1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.68 2008/08/22 09:14:17 sephe Exp $ 69 */ 70 71 #include "opt_ipfw.h" /* for ipfw_fwd */ 72 #include "opt_inet6.h" 73 #include "opt_ipsec.h" 74 #include "opt_tcpdebug.h" 75 #include "opt_tcp_input.h" 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/sysctl.h> 81 #include <sys/malloc.h> 82 #include <sys/mbuf.h> 83 #include <sys/proc.h> /* for proc0 declaration */ 84 #include <sys/protosw.h> 85 #include <sys/socket.h> 86 #include <sys/socketvar.h> 87 #include <sys/syslog.h> 88 #include <sys/in_cksum.h> 89 90 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 91 #include <machine/stdarg.h> 92 93 #include <net/if.h> 94 #include <net/route.h> 95 96 #include <netinet/in.h> 97 #include <netinet/in_systm.h> 98 #include <netinet/ip.h> 99 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 100 #include <netinet/in_var.h> 101 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip6.h> 105 #include <netinet/icmp6.h> 106 #include <netinet6/nd6.h> 107 #include <netinet6/ip6_var.h> 108 #include <netinet6/in6_pcb.h> 109 #include <netinet/tcp.h> 110 #include <netinet/tcp_fsm.h> 111 #include <netinet/tcp_seq.h> 112 #include <netinet/tcp_timer.h> 113 #include <netinet/tcp_timer2.h> 114 #include <netinet/tcp_var.h> 115 #include <netinet6/tcp6_var.h> 116 #include <netinet/tcpip.h> 117 118 #ifdef TCPDEBUG 119 #include <netinet/tcp_debug.h> 120 121 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 122 struct tcphdr tcp_savetcp; 123 #endif 124 125 #ifdef FAST_IPSEC 126 #include <netproto/ipsec/ipsec.h> 127 #include <netproto/ipsec/ipsec6.h> 128 #endif 129 130 #ifdef IPSEC 131 #include <netinet6/ipsec.h> 132 #include <netinet6/ipsec6.h> 133 #include <netproto/key/key.h> 134 #endif 135 136 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 137 138 tcp_cc tcp_ccgen; 139 static int log_in_vain = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 141 &log_in_vain, 0, "Log all incoming TCP connections"); 142 143 static int blackhole = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 145 &blackhole, 0, "Do not send RST when dropping refused connections"); 146 147 int tcp_delack_enabled = 1; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 149 &tcp_delack_enabled, 0, 150 "Delay ACK to try and piggyback it onto a data packet"); 151 152 #ifdef TCP_DROP_SYNFIN 153 static int drop_synfin = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 156 #endif 157 158 static int tcp_do_limitedtransmit = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 161 162 static int tcp_do_early_retransmit = 1; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 164 &tcp_do_early_retransmit, 0, "Early retransmit"); 165 166 int tcp_aggregate_acks = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 169 170 int tcp_do_rfc3390 = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 172 &tcp_do_rfc3390, 0, 173 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 174 175 static int tcp_do_eifel_detect = 1; 176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 177 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 178 179 static int tcp_do_abc = 1; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 181 &tcp_do_abc, 0, 182 "TCP Appropriate Byte Counting (RFC 3465)"); 183 184 /* 185 * Define as tunable for easy testing with SACK on and off. 186 * Warning: do not change setting in the middle of an existing active TCP flow, 187 * else strange things might happen to that flow. 188 */ 189 int tcp_do_sack = 1; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 191 &tcp_do_sack, 0, "Enable SACK Algorithms"); 192 193 int tcp_do_smartsack = 1; 194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 195 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 196 197 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 198 "TCP Segment Reassembly Queue"); 199 200 int tcp_reass_maxseg = 0; 201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 202 &tcp_reass_maxseg, 0, 203 "Global maximum number of TCP Segments in Reassembly Queue"); 204 205 int tcp_reass_qsize = 0; 206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 207 &tcp_reass_qsize, 0, 208 "Global number of TCP Segments currently in Reassembly Queue"); 209 210 static int tcp_reass_overflows = 0; 211 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 212 &tcp_reass_overflows, 0, 213 "Global number of TCP Segment Reassembly Queue Overflows"); 214 215 int tcp_do_autorcvbuf = 1; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 217 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 218 219 int tcp_autorcvbuf_inc = 16*1024; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 221 &tcp_autorcvbuf_inc, 0, 222 "Incrementor step size of automatic receive buffer"); 223 224 int tcp_autorcvbuf_max = 16*1024*1024; 225 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 226 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 227 228 229 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 230 static void tcp_pulloutofband(struct socket *, 231 struct tcphdr *, struct mbuf *, int); 232 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 233 struct mbuf *); 234 static void tcp_xmit_timer(struct tcpcb *, int); 235 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 236 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 237 238 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 239 #ifdef INET6 240 #define ND6_HINT(tp) \ 241 do { \ 242 if ((tp) && (tp)->t_inpcb && \ 243 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 244 (tp)->t_inpcb->in6p_route.ro_rt) \ 245 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 246 } while (0) 247 #else 248 #define ND6_HINT(tp) 249 #endif 250 251 /* 252 * Indicate whether this ack should be delayed. We can delay the ack if 253 * - delayed acks are enabled and 254 * - there is no delayed ack timer in progress and 255 * - our last ack wasn't a 0-sized window. We never want to delay 256 * the ack that opens up a 0-sized window. 257 */ 258 #define DELAY_ACK(tp) \ 259 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 260 !(tp->t_flags & TF_RXWIN0SENT)) 261 262 #define acceptable_window_update(tp, th, tiwin) \ 263 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 264 (tp->snd_wl1 == th->th_seq && \ 265 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 266 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 267 268 static int 269 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 270 { 271 struct tseg_qent *q; 272 struct tseg_qent *p = NULL; 273 struct tseg_qent *te; 274 struct socket *so = tp->t_inpcb->inp_socket; 275 int flags; 276 277 /* 278 * Call with th == NULL after become established to 279 * force pre-ESTABLISHED data up to user socket. 280 */ 281 if (th == NULL) 282 goto present; 283 284 /* 285 * Limit the number of segments in the reassembly queue to prevent 286 * holding on to too many segments (and thus running out of mbufs). 287 * Make sure to let the missing segment through which caused this 288 * queue. Always keep one global queue entry spare to be able to 289 * process the missing segment. 290 */ 291 if (th->th_seq != tp->rcv_nxt && 292 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 293 tcp_reass_overflows++; 294 tcpstat.tcps_rcvmemdrop++; 295 m_freem(m); 296 /* no SACK block to report */ 297 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 298 return (0); 299 } 300 301 /* Allocate a new queue entry. */ 302 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 303 M_INTWAIT | M_NULLOK); 304 if (te == NULL) { 305 tcpstat.tcps_rcvmemdrop++; 306 m_freem(m); 307 /* no SACK block to report */ 308 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 309 return (0); 310 } 311 tcp_reass_qsize++; 312 313 /* 314 * Find a segment which begins after this one does. 315 */ 316 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 317 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 318 break; 319 p = q; 320 } 321 322 /* 323 * If there is a preceding segment, it may provide some of 324 * our data already. If so, drop the data from the incoming 325 * segment. If it provides all of our data, drop us. 326 */ 327 if (p != NULL) { 328 tcp_seq_diff_t i; 329 330 /* conversion to int (in i) handles seq wraparound */ 331 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 332 if (i > 0) { /* overlaps preceding segment */ 333 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 334 /* enclosing block starts w/ preceding segment */ 335 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 336 if (i >= *tlenp) { 337 /* preceding encloses incoming segment */ 338 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 339 p->tqe_len; 340 tcpstat.tcps_rcvduppack++; 341 tcpstat.tcps_rcvdupbyte += *tlenp; 342 m_freem(m); 343 kfree(te, M_TSEGQ); 344 tcp_reass_qsize--; 345 /* 346 * Try to present any queued data 347 * at the left window edge to the user. 348 * This is needed after the 3-WHS 349 * completes. 350 */ 351 goto present; /* ??? */ 352 } 353 m_adj(m, i); 354 *tlenp -= i; 355 th->th_seq += i; 356 /* incoming segment end is enclosing block end */ 357 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 358 ((th->th_flags & TH_FIN) != 0); 359 /* trim end of reported D-SACK block */ 360 tp->reportblk.rblk_end = th->th_seq; 361 } 362 } 363 tcpstat.tcps_rcvoopack++; 364 tcpstat.tcps_rcvoobyte += *tlenp; 365 366 /* 367 * While we overlap succeeding segments trim them or, 368 * if they are completely covered, dequeue them. 369 */ 370 while (q) { 371 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 372 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 373 struct tseg_qent *nq; 374 375 if (i <= 0) 376 break; 377 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 378 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 379 tp->encloseblk = tp->reportblk; 380 /* report trailing duplicate D-SACK segment */ 381 tp->reportblk.rblk_start = q->tqe_th->th_seq; 382 } 383 if ((tp->t_flags & TF_ENCLOSESEG) && 384 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 385 /* extend enclosing block if one exists */ 386 tp->encloseblk.rblk_end = qend; 387 } 388 if (i < q->tqe_len) { 389 q->tqe_th->th_seq += i; 390 q->tqe_len -= i; 391 m_adj(q->tqe_m, i); 392 break; 393 } 394 395 nq = LIST_NEXT(q, tqe_q); 396 LIST_REMOVE(q, tqe_q); 397 m_freem(q->tqe_m); 398 kfree(q, M_TSEGQ); 399 tcp_reass_qsize--; 400 q = nq; 401 } 402 403 /* Insert the new segment queue entry into place. */ 404 te->tqe_m = m; 405 te->tqe_th = th; 406 te->tqe_len = *tlenp; 407 408 /* check if can coalesce with following segment */ 409 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 410 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 411 412 te->tqe_len += q->tqe_len; 413 if (q->tqe_th->th_flags & TH_FIN) 414 te->tqe_th->th_flags |= TH_FIN; 415 m_cat(te->tqe_m, q->tqe_m); 416 tp->encloseblk.rblk_end = tend; 417 /* 418 * When not reporting a duplicate segment, use 419 * the larger enclosing block as the SACK block. 420 */ 421 if (!(tp->t_flags & TF_DUPSEG)) 422 tp->reportblk.rblk_end = tend; 423 LIST_REMOVE(q, tqe_q); 424 kfree(q, M_TSEGQ); 425 tcp_reass_qsize--; 426 } 427 428 if (p == NULL) { 429 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 430 } else { 431 /* check if can coalesce with preceding segment */ 432 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 433 p->tqe_len += te->tqe_len; 434 m_cat(p->tqe_m, te->tqe_m); 435 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 436 /* 437 * When not reporting a duplicate segment, use 438 * the larger enclosing block as the SACK block. 439 */ 440 if (!(tp->t_flags & TF_DUPSEG)) 441 tp->reportblk.rblk_start = p->tqe_th->th_seq; 442 kfree(te, M_TSEGQ); 443 tcp_reass_qsize--; 444 } else 445 LIST_INSERT_AFTER(p, te, tqe_q); 446 } 447 448 present: 449 /* 450 * Present data to user, advancing rcv_nxt through 451 * completed sequence space. 452 */ 453 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 454 return (0); 455 q = LIST_FIRST(&tp->t_segq); 456 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 457 return (0); 458 tp->rcv_nxt += q->tqe_len; 459 if (!(tp->t_flags & TF_DUPSEG)) { 460 /* no SACK block to report since ACK advanced */ 461 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 462 } 463 /* no enclosing block to report since ACK advanced */ 464 tp->t_flags &= ~TF_ENCLOSESEG; 465 flags = q->tqe_th->th_flags & TH_FIN; 466 LIST_REMOVE(q, tqe_q); 467 KASSERT(LIST_EMPTY(&tp->t_segq) || 468 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 469 ("segment not coalesced")); 470 if (so->so_state & SS_CANTRCVMORE) 471 m_freem(q->tqe_m); 472 else 473 ssb_appendstream(&so->so_rcv, q->tqe_m); 474 kfree(q, M_TSEGQ); 475 tcp_reass_qsize--; 476 ND6_HINT(tp); 477 sorwakeup(so); 478 return (flags); 479 } 480 481 /* 482 * TCP input routine, follows pages 65-76 of the 483 * protocol specification dated September, 1981 very closely. 