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 */ 69 70 #include "opt_ipfw.h" /* for ipfw_fwd */ 71 #include "opt_inet.h" 72 #include "opt_inet6.h" 73 #include "opt_ipsec.h" 74 #include "opt_tcpdebug.h" 75 #include "opt_tcp_input.h" 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/sysctl.h> 81 #include <sys/malloc.h> 82 #include <sys/mbuf.h> 83 #include <sys/proc.h> /* for proc0 declaration */ 84 #include <sys/protosw.h> 85 #include <sys/socket.h> 86 #include <sys/socketvar.h> 87 #include <sys/syslog.h> 88 #include <sys/in_cksum.h> 89 90 #include <sys/socketvar2.h> 91 92 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 93 #include <machine/stdarg.h> 94 95 #include <net/if.h> 96 #include <net/route.h> 97 98 #include <netinet/in.h> 99 #include <netinet/in_systm.h> 100 #include <netinet/ip.h> 101 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 102 #include <netinet/in_var.h> 103 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 104 #include <netinet/in_pcb.h> 105 #include <netinet/ip_var.h> 106 #include <netinet/ip6.h> 107 #include <netinet/icmp6.h> 108 #include <netinet6/nd6.h> 109 #include <netinet6/ip6_var.h> 110 #include <netinet6/in6_pcb.h> 111 #include <netinet/tcp.h> 112 #include <netinet/tcp_fsm.h> 113 #include <netinet/tcp_seq.h> 114 #include <netinet/tcp_timer.h> 115 #include <netinet/tcp_timer2.h> 116 #include <netinet/tcp_var.h> 117 #include <netinet6/tcp6_var.h> 118 #include <netinet/tcpip.h> 119 120 #ifdef TCPDEBUG 121 #include <netinet/tcp_debug.h> 122 123 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 124 struct tcphdr tcp_savetcp; 125 #endif 126 127 #ifdef FAST_IPSEC 128 #include <netproto/ipsec/ipsec.h> 129 #include <netproto/ipsec/ipsec6.h> 130 #endif 131 132 #ifdef IPSEC 133 #include <netinet6/ipsec.h> 134 #include <netinet6/ipsec6.h> 135 #include <netproto/key/key.h> 136 #endif 137 138 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 139 140 static int log_in_vain = 0; 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 142 &log_in_vain, 0, "Log all incoming TCP connections"); 143 144 static int blackhole = 0; 145 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 146 &blackhole, 0, "Do not send RST when dropping refused connections"); 147 148 int tcp_delack_enabled = 1; 149 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 150 &tcp_delack_enabled, 0, 151 "Delay ACK to try and piggyback it onto a data packet"); 152 153 #ifdef TCP_DROP_SYNFIN 154 static int drop_synfin = 0; 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 156 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 157 #endif 158 159 static int tcp_do_limitedtransmit = 1; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 161 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 162 163 static int tcp_do_early_retransmit = 1; 164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 165 &tcp_do_early_retransmit, 0, "Early retransmit"); 166 167 int tcp_aggregate_acks = 1; 168 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 169 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 170 171 int tcp_do_rfc3390 = 1; 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 173 &tcp_do_rfc3390, 0, 174 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 175 176 static int tcp_do_eifel_detect = 1; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 178 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 179 180 static int tcp_do_abc = 1; 181 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 182 &tcp_do_abc, 0, 183 "TCP Appropriate Byte Counting (RFC 3465)"); 184 185 /* 186 * Define as tunable for easy testing with SACK on and off. 187 * Warning: do not change setting in the middle of an existing active TCP flow, 188 * else strange things might happen to that flow. 189 */ 190 int tcp_do_sack = 1; 191 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 192 &tcp_do_sack, 0, "Enable SACK Algorithms"); 193 194 int tcp_do_smartsack = 1; 195 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 196 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 197 198 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 199 "TCP Segment Reassembly Queue"); 200 201 int tcp_reass_maxseg = 0; 202 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 203 &tcp_reass_maxseg, 0, 204 "Global maximum number of TCP Segments in Reassembly Queue"); 205 206 int tcp_reass_qsize = 0; 207 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 208 &tcp_reass_qsize, 0, 209 "Global number of TCP Segments currently in Reassembly Queue"); 210 211 static int tcp_reass_overflows = 0; 212 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 213 &tcp_reass_overflows, 0, 214 "Global number of TCP Segment Reassembly Queue Overflows"); 215 216 int tcp_do_autorcvbuf = 1; 217 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 218 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 219 220 int tcp_autorcvbuf_inc = 16*1024; 221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 222 &tcp_autorcvbuf_inc, 0, 223 "Incrementor step size of automatic receive buffer"); 224 225 int tcp_autorcvbuf_max = 2*1024*1024; 226 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 227 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 228 229 int tcp_sosnd_agglim = 2; 230 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_agglim, CTLFLAG_RW, 231 &tcp_sosnd_agglim, 0, "TCP sosend mbuf aggregation limit"); 232 233 int tcp_sosnd_async = 1; 234 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_async, CTLFLAG_RW, 235 &tcp_sosnd_async, 0, "TCP asynchronized pru_send"); 236 237 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t); 238 static void tcp_pulloutofband(struct socket *, 239 struct tcphdr *, struct mbuf *, int); 240 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 241 struct mbuf *); 242 static void tcp_xmit_timer(struct tcpcb *, int); 243 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 244 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 245 static int tcp_rmx_msl(const struct tcpcb *); 246 247 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 248 #ifdef INET6 249 #define ND6_HINT(tp) \ 250 do { \ 251 if ((tp) && (tp)->t_inpcb && \ 252 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 253 (tp)->t_inpcb->in6p_route.ro_rt) \ 254 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 255 } while (0) 256 #else 257 #define ND6_HINT(tp) 258 #endif 259 260 /* 261 * Indicate whether this ack should be delayed. We can delay the ack if 262 * - delayed acks are enabled and 263 * - there is no delayed ack timer in progress and 264 * - our last ack wasn't a 0-sized window. We never want to delay 265 * the ack that opens up a 0-sized window. 266 */ 267 #define DELAY_ACK(tp) \ 268 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 269 !(tp->t_flags & TF_RXWIN0SENT)) 270 271 #define acceptable_window_update(tp, th, tiwin) \ 272 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 273 (tp->snd_wl1 == th->th_seq && \ 274 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 275 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 276 277 static int 278 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 279 { 280 struct tseg_qent *q; 281 struct tseg_qent *p = NULL; 282 struct tseg_qent *te; 283 struct socket *so = tp->t_inpcb->inp_socket; 284 int flags; 285 286 /* 287 * Call with th == NULL after become established to 288 * force pre-ESTABLISHED data up to user socket. 289 */ 290 if (th == NULL) 291 goto present; 292 293 /* 294 * Limit the number of segments in the reassembly queue to prevent 295 * holding on to too many segments (and thus running out of mbufs). 296 * Make sure to let the missing segment through which caused this 297 * queue. Always keep one global queue entry spare to be able to 298 * process the missing segment. 299 */ 300 if (th->th_seq != tp->rcv_nxt && 301 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 302 tcp_reass_overflows++; 303 tcpstat.tcps_rcvmemdrop++; 304 m_freem(m); 305 /* no SACK block to report */ 306 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 307 return (0); 308 } 309 310 /* Allocate a new queue entry. */ 311 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 312 if (te == NULL) { 313 tcpstat.tcps_rcvmemdrop++; 314 m_freem(m); 315 /* no SACK block to report */ 316 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 317 return (0); 318 } 319 atomic_add_int(&tcp_reass_qsize, 1); 320 321 /* 322 * Find a segment which begins after this one does. 323 */ 324 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 325 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 326 break; 327 p = q; 328 } 329 330 /* 331 * If there is a preceding segment, it may provide some of 332 * our data already. If so, drop the data from the incoming 333 * segment. If it provides all of our data, drop us. 334 */ 335 if (p != NULL) { 336 tcp_seq_diff_t i; 337 338 /* conversion to int (in i) handles seq wraparound */ 339 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 340 if (i > 0) { /* overlaps preceding segment */ 341 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 342 /* enclosing block starts w/ preceding segment */ 343 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 344 if (i >= *tlenp) { 345 /* preceding encloses incoming segment */ 346 tp->encloseblk.rblk_end = p->tqe_th->th_seq + 347 p->tqe_len; 348 tcpstat.tcps_rcvduppack++; 349 tcpstat.tcps_rcvdupbyte += *tlenp; 350 m_freem(m); 351 kfree(te, M_TSEGQ); 352 atomic_add_int(&tcp_reass_qsize, -1); 353 /* 354 * Try to present any queued data 355 * at the left window edge to the user. 356 * This is needed after the 3-WHS 357 * completes. 358 */ 359 goto present; /* ??? */ 360 } 361 m_adj(m, i); 362 *tlenp -= i; 363 th->th_seq += i; 364 /* incoming segment end is enclosing block end */ 365 tp->encloseblk.rblk_end = th->th_seq + *tlenp + 366 ((th->th_flags & TH_FIN) != 0); 367 /* trim end of reported D-SACK block */ 368 tp->reportblk.rblk_end = th->th_seq; 369 } 370 } 371 tcpstat.tcps_rcvoopack++; 372 tcpstat.tcps_rcvoobyte += *tlenp; 373 374 /* 375 * While we overlap succeeding segments trim them or, 376 * if they are completely covered, dequeue them. 377 */ 378 while (q) { 379 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 380 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 381 struct tseg_qent *nq; 382 383 if (i <= 0) 384 break; 385 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 386 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 387 tp->encloseblk = tp->reportblk; 388 /* report trailing duplicate D-SACK segment */ 389 tp->reportblk.rblk_start = q->tqe_th->th_seq; 390 } 391 if ((tp->t_flags & TF_ENCLOSESEG) && 392 SEQ_GT(qend, tp->encloseblk.rblk_end)) { 393 /* extend enclosing block if one exists */ 394 tp->encloseblk.rblk_end = qend; 395 } 396 if (i < q->tqe_len) { 397 q->tqe_th->th_seq += i; 398 q->tqe_len -= i; 399 m_adj(q->tqe_m, i); 400 break; 401 } 402 403 nq = LIST_NEXT(q, tqe_q); 404 LIST_REMOVE(q, tqe_q); 405 m_freem(q->tqe_m); 406 kfree(q, M_TSEGQ); 407 atomic_add_int(&tcp_reass_qsize, -1); 408 q = nq; 409 } 410 411 /* Insert the new segment queue entry into place. */ 412 te->tqe_m = m; 413 te->tqe_th = th; 414 te->tqe_len = *tlenp; 415 416 /* check if can coalesce with following segment */ 417 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 418 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 419 420 te->tqe_len += q->tqe_len; 421 if (q->tqe_th->th_flags & TH_FIN) 422 te->tqe_th->th_flags |= TH_FIN; 423 m_cat(te->tqe_m, q->tqe_m); 424 tp->encloseblk.rblk_end = tend; 425 /* 426 * When not reporting a duplicate segment, use 427 * the larger enclosing block as the SACK block. 428 */ 429 if (!(tp->t_flags & TF_DUPSEG)) 430 tp->reportblk.rblk_end = tend; 431 LIST_REMOVE(q, tqe_q); 432 kfree(q, M_TSEGQ); 433 atomic_add_int(&tcp_reass_qsize, -1); 434 } 435 436 if (p == NULL) { 437 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 438 } else { 439 /* check if can coalesce with preceding segment */ 440 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 441 p->tqe_len += te->tqe_len; 442 m_cat(p->tqe_m, te->tqe_m); 443 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 444 /* 445 * When not reporting a duplicate segment, use 446 * the larger enclosing block as the SACK block. 447 */ 448 if (!