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sys/netinet/tcp_input.c
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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. Neither the name of the University nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60 * SUCH DAMAGE. 61 * 62 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 63 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 64 */ 65 66 #include "opt_inet.h" 67 #include "opt_inet6.h" 68 #include "opt_ipsec.h" 69 #include "opt_tcpdebug.h" 70 #include "opt_tcp_input.h" 71 72 #include <sys/param.h> 73 #include <sys/systm.h> 74 #include <sys/kernel.h> 75 #include <sys/sysctl.h> 76 #include <sys/malloc.h> 77 #include <sys/mbuf.h> 78 #include <sys/proc.h> /* for proc0 declaration */ 79 #include <sys/protosw.h> 80 #include <sys/socket.h> 81 #include <sys/socketvar.h> 82 #include <sys/syslog.h> 83 #include <sys/in_cksum.h> 84 85 #include <sys/socketvar2.h> 86 87 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 88 #include <machine/stdarg.h> 89 90 #include <net/if.h> 91 #include <net/route.h> 92 93 #include <netinet/in.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 97 #include <netinet/in_var.h> 98 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 99 #include <netinet/in_pcb.h> 100 #include <netinet/ip_var.h> 101 #include <netinet/ip6.h> 102 #include <netinet/icmp6.h> 103 #include <netinet6/nd6.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/in6_pcb.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_seq.h> 109 #include <netinet/tcp_timer.h> 110 #include <netinet/tcp_timer2.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 115 #ifdef TCPDEBUG 116 #include <netinet/tcp_debug.h> 117 118 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 119 struct tcphdr tcp_savetcp; 120 #endif 121 122 #ifdef FAST_IPSEC 123 #include <netproto/ipsec/ipsec.h> 124 #include <netproto/ipsec/ipsec6.h> 125 #endif 126 127 #ifdef IPSEC 128 #include <netinet6/ipsec.h> 129 #include <netinet6/ipsec6.h> 130 #include <netproto/key/key.h> 131 #endif 132 133 /* 134 * Limit burst of new packets during SACK based fast recovery 135 * or extended limited transmit. 136 */ 137 #define TCP_SACK_MAXBURST 4 138 139 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 140 141 static int log_in_vain = 0; 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 143 &log_in_vain, 0, "Log all incoming TCP connections"); 144 145 static int blackhole = 0; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 147 &blackhole, 0, "Do not send RST when dropping refused connections"); 148 149 int tcp_delack_enabled = 1; 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 151 &tcp_delack_enabled, 0, 152 "Delay ACK to try and piggyback it onto a data packet"); 153 154 #ifdef TCP_DROP_SYNFIN 155 static int drop_synfin = 0; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 157 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 158 #endif 159 160 static int tcp_do_limitedtransmit = 1; 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 162 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 163 164 static int tcp_do_early_retransmit = 1; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 166 &tcp_do_early_retransmit, 0, "Early retransmit"); 167 168 int tcp_aggregate_acks = 1; 169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 170 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 171 172 static int tcp_do_eifel_detect = 1; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 174 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 175 176 static int tcp_do_abc = 1; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 178 &tcp_do_abc, 0, 179 "TCP Appropriate Byte Counting (RFC 3465)"); 180 181 /* 182 * The following value actually takes range [25ms, 250ms], 183 * given that most modern systems use 1ms ~ 10ms as the unit 184 * of timestamp option. 185 */ 186 static u_int tcp_paws_tolerance = 25; 187 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW, 188 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance"); 189 190 /* 191 * Define as tunable for easy testing with SACK on and off. 192 * Warning: do not change setting in the middle of an existing active TCP flow, 193 * else strange things might happen to that flow. 194 */ 195 int tcp_do_sack = 1; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 197 &tcp_do_sack, 0, "Enable SACK Algorithms"); 198 199 int tcp_do_smartsack = 1; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 201 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 202 203 int tcp_do_rescuesack = 1; 204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, 205 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); 206 207 int tcp_aggressive_rescuesack = 0; 208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, 209 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); 210 211 static int tcp_force_sackrxt = 1; 212 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW, 213 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst"); 214 215 int tcp_do_rfc6675 = 1; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW, 217 &tcp_do_rfc6675, 0, "Enable RFC6675"); 218 219 int tcp_rfc6675_rxt = 0; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW, 221 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit"); 222 223 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 224 "TCP Segment Reassembly Queue"); 225 226 int tcp_reass_maxseg = 0; 227 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 228 &tcp_reass_maxseg, 0, 229 "Global maximum number of TCP Segments in Reassembly Queue"); 230 231 int tcp_reass_qsize = 0; 232 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 233 &tcp_reass_qsize, 0, 234 "Global number of TCP Segments currently in Reassembly Queue"); 235 236 static int tcp_reass_overflows = 0; 237 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 238 &tcp_reass_overflows, 0, 239 "Global number of TCP Segment Reassembly Queue Overflows"); 240 241 int tcp_do_autorcvbuf = 1; 242 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 243 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 244 245 int tcp_autorcvbuf_inc = 16*1024; 246 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 247 &tcp_autorcvbuf_inc, 0, 248 "Incrementor step size of automatic receive buffer"); 249 250 int tcp_autorcvbuf_max = 2*1024*1024; 251 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 252 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 253 254 int tcp_sosend_agglim = 2; 255 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 256 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 257 258 int tcp_sosend_async = 1; 259 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 260 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 261 262 int tcp_sosend_jcluster = 1; 263 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_jcluster, CTLFLAG_RW, 264 &tcp_sosend_jcluster, 0, "TCP output uses jcluster"); 265 266 static int tcp_ignore_redun_dsack = 1; 267 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW, 268 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK"); 269 270 static int tcp_reuseport_ext = 1; 271 SYSCTL_INT(_net_inet_tcp, OID_AUTO, reuseport_ext, CTLFLAG_RW, 272 &tcp_reuseport_ext, 0, "SO_REUSEPORT extension"); 273 274 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, 275 tcp_seq); 276 static void tcp_pulloutofband(struct socket *, 277 struct tcphdr *, struct mbuf *, int); 278 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 279 struct mbuf *); 280 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); 281 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 282 static void tcp_sack_rexmt(struct tcpcb *, boolean_t); 283 static boolean_t tcp_sack_limitedxmit(struct tcpcb *); 284 static int tcp_rmx_msl(const struct tcpcb *); 285 static void tcp_established(struct tcpcb *); 286 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int); 287 288 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 289 #ifdef INET6 290 #define ND6_HINT(tp) \ 291 do { \ 292 if ((tp) && (tp)->t_inpcb && \ 293 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 294 (tp)->t_inpcb->in6p_route.ro_rt) \ 295 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 296 } while (0) 297 #else 298 #define ND6_HINT(tp) 299 #endif 300 301 /* 302 * Indicate whether this ack should be delayed. We can delay the ack if 303 * - delayed acks are enabled and 304 * - there is no delayed ack timer in progress and 305 * - our last ack wasn't a 0-sized window. We never want to delay 306 * the ack that opens up a 0-sized window. 307 */ 308 #define DELAY_ACK(tp) \ 309 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 310 !(tp->t_flags & TF_RXWIN0SENT)) 311 312 #define acceptable_window_update(tp, th, tiwin) \ 313 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 314 (tp->snd_wl1 == th->th_seq && \ 315 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 316 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 317 318 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 319 #define need_early_retransmit(tp, ownd) \ 320 (tcp_do_early_retransmit && \ 321 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \ 322 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \ 323 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \ 324 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \ 325 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg))) 326 327 /* 328 * Returns TRUE, if this segment can be merged with the last 329 * pending segment in the reassemble queue and this segment 330 * does not overlap with the pending segment immediately 331 * preceeding the last pending segment. 332 */ 333 static __inline boolean_t 334 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen) 335 { 336 const struct tseg_qent *last, *prev; 337 338 last = TAILQ_LAST(&tp->t_segq, tsegqe_head); 339 if (last == NULL) 340 return FALSE; 341 342 /* This segment comes immediately after the last pending segment */ 343 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) { 344 if (last->tqe_th->th_flags & TH_FIN) { 345 /* No segments should follow segment w/ FIN */ 346 return FALSE; 347 } 348 return TRUE; 349 } 350 351 if (th->th_seq + tlen != last->tqe_th->th_seq) 352 return FALSE; 353 /* This segment comes immediately before the last pending segment */ 354 355 prev = TAILQ_PREV(last, tsegqe_head, tqe_q); 356 if (prev == NULL) { 357 /* 358 * No pending preceeding segment, we assume this segment 359 * could be reassembled. 360 */ 361 return TRUE; 362 } 363 364 /* This segment does not overlap with the preceeding segment */ 365 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len)) 366 return TRUE; 367 368 return FALSE; 369 } 370 371 static __inline void 372 tcp_ncr_update_rxtthresh(struct tcpcb *tp) 373 { 374 int old_rxtthresh = tp->t_rxtthresh; 375 uint32_t ownd = tp->snd_max - tp->snd_una; 376 377 tp->t_rxtthresh = max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1)); 378 if (tp->t_rxtthresh != old_rxtthresh) { 379 tcp_sack_update_lostseq(&tp->scb, tp->snd_una, 380 tp->t_maxseg, tp->t_rxtthresh); 381 } 382 } 383 384 static int 385 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 386 { 387 struct tseg_qent *q; 388 struct tseg_qent *p = NULL; 389 struct tseg_qent *te; 390 struct socket *so = tp->t_inpcb->inp_socket; 391 int flags; 392 393 /* 394 * Call with th == NULL after become established to 395 * force pre-ESTABLISHED data up to user socket. 396 */ 397 if (th == NULL) 398 goto present; 399 400 /* 401 * Limit the number of segments in the reassembly queue to prevent 402 * holding on to too many segments (and thus running out of mbufs). 403 * Make sure to let the missing segment through which caused this 404 * queue. Always keep one global queue entry spare to be able to 405 * process the missing segment. 406 */ 407 if (th->th_seq != tp->rcv_nxt && 408 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 409 tcp_reass_overflows++; 410 tcpstat.tcps_rcvmemdrop++; 411 m_freem(m); 412 /* no SACK block to report */ 413 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 414 return (0); 415 } 416 417 /* Allocate a new queue entry. */ 418 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 419 if (te == NULL) { 420 tcpstat.tcps_rcvmemdrop++; 421 m_freem(m); 422 /* no SACK block to report */ 423 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 424 return (0); 425 } 426 atomic_add_int(&tcp_reass_qsize, 1); 427 428 if (th->th_flags & TH_FIN) 429 tp->t_flags |= TF_QUEDFIN; 430 431 /* 432 * Find a segment which begins after this one does. 433 */ 434 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) { 435 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 436 break; 437 p = q; 438 } 439 440 /* 441 * If there is a preceding segment, it may provide some of 442 * our data already. If so, drop the data from the incoming 443 * segment. If it provides all of our data, drop us. 444 */ 445 if (p != NULL) { 446 tcp_seq_diff_t i; 447 448 /* conversion to int (in i) handles seq wraparound */ 449 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 450 if (i > 0) { /* overlaps preceding segment */ 451 tp->sack_flags |= 452 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 453 /* enclosing block starts w/ preceding segment */ 454 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 455 if (i >= *tlenp) { 456 if (th->th_flags & TH_FIN) 457 p->tqe_th->th_flags |= TH_FIN; 458 459 /* preceding encloses incoming segment */ 460 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 461 p->tqe_th->th_seq + p->tqe_len, 462 p->tqe_th->th_flags); 463 tcpstat.tcps_rcvduppack++; 464 tcpstat.tcps_rcvdupbyte += *tlenp; 465 m_freem(m); 466 kfree(te, M_TSEGQ); 467 atomic_add_int(&tcp_reass_qsize, -1); 468 /* 469 * Try to present any queued data 470 * at the left window edge to the user. 471 * This is needed after the 3-WHS 472 * completes. 