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 #include <netinet/tcp_ecn.h> 127 #include <netinet/udp.h> 128 129 #include <netipsec/ipsec_support.h> 130 131 #include <machine/in_cksum.h> 132 133 #include <security/mac/mac_framework.h> 134 135 const int tcprexmtthresh = 3; 136 137 VNET_DEFINE(int, tcp_log_in_vain) = 0; 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_VNET | CTLFLAG_RW, 139 &VNET_NAME(tcp_log_in_vain), 0, 140 "Log all incoming TCP segments to closed ports"); 141 142 VNET_DEFINE(int, blackhole) = 0; 143 #define V_blackhole VNET(blackhole) 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 145 &VNET_NAME(blackhole), 0, 146 "Do not send RST on segments to closed ports"); 147 148 VNET_DEFINE(bool, blackhole_local) = false; 149 #define V_blackhole_local VNET(blackhole_local) 150 SYSCTL_BOOL(_net_inet_tcp, OID_AUTO, blackhole_local, CTLFLAG_VNET | 151 CTLFLAG_RW, &VNET_NAME(blackhole_local), false, 152 "Enforce net.inet.tcp.blackhole for locally originated packets"); 153 154 VNET_DEFINE(int, tcp_delack_enabled) = 1; 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 156 &VNET_NAME(tcp_delack_enabled), 0, 157 "Delay ACK to try and piggyback it onto a data packet"); 158 159 VNET_DEFINE(int, drop_synfin) = 0; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 161 &VNET_NAME(drop_synfin), 0, 162 "Drop TCP packets with SYN+FIN set"); 163 164 VNET_DEFINE(int, tcp_do_prr_conservative) = 0; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_prr_conservative, CTLFLAG_VNET | CTLFLAG_RW, 166 &VNET_NAME(tcp_do_prr_conservative), 0, 167 "Do conservative Proportional Rate Reduction"); 168 169 VNET_DEFINE(int, tcp_do_prr) = 1; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_prr, CTLFLAG_VNET | CTLFLAG_RW, 171 &VNET_NAME(tcp_do_prr), 1, 172 "Enable Proportional Rate Reduction per RFC 6937"); 173 174 VNET_DEFINE(int, tcp_do_lrd) = 0; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_lrd, CTLFLAG_VNET | CTLFLAG_RW, 176 &VNET_NAME(tcp_do_lrd), 1, 177 "Perform Lost Retransmission Detection"); 178 179 VNET_DEFINE(int, tcp_do_newcwv) = 0; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW, 181 &VNET_NAME(tcp_do_newcwv), 0, 182 "Enable New Congestion Window Validation per RFC7661"); 183 184 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 185 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 186 &VNET_NAME(tcp_do_rfc3042), 0, 187 "Enable RFC 3042 (Limited Transmit)"); 188 189 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 191 &VNET_NAME(tcp_do_rfc3390), 0, 192 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 193 194 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 195 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 196 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 197 "Slow-start flight size (initial congestion window) in number of segments"); 198 199 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 201 &VNET_NAME(tcp_do_rfc3465), 0, 202 "Enable RFC 3465 (Appropriate Byte Counting)"); 203 204 VNET_DEFINE(int, tcp_abc_l_var) = 2; 205 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 206 &VNET_NAME(tcp_abc_l_var), 2, 207 "Cap the max cwnd increment during slow-start to this number of segments"); 208 209 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, 210 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 211 "TCP ECN"); 212 213 VNET_DEFINE(int, tcp_do_ecn) = 2; 214 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 215 &VNET_NAME(tcp_do_ecn), 0, 216 "TCP ECN support"); 217 218 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 219 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 220 &VNET_NAME(tcp_ecn_maxretries), 0, 221 "Max retries before giving up on ECN"); 222 223 VNET_DEFINE(int, tcp_insecure_syn) = 0; 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 225 &VNET_NAME(tcp_insecure_syn), 0, 226 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 227 228 VNET_DEFINE(int, tcp_insecure_rst) = 0; 229 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 230 &VNET_NAME(tcp_insecure_rst), 0, 231 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 232 233 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 234 #define V_tcp_recvspace VNET(tcp_recvspace) 235 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 236 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 237 238 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 239 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 240 &VNET_NAME(tcp_do_autorcvbuf), 0, 241 "Enable automatic receive buffer sizing"); 242 243 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 244 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 245 &VNET_NAME(tcp_autorcvbuf_max), 0, 246 "Max size of automatic receive buffer"); 247 248 VNET_DEFINE(struct inpcbinfo, tcbinfo); 249 250 /* 251 * TCP statistics are stored in an array of counter(9)s, which size matches 252 * size of struct tcpstat. TCP running connection count is a regular array. 253 */ 254 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 255 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 256 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 257 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 258 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 259 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 260 "TCP connection counts by TCP state"); 261 262 /* 263 * Kernel module interface for updating tcpstat. The first argument is an index 264 * into tcpstat treated as an array. 265 */ 266 void 267 kmod_tcpstat_add(int statnum, int val) 268 { 269 270 counter_u64_add(VNET(tcpstat)[statnum], val); 271 } 272 273 #ifdef TCP_HHOOK 274 /* 275 * Wrapper for the TCP established input helper hook. 276 */ 277 void 278 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 279 { 280 struct tcp_hhook_data hhook_data; 281 282 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 283 hhook_data.tp = tp; 284 hhook_data.th = th; 285 hhook_data.to = to; 286 287 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 288 tp->osd); 289 } 290 } 291 #endif 292 293 /* 294 * CC wrapper hook functions 295 */ 296 void 297 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 298 uint16_t type) 299 { 300 #ifdef STATS 301 int32_t gput; 302 #endif 303 304 INP_WLOCK_ASSERT(tp->t_inpcb); 305 306 tp->ccv->nsegs = nsegs; 307 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 308 if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) || 309 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) && 310 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2)))) 311 tp->ccv->flags |= CCF_CWND_LIMITED; 312 else 313 tp->ccv->flags &= ~CCF_CWND_LIMITED; 314 315 if (type == CC_ACK) { 316 #ifdef STATS 317 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF, 318 ((int32_t)tp->snd_cwnd) - tp->snd_wnd); 319 if (!IN_RECOVERY(tp->t_flags)) 320 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN, 321 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs)); 322 if ((tp->t_flags & TF_GPUTINPROG) && 323 SEQ_GEQ(th->th_ack, tp->gput_ack)) { 324 /* 325 * Compute goodput in bits per millisecond. 326 */ 327 gput = (((int64_t)SEQ_SUB(th->th_ack, tp->gput_seq)) << 3) / 328 max(1, tcp_ts_getticks() - tp->gput_ts); 329 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT, 330 gput); 331 /* 332 * XXXLAS: This is a temporary hack, and should be 333 * chained off VOI_TCP_GPUT when stats(9) grows an API 334 * to deal with chained VOIs. 335 */ 336 if (tp->t_stats_gput_prev > 0) 337 stats_voi_update_abs_s32(tp->t_stats, 338 VOI_TCP_GPUT_ND, 339 ((gput - tp->t_stats_gput_prev) * 100) / 340 tp->t_stats_gput_prev); 341 tp->t_flags &= ~TF_GPUTINPROG; 342 tp->t_stats_gput_prev = gput; 343 } 344 #endif /* STATS */ 345 if (tp->snd_cwnd > tp->snd_ssthresh) { 346 tp->t_bytes_acked += tp->ccv->bytes_this_ack; 347 if (tp->t_bytes_acked >= tp->snd_cwnd) { 348 tp->t_bytes_acked -= tp->snd_cwnd; 349 tp->ccv->flags |= CCF_ABC_SENTAWND; 350 } 351 } else { 352 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 353 tp->t_bytes_acked = 0; 354 } 355 } 356 357 if (CC_ALGO(tp)->ack_received != NULL) { 358 /* XXXLAS: Find a way to live without this */ 359 tp->ccv->curack = th->th_ack; 360 CC_ALGO(tp)->ack_received(tp->ccv, type); 361 } 362 #ifdef STATS 363 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd); 364 #endif 365 } 366 367 void 368 cc_conn_init(struct tcpcb *tp) 369 { 370 struct hc_metrics_lite metrics; 371 struct inpcb *inp = tp->t_inpcb; 372 u_int maxseg; 373 int rtt; 374 375 INP_WLOCK_ASSERT(tp->t_inpcb); 376 377 tcp_hc_get(&inp->inp_inc, &metrics); 378 maxseg = tcp_maxseg(tp); 379 380 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 381 tp->t_srtt = rtt; 382 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 383 TCPSTAT_INC(tcps_usedrtt); 384 if (metrics.rmx_rttvar) { 385 tp->t_rttvar = metrics.rmx_rttvar; 386 TCPSTAT_INC(tcps_usedrttvar); 387 } else { 388 /* default variation is +- 1 rtt */ 389 tp->t_rttvar = 390 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 391 } 392 TCPT_RANGESET(tp->t_rxtcur, 393 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 394 tp->t_rttmin, TCPTV_REXMTMAX); 395 } 396 if (metrics.rmx_ssthresh) { 397 /* 398 * There's some sort of gateway or interface 399 * buffer limit on the path. Use this to set 400 * the slow start threshold, but set the 401 * threshold to no less than 2*mss. 402 */ 403 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 404 TCPSTAT_INC(tcps_usedssthresh); 405 } 406 407 /* 408 * Set the initial slow-start flight size. 409 * 410 * If a SYN or SYN/ACK was lost and retransmitted, we have to 411 * reduce the initial CWND to one segment as congestion is likely 412 * requiring us to be cautious. 413 */ 414 if (tp->snd_cwnd == 1) 415 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 416 else 417 tp->snd_cwnd = tcp_compute_initwnd(maxseg); 418 419 if (CC_ALGO(tp)->conn_init != NULL) 420 CC_ALGO(tp)->conn_init(tp->ccv); 421 } 422 423 void inline 424 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 425 { 426 INP_WLOCK_ASSERT(tp->t_inpcb); 427 428 #ifdef STATS 429 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type); 430 #endif 431 432 switch(type) { 433 case CC_NDUPACK: 434 if (!IN_FASTRECOVERY(tp->t_flags)) { 435 tp->snd_recover = tp->snd_max; 436 if (tp->t_flags2 & TF2_ECN_PERMIT) 437 tp->t_flags2 |= TF2_ECN_SND_CWR; 438 } 439 break; 440 case CC_ECN: 441 if (!IN_CONGRECOVERY(tp->t_flags) || 442 /* 443 * Allow ECN reaction on ACK to CWR, if 444 * that data segment was also CE marked. 445 */ 446 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 447 EXIT_CONGRECOVERY(tp->t_flags); 448 TCPSTAT_INC(tcps_ecn_rcwnd); 449 tp->snd_recover = tp->snd_max + 1; 450 if (tp->t_flags2 & TF2_ECN_PERMIT) 451 tp->t_flags2 |= TF2_ECN_SND_CWR; 452 } 453 break; 454 case CC_RTO: 455 tp->t_dupacks = 0; 456 tp->t_bytes_acked = 0; 457 EXIT_RECOVERY(tp->t_flags); 458 if (tp->t_flags2 & TF2_ECN_PERMIT) 459 tp->t_flags2 |= TF2_ECN_SND_CWR; 460 break; 461 case CC_RTO_ERR: 462 TCPSTAT_INC(tcps_sndrexmitbad); 463 /* RTO was unnecessary, so reset everything. */ 464 tp->snd_cwnd = tp->snd_cwnd_prev; 465 tp->snd_ssthresh = tp->snd_ssthresh_prev; 466 tp->snd_recover = tp->snd_recover_prev; 467 if (tp->t_flags & TF_WASFRECOVERY) 468 ENTER_FASTRECOVERY(tp->t_flags); 469 if (tp->t_flags & TF_WASCRECOVERY) 470 ENTER_CONGRECOVERY(tp->t_flags); 471 tp->snd_nxt = tp->snd_max; 472 tp->t_flags &= ~TF_PREVVALID; 473 tp->t_badrxtwin = 0; 474 break; 475 } 476 477 if (CC_ALGO(tp)->cong_signal != NULL) { 478 if (th != NULL) 479 tp->ccv->curack = th->th_ack; 480 CC_ALGO(tp)->cong_signal(tp->ccv, type); 481 } 482 } 483 484 void inline 485 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 486 { 487 INP_WLOCK_ASSERT(tp->t_inpcb); 488 489 /* XXXLAS: KASSERT that we're in recovery? */ 490 491 if (CC_ALGO(tp)->post_recovery != NULL) { 492 tp->ccv->curack = th->th_ack; 493 CC_ALGO(tp)->post_recovery(tp->ccv); 494 } 495 /* XXXLAS: EXIT_RECOVERY ? */ 496 tp->t_bytes_acked = 0; 497 tp->sackhint.delivered_data = 0; 498 tp->sackhint.prr_out = 0; 499 } 500 501 /* 502 * Indicate whether this ack should be delayed. We can delay the ack if 503 * following conditions are met: 504 * - There is no delayed ack timer in progress. 505 * - Our last ack wasn't a 0-sized window. We never want to delay 506 * the ack that opens up a 0-sized window. 507 * - LRO wasn't used for this segment. We make sure by checking that the 508 * segment size is not larger than the MSS. 509 */ 510 #define DELAY_ACK(tp, tlen) \ 511 ((!tcp_timer_active(tp, TT_DELACK) && \ 512 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 513 (tlen <= tp->t_maxseg) && \ 514 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 515 516 void inline 517 cc_ecnpkt_handler_flags(struct tcpcb *tp, uint16_t flags, uint8_t iptos) 518 { 519 INP_WLOCK_ASSERT(tp->t_inpcb); 520 521 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 522 switch (iptos & IPTOS_ECN_MASK) { 523 case IPTOS_ECN_CE: 524 tp->ccv->flags |= CCF_IPHDR_CE; 525 break; 526 case IPTOS_ECN_ECT0: 527 /* FALLTHROUGH */ 528 case IPTOS_ECN_ECT1: 529 /* FALLTHROUGH */ 530 case IPTOS_ECN_NOTECT: 531 tp->ccv->flags &= ~CCF_IPHDR_CE; 532 break; 533 } 534 535 if (flags & TH_CWR) 536 tp->ccv->flags |= CCF_TCPHDR_CWR; 537 else 538 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 539 540 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 541 542 if (tp->ccv->flags & CCF_ACKNOW) { 543 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 544 tp->t_flags |= TF_ACKNOW; 545 } 546 } 547 } 548 549 void inline 550 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 551 { 552 cc_ecnpkt_handler_flags(tp, tcp_get_flags(th), iptos); 553 } 554 555 /* 556 * TCP input handling is split into multiple parts: 557 * tcp6_input is a thin wrapper around tcp_input for the extended 558 * ip6_protox[] call format in ip6_input 559 * tcp_input handles primary segment validation, inpcb lookup and 560 * SYN processing on listen sockets 561 * tcp_do_segment processes the ACK and text of the segment for 562 * establishing, established and closing connections 563 */ 564 #ifdef INET6 565 int 566 tcp6_input_with_port(struct mbuf **mp, int *offp, int proto, uint16_t port) 567 { 568 struct mbuf *m; 569 struct in6_ifaddr *ia6; 570 struct ip6_hdr *ip6; 571 572 m = *mp; 573 if (m->m_len < *offp + sizeof(struct tcphdr)) { 574 m = m_pullup(m, *offp + sizeof(struct tcphdr)); 575 if (m == NULL) { 576 *mp = m; 577 TCPSTAT_INC(tcps_rcvshort); 578 return (IPPROTO_DONE); 579 } 580 } 581 582 /* 583 * draft-itojun-ipv6-tcp-to-anycast 584 * better place to put this in? 585 */ 586 ip6 = mtod(m, struct ip6_hdr *); 587 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false); 588 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 589 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 590 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 591 *mp = NULL; 592 return (IPPROTO_DONE); 593 } 594 595 *mp = m; 596 return (tcp_input_with_port(mp, offp, proto, port)); 597 } 598 599 int 600 tcp6_input(struct mbuf **mp, int *offp, int proto) 601 { 602 603 return(tcp6_input_with_port(mp, offp, proto, 0)); 604 } 605 #endif /* INET6 */ 606 607 int 608 tcp_input_with_port(struct mbuf **mp, int *offp, int proto, uint16_t port) 609 { 610 struct mbuf *m = *mp; 611 struct tcphdr *th = NULL; 612 struct ip *ip = NULL; 613 struct inpcb *inp = NULL; 614 struct tcpcb *tp = NULL; 615 struct socket *so = NULL; 616 u_char *optp = NULL; 617 int off0; 618 int optlen = 0; 619 #ifdef INET 620 int len; 621 uint8_t ipttl; 622 #endif 623 int tlen = 0, off; 624 int drop_hdrlen; 625 int thflags; 626 int rstreason = 0; /* For badport_bandlim accounting purposes */ 627 int lookupflag; 628 uint8_t iptos; 629 struct m_tag *fwd_tag = NULL; 630 #ifdef INET6 631 struct ip6_hdr *ip6 = NULL; 632 int isipv6; 633 #else 634 const void *ip6 = NULL; 635 #endif /* INET6 */ 636 struct tcpopt to; /* options in this segment */ 637 char *s = NULL; /* address and port logging */ 638 #ifdef TCPDEBUG 639 /* 640 * The size of tcp_saveipgen must be the size of the max ip header, 641 * now IPv6. 