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 <lstewart@freebsd.org> 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/arb.h> 62 #include <sys/kernel.h> 63 #ifdef TCP_HHOOK 64 #include <sys/hhook.h> 65 #endif 66 #include <sys/malloc.h> 67 #include <sys/mbuf.h> 68 #include <sys/proc.h> /* for proc0 declaration */ 69 #include <sys/protosw.h> 70 #include <sys/qmath.h> 71 #include <sys/sdt.h> 72 #include <sys/signalvar.h> 73 #include <sys/socket.h> 74 #include <sys/socketvar.h> 75 #include <sys/sysctl.h> 76 #include <sys/syslog.h> 77 #include <sys/systm.h> 78 #include <sys/stats.h> 79 80 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 81 82 #include <vm/uma.h> 83 84 #include <net/if.h> 85 #include <net/if_var.h> 86 #include <net/route.h> 87 #include <net/vnet.h> 88 89 #define TCPSTATES /* for logging */ 90 91 #include <netinet/in.h> 92 #include <netinet/in_kdtrace.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 98 #include <netinet/ip_var.h> 99 #include <netinet/ip_options.h> 100 #include <netinet/ip6.h> 101 #include <netinet/icmp6.h> 102 #include <netinet6/in6_pcb.h> 103 #include <netinet6/in6_var.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/nd6.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_log_buf.h> 109 #include <netinet/tcp_seq.h> 110 #include <netinet/tcp_timer.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 #include <netinet/cc/cc.h> 115 #include <netinet/tcp_fastopen.h> 116 #ifdef TCPPCAP 117 #include <netinet/tcp_pcap.h> 118 #endif 119 #include <netinet/tcp_syncache.h> 120 #ifdef TCPDEBUG 121 #include <netinet/tcp_debug.h> 122 #endif /* TCPDEBUG */ 123 #ifdef TCP_OFFLOAD 124 #include <netinet/tcp_offload.h> 125 #endif 126 127 #include <netipsec/ipsec_support.h> 128 129 #include <machine/in_cksum.h> 130 131 #include <security/mac/mac_framework.h> 132 133 const int tcprexmtthresh = 3; 134 135 int tcp_log_in_vain = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 137 &tcp_log_in_vain, 0, 138 "Log all incoming TCP segments to closed ports"); 139 140 VNET_DEFINE(int, blackhole) = 0; 141 #define V_blackhole VNET(blackhole) 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 143 &VNET_NAME(blackhole), 0, 144 "Do not send RST on segments to closed ports"); 145 146 VNET_DEFINE(int, tcp_delack_enabled) = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 148 &VNET_NAME(tcp_delack_enabled), 0, 149 "Delay ACK to try and piggyback it onto a data packet"); 150 151 VNET_DEFINE(int, drop_synfin) = 0; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 153 &VNET_NAME(drop_synfin), 0, 154 "Drop TCP packets with SYN+FIN set"); 155 156 VNET_DEFINE(int, tcp_do_newcwv) = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW, 158 &VNET_NAME(tcp_do_newcwv), 0, 159 "Enable New Congestion Window Validation per RFC7661"); 160 161 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 163 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 164 "Use calculated pipe/in-flight bytes per RFC 6675"); 165 166 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 168 &VNET_NAME(tcp_do_rfc3042), 0, 169 "Enable RFC 3042 (Limited Transmit)"); 170 171 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 173 &VNET_NAME(tcp_do_rfc3390), 0, 174 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 175 176 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 178 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 179 "Slow-start flight size (initial congestion window) in number of segments"); 180 181 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 183 &VNET_NAME(tcp_do_rfc3465), 0, 184 "Enable RFC 3465 (Appropriate Byte Counting)"); 185 186 VNET_DEFINE(int, tcp_abc_l_var) = 2; 187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 188 &VNET_NAME(tcp_abc_l_var), 2, 189 "Cap the max cwnd increment during slow-start to this number of segments"); 190 191 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 192 193 VNET_DEFINE(int, tcp_do_ecn) = 2; 194 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 195 &VNET_NAME(tcp_do_ecn), 0, 196 "TCP ECN support"); 197 198 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 199 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 200 &VNET_NAME(tcp_ecn_maxretries), 0, 201 "Max retries before giving up on ECN"); 202 203 VNET_DEFINE(int, tcp_insecure_syn) = 0; 204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 205 &VNET_NAME(tcp_insecure_syn), 0, 206 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 207 208 VNET_DEFINE(int, tcp_insecure_rst) = 0; 209 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 210 &VNET_NAME(tcp_insecure_rst), 0, 211 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 212 213 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 214 #define V_tcp_recvspace VNET(tcp_recvspace) 215 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 216 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 217 218 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 219 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 220 &VNET_NAME(tcp_do_autorcvbuf), 0, 221 "Enable automatic receive buffer sizing"); 222 223 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 225 &VNET_NAME(tcp_autorcvbuf_max), 0, 226 "Max size of automatic receive buffer"); 227 228 VNET_DEFINE(struct inpcbhead, tcb); 229 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 230 VNET_DEFINE(struct inpcbinfo, tcbinfo); 231 232 /* 233 * TCP statistics are stored in an array of counter(9)s, which size matches 234 * size of struct tcpstat. TCP running connection count is a regular array. 235 */ 236 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 237 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 238 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 239 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 240 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 241 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 242 "TCP connection counts by TCP state"); 243 244 static void 245 tcp_vnet_init(const void *unused) 246 { 247 248 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 249 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 250 } 251 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 252 tcp_vnet_init, NULL); 253 254 #ifdef VIMAGE 255 static void 256 tcp_vnet_uninit(const void *unused) 257 { 258 259 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 260 VNET_PCPUSTAT_FREE(tcpstat); 261 } 262 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 263 tcp_vnet_uninit, NULL); 264 #endif /* VIMAGE */ 265 266 /* 267 * Kernel module interface for updating tcpstat. The argument is an index 268 * into tcpstat treated as an array. 269 */ 270 void 271 kmod_tcpstat_inc(int statnum) 272 { 273 274 counter_u64_add(VNET(tcpstat)[statnum], 1); 275 } 276 277 #ifdef TCP_HHOOK 278 /* 279 * Wrapper for the TCP established input helper hook. 280 */ 281 void 282 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 283 { 284 struct tcp_hhook_data hhook_data; 285 286 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 287 hhook_data.tp = tp; 288 hhook_data.th = th; 289 hhook_data.to = to; 290 291 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 292 tp->osd); 293 } 294 } 295 #endif 296 297 /* 298 * CC wrapper hook functions 299 */ 300 void 301 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 302 uint16_t type) 303 { 304 #ifdef STATS 305 int32_t gput; 306 #endif 307 308 INP_WLOCK_ASSERT(tp->t_inpcb); 309 310 tp->ccv->nsegs = nsegs; 311 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 312 if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) || 313 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) && 314 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2)))) 315 tp->ccv->flags |= CCF_CWND_LIMITED; 316 else 317 tp->ccv->flags &= ~CCF_CWND_LIMITED; 318 319 if (type == CC_ACK) { 320 #ifdef STATS 321 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF, 322 ((int32_t)tp->snd_cwnd) - tp->snd_wnd); 323 if (!IN_RECOVERY(tp->t_flags)) 324 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN, 325 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs)); 326 if ((tp->t_flags & TF_GPUTINPROG) && 327 SEQ_GEQ(th->th_ack, tp->gput_ack)) { 328 /* 329 * Compute goodput in bits per millisecond. 330 */ 331 gput = (((int64_t)(th->th_ack - tp->gput_seq)) << 3) / 332 max(1, tcp_ts_getticks() - tp->gput_ts); 333 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT, 334 gput); 335 /* 336 * XXXLAS: This is a temporary hack, and should be 337 * chained off VOI_TCP_GPUT when stats(9) grows an API 338 * to deal with chained VOIs. 339 */ 340 if (tp->t_stats_gput_prev > 0) 341 stats_voi_update_abs_s32(tp->t_stats, 342 VOI_TCP_GPUT_ND, 343 ((gput - tp->t_stats_gput_prev) * 100) / 344 tp->t_stats_gput_prev); 345 tp->t_flags &= ~TF_GPUTINPROG; 346 tp->t_stats_gput_prev = gput; 347 } 348 #endif /* STATS */ 349 if (tp->snd_cwnd > tp->snd_ssthresh) { 350 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 351 nsegs * V_tcp_abc_l_var * tcp_maxseg(tp)); 352 if (tp->t_bytes_acked >= tp->snd_cwnd) { 353 tp->t_bytes_acked -= tp->snd_cwnd; 354 tp->ccv->flags |= CCF_ABC_SENTAWND; 355 } 356 } else { 357 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 358 tp->t_bytes_acked = 0; 359 } 360 } 361 362 if (CC_ALGO(tp)->ack_received != NULL) { 363 /* XXXLAS: Find a way to live without this */ 364 tp->ccv->curack = th->th_ack; 365 CC_ALGO(tp)->ack_received(tp->ccv, type); 366 } 367 #ifdef STATS 368 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd); 369 #endif 370 } 371 372 void 373 cc_conn_init(struct tcpcb *tp) 374 { 375 struct hc_metrics_lite metrics; 376 struct inpcb *inp = tp->t_inpcb; 377 u_int maxseg; 378 int rtt; 379 380 INP_WLOCK_ASSERT(tp->t_inpcb); 381 382 tcp_hc_get(&inp->inp_inc, &metrics); 383 maxseg = tcp_maxseg(tp); 384 385 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 386 tp->t_srtt = rtt; 387 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 388 TCPSTAT_INC(tcps_usedrtt); 389 if (metrics.rmx_rttvar) { 390 tp->t_rttvar = metrics.rmx_rttvar; 391 TCPSTAT_INC(tcps_usedrttvar); 392 } else { 393 /* default variation is +- 1 rtt */ 394 tp->t_rttvar = 395 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 396 } 397 TCPT_RANGESET(tp->t_rxtcur, 398 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 399 tp->t_rttmin, TCPTV_REXMTMAX); 400 } 401 if (metrics.rmx_ssthresh) { 402 /* 403 * There's some sort of gateway or interface 404 * buffer limit on the path. Use this to set 405 * the slow start threshold, but set the 406 * threshold to no less than 2*mss. 407 */ 408 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 409 TCPSTAT_INC(tcps_usedssthresh); 410 } 411 412 /* 413 * Set the initial slow-start flight size. 414 * 415 * If a SYN or SYN/ACK was lost and retransmitted, we have to 416 * reduce the initial CWND to one segment as congestion is likely 417 * requiring us to be cautious. 418 */ 419 if (tp->snd_cwnd == 1) 420 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 421 else 422 tp->snd_cwnd = tcp_compute_initwnd(maxseg); 423 424 if (CC_ALGO(tp)->conn_init != NULL) 425 CC_ALGO(tp)->conn_init(tp->ccv); 426 } 427 428 void inline 429 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 430 { 431 u_int maxseg; 432 433 INP_WLOCK_ASSERT(tp->t_inpcb); 434 435 #ifdef STATS 436 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type); 437 #endif 438 439 switch(type) { 440 case CC_NDUPACK: 441 if (!IN_FASTRECOVERY(tp->t_flags)) { 442 tp->snd_recover = tp->snd_max; 443 if (tp->t_flags2 & TF2_ECN_PERMIT) 444 tp->t_flags2 |= TF2_ECN_SND_CWR; 445 } 446 break; 447 case CC_ECN: 448 if (!IN_CONGRECOVERY(tp->t_flags)) { 449 TCPSTAT_INC(tcps_ecn_rcwnd); 450 tp->snd_recover = tp->snd_max; 451 if (tp->t_flags2 & TF2_ECN_PERMIT) 452 tp->t_flags2 |= TF2_ECN_SND_CWR; 453 } 454 break; 455 case CC_RTO: 456 maxseg = tcp_maxseg(tp); 457 tp->t_dupacks = 0; 458 tp->t_bytes_acked = 0; 459 EXIT_RECOVERY(tp->t_flags); 460 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 461 maxseg) * maxseg; 462 tp->snd_cwnd = maxseg; 463 break; 464 case CC_RTO_ERR: 465 TCPSTAT_INC(tcps_sndrexmitbad); 466 /* RTO was unnecessary, so reset everything. */ 467 tp->snd_cwnd = tp->snd_cwnd_prev; 468 tp->snd_ssthresh = tp->snd_ssthresh_prev; 469 tp->snd_recover = tp->snd_recover_prev; 470 if (tp->t_flags & TF_WASFRECOVERY) 471 ENTER_FASTRECOVERY(tp->t_flags); 472 if (tp->t_flags & TF_WASCRECOVERY) 473 ENTER_CONGRECOVERY(tp->t_flags); 474 tp->snd_nxt = tp->snd_max; 475 tp->t_flags &= ~TF_PREVVALID; 476 tp->t_badrxtwin = 0; 477 break; 478 } 479 480 if (CC_ALGO(tp)->cong_signal != NULL) { 481 if (th != NULL) 482 tp->ccv->curack = th->th_ack; 483 CC_ALGO(tp)->cong_signal(tp->ccv, type); 484 } 485 } 486 487 void inline 488 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 489 { 490 INP_WLOCK_ASSERT(tp->t_inpcb); 491 492 /* XXXLAS: KASSERT that we're in recovery? */ 493 494 if (CC_ALGO(tp)->post_recovery != NULL) { 495 tp->ccv->curack = th->th_ack; 496 CC_ALGO(tp)->post_recovery(tp->ccv); 497 } 498 /* XXXLAS: EXIT_RECOVERY ? */ 499 tp->t_bytes_acked = 0; 500 } 501 502 /* 503 * Indicate whether this ack should be delayed. We can delay the ack if 504 * following conditions are met: 505 * - There is no delayed ack timer in progress. 506 * - Our last ack wasn't a 0-sized window. We never want to delay 507 * the ack that opens up a 0-sized window. 