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_inet.h" 73 #include "opt_inet6.h" 74 #include "opt_ipsec.h" 75 #include "opt_tcpdebug.h" 76 #include "opt_tcp_input.h" 77 78 #include <sys/param.h> 79 #include <sys/systm.h> 80 #include <sys/kernel.h> 81 #include <sys/sysctl.h> 82 #include <sys/malloc.h> 83 #include <sys/mbuf.h> 84 #include <sys/proc.h> /* for proc0 declaration */ 85 #include <sys/protosw.h> 86 #include <sys/socket.h> 87 #include <sys/socketvar.h> 88 #include <sys/syslog.h> 89 #include <sys/in_cksum.h> 90 91 #include <sys/socketvar2.h> 92 93 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 94 #include <machine/stdarg.h> 95 96 #include <net/if.h> 97 #include <net/route.h> 98 99 #include <netinet/in.h> 100 #include <netinet/in_systm.h> 101 #include <netinet/ip.h> 102 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 103 #include <netinet/in_var.h> 104 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 105 #include <netinet/in_pcb.h> 106 #include <netinet/ip_var.h> 107 #include <netinet/ip6.h> 108 #include <netinet/icmp6.h> 109 #include <netinet6/nd6.h> 110 #include <netinet6/ip6_var.h> 111 #include <netinet6/in6_pcb.h> 112 #include <netinet/tcp.h> 113 #include <netinet/tcp_fsm.h> 114 #include <netinet/tcp_seq.h> 115 #include <netinet/tcp_timer.h> 116 #include <netinet/tcp_timer2.h> 117 #include <netinet/tcp_var.h> 118 #include <netinet6/tcp6_var.h> 119 #include <netinet/tcpip.h> 120 121 #ifdef TCPDEBUG 122 #include <netinet/tcp_debug.h> 123 124 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 125 struct tcphdr tcp_savetcp; 126 #endif 127 128 #ifdef FAST_IPSEC 129 #include <netproto/ipsec/ipsec.h> 130 #include <netproto/ipsec/ipsec6.h> 131 #endif 132 133 #ifdef IPSEC 134 #include <netinet6/ipsec.h> 135 #include <netinet6/ipsec6.h> 136 #include <netproto/key/key.h> 137 #endif 138 139 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 140 141 static int log_in_vain = 0; 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 143 &log_in_vain, 0, "Log all incoming TCP connections"); 144 145 static int blackhole = 0; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 147 &blackhole, 0, "Do not send RST when dropping refused connections"); 148 149 int tcp_delack_enabled = 1; 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 151 &tcp_delack_enabled, 0, 152 "Delay ACK to try and piggyback it onto a data packet"); 153 154 #ifdef TCP_DROP_SYNFIN 155 static int drop_synfin = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 157 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 158 #endif 159 160 static int tcp_do_limitedtransmit = 1; 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 162 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 163 164 static int tcp_do_early_retransmit = 1; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 166 &tcp_do_early_retransmit, 0, "Early retransmit"); 167 168 int tcp_aggregate_acks = 1; 169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 170 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 171 172 int tcp_do_rfc3390 = 1; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 174 &tcp_do_rfc3390, 0, 175 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 176 177 static int tcp_do_eifel_detect = 1; 178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 179 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 180 181 static int tcp_do_abc = 1; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 183 &tcp_do_abc, 0, 184 "TCP Appropriate Byte Counting (RFC 3465)"); 185 186 /* 187 * Define as tunable for easy testing with SACK on and off. 188 * Warning: do not change setting in the middle of an existing active TCP flow, 189 * else strange things might happen to that flow. 190 */ 191 int tcp_do_sack = 1; 192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 193 &tcp_do_sack, 0, "Enable SACK Algorithms"); 194 195 int tcp_do_smartsack = 1; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 197 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 198 199 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 200 "TCP Segment Reassembly Queue"); 201 202 int tcp_reass_maxseg = 0; 203 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 204 &tcp_reass_maxseg, 0, 205 "Global maximum number of TCP Segments in Reassembly Queue"); 206 207 int tcp_reass_qsize = 0; 208 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 209 &tcp_reass_qsize, 0, 210 "Global number of TCP Segments currently in Reassembly Queue"); 211 212 static int tcp_reass_overflows = 0; 213 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 214 &tcp_reass_overflows, 0, 215 "Global number of TCP Segment Reassembly Queue Overflows"); 216 217 int tcp_do_autorcvbuf = 1; 218 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 219 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 220 221 int tcp_autorcvbuf_inc = 16*1024; 222 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 223 &tcp_autorcvbuf_inc, 0, 224 "Incrementor step size of automatic receive buffer"); 225 226 int tcp_autorcvbuf_max = 2*1024*1024; 227 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 228 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 229 230 231 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 232 static void tcp_pulloutofband(struct socket *, 233 struct tcphdr *, struct mbuf *, int); 234 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 235 struct mbuf *); 236 static void tcp_xmit_timer(struct tcpcb *, int); 237 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 238 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 239 240 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 241 #ifdef INET6 242 #define ND6_HINT(tp) \ 243 do { \ 244 if ((tp) && (tp)->t_inpcb && \ 245 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 246 (tp)->t_inpcb->in6p_route.ro_rt) \ 247 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 248 } while (0) 249 #else 250 #define ND6_HINT(tp) 251 #endif 252 253 /* 254 * Indicate whether this ack should be delayed. We can delay the ack if 255 * - delayed acks are enabled and 256 * - there is no delayed ack timer in progress and 257 * - our last ack wasn't a 0-sized window. We never want to delay 258 * the ack that opens up a 0-sized window. 259 */ 260 #define DELAY_ACK(tp) \ 261 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 262 !(tp->t_flags & TF_RXWIN0SENT)) 263 264 #define acceptable_window_update(tp, th, tiwin) \ 265 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 266 (tp->snd_wl1 == th->th_seq && \ 267 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 268 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 269 270 static int 271 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 272 { 273 struct tseg_qent *q; 274 struct tseg_qent *p = NULL; 275 struct tseg_qent *te; 276 struct socket *so = tp->t_inpcb->inp_socket; 277 int flags; 278 279 /* 280 * Call with th == NULL after become established to 281 * force pre-ESTABLISHED data up to user socket. 282 */ 283 if (th == NULL) 284 goto present; 285 286 /* 287 * Limit the number of segments in the reassembly queue to prevent 288 * holding on to too many segments (and thus running out of mbufs). 289 * Make sure to let the missing segment through which caused this 290 * queue. Always keep one global queue entry spare to be able to 291 * process the missing segment. 292 */ 293 if (th->th_seq != tp->rcv_nxt && 294 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 295 tcp_reass_overflows++; 296 tcpstat.tcps_rcvmemdrop++; 297 m_freem(m); 298 /* no SACK block to report */ 299 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 300 return (0); 301 } 302 303 /* Allocate a new queue entry. */ 304 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 305 M_INTWAIT | M_NULLOK); 306 if (te == NULL) { 307 tcpstat.tcps_rcvmemdrop++; 308 m_freem(m); 309 /* no SACK block to report */ 310 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 311 return (0); 312 } 313 atomic_add_int(&tcp_reass_qsize, 1); 314 315 /* 316 * Find a segment which begins after this one does. 317 */ 318 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 319 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 320 break; 321 p = q; 322 } 323 324 /* 325 * If there is a preceding segment, it may provide some of 326 * our data already. If so, drop the data from the incoming 327 * segment. If it provides all of our data, drop us. 328 */ 329 if (p != NULL) { 330 tcp_seq_diff_t i; 331 332 /* conversion to int (in i) handles seq wraparound */ 333 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 334 if (i > 0) { /* overlaps preceding segment */ 335 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 336 /* enclosing block starts w/ preceding segment */ 337 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 338 if (i >= *tlenp) { 339 /* preceding encloses incoming segment */ 340 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 341 p->tqe_len; 342 tcpstat.tcps_rcvduppack++; 343 tcpstat.tcps_rcvdupbyte += *tlenp; 344 m_freem(m); 345 kfree(te, M_TSEGQ); 346 atomic_add_int(&tcp_reass_qsize, -1); 347 /* 348 * Try to present any queued data 349 * at the left window edge to the user. 350 * This is needed after the 3-WHS 351 * completes. 352 */ 353 goto present; /* ??? */ 354 } 355 m_adj(m, i); 356 *tlenp -= i; 357 th->th_seq += i; 358 /* incoming segment end is enclosing block end */ 359 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 360 ((th->th_flags & TH_FIN) != 0); 361 /* trim end of reported D-SACK block */ 362 tp->reportblk.rblk_end = th->th_seq; 363 } 364 } 365 tcpstat.tcps_rcvoopack++; 366 tcpstat.tcps_rcvoobyte += *tlenp; 367 368 /* 369 * While we overlap succeeding segments trim them or, 370 * if they are completely covered, dequeue them. 371 */ 372 while (q) { 373 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 374 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 375 struct tseg_qent *nq; 376 377 if (i <= 0) 378 break; 379 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 380 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 381 tp->encloseblk = tp->reportblk; 382 /* report trailing duplicate D-SACK segment */ 383 tp->reportblk.rblk_start = q->tqe_th->th_seq; 384 } 385 if ((tp->t_flags & TF_ENCLOSESEG) && 386 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 387 /* extend enclosing block if one exists */ 388 tp->encloseblk.rblk_end = qend; 389 } 390 if (i < q->tqe_len) { 391 q->tqe_th->th_seq += i; 392 q->tqe_len -= i; 393 m_adj(q->tqe_m, i); 394 break; 395 } 396 397 nq = LIST_NEXT(q, tqe_q); 398 LIST_REMOVE(q, tqe_q); 399 m_freem(q->tqe_m); 400 kfree(q, M_TSEGQ); 401 atomic_add_int(&tcp_reass_qsize, -1); 402 q = nq; 403 } 404 405 /* Insert the new segment queue entry into place. */ 406 te->tqe_m = m; 407 te->tqe_th = th; 408 te->tqe_len = *tlenp; 409 410 /* check if can coalesce with following segment */ 411 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 412 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 413 414 te->tqe_len += q->tqe_len; 415 if (q->tqe_th->th_flags & TH_FIN) 416 te->tqe_th->th_flags |= TH_FIN; 417 m_cat(te->tqe_m, q->tqe_m); 418 tp->encloseblk.rblk_end = tend; 419 /* 420 * When not reporting a duplicate segment, use 421 * the larger enclosing block as the SACK block. 422 */ 423 if (!(tp->t_flags & TF_DUPSEG)) 424 tp->reportblk.rblk_end = tend; 425 LIST_REMOVE(q, tqe_q); 426 kfree(q, M_TSEGQ); 427 atomic_add_int(&tcp_reass_qsize, -1); 428 } 429 430 if (p == NULL) { 431 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 432 } else { 433 /* check if can coalesce with preceding segment */ 434 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 435 p->tqe_len += te->tqe_len; 436 m_cat(p->tqe_m, te->tqe_m); 437 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 438 /* 439 * When not reporting a duplicate segment, use 440 * the larger enclosing block as the SACK block. 441 */ 442 if (!(tp->t_flags & TF_DUPSEG)) 443 tp->reportblk.rblk_start = p->tqe_th->th_seq; 444 kfree(te, M_TSEGQ); 445 atomic_add_int(&tcp_reass_qsize, -1); 446 } else { 447 LIST_INSERT_AFTER(p, te, tqe_q); 448 } 449 } 450 451 present: 452 /* 453 * Present data to user, advancing rcv_nxt through 454 * completed sequence space. 