1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 2007-2008,2010 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 9 * Copyright (c) 2010 The FreeBSD Foundation 10 * Copyright (c) 2010-2011 Juniper Networks, Inc. 11 * All rights reserved. 12 * 13 * Portions of this software were developed at the Centre for Advanced Internet 14 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 15 * James Healy and David Hayes, made possible in part by a grant from the Cisco 16 * University Research Program Fund at Community Foundation Silicon Valley. 17 * 18 * Portions of this software were developed at the Centre for Advanced 19 * Internet Architectures, Swinburne University of Technology, Melbourne, 20 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 21 * 22 * Portions of this software were developed by Robert N. M. Watson under 23 * contract to Juniper Networks, Inc. 24 * 25 * Redistribution and use in source and binary forms, with or without 26 * modification, are permitted provided that the following conditions 27 * are met: 28 * 1. Redistributions of source code must retain the above copyright 29 * notice, this list of conditions and the following disclaimer. 30 * 2. Redistributions in binary form must reproduce the above copyright 31 * notice, this list of conditions and the following disclaimer in the 32 * documentation and/or other materials provided with the distribution. 33 * 3. Neither the name of the University nor the names of its contributors 34 * may be used to endorse or promote products derived from this software 35 * without specific prior written permission. 36 * 37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 47 * SUCH DAMAGE. 48 * 49 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 50 */ 51 52 #include <sys/cdefs.h> 53 __FBSDID("$FreeBSD$"); 54 55 #include "opt_inet.h" 56 #include "opt_inet6.h" 57 #include "opt_ipsec.h" 58 #include "opt_tcpdebug.h" 59 60 #include <sys/param.h> 61 #include <sys/arb.h> 62 #include <sys/kernel.h> 63 #ifdef TCP_HHOOK 64 #include <sys/hhook.h> 65 #endif 66 #include <sys/malloc.h> 67 #include <sys/mbuf.h> 68 #include <sys/proc.h> /* for proc0 declaration */ 69 #include <sys/protosw.h> 70 #include <sys/qmath.h> 71 #include <sys/sdt.h> 72 #include <sys/signalvar.h> 73 #include <sys/socket.h> 74 #include <sys/socketvar.h> 75 #include <sys/sysctl.h> 76 #include <sys/syslog.h> 77 #include <sys/systm.h> 78 #include <sys/stats.h> 79 80 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 81 82 #include <vm/uma.h> 83 84 #include <net/if.h> 85 #include <net/if_var.h> 86 #include <net/route.h> 87 #include <net/vnet.h> 88 89 #define TCPSTATES /* for logging */ 90 91 #include <netinet/in.h> 92 #include <netinet/in_kdtrace.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 98 #include <netinet/ip_var.h> 99 #include <netinet/ip_options.h> 100 #include <netinet/ip6.h> 101 #include <netinet/icmp6.h> 102 #include <netinet6/in6_pcb.h> 103 #include <netinet6/in6_var.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/nd6.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_log_buf.h> 109 #include <netinet/tcp_seq.h> 110 #include <netinet/tcp_timer.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 #include <netinet/cc/cc.h> 115 #include <netinet/tcp_fastopen.h> 116 #ifdef TCPPCAP 117 #include <netinet/tcp_pcap.h> 118 #endif 119 #include <netinet/tcp_syncache.h> 120 #ifdef TCPDEBUG 121 #include <netinet/tcp_debug.h> 122 #endif /* TCPDEBUG */ 123 #ifdef TCP_OFFLOAD 124 #include <netinet/tcp_offload.h> 125 #endif 126 127 #include <netipsec/ipsec_support.h> 128 129 #include <machine/in_cksum.h> 130 131 #include <security/mac/mac_framework.h> 132 133 const int tcprexmtthresh = 3; 134 135 VNET_DEFINE(int, tcp_log_in_vain) = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_VNET | CTLFLAG_RW, 137 &VNET_NAME(tcp_log_in_vain), 0, 138 "Log all incoming TCP segments to closed ports"); 139 140 VNET_DEFINE(int, blackhole) = 0; 141 #define V_blackhole VNET(blackhole) 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 143 &VNET_NAME(blackhole), 0, 144 "Do not send RST on segments to closed ports"); 145 146 VNET_DEFINE(int, tcp_delack_enabled) = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 148 &VNET_NAME(tcp_delack_enabled), 0, 149 "Delay ACK to try and piggyback it onto a data packet"); 150 151 VNET_DEFINE(int, drop_synfin) = 0; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 153 &VNET_NAME(drop_synfin), 0, 154 "Drop TCP packets with SYN+FIN set"); 155 156 VNET_DEFINE(int, tcp_do_prr_conservative) = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_prr_conservative, CTLFLAG_VNET | CTLFLAG_RW, 158 &VNET_NAME(tcp_do_prr_conservative), 0, 159 "Do conservative Proportional Rate Reduction"); 160 161 VNET_DEFINE(int, tcp_do_prr) = 1; 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_prr, CTLFLAG_VNET | CTLFLAG_RW, 163 &VNET_NAME(tcp_do_prr), 1, 164 "Enable Proportional Rate Reduction per RFC 6937"); 165 166 VNET_DEFINE(int, tcp_do_newcwv) = 0; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW, 168 &VNET_NAME(tcp_do_newcwv), 0, 169 "Enable New Congestion Window Validation per RFC7661"); 170 171 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 173 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 174 "Use calculated pipe/in-flight bytes per RFC 6675"); 175 176 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 178 &VNET_NAME(tcp_do_rfc3042), 0, 179 "Enable RFC 3042 (Limited Transmit)"); 180 181 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 183 &VNET_NAME(tcp_do_rfc3390), 0, 184 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 185 186 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 188 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 189 "Slow-start flight size (initial congestion window) in number of segments"); 190 191 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 193 &VNET_NAME(tcp_do_rfc3465), 0, 194 "Enable RFC 3465 (Appropriate Byte Counting)"); 195 196 VNET_DEFINE(int, tcp_abc_l_var) = 2; 197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 198 &VNET_NAME(tcp_abc_l_var), 2, 199 "Cap the max cwnd increment during slow-start to this number of segments"); 200 201 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, 202 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 203 "TCP ECN"); 204 205 VNET_DEFINE(int, tcp_do_ecn) = 2; 206 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 207 &VNET_NAME(tcp_do_ecn), 0, 208 "TCP ECN support"); 209 210 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 211 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 212 &VNET_NAME(tcp_ecn_maxretries), 0, 213 "Max retries before giving up on ECN"); 214 215 VNET_DEFINE(int, tcp_insecure_syn) = 0; 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 217 &VNET_NAME(tcp_insecure_syn), 0, 218 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 219 220 VNET_DEFINE(int, tcp_insecure_rst) = 0; 221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 222 &VNET_NAME(tcp_insecure_rst), 0, 223 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 224 225 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 226 #define V_tcp_recvspace VNET(tcp_recvspace) 227 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 228 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 229 230 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 231 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 232 &VNET_NAME(tcp_do_autorcvbuf), 0, 233 "Enable automatic receive buffer sizing"); 234 235 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 236 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 237 &VNET_NAME(tcp_autorcvbuf_max), 0, 238 "Max size of automatic receive buffer"); 239 240 VNET_DEFINE(struct inpcbhead, tcb); 241 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 242 VNET_DEFINE(struct inpcbinfo, tcbinfo); 243 244 /* 245 * TCP statistics are stored in an array of counter(9)s, which size matches 246 * size of struct tcpstat. TCP running connection count is a regular array. 247 */ 248 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 249 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 250 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 251 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 252 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 253 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 254 "TCP connection counts by TCP state"); 255 256 static void 257 tcp_vnet_init(const void *unused) 258 { 259 260 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 261 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 262 } 263 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 264 tcp_vnet_init, NULL); 265 266 #ifdef VIMAGE 267 static void 268 tcp_vnet_uninit(const void *unused) 269 { 270 271 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 272 VNET_PCPUSTAT_FREE(tcpstat); 273 } 274 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 275 tcp_vnet_uninit, NULL); 276 #endif /* VIMAGE */ 277 278 /* 279 * Kernel module interface for updating tcpstat. The first argument is an index 280 * into tcpstat treated as an array. 281 */ 282 void 283 kmod_tcpstat_add(int statnum, int val) 284 { 285 286 counter_u64_add(VNET(tcpstat)[statnum], val); 287 } 288 289 #ifdef TCP_HHOOK 290 /* 291 * Wrapper for the TCP established input helper hook. 292 */ 293 void 294 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 295 { 296 struct tcp_hhook_data hhook_data; 297 298 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 299 hhook_data.tp = tp; 300 hhook_data.th = th; 301 hhook_data.to = to; 302 303 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 304 tp->osd); 305 } 306 } 307 #endif 308 309 /* 310 * CC wrapper hook functions 311 */ 312 void 313 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 314 uint16_t type) 315 { 316 #ifdef STATS 317 int32_t gput; 318 #endif 319 320 INP_WLOCK_ASSERT(tp->t_inpcb); 321 322 tp->ccv->nsegs = nsegs; 323 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 324 if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) || 325 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) && 326 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2)))) 327 tp->ccv->flags |= CCF_CWND_LIMITED; 328 else 329 tp->ccv->flags &= ~CCF_CWND_LIMITED; 330 331 if (type == CC_ACK) { 332 #ifdef STATS 333 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF, 334 ((int32_t)tp->snd_cwnd) - tp->snd_wnd); 335 if (!IN_RECOVERY(tp->t_flags)) 336 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN, 337 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs)); 338 if ((tp->t_flags & TF_GPUTINPROG) && 339 SEQ_GEQ(th->th_ack, tp->gput_ack)) { 340 /* 341 * Compute goodput in bits per millisecond. 342 */ 343 gput = (((int64_t)(th->th_ack - tp->gput_seq)) << 3) / 344 max(1, tcp_ts_getticks() - tp->gput_ts); 345 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT, 346 gput); 347 /* 348 * XXXLAS: This is a temporary hack, and should be 349 * chained off VOI_TCP_GPUT when stats(9) grows an API 350 * to deal with chained VOIs. 351 */ 352 if (tp->t_stats_gput_prev > 0) 353 stats_voi_update_abs_s32(tp->t_stats, 354 VOI_TCP_GPUT_ND, 355 ((gput - tp->t_stats_gput_prev) * 100) / 356 tp->t_stats_gput_prev); 357 tp->t_flags &= ~TF_GPUTINPROG; 358 tp->t_stats_gput_prev = gput; 359 } 360 #endif /* STATS */ 361 if (tp->snd_cwnd > tp->snd_ssthresh) { 362 tp->t_bytes_acked += tp->ccv->bytes_this_ack; 363 if (tp->t_bytes_acked >= tp->snd_cwnd) { 364 tp->t_bytes_acked -= tp->snd_cwnd; 365 tp->ccv->flags |= CCF_ABC_SENTAWND; 366 } 367 } else { 368 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 369 tp->t_bytes_acked = 0; 370 } 371 } 372 373 if (CC_ALGO(tp)->ack_received != NULL) { 374 /* XXXLAS: Find a way to live without this */ 375 tp->ccv->curack = th->th_ack; 376 CC_ALGO(tp)->ack_received(tp->ccv, type); 377 } 378 #ifdef STATS 379 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd); 380 #endif 381 } 382 383 void 384 cc_conn_init(struct tcpcb *tp) 385 { 386 struct hc_metrics_lite metrics; 387 struct inpcb *inp = tp->t_inpcb; 388 u_int maxseg; 389 int rtt; 390 391 INP_WLOCK_ASSERT(tp->t_inpcb); 392 393 tcp_hc_get(&inp->inp_inc, &metrics); 394 maxseg = tcp_maxseg(tp); 395 396 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 397 tp->t_srtt = rtt; 398 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 399 TCPSTAT_INC(tcps_usedrtt); 400 if (metrics.rmx_rttvar) { 401 tp->t_rttvar = metrics.rmx_rttvar; 402 TCPSTAT_INC(tcps_usedrttvar); 403 } else { 404 /* default variation is +- 1 rtt */ 405 tp->t_rttvar = 406 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 407 } 408 TCPT_RANGESET(tp->t_rxtcur, 409 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 410 tp->t_rttmin, TCPTV_REXMTMAX); 411 } 412 if (metrics.rmx_ssthresh) { 413 /* 414 * There's some sort of gateway or interface 415 * buffer limit on the path. Use this to set 416 * the slow start threshold, but set the 417 * threshold to no less than 2*mss. 418 */ 419 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 420 TCPSTAT_INC(tcps_usedssthresh); 421 } 422 423 /* 424 * Set the initial slow-start flight size. 425 * 426 * If a SYN or SYN/ACK was lost and retransmitted, we have to 427 * reduce the initial CWND to one segment as congestion is likely 428 * requiring us to be cautious. 429 */ 430 if (tp->snd_cwnd == 1) 431 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 432 else 433 tp->snd_cwnd = tcp_compute_initwnd(maxseg); 434 435 if (CC_ALGO(tp)->conn_init != NULL) 436 CC_ALGO(tp)->conn_init(tp->ccv); 437 } 438 439 void inline 440 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 441 { 442 INP_WLOCK_ASSERT(tp->t_inpcb); 443 444 #ifdef STATS 445 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type); 446 #endif 447 448 switch(type) { 449 case CC_NDUPACK: 450 if (!IN_FASTRECOVERY(tp->t_flags)) { 451 tp->snd_recover = tp->snd_max; 452 if (tp->t_flags2 & TF2_ECN_PERMIT) 453 tp->t_flags2 |= TF2_ECN_SND_CWR; 454 } 455 break; 456 case CC_ECN: 457 if (!IN_CONGRECOVERY(tp->t_flags) || 458 /* 459 * Allow ECN reaction on ACK to CWR, if 460 * that data segment was also CE marked. 461 */ 462 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 463 EXIT_CONGRECOVERY(tp->t_flags); 464 TCPSTAT_INC(tcps_ecn_rcwnd); 465 tp->snd_recover = tp->snd_max + 1; 466 if (tp->t_flags2 & TF2_ECN_PERMIT) 467 tp->t_flags2 |= TF2_ECN_SND_CWR; 468 } 469 break; 470 case CC_RTO: 471 tp->t_dupacks = 0; 472 tp->t_bytes_acked = 0; 473 EXIT_RECOVERY(tp->t_flags); 474 if (tp->t_flags2 & TF2_ECN_PERMIT) 475 tp->t_flags2 |= TF2_ECN_SND_CWR; 476 break; 477 case CC_RTO_ERR: 478 TCPSTAT_INC(tcps_sndrexmitbad); 479 /* RTO was unnecessary, so reset everything. */ 480 tp->snd_cwnd = tp->snd_cwnd_prev; 481 tp->snd_ssthresh = tp->snd_ssthresh_prev; 482 tp->snd_recover = tp->snd_recover_prev; 483 if (tp->t_flags & TF_WASFRECOVERY) 484 ENTER_FASTRECOVERY(tp->t_flags); 485 if (tp->t_flags & TF_WASCRECOVERY) 486 ENTER_CONGRECOVERY(tp->t_flags); 487 tp->snd_nxt = tp->snd_max; 488 tp->t_flags &= ~TF_PREVVALID; 489 tp->t_badrxtwin = 0; 490 break; 491 } 492 493 if (CC_ALGO(tp)->cong_signal != NULL) { 494 if (th != NULL) 495 tp->ccv->curack = th->th_ack; 496 CC_ALGO(tp)->cong_signal(tp->ccv, type); 497 } 498 } 499 500 void inline 501 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 502 { 503 INP_WLOCK_ASSERT(tp->t_inpcb); 504 505 /* XXXLAS: KASSERT that we're in recovery? */ 506 507 if (CC_ALGO(tp)->post_recovery != NULL) { 508 tp->ccv->curack = th->th_ack; 509 CC_ALGO(tp)->post_recovery(tp->ccv); 510 } 511 /* XXXLAS: EXIT_RECOVERY ? */ 512 tp->t_bytes_acked = 0; 513 tp->sackhint.recover_fs = 0; 514 } 515 516 /* 517 * Indicate whether this ack should be delayed. We can delay the ack if 518 * following conditions are met: 519 * - There is no delayed ack timer in progress. 