508 * - LRO wasn't used for this segment. We make sure by checking that the 509 * segment size is not larger than the MSS. 510 */ 511 #define DELAY_ACK(tp, tlen) \ 512 ((!tcp_timer_active(tp, TT_DELACK) && \ 513 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 514 (tlen <= tp->t_maxseg) && \ 515 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 516 517 static void inline 518 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 519 { 520 INP_WLOCK_ASSERT(tp->t_inpcb); 521 522 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 523 switch (iptos & IPTOS_ECN_MASK) { 524 case IPTOS_ECN_CE: 525 tp->ccv->flags |= CCF_IPHDR_CE; 526 break; 527 case IPTOS_ECN_ECT0: 528 /* FALLTHROUGH */ 529 case IPTOS_ECN_ECT1: 530 /* FALLTHROUGH */ 531 case IPTOS_ECN_NOTECT: 532 tp->ccv->flags &= ~CCF_IPHDR_CE; 533 break; 534 } 535 536 if (th->th_flags & TH_CWR) 537 tp->ccv->flags |= CCF_TCPHDR_CWR; 538 else 539 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 540 541 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 542 543 if (tp->ccv->flags & CCF_ACKNOW) { 544 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 545 tp->t_flags |= TF_ACKNOW; 546 } 547 } 548 } 549 550 /* 551 * TCP input handling is split into multiple parts: 552 * tcp6_input is a thin wrapper around tcp_input for the extended 553 * ip6_protox[] call format in ip6_input 554 * tcp_input handles primary segment validation, inpcb lookup and 555 * SYN processing on listen sockets 556 * tcp_do_segment processes the ACK and text of the segment for 557 * establishing, established and closing connections 558 */ 559 #ifdef INET6 560 int 561 tcp6_input(struct mbuf **mp, int *offp, int proto) 562 { 563 struct mbuf *m; 564 struct in6_ifaddr *ia6; 565 struct ip6_hdr *ip6; 566 567 m = *mp; 568 if (m->m_len < *offp + sizeof(struct tcphdr)) { 569 m = m_pullup(m, *offp + sizeof(struct tcphdr)); 570 if (m == NULL) { 571 *mp = m; 572 TCPSTAT_INC(tcps_rcvshort); 573 return (IPPROTO_DONE); 574 } 575 } 576 577 /* 578 * draft-itojun-ipv6-tcp-to-anycast 579 * better place to put this in? 580 */ 581 ip6 = mtod(m, struct ip6_hdr *); 582 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 583 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 584 585 ifa_free(&ia6->ia_ifa); 586 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 587 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 588 *mp = NULL; 589 return (IPPROTO_DONE); 590 } 591 if (ia6) 592 ifa_free(&ia6->ia_ifa); 593 594 *mp = m; 595 return (tcp_input(mp, offp, proto)); 596 } 597 #endif /* INET6 */ 598 599 int 600 tcp_input(struct mbuf **mp, int *offp, int proto) 601 { 602 struct mbuf *m = *mp; 603 struct tcphdr *th = NULL; 604 struct ip *ip = NULL; 605 struct inpcb *inp = NULL; 606 struct tcpcb *tp = NULL; 607 struct socket *so = NULL; 608 u_char *optp = NULL; 609 int off0; 610 int optlen = 0; 611 #ifdef INET 612 int len; 613 uint8_t ipttl; 614 #endif 615 int tlen = 0, off; 616 int drop_hdrlen; 617 int thflags; 618 int rstreason = 0; /* For badport_bandlim accounting purposes */ 619 uint8_t iptos; 620 struct m_tag *fwd_tag = NULL; 621 #ifdef INET6 622 struct ip6_hdr *ip6 = NULL; 623 int isipv6; 624 #else 625 const void *ip6 = NULL; 626 #endif /* INET6 */ 627 struct tcpopt to; /* options in this segment */ 628 char *s = NULL; /* address and port logging */ 629 #ifdef TCPDEBUG 630 /* 631 * The size of tcp_saveipgen must be the size of the max ip header, 632 * now IPv6. 633 */ 634 u_char tcp_saveipgen[IP6_HDR_LEN]; 635 struct tcphdr tcp_savetcp; 636 short ostate = 0; 637 #endif 638 639 NET_EPOCH_ASSERT(); 640 641 #ifdef INET6 642 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 643 #endif 644 645 off0 = *offp; 646 m = *mp; 647 *mp = NULL; 648 to.to_flags = 0; 649 TCPSTAT_INC(tcps_rcvtotal); 650 651 #ifdef INET6 652 if (isipv6) { 653 654 ip6 = mtod(m, struct ip6_hdr *); 655 th = (struct tcphdr *)((caddr_t)ip6 + off0); 656 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 657 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 658 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 659 th->th_sum = m->m_pkthdr.csum_data; 660 else 661 th->th_sum = in6_cksum_pseudo(ip6, tlen, 662 IPPROTO_TCP, m->m_pkthdr.csum_data); 663 th->th_sum ^= 0xffff; 664 } else 665 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 666 if (th->th_sum) { 667 TCPSTAT_INC(tcps_rcvbadsum); 668 goto drop; 669 } 670 671 /* 672 * Be proactive about unspecified IPv6 address in source. 673 * As we use all-zero to indicate unbounded/unconnected pcb, 674 * unspecified IPv6 address can be used to confuse us. 675 * 676 * Note that packets with unspecified IPv6 destination is 677 * already dropped in ip6_input. 678 */ 679 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 680 /* XXX stat */ 681 goto drop; 682 } 683 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 684 } 685 #endif 686 #if defined(INET) && defined(INET6) 687 else 688 #endif 689 #ifdef INET 690 { 691 /* 692 * Get IP and TCP header together in first mbuf. 693 * Note: IP leaves IP header in first mbuf. 694 */ 695 if (off0 > sizeof (struct ip)) { 696 ip_stripoptions(m); 697 off0 = sizeof(struct ip); 698 } 699 if (m->m_len < sizeof (struct tcpiphdr)) { 700 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 701 == NULL) { 702 TCPSTAT_INC(tcps_rcvshort); 703 return (IPPROTO_DONE); 704 } 705 } 706 ip = mtod(m, struct ip *); 707 th = (struct tcphdr *)((caddr_t)ip + off0); 708 tlen = ntohs(ip->ip_len) - off0; 709 710 iptos = ip->ip_tos; 711 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 712 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 713 th->th_sum = m->m_pkthdr.csum_data; 714 else 715 th->th_sum = in_pseudo(ip->ip_src.s_addr, 716 ip->ip_dst.s_addr, 717 htonl(m->m_pkthdr.csum_data + tlen + 718 IPPROTO_TCP)); 719 th->th_sum ^= 0xffff; 720 } else { 721 struct ipovly *ipov = (struct ipovly *)ip; 722 723 /* 724 * Checksum extended TCP header and data. 725 */ 726 len = off0 + tlen; 727 ipttl = ip->ip_ttl; 728 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 729 ipov->ih_len = htons(tlen); 730 th->th_sum = in_cksum(m, len); 731 /* Reset length for SDT probes. */ 732 ip->ip_len = htons(len); 733 /* Reset TOS bits */ 734 ip->ip_tos = iptos; 735 /* Re-initialization for later version check */ 736 ip->ip_ttl = ipttl; 737 ip->ip_v = IPVERSION; 738 ip->ip_hl = off0 >> 2; 739 } 740 741 if (th->th_sum) { 742 TCPSTAT_INC(tcps_rcvbadsum); 743 goto drop; 744 } 745 } 746 #endif /* INET */ 747 748 /* 749 * Check that TCP offset makes sense, 750 * pull out TCP options and adjust length. XXX 751 */ 752 off = th->th_off << 2; 753 if (off < sizeof (struct tcphdr) || off > tlen) { 754 TCPSTAT_INC(tcps_rcvbadoff); 755 goto drop; 756 } 757 tlen -= off; /* tlen is used instead of ti->ti_len */ 758 if (off > sizeof (struct tcphdr)) { 759 #ifdef INET6 760 if (isipv6) { 761 if (m->m_len < off0 + off) { 762 m = m_pullup(m, off0 + off); 763 if (m == NULL) { 764 TCPSTAT_INC(tcps_rcvshort); 765 return (IPPROTO_DONE); 766 } 767 } 768 ip6 = mtod(m, struct ip6_hdr *); 769 th = (struct tcphdr *)((caddr_t)ip6 + off0); 770 } 771 #endif 772 #if defined(INET) && defined(INET6) 773 else 774 #endif 775 #ifdef INET 776 { 777 if (m->m_len < sizeof(struct ip) + off) { 778 if ((m = m_pullup(m, sizeof (struct ip) + off)) 779 == NULL) { 780 TCPSTAT_INC(tcps_rcvshort); 781 return (IPPROTO_DONE); 782 } 783 ip = mtod(m, struct ip *); 784 th = (struct tcphdr *)((caddr_t)ip + off0); 785 } 786 } 787 #endif 788 optlen = off - sizeof (struct tcphdr); 789 optp = (u_char *)(th + 1); 790 } 791 thflags = th->th_flags; 792 793 /* 794 * Convert TCP protocol specific fields to host format. 795 */ 796 tcp_fields_to_host(th); 797 798 /* 799 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 800 */ 801 drop_hdrlen = off0 + off; 802 803 /* 804 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 805 */ 806 if ( 807 #ifdef INET6 808 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 809 #ifdef INET 810 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 811 #endif 812 #endif 813 #if defined(INET) && !defined(INET6) 814 (m->m_flags & M_IP_NEXTHOP) 815 #endif 816 ) 817 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 818 819 findpcb: 820 #ifdef INET6 821 if (isipv6 && fwd_tag != NULL) { 822 struct sockaddr_in6 *next_hop6; 823 824 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 825 /* 826 * Transparently forwarded. Pretend to be the destination. 827 * Already got one like this? 828 */ 829 inp = in6_pcblookup_mbuf(&V_tcbinfo, 830 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 831 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 832 if (!inp) { 833 /* 834 * It's new. Try to find the ambushing socket. 835 * Because we've rewritten the destination address, 836 * any hardware-generated hash is ignored. 837 */ 838 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 839 th->th_sport, &next_hop6->sin6_addr, 840 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 841 th->th_dport, INPLOOKUP_WILDCARD | 842 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 843 } 844 } else if (isipv6) { 845 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 846 th->th_sport, &ip6->ip6_dst, th->th_dport, 847 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 848 m->m_pkthdr.rcvif, m); 849 } 850 #endif /* INET6 */ 851 #if defined(INET6) && defined(INET) 852 else 853 #endif 854 #ifdef INET 855 if (fwd_tag != NULL) { 856 struct sockaddr_in *next_hop; 857 858 next_hop = (struct sockaddr_in *)(fwd_tag+1); 859 /* 860 * Transparently forwarded. Pretend to be the destination. 861 * already got one like this? 862 */ 863 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 864 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 865 m->m_pkthdr.rcvif, m); 866 if (!inp) { 867 /* 868 * It's new. Try to find the ambushing socket. 869 * Because we've rewritten the destination address, 870 * any hardware-generated hash is ignored. 871 */ 872 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 873 th->th_sport, next_hop->sin_addr, 874 next_hop->sin_port ? ntohs(next_hop->sin_port) : 875 th->th_dport, INPLOOKUP_WILDCARD | 876 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 877 } 878 } else 879 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 880 th->th_sport, ip->ip_dst, th->th_dport, 881 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 882 m->m_pkthdr.rcvif, m); 883 #endif /* INET */ 884 885 /* 886 * If the INPCB does not exist then all data in the incoming 887 * segment is discarded and an appropriate RST is sent back. 888 * XXX MRT Send RST using which routing table? 889 */ 890 if (inp == NULL) { 891 /* 892 * Log communication attempts to ports that are not 893 * in use. 894 */ 895 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 896 tcp_log_in_vain == 2) { 897 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 898 log(LOG_INFO, "%s; %s: Connection attempt " 899 "to closed port\n", s, __func__); 900 } 901 /* 902 * When blackholing do not respond with a RST but 903 * completely ignore the segment and drop it. 904 */ 905 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 906 V_blackhole == 2) 907 goto dropunlock; 908 909 rstreason = BANDLIM_RST_CLOSEDPORT; 910 goto dropwithreset; 911 } 912 INP_WLOCK_ASSERT(inp); 913 /* 914 * While waiting for inp lock during the lookup, another thread 915 * can have dropped the inpcb, in which case we need to loop back 916 * and try to find a new inpcb to deliver to. 917 */ 918 if (inp->inp_flags & INP_DROPPED) { 919 INP_WUNLOCK(inp); 920 inp = NULL; 921 goto findpcb; 922 } 923 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 924 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 925 ((inp->inp_socket == NULL) || 926 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 927 inp->inp_flowid = m->m_pkthdr.flowid; 928 inp->inp_flowtype = M_HASHTYPE_GET(m); 929 } 930 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 931 #ifdef INET6 932 if (isipv6 && IPSEC_ENABLED(ipv6) && 933 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 934 goto dropunlock; 935 } 936 #ifdef INET 937 else 938 #endif 939 #endif /* INET6 */ 940 #ifdef INET 941 if (IPSEC_ENABLED(ipv4) && 942 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 943 goto dropunlock; 944 } 945 #endif /* INET */ 946 #endif /* IPSEC */ 947 948 /* 949 * Check the minimum TTL for socket. 950 */ 951 if (inp->inp_ip_minttl != 0) { 952 #ifdef INET6 953 if (isipv6) { 954 if (inp->inp_ip_minttl > ip6->ip6_hlim) 955 goto dropunlock; 956 } else 957 #endif 958 if (inp->inp_ip_minttl > ip->ip_ttl) 959 goto dropunlock; 960 } 961 962 /* 963 * A previous connection in TIMEWAIT state is supposed to catch stray 964 * or duplicate segments arriving late. If this segment was a 965 * legitimate new connection attempt, the old INPCB gets removed and 966 * we can try again to find a listening socket. 967 * 968 * At this point, due to earlier optimism, we may hold only an inpcb 969 * lock, and not the inpcbinfo write lock. If so, we need to try to 970 * acquire it, or if that fails, acquire a reference on the inpcb, 971 * drop all locks, acquire a global write lock, and then re-acquire 972 * the inpcb lock. We may at that point discover that another thread 973 * has tried to free the inpcb, in which case we need to loop back 974 * and try to find a new inpcb to deliver to. 975 * 976 * XXXRW: It may be time to rethink timewait locking. 977 */ 978 if (inp->inp_flags & INP_TIMEWAIT) { 979 if (thflags & TH_SYN) 980 tcp_dooptions(&to, optp, optlen, TO_SYN); 981 /* 982 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 983 */ 984 if (tcp_twcheck(inp, &to, th, m, tlen)) 985 goto findpcb; 986 return (IPPROTO_DONE); 987 } 988 /* 989 * The TCPCB may no longer exist if the connection is winding 990 * down or it is in the CLOSED state. Either way we drop the 991 * segment and send an appropriate response. 992 */ 993 tp = intotcpcb(inp); 994 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 995 rstreason = BANDLIM_RST_CLOSEDPORT; 996 goto dropwithreset; 997 } 998 999 #ifdef TCP_OFFLOAD 1000 if (tp->t_flags & TF_TOE) { 1001 tcp_offload_input(tp, m); 1002 m = NULL; /* consumed by the TOE driver */ 1003 goto dropunlock; 1004 } 1005 #endif 1006 1007 #ifdef MAC 1008 INP_WLOCK_ASSERT(inp); 1009 if (mac_inpcb_check_deliver(inp, m)) 1010 goto dropunlock; 1011 #endif 1012 so = inp->inp_socket; 1013 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1014 #ifdef TCPDEBUG 1015 if (so->so_options & SO_DEBUG) { 1016 ostate = tp->t_state; 1017 #ifdef INET6 1018 if (isipv6) { 1019 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1020 } else 1021 #endif 1022 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1023 tcp_savetcp = *th; 1024 } 1025 #endif /* TCPDEBUG */ 1026 /* 1027 * When the socket is accepting connections (the INPCB is in LISTEN 1028 * state) we look into the SYN cache if this is a new connection 1029 * attempt or the completion of a previous one. 1030 */ 1031 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1032 ("%s: so accepting but tp %p not listening", __func__, tp)); 1033 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1034 struct in_conninfo inc; 1035 1036 bzero(&inc, sizeof(inc)); 1037 #ifdef INET6 1038 if (isipv6) { 1039 inc.inc_flags |= INC_ISIPV6; 1040 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1041 inc.inc_flags |= INC_IPV6MINMTU; 1042 inc.inc6_faddr = ip6->ip6_src; 1043 inc.inc6_laddr = ip6->ip6_dst; 1044 } else 1045 #endif 1046 { 1047 inc.inc_faddr = ip->ip_src; 1048 inc.inc_laddr = ip->ip_dst; 1049 } 1050 inc.inc_fport = th->th_sport; 1051 inc.inc_lport = th->th_dport; 1052 inc.inc_fibnum = so->so_fibnum; 1053 1054 /* 1055 * Check for an existing connection attempt in syncache if 1056 * the flag is only ACK. A successful lookup creates a new 1057 * socket appended to the listen queue in SYN_RECEIVED state. 