484 */ 485 #ifdef INET6 486 int 487 tcp6_input(struct mbuf **mp, int *offp, int proto) 488 { 489 struct mbuf *m = *mp; 490 struct in6_ifaddr *ia6; 491 492 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 493 494 /* 495 * draft-itojun-ipv6-tcp-to-anycast 496 * better place to put this in? 497 */ 498 ia6 = ip6_getdstifaddr(m); 499 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 500 struct ip6_hdr *ip6; 501 502 ip6 = mtod(m, struct ip6_hdr *); 503 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 504 offsetof(struct ip6_hdr, ip6_dst)); 505 return (IPPROTO_DONE); 506 } 507 508 tcp_input(m, *offp, proto); 509 return (IPPROTO_DONE); 510 } 511 #endif 512 513 void 514 tcp_input(struct mbuf *m, ...) 515 { 516 __va_list ap; 517 int off0, proto; 518 struct tcphdr *th; 519 struct ip *ip = NULL; 520 struct ipovly *ipov; 521 struct inpcb *inp = NULL; 522 u_char *optp = NULL; 523 int optlen = 0; 524 int len, tlen, off; 525 int drop_hdrlen; 526 struct tcpcb *tp = NULL; 527 int thflags; 528 struct socket *so = 0; 529 int todrop, acked; 530 boolean_t ourfinisacked, needoutput = FALSE; 531 u_long tiwin; 532 int recvwin; 533 struct tcpopt to; /* options in this segment */ 534 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 535 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 536 struct sockaddr_in *next_hop = NULL; 537 int rstreason; /* For badport_bandlim accounting purposes */ 538 int cpu; 539 struct ip6_hdr *ip6 = NULL; 540 #ifdef INET6 541 boolean_t isipv6; 542 #else 543 const boolean_t isipv6 = FALSE; 544 #endif 545 #ifdef TCPDEBUG 546 short ostate = 0; 547 #endif 548 549 __va_start(ap, m); 550 off0 = __va_arg(ap, int); 551 proto = __va_arg(ap, int); 552 __va_end(ap); 553 554 tcpstat.tcps_rcvtotal++; 555 556 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 557 struct m_tag *mtag; 558 559 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 560 KKASSERT(mtag != NULL); 561 next_hop = m_tag_data(mtag); 562 } 563 564 #ifdef INET6 565 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 566 #endif 567 568 if (isipv6) { 569 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 570 ip6 = mtod(m, struct ip6_hdr *); 571 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 572 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 573 tcpstat.tcps_rcvbadsum++; 574 goto drop; 575 } 576 th = (struct tcphdr *)((caddr_t)ip6 + off0); 577 578 /* 579 * Be proactive about unspecified IPv6 address in source. 580 * As we use all-zero to indicate unbounded/unconnected pcb, 581 * unspecified IPv6 address can be used to confuse us. 582 * 583 * Note that packets with unspecified IPv6 destination is 584 * already dropped in ip6_input. 585 */ 586 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 587 /* XXX stat */ 588 goto drop; 589 } 590 } else { 591 /* 592 * Get IP and TCP header together in first mbuf. 593 * Note: IP leaves IP header in first mbuf. 594 */ 595 if (off0 > sizeof(struct ip)) { 596 ip_stripoptions(m); 597 off0 = sizeof(struct ip); 598 } 599 /* already checked and pulled up in ip_demux() */ 600 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 601 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 602 ip = mtod(m, struct ip *); 603 ipov = (struct ipovly *)ip; 604 th = (struct tcphdr *)((caddr_t)ip + off0); 605 tlen = ip->ip_len; 606 607 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 608 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 609 th->th_sum = m->m_pkthdr.csum_data; 610 else 611 th->th_sum = in_pseudo(ip->ip_src.s_addr, 612 ip->ip_dst.s_addr, 613 htonl(m->m_pkthdr.csum_data + 614 ip->ip_len + 615 IPPROTO_TCP)); 616 th->th_sum ^= 0xffff; 617 } else { 618 /* 619 * Checksum extended TCP header and data. 620 */ 621 len = sizeof(struct ip) + tlen; 622 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 623 ipov->ih_len = (u_short)tlen; 624 ipov->ih_len = htons(ipov->ih_len); 625 th->th_sum = in_cksum(m, len); 626 } 627 if (th->th_sum) { 628 tcpstat.tcps_rcvbadsum++; 629 goto drop; 630 } 631 #ifdef INET6 632 /* Re-initialization for later version check */ 633 ip->ip_v = IPVERSION; 634 #endif 635 } 636 637 /* 638 * Check that TCP offset makes sense, 639 * pull out TCP options and adjust length. XXX 640 */ 641 off = th->th_off << 2; 642 /* already checked and pulled up in ip_demux() */ 643 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 644 ("bad TCP data offset %d (tlen %d)", off, tlen)); 645 tlen -= off; /* tlen is used instead of ti->ti_len */ 646 if (off > sizeof(struct tcphdr)) { 647 if (isipv6) { 648 IP6_EXTHDR_CHECK(m, off0, off, ); 649 ip6 = mtod(m, struct ip6_hdr *); 650 th = (struct tcphdr *)((caddr_t)ip6 + off0); 651 } else { 652 /* already pulled up in ip_demux() */ 653 KASSERT(m->m_len >= sizeof(struct ip) + off, 654 ("TCP header and options not in one mbuf: " 655 "m_len %d, off %d", m->m_len, off)); 656 } 657 optlen = off - sizeof(struct tcphdr); 658 optp = (u_char *)(th + 1); 659 } 660 thflags = th->th_flags; 661 662 #ifdef TCP_DROP_SYNFIN 663 /* 664 * If the drop_synfin option is enabled, drop all packets with 665 * both the SYN and FIN bits set. This prevents e.g. nmap from 666 * identifying the TCP/IP stack. 667 * 668 * This is a violation of the TCP specification. 669 */ 670 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 671 goto drop; 672 #endif 673 674 /* 675 * Convert TCP protocol specific fields to host format. 676 */ 677 th->th_seq = ntohl(th->th_seq); 678 th->th_ack = ntohl(th->th_ack); 679 th->th_win = ntohs(th->th_win); 680 th->th_urp = ntohs(th->th_urp); 681 682 /* 683 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 684 * until after ip6_savecontrol() is called and before other functions 685 * which don't want those proto headers. 686 * Because ip6_savecontrol() is going to parse the mbuf to 687 * search for data to be passed up to user-land, it wants mbuf 688 * parameters to be unchanged. 689 * XXX: the call of ip6_savecontrol() has been obsoleted based on 690 * latest version of the advanced API (20020110). 691 */ 692 drop_hdrlen = off0 + off; 693 694 /* 695 * Locate pcb for segment. 696 */ 697 findpcb: 698 /* IPFIREWALL_FORWARD section */ 699 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 700 /* 701 * Transparently forwarded. Pretend to be the destination. 702 * already got one like this? 703 */ 704 cpu = mycpu->gd_cpuid; 705 inp = in_pcblookup_hash(&tcbinfo[cpu], 706 ip->ip_src, th->th_sport, 707 ip->ip_dst, th->th_dport, 708 0, m->m_pkthdr.rcvif); 709 if (!inp) { 710 /* 711 * It's new. Try to find the ambushing socket. 712 */ 713 714 /* 715 * The rest of the ipfw code stores the port in 716 * host order. XXX 717 * (The IP address is still in network order.) 718 */ 719 in_port_t dport = next_hop->sin_port ? 720 htons(next_hop->sin_port) : 721 th->th_dport; 722 723 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 724 next_hop->sin_addr.s_addr, dport); 725 inp = in_pcblookup_hash(&tcbinfo[cpu], 726 ip->ip_src, th->th_sport, 727 next_hop->sin_addr, dport, 728 1, m->m_pkthdr.rcvif); 729 } 730 } else { 731 if (isipv6) { 732 inp = in6_pcblookup_hash(&tcbinfo[0], 733 &ip6->ip6_src, th->th_sport, 734 &ip6->ip6_dst, th->th_dport, 735 1, m->m_pkthdr.rcvif); 736 } else { 737 cpu = mycpu->gd_cpuid; 738 inp = in_pcblookup_hash(&tcbinfo[cpu], 739 ip->ip_src, th->th_sport, 740 ip->ip_dst, th->th_dport, 741 1, m->m_pkthdr.rcvif); 742 } 743 } 744 745 /* 746 * If the state is CLOSED (i.e., TCB does not exist) then 747 * all data in the incoming segment is discarded. 748 * If the TCB exists but is in CLOSED state, it is embryonic, 749 * but should either do a listen or a connect soon. 750 */ 751 if (inp == NULL) { 752 if (log_in_vain) { 753 #ifdef INET6 754 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 755 #else 756 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 757 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 758 #endif 759 if (isipv6) { 760 strcpy(dbuf, "["); 761 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 762 strcat(dbuf, "]"); 763 strcpy(sbuf, "["); 764 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 765 strcat(sbuf, "]"); 766 } else { 767 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 768 strcpy(sbuf, inet_ntoa(ip->ip_src)); 769 } 770 switch (log_in_vain) { 771 case 1: 772 if (!(thflags & TH_SYN)) 773 break; 774 case 2: 775 log(LOG_INFO, 776 "Connection attempt to TCP %s:%d " 777 "from %s:%d flags:0x%02x\n", 778 dbuf, ntohs(th->th_dport), sbuf, 779 ntohs(th->th_sport), thflags); 780 break; 781 default: 782 break; 783 } 784 } 785 if (blackhole) { 786 switch (blackhole) { 787 case 1: 788 if (thflags & TH_SYN) 789 goto drop; 790 break; 791 case 2: 792 goto drop; 793 default: 794 goto drop; 795 } 796 } 797 rstreason = BANDLIM_RST_CLOSEDPORT; 798 goto dropwithreset; 799 } 800 801 #ifdef IPSEC 802 if (isipv6) { 803 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 804 ipsec6stat.in_polvio++; 805 goto drop; 806 } 807 } else { 808 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 809 ipsecstat.in_polvio++; 810 goto drop; 811 } 812 } 813 #endif 814 #ifdef FAST_IPSEC 815 if (isipv6) { 816 if (ipsec6_in_reject(m, inp)) 817 goto drop; 818 } else { 819 if (ipsec4_in_reject(m, inp)) 820 goto drop; 821 } 822 #endif 823 /* Check the minimum TTL for socket. */ 824 #ifdef INET6 825 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 826 goto drop; 827 #endif 828 829 tp = intotcpcb(inp); 830 if (tp == NULL) { 831 rstreason = BANDLIM_RST_CLOSEDPORT; 832 goto dropwithreset; 833 } 834 if (tp->t_state <= TCPS_CLOSED) 835 goto drop; 836 837 /* Unscale the window into a 32-bit value. */ 838 if (!(thflags & TH_SYN)) 839 tiwin = th->th_win << tp->snd_scale; 840 else 841 tiwin = th->th_win; 842 843 so = inp->inp_socket; 844 845 #ifdef TCPDEBUG 846 if (so->so_options & SO_DEBUG) { 847 ostate = tp->t_state; 848 if (isipv6) 849 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 850 else 851 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 852 tcp_savetcp = *th; 853 } 854 #endif 855 856 bzero(&to, sizeof to); 857 858 if (so->so_options & SO_ACCEPTCONN) { 859 struct in_conninfo inc; 860 861 #ifdef INET6 862 inc.inc_isipv6 = (isipv6 == TRUE); 863 #endif 864 if (isipv6) { 865 inc.inc6_faddr = ip6->ip6_src; 866 inc.inc6_laddr = ip6->ip6_dst; 867 inc.inc6_route.ro_rt = NULL; /* XXX */ 868 } else { 869 inc.inc_faddr = ip->ip_src; 870 inc.inc_laddr = ip->ip_dst; 871 inc.inc_route.ro_rt = NULL; /* XXX */ 872 } 873 inc.inc_fport = th->th_sport; 874 inc.inc_lport = th->th_dport; 875 876 /* 877 * If the state is LISTEN then ignore segment if it contains 878 * a RST. If the segment contains an ACK then it is bad and 879 * send a RST. If it does not contain a SYN then it is not 880 * interesting; drop it. 881 * 882 * If the state is SYN_RECEIVED (syncache) and seg contains 883 * an ACK, but not for our SYN/ACK, send a RST. If the seg 884 * contains a RST, check the sequence number to see if it 885 * is a valid reset segment. 886 */ 887 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 888 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 889 if (!syncache_expand(&inc, th, &so, m)) { 890 /* 891 * No syncache entry, or ACK was not 892 * for our SYN/ACK. Send a RST. 893 */ 894 tcpstat.tcps_badsyn++; 895 rstreason = BANDLIM_RST_OPENPORT; 896 goto dropwithreset; 897 } 898 if (so == NULL) 899 /* 900 * Could not complete 3-way handshake, 901 * connection is being closed down, and 902 * syncache will free mbuf. 903 */ 904 return; 905 /* 906 * Socket is created in state SYN_RECEIVED. 907 * Continue processing segment. 908 */ 909 inp = so->so_pcb; 910 tp = intotcpcb(inp); 911 /* 912 * This is what would have happened in 913 * tcp_output() when the SYN,ACK was sent. 914 */ 915 tp->snd_up = tp->snd_una; 916 tp->snd_max = tp->snd_nxt = tp->iss + 1; 917 tp->last_ack_sent = tp->rcv_nxt; 918 /* 919 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 920 * until the _second_ ACK is received: 921 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 922 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 923 * move to ESTAB, set snd_wnd to tiwin. 924 */ 925 tp->snd_wnd = tiwin; /* unscaled */ 926 goto after_listen; 927 } 928 if (thflags & TH_RST) { 929 syncache_chkrst(&inc, th); 930 goto drop; 931 } 932 if (thflags & TH_ACK) { 933 syncache_badack(&inc); 934 tcpstat.tcps_badsyn++; 935 rstreason = BANDLIM_RST_OPENPORT; 936 goto dropwithreset; 937 } 938 goto drop; 939 } 940 941 /* 942 * Segment's flags are (SYN) or (SYN | FIN). 943 */ 944 #ifdef INET6 945 /* 946 * If deprecated address is forbidden, 947 * we do not accept SYN to deprecated interface 948 * address to prevent any new inbound connection from 949 * getting established. 