1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 68 */ 69 70 #include "opt_inet.h" 71 #include "opt_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 #include "opt_tcp_input.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/proc.h> /* for proc0 declaration */ 83 #include <sys/protosw.h> 84 #include <sys/socket.h> 85 #include <sys/socketvar.h> 86 #include <sys/syslog.h> 87 #include <sys/in_cksum.h> 88 89 #include <sys/socketvar2.h> 90 91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 92 #include <machine/stdarg.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 101 #include <netinet/in_var.h> 102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 103 #include <netinet/in_pcb.h> 104 #include <netinet/ip_var.h> 105 #include <netinet/ip6.h> 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 #include <netinet/tcpip.h> 118 119 #ifdef TCPDEBUG 120 #include <netinet/tcp_debug.h> 121 122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 123 struct tcphdr tcp_savetcp; 124 #endif 125 126 #ifdef FAST_IPSEC 127 #include <netproto/ipsec/ipsec.h> 128 #include <netproto/ipsec/ipsec6.h> 129 #endif 130 131 #ifdef IPSEC 132 #include <netinet6/ipsec.h> 133 #include <netinet6/ipsec6.h> 134 #include <netproto/key/key.h> 135 #endif 136 137 /* 138 * Limit burst of new packets during SACK based fast recovery 139 * or extended limited transmit. 140 */ 141 #define TCP_SACK_MAXBURST 4 142 143 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 144 145 static int log_in_vain = 0; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 147 &log_in_vain, 0, "Log all incoming TCP connections"); 148 149 static int blackhole = 0; 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 151 &blackhole, 0, "Do not send RST when dropping refused connections"); 152 153 int tcp_delack_enabled = 1; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 155 &tcp_delack_enabled, 0, 156 "Delay ACK to try and piggyback it onto a data packet"); 157 158 #ifdef TCP_DROP_SYNFIN 159 static int drop_synfin = 0; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 161 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 162 #endif 163 164 static int tcp_do_limitedtransmit = 1; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 166 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 167 168 static int tcp_do_early_retransmit = 1; 169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 170 &tcp_do_early_retransmit, 0, "Early retransmit"); 171 172 int tcp_aggregate_acks = 1; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 174 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 175 176 static int tcp_do_eifel_detect = 1; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 178 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 179 180 static int tcp_do_abc = 1; 181 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 182 &tcp_do_abc, 0, 183 "TCP Appropriate Byte Counting (RFC 3465)"); 184 185 /* 186 * The following value actually takes range [25ms, 250ms], 187 * given that most modern systems use 1ms ~ 10ms as the unit 188 * of timestamp option. 189 */ 190 static u_int tcp_paws_tolerance = 25; 191 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW, 192 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance"); 193 194 /* 195 * Define as tunable for easy testing with SACK on and off. 196 * Warning: do not change setting in the middle of an existing active TCP flow, 197 * else strange things might happen to that flow. 198 */ 199 int tcp_do_sack = 1; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 201 &tcp_do_sack, 0, "Enable SACK Algorithms"); 202 203 int tcp_do_smartsack = 1; 204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 205 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 206 207 int tcp_do_rescuesack = 1; 208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, 209 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); 210 211 int tcp_aggressive_rescuesack = 0; 212 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, 213 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); 214 215 static int tcp_force_sackrxt = 1; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW, 217 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst"); 218 219 int tcp_do_rfc6675 = 1; 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW, 221 &tcp_do_rfc6675, 0, "Enable RFC6675"); 222 223 int tcp_rfc6675_rxt = 0; 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW, 225 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit"); 226 227 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 228 "TCP Segment Reassembly Queue"); 229 230 int tcp_reass_maxseg = 0; 231 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 232 &tcp_reass_maxseg, 0, 233 "Global maximum number of TCP Segments in Reassembly Queue"); 234 235 int tcp_reass_qsize = 0; 236 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 237 &tcp_reass_qsize, 0, 238 "Global number of TCP Segments currently in Reassembly Queue"); 239 240 static int tcp_reass_overflows = 0; 241 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 242 &tcp_reass_overflows, 0, 243 "Global number of TCP Segment Reassembly Queue Overflows"); 244 245 int tcp_do_autorcvbuf = 1; 246 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 247 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 248 249 int tcp_autorcvbuf_inc = 16*1024; 250 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 251 &tcp_autorcvbuf_inc, 0, 252 "Incrementor step size of automatic receive buffer"); 253 254 int tcp_autorcvbuf_max = 2*1024*1024; 255 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 256 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 257 258 int tcp_sosend_agglim = 3; 259 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 260 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 261 262 int tcp_sosend_async = 1; 263 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 264 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 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 void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, 271 tcp_seq); 272 static void tcp_pulloutofband(struct socket *, 273 struct tcphdr *, struct mbuf *, int); 274 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 275 struct mbuf *); 276 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); 277 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 278 static void tcp_sack_rexmt(struct tcpcb *, boolean_t); 279 static boolean_t tcp_sack_limitedxmit(struct tcpcb *); 280 static int tcp_rmx_msl(const struct tcpcb *); 281 static void tcp_established(struct tcpcb *); 282 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int); 283 284 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 285 #ifdef INET6 286 #define ND6_HINT(tp) \ 287 do { \ 288 if ((tp) && (tp)->t_inpcb && \ 289 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ 290 (tp)->t_inpcb->in6p_route.ro_rt) \ 291 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 292 } while (0) 293 #else 294 #define ND6_HINT(tp) 295 #endif 296 297 /* 298 * Indicate whether this ack should be delayed. We can delay the ack if 299 * - delayed acks are enabled and 300 * - there is no delayed ack timer in progress and 301 * - our last ack wasn't a 0-sized window. We never want to delay 302 * the ack that opens up a 0-sized window. 303 */ 304 #define DELAY_ACK(tp) \ 305 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 306 !(tp->t_flags & TF_RXWIN0SENT)) 307 308 #define acceptable_window_update(tp, th, tiwin) \ 309 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 310 (tp->snd_wl1 == th->th_seq && \ 311 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 312 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 313 314 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 315 #define need_early_retransmit(tp, ownd) \ 316 (tcp_do_early_retransmit && \ 317 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \ 318 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \ 319 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \ 320 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \ 321 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg))) 322 323 /* 324 * Returns TRUE, if this segment can be merged with the last 325 * pending segment in the reassemble queue and this segment 326 * does not overlap with the pending segment immediately 327 * preceeding the last pending segment. 328 */ 329 static __inline boolean_t 330 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen) 331 { 332 const struct tseg_qent *last, *prev; 333 334 last = TAILQ_LAST(&tp->t_segq, tsegqe_head); 335 if (last == NULL) 336 return FALSE; 337 338 /* This segment comes immediately after the last pending segment */ 339 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) { 340 if (last->tqe_th->th_flags & TH_FIN) { 341 /* No segments should follow segment w/ FIN */ 342 return FALSE; 343 } 344 return TRUE; 345 } 346 347 if (th->th_seq + tlen != last->tqe_th->th_seq) 348 return FALSE; 349 /* This segment comes immediately before the last pending segment */ 350 351 prev = TAILQ_PREV(last, tsegqe_head, tqe_q); 352 if (prev == NULL) { 353 /* 354 * No pending preceeding segment, we assume this segment 355 * could be reassembled. 356 */ 357 return TRUE; 358 } 359 360 /* This segment does not overlap with the preceeding segment */ 361 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len)) 362 return TRUE; 363 364 return FALSE; 365 } 366 367 static __inline void 368 tcp_ncr_update_rxtthresh(struct tcpcb *tp) 369 { 370 int old_rxtthresh = tp->t_rxtthresh; 371 uint32_t ownd = tp->snd_max - tp->snd_una; 372 373 tp->t_rxtthresh = max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1)); 374 if (tp->t_rxtthresh != old_rxtthresh) { 375 tcp_sack_update_lostseq(&tp->scb, tp->snd_una, 376 tp->t_maxseg, tp->t_rxtthresh); 377 } 378 } 379 380 static int 381 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 382 { 383 struct tseg_qent *q; 384 struct tseg_qent *p = NULL; 385 struct tseg_qent *te; 386 struct socket *so = tp->t_inpcb->inp_socket; 387 int flags; 388 389 /* 390 * Call with th == NULL after become established to 391 * force pre-ESTABLISHED data up to user socket. 392 */ 393 if (th == NULL) 394 goto present; 395 396 /* 397 * Limit the number of segments in the reassembly queue to prevent 398 * holding on to too many segments (and thus running out of mbufs). 399 * Make sure to let the missing segment through which caused this 400 * queue. Always keep one global queue entry spare to be able to 401 * process the missing segment. 402 */ 403 if (th->th_seq != tp->rcv_nxt && 404 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 405 tcp_reass_overflows++; 406 tcpstat.tcps_rcvmemdrop++; 407 m_freem(m); 408 /* no SACK block to report */ 409 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 410 return (0); 411 } 412 413 /* Allocate a new queue entry. */ 414 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 415 if (te == NULL) { 416 tcpstat.tcps_rcvmemdrop++; 417 m_freem(m); 418 /* no SACK block to report */ 419 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 420 return (0); 421 } 422 atomic_add_int(&tcp_reass_qsize, 1); 423 424 if (th->th_flags & TH_FIN) 425 tp->t_flags |= TF_QUEDFIN; 426 427 /* 428 * Find a segment which begins after this one does. 429 */ 430 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) { 431 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 432 break; 433 p = q; 434 } 435 436 /* 437 * If there is a preceding segment, it may provide some of 438 * our data already. If so, drop the data from the incoming 439 * segment. If it provides all of our data, drop us. 440 */ 441 if (p != NULL) { 442 tcp_seq_diff_t i; 443 444 /* conversion to int (in i) handles seq wraparound */ 445 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 446 if (i > 0) { /* overlaps preceding segment */ 447 tp->sack_flags |= 448 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 449 /* enclosing block starts w/ preceding segment */ 450 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 451 if (i >= *tlenp) { 452 if (th->th_flags & TH_FIN) 453 p->tqe_th->th_flags |= TH_FIN; 454 455 /* preceding encloses incoming segment */ 456 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 457 p->tqe_th->th_seq + p->tqe_len, 458 p->tqe_th->th_flags); 459 tcpstat.tcps_rcvduppack++; 460 tcpstat.tcps_rcvdupbyte += *tlenp; 461 m_freem(m); 462 kfree(te, M_TSEGQ); 463 atomic_add_int(&tcp_reass_qsize, -1); 464 /* 465 * Try to present any queued data 466 * at the left window edge to the user. 467 * This is needed after the 3-WHS 468 * completes. 469 */ 470 goto present; /* ??? */ 471 } 472 m_adj(m, i); 473 *tlenp -= i; 474 th->th_seq += i; 475 /* incoming segment end is enclosing block end */ 476 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 477 th->th_seq + *tlenp, th->th_flags); 478 /* trim end of reported D-SACK block */ 479 tp->reportblk.rblk_end = th->th_seq; 480 } 481 } 482 tcpstat.tcps_rcvoopack++; 483 tcpstat.tcps_rcvoobyte += *tlenp; 484 485 /* 486 * While we overlap succeeding segments trim them or, 487 * if they are completely covered, dequeue them. 488 */ 489 while (q) { 490 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 491 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 492 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 493 struct tseg_qent *nq; 494 495 if (i <= 0) 496 break; 497 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 498 /* first time through */ 499 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 500 tp->encloseblk = tp->reportblk; 501 /* report trailing duplicate D-SACK segment */ 502 tp->reportblk.rblk_start = q->tqe_th->th_seq; 503 } 504 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) && 505 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 506 /* extend enclosing block if one exists */ 507 tp->encloseblk.rblk_end = qend_sack; 508 } 509 if (i < q->tqe_len) { 510 q->tqe_th->th_seq += i; 511 q->tqe_len -= i; 512 m_adj(q->tqe_m, i); 513 break; 514 } 515 516 if (q->tqe_th->th_flags & TH_FIN) 517 th->th_flags |= TH_FIN; 518 519 nq = TAILQ_NEXT(q, tqe_q); 520 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 521 m_freem(q->tqe_m); 522 kfree(q, M_TSEGQ); 523 atomic_add_int(&tcp_reass_qsize, -1); 524 q = nq; 525 } 526 527 /* Insert the new segment queue entry into place. */ 528 te->tqe_m = m; 529 te->tqe_th = th; 530 te->tqe_len = *tlenp; 531 532 /* check if can coalesce with following segment */ 533 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 534 tcp_seq tend_sack; 535 536 te->tqe_len += q->tqe_len; 537 if (q->tqe_th->th_flags & TH_FIN) 538 te->tqe_th->th_flags |= TH_FIN; 539 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len, 540 te->tqe_th->th_flags); 541 542 m_cat(te->tqe_m, q->tqe_m); 543 tp->encloseblk.rblk_end = tend_sack; 544 /* 545 * When not reporting a duplicate segment, use 546 * the larger enclosing block as the SACK block. 