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_inet.h" 71 #include "opt_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 #include "opt_tcp_input.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/proc.h> /* for proc0 declaration */ 83 #include <sys/protosw.h> 84 #include <sys/socket.h> 85 #include <sys/socketvar.h> 86 #include <sys/syslog.h> 87 #include <sys/in_cksum.h> 88 89 #include <sys/socketvar2.h> 90 91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 92 #include <machine/stdarg.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 101 #include <netinet/in_var.h> 102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 103 #include <netinet/in_pcb.h> 104 #include <netinet/ip_var.h> 105 #include <netinet/ip6.h> 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 #include <netinet/tcpip.h> 118 119 #ifdef TCPDEBUG 120 #include <netinet/tcp_debug.h> 121 122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 123 struct tcphdr tcp_savetcp; 124 #endif 125 126 #ifdef FAST_IPSEC 127 #include <netproto/ipsec/ipsec.h> 128 #include <netproto/ipsec/ipsec6.h> 129 #endif 130 131 #ifdef IPSEC 132 #include <netinet6/ipsec.h> 133 #include <netinet6/ipsec6.h> 134 #include <netproto/key/key.h> 135 #endif 136 137 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 138 139 static int log_in_vain = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 141 &log_in_vain, 0, "Log all incoming TCP connections"); 142 143 static int blackhole = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 145 &blackhole, 0, "Do not send RST when dropping refused connections"); 146 147 int tcp_delack_enabled = 1; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 149 &tcp_delack_enabled, 0, 150 "Delay ACK to try and piggyback it onto a data packet"); 151 152 #ifdef TCP_DROP_SYNFIN 153 static int drop_synfin = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 156 #endif 157 158 static int tcp_do_limitedtransmit = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 161 162 static int tcp_do_early_retransmit = 1; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 164 &tcp_do_early_retransmit, 0, "Early retransmit"); 165 166 int tcp_aggregate_acks = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 169 170 static int tcp_do_eifel_detect = 1; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 172 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 173 174 static int tcp_do_abc = 1; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 176 &tcp_do_abc, 0, 177 "TCP Appropriate Byte Counting (RFC 3465)"); 178 179 /* 180 * Define as tunable for easy testing with SACK on and off. 181 * Warning: do not change setting in the middle of an existing active TCP flow, 182 * else strange things might happen to that flow. 183 */ 184 int tcp_do_sack = 1; 185 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 186 &tcp_do_sack, 0, "Enable SACK Algorithms"); 187 188 int tcp_do_smartsack = 1; 189 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 190 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 191 192 int tcp_do_rescuesack = 1; 193 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, 194 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); 195 196 int tcp_aggressive_rescuesack = 0; 197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, 198 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); 199 200 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 201 "TCP Segment Reassembly Queue"); 202 203 int tcp_reass_maxseg = 0; 204 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 205 &tcp_reass_maxseg, 0, 206 "Global maximum number of TCP Segments in Reassembly Queue"); 207 208 int tcp_reass_qsize = 0; 209 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 210 &tcp_reass_qsize, 0, 211 "Global number of TCP Segments currently in Reassembly Queue"); 212 213 static int tcp_reass_overflows = 0; 214 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 215 &tcp_reass_overflows, 0, 216 "Global number of TCP Segment Reassembly Queue Overflows"); 217 218 int tcp_do_autorcvbuf = 1; 219 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 220 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 221 222 int tcp_autorcvbuf_inc = 16*1024; 223 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 224 &tcp_autorcvbuf_inc, 0, 225 "Incrementor step size of automatic receive buffer"); 226 227 int tcp_autorcvbuf_max = 2*1024*1024; 228 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 229 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 230 231 int tcp_sosend_agglim = 2; 232 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 233 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 234 235 int tcp_sosend_async = 1; 236 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 237 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 238 239 static int tcp_ignore_redun_dsack = 1; 240 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW, 241 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK"); 242 243 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, 244 tcp_seq); 245 static void tcp_pulloutofband(struct socket *, 246 struct tcphdr *, struct mbuf *, int); 247 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 248 struct mbuf *); 249 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); 250 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 251 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); 252 static int tcp_rmx_msl(const struct tcpcb *); 253 static void tcp_established(struct tcpcb *); 254 255 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 256 #ifdef INET6 257 #define ND6_HINT(tp) \ 258 do { \ 259 if ((tp) && (tp)->t_inpcb && \ 260 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 261 (tp)->t_inpcb->in6p_route.ro_rt) \ 262 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 263 } while (0) 264 #else 265 #define ND6_HINT(tp) 266 #endif 267 268 /* 269 * Indicate whether this ack should be delayed. We can delay the ack if 270 * - delayed acks are enabled and 271 * - there is no delayed ack timer in progress and 272 * - our last ack wasn't a 0-sized window. We never want to delay 273 * the ack that opens up a 0-sized window. 274 */ 275 #define DELAY_ACK(tp) \ 276 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 277 !(tp->t_flags & TF_RXWIN0SENT)) 278 279 #define acceptable_window_update(tp, th, tiwin) \ 280 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 281 (tp->snd_wl1 == th->th_seq && \ 282 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 283 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 284 285 static int 286 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 287 { 288 struct tseg_qent *q; 289 struct tseg_qent *p = NULL; 290 struct tseg_qent *te; 291 struct socket *so = tp->t_inpcb->inp_socket; 292 int flags; 293 294 /* 295 * Call with th == NULL after become established to 296 * force pre-ESTABLISHED data up to user socket. 297 */ 298 if (th == NULL) 299 goto present; 300 301 /* 302 * Limit the number of segments in the reassembly queue to prevent 303 * holding on to too many segments (and thus running out of mbufs). 304 * Make sure to let the missing segment through which caused this 305 * queue. Always keep one global queue entry spare to be able to 306 * process the missing segment. 307 */ 308 if (th->th_seq != tp->rcv_nxt && 309 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 310 tcp_reass_overflows++; 311 tcpstat.tcps_rcvmemdrop++; 312 m_freem(m); 313 /* no SACK block to report */ 314 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 315 return (0); 316 } 317 318 /* Allocate a new queue entry. */ 319 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 320 if (te == NULL) { 321 tcpstat.tcps_rcvmemdrop++; 322 m_freem(m); 323 /* no SACK block to report */ 324 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 325 return (0); 326 } 327 atomic_add_int(&tcp_reass_qsize, 1); 328 329 /* 330 * Find a segment which begins after this one does. 331 */ 332 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 333 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 334 break; 335 p = q; 336 } 337 338 /* 339 * If there is a preceding segment, it may provide some of 340 * our data already. If so, drop the data from the incoming 341 * segment. If it provides all of our data, drop us. 342 */ 343 if (p != NULL) { 344 tcp_seq_diff_t i; 345 346 /* conversion to int (in i) handles seq wraparound */ 347 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 348 if (i > 0) { /* overlaps preceding segment */ 349 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 350 /* enclosing block starts w/ preceding segment */ 351 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 352 if (i >= *tlenp) { 353 /* preceding encloses incoming segment */ 354 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 355 p->tqe_th->th_seq + p->tqe_len, 356 p->tqe_th->th_flags); 357 tcpstat.tcps_rcvduppack++; 358 tcpstat.tcps_rcvdupbyte += *tlenp; 359 m_freem(m); 360 kfree(te, M_TSEGQ); 361 atomic_add_int(&tcp_reass_qsize, -1); 362 /* 363 * Try to present any queued data 364 * at the left window edge to the user. 365 * This is needed after the 3-WHS 366 * completes. 367 */ 368 goto present; /* ??? */ 369 } 370 m_adj(m, i); 371 *tlenp -= i; 372 th->th_seq += i; 373 /* incoming segment end is enclosing block end */ 374 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 375 th->th_seq + *tlenp, th->th_flags); 376 /* trim end of reported D-SACK block */ 377 tp->reportblk.rblk_end = th->th_seq; 378 } 379 } 380 tcpstat.tcps_rcvoopack++; 381 tcpstat.tcps_rcvoobyte += *tlenp; 382 383 /* 384 * While we overlap succeeding segments trim them or, 385 * if they are completely covered, dequeue them. 386 */ 387 while (q) { 388 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 389 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 390 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 391 struct tseg_qent *nq; 392 393 if (i <= 0) 394 break; 395 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */ 396 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG); 397 tp->encloseblk = tp->reportblk; 398 /* report trailing duplicate D-SACK segment */ 399 tp->reportblk.rblk_start = q->tqe_th->th_seq; 400 } 401 if ((tp->t_flags & TF_ENCLOSESEG) && 402 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 403 /* extend enclosing block if one exists */ 404 tp->encloseblk.rblk_end = qend_sack; 405 } 406 if (i < q->tqe_len) { 407 q->tqe_th->th_seq += i; 408 q->tqe_len -= i; 409 m_adj(q->tqe_m, i); 410 break; 411 } 412 413 nq = LIST_NEXT(q, tqe_q); 414 LIST_REMOVE(q, tqe_q); 415 m_freem(q->tqe_m); 416 kfree(q, M_TSEGQ); 417 atomic_add_int(&tcp_reass_qsize, -1); 418 q = nq; 419 } 420 421 /* Insert the new segment queue entry into place. */ 422 te->tqe_m = m; 423 te->tqe_th = th; 424 te->tqe_len = *tlenp; 425 426 /* check if can coalesce with following segment */ 427 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 428 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; 429 tcp_seq tend_sack = TCP_SACK_BLKEND(tend, te->tqe_th->th_flags); 430 431 te->tqe_len += q->tqe_len; 432 if (q->tqe_th->th_flags & TH_FIN) 433 te->tqe_th->th_flags |= TH_FIN; 434 m_cat(te->tqe_m, q->tqe_m); 435 tp->encloseblk.rblk_end = tend_sack; 436 /* 437 * When not reporting a duplicate segment, use 438 * the larger enclosing block as the SACK block. 439 */ 440 if (!(tp->t_flags & TF_DUPSEG)) 441 tp->reportblk.rblk_end = tend_sack; 442 LIST_REMOVE(q, tqe_q); 443 kfree(q, M_TSEGQ); 444 atomic_add_int(&tcp_reass_qsize, -1); 445 } 446 447 if (p == NULL) { 448 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 449 } else { 450 /* check if can coalesce with preceding segment */ 451 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 452 p->tqe_len += te->tqe_len; 453 m_cat(p->tqe_m, te->tqe_m); 454 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 455 /* 456 * When not reporting a duplicate segment, use 457 * the larger enclosing block as the SACK block. 458 */ 459 if (!(tp->t_flags & TF_DUPSEG)) 460 tp->reportblk.rblk_start = p->tqe_th->th_seq; 461 kfree(te, M_TSEGQ); 462 atomic_add_int(&tcp_reass_qsize, -1); 463 } else { 464 LIST_INSERT_AFTER(p, te, tqe_q); 465 } 466 } 467 468 present: 469 /* 470 * Present data to user, advancing rcv_nxt through 471 * completed sequence space. 472 */ 473 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 474 return (0); 475 q = LIST_FIRST(&tp->t_segq); 476 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 477 return (0); 478 tp->rcv_nxt += q->tqe_len; 479 if (!