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