520 * - Our last ack wasn't a 0-sized window. We never want to delay 521 * the ack that opens up a 0-sized window. 522 * - LRO wasn't used for this segment. We make sure by checking that the 523 * segment size is not larger than the MSS. 524 */ 525 #define DELAY_ACK(tp, tlen) \ 526 ((!tcp_timer_active(tp, TT_DELACK) && \ 527 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 528 (tlen <= tp->t_maxseg) && \ 529 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 530 531 void inline 532 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 533 { 534 INP_WLOCK_ASSERT(tp->t_inpcb); 535 536 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 537 switch (iptos & IPTOS_ECN_MASK) { 538 case IPTOS_ECN_CE: 539 tp->ccv->flags |= CCF_IPHDR_CE; 540 break; 541 case IPTOS_ECN_ECT0: 542 /* FALLTHROUGH */ 543 case IPTOS_ECN_ECT1: 544 /* FALLTHROUGH */ 545 case IPTOS_ECN_NOTECT: 546 tp->ccv->flags &= ~CCF_IPHDR_CE; 547 break; 548 } 549 550 if (th->th_flags & TH_CWR) 551 tp->ccv->flags |= CCF_TCPHDR_CWR; 552 else 553 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 554 555 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 556 557 if (tp->ccv->flags & CCF_ACKNOW) { 558 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 559 tp->t_flags |= TF_ACKNOW; 560 } 561 } 562 } 563 564 /* 565 * TCP input handling is split into multiple parts: 566 * tcp6_input is a thin wrapper around tcp_input for the extended 567 * ip6_protox[] call format in ip6_input 568 * tcp_input handles primary segment validation, inpcb lookup and 569 * SYN processing on listen sockets 570 * tcp_do_segment processes the ACK and text of the segment for 571 * establishing, established and closing connections 572 */ 573 #ifdef INET6 574 int 575 tcp6_input(struct mbuf **mp, int *offp, int proto) 576 { 577 struct mbuf *m; 578 struct in6_ifaddr *ia6; 579 struct ip6_hdr *ip6; 580 581 m = *mp; 582 if (m->m_len < *offp + sizeof(struct tcphdr)) { 583 m = m_pullup(m, *offp + sizeof(struct tcphdr)); 584 if (m == NULL) { 585 *mp = m; 586 TCPSTAT_INC(tcps_rcvshort); 587 return (IPPROTO_DONE); 588 } 589 } 590 591 /* 592 * draft-itojun-ipv6-tcp-to-anycast 593 * better place to put this in? 594 */ 595 ip6 = mtod(m, struct ip6_hdr *); 596 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 597 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 598 ifa_free(&ia6->ia_ifa); 599 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 600 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 601 *mp = NULL; 602 return (IPPROTO_DONE); 603 } 604 if (ia6) 605 ifa_free(&ia6->ia_ifa); 606 607 *mp = m; 608 return (tcp_input(mp, offp, proto)); 609 } 610 #endif /* INET6 */ 611 612 int 613 tcp_input(struct mbuf **mp, int *offp, int proto) 614 { 615 struct mbuf *m = *mp; 616 struct tcphdr *th = NULL; 617 struct ip *ip = NULL; 618 struct inpcb *inp = NULL; 619 struct tcpcb *tp = NULL; 620 struct socket *so = NULL; 621 u_char *optp = NULL; 622 int off0; 623 int optlen = 0; 624 #ifdef INET 625 int len; 626 uint8_t ipttl; 627 #endif 628 int tlen = 0, off; 629 int drop_hdrlen; 630 int thflags; 631 int rstreason = 0; /* For badport_bandlim accounting purposes */ 632 uint8_t iptos; 633 struct m_tag *fwd_tag = NULL; 634 #ifdef INET6 635 struct ip6_hdr *ip6 = NULL; 636 int isipv6; 637 #else 638 const void *ip6 = NULL; 639 #endif /* INET6 */ 640 struct tcpopt to; /* options in this segment */ 641 char *s = NULL; /* address and port logging */ 642 #ifdef TCPDEBUG 643 /* 644 * The size of tcp_saveipgen must be the size of the max ip header, 645 * now IPv6. 646 */ 647 u_char tcp_saveipgen[IP6_HDR_LEN]; 648 struct tcphdr tcp_savetcp; 649 short ostate = 0; 650 #endif 651 652 NET_EPOCH_ASSERT(); 653 654 #ifdef INET6 655 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 656 #endif 657 658 off0 = *offp; 659 m = *mp; 660 *mp = NULL; 661 to.to_flags = 0; 662 TCPSTAT_INC(tcps_rcvtotal); 663 664 #ifdef INET6 665 if (isipv6) { 666 ip6 = mtod(m, struct ip6_hdr *); 667 th = (struct tcphdr *)((caddr_t)ip6 + off0); 668 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 669 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 670 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 671 th->th_sum = m->m_pkthdr.csum_data; 672 else 673 th->th_sum = in6_cksum_pseudo(ip6, tlen, 674 IPPROTO_TCP, m->m_pkthdr.csum_data); 675 th->th_sum ^= 0xffff; 676 } else 677 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 678 if (th->th_sum) { 679 TCPSTAT_INC(tcps_rcvbadsum); 680 goto drop; 681 } 682 683 /* 684 * Be proactive about unspecified IPv6 address in source. 685 * As we use all-zero to indicate unbounded/unconnected pcb, 686 * unspecified IPv6 address can be used to confuse us. 687 * 688 * Note that packets with unspecified IPv6 destination is 689 * already dropped in ip6_input. 690 */ 691 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 692 /* XXX stat */ 693 goto drop; 694 } 695 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 696 } 697 #endif 698 #if defined(INET) && defined(INET6) 699 else 700 #endif 701 #ifdef INET 702 { 703 /* 704 * Get IP and TCP header together in first mbuf. 705 * Note: IP leaves IP header in first mbuf. 706 */ 707 if (off0 > sizeof (struct ip)) { 708 ip_stripoptions(m); 709 off0 = sizeof(struct ip); 710 } 711 if (m->m_len < sizeof (struct tcpiphdr)) { 712 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 713 == NULL) { 714 TCPSTAT_INC(tcps_rcvshort); 715 return (IPPROTO_DONE); 716 } 717 } 718 ip = mtod(m, struct ip *); 719 th = (struct tcphdr *)((caddr_t)ip + off0); 720 tlen = ntohs(ip->ip_len) - off0; 721 722 iptos = ip->ip_tos; 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 } 752 753 if (th->th_sum) { 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 = th->th_flags; 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 findpcb: 832 #ifdef INET6 833 if (isipv6 && fwd_tag != NULL) { 834 struct sockaddr_in6 *next_hop6; 835 836 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 837 /* 838 * Transparently forwarded. Pretend to be the destination. 839 * Already got one like this? 840 */ 841 inp = in6_pcblookup_mbuf(&V_tcbinfo, 842 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 843 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 844 if (!inp) { 845 /* 846 * It's new. Try to find the ambushing socket. 847 * Because we've rewritten the destination address, 848 * any hardware-generated hash is ignored. 849 */ 850 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 851 th->th_sport, &next_hop6->sin6_addr, 852 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 853 th->th_dport, INPLOOKUP_WILDCARD | 854 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 855 } 856 } else if (isipv6) { 857 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 858 th->th_sport, &ip6->ip6_dst, th->th_dport, 859 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 860 m->m_pkthdr.rcvif, m); 861 } 862 #endif /* INET6 */ 863 #if defined(INET6) && defined(INET) 864 else 865 #endif 866 #ifdef INET 867 if (fwd_tag != NULL) { 868 struct sockaddr_in *next_hop; 869 870 next_hop = (struct sockaddr_in *)(fwd_tag+1); 871 /* 872 * Transparently forwarded. Pretend to be the destination. 873 * already got one like this? 874 */ 875 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 876 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 877 m->m_pkthdr.rcvif, m); 878 if (!inp) { 879 /* 880 * It's new. Try to find the ambushing socket. 881 * Because we've rewritten the destination address, 882 * any hardware-generated hash is ignored. 883 */ 884 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 885 th->th_sport, next_hop->sin_addr, 886 next_hop->sin_port ? ntohs(next_hop->sin_port) : 887 th->th_dport, INPLOOKUP_WILDCARD | 888 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 889 } 890 } else 891 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 892 th->th_sport, ip->ip_dst, th->th_dport, 893 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 894 m->m_pkthdr.rcvif, m); 895 #endif /* INET */ 896 897 /* 898 * If the INPCB does not exist then all data in the incoming 899 * segment is discarded and an appropriate RST is sent back. 900 * XXX MRT Send RST using which routing table? 901 */ 902 if (inp == NULL) { 903 /* 904 * Log communication attempts to ports that are not 905 * in use. 906 */ 907 if ((V_tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 908 V_tcp_log_in_vain == 2) { 909 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 910 log(LOG_INFO, "%s; %s: Connection attempt " 911 "to closed port\n", s, __func__); 912 } 913 /* 914 * When blackholing do not respond with a RST but 915 * completely ignore the segment and drop it. 916 */ 917 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 918 V_blackhole == 2) 919 goto dropunlock; 920 921 rstreason = BANDLIM_RST_CLOSEDPORT; 922 goto dropwithreset; 923 } 924 INP_WLOCK_ASSERT(inp); 925 /* 926 * While waiting for inp lock during the lookup, another thread 927 * can have dropped the inpcb, in which case we need to loop back 928 * and try to find a new inpcb to deliver to. 929 */ 930 if (inp->inp_flags & INP_DROPPED) { 931 INP_WUNLOCK(inp); 932 inp = NULL; 933 goto findpcb; 934 } 935 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 936 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 937 ((inp->inp_socket == NULL) || 938 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 939 inp->inp_flowid = m->m_pkthdr.flowid; 940 inp->inp_flowtype = M_HASHTYPE_GET(m); 941 } 942 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 943 #ifdef INET6 944 if (isipv6 && IPSEC_ENABLED(ipv6) && 945 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 946 goto dropunlock; 947 } 948 #ifdef INET 949 else 950 #endif 951 #endif /* INET6 */ 952 #ifdef INET 953 if (IPSEC_ENABLED(ipv4) && 954 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 955 goto dropunlock; 956 } 957 #endif /* INET */ 958 #endif /* IPSEC */ 959 960 /* 961 * Check the minimum TTL for socket. 962 */ 963 if (inp->inp_ip_minttl != 0) { 964 #ifdef INET6 965 if (isipv6) { 966 if (inp->inp_ip_minttl > ip6->ip6_hlim) 967 goto dropunlock; 968 } else 969 #endif 970 if (inp->inp_ip_minttl > ip->ip_ttl) 971 goto dropunlock; 972 } 973 974 /* 975 * A previous connection in TIMEWAIT state is supposed to catch stray 976 * or duplicate segments arriving late. If this segment was a 977 * legitimate new connection attempt, the old INPCB gets removed and 978 * we can try again to find a listening socket. 979 * 980 * At this point, due to earlier optimism, we may hold only an inpcb 981 * lock, and not the inpcbinfo write lock. If so, we need to try to 982 * acquire it, or if that fails, acquire a reference on the inpcb, 983 * drop all locks, acquire a global write lock, and then re-acquire 984 * the inpcb lock. We may at that point discover that another thread 985 * has tried to free the inpcb, in which case we need to loop back 986 * and try to find a new inpcb to deliver to. 987 * 988 * XXXRW: It may be time to rethink timewait locking. 989 */ 990 if (inp->inp_flags & INP_TIMEWAIT) { 991 tcp_dooptions(&to, optp, optlen, 992 (thflags & TH_SYN) ? TO_SYN : 0); 993 /* 994 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 995 */ 996 if (tcp_twcheck(inp, &to, th, m, tlen)) 997 goto findpcb; 998 return (IPPROTO_DONE); 999 } 1000 /* 1001 * The TCPCB may no longer exist if the connection is winding 1002 * down or it is in the CLOSED state. Either way we drop the 1003 * segment and send an appropriate response. 1004 */ 1005 tp = intotcpcb(inp); 1006 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1007 rstreason = BANDLIM_RST_CLOSEDPORT; 1008 goto dropwithreset; 1009 } 1010 1011 #ifdef TCP_OFFLOAD 1012 if (tp->t_flags & TF_TOE) { 1013 tcp_offload_input(tp, m); 1014 m = NULL; /* consumed by the TOE driver */ 1015 goto dropunlock; 1016 } 1017 #endif 1018 1019 #ifdef MAC 1020 INP_WLOCK_ASSERT(inp); 1021 if (mac_inpcb_check_deliver(inp, m)) 1022 goto dropunlock; 1023 #endif 1024 so = inp->inp_socket; 1025 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1026 #ifdef TCPDEBUG 1027 if (so->so_options & SO_DEBUG) { 1028 ostate = tp->t_state; 1029 #ifdef INET6 1030 if (isipv6) { 1031 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1032 } else 1033 #endif 1034 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1035 tcp_savetcp = *th; 1036 } 1037 #endif /* TCPDEBUG */ 1038 /* 1039 * When the socket is accepting connections (the INPCB is in LISTEN 1040 * state) we look into the SYN cache if this is a new connection 1041 * attempt or the completion of a previous one. 1042 */ 1043 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1044 ("%s: so accepting but tp %p not listening", __func__, tp)); 1045 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1046 struct in_conninfo inc; 1047 1048 bzero(&inc, sizeof(inc)); 1049 #ifdef INET6 1050 if (isipv6) { 1051 inc.inc_flags |= INC_ISIPV6; 1052 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1053 inc.inc_flags |= INC_IPV6MINMTU; 1054 inc.inc6_faddr = ip6->ip6_src; 1055 inc.inc6_laddr = ip6->ip6_dst; 1056 } else 1057 #endif 1058 { 1059 inc.inc_faddr = ip->ip_src; 1060 inc.inc_laddr = ip->ip_dst; 1061 } 1062 inc.inc_fport = th->th_sport; 1063 inc.inc_lport = th->th_dport; 1064 inc.inc_fibnum = so->so_fibnum; 1065 1066 /* 1067 * Check for an existing connection attempt in syncache if 1068 * the flag is only ACK. A successful lookup creates a new 1069 * socket appended to the listen queue in SYN_RECEIVED state. 1070 */ 1071 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1072 /* 1073 * Parse the TCP options here because 1074 * syncookies need access to the reflected 1075 * timestamp. 1076 */ 1077 tcp_dooptions(&to, optp, optlen, 0); 1078 /* 1079 * NB: syncache_expand() doesn't unlock 1080 * inp and tcpinfo locks. 1081 */ 1082 rstreason = syncache_expand(&inc, &to, th, &so, m); 1083 if (rstreason < 0) { 1084 /* 1085 * A failing TCP MD5 signature comparison 1086 * must result in the segment being dropped 1087 * and must not produce any response back 1088 * to the sender. 1089 */ 1090 goto dropunlock; 1091 } else if (rstreason == 0) { 1092 /* 1093 * No syncache entry or ACK was not 1094 * for our SYN/ACK. Send a RST. 1095 * NB: syncache did its own logging 1096 * of the failure cause. 1097 */ 1098 rstreason = BANDLIM_RST_OPENPORT; 1099 goto dropwithreset; 1100 } 1101 tfo_socket_result: 1102 if (so == NULL) { 1103 /* 1104 * We completed the 3-way handshake 1105 * but could not allocate a socket 1106 * either due to memory shortage, 1107 * listen queue length limits or 1108 * global socket limits. Send RST 1109 * or wait and have the remote end 1110 * retransmit the ACK for another 1111 * try. 1112 */ 1113 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1114 log(LOG_DEBUG, "%s; %s: Listen socket: " 1115 "Socket allocation failed due to " 1116 "limits or memory shortage, %s\n", 1117 s, __func__, 1118 V_tcp_sc_rst_sock_fail ? 