1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 2007-2008,2010 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Copyright (c) 2009-2010 Lawrence Stewart <[email protected]> 9 * Copyright (c) 2010 The FreeBSD Foundation 10 * Copyright (c) 2010-2011 Juniper Networks, Inc. 11 * All rights reserved. 12 * 13 * Portions of this software were developed at the Centre for Advanced Internet 14 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 15 * James Healy and David Hayes, made possible in part by a grant from the Cisco 16 * University Research Program Fund at Community Foundation Silicon Valley. 17 * 18 * Portions of this software were developed at the Centre for Advanced 19 * Internet Architectures, Swinburne University of Technology, Melbourne, 20 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 21 * 22 * Portions of this software were developed by Robert N. M. Watson under 23 * contract to Juniper Networks, Inc. 24 * 25 * Redistribution and use in source and binary forms, with or without 26 * modification, are permitted provided that the following conditions 27 * are met: 28 * 1. Redistributions of source code must retain the above copyright 29 * notice, this list of conditions and the following disclaimer. 30 * 2. Redistributions in binary form must reproduce the above copyright 31 * notice, this list of conditions and the following disclaimer in the 32 * documentation and/or other materials provided with the distribution. 33 * 3. Neither the name of the University nor the names of its contributors 34 * may be used to endorse or promote products derived from this software 35 * without specific prior written permission. 36 * 37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 47 * SUCH DAMAGE. 48 * 49 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 50 */ 51 52 #include <sys/cdefs.h> 53 __FBSDID("$FreeBSD$"); 54 55 #include "opt_inet.h" 56 #include "opt_inet6.h" 57 #include "opt_ipsec.h" 58 #include "opt_tcpdebug.h" 59 60 #include <sys/param.h> 61 #include <sys/kernel.h> 62 #ifdef TCP_HHOOK 63 #include <sys/hhook.h> 64 #endif 65 #include <sys/malloc.h> 66 #include <sys/mbuf.h> 67 #include <sys/proc.h> /* for proc0 declaration */ 68 #include <sys/protosw.h> 69 #include <sys/sdt.h> 70 #include <sys/signalvar.h> 71 #include <sys/socket.h> 72 #include <sys/socketvar.h> 73 #include <sys/sysctl.h> 74 #include <sys/syslog.h> 75 #include <sys/systm.h> 76 77 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 78 79 #include <vm/uma.h> 80 81 #include <net/if.h> 82 #include <net/if_var.h> 83 #include <net/route.h> 84 #include <net/vnet.h> 85 86 #define TCPSTATES /* for logging */ 87 88 #include <netinet/in.h> 89 #include <netinet/in_kdtrace.h> 90 #include <netinet/in_pcb.h> 91 #include <netinet/in_systm.h> 92 #include <netinet/ip.h> 93 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 94 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 95 #include <netinet/ip_var.h> 96 #include <netinet/ip_options.h> 97 #include <netinet/ip6.h> 98 #include <netinet/icmp6.h> 99 #include <netinet6/in6_pcb.h> 100 #include <netinet6/in6_var.h> 101 #include <netinet6/ip6_var.h> 102 #include <netinet6/nd6.h> 103 #include <netinet/tcp.h> 104 #include <netinet/tcp_fsm.h> 105 #include <netinet/tcp_log_buf.h> 106 #include <netinet/tcp_seq.h> 107 #include <netinet/tcp_timer.h> 108 #include <netinet/tcp_var.h> 109 #include <netinet6/tcp6_var.h> 110 #include <netinet/tcpip.h> 111 #include <netinet/cc/cc.h> 112 #include <netinet/tcp_fastopen.h> 113 #ifdef TCPPCAP 114 #include <netinet/tcp_pcap.h> 115 #endif 116 #include <netinet/tcp_syncache.h> 117 #ifdef TCPDEBUG 118 #include <netinet/tcp_debug.h> 119 #endif /* TCPDEBUG */ 120 #ifdef TCP_OFFLOAD 121 #include <netinet/tcp_offload.h> 122 #endif 123 124 #include <netipsec/ipsec_support.h> 125 126 #include <machine/in_cksum.h> 127 128 #include <security/mac/mac_framework.h> 129 130 const int tcprexmtthresh = 3; 131 132 int tcp_log_in_vain = 0; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 134 &tcp_log_in_vain, 0, 135 "Log all incoming TCP segments to closed ports"); 136 137 VNET_DEFINE(int, blackhole) = 0; 138 #define V_blackhole VNET(blackhole) 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 140 &VNET_NAME(blackhole), 0, 141 "Do not send RST on segments to closed ports"); 142 143 VNET_DEFINE(int, tcp_delack_enabled) = 1; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 145 &VNET_NAME(tcp_delack_enabled), 0, 146 "Delay ACK to try and piggyback it onto a data packet"); 147 148 VNET_DEFINE(int, drop_synfin) = 0; 149 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 150 &VNET_NAME(drop_synfin), 0, 151 "Drop TCP packets with SYN+FIN set"); 152 153 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 155 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 156 "Use calculated pipe/in-flight bytes per RFC 6675"); 157 158 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 160 &VNET_NAME(tcp_do_rfc3042), 0, 161 "Enable RFC 3042 (Limited Transmit)"); 162 163 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 165 &VNET_NAME(tcp_do_rfc3390), 0, 166 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 167 168 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 170 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 171 "Slow-start flight size (initial congestion window) in number of segments"); 172 173 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 174 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 175 &VNET_NAME(tcp_do_rfc3465), 0, 176 "Enable RFC 3465 (Appropriate Byte Counting)"); 177 178 VNET_DEFINE(int, tcp_abc_l_var) = 2; 179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 180 &VNET_NAME(tcp_abc_l_var), 2, 181 "Cap the max cwnd increment during slow-start to this number of segments"); 182 183 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 184 185 VNET_DEFINE(int, tcp_do_ecn) = 2; 186 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 187 &VNET_NAME(tcp_do_ecn), 0, 188 "TCP ECN support"); 189 190 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 191 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 192 &VNET_NAME(tcp_ecn_maxretries), 0, 193 "Max retries before giving up on ECN"); 194 195 VNET_DEFINE(int, tcp_insecure_syn) = 0; 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 197 &VNET_NAME(tcp_insecure_syn), 0, 198 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 199 200 VNET_DEFINE(int, tcp_insecure_rst) = 0; 201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 202 &VNET_NAME(tcp_insecure_rst), 0, 203 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 204 205 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 206 #define V_tcp_recvspace VNET(tcp_recvspace) 207 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 208 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 209 210 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 211 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 212 &VNET_NAME(tcp_do_autorcvbuf), 0, 213 "Enable automatic receive buffer sizing"); 214 215 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 217 &VNET_NAME(tcp_autorcvbuf_inc), 0, 218 "Incrementor step size of automatic receive buffer"); 219 220 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 222 &VNET_NAME(tcp_autorcvbuf_max), 0, 223 "Max size of automatic receive buffer"); 224 225 VNET_DEFINE(struct inpcbhead, tcb); 226 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 227 VNET_DEFINE(struct inpcbinfo, tcbinfo); 228 229 /* 230 * TCP statistics are stored in an array of counter(9)s, which size matches 231 * size of struct tcpstat. TCP running connection count is a regular array. 232 */ 233 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 234 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 235 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 236 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 237 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 238 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 239 "TCP connection counts by TCP state"); 240 241 static void 242 tcp_vnet_init(const void *unused) 243 { 244 245 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 246 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 247 } 248 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 249 tcp_vnet_init, NULL); 250 251 #ifdef VIMAGE 252 static void 253 tcp_vnet_uninit(const void *unused) 254 { 255 256 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 257 VNET_PCPUSTAT_FREE(tcpstat); 258 } 259 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 260 tcp_vnet_uninit, NULL); 261 #endif /* VIMAGE */ 262 263 /* 264 * Kernel module interface for updating tcpstat. The argument is an index 265 * into tcpstat treated as an array. 266 */ 267 void 268 kmod_tcpstat_inc(int statnum) 269 { 270 271 counter_u64_add(VNET(tcpstat)[statnum], 1); 272 } 273 274 #ifdef TCP_HHOOK 275 /* 276 * Wrapper for the TCP established input helper hook. 277 */ 278 void 279 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 280 { 281 struct tcp_hhook_data hhook_data; 282 283 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 284 hhook_data.tp = tp; 285 hhook_data.th = th; 286 hhook_data.to = to; 287 288 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 289 tp->osd); 290 } 291 } 292 #endif 293 294 /* 295 * CC wrapper hook functions 296 */ 297 void 298 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 299 uint16_t type) 300 { 301 INP_WLOCK_ASSERT(tp->t_inpcb); 302 303 tp->ccv->nsegs = nsegs; 304 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 305 if (tp->snd_cwnd <= tp->snd_wnd) 306 tp->ccv->flags |= CCF_CWND_LIMITED; 307 else 308 tp->ccv->flags &= ~CCF_CWND_LIMITED; 309 310 if (type == CC_ACK) { 311 if (tp->snd_cwnd > tp->snd_ssthresh) { 312 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 313 nsegs * V_tcp_abc_l_var * tcp_maxseg(tp)); 314 if (tp->t_bytes_acked >= tp->snd_cwnd) { 315 tp->t_bytes_acked -= tp->snd_cwnd; 316 tp->ccv->flags |= CCF_ABC_SENTAWND; 317 } 318 } else { 319 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 320 tp->t_bytes_acked = 0; 321 } 322 } 323 324 if (CC_ALGO(tp)->ack_received != NULL) { 325 /* XXXLAS: Find a way to live without this */ 326 tp->ccv->curack = th->th_ack; 327 CC_ALGO(tp)->ack_received(tp->ccv, type); 328 } 329 } 330 331 void 332 cc_conn_init(struct tcpcb *tp) 333 { 334 struct hc_metrics_lite metrics; 335 struct inpcb *inp = tp->t_inpcb; 336 u_int maxseg; 337 int rtt; 338 339 INP_WLOCK_ASSERT(tp->t_inpcb); 340 341 tcp_hc_get(&inp->inp_inc, &metrics); 342 maxseg = tcp_maxseg(tp); 343 344 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 345 tp->t_srtt = rtt; 346 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 347 TCPSTAT_INC(tcps_usedrtt); 348 if (metrics.rmx_rttvar) { 349 tp->t_rttvar = metrics.rmx_rttvar; 350 TCPSTAT_INC(tcps_usedrttvar); 351 } else { 352 /* default variation is +- 1 rtt */ 353 tp->t_rttvar = 354 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 355 } 356 TCPT_RANGESET(tp->t_rxtcur, 357 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 358 tp->t_rttmin, TCPTV_REXMTMAX); 359 } 360 if (metrics.rmx_ssthresh) { 361 /* 362 * There's some sort of gateway or interface 363 * buffer limit on the path. Use this to set 364 * the slow start threshold, but set the 365 * threshold to no less than 2*mss. 366 */ 367 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 368 TCPSTAT_INC(tcps_usedssthresh); 369 } 370 371 /* 372 * Set the initial slow-start flight size. 373 * 374 * RFC5681 Section 3.1 specifies the default conservative values. 375 * RFC3390 specifies slightly more aggressive values. 376 * RFC6928 increases it to ten segments. 377 * Support for user specified value for initial flight size. 378 * 379 * If a SYN or SYN/ACK was lost and retransmitted, we have to 380 * reduce the initial CWND to one segment as congestion is likely 381 * requiring us to be cautious. 382 */ 383 if (tp->snd_cwnd == 1) 384 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 385 else if (V_tcp_initcwnd_segments) 386 tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg, 387 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 388 else if (V_tcp_do_rfc3390) 389 tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380)); 390 else { 391 /* Per RFC5681 Section 3.1 */ 392 if (maxseg > 2190) 393 tp->snd_cwnd = 2 * maxseg; 394 else if (maxseg > 1095) 395 tp->snd_cwnd = 3 * maxseg; 396 else 397 tp->snd_cwnd = 4 * maxseg; 398 } 399 400 if (CC_ALGO(tp)->conn_init != NULL) 401 CC_ALGO(tp)->conn_init(tp->ccv); 402 } 403 404 void inline 405 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 406 { 407 u_int maxseg; 408 409 INP_WLOCK_ASSERT(tp->t_inpcb); 410 411 switch(type) { 412 case CC_NDUPACK: 413 if (!IN_FASTRECOVERY(tp->t_flags)) { 414 tp->snd_recover = tp->snd_max; 415 if (tp->t_flags & TF_ECN_PERMIT) 416 tp->t_flags |= TF_ECN_SND_CWR; 417 } 418 break; 419 case CC_ECN: 420 if (!IN_CONGRECOVERY(tp->t_flags)) { 421 TCPSTAT_INC(tcps_ecn_rcwnd); 422 tp->snd_recover = tp->snd_max; 423 if (tp->t_flags & TF_ECN_PERMIT) 424 tp->t_flags |= TF_ECN_SND_CWR; 425 } 426 break; 427 case CC_RTO: 428 maxseg = tcp_maxseg(tp); 429 tp->t_dupacks = 0; 430 tp->t_bytes_acked = 0; 431 EXIT_RECOVERY(tp->t_flags); 432 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 433 maxseg) * maxseg; 434 tp->snd_cwnd = maxseg; 435 break; 436 case CC_RTO_ERR: 437 TCPSTAT_INC(tcps_sndrexmitbad); 438 /* RTO was unnecessary, so reset everything. */ 439 tp->snd_cwnd = tp->snd_cwnd_prev; 440 tp->snd_ssthresh = tp->snd_ssthresh_prev; 441 tp->snd_recover = tp->snd_recover_prev; 442 if (tp->t_flags & TF_WASFRECOVERY) 443 ENTER_FASTRECOVERY(tp->t_flags); 444 if (tp->t_flags & TF_WASCRECOVERY) 445 ENTER_CONGRECOVERY(tp->t_flags); 446 tp->snd_nxt = tp->snd_max; 447 tp->t_flags &= ~TF_PREVVALID; 448 tp->t_badrxtwin = 0; 449 break; 450 } 451 452 if (CC_ALGO(tp)->cong_signal != NULL) { 453 if (th != NULL) 454 tp->ccv->curack = th->th_ack; 455 CC_ALGO(tp)->cong_signal(tp->ccv, type); 456 } 457 } 458 459 void inline 460 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 461 { 462 INP_WLOCK_ASSERT(tp->t_inpcb); 463 464 /* XXXLAS: KASSERT that we're in recovery? */ 465 466 if (CC_ALGO(tp)->post_recovery != NULL) { 467 tp->ccv->curack = th->th_ack; 468 CC_ALGO(tp)->post_recovery(tp->ccv); 469 } 470 /* XXXLAS: EXIT_RECOVERY ? */ 471 tp->t_bytes_acked = 0; 472 } 473 474 /* 475 * Indicate whether this ack should be delayed. We can delay the ack if 476 * following conditions are met: 477 * - There is no delayed ack timer in progress. 478 * - Our last ack wasn't a 0-sized window. We never want to delay 479 * the ack that opens up a 0-sized window. 