455 */ 456 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 457 return (0); 458 q = LIST_FIRST(&tp->t_segq); 459 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 460 return (0); 461 tp->rcv_nxt += q->tqe_len; 462 if (!(tp->t_flags & TF_DUPSEG)) { 463 /* no SACK block to report since ACK advanced */ 464 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 465 } 466 /* no enclosing block to report since ACK advanced */ 467 tp->t_flags &= ~TF_ENCLOSESEG; 468 flags = q->tqe_th->th_flags & TH_FIN; 469 LIST_REMOVE(q, tqe_q); 470 KASSERT(LIST_EMPTY(&tp->t_segq) || 471 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 472 ("segment not coalesced")); 473 if (so->so_state & SS_CANTRCVMORE) { 474 m_freem(q->tqe_m); 475 } else { 476 lwkt_gettoken(&so->so_rcv.ssb_token); 477 ssb_appendstream(&so->so_rcv, q->tqe_m); 478 lwkt_reltoken(&so->so_rcv.ssb_token); 479 } 480 kfree(q, M_TSEGQ); 481 atomic_add_int(&tcp_reass_qsize, -1); 482 ND6_HINT(tp); 483 sorwakeup(so); 484 return (flags); 485 } 486 487 /* 488 * TCP input routine, follows pages 65-76 of the 489 * protocol specification dated September, 1981 very closely. 490 */ 491 #ifdef INET6 492 int 493 tcp6_input(struct mbuf **mp, int *offp, int proto) 494 { 495 struct mbuf *m = *mp; 496 struct in6_ifaddr *ia6; 497 498 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 499 500 /* 501 * draft-itojun-ipv6-tcp-to-anycast 502 * better place to put this in? 503 */ 504 ia6 = ip6_getdstifaddr(m); 505 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 506 struct ip6_hdr *ip6; 507 508 ip6 = mtod(m, struct ip6_hdr *); 509 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 510 offsetof(struct ip6_hdr, ip6_dst)); 511 return (IPPROTO_DONE); 512 } 513 514 tcp_input(mp, offp, proto); 515 return (IPPROTO_DONE); 516 } 517 #endif 518 519 int 520 tcp_input(struct mbuf **mp, int *offp, int proto) 521 { 522 int off0; 523 struct tcphdr *th; 524 struct ip *ip = NULL; 525 struct ipovly *ipov; 526 struct inpcb *inp = NULL; 527 u_char *optp = NULL; 528 int optlen = 0; 529 int tlen, off; 530 int len = 0; 531 int drop_hdrlen; 532 struct tcpcb *tp = NULL; 533 int thflags; 534 struct socket *so = 0; 535 int todrop, acked; 536 boolean_t ourfinisacked, needoutput = FALSE; 537 u_long tiwin; 538 int recvwin; 539 struct tcpopt to; /* options in this segment */ 540 struct sockaddr_in *next_hop = NULL; 541 int rstreason; /* For badport_bandlim accounting purposes */ 542 int cpu; 543 struct ip6_hdr *ip6 = NULL; 544 struct mbuf *m; 545 #ifdef INET6 546 boolean_t isipv6; 547 #else 548 const boolean_t isipv6 = FALSE; 549 #endif 550 #ifdef TCPDEBUG 551 short ostate = 0; 552 #endif 553 554 off0 = *offp; 555 m = *mp; 556 *mp = NULL; 557 558 tcpstat.tcps_rcvtotal++; 559 560 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 561 struct m_tag *mtag; 562 563 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 564 KKASSERT(mtag != NULL); 565 next_hop = m_tag_data(mtag); 566 } 567 568 #ifdef INET6 569 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 570 #endif 571 572 if (isipv6) { 573 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 574 ip6 = mtod(m, struct ip6_hdr *); 575 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 576 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 577 tcpstat.tcps_rcvbadsum++; 578 goto drop; 579 } 580 th = (struct tcphdr *)((caddr_t)ip6 + off0); 581 582 /* 583 * Be proactive about unspecified IPv6 address in source. 584 * As we use all-zero to indicate unbounded/unconnected pcb, 585 * unspecified IPv6 address can be used to confuse us. 586 * 587 * Note that packets with unspecified IPv6 destination is 588 * already dropped in ip6_input. 589 */ 590 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 591 /* XXX stat */ 592 goto drop; 593 } 594 } else { 595 /* 596 * Get IP and TCP header together in first mbuf. 597 * Note: IP leaves IP header in first mbuf. 598 */ 599 if (off0 > sizeof(struct ip)) { 600 ip_stripoptions(m); 601 off0 = sizeof(struct ip); 602 } 603 /* already checked and pulled up in ip_demux() */ 604 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 605 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 606 ip = mtod(m, struct ip *); 607 ipov = (struct ipovly *)ip; 608 th = (struct tcphdr *)((caddr_t)ip + off0); 609 tlen = ip->ip_len; 610 611 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 612 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 613 th->th_sum = m->m_pkthdr.csum_data; 614 else 615 th->th_sum = in_pseudo(ip->ip_src.s_addr, 616 ip->ip_dst.s_addr, 617 htonl(m->m_pkthdr.csum_data + 618 ip->ip_len + 619 IPPROTO_TCP)); 620 th->th_sum ^= 0xffff; 621 } else { 622 /* 623 * Checksum extended TCP header and data. 624 */ 625 len = sizeof(struct ip) + tlen; 626 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 627 ipov->ih_len = (u_short)tlen; 628 ipov->ih_len = htons(ipov->ih_len); 629 th->th_sum = in_cksum(m, len); 630 } 631 if (th->th_sum) { 632 tcpstat.tcps_rcvbadsum++; 633 goto drop; 634 } 635 #ifdef INET6 636 /* Re-initialization for later version check */ 637 ip->ip_v = IPVERSION; 638 #endif 639 } 640 641 /* 642 * Check that TCP offset makes sense, 643 * pull out TCP options and adjust length. XXX 644 */ 645 off = th->th_off << 2; 646 /* already checked and pulled up in ip_demux() */ 647 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 648 ("bad TCP data offset %d (tlen %d)", off, tlen)); 649 tlen -= off; /* tlen is used instead of ti->ti_len */ 650 if (off > sizeof(struct tcphdr)) { 651 if (isipv6) { 652 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 653 ip6 = mtod(m, struct ip6_hdr *); 654 th = (struct tcphdr *)((caddr_t)ip6 + off0); 655 } else { 656 /* already pulled up in ip_demux() */ 657 KASSERT(m->m_len >= sizeof(struct ip) + off, 658 ("TCP header and options not in one mbuf: " 659 "m_len %d, off %d", m->m_len, off)); 660 } 661 optlen = off - sizeof(struct tcphdr); 662 optp = (u_char *)(th + 1); 663 } 664 thflags = th->th_flags; 665 666 #ifdef TCP_DROP_SYNFIN 667 /* 668 * If the drop_synfin option is enabled, drop all packets with 669 * both the SYN and FIN bits set. This prevents e.g. nmap from 670 * identifying the TCP/IP stack. 671 * 672 * This is a violation of the TCP specification. 673 */ 674 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 675 goto drop; 676 #endif 677 678 /* 679 * Convert TCP protocol specific fields to host format. 680 */ 681 th->th_seq = ntohl(th->th_seq); 682 th->th_ack = ntohl(th->th_ack); 683 th->th_win = ntohs(th->th_win); 684 th->th_urp = ntohs(th->th_urp); 685 686 /* 687 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 688 * until after ip6_savecontrol() is called and before other functions 689 * which don't want those proto headers. 690 * Because ip6_savecontrol() is going to parse the mbuf to 691 * search for data to be passed up to user-land, it wants mbuf 692 * parameters to be unchanged. 693 * XXX: the call of ip6_savecontrol() has been obsoleted based on 694 * latest version of the advanced API (20020110). 695 */ 696 drop_hdrlen = off0 + off; 697 698 /* 699 * Locate pcb for segment. 700 */ 701 findpcb: 702 /* IPFIREWALL_FORWARD section */ 703 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 704 /* 705 * Transparently forwarded. Pretend to be the destination. 706 * already got one like this? 707 */ 708 cpu = mycpu->gd_cpuid; 709 inp = in_pcblookup_hash(&tcbinfo[cpu], 710 ip->ip_src, th->th_sport, 711 ip->ip_dst, th->th_dport, 712 0, m->m_pkthdr.rcvif); 713 if (!inp) { 714 /* 715 * It's new. Try to find the ambushing socket. 716 */ 717 718 /* 719 * The rest of the ipfw code stores the port in 720 * host order. XXX 721 * (The IP address is still in network order.) 722 */ 723 in_port_t dport = next_hop->sin_port ? 724 htons(next_hop->sin_port) : 725 th->th_dport; 726 727 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 728 next_hop->sin_addr.s_addr, dport); 729 inp = in_pcblookup_hash(&tcbinfo[cpu], 730 ip->ip_src, th->th_sport, 731 next_hop->sin_addr, dport, 732 1, m->m_pkthdr.rcvif); 733 } 734 } else { 735 if (isipv6) { 736 inp = in6_pcblookup_hash(&tcbinfo[0], 737 &ip6->ip6_src, th->th_sport, 738 &ip6->ip6_dst, th->th_dport, 739 1, m->m_pkthdr.rcvif); 740 } else { 741 cpu = mycpu->gd_cpuid; 742 inp = in_pcblookup_hash(&tcbinfo[cpu], 743 ip->ip_src, th->th_sport, 744 ip->ip_dst, th->th_dport, 745 1, m->m_pkthdr.rcvif); 746 } 747 } 748 749 /* 750 * If the state is CLOSED (i.e., TCB does not exist) then 751 * all data in the incoming segment is discarded. 752 * If the TCB exists but is in CLOSED state, it is embryonic, 753 * but should either do a listen or a connect soon. 754 */ 755 if (inp == NULL) { 756 if (log_in_vain) { 757 #ifdef INET6 758 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 759 #else 760 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 761 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 762 #endif 763 if (isipv6) { 764 strcpy(dbuf, "["); 765 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 766 strcat(dbuf, "]"); 767 strcpy(sbuf, "["); 768 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 769 strcat(sbuf, "]"); 770 } else { 771 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 772 strcpy(sbuf, inet_ntoa(ip->ip_src)); 773 } 774 switch (log_in_vain) { 775 case 1: 776 if (!(thflags & TH_SYN)) 777 break; 778 case 2: 779 log(LOG_INFO, 780 "Connection attempt to TCP %s:%d " 781 "from %s:%d flags:0x%02x\n", 782 dbuf, ntohs(th->th_dport), sbuf, 783 ntohs(th->th_sport), thflags); 784 break; 785 default: 786 break; 787 } 788 } 789 if (blackhole) { 790 switch (blackhole) { 791 case 1: 792 if (thflags & TH_SYN) 793 goto drop; 794 break; 795 case 2: 796 goto drop; 797 default: 798 goto drop; 799 } 800 } 801 rstreason = BANDLIM_RST_CLOSEDPORT; 802 goto dropwithreset; 803 } 804 805 #ifdef IPSEC 806 if (isipv6) { 807 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 808 ipsec6stat.in_polvio++; 809 goto drop; 810 } 811 } else { 812 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 813 ipsecstat.in_polvio++; 814 goto drop; 815 } 816 } 817 #endif 818 #ifdef FAST_IPSEC 819 if (isipv6) { 820 if (ipsec6_in_reject(m, inp)) 821 goto drop; 822 } else { 823 if (ipsec4_in_reject(m, inp)) 824 goto drop; 825 } 826 #endif 827 /* Check the minimum TTL for socket. */ 828 #ifdef INET6 829 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 830 goto drop; 831 #endif 832 833 tp = intotcpcb(inp); 834 if (tp == NULL) { 835 rstreason = BANDLIM_RST_CLOSEDPORT; 836 goto dropwithreset; 837 } 838 if (tp->t_state <= TCPS_CLOSED) 839 goto drop; 840 841 /* Unscale the window into a 32-bit value. */ 842 if (!(thflags & TH_SYN)) 843 tiwin = th->th_win << tp->snd_scale; 844 else 845 tiwin = th->th_win; 846 847 so = inp->inp_socket; 848 849 #ifdef TCPDEBUG 850 if (so->so_options & SO_DEBUG) { 851 ostate = tp->t_state; 852 if (isipv6) 853 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 854 else 855 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 856 tcp_savetcp = *th; 857 } 858 #endif 859 860 bzero(&to, sizeof to); 861 862 if (so->so_options & SO_ACCEPTCONN) { 863 struct in_conninfo inc; 864 865 #ifdef INET6 866 inc.inc_isipv6 = (isipv6 == TRUE); 867 #endif 868 if (isipv6) { 869 inc.inc6_faddr = ip6->ip6_src; 870 inc.inc6_laddr = ip6->ip6_dst; 871 inc.inc6_route.ro_rt = NULL; /* XXX */ 872 } else { 873 inc.inc_faddr = ip->ip_src; 874 inc.inc_laddr = ip->ip_dst; 875 inc.inc_route.ro_rt = NULL; /* XXX */ 876 } 877 inc.inc_fport = th->th_sport; 878 inc.inc_lport = th->th_dport; 879 880 /* 881 * If the state is LISTEN then ignore segment if it contains 882 * a RST. If the segment contains an ACK then it is bad and 883 * send a RST. If it does not contain a SYN then it is not 884 * interesting; drop it. 885 * 886 * If the state is SYN_RECEIVED (syncache) and seg contains 887 * an ACK, but not for our SYN/ACK, send a RST. If the seg 888 * contains a RST, check the sequence number to see if it 889 * is a valid reset segment. 890 */ 891 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 892 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 893 if (!syncache_expand(&inc, th, &so, m)) { 894 /* 895 * No syncache entry, or ACK was not 896 * for our SYN/ACK. Send a RST. 897 */ 898 tcpstat.tcps_badsyn++; 899 rstreason = BANDLIM_RST_OPENPORT; 900 goto dropwithreset; 901 } 902 903 /* 904 * Could not complete 3-way handshake, 905 * connection is being closed down, and 906 * syncache will free mbuf. 907 */ 908 if (so == NULL) 909 return(IPPROTO_DONE); 910 911 /* 912 * We must be in the correct protocol thread 913 * for this connection. 