473 */ 474 goto present; /* ??? */ 475 } 476 m_adj(m, i); 477 *tlenp -= i; 478 th->th_seq += i; 479 /* incoming segment end is enclosing block end */ 480 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 481 th->th_seq + *tlenp, th->th_flags); 482 /* trim end of reported D-SACK block */ 483 tp->reportblk.rblk_end = th->th_seq; 484 } 485 } 486 tcpstat.tcps_rcvoopack++; 487 tcpstat.tcps_rcvoobyte += *tlenp; 488 489 /* 490 * While we overlap succeeding segments trim them or, 491 * if they are completely covered, dequeue them. 492 */ 493 while (q) { 494 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 495 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 496 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 497 struct tseg_qent *nq; 498 499 if (i <= 0) 500 break; 501 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 502 /* first time through */ 503 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 504 tp->encloseblk = tp->reportblk; 505 /* report trailing duplicate D-SACK segment */ 506 tp->reportblk.rblk_start = q->tqe_th->th_seq; 507 } 508 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) && 509 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 510 /* extend enclosing block if one exists */ 511 tp->encloseblk.rblk_end = qend_sack; 512 } 513 if (i < q->tqe_len) { 514 q->tqe_th->th_seq += i; 515 q->tqe_len -= i; 516 m_adj(q->tqe_m, i); 517 break; 518 } 519 520 if (q->tqe_th->th_flags & TH_FIN) 521 th->th_flags |= TH_FIN; 522 523 nq = TAILQ_NEXT(q, tqe_q); 524 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 525 m_freem(q->tqe_m); 526 kfree(q, M_TSEGQ); 527 atomic_add_int(&tcp_reass_qsize, -1); 528 q = nq; 529 } 530 531 /* Insert the new segment queue entry into place. */ 532 te->tqe_m = m; 533 te->tqe_th = th; 534 te->tqe_len = *tlenp; 535 536 /* check if can coalesce with following segment */ 537 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 538 tcp_seq tend_sack; 539 540 te->tqe_len += q->tqe_len; 541 if (q->tqe_th->th_flags & TH_FIN) 542 te->tqe_th->th_flags |= TH_FIN; 543 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len, 544 te->tqe_th->th_flags); 545 546 m_cat(te->tqe_m, q->tqe_m); 547 tp->encloseblk.rblk_end = tend_sack; 548 /* 549 * When not reporting a duplicate segment, use 550 * the larger enclosing block as the SACK block. 551 */ 552 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 553 tp->reportblk.rblk_end = tend_sack; 554 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 555 kfree(q, M_TSEGQ); 556 atomic_add_int(&tcp_reass_qsize, -1); 557 } 558 559 if (p == NULL) { 560 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q); 561 } else { 562 /* check if can coalesce with preceding segment */ 563 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 564 if (te->tqe_th->th_flags & TH_FIN) 565 p->tqe_th->th_flags |= TH_FIN; 566 p->tqe_len += te->tqe_len; 567 m_cat(p->tqe_m, te->tqe_m); 568 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 569 /* 570 * When not reporting a duplicate segment, use 571 * the larger enclosing block as the SACK block. 572 */ 573 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 574 tp->reportblk.rblk_start = p->tqe_th->th_seq; 575 kfree(te, M_TSEGQ); 576 atomic_add_int(&tcp_reass_qsize, -1); 577 } else { 578 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q); 579 } 580 } 581 582 present: 583 /* 584 * Present data to user, advancing rcv_nxt through 585 * completed sequence space. 586 */ 587 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 588 return (0); 589 q = TAILQ_FIRST(&tp->t_segq); 590 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 591 return (0); 592 tp->rcv_nxt += q->tqe_len; 593 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 594 /* no SACK block to report since ACK advanced */ 595 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 596 } 597 /* no enclosing block to report since ACK advanced */ 598 tp->sack_flags &= ~TSACK_F_ENCLOSESEG; 599 flags = q->tqe_th->th_flags & TH_FIN; 600 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 601 KASSERT(TAILQ_EMPTY(&tp->t_segq) || 602 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 603 ("segment not coalesced")); 604 if (so->so_state & SS_CANTRCVMORE) { 605 m_freem(q->tqe_m); 606 } else { 607 lwkt_gettoken(&so->so_rcv.ssb_token); 608 ssb_appendstream(&so->so_rcv, q->tqe_m); 609 lwkt_reltoken(&so->so_rcv.ssb_token); 610 } 611 kfree(q, M_TSEGQ); 612 atomic_add_int(&tcp_reass_qsize, -1); 613 ND6_HINT(tp); 614 sorwakeup(so); 615 return (flags); 616 } 617 618 /* 619 * TCP input routine, follows pages 65-76 of the 620 * protocol specification dated September, 1981 very closely. 621 */ 622 #ifdef INET6 623 int 624 tcp6_input(struct mbuf **mp, int *offp, int proto) 625 { 626 struct mbuf *m = *mp; 627 struct in6_ifaddr *ia6; 628 629 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 630 631 /* 632 * draft-itojun-ipv6-tcp-to-anycast 633 * better place to put this in? 634 */ 635 ia6 = ip6_getdstifaddr(m); 636 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 637 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 638 offsetof(struct ip6_hdr, ip6_dst)); 639 return (IPPROTO_DONE); 640 } 641 642 tcp_input(mp, offp, proto); 643 return (IPPROTO_DONE); 644 } 645 #endif 646 647 int 648 tcp_input(struct mbuf **mp, int *offp, int proto) 649 { 650 int off0; 651 struct tcphdr *th; 652 struct ip *ip = NULL; 653 struct ipovly *ipov; 654 struct inpcb *inp = NULL; 655 u_char *optp = NULL; 656 int optlen = 0; 657 int tlen, off; 658 int len = 0; 659 int drop_hdrlen; 660 struct tcpcb *tp = NULL; 661 int thflags; 662 struct socket *so = NULL; 663 int todrop, acked; 664 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE; 665 tcp_seq th_dupack = 0; /* XXX gcc warning */ 666 u_int to_flags = 0; /* XXX gcc warning */ 667 u_long tiwin; 668 int recvwin; 669 struct tcpopt to; /* options in this segment */ 670 struct sockaddr_in *next_hop = NULL; 671 int rstreason; /* For badport_bandlim accounting purposes */ 672 int cpu; 673 struct ip6_hdr *ip6 = NULL; 674 struct mbuf *m; 675 #ifdef INET6 676 boolean_t isipv6; 677 #else 678 const boolean_t isipv6 = FALSE; 679 #endif 680 #ifdef TCPDEBUG 681 short ostate = 0; 682 #endif 683 684 off0 = *offp; 685 m = *mp; 686 *mp = NULL; 687 688 tcpstat.tcps_rcvtotal++; 689 690 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 691 struct m_tag *mtag; 692 693 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 694 KKASSERT(mtag != NULL); 695 next_hop = m_tag_data(mtag); 696 } 697 698 #ifdef INET6 699 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 700 #endif 701 702 if (isipv6) { 703 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 704 ip6 = mtod(m, struct ip6_hdr *); 705 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 706 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 707 tcpstat.tcps_rcvbadsum++; 708 goto drop; 709 } 710 th = (struct tcphdr *)((caddr_t)ip6 + off0); 711 712 /* 713 * Be proactive about unspecified IPv6 address in source. 714 * As we use all-zero to indicate unbounded/unconnected pcb, 715 * unspecified IPv6 address can be used to confuse us. 716 * 717 * Note that packets with unspecified IPv6 destination is 718 * already dropped in ip6_input. 719 */ 720 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 721 /* XXX stat */ 722 goto drop; 723 } 724 } else { 725 /* 726 * Get IP and TCP header together in first mbuf. 727 * Note: IP leaves IP header in first mbuf. 728 */ 729 if (off0 > sizeof(struct ip)) { 730 ip_stripoptions(m); 731 off0 = sizeof(struct ip); 732 } 733 /* already checked and pulled up in ip_demux() */ 734 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 735 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 736 ip = mtod(m, struct ip *); 737 ipov = (struct ipovly *)ip; 738 th = (struct tcphdr *)((caddr_t)ip + off0); 739 tlen = ip->ip_len; 740 741 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 742 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 743 th->th_sum = m->m_pkthdr.csum_data; 744 else 745 th->th_sum = in_pseudo(ip->ip_src.s_addr, 746 ip->ip_dst.s_addr, 747 htonl(m->m_pkthdr.csum_data + 748 ip->ip_len + 749 IPPROTO_TCP)); 750 th->th_sum ^= 0xffff; 751 } else { 752 /* 753 * Checksum extended TCP header and data. 754 */ 755 len = sizeof(struct ip) + tlen; 756 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 757 ipov->ih_len = (u_short)tlen; 758 ipov->ih_len = htons(ipov->ih_len); 759 th->th_sum = in_cksum(m, len); 760 } 761 if (th->th_sum) { 762 tcpstat.tcps_rcvbadsum++; 763 goto drop; 764 } 765 #ifdef INET6 766 /* Re-initialization for later version check */ 767 ip->ip_v = IPVERSION; 768 #endif 769 } 770 771 /* 772 * Check that TCP offset makes sense, 773 * pull out TCP options and adjust length. XXX 774 */ 775 off = th->th_off << 2; 776 /* already checked and pulled up in ip_demux() */ 777 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 778 ("bad TCP data offset %d (tlen %d)", off, tlen)); 779 tlen -= off; /* tlen is used instead of ti->ti_len */ 780 if (off > sizeof(struct tcphdr)) { 781 if (isipv6) { 782 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 783 ip6 = mtod(m, struct ip6_hdr *); 784 th = (struct tcphdr *)((caddr_t)ip6 + off0); 785 } else { 786 /* already pulled up in ip_demux() */ 787 KASSERT(m->m_len >= sizeof(struct ip) + off, 788 ("TCP header and options not in one mbuf: " 789 "m_len %d, off %d", m->m_len, off)); 790 } 791 optlen = off - sizeof(struct tcphdr); 792 optp = (u_char *)(th + 1); 793 } 794 thflags = th->th_flags; 795 796 #ifdef TCP_DROP_SYNFIN 797 /* 798 * If the drop_synfin option is enabled, drop all packets with 799 * both the SYN and FIN bits set. This prevents e.g. nmap from 800 * identifying the TCP/IP stack. 801 * 802 * This is a violation of the TCP specification. 803 */ 804 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 805 goto drop; 806 #endif 807 808 /* 809 * Convert TCP protocol specific fields to host format. 810 */ 811 th->th_seq = ntohl(th->th_seq); 812 th->th_ack = ntohl(th->th_ack); 813 th->th_win = ntohs(th->th_win); 814 th->th_urp = ntohs(th->th_urp); 815 816 /* 817 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 818 * until after ip6_savecontrol() is called and before other functions 819 * which don't want those proto headers. 820 * Because ip6_savecontrol() is going to parse the mbuf to 821 * search for data to be passed up to user-land, it wants mbuf 822 * parameters to be unchanged. 823 * XXX: the call of ip6_savecontrol() has been obsoleted based on 824 * latest version of the advanced API (20020110). 825 */ 826 drop_hdrlen = off0 + off; 827 828 /* 829 * Locate pcb for segment. 830 */ 831 findpcb: 832 /* IPFIREWALL_FORWARD section */ 833 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 834 /* 835 * Transparently forwarded. Pretend to be the destination. 836 * already got one like this? 837 */ 838 cpu = mycpu->gd_cpuid; 839 inp = in_pcblookup_hash(&tcbinfo[cpu], 840 ip->ip_src, th->th_sport, 841 ip->ip_dst, th->th_dport, 842 0, m->m_pkthdr.rcvif); 843 if (!inp) { 844 /* 845 * It's new. Try to find the ambushing socket. 846 */ 847 848 /* 849 * The rest of the ipfw code stores the port in 850 * host order. XXX 851 * (The IP address is still in network order.) 852 */ 853 in_port_t dport = next_hop->sin_port ? 854 htons(next_hop->sin_port) : 855 th->th_dport; 856 857 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 858 next_hop->sin_addr.s_addr, dport); 859 inp = in_pcblookup_hash(&tcbinfo[cpu], 860 ip->ip_src, th->th_sport, 861 next_hop->sin_addr, dport, 862 1, m->m_pkthdr.rcvif); 863 } 864 } else { 865 if (isipv6) { 866 inp = in6_pcblookup_hash(&tcbinfo[0], 867 &ip6->ip6_src, th->th_sport, 868 &ip6->ip6_dst, th->th_dport, 869 1, m->m_pkthdr.rcvif); 870 } else { 871 cpu = mycpu->gd_cpuid; 872 inp = in_pcblookup_pkthash(&tcbinfo[cpu], 873 ip->ip_src, th->th_sport, 874 ip->ip_dst, th->th_dport, 875 1, m->m_pkthdr.rcvif, 876 tcp_reuseport_ext ? m : NULL); 877 } 878 } 879 880 /* 881 * If the state is CLOSED (i.e., TCB does not exist) then 882 * all data in the incoming segment is discarded. 883 * If the TCB exists but is in CLOSED state, it is embryonic, 884 * but should either do a listen or a connect soon. 885 */ 886 if (inp == NULL) { 887 if (log_in_vain) { 888 #ifdef INET6 889 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 890 #else 891 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 892 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 893 #endif 894 if (isipv6) { 895 strcpy(dbuf, "["); 896 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 897 strcat(dbuf, "]"); 898 strcpy(sbuf, "["); 899 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 900 strcat(sbuf, "]"); 901 } else { 902 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 903 strcpy(sbuf, inet_ntoa(ip->ip_src)); 904 } 905 switch (log_in_vain) { 906 case 1: 907 if (!(thflags & TH_SYN)) 908 break; 909 case 2: 910 log(LOG_INFO, 911 "Connection attempt to TCP %s:%d " 912 "from %s:%d flags:0x%02x\n", 913 dbuf, ntohs(th->th_dport), sbuf, 914 ntohs(th->th_sport), thflags); 915 break; 916 default: 917 break; 918 } 919 } 920 if (blackhole) { 921 switch (blackhole) { 922 case 1: 923 if (thflags & TH_SYN) 924 goto drop; 925 break; 926 case 2: 927 goto drop; 928 default: 929 goto drop; 930 } 931 } 932 rstreason = BANDLIM_RST_CLOSEDPORT; 933 goto dropwithreset; 934 } 935 936 #ifdef IPSEC 937 if (isipv6) { 938 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 939 ipsec6stat.in_polvio++; 940 goto drop; 941 } 942 } else { 943 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 944 ipsecstat.in_polvio++; 945 goto drop; 946 } 947 } 948 #endif 949 #ifdef FAST_IPSEC 950 if (isipv6) { 951 if (ipsec6_in_reject(m, inp)) 952 goto drop; 953 } else { 954 if (ipsec4_in_reject(m, inp)) 955 goto drop; 956 } 957 #endif 958 /* Check the minimum TTL for socket. */ 959 #ifdef INET6 960 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 961 goto drop; 962 #endif 963 964 tp = intotcpcb(inp); 965 if (tp == NULL) { 966 rstreason = BANDLIM_RST_CLOSEDPORT; 967 goto dropwithreset; 968 } 969 if (tp->t_state <= TCPS_CLOSED) 970 goto drop; 971 972 so = inp->inp_socket; 973 974 #ifdef TCPDEBUG 975 if (so->so_options & SO_DEBUG) { 976 ostate = tp->t_state; 977 if (isipv6) 978 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 979 else 980 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 981 tcp_savetcp = *th; 982 } 983 #endif 984 985 bzero(&to, sizeof to); 986 987 if (so->so_options & SO_ACCEPTCONN) { 988 struct in_conninfo inc; 989 990 #ifdef INET6 991 inc.inc_isipv6 = (isipv6 == TRUE); 992 #endif 993 if (isipv6) { 994 inc.inc6_faddr = ip6->ip6_src; 995 inc.inc6_laddr = ip6->ip6_dst; 996 inc.inc6_route.ro_rt = NULL; /* XXX */ 997 } else { 998 inc.inc_faddr = ip->ip_src; 999 inc.inc_laddr = ip->ip_dst; 1000 inc.inc_route.ro_rt = NULL; /* XXX */ 1001 } 1002 inc.inc_fport = th->th_sport; 1003 inc.inc_lport = th->th_dport; 1004 1005 /* 1006 * If the state is LISTEN then ignore segment if it contains 1007 * a RST. If the segment contains an ACK then it is bad and 1008 * send a RST. If it does not contain a SYN then it is not 1009 * interesting; drop it. 1010 * 1011 * If the state is SYN_RECEIVED (syncache) and seg contains 1012 * an ACK, but not for our SYN/ACK, send a RST. If the seg 1013 * contains a RST, check the sequence number to see if it 1014 * is a valid reset segment. 