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 = 2*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 u_long 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 ulmin(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, give up when 1350 * limit is reached. 1351 * 1352 * Adjusting the size can mess up ACK 1353 * sequencing when pure window updates are 1354 * being avoided (which is the default), 1355 * so force an ack. 1356 */ 1357 if (newsize) { 1358 tp->t_flags |= TF_RXRESIZED; 1359 if (!ssb_reserve(&so->so_rcv, newsize, 1360 so, NULL)) { 1361 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE; 1362 } 1363 if (newsize >= 1364 (TCP_MAXWIN << tp->rcv_scale)) { 1365 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE; 1366 } 1367 } 1368 m_adj(m, drop_hdrlen); /* delayed header drop */ 1369 ssb_appendstream(&so->so_rcv, m); 1370 } 1371 sorwakeup(so); 1372 /* 1373 * This code is responsible for most of the ACKs 1374 * the TCP stack sends back after receiving a data 1375 * packet. Note that the DELAY_ACK check fails if 1376 * the delack timer is already running, which results 1377 * in an ack being sent every other packet (which is 1378 * what we want). 1379 * 1380 * We then further aggregate acks by not actually 1381 * sending one until the protocol thread has completed 1382 * processing the current backlog of packets. This 1383 * does not delay the ack any further, but allows us 1384 * to take advantage of the packet aggregation that 1385 * high speed NICs do (usually blocks of 8-10 packets) 1386 * to send a single ack rather then four or five acks, 1387 * greatly reducing the ack rate, the return channel 1388 * bandwidth, and the protocol overhead on both ends. 1389 * 1390 * Since this also has the effect of slowing down 1391 * the exponential slow-start ramp-up, systems with 1392 * very large bandwidth-delay products might want 1393 * to turn the feature off. 1394 */ 1395 if (DELAY_ACK(tp)) { 1396 tcp_callout_reset(tp, tp->tt_delack, 1397 tcp_delacktime, tcp_timer_delack); 1398 } else if (tcp_aggregate_acks) { 1399 tp->t_flags |= TF_ACKNOW; 1400 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1401 tp->t_flags |= TF_ONOUTPUTQ; 1402 tp->tt_cpu = mycpu->gd_cpuid; 1403 TAILQ_INSERT_TAIL( 1404 &tcpcbackq[tp->tt_cpu], 1405 tp, t_outputq); 1406 } 1407 } else { 1408 tp->t_flags |= TF_ACKNOW; 1409 tcp_output(tp); 1410 } 1411 return; 1412 } 1413 } 1414 1415 /* 1416 * Calculate amount of space in receive window, 1417 * and then do TCP input processing. 1418 * Receive window is amount of space in rcv queue, 1419 * but not less than advertised window. 1420 */ 1421 recvwin = ssb_space(&so->so_rcv); 1422 if (recvwin < 0) 1423 recvwin = 0; 1424 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1425 1426 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1427 tp->rfbuf_ts = 0; 1428 tp->rfbuf_cnt = 0; 1429 1430 switch (tp->t_state) { 1431 /* 1432 * If the state is SYN_RECEIVED: 1433 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1434 */ 1435 case TCPS_SYN_RECEIVED: 1436 if ((thflags & TH_ACK) && 1437 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1438 SEQ_GT(th->th_ack, tp->snd_max))) { 1439 rstreason = BANDLIM_RST_OPENPORT; 1440 goto dropwithreset; 1441 } 1442 break; 1443 1444 /* 1445 * If the state is SYN_SENT: 1446 * if seg contains an ACK, but not for our SYN, drop the input. 1447 * if seg contains a RST, then drop the connection. 1448 * if seg does not contain SYN, then drop it. 1449 * Otherwise this is an acceptable SYN segment 1450 * initialize tp->rcv_nxt and tp->irs 1451 * if seg contains ack then advance tp->snd_una 1452 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1453 * arrange for segment to be acked (eventually) 1454 * continue processing rest of data/controls, beginning with URG 1455 */ 1456 case TCPS_SYN_SENT: 1457 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1458 taop = &tao_noncached; 1459 bzero(taop, sizeof *taop); 1460 } 1461 1462 if ((thflags & TH_ACK) && 1463 (SEQ_LEQ(th->th_ack, tp->iss) || 1464 SEQ_GT(th->th_ack, tp->snd_max))) { 1465 /* 1466 * If we have a cached CCsent for the remote host, 1467 * hence we haven't just crashed and restarted, 1468 * do not send a RST. This may be a retransmission 1469 * from the other side after our earlier ACK was lost. 1470 * Our new SYN, when it arrives, will serve as the 1471 * needed ACK. 1472 */ 1473 if (taop->tao_ccsent != 0) 1474 goto drop; 1475 else { 1476 rstreason = BANDLIM_UNLIMITED; 1477 goto dropwithreset; 1478 } 1479 } 1480 if (thflags & TH_RST) { 1481 if (thflags & TH_ACK) 1482 tp = tcp_drop(tp, ECONNREFUSED); 1483 goto drop; 1484 } 1485 if (!(thflags & TH_SYN)) 1486 goto drop; 1487 tp->snd_wnd = th->th_win; /* initial send window */ 1488 tp->cc_recv = to.to_cc; /* foreign CC */ 1489 1490 tp->irs = th->th_seq; 1491 tcp_rcvseqinit(tp); 1492 if (thflags & TH_ACK) { 1493 /* 1494 * Our SYN was acked. If segment contains CC.ECHO 1495 * option, check it to make sure this segment really 1496 * matches our SYN. If not, just drop it as old 1497 * duplicate, but send an RST if we're still playing 1498 * by the old rules. If no CC.ECHO option, make sure 1499 * we don't get fooled into using T/TCP. 1500 */ 1501 if (to.to_flags & TOF_CCECHO) { 1502 if (tp->cc_send != to.to_ccecho) { 1503 if (taop->tao_ccsent != 0) 1504 goto drop; 1505 else { 1506 rstreason = BANDLIM_UNLIMITED; 1507 goto dropwithreset; 1508 } 1509 } 1510 } else 1511 tp->t_flags &= ~TF_RCVD_CC; 1512 tcpstat.tcps_connects++; 1513 soisconnected(so); 1514 /* Do window scaling on this connection? */ 1515 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1516 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1517 tp->snd_scale = tp->requested_s_scale; 1518 tp->rcv_scale = tp->request_r_scale; 1519 } 1520 /* Segment is acceptable, update cache if undefined. */ 1521 if (taop->tao_ccsent == 0) 1522 taop->tao_ccsent = to.to_ccecho; 1523 1524 tp->rcv_adv += tp->rcv_wnd; 1525 tp->snd_una++; /* SYN is acked */ 1526 tcp_callout_stop(tp, tp->tt_rexmt); 1527 /* 1528 * If there's data, delay ACK; if there's also a FIN 1529 * ACKNOW will be turned on later. 1530 */ 1531 if (DELAY_ACK(tp) && tlen != 0) { 1532 tcp_callout_reset(tp, tp->tt_delack, 1533 tcp_delacktime, tcp_timer_delack); 1534 } else { 1535 tp->t_flags |= TF_ACKNOW; 1536 } 1537 /* 1538 * Received <SYN,ACK> in SYN_SENT[*] state. 1539 * Transitions: 1540 * SYN_SENT --> ESTABLISHED 1541 * SYN_SENT* --> FIN_WAIT_1 1542 */ 1543 tp->t_starttime = ticks; 1544 if (tp->t_flags & TF_NEEDFIN) { 1545 tp->t_state = TCPS_FIN_WAIT_1; 1546 tp->t_flags &= ~TF_NEEDFIN; 1547 thflags &= ~TH_SYN; 1548 } else { 1549 tp->t_state = TCPS_ESTABLISHED; 1550 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1551 tcp_timer_keep); 1552 } 1553 } else { 1554 /* 1555 * Received initial SYN in SYN-SENT[*] state => 1556 * simultaneous open. If segment contains CC option 1557 * and there is a cached CC, apply TAO test. 1558 * If it succeeds, connection is * half-synchronized. 1559 * Otherwise, do 3-way handshake: 1560 * SYN-SENT -> SYN-RECEIVED 1561 * SYN-SENT* -> SYN-RECEIVED* 1562 * If there was no CC option, clear cached CC value. 1563 */ 1564 tp->t_flags |= TF_ACKNOW; 1565 tcp_callout_stop(tp, tp->tt_rexmt); 1566 if (to.to_flags & TOF_CC) { 1567 if (taop->tao_cc != 0 && 1568 CC_GT(to.to_cc, taop->tao_cc)) { 1569 /* 1570 * update cache and make transition: 1571 * SYN-SENT -> ESTABLISHED* 1572 * SYN-SENT* -> FIN-WAIT-1* 1573 */ 1574 taop->tao_cc = to.to_cc; 1575 tp->t_starttime = ticks; 1576 if (tp->t_flags & TF_NEEDFIN) { 1577 tp->t_state = TCPS_FIN_WAIT_1; 1578 tp->t_flags &= ~TF_NEEDFIN; 1579 } else { 1580 tp->t_state = TCPS_ESTABLISHED; 1581 tcp_callout_reset(tp, 1582 tp->tt_keep, tcp_keepidle, 1583 tcp_timer_keep); 1584 } 1585 tp->t_flags |= TF_NEEDSYN; 1586 } else 1587 tp->t_state = TCPS_SYN_RECEIVED; 1588 } else { 1589 /* CC.NEW or no option => invalidate cache */ 1590 taop->tao_cc = 0; 1591 tp->t_state = TCPS_SYN_RECEIVED; 1592 } 1593 } 1594 1595 trimthenstep6: 1596 /* 1597 * Advance th->th_seq to correspond to first data byte. 1598 * If data, trim to stay within window, 1599 * dropping FIN if necessary. 