914 */ 915 KKASSERT(so->so_port == &curthread->td_msgport); 916 917 /* 918 * Socket is created in state SYN_RECEIVED. 919 * Continue processing segment. 920 */ 921 inp = so->so_pcb; 922 tp = intotcpcb(inp); 923 /* 924 * This is what would have happened in 925 * tcp_output() when the SYN,ACK was sent. 926 */ 927 tp->snd_up = tp->snd_una; 928 tp->snd_max = tp->snd_nxt = tp->iss + 1; 929 tp->last_ack_sent = tp->rcv_nxt; 930 /* 931 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 932 * until the _second_ ACK is received: 933 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 934 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 935 * move to ESTAB, set snd_wnd to tiwin. 936 */ 937 tp->snd_wnd = tiwin; /* unscaled */ 938 goto after_listen; 939 } 940 if (thflags & TH_RST) { 941 syncache_chkrst(&inc, th); 942 goto drop; 943 } 944 if (thflags & TH_ACK) { 945 syncache_badack(&inc); 946 tcpstat.tcps_badsyn++; 947 rstreason = BANDLIM_RST_OPENPORT; 948 goto dropwithreset; 949 } 950 goto drop; 951 } 952 953 /* 954 * Segment's flags are (SYN) or (SYN | FIN). 955 */ 956 #ifdef INET6 957 /* 958 * If deprecated address is forbidden, 959 * we do not accept SYN to deprecated interface 960 * address to prevent any new inbound connection from 961 * getting established. 962 * When we do not accept SYN, we send a TCP RST, 963 * with deprecated source address (instead of dropping 964 * it). We compromise it as it is much better for peer 965 * to send a RST, and RST will be the final packet 966 * for the exchange. 967 * 968 * If we do not forbid deprecated addresses, we accept 969 * the SYN packet. RFC2462 does not suggest dropping 970 * SYN in this case. 971 * If we decipher RFC2462 5.5.4, it says like this: 972 * 1. use of deprecated addr with existing 973 * communication is okay - "SHOULD continue to be 974 * used" 975 * 2. use of it with new communication: 976 * (2a) "SHOULD NOT be used if alternate address 977 * with sufficient scope is available" 978 * (2b) nothing mentioned otherwise. 979 * Here we fall into (2b) case as we have no choice in 980 * our source address selection - we must obey the peer. 981 * 982 * The wording in RFC2462 is confusing, and there are 983 * multiple description text for deprecated address 984 * handling - worse, they are not exactly the same. 985 * I believe 5.5.4 is the best one, so we follow 5.5.4. 986 */ 987 if (isipv6 && !ip6_use_deprecated) { 988 struct in6_ifaddr *ia6; 989 990 if ((ia6 = ip6_getdstifaddr(m)) && 991 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 992 tp = NULL; 993 rstreason = BANDLIM_RST_OPENPORT; 994 goto dropwithreset; 995 } 996 } 997 #endif 998 /* 999 * If it is from this socket, drop it, it must be forged. 1000 * Don't bother responding if the destination was a broadcast. 1001 */ 1002 if (th->th_dport == th->th_sport) { 1003 if (isipv6) { 1004 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1005 &ip6->ip6_src)) 1006 goto drop; 1007 } else { 1008 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1009 goto drop; 1010 } 1011 } 1012 /* 1013 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1014 * 1015 * Note that it is quite possible to receive unicast 1016 * link-layer packets with a broadcast IP address. Use 1017 * in_broadcast() to find them. 1018 */ 1019 if (m->m_flags & (M_BCAST | M_MCAST)) 1020 goto drop; 1021 if (isipv6) { 1022 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1023 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1024 goto drop; 1025 } else { 1026 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1027 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1028 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1029 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1030 goto drop; 1031 } 1032 /* 1033 * SYN appears to be valid; create compressed TCP state 1034 * for syncache, or perform t/tcp connection. 1035 */ 1036 if (so->so_qlen <= so->so_qlimit) { 1037 tcp_dooptions(&to, optp, optlen, TRUE); 1038 if (!syncache_add(&inc, &to, th, &so, m)) 1039 goto drop; 1040 1041 /* 1042 * Entry added to syncache, mbuf used to 1043 * send SYN,ACK packet. 1044 */ 1045 if (so == NULL) 1046 return(IPPROTO_DONE); 1047 1048 /* 1049 * We must be in the correct protocol thread for 1050 * this connection. 1051 */ 1052 KKASSERT(so->so_port == &curthread->td_msgport); 1053 1054 inp = so->so_pcb; 1055 tp = intotcpcb(inp); 1056 tp->snd_wnd = tiwin; 1057 tp->t_starttime = ticks; 1058 tp->t_state = TCPS_ESTABLISHED; 1059 1060 /* 1061 * If there is a FIN, or if there is data and the 1062 * connection is local, then delay SYN,ACK(SYN) in 1063 * the hope of piggy-backing it on a response 1064 * segment. Otherwise must send ACK now in case 1065 * the other side is slow starting. 1066 */ 1067 if (DELAY_ACK(tp) && 1068 ((thflags & TH_FIN) || 1069 (tlen != 0 && 1070 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1071 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1072 tcp_callout_reset(tp, tp->tt_delack, 1073 tcp_delacktime, tcp_timer_delack); 1074 tp->t_flags |= TF_NEEDSYN; 1075 } else { 1076 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1077 } 1078 1079 tcpstat.tcps_connects++; 1080 soisconnected(so); 1081 goto trimthenstep6; 1082 } 1083 goto drop; 1084 } 1085 1086 after_listen: 1087 /* 1088 * Should not happen - syncache should pick up these connections. 1089 * 1090 * Once we are past handling listen sockets we must be in the 1091 * correct protocol processing thread. 1092 */ 1093 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1094 KKASSERT(so->so_port == &curthread->td_msgport); 1095 1096 /* 1097 * This is the second part of the MSS DoS prevention code (after 1098 * minmss on the sending side) and it deals with too many too small 1099 * tcp packets in a too short timeframe (1 second). 1100 * 1101 * XXX Removed. This code was crap. It does not scale to network 1102 * speed, and default values break NFS. Gone. 1103 */ 1104 /* REMOVED */ 1105 1106 /* 1107 * Segment received on connection. 1108 * 1109 * Reset idle time and keep-alive timer. Don't waste time if less 1110 * then a second has elapsed. 1111 */ 1112 if ((int)(ticks - tp->t_rcvtime) > hz) 1113 tcp_timer_keep_activity(tp, thflags); 1114 1115 /* 1116 * Process options. 1117 * XXX this is tradtitional behavior, may need to be cleaned up. 1118 */ 1119 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1120 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1121 if (to.to_flags & TOF_SCALE) { 1122 tp->t_flags |= TF_RCVD_SCALE; 1123 tp->requested_s_scale = to.to_requested_s_scale; 1124 } 1125 if (to.to_flags & TOF_TS) { 1126 tp->t_flags |= TF_RCVD_TSTMP; 1127 tp->ts_recent = to.to_tsval; 1128 tp->ts_recent_age = ticks; 1129 } 1130 if (to.to_flags & TOF_MSS) 1131 tcp_mss(tp, to.to_mss); 1132 /* 1133 * Only set the TF_SACK_PERMITTED per-connection flag 1134 * if we got a SACK_PERMITTED option from the other side 1135 * and the global tcp_do_sack variable is true. 1136 */ 1137 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1138 tp->t_flags |= TF_SACK_PERMITTED; 1139 } 1140 1141 /* 1142 * Header prediction: check for the two common cases 1143 * of a uni-directional data xfer. If the packet has 1144 * no control flags, is in-sequence, the window didn't 1145 * change and we're not retransmitting, it's a 1146 * candidate. If the length is zero and the ack moved 1147 * forward, we're the sender side of the xfer. Just 1148 * free the data acked & wake any higher level process 1149 * that was blocked waiting for space. If the length 1150 * is non-zero and the ack didn't move, we're the 1151 * receiver side. If we're getting packets in-order 1152 * (the reassembly queue is empty), add the data to 1153 * the socket buffer and note that we need a delayed ack. 1154 * Make sure that the hidden state-flags are also off. 1155 * Since we check for TCPS_ESTABLISHED above, it can only 1156 * be TH_NEEDSYN. 1157 */ 1158 if (tp->t_state == TCPS_ESTABLISHED && 1159 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1160 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1161 (!(to.to_flags & TOF_TS) || 1162 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1163 th->th_seq == tp->rcv_nxt && 1164 tp->snd_nxt == tp->snd_max) { 1165 1166 /* 1167 * If last ACK falls within this segment's sequence numbers, 1168 * record the timestamp. 1169 * NOTE that the test is modified according to the latest 1170 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1171 */ 1172 if ((to.to_flags & TOF_TS) && 1173 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1174 tp->ts_recent_age = ticks; 1175 tp->ts_recent = to.to_tsval; 1176 } 1177 1178 if (tlen == 0) { 1179 if (SEQ_GT(th->th_ack, tp->snd_una) && 1180 SEQ_LEQ(th->th_ack, tp->snd_max) && 1181 tp->snd_cwnd >= tp->snd_wnd && 1182 !IN_FASTRECOVERY(tp)) { 1183 /* 1184 * This is a pure ack for outstanding data. 1185 */ 1186 ++tcpstat.tcps_predack; 1187 /* 1188 * "bad retransmit" recovery 1189 * 1190 * If Eifel detection applies, then 1191 * it is deterministic, so use it 1192 * unconditionally over the old heuristic. 1193 * Otherwise, fall back to the old heuristic. 1194 */ 1195 if (tcp_do_eifel_detect && 1196 (to.to_flags & TOF_TS) && to.to_tsecr && 1197 (tp->t_flags & TF_FIRSTACCACK)) { 1198 /* Eifel detection applicable. */ 1199 if (to.to_tsecr < tp->t_rexmtTS) { 1200 tcp_revert_congestion_state(tp); 1201 ++tcpstat.tcps_eifeldetected; 1202 } 1203 } else if (tp->t_rxtshift == 1 && 1204 ticks < tp->t_badrxtwin) { 1205 tcp_revert_congestion_state(tp); 1206 ++tcpstat.tcps_rttdetected; 1207 } 1208 tp->t_flags &= ~(TF_FIRSTACCACK | 1209 TF_FASTREXMT | TF_EARLYREXMT); 1210 /* 1211 * Recalculate the retransmit timer / rtt. 1212 * 1213 * Some machines (certain windows boxes) 1214 * send broken timestamp replies during the 1215 * SYN+ACK phase, ignore timestamps of 0. 1216 */ 1217 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1218 tcp_xmit_timer(tp, 1219 ticks - to.to_tsecr + 1); 1220 } else if (tp->t_rtttime && 1221 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1222 tcp_xmit_timer(tp, 1223 ticks - tp->t_rtttime); 1224 } 1225 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1226 acked = th->th_ack - tp->snd_una; 1227 tcpstat.tcps_rcvackpack++; 1228 tcpstat.tcps_rcvackbyte += acked; 1229 sbdrop(&so->so_snd.sb, acked); 1230 tp->snd_recover = th->th_ack - 1; 1231 tp->snd_una = th->th_ack; 1232 tp->t_dupacks = 0; 1233 /* 1234 * Update window information. 1235 */ 1236 if (tiwin != tp->snd_wnd && 1237 acceptable_window_update(tp, th, tiwin)) { 1238 /* keep track of pure window updates */ 1239 if (tp->snd_wl2 == th->th_ack && 1240 tiwin > tp->snd_wnd) 1241 tcpstat.tcps_rcvwinupd++; 1242 tp->snd_wnd = tiwin; 1243 tp->snd_wl1 = th->th_seq; 1244 tp->snd_wl2 = th->th_ack; 1245 if (tp->snd_wnd > tp->max_sndwnd) 1246 tp->max_sndwnd = tp->snd_wnd; 1247 } 1248 m_freem(m); 1249 ND6_HINT(tp); /* some progress has been done */ 1250 /* 1251 * If all outstanding data are acked, stop 1252 * retransmit timer, otherwise restart timer 1253 * using current (possibly backed-off) value. 1254 * If process is waiting for space, 1255 * wakeup/selwakeup/signal. If data 1256 * are ready to send, let tcp_output 1257 * decide between more output or persist. 1258 */ 1259 if (tp->snd_una == tp->snd_max) { 1260 tcp_callout_stop(tp, tp->tt_rexmt); 1261 } else if (!tcp_callout_active(tp, 1262 tp->tt_persist)) { 1263 tcp_callout_reset(tp, tp->tt_rexmt, 1264 tp->t_rxtcur, tcp_timer_rexmt); 1265 } 1266 sowwakeup(so); 1267 if (so->so_snd.ssb_cc > 0) 1268 tcp_output(tp); 1269 return(IPPROTO_DONE); 1270 } 1271 } else if (tiwin == tp->snd_wnd && 1272 th->th_ack == tp->snd_una && 1273 LIST_EMPTY(&tp->t_segq) && 1274 tlen <= ssb_space(&so->so_rcv)) { 1275 u_long newsize = 0; /* automatic sockbuf scaling */ 1276 /* 1277 * This is a pure, in-sequence data packet 1278 * with nothing on the reassembly queue and 1279 * we have enough buffer space to take it. 1280 */ 1281 ++tcpstat.tcps_preddat; 1282 tp->rcv_nxt += tlen; 1283 tcpstat.tcps_rcvpack++; 1284 tcpstat.tcps_rcvbyte += tlen; 1285 ND6_HINT(tp); /* some progress has been done */ 1286 /* 1287 * Automatic sizing of receive socket buffer. Often the send 1288 * buffer size is not optimally adjusted to the actual network 1289 * conditions at hand (delay bandwidth product). Setting the 1290 * buffer size too small limits throughput on links with high 1291 * bandwidth and high delay (eg. trans-continental/oceanic links). 