480 * - LRO wasn't used for this segment. We make sure by checking that the 481 * segment size is not larger than the MSS. 482 */ 483 #define DELAY_ACK(tp, tlen) \ 484 ((!tcp_timer_active(tp, TT_DELACK) && \ 485 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 486 (tlen <= tp->t_maxseg) && \ 487 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 488 489 static void inline 490 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 491 { 492 INP_WLOCK_ASSERT(tp->t_inpcb); 493 494 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 495 switch (iptos & IPTOS_ECN_MASK) { 496 case IPTOS_ECN_CE: 497 tp->ccv->flags |= CCF_IPHDR_CE; 498 break; 499 case IPTOS_ECN_ECT0: 500 tp->ccv->flags &= ~CCF_IPHDR_CE; 501 break; 502 case IPTOS_ECN_ECT1: 503 tp->ccv->flags &= ~CCF_IPHDR_CE; 504 break; 505 } 506 507 if (th->th_flags & TH_CWR) 508 tp->ccv->flags |= CCF_TCPHDR_CWR; 509 else 510 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 511 512 if (tp->t_flags & TF_DELACK) 513 tp->ccv->flags |= CCF_DELACK; 514 else 515 tp->ccv->flags &= ~CCF_DELACK; 516 517 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 518 519 if (tp->ccv->flags & CCF_ACKNOW) 520 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 521 } 522 } 523 524 /* 525 * TCP input handling is split into multiple parts: 526 * tcp6_input is a thin wrapper around tcp_input for the extended 527 * ip6_protox[] call format in ip6_input 528 * tcp_input handles primary segment validation, inpcb lookup and 529 * SYN processing on listen sockets 530 * tcp_do_segment processes the ACK and text of the segment for 531 * establishing, established and closing connections 532 */ 533 #ifdef INET6 534 int 535 tcp6_input(struct mbuf **mp, int *offp, int proto) 536 { 537 struct mbuf *m = *mp; 538 struct in6_ifaddr *ia6; 539 struct ip6_hdr *ip6; 540 541 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 542 543 /* 544 * draft-itojun-ipv6-tcp-to-anycast 545 * better place to put this in? 546 */ 547 ip6 = mtod(m, struct ip6_hdr *); 548 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 549 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 550 struct ip6_hdr *ip6; 551 552 ifa_free(&ia6->ia_ifa); 553 ip6 = mtod(m, struct ip6_hdr *); 554 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 555 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 556 return (IPPROTO_DONE); 557 } 558 if (ia6) 559 ifa_free(&ia6->ia_ifa); 560 561 return (tcp_input(mp, offp, proto)); 562 } 563 #endif /* INET6 */ 564 565 int 566 tcp_input(struct mbuf **mp, int *offp, int proto) 567 { 568 struct mbuf *m = *mp; 569 struct tcphdr *th = NULL; 570 struct ip *ip = NULL; 571 struct inpcb *inp = NULL; 572 struct tcpcb *tp = NULL; 573 struct socket *so = NULL; 574 u_char *optp = NULL; 575 int off0; 576 int optlen = 0; 577 #ifdef INET 578 int len; 579 #endif 580 int tlen = 0, off; 581 int drop_hdrlen; 582 int thflags; 583 int rstreason = 0; /* For badport_bandlim accounting purposes */ 584 uint8_t iptos; 585 struct m_tag *fwd_tag = NULL; 586 struct epoch_tracker et; 587 #ifdef INET6 588 struct ip6_hdr *ip6 = NULL; 589 int isipv6; 590 #else 591 const void *ip6 = NULL; 592 #endif /* INET6 */ 593 struct tcpopt to; /* options in this segment */ 594 char *s = NULL; /* address and port logging */ 595 int ti_locked; 596 #ifdef TCPDEBUG 597 /* 598 * The size of tcp_saveipgen must be the size of the max ip header, 599 * now IPv6. 600 */ 601 u_char tcp_saveipgen[IP6_HDR_LEN]; 602 struct tcphdr tcp_savetcp; 603 short ostate = 0; 604 #endif 605 606 #ifdef INET6 607 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 608 #endif 609 610 off0 = *offp; 611 m = *mp; 612 *mp = NULL; 613 to.to_flags = 0; 614 TCPSTAT_INC(tcps_rcvtotal); 615 616 #ifdef INET6 617 if (isipv6) { 618 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 619 620 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 621 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 622 if (m == NULL) { 623 TCPSTAT_INC(tcps_rcvshort); 624 return (IPPROTO_DONE); 625 } 626 } 627 628 ip6 = mtod(m, struct ip6_hdr *); 629 th = (struct tcphdr *)((caddr_t)ip6 + off0); 630 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 631 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 632 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 633 th->th_sum = m->m_pkthdr.csum_data; 634 else 635 th->th_sum = in6_cksum_pseudo(ip6, tlen, 636 IPPROTO_TCP, m->m_pkthdr.csum_data); 637 th->th_sum ^= 0xffff; 638 } else 639 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 640 if (th->th_sum) { 641 TCPSTAT_INC(tcps_rcvbadsum); 642 goto drop; 643 } 644 645 /* 646 * Be proactive about unspecified IPv6 address in source. 647 * As we use all-zero to indicate unbounded/unconnected pcb, 648 * unspecified IPv6 address can be used to confuse us. 649 * 650 * Note that packets with unspecified IPv6 destination is 651 * already dropped in ip6_input. 652 */ 653 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 654 /* XXX stat */ 655 goto drop; 656 } 657 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 658 } 659 #endif 660 #if defined(INET) && defined(INET6) 661 else 662 #endif 663 #ifdef INET 664 { 665 /* 666 * Get IP and TCP header together in first mbuf. 667 * Note: IP leaves IP header in first mbuf. 668 */ 669 if (off0 > sizeof (struct ip)) { 670 ip_stripoptions(m); 671 off0 = sizeof(struct ip); 672 } 673 if (m->m_len < sizeof (struct tcpiphdr)) { 674 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 675 == NULL) { 676 TCPSTAT_INC(tcps_rcvshort); 677 return (IPPROTO_DONE); 678 } 679 } 680 ip = mtod(m, struct ip *); 681 th = (struct tcphdr *)((caddr_t)ip + off0); 682 tlen = ntohs(ip->ip_len) - off0; 683 684 iptos = ip->ip_tos; 685 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 686 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 687 th->th_sum = m->m_pkthdr.csum_data; 688 else 689 th->th_sum = in_pseudo(ip->ip_src.s_addr, 690 ip->ip_dst.s_addr, 691 htonl(m->m_pkthdr.csum_data + tlen + 692 IPPROTO_TCP)); 693 th->th_sum ^= 0xffff; 694 } else { 695 struct ipovly *ipov = (struct ipovly *)ip; 696 697 /* 698 * Checksum extended TCP header and data. 699 */ 700 len = off0 + tlen; 701 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 702 ipov->ih_len = htons(tlen); 703 th->th_sum = in_cksum(m, len); 704 /* Reset length for SDT probes. */ 705 ip->ip_len = htons(len); 706 /* Reset TOS bits */ 707 ip->ip_tos = iptos; 708 /* Re-initialization for later version check */ 709 ip->ip_v = IPVERSION; 710 ip->ip_hl = off0 >> 2; 711 } 712 713 if (th->th_sum) { 714 TCPSTAT_INC(tcps_rcvbadsum); 715 goto drop; 716 } 717 } 718 #endif /* INET */ 719 720 /* 721 * Check that TCP offset makes sense, 722 * pull out TCP options and adjust length. XXX 723 */ 724 off = th->th_off << 2; 725 if (off < sizeof (struct tcphdr) || off > tlen) { 726 TCPSTAT_INC(tcps_rcvbadoff); 727 goto drop; 728 } 729 tlen -= off; /* tlen is used instead of ti->ti_len */ 730 if (off > sizeof (struct tcphdr)) { 731 #ifdef INET6 732 if (isipv6) { 733 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 734 ip6 = mtod(m, struct ip6_hdr *); 735 th = (struct tcphdr *)((caddr_t)ip6 + off0); 736 } 737 #endif 738 #if defined(INET) && defined(INET6) 739 else 740 #endif 741 #ifdef INET 742 { 743 if (m->m_len < sizeof(struct ip) + off) { 744 if ((m = m_pullup(m, sizeof (struct ip) + off)) 745 == NULL) { 746 TCPSTAT_INC(tcps_rcvshort); 747 return (IPPROTO_DONE); 748 } 749 ip = mtod(m, struct ip *); 750 th = (struct tcphdr *)((caddr_t)ip + off0); 751 } 752 } 753 #endif 754 optlen = off - sizeof (struct tcphdr); 755 optp = (u_char *)(th + 1); 756 } 757 thflags = th->th_flags; 758 759 /* 760 * Convert TCP protocol specific fields to host format. 761 */ 762 tcp_fields_to_host(th); 763 764 /* 765 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 766 */ 767 drop_hdrlen = off0 + off; 768 769 /* 770 * Locate pcb for segment; if we're likely to add or remove a 771 * connection then first acquire pcbinfo lock. There are three cases 772 * where we might discover later we need a write lock despite the 773 * flags: ACKs moving a connection out of the syncache, ACKs for a 774 * connection in TIMEWAIT and SYNs not targeting a listening socket. 775 */ 776 if ((thflags & (TH_FIN | TH_RST)) != 0) { 777 INP_INFO_RLOCK_ET(&V_tcbinfo, et); 778 ti_locked = TI_RLOCKED; 779 } else 780 ti_locked = TI_UNLOCKED; 781 782 /* 783 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 784 */ 785 if ( 786 #ifdef INET6 787 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 788 #ifdef INET 789 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 790 #endif 791 #endif 792 #if defined(INET) && !defined(INET6) 793 (m->m_flags & M_IP_NEXTHOP) 794 #endif 795 ) 796 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 797 798 findpcb: 799 #ifdef INVARIANTS 800 if (ti_locked == TI_RLOCKED) { 801 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 802 } else { 803 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 804 } 805 #endif 806 #ifdef INET6 807 if (isipv6 && fwd_tag != NULL) { 808 struct sockaddr_in6 *next_hop6; 809 810 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 811 /* 812 * Transparently forwarded. Pretend to be the destination. 813 * Already got one like this? 814 */ 815 inp = in6_pcblookup_mbuf(&V_tcbinfo, 816 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 817 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 818 if (!inp) { 819 /* 820 * It's new. Try to find the ambushing socket. 821 * Because we've rewritten the destination address, 822 * any hardware-generated hash is ignored. 823 */ 824 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 825 th->th_sport, &next_hop6->sin6_addr, 826 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 827 th->th_dport, INPLOOKUP_WILDCARD | 828 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 829 } 830 } else if (isipv6) { 831 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 832 th->th_sport, &ip6->ip6_dst, th->th_dport, 833 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 834 m->m_pkthdr.rcvif, m); 835 } 836 #endif /* INET6 */ 837 #if defined(INET6) && defined(INET) 838 else 839 #endif 840 #ifdef INET 841 if (fwd_tag != NULL) { 842 struct sockaddr_in *next_hop; 843 844 next_hop = (struct sockaddr_in *)(fwd_tag+1); 845 /* 846 * Transparently forwarded. Pretend to be the destination. 847 * already got one like this? 848 */ 849 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 850 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 851 m->m_pkthdr.rcvif, m); 852 if (!inp) { 853 /* 854 * It's new. Try to find the ambushing socket. 855 * Because we've rewritten the destination address, 856 * any hardware-generated hash is ignored. 857 */ 858 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 859 th->th_sport, next_hop->sin_addr, 860 next_hop->sin_port ? ntohs(next_hop->sin_port) : 861 th->th_dport, INPLOOKUP_WILDCARD | 862 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 863 } 864 } else 865 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 866 th->th_sport, ip->ip_dst, th->th_dport, 867 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 868 m->m_pkthdr.rcvif, m); 869 #endif /* INET */ 870 871 /* 872 * If the INPCB does not exist then all data in the incoming 873 * segment is discarded and an appropriate RST is sent back. 874 * XXX MRT Send RST using which routing table? 875 */ 876 if (inp == NULL) { 877 /* 878 * Log communication attempts to ports that are not 879 * in use. 880 */ 881 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 882 tcp_log_in_vain == 2) { 883 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 884 log(LOG_INFO, "%s; %s: Connection attempt " 885 "to closed port\n", s, __func__); 886 } 887 /* 888 * When blackholing do not respond with a RST but 889 * completely ignore the segment and drop it. 890 */ 891 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 892 V_blackhole == 2) 893 goto dropunlock; 894 895 rstreason = BANDLIM_RST_CLOSEDPORT; 896 goto dropwithreset; 897 } 898 INP_WLOCK_ASSERT(inp); 899 /* 900 * While waiting for inp lock during the lookup, another thread 901 * can have dropped the inpcb, in which case we need to loop back 902 * and try to find a new inpcb to deliver to. 903 */ 904 if (inp->inp_flags & INP_DROPPED) { 905 INP_WUNLOCK(inp); 906 inp = NULL; 907 goto findpcb; 908 } 909 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 910 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 911 ((inp->inp_socket == NULL) || 912 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 913 inp->inp_flowid = m->m_pkthdr.flowid; 914 inp->inp_flowtype = M_HASHTYPE_GET(m); 915 } 916 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 917 #ifdef INET6 918 if (isipv6 && IPSEC_ENABLED(ipv6) && 919 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 920 goto dropunlock; 921 } 922 #ifdef INET 923 else 924 #endif 925 #endif /* INET6 */ 926 #ifdef INET 927 if (IPSEC_ENABLED(ipv4) && 928 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 929 goto dropunlock; 930 } 931 #endif /* INET */ 932 #endif /* IPSEC */ 933 934 /* 935 * Check the minimum TTL for socket. 936 */ 937 if (inp->inp_ip_minttl != 0) { 938 #ifdef INET6 939 if (isipv6) { 940 if (inp->inp_ip_minttl > ip6->ip6_hlim) 941 goto dropunlock; 942 } else 943 #endif 944 if (inp->inp_ip_minttl > ip->ip_ttl) 945 goto dropunlock; 946 } 947 948 /* 949 * A previous connection in TIMEWAIT state is supposed to catch stray 950 * or duplicate segments arriving late. If this segment was a 951 * legitimate new connection attempt, the old INPCB gets removed and 952 * we can try again to find a listening socket. 953 * 954 * At this point, due to earlier optimism, we may hold only an inpcb 955 * lock, and not the inpcbinfo write lock. If so, we need to try to 956 * acquire it, or if that fails, acquire a reference on the inpcb, 957 * drop all locks, acquire a global write lock, and then re-acquire 958 * the inpcb lock. We may at that point discover that another thread 959 * has tried to free the inpcb, in which case we need to loop back 960 * and try to find a new inpcb to deliver to. 961 * 962 * XXXRW: It may be time to rethink timewait locking. 963 */ 964 if (inp->inp_flags & INP_TIMEWAIT) { 965 if (ti_locked == TI_UNLOCKED) { 966 INP_INFO_RLOCK_ET(&V_tcbinfo, et); 967 ti_locked = TI_RLOCKED; 968 } 969 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 970 971 if (thflags & TH_SYN) 972 tcp_dooptions(&to, optp, optlen, TO_SYN); 973 /* 974 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 975 */ 976 if (tcp_twcheck(inp, &to, th, m, tlen)) 977 goto findpcb; 978 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et); 979 return (IPPROTO_DONE); 980 } 981 /* 982 * The TCPCB may no longer exist if the connection is winding 983 * down or it is in the CLOSED state. Either way we drop the 984 * segment and send an appropriate response. 985 */ 986 tp = intotcpcb(inp); 987 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 988 rstreason = BANDLIM_RST_CLOSEDPORT; 989 goto dropwithreset; 990 } 991 992 #ifdef TCP_OFFLOAD 993 if (tp->t_flags & TF_TOE) { 994 tcp_offload_input(tp, m); 995 m = NULL; /* consumed by the TOE driver */ 996 goto dropunlock; 997 } 998 #endif 999 1000 /* 1001 * We've identified a valid inpcb, but it could be that we need an 1002 * inpcbinfo write lock but don't hold it. In this case, attempt to 1003 * acquire using the same strategy as the TIMEWAIT case above. If we 1004 * relock, we have to jump back to 'relocked' as the connection might 1005 * now be in TIMEWAIT. 