1015 */ 1016 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 1017 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 1018 if (!syncache_expand(&inc, th, &so, m)) { 1019 /* 1020 * No syncache entry, or ACK was not 1021 * for our SYN/ACK. Send a RST. 1022 */ 1023 tcpstat.tcps_badsyn++; 1024 rstreason = BANDLIM_RST_OPENPORT; 1025 goto dropwithreset; 1026 } 1027 1028 /* 1029 * Could not complete 3-way handshake, 1030 * connection is being closed down, and 1031 * syncache will free mbuf. 1032 */ 1033 if (so == NULL) 1034 return(IPPROTO_DONE); 1035 1036 /* 1037 * We must be in the correct protocol thread 1038 * for this connection. 1039 */ 1040 KKASSERT(so->so_port == &curthread->td_msgport); 1041 1042 /* 1043 * Socket is created in state SYN_RECEIVED. 1044 * Continue processing segment. 1045 */ 1046 inp = so->so_pcb; 1047 tp = intotcpcb(inp); 1048 /* 1049 * This is what would have happened in 1050 * tcp_output() when the SYN,ACK was sent. 1051 */ 1052 tp->snd_up = tp->snd_una; 1053 tp->snd_max = tp->snd_nxt = tp->iss + 1; 1054 tp->last_ack_sent = tp->rcv_nxt; 1055 1056 goto after_listen; 1057 } 1058 if (thflags & TH_RST) { 1059 syncache_chkrst(&inc, th); 1060 goto drop; 1061 } 1062 if (thflags & TH_ACK) { 1063 syncache_badack(&inc); 1064 tcpstat.tcps_badsyn++; 1065 rstreason = BANDLIM_RST_OPENPORT; 1066 goto dropwithreset; 1067 } 1068 goto drop; 1069 } 1070 1071 /* 1072 * Segment's flags are (SYN) or (SYN | FIN). 1073 */ 1074 #ifdef INET6 1075 /* 1076 * If deprecated address is forbidden, 1077 * we do not accept SYN to deprecated interface 1078 * address to prevent any new inbound connection from 1079 * getting established. 1080 * When we do not accept SYN, we send a TCP RST, 1081 * with deprecated source address (instead of dropping 1082 * it). We compromise it as it is much better for peer 1083 * to send a RST, and RST will be the final packet 1084 * for the exchange. 1085 * 1086 * If we do not forbid deprecated addresses, we accept 1087 * the SYN packet. RFC2462 does not suggest dropping 1088 * SYN in this case. 1089 * If we decipher RFC2462 5.5.4, it says like this: 1090 * 1. use of deprecated addr with existing 1091 * communication is okay - "SHOULD continue to be 1092 * used" 1093 * 2. use of it with new communication: 1094 * (2a) "SHOULD NOT be used if alternate address 1095 * with sufficient scope is available" 1096 * (2b) nothing mentioned otherwise. 1097 * Here we fall into (2b) case as we have no choice in 1098 * our source address selection - we must obey the peer. 1099 * 1100 * The wording in RFC2462 is confusing, and there are 1101 * multiple description text for deprecated address 1102 * handling - worse, they are not exactly the same. 1103 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1104 */ 1105 if (isipv6 && !ip6_use_deprecated) { 1106 struct in6_ifaddr *ia6; 1107 1108 if ((ia6 = ip6_getdstifaddr(m)) && 1109 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1110 tp = NULL; 1111 rstreason = BANDLIM_RST_OPENPORT; 1112 goto dropwithreset; 1113 } 1114 } 1115 #endif 1116 /* 1117 * If it is from this socket, drop it, it must be forged. 1118 * Don't bother responding if the destination was a broadcast. 1119 */ 1120 if (th->th_dport == th->th_sport) { 1121 if (isipv6) { 1122 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1123 &ip6->ip6_src)) 1124 goto drop; 1125 } else { 1126 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1127 goto drop; 1128 } 1129 } 1130 /* 1131 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1132 * 1133 * Note that it is quite possible to receive unicast 1134 * link-layer packets with a broadcast IP address. Use 1135 * in_broadcast() to find them. 1136 */ 1137 if (m->m_flags & (M_BCAST | M_MCAST)) 1138 goto drop; 1139 if (isipv6) { 1140 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1141 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1142 goto drop; 1143 } else { 1144 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1145 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1146 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1147 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1148 goto drop; 1149 } 1150 /* 1151 * SYN appears to be valid; create compressed TCP state 1152 * for syncache, or perform t/tcp connection. 1153 */ 1154 if (so->so_qlen <= so->so_qlimit) { 1155 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); 1156 if (!syncache_add(&inc, &to, th, so, m)) 1157 goto drop; 1158 1159 /* 1160 * Entry added to syncache, mbuf used to 1161 * send SYN,ACK packet. 1162 */ 1163 return(IPPROTO_DONE); 1164 } 1165 goto drop; 1166 } 1167 1168 after_listen: 1169 /* 1170 * Should not happen - syncache should pick up these connections. 1171 * 1172 * Once we are past handling listen sockets we must be in the 1173 * correct protocol processing thread. 1174 */ 1175 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1176 KKASSERT(so->so_port == &curthread->td_msgport); 1177 1178 /* Unscale the window into a 32-bit value. */ 1179 if (!(thflags & TH_SYN)) 1180 tiwin = th->th_win << tp->snd_scale; 1181 else 1182 tiwin = th->th_win; 1183 1184 /* 1185 * This is the second part of the MSS DoS prevention code (after 1186 * minmss on the sending side) and it deals with too many too small 1187 * tcp packets in a too short timeframe (1 second). 1188 * 1189 * XXX Removed. This code was crap. It does not scale to network 1190 * speed, and default values break NFS. Gone. 1191 */ 1192 /* REMOVED */ 1193 1194 /* 1195 * Segment received on connection. 1196 * 1197 * Reset idle time and keep-alive timer. Don't waste time if less 1198 * then a second has elapsed. 1199 */ 1200 if ((int)(ticks - tp->t_rcvtime) > hz) 1201 tcp_timer_keep_activity(tp, thflags); 1202 1203 /* 1204 * Process options. 1205 * XXX this is tradtitional behavior, may need to be cleaned up. 1206 */ 1207 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); 1208 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1209 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { 1210 tp->t_flags |= TF_RCVD_SCALE; 1211 tp->snd_scale = to.to_requested_s_scale; 1212 } 1213 1214 /* 1215 * Initial send window; will be updated upon next ACK 1216 */ 1217 tp->snd_wnd = th->th_win; 1218 1219 if (to.to_flags & TOF_TS) { 1220 tp->t_flags |= TF_RCVD_TSTMP; 1221 tp->ts_recent = to.to_tsval; 1222 tp->ts_recent_age = ticks; 1223 } 1224 if (!(to.to_flags & TOF_MSS)) 1225 to.to_mss = 0; 1226 tcp_mss(tp, to.to_mss); 1227 /* 1228 * Only set the TF_SACK_PERMITTED per-connection flag 1229 * if we got a SACK_PERMITTED option from the other side 1230 * and the global tcp_do_sack variable is true. 1231 */ 1232 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1233 tp->t_flags |= TF_SACK_PERMITTED; 1234 } 1235 1236 /* 1237 * Header prediction: check for the two common cases 1238 * of a uni-directional data xfer. If the packet has 1239 * no control flags, is in-sequence, the window didn't 1240 * change and we're not retransmitting, it's a 1241 * candidate. If the length is zero and the ack moved 1242 * forward, we're the sender side of the xfer. Just 1243 * free the data acked & wake any higher level process 1244 * that was blocked waiting for space. If the length 1245 * is non-zero and the ack didn't move, we're the 1246 * receiver side. If we're getting packets in-order 1247 * (the reassembly queue is empty), add the data to 1248 * the socket buffer and note that we need a delayed ack. 1249 * Make sure that the hidden state-flags are also off. 1250 * Since we check for TCPS_ESTABLISHED above, it can only 1251 * be TH_NEEDSYN. 1252 */ 1253 if (tp->t_state == TCPS_ESTABLISHED && 1254 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1255 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1256 (!(to.to_flags & TOF_TS) || 1257 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1258 th->th_seq == tp->rcv_nxt && 1259 tp->snd_nxt == tp->snd_max) { 1260 1261 /* 1262 * If last ACK falls within this segment's sequence numbers, 1263 * record the timestamp. 1264 * NOTE that the test is modified according to the latest 1265 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1266 */ 1267 if ((to.to_flags & TOF_TS) && 1268 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1269 tp->ts_recent_age = ticks; 1270 tp->ts_recent = to.to_tsval; 1271 } 1272 1273 if (tlen == 0) { 1274 if (SEQ_GT(th->th_ack, tp->snd_una) && 1275 SEQ_LEQ(th->th_ack, tp->snd_max) && 1276 tp->snd_cwnd >= tp->snd_wnd && 1277 !IN_FASTRECOVERY(tp)) { 1278 /* 1279 * This is a pure ack for outstanding data. 1280 */ 1281 ++tcpstat.tcps_predack; 1282 /* 1283 * "bad retransmit" recovery 1284 * 1285 * If Eifel detection applies, then 1286 * it is deterministic, so use it 1287 * unconditionally over the old heuristic. 1288 * Otherwise, fall back to the old heuristic. 1289 */ 1290 if (tcp_do_eifel_detect && 1291 (to.to_flags & TOF_TS) && to.to_tsecr && 1292 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 1293 /* Eifel detection applicable. */ 1294 if (to.to_tsecr < tp->t_rexmtTS) { 1295 tcp_revert_congestion_state(tp); 1296 ++tcpstat.tcps_eifeldetected; 1297 if (tp->t_rxtshift != 1 || 1298 ticks >= tp->t_badrxtwin) 1299 ++tcpstat.tcps_rttcantdetect; 1300 } 1301 } else if (tp->t_rxtshift == 1 && 1302 ticks < tp->t_badrxtwin) { 1303 tcp_revert_congestion_state(tp); 1304 ++tcpstat.tcps_rttdetected; 1305 } 1306 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 1307 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 1308 /* 1309 * Recalculate the retransmit timer / rtt. 1310 * 1311 * Some machines (certain windows boxes) 1312 * send broken timestamp replies during the 1313 * SYN+ACK phase, ignore timestamps of 0. 1314 */ 1315 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1316 tcp_xmit_timer(tp, 1317 ticks - to.to_tsecr + 1, 1318 th->th_ack); 1319 } else if (tp->t_rtttime && 1320 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1321 tcp_xmit_timer(tp, 1322 ticks - tp->t_rtttime, 1323 th->th_ack); 1324 } 1325 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1326 acked = th->th_ack - tp->snd_una; 1327 tcpstat.tcps_rcvackpack++; 1328 tcpstat.tcps_rcvackbyte += acked; 1329 sbdrop(&so->so_snd.sb, acked); 1330 tp->snd_recover = th->th_ack - 1; 1331 tp->snd_una = th->th_ack; 1332 tp->t_dupacks = 0; 1333 /* 1334 * Update window information. 1335 */ 1336 if (tiwin != tp->snd_wnd && 1337 acceptable_window_update(tp, th, tiwin)) { 1338 /* keep track of pure window updates */ 1339 if (tp->snd_wl2 == th->th_ack && 1340 tiwin > tp->snd_wnd) 1341 tcpstat.tcps_rcvwinupd++; 1342 tp->snd_wnd = tiwin; 1343 tp->snd_wl1 = th->th_seq; 1344 tp->snd_wl2 = th->th_ack; 1345 if (tp->snd_wnd > tp->max_sndwnd) 1346 tp->max_sndwnd = tp->snd_wnd; 1347 } 1348 m_freem(m); 1349 ND6_HINT(tp); /* some progress has been done */ 1350 /* 1351 * If all outstanding data are acked, stop 1352 * retransmit timer, otherwise restart timer 1353 * using current (possibly backed-off) value. 1354 * If process is waiting for space, 1355 * wakeup/selwakeup/signal. If data 1356 * are ready to send, let tcp_output 1357 * decide between more output or persist. 1358 */ 1359 if (tp->snd_una == tp->snd_max) { 1360 tcp_callout_stop(tp, tp->tt_rexmt); 1361 } else if (!tcp_callout_active(tp, 1362 tp->tt_persist)) { 1363 tcp_callout_reset(tp, tp->tt_rexmt, 1364 tp->t_rxtcur, tcp_timer_rexmt); 1365 } 1366 sowwakeup(so); 1367 if (so->so_snd.ssb_cc > 0 && 1368 !tcp_output_pending(tp)) 1369 tcp_output_fair(tp); 1370 return(IPPROTO_DONE); 1371 } 1372 } else if (tiwin == tp->snd_wnd && 1373 th->th_ack == tp->snd_una && 1374 TAILQ_EMPTY(&tp->t_segq) && 1375 tlen <= ssb_space(&so->so_rcv)) { 1376 u_long newsize = 0; /* automatic sockbuf scaling */ 1377 /* 1378 * This is a pure, in-sequence data packet 1379 * with nothing on the reassembly queue and 1380 * we have enough buffer space to take it. 1381 */ 1382 ++tcpstat.tcps_preddat; 1383 tp->rcv_nxt += tlen; 1384 tcpstat.tcps_rcvpack++; 1385 tcpstat.tcps_rcvbyte += tlen; 1386 ND6_HINT(tp); /* some progress has been done */ 1387 /* 1388 * Automatic sizing of receive socket buffer. Often the send 1389 * buffer size is not optimally adjusted to the actual network 1390 * conditions at hand (delay bandwidth product). Setting the 1391 * buffer size too small limits throughput on links with high 1392 * bandwidth and high delay (eg. trans-continental/oceanic links). 1393 * 1394 * On the receive side the socket buffer memory is only rarely 1395 * used to any significant extent. This allows us to be much 1396 * more aggressive in scaling the receive socket buffer. For 1397 * the case that the buffer space is actually used to a large 1398 * extent and we run out of kernel memory we can simply drop 1399 * the new segments; TCP on the sender will just retransmit it 1400 * later. Setting the buffer size too big may only consume too 1401 * much kernel memory if the application doesn't read() from 1402 * the socket or packet loss or reordering makes use of the 1403 * reassembly queue. 1404 * 1405 * The criteria to step up the receive buffer one notch are: 1406 * 1. the number of bytes received during the time it takes 1407 * one timestamp to be reflected back to us (the RTT); 1408 * 2. received bytes per RTT is within seven eighth of the 1409 * current socket buffer size; 1410 * 3. receive buffer size has not hit maximal automatic size; 1411 * 1412 * This algorithm does one step per RTT at most and only if 1413 * we receive a bulk stream w/o packet losses or reorderings. 