(tp->t_flags & TF_DUPSEG)) 449 tp->reportblk.rblk_start = p->tqe_th->th_seq; 450 kfree(te, M_TSEGQ); 451 atomic_add_int(&tcp_reass_qsize, -1); 452 } else { 453 LIST_INSERT_AFTER(p, te, tqe_q); 454 } 455 } 456 457 present: 458 /* 459 * Present data to user, advancing rcv_nxt through 460 * completed sequence space. 461 */ 462 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 463 return (0); 464 q = LIST_FIRST(&tp->t_segq); 465 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 466 return (0); 467 tp->rcv_nxt += q->tqe_len; 468 if (!(tp->t_flags & TF_DUPSEG)) { 469 /* no SACK block to report since ACK advanced */ 470 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 471 } 472 /* no enclosing block to report since ACK advanced */ 473 tp->t_flags &= ~TF_ENCLOSESEG; 474 flags = q->tqe_th->th_flags & TH_FIN; 475 LIST_REMOVE(q, tqe_q); 476 KASSERT(LIST_EMPTY(&tp->t_segq) || 477 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 478 ("segment not coalesced")); 479 if (so->so_state & SS_CANTRCVMORE) { 480 m_freem(q->tqe_m); 481 } else { 482 lwkt_gettoken(&so->so_rcv.ssb_token); 483 ssb_appendstream(&so->so_rcv, q->tqe_m); 484 lwkt_reltoken(&so->so_rcv.ssb_token); 485 } 486 kfree(q, M_TSEGQ); 487 atomic_add_int(&tcp_reass_qsize, -1); 488 ND6_HINT(tp); 489 sorwakeup(so); 490 return (flags); 491 } 492 493 /* 494 * TCP input routine, follows pages 65-76 of the 495 * protocol specification dated September, 1981 very closely. 496 */ 497 #ifdef INET6 498 int 499 tcp6_input(struct mbuf **mp, int *offp, int proto) 500 { 501 struct mbuf *m = *mp; 502 struct in6_ifaddr *ia6; 503 504 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 505 506 /* 507 * draft-itojun-ipv6-tcp-to-anycast 508 * better place to put this in? 509 */ 510 ia6 = ip6_getdstifaddr(m); 511 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 512 struct ip6_hdr *ip6; 513 514 ip6 = mtod(m, struct ip6_hdr *); 515 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 516 offsetof(struct ip6_hdr, ip6_dst)); 517 return (IPPROTO_DONE); 518 } 519 520 tcp_input(mp, offp, proto); 521 return (IPPROTO_DONE); 522 } 523 #endif 524 525 int 526 tcp_input(struct mbuf **mp, int *offp, int proto) 527 { 528 int off0; 529 struct tcphdr *th; 530 struct ip *ip = NULL; 531 struct ipovly *ipov; 532 struct inpcb *inp = NULL; 533 u_char *optp = NULL; 534 int optlen = 0; 535 int tlen, off; 536 int len = 0; 537 int drop_hdrlen; 538 struct tcpcb *tp = NULL; 539 int thflags; 540 struct socket *so = NULL; 541 int todrop, acked; 542 boolean_t ourfinisacked, needoutput = FALSE; 543 u_long tiwin; 544 int recvwin; 545 struct tcpopt to; /* options in this segment */ 546 struct sockaddr_in *next_hop = NULL; 547 int rstreason; /* For badport_bandlim accounting purposes */ 548 int cpu; 549 struct ip6_hdr *ip6 = NULL; 550 struct mbuf *m; 551 #ifdef INET6 552 boolean_t isipv6; 553 #else 554 const boolean_t isipv6 = FALSE; 555 #endif 556 #ifdef TCPDEBUG 557 short ostate = 0; 558 #endif 559 560 off0 = *offp; 561 m = *mp; 562 *mp = NULL; 563 564 tcpstat.tcps_rcvtotal++; 565 566 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 567 struct m_tag *mtag; 568 569 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 570 KKASSERT(mtag != NULL); 571 next_hop = m_tag_data(mtag); 572 } 573 574 #ifdef INET6 575 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 576 #endif 577 578 if (isipv6) { 579 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 580 ip6 = mtod(m, struct ip6_hdr *); 581 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 582 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 583 tcpstat.tcps_rcvbadsum++; 584 goto drop; 585 } 586 th = (struct tcphdr *)((caddr_t)ip6 + off0); 587 588 /* 589 * Be proactive about unspecified IPv6 address in source. 590 * As we use all-zero to indicate unbounded/unconnected pcb, 591 * unspecified IPv6 address can be used to confuse us. 592 * 593 * Note that packets with unspecified IPv6 destination is 594 * already dropped in ip6_input. 595 */ 596 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 597 /* XXX stat */ 598 goto drop; 599 } 600 } else { 601 /* 602 * Get IP and TCP header together in first mbuf. 603 * Note: IP leaves IP header in first mbuf. 604 */ 605 if (off0 > sizeof(struct ip)) { 606 ip_stripoptions(m); 607 off0 = sizeof(struct ip); 608 } 609 /* already checked and pulled up in ip_demux() */ 610 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 611 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 612 ip = mtod(m, struct ip *); 613 ipov = (struct ipovly *)ip; 614 th = (struct tcphdr *)((caddr_t)ip + off0); 615 tlen = ip->ip_len; 616 617 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 618 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 619 th->th_sum = m->m_pkthdr.csum_data; 620 else 621 th->th_sum = in_pseudo(ip->ip_src.s_addr, 622 ip->ip_dst.s_addr, 623 htonl(m->m_pkthdr.csum_data + 624 ip->ip_len + 625 IPPROTO_TCP)); 626 th->th_sum ^= 0xffff; 627 } else { 628 /* 629 * Checksum extended TCP header and data. 630 */ 631 len = sizeof(struct ip) + tlen; 632 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 633 ipov->ih_len = (u_short)tlen; 634 ipov->ih_len = htons(ipov->ih_len); 635 th->th_sum = in_cksum(m, len); 636 } 637 if (th->th_sum) { 638 tcpstat.tcps_rcvbadsum++; 639 goto drop; 640 } 641 #ifdef INET6 642 /* Re-initialization for later version check */ 643 ip->ip_v = IPVERSION; 644 #endif 645 } 646 647 /* 648 * Check that TCP offset makes sense, 649 * pull out TCP options and adjust length. XXX 650 */ 651 off = th->th_off << 2; 652 /* already checked and pulled up in ip_demux() */ 653 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 654 ("bad TCP data offset %d (tlen %d)", off, tlen)); 655 tlen -= off; /* tlen is used instead of ti->ti_len */ 656 if (off > sizeof(struct tcphdr)) { 657 if (isipv6) { 658 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 659 ip6 = mtod(m, struct ip6_hdr *); 660 th = (struct tcphdr *)((caddr_t)ip6 + off0); 661 } else { 662 /* already pulled up in ip_demux() */ 663 KASSERT(m->m_len >= sizeof(struct ip) + off, 664 ("TCP header and options not in one mbuf: " 665 "m_len %d, off %d", m->m_len, off)); 666 } 667 optlen = off - sizeof(struct tcphdr); 668 optp = (u_char *)(th + 1); 669 } 670 thflags = th->th_flags; 671 672 #ifdef TCP_DROP_SYNFIN 673 /* 674 * If the drop_synfin option is enabled, drop all packets with 675 * both the SYN and FIN bits set. This prevents e.g. nmap from 676 * identifying the TCP/IP stack. 677 * 678 * This is a violation of the TCP specification. 679 */ 680 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 681 goto drop; 682 #endif 683 684 /* 685 * Convert TCP protocol specific fields to host format. 686 */ 687 th->th_seq = ntohl(th->th_seq); 688 th->th_ack = ntohl(th->th_ack); 689 th->th_win = ntohs(th->th_win); 690 th->th_urp = ntohs(th->th_urp); 691 692 /* 693 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 694 * until after ip6_savecontrol() is called and before other functions 695 * which don't want those proto headers. 696 * Because ip6_savecontrol() is going to parse the mbuf to 697 * search for data to be passed up to user-land, it wants mbuf 698 * parameters to be unchanged. 699 * XXX: the call of ip6_savecontrol() has been obsoleted based on 700 * latest version of the advanced API (20020110). 701 */ 702 drop_hdrlen = off0 + off; 703 704 /* 705 * Locate pcb for segment. 706 */ 707 findpcb: 708 /* IPFIREWALL_FORWARD section */ 709 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 710 /* 711 * Transparently forwarded. Pretend to be the destination. 712 * already got one like this? 713 */ 714 cpu = mycpu->gd_cpuid; 715 inp = in_pcblookup_hash(&tcbinfo[cpu], 716 ip->ip_src, th->th_sport, 717 ip->ip_dst, th->th_dport, 718 0, m->m_pkthdr.rcvif); 719 if (!inp) { 720 /* 721 * It's new. Try to find the ambushing socket. 722 */ 723 724 /* 725 * The rest of the ipfw code stores the port in 726 * host order. XXX 727 * (The IP address is still in network order.) 728 */ 729 in_port_t dport = next_hop->sin_port ? 730 htons(next_hop->sin_port) : 731 th->th_dport; 732 733 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 734 next_hop->sin_addr.s_addr, dport); 735 inp = in_pcblookup_hash(&tcbinfo[cpu], 736 ip->ip_src, th->th_sport, 737 next_hop->sin_addr, dport, 738 1, m->m_pkthdr.rcvif); 739 } 740 } else { 741 if (isipv6) { 742 inp = in6_pcblookup_hash(&tcbinfo[0], 743 &ip6->ip6_src, th->th_sport, 744 &ip6->ip6_dst, th->th_dport, 745 1, m->m_pkthdr.rcvif); 746 } else { 747 cpu = mycpu->gd_cpuid; 748 inp = in_pcblookup_hash(&tcbinfo[cpu], 749 ip->ip_src, th->th_sport, 750 ip->ip_dst, th->th_dport, 751 1, m->m_pkthdr.rcvif); 752 } 753 } 754 755 /* 756 * If the state is CLOSED (i.e., TCB does not exist) then 757 * all data in the incoming segment is discarded. 758 * If the TCB exists but is in CLOSED state, it is embryonic, 759 * but should either do a listen or a connect soon. 760 */ 761 if (inp == NULL) { 762 if (log_in_vain) { 763 #ifdef INET6 764 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 765 #else 766 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 767 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 768 #endif 769 if (isipv6) { 770 strcpy(dbuf, "["); 771 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 772 strcat(dbuf, "]"); 773 strcpy(sbuf, "["); 774 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 775 strcat(sbuf, "]"); 776 } else { 777 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 778 strcpy(sbuf, inet_ntoa(ip->ip_src)); 779 } 780 switch (log_in_vain) { 781 case 1: 782 if (!(thflags & TH_SYN)) 783 break; 784 case 2: 785 log(LOG_INFO, 786 "Connection attempt to TCP %s:%d " 787 "from %s:%d flags:0x%02x\n", 788 dbuf, ntohs(th->th_dport), sbuf, 789 ntohs(th->th_sport), thflags); 790 break; 791 default: 792 break; 793 } 794 } 795 if (blackhole) { 796 switch (blackhole) { 797 case 1: 798 if (thflags & TH_SYN) 799 goto drop; 800 break; 801 case 2: 802 goto drop; 803 default: 804 goto drop; 805 } 806 } 807 rstreason = BANDLIM_RST_CLOSEDPORT; 808 goto dropwithreset; 809 } 810 811 #ifdef IPSEC 812 if (isipv6) { 813 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 814 ipsec6stat.in_polvio++; 815 goto drop; 816 } 817 } else { 818 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 819 ipsecstat.in_polvio++; 820 goto drop; 821 } 822 } 823 #endif 824 #ifdef FAST_IPSEC 825 if (isipv6) { 826 if (ipsec6_in_reject(m, inp)) 827 goto drop; 828 } else { 829 if (ipsec4_in_reject(m, inp)) 830 goto drop; 831 } 832 #endif 833 /* Check the minimum TTL for socket. */ 834 #ifdef INET6 835 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 836 goto drop; 837 #endif 838 839 tp = intotcpcb(inp); 840 if (tp == NULL) { 841 rstreason = BANDLIM_RST_CLOSEDPORT; 842 goto dropwithreset; 843 } 844 if (tp->t_state <= TCPS_CLOSED) 845 goto drop; 846 847 /* Unscale the window into a 32-bit value. */ 848 if (!(thflags & TH_SYN)) 849 tiwin = th->th_win << tp->snd_scale; 850 else 851 tiwin = th->th_win; 852 853 so = inp->inp_socket; 854 855 #ifdef TCPDEBUG 856 if (so->so_options & SO_DEBUG) { 857 ostate = tp->t_state; 858 if (isipv6) 859 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 860 else 861 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 862 tcp_savetcp = *th; 863 } 864 #endif 865 866 bzero(&to, sizeof to); 867 868 if (so->so_options & SO_ACCEPTCONN) { 869 struct in_conninfo inc; 870 871 #ifdef INET6 872 inc.inc_isipv6 = (isipv6 == TRUE); 873 #endif 874 if (isipv6) { 875 inc.inc6_faddr = ip6->ip6_src; 876 inc.inc6_laddr = ip6->ip6_dst; 877 inc.inc6_route.ro_rt = NULL; /* XXX */ 878 } else { 879 inc.inc_faddr = ip->ip_src; 880 inc.inc_laddr = ip->ip_dst; 881 inc.inc_route.ro_rt = NULL; /* XXX */ 882 } 883 inc.inc_fport = th->th_sport; 884 inc.inc_lport = th->th_dport; 885 886 /* 887 * If the state is LISTEN then ignore segment if it contains 888 * a RST. If the segment contains an ACK then it is bad and 889 * send a RST. If it does not contain a SYN then it is not 890 * interesting; drop it. 891 * 892 * If the state is SYN_RECEIVED (syncache) and seg contains 893 * an ACK, but not for our SYN/ACK, send a RST. If the seg 894 * contains a RST, check the sequence number to see if it 895 * is a valid reset segment. 896 */ 897 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 898 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 899 if (!syncache_expand(&inc, th, &so, m)) { 900 /* 901 * No syncache entry, or ACK was not 902 * for our SYN/ACK. Send a RST. 903 */ 904 tcpstat.tcps_badsyn++; 905 rstreason = BANDLIM_RST_OPENPORT; 906 goto dropwithreset; 907 } 908 909 /* 910 * Could not complete 3-way handshake, 911 * connection is being closed down, and 912 * syncache will free mbuf. 913 */ 914 if (so == NULL) 915 return(IPPROTO_DONE); 916 917 /* 918 * We must be in the correct protocol thread 919 * for this connection. 