547 */ 548 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 549 tp->reportblk.rblk_end = tend_sack; 550 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 551 kfree(q, M_TSEGQ); 552 atomic_add_int(&tcp_reass_qsize, -1); 553 } 554 555 if (p == NULL) { 556 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q); 557 } else { 558 /* check if can coalesce with preceding segment */ 559 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 560 if (te->tqe_th->th_flags & TH_FIN) 561 p->tqe_th->th_flags |= TH_FIN; 562 p->tqe_len += te->tqe_len; 563 m_cat(p->tqe_m, te->tqe_m); 564 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 565 /* 566 * When not reporting a duplicate segment, use 567 * the larger enclosing block as the SACK block. 568 */ 569 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 570 tp->reportblk.rblk_start = p->tqe_th->th_seq; 571 kfree(te, M_TSEGQ); 572 atomic_add_int(&tcp_reass_qsize, -1); 573 } else { 574 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q); 575 } 576 } 577 578 present: 579 /* 580 * Present data to user, advancing rcv_nxt through 581 * completed sequence space. 582 */ 583 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 584 return (0); 585 q = TAILQ_FIRST(&tp->t_segq); 586 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 587 return (0); 588 tp->rcv_nxt += q->tqe_len; 589 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 590 /* no SACK block to report since ACK advanced */ 591 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 592 } 593 /* no enclosing block to report since ACK advanced */ 594 tp->sack_flags &= ~TSACK_F_ENCLOSESEG; 595 flags = q->tqe_th->th_flags & TH_FIN; 596 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 597 KASSERT(TAILQ_EMPTY(&tp->t_segq) || 598 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 599 ("segment not coalesced")); 600 if (so->so_state & SS_CANTRCVMORE) { 601 m_freem(q->tqe_m); 602 } else { 603 lwkt_gettoken(&so->so_rcv.ssb_token); 604 ssb_appendstream(&so->so_rcv, q->tqe_m); 605 lwkt_reltoken(&so->so_rcv.ssb_token); 606 } 607 kfree(q, M_TSEGQ); 608 atomic_add_int(&tcp_reass_qsize, -1); 609 ND6_HINT(tp); 610 sorwakeup(so); 611 return (flags); 612 } 613 614 /* 615 * TCP input routine, follows pages 65-76 of the 616 * protocol specification dated September, 1981 very closely. 617 */ 618 #ifdef INET6 619 int 620 tcp6_input(struct mbuf **mp, int *offp, int proto) 621 { 622 struct mbuf *m = *mp; 623 struct in6_ifaddr *ia6; 624 625 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 626 627 /* 628 * draft-itojun-ipv6-tcp-to-anycast 629 * better place to put this in? 630 */ 631 ia6 = ip6_getdstifaddr(m); 632 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 633 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 634 offsetof(struct ip6_hdr, ip6_dst)); 635 return (IPPROTO_DONE); 636 } 637 638 tcp_input(mp, offp, proto); 639 return (IPPROTO_DONE); 640 } 641 #endif 642 643 int 644 tcp_input(struct mbuf **mp, int *offp, int proto) 645 { 646 int off0; 647 struct tcphdr *th; 648 struct ip *ip = NULL; 649 struct ipovly *ipov; 650 struct inpcb *inp = NULL; 651 u_char *optp = NULL; 652 int optlen = 0; 653 int tlen, off; 654 int len = 0; 655 int drop_hdrlen; 656 struct tcpcb *tp = NULL; 657 int thflags; 658 struct socket *so = NULL; 659 int todrop, acked; 660 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE; 661 tcp_seq th_dupack = 0; /* XXX gcc warning */ 662 u_int to_flags = 0; /* XXX gcc warning */ 663 u_long tiwin; 664 int recvwin; 665 struct tcpopt to; /* options in this segment */ 666 struct sockaddr_in *next_hop = NULL; 667 int rstreason; /* For badport_bandlim accounting purposes */ 668 int cpu; 669 struct ip6_hdr *ip6 = NULL; 670 struct mbuf *m; 671 #ifdef INET6 672 boolean_t isipv6; 673 #else 674 const boolean_t isipv6 = FALSE; 675 #endif 676 #ifdef TCPDEBUG 677 short ostate = 0; 678 #endif 679 680 off0 = *offp; 681 m = *mp; 682 *mp = NULL; 683 684 tcpstat.tcps_rcvtotal++; 685 686 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 687 struct m_tag *mtag; 688 689 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 690 KKASSERT(mtag != NULL); 691 next_hop = m_tag_data(mtag); 692 } 693 694 #ifdef INET6 695 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 696 #endif 697 698 if (isipv6) { 699 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 700 ip6 = mtod(m, struct ip6_hdr *); 701 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 702 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 703 tcpstat.tcps_rcvbadsum++; 704 goto drop; 705 } 706 th = (struct tcphdr *)((caddr_t)ip6 + off0); 707 708 /* 709 * Be proactive about unspecified IPv6 address in source. 710 * As we use all-zero to indicate unbounded/unconnected pcb, 711 * unspecified IPv6 address can be used to confuse us. 712 * 713 * Note that packets with unspecified IPv6 destination is 714 * already dropped in ip6_input. 715 */ 716 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 717 /* XXX stat */ 718 goto drop; 719 } 720 } else { 721 /* 722 * Get IP and TCP header together in first mbuf. 723 * Note: IP leaves IP header in first mbuf. 724 */ 725 if (off0 > sizeof(struct ip)) { 726 ip_stripoptions(m); 727 off0 = sizeof(struct ip); 728 } 729 /* already checked and pulled up in ip_demux() */ 730 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 731 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 732 ip = mtod(m, struct ip *); 733 ipov = (struct ipovly *)ip; 734 th = (struct tcphdr *)((caddr_t)ip + off0); 735 tlen = ip->ip_len; 736 737 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 738 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 739 th->th_sum = m->m_pkthdr.csum_data; 740 else 741 th->th_sum = in_pseudo(ip->ip_src.s_addr, 742 ip->ip_dst.s_addr, 743 htonl(m->m_pkthdr.csum_data + 744 ip->ip_len + 745 IPPROTO_TCP)); 746 th->th_sum ^= 0xffff; 747 } else { 748 /* 749 * Checksum extended TCP header and data. 750 */ 751 len = sizeof(struct ip) + tlen; 752 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 753 ipov->ih_len = (u_short)tlen; 754 ipov->ih_len = htons(ipov->ih_len); 755 th->th_sum = in_cksum(m, len); 756 } 757 if (th->th_sum) { 758 tcpstat.tcps_rcvbadsum++; 759 goto drop; 760 } 761 #ifdef INET6 762 /* Re-initialization for later version check */ 763 ip->ip_v = IPVERSION; 764 #endif 765 } 766 767 /* 768 * Check that TCP offset makes sense, 769 * pull out TCP options and adjust length. XXX 770 */ 771 off = th->th_off << 2; 772 /* already checked and pulled up in ip_demux() */ 773 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 774 ("bad TCP data offset %d (tlen %d)", off, tlen)); 775 tlen -= off; /* tlen is used instead of ti->ti_len */ 776 if (off > sizeof(struct tcphdr)) { 777 if (isipv6) { 778 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 779 ip6 = mtod(m, struct ip6_hdr *); 780 th = (struct tcphdr *)((caddr_t)ip6 + off0); 781 } else { 782 /* already pulled up in ip_demux() */ 783 KASSERT(m->m_len >= sizeof(struct ip) + off, 784 ("TCP header and options not in one mbuf: " 785 "m_len %d, off %d", m->m_len, off)); 786 } 787 optlen = off - sizeof(struct tcphdr); 788 optp = (u_char *)(th + 1); 789 } 790 thflags = th->th_flags; 791 792 #ifdef TCP_DROP_SYNFIN 793 /* 794 * If the drop_synfin option is enabled, drop all packets with 795 * both the SYN and FIN bits set. This prevents e.g. nmap from 796 * identifying the TCP/IP stack. 797 * 798 * This is a violation of the TCP specification. 799 */ 800 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 801 goto drop; 802 #endif 803 804 /* 805 * Convert TCP protocol specific fields to host format. 806 */ 807 th->th_seq = ntohl(th->th_seq); 808 th->th_ack = ntohl(th->th_ack); 809 th->th_win = ntohs(th->th_win); 810 th->th_urp = ntohs(th->th_urp); 811 812 /* 813 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 814 * until after ip6_savecontrol() is called and before other functions 815 * which don't want those proto headers. 816 * Because ip6_savecontrol() is going to parse the mbuf to 817 * search for data to be passed up to user-land, it wants mbuf 818 * parameters to be unchanged. 819 * XXX: the call of ip6_savecontrol() has been obsoleted based on 820 * latest version of the advanced API (20020110). 821 */ 822 drop_hdrlen = off0 + off; 823 824 /* 825 * Locate pcb for segment. 826 */ 827 findpcb: 828 /* IPFIREWALL_FORWARD section */ 829 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 830 /* 831 * Transparently forwarded. Pretend to be the destination. 832 * already got one like this? 833 */ 834 cpu = mycpu->gd_cpuid; 835 inp = in_pcblookup_hash(&tcbinfo[cpu], 836 ip->ip_src, th->th_sport, 837 ip->ip_dst, th->th_dport, 838 0, m->m_pkthdr.rcvif); 839 if (!inp) { 840 /* 841 * It's new. Try to find the ambushing socket. 842 */ 843 844 /* 845 * The rest of the ipfw code stores the port in 846 * host order. XXX 847 * (The IP address is still in network order.) 848 */ 849 in_port_t dport = next_hop->sin_port ? 850 htons(next_hop->sin_port) : 851 th->th_dport; 852 853 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 854 next_hop->sin_addr.s_addr, dport); 855 inp = in_pcblookup_hash(&tcbinfo[cpu], 856 ip->ip_src, th->th_sport, 857 next_hop->sin_addr, dport, 858 1, m->m_pkthdr.rcvif); 859 } 860 } else { 861 if (isipv6) { 862 inp = in6_pcblookup_hash(&tcbinfo[0], 863 &ip6->ip6_src, th->th_sport, 864 &ip6->ip6_dst, th->th_dport, 865 1, m->m_pkthdr.rcvif); 866 } else { 867 cpu = mycpu->gd_cpuid; 868 inp = in_pcblookup_hash(&tcbinfo[cpu], 869 ip->ip_src, th->th_sport, 870 ip->ip_dst, th->th_dport, 871 1, m->m_pkthdr.rcvif); 872 } 873 } 874 875 /* 876 * If the state is CLOSED (i.e., TCB does not exist) then 877 * all data in the incoming segment is discarded. 878 * If the TCB exists but is in CLOSED state, it is embryonic, 879 * but should either do a listen or a connect soon. 880 */ 881 if (inp == NULL) { 882 if (log_in_vain) { 883 #ifdef INET6 884 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 885 #else 886 char dbuf[sizeof "aaa.bbb.ccc.ddd"]; 887 char sbuf[sizeof "aaa.bbb.ccc.ddd"]; 888 #endif 889 if (isipv6) { 890 strcpy(dbuf, "["); 891 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 892 strcat(dbuf, "]"); 893 strcpy(sbuf, "["); 894 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 895 strcat(sbuf, "]"); 896 } else { 897 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 898 strcpy(sbuf, inet_ntoa(ip->ip_src)); 899 } 900 switch (log_in_vain) { 901 case 1: 902 if (!(thflags & TH_SYN)) 903 break; 904 case 2: 905 log(LOG_INFO, 906 "Connection attempt to TCP %s:%d " 907 "from %s:%d flags:0x%02x\n", 908 dbuf, ntohs(th->th_dport), sbuf, 909 ntohs(th->th_sport), thflags); 910 break; 911 default: 912 break; 913 } 914 } 915 if (blackhole) { 916 switch (blackhole) { 917 case 1: 918 if (thflags & TH_SYN) 919 goto drop; 920 break; 921 case 2: 922 goto drop; 923 default: 924 goto drop; 925 } 926 } 927 rstreason = BANDLIM_RST_CLOSEDPORT; 928 goto dropwithreset; 929 } 930 931 #ifdef IPSEC 932 if (isipv6) { 933 if (ipsec6_in_reject_so(m, inp->inp_socket)) { 934 ipsec6stat.in_polvio++; 935 goto drop; 936 } 937 } else { 938 if (ipsec4_in_reject_so(m, inp->inp_socket)) { 939 ipsecstat.in_polvio++; 940 goto drop; 941 } 942 } 943 #endif 944 #ifdef FAST_IPSEC 945 if (isipv6) { 946 if (ipsec6_in_reject(m, inp)) 947 goto drop; 948 } else { 949 if (ipsec4_in_reject(m, inp)) 950 goto drop; 951 } 952 #endif 953 /* Check the minimum TTL for socket. */ 954 #ifdef INET6 955 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 956 goto drop; 957 #endif 958 959 tp = intotcpcb(inp); 960 if (tp == NULL) { 961 rstreason = BANDLIM_RST_CLOSEDPORT; 962 goto dropwithreset; 963 } 964 if (tp->t_state <= TCPS_CLOSED) 965 goto drop; 966 967 so = inp->inp_socket; 968 969 #ifdef TCPDEBUG 970 if (so->so_options & SO_DEBUG) { 971 ostate = tp->t_state; 972 if (isipv6) 973 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 974 else 975 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 976 tcp_savetcp = *th; 977 } 978 #endif 979 980 bzero(&to, sizeof to); 981 982 if (so->so_options & SO_ACCEPTCONN) { 983 struct in_conninfo inc; 984 985 #ifdef INET6 986 inc.inc_isipv6 = (isipv6 == TRUE); 987 #endif 988 if (isipv6) { 989 inc.inc6_faddr = ip6->ip6_src; 990 inc.inc6_laddr = ip6->ip6_dst; 991 inc.inc6_route.ro_rt = NULL; /* XXX */ 992 } else { 993 inc.inc_faddr = ip->ip_src; 994 inc.inc_laddr = ip->ip_dst; 995 inc.inc_route.ro_rt = NULL; /* XXX */ 996 } 997 inc.inc_fport = th->th_sport; 998 inc.inc_lport = th->th_dport; 999 1000 /* 1001 * If the state is LISTEN then ignore segment if it contains 1002 * a RST. If the segment contains an ACK then it is bad and 1003 * send a RST. If it does not contain a SYN then it is not 1004 * interesting; drop it. 1005 * 1006 * If the state is SYN_RECEIVED (syncache) and seg contains 1007 * an ACK, but not for our SYN/ACK, send a RST. If the seg 1008 * contains a RST, check the sequence number to see if it 1009 * is a valid reset segment. 