1414 * Shrinking the buffer during idle times is not necessary as 1415 * it doesn't consume any memory when idle. 1416 * 1417 * TODO: Only step up if the application is actually serving 1418 * the buffer to better manage the socket buffer resources. 1419 */ 1420 if (tcp_do_autorcvbuf && 1421 to.to_tsecr && 1422 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1423 if (to.to_tsecr > tp->rfbuf_ts && 1424 to.to_tsecr - tp->rfbuf_ts < hz) { 1425 if (tp->rfbuf_cnt > 1426 (so->so_rcv.ssb_hiwat / 8 * 7) && 1427 so->so_rcv.ssb_hiwat < 1428 tcp_autorcvbuf_max) { 1429 newsize = 1430 ulmin(so->so_rcv.ssb_hiwat + 1431 tcp_autorcvbuf_inc, 1432 tcp_autorcvbuf_max); 1433 } 1434 /* Start over with next RTT. */ 1435 tp->rfbuf_ts = 0; 1436 tp->rfbuf_cnt = 0; 1437 } else 1438 tp->rfbuf_cnt += tlen; /* add up */ 1439 } 1440 /* 1441 * Add data to socket buffer. 1442 */ 1443 if (so->so_state & SS_CANTRCVMORE) { 1444 m_freem(m); 1445 } else { 1446 /* 1447 * Set new socket buffer size, give up when 1448 * limit is reached. 1449 * 1450 * Adjusting the size can mess up ACK 1451 * sequencing when pure window updates are 1452 * being avoided (which is the default), 1453 * so force an ack. 1454 */ 1455 lwkt_gettoken(&so->so_rcv.ssb_token); 1456 if (newsize) { 1457 tp->t_flags |= TF_RXRESIZED; 1458 if (!ssb_reserve(&so->so_rcv, newsize, 1459 so, NULL)) { 1460 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1461 } 1462 if (newsize >= 1463 (TCP_MAXWIN << tp->rcv_scale)) { 1464 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1465 } 1466 } 1467 m_adj(m, drop_hdrlen); /* delayed header drop */ 1468 ssb_appendstream(&so->so_rcv, m); 1469 lwkt_reltoken(&so->so_rcv.ssb_token); 1470 } 1471 sorwakeup(so); 1472 /* 1473 * This code is responsible for most of the ACKs 1474 * the TCP stack sends back after receiving a data 1475 * packet. Note that the DELAY_ACK check fails if 1476 * the delack timer is already running, which results 1477 * in an ack being sent every other packet (which is 1478 * what we want). 1479 * 1480 * We then further aggregate acks by not actually 1481 * sending one until the protocol thread has completed 1482 * processing the current backlog of packets. This 1483 * does not delay the ack any further, but allows us 1484 * to take advantage of the packet aggregation that 1485 * high speed NICs do (usually blocks of 8-10 packets) 1486 * to send a single ack rather then four or five acks, 1487 * greatly reducing the ack rate, the return channel 1488 * bandwidth, and the protocol overhead on both ends. 1489 * 1490 * Since this also has the effect of slowing down 1491 * the exponential slow-start ramp-up, systems with 1492 * very large bandwidth-delay products might want 1493 * to turn the feature off. 1494 */ 1495 if (DELAY_ACK(tp)) { 1496 tcp_callout_reset(tp, tp->tt_delack, 1497 tcp_delacktime, tcp_timer_delack); 1498 } else if (tcp_aggregate_acks) { 1499 tp->t_flags |= TF_ACKNOW; 1500 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1501 tp->t_flags |= TF_ONOUTPUTQ; 1502 tp->tt_cpu = mycpu->gd_cpuid; 1503 TAILQ_INSERT_TAIL( 1504 &tcpcbackq[tp->tt_cpu], 1505 tp, t_outputq); 1506 } 1507 } else { 1508 tp->t_flags |= TF_ACKNOW; 1509 tcp_output(tp); 1510 } 1511 return(IPPROTO_DONE); 1512 } 1513 } 1514 1515 /* 1516 * Calculate amount of space in receive window, 1517 * and then do TCP input processing. 1518 * Receive window is amount of space in rcv queue, 1519 * but not less than advertised window. 1520 */ 1521 recvwin = ssb_space(&so->so_rcv); 1522 if (recvwin < 0) 1523 recvwin = 0; 1524 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1525 1526 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1527 tp->rfbuf_ts = 0; 1528 tp->rfbuf_cnt = 0; 1529 1530 switch (tp->t_state) { 1531 /* 1532 * If the state is SYN_RECEIVED: 1533 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1534 */ 1535 case TCPS_SYN_RECEIVED: 1536 if ((thflags & TH_ACK) && 1537 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1538 SEQ_GT(th->th_ack, tp->snd_max))) { 1539 rstreason = BANDLIM_RST_OPENPORT; 1540 goto dropwithreset; 1541 } 1542 break; 1543 1544 /* 1545 * If the state is SYN_SENT: 1546 * if seg contains an ACK, but not for our SYN, drop the input. 1547 * if seg contains a RST, then drop the connection. 1548 * if seg does not contain SYN, then drop it. 1549 * Otherwise this is an acceptable SYN segment 1550 * initialize tp->rcv_nxt and tp->irs 1551 * if seg contains ack then advance tp->snd_una 1552 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1553 * arrange for segment to be acked (eventually) 1554 * continue processing rest of data/controls, beginning with URG 1555 */ 1556 case TCPS_SYN_SENT: 1557 if ((thflags & TH_ACK) && 1558 (SEQ_LEQ(th->th_ack, tp->iss) || 1559 SEQ_GT(th->th_ack, tp->snd_max))) { 1560 rstreason = BANDLIM_UNLIMITED; 1561 goto dropwithreset; 1562 } 1563 if (thflags & TH_RST) { 1564 if (thflags & TH_ACK) 1565 tp = tcp_drop(tp, ECONNREFUSED); 1566 goto drop; 1567 } 1568 if (!(thflags & TH_SYN)) 1569 goto drop; 1570 1571 tp->irs = th->th_seq; 1572 tcp_rcvseqinit(tp); 1573 if (thflags & TH_ACK) { 1574 /* Our SYN was acked. */ 1575 tcpstat.tcps_connects++; 1576 soisconnected(so); 1577 /* Do window scaling on this connection? */ 1578 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1579 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1580 tp->rcv_scale = tp->request_r_scale; 1581 tp->rcv_adv += tp->rcv_wnd; 1582 tp->snd_una++; /* SYN is acked */ 1583 tcp_callout_stop(tp, tp->tt_rexmt); 1584 /* 1585 * If there's data, delay ACK; if there's also a FIN 1586 * ACKNOW will be turned on later. 1587 */ 1588 if (DELAY_ACK(tp) && tlen != 0) { 1589 tcp_callout_reset(tp, tp->tt_delack, 1590 tcp_delacktime, tcp_timer_delack); 1591 } else { 1592 tp->t_flags |= TF_ACKNOW; 1593 } 1594 /* 1595 * Received <SYN,ACK> in SYN_SENT[*] state. 1596 * Transitions: 1597 * SYN_SENT --> ESTABLISHED 1598 * SYN_SENT* --> FIN_WAIT_1 1599 */ 1600 tp->t_starttime = ticks; 1601 if (tp->t_flags & TF_NEEDFIN) { 1602 tp->t_state = TCPS_FIN_WAIT_1; 1603 tp->t_flags &= ~TF_NEEDFIN; 1604 thflags &= ~TH_SYN; 1605 } else { 1606 tcp_established(tp); 1607 } 1608 } else { 1609 /* 1610 * Received initial SYN in SYN-SENT[*] state => 1611 * simultaneous open. 1612 * Do 3-way handshake: 1613 * SYN-SENT -> SYN-RECEIVED 1614 * SYN-SENT* -> SYN-RECEIVED* 1615 */ 1616 tp->t_flags |= TF_ACKNOW; 1617 tcp_callout_stop(tp, tp->tt_rexmt); 1618 tp->t_state = TCPS_SYN_RECEIVED; 1619 } 1620 1621 /* 1622 * Advance th->th_seq to correspond to first data byte. 1623 * If data, trim to stay within window, 1624 * dropping FIN if necessary. 1625 */ 1626 th->th_seq++; 1627 if (tlen > tp->rcv_wnd) { 1628 todrop = tlen - tp->rcv_wnd; 1629 m_adj(m, -todrop); 1630 tlen = tp->rcv_wnd; 1631 thflags &= ~TH_FIN; 1632 tcpstat.tcps_rcvpackafterwin++; 1633 tcpstat.tcps_rcvbyteafterwin += todrop; 1634 } 1635 tp->snd_wl1 = th->th_seq - 1; 1636 tp->rcv_up = th->th_seq; 1637 /* 1638 * Client side of transaction: already sent SYN and data. 1639 * If the remote host used T/TCP to validate the SYN, 1640 * our data will be ACK'd; if so, enter normal data segment 1641 * processing in the middle of step 5, ack processing. 1642 * Otherwise, goto step 6. 1643 */ 1644 if (thflags & TH_ACK) 1645 goto process_ACK; 1646 1647 goto step6; 1648 1649 /* 1650 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1651 * do normal processing (we no longer bother with T/TCP). 1652 */ 1653 case TCPS_LAST_ACK: 1654 case TCPS_CLOSING: 1655 case TCPS_TIME_WAIT: 1656 break; /* continue normal processing */ 1657 } 1658 1659 /* 1660 * States other than LISTEN or SYN_SENT. 1661 * First check the RST flag and sequence number since reset segments 1662 * are exempt from the timestamp and connection count tests. This 1663 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1664 * below which allowed reset segments in half the sequence space 1665 * to fall though and be processed (which gives forged reset 1666 * segments with a random sequence number a 50 percent chance of 1667 * killing a connection). 1668 * Then check timestamp, if present. 1669 * Then check the connection count, if present. 1670 * Then check that at least some bytes of segment are within 1671 * receive window. If segment begins before rcv_nxt, 1672 * drop leading data (and SYN); if nothing left, just ack. 1673 * 1674 * 1675 * If the RST bit is set, check the sequence number to see 1676 * if this is a valid reset segment. 1677 * RFC 793 page 37: 1678 * In all states except SYN-SENT, all reset (RST) segments 1679 * are validated by checking their SEQ-fields. A reset is 1680 * valid if its sequence number is in the window. 1681 * Note: this does not take into account delayed ACKs, so 1682 * we should test against last_ack_sent instead of rcv_nxt. 1683 * The sequence number in the reset segment is normally an 1684 * echo of our outgoing acknowledgement numbers, but some hosts 1685 * send a reset with the sequence number at the rightmost edge 1686 * of our receive window, and we have to handle this case. 1687 * If we have multiple segments in flight, the intial reset 1688 * segment sequence numbers will be to the left of last_ack_sent, 1689 * but they will eventually catch up. 1690 * In any case, it never made sense to trim reset segments to 1691 * fit the receive window since RFC 1122 says: 1692 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1693 * 1694 * A TCP SHOULD allow a received RST segment to include data. 1695 * 1696 * DISCUSSION 1697 * It has been suggested that a RST segment could contain 1698 * ASCII text that encoded and explained the cause of the 1699 * RST. No standard has yet been established for such 1700 * data. 1701 * 1702 * If the reset segment passes the sequence number test examine 1703 * the state: 1704 * SYN_RECEIVED STATE: 1705 * If passive open, return to LISTEN state. 1706 * If active open, inform user that connection was refused. 1707 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1708 * Inform user that connection was reset, and close tcb. 1709 * CLOSING, LAST_ACK STATES: 1710 * Close the tcb. 1711 * TIME_WAIT STATE: 1712 * Drop the segment - see Stevens, vol. 2, p. 964 and 1713 * RFC 1337. 1714 */ 1715 if (thflags & TH_RST) { 1716 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1717 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1718 switch (tp->t_state) { 1719 1720 case TCPS_SYN_RECEIVED: 1721 so->so_error = ECONNREFUSED; 1722 goto close; 1723 1724 case TCPS_ESTABLISHED: 1725 case TCPS_FIN_WAIT_1: 1726 case TCPS_FIN_WAIT_2: 1727 case TCPS_CLOSE_WAIT: 1728 so->so_error = ECONNRESET; 1729 close: 1730 tp->t_state = TCPS_CLOSED; 1731 tcpstat.tcps_drops++; 1732 tp = tcp_close(tp); 1733 break; 1734 1735 case TCPS_CLOSING: 1736 case TCPS_LAST_ACK: 1737 tp = tcp_close(tp); 1738 break; 1739 1740 case TCPS_TIME_WAIT: 1741 break; 1742 } 1743 } 1744 goto drop; 1745 } 1746 1747 /* 1748 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1749 * and it's less than ts_recent, drop it. 1750 */ 1751 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1752 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1753 /* Check to see if ts_recent is over 24 days old. */ 1754 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1755 /* 1756 * Invalidate ts_recent. If this segment updates 1757 * ts_recent, the age will be reset later and ts_recent 1758 * will get a valid value. If it does not, setting 1759 * ts_recent to zero will at least satisfy the 1760 * requirement that zero be placed in the timestamp 1761 * echo reply when ts_recent isn't valid. The 1762 * age isn't reset until we get a valid ts_recent 1763 * because we don't want out-of-order segments to be 1764 * dropped when ts_recent is old. 1765 */ 1766 tp->ts_recent = 0; 1767 } else if (tcp_paws_tolerance && tlen != 0 && 1768 tp->t_state == TCPS_ESTABLISHED && 1769 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&& 1770 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1771 th->th_ack == tp->snd_una && 1772 tiwin == tp->snd_wnd && 1773 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&& 1774 (th->th_seq == tp->rcv_nxt || 1775 (SEQ_GT(th->th_seq, tp->rcv_nxt) && 1776 tcp_paws_canreasslast(tp, th, tlen)))) { 1777 /* 1778 * This tends to prevent valid new segments from being 1779 * dropped by the reordered segments sent by the fast 1780 * retransmission algorithm on the sending side, i.e. 1781 * the fast retransmitted segment w/ larger timestamp 1782 * arrives earlier than the previously sent new segments 1783 * w/ smaller timestamp. 1784 * 1785 * If following conditions are met, the segment is 1786 * accepted: 1787 * - The segment contains data 1788 * - The connection is established 1789 * - The header does not contain important flags 1790 * - SYN or FIN is not needed 1791 * - It does not acknowledge new data 1792 * - Receive window is not changed 1793 * - The timestamp is within "acceptable" range 1794 * - The new segment is what we are expecting or 1795 * the new segment could be merged w/ the last 1796 * pending segment on the reassemble queue 1797 */ 1798 tcpstat.tcps_pawsaccept++; 1799 tcpstat.tcps_pawsdrop++; 1800 } else { 1801 tcpstat.tcps_rcvduppack++; 1802 tcpstat.tcps_rcvdupbyte += tlen; 1803 tcpstat.tcps_pawsdrop++; 1804 if (tlen) 1805 goto dropafterack; 1806 goto drop; 1807 } 1808 } 1809 1810 /* 1811 * In the SYN-RECEIVED state, validate that the packet belongs to 1812 * this connection before trimming the data to fit the receive 1813 * window. Check the sequence number versus IRS since we know 1814 * the sequence numbers haven't wrapped. This is a partial fix 1815 * for the "LAND" DoS attack. 1816 */ 1817 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1818 rstreason = BANDLIM_RST_OPENPORT; 1819 goto dropwithreset; 1820 } 1821 1822 todrop = tp->rcv_nxt - th->th_seq; 1823 if (todrop > 0) { 1824 if (TCP_DO_SACK(tp)) { 1825 /* Report duplicate segment at head of packet. */ 1826 tp->reportblk.rblk_start = th->th_seq; 1827 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1828 th->th_seq + tlen, thflags); 1829 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1830 tp->reportblk.rblk_end = tp->rcv_nxt; 1831 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT); 1832 tp->t_flags |= TF_ACKNOW; 1833 } 1834 if (thflags & TH_SYN) { 1835 thflags &= ~TH_SYN; 1836 th->th_seq++; 1837 if (th->th_urp > 1) 1838 th->th_urp--; 1839 else 1840 thflags &= ~TH_URG; 1841 todrop--; 1842 } 1843 /* 1844 * Following if statement from Stevens, vol. 2, p. 960. 