642 */ 643 u_char tcp_saveipgen[IP6_HDR_LEN]; 644 struct tcphdr tcp_savetcp; 645 short ostate = 0; 646 #endif 647 648 NET_EPOCH_ASSERT(); 649 650 #ifdef INET6 651 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 652 #endif 653 654 off0 = *offp; 655 m = *mp; 656 *mp = NULL; 657 to.to_flags = 0; 658 TCPSTAT_INC(tcps_rcvtotal); 659 660 #ifdef INET6 661 if (isipv6) { 662 ip6 = mtod(m, struct ip6_hdr *); 663 th = (struct tcphdr *)((caddr_t)ip6 + off0); 664 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 665 if (port) 666 goto skip6_csum; 667 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 668 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 669 th->th_sum = m->m_pkthdr.csum_data; 670 else 671 th->th_sum = in6_cksum_pseudo(ip6, tlen, 672 IPPROTO_TCP, m->m_pkthdr.csum_data); 673 th->th_sum ^= 0xffff; 674 } else 675 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 676 if (th->th_sum) { 677 TCPSTAT_INC(tcps_rcvbadsum); 678 goto drop; 679 } 680 skip6_csum: 681 /* 682 * Be proactive about unspecified IPv6 address in source. 683 * As we use all-zero to indicate unbounded/unconnected pcb, 684 * unspecified IPv6 address can be used to confuse us. 685 * 686 * Note that packets with unspecified IPv6 destination is 687 * already dropped in ip6_input. 688 */ 689 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 690 /* XXX stat */ 691 goto drop; 692 } 693 iptos = IPV6_TRAFFIC_CLASS(ip6); 694 } 695 #endif 696 #if defined(INET) && defined(INET6) 697 else 698 #endif 699 #ifdef INET 700 { 701 /* 702 * Get IP and TCP header together in first mbuf. 703 * Note: IP leaves IP header in first mbuf. 704 */ 705 if (off0 > sizeof (struct ip)) { 706 ip_stripoptions(m); 707 off0 = sizeof(struct ip); 708 } 709 if (m->m_len < sizeof (struct tcpiphdr)) { 710 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 711 == NULL) { 712 TCPSTAT_INC(tcps_rcvshort); 713 return (IPPROTO_DONE); 714 } 715 } 716 ip = mtod(m, struct ip *); 717 th = (struct tcphdr *)((caddr_t)ip + off0); 718 tlen = ntohs(ip->ip_len) - off0; 719 720 iptos = ip->ip_tos; 721 if (port) 722 goto skip_csum; 723 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 724 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 725 th->th_sum = m->m_pkthdr.csum_data; 726 else 727 th->th_sum = in_pseudo(ip->ip_src.s_addr, 728 ip->ip_dst.s_addr, 729 htonl(m->m_pkthdr.csum_data + tlen + 730 IPPROTO_TCP)); 731 th->th_sum ^= 0xffff; 732 } else { 733 struct ipovly *ipov = (struct ipovly *)ip; 734 735 /* 736 * Checksum extended TCP header and data. 737 */ 738 len = off0 + tlen; 739 ipttl = ip->ip_ttl; 740 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 741 ipov->ih_len = htons(tlen); 742 th->th_sum = in_cksum(m, len); 743 /* Reset length for SDT probes. */ 744 ip->ip_len = htons(len); 745 /* Reset TOS bits */ 746 ip->ip_tos = iptos; 747 /* Re-initialization for later version check */ 748 ip->ip_ttl = ipttl; 749 ip->ip_v = IPVERSION; 750 ip->ip_hl = off0 >> 2; 751 } 752 skip_csum: 753 if (th->th_sum && (port == 0)) { 754 TCPSTAT_INC(tcps_rcvbadsum); 755 goto drop; 756 } 757 } 758 #endif /* INET */ 759 760 /* 761 * Check that TCP offset makes sense, 762 * pull out TCP options and adjust length. XXX 763 */ 764 off = th->th_off << 2; 765 if (off < sizeof (struct tcphdr) || off > tlen) { 766 TCPSTAT_INC(tcps_rcvbadoff); 767 goto drop; 768 } 769 tlen -= off; /* tlen is used instead of ti->ti_len */ 770 if (off > sizeof (struct tcphdr)) { 771 #ifdef INET6 772 if (isipv6) { 773 if (m->m_len < off0 + off) { 774 m = m_pullup(m, off0 + off); 775 if (m == NULL) { 776 TCPSTAT_INC(tcps_rcvshort); 777 return (IPPROTO_DONE); 778 } 779 } 780 ip6 = mtod(m, struct ip6_hdr *); 781 th = (struct tcphdr *)((caddr_t)ip6 + off0); 782 } 783 #endif 784 #if defined(INET) && defined(INET6) 785 else 786 #endif 787 #ifdef INET 788 { 789 if (m->m_len < sizeof(struct ip) + off) { 790 if ((m = m_pullup(m, sizeof (struct ip) + off)) 791 == NULL) { 792 TCPSTAT_INC(tcps_rcvshort); 793 return (IPPROTO_DONE); 794 } 795 ip = mtod(m, struct ip *); 796 th = (struct tcphdr *)((caddr_t)ip + off0); 797 } 798 } 799 #endif 800 optlen = off - sizeof (struct tcphdr); 801 optp = (u_char *)(th + 1); 802 } 803 thflags = tcp_get_flags(th); 804 805 /* 806 * Convert TCP protocol specific fields to host format. 807 */ 808 tcp_fields_to_host(th); 809 810 /* 811 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 812 */ 813 drop_hdrlen = off0 + off; 814 815 /* 816 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 817 */ 818 if ( 819 #ifdef INET6 820 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 821 #ifdef INET 822 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 823 #endif 824 #endif 825 #if defined(INET) && !defined(INET6) 826 (m->m_flags & M_IP_NEXTHOP) 827 #endif 828 ) 829 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 830 831 /* 832 * For initial SYN packets we don't need write lock on matching 833 * PCB, be it a listening one or a synchronized one. The packet 834 * shall not modify its state. 835 */ 836 lookupflag = (thflags & (TH_ACK|TH_SYN)) == TH_SYN ? 837 INPLOOKUP_RLOCKPCB : INPLOOKUP_WLOCKPCB; 838 findpcb: 839 #ifdef INET6 840 if (isipv6 && fwd_tag != NULL) { 841 struct sockaddr_in6 *next_hop6; 842 843 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 844 /* 845 * Transparently forwarded. Pretend to be the destination. 846 * Already got one like this? 847 */ 848 inp = in6_pcblookup_mbuf(&V_tcbinfo, 849 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 850 lookupflag, m->m_pkthdr.rcvif, m); 851 if (!inp) { 852 /* 853 * It's new. Try to find the ambushing socket. 854 * Because we've rewritten the destination address, 855 * any hardware-generated hash is ignored. 856 */ 857 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 858 th->th_sport, &next_hop6->sin6_addr, 859 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 860 th->th_dport, INPLOOKUP_WILDCARD | lookupflag, 861 m->m_pkthdr.rcvif); 862 } 863 } else if (isipv6) { 864 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 865 th->th_sport, &ip6->ip6_dst, th->th_dport, 866 INPLOOKUP_WILDCARD | lookupflag, m->m_pkthdr.rcvif, m); 867 } 868 #endif /* INET6 */ 869 #if defined(INET6) && defined(INET) 870 else 871 #endif 872 #ifdef INET 873 if (fwd_tag != NULL) { 874 struct sockaddr_in *next_hop; 875 876 next_hop = (struct sockaddr_in *)(fwd_tag+1); 877 /* 878 * Transparently forwarded. Pretend to be the destination. 879 * already got one like this? 880 */ 881 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 882 ip->ip_dst, th->th_dport, lookupflag, m->m_pkthdr.rcvif, m); 883 if (!inp) { 884 /* 885 * It's new. Try to find the ambushing socket. 886 * Because we've rewritten the destination address, 887 * any hardware-generated hash is ignored. 888 */ 889 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 890 th->th_sport, next_hop->sin_addr, 891 next_hop->sin_port ? ntohs(next_hop->sin_port) : 892 th->th_dport, INPLOOKUP_WILDCARD | lookupflag, 893 m->m_pkthdr.rcvif); 894 } 895 } else 896 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 897 th->th_sport, ip->ip_dst, th->th_dport, 898 INPLOOKUP_WILDCARD | lookupflag, m->m_pkthdr.rcvif, m); 899 #endif /* INET */ 900 901 /* 902 * If the INPCB does not exist then all data in the incoming 903 * segment is discarded and an appropriate RST is sent back. 904 * XXX MRT Send RST using which routing table? 905 */ 906 if (inp == NULL) { 907 /* 908 * Log communication attempts to ports that are not 909 * in use. 910 */ 911 if ((V_tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 912 V_tcp_log_in_vain == 2) { 913 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 914 log(LOG_INFO, "%s; %s: Connection attempt " 915 "to closed port\n", s, __func__); 916 } 917 /* 918 * When blackholing do not respond with a RST but 919 * completely ignore the segment and drop it. 920 */ 921 if (((V_blackhole == 1 && (thflags & TH_SYN)) || 922 V_blackhole == 2) && (V_blackhole_local || ( 923 #ifdef INET6 924 isipv6 ? !in6_localaddr(&ip6->ip6_src) : 925 #endif 926 #ifdef INET 927 !in_localip(ip->ip_src) 928 #else 929 true 930 #endif 931 ))) 932 goto dropunlock; 933 934 rstreason = BANDLIM_RST_CLOSEDPORT; 935 goto dropwithreset; 936 } 937 INP_LOCK_ASSERT(inp); 938 /* 939 * While waiting for inp lock during the lookup, another thread 940 * can have dropped the inpcb, in which case we need to loop back 941 * and try to find a new inpcb to deliver to. 942 */ 943 if (inp->inp_flags & INP_DROPPED) { 944 INP_UNLOCK(inp); 945 inp = NULL; 946 goto findpcb; 947 } 948 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 949 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 950 ((inp->inp_socket == NULL) || !SOLISTENING(inp->inp_socket))) { 951 inp->inp_flowid = m->m_pkthdr.flowid; 952 inp->inp_flowtype = M_HASHTYPE_GET(m); 953 } 954 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 955 #ifdef INET6 956 if (isipv6 && IPSEC_ENABLED(ipv6) && 957 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 958 goto dropunlock; 959 } 960 #ifdef INET 961 else 962 #endif 963 #endif /* INET6 */ 964 #ifdef INET 965 if (IPSEC_ENABLED(ipv4) && 966 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 967 goto dropunlock; 968 } 969 #endif /* INET */ 970 #endif /* IPSEC */ 971 972 /* 973 * Check the minimum TTL for socket. 974 */ 975 if (inp->inp_ip_minttl != 0) { 976 #ifdef INET6 977 if (isipv6) { 978 if (inp->inp_ip_minttl > ip6->ip6_hlim) 979 goto dropunlock; 980 } else 981 #endif 982 if (inp->inp_ip_minttl > ip->ip_ttl) 983 goto dropunlock; 984 } 985 986 /* 987 * A previous connection in TIMEWAIT state is supposed to catch stray 988 * or duplicate segments arriving late. If this segment was a 989 * legitimate new connection attempt, the old INPCB gets removed and 990 * we can try again to find a listening socket. 991 */ 992 if (inp->inp_flags & INP_TIMEWAIT) { 993 tcp_dooptions(&to, optp, optlen, 994 (thflags & TH_SYN) ? TO_SYN : 0); 995 /* 996 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 997 */ 998 if (tcp_twcheck(inp, &to, th, m, tlen)) 999 goto findpcb; 1000 return (IPPROTO_DONE); 1001 } 1002 /* 1003 * The TCPCB may no longer exist if the connection is winding 1004 * down or it is in the CLOSED state. Either way we drop the 1005 * segment and send an appropriate response. 1006 */ 1007 tp = intotcpcb(inp); 1008 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1009 rstreason = BANDLIM_RST_CLOSEDPORT; 1010 goto dropwithreset; 1011 } 1012 1013 if ((tp->t_port != port) && (tp->t_state > TCPS_LISTEN)) { 1014 rstreason = BANDLIM_RST_CLOSEDPORT; 1015 goto dropwithreset; 1016 } 1017 1018 #ifdef TCP_OFFLOAD 1019 if (tp->t_flags & TF_TOE) { 1020 tcp_offload_input(tp, m); 1021 m = NULL; /* consumed by the TOE driver */ 1022 goto dropunlock; 1023 } 1024 #endif 1025 1026 #ifdef MAC 1027 if (mac_inpcb_check_deliver(inp, m)) 1028 goto dropunlock; 1029 #endif 1030 so = inp->inp_socket; 1031 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1032 #ifdef TCPDEBUG 1033 if (so->so_options & SO_DEBUG) { 1034 ostate = tp->t_state; 1035 #ifdef INET6 1036 if (isipv6) { 1037 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1038 } else 1039 #endif 1040 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1041 tcp_savetcp = *th; 1042 } 1043 #endif /* TCPDEBUG */ 1044 /* 1045 * When the socket is accepting connections (the INPCB is in LISTEN 1046 * state) we look into the SYN cache if this is a new connection 1047 * attempt or the completion of a previous one. 1048 */ 1049 KASSERT(tp->t_state == TCPS_LISTEN || !SOLISTENING(so), 1050 ("%s: so accepting but tp %p not listening", __func__, tp)); 1051 if (tp->t_state == TCPS_LISTEN && SOLISTENING(so)) { 1052 struct in_conninfo inc; 1053 1054 bzero(&inc, sizeof(inc)); 1055 #ifdef INET6 1056 if (isipv6) { 1057 inc.inc_flags |= INC_ISIPV6; 1058 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1059 inc.inc_flags |= INC_IPV6MINMTU; 1060 inc.inc6_faddr = ip6->ip6_src; 1061 inc.inc6_laddr = ip6->ip6_dst; 1062 } else 1063 #endif 1064 { 1065 inc.inc_faddr = ip->ip_src; 1066 inc.inc_laddr = ip->ip_dst; 1067 } 1068 inc.inc_fport = th->th_sport; 1069 inc.inc_lport = th->th_dport; 1070 inc.inc_fibnum = so->so_fibnum; 1071 1072 /* 1073 * Check for an existing connection attempt in syncache if 1074 * the flag is only ACK. A successful lookup creates a new 1075 * socket appended to the listen queue in SYN_RECEIVED state. 1076 */ 1077 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1078 /* 1079 * Parse the TCP options here because 1080 * syncookies need access to the reflected 1081 * timestamp. 1082 */ 1083 tcp_dooptions(&to, optp, optlen, 0); 1084 /* 1085 * NB: syncache_expand() doesn't unlock inp. 1086 */ 1087 rstreason = syncache_expand(&inc, &to, th, &so, m, port); 1088 if (rstreason < 0) { 1089 /* 1090 * A failing TCP MD5 signature comparison 1091 * must result in the segment being dropped 1092 * and must not produce any response back 1093 * to the sender. 1094 */ 1095 goto dropunlock; 1096 } else if (rstreason == 0) { 1097 /* 1098 * No syncache entry or ACK was not 1099 * for our SYN/ACK. Send a RST. 1100 * NB: syncache did its own logging 1101 * of the failure cause. 1102 */ 1103 rstreason = BANDLIM_RST_OPENPORT; 1104 goto dropwithreset; 1105 } 1106 tfo_socket_result: 1107 if (so == NULL) { 1108 /* 1109 * We completed the 3-way handshake 1110 * but could not allocate a socket 1111 * either due to memory shortage, 1112 * listen queue length limits or 1113 * global socket limits. Send RST 1114 * or wait and have the remote end 1115 * retransmit the ACK for another 1116 * try. 1117 */ 1118 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1119 log(LOG_DEBUG, "%s; %s: Listen socket: " 1120 "Socket allocation failed due to " 1121 "limits or memory shortage, %s\n", 1122 s, __func__, 1123 V_tcp_sc_rst_sock_fail ? 1124 "sending RST" : "try again"); 1125 if (V_tcp_sc_rst_sock_fail) { 1126 rstreason = BANDLIM_UNLIMITED; 1127 goto dropwithreset; 1128 } else 1129 goto dropunlock; 1130 } 1131 /* 1132 * Socket is created in state SYN_RECEIVED. 1133 * Unlock the listen socket, lock the newly 1134 * created socket and update the tp variable. 1135 * If we came here via jump to tfo_socket_result, 1136 * then listening socket is read-locked. 1137 */ 1138 INP_UNLOCK(inp); /* listen socket */ 1139 inp = sotoinpcb(so); 1140 /* 1141 * New connection inpcb is already locked by 1142 * syncache_expand(). 1143 */ 1144 INP_WLOCK_ASSERT(inp); 1145 tp = intotcpcb(inp); 1146 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1147 ("%s: ", __func__)); 1148 /* 1149 * Process the segment and the data it 1150 * contains. tcp_do_segment() consumes 1151 * the mbuf chain and unlocks the inpcb. 