(tp->t_flags & TF_DUPSEG)) { 480 /* no SACK block to report since ACK advanced */ 481 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 482 } 483 /* no enclosing block to report since ACK advanced */ 484 tp->t_flags &= ~TF_ENCLOSESEG; 485 flags = q->tqe_th->th_flags & TH_FIN; 486 LIST_REMOVE(q, tqe_q); 487 KASSERT(LIST_EMPTY(&tp->t_segq) || 488 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 489 ("segment not coalesced")); 490 if (so->so_state & SS_CANTRCVMORE) { 491 m_freem(q->tqe_m); 492 } else { 493 lwkt_gettoken(&so->so_rcv.ssb_token); 494 ssb_appendstream(&so->so_rcv, q->tqe_m); 495 lwkt_reltoken(&so->so_rcv.ssb_token); 496 } 497 kfree(q, M_TSEGQ); 498 atomic_add_int(&tcp_reass_qsize, -1); 499 ND6_HINT(tp); 500 sorwakeup(so); 501 return (flags); 502 } 503 504 /* 505 * TCP input routine, follows pages 65-76 of the 506 * protocol specification dated September, 1981 very closely. 507 */ 508 #ifdef INET6 509 int 510 tcp6_input(struct mbuf **mp, int *offp, int proto) 511 { 512 struct mbuf *m = *mp; 513 struct in6_ifaddr *ia6; 514 515 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 516 517 /* 518 * draft-itojun-ipv6-tcp-to-anycast 519 * better place to put this in? 520 */ 521 ia6 = ip6_getdstifaddr(m); 522 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 523 struct ip6_hdr *ip6; 524 525 ip6 = mtod(m, struct ip6_hdr *); 526 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 527 offsetof(struct ip6_hdr, ip6_dst)); 528 return (IPPROTO_DONE); 529 } 530 531 tcp_input(mp, offp, proto); 532 return (IPPROTO_DONE); 533 } 534 #endif 535 536 int 537 tcp_input(struct mbuf **mp, int *offp, int proto) 538 { 539 int off0; 540 struct tcphdr *th; 541 struct ip *ip = NULL; 542 struct ipovly *ipov; 543 struct inpcb *inp = NULL; 544 u_char *optp = NULL; 545 int optlen = 0; 546 int tlen, off; 547 int len = 0; 548 int drop_hdrlen; 549 struct tcpcb *tp = NULL; 550 int thflags; 551 struct socket *so = NULL; 552 int todrop, acked; 553 boolean_t ourfinisacked, needoutput = FALSE; 554 u_long tiwin; 555 int recvwin; 556 struct tcpopt to; /* options in this segment */ 557 struct sockaddr_in *next_hop = NULL; 558 int rstreason; /* For badport_bandlim accounting purposes */ 559 int cpu; 560 struct ip6_hdr *ip6 = NULL; 561 struct mbuf *m; 562 #ifdef INET6 563 boolean_t isipv6; 564 #else 565 const boolean_t isipv6 = FALSE; 566 #endif 567 #ifdef TCPDEBUG 568 short ostate = 0; 569 #endif 570 571 off0 = *offp; 572 m = *mp; 573 *mp = NULL; 574 575 tcpstat.tcps_rcvtotal++; 576 577 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 578 struct m_tag *mtag; 579 580 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 581 KKASSERT(mtag != NULL); 582 next_hop = m_tag_data(mtag); 583 } 584 585 #ifdef INET6 586 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 587 #endif 588 589 if (isipv6) { 590 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 591 ip6 = mtod(m, struct ip6_hdr *); 592 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 593 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 594 tcpstat.tcps_rcvbadsum++; 595 goto drop; 596 } 597 th = (struct tcphdr *)((caddr_t)ip6 + off0); 598 599 /* 600 * Be proactive about unspecified IPv6 address in source. 601 * As we use all-zero to indicate unbounded/unconnected pcb, 602 * unspecified IPv6 address can be used to confuse us. 603 * 604 * Note that packets with unspecified IPv6 destination is 605 * already dropped in ip6_input. 606 */ 607 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 608 /* XXX stat */ 609 goto drop; 610 } 611 } else { 612 /* 613 * Get IP and TCP header together in first mbuf. 614 * Note: IP leaves IP header in first mbuf. 615 */ 616 if (off0 > sizeof(struct ip)) { 617 ip_stripoptions(m); 618 off0 = sizeof(struct ip); 619 } 620 /* already checked and pulled up in ip_demux() */ 621 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 622 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 623 ip = mtod(m, struct ip *); 624 ipov = (struct ipovly *)ip; 625 th = (struct tcphdr *)((caddr_t)ip + off0); 626 tlen = ip->ip_len; 627 628 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 629 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 630 th->th_sum = m->m_pkthdr.csum_data; 631 else 632 th->th_sum = in_pseudo(ip->ip_src.s_addr, 633 ip->ip_dst.s_addr, 634 htonl(m->m_pkthdr.csum_data + 635 ip->ip_len + 636 IPPROTO_TCP)); 637 th->th_sum ^= 0xffff; 638 } else { 639 /* 640 * Checksum extended TCP header and data. 641 */ 642 len = sizeof(struct ip) + tlen; 643 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 644 ipov->ih_len = (u_short)tlen; 645 ipov->ih_len = htons(ipov->ih_len); 646 th->th_sum = in_cksum(m, len); 647 } 648 if (th->th_sum) { 649 tcpstat.tcps_rcvbadsum++; 650 goto drop; 651 } 652 #ifdef INET6 653 /* Re-initialization for later version check */ 654 ip->ip_v = IPVERSION; 655 #endif 656 } 657 658 /* 659 * Check that TCP offset makes sense, 660 * pull out TCP options and adjust length. XXX 661 */ 662 off = th->th_off << 2; 663 /* already checked and pulled up in ip_demux() */ 664 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 665 ("bad TCP data offset %d (tlen %d)", off, tlen)); 666 tlen -= off; /* tlen is used instead of ti->ti_len */ 667 if (off > sizeof(struct tcphdr)) { 668 if (isipv6) { 669 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 670 ip6 = mtod(m, struct ip6_hdr *); 671 th = (struct tcphdr *)((caddr_t)ip6 + off0); 672 } else { 673 /* already pulled up in ip_demux() */ 674 KASSERT(m->m_len >= sizeof(struct ip) + off, 675 ("TCP header and options not in one mbuf: " 676 "m_len %d, off %d", m->m_len, off)); 677 } 678 optlen = off - sizeof(struct tcphdr); 679 optp = (u_char *)(th + 1); 680 } 681 thflags = th->th_flags; 682 683 #ifdef TCP_DROP_SYNFIN 684 /* 685 * If the drop_synfin option is enabled, drop all packets with 686 * both the SYN and FIN bits set. This prevents e.g. nmap from 687 * identifying the TCP/IP stack. 688 * 689 * This is a violation of the TCP specification. 690 */ 691 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 692 goto drop; 693 #endif 694 695 /* 696 * Convert TCP protocol specific fields to host format. 697 */ 698 th->th_seq = ntohl(th->th_seq); 699 th->th_ack = ntohl(th->th_ack); 700 th->th_win = ntohs(th->th_win); 701 th->th_urp = ntohs(th->th_urp); 702 703 /* 704 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 705 * until after ip6_savecontrol() is called and before other functions 706 * which don't want those proto headers. 707 * Because ip6_savecontrol() is going to parse the mbuf to 708 * search for data to be passed up to user-land, it wants mbuf 709 * parameters to be unchanged. 710 * XXX: the call of ip6_savecontrol() has been obsoleted based on 711 * latest version of the advanced API (20020110). 712 */ 713 drop_hdrlen = off0 + off; 714 715 /* 716 * Locate pcb for segment. 717 */ 718 findpcb: 719 /* IPFIREWALL_FORWARD section */ 720 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 721 /* 722 * Transparently forwarded. Pretend to be the destination. 723 * already got one like this? 724 */ 725 cpu = mycpu->gd_cpuid; 726 inp = in_pcblookup_hash(&tcbinfo[cpu], 727 ip->ip_src, th->th_sport, 728 ip->ip_dst, th->th_dport, 729 0, m->m_pkthdr.rcvif); 730 if (!inp) { 731 /* 732 * It's new. Try to find the ambushing socket. 733 */ 734 735 /* 736 * The rest of the ipfw code stores the port in 737 * host order. XXX 738 * (The IP address is still in network order.) 739 */ 740 in_port_t dport = next_hop->sin_port ? 741 htons(next_hop->sin_port) : 742 th->th_dport; 743 744 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 745 next_hop->sin_addr.s_addr, dport); 746 inp = in_pcblookup_hash(&tcbinfo[cpu], 747 ip->ip_src, th->th_sport, 748 next_hop->sin_addr, dport, 749 1, m->m_pkthdr.rcvif); 750 } 751 } else { 752 if (isipv6) { 753 inp = in6_pcblookup_hash(&tcbinfo[0], 754 &ip6->ip6_src, th->th_sport, 755 &ip6->ip6_dst, th->th_dport, 756 1, m->m_pkthdr.rcvif); 757 } else { 758 cpu = mycpu->gd_cpuid; 759 inp = in_pcblookup_hash(&tcbinfo[cpu], 760 ip->ip_src, th->th_sport, 761 ip->ip_dst, th->th_dport, 762 1, m->m_pkthdr.rcvif); 763 } 764 } 765 766 /* 767 * If the state is CLOSED (i.e., TCB does not exist) then 768 * all data in the incoming segment is discarded. 769 * If the TCB exists but is in CLOSED state, it is embryonic, 770 * but should either do a listen or a connect soon. 771 */ 772 if (inp == NULL) { 773 if (log_in_vain) { 774 #ifdef INET6 775 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 776 #else 777 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 778 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 779 #endif 780 if (isipv6) { 781 strcpy(dbuf, "["); 782 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 783 strcat(dbuf, "]"); 784 strcpy(sbuf, "["); 785 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 786 strcat(sbuf, "]"); 787 } else { 788 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 789 strcpy(sbuf, inet_ntoa(ip->ip_src)); 790 } 791 switch (log_in_vain) { 792 case 1: 793 if (!(thflags & TH_SYN)) 794 break; 795 case 2: 796 log(LOG_INFO, 797 "Connection attempt to TCP %s:%d " 798 "from %s:%d flags:0x%02x\n", 799 dbuf, ntohs(th->th_dport), sbuf, 800 ntohs(th->th_sport), thflags); 801 break; 802 default: 803 break; 804 } 805 } 806 if (blackhole) { 807 switch (blackhole) { 808 case 1: 809 if (thflags & TH_SYN) 810 goto drop; 811 break; 812 case 2: 813 goto drop; 814 default: 815 goto drop; 816 } 817 } 818 rstreason = BANDLIM_RST_CLOSEDPORT; 819 goto dropwithreset; 820 } 821 822 #ifdef IPSEC 823 if (isipv6) { 824 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 825 ipsec6stat.in_polvio++; 826 goto drop; 827 } 828 } else { 829 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 830 ipsecstat.in_polvio++; 831 goto drop; 832 } 833 } 834 #endif 835 #ifdef FAST_IPSEC 836 if (isipv6) { 837 if (ipsec6_in_reject(m, inp)) 838 goto drop; 839 } else { 840 if (ipsec4_in_reject(m, inp)) 841 goto drop; 842 } 843 #endif 844 /* Check the minimum TTL for socket. */ 845 #ifdef INET6 846 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 847 goto drop; 848 #endif 849 850 tp = intotcpcb(inp); 851 if (tp == NULL) { 852 rstreason = BANDLIM_RST_CLOSEDPORT; 853 goto dropwithreset; 854 } 855 if (tp->t_state <= TCPS_CLOSED) 856 goto drop; 857 858 so = inp->inp_socket; 859 860 #ifdef TCPDEBUG 861 if (so->so_options & SO_DEBUG) { 862 ostate = tp->t_state; 863 if (isipv6) 864 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 865 else 866 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 867 tcp_savetcp = *th; 868 } 869 #endif 870 871 bzero(&to, sizeof to); 872 873 if (so->so_options & SO_ACCEPTCONN) { 874 struct in_conninfo inc; 875 876 #ifdef INET6 877 inc.inc_isipv6 = (isipv6 == TRUE); 878 #endif 879 if (isipv6) { 880 inc.inc6_faddr = ip6->ip6_src; 881 inc.inc6_laddr = ip6->ip6_dst; 882 inc.inc6_route.ro_rt = NULL; /* XXX */ 883 } else { 884 inc.inc_faddr = ip->ip_src; 885 inc.inc_laddr = ip->ip_dst; 886 inc.inc_route.ro_rt = NULL; /* XXX */ 887 } 888 inc.inc_fport = th->th_sport; 889 inc.inc_lport = th->th_dport; 890 891 /* 892 * If the state is LISTEN then ignore segment if it contains 893 * a RST. If the segment contains an ACK then it is bad and 894 * send a RST. If it does not contain a SYN then it is not 895 * interesting; drop it. 896 * 897 * If the state is SYN_RECEIVED (syncache) and seg contains 898 * an ACK, but not for our SYN/ACK, send a RST. If the seg 899 * contains a RST, check the sequence number to see if it 900 * is a valid reset segment. 901 */ 902 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 903 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 904 if (!syncache_expand(&inc, th, &so, m)) { 905 /* 906 * No syncache entry, or ACK was not 907 * for our SYN/ACK. Send a RST. 908 */ 909 tcpstat.tcps_badsyn++; 910 rstreason = BANDLIM_RST_OPENPORT; 911 goto dropwithreset; 912 } 913 914 /* 915 * Could not complete 3-way handshake, 916 * connection is being closed down, and 917 * syncache will free mbuf. 918 */ 919 if (so == NULL) 920 return(IPPROTO_DONE); 921 922 /* 923 * We must be in the correct protocol thread 924 * for this connection. 925 */ 926 KKASSERT(so->so_port == &curthread->td_msgport); 927 928 /* 929 * Socket is created in state SYN_RECEIVED. 930 * Continue processing segment. 931 */ 932 inp = so->so_pcb; 933 tp = intotcpcb(inp); 934 /* 935 * This is what would have happened in 936 * tcp_output() when the SYN,ACK was sent. 937 */ 938 tp->snd_up = tp->snd_una; 939 tp->snd_max = tp->snd_nxt = tp->iss + 1; 940 tp->last_ack_sent = tp->rcv_nxt; 941 942 goto after_listen; 943 } 944 if (thflags & TH_RST) { 945 syncache_chkrst(&inc, th); 946 goto drop; 947 } 948 if (thflags & TH_ACK) { 949 syncache_badack(&inc); 950 tcpstat.tcps_badsyn++; 951 rstreason = BANDLIM_RST_OPENPORT; 952 goto dropwithreset; 953 } 954 goto drop; 955 } 956 957 /* 958 * Segment's flags are (SYN) or (SYN | FIN). 