1845 */ 1846 if (todrop > tlen || 1847 (todrop == tlen && !(thflags & TH_FIN))) { 1848 /* 1849 * Any valid FIN must be to the left of the window. 1850 * At this point the FIN must be a duplicate or out 1851 * of sequence; drop it. 1852 */ 1853 thflags &= ~TH_FIN; 1854 1855 /* 1856 * Send an ACK to resynchronize and drop any data. 1857 * But keep on processing for RST or ACK. 1858 */ 1859 tp->t_flags |= TF_ACKNOW; 1860 todrop = tlen; 1861 tcpstat.tcps_rcvduppack++; 1862 tcpstat.tcps_rcvdupbyte += todrop; 1863 } else { 1864 tcpstat.tcps_rcvpartduppack++; 1865 tcpstat.tcps_rcvpartdupbyte += todrop; 1866 } 1867 drop_hdrlen += todrop; /* drop from the top afterwards */ 1868 th->th_seq += todrop; 1869 tlen -= todrop; 1870 if (th->th_urp > todrop) 1871 th->th_urp -= todrop; 1872 else { 1873 thflags &= ~TH_URG; 1874 th->th_urp = 0; 1875 } 1876 } 1877 1878 /* 1879 * If new data are received on a connection after the 1880 * user processes are gone, then RST the other end. 1881 */ 1882 if ((so->so_state & SS_NOFDREF) && 1883 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1884 tp = tcp_close(tp); 1885 tcpstat.tcps_rcvafterclose++; 1886 rstreason = BANDLIM_UNLIMITED; 1887 goto dropwithreset; 1888 } 1889 1890 /* 1891 * If segment ends after window, drop trailing data 1892 * (and PUSH and FIN); if nothing left, just ACK. 1893 */ 1894 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1895 if (todrop > 0) { 1896 tcpstat.tcps_rcvpackafterwin++; 1897 if (todrop >= tlen) { 1898 tcpstat.tcps_rcvbyteafterwin += tlen; 1899 /* 1900 * If a new connection request is received 1901 * while in TIME_WAIT, drop the old connection 1902 * and start over if the sequence numbers 1903 * are above the previous ones. 1904 */ 1905 if (thflags & TH_SYN && 1906 tp->t_state == TCPS_TIME_WAIT && 1907 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1908 tp = tcp_close(tp); 1909 goto findpcb; 1910 } 1911 /* 1912 * If window is closed can only take segments at 1913 * window edge, and have to drop data and PUSH from 1914 * incoming segments. Continue processing, but 1915 * remember to ack. Otherwise, drop segment 1916 * and ack. 1917 */ 1918 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1919 tp->t_flags |= TF_ACKNOW; 1920 tcpstat.tcps_rcvwinprobe++; 1921 } else 1922 goto dropafterack; 1923 } else 1924 tcpstat.tcps_rcvbyteafterwin += todrop; 1925 m_adj(m, -todrop); 1926 tlen -= todrop; 1927 thflags &= ~(TH_PUSH | TH_FIN); 1928 } 1929 1930 /* 1931 * If last ACK falls within this segment's sequence numbers, 1932 * record its timestamp. 1933 * NOTE: 1934 * 1) That the test incorporates suggestions from the latest 1935 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1936 * 2) That updating only on newer timestamps interferes with 1937 * our earlier PAWS tests, so this check should be solely 1938 * predicated on the sequence space of this segment. 1939 * 3) That we modify the segment boundary check to be 1940 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1941 * instead of RFC1323's 1942 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1943 * This modified check allows us to overcome RFC1323's 1944 * limitations as described in Stevens TCP/IP Illustrated 1945 * Vol. 2 p.869. In such cases, we can still calculate the 1946 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1947 */ 1948 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1949 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1950 + ((thflags & TH_SYN) != 0) 1951 + ((thflags & TH_FIN) != 0)))) { 1952 tp->ts_recent_age = ticks; 1953 tp->ts_recent = to.to_tsval; 1954 } 1955 1956 /* 1957 * If a SYN is in the window, then this is an 1958 * error and we send an RST and drop the connection. 1959 */ 1960 if (thflags & TH_SYN) { 1961 tp = tcp_drop(tp, ECONNRESET); 1962 rstreason = BANDLIM_UNLIMITED; 1963 goto dropwithreset; 1964 } 1965 1966 /* 1967 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1968 * flag is on (half-synchronized state), then queue data for 1969 * later processing; else drop segment and return. 1970 */ 1971 if (!(thflags & TH_ACK)) { 1972 if (tp->t_state == TCPS_SYN_RECEIVED || 1973 (tp->t_flags & TF_NEEDSYN)) 1974 goto step6; 1975 else 1976 goto drop; 1977 } 1978 1979 /* 1980 * Ack processing. 1981 */ 1982 switch (tp->t_state) { 1983 /* 1984 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1985 * ESTABLISHED state and continue processing. 1986 * The ACK was checked above. 1987 */ 1988 case TCPS_SYN_RECEIVED: 1989 1990 tcpstat.tcps_connects++; 1991 soisconnected(so); 1992 /* Do window scaling? */ 1993 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1994 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1995 tp->rcv_scale = tp->request_r_scale; 1996 /* 1997 * Make transitions: 1998 * SYN-RECEIVED -> ESTABLISHED 1999 * SYN-RECEIVED* -> FIN-WAIT-1 2000 */ 2001 tp->t_starttime = ticks; 2002 if (tp->t_flags & TF_NEEDFIN) { 2003 tp->t_state = TCPS_FIN_WAIT_1; 2004 tp->t_flags &= ~TF_NEEDFIN; 2005 } else { 2006 tcp_established(tp); 2007 } 2008 /* 2009 * If segment contains data or ACK, will call tcp_reass() 2010 * later; if not, do so now to pass queued data to user. 2011 */ 2012 if (tlen == 0 && !(thflags & TH_FIN)) 2013 tcp_reass(tp, NULL, NULL, NULL); 2014 /* fall into ... */ 2015 2016 /* 2017 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2018 * ACKs. If the ack is in the range 2019 * tp->snd_una < th->th_ack <= tp->snd_max 2020 * then advance tp->snd_una to th->th_ack and drop 2021 * data from the retransmission queue. If this ACK reflects 2022 * more up to date window information we update our window information. 2023 */ 2024 case TCPS_ESTABLISHED: 2025 case TCPS_FIN_WAIT_1: 2026 case TCPS_FIN_WAIT_2: 2027 case TCPS_CLOSE_WAIT: 2028 case TCPS_CLOSING: 2029 case TCPS_LAST_ACK: 2030 case TCPS_TIME_WAIT: 2031 2032 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2033 boolean_t maynotdup = FALSE; 2034 2035 if (TCP_DO_SACK(tp)) 2036 tcp_sack_update_scoreboard(tp, &to); 2037 2038 if (tlen != 0 || tiwin != tp->snd_wnd || 2039 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN))) 2040 maynotdup = TRUE; 2041 2042 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2043 th->th_ack != tp->snd_una) { 2044 if (!maynotdup) 2045 tcpstat.tcps_rcvdupack++; 2046 tp->t_dupacks = 0; 2047 break; 2048 } 2049 2050 #define DELAY_DUPACK \ 2051 do { \ 2052 delayed_dupack = TRUE; \ 2053 th_dupack = th->th_ack; \ 2054 to_flags = to.to_flags; \ 2055 } while (0) 2056 if (maynotdup) { 2057 if (!tcp_do_rfc6675 || 2058 !TCP_DO_SACK(tp) || 2059 (to.to_flags & 2060 (TOF_SACK | TOF_SACK_REDUNDANT)) 2061 != TOF_SACK) { 2062 tp->t_dupacks = 0; 2063 } else { 2064 DELAY_DUPACK; 2065 } 2066 break; 2067 } 2068 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) { 2069 /* 2070 * This could happen, if the reassemable 2071 * queue overflew or was drained. Don't 2072 * drop this FIN here; defer the duplicated 2073 * ACK processing until this FIN gets queued. 2074 */ 2075 DELAY_DUPACK; 2076 break; 2077 } 2078 #undef DELAY_DUPACK 2079 2080 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags)) 2081 goto drop; 2082 else 2083 break; 2084 } 2085 2086 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2087 tp->t_dupacks = 0; 2088 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2089 /* 2090 * Detected optimistic ACK attack. 2091 * Force slow-start to de-synchronize attack. 2092 */ 2093 tp->snd_cwnd = tp->t_maxseg; 2094 tp->snd_wacked = 0; 2095 2096 tcpstat.tcps_rcvacktoomuch++; 2097 goto dropafterack; 2098 } 2099 /* 2100 * If we reach this point, ACK is not a duplicate, 2101 * i.e., it ACKs something we sent. 2102 */ 2103 if (tp->t_flags & TF_NEEDSYN) { 2104 /* 2105 * T/TCP: Connection was half-synchronized, and our 2106 * SYN has been ACK'd (so connection is now fully 2107 * synchronized). Go to non-starred state, 2108 * increment snd_una for ACK of SYN, and check if 2109 * we can do window scaling. 2110 */ 2111 tp->t_flags &= ~TF_NEEDSYN; 2112 tp->snd_una++; 2113 /* Do window scaling? */ 2114 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2115 (TF_RCVD_SCALE | TF_REQ_SCALE)) 2116 tp->rcv_scale = tp->request_r_scale; 2117 } 2118 2119 process_ACK: 2120 acked = th->th_ack - tp->snd_una; 2121 tcpstat.tcps_rcvackpack++; 2122 tcpstat.tcps_rcvackbyte += acked; 2123 2124 if (tcp_do_eifel_detect && acked > 0 && 2125 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2126 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 2127 /* Eifel detection applicable. */ 2128 if (to.to_tsecr < tp->t_rexmtTS) { 2129 ++tcpstat.tcps_eifeldetected; 2130 tcp_revert_congestion_state(tp); 2131 if (tp->t_rxtshift != 1 || 2132 ticks >= tp->t_badrxtwin) 2133 ++tcpstat.tcps_rttcantdetect; 2134 } 2135 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2136 /* 2137 * If we just performed our first retransmit, 2138 * and the ACK arrives within our recovery window, 2139 * then it was a mistake to do the retransmit 2140 * in the first place. Recover our original cwnd 2141 * and ssthresh, and proceed to transmit where we 2142 * left off. 2143 */ 2144 tcp_revert_congestion_state(tp); 2145 ++tcpstat.tcps_rttdetected; 2146 } 2147 2148 /* 2149 * If we have a timestamp reply, update smoothed 2150 * round trip time. If no timestamp is present but 2151 * transmit timer is running and timed sequence 2152 * number was acked, update smoothed round trip time. 2153 * Since we now have an rtt measurement, cancel the 2154 * timer backoff (cf., Phil Karn's retransmit alg.). 2155 * Recompute the initial retransmit timer. 2156 * 2157 * Some machines (certain windows boxes) send broken 2158 * timestamp replies during the SYN+ACK phase, ignore 2159 * timestamps of 0. 2160 */ 2161 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2162 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); 2163 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2164 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); 2165 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2166 2167 /* 2168 * If no data (only SYN) was ACK'd, 2169 * skip rest of ACK processing. 2170 */ 2171 if (acked == 0) 2172 goto step6; 2173 2174 /* Stop looking for an acceptable ACK since one was received. */ 2175 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 2176 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 2177 2178 if (acked > so->so_snd.ssb_cc) { 2179 tp->snd_wnd -= so->so_snd.ssb_cc; 2180 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2181 ourfinisacked = TRUE; 2182 } else { 2183 sbdrop(&so->so_snd.sb, acked); 2184 tp->snd_wnd -= acked; 2185 ourfinisacked = FALSE; 2186 } 2187 sowwakeup(so); 2188 2189 /* 2190 * Update window information. 2191 */ 2192 if (acceptable_window_update(tp, th, tiwin)) { 2193 /* keep track of pure window updates */ 2194 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2195 tiwin > tp->snd_wnd) 2196 tcpstat.tcps_rcvwinupd++; 2197 tp->snd_wnd = tiwin; 2198 tp->snd_wl1 = th->th_seq; 2199 tp->snd_wl2 = th->th_ack; 2200 if (tp->snd_wnd > tp->max_sndwnd) 2201 tp->max_sndwnd = tp->snd_wnd; 2202 needoutput = TRUE; 2203 } 2204 2205 tp->snd_una = th->th_ack; 2206 if (TCP_DO_SACK(tp)) 2207 tcp_sack_update_scoreboard(tp, &to); 2208 if (IN_FASTRECOVERY(tp)) { 2209 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2210 EXIT_FASTRECOVERY(tp); 2211 needoutput = TRUE; 2212 /* 2213 * If the congestion window was inflated 2214 * to account for the other side's 2215 * cached packets, retract it. 2216 */ 2217 if (!TCP_DO_SACK(tp)) 2218 tp->snd_cwnd = tp->snd_ssthresh; 2219 2220 /* 2221 * Window inflation should have left us 2222 * with approximately snd_ssthresh outstanding 2223 * data. But, in case we would be inclined 2224 * to send a burst, better do it using 2225 * slow start. 2226 */ 2227 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2228 tp->snd_max + 2 * tp->t_maxseg)) 2229 tp->snd_cwnd = 2230 (tp->snd_max - tp->snd_una) + 2231 2 * tp->t_maxseg; 2232 2233 tp->snd_wacked = 0; 2234 } else { 2235 if (TCP_DO_SACK(tp)) { 2236 tp->snd_max_rexmt = tp->snd_max; 2237 tcp_sack_rexmt(tp, 2238 tp->snd_una == tp->rexmt_high); 2239 } else { 2240 tcp_newreno_partial_ack(tp, th, acked); 2241 } 2242 needoutput = FALSE; 2243 } 2244 } else { 2245 /* 2246 * Open the congestion window. When in slow-start, 2247 * open exponentially: maxseg per packet. Otherwise, 2248 * open linearly: maxseg per window. 2249 */ 2250 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2251 u_int abc_sslimit = 2252 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2253 tp->t_maxseg : 2 * tp->t_maxseg); 2254 2255 /* slow-start */ 2256 tp->snd_cwnd += tcp_do_abc ? 2257 min(acked, abc_sslimit) : tp->t_maxseg; 2258 } else { 2259 /* linear increase */ 2260 tp->snd_wacked += tcp_do_abc ? acked : 2261 tp->t_maxseg; 2262 if (tp->snd_wacked >= tp->snd_cwnd) { 2263 tp->snd_wacked -= tp->snd_cwnd; 2264 tp->snd_cwnd += tp->t_maxseg; 2265 } 2266 } 2267 tp->snd_cwnd = min(tp->snd_cwnd, 2268 TCP_MAXWIN << tp->snd_scale); 2269 tp->snd_recover = th->th_ack - 1; 2270 } 2271 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2272 tp->snd_nxt = tp->snd_una; 2273 2274 /* 2275 * If all outstanding data is acked, stop retransmit 2276 * timer and remember to restart (more output or persist). 2277 * If there is more data to be acked, restart retransmit 2278 * timer, using current (possibly backed-off) value. 2279 */ 2280 if (th->th_ack == tp->snd_max) { 2281 tcp_callout_stop(tp, tp->tt_rexmt); 2282 needoutput = TRUE; 2283 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2284 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2285 tcp_timer_rexmt); 2286 } 2287 2288 switch (tp->t_state) { 2289 /* 2290 * In FIN_WAIT_1 STATE in addition to the processing 2291 * for the ESTABLISHED state if our FIN is now acknowledged 2292 * then enter FIN_WAIT_2. 2293 */ 2294 case TCPS_FIN_WAIT_1: 2295 if (ourfinisacked) { 2296 /* 2297 * If we can't receive any more 2298 * data, then closing user can proceed. 