1600 */ 1601 th->th_seq++; 1602 if (tlen > tp->rcv_wnd) { 1603 todrop = tlen - tp->rcv_wnd; 1604 m_adj(m, -todrop); 1605 tlen = tp->rcv_wnd; 1606 thflags &= ~TH_FIN; 1607 tcpstat.tcps_rcvpackafterwin++; 1608 tcpstat.tcps_rcvbyteafterwin += todrop; 1609 } 1610 tp->snd_wl1 = th->th_seq - 1; 1611 tp->rcv_up = th->th_seq; 1612 /* 1613 * Client side of transaction: already sent SYN and data. 1614 * If the remote host used T/TCP to validate the SYN, 1615 * our data will be ACK'd; if so, enter normal data segment 1616 * processing in the middle of step 5, ack processing. 1617 * Otherwise, goto step 6. 1618 */ 1619 if (thflags & TH_ACK) 1620 goto process_ACK; 1621 1622 goto step6; 1623 1624 /* 1625 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1626 * if segment contains a SYN and CC [not CC.NEW] option: 1627 * if state == TIME_WAIT and connection duration > MSL, 1628 * drop packet and send RST; 1629 * 1630 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1631 * ack the FIN (and data) in retransmission queue. 1632 * Complete close and delete TCPCB. Then reprocess 1633 * segment, hoping to find new TCPCB in LISTEN state; 1634 * 1635 * else must be old SYN; drop it. 1636 * else do normal processing. 1637 */ 1638 case TCPS_LAST_ACK: 1639 case TCPS_CLOSING: 1640 case TCPS_TIME_WAIT: 1641 if ((thflags & TH_SYN) && 1642 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1643 if (tp->t_state == TCPS_TIME_WAIT && 1644 (ticks - tp->t_starttime) > tcp_msl) { 1645 rstreason = BANDLIM_UNLIMITED; 1646 goto dropwithreset; 1647 } 1648 if (CC_GT(to.to_cc, tp->cc_recv)) { 1649 tp = tcp_close(tp); 1650 goto findpcb; 1651 } 1652 else 1653 goto drop; 1654 } 1655 break; /* continue normal processing */ 1656 } 1657 1658 /* 1659 * States other than LISTEN or SYN_SENT. 1660 * First check the RST flag and sequence number since reset segments 1661 * are exempt from the timestamp and connection count tests. This 1662 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1663 * below which allowed reset segments in half the sequence space 1664 * to fall though and be processed (which gives forged reset 1665 * segments with a random sequence number a 50 percent chance of 1666 * killing a connection). 1667 * Then check timestamp, if present. 1668 * Then check the connection count, if present. 1669 * Then check that at least some bytes of segment are within 1670 * receive window. If segment begins before rcv_nxt, 1671 * drop leading data (and SYN); if nothing left, just ack. 1672 * 1673 * 1674 * If the RST bit is set, check the sequence number to see 1675 * if this is a valid reset segment. 1676 * RFC 793 page 37: 1677 * In all states except SYN-SENT, all reset (RST) segments 1678 * are validated by checking their SEQ-fields. A reset is 1679 * valid if its sequence number is in the window. 1680 * Note: this does not take into account delayed ACKs, so 1681 * we should test against last_ack_sent instead of rcv_nxt. 1682 * The sequence number in the reset segment is normally an 1683 * echo of our outgoing acknowledgement numbers, but some hosts 1684 * send a reset with the sequence number at the rightmost edge 1685 * of our receive window, and we have to handle this case. 1686 * If we have multiple segments in flight, the intial reset 1687 * segment sequence numbers will be to the left of last_ack_sent, 1688 * but they will eventually catch up. 1689 * In any case, it never made sense to trim reset segments to 1690 * fit the receive window since RFC 1122 says: 1691 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1692 * 1693 * A TCP SHOULD allow a received RST segment to include data. 1694 * 1695 * DISCUSSION 1696 * It has been suggested that a RST segment could contain 1697 * ASCII text that encoded and explained the cause of the 1698 * RST. No standard has yet been established for such 1699 * data. 1700 * 1701 * If the reset segment passes the sequence number test examine 1702 * the state: 1703 * SYN_RECEIVED STATE: 1704 * If passive open, return to LISTEN state. 1705 * If active open, inform user that connection was refused. 1706 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1707 * Inform user that connection was reset, and close tcb. 1708 * CLOSING, LAST_ACK STATES: 1709 * Close the tcb. 1710 * TIME_WAIT STATE: 1711 * Drop the segment - see Stevens, vol. 2, p. 964 and 1712 * RFC 1337. 1713 */ 1714 if (thflags & TH_RST) { 1715 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1716 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1717 switch (tp->t_state) { 1718 1719 case TCPS_SYN_RECEIVED: 1720 so->so_error = ECONNREFUSED; 1721 goto close; 1722 1723 case TCPS_ESTABLISHED: 1724 case TCPS_FIN_WAIT_1: 1725 case TCPS_FIN_WAIT_2: 1726 case TCPS_CLOSE_WAIT: 1727 so->so_error = ECONNRESET; 1728 close: 1729 tp->t_state = TCPS_CLOSED; 1730 tcpstat.tcps_drops++; 1731 tp = tcp_close(tp); 1732 break; 1733 1734 case TCPS_CLOSING: 1735 case TCPS_LAST_ACK: 1736 tp = tcp_close(tp); 1737 break; 1738 1739 case TCPS_TIME_WAIT: 1740 break; 1741 } 1742 } 1743 goto drop; 1744 } 1745 1746 /* 1747 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1748 * and it's less than ts_recent, drop it. 1749 */ 1750 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1751 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1752 1753 /* Check to see if ts_recent is over 24 days old. */ 1754 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1755 /* 1756 * Invalidate ts_recent. If this segment updates 1757 * ts_recent, the age will be reset later and ts_recent 1758 * will get a valid value. If it does not, setting 1759 * ts_recent to zero will at least satisfy the 1760 * requirement that zero be placed in the timestamp 1761 * echo reply when ts_recent isn't valid. The 1762 * age isn't reset until we get a valid ts_recent 1763 * because we don't want out-of-order segments to be 1764 * dropped when ts_recent is old. 1765 */ 1766 tp->ts_recent = 0; 1767 } else { 1768 tcpstat.tcps_rcvduppack++; 1769 tcpstat.tcps_rcvdupbyte += tlen; 1770 tcpstat.tcps_pawsdrop++; 1771 if (tlen) 1772 goto dropafterack; 1773 goto drop; 1774 } 1775 } 1776 1777 /* 1778 * T/TCP mechanism 1779 * If T/TCP was negotiated and the segment doesn't have CC, 1780 * or if its CC is wrong then drop the segment. 1781 * RST segments do not have to comply with this. 1782 */ 1783 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1784 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc)) 1785 goto dropafterack; 1786 1787 /* 1788 * In the SYN-RECEIVED state, validate that the packet belongs to 1789 * this connection before trimming the data to fit the receive 1790 * window. Check the sequence number versus IRS since we know 1791 * the sequence numbers haven't wrapped. This is a partial fix 1792 * for the "LAND" DoS attack. 1793 */ 1794 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1795 rstreason = BANDLIM_RST_OPENPORT; 1796 goto dropwithreset; 1797 } 1798 1799 todrop = tp->rcv_nxt - th->th_seq; 1800 if (todrop > 0) { 1801 if (TCP_DO_SACK(tp)) { 1802 /* Report duplicate segment at head of packet. */ 1803 tp->reportblk.rblk_start = th->th_seq; 1804 tp->reportblk.rblk_end = th->th_seq + tlen; 1805 if (thflags & TH_FIN) 1806 ++tp->reportblk.rblk_end; 1807 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1808 tp->reportblk.rblk_end = tp->rcv_nxt; 1809 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1810 } 1811 if (thflags & TH_SYN) { 1812 thflags &= ~TH_SYN; 1813 th->th_seq++; 1814 if (th->th_urp > 1) 1815 th->th_urp--; 1816 else 1817 thflags &= ~TH_URG; 1818 todrop--; 1819 } 1820 /* 1821 * Following if statement from Stevens, vol. 2, p. 960. 