959 */ 960 #ifdef INET6 961 /* 962 * If deprecated address is forbidden, 963 * we do not accept SYN to deprecated interface 964 * address to prevent any new inbound connection from 965 * getting established. 966 * When we do not accept SYN, we send a TCP RST, 967 * with deprecated source address (instead of dropping 968 * it). We compromise it as it is much better for peer 969 * to send a RST, and RST will be the final packet 970 * for the exchange. 971 * 972 * If we do not forbid deprecated addresses, we accept 973 * the SYN packet. RFC2462 does not suggest dropping 974 * SYN in this case. 975 * If we decipher RFC2462 5.5.4, it says like this: 976 * 1. use of deprecated addr with existing 977 * communication is okay - "SHOULD continue to be 978 * used" 979 * 2. use of it with new communication: 980 * (2a) "SHOULD NOT be used if alternate address 981 * with sufficient scope is available" 982 * (2b) nothing mentioned otherwise. 983 * Here we fall into (2b) case as we have no choice in 984 * our source address selection - we must obey the peer. 985 * 986 * The wording in RFC2462 is confusing, and there are 987 * multiple description text for deprecated address 988 * handling - worse, they are not exactly the same. 989 * I believe 5.5.4 is the best one, so we follow 5.5.4. 990 */ 991 if (isipv6 && !ip6_use_deprecated) { 992 struct in6_ifaddr *ia6; 993 994 if ((ia6 = ip6_getdstifaddr(m)) && 995 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 996 tp = NULL; 997 rstreason = BANDLIM_RST_OPENPORT; 998 goto dropwithreset; 999 } 1000 } 1001 #endif 1002 /* 1003 * If it is from this socket, drop it, it must be forged. 1004 * Don't bother responding if the destination was a broadcast. 1005 */ 1006 if (th->th_dport == th->th_sport) { 1007 if (isipv6) { 1008 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1009 &ip6->ip6_src)) 1010 goto drop; 1011 } else { 1012 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1013 goto drop; 1014 } 1015 } 1016 /* 1017 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1018 * 1019 * Note that it is quite possible to receive unicast 1020 * link-layer packets with a broadcast IP address. Use 1021 * in_broadcast() to find them. 1022 */ 1023 if (m->m_flags & (M_BCAST | M_MCAST)) 1024 goto drop; 1025 if (isipv6) { 1026 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1027 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1028 goto drop; 1029 } else { 1030 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1031 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1032 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1033 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1034 goto drop; 1035 } 1036 /* 1037 * SYN appears to be valid; create compressed TCP state 1038 * for syncache, or perform t/tcp connection. 1039 */ 1040 if (so->so_qlen <= so->so_qlimit) { 1041 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); 1042 if (!syncache_add(&inc, &to, th, so, m)) 1043 goto drop; 1044 1045 /* 1046 * Entry added to syncache, mbuf used to 1047 * send SYN,ACK packet. 1048 */ 1049 return(IPPROTO_DONE); 1050 } 1051 goto drop; 1052 } 1053 1054 after_listen: 1055 /* 1056 * Should not happen - syncache should pick up these connections. 1057 * 1058 * Once we are past handling listen sockets we must be in the 1059 * correct protocol processing thread. 1060 */ 1061 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1062 KKASSERT(so->so_port == &curthread->td_msgport); 1063 1064 /* Unscale the window into a 32-bit value. */ 1065 if (!(thflags & TH_SYN)) 1066 tiwin = th->th_win << tp->snd_scale; 1067 else 1068 tiwin = th->th_win; 1069 1070 /* 1071 * This is the second part of the MSS DoS prevention code (after 1072 * minmss on the sending side) and it deals with too many too small 1073 * tcp packets in a too short timeframe (1 second). 1074 * 1075 * XXX Removed. This code was crap. It does not scale to network 1076 * speed, and default values break NFS. Gone. 1077 */ 1078 /* REMOVED */ 1079 1080 /* 1081 * Segment received on connection. 1082 * 1083 * Reset idle time and keep-alive timer. Don't waste time if less 1084 * then a second has elapsed. 1085 */ 1086 if ((int)(ticks - tp->t_rcvtime) > hz) 1087 tcp_timer_keep_activity(tp, thflags); 1088 1089 /* 1090 * Process options. 1091 * XXX this is tradtitional behavior, may need to be cleaned up. 1092 */ 1093 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); 1094 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1095 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { 1096 tp->t_flags |= TF_RCVD_SCALE; 1097 tp->snd_scale = to.to_requested_s_scale; 1098 } 1099 1100 /* 1101 * Initial send window; will be updated upon next ACK 1102 */ 1103 tp->snd_wnd = th->th_win; 1104 1105 if (to.to_flags & TOF_TS) { 1106 tp->t_flags |= TF_RCVD_TSTMP; 1107 tp->ts_recent = to.to_tsval; 1108 tp->ts_recent_age = ticks; 1109 } 1110 if (!(to.to_flags & TOF_MSS)) 1111 to.to_mss = 0; 1112 tcp_mss(tp, to.to_mss); 1113 /* 1114 * Only set the TF_SACK_PERMITTED per-connection flag 1115 * if we got a SACK_PERMITTED option from the other side 1116 * and the global tcp_do_sack variable is true. 1117 */ 1118 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1119 tp->t_flags |= TF_SACK_PERMITTED; 1120 } 1121 1122 /* 1123 * Header prediction: check for the two common cases 1124 * of a uni-directional data xfer. If the packet has 1125 * no control flags, is in-sequence, the window didn't 1126 * change and we're not retransmitting, it's a 1127 * candidate. If the length is zero and the ack moved 1128 * forward, we're the sender side of the xfer. Just 1129 * free the data acked & wake any higher level process 1130 * that was blocked waiting for space. If the length 1131 * is non-zero and the ack didn't move, we're the 1132 * receiver side. If we're getting packets in-order 1133 * (the reassembly queue is empty), add the data to 1134 * the socket buffer and note that we need a delayed ack. 1135 * Make sure that the hidden state-flags are also off. 1136 * Since we check for TCPS_ESTABLISHED above, it can only 1137 * be TH_NEEDSYN. 1138 */ 1139 if (tp->t_state == TCPS_ESTABLISHED && 1140 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1141 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1142 (!(to.to_flags & TOF_TS) || 1143 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1144 th->th_seq == tp->rcv_nxt && 1145 tp->snd_nxt == tp->snd_max) { 1146 1147 /* 1148 * If last ACK falls within this segment's sequence numbers, 1149 * record the timestamp. 1150 * NOTE that the test is modified according to the latest 1151 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1152 */ 1153 if ((to.to_flags & TOF_TS) && 1154 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1155 tp->ts_recent_age = ticks; 1156 tp->ts_recent = to.to_tsval; 1157 } 1158 1159 if (tlen == 0) { 1160 if (SEQ_GT(th->th_ack, tp->snd_una) && 1161 SEQ_LEQ(th->th_ack, tp->snd_max) && 1162 tp->snd_cwnd >= tp->snd_wnd && 1163 !IN_FASTRECOVERY(tp)) { 1164 /* 1165 * This is a pure ack for outstanding data. 1166 */ 1167 ++tcpstat.tcps_predack; 1168 /* 1169 * "bad retransmit" recovery 1170 * 1171 * If Eifel detection applies, then 1172 * it is deterministic, so use it 1173 * unconditionally over the old heuristic. 1174 * Otherwise, fall back to the old heuristic. 1175 */ 1176 if (tcp_do_eifel_detect && 1177 (to.to_flags & TOF_TS) && to.to_tsecr && 1178 (tp->t_flags & TF_FIRSTACCACK)) { 1179 /* Eifel detection applicable. */ 1180 if (to.to_tsecr < tp->t_rexmtTS) { 1181 tcp_revert_congestion_state(tp); 1182 ++tcpstat.tcps_eifeldetected; 1183 if (tp->t_rxtshift != 1 || 1184 ticks >= tp->t_badrxtwin) 1185 ++tcpstat.tcps_rttcantdetect; 1186 } 1187 } else if (tp->t_rxtshift == 1 && 1188 ticks < tp->t_badrxtwin) { 1189 tcp_revert_congestion_state(tp); 1190 ++tcpstat.tcps_rttdetected; 1191 } 1192 tp->t_flags &= ~(TF_FIRSTACCACK | 1193 TF_FASTREXMT | TF_EARLYREXMT); 1194 /* 1195 * Recalculate the retransmit timer / rtt. 1196 * 1197 * Some machines (certain windows boxes) 1198 * send broken timestamp replies during the 1199 * SYN+ACK phase, ignore timestamps of 0. 1200 */ 1201 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1202 tcp_xmit_timer(tp, 1203 ticks - to.to_tsecr + 1, 1204 th->th_ack); 1205 } else if (tp->t_rtttime && 1206 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1207 tcp_xmit_timer(tp, 1208 ticks - tp->t_rtttime, 1209 th->th_ack); 1210 } 1211 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1212 acked = th->th_ack - tp->snd_una; 1213 tcpstat.tcps_rcvackpack++; 1214 tcpstat.tcps_rcvackbyte += acked; 1215 sbdrop(&so->so_snd.sb, acked); 1216 tp->snd_recover = th->th_ack - 1; 1217 tp->snd_una = th->th_ack; 1218 tp->t_dupacks = 0; 1219 /* 1220 * Update window information. 1221 */ 1222 if (tiwin != tp->snd_wnd && 1223 acceptable_window_update(tp, th, tiwin)) { 1224 /* keep track of pure window updates */ 1225 if (tp->snd_wl2 == th->th_ack && 1226 tiwin > tp->snd_wnd) 1227 tcpstat.tcps_rcvwinupd++; 1228 tp->snd_wnd = tiwin; 1229 tp->snd_wl1 = th->th_seq; 1230 tp->snd_wl2 = th->th_ack; 1231 if (tp->snd_wnd > tp->max_sndwnd) 1232 tp->max_sndwnd = tp->snd_wnd; 1233 } 1234 m_freem(m); 1235 ND6_HINT(tp); /* some progress has been done */ 1236 /* 1237 * If all outstanding data are acked, stop 1238 * retransmit timer, otherwise restart timer 1239 * using current (possibly backed-off) value. 1240 * If process is waiting for space, 1241 * wakeup/selwakeup/signal. If data 1242 * are ready to send, let tcp_output 1243 * decide between more output or persist. 1244 */ 1245 if (tp->snd_una == tp->snd_max) { 1246 tcp_callout_stop(tp, tp->tt_rexmt); 1247 } else if (!tcp_callout_active(tp, 1248 tp->tt_persist)) { 1249 tcp_callout_reset(tp, tp->tt_rexmt, 1250 tp->t_rxtcur, tcp_timer_rexmt); 1251 } 1252 sowwakeup(so); 1253 if (so->so_snd.ssb_cc > 0) 1254 tcp_output(tp); 1255 return(IPPROTO_DONE); 1256 } 1257 } else if (tiwin == tp->snd_wnd && 1258 th->th_ack == tp->snd_una && 1259 LIST_EMPTY(&tp->t_segq) && 1260 tlen <= ssb_space(&so->so_rcv)) { 1261 u_long newsize = 0; /* automatic sockbuf scaling */ 1262 /* 1263 * This is a pure, in-sequence data packet 1264 * with nothing on the reassembly queue and 1265 * we have enough buffer space to take it. 1266 */ 1267 ++tcpstat.tcps_preddat; 1268 tp->rcv_nxt += tlen; 1269 tcpstat.tcps_rcvpack++; 1270 tcpstat.tcps_rcvbyte += tlen; 1271 ND6_HINT(tp); /* some progress has been done */ 1272 /* 1273 * Automatic sizing of receive socket buffer. Often the send 1274 * buffer size is not optimally adjusted to the actual network 1275 * conditions at hand (delay bandwidth product). Setting the 1276 * buffer size too small limits throughput on links with high 1277 * bandwidth and high delay (eg. trans-continental/oceanic links). 1278 * 1279 * On the receive side the socket buffer memory is only rarely 1280 * used to any significant extent. This allows us to be much 1281 * more aggressive in scaling the receive socket buffer. For 1282 * the case that the buffer space is actually used to a large 1283 * extent and we run out of kernel memory we can simply drop 1284 * the new segments; TCP on the sender will just retransmit it 1285 * later. Setting the buffer size too big may only consume too 1286 * much kernel memory if the application doesn't read() from 1287 * the socket or packet loss or reordering makes use of the 1288 * reassembly queue. 1289 * 1290 * The criteria to step up the receive buffer one notch are: 1291 * 1. the number of bytes received during the time it takes 1292 * one timestamp to be reflected back to us (the RTT); 1293 * 2. received bytes per RTT is within seven eighth of the 1294 * current socket buffer size; 1295 * 3. receive buffer size has not hit maximal automatic size; 1296 * 1297 * This algorithm does one step per RTT at most and only if 1298 * we receive a bulk stream w/o packet losses or reorderings. 1299 * Shrinking the buffer during idle times is not necessary as 1300 * it doesn't consume any memory when idle. 1301 * 1302 * TODO: Only step up if the application is actually serving 1303 * the buffer to better manage the socket buffer resources. 1304 */ 1305 if (tcp_do_autorcvbuf && 1306 to.to_tsecr && 1307 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1308 if (to.to_tsecr > tp->rfbuf_ts && 1309 to.to_tsecr - tp->rfbuf_ts < hz) { 1310 if (tp->rfbuf_cnt > 1311 (so->so_rcv.ssb_hiwat / 8 * 7) && 1312 so->so_rcv.ssb_hiwat < 1313 tcp_autorcvbuf_max) { 1314 newsize = 1315 ulmin(so->so_rcv.ssb_hiwat + 1316 tcp_autorcvbuf_inc, 1317 tcp_autorcvbuf_max); 1318 } 1319 /* Start over with next RTT. */ 1320 tp->rfbuf_ts = 0; 1321 tp->rfbuf_cnt = 0; 1322 } else 1323 tp->rfbuf_cnt += tlen; /* add up */ 1324 } 1325 /* 1326 * Add data to socket buffer. 