1006 */ 1007 #ifdef INVARIANTS 1008 if ((thflags & (TH_FIN | TH_RST)) != 0) 1009 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1010 #endif 1011 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) || 1012 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) && 1013 !IS_FASTOPEN(tp->t_flags)))) { 1014 if (ti_locked == TI_UNLOCKED) { 1015 INP_INFO_RLOCK_ET(&V_tcbinfo, et); 1016 ti_locked = TI_RLOCKED; 1017 } 1018 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1019 } 1020 1021 #ifdef MAC 1022 INP_WLOCK_ASSERT(inp); 1023 if (mac_inpcb_check_deliver(inp, m)) 1024 goto dropunlock; 1025 #endif 1026 so = inp->inp_socket; 1027 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1028 #ifdef TCPDEBUG 1029 if (so->so_options & SO_DEBUG) { 1030 ostate = tp->t_state; 1031 #ifdef INET6 1032 if (isipv6) { 1033 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1034 } else 1035 #endif 1036 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1037 tcp_savetcp = *th; 1038 } 1039 #endif /* TCPDEBUG */ 1040 /* 1041 * When the socket is accepting connections (the INPCB is in LISTEN 1042 * state) we look into the SYN cache if this is a new connection 1043 * attempt or the completion of a previous one. 1044 */ 1045 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1046 ("%s: so accepting but tp %p not listening", __func__, tp)); 1047 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1048 struct in_conninfo inc; 1049 1050 bzero(&inc, sizeof(inc)); 1051 #ifdef INET6 1052 if (isipv6) { 1053 inc.inc_flags |= INC_ISIPV6; 1054 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1055 inc.inc_flags |= INC_IPV6MINMTU; 1056 inc.inc6_faddr = ip6->ip6_src; 1057 inc.inc6_laddr = ip6->ip6_dst; 1058 } else 1059 #endif 1060 { 1061 inc.inc_faddr = ip->ip_src; 1062 inc.inc_laddr = ip->ip_dst; 1063 } 1064 inc.inc_fport = th->th_sport; 1065 inc.inc_lport = th->th_dport; 1066 inc.inc_fibnum = so->so_fibnum; 1067 1068 /* 1069 * Check for an existing connection attempt in syncache if 1070 * the flag is only ACK. A successful lookup creates a new 1071 * socket appended to the listen queue in SYN_RECEIVED state. 1072 */ 1073 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1074 1075 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1076 /* 1077 * Parse the TCP options here because 1078 * syncookies need access to the reflected 1079 * timestamp. 1080 */ 1081 tcp_dooptions(&to, optp, optlen, 0); 1082 /* 1083 * NB: syncache_expand() doesn't unlock 1084 * inp and tcpinfo locks. 1085 */ 1086 rstreason = syncache_expand(&inc, &to, th, &so, m); 1087 if (rstreason < 0) { 1088 /* 1089 * A failing TCP MD5 signature comparison 1090 * must result in the segment being dropped 1091 * and must not produce any response back 1092 * to the sender. 1093 */ 1094 goto dropunlock; 1095 } else if (rstreason == 0) { 1096 /* 1097 * No syncache entry or ACK was not 1098 * for our SYN/ACK. Send a RST. 1099 * NB: syncache did its own logging 1100 * of the failure cause. 1101 */ 1102 rstreason = BANDLIM_RST_OPENPORT; 1103 goto dropwithreset; 1104 } 1105 tfo_socket_result: 1106 if (so == NULL) { 1107 /* 1108 * We completed the 3-way handshake 1109 * but could not allocate a socket 1110 * either due to memory shortage, 1111 * listen queue length limits or 1112 * global socket limits. Send RST 1113 * or wait and have the remote end 1114 * retransmit the ACK for another 1115 * try. 1116 */ 1117 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1118 log(LOG_DEBUG, "%s; %s: Listen socket: " 1119 "Socket allocation failed due to " 1120 "limits or memory shortage, %s\n", 1121 s, __func__, 1122 V_tcp_sc_rst_sock_fail ? 1123 "sending RST" : "try again"); 1124 if (V_tcp_sc_rst_sock_fail) { 1125 rstreason = BANDLIM_UNLIMITED; 1126 goto dropwithreset; 1127 } else 1128 goto dropunlock; 1129 } 1130 /* 1131 * Socket is created in state SYN_RECEIVED. 1132 * Unlock the listen socket, lock the newly 1133 * created socket and update the tp variable. 1134 */ 1135 INP_WUNLOCK(inp); /* listen socket */ 1136 inp = sotoinpcb(so); 1137 /* 1138 * New connection inpcb is already locked by 1139 * syncache_expand(). 1140 */ 1141 INP_WLOCK_ASSERT(inp); 1142 tp = intotcpcb(inp); 1143 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1144 ("%s: ", __func__)); 1145 /* 1146 * Process the segment and the data it 1147 * contains. tcp_do_segment() consumes 1148 * the mbuf chain and unlocks the inpcb. 1149 */ 1150 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1151 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1152 iptos); 1153 if (ti_locked == TI_RLOCKED) 1154 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et); 1155 return (IPPROTO_DONE); 1156 } 1157 /* 1158 * Segment flag validation for new connection attempts: 1159 * 1160 * Our (SYN|ACK) response was rejected. 1161 * Check with syncache and remove entry to prevent 1162 * retransmits. 1163 * 1164 * NB: syncache_chkrst does its own logging of failure 1165 * causes. 1166 */ 1167 if (thflags & TH_RST) { 1168 syncache_chkrst(&inc, th, m); 1169 goto dropunlock; 1170 } 1171 /* 1172 * We can't do anything without SYN. 1173 */ 1174 if ((thflags & TH_SYN) == 0) { 1175 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1176 log(LOG_DEBUG, "%s; %s: Listen socket: " 1177 "SYN is missing, segment ignored\n", 1178 s, __func__); 1179 TCPSTAT_INC(tcps_badsyn); 1180 goto dropunlock; 1181 } 1182 /* 1183 * (SYN|ACK) is bogus on a listen socket. 1184 */ 1185 if (thflags & TH_ACK) { 1186 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1187 log(LOG_DEBUG, "%s; %s: Listen socket: " 1188 "SYN|ACK invalid, segment rejected\n", 1189 s, __func__); 1190 syncache_badack(&inc); /* XXX: Not needed! */ 1191 TCPSTAT_INC(tcps_badsyn); 1192 rstreason = BANDLIM_RST_OPENPORT; 1193 goto dropwithreset; 1194 } 1195 /* 1196 * If the drop_synfin option is enabled, drop all 1197 * segments with both the SYN and FIN bits set. 1198 * This prevents e.g. nmap from identifying the 1199 * TCP/IP stack. 1200 * XXX: Poor reasoning. nmap has other methods 1201 * and is constantly refining its stack detection 1202 * strategies. 1203 * XXX: This is a violation of the TCP specification 1204 * and was used by RFC1644. 1205 */ 1206 if ((thflags & TH_FIN) && V_drop_synfin) { 1207 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1208 log(LOG_DEBUG, "%s; %s: Listen socket: " 1209 "SYN|FIN segment ignored (based on " 1210 "sysctl setting)\n", s, __func__); 1211 TCPSTAT_INC(tcps_badsyn); 1212 goto dropunlock; 1213 } 1214 /* 1215 * Segment's flags are (SYN) or (SYN|FIN). 1216 * 1217 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1218 * as they do not affect the state of the TCP FSM. 1219 * The data pointed to by TH_URG and th_urp is ignored. 1220 */ 1221 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1222 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1223 KASSERT(thflags & (TH_SYN), 1224 ("%s: Listen socket: TH_SYN not set", __func__)); 1225 #ifdef INET6 1226 /* 1227 * If deprecated address is forbidden, 1228 * we do not accept SYN to deprecated interface 1229 * address to prevent any new inbound connection from 1230 * getting established. 1231 * When we do not accept SYN, we send a TCP RST, 1232 * with deprecated source address (instead of dropping 1233 * it). We compromise it as it is much better for peer 1234 * to send a RST, and RST will be the final packet 1235 * for the exchange. 1236 * 1237 * If we do not forbid deprecated addresses, we accept 1238 * the SYN packet. RFC2462 does not suggest dropping 1239 * SYN in this case. 1240 * If we decipher RFC2462 5.5.4, it says like this: 1241 * 1. use of deprecated addr with existing 1242 * communication is okay - "SHOULD continue to be 1243 * used" 1244 * 2. use of it with new communication: 1245 * (2a) "SHOULD NOT be used if alternate address 1246 * with sufficient scope is available" 1247 * (2b) nothing mentioned otherwise. 1248 * Here we fall into (2b) case as we have no choice in 1249 * our source address selection - we must obey the peer. 1250 * 1251 * The wording in RFC2462 is confusing, and there are 1252 * multiple description text for deprecated address 1253 * handling - worse, they are not exactly the same. 1254 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1255 */ 1256 if (isipv6 && !V_ip6_use_deprecated) { 1257 struct in6_ifaddr *ia6; 1258 1259 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1260 if (ia6 != NULL && 1261 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1262 ifa_free(&ia6->ia_ifa); 1263 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1264 log(LOG_DEBUG, "%s; %s: Listen socket: " 1265 "Connection attempt to deprecated " 1266 "IPv6 address rejected\n", 1267 s, __func__); 1268 rstreason = BANDLIM_RST_OPENPORT; 1269 goto dropwithreset; 1270 } 1271 if (ia6) 1272 ifa_free(&ia6->ia_ifa); 1273 } 1274 #endif /* INET6 */ 1275 /* 1276 * Basic sanity checks on incoming SYN requests: 1277 * Don't respond if the destination is a link layer 1278 * broadcast according to RFC1122 4.2.3.10, p. 104. 1279 * If it is from this socket it must be forged. 1280 * Don't respond if the source or destination is a 1281 * global or subnet broad- or multicast address. 1282 * Note that it is quite possible to receive unicast 1283 * link-layer packets with a broadcast IP address. Use 1284 * in_broadcast() to find them. 1285 */ 1286 if (m->m_flags & (M_BCAST|M_MCAST)) { 1287 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1288 log(LOG_DEBUG, "%s; %s: Listen socket: " 1289 "Connection attempt from broad- or multicast " 1290 "link layer address ignored\n", s, __func__); 1291 goto dropunlock; 1292 } 1293 #ifdef INET6 1294 if (isipv6) { 1295 if (th->th_dport == th->th_sport && 1296 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1297 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1298 log(LOG_DEBUG, "%s; %s: Listen socket: " 1299 "Connection attempt to/from self " 1300 "ignored\n", s, __func__); 1301 goto dropunlock; 1302 } 1303 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1304 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1305 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1306 log(LOG_DEBUG, "%s; %s: Listen socket: " 1307 "Connection attempt from/to multicast " 1308 "address ignored\n", s, __func__); 1309 goto dropunlock; 1310 } 1311 } 1312 #endif 1313 #if defined(INET) && defined(INET6) 1314 else 1315 #endif 1316 #ifdef INET 1317 { 1318 if (th->th_dport == th->th_sport && 1319 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1320 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1321 log(LOG_DEBUG, "%s; %s: Listen socket: " 1322 "Connection attempt from/to self " 1323 "ignored\n", s, __func__); 1324 goto dropunlock; 1325 } 1326 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1327 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1328 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1329 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1330 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1331 log(LOG_DEBUG, "%s; %s: Listen socket: " 1332 "Connection attempt from/to broad- " 1333 "or multicast address ignored\n", 1334 s, __func__); 1335 goto dropunlock; 1336 } 1337 } 1338 #endif 1339 /* 1340 * SYN appears to be valid. Create compressed TCP state 1341 * for syncache. 1342 */ 1343 #ifdef TCPDEBUG 1344 if (so->so_options & SO_DEBUG) 1345 tcp_trace(TA_INPUT, ostate, tp, 1346 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1347 #endif 1348 TCP_PROBE3(debug__input, tp, th, m); 1349 tcp_dooptions(&to, optp, optlen, TO_SYN); 1350 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL)) 1351 goto tfo_socket_result; 1352 1353 /* 1354 * Entry added to syncache and mbuf consumed. 1355 * Only the listen socket is unlocked by syncache_add(). 1356 */ 1357 if (ti_locked == TI_RLOCKED) { 1358 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et); 1359 ti_locked = TI_UNLOCKED; 1360 } 1361 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1362 return (IPPROTO_DONE); 1363 } else if (tp->t_state == TCPS_LISTEN) { 1364 /* 1365 * When a listen socket is torn down the SO_ACCEPTCONN 1366 * flag is removed first while connections are drained 1367 * from the accept queue in a unlock/lock cycle of the 1368 * ACCEPT_LOCK, opening a race condition allowing a SYN 1369 * attempt go through unhandled. 1370 */ 1371 goto dropunlock; 1372 } 1373 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1374 if (tp->t_flags & TF_SIGNATURE) { 1375 tcp_dooptions(&to, optp, optlen, thflags); 1376 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1377 TCPSTAT_INC(tcps_sig_err_nosigopt); 1378 goto dropunlock; 1379 } 1380 if (!TCPMD5_ENABLED() || 1381 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1382 goto dropunlock; 1383 } 1384 #endif 1385 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1386 1387 /* 1388 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1389 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1390 * the inpcb, and unlocks pcbinfo. 1391 */ 1392 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1393 if (ti_locked == TI_RLOCKED) 1394 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et); 1395 return (IPPROTO_DONE); 1396 1397 dropwithreset: 1398 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1399 1400 if (ti_locked == TI_RLOCKED) { 1401 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et); 1402 ti_locked = TI_UNLOCKED; 1403 } 1404 #ifdef INVARIANTS 1405 else { 1406 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1407 "ti_locked: %d", __func__, ti_locked)); 1408 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1409 } 1410 #endif 1411 1412 if (inp != NULL) { 1413 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1414 INP_WUNLOCK(inp); 1415 } else 1416 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1417 m = NULL; /* mbuf chain got consumed. */ 1418 goto drop; 1419 1420 dropunlock: 1421 if (m != NULL) 1422 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1423 1424 if (ti_locked == TI_RLOCKED) { 1425 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et); 1426 ti_locked = TI_UNLOCKED; 1427 } 1428 #ifdef INVARIANTS 1429 else { 1430 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1431 "ti_locked: %d", __func__, ti_locked)); 1432 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1433 } 1434 #endif 1435 1436 if (inp != NULL) 1437 INP_WUNLOCK(inp); 1438 1439 drop: 1440 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1441 if (s != NULL) 1442 free(s, M_TCPLOG); 1443 if (m != NULL) 1444 m_freem(m); 1445 return (IPPROTO_DONE); 1446 } 1447 1448 /* 1449 * Automatic sizing of receive socket buffer. Often the send 1450 * buffer size is not optimally adjusted to the actual network 1451 * conditions at hand (delay bandwidth product). Setting the 1452 * buffer size too small limits throughput on links with high 1453 * bandwidth and high delay (eg. trans-continental/oceanic links). 