1058 */ 1059 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1060 1061 /* 1062 * Parse the TCP options here because 1063 * syncookies need access to the reflected 1064 * timestamp. 1065 */ 1066 tcp_dooptions(&to, optp, optlen, 0); 1067 /* 1068 * NB: syncache_expand() doesn't unlock 1069 * inp and tcpinfo locks. 1070 */ 1071 rstreason = syncache_expand(&inc, &to, th, &so, m); 1072 if (rstreason < 0) { 1073 /* 1074 * A failing TCP MD5 signature comparison 1075 * must result in the segment being dropped 1076 * and must not produce any response back 1077 * to the sender. 1078 */ 1079 goto dropunlock; 1080 } else if (rstreason == 0) { 1081 /* 1082 * No syncache entry or ACK was not 1083 * for our SYN/ACK. Send a RST. 1084 * NB: syncache did its own logging 1085 * of the failure cause. 1086 */ 1087 rstreason = BANDLIM_RST_OPENPORT; 1088 goto dropwithreset; 1089 } 1090 tfo_socket_result: 1091 if (so == NULL) { 1092 /* 1093 * We completed the 3-way handshake 1094 * but could not allocate a socket 1095 * either due to memory shortage, 1096 * listen queue length limits or 1097 * global socket limits. Send RST 1098 * or wait and have the remote end 1099 * retransmit the ACK for another 1100 * try. 1101 */ 1102 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1103 log(LOG_DEBUG, "%s; %s: Listen socket: " 1104 "Socket allocation failed due to " 1105 "limits or memory shortage, %s\n", 1106 s, __func__, 1107 V_tcp_sc_rst_sock_fail ? 1108 "sending RST" : "try again"); 1109 if (V_tcp_sc_rst_sock_fail) { 1110 rstreason = BANDLIM_UNLIMITED; 1111 goto dropwithreset; 1112 } else 1113 goto dropunlock; 1114 } 1115 /* 1116 * Socket is created in state SYN_RECEIVED. 1117 * Unlock the listen socket, lock the newly 1118 * created socket and update the tp variable. 1119 */ 1120 INP_WUNLOCK(inp); /* listen socket */ 1121 inp = sotoinpcb(so); 1122 /* 1123 * New connection inpcb is already locked by 1124 * syncache_expand(). 1125 */ 1126 INP_WLOCK_ASSERT(inp); 1127 tp = intotcpcb(inp); 1128 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1129 ("%s: ", __func__)); 1130 /* 1131 * Process the segment and the data it 1132 * contains. tcp_do_segment() consumes 1133 * the mbuf chain and unlocks the inpcb. 1134 */ 1135 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1136 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1137 iptos); 1138 return (IPPROTO_DONE); 1139 } 1140 /* 1141 * Segment flag validation for new connection attempts: 1142 * 1143 * Our (SYN|ACK) response was rejected. 1144 * Check with syncache and remove entry to prevent 1145 * retransmits. 1146 * 1147 * NB: syncache_chkrst does its own logging of failure 1148 * causes. 1149 */ 1150 if (thflags & TH_RST) { 1151 syncache_chkrst(&inc, th, m); 1152 goto dropunlock; 1153 } 1154 /* 1155 * We can't do anything without SYN. 1156 */ 1157 if ((thflags & TH_SYN) == 0) { 1158 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1159 log(LOG_DEBUG, "%s; %s: Listen socket: " 1160 "SYN is missing, segment ignored\n", 1161 s, __func__); 1162 TCPSTAT_INC(tcps_badsyn); 1163 goto dropunlock; 1164 } 1165 /* 1166 * (SYN|ACK) is bogus on a listen socket. 1167 */ 1168 if (thflags & TH_ACK) { 1169 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1170 log(LOG_DEBUG, "%s; %s: Listen socket: " 1171 "SYN|ACK invalid, segment rejected\n", 1172 s, __func__); 1173 syncache_badack(&inc); /* XXX: Not needed! */ 1174 TCPSTAT_INC(tcps_badsyn); 1175 rstreason = BANDLIM_RST_OPENPORT; 1176 goto dropwithreset; 1177 } 1178 /* 1179 * If the drop_synfin option is enabled, drop all 1180 * segments with both the SYN and FIN bits set. 1181 * This prevents e.g. nmap from identifying the 1182 * TCP/IP stack. 1183 * XXX: Poor reasoning. nmap has other methods 1184 * and is constantly refining its stack detection 1185 * strategies. 1186 * XXX: This is a violation of the TCP specification 1187 * and was used by RFC1644. 1188 */ 1189 if ((thflags & TH_FIN) && V_drop_synfin) { 1190 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1191 log(LOG_DEBUG, "%s; %s: Listen socket: " 1192 "SYN|FIN segment ignored (based on " 1193 "sysctl setting)\n", s, __func__); 1194 TCPSTAT_INC(tcps_badsyn); 1195 goto dropunlock; 1196 } 1197 /* 1198 * Segment's flags are (SYN) or (SYN|FIN). 1199 * 1200 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1201 * as they do not affect the state of the TCP FSM. 1202 * The data pointed to by TH_URG and th_urp is ignored. 1203 */ 1204 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1205 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1206 KASSERT(thflags & (TH_SYN), 1207 ("%s: Listen socket: TH_SYN not set", __func__)); 1208 #ifdef INET6 1209 /* 1210 * If deprecated address is forbidden, 1211 * we do not accept SYN to deprecated interface 1212 * address to prevent any new inbound connection from 1213 * getting established. 1214 * When we do not accept SYN, we send a TCP RST, 1215 * with deprecated source address (instead of dropping 1216 * it). We compromise it as it is much better for peer 1217 * to send a RST, and RST will be the final packet 1218 * for the exchange. 1219 * 1220 * If we do not forbid deprecated addresses, we accept 1221 * the SYN packet. RFC2462 does not suggest dropping 1222 * SYN in this case. 1223 * If we decipher RFC2462 5.5.4, it says like this: 1224 * 1. use of deprecated addr with existing 1225 * communication is okay - "SHOULD continue to be 1226 * used" 1227 * 2. use of it with new communication: 1228 * (2a) "SHOULD NOT be used if alternate address 1229 * with sufficient scope is available" 1230 * (2b) nothing mentioned otherwise. 1231 * Here we fall into (2b) case as we have no choice in 1232 * our source address selection - we must obey the peer. 1233 * 1234 * The wording in RFC2462 is confusing, and there are 1235 * multiple description text for deprecated address 1236 * handling - worse, they are not exactly the same. 1237 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1238 */ 1239 if (isipv6 && !V_ip6_use_deprecated) { 1240 struct in6_ifaddr *ia6; 1241 1242 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1243 if (ia6 != NULL && 1244 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1245 ifa_free(&ia6->ia_ifa); 1246 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1247 log(LOG_DEBUG, "%s; %s: Listen socket: " 1248 "Connection attempt to deprecated " 1249 "IPv6 address rejected\n", 1250 s, __func__); 1251 rstreason = BANDLIM_RST_OPENPORT; 1252 goto dropwithreset; 1253 } 1254 if (ia6) 1255 ifa_free(&ia6->ia_ifa); 1256 } 1257 #endif /* INET6 */ 1258 /* 1259 * Basic sanity checks on incoming SYN requests: 1260 * Don't respond if the destination is a link layer 1261 * broadcast according to RFC1122 4.2.3.10, p. 104. 1262 * If it is from this socket it must be forged. 1263 * Don't respond if the source or destination is a 1264 * global or subnet broad- or multicast address. 1265 * Note that it is quite possible to receive unicast 1266 * link-layer packets with a broadcast IP address. Use 1267 * in_broadcast() to find them. 1268 */ 1269 if (m->m_flags & (M_BCAST|M_MCAST)) { 1270 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1271 log(LOG_DEBUG, "%s; %s: Listen socket: " 1272 "Connection attempt from broad- or multicast " 1273 "link layer address ignored\n", s, __func__); 1274 goto dropunlock; 1275 } 1276 #ifdef INET6 1277 if (isipv6) { 1278 if (th->th_dport == th->th_sport && 1279 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1280 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1281 log(LOG_DEBUG, "%s; %s: Listen socket: " 1282 "Connection attempt to/from self " 1283 "ignored\n", s, __func__); 1284 goto dropunlock; 1285 } 1286 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1287 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1288 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1289 log(LOG_DEBUG, "%s; %s: Listen socket: " 1290 "Connection attempt from/to multicast " 1291 "address ignored\n", s, __func__); 1292 goto dropunlock; 1293 } 1294 } 1295 #endif 1296 #if defined(INET) && defined(INET6) 1297 else 1298 #endif 1299 #ifdef INET 1300 { 1301 if (th->th_dport == th->th_sport && 1302 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1303 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1304 log(LOG_DEBUG, "%s; %s: Listen socket: " 1305 "Connection attempt from/to self " 1306 "ignored\n", s, __func__); 1307 goto dropunlock; 1308 } 1309 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1310 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1311 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1312 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1313 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1314 log(LOG_DEBUG, "%s; %s: Listen socket: " 1315 "Connection attempt from/to broad- " 1316 "or multicast address ignored\n", 1317 s, __func__); 1318 goto dropunlock; 1319 } 1320 } 1321 #endif 1322 /* 1323 * SYN appears to be valid. Create compressed TCP state 1324 * for syncache. 1325 */ 1326 #ifdef TCPDEBUG 1327 if (so->so_options & SO_DEBUG) 1328 tcp_trace(TA_INPUT, ostate, tp, 1329 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1330 #endif 1331 TCP_PROBE3(debug__input, tp, th, m); 1332 tcp_dooptions(&to, optp, optlen, TO_SYN); 1333 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL, iptos)) 1334 goto tfo_socket_result; 1335 1336 /* 1337 * Entry added to syncache and mbuf consumed. 1338 * Only the listen socket is unlocked by syncache_add(). 1339 */ 1340 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1341 return (IPPROTO_DONE); 1342 } else if (tp->t_state == TCPS_LISTEN) { 1343 /* 1344 * When a listen socket is torn down the SO_ACCEPTCONN 1345 * flag is removed first while connections are drained 1346 * from the accept queue in a unlock/lock cycle of the 1347 * ACCEPT_LOCK, opening a race condition allowing a SYN 1348 * attempt go through unhandled. 1349 */ 1350 goto dropunlock; 1351 } 1352 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1353 if (tp->t_flags & TF_SIGNATURE) { 1354 tcp_dooptions(&to, optp, optlen, thflags); 1355 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1356 TCPSTAT_INC(tcps_sig_err_nosigopt); 1357 goto dropunlock; 1358 } 1359 if (!TCPMD5_ENABLED() || 1360 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1361 goto dropunlock; 1362 } 1363 #endif 1364 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1365 1366 /* 1367 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1368 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1369 * the inpcb, and unlocks pcbinfo. 1370 */ 1371 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1372 return (IPPROTO_DONE); 1373 1374 dropwithreset: 1375 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1376 1377 if (inp != NULL) { 1378 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1379 INP_WUNLOCK(inp); 1380 } else 1381 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1382 m = NULL; /* mbuf chain got consumed. */ 1383 goto drop; 1384 1385 dropunlock: 1386 if (m != NULL) 1387 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1388 1389 if (inp != NULL) 1390 INP_WUNLOCK(inp); 1391 1392 drop: 1393 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1394 if (s != NULL) 1395 free(s, M_TCPLOG); 1396 if (m != NULL) 1397 m_freem(m); 1398 return (IPPROTO_DONE); 1399 } 1400 1401 /* 1402 * Automatic sizing of receive socket buffer. Often the send 1403 * buffer size is not optimally adjusted to the actual network 1404 * conditions at hand (delay bandwidth product). Setting the 1405 * buffer size too small limits throughput on links with high 1406 * bandwidth and high delay (eg. trans-continental/oceanic links). 1407 * 1408 * On the receive side the socket buffer memory is only rarely 1409 * used to any significant extent. This allows us to be much 1410 * more aggressive in scaling the receive socket buffer. For 1411 * the case that the buffer space is actually used to a large 1412 * extent and we run out of kernel memory we can simply drop 1413 * the new segments; TCP on the sender will just retransmit it 1414 * later. Setting the buffer size too big may only consume too 1415 * much kernel memory if the application doesn't read() from 1416 * the socket or packet loss or reordering makes use of the 1417 * reassembly queue. 1418 * 1419 * The criteria to step up the receive buffer one notch are: 1420 * 1. Application has not set receive buffer size with 1421 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1422 * 2. the number of bytes received during 1/2 of an sRTT 1423 * is at least 3/8 of the current socket buffer size. 1424 * 3. receive buffer size has not hit maximal automatic size; 1425 * 1426 * If all of the criteria are met we increaset the socket buffer 1427 * by a 1/2 (bounded by the max). This allows us to keep ahead 1428 * of slow-start but also makes it so our peer never gets limited 1429 * by our rwnd which we then open up causing a burst. 1430 * 1431 * This algorithm does two steps per RTT at most and only if 1432 * we receive a bulk stream w/o packet losses or reorderings. 1433 * Shrinking the buffer during idle times is not necessary as 1434 * it doesn't consume any memory when idle. 1435 * 1436 * TODO: Only step up if the application is actually serving 1437 * the buffer to better manage the socket buffer resources. 1438 */ 1439 int 1440 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1441 struct tcpcb *tp, int tlen) 1442 { 1443 int newsize = 0; 1444 1445 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1446 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1447 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1448 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) { 1449 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) && 1450 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1451 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max); 1452 } 1453 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1454 1455 /* Start over with next RTT. */ 1456 tp->rfbuf_ts = 0; 1457 tp->rfbuf_cnt = 0; 1458 } else { 1459 tp->rfbuf_cnt += tlen; /* add up */ 1460 } 1461 return (newsize); 1462 } 1463 1464 void 1465 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1466 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1467 { 1468 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1469 int rstreason, todrop, win; 1470 uint32_t tiwin; 1471 uint16_t nsegs; 1472 char *s; 1473 struct in_conninfo *inc; 1474 struct mbuf *mfree; 1475 struct tcpopt to; 1476 int tfo_syn; 1477 1478 #ifdef TCPDEBUG 1479 /* 1480 * The size of tcp_saveipgen must be the size of the max ip header, 1481 * now IPv6. 