950 * When we do not accept SYN, we send a TCP RST, 951 * with deprecated source address (instead of dropping 952 * it). We compromise it as it is much better for peer 953 * to send a RST, and RST will be the final packet 954 * for the exchange. 955 * 956 * If we do not forbid deprecated addresses, we accept 957 * the SYN packet. RFC2462 does not suggest dropping 958 * SYN in this case. 959 * If we decipher RFC2462 5.5.4, it says like this: 960 * 1. use of deprecated addr with existing 961 * communication is okay - "SHOULD continue to be 962 * used" 963 * 2. use of it with new communication: 964 * (2a) "SHOULD NOT be used if alternate address 965 * with sufficient scope is available" 966 * (2b) nothing mentioned otherwise. 967 * Here we fall into (2b) case as we have no choice in 968 * our source address selection - we must obey the peer. 969 * 970 * The wording in RFC2462 is confusing, and there are 971 * multiple description text for deprecated address 972 * handling - worse, they are not exactly the same. 973 * I believe 5.5.4 is the best one, so we follow 5.5.4. 974 */ 975 if (isipv6 && !ip6_use_deprecated) { 976 struct in6_ifaddr *ia6; 977 978 if ((ia6 = ip6_getdstifaddr(m)) && 979 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 980 tp = NULL; 981 rstreason = BANDLIM_RST_OPENPORT; 982 goto dropwithreset; 983 } 984 } 985 #endif 986 /* 987 * If it is from this socket, drop it, it must be forged. 988 * Don't bother responding if the destination was a broadcast. 989 */ 990 if (th->th_dport == th->th_sport) { 991 if (isipv6) { 992 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 993 &ip6->ip6_src)) 994 goto drop; 995 } else { 996 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 997 goto drop; 998 } 999 } 1000 /* 1001 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1002 * 1003 * Note that it is quite possible to receive unicast 1004 * link-layer packets with a broadcast IP address. Use 1005 * in_broadcast() to find them. 1006 */ 1007 if (m->m_flags & (M_BCAST | M_MCAST)) 1008 goto drop; 1009 if (isipv6) { 1010 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1011 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1012 goto drop; 1013 } else { 1014 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1015 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1016 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1017 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1018 goto drop; 1019 } 1020 /* 1021 * SYN appears to be valid; create compressed TCP state 1022 * for syncache, or perform t/tcp connection. 1023 */ 1024 if (so->so_qlen <= so->so_qlimit) { 1025 tcp_dooptions(&to, optp, optlen, TRUE); 1026 if (!syncache_add(&inc, &to, th, &so, m)) 1027 goto drop; 1028 if (so == NULL) 1029 /* 1030 * Entry added to syncache, mbuf used to 1031 * send SYN,ACK packet. 1032 */ 1033 return; 1034 /* 1035 * Segment passed TAO tests. 1036 */ 1037 inp = so->so_pcb; 1038 tp = intotcpcb(inp); 1039 tp->snd_wnd = tiwin; 1040 tp->t_starttime = ticks; 1041 tp->t_state = TCPS_ESTABLISHED; 1042 1043 /* 1044 * If there is a FIN, or if there is data and the 1045 * connection is local, then delay SYN,ACK(SYN) in 1046 * the hope of piggy-backing it on a response 1047 * segment. Otherwise must send ACK now in case 1048 * the other side is slow starting. 1049 */ 1050 if (DELAY_ACK(tp) && 1051 ((thflags & TH_FIN) || 1052 (tlen != 0 && 1053 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1054 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1055 tcp_callout_reset(tp, tp->tt_delack, 1056 tcp_delacktime, tcp_timer_delack); 1057 tp->t_flags |= TF_NEEDSYN; 1058 } else { 1059 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1060 } 1061 1062 tcpstat.tcps_connects++; 1063 soisconnected(so); 1064 goto trimthenstep6; 1065 } 1066 goto drop; 1067 } 1068 after_listen: 1069 1070 /* should not happen - syncache should pick up these connections */ 1071 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1072 1073 /* 1074 * This is the second part of the MSS DoS prevention code (after 1075 * minmss on the sending side) and it deals with too many too small 1076 * tcp packets in a too short timeframe (1 second). 1077 * 1078 * XXX Removed. This code was crap. It does not scale to network 1079 * speed, and default values break NFS. Gone. 1080 */ 1081 /* REMOVED */ 1082 1083 /* 1084 * Segment received on connection. 1085 * 1086 * Reset idle time and keep-alive timer. Don't waste time if less 1087 * then a second has elapsed. Only update t_rcvtime for non-SYN 1088 * packets. 1089 * 1090 * Handle the case where one side thinks the connection is established 1091 * but the other side has, say, rebooted without cleaning out the 1092 * connection. The SYNs could be construed as an attack and wind 1093 * up ignored, but in case it isn't an attack we can validate the 1094 * connection by forcing a keepalive. 1095 */ 1096 if (TCPS_HAVEESTABLISHED(tp->t_state) && (ticks - tp->t_rcvtime) > hz) { 1097 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 1098 tp->t_flags |= TF_KEEPALIVE; 1099 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 1100 tcp_timer_keep); 1101 } else { 1102 tp->t_rcvtime = ticks; 1103 tp->t_flags &= ~TF_KEEPALIVE; 1104 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1105 tcp_timer_keep); 1106 } 1107 } 1108 1109 /* 1110 * Process options. 1111 * XXX this is tradtitional behavior, may need to be cleaned up. 1112 */ 1113 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1114 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1115 if (to.to_flags & TOF_SCALE) { 1116 tp->t_flags |= TF_RCVD_SCALE; 1117 tp->requested_s_scale = to.to_requested_s_scale; 1118 } 1119 if (to.to_flags & TOF_TS) { 1120 tp->t_flags |= TF_RCVD_TSTMP; 1121 tp->ts_recent = to.to_tsval; 1122 tp->ts_recent_age = ticks; 1123 } 1124 if (to.to_flags & (TOF_CC | TOF_CCNEW)) 1125 tp->t_flags |= TF_RCVD_CC; 1126 if (to.to_flags & TOF_MSS) 1127 tcp_mss(tp, to.to_mss); 1128 /* 1129 * Only set the TF_SACK_PERMITTED per-connection flag 1130 * if we got a SACK_PERMITTED option from the other side 1131 * and the global tcp_do_sack variable is true. 1132 */ 1133 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1134 tp->t_flags |= TF_SACK_PERMITTED; 1135 } 1136 1137 /* 1138 * Header prediction: check for the two common cases 1139 * of a uni-directional data xfer. If the packet has 1140 * no control flags, is in-sequence, the window didn't 1141 * change and we're not retransmitting, it's a 1142 * candidate. If the length is zero and the ack moved 1143 * forward, we're the sender side of the xfer. Just 1144 * free the data acked & wake any higher level process 1145 * that was blocked waiting for space. If the length 1146 * is non-zero and the ack didn't move, we're the 1147 * receiver side. If we're getting packets in-order 1148 * (the reassembly queue is empty), add the data to 1149 * the socket buffer and note that we need a delayed ack. 1150 * Make sure that the hidden state-flags are also off. 1151 * Since we check for TCPS_ESTABLISHED above, it can only 1152 * be TH_NEEDSYN. 1153 */ 1154 if (tp->t_state == TCPS_ESTABLISHED && 1155 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1156 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1157 (!(to.to_flags & TOF_TS) || 1158 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1159 /* 1160 * Using the CC option is compulsory if once started: 1161 * the segment is OK if no T/TCP was negotiated or 1162 * if the segment has a CC option equal to CCrecv 1163 */ 1164 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 1165 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) && 1166 th->th_seq == tp->rcv_nxt && 1167 tp->snd_nxt == tp->snd_max) { 1168 1169 /* 1170 * If last ACK falls within this segment's sequence numbers, 1171 * record the timestamp. 1172 * NOTE that the test is modified according to the latest 1173 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1174 */ 1175 if ((to.to_flags & TOF_TS) && 1176 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1177 tp->ts_recent_age = ticks; 1178 tp->ts_recent = to.to_tsval; 1179 } 1180 1181 if (tlen == 0) { 1182 if (SEQ_GT(th->th_ack, tp->snd_una) && 1183 SEQ_LEQ(th->th_ack, tp->snd_max) && 1184 tp->snd_cwnd >= tp->snd_wnd && 1185 !IN_FASTRECOVERY(tp)) { 1186 /* 1187 * This is a pure ack for outstanding data. 1188 */ 1189 ++tcpstat.tcps_predack; 1190 /* 1191 * "bad retransmit" recovery 1192 * 1193 * If Eifel detection applies, then 1194 * it is deterministic, so use it 1195 * unconditionally over the old heuristic. 1196 * Otherwise, fall back to the old heuristic. 1197 */ 1198 if (tcp_do_eifel_detect && 1199 (to.to_flags & TOF_TS) && to.to_tsecr && 1200 (tp->t_flags & TF_FIRSTACCACK)) { 1201 /* Eifel detection applicable. */ 1202 if (to.to_tsecr < tp->t_rexmtTS) { 1203 tcp_revert_congestion_state(tp); 1204 ++tcpstat.tcps_eifeldetected; 1205 } 1206 } else if (tp->t_rxtshift == 1 && 1207 ticks < tp->t_badrxtwin) { 1208 tcp_revert_congestion_state(tp); 1209 ++tcpstat.tcps_rttdetected; 1210 } 1211 tp->t_flags &= ~(TF_FIRSTACCACK | 1212 TF_FASTREXMT | TF_EARLYREXMT); 1213 /* 1214 * Recalculate the retransmit timer / rtt. 1215 * 1216 * Some machines (certain windows boxes) 1217 * send broken timestamp replies during the 1218 * SYN+ACK phase, ignore timestamps of 0. 1219 */ 1220 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1221 tcp_xmit_timer(tp, 1222 ticks - to.to_tsecr + 1); 1223 } else if (tp->t_rtttime && 1224 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1225 tcp_xmit_timer(tp, 1226 ticks - tp->t_rtttime); 1227 } 1228 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1229 acked = th->th_ack - tp->snd_una; 1230 tcpstat.tcps_rcvackpack++; 1231 tcpstat.tcps_rcvackbyte += acked; 1232 sbdrop(&so->so_snd.sb, acked); 1233 tp->snd_recover = th->th_ack - 1; 1234 tp->snd_una = th->th_ack; 1235 tp->t_dupacks = 0; 1236 /* 1237 * Update window information. 1238 */ 1239 if (tiwin != tp->snd_wnd && 1240 acceptable_window_update(tp, th, tiwin)) { 1241 /* keep track of pure window updates */ 1242 if (tp->snd_wl2 == th->th_ack && 1243 tiwin > tp->snd_wnd) 1244 tcpstat.tcps_rcvwinupd++; 1245 tp->snd_wnd = tiwin; 1246 tp->snd_wl1 = th->th_seq; 1247 tp->snd_wl2 = th->th_ack; 1248 if (tp->snd_wnd > tp->max_sndwnd) 1249 tp->max_sndwnd = tp->snd_wnd; 1250 } 1251 m_freem(m); 1252 ND6_HINT(tp); /* some progress has been done */ 1253 /* 1254 * If all outstanding data are acked, stop 1255 * retransmit timer, otherwise restart timer 1256 * using current (possibly backed-off) value. 1257 * If process is waiting for space, 1258 * wakeup/selwakeup/signal. If data 1259 * are ready to send, let tcp_output 1260 * decide between more output or persist. 1261 */ 1262 if (tp->snd_una == tp->snd_max) { 1263 tcp_callout_stop(tp, tp->tt_rexmt); 1264 } else if (!tcp_callout_active(tp, 1265 tp->tt_persist)) { 1266 tcp_callout_reset(tp, tp->tt_rexmt, 1267 tp->t_rxtcur, tcp_timer_rexmt); 1268 } 1269 sowwakeup(so); 1270 if (so->so_snd.ssb_cc > 0) 1271 tcp_output(tp); 1272 return; 1273 } 1274 } else if (tiwin == tp->snd_wnd && 1275 th->th_ack == tp->snd_una && 1276 LIST_EMPTY(&tp->t_segq) && 1277 tlen <= ssb_space(&so->so_rcv)) { 1278 int newsize = 0; /* automatic sockbuf scaling */ 1279 /* 1280 * This is a pure, in-sequence data packet 1281 * with nothing on the reassembly queue and 1282 * we have enough buffer space to take it. 1283 */ 1284 ++tcpstat.tcps_preddat; 1285 tp->rcv_nxt += tlen; 1286 tcpstat.tcps_rcvpack++; 1287 tcpstat.tcps_rcvbyte += tlen; 1288 ND6_HINT(tp); /* some progress has been done */ 1289 /* 1290 * Automatic sizing of receive socket buffer. Often the send 1291 * buffer size is not optimally adjusted to the actual network 1292 * conditions at hand (delay bandwidth product). Setting the 1293 * buffer size too small limits throughput on links with high 1294 * bandwidth and high delay (eg. trans-continental/oceanic links). 1295 * 1296 * On the receive side the socket buffer memory is only rarely 1297 * used to any significant extent. This allows us to be much 1298 * more aggressive in scaling the receive socket buffer. For 1299 * the case that the buffer space is actually used to a large 1300 * extent and we run out of kernel memory we can simply drop 1301 * the new segments; TCP on the sender will just retransmit it 1302 * later. Setting the buffer size too big may only consume too 1303 * much kernel memory if the application doesn't read() from 1304 * the socket or packet loss or reordering makes use of the 1305 * reassembly queue. 