1822 */ 1823 if (todrop > tlen || 1824 (todrop == tlen && !(thflags & TH_FIN))) { 1825 /* 1826 * Any valid FIN must be to the left of the window. 1827 * At this point the FIN must be a duplicate or out 1828 * of sequence; drop it. 1829 */ 1830 thflags &= ~TH_FIN; 1831 1832 /* 1833 * Send an ACK to resynchronize and drop any data. 1834 * But keep on processing for RST or ACK. 1835 */ 1836 tp->t_flags |= TF_ACKNOW; 1837 todrop = tlen; 1838 tcpstat.tcps_rcvduppack++; 1839 tcpstat.tcps_rcvdupbyte += todrop; 1840 } else { 1841 tcpstat.tcps_rcvpartduppack++; 1842 tcpstat.tcps_rcvpartdupbyte += todrop; 1843 } 1844 drop_hdrlen += todrop; /* drop from the top afterwards */ 1845 th->th_seq += todrop; 1846 tlen -= todrop; 1847 if (th->th_urp > todrop) 1848 th->th_urp -= todrop; 1849 else { 1850 thflags &= ~TH_URG; 1851 th->th_urp = 0; 1852 } 1853 } 1854 1855 /* 1856 * If new data are received on a connection after the 1857 * user processes are gone, then RST the other end. 1858 */ 1859 if ((so->so_state & SS_NOFDREF) && 1860 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1861 tp = tcp_close(tp); 1862 tcpstat.tcps_rcvafterclose++; 1863 rstreason = BANDLIM_UNLIMITED; 1864 goto dropwithreset; 1865 } 1866 1867 /* 1868 * If segment ends after window, drop trailing data 1869 * (and PUSH and FIN); if nothing left, just ACK. 1870 */ 1871 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1872 if (todrop > 0) { 1873 tcpstat.tcps_rcvpackafterwin++; 1874 if (todrop >= tlen) { 1875 tcpstat.tcps_rcvbyteafterwin += tlen; 1876 /* 1877 * If a new connection request is received 1878 * while in TIME_WAIT, drop the old connection 1879 * and start over if the sequence numbers 1880 * are above the previous ones. 1881 */ 1882 if (thflags & TH_SYN && 1883 tp->t_state == TCPS_TIME_WAIT && 1884 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1885 tp = tcp_close(tp); 1886 goto findpcb; 1887 } 1888 /* 1889 * If window is closed can only take segments at 1890 * window edge, and have to drop data and PUSH from 1891 * incoming segments. Continue processing, but 1892 * remember to ack. Otherwise, drop segment 1893 * and ack. 1894 */ 1895 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1896 tp->t_flags |= TF_ACKNOW; 1897 tcpstat.tcps_rcvwinprobe++; 1898 } else 1899 goto dropafterack; 1900 } else 1901 tcpstat.tcps_rcvbyteafterwin += todrop; 1902 m_adj(m, -todrop); 1903 tlen -= todrop; 1904 thflags &= ~(TH_PUSH | TH_FIN); 1905 } 1906 1907 /* 1908 * If last ACK falls within this segment's sequence numbers, 1909 * record its timestamp. 1910 * NOTE: 1911 * 1) That the test incorporates suggestions from the latest 1912 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1913 * 2) That updating only on newer timestamps interferes with 1914 * our earlier PAWS tests, so this check should be solely 1915 * predicated on the sequence space of this segment. 1916 * 3) That we modify the segment boundary check to be 1917 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1918 * instead of RFC1323's 1919 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1920 * This modified check allows us to overcome RFC1323's 1921 * limitations as described in Stevens TCP/IP Illustrated 1922 * Vol. 2 p.869. In such cases, we can still calculate the 1923 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1924 */ 1925 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1926 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1927 + ((thflags & TH_SYN) != 0) 1928 + ((thflags & TH_FIN) != 0)))) { 1929 tp->ts_recent_age = ticks; 1930 tp->ts_recent = to.to_tsval; 1931 } 1932 1933 /* 1934 * If a SYN is in the window, then this is an 1935 * error and we send an RST and drop the connection. 1936 */ 1937 if (thflags & TH_SYN) { 1938 tp = tcp_drop(tp, ECONNRESET); 1939 rstreason = BANDLIM_UNLIMITED; 1940 goto dropwithreset; 1941 } 1942 1943 /* 1944 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1945 * flag is on (half-synchronized state), then queue data for 1946 * later processing; else drop segment and return. 1947 */ 1948 if (!(thflags & TH_ACK)) { 1949 if (tp->t_state == TCPS_SYN_RECEIVED || 1950 (tp->t_flags & TF_NEEDSYN)) 1951 goto step6; 1952 else 1953 goto drop; 1954 } 1955 1956 /* 1957 * Ack processing. 1958 */ 1959 switch (tp->t_state) { 1960 /* 1961 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1962 * ESTABLISHED state and continue processing. 1963 * The ACK was checked above. 1964 */ 1965 case TCPS_SYN_RECEIVED: 1966 1967 tcpstat.tcps_connects++; 1968 soisconnected(so); 1969 /* Do window scaling? */ 1970 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1971 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1972 tp->snd_scale = tp->requested_s_scale; 1973 tp->rcv_scale = tp->request_r_scale; 1974 } 1975 /* 1976 * Upon successful completion of 3-way handshake, 1977 * update cache.CC if it was undefined, pass any queued 1978 * data to the user, and advance state appropriately. 1979 */ 1980 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1981 taop->tao_cc == 0) 1982 taop->tao_cc = tp->cc_recv; 1983 1984 /* 1985 * Make transitions: 1986 * SYN-RECEIVED -> ESTABLISHED 1987 * SYN-RECEIVED* -> FIN-WAIT-1 1988 */ 1989 tp->t_starttime = ticks; 1990 if (tp->t_flags & TF_NEEDFIN) { 1991 tp->t_state = TCPS_FIN_WAIT_1; 1992 tp->t_flags &= ~TF_NEEDFIN; 1993 } else { 1994 tp->t_state = TCPS_ESTABLISHED; 1995 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 1996 tcp_timer_keep); 1997 } 1998 /* 1999 * If segment contains data or ACK, will call tcp_reass() 2000 * later; if not, do so now to pass queued data to user. 2001 */ 2002 if (tlen == 0 && !(thflags & TH_FIN)) 2003 tcp_reass(tp, NULL, NULL, NULL); 2004 /* fall into ... */ 2005 2006 /* 2007 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2008 * ACKs. If the ack is in the range 2009 * tp->snd_una < th->th_ack <= tp->snd_max 2010 * then advance tp->snd_una to th->th_ack and drop 2011 * data from the retransmission queue. If this ACK reflects 2012 * more up to date window information we update our window information. 2013 */ 2014 case TCPS_ESTABLISHED: 2015 case TCPS_FIN_WAIT_1: 2016 case TCPS_FIN_WAIT_2: 2017 case TCPS_CLOSE_WAIT: 2018 case TCPS_CLOSING: 2019 case TCPS_LAST_ACK: 2020 case TCPS_TIME_WAIT: 2021 2022 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2023 if (TCP_DO_SACK(tp)) 2024 tcp_sack_update_scoreboard(tp, &to); 2025 if (tlen != 0 || tiwin != tp->snd_wnd) { 2026 tp->t_dupacks = 0; 2027 break; 2028 } 2029 tcpstat.tcps_rcvdupack++; 2030 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2031 th->th_ack != tp->snd_una) { 2032 tp->t_dupacks = 0; 2033 break; 2034 } 2035 /* 2036 * We have outstanding data (other than 2037 * a window probe), this is a completely 2038 * duplicate ack (ie, window info didn't 2039 * change), the ack is the biggest we've 2040 * seen and we've seen exactly our rexmt 2041 * threshhold of them, so assume a packet 2042 * has been dropped and retransmit it. 2043 * Kludge snd_nxt & the congestion 2044 * window so we send only this one 2045 * packet. 2046 */ 2047 if (IN_FASTRECOVERY(tp)) { 2048 if (TCP_DO_SACK(tp)) { 2049 /* No artifical cwnd inflation. */ 2050 tcp_sack_rexmt(tp, th); 2051 } else { 2052 /* 2053 * Dup acks mean that packets 2054 * have left the network 2055 * (they're now cached at the 2056 * receiver) so bump cwnd by 2057 * the amount in the receiver 2058 * to keep a constant cwnd 2059 * packets in the network. 2060 */ 2061 tp->snd_cwnd += tp->t_maxseg; 2062 tcp_output(tp); 2063 } 2064 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2065 tp->t_dupacks = 0; 2066 break; 2067 } else if (++tp->t_dupacks == tcprexmtthresh) { 2068 tcp_seq old_snd_nxt; 2069 u_int win; 2070 2071 fastretransmit: 2072 if (tcp_do_eifel_detect && 2073 (tp->t_flags & TF_RCVD_TSTMP)) { 2074 tcp_save_congestion_state(tp); 2075 tp->t_flags |= TF_FASTREXMT; 2076 } 2077 /* 2078 * We know we're losing at the current 2079 * window size, so do congestion avoidance: 2080 * set ssthresh to half the current window 2081 * and pull our congestion window back to the 2082 * new ssthresh. 