1 /* 2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. Neither the name of the University nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 60 * SUCH DAMAGE. 61 * 62 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 63 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 64 */ 65 66 #include "opt_inet.h" 67 #include "opt_inet6.h" 68 #include "opt_tcpdebug.h" 69 #include "opt_tcp_input.h" 70 71 #include <sys/param.h> 72 #include <sys/systm.h> 73 #include <sys/kernel.h> 74 #include <sys/sysctl.h> 75 #include <sys/malloc.h> 76 #include <sys/mbuf.h> 77 #include <sys/proc.h> /* for proc0 declaration */ 78 #include <sys/protosw.h> 79 #include <sys/socket.h> 80 #include <sys/socketvar.h> 81 #include <sys/syslog.h> 82 #include <sys/in_cksum.h> 83 84 #include <sys/socketvar2.h> 85 86 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 87 #include <machine/stdarg.h> 88 89 #include <net/if.h> 90 #include <net/route.h> 91 92 #include <netinet/in.h> 93 #include <netinet/in_systm.h> 94 #include <netinet/ip.h> 95 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 96 #include <netinet/in_var.h> 97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 98 #include <netinet/in_pcb.h> 99 #include <netinet/ip_var.h> 100 #include <netinet/ip6.h> 101 #include <netinet/icmp6.h> 102 #include <netinet6/nd6.h> 103 #include <netinet6/ip6_var.h> 104 #include <netinet6/in6_pcb.h> 105 #include <netinet/tcp.h> 106 #include <netinet/tcp_fsm.h> 107 #include <netinet/tcp_seq.h> 108 #include <netinet/tcp_timer.h> 109 #include <netinet/tcp_timer2.h> 110 #include <netinet/tcp_var.h> 111 #include <netinet6/tcp6_var.h> 112 #include <netinet/tcpip.h> 113 114 #ifdef TCPDEBUG 115 #include <netinet/tcp_debug.h> 116 117 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 118 struct tcphdr tcp_savetcp; 119 #endif 120 121 /* 122 * Limit burst of new packets during SACK based fast recovery 123 * or extended limited transmit. 124 */ 125 #define TCP_SACK_MAXBURST 4 126 127 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 128 129 static int log_in_vain = 0; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 131 &log_in_vain, 0, "Log all incoming TCP connections"); 132 133 static int blackhole = 0; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 135 &blackhole, 0, "Do not send RST when dropping refused connections"); 136 137 int tcp_delack_enabled = 1; 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 139 &tcp_delack_enabled, 0, 140 "Delay ACK to try to piggyback it onto a data packet"); 141 142 #ifdef TCP_DROP_SYNFIN 143 static int drop_synfin = 0; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 145 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 146 #endif 147 148 static int tcp_do_limitedtransmit = 1; 149 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, 150 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); 151 152 static int tcp_do_early_retransmit = 1; 153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, 154 &tcp_do_early_retransmit, 0, "Early retransmit"); 155 156 int tcp_aggregate_acks = 1; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, 158 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); 159 160 static int tcp_do_eifel_detect = 1; 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, 162 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); 163 164 static int tcp_do_abc = 1; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, 166 &tcp_do_abc, 0, 167 "TCP Appropriate Byte Counting (RFC 3465)"); 168 169 /* 170 * The following value actually takes range [25ms, 250ms], 171 * given that most modern systems use 1ms ~ 10ms as the unit 172 * of timestamp option. 173 */ 174 static u_int tcp_paws_tolerance = 25; 175 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW, 176 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance"); 177 178 /* 179 * Define as tunable for easy testing with SACK on and off. 180 * Warning: do not change setting in the middle of an existing active TCP flow, 181 * else strange things might happen to that flow. 182 */ 183 int tcp_do_sack = 1; 184 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 185 &tcp_do_sack, 0, "Enable SACK Algorithms"); 186 187 int tcp_do_smartsack = 1; 188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, 189 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); 190 191 int tcp_do_rescuesack = 1; 192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, 193 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); 194 195 int tcp_aggressive_rescuesack = 0; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, 197 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); 198 199 static int tcp_force_sackrxt = 1; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW, 201 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst"); 202 203 int tcp_do_rfc6675 = 1; 204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW, 205 &tcp_do_rfc6675, 0, "Enable RFC6675"); 206 207 int tcp_rfc6675_rxt = 0; 208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW, 209 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit"); 210 211 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, 212 "TCP Segment Reassembly Queue"); 213 214 int tcp_reass_maxseg = 0; 215 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, 216 &tcp_reass_maxseg, 0, 217 "Global maximum number of TCP Segments in Reassembly Queue"); 218 219 int tcp_reass_qsize = 0; 220 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, 221 &tcp_reass_qsize, 0, 222 "Global number of TCP Segments currently in Reassembly Queue"); 223 224 static int tcp_reass_overflows = 0; 225 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, 226 &tcp_reass_overflows, 0, 227 "Global number of TCP Segment Reassembly Queue Overflows"); 228 229 int tcp_do_autorcvbuf = 1; 230 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 231 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 232 233 int tcp_autorcvbuf_inc = 16*1024; 234 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 235 &tcp_autorcvbuf_inc, 0, 236 "Incrementor step size of automatic receive buffer"); 237 238 int tcp_autorcvbuf_max = 2*1024*1024; 239 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 240 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 241 242 int tcp_sosend_agglim = 2; 243 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, 244 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); 245 246 int tcp_sosend_async = 1; 247 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, 248 &tcp_sosend_async, 0, "TCP asynchronized pru_send"); 249 250 int tcp_sosend_jcluster = 1; 251 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_jcluster, CTLFLAG_RW, 252 &tcp_sosend_jcluster, 0, "TCP output uses jcluster"); 253 254 static int tcp_ignore_redun_dsack = 1; 255 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW, 256 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK"); 257 258 static int tcp_reuseport_ext = 1; 259 SYSCTL_INT(_net_inet_tcp, OID_AUTO, reuseport_ext, CTLFLAG_RW, 260 &tcp_reuseport_ext, 0, "SO_REUSEPORT extension"); 261 262 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, 263 tcp_seq); 264 static void tcp_pulloutofband(struct socket *, 265 struct tcphdr *, struct mbuf *, int); 266 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 267 struct mbuf *); 268 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); 269 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); 270 static void tcp_sack_rexmt(struct tcpcb *, boolean_t); 271 static boolean_t tcp_sack_limitedxmit(struct tcpcb *); 272 static int tcp_rmx_msl(const struct tcpcb *); 273 static void tcp_established(struct tcpcb *); 274 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int); 275 276 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 277 #ifdef INET6 278 #define ND6_HINT(tp) \ 279 do { \ 280 if ((tp) && (tp)->t_inpcb && \ 281 INP_ISIPV6((tp)->t_inpcb) && \ 282 (tp)->t_inpcb->in6p_route.ro_rt) \ 283 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 284 } while (0) 285 #else 286 #define ND6_HINT(tp) 287 #endif 288 289 /* 290 * Indicate whether this ack should be delayed. We can delay the ack if 291 * - delayed acks are enabled and 292 * - there is no delayed ack timer in progress and 293 * - our last ack wasn't a 0-sized window. We never want to delay 294 * the ack that opens up a 0-sized window. 295 */ 296 #define DELAY_ACK(tp) \ 297 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ 298 !(tp->t_flags & TF_RXWIN0SENT)) 299 300 #define acceptable_window_update(tp, th, tiwin) \ 301 (SEQ_LT(tp->snd_wl1, th->th_seq) || \ 302 (tp->snd_wl1 == th->th_seq && \ 303 (SEQ_LT(tp->snd_wl2, th->th_ack) || \ 304 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) 305 306 #define iceildiv(n, d) (((n)+(d)-1) / (d)) 307 #define need_early_retransmit(tp, ownd) \ 308 (tcp_do_early_retransmit && \ 309 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \ 310 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \ 311 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \ 312 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \ 313 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg))) 314 315 /* 316 * Returns TRUE, if this segment can be merged with the last 317 * pending segment in the reassemble queue and this segment 318 * does not overlap with the pending segment immediately 319 * preceeding the last pending segment. 320 */ 321 static __inline boolean_t 322 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen) 323 { 324 const struct tseg_qent *last, *prev; 325 326 last = TAILQ_LAST(&tp->t_segq, tsegqe_head); 327 if (last == NULL) 328 return FALSE; 329 330 /* This segment comes immediately after the last pending segment */ 331 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) { 332 if (last->tqe_th->th_flags & TH_FIN) { 333 /* No segments should follow segment w/ FIN */ 334 return FALSE; 335 } 336 return TRUE; 337 } 338 339 if (th->th_seq + tlen != last->tqe_th->th_seq) 340 return FALSE; 341 /* This segment comes immediately before the last pending segment */ 342 343 prev = TAILQ_PREV(last, tsegqe_head, tqe_q); 344 if (prev == NULL) { 345 /* 346 * No pending preceeding segment, we assume this segment 347 * could be reassembled. 348 */ 349 return TRUE; 350 } 351 352 /* This segment does not overlap with the preceeding segment */ 353 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len)) 354 return TRUE; 355 356 return FALSE; 357 } 358 359 static __inline void 360 tcp_ncr_update_rxtthresh(struct tcpcb *tp) 361 { 362 int old_rxtthresh = tp->t_rxtthresh; 363 uint32_t ownd = tp->snd_max - tp->snd_una; 364 365 tp->t_rxtthresh = min(tcp_ncr_rxtthresh_max, 366 max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1))); 367 if (tp->t_rxtthresh != old_rxtthresh) { 368 tcp_sack_update_lostseq(&tp->scb, tp->snd_una, 369 tp->t_maxseg, tp->t_rxtthresh); 370 } 371 } 372 373 static int 374 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) 375 { 376 struct tseg_qent *q; 377 struct tseg_qent *p = NULL; 378 struct tseg_qent *te; 379 struct socket *so = tp->t_inpcb->inp_socket; 380 int flags; 381 382 /* 383 * Call with th == NULL after become established to 384 * force pre-ESTABLISHED data up to user socket. 385 */ 386 if (th == NULL) 387 goto present; 388 389 /* 390 * Limit the number of segments in the reassembly queue to prevent 391 * holding on to too many segments (and thus running out of mbufs). 392 * Make sure to let the missing segment through which caused this 393 * queue. Always keep one global queue entry spare to be able to 394 * process the missing segment. 395 */ 396 if (th->th_seq != tp->rcv_nxt && 397 tcp_reass_qsize + 1 >= tcp_reass_maxseg) { 398 tcp_reass_overflows++; 399 tcpstat.tcps_rcvmemdrop++; 400 m_freem(m); 401 /* no SACK block to report */ 402 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 403 return (0); 404 } 405 406 /* Allocate a new queue entry. */ 407 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); 408 if (te == NULL) { 409 tcpstat.tcps_rcvmemdrop++; 410 m_freem(m); 411 /* no SACK block to report */ 412 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 413 return (0); 414 } 415 atomic_add_int(&tcp_reass_qsize, 1); 416 417 if (th->th_flags & TH_FIN) 418 tp->t_flags |= TF_QUEDFIN; 419 420 /* 421 * Find a segment which begins after this one does. 422 */ 423 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) { 424 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 425 break; 426 p = q; 427 } 428 429 /* 430 * If there is a preceding segment, it may provide some of 431 * our data already. If so, drop the data from the incoming 432 * segment. If it provides all of our data, drop us. 433 */ 434 if (p != NULL) { 435 tcp_seq_diff_t i; 436 437 /* conversion to int (in i) handles seq wraparound */ 438 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 439 if (i > 0) { /* overlaps preceding segment */ 440 tp->sack_flags |= 441 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 442 /* enclosing block starts w/ preceding segment */ 443 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 444 if (i >= *tlenp) { 445 if (th->th_flags & TH_FIN) 446 p->tqe_th->th_flags |= TH_FIN; 447 448 /* preceding encloses incoming segment */ 449 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 450 p->tqe_th->th_seq + p->tqe_len, 451 p->tqe_th->th_flags); 452 tcpstat.tcps_rcvduppack++; 453 tcpstat.tcps_rcvdupbyte += *tlenp; 454 m_freem(m); 455 kfree(te, M_TSEGQ); 456 atomic_add_int(&tcp_reass_qsize, -1); 457 /* 458 * Try to present any queued data 459 * at the left window edge to the user. 460 * This is needed after the 3-WHS 461 * completes. 