920 */ 921 KKASSERT(so->so_port == &curthread->td_msgport); 922 923 /* 924 * Socket is created in state SYN_RECEIVED. 925 * Continue processing segment. 926 */ 927 inp = so->so_pcb; 928 tp = intotcpcb(inp); 929 /* 930 * This is what would have happened in 931 * tcp_output() when the SYN,ACK was sent. 932 */ 933 tp->snd_up = tp->snd_una; 934 tp->snd_max = tp->snd_nxt = tp->iss + 1; 935 tp->last_ack_sent = tp->rcv_nxt; 936 /* 937 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 938 * until the _second_ ACK is received: 939 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 940 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 941 * move to ESTAB, set snd_wnd to tiwin. 942 */ 943 tp->snd_wnd = tiwin; /* unscaled */ 944 goto after_listen; 945 } 946 if (thflags & TH_RST) { 947 syncache_chkrst(&inc, th); 948 goto drop; 949 } 950 if (thflags & TH_ACK) { 951 syncache_badack(&inc); 952 tcpstat.tcps_badsyn++; 953 rstreason = BANDLIM_RST_OPENPORT; 954 goto dropwithreset; 955 } 956 goto drop; 957 } 958 959 /* 960 * Segment's flags are (SYN) or (SYN | FIN). 961 */ 962 #ifdef INET6 963 /* 964 * If deprecated address is forbidden, 965 * we do not accept SYN to deprecated interface 966 * address to prevent any new inbound connection from 967 * getting established. 968 * When we do not accept SYN, we send a TCP RST, 969 * with deprecated source address (instead of dropping 970 * it). We compromise it as it is much better for peer 971 * to send a RST, and RST will be the final packet 972 * for the exchange. 973 * 974 * If we do not forbid deprecated addresses, we accept 975 * the SYN packet. RFC2462 does not suggest dropping 976 * SYN in this case. 977 * If we decipher RFC2462 5.5.4, it says like this: 978 * 1. use of deprecated addr with existing 979 * communication is okay - "SHOULD continue to be 980 * used" 981 * 2. use of it with new communication: 982 * (2a) "SHOULD NOT be used if alternate address 983 * with sufficient scope is available" 984 * (2b) nothing mentioned otherwise. 985 * Here we fall into (2b) case as we have no choice in 986 * our source address selection - we must obey the peer. 987 * 988 * The wording in RFC2462 is confusing, and there are 989 * multiple description text for deprecated address 990 * handling - worse, they are not exactly the same. 991 * I believe 5.5.4 is the best one, so we follow 5.5.4. 992 */ 993 if (isipv6 && !ip6_use_deprecated) { 994 struct in6_ifaddr *ia6; 995 996 if ((ia6 = ip6_getdstifaddr(m)) && 997 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 998 tp = NULL; 999 rstreason = BANDLIM_RST_OPENPORT; 1000 goto dropwithreset; 1001 } 1002 } 1003 #endif 1004 /* 1005 * If it is from this socket, drop it, it must be forged. 1006 * Don't bother responding if the destination was a broadcast. 1007 */ 1008 if (th->th_dport == th->th_sport) { 1009 if (isipv6) { 1010 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1011 &ip6->ip6_src)) 1012 goto drop; 1013 } else { 1014 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1015 goto drop; 1016 } 1017 } 1018 /* 1019 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1020 * 1021 * Note that it is quite possible to receive unicast 1022 * link-layer packets with a broadcast IP address. Use 1023 * in_broadcast() to find them. 1024 */ 1025 if (m->m_flags & (M_BCAST | M_MCAST)) 1026 goto drop; 1027 if (isipv6) { 1028 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1029 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1030 goto drop; 1031 } else { 1032 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1033 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1034 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1035 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1036 goto drop; 1037 } 1038 /* 1039 * SYN appears to be valid; create compressed TCP state 1040 * for syncache, or perform t/tcp connection. 1041 */ 1042 if (so->so_qlen <= so->so_qlimit) { 1043 tcp_dooptions(&to, optp, optlen, TRUE); 1044 if (!syncache_add(&inc, &to, th, &so, m)) 1045 goto drop; 1046 1047 /* 1048 * Entry added to syncache, mbuf used to 1049 * send SYN,ACK packet. 1050 */ 1051 if (so == NULL) 1052 return(IPPROTO_DONE); 1053 1054 /* 1055 * We must be in the correct protocol thread for 1056 * this connection. 1057 */ 1058 KKASSERT(so->so_port == &curthread->td_msgport); 1059 1060 inp = so->so_pcb; 1061 tp = intotcpcb(inp); 1062 tp->snd_wnd = tiwin; 1063 tp->t_starttime = ticks; 1064 tp->t_state = TCPS_ESTABLISHED; 1065 1066 /* 1067 * If there is a FIN, or if there is data and the 1068 * connection is local, then delay SYN,ACK(SYN) in 1069 * the hope of piggy-backing it on a response 1070 * segment. Otherwise must send ACK now in case 1071 * the other side is slow starting. 1072 */ 1073 if (DELAY_ACK(tp) && 1074 ((thflags & TH_FIN) || 1075 (tlen != 0 && 1076 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 1077 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 1078 tcp_callout_reset(tp, tp->tt_delack, 1079 tcp_delacktime, tcp_timer_delack); 1080 tp->t_flags |= TF_NEEDSYN; 1081 } else { 1082 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1083 } 1084 1085 tcpstat.tcps_connects++; 1086 soisconnected(so); 1087 goto trimthenstep6; 1088 } 1089 goto drop; 1090 } 1091 1092 after_listen: 1093 /* 1094 * Should not happen - syncache should pick up these connections. 1095 * 1096 * Once we are past handling listen sockets we must be in the 1097 * correct protocol processing thread. 1098 */ 1099 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1100 KKASSERT(so->so_port == &curthread->td_msgport); 1101 1102 /* 1103 * This is the second part of the MSS DoS prevention code (after 1104 * minmss on the sending side) and it deals with too many too small 1105 * tcp packets in a too short timeframe (1 second). 1106 * 1107 * XXX Removed. This code was crap. It does not scale to network 1108 * speed, and default values break NFS. Gone. 1109 */ 1110 /* REMOVED */ 1111 1112 /* 1113 * Segment received on connection. 1114 * 1115 * Reset idle time and keep-alive timer. Don't waste time if less 1116 * then a second has elapsed. 1117 */ 1118 if ((int)(ticks - tp->t_rcvtime) > hz) 1119 tcp_timer_keep_activity(tp, thflags); 1120 1121 /* 1122 * Process options. 1123 * XXX this is tradtitional behavior, may need to be cleaned up. 1124 */ 1125 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0); 1126 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1127 if (to.to_flags & TOF_SCALE) { 1128 tp->t_flags |= TF_RCVD_SCALE; 1129 tp->requested_s_scale = to.to_requested_s_scale; 1130 } 1131 if (to.to_flags & TOF_TS) { 1132 tp->t_flags |= TF_RCVD_TSTMP; 1133 tp->ts_recent = to.to_tsval; 1134 tp->ts_recent_age = ticks; 1135 } 1136 if (to.to_flags & TOF_MSS) 1137 tcp_mss(tp, to.to_mss); 1138 /* 1139 * Only set the TF_SACK_PERMITTED per-connection flag 1140 * if we got a SACK_PERMITTED option from the other side 1141 * and the global tcp_do_sack variable is true. 1142 */ 1143 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1144 tp->t_flags |= TF_SACK_PERMITTED; 1145 } 1146 1147 /* 1148 * Header prediction: check for the two common cases 1149 * of a uni-directional data xfer. If the packet has 1150 * no control flags, is in-sequence, the window didn't 1151 * change and we're not retransmitting, it's a 1152 * candidate. If the length is zero and the ack moved 1153 * forward, we're the sender side of the xfer. Just 1154 * free the data acked & wake any higher level process 1155 * that was blocked waiting for space. If the length 1156 * is non-zero and the ack didn't move, we're the 1157 * receiver side. If we're getting packets in-order 1158 * (the reassembly queue is empty), add the data to 1159 * the socket buffer and note that we need a delayed ack. 1160 * Make sure that the hidden state-flags are also off. 1161 * Since we check for TCPS_ESTABLISHED above, it can only 1162 * be TH_NEEDSYN. 1163 */ 1164 if (tp->t_state == TCPS_ESTABLISHED && 1165 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1166 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1167 (!(to.to_flags & TOF_TS) || 1168 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1169 th->th_seq == tp->rcv_nxt && 1170 tp->snd_nxt == tp->snd_max) { 1171 1172 /* 1173 * If last ACK falls within this segment's sequence numbers, 1174 * record the timestamp. 1175 * NOTE that the test is modified according to the latest 1176 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1177 */ 1178 if ((to.to_flags & TOF_TS) && 1179 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1180 tp->ts_recent_age = ticks; 1181 tp->ts_recent = to.to_tsval; 1182 } 1183 1184 if (tlen == 0) { 1185 if (SEQ_GT(th->th_ack, tp->snd_una) && 1186 SEQ_LEQ(th->th_ack, tp->snd_max) && 1187 tp->snd_cwnd >= tp->snd_wnd && 1188 !IN_FASTRECOVERY(tp)) { 1189 /* 1190 * This is a pure ack for outstanding data. 1191 */ 1192 ++tcpstat.tcps_predack; 1193 /* 1194 * "bad retransmit" recovery 1195 * 1196 * If Eifel detection applies, then 1197 * it is deterministic, so use it 1198 * unconditionally over the old heuristic. 1199 * Otherwise, fall back to the old heuristic. 1200 */ 1201 if (tcp_do_eifel_detect && 1202 (to.to_flags & TOF_TS) && to.to_tsecr && 1203 (tp->t_flags & TF_FIRSTACCACK)) { 1204 /* Eifel detection applicable. */ 1205 if (to.to_tsecr < tp->t_rexmtTS) { 1206 tcp_revert_congestion_state(tp); 1207 ++tcpstat.tcps_eifeldetected; 1208 } 1209 } else if (tp->t_rxtshift == 1 && 1210 ticks < tp->t_badrxtwin) { 1211 tcp_revert_congestion_state(tp); 1212 ++tcpstat.tcps_rttdetected; 1213 } 1214 tp->t_flags &= ~(TF_FIRSTACCACK | 1215 TF_FASTREXMT | TF_EARLYREXMT); 1216 /* 1217 * Recalculate the retransmit timer / rtt. 1218 * 1219 * Some machines (certain windows boxes) 1220 * send broken timestamp replies during the 1221 * SYN+ACK phase, ignore timestamps of 0. 1222 */ 1223 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1224 tcp_xmit_timer(tp, 1225 ticks - to.to_tsecr + 1); 1226 } else if (tp->t_rtttime && 1227 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1228 tcp_xmit_timer(tp, 1229 ticks - tp->t_rtttime); 1230 } 1231 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1232 acked = th->th_ack - tp->snd_una; 1233 tcpstat.tcps_rcvackpack++; 1234 tcpstat.tcps_rcvackbyte += acked; 1235 sbdrop(&so->so_snd.sb, acked); 1236 tp->snd_recover = th->th_ack - 1; 1237 tp->snd_una = th->th_ack; 1238 tp->t_dupacks = 0; 1239 /* 1240 * Update window information. 1241 */ 1242 if (tiwin != tp->snd_wnd && 1243 acceptable_window_update(tp, th, tiwin)) { 1244 /* keep track of pure window updates */ 1245 if (tp->snd_wl2 == th->th_ack && 1246 tiwin > tp->snd_wnd) 1247 tcpstat.tcps_rcvwinupd++; 1248 tp->snd_wnd = tiwin; 1249 tp->snd_wl1 = th->th_seq; 1250 tp->snd_wl2 = th->th_ack; 1251 if (tp->snd_wnd > tp->max_sndwnd) 1252 tp->max_sndwnd = tp->snd_wnd; 1253 } 1254 m_freem(m); 1255 ND6_HINT(tp); /* some progress has been done */ 1256 /* 1257 * If all outstanding data are acked, stop 1258 * retransmit timer, otherwise restart timer 1259 * using current (possibly backed-off) value. 1260 * If process is waiting for space, 1261 * wakeup/selwakeup/signal. If data 1262 * are ready to send, let tcp_output 1263 * decide between more output or persist. 1264 */ 1265 if (tp->snd_una == tp->snd_max) { 1266 tcp_callout_stop(tp, tp->tt_rexmt); 1267 } else if (!tcp_callout_active(tp, 1268 tp->tt_persist)) { 1269 tcp_callout_reset(tp, tp->tt_rexmt, 1270 tp->t_rxtcur, tcp_timer_rexmt); 1271 } 1272 sowwakeup(so); 1273 if (so->so_snd.ssb_cc > 0) 1274 tcp_output(tp); 1275 return(IPPROTO_DONE); 1276 } 1277 } else if (tiwin == tp->snd_wnd && 1278 th->th_ack == tp->snd_una && 1279 LIST_EMPTY(&tp->t_segq) && 1280 tlen <= ssb_space(&so->so_rcv)) { 1281 u_long newsize = 0; /* automatic sockbuf scaling */ 1282 /* 1283 * This is a pure, in-sequence data packet 1284 * with nothing on the reassembly queue and 1285 * we have enough buffer space to take it. 1286 */ 1287 ++tcpstat.tcps_preddat; 1288 tp->rcv_nxt += tlen; 1289 tcpstat.tcps_rcvpack++; 1290 tcpstat.tcps_rcvbyte += tlen; 1291 ND6_HINT(tp); /* some progress has been done */ 1292 /* 1293 * Automatic sizing of receive socket buffer. Often the send 1294 * buffer size is not optimally adjusted to the actual network 1295 * conditions at hand (delay bandwidth product). Setting the 1296 * buffer size too small limits throughput on links with high 1297 * bandwidth and high delay (eg. trans-continental/oceanic links). 