1306 * 1307 * The criteria to step up the receive buffer one notch are: 1308 * 1. the number of bytes received during the time it takes 1309 * one timestamp to be reflected back to us (the RTT); 1310 * 2. received bytes per RTT is within seven eighth of the 1311 * current socket buffer size; 1312 * 3. receive buffer size has not hit maximal automatic size; 1313 * 1314 * This algorithm does one step per RTT at most and only if 1315 * we receive a bulk stream w/o packet losses or reorderings. 1316 * Shrinking the buffer during idle times is not necessary as 1317 * it doesn't consume any memory when idle. 1318 * 1319 * TODO: Only step up if the application is actually serving 1320 * the buffer to better manage the socket buffer resources. 1321 */ 1322 if (tcp_do_autorcvbuf && 1323 to.to_tsecr && 1324 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1325 if (to.to_tsecr > tp->rfbuf_ts && 1326 to.to_tsecr - tp->rfbuf_ts < hz) { 1327 if (tp->rfbuf_cnt > 1328 (so->so_rcv.ssb_hiwat / 8 * 7) && 1329 so->so_rcv.ssb_hiwat < 1330 tcp_autorcvbuf_max) { 1331 newsize = 1332 min(so->so_rcv.ssb_hiwat + 1333 tcp_autorcvbuf_inc, 1334 tcp_autorcvbuf_max); 1335 } 1336 /* Start over with next RTT. */ 1337 tp->rfbuf_ts = 0; 1338 tp->rfbuf_cnt = 0; 1339 } else 1340 tp->rfbuf_cnt += tlen; /* add up */ 1341 } 1342 /* 1343 * Add data to socket buffer. 1344 */ 1345 if (so->so_state & SS_CANTRCVMORE) { 1346 m_freem(m); 1347 } else { 1348 /* 1349 * Set new socket buffer size. 1350 * Give up when limit is reached. 1351 */ 1352 if (newsize) 1353 if (!ssb_reserve(&so->so_rcv, newsize, 1354 so, NULL)) 1355 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE; 1356 m_adj(m, drop_hdrlen); /* delayed header drop */ 1357 ssb_appendstream(&so->so_rcv, m); 1358 } 1359 sorwakeup(so); 1360 /* 1361 * This code is responsible for most of the ACKs 1362 * the TCP stack sends back after receiving a data 1363 * packet. Note that the DELAY_ACK check fails if 1364 * the delack timer is already running, which results 1365 * in an ack being sent every other packet (which is 1366 * what we want). 1367 * 1368 * We then further aggregate acks by not actually 1369 * sending one until the protocol thread has completed 1370 * processing the current backlog of packets. This 1371 * does not delay the ack any further, but allows us 1372 * to take advantage of the packet aggregation that 1373 * high speed NICs do (usually blocks of 8-10 packets) 1374 * to send a single ack rather then four or five acks, 1375 * greatly reducing the ack rate, the return channel 1376 * bandwidth, and the protocol overhead on both ends. 1377 * 1378 * Since this also has the effect of slowing down 1379 * the exponential slow-start ramp-up, systems with 1380 * very large bandwidth-delay products might want 1381 * to turn the feature off. 1382 */ 1383 if (DELAY_ACK(tp)) { 1384 tcp_callout_reset(tp, tp->tt_delack, 1385 tcp_delacktime, tcp_timer_delack); 1386 } else if (tcp_aggregate_acks) { 1387 tp->t_flags |= TF_ACKNOW; 1388 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1389 tp->t_flags |= TF_ONOUTPUTQ; 1390 tp->tt_cpu = mycpu->gd_cpuid; 1391 TAILQ_INSERT_TAIL( 1392 &tcpcbackq[tp->tt_cpu], 1393 tp, t_outputq); 1394 } 1395 } else { 1396 tp->t_flags |= TF_ACKNOW; 1397 tcp_output(tp); 1398 } 1399 return; 1400 } 1401 } 1402 1403 /* 1404 * Calculate amount of space in receive window, 1405 * and then do TCP input processing. 1406 * Receive window is amount of space in rcv queue, 1407 * but not less than advertised window. 1408 */ 1409 recvwin = ssb_space(&so->so_rcv); 1410 if (recvwin < 0) 1411 recvwin = 0; 1412 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1413 1414 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1415 tp->rfbuf_ts = 0; 1416 tp->rfbuf_cnt = 0; 1417 1418 switch (tp->t_state) { 1419 /* 1420 * If the state is SYN_RECEIVED: 1421 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1422 */ 1423 case TCPS_SYN_RECEIVED: 1424 if ((thflags & TH_ACK) && 1425 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1426 SEQ_GT(th->th_ack, tp->snd_max))) { 1427 rstreason = BANDLIM_RST_OPENPORT; 1428 goto dropwithreset; 1429 } 1430 break; 1431 1432 /* 1433 * If the state is SYN_SENT: 1434 * if seg contains an ACK, but not for our SYN, drop the input. 1435 * if seg contains a RST, then drop the connection. 1436 * if seg does not contain SYN, then drop it. 1437 * Otherwise this is an acceptable SYN segment 1438 * initialize tp->rcv_nxt and tp->irs 1439 * if seg contains ack then advance tp->snd_una 1440 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1441 * arrange for segment to be acked (eventually) 1442 * continue processing rest of data/controls, beginning with URG 1443 */ 1444 case TCPS_SYN_SENT: 1445 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1446 taop = &tao_noncached; 1447 bzero(taop, sizeof *taop); 1448 } 1449 1450 if ((thflags & TH_ACK) && 1451 (SEQ_LEQ(th->th_ack, tp->iss) || 1452 SEQ_GT(th->th_ack, tp->snd_max))) { 1453 /* 1454 * If we have a cached CCsent for the remote host, 1455 * hence we haven't just crashed and restarted, 1456 * do not send a RST. This may be a retransmission 1457 * from the other side after our earlier ACK was lost. 1458 * Our new SYN, when it arrives, will serve as the 1459 * needed ACK. 1460 */ 1461 if (taop->tao_ccsent != 0) 1462 goto drop; 1463 else { 1464 rstreason = BANDLIM_UNLIMITED; 1465 goto dropwithreset; 1466 } 1467 } 1468 if (thflags & TH_RST) { 1469 if (thflags & TH_ACK) 1470 tp = tcp_drop(tp, ECONNREFUSED); 1471 goto drop; 1472 } 1473 if (!(thflags & TH_SYN)) 1474 goto drop; 1475 tp->snd_wnd = th->th_win; /* initial send window */ 1476 tp->cc_recv = to.to_cc; /* foreign CC */ 1477 1478 tp->irs = th->th_seq; 1479 tcp_rcvseqinit(tp); 1480 if (thflags & TH_ACK) { 1481 /* 1482 * Our SYN was acked. If segment contains CC.ECHO 1483 * option, check it to make sure this segment really 1484 * matches our SYN. If not, just drop it as old 1485 * duplicate, but send an RST if we're still playing 1486 * by the old rules. If no CC.ECHO option, make sure 1487 * we don't get fooled into using T/TCP. 1488 */ 1489 if (to.to_flags & TOF_CCECHO) { 1490 if (tp->cc_send != to.to_ccecho) { 1491 if (taop->tao_ccsent != 0) 1492 goto drop; 1493 else { 1494 rstreason = BANDLIM_UNLIMITED; 1495 goto dropwithreset; 1496 } 1497 } 1498 } else 1499 tp->t_flags &= ~TF_RCVD_CC; 1500 tcpstat.tcps_connects++; 1501 soisconnected(so); 1502 /* Do window scaling on this connection? */ 1503 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1504 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1505 tp->snd_scale = tp->requested_s_scale; 1506 tp->rcv_scale = tp->request_r_scale; 1507 } 1508 /* Segment is acceptable, update cache if undefined. */ 1509 if (taop->tao_ccsent == 0) 1510 taop->tao_ccsent = to.to_ccecho; 1511 1512 tp->rcv_adv += tp->rcv_wnd; 1513 tp->snd_una++; /* SYN is acked */ 1514 tcp_callout_stop(tp, tp->tt_rexmt); 1515 /* 1516 * If there's data, delay ACK; if there's also a FIN 1517 * ACKNOW will be turned on later. 1518 */ 1519 if (DELAY_ACK(tp) && tlen != 0) { 1520 tcp_callout_reset(tp, tp->tt_delack, 1521 tcp_delacktime, tcp_timer_delack); 1522 } else { 1523 tp->t_flags |= TF_ACKNOW; 1524 } 1525 /* 1526 * Received <SYN,ACK> in SYN_SENT[*] state. 1527 * Transitions: 1528 * SYN_SENT --> ESTABLISHED 1529 * SYN_SENT* --> FIN_WAIT_1 1530 */ 1531 tp->t_starttime = ticks; 1532 if (tp->t_flags & TF_NEEDFIN) { 1533 tp->t_state = TCPS_FIN_WAIT_1; 1534 tp->t_flags &= ~TF_NEEDFIN; 1535 thflags &= ~TH_SYN; 1536 } else { 1537 tp->t_state = TCPS_ESTABLISHED; 1538 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1539 tcp_timer_keep); 1540 } 1541 } else { 1542 /* 1543 * Received initial SYN in SYN-SENT[*] state => 1544 * simultaneous open. If segment contains CC option 1545 * and there is a cached CC, apply TAO test. 1546 * If it succeeds, connection is * half-synchronized. 1547 * Otherwise, do 3-way handshake: 1548 * SYN-SENT -> SYN-RECEIVED 1549 * SYN-SENT* -> SYN-RECEIVED* 1550 * If there was no CC option, clear cached CC value. 1551 */ 1552 tp->t_flags |= TF_ACKNOW; 1553 tcp_callout_stop(tp, tp->tt_rexmt); 1554 if (to.to_flags & TOF_CC) { 1555 if (taop->tao_cc != 0 && 1556 CC_GT(to.to_cc, taop->tao_cc)) { 1557 /* 1558 * update cache and make transition: 1559 * SYN-SENT -> ESTABLISHED* 1560 * SYN-SENT* -> FIN-WAIT-1* 1561 */ 1562 taop->tao_cc = to.to_cc; 1563 tp->t_starttime = ticks; 1564 if (tp->t_flags & TF_NEEDFIN) { 1565 tp->t_state = TCPS_FIN_WAIT_1; 1566 tp->t_flags &= ~TF_NEEDFIN; 1567 } else { 1568 tp->t_state = TCPS_ESTABLISHED; 1569 tcp_callout_reset(tp, 1570 tp->tt_keep, tcp_keepidle, 1571 tcp_timer_keep); 1572 } 1573 tp->t_flags |= TF_NEEDSYN; 1574 } else 1575 tp->t_state = TCPS_SYN_RECEIVED; 1576 } else { 1577 /* CC.NEW or no option => invalidate cache */ 1578 taop->tao_cc = 0; 1579 tp->t_state = TCPS_SYN_RECEIVED; 1580 } 1581 } 1582 1583 trimthenstep6: 1584 /* 1585 * Advance th->th_seq to correspond to first data byte. 1586 * If data, trim to stay within window, 1587 * dropping FIN if necessary. 1588 */ 1589 th->th_seq++; 1590 if (tlen > tp->rcv_wnd) { 1591 todrop = tlen - tp->rcv_wnd; 1592 m_adj(m, -todrop); 1593 tlen = tp->rcv_wnd; 1594 thflags &= ~TH_FIN; 1595 tcpstat.tcps_rcvpackafterwin++; 1596 tcpstat.tcps_rcvbyteafterwin += todrop; 1597 } 1598 tp->snd_wl1 = th->th_seq - 1; 1599 tp->rcv_up = th->th_seq; 1600 /* 1601 * Client side of transaction: already sent SYN and data. 1602 * If the remote host used T/TCP to validate the SYN, 1603 * our data will be ACK'd; if so, enter normal data segment 1604 * processing in the middle of step 5, ack processing. 1605 * Otherwise, goto step 6. 1606 */ 1607 if (thflags & TH_ACK) 1608 goto process_ACK; 1609 1610 goto step6; 1611 1612 /* 1613 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1614 * if segment contains a SYN and CC [not CC.NEW] option: 1615 * if state == TIME_WAIT and connection duration > MSL, 1616 * drop packet and send RST; 1617 * 1618 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1619 * ack the FIN (and data) in retransmission queue. 1620 * Complete close and delete TCPCB. Then reprocess 1621 * segment, hoping to find new TCPCB in LISTEN state; 1622 * 1623 * else must be old SYN; drop it. 1624 * else do normal processing. 1625 */ 1626 case TCPS_LAST_ACK: 1627 case TCPS_CLOSING: 1628 case TCPS_TIME_WAIT: 1629 if ((thflags & TH_SYN) && 1630 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1631 if (tp->t_state == TCPS_TIME_WAIT && 1632 (ticks - tp->t_starttime) > tcp_msl) { 1633 rstreason = BANDLIM_UNLIMITED; 1634 goto dropwithreset; 1635 } 1636 if (CC_GT(to.to_cc, tp->cc_recv)) { 1637 tp = tcp_close(tp); 1638 goto findpcb; 1639 } 1640 else 1641 goto drop; 1642 } 1643 break; /* continue normal processing */ 1644 } 1645 1646 /* 1647 * States other than LISTEN or SYN_SENT. 1648 * First check the RST flag and sequence number since reset segments 1649 * are exempt from the timestamp and connection count tests. This 1650 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1651 * below which allowed reset segments in half the sequence space 1652 * to fall though and be processed (which gives forged reset 1653 * segments with a random sequence number a 50 percent chance of 1654 * killing a connection). 1655 * Then check timestamp, if present. 1656 * Then check the connection count, if present. 1657 * Then check that at least some bytes of segment are within 1658 * receive window. If segment begins before rcv_nxt, 1659 * drop leading data (and SYN); if nothing left, just ack. 1660 * 1661 * 1662 * If the RST bit is set, check the sequence number to see 1663 * if this is a valid reset segment. 1664 * RFC 793 page 37: 1665 * In all states except SYN-SENT, all reset (RST) segments 1666 * are validated by checking their SEQ-fields. A reset is 1667 * valid if its sequence number is in the window. 1668 * Note: this does not take into account delayed ACKs, so 1669 * we should test against last_ack_sent instead of rcv_nxt. 1670 * The sequence number in the reset segment is normally an 1671 * echo of our outgoing acknowledgement numbers, but some hosts 1672 * send a reset with the sequence number at the rightmost edge 1673 * of our receive window, and we have to handle this case. 1674 * If we have multiple segments in flight, the intial reset 1675 * segment sequence numbers will be to the left of last_ack_sent, 1676 * but they will eventually catch up. 1677 * In any case, it never made sense to trim reset segments to 1678 * fit the receive window since RFC 1122 says: 1679 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1680 * 1681 * A TCP SHOULD allow a received RST segment to include data. 1682 * 1683 * DISCUSSION 1684 * It has been suggested that a RST segment could contain 1685 * ASCII text that encoded and explained the cause of the 1686 * RST. No standard has yet been established for such 1687 * data. 1688 * 1689 * If the reset segment passes the sequence number test examine 1690 * the state: 1691 * SYN_RECEIVED STATE: 1692 * If passive open, return to LISTEN state. 