462 */ 463 goto present; /* ??? */ 464 } 465 m_adj(m, i); 466 *tlenp -= i; 467 th->th_seq += i; 468 /* incoming segment end is enclosing block end */ 469 tp->encloseblk.rblk_end = TCP_SACK_BLKEND( 470 th->th_seq + *tlenp, th->th_flags); 471 /* trim end of reported D-SACK block */ 472 tp->reportblk.rblk_end = th->th_seq; 473 } 474 } 475 tcpstat.tcps_rcvoopack++; 476 tcpstat.tcps_rcvoobyte += *tlenp; 477 478 /* 479 * While we overlap succeeding segments trim them or, 480 * if they are completely covered, dequeue them. 481 */ 482 while (q) { 483 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 484 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; 485 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); 486 struct tseg_qent *nq; 487 488 if (i <= 0) 489 break; 490 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 491 /* first time through */ 492 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); 493 tp->encloseblk = tp->reportblk; 494 /* report trailing duplicate D-SACK segment */ 495 tp->reportblk.rblk_start = q->tqe_th->th_seq; 496 } 497 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) && 498 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { 499 /* extend enclosing block if one exists */ 500 tp->encloseblk.rblk_end = qend_sack; 501 } 502 if (i < q->tqe_len) { 503 q->tqe_th->th_seq += i; 504 q->tqe_len -= i; 505 m_adj(q->tqe_m, i); 506 break; 507 } 508 509 if (q->tqe_th->th_flags & TH_FIN) 510 th->th_flags |= TH_FIN; 511 512 nq = TAILQ_NEXT(q, tqe_q); 513 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 514 m_freem(q->tqe_m); 515 kfree(q, M_TSEGQ); 516 atomic_add_int(&tcp_reass_qsize, -1); 517 q = nq; 518 } 519 520 /* Insert the new segment queue entry into place. */ 521 te->tqe_m = m; 522 te->tqe_th = th; 523 te->tqe_len = *tlenp; 524 525 /* check if can coalesce with following segment */ 526 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { 527 tcp_seq tend_sack; 528 529 te->tqe_len += q->tqe_len; 530 if (q->tqe_th->th_flags & TH_FIN) 531 te->tqe_th->th_flags |= TH_FIN; 532 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len, 533 te->tqe_th->th_flags); 534 535 m_cat(te->tqe_m, q->tqe_m); 536 tp->encloseblk.rblk_end = tend_sack; 537 /* 538 * When not reporting a duplicate segment, use 539 * the larger enclosing block as the SACK block. 540 */ 541 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 542 tp->reportblk.rblk_end = tend_sack; 543 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 544 kfree(q, M_TSEGQ); 545 atomic_add_int(&tcp_reass_qsize, -1); 546 } 547 548 if (p == NULL) { 549 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q); 550 } else { 551 /* check if can coalesce with preceding segment */ 552 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { 553 if (te->tqe_th->th_flags & TH_FIN) 554 p->tqe_th->th_flags |= TH_FIN; 555 p->tqe_len += te->tqe_len; 556 m_cat(p->tqe_m, te->tqe_m); 557 tp->encloseblk.rblk_start = p->tqe_th->th_seq; 558 /* 559 * When not reporting a duplicate segment, use 560 * the larger enclosing block as the SACK block. 561 */ 562 if (!(tp->sack_flags & TSACK_F_DUPSEG)) 563 tp->reportblk.rblk_start = p->tqe_th->th_seq; 564 kfree(te, M_TSEGQ); 565 atomic_add_int(&tcp_reass_qsize, -1); 566 } else { 567 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q); 568 } 569 } 570 571 present: 572 /* 573 * Present data to user, advancing rcv_nxt through 574 * completed sequence space. 575 */ 576 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 577 return (0); 578 q = TAILQ_FIRST(&tp->t_segq); 579 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) 580 return (0); 581 tp->rcv_nxt += q->tqe_len; 582 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 583 /* no SACK block to report since ACK advanced */ 584 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 585 } 586 /* no enclosing block to report since ACK advanced */ 587 tp->sack_flags &= ~TSACK_F_ENCLOSESEG; 588 flags = q->tqe_th->th_flags & TH_FIN; 589 TAILQ_REMOVE(&tp->t_segq, q, tqe_q); 590 KASSERT(TAILQ_EMPTY(&tp->t_segq) || 591 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, 592 ("segment not coalesced")); 593 if (so->so_state & SS_CANTRCVMORE) { 594 m_freem(q->tqe_m); 595 } else { 596 lwkt_gettoken(&so->so_rcv.ssb_token); 597 ssb_appendstream(&so->so_rcv, q->tqe_m); 598 lwkt_reltoken(&so->so_rcv.ssb_token); 599 } 600 kfree(q, M_TSEGQ); 601 atomic_add_int(&tcp_reass_qsize, -1); 602 ND6_HINT(tp); 603 sorwakeup(so); 604 return (flags); 605 } 606 607 /* 608 * TCP input routine, follows pages 65-76 of the 609 * protocol specification dated September, 1981 very closely. 610 */ 611 #ifdef INET6 612 int 613 tcp6_input(struct mbuf **mp, int *offp, int proto) 614 { 615 struct mbuf *m = *mp; 616 struct in6_ifaddr *ia6; 617 618 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 619 620 /* 621 * draft-itojun-ipv6-tcp-to-anycast 622 * better place to put this in? 623 */ 624 ia6 = ip6_getdstifaddr(m); 625 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 626 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 627 offsetof(struct ip6_hdr, ip6_dst)); 628 return (IPPROTO_DONE); 629 } 630 631 tcp_input(mp, offp, proto); 632 return (IPPROTO_DONE); 633 } 634 #endif 635 636 int 637 tcp_input(struct mbuf **mp, int *offp, int proto) 638 { 639 int off0; 640 struct tcphdr *th; 641 struct ip *ip = NULL; 642 struct ipovly *ipov; 643 struct inpcb *inp = NULL; 644 u_char *optp = NULL; 645 int optlen = 0; 646 int tlen, off; 647 int len = 0; 648 int drop_hdrlen; 649 struct tcpcb *tp = NULL; 650 int thflags; 651 struct socket *so = NULL; 652 int todrop, acked; 653 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE; 654 tcp_seq th_dupack = 0; /* XXX gcc warning */ 655 u_int to_flags = 0; /* XXX gcc warning */ 656 u_long tiwin; 657 int recvwin; 658 struct tcpopt to; /* options in this segment */ 659 struct sockaddr_in *next_hop = NULL; 660 int rstreason; /* For badport_bandlim accounting purposes */ 661 int cpu; 662 struct ip6_hdr *ip6 = NULL; 663 struct mbuf *m; 664 #ifdef INET6 665 boolean_t isipv6; 666 #else 667 const boolean_t isipv6 = FALSE; 668 #endif 669 #ifdef TCPDEBUG 670 short ostate = 0; 671 #endif 672 673 off0 = *offp; 674 m = *mp; 675 *mp = NULL; 676 677 tcpstat.tcps_rcvtotal++; 678 679 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { 680 struct m_tag *mtag; 681 682 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 683 KKASSERT(mtag != NULL); 684 next_hop = m_tag_data(mtag); 685 } 686 687 #ifdef INET6 688 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; 689 #endif 690 691 if (isipv6) { 692 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 693 ip6 = mtod(m, struct ip6_hdr *); 694 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; 695 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 696 tcpstat.tcps_rcvbadsum++; 697 goto drop; 698 } 699 th = (struct tcphdr *)((caddr_t)ip6 + off0); 700 701 /* 702 * Be proactive about unspecified IPv6 address in source. 703 * As we use all-zero to indicate unbounded/unconnected pcb, 704 * unspecified IPv6 address can be used to confuse us. 705 * 706 * Note that packets with unspecified IPv6 destination is 707 * already dropped in ip6_input. 708 */ 709 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 710 /* XXX stat */ 711 goto drop; 712 } 713 } else { 714 /* 715 * Get IP and TCP header together in first mbuf. 716 * Note: IP leaves IP header in first mbuf. 717 */ 718 if (off0 > sizeof(struct ip)) { 719 ip_stripoptions(m); 720 off0 = sizeof(struct ip); 721 } 722 /* already checked and pulled up in ip_demux() */ 723 KASSERT(m->m_len >= sizeof(struct tcpiphdr), 724 ("TCP header not in one mbuf: m->m_len %d", m->m_len)); 725 ip = mtod(m, struct ip *); 726 ipov = (struct ipovly *)ip; 727 th = (struct tcphdr *)((caddr_t)ip + off0); 728 tlen = ntohs(ip->ip_len) - off0; 729 730 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 731 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 732 th->th_sum = m->m_pkthdr.csum_data; 733 else 734 th->th_sum = in_pseudo(ip->ip_src.s_addr, 735 ip->ip_dst.s_addr, 736 htonl(m->m_pkthdr.csum_data + 737 ntohs(ip->ip_len) + 738 IPPROTO_TCP)); 739 th->th_sum ^= 0xffff; 740 } else { 741 /* 742 * Checksum extended TCP header and data. 743 */ 744 len = sizeof(struct ip) + tlen; 745 bzero(ipov->ih_x1, sizeof ipov->ih_x1); 746 ipov->ih_len = (u_short)tlen; 747 ipov->ih_len = htons(ipov->ih_len); 748 th->th_sum = in_cksum(m, len); 749 } 750 if (th->th_sum) { 751 tcpstat.tcps_rcvbadsum++; 752 goto drop; 753 } 754 #ifdef INET6 755 /* Re-initialization for later version check */ 756 ip->ip_v = IPVERSION; 757 #endif 758 } 759 760 /* 761 * Check that TCP offset makes sense, 762 * pull out TCP options and adjust length. XXX 763 */ 764 off = th->th_off << 2; 765 /* already checked and pulled up in ip_demux() */ 766 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, 767 ("bad TCP data offset %d (tlen %d)", off, tlen)); 768 tlen -= off; /* tlen is used instead of ti->ti_len */ 769 if (off > sizeof(struct tcphdr)) { 770 if (isipv6) { 771 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 772 ip6 = mtod(m, struct ip6_hdr *); 773 th = (struct tcphdr *)((caddr_t)ip6 + off0); 774 } else { 775 /* already pulled up in ip_demux() */ 776 KASSERT(m->m_len >= sizeof(struct ip) + off, 777 ("TCP header and options not in one mbuf: " 778 "m_len %d, off %d", m->m_len, off)); 779 } 780 optlen = off - sizeof(struct tcphdr); 781 optp = (u_char *)(th + 1); 782 } 783 thflags = th->th_flags; 784 785 #ifdef TCP_DROP_SYNFIN 786 /* 787 * If the drop_synfin option is enabled, drop all packets with 788 * both the SYN and FIN bits set. This prevents e.g. nmap from 789 * identifying the TCP/IP stack. 790 * 791 * This is a violation of the TCP specification. 792 */ 793 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) 794 goto drop; 795 #endif 796 797 /* 798 * Convert TCP protocol specific fields to host format. 799 */ 800 th->th_seq = ntohl(th->th_seq); 801 th->th_ack = ntohl(th->th_ack); 802 th->th_win = ntohs(th->th_win); 803 th->th_urp = ntohs(th->th_urp); 804 805 /* 806 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, 807 * until after ip6_savecontrol() is called and before other functions 808 * which don't want those proto headers. 809 * Because ip6_savecontrol() is going to parse the mbuf to 810 * search for data to be passed up to user-land, it wants mbuf 811 * parameters to be unchanged. 812 * XXX: the call of ip6_savecontrol() has been obsoleted based on 813 * latest version of the advanced API (20020110). 814 */ 815 drop_hdrlen = off0 + off; 816 817 /* 818 * Locate pcb for segment. 819 */ 820 findpcb: 821 /* IPFIREWALL_FORWARD section */ 822 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ 823 /* 824 * Transparently forwarded. Pretend to be the destination. 825 * already got one like this? 826 */ 827 cpu = mycpu->gd_cpuid; 828 inp = in_pcblookup_hash(&tcbinfo[cpu], 829 ip->ip_src, th->th_sport, 830 ip->ip_dst, th->th_dport, 831 0, m->m_pkthdr.rcvif); 832 if (!inp) { 833 /* 834 * It's new. Try to find the ambushing socket. 835 */ 836 837 /* 838 * The rest of the ipfw code stores the port in 839 * host order. XXX 840 * (The IP address is still in network order.) 841 */ 842 in_port_t dport = next_hop->sin_port ? 843 htons(next_hop->sin_port) : 844 th->th_dport; 845 846 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, 847 next_hop->sin_addr.s_addr, dport); 848 inp = in_pcblookup_hash(&tcbinfo[cpu], 849 ip->ip_src, th->th_sport, 850 next_hop->sin_addr, dport, 851 1, m->m_pkthdr.rcvif); 852 } 853 } else { 854 if (isipv6) { 855 inp = in6_pcblookup_hash(&tcbinfo[0], 856 &ip6->ip6_src, th->th_sport, 857 &ip6->ip6_dst, th->th_dport, 858 1, m->m_pkthdr.rcvif); 859 } else { 860 cpu = mycpu->gd_cpuid; 861 inp = in_pcblookup_pkthash(&tcbinfo[cpu], 862 ip->ip_src, th->th_sport, 863 ip->ip_dst, th->th_dport, 864 1, m->m_pkthdr.rcvif, 865 tcp_reuseport_ext ? m : NULL); 866 } 867 } 868 869 /* 870 * If the state is CLOSED (i.e., TCB does not exist) then 871 * all data in the incoming segment is discarded. 872 * If the TCB exists but is in CLOSED state, it is embryonic, 873 * but should either do a listen or a connect soon. 874 */ 875 if (inp == NULL) { 876 if (log_in_vain) { 877 #ifdef INET6 878 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 879 #else 880 char dbuf[INET_ADDRSTRLEN], sbuf[INET_ADDRSTRLEN]; 881 #endif 882 if (isipv6) { 883 strcpy(dbuf, "["); 884 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 885 strcat(dbuf, "]"); 886 strcpy(sbuf, "["); 887 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 888 strcat(sbuf, "]"); 889 } else { 890 kinet_ntoa(ip->ip_dst, dbuf); 891 kinet_ntoa(ip->ip_src, sbuf); 892 } 893 switch (log_in_vain) { 894 case 1: 895 if (!(thflags & TH_SYN)) 896 break; 897 case 2: 898 log(LOG_INFO, 899 "Connection attempt to TCP %s:%d " 900 "from %s:%d flags:0x%02x\n", 901 dbuf, ntohs(th->th_dport), sbuf, 902 ntohs(th->th_sport), thflags); 903 break; 904 default: 905 break; 906 } 907 } 908 if (blackhole) { 909 switch (blackhole) { 910 case 1: 911 if (thflags & TH_SYN) 912 goto drop; 913 break; 914 case 2: 915 goto drop; 916 default: 917 goto drop; 918 } 919 } 920 rstreason = BANDLIM_RST_CLOSEDPORT; 921 goto dropwithreset; 922 } 923 924 /* Check the minimum TTL for socket. */ 925 #ifdef INET6 926 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) 927 goto drop; 928 #endif 929 930 tp = intotcpcb(inp); 931 KASSERT(tp != NULL, ("tcp_input: tp is NULL")); 932 if (tp->t_state <= TCPS_CLOSED) 933 goto drop; 934 935 so = inp->inp_socket; 936 937 #ifdef TCPDEBUG 938 if (so->so_options & SO_DEBUG) { 939 ostate = tp->t_state; 940 if (isipv6) 941 bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); 942 else 943 bcopy(ip, tcp_saveipgen, sizeof(*ip)); 944 tcp_savetcp = *th; 945 } 946 #endif 947 948 bzero(&to, sizeof to); 949 950 if (so->so_options & SO_ACCEPTCONN) { 951 struct in_conninfo inc; 952 953 #ifdef INET6 954 inc.inc_isipv6 = (isipv6 == TRUE); 955 #endif 956 if (isipv6) { 957 inc.inc6_faddr = ip6->ip6_src; 958 inc.inc6_laddr = ip6->ip6_dst; 959 inc.inc6_route.ro_rt = NULL; /* XXX */ 960 } else { 961 inc.inc_faddr = ip->ip_src; 962 inc.inc_laddr = ip->ip_dst; 963 inc.inc_route.ro_rt = NULL; /* XXX */ 964 } 965 inc.inc_fport = th->th_sport; 966 inc.inc_lport = th->th_dport; 967 968 /* 969 * If the state is LISTEN then ignore segment if it contains 970 * a RST. If the segment contains an ACK then it is bad and 971 * send a RST. If it does not contain a SYN then it is not 972 * interesting; drop it. 973 * 974 * If the state is SYN_RECEIVED (syncache) and seg contains 975 * an ACK, but not for our SYN/ACK, send a RST. If the seg 976 * contains a RST, check the sequence number to see if it 977 * is a valid reset segment. 