlen); 2398 } 2399 } else { 2400 /* 2401 * If no out of band data is expected, 2402 * pull receive urgent pointer along 2403 * with the receive window. 2404 */ 2405 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2406 tp->rcv_up = tp->rcv_nxt; 2407 } 2408 2409 dodata: /* XXX */ 2410 /* 2411 * Process the segment text, merging it into the TCP sequencing queue, 2412 * and arranging for acknowledgment of receipt if necessary. 2413 * This process logically involves adjusting tp->rcv_wnd as data 2414 * is presented to the user (this happens in tcp_usrreq.c, 2415 * case PRU_RCVD). If a FIN has already been received on this 2416 * connection then we just ignore the text. 2417 */ 2418 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2419 m_adj(m, drop_hdrlen); /* delayed header drop */ 2420 /* 2421 * Insert segment which includes th into TCP reassembly queue 2422 * with control block tp. Set thflags to whether reassembly now 2423 * includes a segment with FIN. This handles the common case 2424 * inline (segment is the next to be received on an established 2425 * connection, and the queue is empty), avoiding linkage into 2426 * and removal from the queue and repetition of various 2427 * conversions. 2428 * Set DELACK for segments received in order, but ack 2429 * immediately when segments are out of order (so 2430 * fast retransmit can work). 2431 */ 2432 if (th->th_seq == tp->rcv_nxt && 2433 LIST_EMPTY(&tp->t_segq) && 2434 TCPS_HAVEESTABLISHED(tp->t_state)) { 2435 if (DELAY_ACK(tp)) 2436 callout_reset(tp->tt_delack, tcp_delacktime, 2437 tcp_timer_delack, tp); 2438 else 2439 tp->t_flags |= TF_ACKNOW; 2440 tp->rcv_nxt += tlen; 2441 thflags = th->th_flags & TH_FIN; 2442 tcpstat.tcps_rcvpack++; 2443 tcpstat.tcps_rcvbyte += tlen; 2444 ND6_HINT(tp); 2445 if (so->so_state & SS_CANTRCVMORE) 2446 m_freem(m); 2447 else 2448 sbappendstream(&so->so_rcv, m); 2449 sorwakeup(so); 2450 } else { 2451 if (!(tp->t_flags & TF_DUPSEG)) { 2452 /* Initialize SACK report block. */ 2453 tp->reportblk.rblk_start = th->th_seq; 2454 tp->reportblk.rblk_end = th->th_seq + tlen + 2455 ((thflags & TH_FIN) != 0); 2456 } 2457 thflags = tcp_reass(tp, th, &tlen, m); 2458 tp->t_flags |= TF_ACKNOW; 2459 } 2460 2461 /* 2462 * Note the amount of data that peer has sent into 2463 * our window, in order to estimate the sender's 2464 * buffer size. 2465 */ 2466 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2467 } else { 2468 m_freem(m); 2469 thflags &= ~TH_FIN; 2470 } 2471 2472 /* 2473 * If FIN is received ACK the FIN and let the user know 2474 * that the connection is closing. 2475 */ 2476 if (thflags & TH_FIN) { 2477 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2478 socantrcvmore(so); 2479 /* 2480 * If connection is half-synchronized 2481 * (ie NEEDSYN flag on) then delay ACK, 2482 * so it may be piggybacked when SYN is sent. 2483 * Otherwise, since we received a FIN then no 2484 * more input can be expected, send ACK now. 2485 */ 2486 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2487 callout_reset(tp->tt_delack, tcp_delacktime, 2488 tcp_timer_delack, tp); 2489 else 2490 tp->t_flags |= TF_ACKNOW; 2491 tp->rcv_nxt++; 2492 } 2493 2494 switch (tp->t_state) { 2495 /* 2496 * In SYN_RECEIVED and ESTABLISHED STATES 2497 * enter the CLOSE_WAIT state. 2498 */ 2499 case TCPS_SYN_RECEIVED: 2500 tp->t_starttime = ticks; 2501 /*FALLTHROUGH*/ 2502 case TCPS_ESTABLISHED: 2503 tp->t_state = TCPS_CLOSE_WAIT; 2504 break; 2505 2506 /* 2507 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2508 * enter the CLOSING state. 2509 */ 2510 case TCPS_FIN_WAIT_1: 2511 tp->t_state = TCPS_CLOSING; 2512 break; 2513 2514 /* 2515 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2516 * starting the time-wait timer, turning off the other 2517 * standard timers. 