1152 */ 1153 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1154 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1155 iptos); 1156 return (IPPROTO_DONE); 1157 } 1158 /* 1159 * Segment flag validation for new connection attempts: 1160 * 1161 * Our (SYN|ACK) response was rejected. 1162 * Check with syncache and remove entry to prevent 1163 * retransmits. 1164 * 1165 * NB: syncache_chkrst does its own logging of failure 1166 * causes. 1167 */ 1168 if (thflags & TH_RST) { 1169 syncache_chkrst(&inc, th, m, port); 1170 goto dropunlock; 1171 } 1172 /* 1173 * We can't do anything without SYN. 1174 */ 1175 if ((thflags & TH_SYN) == 0) { 1176 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1177 log(LOG_DEBUG, "%s; %s: Listen socket: " 1178 "SYN is missing, segment ignored\n", 1179 s, __func__); 1180 TCPSTAT_INC(tcps_badsyn); 1181 goto dropunlock; 1182 } 1183 /* 1184 * (SYN|ACK) is bogus on a listen socket. 1185 */ 1186 if (thflags & TH_ACK) { 1187 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1188 log(LOG_DEBUG, "%s; %s: Listen socket: " 1189 "SYN|ACK invalid, segment rejected\n", 1190 s, __func__); 1191 syncache_badack(&inc, port); /* XXX: Not needed! */ 1192 TCPSTAT_INC(tcps_badsyn); 1193 rstreason = BANDLIM_RST_OPENPORT; 1194 goto dropwithreset; 1195 } 1196 /* 1197 * If the drop_synfin option is enabled, drop all 1198 * segments with both the SYN and FIN bits set. 1199 * This prevents e.g. nmap from identifying the 1200 * TCP/IP stack. 1201 * XXX: Poor reasoning. nmap has other methods 1202 * and is constantly refining its stack detection 1203 * strategies. 1204 * XXX: This is a violation of the TCP specification 1205 * and was used by RFC1644. 1206 */ 1207 if ((thflags & TH_FIN) && V_drop_synfin) { 1208 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1209 log(LOG_DEBUG, "%s; %s: Listen socket: " 1210 "SYN|FIN segment ignored (based on " 1211 "sysctl setting)\n", s, __func__); 1212 TCPSTAT_INC(tcps_badsyn); 1213 goto dropunlock; 1214 } 1215 /* 1216 * Segment's flags are (SYN) or (SYN|FIN). 1217 * 1218 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1219 * as they do not affect the state of the TCP FSM. 1220 * The data pointed to by TH_URG and th_urp is ignored. 1221 */ 1222 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1223 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1224 KASSERT(thflags & (TH_SYN), 1225 ("%s: Listen socket: TH_SYN not set", __func__)); 1226 INP_RLOCK_ASSERT(inp); 1227 #ifdef INET6 1228 /* 1229 * If deprecated address is forbidden, 1230 * we do not accept SYN to deprecated interface 1231 * address to prevent any new inbound connection from 1232 * getting established. 1233 * When we do not accept SYN, we send a TCP RST, 1234 * with deprecated source address (instead of dropping 1235 * it). We compromise it as it is much better for peer 1236 * to send a RST, and RST will be the final packet 1237 * for the exchange. 1238 * 1239 * If we do not forbid deprecated addresses, we accept 1240 * the SYN packet. RFC2462 does not suggest dropping 1241 * SYN in this case. 1242 * If we decipher RFC2462 5.5.4, it says like this: 1243 * 1. use of deprecated addr with existing 1244 * communication is okay - "SHOULD continue to be 1245 * used" 1246 * 2. use of it with new communication: 1247 * (2a) "SHOULD NOT be used if alternate address 1248 * with sufficient scope is available" 1249 * (2b) nothing mentioned otherwise. 1250 * Here we fall into (2b) case as we have no choice in 1251 * our source address selection - we must obey the peer. 1252 * 1253 * The wording in RFC2462 is confusing, and there are 1254 * multiple description text for deprecated address 1255 * handling - worse, they are not exactly the same. 1256 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1257 */ 1258 if (isipv6 && !V_ip6_use_deprecated) { 1259 struct in6_ifaddr *ia6; 1260 1261 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false); 1262 if (ia6 != NULL && 1263 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1264 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1265 log(LOG_DEBUG, "%s; %s: Listen socket: " 1266 "Connection attempt to deprecated " 1267 "IPv6 address rejected\n", 1268 s, __func__); 1269 rstreason = BANDLIM_RST_OPENPORT; 1270 goto dropwithreset; 1271 } 1272 } 1273 #endif /* INET6 */ 1274 /* 1275 * Basic sanity checks on incoming SYN requests: 1276 * Don't respond if the destination is a link layer 1277 * broadcast according to RFC1122 4.2.3.10, p. 104. 1278 * If it is from this socket it must be forged. 1279 * Don't respond if the source or destination is a 1280 * global or subnet broad- or multicast address. 1281 * Note that it is quite possible to receive unicast 1282 * link-layer packets with a broadcast IP address. Use 1283 * in_broadcast() to find them. 1284 */ 1285 if (m->m_flags & (M_BCAST|M_MCAST)) { 1286 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1287 log(LOG_DEBUG, "%s; %s: Listen socket: " 1288 "Connection attempt from broad- or multicast " 1289 "link layer address ignored\n", s, __func__); 1290 goto dropunlock; 1291 } 1292 #ifdef INET6 1293 if (isipv6) { 1294 if (th->th_dport == th->th_sport && 1295 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1296 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1297 log(LOG_DEBUG, "%s; %s: Listen socket: " 1298 "Connection attempt to/from self " 1299 "ignored\n", s, __func__); 1300 goto dropunlock; 1301 } 1302 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1303 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1304 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1305 log(LOG_DEBUG, "%s; %s: Listen socket: " 1306 "Connection attempt from/to multicast " 1307 "address ignored\n", s, __func__); 1308 goto dropunlock; 1309 } 1310 } 1311 #endif 1312 #if defined(INET) && defined(INET6) 1313 else 1314 #endif 1315 #ifdef INET 1316 { 1317 if (th->th_dport == th->th_sport && 1318 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1319 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1320 log(LOG_DEBUG, "%s; %s: Listen socket: " 1321 "Connection attempt from/to self " 1322 "ignored\n", s, __func__); 1323 goto dropunlock; 1324 } 1325 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1326 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1327 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1328 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1329 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1330 log(LOG_DEBUG, "%s; %s: Listen socket: " 1331 "Connection attempt from/to broad- " 1332 "or multicast address ignored\n", 1333 s, __func__); 1334 goto dropunlock; 1335 } 1336 } 1337 #endif 1338 /* 1339 * SYN appears to be valid. Create compressed TCP state 1340 * for syncache. 1341 */ 1342 #ifdef TCPDEBUG 1343 if (so->so_options & SO_DEBUG) 1344 tcp_trace(TA_INPUT, ostate, tp, 1345 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1346 #endif 1347 TCP_PROBE3(debug__input, tp, th, m); 1348 tcp_dooptions(&to, optp, optlen, TO_SYN); 1349 if ((so = syncache_add(&inc, &to, th, inp, so, m, NULL, NULL, 1350 iptos, port)) != NULL) 1351 goto tfo_socket_result; 1352 1353 /* 1354 * Entry added to syncache and mbuf consumed. 1355 * Only the listen socket is unlocked by syncache_add(). 1356 */ 1357 return (IPPROTO_DONE); 1358 } else if (tp->t_state == TCPS_LISTEN) { 1359 /* 1360 * When a listen socket is torn down the SO_ACCEPTCONN 1361 * flag is removed first while connections are drained 1362 * from the accept queue in a unlock/lock cycle of the 1363 * ACCEPT_LOCK, opening a race condition allowing a SYN 1364 * attempt go through unhandled. 1365 */ 1366 goto dropunlock; 1367 } 1368 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1369 if (tp->t_flags & TF_SIGNATURE) { 1370 tcp_dooptions(&to, optp, optlen, thflags); 1371 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1372 TCPSTAT_INC(tcps_sig_err_nosigopt); 1373 goto dropunlock; 1374 } 1375 if (!TCPMD5_ENABLED() || 1376 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1377 goto dropunlock; 1378 } 1379 #endif 1380 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1381 1382 /* 1383 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1384 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1385 * the inpcb, and unlocks pcbinfo. 1386 * 1387 * XXXGL: in case of a pure SYN arriving on existing connection 1388 * TCP stacks won't need to modify the PCB, they would either drop 1389 * the segment silently, or send a challenge ACK. However, we try 1390 * to upgrade the lock, because calling convention for stacks is 1391 * write-lock on PCB. If upgrade fails, drop the SYN. 1392 */ 1393 if (lookupflag == INPLOOKUP_RLOCKPCB && INP_TRY_UPGRADE(inp) == 0) 1394 goto dropunlock; 1395 1396 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1397 return (IPPROTO_DONE); 1398 1399 dropwithreset: 1400 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1401 1402 if (inp != NULL) { 1403 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1404 INP_UNLOCK(inp); 1405 } else 1406 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1407 m = NULL; /* mbuf chain got consumed. */ 1408 goto drop; 1409 1410 dropunlock: 1411 if (m != NULL) 1412 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1413 1414 if (inp != NULL) 1415 INP_UNLOCK(inp); 1416 1417 drop: 1418 if (s != NULL) 1419 free(s, M_TCPLOG); 1420 if (m != NULL) 1421 m_freem(m); 1422 return (IPPROTO_DONE); 1423 } 1424 1425 /* 1426 * Automatic sizing of receive socket buffer. Often the send 1427 * buffer size is not optimally adjusted to the actual network 1428 * conditions at hand (delay bandwidth product). Setting the 1429 * buffer size too small limits throughput on links with high 1430 * bandwidth and high delay (eg. trans-continental/oceanic links). 1431 * 1432 * On the receive side the socket buffer memory is only rarely 1433 * used to any significant extent. This allows us to be much 1434 * more aggressive in scaling the receive socket buffer. For 1435 * the case that the buffer space is actually used to a large 1436 * extent and we run out of kernel memory we can simply drop 1437 * the new segments; TCP on the sender will just retransmit it 1438 * later. Setting the buffer size too big may only consume too 1439 * much kernel memory if the application doesn't read() from 1440 * the socket or packet loss or reordering makes use of the 1441 * reassembly queue. 1442 * 1443 * The criteria to step up the receive buffer one notch are: 1444 * 1. Application has not set receive buffer size with 1445 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1446 * 2. the number of bytes received during 1/2 of an sRTT 1447 * is at least 3/8 of the current socket buffer size. 1448 * 3. receive buffer size has not hit maximal automatic size; 1449 * 1450 * If all of the criteria are met we increaset the socket buffer 1451 * by a 1/2 (bounded by the max). This allows us to keep ahead 1452 * of slow-start but also makes it so our peer never gets limited 1453 * by our rwnd which we then open up causing a burst. 1454 * 1455 * This algorithm does two steps per RTT at most and only if 1456 * we receive a bulk stream w/o packet losses or reorderings. 1457 * Shrinking the buffer during idle times is not necessary as 1458 * it doesn't consume any memory when idle. 1459 * 1460 * TODO: Only step up if the application is actually serving 1461 * the buffer to better manage the socket buffer resources. 1462 */ 1463 int 1464 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1465 struct tcpcb *tp, int tlen) 1466 { 1467 int newsize = 0; 1468 1469 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1470 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1471 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1472 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) { 1473 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) && 1474 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1475 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max); 1476 } 1477 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1478 1479 /* Start over with next RTT. */ 1480 tp->rfbuf_ts = 0; 1481 tp->rfbuf_cnt = 0; 1482 } else { 1483 tp->rfbuf_cnt += tlen; /* add up */ 1484 } 1485 return (newsize); 1486 } 1487 1488 int 1489 tcp_input(struct mbuf **mp, int *offp, int proto) 1490 { 1491 return(tcp_input_with_port(mp, offp, proto, 0)); 1492 } 1493 1494 void 1495 tcp_handle_wakeup(struct tcpcb *tp, struct socket *so) 1496 { 1497 /* 1498 * Since tp might be gone if the session entered 1499 * the TIME_WAIT state before coming here, we need 1500 * to check if the socket is still connected. 1501 */ 1502 if (tp == NULL) { 1503 return; 1504 } 1505 if (so == NULL) { 1506 return; 1507 } 1508 INP_LOCK_ASSERT(tp->t_inpcb); 1509 if (tp->t_flags & TF_WAKESOR) { 1510 tp->t_flags &= ~TF_WAKESOR; 1511 SOCKBUF_LOCK_ASSERT(&so->so_rcv); 1512 sorwakeup_locked(so); 1513 } 1514 } 1515 1516 void 1517 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1518 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1519 { 1520 uint16_t thflags; 1521 int acked, ourfinisacked, needoutput = 0, sack_changed; 1522 int rstreason, todrop, win, incforsyn = 0; 1523 uint32_t tiwin; 1524 uint16_t nsegs; 1525 char *s; 1526 struct in_conninfo *inc; 1527 struct mbuf *mfree; 1528 struct tcpopt to; 1529 int tfo_syn; 1530 u_int maxseg; 1531 1532 #ifdef TCPDEBUG 1533 /* 1534 * The size of tcp_saveipgen must be the size of the max ip header, 1535 * now IPv6. 1536 */ 1537 u_char tcp_saveipgen[IP6_HDR_LEN]; 1538 struct tcphdr tcp_savetcp; 1539 short ostate = 0; 1540 #endif 1541 thflags = tcp_get_flags(th); 1542 inc = &tp->t_inpcb->inp_inc; 1543 tp->sackhint.last_sack_ack = 0; 1544 sack_changed = 0; 1545 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1546 1547 NET_EPOCH_ASSERT(); 1548 INP_WLOCK_ASSERT(tp->t_inpcb); 1549 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1550 __func__)); 1551 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1552 __func__)); 1553 1554 #ifdef TCPPCAP 1555 /* Save segment, if requested. */ 1556 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1557 #endif 1558 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1559 tlen, NULL, true); 1560 1561 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1562 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1563 log(LOG_DEBUG, "%s; %s: " 1564 "SYN|FIN segment ignored (based on " 1565 "sysctl setting)\n", s, __func__); 1566 free(s, M_TCPLOG); 1567 } 1568 goto drop; 1569 } 1570 1571 /* 1572 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1573 * check SEQ.ACK first. 1574 */ 1575 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1576 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1577 rstreason = BANDLIM_UNLIMITED; 1578 goto dropwithreset; 1579 } 1580 1581 /* 1582 * Segment received on connection. 1583 * Reset idle time and keep-alive timer. 1584 * XXX: This should be done after segment 1585 * validation to ignore broken/spoofed segs. 1586 */ 1587 tp->t_rcvtime = ticks; 1588 1589 /* 1590 * Scale up the window into a 32-bit value. 1591 * For the SYN_SENT state the scale is zero. 1592 */ 1593 tiwin = th->th_win << tp->snd_scale; 1594 #ifdef STATS 1595 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin); 1596 #endif 1597 1598 /* 1599 * TCP ECN processing. 1600 */ 1601 if (tcp_ecn_input_segment(tp, thflags, iptos)) 1602 cc_cong_signal(tp, th, CC_ECN); 1603 1604 /* 1605 * Parse options on any incoming segment. 