1292 * 1293 * On the receive side the socket buffer memory is only rarely 1294 * used to any significant extent. This allows us to be much 1295 * more aggressive in scaling the receive socket buffer. For 1296 * the case that the buffer space is actually used to a large 1297 * extent and we run out of kernel memory we can simply drop 1298 * the new segments; TCP on the sender will just retransmit it 1299 * later. Setting the buffer size too big may only consume too 1300 * much kernel memory if the application doesn't read() from 1301 * the socket or packet loss or reordering makes use of the 1302 * reassembly queue. 1303 * 1304 * The criteria to step up the receive buffer one notch are: 1305 * 1. the number of bytes received during the time it takes 1306 * one timestamp to be reflected back to us (the RTT); 1307 * 2. received bytes per RTT is within seven eighth of the 1308 * current socket buffer size; 1309 * 3. receive buffer size has not hit maximal automatic size; 1310 * 1311 * This algorithm does one step per RTT at most and only if 1312 * we receive a bulk stream w/o packet losses or reorderings. 1313 * Shrinking the buffer during idle times is not necessary as 1314 * it doesn't consume any memory when idle. 1315 * 1316 * TODO: Only step up if the application is actually serving 1317 * the buffer to better manage the socket buffer resources. 1318 */ 1319 if (tcp_do_autorcvbuf && 1320 to.to_tsecr && 1321 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1322 if (to.to_tsecr > tp->rfbuf_ts && 1323 to.to_tsecr - tp->rfbuf_ts < hz) { 1324 if (tp->rfbuf_cnt > 1325 (so->so_rcv.ssb_hiwat / 8 * 7) && 1326 so->so_rcv.ssb_hiwat < 1327 tcp_autorcvbuf_max) { 1328 newsize = 1329 ulmin(so->so_rcv.ssb_hiwat + 1330 tcp_autorcvbuf_inc, 1331 tcp_autorcvbuf_max); 1332 } 1333 /* Start over with next RTT. */ 1334 tp->rfbuf_ts = 0; 1335 tp->rfbuf_cnt = 0; 1336 } else 1337 tp->rfbuf_cnt += tlen; /* add up */ 1338 } 1339 /* 1340 * Add data to socket buffer. 1341 */ 1342 if (so->so_state & SS_CANTRCVMORE) { 1343 m_freem(m); 1344 } else { 1345 /* 1346 * Set new socket buffer size, give up when 1347 * limit is reached. 1348 * 1349 * Adjusting the size can mess up ACK 1350 * sequencing when pure window updates are 1351 * being avoided (which is the default), 1352 * so force an ack. 1353 */ 1354 lwkt_gettoken(&so->so_rcv.ssb_token); 1355 if (newsize) { 1356 tp->t_flags |= TF_RXRESIZED; 1357 if (!ssb_reserve(&so->so_rcv, newsize, 1358 so, NULL)) { 1359 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1360 } 1361 if (newsize >= 1362 (TCP_MAXWIN << tp->rcv_scale)) { 1363 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1364 } 1365 } 1366 m_adj(m, drop_hdrlen); /* delayed header drop */ 1367 ssb_appendstream(&so->so_rcv, m); 1368 lwkt_reltoken(&so->so_rcv.ssb_token); 1369 } 1370 sorwakeup(so); 1371 /* 1372 * This code is responsible for most of the ACKs 1373 * the TCP stack sends back after receiving a data 1374 * packet. Note that the DELAY_ACK check fails if 1375 * the delack timer is already running, which results 1376 * in an ack being sent every other packet (which is 1377 * what we want). 1378 * 1379 * We then further aggregate acks by not actually 1380 * sending one until the protocol thread has completed 1381 * processing the current backlog of packets. This 1382 * does not delay the ack any further, but allows us 1383 * to take advantage of the packet aggregation that 1384 * high speed NICs do (usually blocks of 8-10 packets) 1385 * to send a single ack rather then four or five acks, 1386 * greatly reducing the ack rate, the return channel 1387 * bandwidth, and the protocol overhead on both ends. 1388 * 1389 * Since this also has the effect of slowing down 1390 * the exponential slow-start ramp-up, systems with 1391 * very large bandwidth-delay products might want 1392 * to turn the feature off. 1393 */ 1394 if (DELAY_ACK(tp)) { 1395 tcp_callout_reset(tp, tp->tt_delack, 1396 tcp_delacktime, tcp_timer_delack); 1397 } else if (tcp_aggregate_acks) { 1398 tp->t_flags |= TF_ACKNOW; 1399 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1400 tp->t_flags |= TF_ONOUTPUTQ; 1401 tp->tt_cpu = mycpu->gd_cpuid; 1402 TAILQ_INSERT_TAIL( 1403 &tcpcbackq[tp->tt_cpu], 1404 tp, t_outputq); 1405 } 1406 } else { 1407 tp->t_flags |= TF_ACKNOW; 1408 tcp_output(tp); 1409 } 1410 return(IPPROTO_DONE); 1411 } 1412 } 1413 1414 /* 1415 * Calculate amount of space in receive window, 1416 * and then do TCP input processing. 1417 * Receive window is amount of space in rcv queue, 1418 * but not less than advertised window. 1419 */ 1420 recvwin = ssb_space(&so->so_rcv); 1421 if (recvwin < 0) 1422 recvwin = 0; 1423 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1424 1425 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1426 tp->rfbuf_ts = 0; 1427 tp->rfbuf_cnt = 0; 1428 1429 switch (tp->t_state) { 1430 /* 1431 * If the state is SYN_RECEIVED: 1432 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1433 */ 1434 case TCPS_SYN_RECEIVED: 1435 if ((thflags & TH_ACK) && 1436 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1437 SEQ_GT(th->th_ack, tp->snd_max))) { 1438 rstreason = BANDLIM_RST_OPENPORT; 1439 goto dropwithreset; 1440 } 1441 break; 1442 1443 /* 1444 * If the state is SYN_SENT: 1445 * if seg contains an ACK, but not for our SYN, drop the input. 1446 * if seg contains a RST, then drop the connection. 1447 * if seg does not contain SYN, then drop it. 1448 * Otherwise this is an acceptable SYN segment 1449 * initialize tp->rcv_nxt and tp->irs 1450 * if seg contains ack then advance tp->snd_una 1451 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1452 * arrange for segment to be acked (eventually) 1453 * continue processing rest of data/controls, beginning with URG 1454 */ 1455 case TCPS_SYN_SENT: 1456 if ((thflags & TH_ACK) && 1457 (SEQ_LEQ(th->th_ack, tp->iss) || 1458 SEQ_GT(th->th_ack, tp->snd_max))) { 1459 rstreason = BANDLIM_UNLIMITED; 1460 goto dropwithreset; 1461 } 1462 if (thflags & TH_RST) { 1463 if (thflags & TH_ACK) 1464 tp = tcp_drop(tp, ECONNREFUSED); 1465 goto drop; 1466 } 1467 if (!(thflags & TH_SYN)) 1468 goto drop; 1469 tp->snd_wnd = th->th_win; /* initial send window */ 1470 1471 tp->irs = th->th_seq; 1472 tcp_rcvseqinit(tp); 1473 if (thflags & TH_ACK) { 1474 /* Our SYN was acked. */ 1475 tcpstat.tcps_connects++; 1476 soisconnected(so); 1477 /* Do window scaling on this connection? */ 1478 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1479 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1480 tp->snd_scale = tp->requested_s_scale; 1481 tp->rcv_scale = tp->request_r_scale; 1482 } 1483 tp->rcv_adv += tp->rcv_wnd; 1484 tp->snd_una++; /* SYN is acked */ 1485 tcp_callout_stop(tp, tp->tt_rexmt); 1486 /* 1487 * If there's data, delay ACK; if there's also a FIN 1488 * ACKNOW will be turned on later. 1489 */ 1490 if (DELAY_ACK(tp) && tlen != 0) { 1491 tcp_callout_reset(tp, tp->tt_delack, 1492 tcp_delacktime, tcp_timer_delack); 1493 } else { 1494 tp->t_flags |= TF_ACKNOW; 1495 } 1496 /* 1497 * Received <SYN,ACK> in SYN_SENT[*] state. 1498 * Transitions: 1499 * SYN_SENT --> ESTABLISHED 1500 * SYN_SENT* --> FIN_WAIT_1 1501 */ 1502 tp->t_starttime = ticks; 1503 if (tp->t_flags & TF_NEEDFIN) { 1504 tp->t_state = TCPS_FIN_WAIT_1; 1505 tp->t_flags &= ~TF_NEEDFIN; 1506 thflags &= ~TH_SYN; 1507 } else { 1508 tp->t_state = TCPS_ESTABLISHED; 1509 tcp_callout_reset(tp, tp->tt_keep, 1510 tcp_getkeepidle(tp), 1511 tcp_timer_keep); 1512 } 1513 } else { 1514 /* 1515 * Received initial SYN in SYN-SENT[*] state => 1516 * simultaneous open. 1517 * Do 3-way handshake: 1518 * SYN-SENT -> SYN-RECEIVED 1519 * SYN-SENT* -> SYN-RECEIVED* 1520 */ 1521 tp->t_flags |= TF_ACKNOW; 1522 tcp_callout_stop(tp, tp->tt_rexmt); 1523 tp->t_state = TCPS_SYN_RECEIVED; 1524 } 1525 1526 trimthenstep6: 1527 /* 1528 * Advance th->th_seq to correspond to first data byte. 1529 * If data, trim to stay within window, 1530 * dropping FIN if necessary. 1531 */ 1532 th->th_seq++; 1533 if (tlen > tp->rcv_wnd) { 1534 todrop = tlen - tp->rcv_wnd; 1535 m_adj(m, -todrop); 1536 tlen = tp->rcv_wnd; 1537 thflags &= ~TH_FIN; 1538 tcpstat.tcps_rcvpackafterwin++; 1539 tcpstat.tcps_rcvbyteafterwin += todrop; 1540 } 1541 tp->snd_wl1 = th->th_seq - 1; 1542 tp->rcv_up = th->th_seq; 1543 /* 1544 * Client side of transaction: already sent SYN and data. 1545 * If the remote host used T/TCP to validate the SYN, 1546 * our data will be ACK'd; if so, enter normal data segment 1547 * processing in the middle of step 5, ack processing. 1548 * Otherwise, goto step 6. 1549 */ 1550 if (thflags & TH_ACK) 1551 goto process_ACK; 1552 1553 goto step6; 1554 1555 /* 1556 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1557 * do normal processing (we no longer bother with T/TCP). 1558 */ 1559 case TCPS_LAST_ACK: 1560 case TCPS_CLOSING: 1561 case TCPS_TIME_WAIT: 1562 break; /* continue normal processing */ 1563 } 1564 1565 /* 1566 * States other than LISTEN or SYN_SENT. 1567 * First check the RST flag and sequence number since reset segments 1568 * are exempt from the timestamp and connection count tests. This 1569 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1570 * below which allowed reset segments in half the sequence space 1571 * to fall though and be processed (which gives forged reset 1572 * segments with a random sequence number a 50 percent chance of 1573 * killing a connection). 1574 * Then check timestamp, if present. 1575 * Then check the connection count, if present. 1576 * Then check that at least some bytes of segment are within 1577 * receive window. If segment begins before rcv_nxt, 1578 * drop leading data (and SYN); if nothing left, just ack. 1579 * 1580 * 1581 * If the RST bit is set, check the sequence number to see 1582 * if this is a valid reset segment. 1583 * RFC 793 page 37: 1584 * In all states except SYN-SENT, all reset (RST) segments 1585 * are validated by checking their SEQ-fields. A reset is 1586 * valid if its sequence number is in the window. 1587 * Note: this does not take into account delayed ACKs, so 1588 * we should test against last_ack_sent instead of rcv_nxt. 1589 * The sequence number in the reset segment is normally an 1590 * echo of our outgoing acknowledgement numbers, but some hosts 1591 * send a reset with the sequence number at the rightmost edge 1592 * of our receive window, and we have to handle this case. 1593 * If we have multiple segments in flight, the intial reset 1594 * segment sequence numbers will be to the left of last_ack_sent, 1595 * but they will eventually catch up. 1596 * In any case, it never made sense to trim reset segments to 1597 * fit the receive window since RFC 1122 says: 1598 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1599 * 1600 * A TCP SHOULD allow a received RST segment to include data. 1601 * 1602 * DISCUSSION 1603 * It has been suggested that a RST segment could contain 1604 * ASCII text that encoded and explained the cause of the 1605 * RST. No standard has yet been established for such 1606 * data. 1607 * 1608 * If the reset segment passes the sequence number test examine 1609 * the state: 1610 * SYN_RECEIVED STATE: 1611 * If passive open, return to LISTEN state. 1612 * If active open, inform user that connection was refused. 1613 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1614 * Inform user that connection was reset, and close tcb. 1615 * CLOSING, LAST_ACK STATES: 1616 * Close the tcb. 1617 * TIME_WAIT STATE: 1618 * Drop the segment - see Stevens, vol. 2, p. 964 and 1619 * RFC 1337. 