1693 * If active open, inform user that connection was refused. 1694 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1695 * Inform user that connection was reset, and close tcb. 1696 * CLOSING, LAST_ACK STATES: 1697 * Close the tcb. 1698 * TIME_WAIT STATE: 1699 * Drop the segment - see Stevens, vol. 2, p. 964 and 1700 * RFC 1337. 1701 */ 1702 if (thflags & TH_RST) { 1703 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1704 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1705 switch (tp->t_state) { 1706 1707 case TCPS_SYN_RECEIVED: 1708 so->so_error = ECONNREFUSED; 1709 goto close; 1710 1711 case TCPS_ESTABLISHED: 1712 case TCPS_FIN_WAIT_1: 1713 case TCPS_FIN_WAIT_2: 1714 case TCPS_CLOSE_WAIT: 1715 so->so_error = ECONNRESET; 1716 close: 1717 tp->t_state = TCPS_CLOSED; 1718 tcpstat.tcps_drops++; 1719 tp = tcp_close(tp); 1720 break; 1721 1722 case TCPS_CLOSING: 1723 case TCPS_LAST_ACK: 1724 tp = tcp_close(tp); 1725 break; 1726 1727 case TCPS_TIME_WAIT: 1728 break; 1729 } 1730 } 1731 goto drop; 1732 } 1733 1734 /* 1735 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1736 * and it's less than ts_recent, drop it. 1737 */ 1738 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1739 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1740 1741 /* Check to see if ts_recent is over 24 days old. */ 1742 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1743 /* 1744 * Invalidate ts_recent. If this segment updates 1745 * ts_recent, the age will be reset later and ts_recent 1746 * will get a valid value. If it does not, setting 1747 * ts_recent to zero will at least satisfy the 1748 * requirement that zero be placed in the timestamp 1749 * echo reply when ts_recent isn't valid. The 1750 * age isn't reset until we get a valid ts_recent 1751 * because we don't want out-of-order segments to be 1752 * dropped when ts_recent is old. 1753 */ 1754 tp->ts_recent = 0; 1755 } else { 1756 tcpstat.tcps_rcvduppack++; 1757 tcpstat.tcps_rcvdupbyte += tlen; 1758 tcpstat.tcps_pawsdrop++; 1759 if (tlen) 1760 goto dropafterack; 1761 goto drop; 1762 } 1763 } 1764 1765 /* 1766 * T/TCP mechanism 1767 * If T/TCP was negotiated and the segment doesn't have CC, 1768 * or if its CC is wrong then drop the segment. 1769 * RST segments do not have to comply with this. 1770 */ 1771 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1772 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1773 goto dropafterack; 1774 1775 /* 1776 * In the SYN-RECEIVED state, validate that the packet belongs to 1777 * this connection before trimming the data to fit the receive 1778 * window. Check the sequence number versus IRS since we know 1779 * the sequence numbers haven't wrapped. This is a partial fix 1780 * for the "LAND" DoS attack. 1781 */ 1782 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1783 rstreason = BANDLIM_RST_OPENPORT; 1784 goto dropwithreset; 1785 } 1786 1787 todrop = tp->rcv_nxt - th->th_seq; 1788 if (todrop > 0) { 1789 if (TCP_DO_SACK(tp)) { 1790 /* Report duplicate segment at head of packet. */ 1791 tp->reportblk.rblk_start = th->th_seq; 1792 tp->reportblk.rblk_end = th->th_seq + tlen; 1793 if (thflags & TH_FIN) 1794 ++tp->reportblk.rblk_end; 1795 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1796 tp->reportblk.rblk_end = tp->rcv_nxt; 1797 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1798 } 1799 if (thflags & TH_SYN) { 1800 thflags &= ~TH_SYN; 1801 th->th_seq++; 1802 if (th->th_urp > 1) 1803 th->th_urp--; 1804 else 1805 thflags &= ~TH_URG; 1806 todrop--; 1807 } 1808 /* 1809 * Following if statement from Stevens, vol. 2, p. 960. 1810 */ 1811 if (todrop > tlen || 1812 (todrop == tlen && !(thflags & TH_FIN))) { 1813 /* 1814 * Any valid FIN must be to the left of the window. 1815 * At this point the FIN must be a duplicate or out 1816 * of sequence; drop it. 1817 */ 1818 thflags &= ~TH_FIN; 1819 1820 /* 1821 * Send an ACK to resynchronize and drop any data. 1822 * But keep on processing for RST or ACK. 1823 */ 1824 tp->t_flags |= TF_ACKNOW; 1825 todrop = tlen; 1826 tcpstat.tcps_rcvduppack++; 1827 tcpstat.tcps_rcvdupbyte += todrop; 1828 } else { 1829 tcpstat.tcps_rcvpartduppack++; 1830 tcpstat.tcps_rcvpartdupbyte += todrop; 1831 } 1832 drop_hdrlen += todrop; /* drop from the top afterwards */ 1833 th->th_seq += todrop; 1834 tlen -= todrop; 1835 if (th->th_urp > todrop) 1836 th->th_urp -= todrop; 1837 else { 1838 thflags &= ~TH_URG; 1839 th->th_urp = 0; 1840 } 1841 } 1842 1843 /* 1844 * If new data are received on a connection after the 1845 * user processes are gone, then RST the other end. 1846 */ 1847 if ((so->so_state & SS_NOFDREF) && 1848 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1849 tp = tcp_close(tp); 1850 tcpstat.tcps_rcvafterclose++; 1851 rstreason = BANDLIM_UNLIMITED; 1852 goto dropwithreset; 1853 } 1854 1855 /* 1856 * If segment ends after window, drop trailing data 1857 * (and PUSH and FIN); if nothing left, just ACK. 1858 */ 1859 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1860 if (todrop > 0) { 1861 tcpstat.tcps_rcvpackafterwin++; 1862 if (todrop >= tlen) { 1863 tcpstat.tcps_rcvbyteafterwin += tlen; 1864 /* 1865 * If a new connection request is received 1866 * while in TIME_WAIT, drop the old connection 1867 * and start over if the sequence numbers 1868 * are above the previous ones. 1869 */ 1870 if (thflags & TH_SYN && 1871 tp->t_state == TCPS_TIME_WAIT && 1872 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1873 tp = tcp_close(tp); 1874 goto findpcb; 1875 } 1876 /* 1877 * If window is closed can only take segments at 1878 * window edge, and have to drop data and PUSH from 1879 * incoming segments. Continue processing, but 1880 * remember to ack. Otherwise, drop segment 1881 * and ack. 1882 */ 1883 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1884 tp->t_flags |= TF_ACKNOW; 1885 tcpstat.tcps_rcvwinprobe++; 1886 } else 1887 goto dropafterack; 1888 } else 1889 tcpstat.tcps_rcvbyteafterwin += todrop; 1890 m_adj(m, -todrop); 1891 tlen -= todrop; 1892 thflags &= ~(TH_PUSH | TH_FIN); 1893 } 1894 1895 /* 1896 * If last ACK falls within this segment's sequence numbers, 1897 * record its timestamp. 1898 * NOTE: 1899 * 1) That the test incorporates suggestions from the latest 1900 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1901 * 2) That updating only on newer timestamps interferes with 1902 * our earlier PAWS tests, so this check should be solely 1903 * predicated on the sequence space of this segment. 1904 * 3) That we modify the segment boundary check to be 1905 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1906 * instead of RFC1323's 1907 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1908 * This modified check allows us to overcome RFC1323's 1909 * limitations as described in Stevens TCP/IP Illustrated 1910 * Vol. 2 p.869. In such cases, we can still calculate the 1911 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1912 */ 1913 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1914 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1915 + ((thflags & TH_SYN) != 0) 1916 + ((thflags & TH_FIN) != 0)))) { 1917 tp->ts_recent_age = ticks; 1918 tp->ts_recent = to.to_tsval; 1919 } 1920 1921 /* 1922 * If a SYN is in the window, then this is an 1923 * error and we send an RST and drop the connection. 1924 */ 1925 if (thflags & TH_SYN) { 1926 tp = tcp_drop(tp, ECONNRESET); 1927 rstreason = BANDLIM_UNLIMITED; 1928 goto dropwithreset; 1929 } 1930 1931 /* 1932 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1933 * flag is on (half-synchronized state), then queue data for 1934 * later processing; else drop segment and return. 1935 */ 1936 if (!(thflags & TH_ACK)) { 1937 if (tp->t_state == TCPS_SYN_RECEIVED || 1938 (tp->t_flags & TF_NEEDSYN)) 1939 goto step6; 1940 else 1941 goto drop; 1942 } 1943 1944 /* 1945 * Ack processing. 1946 */ 1947 switch (tp->t_state) { 1948 /* 1949 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1950 * ESTABLISHED state and continue processing. 1951 * The ACK was checked above. 1952 */ 1953 case TCPS_SYN_RECEIVED: 1954 1955 tcpstat.tcps_connects++; 1956 soisconnected(so); 1957 /* Do window scaling? */ 1958 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1959 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1960 tp->snd_scale = tp->requested_s_scale; 1961 tp->rcv_scale = tp->request_r_scale; 1962 } 1963 /* 1964 * Upon successful completion of 3-way handshake, 1965 * update cache.CC if it was undefined, pass any queued 1966 * data to the user, and advance state appropriately. 1967 */ 1968 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1969 taop->tao_cc == 0) 1970 taop->tao_cc = tp->cc_recv; 1971 1972 /* 1973 * Make transitions: 1974 * SYN-RECEIVED -> ESTABLISHED 1975 * SYN-RECEIVED* -> FIN-WAIT-1 1976 */ 1977 tp->t_starttime = ticks; 1978 if (tp->t_flags & TF_NEEDFIN) { 1979 tp->t_state = TCPS_FIN_WAIT_1; 1980 tp->t_flags &= ~TF_NEEDFIN; 1981 } else { 1982 tp->t_state = TCPS_ESTABLISHED; 1983 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1984 tcp_timer_keep); 1985 } 1986 /* 1987 * If segment contains data or ACK, will call tcp_reass() 1988 * later; if not, do so now to pass queued data to user. 1989 */ 1990 if (tlen == 0 && !(thflags & TH_FIN)) 1991 tcp_reass(tp, NULL, NULL, NULL); 1992 /* fall into ... */ 1993 1994 /* 1995 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1996 * ACKs. If the ack is in the range 1997 * tp->snd_una < th->th_ack <= tp->snd_max 1998 * then advance tp->snd_una to th->th_ack and drop 1999 * data from the retransmission queue. If this ACK reflects 2000 * more up to date window information we update our window information. 2001 */ 2002 case TCPS_ESTABLISHED: 2003 case TCPS_FIN_WAIT_1: 2004 case TCPS_FIN_WAIT_2: 2005 case TCPS_CLOSE_WAIT: 2006 case TCPS_CLOSING: 2007 case TCPS_LAST_ACK: 2008 case TCPS_TIME_WAIT: 2009 2010 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2011 if (TCP_DO_SACK(tp)) 2012 tcp_sack_update_scoreboard(tp, &to); 2013 if (tlen != 0 || tiwin != tp->snd_wnd) { 2014 tp->t_dupacks = 0; 2015 break; 2016 } 2017 tcpstat.tcps_rcvdupack++; 2018 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2019 th->th_ack != tp->snd_una) { 2020 tp->t_dupacks = 0; 2021 break; 2022 } 2023 /* 2024 * We have outstanding data (other than 2025 * a window probe), this is a completely 2026 * duplicate ack (ie, window info didn't 2027 * change), the ack is the biggest we've 2028 * seen and we've seen exactly our rexmt 2029 * threshhold of them, so assume a packet 2030 * has been dropped and retransmit it. 2031 * Kludge snd_nxt & the congestion 2032 * window so we send only this one 2033 * packet. 2034 */ 2035 if (IN_FASTRECOVERY(tp)) { 2036 if (TCP_DO_SACK(tp)) { 2037 /* No artifical cwnd inflation. */ 2038 tcp_sack_rexmt(tp, th); 2039 } else { 2040 /* 2041 * Dup acks mean that packets 2042 * have left the network 2043 * (they're now cached at the 2044 * receiver) so bump cwnd by 2045 * the amount in the receiver 2046 * to keep a constant cwnd 2047 * packets in the network. 2048 */ 2049 tp->snd_cwnd += tp->t_maxseg; 2050 tcp_output(tp); 2051 } 2052 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2053 tp->t_dupacks = 0; 2054 break; 2055 } else if (++tp->t_dupacks == tcprexmtthresh) { 2056 tcp_seq old_snd_nxt; 2057 u_int win; 2058 2059 fastretransmit: 2060 if (tcp_do_eifel_detect && 2061 (tp->t_flags & TF_RCVD_TSTMP)) { 2062 tcp_save_congestion_state(tp); 2063 tp->t_flags |= TF_FASTREXMT; 2064 } 2065 /* 2066 * We know we're losing at the current 2067 * window size, so do congestion avoidance: 2068 * set ssthresh to half the current window 2069 * and pull our congestion window back to the 2070 * new ssthresh. 