1606 */ 1607 tcp_dooptions(&to, (u_char *)(th + 1), 1608 (th->th_off << 2) - sizeof(struct tcphdr), 1609 (thflags & TH_SYN) ? TO_SYN : 0); 1610 1611 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1612 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1613 (to.to_flags & TOF_SIGNATURE) == 0) { 1614 TCPSTAT_INC(tcps_sig_err_sigopt); 1615 /* XXX: should drop? */ 1616 } 1617 #endif 1618 /* 1619 * If echoed timestamp is later than the current time, 1620 * fall back to non RFC1323 RTT calculation. Normalize 1621 * timestamp if syncookies were used when this connection 1622 * was established. 1623 */ 1624 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1625 to.to_tsecr -= tp->ts_offset; 1626 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1627 to.to_tsecr = 0; 1628 else if (tp->t_rxtshift == 1 && 1629 tp->t_flags & TF_PREVVALID && 1630 tp->t_badrxtwin != 0 && 1631 TSTMP_LT(to.to_tsecr, tp->t_badrxtwin)) 1632 cc_cong_signal(tp, th, CC_RTO_ERR); 1633 } 1634 /* 1635 * Process options only when we get SYN/ACK back. The SYN case 1636 * for incoming connections is handled in tcp_syncache. 1637 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1638 * or <SYN,ACK>) segment itself is never scaled. 1639 * XXX this is traditional behavior, may need to be cleaned up. 1640 */ 1641 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1642 /* Handle parallel SYN for ECN */ 1643 tcp_ecn_input_parallel_syn(tp, thflags, iptos); 1644 if ((to.to_flags & TOF_SCALE) && 1645 (tp->t_flags & TF_REQ_SCALE) && 1646 !(tp->t_flags & TF_NOOPT)) { 1647 tp->t_flags |= TF_RCVD_SCALE; 1648 tp->snd_scale = to.to_wscale; 1649 } else 1650 tp->t_flags &= ~TF_REQ_SCALE; 1651 /* 1652 * Initial send window. It will be updated with 1653 * the next incoming segment to the scaled value. 1654 */ 1655 tp->snd_wnd = th->th_win; 1656 if ((to.to_flags & TOF_TS) && 1657 (tp->t_flags & TF_REQ_TSTMP) && 1658 !(tp->t_flags & TF_NOOPT)) { 1659 tp->t_flags |= TF_RCVD_TSTMP; 1660 tp->ts_recent = to.to_tsval; 1661 tp->ts_recent_age = tcp_ts_getticks(); 1662 } else 1663 tp->t_flags &= ~TF_REQ_TSTMP; 1664 if (to.to_flags & TOF_MSS) 1665 tcp_mss(tp, to.to_mss); 1666 if ((tp->t_flags & TF_SACK_PERMIT) && 1667 (!(to.to_flags & TOF_SACKPERM) || 1668 (tp->t_flags & TF_NOOPT))) 1669 tp->t_flags &= ~TF_SACK_PERMIT; 1670 if (IS_FASTOPEN(tp->t_flags)) { 1671 if ((to.to_flags & TOF_FASTOPEN) && 1672 !(tp->t_flags & TF_NOOPT)) { 1673 uint16_t mss; 1674 1675 if (to.to_flags & TOF_MSS) 1676 mss = to.to_mss; 1677 else 1678 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1679 mss = TCP6_MSS; 1680 else 1681 mss = TCP_MSS; 1682 tcp_fastopen_update_cache(tp, mss, 1683 to.to_tfo_len, to.to_tfo_cookie); 1684 } else 1685 tcp_fastopen_disable_path(tp); 1686 } 1687 } 1688 1689 /* 1690 * If timestamps were negotiated during SYN/ACK and a 1691 * segment without a timestamp is received, silently drop 1692 * the segment, unless it is a RST segment or missing timestamps are 1693 * tolerated. 1694 * See section 3.2 of RFC 7323. 1695 */ 1696 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1697 if (((thflags & TH_RST) != 0) || V_tcp_tolerate_missing_ts) { 1698 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1699 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1700 "segment processed normally\n", 1701 s, __func__); 1702 free(s, M_TCPLOG); 1703 } 1704 } else { 1705 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1706 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1707 "segment silently dropped\n", s, __func__); 1708 free(s, M_TCPLOG); 1709 } 1710 goto drop; 1711 } 1712 } 1713 /* 1714 * If timestamps were not negotiated during SYN/ACK and a 1715 * segment with a timestamp is received, ignore the 1716 * timestamp and process the packet normally. 1717 * See section 3.2 of RFC 7323. 1718 */ 1719 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1720 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1721 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1722 "segment processed normally\n", s, __func__); 1723 free(s, M_TCPLOG); 1724 } 1725 } 1726 1727 /* 1728 * Header prediction: check for the two common cases 1729 * of a uni-directional data xfer. If the packet has 1730 * no control flags, is in-sequence, the window didn't 1731 * change and we're not retransmitting, it's a 1732 * candidate. If the length is zero and the ack moved 1733 * forward, we're the sender side of the xfer. Just 1734 * free the data acked & wake any higher level process 1735 * that was blocked waiting for space. If the length 1736 * is non-zero and the ack didn't move, we're the 1737 * receiver side. If we're getting packets in-order 1738 * (the reassembly queue is empty), add the data to 1739 * the socket buffer and note that we need a delayed ack. 1740 * Make sure that the hidden state-flags are also off. 1741 * Since we check for TCPS_ESTABLISHED first, it can only 1742 * be TH_NEEDSYN. 1743 */ 1744 if (tp->t_state == TCPS_ESTABLISHED && 1745 th->th_seq == tp->rcv_nxt && 1746 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1747 tp->snd_nxt == tp->snd_max && 1748 tiwin && tiwin == tp->snd_wnd && 1749 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1750 SEGQ_EMPTY(tp) && 1751 ((to.to_flags & TOF_TS) == 0 || 1752 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1753 /* 1754 * If last ACK falls within this segment's sequence numbers, 1755 * record the timestamp. 1756 * NOTE that the test is modified according to the latest 1757 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1758 */ 1759 if ((to.to_flags & TOF_TS) != 0 && 1760 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1761 tp->ts_recent_age = tcp_ts_getticks(); 1762 tp->ts_recent = to.to_tsval; 1763 } 1764 1765 if (tlen == 0) { 1766 if (SEQ_GT(th->th_ack, tp->snd_una) && 1767 SEQ_LEQ(th->th_ack, tp->snd_max) && 1768 !IN_RECOVERY(tp->t_flags) && 1769 (to.to_flags & TOF_SACK) == 0 && 1770 TAILQ_EMPTY(&tp->snd_holes)) { 1771 /* 1772 * This is a pure ack for outstanding data. 1773 */ 1774 TCPSTAT_INC(tcps_predack); 1775 1776 /* 1777 * "bad retransmit" recovery without timestamps. 1778 */ 1779 if ((to.to_flags & TOF_TS) == 0 && 1780 tp->t_rxtshift == 1 && 1781 tp->t_flags & TF_PREVVALID && 1782 tp->t_badrxtwin != 0 && 1783 TSTMP_LT(ticks, tp->t_badrxtwin)) { 1784 cc_cong_signal(tp, th, CC_RTO_ERR); 1785 } 1786 1787 /* 1788 * Recalculate the transmit timer / rtt. 1789 * 1790 * Some boxes send broken timestamp replies 1791 * during the SYN+ACK phase, ignore 1792 * timestamps of 0 or we could calculate a 1793 * huge RTT and blow up the retransmit timer. 1794 */ 1795 if ((to.to_flags & TOF_TS) != 0 && 1796 to.to_tsecr) { 1797 uint32_t t; 1798 1799 t = tcp_ts_getticks() - to.to_tsecr; 1800 if (!tp->t_rttlow || tp->t_rttlow > t) 1801 tp->t_rttlow = t; 1802 tcp_xmit_timer(tp, 1803 TCP_TS_TO_TICKS(t) + 1); 1804 } else if (tp->t_rtttime && 1805 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1806 if (!tp->t_rttlow || 1807 tp->t_rttlow > ticks - tp->t_rtttime) 1808 tp->t_rttlow = ticks - tp->t_rtttime; 1809 tcp_xmit_timer(tp, 1810 ticks - tp->t_rtttime); 1811 } 1812 acked = BYTES_THIS_ACK(tp, th); 1813 1814 #ifdef TCP_HHOOK 1815 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1816 hhook_run_tcp_est_in(tp, th, &to); 1817 #endif 1818 1819 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1820 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1821 sbdrop(&so->so_snd, acked); 1822 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1823 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1824 tp->snd_recover = th->th_ack - 1; 1825 1826 /* 1827 * Let the congestion control algorithm update 1828 * congestion control related information. This 1829 * typically means increasing the congestion 1830 * window. 1831 */ 1832 cc_ack_received(tp, th, nsegs, CC_ACK); 1833 1834 tp->snd_una = th->th_ack; 1835 /* 1836 * Pull snd_wl2 up to prevent seq wrap relative 1837 * to th_ack. 1838 */ 1839 tp->snd_wl2 = th->th_ack; 1840 tp->t_dupacks = 0; 1841 m_freem(m); 1842 1843 /* 1844 * If all outstanding data are acked, stop 1845 * retransmit timer, otherwise restart timer 1846 * using current (possibly backed-off) value. 1847 * If process is waiting for space, 1848 * wakeup/selwakeup/signal. If data 1849 * are ready to send, let tcp_output 1850 * decide between more output or persist. 1851 */ 1852 #ifdef TCPDEBUG 1853 if (so->so_options & SO_DEBUG) 1854 tcp_trace(TA_INPUT, ostate, tp, 1855 (void *)tcp_saveipgen, 1856 &tcp_savetcp, 0); 1857 #endif 1858 TCP_PROBE3(debug__input, tp, th, m); 1859 if (tp->snd_una == tp->snd_max) 1860 tcp_timer_activate(tp, TT_REXMT, 0); 1861 else if (!tcp_timer_active(tp, TT_PERSIST)) 1862 tcp_timer_activate(tp, TT_REXMT, 1863 tp->t_rxtcur); 1864 sowwakeup(so); 1865 if (sbavail(&so->so_snd)) 1866 (void) tcp_output(tp); 1867 goto check_delack; 1868 } 1869 } else if (th->th_ack == tp->snd_una && 1870 tlen <= sbspace(&so->so_rcv)) { 1871 int newsize = 0; /* automatic sockbuf scaling */ 1872 1873 /* 1874 * This is a pure, in-sequence data packet with 1875 * nothing on the reassembly queue and we have enough 1876 * buffer space to take it. 1877 */ 1878 /* Clean receiver SACK report if present */ 1879 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1880 tcp_clean_sackreport(tp); 1881 TCPSTAT_INC(tcps_preddat); 1882 tp->rcv_nxt += tlen; 1883 if (tlen && 1884 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 1885 (tp->t_fbyte_in == 0)) { 1886 tp->t_fbyte_in = ticks; 1887 if (tp->t_fbyte_in == 0) 1888 tp->t_fbyte_in = 1; 1889 if (tp->t_fbyte_out && tp->t_fbyte_in) 1890 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 1891 } 1892 /* 1893 * Pull snd_wl1 up to prevent seq wrap relative to 1894 * th_seq. 1895 */ 1896 tp->snd_wl1 = th->th_seq; 1897 /* 1898 * Pull rcv_up up to prevent seq wrap relative to 1899 * rcv_nxt. 1900 */ 1901 tp->rcv_up = tp->rcv_nxt; 1902 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1903 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1904 #ifdef TCPDEBUG 1905 if (so->so_options & SO_DEBUG) 1906 tcp_trace(TA_INPUT, ostate, tp, 1907 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1908 #endif 1909 TCP_PROBE3(debug__input, tp, th, m); 1910 1911 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1912 1913 /* Add data to socket buffer. */ 1914 SOCKBUF_LOCK(&so->so_rcv); 1915 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1916 m_freem(m); 1917 } else { 1918 /* 1919 * Set new socket buffer size. 1920 * Give up when limit is reached. 1921 */ 1922 if (newsize) 1923 if (!sbreserve_locked(so, SO_RCV, 1924 newsize, NULL)) 1925 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1926 m_adj(m, drop_hdrlen); /* delayed header drop */ 1927 sbappendstream_locked(&so->so_rcv, m, 0); 1928 } 1929 /* NB: sorwakeup_locked() does an implicit unlock. */ 1930 sorwakeup_locked(so); 1931 if (DELAY_ACK(tp, tlen)) { 1932 tp->t_flags |= TF_DELACK; 1933 } else { 1934 tp->t_flags |= TF_ACKNOW; 1935 tcp_output(tp); 1936 } 1937 goto check_delack; 1938 } 1939 } 1940 1941 /* 1942 * Calculate amount of space in receive window, 1943 * and then do TCP input processing. 1944 * Receive window is amount of space in rcv queue, 1945 * but not less than advertised window. 1946 */ 1947 win = sbspace(&so->so_rcv); 1948 if (win < 0) 1949 win = 0; 1950 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1951 1952 switch (tp->t_state) { 1953 /* 1954 * If the state is SYN_RECEIVED: 1955 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1956 */ 1957 case TCPS_SYN_RECEIVED: 1958 if ((thflags & TH_ACK) && 1959 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1960 SEQ_GT(th->th_ack, tp->snd_max))) { 1961 rstreason = BANDLIM_RST_OPENPORT; 1962 goto dropwithreset; 1963 } 1964 if (IS_FASTOPEN(tp->t_flags)) { 1965 /* 1966 * When a TFO connection is in SYN_RECEIVED, the 1967 * only valid packets are the initial SYN, a 1968 * retransmit/copy of the initial SYN (possibly with 1969 * a subset of the original data), a valid ACK, a 1970 * FIN, or a RST. 1971 */ 1972 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1973 rstreason = BANDLIM_RST_OPENPORT; 1974 goto dropwithreset; 1975 } else if (thflags & TH_SYN) { 1976 /* non-initial SYN is ignored */ 1977 if ((tcp_timer_active(tp, TT_DELACK) || 1978 tcp_timer_active(tp, TT_REXMT))) 1979 goto drop; 1980 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1981 goto drop; 1982 } 1983 } 1984 break; 1985 1986 /* 1987 * If the state is SYN_SENT: 1988 * if seg contains a RST with valid ACK (SEQ.ACK has already 1989 * been verified), then drop the connection. 1990 * if seg contains a RST without an ACK, drop the seg. 1991 * if seg does not contain SYN, then drop the seg. 1992 * Otherwise this is an acceptable SYN segment 1993 * initialize tp->rcv_nxt and tp->irs 1994 * if seg contains ack then advance tp->snd_una 1995 * if seg contains an ECE and ECN support is enabled, the stream 1996 * is ECN capable. 1997 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1998 * arrange for segment to be acked (eventually) 1999 * continue processing rest of data/controls, beginning with URG 2000 */ 2001 case TCPS_SYN_SENT: 2002 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 2003 TCP_PROBE5(connect__refused, NULL, tp, 2004 m, tp, th); 2005 tp = tcp_drop(tp, ECONNREFUSED); 2006 } 2007 if (thflags & TH_RST) 2008 goto drop; 2009 if (!(thflags & TH_SYN)) 2010 goto drop; 2011 2012 tp->irs = th->th_seq; 2013 tcp_rcvseqinit(tp); 2014 if (thflags & TH_ACK) { 2015 int tfo_partial_ack = 0; 2016 2017 TCPSTAT_INC(tcps_connects); 2018 soisconnected(so); 2019 #ifdef MAC 2020 mac_socketpeer_set_from_mbuf(m, so); 2021 #endif 2022 /* Do window scaling on this connection? */ 2023 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2024 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2025 tp->rcv_scale = tp->request_r_scale; 2026 } 2027 tp->rcv_adv += min(tp->rcv_wnd, 2028 TCP_MAXWIN << tp->rcv_scale); 2029 tp->snd_una++; /* SYN is acked */ 2030 /* 2031 * If not all the data that was sent in the TFO SYN 2032 * has been acked, resend the remainder right away. 2033 */ 2034 if (IS_FASTOPEN(tp->t_flags) && 2035 (tp->snd_una != tp->snd_max)) { 2036 tp->snd_nxt = th->th_ack; 2037 tfo_partial_ack = 1; 2038 } 2039 /* 2040 * If there's data, delay ACK; if there's also a FIN 2041 * ACKNOW will be turned on later. 2042 */ 2043 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 2044 tcp_timer_activate(tp, TT_DELACK, 2045 tcp_delacktime); 2046 else 2047 tp->t_flags |= TF_ACKNOW; 2048 2049 tcp_ecn_input_syn_sent(tp, thflags, iptos); 2050 2051 /* 2052 * Received <SYN,ACK> in SYN_SENT[*] state. 2053 * Transitions: 2054 * SYN_SENT --> ESTABLISHED 2055 * SYN_SENT* --> FIN_WAIT_1 2056 */ 2057 tp->t_starttime = ticks; 2058 if (tp->t_flags & TF_NEEDFIN) { 2059 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2060 tp->t_flags &= ~TF_NEEDFIN; 2061 thflags &= ~TH_SYN; 2062 } else { 2063 tcp_state_change(tp, TCPS_ESTABLISHED); 2064 TCP_PROBE5(connect__established, NULL, tp, 2065 m, tp, th); 2066 cc_conn_init(tp); 2067 tcp_timer_activate(tp, TT_KEEP, 2068 TP_KEEPIDLE(tp)); 2069 } 2070 } else { 2071 /* 2072 * Received initial SYN in SYN-SENT[*] state => 2073 * simultaneous open. 2074 * If it succeeds, connection is * half-synchronized. 2075 * Otherwise, do 3-way handshake: 2076 * SYN-SENT -> SYN-RECEIVED 2077 * SYN-SENT* -> SYN-RECEIVED* 2078 */ 2079 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2080 tcp_timer_activate(tp, TT_REXMT, 0); 2081 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2082 } 2083 2084 INP_WLOCK_ASSERT(tp->t_inpcb); 2085 2086 /* 2087 * Advance th->th_seq to correspond to first data byte. 2088 * If data, trim to stay within window, 2089 * dropping FIN if necessary. 