1620 */ 1621 if (thflags & TH_RST) { 1622 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1623 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1624 switch (tp->t_state) { 1625 1626 case TCPS_SYN_RECEIVED: 1627 so->so_error = ECONNREFUSED; 1628 goto close; 1629 1630 case TCPS_ESTABLISHED: 1631 case TCPS_FIN_WAIT_1: 1632 case TCPS_FIN_WAIT_2: 1633 case TCPS_CLOSE_WAIT: 1634 so->so_error = ECONNRESET; 1635 close: 1636 tp->t_state = TCPS_CLOSED; 1637 tcpstat.tcps_drops++; 1638 tp = tcp_close(tp); 1639 break; 1640 1641 case TCPS_CLOSING: 1642 case TCPS_LAST_ACK: 1643 tp = tcp_close(tp); 1644 break; 1645 1646 case TCPS_TIME_WAIT: 1647 break; 1648 } 1649 } 1650 goto drop; 1651 } 1652 1653 /* 1654 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1655 * and it's less than ts_recent, drop it. 1656 */ 1657 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1658 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1659 1660 /* Check to see if ts_recent is over 24 days old. */ 1661 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1662 /* 1663 * Invalidate ts_recent. If this segment updates 1664 * ts_recent, the age will be reset later and ts_recent 1665 * will get a valid value. If it does not, setting 1666 * ts_recent to zero will at least satisfy the 1667 * requirement that zero be placed in the timestamp 1668 * echo reply when ts_recent isn't valid. The 1669 * age isn't reset until we get a valid ts_recent 1670 * because we don't want out-of-order segments to be 1671 * dropped when ts_recent is old. 1672 */ 1673 tp->ts_recent = 0; 1674 } else { 1675 tcpstat.tcps_rcvduppack++; 1676 tcpstat.tcps_rcvdupbyte += tlen; 1677 tcpstat.tcps_pawsdrop++; 1678 if (tlen) 1679 goto dropafterack; 1680 goto drop; 1681 } 1682 } 1683 1684 /* 1685 * In the SYN-RECEIVED state, validate that the packet belongs to 1686 * this connection before trimming the data to fit the receive 1687 * window. Check the sequence number versus IRS since we know 1688 * the sequence numbers haven't wrapped. This is a partial fix 1689 * for the "LAND" DoS attack. 1690 */ 1691 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1692 rstreason = BANDLIM_RST_OPENPORT; 1693 goto dropwithreset; 1694 } 1695 1696 todrop = tp->rcv_nxt - th->th_seq; 1697 if (todrop > 0) { 1698 if (TCP_DO_SACK(tp)) { 1699 /* Report duplicate segment at head of packet. */ 1700 tp->reportblk.rblk_start = th->th_seq; 1701 tp->reportblk.rblk_end = th->th_seq + tlen; 1702 if (thflags & TH_FIN) 1703 ++tp->reportblk.rblk_end; 1704 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1705 tp->reportblk.rblk_end = tp->rcv_nxt; 1706 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1707 } 1708 if (thflags & TH_SYN) { 1709 thflags &= ~TH_SYN; 1710 th->th_seq++; 1711 if (th->th_urp > 1) 1712 th->th_urp--; 1713 else 1714 thflags &= ~TH_URG; 1715 todrop--; 1716 } 1717 /* 1718 * Following if statement from Stevens, vol. 2, p. 960. 1719 */ 1720 if (todrop > tlen || 1721 (todrop == tlen && !(thflags & TH_FIN))) { 1722 /* 1723 * Any valid FIN must be to the left of the window. 1724 * At this point the FIN must be a duplicate or out 1725 * of sequence; drop it. 1726 */ 1727 thflags &= ~TH_FIN; 1728 1729 /* 1730 * Send an ACK to resynchronize and drop any data. 1731 * But keep on processing for RST or ACK. 1732 */ 1733 tp->t_flags |= TF_ACKNOW; 1734 todrop = tlen; 1735 tcpstat.tcps_rcvduppack++; 1736 tcpstat.tcps_rcvdupbyte += todrop; 1737 } else { 1738 tcpstat.tcps_rcvpartduppack++; 1739 tcpstat.tcps_rcvpartdupbyte += todrop; 1740 } 1741 drop_hdrlen += todrop; /* drop from the top afterwards */ 1742 th->th_seq += todrop; 1743 tlen -= todrop; 1744 if (th->th_urp > todrop) 1745 th->th_urp -= todrop; 1746 else { 1747 thflags &= ~TH_URG; 1748 th->th_urp = 0; 1749 } 1750 } 1751 1752 /* 1753 * If new data are received on a connection after the 1754 * user processes are gone, then RST the other end. 1755 */ 1756 if ((so->so_state & SS_NOFDREF) && 1757 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1758 tp = tcp_close(tp); 1759 tcpstat.tcps_rcvafterclose++; 1760 rstreason = BANDLIM_UNLIMITED; 1761 goto dropwithreset; 1762 } 1763 1764 /* 1765 * If segment ends after window, drop trailing data 1766 * (and PUSH and FIN); if nothing left, just ACK. 1767 */ 1768 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1769 if (todrop > 0) { 1770 tcpstat.tcps_rcvpackafterwin++; 1771 if (todrop >= tlen) { 1772 tcpstat.tcps_rcvbyteafterwin += tlen; 1773 /* 1774 * If a new connection request is received 1775 * while in TIME_WAIT, drop the old connection 1776 * and start over if the sequence numbers 1777 * are above the previous ones. 1778 */ 1779 if (thflags & TH_SYN && 1780 tp->t_state == TCPS_TIME_WAIT && 1781 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1782 tp = tcp_close(tp); 1783 goto findpcb; 1784 } 1785 /* 1786 * If window is closed can only take segments at 1787 * window edge, and have to drop data and PUSH from 1788 * incoming segments. Continue processing, but 1789 * remember to ack. Otherwise, drop segment 1790 * and ack. 1791 */ 1792 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1793 tp->t_flags |= TF_ACKNOW; 1794 tcpstat.tcps_rcvwinprobe++; 1795 } else 1796 goto dropafterack; 1797 } else 1798 tcpstat.tcps_rcvbyteafterwin += todrop; 1799 m_adj(m, -todrop); 1800 tlen -= todrop; 1801 thflags &= ~(TH_PUSH | TH_FIN); 1802 } 1803 1804 /* 1805 * If last ACK falls within this segment's sequence numbers, 1806 * record its timestamp. 1807 * NOTE: 1808 * 1) That the test incorporates suggestions from the latest 1809 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1810 * 2) That updating only on newer timestamps interferes with 1811 * our earlier PAWS tests, so this check should be solely 1812 * predicated on the sequence space of this segment. 1813 * 3) That we modify the segment boundary check to be 1814 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1815 * instead of RFC1323's 1816 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1817 * This modified check allows us to overcome RFC1323's 1818 * limitations as described in Stevens TCP/IP Illustrated 1819 * Vol. 2 p.869. In such cases, we can still calculate the 1820 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1821 */ 1822 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1823 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1824 + ((thflags & TH_SYN) != 0) 1825 + ((thflags & TH_FIN) != 0)))) { 1826 tp->ts_recent_age = ticks; 1827 tp->ts_recent = to.to_tsval; 1828 } 1829 1830 /* 1831 * If a SYN is in the window, then this is an 1832 * error and we send an RST and drop the connection. 1833 */ 1834 if (thflags & TH_SYN) { 1835 tp = tcp_drop(tp, ECONNRESET); 1836 rstreason = BANDLIM_UNLIMITED; 1837 goto dropwithreset; 1838 } 1839 1840 /* 1841 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1842 * flag is on (half-synchronized state), then queue data for 1843 * later processing; else drop segment and return. 1844 */ 1845 if (!(thflags & TH_ACK)) { 1846 if (tp->t_state == TCPS_SYN_RECEIVED || 1847 (tp->t_flags & TF_NEEDSYN)) 1848 goto step6; 1849 else 1850 goto drop; 1851 } 1852 1853 /* 1854 * Ack processing. 1855 */ 1856 switch (tp->t_state) { 1857 /* 1858 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1859 * ESTABLISHED state and continue processing. 1860 * The ACK was checked above. 1861 */ 1862 case TCPS_SYN_RECEIVED: 1863 1864 tcpstat.tcps_connects++; 1865 soisconnected(so); 1866 /* Do window scaling? */ 1867 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1868 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1869 tp->snd_scale = tp->requested_s_scale; 1870 tp->rcv_scale = tp->request_r_scale; 1871 } 1872 /* 1873 * Make transitions: 1874 * SYN-RECEIVED -> ESTABLISHED 1875 * SYN-RECEIVED* -> FIN-WAIT-1 1876 */ 1877 tp->t_starttime = ticks; 1878 if (tp->t_flags & TF_NEEDFIN) { 1879 tp->t_state = TCPS_FIN_WAIT_1; 1880 tp->t_flags &= ~TF_NEEDFIN; 1881 } else { 1882 tp->t_state = TCPS_ESTABLISHED; 1883 tcp_callout_reset(tp, tp->tt_keep, 1884 tcp_getkeepidle(tp), 1885 tcp_timer_keep); 1886 } 1887 /* 1888 * If segment contains data or ACK, will call tcp_reass() 1889 * later; if not, do so now to pass queued data to user. 1890 */ 1891 if (tlen == 0 && !(thflags & TH_FIN)) 1892 tcp_reass(tp, NULL, NULL, NULL); 1893 /* fall into ... */ 1894 1895 /* 1896 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1897 * ACKs. If the ack is in the range 1898 * tp->snd_una < th->th_ack <= tp->snd_max 1899 * then advance tp->snd_una to th->th_ack and drop 1900 * data from the retransmission queue. If this ACK reflects 1901 * more up to date window information we update our window information. 1902 */ 1903 case TCPS_ESTABLISHED: 1904 case TCPS_FIN_WAIT_1: 1905 case TCPS_FIN_WAIT_2: 1906 case TCPS_CLOSE_WAIT: 1907 case TCPS_CLOSING: 1908 case TCPS_LAST_ACK: 1909 case TCPS_TIME_WAIT: 1910 1911 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1912 if (TCP_DO_SACK(tp)) 1913 tcp_sack_update_scoreboard(tp, &to); 1914 if (tlen != 0 || tiwin != tp->snd_wnd) { 1915 tp->t_dupacks = 0; 1916 break; 1917 } 1918 tcpstat.tcps_rcvdupack++; 1919 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1920 th->th_ack != tp->snd_una) { 1921 tp->t_dupacks = 0; 1922 break; 1923 } 1924 /* 1925 * We have outstanding data (other than 1926 * a window probe), this is a completely 1927 * duplicate ack (ie, window info didn't 1928 * change), the ack is the biggest we've 1929 * seen and we've seen exactly our rexmt 1930 * threshhold of them, so assume a packet 1931 * has been dropped and retransmit it. 1932 * Kludge snd_nxt & the congestion 1933 * window so we send only this one 1934 * packet. 1935 */ 1936 if (IN_FASTRECOVERY(tp)) { 1937 if (TCP_DO_SACK(tp)) { 1938 /* No artifical cwnd inflation. */ 1939 tcp_sack_rexmt(tp, th); 1940 } else { 1941 /* 1942 * Dup acks mean that packets 1943 * have left the network 1944 * (they're now cached at the 1945 * receiver) so bump cwnd by 1946 * the amount in the receiver 1947 * to keep a constant cwnd 1948 * packets in the network. 1949 */ 1950 tp->snd_cwnd += tp->t_maxseg; 1951 tcp_output(tp); 1952 } 1953 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1954 tp->t_dupacks = 0; 1955 break; 1956 } else if (++tp->t_dupacks == tcprexmtthresh) { 1957 tcp_seq old_snd_nxt; 1958 u_int win; 1959 1960 fastretransmit: 1961 if (tcp_do_eifel_detect && 1962 (tp->t_flags & TF_RCVD_TSTMP)) { 1963 tcp_save_congestion_state(tp); 1964 tp->t_flags |= TF_FASTREXMT; 1965 } 1966 /* 1967 * We know we're losing at the current 1968 * window size, so do congestion avoidance: 1969 * set ssthresh to half the current window 1970 * and pull our congestion window back to the 1971 * new ssthresh. 1972 */ 1973 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1974 tp->t_maxseg; 1975 if (win < 2) 1976 win = 2; 1977 tp->snd_ssthresh = win * tp->t_maxseg; 1978 ENTER_FASTRECOVERY(tp); 1979 tp->snd_recover = tp->snd_max; 1980 tcp_callout_stop(tp, tp->tt_rexmt); 1981 tp->t_rtttime = 0; 1982 old_snd_nxt = tp->snd_nxt; 1983 tp->snd_nxt = th->th_ack; 1984 tp->snd_cwnd = tp->t_maxseg; 1985 tcp_output(tp); 1986 ++tcpstat.tcps_sndfastrexmit; 1987 tp->snd_cwnd = tp->snd_ssthresh; 1988 tp->rexmt_high = tp->snd_nxt; 1989 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1990 tp->snd_nxt = old_snd_nxt; 1991 KASSERT(tp->snd_limited <= 2, 1992 ("tp->snd_limited too big")); 1993 if (TCP_DO_SACK(tp)) 1994 tcp_sack_rexmt(tp, th); 1995 else 1996 tp->snd_cwnd += tp->t_maxseg * 1997 (tp->t_dupacks - tp->snd_limited); 1998 } else if (tcp_do_limitedtransmit) { 1999 u_long oldcwnd = tp->snd_cwnd; 2000 tcp_seq oldsndmax = tp->snd_max; 2001 tcp_seq oldsndnxt = tp->snd_nxt; 2002 /* outstanding data */ 2003 uint32_t ownd = tp->snd_max - tp->snd_una; 2004 u_int sent; 2005 2006 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2007 2008 KASSERT(tp->t_dupacks == 1 || 2009 tp->t_dupacks == 2, 2010 ("dupacks not 1 or 2")); 2011 if (tp->t_dupacks == 1) 2012 tp->snd_limited = 0; 2013 tp->snd_nxt = tp->snd_max; 2014 tp->snd_cwnd = ownd + 2015 (tp->t_dupacks - tp->snd_limited) * 2016 tp->t_maxseg; 2017 tcp_output(tp); 2018 2019 /* 2020 * Other acks may have been processed, 2021 * snd_nxt cannot be reset to a value less 2022 * then snd_una. 2023 */ 2024 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2025 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2026 tp->snd_nxt = oldsndnxt; 2027 else 2028 tp->snd_nxt = tp->snd_una; 2029 } 2030 tp->snd_cwnd = oldcwnd; 2031 sent = tp->snd_max - oldsndmax; 2032 if (sent > tp->t_maxseg) { 2033 KASSERT((tp->t_dupacks == 2 && 2034 tp->snd_limited == 0) || 2035 (sent == tp->t_maxseg + 1 && 2036 tp->t_flags & TF_SENTFIN), 2037 ("sent too much")); 2038 KASSERT(sent <= tp->t_maxseg * 2, 2039 ("sent too many segments")); 2040 tp->snd_limited = 2; 2041 tcpstat.tcps_sndlimited += 2; 2042 } else if (sent > 0) { 2043 ++tp->snd_limited; 2044 ++tcpstat.tcps_sndlimited; 2045 } else if (tcp_do_early_retransmit && 2046 (tcp_do_eifel_detect && 2047 (tp->t_flags & TF_RCVD_TSTMP)) && 2048 ownd < 4 * tp->t_maxseg && 2049 tp->t_dupacks + 1 >= 2050 iceildiv(ownd, tp->t_maxseg) && 2051 (!TCP_DO_SACK(tp) || 2052 ownd <= tp->t_maxseg || 2053 tcp_sack_has_sacked(&tp->scb, 2054 ownd - tp->t_maxseg))) { 2055 ++tcpstat.tcps_sndearlyrexmit; 2056 tp->t_flags |= TF_EARLYREXMT; 2057 goto fastretransmit; 2058 } 2059 } 2060 goto drop; 2061 } 2062 2063 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2064 tp->t_dupacks = 0; 2065 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2066 /* 2067 * Detected optimistic ACK attack. 