1010 */ 1011 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 1012 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 1013 if (!syncache_expand(&inc, th, &so, m)) { 1014 /* 1015 * No syncache entry, or ACK was not 1016 * for our SYN/ACK. Send a RST. 1017 */ 1018 tcpstat.tcps_badsyn++; 1019 rstreason = BANDLIM_RST_OPENPORT; 1020 goto dropwithreset; 1021 } 1022 1023 /* 1024 * Could not complete 3-way handshake, 1025 * connection is being closed down, and 1026 * syncache will free mbuf. 1027 */ 1028 if (so == NULL) 1029 return(IPPROTO_DONE); 1030 1031 /* 1032 * We must be in the correct protocol thread 1033 * for this connection. 1034 */ 1035 KKASSERT(so->so_port == &curthread->td_msgport); 1036 1037 /* 1038 * Socket is created in state SYN_RECEIVED. 1039 * Continue processing segment. 1040 */ 1041 inp = so->so_pcb; 1042 tp = intotcpcb(inp); 1043 /* 1044 * This is what would have happened in 1045 * tcp_output() when the SYN,ACK was sent. 1046 */ 1047 tp->snd_up = tp->snd_una; 1048 tp->snd_max = tp->snd_nxt = tp->iss + 1; 1049 tp->last_ack_sent = tp->rcv_nxt; 1050 1051 goto after_listen; 1052 } 1053 if (thflags & TH_RST) { 1054 syncache_chkrst(&inc, th); 1055 goto drop; 1056 } 1057 if (thflags & TH_ACK) { 1058 syncache_badack(&inc); 1059 tcpstat.tcps_badsyn++; 1060 rstreason = BANDLIM_RST_OPENPORT; 1061 goto dropwithreset; 1062 } 1063 goto drop; 1064 } 1065 1066 /* 1067 * Segment's flags are (SYN) or (SYN | FIN). 1068 */ 1069 #ifdef INET6 1070 /* 1071 * If deprecated address is forbidden, 1072 * we do not accept SYN to deprecated interface 1073 * address to prevent any new inbound connection from 1074 * getting established. 1075 * When we do not accept SYN, we send a TCP RST, 1076 * with deprecated source address (instead of dropping 1077 * it). We compromise it as it is much better for peer 1078 * to send a RST, and RST will be the final packet 1079 * for the exchange. 1080 * 1081 * If we do not forbid deprecated addresses, we accept 1082 * the SYN packet. RFC2462 does not suggest dropping 1083 * SYN in this case. 1084 * If we decipher RFC2462 5.5.4, it says like this: 1085 * 1. use of deprecated addr with existing 1086 * communication is okay - "SHOULD continue to be 1087 * used" 1088 * 2. use of it with new communication: 1089 * (2a) "SHOULD NOT be used if alternate address 1090 * with sufficient scope is available" 1091 * (2b) nothing mentioned otherwise. 1092 * Here we fall into (2b) case as we have no choice in 1093 * our source address selection - we must obey the peer. 1094 * 1095 * The wording in RFC2462 is confusing, and there are 1096 * multiple description text for deprecated address 1097 * handling - worse, they are not exactly the same. 1098 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1099 */ 1100 if (isipv6 && !ip6_use_deprecated) { 1101 struct in6_ifaddr *ia6; 1102 1103 if ((ia6 = ip6_getdstifaddr(m)) && 1104 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1105 tp = NULL; 1106 rstreason = BANDLIM_RST_OPENPORT; 1107 goto dropwithreset; 1108 } 1109 } 1110 #endif 1111 /* 1112 * If it is from this socket, drop it, it must be forged. 1113 * Don't bother responding if the destination was a broadcast. 1114 */ 1115 if (th->th_dport == th->th_sport) { 1116 if (isipv6) { 1117 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1118 &ip6->ip6_src)) 1119 goto drop; 1120 } else { 1121 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1122 goto drop; 1123 } 1124 } 1125 /* 1126 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1127 * 1128 * Note that it is quite possible to receive unicast 1129 * link-layer packets with a broadcast IP address. Use 1130 * in_broadcast() to find them. 1131 */ 1132 if (m->m_flags & (M_BCAST | M_MCAST)) 1133 goto drop; 1134 if (isipv6) { 1135 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1136 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1137 goto drop; 1138 } else { 1139 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1140 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1141 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1142 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1143 goto drop; 1144 } 1145 /* 1146 * SYN appears to be valid; create compressed TCP state 1147 * for syncache, or perform t/tcp connection. 1148 */ 1149 if (so->so_qlen <= so->so_qlimit) { 1150 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); 1151 if (!syncache_add(&inc, &to, th, so, m)) 1152 goto drop; 1153 1154 /* 1155 * Entry added to syncache, mbuf used to 1156 * send SYN,ACK packet. 1157 */ 1158 return(IPPROTO_DONE); 1159 } 1160 goto drop; 1161 } 1162 1163 after_listen: 1164 /* 1165 * Should not happen - syncache should pick up these connections. 1166 * 1167 * Once we are past handling listen sockets we must be in the 1168 * correct protocol processing thread. 1169 */ 1170 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1171 KKASSERT(so->so_port == &curthread->td_msgport); 1172 1173 /* Unscale the window into a 32-bit value. */ 1174 if (!(thflags & TH_SYN)) 1175 tiwin = th->th_win << tp->snd_scale; 1176 else 1177 tiwin = th->th_win; 1178 1179 /* 1180 * This is the second part of the MSS DoS prevention code (after 1181 * minmss on the sending side) and it deals with too many too small 1182 * tcp packets in a too short timeframe (1 second). 1183 * 1184 * XXX Removed. This code was crap. It does not scale to network 1185 * speed, and default values break NFS. Gone. 1186 */ 1187 /* REMOVED */ 1188 1189 /* 1190 * Segment received on connection. 1191 * 1192 * Reset idle time and keep-alive timer. Don't waste time if less 1193 * then a second has elapsed. 1194 */ 1195 if ((int)(ticks - tp->t_rcvtime) > hz) 1196 tcp_timer_keep_activity(tp, thflags); 1197 1198 /* 1199 * Process options. 1200 * XXX this is tradtitional behavior, may need to be cleaned up. 1201 */ 1202 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); 1203 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1204 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { 1205 tp->t_flags |= TF_RCVD_SCALE; 1206 tp->snd_scale = to.to_requested_s_scale; 1207 } 1208 1209 /* 1210 * Initial send window; will be updated upon next ACK 1211 */ 1212 tp->snd_wnd = th->th_win; 1213 1214 if (to.to_flags & TOF_TS) { 1215 tp->t_flags |= TF_RCVD_TSTMP; 1216 tp->ts_recent = to.to_tsval; 1217 tp->ts_recent_age = ticks; 1218 } 1219 if (!(to.to_flags & TOF_MSS)) 1220 to.to_mss = 0; 1221 tcp_mss(tp, to.to_mss); 1222 /* 1223 * Only set the TF_SACK_PERMITTED per-connection flag 1224 * if we got a SACK_PERMITTED option from the other side 1225 * and the global tcp_do_sack variable is true. 1226 */ 1227 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1228 tp->t_flags |= TF_SACK_PERMITTED; 1229 } 1230 1231 /* 1232 * Header prediction: check for the two common cases 1233 * of a uni-directional data xfer. If the packet has 1234 * no control flags, is in-sequence, the window didn't 1235 * change and we're not retransmitting, it's a 1236 * candidate. If the length is zero and the ack moved 1237 * forward, we're the sender side of the xfer. Just 1238 * free the data acked & wake any higher level process 1239 * that was blocked waiting for space. If the length 1240 * is non-zero and the ack didn't move, we're the 1241 * receiver side. If we're getting packets in-order 1242 * (the reassembly queue is empty), add the data to 1243 * the socket buffer and note that we need a delayed ack. 1244 * Make sure that the hidden state-flags are also off. 1245 * Since we check for TCPS_ESTABLISHED above, it can only 1246 * be TH_NEEDSYN. 1247 */ 1248 if (tp->t_state == TCPS_ESTABLISHED && 1249 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1250 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1251 (!(to.to_flags & TOF_TS) || 1252 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1253 th->th_seq == tp->rcv_nxt && 1254 tp->snd_nxt == tp->snd_max) { 1255 1256 /* 1257 * If last ACK falls within this segment's sequence numbers, 1258 * record the timestamp. 1259 * NOTE that the test is modified according to the latest 1260 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1261 */ 1262 if ((to.to_flags & TOF_TS) && 1263 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1264 tp->ts_recent_age = ticks; 1265 tp->ts_recent = to.to_tsval; 1266 } 1267 1268 if (tlen == 0) { 1269 if (SEQ_GT(th->th_ack, tp->snd_una) && 1270 SEQ_LEQ(th->th_ack, tp->snd_max) && 1271 tp->snd_cwnd >= tp->snd_wnd && 1272 !IN_FASTRECOVERY(tp)) { 1273 /* 1274 * This is a pure ack for outstanding data. 1275 */ 1276 ++tcpstat.tcps_predack; 1277 /* 1278 * "bad retransmit" recovery 1279 * 1280 * If Eifel detection applies, then 1281 * it is deterministic, so use it 1282 * unconditionally over the old heuristic. 1283 * Otherwise, fall back to the old heuristic. 1284 */ 1285 if (tcp_do_eifel_detect && 1286 (to.to_flags & TOF_TS) && to.to_tsecr && 1287 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 1288 /* Eifel detection applicable. */ 1289 if (to.to_tsecr < tp->t_rexmtTS) { 1290 tcp_revert_congestion_state(tp); 1291 ++tcpstat.tcps_eifeldetected; 1292 if (tp->t_rxtshift != 1 || 1293 ticks >= tp->t_badrxtwin) 1294 ++tcpstat.tcps_rttcantdetect; 1295 } 1296 } else if (tp->t_rxtshift == 1 && 1297 ticks < tp->t_badrxtwin) { 1298 tcp_revert_congestion_state(tp); 1299 ++tcpstat.tcps_rttdetected; 1300 } 1301 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 1302 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 1303 /* 1304 * Recalculate the retransmit timer / rtt. 1305 * 1306 * Some machines (certain windows boxes) 1307 * send broken timestamp replies during the 1308 * SYN+ACK phase, ignore timestamps of 0. 1309 */ 1310 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1311 tcp_xmit_timer(tp, 1312 ticks - to.to_tsecr + 1, 1313 th->th_ack); 1314 } else if (tp->t_rtttime && 1315 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1316 tcp_xmit_timer(tp, 1317 ticks - tp->t_rtttime, 1318 th->th_ack); 1319 } 1320 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1321 acked = th->th_ack - tp->snd_una; 1322 tcpstat.tcps_rcvackpack++; 1323 tcpstat.tcps_rcvackbyte += acked; 1324 sbdrop(&so->so_snd.sb, acked); 1325 tp->snd_recover = th->th_ack - 1; 1326 tp->snd_una = th->th_ack; 1327 tp->t_dupacks = 0; 1328 /* 1329 * Update window information. 1330 */ 1331 if (tiwin != tp->snd_wnd && 1332 acceptable_window_update(tp, th, tiwin)) { 1333 /* keep track of pure window updates */ 1334 if (tp->snd_wl2 == th->th_ack && 1335 tiwin > tp->snd_wnd) 1336 tcpstat.tcps_rcvwinupd++; 1337 tp->snd_wnd = tiwin; 1338 tp->snd_wl1 = th->th_seq; 1339 tp->snd_wl2 = th->th_ack; 1340 if (tp->snd_wnd > tp->max_sndwnd) 1341 tp->max_sndwnd = tp->snd_wnd; 1342 } 1343 m_freem(m); 1344 ND6_HINT(tp); /* some progress has been done */ 1345 /* 1346 * If all outstanding data are acked, stop 1347 * retransmit timer, otherwise restart timer 1348 * using current (possibly backed-off) value. 1349 * If process is waiting for space, 1350 * wakeup/selwakeup/signal. If data 1351 * are ready to send, let tcp_output 1352 * decide between more output or persist. 1353 */ 1354 if (tp->snd_una == tp->snd_max) { 1355 tcp_callout_stop(tp, tp->tt_rexmt); 1356 } else if (!tcp_callout_active(tp, 1357 tp->tt_persist)) { 1358 tcp_callout_reset(tp, tp->tt_rexmt, 1359 tp->t_rxtcur, tcp_timer_rexmt); 1360 } 1361 sowwakeup(so); 1362 if (so->so_snd.ssb_cc > 0 && 1363 !tcp_output_pending(tp)) 1364 tcp_output_fair(tp); 1365 return(IPPROTO_DONE); 1366 } 1367 } else if (tiwin == tp->snd_wnd && 1368 th->th_ack == tp->snd_una && 1369 TAILQ_EMPTY(&tp->t_segq) && 1370 tlen <= ssb_space(&so->so_rcv)) { 1371 u_long newsize = 0; /* automatic sockbuf scaling */ 1372 /* 1373 * This is a pure, in-sequence data packet 1374 * with nothing on the reassembly queue and 1375 * we have enough buffer space to take it. 1376 */ 1377 ++tcpstat.tcps_preddat; 1378 tp->rcv_nxt += tlen; 1379 tcpstat.tcps_rcvpack++; 1380 tcpstat.tcps_rcvbyte += tlen; 1381 ND6_HINT(tp); /* some progress has been done */ 1382 /* 1383 * Automatic sizing of receive socket buffer. Often the send 1384 * buffer size is not optimally adjusted to the actual network 1385 * conditions at hand (delay bandwidth product). Setting the 1386 * buffer size too small limits throughput on links with high 1387 * bandwidth and high delay (eg. trans-continental/oceanic links). 1388 * 1389 * On the receive side the socket buffer memory is only rarely 1390 * used to any significant extent. This allows us to be much 1391 * more aggressive in scaling the receive socket buffer. For 1392 * the case that the buffer space is actually used to a large 1393 * extent and we run out of kernel memory we can simply drop 1394 * the new segments; TCP on the sender will just retransmit it 1395 * later. Setting the buffer size too big may only consume too 1396 * much kernel memory if the application doesn't read() from 1397 * the socket or packet loss or reordering makes use of the 1398 * reassembly queue. 1399 * 1400 * The criteria to step up the receive buffer one notch are: 1401 * 1. the number of bytes received during the time it takes 1402 * one timestamp to be reflected back to us (the RTT); 1403 * 2. received bytes per RTT is within seven eighth of the 1404 * current socket buffer size; 1405 * 3. receive buffer size has not hit maximal automatic size; 1406 * 1407 * This algorithm does one step per RTT at most and only if 1408 * we receive a bulk stream w/o packet losses or reorderings. 1409 * Shrinking the buffer during idle times is not necessary as 1410 * it doesn't consume any memory when idle. 1411 * 1412 * TODO: Only step up if the application is actually serving 1413 * the buffer to better manage the socket buffer resources. 1414 */ 1415 if (tcp_do_autorcvbuf && 1416 to.to_tsecr && 1417 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1418 if (to.to_tsecr > tp->rfbuf_ts && 1419 to.to_tsecr - tp->rfbuf_ts < hz) { 1420 if (tp->rfbuf_cnt > 1421 (so->so_rcv.ssb_hiwat / 8 * 7) && 1422 so->so_rcv.ssb_hiwat < 1423 tcp_autorcvbuf_max) { 1424 newsize = 1425 ulmin(so->so_rcv.ssb_hiwat + 1426 tcp_autorcvbuf_inc, 1427 tcp_autorcvbuf_max); 1428 } 1429 /* Start over with next RTT. */ 1430 tp->rfbuf_ts = 0; 1431 tp->rfbuf_cnt = 0; 1432 } else 1433 tp->rfbuf_cnt += tlen; /* add up */ 1434 } 1435 /* 1436 * Add data to socket buffer. 