2083 */ 2084 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 2085 tp->t_maxseg; 2086 if (win < 2) 2087 win = 2; 2088 tp->snd_ssthresh = win * tp->t_maxseg; 2089 ENTER_FASTRECOVERY(tp); 2090 tp->snd_recover = tp->snd_max; 2091 tcp_callout_stop(tp, tp->tt_rexmt); 2092 tp->t_rtttime = 0; 2093 old_snd_nxt = tp->snd_nxt; 2094 tp->snd_nxt = th->th_ack; 2095 tp->snd_cwnd = tp->t_maxseg; 2096 tcp_output(tp); 2097 ++tcpstat.tcps_sndfastrexmit; 2098 tp->snd_cwnd = tp->snd_ssthresh; 2099 tp->rexmt_high = tp->snd_nxt; 2100 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 2101 tp->snd_nxt = old_snd_nxt; 2102 KASSERT(tp->snd_limited <= 2, 2103 ("tp->snd_limited too big")); 2104 if (TCP_DO_SACK(tp)) 2105 tcp_sack_rexmt(tp, th); 2106 else 2107 tp->snd_cwnd += tp->t_maxseg * 2108 (tp->t_dupacks - tp->snd_limited); 2109 } else if (tcp_do_limitedtransmit) { 2110 u_long oldcwnd = tp->snd_cwnd; 2111 tcp_seq oldsndmax = tp->snd_max; 2112 tcp_seq oldsndnxt = tp->snd_nxt; 2113 /* outstanding data */ 2114 uint32_t ownd = tp->snd_max - tp->snd_una; 2115 u_int sent; 2116 2117 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2118 2119 KASSERT(tp->t_dupacks == 1 || 2120 tp->t_dupacks == 2, 2121 ("dupacks not 1 or 2")); 2122 if (tp->t_dupacks == 1) 2123 tp->snd_limited = 0; 2124 tp->snd_nxt = tp->snd_max; 2125 tp->snd_cwnd = ownd + 2126 (tp->t_dupacks - tp->snd_limited) * 2127 tp->t_maxseg; 2128 tcp_output(tp); 2129 2130 /* 2131 * Other acks may have been processed, 2132 * snd_nxt cannot be reset to a value less 2133 * then snd_una. 2134 */ 2135 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2136 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2137 tp->snd_nxt = oldsndnxt; 2138 else 2139 tp->snd_nxt = tp->snd_una; 2140 } 2141 tp->snd_cwnd = oldcwnd; 2142 sent = tp->snd_max - oldsndmax; 2143 if (sent > tp->t_maxseg) { 2144 KASSERT((tp->t_dupacks == 2 && 2145 tp->snd_limited == 0) || 2146 (sent == tp->t_maxseg + 1 && 2147 tp->t_flags & TF_SENTFIN), 2148 ("sent too much")); 2149 KASSERT(sent <= tp->t_maxseg * 2, 2150 ("sent too many segments")); 2151 tp->snd_limited = 2; 2152 tcpstat.tcps_sndlimited += 2; 2153 } else if (sent > 0) { 2154 ++tp->snd_limited; 2155 ++tcpstat.tcps_sndlimited; 2156 } else if (tcp_do_early_retransmit && 2157 (tcp_do_eifel_detect && 2158 (tp->t_flags & TF_RCVD_TSTMP)) && 2159 ownd < 4 * tp->t_maxseg && 2160 tp->t_dupacks + 1 >= 2161 iceildiv(ownd, tp->t_maxseg) && 2162 (!TCP_DO_SACK(tp) || 2163 ownd <= tp->t_maxseg || 2164 tcp_sack_has_sacked(&tp->scb, 2165 ownd - tp->t_maxseg))) { 2166 ++tcpstat.tcps_sndearlyrexmit; 2167 tp->t_flags |= TF_EARLYREXMT; 2168 goto fastretransmit; 2169 } 2170 } 2171 goto drop; 2172 } 2173 2174 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2175 tp->t_dupacks = 0; 2176 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2177 /* 2178 * Detected optimistic ACK attack. 2179 * Force slow-start to de-synchronize attack. 2180 */ 2181 tp->snd_cwnd = tp->t_maxseg; 2182 tp->snd_wacked = 0; 2183 2184 tcpstat.tcps_rcvacktoomuch++; 2185 goto dropafterack; 2186 } 2187 /* 2188 * If we reach this point, ACK is not a duplicate, 2189 * i.e., it ACKs something we sent. 2190 */ 2191 if (tp->t_flags & TF_NEEDSYN) { 2192 /* 2193 * T/TCP: Connection was half-synchronized, and our 2194 * SYN has been ACK'd (so connection is now fully 2195 * synchronized). Go to non-starred state, 2196 * increment snd_una for ACK of SYN, and check if 2197 * we can do window scaling. 2198 */ 2199 tp->t_flags &= ~TF_NEEDSYN; 2200 tp->snd_una++; 2201 /* Do window scaling? */ 2202 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2203 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2204 tp->snd_scale = tp->requested_s_scale; 2205 tp->rcv_scale = tp->request_r_scale; 2206 } 2207 } 2208 2209 process_ACK: 2210 acked = th->th_ack - tp->snd_una; 2211 tcpstat.tcps_rcvackpack++; 2212 tcpstat.tcps_rcvackbyte += acked; 2213 2214 if (tcp_do_eifel_detect && acked > 0 && 2215 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2216 (tp->t_flags & TF_FIRSTACCACK)) { 2217 /* Eifel detection applicable. */ 2218 if (to.to_tsecr < tp->t_rexmtTS) { 2219 ++tcpstat.tcps_eifeldetected; 2220 tcp_revert_congestion_state(tp); 2221 if (tp->t_rxtshift == 1 && 2222 ticks >= tp->t_badrxtwin) 2223 ++tcpstat.tcps_rttcantdetect; 2224 } 2225 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2226 /* 2227 * If we just performed our first retransmit, 2228 * and the ACK arrives within our recovery window, 2229 * then it was a mistake to do the retransmit 2230 * in the first place. Recover our original cwnd 2231 * and ssthresh, and proceed to transmit where we 2232 * left off. 2233 */ 2234 tcp_revert_congestion_state(tp); 2235 ++tcpstat.tcps_rttdetected; 2236 } 2237 2238 /* 2239 * If we have a timestamp reply, update smoothed 2240 * round trip time. If no timestamp is present but 2241 * transmit timer is running and timed sequence 2242 * number was acked, update smoothed round trip time. 2243 * Since we now have an rtt measurement, cancel the 2244 * timer backoff (cf., Phil Karn's retransmit alg.). 2245 * Recompute the initial retransmit timer. 2246 * 2247 * Some machines (certain windows boxes) send broken 2248 * timestamp replies during the SYN+ACK phase, ignore 2249 * timestamps of 0. 2250 */ 2251 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2252 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2253 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2254 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2255 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2256 2257 /* 2258 * If no data (only SYN) was ACK'd, 2259 * skip rest of ACK processing. 2260 */ 2261 if (acked == 0) 2262 goto step6; 2263 2264 /* Stop looking for an acceptable ACK since one was received. */ 2265 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2266 2267 if (acked > so->so_snd.ssb_cc) { 2268 tp->snd_wnd -= so->so_snd.ssb_cc; 2269 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2270 ourfinisacked = TRUE; 2271 } else { 2272 sbdrop(&so->so_snd.sb, acked); 2273 tp->snd_wnd -= acked; 2274 ourfinisacked = FALSE; 2275 } 2276 sowwakeup(so); 2277 2278 /* 2279 * Update window information. 2280 * Don't look at window if no ACK: 2281 * TAC's send garbage on first SYN. 2282 */ 2283 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2284 (tp->snd_wl1 == th->th_seq && 2285 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2286 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2287 /* keep track of pure window updates */ 2288 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2289 tiwin > tp->snd_wnd) 2290 tcpstat.tcps_rcvwinupd++; 2291 tp->snd_wnd = tiwin; 2292 tp->snd_wl1 = th->th_seq; 2293 tp->snd_wl2 = th->th_ack; 2294 if (tp->snd_wnd > tp->max_sndwnd) 2295 tp->max_sndwnd = tp->snd_wnd; 2296 needoutput = TRUE; 2297 } 2298 2299 tp->snd_una = th->th_ack; 2300 if (TCP_DO_SACK(tp)) 2301 tcp_sack_update_scoreboard(tp, &to); 2302 if (IN_FASTRECOVERY(tp)) { 2303 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2304 EXIT_FASTRECOVERY(tp); 2305 needoutput = TRUE; 2306 /* 2307 * If the congestion window was inflated 2308 * to account for the other side's 2309 * cached packets, retract it. 2310 */ 2311 if (!TCP_DO_SACK(tp)) 2312 tp->snd_cwnd = tp->snd_ssthresh; 2313 2314 /* 2315 * Window inflation should have left us 2316 * with approximately snd_ssthresh outstanding 2317 * data. But, in case we would be inclined 2318 * to send a burst, better do it using 2319 * slow start. 