2068 * Force slow-start to de-synchronize attack. 2069 */ 2070 tp->snd_cwnd = tp->t_maxseg; 2071 tp->snd_wacked = 0; 2072 2073 tcpstat.tcps_rcvacktoomuch++; 2074 goto dropafterack; 2075 } 2076 /* 2077 * If we reach this point, ACK is not a duplicate, 2078 * i.e., it ACKs something we sent. 2079 */ 2080 if (tp->t_flags & TF_NEEDSYN) { 2081 /* 2082 * T/TCP: Connection was half-synchronized, and our 2083 * SYN has been ACK'd (so connection is now fully 2084 * synchronized). Go to non-starred state, 2085 * increment snd_una for ACK of SYN, and check if 2086 * we can do window scaling. 2087 */ 2088 tp->t_flags &= ~TF_NEEDSYN; 2089 tp->snd_una++; 2090 /* Do window scaling? */ 2091 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2092 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2093 tp->snd_scale = tp->requested_s_scale; 2094 tp->rcv_scale = tp->request_r_scale; 2095 } 2096 } 2097 2098 process_ACK: 2099 acked = th->th_ack - tp->snd_una; 2100 tcpstat.tcps_rcvackpack++; 2101 tcpstat.tcps_rcvackbyte += acked; 2102 2103 if (tcp_do_eifel_detect && acked > 0 && 2104 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2105 (tp->t_flags & TF_FIRSTACCACK)) { 2106 /* Eifel detection applicable. */ 2107 if (to.to_tsecr < tp->t_rexmtTS) { 2108 ++tcpstat.tcps_eifeldetected; 2109 tcp_revert_congestion_state(tp); 2110 if (tp->t_rxtshift == 1 && 2111 ticks >= tp->t_badrxtwin) 2112 ++tcpstat.tcps_rttcantdetect; 2113 } 2114 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2115 /* 2116 * If we just performed our first retransmit, 2117 * and the ACK arrives within our recovery window, 2118 * then it was a mistake to do the retransmit 2119 * in the first place. Recover our original cwnd 2120 * and ssthresh, and proceed to transmit where we 2121 * left off. 2122 */ 2123 tcp_revert_congestion_state(tp); 2124 ++tcpstat.tcps_rttdetected; 2125 } 2126 2127 /* 2128 * If we have a timestamp reply, update smoothed 2129 * round trip time. If no timestamp is present but 2130 * transmit timer is running and timed sequence 2131 * number was acked, update smoothed round trip time. 2132 * Since we now have an rtt measurement, cancel the 2133 * timer backoff (cf., Phil Karn's retransmit alg.). 2134 * Recompute the initial retransmit timer. 2135 * 2136 * Some machines (certain windows boxes) send broken 2137 * timestamp replies during the SYN+ACK phase, ignore 2138 * timestamps of 0. 2139 */ 2140 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2141 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2142 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2143 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2144 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2145 2146 /* 2147 * If no data (only SYN) was ACK'd, 2148 * skip rest of ACK processing. 2149 */ 2150 if (acked == 0) 2151 goto step6; 2152 2153 /* Stop looking for an acceptable ACK since one was received. */ 2154 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2155 2156 if (acked > so->so_snd.ssb_cc) { 2157 tp->snd_wnd -= so->so_snd.ssb_cc; 2158 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2159 ourfinisacked = TRUE; 2160 } else { 2161 sbdrop(&so->so_snd.sb, acked); 2162 tp->snd_wnd -= acked; 2163 ourfinisacked = FALSE; 2164 } 2165 sowwakeup(so); 2166 2167 /* 2168 * Update window information. 2169 * Don't look at window if no ACK: 2170 * TAC's send garbage on first SYN. 2171 */ 2172 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2173 (tp->snd_wl1 == th->th_seq && 2174 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2175 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2176 /* keep track of pure window updates */ 2177 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2178 tiwin > tp->snd_wnd) 2179 tcpstat.tcps_rcvwinupd++; 2180 tp->snd_wnd = tiwin; 2181 tp->snd_wl1 = th->th_seq; 2182 tp->snd_wl2 = th->th_ack; 2183 if (tp->snd_wnd > tp->max_sndwnd) 2184 tp->max_sndwnd = tp->snd_wnd; 2185 needoutput = TRUE; 2186 } 2187 2188 tp->snd_una = th->th_ack; 2189 if (TCP_DO_SACK(tp)) 2190 tcp_sack_update_scoreboard(tp, &to); 2191 if (IN_FASTRECOVERY(tp)) { 2192 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2193 EXIT_FASTRECOVERY(tp); 2194 needoutput = TRUE; 2195 /* 2196 * If the congestion window was inflated 2197 * to account for the other side's 2198 * cached packets, retract it. 2199 */ 2200 if (!TCP_DO_SACK(tp)) 2201 tp->snd_cwnd = tp->snd_ssthresh; 2202 2203 /* 2204 * Window inflation should have left us 2205 * with approximately snd_ssthresh outstanding 2206 * data. But, in case we would be inclined 2207 * to send a burst, better do it using 2208 * slow start. 2209 */ 2210 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2211 tp->snd_max + 2 * tp->t_maxseg)) 2212 tp->snd_cwnd = 2213 (tp->snd_max - tp->snd_una) + 2214 2 * tp->t_maxseg; 2215 2216 tp->snd_wacked = 0; 2217 } else { 2218 if (TCP_DO_SACK(tp)) { 2219 tp->snd_max_rexmt = tp->snd_max; 2220 tcp_sack_rexmt(tp, th); 2221 } else { 2222 tcp_newreno_partial_ack(tp, th, acked); 2223 } 2224 needoutput = FALSE; 2225 } 2226 } else { 2227 /* 2228 * Open the congestion window. When in slow-start, 2229 * open exponentially: maxseg per packet. Otherwise, 2230 * open linearly: maxseg per window. 2231 */ 2232 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2233 u_int abc_sslimit = 2234 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2235 tp->t_maxseg : 2 * tp->t_maxseg); 2236 2237 /* slow-start */ 2238 tp->snd_cwnd += tcp_do_abc ? 2239 min(acked, abc_sslimit) : tp->t_maxseg; 2240 } else { 2241 /* linear increase */ 2242 tp->snd_wacked += tcp_do_abc ? acked : 2243 tp->t_maxseg; 2244 if (tp->snd_wacked >= tp->snd_cwnd) { 2245 tp->snd_wacked -= tp->snd_cwnd; 2246 tp->snd_cwnd += tp->t_maxseg; 2247 } 2248 } 2249 tp->snd_cwnd = min(tp->snd_cwnd, 2250 TCP_MAXWIN << tp->snd_scale); 2251 tp->snd_recover = th->th_ack - 1; 2252 } 2253 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2254 tp->snd_nxt = tp->snd_una; 2255 2256 /* 2257 * If all outstanding data is acked, stop retransmit 2258 * timer and remember to restart (more output or persist). 2259 * If there is more data to be acked, restart retransmit 2260 * timer, using current (possibly backed-off) value. 2261 */ 2262 if (th->th_ack == tp->snd_max) { 2263 tcp_callout_stop(tp, tp->tt_rexmt); 2264 needoutput = TRUE; 2265 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2266 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2267 tcp_timer_rexmt); 2268 } 2269 2270 switch (tp->t_state) { 2271 /* 2272 * In FIN_WAIT_1 STATE in addition to the processing 2273 * for the ESTABLISHED state if our FIN is now acknowledged 2274 * then enter FIN_WAIT_2. 2275 */ 2276 case TCPS_FIN_WAIT_1: 2277 if (ourfinisacked) { 2278 /* 2279 * If we can't receive any more 2280 * data, then closing user can proceed. 2281 * Starting the timer is contrary to the 2282 * specification, but if we don't get a FIN 2283 * we'll hang forever. 2284 */ 2285 if (so->so_state & SS_CANTRCVMORE) { 2286 soisdisconnected(so); 2287 tcp_callout_reset(tp, tp->tt_2msl, 2288 tcp_maxidle, tcp_timer_2msl); 2289 } 2290 tp->t_state = TCPS_FIN_WAIT_2; 2291 } 2292 break; 2293 2294 /* 2295 * In CLOSING STATE in addition to the processing for 2296 * the ESTABLISHED state if the ACK acknowledges our FIN 2297 * then enter the TIME-WAIT state, otherwise ignore 2298 * the segment. 2299 */ 2300 case TCPS_CLOSING: 2301 if (ourfinisacked) { 2302 tp->t_state = TCPS_TIME_WAIT; 2303 tcp_canceltimers(tp); 2304 tcp_callout_reset(tp, tp->tt_2msl, 2305 2 * tcp_msl, tcp_timer_2msl); 2306 soisdisconnected(so); 2307 } 2308 break; 2309 2310 /* 2311 * In LAST_ACK, we may still be waiting for data to drain 2312 * and/or to be acked, as well as for the ack of our FIN. 2313 * If our FIN is now acknowledged, delete the TCB, 2314 * enter the closed state and return. 2315 */ 2316 case TCPS_LAST_ACK: 2317 if (ourfinisacked) { 2318 tp = tcp_close(tp); 2319 goto drop; 2320 } 2321 break; 2322 2323 /* 2324 * In TIME_WAIT state the only thing that should arrive 2325 * is a retransmission of the remote FIN. Acknowledge 2326 * it and restart the finack timer. 2327 */ 2328 case TCPS_TIME_WAIT: 2329 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2330 tcp_timer_2msl); 2331 goto dropafterack; 2332 } 2333 } 2334 2335 step6: 2336 /* 2337 * Update window information. 2338 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2339 */ 2340 if ((thflags & TH_ACK) && 2341 acceptable_window_update(tp, th, tiwin)) { 2342 /* keep track of pure window updates */ 2343 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2344 tiwin > tp->snd_wnd) 2345 tcpstat.tcps_rcvwinupd++; 2346 tp->snd_wnd = tiwin; 2347 tp->snd_wl1 = th->th_seq; 2348 tp->snd_wl2 = th->th_ack; 2349 if (tp->snd_wnd > tp->max_sndwnd) 2350 tp->max_sndwnd = tp->snd_wnd; 2351 needoutput = TRUE; 2352 } 2353 2354 /* 2355 * Process segments with URG. 2356 */ 2357 if ((thflags & TH_URG) && th->th_urp && 2358 !TCPS_HAVERCVDFIN(tp->t_state)) { 2359 /* 2360 * This is a kludge, but if we receive and accept 2361 * random urgent pointers, we'll crash in 2362 * soreceive. It's hard to imagine someone 2363 * actually wanting to send this much urgent data. 2364 */ 2365 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2366 th->th_urp = 0; /* XXX */ 2367 thflags &= ~TH_URG; /* XXX */ 2368 goto dodata; /* XXX */ 2369 } 2370 /* 2371 * If this segment advances the known urgent pointer, 2372 * then mark the data stream. This should not happen 2373 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2374 * a FIN has been received from the remote side. 2375 * In these states we ignore the URG. 2376 * 2377 * According to RFC961 (Assigned Protocols), 2378 * the urgent pointer points to the last octet 2379 * of urgent data. We continue, however, 2380 * to consider it to indicate the first octet 2381 * of data past the urgent section as the original 2382 * spec states (in one of two places). 2383 */ 2384 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2385 tp->rcv_up = th->th_seq + th->th_urp; 2386 so->so_oobmark = so->so_rcv.ssb_cc + 2387 (tp->rcv_up - tp->rcv_nxt) - 1; 2388 if (so->so_oobmark == 0) 2389 sosetstate(so, SS_RCVATMARK); 2390 sohasoutofband(so); 2391 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2392 } 2393 /* 2394 * Remove out of band data so doesn't get presented to user. 2395 * This can happen independent of advancing the URG pointer, 2396 * but if two URG's are pending at once, some out-of-band 2397 * data may creep in... ick. 2398 */ 2399 if (th->th_urp <= (u_long)tlen && 2400 !(so->so_options & SO_OOBINLINE)) { 2401 /* hdr drop is delayed */ 2402 tcp_pulloutofband(so, th, m, drop_hdrlen); 2403 } 2404 } else { 2405 /* 2406 * If no out of band data is expected, 2407 * pull receive urgent pointer along 2408 * with the receive window. 2409 */ 2410 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2411 tp->rcv_up = tp->rcv_nxt; 2412 } 2413 2414 dodata: /* XXX */ 2415 /* 2416 * Process the segment text, merging it into the TCP sequencing queue, 2417 * and arranging for acknowledgment of receipt if necessary. 2418 * This process logically involves adjusting tp->rcv_wnd as data 2419 * is presented to the user (this happens in tcp_usrreq.c, 2420 * case PRU_RCVD). If a FIN has already been received on this 2421 * connection then we just ignore the text. 2422 */ 2423 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2424 m_adj(m, drop_hdrlen); /* delayed header drop */ 2425 /* 2426 * Insert segment which includes th into TCP reassembly queue 2427 * with control block tp. Set thflags to whether reassembly now 2428 * includes a segment with FIN. This handles the common case 2429 * inline (segment is the next to be received on an established 2430 * connection, and the queue is empty), avoiding linkage into 2431 * and removal from the queue and repetition of various 2432 * conversions. 