1437 */ 1438 if (so->so_state & SS_CANTRCVMORE) { 1439 m_freem(m); 1440 } else { 1441 /* 1442 * Set new socket buffer size, give up when 1443 * limit is reached. 1444 * 1445 * Adjusting the size can mess up ACK 1446 * sequencing when pure window updates are 1447 * being avoided (which is the default), 1448 * so force an ack. 1449 */ 1450 lwkt_gettoken(&so->so_rcv.ssb_token); 1451 if (newsize) { 1452 tp->t_flags |= TF_RXRESIZED; 1453 if (!ssb_reserve(&so->so_rcv, newsize, 1454 so, NULL)) { 1455 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1456 } 1457 if (newsize >= 1458 (TCP_MAXWIN << tp->rcv_scale)) { 1459 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1460 } 1461 } 1462 m_adj(m, drop_hdrlen); /* delayed header drop */ 1463 ssb_appendstream(&so->so_rcv, m); 1464 lwkt_reltoken(&so->so_rcv.ssb_token); 1465 } 1466 sorwakeup(so); 1467 /* 1468 * This code is responsible for most of the ACKs 1469 * the TCP stack sends back after receiving a data 1470 * packet. Note that the DELAY_ACK check fails if 1471 * the delack timer is already running, which results 1472 * in an ack being sent every other packet (which is 1473 * what we want). 1474 * 1475 * We then further aggregate acks by not actually 1476 * sending one until the protocol thread has completed 1477 * processing the current backlog of packets. This 1478 * does not delay the ack any further, but allows us 1479 * to take advantage of the packet aggregation that 1480 * high speed NICs do (usually blocks of 8-10 packets) 1481 * to send a single ack rather then four or five acks, 1482 * greatly reducing the ack rate, the return channel 1483 * bandwidth, and the protocol overhead on both ends. 1484 * 1485 * Since this also has the effect of slowing down 1486 * the exponential slow-start ramp-up, systems with 1487 * very large bandwidth-delay products might want 1488 * to turn the feature off. 1489 */ 1490 if (DELAY_ACK(tp)) { 1491 tcp_callout_reset(tp, tp->tt_delack, 1492 tcp_delacktime, tcp_timer_delack); 1493 } else if (tcp_aggregate_acks) { 1494 tp->t_flags |= TF_ACKNOW; 1495 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1496 tp->t_flags |= TF_ONOUTPUTQ; 1497 tp->tt_cpu = mycpu->gd_cpuid; 1498 TAILQ_INSERT_TAIL( 1499 &tcpcbackq[tp->tt_cpu], 1500 tp, t_outputq); 1501 } 1502 } else { 1503 tp->t_flags |= TF_ACKNOW; 1504 tcp_output(tp); 1505 } 1506 return(IPPROTO_DONE); 1507 } 1508 } 1509 1510 /* 1511 * Calculate amount of space in receive window, 1512 * and then do TCP input processing. 1513 * Receive window is amount of space in rcv queue, 1514 * but not less than advertised window. 1515 */ 1516 recvwin = ssb_space(&so->so_rcv); 1517 if (recvwin < 0) 1518 recvwin = 0; 1519 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1520 1521 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1522 tp->rfbuf_ts = 0; 1523 tp->rfbuf_cnt = 0; 1524 1525 switch (tp->t_state) { 1526 /* 1527 * If the state is SYN_RECEIVED: 1528 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1529 */ 1530 case TCPS_SYN_RECEIVED: 1531 if ((thflags & TH_ACK) && 1532 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1533 SEQ_GT(th->th_ack, tp->snd_max))) { 1534 rstreason = BANDLIM_RST_OPENPORT; 1535 goto dropwithreset; 1536 } 1537 break; 1538 1539 /* 1540 * If the state is SYN_SENT: 1541 * if seg contains an ACK, but not for our SYN, drop the input. 1542 * if seg contains a RST, then drop the connection. 1543 * if seg does not contain SYN, then drop it. 1544 * Otherwise this is an acceptable SYN segment 1545 * initialize tp->rcv_nxt and tp->irs 1546 * if seg contains ack then advance tp->snd_una 1547 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1548 * arrange for segment to be acked (eventually) 1549 * continue processing rest of data/controls, beginning with URG 1550 */ 1551 case TCPS_SYN_SENT: 1552 if ((thflags & TH_ACK) && 1553 (SEQ_LEQ(th->th_ack, tp->iss) || 1554 SEQ_GT(th->th_ack, tp->snd_max))) { 1555 rstreason = BANDLIM_UNLIMITED; 1556 goto dropwithreset; 1557 } 1558 if (thflags & TH_RST) { 1559 if (thflags & TH_ACK) 1560 tp = tcp_drop(tp, ECONNREFUSED); 1561 goto drop; 1562 } 1563 if (!(thflags & TH_SYN)) 1564 goto drop; 1565 1566 tp->irs = th->th_seq; 1567 tcp_rcvseqinit(tp); 1568 if (thflags & TH_ACK) { 1569 /* Our SYN was acked. */ 1570 tcpstat.tcps_connects++; 1571 soisconnected(so); 1572 /* Do window scaling on this connection? */ 1573 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1574 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1575 tp->rcv_scale = tp->request_r_scale; 1576 tp->rcv_adv += tp->rcv_wnd; 1577 tp->snd_una++; /* SYN is acked */ 1578 tcp_callout_stop(tp, tp->tt_rexmt); 1579 /* 1580 * If there's data, delay ACK; if there's also a FIN 1581 * ACKNOW will be turned on later. 1582 */ 1583 if (DELAY_ACK(tp) && tlen != 0) { 1584 tcp_callout_reset(tp, tp->tt_delack, 1585 tcp_delacktime, tcp_timer_delack); 1586 } else { 1587 tp->t_flags |= TF_ACKNOW; 1588 } 1589 /* 1590 * Received <SYN,ACK> in SYN_SENT[*] state. 1591 * Transitions: 1592 * SYN_SENT --> ESTABLISHED 1593 * SYN_SENT* --> FIN_WAIT_1 1594 */ 1595 tp->t_starttime = ticks; 1596 if (tp->t_flags & TF_NEEDFIN) { 1597 tp->t_state = TCPS_FIN_WAIT_1; 1598 tp->t_flags &= ~TF_NEEDFIN; 1599 thflags &= ~TH_SYN; 1600 } else { 1601 tcp_established(tp); 1602 } 1603 } else { 1604 /* 1605 * Received initial SYN in SYN-SENT[*] state => 1606 * simultaneous open. 1607 * Do 3-way handshake: 1608 * SYN-SENT -> SYN-RECEIVED 1609 * SYN-SENT* -> SYN-RECEIVED* 1610 */ 1611 tp->t_flags |= TF_ACKNOW; 1612 tcp_callout_stop(tp, tp->tt_rexmt); 1613 tp->t_state = TCPS_SYN_RECEIVED; 1614 } 1615 1616 /* 1617 * Advance th->th_seq to correspond to first data byte. 1618 * If data, trim to stay within window, 1619 * dropping FIN if necessary. 1620 */ 1621 th->th_seq++; 1622 if (tlen > tp->rcv_wnd) { 1623 todrop = tlen - tp->rcv_wnd; 1624 m_adj(m, -todrop); 1625 tlen = tp->rcv_wnd; 1626 thflags &= ~TH_FIN; 1627 tcpstat.tcps_rcvpackafterwin++; 1628 tcpstat.tcps_rcvbyteafterwin += todrop; 1629 } 1630 tp->snd_wl1 = th->th_seq - 1; 1631 tp->rcv_up = th->th_seq; 1632 /* 1633 * Client side of transaction: already sent SYN and data. 1634 * If the remote host used T/TCP to validate the SYN, 1635 * our data will be ACK'd; if so, enter normal data segment 1636 * processing in the middle of step 5, ack processing. 1637 * Otherwise, goto step 6. 1638 */ 1639 if (thflags & TH_ACK) 1640 goto process_ACK; 1641 1642 goto step6; 1643 1644 /* 1645 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1646 * do normal processing (we no longer bother with T/TCP). 1647 */ 1648 case TCPS_LAST_ACK: 1649 case TCPS_CLOSING: 1650 case TCPS_TIME_WAIT: 1651 break; /* continue normal processing */ 1652 } 1653 1654 /* 1655 * States other than LISTEN or SYN_SENT. 1656 * First check the RST flag and sequence number since reset segments 1657 * are exempt from the timestamp and connection count tests. This 1658 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1659 * below which allowed reset segments in half the sequence space 1660 * to fall though and be processed (which gives forged reset 1661 * segments with a random sequence number a 50 percent chance of 1662 * killing a connection). 1663 * Then check timestamp, if present. 1664 * Then check the connection count, if present. 1665 * Then check that at least some bytes of segment are within 1666 * receive window. If segment begins before rcv_nxt, 1667 * drop leading data (and SYN); if nothing left, just ack. 1668 * 1669 * 1670 * If the RST bit is set, check the sequence number to see 1671 * if this is a valid reset segment. 1672 * RFC 793 page 37: 1673 * In all states except SYN-SENT, all reset (RST) segments 1674 * are validated by checking their SEQ-fields. A reset is 1675 * valid if its sequence number is in the window. 1676 * Note: this does not take into account delayed ACKs, so 1677 * we should test against last_ack_sent instead of rcv_nxt. 1678 * The sequence number in the reset segment is normally an 1679 * echo of our outgoing acknowledgement numbers, but some hosts 1680 * send a reset with the sequence number at the rightmost edge 1681 * of our receive window, and we have to handle this case. 1682 * If we have multiple segments in flight, the intial reset 1683 * segment sequence numbers will be to the left of last_ack_sent, 1684 * but they will eventually catch up. 1685 * In any case, it never made sense to trim reset segments to 1686 * fit the receive window since RFC 1122 says: 1687 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1688 * 1689 * A TCP SHOULD allow a received RST segment to include data. 1690 * 1691 * DISCUSSION 1692 * It has been suggested that a RST segment could contain 1693 * ASCII text that encoded and explained the cause of the 1694 * RST. No standard has yet been established for such 1695 * data. 1696 * 1697 * If the reset segment passes the sequence number test examine 1698 * the state: 1699 * SYN_RECEIVED STATE: 1700 * If passive open, return to LISTEN state. 1701 * If active open, inform user that connection was refused. 1702 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1703 * Inform user that connection was reset, and close tcb. 1704 * CLOSING, LAST_ACK STATES: 1705 * Close the tcb. 1706 * TIME_WAIT STATE: 1707 * Drop the segment - see Stevens, vol. 2, p. 964 and 1708 * RFC 1337. 1709 */ 1710 if (thflags & TH_RST) { 1711 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1712 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1713 switch (tp->t_state) { 1714 1715 case TCPS_SYN_RECEIVED: 1716 so->so_error = ECONNREFUSED; 1717 goto close; 1718 1719 case TCPS_ESTABLISHED: 1720 case TCPS_FIN_WAIT_1: 1721 case TCPS_FIN_WAIT_2: 1722 case TCPS_CLOSE_WAIT: 1723 so->so_error = ECONNRESET; 1724 close: 1725 tp->t_state = TCPS_CLOSED; 1726 tcpstat.tcps_drops++; 1727 tp = tcp_close(tp); 1728 break; 1729 1730 case TCPS_CLOSING: 1731 case TCPS_LAST_ACK: 1732 tp = tcp_close(tp); 1733 break; 1734 1735 case TCPS_TIME_WAIT: 1736 break; 1737 } 1738 } 1739 goto drop; 1740 } 1741 1742 /* 1743 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1744 * and it's less than ts_recent, drop it. 1745 */ 1746 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1747 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1748 /* Check to see if ts_recent is over 24 days old. */ 1749 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1750 /* 1751 * Invalidate ts_recent. If this segment updates 1752 * ts_recent, the age will be reset later and ts_recent 1753 * will get a valid value. If it does not, setting 1754 * ts_recent to zero will at least satisfy the 1755 * requirement that zero be placed in the timestamp 1756 * echo reply when ts_recent isn't valid. The 1757 * age isn't reset until we get a valid ts_recent 1758 * because we don't want out-of-order segments to be 1759 * dropped when ts_recent is old. 1760 */ 1761 tp->ts_recent = 0; 1762 } else if (tcp_paws_tolerance && tlen != 0 && 1763 tp->t_state == TCPS_ESTABLISHED && 1764 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&& 1765 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1766 th->th_ack == tp->snd_una && 1767 tiwin == tp->snd_wnd && 1768 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&& 1769 (th->th_seq == tp->rcv_nxt || 1770 (SEQ_GT(th->th_seq, tp->rcv_nxt) && 1771 tcp_paws_canreasslast(tp, th, tlen)))) { 1772 /* 1773 * This tends to prevent valid new segments from being 1774 * dropped by the reordered segments sent by the fast 1775 * retransmission algorithm on the sending side, i.e. 1776 * the fast retransmitted segment w/ larger timestamp 1777 * arrives earlier than the previously sent new segments 1778 * w/ smaller timestamp. 1779 * 1780 * If following conditions are met, the segment is 1781 * accepted: 1782 * - The segment contains data 1783 * - The connection is established 1784 * - The header does not contain important flags 1785 * - SYN or FIN is not needed 1786 * - It does not acknowledge new data 1787 * - Receive window is not changed 1788 * - The timestamp is within "acceptable" range 1789 * - The new segment is what we are expecting or 1790 * the new segment could be merged w/ the last 1791 * pending segment on the reassemble queue 1792 */ 1793 tcpstat.tcps_pawsaccept++; 1794 tcpstat.tcps_pawsdrop++; 1795 } else { 1796 tcpstat.tcps_rcvduppack++; 1797 tcpstat.tcps_rcvdupbyte += tlen; 1798 tcpstat.tcps_pawsdrop++; 1799 if (tlen) 1800 goto dropafterack; 1801 goto drop; 1802 } 1803 } 1804 1805 /* 1806 * In the SYN-RECEIVED state, validate that the packet belongs to 1807 * this connection before trimming the data to fit the receive 1808 * window. Check the sequence number versus IRS since we know 1809 * the sequence numbers haven't wrapped. This is a partial fix 1810 * for the "LAND" DoS attack. 1811 */ 1812 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1813 rstreason = BANDLIM_RST_OPENPORT; 1814 goto dropwithreset; 1815 } 1816 1817 todrop = tp->rcv_nxt - th->th_seq; 1818 if (todrop > 0) { 1819 if (TCP_DO_SACK(tp)) { 1820 /* Report duplicate segment at head of packet. */ 1821 tp->reportblk.rblk_start = th->th_seq; 1822 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1823 th->th_seq + tlen, thflags); 1824 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1825 tp->reportblk.rblk_end = tp->rcv_nxt; 1826 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT); 1827 tp->t_flags |= TF_ACKNOW; 1828 } 1829 if (thflags & TH_SYN) { 1830 thflags &= ~TH_SYN; 1831 th->th_seq++; 1832 if (th->th_urp > 1) 1833 th->th_urp--; 1834 else 1835 thflags &= ~TH_URG; 1836 todrop--; 1837 } 1838 /* 1839 * Following if statement from Stevens, vol. 2, p. 960. 1840 */ 1841 if (todrop > tlen || 1842 (todrop == tlen && !(thflags & TH_FIN))) { 1843 /* 1844 * Any valid FIN must be to the left of the window. 