2320 */ 2321 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2322 tp->snd_max + 2 * tp->t_maxseg)) 2323 tp->snd_cwnd = 2324 (tp->snd_max - tp->snd_una) + 2325 2 * tp->t_maxseg; 2326 2327 tp->snd_wacked = 0; 2328 } else { 2329 if (TCP_DO_SACK(tp)) { 2330 tp->snd_max_rexmt = tp->snd_max; 2331 tcp_sack_rexmt(tp, th); 2332 } else { 2333 tcp_newreno_partial_ack(tp, th, acked); 2334 } 2335 needoutput = FALSE; 2336 } 2337 } else { 2338 /* 2339 * Open the congestion window. When in slow-start, 2340 * open exponentially: maxseg per packet. Otherwise, 2341 * open linearly: maxseg per window. 2342 */ 2343 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2344 u_int abc_sslimit = 2345 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2346 tp->t_maxseg : 2 * tp->t_maxseg); 2347 2348 /* slow-start */ 2349 tp->snd_cwnd += tcp_do_abc ? 2350 min(acked, abc_sslimit) : tp->t_maxseg; 2351 } else { 2352 /* linear increase */ 2353 tp->snd_wacked += tcp_do_abc ? acked : 2354 tp->t_maxseg; 2355 if (tp->snd_wacked >= tp->snd_cwnd) { 2356 tp->snd_wacked -= tp->snd_cwnd; 2357 tp->snd_cwnd += tp->t_maxseg; 2358 } 2359 } 2360 tp->snd_cwnd = min(tp->snd_cwnd, 2361 TCP_MAXWIN << tp->snd_scale); 2362 tp->snd_recover = th->th_ack - 1; 2363 } 2364 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2365 tp->snd_nxt = tp->snd_una; 2366 2367 /* 2368 * If all outstanding data is acked, stop retransmit 2369 * timer and remember to restart (more output or persist). 2370 * If there is more data to be acked, restart retransmit 2371 * timer, using current (possibly backed-off) value. 2372 */ 2373 if (th->th_ack == tp->snd_max) { 2374 tcp_callout_stop(tp, tp->tt_rexmt); 2375 needoutput = TRUE; 2376 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2377 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2378 tcp_timer_rexmt); 2379 } 2380 2381 switch (tp->t_state) { 2382 /* 2383 * In FIN_WAIT_1 STATE in addition to the processing 2384 * for the ESTABLISHED state if our FIN is now acknowledged 2385 * then enter FIN_WAIT_2. 2386 */ 2387 case TCPS_FIN_WAIT_1: 2388 if (ourfinisacked) { 2389 /* 2390 * If we can't receive any more 2391 * data, then closing user can proceed. 2392 * Starting the timer is contrary to the 2393 * specification, but if we don't get a FIN 2394 * we'll hang forever. 2395 */ 2396 if (so->so_state & SS_CANTRCVMORE) { 2397 soisdisconnected(so); 2398 tcp_callout_reset(tp, tp->tt_2msl, 2399 tcp_maxidle, tcp_timer_2msl); 2400 } 2401 tp->t_state = TCPS_FIN_WAIT_2; 2402 } 2403 break; 2404 2405 /* 2406 * In CLOSING STATE in addition to the processing for 2407 * the ESTABLISHED state if the ACK acknowledges our FIN 2408 * then enter the TIME-WAIT state, otherwise ignore 2409 * the segment. 2410 */ 2411 case TCPS_CLOSING: 2412 if (ourfinisacked) { 2413 tp->t_state = TCPS_TIME_WAIT; 2414 tcp_canceltimers(tp); 2415 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2416 if (tp->cc_recv != 0 && 2417 (ticks - tp->t_starttime) < tcp_msl) { 2418 tcp_callout_reset(tp, tp->tt_2msl, 2419 tp->t_rxtcur * TCPTV_TWTRUNC, 2420 tcp_timer_2msl); 2421 } else { 2422 tcp_callout_reset(tp, tp->tt_2msl, 2423 2 * tcp_msl, tcp_timer_2msl); 2424 } 2425 soisdisconnected(so); 2426 } 2427 break; 2428 2429 /* 2430 * In LAST_ACK, we may still be waiting for data to drain 2431 * and/or to be acked, as well as for the ack of our FIN. 2432 * If our FIN is now acknowledged, delete the TCB, 2433 * enter the closed state and return. 2434 */ 2435 case TCPS_LAST_ACK: 2436 if (ourfinisacked) { 2437 tp = tcp_close(tp); 2438 goto drop; 2439 } 2440 break; 2441 2442 /* 2443 * In TIME_WAIT state the only thing that should arrive 2444 * is a retransmission of the remote FIN. Acknowledge 2445 * it and restart the finack timer. 2446 */ 2447 case TCPS_TIME_WAIT: 2448 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2449 tcp_timer_2msl); 2450 goto dropafterack; 2451 } 2452 } 2453 2454 step6: 2455 /* 2456 * Update window information. 2457 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2458 */ 2459 if ((thflags & TH_ACK) && 2460 acceptable_window_update(tp, th, tiwin)) { 2461 /* keep track of pure window updates */ 2462 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2463 tiwin > tp->snd_wnd) 2464 tcpstat.tcps_rcvwinupd++; 2465 tp->snd_wnd = tiwin; 2466 tp->snd_wl1 = th->th_seq; 2467 tp->snd_wl2 = th->th_ack; 2468 if (tp->snd_wnd > tp->max_sndwnd) 2469 tp->max_sndwnd = tp->snd_wnd; 2470 needoutput = TRUE; 2471 } 2472 2473 /* 2474 * Process segments with URG. 2475 */ 2476 if ((thflags & TH_URG) && th->th_urp && 2477 !TCPS_HAVERCVDFIN(tp->t_state)) { 2478 /* 2479 * This is a kludge, but if we receive and accept 2480 * random urgent pointers, we'll crash in 2481 * soreceive. It's hard to imagine someone 2482 * actually wanting to send this much urgent data. 2483 */ 2484 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2485 th->th_urp = 0; /* XXX */ 2486 thflags &= ~TH_URG; /* XXX */ 2487 goto dodata; /* XXX */ 2488 } 2489 /* 2490 * If this segment advances the known urgent pointer, 2491 * then mark the data stream. This should not happen 2492 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2493 * a FIN has been received from the remote side. 2494 * In these states we ignore the URG. 2495 * 2496 * According to RFC961 (Assigned Protocols), 2497 * the urgent pointer points to the last octet 2498 * of urgent data. We continue, however, 2499 * to consider it to indicate the first octet 2500 * of data past the urgent section as the original 2501 * spec states (in one of two places). 2502 */ 2503 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2504 tp->rcv_up = th->th_seq + th->th_urp; 2505 so->so_oobmark = so->so_rcv.ssb_cc + 2506 (tp->rcv_up - tp->rcv_nxt) - 1; 2507 if (so->so_oobmark == 0) 2508 so->so_state |= SS_RCVATMARK; 2509 sohasoutofband(so); 2510 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2511 } 2512 /* 2513 * Remove out of band data so doesn't get presented to user. 2514 * This can happen independent of advancing the URG pointer, 2515 * but if two URG's are pending at once, some out-of-band 2516 * data may creep in... ick. 2517 */ 2518 if (th->th_urp <= (u_long)tlen && 2519 !(so->so_options & SO_OOBINLINE)) { 2520 /* hdr drop is delayed */ 2521 tcp_pulloutofband(so, th, m, drop_hdrlen); 2522 } 2523 } else { 2524 /* 2525 * If no out of band data is expected, 2526 * pull receive urgent pointer along 2527 * with the receive window. 2528 */ 2529 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2530 tp->rcv_up = tp->rcv_nxt; 2531 } 2532 2533 dodata: /* XXX */ 2534 /* 2535 * Process the segment text, merging it into the TCP sequencing queue, 2536 * and arranging for acknowledgment of receipt if necessary. 2537 * This process logically involves adjusting tp->rcv_wnd as data 2538 * is presented to the user (this happens in tcp_usrreq.c, 2539 * case PRU_RCVD). If a FIN has already been received on this 2540 * connection then we just ignore the text. 2541 */ 2542 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2543 m_adj(m, drop_hdrlen); /* delayed header drop */ 2544 /* 2545 * Insert segment which includes th into TCP reassembly queue 2546 * with control block tp. Set thflags to whether reassembly now 2547 * includes a segment with FIN. This handles the common case 2548 * inline (segment is the next to be received on an established 2549 * connection, and the queue is empty), avoiding linkage into 2550 * and removal from the queue and repetition of various 2551 * conversions. 2552 * Set DELACK for segments received in order, but ack 2553 * immediately when segments are out of order (so 2554 * fast retransmit can work). 2555 */ 2556 if (th->th_seq == tp->rcv_nxt && 2557 LIST_EMPTY(&tp->t_segq) && 2558 TCPS_HAVEESTABLISHED(tp->t_state)) { 2559 if (DELAY_ACK(tp)) { 2560 tcp_callout_reset(tp, tp->tt_delack, 2561 tcp_delacktime, tcp_timer_delack); 2562 } else { 2563 tp->t_flags |= TF_ACKNOW; 2564 } 2565 tp->rcv_nxt += tlen; 2566 thflags = th->th_flags & TH_FIN; 2567 tcpstat.tcps_rcvpack++; 2568 tcpstat.tcps_rcvbyte += tlen; 2569 ND6_HINT(tp); 2570 if (so->so_state & SS_CANTRCVMORE) 2571 m_freem(m); 2572 else 2573 ssb_appendstream(&so->so_rcv, m); 2574 sorwakeup(so); 2575 } else { 2576 if (!