2433 * Set DELACK for segments received in order, but ack 2434 * immediately when segments are out of order (so 2435 * fast retransmit can work). 2436 */ 2437 if (th->th_seq == tp->rcv_nxt && 2438 LIST_EMPTY(&tp->t_segq) && 2439 TCPS_HAVEESTABLISHED(tp->t_state)) { 2440 if (DELAY_ACK(tp)) { 2441 tcp_callout_reset(tp, tp->tt_delack, 2442 tcp_delacktime, tcp_timer_delack); 2443 } else { 2444 tp->t_flags |= TF_ACKNOW; 2445 } 2446 tp->rcv_nxt += tlen; 2447 thflags = th->th_flags & TH_FIN; 2448 tcpstat.tcps_rcvpack++; 2449 tcpstat.tcps_rcvbyte += tlen; 2450 ND6_HINT(tp); 2451 if (so->so_state & SS_CANTRCVMORE) { 2452 m_freem(m); 2453 } else { 2454 lwkt_gettoken(&so->so_rcv.ssb_token); 2455 ssb_appendstream(&so->so_rcv, m); 2456 lwkt_reltoken(&so->so_rcv.ssb_token); 2457 } 2458 sorwakeup(so); 2459 } else { 2460 if (!(tp->t_flags & TF_DUPSEG)) { 2461 /* Initialize SACK report block. */ 2462 tp->reportblk.rblk_start = th->th_seq; 2463 tp->reportblk.rblk_end = th->th_seq + tlen + 2464 ((thflags & TH_FIN) != 0); 2465 } 2466 thflags = tcp_reass(tp, th, &tlen, m); 2467 tp->t_flags |= TF_ACKNOW; 2468 } 2469 2470 /* 2471 * Note the amount of data that peer has sent into 2472 * our window, in order to estimate the sender's 2473 * buffer size. 2474 */ 2475 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2476 } else { 2477 m_freem(m); 2478 thflags &= ~TH_FIN; 2479 } 2480 2481 /* 2482 * If FIN is received ACK the FIN and let the user know 2483 * that the connection is closing. 2484 */ 2485 if (thflags & TH_FIN) { 2486 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2487 socantrcvmore(so); 2488 /* 2489 * If connection is half-synchronized 2490 * (ie NEEDSYN flag on) then delay ACK, 2491 * so it may be piggybacked when SYN is sent. 2492 * Otherwise, since we received a FIN then no 2493 * more input can be expected, send ACK now. 2494 */ 2495 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2496 tcp_callout_reset(tp, tp->tt_delack, 2497 tcp_delacktime, tcp_timer_delack); 2498 } else { 2499 tp->t_flags |= TF_ACKNOW; 2500 } 2501 tp->rcv_nxt++; 2502 } 2503 2504 switch (tp->t_state) { 2505 /* 2506 * In SYN_RECEIVED and ESTABLISHED STATES 2507 * enter the CLOSE_WAIT state. 2508 */ 2509 case TCPS_SYN_RECEIVED: 2510 tp->t_starttime = ticks; 2511 /*FALLTHROUGH*/ 2512 case TCPS_ESTABLISHED: 2513 tp->t_state = TCPS_CLOSE_WAIT; 2514 break; 2515 2516 /* 2517 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2518 * enter the CLOSING state. 2519 */ 2520 case TCPS_FIN_WAIT_1: 2521 tp->t_state = TCPS_CLOSING; 2522 break; 2523 2524 /* 2525 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2526 * starting the time-wait timer, turning off the other 2527 * standard timers. 2528 */ 2529 case TCPS_FIN_WAIT_2: 2530 tp->t_state = TCPS_TIME_WAIT; 2531 tcp_canceltimers(tp); 2532 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2533 tcp_timer_2msl); 2534 soisdisconnected(so); 2535 break; 2536 2537 /* 2538 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2539 */ 2540 case TCPS_TIME_WAIT: 2541 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl, 2542 tcp_timer_2msl); 2543 break; 2544 } 2545 } 2546 2547 #ifdef TCPDEBUG 2548 if (so->so_options & SO_DEBUG) 2549 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2550 #endif 2551 2552 /* 2553 * Return any desired output. 2554 */ 2555 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2556 tcp_output(tp); 2557 return(IPPROTO_DONE); 2558 2559 dropafterack: 2560 /* 2561 * Generate an ACK dropping incoming segment if it occupies 2562 * sequence space, where the ACK reflects our state. 2563 * 2564 * We can now skip the test for the RST flag since all 2565 * paths to this code happen after packets containing 2566 * RST have been dropped. 2567 * 2568 * In the SYN-RECEIVED state, don't send an ACK unless the 2569 * segment we received passes the SYN-RECEIVED ACK test. 2570 * If it fails send a RST. This breaks the loop in the 2571 * "LAND" DoS attack, and also prevents an ACK storm 2572 * between two listening ports that have been sent forged 2573 * SYN segments, each with the source address of the other. 2574 */ 2575 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2576 (SEQ_GT(tp->snd_una, th->th_ack) || 2577 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2578 rstreason = BANDLIM_RST_OPENPORT; 2579 goto dropwithreset; 2580 } 2581 #ifdef TCPDEBUG 2582 if (so->so_options & SO_DEBUG) 2583 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2584 #endif 2585 m_freem(m); 2586 tp->t_flags |= TF_ACKNOW; 2587 tcp_output(tp); 2588 return(IPPROTO_DONE); 2589 2590 dropwithreset: 2591 /* 2592 * Generate a RST, dropping incoming segment. 2593 * Make ACK acceptable to originator of segment. 2594 * Don't bother to respond if destination was broadcast/multicast. 2595 */ 2596 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2597 goto drop; 2598 if (isipv6) { 2599 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2600 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2601 goto drop; 2602 } else { 2603 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2604 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2605 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2606 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2607 goto drop; 2608 } 2609 /* IPv6 anycast check is done at tcp6_input() */ 2610 2611 /* 2612 * Perform bandwidth limiting. 2613 */ 2614 #ifdef ICMP_BANDLIM 2615 if (badport_bandlim(rstreason) < 0) 2616 goto drop; 2617 #endif 2618 2619 #ifdef TCPDEBUG 2620 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2621 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2622 #endif 2623 if (thflags & TH_ACK) 2624 /* mtod() below is safe as long as hdr dropping is delayed */ 2625 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2626 TH_RST); 2627 else { 2628 if (thflags & TH_SYN) 2629 tlen++; 2630 /* mtod() below is safe as long as hdr dropping is delayed */ 2631 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2632 (tcp_seq)0, TH_RST | TH_ACK); 2633 } 2634 return(IPPROTO_DONE); 2635 2636 drop: 2637 /* 2638 * Drop space held by incoming segment and return. 2639 */ 2640 #ifdef TCPDEBUG 2641 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2642 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2643 #endif 2644 m_freem(m); 2645 return(IPPROTO_DONE); 2646 } 2647 2648 /* 2649 * Parse TCP options and place in tcpopt. 2650 */ 2651 static void 2652 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2653 { 2654 int opt, optlen, i; 2655 2656 to->to_flags = 0; 2657 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2658 opt = cp[0]; 2659 if (opt == TCPOPT_EOL) 2660 break; 2661 if (opt == TCPOPT_NOP) 2662 optlen = 1; 2663 else { 2664 if (cnt < 2) 2665 break; 2666 optlen = cp[1]; 2667 if (optlen < 2 || optlen > cnt) 2668 break; 2669 } 2670 switch (opt) { 2671 case TCPOPT_MAXSEG: 2672 if (optlen != TCPOLEN_MAXSEG) 2673 continue; 2674 if (!is_syn) 2675 continue; 2676 to->to_flags |= TOF_MSS; 2677 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2678 to->to_mss = ntohs(to->to_mss); 2679 break; 2680 case TCPOPT_WINDOW: 2681 if (optlen != TCPOLEN_WINDOW) 2682 continue; 2683 if (!is_syn) 2684 continue; 2685 to->to_flags |= TOF_SCALE; 2686 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2687 break; 2688 case TCPOPT_TIMESTAMP: 2689 if (optlen != TCPOLEN_TIMESTAMP) 2690 continue; 2691 to->to_flags |= TOF_TS; 2692 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2693 to->to_tsval = ntohl(to->to_tsval); 2694 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2695 to->to_tsecr = ntohl(to->to_tsecr); 2696 /* 2697 * If echoed timestamp is later than the current time, 2698 * fall back to non RFC1323 RTT calculation. 2699 */ 2700 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2701 to->to_tsecr = 0; 2702 break; 2703 case TCPOPT_SACK_PERMITTED: 2704 if (optlen != TCPOLEN_SACK_PERMITTED) 2705 continue; 2706 if (!is_syn) 2707 continue; 2708 to->to_flags |= TOF_SACK_PERMITTED; 2709 break; 2710 case TCPOPT_SACK: 2711 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2712 continue; 2713 to->to_nsackblocks = (optlen - 2) / 8; 2714 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2715 to->to_flags |= TOF_SACK; 2716 for (i = 0; i < to->to_nsackblocks; i++) { 2717 struct raw_sackblock *r = &to->to_sackblocks[i]; 2718 2719 r->rblk_start = ntohl(r->rblk_start); 2720 r->rblk_end = ntohl(r->rblk_end); 2721 } 2722 break; 2723 #ifdef TCP_SIGNATURE 2724 /* 2725 * XXX In order to reply to a host which has set the 2726 * TCP_SIGNATURE option in its initial SYN, we have to 2727 * record the fact that the option was observed here 2728 * for the syncache code to perform the correct response. 2729 */ 2730 case TCPOPT_SIGNATURE: 2731 if (optlen != TCPOLEN_SIGNATURE) 2732 continue; 2733 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2734 break; 2735 #endif /* TCP_SIGNATURE */ 2736 default: 2737 continue; 2738 } 2739 } 2740 } 2741 2742 /* 2743 * Pull out of band byte out of a segment so 2744 * it doesn't appear in the user's data queue. 2745 * It is still reflected in the segment length for 2746 * sequencing purposes. 2747 * "off" is the delayed to be dropped hdrlen. 2748 */ 2749 static void 2750 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2751 { 2752 int cnt = off + th->th_urp - 1; 2753 2754 while (cnt >= 0) { 2755 if (m->m_len > cnt) { 2756 char *cp = mtod(m, caddr_t) + cnt; 2757 struct tcpcb *tp = sototcpcb(so); 2758 2759 tp->t_iobc = *cp; 2760 tp->t_oobflags |= TCPOOB_HAVEDATA; 2761 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2762 m->m_len--; 2763 if (m->m_flags & M_PKTHDR) 2764 m->m_pkthdr.len--; 2765 return; 2766 } 2767 cnt -= m->m_len; 2768 m = m->m_next; 2769 if (m == 0) 2770 break; 2771 } 2772 panic("tcp_pulloutofband"); 2773 } 2774 2775 /* 2776 * Collect new round-trip time estimate 2777 * and update averages and current timeout. 2778 */ 2779 static void 2780 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2781 { 2782 int delta; 2783 2784 tcpstat.tcps_rttupdated++; 2785 tp->t_rttupdated++; 2786 if (tp->t_srtt != 0) { 2787 /* 2788 * srtt is stored as fixed point with 5 bits after the 2789 * binary point (i.e., scaled by 8). The following magic 2790 * is equivalent to the smoothing algorithm in rfc793 with 2791 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2792 * point). Adjust rtt to origin 0. 2793 */ 2794 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2795 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2796 2797 if ((tp->t_srtt += delta) <= 0) 2798 tp->t_srtt = 1; 2799 2800 /* 2801 * We accumulate a smoothed rtt variance (actually, a 2802 * smoothed mean difference), then set the retransmit 2803 * timer to smoothed rtt + 4 times the smoothed variance. 2804 * rttvar is stored as fixed point with 4 bits after the 2805 * binary point (scaled by 16). The following is 2806 * equivalent to rfc793 smoothing with an alpha of .75 2807 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2808 * rfc793's wired-in beta. 2809 */ 2810 if (delta < 0) 2811 delta = -delta; 2812 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2813 if ((tp->t_rttvar += delta) <= 0) 2814 tp->t_rttvar = 1; 2815 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2816 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2817 } else { 2818 /* 2819 * No rtt measurement yet - use the unsmoothed rtt. 2820 * Set the variance to half the rtt (so our first 2821 * retransmit happens at 3*rtt). 2822 */ 2823 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2824 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2825 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2826 } 2827 tp->t_rtttime = 0; 2828 tp->t_rxtshift = 0; 2829 2830 /* 2831 * the retransmit should happen at rtt + 4 * rttvar. 2832 * Because of the way we do the smoothing, srtt and rttvar 2833 * will each average +1/2 tick of bias. When we compute 2834 * the retransmit timer, we want 1/2 tick of rounding and 2835 * 1 extra tick because of +-1/2 tick uncertainty in the 2836 * firing of the timer. The bias will give us exactly the 2837 * 1.5 tick we need. But, because the bias is 2838 * statistical, we have to test that we don't drop below 2839 * the minimum feasible timer (which is 2 ticks). 