1298 * 1299 * On the receive side the socket buffer memory is only rarely 1300 * used to any significant extent. This allows us to be much 1301 * more aggressive in scaling the receive socket buffer. For 1302 * the case that the buffer space is actually used to a large 1303 * extent and we run out of kernel memory we can simply drop 1304 * the new segments; TCP on the sender will just retransmit it 1305 * later. Setting the buffer size too big may only consume too 1306 * much kernel memory if the application doesn't read() from 1307 * the socket or packet loss or reordering makes use of the 1308 * reassembly queue. 1309 * 1310 * The criteria to step up the receive buffer one notch are: 1311 * 1. the number of bytes received during the time it takes 1312 * one timestamp to be reflected back to us (the RTT); 1313 * 2. received bytes per RTT is within seven eighth of the 1314 * current socket buffer size; 1315 * 3. receive buffer size has not hit maximal automatic size; 1316 * 1317 * This algorithm does one step per RTT at most and only if 1318 * we receive a bulk stream w/o packet losses or reorderings. 1319 * Shrinking the buffer during idle times is not necessary as 1320 * it doesn't consume any memory when idle. 1321 * 1322 * TODO: Only step up if the application is actually serving 1323 * the buffer to better manage the socket buffer resources. 1324 */ 1325 if (tcp_do_autorcvbuf && 1326 to.to_tsecr && 1327 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1328 if (to.to_tsecr > tp->rfbuf_ts && 1329 to.to_tsecr - tp->rfbuf_ts < hz) { 1330 if (tp->rfbuf_cnt > 1331 (so->so_rcv.ssb_hiwat / 8 * 7) && 1332 so->so_rcv.ssb_hiwat < 1333 tcp_autorcvbuf_max) { 1334 newsize = 1335 ulmin(so->so_rcv.ssb_hiwat + 1336 tcp_autorcvbuf_inc, 1337 tcp_autorcvbuf_max); 1338 } 1339 /* Start over with next RTT. */ 1340 tp->rfbuf_ts = 0; 1341 tp->rfbuf_cnt = 0; 1342 } else 1343 tp->rfbuf_cnt += tlen; /* add up */ 1344 } 1345 /* 1346 * Add data to socket buffer. 1347 */ 1348 if (so->so_state & SS_CANTRCVMORE) { 1349 m_freem(m); 1350 } else { 1351 /* 1352 * Set new socket buffer size, give up when 1353 * limit is reached. 1354 * 1355 * Adjusting the size can mess up ACK 1356 * sequencing when pure window updates are 1357 * being avoided (which is the default), 1358 * so force an ack. 1359 */ 1360 lwkt_gettoken(&so->so_rcv.ssb_token); 1361 if (newsize) { 1362 tp->t_flags |= TF_RXRESIZED; 1363 if (!ssb_reserve(&so->so_rcv, newsize, 1364 so, NULL)) { 1365 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1366 } 1367 if (newsize >= 1368 (TCP_MAXWIN << tp->rcv_scale)) { 1369 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1370 } 1371 } 1372 m_adj(m, drop_hdrlen); /* delayed header drop */ 1373 ssb_appendstream(&so->so_rcv, m); 1374 lwkt_reltoken(&so->so_rcv.ssb_token); 1375 } 1376 sorwakeup(so); 1377 /* 1378 * This code is responsible for most of the ACKs 1379 * the TCP stack sends back after receiving a data 1380 * packet. Note that the DELAY_ACK check fails if 1381 * the delack timer is already running, which results 1382 * in an ack being sent every other packet (which is 1383 * what we want). 1384 * 1385 * We then further aggregate acks by not actually 1386 * sending one until the protocol thread has completed 1387 * processing the current backlog of packets. This 1388 * does not delay the ack any further, but allows us 1389 * to take advantage of the packet aggregation that 1390 * high speed NICs do (usually blocks of 8-10 packets) 1391 * to send a single ack rather then four or five acks, 1392 * greatly reducing the ack rate, the return channel 1393 * bandwidth, and the protocol overhead on both ends. 1394 * 1395 * Since this also has the effect of slowing down 1396 * the exponential slow-start ramp-up, systems with 1397 * very large bandwidth-delay products might want 1398 * to turn the feature off. 1399 */ 1400 if (DELAY_ACK(tp)) { 1401 tcp_callout_reset(tp, tp->tt_delack, 1402 tcp_delacktime, tcp_timer_delack); 1403 } else if (tcp_aggregate_acks) { 1404 tp->t_flags |= TF_ACKNOW; 1405 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1406 tp->t_flags |= TF_ONOUTPUTQ; 1407 tp->tt_cpu = mycpu->gd_cpuid; 1408 TAILQ_INSERT_TAIL( 1409 &tcpcbackq[tp->tt_cpu], 1410 tp, t_outputq); 1411 } 1412 } else { 1413 tp->t_flags |= TF_ACKNOW; 1414 tcp_output(tp); 1415 } 1416 return(IPPROTO_DONE); 1417 } 1418 } 1419 1420 /* 1421 * Calculate amount of space in receive window, 1422 * and then do TCP input processing. 1423 * Receive window is amount of space in rcv queue, 1424 * but not less than advertised window. 1425 */ 1426 recvwin = ssb_space(&so->so_rcv); 1427 if (recvwin < 0) 1428 recvwin = 0; 1429 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1430 1431 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1432 tp->rfbuf_ts = 0; 1433 tp->rfbuf_cnt = 0; 1434 1435 switch (tp->t_state) { 1436 /* 1437 * If the state is SYN_RECEIVED: 1438 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1439 */ 1440 case TCPS_SYN_RECEIVED: 1441 if ((thflags & TH_ACK) && 1442 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1443 SEQ_GT(th->th_ack, tp->snd_max))) { 1444 rstreason = BANDLIM_RST_OPENPORT; 1445 goto dropwithreset; 1446 } 1447 break; 1448 1449 /* 1450 * If the state is SYN_SENT: 1451 * if seg contains an ACK, but not for our SYN, drop the input. 1452 * if seg contains a RST, then drop the connection. 1453 * if seg does not contain SYN, then drop it. 1454 * Otherwise this is an acceptable SYN segment 1455 * initialize tp->rcv_nxt and tp->irs 1456 * if seg contains ack then advance tp->snd_una 1457 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1458 * arrange for segment to be acked (eventually) 1459 * continue processing rest of data/controls, beginning with URG 1460 */ 1461 case TCPS_SYN_SENT: 1462 if ((thflags & TH_ACK) && 1463 (SEQ_LEQ(th->th_ack, tp->iss) || 1464 SEQ_GT(th->th_ack, tp->snd_max))) { 1465 rstreason = BANDLIM_UNLIMITED; 1466 goto dropwithreset; 1467 } 1468 if (thflags & TH_RST) { 1469 if (thflags & TH_ACK) 1470 tp = tcp_drop(tp, ECONNREFUSED); 1471 goto drop; 1472 } 1473 if (!(thflags & TH_SYN)) 1474 goto drop; 1475 tp->snd_wnd = th->th_win; /* initial send window */ 1476 1477 tp->irs = th->th_seq; 1478 tcp_rcvseqinit(tp); 1479 if (thflags & TH_ACK) { 1480 /* Our SYN was acked. */ 1481 tcpstat.tcps_connects++; 1482 soisconnected(so); 1483 /* Do window scaling on this connection? */ 1484 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1485 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1486 tp->snd_scale = tp->requested_s_scale; 1487 tp->rcv_scale = tp->request_r_scale; 1488 } 1489 tp->rcv_adv += tp->rcv_wnd; 1490 tp->snd_una++; /* SYN is acked */ 1491 tcp_callout_stop(tp, tp->tt_rexmt); 1492 /* 1493 * If there's data, delay ACK; if there's also a FIN 1494 * ACKNOW will be turned on later. 1495 */ 1496 if (DELAY_ACK(tp) && tlen != 0) { 1497 tcp_callout_reset(tp, tp->tt_delack, 1498 tcp_delacktime, tcp_timer_delack); 1499 } else { 1500 tp->t_flags |= TF_ACKNOW; 1501 } 1502 /* 1503 * Received <SYN,ACK> in SYN_SENT[*] state. 1504 * Transitions: 1505 * SYN_SENT --> ESTABLISHED 1506 * SYN_SENT* --> FIN_WAIT_1 1507 */ 1508 tp->t_starttime = ticks; 1509 if (tp->t_flags & TF_NEEDFIN) { 1510 tp->t_state = TCPS_FIN_WAIT_1; 1511 tp->t_flags &= ~TF_NEEDFIN; 1512 thflags &= ~TH_SYN; 1513 } else { 1514 tp->t_state = TCPS_ESTABLISHED; 1515 tcp_callout_reset(tp, tp->tt_keep, 1516 tcp_getkeepidle(tp), 1517 tcp_timer_keep); 1518 } 1519 } else { 1520 /* 1521 * Received initial SYN in SYN-SENT[*] state => 1522 * simultaneous open. 1523 * Do 3-way handshake: 1524 * SYN-SENT -> SYN-RECEIVED 1525 * SYN-SENT* -> SYN-RECEIVED* 1526 */ 1527 tp->t_flags |= TF_ACKNOW; 1528 tcp_callout_stop(tp, tp->tt_rexmt); 1529 tp->t_state = TCPS_SYN_RECEIVED; 1530 } 1531 1532 trimthenstep6: 1533 /* 1534 * Advance th->th_seq to correspond to first data byte. 1535 * If data, trim to stay within window, 1536 * dropping FIN if necessary. 1537 */ 1538 th->th_seq++; 1539 if (tlen > tp->rcv_wnd) { 1540 todrop = tlen - tp->rcv_wnd; 1541 m_adj(m, -todrop); 1542 tlen = tp->rcv_wnd; 1543 thflags &= ~TH_FIN; 1544 tcpstat.tcps_rcvpackafterwin++; 1545 tcpstat.tcps_rcvbyteafterwin += todrop; 1546 } 1547 tp->snd_wl1 = th->th_seq - 1; 1548 tp->rcv_up = th->th_seq; 1549 /* 1550 * Client side of transaction: already sent SYN and data. 1551 * If the remote host used T/TCP to validate the SYN, 1552 * our data will be ACK'd; if so, enter normal data segment 1553 * processing in the middle of step 5, ack processing. 1554 * Otherwise, goto step 6. 1555 */ 1556 if (thflags & TH_ACK) 1557 goto process_ACK; 1558 1559 goto step6; 1560 1561 /* 1562 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1563 * do normal processing (we no longer bother with T/TCP). 1564 */ 1565 case TCPS_LAST_ACK: 1566 case TCPS_CLOSING: 1567 case TCPS_TIME_WAIT: 1568 break; /* continue normal processing */ 1569 } 1570 1571 /* 1572 * States other than LISTEN or SYN_SENT. 1573 * First check the RST flag and sequence number since reset segments 1574 * are exempt from the timestamp and connection count tests. This 1575 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1576 * below which allowed reset segments in half the sequence space 1577 * to fall though and be processed (which gives forged reset 1578 * segments with a random sequence number a 50 percent chance of 1579 * killing a connection). 1580 * Then check timestamp, if present. 1581 * Then check the connection count, if present. 1582 * Then check that at least some bytes of segment are within 1583 * receive window. If segment begins before rcv_nxt, 1584 * drop leading data (and SYN); if nothing left, just ack. 1585 * 1586 * 1587 * If the RST bit is set, check the sequence number to see 1588 * if this is a valid reset segment. 1589 * RFC 793 page 37: 1590 * In all states except SYN-SENT, all reset (RST) segments 1591 * are validated by checking their SEQ-fields. A reset is 1592 * valid if its sequence number is in the window. 1593 * Note: this does not take into account delayed ACKs, so 1594 * we should test against last_ack_sent instead of rcv_nxt. 1595 * The sequence number in the reset segment is normally an 1596 * echo of our outgoing acknowledgement numbers, but some hosts 1597 * send a reset with the sequence number at the rightmost edge 1598 * of our receive window, and we have to handle this case. 1599 * If we have multiple segments in flight, the intial reset 1600 * segment sequence numbers will be to the left of last_ack_sent, 1601 * but they will eventually catch up. 1602 * In any case, it never made sense to trim reset segments to 1603 * fit the receive window since RFC 1122 says: 1604 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1605 * 1606 * A TCP SHOULD allow a received RST segment to include data. 1607 * 1608 * DISCUSSION 1609 * It has been suggested that a RST segment could contain 1610 * ASCII text that encoded and explained the cause of the 1611 * RST. No standard has yet been established for such 1612 * data. 1613 * 1614 * If the reset segment passes the sequence number test examine 1615 * the state: 1616 * SYN_RECEIVED STATE: 1617 * If passive open, return to LISTEN state. 1618 * If active open, inform user that connection was refused. 1619 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1620 * Inform user that connection was reset, and close tcb. 1621 * CLOSING, LAST_ACK STATES: 1622 * Close the tcb. 1623 * TIME_WAIT STATE: 1624 * Drop the segment - see Stevens, vol. 2, p. 964 and 1625 * RFC 1337. 