1482 */ 1483 u_char tcp_saveipgen[IP6_HDR_LEN]; 1484 struct tcphdr tcp_savetcp; 1485 short ostate = 0; 1486 #endif 1487 thflags = th->th_flags; 1488 inc = &tp->t_inpcb->inp_inc; 1489 tp->sackhint.last_sack_ack = 0; 1490 sack_changed = 0; 1491 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1492 1493 NET_EPOCH_ASSERT(); 1494 INP_WLOCK_ASSERT(tp->t_inpcb); 1495 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1496 __func__)); 1497 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1498 __func__)); 1499 1500 #ifdef TCPPCAP 1501 /* Save segment, if requested. */ 1502 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1503 #endif 1504 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1505 tlen, NULL, true); 1506 1507 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1508 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1509 log(LOG_DEBUG, "%s; %s: " 1510 "SYN|FIN segment ignored (based on " 1511 "sysctl setting)\n", s, __func__); 1512 free(s, M_TCPLOG); 1513 } 1514 goto drop; 1515 } 1516 1517 /* 1518 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1519 * check SEQ.ACK first. 1520 */ 1521 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1522 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1523 rstreason = BANDLIM_UNLIMITED; 1524 goto dropwithreset; 1525 } 1526 1527 /* 1528 * Segment received on connection. 1529 * Reset idle time and keep-alive timer. 1530 * XXX: This should be done after segment 1531 * validation to ignore broken/spoofed segs. 1532 */ 1533 tp->t_rcvtime = ticks; 1534 1535 /* 1536 * Scale up the window into a 32-bit value. 1537 * For the SYN_SENT state the scale is zero. 1538 */ 1539 tiwin = th->th_win << tp->snd_scale; 1540 #ifdef STATS 1541 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin); 1542 #endif 1543 1544 /* 1545 * TCP ECN processing. 1546 */ 1547 if (tp->t_flags2 & TF2_ECN_PERMIT) { 1548 if (thflags & TH_CWR) 1549 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1550 switch (iptos & IPTOS_ECN_MASK) { 1551 case IPTOS_ECN_CE: 1552 tp->t_flags2 |= TF2_ECN_SND_ECE; 1553 TCPSTAT_INC(tcps_ecn_ce); 1554 break; 1555 case IPTOS_ECN_ECT0: 1556 TCPSTAT_INC(tcps_ecn_ect0); 1557 break; 1558 case IPTOS_ECN_ECT1: 1559 TCPSTAT_INC(tcps_ecn_ect1); 1560 break; 1561 } 1562 1563 /* Process a packet differently from RFC3168. */ 1564 cc_ecnpkt_handler(tp, th, iptos); 1565 1566 /* Congestion experienced. */ 1567 if (thflags & TH_ECE) { 1568 cc_cong_signal(tp, th, CC_ECN); 1569 } 1570 } 1571 1572 /* 1573 * Parse options on any incoming segment. 1574 */ 1575 tcp_dooptions(&to, (u_char *)(th + 1), 1576 (th->th_off << 2) - sizeof(struct tcphdr), 1577 (thflags & TH_SYN) ? TO_SYN : 0); 1578 1579 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1580 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1581 (to.to_flags & TOF_SIGNATURE) == 0) { 1582 TCPSTAT_INC(tcps_sig_err_sigopt); 1583 /* XXX: should drop? */ 1584 } 1585 #endif 1586 /* 1587 * If echoed timestamp is later than the current time, 1588 * fall back to non RFC1323 RTT calculation. Normalize 1589 * timestamp if syncookies were used when this connection 1590 * was established. 1591 */ 1592 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1593 to.to_tsecr -= tp->ts_offset; 1594 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1595 to.to_tsecr = 0; 1596 else if (tp->t_flags & TF_PREVVALID && 1597 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 1598 cc_cong_signal(tp, th, CC_RTO_ERR); 1599 } 1600 /* 1601 * Process options only when we get SYN/ACK back. The SYN case 1602 * for incoming connections is handled in tcp_syncache. 1603 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1604 * or <SYN,ACK>) segment itself is never scaled. 1605 * XXX this is traditional behavior, may need to be cleaned up. 1606 */ 1607 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1608 if ((to.to_flags & TOF_SCALE) && 1609 (tp->t_flags & TF_REQ_SCALE)) { 1610 tp->t_flags |= TF_RCVD_SCALE; 1611 tp->snd_scale = to.to_wscale; 1612 } 1613 /* 1614 * Initial send window. It will be updated with 1615 * the next incoming segment to the scaled value. 1616 */ 1617 tp->snd_wnd = th->th_win; 1618 if (to.to_flags & TOF_TS) { 1619 tp->t_flags |= TF_RCVD_TSTMP; 1620 tp->ts_recent = to.to_tsval; 1621 tp->ts_recent_age = tcp_ts_getticks(); 1622 } 1623 if (to.to_flags & TOF_MSS) 1624 tcp_mss(tp, to.to_mss); 1625 if ((tp->t_flags & TF_SACK_PERMIT) && 1626 (to.to_flags & TOF_SACKPERM) == 0) 1627 tp->t_flags &= ~TF_SACK_PERMIT; 1628 if (IS_FASTOPEN(tp->t_flags)) { 1629 if (to.to_flags & TOF_FASTOPEN) { 1630 uint16_t mss; 1631 1632 if (to.to_flags & TOF_MSS) 1633 mss = to.to_mss; 1634 else 1635 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1636 mss = TCP6_MSS; 1637 else 1638 mss = TCP_MSS; 1639 tcp_fastopen_update_cache(tp, mss, 1640 to.to_tfo_len, to.to_tfo_cookie); 1641 } else 1642 tcp_fastopen_disable_path(tp); 1643 } 1644 } 1645 1646 /* 1647 * If timestamps were negotiated during SYN/ACK they should 1648 * appear on every segment during this session and vice versa. 1649 */ 1650 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1651 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1652 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1653 "no action\n", s, __func__); 1654 free(s, M_TCPLOG); 1655 } 1656 } 1657 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1658 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1659 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1660 "no action\n", s, __func__); 1661 free(s, M_TCPLOG); 1662 } 1663 } 1664 1665 /* 1666 * Header prediction: check for the two common cases 1667 * of a uni-directional data xfer. If the packet has 1668 * no control flags, is in-sequence, the window didn't 1669 * change and we're not retransmitting, it's a 1670 * candidate. If the length is zero and the ack moved 1671 * forward, we're the sender side of the xfer. Just 1672 * free the data acked & wake any higher level process 1673 * that was blocked waiting for space. If the length 1674 * is non-zero and the ack didn't move, we're the 1675 * receiver side. If we're getting packets in-order 1676 * (the reassembly queue is empty), add the data to 1677 * the socket buffer and note that we need a delayed ack. 1678 * Make sure that the hidden state-flags are also off. 1679 * Since we check for TCPS_ESTABLISHED first, it can only 1680 * be TH_NEEDSYN. 1681 */ 1682 if (tp->t_state == TCPS_ESTABLISHED && 1683 th->th_seq == tp->rcv_nxt && 1684 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1685 tp->snd_nxt == tp->snd_max && 1686 tiwin && tiwin == tp->snd_wnd && 1687 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1688 SEGQ_EMPTY(tp) && 1689 ((to.to_flags & TOF_TS) == 0 || 1690 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1691 1692 /* 1693 * If last ACK falls within this segment's sequence numbers, 1694 * record the timestamp. 1695 * NOTE that the test is modified according to the latest 1696 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1697 */ 1698 if ((to.to_flags & TOF_TS) != 0 && 1699 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1700 tp->ts_recent_age = tcp_ts_getticks(); 1701 tp->ts_recent = to.to_tsval; 1702 } 1703 1704 if (tlen == 0) { 1705 if (SEQ_GT(th->th_ack, tp->snd_una) && 1706 SEQ_LEQ(th->th_ack, tp->snd_max) && 1707 !IN_RECOVERY(tp->t_flags) && 1708 (to.to_flags & TOF_SACK) == 0 && 1709 TAILQ_EMPTY(&tp->snd_holes)) { 1710 /* 1711 * This is a pure ack for outstanding data. 1712 */ 1713 TCPSTAT_INC(tcps_predack); 1714 1715 /* 1716 * "bad retransmit" recovery without timestamps. 1717 */ 1718 if ((to.to_flags & TOF_TS) == 0 && 1719 tp->t_rxtshift == 1 && 1720 tp->t_flags & TF_PREVVALID && 1721 (int)(ticks - tp->t_badrxtwin) < 0) { 1722 cc_cong_signal(tp, th, CC_RTO_ERR); 1723 } 1724 1725 /* 1726 * Recalculate the transmit timer / rtt. 1727 * 1728 * Some boxes send broken timestamp replies 1729 * during the SYN+ACK phase, ignore 1730 * timestamps of 0 or we could calculate a 1731 * huge RTT and blow up the retransmit timer. 1732 */ 1733 if ((to.to_flags & TOF_TS) != 0 && 1734 to.to_tsecr) { 1735 uint32_t t; 1736 1737 t = tcp_ts_getticks() - to.to_tsecr; 1738 if (!tp->t_rttlow || tp->t_rttlow > t) 1739 tp->t_rttlow = t; 1740 tcp_xmit_timer(tp, 1741 TCP_TS_TO_TICKS(t) + 1); 1742 } else if (tp->t_rtttime && 1743 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1744 if (!tp->t_rttlow || 1745 tp->t_rttlow > ticks - tp->t_rtttime) 1746 tp->t_rttlow = ticks - tp->t_rtttime; 1747 tcp_xmit_timer(tp, 1748 ticks - tp->t_rtttime); 1749 } 1750 acked = BYTES_THIS_ACK(tp, th); 1751 1752 #ifdef TCP_HHOOK 1753 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1754 hhook_run_tcp_est_in(tp, th, &to); 1755 #endif 1756 1757 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1758 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1759 sbdrop(&so->so_snd, acked); 1760 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1761 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1762 tp->snd_recover = th->th_ack - 1; 1763 1764 /* 1765 * Let the congestion control algorithm update 1766 * congestion control related information. This 1767 * typically means increasing the congestion 1768 * window. 1769 */ 1770 cc_ack_received(tp, th, nsegs, CC_ACK); 1771 1772 tp->snd_una = th->th_ack; 1773 /* 1774 * Pull snd_wl2 up to prevent seq wrap relative 1775 * to th_ack. 1776 */ 1777 tp->snd_wl2 = th->th_ack; 1778 tp->t_dupacks = 0; 1779 m_freem(m); 1780 1781 /* 1782 * If all outstanding data are acked, stop 1783 * retransmit timer, otherwise restart timer 1784 * using current (possibly backed-off) value. 1785 * If process is waiting for space, 1786 * wakeup/selwakeup/signal. If data 1787 * are ready to send, let tcp_output 1788 * decide between more output or persist. 1789 */ 1790 #ifdef TCPDEBUG 1791 if (so->so_options & SO_DEBUG) 1792 tcp_trace(TA_INPUT, ostate, tp, 1793 (void *)tcp_saveipgen, 1794 &tcp_savetcp, 0); 1795 #endif 1796 TCP_PROBE3(debug__input, tp, th, m); 1797 if (tp->snd_una == tp->snd_max) 1798 tcp_timer_activate(tp, TT_REXMT, 0); 1799 else if (!tcp_timer_active(tp, TT_PERSIST)) 1800 tcp_timer_activate(tp, TT_REXMT, 1801 tp->t_rxtcur); 1802 sowwakeup(so); 1803 if (sbavail(&so->so_snd)) 1804 (void) tp->t_fb->tfb_tcp_output(tp); 1805 goto check_delack; 1806 } 1807 } else if (th->th_ack == tp->snd_una && 1808 tlen <= sbspace(&so->so_rcv)) { 1809 int newsize = 0; /* automatic sockbuf scaling */ 1810 1811 /* 1812 * This is a pure, in-sequence data packet with 1813 * nothing on the reassembly queue and we have enough 1814 * buffer space to take it. 1815 */ 1816 /* Clean receiver SACK report if present */ 1817 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1818 tcp_clean_sackreport(tp); 1819 TCPSTAT_INC(tcps_preddat); 1820 tp->rcv_nxt += tlen; 1821 /* 1822 * Pull snd_wl1 up to prevent seq wrap relative to 1823 * th_seq. 1824 */ 1825 tp->snd_wl1 = th->th_seq; 1826 /* 1827 * Pull rcv_up up to prevent seq wrap relative to 1828 * rcv_nxt. 1829 */ 1830 tp->rcv_up = tp->rcv_nxt; 1831 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1832 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1833 #ifdef TCPDEBUG 1834 if (so->so_options & SO_DEBUG) 1835 tcp_trace(TA_INPUT, ostate, tp, 1836 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1837 #endif 1838 TCP_PROBE3(debug__input, tp, th, m); 1839 1840 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1841 1842 /* Add data to socket buffer. */ 1843 SOCKBUF_LOCK(&so->so_rcv); 1844 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1845 m_freem(m); 1846 } else { 1847 /* 1848 * Set new socket buffer size. 1849 * Give up when limit is reached. 1850 */ 1851 if (newsize) 1852 if (!sbreserve_locked(&so->so_rcv, 1853 newsize, so, NULL)) 1854 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1855 m_adj(m, drop_hdrlen); /* delayed header drop */ 1856 sbappendstream_locked(&so->so_rcv, m, 0); 1857 } 1858 /* NB: sorwakeup_locked() does an implicit unlock. */ 1859 sorwakeup_locked(so); 1860 if (DELAY_ACK(tp, tlen)) { 1861 tp->t_flags |= TF_DELACK; 1862 } else { 1863 tp->t_flags |= TF_ACKNOW; 1864 tp->t_fb->tfb_tcp_output(tp); 1865 } 1866 goto check_delack; 1867 } 1868 } 1869 1870 /* 1871 * Calculate amount of space in receive window, 1872 * and then do TCP input processing. 1873 * Receive window is amount of space in rcv queue, 1874 * but not less than advertised window. 1875 */ 1876 win = sbspace(&so->so_rcv); 1877 if (win < 0) 1878 win = 0; 1879 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1880 1881 switch (tp->t_state) { 1882 1883 /* 1884 * If the state is SYN_RECEIVED: 1885 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1886 */ 1887 case TCPS_SYN_RECEIVED: 1888 if ((thflags & TH_ACK) && 1889 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1890 SEQ_GT(th->th_ack, tp->snd_max))) { 1891 rstreason = BANDLIM_RST_OPENPORT; 1892 goto dropwithreset; 1893 } 1894 if (IS_FASTOPEN(tp->t_flags)) { 1895 /* 1896 * When a TFO connection is in SYN_RECEIVED, the 1897 * only valid packets are the initial SYN, a 1898 * retransmit/copy of the initial SYN (possibly with 1899 * a subset of the original data), a valid ACK, a 1900 * FIN, or a RST. 1901 */ 1902 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1903 rstreason = BANDLIM_RST_OPENPORT; 1904 goto dropwithreset; 1905 } else if (thflags & TH_SYN) { 1906 /* non-initial SYN is ignored */ 1907 if ((tcp_timer_active(tp, TT_DELACK) || 1908 tcp_timer_active(tp, TT_REXMT))) 1909 goto drop; 1910 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1911 goto drop; 1912 } 1913 } 1914 break; 1915 1916 /* 1917 * If the state is SYN_SENT: 1918 * if seg contains a RST with valid ACK (SEQ.ACK has already 1919 * been verified), then drop the connection. 1920 * if seg contains a RST without an ACK, drop the seg. 1921 * if seg does not contain SYN, then drop the seg. 1922 * Otherwise this is an acceptable SYN segment 1923 * initialize tp->rcv_nxt and tp->irs 1924 * if seg contains ack then advance tp->snd_una 1925 * if seg contains an ECE and ECN support is enabled, the stream 1926 * is ECN capable. 1927 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1928 * arrange for segment to be acked (eventually) 1929 * continue processing rest of data/controls, beginning with URG 1930 */ 1931 case TCPS_SYN_SENT: 1932 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1933 TCP_PROBE5(connect__refused, NULL, tp, 1934 m, tp, th); 1935 tp = tcp_drop(tp, ECONNREFUSED); 1936 } 1937 if (thflags & TH_RST) 1938 goto drop; 1939 if (!