1845 * At this point the FIN must be a duplicate or out 1846 * of sequence; drop it. 1847 */ 1848 thflags &= ~TH_FIN; 1849 1850 /* 1851 * Send an ACK to resynchronize and drop any data. 1852 * But keep on processing for RST or ACK. 1853 */ 1854 tp->t_flags |= TF_ACKNOW; 1855 todrop = tlen; 1856 tcpstat.tcps_rcvduppack++; 1857 tcpstat.tcps_rcvdupbyte += todrop; 1858 } else { 1859 tcpstat.tcps_rcvpartduppack++; 1860 tcpstat.tcps_rcvpartdupbyte += todrop; 1861 } 1862 drop_hdrlen += todrop; /* drop from the top afterwards */ 1863 th->th_seq += todrop; 1864 tlen -= todrop; 1865 if (th->th_urp > todrop) 1866 th->th_urp -= todrop; 1867 else { 1868 thflags &= ~TH_URG; 1869 th->th_urp = 0; 1870 } 1871 } 1872 1873 /* 1874 * If new data are received on a connection after the 1875 * user processes are gone, then RST the other end. 1876 */ 1877 if ((so->so_state & SS_NOFDREF) && 1878 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1879 tp = tcp_close(tp); 1880 tcpstat.tcps_rcvafterclose++; 1881 rstreason = BANDLIM_UNLIMITED; 1882 goto dropwithreset; 1883 } 1884 1885 /* 1886 * If segment ends after window, drop trailing data 1887 * (and PUSH and FIN); if nothing left, just ACK. 1888 */ 1889 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1890 if (todrop > 0) { 1891 tcpstat.tcps_rcvpackafterwin++; 1892 if (todrop >= tlen) { 1893 tcpstat.tcps_rcvbyteafterwin += tlen; 1894 /* 1895 * If a new connection request is received 1896 * while in TIME_WAIT, drop the old connection 1897 * and start over if the sequence numbers 1898 * are above the previous ones. 1899 */ 1900 if (thflags & TH_SYN && 1901 tp->t_state == TCPS_TIME_WAIT && 1902 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1903 tp = tcp_close(tp); 1904 goto findpcb; 1905 } 1906 /* 1907 * If window is closed can only take segments at 1908 * window edge, and have to drop data and PUSH from 1909 * incoming segments. Continue processing, but 1910 * remember to ack. Otherwise, drop segment 1911 * and ack. 1912 */ 1913 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1914 tp->t_flags |= TF_ACKNOW; 1915 tcpstat.tcps_rcvwinprobe++; 1916 } else 1917 goto dropafterack; 1918 } else 1919 tcpstat.tcps_rcvbyteafterwin += todrop; 1920 m_adj(m, -todrop); 1921 tlen -= todrop; 1922 thflags &= ~(TH_PUSH | TH_FIN); 1923 } 1924 1925 /* 1926 * If last ACK falls within this segment's sequence numbers, 1927 * record its timestamp. 1928 * NOTE: 1929 * 1) That the test incorporates suggestions from the latest 1930 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1931 * 2) That updating only on newer timestamps interferes with 1932 * our earlier PAWS tests, so this check should be solely 1933 * predicated on the sequence space of this segment. 1934 * 3) That we modify the segment boundary check to be 1935 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1936 * instead of RFC1323's 1937 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1938 * This modified check allows us to overcome RFC1323's 1939 * limitations as described in Stevens TCP/IP Illustrated 1940 * Vol. 2 p.869. In such cases, we can still calculate the 1941 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1942 */ 1943 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1944 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1945 + ((thflags & TH_SYN) != 0) 1946 + ((thflags & TH_FIN) != 0)))) { 1947 tp->ts_recent_age = ticks; 1948 tp->ts_recent = to.to_tsval; 1949 } 1950 1951 /* 1952 * If a SYN is in the window, then this is an 1953 * error and we send an RST and drop the connection. 1954 */ 1955 if (thflags & TH_SYN) { 1956 tp = tcp_drop(tp, ECONNRESET); 1957 rstreason = BANDLIM_UNLIMITED; 1958 goto dropwithreset; 1959 } 1960 1961 /* 1962 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1963 * flag is on (half-synchronized state), then queue data for 1964 * later processing; else drop segment and return. 1965 */ 1966 if (!(thflags & TH_ACK)) { 1967 if (tp->t_state == TCPS_SYN_RECEIVED || 1968 (tp->t_flags & TF_NEEDSYN)) 1969 goto step6; 1970 else 1971 goto drop; 1972 } 1973 1974 /* 1975 * Ack processing. 1976 */ 1977 switch (tp->t_state) { 1978 /* 1979 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1980 * ESTABLISHED state and continue processing. 1981 * The ACK was checked above. 1982 */ 1983 case TCPS_SYN_RECEIVED: 1984 1985 tcpstat.tcps_connects++; 1986 soisconnected(so); 1987 /* Do window scaling? */ 1988 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1989 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1990 tp->rcv_scale = tp->request_r_scale; 1991 /* 1992 * Make transitions: 1993 * SYN-RECEIVED -> ESTABLISHED 1994 * SYN-RECEIVED* -> FIN-WAIT-1 1995 */ 1996 tp->t_starttime = ticks; 1997 if (tp->t_flags & TF_NEEDFIN) { 1998 tp->t_state = TCPS_FIN_WAIT_1; 1999 tp->t_flags &= ~TF_NEEDFIN; 2000 } else { 2001 tcp_established(tp); 2002 } 2003 /* 2004 * If segment contains data or ACK, will call tcp_reass() 2005 * later; if not, do so now to pass queued data to user. 2006 */ 2007 if (tlen == 0 && !(thflags & TH_FIN)) 2008 tcp_reass(tp, NULL, NULL, NULL); 2009 /* fall into ... */ 2010 2011 /* 2012 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2013 * ACKs. If the ack is in the range 2014 * tp->snd_una < th->th_ack <= tp->snd_max 2015 * then advance tp->snd_una to th->th_ack and drop 2016 * data from the retransmission queue. If this ACK reflects 2017 * more up to date window information we update our window information. 2018 */ 2019 case TCPS_ESTABLISHED: 2020 case TCPS_FIN_WAIT_1: 2021 case TCPS_FIN_WAIT_2: 2022 case TCPS_CLOSE_WAIT: 2023 case TCPS_CLOSING: 2024 case TCPS_LAST_ACK: 2025 case TCPS_TIME_WAIT: 2026 2027 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2028 boolean_t maynotdup = FALSE; 2029 2030 if (TCP_DO_SACK(tp)) 2031 tcp_sack_update_scoreboard(tp, &to); 2032 2033 if (tlen != 0 || tiwin != tp->snd_wnd || 2034 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN))) 2035 maynotdup = TRUE; 2036 2037 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2038 th->th_ack != tp->snd_una) { 2039 if (!maynotdup) 2040 tcpstat.tcps_rcvdupack++; 2041 tp->t_dupacks = 0; 2042 break; 2043 } 2044 2045 #define DELAY_DUPACK \ 2046 do { \ 2047 delayed_dupack = TRUE; \ 2048 th_dupack = th->th_ack; \ 2049 to_flags = to.to_flags; \ 2050 } while (0) 2051 if (maynotdup) { 2052 if (!tcp_do_rfc6675 || 2053 !TCP_DO_SACK(tp) || 2054 (to.to_flags & 2055 (TOF_SACK | TOF_SACK_REDUNDANT)) 2056 != TOF_SACK) { 2057 tp->t_dupacks = 0; 2058 } else { 2059 DELAY_DUPACK; 2060 } 2061 break; 2062 } 2063 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) { 2064 /* 2065 * This could happen, if the reassemable 2066 * queue overflew or was drained. Don't 2067 * drop this FIN here; defer the duplicated 2068 * ACK processing until this FIN gets queued. 2069 */ 2070 DELAY_DUPACK; 2071 break; 2072 } 2073 #undef DELAY_DUPACK 2074 2075 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags)) 2076 goto drop; 2077 else 2078 break; 2079 } 2080 2081 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2082 tp->t_dupacks = 0; 2083 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2084 /* 2085 * Detected optimistic ACK attack. 2086 * Force slow-start to de-synchronize attack. 2087 */ 2088 tp->snd_cwnd = tp->t_maxseg; 2089 tp->snd_wacked = 0; 2090 2091 tcpstat.tcps_rcvacktoomuch++; 2092 goto dropafterack; 2093 } 2094 /* 2095 * If we reach this point, ACK is not a duplicate, 2096 * i.e., it ACKs something we sent. 2097 */ 2098 if (tp->t_flags & TF_NEEDSYN) { 2099 /* 2100 * T/TCP: Connection was half-synchronized, and our 2101 * SYN has been ACK'd (so connection is now fully 2102 * synchronized). Go to non-starred state, 2103 * increment snd_una for ACK of SYN, and check if 2104 * we can do window scaling. 2105 */ 2106 tp->t_flags &= ~TF_NEEDSYN; 2107 tp->snd_una++; 2108 /* Do window scaling? */ 2109 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2110 (TF_RCVD_SCALE | TF_REQ_SCALE)) 2111 tp->rcv_scale = tp->request_r_scale; 2112 } 2113 2114 process_ACK: 2115 acked = th->th_ack - tp->snd_una; 2116 tcpstat.tcps_rcvackpack++; 2117 tcpstat.tcps_rcvackbyte += acked; 2118 2119 if (tcp_do_eifel_detect && acked > 0 && 2120 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2121 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 2122 /* Eifel detection applicable. */ 2123 if (to.to_tsecr < tp->t_rexmtTS) { 2124 ++tcpstat.tcps_eifeldetected; 2125 tcp_revert_congestion_state(tp); 2126 if (tp->t_rxtshift != 1 || 2127 ticks >= tp->t_badrxtwin) 2128 ++tcpstat.tcps_rttcantdetect; 2129 } 2130 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2131 /* 2132 * If we just performed our first retransmit, 2133 * and the ACK arrives within our recovery window, 2134 * then it was a mistake to do the retransmit 2135 * in the first place. Recover our original cwnd 2136 * and ssthresh, and proceed to transmit where we 2137 * left off. 2138 */ 2139 tcp_revert_congestion_state(tp); 2140 ++tcpstat.tcps_rttdetected; 2141 } 2142 2143 /* 2144 * If we have a timestamp reply, update smoothed 2145 * round trip time. If no timestamp is present but 2146 * transmit timer is running and timed sequence 2147 * number was acked, update smoothed round trip time. 2148 * Since we now have an rtt measurement, cancel the 2149 * timer backoff (cf., Phil Karn's retransmit alg.). 2150 * Recompute the initial retransmit timer. 2151 * 2152 * Some machines (certain windows boxes) send broken 2153 * timestamp replies during the SYN+ACK phase, ignore 2154 * timestamps of 0. 2155 */ 2156 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2157 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); 2158 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2159 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); 2160 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2161 2162 /* 2163 * If no data (only SYN) was ACK'd, 2164 * skip rest of ACK processing. 2165 */ 2166 if (acked == 0) 2167 goto step6; 2168 2169 /* Stop looking for an acceptable ACK since one was received. */ 2170 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 2171 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 2172 2173 if (acked > so->so_snd.ssb_cc) { 2174 tp->snd_wnd -= so->so_snd.ssb_cc; 2175 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2176 ourfinisacked = TRUE; 2177 } else { 2178 sbdrop(&so->so_snd.sb, acked); 2179 tp->snd_wnd -= acked; 2180 ourfinisacked = FALSE; 2181 } 2182 sowwakeup(so); 2183 2184 /* 2185 * Update window information. 2186 */ 2187 if (acceptable_window_update(tp, th, tiwin)) { 2188 /* keep track of pure window updates */ 2189 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2190 tiwin > tp->snd_wnd) 2191 tcpstat.tcps_rcvwinupd++; 2192 tp->snd_wnd = tiwin; 2193 tp->snd_wl1 = th->th_seq; 2194 tp->snd_wl2 = th->th_ack; 2195 if (tp->snd_wnd > tp->max_sndwnd) 2196 tp->max_sndwnd = tp->snd_wnd; 2197 needoutput = TRUE; 2198 } 2199 2200 tp->snd_una = th->th_ack; 2201 if (TCP_DO_SACK(tp)) 2202 tcp_sack_update_scoreboard(tp, &to); 2203 if (IN_FASTRECOVERY(tp)) { 2204 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2205 EXIT_FASTRECOVERY(tp); 2206 needoutput = TRUE; 2207 /* 2208 * If the congestion window was inflated 2209 * to account for the other side's 2210 * cached packets, retract it. 2211 */ 2212 if (!TCP_DO_SACK(tp)) 2213 tp->snd_cwnd = tp->snd_ssthresh; 2214 2215 /* 2216 * Window inflation should have left us 2217 * with approximately snd_ssthresh outstanding 2218 * data. But, in case we would be inclined 2219 * to send a burst, better do it using 2220 * slow start. 2221 */ 2222 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2223 tp->snd_max + 2 * tp->t_maxseg)) 2224 tp->snd_cwnd = 2225 (tp->snd_max - tp->snd_una) + 2226 2 * tp->t_maxseg; 2227 2228 tp->snd_wacked = 0; 2229 } else { 2230 if (TCP_DO_SACK(tp)) { 2231 tp->snd_max_rexmt = tp->snd_max; 2232 tcp_sack_rexmt(tp, 2233 tp->snd_una == tp->rexmt_high); 2234 } else { 2235 tcp_newreno_partial_ack(tp, th, acked); 2236 } 2237 needoutput = FALSE; 2238 } 2239 } else { 2240 /* 2241 * Open the congestion window. When in slow-start, 2242 * open exponentially: maxseg per packet. Otherwise, 2243 * open linearly: maxseg per window. 2244 */ 2245 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2246 u_int abc_sslimit = 2247 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2248 tp->t_maxseg : 2 * tp->t_maxseg); 2249 2250 /* slow-start */ 2251 tp->snd_cwnd += tcp_do_abc ? 2252 min(acked, abc_sslimit) : tp->t_maxseg; 2253 } else { 2254 /* linear increase */ 2255 tp->snd_wacked += tcp_do_abc ? acked : 2256 tp->t_maxseg; 2257 if (tp->snd_wacked >= tp->snd_cwnd) { 2258 tp->snd_wacked -= tp->snd_cwnd; 2259 tp->snd_cwnd += tp->t_maxseg; 2260 } 2261 } 2262 tp->snd_cwnd = min(tp->snd_cwnd, 2263 TCP_MAXWIN << tp->snd_scale); 2264 tp->snd_recover = th->th_ack - 1; 2265 } 2266 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2267 tp->snd_nxt = tp->snd_una; 2268 2269 /* 2270 * If all outstanding data is acked, stop retransmit 2271 * timer and remember to restart (more output or persist). 2272 * If there is more data to be acked, restart retransmit 2273 * timer, using current (possibly backed-off) value. 2274 */ 2275 if (th->th_ack == tp->snd_max) { 2276 tcp_callout_stop(tp, tp->tt_rexmt); 2277 needoutput = TRUE; 2278 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2279 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2280 tcp_timer_rexmt); 2281 } 2282 2283 switch (tp->t_state) { 2284 /* 2285 * In FIN_WAIT_1 STATE in addition to the processing 2286 * for the ESTABLISHED state if our FIN is now acknowledged 2287 * then enter FIN_WAIT_2. 2288 */ 2289 case TCPS_FIN_WAIT_1: 2290 if (ourfinisacked) { 2291 /* 2292 * If we can't receive any more 2293 * data, then closing user can proceed. 2294 * Starting the timer is contrary to the 2295 * specification, but if we don't get a FIN 2296 * we'll hang forever. 2297 */ 2298 if (so->so_state & SS_CANTRCVMORE) { 2299 soisdisconnected(so); 2300 tcp_callout_reset(tp, tp->tt_2msl, 2301 tp->t_maxidle, tcp_timer_2msl); 2302 } 2303 tp->t_state = TCPS_FIN_WAIT_2; 2304 } 2305 break; 2306 2307 /* 2308 * In CLOSING STATE in addition to the processing for 2309 * the ESTABLISHED state if the ACK acknowledges our FIN 2310 * then enter the TIME-WAIT state, otherwise ignore 2311 * the segment. 