1626 */ 1627 if (thflags & TH_RST) { 1628 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1629 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1630 switch (tp->t_state) { 1631 1632 case TCPS_SYN_RECEIVED: 1633 so->so_error = ECONNREFUSED; 1634 goto close; 1635 1636 case TCPS_ESTABLISHED: 1637 case TCPS_FIN_WAIT_1: 1638 case TCPS_FIN_WAIT_2: 1639 case TCPS_CLOSE_WAIT: 1640 so->so_error = ECONNRESET; 1641 close: 1642 tp->t_state = TCPS_CLOSED; 1643 tcpstat.tcps_drops++; 1644 tp = tcp_close(tp); 1645 break; 1646 1647 case TCPS_CLOSING: 1648 case TCPS_LAST_ACK: 1649 tp = tcp_close(tp); 1650 break; 1651 1652 case TCPS_TIME_WAIT: 1653 break; 1654 } 1655 } 1656 goto drop; 1657 } 1658 1659 /* 1660 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1661 * and it's less than ts_recent, drop it. 1662 */ 1663 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1664 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1665 1666 /* Check to see if ts_recent is over 24 days old. */ 1667 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1668 /* 1669 * Invalidate ts_recent. If this segment updates 1670 * ts_recent, the age will be reset later and ts_recent 1671 * will get a valid value. If it does not, setting 1672 * ts_recent to zero will at least satisfy the 1673 * requirement that zero be placed in the timestamp 1674 * echo reply when ts_recent isn't valid. The 1675 * age isn't reset until we get a valid ts_recent 1676 * because we don't want out-of-order segments to be 1677 * dropped when ts_recent is old. 1678 */ 1679 tp->ts_recent = 0; 1680 } else { 1681 tcpstat.tcps_rcvduppack++; 1682 tcpstat.tcps_rcvdupbyte += tlen; 1683 tcpstat.tcps_pawsdrop++; 1684 if (tlen) 1685 goto dropafterack; 1686 goto drop; 1687 } 1688 } 1689 1690 /* 1691 * In the SYN-RECEIVED state, validate that the packet belongs to 1692 * this connection before trimming the data to fit the receive 1693 * window. Check the sequence number versus IRS since we know 1694 * the sequence numbers haven't wrapped. This is a partial fix 1695 * for the "LAND" DoS attack. 1696 */ 1697 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1698 rstreason = BANDLIM_RST_OPENPORT; 1699 goto dropwithreset; 1700 } 1701 1702 todrop = tp->rcv_nxt - th->th_seq; 1703 if (todrop > 0) { 1704 if (TCP_DO_SACK(tp)) { 1705 /* Report duplicate segment at head of packet. */ 1706 tp->reportblk.rblk_start = th->th_seq; 1707 tp->reportblk.rblk_end = th->th_seq + tlen; 1708 if (thflags & TH_FIN) 1709 ++tp->reportblk.rblk_end; 1710 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1711 tp->reportblk.rblk_end = tp->rcv_nxt; 1712 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1713 } 1714 if (thflags & TH_SYN) { 1715 thflags &= ~TH_SYN; 1716 th->th_seq++; 1717 if (th->th_urp > 1) 1718 th->th_urp--; 1719 else 1720 thflags &= ~TH_URG; 1721 todrop--; 1722 } 1723 /* 1724 * Following if statement from Stevens, vol. 2, p. 960. 1725 */ 1726 if (todrop > tlen || 1727 (todrop == tlen && !(thflags & TH_FIN))) { 1728 /* 1729 * Any valid FIN must be to the left of the window. 1730 * At this point the FIN must be a duplicate or out 1731 * of sequence; drop it. 1732 */ 1733 thflags &= ~TH_FIN; 1734 1735 /* 1736 * Send an ACK to resynchronize and drop any data. 1737 * But keep on processing for RST or ACK. 1738 */ 1739 tp->t_flags |= TF_ACKNOW; 1740 todrop = tlen; 1741 tcpstat.tcps_rcvduppack++; 1742 tcpstat.tcps_rcvdupbyte += todrop; 1743 } else { 1744 tcpstat.tcps_rcvpartduppack++; 1745 tcpstat.tcps_rcvpartdupbyte += todrop; 1746 } 1747 drop_hdrlen += todrop; /* drop from the top afterwards */ 1748 th->th_seq += todrop; 1749 tlen -= todrop; 1750 if (th->th_urp > todrop) 1751 th->th_urp -= todrop; 1752 else { 1753 thflags &= ~TH_URG; 1754 th->th_urp = 0; 1755 } 1756 } 1757 1758 /* 1759 * If new data are received on a connection after the 1760 * user processes are gone, then RST the other end. 1761 */ 1762 if ((so->so_state & SS_NOFDREF) && 1763 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1764 tp = tcp_close(tp); 1765 tcpstat.tcps_rcvafterclose++; 1766 rstreason = BANDLIM_UNLIMITED; 1767 goto dropwithreset; 1768 } 1769 1770 /* 1771 * If segment ends after window, drop trailing data 1772 * (and PUSH and FIN); if nothing left, just ACK. 1773 */ 1774 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1775 if (todrop > 0) { 1776 tcpstat.tcps_rcvpackafterwin++; 1777 if (todrop >= tlen) { 1778 tcpstat.tcps_rcvbyteafterwin += tlen; 1779 /* 1780 * If a new connection request is received 1781 * while in TIME_WAIT, drop the old connection 1782 * and start over if the sequence numbers 1783 * are above the previous ones. 1784 */ 1785 if (thflags & TH_SYN && 1786 tp->t_state == TCPS_TIME_WAIT && 1787 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1788 tp = tcp_close(tp); 1789 goto findpcb; 1790 } 1791 /* 1792 * If window is closed can only take segments at 1793 * window edge, and have to drop data and PUSH from 1794 * incoming segments. Continue processing, but 1795 * remember to ack. Otherwise, drop segment 1796 * and ack. 1797 */ 1798 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1799 tp->t_flags |= TF_ACKNOW; 1800 tcpstat.tcps_rcvwinprobe++; 1801 } else 1802 goto dropafterack; 1803 } else 1804 tcpstat.tcps_rcvbyteafterwin += todrop; 1805 m_adj(m, -todrop); 1806 tlen -= todrop; 1807 thflags &= ~(TH_PUSH | TH_FIN); 1808 } 1809 1810 /* 1811 * If last ACK falls within this segment's sequence numbers, 1812 * record its timestamp. 1813 * NOTE: 1814 * 1) That the test incorporates suggestions from the latest 1815 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1816 * 2) That updating only on newer timestamps interferes with 1817 * our earlier PAWS tests, so this check should be solely 1818 * predicated on the sequence space of this segment. 1819 * 3) That we modify the segment boundary check to be 1820 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1821 * instead of RFC1323's 1822 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1823 * This modified check allows us to overcome RFC1323's 1824 * limitations as described in Stevens TCP/IP Illustrated 1825 * Vol. 2 p.869. In such cases, we can still calculate the 1826 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1827 */ 1828 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1829 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1830 + ((thflags & TH_SYN) != 0) 1831 + ((thflags & TH_FIN) != 0)))) { 1832 tp->ts_recent_age = ticks; 1833 tp->ts_recent = to.to_tsval; 1834 } 1835 1836 /* 1837 * If a SYN is in the window, then this is an 1838 * error and we send an RST and drop the connection. 1839 */ 1840 if (thflags & TH_SYN) { 1841 tp = tcp_drop(tp, ECONNRESET); 1842 rstreason = BANDLIM_UNLIMITED; 1843 goto dropwithreset; 1844 } 1845 1846 /* 1847 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1848 * flag is on (half-synchronized state), then queue data for 1849 * later processing; else drop segment and return. 1850 */ 1851 if (!(thflags & TH_ACK)) { 1852 if (tp->t_state == TCPS_SYN_RECEIVED || 1853 (tp->t_flags & TF_NEEDSYN)) 1854 goto step6; 1855 else 1856 goto drop; 1857 } 1858 1859 /* 1860 * Ack processing. 1861 */ 1862 switch (tp->t_state) { 1863 /* 1864 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1865 * ESTABLISHED state and continue processing. 1866 * The ACK was checked above. 1867 */ 1868 case TCPS_SYN_RECEIVED: 1869 1870 tcpstat.tcps_connects++; 1871 soisconnected(so); 1872 /* Do window scaling? */ 1873 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1874 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 1875 tp->snd_scale = tp->requested_s_scale; 1876 tp->rcv_scale = tp->request_r_scale; 1877 } 1878 /* 1879 * Make transitions: 1880 * SYN-RECEIVED -> ESTABLISHED 1881 * SYN-RECEIVED* -> FIN-WAIT-1 1882 */ 1883 tp->t_starttime = ticks; 1884 if (tp->t_flags & TF_NEEDFIN) { 1885 tp->t_state = TCPS_FIN_WAIT_1; 1886 tp->t_flags &= ~TF_NEEDFIN; 1887 } else { 1888 tp->t_state = TCPS_ESTABLISHED; 1889 tcp_callout_reset(tp, tp->tt_keep, 1890 tcp_getkeepidle(tp), 1891 tcp_timer_keep); 1892 } 1893 /* 1894 * If segment contains data or ACK, will call tcp_reass() 1895 * later; if not, do so now to pass queued data to user. 1896 */ 1897 if (tlen == 0 && !(thflags & TH_FIN)) 1898 tcp_reass(tp, NULL, NULL, NULL); 1899 /* fall into ... */ 1900 1901 /* 1902 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1903 * ACKs. If the ack is in the range 1904 * tp->snd_una < th->th_ack <= tp->snd_max 1905 * then advance tp->snd_una to th->th_ack and drop 1906 * data from the retransmission queue. If this ACK reflects 1907 * more up to date window information we update our window information. 1908 */ 1909 case TCPS_ESTABLISHED: 1910 case TCPS_FIN_WAIT_1: 1911 case TCPS_FIN_WAIT_2: 1912 case TCPS_CLOSE_WAIT: 1913 case TCPS_CLOSING: 1914 case TCPS_LAST_ACK: 1915 case TCPS_TIME_WAIT: 1916 1917 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1918 if (TCP_DO_SACK(tp)) 1919 tcp_sack_update_scoreboard(tp, &to); 1920 if (tlen != 0 || tiwin != tp->snd_wnd) { 1921 tp->t_dupacks = 0; 1922 break; 1923 } 1924 tcpstat.tcps_rcvdupack++; 1925 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1926 th->th_ack != tp->snd_una) { 1927 tp->t_dupacks = 0; 1928 break; 1929 } 1930 /* 1931 * We have outstanding data (other than 1932 * a window probe), this is a completely 1933 * duplicate ack (ie, window info didn't 1934 * change), the ack is the biggest we've 1935 * seen and we've seen exactly our rexmt 1936 * threshhold of them, so assume a packet 1937 * has been dropped and retransmit it. 1938 * Kludge snd_nxt & the congestion 1939 * window so we send only this one 1940 * packet. 1941 */ 1942 if (IN_FASTRECOVERY(tp)) { 1943 if (TCP_DO_SACK(tp)) { 1944 /* No artifical cwnd inflation. */ 1945 tcp_sack_rexmt(tp, th); 1946 } else { 1947 /* 1948 * Dup acks mean that packets 1949 * have left the network 1950 * (they're now cached at the 1951 * receiver) so bump cwnd by 1952 * the amount in the receiver 1953 * to keep a constant cwnd 1954 * packets in the network. 1955 */ 1956 tp->snd_cwnd += tp->t_maxseg; 1957 tcp_output(tp); 1958 } 1959 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1960 tp->t_dupacks = 0; 1961 break; 1962 } else if (++tp->t_dupacks == tcprexmtthresh) { 1963 tcp_seq old_snd_nxt; 1964 u_int win; 1965 1966 fastretransmit: 1967 if (tcp_do_eifel_detect && 1968 (tp->t_flags & TF_RCVD_TSTMP)) { 1969 tcp_save_congestion_state(tp); 1970 tp->t_flags |= TF_FASTREXMT; 1971 } 1972 /* 1973 * We know we're losing at the current 1974 * window size, so do congestion avoidance: 1975 * set ssthresh to half the current window 1976 * and pull our congestion window back to the 1977 * new ssthresh. 1978 */ 1979 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1980 tp->t_maxseg; 1981 if (win < 2) 1982 win = 2; 1983 tp->snd_ssthresh = win * tp->t_maxseg; 1984 ENTER_FASTRECOVERY(tp); 1985 tp->snd_recover = tp->snd_max; 1986 tcp_callout_stop(tp, tp->tt_rexmt); 1987 tp->t_rtttime = 0; 1988 old_snd_nxt = tp->snd_nxt; 1989 tp->snd_nxt = th->th_ack; 1990 tp->snd_cwnd = tp->t_maxseg; 1991 tcp_output(tp); 1992 ++tcpstat.tcps_sndfastrexmit; 1993 tp->snd_cwnd = tp->snd_ssthresh; 1994 tp->rexmt_high = tp->snd_nxt; 1995 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1996 tp->snd_nxt = old_snd_nxt; 1997 KASSERT(tp->snd_limited <= 2, 1998 ("tp->snd_limited too big")); 1999 if (TCP_DO_SACK(tp)) 2000 tcp_sack_rexmt(tp, th); 2001 else 2002 tp->snd_cwnd += tp->t_maxseg * 2003 (tp->t_dupacks - tp->snd_limited); 2004 } else if (tcp_do_limitedtransmit) { 2005 u_long oldcwnd = tp->snd_cwnd; 2006 tcp_seq oldsndmax = tp->snd_max; 2007 tcp_seq oldsndnxt = tp->snd_nxt; 2008 /* outstanding data */ 2009 uint32_t ownd = tp->snd_max - tp->snd_una; 2010 u_int sent; 2011 2012 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2013 2014 KASSERT(tp->t_dupacks == 1 || 2015 tp->t_dupacks == 2, 2016 ("dupacks not 1 or 2")); 2017 if (tp->t_dupacks == 1) 2018 tp->snd_limited = 0; 2019 tp->snd_nxt = tp->snd_max; 2020 tp->snd_cwnd = ownd + 2021 (tp->t_dupacks - tp->snd_limited) * 2022 tp->t_maxseg; 2023 tcp_output(tp); 2024 2025 /* 2026 * Other acks may have been processed, 2027 * snd_nxt cannot be reset to a value less 2028 * then snd_una. 2029 */ 2030 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2031 if (SEQ_GT(oldsndnxt, tp->snd_una)) 2032 tp->snd_nxt = oldsndnxt; 2033 else 2034 tp->snd_nxt = tp->snd_una; 2035 } 2036 tp->snd_cwnd = oldcwnd; 2037 sent = tp->snd_max - oldsndmax; 2038 if (sent > tp->t_maxseg) { 2039 KASSERT((tp->t_dupacks == 2 && 2040 tp->snd_limited == 0) || 2041 (sent == tp->t_maxseg + 1 && 2042 tp->t_flags & TF_SENTFIN), 2043 ("sent too much")); 2044 KASSERT(sent <= tp->t_maxseg * 2, 2045 ("sent too many segments")); 2046 tp->snd_limited = 2; 2047 tcpstat.tcps_sndlimited += 2; 2048 } else if (sent > 0) { 2049 ++tp->snd_limited; 2050 ++tcpstat.tcps_sndlimited; 2051 } else if (tcp_do_early_retransmit && 2052 (tcp_do_eifel_detect && 2053 (tp->t_flags & TF_RCVD_TSTMP)) && 2054 ownd < 4 * tp->t_maxseg && 2055 tp->t_dupacks + 1 >= 2056 iceildiv(ownd, tp->t_maxseg) && 2057 (!TCP_DO_SACK(tp) || 2058 ownd <= tp->t_maxseg || 2059 tcp_sack_has_sacked(&tp->scb, 2060 ownd - tp->t_maxseg))) { 2061 ++tcpstat.tcps_sndearlyrexmit; 2062 tp->t_flags |= TF_EARLYREXMT; 2063 goto fastretransmit; 2064 } 2065 } 2066 goto drop; 2067 } 2068 2069 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2070 tp->t_dupacks = 0; 2071 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2072 /* 2073 * Detected optimistic ACK attack. 