1454 * 1455 * On the receive side the socket buffer memory is only rarely 1456 * used to any significant extent. This allows us to be much 1457 * more aggressive in scaling the receive socket buffer. For 1458 * the case that the buffer space is actually used to a large 1459 * extent and we run out of kernel memory we can simply drop 1460 * the new segments; TCP on the sender will just retransmit it 1461 * later. Setting the buffer size too big may only consume too 1462 * much kernel memory if the application doesn't read() from 1463 * the socket or packet loss or reordering makes use of the 1464 * reassembly queue. 1465 * 1466 * The criteria to step up the receive buffer one notch are: 1467 * 1. Application has not set receive buffer size with 1468 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1469 * 2. the number of bytes received during the time it takes 1470 * one timestamp to be reflected back to us (the RTT); 1471 * 3. received bytes per RTT is within seven eighth of the 1472 * current socket buffer size; 1473 * 4. receive buffer size has not hit maximal automatic size; 1474 * 1475 * This algorithm does one step per RTT at most and only if 1476 * we receive a bulk stream w/o packet losses or reorderings. 1477 * Shrinking the buffer during idle times is not necessary as 1478 * it doesn't consume any memory when idle. 1479 * 1480 * TODO: Only step up if the application is actually serving 1481 * the buffer to better manage the socket buffer resources. 1482 */ 1483 int 1484 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1485 struct tcpcb *tp, int tlen) 1486 { 1487 int newsize = 0; 1488 1489 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1490 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1491 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1492 (tp->t_srtt >> TCP_RTT_SHIFT)) { 1493 if (tp->rfbuf_cnt > (so->so_rcv.sb_hiwat / 8 * 7) && 1494 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1495 newsize = min(so->so_rcv.sb_hiwat + 1496 V_tcp_autorcvbuf_inc, V_tcp_autorcvbuf_max); 1497 } 1498 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1499 1500 /* Start over with next RTT. */ 1501 tp->rfbuf_ts = 0; 1502 tp->rfbuf_cnt = 0; 1503 } else { 1504 tp->rfbuf_cnt += tlen; /* add up */ 1505 } 1506 1507 return (newsize); 1508 } 1509 1510 void 1511 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1512 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1513 { 1514 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1515 int rstreason, todrop, win; 1516 uint32_t tiwin; 1517 uint16_t nsegs; 1518 char *s; 1519 struct in_conninfo *inc; 1520 struct mbuf *mfree; 1521 struct tcpopt to; 1522 int tfo_syn; 1523 1524 #ifdef TCPDEBUG 1525 /* 1526 * The size of tcp_saveipgen must be the size of the max ip header, 1527 * now IPv6. 1528 */ 1529 u_char tcp_saveipgen[IP6_HDR_LEN]; 1530 struct tcphdr tcp_savetcp; 1531 short ostate = 0; 1532 #endif 1533 thflags = th->th_flags; 1534 inc = &tp->t_inpcb->inp_inc; 1535 tp->sackhint.last_sack_ack = 0; 1536 sack_changed = 0; 1537 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1538 /* 1539 * If this is either a state-changing packet or current state isn't 1540 * established, we require a write lock on tcbinfo. Otherwise, we 1541 * allow the tcbinfo to be in either alocked or unlocked, as the 1542 * caller may have unnecessarily acquired a write lock due to a race. 1543 */ 1544 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1545 tp->t_state != TCPS_ESTABLISHED) { 1546 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1547 } 1548 INP_WLOCK_ASSERT(tp->t_inpcb); 1549 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1550 __func__)); 1551 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1552 __func__)); 1553 1554 #ifdef TCPPCAP 1555 /* Save segment, if requested. */ 1556 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1557 #endif 1558 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1559 tlen, NULL, true); 1560 1561 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1562 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1563 log(LOG_DEBUG, "%s; %s: " 1564 "SYN|FIN segment ignored (based on " 1565 "sysctl setting)\n", s, __func__); 1566 free(s, M_TCPLOG); 1567 } 1568 goto drop; 1569 } 1570 1571 /* 1572 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1573 * check SEQ.ACK first. 1574 */ 1575 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1576 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1577 rstreason = BANDLIM_UNLIMITED; 1578 goto dropwithreset; 1579 } 1580 1581 /* 1582 * Segment received on connection. 1583 * Reset idle time and keep-alive timer. 1584 * XXX: This should be done after segment 1585 * validation to ignore broken/spoofed segs. 1586 */ 1587 tp->t_rcvtime = ticks; 1588 1589 /* 1590 * Scale up the window into a 32-bit value. 1591 * For the SYN_SENT state the scale is zero. 1592 */ 1593 tiwin = th->th_win << tp->snd_scale; 1594 1595 /* 1596 * TCP ECN processing. 1597 */ 1598 if (tp->t_flags & TF_ECN_PERMIT) { 1599 if (thflags & TH_CWR) 1600 tp->t_flags &= ~TF_ECN_SND_ECE; 1601 switch (iptos & IPTOS_ECN_MASK) { 1602 case IPTOS_ECN_CE: 1603 tp->t_flags |= TF_ECN_SND_ECE; 1604 TCPSTAT_INC(tcps_ecn_ce); 1605 break; 1606 case IPTOS_ECN_ECT0: 1607 TCPSTAT_INC(tcps_ecn_ect0); 1608 break; 1609 case IPTOS_ECN_ECT1: 1610 TCPSTAT_INC(tcps_ecn_ect1); 1611 break; 1612 } 1613 1614 /* Process a packet differently from RFC3168. */ 1615 cc_ecnpkt_handler(tp, th, iptos); 1616 1617 /* Congestion experienced. */ 1618 if (thflags & TH_ECE) { 1619 cc_cong_signal(tp, th, CC_ECN); 1620 } 1621 } 1622 1623 /* 1624 * Parse options on any incoming segment. 1625 */ 1626 tcp_dooptions(&to, (u_char *)(th + 1), 1627 (th->th_off << 2) - sizeof(struct tcphdr), 1628 (thflags & TH_SYN) ? TO_SYN : 0); 1629 1630 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1631 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1632 (to.to_flags & TOF_SIGNATURE) == 0) { 1633 TCPSTAT_INC(tcps_sig_err_sigopt); 1634 /* XXX: should drop? */ 1635 } 1636 #endif 1637 /* 1638 * If echoed timestamp is later than the current time, 1639 * fall back to non RFC1323 RTT calculation. Normalize 1640 * timestamp if syncookies were used when this connection 1641 * was established. 1642 */ 1643 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1644 to.to_tsecr -= tp->ts_offset; 1645 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1646 to.to_tsecr = 0; 1647 else if (tp->t_flags & TF_PREVVALID && 1648 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 1649 cc_cong_signal(tp, th, CC_RTO_ERR); 1650 } 1651 /* 1652 * Process options only when we get SYN/ACK back. The SYN case 1653 * for incoming connections is handled in tcp_syncache. 1654 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1655 * or <SYN,ACK>) segment itself is never scaled. 1656 * XXX this is traditional behavior, may need to be cleaned up. 1657 */ 1658 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1659 if ((to.to_flags & TOF_SCALE) && 1660 (tp->t_flags & TF_REQ_SCALE)) { 1661 tp->t_flags |= TF_RCVD_SCALE; 1662 tp->snd_scale = to.to_wscale; 1663 } 1664 /* 1665 * Initial send window. It will be updated with 1666 * the next incoming segment to the scaled value. 1667 */ 1668 tp->snd_wnd = th->th_win; 1669 if (to.to_flags & TOF_TS) { 1670 tp->t_flags |= TF_RCVD_TSTMP; 1671 tp->ts_recent = to.to_tsval; 1672 tp->ts_recent_age = tcp_ts_getticks(); 1673 } 1674 if (to.to_flags & TOF_MSS) 1675 tcp_mss(tp, to.to_mss); 1676 if ((tp->t_flags & TF_SACK_PERMIT) && 1677 (to.to_flags & TOF_SACKPERM) == 0) 1678 tp->t_flags &= ~TF_SACK_PERMIT; 1679 if (IS_FASTOPEN(tp->t_flags)) { 1680 if (to.to_flags & TOF_FASTOPEN) { 1681 uint16_t mss; 1682 1683 if (to.to_flags & TOF_MSS) 1684 mss = to.to_mss; 1685 else 1686 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1687 mss = TCP6_MSS; 1688 else 1689 mss = TCP_MSS; 1690 tcp_fastopen_update_cache(tp, mss, 1691 to.to_tfo_len, to.to_tfo_cookie); 1692 } else 1693 tcp_fastopen_disable_path(tp); 1694 } 1695 } 1696 1697 /* 1698 * If timestamps were negotiated during SYN/ACK they should 1699 * appear on every segment during this session and vice versa. 1700 */ 1701 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1702 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1703 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1704 "no action\n", s, __func__); 1705 free(s, M_TCPLOG); 1706 } 1707 } 1708 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1709 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1710 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1711 "no action\n", s, __func__); 1712 free(s, M_TCPLOG); 1713 } 1714 } 1715 1716 /* 1717 * Header prediction: check for the two common cases 1718 * of a uni-directional data xfer. If the packet has 1719 * no control flags, is in-sequence, the window didn't 1720 * change and we're not retransmitting, it's a 1721 * candidate. If the length is zero and the ack moved 1722 * forward, we're the sender side of the xfer. Just 1723 * free the data acked & wake any higher level process 1724 * that was blocked waiting for space. If the length 1725 * is non-zero and the ack didn't move, we're the 1726 * receiver side. If we're getting packets in-order 1727 * (the reassembly queue is empty), add the data to 1728 * the socket buffer and note that we need a delayed ack. 1729 * Make sure that the hidden state-flags are also off. 1730 * Since we check for TCPS_ESTABLISHED first, it can only 1731 * be TH_NEEDSYN. 1732 */ 1733 if (tp->t_state == TCPS_ESTABLISHED && 1734 th->th_seq == tp->rcv_nxt && 1735 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1736 tp->snd_nxt == tp->snd_max && 1737 tiwin && tiwin == tp->snd_wnd && 1738 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1739 SEGQ_EMPTY(tp) && 1740 ((to.to_flags & TOF_TS) == 0 || 1741 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1742 1743 /* 1744 * If last ACK falls within this segment's sequence numbers, 1745 * record the timestamp. 1746 * NOTE that the test is modified according to the latest 1747 * proposal of the [email protected] list (Braden 1993/04/26). 1748 */ 1749 if ((to.to_flags & TOF_TS) != 0 && 1750 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1751 tp->ts_recent_age = tcp_ts_getticks(); 1752 tp->ts_recent = to.to_tsval; 1753 } 1754 1755 if (tlen == 0) { 1756 if (SEQ_GT(th->th_ack, tp->snd_una) && 1757 SEQ_LEQ(th->th_ack, tp->snd_max) && 1758 !IN_RECOVERY(tp->t_flags) && 1759 (to.to_flags & TOF_SACK) == 0 && 1760 TAILQ_EMPTY(&tp->snd_holes)) { 1761 /* 1762 * This is a pure ack for outstanding data. 1763 */ 1764 TCPSTAT_INC(tcps_predack); 1765 1766 /* 1767 * "bad retransmit" recovery without timestamps. 1768 */ 1769 if ((to.to_flags & TOF_TS) == 0 && 1770 tp->t_rxtshift == 1 && 1771 tp->t_flags & TF_PREVVALID && 1772 (int)(ticks - tp->t_badrxtwin) < 0) { 1773 cc_cong_signal(tp, th, CC_RTO_ERR); 1774 } 1775 1776 /* 1777 * Recalculate the transmit timer / rtt. 1778 * 1779 * Some boxes send broken timestamp replies 1780 * during the SYN+ACK phase, ignore 1781 * timestamps of 0 or we could calculate a 1782 * huge RTT and blow up the retransmit timer. 1783 */ 1784 if ((to.to_flags & TOF_TS) != 0 && 1785 to.to_tsecr) { 1786 uint32_t t; 1787 1788 t = tcp_ts_getticks() - to.to_tsecr; 1789 if (!tp->t_rttlow || tp->t_rttlow > t) 1790 tp->t_rttlow = t; 1791 tcp_xmit_timer(tp, 1792 TCP_TS_TO_TICKS(t) + 1); 1793 } else if (tp->t_rtttime && 1794 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1795 if (!tp->t_rttlow || 1796 tp->t_rttlow > ticks - tp->t_rtttime) 1797 tp->t_rttlow = ticks - tp->t_rtttime; 1798 tcp_xmit_timer(tp, 1799 ticks - tp->t_rtttime); 1800 } 1801 acked = BYTES_THIS_ACK(tp, th); 1802 1803 #ifdef TCP_HHOOK 1804 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1805 hhook_run_tcp_est_in(tp, th, &to); 1806 #endif 1807 1808 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1809 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1810 sbdrop(&so->so_snd, acked); 1811 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1812 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1813 tp->snd_recover = th->th_ack - 1; 1814 1815 /* 1816 * Let the congestion control algorithm update 1817 * congestion control related information. This 1818 * typically means increasing the congestion 1819 * window. 1820 */ 1821 cc_ack_received(tp, th, nsegs, CC_ACK); 1822 1823 tp->snd_una = th->th_ack; 1824 /* 1825 * Pull snd_wl2 up to prevent seq wrap relative 1826 * to th_ack. 1827 */ 1828 tp->snd_wl2 = th->th_ack; 1829 tp->t_dupacks = 0; 1830 m_freem(m); 1831 1832 /* 1833 * If all outstanding data are acked, stop 1834 * retransmit timer, otherwise restart timer 1835 * using current (possibly backed-off) value. 1836 * If process is waiting for space, 1837 * wakeup/selwakeup/signal. If data 1838 * are ready to send, let tcp_output 1839 * decide between more output or persist. 1840 */ 1841 #ifdef TCPDEBUG 1842 if (so->so_options & SO_DEBUG) 1843 tcp_trace(TA_INPUT, ostate, tp, 1844 (void *)tcp_saveipgen, 1845 &tcp_savetcp, 0); 1846 #endif 1847 TCP_PROBE3(debug__input, tp, th, m); 1848 if (tp->snd_una == tp->snd_max) 1849 tcp_timer_activate(tp, TT_REXMT, 0); 1850 else if (!tcp_timer_active(tp, TT_PERSIST)) 1851 tcp_timer_activate(tp, TT_REXMT, 1852 tp->t_rxtcur); 1853 sowwakeup(so); 1854 if (sbavail(&so->so_snd)) 1855 (void) tp->t_fb->tfb_tcp_output(tp); 1856 goto check_delack; 1857 } 1858 } else if (th->th_ack == tp->snd_una && 1859 tlen <= sbspace(&so->so_rcv)) { 1860 int newsize = 0; /* automatic sockbuf scaling */ 1861 1862 /* 1863 * This is a pure, in-sequence data packet with 1864 * nothing on the reassembly queue and we have enough 1865 * buffer space to take it. 1866 */ 1867 /* Clean receiver SACK report if present */ 1868 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1869 tcp_clean_sackreport(tp); 1870 TCPSTAT_INC(tcps_preddat); 1871 tp->rcv_nxt += tlen; 1872 /* 1873 * Pull snd_wl1 up to prevent seq wrap relative to 1874 * th_seq. 1875 */ 1876 tp->snd_wl1 = th->th_seq; 1877 /* 1878 * Pull rcv_up up to prevent seq wrap relative to 1879 * rcv_nxt. 1880 */ 1881 tp->rcv_up = tp->rcv_nxt; 1882 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1883 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1884 #ifdef TCPDEBUG 1885 if (so->so_options & SO_DEBUG) 1886 tcp_trace(TA_INPUT, ostate, tp, 1887 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1888 #endif 1889 TCP_PROBE3(debug__input, tp, th, m); 1890 1891 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1892 1893 /* Add data to socket buffer. */ 1894 SOCKBUF_LOCK(&so->so_rcv); 1895 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1896 m_freem(m); 1897 } else { 1898 /* 1899 * Set new socket buffer size. 1900 * Give up when limit is reached. 1901 */ 1902 if (newsize) 1903 if (!sbreserve_locked(&so->so_rcv, 1904 newsize, so, NULL)) 1905 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1906 m_adj(m, drop_hdrlen); /* delayed header drop */ 1907 sbappendstream_locked(&so->so_rcv, m, 0); 1908 } 1909 /* NB: sorwakeup_locked() does an implicit unlock. */ 1910 sorwakeup_locked(so); 1911 if (DELAY_ACK(tp, tlen)) { 1912 tp->t_flags |= TF_DELACK; 1913 } else { 1914 tp->t_flags |= TF_ACKNOW; 1915 tp->t_fb->tfb_tcp_output(tp); 1916 } 1917 goto check_delack; 1918 } 1919 } 1920 1921 /* 1922 * Calculate amount of space in receive window, 1923 * and then do TCP input processing. 