2090 */ 2091 th->th_seq++; 2092 if (tlen > tp->rcv_wnd) { 2093 todrop = tlen - tp->rcv_wnd; 2094 m_adj(m, -todrop); 2095 tlen = tp->rcv_wnd; 2096 thflags &= ~TH_FIN; 2097 TCPSTAT_INC(tcps_rcvpackafterwin); 2098 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2099 } 2100 tp->snd_wl1 = th->th_seq - 1; 2101 tp->rcv_up = th->th_seq; 2102 /* 2103 * Client side of transaction: already sent SYN and data. 2104 * If the remote host used T/TCP to validate the SYN, 2105 * our data will be ACK'd; if so, enter normal data segment 2106 * processing in the middle of step 5, ack processing. 2107 * Otherwise, goto step 6. 2108 */ 2109 if (thflags & TH_ACK) 2110 goto process_ACK; 2111 2112 goto step6; 2113 2114 /* 2115 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2116 * do normal processing. 2117 * 2118 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2119 */ 2120 case TCPS_LAST_ACK: 2121 case TCPS_CLOSING: 2122 break; /* continue normal processing */ 2123 } 2124 2125 /* 2126 * States other than LISTEN or SYN_SENT. 2127 * First check the RST flag and sequence number since reset segments 2128 * are exempt from the timestamp and connection count tests. This 2129 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2130 * below which allowed reset segments in half the sequence space 2131 * to fall though and be processed (which gives forged reset 2132 * segments with a random sequence number a 50 percent chance of 2133 * killing a connection). 2134 * Then check timestamp, if present. 2135 * Then check the connection count, if present. 2136 * Then check that at least some bytes of segment are within 2137 * receive window. If segment begins before rcv_nxt, 2138 * drop leading data (and SYN); if nothing left, just ack. 2139 */ 2140 if (thflags & TH_RST) { 2141 /* 2142 * RFC5961 Section 3.2 2143 * 2144 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2145 * - If RST is in window, we send challenge ACK. 2146 * 2147 * Note: to take into account delayed ACKs, we should 2148 * test against last_ack_sent instead of rcv_nxt. 2149 * Note 2: we handle special case of closed window, not 2150 * covered by the RFC. 2151 */ 2152 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2153 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2154 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2155 KASSERT(tp->t_state != TCPS_SYN_SENT, 2156 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2157 __func__, th, tp)); 2158 2159 if (V_tcp_insecure_rst || 2160 tp->last_ack_sent == th->th_seq) { 2161 TCPSTAT_INC(tcps_drops); 2162 /* Drop the connection. */ 2163 switch (tp->t_state) { 2164 case TCPS_SYN_RECEIVED: 2165 so->so_error = ECONNREFUSED; 2166 goto close; 2167 case TCPS_ESTABLISHED: 2168 case TCPS_FIN_WAIT_1: 2169 case TCPS_FIN_WAIT_2: 2170 case TCPS_CLOSE_WAIT: 2171 case TCPS_CLOSING: 2172 case TCPS_LAST_ACK: 2173 so->so_error = ECONNRESET; 2174 close: 2175 /* FALLTHROUGH */ 2176 default: 2177 tp = tcp_close(tp); 2178 } 2179 } else { 2180 TCPSTAT_INC(tcps_badrst); 2181 /* Send challenge ACK. */ 2182 tcp_respond(tp, mtod(m, void *), th, m, 2183 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2184 tp->last_ack_sent = tp->rcv_nxt; 2185 m = NULL; 2186 } 2187 } 2188 goto drop; 2189 } 2190 2191 /* 2192 * RFC5961 Section 4.2 2193 * Send challenge ACK for any SYN in synchronized state. 2194 */ 2195 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2196 tp->t_state != TCPS_SYN_RECEIVED) { 2197 TCPSTAT_INC(tcps_badsyn); 2198 if (V_tcp_insecure_syn && 2199 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2200 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2201 tp = tcp_drop(tp, ECONNRESET); 2202 rstreason = BANDLIM_UNLIMITED; 2203 } else { 2204 /* Send challenge ACK. */ 2205 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2206 tp->snd_nxt, TH_ACK); 2207 tp->last_ack_sent = tp->rcv_nxt; 2208 m = NULL; 2209 } 2210 goto drop; 2211 } 2212 2213 /* 2214 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2215 * and it's less than ts_recent, drop it. 2216 */ 2217 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2218 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2219 /* Check to see if ts_recent is over 24 days old. */ 2220 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2221 /* 2222 * Invalidate ts_recent. If this segment updates 2223 * ts_recent, the age will be reset later and ts_recent 2224 * will get a valid value. If it does not, setting 2225 * ts_recent to zero will at least satisfy the 2226 * requirement that zero be placed in the timestamp 2227 * echo reply when ts_recent isn't valid. The 2228 * age isn't reset until we get a valid ts_recent 2229 * because we don't want out-of-order segments to be 2230 * dropped when ts_recent is old. 2231 */ 2232 tp->ts_recent = 0; 2233 } else { 2234 TCPSTAT_INC(tcps_rcvduppack); 2235 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2236 TCPSTAT_INC(tcps_pawsdrop); 2237 if (tlen) 2238 goto dropafterack; 2239 goto drop; 2240 } 2241 } 2242 2243 /* 2244 * In the SYN-RECEIVED state, validate that the packet belongs to 2245 * this connection before trimming the data to fit the receive 2246 * window. Check the sequence number versus IRS since we know 2247 * the sequence numbers haven't wrapped. This is a partial fix 2248 * for the "LAND" DoS attack. 2249 */ 2250 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2251 rstreason = BANDLIM_RST_OPENPORT; 2252 goto dropwithreset; 2253 } 2254 2255 todrop = tp->rcv_nxt - th->th_seq; 2256 if (todrop > 0) { 2257 if (thflags & TH_SYN) { 2258 thflags &= ~TH_SYN; 2259 th->th_seq++; 2260 if (th->th_urp > 1) 2261 th->th_urp--; 2262 else 2263 thflags &= ~TH_URG; 2264 todrop--; 2265 } 2266 /* 2267 * Following if statement from Stevens, vol. 2, p. 960. 2268 */ 2269 if (todrop > tlen 2270 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2271 /* 2272 * Any valid FIN must be to the left of the window. 2273 * At this point the FIN must be a duplicate or out 2274 * of sequence; drop it. 2275 */ 2276 thflags &= ~TH_FIN; 2277 2278 /* 2279 * Send an ACK to resynchronize and drop any data. 2280 * But keep on processing for RST or ACK. 2281 */ 2282 tp->t_flags |= TF_ACKNOW; 2283 todrop = tlen; 2284 TCPSTAT_INC(tcps_rcvduppack); 2285 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2286 } else { 2287 TCPSTAT_INC(tcps_rcvpartduppack); 2288 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2289 } 2290 /* 2291 * DSACK - add SACK block for dropped range 2292 */ 2293 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) { 2294 tcp_update_sack_list(tp, th->th_seq, 2295 th->th_seq + todrop); 2296 /* 2297 * ACK now, as the next in-sequence segment 2298 * will clear the DSACK block again 2299 */ 2300 tp->t_flags |= TF_ACKNOW; 2301 } 2302 drop_hdrlen += todrop; /* drop from the top afterwards */ 2303 th->th_seq += todrop; 2304 tlen -= todrop; 2305 if (th->th_urp > todrop) 2306 th->th_urp -= todrop; 2307 else { 2308 thflags &= ~TH_URG; 2309 th->th_urp = 0; 2310 } 2311 } 2312 2313 /* 2314 * If new data are received on a connection after the 2315 * user processes are gone, then RST the other end. 2316 */ 2317 if ((tp->t_flags & TF_CLOSED) && tlen) { 2318 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2319 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2320 "after socket was closed, " 2321 "sending RST and removing tcpcb\n", 2322 s, __func__, tcpstates[tp->t_state], tlen); 2323 free(s, M_TCPLOG); 2324 } 2325 tp = tcp_close(tp); 2326 TCPSTAT_INC(tcps_rcvafterclose); 2327 rstreason = BANDLIM_UNLIMITED; 2328 goto dropwithreset; 2329 } 2330 2331 /* 2332 * If segment ends after window, drop trailing data 2333 * (and PUSH and FIN); if nothing left, just ACK. 2334 */ 2335 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2336 if (todrop > 0) { 2337 TCPSTAT_INC(tcps_rcvpackafterwin); 2338 if (todrop >= tlen) { 2339 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2340 /* 2341 * If window is closed can only take segments at 2342 * window edge, and have to drop data and PUSH from 2343 * incoming segments. Continue processing, but 2344 * remember to ack. Otherwise, drop segment 2345 * and ack. 2346 */ 2347 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2348 tp->t_flags |= TF_ACKNOW; 2349 TCPSTAT_INC(tcps_rcvwinprobe); 2350 } else 2351 goto dropafterack; 2352 } else 2353 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2354 m_adj(m, -todrop); 2355 tlen -= todrop; 2356 thflags &= ~(TH_PUSH|TH_FIN); 2357 } 2358 2359 /* 2360 * If last ACK falls within this segment's sequence numbers, 2361 * record its timestamp. 2362 * NOTE: 2363 * 1) That the test incorporates suggestions from the latest 2364 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2365 * 2) That updating only on newer timestamps interferes with 2366 * our earlier PAWS tests, so this check should be solely 2367 * predicated on the sequence space of this segment. 2368 * 3) That we modify the segment boundary check to be 2369 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2370 * instead of RFC1323's 2371 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2372 * This modified check allows us to overcome RFC1323's 2373 * limitations as described in Stevens TCP/IP Illustrated 2374 * Vol. 2 p.869. In such cases, we can still calculate the 2375 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2376 */ 2377 if ((to.to_flags & TOF_TS) != 0 && 2378 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2379 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2380 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2381 tp->ts_recent_age = tcp_ts_getticks(); 2382 tp->ts_recent = to.to_tsval; 2383 } 2384 2385 /* 2386 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2387 * flag is on (half-synchronized state), then queue data for 2388 * later processing; else drop segment and return. 2389 */ 2390 if ((thflags & TH_ACK) == 0) { 2391 if (tp->t_state == TCPS_SYN_RECEIVED || 2392 (tp->t_flags & TF_NEEDSYN)) { 2393 if (tp->t_state == TCPS_SYN_RECEIVED && 2394 IS_FASTOPEN(tp->t_flags)) { 2395 tp->snd_wnd = tiwin; 2396 cc_conn_init(tp); 2397 } 2398 goto step6; 2399 } else if (tp->t_flags & TF_ACKNOW) 2400 goto dropafterack; 2401 else 2402 goto drop; 2403 } 2404 2405 /* 2406 * Ack processing. 2407 */ 2408 switch (tp->t_state) { 2409 /* 2410 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2411 * ESTABLISHED state and continue processing. 2412 * The ACK was checked above. 2413 */ 2414 case TCPS_SYN_RECEIVED: 2415 2416 TCPSTAT_INC(tcps_connects); 2417 soisconnected(so); 2418 /* Do window scaling? */ 2419 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2420 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2421 tp->rcv_scale = tp->request_r_scale; 2422 } 2423 tp->snd_wnd = tiwin; 2424 /* 2425 * Make transitions: 2426 * SYN-RECEIVED -> ESTABLISHED 2427 * SYN-RECEIVED* -> FIN-WAIT-1 2428 */ 2429 tp->t_starttime = ticks; 2430 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2431 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2432 tp->t_tfo_pending = NULL; 2433 } 2434 if (tp->t_flags & TF_NEEDFIN) { 2435 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2436 tp->t_flags &= ~TF_NEEDFIN; 2437 } else { 2438 tcp_state_change(tp, TCPS_ESTABLISHED); 2439 TCP_PROBE5(accept__established, NULL, tp, 2440 m, tp, th); 2441 /* 2442 * TFO connections call cc_conn_init() during SYN 2443 * processing. Calling it again here for such 2444 * connections is not harmless as it would undo the 2445 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2446 * is retransmitted. 2447 */ 2448 if (!IS_FASTOPEN(tp->t_flags)) 2449 cc_conn_init(tp); 2450 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2451 } 2452 /* 2453 * Account for the ACK of our SYN prior to 2454 * regular ACK processing below, except for 2455 * simultaneous SYN, which is handled later. 2456 */ 2457 if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) 2458 incforsyn = 1; 2459 /* 2460 * If segment contains data or ACK, will call tcp_reass() 2461 * later; if not, do so now to pass queued data to user. 2462 */ 2463 if (tlen == 0 && (thflags & TH_FIN) == 0) { 2464 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2465 (struct mbuf *)0); 2466 tcp_handle_wakeup(tp, so); 2467 } 2468 tp->snd_wl1 = th->th_seq - 1; 2469 /* FALLTHROUGH */ 2470 2471 /* 2472 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2473 * ACKs. If the ack is in the range 2474 * tp->snd_una < th->th_ack <= tp->snd_max 2475 * then advance tp->snd_una to th->th_ack and drop 2476 * data from the retransmission queue. If this ACK reflects 2477 * more up to date window information we update our window information. 2478 */ 2479 case TCPS_ESTABLISHED: 2480 case TCPS_FIN_WAIT_1: 2481 case TCPS_FIN_WAIT_2: 2482 case TCPS_CLOSE_WAIT: 2483 case TCPS_CLOSING: 2484 case TCPS_LAST_ACK: 2485 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2486 TCPSTAT_INC(tcps_rcvacktoomuch); 2487 goto dropafterack; 2488 } 2489 if ((tp->t_flags & TF_SACK_PERMIT) && 2490 ((to.to_flags & TOF_SACK) || 2491 !TAILQ_EMPTY(&tp->snd_holes))) { 2492 if (((sack_changed = tcp_sack_doack(tp, &to, th->th_ack)) != 0) && 2493 (tp->t_flags & TF_LRD)) { 2494 tcp_sack_lost_retransmission(tp, th); 2495 } 2496 } else 2497 /* 2498 * Reset the value so that previous (valid) value 2499 * from the last ack with SACK doesn't get used. 2500 */ 2501 tp->sackhint.sacked_bytes = 0; 2502 2503 #ifdef TCP_HHOOK 2504 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2505 hhook_run_tcp_est_in(tp, th, &to); 2506 #endif 2507 2508 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2509 maxseg = tcp_maxseg(tp); 2510 if (tlen == 0 && 2511 (tiwin == tp->snd_wnd || 2512 (tp->t_flags & TF_SACK_PERMIT))) { 2513 /* 2514 * If this is the first time we've seen a 2515 * FIN from the remote, this is not a 2516 * duplicate and it needs to be processed 2517 * normally. This happens during a 2518 * simultaneous close. 2519 */ 2520 if ((thflags & TH_FIN) && 2521 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2522 tp->t_dupacks = 0; 2523 break; 2524 } 2525 TCPSTAT_INC(tcps_rcvdupack); 2526 /* 2527 * If we have outstanding data (other than 2528 * a window probe), this is a completely 2529 * duplicate ack (ie, window info didn't 2530 * change and FIN isn't set), 2531 * the ack is the biggest we've 2532 * seen and we've seen exactly our rexmt 2533 * threshold of them, assume a packet 2534 * has been dropped and retransmit it. 2535 * Kludge snd_nxt & the congestion 2536 * window so we send only this one 2537 * packet. 2538 * 2539 * We know we're losing at the current 2540 * window size so do congestion avoidance 2541 * (set ssthresh to half the current window 2542 * and pull our congestion window back to 2543 * the new ssthresh). 2544 * 2545 * Dup acks mean that packets have left the 2546 * network (they're now cached at the receiver) 2547 * so bump cwnd by the amount in the receiver 2548 * to keep a constant cwnd packets in the 2549 * network. 2550 * 2551 * When using TCP ECN, notify the peer that 2552 * we reduced the cwnd. 2553 */ 2554 /* 2555 * Following 2 kinds of acks should not affect 2556 * dupack counting: 2557 * 1) Old acks 2558 * 2) Acks with SACK but without any new SACK 2559 * information in them. These could result from 2560 * any anomaly in the network like a switch 2561 * duplicating packets or a possible DoS attack. 