1327 */ 1328 if (so->so_state & SS_CANTRCVMORE) { 1329 m_freem(m); 1330 } else { 1331 /* 1332 * Set new socket buffer size, give up when 1333 * limit is reached. 1334 * 1335 * Adjusting the size can mess up ACK 1336 * sequencing when pure window updates are 1337 * being avoided (which is the default), 1338 * so force an ack. 1339 */ 1340 lwkt_gettoken(&so->so_rcv.ssb_token); 1341 if (newsize) { 1342 tp->t_flags |= TF_RXRESIZED; 1343 if (!ssb_reserve(&so->so_rcv, newsize, 1344 so, NULL)) { 1345 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1346 } 1347 if (newsize >= 1348 (TCP_MAXWIN << tp->rcv_scale)) { 1349 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1350 } 1351 } 1352 m_adj(m, drop_hdrlen); /* delayed header drop */ 1353 ssb_appendstream(&so->so_rcv, m); 1354 lwkt_reltoken(&so->so_rcv.ssb_token); 1355 } 1356 sorwakeup(so); 1357 /* 1358 * This code is responsible for most of the ACKs 1359 * the TCP stack sends back after receiving a data 1360 * packet. Note that the DELAY_ACK check fails if 1361 * the delack timer is already running, which results 1362 * in an ack being sent every other packet (which is 1363 * what we want). 1364 * 1365 * We then further aggregate acks by not actually 1366 * sending one until the protocol thread has completed 1367 * processing the current backlog of packets. This 1368 * does not delay the ack any further, but allows us 1369 * to take advantage of the packet aggregation that 1370 * high speed NICs do (usually blocks of 8-10 packets) 1371 * to send a single ack rather then four or five acks, 1372 * greatly reducing the ack rate, the return channel 1373 * bandwidth, and the protocol overhead on both ends. 1374 * 1375 * Since this also has the effect of slowing down 1376 * the exponential slow-start ramp-up, systems with 1377 * very large bandwidth-delay products might want 1378 * to turn the feature off. 1379 */ 1380 if (DELAY_ACK(tp)) { 1381 tcp_callout_reset(tp, tp->tt_delack, 1382 tcp_delacktime, tcp_timer_delack); 1383 } else if (tcp_aggregate_acks) { 1384 tp->t_flags |= TF_ACKNOW; 1385 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1386 tp->t_flags |= TF_ONOUTPUTQ; 1387 tp->tt_cpu = mycpu->gd_cpuid; 1388 TAILQ_INSERT_TAIL( 1389 &tcpcbackq[tp->tt_cpu], 1390 tp, t_outputq); 1391 } 1392 } else { 1393 tp->t_flags |= TF_ACKNOW; 1394 tcp_output(tp); 1395 } 1396 return(IPPROTO_DONE); 1397 } 1398 } 1399 1400 /* 1401 * Calculate amount of space in receive window, 1402 * and then do TCP input processing. 1403 * Receive window is amount of space in rcv queue, 1404 * but not less than advertised window. 1405 */ 1406 recvwin = ssb_space(&so->so_rcv); 1407 if (recvwin < 0) 1408 recvwin = 0; 1409 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1410 1411 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1412 tp->rfbuf_ts = 0; 1413 tp->rfbuf_cnt = 0; 1414 1415 switch (tp->t_state) { 1416 /* 1417 * If the state is SYN_RECEIVED: 1418 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1419 */ 1420 case TCPS_SYN_RECEIVED: 1421 if ((thflags & TH_ACK) && 1422 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1423 SEQ_GT(th->th_ack, tp->snd_max))) { 1424 rstreason = BANDLIM_RST_OPENPORT; 1425 goto dropwithreset; 1426 } 1427 break; 1428 1429 /* 1430 * If the state is SYN_SENT: 1431 * if seg contains an ACK, but not for our SYN, drop the input. 1432 * if seg contains a RST, then drop the connection. 1433 * if seg does not contain SYN, then drop it. 1434 * Otherwise this is an acceptable SYN segment 1435 * initialize tp->rcv_nxt and tp->irs 1436 * if seg contains ack then advance tp->snd_una 1437 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1438 * arrange for segment to be acked (eventually) 1439 * continue processing rest of data/controls, beginning with URG 1440 */ 1441 case TCPS_SYN_SENT: 1442 if ((thflags & TH_ACK) && 1443 (SEQ_LEQ(th->th_ack, tp->iss) || 1444 SEQ_GT(th->th_ack, tp->snd_max))) { 1445 rstreason = BANDLIM_UNLIMITED; 1446 goto dropwithreset; 1447 } 1448 if (thflags & TH_RST) { 1449 if (thflags & TH_ACK) 1450 tp = tcp_drop(tp, ECONNREFUSED); 1451 goto drop; 1452 } 1453 if (!(thflags & TH_SYN)) 1454 goto drop; 1455 1456 tp->irs = th->th_seq; 1457 tcp_rcvseqinit(tp); 1458 if (thflags & TH_ACK) { 1459 /* Our SYN was acked. */ 1460 tcpstat.tcps_connects++; 1461 soisconnected(so); 1462 /* Do window scaling on this connection? */ 1463 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1464 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1465 tp->rcv_scale = tp->request_r_scale; 1466 tp->rcv_adv += tp->rcv_wnd; 1467 tp->snd_una++; /* SYN is acked */ 1468 tcp_callout_stop(tp, tp->tt_rexmt); 1469 /* 1470 * If there's data, delay ACK; if there's also a FIN 1471 * ACKNOW will be turned on later. 1472 */ 1473 if (DELAY_ACK(tp) && tlen != 0) { 1474 tcp_callout_reset(tp, tp->tt_delack, 1475 tcp_delacktime, tcp_timer_delack); 1476 } else { 1477 tp->t_flags |= TF_ACKNOW; 1478 } 1479 /* 1480 * Received <SYN,ACK> in SYN_SENT[*] state. 1481 * Transitions: 1482 * SYN_SENT --> ESTABLISHED 1483 * SYN_SENT* --> FIN_WAIT_1 1484 */ 1485 tp->t_starttime = ticks; 1486 if (tp->t_flags & TF_NEEDFIN) { 1487 tp->t_state = TCPS_FIN_WAIT_1; 1488 tp->t_flags &= ~TF_NEEDFIN; 1489 thflags &= ~TH_SYN; 1490 } else { 1491 tcp_established(tp); 1492 } 1493 } else { 1494 /* 1495 * Received initial SYN in SYN-SENT[*] state => 1496 * simultaneous open. 1497 * Do 3-way handshake: 1498 * SYN-SENT -> SYN-RECEIVED 1499 * SYN-SENT* -> SYN-RECEIVED* 1500 */ 1501 tp->t_flags |= TF_ACKNOW; 1502 tcp_callout_stop(tp, tp->tt_rexmt); 1503 tp->t_state = TCPS_SYN_RECEIVED; 1504 } 1505 1506 /* 1507 * Advance th->th_seq to correspond to first data byte. 1508 * If data, trim to stay within window, 1509 * dropping FIN if necessary. 1510 */ 1511 th->th_seq++; 1512 if (tlen > tp->rcv_wnd) { 1513 todrop = tlen - tp->rcv_wnd; 1514 m_adj(m, -todrop); 1515 tlen = tp->rcv_wnd; 1516 thflags &= ~TH_FIN; 1517 tcpstat.tcps_rcvpackafterwin++; 1518 tcpstat.tcps_rcvbyteafterwin += todrop; 1519 } 1520 tp->snd_wl1 = th->th_seq - 1; 1521 tp->rcv_up = th->th_seq; 1522 /* 1523 * Client side of transaction: already sent SYN and data. 1524 * If the remote host used T/TCP to validate the SYN, 1525 * our data will be ACK'd; if so, enter normal data segment 1526 * processing in the middle of step 5, ack processing. 1527 * Otherwise, goto step 6. 1528 */ 1529 if (thflags & TH_ACK) 1530 goto process_ACK; 1531 1532 goto step6; 1533 1534 /* 1535 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1536 * do normal processing (we no longer bother with T/TCP). 1537 */ 1538 case TCPS_LAST_ACK: 1539 case TCPS_CLOSING: 1540 case TCPS_TIME_WAIT: 1541 break; /* continue normal processing */ 1542 } 1543 1544 /* 1545 * States other than LISTEN or SYN_SENT. 1546 * First check the RST flag and sequence number since reset segments 1547 * are exempt from the timestamp and connection count tests. This 1548 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1549 * below which allowed reset segments in half the sequence space 1550 * to fall though and be processed (which gives forged reset 1551 * segments with a random sequence number a 50 percent chance of 1552 * killing a connection). 1553 * Then check timestamp, if present. 1554 * Then check the connection count, if present. 1555 * Then check that at least some bytes of segment are within 1556 * receive window. If segment begins before rcv_nxt, 1557 * drop leading data (and SYN); if nothing left, just ack. 1558 * 1559 * 1560 * If the RST bit is set, check the sequence number to see 1561 * if this is a valid reset segment. 1562 * RFC 793 page 37: 1563 * In all states except SYN-SENT, all reset (RST) segments 1564 * are validated by checking their SEQ-fields. A reset is 1565 * valid if its sequence number is in the window. 1566 * Note: this does not take into account delayed ACKs, so 1567 * we should test against last_ack_sent instead of rcv_nxt. 1568 * The sequence number in the reset segment is normally an 1569 * echo of our outgoing acknowledgement numbers, but some hosts 1570 * send a reset with the sequence number at the rightmost edge 1571 * of our receive window, and we have to handle this case. 1572 * If we have multiple segments in flight, the intial reset 1573 * segment sequence numbers will be to the left of last_ack_sent, 1574 * but they will eventually catch up. 1575 * In any case, it never made sense to trim reset segments to 1576 * fit the receive window since RFC 1122 says: 1577 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1578 * 1579 * A TCP SHOULD allow a received RST segment to include data. 1580 * 1581 * DISCUSSION 1582 * It has been suggested that a RST segment could contain 1583 * ASCII text that encoded and explained the cause of the 1584 * RST. No standard has yet been established for such 1585 * data. 1586 * 1587 * If the reset segment passes the sequence number test examine 1588 * the state: 1589 * SYN_RECEIVED STATE: 1590 * If passive open, return to LISTEN state. 1591 * If active open, inform user that connection was refused. 1592 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1593 * Inform user that connection was reset, and close tcb. 1594 * CLOSING, LAST_ACK STATES: 1595 * Close the tcb. 1596 * TIME_WAIT STATE: 1597 * Drop the segment - see Stevens, vol. 2, p. 964 and 1598 * RFC 1337. 1599 */ 1600 if (thflags & TH_RST) { 1601 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1602 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1603 switch (tp->t_state) { 1604 1605 case TCPS_SYN_RECEIVED: 1606 so->so_error = ECONNREFUSED; 1607 goto close; 1608 1609 case TCPS_ESTABLISHED: 1610 case TCPS_FIN_WAIT_1: 1611 case TCPS_FIN_WAIT_2: 1612 case TCPS_CLOSE_WAIT: 1613 so->so_error = ECONNRESET; 1614 close: 1615 tp->t_state = TCPS_CLOSED; 1616 tcpstat.tcps_drops++; 1617 tp = tcp_close(tp); 1618 break; 1619 1620 case TCPS_CLOSING: 1621 case TCPS_LAST_ACK: 1622 tp = tcp_close(tp); 1623 break; 1624 1625 case TCPS_TIME_WAIT: 1626 break; 1627 } 1628 } 1629 goto drop; 1630 } 1631 1632 /* 1633 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1634 * and it's less than ts_recent, drop it. 1635 */ 1636 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1637 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1638 1639 /* Check to see if ts_recent is over 24 days old. */ 1640 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1641 /* 1642 * Invalidate ts_recent. If this segment updates 1643 * ts_recent, the age will be reset later and ts_recent 1644 * will get a valid value. If it does not, setting 1645 * ts_recent to zero will at least satisfy the 1646 * requirement that zero be placed in the timestamp 1647 * echo reply when ts_recent isn't valid. The 1648 * age isn't reset until we get a valid ts_recent 1649 * because we don't want out-of-order segments to be 1650 * dropped when ts_recent is old. 1651 */ 1652 tp->ts_recent = 0; 1653 } else { 1654 tcpstat.tcps_rcvduppack++; 1655 tcpstat.tcps_rcvdupbyte += tlen; 1656 tcpstat.tcps_pawsdrop++; 1657 if (tlen) 1658 goto dropafterack; 1659 goto drop; 1660 } 1661 } 1662 1663 /* 1664 * In the SYN-RECEIVED state, validate that the packet belongs to 1665 * this connection before trimming the data to fit the receive 1666 * window. Check the sequence number versus IRS since we know 1667 * the sequence numbers haven't wrapped. This is a partial fix 1668 * for the "LAND" DoS attack. 1669 */ 1670 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1671 rstreason = BANDLIM_RST_OPENPORT; 1672 goto dropwithreset; 1673 } 1674 1675 todrop = tp->rcv_nxt - th->th_seq; 1676 if (todrop > 0) { 1677 if (TCP_DO_SACK(tp)) { 1678 /* Report duplicate segment at head of packet. */ 1679 tp->reportblk.rblk_start = th->th_seq; 1680 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1681 th->th_seq + tlen, thflags); 1682 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1683 tp->reportblk.rblk_end = tp->rcv_nxt; 1684 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW); 1685 } 1686 if (thflags & TH_SYN) { 1687 thflags &= ~TH_SYN; 1688 th->th_seq++; 1689 if (th->th_urp > 1) 1690 th->th_urp--; 1691 else 1692 thflags &= ~TH_URG; 1693 todrop--; 1694 } 1695 /* 1696 * Following if statement from Stevens, vol. 2, p. 960. 1697 */ 1698 if (todrop > tlen || 1699 (todrop == tlen && !(thflags & TH_FIN))) { 1700 /* 1701 * Any valid FIN must be to the left of the window. 