1119 "sending RST" : "try again"); 1120 if (V_tcp_sc_rst_sock_fail) { 1121 rstreason = BANDLIM_UNLIMITED; 1122 goto dropwithreset; 1123 } else 1124 goto dropunlock; 1125 } 1126 /* 1127 * Socket is created in state SYN_RECEIVED. 1128 * Unlock the listen socket, lock the newly 1129 * created socket and update the tp variable. 1130 */ 1131 INP_WUNLOCK(inp); /* listen socket */ 1132 inp = sotoinpcb(so); 1133 /* 1134 * New connection inpcb is already locked by 1135 * syncache_expand(). 1136 */ 1137 INP_WLOCK_ASSERT(inp); 1138 tp = intotcpcb(inp); 1139 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1140 ("%s: ", __func__)); 1141 /* 1142 * Process the segment and the data it 1143 * contains. tcp_do_segment() consumes 1144 * the mbuf chain and unlocks the inpcb. 1145 */ 1146 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1147 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1148 iptos); 1149 return (IPPROTO_DONE); 1150 } 1151 /* 1152 * Segment flag validation for new connection attempts: 1153 * 1154 * Our (SYN|ACK) response was rejected. 1155 * Check with syncache and remove entry to prevent 1156 * retransmits. 1157 * 1158 * NB: syncache_chkrst does its own logging of failure 1159 * causes. 1160 */ 1161 if (thflags & TH_RST) { 1162 syncache_chkrst(&inc, th, m); 1163 goto dropunlock; 1164 } 1165 /* 1166 * We can't do anything without SYN. 1167 */ 1168 if ((thflags & TH_SYN) == 0) { 1169 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1170 log(LOG_DEBUG, "%s; %s: Listen socket: " 1171 "SYN is missing, segment ignored\n", 1172 s, __func__); 1173 TCPSTAT_INC(tcps_badsyn); 1174 goto dropunlock; 1175 } 1176 /* 1177 * (SYN|ACK) is bogus on a listen socket. 1178 */ 1179 if (thflags & TH_ACK) { 1180 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1181 log(LOG_DEBUG, "%s; %s: Listen socket: " 1182 "SYN|ACK invalid, segment rejected\n", 1183 s, __func__); 1184 syncache_badack(&inc); /* XXX: Not needed! */ 1185 TCPSTAT_INC(tcps_badsyn); 1186 rstreason = BANDLIM_RST_OPENPORT; 1187 goto dropwithreset; 1188 } 1189 /* 1190 * If the drop_synfin option is enabled, drop all 1191 * segments with both the SYN and FIN bits set. 1192 * This prevents e.g. nmap from identifying the 1193 * TCP/IP stack. 1194 * XXX: Poor reasoning. nmap has other methods 1195 * and is constantly refining its stack detection 1196 * strategies. 1197 * XXX: This is a violation of the TCP specification 1198 * and was used by RFC1644. 1199 */ 1200 if ((thflags & TH_FIN) && V_drop_synfin) { 1201 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1202 log(LOG_DEBUG, "%s; %s: Listen socket: " 1203 "SYN|FIN segment ignored (based on " 1204 "sysctl setting)\n", s, __func__); 1205 TCPSTAT_INC(tcps_badsyn); 1206 goto dropunlock; 1207 } 1208 /* 1209 * Segment's flags are (SYN) or (SYN|FIN). 1210 * 1211 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1212 * as they do not affect the state of the TCP FSM. 1213 * The data pointed to by TH_URG and th_urp is ignored. 1214 */ 1215 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1216 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1217 KASSERT(thflags & (TH_SYN), 1218 ("%s: Listen socket: TH_SYN not set", __func__)); 1219 #ifdef INET6 1220 /* 1221 * If deprecated address is forbidden, 1222 * we do not accept SYN to deprecated interface 1223 * address to prevent any new inbound connection from 1224 * getting established. 1225 * When we do not accept SYN, we send a TCP RST, 1226 * with deprecated source address (instead of dropping 1227 * it). We compromise it as it is much better for peer 1228 * to send a RST, and RST will be the final packet 1229 * for the exchange. 1230 * 1231 * If we do not forbid deprecated addresses, we accept 1232 * the SYN packet. RFC2462 does not suggest dropping 1233 * SYN in this case. 1234 * If we decipher RFC2462 5.5.4, it says like this: 1235 * 1. use of deprecated addr with existing 1236 * communication is okay - "SHOULD continue to be 1237 * used" 1238 * 2. use of it with new communication: 1239 * (2a) "SHOULD NOT be used if alternate address 1240 * with sufficient scope is available" 1241 * (2b) nothing mentioned otherwise. 1242 * Here we fall into (2b) case as we have no choice in 1243 * our source address selection - we must obey the peer. 1244 * 1245 * The wording in RFC2462 is confusing, and there are 1246 * multiple description text for deprecated address 1247 * handling - worse, they are not exactly the same. 1248 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1249 */ 1250 if (isipv6 && !V_ip6_use_deprecated) { 1251 struct in6_ifaddr *ia6; 1252 1253 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1254 if (ia6 != NULL && 1255 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1256 ifa_free(&ia6->ia_ifa); 1257 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1258 log(LOG_DEBUG, "%s; %s: Listen socket: " 1259 "Connection attempt to deprecated " 1260 "IPv6 address rejected\n", 1261 s, __func__); 1262 rstreason = BANDLIM_RST_OPENPORT; 1263 goto dropwithreset; 1264 } 1265 if (ia6) 1266 ifa_free(&ia6->ia_ifa); 1267 } 1268 #endif /* INET6 */ 1269 /* 1270 * Basic sanity checks on incoming SYN requests: 1271 * Don't respond if the destination is a link layer 1272 * broadcast according to RFC1122 4.2.3.10, p. 104. 1273 * If it is from this socket it must be forged. 1274 * Don't respond if the source or destination is a 1275 * global or subnet broad- or multicast address. 1276 * Note that it is quite possible to receive unicast 1277 * link-layer packets with a broadcast IP address. Use 1278 * in_broadcast() to find them. 1279 */ 1280 if (m->m_flags & (M_BCAST|M_MCAST)) { 1281 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1282 log(LOG_DEBUG, "%s; %s: Listen socket: " 1283 "Connection attempt from broad- or multicast " 1284 "link layer address ignored\n", s, __func__); 1285 goto dropunlock; 1286 } 1287 #ifdef INET6 1288 if (isipv6) { 1289 if (th->th_dport == th->th_sport && 1290 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1291 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1292 log(LOG_DEBUG, "%s; %s: Listen socket: " 1293 "Connection attempt to/from self " 1294 "ignored\n", s, __func__); 1295 goto dropunlock; 1296 } 1297 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1298 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1299 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1300 log(LOG_DEBUG, "%s; %s: Listen socket: " 1301 "Connection attempt from/to multicast " 1302 "address ignored\n", s, __func__); 1303 goto dropunlock; 1304 } 1305 } 1306 #endif 1307 #if defined(INET) && defined(INET6) 1308 else 1309 #endif 1310 #ifdef INET 1311 { 1312 if (th->th_dport == th->th_sport && 1313 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1314 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1315 log(LOG_DEBUG, "%s; %s: Listen socket: " 1316 "Connection attempt from/to self " 1317 "ignored\n", s, __func__); 1318 goto dropunlock; 1319 } 1320 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1321 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1322 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1323 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1324 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1325 log(LOG_DEBUG, "%s; %s: Listen socket: " 1326 "Connection attempt from/to broad- " 1327 "or multicast address ignored\n", 1328 s, __func__); 1329 goto dropunlock; 1330 } 1331 } 1332 #endif 1333 /* 1334 * SYN appears to be valid. Create compressed TCP state 1335 * for syncache. 1336 */ 1337 #ifdef TCPDEBUG 1338 if (so->so_options & SO_DEBUG) 1339 tcp_trace(TA_INPUT, ostate, tp, 1340 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1341 #endif 1342 TCP_PROBE3(debug__input, tp, th, m); 1343 tcp_dooptions(&to, optp, optlen, TO_SYN); 1344 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL, iptos)) 1345 goto tfo_socket_result; 1346 1347 /* 1348 * Entry added to syncache and mbuf consumed. 1349 * Only the listen socket is unlocked by syncache_add(). 1350 */ 1351 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1352 return (IPPROTO_DONE); 1353 } else if (tp->t_state == TCPS_LISTEN) { 1354 /* 1355 * When a listen socket is torn down the SO_ACCEPTCONN 1356 * flag is removed first while connections are drained 1357 * from the accept queue in a unlock/lock cycle of the 1358 * ACCEPT_LOCK, opening a race condition allowing a SYN 1359 * attempt go through unhandled. 1360 */ 1361 goto dropunlock; 1362 } 1363 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1364 if (tp->t_flags & TF_SIGNATURE) { 1365 tcp_dooptions(&to, optp, optlen, thflags); 1366 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1367 TCPSTAT_INC(tcps_sig_err_nosigopt); 1368 goto dropunlock; 1369 } 1370 if (!TCPMD5_ENABLED() || 1371 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1372 goto dropunlock; 1373 } 1374 #endif 1375 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1376 1377 /* 1378 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1379 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1380 * the inpcb, and unlocks pcbinfo. 1381 */ 1382 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1383 return (IPPROTO_DONE); 1384 1385 dropwithreset: 1386 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1387 1388 if (inp != NULL) { 1389 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1390 INP_WUNLOCK(inp); 1391 } else 1392 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1393 m = NULL; /* mbuf chain got consumed. */ 1394 goto drop; 1395 1396 dropunlock: 1397 if (m != NULL) 1398 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1399 1400 if (inp != NULL) 1401 INP_WUNLOCK(inp); 1402 1403 drop: 1404 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1405 if (s != NULL) 1406 free(s, M_TCPLOG); 1407 if (m != NULL) 1408 m_freem(m); 1409 return (IPPROTO_DONE); 1410 } 1411 1412 /* 1413 * Automatic sizing of receive socket buffer. Often the send 1414 * buffer size is not optimally adjusted to the actual network 1415 * conditions at hand (delay bandwidth product). Setting the 1416 * buffer size too small limits throughput on links with high 1417 * bandwidth and high delay (eg. trans-continental/oceanic links). 1418 * 1419 * On the receive side the socket buffer memory is only rarely 1420 * used to any significant extent. This allows us to be much 1421 * more aggressive in scaling the receive socket buffer. For 1422 * the case that the buffer space is actually used to a large 1423 * extent and we run out of kernel memory we can simply drop 1424 * the new segments; TCP on the sender will just retransmit it 1425 * later. Setting the buffer size too big may only consume too 1426 * much kernel memory if the application doesn't read() from 1427 * the socket or packet loss or reordering makes use of the 1428 * reassembly queue. 1429 * 1430 * The criteria to step up the receive buffer one notch are: 1431 * 1. Application has not set receive buffer size with 1432 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1433 * 2. the number of bytes received during 1/2 of an sRTT 1434 * is at least 3/8 of the current socket buffer size. 1435 * 3. receive buffer size has not hit maximal automatic size; 1436 * 1437 * If all of the criteria are met we increaset the socket buffer 1438 * by a 1/2 (bounded by the max). This allows us to keep ahead 1439 * of slow-start but also makes it so our peer never gets limited 1440 * by our rwnd which we then open up causing a burst. 1441 * 1442 * This algorithm does two steps per RTT at most and only if 1443 * we receive a bulk stream w/o packet losses or reorderings. 1444 * Shrinking the buffer during idle times is not necessary as 1445 * it doesn't consume any memory when idle. 1446 * 1447 * TODO: Only step up if the application is actually serving 1448 * the buffer to better manage the socket buffer resources. 1449 */ 1450 int 1451 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1452 struct tcpcb *tp, int tlen) 1453 { 1454 int newsize = 0; 1455 1456 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1457 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1458 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1459 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) { 1460 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) && 1461 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1462 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max); 1463 } 1464 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1465 1466 /* Start over with next RTT. */ 1467 tp->rfbuf_ts = 0; 1468 tp->rfbuf_cnt = 0; 1469 } else { 1470 tp->rfbuf_cnt += tlen; /* add up */ 1471 } 1472 return (newsize); 1473 } 1474 1475 void 1476 tcp_handle_wakeup(struct tcpcb *tp, struct socket *so) 1477 { 1478 /* 1479 * Since tp might be gone if the session entered 1480 * the TIME_WAIT state before coming here, we need 1481 * to check if the socket is still connected. 1482 */ 1483 if ((so->so_state & SS_ISCONNECTED) == 0) 1484 return; 1485 INP_LOCK_ASSERT(tp->t_inpcb); 1486 if (tp->t_flags & TF_WAKESOR) { 1487 tp->t_flags &= ~TF_WAKESOR; 1488 SOCKBUF_UNLOCK_ASSERT(&so->so_rcv); 1489 sorwakeup(so); 1490 } 1491 if (tp->t_flags & TF_WAKESOW) { 1492 tp->t_flags &= ~TF_WAKESOW; 1493 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1494 sowwakeup(so); 1495 } 1496 } 1497 1498 void 1499 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1500 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1501 { 1502 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1503 int rstreason, todrop, win, incforsyn = 0; 1504 uint32_t tiwin; 1505 uint16_t nsegs; 1506 char *s; 1507 struct in_conninfo *inc; 1508 struct mbuf *mfree; 1509 struct tcpopt to; 1510 int tfo_syn; 1511 1512 #ifdef TCPDEBUG 1513 /* 1514 * The size of tcp_saveipgen must be the size of the max ip header, 1515 * now IPv6. 1516 */ 1517 u_char tcp_saveipgen[IP6_HDR_LEN]; 1518 struct tcphdr tcp_savetcp; 1519 short ostate = 0; 1520 #endif 1521 thflags = th->th_flags; 1522 inc = &tp->t_inpcb->inp_inc; 1523 tp->sackhint.last_sack_ack = 0; 1524 sack_changed = 0; 1525 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1526 1527 NET_EPOCH_ASSERT(); 1528 INP_WLOCK_ASSERT(tp->t_inpcb); 1529 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1530 __func__)); 1531 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1532 __func__)); 1533 1534 #ifdef TCPPCAP 1535 /* Save segment, if requested. */ 1536 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1537 #endif 1538 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1539 tlen, NULL, true); 1540 1541 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1542 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1543 log(LOG_DEBUG, "%s; %s: " 1544 "SYN|FIN segment ignored (based on " 1545 "sysctl setting)\n", s, __func__); 1546 free(s, M_TCPLOG); 1547 } 1548 goto drop; 1549 } 1550 1551 /* 1552 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1553 * check SEQ.ACK first. 1554 */ 1555 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1556 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1557 rstreason = BANDLIM_UNLIMITED; 1558 goto dropwithreset; 1559 } 1560 1561 /* 1562 * Segment received on connection. 1563 * Reset idle time and keep-alive timer. 1564 * XXX: This should be done after segment 1565 * validation to ignore broken/spoofed segs. 1566 */ 1567 tp->t_rcvtime = ticks; 1568 1569 /* 1570 * Scale up the window into a 32-bit value. 