2840 */ 2841 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2842 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2843 2844 /* 2845 * We received an ack for a packet that wasn't retransmitted; 2846 * it is probably safe to discard any error indications we've 2847 * received recently. This isn't quite right, but close enough 2848 * for now (a route might have failed after we sent a segment, 2849 * and the return path might not be symmetrical). 2850 */ 2851 tp->t_softerror = 0; 2852 } 2853 2854 /* 2855 * Determine a reasonable value for maxseg size. 2856 * If the route is known, check route for mtu. 2857 * If none, use an mss that can be handled on the outgoing 2858 * interface without forcing IP to fragment; if bigger than 2859 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2860 * to utilize large mbufs. If no route is found, route has no mtu, 2861 * or the destination isn't local, use a default, hopefully conservative 2862 * size (usually 512 or the default IP max size, but no more than the mtu 2863 * of the interface), as we can't discover anything about intervening 2864 * gateways or networks. We also initialize the congestion/slow start 2865 * window to be a single segment if the destination isn't local. 2866 * While looking at the routing entry, we also initialize other path-dependent 2867 * parameters from pre-set or cached values in the routing entry. 2868 * 2869 * Also take into account the space needed for options that we 2870 * send regularly. Make maxseg shorter by that amount to assure 2871 * that we can send maxseg amount of data even when the options 2872 * are present. Store the upper limit of the length of options plus 2873 * data in maxopd. 2874 * 2875 * NOTE that this routine is only called when we process an incoming 2876 * segment, for outgoing segments only tcp_mssopt is called. 2877 */ 2878 void 2879 tcp_mss(struct tcpcb *tp, int offer) 2880 { 2881 struct rtentry *rt; 2882 struct ifnet *ifp; 2883 int rtt, mss; 2884 u_long bufsize; 2885 struct inpcb *inp = tp->t_inpcb; 2886 struct socket *so; 2887 #ifdef INET6 2888 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2889 size_t min_protoh = isipv6 ? 2890 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2891 sizeof(struct tcpiphdr); 2892 #else 2893 const boolean_t isipv6 = FALSE; 2894 const size_t min_protoh = sizeof(struct tcpiphdr); 2895 #endif 2896 2897 if (isipv6) 2898 rt = tcp_rtlookup6(&inp->inp_inc); 2899 else 2900 rt = tcp_rtlookup(&inp->inp_inc); 2901 if (rt == NULL) { 2902 tp->t_maxopd = tp->t_maxseg = 2903 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2904 return; 2905 } 2906 ifp = rt->rt_ifp; 2907 so = inp->inp_socket; 2908 2909 /* 2910 * Offer == 0 means that there was no MSS on the SYN segment, 2911 * in this case we use either the interface mtu or tcp_mssdflt. 2912 * 2913 * An offer which is too large will be cut down later. 2914 */ 2915 if (offer == 0) { 2916 if (isipv6) { 2917 if (in6_localaddr(&inp->in6p_faddr)) { 2918 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2919 min_protoh; 2920 } else { 2921 offer = tcp_v6mssdflt; 2922 } 2923 } else { 2924 if (in_localaddr(inp->inp_faddr)) 2925 offer = ifp->if_mtu - min_protoh; 2926 else 2927 offer = tcp_mssdflt; 2928 } 2929 } 2930 2931 /* 2932 * Prevent DoS attack with too small MSS. Round up 2933 * to at least minmss. 2934 * 2935 * Sanity check: make sure that maxopd will be large 2936 * enough to allow some data on segments even is the 2937 * all the option space is used (40bytes). Otherwise 2938 * funny things may happen in tcp_output. 2939 */ 2940 offer = max(offer, tcp_minmss); 2941 offer = max(offer, 64); 2942 2943 rt->rt_rmx.rmx_mssopt = offer; 2944 2945 /* 2946 * While we're here, check if there's an initial rtt 2947 * or rttvar. Convert from the route-table units 2948 * to scaled multiples of the slow timeout timer. 2949 */ 2950 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2951 /* 2952 * XXX the lock bit for RTT indicates that the value 2953 * is also a minimum value; this is subject to time. 2954 */ 2955 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2956 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2957 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2958 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2959 tcpstat.tcps_usedrtt++; 2960 if (rt->rt_rmx.rmx_rttvar) { 2961 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2962 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2963 tcpstat.tcps_usedrttvar++; 2964 } else { 2965 /* default variation is +- 1 rtt */ 2966 tp->t_rttvar = 2967 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2968 } 2969 TCPT_RANGESET(tp->t_rxtcur, 2970 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2971 tp->t_rttmin, TCPTV_REXMTMAX); 2972 } 2973 2974 /* 2975 * if there's an mtu associated with the route, use it 2976 * else, use the link mtu. Take the smaller of mss or offer 2977 * as our final mss. 2978 */ 2979 if (rt->rt_rmx.rmx_mtu) { 2980 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2981 } else { 2982 if (isipv6) 2983 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2984 else 2985 mss = ifp->if_mtu - min_protoh; 2986 } 2987 mss = min(mss, offer); 2988 2989 /* 2990 * maxopd stores the maximum length of data AND options 2991 * in a segment; maxseg is the amount of data in a normal 2992 * segment. We need to store this value (maxopd) apart 2993 * from maxseg, because now every segment carries options 2994 * and thus we normally have somewhat less data in segments. 2995 */ 2996 tp->t_maxopd = mss; 2997 2998 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 2999 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3000 mss -= TCPOLEN_TSTAMP_APPA; 3001 3002 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3003 if (mss > MCLBYTES) 3004 mss &= ~(MCLBYTES-1); 3005 #else 3006 if (mss > MCLBYTES) 3007 mss = mss / MCLBYTES * MCLBYTES; 3008 #endif 3009 /* 3010 * If there's a pipesize, change the socket buffer 3011 * to that size. Make the socket buffers an integral 3012 * number of mss units; if the mss is larger than 3013 * the socket buffer, decrease the mss. 3014 */ 3015 #ifdef RTV_SPIPE 3016 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3017 #endif 3018 bufsize = so->so_snd.ssb_hiwat; 3019 if (bufsize < mss) 3020 mss = bufsize; 3021 else { 3022 bufsize = roundup(bufsize, mss); 3023 if (bufsize > sb_max) 3024 bufsize = sb_max; 3025 if (bufsize > so->so_snd.ssb_hiwat) 3026 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3027 } 3028 tp->t_maxseg = mss; 3029 3030 #ifdef RTV_RPIPE 3031 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3032 #endif 3033 bufsize = so->so_rcv.ssb_hiwat; 3034 if (bufsize > mss) { 3035 bufsize = roundup(bufsize, mss); 3036 if (bufsize > sb_max) 3037 bufsize = sb_max; 3038 if (bufsize > so->so_rcv.ssb_hiwat) { 3039 lwkt_gettoken(&so->so_rcv.ssb_token); 3040 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3041 lwkt_reltoken(&so->so_rcv.ssb_token); 3042 } 3043 } 3044 3045 /* 3046 * Set the slow-start flight size depending on whether this 3047 * is a local network or not. 3048 */ 3049 if (tcp_do_rfc3390) 3050 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3051 else 3052 tp->snd_cwnd = mss; 3053 3054 if (rt->rt_rmx.rmx_ssthresh) { 3055 /* 3056 * There's some sort of gateway or interface 3057 * buffer limit on the path. Use this to set 3058 * the slow start threshhold, but set the 3059 * threshold to no less than 2*mss. 3060 */ 3061 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3062 tcpstat.tcps_usedssthresh++; 3063 } 3064 } 3065 3066 /* 3067 * Determine the MSS option to send on an outgoing SYN. 3068 */ 3069 int 3070 tcp_mssopt(struct tcpcb *tp) 3071 { 3072 struct rtentry *rt; 3073 #ifdef INET6 3074 boolean_t isipv6 = 3075 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3076 int min_protoh = isipv6 ? 3077 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3078 sizeof(struct tcpiphdr); 3079 #else 3080 const boolean_t isipv6 = FALSE; 3081 const size_t min_protoh = sizeof(struct tcpiphdr); 3082 #endif 3083 3084 if (isipv6) 3085 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3086 else 3087 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3088 if (rt == NULL) 3089 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3090 3091 return (rt->rt_ifp->if_mtu - min_protoh); 3092 } 3093 3094 /* 3095 * When a partial ack arrives, force the retransmission of the 3096 * next unacknowledged segment. Do not exit Fast Recovery. 3097 * 3098 * Implement the Slow-but-Steady variant of NewReno by restarting the 3099 * the retransmission timer. Turn it off here so it can be restarted 3100 * later in tcp_output(). 3101 */ 3102 static void 3103 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3104 { 3105 tcp_seq old_snd_nxt = tp->snd_nxt; 3106 u_long ocwnd = tp->snd_cwnd; 3107 3108 tcp_callout_stop(tp, tp->tt_rexmt); 3109 tp->t_rtttime = 0; 3110 tp->snd_nxt = th->th_ack; 3111 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3112 tp->snd_cwnd = tp->t_maxseg; 3113 tp->t_flags |= TF_ACKNOW; 3114 tcp_output(tp); 3115 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3116 tp->snd_nxt = old_snd_nxt; 3117 /* partial window deflation */ 3118 if (ocwnd > acked) 3119 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3120 else 3121 tp->snd_cwnd = tp->t_maxseg; 3122 } 3123 3124 /* 3125 * In contrast to the Slow-but-Steady NewReno variant, 3126 * we do not reset the retransmission timer for SACK retransmissions, 3127 * except when retransmitting snd_una. 3128 */ 3129 static void 3130 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3131 { 3132 uint32_t pipe, seglen; 3133 tcp_seq nextrexmt; 3134 boolean_t lostdup; 3135 tcp_seq old_snd_nxt = tp->snd_nxt; 3136 u_long ocwnd = tp->snd_cwnd; 3137 int nseg = 0; /* consecutive new segments */ 3138 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3139 3140 tp->t_rtttime = 0; 3141 pipe = tcp_sack_compute_pipe(tp); 3142 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3143 (!tcp_do_smartsack || nseg < MAXBURST) && 3144 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3145 uint32_t sent; 3146 tcp_seq old_snd_max; 3147 int error; 3148 3149 if (nextrexmt == tp->snd_max) 3150 ++nseg; 3151 tp->snd_nxt = nextrexmt; 3152 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3153 old_snd_max = tp->snd_max; 3154 if (nextrexmt == tp->snd_una) 3155 tcp_callout_stop(tp, tp->tt_rexmt); 3156 error = tcp_output(tp); 3157 if (error != 0) 3158 break; 3159 sent = tp->snd_nxt - nextrexmt; 3160 if (sent <= 0) 3161 break; 3162 if (!lostdup) 3163 pipe += sent; 3164 tcpstat.tcps_sndsackpack++; 3165 tcpstat.tcps_sndsackbyte += sent; 3166 if (SEQ_LT(nextrexmt, old_snd_max) && 3167 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3168 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3169 } 3170 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3171 tp->snd_nxt = old_snd_nxt; 3172 tp->snd_cwnd = ocwnd; 3173 } 3174 3175 /* 3176 * Reset idle time and keep-alive timer, typically called when a valid 3177 * tcp packet is received but may also be called when FASTKEEP is set 3178 * to prevent the previous long-timeout from calculating to a drop. 3179 * 3180 * Only update t_rcvtime for non-SYN packets. 3181 * 3182 * Handle the case where one side thinks the connection is established 3183 * but the other side has, say, rebooted without cleaning out the 3184 * connection. The SYNs could be construed as an attack and wind 3185 * up ignored, but in case it isn't an attack we can validate the 3186 * connection by forcing a keepalive. 3187 */ 3188 void 3189 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3190 { 3191 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3192 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3193 tp->t_flags |= TF_KEEPALIVE; 3194 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3195 tcp_timer_keep); 3196 } else { 3197 tp->t_rcvtime = ticks; 3198 tp->t_flags &= ~TF_KEEPALIVE; 3199 tcp_callout_reset(tp, tp->tt_keep, 3200 tcp_getkeepidle(tp), 3201 tcp_timer_keep); 3202 } 3203 } 3204 } 3205