1702 * At this point the FIN must be a duplicate or out 1703 * of sequence; drop it. 1704 */ 1705 thflags &= ~TH_FIN; 1706 1707 /* 1708 * Send an ACK to resynchronize and drop any data. 1709 * But keep on processing for RST or ACK. 1710 */ 1711 tp->t_flags |= TF_ACKNOW; 1712 todrop = tlen; 1713 tcpstat.tcps_rcvduppack++; 1714 tcpstat.tcps_rcvdupbyte += todrop; 1715 } else { 1716 tcpstat.tcps_rcvpartduppack++; 1717 tcpstat.tcps_rcvpartdupbyte += todrop; 1718 } 1719 drop_hdrlen += todrop; /* drop from the top afterwards */ 1720 th->th_seq += todrop; 1721 tlen -= todrop; 1722 if (th->th_urp > todrop) 1723 th->th_urp -= todrop; 1724 else { 1725 thflags &= ~TH_URG; 1726 th->th_urp = 0; 1727 } 1728 } 1729 1730 /* 1731 * If new data are received on a connection after the 1732 * user processes are gone, then RST the other end. 1733 */ 1734 if ((so->so_state & SS_NOFDREF) && 1735 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1736 tp = tcp_close(tp); 1737 tcpstat.tcps_rcvafterclose++; 1738 rstreason = BANDLIM_UNLIMITED; 1739 goto dropwithreset; 1740 } 1741 1742 /* 1743 * If segment ends after window, drop trailing data 1744 * (and PUSH and FIN); if nothing left, just ACK. 1745 */ 1746 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1747 if (todrop > 0) { 1748 tcpstat.tcps_rcvpackafterwin++; 1749 if (todrop >= tlen) { 1750 tcpstat.tcps_rcvbyteafterwin += tlen; 1751 /* 1752 * If a new connection request is received 1753 * while in TIME_WAIT, drop the old connection 1754 * and start over if the sequence numbers 1755 * are above the previous ones. 1756 */ 1757 if (thflags & TH_SYN && 1758 tp->t_state == TCPS_TIME_WAIT && 1759 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1760 tp = tcp_close(tp); 1761 goto findpcb; 1762 } 1763 /* 1764 * If window is closed can only take segments at 1765 * window edge, and have to drop data and PUSH from 1766 * incoming segments. Continue processing, but 1767 * remember to ack. Otherwise, drop segment 1768 * and ack. 1769 */ 1770 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1771 tp->t_flags |= TF_ACKNOW; 1772 tcpstat.tcps_rcvwinprobe++; 1773 } else 1774 goto dropafterack; 1775 } else 1776 tcpstat.tcps_rcvbyteafterwin += todrop; 1777 m_adj(m, -todrop); 1778 tlen -= todrop; 1779 thflags &= ~(TH_PUSH | TH_FIN); 1780 } 1781 1782 /* 1783 * If last ACK falls within this segment's sequence numbers, 1784 * record its timestamp. 1785 * NOTE: 1786 * 1) That the test incorporates suggestions from the latest 1787 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1788 * 2) That updating only on newer timestamps interferes with 1789 * our earlier PAWS tests, so this check should be solely 1790 * predicated on the sequence space of this segment. 1791 * 3) That we modify the segment boundary check to be 1792 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1793 * instead of RFC1323's 1794 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1795 * This modified check allows us to overcome RFC1323's 1796 * limitations as described in Stevens TCP/IP Illustrated 1797 * Vol. 2 p.869. In such cases, we can still calculate the 1798 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1799 */ 1800 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1801 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1802 + ((thflags & TH_SYN) != 0) 1803 + ((thflags & TH_FIN) != 0)))) { 1804 tp->ts_recent_age = ticks; 1805 tp->ts_recent = to.to_tsval; 1806 } 1807 1808 /* 1809 * If a SYN is in the window, then this is an 1810 * error and we send an RST and drop the connection. 1811 */ 1812 if (thflags & TH_SYN) { 1813 tp = tcp_drop(tp, ECONNRESET); 1814 rstreason = BANDLIM_UNLIMITED; 1815 goto dropwithreset; 1816 } 1817 1818 /* 1819 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1820 * flag is on (half-synchronized state), then queue data for 1821 * later processing; else drop segment and return. 1822 */ 1823 if (!(thflags & TH_ACK)) { 1824 if (tp->t_state == TCPS_SYN_RECEIVED || 1825 (tp->t_flags & TF_NEEDSYN)) 1826 goto step6; 1827 else 1828 goto drop; 1829 } 1830 1831 /* 1832 * Ack processing. 1833 */ 1834 switch (tp->t_state) { 1835 /* 1836 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1837 * ESTABLISHED state and continue processing. 1838 * The ACK was checked above. 1839 */ 1840 case TCPS_SYN_RECEIVED: 1841 1842 tcpstat.tcps_connects++; 1843 soisconnected(so); 1844 /* Do window scaling? */ 1845 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1846 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1847 tp->rcv_scale = tp->request_r_scale; 1848 /* 1849 * Make transitions: 1850 * SYN-RECEIVED -> ESTABLISHED 1851 * SYN-RECEIVED* -> FIN-WAIT-1 1852 */ 1853 tp->t_starttime = ticks; 1854 if (tp->t_flags & TF_NEEDFIN) { 1855 tp->t_state = TCPS_FIN_WAIT_1; 1856 tp->t_flags &= ~TF_NEEDFIN; 1857 } else { 1858 tcp_established(tp); 1859 } 1860 /* 1861 * If segment contains data or ACK, will call tcp_reass() 1862 * later; if not, do so now to pass queued data to user. 1863 */ 1864 if (tlen == 0 && !(thflags & TH_FIN)) 1865 tcp_reass(tp, NULL, NULL, NULL); 1866 /* fall into ... */ 1867 1868 /* 1869 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1870 * ACKs. If the ack is in the range 1871 * tp->snd_una < th->th_ack <= tp->snd_max 1872 * then advance tp->snd_una to th->th_ack and drop 1873 * data from the retransmission queue. If this ACK reflects 1874 * more up to date window information we update our window information. 1875 */ 1876 case TCPS_ESTABLISHED: 1877 case TCPS_FIN_WAIT_1: 1878 case TCPS_FIN_WAIT_2: 1879 case TCPS_CLOSE_WAIT: 1880 case TCPS_CLOSING: 1881 case TCPS_LAST_ACK: 1882 case TCPS_TIME_WAIT: 1883 1884 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1885 if (TCP_DO_SACK(tp)) 1886 tcp_sack_update_scoreboard(tp, &to); 1887 if (tlen != 0 || tiwin != tp->snd_wnd) { 1888 tp->t_dupacks = 0; 1889 break; 1890 } 1891 tcpstat.tcps_rcvdupack++; 1892 if (!tcp_callout_active(tp, tp->tt_rexmt) || 1893 th->th_ack != tp->snd_una) { 1894 tp->t_dupacks = 0; 1895 break; 1896 } 1897 /* 1898 * We have outstanding data (other than 1899 * a window probe), this is a completely 1900 * duplicate ack (ie, window info didn't 1901 * change), the ack is the biggest we've 1902 * seen and we've seen exactly our rexmt 1903 * threshhold of them, so assume a packet 1904 * has been dropped and retransmit it. 1905 * Kludge snd_nxt & the congestion 1906 * window so we send only this one 1907 * packet. 1908 */ 1909 if (IN_FASTRECOVERY(tp)) { 1910 if (TCP_DO_SACK(tp)) { 1911 /* No artifical cwnd inflation. */ 1912 tcp_sack_rexmt(tp, th); 1913 } else { 1914 /* 1915 * Dup acks mean that packets 1916 * have left the network 1917 * (they're now cached at the 1918 * receiver) so bump cwnd by 1919 * the amount in the receiver 1920 * to keep a constant cwnd 1921 * packets in the network. 1922 */ 1923 tp->snd_cwnd += tp->t_maxseg; 1924 tcp_output(tp); 1925 } 1926 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1927 tp->t_dupacks = 0; 1928 break; 1929 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && 1930 (to.to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == 1931 (TOF_DSACK | TOF_SACK_REDUNDANT)) { 1932 /* 1933 * If the ACK carries DSACK and other 1934 * SACK blocks carry information that 1935 * we have already known, don't count 1936 * this ACK as duplicate ACK. This 1937 * prevents spurious early retransmit 1938 * and fast retransmit. This also 1939 * meets the requirement of RFC3042 1940 * that new segments should not be sent 1941 * if the SACK blocks do not contain 1942 * new information (XXX we actually 1943 * loosen the requirment that only DSACK 1944 * is checked here). 1945 * 1946 * This kind of ACKs are usually sent 1947 * after spurious retransmit. 1948 */ 1949 /* Do nothing; don't change t_dupacks */ 1950 } else if (++tp->t_dupacks == tp->t_rxtthresh) { 1951 tcp_seq old_snd_nxt; 1952 u_int win; 1953 1954 fastretransmit: 1955 if (tcp_do_eifel_detect && 1956 (tp->t_flags & TF_RCVD_TSTMP)) { 1957 tcp_save_congestion_state(tp); 1958 tp->t_flags |= TF_FASTREXMT; 1959 } 1960 /* 1961 * We know we're losing at the current 1962 * window size, so do congestion avoidance: 1963 * set ssthresh to half the current window 1964 * and pull our congestion window back to the 1965 * new ssthresh. 1966 */ 1967 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1968 tp->t_maxseg; 1969 if (win < 2) 1970 win = 2; 1971 tp->snd_ssthresh = win * tp->t_maxseg; 1972 ENTER_FASTRECOVERY(tp); 1973 tp->snd_recover = tp->snd_max; 1974 tcp_callout_stop(tp, tp->tt_rexmt); 1975 tp->t_rtttime = 0; 1976 old_snd_nxt = tp->snd_nxt; 1977 tp->snd_nxt = th->th_ack; 1978 tp->snd_cwnd = tp->t_maxseg; 1979 tcp_output(tp); 1980 ++tcpstat.tcps_sndfastrexmit; 1981 tp->snd_cwnd = tp->snd_ssthresh; 1982 tp->rexmt_high = tp->snd_nxt; 1983 tp->t_flags &= ~TF_SACKRESCUED; 1984 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 1985 tp->snd_nxt = old_snd_nxt; 1986 KASSERT(tp->snd_limited <= 2, 1987 ("tp->snd_limited too big")); 1988 if (TCP_DO_SACK(tp)) 1989 tcp_sack_rexmt(tp, th); 1990 else 1991 tp->snd_cwnd += tp->t_maxseg * 1992 (tp->t_dupacks - tp->snd_limited); 1993 } else if (tcp_do_limitedtransmit) { 1994 u_long oldcwnd = tp->snd_cwnd; 1995 tcp_seq oldsndmax = tp->snd_max; 1996 tcp_seq oldsndnxt = tp->snd_nxt; 1997 /* outstanding data */ 1998 uint32_t ownd = tp->snd_max - tp->snd_una; 1999 u_int sent; 2000 2001 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 2002 2003 KASSERT(tp->t_dupacks == 1 || 2004 tp->t_dupacks == 2, 2005 ("dupacks not 1 or 2")); 2006 if (tp->t_dupacks == 1) 2007 tp->snd_limited = 0; 2008 tp->snd_nxt = tp->snd_max; 2009 tp->snd_cwnd = ownd + 2010 (tp->t_dupacks - tp->snd_limited) * 2011 tp->t_maxseg; 2012 tcp_output(tp); 2013 2014 if (SEQ_LT(oldsndnxt, oldsndmax)) { 2015 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 2016 ("snd_una moved in other threads")); 2017 tp->snd_nxt = oldsndnxt; 2018 } 2019 tp->snd_cwnd = oldcwnd; 2020 sent = tp->snd_max - oldsndmax; 2021 if (sent > tp->t_maxseg) { 2022 KASSERT((tp->t_dupacks == 2 && 2023 tp->snd_limited == 0) || 2024 (sent == tp->t_maxseg + 1 && 2025 tp->t_flags & TF_SENTFIN), 2026 ("sent too much")); 2027 KASSERT(sent <= tp->t_maxseg * 2, 2028 ("sent too many segments")); 2029 tp->snd_limited = 2; 2030 tcpstat.tcps_sndlimited += 2; 2031 } else if (sent > 0) { 2032 ++tp->snd_limited; 2033 ++tcpstat.tcps_sndlimited; 2034 } else if (tcp_do_early_retransmit && 2035 (tcp_do_eifel_detect && 2036 (tp->t_flags & TF_RCVD_TSTMP)) && 2037 ownd < 4 * tp->t_maxseg && 2038 tp->t_dupacks + 1 >= 2039 iceildiv(ownd, tp->t_maxseg) && 2040 (!TCP_DO_SACK(tp) || 2041 ownd <= tp->t_maxseg || 2042 tcp_sack_has_sacked(&tp->scb, 2043 ownd - tp->t_maxseg))) { 2044 ++tcpstat.tcps_sndearlyrexmit; 2045 tp->t_flags |= TF_EARLYREXMT; 2046 goto fastretransmit; 2047 } 2048 } 2049 goto drop; 2050 } 2051 2052 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2053 tp->t_dupacks = 0; 2054 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2055 /* 2056 * Detected optimistic ACK attack. 2057 * Force slow-start to de-synchronize attack. 2058 */ 2059 tp->snd_cwnd = tp->t_maxseg; 2060 tp->snd_wacked = 0; 2061 2062 tcpstat.tcps_rcvacktoomuch++; 2063 goto dropafterack; 2064 } 2065 /* 2066 * If we reach this point, ACK is not a duplicate, 2067 * i.e., it ACKs something we sent. 2068 */ 2069 if (tp->t_flags & TF_NEEDSYN) { 2070 /* 2071 * T/TCP: Connection was half-synchronized, and our 2072 * SYN has been ACK'd (so connection is now fully 2073 * synchronized). Go to non-starred state, 2074 * increment snd_una for ACK of SYN, and check if 2075 * we can do window scaling. 2076 */ 2077 tp->t_flags &= ~TF_NEEDSYN; 2078 tp->snd_una++; 2079 /* Do window scaling? */ 2080 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2081 (TF_RCVD_SCALE | TF_REQ_SCALE)) 2082 tp->rcv_scale = tp->request_r_scale; 2083 } 2084 2085 process_ACK: 2086 acked = th->th_ack - tp->snd_una; 2087 tcpstat.tcps_rcvackpack++; 2088 tcpstat.tcps_rcvackbyte += acked; 2089 2090 if (tcp_do_eifel_detect && acked > 0 && 2091 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2092 (tp->t_flags & TF_FIRSTACCACK)) { 2093 /* Eifel detection applicable. */ 2094 if (to.to_tsecr < tp->t_rexmtTS) { 2095 ++tcpstat.tcps_eifeldetected; 2096 tcp_revert_congestion_state(tp); 2097 if (tp->t_rxtshift != 1 || 2098 ticks >= tp->t_badrxtwin) 2099 ++tcpstat.tcps_rttcantdetect; 2100 } 2101 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2102 /* 2103 * If we just performed our first retransmit, 2104 * and the ACK arrives within our recovery window, 2105 * then it was a mistake to do the retransmit 2106 * in the first place. Recover our original cwnd 2107 * and ssthresh, and proceed to transmit where we 2108 * left off. 2109 */ 2110 tcp_revert_congestion_state(tp); 2111 ++tcpstat.tcps_rttdetected; 2112 } 2113 2114 /* 2115 * If we have a timestamp reply, update smoothed 2116 * round trip time. If no timestamp is present but 2117 * transmit timer is running and timed sequence 2118 * number was acked, update smoothed round trip time. 2119 * Since we now have an rtt measurement, cancel the 2120 * timer backoff (cf., Phil Karn's retransmit alg.). 2121 * Recompute the initial retransmit timer. 