1571 * For the SYN_SENT state the scale is zero. 1572 */ 1573 tiwin = th->th_win << tp->snd_scale; 1574 #ifdef STATS 1575 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin); 1576 #endif 1577 1578 /* 1579 * TCP ECN processing. 1580 */ 1581 if (tp->t_flags2 & TF2_ECN_PERMIT) { 1582 if (thflags & TH_CWR) { 1583 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1584 tp->t_flags |= TF_ACKNOW; 1585 } 1586 switch (iptos & IPTOS_ECN_MASK) { 1587 case IPTOS_ECN_CE: 1588 tp->t_flags2 |= TF2_ECN_SND_ECE; 1589 TCPSTAT_INC(tcps_ecn_ce); 1590 break; 1591 case IPTOS_ECN_ECT0: 1592 TCPSTAT_INC(tcps_ecn_ect0); 1593 break; 1594 case IPTOS_ECN_ECT1: 1595 TCPSTAT_INC(tcps_ecn_ect1); 1596 break; 1597 } 1598 1599 /* Process a packet differently from RFC3168. */ 1600 cc_ecnpkt_handler(tp, th, iptos); 1601 1602 /* Congestion experienced. */ 1603 if (thflags & TH_ECE) { 1604 cc_cong_signal(tp, th, CC_ECN); 1605 } 1606 } 1607 1608 /* 1609 * Parse options on any incoming segment. 1610 */ 1611 tcp_dooptions(&to, (u_char *)(th + 1), 1612 (th->th_off << 2) - sizeof(struct tcphdr), 1613 (thflags & TH_SYN) ? TO_SYN : 0); 1614 1615 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1616 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1617 (to.to_flags & TOF_SIGNATURE) == 0) { 1618 TCPSTAT_INC(tcps_sig_err_sigopt); 1619 /* XXX: should drop? */ 1620 } 1621 #endif 1622 /* 1623 * If echoed timestamp is later than the current time, 1624 * fall back to non RFC1323 RTT calculation. Normalize 1625 * timestamp if syncookies were used when this connection 1626 * was established. 1627 */ 1628 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1629 to.to_tsecr -= tp->ts_offset; 1630 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1631 to.to_tsecr = 0; 1632 else if (tp->t_flags & TF_PREVVALID && 1633 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 1634 cc_cong_signal(tp, th, CC_RTO_ERR); 1635 } 1636 /* 1637 * Process options only when we get SYN/ACK back. The SYN case 1638 * for incoming connections is handled in tcp_syncache. 1639 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1640 * or <SYN,ACK>) segment itself is never scaled. 1641 * XXX this is traditional behavior, may need to be cleaned up. 1642 */ 1643 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1644 /* Handle parallel SYN for ECN */ 1645 if (!(thflags & TH_ACK) && 1646 ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) && 1647 ((V_tcp_do_ecn == 1) || (V_tcp_do_ecn == 2))) { 1648 tp->t_flags2 |= TF2_ECN_PERMIT; 1649 tp->t_flags2 |= TF2_ECN_SND_ECE; 1650 TCPSTAT_INC(tcps_ecn_shs); 1651 } 1652 if ((to.to_flags & TOF_SCALE) && 1653 (tp->t_flags & TF_REQ_SCALE)) { 1654 tp->t_flags |= TF_RCVD_SCALE; 1655 tp->snd_scale = to.to_wscale; 1656 } else 1657 tp->t_flags &= ~TF_REQ_SCALE; 1658 /* 1659 * Initial send window. It will be updated with 1660 * the next incoming segment to the scaled value. 1661 */ 1662 tp->snd_wnd = th->th_win; 1663 if ((to.to_flags & TOF_TS) && 1664 (tp->t_flags & TF_REQ_TSTMP)) { 1665 tp->t_flags |= TF_RCVD_TSTMP; 1666 tp->ts_recent = to.to_tsval; 1667 tp->ts_recent_age = tcp_ts_getticks(); 1668 } else 1669 tp->t_flags &= ~TF_REQ_TSTMP; 1670 if (to.to_flags & TOF_MSS) 1671 tcp_mss(tp, to.to_mss); 1672 if ((tp->t_flags & TF_SACK_PERMIT) && 1673 (to.to_flags & TOF_SACKPERM) == 0) 1674 tp->t_flags &= ~TF_SACK_PERMIT; 1675 if (IS_FASTOPEN(tp->t_flags)) { 1676 if (to.to_flags & TOF_FASTOPEN) { 1677 uint16_t mss; 1678 1679 if (to.to_flags & TOF_MSS) 1680 mss = to.to_mss; 1681 else 1682 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1683 mss = TCP6_MSS; 1684 else 1685 mss = TCP_MSS; 1686 tcp_fastopen_update_cache(tp, mss, 1687 to.to_tfo_len, to.to_tfo_cookie); 1688 } else 1689 tcp_fastopen_disable_path(tp); 1690 } 1691 } 1692 1693 /* 1694 * If timestamps were negotiated during SYN/ACK and a 1695 * segment without a timestamp is received, silently drop 1696 * the segment, unless it is a RST segment or missing timestamps are 1697 * tolerated. 1698 * See section 3.2 of RFC 7323. 1699 */ 1700 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1701 if (((thflags & TH_RST) != 0) || V_tcp_tolerate_missing_ts) { 1702 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1703 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1704 "segment processed normally\n", 1705 s, __func__); 1706 free(s, M_TCPLOG); 1707 } 1708 } else { 1709 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1710 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1711 "segment silently dropped\n", s, __func__); 1712 free(s, M_TCPLOG); 1713 } 1714 goto drop; 1715 } 1716 } 1717 /* 1718 * If timestamps were not negotiated during SYN/ACK and a 1719 * segment with a timestamp is received, ignore the 1720 * timestamp and process the packet normally. 1721 * See section 3.2 of RFC 7323. 1722 */ 1723 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1724 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1725 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1726 "segment processed normally\n", s, __func__); 1727 free(s, M_TCPLOG); 1728 } 1729 } 1730 1731 /* 1732 * Header prediction: check for the two common cases 1733 * of a uni-directional data xfer. If the packet has 1734 * no control flags, is in-sequence, the window didn't 1735 * change and we're not retransmitting, it's a 1736 * candidate. If the length is zero and the ack moved 1737 * forward, we're the sender side of the xfer. Just 1738 * free the data acked & wake any higher level process 1739 * that was blocked waiting for space. If the length 1740 * is non-zero and the ack didn't move, we're the 1741 * receiver side. If we're getting packets in-order 1742 * (the reassembly queue is empty), add the data to 1743 * the socket buffer and note that we need a delayed ack. 1744 * Make sure that the hidden state-flags are also off. 1745 * Since we check for TCPS_ESTABLISHED first, it can only 1746 * be TH_NEEDSYN. 1747 */ 1748 if (tp->t_state == TCPS_ESTABLISHED && 1749 th->th_seq == tp->rcv_nxt && 1750 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1751 tp->snd_nxt == tp->snd_max && 1752 tiwin && tiwin == tp->snd_wnd && 1753 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1754 SEGQ_EMPTY(tp) && 1755 ((to.to_flags & TOF_TS) == 0 || 1756 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1757 /* 1758 * If last ACK falls within this segment's sequence numbers, 1759 * record the timestamp. 1760 * NOTE that the test is modified according to the latest 1761 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1762 */ 1763 if ((to.to_flags & TOF_TS) != 0 && 1764 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1765 tp->ts_recent_age = tcp_ts_getticks(); 1766 tp->ts_recent = to.to_tsval; 1767 } 1768 1769 if (tlen == 0) { 1770 if (SEQ_GT(th->th_ack, tp->snd_una) && 1771 SEQ_LEQ(th->th_ack, tp->snd_max) && 1772 !IN_RECOVERY(tp->t_flags) && 1773 (to.to_flags & TOF_SACK) == 0 && 1774 TAILQ_EMPTY(&tp->snd_holes)) { 1775 /* 1776 * This is a pure ack for outstanding data. 1777 */ 1778 TCPSTAT_INC(tcps_predack); 1779 1780 /* 1781 * "bad retransmit" recovery without timestamps. 1782 */ 1783 if ((to.to_flags & TOF_TS) == 0 && 1784 tp->t_rxtshift == 1 && 1785 tp->t_flags & TF_PREVVALID && 1786 (int)(ticks - tp->t_badrxtwin) < 0) { 1787 cc_cong_signal(tp, th, CC_RTO_ERR); 1788 } 1789 1790 /* 1791 * Recalculate the transmit timer / rtt. 1792 * 1793 * Some boxes send broken timestamp replies 1794 * during the SYN+ACK phase, ignore 1795 * timestamps of 0 or we could calculate a 1796 * huge RTT and blow up the retransmit timer. 1797 */ 1798 if ((to.to_flags & TOF_TS) != 0 && 1799 to.to_tsecr) { 1800 uint32_t t; 1801 1802 t = tcp_ts_getticks() - to.to_tsecr; 1803 if (!tp->t_rttlow || tp->t_rttlow > t) 1804 tp->t_rttlow = t; 1805 tcp_xmit_timer(tp, 1806 TCP_TS_TO_TICKS(t) + 1); 1807 } else if (tp->t_rtttime && 1808 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1809 if (!tp->t_rttlow || 1810 tp->t_rttlow > ticks - tp->t_rtttime) 1811 tp->t_rttlow = ticks - tp->t_rtttime; 1812 tcp_xmit_timer(tp, 1813 ticks - tp->t_rtttime); 1814 } 1815 acked = BYTES_THIS_ACK(tp, th); 1816 1817 #ifdef TCP_HHOOK 1818 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1819 hhook_run_tcp_est_in(tp, th, &to); 1820 #endif 1821 1822 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1823 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1824 sbdrop(&so->so_snd, acked); 1825 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1826 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1827 tp->snd_recover = th->th_ack - 1; 1828 1829 /* 1830 * Let the congestion control algorithm update 1831 * congestion control related information. This 1832 * typically means increasing the congestion 1833 * window. 1834 */ 1835 cc_ack_received(tp, th, nsegs, CC_ACK); 1836 1837 tp->snd_una = th->th_ack; 1838 /* 1839 * Pull snd_wl2 up to prevent seq wrap relative 1840 * to th_ack. 1841 */ 1842 tp->snd_wl2 = th->th_ack; 1843 tp->t_dupacks = 0; 1844 m_freem(m); 1845 1846 /* 1847 * If all outstanding data are acked, stop 1848 * retransmit timer, otherwise restart timer 1849 * using current (possibly backed-off) value. 1850 * If process is waiting for space, 1851 * wakeup/selwakeup/signal. If data 1852 * are ready to send, let tcp_output 1853 * decide between more output or persist. 1854 */ 1855 #ifdef TCPDEBUG 1856 if (so->so_options & SO_DEBUG) 1857 tcp_trace(TA_INPUT, ostate, tp, 1858 (void *)tcp_saveipgen, 1859 &tcp_savetcp, 0); 1860 #endif 1861 TCP_PROBE3(debug__input, tp, th, m); 1862 if (tp->snd_una == tp->snd_max) 1863 tcp_timer_activate(tp, TT_REXMT, 0); 1864 else if (!tcp_timer_active(tp, TT_PERSIST)) 1865 tcp_timer_activate(tp, TT_REXMT, 1866 tp->t_rxtcur); 1867 tp->t_flags |= TF_WAKESOW; 1868 if (sbavail(&so->so_snd)) 1869 (void) tp->t_fb->tfb_tcp_output(tp); 1870 goto check_delack; 1871 } 1872 } else if (th->th_ack == tp->snd_una && 1873 tlen <= sbspace(&so->so_rcv)) { 1874 int newsize = 0; /* automatic sockbuf scaling */ 1875 1876 /* 1877 * This is a pure, in-sequence data packet with 1878 * nothing on the reassembly queue and we have enough 1879 * buffer space to take it. 1880 */ 1881 /* Clean receiver SACK report if present */ 1882 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1883 tcp_clean_sackreport(tp); 1884 TCPSTAT_INC(tcps_preddat); 1885 tp->rcv_nxt += tlen; 1886 if (tlen && 1887 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 1888 (tp->t_fbyte_in == 0)) { 1889 tp->t_fbyte_in = ticks; 1890 if (tp->t_fbyte_in == 0) 1891 tp->t_fbyte_in = 1; 1892 if (tp->t_fbyte_out && tp->t_fbyte_in) 1893 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 1894 } 1895 /* 1896 * Pull snd_wl1 up to prevent seq wrap relative to 1897 * th_seq. 1898 */ 1899 tp->snd_wl1 = th->th_seq; 1900 /* 1901 * Pull rcv_up up to prevent seq wrap relative to 1902 * rcv_nxt. 1903 */ 1904 tp->rcv_up = tp->rcv_nxt; 1905 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1906 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1907 #ifdef TCPDEBUG 1908 if (so->so_options & SO_DEBUG) 1909 tcp_trace(TA_INPUT, ostate, tp, 1910 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1911 #endif 1912 TCP_PROBE3(debug__input, tp, th, m); 1913 1914 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1915 1916 /* Add data to socket buffer. */ 1917 SOCKBUF_LOCK(&so->so_rcv); 1918 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1919 m_freem(m); 1920 } else { 1921 /* 1922 * Set new socket buffer size. 1923 * Give up when limit is reached. 1924 */ 1925 if (newsize) 1926 if (!sbreserve_locked(&so->so_rcv, 1927 newsize, so, NULL)) 1928 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1929 m_adj(m, drop_hdrlen); /* delayed header drop */ 1930 sbappendstream_locked(&so->so_rcv, m, 0); 1931 } 1932 SOCKBUF_UNLOCK(&so->so_rcv); 1933 tp->t_flags |= TF_WAKESOR; 1934 if (DELAY_ACK(tp, tlen)) { 1935 tp->t_flags |= TF_DELACK; 1936 } else { 1937 tp->t_flags |= TF_ACKNOW; 1938 tp->t_fb->tfb_tcp_output(tp); 1939 } 1940 goto check_delack; 1941 } 1942 } 1943 1944 /* 1945 * Calculate amount of space in receive window, 1946 * and then do TCP input processing. 1947 * Receive window is amount of space in rcv queue, 1948 * but not less than advertised window. 1949 */ 1950 win = sbspace(&so->so_rcv); 1951 if (win < 0) 1952 win = 0; 1953 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1954 1955 switch (tp->t_state) { 1956 /* 1957 * If the state is SYN_RECEIVED: 1958 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1959 */ 1960 case TCPS_SYN_RECEIVED: 1961 if ((thflags & TH_ACK) && 1962 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1963 SEQ_GT(th->th_ack, tp->snd_max))) { 1964 rstreason = BANDLIM_RST_OPENPORT; 1965 goto dropwithreset; 1966 } 1967 if (IS_FASTOPEN(tp->t_flags)) { 1968 /* 1969 * When a TFO connection is in SYN_RECEIVED, the 1970 * only valid packets are the initial SYN, a 1971 * retransmit/copy of the initial SYN (possibly with 1972 * a subset of the original data), a valid ACK, a 1973 * FIN, or a RST. 1974 */ 1975 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1976 rstreason = BANDLIM_RST_OPENPORT; 1977 goto dropwithreset; 1978 } else if (thflags & TH_SYN) { 1979 /* non-initial SYN is ignored */ 1980 if ((tcp_timer_active(tp, TT_DELACK) || 1981 tcp_timer_active(tp, TT_REXMT))) 1982 goto drop; 1983 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1984 goto drop; 1985 } 1986 } 1987 break; 1988 1989 /* 1990 * If the state is SYN_SENT: 1991 * if seg contains a RST with valid ACK (SEQ.ACK has already 1992 * been verified), then drop the connection. 1993 * if seg contains a RST without an ACK, drop the seg. 1994 * if seg does not contain SYN, then drop the seg. 1995 * Otherwise this is an acceptable SYN segment 1996 * initialize tp->rcv_nxt and tp->irs 1997 * if seg contains ack then advance tp->snd_una 1998 * if seg contains an ECE and ECN support is enabled, the stream 1999 * is ECN capable. 2000 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 2001 * arrange for segment to be acked (eventually) 2002 * continue processing rest of data/controls, beginning with URG 2003 */ 2004 case TCPS_SYN_SENT: 2005 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 2006 TCP_PROBE5(connect__refused, NULL, tp, 2007 m, tp, th); 2008 tp = tcp_drop(tp, ECONNREFUSED); 2009 } 2010 if (thflags & TH_RST) 2011 goto drop; 2012 if (!(thflags & TH_SYN)) 2013 goto drop; 2014 2015 tp->irs = th->th_seq; 2016 tcp_rcvseqinit(tp); 2017 if (thflags & TH_ACK) { 2018 int tfo_partial_ack = 0; 2019 2020 TCPSTAT_INC(tcps_connects); 2021 soisconnected(so); 2022 #ifdef MAC 2023 mac_socketpeer_set_from_mbuf(m, so); 2024 #endif 2025 /* Do window scaling on this connection? */ 2026 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2027 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2028 tp->rcv_scale = tp->request_r_scale; 2029 } 2030 tp->rcv_adv += min(tp->rcv_wnd, 2031 TCP_MAXWIN << tp->rcv_scale); 2032 tp->snd_una++; /* SYN is acked */ 2033 /* 2034 * If not all the data that was sent in the TFO SYN 2035 * has been acked, resend the remainder right away. 2036 */ 2037 if (IS_FASTOPEN(tp->t_flags) && 2038 (tp->snd_una != tp->snd_max)) { 2039 tp->snd_nxt = th->th_ack; 2040 tfo_partial_ack = 1; 2041 } 2042 /* 2043 * If there's data, delay ACK; if there's also a FIN 2044 * ACKNOW will be turned on later. 