2518 */ 2519 case TCPS_FIN_WAIT_2: 2520 tp->t_state = TCPS_TIME_WAIT; 2521 tcp_canceltimers(tp); 2522 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2523 if (tp->cc_recv != 0 && 2524 (ticks - tp->t_starttime) < tcp_msl) { 2525 callout_reset(tp->tt_2msl, 2526 tp->t_rxtcur * TCPTV_TWTRUNC, 2527 tcp_timer_2msl, tp); 2528 /* For transaction client, force ACK now. */ 2529 tp->t_flags |= TF_ACKNOW; 2530 } 2531 else 2532 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2533 tcp_timer_2msl, tp); 2534 soisdisconnected(so); 2535 break; 2536 2537 /* 2538 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2539 */ 2540 case TCPS_TIME_WAIT: 2541 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2542 tcp_timer_2msl, tp); 2543 break; 2544 } 2545 } 2546 2547 #ifdef TCPDEBUG 2548 if (so->so_options & SO_DEBUG) 2549 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2550 #endif 2551 2552 /* 2553 * Return any desired output. 2554 */ 2555 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2556 tcp_output(tp); 2557 return; 2558 2559 dropafterack: 2560 /* 2561 * Generate an ACK dropping incoming segment if it occupies 2562 * sequence space, where the ACK reflects our state. 2563 * 2564 * We can now skip the test for the RST flag since all 2565 * paths to this code happen after packets containing 2566 * RST have been dropped. 2567 * 2568 * In the SYN-RECEIVED state, don't send an ACK unless the 2569 * segment we received passes the SYN-RECEIVED ACK test. 2570 * If it fails send a RST. This breaks the loop in the 2571 * "LAND" DoS attack, and also prevents an ACK storm 2572 * between two listening ports that have been sent forged 2573 * SYN segments, each with the source address of the other. 2574 */ 2575 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2576 (SEQ_GT(tp->snd_una, th->th_ack) || 2577 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2578 rstreason = BANDLIM_RST_OPENPORT; 2579 goto dropwithreset; 2580 } 2581 #ifdef TCPDEBUG 2582 if (so->so_options & SO_DEBUG) 2583 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2584 #endif 2585 m_freem(m); 2586 tp->t_flags |= TF_ACKNOW; 2587 tcp_output(tp); 2588 return; 2589 2590 dropwithreset: 2591 /* 2592 * Generate a RST, dropping incoming segment. 2593 * Make ACK acceptable to originator of segment. 2594 * Don't bother to respond if destination was broadcast/multicast. 2595 */ 2596 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2597 goto drop; 2598 if (isipv6) { 2599 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2600 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2601 goto drop; 2602 } else { 2603 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2604 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2605 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2606 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2607 goto drop; 2608 } 2609 /* IPv6 anycast check is done at tcp6_input() */ 2610 2611 /* 2612 * Perform bandwidth limiting. 2613 */ 2614 #ifdef ICMP_BANDLIM 2615 if (badport_bandlim(rstreason) < 0) 2616 goto drop; 2617 #endif 2618 2619 #ifdef TCPDEBUG 2620 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2621 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2622 #endif 2623 if (thflags & TH_ACK) 2624 /* mtod() below is safe as long as hdr dropping is delayed */ 2625 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2626 TH_RST); 2627 else { 2628 if (thflags & TH_SYN) 2629 tlen++; 2630 /* mtod() below is safe as long as hdr dropping is delayed */ 2631 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2632 (tcp_seq)0, TH_RST | TH_ACK); 2633 } 2634 return; 2635 2636 drop: 2637 /* 2638 * Drop space held by incoming segment and return. 2639 */ 2640 #ifdef TCPDEBUG 2641 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2642 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2643 #endif 2644 m_freem(m); 2645 return; 2646 } 2647 2648 /* 2649 * Parse TCP options and place in tcpopt. 