2074 * Force slow-start to de-synchronize attack. 2075 */ 2076 tp->snd_cwnd = tp->t_maxseg; 2077 tp->snd_wacked = 0; 2078 2079 tcpstat.tcps_rcvacktoomuch++; 2080 goto dropafterack; 2081 } 2082 /* 2083 * If we reach this point, ACK is not a duplicate, 2084 * i.e., it ACKs something we sent. 2085 */ 2086 if (tp->t_flags & TF_NEEDSYN) { 2087 /* 2088 * T/TCP: Connection was half-synchronized, and our 2089 * SYN has been ACK'd (so connection is now fully 2090 * synchronized). Go to non-starred state, 2091 * increment snd_una for ACK of SYN, and check if 2092 * we can do window scaling. 2093 */ 2094 tp->t_flags &= ~TF_NEEDSYN; 2095 tp->snd_una++; 2096 /* Do window scaling? */ 2097 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2098 (TF_RCVD_SCALE | TF_REQ_SCALE)) { 2099 tp->snd_scale = tp->requested_s_scale; 2100 tp->rcv_scale = tp->request_r_scale; 2101 } 2102 } 2103 2104 process_ACK: 2105 acked = th->th_ack - tp->snd_una; 2106 tcpstat.tcps_rcvackpack++; 2107 tcpstat.tcps_rcvackbyte += acked; 2108 2109 if (tcp_do_eifel_detect && acked > 0 && 2110 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2111 (tp->t_flags & TF_FIRSTACCACK)) { 2112 /* Eifel detection applicable. */ 2113 if (to.to_tsecr < tp->t_rexmtTS) { 2114 ++tcpstat.tcps_eifeldetected; 2115 tcp_revert_congestion_state(tp); 2116 if (tp->t_rxtshift == 1 && 2117 ticks >= tp->t_badrxtwin) 2118 ++tcpstat.tcps_rttcantdetect; 2119 } 2120 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2121 /* 2122 * If we just performed our first retransmit, 2123 * and the ACK arrives within our recovery window, 2124 * then it was a mistake to do the retransmit 2125 * in the first place. Recover our original cwnd 2126 * and ssthresh, and proceed to transmit where we 2127 * left off. 2128 */ 2129 tcp_revert_congestion_state(tp); 2130 ++tcpstat.tcps_rttdetected; 2131 } 2132 2133 /* 2134 * If we have a timestamp reply, update smoothed 2135 * round trip time. If no timestamp is present but 2136 * transmit timer is running and timed sequence 2137 * number was acked, update smoothed round trip time. 2138 * Since we now have an rtt measurement, cancel the 2139 * timer backoff (cf., Phil Karn's retransmit alg.). 2140 * Recompute the initial retransmit timer. 2141 * 2142 * Some machines (certain windows boxes) send broken 2143 * timestamp replies during the SYN+ACK phase, ignore 2144 * timestamps of 0. 2145 */ 2146 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2147 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 2148 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2149 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2150 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2151 2152 /* 2153 * If no data (only SYN) was ACK'd, 2154 * skip rest of ACK processing. 2155 */ 2156 if (acked == 0) 2157 goto step6; 2158 2159 /* Stop looking for an acceptable ACK since one was received. */ 2160 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2161 2162 if (acked > so->so_snd.ssb_cc) { 2163 tp->snd_wnd -= so->so_snd.ssb_cc; 2164 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2165 ourfinisacked = TRUE; 2166 } else { 2167 sbdrop(&so->so_snd.sb, acked); 2168 tp->snd_wnd -= acked; 2169 ourfinisacked = FALSE; 2170 } 2171 sowwakeup(so); 2172 2173 /* 2174 * Update window information. 2175 * Don't look at window if no ACK: 2176 * TAC's send garbage on first SYN. 2177 */ 2178 if (SEQ_LT(tp->snd_wl1, th->th_seq) || 2179 (tp->snd_wl1 == th->th_seq && 2180 (SEQ_LT(tp->snd_wl2, th->th_ack) || 2181 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) { 2182 /* keep track of pure window updates */ 2183 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2184 tiwin > tp->snd_wnd) 2185 tcpstat.tcps_rcvwinupd++; 2186 tp->snd_wnd = tiwin; 2187 tp->snd_wl1 = th->th_seq; 2188 tp->snd_wl2 = th->th_ack; 2189 if (tp->snd_wnd > tp->max_sndwnd) 2190 tp->max_sndwnd = tp->snd_wnd; 2191 needoutput = TRUE; 2192 } 2193 2194 tp->snd_una = th->th_ack; 2195 if (TCP_DO_SACK(tp)) 2196 tcp_sack_update_scoreboard(tp, &to); 2197 if (IN_FASTRECOVERY(tp)) { 2198 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2199 EXIT_FASTRECOVERY(tp); 2200 needoutput = TRUE; 2201 /* 2202 * If the congestion window was inflated 2203 * to account for the other side's 2204 * cached packets, retract it. 2205 */ 2206 if (!TCP_DO_SACK(tp)) 2207 tp->snd_cwnd = tp->snd_ssthresh; 2208 2209 /* 2210 * Window inflation should have left us 2211 * with approximately snd_ssthresh outstanding 2212 * data. But, in case we would be inclined 2213 * to send a burst, better do it using 2214 * slow start. 2215 */ 2216 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2217 tp->snd_max + 2 * tp->t_maxseg)) 2218 tp->snd_cwnd = 2219 (tp->snd_max - tp->snd_una) + 2220 2 * tp->t_maxseg; 2221 2222 tp->snd_wacked = 0; 2223 } else { 2224 if (TCP_DO_SACK(tp)) { 2225 tp->snd_max_rexmt = tp->snd_max; 2226 tcp_sack_rexmt(tp, th); 2227 } else { 2228 tcp_newreno_partial_ack(tp, th, acked); 2229 } 2230 needoutput = FALSE; 2231 } 2232 } else { 2233 /* 2234 * Open the congestion window. When in slow-start, 2235 * open exponentially: maxseg per packet. Otherwise, 2236 * open linearly: maxseg per window. 2237 */ 2238 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2239 u_int abc_sslimit = 2240 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2241 tp->t_maxseg : 2 * tp->t_maxseg); 2242 2243 /* slow-start */ 2244 tp->snd_cwnd += tcp_do_abc ? 2245 min(acked, abc_sslimit) : tp->t_maxseg; 2246 } else { 2247 /* linear increase */ 2248 tp->snd_wacked += tcp_do_abc ? acked : 2249 tp->t_maxseg; 2250 if (tp->snd_wacked >= tp->snd_cwnd) { 2251 tp->snd_wacked -= tp->snd_cwnd; 2252 tp->snd_cwnd += tp->t_maxseg; 2253 } 2254 } 2255 tp->snd_cwnd = min(tp->snd_cwnd, 2256 TCP_MAXWIN << tp->snd_scale); 2257 tp->snd_recover = th->th_ack - 1; 2258 } 2259 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2260 tp->snd_nxt = tp->snd_una; 2261 2262 /* 2263 * If all outstanding data is acked, stop retransmit 2264 * timer and remember to restart (more output or persist). 2265 * If there is more data to be acked, restart retransmit 2266 * timer, using current (possibly backed-off) value. 2267 */ 2268 if (th->th_ack == tp->snd_max) { 2269 tcp_callout_stop(tp, tp->tt_rexmt); 2270 needoutput = TRUE; 2271 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2272 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2273 tcp_timer_rexmt); 2274 } 2275 2276 switch (tp->t_state) { 2277 /* 2278 * In FIN_WAIT_1 STATE in addition to the processing 2279 * for the ESTABLISHED state if our FIN is now acknowledged 2280 * then enter FIN_WAIT_2. 2281 */ 2282 case TCPS_FIN_WAIT_1: 2283 if (ourfinisacked) { 2284 /* 2285 * If we can't receive any more 2286 * data, then closing user can proceed. 2287 * Starting the timer is contrary to the 2288 * specification, but if we don't get a FIN 2289 * we'll hang forever. 2290 */ 2291 if (so->so_state & SS_CANTRCVMORE) { 2292 soisdisconnected(so); 2293 tcp_callout_reset(tp, tp->tt_2msl, 2294 tp->t_maxidle, tcp_timer_2msl); 2295 } 2296 tp->t_state = TCPS_FIN_WAIT_2; 2297 } 2298 break; 2299 2300 /* 2301 * In CLOSING STATE in addition to the processing for 2302 * the ESTABLISHED state if the ACK acknowledges our FIN 2303 * then enter the TIME-WAIT state, otherwise ignore 2304 * the segment. 2305 */ 2306 case TCPS_CLOSING: 2307 if (ourfinisacked) { 2308 tp->t_state = TCPS_TIME_WAIT; 2309 tcp_canceltimers(tp); 2310 tcp_callout_reset(tp, tp->tt_2msl, 2311 2 * tcp_rmx_msl(tp), 2312 tcp_timer_2msl); 2313 soisdisconnected(so); 2314 } 2315 break; 2316 2317 /* 2318 * In LAST_ACK, we may still be waiting for data to drain 2319 * and/or to be acked, as well as for the ack of our FIN. 2320 * If our FIN is now acknowledged, delete the TCB, 2321 * enter the closed state and return. 2322 */ 2323 case TCPS_LAST_ACK: 2324 if (ourfinisacked) { 2325 tp = tcp_close(tp); 2326 goto drop; 2327 } 2328 break; 2329 2330 /* 2331 * In TIME_WAIT state the only thing that should arrive 2332 * is a retransmission of the remote FIN. Acknowledge 2333 * it and restart the finack timer. 2334 */ 2335 case TCPS_TIME_WAIT: 2336 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2337 tcp_timer_2msl); 2338 goto dropafterack; 2339 } 2340 } 2341 2342 step6: 2343 /* 2344 * Update window information. 2345 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2346 */ 2347 if ((thflags & TH_ACK) && 2348 acceptable_window_update(tp, th, tiwin)) { 2349 /* keep track of pure window updates */ 2350 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2351 tiwin > tp->snd_wnd) 2352 tcpstat.tcps_rcvwinupd++; 2353 tp->snd_wnd = tiwin; 2354 tp->snd_wl1 = th->th_seq; 2355 tp->snd_wl2 = th->th_ack; 2356 if (tp->snd_wnd > tp->max_sndwnd) 2357 tp->max_sndwnd = tp->snd_wnd; 2358 needoutput = TRUE; 2359 } 2360 2361 /* 2362 * Process segments with URG. 2363 */ 2364 if ((thflags & TH_URG) && th->th_urp && 2365 !TCPS_HAVERCVDFIN(tp->t_state)) { 2366 /* 2367 * This is a kludge, but if we receive and accept 2368 * random urgent pointers, we'll crash in 2369 * soreceive. It's hard to imagine someone 2370 * actually wanting to send this much urgent data. 2371 */ 2372 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2373 th->th_urp = 0; /* XXX */ 2374 thflags &= ~TH_URG; /* XXX */ 2375 goto dodata; /* XXX */ 2376 } 2377 /* 2378 * If this segment advances the known urgent pointer, 2379 * then mark the data stream. This should not happen 2380 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2381 * a FIN has been received from the remote side. 2382 * In these states we ignore the URG. 2383 * 2384 * According to RFC961 (Assigned Protocols), 2385 * the urgent pointer points to the last octet 2386 * of urgent data. We continue, however, 2387 * to consider it to indicate the first octet 2388 * of data past the urgent section as the original 2389 * spec states (in one of two places). 2390 */ 2391 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2392 tp->rcv_up = th->th_seq + th->th_urp; 2393 so->so_oobmark = so->so_rcv.ssb_cc + 2394 (tp->rcv_up - tp->rcv_nxt) - 1; 2395 if (so->so_oobmark == 0) 2396 sosetstate(so, SS_RCVATMARK); 2397 sohasoutofband(so); 2398 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2399 } 2400 /* 2401 * Remove out of band data so doesn't get presented to user. 2402 * This can happen independent of advancing the URG pointer, 2403 * but if two URG's are pending at once, some out-of-band 2404 * data may creep in... ick. 2405 */ 2406 if (th->th_urp <= (u_long)tlen && 2407 !(so->so_options & SO_OOBINLINE)) { 2408 /* hdr drop is delayed */ 2409 tcp_pulloutofband(so, th, m, drop_hdrlen); 2410 } 2411 } else { 2412 /* 2413 * If no out of band data is expected, 2414 * pull receive urgent pointer along 2415 * with the receive window. 2416 */ 2417 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2418 tp->rcv_up = tp->rcv_nxt; 2419 } 2420 2421 dodata: /* XXX */ 2422 /* 2423 * Process the segment text, merging it into the TCP sequencing queue, 2424 * and arranging for acknowledgment of receipt if necessary. 2425 * This process logically involves adjusting tp->rcv_wnd as data 2426 * is presented to the user (this happens in tcp_usrreq.c, 2427 * case PRU_RCVD). If a FIN has already been received on this 2428 * connection then we just ignore the text. 2429 */ 2430 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2431 m_adj(m, drop_hdrlen); /* delayed header drop */ 2432 /* 2433 * Insert segment which includes th into TCP reassembly queue 2434 * with control block tp. Set thflags to whether reassembly now 2435 * includes a segment with FIN. This handles the common case 2436 * inline (segment is the next to be received on an established 2437 * connection, and the queue is empty), avoiding linkage into 2438 * and removal from the queue and repetition of various 2439 * conversions. 