2071 */ 2072 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 2073 tp->t_maxseg; 2074 if (win < 2) 2075 win = 2; 2076 tp->snd_ssthresh = win * tp->t_maxseg; 2077 ENTER_FASTRECOVERY(tp); 2078 tp->snd_recover = tp->snd_max; 2079 tcp_callout_stop(tp, tp->tt_rexmt); 2080 tp->t_rtttime = 0; 2081 old_snd_nxt = tp->snd_nxt; 2082 tp->snd_nxt = th->th_ack; 2083 tp->snd_cwnd = tp->t_maxseg; 2084 tcp_output(tp); 2085 ++tcpstat.tcps_sndfastrexmit; 2086 tp->snd_cwnd = tp->snd_ssthresh; 2087 tp->rexmt_high = tp->snd_nxt; 2088 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 2089 tp->snd_nxt = old_snd_nxt; 2090 KASSERT(tp->snd_limited <= 2, 2091 ("tp->snd_limited too big")); 2092 if (TCP_DO_SACK(tp)) 2093 tcp_sack_rexmt(tp, th); 2094 else 2095 tp->snd_cwnd += tp->t_maxseg * 2096 (tp->t_dupacks - tp->snd_limited); 2097 } else if (tcp_do_limitedtransmit) { 2098 u_long oldcwnd = tp->snd_cwnd; 2099 tcp_seq oldsndmax = tp->snd_max; 2100 tcp_seq oldsndnxt = tp->snd_nxt; 2101 /* outstanding data */ 2102 uint32_t ownd = tp->snd_max - tp->snd_una; 2103 u_int sent; 2104 2105 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2106 2107 KASSERT(tp->t_dupacks == 1 || 2108 tp->t_dupacks == 2, 2109 ("dupacks not 1 or 2")); 2110 if (tp->t_dupacks == 1) 2111 tp->snd_limited = 0; 2112 tp->snd_nxt = tp->snd_max; 2113 tp->snd_cwnd = ownd + 2114 (tp->t_dupacks - tp->snd_limited) * 2115 tp->t_maxseg; 2116 tcp_output(tp); 2117 2118 /* 2119 * Other acks may have been processed, 2120 * snd_nxt cannot be reset to a value less 2121 * then snd_una. 2122 */ 2123 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2124 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2125 tp->snd_nxt = oldsndnxt; 2126 else 2127 tp->snd_nxt = tp->snd_una; 2128 } 2129 tp->snd_cwnd = oldcwnd; 2130 sent = tp->snd_max - oldsndmax; 2131 if (sent > tp->t_maxseg) { 2132 KASSERT((tp->t_dupacks == 2 && 2133 tp->snd_limited == 0) || 2134 (sent == tp->t_maxseg + 1 && 2135 tp->t_flags & TF_SENTFIN), 2136 ("sent too much")); 2137 KASSERT(sent <= tp->t_maxseg * 2, 2138 ("sent too many segments")); 2139 tp->snd_limited = 2; 2140 tcpstat.tcps_sndlimited += 2; 2141 } else if (sent > 0) { 2142 ++tp->snd_limited; 2143 ++tcpstat.tcps_sndlimited; 2144 } else if (tcp_do_early_retransmit && 2145 (tcp_do_eifel_detect && 2146 (tp->t_flags & TF_RCVD_TSTMP)) && 2147 ownd < 4 * tp->t_maxseg && 2148 tp->t_dupacks + 1 >= 2149 iceildiv(ownd, tp->t_maxseg) && 2150 (!TCP_DO_SACK(tp) || 2151 ownd <= tp->t_maxseg || 2152 tcp_sack_has_sacked(&tp->scb, 2153 ownd - tp->t_maxseg))) { 2154 ++tcpstat.tcps_sndearlyrexmit; 2155 tp->t_flags |= TF_EARLYREXMT; 2156 goto fastretransmit; 2157 } 2158 } 2159 goto drop; 2160 } 2161 2162 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2163 tp->t_dupacks = 0; 2164 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2165 /* 2166 * Detected optimistic ACK attack. 2167 * Force slow-start to de-synchronize attack. 2168 */ 2169 tp->snd_cwnd = tp->t_maxseg; 2170 tp->snd_wacked = 0; 2171 2172 tcpstat.tcps_rcvacktoomuch++; 2173 goto dropafterack; 2174 } 2175 /* 2176 * If we reach this point, ACK is not a duplicate, 2177 * i.e., it ACKs something we sent. 2178 */ 2179 if (tp->t_flags & TF_NEEDSYN) { 2180 /* 2181 * T/TCP: Connection was half-synchronized, and our 2182 * SYN has been ACK'd (so connection is now fully 2183 * synchronized). Go to non-starred state, 2184 * increment snd_una for ACK of SYN, and check if 2185 * we can do window scaling. 2186 */ 2187 tp->t_flags &= ~TF_NEEDSYN; 2188 tp->snd_una++; 2189 /* Do window scaling? */ 2190 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2191 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2192 tp->snd_scale = tp->requested_s_scale; 2193 tp->rcv_scale = tp->request_r_scale; 2194 } 2195 } 2196 2197 process_ACK: 2198 acked = th->th_ack - tp->snd_una; 2199 tcpstat.tcps_rcvackpack++; 2200 tcpstat.tcps_rcvackbyte += acked; 2201 2202 if (tcp_do_eifel_detect && acked > 0 && 2203 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2204 (tp->t_flags & TF_FIRSTACCACK)) { 2205 /* Eifel detection applicable. */ 2206 if (to.to_tsecr < tp->t_rexmtTS) { 2207 ++tcpstat.tcps_eifeldetected; 2208 tcp_revert_congestion_state(tp); 2209 if (tp->t_rxtshift == 1 && 2210 ticks >= tp->t_badrxtwin) 2211 ++tcpstat.tcps_rttcantdetect; 2212 } 2213 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2214 /* 2215 * If we just performed our first retransmit, 2216 * and the ACK arrives within our recovery window, 2217 * then it was a mistake to do the retransmit 2218 * in the first place. Recover our original cwnd 2219 * and ssthresh, and proceed to transmit where we 2220 * left off. 2221 */ 2222 tcp_revert_congestion_state(tp); 2223 ++tcpstat.tcps_rttdetected; 2224 } 2225 2226 /* 2227 * If we have a timestamp reply, update smoothed 2228 * round trip time. If no timestamp is present but 2229 * transmit timer is running and timed sequence 2230 * number was acked, update smoothed round trip time. 2231 * Since we now have an rtt measurement, cancel the 2232 * timer backoff (cf., Phil Karn's retransmit alg.). 2233 * Recompute the initial retransmit timer. 2234 * 2235 * Some machines (certain windows boxes) send broken 2236 * timestamp replies during the SYN+ACK phase, ignore 2237 * timestamps of 0. 2238 */ 2239 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2240 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2241 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2242 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2243 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2244 2245 /* 2246 * If no data (only SYN) was ACK'd, 2247 * skip rest of ACK processing. 2248 */ 2249 if (acked == 0) 2250 goto step6; 2251 2252 /* Stop looking for an acceptable ACK since one was received. */ 2253 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2254 2255 if (acked > so->so_snd.ssb_cc) { 2256 tp->snd_wnd -= so->so_snd.ssb_cc; 2257 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2258 ourfinisacked = TRUE; 2259 } else { 2260 sbdrop(&so->so_snd.sb, acked); 2261 tp->snd_wnd -= acked; 2262 ourfinisacked = FALSE; 2263 } 2264 sowwakeup(so); 2265 2266 /* 2267 * Update window information. 2268 * Don't look at window if no ACK: 2269 * TAC's send garbage on first SYN. 2270 */ 2271 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2272 (tp->snd_wl1 == th->th_seq && 2273 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2274 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2275 /* keep track of pure window updates */ 2276 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2277 tiwin > tp->snd_wnd) 2278 tcpstat.tcps_rcvwinupd++; 2279 tp->snd_wnd = tiwin; 2280 tp->snd_wl1 = th->th_seq; 2281 tp->snd_wl2 = th->th_ack; 2282 if (tp->snd_wnd > tp->max_sndwnd) 2283 tp->max_sndwnd = tp->snd_wnd; 2284 needoutput = TRUE; 2285 } 2286 2287 tp->snd_una = th->th_ack; 2288 if (TCP_DO_SACK(tp)) 2289 tcp_sack_update_scoreboard(tp, &to); 2290 if (IN_FASTRECOVERY(tp)) { 2291 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2292 EXIT_FASTRECOVERY(tp); 2293 needoutput = TRUE; 2294 /* 2295 * If the congestion window was inflated 2296 * to account for the other side's 2297 * cached packets, retract it. 2298 */ 2299 if (!TCP_DO_SACK(tp)) 2300 tp->snd_cwnd = tp->snd_ssthresh; 2301 2302 /* 2303 * Window inflation should have left us 2304 * with approximately snd_ssthresh outstanding 2305 * data. But, in case we would be inclined 2306 * to send a burst, better do it using 2307 * slow start. 2308 */ 2309 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2310 tp->snd_max + 2 * tp->t_maxseg)) 2311 tp->snd_cwnd = 2312 (tp->snd_max - tp->snd_una) + 2313 2 * tp->t_maxseg; 2314 2315 tp->snd_wacked = 0; 2316 } else { 2317 if (TCP_DO_SACK(tp)) { 2318 tp->snd_max_rexmt = tp->snd_max; 2319 tcp_sack_rexmt(tp, th); 2320 } else { 2321 tcp_newreno_partial_ack(tp, th, acked); 2322 } 2323 needoutput = FALSE; 2324 } 2325 } else { 2326 /* 2327 * Open the congestion window. When in slow-start, 2328 * open exponentially: maxseg per packet. Otherwise, 2329 * open linearly: maxseg per window. 2330 */ 2331 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2332 u_int abc_sslimit = 2333 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2334 tp->t_maxseg : 2 * tp->t_maxseg); 2335 2336 /* slow-start */ 2337 tp->snd_cwnd += tcp_do_abc ? 2338 min(acked, abc_sslimit) : tp->t_maxseg; 2339 } else { 2340 /* linear increase */ 2341 tp->snd_wacked += tcp_do_abc ? acked : 2342 tp->t_maxseg; 2343 if (tp->snd_wacked >= tp->snd_cwnd) { 2344 tp->snd_wacked -= tp->snd_cwnd; 2345 tp->snd_cwnd += tp->t_maxseg; 2346 } 2347 } 2348 tp->snd_cwnd = min(tp->snd_cwnd, 2349 TCP_MAXWIN << tp->snd_scale); 2350 tp->snd_recover = th->th_ack - 1; 2351 } 2352 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2353 tp->snd_nxt = tp->snd_una; 2354 2355 /* 2356 * If all outstanding data is acked, stop retransmit 2357 * timer and remember to restart (more output or persist). 2358 * If there is more data to be acked, restart retransmit 2359 * timer, using current (possibly backed-off) value. 2360 */ 2361 if (th->th_ack == tp->snd_max) { 2362 tcp_callout_stop(tp, tp->tt_rexmt); 2363 needoutput = TRUE; 2364 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2365 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2366 tcp_timer_rexmt); 2367 } 2368 2369 switch (tp->t_state) { 2370 /* 2371 * In FIN_WAIT_1 STATE in addition to the processing 2372 * for the ESTABLISHED state if our FIN is now acknowledged 2373 * then enter FIN_WAIT_2. 2374 */ 2375 case TCPS_FIN_WAIT_1: 2376 if (ourfinisacked) { 2377 /* 2378 * If we can't receive any more 2379 * data, then closing user can proceed. 2380 * Starting the timer is contrary to the 2381 * specification, but if we don't get a FIN 2382 * we'll hang forever. 2383 */ 2384 if (so->so_state & SS_CANTRCVMORE) { 2385 soisdisconnected(so); 2386 tcp_callout_reset(tp, tp->tt_2msl, 2387 tcp_maxidle, tcp_timer_2msl); 2388 } 2389 tp->t_state = TCPS_FIN_WAIT_2; 2390 } 2391 break; 2392 2393 /* 2394 * In CLOSING STATE in addition to the processing for 2395 * the ESTABLISHED state if the ACK acknowledges our FIN 2396 * then enter the TIME-WAIT state, otherwise ignore 2397 * the segment. 2398 */ 2399 case TCPS_CLOSING: 2400 if (ourfinisacked) { 2401 tp->t_state = TCPS_TIME_WAIT; 2402 tcp_canceltimers(tp); 2403 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2404 if (tp->cc_recv != 0 && 2405 (ticks - tp->t_starttime) < tcp_msl) { 2406 tcp_callout_reset(tp, tp->tt_2msl, 2407 tp->t_rxtcur * TCPTV_TWTRUNC, 2408 tcp_timer_2msl); 2409 } else { 2410 tcp_callout_reset(tp, tp->tt_2msl, 2411 2 * tcp_msl, tcp_timer_2msl); 2412 } 2413 soisdisconnected(so); 2414 } 2415 break; 2416 2417 /* 2418 * In LAST_ACK, we may still be waiting for data to drain 2419 * and/or to be acked, as well as for the ack of our FIN. 2420 * If our FIN is now acknowledged, delete the TCB, 2421 * enter the closed state and return. 2422 */ 2423 case TCPS_LAST_ACK: 2424 if (ourfinisacked) { 2425 tp = tcp_close(tp); 2426 goto drop; 2427 } 2428 break; 2429 2430 /* 2431 * In TIME_WAIT state the only thing that should arrive 2432 * is a retransmission of the remote FIN. Acknowledge 2433 * it and restart the finack timer. 2434 */ 2435 case TCPS_TIME_WAIT: 2436 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2437 tcp_timer_2msl); 2438 goto dropafterack; 2439 } 2440 } 2441 2442 step6: 2443 /* 2444 * Update window information. 2445 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2446 */ 2447 if ((thflags & TH_ACK) && 2448 acceptable_window_update(tp, th, tiwin)) { 2449 /* keep track of pure window updates */ 2450 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2451 tiwin > tp->snd_wnd) 2452 tcpstat.tcps_rcvwinupd++; 2453 tp->snd_wnd = tiwin; 2454 tp->snd_wl1 = th->th_seq; 2455 tp->snd_wl2 = th->th_ack; 2456 if (tp->snd_wnd > tp->max_sndwnd) 2457 tp->max_sndwnd = tp->snd_wnd; 2458 needoutput = TRUE; 2459 } 2460 2461 /* 2462 * Process segments with URG. 2463 */ 2464 if ((thflags & TH_URG) && th->th_urp && 2465 !TCPS_HAVERCVDFIN(tp->t_state)) { 2466 /* 2467 * This is a kludge, but if we receive and accept 2468 * random urgent pointers, we'll crash in 2469 * soreceive. It's hard to imagine someone 2470 * actually wanting to send this much urgent data. 2471 */ 2472 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2473 th->th_urp = 0; /* XXX */ 2474 thflags &= ~TH_URG; /* XXX */ 2475 goto dodata; /* XXX */ 2476 } 2477 /* 2478 * If this segment advances the known urgent pointer, 2479 * then mark the data stream. This should not happen 2480 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2481 * a FIN has been received from the remote side. 2482 * In these states we ignore the URG. 2483 * 2484 * According to RFC961 (Assigned Protocols), 2485 * the urgent pointer points to the last octet 2486 * of urgent data. We continue, however, 2487 * to consider it to indicate the first octet 2488 * of data past the urgent section as the original 2489 * spec states (in one of two places). 2490 */ 2491 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2492 tp->rcv_up = th->th_seq + th->th_urp; 2493 so->so_oobmark = so->so_rcv.ssb_cc + 2494 (tp->rcv_up - tp->rcv_nxt) - 1; 2495 if (so->so_oobmark == 0) 2496 so->so_state |= SS_RCVATMARK; 2497 sohasoutofband(so); 2498 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2499 } 2500 /* 2501 * Remove out of band data so doesn't get presented to user. 2502 * This can happen independent of advancing the URG pointer, 2503 * but if two URG's are pending at once, some out-of-band 2504 * data may creep in... ick. 2505 */ 2506 if (th->th_urp <= (u_long)tlen && 2507 !