2650 */ 2651 static void 2652 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2653 { 2654 int opt, optlen, i; 2655 2656 to->to_flags = 0; 2657 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2658 opt = cp[0]; 2659 if (opt == TCPOPT_EOL) 2660 break; 2661 if (opt == TCPOPT_NOP) 2662 optlen = 1; 2663 else { 2664 if (cnt < 2) 2665 break; 2666 optlen = cp[1]; 2667 if (optlen < 2 || optlen > cnt) 2668 break; 2669 } 2670 switch (opt) { 2671 case TCPOPT_MAXSEG: 2672 if (optlen != TCPOLEN_MAXSEG) 2673 continue; 2674 if (!is_syn) 2675 continue; 2676 to->to_flags |= TOF_MSS; 2677 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2678 to->to_mss = ntohs(to->to_mss); 2679 break; 2680 case TCPOPT_WINDOW: 2681 if (optlen != TCPOLEN_WINDOW) 2682 continue; 2683 if (!is_syn) 2684 continue; 2685 to->to_flags |= TOF_SCALE; 2686 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2687 break; 2688 case TCPOPT_TIMESTAMP: 2689 if (optlen != TCPOLEN_TIMESTAMP) 2690 continue; 2691 to->to_flags |= TOF_TS; 2692 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2693 to->to_tsval = ntohl(to->to_tsval); 2694 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2695 to->to_tsecr = ntohl(to->to_tsecr); 2696 /* 2697 * If echoed timestamp is later than the current time, 2698 * fall back to non RFC1323 RTT calculation. 2699 */ 2700 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2701 to->to_tsecr = 0; 2702 break; 2703 case TCPOPT_CC: 2704 if (optlen != TCPOLEN_CC) 2705 continue; 2706 to->to_flags |= TOF_CC; 2707 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2708 to->to_cc = ntohl(to->to_cc); 2709 break; 2710 case TCPOPT_CCNEW: 2711 if (optlen != TCPOLEN_CC) 2712 continue; 2713 if (!is_syn) 2714 continue; 2715 to->to_flags |= TOF_CCNEW; 2716 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2717 to->to_cc = ntohl(to->to_cc); 2718 break; 2719 case TCPOPT_CCECHO: 2720 if (optlen != TCPOLEN_CC) 2721 continue; 2722 if (!is_syn) 2723 continue; 2724 to->to_flags |= TOF_CCECHO; 2725 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho); 2726 to->to_ccecho = ntohl(to->to_ccecho); 2727 break; 2728 case TCPOPT_SACK_PERMITTED: 2729 if (optlen != TCPOLEN_SACK_PERMITTED) 2730 continue; 2731 if (!is_syn) 2732 continue; 2733 to->to_flags |= TOF_SACK_PERMITTED; 2734 break; 2735 case TCPOPT_SACK: 2736 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2737 continue; 2738 to->to_nsackblocks = (optlen - 2) / 8; 2739 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2740 to->to_flags |= TOF_SACK; 2741 for (i = 0; i < to->to_nsackblocks; i++) { 2742 struct raw_sackblock *r = &to->to_sackblocks[i]; 2743 2744 r->rblk_start = ntohl(r->rblk_start); 2745 r->rblk_end = ntohl(r->rblk_end); 2746 } 2747 break; 2748 default: 2749 continue; 2750 } 2751 } 2752 } 2753 2754 /* 2755 * Pull out of band byte out of a segment so 2756 * it doesn't appear in the user's data queue. 2757 * It is still reflected in the segment length for 2758 * sequencing purposes. 2759 * "off" is the delayed to be dropped hdrlen. 2760 */ 2761 static void 2762 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2763 { 2764 int cnt = off + th->th_urp - 1; 2765 2766 while (cnt >= 0) { 2767 if (m->m_len > cnt) { 2768 char *cp = mtod(m, caddr_t) + cnt; 2769 struct tcpcb *tp = sototcpcb(so); 2770 2771 tp->t_iobc = *cp; 2772 tp->t_oobflags |= TCPOOB_HAVEDATA; 2773 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2774 m->m_len--; 2775 if (m->m_flags & M_PKTHDR) 2776 m->m_pkthdr.len--; 2777 return; 2778 } 2779 cnt -= m->m_len; 2780 m = m->m_next; 2781 if (m == 0) 2782 break; 2783 } 2784 panic("tcp_pulloutofband"); 2785 } 2786 2787 /* 2788 * Collect new round-trip time estimate 2789 * and update averages and current timeout. 2790 */ 2791 static void 2792 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2793 { 2794 int delta; 2795 2796 tcpstat.tcps_rttupdated++; 2797 tp->t_rttupdated++; 2798 if (tp->t_srtt != 0) { 2799 /* 2800 * srtt is stored as fixed point with 5 bits after the 2801 * binary point (i.e., scaled by 8). The following magic 2802 * is equivalent to the smoothing algorithm in rfc793 with 2803 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2804 * point). Adjust rtt to origin 0. 2805 */ 2806 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2807 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2808 2809 if ((tp->t_srtt += delta) <= 0) 2810 tp->t_srtt = 1; 2811 2812 /* 2813 * We accumulate a smoothed rtt variance (actually, a 2814 * smoothed mean difference), then set the retransmit 2815 * timer to smoothed rtt + 4 times the smoothed variance. 