2440 * Set DELACK for segments received in order, but ack 2441 * immediately when segments are out of order (so 2442 * fast retransmit can work). 2443 */ 2444 if (th->th_seq == tp->rcv_nxt && 2445 LIST_EMPTY(&tp->t_segq) && 2446 TCPS_HAVEESTABLISHED(tp->t_state)) { 2447 if (DELAY_ACK(tp)) { 2448 tcp_callout_reset(tp, tp->tt_delack, 2449 tcp_delacktime, tcp_timer_delack); 2450 } else { 2451 tp->t_flags |= TF_ACKNOW; 2452 } 2453 tp->rcv_nxt += tlen; 2454 thflags = th->th_flags & TH_FIN; 2455 tcpstat.tcps_rcvpack++; 2456 tcpstat.tcps_rcvbyte += tlen; 2457 ND6_HINT(tp); 2458 if (so->so_state & SS_CANTRCVMORE) { 2459 m_freem(m); 2460 } else { 2461 lwkt_gettoken(&so->so_rcv.ssb_token); 2462 ssb_appendstream(&so->so_rcv, m); 2463 lwkt_reltoken(&so->so_rcv.ssb_token); 2464 } 2465 sorwakeup(so); 2466 } else { 2467 if (!(tp->t_flags & TF_DUPSEG)) { 2468 /* Initialize SACK report block. */ 2469 tp->reportblk.rblk_start = th->th_seq; 2470 tp->reportblk.rblk_end = th->th_seq + tlen + 2471 ((thflags & TH_FIN) != 0); 2472 } 2473 thflags = tcp_reass(tp, th, &tlen, m); 2474 tp->t_flags |= TF_ACKNOW; 2475 } 2476 2477 /* 2478 * Note the amount of data that peer has sent into 2479 * our window, in order to estimate the sender's 2480 * buffer size. 2481 */ 2482 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2483 } else { 2484 m_freem(m); 2485 thflags &= ~TH_FIN; 2486 } 2487 2488 /* 2489 * If FIN is received ACK the FIN and let the user know 2490 * that the connection is closing. 2491 */ 2492 if (thflags & TH_FIN) { 2493 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2494 socantrcvmore(so); 2495 /* 2496 * If connection is half-synchronized 2497 * (ie NEEDSYN flag on) then delay ACK, 2498 * so it may be piggybacked when SYN is sent. 2499 * Otherwise, since we received a FIN then no 2500 * more input can be expected, send ACK now. 2501 */ 2502 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2503 tcp_callout_reset(tp, tp->tt_delack, 2504 tcp_delacktime, tcp_timer_delack); 2505 } else { 2506 tp->t_flags |= TF_ACKNOW; 2507 } 2508 tp->rcv_nxt++; 2509 } 2510 2511 switch (tp->t_state) { 2512 /* 2513 * In SYN_RECEIVED and ESTABLISHED STATES 2514 * enter the CLOSE_WAIT state. 2515 */ 2516 case TCPS_SYN_RECEIVED: 2517 tp->t_starttime = ticks; 2518 /*FALLTHROUGH*/ 2519 case TCPS_ESTABLISHED: 2520 tp->t_state = TCPS_CLOSE_WAIT; 2521 break; 2522 2523 /* 2524 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2525 * enter the CLOSING state. 2526 */ 2527 case TCPS_FIN_WAIT_1: 2528 tp->t_state = TCPS_CLOSING; 2529 break; 2530 2531 /* 2532 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2533 * starting the time-wait timer, turning off the other 2534 * standard timers. 2535 */ 2536 case TCPS_FIN_WAIT_2: 2537 tp->t_state = TCPS_TIME_WAIT; 2538 tcp_canceltimers(tp); 2539 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2540 tcp_timer_2msl); 2541 soisdisconnected(so); 2542 break; 2543 2544 /* 2545 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2546 */ 2547 case TCPS_TIME_WAIT: 2548 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2549 tcp_timer_2msl); 2550 break; 2551 } 2552 } 2553 2554 #ifdef TCPDEBUG 2555 if (so->so_options & SO_DEBUG) 2556 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2557 #endif 2558 2559 /* 2560 * Return any desired output. 2561 */ 2562 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2563 tcp_output(tp); 2564 return(IPPROTO_DONE); 2565 2566 dropafterack: 2567 /* 2568 * Generate an ACK dropping incoming segment if it occupies 2569 * sequence space, where the ACK reflects our state. 2570 * 2571 * We can now skip the test for the RST flag since all 2572 * paths to this code happen after packets containing 2573 * RST have been dropped. 2574 * 2575 * In the SYN-RECEIVED state, don't send an ACK unless the 2576 * segment we received passes the SYN-RECEIVED ACK test. 2577 * If it fails send a RST. This breaks the loop in the 2578 * "LAND" DoS attack, and also prevents an ACK storm 2579 * between two listening ports that have been sent forged 2580 * SYN segments, each with the source address of the other. 2581 */ 2582 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2583 (SEQ_GT(tp->snd_una, th->th_ack) || 2584 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2585 rstreason = BANDLIM_RST_OPENPORT; 2586 goto dropwithreset; 2587 } 2588 #ifdef TCPDEBUG 2589 if (so->so_options & SO_DEBUG) 2590 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2591 #endif 2592 m_freem(m); 2593 tp->t_flags |= TF_ACKNOW; 2594 tcp_output(tp); 2595 return(IPPROTO_DONE); 2596 2597 dropwithreset: 2598 /* 2599 * Generate a RST, dropping incoming segment. 2600 * Make ACK acceptable to originator of segment. 2601 * Don't bother to respond if destination was broadcast/multicast. 2602 */ 2603 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2604 goto drop; 2605 if (isipv6) { 2606 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2607 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2608 goto drop; 2609 } else { 2610 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2611 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2612 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2613 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2614 goto drop; 2615 } 2616 /* IPv6 anycast check is done at tcp6_input() */ 2617 2618 /* 2619 * Perform bandwidth limiting. 2620 */ 2621 #ifdef ICMP_BANDLIM 2622 if (badport_bandlim(rstreason) < 0) 2623 goto drop; 2624 #endif 2625 2626 #ifdef TCPDEBUG 2627 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2628 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2629 #endif 2630 if (thflags & TH_ACK) 2631 /* mtod() below is safe as long as hdr dropping is delayed */ 2632 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2633 TH_RST); 2634 else { 2635 if (thflags & TH_SYN) 2636 tlen++; 2637 /* mtod() below is safe as long as hdr dropping is delayed */ 2638 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2639 (tcp_seq)0, TH_RST | TH_ACK); 2640 } 2641 return(IPPROTO_DONE); 2642 2643 drop: 2644 /* 2645 * Drop space held by incoming segment and return. 2646 */ 2647 #ifdef TCPDEBUG 2648 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2649 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2650 #endif 2651 m_freem(m); 2652 return(IPPROTO_DONE); 2653 } 2654 2655 /* 2656 * Parse TCP options and place in tcpopt. 2657 */ 2658 static void 2659 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn) 2660 { 2661 int opt, optlen, i; 2662 2663 to->to_flags = 0; 2664 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2665 opt = cp[0]; 2666 if (opt == TCPOPT_EOL) 2667 break; 2668 if (opt == TCPOPT_NOP) 2669 optlen = 1; 2670 else { 2671 if (cnt < 2) 2672 break; 2673 optlen = cp[1]; 2674 if (optlen < 2 || optlen > cnt) 2675 break; 2676 } 2677 switch (opt) { 2678 case TCPOPT_MAXSEG: 2679 if (optlen != TCPOLEN_MAXSEG) 2680 continue; 2681 if (!is_syn) 2682 continue; 2683 to->to_flags |= TOF_MSS; 2684 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2685 to->to_mss = ntohs(to->to_mss); 2686 break; 2687 case TCPOPT_WINDOW: 2688 if (optlen != TCPOLEN_WINDOW) 2689 continue; 2690 if (!is_syn) 2691 continue; 2692 to->to_flags |= TOF_SCALE; 2693 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2694 break; 2695 case TCPOPT_TIMESTAMP: 2696 if (optlen != TCPOLEN_TIMESTAMP) 2697 continue; 2698 to->to_flags |= TOF_TS; 2699 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2700 to->to_tsval = ntohl(to->to_tsval); 2701 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2702 to->to_tsecr = ntohl(to->to_tsecr); 2703 /* 2704 * If echoed timestamp is later than the current time, 2705 * fall back to non RFC1323 RTT calculation. 2706 */ 2707 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2708 to->to_tsecr = 0; 2709 break; 2710 case TCPOPT_SACK_PERMITTED: 2711 if (optlen != TCPOLEN_SACK_PERMITTED) 2712 continue; 2713 if (!is_syn) 2714 continue; 2715 to->to_flags |= TOF_SACK_PERMITTED; 2716 break; 2717 case TCPOPT_SACK: 2718 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2719 continue; 2720 to->to_nsackblocks = (optlen - 2) / 8; 2721 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2722 to->to_flags |= TOF_SACK; 2723 for (i = 0; i < to->to_nsackblocks; i++) { 2724 struct raw_sackblock *r = &to->to_sackblocks[i]; 2725 2726 r->rblk_start = ntohl(r->rblk_start); 2727 r->rblk_end = ntohl(r->rblk_end); 2728 } 2729 break; 2730 #ifdef TCP_SIGNATURE 2731 /* 2732 * XXX In order to reply to a host which has set the 2733 * TCP_SIGNATURE option in its initial SYN, we have to 2734 * record the fact that the option was observed here 2735 * for the syncache code to perform the correct response. 2736 */ 2737 case TCPOPT_SIGNATURE: 2738 if (optlen != TCPOLEN_SIGNATURE) 2739 continue; 2740 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2741 break; 2742 #endif /* TCP_SIGNATURE */ 2743 default: 2744 continue; 2745 } 2746 } 2747 } 2748 2749 /* 2750 * Pull out of band byte out of a segment so 2751 * it doesn't appear in the user's data queue. 2752 * It is still reflected in the segment length for 2753 * sequencing purposes. 2754 * "off" is the delayed to be dropped hdrlen. 2755 */ 2756 static void 2757 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2758 { 2759 int cnt = off + th->th_urp - 1; 2760 2761 while (cnt >= 0) { 2762 if (m->m_len > cnt) { 2763 char *cp = mtod(m, caddr_t) + cnt; 2764 struct tcpcb *tp = sototcpcb(so); 2765 2766 tp->t_iobc = *cp; 2767 tp->t_oobflags |= TCPOOB_HAVEDATA; 2768 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2769 m->m_len--; 2770 if (m->m_flags & M_PKTHDR) 2771 m->m_pkthdr.len--; 2772 return; 2773 } 2774 cnt -= m->m_len; 2775 m = m->m_next; 2776 if (m == NULL) 2777 break; 2778 } 2779 panic("tcp_pulloutofband"); 2780 } 2781 2782 /* 2783 * Collect new round-trip time estimate 2784 * and update averages and current timeout. 2785 */ 2786 static void 2787 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2788 { 2789 int delta; 2790 2791 tcpstat.tcps_rttupdated++; 2792 tp->t_rttupdated++; 2793 if (tp->t_srtt != 0) { 2794 /* 2795 * srtt is stored as fixed point with 5 bits after the 2796 * binary point (i.e., scaled by 8). The following magic 2797 * is equivalent to the smoothing algorithm in rfc793 with 2798 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2799 * point). Adjust rtt to origin 0. 2800 */ 2801 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2802 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2803 2804 if ((tp->t_srtt += delta) <= 0) 2805 tp->t_srtt = 1; 2806 2807 /* 2808 * We accumulate a smoothed rtt variance (actually, a 2809 * smoothed mean difference), then set the retransmit 2810 * timer to smoothed rtt + 4 times the smoothed variance. 2811 * rttvar is stored as fixed point with 4 bits after the 2812 * binary point (scaled by 16). The following is 2813 * equivalent to rfc793 smoothing with an alpha of .75 2814 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2815 * rfc793's wired-in beta. 2816 */ 2817 if (delta < 0) 2818 delta = -delta; 2819 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2820 if ((tp->t_rttvar += delta) <= 0) 2821 tp->t_rttvar = 1; 2822 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2823 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2824 } else { 2825 /* 2826 * No rtt measurement yet - use the unsmoothed rtt. 2827 * Set the variance to half the rtt (so our first 2828 * retransmit happens at 3*rtt). 2829 */ 2830 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2831 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2832 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2833 } 2834 tp->t_rtttime = 0; 2835 tp->t_rxtshift = 0; 2836 2837 /* 2838 * the retransmit should happen at rtt + 4 * rttvar. 2839 * Because of the way we do the smoothing, srtt and rttvar 2840 * will each average +1/2 tick of bias. When we compute 2841 * the retransmit timer, we want 1/2 tick of rounding and 2842 * 1 extra tick because of +-1/2 tick uncertainty in the 2843 * firing of the timer. The bias will give us exactly the 2844 * 1.5 tick we need. But, because the bias is 2845 * statistical, we have to test that we don't drop below 2846 * the minimum feasible timer (which is 2 ticks). 2847 */ 2848 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2849 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2850 2851 /* 2852 * We received an ack for a packet that wasn't retransmitted; 2853 * it is probably safe to discard any error indications we've 2854 * received recently. This isn't quite right, but close enough 2855 * for now (a route might have failed after we sent a segment, 2856 * and the return path might not be symmetrical). 