(thflags & TH_SYN)) 1940 goto drop; 1941 1942 tp->irs = th->th_seq; 1943 tcp_rcvseqinit(tp); 1944 if (thflags & TH_ACK) { 1945 int tfo_partial_ack = 0; 1946 1947 TCPSTAT_INC(tcps_connects); 1948 soisconnected(so); 1949 #ifdef MAC 1950 mac_socketpeer_set_from_mbuf(m, so); 1951 #endif 1952 /* Do window scaling on this connection? */ 1953 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1954 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1955 tp->rcv_scale = tp->request_r_scale; 1956 } 1957 tp->rcv_adv += min(tp->rcv_wnd, 1958 TCP_MAXWIN << tp->rcv_scale); 1959 tp->snd_una++; /* SYN is acked */ 1960 /* 1961 * If not all the data that was sent in the TFO SYN 1962 * has been acked, resend the remainder right away. 1963 */ 1964 if (IS_FASTOPEN(tp->t_flags) && 1965 (tp->snd_una != tp->snd_max)) { 1966 tp->snd_nxt = th->th_ack; 1967 tfo_partial_ack = 1; 1968 } 1969 /* 1970 * If there's data, delay ACK; if there's also a FIN 1971 * ACKNOW will be turned on later. 1972 */ 1973 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 1974 tcp_timer_activate(tp, TT_DELACK, 1975 tcp_delacktime); 1976 else 1977 tp->t_flags |= TF_ACKNOW; 1978 1979 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) && 1980 V_tcp_do_ecn) { 1981 tp->t_flags2 |= TF2_ECN_PERMIT; 1982 TCPSTAT_INC(tcps_ecn_shs); 1983 } 1984 1985 /* 1986 * Received <SYN,ACK> in SYN_SENT[*] state. 1987 * Transitions: 1988 * SYN_SENT --> ESTABLISHED 1989 * SYN_SENT* --> FIN_WAIT_1 1990 */ 1991 tp->t_starttime = ticks; 1992 if (tp->t_flags & TF_NEEDFIN) { 1993 tcp_state_change(tp, TCPS_FIN_WAIT_1); 1994 tp->t_flags &= ~TF_NEEDFIN; 1995 thflags &= ~TH_SYN; 1996 } else { 1997 tcp_state_change(tp, TCPS_ESTABLISHED); 1998 TCP_PROBE5(connect__established, NULL, tp, 1999 m, tp, th); 2000 cc_conn_init(tp); 2001 tcp_timer_activate(tp, TT_KEEP, 2002 TP_KEEPIDLE(tp)); 2003 } 2004 } else { 2005 /* 2006 * Received initial SYN in SYN-SENT[*] state => 2007 * simultaneous open. 2008 * If it succeeds, connection is * half-synchronized. 2009 * Otherwise, do 3-way handshake: 2010 * SYN-SENT -> SYN-RECEIVED 2011 * SYN-SENT* -> SYN-RECEIVED* 2012 */ 2013 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2014 tcp_timer_activate(tp, TT_REXMT, 0); 2015 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2016 } 2017 2018 INP_WLOCK_ASSERT(tp->t_inpcb); 2019 2020 /* 2021 * Advance th->th_seq to correspond to first data byte. 2022 * If data, trim to stay within window, 2023 * dropping FIN if necessary. 2024 */ 2025 th->th_seq++; 2026 if (tlen > tp->rcv_wnd) { 2027 todrop = tlen - tp->rcv_wnd; 2028 m_adj(m, -todrop); 2029 tlen = tp->rcv_wnd; 2030 thflags &= ~TH_FIN; 2031 TCPSTAT_INC(tcps_rcvpackafterwin); 2032 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2033 } 2034 tp->snd_wl1 = th->th_seq - 1; 2035 tp->rcv_up = th->th_seq; 2036 /* 2037 * Client side of transaction: already sent SYN and data. 2038 * If the remote host used T/TCP to validate the SYN, 2039 * our data will be ACK'd; if so, enter normal data segment 2040 * processing in the middle of step 5, ack processing. 2041 * Otherwise, goto step 6. 2042 */ 2043 if (thflags & TH_ACK) 2044 goto process_ACK; 2045 2046 goto step6; 2047 2048 /* 2049 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2050 * do normal processing. 2051 * 2052 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2053 */ 2054 case TCPS_LAST_ACK: 2055 case TCPS_CLOSING: 2056 break; /* continue normal processing */ 2057 } 2058 2059 /* 2060 * States other than LISTEN or SYN_SENT. 2061 * First check the RST flag and sequence number since reset segments 2062 * are exempt from the timestamp and connection count tests. This 2063 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2064 * below which allowed reset segments in half the sequence space 2065 * to fall though and be processed (which gives forged reset 2066 * segments with a random sequence number a 50 percent chance of 2067 * killing a connection). 2068 * Then check timestamp, if present. 2069 * Then check the connection count, if present. 2070 * Then check that at least some bytes of segment are within 2071 * receive window. If segment begins before rcv_nxt, 2072 * drop leading data (and SYN); if nothing left, just ack. 2073 */ 2074 if (thflags & TH_RST) { 2075 /* 2076 * RFC5961 Section 3.2 2077 * 2078 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2079 * - If RST is in window, we send challenge ACK. 2080 * 2081 * Note: to take into account delayed ACKs, we should 2082 * test against last_ack_sent instead of rcv_nxt. 2083 * Note 2: we handle special case of closed window, not 2084 * covered by the RFC. 2085 */ 2086 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2087 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2088 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2089 2090 KASSERT(tp->t_state != TCPS_SYN_SENT, 2091 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2092 __func__, th, tp)); 2093 2094 if (V_tcp_insecure_rst || 2095 tp->last_ack_sent == th->th_seq) { 2096 TCPSTAT_INC(tcps_drops); 2097 /* Drop the connection. */ 2098 switch (tp->t_state) { 2099 case TCPS_SYN_RECEIVED: 2100 so->so_error = ECONNREFUSED; 2101 goto close; 2102 case TCPS_ESTABLISHED: 2103 case TCPS_FIN_WAIT_1: 2104 case TCPS_FIN_WAIT_2: 2105 case TCPS_CLOSE_WAIT: 2106 case TCPS_CLOSING: 2107 case TCPS_LAST_ACK: 2108 so->so_error = ECONNRESET; 2109 close: 2110 /* FALLTHROUGH */ 2111 default: 2112 tp = tcp_close(tp); 2113 } 2114 } else { 2115 TCPSTAT_INC(tcps_badrst); 2116 /* Send challenge ACK. */ 2117 tcp_respond(tp, mtod(m, void *), th, m, 2118 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2119 tp->last_ack_sent = tp->rcv_nxt; 2120 m = NULL; 2121 } 2122 } 2123 goto drop; 2124 } 2125 2126 /* 2127 * RFC5961 Section 4.2 2128 * Send challenge ACK for any SYN in synchronized state. 2129 */ 2130 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2131 tp->t_state != TCPS_SYN_RECEIVED) { 2132 TCPSTAT_INC(tcps_badsyn); 2133 if (V_tcp_insecure_syn && 2134 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2135 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2136 tp = tcp_drop(tp, ECONNRESET); 2137 rstreason = BANDLIM_UNLIMITED; 2138 } else { 2139 /* Send challenge ACK. */ 2140 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2141 tp->snd_nxt, TH_ACK); 2142 tp->last_ack_sent = tp->rcv_nxt; 2143 m = NULL; 2144 } 2145 goto drop; 2146 } 2147 2148 /* 2149 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2150 * and it's less than ts_recent, drop it. 2151 */ 2152 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2153 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2154 2155 /* Check to see if ts_recent is over 24 days old. */ 2156 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2157 /* 2158 * Invalidate ts_recent. If this segment updates 2159 * ts_recent, the age will be reset later and ts_recent 2160 * will get a valid value. If it does not, setting 2161 * ts_recent to zero will at least satisfy the 2162 * requirement that zero be placed in the timestamp 2163 * echo reply when ts_recent isn't valid. The 2164 * age isn't reset until we get a valid ts_recent 2165 * because we don't want out-of-order segments to be 2166 * dropped when ts_recent is old. 2167 */ 2168 tp->ts_recent = 0; 2169 } else { 2170 TCPSTAT_INC(tcps_rcvduppack); 2171 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2172 TCPSTAT_INC(tcps_pawsdrop); 2173 if (tlen) 2174 goto dropafterack; 2175 goto drop; 2176 } 2177 } 2178 2179 /* 2180 * In the SYN-RECEIVED state, validate that the packet belongs to 2181 * this connection before trimming the data to fit the receive 2182 * window. Check the sequence number versus IRS since we know 2183 * the sequence numbers haven't wrapped. This is a partial fix 2184 * for the "LAND" DoS attack. 2185 */ 2186 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2187 rstreason = BANDLIM_RST_OPENPORT; 2188 goto dropwithreset; 2189 } 2190 2191 todrop = tp->rcv_nxt - th->th_seq; 2192 if (todrop > 0) { 2193 if (thflags & TH_SYN) { 2194 thflags &= ~TH_SYN; 2195 th->th_seq++; 2196 if (th->th_urp > 1) 2197 th->th_urp--; 2198 else 2199 thflags &= ~TH_URG; 2200 todrop--; 2201 } 2202 /* 2203 * Following if statement from Stevens, vol. 2, p. 960. 2204 */ 2205 if (todrop > tlen 2206 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2207 /* 2208 * Any valid FIN must be to the left of the window. 2209 * At this point the FIN must be a duplicate or out 2210 * of sequence; drop it. 2211 */ 2212 thflags &= ~TH_FIN; 2213 2214 /* 2215 * Send an ACK to resynchronize and drop any data. 2216 * But keep on processing for RST or ACK. 2217 */ 2218 tp->t_flags |= TF_ACKNOW; 2219 todrop = tlen; 2220 TCPSTAT_INC(tcps_rcvduppack); 2221 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2222 } else { 2223 TCPSTAT_INC(tcps_rcvpartduppack); 2224 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2225 } 2226 /* 2227 * DSACK - add SACK block for dropped range 2228 */ 2229 if (tp->t_flags & TF_SACK_PERMIT) { 2230 tcp_update_sack_list(tp, th->th_seq, 2231 th->th_seq + todrop); 2232 /* 2233 * ACK now, as the next in-sequence segment 2234 * will clear the DSACK block again 2235 */ 2236 tp->t_flags |= TF_ACKNOW; 2237 } 2238 drop_hdrlen += todrop; /* drop from the top afterwards */ 2239 th->th_seq += todrop; 2240 tlen -= todrop; 2241 if (th->th_urp > todrop) 2242 th->th_urp -= todrop; 2243 else { 2244 thflags &= ~TH_URG; 2245 th->th_urp = 0; 2246 } 2247 } 2248 2249 /* 2250 * If new data are received on a connection after the 2251 * user processes are gone, then RST the other end. 2252 */ 2253 if ((so->so_state & SS_NOFDREF) && 2254 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2255 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2256 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2257 "after socket was closed, " 2258 "sending RST and removing tcpcb\n", 2259 s, __func__, tcpstates[tp->t_state], tlen); 2260 free(s, M_TCPLOG); 2261 } 2262 tp = tcp_close(tp); 2263 TCPSTAT_INC(tcps_rcvafterclose); 2264 rstreason = BANDLIM_UNLIMITED; 2265 goto dropwithreset; 2266 } 2267 2268 /* 2269 * If segment ends after window, drop trailing data 2270 * (and PUSH and FIN); if nothing left, just ACK. 2271 */ 2272 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2273 if (todrop > 0) { 2274 TCPSTAT_INC(tcps_rcvpackafterwin); 2275 if (todrop >= tlen) { 2276 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2277 /* 2278 * If window is closed can only take segments at 2279 * window edge, and have to drop data and PUSH from 2280 * incoming segments. Continue processing, but 2281 * remember to ack. Otherwise, drop segment 2282 * and ack. 2283 */ 2284 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2285 tp->t_flags |= TF_ACKNOW; 2286 TCPSTAT_INC(tcps_rcvwinprobe); 2287 } else 2288 goto dropafterack; 2289 } else 2290 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2291 m_adj(m, -todrop); 2292 tlen -= todrop; 2293 thflags &= ~(TH_PUSH|TH_FIN); 2294 } 2295 2296 /* 2297 * If last ACK falls within this segment's sequence numbers, 2298 * record its timestamp. 2299 * NOTE: 2300 * 1) That the test incorporates suggestions from the latest 2301 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2302 * 2) That updating only on newer timestamps interferes with 2303 * our earlier PAWS tests, so this check should be solely 2304 * predicated on the sequence space of this segment. 2305 * 3) That we modify the segment boundary check to be 2306 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2307 * instead of RFC1323's 2308 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2309 * This modified check allows us to overcome RFC1323's 2310 * limitations as described in Stevens TCP/IP Illustrated 2311 * Vol. 2 p.869. In such cases, we can still calculate the 2312 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2313 */ 2314 if ((to.to_flags & TOF_TS) != 0 && 2315 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2316 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2317 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2318 tp->ts_recent_age = tcp_ts_getticks(); 2319 tp->ts_recent = to.to_tsval; 2320 } 2321 2322 /* 2323 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2324 * flag is on (half-synchronized state), then queue data for 2325 * later processing; else drop segment and return. 2326 */ 2327 if ((thflags & TH_ACK) == 0) { 2328 if (tp->t_state == TCPS_SYN_RECEIVED || 2329 (tp->t_flags & TF_NEEDSYN)) { 2330 if (tp->t_state == TCPS_SYN_RECEIVED && 2331 IS_FASTOPEN(tp->t_flags)) { 2332 tp->snd_wnd = tiwin; 2333 cc_conn_init(tp); 2334 } 2335 goto step6; 2336 } else if (tp->t_flags & TF_ACKNOW) 2337 goto dropafterack; 2338 else 2339 goto drop; 2340 } 2341 2342 /* 2343 * Ack processing. 2344 */ 2345 switch (tp->t_state) { 2346 2347 /* 2348 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2349 * ESTABLISHED state and continue processing. 2350 * The ACK was checked above. 2351 */ 2352 case TCPS_SYN_RECEIVED: 2353 2354 TCPSTAT_INC(tcps_connects); 2355 soisconnected(so); 2356 /* Do window scaling? */ 2357 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2358 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2359 tp->rcv_scale = tp->request_r_scale; 2360 } 2361 tp->snd_wnd = tiwin; 2362 /* 2363 * Make transitions: 2364 * SYN-RECEIVED -> ESTABLISHED 2365 * SYN-RECEIVED* -> FIN-WAIT-1 2366 */ 2367 tp->t_starttime = ticks; 2368 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2369 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2370 tp->t_tfo_pending = NULL; 2371 2372 /* 2373 * Account for the ACK of our SYN prior to 2374 * regular ACK processing below. 2375 */ 2376 tp->snd_una++; 2377 } 2378 if (tp->t_flags & TF_NEEDFIN) { 2379 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2380 tp->t_flags &= ~TF_NEEDFIN; 2381 } else { 2382 tcp_state_change(tp, TCPS_ESTABLISHED); 2383 TCP_PROBE5(accept__established, NULL, tp, 2384 m, tp, th); 2385 /* 2386 * TFO connections call cc_conn_init() during SYN 2387 * processing. Calling it again here for such 2388 * connections is not harmless as it would undo the 2389 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2390 * is retransmitted. 2391 */ 2392 if (!IS_FASTOPEN(tp->t_flags)) 2393 cc_conn_init(tp); 2394 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2395 } 2396 /* 2397 * If segment contains data or ACK, will call tcp_reass() 2398 * later; if not, do so now to pass queued data to user. 2399 */ 2400 if (tlen == 0 && (thflags & TH_FIN) == 0) 2401 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2402 (struct mbuf *)0); 2403 tp->snd_wl1 = th->th_seq - 1; 2404 /* FALLTHROUGH */ 2405 2406 /* 2407 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2408 * ACKs. If the ack is in the range 2409 * tp->snd_una < th->th_ack <= tp->snd_max 2410 * then advance tp->snd_una to th->th_ack and drop 2411 * data from the retransmission queue. If this ACK reflects 2412 * more up to date window information we update our window information. 