2122 * 2123 * Some machines (certain windows boxes) send broken 2124 * timestamp replies during the SYN+ACK phase, ignore 2125 * timestamps of 0. 2126 */ 2127 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2128 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); 2129 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2130 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); 2131 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2132 2133 /* 2134 * If no data (only SYN) was ACK'd, 2135 * skip rest of ACK processing. 2136 */ 2137 if (acked == 0) 2138 goto step6; 2139 2140 /* Stop looking for an acceptable ACK since one was received. */ 2141 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT); 2142 2143 if (acked > so->so_snd.ssb_cc) { 2144 tp->snd_wnd -= so->so_snd.ssb_cc; 2145 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2146 ourfinisacked = TRUE; 2147 } else { 2148 sbdrop(&so->so_snd.sb, acked); 2149 tp->snd_wnd -= acked; 2150 ourfinisacked = FALSE; 2151 } 2152 sowwakeup(so); 2153 2154 /* 2155 * Update window information. 2156 */ 2157 if (acceptable_window_update(tp, th, tiwin)) { 2158 /* keep track of pure window updates */ 2159 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2160 tiwin > tp->snd_wnd) 2161 tcpstat.tcps_rcvwinupd++; 2162 tp->snd_wnd = tiwin; 2163 tp->snd_wl1 = th->th_seq; 2164 tp->snd_wl2 = th->th_ack; 2165 if (tp->snd_wnd > tp->max_sndwnd) 2166 tp->max_sndwnd = tp->snd_wnd; 2167 needoutput = TRUE; 2168 } 2169 2170 tp->snd_una = th->th_ack; 2171 if (TCP_DO_SACK(tp)) 2172 tcp_sack_update_scoreboard(tp, &to); 2173 if (IN_FASTRECOVERY(tp)) { 2174 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2175 EXIT_FASTRECOVERY(tp); 2176 needoutput = TRUE; 2177 /* 2178 * If the congestion window was inflated 2179 * to account for the other side's 2180 * cached packets, retract it. 2181 */ 2182 if (!TCP_DO_SACK(tp)) 2183 tp->snd_cwnd = tp->snd_ssthresh; 2184 2185 /* 2186 * Window inflation should have left us 2187 * with approximately snd_ssthresh outstanding 2188 * data. But, in case we would be inclined 2189 * to send a burst, better do it using 2190 * slow start. 2191 */ 2192 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2193 tp->snd_max + 2 * tp->t_maxseg)) 2194 tp->snd_cwnd = 2195 (tp->snd_max - tp->snd_una) + 2196 2 * tp->t_maxseg; 2197 2198 tp->snd_wacked = 0; 2199 } else { 2200 if (TCP_DO_SACK(tp)) { 2201 tp->snd_max_rexmt = tp->snd_max; 2202 tcp_sack_rexmt(tp, th); 2203 } else { 2204 tcp_newreno_partial_ack(tp, th, acked); 2205 } 2206 needoutput = FALSE; 2207 } 2208 } else { 2209 /* 2210 * Open the congestion window. When in slow-start, 2211 * open exponentially: maxseg per packet. Otherwise, 2212 * open linearly: maxseg per window. 2213 */ 2214 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2215 u_int abc_sslimit = 2216 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2217 tp->t_maxseg : 2 * tp->t_maxseg); 2218 2219 /* slow-start */ 2220 tp->snd_cwnd += tcp_do_abc ? 2221 min(acked, abc_sslimit) : tp->t_maxseg; 2222 } else { 2223 /* linear increase */ 2224 tp->snd_wacked += tcp_do_abc ? acked : 2225 tp->t_maxseg; 2226 if (tp->snd_wacked >= tp->snd_cwnd) { 2227 tp->snd_wacked -= tp->snd_cwnd; 2228 tp->snd_cwnd += tp->t_maxseg; 2229 } 2230 } 2231 tp->snd_cwnd = min(tp->snd_cwnd, 2232 TCP_MAXWIN << tp->snd_scale); 2233 tp->snd_recover = th->th_ack - 1; 2234 } 2235 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2236 tp->snd_nxt = tp->snd_una; 2237 2238 /* 2239 * If all outstanding data is acked, stop retransmit 2240 * timer and remember to restart (more output or persist). 2241 * If there is more data to be acked, restart retransmit 2242 * timer, using current (possibly backed-off) value. 2243 */ 2244 if (th->th_ack == tp->snd_max) { 2245 tcp_callout_stop(tp, tp->tt_rexmt); 2246 needoutput = TRUE; 2247 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2248 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2249 tcp_timer_rexmt); 2250 } 2251 2252 switch (tp->t_state) { 2253 /* 2254 * In FIN_WAIT_1 STATE in addition to the processing 2255 * for the ESTABLISHED state if our FIN is now acknowledged 2256 * then enter FIN_WAIT_2. 2257 */ 2258 case TCPS_FIN_WAIT_1: 2259 if (ourfinisacked) { 2260 /* 2261 * If we can't receive any more 2262 * data, then closing user can proceed. 2263 * Starting the timer is contrary to the 2264 * specification, but if we don't get a FIN 2265 * we'll hang forever. 2266 */ 2267 if (so->so_state & SS_CANTRCVMORE) { 2268 soisdisconnected(so); 2269 tcp_callout_reset(tp, tp->tt_2msl, 2270 tp->t_maxidle, tcp_timer_2msl); 2271 } 2272 tp->t_state = TCPS_FIN_WAIT_2; 2273 } 2274 break; 2275 2276 /* 2277 * In CLOSING STATE in addition to the processing for 2278 * the ESTABLISHED state if the ACK acknowledges our FIN 2279 * then enter the TIME-WAIT state, otherwise ignore 2280 * the segment. 2281 */ 2282 case TCPS_CLOSING: 2283 if (ourfinisacked) { 2284 tp->t_state = TCPS_TIME_WAIT; 2285 tcp_canceltimers(tp); 2286 tcp_callout_reset(tp, tp->tt_2msl, 2287 2 * tcp_rmx_msl(tp), 2288 tcp_timer_2msl); 2289 soisdisconnected(so); 2290 } 2291 break; 2292 2293 /* 2294 * In LAST_ACK, we may still be waiting for data to drain 2295 * and/or to be acked, as well as for the ack of our FIN. 2296 * If our FIN is now acknowledged, delete the TCB, 2297 * enter the closed state and return. 2298 */ 2299 case TCPS_LAST_ACK: 2300 if (ourfinisacked) { 2301 tp = tcp_close(tp); 2302 goto drop; 2303 } 2304 break; 2305 2306 /* 2307 * In TIME_WAIT state the only thing that should arrive 2308 * is a retransmission of the remote FIN. Acknowledge 2309 * it and restart the finack timer. 2310 */ 2311 case TCPS_TIME_WAIT: 2312 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2313 tcp_timer_2msl); 2314 goto dropafterack; 2315 } 2316 } 2317 2318 step6: 2319 /* 2320 * Update window information. 2321 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2322 */ 2323 if ((thflags & TH_ACK) && 2324 acceptable_window_update(tp, th, tiwin)) { 2325 /* keep track of pure window updates */ 2326 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2327 tiwin > tp->snd_wnd) 2328 tcpstat.tcps_rcvwinupd++; 2329 tp->snd_wnd = tiwin; 2330 tp->snd_wl1 = th->th_seq; 2331 tp->snd_wl2 = th->th_ack; 2332 if (tp->snd_wnd > tp->max_sndwnd) 2333 tp->max_sndwnd = tp->snd_wnd; 2334 needoutput = TRUE; 2335 } 2336 2337 /* 2338 * Process segments with URG. 2339 */ 2340 if ((thflags & TH_URG) && th->th_urp && 2341 !TCPS_HAVERCVDFIN(tp->t_state)) { 2342 /* 2343 * This is a kludge, but if we receive and accept 2344 * random urgent pointers, we'll crash in 2345 * soreceive. It's hard to imagine someone 2346 * actually wanting to send this much urgent data. 2347 */ 2348 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2349 th->th_urp = 0; /* XXX */ 2350 thflags &= ~TH_URG; /* XXX */ 2351 goto dodata; /* XXX */ 2352 } 2353 /* 2354 * If this segment advances the known urgent pointer, 2355 * then mark the data stream. This should not happen 2356 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2357 * a FIN has been received from the remote side. 2358 * In these states we ignore the URG. 2359 * 2360 * According to RFC961 (Assigned Protocols), 2361 * the urgent pointer points to the last octet 2362 * of urgent data. We continue, however, 2363 * to consider it to indicate the first octet 2364 * of data past the urgent section as the original 2365 * spec states (in one of two places). 2366 */ 2367 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2368 tp->rcv_up = th->th_seq + th->th_urp; 2369 so->so_oobmark = so->so_rcv.ssb_cc + 2370 (tp->rcv_up - tp->rcv_nxt) - 1; 2371 if (so->so_oobmark == 0) 2372 sosetstate(so, SS_RCVATMARK); 2373 sohasoutofband(so); 2374 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2375 } 2376 /* 2377 * Remove out of band data so doesn't get presented to user. 2378 * This can happen independent of advancing the URG pointer, 2379 * but if two URG's are pending at once, some out-of-band 2380 * data may creep in... ick. 2381 */ 2382 if (th->th_urp <= (u_long)tlen && 2383 !(so->so_options & SO_OOBINLINE)) { 2384 /* hdr drop is delayed */ 2385 tcp_pulloutofband(so, th, m, drop_hdrlen); 2386 } 2387 } else { 2388 /* 2389 * If no out of band data is expected, 2390 * pull receive urgent pointer along 2391 * with the receive window. 2392 */ 2393 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2394 tp->rcv_up = tp->rcv_nxt; 2395 } 2396 2397 dodata: /* XXX */ 2398 /* 2399 * Process the segment text, merging it into the TCP sequencing queue, 2400 * and arranging for acknowledgment of receipt if necessary. 2401 * This process logically involves adjusting tp->rcv_wnd as data 2402 * is presented to the user (this happens in tcp_usrreq.c, 2403 * case PRU_RCVD). If a FIN has already been received on this 2404 * connection then we just ignore the text. 2405 */ 2406 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2407 m_adj(m, drop_hdrlen); /* delayed header drop */ 2408 /* 2409 * Insert segment which includes th into TCP reassembly queue 2410 * with control block tp. Set thflags to whether reassembly now 2411 * includes a segment with FIN. This handles the common case 2412 * inline (segment is the next to be received on an established 2413 * connection, and the queue is empty), avoiding linkage into 2414 * and removal from the queue and repetition of various 2415 * conversions. 2416 * Set DELACK for segments received in order, but ack 2417 * immediately when segments are out of order (so 2418 * fast retransmit can work). 2419 */ 2420 if (th->th_seq == tp->rcv_nxt && 2421 LIST_EMPTY(&tp->t_segq) && 2422 TCPS_HAVEESTABLISHED(tp->t_state)) { 2423 if (DELAY_ACK(tp)) { 2424 tcp_callout_reset(tp, tp->tt_delack, 2425 tcp_delacktime, tcp_timer_delack); 2426 } else { 2427 tp->t_flags |= TF_ACKNOW; 2428 } 2429 tp->rcv_nxt += tlen; 2430 thflags = th->th_flags & TH_FIN; 2431 tcpstat.tcps_rcvpack++; 2432 tcpstat.tcps_rcvbyte += tlen; 2433 ND6_HINT(tp); 2434 if (so->so_state & SS_CANTRCVMORE) { 2435 m_freem(m); 2436 } else { 2437 lwkt_gettoken(&so->so_rcv.ssb_token); 2438 ssb_appendstream(&so->so_rcv, m); 2439 lwkt_reltoken(&so->so_rcv.ssb_token); 2440 } 2441 sorwakeup(so); 2442 } else { 2443 if (!(tp->t_flags & TF_DUPSEG)) { 2444 /* Initialize SACK report block. */ 2445 tp->reportblk.rblk_start = th->th_seq; 2446 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2447 th->th_seq + tlen, thflags); 2448 } 2449 thflags = tcp_reass(tp, th, &tlen, m); 2450 tp->t_flags |= TF_ACKNOW; 2451 } 2452 2453 /* 2454 * Note the amount of data that peer has sent into 2455 * our window, in order to estimate the sender's 2456 * buffer size. 2457 */ 2458 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2459 } else { 2460 m_freem(m); 2461 thflags &= ~TH_FIN; 2462 } 2463 2464 /* 2465 * If FIN is received ACK the FIN and let the user know 2466 * that the connection is closing. 2467 */ 2468 if (thflags & TH_FIN) { 2469 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2470 socantrcvmore(so); 2471 /* 2472 * If connection is half-synchronized 2473 * (ie NEEDSYN flag on) then delay ACK, 2474 * so it may be piggybacked when SYN is sent. 2475 * Otherwise, since we received a FIN then no 2476 * more input can be expected, send ACK now. 2477 */ 2478 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2479 tcp_callout_reset(tp, tp->tt_delack, 2480 tcp_delacktime, tcp_timer_delack); 2481 } else { 2482 tp->t_flags |= TF_ACKNOW; 2483 } 2484 tp->rcv_nxt++; 2485 } 2486 2487 switch (tp->t_state) { 2488 /* 2489 * In SYN_RECEIVED and ESTABLISHED STATES 2490 * enter the CLOSE_WAIT state. 2491 */ 2492 case TCPS_SYN_RECEIVED: 2493 tp->t_starttime = ticks; 2494 /*FALLTHROUGH*/ 2495 case TCPS_ESTABLISHED: 2496 tp->t_state = TCPS_CLOSE_WAIT; 2497 break; 2498 2499 /* 2500 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2501 * enter the CLOSING state. 2502 */ 2503 case TCPS_FIN_WAIT_1: 2504 tp->t_state = TCPS_CLOSING; 2505 break; 2506 2507 /* 2508 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2509 * starting the time-wait timer, turning off the other 2510 * standard timers. 2511 */ 2512 case TCPS_FIN_WAIT_2: 2513 tp->t_state = TCPS_TIME_WAIT; 2514 tcp_canceltimers(tp); 2515 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2516 tcp_timer_2msl); 2517 soisdisconnected(so); 2518 break; 2519 2520 /* 2521 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2522 */ 2523 case TCPS_TIME_WAIT: 2524 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2525 tcp_timer_2msl); 2526 break; 2527 } 2528 } 2529 2530 #ifdef TCPDEBUG 2531 if (so->so_options & SO_DEBUG) 2532 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2533 #endif 2534 2535 /* 2536 * Return any desired output. 