2816 * rttvar is stored as fixed point with 4 bits after the 2817 * binary point (scaled by 16). The following is 2818 * equivalent to rfc793 smoothing with an alpha of .75 2819 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2820 * rfc793's wired-in beta. 2821 */ 2822 if (delta < 0) 2823 delta = -delta; 2824 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2825 if ((tp->t_rttvar += delta) <= 0) 2826 tp->t_rttvar = 1; 2827 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2828 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2829 } else { 2830 /* 2831 * No rtt measurement yet - use the unsmoothed rtt. 2832 * Set the variance to half the rtt (so our first 2833 * retransmit happens at 3*rtt). 2834 */ 2835 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2836 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2837 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2838 } 2839 tp->t_rtttime = 0; 2840 tp->t_rxtshift = 0; 2841 2842 /* 2843 * the retransmit should happen at rtt + 4 * rttvar. 2844 * Because of the way we do the smoothing, srtt and rttvar 2845 * will each average +1/2 tick of bias. When we compute 2846 * the retransmit timer, we want 1/2 tick of rounding and 2847 * 1 extra tick because of +-1/2 tick uncertainty in the 2848 * firing of the timer. The bias will give us exactly the 2849 * 1.5 tick we need. But, because the bias is 2850 * statistical, we have to test that we don't drop below 2851 * the minimum feasible timer (which is 2 ticks). 2852 */ 2853 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2854 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2855 2856 /* 2857 * We received an ack for a packet that wasn't retransmitted; 2858 * it is probably safe to discard any error indications we've 2859 * received recently. This isn't quite right, but close enough 2860 * for now (a route might have failed after we sent a segment, 2861 * and the return path might not be symmetrical). 2862 */ 2863 tp->t_softerror = 0; 2864 } 2865 2866 /* 2867 * Determine a reasonable value for maxseg size. 2868 * If the route is known, check route for mtu. 2869 * If none, use an mss that can be handled on the outgoing 2870 * interface without forcing IP to fragment; if bigger than 2871 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2872 * to utilize large mbufs. If no route is found, route has no mtu, 2873 * or the destination isn't local, use a default, hopefully conservative 2874 * size (usually 512 or the default IP max size, but no more than the mtu 2875 * of the interface), as we can't discover anything about intervening 2876 * gateways or networks. We also initialize the congestion/slow start 2877 * window to be a single segment if the destination isn't local. 2878 * While looking at the routing entry, we also initialize other path-dependent 2879 * parameters from pre-set or cached values in the routing entry. 2880 * 2881 * Also take into account the space needed for options that we 2882 * send regularly. Make maxseg shorter by that amount to assure 2883 * that we can send maxseg amount of data even when the options 2884 * are present. Store the upper limit of the length of options plus 2885 * data in maxopd. 2886 * 2887 * NOTE that this routine is only called when we process an incoming 2888 * segment, for outgoing segments only tcp_mssopt is called. 2889 * 2890 * In case of T/TCP, we call this routine during implicit connection 2891 * setup as well (offer = -1), to initialize maxseg from the cached 2892 * MSS of our peer. 2893 */ 2894 void 2895 tcp_mss(struct tcpcb *tp, int offer) 2896 { 2897 struct rtentry *rt; 2898 struct ifnet *ifp; 2899 int rtt, mss; 2900 u_long bufsize; 2901 struct inpcb *inp = tp->t_inpcb; 2902 struct socket *so; 2903 struct rmxp_tao *taop; 2904 int origoffer = offer; 2905 #ifdef INET6 2906 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2907 size_t min_protoh = isipv6 ? 2908 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2909 sizeof(struct tcpiphdr); 2910 #else 2911 const boolean_t isipv6 = FALSE; 2912 const size_t min_protoh = sizeof(struct tcpiphdr); 2913 #endif 2914 2915 if (isipv6) 2916 rt = tcp_rtlookup6(&inp->inp_inc); 2917 else 2918 rt = tcp_rtlookup(&inp->inp_inc); 2919 if (rt == NULL) { 2920 tp->t_maxopd = tp->t_maxseg = 2921 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2922 return; 2923 } 2924 ifp = rt->rt_ifp; 2925 so = inp->inp_socket; 2926 2927 taop = rmx_taop(rt->rt_rmx); 2928 /* 2929 * Offer == -1 means that we didn't receive SYN yet, 2930 * use cached value in that case; 2931 */ 2932 if (offer == -1) 2933 offer = taop->tao_mssopt; 2934 /* 2935 * Offer == 0 means that there was no MSS on the SYN segment, 2936 * in this case we use tcp_mssdflt. 