(so->so_options & SO_OOBINLINE)) { 2508 /* hdr drop is delayed */ 2509 tcp_pulloutofband(so, th, m, drop_hdrlen); 2510 } 2511 } else { 2512 /* 2513 * If no out of band data is expected, 2514 * pull receive urgent pointer along 2515 * with the receive window. 2516 */ 2517 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2518 tp->rcv_up = tp->rcv_nxt; 2519 } 2520 2521 dodata: /* XXX */ 2522 /* 2523 * Process the segment text, merging it into the TCP sequencing queue, 2524 * and arranging for acknowledgment of receipt if necessary. 2525 * This process logically involves adjusting tp->rcv_wnd as data 2526 * is presented to the user (this happens in tcp_usrreq.c, 2527 * case PRU_RCVD). If a FIN has already been received on this 2528 * connection then we just ignore the text. 2529 */ 2530 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2531 m_adj(m, drop_hdrlen); /* delayed header drop */ 2532 /* 2533 * Insert segment which includes th into TCP reassembly queue 2534 * with control block tp. Set thflags to whether reassembly now 2535 * includes a segment with FIN. This handles the common case 2536 * inline (segment is the next to be received on an established 2537 * connection, and the queue is empty), avoiding linkage into 2538 * and removal from the queue and repetition of various 2539 * conversions. 2540 * Set DELACK for segments received in order, but ack 2541 * immediately when segments are out of order (so 2542 * fast retransmit can work). 2543 */ 2544 if (th->th_seq == tp->rcv_nxt && 2545 LIST_EMPTY(&tp->t_segq) && 2546 TCPS_HAVEESTABLISHED(tp->t_state)) { 2547 if (DELAY_ACK(tp)) { 2548 tcp_callout_reset(tp, tp->tt_delack, 2549 tcp_delacktime, tcp_timer_delack); 2550 } else { 2551 tp->t_flags |= TF_ACKNOW; 2552 } 2553 tp->rcv_nxt += tlen; 2554 thflags = th->th_flags & TH_FIN; 2555 tcpstat.tcps_rcvpack++; 2556 tcpstat.tcps_rcvbyte += tlen; 2557 ND6_HINT(tp); 2558 if (so->so_state & SS_CANTRCVMORE) 2559 m_freem(m); 2560 else 2561 ssb_appendstream(&so->so_rcv, m); 2562 sorwakeup(so); 2563 } else { 2564 if (!(tp->t_flags & TF_DUPSEG)) { 2565 /* Initialize SACK report block. */ 2566 tp->reportblk.rblk_start = th->th_seq; 2567 tp->reportblk.rblk_end = th->th_seq + tlen + 2568 ((thflags & TH_FIN) != 0); 2569 } 2570 thflags = tcp_reass(tp, th, &tlen, m); 2571 tp->t_flags |= TF_ACKNOW; 2572 } 2573 2574 /* 2575 * Note the amount of data that peer has sent into 2576 * our window, in order to estimate the sender's 2577 * buffer size. 2578 */ 2579 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2580 } else { 2581 m_freem(m); 2582 thflags &= ~TH_FIN; 2583 } 2584 2585 /* 2586 * If FIN is received ACK the FIN and let the user know 2587 * that the connection is closing. 2588 */ 2589 if (thflags & TH_FIN) { 2590 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2591 socantrcvmore(so); 2592 /* 2593 * If connection is half-synchronized 2594 * (ie NEEDSYN flag on) then delay ACK, 2595 * so it may be piggybacked when SYN is sent. 2596 * Otherwise, since we received a FIN then no 2597 * more input can be expected, send ACK now. 2598 */ 2599 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2600 tcp_callout_reset(tp, tp->tt_delack, 2601 tcp_delacktime, tcp_timer_delack); 2602 } else { 2603 tp->t_flags |= TF_ACKNOW; 2604 } 2605 tp->rcv_nxt++; 2606 } 2607 2608 switch (tp->t_state) { 2609 /* 2610 * In SYN_RECEIVED and ESTABLISHED STATES 2611 * enter the CLOSE_WAIT state. 2612 */ 2613 case TCPS_SYN_RECEIVED: 2614 tp->t_starttime = ticks; 2615 /*FALLTHROUGH*/ 2616 case TCPS_ESTABLISHED: 2617 tp->t_state = TCPS_CLOSE_WAIT; 2618 break; 2619 2620 /* 2621 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2622 * enter the CLOSING state. 2623 */ 2624 case TCPS_FIN_WAIT_1: 2625 tp->t_state = TCPS_CLOSING; 2626 break; 2627 2628 /* 2629 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2630 * starting the time-wait timer, turning off the other 2631 * standard timers. 2632 */ 2633 case TCPS_FIN_WAIT_2: 2634 tp->t_state = TCPS_TIME_WAIT; 2635 tcp_canceltimers(tp); 2636 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2637 if (tp->cc_recv != 0 && 2638 (ticks - tp->t_starttime) < tcp_msl) { 2639 tcp_callout_reset(tp, tp->tt_2msl, 2640 tp->t_rxtcur * TCPTV_TWTRUNC, 2641 tcp_timer_2msl); 2642 /* For transaction client, force ACK now. */ 2643 tp->t_flags |= TF_ACKNOW; 2644 } else { 2645 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2646 tcp_timer_2msl); 2647 } 2648 soisdisconnected(so); 2649 break; 2650 2651 /* 2652 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2653 */ 2654 case TCPS_TIME_WAIT: 2655 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2656 tcp_timer_2msl); 2657 break; 2658 } 2659 } 2660 2661 #ifdef TCPDEBUG 2662 if (so->so_options & SO_DEBUG) 2663 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2664 #endif 2665 2666 /* 2667 * Return any desired output. 2668 */ 2669 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2670 tcp_output(tp); 2671 return; 2672 2673 dropafterack: 2674 /* 2675 * Generate an ACK dropping incoming segment if it occupies 2676 * sequence space, where the ACK reflects our state. 2677 * 2678 * We can now skip the test for the RST flag since all 2679 * paths to this code happen after packets containing 2680 * RST have been dropped. 2681 * 2682 * In the SYN-RECEIVED state, don't send an ACK unless the 2683 * segment we received passes the SYN-RECEIVED ACK test. 2684 * If it fails send a RST. This breaks the loop in the 2685 * "LAND" DoS attack, and also prevents an ACK storm 2686 * between two listening ports that have been sent forged 2687 * SYN segments, each with the source address of the other. 2688 */ 2689 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2690 (SEQ_GT(tp->snd_una, th->th_ack) || 2691 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2692 rstreason = BANDLIM_RST_OPENPORT; 2693 goto dropwithreset; 2694 } 2695 #ifdef TCPDEBUG 2696 if (so->so_options & SO_DEBUG) 2697 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2698 #endif 2699 m_freem(m); 2700 tp->t_flags |= TF_ACKNOW; 2701 tcp_output(tp); 2702 return; 2703 2704 dropwithreset: 2705 /* 2706 * Generate a RST, dropping incoming segment. 2707 * Make ACK acceptable to originator of segment. 2708 * Don't bother to respond if destination was broadcast/multicast. 2709 */ 2710 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2711 goto drop; 2712 if (isipv6) { 2713 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2714 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2715 goto drop; 2716 } else { 2717 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2718 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2719 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2720 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2721 goto drop; 2722 } 2723 /* IPv6 anycast check is done at tcp6_input() */ 2724 2725 /* 2726 * Perform bandwidth limiting. 2727 */ 2728 #ifdef ICMP_BANDLIM 2729 if (badport_bandlim(rstreason) < 0) 2730 goto drop; 2731 #endif 2732 2733 #ifdef TCPDEBUG 2734 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2735 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2736 #endif 2737 if (thflags & TH_ACK) 2738 /* mtod() below is safe as long as hdr dropping is delayed */ 2739 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2740 TH_RST); 2741 else { 2742 if (thflags & TH_SYN) 2743 tlen++; 2744 /* mtod() below is safe as long as hdr dropping is delayed */ 2745 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2746 (tcp_seq)0, TH_RST | TH_ACK); 2747 } 2748 return; 2749 2750 drop: 2751 /* 2752 * Drop space held by incoming segment and return. 2753 */ 2754 #ifdef TCPDEBUG 2755 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2756 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2757 #endif 2758 m_freem(m); 2759 return; 2760 } 2761 2762 /* 2763 * Parse TCP options and place in tcpopt. 2764 */ 2765 static void 2766 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2767 { 2768 int opt, optlen, i; 2769 2770 to->to_flags = 0; 2771 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2772 opt = cp[0]; 2773 if (opt == TCPOPT_EOL) 2774 break; 2775 if (opt == TCPOPT_NOP) 2776 optlen = 1; 2777 else { 2778 if (cnt < 2) 2779 break; 2780 optlen = cp[1]; 2781 if (optlen < 2 || optlen > cnt) 2782 break; 2783 } 2784 switch (opt) { 2785 case TCPOPT_MAXSEG: 2786 if (optlen != TCPOLEN_MAXSEG) 2787 continue; 2788 if (!is_syn) 2789 continue; 2790 to->to_flags |= TOF_MSS; 2791 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2792 to->to_mss = ntohs(to->to_mss); 2793 break; 2794 case TCPOPT_WINDOW: 2795 if (optlen != TCPOLEN_WINDOW) 2796 continue; 2797 if (!is_syn) 2798 continue; 2799 to->to_flags |= TOF_SCALE; 2800 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2801 break; 2802 case TCPOPT_TIMESTAMP: 2803 if (optlen != TCPOLEN_TIMESTAMP) 2804 continue; 2805 to->to_flags |= TOF_TS; 2806 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2807 to->to_tsval = ntohl(to->to_tsval); 2808 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2809 to->to_tsecr = ntohl(to->to_tsecr); 2810 /* 2811 * If echoed timestamp is later than the current time, 2812 * fall back to non RFC1323 RTT calculation. 2813 */ 2814 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2815 to->to_tsecr = 0; 2816 break; 2817 case TCPOPT_CC: 2818 if (optlen != TCPOLEN_CC) 2819 continue; 2820 to->to_flags |= TOF_CC; 2821 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2822 to->to_cc = ntohl(to->to_cc); 2823 break; 2824 case TCPOPT_CCNEW: 2825 if (optlen != TCPOLEN_CC) 2826 continue; 2827 if (!is_syn) 2828 continue; 2829 to->to_flags |= TOF_CCNEW; 2830 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2831 to->to_cc = ntohl(to->to_cc); 2832 break; 2833 case TCPOPT_CCECHO: 2834 if (optlen != TCPOLEN_CC) 2835 continue; 2836 if (!is_syn) 2837 continue; 2838 to->to_flags |= TOF_CCECHO; 2839 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho); 2840 to->to_ccecho = ntohl(to->to_ccecho); 2841 break; 2842 case TCPOPT_SACK_PERMITTED: 2843 if (optlen != TCPOLEN_SACK_PERMITTED) 2844 continue; 2845 if (!is_syn) 2846 continue; 2847 to->to_flags |= TOF_SACK_PERMITTED; 2848 break; 2849 case TCPOPT_SACK: 2850 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2851 continue; 2852 to->to_nsackblocks = (optlen - 2) / 8; 2853 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2854 to->to_flags |= TOF_SACK; 2855 for (i = 0; i < to->to_nsackblocks; i++) { 2856 struct raw_sackblock *r = &to->to_sackblocks[i]; 2857 2858 r->rblk_start = ntohl(r->rblk_start); 2859 r->rblk_end = ntohl(r->rblk_end); 2860 } 2861 break; 2862 default: 2863 continue; 2864 } 2865 } 2866 } 2867 2868 /* 2869 * Pull out of band byte out of a segment so 2870 * it doesn't appear in the user's data queue. 2871 * It is still reflected in the segment length for 2872 * sequencing purposes. 2873 * "off" is the delayed to be dropped hdrlen. 2874 */ 2875 static void 2876 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2877 { 2878 int cnt = off + th->th_urp - 1; 2879 2880 while (cnt >= 0) { 2881 if (m->m_len > cnt) { 2882 char *cp = mtod(m, caddr_t) + cnt; 2883 struct tcpcb *tp = sototcpcb(so); 2884 2885 tp->t_iobc = *cp; 2886 tp->t_oobflags |= TCPOOB_HAVEDATA; 2887 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2888 m->m_len--; 2889 if (m->m_flags & M_PKTHDR) 2890 m->m_pkthdr.len--; 2891 return; 2892 } 2893 cnt -= m->m_len; 2894 m = m->m_next; 2895 if (m == 0) 2896 break; 2897 } 2898 panic("tcp_pulloutofband"); 2899 } 2900 2901 /* 2902 * Collect new round-trip time estimate 2903 * and update averages and current timeout. 2904 */ 2905 static void 2906 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2907 { 2908 int delta; 2909 2910 tcpstat.tcps_rttupdated++; 2911 tp->t_rttupdated++; 2912 if (tp->t_srtt != 0) { 2913 /* 2914 * srtt is stored as fixed point with 5 bits after the 2915 * binary point (i.e., scaled by 8). The following magic 2916 * is equivalent to the smoothing algorithm in rfc793 with 2917 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2918 * point). Adjust rtt to origin 0. 2919 */ 2920 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2921 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2922 2923 if ((tp->t_srtt += delta) <= 0) 2924 tp->t_srtt = 1; 2925 2926 /* 2927 * We accumulate a smoothed rtt variance (actually, a 2928 * smoothed mean difference), then set the retransmit 2929 * timer to smoothed rtt + 4 times the smoothed variance. 