2045 */ 2046 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 2047 tcp_timer_activate(tp, TT_DELACK, 2048 tcp_delacktime); 2049 else 2050 tp->t_flags |= TF_ACKNOW; 2051 2052 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) && 2053 (V_tcp_do_ecn == 1)) { 2054 tp->t_flags2 |= TF2_ECN_PERMIT; 2055 TCPSTAT_INC(tcps_ecn_shs); 2056 } 2057 2058 /* 2059 * Received <SYN,ACK> in SYN_SENT[*] state. 2060 * Transitions: 2061 * SYN_SENT --> ESTABLISHED 2062 * SYN_SENT* --> FIN_WAIT_1 2063 */ 2064 tp->t_starttime = ticks; 2065 if (tp->t_flags & TF_NEEDFIN) { 2066 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2067 tp->t_flags &= ~TF_NEEDFIN; 2068 thflags &= ~TH_SYN; 2069 } else { 2070 tcp_state_change(tp, TCPS_ESTABLISHED); 2071 TCP_PROBE5(connect__established, NULL, tp, 2072 m, tp, th); 2073 cc_conn_init(tp); 2074 tcp_timer_activate(tp, TT_KEEP, 2075 TP_KEEPIDLE(tp)); 2076 } 2077 } else { 2078 /* 2079 * Received initial SYN in SYN-SENT[*] state => 2080 * simultaneous open. 2081 * If it succeeds, connection is * half-synchronized. 2082 * Otherwise, do 3-way handshake: 2083 * SYN-SENT -> SYN-RECEIVED 2084 * SYN-SENT* -> SYN-RECEIVED* 2085 */ 2086 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2087 tcp_timer_activate(tp, TT_REXMT, 0); 2088 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2089 } 2090 2091 INP_WLOCK_ASSERT(tp->t_inpcb); 2092 2093 /* 2094 * Advance th->th_seq to correspond to first data byte. 2095 * If data, trim to stay within window, 2096 * dropping FIN if necessary. 2097 */ 2098 th->th_seq++; 2099 if (tlen > tp->rcv_wnd) { 2100 todrop = tlen - tp->rcv_wnd; 2101 m_adj(m, -todrop); 2102 tlen = tp->rcv_wnd; 2103 thflags &= ~TH_FIN; 2104 TCPSTAT_INC(tcps_rcvpackafterwin); 2105 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2106 } 2107 tp->snd_wl1 = th->th_seq - 1; 2108 tp->rcv_up = th->th_seq; 2109 /* 2110 * Client side of transaction: already sent SYN and data. 2111 * If the remote host used T/TCP to validate the SYN, 2112 * our data will be ACK'd; if so, enter normal data segment 2113 * processing in the middle of step 5, ack processing. 2114 * Otherwise, goto step 6. 2115 */ 2116 if (thflags & TH_ACK) 2117 goto process_ACK; 2118 2119 goto step6; 2120 2121 /* 2122 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2123 * do normal processing. 2124 * 2125 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2126 */ 2127 case TCPS_LAST_ACK: 2128 case TCPS_CLOSING: 2129 break; /* continue normal processing */ 2130 } 2131 2132 /* 2133 * States other than LISTEN or SYN_SENT. 2134 * First check the RST flag and sequence number since reset segments 2135 * are exempt from the timestamp and connection count tests. This 2136 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2137 * below which allowed reset segments in half the sequence space 2138 * to fall though and be processed (which gives forged reset 2139 * segments with a random sequence number a 50 percent chance of 2140 * killing a connection). 2141 * Then check timestamp, if present. 2142 * Then check the connection count, if present. 2143 * Then check that at least some bytes of segment are within 2144 * receive window. If segment begins before rcv_nxt, 2145 * drop leading data (and SYN); if nothing left, just ack. 2146 */ 2147 if (thflags & TH_RST) { 2148 /* 2149 * RFC5961 Section 3.2 2150 * 2151 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2152 * - If RST is in window, we send challenge ACK. 2153 * 2154 * Note: to take into account delayed ACKs, we should 2155 * test against last_ack_sent instead of rcv_nxt. 2156 * Note 2: we handle special case of closed window, not 2157 * covered by the RFC. 2158 */ 2159 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2160 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2161 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2162 KASSERT(tp->t_state != TCPS_SYN_SENT, 2163 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2164 __func__, th, tp)); 2165 2166 if (V_tcp_insecure_rst || 2167 tp->last_ack_sent == th->th_seq) { 2168 TCPSTAT_INC(tcps_drops); 2169 /* Drop the connection. */ 2170 switch (tp->t_state) { 2171 case TCPS_SYN_RECEIVED: 2172 so->so_error = ECONNREFUSED; 2173 goto close; 2174 case TCPS_ESTABLISHED: 2175 case TCPS_FIN_WAIT_1: 2176 case TCPS_FIN_WAIT_2: 2177 case TCPS_CLOSE_WAIT: 2178 case TCPS_CLOSING: 2179 case TCPS_LAST_ACK: 2180 so->so_error = ECONNRESET; 2181 close: 2182 /* FALLTHROUGH */ 2183 default: 2184 tp = tcp_close(tp); 2185 } 2186 } else { 2187 TCPSTAT_INC(tcps_badrst); 2188 /* Send challenge ACK. */ 2189 tcp_respond(tp, mtod(m, void *), th, m, 2190 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2191 tp->last_ack_sent = tp->rcv_nxt; 2192 m = NULL; 2193 } 2194 } 2195 goto drop; 2196 } 2197 2198 /* 2199 * RFC5961 Section 4.2 2200 * Send challenge ACK for any SYN in synchronized state. 2201 */ 2202 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2203 tp->t_state != TCPS_SYN_RECEIVED) { 2204 TCPSTAT_INC(tcps_badsyn); 2205 if (V_tcp_insecure_syn && 2206 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2207 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2208 tp = tcp_drop(tp, ECONNRESET); 2209 rstreason = BANDLIM_UNLIMITED; 2210 } else { 2211 /* Send challenge ACK. */ 2212 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2213 tp->snd_nxt, TH_ACK); 2214 tp->last_ack_sent = tp->rcv_nxt; 2215 m = NULL; 2216 } 2217 goto drop; 2218 } 2219 2220 /* 2221 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2222 * and it's less than ts_recent, drop it. 2223 */ 2224 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2225 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2226 /* Check to see if ts_recent is over 24 days old. */ 2227 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2228 /* 2229 * Invalidate ts_recent. If this segment updates 2230 * ts_recent, the age will be reset later and ts_recent 2231 * will get a valid value. If it does not, setting 2232 * ts_recent to zero will at least satisfy the 2233 * requirement that zero be placed in the timestamp 2234 * echo reply when ts_recent isn't valid. The 2235 * age isn't reset until we get a valid ts_recent 2236 * because we don't want out-of-order segments to be 2237 * dropped when ts_recent is old. 2238 */ 2239 tp->ts_recent = 0; 2240 } else { 2241 TCPSTAT_INC(tcps_rcvduppack); 2242 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2243 TCPSTAT_INC(tcps_pawsdrop); 2244 if (tlen) 2245 goto dropafterack; 2246 goto drop; 2247 } 2248 } 2249 2250 /* 2251 * In the SYN-RECEIVED state, validate that the packet belongs to 2252 * this connection before trimming the data to fit the receive 2253 * window. Check the sequence number versus IRS since we know 2254 * the sequence numbers haven't wrapped. This is a partial fix 2255 * for the "LAND" DoS attack. 2256 */ 2257 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2258 rstreason = BANDLIM_RST_OPENPORT; 2259 goto dropwithreset; 2260 } 2261 2262 todrop = tp->rcv_nxt - th->th_seq; 2263 if (todrop > 0) { 2264 if (thflags & TH_SYN) { 2265 thflags &= ~TH_SYN; 2266 th->th_seq++; 2267 if (th->th_urp > 1) 2268 th->th_urp--; 2269 else 2270 thflags &= ~TH_URG; 2271 todrop--; 2272 } 2273 /* 2274 * Following if statement from Stevens, vol. 2, p. 960. 2275 */ 2276 if (todrop > tlen 2277 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2278 /* 2279 * Any valid FIN must be to the left of the window. 2280 * At this point the FIN must be a duplicate or out 2281 * of sequence; drop it. 2282 */ 2283 thflags &= ~TH_FIN; 2284 2285 /* 2286 * Send an ACK to resynchronize and drop any data. 2287 * But keep on processing for RST or ACK. 2288 */ 2289 tp->t_flags |= TF_ACKNOW; 2290 todrop = tlen; 2291 TCPSTAT_INC(tcps_rcvduppack); 2292 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2293 } else { 2294 TCPSTAT_INC(tcps_rcvpartduppack); 2295 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2296 } 2297 /* 2298 * DSACK - add SACK block for dropped range 2299 */ 2300 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) { 2301 tcp_update_sack_list(tp, th->th_seq, 2302 th->th_seq + todrop); 2303 /* 2304 * ACK now, as the next in-sequence segment 2305 * will clear the DSACK block again 2306 */ 2307 tp->t_flags |= TF_ACKNOW; 2308 } 2309 drop_hdrlen += todrop; /* drop from the top afterwards */ 2310 th->th_seq += todrop; 2311 tlen -= todrop; 2312 if (th->th_urp > todrop) 2313 th->th_urp -= todrop; 2314 else { 2315 thflags &= ~TH_URG; 2316 th->th_urp = 0; 2317 } 2318 } 2319 2320 /* 2321 * If new data are received on a connection after the 2322 * user processes are gone, then RST the other end. 2323 */ 2324 if ((so->so_state & SS_NOFDREF) && 2325 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2326 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2327 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2328 "after socket was closed, " 2329 "sending RST and removing tcpcb\n", 2330 s, __func__, tcpstates[tp->t_state], tlen); 2331 free(s, M_TCPLOG); 2332 } 2333 tp = tcp_close(tp); 2334 TCPSTAT_INC(tcps_rcvafterclose); 2335 rstreason = BANDLIM_UNLIMITED; 2336 goto dropwithreset; 2337 } 2338 2339 /* 2340 * If segment ends after window, drop trailing data 2341 * (and PUSH and FIN); if nothing left, just ACK. 2342 */ 2343 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2344 if (todrop > 0) { 2345 TCPSTAT_INC(tcps_rcvpackafterwin); 2346 if (todrop >= tlen) { 2347 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2348 /* 2349 * If window is closed can only take segments at 2350 * window edge, and have to drop data and PUSH from 2351 * incoming segments. Continue processing, but 2352 * remember to ack. Otherwise, drop segment 2353 * and ack. 2354 */ 2355 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2356 tp->t_flags |= TF_ACKNOW; 2357 TCPSTAT_INC(tcps_rcvwinprobe); 2358 } else 2359 goto dropafterack; 2360 } else 2361 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2362 m_adj(m, -todrop); 2363 tlen -= todrop; 2364 thflags &= ~(TH_PUSH|TH_FIN); 2365 } 2366 2367 /* 2368 * If last ACK falls within this segment's sequence numbers, 2369 * record its timestamp. 2370 * NOTE: 2371 * 1) That the test incorporates suggestions from the latest 2372 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2373 * 2) That updating only on newer timestamps interferes with 2374 * our earlier PAWS tests, so this check should be solely 2375 * predicated on the sequence space of this segment. 2376 * 3) That we modify the segment boundary check to be 2377 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2378 * instead of RFC1323's 2379 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2380 * This modified check allows us to overcome RFC1323's 2381 * limitations as described in Stevens TCP/IP Illustrated 2382 * Vol. 2 p.869. In such cases, we can still calculate the 2383 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2384 */ 2385 if ((to.to_flags & TOF_TS) != 0 && 2386 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2387 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2388 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2389 tp->ts_recent_age = tcp_ts_getticks(); 2390 tp->ts_recent = to.to_tsval; 2391 } 2392 2393 /* 2394 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2395 * flag is on (half-synchronized state), then queue data for 2396 * later processing; else drop segment and return. 2397 */ 2398 if ((thflags & TH_ACK) == 0) { 2399 if (tp->t_state == TCPS_SYN_RECEIVED || 2400 (tp->t_flags & TF_NEEDSYN)) { 2401 if (tp->t_state == TCPS_SYN_RECEIVED && 2402 IS_FASTOPEN(tp->t_flags)) { 2403 tp->snd_wnd = tiwin; 2404 cc_conn_init(tp); 2405 } 2406 goto step6; 2407 } else if (tp->t_flags & TF_ACKNOW) 2408 goto dropafterack; 2409 else 2410 goto drop; 2411 } 2412 2413 /* 2414 * Ack processing. 2415 */ 2416 switch (tp->t_state) { 2417 /* 2418 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2419 * ESTABLISHED state and continue processing. 2420 * The ACK was checked above. 2421 */ 2422 case TCPS_SYN_RECEIVED: 2423 2424 TCPSTAT_INC(tcps_connects); 2425 soisconnected(so); 2426 /* Do window scaling? */ 2427 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2428 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2429 tp->rcv_scale = tp->request_r_scale; 2430 } 2431 tp->snd_wnd = tiwin; 2432 /* 2433 * Make transitions: 2434 * SYN-RECEIVED -> ESTABLISHED 2435 * SYN-RECEIVED* -> FIN-WAIT-1 2436 */ 2437 tp->t_starttime = ticks; 2438 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2439 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2440 tp->t_tfo_pending = NULL; 2441 } 2442 if (tp->t_flags & TF_NEEDFIN) { 2443 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2444 tp->t_flags &= ~TF_NEEDFIN; 2445 } else { 2446 tcp_state_change(tp, TCPS_ESTABLISHED); 2447 TCP_PROBE5(accept__established, NULL, tp, 2448 m, tp, th); 2449 /* 2450 * TFO connections call cc_conn_init() during SYN 2451 * processing. Calling it again here for such 2452 * connections is not harmless as it would undo the 2453 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2454 * is retransmitted. 2455 */ 2456 if (!IS_FASTOPEN(tp->t_flags)) 2457 cc_conn_init(tp); 2458 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2459 } 2460 /* 2461 * Account for the ACK of our SYN prior to 2462 * regular ACK processing below, except for 2463 * simultaneous SYN, which is handled later. 2464 */ 2465 if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) 2466 incforsyn = 1; 2467 /* 2468 * If segment contains data or ACK, will call tcp_reass() 2469 * later; if not, do so now to pass queued data to user. 2470 */ 2471 if (tlen == 0 && (thflags & TH_FIN) == 0) 2472 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2473 (struct mbuf *)0); 2474 tp->snd_wl1 = th->th_seq - 1; 2475 /* FALLTHROUGH */ 2476 2477 /* 2478 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2479 * ACKs. If the ack is in the range 2480 * tp->snd_una < th->th_ack <= tp->snd_max 2481 * then advance tp->snd_una to th->th_ack and drop 2482 * data from the retransmission queue. If this ACK reflects 2483 * more up to date window information we update our window information. 2484 */ 2485 case TCPS_ESTABLISHED: 2486 case TCPS_FIN_WAIT_1: 2487 case TCPS_FIN_WAIT_2: 2488 case TCPS_CLOSE_WAIT: 2489 case TCPS_CLOSING: 2490 case TCPS_LAST_ACK: 2491 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2492 TCPSTAT_INC(tcps_rcvacktoomuch); 2493 goto dropafterack; 2494 } 2495 if ((tp->t_flags & TF_SACK_PERMIT) && 2496 ((to.to_flags & TOF_SACK) || 2497 !TAILQ_EMPTY(&tp->snd_holes))) 2498 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2499 else 2500 /* 2501 * Reset the value so that previous (valid) value 2502 * from the last ack with SACK doesn't get used. 2503 */ 2504 tp->sackhint.sacked_bytes = 0; 2505 2506 #ifdef TCP_HHOOK 2507 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2508 hhook_run_tcp_est_in(tp, th, &to); 2509 #endif 2510 2511 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2512 u_int maxseg; 2513 2514 maxseg = tcp_maxseg(tp); 2515 if (tlen == 0 && 2516 (tiwin == tp->snd_wnd || 2517 (tp->t_flags & TF_SACK_PERMIT))) { 2518 /* 2519 * If this is the first time we've seen a 2520 * FIN from the remote, this is not a 2521 * duplicate and it needs to be processed 2522 * normally. This happens during a 2523 * simultaneous close. 