2937 */ 2938 if (offer == 0) 2939 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2940 else 2941 /* 2942 * Sanity check: make sure that maxopd will be large 2943 * enough to allow some data on segments even is the 2944 * all the option space is used (40bytes). Otherwise 2945 * funny things may happen in tcp_output. 2946 */ 2947 offer = max(offer, 64); 2948 taop->tao_mssopt = offer; 2949 2950 /* 2951 * While we're here, check if there's an initial rtt 2952 * or rttvar. Convert from the route-table units 2953 * to scaled multiples of the slow timeout timer. 2954 */ 2955 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2956 /* 2957 * XXX the lock bit for RTT indicates that the value 2958 * is also a minimum value; this is subject to time. 2959 */ 2960 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2961 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2962 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2963 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2964 tcpstat.tcps_usedrtt++; 2965 if (rt->rt_rmx.rmx_rttvar) { 2966 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2967 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2968 tcpstat.tcps_usedrttvar++; 2969 } else { 2970 /* default variation is +- 1 rtt */ 2971 tp->t_rttvar = 2972 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2973 } 2974 TCPT_RANGESET(tp->t_rxtcur, 2975 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2976 tp->t_rttmin, TCPTV_REXMTMAX); 2977 } 2978 /* 2979 * if there's an mtu associated with the route, use it 2980 * else, use the link mtu. 2981 */ 2982 if (rt->rt_rmx.rmx_mtu) 2983 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2984 else { 2985 if (isipv6) { 2986 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2987 if (!in6_localaddr(&inp->in6p_faddr)) 2988 mss = min(mss, tcp_v6mssdflt); 2989 } else { 2990 mss = ifp->if_mtu - min_protoh; 2991 if (!in_localaddr(inp->inp_faddr)) 2992 mss = min(mss, tcp_mssdflt); 2993 } 2994 } 2995 mss = min(mss, offer); 2996 /* 2997 * maxopd stores the maximum length of data AND options 2998 * in a segment; maxseg is the amount of data in a normal 2999 * segment. We need to store this value (maxopd) apart 3000 * from maxseg, because now every segment carries options 3001 * and thus we normally have somewhat less data in segments. 3002 */ 3003 tp->t_maxopd = mss; 3004 3005 /* 3006 * In case of T/TCP, origoffer==-1 indicates, that no segments 3007 * were received yet. In this case we just guess, otherwise 3008 * we do the same as before T/TCP. 3009 */ 3010 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3011 (origoffer == -1 || 3012 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3013 mss -= TCPOLEN_TSTAMP_APPA; 3014 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 3015 (origoffer == -1 || 3016 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3017 mss -= TCPOLEN_CC_APPA; 3018 3019 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3020 if (mss > MCLBYTES) 3021 mss &= ~(MCLBYTES-1); 3022 #else 3023 if (mss > MCLBYTES) 3024 mss = mss / MCLBYTES * MCLBYTES; 3025 #endif 3026 /* 3027 * If there's a pipesize, change the socket buffer 3028 * to that size. Make the socket buffers an integral 3029 * number of mss units; if the mss is larger than 3030 * the socket buffer, decrease the mss. 3031 */ 3032 #ifdef RTV_SPIPE 3033 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3034 #endif 3035 bufsize = so->so_snd.sb_hiwat; 3036 if (bufsize < mss) 3037 mss = bufsize; 3038 else { 3039 bufsize = roundup(bufsize, mss); 3040 if (bufsize > sb_max) 3041 bufsize = sb_max; 3042 if (bufsize > so->so_snd.sb_hiwat) 3043 sbreserve(&so->so_snd, bufsize, so, NULL); 3044 } 3045 tp->t_maxseg = mss; 3046 3047 #ifdef RTV_RPIPE 3048 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3049 #endif 3050 bufsize = so->so_rcv.sb_hiwat; 3051 if (bufsize > mss) { 3052 bufsize = roundup(bufsize, mss); 3053 if (bufsize > sb_max) 3054 bufsize = sb_max; 3055 if (bufsize > so->so_rcv.sb_hiwat) 3056 sbreserve(&so->so_rcv, bufsize, so, NULL); 3057 } 3058 3059 /* 3060 * Set the slow-start flight size depending on whether this 3061 * is a local network or not. 3062 */ 3063 if (tcp_do_rfc3390) 3064 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3065 else 3066 tp->snd_cwnd = mss; 3067 3068 if (rt->rt_rmx.rmx_ssthresh) { 3069 /* 3070 * There's some sort of gateway or interface 3071 * buffer limit on the path. Use this to set 3072 * the slow start threshhold, but set the 3073 * threshold to no less than 2*mss. 3074 */ 3075 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3076 tcpstat.tcps_usedssthresh++; 3077 } 3078 } 3079 3080 /* 3081 * Determine the MSS option to send on an outgoing SYN. 3082 */ 3083 int 3084 tcp_mssopt(struct tcpcb *tp) 3085 { 3086 struct rtentry *rt; 3087 #ifdef INET6 3088 boolean_t isipv6 = 3089 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3090 int min_protoh = isipv6 ? 3091 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3092 sizeof(struct tcpiphdr); 3093 #else 3094 const boolean_t isipv6 = FALSE; 3095 const size_t min_protoh = sizeof(struct tcpiphdr); 3096 #endif 3097 3098 if (isipv6) 3099 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3100 else 3101 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3102 if (rt == NULL) 3103 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3104 3105 return (rt->rt_ifp->if_mtu - min_protoh); 3106 } 3107 3108 /* 3109 * When a partial ack arrives, force the retransmission of the 3110 * next unacknowledged segment. Do not exit Fast Recovery. 3111 * 3112 * Implement the Slow-but-Steady variant of NewReno by restarting the 3113 * the retransmission timer. Turn it off here so it can be restarted 3114 * later in tcp_output(). 3115 */ 3116 static void 3117 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3118 { 3119 tcp_seq old_snd_nxt = tp->snd_nxt; 3120 u_long ocwnd = tp->snd_cwnd; 3121 3122 callout_stop(tp->tt_rexmt); 3123 tp->t_rtttime = 0; 3124 tp->snd_nxt = th->th_ack; 3125 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3126 tp->snd_cwnd = tp->t_maxseg; 3127 tp->t_flags |= TF_ACKNOW; 3128 tcp_output(tp); 3129 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3130 tp->snd_nxt = old_snd_nxt; 3131 /* partial window deflation */ 3132 if (ocwnd > acked) 3133 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3134 else 3135 tp->snd_cwnd = tp->t_maxseg; 3136 } 3137 3138 /* 3139 * In contrast to the Slow-but-Steady NewReno variant, 3140 * we do not reset the retransmission timer for SACK retransmissions, 3141 * except when retransmitting snd_una. 3142 */ 3143 static void 3144 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3145 { 3146 uint32_t pipe, seglen; 3147 tcp_seq nextrexmt; 3148 boolean_t lostdup; 3149 tcp_seq old_snd_nxt = tp->snd_nxt; 3150 u_long ocwnd = tp->snd_cwnd; 3151 int nseg = 0; /* consecutive new segments */ 3152 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3153 3154 tp->t_rtttime = 0; 3155 pipe = tcp_sack_compute_pipe(tp); 3156 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3157 (!tcp_do_smartsack || nseg < MAXBURST) && 3158 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3159 uint32_t sent; 3160 tcp_seq old_snd_max; 3161 int error; 3162 3163 if (nextrexmt == tp->snd_max) ++nseg; 3164 tp->snd_nxt = nextrexmt; 3165 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3166 old_snd_max = tp->snd_max; 3167 if (nextrexmt == tp->snd_una) 3168 callout_stop(tp->tt_rexmt); 3169 error = tcp_output(tp); 3170 if (error != 0) 3171 break; 3172 sent = tp->snd_nxt - nextrexmt; 3173 if (sent <= 0) 3174 break; 3175 if (!lostdup) 3176 pipe += sent; 3177 tcpstat.tcps_sndsackpack++; 3178 tcpstat.tcps_sndsackbyte += sent; 3179 if (SEQ_LT(nextrexmt, old_snd_max) && 3180 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3181 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3182 } 3183 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3184 tp->snd_nxt = old_snd_nxt; 3185 tp->snd_cwnd = ocwnd; 3186 } 3187