978 */ 979 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { 980 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { 981 if (!syncache_expand(&inc, th, &so, m)) { 982 /* 983 * No syncache entry, or ACK was not 984 * for our SYN/ACK. Send a RST. 985 */ 986 tcpstat.tcps_badsyn++; 987 rstreason = BANDLIM_RST_OPENPORT; 988 goto dropwithreset; 989 } 990 991 /* 992 * Could not complete 3-way handshake, 993 * connection is being closed down, and 994 * syncache will free mbuf. 995 */ 996 if (so == NULL) 997 return(IPPROTO_DONE); 998 999 /* 1000 * We must be in the correct protocol thread 1001 * for this connection. 1002 */ 1003 KKASSERT(so->so_port == &curthread->td_msgport); 1004 1005 /* 1006 * Socket is created in state SYN_RECEIVED. 1007 * Continue processing segment. 1008 */ 1009 inp = so->so_pcb; 1010 tp = intotcpcb(inp); 1011 /* 1012 * This is what would have happened in 1013 * tcp_output() when the SYN,ACK was sent. 1014 */ 1015 tp->snd_up = tp->snd_una; 1016 tp->snd_max = tp->snd_nxt = tp->iss + 1; 1017 tp->last_ack_sent = tp->rcv_nxt; 1018 1019 goto after_listen; 1020 } 1021 if (thflags & TH_RST) { 1022 syncache_chkrst(&inc, th); 1023 goto drop; 1024 } 1025 if (thflags & TH_ACK) { 1026 syncache_badack(&inc); 1027 tcpstat.tcps_badsyn++; 1028 rstreason = BANDLIM_RST_OPENPORT; 1029 goto dropwithreset; 1030 } 1031 goto drop; 1032 } 1033 1034 /* 1035 * Segment's flags are (SYN) or (SYN | FIN). 1036 */ 1037 #ifdef INET6 1038 /* 1039 * If deprecated address is forbidden, 1040 * we do not accept SYN to deprecated interface 1041 * address to prevent any new inbound connection from 1042 * getting established. 1043 * When we do not accept SYN, we send a TCP RST, 1044 * with deprecated source address (instead of dropping 1045 * it). We compromise it as it is much better for peer 1046 * to send a RST, and RST will be the final packet 1047 * for the exchange. 1048 * 1049 * If we do not forbid deprecated addresses, we accept 1050 * the SYN packet. RFC2462 does not suggest dropping 1051 * SYN in this case. 1052 * If we decipher RFC2462 5.5.4, it says like this: 1053 * 1. use of deprecated addr with existing 1054 * communication is okay - "SHOULD continue to be 1055 * used" 1056 * 2. use of it with new communication: 1057 * (2a) "SHOULD NOT be used if alternate address 1058 * with sufficient scope is available" 1059 * (2b) nothing mentioned otherwise. 1060 * Here we fall into (2b) case as we have no choice in 1061 * our source address selection - we must obey the peer. 1062 * 1063 * The wording in RFC2462 is confusing, and there are 1064 * multiple description text for deprecated address 1065 * handling - worse, they are not exactly the same. 1066 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1067 */ 1068 if (isipv6 && !ip6_use_deprecated) { 1069 struct in6_ifaddr *ia6; 1070 1071 if ((ia6 = ip6_getdstifaddr(m)) && 1072 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1073 tp = NULL; 1074 rstreason = BANDLIM_RST_OPENPORT; 1075 goto dropwithreset; 1076 } 1077 } 1078 #endif 1079 /* 1080 * If it is from this socket, drop it, it must be forged. 1081 * Don't bother responding if the destination was a broadcast. 1082 */ 1083 if (th->th_dport == th->th_sport) { 1084 if (isipv6) { 1085 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 1086 &ip6->ip6_src)) 1087 goto drop; 1088 } else { 1089 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 1090 goto drop; 1091 } 1092 } 1093 /* 1094 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 1095 * 1096 * Note that it is quite possible to receive unicast 1097 * link-layer packets with a broadcast IP address. Use 1098 * in_broadcast() to find them. 1099 */ 1100 if (m->m_flags & (M_BCAST | M_MCAST)) 1101 goto drop; 1102 if (isipv6) { 1103 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1104 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 1105 goto drop; 1106 } else { 1107 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1108 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1109 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1110 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 1111 goto drop; 1112 } 1113 /* 1114 * SYN appears to be valid; create compressed TCP state 1115 * for syncache. 1116 */ 1117 if (so->so_qlen <= so->so_qlimit) { 1118 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); 1119 if (!syncache_add(&inc, &to, th, so, m)) 1120 goto drop; 1121 1122 /* 1123 * Entry added to syncache, mbuf used to 1124 * send SYN,ACK packet. 1125 */ 1126 return(IPPROTO_DONE); 1127 } 1128 goto drop; 1129 } 1130 1131 after_listen: 1132 /* 1133 * Should not happen - syncache should pick up these connections. 1134 * 1135 * Once we are past handling listen sockets we must be in the 1136 * correct protocol processing thread. 1137 */ 1138 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); 1139 KKASSERT(so->so_port == &curthread->td_msgport); 1140 1141 /* Unscale the window into a 32-bit value. */ 1142 if (!(thflags & TH_SYN)) 1143 tiwin = th->th_win << tp->snd_scale; 1144 else 1145 tiwin = th->th_win; 1146 1147 /* 1148 * This is the second part of the MSS DoS prevention code (after 1149 * minmss on the sending side) and it deals with too many too small 1150 * tcp packets in a too short timeframe (1 second). 1151 * 1152 * XXX Removed. This code was crap. It does not scale to network 1153 * speed, and default values break NFS. Gone. 1154 */ 1155 /* REMOVED */ 1156 1157 /* 1158 * Segment received on connection. 1159 * 1160 * Reset idle time and keep-alive timer. Don't waste time if less 1161 * then a second has elapsed. 1162 */ 1163 if ((int)(ticks - tp->t_rcvtime) > hz) 1164 tcp_timer_keep_activity(tp, thflags); 1165 1166 /* 1167 * Process options. 1168 * XXX this is tradtitional behavior, may need to be cleaned up. 1169 */ 1170 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); 1171 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1172 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { 1173 tp->t_flags |= TF_RCVD_SCALE; 1174 tp->snd_scale = to.to_requested_s_scale; 1175 } 1176 1177 /* 1178 * Initial send window; will be updated upon next ACK 1179 */ 1180 tp->snd_wnd = th->th_win; 1181 1182 if (to.to_flags & TOF_TS) { 1183 tp->t_flags |= TF_RCVD_TSTMP; 1184 tp->ts_recent = to.to_tsval; 1185 tp->ts_recent_age = ticks; 1186 } 1187 if (!(to.to_flags & TOF_MSS)) 1188 to.to_mss = 0; 1189 tcp_rmx_init(tp, to.to_mss); 1190 /* 1191 * Only set the TF_SACK_PERMITTED per-connection flag 1192 * if we got a SACK_PERMITTED option from the other side 1193 * and the global tcp_do_sack variable is true. 1194 */ 1195 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) 1196 tp->t_flags |= TF_SACK_PERMITTED; 1197 } 1198 1199 /* 1200 * Header prediction: check for the two common cases 1201 * of a uni-directional data xfer. If the packet has 1202 * no control flags, is in-sequence, the window didn't 1203 * change and we're not retransmitting, it's a 1204 * candidate. If the length is zero and the ack moved 1205 * forward, we're the sender side of the xfer. Just 1206 * free the data acked & wake any higher level process 1207 * that was blocked waiting for space. If the length 1208 * is non-zero and the ack didn't move, we're the 1209 * receiver side. If we're getting packets in-order 1210 * (the reassembly queue is empty), add the data to 1211 * the socket buffer and note that we need a delayed ack. 1212 * Make sure that the hidden state-flags are also off. 1213 * Since we check for TCPS_ESTABLISHED above, it can only 1214 * be TH_NEEDSYN. 1215 */ 1216 if (tp->t_state == TCPS_ESTABLISHED && 1217 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1218 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1219 (!(to.to_flags & TOF_TS) || 1220 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 1221 th->th_seq == tp->rcv_nxt && 1222 tp->snd_nxt == tp->snd_max) { 1223 1224 /* 1225 * If last ACK falls within this segment's sequence numbers, 1226 * record the timestamp. 1227 * NOTE that the test is modified according to the latest 1228 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1229 */ 1230 if ((to.to_flags & TOF_TS) && 1231 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1232 tp->ts_recent_age = ticks; 1233 tp->ts_recent = to.to_tsval; 1234 } 1235 1236 if (tlen == 0) { 1237 if (SEQ_GT(th->th_ack, tp->snd_una) && 1238 SEQ_LEQ(th->th_ack, tp->snd_max) && 1239 tp->snd_cwnd >= tp->snd_wnd && 1240 !IN_FASTRECOVERY(tp)) { 1241 /* 1242 * This is a pure ack for outstanding data. 1243 */ 1244 ++tcpstat.tcps_predack; 1245 /* 1246 * "bad retransmit" recovery 1247 * 1248 * If Eifel detection applies, then 1249 * it is deterministic, so use it 1250 * unconditionally over the old heuristic. 1251 * Otherwise, fall back to the old heuristic. 1252 */ 1253 if (tcp_do_eifel_detect && 1254 (to.to_flags & TOF_TS) && to.to_tsecr && 1255 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 1256 /* Eifel detection applicable. */ 1257 if (to.to_tsecr < tp->t_rexmtTS) { 1258 tcp_revert_congestion_state(tp); 1259 ++tcpstat.tcps_eifeldetected; 1260 if (tp->t_rxtshift != 1 || 1261 ticks >= tp->t_badrxtwin) 1262 ++tcpstat.tcps_rttcantdetect; 1263 } 1264 } else if (tp->t_rxtshift == 1 && 1265 ticks < tp->t_badrxtwin) { 1266 tcp_revert_congestion_state(tp); 1267 ++tcpstat.tcps_rttdetected; 1268 } 1269 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 1270 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 1271 /* 1272 * Recalculate the retransmit timer / rtt. 1273 * 1274 * Some machines (certain windows boxes) 1275 * send broken timestamp replies during the 1276 * SYN+ACK phase, ignore timestamps of 0. 1277 */ 1278 if ((to.to_flags & TOF_TS) && to.to_tsecr) { 1279 tcp_xmit_timer(tp, 1280 ticks - to.to_tsecr + 1, 1281 th->th_ack); 1282 } else if (tp->t_rtttime && 1283 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1284 tcp_xmit_timer(tp, 1285 ticks - tp->t_rtttime + 1, 1286 th->th_ack); 1287 } 1288 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1289 acked = th->th_ack - tp->snd_una; 1290 tcpstat.tcps_rcvackpack++; 1291 tcpstat.tcps_rcvackbyte += acked; 1292 sbdrop(&so->so_snd.sb, acked); 1293 tp->snd_recover = th->th_ack - 1; 1294 tp->snd_una = th->th_ack; 1295 tp->t_dupacks = 0; 1296 /* 1297 * Update window information. 1298 */ 1299 if (tiwin != tp->snd_wnd && 1300 acceptable_window_update(tp, th, tiwin)) { 1301 /* keep track of pure window updates */ 1302 if (tp->snd_wl2 == th->th_ack && 1303 tiwin > tp->snd_wnd) 1304 tcpstat.tcps_rcvwinupd++; 1305 tp->snd_wnd = tiwin; 1306 tp->snd_wl1 = th->th_seq; 1307 tp->snd_wl2 = th->th_ack; 1308 if (tp->snd_wnd > tp->max_sndwnd) 1309 tp->max_sndwnd = tp->snd_wnd; 1310 } 1311 m_freem(m); 1312 ND6_HINT(tp); /* some progress has been done */ 1313 /* 1314 * If all outstanding data are acked, stop 1315 * retransmit timer, otherwise restart timer 1316 * using current (possibly backed-off) value. 1317 * If process is waiting for space, 1318 * wakeup/selwakeup/signal. If data 1319 * are ready to send, let tcp_output 1320 * decide between more output or persist. 1321 */ 1322 if (tp->snd_una == tp->snd_max) { 1323 tcp_callout_stop(tp, tp->tt_rexmt); 1324 } else if (!tcp_callout_active(tp, 1325 tp->tt_persist)) { 1326 tcp_callout_reset(tp, tp->tt_rexmt, 1327 tp->t_rxtcur, tcp_timer_rexmt); 1328 } 1329 sowwakeup(so); 1330 if (so->so_snd.ssb_cc > 0 && 1331 !tcp_output_pending(tp)) 1332 tcp_output_fair(tp); 1333 return(IPPROTO_DONE); 1334 } 1335 } else if (tiwin == tp->snd_wnd && 1336 th->th_ack == tp->snd_una && 1337 TAILQ_EMPTY(&tp->t_segq) && 1338 tlen <= ssb_space(&so->so_rcv)) { 1339 u_long newsize = 0; /* automatic sockbuf scaling */ 1340 /* 1341 * This is a pure, in-sequence data packet 1342 * with nothing on the reassembly queue and 1343 * we have enough buffer space to take it. 1344 */ 1345 ++tcpstat.tcps_preddat; 1346 tp->rcv_nxt += tlen; 1347 tcpstat.tcps_rcvpack++; 1348 tcpstat.tcps_rcvbyte += tlen; 1349 ND6_HINT(tp); /* some progress has been done */ 1350 /* 1351 * Automatic sizing of receive socket buffer. Often the send 1352 * buffer size is not optimally adjusted to the actual network 1353 * conditions at hand (delay bandwidth product). Setting the 1354 * buffer size too small limits throughput on links with high 1355 * bandwidth and high delay (eg. trans-continental/oceanic links). 1356 * 1357 * On the receive side the socket buffer memory is only rarely 1358 * used to any significant extent. This allows us to be much 1359 * more aggressive in scaling the receive socket buffer. For 1360 * the case that the buffer space is actually used to a large 1361 * extent and we run out of kernel memory we can simply drop 1362 * the new segments; TCP on the sender will just retransmit it 1363 * later. Setting the buffer size too big may only consume too 1364 * much kernel memory if the application doesn't read() from 1365 * the socket or packet loss or reordering makes use of the 1366 * reassembly queue. 1367 * 1368 * The criteria to step up the receive buffer one notch are: 1369 * 1. the number of bytes received during the time it takes 1370 * one timestamp to be reflected back to us (the RTT); 1371 * 2. received bytes per RTT is within seven eighth of the 1372 * current socket buffer size; 1373 * 3. receive buffer size has not hit maximal automatic size; 1374 * 1375 * This algorithm does one step per RTT at most and only if 1376 * we receive a bulk stream w/o packet losses or reorderings. 1377 * Shrinking the buffer during idle times is not necessary as 1378 * it doesn't consume any memory when idle. 1379 * 1380 * TODO: Only step up if the application is actually serving 1381 * the buffer to better manage the socket buffer resources. 1382 */ 1383 if (tcp_do_autorcvbuf && 1384 to.to_tsecr && 1385 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { 1386 if (to.to_tsecr > tp->rfbuf_ts && 1387 to.to_tsecr - tp->rfbuf_ts < hz) { 1388 if (tp->rfbuf_cnt > 1389 (so->so_rcv.ssb_hiwat / 8 * 7) && 1390 so->so_rcv.ssb_hiwat < 1391 tcp_autorcvbuf_max) { 1392 newsize = 1393 ulmin(so->so_rcv.ssb_hiwat + 1394 tcp_autorcvbuf_inc, 1395 tcp_autorcvbuf_max); 1396 } 1397 /* Start over with next RTT. */ 1398 tp->rfbuf_ts = 0; 1399 tp->rfbuf_cnt = 0; 1400 } else 1401 tp->rfbuf_cnt += tlen; /* add up */ 1402 } 1403 /* 1404 * Add data to socket buffer. 