1924 * Receive window is amount of space in rcv queue, 1925 * but not less than advertised window. 1926 */ 1927 win = sbspace(&so->so_rcv); 1928 if (win < 0) 1929 win = 0; 1930 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1931 1932 switch (tp->t_state) { 1933 1934 /* 1935 * If the state is SYN_RECEIVED: 1936 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1937 */ 1938 case TCPS_SYN_RECEIVED: 1939 if ((thflags & TH_ACK) && 1940 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1941 SEQ_GT(th->th_ack, tp->snd_max))) { 1942 rstreason = BANDLIM_RST_OPENPORT; 1943 goto dropwithreset; 1944 } 1945 if (IS_FASTOPEN(tp->t_flags)) { 1946 /* 1947 * When a TFO connection is in SYN_RECEIVED, the 1948 * only valid packets are the initial SYN, a 1949 * retransmit/copy of the initial SYN (possibly with 1950 * a subset of the original data), a valid ACK, a 1951 * FIN, or a RST. 1952 */ 1953 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1954 rstreason = BANDLIM_RST_OPENPORT; 1955 goto dropwithreset; 1956 } else if (thflags & TH_SYN) { 1957 /* non-initial SYN is ignored */ 1958 if ((tcp_timer_active(tp, TT_DELACK) || 1959 tcp_timer_active(tp, TT_REXMT))) 1960 goto drop; 1961 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1962 goto drop; 1963 } 1964 } 1965 break; 1966 1967 /* 1968 * If the state is SYN_SENT: 1969 * if seg contains a RST with valid ACK (SEQ.ACK has already 1970 * been verified), then drop the connection. 1971 * if seg contains a RST without an ACK, drop the seg. 1972 * if seg does not contain SYN, then drop the seg. 1973 * Otherwise this is an acceptable SYN segment 1974 * initialize tp->rcv_nxt and tp->irs 1975 * if seg contains ack then advance tp->snd_una 1976 * if seg contains an ECE and ECN support is enabled, the stream 1977 * is ECN capable. 1978 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1979 * arrange for segment to be acked (eventually) 1980 * continue processing rest of data/controls, beginning with URG 1981 */ 1982 case TCPS_SYN_SENT: 1983 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1984 TCP_PROBE5(connect__refused, NULL, tp, 1985 m, tp, th); 1986 tp = tcp_drop(tp, ECONNREFUSED); 1987 } 1988 if (thflags & TH_RST) 1989 goto drop; 1990 if (!(thflags & TH_SYN)) 1991 goto drop; 1992 1993 tp->irs = th->th_seq; 1994 tcp_rcvseqinit(tp); 1995 if (thflags & TH_ACK) { 1996 int tfo_partial_ack = 0; 1997 1998 TCPSTAT_INC(tcps_connects); 1999 soisconnected(so); 2000 #ifdef MAC 2001 mac_socketpeer_set_from_mbuf(m, so); 2002 #endif 2003 /* Do window scaling on this connection? */ 2004 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2005 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2006 tp->rcv_scale = tp->request_r_scale; 2007 } 2008 tp->rcv_adv += min(tp->rcv_wnd, 2009 TCP_MAXWIN << tp->rcv_scale); 2010 tp->snd_una++; /* SYN is acked */ 2011 /* 2012 * If not all the data that was sent in the TFO SYN 2013 * has been acked, resend the remainder right away. 2014 */ 2015 if (IS_FASTOPEN(tp->t_flags) && 2016 (tp->snd_una != tp->snd_max)) { 2017 tp->snd_nxt = th->th_ack; 2018 tfo_partial_ack = 1; 2019 } 2020 /* 2021 * If there's data, delay ACK; if there's also a FIN 2022 * ACKNOW will be turned on later. 2023 */ 2024 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 2025 tcp_timer_activate(tp, TT_DELACK, 2026 tcp_delacktime); 2027 else 2028 tp->t_flags |= TF_ACKNOW; 2029 2030 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) && 2031 V_tcp_do_ecn) { 2032 tp->t_flags |= TF_ECN_PERMIT; 2033 TCPSTAT_INC(tcps_ecn_shs); 2034 } 2035 2036 /* 2037 * Received <SYN,ACK> in SYN_SENT[*] state. 2038 * Transitions: 2039 * SYN_SENT --> ESTABLISHED 2040 * SYN_SENT* --> FIN_WAIT_1 2041 */ 2042 tp->t_starttime = ticks; 2043 if (tp->t_flags & TF_NEEDFIN) { 2044 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2045 tp->t_flags &= ~TF_NEEDFIN; 2046 thflags &= ~TH_SYN; 2047 } else { 2048 tcp_state_change(tp, TCPS_ESTABLISHED); 2049 TCP_PROBE5(connect__established, NULL, tp, 2050 m, tp, th); 2051 cc_conn_init(tp); 2052 tcp_timer_activate(tp, TT_KEEP, 2053 TP_KEEPIDLE(tp)); 2054 } 2055 } else { 2056 /* 2057 * Received initial SYN in SYN-SENT[*] state => 2058 * simultaneous open. 2059 * If it succeeds, connection is * half-synchronized. 2060 * Otherwise, do 3-way handshake: 2061 * SYN-SENT -> SYN-RECEIVED 2062 * SYN-SENT* -> SYN-RECEIVED* 2063 */ 2064 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2065 tcp_timer_activate(tp, TT_REXMT, 0); 2066 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2067 } 2068 2069 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2070 INP_WLOCK_ASSERT(tp->t_inpcb); 2071 2072 /* 2073 * Advance th->th_seq to correspond to first data byte. 2074 * If data, trim to stay within window, 2075 * dropping FIN if necessary. 2076 */ 2077 th->th_seq++; 2078 if (tlen > tp->rcv_wnd) { 2079 todrop = tlen - tp->rcv_wnd; 2080 m_adj(m, -todrop); 2081 tlen = tp->rcv_wnd; 2082 thflags &= ~TH_FIN; 2083 TCPSTAT_INC(tcps_rcvpackafterwin); 2084 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2085 } 2086 tp->snd_wl1 = th->th_seq - 1; 2087 tp->rcv_up = th->th_seq; 2088 /* 2089 * Client side of transaction: already sent SYN and data. 2090 * If the remote host used T/TCP to validate the SYN, 2091 * our data will be ACK'd; if so, enter normal data segment 2092 * processing in the middle of step 5, ack processing. 2093 * Otherwise, goto step 6. 2094 */ 2095 if (thflags & TH_ACK) 2096 goto process_ACK; 2097 2098 goto step6; 2099 2100 /* 2101 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2102 * do normal processing. 2103 * 2104 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2105 */ 2106 case TCPS_LAST_ACK: 2107 case TCPS_CLOSING: 2108 break; /* continue normal processing */ 2109 } 2110 2111 /* 2112 * States other than LISTEN or SYN_SENT. 2113 * First check the RST flag and sequence number since reset segments 2114 * are exempt from the timestamp and connection count tests. This 2115 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2116 * below which allowed reset segments in half the sequence space 2117 * to fall though and be processed (which gives forged reset 2118 * segments with a random sequence number a 50 percent chance of 2119 * killing a connection). 2120 * Then check timestamp, if present. 2121 * Then check the connection count, if present. 2122 * Then check that at least some bytes of segment are within 2123 * receive window. If segment begins before rcv_nxt, 2124 * drop leading data (and SYN); if nothing left, just ack. 2125 */ 2126 if (thflags & TH_RST) { 2127 /* 2128 * RFC5961 Section 3.2 2129 * 2130 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2131 * - If RST is in window, we send challenge ACK. 2132 * 2133 * Note: to take into account delayed ACKs, we should 2134 * test against last_ack_sent instead of rcv_nxt. 2135 * Note 2: we handle special case of closed window, not 2136 * covered by the RFC. 2137 */ 2138 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2139 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2140 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2141 2142 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2143 KASSERT(tp->t_state != TCPS_SYN_SENT, 2144 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2145 __func__, th, tp)); 2146 2147 if (V_tcp_insecure_rst || 2148 tp->last_ack_sent == th->th_seq) { 2149 TCPSTAT_INC(tcps_drops); 2150 /* Drop the connection. */ 2151 switch (tp->t_state) { 2152 case TCPS_SYN_RECEIVED: 2153 so->so_error = ECONNREFUSED; 2154 goto close; 2155 case TCPS_ESTABLISHED: 2156 case TCPS_FIN_WAIT_1: 2157 case TCPS_FIN_WAIT_2: 2158 case TCPS_CLOSE_WAIT: 2159 case TCPS_CLOSING: 2160 case TCPS_LAST_ACK: 2161 so->so_error = ECONNRESET; 2162 close: 2163 /* FALLTHROUGH */ 2164 default: 2165 tp = tcp_close(tp); 2166 } 2167 } else { 2168 TCPSTAT_INC(tcps_badrst); 2169 /* Send challenge ACK. */ 2170 tcp_respond(tp, mtod(m, void *), th, m, 2171 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2172 tp->last_ack_sent = tp->rcv_nxt; 2173 m = NULL; 2174 } 2175 } 2176 goto drop; 2177 } 2178 2179 /* 2180 * RFC5961 Section 4.2 2181 * Send challenge ACK for any SYN in synchronized state. 2182 */ 2183 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2184 tp->t_state != TCPS_SYN_RECEIVED) { 2185 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2186 2187 TCPSTAT_INC(tcps_badsyn); 2188 if (V_tcp_insecure_syn && 2189 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2190 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2191 tp = tcp_drop(tp, ECONNRESET); 2192 rstreason = BANDLIM_UNLIMITED; 2193 } else { 2194 /* Send challenge ACK. */ 2195 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2196 tp->snd_nxt, TH_ACK); 2197 tp->last_ack_sent = tp->rcv_nxt; 2198 m = NULL; 2199 } 2200 goto drop; 2201 } 2202 2203 /* 2204 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2205 * and it's less than ts_recent, drop it. 2206 */ 2207 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2208 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2209 2210 /* Check to see if ts_recent is over 24 days old. */ 2211 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2212 /* 2213 * Invalidate ts_recent. If this segment updates 2214 * ts_recent, the age will be reset later and ts_recent 2215 * will get a valid value. If it does not, setting 2216 * ts_recent to zero will at least satisfy the 2217 * requirement that zero be placed in the timestamp 2218 * echo reply when ts_recent isn't valid. The 2219 * age isn't reset until we get a valid ts_recent 2220 * because we don't want out-of-order segments to be 2221 * dropped when ts_recent is old. 2222 */ 2223 tp->ts_recent = 0; 2224 } else { 2225 TCPSTAT_INC(tcps_rcvduppack); 2226 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2227 TCPSTAT_INC(tcps_pawsdrop); 2228 if (tlen) 2229 goto dropafterack; 2230 goto drop; 2231 } 2232 } 2233 2234 /* 2235 * In the SYN-RECEIVED state, validate that the packet belongs to 2236 * this connection before trimming the data to fit the receive 2237 * window. Check the sequence number versus IRS since we know 2238 * the sequence numbers haven't wrapped. This is a partial fix 2239 * for the "LAND" DoS attack. 2240 */ 2241 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2242 rstreason = BANDLIM_RST_OPENPORT; 2243 goto dropwithreset; 2244 } 2245 2246 todrop = tp->rcv_nxt - th->th_seq; 2247 if (todrop > 0) { 2248 if (thflags & TH_SYN) { 2249 thflags &= ~TH_SYN; 2250 th->th_seq++; 2251 if (th->th_urp > 1) 2252 th->th_urp--; 2253 else 2254 thflags &= ~TH_URG; 2255 todrop--; 2256 } 2257 /* 2258 * Following if statement from Stevens, vol. 2, p. 960. 2259 */ 2260 if (todrop > tlen 2261 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2262 /* 2263 * Any valid FIN must be to the left of the window. 2264 * At this point the FIN must be a duplicate or out 2265 * of sequence; drop it. 2266 */ 2267 thflags &= ~TH_FIN; 2268 2269 /* 2270 * Send an ACK to resynchronize and drop any data. 2271 * But keep on processing for RST or ACK. 2272 */ 2273 tp->t_flags |= TF_ACKNOW; 2274 todrop = tlen; 2275 TCPSTAT_INC(tcps_rcvduppack); 2276 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2277 } else { 2278 TCPSTAT_INC(tcps_rcvpartduppack); 2279 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2280 } 2281 /* 2282 * DSACK - add SACK block for dropped range 2283 */ 2284 if (tp->t_flags & TF_SACK_PERMIT) { 2285 tcp_update_sack_list(tp, th->th_seq, th->th_seq+tlen); 2286 /* 2287 * ACK now, as the next in-sequence segment 2288 * will clear the DSACK block again 2289 */ 2290 tp->t_flags |= TF_ACKNOW; 2291 } 2292 drop_hdrlen += todrop; /* drop from the top afterwards */ 2293 th->th_seq += todrop; 2294 tlen -= todrop; 2295 if (th->th_urp > todrop) 2296 th->th_urp -= todrop; 2297 else { 2298 thflags &= ~TH_URG; 2299 th->th_urp = 0; 2300 } 2301 } 2302 2303 /* 2304 * If new data are received on a connection after the 2305 * user processes are gone, then RST the other end. 2306 */ 2307 if ((so->so_state & SS_NOFDREF) && 2308 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2309 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2310 2311 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2312 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2313 "after socket was closed, " 2314 "sending RST and removing tcpcb\n", 2315 s, __func__, tcpstates[tp->t_state], tlen); 2316 free(s, M_TCPLOG); 2317 } 2318 tp = tcp_close(tp); 2319 TCPSTAT_INC(tcps_rcvafterclose); 2320 rstreason = BANDLIM_UNLIMITED; 2321 goto dropwithreset; 2322 } 2323 2324 /* 2325 * If segment ends after window, drop trailing data 2326 * (and PUSH and FIN); if nothing left, just ACK. 2327 */ 2328 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2329 if (todrop > 0) { 2330 TCPSTAT_INC(tcps_rcvpackafterwin); 2331 if (todrop >= tlen) { 2332 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2333 /* 2334 * If window is closed can only take segments at 2335 * window edge, and have to drop data and PUSH from 2336 * incoming segments. Continue processing, but 2337 * remember to ack. Otherwise, drop segment 2338 * and ack. 2339 */ 2340 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2341 tp->t_flags |= TF_ACKNOW; 2342 TCPSTAT_INC(tcps_rcvwinprobe); 2343 } else 2344 goto dropafterack; 2345 } else 2346 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2347 m_adj(m, -todrop); 2348 tlen -= todrop; 2349 thflags &= ~(TH_PUSH|TH_FIN); 2350 } 2351 2352 /* 2353 * If last ACK falls within this segment's sequence numbers, 2354 * record its timestamp. 2355 * NOTE: 2356 * 1) That the test incorporates suggestions from the latest 2357 * proposal of the [email protected] list (Braden 1993/04/26). 2358 * 2) That updating only on newer timestamps interferes with 2359 * our earlier PAWS tests, so this check should be solely 2360 * predicated on the sequence space of this segment. 2361 * 3) That we modify the segment boundary check to be 2362 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2363 * instead of RFC1323's 2364 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2365 * This modified check allows us to overcome RFC1323's 2366 * limitations as described in Stevens TCP/IP Illustrated 2367 * Vol. 2 p.869. In such cases, we can still calculate the 2368 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2369 */ 2370 if ((to.to_flags & TOF_TS) != 0 && 2371 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2372 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2373 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2374 tp->ts_recent_age = tcp_ts_getticks(); 2375 tp->ts_recent = to.to_tsval; 2376 } 2377 2378 /* 2379 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2380 * flag is on (half-synchronized state), then queue data for 2381 * later processing; else drop segment and return. 