2413 */ 2414 case TCPS_ESTABLISHED: 2415 case TCPS_FIN_WAIT_1: 2416 case TCPS_FIN_WAIT_2: 2417 case TCPS_CLOSE_WAIT: 2418 case TCPS_CLOSING: 2419 case TCPS_LAST_ACK: 2420 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2421 TCPSTAT_INC(tcps_rcvacktoomuch); 2422 goto dropafterack; 2423 } 2424 if ((tp->t_flags & TF_SACK_PERMIT) && 2425 ((to.to_flags & TOF_SACK) || 2426 !TAILQ_EMPTY(&tp->snd_holes))) 2427 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2428 else 2429 /* 2430 * Reset the value so that previous (valid) value 2431 * from the last ack with SACK doesn't get used. 2432 */ 2433 tp->sackhint.sacked_bytes = 0; 2434 2435 #ifdef TCP_HHOOK 2436 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2437 hhook_run_tcp_est_in(tp, th, &to); 2438 #endif 2439 2440 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2441 u_int maxseg; 2442 2443 maxseg = tcp_maxseg(tp); 2444 if (tlen == 0 && 2445 (tiwin == tp->snd_wnd || 2446 (tp->t_flags & TF_SACK_PERMIT))) { 2447 /* 2448 * If this is the first time we've seen a 2449 * FIN from the remote, this is not a 2450 * duplicate and it needs to be processed 2451 * normally. This happens during a 2452 * simultaneous close. 2453 */ 2454 if ((thflags & TH_FIN) && 2455 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2456 tp->t_dupacks = 0; 2457 break; 2458 } 2459 TCPSTAT_INC(tcps_rcvdupack); 2460 /* 2461 * If we have outstanding data (other than 2462 * a window probe), this is a completely 2463 * duplicate ack (ie, window info didn't 2464 * change and FIN isn't set), 2465 * the ack is the biggest we've 2466 * seen and we've seen exactly our rexmt 2467 * threshold of them, assume a packet 2468 * has been dropped and retransmit it. 2469 * Kludge snd_nxt & the congestion 2470 * window so we send only this one 2471 * packet. 2472 * 2473 * We know we're losing at the current 2474 * window size so do congestion avoidance 2475 * (set ssthresh to half the current window 2476 * and pull our congestion window back to 2477 * the new ssthresh). 2478 * 2479 * Dup acks mean that packets have left the 2480 * network (they're now cached at the receiver) 2481 * so bump cwnd by the amount in the receiver 2482 * to keep a constant cwnd packets in the 2483 * network. 2484 * 2485 * When using TCP ECN, notify the peer that 2486 * we reduced the cwnd. 2487 */ 2488 /* 2489 * Following 2 kinds of acks should not affect 2490 * dupack counting: 2491 * 1) Old acks 2492 * 2) Acks with SACK but without any new SACK 2493 * information in them. These could result from 2494 * any anomaly in the network like a switch 2495 * duplicating packets or a possible DoS attack. 2496 */ 2497 if (th->th_ack != tp->snd_una || 2498 ((tp->t_flags & TF_SACK_PERMIT) && 2499 !sack_changed)) 2500 break; 2501 else if (!tcp_timer_active(tp, TT_REXMT)) 2502 tp->t_dupacks = 0; 2503 else if (++tp->t_dupacks > tcprexmtthresh || 2504 IN_FASTRECOVERY(tp->t_flags)) { 2505 cc_ack_received(tp, th, nsegs, 2506 CC_DUPACK); 2507 if ((tp->t_flags & TF_SACK_PERMIT) && 2508 IN_FASTRECOVERY(tp->t_flags)) { 2509 int awnd; 2510 2511 /* 2512 * Compute the amount of data in flight first. 2513 * We can inject new data into the pipe iff 2514 * we have less than 1/2 the original window's 2515 * worth of data in flight. 2516 */ 2517 if (V_tcp_do_rfc6675_pipe) 2518 awnd = tcp_compute_pipe(tp); 2519 else 2520 awnd = (tp->snd_nxt - tp->snd_fack) + 2521 tp->sackhint.sack_bytes_rexmit; 2522 2523 if (awnd < tp->snd_ssthresh) { 2524 tp->snd_cwnd += maxseg; 2525 if (tp->snd_cwnd > tp->snd_ssthresh) 2526 tp->snd_cwnd = tp->snd_ssthresh; 2527 } 2528 } else 2529 tp->snd_cwnd += maxseg; 2530 (void) tp->t_fb->tfb_tcp_output(tp); 2531 goto drop; 2532 } else if (tp->t_dupacks == tcprexmtthresh) { 2533 tcp_seq onxt = tp->snd_nxt; 2534 2535 /* 2536 * If we're doing sack, check to 2537 * see if we're already in sack 2538 * recovery. If we're not doing sack, 2539 * check to see if we're in newreno 2540 * recovery. 2541 */ 2542 if (tp->t_flags & TF_SACK_PERMIT) { 2543 if (IN_FASTRECOVERY(tp->t_flags)) { 2544 tp->t_dupacks = 0; 2545 break; 2546 } 2547 } else { 2548 if (SEQ_LEQ(th->th_ack, 2549 tp->snd_recover)) { 2550 tp->t_dupacks = 0; 2551 break; 2552 } 2553 } 2554 /* Congestion signal before ack. */ 2555 cc_cong_signal(tp, th, CC_NDUPACK); 2556 cc_ack_received(tp, th, nsegs, 2557 CC_DUPACK); 2558 tcp_timer_activate(tp, TT_REXMT, 0); 2559 tp->t_rtttime = 0; 2560 if (tp->t_flags & TF_SACK_PERMIT) { 2561 TCPSTAT_INC( 2562 tcps_sack_recovery_episode); 2563 tp->sack_newdata = tp->snd_nxt; 2564 tp->snd_cwnd = maxseg; 2565 (void) tp->t_fb->tfb_tcp_output(tp); 2566 goto drop; 2567 } 2568 tp->snd_nxt = th->th_ack; 2569 tp->snd_cwnd = maxseg; 2570 (void) tp->t_fb->tfb_tcp_output(tp); 2571 KASSERT(tp->snd_limited <= 2, 2572 ("%s: tp->snd_limited too big", 2573 __func__)); 2574 tp->snd_cwnd = tp->snd_ssthresh + 2575 maxseg * 2576 (tp->t_dupacks - tp->snd_limited); 2577 if (SEQ_GT(onxt, tp->snd_nxt)) 2578 tp->snd_nxt = onxt; 2579 goto drop; 2580 } else if (V_tcp_do_rfc3042) { 2581 /* 2582 * Process first and second duplicate 2583 * ACKs. Each indicates a segment 2584 * leaving the network, creating room 2585 * for more. Make sure we can send a 2586 * packet on reception of each duplicate 2587 * ACK by increasing snd_cwnd by one 2588 * segment. Restore the original 2589 * snd_cwnd after packet transmission. 2590 */ 2591 cc_ack_received(tp, th, nsegs, 2592 CC_DUPACK); 2593 uint32_t oldcwnd = tp->snd_cwnd; 2594 tcp_seq oldsndmax = tp->snd_max; 2595 u_int sent; 2596 int avail; 2597 2598 KASSERT(tp->t_dupacks == 1 || 2599 tp->t_dupacks == 2, 2600 ("%s: dupacks not 1 or 2", 2601 __func__)); 2602 if (tp->t_dupacks == 1) 2603 tp->snd_limited = 0; 2604 tp->snd_cwnd = 2605 (tp->snd_nxt - tp->snd_una) + 2606 (tp->t_dupacks - tp->snd_limited) * 2607 maxseg; 2608 /* 2609 * Only call tcp_output when there 2610 * is new data available to be sent. 2611 * Otherwise we would send pure ACKs. 2612 */ 2613 SOCKBUF_LOCK(&so->so_snd); 2614 avail = sbavail(&so->so_snd) - 2615 (tp->snd_nxt - tp->snd_una); 2616 SOCKBUF_UNLOCK(&so->so_snd); 2617 if (avail > 0) 2618 (void) tp->t_fb->tfb_tcp_output(tp); 2619 sent = tp->snd_max - oldsndmax; 2620 if (sent > maxseg) { 2621 KASSERT((tp->t_dupacks == 2 && 2622 tp->snd_limited == 0) || 2623 (sent == maxseg + 1 && 2624 tp->t_flags & TF_SENTFIN), 2625 ("%s: sent too much", 2626 __func__)); 2627 tp->snd_limited = 2; 2628 } else if (sent > 0) 2629 ++tp->snd_limited; 2630 tp->snd_cwnd = oldcwnd; 2631 goto drop; 2632 } 2633 } 2634 break; 2635 } else { 2636 /* 2637 * This ack is advancing the left edge, reset the 2638 * counter. 2639 */ 2640 tp->t_dupacks = 0; 2641 /* 2642 * If this ack also has new SACK info, increment the 2643 * counter as per rfc6675. 2644 */ 2645 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed) 2646 tp->t_dupacks++; 2647 } 2648 2649 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2650 ("%s: th_ack <= snd_una", __func__)); 2651 2652 /* 2653 * If the congestion window was inflated to account 2654 * for the other side's cached packets, retract it. 2655 */ 2656 if (IN_FASTRECOVERY(tp->t_flags)) { 2657 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2658 if (tp->t_flags & TF_SACK_PERMIT) 2659 tcp_sack_partialack(tp, th); 2660 else 2661 tcp_newreno_partial_ack(tp, th); 2662 } else 2663 cc_post_recovery(tp, th); 2664 } 2665 /* 2666 * If we reach this point, ACK is not a duplicate, 2667 * i.e., it ACKs something we sent. 2668 */ 2669 if (tp->t_flags & TF_NEEDSYN) { 2670 /* 2671 * T/TCP: Connection was half-synchronized, and our 2672 * SYN has been ACK'd (so connection is now fully 2673 * synchronized). Go to non-starred state, 2674 * increment snd_una for ACK of SYN, and check if 2675 * we can do window scaling. 2676 */ 2677 tp->t_flags &= ~TF_NEEDSYN; 2678 tp->snd_una++; 2679 /* Do window scaling? */ 2680 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2681 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2682 tp->rcv_scale = tp->request_r_scale; 2683 /* Send window already scaled. */ 2684 } 2685 } 2686 2687 process_ACK: 2688 INP_WLOCK_ASSERT(tp->t_inpcb); 2689 2690 acked = BYTES_THIS_ACK(tp, th); 2691 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2692 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2693 tp->snd_una, th->th_ack, tp, m)); 2694 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2695 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2696 2697 /* 2698 * If we just performed our first retransmit, and the ACK 2699 * arrives within our recovery window, then it was a mistake 2700 * to do the retransmit in the first place. Recover our 2701 * original cwnd and ssthresh, and proceed to transmit where 2702 * we left off. 2703 */ 2704 if (tp->t_rxtshift == 1 && 2705 tp->t_flags & TF_PREVVALID && 2706 tp->t_badrxtwin && 2707 SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 2708 cc_cong_signal(tp, th, CC_RTO_ERR); 2709 2710 /* 2711 * If we have a timestamp reply, update smoothed 2712 * round trip time. If no timestamp is present but 2713 * transmit timer is running and timed sequence 2714 * number was acked, update smoothed round trip time. 2715 * Since we now have an rtt measurement, cancel the 2716 * timer backoff (cf., Phil Karn's retransmit alg.). 2717 * Recompute the initial retransmit timer. 2718 * 2719 * Some boxes send broken timestamp replies 2720 * during the SYN+ACK phase, ignore 2721 * timestamps of 0 or we could calculate a 2722 * huge RTT and blow up the retransmit timer. 2723 */ 2724 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2725 uint32_t t; 2726 2727 t = tcp_ts_getticks() - to.to_tsecr; 2728 if (!tp->t_rttlow || tp->t_rttlow > t) 2729 tp->t_rttlow = t; 2730 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2731 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2732 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2733 tp->t_rttlow = ticks - tp->t_rtttime; 2734 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2735 } 2736 2737 /* 2738 * If all outstanding data is acked, stop retransmit 2739 * timer and remember to restart (more output or persist). 2740 * If there is more data to be acked, restart retransmit 2741 * timer, using current (possibly backed-off) value. 2742 */ 2743 if (th->th_ack == tp->snd_max) { 2744 tcp_timer_activate(tp, TT_REXMT, 0); 2745 needoutput = 1; 2746 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2747 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2748 2749 /* 2750 * If no data (only SYN) was ACK'd, 2751 * skip rest of ACK processing. 2752 */ 2753 if (acked == 0) 2754 goto step6; 2755 2756 /* 2757 * Let the congestion control algorithm update congestion 2758 * control related information. This typically means increasing 2759 * the congestion window. 2760 */ 2761 cc_ack_received(tp, th, nsegs, CC_ACK); 2762 2763 SOCKBUF_LOCK(&so->so_snd); 2764 if (acked > sbavail(&so->so_snd)) { 2765 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2766 tp->snd_wnd -= sbavail(&so->so_snd); 2767 else 2768 tp->snd_wnd = 0; 2769 mfree = sbcut_locked(&so->so_snd, 2770 (int)sbavail(&so->so_snd)); 2771 ourfinisacked = 1; 2772 } else { 2773 mfree = sbcut_locked(&so->so_snd, acked); 2774 if (tp->snd_wnd >= (uint32_t) acked) 2775 tp->snd_wnd -= acked; 2776 else 2777 tp->snd_wnd = 0; 2778 ourfinisacked = 0; 2779 } 2780 /* NB: sowwakeup_locked() does an implicit unlock. */ 2781 sowwakeup_locked(so); 2782 m_freem(mfree); 2783 /* Detect una wraparound. */ 2784 if (!IN_RECOVERY(tp->t_flags) && 2785 SEQ_GT(tp->snd_una, tp->snd_recover) && 2786 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2787 tp->snd_recover = th->th_ack - 1; 2788 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2789 if (IN_RECOVERY(tp->t_flags) && 2790 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2791 EXIT_RECOVERY(tp->t_flags); 2792 } 2793 tp->snd_una = th->th_ack; 2794 if (tp->t_flags & TF_SACK_PERMIT) { 2795 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2796 tp->snd_recover = tp->snd_una; 2797 } 2798 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2799 tp->snd_nxt = tp->snd_una; 2800 2801 switch (tp->t_state) { 2802 2803 /* 2804 * In FIN_WAIT_1 STATE in addition to the processing 2805 * for the ESTABLISHED state if our FIN is now acknowledged 2806 * then enter FIN_WAIT_2. 2807 */ 2808 case TCPS_FIN_WAIT_1: 2809 if (ourfinisacked) { 2810 /* 2811 * If we can't receive any more 2812 * data, then closing user can proceed. 2813 * Starting the timer is contrary to the 2814 * specification, but if we don't get a FIN 2815 * we'll hang forever. 2816 * 2817 * XXXjl: 2818 * we should release the tp also, and use a 2819 * compressed state. 2820 */ 2821 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2822 soisdisconnected(so); 2823 tcp_timer_activate(tp, TT_2MSL, 2824 (tcp_fast_finwait2_recycle ? 2825 tcp_finwait2_timeout : 2826 TP_MAXIDLE(tp))); 2827 } 2828 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2829 } 2830 break; 2831 2832 /* 2833 * In CLOSING STATE in addition to the processing for 2834 * the ESTABLISHED state if the ACK acknowledges our FIN 2835 * then enter the TIME-WAIT state, otherwise ignore 2836 * the segment. 2837 */ 2838 case TCPS_CLOSING: 2839 if (ourfinisacked) { 2840 tcp_twstart(tp); 2841 m_freem(m); 2842 return; 2843 } 2844 break; 2845 2846 /* 2847 * In LAST_ACK, we may still be waiting for data to drain 2848 * and/or to be acked, as well as for the ack of our FIN. 2849 * If our FIN is now acknowledged, delete the TCB, 2850 * enter the closed state and return. 2851 */ 2852 case TCPS_LAST_ACK: 2853 if (ourfinisacked) { 2854 tp = tcp_close(tp); 2855 goto drop; 2856 } 2857 break; 2858 } 2859 } 2860 2861 step6: 2862 INP_WLOCK_ASSERT(tp->t_inpcb); 2863 2864 /* 2865 * Update window information. 