2524 */ 2525 if ((thflags & TH_FIN) && 2526 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2527 tp->t_dupacks = 0; 2528 break; 2529 } 2530 TCPSTAT_INC(tcps_rcvdupack); 2531 /* 2532 * If we have outstanding data (other than 2533 * a window probe), this is a completely 2534 * duplicate ack (ie, window info didn't 2535 * change and FIN isn't set), 2536 * the ack is the biggest we've 2537 * seen and we've seen exactly our rexmt 2538 * threshold of them, assume a packet 2539 * has been dropped and retransmit it. 2540 * Kludge snd_nxt & the congestion 2541 * window so we send only this one 2542 * packet. 2543 * 2544 * We know we're losing at the current 2545 * window size so do congestion avoidance 2546 * (set ssthresh to half the current window 2547 * and pull our congestion window back to 2548 * the new ssthresh). 2549 * 2550 * Dup acks mean that packets have left the 2551 * network (they're now cached at the receiver) 2552 * so bump cwnd by the amount in the receiver 2553 * to keep a constant cwnd packets in the 2554 * network. 2555 * 2556 * When using TCP ECN, notify the peer that 2557 * we reduced the cwnd. 2558 */ 2559 /* 2560 * Following 2 kinds of acks should not affect 2561 * dupack counting: 2562 * 1) Old acks 2563 * 2) Acks with SACK but without any new SACK 2564 * information in them. These could result from 2565 * any anomaly in the network like a switch 2566 * duplicating packets or a possible DoS attack. 2567 */ 2568 if (th->th_ack != tp->snd_una || 2569 ((tp->t_flags & TF_SACK_PERMIT) && 2570 !sack_changed)) 2571 break; 2572 else if (!tcp_timer_active(tp, TT_REXMT)) 2573 tp->t_dupacks = 0; 2574 else if (++tp->t_dupacks > tcprexmtthresh || 2575 IN_FASTRECOVERY(tp->t_flags)) { 2576 cc_ack_received(tp, th, nsegs, 2577 CC_DUPACK); 2578 if (V_tcp_do_prr && 2579 IN_FASTRECOVERY(tp->t_flags) && 2580 (tp->t_flags & TF_SACK_PERMIT)) { 2581 long snd_cnt = 0, limit = 0; 2582 long del_data = 0, pipe = 0; 2583 /* 2584 * In a duplicate ACK del_data is only the 2585 * diff_in_sack. If no SACK is used del_data 2586 * will be 0. Pipe is the amount of data we 2587 * estimate to be in the network. 2588 */ 2589 del_data = tp->sackhint.delivered_data; 2590 pipe = (tp->snd_nxt - tp->snd_fack) + 2591 tp->sackhint.sack_bytes_rexmit; 2592 tp->sackhint.prr_delivered += del_data; 2593 if (pipe > tp->snd_ssthresh) { 2594 if (tp->sackhint.recover_fs == 0) 2595 tp->sackhint.recover_fs = 2596 max(1, tp->snd_nxt - tp->snd_una); 2597 snd_cnt = (tp->sackhint.prr_delivered * 2598 tp->snd_ssthresh / 2599 tp->sackhint.recover_fs) + 2600 1 - tp->sackhint.sack_bytes_rexmit; 2601 } else { 2602 if (V_tcp_do_prr_conservative) 2603 limit = tp->sackhint.prr_delivered - 2604 tp->sackhint.sack_bytes_rexmit; 2605 else 2606 if ((tp->sackhint.prr_delivered - 2607 tp->sackhint.sack_bytes_rexmit) > 2608 del_data) 2609 limit = tp->sackhint.prr_delivered - 2610 tp->sackhint.sack_bytes_rexmit + 2611 maxseg; 2612 else 2613 limit = del_data + maxseg; 2614 if ((tp->snd_ssthresh - pipe) < limit) 2615 snd_cnt = tp->snd_ssthresh - pipe; 2616 else 2617 snd_cnt = limit; 2618 } 2619 snd_cnt = max((snd_cnt / maxseg), 0); 2620 /* 2621 * Send snd_cnt new data into the network in 2622 * response to this ACK. If there is a going 2623 * to be a SACK retransmission, adjust snd_cwnd 2624 * accordingly. 2625 */ 2626 tp->snd_cwnd = tp->snd_nxt - tp->snd_recover + 2627 tp->sackhint.sack_bytes_rexmit + 2628 (snd_cnt * maxseg); 2629 } else if ((tp->t_flags & TF_SACK_PERMIT) && 2630 IN_FASTRECOVERY(tp->t_flags)) { 2631 int awnd; 2632 2633 /* 2634 * Compute the amount of data in flight first. 2635 * We can inject new data into the pipe iff 2636 * we have less than 1/2 the original window's 2637 * worth of data in flight. 2638 */ 2639 if (V_tcp_do_rfc6675_pipe) 2640 awnd = tcp_compute_pipe(tp); 2641 else 2642 awnd = (tp->snd_nxt - tp->snd_fack) + 2643 tp->sackhint.sack_bytes_rexmit; 2644 2645 if (awnd < tp->snd_ssthresh) { 2646 tp->snd_cwnd += maxseg; 2647 if (tp->snd_cwnd > tp->snd_ssthresh) 2648 tp->snd_cwnd = tp->snd_ssthresh; 2649 } 2650 } else 2651 tp->snd_cwnd += maxseg; 2652 (void) tp->t_fb->tfb_tcp_output(tp); 2653 goto drop; 2654 } else if (tp->t_dupacks == tcprexmtthresh) { 2655 tcp_seq onxt = tp->snd_nxt; 2656 2657 /* 2658 * If we're doing sack, or prr, check 2659 * to see if we're already in sack 2660 * recovery. If we're not doing sack, 2661 * check to see if we're in newreno 2662 * recovery. 2663 */ 2664 if (V_tcp_do_prr || 2665 (tp->t_flags & TF_SACK_PERMIT)) { 2666 if (IN_FASTRECOVERY(tp->t_flags)) { 2667 tp->t_dupacks = 0; 2668 break; 2669 } 2670 } else { 2671 if (SEQ_LEQ(th->th_ack, 2672 tp->snd_recover)) { 2673 tp->t_dupacks = 0; 2674 break; 2675 } 2676 } 2677 /* Congestion signal before ack. */ 2678 cc_cong_signal(tp, th, CC_NDUPACK); 2679 cc_ack_received(tp, th, nsegs, 2680 CC_DUPACK); 2681 tcp_timer_activate(tp, TT_REXMT, 0); 2682 tp->t_rtttime = 0; 2683 if (V_tcp_do_prr) { 2684 /* 2685 * snd_ssthresh is already updated by 2686 * cc_cong_signal. 2687 */ 2688 tp->sackhint.prr_delivered = 0; 2689 tp->sackhint.sack_bytes_rexmit = 0; 2690 tp->sackhint.recover_fs = max(1, 2691 tp->snd_nxt - tp->snd_una); 2692 } 2693 if (tp->t_flags & TF_SACK_PERMIT) { 2694 TCPSTAT_INC( 2695 tcps_sack_recovery_episode); 2696 tp->snd_recover = tp->snd_nxt; 2697 tp->snd_cwnd = maxseg; 2698 (void) tp->t_fb->tfb_tcp_output(tp); 2699 goto drop; 2700 } 2701 tp->snd_nxt = th->th_ack; 2702 tp->snd_cwnd = maxseg; 2703 (void) tp->t_fb->tfb_tcp_output(tp); 2704 KASSERT(tp->snd_limited <= 2, 2705 ("%s: tp->snd_limited too big", 2706 __func__)); 2707 tp->snd_cwnd = tp->snd_ssthresh + 2708 maxseg * 2709 (tp->t_dupacks - tp->snd_limited); 2710 if (SEQ_GT(onxt, tp->snd_nxt)) 2711 tp->snd_nxt = onxt; 2712 goto drop; 2713 } else if (V_tcp_do_rfc3042) { 2714 /* 2715 * Process first and second duplicate 2716 * ACKs. Each indicates a segment 2717 * leaving the network, creating room 2718 * for more. Make sure we can send a 2719 * packet on reception of each duplicate 2720 * ACK by increasing snd_cwnd by one 2721 * segment. Restore the original 2722 * snd_cwnd after packet transmission. 2723 */ 2724 cc_ack_received(tp, th, nsegs, 2725 CC_DUPACK); 2726 uint32_t oldcwnd = tp->snd_cwnd; 2727 tcp_seq oldsndmax = tp->snd_max; 2728 u_int sent; 2729 int avail; 2730 2731 KASSERT(tp->t_dupacks == 1 || 2732 tp->t_dupacks == 2, 2733 ("%s: dupacks not 1 or 2", 2734 __func__)); 2735 if (tp->t_dupacks == 1) 2736 tp->snd_limited = 0; 2737 tp->snd_cwnd = 2738 (tp->snd_nxt - tp->snd_una) + 2739 (tp->t_dupacks - tp->snd_limited) * 2740 maxseg; 2741 /* 2742 * Only call tcp_output when there 2743 * is new data available to be sent. 2744 * Otherwise we would send pure ACKs. 2745 */ 2746 SOCKBUF_LOCK(&so->so_snd); 2747 avail = sbavail(&so->so_snd) - 2748 (tp->snd_nxt - tp->snd_una); 2749 SOCKBUF_UNLOCK(&so->so_snd); 2750 if (avail > 0) 2751 (void) tp->t_fb->tfb_tcp_output(tp); 2752 sent = tp->snd_max - oldsndmax; 2753 if (sent > maxseg) { 2754 KASSERT((tp->t_dupacks == 2 && 2755 tp->snd_limited == 0) || 2756 (sent == maxseg + 1 && 2757 tp->t_flags & TF_SENTFIN), 2758 ("%s: sent too much", 2759 __func__)); 2760 tp->snd_limited = 2; 2761 } else if (sent > 0) 2762 ++tp->snd_limited; 2763 tp->snd_cwnd = oldcwnd; 2764 goto drop; 2765 } 2766 } 2767 break; 2768 } else { 2769 /* 2770 * This ack is advancing the left edge, reset the 2771 * counter. 2772 */ 2773 tp->t_dupacks = 0; 2774 /* 2775 * If this ack also has new SACK info, increment the 2776 * counter as per rfc6675. The variable 2777 * sack_changed tracks all changes to the SACK 2778 * scoreboard, including when partial ACKs without 2779 * SACK options are received, and clear the scoreboard 2780 * from the left side. Such partial ACKs should not be 2781 * counted as dupacks here. 2782 */ 2783 if ((tp->t_flags & TF_SACK_PERMIT) && 2784 (to.to_flags & TOF_SACK) && 2785 sack_changed) 2786 tp->t_dupacks++; 2787 } 2788 2789 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2790 ("%s: th_ack <= snd_una", __func__)); 2791 2792 /* 2793 * If the congestion window was inflated to account 2794 * for the other side's cached packets, retract it. 2795 */ 2796 if (IN_FASTRECOVERY(tp->t_flags)) { 2797 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2798 if (tp->t_flags & TF_SACK_PERMIT) 2799 if (V_tcp_do_prr) 2800 tcp_prr_partialack(tp, th); 2801 else 2802 tcp_sack_partialack(tp, th); 2803 else 2804 tcp_newreno_partial_ack(tp, th); 2805 } else 2806 cc_post_recovery(tp, th); 2807 } 2808 /* 2809 * If we reach this point, ACK is not a duplicate, 2810 * i.e., it ACKs something we sent. 2811 */ 2812 if (tp->t_flags & TF_NEEDSYN) { 2813 /* 2814 * T/TCP: Connection was half-synchronized, and our 2815 * SYN has been ACK'd (so connection is now fully 2816 * synchronized). Go to non-starred state, 2817 * increment snd_una for ACK of SYN, and check if 2818 * we can do window scaling. 2819 */ 2820 tp->t_flags &= ~TF_NEEDSYN; 2821 tp->snd_una++; 2822 /* Do window scaling? */ 2823 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2824 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2825 tp->rcv_scale = tp->request_r_scale; 2826 /* Send window already scaled. */ 2827 } 2828 } 2829 2830 process_ACK: 2831 INP_WLOCK_ASSERT(tp->t_inpcb); 2832 2833 /* 2834 * Adjust for the SYN bit in sequence space, 2835 * but don't account for it in cwnd calculations. 2836 * This is for the SYN_RECEIVED, non-simultaneous 2837 * SYN case. SYN_SENT and simultaneous SYN are 2838 * treated elsewhere. 2839 */ 2840 if (incforsyn) 2841 tp->snd_una++; 2842 acked = BYTES_THIS_ACK(tp, th); 2843 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2844 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2845 tp->snd_una, th->th_ack, tp, m)); 2846 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2847 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2848 2849 /* 2850 * If we just performed our first retransmit, and the ACK 2851 * arrives within our recovery window, then it was a mistake 2852 * to do the retransmit in the first place. Recover our 2853 * original cwnd and ssthresh, and proceed to transmit where 2854 * we left off. 2855 */ 2856 if (tp->t_rxtshift == 1 && 2857 tp->t_flags & TF_PREVVALID && 2858 tp->t_badrxtwin && 2859 SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 2860 cc_cong_signal(tp, th, CC_RTO_ERR); 2861 2862 /* 2863 * If we have a timestamp reply, update smoothed 2864 * round trip time. If no timestamp is present but 2865 * transmit timer is running and timed sequence 2866 * number was acked, update smoothed round trip time. 2867 * Since we now have an rtt measurement, cancel the 2868 * timer backoff (cf., Phil Karn's retransmit alg.). 2869 * Recompute the initial retransmit timer. 2870 * 2871 * Some boxes send broken timestamp replies 2872 * during the SYN+ACK phase, ignore 2873 * timestamps of 0 or we could calculate a 2874 * huge RTT and blow up the retransmit timer. 2875 */ 2876 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2877 uint32_t t; 2878 2879 t = tcp_ts_getticks() - to.to_tsecr; 2880 if (!tp->t_rttlow || tp->t_rttlow > t) 2881 tp->t_rttlow = t; 2882 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2883 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2884 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2885 tp->t_rttlow = ticks - tp->t_rtttime; 2886 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2887 } 2888 2889 /* 2890 * If all outstanding data is acked, stop retransmit 2891 * timer and remember to restart (more output or persist). 2892 * If there is more data to be acked, restart retransmit 2893 * timer, using current (possibly backed-off) value. 2894 */ 2895 if (th->th_ack == tp->snd_max) { 2896 tcp_timer_activate(tp, TT_REXMT, 0); 2897 needoutput = 1; 2898 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2899 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2900 2901 /* 2902 * If no data (only SYN) was ACK'd, 2903 * skip rest of ACK processing. 2904 */ 2905 if (acked == 0) 2906 goto step6; 2907 2908 /* 2909 * Let the congestion control algorithm update congestion 2910 * control related information. This typically means increasing 2911 * the congestion window. 2912 */ 2913 cc_ack_received(tp, th, nsegs, CC_ACK); 2914 2915 SOCKBUF_LOCK(&so->so_snd); 2916 if (acked > sbavail(&so->so_snd)) { 2917 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2918 tp->snd_wnd -= sbavail(&so->so_snd); 2919 else 2920 tp->snd_wnd = 0; 2921 mfree = sbcut_locked(&so->so_snd, 2922 (int)sbavail(&so->so_snd)); 2923 ourfinisacked = 1; 2924 } else { 2925 mfree = sbcut_locked(&so->so_snd, acked); 2926 if (tp->snd_wnd >= (uint32_t) acked) 2927 tp->snd_wnd -= acked; 2928 else 2929 tp->snd_wnd = 0; 2930 ourfinisacked = 0; 2931 } 2932 SOCKBUF_UNLOCK(&so->so_snd); 2933 tp->t_flags |= TF_WAKESOW; 2934 m_freem(mfree); 2935 /* Detect una wraparound. */ 2936 if (!IN_RECOVERY(tp->t_flags) && 2937 SEQ_GT(tp->snd_una, tp->snd_recover) && 2938 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2939 tp->snd_recover = th->th_ack - 1; 2940 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2941 if (IN_RECOVERY(tp->t_flags) && 2942 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2943 EXIT_RECOVERY(tp->t_flags); 2944 } 2945 tp->snd_una = th->th_ack; 2946 if (tp->t_flags & TF_SACK_PERMIT) { 2947 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2948 tp->snd_recover = tp->snd_una; 2949 } 2950 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2951 tp->snd_nxt = tp->snd_una; 2952 2953 switch (tp->t_state) { 2954 /* 2955 * In FIN_WAIT_1 STATE in addition to the processing 2956 * for the ESTABLISHED state if our FIN is now acknowledged 2957 * then enter FIN_WAIT_2. 2958 */ 2959 case TCPS_FIN_WAIT_1: 2960 if (ourfinisacked) { 2961 /* 2962 * If we can't receive any more 2963 * data, then closing user can proceed. 2964 * Starting the timer is contrary to the 2965 * specification, but if we don't get a FIN 2966 * we'll hang forever. 2967 * 2968 * XXXjl: 2969 * we should release the tp also, and use a 2970 * compressed state. 2971 */ 2972 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2973 soisdisconnected(so); 2974 tcp_timer_activate(tp, TT_2MSL, 2975 (tcp_fast_finwait2_recycle ? 2976 tcp_finwait2_timeout : 2977 TP_MAXIDLE(tp))); 2978 } 2979 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2980 } 2981 break; 2982 2983 /* 2984 * In CLOSING STATE in addition to the processing for 2985 * the ESTABLISHED state if the ACK acknowledges our FIN 2986 * then enter the TIME-WAIT state, otherwise ignore 2987 * the segment. 2988 */ 2989 case TCPS_CLOSING: 2990 if (ourfinisacked) { 2991 tcp_twstart(tp); 2992 m_freem(m); 2993 return; 2994 } 2995 break; 2996 2997 /* 2998 * In LAST_ACK, we may still be waiting for data to drain 2999 * and/or to be acked, as well as for the ack of our FIN. 3000 * If our FIN is now acknowledged, delete the TCB, 3001 * enter the closed state and return. 3002 */ 3003 case TCPS_LAST_ACK: 3004 if (ourfinisacked) { 3005 tp = tcp_close(tp); 3006 goto drop; 3007 } 3008 break; 3009 } 3010 } 3011 3012 step6: 3013 INP_WLOCK_ASSERT(tp->t_inpcb); 3014 3015 /* 3016 * Update window information. 