2312 */ 2313 case TCPS_CLOSING: 2314 if (ourfinisacked) { 2315 tp->t_state = TCPS_TIME_WAIT; 2316 tcp_canceltimers(tp); 2317 tcp_callout_reset(tp, tp->tt_2msl, 2318 2 * tcp_rmx_msl(tp), 2319 tcp_timer_2msl); 2320 soisdisconnected(so); 2321 } 2322 break; 2323 2324 /* 2325 * In LAST_ACK, we may still be waiting for data to drain 2326 * and/or to be acked, as well as for the ack of our FIN. 2327 * If our FIN is now acknowledged, delete the TCB, 2328 * enter the closed state and return. 2329 */ 2330 case TCPS_LAST_ACK: 2331 if (ourfinisacked) { 2332 tp = tcp_close(tp); 2333 goto drop; 2334 } 2335 break; 2336 2337 /* 2338 * In TIME_WAIT state the only thing that should arrive 2339 * is a retransmission of the remote FIN. Acknowledge 2340 * it and restart the finack timer. 2341 */ 2342 case TCPS_TIME_WAIT: 2343 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2344 tcp_timer_2msl); 2345 goto dropafterack; 2346 } 2347 } 2348 2349 step6: 2350 /* 2351 * Update window information. 2352 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2353 */ 2354 if ((thflags & TH_ACK) && 2355 acceptable_window_update(tp, th, tiwin)) { 2356 /* keep track of pure window updates */ 2357 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2358 tiwin > tp->snd_wnd) 2359 tcpstat.tcps_rcvwinupd++; 2360 tp->snd_wnd = tiwin; 2361 tp->snd_wl1 = th->th_seq; 2362 tp->snd_wl2 = th->th_ack; 2363 if (tp->snd_wnd > tp->max_sndwnd) 2364 tp->max_sndwnd = tp->snd_wnd; 2365 needoutput = TRUE; 2366 } 2367 2368 /* 2369 * Process segments with URG. 2370 */ 2371 if ((thflags & TH_URG) && th->th_urp && 2372 !TCPS_HAVERCVDFIN(tp->t_state)) { 2373 /* 2374 * This is a kludge, but if we receive and accept 2375 * random urgent pointers, we'll crash in 2376 * soreceive. It's hard to imagine someone 2377 * actually wanting to send this much urgent data. 2378 */ 2379 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2380 th->th_urp = 0; /* XXX */ 2381 thflags &= ~TH_URG; /* XXX */ 2382 goto dodata; /* XXX */ 2383 } 2384 /* 2385 * If this segment advances the known urgent pointer, 2386 * then mark the data stream. This should not happen 2387 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2388 * a FIN has been received from the remote side. 2389 * In these states we ignore the URG. 2390 * 2391 * According to RFC961 (Assigned Protocols), 2392 * the urgent pointer points to the last octet 2393 * of urgent data. We continue, however, 2394 * to consider it to indicate the first octet 2395 * of data past the urgent section as the original 2396 * spec states (in one of two places). 2397 */ 2398 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2399 tp->rcv_up = th->th_seq + th->th_urp; 2400 so->so_oobmark = so->so_rcv.ssb_cc + 2401 (tp->rcv_up - tp->rcv_nxt) - 1; 2402 if (so->so_oobmark == 0) 2403 sosetstate(so, SS_RCVATMARK); 2404 sohasoutofband(so); 2405 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2406 } 2407 /* 2408 * Remove out of band data so doesn't get presented to user. 2409 * This can happen independent of advancing the URG pointer, 2410 * but if two URG's are pending at once, some out-of-band 2411 * data may creep in... ick. 2412 */ 2413 if (th->th_urp <= (u_long)tlen && 2414 !(so->so_options & SO_OOBINLINE)) { 2415 /* hdr drop is delayed */ 2416 tcp_pulloutofband(so, th, m, drop_hdrlen); 2417 } 2418 } else { 2419 /* 2420 * If no out of band data is expected, 2421 * pull receive urgent pointer along 2422 * with the receive window. 2423 */ 2424 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2425 tp->rcv_up = tp->rcv_nxt; 2426 } 2427 2428 dodata: /* XXX */ 2429 /* 2430 * Process the segment text, merging it into the TCP sequencing queue, 2431 * and arranging for acknowledgment of receipt if necessary. 2432 * This process logically involves adjusting tp->rcv_wnd as data 2433 * is presented to the user (this happens in tcp_usrreq.c, 2434 * case PRU_RCVD). If a FIN has already been received on this 2435 * connection then we just ignore the text. 2436 */ 2437 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2438 if (thflags & TH_FIN) 2439 tp->t_flags |= TF_SAWFIN; 2440 m_adj(m, drop_hdrlen); /* delayed header drop */ 2441 /* 2442 * Insert segment which includes th into TCP reassembly queue 2443 * with control block tp. Set thflags to whether reassembly now 2444 * includes a segment with FIN. This handles the common case 2445 * inline (segment is the next to be received on an established 2446 * connection, and the queue is empty), avoiding linkage into 2447 * and removal from the queue and repetition of various 2448 * conversions. 2449 * Set DELACK for segments received in order, but ack 2450 * immediately when segments are out of order (so 2451 * fast retransmit can work). 2452 */ 2453 if (th->th_seq == tp->rcv_nxt && 2454 TAILQ_EMPTY(&tp->t_segq) && 2455 TCPS_HAVEESTABLISHED(tp->t_state)) { 2456 if (thflags & TH_FIN) 2457 tp->t_flags |= TF_QUEDFIN; 2458 if (DELAY_ACK(tp)) { 2459 tcp_callout_reset(tp, tp->tt_delack, 2460 tcp_delacktime, tcp_timer_delack); 2461 } else { 2462 tp->t_flags |= TF_ACKNOW; 2463 } 2464 tp->rcv_nxt += tlen; 2465 thflags = th->th_flags & TH_FIN; 2466 tcpstat.tcps_rcvpack++; 2467 tcpstat.tcps_rcvbyte += tlen; 2468 ND6_HINT(tp); 2469 if (so->so_state & SS_CANTRCVMORE) { 2470 m_freem(m); 2471 } else { 2472 lwkt_gettoken(&so->so_rcv.ssb_token); 2473 ssb_appendstream(&so->so_rcv, m); 2474 lwkt_reltoken(&so->so_rcv.ssb_token); 2475 } 2476 sorwakeup(so); 2477 } else { 2478 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 2479 /* Initialize SACK report block. */ 2480 tp->reportblk.rblk_start = th->th_seq; 2481 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2482 th->th_seq + tlen, thflags); 2483 } 2484 thflags = tcp_reass(tp, th, &tlen, m); 2485 tp->t_flags |= TF_ACKNOW; 2486 } 2487 2488 /* 2489 * Note the amount of data that peer has sent into 2490 * our window, in order to estimate the sender's 2491 * buffer size. 2492 */ 2493 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2494 } else { 2495 m_freem(m); 2496 thflags &= ~TH_FIN; 2497 } 2498 2499 /* 2500 * If FIN is received ACK the FIN and let the user know 2501 * that the connection is closing. 2502 */ 2503 if (thflags & TH_FIN) { 2504 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2505 socantrcvmore(so); 2506 /* 2507 * If connection is half-synchronized 2508 * (ie NEEDSYN flag on) then delay ACK, 2509 * so it may be piggybacked when SYN is sent. 2510 * Otherwise, since we received a FIN then no 2511 * more input can be expected, send ACK now. 2512 */ 2513 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2514 tcp_callout_reset(tp, tp->tt_delack, 2515 tcp_delacktime, tcp_timer_delack); 2516 } else { 2517 tp->t_flags |= TF_ACKNOW; 2518 } 2519 tp->rcv_nxt++; 2520 } 2521 2522 switch (tp->t_state) { 2523 /* 2524 * In SYN_RECEIVED and ESTABLISHED STATES 2525 * enter the CLOSE_WAIT state. 2526 */ 2527 case TCPS_SYN_RECEIVED: 2528 tp->t_starttime = ticks; 2529 /*FALLTHROUGH*/ 2530 case TCPS_ESTABLISHED: 2531 tp->t_state = TCPS_CLOSE_WAIT; 2532 break; 2533 2534 /* 2535 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2536 * enter the CLOSING state. 2537 */ 2538 case TCPS_FIN_WAIT_1: 2539 tp->t_state = TCPS_CLOSING; 2540 break; 2541 2542 /* 2543 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2544 * starting the time-wait timer, turning off the other 2545 * standard timers. 2546 */ 2547 case TCPS_FIN_WAIT_2: 2548 tp->t_state = TCPS_TIME_WAIT; 2549 tcp_canceltimers(tp); 2550 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2551 tcp_timer_2msl); 2552 soisdisconnected(so); 2553 break; 2554 2555 /* 2556 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2557 */ 2558 case TCPS_TIME_WAIT: 2559 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2560 tcp_timer_2msl); 2561 break; 2562 } 2563 } 2564 2565 #ifdef TCPDEBUG 2566 if (so->so_options & SO_DEBUG) 2567 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2568 #endif 2569 2570 /* 2571 * Delayed duplicated ACK processing 2572 */ 2573 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags)) 2574 needoutput = FALSE; 2575 2576 /* 2577 * Return any desired output. 2578 */ 2579 if ((tp->t_flags & TF_ACKNOW) || 2580 (needoutput && tcp_sack_report_needed(tp))) { 2581 tcp_output_cancel(tp); 2582 tcp_output_fair(tp); 2583 } else if (needoutput && !tcp_output_pending(tp)) { 2584 tcp_output_fair(tp); 2585 } 2586 tcp_sack_report_cleanup(tp); 2587 return(IPPROTO_DONE); 2588 2589 dropafterack: 2590 /* 2591 * Generate an ACK dropping incoming segment if it occupies 2592 * sequence space, where the ACK reflects our state. 2593 * 2594 * We can now skip the test for the RST flag since all 2595 * paths to this code happen after packets containing 2596 * RST have been dropped. 2597 * 2598 * In the SYN-RECEIVED state, don't send an ACK unless the 2599 * segment we received passes the SYN-RECEIVED ACK test. 2600 * If it fails send a RST. This breaks the loop in the 2601 * "LAND" DoS attack, and also prevents an ACK storm 2602 * between two listening ports that have been sent forged 2603 * SYN segments, each with the source address of the other. 2604 */ 2605 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2606 (SEQ_GT(tp->snd_una, th->th_ack) || 2607 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2608 rstreason = BANDLIM_RST_OPENPORT; 2609 goto dropwithreset; 2610 } 2611 #ifdef TCPDEBUG 2612 if (so->so_options & SO_DEBUG) 2613 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2614 #endif 2615 m_freem(m); 2616 tp->t_flags |= TF_ACKNOW; 2617 tcp_output(tp); 2618 tcp_sack_report_cleanup(tp); 2619 return(IPPROTO_DONE); 2620 2621 dropwithreset: 2622 /* 2623 * Generate a RST, dropping incoming segment. 2624 * Make ACK acceptable to originator of segment. 2625 * Don't bother to respond if destination was broadcast/multicast. 2626 */ 2627 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2628 goto drop; 2629 if (isipv6) { 2630 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2631 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2632 goto drop; 2633 } else { 2634 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2635 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2636 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2637 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2638 goto drop; 2639 } 2640 /* IPv6 anycast check is done at tcp6_input() */ 2641 2642 /* 2643 * Perform bandwidth limiting. 2644 */ 2645 #ifdef ICMP_BANDLIM 2646 if (badport_bandlim(rstreason) < 0) 2647 goto drop; 2648 #endif 2649 2650 #ifdef TCPDEBUG 2651 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2652 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2653 #endif 2654 if (thflags & TH_ACK) 2655 /* mtod() below is safe as long as hdr dropping is delayed */ 2656 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2657 TH_RST); 2658 else { 2659 if (thflags & TH_SYN) 2660 tlen++; 2661 /* mtod() below is safe as long as hdr dropping is delayed */ 2662 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2663 (tcp_seq)0, TH_RST | TH_ACK); 2664 } 2665 if (tp != NULL) 2666 tcp_sack_report_cleanup(tp); 2667 return(IPPROTO_DONE); 2668 2669 drop: 2670 /* 2671 * Drop space held by incoming segment and return. 2672 */ 2673 #ifdef TCPDEBUG 2674 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2675 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2676 #endif 2677 m_freem(m); 2678 if (tp != NULL) 2679 tcp_sack_report_cleanup(tp); 2680 return(IPPROTO_DONE); 2681 } 2682 2683 /* 2684 * Parse TCP options and place in tcpopt. 2685 */ 2686 static void 2687 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, 2688 tcp_seq ack) 2689 { 2690 int opt, optlen, i; 2691 2692 to->to_flags = 0; 2693 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2694 opt = cp[0]; 2695 if (opt == TCPOPT_EOL) 2696 break; 2697 if (opt == TCPOPT_NOP) 2698 optlen = 1; 2699 else { 2700 if (cnt < 2) 2701 break; 2702 optlen = cp[1]; 2703 if (optlen < 2 || optlen > cnt) 2704 break; 2705 } 2706 switch (opt) { 2707 case TCPOPT_MAXSEG: 2708 if (optlen != TCPOLEN_MAXSEG) 2709 continue; 2710 if (!is_syn) 2711 continue; 2712 to->to_flags |= TOF_MSS; 2713 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2714 to->to_mss = ntohs(to->to_mss); 2715 break; 2716 case TCPOPT_WINDOW: 2717 if (optlen != TCPOLEN_WINDOW) 2718 continue; 2719 if (!is_syn) 2720 continue; 2721 to->to_flags |= TOF_SCALE; 2722 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2723 break; 2724 case TCPOPT_TIMESTAMP: 2725 if (optlen != TCPOLEN_TIMESTAMP) 2726 continue; 2727 to->to_flags |= TOF_TS; 2728 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2729 to->to_tsval = ntohl(to->to_tsval); 2730 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2731 to->to_tsecr = ntohl(to->to_tsecr); 2732 /* 2733 * If echoed timestamp is later than the current time, 2734 * fall back to non RFC1323 RTT calculation. 2735 */ 2736 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2737 to->to_tsecr = 0; 2738 break; 2739 case TCPOPT_SACK_PERMITTED: 2740 if (optlen != TCPOLEN_SACK_PERMITTED) 2741 continue; 2742 if (!is_syn) 2743 continue; 2744 to->to_flags |= TOF_SACK_PERMITTED; 2745 break; 2746 case TCPOPT_SACK: 2747 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2748 continue; 2749 to->to_nsackblocks = (optlen - 2) / 8; 2750 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2751 to->to_flags |= TOF_SACK; 2752 for (i = 0; i < to->to_nsackblocks; i++) { 2753 struct raw_sackblock *r = &to->to_sackblocks[i]; 2754 2755 r->rblk_start = ntohl(r->rblk_start); 2756 r->rblk_end = ntohl(r->rblk_end); 2757 2758 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2759 /* 2760 * Invalid SACK block; discard all 2761 * SACK blocks 2762 */ 2763 tcpstat.tcps_rcvbadsackopt++; 2764 to->to_nsackblocks = 0; 2765 to->to_sackblocks = NULL; 2766 to->to_flags &= ~TOF_SACK; 2767 break; 2768 } 2769 } 2770 if ((to->to_flags & TOF_SACK) && 2771 tcp_sack_ndsack_blocks(to->to_sackblocks, 2772 to->to_nsackblocks, ack)) 2773 to->to_flags |= TOF_DSACK; 2774 break; 2775 #ifdef TCP_SIGNATURE 2776 /* 2777 * XXX In order to reply to a host which has set the 2778 * TCP_SIGNATURE option in its initial SYN, we have to 2779 * record the fact that the option was observed here 2780 * for the syncache code to perform the correct response. 