2930 * rttvar is stored as fixed point with 4 bits after the 2931 * binary point (scaled by 16). The following is 2932 * equivalent to rfc793 smoothing with an alpha of .75 2933 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2934 * rfc793's wired-in beta. 2935 */ 2936 if (delta < 0) 2937 delta = -delta; 2938 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2939 if ((tp->t_rttvar += delta) <= 0) 2940 tp->t_rttvar = 1; 2941 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2942 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2943 } else { 2944 /* 2945 * No rtt measurement yet - use the unsmoothed rtt. 2946 * Set the variance to half the rtt (so our first 2947 * retransmit happens at 3*rtt). 2948 */ 2949 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2950 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2951 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2952 } 2953 tp->t_rtttime = 0; 2954 tp->t_rxtshift = 0; 2955 2956 /* 2957 * the retransmit should happen at rtt + 4 * rttvar. 2958 * Because of the way we do the smoothing, srtt and rttvar 2959 * will each average +1/2 tick of bias. When we compute 2960 * the retransmit timer, we want 1/2 tick of rounding and 2961 * 1 extra tick because of +-1/2 tick uncertainty in the 2962 * firing of the timer. The bias will give us exactly the 2963 * 1.5 tick we need. But, because the bias is 2964 * statistical, we have to test that we don't drop below 2965 * the minimum feasible timer (which is 2 ticks). 2966 */ 2967 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2968 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2969 2970 /* 2971 * We received an ack for a packet that wasn't retransmitted; 2972 * it is probably safe to discard any error indications we've 2973 * received recently. This isn't quite right, but close enough 2974 * for now (a route might have failed after we sent a segment, 2975 * and the return path might not be symmetrical). 2976 */ 2977 tp->t_softerror = 0; 2978 } 2979 2980 /* 2981 * Determine a reasonable value for maxseg size. 2982 * If the route is known, check route for mtu. 2983 * If none, use an mss that can be handled on the outgoing 2984 * interface without forcing IP to fragment; if bigger than 2985 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2986 * to utilize large mbufs. If no route is found, route has no mtu, 2987 * or the destination isn't local, use a default, hopefully conservative 2988 * size (usually 512 or the default IP max size, but no more than the mtu 2989 * of the interface), as we can't discover anything about intervening 2990 * gateways or networks. We also initialize the congestion/slow start 2991 * window to be a single segment if the destination isn't local. 2992 * While looking at the routing entry, we also initialize other path-dependent 2993 * parameters from pre-set or cached values in the routing entry. 2994 * 2995 * Also take into account the space needed for options that we 2996 * send regularly. Make maxseg shorter by that amount to assure 2997 * that we can send maxseg amount of data even when the options 2998 * are present. Store the upper limit of the length of options plus 2999 * data in maxopd. 3000 * 3001 * NOTE that this routine is only called when we process an incoming 3002 * segment, for outgoing segments only tcp_mssopt is called. 3003 * 3004 * In case of T/TCP, we call this routine during implicit connection 3005 * setup as well (offer = -1), to initialize maxseg from the cached 3006 * MSS of our peer. 3007 */ 3008 void 3009 tcp_mss(struct tcpcb *tp, int offer) 3010 { 3011 struct rtentry *rt; 3012 struct ifnet *ifp; 3013 int rtt, mss; 3014 u_long bufsize; 3015 struct inpcb *inp = tp->t_inpcb; 3016 struct socket *so; 3017 struct rmxp_tao *taop; 3018 int origoffer = offer; 3019 #ifdef INET6 3020 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3021 size_t min_protoh = isipv6 ? 3022 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3023 sizeof(struct tcpiphdr); 3024 #else 3025 const boolean_t isipv6 = FALSE; 3026 const size_t min_protoh = sizeof(struct tcpiphdr); 3027 #endif 3028 3029 if (isipv6) 3030 rt = tcp_rtlookup6(&inp->inp_inc); 3031 else 3032 rt = tcp_rtlookup(&inp->inp_inc); 3033 if (rt == NULL) { 3034 tp->t_maxopd = tp->t_maxseg = 3035 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3036 return; 3037 } 3038 ifp = rt->rt_ifp; 3039 so = inp->inp_socket; 3040 3041 taop = rmx_taop(rt->rt_rmx); 3042 /* 3043 * Offer == -1 means that we didn't receive SYN yet, 3044 * use cached value in that case; 3045 */ 3046 if (offer == -1) 3047 offer = taop->tao_mssopt; 3048 /* 3049 * Offer == 0 means that there was no MSS on the SYN segment, 3050 * in this case we use tcp_mssdflt. 3051 */ 3052 if (offer == 0) { 3053 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3054 } else { 3055 /* 3056 * Prevent DoS attack with too small MSS. Round up 3057 * to at least minmss. 3058 */ 3059 offer = max(offer, tcp_minmss); 3060 /* 3061 * Sanity check: make sure that maxopd will be large 3062 * enough to allow some data on segments even is the 3063 * all the option space is used (40bytes). Otherwise 3064 * funny things may happen in tcp_output. 3065 */ 3066 offer = max(offer, 64); 3067 } 3068 taop->tao_mssopt = offer; 3069 3070 /* 3071 * While we're here, check if there's an initial rtt 3072 * or rttvar. Convert from the route-table units 3073 * to scaled multiples of the slow timeout timer. 3074 */ 3075 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3076 /* 3077 * XXX the lock bit for RTT indicates that the value 3078 * is also a minimum value; this is subject to time. 3079 */ 3080 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3081 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3082 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3083 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3084 tcpstat.tcps_usedrtt++; 3085 if (rt->rt_rmx.rmx_rttvar) { 3086 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3087 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3088 tcpstat.tcps_usedrttvar++; 3089 } else { 3090 /* default variation is +- 1 rtt */ 3091 tp->t_rttvar = 3092 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3093 } 3094 TCPT_RANGESET(tp->t_rxtcur, 3095 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3096 tp->t_rttmin, TCPTV_REXMTMAX); 3097 } 3098 /* 3099 * if there's an mtu associated with the route, use it 3100 * else, use the link mtu. 3101 */ 3102 if (rt->rt_rmx.rmx_mtu) 3103 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3104 else { 3105 if (isipv6) { 3106 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3107 if (!in6_localaddr(&inp->in6p_faddr)) 3108 mss = min(mss, tcp_v6mssdflt); 3109 } else { 3110 mss = ifp->if_mtu - min_protoh; 3111 if (!in_localaddr(inp->inp_faddr)) 3112 mss = min(mss, tcp_mssdflt); 3113 } 3114 } 3115 mss = min(mss, offer); 3116 /* 3117 * maxopd stores the maximum length of data AND options 3118 * in a segment; maxseg is the amount of data in a normal 3119 * segment. We need to store this value (maxopd) apart 3120 * from maxseg, because now every segment carries options 3121 * and thus we normally have somewhat less data in segments. 3122 */ 3123 tp->t_maxopd = mss; 3124 3125 /* 3126 * In case of T/TCP, origoffer==-1 indicates, that no segments 3127 * were received yet. In this case we just guess, otherwise 3128 * we do the same as before T/TCP. 3129 */ 3130 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3131 (origoffer == -1 || 3132 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3133 mss -= TCPOLEN_TSTAMP_APPA; 3134 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 3135 (origoffer == -1 || 3136 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3137 mss -= TCPOLEN_CC_APPA; 3138 3139 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3140 if (mss > MCLBYTES) 3141 mss &= ~(MCLBYTES-1); 3142 #else 3143 if (mss > MCLBYTES) 3144 mss = mss / MCLBYTES * MCLBYTES; 3145 #endif 3146 /* 3147 * If there's a pipesize, change the socket buffer 3148 * to that size. Make the socket buffers an integral 3149 * number of mss units; if the mss is larger than 3150 * the socket buffer, decrease the mss. 3151 */ 3152 #ifdef RTV_SPIPE 3153 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3154 #endif 3155 bufsize = so->so_snd.ssb_hiwat; 3156 if (bufsize < mss) 3157 mss = bufsize; 3158 else { 3159 bufsize = roundup(bufsize, mss); 3160 if (bufsize > sb_max) 3161 bufsize = sb_max; 3162 if (bufsize > so->so_snd.ssb_hiwat) 3163 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3164 } 3165 tp->t_maxseg = mss; 3166 3167 #ifdef RTV_RPIPE 3168 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3169 #endif 3170 bufsize = so->so_rcv.ssb_hiwat; 3171 if (bufsize > mss) { 3172 bufsize = roundup(bufsize, mss); 3173 if (bufsize > sb_max) 3174 bufsize = sb_max; 3175 if (bufsize > so->so_rcv.ssb_hiwat) 3176 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3177 } 3178 3179 /* 3180 * Set the slow-start flight size depending on whether this 3181 * is a local network or not. 3182 */ 3183 if (tcp_do_rfc3390) 3184 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3185 else 3186 tp->snd_cwnd = mss; 3187 3188 if (rt->rt_rmx.rmx_ssthresh) { 3189 /* 3190 * There's some sort of gateway or interface 3191 * buffer limit on the path. Use this to set 3192 * the slow start threshhold, but set the 3193 * threshold to no less than 2*mss. 3194 */ 3195 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3196 tcpstat.tcps_usedssthresh++; 3197 } 3198 } 3199 3200 /* 3201 * Determine the MSS option to send on an outgoing SYN. 3202 */ 3203 int 3204 tcp_mssopt(struct tcpcb *tp) 3205 { 3206 struct rtentry *rt; 3207 #ifdef INET6 3208 boolean_t isipv6 = 3209 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3210 int min_protoh = isipv6 ? 3211 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3212 sizeof(struct tcpiphdr); 3213 #else 3214 const boolean_t isipv6 = FALSE; 3215 const size_t min_protoh = sizeof(struct tcpiphdr); 3216 #endif 3217 3218 if (isipv6) 3219 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3220 else 3221 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3222 if (rt == NULL) 3223 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3224 3225 return (rt->rt_ifp->if_mtu - min_protoh); 3226 } 3227 3228 /* 3229 * When a partial ack arrives, force the retransmission of the 3230 * next unacknowledged segment. Do not exit Fast Recovery. 3231 * 3232 * Implement the Slow-but-Steady variant of NewReno by restarting the 3233 * the retransmission timer. Turn it off here so it can be restarted 3234 * later in tcp_output(). 3235 */ 3236 static void 3237 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3238 { 3239 tcp_seq old_snd_nxt = tp->snd_nxt; 3240 u_long ocwnd = tp->snd_cwnd; 3241 3242 tcp_callout_stop(tp, tp->tt_rexmt); 3243 tp->t_rtttime = 0; 3244 tp->snd_nxt = th->th_ack; 3245 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3246 tp->snd_cwnd = tp->t_maxseg; 3247 tp->t_flags |= TF_ACKNOW; 3248 tcp_output(tp); 3249 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3250 tp->snd_nxt = old_snd_nxt; 3251 /* partial window deflation */ 3252 if (ocwnd > acked) 3253 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3254 else 3255 tp->snd_cwnd = tp->t_maxseg; 3256 } 3257 3258 /* 3259 * In contrast to the Slow-but-Steady NewReno variant, 3260 * we do not reset the retransmission timer for SACK retransmissions, 3261 * except when retransmitting snd_una. 3262 */ 3263 static void 3264 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3265 { 3266 uint32_t pipe, seglen; 3267 tcp_seq nextrexmt; 3268 boolean_t lostdup; 3269 tcp_seq old_snd_nxt = tp->snd_nxt; 3270 u_long ocwnd = tp->snd_cwnd; 3271 int nseg = 0; /* consecutive new segments */ 3272 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3273 3274 tp->t_rtttime = 0; 3275 pipe = tcp_sack_compute_pipe(tp); 3276 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3277 (!tcp_do_smartsack || nseg < MAXBURST) && 3278 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3279 uint32_t sent; 3280 tcp_seq old_snd_max; 3281 int error; 3282 3283 if (nextrexmt == tp->snd_max) 3284 ++nseg; 3285 tp->snd_nxt = nextrexmt; 3286 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3287 old_snd_max = tp->snd_max; 3288 if (nextrexmt == tp->snd_una) 3289 tcp_callout_stop(tp, tp->tt_rexmt); 3290 error = tcp_output(tp); 3291 if (error != 0) 3292 break; 3293 sent = tp->snd_nxt - nextrexmt; 3294 if (sent <= 0) 3295 break; 3296 if (!lostdup) 3297 pipe += sent; 3298 tcpstat.tcps_sndsackpack++; 3299 tcpstat.tcps_sndsackbyte += sent; 3300 if (SEQ_LT(nextrexmt, old_snd_max) && 3301 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3302 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3303 } 3304 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3305 tp->snd_nxt = old_snd_nxt; 3306 tp->snd_cwnd = ocwnd; 3307 } 3308