2382 */ 2383 if ((thflags & TH_ACK) == 0) { 2384 if (tp->t_state == TCPS_SYN_RECEIVED || 2385 (tp->t_flags & TF_NEEDSYN)) { 2386 if (tp->t_state == TCPS_SYN_RECEIVED && 2387 IS_FASTOPEN(tp->t_flags)) { 2388 tp->snd_wnd = tiwin; 2389 cc_conn_init(tp); 2390 } 2391 goto step6; 2392 } else if (tp->t_flags & TF_ACKNOW) 2393 goto dropafterack; 2394 else 2395 goto drop; 2396 } 2397 2398 /* 2399 * Ack processing. 2400 */ 2401 switch (tp->t_state) { 2402 2403 /* 2404 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2405 * ESTABLISHED state and continue processing. 2406 * The ACK was checked above. 2407 */ 2408 case TCPS_SYN_RECEIVED: 2409 2410 TCPSTAT_INC(tcps_connects); 2411 soisconnected(so); 2412 /* Do window scaling? */ 2413 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2414 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2415 tp->rcv_scale = tp->request_r_scale; 2416 } 2417 tp->snd_wnd = tiwin; 2418 /* 2419 * Make transitions: 2420 * SYN-RECEIVED -> ESTABLISHED 2421 * SYN-RECEIVED* -> FIN-WAIT-1 2422 */ 2423 tp->t_starttime = ticks; 2424 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2425 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2426 tp->t_tfo_pending = NULL; 2427 2428 /* 2429 * Account for the ACK of our SYN prior to 2430 * regular ACK processing below. 2431 */ 2432 tp->snd_una++; 2433 } 2434 if (tp->t_flags & TF_NEEDFIN) { 2435 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2436 tp->t_flags &= ~TF_NEEDFIN; 2437 } else { 2438 tcp_state_change(tp, TCPS_ESTABLISHED); 2439 TCP_PROBE5(accept__established, NULL, tp, 2440 m, tp, th); 2441 /* 2442 * TFO connections call cc_conn_init() during SYN 2443 * processing. Calling it again here for such 2444 * connections is not harmless as it would undo the 2445 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2446 * is retransmitted. 2447 */ 2448 if (!IS_FASTOPEN(tp->t_flags)) 2449 cc_conn_init(tp); 2450 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2451 } 2452 /* 2453 * If segment contains data or ACK, will call tcp_reass() 2454 * later; if not, do so now to pass queued data to user. 2455 */ 2456 if (tlen == 0 && (thflags & TH_FIN) == 0) 2457 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2458 (struct mbuf *)0); 2459 tp->snd_wl1 = th->th_seq - 1; 2460 /* FALLTHROUGH */ 2461 2462 /* 2463 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2464 * ACKs. If the ack is in the range 2465 * tp->snd_una < th->th_ack <= tp->snd_max 2466 * then advance tp->snd_una to th->th_ack and drop 2467 * data from the retransmission queue. If this ACK reflects 2468 * more up to date window information we update our window information. 2469 */ 2470 case TCPS_ESTABLISHED: 2471 case TCPS_FIN_WAIT_1: 2472 case TCPS_FIN_WAIT_2: 2473 case TCPS_CLOSE_WAIT: 2474 case TCPS_CLOSING: 2475 case TCPS_LAST_ACK: 2476 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2477 TCPSTAT_INC(tcps_rcvacktoomuch); 2478 goto dropafterack; 2479 } 2480 if ((tp->t_flags & TF_SACK_PERMIT) && 2481 ((to.to_flags & TOF_SACK) || 2482 !TAILQ_EMPTY(&tp->snd_holes))) 2483 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2484 else 2485 /* 2486 * Reset the value so that previous (valid) value 2487 * from the last ack with SACK doesn't get used. 2488 */ 2489 tp->sackhint.sacked_bytes = 0; 2490 2491 #ifdef TCP_HHOOK 2492 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2493 hhook_run_tcp_est_in(tp, th, &to); 2494 #endif 2495 2496 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2497 u_int maxseg; 2498 2499 maxseg = tcp_maxseg(tp); 2500 if (tlen == 0 && 2501 (tiwin == tp->snd_wnd || 2502 (tp->t_flags & TF_SACK_PERMIT))) { 2503 /* 2504 * If this is the first time we've seen a 2505 * FIN from the remote, this is not a 2506 * duplicate and it needs to be processed 2507 * normally. This happens during a 2508 * simultaneous close. 2509 */ 2510 if ((thflags & TH_FIN) && 2511 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2512 tp->t_dupacks = 0; 2513 break; 2514 } 2515 TCPSTAT_INC(tcps_rcvdupack); 2516 /* 2517 * If we have outstanding data (other than 2518 * a window probe), this is a completely 2519 * duplicate ack (ie, window info didn't 2520 * change and FIN isn't set), 2521 * the ack is the biggest we've 2522 * seen and we've seen exactly our rexmt 2523 * threshold of them, assume a packet 2524 * has been dropped and retransmit it. 2525 * Kludge snd_nxt & the congestion 2526 * window so we send only this one 2527 * packet. 2528 * 2529 * We know we're losing at the current 2530 * window size so do congestion avoidance 2531 * (set ssthresh to half the current window 2532 * and pull our congestion window back to 2533 * the new ssthresh). 2534 * 2535 * Dup acks mean that packets have left the 2536 * network (they're now cached at the receiver) 2537 * so bump cwnd by the amount in the receiver 2538 * to keep a constant cwnd packets in the 2539 * network. 2540 * 2541 * When using TCP ECN, notify the peer that 2542 * we reduced the cwnd. 2543 */ 2544 /* 2545 * Following 2 kinds of acks should not affect 2546 * dupack counting: 2547 * 1) Old acks 2548 * 2) Acks with SACK but without any new SACK 2549 * information in them. These could result from 2550 * any anomaly in the network like a switch 2551 * duplicating packets or a possible DoS attack. 2552 */ 2553 if (th->th_ack != tp->snd_una || 2554 ((tp->t_flags & TF_SACK_PERMIT) && 2555 !sack_changed)) 2556 break; 2557 else if (!tcp_timer_active(tp, TT_REXMT)) 2558 tp->t_dupacks = 0; 2559 else if (++tp->t_dupacks > tcprexmtthresh || 2560 IN_FASTRECOVERY(tp->t_flags)) { 2561 cc_ack_received(tp, th, nsegs, 2562 CC_DUPACK); 2563 if ((tp->t_flags & TF_SACK_PERMIT) && 2564 IN_FASTRECOVERY(tp->t_flags)) { 2565 int awnd; 2566 2567 /* 2568 * Compute the amount of data in flight first. 2569 * We can inject new data into the pipe iff 2570 * we have less than 1/2 the original window's 2571 * worth of data in flight. 2572 */ 2573 if (V_tcp_do_rfc6675_pipe) 2574 awnd = tcp_compute_pipe(tp); 2575 else 2576 awnd = (tp->snd_nxt - tp->snd_fack) + 2577 tp->sackhint.sack_bytes_rexmit; 2578 2579 if (awnd < tp->snd_ssthresh) { 2580 tp->snd_cwnd += maxseg; 2581 if (tp->snd_cwnd > tp->snd_ssthresh) 2582 tp->snd_cwnd = tp->snd_ssthresh; 2583 } 2584 } else 2585 tp->snd_cwnd += maxseg; 2586 (void) tp->t_fb->tfb_tcp_output(tp); 2587 goto drop; 2588 } else if (tp->t_dupacks == tcprexmtthresh) { 2589 tcp_seq onxt = tp->snd_nxt; 2590 2591 /* 2592 * If we're doing sack, check to 2593 * see if we're already in sack 2594 * recovery. If we're not doing sack, 2595 * check to see if we're in newreno 2596 * recovery. 2597 */ 2598 if (tp->t_flags & TF_SACK_PERMIT) { 2599 if (IN_FASTRECOVERY(tp->t_flags)) { 2600 tp->t_dupacks = 0; 2601 break; 2602 } 2603 } else { 2604 if (SEQ_LEQ(th->th_ack, 2605 tp->snd_recover)) { 2606 tp->t_dupacks = 0; 2607 break; 2608 } 2609 } 2610 /* Congestion signal before ack. */ 2611 cc_cong_signal(tp, th, CC_NDUPACK); 2612 cc_ack_received(tp, th, nsegs, 2613 CC_DUPACK); 2614 tcp_timer_activate(tp, TT_REXMT, 0); 2615 tp->t_rtttime = 0; 2616 if (tp->t_flags & TF_SACK_PERMIT) { 2617 TCPSTAT_INC( 2618 tcps_sack_recovery_episode); 2619 tp->sack_newdata = tp->snd_nxt; 2620 tp->snd_cwnd = maxseg; 2621 (void) tp->t_fb->tfb_tcp_output(tp); 2622 goto drop; 2623 } 2624 tp->snd_nxt = th->th_ack; 2625 tp->snd_cwnd = maxseg; 2626 (void) tp->t_fb->tfb_tcp_output(tp); 2627 KASSERT(tp->snd_limited <= 2, 2628 ("%s: tp->snd_limited too big", 2629 __func__)); 2630 tp->snd_cwnd = tp->snd_ssthresh + 2631 maxseg * 2632 (tp->t_dupacks - tp->snd_limited); 2633 if (SEQ_GT(onxt, tp->snd_nxt)) 2634 tp->snd_nxt = onxt; 2635 goto drop; 2636 } else if (V_tcp_do_rfc3042) { 2637 /* 2638 * Process first and second duplicate 2639 * ACKs. Each indicates a segment 2640 * leaving the network, creating room 2641 * for more. Make sure we can send a 2642 * packet on reception of each duplicate 2643 * ACK by increasing snd_cwnd by one 2644 * segment. Restore the original 2645 * snd_cwnd after packet transmission. 2646 */ 2647 cc_ack_received(tp, th, nsegs, 2648 CC_DUPACK); 2649 uint32_t oldcwnd = tp->snd_cwnd; 2650 tcp_seq oldsndmax = tp->snd_max; 2651 u_int sent; 2652 int avail; 2653 2654 KASSERT(tp->t_dupacks == 1 || 2655 tp->t_dupacks == 2, 2656 ("%s: dupacks not 1 or 2", 2657 __func__)); 2658 if (tp->t_dupacks == 1) 2659 tp->snd_limited = 0; 2660 tp->snd_cwnd = 2661 (tp->snd_nxt - tp->snd_una) + 2662 (tp->t_dupacks - tp->snd_limited) * 2663 maxseg; 2664 /* 2665 * Only call tcp_output when there 2666 * is new data available to be sent. 2667 * Otherwise we would send pure ACKs. 2668 */ 2669 SOCKBUF_LOCK(&so->so_snd); 2670 avail = sbavail(&so->so_snd) - 2671 (tp->snd_nxt - tp->snd_una); 2672 SOCKBUF_UNLOCK(&so->so_snd); 2673 if (avail > 0) 2674 (void) tp->t_fb->tfb_tcp_output(tp); 2675 sent = tp->snd_max - oldsndmax; 2676 if (sent > maxseg) { 2677 KASSERT((tp->t_dupacks == 2 && 2678 tp->snd_limited == 0) || 2679 (sent == maxseg + 1 && 2680 tp->t_flags & TF_SENTFIN), 2681 ("%s: sent too much", 2682 __func__)); 2683 tp->snd_limited = 2; 2684 } else if (sent > 0) 2685 ++tp->snd_limited; 2686 tp->snd_cwnd = oldcwnd; 2687 goto drop; 2688 } 2689 } 2690 break; 2691 } else { 2692 /* 2693 * This ack is advancing the left edge, reset the 2694 * counter. 2695 */ 2696 tp->t_dupacks = 0; 2697 /* 2698 * If this ack also has new SACK info, increment the 2699 * counter as per rfc6675. 2700 */ 2701 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed) 2702 tp->t_dupacks++; 2703 } 2704 2705 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2706 ("%s: th_ack <= snd_una", __func__)); 2707 2708 /* 2709 * If the congestion window was inflated to account 2710 * for the other side's cached packets, retract it. 2711 */ 2712 if (IN_FASTRECOVERY(tp->t_flags)) { 2713 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2714 if (tp->t_flags & TF_SACK_PERMIT) 2715 tcp_sack_partialack(tp, th); 2716 else 2717 tcp_newreno_partial_ack(tp, th); 2718 } else 2719 cc_post_recovery(tp, th); 2720 } 2721 /* 2722 * If we reach this point, ACK is not a duplicate, 2723 * i.e., it ACKs something we sent. 2724 */ 2725 if (tp->t_flags & TF_NEEDSYN) { 2726 /* 2727 * T/TCP: Connection was half-synchronized, and our 2728 * SYN has been ACK'd (so connection is now fully 2729 * synchronized). Go to non-starred state, 2730 * increment snd_una for ACK of SYN, and check if 2731 * we can do window scaling. 2732 */ 2733 tp->t_flags &= ~TF_NEEDSYN; 2734 tp->snd_una++; 2735 /* Do window scaling? */ 2736 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2737 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2738 tp->rcv_scale = tp->request_r_scale; 2739 /* Send window already scaled. */ 2740 } 2741 } 2742 2743 process_ACK: 2744 INP_WLOCK_ASSERT(tp->t_inpcb); 2745 2746 acked = BYTES_THIS_ACK(tp, th); 2747 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2748 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2749 tp->snd_una, th->th_ack, tp, m)); 2750 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2751 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2752 2753 /* 2754 * If we just performed our first retransmit, and the ACK 2755 * arrives within our recovery window, then it was a mistake 2756 * to do the retransmit in the first place. Recover our 2757 * original cwnd and ssthresh, and proceed to transmit where 2758 * we left off. 2759 */ 2760 if (tp->t_rxtshift == 1 && 2761 tp->t_flags & TF_PREVVALID && 2762 tp->t_badrxtwin && 2763 SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 2764 cc_cong_signal(tp, th, CC_RTO_ERR); 2765 2766 /* 2767 * If we have a timestamp reply, update smoothed 2768 * round trip time. If no timestamp is present but 2769 * transmit timer is running and timed sequence 2770 * number was acked, update smoothed round trip time. 2771 * Since we now have an rtt measurement, cancel the 2772 * timer backoff (cf., Phil Karn's retransmit alg.). 2773 * Recompute the initial retransmit timer. 2774 * 2775 * Some boxes send broken timestamp replies 2776 * during the SYN+ACK phase, ignore 2777 * timestamps of 0 or we could calculate a 2778 * huge RTT and blow up the retransmit timer. 2779 */ 2780 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2781 uint32_t t; 2782 2783 t = tcp_ts_getticks() - to.to_tsecr; 2784 if (!tp->t_rttlow || tp->t_rttlow > t) 2785 tp->t_rttlow = t; 2786 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2787 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2788 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2789 tp->t_rttlow = ticks - tp->t_rtttime; 2790 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2791 } 2792 2793 /* 2794 * If all outstanding data is acked, stop retransmit 2795 * timer and remember to restart (more output or persist). 2796 * If there is more data to be acked, restart retransmit 2797 * timer, using current (possibly backed-off) value. 2798 */ 2799 if (th->th_ack == tp->snd_max) { 2800 tcp_timer_activate(tp, TT_REXMT, 0); 2801 needoutput = 1; 2802 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2803 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2804 2805 /* 2806 * If no data (only SYN) was ACK'd, 2807 * skip rest of ACK processing. 2808 */ 2809 if (acked == 0) 2810 goto step6; 2811 2812 /* 2813 * Let the congestion control algorithm update congestion 2814 * control related information. This typically means increasing 2815 * the congestion window. 2816 */ 2817 cc_ack_received(tp, th, nsegs, CC_ACK); 2818 2819 SOCKBUF_LOCK(&so->so_snd); 2820 if (acked > sbavail(&so->so_snd)) { 2821 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2822 tp->snd_wnd -= sbavail(&so->so_snd); 2823 else 2824 tp->snd_wnd = 0; 2825 mfree = sbcut_locked(&so->so_snd, 2826 (int)sbavail(&so->so_snd)); 2827 ourfinisacked = 1; 2828 } else { 2829 mfree = sbcut_locked(&so->so_snd, acked); 2830 if (tp->snd_wnd >= (uint32_t) acked) 2831 tp->snd_wnd -= acked; 2832 else 2833 tp->snd_wnd = 0; 2834 ourfinisacked = 0; 2835 } 2836 /* NB: sowwakeup_locked() does an implicit unlock. */ 2837 sowwakeup_locked(so); 2838 m_freem(mfree); 2839 /* Detect una wraparound. */ 2840 if (!IN_RECOVERY(tp->t_flags) && 2841 SEQ_GT(tp->snd_una, tp->snd_recover) && 2842 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2843 tp->snd_recover = th->th_ack - 1; 2844 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2845 if (IN_RECOVERY(tp->t_flags) && 2846 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2847 EXIT_RECOVERY(tp->t_flags); 2848 } 2849 tp->snd_una = th->th_ack; 2850 if (tp->t_flags & TF_SACK_PERMIT) { 2851 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2852 tp->snd_recover = tp->snd_una; 2853 } 2854 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2855 tp->snd_nxt = tp->snd_una; 2856 2857 switch (tp->t_state) { 2858 2859 /* 2860 * In FIN_WAIT_1 STATE in addition to the processing 2861 * for the ESTABLISHED state if our FIN is now acknowledged 2862 * then enter FIN_WAIT_2. 2863 */ 2864 case TCPS_FIN_WAIT_1: 2865 if (ourfinisacked) { 2866 /* 2867 * If we can't receive any more 2868 * data, then closing user can proceed. 