2781 */ 2782 case TCPOPT_SIGNATURE: 2783 if (optlen != TCPOLEN_SIGNATURE) 2784 continue; 2785 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2786 break; 2787 #endif /* TCP_SIGNATURE */ 2788 default: 2789 continue; 2790 } 2791 } 2792 } 2793 2794 /* 2795 * Pull out of band byte out of a segment so 2796 * it doesn't appear in the user's data queue. 2797 * It is still reflected in the segment length for 2798 * sequencing purposes. 2799 * "off" is the delayed to be dropped hdrlen. 2800 */ 2801 static void 2802 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2803 { 2804 int cnt = off + th->th_urp - 1; 2805 2806 while (cnt >= 0) { 2807 if (m->m_len > cnt) { 2808 char *cp = mtod(m, caddr_t) + cnt; 2809 struct tcpcb *tp = sototcpcb(so); 2810 2811 tp->t_iobc = *cp; 2812 tp->t_oobflags |= TCPOOB_HAVEDATA; 2813 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2814 m->m_len--; 2815 if (m->m_flags & M_PKTHDR) 2816 m->m_pkthdr.len--; 2817 return; 2818 } 2819 cnt -= m->m_len; 2820 m = m->m_next; 2821 if (m == NULL) 2822 break; 2823 } 2824 panic("tcp_pulloutofband"); 2825 } 2826 2827 /* 2828 * Collect new round-trip time estimate 2829 * and update averages and current timeout. 2830 */ 2831 static void 2832 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) 2833 { 2834 int rebaserto = 0; 2835 2836 tcpstat.tcps_rttupdated++; 2837 tp->t_rttupdated++; 2838 if ((tp->rxt_flags & TRXT_F_REBASERTO) && 2839 SEQ_GT(ack, tp->snd_max_prev)) { 2840 #ifdef DEBUG_EIFEL_RESPONSE 2841 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", 2842 tp->t_srtt_prev, tp->t_rttvar_prev, 2843 tp->t_srtt, tp->t_rttvar); 2844 #endif 2845 2846 tcpstat.tcps_eifelresponse++; 2847 rebaserto = 1; 2848 tp->rxt_flags &= ~TRXT_F_REBASERTO; 2849 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); 2850 tp->t_rttvar = max(tp->t_rttvar_prev, 2851 (rtt << (TCP_RTTVAR_SHIFT - 1))); 2852 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2853 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2854 2855 #ifdef DEBUG_EIFEL_RESPONSE 2856 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); 2857 #endif 2858 } else if (tp->t_srtt != 0) { 2859 int delta; 2860 2861 /* 2862 * srtt is stored as fixed point with 5 bits after the 2863 * binary point (i.e., scaled by 8). The following magic 2864 * is equivalent to the smoothing algorithm in rfc793 with 2865 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2866 * point). Adjust rtt to origin 0. 2867 */ 2868 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2869 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2870 2871 if ((tp->t_srtt += delta) <= 0) 2872 tp->t_srtt = 1; 2873 2874 /* 2875 * We accumulate a smoothed rtt variance (actually, a 2876 * smoothed mean difference), then set the retransmit 2877 * timer to smoothed rtt + 4 times the smoothed variance. 2878 * rttvar is stored as fixed point with 4 bits after the 2879 * binary point (scaled by 16). The following is 2880 * equivalent to rfc793 smoothing with an alpha of .75 2881 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2882 * rfc793's wired-in beta. 2883 */ 2884 if (delta < 0) 2885 delta = -delta; 2886 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2887 if ((tp->t_rttvar += delta) <= 0) 2888 tp->t_rttvar = 1; 2889 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2890 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2891 } else { 2892 /* 2893 * No rtt measurement yet - use the unsmoothed rtt. 2894 * Set the variance to half the rtt (so our first 2895 * retransmit happens at 3*rtt). 2896 */ 2897 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2898 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2899 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2900 } 2901 tp->t_rtttime = 0; 2902 tp->t_rxtshift = 0; 2903 2904 #ifdef DEBUG_EIFEL_RESPONSE 2905 if (rebaserto) { 2906 kprintf("| rxtcur prev %d, old %d, ", 2907 tp->t_rxtcur_prev, tp->t_rxtcur); 2908 } 2909 #endif 2910 2911 /* 2912 * the retransmit should happen at rtt + 4 * rttvar. 2913 * Because of the way we do the smoothing, srtt and rttvar 2914 * will each average +1/2 tick of bias. When we compute 2915 * the retransmit timer, we want 1/2 tick of rounding and 2916 * 1 extra tick because of +-1/2 tick uncertainty in the 2917 * firing of the timer. The bias will give us exactly the 2918 * 1.5 tick we need. But, because the bias is 2919 * statistical, we have to test that we don't drop below 2920 * the minimum feasible timer (which is 2 ticks). 2921 */ 2922 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2923 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2924 2925 if (rebaserto) { 2926 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { 2927 /* 2928 * RFC4015 requires that the new RTO is at least 2929 * 2*G (tcp_eifel_rtoinc) greater then the RTO 2930 * (t_rxtcur_prev) when the spurious retransmit 2931 * timeout happens. 2932 * 2933 * The above condition could be true, if the SRTT 2934 * and RTTVAR used to calculate t_rxtcur_prev 2935 * resulted in a value less than t_rttmin. So 2936 * simply increasing SRTT by tcp_eifel_rtoinc when 2937 * preparing for the Eifel response could not ensure 2938 * that the new RTO will be tcp_eifel_rtoinc greater 2939 * t_rxtcur_prev. 2940 */ 2941 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; 2942 } 2943 #ifdef DEBUG_EIFEL_RESPONSE 2944 kprintf("new %d\n", tp->t_rxtcur); 2945 #endif 2946 } 2947 2948 /* 2949 * We received an ack for a packet that wasn't retransmitted; 2950 * it is probably safe to discard any error indications we've 2951 * received recently. This isn't quite right, but close enough 2952 * for now (a route might have failed after we sent a segment, 2953 * and the return path might not be symmetrical). 2954 */ 2955 tp->t_softerror = 0; 2956 } 2957 2958 /* 2959 * Determine a reasonable value for maxseg size. 2960 * If the route is known, check route for mtu. 2961 * If none, use an mss that can be handled on the outgoing 2962 * interface without forcing IP to fragment; if bigger than 2963 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2964 * to utilize large mbufs. If no route is found, route has no mtu, 2965 * or the destination isn't local, use a default, hopefully conservative 2966 * size (usually 512 or the default IP max size, but no more than the mtu 2967 * of the interface), as we can't discover anything about intervening 2968 * gateways or networks. We also initialize the congestion/slow start 2969 * window to be a single segment if the destination isn't local. 2970 * While looking at the routing entry, we also initialize other path-dependent 2971 * parameters from pre-set or cached values in the routing entry. 2972 * 2973 * Also take into account the space needed for options that we 2974 * send regularly. Make maxseg shorter by that amount to assure 2975 * that we can send maxseg amount of data even when the options 2976 * are present. Store the upper limit of the length of options plus 2977 * data in maxopd. 2978 * 2979 * NOTE that this routine is only called when we process an incoming 2980 * segment, for outgoing segments only tcp_mssopt is called. 2981 */ 2982 void 2983 tcp_mss(struct tcpcb *tp, int offer) 2984 { 2985 struct rtentry *rt; 2986 struct ifnet *ifp; 2987 int rtt, mss; 2988 u_long bufsize; 2989 struct inpcb *inp = tp->t_inpcb; 2990 struct socket *so; 2991 #ifdef INET6 2992 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 2993 size_t min_protoh = isipv6 ? 2994 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2995 sizeof(struct tcpiphdr); 2996 #else 2997 const boolean_t isipv6 = FALSE; 2998 const size_t min_protoh = sizeof(struct tcpiphdr); 2999 #endif 3000 3001 if (isipv6) 3002 rt = tcp_rtlookup6(&inp->inp_inc); 3003 else 3004 rt = tcp_rtlookup(&inp->inp_inc); 3005 if (rt == NULL) { 3006 tp->t_maxopd = tp->t_maxseg = 3007 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3008 return; 3009 } 3010 ifp = rt->rt_ifp; 3011 so = inp->inp_socket; 3012 3013 /* 3014 * Offer == 0 means that there was no MSS on the SYN segment, 3015 * in this case we use either the interface mtu or tcp_mssdflt. 3016 * 3017 * An offer which is too large will be cut down later. 3018 */ 3019 if (offer == 0) { 3020 if (isipv6) { 3021 if (in6_localaddr(&inp->in6p_faddr)) { 3022 offer = ND_IFINFO(rt->rt_ifp)->linkmtu - 3023 min_protoh; 3024 } else { 3025 offer = tcp_v6mssdflt; 3026 } 3027 } else { 3028 if (in_localaddr(inp->inp_faddr)) 3029 offer = ifp->if_mtu - min_protoh; 3030 else 3031 offer = tcp_mssdflt; 3032 } 3033 } 3034 3035 /* 3036 * Prevent DoS attack with too small MSS. Round up 3037 * to at least minmss. 3038 * 3039 * Sanity check: make sure that maxopd will be large 3040 * enough to allow some data on segments even is the 3041 * all the option space is used (40bytes). Otherwise 3042 * funny things may happen in tcp_output. 3043 */ 3044 offer = max(offer, tcp_minmss); 3045 offer = max(offer, 64); 3046 3047 rt->rt_rmx.rmx_mssopt = offer; 3048 3049 /* 3050 * While we're here, check if there's an initial rtt 3051 * or rttvar. Convert from the route-table units 3052 * to scaled multiples of the slow timeout timer. 3053 */ 3054 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3055 /* 3056 * XXX the lock bit for RTT indicates that the value 3057 * is also a minimum value; this is subject to time. 3058 */ 3059 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3060 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3061 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3062 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3063 tcpstat.tcps_usedrtt++; 3064 if (rt->rt_rmx.rmx_rttvar) { 3065 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3066 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3067 tcpstat.tcps_usedrttvar++; 3068 } else { 3069 /* default variation is +- 1 rtt */ 3070 tp->t_rttvar = 3071 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3072 } 3073 TCPT_RANGESET(tp->t_rxtcur, 3074 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3075 tp->t_rttmin, TCPTV_REXMTMAX); 3076 } 3077 3078 /* 3079 * if there's an mtu associated with the route, use it 3080 * else, use the link mtu. Take the smaller of mss or offer 3081 * as our final mss. 3082 */ 3083 if (rt->rt_rmx.rmx_mtu) { 3084 mss = rt->rt_rmx.rmx_mtu - min_protoh; 3085 } else { 3086 if (isipv6) 3087 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; 3088 else 3089 mss = ifp->if_mtu - min_protoh; 3090 } 3091 mss = min(mss, offer); 3092 3093 /* 3094 * maxopd stores the maximum length of data AND options 3095 * in a segment; maxseg is the amount of data in a normal 3096 * segment. We need to store this value (maxopd) apart 3097 * from maxseg, because now every segment carries options 3098 * and thus we normally have somewhat less data in segments. 3099 */ 3100 tp->t_maxopd = mss; 3101 3102 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3103 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3104 mss -= TCPOLEN_TSTAMP_APPA; 3105 3106 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3107 if (mss > MCLBYTES) 3108 mss &= ~(MCLBYTES-1); 3109 #else 3110 if (mss > MCLBYTES) 3111 mss = mss / MCLBYTES * MCLBYTES; 3112 #endif 3113 /* 3114 * If there's a pipesize, change the socket buffer 3115 * to that size. Make the socket buffers an integral 3116 * number of mss units; if the mss is larger than 3117 * the socket buffer, decrease the mss. 3118 */ 3119 #ifdef RTV_SPIPE 3120 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3121 #endif 3122 bufsize = so->so_snd.ssb_hiwat; 3123 if (bufsize < mss) 3124 mss = bufsize; 3125 else { 3126 bufsize = roundup(bufsize, mss); 3127 if (bufsize > sb_max) 3128 bufsize = sb_max; 3129 if (bufsize > so->so_snd.ssb_hiwat) 3130 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3131 } 3132 tp->t_maxseg = mss; 3133 3134 #ifdef RTV_RPIPE 3135 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3136 #endif 3137 bufsize = so->so_rcv.ssb_hiwat; 3138 if (bufsize > mss) { 3139 bufsize = roundup(bufsize, mss); 3140 if (bufsize > sb_max) 3141 bufsize = sb_max; 3142 if (bufsize > so->so_rcv.ssb_hiwat) { 3143 lwkt_gettoken(&so->so_rcv.ssb_token); 3144 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3145 lwkt_reltoken(&so->so_rcv.ssb_token); 3146 } 3147 } 3148 3149 /* 3150 * Set the slow-start flight size 3151 * 3152 * NOTE: t_maxseg must have been configured! 3153 */ 3154 tp->snd_cwnd = tcp_initial_window(tp); 3155 3156 if (rt->rt_rmx.rmx_ssthresh) { 3157 /* 3158 * There's some sort of gateway or interface 3159 * buffer limit on the path. Use this to set 3160 * the slow start threshhold, but set the 3161 * threshold to no less than 2*mss. 3162 */ 3163 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3164 tcpstat.tcps_usedssthresh++; 3165 } 3166 } 3167 3168 /* 3169 * Determine the MSS option to send on an outgoing SYN. 3170 */ 3171 int 3172 tcp_mssopt(struct tcpcb *tp) 3173 { 3174 struct rtentry *rt; 3175 #ifdef INET6 3176 boolean_t isipv6 = 3177 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3178 int min_protoh = isipv6 ? 3179 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3180 sizeof(struct tcpiphdr); 3181 #else 3182 const boolean_t isipv6 = FALSE; 3183 const size_t min_protoh = sizeof(struct tcpiphdr); 3184 #endif 3185 3186 if (isipv6) 3187 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3188 else 3189 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3190 if (rt == NULL) 3191 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3192 3193 return (rt->rt_ifp->if_mtu - min_protoh); 3194 } 3195 3196 /* 3197 * When a partial ack arrives, force the retransmission of the 3198 * next unacknowledged segment. Do not exit Fast Recovery. 