2562 */ 2563 if (th->th_ack != tp->snd_una || 2564 ((tp->t_flags & TF_SACK_PERMIT) && 2565 (to.to_flags & TOF_SACK) && 2566 !sack_changed)) 2567 break; 2568 else if (!tcp_timer_active(tp, TT_REXMT)) 2569 tp->t_dupacks = 0; 2570 else if (++tp->t_dupacks > tcprexmtthresh || 2571 IN_FASTRECOVERY(tp->t_flags)) { 2572 cc_ack_received(tp, th, nsegs, 2573 CC_DUPACK); 2574 if (V_tcp_do_prr && 2575 IN_FASTRECOVERY(tp->t_flags)) { 2576 tcp_do_prr_ack(tp, th, &to); 2577 } else if ((tp->t_flags & TF_SACK_PERMIT) && 2578 (to.to_flags & TOF_SACK) && 2579 IN_FASTRECOVERY(tp->t_flags)) { 2580 int awnd; 2581 2582 /* 2583 * Compute the amount of data in flight first. 2584 * We can inject new data into the pipe iff 2585 * we have less than 1/2 the original window's 2586 * worth of data in flight. 2587 */ 2588 if (V_tcp_do_newsack) 2589 awnd = tcp_compute_pipe(tp); 2590 else 2591 awnd = (tp->snd_nxt - tp->snd_fack) + 2592 tp->sackhint.sack_bytes_rexmit; 2593 2594 if (awnd < tp->snd_ssthresh) { 2595 tp->snd_cwnd += maxseg; 2596 if (tp->snd_cwnd > tp->snd_ssthresh) 2597 tp->snd_cwnd = tp->snd_ssthresh; 2598 } 2599 } else 2600 tp->snd_cwnd += maxseg; 2601 (void) tcp_output(tp); 2602 goto drop; 2603 } else if (tp->t_dupacks == tcprexmtthresh || 2604 (tp->t_flags & TF_SACK_PERMIT && 2605 V_tcp_do_newsack && 2606 tp->sackhint.sacked_bytes > 2607 (tcprexmtthresh - 1) * maxseg)) { 2608 enter_recovery: 2609 /* 2610 * Above is the RFC6675 trigger condition of 2611 * more than (dupthresh-1)*maxseg sacked data. 2612 * If the count of holes in the 2613 * scoreboard is >= dupthresh, we could 2614 * also enter loss recovery, but don't 2615 * have that value readily available. 2616 */ 2617 tp->t_dupacks = tcprexmtthresh; 2618 tcp_seq onxt = tp->snd_nxt; 2619 2620 /* 2621 * If we're doing sack, or prr, check 2622 * to see if we're already in sack 2623 * recovery. If we're not doing sack, 2624 * check to see if we're in newreno 2625 * recovery. 2626 */ 2627 if (V_tcp_do_prr || 2628 (tp->t_flags & TF_SACK_PERMIT)) { 2629 if (IN_FASTRECOVERY(tp->t_flags)) { 2630 tp->t_dupacks = 0; 2631 break; 2632 } 2633 } else { 2634 if (SEQ_LEQ(th->th_ack, 2635 tp->snd_recover)) { 2636 tp->t_dupacks = 0; 2637 break; 2638 } 2639 } 2640 /* Congestion signal before ack. */ 2641 cc_cong_signal(tp, th, CC_NDUPACK); 2642 cc_ack_received(tp, th, nsegs, 2643 CC_DUPACK); 2644 tcp_timer_activate(tp, TT_REXMT, 0); 2645 tp->t_rtttime = 0; 2646 if (V_tcp_do_prr) { 2647 /* 2648 * snd_ssthresh is already updated by 2649 * cc_cong_signal. 2650 */ 2651 if ((tp->t_flags & TF_SACK_PERMIT) && 2652 (to.to_flags & TOF_SACK)) { 2653 tp->sackhint.prr_delivered = 2654 tp->sackhint.sacked_bytes; 2655 } else { 2656 tp->sackhint.prr_delivered = 2657 imin(tp->snd_max - tp->snd_una, 2658 imin(INT_MAX / 65536, 2659 tp->t_dupacks) * maxseg); 2660 } 2661 tp->sackhint.recover_fs = max(1, 2662 tp->snd_nxt - tp->snd_una); 2663 } 2664 if ((tp->t_flags & TF_SACK_PERMIT) && 2665 (to.to_flags & TOF_SACK)) { 2666 TCPSTAT_INC( 2667 tcps_sack_recovery_episode); 2668 tp->snd_recover = tp->snd_nxt; 2669 tp->snd_cwnd = maxseg; 2670 (void) tcp_output(tp); 2671 if (SEQ_GT(th->th_ack, tp->snd_una)) 2672 goto resume_partialack; 2673 goto drop; 2674 } 2675 tp->snd_nxt = th->th_ack; 2676 tp->snd_cwnd = maxseg; 2677 (void) tcp_output(tp); 2678 KASSERT(tp->snd_limited <= 2, 2679 ("%s: tp->snd_limited too big", 2680 __func__)); 2681 tp->snd_cwnd = tp->snd_ssthresh + 2682 maxseg * 2683 (tp->t_dupacks - tp->snd_limited); 2684 if (SEQ_GT(onxt, tp->snd_nxt)) 2685 tp->snd_nxt = onxt; 2686 goto drop; 2687 } else if (V_tcp_do_rfc3042) { 2688 /* 2689 * Process first and second duplicate 2690 * ACKs. Each indicates a segment 2691 * leaving the network, creating room 2692 * for more. Make sure we can send a 2693 * packet on reception of each duplicate 2694 * ACK by increasing snd_cwnd by one 2695 * segment. Restore the original 2696 * snd_cwnd after packet transmission. 2697 */ 2698 cc_ack_received(tp, th, nsegs, 2699 CC_DUPACK); 2700 uint32_t oldcwnd = tp->snd_cwnd; 2701 tcp_seq oldsndmax = tp->snd_max; 2702 u_int sent; 2703 int avail; 2704 2705 KASSERT(tp->t_dupacks == 1 || 2706 tp->t_dupacks == 2, 2707 ("%s: dupacks not 1 or 2", 2708 __func__)); 2709 if (tp->t_dupacks == 1) 2710 tp->snd_limited = 0; 2711 tp->snd_cwnd = 2712 (tp->snd_nxt - tp->snd_una) + 2713 (tp->t_dupacks - tp->snd_limited) * 2714 maxseg; 2715 /* 2716 * Only call tcp_output when there 2717 * is new data available to be sent. 2718 * Otherwise we would send pure ACKs. 2719 */ 2720 SOCKBUF_LOCK(&so->so_snd); 2721 avail = sbavail(&so->so_snd) - 2722 (tp->snd_nxt - tp->snd_una); 2723 SOCKBUF_UNLOCK(&so->so_snd); 2724 if (avail > 0) 2725 (void) tcp_output(tp); 2726 sent = tp->snd_max - oldsndmax; 2727 if (sent > maxseg) { 2728 KASSERT((tp->t_dupacks == 2 && 2729 tp->snd_limited == 0) || 2730 (sent == maxseg + 1 && 2731 tp->t_flags & TF_SENTFIN), 2732 ("%s: sent too much", 2733 __func__)); 2734 tp->snd_limited = 2; 2735 } else if (sent > 0) 2736 ++tp->snd_limited; 2737 tp->snd_cwnd = oldcwnd; 2738 goto drop; 2739 } 2740 } 2741 break; 2742 } else { 2743 /* 2744 * This ack is advancing the left edge, reset the 2745 * counter. 2746 */ 2747 tp->t_dupacks = 0; 2748 /* 2749 * If this ack also has new SACK info, increment the 2750 * counter as per rfc6675. The variable 2751 * sack_changed tracks all changes to the SACK 2752 * scoreboard, including when partial ACKs without 2753 * SACK options are received, and clear the scoreboard 2754 * from the left side. Such partial ACKs should not be 2755 * counted as dupacks here. 2756 */ 2757 if ((tp->t_flags & TF_SACK_PERMIT) && 2758 (to.to_flags & TOF_SACK) && 2759 sack_changed) { 2760 tp->t_dupacks++; 2761 /* limit overhead by setting maxseg last */ 2762 if (!IN_FASTRECOVERY(tp->t_flags) && 2763 (tp->sackhint.sacked_bytes > 2764 ((tcprexmtthresh - 1) * 2765 (maxseg = tcp_maxseg(tp))))) { 2766 goto enter_recovery; 2767 } 2768 } 2769 } 2770 2771 resume_partialack: 2772 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2773 ("%s: th_ack <= snd_una", __func__)); 2774 2775 /* 2776 * If the congestion window was inflated to account 2777 * for the other side's cached packets, retract it. 2778 */ 2779 if (IN_FASTRECOVERY(tp->t_flags)) { 2780 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2781 if (tp->t_flags & TF_SACK_PERMIT) 2782 if (V_tcp_do_prr && to.to_flags & TOF_SACK) { 2783 tcp_timer_activate(tp, TT_REXMT, 0); 2784 tp->t_rtttime = 0; 2785 tcp_do_prr_ack(tp, th, &to); 2786 tp->t_flags |= TF_ACKNOW; 2787 (void) tcp_output(tp); 2788 } else 2789 tcp_sack_partialack(tp, th); 2790 else 2791 tcp_newreno_partial_ack(tp, th); 2792 } else 2793 cc_post_recovery(tp, th); 2794 } else if (IN_CONGRECOVERY(tp->t_flags)) { 2795 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2796 if (V_tcp_do_prr) { 2797 tp->sackhint.delivered_data = BYTES_THIS_ACK(tp, th); 2798 tp->snd_fack = th->th_ack; 2799 tcp_do_prr_ack(tp, th, &to); 2800 (void) tcp_output(tp); 2801 } 2802 } else 2803 cc_post_recovery(tp, th); 2804 } 2805 /* 2806 * If we reach this point, ACK is not a duplicate, 2807 * i.e., it ACKs something we sent. 2808 */ 2809 if (tp->t_flags & TF_NEEDSYN) { 2810 /* 2811 * T/TCP: Connection was half-synchronized, and our 2812 * SYN has been ACK'd (so connection is now fully 2813 * synchronized). Go to non-starred state, 2814 * increment snd_una for ACK of SYN, and check if 2815 * we can do window scaling. 2816 */ 2817 tp->t_flags &= ~TF_NEEDSYN; 2818 tp->snd_una++; 2819 /* Do window scaling? */ 2820 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2821 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2822 tp->rcv_scale = tp->request_r_scale; 2823 /* Send window already scaled. */ 2824 } 2825 } 2826 2827 process_ACK: 2828 INP_WLOCK_ASSERT(tp->t_inpcb); 2829 2830 /* 2831 * Adjust for the SYN bit in sequence space, 2832 * but don't account for it in cwnd calculations. 2833 * This is for the SYN_RECEIVED, non-simultaneous 2834 * SYN case. SYN_SENT and simultaneous SYN are 2835 * treated elsewhere. 2836 */ 2837 if (incforsyn) 2838 tp->snd_una++; 2839 acked = BYTES_THIS_ACK(tp, th); 2840 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2841 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2842 tp->snd_una, th->th_ack, tp, m)); 2843 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2844 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2845 2846 /* 2847 * If we just performed our first retransmit, and the ACK 2848 * arrives within our recovery window, then it was a mistake 2849 * to do the retransmit in the first place. Recover our 2850 * original cwnd and ssthresh, and proceed to transmit where 2851 * we left off. 2852 */ 2853 if (tp->t_rxtshift == 1 && 2854 tp->t_flags & TF_PREVVALID && 2855 tp->t_badrxtwin != 0 && 2856 to.to_flags & TOF_TS && 2857 to.to_tsecr != 0 && 2858 TSTMP_LT(to.to_tsecr, tp->t_badrxtwin)) 2859 cc_cong_signal(tp, th, CC_RTO_ERR); 2860 2861 /* 2862 * If we have a timestamp reply, update smoothed 2863 * round trip time. If no timestamp is present but 2864 * transmit timer is running and timed sequence 2865 * number was acked, update smoothed round trip time. 2866 * Since we now have an rtt measurement, cancel the 2867 * timer backoff (cf., Phil Karn's retransmit alg.). 2868 * Recompute the initial retransmit timer. 2869 * 2870 * Some boxes send broken timestamp replies 2871 * during the SYN+ACK phase, ignore 2872 * timestamps of 0 or we could calculate a 2873 * huge RTT and blow up the retransmit timer. 2874 */ 2875 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2876 uint32_t t; 2877 2878 t = tcp_ts_getticks() - to.to_tsecr; 2879 if (!tp->t_rttlow || tp->t_rttlow > t) 2880 tp->t_rttlow = t; 2881 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2882 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2883 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2884 tp->t_rttlow = ticks - tp->t_rtttime; 2885 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2886 } 2887 2888 /* 2889 * If all outstanding data is acked, stop retransmit 2890 * timer and remember to restart (more output or persist). 2891 * If there is more data to be acked, restart retransmit 2892 * timer, using current (possibly backed-off) value. 2893 */ 2894 if (th->th_ack == tp->snd_max) { 2895 tcp_timer_activate(tp, TT_REXMT, 0); 2896 needoutput = 1; 2897 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2898 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2899 2900 /* 2901 * If no data (only SYN) was ACK'd, 2902 * skip rest of ACK processing. 2903 */ 2904 if (acked == 0) 2905 goto step6; 2906 2907 /* 2908 * Let the congestion control algorithm update congestion 2909 * control related information. This typically means increasing 2910 * the congestion window. 2911 */ 2912 cc_ack_received(tp, th, nsegs, CC_ACK); 2913 2914 SOCKBUF_LOCK(&so->so_snd); 2915 if (acked > sbavail(&so->so_snd)) { 2916 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2917 tp->snd_wnd -= sbavail(&so->so_snd); 2918 else 2919 tp->snd_wnd = 0; 2920 mfree = sbcut_locked(&so->so_snd, 2921 (int)sbavail(&so->so_snd)); 2922 ourfinisacked = 1; 2923 } else { 2924 mfree = sbcut_locked(&so->so_snd, acked); 2925 if (tp->snd_wnd >= (uint32_t) acked) 2926 tp->snd_wnd -= acked; 2927 else 2928 tp->snd_wnd = 0; 2929 ourfinisacked = 0; 2930 } 2931 /* NB: sowwakeup_locked() does an implicit unlock. */ 2932 sowwakeup_locked(so); 2933 m_freem(mfree); 2934 /* Detect una wraparound. */ 2935 if (!IN_RECOVERY(tp->t_flags) && 2936 SEQ_GT(tp->snd_una, tp->snd_recover) && 2937 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2938 tp->snd_recover = th->th_ack - 1; 2939 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2940 if (IN_RECOVERY(tp->t_flags) && 2941 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2942 EXIT_RECOVERY(tp->t_flags); 2943 } 2944 tp->snd_una = th->th_ack; 2945 if (tp->t_flags & TF_SACK_PERMIT) { 2946 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2947 tp->snd_recover = tp->snd_una; 2948 } 2949 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2950 tp->snd_nxt = tp->snd_una; 2951 2952 switch (tp->t_state) { 2953 /* 2954 * In FIN_WAIT_1 STATE in addition to the processing 2955 * for the ESTABLISHED state if our FIN is now acknowledged 2956 * then enter FIN_WAIT_2. 2957 */ 2958 case TCPS_FIN_WAIT_1: 2959 if (ourfinisacked) { 2960 /* 2961 * If we can't receive any more 2962 * data, then closing user can proceed. 2963 * Starting the timer is contrary to the 2964 * specification, but if we don't get a FIN 2965 * we'll hang forever. 2966 * 2967 * XXXjl: 2968 * we should release the tp also, and use a 2969 * compressed state. 2970 */ 2971 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2972 soisdisconnected(so); 2973 tcp_timer_activate(tp, TT_2MSL, 2974 (tcp_fast_finwait2_recycle ? 2975 tcp_finwait2_timeout : 2976 TP_MAXIDLE(tp))); 2977 } 2978 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2979 } 2980 break; 2981 2982 /* 2983 * In CLOSING STATE in addition to the processing for 2984 * the ESTABLISHED state if the ACK acknowledges our FIN 2985 * then enter the TIME-WAIT state, otherwise ignore 2986 * the segment. 2987 */ 2988 case TCPS_CLOSING: 2989 if (ourfinisacked) { 2990 tcp_twstart(tp); 2991 m_freem(m); 2992 return; 2993 } 2994 break; 2995 2996 /* 2997 * In LAST_ACK, we may still be waiting for data to drain 2998 * and/or to be acked, as well as for the ack of our FIN. 2999 * If our FIN is now acknowledged, delete the TCB, 3000 * enter the closed state and return. 3001 */ 3002 case TCPS_LAST_ACK: 3003 if (ourfinisacked) { 3004 tp = tcp_close(tp); 3005 goto drop; 3006 } 3007 break; 3008 } 3009 } 3010 3011 step6: 3012 INP_WLOCK_ASSERT(tp->t_inpcb); 3013 3014 /* 3015 * Update window information. 3016 * Don't look at window if no ACK: TAC's send garbage on first SYN. 3017 */ 3018 if ((thflags & TH_ACK) && 3019 (SEQ_LT(tp->snd_wl1, th->th_seq) || 3020 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 3021 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 3022 /* keep track of pure window updates */ 3023 if (tlen == 0 && 3024 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 3025 TCPSTAT_INC(tcps_rcvwinupd); 3026 tp->snd_wnd = tiwin; 3027 tp->snd_wl1 = th->th_seq; 3028 tp->snd_wl2 = th->th_ack; 3029 if (tp->snd_wnd > tp->max_sndwnd) 3030 tp->max_sndwnd = tp->snd_wnd; 3031 needoutput = 1; 3032 } 3033 3034 /* 3035 * Process segments with URG. 3036 */ 3037 if ((thflags & TH_URG) && th->th_urp && 3038 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3039 /* 3040 * This is a kludge, but if we receive and accept 3041 * random urgent pointers, we'll crash in 3042 * soreceive. It's hard to imagine someone 3043 * actually wanting to send this much urgent data. 3044 */ 3045 SOCKBUF_LOCK(&so->so_rcv); 3046 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 3047 th->th_urp = 0; /* XXX */ 3048 thflags &= ~TH_URG; /* XXX */ 3049 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 3050 goto dodata; /* XXX */ 3051 } 3052 /* 3053 * If this segment advances the known urgent pointer, 3054 * then mark the data stream. This should not happen 3055 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 3056 * a FIN has been received from the remote side. 3057 * In these states we ignore the URG. 3058 * 3059 * According to RFC961 (Assigned Protocols), 3060 * the urgent pointer points to the last octet 3061 * of urgent data. We continue, however, 3062 * to consider it to indicate the first octet 3063 * of data past the urgent section as the original 3064 * spec states (in one of two places). 