(tp->t_flags & TF_DUPSEG)) { 2577 /* Initialize SACK report block. */ 2578 tp->reportblk.rblk_start = th->th_seq; 2579 tp->reportblk.rblk_end = th->th_seq + tlen + 2580 ((thflags & TH_FIN) != 0); 2581 } 2582 thflags = tcp_reass(tp, th, &tlen, m); 2583 tp->t_flags |= TF_ACKNOW; 2584 } 2585 2586 /* 2587 * Note the amount of data that peer has sent into 2588 * our window, in order to estimate the sender's 2589 * buffer size. 2590 */ 2591 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2592 } else { 2593 m_freem(m); 2594 thflags &= ~TH_FIN; 2595 } 2596 2597 /* 2598 * If FIN is received ACK the FIN and let the user know 2599 * that the connection is closing. 2600 */ 2601 if (thflags & TH_FIN) { 2602 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2603 socantrcvmore(so); 2604 /* 2605 * If connection is half-synchronized 2606 * (ie NEEDSYN flag on) then delay ACK, 2607 * so it may be piggybacked when SYN is sent. 2608 * Otherwise, since we received a FIN then no 2609 * more input can be expected, send ACK now. 2610 */ 2611 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2612 tcp_callout_reset(tp, tp->tt_delack, 2613 tcp_delacktime, tcp_timer_delack); 2614 } else { 2615 tp->t_flags |= TF_ACKNOW; 2616 } 2617 tp->rcv_nxt++; 2618 } 2619 2620 switch (tp->t_state) { 2621 /* 2622 * In SYN_RECEIVED and ESTABLISHED STATES 2623 * enter the CLOSE_WAIT state. 2624 */ 2625 case TCPS_SYN_RECEIVED: 2626 tp->t_starttime = ticks; 2627 /*FALLTHROUGH*/ 2628 case TCPS_ESTABLISHED: 2629 tp->t_state = TCPS_CLOSE_WAIT; 2630 break; 2631 2632 /* 2633 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2634 * enter the CLOSING state. 2635 */ 2636 case TCPS_FIN_WAIT_1: 2637 tp->t_state = TCPS_CLOSING; 2638 break; 2639 2640 /* 2641 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2642 * starting the time-wait timer, turning off the other 2643 * standard timers. 2644 */ 2645 case TCPS_FIN_WAIT_2: 2646 tp->t_state = TCPS_TIME_WAIT; 2647 tcp_canceltimers(tp); 2648 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2649 if (tp->cc_recv != 0 && 2650 (ticks - tp->t_starttime) < tcp_msl) { 2651 tcp_callout_reset(tp, tp->tt_2msl, 2652 tp->t_rxtcur * TCPTV_TWTRUNC, 2653 tcp_timer_2msl); 2654 /* For transaction client, force ACK now. */ 2655 tp->t_flags |= TF_ACKNOW; 2656 } else { 2657 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2658 tcp_timer_2msl); 2659 } 2660 soisdisconnected(so); 2661 break; 2662 2663 /* 2664 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2665 */ 2666 case TCPS_TIME_WAIT: 2667 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2668 tcp_timer_2msl); 2669 break; 2670 } 2671 } 2672 2673 #ifdef TCPDEBUG 2674 if (so->so_options & SO_DEBUG) 2675 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2676 #endif 2677 2678 /* 2679 * Return any desired output. 2680 */ 2681 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2682 tcp_output(tp); 2683 return; 2684 2685 dropafterack: 2686 /* 2687 * Generate an ACK dropping incoming segment if it occupies 2688 * sequence space, where the ACK reflects our state. 2689 * 2690 * We can now skip the test for the RST flag since all 2691 * paths to this code happen after packets containing 2692 * RST have been dropped. 2693 * 2694 * In the SYN-RECEIVED state, don't send an ACK unless the 2695 * segment we received passes the SYN-RECEIVED ACK test. 2696 * If it fails send a RST. This breaks the loop in the 2697 * "LAND" DoS attack, and also prevents an ACK storm 2698 * between two listening ports that have been sent forged 2699 * SYN segments, each with the source address of the other. 2700 */ 2701 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2702 (SEQ_GT(tp->snd_una, th->th_ack) || 2703 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2704 rstreason = BANDLIM_RST_OPENPORT; 2705 goto dropwithreset; 2706 } 2707 #ifdef TCPDEBUG 2708 if (so->so_options & SO_DEBUG) 2709 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2710 #endif 2711 m_freem(m); 2712 tp->t_flags |= TF_ACKNOW; 2713 tcp_output(tp); 2714 return; 2715 2716 dropwithreset: 2717 /* 2718 * Generate a RST, dropping incoming segment. 2719 * Make ACK acceptable to originator of segment. 2720 * Don't bother to respond if destination was broadcast/multicast. 2721 */ 2722 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2723 goto drop; 2724 if (isipv6) { 2725 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2726 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2727 goto drop; 2728 } else { 2729 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2730 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2731 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2732 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2733 goto drop; 2734 } 2735 /* IPv6 anycast check is done at tcp6_input() */ 2736 2737 /* 2738 * Perform bandwidth limiting. 2739 */ 2740 #ifdef ICMP_BANDLIM 2741 if (badport_bandlim(rstreason) < 0) 2742 goto drop; 2743 #endif 2744 2745 #ifdef TCPDEBUG 2746 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2747 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2748 #endif 2749 if (thflags & TH_ACK) 2750 /* mtod() below is safe as long as hdr dropping is delayed */ 2751 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2752 TH_RST); 2753 else { 2754 if (thflags & TH_SYN) 2755 tlen++; 2756 /* mtod() below is safe as long as hdr dropping is delayed */ 2757 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2758 (tcp_seq)0, TH_RST | TH_ACK); 2759 } 2760 return; 2761 2762 drop: 2763 /* 2764 * Drop space held by incoming segment and return. 2765 */ 2766 #ifdef TCPDEBUG 2767 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2768 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2769 #endif 2770 m_freem(m); 2771 return; 2772 } 2773 2774 /* 2775 * Parse TCP options and place in tcpopt. 2776 */ 2777 static void 2778 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2779 { 2780 int opt, optlen, i; 2781 2782 to->to_flags = 0; 2783 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2784 opt = cp[0]; 2785 if (opt == TCPOPT_EOL) 2786 break; 2787 if (opt == TCPOPT_NOP) 2788 optlen = 1; 2789 else { 2790 if (cnt < 2) 2791 break; 2792 optlen = cp[1]; 2793 if (optlen < 2 || optlen > cnt) 2794 break; 2795 } 2796 switch (opt) { 2797 case TCPOPT_MAXSEG: 2798 if (optlen != TCPOLEN_MAXSEG) 2799 continue; 2800 if (!is_syn) 2801 continue; 2802 to->to_flags |= TOF_MSS; 2803 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2804 to->to_mss = ntohs(to->to_mss); 2805 break; 2806 case TCPOPT_WINDOW: 2807 if (optlen != TCPOLEN_WINDOW) 2808 continue; 2809 if (!is_syn) 2810 continue; 2811 to->to_flags |= TOF_SCALE; 2812 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2813 break; 2814 case TCPOPT_TIMESTAMP: 2815 if (optlen != TCPOLEN_TIMESTAMP) 2816 continue; 2817 to->to_flags |= TOF_TS; 2818 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2819 to->to_tsval = ntohl(to->to_tsval); 2820 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2821 to->to_tsecr = ntohl(to->to_tsecr); 2822 /* 2823 * If echoed timestamp is later than the current time, 2824 * fall back to non RFC1323 RTT calculation. 