1405 */ 1406 if (so->so_state & SS_CANTRCVMORE) { 1407 m_freem(m); 1408 } else { 1409 /* 1410 * Set new socket buffer size, give up when 1411 * limit is reached. 1412 * 1413 * Adjusting the size can mess up ACK 1414 * sequencing when pure window updates are 1415 * being avoided (which is the default), 1416 * so force an ack. 1417 */ 1418 lwkt_gettoken(&so->so_rcv.ssb_token); 1419 if (newsize) { 1420 tp->t_flags |= TF_RXRESIZED; 1421 if (!ssb_reserve(&so->so_rcv, newsize, 1422 so, NULL)) { 1423 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1424 } 1425 if (newsize >= 1426 (TCP_MAXWIN << tp->rcv_scale)) { 1427 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); 1428 } 1429 } 1430 m_adj(m, drop_hdrlen); /* delayed header drop */ 1431 ssb_appendstream(&so->so_rcv, m); 1432 lwkt_reltoken(&so->so_rcv.ssb_token); 1433 } 1434 sorwakeup(so); 1435 /* 1436 * This code is responsible for most of the ACKs 1437 * the TCP stack sends back after receiving a data 1438 * packet. Note that the DELAY_ACK check fails if 1439 * the delack timer is already running, which results 1440 * in an ack being sent every other packet (which is 1441 * what we want). 1442 * 1443 * We then further aggregate acks by not actually 1444 * sending one until the protocol thread has completed 1445 * processing the current backlog of packets. This 1446 * does not delay the ack any further, but allows us 1447 * to take advantage of the packet aggregation that 1448 * high speed NICs do (usually blocks of 8-10 packets) 1449 * to send a single ack rather then four or five acks, 1450 * greatly reducing the ack rate, the return channel 1451 * bandwidth, and the protocol overhead on both ends. 1452 * 1453 * Since this also has the effect of slowing down 1454 * the exponential slow-start ramp-up, systems with 1455 * very large bandwidth-delay products might want 1456 * to turn the feature off. 1457 */ 1458 if (DELAY_ACK(tp)) { 1459 tcp_callout_reset(tp, tp->tt_delack, 1460 tcp_delacktime, tcp_timer_delack); 1461 } else if (tcp_aggregate_acks) { 1462 tp->t_flags |= TF_ACKNOW; 1463 if (!(tp->t_flags & TF_ONOUTPUTQ)) { 1464 tp->t_flags |= TF_ONOUTPUTQ; 1465 tp->tt_cpu = mycpu->gd_cpuid; 1466 TAILQ_INSERT_TAIL( 1467 &tcpcbackq[tp->tt_cpu].head, 1468 tp, t_outputq); 1469 } 1470 } else { 1471 tp->t_flags |= TF_ACKNOW; 1472 tcp_output(tp); 1473 } 1474 return(IPPROTO_DONE); 1475 } 1476 } 1477 1478 /* 1479 * Calculate amount of space in receive window, 1480 * and then do TCP input processing. 1481 * Receive window is amount of space in rcv queue, 1482 * but not less than advertised window. 1483 */ 1484 recvwin = ssb_space(&so->so_rcv); 1485 if (recvwin < 0) 1486 recvwin = 0; 1487 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt)); 1488 1489 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1490 tp->rfbuf_ts = 0; 1491 tp->rfbuf_cnt = 0; 1492 1493 switch (tp->t_state) { 1494 /* 1495 * If the state is SYN_RECEIVED: 1496 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1497 */ 1498 case TCPS_SYN_RECEIVED: 1499 if ((thflags & TH_ACK) && 1500 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1501 SEQ_GT(th->th_ack, tp->snd_max))) { 1502 rstreason = BANDLIM_RST_OPENPORT; 1503 goto dropwithreset; 1504 } 1505 break; 1506 1507 /* 1508 * If the state is SYN_SENT: 1509 * if seg contains an ACK, but not for our SYN, drop the input. 1510 * if seg contains a RST, then drop the connection. 1511 * if seg does not contain SYN, then drop it. 1512 * Otherwise this is an acceptable SYN segment 1513 * initialize tp->rcv_nxt and tp->irs 1514 * if seg contains ack then advance tp->snd_una 1515 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1516 * arrange for segment to be acked (eventually) 1517 * continue processing rest of data/controls, beginning with URG 1518 */ 1519 case TCPS_SYN_SENT: 1520 if ((thflags & TH_ACK) && 1521 (SEQ_LEQ(th->th_ack, tp->iss) || 1522 SEQ_GT(th->th_ack, tp->snd_max))) { 1523 rstreason = BANDLIM_UNLIMITED; 1524 goto dropwithreset; 1525 } 1526 if (thflags & TH_RST) { 1527 if (thflags & TH_ACK) 1528 tp = tcp_drop(tp, ECONNREFUSED); 1529 goto drop; 1530 } 1531 if (!(thflags & TH_SYN)) 1532 goto drop; 1533 1534 tp->irs = th->th_seq; 1535 tcp_rcvseqinit(tp); 1536 if (thflags & TH_ACK) { 1537 /* Our SYN was acked. */ 1538 tcpstat.tcps_connects++; 1539 soisconnected(so); 1540 /* Do window scaling on this connection? */ 1541 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1542 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1543 tp->rcv_scale = tp->request_r_scale; 1544 tp->rcv_adv += tp->rcv_wnd; 1545 tp->snd_una++; /* SYN is acked */ 1546 tcp_callout_stop(tp, tp->tt_rexmt); 1547 /* 1548 * If there's data, delay ACK; if there's also a FIN 1549 * ACKNOW will be turned on later. 1550 */ 1551 if (DELAY_ACK(tp) && tlen != 0) { 1552 tcp_callout_reset(tp, tp->tt_delack, 1553 tcp_delacktime, tcp_timer_delack); 1554 } else { 1555 tp->t_flags |= TF_ACKNOW; 1556 } 1557 /* 1558 * Received <SYN,ACK> in SYN_SENT[*] state. 1559 * Transitions: 1560 * SYN_SENT --> ESTABLISHED 1561 * SYN_SENT* --> FIN_WAIT_1 1562 */ 1563 tp->t_starttime = ticks; 1564 if (tp->t_flags & TF_NEEDFIN) { 1565 TCP_STATE_CHANGE(tp, TCPS_FIN_WAIT_1); 1566 tp->t_flags &= ~TF_NEEDFIN; 1567 thflags &= ~TH_SYN; 1568 } else { 1569 tcp_established(tp); 1570 } 1571 } else { 1572 /* 1573 * Received initial SYN in SYN-SENT[*] state => 1574 * simultaneous open. 1575 * Do 3-way handshake: 1576 * SYN-SENT -> SYN-RECEIVED 1577 * SYN-SENT* -> SYN-RECEIVED* 1578 */ 1579 tp->t_flags |= TF_ACKNOW; 1580 tcp_callout_stop(tp, tp->tt_rexmt); 1581 TCP_STATE_CHANGE(tp, TCPS_SYN_RECEIVED); 1582 } 1583 1584 /* 1585 * Advance th->th_seq to correspond to first data byte. 1586 * If data, trim to stay within window, 1587 * dropping FIN if necessary. 1588 */ 1589 th->th_seq++; 1590 if (tlen > tp->rcv_wnd) { 1591 todrop = tlen - tp->rcv_wnd; 1592 m_adj(m, -todrop); 1593 tlen = tp->rcv_wnd; 1594 thflags &= ~TH_FIN; 1595 tcpstat.tcps_rcvpackafterwin++; 1596 tcpstat.tcps_rcvbyteafterwin += todrop; 1597 } 1598 tp->snd_wl1 = th->th_seq - 1; 1599 tp->rcv_up = th->th_seq; 1600 /* 1601 * Client side of transaction: already sent SYN and data. 1602 * If the remote host used T/TCP to validate the SYN, 1603 * our data will be ACK'd; if so, enter normal data segment 1604 * processing in the middle of step 5, ack processing. 1605 * Otherwise, goto step 6. 1606 */ 1607 if (thflags & TH_ACK) 1608 goto process_ACK; 1609 1610 goto step6; 1611 1612 /* 1613 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1614 * do normal processing (we no longer bother with T/TCP). 1615 */ 1616 case TCPS_LAST_ACK: 1617 case TCPS_CLOSING: 1618 case TCPS_TIME_WAIT: 1619 /* 1620 * Continue normal processing 1621 */ 1622 break; 1623 } 1624 1625 /* 1626 * States other than LISTEN or SYN_SENT. 1627 * First check the RST flag and sequence number since reset segments 1628 * are exempt from the timestamp and connection count tests. This 1629 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1630 * below which allowed reset segments in half the sequence space 1631 * to fall though and be processed (which gives forged reset 1632 * segments with a random sequence number a 50 percent chance of 1633 * killing a connection). 1634 * Then check timestamp, if present. 1635 * Then check the connection count, if present. 1636 * Then check that at least some bytes of segment are within 1637 * receive window. If segment begins before rcv_nxt, 1638 * drop leading data (and SYN); if nothing left, just ack. 1639 * 1640 * 1641 * If the RST bit is set, check the sequence number to see 1642 * if this is a valid reset segment. 1643 * RFC 793 page 37: 1644 * In all states except SYN-SENT, all reset (RST) segments 1645 * are validated by checking their SEQ-fields. A reset is 1646 * valid if its sequence number is in the window. 1647 * Note: this does not take into account delayed ACKs, so 1648 * we should test against last_ack_sent instead of rcv_nxt. 1649 * The sequence number in the reset segment is normally an 1650 * echo of our outgoing acknowledgement numbers, but some hosts 1651 * send a reset with the sequence number at the rightmost edge 1652 * of our receive window, and we have to handle this case. 1653 * If we have multiple segments in flight, the intial reset 1654 * segment sequence numbers will be to the left of last_ack_sent, 1655 * but they will eventually catch up. 1656 * In any case, it never made sense to trim reset segments to 1657 * fit the receive window since RFC 1122 says: 1658 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1659 * 1660 * A TCP SHOULD allow a received RST segment to include data. 1661 * 1662 * DISCUSSION 1663 * It has been suggested that a RST segment could contain 1664 * ASCII text that encoded and explained the cause of the 1665 * RST. No standard has yet been established for such 1666 * data. 1667 * 1668 * If the reset segment passes the sequence number test examine 1669 * the state: 1670 * SYN_RECEIVED STATE: 1671 * If passive open, return to LISTEN state. 1672 * If active open, inform user that connection was refused. 1673 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1674 * Inform user that connection was reset, and close tcb. 1675 * CLOSING, LAST_ACK STATES: 1676 * Close the tcb. 1677 * TIME_WAIT STATE: 1678 * Drop the segment - see Stevens, vol. 2, p. 964 and 1679 * RFC 1337. 1680 */ 1681 if (thflags & TH_RST) { 1682 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1683 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1684 switch (tp->t_state) { 1685 1686 case TCPS_SYN_RECEIVED: 1687 so->so_error = ECONNREFUSED; 1688 goto close; 1689 1690 case TCPS_ESTABLISHED: 1691 case TCPS_FIN_WAIT_1: 1692 case TCPS_FIN_WAIT_2: 1693 case TCPS_CLOSE_WAIT: 1694 so->so_error = ECONNRESET; 1695 close: 1696 TCP_STATE_CHANGE(tp, TCPS_CLOSED); 1697 tcpstat.tcps_drops++; 1698 tp = tcp_close(tp); 1699 break; 1700 1701 case TCPS_CLOSING: 1702 case TCPS_LAST_ACK: 1703 tp = tcp_close(tp); 1704 break; 1705 1706 case TCPS_TIME_WAIT: 1707 break; 1708 } 1709 } 1710 goto drop; 1711 } 1712 1713 /* 1714 * Allow a new connection to replace an existing connection that is 1715 * in the TIME_WAIT state if the new connection's SYN seq is different 1716 * from tp->irs. 1717 */ 1718 if ((thflags & TH_SYN) && 1719 tp->t_state == TCPS_TIME_WAIT && 1720 th->th_seq != tp->irs) { 1721 tp = tcp_close(tp); 1722 goto findpcb; 1723 } 1724 1725 /* 1726 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1727 * and it's less than ts_recent, drop it. 1728 */ 1729 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && 1730 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1731 /* Check to see if ts_recent is over 24 days old. */ 1732 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1733 /* 1734 * Invalidate ts_recent. If this segment updates 1735 * ts_recent, the age will be reset later and ts_recent 1736 * will get a valid value. If it does not, setting 1737 * ts_recent to zero will at least satisfy the 1738 * requirement that zero be placed in the timestamp 1739 * echo reply when ts_recent isn't valid. The 1740 * age isn't reset until we get a valid ts_recent 1741 * because we don't want out-of-order segments to be 1742 * dropped when ts_recent is old. 1743 */ 1744 tp->ts_recent = 0; 1745 } else if (tcp_paws_tolerance && tlen != 0 && 1746 tp->t_state == TCPS_ESTABLISHED && 1747 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&& 1748 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && 1749 th->th_ack == tp->snd_una && 1750 tiwin == tp->snd_wnd && 1751 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&& 1752 (th->th_seq == tp->rcv_nxt || 1753 (SEQ_GT(th->th_seq, tp->rcv_nxt) && 1754 tcp_paws_canreasslast(tp, th, tlen)))) { 1755 /* 1756 * This tends to prevent valid new segments from being 1757 * dropped by the reordered segments sent by the fast 1758 * retransmission algorithm on the sending side, i.e. 1759 * the fast retransmitted segment w/ larger timestamp 1760 * arrives earlier than the previously sent new segments 1761 * w/ smaller timestamp. 1762 * 1763 * If following conditions are met, the segment is 1764 * accepted: 1765 * - The segment contains data 1766 * - The connection is established 1767 * - The header does not contain important flags 1768 * - SYN or FIN is not needed 1769 * - It does not acknowledge new data 1770 * - Receive window is not changed 1771 * - The timestamp is within "acceptable" range 1772 * - The new segment is what we are expecting or 1773 * the new segment could be merged w/ the last 1774 * pending segment on the reassemble queue 1775 */ 1776 tcpstat.tcps_pawsaccept++; 1777 tcpstat.tcps_pawsdrop++; 1778 } else { 1779 tcpstat.tcps_rcvduppack++; 1780 tcpstat.tcps_rcvdupbyte += tlen; 1781 tcpstat.tcps_pawsdrop++; 1782 if (tlen) 1783 goto dropafterack; 1784 goto drop; 1785 } 1786 } 1787 1788 /* 1789 * In the SYN-RECEIVED state, validate that the packet belongs to 1790 * this connection before trimming the data to fit the receive 1791 * window. Check the sequence number versus IRS since we know 1792 * the sequence numbers haven't wrapped. This is a partial fix 1793 * for the "LAND" DoS attack. 1794 */ 1795 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1796 rstreason = BANDLIM_RST_OPENPORT; 1797 goto dropwithreset; 1798 } 1799 1800 todrop = tp->rcv_nxt - th->th_seq; 1801 if (todrop > 0) { 1802 if (TCP_DO_SACK(tp)) { 1803 /* Report duplicate segment at head of packet. */ 1804 tp->reportblk.rblk_start = th->th_seq; 1805 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 1806 th->th_seq + tlen, thflags); 1807 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) 1808 tp->reportblk.rblk_end = tp->rcv_nxt; 1809 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT); 1810 tp->t_flags |= TF_ACKNOW; 1811 } 1812 if (thflags & TH_SYN) { 1813 thflags &= ~TH_SYN; 1814 th->th_seq++; 1815 if (th->th_urp > 1) 1816 th->th_urp--; 1817 else 1818 thflags &= ~TH_URG; 1819 todrop--; 1820 } 1821 /* 1822 * Following if statement from Stevens, vol. 2, p. 960. 