2537 */ 2538 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2539 tcp_output(tp); 2540 tcp_sack_report_cleanup(tp); 2541 return(IPPROTO_DONE); 2542 2543 dropafterack: 2544 /* 2545 * Generate an ACK dropping incoming segment if it occupies 2546 * sequence space, where the ACK reflects our state. 2547 * 2548 * We can now skip the test for the RST flag since all 2549 * paths to this code happen after packets containing 2550 * RST have been dropped. 2551 * 2552 * In the SYN-RECEIVED state, don't send an ACK unless the 2553 * segment we received passes the SYN-RECEIVED ACK test. 2554 * If it fails send a RST. This breaks the loop in the 2555 * "LAND" DoS attack, and also prevents an ACK storm 2556 * between two listening ports that have been sent forged 2557 * SYN segments, each with the source address of the other. 2558 */ 2559 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2560 (SEQ_GT(tp->snd_una, th->th_ack) || 2561 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2562 rstreason = BANDLIM_RST_OPENPORT; 2563 goto dropwithreset; 2564 } 2565 #ifdef TCPDEBUG 2566 if (so->so_options & SO_DEBUG) 2567 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2568 #endif 2569 m_freem(m); 2570 tp->t_flags |= TF_ACKNOW; 2571 tcp_output(tp); 2572 tcp_sack_report_cleanup(tp); 2573 return(IPPROTO_DONE); 2574 2575 dropwithreset: 2576 /* 2577 * Generate a RST, dropping incoming segment. 2578 * Make ACK acceptable to originator of segment. 2579 * Don't bother to respond if destination was broadcast/multicast. 2580 */ 2581 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2582 goto drop; 2583 if (isipv6) { 2584 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2585 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2586 goto drop; 2587 } else { 2588 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2589 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2590 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2591 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2592 goto drop; 2593 } 2594 /* IPv6 anycast check is done at tcp6_input() */ 2595 2596 /* 2597 * Perform bandwidth limiting. 2598 */ 2599 #ifdef ICMP_BANDLIM 2600 if (badport_bandlim(rstreason) < 0) 2601 goto drop; 2602 #endif 2603 2604 #ifdef TCPDEBUG 2605 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2606 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2607 #endif 2608 if (thflags & TH_ACK) 2609 /* mtod() below is safe as long as hdr dropping is delayed */ 2610 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2611 TH_RST); 2612 else { 2613 if (thflags & TH_SYN) 2614 tlen++; 2615 /* mtod() below is safe as long as hdr dropping is delayed */ 2616 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2617 (tcp_seq)0, TH_RST | TH_ACK); 2618 } 2619 if (tp != NULL) 2620 tcp_sack_report_cleanup(tp); 2621 return(IPPROTO_DONE); 2622 2623 drop: 2624 /* 2625 * Drop space held by incoming segment and return. 2626 */ 2627 #ifdef TCPDEBUG 2628 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2629 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2630 #endif 2631 m_freem(m); 2632 if (tp != NULL) 2633 tcp_sack_report_cleanup(tp); 2634 return(IPPROTO_DONE); 2635 } 2636 2637 /* 2638 * Parse TCP options and place in tcpopt. 2639 */ 2640 static void 2641 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, 2642 tcp_seq ack) 2643 { 2644 int opt, optlen, i; 2645 2646 to->to_flags = 0; 2647 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2648 opt = cp[0]; 2649 if (opt == TCPOPT_EOL) 2650 break; 2651 if (opt == TCPOPT_NOP) 2652 optlen = 1; 2653 else { 2654 if (cnt < 2) 2655 break; 2656 optlen = cp[1]; 2657 if (optlen < 2 || optlen > cnt) 2658 break; 2659 } 2660 switch (opt) { 2661 case TCPOPT_MAXSEG: 2662 if (optlen != TCPOLEN_MAXSEG) 2663 continue; 2664 if (!is_syn) 2665 continue; 2666 to->to_flags |= TOF_MSS; 2667 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2668 to->to_mss = ntohs(to->to_mss); 2669 break; 2670 case TCPOPT_WINDOW: 2671 if (optlen != TCPOLEN_WINDOW) 2672 continue; 2673 if (!is_syn) 2674 continue; 2675 to->to_flags |= TOF_SCALE; 2676 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2677 break; 2678 case TCPOPT_TIMESTAMP: 2679 if (optlen != TCPOLEN_TIMESTAMP) 2680 continue; 2681 to->to_flags |= TOF_TS; 2682 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2683 to->to_tsval = ntohl(to->to_tsval); 2684 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2685 to->to_tsecr = ntohl(to->to_tsecr); 2686 /* 2687 * If echoed timestamp is later than the current time, 2688 * fall back to non RFC1323 RTT calculation. 2689 */ 2690 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2691 to->to_tsecr = 0; 2692 break; 2693 case TCPOPT_SACK_PERMITTED: 2694 if (optlen != TCPOLEN_SACK_PERMITTED) 2695 continue; 2696 if (!is_syn) 2697 continue; 2698 to->to_flags |= TOF_SACK_PERMITTED; 2699 break; 2700 case TCPOPT_SACK: 2701 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2702 continue; 2703 to->to_nsackblocks = (optlen - 2) / 8; 2704 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2705 to->to_flags |= TOF_SACK; 2706 for (i = 0; i < to->to_nsackblocks; i++) { 2707 struct raw_sackblock *r = &to->to_sackblocks[i]; 2708 2709 r->rblk_start = ntohl(r->rblk_start); 2710 r->rblk_end = ntohl(r->rblk_end); 2711 2712 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2713 /* 2714 * Invalid SACK block; discard all 2715 * SACK blocks 2716 */ 2717 tcpstat.tcps_rcvbadsackopt++; 2718 to->to_nsackblocks = 0; 2719 to->to_sackblocks = NULL; 2720 to->to_flags &= ~TOF_SACK; 2721 break; 2722 } 2723 } 2724 if ((to->to_flags & TOF_SACK) && 2725 tcp_sack_ndsack_blocks(to->to_sackblocks, 2726 to->to_nsackblocks, ack)) 2727 to->to_flags |= TOF_DSACK; 2728 break; 2729 #ifdef TCP_SIGNATURE 2730 /* 2731 * XXX In order to reply to a host which has set the 2732 * TCP_SIGNATURE option in its initial SYN, we have to 2733 * record the fact that the option was observed here 2734 * for the syncache code to perform the correct response. 2735 */ 2736 case TCPOPT_SIGNATURE: 2737 if (optlen != TCPOLEN_SIGNATURE) 2738 continue; 2739 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2740 break; 2741 #endif /* TCP_SIGNATURE */ 2742 default: 2743 continue; 2744 } 2745 } 2746 } 2747 2748 /* 2749 * Pull out of band byte out of a segment so 2750 * it doesn't appear in the user's data queue. 2751 * It is still reflected in the segment length for 2752 * sequencing purposes. 2753 * "off" is the delayed to be dropped hdrlen. 2754 */ 2755 static void 2756 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2757 { 2758 int cnt = off + th->th_urp - 1; 2759 2760 while (cnt >= 0) { 2761 if (m->m_len > cnt) { 2762 char *cp = mtod(m, caddr_t) + cnt; 2763 struct tcpcb *tp = sototcpcb(so); 2764 2765 tp->t_iobc = *cp; 2766 tp->t_oobflags |= TCPOOB_HAVEDATA; 2767 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2768 m->m_len--; 2769 if (m->m_flags & M_PKTHDR) 2770 m->m_pkthdr.len--; 2771 return; 2772 } 2773 cnt -= m->m_len; 2774 m = m->m_next; 2775 if (m == NULL) 2776 break; 2777 } 2778 panic("tcp_pulloutofband"); 2779 } 2780 2781 /* 2782 * Collect new round-trip time estimate 2783 * and update averages and current timeout. 2784 */ 2785 static void 2786 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) 2787 { 2788 int rebaserto = 0; 2789 2790 tcpstat.tcps_rttupdated++; 2791 tp->t_rttupdated++; 2792 if ((tp->t_flags & TF_REBASERTO) && SEQ_GT(ack, tp->snd_max_prev)) { 2793 #ifdef DEBUG_EIFEL_RESPONSE 2794 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", 2795 tp->t_srtt_prev, tp->t_rttvar_prev, 2796 tp->t_srtt, tp->t_rttvar); 2797 #endif 2798 2799 tcpstat.tcps_eifelresponse++; 2800 rebaserto = 1; 2801 tp->t_flags &= ~TF_REBASERTO; 2802 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); 2803 tp->t_rttvar = max(tp->t_rttvar_prev, 2804 (rtt << (TCP_RTTVAR_SHIFT - 1))); 2805 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2806 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2807 2808 #ifdef DEBUG_EIFEL_RESPONSE 2809 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); 2810 #endif 2811 } else if (tp->t_srtt != 0) { 2812 int delta; 2813 2814 /* 2815 * srtt is stored as fixed point with 5 bits after the 2816 * binary point (i.e., scaled by 8). The following magic 2817 * is equivalent to the smoothing algorithm in rfc793 with 2818 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2819 * point). Adjust rtt to origin 0. 2820 */ 2821 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2822 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2823 2824 if ((tp->t_srtt += delta) <= 0) 2825 tp->t_srtt = 1; 2826 2827 /* 2828 * We accumulate a smoothed rtt variance (actually, a 2829 * smoothed mean difference), then set the retransmit 2830 * timer to smoothed rtt + 4 times the smoothed variance. 2831 * rttvar is stored as fixed point with 4 bits after the 2832 * binary point (scaled by 16). The following is 2833 * equivalent to rfc793 smoothing with an alpha of .75 2834 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2835 * rfc793's wired-in beta. 2836 */ 2837 if (delta < 0) 2838 delta = -delta; 2839 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2840 if ((tp->t_rttvar += delta) <= 0) 2841 tp->t_rttvar = 1; 2842 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2843 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2844 } else { 2845 /* 2846 * No rtt measurement yet - use the unsmoothed rtt. 2847 * Set the variance to half the rtt (so our first 2848 * retransmit happens at 3*rtt). 2849 */ 2850 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2851 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2852 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2853 } 2854 tp->t_rtttime = 0; 2855 tp->t_rxtshift = 0; 2856 2857 #ifdef DEBUG_EIFEL_RESPONSE 2858 if (rebaserto) { 2859 kprintf("| rxtcur prev %d, old %d, ", 2860 tp->t_rxtcur_prev, tp->t_rxtcur); 2861 } 2862 #endif 2863 2864 /* 2865 * the retransmit should happen at rtt + 4 * rttvar. 2866 * Because of the way we do the smoothing, srtt and rttvar 2867 * will each average +1/2 tick of bias. When we compute 2868 * the retransmit timer, we want 1/2 tick of rounding and 2869 * 1 extra tick because of +-1/2 tick uncertainty in the 2870 * firing of the timer. The bias will give us exactly the 2871 * 1.5 tick we need. But, because the bias is 2872 * statistical, we have to test that we don't drop below 2873 * the minimum feasible timer (which is 2 ticks). 2874 */ 2875 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2876 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2877 2878 if (rebaserto) { 2879 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { 2880 /* 2881 * RFC4015 requires that the new RTO is at least 2882 * 2*G (tcp_eifel_rtoinc) greater then the RTO 2883 * (t_rxtcur_prev) when the spurious retransmit 2884 * timeout happens. 2885 * 2886 * The above condition could be true, if the SRTT 2887 * and RTTVAR used to calculate t_rxtcur_prev 2888 * resulted in a value less than t_rttmin. So 2889 * simply increasing SRTT by tcp_eifel_rtoinc when 2890 * preparing for the Eifel response in 2891 * tcp_save_congestion_state() could not ensure 2892 * that the new RTO will be tcp_eifel_rtoinc greater 2893 * t_rxtcur_prev. 2894 */ 2895 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; 2896 } 2897 #ifdef DEBUG_EIFEL_RESPONSE 2898 kprintf("new %d\n", tp->t_rxtcur); 2899 #endif 2900 } 2901 2902 /* 2903 * We received an ack for a packet that wasn't retransmitted; 2904 * it is probably safe to discard any error indications we've 2905 * received recently. This isn't quite right, but close enough 2906 * for now (a route might have failed after we sent a segment, 2907 * and the return path might not be symmetrical). 2908 */ 2909 tp->t_softerror = 0; 2910 } 2911 2912 /* 2913 * Determine a reasonable value for maxseg size. 2914 * If the route is known, check route for mtu. 2915 * If none, use an mss that can be handled on the outgoing 2916 * interface without forcing IP to fragment; if bigger than 2917 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2918 * to utilize large mbufs. If no route is found, route has no mtu, 2919 * or the destination isn't local, use a default, hopefully conservative 2920 * size (usually 512 or the default IP max size, but no more than the mtu 2921 * of the interface), as we can't discover anything about intervening 2922 * gateways or networks. We also initialize the congestion/slow start 2923 * window to be a single segment if the destination isn't local. 2924 * While looking at the routing entry, we also initialize other path-dependent 2925 * parameters from pre-set or cached values in the routing entry. 