2825 */ 2826 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2827 to->to_tsecr = 0; 2828 break; 2829 case TCPOPT_CC: 2830 if (optlen != TCPOLEN_CC) 2831 continue; 2832 to->to_flags |= TOF_CC; 2833 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2834 to->to_cc = ntohl(to->to_cc); 2835 break; 2836 case TCPOPT_CCNEW: 2837 if (optlen != TCPOLEN_CC) 2838 continue; 2839 if (!is_syn) 2840 continue; 2841 to->to_flags |= TOF_CCNEW; 2842 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc); 2843 to->to_cc = ntohl(to->to_cc); 2844 break; 2845 case TCPOPT_CCECHO: 2846 if (optlen != TCPOLEN_CC) 2847 continue; 2848 if (!is_syn) 2849 continue; 2850 to->to_flags |= TOF_CCECHO; 2851 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho); 2852 to->to_ccecho = ntohl(to->to_ccecho); 2853 break; 2854 case TCPOPT_SACK_PERMITTED: 2855 if (optlen != TCPOLEN_SACK_PERMITTED) 2856 continue; 2857 if (!is_syn) 2858 continue; 2859 to->to_flags |= TOF_SACK_PERMITTED; 2860 break; 2861 case TCPOPT_SACK: 2862 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2863 continue; 2864 to->to_nsackblocks = (optlen - 2) / 8; 2865 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2866 to->to_flags |= TOF_SACK; 2867 for (i = 0; i < to->to_nsackblocks; i++) { 2868 struct raw_sackblock *r = &to->to_sackblocks[i]; 2869 2870 r->rblk_start = ntohl(r->rblk_start); 2871 r->rblk_end = ntohl(r->rblk_end); 2872 } 2873 break; 2874 default: 2875 continue; 2876 } 2877 } 2878 } 2879 2880 /* 2881 * Pull out of band byte out of a segment so 2882 * it doesn't appear in the user's data queue. 2883 * It is still reflected in the segment length for 2884 * sequencing purposes. 2885 * "off" is the delayed to be dropped hdrlen. 2886 */ 2887 static void 2888 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2889 { 2890 int cnt = off + th->th_urp - 1; 2891 2892 while (cnt >= 0) { 2893 if (m->m_len > cnt) { 2894 char *cp = mtod(m, caddr_t) + cnt; 2895 struct tcpcb *tp = sototcpcb(so); 2896 2897 tp->t_iobc = *cp; 2898 tp->t_oobflags |= TCPOOB_HAVEDATA; 2899 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2900 m->m_len--; 2901 if (m->m_flags & M_PKTHDR) 2902 m->m_pkthdr.len--; 2903 return; 2904 } 2905 cnt -= m->m_len; 2906 m = m->m_next; 2907 if (m == 0) 2908 break; 2909 } 2910 panic("tcp_pulloutofband"); 2911 } 2912 2913 /* 2914 * Collect new round-trip time estimate 2915 * and update averages and current timeout. 2916 */ 2917 static void 2918 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2919 { 2920 int delta; 2921 2922 tcpstat.tcps_rttupdated++; 2923 tp->t_rttupdated++; 2924 if (tp->t_srtt != 0) { 2925 /* 2926 * srtt is stored as fixed point with 5 bits after the 2927 * binary point (i.e., scaled by 8). The following magic 2928 * is equivalent to the smoothing algorithm in rfc793 with 2929 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2930 * point). Adjust rtt to origin 0. 2931 */ 2932 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2933 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2934 2935 if ((tp->t_srtt += delta) <= 0) 2936 tp->t_srtt = 1; 2937 2938 /* 2939 * We accumulate a smoothed rtt variance (actually, a 2940 * smoothed mean difference), then set the retransmit 2941 * timer to smoothed rtt + 4 times the smoothed variance. 2942 * rttvar is stored as fixed point with 4 bits after the 2943 * binary point (scaled by 16). The following is 2944 * equivalent to rfc793 smoothing with an alpha of .75 2945 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2946 * rfc793's wired-in beta. 2947 */ 2948 if (delta < 0) 2949 delta = -delta; 2950 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2951 if ((tp->t_rttvar += delta) <= 0) 2952 tp->t_rttvar = 1; 2953 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2954 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2955 } else { 2956 /* 2957 * No rtt measurement yet - use the unsmoothed rtt. 2958 * Set the variance to half the rtt (so our first 2959 * retransmit happens at 3*rtt). 2960 */ 2961 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2962 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2963 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2964 } 2965 tp->t_rtttime = 0; 2966 tp->t_rxtshift = 0; 2967 2968 /* 2969 * the retransmit should happen at rtt + 4 * rttvar. 2970 * Because of the way we do the smoothing, srtt and rttvar 2971 * will each average +1/2 tick of bias. When we compute 2972 * the retransmit timer, we want 1/2 tick of rounding and 2973 * 1 extra tick because of +-1/2 tick uncertainty in the 2974 * firing of the timer. The bias will give us exactly the 2975 * 1.5 tick we need. But, because the bias is 2976 * statistical, we have to test that we don't drop below 2977 * the minimum feasible timer (which is 2 ticks). 2978 */ 2979 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2980 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2981 2982 /* 2983 * We received an ack for a packet that wasn't retransmitted; 2984 * it is probably safe to discard any error indications we've 2985 * received recently. This isn't quite right, but close enough 2986 * for now (a route might have failed after we sent a segment, 2987 * and the return path might not be symmetrical). 2988 */ 2989 tp->t_softerror = 0; 2990 } 2991 2992 /* 2993 * Determine a reasonable value for maxseg size. 2994 * If the route is known, check route for mtu. 2995 * If none, use an mss that can be handled on the outgoing 2996 * interface without forcing IP to fragment; if bigger than 2997 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2998 * to utilize large mbufs. If no route is found, route has no mtu, 2999 * or the destination isn't local, use a default, hopefully conservative 3000 * size (usually 512 or the default IP max size, but no more than the mtu 3001 * of the interface), as we can't discover anything about intervening 3002 * gateways or networks. We also initialize the congestion/slow start 3003 * window to be a single segment if the destination isn't local. 3004 * While looking at the routing entry, we also initialize other path-dependent 3005 * parameters from pre-set or cached values in the routing entry. 3006 * 3007 * Also take into account the space needed for options that we 3008 * send regularly. Make maxseg shorter by that amount to assure 3009 * that we can send maxseg amount of data even when the options 3010 * are present. Store the upper limit of the length of options plus 3011 * data in maxopd. 3012 * 3013 * NOTE that this routine is only called when we process an incoming 3014 * segment, for outgoing segments only tcp_mssopt is called. 3015 * 3016 * In case of T/TCP, we call this routine during implicit connection 3017 * setup as well (offer = -1), to initialize maxseg from the cached 3018 * MSS of our peer. 3019 */ 3020 void 3021 tcp_mss(struct tcpcb *tp, int offer) 3022 { 3023 struct rtentry *rt; 3024 struct ifnet *ifp; 3025 int rtt, mss; 3026 u_long bufsize; 3027 struct inpcb *inp = tp->t_inpcb; 3028 struct socket *so; 3029 struct rmxp_tao *taop; 3030 int origoffer = offer; 3031 #ifdef INET6 3032 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3033 size_t min_protoh = isipv6 ? 3034 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3035 sizeof(struct tcpiphdr); 3036 #else 3037 const boolean_t isipv6 = FALSE; 3038 const size_t min_protoh = sizeof(struct tcpiphdr); 3039 #endif 3040 3041 if (isipv6) 3042 rt = tcp_rtlookup6(&inp->inp_inc); 3043 else 3044 rt = tcp_rtlookup(&inp->inp_inc); 3045 if (rt == NULL) { 3046 tp->t_maxopd = tp->t_maxseg = 3047 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3048 return; 3049 } 3050 ifp = rt->rt_ifp; 3051 so = inp->inp_socket; 3052 3053 taop = rmx_taop(rt->rt_rmx); 3054 3055 /* 3056 * Offer == -1 means that we didn't receive SYN yet, 3057 * use cached value in that case; 3058 */ 3059 if (offer == -1) 3060 offer = taop->tao_mssopt; 3061 3062 /* 3063 * Offer == 0 means that there was no MSS on the SYN segment, 3064 * in this case we use either the interface mtu or tcp_mssdflt. 3065 * 3066 * An offer which is too large will be cut down later. 3067 */ 3068 if (offer == 0) { 3069 if (isipv6) { 3070 if (in6_localaddr(&inp->in6p_faddr)) { 3071 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 3072 min_protoh; 3073 } else { 3074 offer = tcp_v6mssdflt; 3075 } 3076 } else { 3077 if (in_localaddr(inp->inp_faddr)) 3078 offer = ifp->if_mtu - min_protoh; 3079 else 3080 offer = tcp_mssdflt; 3081 } 3082 } 3083 3084 /* 3085 * Prevent DoS attack with too small MSS. Round up 3086 * to at least minmss. 