1823 */ 1824 if (todrop > tlen || 1825 (todrop == tlen && !(thflags & TH_FIN))) { 1826 /* 1827 * Any valid FIN must be to the left of the window. 1828 * At this point the FIN must be a duplicate or out 1829 * of sequence; drop it. 1830 */ 1831 thflags &= ~TH_FIN; 1832 1833 /* 1834 * Send an ACK to resynchronize and drop any data. 1835 * But keep on processing for RST or ACK. 1836 */ 1837 tp->t_flags |= TF_ACKNOW; 1838 todrop = tlen; 1839 tcpstat.tcps_rcvduppack++; 1840 tcpstat.tcps_rcvdupbyte += todrop; 1841 } else { 1842 tcpstat.tcps_rcvpartduppack++; 1843 tcpstat.tcps_rcvpartdupbyte += todrop; 1844 } 1845 drop_hdrlen += todrop; /* drop from the top afterwards */ 1846 th->th_seq += todrop; 1847 tlen -= todrop; 1848 if (th->th_urp > todrop) 1849 th->th_urp -= todrop; 1850 else { 1851 thflags &= ~TH_URG; 1852 th->th_urp = 0; 1853 } 1854 } 1855 1856 /* 1857 * If new data are received on a connection after the 1858 * user processes are gone, then RST the other end. 1859 */ 1860 if ((so->so_state & SS_NOFDREF) && 1861 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1862 tp = tcp_close(tp); 1863 tcpstat.tcps_rcvafterclose++; 1864 rstreason = BANDLIM_UNLIMITED; 1865 goto dropwithreset; 1866 } 1867 1868 /* 1869 * If segment ends after window, drop trailing data 1870 * (and PUSH and FIN); if nothing left, just ACK. 1871 */ 1872 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1873 if (todrop > 0) { 1874 tcpstat.tcps_rcvpackafterwin++; 1875 if (todrop >= tlen) { 1876 tcpstat.tcps_rcvbyteafterwin += tlen; 1877 1878 /* 1879 * If window is closed can only take segments at 1880 * window edge, and have to drop data and PUSH from 1881 * incoming segments. Continue processing, but 1882 * remember to ack. Otherwise, drop segment 1883 * and ack. 1884 */ 1885 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1886 tp->t_flags |= TF_ACKNOW; 1887 tcpstat.tcps_rcvwinprobe++; 1888 } else 1889 goto dropafterack; 1890 } else 1891 tcpstat.tcps_rcvbyteafterwin += todrop; 1892 m_adj(m, -todrop); 1893 tlen -= todrop; 1894 thflags &= ~(TH_PUSH | TH_FIN); 1895 } 1896 1897 /* 1898 * If last ACK falls within this segment's sequence numbers, 1899 * record its timestamp. 1900 * NOTE: 1901 * 1) That the test incorporates suggestions from the latest 1902 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1903 * 2) That updating only on newer timestamps interferes with 1904 * our earlier PAWS tests, so this check should be solely 1905 * predicated on the sequence space of this segment. 1906 * 3) That we modify the segment boundary check to be 1907 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN 1908 * instead of RFC1323's 1909 * Last.ACK.Sent < SEG.SEQ + SEG.LEN, 1910 * This modified check allows us to overcome RFC1323's 1911 * limitations as described in Stevens TCP/IP Illustrated 1912 * Vol. 2 p.869. In such cases, we can still calculate the 1913 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1914 */ 1915 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1916 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen 1917 + ((thflags & TH_SYN) != 0) 1918 + ((thflags & TH_FIN) != 0)))) { 1919 tp->ts_recent_age = ticks; 1920 tp->ts_recent = to.to_tsval; 1921 } 1922 1923 /* 1924 * If a SYN is in the window, then this is an 1925 * error and we send an RST and drop the connection. 1926 */ 1927 if (thflags & TH_SYN) { 1928 tp = tcp_drop(tp, ECONNRESET); 1929 rstreason = BANDLIM_UNLIMITED; 1930 goto dropwithreset; 1931 } 1932 1933 /* 1934 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1935 * flag is on (half-synchronized state), then queue data for 1936 * later processing; else drop segment and return. 1937 */ 1938 if (!(thflags & TH_ACK)) { 1939 if (tp->t_state == TCPS_SYN_RECEIVED || 1940 (tp->t_flags & TF_NEEDSYN)) 1941 goto step6; 1942 else 1943 goto drop; 1944 } 1945 1946 /* 1947 * Ack processing. 1948 */ 1949 switch (tp->t_state) { 1950 /* 1951 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter 1952 * ESTABLISHED state and continue processing. 1953 * The ACK was checked above. 1954 */ 1955 case TCPS_SYN_RECEIVED: 1956 1957 tcpstat.tcps_connects++; 1958 soisconnected(so); 1959 /* Do window scaling? */ 1960 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 1961 (TF_RCVD_SCALE | TF_REQ_SCALE)) 1962 tp->rcv_scale = tp->request_r_scale; 1963 /* 1964 * Make transitions: 1965 * SYN-RECEIVED -> ESTABLISHED 1966 * SYN-RECEIVED* -> FIN-WAIT-1 1967 */ 1968 tp->t_starttime = ticks; 1969 if (tp->t_flags & TF_NEEDFIN) { 1970 TCP_STATE_CHANGE(tp, TCPS_FIN_WAIT_1); 1971 tp->t_flags &= ~TF_NEEDFIN; 1972 } else { 1973 tcp_established(tp); 1974 } 1975 /* 1976 * If segment contains data or ACK, will call tcp_reass() 1977 * later; if not, do so now to pass queued data to user. 1978 */ 1979 if (tlen == 0 && !(thflags & TH_FIN)) 1980 tcp_reass(tp, NULL, NULL, NULL); 1981 /* fall into ... */ 1982 1983 /* 1984 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1985 * ACKs. If the ack is in the range 1986 * tp->snd_una < th->th_ack <= tp->snd_max 1987 * then advance tp->snd_una to th->th_ack and drop 1988 * data from the retransmission queue. If this ACK reflects 1989 * more up to date window information we update our window information. 1990 */ 1991 case TCPS_ESTABLISHED: 1992 case TCPS_FIN_WAIT_1: 1993 case TCPS_FIN_WAIT_2: 1994 case TCPS_CLOSE_WAIT: 1995 case TCPS_CLOSING: 1996 case TCPS_LAST_ACK: 1997 case TCPS_TIME_WAIT: 1998 1999 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2000 boolean_t maynotdup = FALSE; 2001 2002 if (TCP_DO_SACK(tp)) 2003 tcp_sack_update_scoreboard(tp, &to); 2004 2005 if (tlen != 0 || tiwin != tp->snd_wnd || 2006 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN))) 2007 maynotdup = TRUE; 2008 2009 if (!tcp_callout_active(tp, tp->tt_rexmt) || 2010 th->th_ack != tp->snd_una) { 2011 if (!maynotdup) 2012 tcpstat.tcps_rcvdupack++; 2013 tp->t_dupacks = 0; 2014 break; 2015 } 2016 2017 #define DELAY_DUPACK \ 2018 do { \ 2019 delayed_dupack = TRUE; \ 2020 th_dupack = th->th_ack; \ 2021 to_flags = to.to_flags; \ 2022 } while (0) 2023 if (maynotdup) { 2024 if (!tcp_do_rfc6675 || 2025 !TCP_DO_SACK(tp) || 2026 (to.to_flags & 2027 (TOF_SACK | TOF_SACK_REDUNDANT)) 2028 != TOF_SACK) { 2029 tp->t_dupacks = 0; 2030 } else { 2031 DELAY_DUPACK; 2032 } 2033 break; 2034 } 2035 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) { 2036 /* 2037 * This could happen, if the reassemable 2038 * queue overflew or was drained. Don't 2039 * drop this FIN here; defer the duplicated 2040 * ACK processing until this FIN gets queued. 2041 */ 2042 DELAY_DUPACK; 2043 break; 2044 } 2045 #undef DELAY_DUPACK 2046 2047 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags)) 2048 goto drop; 2049 else 2050 break; 2051 } 2052 2053 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 2054 tp->t_dupacks = 0; 2055 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2056 /* 2057 * Detected optimistic ACK attack. 2058 * Force slow-start to de-synchronize attack. 2059 */ 2060 tp->snd_cwnd = tp->t_maxseg; 2061 tp->snd_wacked = 0; 2062 2063 tcpstat.tcps_rcvacktoomuch++; 2064 goto dropafterack; 2065 } 2066 /* 2067 * If we reach this point, ACK is not a duplicate, 2068 * i.e., it ACKs something we sent. 2069 */ 2070 if (tp->t_flags & TF_NEEDSYN) { 2071 /* 2072 * T/TCP: Connection was half-synchronized, and our 2073 * SYN has been ACK'd (so connection is now fully 2074 * synchronized). Go to non-starred state, 2075 * increment snd_una for ACK of SYN, and check if 2076 * we can do window scaling. 2077 */ 2078 tp->t_flags &= ~TF_NEEDSYN; 2079 tp->snd_una++; 2080 /* Do window scaling? */ 2081 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == 2082 (TF_RCVD_SCALE | TF_REQ_SCALE)) 2083 tp->rcv_scale = tp->request_r_scale; 2084 } 2085 2086 process_ACK: 2087 acked = th->th_ack - tp->snd_una; 2088 tcpstat.tcps_rcvackpack++; 2089 tcpstat.tcps_rcvackbyte += acked; 2090 2091 if (tcp_do_eifel_detect && acked > 0 && 2092 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && 2093 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { 2094 /* Eifel detection applicable. */ 2095 if (to.to_tsecr < tp->t_rexmtTS) { 2096 ++tcpstat.tcps_eifeldetected; 2097 tcp_revert_congestion_state(tp); 2098 if (tp->t_rxtshift != 1 || 2099 ticks >= tp->t_badrxtwin) 2100 ++tcpstat.tcps_rttcantdetect; 2101 } 2102 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 2103 /* 2104 * If we just performed our first retransmit, 2105 * and the ACK arrives within our recovery window, 2106 * then it was a mistake to do the retransmit 2107 * in the first place. Recover our original cwnd 2108 * and ssthresh, and proceed to transmit where we 2109 * left off. 2110 */ 2111 tcp_revert_congestion_state(tp); 2112 ++tcpstat.tcps_rttdetected; 2113 } 2114 2115 /* 2116 * If we have a timestamp reply, update smoothed 2117 * round trip time. If no timestamp is present but 2118 * transmit timer is running and timed sequence 2119 * number was acked, update smoothed round trip time. 2120 * Since we now have an rtt measurement, cancel the 2121 * timer backoff (cf., Phil Karn's retransmit alg.). 2122 * Recompute the initial retransmit timer. 2123 * 2124 * Some machines (certain windows boxes) send broken 2125 * timestamp replies during the SYN+ACK phase, ignore 2126 * timestamps of 0. 2127 */ 2128 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) 2129 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, 2130 th->th_ack); 2131 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) 2132 tcp_xmit_timer(tp, ticks - tp->t_rtttime + 1, 2133 th->th_ack); 2134 tcp_xmit_bandwidth_limit(tp, th->th_ack); 2135 2136 /* 2137 * If no data (only SYN) was ACK'd, 2138 * skip rest of ACK processing. 2139 */ 2140 if (acked == 0) 2141 goto step6; 2142 2143 /* Stop looking for an acceptable ACK since one was received. */ 2144 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | 2145 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); 2146 2147 if (acked > so->so_snd.ssb_cc) { 2148 tp->snd_wnd -= so->so_snd.ssb_cc; 2149 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); 2150 ourfinisacked = TRUE; 2151 } else { 2152 sbdrop(&so->so_snd.sb, acked); 2153 tp->snd_wnd -= acked; 2154 ourfinisacked = FALSE; 2155 } 2156 sowwakeup(so); 2157 2158 /* 2159 * Update window information. 2160 */ 2161 if (acceptable_window_update(tp, th, tiwin)) { 2162 /* keep track of pure window updates */ 2163 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2164 tiwin > tp->snd_wnd) 2165 tcpstat.tcps_rcvwinupd++; 2166 tp->snd_wnd = tiwin; 2167 tp->snd_wl1 = th->th_seq; 2168 tp->snd_wl2 = th->th_ack; 2169 if (tp->snd_wnd > tp->max_sndwnd) 2170 tp->max_sndwnd = tp->snd_wnd; 2171 needoutput = TRUE; 2172 } 2173 2174 tp->snd_una = th->th_ack; 2175 if (TCP_DO_SACK(tp)) 2176 tcp_sack_update_scoreboard(tp, &to); 2177 if (IN_FASTRECOVERY(tp)) { 2178 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2179 EXIT_FASTRECOVERY(tp); 2180 needoutput = TRUE; 2181 /* 2182 * If the congestion window was inflated 2183 * to account for the other side's 2184 * cached packets, retract it. 2185 */ 2186 if (!TCP_DO_SACK(tp)) 2187 tp->snd_cwnd = tp->snd_ssthresh; 2188 2189 /* 2190 * Window inflation should have left us 2191 * with approximately snd_ssthresh outstanding 2192 * data. But, in case we would be inclined 2193 * to send a burst, better do it using 2194 * slow start. 2195 */ 2196 if (SEQ_GT(th->th_ack + tp->snd_cwnd, 2197 tp->snd_max + 2 * tp->t_maxseg)) 2198 tp->snd_cwnd = 2199 (tp->snd_max - tp->snd_una) + 2200 2 * tp->t_maxseg; 2201 2202 tp->snd_wacked = 0; 2203 } else { 2204 if (TCP_DO_SACK(tp)) { 2205 tp->snd_max_rexmt = tp->snd_max; 2206 tcp_sack_rexmt(tp, 2207 tp->snd_una == tp->rexmt_high); 2208 } else { 2209 tcp_newreno_partial_ack(tp, th, acked); 2210 } 2211 needoutput = FALSE; 2212 } 2213 } else { 2214 /* 2215 * Open the congestion window. When in slow-start, 2216 * open exponentially: maxseg per packet. Otherwise, 2217 * open linearly: maxseg per window. 2218 */ 2219 if (tp->snd_cwnd <= tp->snd_ssthresh) { 2220 u_int abc_sslimit = 2221 (SEQ_LT(tp->snd_nxt, tp->snd_max) ? 2222 tp->t_maxseg : 2 * tp->t_maxseg); 2223 2224 /* slow-start */ 2225 tp->snd_cwnd += tcp_do_abc ? 2226 min(acked, abc_sslimit) : tp->t_maxseg; 2227 } else { 2228 /* linear increase */ 2229 tp->snd_wacked += tcp_do_abc ? acked : 2230 tp->t_maxseg; 2231 if (tp->snd_wacked >= tp->snd_cwnd) { 2232 tp->snd_wacked -= tp->snd_cwnd; 2233 tp->snd_cwnd += tp->t_maxseg; 2234 } 2235 } 2236 tp->snd_cwnd = min(tp->snd_cwnd, 2237 TCP_MAXWIN << tp->snd_scale); 2238 tp->snd_recover = th->th_ack - 1; 2239 } 2240 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2241 tp->snd_nxt = tp->snd_una; 2242 2243 /* 2244 * If all outstanding data is acked, stop retransmit 2245 * timer and remember to restart (more output or persist). 2246 * If there is more data to be acked, restart retransmit 2247 * timer, using current (possibly backed-off) value. 2248 */ 2249 if (th->th_ack == tp->snd_max) { 2250 tcp_callout_stop(tp, tp->tt_rexmt); 2251 needoutput = TRUE; 2252 } else if (!tcp_callout_active(tp, tp->tt_persist)) { 2253 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 2254 tcp_timer_rexmt); 2255 } 2256 2257 switch (tp->t_state) { 2258 /* 2259 * In FIN_WAIT_1 STATE in addition to the processing 2260 * for the ESTABLISHED state if our FIN is now acknowledged 2261 * then enter FIN_WAIT_2. 2262 */ 2263 case TCPS_FIN_WAIT_1: 2264 if (ourfinisacked) { 2265 /* 2266 * If we can't receive any more 2267 * data, then closing user can proceed. 2268 * Starting the timer is contrary to the 2269 * specification, but if we don't get a FIN 2270 * we'll hang forever. 2271 */ 2272 if (so->so_state & SS_CANTRCVMORE) { 2273 soisdisconnected(so); 2274 tcp_callout_reset(tp, tp->tt_2msl, 2275 tp->t_maxidle, tcp_timer_2msl); 2276 } 2277 TCP_STATE_CHANGE(tp, TCPS_FIN_WAIT_2); 2278 } 2279 break; 2280 2281 /* 2282 * In CLOSING STATE in addition to the processing for 2283 * the ESTABLISHED state if the ACK acknowledges our FIN 2284 * then enter the TIME-WAIT state, otherwise ignore 2285 * the segment. 