2926 * 2927 * Also take into account the space needed for options that we 2928 * send regularly. Make maxseg shorter by that amount to assure 2929 * that we can send maxseg amount of data even when the options 2930 * are present. Store the upper limit of the length of options plus 2931 * data in maxopd. 2932 * 2933 * NOTE that this routine is only called when we process an incoming 2934 * segment, for outgoing segments only tcp_mssopt is called. 2935 */ 2936 void 2937 tcp_mss(struct tcpcb *tp, int offer) 2938 { 2939 struct rtentry *rt; 2940 struct ifnet *ifp; 2941 int rtt, mss; 2942 u_long bufsize; 2943 struct inpcb *inp = tp->t_inpcb; 2944 struct socket *so; 2945 #ifdef INET6 2946 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2947 size_t min_protoh = isipv6 ? 2948 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2949 sizeof(struct tcpiphdr); 2950 #else 2951 const boolean_t isipv6 = FALSE; 2952 const size_t min_protoh = sizeof(struct tcpiphdr); 2953 #endif 2954 2955 if (isipv6) 2956 rt = tcp_rtlookup6(&inp->inp_inc); 2957 else 2958 rt = tcp_rtlookup(&inp->inp_inc); 2959 if (rt == NULL) { 2960 tp->t_maxopd = tp->t_maxseg = 2961 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2962 return; 2963 } 2964 ifp = rt->rt_ifp; 2965 so = inp->inp_socket; 2966 2967 /* 2968 * Offer == 0 means that there was no MSS on the SYN segment, 2969 * in this case we use either the interface mtu or tcp_mssdflt. 2970 * 2971 * An offer which is too large will be cut down later. 2972 */ 2973 if (offer == 0) { 2974 if (isipv6) { 2975 if (in6_localaddr(&inp->in6p_faddr)) { 2976 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 2977 min_protoh; 2978 } else { 2979 offer = tcp_v6mssdflt; 2980 } 2981 } else { 2982 if (in_localaddr(inp->inp_faddr)) 2983 offer = ifp->if_mtu - min_protoh; 2984 else 2985 offer = tcp_mssdflt; 2986 } 2987 } 2988 2989 /* 2990 * Prevent DoS attack with too small MSS. Round up 2991 * to at least minmss. 2992 * 2993 * Sanity check: make sure that maxopd will be large 2994 * enough to allow some data on segments even is the 2995 * all the option space is used (40bytes). Otherwise 2996 * funny things may happen in tcp_output. 2997 */ 2998 offer = max(offer, tcp_minmss); 2999 offer = max(offer, 64); 3000 3001 rt->rt_rmx.rmx_mssopt = offer; 3002 3003 /* 3004 * While we're here, check if there's an initial rtt 3005 * or rttvar. Convert from the route-table units 3006 * to scaled multiples of the slow timeout timer. 3007 */ 3008 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3009 /* 3010 * XXX the lock bit for RTT indicates that the value 3011 * is also a minimum value; this is subject to time. 3012 */ 3013 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3014 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3015 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3016 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3017 tcpstat.tcps_usedrtt++; 3018 if (rt->rt_rmx.rmx_rttvar) { 3019 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3020 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3021 tcpstat.tcps_usedrttvar++; 3022 } else { 3023 /* default variation is +- 1 rtt */ 3024 tp->t_rttvar = 3025 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3026 } 3027 TCPT_RANGESET(tp->t_rxtcur, 3028 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3029 tp->t_rttmin, TCPTV_REXMTMAX); 3030 } 3031 3032 /* 3033 * if there's an mtu associated with the route, use it 3034 * else, use the link mtu. Take the smaller of mss or offer 3035 * as our final mss. 3036 */ 3037 if (rt->rt_rmx.rmx_mtu) { 3038 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3039 } else { 3040 if (isipv6) 3041 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3042 else 3043 mss = ifp->if_mtu - min_protoh; 3044 } 3045 mss = min(mss, offer); 3046 3047 /* 3048 * maxopd stores the maximum length of data AND options 3049 * in a segment; maxseg is the amount of data in a normal 3050 * segment. We need to store this value (maxopd) apart 3051 * from maxseg, because now every segment carries options 3052 * and thus we normally have somewhat less data in segments. 3053 */ 3054 tp->t_maxopd = mss; 3055 3056 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3057 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3058 mss -= TCPOLEN_TSTAMP_APPA; 3059 3060 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3061 if (mss > MCLBYTES) 3062 mss &= ~(MCLBYTES-1); 3063 #else 3064 if (mss > MCLBYTES) 3065 mss = mss / MCLBYTES * MCLBYTES; 3066 #endif 3067 /* 3068 * If there's a pipesize, change the socket buffer 3069 * to that size. Make the socket buffers an integral 3070 * number of mss units; if the mss is larger than 3071 * the socket buffer, decrease the mss. 3072 */ 3073 #ifdef RTV_SPIPE 3074 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3075 #endif 3076 bufsize = so->so_snd.ssb_hiwat; 3077 if (bufsize < mss) 3078 mss = bufsize; 3079 else { 3080 bufsize = roundup(bufsize, mss); 3081 if (bufsize > sb_max) 3082 bufsize = sb_max; 3083 if (bufsize > so->so_snd.ssb_hiwat) 3084 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3085 } 3086 tp->t_maxseg = mss; 3087 3088 #ifdef RTV_RPIPE 3089 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3090 #endif 3091 bufsize = so->so_rcv.ssb_hiwat; 3092 if (bufsize > mss) { 3093 bufsize = roundup(bufsize, mss); 3094 if (bufsize > sb_max) 3095 bufsize = sb_max; 3096 if (bufsize > so->so_rcv.ssb_hiwat) { 3097 lwkt_gettoken(&so->so_rcv.ssb_token); 3098 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3099 lwkt_reltoken(&so->so_rcv.ssb_token); 3100 } 3101 } 3102 3103 /* 3104 * Set the slow-start flight size 3105 * 3106 * NOTE: t_maxseg must have been configured! 3107 */ 3108 tp->snd_cwnd = tcp_initial_window(tp); 3109 3110 if (rt->rt_rmx.rmx_ssthresh) { 3111 /* 3112 * There's some sort of gateway or interface 3113 * buffer limit on the path. Use this to set 3114 * the slow start threshhold, but set the 3115 * threshold to no less than 2*mss. 3116 */ 3117 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3118 tcpstat.tcps_usedssthresh++; 3119 } 3120 } 3121 3122 /* 3123 * Determine the MSS option to send on an outgoing SYN. 3124 */ 3125 int 3126 tcp_mssopt(struct tcpcb *tp) 3127 { 3128 struct rtentry *rt; 3129 #ifdef INET6 3130 boolean_t isipv6 = 3131 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3132 int min_protoh = isipv6 ? 3133 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3134 sizeof(struct tcpiphdr); 3135 #else 3136 const boolean_t isipv6 = FALSE; 3137 const size_t min_protoh = sizeof(struct tcpiphdr); 3138 #endif 3139 3140 if (isipv6) 3141 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3142 else 3143 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3144 if (rt == NULL) 3145 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3146 3147 return (rt->rt_ifp->if_mtu - min_protoh); 3148 } 3149 3150 /* 3151 * When a partial ack arrives, force the retransmission of the 3152 * next unacknowledged segment. Do not exit Fast Recovery. 3153 * 3154 * Implement the Slow-but-Steady variant of NewReno by restarting the 3155 * the retransmission timer. Turn it off here so it can be restarted 3156 * later in tcp_output(). 3157 */ 3158 static void 3159 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3160 { 3161 tcp_seq old_snd_nxt = tp->snd_nxt; 3162 u_long ocwnd = tp->snd_cwnd; 3163 3164 tcp_callout_stop(tp, tp->tt_rexmt); 3165 tp->t_rtttime = 0; 3166 tp->snd_nxt = th->th_ack; 3167 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3168 tp->snd_cwnd = tp->t_maxseg; 3169 tp->t_flags |= TF_ACKNOW; 3170 tcp_output(tp); 3171 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3172 tp->snd_nxt = old_snd_nxt; 3173 /* partial window deflation */ 3174 if (ocwnd > acked) 3175 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3176 else 3177 tp->snd_cwnd = tp->t_maxseg; 3178 } 3179 3180 /* 3181 * In contrast to the Slow-but-Steady NewReno variant, 3182 * we do not reset the retransmission timer for SACK retransmissions, 3183 * except when retransmitting snd_una. 3184 */ 3185 static void 3186 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) 3187 { 3188 tcp_seq old_snd_nxt = tp->snd_nxt; 3189 u_long ocwnd = tp->snd_cwnd; 3190 uint32_t pipe; 3191 int nseg = 0; /* consecutive new segments */ 3192 int nseg_rexmt = 0; /* retransmitted segments */ 3193 #define MAXBURST 4 /* limit burst of new packets on partial ack */ 3194 3195 tp->t_rtttime = 0; 3196 pipe = tcp_sack_compute_pipe(tp); 3197 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && 3198 (!tcp_do_smartsack || nseg < MAXBURST)) { 3199 tcp_seq old_snd_max, old_rexmt_high, nextrexmt; 3200 uint32_t sent, seglen; 3201 boolean_t rescue; 3202 int error; 3203 3204 old_rexmt_high = tp->rexmt_high; 3205 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { 3206 tp->rexmt_high = old_rexmt_high; 3207 break; 3208 } 3209 3210 /* 3211 * If the next tranmission is a rescue retranmission, 3212 * we check whether we have already sent some data 3213 * (either new segments or retransmitted segments) 3214 * into the the network or not. Since the idea of rescue 3215 * retransmission is to sustain ACK clock, as long as 3216 * some segments are in the network, ACK clock will be 3217 * kept ticking. 3218 */ 3219 if (rescue && (nseg_rexmt > 0 || nseg > 0)) { 3220 tp->rexmt_high = old_rexmt_high; 3221 break; 3222 } 3223 3224 if (nextrexmt == tp->snd_max) 3225 ++nseg; 3226 else 3227 ++nseg_rexmt; 3228 tp->snd_nxt = nextrexmt; 3229 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3230 old_snd_max = tp->snd_max; 3231 if (nextrexmt == tp->snd_una) 3232 tcp_callout_stop(tp, tp->tt_rexmt); 3233 error = tcp_output(tp); 3234 if (error != 0) { 3235 tp->rexmt_high = old_rexmt_high; 3236 break; 3237 } 3238 sent = tp->snd_nxt - nextrexmt; 3239 if (sent <= 0) { 3240 tp->rexmt_high = old_rexmt_high; 3241 break; 3242 } 3243 pipe += sent; 3244 tcpstat.tcps_sndsackpack++; 3245 tcpstat.tcps_sndsackbyte += sent; 3246 3247 if (rescue) { 3248 tcpstat.tcps_sackrescue++; 3249 tp->rexmt_rescue = tp->snd_nxt; 3250 tp->t_flags |= TF_SACKRESCUED; 3251 break; 3252 } 3253 if (SEQ_LT(nextrexmt, old_snd_max) && 3254 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { 3255 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3256 if (tcp_aggressive_rescuesack && 3257 (tp->t_flags & TF_SACKRESCUED) && 3258 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 3259 /* Drag RescueRxt along with HighRxt */ 3260 tp->rexmt_rescue = tp->rexmt_high; 3261 } 3262 } 3263 } 3264 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3265 tp->snd_nxt = old_snd_nxt; 3266 tp->snd_cwnd = ocwnd; 3267 } 3268 3269 /* 3270 * Reset idle time and keep-alive timer, typically called when a valid 3271 * tcp packet is received but may also be called when FASTKEEP is set 3272 * to prevent the previous long-timeout from calculating to a drop. 3273 * 3274 * Only update t_rcvtime for non-SYN packets. 3275 * 3276 * Handle the case where one side thinks the connection is established 3277 * but the other side has, say, rebooted without cleaning out the 3278 * connection. The SYNs could be construed as an attack and wind 3279 * up ignored, but in case it isn't an attack we can validate the 3280 * connection by forcing a keepalive. 3281 */ 3282 void 3283 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3284 { 3285 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3286 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3287 tp->t_flags |= TF_KEEPALIVE; 3288 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3289 tcp_timer_keep); 3290 } else { 3291 tp->t_rcvtime = ticks; 3292 tp->t_flags &= ~TF_KEEPALIVE; 3293 tcp_callout_reset(tp, tp->tt_keep, 3294 tp->t_keepidle, 3295 tcp_timer_keep); 3296 } 3297 } 3298 } 3299 3300 static int 3301 tcp_rmx_msl(const struct tcpcb *tp) 3302 { 3303 struct rtentry *rt; 3304 struct inpcb *inp = tp->t_inpcb; 3305 int msl; 3306 #ifdef INET6 3307 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3308 #else 3309 const boolean_t isipv6 = FALSE; 3310 #endif 3311 3312 if (isipv6) 3313 rt = tcp_rtlookup6(&inp->inp_inc); 3314 else 3315 rt = tcp_rtlookup(&inp->inp_inc); 3316 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3317 return tcp_msl; 3318 3319 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3320 if (msl == 0) 3321 msl = 1; 3322 3323 return msl; 3324 } 3325 3326 static void 3327 tcp_established(struct tcpcb *tp) 3328 { 3329 tp->t_state = TCPS_ESTABLISHED; 3330 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3331 3332 if (tp->t_rxtsyn > 0) { 3333 /* 3334 * RFC6298: 3335 * "If the timer expires awaiting the ACK of a SYN segment 3336 * and the TCP implementation is using an RTO less than 3 3337 * seconds, the RTO MUST be re-initialized to 3 seconds 3338 * when data transmission begins" 3339 */ 3340 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3341 tp->t_rxtcur = TCPTV_RTOBASE3; 3342 } 3343 } 3344