2299 * Starting the timer is contrary to the 2300 * specification, but if we don't get a FIN 2301 * we'll hang forever. 2302 */ 2303 if (so->so_state & SS_CANTRCVMORE) { 2304 soisdisconnected(so); 2305 tcp_callout_reset(tp, tp->tt_2msl, 2306 tp->t_maxidle, tcp_timer_2msl); 2307 } 2308 tp->t_state = TCPS_FIN_WAIT_2; 2309 } 2310 break; 2311 2312 /* 2313 * In CLOSING STATE in addition to the processing for 2314 * the ESTABLISHED state if the ACK acknowledges our FIN 2315 * then enter the TIME-WAIT state, otherwise ignore 2316 * the segment. 2317 */ 2318 case TCPS_CLOSING: 2319 if (ourfinisacked) { 2320 tp->t_state = TCPS_TIME_WAIT; 2321 tcp_canceltimers(tp); 2322 tcp_callout_reset(tp, tp->tt_2msl, 2323 2 * tcp_rmx_msl(tp), 2324 tcp_timer_2msl); 2325 soisdisconnected(so); 2326 } 2327 break; 2328 2329 /* 2330 * In LAST_ACK, we may still be waiting for data to drain 2331 * and/or to be acked, as well as for the ack of our FIN. 2332 * If our FIN is now acknowledged, delete the TCB, 2333 * enter the closed state and return. 2334 */ 2335 case TCPS_LAST_ACK: 2336 if (ourfinisacked) { 2337 tp = tcp_close(tp); 2338 goto drop; 2339 } 2340 break; 2341 2342 /* 2343 * In TIME_WAIT state the only thing that should arrive 2344 * is a retransmission of the remote FIN. Acknowledge 2345 * it and restart the finack timer. 2346 */ 2347 case TCPS_TIME_WAIT: 2348 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2349 tcp_timer_2msl); 2350 goto dropafterack; 2351 } 2352 } 2353 2354 step6: 2355 /* 2356 * Update window information. 2357 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2358 */ 2359 if ((thflags & TH_ACK) && 2360 acceptable_window_update(tp, th, tiwin)) { 2361 /* keep track of pure window updates */ 2362 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2363 tiwin > tp->snd_wnd) 2364 tcpstat.tcps_rcvwinupd++; 2365 tp->snd_wnd = tiwin; 2366 tp->snd_wl1 = th->th_seq; 2367 tp->snd_wl2 = th->th_ack; 2368 if (tp->snd_wnd > tp->max_sndwnd) 2369 tp->max_sndwnd = tp->snd_wnd; 2370 needoutput = TRUE; 2371 } 2372 2373 /* 2374 * Process segments with URG. 2375 */ 2376 if ((thflags & TH_URG) && th->th_urp && 2377 !TCPS_HAVERCVDFIN(tp->t_state)) { 2378 /* 2379 * This is a kludge, but if we receive and accept 2380 * random urgent pointers, we'll crash in 2381 * soreceive. It's hard to imagine someone 2382 * actually wanting to send this much urgent data. 2383 */ 2384 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2385 th->th_urp = 0; /* XXX */ 2386 thflags &= ~TH_URG; /* XXX */ 2387 goto dodata; /* XXX */ 2388 } 2389 /* 2390 * If this segment advances the known urgent pointer, 2391 * then mark the data stream. This should not happen 2392 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2393 * a FIN has been received from the remote side. 2394 * In these states we ignore the URG. 2395 * 2396 * According to RFC961 (Assigned Protocols), 2397 * the urgent pointer points to the last octet 2398 * of urgent data. We continue, however, 2399 * to consider it to indicate the first octet 2400 * of data past the urgent section as the original 2401 * spec states (in one of two places). 2402 */ 2403 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2404 tp->rcv_up = th->th_seq + th->th_urp; 2405 so->so_oobmark = so->so_rcv.ssb_cc + 2406 (tp->rcv_up - tp->rcv_nxt) - 1; 2407 if (so->so_oobmark == 0) 2408 sosetstate(so, SS_RCVATMARK); 2409 sohasoutofband(so); 2410 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2411 } 2412 /* 2413 * Remove out of band data so doesn't get presented to user. 2414 * This can happen independent of advancing the URG pointer, 2415 * but if two URG's are pending at once, some out-of-band 2416 * data may creep in... ick. 2417 */ 2418 if (th->th_urp <= (u_long)tlen && 2419 !(so->so_options & SO_OOBINLINE)) { 2420 /* hdr drop is delayed */ 2421 tcp_pulloutofband(so, th, m, drop_hdrlen); 2422 } 2423 } else { 2424 /* 2425 * If no out of band data is expected, 2426 * pull receive urgent pointer along 2427 * with the receive window. 2428 */ 2429 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2430 tp->rcv_up = tp->rcv_nxt; 2431 } 2432 2433 dodata: /* XXX */ 2434 /* 2435 * Process the segment text, merging it into the TCP sequencing queue, 2436 * and arranging for acknowledgment of receipt if necessary. 2437 * This process logically involves adjusting tp->rcv_wnd as data 2438 * is presented to the user (this happens in tcp_usrreq.c, 2439 * case PRU_RCVD). If a FIN has already been received on this 2440 * connection then we just ignore the text. 2441 */ 2442 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2443 if (thflags & TH_FIN) 2444 tp->t_flags |= TF_SAWFIN; 2445 m_adj(m, drop_hdrlen); /* delayed header drop */ 2446 /* 2447 * Insert segment which includes th into TCP reassembly queue 2448 * with control block tp. Set thflags to whether reassembly now 2449 * includes a segment with FIN. This handles the common case 2450 * inline (segment is the next to be received on an established 2451 * connection, and the queue is empty), avoiding linkage into 2452 * and removal from the queue and repetition of various 2453 * conversions. 2454 * Set DELACK for segments received in order, but ack 2455 * immediately when segments are out of order (so 2456 * fast retransmit can work). 2457 */ 2458 if (th->th_seq == tp->rcv_nxt && 2459 TAILQ_EMPTY(&tp->t_segq) && 2460 TCPS_HAVEESTABLISHED(tp->t_state)) { 2461 if (thflags & TH_FIN) 2462 tp->t_flags |= TF_QUEDFIN; 2463 if (DELAY_ACK(tp)) { 2464 tcp_callout_reset(tp, tp->tt_delack, 2465 tcp_delacktime, tcp_timer_delack); 2466 } else { 2467 tp->t_flags |= TF_ACKNOW; 2468 } 2469 tp->rcv_nxt += tlen; 2470 thflags = th->th_flags & TH_FIN; 2471 tcpstat.tcps_rcvpack++; 2472 tcpstat.tcps_rcvbyte += tlen; 2473 ND6_HINT(tp); 2474 if (so->so_state & SS_CANTRCVMORE) { 2475 m_freem(m); 2476 } else { 2477 lwkt_gettoken(&so->so_rcv.ssb_token); 2478 ssb_appendstream(&so->so_rcv, m); 2479 lwkt_reltoken(&so->so_rcv.ssb_token); 2480 } 2481 sorwakeup(so); 2482 } else { 2483 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 2484 /* Initialize SACK report block. */ 2485 tp->reportblk.rblk_start = th->th_seq; 2486 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2487 th->th_seq + tlen, thflags); 2488 } 2489 thflags = tcp_reass(tp, th, &tlen, m); 2490 tp->t_flags |= TF_ACKNOW; 2491 } 2492 2493 /* 2494 * Note the amount of data that peer has sent into 2495 * our window, in order to estimate the sender's 2496 * buffer size. 2497 */ 2498 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2499 } else { 2500 m_freem(m); 2501 thflags &= ~TH_FIN; 2502 } 2503 2504 /* 2505 * If FIN is received ACK the FIN and let the user know 2506 * that the connection is closing. 2507 */ 2508 if (thflags & TH_FIN) { 2509 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2510 socantrcvmore(so); 2511 /* 2512 * If connection is half-synchronized 2513 * (ie NEEDSYN flag on) then delay ACK, 2514 * so it may be piggybacked when SYN is sent. 2515 * Otherwise, since we received a FIN then no 2516 * more input can be expected, send ACK now. 2517 */ 2518 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2519 tcp_callout_reset(tp, tp->tt_delack, 2520 tcp_delacktime, tcp_timer_delack); 2521 } else { 2522 tp->t_flags |= TF_ACKNOW; 2523 } 2524 tp->rcv_nxt++; 2525 } 2526 2527 switch (tp->t_state) { 2528 /* 2529 * In SYN_RECEIVED and ESTABLISHED STATES 2530 * enter the CLOSE_WAIT state. 2531 */ 2532 case TCPS_SYN_RECEIVED: 2533 tp->t_starttime = ticks; 2534 /*FALLTHROUGH*/ 2535 case TCPS_ESTABLISHED: 2536 tp->t_state = TCPS_CLOSE_WAIT; 2537 break; 2538 2539 /* 2540 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2541 * enter the CLOSING state. 2542 */ 2543 case TCPS_FIN_WAIT_1: 2544 tp->t_state = TCPS_CLOSING; 2545 break; 2546 2547 /* 2548 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2549 * starting the time-wait timer, turning off the other 2550 * standard timers. 2551 */ 2552 case TCPS_FIN_WAIT_2: 2553 tp->t_state = TCPS_TIME_WAIT; 2554 tcp_canceltimers(tp); 2555 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2556 tcp_timer_2msl); 2557 soisdisconnected(so); 2558 break; 2559 2560 /* 2561 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2562 */ 2563 case TCPS_TIME_WAIT: 2564 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2565 tcp_timer_2msl); 2566 break; 2567 } 2568 } 2569 2570 #ifdef TCPDEBUG 2571 if (so->so_options & SO_DEBUG) 2572 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2573 #endif 2574 2575 /* 2576 * Delayed duplicated ACK processing 2577 */ 2578 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags)) 2579 needoutput = FALSE; 2580 2581 /* 2582 * Return any desired output. 2583 */ 2584 if ((tp->t_flags & TF_ACKNOW) || 2585 (needoutput && tcp_sack_report_needed(tp))) { 2586 tcp_output_cancel(tp); 2587 tcp_output_fair(tp); 2588 } else if (needoutput && !tcp_output_pending(tp)) { 2589 tcp_output_fair(tp); 2590 } 2591 tcp_sack_report_cleanup(tp); 2592 return(IPPROTO_DONE); 2593 2594 dropafterack: 2595 /* 2596 * Generate an ACK dropping incoming segment if it occupies 2597 * sequence space, where the ACK reflects our state. 2598 * 2599 * We can now skip the test for the RST flag since all 2600 * paths to this code happen after packets containing 2601 * RST have been dropped. 2602 * 2603 * In the SYN-RECEIVED state, don't send an ACK unless the 2604 * segment we received passes the SYN-RECEIVED ACK test. 2605 * If it fails send a RST. This breaks the loop in the 2606 * "LAND" DoS attack, and also prevents an ACK storm 2607 * between two listening ports that have been sent forged 2608 * SYN segments, each with the source address of the other. 2609 */ 2610 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2611 (SEQ_GT(tp->snd_una, th->th_ack) || 2612 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2613 rstreason = BANDLIM_RST_OPENPORT; 2614 goto dropwithreset; 2615 } 2616 #ifdef TCPDEBUG 2617 if (so->so_options & SO_DEBUG) 2618 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2619 #endif 2620 m_freem(m); 2621 tp->t_flags |= TF_ACKNOW; 2622 tcp_output(tp); 2623 tcp_sack_report_cleanup(tp); 2624 return(IPPROTO_DONE); 2625 2626 dropwithreset: 2627 /* 2628 * Generate a RST, dropping incoming segment. 2629 * Make ACK acceptable to originator of segment. 2630 * Don't bother to respond if destination was broadcast/multicast. 2631 */ 2632 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2633 goto drop; 2634 if (isipv6) { 2635 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2636 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2637 goto drop; 2638 } else { 2639 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2640 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2641 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2642 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2643 goto drop; 2644 } 2645 /* IPv6 anycast check is done at tcp6_input() */ 2646 2647 /* 2648 * Perform bandwidth limiting. 2649 */ 2650 #ifdef ICMP_BANDLIM 2651 if (badport_bandlim(rstreason) < 0) 2652 goto drop; 2653 #endif 2654 2655 #ifdef TCPDEBUG 2656 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2657 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2658 #endif 2659 if (thflags & TH_ACK) 2660 /* mtod() below is safe as long as hdr dropping is delayed */ 2661 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2662 TH_RST); 2663 else { 2664 if (thflags & TH_SYN) 2665 tlen++; 2666 /* mtod() below is safe as long as hdr dropping is delayed */ 2667 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2668 (tcp_seq)0, TH_RST | TH_ACK); 2669 } 2670 if (tp != NULL) 2671 tcp_sack_report_cleanup(tp); 2672 return(IPPROTO_DONE); 2673 2674 drop: 2675 /* 2676 * Drop space held by incoming segment and return. 2677 */ 2678 #ifdef TCPDEBUG 2679 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2680 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2681 #endif 2682 m_freem(m); 2683 if (tp != NULL) 2684 tcp_sack_report_cleanup(tp); 2685 return(IPPROTO_DONE); 2686 } 2687 2688 /* 2689 * Parse TCP options and place in tcpopt. 2690 */ 2691 static void 2692 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, 2693 tcp_seq ack) 2694 { 2695 int opt, optlen, i; 2696 2697 to->to_flags = 0; 2698 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2699 opt = cp[0]; 2700 if (opt == TCPOPT_EOL) 2701 break; 2702 if (opt == TCPOPT_NOP) 2703 optlen = 1; 2704 else { 2705 if (cnt < 2) 2706 break; 2707 optlen = cp[1]; 2708 if (optlen < 2 || optlen > cnt) 2709 break; 2710 } 2711 switch (opt) { 2712 case TCPOPT_MAXSEG: 2713 if (optlen != TCPOLEN_MAXSEG) 2714 continue; 2715 if (!is_syn) 2716 continue; 2717 to->to_flags |= TOF_MSS; 2718 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2719 to->to_mss = ntohs(to->to_mss); 2720 break; 2721 case TCPOPT_WINDOW: 2722 if (optlen != TCPOLEN_WINDOW) 2723 continue; 2724 if (!is_syn) 2725 continue; 2726 to->to_flags |= TOF_SCALE; 2727 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2728 break; 2729 case TCPOPT_TIMESTAMP: 2730 if (optlen != TCPOLEN_TIMESTAMP) 2731 continue; 2732 to->to_flags |= TOF_TS; 2733 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2734 to->to_tsval = ntohl(to->to_tsval); 2735 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2736 to->to_tsecr = ntohl(to->to_tsecr); 2737 /* 2738 * If echoed timestamp is later than the current time, 2739 * fall back to non RFC1323 RTT calculation. 2740 */ 2741 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2742 to->to_tsecr = 0; 2743 break; 2744 case TCPOPT_SACK_PERMITTED: 2745 if (optlen != TCPOLEN_SACK_PERMITTED) 2746 continue; 2747 if (!is_syn) 2748 continue; 2749 to->to_flags |= TOF_SACK_PERMITTED; 2750 break; 2751 case TCPOPT_SACK: 2752 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2753 continue; 2754 to->to_nsackblocks = (optlen - 2) / 8; 2755 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2756 to->to_flags |= TOF_SACK; 2757 for (i = 0; i < to->to_nsackblocks; i++) { 2758 struct raw_sackblock *r = &to->to_sackblocks[i]; 2759 2760 r->rblk_start = ntohl(r->rblk_start); 2761 r->rblk_end = ntohl(r->rblk_end); 2762 2763 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2764 /* 2765 * Invalid SACK block; discard all 2766 * SACK blocks 2767 */ 2768 tcpstat.tcps_rcvbadsackopt++; 2769 to->to_nsackblocks = 0; 2770 to->to_sackblocks = NULL; 2771 to->to_flags &= ~TOF_SACK; 2772 break; 2773 } 2774 } 2775 if ((to->to_flags & TOF_SACK) && 2776 tcp_sack_ndsack_blocks(to->to_sackblocks, 2777 to->to_nsackblocks, ack)) 2778 to->to_flags |= TOF_DSACK; 2779 break; 2780 #ifdef TCP_SIGNATURE 2781 /* 2782 * XXX In order to reply to a host which has set the 2783 * TCP_SIGNATURE option in its initial SYN, we have to 2784 * record the fact that the option was observed here 2785 * for the syncache code to perform the correct response. 