3199 * 3200 * Implement the Slow-but-Steady variant of NewReno by restarting the 3201 * the retransmission timer. Turn it off here so it can be restarted 3202 * later in tcp_output(). 3203 */ 3204 static void 3205 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3206 { 3207 tcp_seq old_snd_nxt = tp->snd_nxt; 3208 u_long ocwnd = tp->snd_cwnd; 3209 3210 tcp_callout_stop(tp, tp->tt_rexmt); 3211 tp->t_rtttime = 0; 3212 tp->snd_nxt = th->th_ack; 3213 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3214 tp->snd_cwnd = tp->t_maxseg; 3215 tp->t_flags |= TF_ACKNOW; 3216 tcp_output(tp); 3217 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3218 tp->snd_nxt = old_snd_nxt; 3219 /* partial window deflation */ 3220 if (ocwnd > acked) 3221 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3222 else 3223 tp->snd_cwnd = tp->t_maxseg; 3224 } 3225 3226 /* 3227 * In contrast to the Slow-but-Steady NewReno variant, 3228 * we do not reset the retransmission timer for SACK retransmissions, 3229 * except when retransmitting snd_una. 3230 */ 3231 static void 3232 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force) 3233 { 3234 tcp_seq old_snd_nxt = tp->snd_nxt; 3235 u_long ocwnd = tp->snd_cwnd; 3236 uint32_t pipe; 3237 int nseg = 0; /* consecutive new segments */ 3238 int nseg_rexmt = 0; /* retransmitted segments */ 3239 int maxrexmt = 0; 3240 3241 if (force) { 3242 uint32_t unsacked = tcp_sack_first_unsacked_len(tp); 3243 3244 /* 3245 * Try to fill the first hole in the receiver's 3246 * reassemble queue. 3247 */ 3248 maxrexmt = howmany(unsacked, tp->t_maxseg); 3249 if (maxrexmt > tcp_force_sackrxt) 3250 maxrexmt = tcp_force_sackrxt; 3251 } 3252 3253 tp->t_rtttime = 0; 3254 pipe = tcp_sack_compute_pipe(tp); 3255 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg 3256 || (force && nseg_rexmt < maxrexmt && nseg == 0)) && 3257 (!tcp_do_smartsack || nseg < TCP_SACK_MAXBURST)) { 3258 tcp_seq old_snd_max, old_rexmt_high, nextrexmt; 3259 uint32_t sent, seglen; 3260 boolean_t rescue; 3261 int error; 3262 3263 old_rexmt_high = tp->rexmt_high; 3264 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { 3265 tp->rexmt_high = old_rexmt_high; 3266 break; 3267 } 3268 3269 /* 3270 * If the next tranmission is a rescue retranmission, 3271 * we check whether we have already sent some data 3272 * (either new segments or retransmitted segments) 3273 * into the the network or not. Since the idea of rescue 3274 * retransmission is to sustain ACK clock, as long as 3275 * some segments are in the network, ACK clock will be 3276 * kept ticking. 3277 */ 3278 if (rescue && (nseg_rexmt > 0 || nseg > 0)) { 3279 tp->rexmt_high = old_rexmt_high; 3280 break; 3281 } 3282 3283 if (nextrexmt == tp->snd_max) 3284 ++nseg; 3285 else 3286 ++nseg_rexmt; 3287 tp->snd_nxt = nextrexmt; 3288 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3289 old_snd_max = tp->snd_max; 3290 if (nextrexmt == tp->snd_una) 3291 tcp_callout_stop(tp, tp->tt_rexmt); 3292 tp->t_flags |= TF_XMITNOW; 3293 error = tcp_output(tp); 3294 if (error != 0) { 3295 tp->rexmt_high = old_rexmt_high; 3296 break; 3297 } 3298 sent = tp->snd_nxt - nextrexmt; 3299 if (sent <= 0) { 3300 tp->rexmt_high = old_rexmt_high; 3301 break; 3302 } 3303 pipe += sent; 3304 tcpstat.tcps_sndsackpack++; 3305 tcpstat.tcps_sndsackbyte += sent; 3306 3307 if (rescue) { 3308 tcpstat.tcps_sackrescue++; 3309 tp->rexmt_rescue = tp->snd_nxt; 3310 tp->sack_flags |= TSACK_F_SACKRESCUED; 3311 break; 3312 } 3313 if (SEQ_LT(nextrexmt, old_snd_max) && 3314 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { 3315 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3316 if (tcp_aggressive_rescuesack && 3317 (tp->sack_flags & TSACK_F_SACKRESCUED) && 3318 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 3319 /* Drag RescueRxt along with HighRxt */ 3320 tp->rexmt_rescue = tp->rexmt_high; 3321 } 3322 } 3323 } 3324 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3325 tp->snd_nxt = old_snd_nxt; 3326 tp->snd_cwnd = ocwnd; 3327 } 3328 3329 /* 3330 * Return TRUE, if some new segments are sent 3331 */ 3332 static boolean_t 3333 tcp_sack_limitedxmit(struct tcpcb *tp) 3334 { 3335 tcp_seq oldsndnxt = tp->snd_nxt; 3336 tcp_seq oldsndmax = tp->snd_max; 3337 u_long ocwnd = tp->snd_cwnd; 3338 uint32_t pipe, sent; 3339 boolean_t ret = FALSE; 3340 tcp_seq_diff_t cwnd_left; 3341 tcp_seq next; 3342 3343 tp->rexmt_high = tp->snd_una - 1; 3344 pipe = tcp_sack_compute_pipe(tp); 3345 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe); 3346 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg) 3347 return FALSE; 3348 3349 if (tcp_do_smartsack) 3350 cwnd_left = ulmin(cwnd_left, tp->t_maxseg * TCP_SACK_MAXBURST); 3351 3352 next = tp->snd_nxt = tp->snd_max; 3353 tp->snd_cwnd = tp->snd_nxt - tp->snd_una + 3354 rounddown(cwnd_left, tp->t_maxseg); 3355 3356 tp->t_flags |= TF_XMITNOW; 3357 tcp_output(tp); 3358 3359 sent = tp->snd_nxt - next; 3360 if (sent > 0) { 3361 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg); 3362 ret = TRUE; 3363 } 3364 3365 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3366 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3367 ("snd_una moved in other threads")); 3368 tp->snd_nxt = oldsndnxt; 3369 } 3370 tp->snd_cwnd = ocwnd; 3371 3372 if (ret && TCP_DO_NCR(tp)) 3373 tcp_ncr_update_rxtthresh(tp); 3374 3375 return ret; 3376 } 3377 3378 /* 3379 * Reset idle time and keep-alive timer, typically called when a valid 3380 * tcp packet is received but may also be called when FASTKEEP is set 3381 * to prevent the previous long-timeout from calculating to a drop. 3382 * 3383 * Only update t_rcvtime for non-SYN packets. 3384 * 3385 * Handle the case where one side thinks the connection is established 3386 * but the other side has, say, rebooted without cleaning out the 3387 * connection. The SYNs could be construed as an attack and wind 3388 * up ignored, but in case it isn't an attack we can validate the 3389 * connection by forcing a keepalive. 3390 */ 3391 void 3392 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3393 { 3394 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3395 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3396 tp->t_flags |= TF_KEEPALIVE; 3397 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3398 tcp_timer_keep); 3399 } else { 3400 tp->t_rcvtime = ticks; 3401 tp->t_flags &= ~TF_KEEPALIVE; 3402 tcp_callout_reset(tp, tp->tt_keep, 3403 tp->t_keepidle, 3404 tcp_timer_keep); 3405 } 3406 } 3407 } 3408 3409 static int 3410 tcp_rmx_msl(const struct tcpcb *tp) 3411 { 3412 struct rtentry *rt; 3413 struct inpcb *inp = tp->t_inpcb; 3414 int msl; 3415 #ifdef INET6 3416 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); 3417 #else 3418 const boolean_t isipv6 = FALSE; 3419 #endif 3420 3421 if (isipv6) 3422 rt = tcp_rtlookup6(&inp->inp_inc); 3423 else 3424 rt = tcp_rtlookup(&inp->inp_inc); 3425 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3426 return tcp_msl; 3427 3428 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3429 if (msl == 0) 3430 msl = 1; 3431 3432 return msl; 3433 } 3434 3435 static void 3436 tcp_established(struct tcpcb *tp) 3437 { 3438 tp->t_state = TCPS_ESTABLISHED; 3439 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3440 3441 if (tp->t_rxtsyn > 0) { 3442 /* 3443 * RFC6298: 3444 * "If the timer expires awaiting the ACK of a SYN segment 3445 * and the TCP implementation is using an RTO less than 3 3446 * seconds, the RTO MUST be re-initialized to 3 seconds 3447 * when data transmission begins" 3448 */ 3449 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3450 tp->t_rxtcur = TCPTV_RTOBASE3; 3451 } 3452 } 3453 3454 /* 3455 * Returns TRUE, if the ACK should be dropped 3456 */ 3457 static boolean_t 3458 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags) 3459 { 3460 boolean_t fast_sack_rexmt = TRUE; 3461 3462 tcpstat.tcps_rcvdupack++; 3463 3464 /* 3465 * We have outstanding data (other than a window probe), 3466 * this is a completely duplicate ack (ie, window info 3467 * didn't change), the ack is the biggest we've seen and 3468 * we've seen exactly our rexmt threshhold of them, so 3469 * assume a packet has been dropped and retransmit it. 3470 * Kludge snd_nxt & the congestion window so we send only 3471 * this one packet. 3472 */ 3473 if (IN_FASTRECOVERY(tp)) { 3474 if (TCP_DO_SACK(tp)) { 3475 boolean_t force = FALSE; 3476 3477 if (tp->snd_una == tp->rexmt_high && 3478 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) == 3479 TOF_SACK) { 3480 /* 3481 * New segments got SACKed and 3482 * no retransmit yet. 3483 */ 3484 force = TRUE; 3485 } 3486 3487 /* No artifical cwnd inflation. */ 3488 tcp_sack_rexmt(tp, force); 3489 } else { 3490 /* 3491 * Dup acks mean that packets have left 3492 * the network (they're now cached at the 3493 * receiver) so bump cwnd by the amount in 3494 * the receiver to keep a constant cwnd 3495 * packets in the network. 3496 */ 3497 tp->snd_cwnd += tp->t_maxseg; 3498 tcp_output(tp); 3499 } 3500 return TRUE; 3501 } else if (SEQ_LT(th_ack, tp->snd_recover)) { 3502 tp->t_dupacks = 0; 3503 return FALSE; 3504 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && 3505 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == 3506 (TOF_DSACK | TOF_SACK_REDUNDANT)) { 3507 /* 3508 * If the ACK carries DSACK and other SACK blocks 3509 * carry information that we have already known, 3510 * don't count this ACK as duplicate ACK. This 3511 * prevents spurious early retransmit and fast 3512 * retransmit. This also meets the requirement of 3513 * RFC3042 that new segments should not be sent if 3514 * the SACK blocks do not contain new information 3515 * (XXX we actually loosen the requirment that only 3516 * DSACK is checked here). 3517 * 3518 * This kind of ACKs are usually sent after spurious 3519 * retransmit. 3520 */ 3521 /* Do nothing; don't change t_dupacks */ 3522 return TRUE; 3523 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) { 3524 tcp_ncr_update_rxtthresh(tp); 3525 } 3526 3527 if (++tp->t_dupacks == tp->t_rxtthresh) { 3528 tcp_seq old_snd_nxt; 3529 u_int win; 3530 3531 fastretransmit: 3532 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) { 3533 tcp_save_congestion_state(tp); 3534 tp->rxt_flags |= TRXT_F_FASTREXMT; 3535 } 3536 /* 3537 * We know we're losing at the current window size, 3538 * so do congestion avoidance: set ssthresh to half 3539 * the current window and pull our congestion window 3540 * back to the new ssthresh. 3541 */ 3542 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 3543 if (win < 2) 3544 win = 2; 3545 tp->snd_ssthresh = win * tp->t_maxseg; 3546 ENTER_FASTRECOVERY(tp); 3547 tp->snd_recover = tp->snd_max; 3548 tcp_callout_stop(tp, tp->tt_rexmt); 3549 tp->t_rtttime = 0; 3550 old_snd_nxt = tp->snd_nxt; 3551 tp->snd_nxt = th_ack; 3552 if (TCP_DO_SACK(tp)) { 3553 uint32_t rxtlen; 3554 3555 rxtlen = tcp_sack_first_unsacked_len(tp); 3556 if (rxtlen > tp->t_maxseg) 3557 rxtlen = tp->t_maxseg; 3558 tp->snd_cwnd = rxtlen; 3559 } else { 3560 tp->snd_cwnd = tp->t_maxseg; 3561 } 3562 tcp_output(tp); 3563 ++tcpstat.tcps_sndfastrexmit; 3564 tp->snd_cwnd = tp->snd_ssthresh; 3565 tp->rexmt_high = tp->snd_nxt; 3566 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 3567 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3568 tp->snd_nxt = old_snd_nxt; 3569 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big")); 3570 if (TCP_DO_SACK(tp)) { 3571 if (fast_sack_rexmt) 3572 tcp_sack_rexmt(tp, FALSE); 3573 } else { 3574 tp->snd_cwnd += tp->t_maxseg * 3575 (tp->t_dupacks - tp->snd_limited); 3576 } 3577 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) { 3578 /* 3579 * The RFC6675 recommends to reduce the byte threshold, 3580 * and enter fast retransmit if IsLost(snd_una). However, 3581 * if we use IsLost(snd_una) based fast retransmit here, 3582 * segments reordering will cause spurious retransmit. So 3583 * we defer the IsLost(snd_una) based fast retransmit until 3584 * the extended limited transmit can't send any segments and 3585 * early retransmit can't be done. 3586 */ 3587 if (tcp_rfc6675_rxt && tcp_do_rfc6675 && 3588 tcp_sack_islost(&tp->scb, tp->snd_una)) 3589 goto fastretransmit; 3590 3591 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) { 3592 if (!tcp_sack_limitedxmit(tp)) { 3593 /* outstanding data */ 3594 uint32_t ownd = tp->snd_max - tp->snd_una; 3595 3596 if (need_early_retransmit(tp, ownd)) { 3597 ++tcpstat.tcps_sndearlyrexmit; 3598 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3599 goto fastretransmit; 3600 } else if (tcp_do_rfc6675 && 3601 tcp_sack_islost(&tp->scb, tp->snd_una)) { 3602 fast_sack_rexmt = FALSE; 3603 goto fastretransmit; 3604 } 3605 } 3606 } 3607 } else if (tcp_do_limitedtransmit) { 3608 u_long oldcwnd = tp->snd_cwnd; 3609 tcp_seq oldsndmax = tp->snd_max; 3610 tcp_seq oldsndnxt = tp->snd_nxt; 3611 /* outstanding data */ 3612 uint32_t ownd = tp->snd_max - tp->snd_una; 3613 u_int sent; 3614 3615 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2, 3616 ("dupacks not 1 or 2")); 3617 if (tp->t_dupacks == 1) 3618 tp->snd_limited = 0; 3619 tp->snd_nxt = tp->snd_max; 3620 tp->snd_cwnd = ownd + 3621 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg; 3622 tp->t_flags |= TF_XMITNOW; 3623 tcp_output(tp); 3624 3625 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3626 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3627 ("snd_una moved in other threads")); 3628 tp->snd_nxt = oldsndnxt; 3629 } 3630 tp->snd_cwnd = oldcwnd; 3631 sent = tp->snd_max - oldsndmax; 3632 if (sent > tp->t_maxseg) { 3633 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) || 3634 (sent == tp->t_maxseg + 1 && 3635 (tp->t_flags & TF_SENTFIN)), 3636 ("sent too much")); 3637 KASSERT(sent <= tp->t_maxseg * 2, 3638 ("sent too many segments")); 3639 tp->snd_limited = 2; 3640 tcpstat.tcps_sndlimited += 2; 3641 } else if (sent > 0) { 3642 ++tp->snd_limited; 3643 ++tcpstat.tcps_sndlimited; 3644 } else if (need_early_retransmit(tp, ownd)) { 3645 ++tcpstat.tcps_sndearlyrexmit; 3646 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3647 goto fastretransmit; 3648 } 3649 } 3650 return TRUE; 3651 } 3652