2866 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2867 */ 2868 if ((thflags & TH_ACK) && 2869 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2870 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2871 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2872 /* keep track of pure window updates */ 2873 if (tlen == 0 && 2874 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2875 TCPSTAT_INC(tcps_rcvwinupd); 2876 tp->snd_wnd = tiwin; 2877 tp->snd_wl1 = th->th_seq; 2878 tp->snd_wl2 = th->th_ack; 2879 if (tp->snd_wnd > tp->max_sndwnd) 2880 tp->max_sndwnd = tp->snd_wnd; 2881 needoutput = 1; 2882 } 2883 2884 /* 2885 * Process segments with URG. 2886 */ 2887 if ((thflags & TH_URG) && th->th_urp && 2888 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2889 /* 2890 * This is a kludge, but if we receive and accept 2891 * random urgent pointers, we'll crash in 2892 * soreceive. It's hard to imagine someone 2893 * actually wanting to send this much urgent data. 2894 */ 2895 SOCKBUF_LOCK(&so->so_rcv); 2896 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2897 th->th_urp = 0; /* XXX */ 2898 thflags &= ~TH_URG; /* XXX */ 2899 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2900 goto dodata; /* XXX */ 2901 } 2902 /* 2903 * If this segment advances the known urgent pointer, 2904 * then mark the data stream. This should not happen 2905 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2906 * a FIN has been received from the remote side. 2907 * In these states we ignore the URG. 2908 * 2909 * According to RFC961 (Assigned Protocols), 2910 * the urgent pointer points to the last octet 2911 * of urgent data. We continue, however, 2912 * to consider it to indicate the first octet 2913 * of data past the urgent section as the original 2914 * spec states (in one of two places). 2915 */ 2916 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2917 tp->rcv_up = th->th_seq + th->th_urp; 2918 so->so_oobmark = sbavail(&so->so_rcv) + 2919 (tp->rcv_up - tp->rcv_nxt) - 1; 2920 if (so->so_oobmark == 0) 2921 so->so_rcv.sb_state |= SBS_RCVATMARK; 2922 sohasoutofband(so); 2923 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2924 } 2925 SOCKBUF_UNLOCK(&so->so_rcv); 2926 /* 2927 * Remove out of band data so doesn't get presented to user. 2928 * This can happen independent of advancing the URG pointer, 2929 * but if two URG's are pending at once, some out-of-band 2930 * data may creep in... ick. 2931 */ 2932 if (th->th_urp <= (uint32_t)tlen && 2933 !(so->so_options & SO_OOBINLINE)) { 2934 /* hdr drop is delayed */ 2935 tcp_pulloutofband(so, th, m, drop_hdrlen); 2936 } 2937 } else { 2938 /* 2939 * If no out of band data is expected, 2940 * pull receive urgent pointer along 2941 * with the receive window. 2942 */ 2943 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2944 tp->rcv_up = tp->rcv_nxt; 2945 } 2946 dodata: /* XXX */ 2947 INP_WLOCK_ASSERT(tp->t_inpcb); 2948 2949 /* 2950 * Process the segment text, merging it into the TCP sequencing queue, 2951 * and arranging for acknowledgment of receipt if necessary. 2952 * This process logically involves adjusting tp->rcv_wnd as data 2953 * is presented to the user (this happens in tcp_usrreq.c, 2954 * case PRU_RCVD). If a FIN has already been received on this 2955 * connection then we just ignore the text. 2956 */ 2957 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 2958 IS_FASTOPEN(tp->t_flags)); 2959 if ((tlen || (thflags & TH_FIN) || tfo_syn) && 2960 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2961 tcp_seq save_start = th->th_seq; 2962 tcp_seq save_rnxt = tp->rcv_nxt; 2963 int save_tlen = tlen; 2964 m_adj(m, drop_hdrlen); /* delayed header drop */ 2965 /* 2966 * Insert segment which includes th into TCP reassembly queue 2967 * with control block tp. Set thflags to whether reassembly now 2968 * includes a segment with FIN. This handles the common case 2969 * inline (segment is the next to be received on an established 2970 * connection, and the queue is empty), avoiding linkage into 2971 * and removal from the queue and repetition of various 2972 * conversions. 2973 * Set DELACK for segments received in order, but ack 2974 * immediately when segments are out of order (so 2975 * fast retransmit can work). 2976 */ 2977 if (th->th_seq == tp->rcv_nxt && 2978 SEGQ_EMPTY(tp) && 2979 (TCPS_HAVEESTABLISHED(tp->t_state) || 2980 tfo_syn)) { 2981 if (DELAY_ACK(tp, tlen) || tfo_syn) 2982 tp->t_flags |= TF_DELACK; 2983 else 2984 tp->t_flags |= TF_ACKNOW; 2985 tp->rcv_nxt += tlen; 2986 thflags = th->th_flags & TH_FIN; 2987 TCPSTAT_INC(tcps_rcvpack); 2988 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2989 SOCKBUF_LOCK(&so->so_rcv); 2990 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2991 m_freem(m); 2992 else 2993 sbappendstream_locked(&so->so_rcv, m, 0); 2994 /* NB: sorwakeup_locked() does an implicit unlock. */ 2995 sorwakeup_locked(so); 2996 } else { 2997 /* 2998 * XXX: Due to the header drop above "th" is 2999 * theoretically invalid by now. Fortunately 3000 * m_adj() doesn't actually frees any mbufs 3001 * when trimming from the head. 3002 */ 3003 tcp_seq temp = save_start; 3004 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3005 tp->t_flags |= TF_ACKNOW; 3006 } 3007 if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) { 3008 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) { 3009 /* 3010 * DSACK actually handled in the fastpath 3011 * above. 3012 */ 3013 tcp_update_sack_list(tp, save_start, 3014 save_start + save_tlen); 3015 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3016 if ((tp->rcv_numsacks >= 1) && 3017 (tp->sackblks[0].end == save_start)) { 3018 /* 3019 * Partial overlap, recorded at todrop 3020 * above. 3021 */ 3022 tcp_update_sack_list(tp, 3023 tp->sackblks[0].start, 3024 tp->sackblks[0].end); 3025 } else { 3026 tcp_update_dsack_list(tp, save_start, 3027 save_start + save_tlen); 3028 } 3029 } else if (tlen >= save_tlen) { 3030 /* Update of sackblks. */ 3031 tcp_update_dsack_list(tp, save_start, 3032 save_start + save_tlen); 3033 } else if (tlen > 0) { 3034 tcp_update_dsack_list(tp, save_start, 3035 save_start + tlen); 3036 } 3037 } 3038 #if 0 3039 /* 3040 * Note the amount of data that peer has sent into 3041 * our window, in order to estimate the sender's 3042 * buffer size. 3043 * XXX: Unused. 3044 */ 3045 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3046 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3047 else 3048 len = so->so_rcv.sb_hiwat; 3049 #endif 3050 } else { 3051 m_freem(m); 3052 thflags &= ~TH_FIN; 3053 } 3054 3055 /* 3056 * If FIN is received ACK the FIN and let the user know 3057 * that the connection is closing. 3058 */ 3059 if (thflags & TH_FIN) { 3060 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3061 socantrcvmore(so); 3062 /* 3063 * If connection is half-synchronized 3064 * (ie NEEDSYN flag on) then delay ACK, 3065 * so it may be piggybacked when SYN is sent. 3066 * Otherwise, since we received a FIN then no 3067 * more input can be expected, send ACK now. 3068 */ 3069 if (tp->t_flags & TF_NEEDSYN) 3070 tp->t_flags |= TF_DELACK; 3071 else 3072 tp->t_flags |= TF_ACKNOW; 3073 tp->rcv_nxt++; 3074 } 3075 switch (tp->t_state) { 3076 3077 /* 3078 * In SYN_RECEIVED and ESTABLISHED STATES 3079 * enter the CLOSE_WAIT state. 3080 */ 3081 case TCPS_SYN_RECEIVED: 3082 tp->t_starttime = ticks; 3083 /* FALLTHROUGH */ 3084 case TCPS_ESTABLISHED: 3085 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3086 break; 3087 3088 /* 3089 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3090 * enter the CLOSING state. 3091 */ 3092 case TCPS_FIN_WAIT_1: 3093 tcp_state_change(tp, TCPS_CLOSING); 3094 break; 3095 3096 /* 3097 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3098 * starting the time-wait timer, turning off the other 3099 * standard timers. 3100 */ 3101 case TCPS_FIN_WAIT_2: 3102 tcp_twstart(tp); 3103 return; 3104 } 3105 } 3106 #ifdef TCPDEBUG 3107 if (so->so_options & SO_DEBUG) 3108 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3109 &tcp_savetcp, 0); 3110 #endif 3111 TCP_PROBE3(debug__input, tp, th, m); 3112 3113 /* 3114 * Return any desired output. 3115 */ 3116 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3117 (void) tp->t_fb->tfb_tcp_output(tp); 3118 3119 check_delack: 3120 INP_WLOCK_ASSERT(tp->t_inpcb); 3121 3122 if (tp->t_flags & TF_DELACK) { 3123 tp->t_flags &= ~TF_DELACK; 3124 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3125 } 3126 INP_WUNLOCK(tp->t_inpcb); 3127 return; 3128 3129 dropafterack: 3130 /* 3131 * Generate an ACK dropping incoming segment if it occupies 3132 * sequence space, where the ACK reflects our state. 3133 * 3134 * We can now skip the test for the RST flag since all 3135 * paths to this code happen after packets containing 3136 * RST have been dropped. 3137 * 3138 * In the SYN-RECEIVED state, don't send an ACK unless the 3139 * segment we received passes the SYN-RECEIVED ACK test. 3140 * If it fails send a RST. This breaks the loop in the 3141 * "LAND" DoS attack, and also prevents an ACK storm 3142 * between two listening ports that have been sent forged 3143 * SYN segments, each with the source address of the other. 3144 */ 3145 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3146 (SEQ_GT(tp->snd_una, th->th_ack) || 3147 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3148 rstreason = BANDLIM_RST_OPENPORT; 3149 goto dropwithreset; 3150 } 3151 #ifdef TCPDEBUG 3152 if (so->so_options & SO_DEBUG) 3153 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3154 &tcp_savetcp, 0); 3155 #endif 3156 TCP_PROBE3(debug__input, tp, th, m); 3157 tp->t_flags |= TF_ACKNOW; 3158 (void) tp->t_fb->tfb_tcp_output(tp); 3159 INP_WUNLOCK(tp->t_inpcb); 3160 m_freem(m); 3161 return; 3162 3163 dropwithreset: 3164 if (tp != NULL) { 3165 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3166 INP_WUNLOCK(tp->t_inpcb); 3167 } else 3168 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3169 return; 3170 3171 drop: 3172 /* 3173 * Drop space held by incoming segment and return. 3174 */ 3175 #ifdef TCPDEBUG 3176 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3177 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3178 &tcp_savetcp, 0); 3179 #endif 3180 TCP_PROBE3(debug__input, tp, th, m); 3181 if (tp != NULL) 3182 INP_WUNLOCK(tp->t_inpcb); 3183 m_freem(m); 3184 } 3185 3186 /* 3187 * Issue RST and make ACK acceptable to originator of segment. 3188 * The mbuf must still include the original packet header. 3189 * tp may be NULL. 3190 */ 3191 void 3192 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3193 int tlen, int rstreason) 3194 { 3195 #ifdef INET 3196 struct ip *ip; 3197 #endif 3198 #ifdef INET6 3199 struct ip6_hdr *ip6; 3200 #endif 3201 3202 if (tp != NULL) { 3203 INP_WLOCK_ASSERT(tp->t_inpcb); 3204 } 3205 3206 /* Don't bother if destination was broadcast/multicast. */ 3207 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3208 goto drop; 3209 #ifdef INET6 3210 if (mtod(m, struct ip *)->ip_v == 6) { 3211 ip6 = mtod(m, struct ip6_hdr *); 3212 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3213 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3214 goto drop; 3215 /* IPv6 anycast check is done at tcp6_input() */ 3216 } 3217 #endif 3218 #if defined(INET) && defined(INET6) 3219 else 3220 #endif 3221 #ifdef INET 3222 { 3223 ip = mtod(m, struct ip *); 3224 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3225 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3226 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3227 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3228 goto drop; 3229 } 3230 #endif 3231 3232 /* Perform bandwidth limiting. */ 3233 if (badport_bandlim(rstreason) < 0) 3234 goto drop; 3235 3236 /* tcp_respond consumes the mbuf chain. */ 3237 if (th->th_flags & TH_ACK) { 3238 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3239 th->th_ack, TH_RST); 3240 } else { 3241 if (th->th_flags & TH_SYN) 3242 tlen++; 3243 if (th->th_flags & TH_FIN) 3244 tlen++; 3245 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3246 (tcp_seq)0, TH_RST|TH_ACK); 3247 } 3248 return; 3249 drop: 3250 m_freem(m); 3251 } 3252 3253 /* 3254 * Parse TCP options and place in tcpopt. 3255 */ 3256 void 3257 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3258 { 3259 int opt, optlen; 3260 3261 to->to_flags = 0; 3262 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3263 opt = cp[0]; 3264 if (opt == TCPOPT_EOL) 3265 break; 3266 if (opt == TCPOPT_NOP) 3267 optlen = 1; 3268 else { 3269 if (cnt < 2) 3270 break; 3271 optlen = cp[1]; 3272 if (optlen < 2 || optlen > cnt) 3273 break; 3274 } 3275 switch (opt) { 3276 case TCPOPT_MAXSEG: 3277 if (optlen != TCPOLEN_MAXSEG) 3278 continue; 3279 if (!(flags & TO_SYN)) 3280 continue; 3281 to->to_flags |= TOF_MSS; 3282 bcopy((char *)cp + 2, 3283 (char *)&to->to_mss, sizeof(to->to_mss)); 3284 to->to_mss = ntohs(to->to_mss); 3285 break; 3286 case TCPOPT_WINDOW: 3287 if (optlen != TCPOLEN_WINDOW) 3288 continue; 3289 if (!(flags & TO_SYN)) 3290 continue; 3291 to->to_flags |= TOF_SCALE; 3292 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3293 break; 3294 case TCPOPT_TIMESTAMP: 3295 if (optlen != TCPOLEN_TIMESTAMP) 3296 continue; 3297 to->to_flags |= TOF_TS; 3298 bcopy((char *)cp + 2, 3299 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3300 to->to_tsval = ntohl(to->to_tsval); 3301 bcopy((char *)cp + 6, 3302 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3303 to->to_tsecr = ntohl(to->to_tsecr); 3304 break; 3305 case TCPOPT_SIGNATURE: 3306 /* 3307 * In order to reply to a host which has set the 3308 * TCP_SIGNATURE option in its initial SYN, we have 3309 * to record the fact that the option was observed 3310 * here for the syncache code to perform the correct 3311 * response. 3312 */ 3313 if (optlen != TCPOLEN_SIGNATURE) 3314 continue; 3315 to->to_flags |= TOF_SIGNATURE; 3316 to->to_signature = cp + 2; 3317 break; 3318 case TCPOPT_SACK_PERMITTED: 3319 if (optlen != TCPOLEN_SACK_PERMITTED) 3320 continue; 3321 if (!(flags & TO_SYN)) 3322 continue; 3323 if (!V_tcp_do_sack) 3324 continue; 3325 to->to_flags |= TOF_SACKPERM; 3326 break; 3327 case TCPOPT_SACK: 3328 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3329 continue; 3330 if (flags & TO_SYN) 3331 continue; 3332 to->to_flags |= TOF_SACK; 3333 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3334 to->to_sacks = cp + 2; 3335 TCPSTAT_INC(tcps_sack_rcv_blocks); 3336 break; 3337 case TCPOPT_FAST_OPEN: 3338 /* 3339 * Cookie length validation is performed by the 3340 * server side cookie checking code or the client 3341 * side cookie cache update code. 3342 */ 3343 if (!(flags & TO_SYN)) 3344 continue; 3345 if (!V_tcp_fastopen_client_enable && 3346 !V_tcp_fastopen_server_enable) 3347 continue; 3348 to->to_flags |= TOF_FASTOPEN; 3349 to->to_tfo_len = optlen - 2; 3350 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3351 break; 3352 default: 3353 continue; 3354 } 3355 } 3356 } 3357 3358 /* 3359 * Pull out of band byte out of a segment so 3360 * it doesn't appear in the user's data queue. 3361 * It is still reflected in the segment length for 3362 * sequencing purposes. 