3065 */ 3066 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 3067 tp->rcv_up = th->th_seq + th->th_urp; 3068 so->so_oobmark = sbavail(&so->so_rcv) + 3069 (tp->rcv_up - tp->rcv_nxt) - 1; 3070 if (so->so_oobmark == 0) 3071 so->so_rcv.sb_state |= SBS_RCVATMARK; 3072 sohasoutofband(so); 3073 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 3074 } 3075 SOCKBUF_UNLOCK(&so->so_rcv); 3076 /* 3077 * Remove out of band data so doesn't get presented to user. 3078 * This can happen independent of advancing the URG pointer, 3079 * but if two URG's are pending at once, some out-of-band 3080 * data may creep in... ick. 3081 */ 3082 if (th->th_urp <= (uint32_t)tlen && 3083 !(so->so_options & SO_OOBINLINE)) { 3084 /* hdr drop is delayed */ 3085 tcp_pulloutofband(so, th, m, drop_hdrlen); 3086 } 3087 } else { 3088 /* 3089 * If no out of band data is expected, 3090 * pull receive urgent pointer along 3091 * with the receive window. 3092 */ 3093 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3094 tp->rcv_up = tp->rcv_nxt; 3095 } 3096 dodata: /* XXX */ 3097 INP_WLOCK_ASSERT(tp->t_inpcb); 3098 3099 /* 3100 * Process the segment text, merging it into the TCP sequencing queue, 3101 * and arranging for acknowledgment of receipt if necessary. 3102 * This process logically involves adjusting tp->rcv_wnd as data 3103 * is presented to the user (this happens in tcp_usrreq.c, 3104 * case PRU_RCVD). If a FIN has already been received on this 3105 * connection then we just ignore the text. 3106 */ 3107 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3108 IS_FASTOPEN(tp->t_flags)); 3109 if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) && 3110 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3111 tcp_seq save_start = th->th_seq; 3112 tcp_seq save_rnxt = tp->rcv_nxt; 3113 int save_tlen = tlen; 3114 m_adj(m, drop_hdrlen); /* delayed header drop */ 3115 /* 3116 * Insert segment which includes th into TCP reassembly queue 3117 * with control block tp. Set thflags to whether reassembly now 3118 * includes a segment with FIN. This handles the common case 3119 * inline (segment is the next to be received on an established 3120 * connection, and the queue is empty), avoiding linkage into 3121 * and removal from the queue and repetition of various 3122 * conversions. 3123 * Set DELACK for segments received in order, but ack 3124 * immediately when segments are out of order (so 3125 * fast retransmit can work). 3126 */ 3127 if (th->th_seq == tp->rcv_nxt && 3128 SEGQ_EMPTY(tp) && 3129 (TCPS_HAVEESTABLISHED(tp->t_state) || 3130 tfo_syn)) { 3131 if (DELAY_ACK(tp, tlen) || tfo_syn) 3132 tp->t_flags |= TF_DELACK; 3133 else 3134 tp->t_flags |= TF_ACKNOW; 3135 tp->rcv_nxt += tlen; 3136 if (tlen && 3137 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 3138 (tp->t_fbyte_in == 0)) { 3139 tp->t_fbyte_in = ticks; 3140 if (tp->t_fbyte_in == 0) 3141 tp->t_fbyte_in = 1; 3142 if (tp->t_fbyte_out && tp->t_fbyte_in) 3143 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 3144 } 3145 thflags = tcp_get_flags(th) & TH_FIN; 3146 TCPSTAT_INC(tcps_rcvpack); 3147 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3148 SOCKBUF_LOCK(&so->so_rcv); 3149 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3150 m_freem(m); 3151 else 3152 sbappendstream_locked(&so->so_rcv, m, 0); 3153 tp->t_flags |= TF_WAKESOR; 3154 } else { 3155 /* 3156 * XXX: Due to the header drop above "th" is 3157 * theoretically invalid by now. Fortunately 3158 * m_adj() doesn't actually frees any mbufs 3159 * when trimming from the head. 3160 */ 3161 tcp_seq temp = save_start; 3162 3163 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3164 tp->t_flags |= TF_ACKNOW; 3165 } 3166 if ((tp->t_flags & TF_SACK_PERMIT) && 3167 (save_tlen > 0) && 3168 TCPS_HAVEESTABLISHED(tp->t_state)) { 3169 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) { 3170 /* 3171 * DSACK actually handled in the fastpath 3172 * above. 3173 */ 3174 tcp_update_sack_list(tp, save_start, 3175 save_start + save_tlen); 3176 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3177 if ((tp->rcv_numsacks >= 1) && 3178 (tp->sackblks[0].end == save_start)) { 3179 /* 3180 * Partial overlap, recorded at todrop 3181 * above. 3182 */ 3183 tcp_update_sack_list(tp, 3184 tp->sackblks[0].start, 3185 tp->sackblks[0].end); 3186 } else { 3187 tcp_update_dsack_list(tp, save_start, 3188 save_start + save_tlen); 3189 } 3190 } else if (tlen >= save_tlen) { 3191 /* Update of sackblks. */ 3192 tcp_update_dsack_list(tp, save_start, 3193 save_start + save_tlen); 3194 } else if (tlen > 0) { 3195 tcp_update_dsack_list(tp, save_start, 3196 save_start + tlen); 3197 } 3198 } 3199 tcp_handle_wakeup(tp, so); 3200 #if 0 3201 /* 3202 * Note the amount of data that peer has sent into 3203 * our window, in order to estimate the sender's 3204 * buffer size. 3205 * XXX: Unused. 3206 */ 3207 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3208 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3209 else 3210 len = so->so_rcv.sb_hiwat; 3211 #endif 3212 } else { 3213 m_freem(m); 3214 thflags &= ~TH_FIN; 3215 } 3216 3217 /* 3218 * If FIN is received ACK the FIN and let the user know 3219 * that the connection is closing. 3220 */ 3221 if (thflags & TH_FIN) { 3222 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3223 /* The socket upcall is handled by socantrcvmore. */ 3224 socantrcvmore(so); 3225 /* 3226 * If connection is half-synchronized 3227 * (ie NEEDSYN flag on) then delay ACK, 3228 * so it may be piggybacked when SYN is sent. 3229 * Otherwise, since we received a FIN then no 3230 * more input can be expected, send ACK now. 3231 */ 3232 if (tp->t_flags & TF_NEEDSYN) 3233 tp->t_flags |= TF_DELACK; 3234 else 3235 tp->t_flags |= TF_ACKNOW; 3236 tp->rcv_nxt++; 3237 } 3238 switch (tp->t_state) { 3239 /* 3240 * In SYN_RECEIVED and ESTABLISHED STATES 3241 * enter the CLOSE_WAIT state. 3242 */ 3243 case TCPS_SYN_RECEIVED: 3244 tp->t_starttime = ticks; 3245 /* FALLTHROUGH */ 3246 case TCPS_ESTABLISHED: 3247 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3248 break; 3249 3250 /* 3251 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3252 * enter the CLOSING state. 3253 */ 3254 case TCPS_FIN_WAIT_1: 3255 tcp_state_change(tp, TCPS_CLOSING); 3256 break; 3257 3258 /* 3259 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3260 * starting the time-wait timer, turning off the other 3261 * standard timers. 3262 */ 3263 case TCPS_FIN_WAIT_2: 3264 tcp_twstart(tp); 3265 return; 3266 } 3267 } 3268 #ifdef TCPDEBUG 3269 if (so->so_options & SO_DEBUG) 3270 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3271 &tcp_savetcp, 0); 3272 #endif 3273 TCP_PROBE3(debug__input, tp, th, m); 3274 3275 /* 3276 * Return any desired output. 3277 */ 3278 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3279 (void) tcp_output(tp); 3280 3281 check_delack: 3282 INP_WLOCK_ASSERT(tp->t_inpcb); 3283 3284 if (tp->t_flags & TF_DELACK) { 3285 tp->t_flags &= ~TF_DELACK; 3286 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3287 } 3288 INP_WUNLOCK(tp->t_inpcb); 3289 return; 3290 3291 dropafterack: 3292 /* 3293 * Generate an ACK dropping incoming segment if it occupies 3294 * sequence space, where the ACK reflects our state. 3295 * 3296 * We can now skip the test for the RST flag since all 3297 * paths to this code happen after packets containing 3298 * RST have been dropped. 3299 * 3300 * In the SYN-RECEIVED state, don't send an ACK unless the 3301 * segment we received passes the SYN-RECEIVED ACK test. 3302 * If it fails send a RST. This breaks the loop in the 3303 * "LAND" DoS attack, and also prevents an ACK storm 3304 * between two listening ports that have been sent forged 3305 * SYN segments, each with the source address of the other. 3306 */ 3307 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3308 (SEQ_GT(tp->snd_una, th->th_ack) || 3309 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3310 rstreason = BANDLIM_RST_OPENPORT; 3311 goto dropwithreset; 3312 } 3313 #ifdef TCPDEBUG 3314 if (so->so_options & SO_DEBUG) 3315 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3316 &tcp_savetcp, 0); 3317 #endif 3318 TCP_PROBE3(debug__input, tp, th, m); 3319 tp->t_flags |= TF_ACKNOW; 3320 (void) tcp_output(tp); 3321 INP_WUNLOCK(tp->t_inpcb); 3322 m_freem(m); 3323 return; 3324 3325 dropwithreset: 3326 if (tp != NULL) { 3327 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3328 INP_WUNLOCK(tp->t_inpcb); 3329 } else 3330 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3331 return; 3332 3333 drop: 3334 /* 3335 * Drop space held by incoming segment and return. 3336 */ 3337 #ifdef TCPDEBUG 3338 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3339 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3340 &tcp_savetcp, 0); 3341 #endif 3342 TCP_PROBE3(debug__input, tp, th, m); 3343 if (tp != NULL) { 3344 INP_WUNLOCK(tp->t_inpcb); 3345 } 3346 m_freem(m); 3347 } 3348 3349 /* 3350 * Issue RST and make ACK acceptable to originator of segment. 3351 * The mbuf must still include the original packet header. 3352 * tp may be NULL. 3353 */ 3354 void 3355 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3356 int tlen, int rstreason) 3357 { 3358 #ifdef INET 3359 struct ip *ip; 3360 #endif 3361 #ifdef INET6 3362 struct ip6_hdr *ip6; 3363 #endif 3364 3365 if (tp != NULL) { 3366 INP_LOCK_ASSERT(tp->t_inpcb); 3367 } 3368 3369 /* Don't bother if destination was broadcast/multicast. */ 3370 if ((tcp_get_flags(th) & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3371 goto drop; 3372 #ifdef INET6 3373 if (mtod(m, struct ip *)->ip_v == 6) { 3374 ip6 = mtod(m, struct ip6_hdr *); 3375 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3376 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3377 goto drop; 3378 /* IPv6 anycast check is done at tcp6_input() */ 3379 } 3380 #endif 3381 #if defined(INET) && defined(INET6) 3382 else 3383 #endif 3384 #ifdef INET 3385 { 3386 ip = mtod(m, struct ip *); 3387 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3388 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3389 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3390 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3391 goto drop; 3392 } 3393 #endif 3394 3395 /* Perform bandwidth limiting. */ 3396 if (badport_bandlim(rstreason) < 0) 3397 goto drop; 3398 3399 /* tcp_respond consumes the mbuf chain. */ 3400 if (tcp_get_flags(th) & TH_ACK) { 3401 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3402 th->th_ack, TH_RST); 3403 } else { 3404 if (tcp_get_flags(th) & TH_SYN) 3405 tlen++; 3406 if (tcp_get_flags(th) & TH_FIN) 3407 tlen++; 3408 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3409 (tcp_seq)0, TH_RST|TH_ACK); 3410 } 3411 return; 3412 drop: 3413 m_freem(m); 3414 } 3415 3416 /* 3417 * Parse TCP options and place in tcpopt. 3418 */ 3419 void 3420 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3421 { 3422 int opt, optlen; 3423 3424 to->to_flags = 0; 3425 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3426 opt = cp[0]; 3427 if (opt == TCPOPT_EOL) 3428 break; 3429 if (opt == TCPOPT_NOP) 3430 optlen = 1; 3431 else { 3432 if (cnt < 2) 3433 break; 3434 optlen = cp[1]; 3435 if (optlen < 2 || optlen > cnt) 3436 break; 3437 } 3438 switch (opt) { 3439 case TCPOPT_MAXSEG: 3440 if (optlen != TCPOLEN_MAXSEG) 3441 continue; 3442 if (!(flags & TO_SYN)) 3443 continue; 3444 to->to_flags |= TOF_MSS; 3445 bcopy((char *)cp + 2, 3446 (char *)&to->to_mss, sizeof(to->to_mss)); 3447 to->to_mss = ntohs(to->to_mss); 3448 break; 3449 case TCPOPT_WINDOW: 3450 if (optlen != TCPOLEN_WINDOW) 3451 continue; 3452 if (!(flags & TO_SYN)) 3453 continue; 3454 to->to_flags |= TOF_SCALE; 3455 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3456 break; 3457 case TCPOPT_TIMESTAMP: 3458 if (optlen != TCPOLEN_TIMESTAMP) 3459 continue; 3460 to->to_flags |= TOF_TS; 3461 bcopy((char *)cp + 2, 3462 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3463 to->to_tsval = ntohl(to->to_tsval); 3464 bcopy((char *)cp + 6, 3465 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3466 to->to_tsecr = ntohl(to->to_tsecr); 3467 break; 3468 case TCPOPT_SIGNATURE: 3469 /* 3470 * In order to reply to a host which has set the 3471 * TCP_SIGNATURE option in its initial SYN, we have 3472 * to record the fact that the option was observed 3473 * here for the syncache code to perform the correct 3474 * response. 3475 */ 3476 if (optlen != TCPOLEN_SIGNATURE) 3477 continue; 3478 to->to_flags |= TOF_SIGNATURE; 3479 to->to_signature = cp + 2; 3480 break; 3481 case TCPOPT_SACK_PERMITTED: 3482 if (optlen != TCPOLEN_SACK_PERMITTED) 3483 continue; 3484 if (!(flags & TO_SYN)) 3485 continue; 3486 if (!V_tcp_do_sack) 3487 continue; 3488 to->to_flags |= TOF_SACKPERM; 3489 break; 3490 case TCPOPT_SACK: 3491 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3492 continue; 3493 if (flags & TO_SYN) 3494 continue; 3495 to->to_flags |= TOF_SACK; 3496 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3497 to->to_sacks = cp + 2; 3498 TCPSTAT_INC(tcps_sack_rcv_blocks); 3499 break; 3500 case TCPOPT_FAST_OPEN: 3501 /* 3502 * Cookie length validation is performed by the 3503 * server side cookie checking code or the client 3504 * side cookie cache update code. 3505 */ 3506 if (!(flags & TO_SYN)) 3507 continue; 3508 if (!V_tcp_fastopen_client_enable && 3509 !V_tcp_fastopen_server_enable) 3510 continue; 3511 to->to_flags |= TOF_FASTOPEN; 3512 to->to_tfo_len = optlen - 2; 3513 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3514 break; 3515 default: 3516 continue; 3517 } 3518 } 3519 } 3520 3521 /* 3522 * Pull out of band byte out of a segment so 3523 * it doesn't appear in the user's data queue. 3524 * It is still reflected in the segment length for 3525 * sequencing purposes. 3526 */ 3527 void 3528 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3529 int off) 3530 { 3531 int cnt = off + th->th_urp - 1; 3532 3533 while (cnt >= 0) { 3534 if (m->m_len > cnt) { 3535 char *cp = mtod(m, caddr_t) + cnt; 3536 struct tcpcb *tp = sototcpcb(so); 3537 3538 INP_WLOCK_ASSERT(tp->t_inpcb); 3539 3540 tp->t_iobc = *cp; 3541 tp->t_oobflags |= TCPOOB_HAVEDATA; 3542 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3543 m->m_len--; 3544 if (m->m_flags & M_PKTHDR) 3545 m->m_pkthdr.len--; 3546 return; 3547 } 3548 cnt -= m->m_len; 3549 m = m->m_next; 3550 if (m == NULL) 3551 break; 3552 } 3553 panic("tcp_pulloutofband"); 3554 } 3555 3556 /* 3557 * Collect new round-trip time estimate 3558 * and update averages and current timeout. 3559 */ 3560 void 3561 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3562 { 3563 int delta; 3564 3565 INP_WLOCK_ASSERT(tp->t_inpcb); 3566 3567 TCPSTAT_INC(tcps_rttupdated); 3568 tp->t_rttupdated++; 3569 #ifdef STATS 3570 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, 3571 imax(0, rtt * 1000 / hz)); 3572 #endif 3573 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3574 /* 3575 * srtt is stored as fixed point with 5 bits after the 3576 * binary point (i.e., scaled by 8). The following magic 3577 * is equivalent to the smoothing algorithm in rfc793 with 3578 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3579 * point). Adjust rtt to origin 0. 3580 */ 3581 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3582 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3583 3584 if ((tp->t_srtt += delta) <= 0) 3585 tp->t_srtt = 1; 3586 3587 /* 3588 * We accumulate a smoothed rtt variance (actually, a 3589 * smoothed mean difference), then set the retransmit 3590 * timer to smoothed rtt + 4 times the smoothed variance. 