2869 * Starting the timer is contrary to the 2870 * specification, but if we don't get a FIN 2871 * we'll hang forever. 2872 * 2873 * XXXjl: 2874 * we should release the tp also, and use a 2875 * compressed state. 2876 */ 2877 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2878 soisdisconnected(so); 2879 tcp_timer_activate(tp, TT_2MSL, 2880 (tcp_fast_finwait2_recycle ? 2881 tcp_finwait2_timeout : 2882 TP_MAXIDLE(tp))); 2883 } 2884 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2885 } 2886 break; 2887 2888 /* 2889 * In CLOSING STATE in addition to the processing for 2890 * the ESTABLISHED state if the ACK acknowledges our FIN 2891 * then enter the TIME-WAIT state, otherwise ignore 2892 * the segment. 2893 */ 2894 case TCPS_CLOSING: 2895 if (ourfinisacked) { 2896 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2897 tcp_twstart(tp); 2898 m_freem(m); 2899 return; 2900 } 2901 break; 2902 2903 /* 2904 * In LAST_ACK, we may still be waiting for data to drain 2905 * and/or to be acked, as well as for the ack of our FIN. 2906 * If our FIN is now acknowledged, delete the TCB, 2907 * enter the closed state and return. 2908 */ 2909 case TCPS_LAST_ACK: 2910 if (ourfinisacked) { 2911 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2912 tp = tcp_close(tp); 2913 goto drop; 2914 } 2915 break; 2916 } 2917 } 2918 2919 step6: 2920 INP_WLOCK_ASSERT(tp->t_inpcb); 2921 2922 /* 2923 * Update window information. 2924 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2925 */ 2926 if ((thflags & TH_ACK) && 2927 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2928 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2929 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2930 /* keep track of pure window updates */ 2931 if (tlen == 0 && 2932 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2933 TCPSTAT_INC(tcps_rcvwinupd); 2934 tp->snd_wnd = tiwin; 2935 tp->snd_wl1 = th->th_seq; 2936 tp->snd_wl2 = th->th_ack; 2937 if (tp->snd_wnd > tp->max_sndwnd) 2938 tp->max_sndwnd = tp->snd_wnd; 2939 needoutput = 1; 2940 } 2941 2942 /* 2943 * Process segments with URG. 2944 */ 2945 if ((thflags & TH_URG) && th->th_urp && 2946 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2947 /* 2948 * This is a kludge, but if we receive and accept 2949 * random urgent pointers, we'll crash in 2950 * soreceive. It's hard to imagine someone 2951 * actually wanting to send this much urgent data. 2952 */ 2953 SOCKBUF_LOCK(&so->so_rcv); 2954 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2955 th->th_urp = 0; /* XXX */ 2956 thflags &= ~TH_URG; /* XXX */ 2957 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2958 goto dodata; /* XXX */ 2959 } 2960 /* 2961 * If this segment advances the known urgent pointer, 2962 * then mark the data stream. This should not happen 2963 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2964 * a FIN has been received from the remote side. 2965 * In these states we ignore the URG. 2966 * 2967 * According to RFC961 (Assigned Protocols), 2968 * the urgent pointer points to the last octet 2969 * of urgent data. We continue, however, 2970 * to consider it to indicate the first octet 2971 * of data past the urgent section as the original 2972 * spec states (in one of two places). 2973 */ 2974 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2975 tp->rcv_up = th->th_seq + th->th_urp; 2976 so->so_oobmark = sbavail(&so->so_rcv) + 2977 (tp->rcv_up - tp->rcv_nxt) - 1; 2978 if (so->so_oobmark == 0) 2979 so->so_rcv.sb_state |= SBS_RCVATMARK; 2980 sohasoutofband(so); 2981 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2982 } 2983 SOCKBUF_UNLOCK(&so->so_rcv); 2984 /* 2985 * Remove out of band data so doesn't get presented to user. 2986 * This can happen independent of advancing the URG pointer, 2987 * but if two URG's are pending at once, some out-of-band 2988 * data may creep in... ick. 2989 */ 2990 if (th->th_urp <= (uint32_t)tlen && 2991 !(so->so_options & SO_OOBINLINE)) { 2992 /* hdr drop is delayed */ 2993 tcp_pulloutofband(so, th, m, drop_hdrlen); 2994 } 2995 } else { 2996 /* 2997 * If no out of band data is expected, 2998 * pull receive urgent pointer along 2999 * with the receive window. 3000 */ 3001 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3002 tp->rcv_up = tp->rcv_nxt; 3003 } 3004 dodata: /* XXX */ 3005 INP_WLOCK_ASSERT(tp->t_inpcb); 3006 3007 /* 3008 * Process the segment text, merging it into the TCP sequencing queue, 3009 * and arranging for acknowledgment of receipt if necessary. 3010 * This process logically involves adjusting tp->rcv_wnd as data 3011 * is presented to the user (this happens in tcp_usrreq.c, 3012 * case PRU_RCVD). If a FIN has already been received on this 3013 * connection then we just ignore the text. 3014 */ 3015 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3016 IS_FASTOPEN(tp->t_flags)); 3017 if ((tlen || (thflags & TH_FIN) || tfo_syn) && 3018 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3019 tcp_seq save_start = th->th_seq; 3020 tcp_seq save_rnxt = tp->rcv_nxt; 3021 int save_tlen = tlen; 3022 m_adj(m, drop_hdrlen); /* delayed header drop */ 3023 /* 3024 * Insert segment which includes th into TCP reassembly queue 3025 * with control block tp. Set thflags to whether reassembly now 3026 * includes a segment with FIN. This handles the common case 3027 * inline (segment is the next to be received on an established 3028 * connection, and the queue is empty), avoiding linkage into 3029 * and removal from the queue and repetition of various 3030 * conversions. 3031 * Set DELACK for segments received in order, but ack 3032 * immediately when segments are out of order (so 3033 * fast retransmit can work). 3034 */ 3035 if (th->th_seq == tp->rcv_nxt && 3036 SEGQ_EMPTY(tp) && 3037 (TCPS_HAVEESTABLISHED(tp->t_state) || 3038 tfo_syn)) { 3039 if (DELAY_ACK(tp, tlen) || tfo_syn) 3040 tp->t_flags |= TF_DELACK; 3041 else 3042 tp->t_flags |= TF_ACKNOW; 3043 tp->rcv_nxt += tlen; 3044 thflags = th->th_flags & TH_FIN; 3045 TCPSTAT_INC(tcps_rcvpack); 3046 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3047 SOCKBUF_LOCK(&so->so_rcv); 3048 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3049 m_freem(m); 3050 else 3051 sbappendstream_locked(&so->so_rcv, m, 0); 3052 /* NB: sorwakeup_locked() does an implicit unlock. */ 3053 sorwakeup_locked(so); 3054 } else { 3055 /* 3056 * XXX: Due to the header drop above "th" is 3057 * theoretically invalid by now. Fortunately 3058 * m_adj() doesn't actually frees any mbufs 3059 * when trimming from the head. 3060 */ 3061 tcp_seq temp = save_start; 3062 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3063 tp->t_flags |= TF_ACKNOW; 3064 } 3065 if (tp->t_flags & TF_SACK_PERMIT) { 3066 if (((tlen == 0) && (save_tlen > 0) && 3067 (SEQ_LT(save_start, save_rnxt)))) { 3068 /* 3069 * DSACK actually handled in the fastpath 3070 * above. 3071 */ 3072 tcp_update_sack_list(tp, save_start, save_start + save_tlen); 3073 } else 3074 if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3075 /* 3076 * Cleaning sackblks by using zero length 3077 * update. 3078 */ 3079 tcp_update_sack_list(tp, save_start, save_start); 3080 } else 3081 if ((tlen > 0) && (tlen >= save_tlen)) { 3082 /* Update of sackblks. */ 3083 tcp_update_sack_list(tp, save_start, save_start + save_tlen); 3084 } else 3085 if (tlen > 0) { 3086 tcp_update_sack_list(tp, save_start, save_start+tlen); 3087 } 3088 } 3089 #if 0 3090 /* 3091 * Note the amount of data that peer has sent into 3092 * our window, in order to estimate the sender's 3093 * buffer size. 3094 * XXX: Unused. 3095 */ 3096 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3097 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3098 else 3099 len = so->so_rcv.sb_hiwat; 3100 #endif 3101 } else { 3102 m_freem(m); 3103 thflags &= ~TH_FIN; 3104 } 3105 3106 /* 3107 * If FIN is received ACK the FIN and let the user know 3108 * that the connection is closing. 3109 */ 3110 if (thflags & TH_FIN) { 3111 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3112 socantrcvmore(so); 3113 /* 3114 * If connection is half-synchronized 3115 * (ie NEEDSYN flag on) then delay ACK, 3116 * so it may be piggybacked when SYN is sent. 3117 * Otherwise, since we received a FIN then no 3118 * more input can be expected, send ACK now. 3119 */ 3120 if (tp->t_flags & TF_NEEDSYN) 3121 tp->t_flags |= TF_DELACK; 3122 else 3123 tp->t_flags |= TF_ACKNOW; 3124 tp->rcv_nxt++; 3125 } 3126 switch (tp->t_state) { 3127 3128 /* 3129 * In SYN_RECEIVED and ESTABLISHED STATES 3130 * enter the CLOSE_WAIT state. 3131 */ 3132 case TCPS_SYN_RECEIVED: 3133 tp->t_starttime = ticks; 3134 /* FALLTHROUGH */ 3135 case TCPS_ESTABLISHED: 3136 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3137 break; 3138 3139 /* 3140 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3141 * enter the CLOSING state. 3142 */ 3143 case TCPS_FIN_WAIT_1: 3144 tcp_state_change(tp, TCPS_CLOSING); 3145 break; 3146 3147 /* 3148 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3149 * starting the time-wait timer, turning off the other 3150 * standard timers. 3151 */ 3152 case TCPS_FIN_WAIT_2: 3153 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 3154 3155 tcp_twstart(tp); 3156 return; 3157 } 3158 } 3159 #ifdef TCPDEBUG 3160 if (so->so_options & SO_DEBUG) 3161 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3162 &tcp_savetcp, 0); 3163 #endif 3164 TCP_PROBE3(debug__input, tp, th, m); 3165 3166 /* 3167 * Return any desired output. 3168 */ 3169 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3170 (void) tp->t_fb->tfb_tcp_output(tp); 3171 3172 check_delack: 3173 INP_WLOCK_ASSERT(tp->t_inpcb); 3174 3175 if (tp->t_flags & TF_DELACK) { 3176 tp->t_flags &= ~TF_DELACK; 3177 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3178 } 3179 INP_WUNLOCK(tp->t_inpcb); 3180 return; 3181 3182 dropafterack: 3183 /* 3184 * Generate an ACK dropping incoming segment if it occupies 3185 * sequence space, where the ACK reflects our state. 3186 * 3187 * We can now skip the test for the RST flag since all 3188 * paths to this code happen after packets containing 3189 * RST have been dropped. 3190 * 3191 * In the SYN-RECEIVED state, don't send an ACK unless the 3192 * segment we received passes the SYN-RECEIVED ACK test. 3193 * If it fails send a RST. This breaks the loop in the 3194 * "LAND" DoS attack, and also prevents an ACK storm 3195 * between two listening ports that have been sent forged 3196 * SYN segments, each with the source address of the other. 3197 */ 3198 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3199 (SEQ_GT(tp->snd_una, th->th_ack) || 3200 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3201 rstreason = BANDLIM_RST_OPENPORT; 3202 goto dropwithreset; 3203 } 3204 #ifdef TCPDEBUG 3205 if (so->so_options & SO_DEBUG) 3206 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3207 &tcp_savetcp, 0); 3208 #endif 3209 TCP_PROBE3(debug__input, tp, th, m); 3210 tp->t_flags |= TF_ACKNOW; 3211 (void) tp->t_fb->tfb_tcp_output(tp); 3212 INP_WUNLOCK(tp->t_inpcb); 3213 m_freem(m); 3214 return; 3215 3216 dropwithreset: 3217 if (tp != NULL) { 3218 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3219 INP_WUNLOCK(tp->t_inpcb); 3220 } else 3221 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3222 return; 3223 3224 drop: 3225 /* 3226 * Drop space held by incoming segment and return. 3227 */ 3228 #ifdef TCPDEBUG 3229 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3230 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3231 &tcp_savetcp, 0); 3232 #endif 3233 TCP_PROBE3(debug__input, tp, th, m); 3234 if (tp != NULL) 3235 INP_WUNLOCK(tp->t_inpcb); 3236 m_freem(m); 3237 } 3238 3239 /* 3240 * Issue RST and make ACK acceptable to originator of segment. 3241 * The mbuf must still include the original packet header. 3242 * tp may be NULL. 3243 */ 3244 void 3245 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3246 int tlen, int rstreason) 3247 { 3248 #ifdef INET 3249 struct ip *ip; 3250 #endif 3251 #ifdef INET6 3252 struct ip6_hdr *ip6; 3253 #endif 3254 3255 if (tp != NULL) { 3256 INP_WLOCK_ASSERT(tp->t_inpcb); 3257 } 3258 3259 /* Don't bother if destination was broadcast/multicast. */ 3260 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3261 goto drop; 3262 #ifdef INET6 3263 if (mtod(m, struct ip *)->ip_v == 6) { 3264 ip6 = mtod(m, struct ip6_hdr *); 3265 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3266 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3267 goto drop; 3268 /* IPv6 anycast check is done at tcp6_input() */ 3269 } 3270 #endif 3271 #if defined(INET) && defined(INET6) 3272 else 3273 #endif 3274 #ifdef INET 3275 { 3276 ip = mtod(m, struct ip *); 3277 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3278 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3279 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3280 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3281 goto drop; 3282 } 3283 #endif 3284 3285 /* Perform bandwidth limiting. */ 3286 if (badport_bandlim(rstreason) < 0) 3287 goto drop; 3288 3289 /* tcp_respond consumes the mbuf chain. */ 3290 if (th->th_flags & TH_ACK) { 3291 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3292 th->th_ack, TH_RST); 3293 } else { 3294 if (th->th_flags & TH_SYN) 3295 tlen++; 3296 if (th->th_flags & TH_FIN) 3297 tlen++; 3298 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3299 (tcp_seq)0, TH_RST|TH_ACK); 3300 } 3301 return; 3302 drop: 3303 m_freem(m); 3304 } 3305 3306 /* 3307 * Parse TCP options and place in tcpopt. 3308 */ 3309 void 3310 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3311 { 3312 int opt, optlen; 3313 3314 to->to_flags = 0; 3315 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3316 opt = cp[0]; 3317 if (opt == TCPOPT_EOL) 3318 break; 3319 if (opt == TCPOPT_NOP) 3320 optlen = 1; 3321 else { 3322 if (cnt < 2) 3323 break; 3324 optlen = cp[1]; 3325 if (optlen < 2 || optlen > cnt) 3326 break; 3327 } 3328 switch (opt) { 3329 case TCPOPT_MAXSEG: 3330 if (optlen != TCPOLEN_MAXSEG) 3331 continue; 3332 if (!(flags & TO_SYN)) 3333 continue; 3334 to->to_flags |= TOF_MSS; 3335 bcopy((char *)cp + 2, 3336 (char *)&to->to_mss, sizeof(to->to_mss)); 3337 to->to_mss = ntohs(to->to_mss); 3338 break; 3339 case TCPOPT_WINDOW: 3340 if (optlen != TCPOLEN_WINDOW) 3341 continue; 3342 if (!(flags & TO_SYN)) 3343 continue; 3344 to->to_flags |= TOF_SCALE; 3345 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3346 break; 3347 case TCPOPT_TIMESTAMP: 3348 if (optlen != TCPOLEN_TIMESTAMP) 3349 continue; 3350 to->to_flags |= TOF_TS; 3351 bcopy((char *)cp + 2, 3352 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3353 to->to_tsval = ntohl(to->to_tsval); 3354 bcopy((char *)cp + 6, 3355 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3356 to->to_tsecr = ntohl(to->to_tsecr); 3357 break; 3358 case TCPOPT_SIGNATURE: 3359 /* 3360 * In order to reply to a host which has set the 3361 * TCP_SIGNATURE option in its initial SYN, we have 3362 * to record the fact that the option was observed 3363 * here for the syncache code to perform the correct 3364 * response. 