3363 */ 3364 void 3365 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3366 int off) 3367 { 3368 int cnt = off + th->th_urp - 1; 3369 3370 while (cnt >= 0) { 3371 if (m->m_len > cnt) { 3372 char *cp = mtod(m, caddr_t) + cnt; 3373 struct tcpcb *tp = sototcpcb(so); 3374 3375 INP_WLOCK_ASSERT(tp->t_inpcb); 3376 3377 tp->t_iobc = *cp; 3378 tp->t_oobflags |= TCPOOB_HAVEDATA; 3379 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3380 m->m_len--; 3381 if (m->m_flags & M_PKTHDR) 3382 m->m_pkthdr.len--; 3383 return; 3384 } 3385 cnt -= m->m_len; 3386 m = m->m_next; 3387 if (m == NULL) 3388 break; 3389 } 3390 panic("tcp_pulloutofband"); 3391 } 3392 3393 /* 3394 * Collect new round-trip time estimate 3395 * and update averages and current timeout. 3396 */ 3397 void 3398 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3399 { 3400 int delta; 3401 3402 INP_WLOCK_ASSERT(tp->t_inpcb); 3403 3404 TCPSTAT_INC(tcps_rttupdated); 3405 tp->t_rttupdated++; 3406 #ifdef STATS 3407 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, 3408 imax(0, rtt * 1000 / hz)); 3409 #endif 3410 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3411 /* 3412 * srtt is stored as fixed point with 5 bits after the 3413 * binary point (i.e., scaled by 8). The following magic 3414 * is equivalent to the smoothing algorithm in rfc793 with 3415 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3416 * point). Adjust rtt to origin 0. 3417 */ 3418 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3419 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3420 3421 if ((tp->t_srtt += delta) <= 0) 3422 tp->t_srtt = 1; 3423 3424 /* 3425 * We accumulate a smoothed rtt variance (actually, a 3426 * smoothed mean difference), then set the retransmit 3427 * timer to smoothed rtt + 4 times the smoothed variance. 3428 * rttvar is stored as fixed point with 4 bits after the 3429 * binary point (scaled by 16). The following is 3430 * equivalent to rfc793 smoothing with an alpha of .75 3431 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3432 * rfc793's wired-in beta. 3433 */ 3434 if (delta < 0) 3435 delta = -delta; 3436 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3437 if ((tp->t_rttvar += delta) <= 0) 3438 tp->t_rttvar = 1; 3439 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3440 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3441 } else { 3442 /* 3443 * No rtt measurement yet - use the unsmoothed rtt. 3444 * Set the variance to half the rtt (so our first 3445 * retransmit happens at 3*rtt). 3446 */ 3447 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3448 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3449 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3450 } 3451 tp->t_rtttime = 0; 3452 tp->t_rxtshift = 0; 3453 3454 /* 3455 * the retransmit should happen at rtt + 4 * rttvar. 3456 * Because of the way we do the smoothing, srtt and rttvar 3457 * will each average +1/2 tick of bias. When we compute 3458 * the retransmit timer, we want 1/2 tick of rounding and 3459 * 1 extra tick because of +-1/2 tick uncertainty in the 3460 * firing of the timer. The bias will give us exactly the 3461 * 1.5 tick we need. But, because the bias is 3462 * statistical, we have to test that we don't drop below 3463 * the minimum feasible timer (which is 2 ticks). 3464 */ 3465 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3466 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3467 3468 /* 3469 * We received an ack for a packet that wasn't retransmitted; 3470 * it is probably safe to discard any error indications we've 3471 * received recently. This isn't quite right, but close enough 3472 * for now (a route might have failed after we sent a segment, 3473 * and the return path might not be symmetrical). 3474 */ 3475 tp->t_softerror = 0; 3476 } 3477 3478 /* 3479 * Determine a reasonable value for maxseg size. 3480 * If the route is known, check route for mtu. 3481 * If none, use an mss that can be handled on the outgoing interface 3482 * without forcing IP to fragment. If no route is found, route has no mtu, 3483 * or the destination isn't local, use a default, hopefully conservative 3484 * size (usually 512 or the default IP max size, but no more than the mtu 3485 * of the interface), as we can't discover anything about intervening 3486 * gateways or networks. We also initialize the congestion/slow start 3487 * window to be a single segment if the destination isn't local. 3488 * While looking at the routing entry, we also initialize other path-dependent 3489 * parameters from pre-set or cached values in the routing entry. 3490 * 3491 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3492 * IP options, e.g. IPSEC data, since length of this data may vary, and 3493 * thus it is calculated for every segment separately in tcp_output(). 3494 * 3495 * NOTE that this routine is only called when we process an incoming 3496 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3497 * settings are handled in tcp_mssopt(). 3498 */ 3499 void 3500 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3501 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3502 { 3503 int mss = 0; 3504 uint32_t maxmtu = 0; 3505 struct inpcb *inp = tp->t_inpcb; 3506 struct hc_metrics_lite metrics; 3507 #ifdef INET6 3508 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3509 size_t min_protoh = isipv6 ? 3510 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3511 sizeof (struct tcpiphdr); 3512 #else 3513 const size_t min_protoh = sizeof(struct tcpiphdr); 3514 #endif 3515 3516 INP_WLOCK_ASSERT(tp->t_inpcb); 3517 3518 if (mtuoffer != -1) { 3519 KASSERT(offer == -1, ("%s: conflict", __func__)); 3520 offer = mtuoffer - min_protoh; 3521 } 3522 3523 /* Initialize. */ 3524 #ifdef INET6 3525 if (isipv6) { 3526 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3527 tp->t_maxseg = V_tcp_v6mssdflt; 3528 } 3529 #endif 3530 #if defined(INET) && defined(INET6) 3531 else 3532 #endif 3533 #ifdef INET 3534 { 3535 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3536 tp->t_maxseg = V_tcp_mssdflt; 3537 } 3538 #endif 3539 3540 /* 3541 * No route to sender, stay with default mss and return. 3542 */ 3543 if (maxmtu == 0) { 3544 /* 3545 * In case we return early we need to initialize metrics 3546 * to a defined state as tcp_hc_get() would do for us 3547 * if there was no cache hit. 3548 */ 3549 if (metricptr != NULL) 3550 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3551 return; 3552 } 3553 3554 /* What have we got? */ 3555 switch (offer) { 3556 case 0: 3557 /* 3558 * Offer == 0 means that there was no MSS on the SYN 3559 * segment, in this case we use tcp_mssdflt as 3560 * already assigned to t_maxseg above. 3561 */ 3562 offer = tp->t_maxseg; 3563 break; 3564 3565 case -1: 3566 /* 3567 * Offer == -1 means that we didn't receive SYN yet. 3568 */ 3569 /* FALLTHROUGH */ 3570 3571 default: 3572 /* 3573 * Prevent DoS attack with too small MSS. Round up 3574 * to at least minmss. 3575 */ 3576 offer = max(offer, V_tcp_minmss); 3577 } 3578 3579 /* 3580 * rmx information is now retrieved from tcp_hostcache. 3581 */ 3582 tcp_hc_get(&inp->inp_inc, &metrics); 3583 if (metricptr != NULL) 3584 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3585 3586 /* 3587 * If there's a discovered mtu in tcp hostcache, use it. 3588 * Else, use the link mtu. 3589 */ 3590 if (metrics.rmx_mtu) 3591 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3592 else { 3593 #ifdef INET6 3594 if (isipv6) { 3595 mss = maxmtu - min_protoh; 3596 if (!V_path_mtu_discovery && 3597 !in6_localaddr(&inp->in6p_faddr)) 3598 mss = min(mss, V_tcp_v6mssdflt); 3599 } 3600 #endif 3601 #if defined(INET) && defined(INET6) 3602 else 3603 #endif 3604 #ifdef INET 3605 { 3606 mss = maxmtu - min_protoh; 3607 if (!V_path_mtu_discovery && 3608 !in_localaddr(inp->inp_faddr)) 3609 mss = min(mss, V_tcp_mssdflt); 3610 } 3611 #endif 3612 /* 3613 * XXX - The above conditional (mss = maxmtu - min_protoh) 3614 * probably violates the TCP spec. 3615 * The problem is that, since we don't know the 3616 * other end's MSS, we are supposed to use a conservative 3617 * default. But, if we do that, then MTU discovery will 3618 * never actually take place, because the conservative 3619 * default is much less than the MTUs typically seen 3620 * on the Internet today. For the moment, we'll sweep 3621 * this under the carpet. 3622 * 3623 * The conservative default might not actually be a problem 3624 * if the only case this occurs is when sending an initial 3625 * SYN with options and data to a host we've never talked 3626 * to before. Then, they will reply with an MSS value which 3627 * will get recorded and the new parameters should get 3628 * recomputed. For Further Study. 3629 */ 3630 } 3631 mss = min(mss, offer); 3632 3633 /* 3634 * Sanity check: make sure that maxseg will be large 3635 * enough to allow some data on segments even if the 3636 * all the option space is used (40bytes). Otherwise 3637 * funny things may happen in tcp_output. 3638 * 3639 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3640 */ 3641 mss = max(mss, 64); 3642 3643 tp->t_maxseg = mss; 3644 } 3645 3646 void 3647 tcp_mss(struct tcpcb *tp, int offer) 3648 { 3649 int mss; 3650 uint32_t bufsize; 3651 struct inpcb *inp; 3652 struct socket *so; 3653 struct hc_metrics_lite metrics; 3654 struct tcp_ifcap cap; 3655 3656 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3657 3658 bzero(&cap, sizeof(cap)); 3659 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3660 3661 mss = tp->t_maxseg; 3662 inp = tp->t_inpcb; 3663 3664 /* 3665 * If there's a pipesize, change the socket buffer to that size, 3666 * don't change if sb_hiwat is different than default (then it 3667 * has been changed on purpose with setsockopt). 3668 * Make the socket buffers an integral number of mss units; 3669 * if the mss is larger than the socket buffer, decrease the mss. 3670 */ 3671 so = inp->inp_socket; 3672 SOCKBUF_LOCK(&so->so_snd); 3673 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3674 bufsize = metrics.rmx_sendpipe; 3675 else 3676 bufsize = so->so_snd.sb_hiwat; 3677 if (bufsize < mss) 3678 mss = bufsize; 3679 else { 3680 bufsize = roundup(bufsize, mss); 3681 if (bufsize > sb_max) 3682 bufsize = sb_max; 3683 if (bufsize > so->so_snd.sb_hiwat) 3684 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3685 } 3686 SOCKBUF_UNLOCK(&so->so_snd); 3687 /* 3688 * Sanity check: make sure that maxseg will be large 3689 * enough to allow some data on segments even if the 3690 * all the option space is used (40bytes). Otherwise 3691 * funny things may happen in tcp_output. 3692 * 3693 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3694 */ 3695 tp->t_maxseg = max(mss, 64); 3696 3697 SOCKBUF_LOCK(&so->so_rcv); 3698 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3699 bufsize = metrics.rmx_recvpipe; 3700 else 3701 bufsize = so->so_rcv.sb_hiwat; 3702 if (bufsize > mss) { 3703 bufsize = roundup(bufsize, mss); 3704 if (bufsize > sb_max) 3705 bufsize = sb_max; 3706 if (bufsize > so->so_rcv.sb_hiwat) 3707 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3708 } 3709 SOCKBUF_UNLOCK(&so->so_rcv); 3710 3711 /* Check the interface for TSO capabilities. */ 3712 if (cap.ifcap & CSUM_TSO) { 3713 tp->t_flags |= TF_TSO; 3714 tp->t_tsomax = cap.tsomax; 3715 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3716 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3717 } 3718 } 3719 3720 /* 3721 * Determine the MSS option to send on an outgoing SYN. 3722 */ 3723 int 3724 tcp_mssopt(struct in_conninfo *inc) 3725 { 3726 int mss = 0; 3727 uint32_t thcmtu = 0; 3728 uint32_t maxmtu = 0; 3729 size_t min_protoh; 3730 3731 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3732 3733 #ifdef INET6 3734 if (inc->inc_flags & INC_ISIPV6) { 3735 mss = V_tcp_v6mssdflt; 3736 maxmtu = tcp_maxmtu6(inc, NULL); 3737 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3738 } 3739 #endif 3740 #if defined(INET) && defined(INET6) 3741 else 3742 #endif 3743 #ifdef INET 3744 { 3745 mss = V_tcp_mssdflt; 3746 maxmtu = tcp_maxmtu(inc, NULL); 3747 min_protoh = sizeof(struct tcpiphdr); 3748 } 3749 #endif 3750 #if defined(INET6) || defined(INET) 3751 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3752 #endif 3753 3754 if (maxmtu && thcmtu) 3755 mss = min(maxmtu, thcmtu) - min_protoh; 3756 else if (maxmtu || thcmtu) 3757 mss = max(maxmtu, thcmtu) - min_protoh; 3758 3759 return (mss); 3760 } 3761 3762 3763 /* 3764 * On a partial ack arrives, force the retransmission of the 3765 * next unacknowledged segment. Do not clear tp->t_dupacks. 3766 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3767 * be started again. 3768 */ 3769 void 3770 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3771 { 3772 tcp_seq onxt = tp->snd_nxt; 3773 uint32_t ocwnd = tp->snd_cwnd; 3774 u_int maxseg = tcp_maxseg(tp); 3775 3776 INP_WLOCK_ASSERT(tp->t_inpcb); 3777 3778 tcp_timer_activate(tp, TT_REXMT, 0); 3779 tp->t_rtttime = 0; 3780 tp->snd_nxt = th->th_ack; 3781 /* 3782 * Set snd_cwnd to one segment beyond acknowledged offset. 3783 * (tp->snd_una has not yet been updated when this function is called.) 3784 */ 3785 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3786 tp->t_flags |= TF_ACKNOW; 3787 (void) tp->t_fb->tfb_tcp_output(tp); 3788 tp->snd_cwnd = ocwnd; 3789 if (SEQ_GT(onxt, tp->snd_nxt)) 3790 tp->snd_nxt = onxt; 3791 /* 3792 * Partial window deflation. Relies on fact that tp->snd_una 3793 * not updated yet. 3794 */ 3795 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3796 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3797 else 3798 tp->snd_cwnd = 0; 3799 tp->snd_cwnd += maxseg; 3800 } 3801 3802 int 3803 tcp_compute_pipe(struct tcpcb *tp) 3804 { 3805 return (tp->snd_max - tp->snd_una + 3806 tp->sackhint.sack_bytes_rexmit - 3807 tp->sackhint.sacked_bytes); 3808 } 3809 3810 uint32_t 3811 tcp_compute_initwnd(uint32_t maxseg) 3812 { 3813 /* 3814 * Calculate the Initial Window, also used as Restart Window 3815 * 3816 * RFC5681 Section 3.1 specifies the default conservative values. 3817 * RFC3390 specifies slightly more aggressive values. 3818 * RFC6928 increases it to ten segments. 3819 * Support for user specified value for initial flight size. 3820 */ 3821 if (V_tcp_initcwnd_segments) 3822 return min(V_tcp_initcwnd_segments * maxseg, 3823 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 3824 else if (V_tcp_do_rfc3390) 3825 return min(4 * maxseg, max(2 * maxseg, 4380)); 3826 else { 3827 /* Per RFC5681 Section 3.1 */ 3828 if (maxseg > 2190) 3829 return (2 * maxseg); 3830 else if (maxseg > 1095) 3831 return (3 * maxseg); 3832 else 3833 return (4 * maxseg); 3834 } 3835 } 3836