3087 * 3088 * Sanity check: make sure that maxopd will be large 3089 * enough to allow some data on segments even is the 3090 * all the option space is used (40bytes). Otherwise 3091 * funny things may happen in tcp_output. 3092 */ 3093 offer = max(offer, tcp_minmss); 3094 offer = max(offer, 64); 3095 3096 taop->tao_mssopt = offer; 3097 3098 /* 3099 * While we're here, check if there's an initial rtt 3100 * or rttvar. Convert from the route-table units 3101 * to scaled multiples of the slow timeout timer. 3102 */ 3103 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3104 /* 3105 * XXX the lock bit for RTT indicates that the value 3106 * is also a minimum value; this is subject to time. 3107 */ 3108 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3109 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3110 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3111 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3112 tcpstat.tcps_usedrtt++; 3113 if (rt->rt_rmx.rmx_rttvar) { 3114 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3115 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3116 tcpstat.tcps_usedrttvar++; 3117 } else { 3118 /* default variation is +- 1 rtt */ 3119 tp->t_rttvar = 3120 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3121 } 3122 TCPT_RANGESET(tp->t_rxtcur, 3123 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3124 tp->t_rttmin, TCPTV_REXMTMAX); 3125 } 3126 3127 /* 3128 * if there's an mtu associated with the route, use it 3129 * else, use the link mtu. Take the smaller of mss or offer 3130 * as our final mss. 3131 */ 3132 if (rt->rt_rmx.rmx_mtu) { 3133 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3134 } else { 3135 if (isipv6) 3136 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3137 else 3138 mss = ifp->if_mtu - min_protoh; 3139 } 3140 mss = min(mss, offer); 3141 3142 /* 3143 * maxopd stores the maximum length of data AND options 3144 * in a segment; maxseg is the amount of data in a normal 3145 * segment. We need to store this value (maxopd) apart 3146 * from maxseg, because now every segment carries options 3147 * and thus we normally have somewhat less data in segments. 3148 */ 3149 tp->t_maxopd = mss; 3150 3151 /* 3152 * In case of T/TCP, origoffer==-1 indicates, that no segments 3153 * were received yet. In this case we just guess, otherwise 3154 * we do the same as before T/TCP. 3155 */ 3156 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3157 (origoffer == -1 || 3158 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3159 mss -= TCPOLEN_TSTAMP_APPA; 3160 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 3161 (origoffer == -1 || 3162 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 3163 mss -= TCPOLEN_CC_APPA; 3164 3165 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3166 if (mss > MCLBYTES) 3167 mss &= ~(MCLBYTES-1); 3168 #else 3169 if (mss > MCLBYTES) 3170 mss = mss / MCLBYTES * MCLBYTES; 3171 #endif 3172 /* 3173 * If there's a pipesize, change the socket buffer 3174 * to that size. Make the socket buffers an integral 3175 * number of mss units; if the mss is larger than 3176 * the socket buffer, decrease the mss. 3177 */ 3178 #ifdef RTV_SPIPE 3179 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3180 #endif 3181 bufsize = so->so_snd.ssb_hiwat; 3182 if (bufsize < mss) 3183 mss = bufsize; 3184 else { 3185 bufsize = roundup(bufsize, mss); 3186 if (bufsize > sb_max) 3187 bufsize = sb_max; 3188 if (bufsize > so->so_snd.ssb_hiwat) 3189 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3190 } 3191 tp->t_maxseg = mss; 3192 3193 #ifdef RTV_RPIPE 3194 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3195 #endif 3196 bufsize = so->so_rcv.ssb_hiwat; 3197 if (bufsize > mss) { 3198 bufsize = roundup(bufsize, mss); 3199 if (bufsize > sb_max) 3200 bufsize = sb_max; 3201 if (bufsize > so->so_rcv.ssb_hiwat) 3202 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3203 } 3204 3205 /* 3206 * Set the slow-start flight size depending on whether this 3207 * is a local network or not. 3208 */ 3209 if (tcp_do_rfc3390) 3210 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3211 else 3212 tp->snd_cwnd = mss; 3213 3214 if (rt->rt_rmx.rmx_ssthresh) { 3215 /* 3216 * There's some sort of gateway or interface 3217 * buffer limit on the path. Use this to set 3218 * the slow start threshhold, but set the 3219 * threshold to no less than 2*mss. 3220 */ 3221 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3222 tcpstat.tcps_usedssthresh++; 3223 } 3224 } 3225 3226 /* 3227 * Determine the MSS option to send on an outgoing SYN. 3228 */ 3229 int 3230 tcp_mssopt(struct tcpcb *tp) 3231 { 3232 struct rtentry *rt; 3233 #ifdef INET6 3234 boolean_t isipv6 = 3235 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3236 int min_protoh = isipv6 ? 3237 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3238 sizeof(struct tcpiphdr); 3239 #else 3240 const boolean_t isipv6 = FALSE; 3241 const size_t min_protoh = sizeof(struct tcpiphdr); 3242 #endif 3243 3244 if (isipv6) 3245 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3246 else 3247 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3248 if (rt == NULL) 3249 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3250 3251 return (rt->rt_ifp->if_mtu - min_protoh); 3252 } 3253 3254 /* 3255 * When a partial ack arrives, force the retransmission of the 3256 * next unacknowledged segment. Do not exit Fast Recovery. 3257 * 3258 * Implement the Slow-but-Steady variant of NewReno by restarting the 3259 * the retransmission timer. Turn it off here so it can be restarted 3260 * later in tcp_output(). 3261 */ 3262 static void 3263 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3264 { 3265 tcp_seq old_snd_nxt = tp->snd_nxt; 3266 u_long ocwnd = tp->snd_cwnd; 3267 3268 tcp_callout_stop(tp, tp->tt_rexmt); 3269 tp->t_rtttime = 0; 3270 tp->snd_nxt = th->th_ack; 3271 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3272 tp->snd_cwnd = tp->t_maxseg; 3273 tp->t_flags |= TF_ACKNOW; 3274 tcp_output(tp); 3275 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3276 tp->snd_nxt = old_snd_nxt; 3277 /* partial window deflation */ 3278 if (ocwnd > acked) 3279 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3280 else 3281 tp->snd_cwnd = tp->t_maxseg; 3282 } 3283 3284 /* 3285 * In contrast to the Slow-but-Steady NewReno variant, 3286 * we do not reset the retransmission timer for SACK retransmissions, 3287 * except when retransmitting snd_una. 3288 */ 3289 static void 3290 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3291 { 3292 uint32_t pipe, seglen; 3293 tcp_seq nextrexmt; 3294 boolean_t lostdup; 3295 tcp_seq old_snd_nxt = tp->snd_nxt; 3296 u_long ocwnd = tp->snd_cwnd; 3297 int nseg = 0; /* consecutive new segments */ 3298 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3299 3300 tp->t_rtttime = 0; 3301 pipe = tcp_sack_compute_pipe(tp); 3302 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3303 (!tcp_do_smartsack || nseg < MAXBURST) && 3304 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3305 uint32_t sent; 3306 tcp_seq old_snd_max; 3307 int error; 3308 3309 if (nextrexmt == tp->snd_max) 3310 ++nseg; 3311 tp->snd_nxt = nextrexmt; 3312 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3313 old_snd_max = tp->snd_max; 3314 if (nextrexmt == tp->snd_una) 3315 tcp_callout_stop(tp, tp->tt_rexmt); 3316 error = tcp_output(tp); 3317 if (error != 0) 3318 break; 3319 sent = tp->snd_nxt - nextrexmt; 3320 if (sent <= 0) 3321 break; 3322 if (!lostdup) 3323 pipe += sent; 3324 tcpstat.tcps_sndsackpack++; 3325 tcpstat.tcps_sndsackbyte += sent; 3326 if (SEQ_LT(nextrexmt, old_snd_max) && 3327 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3328 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3329 } 3330 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3331 tp->snd_nxt = old_snd_nxt; 3332 tp->snd_cwnd = ocwnd; 3333 } 3334