3365 */ 3366 if (optlen != TCPOLEN_SIGNATURE) 3367 continue; 3368 to->to_flags |= TOF_SIGNATURE; 3369 to->to_signature = cp + 2; 3370 break; 3371 case TCPOPT_SACK_PERMITTED: 3372 if (optlen != TCPOLEN_SACK_PERMITTED) 3373 continue; 3374 if (!(flags & TO_SYN)) 3375 continue; 3376 if (!V_tcp_do_sack) 3377 continue; 3378 to->to_flags |= TOF_SACKPERM; 3379 break; 3380 case TCPOPT_SACK: 3381 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3382 continue; 3383 if (flags & TO_SYN) 3384 continue; 3385 to->to_flags |= TOF_SACK; 3386 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3387 to->to_sacks = cp + 2; 3388 TCPSTAT_INC(tcps_sack_rcv_blocks); 3389 break; 3390 case TCPOPT_FAST_OPEN: 3391 /* 3392 * Cookie length validation is performed by the 3393 * server side cookie checking code or the client 3394 * side cookie cache update code. 3395 */ 3396 if (!(flags & TO_SYN)) 3397 continue; 3398 if (!V_tcp_fastopen_client_enable && 3399 !V_tcp_fastopen_server_enable) 3400 continue; 3401 to->to_flags |= TOF_FASTOPEN; 3402 to->to_tfo_len = optlen - 2; 3403 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3404 break; 3405 default: 3406 continue; 3407 } 3408 } 3409 } 3410 3411 /* 3412 * Pull out of band byte out of a segment so 3413 * it doesn't appear in the user's data queue. 3414 * It is still reflected in the segment length for 3415 * sequencing purposes. 3416 */ 3417 void 3418 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3419 int off) 3420 { 3421 int cnt = off + th->th_urp - 1; 3422 3423 while (cnt >= 0) { 3424 if (m->m_len > cnt) { 3425 char *cp = mtod(m, caddr_t) + cnt; 3426 struct tcpcb *tp = sototcpcb(so); 3427 3428 INP_WLOCK_ASSERT(tp->t_inpcb); 3429 3430 tp->t_iobc = *cp; 3431 tp->t_oobflags |= TCPOOB_HAVEDATA; 3432 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3433 m->m_len--; 3434 if (m->m_flags & M_PKTHDR) 3435 m->m_pkthdr.len--; 3436 return; 3437 } 3438 cnt -= m->m_len; 3439 m = m->m_next; 3440 if (m == NULL) 3441 break; 3442 } 3443 panic("tcp_pulloutofband"); 3444 } 3445 3446 /* 3447 * Collect new round-trip time estimate 3448 * and update averages and current timeout. 3449 */ 3450 void 3451 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3452 { 3453 int delta; 3454 3455 INP_WLOCK_ASSERT(tp->t_inpcb); 3456 3457 TCPSTAT_INC(tcps_rttupdated); 3458 tp->t_rttupdated++; 3459 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3460 /* 3461 * srtt is stored as fixed point with 5 bits after the 3462 * binary point (i.e., scaled by 8). The following magic 3463 * is equivalent to the smoothing algorithm in rfc793 with 3464 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3465 * point). Adjust rtt to origin 0. 3466 */ 3467 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3468 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3469 3470 if ((tp->t_srtt += delta) <= 0) 3471 tp->t_srtt = 1; 3472 3473 /* 3474 * We accumulate a smoothed rtt variance (actually, a 3475 * smoothed mean difference), then set the retransmit 3476 * timer to smoothed rtt + 4 times the smoothed variance. 3477 * rttvar is stored as fixed point with 4 bits after the 3478 * binary point (scaled by 16). The following is 3479 * equivalent to rfc793 smoothing with an alpha of .75 3480 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3481 * rfc793's wired-in beta. 3482 */ 3483 if (delta < 0) 3484 delta = -delta; 3485 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3486 if ((tp->t_rttvar += delta) <= 0) 3487 tp->t_rttvar = 1; 3488 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3489 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3490 } else { 3491 /* 3492 * No rtt measurement yet - use the unsmoothed rtt. 3493 * Set the variance to half the rtt (so our first 3494 * retransmit happens at 3*rtt). 3495 */ 3496 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3497 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3498 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3499 } 3500 tp->t_rtttime = 0; 3501 tp->t_rxtshift = 0; 3502 3503 /* 3504 * the retransmit should happen at rtt + 4 * rttvar. 3505 * Because of the way we do the smoothing, srtt and rttvar 3506 * will each average +1/2 tick of bias. When we compute 3507 * the retransmit timer, we want 1/2 tick of rounding and 3508 * 1 extra tick because of +-1/2 tick uncertainty in the 3509 * firing of the timer. The bias will give us exactly the 3510 * 1.5 tick we need. But, because the bias is 3511 * statistical, we have to test that we don't drop below 3512 * the minimum feasible timer (which is 2 ticks). 3513 */ 3514 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3515 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3516 3517 /* 3518 * We received an ack for a packet that wasn't retransmitted; 3519 * it is probably safe to discard any error indications we've 3520 * received recently. This isn't quite right, but close enough 3521 * for now (a route might have failed after we sent a segment, 3522 * and the return path might not be symmetrical). 3523 */ 3524 tp->t_softerror = 0; 3525 } 3526 3527 /* 3528 * Determine a reasonable value for maxseg size. 3529 * If the route is known, check route for mtu. 3530 * If none, use an mss that can be handled on the outgoing interface 3531 * without forcing IP to fragment. If no route is found, route has no mtu, 3532 * or the destination isn't local, use a default, hopefully conservative 3533 * size (usually 512 or the default IP max size, but no more than the mtu 3534 * of the interface), as we can't discover anything about intervening 3535 * gateways or networks. We also initialize the congestion/slow start 3536 * window to be a single segment if the destination isn't local. 3537 * While looking at the routing entry, we also initialize other path-dependent 3538 * parameters from pre-set or cached values in the routing entry. 3539 * 3540 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3541 * IP options, e.g. IPSEC data, since length of this data may vary, and 3542 * thus it is calculated for every segment separately in tcp_output(). 3543 * 3544 * NOTE that this routine is only called when we process an incoming 3545 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3546 * settings are handled in tcp_mssopt(). 3547 */ 3548 void 3549 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3550 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3551 { 3552 int mss = 0; 3553 uint32_t maxmtu = 0; 3554 struct inpcb *inp = tp->t_inpcb; 3555 struct hc_metrics_lite metrics; 3556 #ifdef INET6 3557 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3558 size_t min_protoh = isipv6 ? 3559 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3560 sizeof (struct tcpiphdr); 3561 #else 3562 const size_t min_protoh = sizeof(struct tcpiphdr); 3563 #endif 3564 3565 INP_WLOCK_ASSERT(tp->t_inpcb); 3566 3567 if (mtuoffer != -1) { 3568 KASSERT(offer == -1, ("%s: conflict", __func__)); 3569 offer = mtuoffer - min_protoh; 3570 } 3571 3572 /* Initialize. */ 3573 #ifdef INET6 3574 if (isipv6) { 3575 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3576 tp->t_maxseg = V_tcp_v6mssdflt; 3577 } 3578 #endif 3579 #if defined(INET) && defined(INET6) 3580 else 3581 #endif 3582 #ifdef INET 3583 { 3584 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3585 tp->t_maxseg = V_tcp_mssdflt; 3586 } 3587 #endif 3588 3589 /* 3590 * No route to sender, stay with default mss and return. 3591 */ 3592 if (maxmtu == 0) { 3593 /* 3594 * In case we return early we need to initialize metrics 3595 * to a defined state as tcp_hc_get() would do for us 3596 * if there was no cache hit. 3597 */ 3598 if (metricptr != NULL) 3599 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3600 return; 3601 } 3602 3603 /* What have we got? */ 3604 switch (offer) { 3605 case 0: 3606 /* 3607 * Offer == 0 means that there was no MSS on the SYN 3608 * segment, in this case we use tcp_mssdflt as 3609 * already assigned to t_maxseg above. 3610 */ 3611 offer = tp->t_maxseg; 3612 break; 3613 3614 case -1: 3615 /* 3616 * Offer == -1 means that we didn't receive SYN yet. 3617 */ 3618 /* FALLTHROUGH */ 3619 3620 default: 3621 /* 3622 * Prevent DoS attack with too small MSS. Round up 3623 * to at least minmss. 3624 */ 3625 offer = max(offer, V_tcp_minmss); 3626 } 3627 3628 /* 3629 * rmx information is now retrieved from tcp_hostcache. 3630 */ 3631 tcp_hc_get(&inp->inp_inc, &metrics); 3632 if (metricptr != NULL) 3633 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3634 3635 /* 3636 * If there's a discovered mtu in tcp hostcache, use it. 3637 * Else, use the link mtu. 3638 */ 3639 if (metrics.rmx_mtu) 3640 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3641 else { 3642 #ifdef INET6 3643 if (isipv6) { 3644 mss = maxmtu - min_protoh; 3645 if (!V_path_mtu_discovery && 3646 !in6_localaddr(&inp->in6p_faddr)) 3647 mss = min(mss, V_tcp_v6mssdflt); 3648 } 3649 #endif 3650 #if defined(INET) && defined(INET6) 3651 else 3652 #endif 3653 #ifdef INET 3654 { 3655 mss = maxmtu - min_protoh; 3656 if (!V_path_mtu_discovery && 3657 !in_localaddr(inp->inp_faddr)) 3658 mss = min(mss, V_tcp_mssdflt); 3659 } 3660 #endif 3661 /* 3662 * XXX - The above conditional (mss = maxmtu - min_protoh) 3663 * probably violates the TCP spec. 3664 * The problem is that, since we don't know the 3665 * other end's MSS, we are supposed to use a conservative 3666 * default. But, if we do that, then MTU discovery will 3667 * never actually take place, because the conservative 3668 * default is much less than the MTUs typically seen 3669 * on the Internet today. For the moment, we'll sweep 3670 * this under the carpet. 3671 * 3672 * The conservative default might not actually be a problem 3673 * if the only case this occurs is when sending an initial 3674 * SYN with options and data to a host we've never talked 3675 * to before. Then, they will reply with an MSS value which 3676 * will get recorded and the new parameters should get 3677 * recomputed. For Further Study. 3678 */ 3679 } 3680 mss = min(mss, offer); 3681 3682 /* 3683 * Sanity check: make sure that maxseg will be large 3684 * enough to allow some data on segments even if the 3685 * all the option space is used (40bytes). Otherwise 3686 * funny things may happen in tcp_output. 3687 * 3688 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3689 */ 3690 mss = max(mss, 64); 3691 3692 tp->t_maxseg = mss; 3693 } 3694 3695 void 3696 tcp_mss(struct tcpcb *tp, int offer) 3697 { 3698 int mss; 3699 uint32_t bufsize; 3700 struct inpcb *inp; 3701 struct socket *so; 3702 struct hc_metrics_lite metrics; 3703 struct tcp_ifcap cap; 3704 3705 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3706 3707 bzero(&cap, sizeof(cap)); 3708 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3709 3710 mss = tp->t_maxseg; 3711 inp = tp->t_inpcb; 3712 3713 /* 3714 * If there's a pipesize, change the socket buffer to that size, 3715 * don't change if sb_hiwat is different than default (then it 3716 * has been changed on purpose with setsockopt). 3717 * Make the socket buffers an integral number of mss units; 3718 * if the mss is larger than the socket buffer, decrease the mss. 3719 */ 3720 so = inp->inp_socket; 3721 SOCKBUF_LOCK(&so->so_snd); 3722 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3723 bufsize = metrics.rmx_sendpipe; 3724 else 3725 bufsize = so->so_snd.sb_hiwat; 3726 if (bufsize < mss) 3727 mss = bufsize; 3728 else { 3729 bufsize = roundup(bufsize, mss); 3730 if (bufsize > sb_max) 3731 bufsize = sb_max; 3732 if (bufsize > so->so_snd.sb_hiwat) 3733 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3734 } 3735 SOCKBUF_UNLOCK(&so->so_snd); 3736 /* 3737 * Sanity check: make sure that maxseg will be large 3738 * enough to allow some data on segments even if the 3739 * all the option space is used (40bytes). Otherwise 3740 * funny things may happen in tcp_output. 3741 * 3742 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3743 */ 3744 tp->t_maxseg = max(mss, 64); 3745 3746 SOCKBUF_LOCK(&so->so_rcv); 3747 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3748 bufsize = metrics.rmx_recvpipe; 3749 else 3750 bufsize = so->so_rcv.sb_hiwat; 3751 if (bufsize > mss) { 3752 bufsize = roundup(bufsize, mss); 3753 if (bufsize > sb_max) 3754 bufsize = sb_max; 3755 if (bufsize > so->so_rcv.sb_hiwat) 3756 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3757 } 3758 SOCKBUF_UNLOCK(&so->so_rcv); 3759 3760 /* Check the interface for TSO capabilities. */ 3761 if (cap.ifcap & CSUM_TSO) { 3762 tp->t_flags |= TF_TSO; 3763 tp->t_tsomax = cap.tsomax; 3764 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3765 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3766 } 3767 } 3768 3769 /* 3770 * Determine the MSS option to send on an outgoing SYN. 3771 */ 3772 int 3773 tcp_mssopt(struct in_conninfo *inc) 3774 { 3775 int mss = 0; 3776 uint32_t thcmtu = 0; 3777 uint32_t maxmtu = 0; 3778 size_t min_protoh; 3779 3780 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3781 3782 #ifdef INET6 3783 if (inc->inc_flags & INC_ISIPV6) { 3784 mss = V_tcp_v6mssdflt; 3785 maxmtu = tcp_maxmtu6(inc, NULL); 3786 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3787 } 3788 #endif 3789 #if defined(INET) && defined(INET6) 3790 else 3791 #endif 3792 #ifdef INET 3793 { 3794 mss = V_tcp_mssdflt; 3795 maxmtu = tcp_maxmtu(inc, NULL); 3796 min_protoh = sizeof(struct tcpiphdr); 3797 } 3798 #endif 3799 #if defined(INET6) || defined(INET) 3800 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3801 #endif 3802 3803 if (maxmtu && thcmtu) 3804 mss = min(maxmtu, thcmtu) - min_protoh; 3805 else if (maxmtu || thcmtu) 3806 mss = max(maxmtu, thcmtu) - min_protoh; 3807 3808 return (mss); 3809 } 3810 3811 3812 /* 3813 * On a partial ack arrives, force the retransmission of the 3814 * next unacknowledged segment. Do not clear tp->t_dupacks. 3815 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3816 * be started again. 3817 */ 3818 void 3819 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3820 { 3821 tcp_seq onxt = tp->snd_nxt; 3822 uint32_t ocwnd = tp->snd_cwnd; 3823 u_int maxseg = tcp_maxseg(tp); 3824 3825 INP_WLOCK_ASSERT(tp->t_inpcb); 3826 3827 tcp_timer_activate(tp, TT_REXMT, 0); 3828 tp->t_rtttime = 0; 3829 tp->snd_nxt = th->th_ack; 3830 /* 3831 * Set snd_cwnd to one segment beyond acknowledged offset. 3832 * (tp->snd_una has not yet been updated when this function is called.) 3833 */ 3834 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3835 tp->t_flags |= TF_ACKNOW; 3836 (void) tp->t_fb->tfb_tcp_output(tp); 3837 tp->snd_cwnd = ocwnd; 3838 if (SEQ_GT(onxt, tp->snd_nxt)) 3839 tp->snd_nxt = onxt; 3840 /* 3841 * Partial window deflation. Relies on fact that tp->snd_una 3842 * not updated yet. 3843 */ 3844 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3845 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3846 else 3847 tp->snd_cwnd = 0; 3848 tp->snd_cwnd += maxseg; 3849 } 3850 3851 int 3852 tcp_compute_pipe(struct tcpcb *tp) 3853 { 3854 return (tp->snd_max - tp->snd_una + 3855 tp->sackhint.sack_bytes_rexmit - 3856 tp->sackhint.sacked_bytes); 3857 } 3858