3017 * Don't look at window if no ACK: TAC's send garbage on first SYN. 3018 */ 3019 if ((thflags & TH_ACK) && 3020 (SEQ_LT(tp->snd_wl1, th->th_seq) || 3021 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 3022 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 3023 /* keep track of pure window updates */ 3024 if (tlen == 0 && 3025 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 3026 TCPSTAT_INC(tcps_rcvwinupd); 3027 tp->snd_wnd = tiwin; 3028 tp->snd_wl1 = th->th_seq; 3029 tp->snd_wl2 = th->th_ack; 3030 if (tp->snd_wnd > tp->max_sndwnd) 3031 tp->max_sndwnd = tp->snd_wnd; 3032 needoutput = 1; 3033 } 3034 3035 /* 3036 * Process segments with URG. 3037 */ 3038 if ((thflags & TH_URG) && th->th_urp && 3039 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3040 /* 3041 * This is a kludge, but if we receive and accept 3042 * random urgent pointers, we'll crash in 3043 * soreceive. It's hard to imagine someone 3044 * actually wanting to send this much urgent data. 3045 */ 3046 SOCKBUF_LOCK(&so->so_rcv); 3047 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 3048 th->th_urp = 0; /* XXX */ 3049 thflags &= ~TH_URG; /* XXX */ 3050 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 3051 goto dodata; /* XXX */ 3052 } 3053 /* 3054 * If this segment advances the known urgent pointer, 3055 * then mark the data stream. This should not happen 3056 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 3057 * a FIN has been received from the remote side. 3058 * In these states we ignore the URG. 3059 * 3060 * According to RFC961 (Assigned Protocols), 3061 * the urgent pointer points to the last octet 3062 * of urgent data. We continue, however, 3063 * to consider it to indicate the first octet 3064 * of data past the urgent section as the original 3065 * spec states (in one of two places). 3066 */ 3067 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 3068 tp->rcv_up = th->th_seq + th->th_urp; 3069 so->so_oobmark = sbavail(&so->so_rcv) + 3070 (tp->rcv_up - tp->rcv_nxt) - 1; 3071 if (so->so_oobmark == 0) 3072 so->so_rcv.sb_state |= SBS_RCVATMARK; 3073 sohasoutofband(so); 3074 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 3075 } 3076 SOCKBUF_UNLOCK(&so->so_rcv); 3077 /* 3078 * Remove out of band data so doesn't get presented to user. 3079 * This can happen independent of advancing the URG pointer, 3080 * but if two URG's are pending at once, some out-of-band 3081 * data may creep in... ick. 3082 */ 3083 if (th->th_urp <= (uint32_t)tlen && 3084 !(so->so_options & SO_OOBINLINE)) { 3085 /* hdr drop is delayed */ 3086 tcp_pulloutofband(so, th, m, drop_hdrlen); 3087 } 3088 } else { 3089 /* 3090 * If no out of band data is expected, 3091 * pull receive urgent pointer along 3092 * with the receive window. 3093 */ 3094 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3095 tp->rcv_up = tp->rcv_nxt; 3096 } 3097 dodata: /* XXX */ 3098 INP_WLOCK_ASSERT(tp->t_inpcb); 3099 3100 /* 3101 * Process the segment text, merging it into the TCP sequencing queue, 3102 * and arranging for acknowledgment of receipt if necessary. 3103 * This process logically involves adjusting tp->rcv_wnd as data 3104 * is presented to the user (this happens in tcp_usrreq.c, 3105 * case PRU_RCVD). If a FIN has already been received on this 3106 * connection then we just ignore the text. 3107 */ 3108 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3109 IS_FASTOPEN(tp->t_flags)); 3110 if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) && 3111 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3112 tcp_seq save_start = th->th_seq; 3113 tcp_seq save_rnxt = tp->rcv_nxt; 3114 int save_tlen = tlen; 3115 m_adj(m, drop_hdrlen); /* delayed header drop */ 3116 /* 3117 * Insert segment which includes th into TCP reassembly queue 3118 * with control block tp. Set thflags to whether reassembly now 3119 * includes a segment with FIN. This handles the common case 3120 * inline (segment is the next to be received on an established 3121 * connection, and the queue is empty), avoiding linkage into 3122 * and removal from the queue and repetition of various 3123 * conversions. 3124 * Set DELACK for segments received in order, but ack 3125 * immediately when segments are out of order (so 3126 * fast retransmit can work). 3127 */ 3128 if (th->th_seq == tp->rcv_nxt && 3129 SEGQ_EMPTY(tp) && 3130 (TCPS_HAVEESTABLISHED(tp->t_state) || 3131 tfo_syn)) { 3132 if (DELAY_ACK(tp, tlen) || tfo_syn) 3133 tp->t_flags |= TF_DELACK; 3134 else 3135 tp->t_flags |= TF_ACKNOW; 3136 tp->rcv_nxt += tlen; 3137 if (tlen && 3138 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 3139 (tp->t_fbyte_in == 0)) { 3140 tp->t_fbyte_in = ticks; 3141 if (tp->t_fbyte_in == 0) 3142 tp->t_fbyte_in = 1; 3143 if (tp->t_fbyte_out && tp->t_fbyte_in) 3144 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 3145 } 3146 thflags = th->th_flags & TH_FIN; 3147 TCPSTAT_INC(tcps_rcvpack); 3148 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3149 SOCKBUF_LOCK(&so->so_rcv); 3150 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3151 m_freem(m); 3152 else 3153 sbappendstream_locked(&so->so_rcv, m, 0); 3154 SOCKBUF_UNLOCK(&so->so_rcv); 3155 tp->t_flags |= TF_WAKESOR; 3156 } else { 3157 /* 3158 * XXX: Due to the header drop above "th" is 3159 * theoretically invalid by now. Fortunately 3160 * m_adj() doesn't actually frees any mbufs 3161 * when trimming from the head. 3162 */ 3163 tcp_seq temp = save_start; 3164 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3165 tp->t_flags |= TF_ACKNOW; 3166 } 3167 if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) { 3168 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) { 3169 /* 3170 * DSACK actually handled in the fastpath 3171 * above. 3172 */ 3173 tcp_update_sack_list(tp, save_start, 3174 save_start + save_tlen); 3175 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3176 if ((tp->rcv_numsacks >= 1) && 3177 (tp->sackblks[0].end == save_start)) { 3178 /* 3179 * Partial overlap, recorded at todrop 3180 * above. 3181 */ 3182 tcp_update_sack_list(tp, 3183 tp->sackblks[0].start, 3184 tp->sackblks[0].end); 3185 } else { 3186 tcp_update_dsack_list(tp, save_start, 3187 save_start + save_tlen); 3188 } 3189 } else if (tlen >= save_tlen) { 3190 /* Update of sackblks. */ 3191 tcp_update_dsack_list(tp, save_start, 3192 save_start + save_tlen); 3193 } else if (tlen > 0) { 3194 tcp_update_dsack_list(tp, save_start, 3195 save_start + tlen); 3196 } 3197 } 3198 #if 0 3199 /* 3200 * Note the amount of data that peer has sent into 3201 * our window, in order to estimate the sender's 3202 * buffer size. 3203 * XXX: Unused. 3204 */ 3205 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3206 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3207 else 3208 len = so->so_rcv.sb_hiwat; 3209 #endif 3210 } else { 3211 m_freem(m); 3212 thflags &= ~TH_FIN; 3213 } 3214 3215 /* 3216 * If FIN is received ACK the FIN and let the user know 3217 * that the connection is closing. 3218 */ 3219 if (thflags & TH_FIN) { 3220 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3221 socantrcvmore(so); 3222 /* The socket upcall is handled by socantrcvmore. */ 3223 tp->t_flags &= ~TF_WAKESOR; 3224 /* 3225 * If connection is half-synchronized 3226 * (ie NEEDSYN flag on) then delay ACK, 3227 * so it may be piggybacked when SYN is sent. 3228 * Otherwise, since we received a FIN then no 3229 * more input can be expected, send ACK now. 3230 */ 3231 if (tp->t_flags & TF_NEEDSYN) 3232 tp->t_flags |= TF_DELACK; 3233 else 3234 tp->t_flags |= TF_ACKNOW; 3235 tp->rcv_nxt++; 3236 } 3237 switch (tp->t_state) { 3238 /* 3239 * In SYN_RECEIVED and ESTABLISHED STATES 3240 * enter the CLOSE_WAIT state. 3241 */ 3242 case TCPS_SYN_RECEIVED: 3243 tp->t_starttime = ticks; 3244 /* FALLTHROUGH */ 3245 case TCPS_ESTABLISHED: 3246 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3247 break; 3248 3249 /* 3250 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3251 * enter the CLOSING state. 3252 */ 3253 case TCPS_FIN_WAIT_1: 3254 tcp_state_change(tp, TCPS_CLOSING); 3255 break; 3256 3257 /* 3258 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3259 * starting the time-wait timer, turning off the other 3260 * standard timers. 3261 */ 3262 case TCPS_FIN_WAIT_2: 3263 tcp_twstart(tp); 3264 return; 3265 } 3266 } 3267 #ifdef TCPDEBUG 3268 if (so->so_options & SO_DEBUG) 3269 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3270 &tcp_savetcp, 0); 3271 #endif 3272 TCP_PROBE3(debug__input, tp, th, m); 3273 3274 /* 3275 * Return any desired output. 3276 */ 3277 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3278 (void) tp->t_fb->tfb_tcp_output(tp); 3279 3280 check_delack: 3281 INP_WLOCK_ASSERT(tp->t_inpcb); 3282 3283 if (tp->t_flags & TF_DELACK) { 3284 tp->t_flags &= ~TF_DELACK; 3285 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3286 } 3287 tcp_handle_wakeup(tp, so); 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) tp->t_fb->tfb_tcp_output(tp); 3321 tcp_handle_wakeup(tp, so); 3322 INP_WUNLOCK(tp->t_inpcb); 3323 m_freem(m); 3324 return; 3325 3326 dropwithreset: 3327 if (tp != NULL) { 3328 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3329 tcp_handle_wakeup(tp, so); 3330 INP_WUNLOCK(tp->t_inpcb); 3331 } else 3332 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3333 return; 3334 3335 drop: 3336 /* 3337 * Drop space held by incoming segment and return. 3338 */ 3339 #ifdef TCPDEBUG 3340 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3341 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3342 &tcp_savetcp, 0); 3343 #endif 3344 TCP_PROBE3(debug__input, tp, th, m); 3345 if (tp != NULL) { 3346 tcp_handle_wakeup(tp, so); 3347 INP_WUNLOCK(tp->t_inpcb); 3348 } 3349 m_freem(m); 3350 } 3351 3352 /* 3353 * Issue RST and make ACK acceptable to originator of segment. 3354 * The mbuf must still include the original packet header. 3355 * tp may be NULL. 3356 */ 3357 void 3358 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3359 int tlen, int rstreason) 3360 { 3361 #ifdef INET 3362 struct ip *ip; 3363 #endif 3364 #ifdef INET6 3365 struct ip6_hdr *ip6; 3366 #endif 3367 3368 if (tp != NULL) { 3369 INP_WLOCK_ASSERT(tp->t_inpcb); 3370 } 3371 3372 /* Don't bother if destination was broadcast/multicast. */ 3373 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3374 goto drop; 3375 #ifdef INET6 3376 if (mtod(m, struct ip *)->ip_v == 6) { 3377 ip6 = mtod(m, struct ip6_hdr *); 3378 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3379 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3380 goto drop; 3381 /* IPv6 anycast check is done at tcp6_input() */ 3382 } 3383 #endif 3384 #if defined(INET) && defined(INET6) 3385 else 3386 #endif 3387 #ifdef INET 3388 { 3389 ip = mtod(m, struct ip *); 3390 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3391 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3392 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3393 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3394 goto drop; 3395 } 3396 #endif 3397 3398 /* Perform bandwidth limiting. */ 3399 if (badport_bandlim(rstreason) < 0) 3400 goto drop; 3401 3402 /* tcp_respond consumes the mbuf chain. */ 3403 if (th->th_flags & TH_ACK) { 3404 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3405 th->th_ack, TH_RST); 3406 } else { 3407 if (th->th_flags & TH_SYN) 3408 tlen++; 3409 if (th->th_flags & TH_FIN) 3410 tlen++; 3411 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3412 (tcp_seq)0, TH_RST|TH_ACK); 3413 } 3414 return; 3415 drop: 3416 m_freem(m); 3417 } 3418 3419 /* 3420 * Parse TCP options and place in tcpopt. 3421 */ 3422 void 3423 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3424 { 3425 int opt, optlen; 3426 3427 to->to_flags = 0; 3428 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3429 opt = cp[0]; 3430 if (opt == TCPOPT_EOL) 3431 break; 3432 if (opt == TCPOPT_NOP) 3433 optlen = 1; 3434 else { 3435 if (cnt < 2) 3436 break; 3437 optlen = cp[1]; 3438 if (optlen < 2 || optlen > cnt) 3439 break; 3440 } 3441 switch (opt) { 3442 case TCPOPT_MAXSEG: 3443 if (optlen != TCPOLEN_MAXSEG) 3444 continue; 3445 if (!(flags & TO_SYN)) 3446 continue; 3447 to->to_flags |= TOF_MSS; 3448 bcopy((char *)cp + 2, 3449 (char *)&to->to_mss, sizeof(to->to_mss)); 3450 to->to_mss = ntohs(to->to_mss); 3451 break; 3452 case TCPOPT_WINDOW: 3453 if (optlen != TCPOLEN_WINDOW) 3454 continue; 3455 if (!(flags & TO_SYN)) 3456 continue; 3457 to->to_flags |= TOF_SCALE; 3458 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3459 break; 3460 case TCPOPT_TIMESTAMP: 3461 if (optlen != TCPOLEN_TIMESTAMP) 3462 continue; 3463 to->to_flags |= TOF_TS; 3464 bcopy((char *)cp + 2, 3465 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3466 to->to_tsval = ntohl(to->to_tsval); 3467 bcopy((char *)cp + 6, 3468 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3469 to->to_tsecr = ntohl(to->to_tsecr); 3470 break; 3471 case TCPOPT_SIGNATURE: 3472 /* 3473 * In order to reply to a host which has set the 3474 * TCP_SIGNATURE option in its initial SYN, we have 3475 * to record the fact that the option was observed 3476 * here for the syncache code to perform the correct 3477 * response. 3478 */ 3479 if (optlen != TCPOLEN_SIGNATURE) 3480 continue; 3481 to->to_flags |= TOF_SIGNATURE; 3482 to->to_signature = cp + 2; 3483 break; 3484 case TCPOPT_SACK_PERMITTED: 3485 if (optlen != TCPOLEN_SACK_PERMITTED) 3486 continue; 3487 if (!(flags & TO_SYN)) 3488 continue; 3489 if (!V_tcp_do_sack) 3490 continue; 3491 to->to_flags |= TOF_SACKPERM; 3492 break; 3493 case TCPOPT_SACK: 3494 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3495 continue; 3496 if (flags & TO_SYN) 3497 continue; 3498 to->to_flags |= TOF_SACK; 3499 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3500 to->to_sacks = cp + 2; 3501 TCPSTAT_INC(tcps_sack_rcv_blocks); 3502 break; 3503 case TCPOPT_FAST_OPEN: 3504 /* 3505 * Cookie length validation is performed by the 3506 * server side cookie checking code or the client 3507 * side cookie cache update code. 3508 */ 3509 if (!(flags & TO_SYN)) 3510 continue; 3511 if (!V_tcp_fastopen_client_enable && 3512 !V_tcp_fastopen_server_enable) 3513 continue; 3514 to->to_flags |= TOF_FASTOPEN; 3515 to->to_tfo_len = optlen - 2; 3516 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3517 break; 3518 default: 3519 continue; 3520 } 3521 } 3522 } 3523 3524 /* 3525 * Pull out of band byte out of a segment so 3526 * it doesn't appear in the user's data queue. 3527 * It is still reflected in the segment length for 3528 * sequencing purposes. 3529 */ 3530 void 3531 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3532 int off) 3533 { 3534 int cnt = off + th->th_urp - 1; 3535 3536 while (cnt >= 0) { 3537 if (m->m_len > cnt) { 3538 char *cp = mtod(m, caddr_t) + cnt; 3539 struct tcpcb *tp = sototcpcb(so); 3540 3541 INP_WLOCK_ASSERT(tp->t_inpcb); 3542 3543 tp->t_iobc = *cp; 3544 tp->t_oobflags |= TCPOOB_HAVEDATA; 3545 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3546 m->m_len--; 3547 if (m->m_flags & M_PKTHDR) 3548 m->m_pkthdr.len--; 3549 return; 3550 } 3551 cnt -= m->m_len; 3552 m = m->m_next; 3553 if (m == NULL) 3554 break; 3555 } 3556 panic("tcp_pulloutofband"); 3557 } 3558 3559 /* 3560 * Collect new round-trip time estimate 3561 * and update averages and current timeout. 