2286 */ 2287 case TCPS_CLOSING: 2288 if (ourfinisacked) { 2289 TCP_STATE_CHANGE(tp, TCPS_TIME_WAIT); 2290 tcp_canceltimers(tp); 2291 tcp_callout_reset(tp, tp->tt_2msl, 2292 2 * tcp_rmx_msl(tp), 2293 tcp_timer_2msl); 2294 soisdisconnected(so); 2295 } 2296 break; 2297 2298 /* 2299 * In LAST_ACK, we may still be waiting for data to drain 2300 * and/or to be acked, as well as for the ack of our FIN. 2301 * If our FIN is now acknowledged, delete the TCB, 2302 * enter the closed state and return. 2303 */ 2304 case TCPS_LAST_ACK: 2305 if (ourfinisacked) { 2306 tp = tcp_close(tp); 2307 goto drop; 2308 } 2309 break; 2310 2311 /* 2312 * In TIME_WAIT state the only thing that should arrive 2313 * is a retransmission of the remote FIN. Acknowledge 2314 * it and restart the finack timer. 2315 */ 2316 case TCPS_TIME_WAIT: 2317 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2318 tcp_timer_2msl); 2319 goto dropafterack; 2320 } 2321 } 2322 2323 step6: 2324 /* 2325 * Update window information. 2326 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2327 */ 2328 if ((thflags & TH_ACK) && 2329 acceptable_window_update(tp, th, tiwin)) { 2330 /* keep track of pure window updates */ 2331 if (tlen == 0 && tp->snd_wl2 == th->th_ack && 2332 tiwin > tp->snd_wnd) 2333 tcpstat.tcps_rcvwinupd++; 2334 tp->snd_wnd = tiwin; 2335 tp->snd_wl1 = th->th_seq; 2336 tp->snd_wl2 = th->th_ack; 2337 if (tp->snd_wnd > tp->max_sndwnd) 2338 tp->max_sndwnd = tp->snd_wnd; 2339 needoutput = TRUE; 2340 } 2341 2342 /* 2343 * Process segments with URG. 2344 */ 2345 if ((thflags & TH_URG) && th->th_urp && 2346 !TCPS_HAVERCVDFIN(tp->t_state)) { 2347 /* 2348 * This is a kludge, but if we receive and accept 2349 * random urgent pointers, we'll crash in 2350 * soreceive. It's hard to imagine someone 2351 * actually wanting to send this much urgent data. 2352 */ 2353 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) { 2354 th->th_urp = 0; /* XXX */ 2355 thflags &= ~TH_URG; /* XXX */ 2356 goto dodata; /* XXX */ 2357 } 2358 /* 2359 * If this segment advances the known urgent pointer, 2360 * then mark the data stream. This should not happen 2361 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2362 * a FIN has been received from the remote side. 2363 * In these states we ignore the URG. 2364 * 2365 * According to RFC961 (Assigned Protocols), 2366 * the urgent pointer points to the last octet 2367 * of urgent data. We continue, however, 2368 * to consider it to indicate the first octet 2369 * of data past the urgent section as the original 2370 * spec states (in one of two places). 2371 */ 2372 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { 2373 tp->rcv_up = th->th_seq + th->th_urp; 2374 so->so_oobmark = so->so_rcv.ssb_cc + 2375 (tp->rcv_up - tp->rcv_nxt) - 1; 2376 if (so->so_oobmark == 0) 2377 sosetstate(so, SS_RCVATMARK); 2378 sohasoutofband(so); 2379 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2380 } 2381 /* 2382 * Remove out of band data so doesn't get presented to user. 2383 * This can happen independent of advancing the URG pointer, 2384 * but if two URG's are pending at once, some out-of-band 2385 * data may creep in... ick. 2386 */ 2387 if (th->th_urp <= (u_long)tlen && 2388 !(so->so_options & SO_OOBINLINE)) { 2389 /* hdr drop is delayed */ 2390 tcp_pulloutofband(so, th, m, drop_hdrlen); 2391 } 2392 } else { 2393 /* 2394 * If no out of band data is expected, 2395 * pull receive urgent pointer along 2396 * with the receive window. 2397 */ 2398 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2399 tp->rcv_up = tp->rcv_nxt; 2400 } 2401 2402 dodata: /* XXX */ 2403 /* 2404 * Process the segment text, merging it into the TCP sequencing queue, 2405 * and arranging for acknowledgment of receipt if necessary. 2406 * This process logically involves adjusting tp->rcv_wnd as data 2407 * is presented to the user (this happens in tcp_usrreq.c, 2408 * case PRU_RCVD). If a FIN has already been received on this 2409 * connection then we just ignore the text. 2410 */ 2411 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { 2412 if (thflags & TH_FIN) 2413 tp->t_flags |= TF_SAWFIN; 2414 m_adj(m, drop_hdrlen); /* delayed header drop */ 2415 /* 2416 * Insert segment which includes th into TCP reassembly queue 2417 * with control block tp. Set thflags to whether reassembly now 2418 * includes a segment with FIN. This handles the common case 2419 * inline (segment is the next to be received on an established 2420 * connection, and the queue is empty), avoiding linkage into 2421 * and removal from the queue and repetition of various 2422 * conversions. 2423 * Set DELACK for segments received in order, but ack 2424 * immediately when segments are out of order (so 2425 * fast retransmit can work). 2426 */ 2427 if (th->th_seq == tp->rcv_nxt && 2428 TAILQ_EMPTY(&tp->t_segq) && 2429 TCPS_HAVEESTABLISHED(tp->t_state)) { 2430 if (thflags & TH_FIN) 2431 tp->t_flags |= TF_QUEDFIN; 2432 if (DELAY_ACK(tp)) { 2433 tcp_callout_reset(tp, tp->tt_delack, 2434 tcp_delacktime, tcp_timer_delack); 2435 } else { 2436 tp->t_flags |= TF_ACKNOW; 2437 } 2438 tp->rcv_nxt += tlen; 2439 thflags = th->th_flags & TH_FIN; 2440 tcpstat.tcps_rcvpack++; 2441 tcpstat.tcps_rcvbyte += tlen; 2442 ND6_HINT(tp); 2443 if (so->so_state & SS_CANTRCVMORE) { 2444 m_freem(m); 2445 } else { 2446 lwkt_gettoken(&so->so_rcv.ssb_token); 2447 ssb_appendstream(&so->so_rcv, m); 2448 lwkt_reltoken(&so->so_rcv.ssb_token); 2449 } 2450 sorwakeup(so); 2451 } else { 2452 if (!(tp->sack_flags & TSACK_F_DUPSEG)) { 2453 /* Initialize SACK report block. */ 2454 tp->reportblk.rblk_start = th->th_seq; 2455 tp->reportblk.rblk_end = TCP_SACK_BLKEND( 2456 th->th_seq + tlen, thflags); 2457 } 2458 thflags = tcp_reass(tp, th, &tlen, m); 2459 tp->t_flags |= TF_ACKNOW; 2460 } 2461 2462 /* 2463 * Note the amount of data that peer has sent into 2464 * our window, in order to estimate the sender's 2465 * buffer size. 2466 */ 2467 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2468 } else { 2469 m_freem(m); 2470 thflags &= ~TH_FIN; 2471 } 2472 2473 /* 2474 * If FIN is received ACK the FIN and let the user know 2475 * that the connection is closing. 2476 */ 2477 if (thflags & TH_FIN) { 2478 if (!TCPS_HAVERCVDFIN(tp->t_state)) { 2479 socantrcvmore(so); 2480 /* 2481 * If connection is half-synchronized 2482 * (ie NEEDSYN flag on) then delay ACK, 2483 * so it may be piggybacked when SYN is sent. 2484 * Otherwise, since we received a FIN then no 2485 * more input can be expected, send ACK now. 2486 */ 2487 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { 2488 tcp_callout_reset(tp, tp->tt_delack, 2489 tcp_delacktime, tcp_timer_delack); 2490 } else { 2491 tp->t_flags |= TF_ACKNOW; 2492 } 2493 tp->rcv_nxt++; 2494 } 2495 2496 switch (tp->t_state) { 2497 /* 2498 * In SYN_RECEIVED and ESTABLISHED STATES 2499 * enter the CLOSE_WAIT state. 2500 */ 2501 case TCPS_SYN_RECEIVED: 2502 tp->t_starttime = ticks; 2503 /*FALLTHROUGH*/ 2504 case TCPS_ESTABLISHED: 2505 TCP_STATE_CHANGE(tp, TCPS_CLOSE_WAIT); 2506 break; 2507 2508 /* 2509 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2510 * enter the CLOSING state. 2511 */ 2512 case TCPS_FIN_WAIT_1: 2513 TCP_STATE_CHANGE(tp, TCPS_CLOSING); 2514 break; 2515 2516 /* 2517 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2518 * starting the time-wait timer, turning off the other 2519 * standard timers. 2520 */ 2521 case TCPS_FIN_WAIT_2: 2522 TCP_STATE_CHANGE(tp, TCPS_TIME_WAIT); 2523 tcp_canceltimers(tp); 2524 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2525 tcp_timer_2msl); 2526 soisdisconnected(so); 2527 break; 2528 2529 /* 2530 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2531 */ 2532 case TCPS_TIME_WAIT: 2533 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), 2534 tcp_timer_2msl); 2535 break; 2536 } 2537 } 2538 2539 #ifdef TCPDEBUG 2540 if (so->so_options & SO_DEBUG) 2541 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2542 #endif 2543 2544 /* 2545 * Delayed duplicated ACK processing 2546 */ 2547 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags)) 2548 needoutput = FALSE; 2549 2550 /* 2551 * Return any desired output. 2552 */ 2553 if ((tp->t_flags & TF_ACKNOW) || 2554 (needoutput && tcp_sack_report_needed(tp))) { 2555 tcp_output_cancel(tp); 2556 tcp_output_fair(tp); 2557 } else if (needoutput && !tcp_output_pending(tp)) { 2558 tcp_output_fair(tp); 2559 } 2560 tcp_sack_report_cleanup(tp); 2561 return(IPPROTO_DONE); 2562 2563 dropafterack: 2564 /* 2565 * Generate an ACK dropping incoming segment if it occupies 2566 * sequence space, where the ACK reflects our state. 2567 * 2568 * We can now skip the test for the RST flag since all 2569 * paths to this code happen after packets containing 2570 * RST have been dropped. 2571 * 2572 * In the SYN-RECEIVED state, don't send an ACK unless the 2573 * segment we received passes the SYN-RECEIVED ACK test. 2574 * If it fails send a RST. This breaks the loop in the 2575 * "LAND" DoS attack, and also prevents an ACK storm 2576 * between two listening ports that have been sent forged 2577 * SYN segments, each with the source address of the other. 2578 */ 2579 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2580 (SEQ_GT(tp->snd_una, th->th_ack) || 2581 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2582 rstreason = BANDLIM_RST_OPENPORT; 2583 goto dropwithreset; 2584 } 2585 #ifdef TCPDEBUG 2586 if (so->so_options & SO_DEBUG) 2587 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2588 #endif 2589 m_freem(m); 2590 tp->t_flags |= TF_ACKNOW; 2591 tcp_output(tp); 2592 tcp_sack_report_cleanup(tp); 2593 return(IPPROTO_DONE); 2594 2595 dropwithreset: 2596 /* 2597 * Generate a RST, dropping incoming segment. 2598 * Make ACK acceptable to originator of segment. 2599 * Don't bother to respond if destination was broadcast/multicast. 2600 */ 2601 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) 2602 goto drop; 2603 if (isipv6) { 2604 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2605 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2606 goto drop; 2607 } else { 2608 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2609 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2610 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2611 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2612 goto drop; 2613 } 2614 /* IPv6 anycast check is done at tcp6_input() */ 2615 2616 /* 2617 * Perform bandwidth limiting. 2618 */ 2619 #ifdef ICMP_BANDLIM 2620 if (badport_bandlim(rstreason) < 0) 2621 goto drop; 2622 #endif 2623 2624 #ifdef TCPDEBUG 2625 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2626 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2627 #endif 2628 if (thflags & TH_ACK) 2629 /* mtod() below is safe as long as hdr dropping is delayed */ 2630 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2631 TH_RST); 2632 else { 2633 if (thflags & TH_SYN) 2634 tlen++; 2635 /* mtod() below is safe as long as hdr dropping is delayed */ 2636 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, 2637 (tcp_seq)0, TH_RST | TH_ACK); 2638 } 2639 if (tp != NULL) 2640 tcp_sack_report_cleanup(tp); 2641 return(IPPROTO_DONE); 2642 2643 drop: 2644 /* 2645 * Drop space held by incoming segment and return. 2646 */ 2647 #ifdef TCPDEBUG 2648 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2649 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); 2650 #endif 2651 m_freem(m); 2652 if (tp != NULL) 2653 tcp_sack_report_cleanup(tp); 2654 return(IPPROTO_DONE); 2655 } 2656 2657 /* 2658 * Parse TCP options and place in tcpopt. 2659 */ 2660 static void 2661 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, 2662 tcp_seq ack) 2663 { 2664 int opt, optlen, i; 2665 2666 to->to_flags = 0; 2667 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2668 opt = cp[0]; 2669 if (opt == TCPOPT_EOL) 2670 break; 2671 if (opt == TCPOPT_NOP) 2672 optlen = 1; 2673 else { 2674 if (cnt < 2) 2675 break; 2676 optlen = cp[1]; 2677 if (optlen < 2 || optlen > cnt) 2678 break; 2679 } 2680 switch (opt) { 2681 case TCPOPT_MAXSEG: 2682 if (optlen != TCPOLEN_MAXSEG) 2683 continue; 2684 if (!is_syn) 2685 continue; 2686 to->to_flags |= TOF_MSS; 2687 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); 2688 to->to_mss = ntohs(to->to_mss); 2689 break; 2690 case TCPOPT_WINDOW: 2691 if (optlen != TCPOLEN_WINDOW) 2692 continue; 2693 if (!is_syn) 2694 continue; 2695 to->to_flags |= TOF_SCALE; 2696 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2697 break; 2698 case TCPOPT_TIMESTAMP: 2699 if (optlen != TCPOLEN_TIMESTAMP) 2700 continue; 2701 to->to_flags |= TOF_TS; 2702 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); 2703 to->to_tsval = ntohl(to->to_tsval); 2704 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); 2705 to->to_tsecr = ntohl(to->to_tsecr); 2706 /* 2707 * If echoed timestamp is later than the current time, 2708 * fall back to non RFC1323 RTT calculation. 2709 */ 2710 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) 2711 to->to_tsecr = 0; 2712 break; 2713 case TCPOPT_SACK_PERMITTED: 2714 if (optlen != TCPOLEN_SACK_PERMITTED) 2715 continue; 2716 if (!is_syn) 2717 continue; 2718 to->to_flags |= TOF_SACK_PERMITTED; 2719 break; 2720 case TCPOPT_SACK: 2721 if ((optlen - 2) & 0x07) /* not multiple of 8 */ 2722 continue; 2723 to->to_nsackblocks = (optlen - 2) / 8; 2724 to->to_sackblocks = (struct raw_sackblock *) (cp + 2); 2725 to->to_flags |= TOF_SACK; 2726 for (i = 0; i < to->to_nsackblocks; i++) { 2727 struct raw_sackblock *r = &to->to_sackblocks[i]; 2728 2729 r->rblk_start = ntohl(r->rblk_start); 2730 r->rblk_end = ntohl(r->rblk_end); 2731 2732 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { 2733 /* 2734 * Invalid SACK block; discard all 2735 * SACK blocks 2736 */ 2737 tcpstat.tcps_rcvbadsackopt++; 2738 to->to_nsackblocks = 0; 2739 to->to_sackblocks = NULL; 2740 to->to_flags &= ~TOF_SACK; 2741 break; 2742 } 2743 } 2744 if ((to->to_flags & TOF_SACK) && 2745 tcp_sack_ndsack_blocks(to->to_sackblocks, 2746 to->to_nsackblocks, ack)) 2747 to->to_flags |= TOF_DSACK; 2748 break; 2749 #ifdef TCP_SIGNATURE 2750 /* 2751 * XXX In order to reply to a host which has set the 2752 * TCP_SIGNATURE option in its initial SYN, we have to 2753 * record the fact that the option was observed here 2754 * for the syncache code to perform the correct response. 