2786 */ 2787 case TCPOPT_SIGNATURE: 2788 if (optlen != TCPOLEN_SIGNATURE) 2789 continue; 2790 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2791 break; 2792 #endif /* TCP_SIGNATURE */ 2793 default: 2794 continue; 2795 } 2796 } 2797 } 2798 2799 /* 2800 * Pull out of band byte out of a segment so 2801 * it doesn't appear in the user's data queue. 2802 * It is still reflected in the segment length for 2803 * sequencing purposes. 2804 * "off" is the delayed to be dropped hdrlen. 2805 */ 2806 static void 2807 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2808 { 2809 int cnt = off + th->th_urp - 1; 2810 2811 while (cnt >= 0) { 2812 if (m->m_len > cnt) { 2813 char *cp = mtod(m, caddr_t) + cnt; 2814 struct tcpcb *tp = sototcpcb(so); 2815 2816 tp->t_iobc = *cp; 2817 tp->t_oobflags |= TCPOOB_HAVEDATA; 2818 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2819 m->m_len--; 2820 if (m->m_flags & M_PKTHDR) 2821 m->m_pkthdr.len--; 2822 return; 2823 } 2824 cnt -= m->m_len; 2825 m = m->m_next; 2826 if (m == NULL) 2827 break; 2828 } 2829 panic("tcp_pulloutofband"); 2830 } 2831 2832 /* 2833 * Collect new round-trip time estimate 2834 * and update averages and current timeout. 2835 */ 2836 static void 2837 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) 2838 { 2839 int rebaserto = 0; 2840 2841 tcpstat.tcps_rttupdated++; 2842 tp->t_rttupdated++; 2843 if ((tp->rxt_flags & TRXT_F_REBASERTO) && 2844 SEQ_GT(ack, tp->snd_max_prev)) { 2845 #ifdef DEBUG_EIFEL_RESPONSE 2846 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", 2847 tp->t_srtt_prev, tp->t_rttvar_prev, 2848 tp->t_srtt, tp->t_rttvar); 2849 #endif 2850 2851 tcpstat.tcps_eifelresponse++; 2852 rebaserto = 1; 2853 tp->rxt_flags &= ~TRXT_F_REBASERTO; 2854 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); 2855 tp->t_rttvar = max(tp->t_rttvar_prev, 2856 (rtt << (TCP_RTTVAR_SHIFT - 1))); 2857 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2858 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2859 2860 #ifdef DEBUG_EIFEL_RESPONSE 2861 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); 2862 #endif 2863 } else if (tp->t_srtt != 0) { 2864 int delta; 2865 2866 /* 2867 * srtt is stored as fixed point with 5 bits after the 2868 * binary point (i.e., scaled by 8). The following magic 2869 * is equivalent to the smoothing algorithm in rfc793 with 2870 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2871 * point). Adjust rtt to origin 0. 2872 */ 2873 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2874 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2875 2876 if ((tp->t_srtt += delta) <= 0) 2877 tp->t_srtt = 1; 2878 2879 /* 2880 * We accumulate a smoothed rtt variance (actually, a 2881 * smoothed mean difference), then set the retransmit 2882 * timer to smoothed rtt + 4 times the smoothed variance. 2883 * rttvar is stored as fixed point with 4 bits after the 2884 * binary point (scaled by 16). The following is 2885 * equivalent to rfc793 smoothing with an alpha of .75 2886 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2887 * rfc793's wired-in beta. 2888 */ 2889 if (delta < 0) 2890 delta = -delta; 2891 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2892 if ((tp->t_rttvar += delta) <= 0) 2893 tp->t_rttvar = 1; 2894 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2895 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2896 } else { 2897 /* 2898 * No rtt measurement yet - use the unsmoothed rtt. 2899 * Set the variance to half the rtt (so our first 2900 * retransmit happens at 3*rtt). 2901 */ 2902 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2903 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2904 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2905 } 2906 tp->t_rtttime = 0; 2907 tp->t_rxtshift = 0; 2908 2909 #ifdef DEBUG_EIFEL_RESPONSE 2910 if (rebaserto) { 2911 kprintf("| rxtcur prev %d, old %d, ", 2912 tp->t_rxtcur_prev, tp->t_rxtcur); 2913 } 2914 #endif 2915 2916 /* 2917 * the retransmit should happen at rtt + 4 * rttvar. 2918 * Because of the way we do the smoothing, srtt and rttvar 2919 * will each average +1/2 tick of bias. When we compute 2920 * the retransmit timer, we want 1/2 tick of rounding and 2921 * 1 extra tick because of +-1/2 tick uncertainty in the 2922 * firing of the timer. The bias will give us exactly the 2923 * 1.5 tick we need. But, because the bias is 2924 * statistical, we have to test that we don't drop below 2925 * the minimum feasible timer (which is 2 ticks). 2926 */ 2927 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2928 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2929 2930 if (rebaserto) { 2931 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { 2932 /* 2933 * RFC4015 requires that the new RTO is at least 2934 * 2*G (tcp_eifel_rtoinc) greater then the RTO 2935 * (t_rxtcur_prev) when the spurious retransmit 2936 * timeout happens. 2937 * 2938 * The above condition could be true, if the SRTT 2939 * and RTTVAR used to calculate t_rxtcur_prev 2940 * resulted in a value less than t_rttmin. So 2941 * simply increasing SRTT by tcp_eifel_rtoinc when 2942 * preparing for the Eifel response could not ensure 2943 * that the new RTO will be tcp_eifel_rtoinc greater 2944 * t_rxtcur_prev. 2945 */ 2946 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; 2947 } 2948 #ifdef DEBUG_EIFEL_RESPONSE 2949 kprintf("new %d\n", tp->t_rxtcur); 2950 #endif 2951 } 2952 2953 /* 2954 * We received an ack for a packet that wasn't retransmitted; 2955 * it is probably safe to discard any error indications we've 2956 * received recently. This isn't quite right, but close enough 2957 * for now (a route might have failed after we sent a segment, 2958 * and the return path might not be symmetrical). 2959 */ 2960 tp->t_softerror = 0; 2961 } 2962 2963 /* 2964 * Determine a reasonable value for maxseg size. 2965 * If the route is known, check route for mtu. 2966 * If none, use an mss that can be handled on the outgoing 2967 * interface without forcing IP to fragment; if bigger than 2968 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2969 * to utilize large mbufs. If no route is found, route has no mtu, 2970 * or the destination isn't local, use a default, hopefully conservative 2971 * size (usually 512 or the default IP max size, but no more than the mtu 2972 * of the interface), as we can't discover anything about intervening 2973 * gateways or networks. We also initialize the congestion/slow start 2974 * window to be a single segment if the destination isn't local. 2975 * While looking at the routing entry, we also initialize other path-dependent 2976 * parameters from pre-set or cached values in the routing entry. 2977 * 2978 * Also take into account the space needed for options that we 2979 * send regularly. Make maxseg shorter by that amount to assure 2980 * that we can send maxseg amount of data even when the options 2981 * are present. Store the upper limit of the length of options plus 2982 * data in maxopd. 2983 * 2984 * NOTE that this routine is only called when we process an incoming 2985 * segment, for outgoing segments only tcp_mssopt is called. 2986 */ 2987 void 2988 tcp_mss(struct tcpcb *tp, int offer) 2989 { 2990 struct rtentry *rt; 2991 struct ifnet *ifp; 2992 int rtt, mss; 2993 u_long bufsize; 2994 struct inpcb *inp = tp->t_inpcb; 2995 struct socket *so; 2996 #ifdef INET6 2997 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2998 size_t min_protoh = isipv6 ? 2999 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3000 sizeof(struct tcpiphdr); 3001 #else 3002 const boolean_t isipv6 = FALSE; 3003 const size_t min_protoh = sizeof(struct tcpiphdr); 3004 #endif 3005 3006 if (isipv6) 3007 rt = tcp_rtlookup6(&inp->inp_inc); 3008 else 3009 rt = tcp_rtlookup(&inp->inp_inc); 3010 if (rt == NULL) { 3011 tp->t_maxopd = tp->t_maxseg = 3012 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3013 return; 3014 } 3015 ifp = rt->rt_ifp; 3016 so = inp->inp_socket; 3017 3018 /* 3019 * Offer == 0 means that there was no MSS on the SYN segment, 3020 * in this case we use either the interface mtu or tcp_mssdflt. 3021 * 3022 * An offer which is too large will be cut down later. 3023 */ 3024 if (offer == 0) { 3025 if (isipv6) { 3026 if (in6_localaddr(&inp->in6p_faddr)) { 3027 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 3028 min_protoh; 3029 } else { 3030 offer = tcp_v6mssdflt; 3031 } 3032 } else { 3033 if (in_localaddr(inp->inp_faddr)) 3034 offer = ifp->if_mtu - min_protoh; 3035 else 3036 offer = tcp_mssdflt; 3037 } 3038 } 3039 3040 /* 3041 * Prevent DoS attack with too small MSS. Round up 3042 * to at least minmss. 3043 * 3044 * Sanity check: make sure that maxopd will be large 3045 * enough to allow some data on segments even is the 3046 * all the option space is used (40bytes). Otherwise 3047 * funny things may happen in tcp_output. 3048 */ 3049 offer = max(offer, tcp_minmss); 3050 offer = max(offer, 64); 3051 3052 rt->rt_rmx.rmx_mssopt = offer; 3053 3054 /* 3055 * While we're here, check if there's an initial rtt 3056 * or rttvar. Convert from the route-table units 3057 * to scaled multiples of the slow timeout timer. 3058 */ 3059 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3060 /* 3061 * XXX the lock bit for RTT indicates that the value 3062 * is also a minimum value; this is subject to time. 3063 */ 3064 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3065 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3066 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3067 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3068 tcpstat.tcps_usedrtt++; 3069 if (rt->rt_rmx.rmx_rttvar) { 3070 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3071 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3072 tcpstat.tcps_usedrttvar++; 3073 } else { 3074 /* default variation is +- 1 rtt */ 3075 tp->t_rttvar = 3076 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3077 } 3078 TCPT_RANGESET(tp->t_rxtcur, 3079 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3080 tp->t_rttmin, TCPTV_REXMTMAX); 3081 } 3082 3083 /* 3084 * if there's an mtu associated with the route, use it 3085 * else, use the link mtu. Take the smaller of mss or offer 3086 * as our final mss. 3087 */ 3088 if (rt->rt_rmx.rmx_mtu) { 3089 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3090 } else { 3091 if (isipv6) 3092 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3093 else 3094 mss = ifp->if_mtu - min_protoh; 3095 } 3096 mss = min(mss, offer); 3097 3098 /* 3099 * maxopd stores the maximum length of data AND options 3100 * in a segment; maxseg is the amount of data in a normal 3101 * segment. We need to store this value (maxopd) apart 3102 * from maxseg, because now every segment carries options 3103 * and thus we normally have somewhat less data in segments. 3104 */ 3105 tp->t_maxopd = mss; 3106 3107 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3108 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3109 mss -= TCPOLEN_TSTAMP_APPA; 3110 3111 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3112 if (mss > MCLBYTES) 3113 mss &= ~(MCLBYTES-1); 3114 #else 3115 if (mss > MCLBYTES) 3116 mss = mss / MCLBYTES * MCLBYTES; 3117 #endif 3118 /* 3119 * If there's a pipesize, change the socket buffer 3120 * to that size. Make the socket buffers an integral 3121 * number of mss units; if the mss is larger than 3122 * the socket buffer, decrease the mss. 3123 */ 3124 #ifdef RTV_SPIPE 3125 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3126 #endif 3127 bufsize = so->so_snd.ssb_hiwat; 3128 if (bufsize < mss) 3129 mss = bufsize; 3130 else { 3131 bufsize = roundup(bufsize, mss); 3132 if (bufsize > sb_max) 3133 bufsize = sb_max; 3134 if (bufsize > so->so_snd.ssb_hiwat) 3135 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3136 } 3137 tp->t_maxseg = mss; 3138 3139 #ifdef RTV_RPIPE 3140 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3141 #endif 3142 bufsize = so->so_rcv.ssb_hiwat; 3143 if (bufsize > mss) { 3144 bufsize = roundup(bufsize, mss); 3145 if (bufsize > sb_max) 3146 bufsize = sb_max; 3147 if (bufsize > so->so_rcv.ssb_hiwat) { 3148 lwkt_gettoken(&so->so_rcv.ssb_token); 3149 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3150 lwkt_reltoken(&so->so_rcv.ssb_token); 3151 } 3152 } 3153 3154 /* 3155 * Set the slow-start flight size 3156 * 3157 * NOTE: t_maxseg must have been configured! 3158 */ 3159 tp->snd_cwnd = tcp_initial_window(tp); 3160 3161 if (rt->rt_rmx.rmx_ssthresh) { 3162 /* 3163 * There's some sort of gateway or interface 3164 * buffer limit on the path. Use this to set 3165 * the slow start threshhold, but set the 3166 * threshold to no less than 2*mss. 3167 */ 3168 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3169 tcpstat.tcps_usedssthresh++; 3170 } 3171 } 3172 3173 /* 3174 * Determine the MSS option to send on an outgoing SYN. 3175 */ 3176 int 3177 tcp_mssopt(struct tcpcb *tp) 3178 { 3179 struct rtentry *rt; 3180 #ifdef INET6 3181 boolean_t isipv6 = 3182 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3183 int min_protoh = isipv6 ? 3184 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3185 sizeof(struct tcpiphdr); 3186 #else 3187 const boolean_t isipv6 = FALSE; 3188 const size_t min_protoh = sizeof(struct tcpiphdr); 3189 #endif 3190 3191 if (isipv6) 3192 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3193 else 3194 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3195 if (rt == NULL) 3196 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3197 3198 return (rt->rt_ifp->if_mtu - min_protoh); 3199 } 3200 3201 /* 3202 * When a partial ack arrives, force the retransmission of the 3203 * next unacknowledged segment. Do not exit Fast Recovery. 