2857 */ 2858 tp->t_softerror = 0; 2859 } 2860 2861 /* 2862 * Determine a reasonable value for maxseg size. 2863 * If the route is known, check route for mtu. 2864 * If none, use an mss that can be handled on the outgoing 2865 * interface without forcing IP to fragment; if bigger than 2866 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2867 * to utilize large mbufs. If no route is found, route has no mtu, 2868 * or the destination isn't local, use a default, hopefully conservative 2869 * size (usually 512 or the default IP max size, but no more than the mtu 2870 * of the interface), as we can't discover anything about intervening 2871 * gateways or networks. We also initialize the congestion/slow start 2872 * window to be a single segment if the destination isn't local. 2873 * While looking at the routing entry, we also initialize other path-dependent 2874 * parameters from pre-set or cached values in the routing entry. 2875 * 2876 * Also take into account the space needed for options that we 2877 * send regularly. Make maxseg shorter by that amount to assure 2878 * that we can send maxseg amount of data even when the options 2879 * are present. Store the upper limit of the length of options plus 2880 * data in maxopd. 2881 * 2882 * NOTE that this routine is only called when we process an incoming 2883 * segment, for outgoing segments only tcp_mssopt is called. 2884 */ 2885 void 2886 tcp_mss(struct tcpcb *tp, int offer) 2887 { 2888 struct rtentry *rt; 2889 struct ifnet *ifp; 2890 int rtt, mss; 2891 u_long bufsize; 2892 struct inpcb *inp = tp->t_inpcb; 2893 struct socket *so; 2894 #ifdef INET6 2895 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2896 size_t min_protoh = isipv6 ? 2897 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2898 sizeof(struct tcpiphdr); 2899 #else 2900 const boolean_t isipv6 = FALSE; 2901 const size_t min_protoh = sizeof(struct tcpiphdr); 2902 #endif 2903 2904 if (isipv6) 2905 rt = tcp_rtlookup6(&inp->inp_inc); 2906 else 2907 rt = tcp_rtlookup(&inp->inp_inc); 2908 if (rt == NULL) { 2909 tp->t_maxopd = tp->t_maxseg = 2910 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2911 return; 2912 } 2913 ifp = rt->rt_ifp; 2914 so = inp->inp_socket; 2915 2916 /* 2917 * Offer == 0 means that there was no MSS on the SYN segment, 2918 * in this case we use either the interface mtu or tcp_mssdflt. 2919 * 2920 * An offer which is too large will be cut down later. 2921 */ 2922 if (offer == 0) { 2923 if (isipv6) { 2924 if (in6_localaddr(&inp->in6p_faddr)) { 2925 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2926 min_protoh; 2927 } else { 2928 offer = tcp_v6mssdflt; 2929 } 2930 } else { 2931 if (in_localaddr(inp->inp_faddr)) 2932 offer = ifp->if_mtu - min_protoh; 2933 else 2934 offer = tcp_mssdflt; 2935 } 2936 } 2937 2938 /* 2939 * Prevent DoS attack with too small MSS. Round up 2940 * to at least minmss. 2941 * 2942 * Sanity check: make sure that maxopd will be large 2943 * enough to allow some data on segments even is the 2944 * all the option space is used (40bytes). Otherwise 2945 * funny things may happen in tcp_output. 2946 */ 2947 offer = max(offer, tcp_minmss); 2948 offer = max(offer, 64); 2949 2950 rt->rt_rmx.rmx_mssopt = offer; 2951 2952 /* 2953 * While we're here, check if there's an initial rtt 2954 * or rttvar. Convert from the route-table units 2955 * to scaled multiples of the slow timeout timer. 2956 */ 2957 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2958 /* 2959 * XXX the lock bit for RTT indicates that the value 2960 * is also a minimum value; this is subject to time. 2961 */ 2962 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2963 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2964 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2965 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2966 tcpstat.tcps_usedrtt++; 2967 if (rt->rt_rmx.rmx_rttvar) { 2968 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2969 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2970 tcpstat.tcps_usedrttvar++; 2971 } else { 2972 /* default variation is +- 1 rtt */ 2973 tp->t_rttvar = 2974 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2975 } 2976 TCPT_RANGESET(tp->t_rxtcur, 2977 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2978 tp->t_rttmin, TCPTV_REXMTMAX); 2979 } 2980 2981 /* 2982 * if there's an mtu associated with the route, use it 2983 * else, use the link mtu. Take the smaller of mss or offer 2984 * as our final mss. 2985 */ 2986 if (rt->rt_rmx.rmx_mtu) { 2987 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2988 } else { 2989 if (isipv6) 2990 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 2991 else 2992 mss = ifp->if_mtu - min_protoh; 2993 } 2994 mss = min(mss, offer); 2995 2996 /* 2997 * maxopd stores the maximum length of data AND options 2998 * in a segment; maxseg is the amount of data in a normal 2999 * segment. We need to store this value (maxopd) apart 3000 * from maxseg, because now every segment carries options 3001 * and thus we normally have somewhat less data in segments. 3002 */ 3003 tp->t_maxopd = mss; 3004 3005 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3006 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3007 mss -= TCPOLEN_TSTAMP_APPA; 3008 3009 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3010 if (mss > MCLBYTES) 3011 mss &= ~(MCLBYTES-1); 3012 #else 3013 if (mss > MCLBYTES) 3014 mss = mss / MCLBYTES * MCLBYTES; 3015 #endif 3016 /* 3017 * If there's a pipesize, change the socket buffer 3018 * to that size. Make the socket buffers an integral 3019 * number of mss units; if the mss is larger than 3020 * the socket buffer, decrease the mss. 3021 */ 3022 #ifdef RTV_SPIPE 3023 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3024 #endif 3025 bufsize = so->so_snd.ssb_hiwat; 3026 if (bufsize < mss) 3027 mss = bufsize; 3028 else { 3029 bufsize = roundup(bufsize, mss); 3030 if (bufsize > sb_max) 3031 bufsize = sb_max; 3032 if (bufsize > so->so_snd.ssb_hiwat) 3033 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3034 } 3035 tp->t_maxseg = mss; 3036 3037 #ifdef RTV_RPIPE 3038 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3039 #endif 3040 bufsize = so->so_rcv.ssb_hiwat; 3041 if (bufsize > mss) { 3042 bufsize = roundup(bufsize, mss); 3043 if (bufsize > sb_max) 3044 bufsize = sb_max; 3045 if (bufsize > so->so_rcv.ssb_hiwat) { 3046 lwkt_gettoken(&so->so_rcv.ssb_token); 3047 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3048 lwkt_reltoken(&so->so_rcv.ssb_token); 3049 } 3050 } 3051 3052 /* 3053 * Set the slow-start flight size depending on whether this 3054 * is a local network or not. 3055 */ 3056 if (tcp_do_rfc3390) 3057 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 3058 else 3059 tp->snd_cwnd = mss; 3060 3061 if (rt->rt_rmx.rmx_ssthresh) { 3062 /* 3063 * There's some sort of gateway or interface 3064 * buffer limit on the path. Use this to set 3065 * the slow start threshhold, but set the 3066 * threshold to no less than 2*mss. 3067 */ 3068 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3069 tcpstat.tcps_usedssthresh++; 3070 } 3071 } 3072 3073 /* 3074 * Determine the MSS option to send on an outgoing SYN. 3075 */ 3076 int 3077 tcp_mssopt(struct tcpcb *tp) 3078 { 3079 struct rtentry *rt; 3080 #ifdef INET6 3081 boolean_t isipv6 = 3082 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3083 int min_protoh = isipv6 ? 3084 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3085 sizeof(struct tcpiphdr); 3086 #else 3087 const boolean_t isipv6 = FALSE; 3088 const size_t min_protoh = sizeof(struct tcpiphdr); 3089 #endif 3090 3091 if (isipv6) 3092 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3093 else 3094 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3095 if (rt == NULL) 3096 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3097 3098 return (rt->rt_ifp->if_mtu - min_protoh); 3099 } 3100 3101 /* 3102 * When a partial ack arrives, force the retransmission of the 3103 * next unacknowledged segment. Do not exit Fast Recovery. 3104 * 3105 * Implement the Slow-but-Steady variant of NewReno by restarting the 3106 * the retransmission timer. Turn it off here so it can be restarted 3107 * later in tcp_output(). 3108 */ 3109 static void 3110 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3111 { 3112 tcp_seq old_snd_nxt = tp->snd_nxt; 3113 u_long ocwnd = tp->snd_cwnd; 3114 3115 tcp_callout_stop(tp, tp->tt_rexmt); 3116 tp->t_rtttime = 0; 3117 tp->snd_nxt = th->th_ack; 3118 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3119 tp->snd_cwnd = tp->t_maxseg; 3120 tp->t_flags |= TF_ACKNOW; 3121 tcp_output(tp); 3122 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3123 tp->snd_nxt = old_snd_nxt; 3124 /* partial window deflation */ 3125 if (ocwnd > acked) 3126 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3127 else 3128 tp->snd_cwnd = tp->t_maxseg; 3129 } 3130 3131 /* 3132 * In contrast to the Slow-but-Steady NewReno variant, 3133 * we do not reset the retransmission timer for SACK retransmissions, 3134 * except when retransmitting snd_una. 3135 */ 3136 static void 3137 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3138 { 3139 uint32_t pipe, seglen; 3140 tcp_seq nextrexmt; 3141 boolean_t lostdup; 3142 tcp_seq old_snd_nxt = tp->snd_nxt; 3143 u_long ocwnd = tp->snd_cwnd; 3144 int nseg = 0; /* consecutive new segments */ 3145 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3146 3147 tp->t_rtttime = 0; 3148 pipe = tcp_sack_compute_pipe(tp); 3149 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3150 (!tcp_do_smartsack || nseg < MAXBURST) && 3151 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) { 3152 uint32_t sent; 3153 tcp_seq old_snd_max; 3154 int error; 3155 3156 if (nextrexmt == tp->snd_max) 3157 ++nseg; 3158 tp->snd_nxt = nextrexmt; 3159 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3160 old_snd_max = tp->snd_max; 3161 if (nextrexmt == tp->snd_una) 3162 tcp_callout_stop(tp, tp->tt_rexmt); 3163 error = tcp_output(tp); 3164 if (error != 0) 3165 break; 3166 sent = tp->snd_nxt - nextrexmt; 3167 if (sent <= 0) 3168 break; 3169 if (!lostdup) 3170 pipe += sent; 3171 tcpstat.tcps_sndsackpack++; 3172 tcpstat.tcps_sndsackbyte += sent; 3173 if (SEQ_LT(nextrexmt, old_snd_max) && 3174 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) 3175 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3176 } 3177 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3178 tp->snd_nxt = old_snd_nxt; 3179 tp->snd_cwnd = ocwnd; 3180 } 3181 3182 /* 3183 * Reset idle time and keep-alive timer, typically called when a valid 3184 * tcp packet is received but may also be called when FASTKEEP is set 3185 * to prevent the previous long-timeout from calculating to a drop. 3186 * 3187 * Only update t_rcvtime for non-SYN packets. 3188 * 3189 * Handle the case where one side thinks the connection is established 3190 * but the other side has, say, rebooted without cleaning out the 3191 * connection. The SYNs could be construed as an attack and wind 3192 * up ignored, but in case it isn't an attack we can validate the 3193 * connection by forcing a keepalive. 3194 */ 3195 void 3196 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3197 { 3198 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3199 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3200 tp->t_flags |= TF_KEEPALIVE; 3201 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3202 tcp_timer_keep); 3203 } else { 3204 tp->t_rcvtime = ticks; 3205 tp->t_flags &= ~TF_KEEPALIVE; 3206 tcp_callout_reset(tp, tp->tt_keep, 3207 tcp_getkeepidle(tp), 3208 tcp_timer_keep); 3209 } 3210 } 3211 } 3212 3213 static int 3214 tcp_rmx_msl(const struct tcpcb *tp) 3215 { 3216 struct rtentry *rt; 3217 struct inpcb *inp = tp->t_inpcb; 3218 int msl; 3219 #ifdef INET6 3220 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3221 #else 3222 const boolean_t isipv6 = FALSE; 3223 #endif 3224 3225 if (isipv6) 3226 rt = tcp_rtlookup6(&inp->inp_inc); 3227 else 3228 rt = tcp_rtlookup(&inp->inp_inc); 3229 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3230 return tcp_msl; 3231 3232 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3233 if (msl == 0) 3234 msl = 1; 3235 3236 return msl; 3237 } 3238