2755 */ 2756 case TCPOPT_SIGNATURE: 2757 if (optlen != TCPOLEN_SIGNATURE) 2758 continue; 2759 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); 2760 break; 2761 #endif /* TCP_SIGNATURE */ 2762 default: 2763 continue; 2764 } 2765 } 2766 } 2767 2768 /* 2769 * Pull out of band byte out of a segment so 2770 * it doesn't appear in the user's data queue. 2771 * It is still reflected in the segment length for 2772 * sequencing purposes. 2773 * "off" is the delayed to be dropped hdrlen. 2774 */ 2775 static void 2776 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off) 2777 { 2778 int cnt = off + th->th_urp - 1; 2779 2780 while (cnt >= 0) { 2781 if (m->m_len > cnt) { 2782 char *cp = mtod(m, caddr_t) + cnt; 2783 struct tcpcb *tp = sototcpcb(so); 2784 2785 tp->t_iobc = *cp; 2786 tp->t_oobflags |= TCPOOB_HAVEDATA; 2787 bcopy(cp + 1, cp, m->m_len - cnt - 1); 2788 m->m_len--; 2789 if (m->m_flags & M_PKTHDR) 2790 m->m_pkthdr.len--; 2791 return; 2792 } 2793 cnt -= m->m_len; 2794 m = m->m_next; 2795 if (m == NULL) 2796 break; 2797 } 2798 panic("tcp_pulloutofband"); 2799 } 2800 2801 /* 2802 * Collect new round-trip time estimate and update averages and current 2803 * timeout. 2804 */ 2805 static void 2806 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) 2807 { 2808 int rebaserto = 0; 2809 2810 tcpstat.tcps_rttupdated++; 2811 tp->t_rttupdated++; 2812 if ((tp->rxt_flags & TRXT_F_REBASERTO) && 2813 SEQ_GT(ack, tp->snd_max_prev)) { 2814 #ifdef DEBUG_EIFEL_RESPONSE 2815 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", 2816 tp->t_srtt_prev, tp->t_rttvar_prev, 2817 tp->t_srtt, tp->t_rttvar); 2818 #endif 2819 2820 tcpstat.tcps_eifelresponse++; 2821 rebaserto = 1; 2822 tp->rxt_flags &= ~TRXT_F_REBASERTO; 2823 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); 2824 tp->t_rttvar = max(tp->t_rttvar_prev, 2825 (rtt << (TCP_RTTVAR_SHIFT - 1))); 2826 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2827 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2828 2829 #ifdef DEBUG_EIFEL_RESPONSE 2830 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); 2831 #endif 2832 } else if (tp->t_srtt != 0) { 2833 int delta; 2834 2835 /* 2836 * srtt is stored as fixed point with 5 bits after the 2837 * binary point (i.e., scaled by 32). The following magic 2838 * is equivalent to the smoothing algorithm in rfc793 with 2839 * an alpha of .875 (srtt = rtt/32 + srtt*31/32 in fixed 2840 * point). Adjust rtt to origin 0. 2841 */ 2842 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2843 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2844 2845 if ((tp->t_srtt += delta) <= 0) 2846 tp->t_srtt = 1; 2847 2848 /* 2849 * We accumulate a smoothed rtt variance (actually, a 2850 * smoothed mean difference), then set the retransmit 2851 * timer to smoothed rtt + 4 times the smoothed variance. 2852 * rttvar is stored as fixed point with 4 bits after the 2853 * binary point (scaled by 16). The following is 2854 * equivalent to rfc793 smoothing with an alpha of .75 2855 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2856 * rfc793's wired-in beta. 2857 */ 2858 if (delta < 0) 2859 delta = -delta; 2860 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2861 if ((tp->t_rttvar += delta) <= 0) 2862 tp->t_rttvar = 1; 2863 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2864 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2865 } else { 2866 /* 2867 * No rtt measurement yet - use the unsmoothed rtt. 2868 * Set the variance to half the rtt (so our first 2869 * retransmit happens at 3*rtt). 2870 */ 2871 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2872 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2873 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2874 } 2875 tp->t_rtttime = 0; 2876 tp->t_rxtshift = 0; 2877 2878 #ifdef DEBUG_EIFEL_RESPONSE 2879 if (rebaserto) { 2880 kprintf("| rxtcur prev %d, old %d, ", 2881 tp->t_rxtcur_prev, tp->t_rxtcur); 2882 } 2883 #endif 2884 2885 /* 2886 * the retransmit should happen at rtt + 4 * rttvar. 2887 * Because of the way we do the smoothing, srtt and rttvar 2888 * will each average +1/2 tick of bias. When we compute 2889 * the retransmit timer, we want 1/2 tick of rounding and 2890 * 1 extra tick because of +-1/2 tick uncertainty in the 2891 * firing of the timer. The bias will give us exactly the 2892 * 1.5 tick we need. But, because the bias is 2893 * statistical, we have to test that we don't drop below 2894 * the minimum feasible timer (which is 2 ticks). 2895 */ 2896 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2897 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2898 2899 if (rebaserto) { 2900 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { 2901 /* 2902 * RFC4015 requires that the new RTO is at least 2903 * 2*G (tcp_eifel_rtoinc) greater then the RTO 2904 * (t_rxtcur_prev) when the spurious retransmit 2905 * timeout happens. 2906 * 2907 * The above condition could be true, if the SRTT 2908 * and RTTVAR used to calculate t_rxtcur_prev 2909 * resulted in a value less than t_rttmin. So 2910 * simply increasing SRTT by tcp_eifel_rtoinc when 2911 * preparing for the Eifel response could not ensure 2912 * that the new RTO will be tcp_eifel_rtoinc greater 2913 * t_rxtcur_prev. 2914 */ 2915 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; 2916 } 2917 #ifdef DEBUG_EIFEL_RESPONSE 2918 kprintf("new %d\n", tp->t_rxtcur); 2919 #endif 2920 } 2921 2922 /* 2923 * We received an ack for a packet that wasn't retransmitted; 2924 * it is probably safe to discard any error indications we've 2925 * received recently. This isn't quite right, but close enough 2926 * for now (a route might have failed after we sent a segment, 2927 * and the return path might not be symmetrical). 2928 */ 2929 tp->t_softerror = 0; 2930 } 2931 2932 /* 2933 * Determine a reasonable value for maxseg size. 2934 * If the route is known, check route for mtu. 2935 * If none, use an mss that can be handled on the outgoing 2936 * interface without forcing IP to fragment; if bigger than 2937 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2938 * to utilize large mbufs. If no route is found, route has no mtu, 2939 * or the destination isn't local, use a default, hopefully conservative 2940 * size (usually 512 or the default IP max size, but no more than the mtu 2941 * of the interface), as we can't discover anything about intervening 2942 * gateways or networks. We also initialize the congestion/slow start 2943 * window to be a single segment if the destination isn't local. 2944 * 2945 * Also take into account the space needed for options that we 2946 * send regularly. Make maxseg shorter by that amount to assure 2947 * that we can send maxseg amount of data even when the options 2948 * are present. Store the upper limit of the length of options plus 2949 * data in maxopd. 2950 * 2951 * NOTE that this routine is only called when we process an incoming 2952 * segment, for outgoing segments only tcp_mssopt is called. 2953 */ 2954 static void 2955 tcp_rmx_mss(struct tcpcb *tp, struct rtentry *rt, int offer) 2956 { 2957 struct ifnet *ifp; 2958 int mss; 2959 u_long bufsize; 2960 struct inpcb *inp = tp->t_inpcb; 2961 struct socket *so; 2962 #ifdef INET6 2963 boolean_t isipv6 = INP_ISIPV6(inp); 2964 size_t min_protoh = isipv6 ? 2965 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2966 sizeof(struct tcpiphdr); 2967 #else 2968 const boolean_t isipv6 = FALSE; 2969 const size_t min_protoh = sizeof(struct tcpiphdr); 2970 #endif 2971 2972 if (rt == NULL) { 2973 tp->t_maxopd = tp->t_maxseg = 2974 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2975 return; 2976 } 2977 ifp = rt->rt_ifp; 2978 so = inp->inp_socket; 2979 2980 /* 2981 * Offer == 0 means that there was no MSS on the SYN segment, 2982 * in this case we use either the interface mtu or tcp_mssdflt. 2983 * 2984 * An offer which is too large will be cut down later. 2985 */ 2986 if (offer == 0) { 2987 if (isipv6) { 2988 if (in6_localaddr(&inp->in6p_faddr)) 2989 offer = IN6_LINKMTU(rt->rt_ifp) - min_protoh; 2990 else 2991 offer = tcp_v6mssdflt; 2992 } else { 2993 if (in_localaddr(inp->inp_faddr)) 2994 offer = ifp->if_mtu - min_protoh; 2995 else 2996 offer = tcp_mssdflt; 2997 } 2998 } 2999 3000 /* 3001 * Prevent DoS attack with too small MSS. Round up 3002 * to at least minmss. 3003 * 3004 * Sanity check: make sure that maxopd will be large 3005 * enough to allow some data on segments even is the 3006 * all the option space is used (40bytes). Otherwise 3007 * funny things may happen in tcp_output. 3008 */ 3009 offer = max(offer, tcp_minmss); 3010 offer = max(offer, 64); 3011 3012 rt->rt_rmx.rmx_mssopt = offer; 3013 3014 /* 3015 * if there's an mtu associated with the route, use it 3016 * else, use the link mtu. Take the smaller of mss or offer 3017 * as our final mss. 3018 */ 3019 if (rt->rt_rmx.rmx_mtu) { 3020 mss = rt->rt_rmx.rmx_mtu; 3021 } else { 3022 if (isipv6) 3023 mss = IN6_LINKMTU(rt->rt_ifp); 3024 else 3025 mss = ifp->if_mtu; 3026 } 3027 mss -= min_protoh; 3028 mss = min(mss, offer); 3029 3030 /* 3031 * maxopd stores the maximum length of data AND options 3032 * in a segment; maxseg is the amount of data in a normal 3033 * segment. We need to store this value (maxopd) apart 3034 * from maxseg, because now every segment carries options 3035 * and thus we normally have somewhat less data in segments. 3036 */ 3037 tp->t_maxopd = mss; 3038 3039 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 3040 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3041 mss -= TCPOLEN_TSTAMP_APPA; 3042 3043 #if (MCLBYTES & (MCLBYTES - 1)) == 0 3044 if (mss > MCLBYTES) 3045 mss &= ~(MCLBYTES-1); 3046 #else 3047 if (mss > MCLBYTES) 3048 mss = rounddown(mss, MCLBYTES); 3049 #endif 3050 /* 3051 * If there's a pipesize, change the socket buffer 3052 * to that size. Make the socket buffers an integral 3053 * number of mss units; if the mss is larger than 3054 * the socket buffer, decrease the mss. 3055 */ 3056 #ifdef RTV_SPIPE 3057 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 3058 #endif 3059 bufsize = so->so_snd.ssb_hiwat; 3060 if (bufsize < mss) 3061 mss = bufsize; 3062 else { 3063 bufsize = roundup(bufsize, mss); 3064 if (bufsize > sb_max) 3065 bufsize = sb_max; 3066 if (bufsize > so->so_snd.ssb_hiwat) 3067 ssb_reserve(&so->so_snd, bufsize, so, NULL); 3068 } 3069 tp->t_maxseg = mss; 3070 3071 #ifdef RTV_RPIPE 3072 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 3073 #endif 3074 bufsize = so->so_rcv.ssb_hiwat; 3075 if (bufsize > mss) { 3076 bufsize = roundup(bufsize, mss); 3077 if (bufsize > sb_max) 3078 bufsize = sb_max; 3079 if (bufsize > so->so_rcv.ssb_hiwat) { 3080 lwkt_gettoken(&so->so_rcv.ssb_token); 3081 ssb_reserve(&so->so_rcv, bufsize, so, NULL); 3082 lwkt_reltoken(&so->so_rcv.ssb_token); 3083 } 3084 } 3085 3086 /* 3087 * Set the slow-start flight size 3088 * 3089 * NOTE: t_maxseg must have been configured! 3090 */ 3091 tp->snd_cwnd = tcp_initial_window(tp); 3092 3093 if (rt->rt_rmx.rmx_ssthresh) { 3094 /* 3095 * There's some sort of gateway or interface 3096 * buffer limit on the path. Use this to set 3097 * the slow start threshhold, but set the 3098 * threshold to no less than 2*mss. 3099 */ 3100 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 3101 tcpstat.tcps_usedssthresh++; 3102 } 3103 } 3104 3105 static void 3106 tcp_rmx_rtt(struct tcpcb *tp, struct rtentry *rt) 3107 { 3108 int rtt; 3109 3110 if (rt == NULL) 3111 return; 3112 3113 /* 3114 * Check if there's an initial rtt or rttvar. Convert 3115 * from the route-table units to scaled multiples of 3116 * the slow timeout timer. 3117 */ 3118 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 3119 /* 3120 * XXX the lock bit for RTT indicates that the value 3121 * is also a minimum value; this is subject to time. 3122 */ 3123 if (rt->rt_rmx.rmx_locks & RTV_RTT) 3124 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 3125 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 3126 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 3127 tcpstat.tcps_usedrtt++; 3128 if (rt->rt_rmx.rmx_rttvar) { 3129 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 3130 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 3131 tcpstat.tcps_usedrttvar++; 3132 } else { 3133 /* default variation is +- 1 rtt */ 3134 tp->t_rttvar = 3135 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 3136 } 3137 TCPT_RANGESET(tp->t_rxtcur, 3138 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 3139 tp->t_rttmin, TCPTV_REXMTMAX); 3140 } 3141 } 3142 3143 void 3144 tcp_rmx_init(struct tcpcb *tp, int offer) 3145 { 3146 struct inpcb *inp = tp->t_inpcb; 3147 #ifdef INET6 3148 boolean_t isipv6 = INP_ISIPV6(inp); 3149 #else 3150 const boolean_t isipv6 = FALSE; 3151 #endif 3152 struct rtentry *rt; 3153 3154 if (isipv6) 3155 rt = tcp_rtlookup6(&inp->inp_inc); 3156 else 3157 rt = tcp_rtlookup(&inp->inp_inc); 3158 3159 tcp_rmx_mss(tp, rt, offer); 3160 tcp_rmx_rtt(tp, rt); 3161 3162 if (rt != NULL && !tcp_ncr_linklocal && (rt->rt_flags & RTF_LLINFO)) { 3163 /* Don't enable NCR on link-local network. */ 3164 tp->t_flags &= ~TF_NCR; 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 = INP_ISIPV6(tp->t_inpcb); 3177 int min_protoh = isipv6 ? 3178 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 3179 sizeof(struct tcpiphdr); 3180 #else 3181 const boolean_t isipv6 = FALSE; 3182 const size_t min_protoh = sizeof(struct tcpiphdr); 3183 #endif 3184 3185 if (isipv6) 3186 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 3187 else 3188 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 3189 if (rt == NULL) 3190 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 3191 3192 #ifdef INET6 3193 return ((isipv6 ? IN6_LINKMTU(rt->rt_ifp) : rt->rt_ifp->if_mtu) - 3194 min_protoh); 3195 #else 3196 return (rt->rt_ifp->if_mtu - min_protoh); 3197 #endif 3198 } 3199 3200 /* 3201 * When a partial ack arrives, force the retransmission of the 3202 * next unacknowledged segment. Do not exit Fast Recovery. 