3204 * 3205 * Implement the Slow-but-Steady variant of NewReno by restarting the 3206 * the retransmission timer. Turn it off here so it can be restarted 3207 * later in tcp_output(). 3208 */ 3209 static void 3210 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3211 { 3212 tcp_seq old_snd_nxt = tp->snd_nxt; 3213 u_long ocwnd = tp->snd_cwnd; 3214 3215 tcp_callout_stop(tp, tp->tt_rexmt); 3216 tp->t_rtttime = 0; 3217 tp->snd_nxt = th->th_ack; 3218 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3219 tp->snd_cwnd = tp->t_maxseg; 3220 tp->t_flags |= TF_ACKNOW; 3221 tcp_output(tp); 3222 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3223 tp->snd_nxt = old_snd_nxt; 3224 /* partial window deflation */ 3225 if (ocwnd > acked) 3226 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3227 else 3228 tp->snd_cwnd = tp->t_maxseg; 3229 } 3230 3231 /* 3232 * In contrast to the Slow-but-Steady NewReno variant, 3233 * we do not reset the retransmission timer for SACK retransmissions, 3234 * except when retransmitting snd_una. 3235 */ 3236 static void 3237 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force) 3238 { 3239 tcp_seq old_snd_nxt = tp->snd_nxt; 3240 u_long ocwnd = tp->snd_cwnd; 3241 uint32_t pipe; 3242 int nseg = 0; /* consecutive new segments */ 3243 int nseg_rexmt = 0; /* retransmitted segments */ 3244 int maxrexmt = 0; 3245 3246 if (force) { 3247 uint32_t unsacked = tcp_sack_first_unsacked_len(tp); 3248 3249 /* 3250 * Try to fill the first hole in the receiver's 3251 * reassemble queue. 3252 */ 3253 maxrexmt = howmany(unsacked, tp->t_maxseg); 3254 if (maxrexmt > tcp_force_sackrxt) 3255 maxrexmt = tcp_force_sackrxt; 3256 } 3257 3258 tp->t_rtttime = 0; 3259 pipe = tcp_sack_compute_pipe(tp); 3260 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg 3261 || (force && nseg_rexmt < maxrexmt && nseg == 0)) && 3262 (!tcp_do_smartsack || nseg < TCP_SACK_MAXBURST)) { 3263 tcp_seq old_snd_max, old_rexmt_high, nextrexmt; 3264 uint32_t sent, seglen; 3265 boolean_t rescue; 3266 int error; 3267 3268 old_rexmt_high = tp->rexmt_high; 3269 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { 3270 tp->rexmt_high = old_rexmt_high; 3271 break; 3272 } 3273 3274 /* 3275 * If the next tranmission is a rescue retranmission, 3276 * we check whether we have already sent some data 3277 * (either new segments or retransmitted segments) 3278 * into the the network or not. Since the idea of rescue 3279 * retransmission is to sustain ACK clock, as long as 3280 * some segments are in the network, ACK clock will be 3281 * kept ticking. 3282 */ 3283 if (rescue && (nseg_rexmt > 0 || nseg > 0)) { 3284 tp->rexmt_high = old_rexmt_high; 3285 break; 3286 } 3287 3288 if (nextrexmt == tp->snd_max) 3289 ++nseg; 3290 else 3291 ++nseg_rexmt; 3292 tp->snd_nxt = nextrexmt; 3293 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3294 old_snd_max = tp->snd_max; 3295 if (nextrexmt == tp->snd_una) 3296 tcp_callout_stop(tp, tp->tt_rexmt); 3297 tp->t_flags |= TF_XMITNOW; 3298 error = tcp_output(tp); 3299 if (error != 0) { 3300 tp->rexmt_high = old_rexmt_high; 3301 break; 3302 } 3303 sent = tp->snd_nxt - nextrexmt; 3304 if (sent <= 0) { 3305 tp->rexmt_high = old_rexmt_high; 3306 break; 3307 } 3308 pipe += sent; 3309 tcpstat.tcps_sndsackpack++; 3310 tcpstat.tcps_sndsackbyte += sent; 3311 3312 if (rescue) { 3313 tcpstat.tcps_sackrescue++; 3314 tp->rexmt_rescue = tp->snd_nxt; 3315 tp->sack_flags |= TSACK_F_SACKRESCUED; 3316 break; 3317 } 3318 if (SEQ_LT(nextrexmt, old_snd_max) && 3319 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { 3320 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3321 if (tcp_aggressive_rescuesack && 3322 (tp->sack_flags & TSACK_F_SACKRESCUED) && 3323 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 3324 /* Drag RescueRxt along with HighRxt */ 3325 tp->rexmt_rescue = tp->rexmt_high; 3326 } 3327 } 3328 } 3329 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3330 tp->snd_nxt = old_snd_nxt; 3331 tp->snd_cwnd = ocwnd; 3332 } 3333 3334 /* 3335 * Return TRUE, if some new segments are sent 3336 */ 3337 static boolean_t 3338 tcp_sack_limitedxmit(struct tcpcb *tp) 3339 { 3340 tcp_seq oldsndnxt = tp->snd_nxt; 3341 tcp_seq oldsndmax = tp->snd_max; 3342 u_long ocwnd = tp->snd_cwnd; 3343 uint32_t pipe, sent; 3344 boolean_t ret = FALSE; 3345 tcp_seq_diff_t cwnd_left; 3346 tcp_seq next; 3347 3348 tp->rexmt_high = tp->snd_una - 1; 3349 pipe = tcp_sack_compute_pipe(tp); 3350 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe); 3351 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg) 3352 return FALSE; 3353 3354 if (tcp_do_smartsack) 3355 cwnd_left = ulmin(cwnd_left, tp->t_maxseg * TCP_SACK_MAXBURST); 3356 3357 next = tp->snd_nxt = tp->snd_max; 3358 tp->snd_cwnd = tp->snd_nxt - tp->snd_una + 3359 rounddown(cwnd_left, tp->t_maxseg); 3360 3361 tp->t_flags |= TF_XMITNOW; 3362 tcp_output(tp); 3363 3364 sent = tp->snd_nxt - next; 3365 if (sent > 0) { 3366 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg); 3367 ret = TRUE; 3368 } 3369 3370 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3371 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3372 ("snd_una moved in other threads")); 3373 tp->snd_nxt = oldsndnxt; 3374 } 3375 tp->snd_cwnd = ocwnd; 3376 3377 if (ret && TCP_DO_NCR(tp)) 3378 tcp_ncr_update_rxtthresh(tp); 3379 3380 return ret; 3381 } 3382 3383 /* 3384 * Reset idle time and keep-alive timer, typically called when a valid 3385 * tcp packet is received but may also be called when FASTKEEP is set 3386 * to prevent the previous long-timeout from calculating to a drop. 3387 * 3388 * Only update t_rcvtime for non-SYN packets. 3389 * 3390 * Handle the case where one side thinks the connection is established 3391 * but the other side has, say, rebooted without cleaning out the 3392 * connection. The SYNs could be construed as an attack and wind 3393 * up ignored, but in case it isn't an attack we can validate the 3394 * connection by forcing a keepalive. 3395 */ 3396 void 3397 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3398 { 3399 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3400 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3401 tp->t_flags |= TF_KEEPALIVE; 3402 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3403 tcp_timer_keep); 3404 } else { 3405 tp->t_rcvtime = ticks; 3406 tp->t_flags &= ~TF_KEEPALIVE; 3407 tcp_callout_reset(tp, tp->tt_keep, 3408 tp->t_keepidle, 3409 tcp_timer_keep); 3410 } 3411 } 3412 } 3413 3414 static int 3415 tcp_rmx_msl(const struct tcpcb *tp) 3416 { 3417 struct rtentry *rt; 3418 struct inpcb *inp = tp->t_inpcb; 3419 int msl; 3420 #ifdef INET6 3421 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3422 #else 3423 const boolean_t isipv6 = FALSE; 3424 #endif 3425 3426 if (isipv6) 3427 rt = tcp_rtlookup6(&inp->inp_inc); 3428 else 3429 rt = tcp_rtlookup(&inp->inp_inc); 3430 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3431 return tcp_msl; 3432 3433 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3434 if (msl == 0) 3435 msl = 1; 3436 3437 return msl; 3438 } 3439 3440 static void 3441 tcp_established(struct tcpcb *tp) 3442 { 3443 tp->t_state = TCPS_ESTABLISHED; 3444 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3445 3446 if (tp->t_rxtsyn > 0) { 3447 /* 3448 * RFC6298: 3449 * "If the timer expires awaiting the ACK of a SYN segment 3450 * and the TCP implementation is using an RTO less than 3 3451 * seconds, the RTO MUST be re-initialized to 3 seconds 3452 * when data transmission begins" 3453 */ 3454 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3455 tp->t_rxtcur = TCPTV_RTOBASE3; 3456 } 3457 } 3458 3459 /* 3460 * Returns TRUE, if the ACK should be dropped 3461 */ 3462 static boolean_t 3463 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags) 3464 { 3465 boolean_t fast_sack_rexmt = TRUE; 3466 3467 tcpstat.tcps_rcvdupack++; 3468 3469 /* 3470 * We have outstanding data (other than a window probe), 3471 * this is a completely duplicate ack (ie, window info 3472 * didn't change), the ack is the biggest we've seen and 3473 * we've seen exactly our rexmt threshhold of them, so 3474 * assume a packet has been dropped and retransmit it. 3475 * Kludge snd_nxt & the congestion window so we send only 3476 * this one packet. 3477 */ 3478 if (IN_FASTRECOVERY(tp)) { 3479 if (TCP_DO_SACK(tp)) { 3480 boolean_t force = FALSE; 3481 3482 if (tp->snd_una == tp->rexmt_high && 3483 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) == 3484 TOF_SACK) { 3485 /* 3486 * New segments got SACKed and 3487 * no retransmit yet. 3488 */ 3489 force = TRUE; 3490 } 3491 3492 /* No artifical cwnd inflation. */ 3493 tcp_sack_rexmt(tp, force); 3494 } else { 3495 /* 3496 * Dup acks mean that packets have left 3497 * the network (they're now cached at the 3498 * receiver) so bump cwnd by the amount in 3499 * the receiver to keep a constant cwnd 3500 * packets in the network. 3501 */ 3502 tp->snd_cwnd += tp->t_maxseg; 3503 tcp_output(tp); 3504 } 3505 return TRUE; 3506 } else if (SEQ_LT(th_ack, tp->snd_recover)) { 3507 tp->t_dupacks = 0; 3508 return FALSE; 3509 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && 3510 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == 3511 (TOF_DSACK | TOF_SACK_REDUNDANT)) { 3512 /* 3513 * If the ACK carries DSACK and other SACK blocks 3514 * carry information that we have already known, 3515 * don't count this ACK as duplicate ACK. This 3516 * prevents spurious early retransmit and fast 3517 * retransmit. This also meets the requirement of 3518 * RFC3042 that new segments should not be sent if 3519 * the SACK blocks do not contain new information 3520 * (XXX we actually loosen the requirment that only 3521 * DSACK is checked here). 3522 * 3523 * This kind of ACKs are usually sent after spurious 3524 * retransmit. 3525 */ 3526 /* Do nothing; don't change t_dupacks */ 3527 return TRUE; 3528 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) { 3529 tcp_ncr_update_rxtthresh(tp); 3530 } 3531 3532 if (++tp->t_dupacks == tp->t_rxtthresh) { 3533 tcp_seq old_snd_nxt; 3534 u_int win; 3535 3536 fastretransmit: 3537 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) { 3538 tcp_save_congestion_state(tp); 3539 tp->rxt_flags |= TRXT_F_FASTREXMT; 3540 } 3541 /* 3542 * We know we're losing at the current window size, 3543 * so do congestion avoidance: set ssthresh to half 3544 * the current window and pull our congestion window 3545 * back to the new ssthresh. 3546 */ 3547 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 3548 if (win < 2) 3549 win = 2; 3550 tp->snd_ssthresh = win * tp->t_maxseg; 3551 ENTER_FASTRECOVERY(tp); 3552 tp->snd_recover = tp->snd_max; 3553 tcp_callout_stop(tp, tp->tt_rexmt); 3554 tp->t_rtttime = 0; 3555 old_snd_nxt = tp->snd_nxt; 3556 tp->snd_nxt = th_ack; 3557 if (TCP_DO_SACK(tp)) { 3558 uint32_t rxtlen; 3559 3560 rxtlen = tcp_sack_first_unsacked_len(tp); 3561 if (rxtlen > tp->t_maxseg) 3562 rxtlen = tp->t_maxseg; 3563 tp->snd_cwnd = rxtlen; 3564 } else { 3565 tp->snd_cwnd = tp->t_maxseg; 3566 } 3567 tcp_output(tp); 3568 ++tcpstat.tcps_sndfastrexmit; 3569 tp->snd_cwnd = tp->snd_ssthresh; 3570 tp->rexmt_high = tp->snd_nxt; 3571 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 3572 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3573 tp->snd_nxt = old_snd_nxt; 3574 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big")); 3575 if (TCP_DO_SACK(tp)) { 3576 if (fast_sack_rexmt) 3577 tcp_sack_rexmt(tp, FALSE); 3578 } else { 3579 tp->snd_cwnd += tp->t_maxseg * 3580 (tp->t_dupacks - tp->snd_limited); 3581 } 3582 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) { 3583 /* 3584 * The RFC6675 recommends to reduce the byte threshold, 3585 * and enter fast retransmit if IsLost(snd_una). However, 3586 * if we use IsLost(snd_una) based fast retransmit here, 3587 * segments reordering will cause spurious retransmit. So 3588 * we defer the IsLost(snd_una) based fast retransmit until 3589 * the extended limited transmit can't send any segments and 3590 * early retransmit can't be done. 3591 */ 3592 if (tcp_rfc6675_rxt && tcp_do_rfc6675 && 3593 tcp_sack_islost(&tp->scb, tp->snd_una)) 3594 goto fastretransmit; 3595 3596 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) { 3597 if (!tcp_sack_limitedxmit(tp)) { 3598 /* outstanding data */ 3599 uint32_t ownd = tp->snd_max - tp->snd_una; 3600 3601 if (need_early_retransmit(tp, ownd)) { 3602 ++tcpstat.tcps_sndearlyrexmit; 3603 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3604 goto fastretransmit; 3605 } else if (tcp_do_rfc6675 && 3606 tcp_sack_islost(&tp->scb, tp->snd_una)) { 3607 fast_sack_rexmt = FALSE; 3608 goto fastretransmit; 3609 } 3610 } 3611 } 3612 } else if (tcp_do_limitedtransmit) { 3613 u_long oldcwnd = tp->snd_cwnd; 3614 tcp_seq oldsndmax = tp->snd_max; 3615 tcp_seq oldsndnxt = tp->snd_nxt; 3616 /* outstanding data */ 3617 uint32_t ownd = tp->snd_max - tp->snd_una; 3618 u_int sent; 3619 3620 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2, 3621 ("dupacks not 1 or 2")); 3622 if (tp->t_dupacks == 1) 3623 tp->snd_limited = 0; 3624 tp->snd_nxt = tp->snd_max; 3625 tp->snd_cwnd = ownd + 3626 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg; 3627 tp->t_flags |= TF_XMITNOW; 3628 tcp_output(tp); 3629 3630 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3631 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3632 ("snd_una moved in other threads")); 3633 tp->snd_nxt = oldsndnxt; 3634 } 3635 tp->snd_cwnd = oldcwnd; 3636 sent = tp->snd_max - oldsndmax; 3637 if (sent > tp->t_maxseg) { 3638 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) || 3639 (sent == tp->t_maxseg + 1 && 3640 (tp->t_flags & TF_SENTFIN)), 3641 ("sent too much")); 3642 KASSERT(sent <= tp->t_maxseg * 2, 3643 ("sent too many segments")); 3644 tp->snd_limited = 2; 3645 tcpstat.tcps_sndlimited += 2; 3646 } else if (sent > 0) { 3647 ++tp->snd_limited; 3648 ++tcpstat.tcps_sndlimited; 3649 } else if (need_early_retransmit(tp, ownd)) { 3650 ++tcpstat.tcps_sndearlyrexmit; 3651 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3652 goto fastretransmit; 3653 } 3654 } 3655 return TRUE; 3656 }
Cache object: 2364bf8c5d6128b1ff5e7a5e6784c578
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