3591 * rttvar is stored as fixed point with 4 bits after the 3592 * binary point (scaled by 16). The following is 3593 * equivalent to rfc793 smoothing with an alpha of .75 3594 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3595 * rfc793's wired-in beta. 3596 */ 3597 if (delta < 0) 3598 delta = -delta; 3599 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3600 if ((tp->t_rttvar += delta) <= 0) 3601 tp->t_rttvar = 1; 3602 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3603 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3604 } else { 3605 /* 3606 * No rtt measurement yet - use the unsmoothed rtt. 3607 * Set the variance to half the rtt (so our first 3608 * retransmit happens at 3*rtt). 3609 */ 3610 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3611 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3612 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3613 } 3614 tp->t_rtttime = 0; 3615 tp->t_rxtshift = 0; 3616 3617 /* 3618 * the retransmit should happen at rtt + 4 * rttvar. 3619 * Because of the way we do the smoothing, srtt and rttvar 3620 * will each average +1/2 tick of bias. When we compute 3621 * the retransmit timer, we want 1/2 tick of rounding and 3622 * 1 extra tick because of +-1/2 tick uncertainty in the 3623 * firing of the timer. The bias will give us exactly the 3624 * 1.5 tick we need. But, because the bias is 3625 * statistical, we have to test that we don't drop below 3626 * the minimum feasible timer (which is 2 ticks). 3627 */ 3628 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3629 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3630 3631 /* 3632 * We received an ack for a packet that wasn't retransmitted; 3633 * it is probably safe to discard any error indications we've 3634 * received recently. This isn't quite right, but close enough 3635 * for now (a route might have failed after we sent a segment, 3636 * and the return path might not be symmetrical). 3637 */ 3638 tp->t_softerror = 0; 3639 } 3640 3641 /* 3642 * Determine a reasonable value for maxseg size. 3643 * If the route is known, check route for mtu. 3644 * If none, use an mss that can be handled on the outgoing interface 3645 * without forcing IP to fragment. If no route is found, route has no mtu, 3646 * or the destination isn't local, use a default, hopefully conservative 3647 * size (usually 512 or the default IP max size, but no more than the mtu 3648 * of the interface), as we can't discover anything about intervening 3649 * gateways or networks. We also initialize the congestion/slow start 3650 * window to be a single segment if the destination isn't local. 3651 * While looking at the routing entry, we also initialize other path-dependent 3652 * parameters from pre-set or cached values in the routing entry. 3653 * 3654 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3655 * IP options, e.g. IPSEC data, since length of this data may vary, and 3656 * thus it is calculated for every segment separately in tcp_output(). 3657 * 3658 * NOTE that this routine is only called when we process an incoming 3659 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3660 * settings are handled in tcp_mssopt(). 3661 */ 3662 void 3663 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3664 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3665 { 3666 int mss = 0; 3667 uint32_t maxmtu = 0; 3668 struct inpcb *inp = tp->t_inpcb; 3669 struct hc_metrics_lite metrics; 3670 #ifdef INET6 3671 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3672 size_t min_protoh = isipv6 ? 3673 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3674 sizeof (struct tcpiphdr); 3675 #else 3676 size_t min_protoh = sizeof(struct tcpiphdr); 3677 #endif 3678 3679 INP_WLOCK_ASSERT(tp->t_inpcb); 3680 3681 if (tp->t_port) 3682 min_protoh += V_tcp_udp_tunneling_overhead; 3683 if (mtuoffer != -1) { 3684 KASSERT(offer == -1, ("%s: conflict", __func__)); 3685 offer = mtuoffer - min_protoh; 3686 } 3687 3688 /* Initialize. */ 3689 #ifdef INET6 3690 if (isipv6) { 3691 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3692 tp->t_maxseg = V_tcp_v6mssdflt; 3693 } 3694 #endif 3695 #if defined(INET) && defined(INET6) 3696 else 3697 #endif 3698 #ifdef INET 3699 { 3700 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3701 tp->t_maxseg = V_tcp_mssdflt; 3702 } 3703 #endif 3704 3705 /* 3706 * No route to sender, stay with default mss and return. 3707 */ 3708 if (maxmtu == 0) { 3709 /* 3710 * In case we return early we need to initialize metrics 3711 * to a defined state as tcp_hc_get() would do for us 3712 * if there was no cache hit. 3713 */ 3714 if (metricptr != NULL) 3715 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3716 return; 3717 } 3718 3719 /* What have we got? */ 3720 switch (offer) { 3721 case 0: 3722 /* 3723 * Offer == 0 means that there was no MSS on the SYN 3724 * segment, in this case we use tcp_mssdflt as 3725 * already assigned to t_maxseg above. 3726 */ 3727 offer = tp->t_maxseg; 3728 break; 3729 3730 case -1: 3731 /* 3732 * Offer == -1 means that we didn't receive SYN yet. 3733 */ 3734 /* FALLTHROUGH */ 3735 3736 default: 3737 /* 3738 * Prevent DoS attack with too small MSS. Round up 3739 * to at least minmss. 3740 */ 3741 offer = max(offer, V_tcp_minmss); 3742 } 3743 3744 /* 3745 * rmx information is now retrieved from tcp_hostcache. 3746 */ 3747 tcp_hc_get(&inp->inp_inc, &metrics); 3748 if (metricptr != NULL) 3749 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3750 3751 /* 3752 * If there's a discovered mtu in tcp hostcache, use it. 3753 * Else, use the link mtu. 3754 */ 3755 if (metrics.rmx_mtu) 3756 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3757 else { 3758 #ifdef INET6 3759 if (isipv6) { 3760 mss = maxmtu - min_protoh; 3761 if (!V_path_mtu_discovery && 3762 !in6_localaddr(&inp->in6p_faddr)) 3763 mss = min(mss, V_tcp_v6mssdflt); 3764 } 3765 #endif 3766 #if defined(INET) && defined(INET6) 3767 else 3768 #endif 3769 #ifdef INET 3770 { 3771 mss = maxmtu - min_protoh; 3772 if (!V_path_mtu_discovery && 3773 !in_localaddr(inp->inp_faddr)) 3774 mss = min(mss, V_tcp_mssdflt); 3775 } 3776 #endif 3777 /* 3778 * XXX - The above conditional (mss = maxmtu - min_protoh) 3779 * probably violates the TCP spec. 3780 * The problem is that, since we don't know the 3781 * other end's MSS, we are supposed to use a conservative 3782 * default. But, if we do that, then MTU discovery will 3783 * never actually take place, because the conservative 3784 * default is much less than the MTUs typically seen 3785 * on the Internet today. For the moment, we'll sweep 3786 * this under the carpet. 3787 * 3788 * The conservative default might not actually be a problem 3789 * if the only case this occurs is when sending an initial 3790 * SYN with options and data to a host we've never talked 3791 * to before. Then, they will reply with an MSS value which 3792 * will get recorded and the new parameters should get 3793 * recomputed. For Further Study. 3794 */ 3795 } 3796 mss = min(mss, offer); 3797 3798 /* 3799 * Sanity check: make sure that maxseg will be large 3800 * enough to allow some data on segments even if the 3801 * all the option space is used (40bytes). Otherwise 3802 * funny things may happen in tcp_output. 3803 * 3804 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3805 */ 3806 mss = max(mss, 64); 3807 3808 tp->t_maxseg = mss; 3809 } 3810 3811 void 3812 tcp_mss(struct tcpcb *tp, int offer) 3813 { 3814 int mss; 3815 uint32_t bufsize; 3816 struct inpcb *inp; 3817 struct socket *so; 3818 struct hc_metrics_lite metrics; 3819 struct tcp_ifcap cap; 3820 3821 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3822 3823 bzero(&cap, sizeof(cap)); 3824 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3825 3826 mss = tp->t_maxseg; 3827 inp = tp->t_inpcb; 3828 3829 /* 3830 * If there's a pipesize, change the socket buffer to that size, 3831 * don't change if sb_hiwat is different than default (then it 3832 * has been changed on purpose with setsockopt). 3833 * Make the socket buffers an integral number of mss units; 3834 * if the mss is larger than the socket buffer, decrease the mss. 3835 */ 3836 so = inp->inp_socket; 3837 SOCKBUF_LOCK(&so->so_snd); 3838 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3839 bufsize = metrics.rmx_sendpipe; 3840 else 3841 bufsize = so->so_snd.sb_hiwat; 3842 if (bufsize < mss) 3843 mss = bufsize; 3844 else { 3845 bufsize = roundup(bufsize, mss); 3846 if (bufsize > sb_max) 3847 bufsize = sb_max; 3848 if (bufsize > so->so_snd.sb_hiwat) 3849 (void)sbreserve_locked(so, SO_SND, bufsize, NULL); 3850 } 3851 SOCKBUF_UNLOCK(&so->so_snd); 3852 /* 3853 * Sanity check: make sure that maxseg will be large 3854 * enough to allow some data on segments even if the 3855 * all the option space is used (40bytes). Otherwise 3856 * funny things may happen in tcp_output. 3857 * 3858 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3859 */ 3860 tp->t_maxseg = max(mss, 64); 3861 3862 SOCKBUF_LOCK(&so->so_rcv); 3863 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3864 bufsize = metrics.rmx_recvpipe; 3865 else 3866 bufsize = so->so_rcv.sb_hiwat; 3867 if (bufsize > mss) { 3868 bufsize = roundup(bufsize, mss); 3869 if (bufsize > sb_max) 3870 bufsize = sb_max; 3871 if (bufsize > so->so_rcv.sb_hiwat) 3872 (void)sbreserve_locked(so, SO_RCV, bufsize, NULL); 3873 } 3874 SOCKBUF_UNLOCK(&so->so_rcv); 3875 3876 /* Check the interface for TSO capabilities. */ 3877 if (cap.ifcap & CSUM_TSO) { 3878 tp->t_flags |= TF_TSO; 3879 tp->t_tsomax = cap.tsomax; 3880 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3881 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3882 } 3883 } 3884 3885 /* 3886 * Determine the MSS option to send on an outgoing SYN. 3887 */ 3888 int 3889 tcp_mssopt(struct in_conninfo *inc) 3890 { 3891 int mss = 0; 3892 uint32_t thcmtu = 0; 3893 uint32_t maxmtu = 0; 3894 size_t min_protoh; 3895 3896 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3897 3898 #ifdef INET6 3899 if (inc->inc_flags & INC_ISIPV6) { 3900 mss = V_tcp_v6mssdflt; 3901 maxmtu = tcp_maxmtu6(inc, NULL); 3902 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3903 } 3904 #endif 3905 #if defined(INET) && defined(INET6) 3906 else 3907 #endif 3908 #ifdef INET 3909 { 3910 mss = V_tcp_mssdflt; 3911 maxmtu = tcp_maxmtu(inc, NULL); 3912 min_protoh = sizeof(struct tcpiphdr); 3913 } 3914 #endif 3915 #if defined(INET6) || defined(INET) 3916 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3917 #endif 3918 3919 if (maxmtu && thcmtu) 3920 mss = min(maxmtu, thcmtu) - min_protoh; 3921 else if (maxmtu || thcmtu) 3922 mss = max(maxmtu, thcmtu) - min_protoh; 3923 3924 return (mss); 3925 } 3926 3927 void 3928 tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 3929 { 3930 int snd_cnt = 0, limit = 0, del_data = 0, pipe = 0; 3931 int maxseg = tcp_maxseg(tp); 3932 3933 INP_WLOCK_ASSERT(tp->t_inpcb); 3934 3935 /* 3936 * Compute the amount of data that this ACK is indicating 3937 * (del_data) and an estimate of how many bytes are in the 3938 * network. 3939 */ 3940 if (((tp->t_flags & TF_SACK_PERMIT) && 3941 (to->to_flags & TOF_SACK)) || 3942 (IN_CONGRECOVERY(tp->t_flags) && 3943 !IN_FASTRECOVERY(tp->t_flags))) { 3944 del_data = tp->sackhint.delivered_data; 3945 if (V_tcp_do_newsack) 3946 pipe = tcp_compute_pipe(tp); 3947 else 3948 pipe = (tp->snd_nxt - tp->snd_fack) + 3949 tp->sackhint.sack_bytes_rexmit; 3950 } else { 3951 if (tp->sackhint.prr_delivered < (tcprexmtthresh * maxseg + 3952 tp->snd_recover - tp->snd_una)) 3953 del_data = maxseg; 3954 pipe = imax(0, tp->snd_max - tp->snd_una - 3955 imin(INT_MAX / 65536, tp->t_dupacks) * maxseg); 3956 } 3957 tp->sackhint.prr_delivered += del_data; 3958 /* 3959 * Proportional Rate Reduction 3960 */ 3961 if (pipe >= tp->snd_ssthresh) { 3962 if (tp->sackhint.recover_fs == 0) 3963 tp->sackhint.recover_fs = 3964 imax(1, tp->snd_nxt - tp->snd_una); 3965 snd_cnt = howmany((long)tp->sackhint.prr_delivered * 3966 tp->snd_ssthresh, tp->sackhint.recover_fs) - 3967 tp->sackhint.prr_out; 3968 } else { 3969 if (V_tcp_do_prr_conservative || (del_data == 0)) 3970 limit = tp->sackhint.prr_delivered - 3971 tp->sackhint.prr_out; 3972 else 3973 limit = imax(tp->sackhint.prr_delivered - 3974 tp->sackhint.prr_out, del_data) + 3975 maxseg; 3976 snd_cnt = imin((tp->snd_ssthresh - pipe), limit); 3977 } 3978 snd_cnt = imax(snd_cnt, 0) / maxseg; 3979 /* 3980 * Send snd_cnt new data into the network in response to this ack. 3981 * If there is going to be a SACK retransmission, adjust snd_cwnd 3982 * accordingly. 3983 */ 3984 if (IN_FASTRECOVERY(tp->t_flags)) { 3985 if ((tp->t_flags & TF_SACK_PERMIT) && 3986 (to->to_flags & TOF_SACK)) { 3987 tp->snd_cwnd = tp->snd_nxt - tp->snd_recover + 3988 tp->sackhint.sack_bytes_rexmit + 3989 (snd_cnt * maxseg); 3990 } else { 3991 tp->snd_cwnd = (tp->snd_max - tp->snd_una) + 3992 (snd_cnt * maxseg); 3993 } 3994 } else if (IN_CONGRECOVERY(tp->t_flags)) 3995 tp->snd_cwnd = pipe - del_data + (snd_cnt * maxseg); 3996 tp->snd_cwnd = imax(maxseg, tp->snd_cwnd); 3997 } 3998 3999 /* 4000 * On a partial ack arrives, force the retransmission of the 4001 * next unacknowledged segment. Do not clear tp->t_dupacks. 4002 * By setting snd_nxt to ti_ack, this forces retransmission timer to 4003 * be started again. 4004 */ 4005 void 4006 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 4007 { 4008 tcp_seq onxt = tp->snd_nxt; 4009 uint32_t ocwnd = tp->snd_cwnd; 4010 u_int maxseg = tcp_maxseg(tp); 4011 4012 INP_WLOCK_ASSERT(tp->t_inpcb); 4013 4014 tcp_timer_activate(tp, TT_REXMT, 0); 4015 tp->t_rtttime = 0; 4016 tp->snd_nxt = th->th_ack; 4017 /* 4018 * Set snd_cwnd to one segment beyond acknowledged offset. 4019 * (tp->snd_una has not yet been updated when this function is called.) 4020 */ 4021 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 4022 tp->t_flags |= TF_ACKNOW; 4023 (void) tcp_output(tp); 4024 tp->snd_cwnd = ocwnd; 4025 if (SEQ_GT(onxt, tp->snd_nxt)) 4026 tp->snd_nxt = onxt; 4027 /* 4028 * Partial window deflation. Relies on fact that tp->snd_una 4029 * not updated yet. 4030 */ 4031 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 4032 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 4033 else 4034 tp->snd_cwnd = 0; 4035 tp->snd_cwnd += maxseg; 4036 } 4037 4038 int 4039 tcp_compute_pipe(struct tcpcb *tp) 4040 { 4041 return (tp->snd_max - tp->snd_una + 4042 tp->sackhint.sack_bytes_rexmit - 4043 tp->sackhint.sacked_bytes); 4044 } 4045 4046 uint32_t 4047 tcp_compute_initwnd(uint32_t maxseg) 4048 { 4049 /* 4050 * Calculate the Initial Window, also used as Restart Window 4051 * 4052 * RFC5681 Section 3.1 specifies the default conservative values. 4053 * RFC3390 specifies slightly more aggressive values. 4054 * RFC6928 increases it to ten segments. 4055 * Support for user specified value for initial flight size. 4056 */ 4057 if (V_tcp_initcwnd_segments) 4058 return min(V_tcp_initcwnd_segments * maxseg, 4059 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 4060 else if (V_tcp_do_rfc3390) 4061 return min(4 * maxseg, max(2 * maxseg, 4380)); 4062 else { 4063 /* Per RFC5681 Section 3.1 */ 4064 if (maxseg > 2190) 4065 return (2 * maxseg); 4066 else if (maxseg > 1095) 4067 return (3 * maxseg); 4068 else 4069 return (4 * maxseg); 4070 } 4071 } 4072