3203 * 3204 * Implement the Slow-but-Steady variant of NewReno by restarting the 3205 * the retransmission timer. Turn it off here so it can be restarted 3206 * later in tcp_output(). 3207 */ 3208 static void 3209 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) 3210 { 3211 tcp_seq old_snd_nxt = tp->snd_nxt; 3212 u_long ocwnd = tp->snd_cwnd; 3213 3214 tcp_callout_stop(tp, tp->tt_rexmt); 3215 tp->t_rtttime = 0; 3216 tp->snd_nxt = th->th_ack; 3217 /* Set snd_cwnd to one segment beyond acknowledged offset. */ 3218 tp->snd_cwnd = tp->t_maxseg; 3219 tp->t_flags |= TF_ACKNOW; 3220 tcp_output(tp); 3221 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3222 tp->snd_nxt = old_snd_nxt; 3223 /* partial window deflation */ 3224 if (ocwnd > acked) 3225 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; 3226 else 3227 tp->snd_cwnd = tp->t_maxseg; 3228 } 3229 3230 /* 3231 * In contrast to the Slow-but-Steady NewReno variant, 3232 * we do not reset the retransmission timer for SACK retransmissions, 3233 * except when retransmitting snd_una. 3234 */ 3235 static void 3236 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force) 3237 { 3238 tcp_seq old_snd_nxt = tp->snd_nxt; 3239 u_long ocwnd = tp->snd_cwnd; 3240 uint32_t pipe; 3241 int nseg = 0; /* consecutive new segments */ 3242 int nseg_rexmt = 0; /* retransmitted segments */ 3243 int maxrexmt = 0; 3244 3245 if (force) { 3246 uint32_t unsacked = tcp_sack_first_unsacked_len(tp); 3247 3248 /* 3249 * Try to fill the first hole in the receiver's 3250 * reassemble queue. 3251 */ 3252 maxrexmt = howmany(unsacked, tp->t_maxseg); 3253 if (maxrexmt > tcp_force_sackrxt) 3254 maxrexmt = tcp_force_sackrxt; 3255 } 3256 3257 tp->t_rtttime = 0; 3258 pipe = tcp_sack_compute_pipe(tp); 3259 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg 3260 || (force && nseg_rexmt < maxrexmt && nseg == 0)) && 3261 (!tcp_do_smartsack || nseg < TCP_SACK_MAXBURST)) { 3262 tcp_seq old_snd_max, old_rexmt_high, nextrexmt; 3263 uint32_t sent, seglen; 3264 boolean_t rescue; 3265 int error; 3266 3267 old_rexmt_high = tp->rexmt_high; 3268 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { 3269 tp->rexmt_high = old_rexmt_high; 3270 break; 3271 } 3272 3273 /* 3274 * If the next tranmission is a rescue retranmission, 3275 * we check whether we have already sent some data 3276 * (either new segments or retransmitted segments) 3277 * into the the network or not. Since the idea of rescue 3278 * retransmission is to sustain ACK clock, as long as 3279 * some segments are in the network, ACK clock will be 3280 * kept ticking. 3281 */ 3282 if (rescue && (nseg_rexmt > 0 || nseg > 0)) { 3283 tp->rexmt_high = old_rexmt_high; 3284 break; 3285 } 3286 3287 if (nextrexmt == tp->snd_max) 3288 ++nseg; 3289 else 3290 ++nseg_rexmt; 3291 tp->snd_nxt = nextrexmt; 3292 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; 3293 old_snd_max = tp->snd_max; 3294 if (nextrexmt == tp->snd_una) 3295 tcp_callout_stop(tp, tp->tt_rexmt); 3296 tp->t_flags |= TF_XMITNOW; 3297 error = tcp_output(tp); 3298 if (error != 0) { 3299 tp->rexmt_high = old_rexmt_high; 3300 break; 3301 } 3302 sent = tp->snd_nxt - nextrexmt; 3303 if (sent <= 0) { 3304 tp->rexmt_high = old_rexmt_high; 3305 break; 3306 } 3307 pipe += sent; 3308 tcpstat.tcps_sndsackpack++; 3309 tcpstat.tcps_sndsackbyte += sent; 3310 3311 if (rescue) { 3312 tcpstat.tcps_sackrescue++; 3313 tp->rexmt_rescue = tp->snd_nxt; 3314 tp->sack_flags |= TSACK_F_SACKRESCUED; 3315 break; 3316 } 3317 if (SEQ_LT(nextrexmt, old_snd_max) && 3318 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { 3319 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); 3320 if (tcp_aggressive_rescuesack && 3321 (tp->sack_flags & TSACK_F_SACKRESCUED) && 3322 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 3323 /* Drag RescueRxt along with HighRxt */ 3324 tp->rexmt_rescue = tp->rexmt_high; 3325 } 3326 } 3327 } 3328 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3329 tp->snd_nxt = old_snd_nxt; 3330 tp->snd_cwnd = ocwnd; 3331 } 3332 3333 /* 3334 * Return TRUE, if some new segments are sent 3335 */ 3336 static boolean_t 3337 tcp_sack_limitedxmit(struct tcpcb *tp) 3338 { 3339 tcp_seq oldsndnxt = tp->snd_nxt; 3340 tcp_seq oldsndmax = tp->snd_max; 3341 u_long ocwnd = tp->snd_cwnd; 3342 uint32_t pipe, sent; 3343 boolean_t ret = FALSE; 3344 tcp_seq_diff_t cwnd_left; 3345 tcp_seq next; 3346 3347 tp->rexmt_high = tp->snd_una - 1; 3348 pipe = tcp_sack_compute_pipe(tp); 3349 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe); 3350 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg) 3351 return FALSE; 3352 3353 if (tcp_do_smartsack) 3354 cwnd_left = ulmin(cwnd_left, tp->t_maxseg * TCP_SACK_MAXBURST); 3355 3356 next = tp->snd_nxt = tp->snd_max; 3357 tp->snd_cwnd = tp->snd_nxt - tp->snd_una + 3358 rounddown(cwnd_left, tp->t_maxseg); 3359 3360 tp->t_flags |= TF_XMITNOW; 3361 tcp_output(tp); 3362 3363 sent = tp->snd_nxt - next; 3364 if (sent > 0) { 3365 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg); 3366 ret = TRUE; 3367 } 3368 3369 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3370 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3371 ("snd_una moved in other threads")); 3372 tp->snd_nxt = oldsndnxt; 3373 } 3374 tp->snd_cwnd = ocwnd; 3375 3376 if (ret && TCP_DO_NCR(tp)) 3377 tcp_ncr_update_rxtthresh(tp); 3378 3379 return ret; 3380 } 3381 3382 /* 3383 * Reset idle time and keep-alive timer, typically called when a valid 3384 * tcp packet is received but may also be called when FASTKEEP is set 3385 * to prevent the previous long-timeout from calculating to a drop. 3386 * 3387 * Only update t_rcvtime for non-SYN packets. 3388 * 3389 * Handle the case where one side thinks the connection is established 3390 * but the other side has, say, rebooted without cleaning out the 3391 * connection. The SYNs could be construed as an attack and wind 3392 * up ignored, but in case it isn't an attack we can validate the 3393 * connection by forcing a keepalive. 3394 */ 3395 void 3396 tcp_timer_keep_activity(struct tcpcb *tp, int thflags) 3397 { 3398 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 3399 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { 3400 tp->t_flags |= TF_KEEPALIVE; 3401 tcp_callout_reset(tp, tp->tt_keep, hz / 2, 3402 tcp_timer_keep); 3403 } else { 3404 tp->t_rcvtime = ticks; 3405 tp->t_flags &= ~TF_KEEPALIVE; 3406 tcp_callout_reset(tp, tp->tt_keep, 3407 tp->t_keepidle, 3408 tcp_timer_keep); 3409 } 3410 } 3411 } 3412 3413 static int 3414 tcp_rmx_msl(const struct tcpcb *tp) 3415 { 3416 struct rtentry *rt; 3417 struct inpcb *inp = tp->t_inpcb; 3418 int msl; 3419 #ifdef INET6 3420 boolean_t isipv6 = INP_ISIPV6(inp); 3421 #else 3422 const boolean_t isipv6 = FALSE; 3423 #endif 3424 3425 if (isipv6) 3426 rt = tcp_rtlookup6(&inp->inp_inc); 3427 else 3428 rt = tcp_rtlookup(&inp->inp_inc); 3429 if (rt == NULL || rt->rt_rmx.rmx_msl == 0) 3430 return tcp_msl; 3431 3432 msl = (rt->rt_rmx.rmx_msl * hz) / 1000; 3433 if (msl == 0) 3434 msl = 1; 3435 3436 return msl; 3437 } 3438 3439 static void 3440 tcp_established(struct tcpcb *tp) 3441 { 3442 TCP_STATE_CHANGE(tp, TCPS_ESTABLISHED); 3443 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); 3444 3445 if (tp->t_rxtsyn > 0) { 3446 /* 3447 * RFC6298: 3448 * "If the timer expires awaiting the ACK of a SYN segment 3449 * and the TCP implementation is using an RTO less than 3 3450 * seconds, the RTO MUST be re-initialized to 3 seconds 3451 * when data transmission begins" 3452 */ 3453 if (tp->t_rxtcur < TCPTV_RTOBASE3) 3454 tp->t_rxtcur = TCPTV_RTOBASE3; 3455 } 3456 } 3457 3458 /* 3459 * Returns TRUE, if the ACK should be dropped 3460 */ 3461 static boolean_t 3462 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags) 3463 { 3464 boolean_t fast_sack_rexmt = TRUE; 3465 3466 tcpstat.tcps_rcvdupack++; 3467 3468 /* 3469 * We have outstanding data (other than a window probe), 3470 * this is a completely duplicate ack (ie, window info 3471 * didn't change), the ack is the biggest we've seen and 3472 * we've seen exactly our rexmt threshhold of them, so 3473 * assume a packet has been dropped and retransmit it. 3474 * Kludge snd_nxt & the congestion window so we send only 3475 * this one packet. 3476 */ 3477 if (IN_FASTRECOVERY(tp)) { 3478 if (TCP_DO_SACK(tp)) { 3479 boolean_t force = FALSE; 3480 3481 if (tp->snd_una == tp->rexmt_high && 3482 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) == 3483 TOF_SACK) { 3484 /* 3485 * New segments got SACKed and 3486 * no retransmit yet. 3487 */ 3488 force = TRUE; 3489 } 3490 3491 /* No artifical cwnd inflation. */ 3492 tcp_sack_rexmt(tp, force); 3493 } else { 3494 /* 3495 * Dup acks mean that packets have left 3496 * the network (they're now cached at the 3497 * receiver) so bump cwnd by the amount in 3498 * the receiver to keep a constant cwnd 3499 * packets in the network. 3500 */ 3501 tp->snd_cwnd += tp->t_maxseg; 3502 tcp_output(tp); 3503 } 3504 return TRUE; 3505 } else if (SEQ_LT(th_ack, tp->snd_recover)) { 3506 tp->t_dupacks = 0; 3507 return FALSE; 3508 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && 3509 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == 3510 (TOF_DSACK | TOF_SACK_REDUNDANT)) { 3511 /* 3512 * If the ACK carries DSACK and other SACK blocks 3513 * carry information that we have already known, 3514 * don't count this ACK as duplicate ACK. This 3515 * prevents spurious early retransmit and fast 3516 * retransmit. This also meets the requirement of 3517 * RFC3042 that new segments should not be sent if 3518 * the SACK blocks do not contain new information 3519 * (XXX we actually loosen the requirment that only 3520 * DSACK is checked here). 3521 * 3522 * This kind of ACKs are usually sent after spurious 3523 * retransmit. 3524 */ 3525 /* Do nothing; don't change t_dupacks */ 3526 return TRUE; 3527 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) { 3528 tcp_ncr_update_rxtthresh(tp); 3529 } 3530 3531 if (++tp->t_dupacks == tp->t_rxtthresh) { 3532 tcp_seq old_snd_nxt; 3533 u_int win; 3534 3535 fastretransmit: 3536 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) { 3537 tcp_save_congestion_state(tp); 3538 tp->rxt_flags |= TRXT_F_FASTREXMT; 3539 } 3540 /* 3541 * We know we're losing at the current window size, 3542 * so do congestion avoidance: set ssthresh to half 3543 * the current window and pull our congestion window 3544 * back to the new ssthresh. 3545 */ 3546 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 3547 if (win < 2) 3548 win = 2; 3549 tp->snd_ssthresh = win * tp->t_maxseg; 3550 ENTER_FASTRECOVERY(tp); 3551 tp->snd_recover = tp->snd_max; 3552 tcp_callout_stop(tp, tp->tt_rexmt); 3553 tp->t_rtttime = 0; 3554 old_snd_nxt = tp->snd_nxt; 3555 tp->snd_nxt = th_ack; 3556 if (TCP_DO_SACK(tp)) { 3557 uint32_t rxtlen; 3558 3559 rxtlen = tcp_sack_first_unsacked_len(tp); 3560 if (rxtlen > tp->t_maxseg) 3561 rxtlen = tp->t_maxseg; 3562 tp->snd_cwnd = rxtlen; 3563 } else { 3564 tp->snd_cwnd = tp->t_maxseg; 3565 } 3566 tcp_output(tp); 3567 ++tcpstat.tcps_sndfastrexmit; 3568 tp->snd_cwnd = tp->snd_ssthresh; 3569 tp->rexmt_high = tp->snd_nxt; 3570 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 3571 if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) 3572 tp->snd_nxt = old_snd_nxt; 3573 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big")); 3574 if (TCP_DO_SACK(tp)) { 3575 if (fast_sack_rexmt) 3576 tcp_sack_rexmt(tp, FALSE); 3577 } else { 3578 tp->snd_cwnd += tp->t_maxseg * 3579 (tp->t_dupacks - tp->snd_limited); 3580 } 3581 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) { 3582 /* 3583 * The RFC6675 recommends to reduce the byte threshold, 3584 * and enter fast retransmit if IsLost(snd_una). However, 3585 * if we use IsLost(snd_una) based fast retransmit here, 3586 * segments reordering will cause spurious retransmit. So 3587 * we defer the IsLost(snd_una) based fast retransmit until 3588 * the extended limited transmit can't send any segments and 3589 * early retransmit can't be done. 3590 */ 3591 if (tcp_rfc6675_rxt && tcp_do_rfc6675 && 3592 tcp_sack_islost(&tp->scb, tp->snd_una)) 3593 goto fastretransmit; 3594 3595 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) { 3596 if (!tcp_sack_limitedxmit(tp)) { 3597 /* outstanding data */ 3598 uint32_t ownd = tp->snd_max - tp->snd_una; 3599 3600 if (need_early_retransmit(tp, ownd)) { 3601 ++tcpstat.tcps_sndearlyrexmit; 3602 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3603 goto fastretransmit; 3604 } else if (tcp_do_rfc6675 && 3605 tcp_sack_islost(&tp->scb, tp->snd_una)) { 3606 fast_sack_rexmt = FALSE; 3607 goto fastretransmit; 3608 } 3609 } 3610 } 3611 } else if (tcp_do_limitedtransmit) { 3612 u_long oldcwnd = tp->snd_cwnd; 3613 tcp_seq oldsndmax = tp->snd_max; 3614 tcp_seq oldsndnxt = tp->snd_nxt; 3615 /* outstanding data */ 3616 uint32_t ownd = tp->snd_max - tp->snd_una; 3617 u_int sent; 3618 3619 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2, 3620 ("dupacks not 1 or 2")); 3621 if (tp->t_dupacks == 1) 3622 tp->snd_limited = 0; 3623 tp->snd_nxt = tp->snd_max; 3624 tp->snd_cwnd = ownd + 3625 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg; 3626 tp->t_flags |= TF_XMITNOW; 3627 tcp_output(tp); 3628 3629 if (SEQ_LT(oldsndnxt, oldsndmax)) { 3630 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), 3631 ("snd_una moved in other threads")); 3632 tp->snd_nxt = oldsndnxt; 3633 } 3634 tp->snd_cwnd = oldcwnd; 3635 sent = tp->snd_max - oldsndmax; 3636 if (sent > tp->t_maxseg) { 3637 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) || 3638 (sent == tp->t_maxseg + 1 && 3639 (tp->t_flags & TF_SENTFIN)), 3640 ("sent too much")); 3641 KASSERT(sent <= tp->t_maxseg * 2, 3642 ("sent too many segments")); 3643 tp->snd_limited = 2; 3644 tcpstat.tcps_sndlimited += 2; 3645 } else if (sent > 0) { 3646 ++tp->snd_limited; 3647 ++tcpstat.tcps_sndlimited; 3648 } else if (need_early_retransmit(tp, ownd)) { 3649 ++tcpstat.tcps_sndearlyrexmit; 3650 tp->rxt_flags |= TRXT_F_EARLYREXMT; 3651 goto fastretransmit; 3652 } 3653 } 3654 return TRUE; 3655 } 3656