3562 */ 3563 void 3564 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3565 { 3566 int delta; 3567 3568 INP_WLOCK_ASSERT(tp->t_inpcb); 3569 3570 TCPSTAT_INC(tcps_rttupdated); 3571 tp->t_rttupdated++; 3572 #ifdef STATS 3573 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, 3574 imax(0, rtt * 1000 / hz)); 3575 #endif 3576 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3577 /* 3578 * srtt is stored as fixed point with 5 bits after the 3579 * binary point (i.e., scaled by 8). The following magic 3580 * is equivalent to the smoothing algorithm in rfc793 with 3581 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3582 * point). Adjust rtt to origin 0. 3583 */ 3584 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3585 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3586 3587 if ((tp->t_srtt += delta) <= 0) 3588 tp->t_srtt = 1; 3589 3590 /* 3591 * We accumulate a smoothed rtt variance (actually, a 3592 * smoothed mean difference), then set the retransmit 3593 * timer to smoothed rtt + 4 times the smoothed variance. 3594 * rttvar is stored as fixed point with 4 bits after the 3595 * binary point (scaled by 16). The following is 3596 * equivalent to rfc793 smoothing with an alpha of .75 3597 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3598 * rfc793's wired-in beta. 3599 */ 3600 if (delta < 0) 3601 delta = -delta; 3602 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3603 if ((tp->t_rttvar += delta) <= 0) 3604 tp->t_rttvar = 1; 3605 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3606 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3607 } else { 3608 /* 3609 * No rtt measurement yet - use the unsmoothed rtt. 3610 * Set the variance to half the rtt (so our first 3611 * retransmit happens at 3*rtt). 3612 */ 3613 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3614 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3615 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3616 } 3617 tp->t_rtttime = 0; 3618 tp->t_rxtshift = 0; 3619 3620 /* 3621 * the retransmit should happen at rtt + 4 * rttvar. 3622 * Because of the way we do the smoothing, srtt and rttvar 3623 * will each average +1/2 tick of bias. When we compute 3624 * the retransmit timer, we want 1/2 tick of rounding and 3625 * 1 extra tick because of +-1/2 tick uncertainty in the 3626 * firing of the timer. The bias will give us exactly the 3627 * 1.5 tick we need. But, because the bias is 3628 * statistical, we have to test that we don't drop below 3629 * the minimum feasible timer (which is 2 ticks). 3630 */ 3631 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3632 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3633 3634 /* 3635 * We received an ack for a packet that wasn't retransmitted; 3636 * it is probably safe to discard any error indications we've 3637 * received recently. This isn't quite right, but close enough 3638 * for now (a route might have failed after we sent a segment, 3639 * and the return path might not be symmetrical). 3640 */ 3641 tp->t_softerror = 0; 3642 } 3643 3644 /* 3645 * Determine a reasonable value for maxseg size. 3646 * If the route is known, check route for mtu. 3647 * If none, use an mss that can be handled on the outgoing interface 3648 * without forcing IP to fragment. If no route is found, route has no mtu, 3649 * or the destination isn't local, use a default, hopefully conservative 3650 * size (usually 512 or the default IP max size, but no more than the mtu 3651 * of the interface), as we can't discover anything about intervening 3652 * gateways or networks. We also initialize the congestion/slow start 3653 * window to be a single segment if the destination isn't local. 3654 * While looking at the routing entry, we also initialize other path-dependent 3655 * parameters from pre-set or cached values in the routing entry. 3656 * 3657 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3658 * IP options, e.g. IPSEC data, since length of this data may vary, and 3659 * thus it is calculated for every segment separately in tcp_output(). 3660 * 3661 * NOTE that this routine is only called when we process an incoming 3662 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3663 * settings are handled in tcp_mssopt(). 3664 */ 3665 void 3666 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3667 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3668 { 3669 int mss = 0; 3670 uint32_t maxmtu = 0; 3671 struct inpcb *inp = tp->t_inpcb; 3672 struct hc_metrics_lite metrics; 3673 #ifdef INET6 3674 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3675 size_t min_protoh = isipv6 ? 3676 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3677 sizeof (struct tcpiphdr); 3678 #else 3679 const size_t min_protoh = sizeof(struct tcpiphdr); 3680 #endif 3681 3682 INP_WLOCK_ASSERT(tp->t_inpcb); 3683 3684 if (mtuoffer != -1) { 3685 KASSERT(offer == -1, ("%s: conflict", __func__)); 3686 offer = mtuoffer - min_protoh; 3687 } 3688 3689 /* Initialize. */ 3690 #ifdef INET6 3691 if (isipv6) { 3692 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3693 tp->t_maxseg = V_tcp_v6mssdflt; 3694 } 3695 #endif 3696 #if defined(INET) && defined(INET6) 3697 else 3698 #endif 3699 #ifdef INET 3700 { 3701 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3702 tp->t_maxseg = V_tcp_mssdflt; 3703 } 3704 #endif 3705 3706 /* 3707 * No route to sender, stay with default mss and return. 3708 */ 3709 if (maxmtu == 0) { 3710 /* 3711 * In case we return early we need to initialize metrics 3712 * to a defined state as tcp_hc_get() would do for us 3713 * if there was no cache hit. 3714 */ 3715 if (metricptr != NULL) 3716 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3717 return; 3718 } 3719 3720 /* What have we got? */ 3721 switch (offer) { 3722 case 0: 3723 /* 3724 * Offer == 0 means that there was no MSS on the SYN 3725 * segment, in this case we use tcp_mssdflt as 3726 * already assigned to t_maxseg above. 3727 */ 3728 offer = tp->t_maxseg; 3729 break; 3730 3731 case -1: 3732 /* 3733 * Offer == -1 means that we didn't receive SYN yet. 3734 */ 3735 /* FALLTHROUGH */ 3736 3737 default: 3738 /* 3739 * Prevent DoS attack with too small MSS. Round up 3740 * to at least minmss. 3741 */ 3742 offer = max(offer, V_tcp_minmss); 3743 } 3744 3745 /* 3746 * rmx information is now retrieved from tcp_hostcache. 3747 */ 3748 tcp_hc_get(&inp->inp_inc, &metrics); 3749 if (metricptr != NULL) 3750 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3751 3752 /* 3753 * If there's a discovered mtu in tcp hostcache, use it. 3754 * Else, use the link mtu. 3755 */ 3756 if (metrics.rmx_mtu) 3757 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3758 else { 3759 #ifdef INET6 3760 if (isipv6) { 3761 mss = maxmtu - min_protoh; 3762 if (!V_path_mtu_discovery && 3763 !in6_localaddr(&inp->in6p_faddr)) 3764 mss = min(mss, V_tcp_v6mssdflt); 3765 } 3766 #endif 3767 #if defined(INET) && defined(INET6) 3768 else 3769 #endif 3770 #ifdef INET 3771 { 3772 mss = maxmtu - min_protoh; 3773 if (!V_path_mtu_discovery && 3774 !in_localaddr(inp->inp_faddr)) 3775 mss = min(mss, V_tcp_mssdflt); 3776 } 3777 #endif 3778 /* 3779 * XXX - The above conditional (mss = maxmtu - min_protoh) 3780 * probably violates the TCP spec. 3781 * The problem is that, since we don't know the 3782 * other end's MSS, we are supposed to use a conservative 3783 * default. But, if we do that, then MTU discovery will 3784 * never actually take place, because the conservative 3785 * default is much less than the MTUs typically seen 3786 * on the Internet today. For the moment, we'll sweep 3787 * this under the carpet. 3788 * 3789 * The conservative default might not actually be a problem 3790 * if the only case this occurs is when sending an initial 3791 * SYN with options and data to a host we've never talked 3792 * to before. Then, they will reply with an MSS value which 3793 * will get recorded and the new parameters should get 3794 * recomputed. For Further Study. 3795 */ 3796 } 3797 mss = min(mss, offer); 3798 3799 /* 3800 * Sanity check: make sure that maxseg will be large 3801 * enough to allow some data on segments even if the 3802 * all the option space is used (40bytes). Otherwise 3803 * funny things may happen in tcp_output. 3804 * 3805 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3806 */ 3807 mss = max(mss, 64); 3808 3809 tp->t_maxseg = mss; 3810 } 3811 3812 void 3813 tcp_mss(struct tcpcb *tp, int offer) 3814 { 3815 int mss; 3816 uint32_t bufsize; 3817 struct inpcb *inp; 3818 struct socket *so; 3819 struct hc_metrics_lite metrics; 3820 struct tcp_ifcap cap; 3821 3822 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3823 3824 bzero(&cap, sizeof(cap)); 3825 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3826 3827 mss = tp->t_maxseg; 3828 inp = tp->t_inpcb; 3829 3830 /* 3831 * If there's a pipesize, change the socket buffer to that size, 3832 * don't change if sb_hiwat is different than default (then it 3833 * has been changed on purpose with setsockopt). 3834 * Make the socket buffers an integral number of mss units; 3835 * if the mss is larger than the socket buffer, decrease the mss. 3836 */ 3837 so = inp->inp_socket; 3838 SOCKBUF_LOCK(&so->so_snd); 3839 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3840 bufsize = metrics.rmx_sendpipe; 3841 else 3842 bufsize = so->so_snd.sb_hiwat; 3843 if (bufsize < mss) 3844 mss = bufsize; 3845 else { 3846 bufsize = roundup(bufsize, mss); 3847 if (bufsize > sb_max) 3848 bufsize = sb_max; 3849 if (bufsize > so->so_snd.sb_hiwat) 3850 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3851 } 3852 SOCKBUF_UNLOCK(&so->so_snd); 3853 /* 3854 * Sanity check: make sure that maxseg will be large 3855 * enough to allow some data on segments even if the 3856 * all the option space is used (40bytes). Otherwise 3857 * funny things may happen in tcp_output. 3858 * 3859 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3860 */ 3861 tp->t_maxseg = max(mss, 64); 3862 3863 SOCKBUF_LOCK(&so->so_rcv); 3864 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3865 bufsize = metrics.rmx_recvpipe; 3866 else 3867 bufsize = so->so_rcv.sb_hiwat; 3868 if (bufsize > mss) { 3869 bufsize = roundup(bufsize, mss); 3870 if (bufsize > sb_max) 3871 bufsize = sb_max; 3872 if (bufsize > so->so_rcv.sb_hiwat) 3873 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3874 } 3875 SOCKBUF_UNLOCK(&so->so_rcv); 3876 3877 /* Check the interface for TSO capabilities. */ 3878 if (cap.ifcap & CSUM_TSO) { 3879 tp->t_flags |= TF_TSO; 3880 tp->t_tsomax = cap.tsomax; 3881 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3882 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3883 } 3884 } 3885 3886 /* 3887 * Determine the MSS option to send on an outgoing SYN. 3888 */ 3889 int 3890 tcp_mssopt(struct in_conninfo *inc) 3891 { 3892 int mss = 0; 3893 uint32_t thcmtu = 0; 3894 uint32_t maxmtu = 0; 3895 size_t min_protoh; 3896 3897 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3898 3899 #ifdef INET6 3900 if (inc->inc_flags & INC_ISIPV6) { 3901 mss = V_tcp_v6mssdflt; 3902 maxmtu = tcp_maxmtu6(inc, NULL); 3903 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3904 } 3905 #endif 3906 #if defined(INET) && defined(INET6) 3907 else 3908 #endif 3909 #ifdef INET 3910 { 3911 mss = V_tcp_mssdflt; 3912 maxmtu = tcp_maxmtu(inc, NULL); 3913 min_protoh = sizeof(struct tcpiphdr); 3914 } 3915 #endif 3916 #if defined(INET6) || defined(INET) 3917 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3918 #endif 3919 3920 if (maxmtu && thcmtu) 3921 mss = min(maxmtu, thcmtu) - min_protoh; 3922 else if (maxmtu || thcmtu) 3923 mss = max(maxmtu, thcmtu) - min_protoh; 3924 3925 return (mss); 3926 } 3927 3928 void 3929 tcp_prr_partialack(struct tcpcb *tp, struct tcphdr *th) 3930 { 3931 long snd_cnt = 0, limit = 0, del_data = 0, pipe = 0; 3932 int maxseg = tcp_maxseg(tp); 3933 3934 INP_WLOCK_ASSERT(tp->t_inpcb); 3935 3936 tcp_timer_activate(tp, TT_REXMT, 0); 3937 tp->t_rtttime = 0; 3938 /* 3939 * Compute the amount of data that this ACK is indicating 3940 * (del_data) and an estimate of how many bytes are in the 3941 * network. 3942 */ 3943 if (SEQ_GEQ(th->th_ack, tp->snd_una)) 3944 del_data = BYTES_THIS_ACK(tp, th); 3945 del_data += tp->sackhint.delivered_data; 3946 pipe = (tp->snd_nxt - tp->snd_fack) + tp->sackhint.sack_bytes_rexmit; 3947 tp->sackhint.prr_delivered += del_data; 3948 /* 3949 * Proportional Rate Reduction 3950 */ 3951 if (pipe > tp->snd_ssthresh) 3952 snd_cnt = (tp->sackhint.prr_delivered * tp->snd_ssthresh / tp->sackhint.recover_fs) - 3953 tp->sackhint.sack_bytes_rexmit; 3954 else { 3955 if (V_tcp_do_prr_conservative) 3956 limit = tp->sackhint.prr_delivered - tp->sackhint.sack_bytes_rexmit; 3957 else 3958 if ((tp->sackhint.prr_delivered - tp->sackhint.sack_bytes_rexmit) > del_data) 3959 limit = tp->sackhint.prr_delivered - tp->sackhint.sack_bytes_rexmit + maxseg; 3960 else 3961 limit = del_data + maxseg; 3962 snd_cnt = min((tp->snd_ssthresh - pipe), limit); 3963 } 3964 snd_cnt = max((snd_cnt / maxseg), 0); 3965 /* 3966 * Send snd_cnt new data into the network in response to this ack. 3967 * If there is going to be a SACK retransmission, adjust snd_cwnd 3968 * accordingly. 3969 */ 3970 tp->snd_cwnd = tp->snd_nxt - tp->snd_recover + 3971 tp->sackhint.sack_bytes_rexmit + (snd_cnt * maxseg); 3972 tp->t_flags |= TF_ACKNOW; 3973 (void) tcp_output(tp); 3974 } 3975 3976 /* 3977 * On a partial ack arrives, force the retransmission of the 3978 * next unacknowledged segment. Do not clear tp->t_dupacks. 3979 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3980 * be started again. 3981 */ 3982 void 3983 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3984 { 3985 tcp_seq onxt = tp->snd_nxt; 3986 uint32_t ocwnd = tp->snd_cwnd; 3987 u_int maxseg = tcp_maxseg(tp); 3988 3989 INP_WLOCK_ASSERT(tp->t_inpcb); 3990 3991 tcp_timer_activate(tp, TT_REXMT, 0); 3992 tp->t_rtttime = 0; 3993 tp->snd_nxt = th->th_ack; 3994 /* 3995 * Set snd_cwnd to one segment beyond acknowledged offset. 3996 * (tp->snd_una has not yet been updated when this function is called.) 3997 */ 3998 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3999 tp->t_flags |= TF_ACKNOW; 4000 (void) tp->t_fb->tfb_tcp_output(tp); 4001 tp->snd_cwnd = ocwnd; 4002 if (SEQ_GT(onxt, tp->snd_nxt)) 4003 tp->snd_nxt = onxt; 4004 /* 4005 * Partial window deflation. Relies on fact that tp->snd_una 4006 * not updated yet. 4007 */ 4008 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 4009 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 4010 else 4011 tp->snd_cwnd = 0; 4012 tp->snd_cwnd += maxseg; 4013 } 4014 4015 int 4016 tcp_compute_pipe(struct tcpcb *tp) 4017 { 4018 return (tp->snd_max - tp->snd_una + 4019 tp->sackhint.sack_bytes_rexmit - 4020 tp->sackhint.sacked_bytes); 4021 } 4022 4023 uint32_t 4024 tcp_compute_initwnd(uint32_t maxseg) 4025 { 4026 /* 4027 * Calculate the Initial Window, also used as Restart Window 4028 * 4029 * RFC5681 Section 3.1 specifies the default conservative values. 4030 * RFC3390 specifies slightly more aggressive values. 4031 * RFC6928 increases it to ten segments. 4032 * Support for user specified value for initial flight size. 4033 */ 4034 if (V_tcp_initcwnd_segments) 4035 return min(V_tcp_initcwnd_segments * maxseg, 4036 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 4037 else if (V_tcp_do_rfc3390) 4038 return min(4 * maxseg, max(2 * maxseg, 4380)); 4039 else { 4040 /* Per RFC5681 Section 3.1 */ 4041 if (maxseg > 2190) 4042 return (2 * maxseg); 4043 else if (maxseg > 1095) 4044 return (3 * maxseg); 4045 else 4046 return (4 * maxseg); 4047 } 4048 } 4049